Hazardous Waste Management System: Identification and ...the hazardous waste management system under Subtitle C of RCRA as listed hazardous wastes. Today's Notice, commonly referred

66344 Federal Register / Vol. 60, No. 245 / Thursday, December 21, 1995 / Proposed Rules

ENVIRONMENTAL PROTECTIONAGENCY

40 CFR Parts 260, 261, 266, and 268

[FRL-5337-9]

RIN 2050-AE07

Hazardous Waste ManagementSystem: Identification and Listing ofHazardous Waste: Hazardous WasteIdentification Rule (HWIR)

AGENCY: Environmental ProtectionAgency.ACTION: Proposed rule, tentativeresponse to Chemical ManufacturersAssociation petition and the HazardousWaste Identification DialogueCommittee recommendations, andrequest for comments.

SUMMARY: The Environmental ProtectionAgency (EPA) today is proposing toamend its regulations under theResource Conservation and RecoveryAct (RCRA) by establishing constituent-specific exit levels for low-risk solidwastes that are designated as hazardousbecause they are listed, or have beenmixed with, derived from, or containlisted hazardous wastes. Under thisproposal, generators of listed hazardouswastes that meet the self-implementingexit levels would no longer be subject tothe hazardous waste managementsystem under Subtitle C of RCRA aslisted hazardous wastes. Today's Notice,commonly referred to as the HazardousWaste Identification Rule (HWIR),establishes a risk-based "floor" tohazardous waste listings that willencourage pollution prevention, wasteminimization, and the development ofinnovative waste treatmenttechnologies.

Many of the exit levels are establishedusing an innovative risk assessmentwhich evaluates potential exposurepathways, both direct and indirect, froma variety of sources, such as waste pilesand surface impoundments. Thisassessment focuses on both human andenvironmental receptors and ispresented for comment in today'sNotice. The remaining exit levels arebased on an alternative risk analysis.

The Agency is also proposing tomodify some of the land disposalrestriction (LDR) numerical treatmentstandards listed in subpart D of 40 CFRpart 268. This notice proposes to captechnology-based treatment standardswith the risk-based exit levels whichminimize threats to human health andthe environment. This notice also takescomment on several general approachesand one specific approach forconditional exemptions from subtitle C

management. Today's notice alsocontains the Agency's tentative responseto a petition for rulemaking submittedby the Chemical ManufacturersAssociation and the Agency's tentativeresponse to the recommendations madeby the Dialogue Committee onHazardous Waste Identification. Thiscommittee was formally chartered inJuly 1993 in accordance with theFederal Advisory Committee Act(FACA).DATES: EPA will accept publiccomments on this proposed rule untilFebruary 20, 1996. Commentspostmarked after this date may not beconsidered. However, the Agencyrecognizes that, because of thecomplexity of this proposed rulemaking,some commenters may want to requestadditional time for comment submittal.In anticipation of these requests, EPAwill be communicating with thelitigants and the court regarding theimplications on our rulemakingschedule of a possible extension of thecomment period for this proposal. If thecomment period is extended, theAgency will provide notice of such inthe Federal Register.

Any person may request a publichearing on this amendment by filing arequest with Mr. David Bussard, whoseaddress appears below, by January 5,1996.ADDRESSES: The public must send anoriginal, two copies, and wheneverpossible, a 3.5 inch computer diskcontaining the comments in a commonword processing format such asWordPerfect version 5.1 1. to: EPA RCRADocket (5305W), 401 M Street, SW.,Washington, DC 20460.

Place "Docket number F-95-WHWP-FFFFF" on your comments. The RCRAdocket is located at: EPA's CrystalGateway Office, 1235 Jefferson DavisHighway, Arlington, Virginia, and isopen from 9 a.m. to 4 p.m., Mondaythrough Friday, excluding Federalholidays. The public must make anappointment to review docket materialsby calling (703) 603-9230. The publicmay copy material from any regulatorydocket at a cost of $0.15 per page.Copies of the background documents,Integrated Risk Information System(IRIS) chemical files, and otherreferences (which are not readilyavailable) are available for viewing andcopying only in the RCRA docket.

Requests for a public hearing shouldbe addressed to'Mr. David Bussard,Director, Characterization and

I This will greatly facilitate EPA's preparation ofthe comment responses and will~significantlyreduce the cost associated with responding to thecomments.

Assessment Division, Office of SolidWaste (OS-330), U.S. EnvironmentalProtection Agency, 401 M Street, SW.,Washington, DC 20460.FOR FURTHER INFORMATION CONTACT: TheRCRA/Superfund Hotline at (800) 424-9346 or at (703) 412-9810. For technicalinformation contact Mr. William A.Collins, Jr., Mr. Greg Helms, or Ms.Pamela McMains, Office of Solid Waste(5304), U.S. Environmental ProtectionAgency, 401 M Street, S.W.,Washington, DC 20460, (202) 260-4770.-

Preamble OutlineI. AuthorityII. Background

A. Overview of Hazardous WasteIdentification Program

B. The Mixture and Derived-From Rulesand the Contained-In Policy

C. Overview of Expected Impacts of the-Exit Rule

111. Scope of Revisions to the Mixture andDerived-From Rules

A. Rationale for Retention of the Mixtureand Derived-From Rules

B. Revision to Derived-from Rule forWastes Listed Because They Exhibit theCharacteristics of Ignitability,Corrosivity, or Reactivity

IV. Development of Exit Levels and MinimizeThreat Levels

A. Need for an ExitB. Overview of the ExitC. Selection of Constituents of Concern1. Development of the Master List2. Development of the Exit Constituent List3. Constituents of Ecological ConcernD. Risk-Based Information1. Human Health Benchmarksa. Non-carcinogensb. Carcinogensc. Consideration of MCLs2. Ecological Benchmarks3. Sources of Dataa. Humanb. EcologicalE. Risk Assessment1. The Risk Analysisa. Introductionb. How the Analysis was Structuredc. How Uncertainty is Addressedd. Linkage of the Risk Analysis to the

Groundwater Fate and Transporte. Risk Targets Used2. Detailed Overview of the Non-

Groundwater Risk Analysisa. .Waste Management Units1. Use of Subtitle D Survey2. Fate and Transport3. Ash Monofilli. Particle Size Distribution for Air

Dispersion Modelingii. Monofill Characterizationiii. Vehicle Trafficiv. Emission Equations for Ash Blown from

Trucks and Spreading and Compacting4. Land Application Uniti. Particle Size Distribution for Air

Dispersion Modelingii. Area of Land Application Unit Relative

to Agricultural Fieldiii. Application Rateiv. Waste Characteristics

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Federal Register / Vol. 60, No. 245 / Thursday, December 21, 1995 / Proposed Rules

v. Depth of Contaminationvi. Partitioning5. Waste Pilei. Waste Pile Heightii. Particle Size Distribution for Air

Dispersion Modelingiii. Waste Characteristicsiv. Vehicle Trafficv. Emission Equation for Ash Blown fromTrucks

6. Surface Impoundmentsi. Two-Phase Sludge Formation Modelii. Dilution of Waste During a Spill7. Tanki. Unit Characterizationii. Volatilization8. Combustorsb. Fate and Transport1. Pathways2. Equations3. Specific Issues on Pathways and

Equationsi. Chemical Transformationii. Biodegradationiii. Meteorological Dataiv. Soil Datav. Soil Pathwaysvi. Surface Water Pathwaysvii. Food-Chain Pathwaysc. Receptors1. Human Receptors2. Ecological Receptors3. Groundwater Fate and Transport

Modelinga. Fate and Transport Processes1. Effects of groundwater mounding2. Transformation products3. Fate and transport of metalsb. Enhanced solution algorithms1. Linkage between unsaturated zone and

saturated zone modules2. Numerical transport solution3. Solution for metals transport4. Elimination of biases in determination of

receptor well concentrationsc. Revision of Monte Carlo methodology for

nationwide assessments1. Data sources2. Finite-source methodology3. Site-based regional analysisd. Implementation of EPACMTPa. Waste management scenarios1. Landfills2. Surface impoundments3. Waste piles4. Land application unitsf. Determination of regulatory limitsg. Chemical specific fate and transport

processes1. Organic constituents2. Metals4. Other Risk Assessment Issuesa. Difference between groundwater and

nongroundwater pathways1. Infiltration2. Density of waste applied to land

application unit3. Unsaturated zone characteristics4. Hydrolysis ratesb. Other groundwater pathway analysis

issues1. Use of 1000 years versus 10,000 years

exposure time horizon2. Implementation of parameter bounds in

Monte Carlo procedure3. Hydraulic conductivity of surface

impoundment bottom layer

4. Waste pile infiltration rates5. Land application unit infiltration rates6. Aggregate effects of alternative

groundwater modeling proceduresF. Additional Eco-Receptor ConsiderationG. Background Concentrations in Soils and

other Issues Relating to ResultsH. Constituents with Extrapolated Risk-

based LevelsI. Analytical Considerations1. Development of Exemption Quantitation

Criteria (EQC)2. EQCs and LDR Requirements as

Exemption Criteriaa. EQCs as exit levelsb. LDR Requirements in combination with

EQC Exit Levels3. Exemption for Constituents Without

EQCsV. Presentation of Exit Levels

A. Constituents with Modeled orExtrapolated Risk-based Exit Levels

B. Constituents with Quantitation-basedExit Levels

C. How to Read the Exit Level TablesVI. Minimize Threat Levels

A. Background1. Summary of the Hazardous and Solid

Waste Amendments of 19842. EPA's Interpretation of Standard for

Treatment RequirementsB. Risk Assessment and Minimize Threat

Levels1. Rationale2. Public Policy ConsiderationsC. Minimize threat levels1. List of Constituents and Minimize

Threat Concentrations2. Constituents for which Exit Levels are

not Minimize Threat LevelsD. Meeting LDR requirements1. Wastes Below Exit Levels as Generated2. Wastes Above Exit Levels as Generated

VII. DilutionVIII. Implementation of Exit

A. Implementation Requirements1. Testing Requirementsa. Data Evaluationi. Compliance with the Exit Levelsii. Wastewater and Nonwastewater

Categoriesiii. Totals and TCLP Analysesiv. Oily Wastesb. Initial Test2. Notification RequirementsB. Implementation Conditions1. Records Maintained on Site2. Testing Conditions3. Testing Frequency and Process ChangeC. Public Participation

IX. Request for Comment on Options forConditional Exemptions

A. Legal Basis for Conditional ExemptionsB. Improvements in Management of Non-

Hazardous Waste and in RiskAssessment Methodology

C. Overview of Options for ConditionalExemptions

1. National Approacha. Eliminate Disposal in Land Application

Unitsb. Unit-Specific Exit Levels for Each

Disposalc. Consideration of Additional

Management Unit Design or ManagementPractices

2. State Program Approach3. Establish Exit Levels that Consider

Regional or Site-Specific Factors thatmight Affect Constituent Fate andTransport

4. Relief from Land Disposal RestrictionsD. Land Disposal Restrictions for

Contingent Management OptionsE. Contingent Management of Mixed Waste

X. Implementation of Conditional ExemptionOption 1

A. Introduction and OverviewB. When Contingent Management

Exemptions Become Effective1. Placement of the waste in a qualifying

unit2. Point of generationC. Requirements for Obtaining an

Exemption1. Sampling and Testing Requirements for

Contingent Management Exemptions2. Requirements for Public Participation in

contingent Management Exemptions3. Notification Requirements for

Contingent ManagementD. Implementation Conditions1. Tracking conditions2. Qualifying Unit3. Claimant's Duty to Ensure Compliance

with all ConditionsE. Retesting and Recordkeeping Conditions

for Contingent Management ExemptionsF. Compliance Monitoring and

Enforcement for Contingent ManagementExemptions

1. Compliance Monitoring2. EnforcementG. Exports of Wastes Eligible for

Contingent Management ExemptionsH. Land Disposal Restrictions

XI. Relationship to Other RCRA RegulatoryPrograms

A. Hazardous Waste DeterminationB. Characteristic Hazardous WasteC. Toxicity Characteristic Level for LeadD. Hazardous Waste ListingsE. DelistingF. Requirements for Treatment, Storage,

and Disposal Facilities and InterimStatus Facilities

G. ClosureH. HWIR-Media Rule/Subtitle C Corrective

ActionI. Land Disposal Restriction ProgramJ. RCRA Air Emission StandardsK. Hazardous DebrisL. Hazardous Wastes Used in a Manner

Constituting DisposalXII. CERCLA ImpactXIII. State Authority

A. Applicability of Rules in AuthorizedStates

B. Effect of State AuthorizationsC. Streamlining Issues

XIV. Regulatory RequirementsXV. ReferencesAppendix A: Background Tables for Risk

Analysis Receptors and PathwaysAppendix B: Table Comparing Groundwater

Modeling Effects of 1000 vs. 10,000 yearsAppendix C: Tables Comparing the Modeled

or Extrapolated Risk Levels vs. the EQCsfor Each Constituent

Appendix D: Tables Comparing the ExitLevels and the UTS Levels

Regulatory Language

66345




I. AuthorityThese regulations are proposed under

the authority of sections 2002(a), 3001,3002, 3004 and 3006 of the Solid WasteDisposal Act of 1970, as amended by theResource Conservation and RecoveryAct of 1976 (RCRA), as amended by theHazardous and Solid WasteAmendments of 1984 (HSWA), 42U.S.C. 6912(a), 6921, 6922, 6924 and6926.

II. Background

A. Overview of the Hazardous WasteIdentification Program

Section 1004(5) of the ResourceConservation and Recovery Act (RCRA)as amended by the Hazardous arid SolidWaste Amendments (HSWA) of 1984,defines "hazardous waste" as "a solidwaste, or combination of solid waste,which because of its quantity,concentration, or physical, chemical, orinfectious characteristics may (A) cause,or significantly contribute to an increasein the mortality or an increase in seriousirreversible, or incapacitating reversible,illness; or (B) pose a substantial presentor potential hazard to human health orthe environment when improperlytreated, stored, transported, or disposedof, or otherwise managed."

Section 3001 of RCRA requires EPA toidentify those wastes that should beclassified as "hazardous." The Agency'shazardous waste identification rulesdesignate wastes as hazardous in one oftwo ways. First, the Agency hasestablished four hazardous wastecharacteristics which identify propertiesor attributes of wastes which wouldpose a potential hazard if the waste isimproperly managed. See 40 CFR261.21-261.24. Any generator of a solidwaste is responsible for determiningwhether a solid waste exhibits any ofthese characteristics. See 40 CFR 262.11.Any solid waste that exhibits any of thecharacteristics remains hazardous untilit no longer exhibits the characteristics.See 40 CFR 261.4(d)(1).

The other mechanism EPA uses todesignate.wastes as hazardous is"listing." The Agency has reviewed dataon specific waste streams generatedfrom a number of industrial processesand has determined that these wasteswould pose hazards if mismanaged forone or more reasons, including thepresence of significant levels ofhazardous constituents listed inappendix VIII to 40 CFR part 261, themanifestation of one or more of thehazardous waste characteristics, or thepotential to impose detrimental effectson the environment. (See generally 40CFR 261.'41). As discussed in detail inthe preambles and in associated dockets

accompanying the listings, EPA hasgenerally determined that these wastescontain toxic constituents atconcentrations which pose risks whichare unacceptable for human orenvironmental exposure and that theseconstituents are mobile and persistent tothe degree that they can reachenvironmental or human receptors.

On May 19, 1980, as part of the finaland interim final regulationsimplementing section 3001 of RCRA,EPA published two lists of hazardouswastes: One composed of wastesgenerated from non-specific sources(e.g., spent solvents) and one composedof wastes generated from specificsources (e.g., distillation bottoms fromthe production of benzyl chloride). TheAgency also published two lists ofdiscarded commercial chemicalproducts, off-specification species,container residues, and spill residuesthereof which are hazardous wastesunder specific circumstances. Thesefour lists have been amended severaltimes, and are currently published in 40CFR 261.31, 261.32, 261.33(e) and (f),respectively. •

B. The Mixture and Derived-From Rulesand the Contained-In Policy

1. Mixture and Derived-From Rules

a. Scope and Purpose of the Rules

In 1980 EPA promulgated its firstcomprehensive regulatory program forthe management of hazardous wasteunder RCRA. 45 FR 33066 (May 19,.1980). As part of that rulemaking EPApromulgated several rules to identifyhazardous wastes. Two of these rulesclarify the scope of the hazardous wastelistings. Under the mixture rule, a solidwaste is a hazardous waste if it is mixedwith one or more listed hazardouswastes. 40 CFR 261.3(a)(2)(iv). Underthe derived-from rule a solid wastegenerated from the treatment, storage ordisposal of a listed hazardous waste isalso a hazardous waste. 40 CFR261.3(c)(2)(i).

EPA promulgated the mixture andderived-from rules to close potentiallymajor loopholes in the subtitle Cmanagement system. Without a"mixture" rule, generators of hazardouswastes could potentially evaderegulatory requirements by mixinglisted hazardous wastes with otherhazardous wastes or non-hazardoussolid wastes to create a "new" wastethat arguably no longer met the listingdescription, but continued to pose aserious hazard. Such a waste also mightnot exhibit any of the hazardous wastecharacteristics. Similarly, without a"derived-from" rule, hazardous wastegenerators and owners and operators of

hazardous waste treatment, storage, anddisposal facilities (TSDFs) couldpotentially evade regulation byminimally processing or managing ahazardous waste and claiming thatresulting residue was no longer thelisted waste, despite the continuedhazards that could be posed by theresidue even though it does not exhibita characteristic. (See 57 FR 7628).

It is for these reasons that the Agencycontinues to believe that the mixtureand derived-from rules are extremelyimportant in regulating hazardouswastes and reducing risk to humanhealth and the environment. However,EPA acknowledges that the mixture andderived-from rules apply regardless ofthe concentrations and mobilities ofhazardous constituents in the waste.The purpose of this rulemaking is toreduce any overregulation of low-riskwastes captured by the mixture andderived-from rule.

b. Subsequent HistoryNumerous industries that generate

hazardous wastes challenged the 1980mixture and derived-from rules in ShellOil v. EPA, 950 F. 2d 741 (D.C. Cir.1991). In December 1991 the D.C. circuitvacated the rules because they had beenpromulgated without adequate noticeand opportunity to comment. The court,however, suggested that EPA mightwant to consider reinstating the rulespending full notice and comment inorder to ensure continued protection ofhuman health and the environment.

In response to this decision, EPApromulgated an emergency rulereinstating the mixture and derived-from rules as interim final rules withoutproviding notice and opportunity tocomment. 57 FR 7628 (Mar.3, 1992).EPA also promulgated a "sunsetprovision" which provided that themixture and derived-from rules wouldremain in effect only until April 28,1993. Shortly after, EPA published theproposal containing several options forrevising the mixture and derived-fromrules. See 57 FR 21450 (May 20, 1992).This proposal also included options forexempting media contaminated withlisted hazardous wastes that areregulated under the "contained in"policy.

The May 1992 proposal and the timepressure created by the "sunsetprovision" generated significantcontroversy. In response, Congressincluded in EPA's 1992 appropriationsbill several provisions addressing themixture and derived-from rules. Pub. L.No. 102-389, 106 Stat. 1571. First,Congress nullified the sunset provisionby providing that EPA could notpromulgate any revisions to the rules




before October 1, 1993 and by providingthat the reinstated regulations could notbe "terminated or withdrawn" untilrevisions took effect. However, to ensurethat EPA could not postpone the issueof revisions indefinitely, Congress alsoestablished a deadline of October 1,1994 for the promulgation of revisionsto the mixture and derived-from rules.Congress made this deadlineenforceable under RCRA's citizen suitprovision.

On October 30, 1992 EPA publishedtwo notices, one removing the sunsetprovision, and the other withdrawingthe May 1992 proposal. See 57 FR49278, 49280. EPA had received manycomments criticizing the May 1992proposal. The criticisms were due, in alarge part, to the very short scheduleimposed on the regulation developmentprocess itself. Commenters also fearedthat the proposal would result in a"patchwork" of differing State programsbecause some states might not adopt therevisions. This fear was based on thebelief that States would react in anegative manner to the proposal andrefuse to incorporate it into theirprograms. Finally, many commentersalso argued that the risk assessmentused to support the proposed exemptionlevels failed to provide adequateprotection of human health and theenvironment because it evaluated onlythe risks of human consumption ofcontaminated groundwater ignoringother pathways that could pose greaterrisks. Based on these concerns, andbased on the Agency's desire to workthrough the individual elements of theproposal more carefully, the proposalwas withdrawn.

Meanwhile, a group of waste'generating industries challenged theMarch 1992 action that reinstated themixture and derived-from rules withoutchange. Mobil Oil Corp. v. EPA, 35 F.3d579 (D.C. Cir. 1994). EPA argued thatthe 1992 appropriations act made thechallenge moot because it preventedboth EPA and the courts fromterminating or withdrawing the interimrules before EPA revised them, even ifEPA failed to meet the statutorydeadline for the revisions. In September,1994 the D.C. Circuit issued an opinionthat dismissed the challenges as mootunder the rationale that the Agency hadoffered.

In early October 1994 several groupsof waste generating and waste managingindustries filed citizen suits to enforcethe October 1 deadline for revising themixture and derived-from rules. TheU.S. District Court for the District ofColumbia Circuit entered a consentdecree resolving the consolidated caseson May 3, 1993. Environmental

Technology Council v. Browner, C.A.No. 94-2119 (TFH) (D.D.C. 1994) Underthis decree the Administrator must signa proposal to amend the mixture andderived-from rules by November 13,1995 and a notice of final rulemaking byDecember 15, 1996. The decree alsospecifies that the deadlines in the 1992appropriations act do not apply to anyrule revising the separate regulationsthat establish jurisdiction over mediacontaminated with hazardous wastes.

c. Federal Advisory Committees Act(FACA) and Outreach

After the withdrawal of the HWIRproposal, the Agency initiated a seriesof public meetings with invitedrepresentatives from industry,environmental groups, hazardous wastetreaters, and States. These meetingsfocused on three major issues: -RCRAregulation of low hazard wastes with aparticular interest in addressing issuesraised regarding the mixture andderived-from rules; concerns that fullRCRA requirements for contaminatedmedia may unnecessarily impede clean-ups; and need to regulate additionalhigh-risk wastes outside the scope of thecurrent listings and characteristics.

A strong and successful effort wasmade to encourage all the interestedparties to participate in the publicmeetings. EPA forged a solidpartnership with the States (bothASTSWMO and EnvironmentalCommissioners under the NationalGovernors Association) and the staterepresentatives worked closely withEPA as co-regulators in our analyses ofoptions.

In July of 1993, EPA chartered thisgroup as an advisory committee underthe Federal Advisory Committee Act(Pub. L. 92-463)(58 FR 36200).

The committee rather quickly formedtwo sub-committees to allow separatediscussion of the low risk wasteproblem associated with the mixtureand derived-from'rules and the rules formanaging contaminated media andother wastes during remediation.

By September of 1994 the low riskwaste group had made significantprogress in identifying options forcreating exemptions for low risk wastes.Despite significant investment of timeand effort, however, the group wasunable to reach consensus on many keyissues.

With the statutory deadline forrevisions to the mixture and derived-from rules approaching, EPA requestedthat group to present a final report inlate September of 1994. EPA andrepresentatives from several stateenvironmental agencies then took upthe task of selecting options for creating

an exit rule, crafting regulatorylanguage, and developing necessarysupporting materials. The FACAsubcommittee's final report was takeninto consideration during thedevelopment of today's proposal.

2. Contained-In Policy

The Agency also has interpreted itsregulatory definition of hazardous wasteto extend to mixtures of hazardouswastes and environmental media (suchas contaminated soil and groundwater). 2

See 40 CFR 261.3(c)(1) and (d)(2). Mediathat are contaminated with listed orcharacteristically hazardous waste mustbe managed as hazardous wastes untilthey no longer contain such wastes. Todate, the Agency has not issued anygeneral rules as to when, or at whatlevels, environmental mediacontaminated with hazardous wastes areno longer considered to "contain" thosehazardous wastes. Media that containhazardous wastes with constituentconcentrations below the levelsproposed today will be eligible forexemption under the proceduresprnposed today. In addition, in aseparate rulemaking, the Agency plansto propose additional rules reducingregulation of contaminated mediaduring remediation activities.

C. Overview of Expected Impacts of theExit Rule

1. Listed WastesThe purpose of this rule is to exempt

from hazardous waste regulation thosesolid wastes currently designated ashazardous waste even though theycontain constituent concentrations atlevels that pose very low risk to humanhealth and the environment. Whilefacilities generating such wastes canpetition for delisting by rulemakingunder the provisions of 40 CFR § 260.20and 260.22, EPA believes that thedetailed waste-stream specific reviewrequired under delisting is notnecessary for the low risk wastes thatare identified by today's proposal. Thealternative, generic exit rule proposedtoday will be faster and less resource-intensive for both the Agency and theregulated community. By providing anopportunity for a morO self-implementing exemption, the Agencyintends to create incentives for effectiveand innovative waste minimization andwaste treatment and to reduceunnecessary demand for Subtitle Cdisposal capacity, without

2EPA's "contained in" policy was upheld as a

reasonable interpretation of 40 CFR 261.3(c)(1) and(d)(2) by the D.C. Circuit in Chemical WasteManagement, Inc v. U.S. EPA, No. 869 F.2d 1526(D.C. Cir. 1989).

66347




compromising needed environmental-protection.

3

By proposing a risk-based "floor" tolisted wastes, today's proposal shouldgive a very strong incentive togenerators of listed hazardous waste toapply pollution prevention to theirprocesses to avoid Subtitle C control.This action should also give incentivefor the development of innovativetreatment technologies to render wastesless risky.

Today's proposed rule specifiessampling and analysis requirements,public participation, reporting andrecord keeping requirements. Most ofthese provisions are alternatives to thesafeguard of waste-specific reviewprovided under the delisting program..The exit levels are risk-basedconcentrations at which a human orwildlife species could be directly orindirectly exposed to the exemptedwaste, and would be unlikely to sufferadverse health effects. The exposurescenario used to develop these levelsassume that the exempted waste will nolonger be subject to Subtitle C control,-but will be managed as a solid waste inone of a variety of non-hazardous wastemanagement units regulated underSubtitle D.

2. Characteristic Wastes

Listed hazardous wastes exemptedunder today's proposed rule whichexhibit any of the characteristics willcontinue to be regulated as hazardouswastes until the characteristic isremoved. In a number of cases, wasteswere listed on the basis of containingboth toxic hazardous constituents andexhibiting one or more of the hazardouswaste characteristics that do not relateto chemical toxicity (e.g., ignitability,corrosivity, or reactivity). If such awaste still exhibits any characteristicafter complying with the exemptioncriteria proposed in today's proposedrule, it must continue to be managed asa characteristically hazardous waste.

III. Scope of Revisions to the Mixtureand Derived-From Rules

The mixture and derived-from rulespromulgated in 1980 and reinstated in1992 require Subtitle C regulation of allmixtures of listed hazardous wastes andsolid wastes and all residuals fromtreatment of hazardous wastes. Therules proposed today, however, allowrapid exemptions for mixtures and

3As will be discussed further in this notice, the

Agency believes that the delisting process willcontinue to be valuable for certain types of wasteswhich are not eligible for an exemption under thisproposal. Thus the Agency is not proposing toeliminate or modify the delisting program as aresult of this proposal.

derived-from wastes that present nosignificant threats to human health andthe environment. Those wastes thatwould remain subject to the mixtureand derived-from rules typically willpose risks that warrant regulation underSubtitle C. To the extent that this is nottrue for a particular mixture ortreatment residual, the delisting processremains available (at least at the statelevel) to exempt wastes withconstituents at more site- and waste-specific levels. Consequently, EPA hastentatively determined that furtherrevisions of the mixture and derived-from rules, with the exception of theone minor change to .the derived-fromrule discussed later in this section, arenot warranted in this rulemaking.However, EPA requests comment onthis conclusion.

A. Rationale for Retention of theMixture and Derived-From Rules

EPA continues to believe that it hadample statutory and regulatory authorityto promulgate the original rules and thatit also has ample authority to maintainthe rules without further revisions. Themixture and derived-from rules,particularly with the revisions proposedtoday, ensure that hazardous wastes thatare mixed with other wastes or treated'in some fashion do not escaperegulation so long as they are reasonablylikely to continue to pose threats tohuman health and the environment.They thus retain jurisdiction over listedhazardous wastes and clarify that suchwastes are not automatically eligible forexit when they are mixed or treated.Although RCRA sets out criteria for theidentification of hazardous wastes toenter the subtitle C system, it is silenton the question of how to determinethat a waste is eligible to exit thesystem. EPA's interpretation of thestatute is thus entitled to deference solong as it is reasonable and consistentwith RCRA's purposes.

EPA believes that its decision toretain jurisdiction over major portionsof the universe of waste mixtures andtreatment residues is consistent with itsauthorities under sections 3002-3004 ofRCRA to impose requirements on wastehandlers until wastes have "cease[d] topose a hazard to the public". Shell OilCorp. v. EPA, 959 F.2d 741, 754 (D.C.Cir. 1991). See also ChemicalManufacturers Assoc. v. EPA, 919 F.2d158, 162-65 (EPA may regulate thedisposal of nonhazardous wastes in ahazardous waste impoundment undersection 3004) and Chemical WasteManagement, Inc. v. EPA, 976 F.2d 2, 8,13-14 (D.C. Cir. 1992) (EPA may requirefurther treatment of wastes under

section 3004 even though they cease toexhibit a hazardous characteristic).

The mixture and derived-from rulesare also valid exercises of EPA'sauthority to list hazardous wastes undersection 3001. That provision gives EPAbroad authority to promulgate listingcriteria. EPA's 1980 criteria authorizethe listing of classes of hazardouswastes when it has reason to believethat wastes in the class are typically orfrequently hazardous. See 40 CFR261.11(b). Such class listings arepermissible even if some members ofthe class do not actually pose hazards.Nothing in the section 1004(5)definition of hazardous waste, in section3001, or in EPA's listing criteria requireEPA to prove that every member of aclass poses a hazard. In fact, many wastelistings describe "classes" of hazardouswastes because they cover a range ofmaterials that are not identical incomp6sition. The mixture and derived-from rules thus are fully authorized asclass "listings" under section 3001.

EPA has also made a reasonablefactual determination that these classesof waste warrant regulation undersections 3002-3004 and section 3001. In1980 EPA determined that thehazardous constituents contained inthese wastes are not generallyeliminated or rendered nontoxic simplybecause a waste is mixed with otherwastes or managed in some fashion. In1992, when EPA repromulgated themixture and derived-from rules, itdocumented numerous instances ofmixed and derived-from wastes thatcontinued to pose hazards. See 57 FR7629 (March 3, 1992). Today, EPA isproposing that members of this class ofwastes that pose low risks will beeligible for an expedited, self-implementing exemption from SubtitleC regulation. Accordingly, EPA has aneven better basis for believing thatwastes which remain within the scopeof the mixture and derived-from rulespose threats warranting regulation.

Additionally, EPA continues tobelieve, as it did in 1980, that it wouldbe virtually impossible to try to identifyall possible waste mixtures and treatedwastes and assess their hazardsindividually. EPA's rule reasonablyretains jurisdiction over both broadclasses and places the burden of proofon the regulated community to showthat a particular waste has ceased topresent a hazard. Today's self-implementing exit proposal will reducethat burden significantly, ensuring thatthe mixture and derived-from rulesrepresent a reasonable approach toregulating these classes of wastes.




B. Revision to Derived-from Rule forWastes Listed Because They Exhibit theCharacteristics of Ignitability,Corrosivity, or Reactivity

In 1981 EPA responded to a numberof comments on the scope of the original1980 mixture rule by promulgating anumber of exemptions for mixtures ofsolid wastes and listed hazardouswastes which, according to informationsubmitted by commenters, posed nosignificant risk to human health and theenvironment. See 46 FR 56582 (Nov. 17,1981). The 1981 rule included anexemption for mixtures of solid wastesand hazardous wastes listed solelybecause they exhibited one or more ofthe hazardous waste characteristics, ifthe resultant mixtures no longerexhibited a characteristic. Theexemption was based on a finding thatsuch mixtures did not pose threats tohuman health and the environmentwarranting Subtitle C regulation. See 46FR 56568 and the current text of theexemption at § 261.3(a)(2)(iii). EPAnotes that it has never promulgated anylistings for wastes solely on the basisthat they exhibit either the 1980 EPtoxicity characteristic or the 1990toxicity characteristic; consequently,only mixtures containing wastes listedbecause they exhibit the characteristicsof ignitability, corrosivity, or reactivityhave been eligible to exit Subtitle Cwhen they no longer exhibit thecharacteristic.

The 1981 notice focused exclusivelyon issues concerning the mixture rule.Consequently, EPA did not propose anyparallel exemption for such wastes forthe separate derived-from rule (codifiedat § 261.3(c)(2)(i)), even though thederived-from wastes would appear to,present similarly low risks if they nolonger exhibited a characteristic andwere treated to meet LDR standardsbefore land disposal. Recent inquiriesfrom the public have highlighted thediscrepancy in the scope of the mixturerule and the derived-from rule forwastes listed solely because they exhibitcharacteristics. EPA believes it has noreason to treat derivatives of wasteslisted solely because they exhibit thecharacteristic of ignitability, corrosivity,or reactivity any differently from theway it treats mixtures of such wastesbecause both present similar low risksto human health and the environment.

Consequently, EPA is today proposinga revision to the derived-from rule thatwill closely resemble the 1981 revisionto the mixture rule. Since no listings todate have been based on the toxicitycharacteristic, EPA is proposing to limitthe new revision to the derived-fromrule to wastes listed becaus6 they

exhibit only the characteristics ofignitability, corrosivity, or reactivity.EPA is also not proposing to exemptwastes that might in the future be listedonly because of the toxicitycharacteristic because (as this ruleproposal indicates) there can be riskconcerns with the TC constituentsbelow TC levels. EPA requests commenton this proposal to create a newexemption to the derived-from rule forthis limited category of listed wastes.

The proposed exemption Will alsoremind the regulated community of theseparate duty to comply withrequirements imposed by the part 268regulations implementing the LDRprogram. In CWMv. EPA, 976 F.2d 2(D.C. Cir. 1992), the U.S Court ofAppeals for the D.C. Circuit interpretedRCRA section 3004(m) as requiringtreatment of de-characterized hazardouswastes to meet LDR treatment standardseven after the wastes cease exhibiting acharacteristic. EPA believes that de-characterized derived-from residuesfrom wastes listed because they exhibitcharacteristics also must meet LDRrequirements, unless they are eitherdelisted or are exempt at the point ofgeneration pursuant to other provisionsproposed in this rule (e.g., meetingHWIR levels at the point of generation).

In 1992 EPA amended the 1981exemption to mixture rule to provide asimilar cross-reference and clarificationfor mixtures containing de-characterizedlisted wastes. See 57 FR 37194, 37210-11 (Aug. 18, 1992). That 1992clarification, however, only coversnonwastewater mixtures. As explainedin that mixture rule preamble, EPA thenregulated de-characterized wastewatersmuch less stringently under the LDRprogram. Consequently, EPA did notbelieve it was necessary to remind theregulated community to comply withLDR requirements for wastewatermixtures.

Later in 1992 the CWMv. EPAdecision invalidated most of thedistinctions between the LDR rules forwastewaters and nonwastewaters. EPAis now revising the LDR program tocomply with that decision in the LDRPhase III and Phase IV rulemakings. Toreflect the changes in LDR regulation ofwastewaters, the derived-from ruleexemption proposed today reminds theregulated community of the. need tocomply with part 268 LDR requirementsfor all types of derived-from residues.EPA requests comment on thisclarifying language. EPA also requestscomment on whether it should revisethe LDR clarification for the mixturerule as well.

IV. Development of Exit Levels and"Minimize Threat" Levels

A. Need for the Exit

The primary purpose of this rule is toaddress listed hazardous wastes,mixtures of listed hazardous wastes andsolid wastes, and residues derived-frommanaging listed hazardous waste that,under current rules, continue to bedesignated as "hazardous waste"although they are either generated withconstituent concentrations that pose lowrisks or treated in a manner that reducesconstituent concentrations to low levelsof risk.

EPA notes that there are currentlyexemptions, both codified andcontained in policy directives, from thehazardous waste identification system,particularly the mixture and derived-from rules, for certain types of wastes orwastes with certain constituentconcentrations. See e.g. 40 CFR261.3(a)(2)(iv)(A) through (E) and policymemorandums such as the "SkinnerMemorandum" dated August 23, 1995.EPA is not proposing to modify orreplace any of these exemptions andpolicy statements.

B. Overview of the ExitFor 191 of the 376 constituents of

concern, EPA conducted a detailedhuman health risk analysis to developrisk-based levels for either thewastewater or nonwastewater form of aconstituent (or both). To conduct thisanalysis, EPA identified five types ofunits actually and rather frequentlyused to manage nonhazardous wastesthat covered the full range ofenvironmental releases needinganalysis. The May 1992 proposal of exitlevels for listed wastes, like manyprevious RCRA rules, assessed onlyrisks from releases to groundwater. Inresponse to complaints that such anassessment would not protect humanhealth and the environment from othertypes of releases, EPA also assessedpotential releases to air, surface waterand soil in this proposal.

For each category of releases, EPAevaluated both relatively simplepathways (such direct human ingestionof contaminated groundwater) and morecomplex pathways (such as thedeposition of windblown wasteparticles on agricultural land, followedby crop uptake, consumption of the cropby cattle, and consumption ofcontaminated beef or milk by humans).EPA assessed approximately 8 to 27release pathways depending on the typeof waste management unit.

Additionally, EPA screened the samegroup of 191 constituents to identify thehighest priorities for assessment of

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ecological receptors. In addition, EPAconsidered for its assessment thetoxicological effects of silver onecological receptors. EPA conducted aspecific assessment of ecological risksfor 47 constituents using the same fiveunits and the same pathways (modifiedto reflect ecological exposures) for eachunit. This risk assessment is describedin more detail in sections V.B. and C.

Data limitations and resourceconstraints prevented EPA fromconducting a risk analysis for theremaining constituents of concern. Foreach of these constituents, EPAextrapolated exit levels from levelsderived-from the risk assessment forsimilar chemicals. EPA's extrapolationmethodology is described in sectionIV.F.

The current capabilities of analyticalchemistry constrain EPA's ability to usesome of concentrations as exit levels.For approximately one-fourth of theconstituents, EPA found that availablemethods could not routinely measurethe constituent at the modeled orextrapolated risk-based exit level.

C. Selection of Constituents of Concern

1. Development of the Master ListEPA developed an initial "Master

List" of 506 constituents to be evaluatedfor purposes of establishing exit criteria.This master list was developed bycombining the constituents specificallylisted in the following appendices of 40CFR part 261: Appendix VII, Basis forListing Hazardous Waste; Appendix

VIII, Hazardous Constituents; andappendix IX of part 264, the Ground-Water Monitoring List. The master listincludes the full list of constituentsreferenced in appendix VII, includingthe F039 constituents.

Appendix VII to part 261, which wasoriginally promulgated on May 19, 1980(45 FR 33084) sets out the chemicalconstituents found to pose threats tohuman health and the environment thatserved as the actual basis for each ofEPA's original hazardous waste listings.Appendix VIII to Part 261, alsopromulgated in 1980, is a more generallisting of chemicals found to posepotential threats to human health andthe environment. (45 FR 33084). EPAconsiders wastes containing appendixVIII constituents to be candidates forlisting determinations. EPA amendsappendix VII from time to time as EPAidentifies additional potentially toxicconstituents.

EPA later promulgated appendix IX topart 264 to identify those appendix VIIIconstituents which it could routinelyexpect owners and operators ofpermitted hazardous waste treatment,storage and disposal facilities to monitorin groundwater. EPA also included inthis appendix 17 additional constituentsfound to pose significant risks that theSuperfund program routinely monitoredin groundwater. (52 FR 25942, July 9,1987).

EPA established in these rulemakingsthat each of these constituents hadsignificant potential to threaten human

health, and, by implication, potential tothreaten the environment. (Most of thedata EPA utilized predicted toxic effectson humans.) EPA finds it reasonable toinclude each of these constituents onthe list of chemicals of concern.

Further, EPA believes that, with theexception of the six chemicals identifiedbelow, the three appendices identify thechemicals of current concern to EPAthat are likely to be found in listedwastes.

The Agency requests comment onwhether the master list should alsoinclude six constituents that are notlisted in any of the above sources. Thesesix constituents, which are listed inTable 1, are found in six "U" listedwastes (commercial chemical productsthat become hazardous wastes whendiscarded). See 40 CFR 261.33(fo. EPAoriginally listed these wastes becausethey routinely exhibited thecharacteristic of ignitability. Since theoriginal listings, however, sufficienttoxicity data have become available forthese constituents. (The risk number fordimethylamine was recently withdrawn;however, EPA understands that it willshortly be replaced). Because of thetoxicity data associated with theseconstituents, the Agency is takingcomment on whether exit levels shouldbe established for these six constituentsin today's rulemaking. The Agency alsorequests comment on whether these sixconstituents should be added toAppendix VIII.

TABLE 1.-CONSTITUENTS NOT ON APPENDICES VII, VIII, OR IX

NonwastewaterCAS # Constituent Wastewater

Totals Leach

75-07-0 ............. Acetaldehyde (ethanal) .......................................................................................... .................... ......................................98-82-8 ............. Cumene ................................................................................................................... 67 18,000 2.5

124-40-3 ............. Dimethylamine ........................................................................................................ ............. ....................... ..........110-00-9 ............. Furan ....................................................................................................................... 16 1300 .0679-10-7 ............. Acrylic acid ............................................................................................................. (1) (1) (1)98-01-1 ............. 2-Furancarbox- aldehyde (furfural) ........................................................................ (1) . (1) (1)

' No exit levels because no EQC is available for this constituent. The criteria for exit would be to meet LDR treatment standards in § 268.

Full documentation concerning theselection of constituents of concern isavailable in the docket under TheBackground Document to SupportDevelopment of the Final ConstituentList under the Waste Exit Rule.

2. Development of the Exit ConstituentList

The Agency narrowed the list of 506constituents to consist of 376constituents that are included in theexemption list. 130 constituents weredeleted from the master list. Criteria for

constituent deletions from the masterlist include: Reactivity in air, analysis asa different constituent, reactivity inwater, hydrolysis in soil or water, or ispart of a chemical class with a specificconstituent represented on the list.Because different methods andquantitation limits are necessary forsolid and liquid matrices, two separateanalyses were conducted. TheBackground Document to SupportDevelopment of the Final ConstituentList under the Waste Exit Rule in thedocket further justifies deletions of

constituents from the master list andlists the deleted constituents.

Molybdenum is not on theAppendices VII, VIII, or IX, whichprovided the scope of today's master listof constituents. In anticipation of.thePetroleum listing, due to a DrinkingWater Sewage Sludge regulatory level,and due to available toxicityinformation, the Agency has includedmolybdenum on the exemption list. Dueto modeling time constraints,Molybdenum was not modeled forgroundwater isk. The groundwater




leach level was estimated by assuming Two modeled constituents do not phenyl mercuric acetate. The Agencya DAF of 10 and using the RID. The have estimated quantitation criteria requests comment on how to deal withAgency requests comment on whether (EQCs-see section IV.G.) and therefore these two constituents. The followingmolybdenum should be on the list. do not have associated exit levels. These table represents modeled results for

constituents are ethylene thiourea and these constituents for comment.

TABLE 2.-MODELED CONSTITUENTS WITHOUT EQCs

CASNUM Constituent NWW totals NWW leach WW totals

96-45-7 Ethylene thiourea .................................................................................................. 0.51 0.00017 .0005362-38-4 Phenyl mercuric acetate ..................................................................................... 0.0093 0.0045 0.012

EPA modeled chromium VI in the riskassessment. However, totals chromiumappears on the exit tables based on theexit levels calculated from modelingchromium VI. This approach isconsistent with the ToxicityCharacteristic approach to chromium.The Agency asks for comment on thisapproach.

The cyanide exit level wasextrapolated. It is meant to be totalscyanide. The Agency requests commenton whether testing for totals cyanide isappropriate.

The values in the exit tables for silverdo not represent results of humantoxicity data for silver, rather theyrepresent ecological results from the riskassessment. The Agency has determinedthat the effect of silver on humans is nota human health problem, rather it is anaesthetic problem. The groundwatermodel did not model ecologicalexposure, therefore, there is nogroundwater risk level for silver.

3. Constituents of Ecological Concern

As explained above, EPA establishedin previous RCRA rulemakings that theconstituents on the exit list (376)present significant threats to humanhealth. Numerous comments submittedon EPA's May 1992 proposal toestablish exit levels urged EPA toconduct a more specific and detailedanalysis of threats to non-humanspecies. Consequently, in thisrulemaking EPA determined theconstituents it believed to also bereasonably likely to pose risks toecological receptors,

EPA has not set benchmarks forecological impacts for a large number ofconstituents under any of its programs.Establishing such benchmarks for thisproposal would be a resource-intensiveand time-consuming task. Accordingly,EPA narrowed the list of exitconstituents for which ecologicalreceptors would be evaluated. First,EPA decided to consider only the 191constituents which it had alreadytargeted for analysis to protect humanhealth. Second, the Agency developed amethodology for screening the 191

constituents to identify those mostlikely to pose significant risks toecological receptors.

Based on an extensive review ofavailable literature, EPA developed fivecriteria to indicate the potential forecological risks:

(1) Constituents that bioaccumulate(and possibly biomagnify) in the foodchain that can present elevatedexposures-to certain predators;

(2) Persistent constituents that arelikely to increase long-term multi-generational exposures n wildlife;

(3) Constituents that causereproductive and developmental effectsthat can elicit adverse effects atsensitive life stages;.

(4) Constituents that may causeecological effects that have no humananalog (e.g., eggshell thinning); and

(5) Constituents that may cause effectsto ecological receptors continuouslyexposed.

EPA also developed operationaldefinitions for each criterion. Thedefinitions were quantitative wherepossible. Further details can be found inappendix B of the Technical SupportDocument for the Risk Assessment forHuman and Ecological Receptors.

EPA decided to designate asconstituents of ecological concern the47 constituents that exhibited at leasttwo of the five criteria. The Agencybelieves these constituents present thehighest priorities in terms ofenvironmental risk. An additional 36constituents exhibited only onecriterion. EPA, however, chose not todesignate them as constituents ofconcern because time and resourceconstraints would prevent the Agencyfrom completing an analysis with theseconstituents. EPA, nevertheless,believes it has identified and analyzedsufficient constituents of concern toensure that the exit levels proposedtoday provide for reasonable protectionof the environment. Only 83 of 191screened constituents showed anysignificant potential to pose threats tothe environment at levels protective ofhuman health. Further, as discussed inmore detail below, of the 47

constituents that EPA actually assessedfor ecological impacts, only 6wastewater constituents and 18nonwastewater constituents requiredexit levels to protect environmentalreceptors lower than those necessary toprotect human health under the baselineproposal. Consequently, EPA believes itis unlikely that ill of the remainingconstituents will present significantthreats to ecological receptors at levelsthat would adequately protect humanhealth.

D. Risk-Based Information

The Agency's proposed option forestablishing exit values is based on riskmodeling to a hazard quotient of I anda 1 x 10-6 cancer risk. The Agencychose a hazard quotient of 1 as itstoxicity benchmark value for non-carcinogens because evaluation of thesecompounds presumes there is athreshold exposure above whichindividuals would be at significant riskof suffering the adverse effectsattributable to the compound. The HQ isthe Agency's best attempt to estimatethat level. Therefore, the Agencybelieves all exposures should remainbelow HQ 1. Some Agency programsrely on HQ values less than I instandard setting (the drinking waterprogram uses an HQ of 0.20 to providea safety factor which allows forexposure to the constituent from sourcesother than drinking water).

The Agency chose a toxicitybenchmark of 1 x 10-6 cancer risk forcarcinogens for several reasons. Acancer risk level of 1 x 10-5 risk wasused as a clearly hazardous level inestablishing the toxicity characteristic.Second, in the listings program, a I x10-4 cancer risk is used as thepresumptive listing risk, and a 1 x 10-6as the presumptive no-list level. Acancer risk of I x 10-5 represents a levelof initial concern about risk. Therefore,in allowing listed hazardous waste toexit the requirements of Subtitle C, theAgency was targeting waste that isclearly not hazardous. Thus, the Agencybelieves the risk level should be at the

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low end of the risk range used to bringwaste into the hazardous waste system.

Similarly, the Agency sought to beprotective of public health indeveloping its fate and exposuremodeling. For the groundwaterevaluation, the Agency used a DAF 10(which represents an approximate 90thpercentile protection level) for infinitesource type constituents. (Constituent-specific DAFs were developed using thesame input assumptions, and differentDAFs result from modeling ofdegradation or retardation factors in theenvironment). This is the generic DAFused in the delisting program for largevolume wastes. Since this is a nationalprogram which will largely benefit thelargest volume generators, the DAF 10assumption is consistent with delistingpractice. Also, the toxicity characteristicused a DAF of 100 (representing anapproximate 85th percentile protectionlevel) for identifying clearly hazardouswaste (for infinite source typeconstituents; regulation of hydrolyserswas deferred). Again the policy goal ofexits was to strive to be well belowclearly hazardous levels. The Agencyalso modeled exposure at the nearest,downgradient well. The TC rulerestricted well placement to within theplume. Today's proposal attempts tobalance the protectiveness level andwell placement by requiring a moreprotective level than the TC rule, but isless restrictive in well location, e.g.,wells outside of the plume, atsignificantly lower risk, are averaged in.

For modeling of the non-groundwaterpathways, the Agency used four high-end parameter values for which themodeling outcome is most sensitive asinputs to the analysis to be protective ofpublic health and the environment.These include: Two high-endparameters in the waste managementunit characterization and fate portionsand two high-end parameters in theexposure portions of the model. Theremaining input parameters were .evaluated at typical values or centraltendency values. The Agency sought tobe protective of a high percentileexposed population (at least 90thpercentile).

1. Human Health Benchmarks

For each constituent on the masterlist, the Agency evaluated the existingtoxicity information to determinewhether there were sufficient toxicitydata to establish a benchmark. For thoseconstituents with adequate data, thedata were evaluated either by theAgency's CRAVE (Carcinogen RiskAssessment Verification Endeavor)Workgroup, Reference Dose/ReferenceConcentration (RfD/RfC) Workgroup, or

the Office of Research andDevelopment. This approach isconsistent with the approach used inthe Agency's other risk-based RCRA.programs such as the ToxicityCharacteristic, delisting petitionevaluations, listings, as well as theCERCLA program. See Section 4,"Benchmarks," of the TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors for more details.

a. Non-carcinogens

The Agency proposes to use oralreference doses (RfDs) and inhalationreference concentrations (RfCs) as thebasis for developing the exit criteria fornon-carcinogenic constituents. An RfDor RfC is an estimate (with uncertaintyspanning perhaps an order ofmagnitude) of a daily exposure to aconstituent for the human population(including sensitive subgroups) that islikely to be without an appreciable riskof deleterious effects during a lifetime.

The approach used to derive an RfDor RfC is to identify the highest test doseof a constituent associated with noeffects or effects that are not consideredadverse in an appropriate animalbioassay test. These experimental no-observed-adverse-effect-levels(NOAELs) or no-observed-effect-levels(NOELs) are considered to be anestimate of the animal population'sphysiological threshold for adverseeffects. The RD or RfC is derived bydividing the NOAEL or other toxicitybenchmark by suitable uncertainty andmodifying factors. In the event that anappropriate NOAEL or NOEL is notavailable, the lowest-observed-adverse-effect level (LOAEL) may be used withadditional uncertainty factors.

It is important to note that thecontributions of the constituent fromvarious sources in the environment (e.g.,air, food, water) are not considered inthe development of an RfD or RfC.Rather, the RfD or RfC reflects theestimated total permissible daily humanexposure from all sources of exposure.RfDs and RfCs have been calculated formany, but not all, of the non-carcinogenic constituents for which theAgency is establishing exit criteria.

The Agency prefers to use only RfDsand RfCs that have been evaluated andverified by the RfD/RfC Workgroup asthe basis for setting regulatory levels.However, for some constituents, theAgency has not yet completed itsverification process; thus, RfDs and RfCsunder development are being used forpurposes of this proposal for thoseconstituents. If the final verified RfDsand RfCs differ from the RfDs and RfCs

under development proposed in today'snotice, the Agency will adopt the new(i.e., verified) values for the final ruleafter noticing the data in the FederalRegister.

b. Carcinogens

The Agency proposes to use the oralcancer slope factor and inhalationcancer unit risk as the basis fordeveloping exit levels for carcinogenicconstituents unless the non-carcinogenic effects occur at lowerlevels. EPA's CRAVE Workgroup andOffice of Research and Developmenthave estimated the carcinogenic slopefactor (CSF) (i.e., the slope of the "dose-response" curve) and inhalation unitrisks for humans exposed to low-doselevels of carcinogens in theenvironment. The slope factors indicatethe upper-bound confidence limitestimate of excess cancer risk forindividuals experiencing a givenexposure over a 70-year lifetime. Inpractice, a given dose multiplied by theslope factor gives an upper estimate ofthe lifetime risk to an individual ofdeveloping cancer. By specifying a levelof lifetime risk (no matter how small),one can also estimate the correspondingdose using the slope factor.

EPA proposes to quantify on a weight-of-evidence basis, as described below.EPA promulgated "Guidelines forCarcinogen Risk Assessment" onSeptember 24, 1986 (51 FR 33992),which defined a scheme to characterizesubstances based on experimental dataand the kinds of responses induced bya suspect carcinogen. These guidelinesspecify the following fiveclassifications:Group A-Human carcinogen (sufficient

evidence from epidemiologic studies)Group B-Probable human carcinogenGroup B,-Limited evidence of

carcinogenicity in humansGroup B2-A combination of sufficient

evidence in animals and inadequateor no evidence in humans

Group C-Possible human carcinogen(limited evidence of carcinogenicityin the absence of human data)

Group D-Not classifiable, as to humancarcinogenicity (inadequate humanand animal evidence ofcarcinogenicity or no data available)

Group E-Evidence of non-carcinogenicity for humans (noevidence of carcinogenicity in at leasttwo adequate animal tests in differentspecies or in both adequateepidemiologic and animal studies).The weight-of-evidence basis was

used to eliminate Group D and Econstituents from further considerationas carcinogens.




Under each of the regulatory optionspresented in today's proposal, theAgency is using the same risk level forGroups A, B, and C carcinogens. Thisapproach is consistent with the waycarcinogens were treated in the 1990Toxicity Characteristic rule, hazardouswaste listing determinations, and thedelisting program. The rationale for thisapproach is that while theclassifications indicate the type (humanor animal) and strength of the studiesavailable which reflects upon theuncertainty about the carcinogenicpotential, the severity of the effect,cancer, warrants equal treatment. It isimportant to note that a few Group Ccarcinogens do not have slope factors orunit risks. In these cases the Agencyused the benchmark developed for thenon-cancer endpoint.

c. Consideration of MCLsThe Agency is proposing two

approaches for setting human health-based levels for carcinogens and non-carcinogens in routes of exposureinvolving water ingestion. For the firstapproach, the Agency is proposing touse Maximum Contaminant Levels(MCLs) promulgated under the SafeDrinking Water Act (SDWA) of 1974, asamended in 1986, as the human health-based levels for the constituents forwhich they have been established. Ingeneral, MCLs for non-carcinogens arederived from the Reference Doses(RIDs), while MCLs for mostcarcinogens are set as close to zero astechnically and economically feasible;this normally corresponds to risk levelsthat range from 10 - 4 to 10 -

6. (Note that,although the derivation of MCLsconsiders feasibility of treatment,analytic chemistry, and cost factors inaddition to health effects, it alsoconsiders other routes of exposure. TheAgency's policy has been to use MCLs,when available, in other similarconcentration-based programs.) Forthose constituents which do not yethave MCLs, the Agency is proposing touse oral reference doses (RfDs) for non-carcinogens and oral slope factors forcarcinogens as described above.However, if new MCLs are finalizedunder the SDWA prior to thepromulgation of today's rule, theAgency proposes to substitute the newMCLs for the RfDs and slope factor-derived human health-based levels forwater ingestion presented in today'snotice.

For the second approach, the Agencyintends to propose to use only RfDs andslope factors in deriving human health-based levels for water ingestion. TheAgency requests comment on these twoapproaches.

2. Ecological BenchmarksEcological benchmarks were

developed for a variety of ecologicalreceptors based on the availability ofdata. Benchmarks were needed formammals, birds, plants, soil fauna, fish,aquatic invertebrates, aquatic plants,and benthos (sediment-dwellingorganisms). A much smaller number ofconstituents have been evaluated by theAgency for ecological effects than havebeen for human health effects, asdiscussed under V.A. In general,measurement endpoints were selected:(1) For consistency with the Agency'sFramework for Ecological RiskAssessment (U.S. EPA 1992x), the GreatLakes Initiative, and other ecologicalefforts within the Agency, and (2)relevance to the ecological receptor. Asdiscussed in "Section D-RiskAssessment" the ecological assessmentfocussed on inferring the sustainabilityof populations and communities withinecosystems. Therefore, benchmarkswere derived from measurementendpoints (i.e., reproductive,developmental, growth, survival, andmortality) from which such inferencescould be made. Reproductive studies(e.g., number of viable young perfemale) were preferred over otherendpoints. For some constituents, acuteor mortality studies were used,however, this occurred only fordeveloping benchmarks for fish, aquaticinvertebrates, and benthos whereprotocol exists (AWQC development)for using such data. The Agency seekscomment on the measurementendpoints selected for each ecologicalreceptor.

The toxicological benchmarks wereestablished using the more conservativeno effects level (or concentration)approach for ecological receptors ascompared to a 20% effects level. The20% effects level is the lowest level forecological effects that can be detected infield population analyses (Suter et al.,1992). Although the 20% effects levelmay indeed be the lower limit thatcould be reliably confirmed in fieldstudies, this level reflects our currentanalytical abilities and not necessarilythe ecological significance of the effectslevel. The no effects approach was takenbecause the ecological analysis infersthe sustainability of various populationsunder the assumption that if a sufficientnumber of populations within anecosystem is protected, then thelikelihood of adverse effects that arecausally related to the chemical stressorwill be reduced at the ecosystem level.The Agency was concerned that if aneffects approach was taken, then theassumption underlying the ecological

analysis would no longer be valid. TheAgency seeks comment on the approachtaken for setting toxicologicalbenchmarks.

Given the number and variety ofecological receptors included in theanalysis (predatory birds to soil fauna)as well as the variety of effects andendpoints considered, the benchmarkdevelopment process required anapproach that was internally consistentand acknowledged, at leastqualitatively, the uncertainty involved'in estimating ecological benchmarks.The Agency, therefore, developed abenchmark classification scheme toincorporate both the relationship of thebenchmark to the entire toxicity data setand the adequacy of the database usedto derive the benchmark. Threeclassifications were established:Adequate, provisional, and interim.These classifications were developed ona receptor group-specific basis (i.e., fishand aquatic invertebrates, benthos,mammals, birds, soil fauna, andterrestrial plants) and represent aweight-of-evidence designation for thetoxicological benchmark. In manyrespects, this classification scheme issimilar in meaning to the humancarcinogen weight-of-evidence groupsand the difference between "verified"values on IRIS and "unverified" valuesin HEAST. The classifications relate tothe certainty assigned to a givenecological benchmark. The benchmarkswere treated the same in the analysisregardless of classification. See Section4 in the "Technical Support Documentfor the Hazardous Waste IdentificationRule: Risk Assessment for Human andEcological Receptors" for details oneach classification and how they wereused for each ecological receptor group:The Agency seeks comment on theclassification developed for the analysis.

Below is a discussion of howbenchmarks were developed for each ofthe receptor groups. For a detaileddiscussion of each of theirdevelopments, see Section 4,"Benchmarks," and Appendix B,"Toxicological Profiles for EcologicalReceptors," of the "Technical SupportDocument for the Hazardous WasteIdentification Rule: Risk Assessment forHuman and Ecological Receptors." TheAgency seeks comment on the overalldevelopment of each of the ecologicalbenchmarks generated for this proposedrule.

For populations of birds andmammals, the overall approach used toestablish toxicological benchmarks wassimilar to the methods used to establishRfDs for humans as described in IRIS.Each method uses a hierarchy for theselection of toxicity data (e.g., no effects

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levels are generally preferred to lowesteffects levels) and extrapolates from atoxicity benchmark for the test speciesto a toxicity benchmark for the desiredspecies. However, the procedures usedto develop benchmarks (i.e., RfDs) forthe protection for human healthestablish an acceptable daily dose for allindividuals (including sensitive sub-populations) while the development ofecological benchmarks for this analysisestablish a level that will sustain thereproductive fitness in a localpopulation. Consequently, benchmarksfor birds and mammals were establishedusing three key guidelines. First,because the reproducing population wasselected as the assessment endpoint, thebenchmarks were developed frommeasures of reproductive success or, ifunavailable, other effects that couldconceivably impair the maintenance ofthe population.

Second, the taxon of the test specieswas matched to the taxon of the wildlifespecies to the greatest extent possible.The evolutionary processes that resultin obvious differences in taxa (e.g.,morphology) also result in differences inthe physiological processes that governchemical response. Moreover,taxonomic similarities are generallyassociated with similarities in feedinghabits, physiology, and chemicalsensitivity at the family classificationand, to a lesser extent, the orderclassification. For example, herbivoresare generally more resistant to toxicantsthan predators because they are exposedto plant toxins, and the enzymaticsystem that detoxifies plant toxins alsodetoxifies pesticides and other organicchemicals.

Third, a default safety factor of 10 wasadopted only for extrapolating from anlowest-observed-effects level (LOEL) toa no-effects level (NOEL). A ten-foldsafety factor was not applied to sub-chronic studies since reproductive anddevelopmental toxicity studies arefrequently short-term. Even amongtarget organ toxicity studies, there aremany instances where sub-chronicstudies are actually more sensitive thanchronic studies carried out on the samesubstance. Also, for mammals and birds,differences in interspecies uncertaintywere indirectly addressed through theuse of the species-scaling equationdescribed in Section 4 of the "TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors." The Agency requestscomment on the use a safety factor of 10when extrapolating from a LOEL to aNOEL. The Agency also requestscomment on the use of a scalingapproach to address interspecies

uncertainty as described above.Furthermore, the Agency seekscomment on the inability of the RiskAssessment to evaluate the inhalationand dermal routes of exposure for birdsand mammals.

For the terrestrial plants, the approachused to establish toxicologicalbenchmarks was adapted from theEffects Range Low (ER-L) approachdeveloped by the NationalOceanographic and AtmosphericAdministration (NOAA). The NOAAER-L approach estimates a percentile ofthe distribution of various toxic effectsthresholds. The measurement endpointswere generally limited to growth andyield parameters because (1) they arethe most common class of responsereported in phytotoxicity studies and,therefore, will allow for benchmarkcalculations for a large number ofconstituents, and (2) they areecologically significant responses bothin terms of plant populations and, byextension, the ability of producers tosupport higher trophic levels. It shouldbe noted, that these benchmarks werelimited to soil concentrations and donot explicitly consider the adverseimpacts on plants from ambientcontaminant concentrations in the air.Further details can be found in section4.3.3 of the "Technical SupportDocument for the Hazardous WasteIdentification Rule: Risk Assessment forHuman and Ecological Receptors." TheAgency solicits comment on the overallapproach taken to develop benchmarksfor the terrestrial plant community. .

For the soil fauna, the toxicologicalbenchmarks were established based onmethods developed by the Dutch 'National Institute of Public Health andEnvironmental Protection (RIVM). TheRIVM approach estimates a confidenceinterval containing the concentration atwhich the no observed effectsconcentration (NOEC) for p percent(95th percentile was selected) of thespecies within the community is notexceeded 50% of the time. A minimumdata set was established in which keystructural and functional components ofthe soil community (e.g., decomposerand grazing organisms) encompassingdifferent sizes of organisms (i.e.,microfauna, mesofauna, macrofauna)were represented. As with the AmbientWater Quality Criteria, measurementendpoints included reproductive effectsas well as measures of growth, survival,mortality. The Agency requestscomment on the use of the RIVMmethodology, and protecting 95 percentof the community 50 percent of thetime. The Agency also requestscomment on its inability to fullyquantify the effect of soil characteristics

on toxicity of constituents to soilorganisms.

For populations of fish and aquaticinvertebrates (represented by daphnids),a hierarchical approach was taken foruse of data sources in derivingbenchmarks. The first choice was finalchronic values (FCVs) from theSediment Quality Criteria effort by theEPA Office of Water, followed by valuesfrom the Great Lakes Initiative (GLI)effort, and finally, the Ambient WaterQuality Criteria (AWQC). If thesebenchmarks were not available, then abenchmark was developed using AWQCprocedures or, if data were inadequate,the GLI Tier II procedures forestablishing chronic values (termedsecondary chronic values-SCVs). TheAWQC ranked third since many yearshave passed since their establishmentand the SQC and GLI efforts re-evaluated the toxicity data sets ofseveral of these. The Agency solicitscomment on the hierarchical approachdescribed above for deriving toxicitybenchmarks.

For aquatic plants, the approach usedto establish toxicological benchmarkswas adapted from the ER-L approachdeveloped by NOAA. The NOAA ER-Lapproach estimates a percentile of thedistribution of various toxic effectsthresholds. However, due to the generallack of toxicity data, the default ER-Lapproach was used wherein the lowestLOEC for either vascular plants or algaewas used. The Agency solicits commenton the overall approach taken todevelop benchmarks for aquatic plants.

For the sediment organisms, theapproach used to establish toxicologicalbenchmarks for non-ionic, hydrophobicorganic chemicals was based onsediment quality criteria methods fornon-ionic constituents. Two key.assumptions form the basis for theproposed sediment quality criteria.First, benthic species, defined as eitherepibenthic or infaunal species, have asimilar toxicological sensitivity as watercolumn species. As a result, FCVs (orSCVs) developed for the fish andaquatic invertebrates can be used for thebenthic community. Second, pore waterand sediment carbon are assumed to bein equilibrium and the concentrationsare related by a partition coefficient,Koc. This assumption, described asequilibrium partitioning (EqP), providesthe rationale for the equality of water-only and sediment-exposure-effectsconcentrations on a pore water basis:The sediment-pore water equilibriumsystem results in the same effects as awater-only exposure. The Agencyrequests comment on the use of thisapproach in support of today's proposal.In some cases, protecting these




ecological receptors represents thecritical pathway that limits theprojected exit level for management ofa waste stream outside of the Subtitle Chazardous waste program. Theseecological receptors serve as the basisfor the proposed exit levels for 18constituents, including 6 metals. To theextent that contaminants from thesewaste streams reach off site areas, theAgency based its proposal on modelingthe ecological receptors on aneighboring land area of 500 acres or anadjacent stream (with a total length of12 miles). This approach as currentlymodeled, may only serve as an indicatorof a potential nearby threat to ecologicalreceptors (e.g., the soil fauna and plantlife), rather than serving as a measure orindicator of a broader threat to theenvironment. The Agency solicitscomment on the appropriateness andrelevance of these receptors as the basisfor exit levels under the HWIR program

3. Sources of Data

a. Human

The two primary sources used toidentify human health benchmarks werethe Integrated Risk Information System(IRIS) and the Health Effects AssessmentSummary Tables (HEAST). Both of thesesources were developed and aremaintained by the USEPA. For a fewconstituents, other Agency sources suchas Carcinogen Assessment Group (CAG)profiles, Health Effect Assessments(HEAs), and Health AssessmentDocuments (HADs) were used to filldata gaps.

IRIS is the Agency's official repositoryof Agency-wide consensus chronichuman health risk information. IRISevaluation are conducted by theAgency's Work Group review processthat leads to internal Agency scientificconsensus regarding risk assessmentinformation on a chemical. Thisinformation is recorded on IRIS and isconsidered to be "Work GroupVerified."

The HEAST is prepared by EPA'sOffice of Research and Development.They contain risk assessmentinformation on chemicals that haveundergone a more limited review andhave the concurrence of individualAgency program offices; each issupported by an Agency reference. Theinformation has not, however, hadenough review to be recognized asAgency-wide consensus information.

b. Ecological

A thorough literature review wasconducted to identify toxicological datafrom laboratory and field studies foreach of the constituents of ecological

concern. The review includedsecondary sources such as the SynopticReview Series published by the U.S.Fish and Wildlife Service, the AmbientWater Quality Criteria documents, andother Federal compendia of toxicity data(e.g. HEAs, the Derivation of ProposedHuman Health and WildlifeBioaccumulation Factors for the GreatLakes Initiative, Agency for ToxicSubstances and Disease Registrydocuments, PHYTOTOX, GRIN,TERRETOX, and AQUIRE). Toxicitydata on soil organisms were obtained forseveral constituents from van de Meentet al. (1990). In addition to AQUIRE, theother primary data source for toxicitydata on aquatic plants were theToxicological Benchmarks for ScreeningPotential Contaminants of Concern forEffects on Aquatic Biota:1994 Revision(Suter and Mabrey, 1994). On-lineliterature searches were conducted toidentify primary sources of toxicity dataon constituents lacking sufficient datain the secondary sources. Additionalstudies were identified in conventionalliterature reviews.

E. Risk Assessment

1. The Non-groundwater RiskAssessment

a. IntroductionThe risk assessment underlying

today's proposed rule is based upon acomprehensive approach to evaluatingthe movement of many different wasteconstituents from their wastemanagement units, through differentroutes of exposure or pathways, to thepoints where human and ecologicalreceptors are potentially exposed tothese constituents. This risk assessmentis being used in today's proposed ruleto determine which listed hazardouswastes can be defined as "low-risk"wastes, able to exit the Subtitle C systemand be managed in non-Subtitle C units.The previous approach taken in the May20, 1992, proposed HWIR rule alsoaddressed the risks associated with themanagement of wastes containinghazardous constituents with verydiverse physical and chemicalproperties; however, only groundwateringestion exposures from landfill unitswere evaluated. That approach led to aconcern by the Agency, as well ascommenters on the proposed rule, thatleachate from landfills contaminatinggroundwater and subsequentconsumption of the contaminatedgroundwater by humans may not be theonly exposure pathway important toevaluate. Although the ingestion ofcontaminated groundwater pathwaymay be appropriate to propose exitlevels for some wastes and constituents,

it may be under-protective for others,depending on the physical and chemicalproperties of each waste constituent.(For example, some constituents have ahigh potential to bioaccumulate orbioconcentrate in living organisms.Pathways in which these constituentscome in contact with fish, grazinglivestock, wildlife, or edible plantswould be important to evaluate.) Inaddition, over the past 14 years ofimplementing the RCRA program, theAgency has learned more aboutpotential routes of release to theenvironment from various managementpractices.

Therefore, for today's proposal theAgency undertook an extensive riskassessment that examines numerousexposure pathways, rather than just thegroundwater ingestion pathway. Inselecting the exposure pathways,previous rulemakings were used as aguide, as well as other special studies bythe Agency that implement analysesexamining numerous pathways. (TablesA-1 and A-2 contain the human andecological pathways, respectively,evaluated in the assessment, and arepresented in appendix A to today'spreamble.) With regard to wastemanagement units considered in theassessment, it is important to note thatbecause today's proposal establishescriteria for waste to exit the Subtitle Csystem, the assessment evaluatedexposures associated with managingwastes in non-Subtitle C units. Thehuman and ecological receptorsconsidered in the assessment wereselected to represent a range ofbehaviors, activities, dietary habits, andtrophic levels that influence exposurelevels.

The risk assessment supporting thisproposal is currently undergoing reviewby the Science Advisory Board andEPA's Office of Research andDevelopment. As a result of thesereviews, and of comments receivedduring the public comment period, it islikely that EPA would make changes tothe risk assessment or other parts of therule. Topics on which the Agency hasreceived informal comment include theuse of ecological benchmarks forregulation and the overland transport ofwaste constituents. The Agency, to theextent consistent with the schedulenegotiated in the consent decree for thisrulemaking, would publish asupplemental notice proposing anysignificant changes before finalizing therule.

b. How the Assessment is StructuredThe non-groundwater assessment

acknowledges that not all human andecological pathways arise from each

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source; for example, movement ofparticles from an active surfaceimpoundment is not expected to occur.To account for this, the assessmentmatched the environmental transportpathways with both the releases fromvarious types of waste managementunits and the various receptors for thenearly 200 constituents examined. Allconstituents were assessed in allpathways deemed plausible for a givenwaste management unit, if the datapermitted. Tables A-3, A-4, and A-5 ofappendix A show the pathways assessedfor each waste management unit, humanreceptors assessed for each pathway,and ecological receptors assessed foreach pathway, respectively. Theassessment estimated the constituent-specific concentrations in a waste at themanagement unit that could be expectedto result in an acceptable exposure fora human or ecological receptor(determined through using the toxicitybenchmarks discussed in section V.B.),taking into account the variouspathways by which the constituent maymove through the environment from thewaste management unit to the receptor.

The waste management unitsconsidered in the assessment are not all-inclusive but were selected to reflectthose that might be commonlyassociated with the management ofexited hazardous wastes (fromwastewaters to nonwastewaters) in non-Subtitle C waste management units.These units were identified ascommonly used in the management ofsolid wastes in the 1988 Report toCongress entitled Solid Waste Disposalin the United States Report. The Agencybelieves that risks posed by other typesof management of these exited wastes-will be no greater than those from theunits assessed.

There is a high degree of variability inthe physical and chemical properties ofthe approximately 200 constituentsevaluated. An understanding of thoseproperties and how they interact withthe physical and chemical propertiesthat control persistence and mobility inthe environment is an essential elementof the assessment. The managementunits could potentially be located in therange of environments that exist acrossthe United States. These environmentshave differing characteristics (e.g.,meteorological conditions, soil type)that are more conducive for themovement of certain constituents incertain pathways than others. Forexample, an environment with a highprecipitation and high organic soilcontent may result in significantexposures to fishers by constituents thatreadily adsorb to soils (i.e., have a highlog Ko,) through erosion of

contaminated soil and uptake in thefood chain. For other pathways,however, an environment with thesecharacteristics may result in relativelylow exposures. The assessment wasdesigned to determine what conditionswould need to exist to cause higherexposures for each pathway rather thandeveloping a scenario and determiningall the types of exposures and receptorsfor that scenario. By determining theappropriate conditions for which higherexposures from a given pathway willoccur, the Agency believes thatenvironments where the conditions arenot as likely for a constituent to movethrough a pathway are protected.

The assessment was structured usinga deterministic approach. Adeterministic approach uses a single,point estimate of the value of each inputor parameter and calculates a singleresult based on those point estimates.The assessment used the best dataavailable to select typical (i.e.,approximately 50th percentile) andhigh-end (i.e., approximately 90thpercentile) values for each parameter orparameter group as discussed in SectionE.2. below. Sometimes full distributionswere available but, more commonly,ranges of values or point values wereavailable with no description ofdistributions or variability. If there wasnot a sufficient distribution for theparameter, best professional judgementwas used in determining typical andhigh-end values (which sometimeswould be the maximum).

The assessment is constructed as a setof calculations that begin with anacceptable exposure level for aconstituent at a-receptor, and back-calculates to a concentration in a wastein a management unit that correspondsto the acceptable exposure level. For thehuman receptors, the assessment wasdesigned to determine constituentconcentrations in waste for each wastemanagement unit that wouldcorrespond to protecting receptors at thehigh-end of exposure (i.e., above the90th percentile of each of the receptorpopulations and types of exposuresbeing assessed). The Agency estimatedwaste concentrations corresponding tothe high-end exposure by identifyingfour critical or sensitive parameters inthe source/pathway/receptor equationsand using high-end input values forthose parameters and using centraltendency values for the remainingparameters. The Agency also estimatedcentral tendency (approximately the50th percentile) and bounding estimates(worst-case) of constituentconcentrations in waste for each of thereceptor populations and types ofexposures being assessed. For ecological

receptors, the approximate percentilelevel of protection is difficult to discern.The Agency believes the ecologicalanalysis is conservative with respect tothe overall assessment endpoint (e.g.,sustainability of the reproducingpopulations) because of the way thesource, fate and transport parameters areset, the dietary habits assumed, and howthe toxicity benchmarks are developed.However, the degree to which thisconservativeness transfers to ecosystemsis not known.

The steps of the assessment whichprovide estimates of acceptableconstituent-specific concentrations inwaste include the following:

Step 1-Specify acceptable risk levelsfor each constituent and each receptor.See Section V.B. in today's preamble fora discussion of how benchmarks are setfor both human and ecologicalreceptors.

Step 2-Specify the exposuremedium. Using the toxicity benchmarksas a starting point and the exposureequations, the assessment back-calculates the concentration ofcontaminant in the medium (e.g., beef,milk, plant, air, water, soil) thatcorresponds to the "acceptable"exposure level. The exposure equationsinclude a quantitative description ofhow a receptor comes into contact with.the contaminant and how much thereceptor takes in through specificmechanisms (e.g., ingestion, inhalation,dermal adsorption) over some specifiedperiod of time. Thus, for the subsistencefarmer eating contaminated beef, theexposure specifies the amount of.beefeaten on a daily basis, the period of timeover which the contaminated beef iseaten, and descriptions for theindividual such as body weight andlifetime. For this example, theconcentration in the beef is what isback-calculated.

Step 3-Calculate the point of releaseconcentration from the exposure 'concentration. Based on the back-calculated concentration in theexposure medium (from Step 2), theconcentration in the medium to whichthe contaminant is released to theenvironment (i.e., air, soil, groundwater)for each pathway/receptor was modeled.The end result of this calculation is amedium concentration at the point ofrelease from the waste managementunit.

Step 4-Calculate the concentrationin the waste that corresponds to themedium concentration at the point ofrelease. This step depends on thecharacteristics (e.g., area, coverpractices, waste consistency) of thewaste management unit.




The output of the assessment is arange of constituent concentrations,reflecting the range of pathway-receptorcombinations considered for each wastemanagement unit. The lowestconcentration (per constituent) of thisrange represents the highest exposurepathway-receptor combination for thatwaste management unit.

c. How Uncertainty is Addressed

Any analysis of the magnitude used inthis rule-making will have uncertaintyassociated with the outputs generated.The uncertainty can be associated withthe models or equations used and thedata relied on for the model parameters.In addition, policy assumptions, such aswaste management units assessed andreceptors assessed, may also affect thedegree of representativeness of theassessment. In order to be consistentwith Agency policy on thecharacterization of risk, stochastic anddeterministic approaches wereconsidered. A stochastic approach, suchas Monte Carlo analysis, whichproduces a distribution of constituentconcentrations, was initially considereddue to the tremendous interest in, anduse of, these techniques in riskassessment. However, after evaluation ofthe models and data available for use,the Agency decided to use adeterministic approach for the non-groundwater assessment.

The Agency's deterministic approachused for this assessment, like most suchapproaches, uses point values in allcalculations and produced pointestimates of constituent concentrationsfor waste in each management unit-exposure pathway-receptorcombination. However, in selecting anddeveloping point values for parameters,EPA considered all available data.Wherever possible, the Agencydeveloped both a central-tendency andhigh-end value for each parameter usedin the assessment. This was not possiblein all cases because some parameterswere a property, such as density ofwater, and because some values werefixed by Agency-wide policy decisions.(For example, EPA used standardAgency-wide human toxicitybenchmarks and body weights.) EPAthen calculated constituentconcentrations based on a mixture ofcentral-tendency and high-end values.

EPA believes that the deterministicapproach described above (based onidentifying critical parameters and usinghigher-end values only for thoseparameters and central-tendency valuesfor the other parameters) allowed it toderive constituent concentrations inwaste for each waste management unitthat are reasonably protective across a

range.of conditions and for a range ofreceptors. EPA also believes that thisapproach is consistent with EPA's riskassessment policy.

EPA further believes that theapproach chosen allows both theAgency and the public to determinemore easily which parameters playedthe most critical roles in determiningthe constituent concentrations in wastefor each waste management unit. Thisfurthers general understanding of theassessment and helps commenterseffectively target their resources forreviewing what EPA is proposing. It hasalso helped EPA target its own datacollection and input selection efforts. Itis often more difficult to identify criticalparameters in a stochastic assessmentbecause of the greater number ofiterations and because results arereported as probability distributions.This is particularly true for an analysiswith a large number of parameters suchas the assessment used for this proposedrule.

EPA notes that stochastic approachesare also consistent with Agency riskassessment policy. In fact, EPA applieda stochastic "Monte Carlo" approach tothe separate analysis of dilution andattenuation of groundwater performedfor this proposal. That analysis,however, has been under developmentfor many years and EPA is more familiarwith the underlying data and therelationships between variousparameters. In addition, the public hashad a chance to comment on aspects ofthat analysis in previous rule-makings.EPA w&. more comfortable applying astochastic analysis for the groundwateranalysis than a stochastic approach tothe non-groundwater analysis.

EPA believes that it is not necessaryto resolve all issues relating to therelative merits of the two approaches orto .determine which approach would beideal for each of the assessmentsdescribed above. Rather, the debateshould focus on whether the approacheschosen allowed EPA to reach reasonableregulatory decisions.

The Agency solicits comment on theuse of a deterministic approach asdescribed above. Specifically, theAgency seeks comment on whether theapproach proposed is a reasonableapproach for setting protective levelsacross a set of types of managementunits and exposure pathways.

d. Linkage of the Non-groundwater RiskAssessment to the Groundwater RiskAssessment

In the non-groundwater riskassessment, the pathways involvingpotentially contaminated groundwater(e.g., bathing) are back-calculated from

the receptor to the wellhead (i.e., theassessment provides constituentconcentrations in the groundwater at thewell). In order to determine theconcentration of a constituent inleachate coming from a wastemanagement unit that would result inthe estimated constituent concentrationat the water well, the Agency used aseparate groundwater fate and transportrisk analysis. That analysis is describedin detail in Section D.8. elsewhere intoday's proposal. The wellconcentrations estimated from thepathways involving bathing are used asinput to the groundwater fate andtransport modeling from which aleachate concentration is determined.

e. Risk Targets UsedAs previously discussed in Section

V.B. of today's proposed rule, theAgency used existing toxicitybenchmarks when available. However,many ecological benchmarks weredeveloped for this rule-making, asdiscussed in Section V.B. of today'sproposed rule. As described in thatsection, the Agency used a cancer risktarget of 1 x 10-6, and a hazard quotientequal to 1 for non-carcinogens. Forecological benchmarks, a hazardquotient equal to 1 was used. TheAgency solicits comment on the risktargets being used for today's proposedrule.

2. Detailed Overview of the Non-groundwater Risk Analysis

The assessment can be broken downinto six components: Constituents;toxicity benchmarks; receptors;exposure; fate and transport; and wastemanagement units. Each of thesecomponents is discussed in turn below,except the constituents and toxicitybenchmarks which were discussedearlier in section V.A and V.B. It isimportant to recognize that theassessment was not able to evaluate allconstituents in all receptor-pathway-waste management unit combinationsbecause of data gaps in either toxicity orchemical properties, or inadequatemethodologies. Many of these gaps havebeen identified in different sections ofthe Technical Support Document for theHazardous Waste Identification Rule:Risk Assessment for Human andEcological Receptors" (denoted"Uncertainties and Issues of Concern").The Agency requests additional data orother information that would assist infilling these gaps.

a. Waste Management Units

The manner'in which constituents arereleased to environmental media andthe relative quantity released to each

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66358 Federal Register'-/ Vol. 60, No. 245 / Thursday, December 21, 1995 / Proposed Rules,

medium will affect the pathways ofmost concern for a particularconstituent. The pathway presenting thehighest risk to human or ecologicalreceptors is not always easilydetermined because of the complexinteractions of the waste managementunit and its types of releases, thephysical and chemical propertts of theconstituent, and the properties thatcontrol mobility and persistence in aparticular environmental medium. Forsome constituents, the managementpractice will determine which exposurepathway is of most concern. Forexample, benzene tends to migrate toboth air and groundwater. Uponexamining the risks from exposure tothese two media arising from releasesfrom a quiescent surface impoundment,the groundwater ingestion pathway maypose the highest risks. But, whenexamining the risks from these twomedia for releases from an aerated tank,the air inhalation pathway may pose thehigher risks. Further, the air inhalationrisks may even be higher thangroundwater ingestion risks from thequiescent surface impoundment.

Therefore, and as stated earlier, theselection of non-Subtitle C wastemanagement units examined in theassessment attempted to reflect both theinfluence of the type of unit onpathways and those that might becommonly associated with themanagement of exited hazardous wastesin non-Subtitle C waste managementunits. Again, the Agency believes thatrisks posed by other types ofmanagement of these exited wastes willbe no greater than those from the unitsassessed. The management unitsexamined include the following:

* Aerated treatment tanks. Relative toall other types of management, aeratedtanks containing wastewaters canpotentially have the most significantreleases of volatile organics to air.

9 Quiescent surface impoundments.This type of unit containingwastewaters also can potentially resultin significant releases of volatile organicconstituents to air. These units alsohave a potential to affect surface waterbodies if the unit is not well maintainedor constructed. The sludges generated,which may contain high concentrationsof metals and hydrophobic constituents,may impact groundwater. (As discussedabove, the groundwater fate andtransport analysis was conducted in aseparate analysis.)

* Land application. This type of unit,when used for non-wastewaters canpotentially have significant releases ofcertain constituents to nehrby land andsurface water bodies through erosionand runoff, particularly if run-on and

run-off control measures are notpracticed. In addition, significantreleases of volatile organics constituentsto air are possible. Further, after the unitis closed, significant on-site exposuresto some persistent and relativelyimmobile constituents may occur aswell as continued long-term releases tothe nearby land and surface waterbodies. The Agency believes such unitswill pose higher exposures relative tolandfills in all pathways except thosearising from groundwater. Therefore, thenon-groundwater assessment did notexamine landfills, but they wereexamined in the groundwater fate andtransport analysis.

& Ash monofill. This type of unitused for ash disposal can potentiallyhave significant releases of particulatesto air which may be inhaled or maydeposit on land and plants, and resultin exposure through food and soilingestion.

e Wastepiles. This type of unit usedfor nonwastewaters can have significantreleases of particulates to air as well assignificant releases of particulatesthrough erosion and runoff.

Each of the pathways that evaluates areceptor using contaminatedgroundwater other than as a source ofdrinking water (i.e., bathing) are back-calculated to a concentration in adrinking water well. The pathways areapplicable to all of the wastemanagement units modeled (excepttanks). All of the waste managementunit and chemical-specific portions ofthe groundwater fate and transportanalysis and subsequent estimatedleachate concentrations are contained inthe Agency's separate groundwater fateand transport analysis (see Section E.3below);

One exception to the above discussionof the types of waste management unitsevaluated involves the combustion ofwastes. Although the Agency attemptedto include this type of management inthe assessment, it became clear that theemissions from combustion are noteasily predicted from the waste inputsto the units. The combustion processboth destroys and creates constituents.Although destruction of constituentscan be predicted based on certainoperating characteristics of combustionunits, the creation of other constituents,referred to as products of incompletecombustion (PICs), is not easy topredict. It may be possible to make suchpredictions for a specific waste and aspecific combustion unit; however, theextensive data (e.g., on the variety ofcombustion units, waste types,constituent combinations) needed forthe assessment used in this rulemakingrelating wastes with emissions are not

available. Therefore, acceptableconstituent levels in waste going to acombustion unit could not be'established. However, the Agency isdeveloping emission standards forvarious types of combustion units andthose emission standards may be a moreappropriate vehicle for addressingcombustion.

In addition, the assessment does notaddress accidental or catastrophicreleases, such as transportationaccidents or tank failures. The Agencydetermined that, although such releasesare possible, they are of low probabilityand non-routine and, therefore, are notappropriate for developing exit criteriathat apply to all wastes.

The Agency has identified severalspecific areas giving rise to uncertaintyin the characterization of the wastemanagement units and for which theAgency seeks comment:

(1) Use of Subtitle D Survey.9 The Agency relied upon data from

a 1987 survey of Subtitle D facilities tocharacterize waste management units.That survey, used in the 1988 Report toCongress on Solid Waste Disposal in theUnited States, was designed primarily tocollect estimates of the followingparameters:

9 Number of establishments thatmanage Subtitle D wastes on site;

e Number of establishments thatmanage Subtitle D wastes on site in landapplication units, wastepiles, surfaceimpoundments, or landfills;

* Number of land application units,wastepiles, surface impoundments, orlandfills used to manage Subtitle Dwastes;

* Amount of Subtitle D wastesmanaged on site in land applicationunits, wastepiles, surfaceimpoundments, or landfills.

In addition to these parameters, datawere also collected for some otherparameters, such as the area of the wastemanagement units. Although the surveywas not designed to collect accurateestimates for these other parameters, itis the most comprehensive dateavailable to characterize these otherparameters. One difficulty encounteredin using these data is that the surveyrequested information on total area orwaste quantity for all of each type ofunits at a facility. The total area or wastequantity was divided by the number ofeach type of unit at the facility (numberof each unit being one of the primaryparameters the survey was designed toestimate) to estimate average unit area.Further, it is not certain how well theon-site units (which are used routinelyfor wastes generated on-site) reflect thecharacteristics of off-site units.Uncertainty related to the




representativeness of the data isimportant because exited wastes couldbe managed in units off-site as well ason-site. The Agency seeks comment onthe use of the Subtitle D survey tocharacterize the waste managementunits.

In evaluating the waste managementunit components of the risk assessment,the Agency made certain assumptionswhen data were not available or wereincomplete. A description of the wastemanagement unit parameters for whichthere was little to no data is describedbelow. The rationale behind theseassumptions is presented (e.g., results ofany sensitivity analyses, references toother work, etc.). The Agency requestscomment on the specific issues raisedfor each management unit.

(2) Fate and Transport

Fate processes, particularlybiodegradation and hydrolysis, wereaccounted for only in the landapplication unit since that unit hadwastes applied intermittently and thatunit was being examined for on-siterisks after closure (assuming humanoccupation of the site begins 10 yearsafter closure occurs). Because waste iscontinuously applied to the other wastemanagement units, biodegradation andhydrolysis were presumed to haveminimal influence on the subsequentavailability of constituents to the aboveground pathways. The Agency requestscomment on not consideringbiodegradation and hydrolysis in wastemanagement units other than the landapplication unit. The Agency alsorequests comment on theappropriateness of the data and methodsused to account for the fate andtransport of constituents in wastemanagement units, with particularemphasis on data and methods ofdetermining biodegradation andhydrolysis of constituents in landapplication units.

(3) Ash Monofill

(i) Particle Size Distribution-for AirDispersion Modeling

A size distribution of ash particlesthat become airborne from an ashmonofill was not available. Therefore, asensitivity analysis was performed toassess the importance of the particlesize distribution in the calculation of airconcentrations and deposition rates.Different distributions were modeledreflecting a variety of assumptions forparticle size distributions betweenPM10 and PM30 classes. The greatestdeviation among the modeledconditions in the estimated airconcentration of PM10 was 12 percent;

for the estimated deposition rate forPM30 the greatest deviation was 59percent. Given the uncertainties andvariabilities inherent in the assessment,these variations were considered minor,therefore, the Agency assumed an equaldisthbution of particle sizes betweenthe two size classes used in theassessment.

(ii) Monofill Characterization

Because limited data were available tocharacterize hazardous waste ashmonofills, data from municipal wasteash monofills were used. However,because ash generation rates formunicipal waste incinerators ere morethan 100 times greater than ashgeneration rates for hazardous wasteincinerators and reuse-as-fuelcombustors resulting in significantlylarger municipal monofills, EPAcalculated an ash monofill volume forthis analysis based on generation ratesreported in the 1988 National Survey ofHazardous Waste Treatment, Storage,Disposal, and Recycling Facilities,assumed bulk density of the ash, andassumed lifetime of the monofill. TheAgency is not certain that hazardouswaste monofills should be sized in thesame manner as municipal wastemonofills. The Agency also assumedthat each waste monofill would acceptash from only a single combustor.Accepting wastes from more than onecombustor may underestimate monofillsize.

(iii) Vehicle TrafficThe estimates of number of ash trucks

per day are dependent on the size oftruck. Limited data were available onthe sizes of trucks hauling ash. Thesedata were used to characterize a rangeof truck sizes. The truck sizes mayeither under- or overestimate the size oftrucks actually used at hazardous wasteash monofills depending on therepresentativeness of municipal wasteash truck sizes.

No data were available on othervehicular traffic; therefore, these valueswere estimated, introducing additionaluncertainty into the overall amount oftraffic at the ash monofill.

(iv) Emission Equations for Ash BlownFrom Trucks and During Spreading andCompacting

The emission equation used for ashblown from trucks was developed forwindblown emissions from storagepiles. This was adapted to trucks byusing the truck speed to estimatefrequency of wind greater than 5.4 m/s.Because this equation was not derivedfor windblown emissions from movingtrucks, the results of its application to

such emissions are uncertain. It mayover- or underestimate actual emissionsof p articulates blown from trucks.

Similarly, the emission equation usedfor spreading and compacting wasdeveloped for agricultural tilling.Agricultural tilling was thought toapproximate the process of spreadingand compacting; however, the use ofthis equation may under- oroverestimate emissions due to spreadingand compacting.

(4) Land Application Unit

(i) Particle Size Distribution for AirDispersion Modeling

A size distribution of soil particlesthat become airborne was not available.The same assumption was made for soilparticles as was done for ash particleswhen modelling the monofill (seeabove). As described above for ashparticles, the Agency assumed an equaldistribution of particle sizes betweenthe two size classes.

(ii) Area of Land Application UnitRelative to Agricultural Field

The assessment examined the impactof subsistence farming on the landapplication unit beginning 10 years afterclosure. Based on the distribution ofsizes for land application units andagricultural fields, the Agency selecteda combination of fields such that thecentral tendency land application unit(61,000 M2

) is smaller in area than thecentral tendency agricultural field(2,000,000 M

2). The significantly larger

size of the agricultural field sugeststhat the model may inappropriatelyaverage the constituent concentrationover the agricultural field. However, theAgency does not believe this to be asignificant impact on the analysisbecause: (1) The area of the agriculturalfield is not an explicit input to themodel; (2) the size of the landapplication unit is large enough tosupport a subsistelce farmer; and (3)this pathway is driven by theassumptions for the high-end analysis.The Agency requests comment on therelationship between the landapplication unit and the agriculturalfield.

(iii) Application Rate

The waste application rate is animportant parameter in determining theconstituent's soil concentration afterapplication. In practice, this rate is afunction of the characteristics of thewaste being applied, the characteristicsof the receiving soil, the environmentalconditions, and the purposes for whichthe waste is being applied. Informationfrom the Subtitle D survey was used tocalculate the rates, since those rates

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were not expressly requested in thesurvey. The rates were calculated fromthe area receiving the wastes and thewaste quantity applied. This introducesuncertainty for it combines ratesapplicable to both treatment of wastesand rates for specific uses (e.g., farming,mine reclamation). To account for thepotential of having application rates bemuch too high for the site they are beingapplied to, the data on receiving areaand waste quantity applied were linked.

(iv) Waste Characteristics

Limited data were available on thecharacteristics of wastes being landapplied. As a result, soil values for mostparameters (e.g., hydraulic conductivity,moisture retention index) were used tocharacterize nonwastewaters. It is notknown to what extent these soil valuesdiffer from the waste properties.

(v) Depth of Contamination

Depth of contamination affects theamount of constituent available forexposure. For the non-groundwaterpathways, only constituents at the soilsurface were assumed available for eachexposure pathway. The Agency selectedtilling depth as the depth ofcontamination available to the non-groundwater pathways as over time, thedepth of the waste layer would increaseand a portion of the mass of wastewould move out of the zone availablefor the surface pathways. The modelkept the depth of contaminated soilconstant that was available for thesurface Iathways. The Agencyrecognizes that the use of the tillingdepth may underestimate the depth ofcontamination in some cases andoverestimate it in others. Thus, theAgency requests comment on the use oftilling depth as a surrogate for depth ofcontamination.

(vi) Partitioning

Releases from the land applicationunit were partitioned amongvolatilization, evaporative losses,hydrolysis, erosion, runoff, andleaching. Periodic application of wastewas factored into the partitioning modelduring the active life of the unit.Biodegradation was factored in duringboth the active life and closed period.The finite source Jury model was usedto estimate volatilization emissions. TheJury model, which models theconvection of constituents caused by thEflux of water in soil, was used forevaporative losses. Runoff and leachinglosses were calculated using the soil-water partition coefficient (Kd) todetermine constituent concentration inthe soil water and multiplying that bythe land application unit area and

runoff rate for run-off losses or rechargerate for leaching losses. (See TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors, Section 7, Land Applicationfor full description.)

(5) Waste Pile

(i) Waste Pile Height

No data were available on thisparameter; therefore, the value is anestimate based on heights attainable bya front-end loader. This parameter isimportant in the air dispersionmodeling, which is sensitive to theheight of the pile. The Agency requestssuggestions for alternatives todetermining waste pile height and anydata which would support thosedeterminations.

(ii) Particle Size Distribution for AirDispersion Modeling

The same sensitivity analysis andassumptions discussed above for ashmonofills were used for waste piles.Given that the air dispersion analysis isnot very sensitive to particle sizedistribution, the simple assumptiondescribed above was believed to be anadequate approximation for theassessment.

(iii) Waste Characteristics

Limited data were available on thecharacteristics of wastes in waste piles.As a result, soil values for mostparameters (e.g., hydraulic conductivity,moisture retention index) were used tocharacterize the nonwastewatersdisposed in piles. It is not known towhat extent these soil values differ fromthe waste properties. The soil values,however, were not used for the ashwaste pile. The ash disposed in the pileshad the same properties as that disposedof in a monofill.

(iv) Vehicle Traffic

The estimates of number of trucks perday are dependent on the size of truckand waste quantity. Limited data wereavailable on truck sizes. These datawere used to characterize a range oftruck sizes. These truck sizes may eitherunder- or overestimate the size of trucksactually used around waste piles.

(v) Emission Equation for Ash Blownfrom Trucks

As described in the section above onash monofills, the emission equationused for ash blown from trucks wasdeveloped for windblown emissionsfrom waste piles. It may over- orunderestimate actual emissions ofparticulates blown from trucks.

(6) Surface Impoundment

(i) Two-Phase Sludge Formation Model

The two-phase sludge formationmodel simplifies the solidsconcentration gradient in a surfaceimpoundment into two distinct andhomogeneous layers, a liquid layer withthe same average solids content as theinflow and a sediment or sludge layerwith a much higher solidsconcentration.

(ii) Dilution of Waste During a SpillOverflows or breaches associated with

surface impoundments are a wasterelease examined in the assessment. Thealgorithm used for spills does notaccount for dilution of the wastewatercaused by excess run-on. Such run-on ispresumably relatively uncontaminated;thus the spill volume, consisting partlyof contaminated wastewater from theimpoundment and partly ofuncontaminated run-on would have alower concentration than thewastewater in the impoundment. Byusing the concentration in theimpoundment, the mass of contaminantreleased to surface water isoverestimated. This effect could beconsiderable for the central tendencyimpoundment, as the quantity of run-onis significant compared to the capacityof the central tendency impoundment.However, to determine the extent ofsuch dilution, the degree to which suchrun-on becomes mixed with thewastewater would need to be estimated.No model has been found to assist inthis estimation.

(7) Tank

(i) Unit characterization

Limited data were available onSubtitle D tanks. The assessment usedthe profiles (specifies design andoperating parameters) for uncoveredaerqted treatment tanks developed inthe Hazardous Waste TSDF-Background Information for ProposedRCRA Air Emission Standards (TSDF-BID, U.S. EPA, 1991)

(ii) Volatilization

The Agency used the well-mixed flowmodel. This model assumes that thecontents of the system are well mixedand that the equilibrium concentrationin the system is equal to the effluentconcentration. The equilibriumconcentration is the averageconcentration throughout the unit andthe driving force for volatile emissions.

(8) Combustors

For the reasons stated below, EPA didnot modelled a combustion unit in therisk analysis for this regulation. EPA,




however, asks for comments on that'decision.

In initial analyses (see MultipathwayAnalysis Background Documentavailable through the docket), EPAmodeled potential risks from severaltypes of combustion units, usingengineering judgment to make a bestestimate for destruction and removalefficiencies for non-hazardous wastecombustors. Early comments suggestedthat the assumptions might haveoverstated or understated the estimatedrisks by not reflecting actual practice inindustrial boilers or other likelycombustion facilities not regulated bySubtitle C. However, initial comparisonsindicated that the combustion riskestimates back-calculated to thecombustion unit were not often the mostsignificant risk and, therefore, wouldnot be the basis for the limiting exitcriteria.

EPA also recognized that there aremany issues related to organics that areproduced during the combustionprocess, but are not necessarilyoriginally in the waste. The amount andtype of these "products of incompletecombustion" are generally believed tobe dependent on a number of aspects ofthe design and operation of a facility,and not easily related to thecomposition of the wastes fed into thecombustion unit. For purposes of thisproposal, EPA decided that because ofthe high degree of uncertaintyassociated with developing wasteconcentrations from combustion units,it was not appropriate to use risks fromcombustion as a factor in deciding whatwastes remain under the hazardouswaste regulations. Rather, EPA believesthere are more appropriate ways toregulate enissions from combustionunits through various regulatoryauthorities, including regulation of arange of units under the Clean Air Act.

EPA, however, asks comment on theappropriateness of this approach. Inparticular, there may be someconstituents (e.g., certain metals that aredifficult to capture in pollution controlequipment) where a better correlationexists between waste input andpotential risk from combustor emissionsthan for organics that are in the wasteand also created as PICs during the,combustion process.

b. Fate and Transport(1) Pathways

In selecting environmental fate andtransport pathways to include in theassessment, EPA used as a guideprevious rulemakings and other specialstudies by the Agency.that examinenumerous pathways. For example, the

Agency has used similar risk assessmentmethodologies in several recent rulesincluding: Wastes from Wood SurfaceProtection, Final Rule (59 FR 458,January 4, 1994); Standards for Use orDisposal of Sewage Sludge, Final Rule(58 FR 32, February 19, 1993);Corrective Action Management Units,Final Rule (58 FR 29, February 16,1993); and rulemaking efforts on thePulp and Paper Industry (56 FR 21802,May 10, 1991 and 58 FR 66078,December 17, 1993).

The sewage sludge and pulp andpaper rulemakings in particularexamined both human and ecologicalrisk. Other rulemakings underdevelopment within the Office of SolidWaste also use non-groundwater riskassessment methodologies includingvarious hazardous waste listingdeterminations and the dioxin emissionrules for hazardous waste combustionunits. Most of these assessments rely onseveral Agency guidance documentsissued in recent years. In January 1990,the Agency issued an interim report,Methodology for Assessing Health RisksAssociated with Indirect Exposure toCombustor Emissions (EPA/600/6-90/003 and referred to as the IndirectExposure Document). This documentserved as the basis for furtherdevelopment of non-groundwaterpathway assessments by the Agency. InNovember 1993, the Agency issued anAddendum to the Indirect ExposureDocument that updated and revisedportions of the methodology presentedin the Indirect Exposure document. InApril 1994, OSW issued a draftimplementation guidance entitledImplementation Guidance forConducting Indirect Exposure Analysisat RCRA Combustion Units. In June1994, the Agency released a review draftof Estimating Exposure to Dioxin-LikeCompounds: Volumes I-III (EPA/600/6-88/005C), which presents an extensiveand expanded version of the Agency'sprevious multiple pathway exposureassessments. Finally on November 16,1994, the Agency issued Draft SoilScreening Guidance (59 FR 59225),which presents a multiple pathwayassessment using air, groundwater, andsoil pathways for soil screening levels atSuperfund sites. The risk assessmentpresented relies on the methodologiespresented in these Agency guidancedocuments to maintain consistency withprevious Agency efforts.

Based on these efforts by the Agencyin conducting non-groundwaterpathway assessments, comments byreviewers on previous draft versions ofthe risk assessment, and some screeninganalyses to identify pathways that areeither very similar or unimportant

compared to other pathways, theAgency selected the human andecological exposure pathways presentedin Table A-1 (human exposurepathways) of appendix A and Table A-2 (ecological exposure pathway) ofappendix A. These exposure pathwaysare described in greater detail in theTechnical Support Document for theHazardous Waste Identification Rule:Risk Assessment for Human andEcological Receptors.

Tables A-1 and A-2 presents fourcolumns: column 1 (exposure media),identifies the medium, such as air orsoil, to which the receptor is exposed;column 2 (route of exposure), identifiesthe route, such as inhalation oringestion, by which a receptor isexposed to the exposure medium;column 3 (type of fate and transport),classifies the pathway by the primarymode of fate and transport of thecontaminant to the exposure medium,including direct air, air deposition, airdiffusion, groundwater, overland, andsoil; and column 4 (exposure scenario),identifies the compartments in thepathway (e.g., source to air to humans),and describes the exposure scenario(e.g., inhalation of volatiles).

The fate and transport pathwaysexamined can be grouped into six typesof initial release and movement awayfrom a waste management unit, asfollows:

e, Direct air pathways-air emissionsof volatiles and respirable (PMo)particulates;

* Air deposition pathways-airemissions of particulates that deposit onsoil or plant surfaces;

e Air diffusion pathways-airemissions that, while in the vaporphase, diffuse directly into surfacewater or plants;

* Groundwater-groundwaterreleases (These are the pathways thatlink to the separate groundwater fateand transport analysis that then links tothe waste management units.);

* Overland pathways-overlandtransport (i.e., surface runoff and soilerosion) to surface water or transport bysoil erosion to off-site fields;

* Soil pathways-on-site soilexposures.

There are three types of pathways notincluded in the analysis. Pathwaysinvolving the use of contaminated water(groundwater and surface water) forirrigation were removed due tomodeling difficulties that could not beresolved, however early resultsindicated these are not the mostsignificant pathways for any of thewaste management units. Pathwaysinvolving the deposition ofcontaminated particles directly onto

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surface water bodies were not includedbecause previous efforts by the Agencyhave shown these pathways not to be assignificant when compared to particledeposition onto the watershed andsubsequent erosion to the surface waterbody. Pathways involving wetdeposition were not examined. An airmodel recently developed evaluates theimpact of wet deposition and was notavailable to use at the time of thisproposed rule. This new model also wasaddressing problems with the areacomponent of earlier models. When themodel is available, the Agency willdetermine whether its use will have animpact on the proposed exit criteria. Ifthe Agency determines that there will bean impact, it will provide anopportunity for public comment on useof the updated model.

As stated earlier, not all exposurepathways were evaluated for all wastemanagement units. Constituents may bereleased from each waste managementunit by a variety of mechanisms. Eachrelease mechanism may be associatedwith certain exposure pathways. Byexamining the release mechanismsassumed for each waste managementunit and identifying the exposurepathways associated with those releasemechanisms, the appropriate pathwaysto be -modeled for each wastemanagement unit were identified. Theexposure pathways modeled for eachwaste management unit are presented inTable A-5 of appendix A.

b. Equations

Since the objective of the assessmentwas to generate acceptable levels inwaste rather than determining risksposed by waste, the equations, whichare designed to calculate risks, had to beturned around or run in reverse. Theassessment began with a target risk (oracceptable risk to the receptor) that wasused to back-calculate what constituentconcentration in a waste would notexceed the target risk.

Wherever appropriate, the equationsused in the back-calculation were takenfrom Methodology for Assessing HealthRisks Associated with Indirect Exposureto Combustor Emissions (U.S. EPA,1990x; hereafter, the Indirect Exposuredocument, or IED) as modified by theNovember 10, 1993, draft of Addendum:Methodology for Assessing Health RisksAssociated with Indirect Exposure toCombustor Emissions, Working GroupRecommendations (U.S. EPA, 1993x;hereafter, the Addendum). TheAddendum is currently being revisedbased on comments from the ScienceAdvisory Board and is being combinedwith the lED to generate a singlemethodology guidance document.

Therefore, the equations may changeafter that revision is completed. If thisoccurs, the assessment used for thisrule-making will be revised. If such arevision is needed and occurs, theAgency will provide an opportunity forpublic comment on those changes. Forconvenience, the methodologypresented in the lED as modified by theAddendum will be referred to as theIndirect Exposure Methodology, or IEM.

The equations presented in the IEMwere modified to estimate the soilconcentration for constituents erodingto an off-site field. The IEM did notaddress this pathway because it wasdeveloped for stack emissions fromcombustors rather than releases fromland-based units. However, because soilerosion is a critical release pathway forthis analysis, the Agency applied theUniversal Soil Loss Equation (USLE)and other equations presented in theIEM to calculate soil erosion to the off-site field. However, the application ofthese equations resulted inconcentrations greater at the receptorthan in the waste management unit.This phenomenon, first noted in theDioxin reassessment, occurred becausethe equations assumed that the amountof uncontaminated soil that was erodedinto the field was negligible incomparison to the total mass of soil inthe field. Therefore, the Agencymodified these equations to reflecterosion of uncontaminated soil togetherwith the constituents.

Certain modifications to the equationsused in the assessment were made fordioxin-like compounds to reflect thedifferent behavior of these constituentsin the environment. Thesemodifications were based on EstimatingExposure to Dioxin-like Compounds,Volume III: Site-Specific AssessmentProcedures (U.S. EPA, 1994x), hereafterreferred to as the Dioxin document. TheDioxin document defines dioxin-likecompounds as " * * compounds withnonzero Toxicity Equivalency Factor(TEF) values as defined in the 1989International scheme * * * [which]assigns nonzero values to all chlorinateddibenzodioxins (CDDs) and chlorinateddibenzofurans (CDFs) with chlorinessubstituted in the 2,3,7,8 positions.Additionally, the analogous brominatedcompounds (BDDs and BDFs) andcertain polychlorinated biphenyls(PCBs) have recently been identified ashaving dioxin-like toxicity * * * andthus are also included in the definitionof dioxin-like compounds.,,

Although the modifications presentedin the Dioxin document may beapplicable to other highly lipophiliccompounds, in keeping with thisdefinition, the modifications for dioxin-

like compounds were made only for2,3,7,8-TCDDioxin Toxicity Equivalents(TEQs), and PCBs. Other dioxincongeners are addressed through the2,3,7,8-TCDDioxin TEQ. The Agencysolicits comment on not using thesemodifications for other highly lipophiliccompounds.

(3) Specific Issues on Pathways andEquations

Below are specific issues of the riskassessment related to the modeling ofthe fate and transport pathways onwhich the Agency is requestingcomment on their use, improvements tothem, or alternative ways to modelthem. A detailed discussion of theseaspects is in Section 6, Fate andTransport Modeling, of the TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors. (Air emission and dispersionmodeling is discussed in Section 7,Waste Management Units, in thetechnical support document. To beconsistent, issues related to thatmodeling were presented earlier in thispreamble in Section D.2.a.)

(i) Hydrolysis

The Agency accounted for fateprocesses (e.g., biodegradation,hydrolysis) and transport processes(e.g., volatilization) for constituentsthroughout their movement from thepoint at which the constituent leavesthe waste management unit until itreaches the location at which contactwith the receptor occurs. During aninitial screen, the Agency identified fourconstituents that were known tohydrolyze completely or rapidly. Theseconstituents were not included in thedetailed assessment and include:Benzotrichloride (98-07-7); maleicanhydride (108-31-6); phthalicanhydride (85-44-9); and 1,2-diphenylhydrazine (122-66-7). Inaddition, 16 inorganic salts known todissociate completely were also notassessed. These included: Calciumcyanide (592-01-8); copper cyanide(544-92-3); potassium cyanide (151-50-8); potassium silver cyanide (506-61-6); silver cyanide (506-64-9);sodium cyanide (143-33-9); thallium (I)carbonate (6533-73-9); thallium (1)chloride (7791-12-0); thallium (I)nitrate (10102-45-1); thallium (I) sulfate(7446-18-6); zinc cyanide (557-21-1);zinc phosphide (1314-84-7); cyanogenbromide (506-68-3); cyanogen chloride(506-77-4); hydrogen cyanide (74-90-8); and thallium acetate (563-68-8). TheAgency solicits comment on notassessing these constituents.




Of the 192 constituents evaluated inthe non-groundwater analysis, theAgency directly accounted for chemicalhydrolysis for 18 constituents. For theremaining constituents, hydrolysis wasnot considered for the followingreasons: The constituent has nohydrolyzable chemical group;hydrolysis is not expected to beimportant or significant; the degradationhalf-life of the chemical, which includeshydrolysis, is greater than one year; or,there was no data available for theconstituent.

The extent to which fate and transportprocesses play a role in the removal ofa constituent from a pathway, or itsmovement from one environmentalcompartment to another is determinedby site-specific environmentalconditions as well as chemical-specificparameters. To simplify the analysis, theAgency used fate and transport databased on one set of environmentalconditions to represent all possiblespatial and temporal environmentsencountered in any given exposurepathway. The Agency solicits commentson this simplification for modeling fateand transport processes throughout theexposure pathways considered in theMPA.

(ii) Other Fate and Transport Processes

Fate and transport processes otherthan hydrolysis may be important indetermining the concentration of aconstituent reaching a receptor. TheAgency's approach to incorporateconsideration for these other processesinvolved the use of biodegradation andvolatilization rates into the fate andtransport pathways, when applicable.The Agency recognizes that the rate formany chemical-specific fate andtransport processes (in particular,biodegradation) varies withcharacteristics of the environment (e.g.,temperature, soil type). However, theAgency simplified the non-groundwateranalysis by applying chemical-specificfate and transport rates generically.across environmental settings found inthe various exposure pathways. Thissimplification may overestimate the exitlevel in some instances andunderestimate the exit level in otherinstances. The Agency solicitscoinments on this simplification formodeling fate and transport processesthroughout the exposure pathwaysconsidered in the non-groundwateranalysis.

(iii) BioavailabilityWith regard to the metals examined in

the risk assessment, there isconsiderable uncertainty about theirbioavailability that affects their fate,

transport, and uptake in various media(e.g., plant tissue, animal tissue) andreceptors. Speciation and associatedsolubility of metal species in wasteswhich contain metals are key factorsthat influence the bioavailability ofmetals. The Agency had no informationon the speciation, solubility, oravailability of the metals in the wastesin which they are disposed or how theymay transform in the environment. TheAgency assumed that the metals were ina soluble form, mobile, and available. Inthe absence of this information, theAgency assumed that metals are soluble,mobile, and bioavailable. The Agencyseeks comment on this approach, andrequests data on the speciation andsolubility of metals in wastes, togetherwith the conditions of the waste (e.g.,pH) that could be disposed by themethods considered in this rulemakingand methodologies that account for thetransformation of the metals throughchanging environmental conditions.

(iv) Meteorological Data

The approach for setting central-tendency and high-end meteorologicalconditions in the risk assessment was toevaluate sets of meteorological datafrom a variety of locations, and thenselect locations that reflect centraltendency or high-end conditions for agiven exposure pathway.

The Agency used the set of 29meteorological stations identifiedduring its efforts to develop soilscreening levels for Superfund sites.These are considered representative ofthe United States. Central-tendency andhigh-end locations were then selectedfrom these 29 locations for the exposurepathways where meteorologicalconditions were required as input to themodels; these were the air pathways andoverland pathways. The meteorologicaldata were evaluated as location sets asopposed to individual parameters. Oncelocations 'were selected, the annualaverage values for those locations were.used.

For air pathways, which required dataon wind speed, wind direction,temperature, sunshine, cloud cover, andair mixing height, selection ofmeteorological data was wastemanagement unit-specific and based onextensive sensitivity analysis. EPAconsidered only the effect ofmeteorological data on emissions anddispersion in selecting locations for airpathways. However, for consistency,once a pair of high-end and centraltendency locations were selected for apathway, any meteorological data usedin that pathway were selected tocorrespond to the locations chosen,

even in any overland transportcomponent of the pathway.

Overland pathways were driven bysoil erosion, for which the criticalmeteorological input is the UniversalSoil Loss Equation (USLE) rainfall factor(R). Therefore, to select central tendencyand high-end locations for overlandpathways, the 29 locations were rankedbased on the rainfall factor, and the 50thand 90th percentile locations chosen forall overland pathways.

See Section 6.8, Fate and TransportInputs and Section 7.1.5. Air Modeling,of the Technical Support Document forthe Hazardous waste Identification Rule:Risk Assessment for Human andEcological Receptors for a detaileddiscussion of how meteorological datawere selected and used. The Agencysolicits comment on how meteorologicaldata was selected and used in the riskassessment.

(v) Soil DataA variety of soil parameters were

required for the modeling. Theseparameters are interdependent and varywith the type of soil (e.g., loam, clay).However, values for these parametersalso vary within a soil type. Due to theinterdependence of the parameter, theAgency chose to maintain them as a setand determine a central-tendencyproperty set and a high-end propertyset.

The Agency used loam type soils tocharacterize all soils simulated in therisk assessment because these types ofsoils are fairly prevalent in the UnitedStates. All soils are composed of varyingpercentages of sand, silt, and clay.Loam, by definition, is composed ofequal proportions of sand, silt, and clay;therefore, it represents a combination ofeach of the physical properties of theindividual soil textures. Centraltendency and high-end values wereselected from the range of values forloam soil so that each individual soilparameter required by the model isconsistent with a loam soil. (Sec Section6.8,,Fate and Transport Inputs, in theTechnical Support Document for theHazardous Waste Identification Rule:Risk Assessment for Human andEcological Receptors for more detail.)The Agency solicits comments itsapproach for characterizing soil in theassessment.

(vi) Soil PathwaysThe Agency seeks comment on the

following issues related to the modelingof soil pathways:

* Use of the Universal Soil LossEquation to predict soil erosion in ageneric application - This is a widely-used model intended for site-specific

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66364 Federal Register / Vol. 60, No. 245 / Thursday, December 21; 1995 / Proposed Rules

applications where specific input datacan be used for relatively small fields.Its use in a generic application, and forfairly large waste management units,may overestimate quantities of soileroded.

e Handling of the Soil Loss Constant- This term is the sum of loss rates forleaching, erosion, runoff,biodegradation, hydrolysis, andvolatilization. Possible uncertaintiesmay arise because: the assessmentassumes that these terms are first-orderdecay rates and therefore can be addedtogether; loss processes are calculatedindependently, even though they mayoccur simultaneously.

* Use of the Soil Water ContentEquation to predict soil water content ina generic application - The equation isfrom the Superfund ExposureAssessment Manual (U.S. EPA, 1988x),and was developed for site-specificapplications.

e Area of garden and agriculturalfield - No data were available on the sizeof home gardens, gardens on subsistencefarms, or yards of residential lots (forsoil ingestion). Therefore, a single set ofcentral tendency and high-end valueswas estimated for these, based on bestprofessional judgment; this set isreferred to as garden area, even thoughit might also apply to a yard. Because alarger area leads to greater dilution ofdeposited or eroded contaminant, ahigh-end garden would be one that wasrelatively small.

* Areas for agricultural fields wereestimated from data in the 1992 Censusof Agriculture (U.S. Department ofCommerce, 1992). The Census givesaverage farm acreage by State for 48States (the data are not yet complete forthe two missing States). No percentiledata were available. These data do notdistinguish between commercial andsubsistence farms.

o Mixing Depth-Mixing depthreflects the depth of soil to whichdeposited or eroded contaminant ismixed. It is important to distinguishbetween soil that is tilled foragricultural purposes and soil that isuntilled in determining appropriatemixing depth values. A smaller mixingdepth results in less dilution of aconstituent, and therefore higher soilconcentrations; therefore, a high-endmixing depth would be smaller than acentral tendency mixing depth.(vii) Surface Water Pathways

Water column as well as benthicsediment concentrations wereestimated. Water column concentrationsinclude dissolved, sorbed to suspendedsediments, and total (sorbed plusdissolved, or total contaminant divided

by total water volume). Benthicsediment concentrations included:Dissolved in pore water, sorbed tobenthic sediments, and total. The modelaccounts for three routes of constituententry into the water-body wereexamined: Sorbed to soils eroding intothe water-body; dissolved in runoffwater; and diffusion of vapor phasecontaminants into the water-body. Airdeposition of constituents bound toparticles into a water-body was notexamined because earlier analysisdemonstrated that its contributionwould be negligible when compared tothat of eroding particles. Volatilizationof dissolved constituents and removal ofconstituents through burial in bedsediments were modeled as lossprocesses.

Important assumptions made for thesurface water modeling included:Water-body sufficiently large to supportcertain ecological receptors; sufficientfish to support a subsistence fisher;uniform mixing within the water-body(this tends to be more realistic forsmaller water-bodies as compared tolarge river systems); and equilibrium isestablished between constituents withinthe water column, bed sediments, andair.

The Agency seeks comment on thefollowing issues related to the modelingof surface water pathways:

9 Water-body/WatershedCharacterization-The water-bodycharacterization parameters are anotherexample of a set of parameters that areinterdependent and therefore were usedas a group. Watershed characterizationrelates to the water-body (in the case ofthe assessment, a stream)characterization. Streams arecharacterized (flow, water-body area,watershed area, depth, and variousother parameters) by their "order." Afirst-order stream has no tributarychannels; a second-order stream formswhen two first-order streams converge,and so on through stream order 10. TheAgency used a stream order 4 as thehigh-end estimate because EPA believesthis stream order would be among thesmallest stream orders that wouldsupport sufficient fish or a subsistencefisher and the receptors assessed. Astream order 5 was used as the central-tendency estimate based on the numberof streams within each stream order.(See Section 6.8 in the TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors for more detail.)

e Total Suspended Solids-Totalsuspended solids (TSS) can range fromI to 100 mg/L with a typical value being10 mg/L for streams and rivers. This

value is used as the central tendencyvalue. No data on frequency of values inactual streams was available to estimatea 90th percentile value. Since 80 mg/Lis believed to be the maximum tolerablevalue for aquatic life; this value wasused as the high-end value.

9 Bed Sediment Concentration-Thebed sediment concentration term isanalogous to the bulk density for soil inthat it describes the concentration ofsolids in terms of a mass per unitvolume. A single value of I kg/L wasused in the assessment given that this isconsidered a reasonable value in mostsituations and the range is quite narrow,0.5 to 1.5 kg/L.

& Gas-Phase Transfer Coefficient-The gas-phase transfer coefficient isused to estimate volatile losses from thewater-body. Volatile losses arecalculated using a two-layer resistancemodel that incorporates a gas-phasetransfer coefficient and a liquid-phasetransfer coefficient. Both transfercoefficients are controlled by flowinduced turbulence in flowing systems.The liquid-phase transfer coefficient iscalculated based on chemical-specificproperties. A single value of 36,500 m/yr. was used. There is some uncertaintyrelated to setting this parameter to asingle value that is not chemicalspecific. It is reasonable to assume thatchemical properties affecting volatilitywould have some effect on this value,although it is not known how large suchan effect would be.

. Fraction Organic Carbon in BottomSediment-The fraction organic carbonin bottom sediment is derived from thefraction organic carbon in watershedsoils. For a fraction organic carbon ofabout 0.01 in the watershed, the fractionorganic carbon for bottom sediments istypically 0.03 to 0.05. The midpoint ofthis range, 0.04, divided by the fractionorganic carbon of the watershed (0.01)derives a multiplier of 4 for calculatingfraction organic carbon in bottomsediments from fraction organic carbonin watershed soils. The fraction organiccarbon values used of 0.024 and 0.008correspond to the central tendency andhigh-end values for soil fraction organiccarbon of 0.006 and 0.002, respectively.The fraction organic carbon in thebottom sediments was varied with thefraction organic carbon in soil.(viii) Food-Chain Pathways

The Agency seeks comment on thefollowing issues related to the modelingof food-chain pathways: (Please note thefish uptake methodology is describedbelow in Section D.2.c.2), EcologicalReceptors and Exposure; the littoralmethodology is used for humans):




* Use of regression equations basedon Kow to derive biotransfer factors forplants-The biotransfer factors arebased upon empirical relationships withKow defined by studies on relativelyfew chemicals.

o The lack of accounting fortranslocation of contaminants withinplants-The plant uptake models do notaccount for translocation ofcontaminants (should such atranslocation occur) from one part of aplant to another. The Agency isconsidering two models developed byStephan Trapp, plantx and plantE, andsolicits comment on their use.

o Use of regression equations basedon Kow to derive biotransfer factors forbeef and milk-The biotransfer factorsfor beef and milk are based uponempirical relationships with Kowdefined by studies on relatively fewchemicals.

c. ReceptorsBoth human and ecological receptors

are considered in the assessment. Thehuman receptors evaluated wereselected to represent a range ofbehaviors and activities that influenceexposure levels. The Agency believesthat these represent typical and moreexposed types of behaviors andactivities that might exist around wastemanagement units or mediacontaminated by releases from wastemanagement units. Each receptor wasevaluated for individual exposurepathways (i.e., exposure to multiplepathways was not included). Forecological receptors, populations orcommunities were selected for thegeneric terrestrial and freshwaterecosystems based on behavior patternssuch as dietary habits (plant-eater vs.meat-eater) as well as qualities such assignificance and representativeness withrespect to trophic structure in theecosystem (bald eagle). The selection ofecological receptors was limited by thelevel of characterization available suchas food intake and body weight. Again,the Agency believes that these representthe types of organisms that might existaround waste management units ormedia contaminated by releases fromwaste management units.

(1) Human Receptors and Exposure

Human receptors assessed in theassessment included the following:

o Adult resident living in the vicinityof a management unit-This individualis representative of the generalpopulation in the United States and isevaluated independently through thefollowing potential exposure pathways:Inhalation, ingestion of contaminatedsoil, ingestion of contaminated drinking

water, dermal contact withcontaminated soil, and dermal contactduring bathing. In addition, the analysisevaluates exposures to an adult residentliving on-site of a land application unitbegining 10 years after closure of theunit.

* Child resident living in the vicinityof a management unit--Children are aspecial population considered in certainpathways because of their low bodyweight compared to high intake rates orsurface area. A child is evaluatedthrough the following potentialexposure pathways: ingestion ofcontaminated soil, dermal contact withcontaminated soil, and dermal contactduring bathing.

* Home Gardener-This individualrepresents a sub-population thatsupplements their fruit and vegetableconsumption with fruits and vegetablesthey grow on contaminated land.

* Subsistence Fisher-Thisindividual represents a sub-populationthat subsists on contaminated fish.

* General Fish Consumer-Thisindividual represents a sub-populationthat consumes contaminated fish andsupplements their intake with othernon-contaminated foods.

* Subsistence Farmer-Thisindividual represents a sub-populationthat grows or raises most of their ownfood on contaminated land. Thisindividual is evaluated independentlythrough the following exposurepathways: beef ingestion, milkingestion, and fruit and vegetableingestion. •

* On-site Worker-This individualrepresents the working population thatmay be found at the waste managementunits. This individual is evaluatedduring the active phase of the unit forthe following on-site exposures:Inhalation and dermal contact withcontaminated soil.

Each of the receptors has beenmatched with the most relevantexposure routes. Table A-3 in appendixA shows the pathways were modeled foreach receptor.

As previously discussed, theassessment begins with a target humantoxicity benchmark and exposureassumptions tailored to each receptor,and back-calculates to constituent-specific concentrations in each media.In characterizing the exposure, twoexposure parameters are set to high-endvalues and the rest of the exposureparameters are set to central tendency ordefault values. The two high-endexposure values were typically exposureduration and a parameter affectingintake of, or exposure to, a contaminant(e.g., fraction contaminated,consumption rate, inhalation rate).

The exposure equations used for back-calculating media concentrations arebased on standard risk equations usedin most Agency risk assessments. For allifihalation and ingestion pathways,these equations were adapted from RiskAssessment Guidance for Superfund(RAGS): Volume I-Human HealthEvaluation Manual (Part B,Development of Risk-based PreliminaryRemediation Goals) (U.S. EPA, 1991x;hereafter, RAGS Part B) and subsequentmodifications. For dermal pathways,which are not covered in RAGS Part B,the equations presented in DermalExposure Assessment: Principles andApplications, Interim Report (U.S. EPA1992x; hereafter, the Dermal document)were used; this document reflects thecurrent techniques for assessing dermalexposure. The Agency requestscomment on the data sources andassumptions used in the humanexposure portion of the risk assessment,described in detail in Section 5.0 of theTechnical Support Document for theHazardous Waste Identification Rule:Risk Assessment for Human andEcological Receptors.

The Agency seeks comment on thefollowing types of human exposure thatwere not examined:

9 Ingestion of contaminated water byhumans while bathing or swimming-The ingestion rate of water whileswimming or bathing is 30 times smallerthan ,the normal consumption rate ofwater used in the drinking wateringestion pathways; therefore, thedrinking water ingestion pathwayss~iould be protective of the incidentalwater ingestion pathways.

* Inhalation of volatiles whilebathing-No appropriate, chemical-specific equations could be found toaddress this pathway.

* Ingestion of airborne particulates-The ingestion rate of soil used in thesoil ingestion pathways is many timeslarger than the ingestion rate fromairborne particulates; therefore, the soilingestion pathways should be protectiveof the ingestion of airborne particulates.Also, given the way the soil ingestionrates were empirically derived,ingestion of airborne particulatesshould, in effect, be accounted for in theestimated soil ingestion rates.

e Ingestion of contaminated soil byresident on active site-While the wastemanagement units are active, it isassumed that access is limited toworkers.

(2) Ecological Receptors and Exposure

In addition to the human receptors,ecological receptors were evaluated inthe assessment. Lacking an Agencyprecedent for the selection of ecological

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receptors for a generic analysis, a simpleframework was developed for ecologicalreceptor identification based on EPA'sFramework for Ecological RiskAssessment (U.S. EPA, 1992x). Duringthe problem formulation phase, a suiteof ecological receptors was selected toinclude species that represent each ofthe trophic levels or feeding habitswithin an ecosystem. At best, one canonly infer that an ecosystem is protectedfrom chemical stressors. In addition, thetoxicological data support theevaluation of individuals, populations,and occasionally communities, but areinadequate to address the complexitiesof an ecosystem in most cases. Thus, theapproach taken in the assessment was toestimate protective levels for thepopulations and communities (inferredfrom the measurement endpoints used)found in generic ecosystems. Thespecies included in the ecologicalassessment encompass a wide range ofdietary preferences, sizes, and trophiclevels.

In selecting ecological receptors forthe assessment, a number of ecosystemtypes (e.g., lakes, streams, estuaries,deserts, forests, grasslands) wereconsidered because the waste could bedisposed anywhere once it has exitedthe Subtitle C system. Two genericecosystems were designed: Afreshwater-based ecosystem and aterrestrial-based ecosystem. Specificdetails of these ecosystems aredescribed in Section 3, Receptors, in theTechnical Support Document for theHazardous Waste Identification Rule:Risk Assessment of Human andEcological Receptors. The Agencysolicits comment on both the adequacyof the design of the ecosystems used inthe assessment and the use of genericecosystems to assess potential ecologicalhazards.

Generally, ecological receptors. wereidentified at different trophic levels aswell as at different levels of biologicalorganization and included species ofrelatively low ecological significancebuthigh societal relevance (e.g.,American kestrel). The final selection ofreceptors was based primarily on theavailability of data with which to assessthe risks to that receptor. As suggestedin the Framework for Ecological RiskAssessment (1992x), the process ofselecting appropriate assessmentendpoints was iterative, includinginformation from the other activitiesincluded in the assessment phase-thecharacterization of ecological effects.The ecological receptors included in theassessment were:

*. Mammals-Mammals wereevaluated for both generic ecosystemsand include upper trophic level

predators such as the mink or red fox,lower trophic level consumers such asthe whitetail deer, and insectivores suchas the meadow mole; species wereselected to represent a variety of bodysizes, habitats, and dietary habits forwhich data on body weight, food intake,etc., are available. Mammals may beexposed by eating contaminated preyitems (e.g., fish, other vertebrates,insects) or plants, through incidentalingestion of contaminated soil whileeating or preening, or through lactationor placental transfer.

* Birds-Birds were also evaluatedfor both generic ecosystems and includeupper trophic level predators such asthe red-tailed hawk and lower trophiclevel consumers such as the Americanrobin; species were selected to representa variety of body sizes, habitats, anddietary preferences for which inputparameters (e.g., body weight, diet,ingestion rates) are available. Birds areexposed through the ingestion ofcontaminated prey items (e.g., fish,worms), through incidental ingestionthat occurs while eating or preening, orthrough maternal transfer to eggs.

e Terrestrial Plants-Vascular plantsthat might be common in a genericterrestrial ecosystem were evaluated.The species of plants used to representplants within the terrestrial ecosystemwere determined by the availability ofdata and included primarily foragegrasses and food crops. Plants areexposed through soil-to-root uptake,deposition on the surface of leaves orbark, and during air-to-leaf transport ofvolatile or semi-volatile constituents.

* Soil Community-Representativespecies for the soil community werebased on six metrics for measuringecological function: (1) Location, (2)size, (3) abundance, (4) taxon richness,(5) trophic structure, and (6) energymetabolism. Organisms living in or onthe soil are exposed through directcontact (e.g., insects), through theingestion of contaminated soil (e.g.,earthworms), and through the ingestionof other soil dwellers (e.g., centipedes).The Agency solicits comment on therepresentative species selected tocomprise the soil community.

9 Fish-Given the small percentage offreshwater species for whichtoxicological data are available, allspecies of freshwater fish wereconsidered as potential receptors,regardless of size or dietary habits. Fishare subject to continuous exposure tocontaminated water via gill exchangehnd may be exposed to bioaccumulativechemicals through the food chain.

9 Aquatic Invertebrates (Daphnids)-Aquatic invertebrates are believed to beamong the most sensitive aquatic

species (Suter, 1993x), daphnids wereselected to represent free living aquaticinvertebrates. Continuous exposure tocontaminated water is considered theprimary route of exposure.

e Aquatic Plants-Vascular aquaticplants and algae typical of aquaticecosystems were evaluated. Aquaticplants are exposed during sediment-to-root uptake and through water-to-leaftransport.

* Benthic Community-Representative species includeorganisms that fall within any of theeight taxonomic genera used in thedevelopment of the Ambient WaterQuality Criteria for the protection ofaquatic life. Because these organismsspend most (if not all) of their lives inthe sediment, they are exposed throughdirect contact and ingestion ofcontaminated sediments as well a sthrough the ingestion of other sedimentdwellers.

Each of these receptors has beenmatched with the exposure pathwaysand waste management units likely toresult in exposure. Table A-4 ofappendix A shows which pathwayswere modeled for each receptor. TheAgency solicits comment on the use ofa single species to represent majortrophic elements.

The development of medium-specificconcentrations for the protection ofecological receptors was based oningestion of contaminated vegetation,water, soil, or prey or through continualcontact with a contaminated medium(e.g., aquatic invertebrates with water orsoil fauna with soil).

Numerous studies have demonstratedthe capacity of hydrophobic organicchemicals to bioaccumulate in the foodchain that are orders of magnitudeabove the concentration in thecontaminated medium (e.g., Oliver andNiimi, 1988x). However, it is importantto recognize that food-chain pathwaysmay be significant even for constituentsthat do not bioaccumulate appreciably.Dietary exposure to constituents thatconcentrate weakly in fish tissue (e.g.,bioconcentration factor below 10) maybe more significant than exposure tocontaminated drinking water simplybecause a particular animal may ingestrelatively more fish than water.

For constituents that bioaccumulate,particularly those that biomagnify,benchmarks should account forexposure through the ingestion ofcontaminated prey as well as contactwith or ingestion of contaminatedmedia. The majority of toxicologicalstudies examined a single route ofexposure and seldom considered thepotential increase in exposureconcentrations through successive




trophic levels. As a result, toxicitybenchmarks for bioaccumulativeconstituents cannot be used asacceptable medium exposureconcentrations; exposure estimates mustincorporate the bioaccumulationpotential in the food chain. Fornonbioaccumulating constituents,where toxicity benchmarks that aremedium specific (i.e., concentrationunits-mg/kg or mg/L)) can be used asacceptable medium concentrations forecological receptors (e.g., AmbientWater Quality Criteria).

In the aquatic ecosystem, forbioaccumulative chemicals (log Ko.>4),bioaccumulation factors (BAFs) wereestimated using models developed byThomann (1989x) for the limnetic (orpelagic) food chain and Thomann et al.(1992x) for the littoral food chain (i.e.,sediment-based). However, forconstituents with log Ko, above 6.5,only measured values were used. TheAgency is considering using the Gobasmodel since it can be used forconstituents with log Kow above 6.5.Further, switching to the Gobas modelwould be consistent with the GreatLakes Initiative which recently switchedto that model. The results produced byeither the Thomann models or theGobas model are very similar. The tissueconcentration (TC) was estimated forprey based on the intake, body weight,and dietary preference (i.e., trophiclevel of fish consumed) of therepresentative predator species.Protective surface water concentrationwas calculated by dividing the tissueconcentration (TC) by thebioaccumulation factor for theappropriate trophic level. Fornonbioaccumulative chemicals, theprotective surface water concentrationfor fish and aquatic organisms was theFinal Chronic Value (FCV) or SecondaryChronic Value (SCV) as described inSection 4 of the Technical SupportDocument for the Hazardous WasteIdentification Rule: Risk Assessment forHuman and Ecological Receptors. Forupper trophic level aquatic wildlifesuch as mink and osprey, protectivesurface water concentrations werecalculated based on .the consumption ofcontaminated fish and water. Thebenthic community was included in thelittoral ecosystem. Protective sedimentconcentrations were estimated using theequilibrium partitioning (Eqp) methodsdeveloped by Di Toro et al. (1991x). Asexplained in Section 4 of the TechnicalSupport Document for the HazardousWaste Identification Rule: RiskAssessment for Human and EcologicalReceptors, the sediment benchmark wascalculated by multiplying the FCV (or

SCV) by the octanol/carbon partitioncoefficient (Koc) and adjusting for thefraction organic carbon (f..) in thesediment. EPA requests comment on theselection of the bioaccumulation model,the potential switch to the Gobas model,BAFs used, dietary assumptions, andhow tissue concentrations werecalculated.

For receptors in the generic terrestrialecosystem, methods used represented arange of dietary habits across trophiclevels for wildlife, including plants andorganisms that live in the soil (i.e., soilfauna). (See the discussion on thedevelopment of soil and plantbenchmarks elsewhere in today's rule.)For higher trophic level wildlife, dietarypreferences, daily intake, andbioconcentration factors for prey itemswere identified or estimated to calculateprotective soil concentrations. The keyequation used to back-calculate soilconcentrations as a function of dietaryexposure (including soil ingestion), andthe exposure inputs (e.g., body weights,daily intake) for ecological receptors arediscussed in Section 5.3 of the RiskAssessment. The Agency requestscomment on the equations and inputsused in the generic terrestrial ecosystemmodeling.

The following types of exposure werenot assessed in the assessment:

o Inhalation by ecological receptors-No suitable methodology was available.

o Dermal contact with soil-Nosuitable methodology or sufficienttoxicity data were available.

o Dermal contact with water-Nosuitable methodology or sufficienttoxicity data were available.

3. Groundwater Fate and TransportModeling

In the risk analysis previouslydescribed in the section, the pathwaysinvolving groundwater are onlymodeled (back-calculated) to thewellhead, i.e., to the point of exposureat a water well. For groundwatermodeling from the waste managementunit (i.e., surface impoundment) to thewater well, the Agency used a separatefate and transport analysis. This sectiondescribes the groundwater model andthe modeling procedures for the variouswaste management scenarios for thegroundwater path. The details of themodel and the modeling procedures arepresented in the background documents(USEPA, 1995 a-f).

The Agency has developedspecialized subsurface fate andtransport modeling for four wastemanagement options: (1) Landfills; (2)surface impoundments; (3) waste piles;and (4) land application units. All fourwaste management scenarios assume

that the waste if exempted could bemanaged in the respective RCRASubtitle D units. In deriving theexemption levels, the Agency needs toevaluate the fate and transport ofconstituents from the waste unit to thenearby drinking water wells. Thepotential migration of constituents froma waste unit to the leachate at thebottom of the waste unit can besimulated by the laboratory test, theToxicity Leaching Procedure (TCLP), orthe Synthetic Precipitation LeachingProcedure (SPLP), Method 1312.Although one procedure may be moreapplicable for some wastes than theother procedure, as described on page21483 of the Federal Register Notice ofMay 20, 1992 (57 FR 21450), the Agencyis soliciting comments on the -applicability and use of one test over theother for this proposal.

The fate and transport of constituentsin leachate from the bottom of the wasteunit through the unsaturated zone andto a drinking water well in the saturatedzone is estimated using a fate ahdtransport model. The Agency proposesto use EPACMTP (EPA's CompositeModel for leachate migration withTransformation Products) for thispurpose. The EPACMTP considers notonly the subsurface fate and transport ofchemical constituents, but also theformation and the fate and transport oftransformation (daughter) products. TheAgency also solicits comments on thetechnical correctness and applicabilityof the model and the data for thisproposal.

The Agency proposed the use of asubsurface fate and transport model(EPASMOD) on June 13,1986 (51 FR21648) in the Toxicity Characteristic(TC) Rule. However, after receivingnumerous comments, the Agencyrevised the model and the data used inthe model (53 FR 28692) and theenhanced model (EPACML) was used inthe TC Final Rule (55 FR 11798). TheEPACMTP replaces the EPACML for usein this proposal. The EPACMTP wasrecently published in a refereed journal(Kool, Sudicky and Saleem, Journal ofContaminant Hydrology 17(1994) 69-90) and has been reviewed by the EPA'sScience Advisory Board (SAB). TheSAB commended the Agency for makingfor its significant improvements to themodel. They also stated that itrepresents the state of the art for suchanalyses. However, they alsorecommended additional testing of themodel.

The modeling approach used for thisproposed rulemaking includes threemajor categories of enhancements overthe EPACML and the approach for theTC rule. The enhancements fall into the

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following categories: (1) Incorporationof additional fate and transportprocesses (e.g., degradation of chemicalconstituents); (2) Use of enhanced flowand transport solution algorithms andtechniques (e.g., three-dimensionaltransport); and (3) Revision of the MonteCarlo methodology (e.g., site-basedimplementation of available input data).A discussion of the key enhancementswhich have been implemented in theEPACMTP is presented here and thedetails are provided in the backgrounddocuments (USEPA, 1995a-g). TheAgency is soliciting comments on themodeling enhancements and themodeling methodology as well as on thevalues derived for individual chemicalconstituents:

(1) Fate and Transport Processes

Effects of groundwater moundingunderneath waste unit .- The EPACMLwas limited to conditions of uniformgroundwater flow. It could not handleaccurately the conditions of significantgroundwater mounding and non-uniform groundwater flow due to a highrate of infiltration from the waste units.These conditions increase the transversehorizontal as well as the verticalspreading of a contaminant plume. TheEPACMTP accounts, for these effectsdirectly by simulating groundwater flowin the vertical as well as horizontaldirections (USEPA, 1995 a).

Transformation products.-TheEPACMTP model has capability tosimulate the formation and fate ofmultiple transformation products (up toseven) in the unsaturated as well as inthe saturated zones. For constituentswhich have toxic transformationproducts, the EPACMTP can provide anassessment of the groundwater impactof the transformation products, alongwith that of the parent constituent. Thismethodology has been implemented forhydrolyzing organic constituentsincluded in this proposal.

Fate and transport of metals.-TheEPACMTP can simulate fate andtransport of metals, taking into accountgeochemical influences on the mobilityof metals. The EPA's MINTEQA2(USEPA, 1995 0 metals speciationmodel is used to generate effectivesorption isotherms for individualmetals, corresponding to a range ofgeochemical conditions. The transportmodules in EPACMTP have beenenhanced to incorporate the nonlinearMINTEQ sorption isotherms. Thisenhancement provides the model withcapability to simulate, in theunsaturated and in the saturated zones,the impact of Ph, leachate organicmatter, natural organic matter, ironhydroxide and the presence of other

ions in the groundwater on the mobilityof metals.

(2) Enhanced Solution Algorithms andTechniques

Linkage between unsaturated zoneand saturated zone modules.-Thesaturated zone module implemented inthe EPACML was based on a Gaussiandistribution of concentration of achemical constituent in the saturatedzone. The module also used anapproximation to account for the initialmixing of the contaminant entering atthe water table underneath the wasteunit. The approximate nature of thismixing factor could sometimes lead tounrealistic values of contaminantconcentration in the groundwater closeto the waste unit, especially in cases ofa high infiltration rate from the wasteunit. The enhanced model incorporatesa direct linkage between the unsaturatedzone and saturated zone modules whichovercomes these limitations of theEPACML.

Numerical transport solutionmodules.-To enable a greater flexibilityand range of conditions that can bemodeled, the analytical saturated zonetransport module has been replacedwith a numerical module, based on thehighly efficient state-of-the-art LaplaceTransform Galerkin (LTG) technique.The enhanced module can simulate theanisotropic, non-uniform groundwaterflow, and transient, finite source,conditions. The latter requires themodel to calculate a maximum receptor-well concentration over a finite timehorizon, rather than just the steady stateconcentration which was calculated bythe EPACML. The saturated zonemodules have been implemented toprovide either a fully three-dimensionalsolution, or a highly efficient quasi-3Dsolution. The latter has beenimplemented for Monte Carloapplications and provides nearly thesame accuracy as the fully three-dimensional option, but is morecomputationally efficient. Both theunsaturated zone and the saturated zonetransport modules can accommodate theformation and the transport of parent aswell as of the transformation products.

Solution for nonlinear metalstransport.-A highly efficient semi-analytical unsaturated zone transportmodule has been incorporated to handlethe transport of metals in theunsaturated zone and can useMINTEQA2 derived linear or nonlinearsorption isotherms. Conventionalnumerical solution techniques areinadequate to handle extremelynonlinear isotherms. An enhancedmethod-of-characteristic based solutionhas been implemented which

overcomes these problems and therebyenables the simulation of metalstransport in the Monte Carlo framework.Non-linearity in the metals sorptionisotherms is primarily of concern athigher concentration values; for lowconcentrations, the isotherms are linearor close to linear. Because of theattenuation in the unsaturated zone, andthe subsequent dilution in the saturatedzone, concentrations in the saturatedzone are usually low enough so thatproperly linearized isotherms are usedby the model in the saturated zonewithout significant errors.

Elimination of biases in determinationof receptor well location.-The internalroutines in the model which determineplacement of the receptor well relativeto the areal extent of the contaminantplume have been revised and enhancedto eliminate bias which was present inthe implementation in the EPACML.The calculation of the areal extent of theplume has been revised to take intoconsideration the dimensions of thewaste unit. The logic for placing areceptor well inside the plume limitshas been improved to eliminate a biastowards larger waste unit areas and toensure that the placement of the wellinside theselimits, for a given radialdistance from the unit, is trulyrandomly uniform. However, for thisproposal, the closest drinking water wellis located anywhere on thedowngradient side of the waste unit andthe Agency is soliciting any commentson this procedure.

(3) Revisions of Monte Carlomethodology for nationwide assessment

Data sources.-The data sources fromwhich parameter distributions fornationwide Monte Carlo assessments areobtained have been evaluated, andwhere appropriate, have been revised tomake use of the latest data available formodeling. Leachate rates for Subtitle Dwaste units have been revised using thelatest version of the HELP model withthe revised data inputs. Source specificinput parameters (e.g., waste unit areaand volume) have been developed forvarious different types of industrialwaste units besides landfills. Inputvalues for the groundwater relatedparameters have been revised to utilizeinformation from a nationwide industrysurvey of actual contaminated sites.

Finite-source methodology.-Theoriginal version of the model wasimplemented for Monte Carloassessments assuming continuoussource (infinite source) conditions only.This methodology did not take intoaccount the finite volume and/oroperational life of waste units. TheEPACMTP model has been



Federal Register / Vol. 60, No. 245 / Thursday, December 21, 1995 / Proposed Rules 66369

implemented for Monte Carloassessments of either continuous sourceor finite source scenarios. In the latterscenario, predicted groundwater impactis not only based on the concentrationsof contaminants in the leachate, but alsoon the amount of constituent in thewaste unit and/or the operational life ofthe unit. The Monte Carlo methodologywas enhanced to allow determination ofregulatory threshold levels for these twowaste characteristics USEPA, 1995.

Site-based regional analysis.-TheMonte Carlo methodology has beenfundamentally revised and enhanced toaccount for the interdependency amongthe various model input parametersbased on regional distributions. Theoriginal methodology simply assumedthat a waste site could be locatedanywhere in the US, and that theprobability distributions of individualmodel parameters (e.g., infiltration rate,depth to groundwater, etc.) at any wastesite were mutually independent andgiven by their nationwide frequencydistributions. The model therefore onlyhad limited capability to account forcorrelations and dependencies amongthe model parameters. To address thislimitation, a site-based methodology hasbeen implemented, based on the OSW'ssurveys of existing waste facilities in theUS, and their geographical locations.The information of geographicallocation is used in this enhancedapproach to select the other modelparameters, such as infiltration rate andhydrogeological characteristics. Anumber of different sources werereviewed for the development of thesite-based approach. Four of these setswere selected to derive the regionalcharacteristics of the more importantparameters for each sampled site: TheOSW's survey of industrial wastemanagement units (EPA, 1986); theinfiltration and recharge analysisperformed for U.S. climatic regions; theU.S. Geological Survey inventory ofgroundwater resources; and the API's(American Petroleum Institute) surveyof hydrogeologic parameters for thedifferent groundwater environments inthe U.S.

(4) Implementation of EPACMTP

The specific modeling optionsselected for the modeling analyses aresummarized in Table 3 below. Allmodeling analyses were Conducted inthe finite source, Monte Carlo mode, forfour industrial Subtitle D wastemanagement scenarios. Thegroundwater fate and transport modelwas used to predict the maximumconcentration at a receptor well placeddown gradient from the waste unit. A10,000 years time limit was imposed on

the exposure time period, i.e., thecalculated concentration is the highestexposure concentration occurringwithin 10,000 years following the initialrelease from the waste unit. The MonteCarlo fate and transport simulationprovides a probability distribution ofreceptor well exposure concentrationsas a function of waste and leachateconcentrations. For this proposal, thegroundwater modeling results wereused to derive leachate concentrationthresholds. For carcinogenicconstituents, the exposure concentrationcalculated by the model corresponds tothemaximum 30-year average receptorwell concentration. For non-carcinogenic constituents, the peakreceptor well concentration is used. Theregulatory threshold leachateconcentration limits were determinedusing a back-calculation procedure, tocorrespond to an approximate 90thpercentile protection level. This meansthat the closest downgradient drinking-water wells at 90% of the industrialSubtitle D waste management unitswould have water concentrations belowthe HBN/MCL. The wells further awayat 90% of the sites would be protectedat higher protection levels. The wells atthe other 10% of the sites would beprotected at lower protection levels.

The Agency uses a 95th percentileprotection level in the RCRA Delistingprogram and the 85th percentile for thetoxicity characteristic program. Thesetwo programs have slightly differentgoals from the exemption proposedtoday. The recently developedSuperfund soil-screening levels use a90th percentile protection level toidentify sites at which no additionalinvestigation for possible remediation isrequired. The exit proposed today issimilar to the soil-screening levelsprogram. Today's proposed exit isintended to identify wastes no longerneeding Subtitle C management.Finally, the 90th percentile was chosenbecause it is nearly consistent with theprotectiveness level in the otherpathways of the multipath riskassessment performed for today'sproposal as far as could be identified.

Table 3 provides a summary of themethodology and/or data sources usedto obtain values for the source-specificparameters, chemical-specificparameters, unsaturated zoneparameters, saturated zone parameters,and receptor well location parameters.Because the groundwater pathwayanalysis was performed in Monte Carlomode, all parameters are in principledescribed by their probabilitydistributions. Details on the actualdistributions used are provided in thebackground documents (USEPA, 1995a-

g). Probability distributions used for theunsaturated zone parameters, thesaturated zone parameters, and receptorwell location parameters were the samefor all waste management scenarios andindividual constituents that wereanalyzed for today's exit.

(5) Waste Management ScenariosThe waste management unit

represents the source term in the fateand transport model for the wastemanagement scenarios evaluated forgroundwater contamination. In themodeling framework, the source isdefined in terms of four key parameters:(i) Waste unit area, (ii) Leachate flux(infiltration) rate, (iii) Leachateconcentration, and (iv) Duration ofleachate pulse. The first of theseparameters, waste unit area, wasdetermined from the nationwide OSWsurvey of industrial Subtitle D wastemanagement facilities (USEPA, 1995 a-b). After screening out records withunreliable waste site area and/orvolume, the OSW Industrial Subtitle Dsurvey provides data on location, areaand volume of 790 landfills, 1655surface impoundments, 774 waste piles,and 311 land application sitesnationwide. The weighted distributionsof waste unit characteristics used asinput to the model are based on theresults of the survey.

The leachate flux, or infiltration rate,and duration of the leachate pulse aredetermined from the design andoperational characteristics of the wastemanagement scenario being modeled.Consideration of a leachate pulse offinite duration is a fundamental aspectof the present analysis and distinguishesit from the 'continuous source (infinitesource) assumption used for the 1990Toxicity Characteristic (TC) Rule [,55 FR11798). It should be emphasized thoughthat the results of the finite sourceanalysis are not necessarily differentfrom those of the continuous sourceanalysis. If the source leaching durationis long enough to drive the maximumreceptor well concentration to its steadystate value, the finite source andcontinuous source analyses are in factthe same. In practice, the distinctionbetween continuous source and finitesource analysis is the most important forchemicals which are subj.ects tosorption, speciation, and/ordegradation, including hydrolyzingorganics and metals.

The leachate concentration of specificconstituents in the waste forms the basisfor regulating the wastes. The leachateconcentration is not specified a-priori,but rather it is back-calculated at theend of the Monte Carlo analysis tosatisfy the regulatory criterion that the




maximum groundwater exposureconcentration should be at, or below,the constituent-specific health-baseddrinking water standard, in at least 90% of the cases.

The following sections presentbackground on the determination of thesource parameters for each wastemanagement scenario.

Landfills.-The key characteristic ofthe landfill scenario is that the durationof the leachate pulse is independent ofthe operational life of the wastemanagement unit, i.e., the period oftime required to fill the landfill. Thelandfill is taken to be filled to capacityand covered when leaching begins. Thetime period during which the landfill isfilled-up, usually on the order of 20years, is considered to be small relativeto the time required to leach all of theconstituent mass out of the landfill. Themodel simulation results indicate thatthis assumption is not unreasonable; themodel calculated leaching duration (seebelow) is typically on the order ofseveral hundred years.

The leachate flux, or infiltration rate,is determined using the HELP model.The net infiltration rate is calculatedusing a water balance approach, whichconsiders precipitation, evapo-transpiration, and surface run-off. TheHELP model was used to calculatelandfill infiltration rates for arepresentative subtitle D landfill with 2-foot earthen cover, and no liner orleachate collection system, usingclimatic data from 97 climatic stationslocated throughout the US. Thesecorrespond to the reasonable worst caseassumptions as explained in the RiskAssessment Background Document(USEPA, 1995b). The model calculatesthe daily water balance for the totalperiod for which climatic data areavailable. For each waste site in theOSW survey, an infiltration rate wascalculated using the data from theclosest climate station (USEPA, 1995b).

In the landfill scenario, the durationof the leaching period is not prescribed.Instead it is calculated as part of theMonte Carlo simulation from the totalmass of constituent in the landfill, andthe rate of leaching. This relationship isderived from a straight-forward massbalance principles. The methodology isdocumented in the BackgroundDocument for the Finite SourceProcedure (USEPA, 1995-c); only themost salient aspects are presented here.

The duration of the leachate pulse, Tp,is determined by the total mass ofconstituent that is initially present inthe landfill, and the rate at which theconstituent is removed by leaching:Aw. d. Fh . Phw• Cw=Aw• I . CL. Tp

orTp={d. Fh. Phw} over {I} Cw over CL

whereA.=Area of the waste unit (M2 ),d=Depth of waste unit (in),Fh=Fraction of waste unit volume

occupied by this waste,Phw=Density of the waste (g/cm 3),I=Leachate flux (Infiltration) rate (m/

Y),Cw=Constituent waste concentration

(mg/kg), andCL=Constituent leachate

concentration (mg/L).The determination of T, according to

(2) tacitly assumes that the constituentdoes not degrade inside the waste unit,does not consider removal bymechanisms other than leaching (e.g.,volatilization), and assumes that all ofthe constituent mass will eventuallyleach out. The formulation given abovealso assumes that the leachateconcentration, CL, remains constantuntil all of the constituent mass hasleached out. The methodology wasadapted to handle a time-varyingleachate concentration, e.g., a graduallydiminishing leachate concentration torepresent the depletion of thecontaminant mass in the landfill overtime. If it is assumed that the leachingof the constituent from the waste intothe water phase is controlled by a linearequilibrium partitioning process, thereduction of the leachate concentrationwith time can be modeled as a first-order decay process (EPA, 1995c):CL(t)=CLOe{fXt}where

CLO=Initial leaching concentration(mg/L)

X=Apparent decay constant (y-1)t=Time (y)

The rate at which the leachateconcentration is reduced is determinedby the coefficient ), which is given by:X={I} over [{d FhwPhw}{Cw over CLO}]Using (3), the leachate concentrationwill gradually and asymptotically bereduced to zero. The total amount ofconstituent that is released into thesubsurface will be the same whether aconstant leachate concentration of finiteduration, or a gradually diminishingleachate concentration is assumed. Inthe latter case, the duration of therelease period is longer, but the averageleachate concentration lower, ascompared to the former case,

It can be seen from either (2) or (4)that the duration of the leachate pulse,or the rate of depletion, respectively,can be expressed as a function of theinitial leachate concentration, CL. Forthe modeling analyses, equation (3) wasused for organic constituents. Theunderlying assumption that the

concentration is controlled by linearequilibrium partitioning is reasonablefor organic constituents. For metals, thepulse release option (equation 2) withconstant leaching concentration wasused.

The calculation of Tp (or X) requiresa number of ancillary source and wasteparameters. These are the depth of thewaste unit (d), the fraction of the wasteunit occupied by the waste (Fh), and thewaste density (Phw). The waste unitdepth is obtained directly from the OSWwaste site survey. The survey providesdata on both landfill areas and volumes,which allows the depth to be calculatedfor any landfill selected during theMonte Carlo simulation. Th9 fraction ofwaste in the landfill is assigned auniform distribution with lower andupper limits of 0.036 and 1.0,respectively, based on analysis of wastecomposition in Subtitle D landfills(EPA, 1995). The lower bound assuresthat the waste unit will always containsa minimum amount of the waste ofconcern. The waste density is assigneda value based on reported densities ofhazardous waste, and varies between 0.7and 2.1 g/cm 3 (EPA, 1995c).

Surface Impoundment.-The surfaceimpoundment waste managementscenario is that of a non-hazardouswaste industrial impoundment. Thearea of the impoundment is obtainedfrom the OSW Subtitle D IndustrialSurvey (USEPA 1995 b). No direct datais available on the rate of infiltrationfrom surface impoundments. The rate ofinfiltration from the impoundment iscalculated inside the EPACMTP fate andtransport model. The rate of infiltrationis calculated, using Darcy's Law, as afunction of surface impoundment depth,and hydraulic conductivity andthickness of a low-permeabilitysediment layer at the base of theimpoundment.

Impoundment depth is obtained fromthe OSW survey, for each impoundmentsite in the survey, in the same way asthe landfill depth is obtained (seeabove). The sediment layer at the baseof the impoundment is taken to be 2 feetthick, and have an effective equivalentsaturated conductivity of 10

-7 cm/s

These values were selected inrecognition of the fact that most non-hazardous waste surface impoundmentsdo have some kind of liners in place(USEPA, 1995b). During the MonteCarlo fate and transport simulation, theinfiltration rate is calculated using theimpoundment depth value for thespecific unit selected for each MonteCarlo realization.

The leachate concentration again isnot determined a priori, but isdetermined after the analysis, based on




the desired regulatory protection level(90th percentile). The surface-impoundment is taken to have a 20-yearoperational life. After this period, theimpoundment may be filled in, orsimply abandoned. In the latter case, thewaste in the impoundment will drainand/or evaporate relatively quickly. Inthe modeling analysis, the duration ofthe leaching period is therefore set equalto 20-years.

Waste Pile.-The waste pilemanagement scenario is conceptuallysimilar to that of the landfill, but differsin a number of key aspects. In contrastto landfills which represent a long-termwaste management scenario, waste pilesrepresent a more temporarymanagement scenario. During theoperational life of the waste pile, it maybe regarded as an uncovered landfill.Typically at the end of the active life ofa waste pile, the waste material is eitherremoved for land filling, or the wastepile is covered and left in place. If thewaste is removed, there is no longer asource of potential contamination. If awaste pile is covered and left in place,it then becomes equivalent to a landfill,and consequently is to be regulated asa landfill. For the analyses, therefore,only the groundwater impactsassociated with the period that thewaste pile is active, are considered.

Data on the waste pile area areobtained from the OSW Subtitle Dsurvey. Infiltration rates for the wastepile are obtained by treating the wastepile as an uncovered landfill. HELPmodel derived landfill infiltration ratesassuming a sandy loam soil cover wereused to assign infiltration rates for wastepiles. A sandy loam cover represents themost permeable cover considered for thelandfill scenario, and most closelyresembles a situation in which no coveris present. The methodology forassigning an infiltration rate to anyspecific waste pile in the OSW survey,,follows that used for landfills (seeabove).

An active life of 20 years is assumedfor the waste pile. This also determinesthe duration of the leaching period. Aswith the landfill and surfaceimpoundment scenario, the leachateconcentration is determined at the endof the analysis, to satisfy the regulatoryprotection level.

Land Application Units.-Data on thelocation, area and waste applicationrates at industrial land application siteswere obtained from the OSW survey ofindustrial Subtitle D sites. Location-specific infiltration rates were estimatedfor each land application site byapplying the HELP model, usingclimatic data from the nearest climatestation. Because wastes applied at land

application sites typically have a highliquid content, this factor wasaccounted for in the water balancecalculations. An annual wasteapplication rate of six inches of waste,containing 85% water was assumed.This is typical of sludges whichconstitute a large fraction of waste atland application sites. Therefore, anadditional 5.1 inches of water wereadded to the natural precipitation forthe water balance evaluation at eachland application site.

The leaching duration for the landapplication unit was set to 40 years,consistent with the release periodmodeled for the air pathway. No reliabledata were available for the active life ofland application units. Using a longervalue than for surface impoundmentsand waste piles is warranted becausepart of the applied waste material mayremain in the soil at the end of theactive life of a land application unit,and may continue as a source ofcontaminant leaching.

(6) Determination of Regulatory Wasteand Leachate Concentration Limits

The objective of the Monte Carlo fateand transport analysis is thedetermination of regulatory limits forthe concentration of individual toxicconstituents in the leachate, CL. Theselimits are determined so as to satisfy theregulatory criterion that disposal of awaste in a subtitle D waste managementunit should not lead to an exceedanceof the health-based value or the drinkingwater standard, at a receptor well placeddown gradient from the waste unit, inat least 90% of the cases.

The CL limits are specific to eachwaste management scenario, and arealso constituent specific. CL limits areconstituent specific because of theirdependence on constituent specifichealth-based standards, as well as onconstituent specific fate and transportcharacteristics that affect theconcentration received at the receptorwell. The latter factors are discussed inthe following section; this sectiondiscusses the determination ofregulatory CL thresholds.

Using Equation (2) or (3) and (4), thegroundwater exposure concentrationcalculated by the fate and transportmodel can be expressed as a functionCL. All other parameters used in themodeling analysis are obtained fromprescribed probability distributions.Consequently, by comparing thepredicted exposure concentration to theappropriate regulatory standard, e.g.,health-based value or a drinking-waterstandard, threshold levels of CL, can becalculated. Wastes for which theleachate concentration exceeds the CL

threshold would not be exempted.Because the Monte Carlo analysisproduces a probability distribution ofexposure concentrations, the back-calculation of CL threshold levels can beperformed for any desired level ofprotection

For those constituents that degrade(see next subsection) and produce toxicdegradation products, the developmentof regulatory threshold values for CLconsiders not only the exposureconcentration and toxicity of the parentconstituent, but also the exposureconcentration and toxicity of toxictransformation products. For instance,consider two waste constituents thathave similar toxicity values, i.e., similarhealth-based levels, as well as similarfate and transport characteristics, so thatthey show comparable values for themodel simulated receptor well exposureconcentration. However, if one of thetwo chemicals produces toxic off-spring,but the other chemical does not, thechemical which has toxic daughterproducts will have more stringent limitsfor CL.

(7) Chemical-Specific Fate andTransport Processes

The Monte Carlo fate and transportanalysis considers chemical-specificsorption and hydrolysis (degradation)characteristics. These characteristicsdirectly affect the model-predictedgroundwater exposure concentration.Chemicals which are subject to sorptionand/or hydrolysis will exhibit lowerexposure concentration as compared tonon-sorbing, non-degrading chemicals.This translates into higher regulatorywaste and concentration limits. Twobroad groups of chemicals areconsidered under today's proposal.They are organic constituents andmetals.

Organic Constituents.--Organicconstituents account for the largestgroup of chemicals addressed undertoday's proposal. The groundwaterpathway analyses were performed for atotal of 222 organic constituents. Thefate and transport analysis accounts forsorption of organics onto soil andaquifer organic matter, as expressed bya chemical-specific organic-carbonpartition coefficient (Koc), anddegradation due to hydrolysis reactions,as expressed by chemical-specifichydrolysis constants. Sorption ismodeled as a reversible, linearequilibrium process. Degradation due tohydrolysis is modeled as a first-orderkinetic process. The groundwater

-pathway analysis utilizes acomprehensive set of Koc values andhydrolysis rate constants compiled bythe EPA-ORD (Environmental Fate

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Constants for Organic Chemicals UnderConsideration for EPA's HazardousWaste Identification Projects, EPA/600/R-93/132). Chemicals with identicalKoc values and hydrolysis constantswill exhibit the same fate and transportbehavior, and given the same leachateconcentration and leaching period, theywill result in the same exposureconcentration. Note, however, that theymay still have different regulatoryleachate concentration limits, if theyhave different health-based drinkingwater standards and/or produce toxictransformation products.

For the groundwater pathwayanalysis, organic constituents with ahydrolysis half-life of 6,900 years or less(first-order degradation rate of 10-4 orgreater) were classified as degraders, theremainder were classified as non-degraders. The EPACMTP can simulatethe formation and subsequent fate andtransport of transformation daughterproducts, enabling the groundwaterexposure concentrations of any toxictransformation products to bedetermined and, therefore, included inthe determination of leachateconcentration thresholds.

It has been established, by analyzingmodeling results for differentconstituents with a range of sorptionand degradation characteristics that,

after normalizing the results against thechemical-specific HBN/MCL, the effectof sorption and degradation on theregulatory values can be expressed as afunction of the Koc and hydrolysis ratecoefficients, using a straight-forwardscaling relationship. After theserelationships have been established, it isnot actually necessary to conduct theMonte Carlo fate and transportcomputer simulations for eachindividual constituent. Instead, for eachwaste management scenario of concern,a set of reference CL values aregenerated" by running the Monte Carlomodel for a selected range of values ofKoc and hydrolysis rate coefficientsusing a normalized HBN/MCL of 1 mg/L. Constituent-specific CLMIN values arethen determined in two steps: First, thereference curves are scaled to theconstituent'specific Koc value, and (fordegraders) hydrolysis rate coefficients.Secondly, an adjustment is made for theconstituent-specific value of thedrinking water standard. The finalvalues of CLMIN are obtained bymultiplying the concentration limitsbased on the normalized drinking waterstandard, by the actual value of thedrinking water standard of thatparticular constituent. For constituentswith toxic transformation products, this

procedure is repeated for thetransformation products, to find theminimum values of CL (CLMIN) whichensure that the exposure concentrationsof the parent constituent and anydaughter products will not be exceeded.The benefit of this approach is that ifadditional constituents are to beregulated, or a different value of thedrinking water standard HBN/MCL, theappropriate CLMIN can be determinedwith less effort, because it is notnecessary to repeat the time-consumingcomplete Monte Carlo simulation.

Metals.-Fate and transport of metalsin the subsurface may be controlled bycomplex geochemical interactions. Toaccount for these processes, the OSWhas developed and implemented amodeling approach which utilizes theMINTEQA2 metals speciation model inconjunction with the EPACMTPsubsurface fate and transport model.The MINTEQ model has been applied togenerate effective sorption isothermsreflecting variations in four geochemicalmaster variables affecting metals fateand transport. These factors are: Ph,leachate organic matter natural organicmatter in the soil or aquifer, andironhydroxide content. Each of theseparameters has a range of values,reflecting their nationwide probability.

TABLE 3.-EPACMTP MODELING OPTIONS

Management Scenarios ...................................................

Modeling Scenario ...........................................................Regulatory Protection Level ............................................Source Parameters:

W aste Unit Area .......................................................W aste Unit Volume ..................................................Infiltration Rate:

Landfill ...............................................................Surface Impoundm ent .......................................W aste Pile .........................................................Land Application Unit ........................................

Leaching Duration:Landfill ...............................................................Surface Impoundm ent .......................................W aste Pile Land ................................................Application Unit .................................................

Chemical Specific Parameters:Decay Rate:

Organics ............................................................

M etals ................................................................Sorption:

Organics ............................................................

M etals ................................................................

Unsaturated Zone Parameters:Depth to groundwater .......................... ; ....................Soil Hydraulic Parameters ........................................Fraction Organic Carbon ..........................................Bulk Density .............................................................

Saturated Zone Parameters:Recharge Rate .........................................................

Industrial Subtitle D: (i) Landfill; (ii) Surface Impoundment; (iii) Waste Pile; and (iv)Land Application Unit.

Finite Source Monte Carlo.90% (yields an approximate DAF of 10 for a continuous source landfill).

Site based, form OSW Industrial Subtitle D Survey.Site based, from OSW Industrial Subtitle D Survey.

Site-based, derived from water balance using HELP model.Site-based, derived from impoundment depth using Darcy's law.Site-based derived from water balance using HELP model.Site-based, derived from water balance using HELP model.

Derived, continues until all constituent has leached out.20 years (operational life of waste unit).20 years (operational life of waste unit).40 years.

Hydrolysis rates based on measurements or based on appropriate structure-activity re-lationships.

No decay.

K. estimated from Ko, which is based on measurements or based on appropriatestructure-activity relationships.

MINTEQ sorption isotherms (Pb, Hg, Ni, Cr (Ill), Ba, Cd).pH dependent isotherms (As, Cr (VI), Se (VI), Th)

Site-based, from API/USGS hydrogeologic database.National distribution for the main soil types.National distribution for the main soil types.National distribution for the main soil types.

Site-based, derived from precipitation/evaporation and soil type.




TABLE 3.-EPACMTP MODELING OPTIONS-Continued

Saturated Thickness ................................................. Site-based, from API/USGS hydrogeologic database.Hydraulic Conductivity .............................................. Site-based, from API/USGS hydrogeologic database.Porosity ..................... .... Effective porosity derived from national distribution of aquifer particle diameter.Bulk Density ............................................................. Derived from porosity.Dispersivity ............................................................... Derived from a national distribution and is based on distance to the receptor well.Groundwater Temperature ....................................... Site-based, from USGS regional temperature map.Fraction Organic Carbon .......................................... National distribution, from EPA STORET database.pH ............................................................................ National distribution, from EPA STORET database.

Receptor Well Location:Radial Distance ....................................................... Nationwide distribution based the survey.Angle Off-Center ..................................................... Uniform within ± 90 ° from plume centerline.Depth of Intake Point ............................................... (No restriction to be within plume) Uniform throughout saturated thickness of aquifer.

4. Other Risk Assessment Issues

a. Differences Between the Groundwaterand Non-groundwater Analyses

As mentioned previously, the Agencyconducted separate analyses for theevaluation of risks from groundwaterand non-groundwater pathways. Thegroundwater pathways relied on a fullMonte Carlo analysis; whereas the non-groundwater pathway analyses wereperformed using high-end and centraltendency parameters, consistent EPA'srisk characterization guidance (EPA1995).

Although the approaches to themodeling differed, the Agency used thesame data for parameter inputs (i.e.,OSW's Industrial Subtitle D Survey,U.S. EPA 1986) to describe the wastemanagement units common to bothanalyses (i.e, surface impoundments,waste piles, and land application units).However, even though the same datawere used, some differences exist basedon the different modeling approaches.These differences are discussed below.

(1) Infiltration

For the groundwater pathwayanalysig, the Agency used the HELPmodel to calculate the net infiltrationrate for landfills, land application unitsand waste piles, as a function ofregional climatic conditions and wasteunit design characteristics (seeEPACMTP background Document). Theanalysis used the meteorological datafrom 93 meteorological stations locatedthroughout the United States to developinfiltration rate distributions using theHELP model.

For the non-groundwater analysis, theAgency used rainfall to calculate therecharge rate. The rainfall was selectedfrom 29 meteorological stationsdistributed among 9 climate regions.However, the method for selecting therainfall factor differed between the airrelease pathways and the overlandrelease pathways.

* Fdr the air release pathways, theAgency conducted a sensitivity analysisfor each waste management unit type torank the 29 meteorological stations withrespect to several air modeling outputs,including maximum air concentration ofpollutants, average air concentrationsover the agricultural field and waterbody, and average deposition over theagricultural field and water body. Basedon these sensitivity analyses, theAgency selected a central tendencylocation and high-end location for theair pathway for each of the wastemanagement units. Thus, locations withmeteorologic data, including the rainfallfactor, approaching the central tendencyand high-end values were selected foreach waste management unit.

* For the overland release pathways,the Agency ranked the rainfall factorsfrom the 29 meteorological stations andselected the 50th and 90th percentilebased on the distribution of the 29meteorological stations.

(2) Density of Waste Applied to theLand Application Unit

The approach used in thegroundwater analysis assumed the bulkdensity of the applied waste to be 1gram per cubic centimeter (g/cc)because the waste was assumed to becomprised predominantly of water.However, changes in the density ofapplied waste do not significantly affectthe results of the groundwater modelingresults.

The approach used in the non-groundwater analysis assumed the bulkdensity of waste to be analogous to thedensity of sewage sludge (i.e., 1.4 g/cc).The waste in the LAU is a mixture ofindustrial waste and soil. The centraltendency bulk density for soil (i.e., 1.5g/cc) is similar to the bulk densityassumed for industrial waste. Becausethe waste is incorporated into soil, theproperties of the waste/soii mixture areneeded. There is little variability in bulkdensity for the type of soil used in theanalysia (i.e., loam), thus, the same

value was used for central tendency andhigh-end estimates of the waste/soilmixture bulk density.

(3) Unsaturated Zone Characteristics

The groundwater pathway analysisused the characteristics (e.g., percentorganic matter, saturated hydraulicconductivity) of the entire unsaturatedzone as input into the modelinganalysis. The non-groundwater pathwayanalysis used as input thecharacteristics of only the upperportions of the unsaturated zonebecause these characteristics were thosesignificant for the surface exposurepathways.

(4) Hydrolysis Rates

The hydrolysis rate for a chemicalconstituent is used in the Monte Carlogroundwater pathway analysis as afunction of temperature and pH of thegroundwater at the Monte Carlo realizedsite. The Agency used hydrolysis ratesfor constituents that have beenmeasured through appropriate structureactivity relationships. They have beenreviewed by a panel of experts from theAgency's Office of Research andDevelopment (USEPA, 1993). The non-groundwater pathway analysis usedhydrolysis rates from the "Handbook ofEnvironmental Fate and Exposure Datafor Organic Chemicals" (Howard et. al,1993).

b. Other Groundwater Pathway AnalysisIssues

(1) Use of 1,000 Year Versus 10,000 YearExposure Time Horizon

The Agency's proposal is based on a10,000 year time horizon for thegroundwater pathway. This means thatthe determination of leachateconcentration limits is based on thehighest (30-year average) concentrationthat occurs within 10,000 years from thestart of the release. Although this longertime horizon has been used in otherprograms (U.S. Nuclear Regulatory

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Commission and U.S. Department ofEnergy), the Agency is consideringusing 1,000 years as an alternative timehorizon. The Agency requests commenton this issue which is described in moredetail below.

Using this shorter time horizon resultsin an increase of the leachateconcentration limit for a number ofconstituents. The constituents affectedare those which are strongly sorbed inthe subsurface, and which thereforetend to migrate slowly. Theseconstituents include organics withretardation factors (R) significantlygreater than one. The organic carbonpartition coefficient (k,) values forthese constituents are about 3,500 g/cm 3

or greater, and certain metals such aslead and chromium(III). For organicconstituents with k, values less thanabout 3,500 g/cm 3, the highest receptorwell exposure concentration is generallyreached in less than 1,000 years.Reducing the modeling time horizonfrom 10,000 to 1,000 years thereforedoes not affect the results of thepathway analysis for these constituents.The effect of using a 1,000 year versusa 10,000 year time horizon is illustratedin Table 4. The constituent-specificdifferences are shown in Table B-1 ofappendix B to the preamble. The tableis based on a landfill waste managementscenario, and all constituents areassumed to have identical toxicityvalues and not be subject to hydrolysis.For reference, the leachateconcentration limit for constituents withk0=o (no sorption, R=1), and a 10,000year time horizon is equal to 1.0 mg/L.This table shows that the increase inleachate concentration limit for organicconstituents is affected for a shortermodeling horizon (1,000 years) onlywhen kc values (or R values) are verylarge. (About fifteen percent, out of atotal of approximately 200, includingeight metals, fall into this category.) Theeffect of hydrolysis rate is notconsidered in results shown in the table.While hydrolysis influences themagnitude of the exposureconcentration at a receptor well, thetime that it takes for a contaminant toreach the receptor, well is independentfrom the chemical-specific hydrolysisrate. It is, however, strongly influencedby chemical-specific sorptioncharacteristics, which for organics areexpressed in terms of k. or R values.

TABLE 4.-EFFECT OF 1,000 YEARVERSUS 10,000 YEAR MODELINGTIME HORIZON ON LEACHATE CON-CENTRATION LIMIT

k c (cm3/) 10,000 1,000years years

0.0 ............................. 1.0 1.03,384 ......................... . 1.0 1.0(R=10)37,224 ....................... 1.0 60(R=100).

(2) Implementation of Parameter Boundsin Monte Carlo Procedure

The Monte Carlo modeling procedureused in the groundwater pathwayanalysis uses data on waste site locationfrom the EPA's Industrial Subtitle DSurvey (USEPA, 1986). These data arecombined with other data sets forclimatic and hydrogeologicalparameters. Auxiliary parameters forwhich no direct data is available arecalculated internally in the model. Forinstance, ground-water velocity iscalculated from hydraulic conductivity,gradient and effective porosity, and thedispersivity is calculated from thereceptor well distance (See EPACMTPBackground Document and User'sManual). Each parameter furthermorecan have specified upper and lowerbounds to guard against the possibilitythat physically infeasible parametersand/or parameter combinations are notused. When the latter condition occurs,the particular Monte Carlo realization isrejected, and another realization isgenerated. The Agency is considering analternative procedure in which only theoffending parameter is regenerated, or, ifnecessary, set equal to its upper orlower bound to avoid selection of valuesbeyond the minimum to the maximumvalues range. In first case, the frequencydistribution of parameter valuesgenerated by the Monte Carlo module,may be different from its inputdistribution. The Agency hasdetermined that the two alternativeprocedures have little impact on theoverall modeling results in the case oflandfills and land application units, butthat the default procedure tends to favorthe selection of sites with larger wasteunit area in the case of waste piles andsurface impoundments. Therefore itproduces more conservative (lower)values for the final leachateconcentration limits. The analysisresults show that for the two alternativeMonte Carlo procedures for surfaceimpoundments, the default procedureresults in a leachate concentration limitof 1.0 mg/L, the alternative procedureresults in a concentration limit of about31 mg/L for a chemical with R=1. The

effect of changes in the hydrolysis rateor the R value on the resultantregulatory leachate concentration do notimpact the results obtained by using thealternative Monte Carlo proceduredescribed in this subsection. TheAgency is also soliciting comments onthe Monte Carlo parameter rejectionprocedure used for the results presentedin this subsection.

(3) Hydraulic Conductivity of SurfaceImpoundment Bottom Layer

The surface impoundment scenariomodeled in the groundwater pathwayanalysis incorporates a 2 feet thick layerat the base of the impoundment. In thebase case for this proposal, the layer isassigned a hydraulic conductivity of 10-7 cm/sec. The Agency recognizes thatthis value may or may not beappropriate value for bottom sedimentsas a nationwide typical for industrialSubtitle D surface impoundments. Toevaluate the impact of varying thisparameter, the Agency has comparedmodeling results obtained using a 10times higher conductivity of 10-6 cm/sec. A higher conductivity valuecorresponds to a greater leachate fluxfrom the impoundment, and generallyhigher receptor well concentrations,which translates into a moreconservative (lower) regulatory leachateconcentration limit. The regulatory limitcalculated for a conductivity value of10-7 cm/sec is 1.0 mg/L, thecorresponding value for a conductivityof 10-6 cm/sec would be 0.35 mg/L. Theeffect of changes in hydraulicconductivity on the results is believedto be independent of the sorption or thehydrolysis characteristics of thechemical. The Agency is invitingcomments on the appropriate value forthe hydraulic conductivity of the bottomsediment layer for industrial D surfaceimpoundments. In addition, the Agencyrequests the submission of hydraulicconductivity data for industrial SubtitleD.surface impoundment bottom sludges.(4) Waste Pile Infiltration Rates

The Agency used the HELP model tocalculate the net infiltration rate forlandfills, land application units andwaste piles, as a function of regionalclimatic conditions and waste unitdesign characteristics (see EPACMTPbackground Document). For waste piles,the Agency considered two alternatives.The procedure used in the base caseconsidered a waste pile, for the purposeof estimating infiltration rates, to besimilar to an uncovered landfill. TheMonte Carlo modeling analysis thereforeused landfill infiltration ratescorresponding to the most permeable(sandy loam) of the three cover types




used for landfill modeling. As analternative, the Agency has used theHELP model to calculate infiltrationrates for waste piles directly. In theinitial evaluation, the runoff used in thewater balance calculation was computedby the HELP model as a function of soiltexture and vegetative cover (bareground).The Agency has evaluated theimpact of representative bare, butunevenly surfaced, waste piles onsimulated runoff using the HELP model.A comparison of the impact of usingthis alternative procedure against thevalues used in this proposal for the basecase, on the regulatory leachateconcentration limit, was conducted. Thecomparison of regulatory leachateconcentration limits is based on a non-degrading, non-sorbing constituent,which has a concentration limit of 1.0mg/L in the proposal. Using thealternative procedure, thecorresponding leachate concentrationlevel changes to 0.77. The Agency isinviting comments on the two methodsfor the waste piles for the estimation ofinfiltration rates through them. If youhave any data and other information tosupport your comment, send it alongwith your comments to the Docket.

(5) Land Application Unit InfiltrationRates

In the calculation of infiltration ratesfor land application units for the basecase in the proposal, it was assumedthat land application units receive, onaverage, 1,295.4 m 3ha (5.1 inches) ofwater annually through the applicationof the waste. This amount of water wasincluded in the HELP model waterbalance calculation, resulting in anincreased net infiltration as compared toambient conditions. The wasteapplication rate may or may notrepresent true field situations. As analternative to the modeling procedureused for the base case of this proposal,the Agency evaluated the effect of usingambient recharge rates, i.e., theapplication of waste does notsignificantly alter the water balance, onthe calculated leachate concentrationlimits. The comparison of thisalternative with the procedure used forthe base case shows that the regulatoryleachate concentration limits for a non-degrading, non-sorbing constituent inland application units changes to 1.12mg/L from 1.0 mg/L for the procedureused in the base case.

(6) Aggregate Effects of AlternativeGroundwater Modeling Procedures andData

The preceding sections havepresented the effect of alternativemodeling options and data sources thathave been considered by the Agency. A

consequence of the Monte Carloexposure modeling approach is that theeffects of changes in model parametersare not always linearly additive; ratherthe aggregate effect of changing multipleparameters or options may be to eithermagnify or reduce the effect of theindividual changes. The Agency,therefore, has conducted modelinganalyses of the aggregate effect of thealternatives discussed above for each ofthe four waste management scenarios. Inaddition to the alternatives presented inthe preceding subsections, amodification was also made in theprocedure for modeling waste sites forwhich the correspondinghydrogeological region was initiallyassigned as "not classifiable". Ratherthan ignoring the small fraction of sitesinvolved, they were incorporated intothe analysis by assigning themnationwide average vales for thegroundwater parameters. Table 5presents the aggregate effect of allchanges for each of the four wastemanagement scenarios modeled. Themodeling results correspond to a non-degrading, non-sorbing constituent. Theleachate concentration limits arenormalized with respect to a value of1.0 mg/L for the landfill scenario, underthe modeling procedure for the basecase of this proposal. The results arepresented for a 1,000 year time horizon;however for a non-sorbing constituent,these same results also hold for the10,000 year time horizon.

TABLE 5.-AGGREGATE EFFECT OFMODELING ALTERNATIVES ONLEACHATE CONCENTRATION LIMITSFOR NON-DEGRADING, NON-SORBING CONSTITUENTS FOR FOURWASTE MANAGEMENT SCENARIOS

Waste management HWIR Alter-scenario proposal nativeOptions

Landfill ...................... 1.0 0.71Surface Impoundment 0.22 0.27Waste Pile ................ 0.29 484Land Application Unit 0.08 0.22

Table 5 shows that, except forlandfills, the aggregate effect of thecombined alternative options is a lessconservative (higher) leachateconcentration limit. For landfills,adoption of the alternative modelingoptions would have resulted in a 30 %less stringent regulatory leachate limitfor the groundwater pathway for non-sorbing and non-degrading constituents.For surface impoundments, there islittle overall impact because theopposing effects of increasing theimpeding layer hydraulic conductivity,

and the alternative Monte Carloprocedure for handling parameterbound exceedances, nearly cancel out.For waste piles on the other hand, theprocedure used for the base case, resultsin a significantly more conservativeleachate concentration limit ascompared to the alternative modelingoptions. This is due to the handling ofparameter exceedances in the MonteCarlo simulation. Because many wastepiles have very small sizes (surfaceareas), the alternative Monte Carloprocedure has a large impact. For landapplication units, the procedures usedin the proposal for the base case alsoresult in a more conservative regulatorylimit as compared to the alternativemodeling options. The contributingfactors are much the same as for wastepiles, but the overall impact is muchsmaller, primarily because there areonly few land application units withvery small areas.

F. Additional Eco-ReceptorConsiderations

EPA considered two different policygoals with respect to protection ofterrestrial ecological receptors (i.e., soilfauna, birds, mammals, and plants). Onegoal protected terrestrial ecologicalreceptors outside the boundaries of thewaste management site, thus, theconstituent had to travel off-site beforeexposures would be assessed. Thealternative goal protected terrestrialecological receptors on the closed landapplication site.

The Agency chose to propose exitlevels based on off-site impacts forseveral reasons. One reason is that thereare many land use decisions thatsignificantly affect terrestrial ecologicalreceptors on the property of a partymaking those decisions (e.g., a decisionto pave a portion of land as a parkinglot). EPA does not generally regulatethose sort of decisions. However, manyimpacts are judged through local zoningregulations. Congress has typicallyasked EPA or other Federal entities toregulate activities on a property whenthere are significant off-site impacts,.such as a groundwater plume thatmigrates, an air Telease that movesbeyond the property, a wetland (locatedon the property) that is a significantresource for migratory birds and hasbroader ecological significance, or anendangered species with social valuesbeyond the impact on a specificlandowners purview.

EPA asks for comment, however, onthe alternative of protecting terrestrialecological receptors on-site. Therationale for this alternative approachwould relate to protection from impactson bird and mammal populations, and

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other ecological receptors, and to theregulation of certain constituents thatcould potentially result inenvironmental consequences that gosignificantly beyond the bounds of acurrent waste management unit.

G. Background Concentrations in Soilsand Other Issues Relating to Results

EPA has compared the exit levels fornonwastewaters to data on the variationin mean background concentrationsfound in soils. For some metals, the exitlevels calculated based on risks at landapplication units are below 4 mean soilconcentrations. One reason exit criteriamay be below soil concentrations is thatthese metals bioaccumulate, causinggreater exposure for higher trophiclevels. Also, the acceptable levels forsome of the metals that would becalculated for practices other than landapplication are significantly higher andnot below mean soil concentrations.

If the final exit levels are belowtypical soil levels, EPA would considerpromulgating levels based onconcentrations that are either typicalsoil concentrations (national meanlevels) or some percentile or portion ofthe naturally-occurring range such asthe 10th percentile. If the effect ofconcern is an ecological impact, therationale for using the loth percentile(or similar figure if the data availabledoes not allow that precision) would bethat in 90 percent of locations, if the soilalready contains those or greater levels,the ecological receptors existing in thearea should already reflect the toxicityof the waste material; the rational forusing the loth percentile (or similarvalue) value is that human behavioralpractices (e.g., treatment of groundwaterprior to use) may already reflectprotection from the potential toxicity ofconcern. EPA asks for comment onwhether these are reasonable arguments.

EPA is concerned, however, that thereare also issues of the chemical andphysical form in which compound orchemicals exist, in both naturalconditions and in the waste and that asimple comparison of totalconcentrations in soils and in wastesmight be misleading about potentialecological or human impacts. EPArequests comment on these issues.EPA's first preference will be toreexamine the risk modeling to identifyany inappropriate assumptions ormodeling issues that may explain thelow proposed exit level, and to lookmore carefully at those constituentswhere this issue only arises from the

4 When compared with mean soil backgroundlevels provided by the USGS, the exit levels are notmore that 1 order of magnitude more restrictive.

modeling of risks from land applicationunits, to identify potential contingentmanagement solutions to this problem.

Finally, EPA requests comment onwhether these arguments could beextended to site-specific determinationswhere information ori local backgroundconstituent concentrations and form insoil are available and have beenreviewed by a State regulatory authority.EPA assumes that such an approachwould only apply if the backgroundconcentrations were more than verylocalized and the concentrations werenaturally-occurring rather than due topast contamination. If a site-specificdetermination were adopted, twoapproaches are available that have beenused in other contexts. One statisticaltechnique for determining whetherbackground data conform to a normaldistribution assumption includescombining the Student-t difference ofmeans test, presented in the PermitGuidance Manual on Unsaturated ZoneMonitoring for Hazardous Waste LandTreatment Units, (EPA, 1986) with thenormal tolerance interval approachfound in Statistical Analysis of GroundWater at RCRA Facilities-Interim FinalGuidance, (EPA, April 1989). TheStudent-t test compares averaged waste/media concentrations to backgroundconcentrations, and is used to determineif the waste/media as a whole is withina specified criteria. However, even if thewaste/media passes the Student-t test,individual sample concentrations maystill exceed the tolerance interval limit.The normal tolerance interval approachis used to compare sampleconcentrations to an upper tolerancevalue based on the background mean,standard deviation, and sample size.

If such an approach is incorporatedinto the final rule, it would includecriteria for defining and collectingadequate background samples. Morespecifically, the facility would berequired to identify backgroundlocations, sample size, soil depth, etc.for at least four samples in a "differenceof means" demonstration, and six toeight samples for a "tolerance of means"demonstration. The facility would alsoneed to demonstrate the normalcy of thesample distribution. The Agency wouldrequire that this information beincluded as part of the facility'ssampling and analysis plan and subjectto review by the appropriate overseeingauthority.

A more simplified approach would beto establish exit levels at 1/1o of thenaturally occurring background level.The rationale for using 1/lo is that theselevels would not appreciably contributeto the overall risk posed by elevatedlevels in the environmental media. EPA

requests comment of this approach aswell as the rationale.

Alternatively, the rule could defer anybackground level demonstrations to anomnibus authority for the overseeingagency. Under this concept, a claimantcould submit information on naturallyoccurring background level and arequest for modified exit levels to theagency overseeing the exemptionprocess, which would have discretion togrant modifications where they areclearly justified. Comment is requestedon the need for this authority.

The Agency solicits comments onother appropriate and generic ways (1)to identify background levels in soils,and (2) to incorporate the existing 40CFR part 264, subpart F standards forestablishing background levels forgroundwater. Other suggestions thataddress the Agency's intent topromulgate a simplified exemption withlittle reliance on site-specificconsiderations but also allow forconsideration of elevated backgroundlevels will be considered.

EPA also observed that some of theexit levels for organic chemicals appearrelatively high (see, for example, thelevel for xylene). EPA believes thatthese results occurred primarily becausethese chemicals either are toxic only atrelatively high concentrations orundergo high dilution during transport.EPA, however, requests comment onwhether these chemicals are frequentlyco-disposed and, if so, whether theymight pose cumulative risks notassessed by thp risk analysis. EPA isinterested in information on issues suchas whether a waste containing one ormore of these constituents atconcentrations near exit levels would beignitable or threaten the integrity ofcontrol measures such as liners.

H. Constituents with Extrapolated Risk-based Levels

EPA was unable to conduct the riskassessment for 187 of the 376constituents on the exit list. In most ofthese cases, EPA was unable to findacceptable human health benchmarks toserve as the starting place for theassessment. In a few cases, EPA couldnot find values for critical physical orchemical properties, such as log Kows.Based on its past experience, EPAbelieves it would need at least a year todevelop a new human healthbenchmark value for any constituent.EPA has less experience with the typeof research and peer review needed todevelop values for physical andchemical properties, but it believes thatthis process also would be time-consuming.




Rather than not consider the 187constituents for which EPA was unableto conduct the risk assessment aspotential candidate constituents for exitcriteria, EPA developed an approach forestablishing exit criteria for theseconstituents. The Agency grouped theconstituents on the exit list into classes,based on chemical structure. EPAselected the 50th percentile value fromthe range of modeled risk levels for eachchemical class. This 50th percentilevalue serves as the extrapolated risk-based level for the un-modeledconstituents in the correspondingchemical class. The constituents andtheir 50th percentile extrapolated risk-based levels are presented in abackground document BackgroundDocument to Support the Methodologyused in Extrapolating Exit Levels toConstituents with no Health-BasedBenchmarks. EPA is proposing the 50thpercentile level to avoid adding anotherconservative assumption to thederivation of exit levels for theseconstituents. EPA believes that themultipathway approach is alreadysufficiently conservative to protecthuman health and the environmenteven for these chemicals. EPA, however,requests comment on the alternative ofusing the loth percentile or a differentpercentile from the modeled exit levelsfrom each class. Such an approachwould reduce the chances that theactual health benchmark for a particularlevel was lower than the extrapolatedestimate. However, it would alsoincrease the odds that the extrapolatedlevel was higher than needed for manyconstituents. A complete list ofextrapolated constituents and associatedrisk levels may be found in appendix Cto today's preamble.

EPA recognizes that this approach togenerating exit levels is much lesssophisticated and precise than themultipathway analysis. Nonetheless,EPA prefers it to any of the availablealternatives. If EPA set no exit levelsand made wastes containing any ofthese constituents ineligible for exit, asignificant number of waste streamswould probably be ineligible, eventhough they may pose no significantthreat to human health and theenvironment. EPA's RIA data shows thatsome of these constituents, such asCyanide and Anthracene, are fairlyprevalent. Although other constituents,such as those found in the commercialchemical products on the P and U listsof hazardous wastes, are not veryprevalent, they may be significant forgenerators that manage multiple wastestreams in centralized wastewatertreatment plants. In the absence of

extrapolated exit criteria, a generatorwould lose its opportunity to claim anexit for an entire combined stream if anyof these constituents is found in thewaste stream. Furthermore*, it wouldtake a long time to complete the worknecessary to conduct exposure pathwayassessments for any significant numberof these 187 constituents.

Alternatively, EPA could propose toallow wastes to exit without testing forconstituents lacking modeled exitlevels. EPA, however, finds thisapproach insufficiently protective,especially when it can at leastapproximate likely risk levels asdescribed above.

Finally, EPA considered thealternative of basing exit levels for theseconstituents on quantitation limits. Asexplained below, EPA is proposing touse EQCs as exit levels where they arehigher than a constituent'smultipathway or extrapolated exit level.(EPA is also proposing that wastes withsuch constituents meet the technology-based LDR standards for thoseconstituents prior to exit.) EPAconsidered using this EQC and LDRapproach for constituents lackingmultipathway levels. Such an approachwould actually produce moreconservative exit levels, because EPAwould not use extrapolated levels thatare higher than EQCs. EQCs (andtechnology-based LDRs), however, arenot based on risk. EPA prefers theextrapolated approach because it takesinto account the toxicity and fate andtransport of structurally similarchemicals. EPA believes it would beunreasonable to continue to regulate achemical because chemistry can detectit, where the extrapolation describedabove suggests that the chemical posesno significant risks at the EQC level.

EPA finds the option of basing exitlevels on the extrapolation proceduredescribed above to strike a reasonablebalance between the goals of protectinghuman health and the environment andeliminating regulation of low-riskwastes. EPA, however, requestscomment on all of the alternativesdescribed in this section.L Analytical Considerations

Some of the proposed exit levelsestablished by the risk assessment andthe extrapolation methodology are low.In some cases, existing analyticalmethods cannot routinely detect theconstituents at those levels. EPA isproposing to cap these potential exitlevels with reasonable analyticalquantitation limits. The Agency isproposing quantitation limits thatrepresent the lowest levels that can bereliably measured within acceptable

limits of precision and accuracy duringroutine laboratory operating conditionsusing appropriate methods. Theseconcentrations are referred to as"exemption quantitation criteria," orEQCs. It is necessary to specify EQCsbecause a number of the constituents onthe exemption list have either modeledor extrapolated risk-based levels that arenot analytically achievable in allmatrices. Appendix C to today'spreamble lays out the comparisonbetween the modeled or extrapolatedrisk level and the EQC for everyconstituent. Approximately one-quarterof the constituents have proposedmodeled or extrapolated risk-basedlevels lower than EQC.

1. Development of ExemptionQuantitation Criteria (EQC)

To develop the EQCs proposed intoday's notice, EPA compiled a masterlist of the quantitation limits publishedfor the identified constituents in theThird Edition of Test Methods forEvaluating Solid Waste, (SW-846),including the first and second updates(both of which are widely distributedthroughout the regulated community).The Agency believes that the resultantEQCs present achievable quantitationlimits for the proposed exemptionconstituents in most matrices. TheAgency requests comment on theproposed quantitation limits as well asany data supporting those comments.

A regulatory action level (e.g., exitlevels) must provide a clear distinctionbetween those wastes subject to theregulation and those excluded. Actionlevels based on analyticaldeterminations within a methodsquantitative range can be used todetermine regulatory status with a highdegree of confidence. On the otherhand, when an analyte is present at aconcentration equal to the detectionlimit (DL) it will be detected only halfthe time. In other words there is a 50%risk of a false negative result when theanalyte is present at the DLconcentration. There is, however, a lessthan 1% risk of false positive results atthis level. Therefore, regulations set atthe detection limit would not identifynon-compliance reliably.

The Agency is in the process of re-evaluating EQCs for some constituents.Preliminary updated EQCs could not beincorporated into today's proposed rule,but have been included in the docket forcomment.

2. EQCs and LDR Requirements as ExitLevels

A comparison of the modeled orextrapolated risk-based levels with theEQCs reveals a number of cases where

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quantitative measurement of analyteconcentration at the modeled orextrapolated risk-based level cannot bereliably achieved, using standardizedanalytical methods. In today's proposedrule, for wastes containing constituentswith a modeled or extrapolated risk-based level lower than the EQC, exitcriteria include meeting the EQC alongwith an additional requirement that thewaste meet Land Disposal Restrictions(LDR) treatment standards from part268, regardless of whether or not thewaste is to be land disposed. The exittable for constituents with EQCs as exitlevels is proposed appendix X of 40 CFRpart 261, Table B..

a. EQCs as exit levels

Only when the comparison betweenthe modeled or extrapolated risk-basedlevel with that constituent's EQC levelreveals that the constituent cannot bequantitated at the modeled orextrapolated risk-based level, does theEQC become the exit level. For example,the modeled risk-based level for 2-nitropropane in wastewaters is 0.00019jig/L. The EQC for 2-nitropropane inwastewaters is 0.0058 jIg/L. 2-nitropropane is listed in appendix X,Table B, with an exemption level of0.0058 gg/L. In other words, theexemption level for 2-nitropropane hasbeen met if the claimant demonstratesthat the method used can achieve theEQC of 0.0058 tig/L in the waste matrix,and the level detected by the methoddoes not exceed 0.0058 gg/L.

The Agency believes that, for thoseconstituents that have a modeled orextrapolated risk-based level lower thanthe achievable quantitation limit,demonstration that the constituent isnot present above the EQC is the mostreasonable approach to setting anational exemption level. The Agency isproposing that quantitation limits capthe modeled or extrapolated risk-basedlevels because a reliable, consistentmeasure of the constituent below thequantitation limit is not achievable. Byestablishing EQCs as benchmarks (ormaximum allowable quantitationlimits), the Agency is ensuring that allexemption demonstrations will achieveacceptable analytical sensitivity, andthat wastes with high levels ofcontamination that tend to confoundanalytical protocols are not exempted.

The Agency requests comments onwhether an exemption demonstrationshould be considered adequate if allproper method selection and QCprocedures are followed and theconstituents are not detected, eventhough the EQC level has not beenanalytically attained. This situationcould arise even in relatively clean

matrices if the constituents bindstrongly to the matrix or if theconstituents degrade rapidly during theanalysis. However, the Agency wouldnot want the exemption to be allowedif the EQC could not be achievedbecause of interference from othercontaminants in the matrix, or ifinappropriate methodology, i.e., samplepreparation, cleanup (if necessary), ordeterminative, was used.

EPA is not proposing that any exitlevel based on an EQC can serve as a"minimize threat" level capping current40 CFR part 268 treatment standards.Such levels are not sufficiently relatedto a constituent's risk.

b. LDR Requirements for ConstituentsWith EQC Exit Levels

EPA considered the option of settingexit levels for all constituents at theirmodeled or extrapolated levels,regardless of analytical considerations.EPA also considered the alternative ofmaking wastes containing constituentswith analytical limitations ineligible forexit. Both of these options, however, arelikely to constrain significantly thenumber of waste streams eligible forexit. Approximately one-quarter of theconstituents on the exit list have EQCsabove risk-based or extrapolated levels.Some of these constituents, such asBeryllium and Arsenic, are fairlyprevalent. For less prevalentconstituents, EPA has the sameconcerns about limiting exit for wastesmanaged in centralized wastewatertreatment systems that it describedabove in the section on extrapolated risklevels. Further, this approach wouldoverregulate wastes where constituentswere in fact below risk levels. EPAprefers options which would notprohibit all wastes with theseconstituents from exiting.

The most promising alternative EPAfound was setting exit levels for theseconstituents at EQC levels, and alsorequiring all wastes containing theseconstituents to comply with LDRtreatment standards, even where suchwaste are not destined for land disposal.This alternative offers the possibility ofadditional risk reductions and,therefore, reduces the possibility thatwastes posing significant threats willescape Subtitle C control.

EPA is unable to characterize theamount of additional risk reduction fora number of reasons. First, as explainedin more detail in the Minimize Threatsection of the preamble, compliancewith LDRs already will be required afterexit before land disposal for all wastes(except those that are below exit levelsat their point of generation). The LDRrequirement for constituents with EQC

exit levels may provide additional riskreduction, even for those constituentsthat are not managed in land disposalunits. EPA currently does not know howfrequently nonhazardous wastes areburned as fuel, incinerated, or otherwisemanaged outside of land disposal.

Additionally, the Universal TreatmentStandards (UTS) for nonwastewaters,were developed based on similaranalytical chemistry considerations ofdetection limits. The majority of theUTS limits for nonwastewaters werebased, however, on analysis of residualsfrom the treatment of what EPAdetermined to be the most difficult totreat wastes and, as a result, this oftenrepresented the most difficult to analyzetreated matrix (i.e., higher detectionlimits than those represented by theEQCs). The majority of the UTS limitsfor wastewaters, on the other hand, werenot developed based on limits ofdetection but rather they were based onanalysis of treated effluents regulatedunder EPA's National PollutionDischarge Elimination System (NPDES).

LDR requirements for all wastessubject to the UTS would be equal to orhigher than the EQC exit levelsthemselves. However, for wastes subjectto treatment standards based onapplication of specified treatmentmethods under § 268.40, extending LDRrequirements may provide additionalrisk reduction.

EPA believes that the combinedapproach of requiring non-detection atEQC levels and compliance with LDRstandards for all waste streams,regardless of whether or not the wastewill be land disposal, offers a reasonablebalance between the goals of reducingoverregulation and ensuring that wasteswith significant risks remain subject toSubtitle C. EPA, however, requestscomment on all of the alternativesdescribed above. EPA also requestscomment on the option of basing exitlevels for these constituents on EQCsalone and relying on continued,independent applicability of LDRrequirements for wastes that exit and aredestined for land disposal.

3. Exemption for Constituents WithoutEQCs

There are several constituents coveredin today's notice for which EQCs couldnot be developed. The universe of theseconstituents includes 78 constituents,most of which are not widely prevalentin wastes. Most are also found only inP and U listed wastes. Theseconstituents are listed in table B toappendix X without associatedexemption levels. The backgrounddocument Background Document toSupport the Development of Exemption




Quantitation Criteria (EQCs) andDescription of Analytical Methodsunder the Waste Exit Rule explains whyEQCs could not be created.

EPA is proposing that wastescontaining these constituents (i.e.,where an applicant has not documentedthat these constituents are not present-see section VIII.A.l.b.,) may remaineligible for an exemption under today'sproposed rule by complying fully withLDR treatment standards applicable tothe waste, as codified in 40 CFR part268, regardless of whether the waste isto be land disposed. The Agencybelieves that any potential risks posedby these constituents are likely to befurther reduced by applying LDRstandards froln part 268 to the waste,before the waste may be exempt,regardless of whether or not the wasteis destined for land disposal. TheAgency asks for comment on thisapproach.

An alternative approach would be toallow wastes with these constituents toexit without additional LDR obligations,but relying on continued, independentapplicability of LDR treatmentrequirements to wastes destined for landdisposal only. Another approach wouldbe to prohibit wastes containing theseconstituents from being eligible forexemption under today's proposed rule.An additional approach would be thatthese constituents could be deleted fromthe exit table. The Agency requestscomment on each of these alternatives.

EPA is not willing to propose to useLDR standards as exit levels for anyother group of constituents. Thetechnology-based LDR standards are notbased on any risk assessment. Acomparison of these standards with themultipathway risk levels that EPAproduced shows that the LDR standardsare sometimes more stringent andsometimes less stringent than risk-basedlevels. EPA believes that it is moreprudent to base exit levels on riskassessment where possible because thisbetter assures protection of humanhealth and the environment. EPA viewsuse of the LDR standards as the optionof least preference, but necessary forexit for this group of constituents. EPAis willing to consider it only wherethere is no alternative to prohibiting aconstituent from being eligible for exit.

V. Presentation of Exit LevelsToday's proposed exemption criteria

involves setting exemption levels fortoxicants in listed waste, and in somecases requiring additional compliancewith the requirements set forth at 40CFR part 268. To exit Subtitle Cregulation as a listed hazardous waste,all the hazardous constituents listed in

appendix X of part 261 would berequired to be in concentrations lessthan or equal to the numeric exit levelsand when specified, the waste wouldhave to meet the applicablerequirements at 40 CFR part 268.Appendix C to the preamble presentsconstituents, distinguishes betweenmodeled and extrapolated constituents,and includes EQCs for each constituent.

A. Constituents With Modeled orExtrapolated Risk-Based Exit Levels

The Table A of proposed appendix Xto part 261 presents exit levels forconstituents with modeled orextrapolated risk-based levels which canbe reliably quantified. See section IV.H.for a description of how this wasdetermined. Listed hazardous wastewould be required to containconcentrations at or below the specifiedexit levels to be eligible to be exemptedfrom Subtitle C requirements other thanLDR. In some cases we are proposing tochange the land disposal restrictionrequirements at 40 CFR part 268 as well.A totals analysis would be required forboth wastewaters andnonwastewatersto show that the constituent does notexist in the wastestream at levels abovethe exemption level.

For nonwastewaters, the Agency isalso proposing that generators either usethe TCLP test or a calculational screento measure or calculate constituents'leachate from wastes. If the TCLP testshows leachate concentration in thewaste is below the leach exit level, thewaste would be considered to not posea hazard to groundwater.

The Agency has in the pastexperienced difficulty in using theTCLP test for some types of waste. TheAgency solicits comment on how toconsider oily wastes and other wastesthat are difficult to filter in the TCLPtest or whose impact on groundwater isbelieved to be underestimated by theTCLP (such as matbrials subject to non-aqueous phase transport). Comment onalternative tests for these wastes, as wellas comment on how to define suchwastes for regulatory purposes is sought.A more complete discussion of oilywaste can be found in VIII.A.l.a.iv.

Table A of appendix X of 40 CFR part261 presents results of two alternativesfor establishing the exit levels. Thesealternatives differ only in thebenchmark used to calculate themodeled risk-based levels. For certainconstituents there exists both a risk-based toxicity benchmark and amaximum concentration level (MCL)established under the Safe DrinkingWater Act (SDWA). These numbers maydiffer because the MCLs are establishedusing some non-risk considerations

such as the cost of treatment and theavailability of technology and considerexposure contributions from othersources for non-carcinogens. See sectionIV.D. of today's proposal for a completediscussion of toxicity benchmarks andMCLs.

B. Constituents With Quantitation-Based Exit Levels; Table B to AppendixX

Table B of proposed appendix X topart 261 presents quantitation-basedexit levels for constituents withmethods that cannot reliably quantifythe modeled or extrapolated risk-basedlevels. All exit levels on Table B ofappendix X to 40 CFR part 261 arebased on EQCs. (See section IV.I.)Wastes containing any of theseconstituents must also comply with theapplicable treatment standards set forthat 40 CFR part 268, the Land DisposalRestrictions (LDR) in order to meettoday's proposed exemption, regardlessof whether or not the waste is to be landdisposed.

Some constituents on Table B ofappendix X of 40 CFR part 261 do nothave associated exit levels. Waste withthese constituents may exit only aftercomplying with the LDR treatmentstandards for the waste. (See sectionIV.I.2.b.)C. How To Read the Exit Level Tables

For a waste to be eligible to exitSubtitle C under the exit proposed intoday's rulemaking, every constituent inthe waste must be below its exit level.Proposed appendix X of 40 CFR part261, Tables A and B are the exitconstituents and the exit levels. Thefollowing is a description of how to readthe tables.

e The constituent list is derived fromconstituents listed in appendix VII,Basis for Listing Hazardous Waste;Appendix VIII, Hazardous Constituents;and appendix IX of part 264, theGround-Water Monitoring List. (Seesection IV.C.)

• Table A represents constituents andtheir risk exit values-where the riskvalues can be measured analytically.(See sections IV.E., and IV.I.)

* Table B represents constituentswith quantitation limits (EQCs) as exitlevels-where the constituent cannot bemeasured at the modeled orextrapolated risk value., An additionalcondition of exit, compliance withtreatment standards in 40 CFR part 268,exists for any waste becoming exemptunder today's rulemaking by using aconstituent exit level on Table B. (Seesection IV.I.2.b.)

* There will be overlap for someconstituents between Tables A & B. For

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example, the wastewater exit level for aconstituent may be on Table A, whereasthe nonwastewater exit level may be onTable B.

* Where an exit level does not existon Table A or B for a particularconstituent, the waste need not be testedfor that constifuent. For example, someconstituents that are hydrolyzers haveexit levels for nonwastewaters, but notfor wastewaters. A complete discussionof deletions to the master constituentlist can be found in section IV.C.

The tables' columns:* Columns I and 2 are the CAS

numbers & constituent names.* There are two proposed options for

the development of today's proposedexit levels. Option I is the optionwhereby Maximum Contaminant Levels(MCLs) from the Drinking Waterprogram are used as an acceptabletoxicity exposure for human drinkingwater exposure and toxicity benchmarksare used for other exposures. Option 2is the option whereby toxicitybenchmarks are used as acceptableexposure levels for all exposures. Amore complete discussion of these twooptions is found in section IV.D. oftoday's proposed rule. The effect of co-proposing these two options is thatthere are two independent sets ofproposed exit levels.-Columns 3, 4, and 5 represent the exit

levels that were derived by using anMCL benchmark for drinking wateringestion & using toxicity benchmarksfor all other routes of exposure.

-Columns 6, 7, and 8 represent the exitlevels that were derived by usingtoxicity benchmarks for all routes ofexposure.* The definitions of wastewater and

nonwastewater are discussed inVIII.A.l.a.ii.

* Columns 3 & 6 representwastewater exit values. If a generator'determines he/she has a wastewater, ifeach constituent in the waste meetsthese wastewater exit levels, it iseligible for exemption.-Values in columns 3 & 6 were derived

from the most limiting of non-groundwater-ecological receptor, non-groundwater-human receptor, andgroundwater pathway values fromsurface impoundments and tanks (therisk assessment's wastewater units).e Columns (4 and 5) and (7 and 8)

represent nonwastewater exit values. Ifa generator determines he/she has anon-wastewater, if each constituent inthe waste meets both of thesenonwastewater values, it is eligible forexemption. The totals level must be metby a totals analysis. The leach level

must be met by a TCLP test or thecalculational screen.-Values in columns 4 & 7 were derived

from the most limiting of the non-groundwater-ecological receptor andnon-groundwater-human receptorpathway values from land applicationunits, ash monofills, and waste piles(the risk assessment's nonwastewaterunits).

-Values in columns 5 & 8 were derivedfrom the most limiting of thegroundwater pathway values fromland application units, landfills, andwaste piles (the risk assessment'snonwastewater units).

VI. Minimize Threat Levels

A. Background

1. Summary of the Hazardous and SolidWaste Amendments of 1984

The Hazardous and Solid WasteAmendments (HSWA), enacted onNovember 8, 1984, allow hazardouswastes to be land disposed of only ifthey satisfy either of two conditions: (1)They can either be treated or otherwisesatisfy the requirements of section3004(m), which requires EPA to, setlevels or methods of treatment, if any,which substantially diminish thetoxicity of the water or substantiallyreduce the likelihood of migration ofhazardous constituents from the waterso that short term and long term threatsto human health and the environmentare minimized; or (2) they can be landdisposed in units satisfying the so-called no migration standards in'sections 3004(d)(1), (e)(1), and (g)(5).Land disposal includes any placementof hazardous waste in a landfill, surfaceimpoundment, water pile, injectionwell, land treatment facility, salt domeformation, underground mine or cave.See RCRA section 3004(k).

EPA was required to promulgate landdisposal prohibitions and treatmentsstandards by May 8, 1990 for all wastesthat were either listed or identifiedhazardous at the time of the 1984amendments, a task EPA completedwithin the statutory time frames. SeeRCRA section 3004(d), (e), and (g). EPAis also required to promulgateprohibitions and treatment standards forwastes identified or listed after the dateof the 1984 amendments within sixmonths after the listing or identificationtakes effect. See RCRA section306f4(g)(4).

The land disposal restrictions areeffective on promulgation. See RCRAsection 3004(h)(1). However, theAdministrator may grant a nationalcapacity variance from the effective dateand establish a later effective date (notto exceed two years) based on the

earliest date on which adequatealternative treatment, recovery, ordisposal capacity that protects humanhealth and the environment will beavailable. (RCRA section 3004(h)(2).)The Administrator may also grant acase-by-case extension of the effectivedate for up to one year, renewable oncefor up to one additional year when anapplicant(s) successfully makes certaindemonstrations. (RCRA section3004(h)(3).) See 55 FR 22526 (June 1,1990) for a more detailed discussion onnational capacity variances and case-by-case extensions.

As explained in the legislativehistory, the purpose of the land disposalrestrictions is to reduce the risksassociated with land disposal. Congressalso intended the restrictions to reducereliance on land disposal and promotewaste minimization since land disposalwas its least favored method ofmanaging hazardous wastes.

2. EPA's Interpretation of Standard forTreatment Requirements

The heart of the LDRs are thestandards for treatment prior to landdisposal, which must meet the statutoryrequirement to "substantially diminishthe toxicity of the water or substantially,reduce the toxicity of the waste so thatshort term and long term threats tohuman health and the environment areminimized." RCRA Section 3004(m):EPA's interpretation of this "minimizethreat" requirement has evolvedthrough a long series of rulemakings.

When EPA proposed its first set ofLDR treatment standards it took theposition that the most effective way tominimize threats was to base standardson the capabilities of generally availabletreatment technologies. (51 FR 16011(January 14, 1986).) To avoidunnecessary treatment, however, EPAalso proposed to "cap" the technologybased standards with risk-basedscreening levels based on human healthtoxicity thresholds for individualhazardous constituents and modeling ofthe groundwater route for exposure. (51FR 16011-13.)

In the final rule EPA promulgatedonly the technology based standards.EPA explained that although it believedit had authority to promulgate risk-based standards, it was notpromulgating the proposed risk-basedcaps because of extensive commentsraising concerns about the scientificuncertainties of risk analysis. (52 FR40578 (November 7, 1986).) Industrychallenged the final standards, claimingthat they required treatment toconcentrations below "minimize threat"levels. On review, the Court held thatsection 3004(m) authorized both




technology based and risk-basedstandards, but remanded the rule to EPAfor a fuller explanation of its decision torely on technology-based standardsalone. (Hazardous Waste TreatmentCouncil v. EPA, 886 F. 2d 355 (D.C.Circ. 1989). ("HWTC III).) The courtalso held that EPA was not obligated toadopt either the RCRA characteristic testlevels or the Safe Drinking Water ActMaximum Contaminant levels (MCLs)as "minimize threat" levels becauseneither "purports to establish a level atwhich safety is assured or 'threats tohuman health and the environment areminimized'." (886 F. 2d at 363.)

In its response to the remand, EPAstated that the best way to fulfill therequirements of section 3004(m) wouldbe to ensure that no technology-basedtreatment standard required treatment ofhazardous waste containing levels ofhazardous constituents posinginsignificant risks. (55 FR 6641 (Feb. 26,1990).) EPA, however, explained that itwas not yet able to promulgate suchlevels. EPA believed that it lacked areliable predictive model for ground-water exposure, needed to assessexposure scenarios for air pathways,needed to consider impacts onecological receptors, needed to developadditional analytic methods forhazardous constituents, and needed todevelop an approach for constituentswith threshold effect levels lower thandetection limits. (Id. at 6642.)

In the same notice, EPA noted that the"minimize threat" language of section3004(m) could reasonably be interpretedto require more protection than the"normal subtitle C command thatstandards be those necessary to protecthuman health and the environment."(Id. at 6641.) EPA found that the manyportions of the 1984 amendmentsstressing the inherent uncertainties ofland disposal buttressed thisinterpretation. See, e.g., RCRA sections1002(b)(7), 3004(d)(1)(A), 3004(e)(i)(A),3004(g)(5). EPA also found support inthe legislative history. For example, theSenate amendment containing the"minimize threat" standards replaced acommittee bill that only would haverequired treatment to be "protective ofhuman health and the environment."See S. 757, section 3004(b)(7), printed atS. Pep. No. 284, 98th Cong., 2nd Session86. Further, EPA noted that the "nothreat" levels it had been using in site-specific and waste stream specificcontexts, such as clean closures,delistings, and no-migration petitions,*ould not necessarily be appropriate forgenerally applicable standards requiredto minimize threats to health and theenvironment. (55 FR 6641, note 1.)

At the same time, EPA took theposition that section 30004(m) does notrequire the elimination of everyconceivable threat posed by landdisposal of hazardous waste, citing astatement by Senator Chafee that "lilt isnot intended that every waste receiverepetitive levels of treatment, nor mustall inorganic constituents be reclaimed."130 Cong. Rec. S.9179 (daily ed., July25, 1984). (55 FR 6641, note 1.) ClearlyEPA did not interpret the minimizethreat language to require theelimination of all threats.

Today, the Agency is proposing to re-evaluate the basis for some of theexisting performance standardsestablished for listed wastes. SinceEPA's response to the HWTC III remandin 1990, the state-of-the-art in makingquantitative determinations of risk hasadvanced and available methods haveimproved significantly. In addition, theincreased sensitivity of analyticalmethods has lowered achievabledetection limits, better bioassays existthan in the past, and more extensivebiological data is available forextrapolation. As a result, the universeof available health-based and ecologicaldata has grown significantly, and thereliability of this information hasimproved. The Agency now believesthat these data can be used to establishlevels that minimize threats to humanhealth and the environment.

B. Risk Assessment and MinimizeThreat Levels

1. Rationale

a. OverviewToday the Agency is proposing to

establish risk-based LDR treatmentrequirements for some of the hazardousconstituents for which exit levels arebeing proposed. These risk-based LDRrequirements will minimize the short-term and long-term threats to humanhealth and the environment posed bythe hazardous waste constituents. Therisk-based LDR levels (or "minimizethreat" levels) would have the effect ofcapping, or limiting, treatment of thosewaste constituents where the currenttechnology-based UTS standards requirelower concentrations. EPA also hoped topropose most of these constituent-specific levels as "minimize threat"levels under section 3004(m) of RCRAthat would cap current technology-based treatment standards under atthese levels the LDR program. However,EPA is proposing "minimize threat"levels only for those constituents thatwere evaluated under the multipathwayrisk analysis and are not capped byquantitation (EQC) limitations. EPA isproposing to promulgate such levels as

replacements for the constituent-specific treatment levels in the LDRUniversal Treatment Standards (UTS).(As explained in more detail in SectionVI, EPA is not proposing to cap any LDRstandards requiring the use of specifiedtechnologies.) As shown on Table 1,§ 268.60, EPA is proposing "minimizethreat" levels to cap UTS treatmentrequirements for either the wastewateror nonwastewater (or both) forapproximately 70 wastewaterconstituents and 90 nonwastewaterconstituents.

EPA, however, is not proposing thatany extrapolated levels serve as"minimize threat" levels for LDRpurposes. EPA does not have as muchconfidence that this alternativemethodology provides enoughinformation on risks to human healthand the environment to enable EPA todetermine that risks have beenminimized. Similarly, EPA is notproposing that any levels based onquantitation limits serve as "minimizethreat" levels. Such levels are not basedon any analysis of risks to human healthand the environment. In fact, asexplained above, EPA is proposing torequire compliance with technology-based LDR standards for all wasteswhich contain such constituents.

If a claimant finds that allconstituents in a waste are below exitlevels at the waste's point of generationand if the claimant meets all of therequirements for filing an exit claim,EPA will not require compliance withthe LDR treatment standards for thewaste. EPA will take the position thatsuch as waste never became subject tosubtitle C regulations, so that LDRstandards never applied to the waste.EPA is proposing to take this positionfor all exit levels, regardless of whetherthey were generated by themultipathway analysis, thextrapolation method, or EQC

limitations. For further explanation, seesection VI.D.

EPA, however, is proposing that alllisted wastes which as generatedcontain constituents exceeding exitlevels must meet LDR requirements(current or as modified by thisproposal), even if the wastesubsequently becomes exempt fromhazardous waste regulation under thisrule. This requirement resembles EPA'scurrent rules for "de-characterized"wastes, which must meet LDRrequirements even after they cease toexhibit the hazardous characteristic thatmade them subject to Subtitle C in thefirst place.

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b. "Minimize Threat" requirement ofSection 3004(m)

EPA continues to believe that theminimize threat language of section3004(m) does not require theelimination of every conceivable threatposed by land disposal of a hazardouswaste. The legislative history of LDRindicates that Congress did not intend torequire wastes to undergo repetitive orultimate levels of treatment. Rather,Congress wanted to require use ofeffective, but widely available treatmenttechnologies. See 130 Cong. Rec. S 9178(daily ed. July 25, 1984) (statement ofSenator Chafee introducing theamendment that became section3004(m).)). Requiring elimination of allconceivable threats would almostcertainly require use of the mosteffective treatment methods available,and this appears to conflict withCongresses' treatment goals. Moreover,although the DC Circuit has cited thedictionary definition of "minimize" touphold technology-based treatmentstandards below EPA standards such asMCLs and TC levels, EPA doestotbelieve that the court meant that EPAliterally must reduce threats to themaximum extent possible. (SeeHazardous Waste Treatment Council III,886 F.2d at 361; Chemical WasteManagement II, 976 F 2d. at 14.) EPAnotes that the court indicated that risk-based treatment standards would satisfysection 30004(m). Hazdrdous WasteTreatment Council III, 866 F.Zd at 364-65. Further, in his concurring opinion,Judge Silberman stated that Congresswould allow EPA to exercise reasonableamounts of discretion in determiningthe level of risk reduction needed tomeet the minimize threat requirement.Id. at 372.

The Agency believes that today's exitconcentrations can serve as risk-basedland disposal restriction levels forseveral reasons. First, the riskassessment, described in Section IV oftoday's proposal, significantly expandsbeyond the scope of past Agency riskassessment for wastes and wasteconstituents. Where adequate data areavailable, the analysis can evaluate thepotential for waste constituentmigration through almost all significantenvironmental fate and transportpathways leading to exposure forhuman and ecological receptors. Asexplained in more detail below, theAgency is also relying on reasonableconservative risk targets for bothhumans and ecological receptors indeveloping this risk assessment. TheAgency believes that the proposed exitlevels represent levels below Whichfurther treatment would not be needed

to minimize threats to human health,and the environment.

c. Scope of Risk AssessmentThe broad scope of the risk analysis

is a critical factor in the Agency'sconclusion that proposed exit levelsminimize both short term and long-termthreats to human health and theenvironment, for those constituentswhere data are relativel complete.

The risk analysis eva luates all of themost common non-Subtitle C disposaloptions available to waste generatorsand treaters. These include disposal inlandfills/monofills and by land farming,and management in surfaceimpoundments, tanks and waste piles.The risk analysis assumes no minimumlevel of regulation of these facilities, andrelies on available data to characterizethem. As described in detail in SectionIV and in the risk analysis report (EPA1995), EPA modeled each disposalalternative using median values for mostinputs, and high-end or conservativevalues for the two fate and transport andtwo exposure parameters for which themodeling outcome is most sensitive:The Agency believes that the modelingwill also protect against exposures fromsimilar disposal- alternatives notspecifically modeled.

The risk analysis evaluates themovement of waste constituents fromeach of these disposal options throughnumerous environmental fate andtransport pathways. These includepathways involving volatiles andrespirable (PM10) particulates,particulate deposition on soil and plantsurfaces, vapor phase diffusion intosurface water and plants, and surfacerun-off and soil erosion. Many of thesepathways can result in wasteconstituent movement through the food-chains. Therefore, human exppsuresresulting from these fate and transportpathways include inhalation, soil orgroundwater ingestion, and dermalcontact, as well as exposure throughconsumption of contaminated foodssuch as fish, beef or vegetables.

EPA screened all multipathwayconstituents for potential to pose threatsto ecological receptors. For 45constituents, EPA quantitativelyassessed likely risk to selectedecological receptors. Risks to both freshwater aquatic and terrestrial organismswere evaluated, representing differenttrophic levels and feeding habits of theecosystem. Fish, daphnids, and benthicorganisms, mammals, birds, plants, andsoil organisms (nematodes, insects,.etc.)were evaluated. The sustainability of theecosystem and reproducing populationswithin the aquatic and terrestrialecosystems was selected as an

assessment endpoint, as described inSection IV of this Notice and in detailin Chapter 3 of the risk analysis supportdocument (EPA 1995).

In addition, as part of this overall riskassessment effort, the Agency hasreviewed and reevaluated its modelingof waste and waste constituentmovement through groundwater. Asdescribed in Section IV above, thisresponds to comments by interestedparties on the original HWIR proposal,as well as incorporates additional datasubmitted to the Agency (API data base),and updated modeling of leaching fromwastes (new HELP model; get Cite).

In evaluating groundwater, theAgency examined both wells located onthe landfill edge and closest wellsanywhere down-gradient. Also, bothfinite source type and infinite-sourcetype constituents (which behave asthough there is an infinite supply of theconstituent in the landfill, and willcontinue to leach forever) wereevaluated. For finite source typeconstituents, the available constituentwas not apportioned over thegroundwater and other pathways, i.e.,groundwater was modeled separately.Adsorption to soil and degradation ofwaste constituents (but notbiodegradation) is modeled, and thetoxicity of constituent daughterproducts (either more or less toxic thanthe parent compounds) is included.(There is a biodegradation module to themodel; however, data to run thatmodule for national conditions are notadequate at this time, although datawere available for some sites. TheAgency will continue to evaluatebiodegradation data as they becomeavailable, and assess in the futurewhether national biodegradationestimates can be defensibly made).Leaching and groundwater migrationfrom disposal in unregulated industriallandfills, surface impoundments, andwaste piles have been modeled.

In evaluating the results of this seriesof groundwater modeling exercises, theAgency selected the approximate 90thpercentile from a distribution of wellsclosest to modelled sites. This meansthat there is about a 90% probabilitythat the drinking water well closest tothe landfill would be protected at thetarget concentration (MCL or HBNj. Allwells more distant would be protectedto a greater extent.

As described in section VI.E. above,the Agency then reviewed the riskassessment for groundwater and thepathways for each constituent, andselected as the exit level theconcentration, back-calculated to thewaste, from the most limiting (or highestrisk) pathway. By using the most




limiting pathway as the basis for the riskcriterion, the Agency believes it hasaccounted for all significant risksresulting from disposal andmanagement of the waste outside ofSubtitle C.

The agency believes it is alsoimportant to identify and discuss someof the limitations of the risk assessment,especially as they relate to determiningwhether short term and long-termthreats to human health and theenvironment have been minimized.

The analysis does not account foradditivity of risk for exposure tomultiple constituents. Evaluation of riskadditivity can be a complex analysiswhen even a few constituents areincluded. In the case of multiple wasteconstituents, potentially occurring inone or more waste streams that might beconsidered for exit, the complexity ofconducting and analysis of additivity ofrisk quickly becomes overwhelming.However, EPA believes it will often bethe case that one constituent typicallydrives determinations of whether wastestreams exit and additivity would oftenmake little difference with respect to thecalculated exit levels.

Exposures to the same constituentfrom several pathways also are notadded together, even though the riskanalysis does apportion the availablequantity of waste constituents over thedifferent pathways evaluated. Again,EPA believes that often one result (inthis case, one pathway) wouldcontribute most of the risk and littlewould be gained from adding acrosspathways. EPA requests comment onthis issue.

Data also were not available for allhuman exposure routes for allconstituents, although data for high-riskpathways were usually available.Nonetheless, the Agency believes theexit levels can be considered torepresent levels that minimize threats tohuman health and the environmentbecauseof the comprehensiveevaluation of possible exposure routes,consideration of both human andecologic risk, selection of the mostrestrictive pathway overall, and therelatively conservative risk target, 10-6,used in setting the exit levels derivedfrom cancer risk estimates.

As mentioned above, EPA conducteda screening analysis to identify 47 highpriority constituents for ecologicalassessment. EPA did not model theecological impacts for 36 additionalconstituents that displayed onecharacteristic indicating potentialecological impacts. EPA is proposing toset minimize threat levels for 19 of theseconstituents.

EPA believes that it has adequatelyassured that the caps to BDAT treatmentstandards proposed today minimizethreats to the environment. The specificecological risk assessment conducted for45 constituents (19 of which haveminimize threat levels under thisproposal) is the most extensive EPA hasever conducted under the RCRAprogram to date. EPA did not findthreshold effects data for all sevengroups of ecological receptors for anyconstituent evaluated for ecologicalrisks. Rather, EPA typically hadbenchmarks for three to five groups.Nevertheless, its consideration of abroad range of species and use ofreasonably conservative endpointsensures that threats to ecologicalreceptors are minimized.

With regard to chemicals that did notundergo this detailed assessment, EPAhas conducted an extensive review ofrisks to human health, including athorough review of risks posed byindirect pathways and risks posed byconstituents that bioaccumulate inplants and animals consumed byhumans. (Bioaccumulation is a keyconcern for protection of manyecological species.) EPA believes that itis reasonable to assume that the exitlevels identified by this analysis alsominimize threats to ecological receptorsunless it has some definite dataindicating that additional protection iswarranted. Reliance on these levels isparticularly appropriate for thosechemicals that did not display one ofEPA's ecological screeningcharacteristics. EPA finds it alsoappropriate for the 15 "minimizethreat" chemicals which exhibited oneecological screening characteristic. EPAacknowledges that conducting a specificassessment of ecological risks for these15 constituents would have providedadditional assurance that threat toecological receptors were minimized.EPA solicits comment on the option ofdeclining to set minimize threat levelsfor these 15 constituents until it cancomplete an ecological assessment forthem.

d. Risk Targets Minimize Threats

The Agency believes that the risktargets used in the risk analysis to backcalculate to waste concentrationsminimize threats to human health andthe environment. For cancer risks tohuman, a risk target of one in onemillion, over a lifetime is the risk target.For non-carcinogens, a hazard quotient(HQ) based on a reference dose or othercomparable value from the literaturecould not exceed one (hazard quotient(HQ)=I). Reference doses or comparablevalues are based on studies of toxicity

and no-effect levels in test animals andextrapolated, using safety factors, tohumans. For ecological receptorspopulation effects inferred fromindividual effects and effects on asubstantial number of both aquatic andterrestrial species were evaluated.

Other risk targets may be consideredin establishing minimize threat levels.The Agency solicits comment onwhether apportionment of the RfD oughtto be used in establishing minimizethreat levels (i.e., HQ<1). The Agencyuses 20% of the Rfd in setting drinkingwater standards; a similar approachmight be appropriate in establishingminimize threat levels and inestablishing exit levels. EPA requestscomment on this issue.

2. Public Policy ConsiderationsFinally, the Agency believes that it

represents good public policy to reduceor eliminate unneeded or duplicativeregulatory requirements. In this case,the Agency believes that for the initiallist of constituents listed in Table 1 of40 CFR 268.60, treatment to the UTS/LDR standard is no longer requiredbeyond waste constituentconcentrations where risks to humanhealth and the environment areinsignificant. Because there is nopurpose in terms of protecting humanhealth and the environment forretaining the more stringent LDRrequirements, the Agency is proposingto revise them to the risk-based levels.This would reduce the overall numberof different and distinct regulatoryrequirements on waste generators andtreaters, would rationalize the RCRAregulations, and will provide significantpollution prevention opportunities andincentives. Waste generators wouldhave only one target level to direct theirpollution prevention effort toward. Ifgenerators met the LDR/exit levels, thewaste would not be consideredhazardous, and no additional treatmentwould be required before disposal in asubtitle D facility. Where wastecontinues to exceed one or more exitlevels after LDR requirements are met,subtitle C disposal would be required.

C. Pisk-based LDR Levels

1. List of Constituents and MinimizeThreat Concentrations

As was mentioned earlier in thissection, only modeled constituents' risk-level results are eligible to serve as risk-based LDR levels meeting the statutoryrequirement of minimize threat. Inaddition, minimize threat levels areonly proposed for those constituentswhere the risk level is higher (lessstringent) than the associated

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technology-based treatment standard in§ 268.40 or the UTS level in § 268.48.

First, the Agency repeats that it is notproposing to set any alternative risk-based LDR standards expressed asspecified technologies (rather thanconstituent concentrations.)Consequently, the option of complyingwith minimize threat levels in lieu oflevels specified in part 268 will beavailable only for wastes with treatmentstandards expressed as constituentconcentrations. This includes bothwastes subject to waste-specifictreatment requirements under the tableto § 268.40 and wastes subject to theUniversal Treatment Standard levels inthe table to § 268.48

The Agency proposes that forpurposes of establishing nonwastewaterand wastewater minimize threat valuesfor wastes with BDAT treatmentstandards expressed as constituentconcentrations, the levels proposedwould utilize the LDR definitions ofnonwastewater and wastewater from 40CFR 268.2(d) and (f). Therefore, any exitlevels that are considerednonwastewater for purposes of exit willalso be considered nonwastewater forpurposes of minimize threat. Likewise,wastewater exit levels will beconsidered wastewater LDR levels. TheAgency believes that consistentdefinitions of nonwastewater andwastewater is the only practical meansto establish minimize threat levels. TheAgency realizes, however, that themodeling and subsequent developmentof exit levels for today's proposed exitdid not use the part 268 definition ofnonwastewater and wastewater. (Acomplete discussion of this may befound in section VIII.A.l.a.ii.) The effectof this would be that some wastes thatwould be defined as wastewaters undertoday's proposed exit scheme would beconsidered LDR non-wastewaters. TheAgency requests comment on whetherthe definition in Part 268 should beadopted for purposes of establishingminimize threat levels.

The Agency compared the exit levelsto the current LDR treatment levels todetermine whether a constituent's risklevel should be proposed as a minimizethreat level. For wastewater values, theLDR wastewater value was directlycompared to the wastewater exit value.Where the UTS nonwastewater level isa total level, the comparison was madeto the nonwastewater totals exit level.Where the LDR nonwastewater level isa leach level, the comparison was madeto the nonwastewater leach exit level.However, for the reasons explainedbelow, the nonwastewater minimizethreat level would contain both a leachlevel and a totals level. For both

wastewater and nonwastewater, wherethe most comparable exit level is higher(less stringent) than the current LDRlevel, the constituent's risk level isproposed as an optional minimize threatlevel. The Agency requests comment onthis approach to determining which exitlevels are higher than current LDRlevels.

The Agency is proposing that testingrequirements when using minimizethreat levels would be consistent withthe current LDR testing requirementsfound in § 268.7. The Agency proposesthat if a claimant wishes to meet LDRrequirements by complying with aminimize threat level, the claimant mustmeet the minimize threat levels with atotals analysis, and where specified, thewaste must meet the leach level with aleachate analysis. The Agency believesthat a totals analysis is preferable to aleach analysis for establishing minimizethreat levels, as it more directly pertainsto all pathways, not only thegroundwater pathway.

Today's proposed exit levels fornonwastewaters consist of two risklevels for each constituent. The totals(mg/kg) nonwastewater risk level is theresult of the most limiting non-groundwater pathway. The leach (mg/L)nonwastewater risk level is the result ofthe most limiting groundwater pathway.The Agency believes it would bepreferable to have one exit level, but thegroundwater model results are a leach(mg/I), whereas the results from themultipathway analysis are a totals (mg/kg), and the science to extrapolate froma leach to totals is highly variable. Usingonly tho leach or only the total risk levelwould reflect only a portion of the riskspresented by the waste. A waste mustmeet both of these limits before itminimizes threats to human health andthe environment. Consequently, EPA isproposing to include both levels in theminimize threat standards fornonwastewaters. The Agency proposesto allow generators to either use acalculational screen or perform theTCLP to make a determination thatconstituent concentrations do notexceed nonwastewater leach minimizethreat levels. A full discussion andexplanation of the calculational screencan be found in section VIII.A.l.a.iii. oftoday's proposal.

Because extrapolating from a leach toa total varies with each constituent andis not easily measured, EPA has notdirectly compared both of the minimizethreat levels with the LDR standard. TheAgency requests data on specificconstituents where the second, lesseasily-compared nonwastewaterminimize threat level may be harder toachieve than the current LDR standard.

If such results occur, waste handlerswill not be required to use the newminimize threat levels. The levels in thetables to § 268.40 and § 268.48 willcontinue to satisfy LDR requirements asthey always have. The minimize threatlevels will be located in Table 1 of§ 268.60, are optional, and are intendedto be used to provide treatment relief.The Agency believes that minimizethreat levels will only be used wherethey are less stringent than current LDRlevels. The Agency requests commenton the proposed revisions to part 268with respect to minimize threat levels.

Table D-1 of appendix D to thepreamble presents for comparisoncurrent LDR UTS standards andproposed minimize threat levels. TheAgency is proposing that for theconstituents listed below, the risk levelsmay substitute for current UTStreatment levels in 40 CFR 268.48 or fortreatment standards for theseconstituents in 40 CFR 268.40. A tableof the proposed minimize threat levelscan be found at proposed 40 CFR 268.60subpart F in the regulatory textfollowing this preamble.

2. Constituents for Which Exit LevelsAre Not Minimize Threat Levels

As an alternative to the approachdescribed in C.1 above, the Agencysolicits comment on the backgrounddata underlying the risk evaluations forthese constituents. The Agency believes,in general, that the constituentsevaluated in the risk analysis haverelatively complete assessments of risk.The Agency recognizes, however, thatdata quality and completeness can varyamong constituents, even for those forwhich risk can be assessed. The Agencysolicits comment on both generalcriteria for assessing completeness ofdata, and also specific constituents forwhich use as minimize threat levels tocap LDR requirements may beinappropriate.

D. Meeting LDR Requirements

1. Wastes Below Exit Levels asGenerated

EPA proposes that, if a generatorsamples a listed waste stream at itspoint of generation and analysis of thesample shows all constituents to bebelow exit levels, LDR requirementswould not apply to the waste. EPA isproposing this result both forconstituents with exit levels based onmultipathway analysis (where, sinceexit levels can serve as LDR "minimizethreat" levels that cap current treatmentrequirements, the LDR program willnever require treatment to levels lowerthan exit levels) and constituents with




exit levels based on extrapolation fromthe multipath analysis or quantitationlevels (where, since EPA has notproposed to make exit levels into LDRminimize threat levels,the LDRprograms may require treatment tolevels lower than exit levels).

To claim this relief generators wouldhave to certify that they sampled theirwastes at the point of generation. In theinterim between sampling and receipt ofanalytical results, the generator wouldbe required to manage the waste ashazardous. However, EPA would takethe position that this brief period ofSubtitle C regulation would not subjectthe waste to LDR requirements.

EPA believes that position isconsistent with its prior interpretationsof LDR provisions and the D.C. Circuit'sopinion in Chemical WasteManagement I. At issue in that casewas EPA's determination that LDRtreatment standards apply to wastes thatare characteristically hazardous at thepoint of generation but thatsubsequently cease to exhibitcharacteristics and becomenonhazardous wastes. EPA took thatposition to ensure that characteristicwastes receive effective treatment.Without this requirement, for example,it would be possible to dilutecharacteristic wastes and evade LDRtreatment requirements. The Court heldthat EPA must apply this interpretationconsistently to characteristic wastes.

It is not necessary, however, to followthis interpretation for wastes that aregenerated with all constituentconcentrations below exit levels. EPAcan reasonably distinguish betweenwastes that are below exit levels at thepoint of generation and wastes whichachieved such levels at somesubsequent time. Only wastes whichexceed exit levels at the point ofgeneration need continued LDRapplicability to ensure that they reduceconstituent concentration or constituentmobility by complying with LDRstandards rather than using dilution orsome other inferior form of treatment. Agenerator of wastes that meet exit levelsas generated would not use wastetreatment to evade LDR requirements.Rather, he or she might use wasteminimization techniques to reduceconcentration or mobility ofconstituents in the precursor to hiswaste.

EPA notes that it is proposing torequire listed wastes which exceed exitlevels at the point of generation to meetLDR treatment requirements, even if thewaste later meets exit levels. EPAbelieves that this requirement carriesout the LDR requirements set out in the

Third Third rule and the ChemicalWaste decision.

Finally, EPA notes that it would bepossible to articulate alternativerationales for exempting from LDRrequirements wastes which meet today'sexit levels as generatedL For exit levelsbased on extrapolations from themultipathway analysis, EPA could arguethat extrapolated levels are LDR"minimize threat" levels. EPA,however, thinks protection of theenvironment is better served byrefraining from such a step andrequiring wastes which exceed suchlevels at the point of generation to meetcurrent technology-based LDRstandards. (As explained above, EPA isnot entirely certain that theseextrapolated levels actually minimizerisks for all constituents.) For exit levelsbased on quantitation limits, imposingLDR requirements would not have anypractical impact. LDR treatmentstandards are limited by the samequantitation limits proposed for thisrule. Consequently, treatment standardsfor constituents limited by analyticalcapabilities are not lower than the exitlevels.

2. Wastes Above Exit Levels asGenerated

Listed wastes that are above exitlevels as generated would be required tobe treated to the LDR standards in forceat the time if they are placed on theland.

VII. DilutionThe 1984 RCRA Amendments

(HSWA) established a vigorous nationalpolicy for minimizing the generation ofhazardous wastes. Section 1003 ofRCRA, as amended in 1984, establisheda national waste minimization policystating that "wherever feasible, thegeneration of hazardous waste is to bereduced or eliminated as expeditiouslyas possible". The policy also cited theneed to reduce the volume and toxicityof hazardous wastes which isnevertheless generated. Similarly,section 3005(h) prescribed that effectiveSeptember 1, 1985, all RCRA permitteeswho generate waste disposed of, treated,or stored on-site certify, on an annualbasis, that the facility has wasteminimization programs in place. Inaddition, section 3002(b) mandates thathazardous waste generators include acertification with their hazardous wastemanifests that the generator has a wasteminimization program in place and thatthe proposed method of off-sitemanagement minimizes threats tohuman health and the environment. Inconcert with these HSWA mandates, itis the Agency's policy to encourage

source reduction (i.e., wasteminimization) and waste treatment aspreferable to disposal and dilution.

EPA has recognized that successfulimplementation of the land disposalrestrictions requires that, in general,dilution be prohibited as a partial orcomplete substitute for adequatetreatment of restricted wastes. Thelegislative history indicates that such aprohibition "is particularly importantwhere regulations are based onconcentrations of hazardousconstituents" (H.R. Rep. no. 198, Part I,98th Congress, 1st Session 38 (1983)).

The Agency also opposes the dilutionof hazardous wastes for severaltechnical reasons. Most importantly,dilution is an environmentallyinappropriate means to reduce toxicantconcentrations because it does notreduce toxicant loadings to theenvironment. The same mass of toxicantis released to the environment when adiluted waste is disposed as would beif that same waste, prior to dilution,were to be disposed. While massloading of the environment is itself aserious concern, the potential forenvironmental damage is magnifiedwhen toxicants (for example, pesticidesand metals) bioaccumulate in the foodchain. In addition, diluted wastes cancreate an unnecessary demand forscarce solid waste disposal capacity.

For these reasons, dilution isgenerally prohibited as a means toachieve the exemption levels undertoday's proposal. Because today's ruleproposes to amend the some of thecurrent LDR levels by establishingminimize threat levels, allowingdilution as a means of achievingexemptions would be inconsistent withthe ban on dilution included in'the landdisposal restrictions rule (40 CFR268.3). In addition, dilution would beinconsistent with the Congressionalpurpose of encouraging wasteminimization. Thus, today's proposedrule specifically prohibits dilution as ameans of attaining the exemption levelsexcept as provided under the LDRprogram under 40 CFR 268.3(b).VIII. Implementation

Today's proposed rulemaking wouldestablish a generic set of constituent-specific exemption levels for listedhazardous wastes. Wastes withhazardous constituent concentrationsbelow the generic exemption levelswould be conditionally exempt fromSubtitle C. 5 Today's proposed

5Exempted wastes would continue to be solidwastes, and as such would require propermanagement under subtitle D and other applicablestate laws.

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rulemaking would be self-implementing; that is, no priorgovernmental approval or review ofdocumentation would be requiredbefore wastes are eligible to exit.Claimants of an exemption, however,would be required to meet certainprerequisites in addition to the genericconstituent concentration levels beforethe wastes would be considered non-hazardous. These testing andnotification requirements are necessaryto ensure that only those hazardouswastes which truly meet the exemptioncriteria exit the subtitle C system. Inaddition, certain testing and record-keeping conditions would be imposedto maintain the exemption to ensurethat thewaste continued to be eligiblefor the exemption. Failure to satisfy the,conditions would void the exemption.

A. Implementation Requirements

To make an effective claim, personswould need to comply with thefollowing requirements:-The waste must be sampled and

tested in accordance with acomprehensive sampling and analysisplan prepared prior to conductingsampling and analysis (EPArecommends, as guidance, using thebasic elements of sampling andanalysis plans described in ChaptersOne and Nine of SW-846);

-Representative samples collected insupport of an exemption proposed intoday's notice must consist of asufficient number of samples torepresent the spatial and temporalvariability of the waste characteristics;

-The waste must be tested for allhazardous constituents except thosethat should not be present in thewaste as defined by this rule, withdocumentation supportingdetermination not to test anyconstituent available on-site at thetime of the notification;

-If the claimant must test for anyhazardous constituents on table B ofappendix X of 40 CFR part 261, thewaste must also meet treatmentstandards for those constituents listedon UTS table of 40 CFR 268.48;

-A notification must be submitted tothe Regional Administrator (orauthorized State) (hereafter referred toas the implementation authority),

o along with-A certification signed by the

claimant's authorized representativeattesting to the completeness andaccuracy of the notification, and

-Verification that a notice of theexemption claim has been placed in amajor local newspaper of generalcirculation.

Any deficiencies in compliance withthese requirements would prevent theexemption from being valid; that is, thewaste would not exit the subtitle Csystem. Claimants would not be able touse their knowledge of the waste aloneto make a determination. Furthermore,in order to defend a claim that a wastewas exempt under today's proposed ruleand thus exempt from hazardous wasteregulation, claimants would bear theburden in an enforcement action ofestablishing that the waste in questionmet the exit levels and the otherrequirements for the exemption.

1. Testing Requirements

In today's notice, the Agency isproposing concentration-basedexemption criteria below which a listedhazardous waste would be conditionallyexempt from subtitle C compliance. Tobest ensure accurate characterizations ofconstituent concentrations in thesewastes, the Agency is also proposingsampling and analysis requirements forthe exemption determination proposedtoday. Adherence to these requirements,however, does not ensure that thecharacterization is accurate andrepresentative of a waste on a continualbasis. It is the generator's responsibilityto ensure that a waste always meets theexemption requirements proposed todayfor all appendix X of 40 CFR part 261constituents, regardless of whichconstituents the facility is required totest and how often testing is performed.

To be eligible for an exemption, EPAis proposing that facilities must (1)demonstrate that each constituent ofconcern is not present above thespecified exemption level in the waste,(2) demonstrate that the analysis couldhave detected the presence of theconstituent at or below the specifiedexemption level, and, (3) wherespecified, comply with the LDRstandards applicable to the waste.Today's proposed rule allows that anyreliable analytical method may be usedto demonstrate that no constituent ofconcern is present at concentrationsabove the exemption levels. It is theresponsibility of the generator to ensurethat the sampling and analysis isunbiased, precise, and representative ofthe waste.:

The Agency will consider that theexemption level was achieved in thewaste matrix if an analysis in which theconstituent is spiked at the exemptionlevel indicates that the analyte ispresent at that level within analyticalmethod performance limits (e.g., biasand precision). The Agency prefers thisempirical demonstration of methodperformance through the successfulanalysis at the exemption level. The

Agency requests comment on this andany other approaches to demonstratemethod performance.

In general, the Agency is proposingtesting requirements that would consistof an initial test to characterize thewaste as exempt, followed bysubsequent testing to ensure ongoingcompliance with constituents ofconcern. A generator of a listed waste ona one-time basis will only be required tocomply with initial testingrequirements. Wastes produced on aninfrequent (batch) or continuous basiswill have to comply with initial testingrequirements and subsequent testingrequirements as appropriate based onthe volume of the waste. The Agencyasks for comment on this generalapproach to testing requirements.

a. Data Evaluation

i. Compliance With the Exit Levels

The Agency is requesting comment onthree approaches of data evaluation.

First, the Agency is proposing that, forexemptions under today's proposedrule, generators would be required toevaluate their waste based on themaximum detected concentrations ofthe exemption constituents. If anyconstituent concentration is greater thanits specified exit level, then the wastewould be ineligible for exemption undertoday's proposed rule. One advantage ofthis approach is that facilities can useprocess and waste knowledge todetermine the appropriate number ofrepresentative samples without relyingon a complex, potentially costlystatistical approach to determine anappropriate number of samples.However, generators will need to besufficiently knowledgeable about theirwaste and process to make an unbiaseddetermination regarding the appropriatenumber of samples. Actual samplerepresentativeness might be difficult toverify or otherwise assess (on astatistical basis). Finally, the level ofuncertainty associated with the resultscannot be defined. Because of this,under this approach, a single compositesample that-validly exceeds the HWIRexit levels would indicate that the wasteis hazardous and must be handled in,Subtitle C.

Second, the Agency requestscomment on also allowing a second dataevaluation method whereby theanalytical results are evaluated in termsof an upper confidence limit around anaverage concentration. An example ofone method for determining an upperconfidence limit is presented in thestatistical approach found in ChapterNine of SW-846 (Third Edition, asamended by Updates I, II, IIA, and I1B),




where, for the purpose of evaluatingsolid wastes, the probability level(confidence interval) of 80 percent isused. Sample measurements for whichthe upper limit of the 80 percentconfidence interval about the samplemean is below the regulatory level forthe chemical contaminant are notconsidered to be present at levels ofregulatory concern. One main advantageof this approach is that the number ofsamples is statistically determined andthus it eliminates any bias that mightotherwise be introduced when usingknowledge to determine the appropriatenumber of samples. In addition, thelevel of uncertainty associated with theresults can be determined. However, themain disadvantage of this approach isthat it could be more costly for somefacilities than the proposed approach.For example, it might require multiplerounds of sampling to determine themean and variance. Highly variablewastes may require the collection ofmany more additional samples thanmight otherwise be determined to benecessary using the first approach.However, this statistical approachallows occasional samples to be aboveexemption level, as long as the upperconfidence limit of the data overall isbelow the exit level.

The Agency also requests comment ona third data evaluation method thatwould allow facilities to use long-termaverage data to demonstrate compliancewithout consideration of the upperconfidence limit. A rolling average ofsamples would be taken over the courseof a year on a schedule determined bythe initial sampling and analysis plan.As long as the average of the sampleswas below the HWIR exit level, thewaste stream would be considered non-hazardous. This approach would havethe advantage of being simpler than thesecond option, while allowingoccasional exceedences of the exit levelsby single samples, as long as the averageconcentration is below exit levels.

EPA has modelled risk with theassumption that the constituents ofconcern are uniformly distributedwithin the waste at the exitconcentrations. In discussion with theHazardous Waste IdentificationDialogue Group, some representativesnoted that actual levels might need toaverage significantly below the exitlevels if the exit criteria are to beconsistently met. The second and thirddata evaluation methods discussedabove help address this issue.

However, EPA and the States havenoted that the only practical approachfor enforcement purposes is toindependently collect samples foranalysis (which may represent a

composite of materials spatially or overa short time span) and to set up theregulation so that an exceedence by anysingle composite sample during aninspection could constitute a violation.It would then be the responsibility ofthe generator to refute this, usinghistoric sampling data and possiblyadditional samples to show that thesample exceedence does not constitutean overall violation of the HWIR levels.

EPA believes it is important to retainthe practical approach whereby a singlecomposite sample of a waste at somearbitrary point in time or space duringa short visit is considered sufficient forenforcement purposes. However,because the exit numbers were modeledbased on long-term averageconcentrations, the Agency requestscomment on allowing occasionalexceedences as long as the averageconcentration meets the exit level.

In addition to the concern aboutenforceability, however, EPA hasidentified two additional concernsabout using average concentration todetermine compliance. First, not allwaste streams would be disposed of inthe same place. Thus the wastes may onaverage be in compliance when they aregenerated, but the wastes arriving at thedisposal site (possibly from multiplesources) may not be, on average, belowthe exit levels. Second, EPA has notmodeled the constituents for acute risk.While the average concentration ofconstituents may be below the exitlevels, the occasional "high"concentration may be of concern due toacute health or ecological effects.

One possible way to address some ofthese concerns is, in addition torequiring that the average meet the exitlevels (as in the second and third dataevaluation methods), EPA could requirethat all samples be below some "peak"concentration.

Under this approach, if the averageconcentrations are below the exit levels,and all individual samples are belowthe higher peak level, then the generatorwould be in compliance and need takeno further action to support theexemption. EPA or a State would thenbe able to confirm waste status withouttotal reliance on the generator's data andwithout the expense of periodicsampling by EPA or the State. EPArequests comment on this issue,including any information on settingpeak levels.

For any of the three data evaluationapproaches, representative samplesmust be collected in support ofexemption under today's proposed rule,consisting of a sufficient number ofsamples to represent the spatial andtemporal variability of the waste

characteristics, regardless of how thesample number is determined.

For the identification and handling of"outliers", the Agency is recommendingthat testing for outliers should be doneif an observation seems particularlyhigh or low compared to the rest of thedata set. If an outlier is identified, theresult should not be treated as suchuntil a specific reason for the abnormalmeasurement can be determined (e.g.contaminated sampling equipment,laboratory contamination, datatranscription error). If a specific reasonis documented, the result should beexcluded from further data evaluation. Ifa plausible reason cannot be found, theobservations should be treated as a true,albeit extreme, value and not excludedfrom the data evaluation, as wastecomposition can vary. The Agencysolicits comments on implementabletechniques for the identification ofanalytical outliers.

The results of the tests of all of theconstituents on the exemption listwould be required to show theconstituent concentration to be at orbelow the exit level in order for theclaimant to be eligible for an exemption.In the case where a constituent's exitlevel is based on the quantitationcriteria (EQC, as described in sectionIV.E.), in addition to showing a non-detect at the exit level, the waste wouldbe required to meet applicablerequirements set forth at 40 CFR part268. Certain facilities may havedifficulty quantifying a constituent atthe exit level due to matrix interferenceeffects, but the Agency expectsexempted wastes to have relativelyclean matrices such that exit levelsshould be able to be achieved. The.Agency believes that the exit level mustbe met in order for a waste to exitSubtitle C; therefore, waste streams thatcannot meet exit levels would not exitunder today's rule. The Agency asks forcomment on this approach.

ii. Wastewater and NonwastewaterCategories

Throughout today's proposal andbackground documentation, all of theexit levels have been described as beingapplicable to two categories of wastesusing the terms wastewater and non-wastewater 6. EPA used these terms asan initial means of distinguishing twowaste categories that are inherent tohow the exit levels were developed, bytaking into account how these wastes

6The terms "wastewater" and "non-wastewater"

are used generically in today's preamble and rule,and do not represent the land disposal restrictiondefinitions in 40 CFR 268.2(d) and (f), although oneoption EPA is requesting comment on in thissection is the use of those definitions.

66387.




will be managed (i.e., stored, treated,and disposed), and also how the wasteswould be expected to behave in theenvironment. In the development of theexit levels, several waste managementunits were evaluated in the underlyingrisk analysis. The units chosen forevaluation were those that areconsidered most likely to manage thetypes of wastes that would be expectedto exit Subtitle C regulation undertoday's exemption. Although these unitswill likely receive to some degree bothforms of waste, in general there aretechnical, physical, and sometimes legalconstraints on what types of waste aremanaged in each. The Agencyconsidered ash monofills, waste piles,and land application units as typicallymanaging waste materials that can beconsidered "solid" or "non-wastewater," while tanks and surfaceimpoundments typically manage"liquid" or "wastewater." Based onthese assumptions, results from theanalysis of risk from these specificwaste management units were then usedto generate the corresponding exit levelsfor non-wastewater and wastewater.

In considering how to develop finaldefinitions and terms for these twowaste categories, the Agency's goal is toestablish definitions that are clear,concise, and easily distinguishable fromother similar terms such that a generatorcan readily determine which set of exitlevels to apply to the waste beingevaluated for the exemption. EPArequests comment on three options fordefining these two waste categories todetermine which set of exit levels toapply to a listed waste eligible fortoday's proposed exemption. EPAemphasizes that these definitions willonly apply in the context of today's exitrule.

The Agency also requests comment onwhether it is reasonable in all threeoptions to allow a generator thealternative options of separating in thelaboratory the solid (or nonwastewater)portion of the waste from the liquid (orwastewater) portion of the waste,analyzing the resultant portions,comparing the results to thecorresponding exit levels, and treatingthe waste as exempt if all exit levels aremet in both portions.

Option 1: Using Percent Solids-EPAprefers the option of defining the twocategories of exit levels as "solid" and"liquid" exit levels, where thedistinction between solids and liquids isbased upon the percent solids content ofthe waste, as determined using Section7.1 of the Toxicity Characteristic LeachProcedure (TCLP) in SW-846.Specifically, the option would definewastes containing 15 percent solids by

weight or greater as solids,7, whilewastes with less than 15 percent solidsby weight be defined as liquids. EPAbelieves that the 15 percent cutoff is areasonable distinction between the twocategories of exit levels, for thefollowing reasons. Because there aregeneral prohibitions on liquids orwastes containing free liquids in non-hazardous waste landfills acceptingmunicipal wastes, the Agency does notenvision wastes containing less than 15percent solids being managed in theseunits. Similarly, it is unlikely that wastecontaining less than 15 percent solidswill be stored in waste piles due toobvious physical limitations. For landapplication units, EPA believes that 15percent solids content by weight is areasonable lower limit for the types ofwastes typically managed in these units;indeed, this was the value used in theland application unit scenario in thegroundwater modeling portion of therisk assessment underlying today's exitlevels.

Because of these limitations, EPAbelieves that wastes containing less than15 percent solids will more frequentlybe managed in the types of unitsassociated with wastewater treatment,such as tanks and surfaceimpoundments. In fact, EPA believesthat many wastes falling into the liquidcategory under this definition, that canrealistically exit under today's proposedexit rule, will likely be wastewaters thathave undergone treatment and thatcontain much less than 15 percentsolids. EPA presumes that in manycases the separation of'water from solidswill be occurring as part of routinewastewater treatment, and generatorswill be either be evaluating the solidresidues (which would clearly meet oursolid definition), or the treated water,much of which is currently dischargedunder the Clean Water Act and thereforelikely has limits on the amount of solidspresent.

EPA also requests comment onalternative ways of determining percentsolids content, including generatorknowledge of the waste or results ofprevious analyses. The Agency believesthat in many cases, particularly forfairly dry or fairly wet wastes, thegenerator can immediately ascertainfrom a visual inspection that the percentsolids content is well above or wellbelow the 15 percent solids value.

I EPA will avoid use of the term "solid waste"when describing the category of exit levels that aredefined as solids under this option in today'sproposal. This is to avoid confusion with theexisting term "solid waste" in the RCRA program,which has specific statutory and regulatorydefinitions, which have no relationship to whethera waste is a physically a solid or a liquid.

Option 2: Using LDR Definitions-EPA also requests comment on the useof the same terms and definitionscurrently used under the land disposalrestrictions. Wastewater is defined aswaste containing less than 1 percenttotal suspended solids (TSS) and lessthan 1 percent total organic carbon, orTOC (40 CFR 268.2(f)). Non-wastewateris defined as any waste that is not awastewater (40 CFR 268.2(d)). Theprinciple advantage of this approach isit allows the use of consistentdefinitions for wastewater andnonwastewater in both today's exitsystem for listed wastes, and the LDRprogram. The advantage of thisconsistency is particularly apparent forthose cases where LDR treatmentstandards are conditions of exit undertoday's rule. One disadvantage of thisapproach is that it defines wastescontaining greater than 1 percent TSS asnon-wastewater, even though thesewastes will likely be managed-inwastewater treatment systems usingtanks and surface impoundments,which is inconsistent with the way inwhich the results from the risk analysiswere used in developing exit levels. TheAgency requests comment on thisapproach as an alternative to Option 1.

Option 3: Using the Paint FilterLiquids Test-The third option is to usethe terms "liquid" and "solid" as inOption 1, but to use EPA Method 9095from SW-846, the Paint Filter LiquidsTest, to determine whether the wastebeing evaluated for exit is a liquid or asolid. Under this option, any wastedetermined to contain free liquids usingMethod 9095 would be considered aliquid, and the exit numbers currentlyin the wastewater category would applyto that waste. Conversely, a waste wouldbe defined as a solid, and thenonwastewater exit levels would apply,if the waste does not contain free liquidsusing Method 9095. Under this option,EPA realizes that many wastesappearing like solid materials wouldactually be defined as liquids.

Method 9095 is presently used indefining the term "liquid waste" in thesolid waste disposal facility criteria, fordetermining compliance with theprohibition on disposing of bulk orcontainerized liquid in municipal solidwaste landfills (see 40 CFR 258.28).Method 9095 is also used indetermining compliance with theprohibition on bulk or containerizedliquids in hazardous waste landfills(264.314(c)).

iii. Totals and TCLP Analyses

Today's rule proposes that theclaimant would be required to test thewaste for which today's exemption is




being claimed to prove that constituentconcentrations in the waste do notexceed the exit level(s) for eachconstituent that should be present in thewaste.

The claimant would determine whichcategory of exit levels would apply (e.g.,wastewater or nonwastewater) to hiswaste. In a previous section of today'srule, the Agency requests comment onseveral options to define these twocategories. For a wastewater waste to beeligible for exit, every constituent in thewaste must comply with the wastewatertotal constituent exit concentration. Fora nonwastewater waste to be eligible forexit, every constituent in the waste mustcomply with the nonwastewater totalconstituent exit level as well as thenonwastewater leach exit level.

A test for total concentration wouldbe required for each constituent in thewaste regardless of whether the waste isa wastewater or a nonwastewater todetermine that the total constituent exitconcentration has not been exceeded.For non-wastewaters, a claimant mustalso prove that the measurable leachateconcentrations do not exceed thenonwastewater leach exit levels. TheAgency proposes to allow claimants toeither use a calculational screen or touse the Toxicity Characteristic LeachingProcedure (TCLP, Test Method 1311 in"Test Methods for Evaluating SolidWaste, Physical/Chemical Methods,"EPA Publication SW-846) to make adetermination that constituentconcentrations do not exceednonwastewater leach exit levels.Discussion concerning the methodologyof a calculational screen is describedbelow.

Section 1.2 of the TCLP allows for acompositional (total) analysis in lieu ofthe TCLP when the constituent ofconcern is absent from the waste, or ifpresent, is at such a low concentration

that the appropriate regulatory levelcould not be exceeded.

For wastes that are 100% solid asdefined by the TCLP, the maximumtheoretical leachate concentration canbe calculated by dividing the totalconcentration of the constituent by 20.The dilution factor of 20 reflects theliquid to solid ratio employed in theextraction procedure. This value thencan be compared to the appropriateregulatory concentration. If this value isbelow the regulatory concentration, theTCLP need not be performed. If thevalue is above the regulatoryconcentration, the waste may then besubjected to the TCLP to determine itsregulatory status.

The same principal applies to wastesthat are less than 100% solid. In thiscase, however, both the liquid and solidportion of the waste are analyzed fortotal constituency and the results arecombined to determine the maximumleachable concentration of the waste.The following may be used to calculatethe maximum theoretical concentrationin the leachate.

[AxBI+[CxD E

B+[ 2 0-xD

where:A = Concentration of the analyte in

liquid portion of the sample (mg/L)B = Volume of the liquid portion of the

sample (L)C = Concentration of the analyte in the

solid portion of the sample (mg/kg)D = Weight of the solid portion of the

sample (kg)E = Maximum theoretical concentration

in leachate (mg/L)If:E<exitlea.h

Then: A TCLP need not be performedfor this constituent because, even if

100% of the constituent leaches, theTCLP results would be less than theregulatory leach standard. Thiscalculation is adequate proof that thiswaste is at or below its leach exitlevel.The above calculational screen may

be used by a claimant in order not toperform the TCLP. The screen may beused to determine that a total analysisof the waste demonstrates thatindividual contaminants are at such lowconcentrations that the nonwastewaterleach exit level could not possibly beexceeded, thus eliminating, the need torun the TCLP.

Example: To illustrate thecalculational screen, the followingexample is provided: An analyst wishesto determine if a leach processingsludge could fail the nonwastewaterleach exit level for lead. The sludge isreported to have a low concentration oflead, and the analyst decides to performa compositional analysis (totals test). Arepresentative sample of waste issubjected to a preliminary percentsolids determination as described in theTCLP. The percent solids is found to be90%. Thus, for each 100 grams of thiswaste filtered, 10 grams of liquid and 90grams of solid are obtained. It isassumed for the purpose of thiscalculation that the density of thefilterablb liquid is equal to one. Theliquid and solid portion of the sampleare then analyzed for total lead. Thefollowing data are generated:Percent solids = 90%Concentration of lead in the liquid

phase = 0.023 mg/lVolume of filtered liquid = 0.010 LConcentration of lead in the solid phase

= 85 mg/kg (wet weight)Weight of the solid phase = 0.090 kg.The calculated concentration is as

follows:

mg mg[0.023 x 0.OIOL] +[85m x 0.090kg]

L

0.OIOL +[20 L x 0.090kg]kg

= 4.23 mgL

In this case, the maximum leachableconcentration is below the 10 mg/Lregulatory concentration for lead, andthe TCLP need not be performed.

iv. Oily Wastes

In this proposed rulemaking, theAgency has modelled the transport ofsolutes in groundwater as well asmovement along other environmental

pathways. This groundwater modelinginvolves predicting rates of constituentleaching from wastes in land-basedwaste disposal units. In using this fateand transport modeling to developregulatory exit levels, the Agency isproposing to rely on the use of leachtests to ensure that groundwater is notcontaminated. Among the test methodsthat have been developed and employed

to identify wastes which might pose anunacceptable hazard are: Methods 1310(Extraction Procedure), 1311 (ToxicityCharacteristic Leaching Procedure,TCLP), 1320 (Multiple ExtractionProcedure, MEP), and 1330 (Oily WastoExtraction Procedure, OWEP).

However; these leach test proceduresall have deficiencies in predicting themobility of toxic chemicals from oily

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66390 Federal Register / Vol. 60, No. 245 / Thursday, December 21, 1995 /, Proposed Rules

wastes. Method 1311 underestimates themobility of constituents from many oilywastes due to filter clogging problems,can be imprecise for oily wastes, andhas several operational problems.Conversely, Method 1330 is believed tooverestimate mobility of constituentsfrom oily wastes since it emulates aworst case scenario by using solvents toextract contaminants from the oil. Noneof the available laboratory procedures isfully satisfactory. Rather, they bracketthe range of possible leaching for oilywastes.

In addition, EPA does not have a gooddefinition for what constitutes an oilywaste. EPA originally defined oilywastes as those materials that cloggedthe filter during Method 1311 (TCLP)extraction. EPA requests comment onhow to better define what an oily wasteis.

EPA also requests comment on whichof the two tests methods (1311 or 1330)should be used and why should one testbe chosen over the other for predictingthe concentrations of contaminants inleachate from wastes being managed inlandfills. EPA also requests comment onwhether there are any alternative testmethods or models that could be usedfor predicting the mobility of oilymaterials. Such procedures need to beboth scientifically credible andenvironmentally protective. Methodsneed to identify material that might bereleased from the waste and enter thesoil. Release is defined as movement ofeither the liquid phase of the waste orleached contaminants through thebottom of the waste unit to thesubsurface -soil immediately underlyingthe disposal point. Once contaminantspass this point their ultimate fate interms of impact on down-gradient watersupplies can be estimated by theground-water fate and transport model(EPACMOW model).

EPA also requests comment on anyadditional problems with oily wasteleachability not covered here, andwhether the volatilization or otherattributes of constituents should beconsidered in the development of a test.

Oily wastes also pose modelingchallenges in groundwater because theydo not disperse in the same pattern asaqueous liquids. This affects themovement of the constituents in thematerial. In the event of a release ofwaste at or near the soil surface, thewaste will migrate downward until itreaches the water table, Light non-aqueous phase liquids (LNAPLs) willthen tend to migrate laterally, forming apancake on top of the water table. Densenon-aqueous phase liquids (DNAPLs) onthe other hand will sink to the base ofan aquifer and not show much lateral

spreading until an impermeable layer isreached. EPA is requesting comment onwhat sort of wastes or what constituentsexhibit these behaviors and how todefine that set of wastes. Constituentsthat have been associated with DNAPLsinclude dichlorobenzenes, PCBs,napthalenes, chloroform, carbontetrachloride pentachlorophenol,cresols, and several PAHs. However,trace amounts of these constituents areunlikely to pose a DNAPL problem. ADNAPL problem is likely to occur whenthere is sufficient concentration to flowas undissolved liquid that would thenform the sort of complex reservoirs thatsubsequently slowly dissolve intogroundwater. The Agency requestscomment on concentrations of these orsimilar chemicals that are likely to poseDNAPL problems and whether theproposed exit levels in totals or, fornonwastewaters in leach levels, aresufficient to limit wastes exiting forwhich a DNAPL or LNAPL problemwould need to be explicitly evaluated.

The Agency is continuing to work ondeveloping tests-and models fordetermining the leaching potential ofoily materials and may propose them infuture rulemaking. In the meantime,EPA is today proposing to apply thelevels as proposed in this rule to oilywastes, but seeks comment on whetherinstead there is a definable class ofwastes for which these levels cannotreasonably be concluded to beprotective.

b. Initial Test

The Agency is proposing in today'srule that there would be an initial testbefore a facility would be eligible for anexemption. The initial test would be theprimary tool to characterize the waste asexempt. Results from this initial testwould be sent to the implementingagency. The public could request the,implementing agency to make theresults available.

EPA is proposing to require initialtesting of all of the 386 constituents onappendix X of 40 CFR part 261 exceptthose that the claimant determinesshould not be present in the waste. EPAwould require the claimant to documentthe basis of each determination that aconstituent should not be present. Theclaimant must submit thedocumentation to the implementingagency and retain a copy on site forthree years. No claimant may determinethat any of the following categories ofconstituents should not be present:-- Constituents set out in appendix VII

to part 261 as the basis for listing thewastestream for which exemption issought;

-Constituents listed in the table to 40CFR 268.40 as regulated hazardousconstituents for LDR treatment of thewaste stream;

-Constituents detected in any previousanalysis of the same wastestreamconducted by or on behalf of theclaimant;Constituents introduced into theprocess which generates thewastestream; and

-Constituents which the claimantknows or has reason to believe arebyproducts or side reactions to theprocess that generates thewastestream.

The Agency requests comment onwhether these are the appropriatecriteria to be used to determine whatshould not be present in the waste. TheAgency also requests comment onrequiring claimants who are not wastegenerators to consult the generator priorto determining that a constituent is notintroduced into the process or that aconstituent is not a byproduct or sideproduct of the process. EPA believesthat it is unlikely that a non-generatorclaimant would have sufficientknowledge of the production process tomake adequate determinations on theseissues. EPA requests comment on thetype of documentation that it shouldrequire. The generator could co-sign thedocument that sets out the reasons fordetermining that the claimant need nottest for a constituent, or the generatorcould prepare a separate supportingdocument that would be attached to thedocument for submission to theimplementing agency and retention inthe claimant's files.

The Agency is soliciting comment onwhether the absence of constituents inthe following documents couldconstitute sufficient justification for notanalyzing all of the constituents listedin 40 CFR part 261 appendix X.-40 CFR part 261 appendix VII

highlighted to show whichconstituents are listed for each wastecode applicable to that waste;

-40 CFR 268.40 highlighted to showwhich constituents are regulatedunder the land disposal restrictionsfor each waste code applicable to thatwaste;

-EPCRA Toxic Release Inventoryreports highlighted to show whichconstituents are reported as being"used" in the manufacturing processfrom which that waste is generated(based on the EPCRA definition of"use");

-NPDES discharge permits highlightedto show which constituents arerequired to be monitored inwastewaters with which that waste iscommingled or will be commingled;




-State or Local emissions monitoringpermits or documents (e.g., stackemissions, fugitive emissions,groundwater monitoring, wastewaterdischarges, etc.,) highlighted toindicate which constituents arerequired to be monitored is potentialemissions from units in which thatwaste is managed or will be managed;

-Responses to government and/or tradegroup data collection efforts (e.g.,biennial reports, TSD surveys) thatrequire submission of waste-specificconstituent information;

-Published literature (e.g., journals,presentations, chemical andengineering reference documents,health and safety handbooks, materialsafety data sheets, etc.,) highlighted toindicate constituents that are formedor potentially formed from sidereactions, degradation, or reactivity ofthe products, reactants, or solventsused in the manufacturing processgenerating that waste;

-Plant-specific process flow diagramsor process descriptions highlighted toindicate constituents that are formedor potentially formed from sidereactions, degradation, or reactivity ofthe products, reactants, or solventsused in the manufacturing processgenerating that waste;

-Product specifications or constituent-specific labeling requirements underfederal regulations, state regulations,or non-governmental standards (i.e,per product-grade) that identifyconstituents that are expected to bepresent in the products from whichthe waste was generated, highlightedto indicate those constituentsidentified as part of thesespecifications or standards (excludingchemical additives or preservativesthat are placed in the productssubsequent to the generation of thewaste for which exit is claimed);

-Waste profile data sheets, such asthose submitted to commercial wastehandlers, highlighted to show theconstituents that were found orexpected to hie present in that waste;and/or

-A certified, third party engineeringanalysis of the process generating thatwaste that provides qualitativeverification of the theories behind theanticipated absence of certainchemical classes or groups ofAppendix X of 40 CFR 261constituents such as pesticides,pharmaceutical, halogenated solvents,carbamate, organo-sulfur compounds,known gases, cyanides, etc.;

-Any other available quantitative orqualitative constituent informationspecific to that waste

Relevant information includes notonly those document sections thatindicate which constituents are present,but also cover pages that indicate thesource of the document segments andsignature pages to verify authenticity ofgovernment-approved documents(where appropriate). For the verificationpurposes, page numbers should also beclearly identified for each document.EPA is also soliciting information onadditional readily availabledocumentation that could be added tothis list that would not impose anunreasonable records burden on boththe generator and enforcement officials(for example, the Agency believes thatrequiring highlighted copies of copiousamounts of monitoring data would beredundant and would significantlyimpede enforcement review). EPAbelieves that requiring copies of onlyrelevant portions of these documents,highlighted to indicate the chemicalspresent, should minimize the burdenassociated with this documentationrequirement significantly.

Regardless of which constituents afacility tests, the facility is responsiblefor ensuring that each constituent in thewaste meets its applicable exit level.

The Agency believes that the tailoredinitial test described above will ensureaccurate waste characterizations of thewaste streams while focusing testingrequirements to those constituents thatare of concern. A facility coulddetermine whether a constituent wouldbe present. A facility would not beauthorized to determine that theconstituents in the waste meet theexemption levels based on knowledge ofthe waste or material. This approachboth reduces unnecessary testing costsand allows for more frequent monitoringof those constituents that are of concern.

The Agency is soliciting comment onwhether this proposed approach to aninitial test is appropriate.

The Agency asks for comment ontaking the opposite approach: requiringeach claimant to test only for thoseconstituents that the claimantdetermines "could be present" for thatwaste. This would be a systematic wayfor facilities to focus the list ofhazardous constituents to those that aremostly to be present in the waste. EPArequests comment on requiring at aminimum testing of the followingcategories of constituents:-Constituents set out in appendix VII

to part 261 as the basis for listing thewastestream for which exemption issought;

-Constituents listed in the table to 40CFR 268.40 as regulated hazardousconstituents for LDR treatment of thewaste stream ;

-Constituents detected in any previousanalysis of the same wastestreamconducted by or on behalf of theclaimant;

-Constituents introduced into theprocess which generates thewastestream; and

-Gonstituents which the claimantknows or has reason to believe arebyproducts or side reactions to theprocess that generates thewastestream.The Agency asks for comment on the

completeness of the proposedmandatory testing criteria. In addition,the Agency requests comment onwhether testing should be required forthose constituents that do not meet anyof the criteria of "could be present." TheAgency also requests comment onwhether documentation should berequired to demonstrate that thoseconstituents that were not tested did notmeet any of the "could be present"criteria.

EPA requests comment on anotherapproach to determining whichconstituents need to be analyzed by aclaimant. The approach would be thatthe claimant needs to provide data onall additional constituents listed inappendix X of 40 CFR part 261 oftoday's rulemaking for which a methodused by the generator to detect otherconstituents which the claimant isrequired to test can easily determineconcentrations. Thus, for example, if awaste was listed for a constituent forwhich GC/MS is an appropriate methodused by the claimant, the claimantwould also be required to ask thelaboratory to provide information on allother constituents listed in appendix Xof 40 CFR part 261 of today's proposedrulemaking for which the GC/MS is alsoan appropriate method.

EPA did not use this in its primaryproposal because the Agency realizedthat implementation of this conceptbecome more complex than it appears.For example, even when using GC/MS,there may be sample preparationtechniques, dilutions, and similar issuesthat determine which constituents canbe measured in the appropriateconcentration ranges usingthe method.

However, there is somethingintuitively reasonable and attractive inasking claimant to gather and provideinformation that is easily obtainable andwould provide additional confidenceand certainty. EPA solicits comments onthis idea and ways to implement it.

The Agency requests comment onwhether there is some other way tofocus the scope of testing requirementsor if the only way to ensure accuratewaste characterizations would be torequire testing for all 386 constituents.

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The FACA suggested EPA shoulddefine, for major waste streams, a set ofconstituents that it believes would fairlycharacterize those waste streams. TheAgency believes such an approach maybe desirable. However, the Agency notesthat this could require it to expendsignificant resources. The Agencyrequests comments on the feasibility orneed for this approach in the long term.

EPA recognizes that some generatorsmay wish to assert claims for protectionof confidential business information(CBI) for some to the information thatsupports an exit claim. Material that isclassified as CBI may be reviewed byEPA, but may not be released to thepublic. States may have similarprovisions under state law. EPArequests comments on two options foraddressing CBI information.

First, EPA requests comment on theoption of prohibiting any person fromasserting a claim of exit under this ruleif that person wishes to claim CBIprotection for any data or informationused to support the exit claim,including all information submitted tothe implementing agency in thenotification package and all informationrequired to be maintained by theclaimant on site and furnished to theagency on request. A generator whowished to rely on CBI data to supportan exemption claim for a listedhazardous Waste would need to file adelisting petition with EPA or a stateauthorized for delisting.

EPA believes such an approach maybe necessary because the exits proposedtoday are self-implementing. The publicwould not have the assurance ofknowing that EPA or a state agency hadreviewed the claimant's data anddetermined that it showed that theclaimant's waste posed low risks tohuman health and the environment.Members of the public may not feel thatthey are adequately protected by the factthat EPA and authorized states couldobtain the CBI data and use it (withappropriate precautions againstdisclosure) in an enforcement action ifwarranted. They may feel that thenumber of claims will strain agencyinspection and enforcement resources,making it important for them to be ableto bring their own citizen enforcementactions under section 7002 of RCRA.

At the same time EPA is sensitive topotentially legitimate business needs toprotect information supporting an exitclaim. Some firms may not wish torelease detailed information about thechemical composition of their processwaste streams. EPA also recognizes thatthe federal delisting process isconsiderably slower and imposes moreprocedural burdens than the self-

implementing exit scheme. EPArequests comment on the alternative ofcreating a limited prior approval processfor exit claims involving CBI claims.EPA anticipates that rulemaking wouldnot be required. However, states thatwish to obtain authorization for today'sexit program might not be required toadopt this feature because they couldargue that failure to provide a reviewprocess for CBI claims would not maketheir programs less stringent than thefederal program.

EPA also notes that CBI protection isnot absolute. EPA has authority underRCRA to release CBI information to thepublic as necessary to supportrulemaking proceedings. (In fact, EPAcould try to support the first optionabove by arguing that it was exercisingin this proceeding its authority to waiveprotection for all of the individual exitclaims that "implement" the rule.) Also,a citizen that has sufficient evidence ofa violation to file a complaint in courtmay be able to persuade the court toorder a limited release of the data foruse in the enforcement proceedings.

2. Notification Requirements

The Agency is proposing that therequired notification to theimplementing authority would includethe following information:-The name, address, and RCRA ID

number of the person claiming theexemption;

-The applicable EPA Hazardous WasteCodes;

-A brief description of the process thatgenerated the waste;

-An estimate of the average andmaximum monthly and annualquantities of each waste claimed to beexempt;

-Documentation for any claim that aconstituent is not present;

-The results of all analyses andestimates of constituentconcentrations and all quantitationlimits achieved;-

-Documentation that any constituentson Table B to appendix X of 40 CFRpart 261 have met the applicabletreatment standards in § 268.48,unless the claimant is claiming theexemption under § 261.36(e);

-Evidence that the public notificationrequirements have been satisfied; and

-A certification signed by the personclaiming the exemption or hisauthorized representative.The Agency is taking comment on

whether the following additionalinformation should also be sent to theimplementing authority:-The name and address of the

laboratory which performed theanalysis;

-A copy of the sampling and analysisplan used for making the exemptiondetermination;

-A description of any chain-of-custodyprocedures;

-Whether the identity of the disposalfacility should be included in thenotification package;

-Dates of sampling and analysis; and-A description of the (temporal and)

spatial locations of the demonstrationsamples.

Also, the Agency is taking comment onwhether, if the disposal facility isdifferent than the claimant's facility, theclaimant should also include as part ofthe notification package documentationthat the claimant informed the disposalfacility of the exempt status of thewaste. -

A complete notification packagewould include all required informationin the notification and all requiredcertifications signed by the appropriateindividual, as identified in theregulations. Failure to submit anotification package if the exemption isbeing claimed or submission of anincomplete notification package wouldbe a violation of RCRA requirementsand thus subject to penalties andinjunctive relief under section 3008(a)of RCRA and possible criminal liabilityunder section 3008(d) of RCRA. As anecessary prerequisite to claiming anexemption, the burden would be on theclaimant to establish that a completenotification package was submitted tothe implementing authority to assert inan enforcement action that the waste isexempt.

It should be noted that, regardless ofwhether the sampling and analysis planmust be included with the notificationto the implementing agency, a currentsampling and analysis plan must bedeveloped and used to establish thewaste's eligibility for exemption, andmust be available upon request to theimplementing authority at the time thenotification package is submitted and atleast for three years. The sampling andanalysis plan must demdnstrate that thesamples to be taken and analyzed willbe representative of any spatial andtemporal variations in the subject waste.

Furthermore, it should be noted thatsubmission of sampling and analysisplans with the notification to theimplementing authority does not changethe self-implementing nature of theexemption. Submission of such planswould not be for review or approval ofexemption claims prior to theexemption becoming effective. Theimplementing agency would be underno obligation to undertake such reviewor approval prior to the exemption




becoming effective, and failure toundertake such prior review would notpreclude a subsequent enforcementaction should the exemption claim laterbe determined to be inaccurate orotherwise invalid.

As proposed, the certificationrequired to accompany the notificationmust attest that the waste in questionmeets all relevant constituentconcentration exit levels and that theinformation in the notification packageis true, accurate, and complete. TheAgency is taking comment on whetherthis certification is sufficient assurancethat the claimant has made best effortsto accurately characterize the waste or ifadditional certification language oradditional certifications (e.g., from ananalytical laboratory) are necessary.

The notification package would berequired to be submitted by certifiedmail with return receipt requested, orother commercial carrier that providedwritten confirmation of delivery. Noclaim would be effective until theclaimant received the return notificationindicating that the package had beendelivered.

Submission of the notificationpackage to the implementing authority,however, is not equivalent to approvalor verification of the exemption claim.Submission of a notification packagewould not preclude or in any way limitthe implementing authority's ability totake a subsequent enforcement actionshould it determine that the initialrequirements of exemption were nevermet or that the conditions formaintaining the exemption are notsatisfied.

The Agency is taking comment onwhether, instead of the exemptionbecoming effective upon confirmation ofdelivery of the notification package,there should be some brief waitingperiod prior to the exemption becomingeffective.

Such a period (e.g., 30 or 60 days)could be used by the implementingauthority to review notificationpackages for completeness or for indiciaof concerns that would lead toprioritized enforcement, although theexemption would still becomeautomatic after the period regardless ofwhether any action was taken by theimplementing authority. As analternative, the period could bedesigned to provide the implementingauthority an opportunity to determinethat a claimant should not be able toavail itself of the exemption withoutsome further review and to notify theclaimant of its views.

Under either approach, governmentalreview would be discretionary and thelack of such review would not be an

indication of governmental approval ofthe exemption claim. To ensure thatthere would be no confusion on thispoint, the certification could include astatement of recognition that expirationof the delay period without comment bythe overseeing agency is not theequivalent of agency approval that theclaim is accurate. The Agency has notchosen to propose a delayedimplementation approach because itbelieves a short time frame, particularlycombined with an automatic effectivedate, would not provide an opportunity

'for thorough prior review and would, atbest, provide only marginal benefits asa screening device for potentiallyproblematic claims. The Agency,however, requests comment on whethersuch a delay would be beneficial tomonitoring claims and if there areprocedural or other concerns relating tosuch a delay.

B. Implementation Conditions

After the exit claim has becomeeffective, the claimant would have tocontinue to meet certain conditions tomaintain the exemption. Failure tosatisfy any of the conditions would voidthe exemption and subject the waste toapplicable subtitle C requirements.

Under this proposal, wastes mustcontinue to meet the generic exemptionlevels established for exit to remainnon-hazardous. Separate and distinctfrom any requirement or condition thatmight be established under thisrulemaking, all generators-includingclaimants of today's proposedexemption-would have a continuingobligation to identify whether they aregenerating a hazardous waste and tonotify the appropriate governmentalofficial if they are generating ahazardous waste. Section 3010; 40 CFR261.11. If wastes claimed as exemptunder today's proposed rule test aboveexit levels at any time, that waste andsubsequently generated waste, wouldhave to be managed as hazardouswaste-including compliance with allnotification requirements-until testingdemonstrated that the waste was belowexit levels.8

Compliance with HWIR exemption levels willbe measured from the last available test data or fromthe latest representative samples taken from thewaste in question. Testing which shows constituentconcentration levels above exemption levels willnot affect wastes previously generated under a validclaim of exemption based upon representativesamples. Similarly, testing, which shows that awaste which tested above exit levels once againtested below all relevant exit levels will exempt allwaste generated on or after the date the sampleswere taken. Waste which exceeded the exit levelswould not be able to requalify for the exemption.

1. Records Maintained on Site

In addition to the informationdescribed in the Notification Sectionabove, the Agency is also proposing thatthe following information concerningthe initial testing and retesting bemaintained in the files on site at thefacility making the exemption claim forat least three years:-All information required to be

submitted to the implementingauthority as part of the notification ofthe claim;

-The dates and times waste sampleswere obtained, and the dates thesamples were analyzed;

-The names and qualifications of theperson(s) who obtained the samples;

-A description of the (temporal and)spatial locations of the samples;

-The name and address of thelaboratory facility at which analysesof the samples were performed;

-A description of the analyticalmethods used, including any clean-upand extraction methods;

-All quantitation limits achieved andall other quality control results for theanalyses (including method blanks,duplicate analyses, matrix spikes,etc.), laboratory quality assurancedata, and a description of anydeviations from published analyticalmethods or from the plan whichoccurred;

-All laboratory documentation thatsupport the analytical results, unlessa contract between the claimant andthe laboratory provides for thedocumentation to be maintained bythe laboratory for the period specifiedin § 261.36(b)(2) and also provides forthe availability of the documentationto the claimant upon request;

-If the generator claims a waste isexempt from part 268 requirementspursuant to § 261.36(e),documentation to substantiate such aclaim.The Agency requests comment on the

proposed information maintenancerequirements and comment onadditional information that may benecessary.

In addition, claimants will berequired to retain certain informationconcerning retesting of wastes asdescribed below and set out in the textof proposed 40 CFR 261.36(d)(6)(ii).

2. Testing Conditions

Claimants would continue toperiodically test their wastes as acondition of the exemption. 9 Failure totest and maintain documentation of the

9 Wastes generated on a one-time basis would notbe subject to this requirement.

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testing in accordance with therequirements of proposed 40 CFR261.36(d) would void the exemption.The Agency believes that requiredsubsequent testing is necessary tomaintain accurate wastecharacterizations. Subsequent testingwould be an ongoing exemptioncondition and would be the minimumtesting required to maintain anexemption. A tailored constituent listsetting out minimum requirements fortesting purposes should not be confusedwith the facility's ongoing requirementto maintain constituent concentrationsbelow exit levels for all constituents onappendix X of 40 CFR part 261. Resultsfrom subsequent testing would berequired to be maintained on-site.

The scope of subsequent testingwould focus primarily on thoseconstituents from appendix X of 40 CFRpart 261 that are of concern based on theinitial test. The list of constituents forwhich a claimant would be required totest would, at a minimum, include eachconstituent that was detected in theinitial test within an order of magnitudebelow the exit level for that constituent,and any constituent listed in Table B ofappendix X of 40 CFR part 261 that isalso identified as a basis for listing thewaste or appendix VII to part 261 orlisted as a regulated hazardousconstituent for the waste in the table to40 CFR 268.40. The claimant would also'be required to test for any otherconstituent which the claimant hadreason to believe was newly present inthe waste since the most recent previoustest.

The Agency proposes that thefrequency with which a facility wouldbe required to perform subsequenttesting would be determined based onthe volume of waste which the facilityis declaring exempt. Those facilitieswith large-volume waste streams wouldperform subsequent testing more oftenthan those facilities with low- ormedium- volume waste streams. Theclaimant would be responsible fordetermining the volume of annualexempt waste. The Agency asks forideas and comments on whetherguidance should be made available forclaimants on how to measure annualvolumes. Justification of annualvolumes would be sent to the Directorin the notification package. The Agencybelieves that accurate wastecharacterizations are important forwaste volumes of all sizes; however,inaccurately characterized large-volumewastes have greater potential to harmthe environment than do smaller-volume wastes. In today's rule, theAgency is proposing the following

requirements for the first three years ofsubsequent testing:-Wastes generated at the time of

exemption is initially claimed involumes greater than 10,000 tons/yearwould be tested four times a year forthe first three years of the exemption.

-Wastes generated at the time ofexemption is initially claimed involumes greater than 1000 tons/yearbut less than 10,000 tons/year wouldbe tested twice a year for the firstthree years of the exemption.

-Wastes generated at the time ofexemption is initially claimed involumes less than 1000 tons/yearwould be tested once a year for thefirst three years of the exemption.EPA requests comment on whether it

should allow the Agency proposes thatif a waste maintains exempt status forthree years, the frequency of subsequenttesting would then be reduced to oncea year, regardless of the volumeproduced. The Agency believes thatthree years of subsequent testing shouldprovide a facility with adequate data toassess the potential for variability in thewaste. The Agency requests commenton the frequency of subsequent testing.

The Agency requests comment on anapproach that the FACA suggested. The

* approach consisted of a comprehensivetest, similar to an initial test, that isrequired every 3 or 5 years of anexemption because of the strongreliance on the initial test's results indetermining the scope of subsequenttesting.

The Agency also requests comment onwhether follow-up testing should beeliminated entirely after the first threeyear period. In addition, the Agencyasks if a certification of compliance withall relevant exit levels could suffice inlieu of testing at the end of three years.

3. Testing Frequency and ProcessChange

Under today's proposal, the claimanthas a continuing obligation to verify thatthe waste continues to meet theexemption criteria, including meetingthe exemption constituent concentrationlevels. Process changes that may eitherincrease the number of hazardousconstitugnts in the exempted waste orincrease the concentration of hazardousconstituents already present, should puta claimant on notice that there may bechanges in the waste that may affect itscontinued eligibility for exemption. TheAgency, however, is not proposing torequire new sampling and analysiswhenever there is a process change thatmay affect the exempt status of thewaste.

The Agency is taking comment onwhether it is necessary to require as a

condition of maintaining the exemptionthat wastes be re-tested after a processchange and, if so, what the scope ofsuch re-testing should be. The Agencywould like to know if the testingfrequency proposed or more frequenttesting would provide a clearerindicator of waste changes of concernthan triggering re-testing through anarrative description of a processchange. Another alternative is to requirethe claimant to notify the implementingauthority that a process change hasoccurred and to certify that theexemption criteria continue to be met ifthe claimant determines that the wastestill maintains its exempt status. TheAgency is taking comment on howprocess change should be defined in theevent one of the alternatives is chosen.It should be noted that if waste forwhich an exemption has been claimedat any time tests above exemptionlevels, that waste and all subsequentlygenerated waste is hazardous. Theclaimant could not assert a new exitclaim until a new batch of waste testsbelow the exit levels. The exemptionproposed today would not relievegenerators of their responsibility under§ 262.11, nor would any test datapreviously obtained prevent a claimantfrom failing to satisfy the exemptioncriteria should an inspector conductwaste sampling that establisheshazardous constituents atconcentrations above exit levels.

C. Public Participation

As a self-implementing exemptioneffective upon receipt of the notificationby the implementing authority, there isno decision prior to exit being made bythe implementing authority regardingthe waste. The opportunity for publicparticipation in an exemption claim isthe opportunity that exists at all timesfor the public to bring to theimplementing authority's attention anycircumstance that might aid thatauthority in its monitoring andenforcement efforts. The public,furthermore, would have the ability tobring a citizen suit for a claimant'sfailure to comply with any requirementof the exemption.

The Agency is proposing to requirethat the public be notified by theclaimant that an exemption claim isbeing asserted. This notification wouldbe accomplished by publication of anotice in a major newspaper, local to theclaimant and of general circulation, thatcontains the information required by theregulations. Evidence that the notice hasbeen submitted for publication must bepart of the notification packagesubmitted to the implementing facility.




The Agency is requesting comment onwhether such a notice should be placedin a newspaper local to the claimant'sfacility or to the disposal facility orboth, should those facilities be locatedin different areas not served by the samenewspaper.

Requiring notification of facilitiesreceiving exiting wastes has also beenraised to the Agency in discussions. TheAgency solicits public comment on theneed for and possible approaches torequiring that waste generators that areexiting their listed waste, notifyreceiving facilities that wastes are HWIRexited wastes. Additional discussion ofthis issue appears in the docket under"Receiving Facility NotificationProcess."

As discussed above, the Agency isalso taking comment on whetherproviding a "delay" in the effective datewhen the exemption attaches (e.g., 30 or60 days) would provide a significantand meaningful opportunity for publiccomment prior to the waste havingexited the subtitle C system. Possiblebenefits of a waiting period beforeeffectiveness of the exit could includegreater opportunity for State review orcitizen comment before waste is actuallydisposed outside of Subtitle C. Undersuch an approach, the waiting periodwould begin with receipt by the State ofa complete certification package, and'would run for the designated time (30or 60 calendar days).

The Agency is taking comment onwhether access to claim documentationthrough the appropriate implementingagency will be sufficient to providepublic access to documentation. Onealternative would be to require theclaimant to provide access to theinformation. If that option is selected,the Agency requests comment on how,and for how long, the claimant shouldbe required to provide access to thedocumentation, and on what kind ofprotection for CBI would be appropriate.

IX. Request for Comment on Options forConditional Exemptions

The Agency has at different timesconsidered contingent managementapproaches to disposal of hazardouswastes. Under such approaches, wastesthat would be considered hazardous ifmanaged in an uncontrolled manner,could be considered non-hazardous if -managed in a sufficiently controlledmanner. The following section discussesand requests public comment on severalapproaches to setting higher exit levelstied to meeting certain managementrequirements. These approaches wouldallow wastes with higher concentrationsof hazardous constituents to be managedsafely outside of Subtitle C.

Many Subtitle C requirements werewritten generically to address allhazardous wastes and, consequently,provide protection for those wastes thatpose the greatest risks. Others are eitherexplicitly or implicitly technology-based rather than risk-based. Some ofthese requirements are statutory andcannot easily be adjusted to take riskinto account. Nevertheless, EPAgenerally believes that it would bedesirable to tailor waste managementrequirements to more closely coincidewith risks. The exit levels proposedtoday take an initial significant step inthis process by allowing very low-riskhazardous wastes to be exempt fromSubtitle C requirements, leaving themsubject only to less prescriptive federaland state controls for nonhazardouswastes. They also take an initial steptowards setting different exit levels fordifferent situations by recognizing thatwastewater and non-wastewaters aretypically handled in different ways andpose different risks, hence today'snotice proposes different exit levels forwastewaters and non-wastewaters.

Within the time constraints imposedby the court-ordered deadline for thisproposal, EPA has begun exploringwhether it would be possible to createadditional exemptions to allow moreflexible management of additionalwastes now classified as hazardouswithout compromising protection ofhuman health and the environment.These options are premised on thetheory that a waste's risk is due not onlyto its chemical composition, but also themanner in which it is managed, whichcan greatly affect the amount ofchemical constituents that ultimatelyreach a human or environmentalreceptor. The multipathway analysisprepared to support the exit levelsshows that the concentration at which ahazardous constituent threatens humanhealth or the environment variessignificantly with the type ofmanagement that a waste receives-some forms of management appear topresent greater risks than others. Thefollowing discussion presents the legalframework for management-based'exemptions, and outlines in some detailthe options which EPA finds to be mostpromising for rapid promulgation.

A. Legal Basis for ConditionalExemptions

EPA originally interpreted RCRA'sdefinition of hazardous waste to focuson the inherent chemical composition ofthe waste and to assume thatmismanagement would occur so thatpeople or organisms would come intocontact with the waste's constituents.See 45 FR 33113 (May 19, 1980).

However, EPA even in the past tried toconsider "reasonable" mismanagementscenarios, scenarios that wherereasonably likely or plausible even ifnot proven to necessarily have occurredor be typical for a specific waste.However, after more than a decade ofexperience with waste management,EPA believes that it may no longer beaccurate or necessary to assume thatworst-case mismanagement will occur.In recent hazardous waste listingdecisions, for example, EPA hasidentified some likely"mismanagement" scenarios that arereasonable for almost all wastewaters ornon-wastewaters, and looked hard atavailable data to then determine if anyof these are for some reason veryunlikely for the specific wastes beingconsidered, or if other scenarios arelikely given available information aboutcurrent waste management practices. Asa further extension of that logic, EPAnow believes it may be appropriate tofind that, where mismanagement is notlikely or has been adequately addressedby other programs, EPA need notclassify a waste as hazardous and thatthere may be ways to recognizesituations where the limitations onlikely "mismanagement" are specific toa State, a type of waste, or a facility-specific condition on how a waste ismanaged.

EPA believes that it can interpret thedefinition of "hazardous waste" inRCRA section 1004(5) to authorize thisapproach to classifying wastes ashazardous. Section 1004(5)(B) defines as"hazardous" any waste which maypresent a substantial present orpotential hazard "when mismanaged".EPA reads this provision to allow it to.determine the circumstances ,underwhich a waste may present a hazard andto regulate the waste only when thoseconditions occur. Support for thisreading can be found by contrastingsection 1004(5)(B) with section1004(5)(A), which defines certaininherently dangerous wastes as"hazardous" no matter how they aremanaged. The legislative history ofSubtitle C of RCRA also appears tosupport this interpretation, stating that"the basic thrust of this hazardous wastetitle is to identify what wastes arehazardous in what quantities, qualitiesand concentrations, and the methods ofdisposal which may make such wasteshazardous." H.Rep. No. 94-1491, 94thCong., 2d Sess.6 (1976), reprinted in ALegislative History of the Solid WasteDisposal Act, as Amended,Congressional Research Service, Vol.1,567 (1991) (emphasis added).

EPA also believes that section 3001provides it with flexibility to consider

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the need to regulate wastes ashazardous. Section 3001 requires thatEPA, in determining whether to list orotherwise identify a waste as hazardouswaste, decide whether a waste "should"be subject to the requirements ofSubtitle C. Hence, section 3001authorizes EPA to determine thatSubtitle C regulation is not appropriatewhere a waste is not likely to bemanaged in such a way that it willthreaten human health or theenvironment. Moreover, regulation ofsuch waste under Subtitle C would notappear "necessary to protect humanhealth or the environment" under RCRAsections 3002(a), 3003(a) and 3004(a).As noted elsewhere in this proposal,EPA interprets these provisions to giveit broad flexibility in fashioning criteriato allow hazardous wastes to exit theSubtitle C regulatory system. EPA'sexisting regulatory standards for listinghazardous wastes also allowconsideration of a waste's potential formismanagement. See § 261.11(a)(3)(incorporating the language of RCRAsection 1004(5)(B)) and§ 261.11(c)(3)(vii) (requiring EPA toconsider plausible types ofmismanagement). Wheremismanagement of a waste isimplausible, the listing regulations donot require EPA to classify a waste ashazardous.

Two decisions by the U.S. Court ofAppeals for the District of ColumbiaCircuit provide potential support forthis approach to defining hazardous "waste. In Edison Electric Institute v.EPA, 2 F.3d 438, (D.C. Cir. 1993) theCourt remanded EPA's RCRA ToxicityCharacteristic ("TC") as applied tocertain mineral processing wastesbecause the TC was based on modelingof disposal in a municipal solid wastelandfill, yet EPA provided no evidencethat such wastes were ever placed inmunicipal landfills or similar units.This suggests that the Court mightapprove a decision to exempt a wastefrom Subtitle C regulation if EPA wereto find that mismanagement wasunlikely to occur. In the same decisionthe Court upheld a temporaryexemption from Subtitle C forpetroleum-contaminated media becausesuch materials are also subject toUnderground Storage Tanks regulationsunder RCRA Subtitle I. The courtconsidered the fact that the Subtitle Istandards could prevent threats tohuman health and the environment tobe an important factor supporting theexemption. Id. at 466. In NRDC v. EPA,25 F.3d 1063 (D.C. Cir. 1994) the Courtupheld EPA's finding that alternativemanagement standards for used oil

promulgated under section 3014 ofRCRA reduced the risks ofmismanagement and eliminated theneed to list used oil destined forrecycling. (The Court, however, did notconsider arguments that takingmanagement standards into accountviolated the statute because petitionersfailed to raise that issue during thecomment period.)

B. Improvements in Management ofNon-Hazardous Waste and in RiskAssessment Methodology

EPA's early regulations defininghazardous waste reached broadly to

-ensure that wastes presenting hazardswere quickly brought into the system.When EPA promulgated its first listingsand characteristic rules in 1980, itsknowledge of toxic constituents,constituent transport pathways, andwaste management options was morelimited than it is today.

In addition, significant changes andimprovements in waste managementhave occurred since the early 1980's.Many states have established orstrengthened industrial nonhazardouswaste programs since that time. Forexample, currently 26 states requireliners and 28 states require ground-water monitoring for at least somesurface impoundments. Up to 45 statesrequire ground-water monitoring and 38states require liners for at least somelandfills. It is important to recognizehowever, that within a state, applicablerequirements may vary according to a-number of factors, including unit type,waste source, and location. See "StateRequirements for Industrial Non-Hazardous Waste ManagementFacilities" EPA 1994. At the same time,industries have gained experience inmanaging wastes and many haveimproved waste management practicesunder incehtives such as public accesspursuant to the EmergencyPreparedness and Community Right toKnow Act, and avoiding liabilitiesunder Superfund, RCRA correctiveaction and state cleanup programs.

EPA's ability to predict the risks thata waste may pose has also improvedsignificantly. EPA has collected muchmore data on a variety of wastemanagement units and other factors thatimpact the ability of waste constituentsto reach a receptor. Models such as theEPACMTP and the models used in themultipathway analysis provide moresophisticated means of assessing therisks of a range of waste managementoptions. As a result of all these changes,EPA is now in a position to begin toimplement a more carefully tailoredrisk-based approach to regulatinghazardous wastes.

C. Overview of Options for ConditionalExemptions

The Agency has identified severaldifferent approaches to providingconditional exemptions that wouldallow more wastes to exit the Subtitle Csystem. These options fall into twobroad categories: (1) Establishingnational conditional exemptions basedon unit type either with or withoutassuming additional managementcontrols; and (2) granting conditionalexemptions to qualified state programsthat ensure additional managementcontrols.

1. National Approach: EPA WouldEstablish National Exit Levels forContingently Managed Waste

The contingent management programcould be adopted by any state thatwants to implement it, withoutconsideration of state programs for non-hazardous waste. The contingent exitlevels would differ according to thedegree of management/disposalrestrictions imposed as a condition ofexit. The possible options wouldinclude progressively more restrictiverequirements, and allow progressivelyhigher exit levels as disposal options arefurther restricted. The options underthis approach are:

a. Distinguish Between Disposal in LandApplication Units and Other Units

The multipathway risk assessmentmethodology used for this rulemakingtakes into account managementscenarios (such as land treatment of awaste), or exposure pathways (such aswind transport from an uncovered pileor volatilization from an open tank),resulting in calculated exit levels basedon the riskiest scenario. In some casesthis exit level may be significantly lowerthan the next most risky exposurepathway. The riskiest exposure pathwaymay not be applicable to somemanagement situations. On review ofthe risk analysis results, the Agencydetermined that disposal in a landapplication unit is frequently thehighest risk disposal option in both themultipath and groundwater modeling.

As described in detail in Section X.below, the Agency has developed forproposal an approach to contingentmanagement relying on themultipathway exposure analysis, risklevel of 10-6 and HQ of 1, and using thebase case uncontrolled managementscenarios, but with land applicationunits removed from the analysis. Exitconcentrations would still be protectiveacross a wide variety of conditionsnationally, for all non-land applicationunit disposal. The Agency is proposing



Federal Register / Vol. 60, No. 245'/ Thursday, December 21, 1995 / Proposed Rules

one national exit level for eachconstituent based on the next riskiestpathway, on condition that wastes arenot disposed in land application units.

This option was considered by theAgency to be the simplest approach tocontingent management. It would besomewhat easier to enforce than otheroptions described below, since therewould still be only one conditional exitlevel for each constituent.Implementation mechanisms to assurethat the wastes go only to allowable unittypes are described below.

b. Unit-Specific Exit Levels for EachDisposal

Another approach to contingentmanagement considered by the Agencywould be to establish a set of exit levelsfor each waste management unitevaluated based on risks at unregulatedunits of that type. Units that would beevaluated, at HQ 1 and 1 E-6 risk,would be land application units, wastepiles, landfills, surface impoundmentsand tanks. Base case assumptions wouldbe used to describe the units. TheAgency has not included specific exitlevels for this approach here, but solicitscomment on its potential benefits, andpotentially greater complexity ofimplementation and complianceassurance.

Under option 2 the Agency would setseparate exit levels for each type ofwaste management unit. Generatorswould be allowed to choose the type ofnon-subtitle C waste management unitin which to manage their waste, andwould be required to meet the unit-specific exit levels for all constituents inorder to manage the waste in that unit.Testing and implementation would besimilar to the requirements for exitbased on the most limiting pathway.However, the Agency believes thisoption would increase the complexity oftracking wastes that met the varyingconcentration exit levels tied to specificallowable units.

The Agency believes allowing use ofexit levels tailored to waste managementcan be a practical and appropriate wayto allow greater volumes of waste to exitSubtitle C without increasing risks toabove the toxicity benchmarksdescribed in Section IV.D, providingthat characteristics of various waste unittypes can be clearly defined (such as thedifference between surfaceimpoundments, tanks, and perhapscovered tanks for the management ofwastewaters), and providing the Agencycan design a viable implementationscheme that does not rely primarily onstatements of proposed future disposal.Tracking and monitoring of actual wastemanagement could be one way to assure

disposal in the appropriate facilities.Limiting disposal to on-site facilitiescould also better assure proper disposal,although this would limit the usefulnessof contingent management approaches.The Agency requests comment onadditional implementation requirementsthat might be needed to assure the wasteis managed in the designated unit typeonly.

EPA has not developed this as ageneral approach in this rulemakingbecause the risk modelling that wasdone, while more multifaceted andcomprehensive than many pastanalyses, was not designed for thispurpose. For efficiency in modelling,EPA did not always model eachpathway for each specific unit. EPAsometimes only modelled an exposurepathway of concern (such as airemissions) from certain types of unitsthat EPA thought might be the limitingscenario, and risk from organicconstituents in a landfill were notmodeled. Therefore the modelling workto date may not identify the mostlimiting pathway if each unit is judgedindividually. To fully develop exitlevels for a full range of unit types, EPAbelieves it would have to dosupplemental risk analysis to fill in thegaps in modeling for each of the wastemanagement units, or at least evaluatewhether the risk analysis done to dateis sufficiently representative. Tables 21-39 in the November 1995 Supplement tothe multipath analysis present themodeled risk values for each constituentdisposed in each of the five optionsmodeled, and for each pathway. Thesetables can aid commenters inunderstanding what a unit-specific exitvalue for any particular constituentcould be.

c. Consideration of AdditionalManagement Unit Design orManagement Practices

A third option is that EPA would usea somewhat modified multipathwayexposure model to evaluate whetheradding additional specific design oroperating controls for particular unittypes, would allow less conservativeexit levels. These conditional exitconcentrations would be promulgatedon a unit-type specific basis, and couldbe used only by units employing thespecified additional controls that wouldreduce the risk level to 10-6. Such anapproach could be self-implementingfor a facility owner/operator, and wouldnot necessarily be tied into a permittingauthority.

While such an approach could takeinto account the effects of a combinationof added controls on each unit type(such as size of the unit, ground-water

monitoring, liners, caps, etc.) theAgency believes that there are a numberof significant implications associatedwith this approach. It could beinterpreted by industries and states asan indirect way to define a broader setof management standards for industrialnon-hazardous waste managementunits. Also, if the approach were self-implementing, it could be extremelydifficult to ascertain that a particular.unit meets a complex set of controls andtherefore to assure compliance with theconditional exit levels. The morecomplex a judgement required todetermine compliance with theconditions (such as whether a liner thatis hard to inspect during operation isproperly installed and protected fromtears), the more appropriate it is likelyto be that such determinations be madein the context of a permitting authorityor prior approval rather than as acondition on a self-implementingexemption.

As a variation on this approach, TheAgency could take into account certainregional, local, or site-specific factors inestablishing exit levels. These couldinclude the effect of local rainfall,regional hydrogeology, or size of facilityon exit values. These issues aredescribed in greater detail in section 3below.

Because of the complexity ofimplementation, the Agency wouldattempt to define very limitedadditional control(s) to limit exposuresand reduce risks to 10-6 level. EPAparticularly asks for comments on unitdesign attributes that are easilyascertainable in a spot inspection versusthose that require more detailedengineering review, or review ormonitoring of operations. For thisoption, as with options one and two, theAgency would have to conductadditional risk modelling work toadequately evaluate additionalparameters on a unit specific basis.

One issue common to all of theoptions discussed above is the legalstatus of wastes subject to suchconditioned exemptions when there is aviolation of the conditions. The Agencyrequests comments on how to makethem enforceable in a practical way thatis fair to those involved. If the wasteconcentration/unit requirements areconditions of an exemption, anyviolation of a condition means that thewaste generator, or other individualmanaging the waste, has violated thefull range of RCRA requirements andhas been illegally managing a"hazardous waste" as a "nonhazardous"waste. Because the conditionalrequirements are not clearly tied toother non-hazardous waste authorities,

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there would not be a remedy for theviolations outside of the hazardouswaste program. An alternative approachis discussed in the following optionsallowing conditional exit levels in stateswith qualified industrial non-hazardouswaste programs. As long as the state hasclear enforcement authority under itsnon-hazardous waste managementprogram, these conditions could becrafted so that a violation of thecondition was not illegal disposal ofhazardous waste involving multipleRCRA counts. Rather it would beenforced as a violation of the relevantState authorities. The Agency requestscomment on the advantages anddisadvantages of these approaches, aswell as whether there might be otherapproaches to ensure adequate legalremedies for violations of theconditional exit requirements, when thecontingencies are not based on qualifiedstate industrial non-hazardous wasteprograms.

2. State Program Approach

As noted earlier in this section, manystate industrial non-hazardous wasteprograms have improved significantlysince the early days of Subtitle C. Stateprograms may offer the advantages bothof requiring management controls whichensure protection of human health andthe environment and ongoing oversighton a facility specific basis throughpermitting, inspection and enforcementactivities. While every state programmay not be operating at the same level,the Agency believes that a number ofstate programs may offer reasonable,protective systems to serve as the basisfor less stringent exit levels. Qualifiedstate programs would be allowed tomanage listed waste in their non-hazardous waste management programunder certain conditions. Thesequalified state programs would ensurethat risks were reduced to protecthuman health and the environment.

There are three key factors the Agencybelieves would need to be considered inestablishing state-based contingentmanagement programs. These are (1)establishing a risk-based cap on wasteconstituent concentrations that can bemanaged contingently; (2) the type ofprogram review of a state program thatEPA would perform to identify qualifiedstate programs, and (3) the breadth ofstate program controls.

For the risk cap, the Agencyhasconsidered using either a 1 E-4 cancerrisk and HQ 1, or I E-3 cancer risk andHQ 10 as options. The caps would bemodeled based on management inunregulated disposal facilities, as in thebase-case exit level modeling.

Regarding program review, theAgency would either conduct aqualitative review of the State program,examining it to ensure it addresses keyconsiderations, or would require statesto conduct quantitative risk assessmentof planned management practices todemonstrate their safety down to 1 E-6 cancer risk and HQ 1 or an alternativerisk target.

For the qualitative review, EPA wouldspecify environmental and "administrative performance goals andthe state would have to submit anarrative description demonstratinghow the particular combination oftechnical standards and administrativerequirements in their program protectshuman health and the environment andmeets those performance goals, forexample:* Ground-water protection: A state

program must address adequatelycontamination of groundwater from afacility.

e Surface water protection: A stateprogram must address adequatelyprevention of contamination of surfacewater which may occur through the run-off of pollutants from the disposalfacility to surface waters.

• Address other environmental andperformance goals such as controllingair exposures, siting, ensuring long-term'integrity of the site, etc.

• Permitting and enforcementauthorities and public participation: Astate program has appropriateauthorities and a system for priorapproval of waste managementfacilities, and public participation eitheron a site-specific basis or for input todevelopment of class permits.

* Adequate resources: A stateprogram has adequate resources foradministration of the program includingpermitting, inspections andenforcement.

Under a quantitative risk review'approach, a state would have todocument their permitting andenforcement authorities and publicparticipation requirements, as well asthe adequacy of their program resources.The state would also have todemonstrate to EPA how the particularcombination of technical managementcontrols or design standards in itsindustrial non-hazardous waste programwould ensure meeting 10-6 risk levels.In order to do this, EPA would have torefine or expand the multipathwayexposure model. EPA would then eithermake its multipath model available tostates or work with them to demonstratethat unit-specific state program controlswould meet the 10-6 risk level for aparticular class of facilities receivingconditionally exited wastes. The Agency

solicits public comment on whetherstates can propose alternative risktargets for use in state contingentmanagement programs.

Regarding program breadth, theAgency believes either broad, state-wideprograms, or more narrowly focusedcontingent management programs couldbe developed. Under a broad-based stateprogram approach, the Agency wouldapprove as qualified only those statesubtitle D programs that adequatelyregulate all state non-hazardous wastemanagement and wastes. Under thisapproach, states with programs deficientin certain aspects would be required toupgrade before participating in thecontingent management program.However, the Agency recognizes thatstate subtitle D programs vary widely inthe particular units and waste types thatare covered, among other factors.Therefore, as an alternative approach,EPA might determine that a programqualifies for conditional exit only forparticular units (i.e. for landfills only, orfor landfills and surface impoundments,etc.). In other cases, a state programmight focus narrowly on developingappropriate contingent management forparticular waste streams generated bykey industries in the state.

In considering how to use these keyfactors in developing contingentmanagement regulations, the Agencyidentified three options in addition tothe three options described above underthe national programs. These will beidentified in this discussion as optionsfour, five and six.

Under option four, the Agency woulduse the 1 E-4 and HQ 1 risk cap onwaste and would conduct a qualitativereview of the state program using thecriteria described above. This could bedone either on a narrow program basis,or based on a program that qualifiesbroadly.

Under option five, the Agency wouldalso use the I E-4 and HQ 1 risk capfor waste being contingently managed,but would require that states conductrisk modeling of proposed disposal todemonstrate that risks from the waste asdisposed would be not greater than the1E-6 and HQ1 risk targets of the basecase. This approach could be takeneither with the entire state program, oronly certain waste managementpractices. In particular, site-specificfactors, as described below, could beconsidered under this approach. Thesecould include facility size, local rainfall,or local hydrogeology, among others.Location of the nearest drinking waterwell might also be considered by thestate in evaluating risks, if allowedunder state regulations and regulatorypolicies. In this case, the state would be




required to demonstrate to EPA, usingthe multipathway analysis or anotherrisk assessment model, how they wouldensure on a site-specific basis thatfacilities disposing of conditionallyexited wastes meet a 10-6 risk level.Development of this approach mightalso require quite different risk models,since the multipathway model as itcurrently exists incorporates a numberof simplifying assumptions to capture abroad range of possible conditions. TheAgency would have to ensure that amodel used for this analysis canincorporate complex site-specificvariables, or develop a set of simplifiedmodels that could be applied by states.However, this approach would providemaximum flexibility to states andgenerators to tailor exit levels toparticular waste and site characteristics.

Under option six, the Agency wouldallow wastes posing up to 1 E-3 cancerrisk and HQ 10 (in an unregulatedmanagement setting), and allow either aqualitative or quantitative review of thestate program, but allow participationonly by state programs that are broadlyqualified, i.e., that are qualified in allaspects of the program, for currentlymanaged industrial non-hazardouswaste. The Agency would be morecomfortable with this approach becauseit would be more assured of safemanagement of the waste regardless ofwhere in the state it is disposed.

The Agency also solicits publiccomment on whether more than one ofthe options discussed above should bedeveloped at the same time. Forexample, the Agency might establishboth the option 1 proposal describedbelow, and establish a state-basedcontingent management program basedon any of options four, five or six. Bydoing so, the Agency would establishoption I as a minimum nationalstandard, but this approach would allowthat states to go further they choose todo so.

3. Establish Exit Levels That ConsiderRegional or Site-Specific Factors ThatMight Affect Constituent Fate andTransport'

In addition to facility design factors,there are other location-specific factorsthat may substantially affect the risksand the appropriate exit levels for wastemanagement units. Examples of suchfactors include: Rainfall andhydrogeology at the site and thedistance to off-site receptors. Theaverage amount of precipitation fallingon these waste management units mayaffect both the amount of leachate togroundwater and soil run off to off-sitereceptors. Thus, the Agency coulddetermine geographic regions based

upon climatic zones, could requireprecipitation data from the most'appropriate certified rain gauge, orcould require site specific precipitationinformation. However, in order to dothis the Agency would need to verifythat the other model inputs areappropriate for each of the regions orelse develop new region-specific inputs.Therefore, the Agency solicits data andcomment on technically appropriateways to establish exit levels based onrainfall levels.

Other site-specific factors that maysignificantly affect the groundwaterpathway are the hydraulic conductivityof the soil surrounding the wastemanagement unit and the distance tothe nearest drinking water wells. If thehydraulic conductivity of surroundingsoil is relatively low-such as in soilsdominated by clays-then the flow ofany potentially contaminated leachateto ground water could be effectivelyretarded for long periods of time(though flow to surface waters or otherpathways might change, perhapsincreasing). Landfills located in soilswith low hydraulic conductivities (forexample, 10-6 cm/sec or lower) couldprovide an extra level of environmentalprotectiveness for ground water thatcould be considered in developing thisapproach. For example, the Agencymight address this effect by developingexit levels corresponding to differentclasses of hydraulic conductivity.Alternatively, differences in hydraulicconductivity could be consideredthrough a site-specific process. Thisapproach would not be relying onengineered controls, but on naturalattributes of the location. EPA solicitscomments on whether such attributescan be readily determined or in whatcircumstances they can be readilydetermined and relied upon.

The Agency did some limitedsensitivity analysis with respect toground water risk modelling to look atthe concept of developing different exitlevels depending on broadhydrogeological regions. The results ofthat analysis are in the docket. TheAgency requests comment as to thevalue of investing in this approach andpractical considerations the Agencyshould weigh in deciding whether topursue this approach.

Finally, where the nearest drinkingwater wells are at an unusually greatdistance from the waste managementunit, corresponding exit levelconcentrations associated withgroundwater exposures that took thatdistance into account could besignificantly lower if the Agency's goalwere solely the prevention of currentexposure to groundwater contamination.

However, many states have policies tonot degrade groundwater and EPAbelieves it is quite difficult to predictfuture needs for uncontaminatedgroundwater. EPA believes that thegroundwater modelling done for thisrule reflects a balanced view by usingthe distribution of nearest wells.However, EPA expects it will-receivecomments suggesting that it shouldconsider allowing facilities with nomoderately nearby drinking water wellsto take that into account. The Agencyseeks comment on the implementationissues associated with taking thesefactors into -account and the relatedpolicy judgement as to whether the goalof more site-specific assessment shouldbe prevention of risk based on currentground water use, reasonablyforeseeable use, or based on distancesthat would be more protective of thepotential future use of ground water.

The Agency also seeks comment onother location-specific factors orcombinations of factors that may beparticularly important in mitigating therisks associated with waste disposal.The Agency also requests comment onalternative approaches for taking thes6location-specific factors intoconsideration in developing exit levelsfor waste management. One option fordoing so would be to develop additionaltables of exit levels (in addition toOption 2) for waste management unitsthat reflect the effect of some of the mostimportant location-specific factors (e.g.,exit levels for areas with low annualrainfall, or indexed to landfill size). Asan alternative option, the Agency coulddevelop "reduced form" equations thatspecifically relate the exit levelconcentration to critical location-specific factors (such as annual rainfall).The Agency requests comment on themerits of these approaches and onalternative options that might be used tobetter accommodate the effect oflocation-specific factors on exit levels.

D. Land Disposal Restrictions forContingent Management Options

Any conditional exemption wouldoffer muoh more significant relief if iteliminated or reduced the need tocomply with more stringent LDRtreatment requirements. As explainedabove in Section VI of today's proposedrulemaking, however, under ChemicalManufacturers Association v. EPA (the"Third Third" decision) LDR treatmentstandards generally continue to applyeven if a waste ceases to be classified asa hazardous waste. If an LDR treatmentstandard were lower (more stringent)than a contingent management exitlevel, the waste would still need to meetthe LDR standard.

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EPA has proposed two approaches tointegrating HWIR exit levels and LDRtreatment requirements for the baseoption. First, EPA is proposing that LDRtreatment requirements will never applyto wastes that meet all applicable exitlevels at the point of generation.Second, for wastes which meet exitlevels subsequent to the point ofgeneration and, consequently, remainsubject to the LDR regime, EPA isproposing to allow some exit levels toserve as alternative risk-based treatmentstandards meeting the "minimizethreat" standard under RCRA section3004(m). EPA expects these proposals toreduce the burden of complying withLDR requirements.

As explained more fully in thedetailed presentation of option I below,EPA is proposing both of theseapproaches for contingent managementoption 1 (relaxed exit values for wastesthat are not placed in land applicationunits). EPA's rationales are set out inthat discussion.

EPA anticipates that it might also bewilling to propose to use exit levelsdeveloped under option 2 (separate exitlevels for each major type of wastemanagement unit) to serve as risk-based,.minimize threat" standards. If EPAfilled the gaps in its currentmultipathway risk assessment, it wouldfeel fairly confident that themultipathway analysis plus thegroundwater analysis identifiedconstituent concentrations thatminimize threats to human health andthe environment for each class of wastemanagement units. The modeling forboth analyses would assume each typeof unit was located in a "reasonableworst case" physical setting and wassubject to minimal managementcontrols. EPA, however, would expectsome members of the public to arguethat unit-specific exit levels should notbe considered "minimize threat" levelsbecause risks to human health and theenvironment would not be minimized ifexempted waste ended up in the wrongtype of management unit. EPA might tryto address such concerns by imposingconditions such as tracking or reportingsystems on persons claiming theexemptions.

EPA would expect similar objectionsto the option of allowing wastes thatmeet option 2 levels to exit if theirconstituent concentrations met unit-specific exit levels at the point ofgeneration. Members of the public mightagain be concerned about the possibilitythat wastes could be placed in a unittype requiring lower (more restrictive)exit levels. As suggested above,however, EPA could impose conditionsto help ensure that exempted waste goes

only to a unit where the exit levels infact minimize threats.

Providing LDR relief for the remainingoptions for conditional exemptionswould raise additional legal andpractical issues. All of the remainingnational and state-based options rely ondesign or operating controls (such asliners) to help prevent dangerousconcentrations of hazardousconstituents from reaching human orenvironmental receptors. EPA, forexample, would be reluctant to take intoaccount control measures that would bedifficult for inspectors to verify duringsite visits.

It might be somewhat easier to takeinto account factors-such as annualrainfall, depth to groundwater, andsubsurface soil and rock formations-that relate to a unit's physical setting.EPA has already proposed to interpretsection 3004(m) to allow considerationof a unit's physical setting in makingsite-specific minimize threat findings.See the proposed LDR standards forcontaminated soil, 58 Fed. Reg. 48123and 48155 (Sept. 14, 1993). EPArequests comments on all of these issuesrelated to the integration of conditionalexemption options to the LDRstandards.E. Contingent Management of MixedWaste

The Department of Energy (DOE) hasalso expressed interest in EPA'scontingent management approaches tomanaging waste that is mixed radiologicand RCRA hazardous waste ("mixedwaste"). Mixed waste may be managedby DOE-regulated facilities orcommercial facilities regulated by theNuclear Regulatory Commission (NRC).EPA expects that the general approachin today's proposed regulation would beapplicable to mixed wastes as well aslisted-only hazardous wastes. DOE hassuggested that because mixed wastessubject to RCRA are also subject to AEAdisposal requirements which controlreleases of and exposure to radioactivehazards, these AEA requirements mayaddress releases of chemicallyhazardous constituents as well, and itwould be reasonable to allow moremixed wastes to exit Subtitle C becauseof the AEA requirements. DOE believesthese AEA requirements would alsoprovide adequate protection of humanhealth and the environment fromchemically-hazardous constituents. DOEhas submitted several studies to EPA insupport of their views, and the Agencyhas placed those documents in thepublic docket for review. The Agencywill also undertake a review of thesedata to better understand the additionalincrement of protection provided by

AEA low-level waste site performancestandards. With that review ongoing, theAgency is proposing, and requestingpublic comment on, adaption of optionfour above to DOE's specialcircumstances. The Agency requestscomment on allowing mixed wastemeeting conditional exit levels forchemical toxicity estimated at 10-4cancer risk and HQ 1 (modeled at anuncontrolled site), to exit Subtitle C ifmanaged in AEA disposal facilities.

DOE has also urged the Agency toconsider establishing a categoricalexclusion from RCRA requirements formixed waste debris that is immobilized.One of several macro- ormicroencapsulation methods could beused to immobilize the debris, includinguse of portland or other cementproducts, or various polymer products.Under such an exclusion, allimmobilized mixed debris could bemanaged outside of Subtitle C, butwould still be required to be disposedin AEA disposal facilities. No testing ofthe debris would be required to identifytoxic constituents or the levels at whichthey might be present. DOE hasconducted a study of leaching rates forcertain toxic constituents fromstabilized debris and submitted it to theAgency for review in support of DOE'sconclusion that immobilized debris canbe managed safely outside of subtitle Cif disposed in an AEA facility. Becausethe Agency has only recently receivedthis study, it has been unable toadequately review and evaluate the datapresented. The Agency solicits publiccomment on this approach, the DOEstudy, and solicits any other availabledata that are relevant to this topic.

Finally, DOE has developed data onvitrified waste, and requested that theAgency consider the environmentalprotection conferred by this treatmentprocess. Again, the Agency has not hadadequate time to review and evaluatethe DOE data, but has placed it in thepublic docket and solicits publiccomment on the data and DOE'spreferred approach to mixed wastemanagement.

In soliciting comment on these exitprocedures for mixed waste, the Agencyrecognizes that a number of stateshosting DOE facilities have expressedconcern over the proposal's effect ontheir states ability to adequately regulatemixed waste under states and federallaw as intended by RCRA and theFederal Facilities Compliance Act.These states also believe that significantdetails of the DOE proposal are lackingand additional analysis would need tooccur before the procedures can receiveadequate comment. Therefore, theAgency intends, to the extent consistent




with the schedule negotiated in theconsent decree for this rulemaking, topublish a supplemental proposal onHWIR mixed waste exit criteria afterinitial comments have been received.The supplemental proposal wouldfurther describe the regulatory optionsbeing considered and will solicitadditional comment on more specificoptions.

X. Implementation of ConditionalExemption Option 1

A. Introduction

Using the concept of contingentmanagement, EPA is proposing to createa second, alternative set of exit levels fornonwastewaters that are managed inlandfills or monofills, but not landtreatment units. Persons wishing toutilize this alternative exit schemewould not only have to meet therecalculated concentration limits for allconstituents in their wastes, but alsocomply with conditions'prohibitingland treatment. Compliance withnotification and tracking requirementsdescribed in more detail below will alsobe necessary. The exit levels for thisalternative are set out in appendix XI of40 CFR part 261; the requirements andconditions are set out in proposed§ 261.37. Nonwastewaters that do notmeet th exit levels in appendix X to 40CFR part 261 will be eligible for exitonly if they meet the more relaxedlevels in appendix XI of 40 CFR part 261and comply with all relevantconditions.

EPA derived the levels for thisalternative by deleting all of themodeling results for the land treatmentscenario from its risk assessment database, and selecting the lowest remainingexit value from the remaining modelingresults for other types of wastemanagement units. The same approachused to establish exit levels presented inSection V. of today's proposedrulemaking was used to establish exitlevels under this option. That is, wherecomplete risk data was not available,surrogates were used to extrapolatedexit levels (see Section IV.H) and whereanalytical limitations existed, EQCswere used as exit levels (see SectionIV.I). As a practical matter, thisapproach affects only the exit levels fornonwastewaters. As explained above insection IV, EPA created the original exitlevels for nonwastewaters by groupingthe modeling results for the unit typestypically used to manage solid materials(ash monofills, piles, and land treatmentunits) and selecting the lowest valuefrom all pathways modeled for thesescenarios. EPA created the separatewastewater exit levels by grouping the

results from units typically used tomanage liquid wastes (tanks and surfaceimpoundments). Consequently, thewastewater exit levels are not based onthe modeling of land treatment units,and these levels are not affected by thedecision to exclude results from theland treatment scenario.

The Agency is proposing that thecontingent management exemption beself-implementing. Therefore, theclaimant would have the burden ofdemonstrating that all of the provisionsfor the contingent managementexemption described herein have beenmet. In an enforcement action, a wastefor which a contingent managementexemption is claimed would beconsidered a Subtitle C hazardous wasteunless the claimant was able to produceevidence that all of the conditions of theexemption have been met.

B. When Contingent ManagementExemptions Become Effective

The Agency is proposing two optionsfor the point at which the contingentmanagement exemption would becomeeffective.

1. Option 1A-Placement of the Wastein a Qualifying Unit

Under the first option, the conditionalexemption for "contingentmanagement" nonwastewaters wouldnot become effective until the waste hadbeen placed in a qualifying unit. Priorto actual disposal, the nonwastewaterwould be managed as a hazardous wasteaccording to all applicable RCRAprovisions, including 40 CFR parts 262(for generators) and 263 (fortransporters) and part 268 (regardingtreatment prior to land disposal). Theserequirements include compliance withthe waste manifest provisions of 40 CFRpart 262, subpart B, and the pre-transport provisions of 40 CFR part 262,subpart C, which contains, among otherprovisions, the provisions governinghazardous waste accumulation.Treatment and storage prior to disposalwould remain subject to parts 264, 265,and 270.

The Agency believes this approachmakes it easier to ensure consistentimplementation and safe management ofthe waste. It also decreases the potentialimplementation concerns that may ariseif some states adopt this rule as part oftheir authorized programs and others donot. For example, this approach wouldreconcile transportation concerns thatcould arise if waste, conditionally-exempt in one state, were transportedthrough a state that had not adopted thecontingent management exemption aspart of its authorized program.

Under this option, the Agency isconsidering and requesting comment onthe applicability of amending 40 CFR264.1 and 265.1 to allow off-sitedisposal facilities to store candidatecontingent management exempt wastesfor up to 10 days without becoming asubtitle C treatment, storage, anddisposal facility, prior to ultimatedisposal in a monofill or landfill. TheAgency requests comment on whether10 days is a sufficient or appropriatelength of time, and if not, what timeperiod may be appropriate.

Under the above approach, contingentmanagement exempt nonwastewatersbeing disposed of on-site also would notbecome exempt until placed in adisposal unit meeting the requirementsestablished under this rule. However,since the current waste accumulationprovisions of 40 CFR 262.34, allow agenerator to store hazardous waste on-site in tanks, containers or containmentbuildings for 90 days without becominga Subtitle C storage facility, EPAbelieves that this approach should notplace undue burdens on a generator.EPA requests comment on whether§ 262.34 will in fact enable generators ofexempt nonwastewaters to store wasteson-site in unpermitted units for areasonable period of time prior to landdisposal. EPA acknowledges thatnonwastewaters are typically not storedin tanks.

2. Option 1B-Effective Upon Meetingthe Exit Levels

The second option that EPA isconsidering would allow anonwastewater to become exempt fromall hazardous waste requirements exceptpart 268 as soon as it meets appendix XIof 40 CFR part 261 exit levels and theclaimant has met all the requirementsand conditions of the exemption, .including certifying that the waste willbe managed in a monofill or landdisposal unit. The goal of this approachis to ensure nonwastewaters will not bemanaged in a land treatment unit,which was found to pose the greatestrisk for many routes of exposure. Underthis approach, storage, treatment andtransportation of the nonwastewatercould take place outside of Subtitle Ccontrol upon meeting the. requirementsand conditions for the exemption. IfEPA were to adopt such an approach, itwould impose conditions to ensure thatthe exempted nonwastewater reachedthe types of units for which theexemption was designed. Variousoptions are suggested below in SectionD.1.

Finally, EPA notes that the proposedapproaches have different implicationsfor LDR relief. These differences, which

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principally concern the availability ofLDR relief for nonwastewaters whichmeet the appendix XI of 40 CFR part261 exit levels at their point ofgeneration, are discussed in more detailin section H. below.

C. Requirements for Obtaining anExemption

The following requirements would beapplicable to both of the approachesdiscussed above. Requirements formeeting the contingent managementexemption would include the samplingand testing requirements of § 261.37(b)(1), the public notice requirements of§ 261.37 (b)(3) and the notification tothe implementing Agency requirementsof § 261.37 (b)(4), similar to thoserespective requirements for the baseexemption in §§ 261.36 (b) (1), (3) and(4). The Agency notes that theseprovisions would be directlyenforceable Subtitle C requirementsimposed prior to obtaining anexemption rather than conditions formaintaining the exemption.

1. Sampling and Testing Requirementsfor Contingent Management Exemptions

The Agency is proposing that thesampling and testing requirements forthe contingent management exemptionbe the same as those proposed for thebase exemption in Section 261.36 (b)(1).The Agency requests comment onwhether the sampling and testingrequirements for the base exemptionwould be appropriate for the contingentmanagement exemption.

2. Requirements for Public Participationin Contingent Management Exemptions

To provide the public with access toinformation, the Agency is proposing torequire compliance with the publicnotice requirements in proposed§ 261.37(b)(3), similar to those in§ 261.36(b)(3). The first time a claimantprovides the Agency with notification ofan exemption claim for contingentmanagement wastes, he will be requiredto publish a notice of the claim in amajor local newspaper generalcirculation. The notice must include thename and address of the facility, thedescription of the waste (as contained inthe notification), a brief generaldescription of the process producing thewaste, an estimate of the quantities ofwaste claimed to be exempt, andinformation about the Agency where theclaimant has sent the notification andsupporting information. In addition, thepublic notice must include that thewaste meets the contingent managementexemption levels in appendix XI of 40CFR part 261 and that the waste will be

disposed of in a monofill or landdisposal unit.

3. Notification Requirements forContingent Management Exemptions

To qualify for a contingentmanagement exemption, a claimantwould need to submit to the authorizedState Agency Director a formalnotification of its claim that waste meetsthe contingent management exemptionlevels in Appendix XI of 40 CFR part261 and will be managed in accordancewith the management conditions. Inaddition to the requirements under§ 261.36 (b)(4), the contingentmanagement exemption notification tothe implementing Agency must includean accompanying certification that thewaste meets the contingent managementexemption levels in appendix XI of 40CFR part 261 and that the waste will bedisposed of in a monofill or landdisposal unit.

The Agency requests comment onwhether these requirements, similar to§ 261.36 (b)(1),(3) and (4), will provideadequate information to theimplementing agency and the public onwhat exemption levels, i.e., appendix Xto 40 CFR part 261 or appendix XI of 40CFR part 261, are being claimed and onhow. the waste is being managed. Theseprovisions would be requirementsrather than conditions.

D. Implementation Conditions

As set out in § 261.37 (d) andexplained in the base exemptionimplementation preamble (section VIII.B., Implementation Conditions) certainconditions have to be met to maintainthe exemption after the claim hasbecome effective. Under both option 1Aand 1B, the following conditions'wouldhave to be met to maintain thecontingent management option:Submitting changes in notificationinformation to the Director within 10days of the change, following theschedule for retesting, preparing andcomplying with a sampling and analysisplan for every retest, maintainingconstituent concentrations in thenonwastewater at or below theexemption levels in appendix XI,meeting applicable treatment levelsunder § 268.40, and maintaining recordson-site for three years. These conditionsare very similar to those proposed forthe base exit in Section VIII of today'sproposed rulemaking. In addition tothose conditions established for the baseexemption, the claimant would alsohave to ensure that the waste wasmanaged in a quali ing unit.

Claimants, under both options, alwayshave the obligation to identify whetherthey are generating a hazardous waste

and to notify the appropriategovernment official if they aregenerating a hazardous waste. (Section3010; 40 CFR 261.11.) If anynonwastewater claimed as exemptunder the contingent managementproposal tested above the exit levels inappendix XI to 40 CFR part 261 at anytime, that waste and any mixture orderived-from forms of that waste wouldhave to be managed as hazardous waste,including compliance with allnotification requirements, until testingdemonstrated that the waste was belowthe exit levels.

1. Tracking Conditions

EPA is proposing to modify themanifest regulations to reflect the factthat wastes exiting under thisexemption need not be disposed of intreatment, storage or disposal facilitiesthat are subject to the requirements of§ 264.71-264.72 or Section 265.71-264.72 requiring the facility thatreceives the waste to sign and return themanifest. EPA is not proposing torequire the owners and operators ofnonhazardous waste facilities thataccept wastes exempted under thisoption to comply with these duties. AsEPA concluded when it decided not toextend recordkeeping duties related tothe LDR program to nonhazardous wastefacilities accepting de-characterizedhazardous wastes, it would probably bedifficult to provide reasonable notice toall the members of this diverse universe,which has little or no other contact withthe hazardous waste managementregime, of these Subtitle Cresponsibilities.

EPA is proposing instead that theclaimant of the exemption beresponsible for ensuring that themanifest is returned and that it-orsome other document-providesinformation showing that the facilitydesignated on the manifest did in factreceive the waste and did place it in alandfill or monofill (and not a landtreatment unit). Billing documents mayalready supply some of the neededinformation. Where they do not, EPAbelieves that claimants should generallybe able to contract with the receivingfacilities to obtain the necessaryinformation. In some states,nonhazardous waste rules may alsorequire disposers to furnish generatorswith some of the necessary information.EPA proposes to revise the manifestdocument as necessary to ensure thatnonhazardous waste facilities can bedesignated as receiving facilities forlisted wastes meeting all of the otherrequirements for obtaining anexemption under this option.




The alternative to this approachwould be to require owners andoperators of nonhazardous wastefacilities to sign and return manifests asa condition of the exemption. Failure tosatisfy this condition would void theexemption and return the waste to thehazardous waste management regime,even if it were in fact safely placed inan appropriate waste management unit.EPA requests comment on thisalternative.

Under option 1A, where all Subtitle Cregulations apply until placement of thenonwastewater in a monofill or landfill,EPA is proposing conditions that makethe claimant responsible for obtaining acopy of the manifest to ensure the wastehas reached its destination. Theclaimant would also have the burden ofacquiring evidence from the receivingfacility that the waste was placed ineither a monofill or land disposal unit.

Under Option 1B, where theexemption becomes effective upon thewaste meeting-the appendix XI of 40CFR part 261 exit levels, any trackingsystem established would be a conditionthat the claimant would have to meet tomaintain the contingent managementexemption. To ensure that listed wastesexempted under this option actually goto a landfill or monofill, EPA isproposing to require exemptionclaimants to comply with therequirements of part 262 (with themodification discussed above) relatingto the uniform hazardous wastemanifest.

Since this option allows wastes to goto facilities that are not subject to theduty to return the manifest under§ 264.71-264.72 or § 265.71-264.72,EPA is proposing to require the claimantto ensure that the manifest is returnedand that it-or some other document-provides information showing that thefacility designated on the manifest didin fact receive the waste and did placeit in a landfill or monofill (and not aland treatment unit). The duties wouldbe identical to those proposed above forclaimants under the first option. Therationale for imposing the duties on theclaimant-and not the receivingfacility-is also the same.

An alternative which EPA requestscomment on is the concept of imposingconditions that require a uniform,national tracking document similar tothe current uniform manifest toaccompany the waste until it reaches itsfinal destination. This document couldinform transporters and other wastehandlers that the waste is an exempthazardous waste that must be managedin a monofill or land disposal facilityand loses its exemption if it is managedin a land treatment unit. EPA could

further require that the disposal facilitycertify that the nonwastewater wasdisposed in a monofill or land disposalunit and return the tracking documentand certification to the originalexemption claimant. EPA could alsoensure that the implementing agency(EPA or an authorized state) receivednotice of any problems in wastedisposal by imposing requirementssimilar to the current § 262.42 exceptionreporting provisions;

Another alternative would be torequire, in lieu of a tracking document,a contractual agreement between theexemption claimant and the receivingfacility specifying the type of waste thereceiving facility will accept, the type ofunits it will use, and information on thevolume and frequency of deliveries.EPA could require either the claimant orthe receiving facility (or both) tomaintain a copy of the agreement on-siteand make it available to state or EPAinspectors. EPA also could requireexemption claimants and transporters tocreate and keep similar contracts. EPA,however, requests comment on whethertransporters would require claimants toprovide information on the exemptedwaste's origin and the regulatory limitson its disposal options even withoutfederal regulation.

EPA requests comment on whetherany of these alternatives can adequatelyensure that mismanagement will notoccur so that these wastes managedunder this option 1B approach wouldnot need to be classified as hazardous.2. Qualifying Unit

A "qualifying unit" for today'scontingent management proposal is alandfill or monofill. For purposes oftoday's proposal, a landfill is defined in§ 260.10 as being "a disposal facility orpart of I facility where hazardous wasteis placed in or on land and which is nota pile, a land treatment facility, asurface impoundment, an undergroundinjection well, a salt dome formation, asalt bed formation, an undergroundmine, a cave or a corrective actionmanagement unit." The Agency isproposing a definition for monofill in§ 260.10 as a landfill where waste ofonly one kind or type is placed in or onland and which is not a pile, a landtreatment facility, a surfaceimpoundment, an undergroundinjection well, a salt dome formation, asalt bed formation, an undergroundmine, a cave, or a corrective actionmanagement unit. Also, for today'sproposal, a land treatment facility isdefined in § 260.10 as being "a facilityor part of a facility at which hazardouswaste is applied ontb or incorporatedinto the soil surface; such facilities are

disposal facilities if the waste willremain after closure." The Agencyrequests comment on whether otherunits could be considered "qualifyingunits" for contingent managementexempt waste and whether additionalmodeling is needed to assess risks frommanagement of nonwastewaters fromother units.

The Agency modeled risks from wastepiles in both its multipathway andgroundwater analyses. It modeled onlygroundwater risks form landfills. Asexplained elsewhere in this preamble,EPA believes that the nongroundwaterrisks posed by piles generally are higherthan the nongroundwater risks posed bylandfills. EPA, however, is notproposing to allow wastes placed inpiles to be exempt under the exit levelsfor contingent management option 1.Piles, as defined in Part 260, aretemporary units. To ensure thatexempted wastes removed form pileswent only to landfills or monofills, EPAwould have to impose additionaltracking conditions. These could bedifficult to craft and enforce effectively.EPA currently thinks that excludingpiles from eligibility will provide muchbetter assurance that exempted wasteswill not be mismanaqed.

EPA acknowledgeg'that the exit levelsfor this option, which are based in manycases on the evaluation of waste piles,may, for some pathways, be morerestrictive than levels for landfills. IfEPA later completes a multipathwayanalysis of landfill units, it will be ableto use the levels from that modeling inlieu of the modeling from piles to deriveexit levels for this option.

The Agency requests comment on theproposal to exclude wastes placed inpiles from being eligible for exemptionunder this option. The Agency alsorequests comment on the alternatives ofallowing wastes to be exempt eitherpermanently or temporarily (e.g., for oneyear) after they are placed in piles.3. Claimant's Duty To EnsureCompliance With All Requirements andConditions

Today's proposal requires that, inorder to claim a contingent managementexemption, the person submitting theclaim must manage the waste for whichthe exemption is claimed in accordancewith the requirements and conditionsestablished by this rule. To satisfy thisrule, the claimant must ensure that thewaste is actually disposed of in aqualifying unit. The burden of satisfyingall conditions for the exemption falls onthe claimant as the person in the bestposition to determine eligibility of awaste for an exemption and to ensureinformed waste management decisions.The claimant may enter into contractual

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arrangements with receiving facilities toallocate responsibility for satisfaction ofthe conditions among themselvesalthough such arrangements will notrelieve the claimant of liability if thereceiving facility manages the wasteimproperly. It should be noted,however, that facilities receivingcontingent management exemptionwastes could also become liable forviolations of permitting, Subtitle Ctreatment, storage and disposalstandards should they dispose of thenonwastewaters that do not qualify.

Under today's proposal, § 261.37(g),the burden of proof to establishconformance with the exemptioncriteria is on the claimant in the eventof an enforcement action. Onealternative for simplifying theclaimant's burden of provingcompliance with all conditions wouldbe to set out in the rule certaindocumentation that, while notnecessarily required of the claimant,presumptively would be sufficientevidence of satisfaction of themanagement condition. Of course, EPAcould rebut this presumption regardingactual disposal through evidence thatthe claimant's documentation isdeficient or inaccurate. For example,claimants might be able to developrebuttable evidence of proper off-sitedisposal by keeping correspondencewith the receiving facility, indicatingthat the waste went to a landfill ormonofill, and by keeping a returnedmanifest which indicates that the wastereached that facility. The Agency istaking comment on whether establishingcertain evidentiary standards wouldprovide useful guidance to claimants onhow to satisfy the managementcondition and provide helpful incentivefor claimants to maintain properdocumentation of their exemptionclaims.

Comment is also requested onwhether any additional conditions orrequirements, substantive or procedural,should be imposed on claimants toensure that the contingent managementexemption waste is actually managed ina qualifying unit.

E. Retesting and RecordkeepingConditions for Contingent ManagementExemptions

Claimants continuing to generate orotherwise manage waste for which theycontinue to claim a contingentmanagement exemption would berequired, under § 261.37(d)(2), to retestthe waste with the same frequency andunder the same conditions as is beingproposed for the base exemptions,§ 261.36(d)(2). If a claimant finds thatthe exempted waste no longer meets the

constituent concentration levels onAppendix XI of 40 CFR part 261 for thecontingent management exemption, orthat the waste has not been placed in alandfill or monofill, the claimant mustcomply with all applicable requirementsfor generators of listed wastes (includingdisposal of waste at a Subtitle C facility)and the disposal facility would have tocomply with all of the requirements forowner/operators of treatment, storage,and disposal facilities under 40 CFRparts 262-270. The generator anddisposal facility's obligations wouldalso include renotifying the Agency ofhazardous waste management activityusing EPA form 8700-12.

Under § 261.37(d)(6), claimants alsowould be required to maintain on-site,for at least three years after Agencyreceipt of the notification andcertification, all documentation requiredunder this rule including, but notlimited to, the sampling and analysisplan and test data and theaccompanying notification andcertification. These requirements aresimilar to those proposed for the "base"exemption in § 261.36.

The Agency requests comment onalternative record retention periods forclaimants such as 5 years, whichcorresponds to the applicable statute oflimitations period at 28 U.S.C. 2462. Anextended record retention period mayassist claimants in substantiating theirconformance with the contingentmanagement exemption criteria. Thedocumentation must be available forreview by the Agency or an authorizedState at the time of site inspection. Thethree-year claimant record retentionperiod will be automatically extendedduring the course of any unresolvedenforcement action regarding theregulated activity.

F. Compliance Monitoring andEnforcement for ContingentManagement Exemptions

Since contingent managementexemptions are self-implementing, theAgency needs to rely on its enforcementauthorities to ensure that theexemptions are being applied in anappropriate manner and that only thosewastes that are truly nonhazardous arerelieved from Subtitle C disposalrequirements. Compliance monitoringand enforcement of the contingentmanagement program would be carriedout under existing authorities andconditions with which the regulatedcommunity should already be familiar.

Claimants must comply with all of thepreviously described conditions of theexemptioni to qualify for theexemptions. All persons who managewaste for which an exemption has been

claimed must manage the waste asrequired under Subtitle C duringperiods when any of those conditionsare not met. Claimants that fail tocomply with the applicable conditionsof the contingent managementexemption risk enforcement action forviolations of Subtitle C requirements,.including administrative, civil andcriminal penalties.

1. Compliance MonitoringThe Agency is proposing that

compliance monitoring of thecontingent management exemptionoccur through EPA and State oversight,primarily through review ofnotifications and inspections.

The Agency has the authority, undersection 3007 of RCRA, to requiresubmission of information and toconduct inspections of facilities whichEPA has reason to believe may begenerating or managing a hazardouswaste. EPA and States may doconfirmatory sampling and analysis todetermine whether a waste meets theexemption levels. Under this authority,the Agency would be able to inspect anon-Subtitle C facility receivingcontingent management exemptionwaste.

Inspections of off-site laboratoriesmay also be performed.

2. EnforcementThe contingent management

exemption criteria proposed todaywould create an exit from the SubtitleC system only so long as therequirements and conditions establishedfor the exemption are met. Failure tocomply with any of the conditions forthe exemption would mean that thewastes would not be exempt fromSubtitle C, and the claimant could besubject to immediate enforcement actionfor violation of Subtitle C requirements.

The Agency has the authority underthis regulation and RCRA Section 3007to require submission of information onthe management of exempted wastes ina situation where the Agency suspectsthe claimant has not satisfactorilydetermined whether a waste meets theappropriate exemption levels.Alternatively, the Agency may requireimproved analysis using anadministrative or civil action undersection 3013. Failure to manage thecontingent management exemptionwaste in accordance with the conditionswould void the exemption and theconditionally exempt waste would besubject to full Subtitle C regulation. Thereceiving facility, therefore, wouldbecome a Subtitle C treatment, storage,and/or disposal facility requiring apermit.




In an enforcement action, compliancewith the terms and conditions of theexemption may be raised as anaffirmative defense, but the burden willbe on the defendant to establisheligibility for the exemption andcompliance with the conditionsnecessary to maintain the exemption.See 50 FR 642 (Jan. 4, 1985) for adiscussion of EPA's authority to placesuch burdens on defendants.

Claimants may not use the contingentmanagement exemption as a means ofavoiding enforcement actions. Forexample, a generator who is the subjectof an Agency enforcement action cannotclaim that the waste in question isexempted from Subtitle C under thecontingent management exemptionunless a valid exemption notification forthat waste has been previouslysubmitted to the Agency and therequired documentation to support theclaim exists at the facility and satisfiesthe requirements of the regulations. Thecontingent management exemptioncannot be used in a retroactive fashionto avoid enforcement actions. Similarly,these exemptions cannot be used as alegal defense prior to the effective dateof promulgation of this rule.

G. Exports of Wastes Eligible forContingent Management Exemptions

Under option 1A of today's proposal,contingent management exemptionwastes would remain hazardous untilactually disposed of in a qualifying unit.The waste would thus remain subject toall applicable requirements of 40 CFRparts 262 and 263, including exportrequirements.

Under option 1B where the wastebecomes exempt upon meeting thecontingent management exit levels,comment is requested on whether theseexempt wastes should still remainsubject to the export requirements of 40CFR part 262. Comment is requested onwhether these export requirements arenecessary to ensure that the contingentmanagement exemption waste will beproperly managed in the receivingcountry.

H. Land Disposal Restrictions

As discussed above in section VI, EPAis proposing two approaches tointegrating LDR requirements with theexit levels for the base option. First,EPA is proposing that LDR treatmentrequirements will never apply to wastesthat meet exit levels for the base optionat the point of generation. Second, forwastes which remain subject to LDRrequirements, EPA is proposing to allowexit levels based solely on the combinedmultipathway and groundwateranalyses to serve as alternative risk-

based LDR standards meeting the"minimize threat" standard in section3004(m) of RCRA. EPA believes thatboth approaches are appropriate forcontingent management option 1.

To eliminate the duty to comply withthe LDR rules for wastes that meet thebase option exit level at the point ofgeneration, EPA is taking the positionthat such wastes are defined ashazardous waste pursuant to theirlisting descriptions for such a briefperiod of time that they effectivelynever become subject to Subtitle Crequirements, and LDR requirementsnever apply. It is relatively easy to applythis theory to option 1B presented abovein section B.2. that allowsnonwastewaters to exit as soon as theyhave met the appropriate concentrationlimits and to remain exempt so long asthey are managed in landfills ormonofills. Such wastes need only meetthe exit levels to obtain their exemption.If they meet them at the point ofgeneration, they would appear just asentitled to LDR relief as wastes meetingthe exit levels for the base option.

Under option 1A, however,nonwastewaters will not exit until theyboth meet the exit levels and are placedin a landfill or monofill. Such wasteswould not be eligible for exit at thepoint of generation even if theirconstituent concentrations were lowenough. Rather, they would be subjectto Subtitle C regulation for a significantportion of their "cradle-to-grave"management cycle. It would be difficult.to argue that these wastes had neverreally been regulated as hazardouswastes, and that LDR treatmentrequirements did not apply.Consequently, EPA is not proposing toallow nonwastewaters to becomeexempt from LDR requirements at thepoint of generation under this sub-option. EPA requests comment onalternative legal theories that wouldprovide a better basis for arguing thatnonwastewaters subject to this sub-option could be exempt for the LDRrules if they meet exit levels at the pointof generation.

Both options 1A and 1B haveidentical exit levels based on removingthe predictions for land treatment unitsand using the next-highestconcentration as the exit level. EPA isproposing to allow the exit levels thatare based solely on the multipathway/groundwater risk analyses to serve asminimize threat levels for both options1A and lB. These levels representconcentrations posing minimal lowthreats for nonwastewater placed inlandfills, monofills and waste piles.They are based on the same riskassessment used for the assessment for

the base option. They make the same"reasonable woist case" assumptionsabout the units' physical setting and thesame minimal assumptions aboutcontrol measures. Hence, EPA believesthat these exit levels sufficiently reducethreats to human health and theenvironment to meet section 3004(m)'s"minimize threat" standard.

EPA acknowledges that option 1B,allowing wastes to exit Subtitle C beforethey are placed in the right kind of landdisposal unit, presents an additionaltype of risk. Under option 1B, it may bemore difficult for EPA to ensure thatexited wastes will not be placed in landtreatment units. (Under the alternativeoption, option 1A, Subtitle C manifestand tracking requirements wouldapply.) As explained above in sectionB., however, EPA will create conditionsfor option 1B to help ensure thatexempted wastes are not disposed of inland treatment units. EPA believes thatthese conditions will sufficiently reducethe risk of inappropriate disposal thatthe exit levels will continue to minimizethreats. EPA requests comment on thisaspect of the proposal.XI. Relationship to Other RCRARegulatory Programs

Today's rule proposes specificconditions and exit criteria that wouldexempt listed hazardous wastes,including waste mixtures and derived-from wastes, from Subtitle C regulation.Below is a discussion of how thisproposed rule would affect otherrelevant RCRA regulatory programs.

A. Hazardous Waste Determination

Under current RCRA regulations, anyperson who generates a solid wastemust determine if that waste is ahazardous waste in accordance with theprocedures outlined in 40 CFR 262.11.According to 262.11, generators mustfirst determine if their waste is excludedfrom regulation under 40 CFR 261.4.Generators must then determine if thewaste is listed in subpart D of part 261.If the waste was not listed, or forpurposes of compliance with 40 CFRpart 268, generators must thendetermine if the waste exhibits acharacteristic defined in subpart C ofpart 261.

Today's proposed rule is anexemption for listed wastes meeting theexit criteria, and does not change thegeneral requirements for generatorsmaking hazardous waste determinationsunder § 262.11 (see discussion ofcharacteristic waste below).B. Characteristic Hazardous Waste

Today's proposed rule establishesexemption criteria for hazardous

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constituents in eligible listed wastes,waste mixtures, or derived-from wastes.If the waste satisfies the exemptioncriteria proposed today, the wastewould not be considered listedhazardous waste. However, thegenerator must still determine whetherthe waste exhibits any characteristics ofa hazardous waste as specified in 40CFR 261.21 through 261.24 andcontinue to meet hazardous wasterequirements if the waste does exhibit acharacteristic.

C. Toxicity Characteristic Level for Lead

Toxicity characteristic constituentsare among those evaluated for exitvalues in this proposal. In developingthe risk assessment for all constituents,including the TC constituents, theAgency examined risks via groundwaterand other pathways to humans, and alsoenvironmental receptors. In evaluatingrisks resulting from the groundwaterpathway, the Agency used its newlydeveloped CMTP model, and theMINTEQ metals speciation component.The CMTP model estimatesgroundwater transport using finitesource assumptions, and accounting forhydrolysis and adsorption of chemicalsto soils. The MINTEQ componentestimates dissolution and speciation ofmetals in groundwater. Using thesemodels, the Agency has developed andis proposing estimates of transportthrough groundwater specific to eachconstituent. These estimates areanalogous to constituent-specificdilution and attenuation factors (DAFs).These constituent-specific DAFs werecontemplated for several constituentsproposed for regulation in the TCrulemaking, but not finalized, becausethe modeling work was not complete.TC levels were set using generic DAFsof 100.

In developing the constituent-specificDAFs, the Agency estimated that leadmoves through groundwater much moreslowly than predicted by the genericDAF of 100. While the modelinganalyses supporting the TC rule andtoday's proposed rule are somewhatdifferent from one another, theconstituent-specific DAF for leadleaching from a landfill was estimatedas 5000 rather than the 100 used in theTC rule. Higher leqching rates (givinglowerDAF values) were estimated forsome other disposal options evaluatedin the updated modeling, such as landapplication and management in surfaceimpoundments. This analysis raised thequestion of how the TC and today'sproposed rules would relate to oneanother, and whether these resultswarranted consideration of a change tothe TC level of 5 mg/l for lead (updated

groundwater modeling of other TCconstituents did not show the largedisparity between the TC and exit levelproposed in today's notice for lead).

In considering these issues, theAgency reviewed several factors. First,the human health risk evaluation forlead has changed since the TC rule waspromulgated, resulting in the MCL (onwhich the TC is based) for lead beingreduced from 50 ppb to 15 ppb. Usingthe new DAF from the landfill scenarioplus the new drinking water standardcould raise the TC level to 75 mg/l fromthe current 5 mg/I. However, when leadmovement from a land treatmentscenario was modeled, a DAF ofapproximately 770 resulted, and a TClevel based on this and the newdrinking water standard could beapproximately 10 mg/1. Anotherrelevant reference point for lead in theenvironment includes the currentOSWER soil direct ingestion level forlead of 400 ppm (as a totalconcentration, not leachate).

The Agency considered severalapproaches to potentially proposingrevisions to the TC level, includingbasing a new TC level on groundwatermodeling only, basing it on the soilingestion estimate, or basing it on thedriving pathway value and exit level,which considers adverse ecologiceffects.

After carefully considering the issue,the Agency concluded that the issue oflead toxicity and movement through theenvironment is very complex andchanges to existing rules could havesignificant impacts on management oflead-bearing waste and public health.The agency believes regulation of lead-bearing wastes warrants carefulconsideration and full evaluation of andreview of the policy issues associatedwith considering all potential exposurepathways and risk to human health andthe environment. Questions includewhether the TC level would be aleachate or totals value, and whether itwould be based on groundwater only orother exposure routes and whether itwould be human health based or basedon ecological risk considerations. Sucha comprehensive evaluation is notfeasible in the context of the rulemakingproposed today, and so the agency hasdetermined to defer any action on thelead TC level. The Agency recognizesthat this is an issue of considerableinterest to the public, and will considerreview of management of lead-bearingwaste at the soonest practical time. Inthe interim, the lead TC regulation andthe exemption regulation proposedtoday (when finalized) would co-exist asindependent regulations.

As described in Section IV.E.3, theAgency has developed groundwatermodeling based on both 10,000 year and1000 year time frames. Today's proposal.is based on the 10,000 year modelingtime horizon, and the Agency issoliciting public, comment on thealternative of using 1000 years. Oneaspect of the 1000 year modeling resultsis that the groundwater-based exit levelsfor more constituents would be abovecurrent TC levels for those constituents.*These constituents include, in additionto lead, chromium, cadmium, selenium,and mercury. The Agency seeks publiccomment on this aspect of using the1000 year time horizon modeling forrisk assessment in the HWIR rule.

D. Hazardous Waste Listings

The Agency evaluated the likelihoodthat untreated hazardous wastes wouldbe able to meet the exemption criteria inan "pure" state (e.g., untreated andunmixed) and determined that it isunlikely that the constituentconcentrations in many untreatedhazardous wastes would be belowtoday's proposed exemption levels orthe applicable BDAT standards,particularly for nonwastewaters.Specifically, the Agency's hazardouswaste characterization data indicate thatthe concentrations of toxicants ofconcern in untreated listed wastes aretypically present at levels many timeshigher than health-based levels or BDATvalues. Therefore, it is unlikely that theAgency's current criteria for listingwastes as hazardous will change as aresult of the introduction of today's exitcriteria into the RCRA regulations.However, EPA has been utilizing a morecomprehensive risk analysis in thelisting program, looking at multiplepathways for the movement ofconstituents through the environment,similar to the approach taken in today'sproposal. Today's proposed approachmay also provide the Agency with ameans of assessing whether or notfuture listirfgs might inadvertently bringinto the RCRA system the types of low-concentration wastestreams that wouldsubsequently be eligible for exit undertoday's proposal.

E. Delisting

The evaluation criteria used fordelisting may vary from today'sexemption criteria for various reasons.First, delisting is an interactive processthat considerable oversight by EPA orauthorized State agencies. In delisting,the overseeing agency evaluates theprocesses generating a specificwastestream in order to determine theconstituents likely to be present, as wellas the potential variability in the waste.




EPA (or the State) closely reviewssampling procedures, analytical testresults, and the accompanying QA/QCdata. This oversight increases theconfidence in the quality andrepresentativeness of the waste analysis.

Second, delisting is specific to onewastestream, which decreasesuncertainties that arise in the moregeneric approach proposed today. Forexample, a delisting petition willtypically provide the annual generationvolume of the waste. Using a specificwaste volume as an input to variousmodels has allowed EPA to calculateexit levels that may be somewhat higherthan the levels proposed in today's rule.EPA believes that it is reasonable to usehigher exit levels for the smaller wastevolumes in delisting petitions (see 56FR 32993 (Reynolds Metals) for furtherdescription of volume impact).

The delisting process also allowsmore certainty in the plausiblemanagement scenarios that are modeledto generate exit levels. For example, thecharacteristics of the waste may dictatethe likely disposal method (e.g.,disposal in a landfill of de-wateredprocess sludge). In some cases, specialmanagement standards may also be afactor (e.g., radioactive wastes areregulated under the Atomic Energy Act,therefore if such a hazardous waste weredelisted, disposal options would beseverely limited (see 60 FR 6054(Hanford delisting)).

EPA also considers the applicabilityof available groundwater monitoringdata from land-based waste managementunits that have received the petitionedwaste. Such data are typically requiredunder permitting regulations forhazardous waste facilities (see 40 CFRparts 264 and 265). If any contaminationof groundwater appears to be due toconstituents from the petitioned waste,EPA will consider this as a basis to denythe petition. The more generic wasteidentification rule proposed today doesnot incorporate this additionalevaluation criterion.

EPA may also require special testingregimes to ensure waste consistentlymeets delisting criteria (e.g., see (citeReynolds Metals, CSI, Hanford)).Because the overseeing agency reviewsthe petition in som. detail, the testingfrequency may be Llosely tied to thepotential variability of the waste. Afacility that accepts and treats wastefrom diverse sources would typicallyhave frequent testing requirements (see40 CFR part 261 appendix IX (Envirite)).In other cases, the testing requirementsfor some initial period will be extensive,but the subsequent testing may bereduced.

Delisting petitions for wastes thatcontain toxic constituents which exceedthe exemption levels proposed todaywill continue to be accepted andreviewed by the Agency afterpromulgation of today's rule. With theexception of a potentially reducedpetition review burden, the Agency doesnot anticipate any changes in thecurrent review of delisting petitions asa result of the implementation of today'sproposed exemption. EPA does requestcomment on which risk models shouldbe used to evaluate future delistingpetitions.

F. Requirements for Treatment, Storage,and Disposal Facilities and InterimStatus Facilities

In order to implement the changesproposed today, owners or operators ofRCRA permitted or interim statusfacilities may have to amend their wasteanalysis plans if required under 40 CFR264.13 and 265.13. Such changes willmost likely include the addition of theappropriate analysis methods andchanges that may be required in thefrequency of testing.

Permitted facilities, in unauthorizedStates, who elect to employ theexemption procedures and whosubsequently prepare changes to theirwaste analysis plans should, followingpromulgation of this rule, submit a ClassI permit modification to EPA. (EPA isaware that although most States haveeither become authorized for, or haveadopted, the 3-class permit modificationregulations, some states may still beoperating under the older "major/minor" permit modification procedures.Under those procedures, changes to thewaste analysis plan would beconsidered a major modification).

G. Closure

Under today's proposed rule, ahazardous waste management unit thatreceives wastes that are exempt undertoday's exit criteria would continue tobe a regulated Subtitle C unit subject tothe requirements of 40 CFR parts 264 or265, including closure requirements,until the owner/operator completedclean closure of the unit or unless all ofthe waste in the unit were delisted. Aunit receiving only waste that is exemptunder today's proposal would no longerbe receiving hazardous waste upon theeffective date of the exemption; such aunit would normally become subject toSubtitle C closure requirements, whichare triggered by the final receipt ofhazardous waste by the unit. Thefacility owner or operator is required tocomplete closure activities within 180days after receiving the final volume ofhazardous waste. 40 CFR 264.113(b) and

265.113(b). However, RCRA closurerequirements do allow certain wastemanagement units to delay closure,while continuing to receive non-hazardous waste (such as waste exemptunder today's proposed rule), providedcertain conditions are met.

The RCRA delay-of-closureregulations, promulgated on August 14,1989 (54 FR 33376), allow owners oroperators to delay the closure oflandfills, land treatment units, andsurface impoundments in cases wherethe unit stops receiving hazardous wastebut the owner or operator wishes tocontinue using the unit to manage onlynon-hazardous waste. Theserequirements are outlined in 40 CFR264.113(d) and (e) and 265.113(d) and(e). Owners or operators wishing todelay closure must request a permitmodification at least 120 days prior tofinal.receipt of hazardous wastes, or, ifthe facility is in interim status, submitan amended part B application at least180 days prior to the final receipt ofhazardous wastes. The request for apermit modification or the amendedpart B application must includedemonstrations that the unit has theexisting design capacity to manage non-hazardous wastes, and that the non-hazardous wastes are not incompatiblewith any wastes in the unit. In addition,certain facility information includingthe waste analysis plan, groundwatermonitoring plans, closure and post-closure plans, cost estimates, andfinancial assurance demonstrationsmust be updated as necessary to accountfor receipt of only non-hazardous waste.Sections 264.113(d) and 265.113(d). Inaddition, surface impoundments that donot meet the minimum technologicalrequirements (MTRs) for liners andleachate collection of RCRA 3004(o)must comply with additionalrequirements in order to delay closure,including the removal of hazardouswastes to the extent practicable from theunit. Sections 264.113(e) and265.113(e).

The delay of closure regulations applyonly to landfills, land treatment units,and surface impoundments. In the caseof other RCRA units such as tanks andwaste piles, the Agency did not feel thatthe delay-of-closure regulations werenecessary for these types of units inorder to receive only non-hazardouswastes (54 FR 33383). The closurerequirements in subpart G for theseunits include removal ordecontamination of waste residues,containers, liners, bases andcontaminated soils, equipment, andother containment system components;these closure requirements are notincompatible with the reuse of these

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units for receipt of only non-hazardouswaste. Once the unit has been emptiedof all hazardous wastes anddecontaminated, it could receive non-hazardous waste. However, the Agencyalso recognizes that some flexibility maybe warranted in converting the use of aunit such as a tank from hazardous to.non-hazardous waste management. EPAsolicits comment on whether an owneror operator might demonstrate removalof hazardous waste residues from thetank by demonstrating that all waste inthe tank is below exemption levels,without removing the waste from thetank. In cases where the owner oroperator could not demonstrate that allwastes in the tank were belowexemption levels, he or she would haveto remove the hazardous waste in orderto achieve closure of the unit. In somecases, the facility owner or operator maybe able to demonstrate that a tank nolonger managed hazardous waste(because the waste met today's proposedexemption criteria), but did not achieveclean closure because of soil andperhaps groundwater contamination. Inthis case, EPA solicits comment onwhether the facility owner or operatorshould be required to remove thecontamination to clean closure levels, orclose the area as a landfill while usingthe tank to manage nonhazardouswastes, as long as this activity did notinterfere with cleanup activities orcontrol of the contaminated areas.

The Agency also believes that theavailability of a delay-of-closure optionprovides much of the flexibility neededto allow for the uninterruptedmanagement of exempt waste, whileproviding assurance that the protectionsafforded by the closure regulations forSubtitle C units (e.g., evaluation of soiland groundwater at closure) are not lost.This approach makes sense in light ofthe fact that today's proposedexemption is self-implementing, whichthe Agency feels is appropriate for wasteidentification purposes, but not -

necessarily so for determining whethera Subtitle C unit may become a SubtitleD unit without first undergoing closure.H. HWIR-Media Rule/Subtitle CCorrective Action

The Agency is currently planning onproposing a rule ("HWIR Media")addressing waste management issuesrelating to environmental media (e.g.,soil, groundwater, and sediments). Thegoal of this rule is to allow moreeffective cleanups at contaminated sites.As currently drafted, the media proposalwill supplement the regulatory systemunder RCRA for the management ofRCRA hazardous contaminated media,applicable to sites that are undergoing

cleanup overseen by EPA or authorizedStates. Such sites include cleanups atRCRA corrective action sites, Statecleanups, and Superfund remedialactions. The media rule will propose a"bright-line" distinction betweenhazardous contaminated media (i.e.,media containing hazardous waste thatis therefore regulated as hazardous)subject to modified Subtitle C standards,and less contaminated media subject tomore site-specific, flexible standardsimplemented by State agencies. Thisnew system will supplement the currentapproach(es) to identifying RCRAapplicability to the management ofcontaminated media. The rule will alsopropose streamlined permitrequirements for cleanups. It will notspecify cleanup standards.

Today's proposal applies to listedhazardous wastes (e.g. process wastes,sludges, discarded commercial chemicalproducts, etc.), including mixtures ofone or more listed wastes with othersolid wastes, and residues derived fromthe treatment, storage, or disposal of oneor more listed hazardous wastes. Mediathat contain listed hazardous wastes,mixtures, or derived-from wastes withconstituent concentrations belowtoday's proposed exemption levels willbe eligible for exemption under theprocedures proposed today. EPA or anauthorized State may continue to assesscontaminated media withconcentrations higher or lower than theexit levels proposed today on a case-by-case basis by making site-specificdeterminations as to whether a media"contains" a RCRA hazardous waste.

L Land Disposal Restriction Program

Today's rule contains severalimportant areas of overlap with theRCRA Land Disposal Restrictions (LDR)program that are discussed elsewhere intoday's rule. First, as described in moredetail elsewhere in this notice, EPA isproposing that exit levels producedunder the multipathway analysis forconstituents with adequate analyticalmethods should "cap" existingtechnology-based LDR standards, wherethe exit levels are less stringent than thecurrent LDR values. If a waste containsonly constituent with "capped" LDRvalues, it should be able to satisfy LDRrequirements and exit Subtitle C for allother purposes as soon as the wasteachieved those levels.

Under today's proposal the uncappedLDR requirements for listed hazardouswastes continue to apply to a wasteeven after the waste becomes exemptfrom Subtitle C under the exemptioncriteria. Furthermore, for listed wastescontaining certain constituents withanalytical problems, compliance with

the LDRs (either numerical levels,specified treatment, or both) is part ofthe criteria for exempting that wasteunder today's proposal. Specifically, forconstituents where there are noadequate analytical methods fordetermining whether or not the exitlevels have been met, a combination ofmeeting applicable LDR standards and ashowing of non-detect estimatedquantitation concentration is required tosatisfy the exit criteria for theseconstituents. This is explained in moredetail in Section IV.I of today's rule.

If, however, a listed waste is belowthe exit concentrations proposed todayat the point where the waste is "first"generated, that is, the point where thewaste first meets the listing descriptionand is potentially subject to Subtitle C,then a hazardous waste is never really"generated" and the LDR requirementsdo not attach to the waste. The EPAdoes not expect many listed wastes to beat or below the exit criteria at the pointof first generation, where wastecharacterization data indicate that thisis where wastes contain higherconcentrations of hazardousconstituents. Nonetheless, where aparticular process generates a waste thatis perhaps inappropriately captured bya listing, or where pollution preventionefforts by the generator result in a wasteof lower constituent concentrations, ifthe waste meets the exemption criteriaat the moment it is first generated, theLDR requirements would not apply. Incontrast, once a listed waste is generatedand managed the LDR requirementsattach, and remain even after the wasteexits Subtitle C under today'sexemption (unless, as stated, where theexit levels are considered equivalent toa minimize threat standard). This issueis discussed in more detail in Section VIin today's proposal.

It shouldbe noted that the Agency iscurrently reviewing the definition of"point-of-generation" with respect tothe application of the LDRs. SinceNovember 1986 (51 FR 40620), EPA hasrequired LDR determinations to be madeat the point which hazardous wastes aregenerated. In the Phase III LDR rule(March 2,1995, 60 FR 11702), EPAsolicited comment on the issue of wherethe point of generation should bedefined. EPA presentid three options tonarrowly redefine the point at which theland disposal prohibitions attach: (1)Similar wastestreams generated bysimilar processes, (2) wastestreams froma single process, and (3) "batterylimits." With Option 1 the point ofgeneration would be defined at thepoint after which like wastestreams aregenerated from like processes andcombined as a matter of routine




practice. Option 2 would consider thepoint of generation to occur whenwastestreams from a single process arecombined (e.g., residual wastestrearnscollected in a common unit such as asump). In many cases, thesewastestreams are similar in compositionbecause they all come from a commonunit process. The Option 3 "batterylimits," is similar to Option 2; howeverinstead of limiting aggregation to thatnormally occurring within a single unitprocess, the facility would view anentire battery of processes (associatedwith making a single product or relatedgroup of products) as a singlemanufacturing step. In the Phase IHI LDRproposal, EPA identified listedhazardous wastes as situations whereexisting point of generationdeterminations ma remain appropriate.This is because EPA has carefullyreviewed the various waste streams andhas defined the point of generation aspart of the listing description. Therefore,it may be inappropriate to modify thatdescription with a more generic "pointof prohibition" rule. This is importantbecause today's rule applies only tolisted hazardous wastes.

Lastly, under today's proposal,mixtures containing listed hazardouswaste and residues from the treatment,storage, or disposal of listed hazardouswaste that contain some constituentswith concentrations below exit levelsand some constituents withconcentrations above exit levels wouldcontinue to be managed as listedhazardous wastes. Today's notice doesnot allow for partial exemptions,because the Agency does not believethat a self-implemented exemptionprocess is well suited to partialexemptions. It is not always clear whatthe origin of a hazardous constituent is,particularly for constituents that areformed as by-products of treatment orwaste interactions. Further, theproposed exemption criteria are notwaste-specific, and thus are not suitedto waste-specific or partial exemptions.Thus, the determination that a wastethat carries two listing numbers shouldno longer bear one of the listingnumbers is not always a straight-forward decision. The Agency hasdesigned the exemption processproposed today to remove as muchsubjective decision making from theprocess as possible.

However, while the Agency is nottoday proposing an alternative thatwould allow these wastes to use onlythe hazardous waste codes for thoselisted wastes that are the origin of theconstituents above the exit levels, theAgency believes that there could bemerit in the concept for a future

proposed rulemaking should theimplementation concerns stated abovebe overcome. Therefore, the Agencyrequests information on actual caseswith waste characterization data wherea waste bears more than one waste codewhich results in conflicting treatmentstandards under the land disposalrestrictions rules. If the Agency findsthat there is a serious compliance issuefor multiple listing wastes, the Agencymay reconsider this decision, as well asother potential solutions to anydocumented problems.

. RCRA Air Emission Standards

Today's proposed rule, whenpromulgated, may have an impact onthe effectiveness of two other RCRArules developed by the Agency underHSWA authority. Section 3004(n) ofHSWA directed the Agency topromulgate regulations controlling airemissions from hazardous waste TSDFs"as necessary to protect human healthand the environment." SubsequentAgency analysis demonstrated that airemissions from TSDFs do posesubstantial risk in the absence ofcontrols, and that controls weretherefore required under the HSWAmandate. The Agency is fulfilling thismandate in phases; EPA completed thefirst phase when it promulgated RCRAair standards that control organicemissions vented from certainhazardous waste treatment processes, aswell as from leaks in cerfain ancillaryequipment used for hazardous wastemanagement processes (55 FR 25454,June 21, 1990; 40 CFR part 264/265,subparts AA and BB). More recently,EPA completed the second phase whenit promulgated RCRA air standards fortanks, surface impoundments,containers, and miscellaneous unitsoperated at TSDFs (59 FR 62896,December 6, 1994; 40 CFR part 264/265,subpart CC). Together, these ruleswould reduce the risk from airemissions from the vast majority ofthese facilities to well within the riskrange of other RCRA standards. Aftermore thorough analysis, the Agencymay issue a third phase of theseregulations to address any residual risk.The emission reductions achieved bythese rules would also significantlyreduce the formation of ozone, whichhas adverse effects on human health andthe environment.

Hazardous waste that satisfies theexemption criteria proposed today(including any constituent-specific exitconcentrations for volatile organicchemicals, or VOCs), would be exemptfrom Subtitle C regulations, includingregulations promulgated to date underRCRA 3004(n). In other words, once a

waste is no longer regulated ashazardous, any unit in which the wasteis managed (assuming no otherhazardous wastes are being/have beenmanaged in the unit) is not subject toSubtitle C regulations, including 40 CFRparts 264 and 265, subparts AA, BB, andCC. However, the Agency believes thatit is important to ensure that the risksassociated with air emissions both fromhazardous wastes, and from wastes thatwould be eligible for exit under today'sproposal, are adequately addressed. Inthe final rule establishing air emissioncontrols for tanks, surfaceimpoundments, containers, andmiscellaneous units (the "Subpart CC"rule), the Agency established athreshold level of 100 ppmw (parts permillion by weight) for total volatileorganics in a waste, a concentrationwhich if equaled or exceeded thatwould trigger the emission controlrequirements for these units. Becausethere are examples of exit levelsproposed today for specific volatileorganic constituents that exceed this100 ppmw threshold, the Agencyconsidered whether today's exit levelsadequately addressed the air emissionconcerns of 3004(n) in allowing waste toexit Subtitle C. There are important odifferences in the underlying riskmodeling between the two rules.However, the Agency believes that theconstituent-specific risk evaluationdone for this rulemaking results inproposed exit levels that for VOCs willnot be less protective than the standardsestablished to date under RCRA 3004(n).Despite these differences, the Agencyrequests comment on whether or not atotal VOC concentration of 100 ppmw(parts per million weight), which is theconcentration that triggers air emissioncontrols under the Subpart CC rule,would be appropriate for use in the exitrule proposed today, and if so, how thislevel would be used.

K. Hazardous DebrisHazardous debris that contains one or

more listed hazardous wastes is eligiblefor exiting Subtitle C under today'sproposed rule. The EPA notes, however,that certain exemptions already existrelating to hazardous debris. On August18, 1992, the EPA published a final ruleon the Land Disposal Restrictions forNewly Listed Wastes and HazardousDebris (57 FR 37194). In that rule, EPArequired that hazardous debris betreated prior to land disposal, usingspecified treatment technologies fromthe treatment categories of extraction,destruction, or immobilization. (See 40CFR 268.45, Table 1.) EPA also added aconditional exemption at § 261.3(f) fornon-characteristic hazardous debris (i.e.,

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debris that is hazardous solely becauseit contains one or more listed hazardouswastes). Section 261.3(f)(1) exemptsdebris from Subtitle C regulationprovided that the debris is treated usingone of the extraction or destructiontechnologies specified in Table I of§ 268.45. Alternatively, non-characteristic hazardous debris can beexempt under § 261.3(f)(2) if it isdetermined to be no longer hazardousby the Regional Administrator, afterconsidering the extent of contaminationof the debris, i.e., after a "contained-in"determination is made. However, non-characteristic hazardous debriscontaminated with a listed waste, that istreated by a specified immobilizationtechnology is not eligible for theconditional exemption in § 261.3(f)(1),and therefore remains subject to SubtitleC regulation after treatment.

In today's rule, EPA is not proposingto change the current exemption under§ 261.3(f; therefore, non-characteristichazardous debris that requires LDRtreatment by extraction or destructiontechnologies will be exempt fromSubtitle C regulation, once treated. Aswas explained more thoroughly in thefinal rule for hazardous debris, theAgency gave careful consideration tomany factors before exempting certaintreated debris, including whether eachdebris/contaminant type would beeffectively treated by each BDATtechnology to levels that would nolonger pose a hazard to human health orthe environment (57 FR 37240).However, hazardous debris thatcontains listed waste, and for whichimmobilization is the specified LDRtreatment, may exit using today'sproposed exit criteria. See also thediscussion of a contingent managementoption above for a description of analternative for encapsulated debriscontaminated by radioactive "mixed"hazardous wastes. Finally, EPA is notproposing to change the contained-inexemption under § 261.3(f)(2) forhazardous debris; that is, the RegionalAdministrator may continue todetermine on a case-by-case basis thathazardous debris no longer containslisted hazardous waste, and shouldtherefore be exempt from RCRA SubtitleC.

L. Hazardous Wastes Used in a MannerConstituting Disposal

Section 266.20 (b) of the regulationsstates that hazardous wastes andhazardous waste-derived products thatare legitimately recycled by beingapplied to or placed on the land arelargely exempt from subtitle Cregulation provided they satisfy threeconditions: the recyclable materials

must have undergone a chemicalreaction so as not to be separable byphysical means, the product must beproduced for the general public's use,and land disposal restriction treatmentstandards for every hazardous waste inthe hazardous waste-derived productmust be satisfied. (The shorthand forthis type of recycling is "use in amanner constituting disposal". See§ 261.2(c)(1).) EPA developed§ 266.20(b) largely as a stop-gap toprovide some modicum of safety whileEPA studied further whether variousdisposal-like uses of hazardous waste-derived products in fact were safe orwarranted control. 50 FR 614, 628-29,647 (Jan,. 4, 1985). Since then, theAgency has studied particular useconstituting disposal practices anddetermined, or proposed, that such useseither be prohibited or allowed based onmore individualized determinations ofrisk. See 53 FR 31138, 31164 (August17, 1988) (allowing use of fertilizersderived from waste K 061 because ofsimilarity to other zinc-containingfertilizers); 59 FR 43496, 43500 (August24, 1994) (prohibiting anti-skid uses ofK 061-derived sags); 59 FR 67256 (Dec.29, 1994) (proposing to allow certainuses of K 061 if risk-based criteria aresatisfied); 60 FR 11702, 11732 (March 2,1995) (proposing to prohibit hazardouswaste use as fill material)..

EPA solicits comment today on therelationship of today's proposed exitlevels and the general use constitutingdisposal provisions in § 266.20(b)stating that such uses can occur if landdisposal restriction treatment standardsare satisfied. These land disposalrestriction standards are not fullyprotective in all cases: the standards aretechnology-based rather than risk-based,and, for metal hazardous constituents,only control leachable amounts of themetal. Yet in many situations, totalmetal levels, rather than leachablelevels, will be the critical factor becauseof the possibilities of direct contactthrough inhalation of abraded or wind-dispersed contaminants, or surfacerunoff. These exposure pathways arecritical for uses constituting disposalbecause the hazardous waste are notplaced in a confined unit. 60 FR at11733, 59 FR at 43499.

The exit levels proposed today, on theother hand, are risk-based (althoughsome are capped by quantitation limits),are expressed as both total andleachable concentrations, and considerexposure pathways in some casessimilar to those relevant in analyzinguses constituting disposal. The Agencysolicits comment as to theappropriateness of applying these levelsto hazardous wastes used in a manner

constituting disposal (or at least to thoseuses where the hazardous waste-derivedproducts are not comparable to non-hazardous waste based products thatwould be used in their place). Oneapproach would be to replace therequirement to meet LDR treatmentstandards with a requirement to meetthe exit levels proposed today. Thisapproach should assure that exit levelsfor unconfined hazardous wastes (i.e.hazardous wastes used in a mannerconstituting disposal) are never lessstringent than exit levels for hazardouswastes placed in confined units. EPAbelieves that the risk assessment itconducted for the exit levels consideredscenarios sufficiently similar to useconstituting disposal scenarios to ensurethat the exit levels would be reasonablyprotective for uses (and more protectivethan LDR levels, in many cases, becauseof the analysis of impacts from totalconcentrations of constituents). EPA,however, requests comment on thereasonableness of this approach.

Another option would be to requirepersons wishing to use hazardouswastes in s manner constitutingdisposal to meet the lower of the LDRtreatment standards and the exit levels.Because EPA is today proposing settingexit levels for both total and leachableconcentrations, and because LDRstandards are expressed as either total orleachable levels, however, EPA is notcertain how to meaningfully comparerelative stringency.

With respect to the currentrequirement in § 266.20(b) that personswishing to use waste in a mannerconstituting disposal meet the treatmentstandards from the LDR program, EPAnotes that compliance with LDRtracking and recordkeeping rules is not.required. EPA proposes today to requirecompliance only with the exit levelswhere they substitute for LDR treatmentlevels, although it requests comment onthe option of requiring persons usingwastes in this manner also to file theexit notification package proposedtoday. EPA does not intend that suchpersons be required to comply withconditions that continue to apply afterexit, such as periodic retesting.

Finally, EPA proposes to eliminatethe requirement that wastes to be usedin a manner constituting disposalundergo a chemical reaction so as to beinseparable by physical means. EPAdoes not believe it is necessary to retainthis requirement since wastes will beevaluated for total constituentconcentrations. (EPA, however, willretain this requirement for wastes withtreatment standards expressed as aspecified technology, rather thanconcentration levels.)




Were EPA to proceed on this course,the Agency would adjust the timing ofany regulatory action so that it does notsupersede the separate rulemaking theAgency is now conducting on certainuses of residues derived from K 061recovery facilities. 59 FR 67256. Thus,the Agency does not intend to take finalaction affecting these uses until theanalysis begun in that rulemaking iscompleted on the schedule establishedin that rulemaking.

With respect to the other pendingproposal, involving a prohibition onplacement of hazardous waste as fillmaterial, the Agency requests commenton whether it should substitutepermission to use waste that has met theproposed exit levels for the proposedprohibition. The risk assessmentunderlying today's proposal addressedthe major pathways that would arisefrom use as fill, but may not have usedinput values that fully reflect the fillscenario for some important parameters.For example, unit depths may be greaterfor fill sites than for land applicationunits. At the same time, use ofhazardous waste as fill is a proven causeof human health and environmentalharm, contributing significantly to anumber of Superfund sites. See DocketF-95-PH3P-FFFFF (record for thepending proposal). In light of this, theAgency questions whether to substitutetoday's proposed exit approach for theproposed prohibition.

XII. CERCLA ImpactsAll listed hazardous wastes are listed

as hazardous substances under section101(14)(C) of the ComprehensiveEnvironmental Response,Compensation, and Liability Act(CERCLA) of 1980, as amended. Undersection 103(a) of CERCLA, notificationmust be made to the Federalgovernment of a release of any CERCLAhazardous substance in an amount equalto or greater than the reportable quantity(RQ) assigned to that substance withina 24 hour period. (See 40 CFR part 302for a list of CERCLA hazardoussubstances and their Rqs.) If a specificwaste from a particular facility meetsthe exemption criterion in this rule, thewaste is not a listed hazardous wasteand therefore not a hazardous substanceby virtue of its hazardous waste listing.Thus, notification under CERCLA of arelease of the exempted waste may notbe necessary. In this situation, CERCLAnotification of releases of the wastewould only be required if the waste orany of the constituents of the waste areCERCLA hazardous substances by virtueof Section 101(14) (A), (B), (D), (E), or(F) of CERCLA or 40 CFR 302.4(b), andare released in amounts greater than or

equal to their Rqs. The Agency requestscomment on this approach.

Exit levels also may be applicable tothe CERCLA program where it has beendocumented that RCRA listed hazardouswaste has been disposed of at the site.Section 121(d) of CERCLA, as amendedby the Superfund Amendments andReauthorization Act (SARA) of 1986,requires that CERCLA actions complywith, or justify a waiver of, applicableor relevant and appropriaterequirements (ARARs) under federaland state environmental laws. Theoptions proposed in this rule woulddetermine the legal applicability offederal RCRA managementsrequirements to remediation wastesgenerated at Superfund sites. They mayalso be considered in determiningwhether RCRA is relevant andappropriate in cases where it is notapplicable.

At sites undergoing CERCLA remedialactivities where no listed hazardouswastes have been identified, the Agencywill generally use a site-specific riskassessment for all chemicals for whichthere are no ARARs. In some cases,these health-based cleanup levels willbe higher than the exemption levels,based on a reasonably conservativeexposure scenario which does notinclude leachate ingestion. In othercases, the CERCLA health-based clean-up levels will be lower than exemptionlevels when additive effects areconsidered or when specializedanalytical techniques are required inorder to lower quantitation limits. TheCERCLA health-based clean-up levelsmay also be different than exemptionlevels based on the consideration of site-specific factors.

XIII. State Authority

A. %Applicability of Rules in AuthorizedStates

Under section 3006 of RCRA, EPAmay authorize qualified States toadminister and enforce the RCRAprogram within the State. (See 40 CFRpart 271 for the standards andrequirements for authorization.)Following authorization, EPA retainsenforcement authority under sections3008, 7003, and 3013 of RCRA, althoughauthorized States have primaryenforcement responsibility.

Prior to the Hazardous and SolidWaste Amendments (HSWA) of 1984, aState with final authorizationadministered its hazardous wasteprogram entirely in lieu of EPAadministering the Federal program inthat State. The Federal requirements nolonger applied in the authorized Stateand EPA could not issue permits for any

facility in the State that the State wasauthorized to permit. When new, morestringent Federal requirements werepromulgated or enacted, the State wasobliged to enact equivalent authoritywithin specified time frames. NewFederal requirements did not take effectin an authorized State until the Stateadopted the requirements as State law.

In contrast, under section 3006(g) ofRCRA, 42 U.S.C. 6926(g), newrequirements and prohibitions imposedby the HSWA take effect in authorizedStates at the same time that they takeeffect in non-authorized States. EPA isdirected to implement HSWArequirements and prohibitions in anauthorized State, including the issuanceof permits, until the State is grantedauthorization to do so. While Statesmust still adopt HSWA-relatedprovisions as State law to retain finalauthorization, HSWA applies inauthorized States in the interim.

B. Effect of State AuthorizationsToday's proposal, if finalized, will

promulgate regulations that are noteffective under HSWA in authorizedStates. Thus, the exemption will beapplicable only in those States that donot have final authorization.

Authorized States are only required tomodify their programs when EPApromulgates Federal regulations that aremore stringent or broader in scope thanthe authorized State regulations. Forthose changes that are less stringent orreduce the scope of the Federalprogram, States are not required tomodify their programs. This is a resultof section 3009 of RCRA, which allowsStates to impose more stringentregulations than the Federal program.Today's proposal for exit levels isconsidered to be less stringent than, ora reduction in the scope of, the existingFederal regulations because it wouldexempt certain wastes now subject toRCRA Subtitle C. Therefore, authorizedStates are not required to modify theirprograms to adopt regulations consistentwith and equivalent to today's proposal.

Even though States are not required toadopt most options in today's proposal,EPA strongly encourages States to do soas quickly as possible. As alreadyexplained in this preamble, today'sproposal will reduce over-regulation ofdilute wastes and will provide analternative to delisting. States aretherefore urged to consider the adoptionof today's proposal (when promulgated);EPA will expedite review of authorizedState program revision applications.C. Streamlining Issues

EPA is considering a new approach tostate authorization for rules revising the

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RCRA program. Under this newapproach EPA would vary therequirements for state submissions andfor EPA's review to reflect differences inthe scope and complexity of variousprogram revisions. This differentialapproach to authorization also wouldrecognize the fact that many states nowhave more than a decade of experiencein implementing large portions of theRCRA program and commensurateexperience in obtaining authorizationfor program revisions. EPA believes thatadjusting authorization requirementswill strike an appropriate balancebetween recognizing state experienceand ensuring environmental protection.

EPA recently proposed a greatlystreamlined set of procedures for theleast complex changes to the LDRprogram in the "LDR Phase IV"rulemaking. EPA, however, proposed toretain the current authorization processfor other portions of the rule thatpresented more complex and novelregulations.

EPA is also developing a differentapproach to streamlining authorizationfor the "HWIR media" proposalscheduled for publication later in 1995.Although EPA expects some aspects ofthese state authorization procedures tobe unique to the HWIR- mediarulemaking, EPA will determinewhether some of the concepts can beused to craft streamlined procedures foradditional RCRA rules.

EPA was not able to develop astreamlined authorization process forthis rule in time to include it in thisproposal. EPA, however, intends todescribe such a process in more detailin the preamble to the proposed HWIR-media rule. EPA anticipates that mostelements of the basic waste exit schemeproposed in today's notice would beeligible for a greatly streamlinedapproach to authorization. For example,the new LDR standards based on"minimize threat" findings would begood candidates for streamlinedauthorization because states that arealready authorized for significantportions of the LDR program are familiarwith the type of rule changes needed,have adopted all or most of theunderlying LDR program, and haveexperience in implementing andenforcing the rules. The exit levels,along with the self-implementingapproach to exit determinations, arealso likely to be eligible for a greatlystreamlined approach. The scheme isvery similar to the existing program fordetermining whether a waste exhibitsany of the hazardous wastecharacteristics, particularly the 1980 EPToxicity Characteristic and theexpanded 1990 Toxicity Characteristic.

Under both the characteristic rules andtoday's proposal, generators areresponsible for determining whether ornot a waste meets, a numerical definitionof "hazard". States must then enforce byreviewing records of determinationsand/or conducting their own analysis ofwastes determined not to be hazardous.Consequently, States which have beenauthorized for the base program alreadyhave experience in adopting andenforcing rules which resemble the exitscheme proposed today. EPA, however,notes that adopting the exit schemeproposed in today's notice will placeadditional demands on state inspectionand enforcement resources. EPA willgive careful consideration to balancingthe need to ensure that a state hassufficient resources to implement anexit program with the goal ofstreamlining-the authorization process.

Today's scheme does differ from theoriginal characteristics and the 1990Toxicity Characteristic by includingsome requirements which must beenforced as conditions of exit. Theserequirements, however, arerequirements for testing, notificationand recordkeeping that are relativelyeasy to meet and relatively easy todetect if violated. Accordingly, EPAdoes not at this time anticipate thatthese conditions would require it toretain the current authorization process.

EPA currently finds it unlikely that itwill propose a greatly streamlinedauthorization process for any of thecontingent management optionspresented for discussion in today'sproposal. These options will raise novellegal, implementation and enforcementissues. A more conventional approachto the review of state authorities andcapabilities may be warranted. If EPAproposes any of these options in thefuture, it will consider the possibility ofadapting the approach to authorizationthat it is currently developing for theHWIR-media proposal.

XIV. Regulatory Requirements

A. Analytical Requirements

1. Executive Order 12866

Under Executive Order 12866, (58 FR51735 (October 4, 1993)) the Agencymust determine whether this regulatoryaction is "significant." A determinationof significance will subject this action tofull OMB review and compliance underExecutive Order 12866 requirements.The order defines "significantregulatory action" as one that is likelyto result in a rule that may:

(a) Have an annual effect on theeconomy of $100 million or more,adversely affect in a material way theeconomy, a sector of the economy,

productivity, competition, jobs, theenvironment, public health or safety, orstate, local, or tribal governments orcommunities;

(b) Create a serious inconsistency orotherwise interfere with an action takenorplanned by another agency;

(c) Materially alter the budgetaryimpact of entitlement, grants, user fees,or loan programs, or the rights andobligations of recipients thereof; or

(d) Raise novel legal or policy issuesarising out of legal mandates, thePresident's priorities, or the principlesset forth in the terms of the ExecutiveOrder.

The proposed rule is expected to havean annual effect on the economy greaterthan $100 million. Furthermore,although voluntary, the adoption of thisaction may burden state or tribalgovernments with increased regulatoryreview requirements. Today's actionmay also raise novel legal or policyissues as they relate to the President'spriorities for environmental protectionwithin a regulatory system facingresource limitations. The Agency,therefore, has determined that today'sproposed rule is a "significantregulatory action." As a result, thisrulemaking action, and supportinganalyses, are subject to full OMB reviewunder the requirements of the ExecutiveOrder. The Agency has prepared anAssessment of The Potential Costs andBenefits of The Hazardous WasteIdentification Rule for Industrial ProcessWastes, as Proposed, in support oftoday's action. A summary of thisAssessment and findings is presented insection D below.

2. Regulatory Flexibility AnalysisPursuant to the Regulatory Flexibility

Act of 1980, 5 U.S.C. 601 et seq., whenan agency publishes a notice ofrulemaking, for a rule that will have asignificant effect on a substantialnumber of small entities, the agencymust prepare and make available forpublic comment a regulatory flexibilityanalysis. This analysis shall considerthe effect of the rule on small entities(i.e.: Small business, smallorganizations, and small governmentaljurisdictions).

Under the Agency's revisedGuidelines for Implementing theRegulatory Flexibility Act, dated May 4,1992, the Agency committed toconsidering regulatory alternatives inrulemakings when there were anyeconomic impacts estimated on anysmall entities. Previous guidancerequired alternatives to be examinedonly when significant economic effectswere estimated for a substantial numberof small entities. The Agency has




prepared a Regulatory FlexibilityAnalysis in support of today's'action. Asummary of this analysis and findings ispresented in section E below.

3. Environmental Justice

Executive Order 12898, "FederalActions to Address EnvironmentalJustice in Minority Populations andLow-Income Populations," directs eachFederal Agency to "make achievingenvironmental justice part of its missionby identifying and addressing, asappropriate, disproportionately highand adverse human health andenvironmental effects of its programs,policies, and activities on minoritypopulations and low-incomepopulations * .

The Executive Order requires thatwhere environmental justice concernsor the potential for concerns areidentified, appropriate analysis of theissue(s) be evaluated. To the extentpracticable, the ecological, humanhealth (taking into account subsistencepatterns and sensitive populations) andsocio-economic impacts of the proposeddecision-document in minority and low-income communities should also beevaluated.

The Agency has examinedEnvironmental Justice concerns relevantto today's action. A summary of thisanalysis and findings is presented insection F below.

4. Paperwork Reduction Act

The information collectionrequirements in this proposed rule havebeen submitted for approval to theOffice of Management and Budget(OMB) under the Paperwork ReductionAct, 44 U.S.C. 3501 et seq. AnInformation Collection Request (ICR)document has been prepared by EPA(ICR No. 1766.01) and a copy may beobtained from Sandy Farmer, OPPERegulatory Information Division; U.S.Environmental Protection Agency(2137); 401 M St., SW.; Washington, DC20460 or by calling (202) 260-2740.

This information collection irequired to provide documentation ofsolid waste exemptions from Subtitle Crequirements, and will allow forcertification and verification as theprogram evolves. Exemptions undertoday's action require no formalpreapproval. As such, informationcollection, maintenance and reportingissues are especially important due tothe self-implementing nature of thisaction. Successful implementation oftoday's proposal will depend upon thedocumentation, certification, andverification provided by the informationcollection.

The general authority for thisproposal is sections 2002(a), 3001, 3002,3004, and 3006 of the Solid WasteDisposal Act of 1970, as amended by theResource Conservation and RecoveryAct of 1976 (RCRA), as amended by theHazardous and Solid WasteAmendments of 1984 (HSWA), 42U.S.C. 6912(a), 6921, 6922, 6924, and6926. The specific authority for thecollection of information is 40 CFR261.36, Exemption for Listed HazardousWastes Containing Low Concentrationsof Hazardous Constituents.

The Agency has prepared a fullInformation Collection request (ICR) insupport of today's action. A summary ofthe methodology and findings from thisdocument is presented in section Gbelow.

B. Background

In 1976, Congress passed the ResourceConservation and Recovery Act (RCRA)to address problems associated withannual nationwide generation of largequantities of municipal and industrialsolid waste. This Act was significantlyamended in 1984 by the Hazardous andSolid Waste Amendments (HSWA).Under RCRA, the Agency regulates non-hazardous solid waste through theSubtitle D program, and hazardous solidwaste under the Subtitle C program.Subtitle C regulations differ fromSubtitle D in two important areas. First,Subtitle C regulations are developed andpromulgated by EPA, while Subtitle Drequirements have been largelydelegated to the states. Second, non-hazardous wastes regulated underSubtitle D are generally subject tostandards that are considerably lessstringent and less costly than thoseunder Subtitle C. All wastes addressedunder this action are currently managedunder Subtitle C regulations.

RCRA is divided into four programs:Underground storage, medical waste,nonhazardous solid waste, andhazardous solid waste. Under RCRA3001(a), Congress has required EPA toidentify those wastes that should beclassified as hazardous. In accordancewith this provision, the Agency hasdesignated wastes as hazardous in twoways: "characteristic," or "listed."Hazardous waste is consideredcharacteristic if it has any of theproperties or characteristics that wouldpresent a potential hazard if managedimproperly. The Agency has identifiedfour characteristics which, if exhibited,lead to hazardous classification. Theseare: Ignitability, corrosivity, reactivity,and toxicity. Under the toxicitycharacteristic, specific health-basedconcentration standards have beendeveloped for approximately forty (40)

constituents. Wastes exhibiting any ofthese characteristics are subject toSubtitle C regulation. Hazardous wastesare identified as listed based on anextensive listing procedure. Thisprocedure may identify a waste ashazardous under three broad categories:if it exhibits one of the characteristicsidentified above but has not beenclassified as characteristicallyhazardous, if it is determined to beacutely toxic or hazardous, or if thewaste meets the statutory definition ofa hazardous waste.

The Agency, however, was concernedthat generators and managers ofhazardous waste might avoid regulatoryrequirements in two major ways: (1) Bymixing listed hazardous waste withnon-hazardous solid waste, and, (2) byminimal processing and treatment ofhazardous waste. These activities couldresult in a waste or residual materialthat was no longer legally defined ashazardous under Subtitle C. In manycases, the Agency believed thesematerials could continue to poseunacceptable hazards to human healthand the environment. The Agencypromulgated mixture and derived-fromrules in May of 1980, in response tothese potential loopholes.

C. Need for Regulation

The mixture and derived-from rulescreated what was perceived as beingfederal over-regulation, where listedhazardous waste continued to remainunder Subtitle C jurisdiction regardlessof constituent concentration or presencein the waste, either before or aftertreatment. This problem wasexacerbated with the passage of HSWAin 1984. HSWA set Land DisposalRestrictions (LDR) requiring bestdemonstrated available technology(BDAT) treatment for all listedhazardous wastes prior to disposal. Incases where a specific listedwastestream contained relativelyinnocuous constituents, or very lowconcentrations, BDAT treatmentrequirements were felt to be overlyprotective, and unnecessarily expensive.

By requiring Subtitle C managementfor some low risk wastes, the currentRCRA regulatory system may inhibit theefficient allocation of limited societalresources. From a social perspective, toomany resources devoted to managinglow risk wastes may reduce resourceavailability for managing higher riskwastes. Resource availability for generalproductivity investments andinnovative technologies are alsoreduced. The Agency's delistingprogram has not provided an efficientsolution to this problem. The delistingprocess has proven to be overly time

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and resource intensive for both industryand EPA.

The Agency believes that a simplerexemption process is necessary toreduce the over-regulation of low riskhazardous waste while, at the sametime, reducing the time and resourceburden on industry and government.This revised exemption process wouldalso reduce the burden on the delistingprogram which will continue undercurrent regulations. To meet these goals,the Agency is proposing the currentaction that would establish a single setof exit levels for constituents found inlisted hazardous waste. This actionwould cover wastes as-generated,derived-from wastes, including BDATtreatment residuals, mixtures with solidwastes, and environmental media thatcontain hazardous wastes.

D. Assessment of Potential Costs andBenefits

1. Introduction and SummaryThe U.S. Environmental Protection

Agency (EPA) has prepared anAssessment of The Potential Costs andBenefits (Assessment) to accompanytoday's proposed rulemaking action.This action will establish concentration-based exemption criteria for certainhazardous wastes, creating a mechanismto exclude from Subtitle C regulationthose listed industrial process wastesthat the Agency believes are clearly notof Federal regulatory concern. Today'sproposed rule addresses low hazardwastes, mixtures, treatment residuals,and media that contain hazardouswastes.

The Agency anticipates that theproposed rule will provide cost savingsto selected generators and managers oflow hazard wastes. Under the preferredoption, annual nationwide treatmentand disposal cost savings for exemptedwastes may be as high as $75 million.Annual cost savings for a single facility.may be as high as $5.03 million.Potential cost reductions beyondtreatment and disposal savings may beassociated with waste minimizationincentives, avoided treatment costs forwastes remaining within Subtitle C, andadministrative cost savings.

Exemption of eligible wastes fromSubtitle C management requirements isprojected to have negligible effects onhuman health and the environment. Theproposed exemption levels are based ondetailed analysis of numerous possibleroutes of exposure. These exemptionlevels are designed to be protective ofboth human health and ecologicalsystems when exempted wastes aremanaged under Subtitle D, includingstate regulated waste disposal systems.

The Agency has also evaluated otherimpacts of the proposed rule. Theseinclude: Environmental justice,unfunded mandates, regulatory takings,and waste minimization incentives.Environmental justice concernsassociated with today's proposed actionmay be in the form of economic benefitsand/or human health effects. Today'sproposal implements no enforceablerequirements on states. Federalunfunded mandates, therefore, are notrelevant to today's proposedrulemaking. Regulatory takings undertoday's proposed rulemaking will notapproach land or productive valueimpacts discussed in past House andSenate Bills presented on this issue.This rulemaking provides opportunitiesfor generators to implement wasteminimization procedures to gainadditional savings.

The complete document, Assessmentof The Potential Costs and Benefits ofThe Hazardous Waste IdentificationRule for Industrial Process Wastes, asProposed (Assessment), is available inthe docket established for this proposedrule. This document details the data,methodology, findings, regulatoryissues, and analytical limitationsassociated this Assessment. The rapidevolution of this action resulted incontinuous technical modificationsthroughout the development of thisproposal. An Addendum to theAssessment document that details finalquantity and cost savings estimates isincluded in the docket materials.Findings presented in this preamblepresent final estimates.

A summary of the Assessmentmethodology and findings is presentedbelow. The analysis conducted for thisNotice of Proposed Rulemaking is to beconsidered preliminary. The Agencywelcomes review and comment of thisdocument and urges the submission ofdata in support of any comment orresponse.

2. Regulatory Options

The Agency's Assessment, conductedin support of today's action, addressesthe costs, benefits, and other potentialimpacts of the preferred option. TheAssessment also examines various otherregulatory options based on exit levelsthat are both more and less stringent.Findings presented in this preamblediscuss the preferred option and oneprimary alternative. A full discussion offindings associated with variousalternative regulatory options ispresented in the Assessment andAddendum.

a. Preferred (Proposed) Option

Under the preferred option, exitcriteria are established forapproximately 400 constituents,allowing hazardous wastes (includingwaste mixed with or derived-from listedwastes) to exit Subtitle C if theconcentration of all constituents is lessthan or equal to the exemption criteria.The exit levels apply to all listed wastes,regardless of origin.

Exit levels for most constituents arebased on risks posed to human healthand the environment. The Agency's goalis to ensure, through Federal or Statemanagement requirements, that humansare not exposed to carcinogens inconcentrations that will increase thestatistical risk of cancer by more thatone-in-one-million (1 x 10-6). For non-carcinogens, the Agency's goal is toensure that humans are not exposed toconcentrations where the hazardquotient exceeds one (1). The Agencyfeels that, above this level, selectedpopulations may experiencecarcinogenic effects at a 10- risk leveland non-carcinogenic effects at a hazardquotient greater than one (1).

To determine the concentrations atwhich exempt wastes would not posehuman health risks in excess of thesetarget levels, EPA conducted a"Multipathway" Analysis that includedecological exposure pathways. Inaddition, EPA considered the effects ofdirect exposure to contaminants ingroundwater. The analyses considerseveral types of waste managementunits. For non-wastewaters these unittypes include landfills, land applicationunits, waste piles, and ash monofills.For wastewaters management unitsincluded tanks and surfaceimpoundments.

The concentrations from all otherpathways were compared to thegroundwater concentrations indetermining the exit level. The morestringent of the multipathway orgroundwater numbers was chosen as theexit level. Exit levels for someconstituents are based on surrogates, orExemption Quantitation Criteria (EQCs).MCLs were not used in the developmentof exit levels analyzed for this option.The Agency believes that levelsestablished under this process willensure protection of human health andthe environment. These exit levels arepresented in the regulatory language forthis proposed rulemaking.

b. Other Options

In developing the preferred option,the Agency compared the proposed ruleto several alternative regulatory options.These are discussed in the full




document, Assessment of The PotentialCosts and Benefits of The HazardousWaste Identification Rule for IndustrialProcess Wastes, as Proposed. Additionaloptions are discussed in the supportingAddendum to the Assessmentdocument. These options consideralternative waste managementrequirements, target risk levels, dilutionand attenuation factors (DAFs), andexposure pathways. This Preamblediscusses one primary alternative to thepreferred option. This alternative is thesame as the preferred option but dropsland application units fromconsideration as a management source.Exempt nonwastewater wastestreamscould not be land applied. There wouldbe no change for wastewaters.

3. Implementation Requirements

Implementation requirements includethe steps that generators (or wastemanagers) must take to achieveexemption of their wastes, regardless ofthe exit levels selected. Theserequirements include waste samplingand a alysis, and related recordkeepingand reporting. Under the proposed rule,the facility must first perform acomprehensive analysis of the waste,testing for all constituents identified inappendix X to 40 CFR part 261.Reduced initial testing may be possibleonly if a facility is able to document thatsuch constituents are not present in thewaste. The generator must then preparea notificatioilcertification package andsubmit it to the EPA RegionalAdministrator or authorized stateagency. The generator must repeat acomprehensive analysis periodicallyaccording to the schedule established inthe proposed rule, along with morefrequent tailored scans that focus on theconstituents of concern. Relateddocumentation must be maintained on-site and be available for review.

The Agency has estimated annualsampling, analysis, recordkeeping, andreporting costs (collectively referred toas "implementation costs") that may berequired under this rule. Theseestimates range from approximately$21,000 for a less complex, solventwastestream with testing every 12months, to $169,000 for a complex highquantity F039 wastestream with testingevery three months.

4. Analysis and Findings

Under the proposed rule, listedwastes from industrial processes may beeligible for exemption from Subtitle Chazardous waste requirements if theycontain low concentrations ofcontaminants. This exemption mayallow generators and waste managers toavoid some or all costs associated with

Subtitle C requirements. The mostsignificant cost savings relate to wastetreatment and disposal; this rule willallow generators to avoid the costs oftreatment required for compliance withthe Land Disposal Restrictions as wellas the costs of disposing wastes inhighly protective Subtitle C facilities.

In addition to assessing these costsavings, the Assessment addresses anumber of other potential effects of theregulations. It analyzes the relativeeffects of the regulatory options onhuman health and the environment andconsiders issues related to ensuringenvironmental justice, eliminatingfederal mandates, encouraging wasteminimization, and providing flexibilityfor small businesses.

a. Eligible WasteThe universe of annual listed waste

generation, both wastewaters andnonwastewaters, potentially affected bytoday's proposed rulemaking isestimated to total 303.6 million tons.The universe of potentially affectedwastes includes approximately 25,300wastestreams from 10,700 facilities.Wastewaters account for the vastmajority of total waste quantity (99percent).

To determine whether these wastesare likely to be eligible for exemption,EPA developed the Process WasteModel. This model uses data on thecharacteristics of individual listedwaste-streams first collected in 1986 forEPA's National Survey of HazardousWaste Generators, which has since beenupdated, refined, and in some cases,correeted. The model first compares thereported concentrations of constituentsin each wastestream to the proposedrule exit levels to determine whether thewaste is likely to be eligible forexemption without further treatment. Ifthe waste is not eligible as-reported, themodel then considers whether it may beeligible after treatment. In thiscomparison, the concentrationstandards established under EPA's LandDisposal Restrictions (which are basedon the use of the best demonstrated andavailable technology) are used as aproxy for the lowest concentrationsachievable by treatment. If the waste isnot eligible for exemption as-reported orafter treatment, EPA assesses whetherwaste minimization or pollutionprevention methods could be used tocost-effectively achieve the exit levels.This model does not addresscontaminated media.

The analysis indicates that:9 Under the preferred option, total

nonwastewater quantity exempted,including BDAT treatment residuals andsludge from wastewater, is estimated at

0.40 million tons. Total wastewater(liquid) quantity exempted isapproximately 64 million tons.

e Under the primary alternativeoption (no land application),approximately 65 million tons ofwastewaters, and 0.60 million tons ofnonwastewaters, including BDATtreatment residuals and sludge fromwastewaters, may be eligible forexemption.

b. Cost Savings

The proposed rule will allow wastegenerators and managers to avoid costsassociated with Subtitle C requirements.Specifically, this exemption will allowthem to avoid treatment costs and/orcosts of disposing wastes in Subtitle Cfacilities. Wastes which meet exit levelsat the point of generation may accruetreatment cost savings because thewastes will not require any treatmentthat would have been needed to complywith the Subtitle C Land DisposalRestrictions prior to disposal. Allexempt wastes are likely to accruedisposal cost savings because the costsof disposing wastes in non-Subtitle Cfacilities are generally lower than thecost of more protective Subtitle Cfacilities.

The analysis indicates that:e Under the preferred option, the

high-end estimate of annual treatmentand disposal cost savings isapproximately $75 million.-A large portion of these savings are

attributable to avoided treatmentcosts.e Under the primary alternative, the

high-end estimate of cost savings is $99million:

The above estimates for quantitiesexempted and cost savings assume zeroimplementation costs. Theincorporation of implementation costsinto the analytical model will have asignificant impact on facilities andwastestreams affected, while havingonly a marginal impact on totalquantities exempted.

c. Affected Wastestreams and Facilities

Under the preferred option(unconditional exemption), as high as41 percent (10,300) of the potentiallyaffected wastestreams may be eligiblefor exemption. These eligiblewastestreams are generated by 56percent (6000) of the facilitiesproducing listed waste. Totalwastestreams and facilities potentiallyeligible for exemption under theprimary alternative option (no landapplication) are estimated at 12,200 (48percent), and 7,000 (65 percent),respectively.

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The majority of the wastestreamseligible for exemption under thepreferred option are very small inquantity. The median annual generationsize of an eligible wastewaterwastestream is 20 tons. The median foreligible nonwastewaters is 2.0 tons. Forsmall wastestreams, the costs accrueddue to the exemption are likely to becounterbalanced by the costs associatedwith gaining the exemption.

While a relatively large number ofwastestreams and facilities meet theeligibility criteria for exemption, manymay not gain exemption because thecosts of exemption may outweigh theestimated cost savings from exemption.For example, if implementation costsaverage $35,000 annually perwastestream, the estimate of facilitiesgenerating an exempted wastestreammay be overstated by as much as 90percent. However, small generators maychoose to aggregate their wastes to avoidthis problem.d. Relative Impacts on Human Healthand the Environment

Today's proposed rule will allow lowconcentration hazardous wastes to exitRCRA Subtitle C regulation and bedisposed of in Subtitle D nonhazardouswaste units. The Agency believes thattoday's proposed rule will have littleeffect on human health for the followingreasons:

* The acceptable daily exposurelevels used to set the exit levels arebased on maximum risk levels forcarcinogens of 10-6 and on acceptabledaily doses for non-carcinogens atwhich no adverse effects are likely tooccur.

e The waste management unitsmodeled in the Multipathway Analysisprovide high potential release rates forthe various groups of constituents beingconsidered in the analysis based ontheir physical and chemical properties.

* The pathways included in theMultipathway Analysis are generallyconsidered to be the most critical.

* The Multipath way Analysisincludes populations that are likely tobe exposed more than the average adultdue to proximity to a contaminantsource, behavior patterns, activities, andbody size.

e High-end values were used forselected parameters in the MutipathwayAnalysis to calculate acceptable wasteconcentrations.

* Exit levels represent acceptablecestituent concentration Iqvots forSubtitle D waste managemet bsed onaH of the potential combinados ofmanagement units, and ieptws in theMultipathway Analysis.

* Exit levels for several constituentsare below the acceptable wasteconcentrations for human health due tothe inclusion of ecological receptors.

Ecological risks were also evaluatedfor selected key constituents. Theinclusion of such risk in solid wasteregulation at a national level is animportant step, and is preferable toestablishing exit criteria based only onhuman health risks.

5. Other Regulatory Issues

a. Environmental Justice

Economic benefits may occur toselected communities as affected localfacilities reinvest cost savings derivedfrom reduced treatment and/or disposalcosts. Human health effects are expectedto be negligible due to the stringency ofthe exit levels. Included in these exitlevels are pathways of particularconcern for selected low incomepopulations such as subsistence fishingand farming.

b. Other Issues

Today's proposal is expected to haveno impact in the area of UnfundedFederal Mandates or RegulatoryTakings. Waste minimizationprocedures are likely to be stimulatedunder this proposal.

6. Implications and Conclusions

The analysis indicates thatapproximately 11 percent of thequantity of all nonwastewaterscontaining listed codes, and 21 percentof all such wastewaters may be eligiblefor exemption under the proposed rule.This exempt quantity is dominated by asmall number of very largewastestreams, and includes a largenumber of very small wastestreams. Forsome small wastestreams, exemptionmay not be cost effective unlessgenerators aggregate their wastes orotherwise work cooperatively tominimize the costs of gaining theexemptions.

Today's proposal could also provideincentives for industry to implementprocess changes and increased recyclingin an effort to gain additional savings.Preliminary estimates indicate thatsavings from these activities, whencombined with treatment and disposalsavings from the preferred option, arelikely to result in total annual costsavings greater than $100 million.However, limitations of our analysissuggest that the cost savings estimatesfrom such activities are highlyuncertain. Additional savings related toadministrative repirements andreduced treatzwW for hazardous wastesmay also accrue. Tkse potentialadditional cost savings are discussed in

greater detail in the Assessmentdocument.

The Agency believes that today'sproposal will result in a net benefit tosociety. Wastes gaining exemptionunder the preferred option will not poseunacceptable incremental risks tohuman health and the environmentbecause the exit levels are based onextensive analysis of possible humanand ecological risks associated withexempt wastes.

EPA's analysis of the impact oftoday's proposal on industry groupsindicates that a limited number ofindustries are likely to benefit fromexemption. Under the preferred option(unconditional exemption), threeindustries account for 51 percent ofeligible nonwastewater and wastewatersludge quantity and 53 percent of totaltreatment and disposal cost savings.These industries are: Chemicals andallied products (SIC 28); fabricatedmetals (SIC 34); and primarymetals (SIC33).

The Agency also compared benefitsgained from exemption to key industrydata such as national pollutionabatement expenditures and consideredfacility level impacts of the proposal. Toevaluate the relative magnitude of costsavings that would accrue under theproposed rule, EPA compared costsavings estimates to total pollutionabatement expenditures and the totalvalue of industry shipments. Totaltreatment and disposal cost savingsunder the preferred option account forapproximately 3.5 -percent of annualoperating costs for hazardous wastepollution abatement activities, and lessthan 0.002 percent of the total value ofindustry shipments. The facility-levelimpacts of the proposal vary greatly.E. Regulatory Flexibility Analysis.

The Regulatory Flexibility Actrequires analysis of the impact ofregulations on small entities. Because'today's proposal is deregulatory, it isnot expected to have adverse impacts onsmall businesses. In general, generatorsof large quantity wastestreams posinglow hazards will benefit substantiallyfrom the regulations. The impacts onsmall quantity generators is less certainand depends on the degree to whichthey aggregate their wastes and workcooperatively to cost-effectively gainexemption.

F. Environmental justiceIt is the Agency's policy that

environmental justice be considered asan integral part in the development ofl policies, guidance and regulations.Furder, Executive Order 12898,"Federal Actions to Address




Environmental Justice in MinorityPopulations and Low-IncomePopulations", directs each FederalAgency to "make achievingenvironmental justice part of its missionby identifying and addressing, asappropriate, disproportionately highand adverse human health andenvironmental effects of its programs,policies, and activities on minoritypopulations and low-incomepopulations * * *"

The Executive Order requires thatwhere environmental justice concernsor the potential for concerns areidentified, appropriate analysis of theissue(s) be evaluated. To the extentpracticable, the ecological, human.health (taking into account subsistencepatterns and sensitive populations) andsocio-economic impacts of the proposeddecision-document in minority and low-income communities should also beevaluated. Examples include how apolicy on future land use would impactminority or low-income communitiesversus non-minority, affluentcommunities, or how subsistencefarming or fishing patterns relate to risk-assessment policies.

For the purposes of today's proposedrulemaking, the Agency has taken anapproach for proposal consistent withExecutive Order 12898. As currentlydrafted, the multipathway analysiswhich was used to develop the exitlevels takes into account subsistencefarmers and subsistence fishers;however, subsistence fishers wereevaluated using a recreational fisherdatabase (one does not exist forsubsistence fishers). Sensitivepopulations are accounted for in theRfDs, RfCs, and slope factors andecological receptors were alsoevaluated.

G. Paperwork Reduction Act

As stated earlier, the level ofimplementation costs (i.e. sampling,analysis, recordkeeping, and reporting)will have a significant impact on thenumber of wastestreams and facilitiesaffected by this proposal. Assumingannual implementation costs of $35,000per wastestream, as many as 269facilities, generating up to 285 differentwastestreams may seek exemptions, andtherefore be affected by therecordkeeping and reportingrequirements. The actual number offacilities and wastestyeams affected willdepend upon the level ofimplementation costs. The higher theimplementation cogt to tie facility, thefewer the aumber of faciiti" expectedto pwticipate in the HWfR program.

Ttu etimated hour burden rangesfrom 382 hours to 573 hours per

wastestream in the first year, and from31 hours to 146 hours per wastestreamin years two and three. The variation inburden estimates results from differentassumptions in (1) the complexity of thewaste (and therefore of the test methodsrequired), and (2) the frequency ofreporting. The estimated total hourburden over the first three years rangesfrom 206,900 to 293,465 hours,averaging 68,967 to 97,821 hours peryear.

The estimated total start-up cost ofrecordkeeping and reporting in the firstyear ranges from $55,000 to $235,000per wastestream. The annual cost in thesecond and third years is estimated tobe $9,000 to $209,000 per wastestream(of which $8,000 to $203,000 is the costof shipping samples to a laboratory andpaying to have them tested). In yearsfour and five the high-end cost drops to$53,000. The estimated annualrecordkeeping and reporting cost perwastestream, annualized at sevenpercent over five years, is $21,000 to$170,000. The total recordkeeping andreporting cost burden over the first threeyears is $28,000,000 to $32,000,000.

Burden means the total time, effort, orfinancial resources expended by personsto generate, maintain, retain, or discloseor provide information to or for aFederal agency. This includes the timeneeded to review instructions; develop,acquire, install, and utilize technologyand systems for the purposes ofcollecting, validating, and verifyinginformation, processing andmaintaining information, and disclosingand providing information; adjust theexisting ways to comply with anypreviously applicable instructions andrequirements; train personnel to be ableto respond to a collection ofinformation; search data sources;complete and review the collection ofinformation; and trarsmit or otherwisedisclose the informati-n.

An Agency may not conduct orsponsor, and a person is not required torespond to a collection of informationunless it displays a currently valid OMBcontrol number. The OMB controlnumbers for EPA's regulations are listedin 40 CFR part 9 and 48 CFR chapter 15.

Comments are requested on theAgency's need for this information, theaccuracy of the provided burdenestimates, and any suggested methodsfor minimizing respondent burden,including through the use of automatedcollection techniques. Send commentson the ICR to the Director, OPPERegulatory lufortnation Division; U.S.Envirommtal Protection Agency(2137); 401 M St., SW.; Washington, DC20460; and to the Office of Informationand Regulatory Affaiis, Office of

Management and Budget, 725 17th St.,NW., Washington, DC 20503, marked"Attention: Desk Officer for EPA."Include the ICR number in anycorrespondence. Since OMB is requiredto make a decision concerning the ICRbetween 30 and 60 days after December21, 1995, a comment to OMB is bestassured of having its full effect if OMBreceives it by January 22, 1996. Thefinal rule will respond to any OMB orpublic comments on the informationcollection requirements contained inthis proposal.

List of Subjects in 40 CFR 261 and 268Identification and listing of hazardous

waste. Land disposal restrictions.

Dated: November 13, 1995.Carol Browner,Administrator.

XV. ReferencesU.S. Environmental Protection Agency,

Environmental Monitoring SystemsLaboratory; "Performance Testing ofMethod 1312-QA Support for RCRATesting." EPA/600/4--89/022, June 1989.

Research Triangle Institute; "InterlaboratoryComparison of Methods 1310, 1311, and1312 for Lead in Soil". U.S. EPA Contract68-01-7075, November 1988.

U.S. Environmental Protection Agency,Office of Solid Waste and EmergencyResponse; OSWER Directive No. 9285.7;"Human Health Evaluation Manual, Part B:Development of Risk-based PreliminaryRemediation Goals;" from Henry LongestII, Director, Office of Emergency andRemedial Response; and Bruce Diamond,Director, Office of Waste ProgramsEnforcement; to Regional WasteManagement Division Directors; December13, 1991.

U.S. Environmental Protection Agency,Office of Solid Waste and EmergencyResponse; OSWER Directive No. 9850.4;"Interim Final Guidance for Soil IngestionRates;" from J. Winston Porter, OSWERAssistant Administrator; to RegionalAdministrators (I-X); January 27, 1989.

U.S. Environmental Protection Agency,Office of Research and Development,Office of Health and EnvironmentalAssessment; "Exposure FactorsHandbook;" EPA/600/8-89/043, March1990.

U.S. Environmental Protection Agency,Office of Solid Waste: EPA's CompositeModel for Leachate Migration withTransformation Products (EPACMTP),Background Document, 1995a.

U.S. Environmental Protection Agency,Office of Solid Waste: EPA's CompositeModel for Leachate Migration withTransformation Products (EPACMTP),User's Guide, 1995b.

U.S. Environmental Protection Agency,Office of Solid Waste: Finite SourceMethodology for Nou-DegtaAdug andDegrading Chemicals with Tramnsormti"Products, 1995c.

U.S. Environmental Protection Agency,Office of Solid Waste: lackground

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Document for EPACMTP: Fate and U.S. Environmental Protection Agency, U.S. Environmental Protection Agency,Transport Modeling of Metals, 1995d. Office of Research Development Office of Research Development.

U.S. Environmental Protection Agency, MINTEQA2/PRODEFA2, A Geochemical Environmental Fate Constants forOffice of Research Development. Finite Assessment Model for Environmental Chemicals Under Consideration for EPA'sSource Methodology for Wastes Containing Systems: Version 3.0 User's Manual. EPA/ Hazardous Waste Identification Projects,Metals, 1992. 600/3-91/021, March 1991. compiled by Heinz Kollig, 1993.

Appendix A

TABLE A-I.-HUMAN EXPOSURE PATHWAYS

Exposure medium Route of exposure Type of fate and Pathwaytransport

Groundwater ........... Ingestion ................

Air ........................... Inhalation ...............

Groundwater ..........

Direct air ................

Air ........................... Inhalation ............... Direct air ................

Soil .........................

Soil .........................

Ingestion ................ Direct soil ...............

Ingestion ................ Overland ................

Soil ......................... Ingestion ................ Air deposition .........

Soil .........................

Soil .........................

Derm al .................. Direct soil ...............

Derm al ................... I Overland ................

Soil ......................... Derm al ................... Air deposition .........

Plant (veg/root) ....... Ingestion ................ Air deposition .........

Plant (veg) .............. Ingestion ................

Plant (veg/root) ....... Ingestion .... I ...........

Plant (veg/root) .......

Animal (beef/milk)

Air diffusion ............

Direct soil ...............

Ingestion ................ Overland ................

Ingestion ................ Air deposition .........

Animal (beef/milk) .. Ingestion ................ Air diffusion ............

Animal (beef/milk) .. I Ingestion ................ Direct soil ...............

Animal (bedf/milk) .. Ingestion ................ Overland ............... 11Wh

Co

Groundwater ........... Dermal (bathing) .... Groundwater .......... 14

Surface water ......... I Ingestion ................ Air diffusion ............

IWMU - groundwater - humansIngestion of contaminated groundwater as a drinking water source.2a (on site or off site)WMU - air - humansInhalation of volatiles2b (on site or off site)WMU - air - humansInhalation of suspended particulates3 (on site)WMU - humansIngestion of contaminated soil3 (off site)WMU - overland - humansIngestion of contaminated soil

VU - air - deposition to soil - humanslestion of contaminated soilon site)MU - humansrmal contact with contaminated soiloff site)4U - overland - humansrmal contact with contaminated soil

MU - air - deposition to surface soil - humansrmal contact with contaminated soil

AU - air - deposition to soil/gard crops - garen crops - humansnsumption of contaminated crops grown in home gardens,

vIU - air - garden crops - humansnsumption of contaminated crops grown in home gardenson site)VU - garden crops - humansnsumption of contaminated crops grown in home gardensoff site)MU - overland -' garden crops - humansr1dumption of contaminated crops grown in home gardens

VlU - air - deposition to soil/feed crops - cattle - humansnsumption of animal products with elevated levels of toxicant caused byeating contaminated feed crops and soilaAU - air - feed crops - cattle - humansnsumption of animal products with elevated levels of toxicant caused byeating contaminated feed crops(on site)AU - feed crops - cattle - humansnsumption of animal products with elevated levels of toxicant caused byeating contaminated feed crops and soil(off site)AU - overland - feed crops/soil - cattle - humansnsumption of animal products with elevated levels of toxicant caused byeating contaminated feed crops and soil

AU - groundwater - humanslestion of contaminated surface water as a drinking water source

AU - groundwater - humansrmal bathing contact with contaminated groundwater




TABLE A-1.-HUMAN EXPOSURE PATHWAYS-Continued

Exposure medibm Route of exposure Type of fate and Pathwaytransport

Surface water ......... Ingestion ................ Overland .............. 19WMU - overland flow - surface water - humansIngestion of contaminated surface water as a drinking water source

Surface water ......... Ingestion ................ Air deposition : ........ 20WMU - air - deposition to soil - overland flow - surface water - hu-

mansIngestion of contaminated surface water as a drinking water source

Fish ......................... Ingestion ................ Air diffusion ........... 21WMU - air - surface water - fish - humansConsumption f fish contaminated by toxicants in surface water

Fish ......................... Ingestion ................ Overland .............. 23WMU - overland - surface water - fish - humansConsumption f fish contaminated by toxicants in surface water

Fish ......................... Ingestion ................ Air deposition ......... 24WMU - air - deposition to surface soil - overland flow - surface water

- fish - humansConsumption f fish contaminated by toxicants in surface water

Animal (beef/milk) Ingestion ................ Air diffusion ........... 33WMU - air - suface water - cattle - humansConsumption of animal products with elevated levels of toxicant caused by

drinking contaminated surface waterAnimal (beef/milk) Ingestion ................ Overland .............. 35

WMU - overland fiwo - surface water - cattle - humansConsumption of animal products with elevated levels of toxicant caused by

drinking contaminated surface waterAnimal (beef/milk) Ingestion ................ Air deposition ......... 36

WMU - air - deposition to soil - overland flow - surface water - cattle- humans

Consumption of animal products with elevated levels of toxicant caused bydrinking contaminated surface water

Surface water ......... Dermal (bathing) .... Air diffusion ........... 37WMU - air - surface water - humansDermal bathing contact with contaminated surface water

Surface water ......... Dermal (bathing) .... Air deposition ......... 38WMU - air deposition to soil - overland flow - surface water - humansDermal bathing contact with contaminated surface water

Surface water ......... Dermal (bathing) .... Overland .............. 42WMU - overland flow - surface water - humansDermal bathing contact with contaminated surface water

Overland = Soil erosion; Overland flow = Both runoff and sold erosion; or, for surface impoundments, a spill directly to surface water. Veg =Aboveground fruits and vegetables. Root = Belowground (or root) vegetables.

a Some pathway numbers are missing, reflecting pathways that have been eliminated from the analysis or combined with other pathways.

TABLE A-2.-ECOLOGICAL EXPOSURE PATHWAYS

Exposure medium Route of exposure Type of fate and Pathways atransport Pathways__

Soil ......................... Ingestion ................ Direct soil ...............

Soil ......................... Direct contact ......... Direct soil ............

Plant ....................... Ingestion ................ Direct soil ...............

Soil fauna ............... Ingestion ................ Direct soil ...............

Animals ..................

Soil .........................

Ingestion ................ Direct soil ...............

Ingestion ................ I Overland ................

3 (on site)WMU - mammals, birds, soil faunaIngestion of contaminated soil5 (on site)WMU - plants, soil faunaDirect contact with contaminated soil9 (on site)WMU - vegetation - mammals, birdsConsumption of contaminated vegetation (e.g., forage

grasses)11 a (on site)WMU - soil fauna - mammals, birdsConsumption of soil fauna (e.g., earthworms, insects) with

elevated levels of toxicant11 b (on site)WMU - soil fauna/vegetation - animals - predatory mam-

mals, birdsConsumption of animals with elevated levels of toxicant3 (off site)WMU - overland - mammals, birds, soil faunaIngestion of contaminated soil

Terr I ............

Terr II ...........

66419




TABLE A-2.-ECOLOGICAL EXPOSURE PATHWAYS-Continued

Exposure medium Route of exposure I Type of fate and Pathways aII-transportPah ys

Soil ......................... Direct contact ......... Overland ................

Plant ....................... Ingestion ................ Overland ................

Soil fauna ............... I Ingestion ................ Overland ................

Anim als ................. : Ingestion ................ Overland ................

Soil ......................... Ingestion ................

Soil ......................... I Direct contact .........

Plant .......................

Air deposition .........


Ingestion ................ Air deposition .........

Ingestion ................ Air diffusion ............





err V ........... I Plant .......................

Surface water ........ Ingestion ................

Fish ........................ Ingestion ................

Surface water ........ Direct contact .........

Ingestion ................Aq II .............. I Surface water ........

Fish ........................ Ingestion ................ Air deposition .........

Surface water ........ Direct contact ......... Air deposition .........

Surface water ........ Ingestion ................ I Overland ................

Fish ........................ Ingestion ................ Overland ................

Surface water ........ Direct contact ......... I Overland ................

5 (off site)WMU - overland - plants, soil faunaDirect contact with contaminated soil9 (off site)WMU - overland - vegetation - mammals, birdsConsumption of contaminated vegetation (e.g., forage

grasses)11 c (off site)WMU - overland - soil fauna - mammals, birdsConsumption of soil fauna (e.g., earthworms, insects) with

elevated levels of toxicantl1 d (off site)WMU - soil fauna/vegetation - animals - predatory mam-

mals, birdsConsumption of animals with elevated levels of toxicant4WMU - air - deposition to soil - mammals, birds, soil

faunaIngestion of contaminated soil6WMU - air - deposition to surface soil - plants, soil faunaDirect contact with contaminated soil8WMU - air - deposition to soil - vegetation - mammals,

birdsConsumption of contaminated vegetation (e.g., forage

grasses)8WMU - air - vegetation - mammals, birdsConsumption of contaminated vegetation (e.g., forage

grasses)17WMU - air - surface water - mammals, birdsIngestion of contaminated surface water as a drinking water

source21WMU - air - surface water - fish - mammals, birds, fishConsumption of fish contaminated by toxicants in surface

water37WMU - air - surface water - fish, daphnids, benthosDirect contact with contaminated surface water, sediments37WMU - air - deposition to soil - overland flow - surface. water - mammals, birdsIngestion of contaminated surface water as a drinking water

source24WMU - air - deposition to surface soil - overland flow -

surface water - fish - mammals, birds, fishConsumption of fish contaminated by toxicants in surface

water38WMU - air - deposition to soil - overland flow - surface

water - fish, daphnids, benthos 'Direct contact with contaminated surface water, sediments19WMU - overland flow - surface water - mammals, birdsIngestion of contaminated surface water as a drinking water

source23WMU - overland flow - surface water - fish - mammals,

birds, fishConsumption of fish contaminated by toxicants in surface

water42WMU - overland flow - surface water - fish, daphnids,

benthosDirect contact with contaminated surface water, sediments

Overland=Soil erosion. Overland flow=Both runoff and soil erosion; or, for surface impoundments, a spill directly to surface water.

Terr III ..........

Terr IV ..........

Aq I ...............

Aq III .............



Federal Register / Vol. 60, No. 245 /.Thursday, December 21, 1995 / Proposed Rules 66421

a Some pathway numbers are missing, reflecting pathways that have been eliminated from'the analysis.

TABLE A-3.-SUMMARY OF HUMAN RECEPTORS FOR EXPOSURES PATHWAYS

Receptor

Pathway Subs. Home , Subs. FishAdult Child farmer gardener fisher consumer Worker

1: Groundwater-ingestion ..................................................... ,a .........2a: Direct air-inhalation of violates (on site) ........................ a............ ................ ................ ................................ 42a: Direct air-inhalation of volatiles (off site) ............... 4........ ................ ................ . ................ ................ ................ ................2b: Direct air-inhalation of particles (on site) .............. 4 a ............................................................. ............... 42b: Direct air-inhalation of particles (off site) ....................... 4 ................ ................ ................ ................ ................ ...........3: D irect soil-soil ingestion (on site) ..................................... /3 ................................ ................ ................ ...............3: O verland-soil ingestion (off site) ...................................... 4 ................ ................ ................ ................ ................4: Air deposition-soil ingestion .................. 4 ................ ................................................ ................5: Direct soil-dermal (soil) (on site) ...................................... ,a 40 ................ ................ ................................ 45: Direct Soil-derm al (off site) .............................................. 4 4 ................ ................ ................ ................ ...............6: Air deposition-derm al (soil) .............................................. 4 .............. ................ ................ ................ ................8: Air deposition-veg/root ingestion ...................................... 4. ./ 4 ................ ................8a: Air diffusion-veg/root ingestion ...................................... 4 ./ . ...............................................9: Direct soil-veg/root ingestion (on site) .................... /...,... ................ A 4.................................9: Overland-veg/root ingestion (on site) .............................. ... .. ....................4 410: Air deposition-beef/m ilk ingestion ................................. / ................ ................ ................ .........1 Oa: Air diffusion-beef/milk ingestion .................... ........................................11: Direct soil-bee/milk ingestion (on site) ................................. 4 Va ................................................................11: Overland-beef/milk ingestion (off site) ......................... 4........ 4 ................................................................14: G roundw ater-derm al (bathing) ....................................... 4 ................ ................ ................ ................ ................17: Air diffusion-drinking water ingestion ............................. 4 ................ ................ ................ ................ ................ ................19: O verland-drinking water ingestion .................................. 4 ................ ................ ................ ................ ................ ................20: Air deposition-drinking water ingestion .....................2 : Air d sion- i ingestion ........................................... ................ ................ ................21: Air diffusion-fish ingestion ......................... ........... ........... 4 ................24: Ard t-fish ingestion ....................... ...................................... 424: Airv e posind -fish ing estion .............................................. / ................. ................ ................ V/ / ................33: Air diffusiion ( -fih il ingestion ............................................. .......... ................ ................ ................ , ................33: Air diffusion (SW )-beef/milk ing estion .................................. .....................................................................35: Overland (SW)-beef/milk ingestion...................................4/36: Air deposition (OF/SW)-beef/milk ingestion.................36: ir epostio (O F SW )beefm il ing stin ............... ................ ................................. ................. ................. .................

37: Air diffusion (SW )-derm al (bathing) ................................ 4 ................ ................ ................ ................ ................38: Air deposition (O F/SW )-derm al (bathing ........................ 4 ................ ................ ................ ................................42: Overland (SW )-derm al (bathing) .................................... / 4 ...................... ...... ............................. ................

a On-site pathways for receptors other than workers are modeled only for the land application unit after closure.

TABLE A-4.-SUMMARY OF ECOLOGICAL RECEPTORS BY EXPOSURE PATHWAYS

Receptor

PathwayMammals Birds Plants Soil Fish Daphnids Benthosfauna

3: Direct soil-soil ingestion (on site) ..................................... Va 4a ................ 43: Direct soil-soil ingestion (off site) ..................................... V V ................ 4 ................ ............... . ...............4: Air deposition-soil ingestion ............................................. 4 / ............... V ................ ................ ................5: Direct soil-dermal soil (on site) ......................................................5: Direct soil-dermal soil (off site) ........................................ . ./ ................ ................ ................6: A ir deposition-derm al soil ................................................. 4................. ................ 4 ................................8: Air deposition-veg/root ingestion ...................................... / V/ ............................................... .. .............. . ................8a: Air diffusion-veg ingestion .............................................. V ............... ................................ ... ............. ... .............9: Direct soil-veg/root ingestion (on site) ............................. 4 ................ ................ ................ .. .............. .. ..............9: Overland-veg/root ingestion (off site) .............................. 4 V . ................ ................ ................ ................. ...............11 a: Direct soil-soil fauna ingestion (on site) ....................... V 4 ................ ................ ................ ..1 1b: Direct soil-anim als ingestion (on site) .......................... V V ................................. ................ ............... . ...............1 lc: Overland-soil fauna ingestion (off site) ........................ 4 V ................ ................ . .... ............................l1 d: Overland-animals ingestion (off site) ........................... 4 ................ ................ . .... ............ .... ............17: Air diffusion-drinking water ingestion ............................. 4 ................ ................ ................ .. .............. .. ..............18: Groundwater (SW)-drinking water ingestion .................. 4 V .................................19: Overland-drinking water ingestion .................................. V V ................ ................ . .... ............ ... .............20: Air deposition-drinking water ingestion .......................... 4.21: Air diffusion-fish ingestion ......................................... ........... ........ 4 ....... ................22: Groundwater (SW)-fish ingestion ................................... 4 4 ................................ 423: Overland-fish ingestion .......................... 4 V V ................................. / .................24: Air deposition-fish ingestion ........................................... V V ................................ 4 ................ ................37: Air diffusion (SW)-direct contact ....................................................... 4 4 V38: Air deposition (OF/SW)-direct contact ................................................... 4 4 440: Groundwater (SW)-direct contact ......................................................... 4 4 V




TABLE A-4.-SUMMARY OF ECOLOGICAL RECEPTORS BY EXPOSURE PATHWAYS-Continued

ReceptorPathwayMammals Birds Plants Soil ish Daphnids BenthosMammas Bids Pants fauna

42: Overland (SW )-direct contact .. 4.4.................................................... .............aOn-site pathways are modeled only for the land application unit after closure.

TABLE A-5.-PATHWAYS MODELED FOR EACH WASTE MANAGEMENT UNIT

Waste management unitPathway Ash Land Wastepile Surface Tank Water

monofill appl. unit - impound. use

1: Groundwater-ingestion .......................................................................... ................ 4 4 4. ./2a: Direct air-inhalation volatiles .............................................................. ................ 4 4 4 . ...............2b: Direct air-inhalation particles .............................................................. 4 4 4 ................ ................ ................3: Direct soil-soil ingestion ....................................................................... ................ 4 4 ................................ ................4: Air deposition-soil ingestion ................................ 4 4 4/5: Direct soil-derm al (soil) ........................................................................ ................ 4 4 ................................ ................6: Air deposition-derm al (soil) .................................................................. ................ ................ ................8: Air deposition-veg/root ingestion .............................. . 4 4.8a: Air diffusion-veg/root ingestion ........................................................... ................ 4 4 ...............9: Direct soil or overland-veg/root ingestion ................................. . . ............................................ ...10: Air deposition-beef/milk ingestion ............................ 4 4 4.10a: Air diffusion-beef/m ilk ingestion ....................................................... ................ 4 4 ................11: Direct soil or overland-beef/milk ingestion ............................... 4 4/ .14: Groundwater-dermal (bathing).............................. ........................................ 417: Air diffusion-drinking water ingestion ................................... 419: Overland-drinking water ingestion ..................................................... 4...../ ................ ...............20: Air deposition-drinking water ingestion ......................... . . V 4 421: Air diffusion-fish ingestion .................................................................. 4/../.././ ...............23: Overland-fish ingestion .............................................................................. 4 ................ ................24: Air deposition-fish ingestion ............................................................... V V4 ................ ................ ................33: Air diffusion (SW)-beef/milk ingestion ................................................ ...... /. ...............35: Overland (SW)-beef/milk ingestion ................................... 4 .... /. ................ ................36: Air deposition (OF/SW)-beef/milk ingestion ..................... V 4. .37: Air diffusion (SW)-dermal (bathing) ................................... 4 / V ................38: Air deposition (OF/SW)-dermal (bathing) ........................ . 4 4/42: Overland (SW )-dermal (bathing) ........................................................ 4 ................ ................

OF=Overland flow. SW=Surface water.

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. .. . . 0 ^0 0 - a *Q *.a 'C . . . .

•) CD - - - - 0 -F- .- •

" 1C\ '- A 0I CO SO 0 0) ) 0 L ,O W -C - '- ow C1 U0 N

"-- (

t2 C0 0 0r00 • N 0 U) "DC') C ......) :. UCc O C) to 0 ' C ) 0 1-- -N o oL _ )U 0 to o_0o oCo 0 0 o oooo. = -) '.O

0) ._ r, C r r- 0) '? M 0 ... .C 'Co t-n 0 0 0 NT -) 0- N- ,i W 00000000 0 .0 •0)C< . to - Co - R . - -, , - rt - I, , -.- 0)

(D N 00 0) N C' C, . . 0 0MN 0 0 'I 0 0 N 0 C M W N

' ;!I :0)t2 I 2 2 t 202 R 2 0 2 - -I

a)

CM

Ca

Co

0

2C

0

a)a)

Ca

CaCa

Ca

0

0Ica

CCa

aa0 :

Ca w0 C

M CMCa

Ca Ca

20




Appendix C

TABLE C-1.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING ToxiCITY BENCHMARKS

WW totals (mg/I) NWW totals (mg/kg) NWW leach (mg/I)CAS No. Name Multipath Ground Extrapo- Mulipath ExrporoJu, und- Extrapo-

modeled , latedexit WWEQCE modeled It h lated each WW EOC

x v exit level level leach level level each level level

83--32-9 ......208-96-8 ....67-64-1 ......75-05--8 ......98-86-2 ......75-36-5 ......591-08-2 ....53-96-3 ......107-02-8 ....79-06-1 ......107-13-1 ....1402-68-2 ..116-06-3 ....309-00-2107-18-6107-05-1 ....92-67-1 ......2763-96-4 ..504-24-5 ....61-82-5 ......62-53-3 ......120-12-7 ....7440-36-0140-57-87440-38-22465-27-2115-02-6 ....7440-39-3 ..71-43-2 ......92-87-5 ......106-51-4 ....98-07-7 ......50-32-8 ......205-99-2205-82-3 ....207-08-9 ....191-24-2 ....100-51-6 ....100-44-7 ....56-55-3 ......225-51-4 ....7440-41-7 ..39638-32-9111-44-4 ....117-81-7 ....542-88-1 ....598-31-2 ....75-27-4.75-25-2 ......

101-55-3 ....357-57-3 ....71-36-3 ......88-85-7 ......

85--68-7 ......7440-43-9 ..86-74-8 ......75-15-0 ......353-50-456-23-5 ......75-87-6.305-03-3 ....57-74-9 ......494-03-1 ....126-99-8 ....

107-20-0 ....106-47-8 ....108-90-7 ....510-15-6 ....124-48-1 ....75-00-3 ......110-75-867--66-3 ......

Acenaphthene ...............Acenaphthylene ....................Acetone .................................Acetonitrile ............................Acetophenone .......................Acetyl chloride .......................Acetyl-2-thiourea, 1-. ..............Acetylaminofluorene, 2-. .......Acrolein .................................Acrylam ide ............................Acrylonitrile ............................Aflatoxins ...............................Aldicarb .................................Aldrin .........................Allyl alcohol...........Allyl chloride ..........................Am inobiphenyl, 4- . ................Aminomethyl-3-isoxazolol, 5-Am inopyridine, 4-- ..................Am itrole .................................Aniline ...................................Anthracene ............................Antim ony ...............................Aram ite ..................................Arsenic ...................Auram ine ...............................Azaserine ..............................Barium ...................................Benzene ................................Benzidine ..............................Benzoquinone, p- ..................Benzotrichloride ....................Benzo(a)pyrdne .....................Benzo(b)fluoranthene ............Benzoij)fluoranthene .............Benzo(k)fluoranthene ............Benzo[g,hi,]perylene ............Benzyl alcohol .......................Benzyl chloride ......................Benz(a)anthracene ................Benz[c]acridine ......................Beryllium ...............................Bis (2-chloroisopropyl) ether.Bis(2-chlorethyl)ether ............Bis(2-ethylhexyl)phthalate .....Bis(chloromethyl)either.Brom oacetone .......................Bromodichloromethane .........Bromoform

(Tribromomethane).Bromophenyl phenyl ether, 4-Brucine ..................................Butanol ..................................Butyl-4,6-dinitrophenol, 2-

sec- (Dinoseb).Butylbenzylphthalate .............Cadm ium ...............................Carbazole ..............................Carbon lisulfide ....................Carbon oxyfluoride ................Carbon tetrachloride .............Chloral ...................................Chloram bucil .........................Chlordane ..............................Chlom aphazin .......................Chloro-1, 3-butadiene, 2-

(Chloroprene).Chloroacetaldehyde ..............Chloroaniline, p- ....................Chlorobenzene ......................Chlorobenzilate .....................Chlorodibromomethane.Chloroethane (ethyl chloride)Chloroethyl vinyl ether, 2-. ....Chlcroform ............................

31.2.................15.60.7816.8

I........... *0... '0.00285

0.0230.117750.02762

0.000261 .............

49.5

2320006.58

5960

0.002483.67

0.00428

5.640E-07

0.0742

0.444

8210

40.5

0.02090.00015

0.002 31

0.000805

225001.13

0.0138

10.10.569

0.001410.00044

391 ..............................

......... .;.....0.00285

0.020

0.001 1

0.00469

0.. . 053.....

0.. . 136.....

.000384.....

0.134

3.90.000717

0.0008270.007

0.00064812.4

........... .... i 0.02Z3.3 :.085:4:..........

0.178 0.064 ..........

3860015.4

2351600

0.738

0.000014

0.515

5171.5

0.073116.3

0.00759

15.60.192

4370.24

18.4

0.014

0.0998

0.424.76

0.0540.0066

0.057

0.0230.159

0.159

0.023

0.. . 081....0.0810.081

0.023

0.023

0.081

0.00180.02

0.20.015

0.00158

0.020.0130.01

0.008

9480

17400923

1210

2.630.00436

0.961

3.9

30.851.663.28

.05............... .194

0.000034 0.000444 ..................

0.002 2580.02 ..................

14.70.0069415

39

0.027620.159

0.027620.0069415

0.00285

14.7

. 159.....

0.159

14.70.081

0.002850.002860.00285

4.21

8.72

0.17

2080109

0.0000298

0.2273.7

274C37.5

0.1

0.059610.9440.115

.225

19173

18200772

8714.1

330

8.54

0.00976

286

142247C6.8227.5

6.74

3.2819.955

3.280.194

3.9

6900

19.. .955....

19.955

6900142

3.93.9

3.9

19.9

30.85

30.85

30.. . 85...142........

0.07420.7

0.0270.014

0.03

70

0,0750.10.7

0.0006

0.002

0.01320.5

2

0.3031

0.20.0001

0.0420.7

0.0040.06210.0699

0.010.70.7

0.0340.00276

0.08260.03

0.10.05860.0651

0.'143

0.0'0.0012

0.02

0... . 7.....

0.230.042

0.0490.2

0.0002

0.02

0.00099

0.05920.0002

0.0690.000815

0.0050.0060.002

4.9

60.36.4

0.0000380.00034

3.670E-06

0.017

0.053

0.000148

15.50.0054

6.800E-07

7.040E-060.0000661

1515

4.300E-06

0.000320.0019

0.000360.00 112

0.018

60.064

640.11

6.4

0.000 163

1.330.00570.0018

0.. . 017....

0.0000661

0.0156.4

0.00884

.. ..........10.50.48... ...........

15

0.008840.105

0.008840.48

... ...........0.0000661

10.5

0.1050.105

... ...........10.5

0.0317

0.006610.00006610.0000661

0.0000661

0.015

0.0150.105

0.0317

0.015

0.0317

0.00180.020.2

0.0150.00158........ .. ..

0.020.013

0.010.008.................

0.050.000034..............

0.0020.02

..............0.00023

0.0070.0008

0.020.0005

I .......... ¥0.001

0.000040.0025

0.01

0.0000230.000018

0.00020.00020.0008

0.000745.000E-06

0.0000130.00050.0003

0.001450.0003

0.00027I................0.005

0.000080.0002

0.0120

0.0140.00029

0.0000420.00005

0.00121

i..................0.0002 1

00004

0.002

0.000660.000040.005040.00007

0.005

0.00003

0.000230.007

0.00080.02

0.0005

0.0010.00004

0.00250.01

0.000023,0.000018

0.00020.00)020.0008

0.000745.OOOE-06

0.0000130.0005

0.000030.00145

0.00030.00027

0.0050.00008

0.0002

0.01~20

0.0140.00029

0.0000420.00005

0.00121

0.0002 1

0.00004

0.002

0.000660.000D40.005040.00007

0.005

0.00003




TABLE C-i .- SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING ToXICITy BENCHMARKS-Continued

WW totals (mg)) NWW totals (mg/kg) NWW leach (mgA)IGround- GroundCAS No. Name Multipath I Extrapo- Multipath Extrao Groun Extrapo-modeled water lated exit WW EQC NWW water lated each WW

exitlevel modeled model ed W ,v, modeled ated leach . modeled EC

exit level level leach level level eachlevel level

59-50-7 ......107-30-291-58-7 ......95-57-8 ......7005-72-35344-82-1542-76-7 ....7440-47-3 ..218-01-9 ....6358-53-87440-48-47440-50-8108-39-4 ....95-48-7 ......106-44-5 ....4170-30-3 ..57-12-5 ......14901-08-7108-94-1131-89-5 ....

50-18-0 ......20830-81-372-54-8 ......53-19-0 ......72-55-9 ......3424-82-6 ..50-29-3 ......789-02-6 ....2303-16-4 ..132-64-9 ....192-65-4 ....189-64-0 ....189-55-9 ....194-59-2226-36-853-70-3 ......224-42-0 ....96-12-8 ......

764-41-0 ....110-57-6 ....96-23-1 ......95-50-1 ......541-73-1 ....106-46-7 ....91-94-1 ......75-71-8 ......75-34-3 ......107-06-2 ....75-35-4 ......156-59-2 ....156-60-5 ....111-91-198-87-3 ......

120-83-287-65-0 ......94-75-7 ......

78-87-5 ......542-75-6 ....10061-01-510061-02-660-57-1 ......1464-53-5 ..

84-66-2 ......311-45-5

56-53-1 ......94-58-6.60-51-5 ......131-11-3 ....77-78-1 ......

Chloro-m-cresol, p- ...............Chloromethyl methyl ether ....Chloronaphthalene, 2- . .........Chlorophenol, 2- . ..................Clorophenyl phenyl ether, 4-Chlorophenyl thiourea, 1-o-Chloropropionitrile, 3- ............Chromium ..............................Chrysene .................... ...........Citrus red No. 2 ....................Cobalt ....................................Copper ..................................Cresol, m-- .............................Cresol, o- ...............................Cresol, p- ..............................Crotonaldehyde .....................Cyanide .................................Cycasin .................................Cyclohexanone .....................Cyclohexyl-4,6-dinitrophenol,

2-.Cyclophosphamide ................Daunomycin ..........................DDD ......................................DDD (o,p' ) ............................DDE .......................................DDE (o,pt ) ............................DDT .......................................

DDT (o.p1) .............................Diallate ..................................Dibenzofuran .........................Dibenzo[a,e]pyrene ...............Dibenzo[a,h]pyrene ...............Dibenzo[a,i]pyrene ................Dibenzo[c,gjcarbazole, 7H- ...Dibenz(a,h)acridine ...............Dibenz(ah)anthracene ..........Dibenz[a,jlacndine .................Dibromo-3-chloropropane,

1,2-.Dichloro-2-butene, 1A . ........Dichloro-2-butene, trans-1,4-Dichloro-2-propanol, 1,3- ......Dichlorobenzene, 1,2-. ..........Dichlorobenzene, 1,3-. ..........Dichlorobenzene, 1,4-. ..........Dichlorobenzidine, 3,31.. ......Dichlorodifluoromethane .......Dichloroethane, 1,1-. .............Dichloroethane, 1,2 .............Dichloroethylene, 1,1-. ..........Dichloroethylene, cis-1,2 . ....Dichloroethylene, trans-1,2- ..Dichloromethoxy ethane .......Dichloromethylbenzene

(benzal chloride).Dichlorophenol, 2,4-. .............Dichlorophenol, 2,6- ..............Dichlorophenoxyacetic acid,

2,4- (2,4-D).Dichloropropane, 1,2- . ...........Dichloropropene, 1,3- . ..........Dichloropropene, cis-1,3 .....Dichloropropene, trans-i,3- ..Dieldrin ..................................Diepoxybutane, 1,2,3,4-

(2,21-bioxirane).

Diethyl phthalate ...................Diethyl-p-nitrophenyl phos-

phate.Diethylstibestrol .....................Dihydrosafrole .......................Dimethoate ............................Dimethyl phthalate ................Dimethyl sulfate ....................

..................

.................134

13001.32

I..................674615656

63.5

S.................

S................

I...............I..................

0.000126

9.11 OE-06

0.0000181

0.26

I 0.03

/ 0.007

I0.009

-..... .........58.5E-0

0.0763

0.010.0005

..................

...............

........... ...0.9

......... ... ...

............. ...

.................

1.240.1

27908.48.4

0.84

/0.0016

|0.00429

/ 1.68Ii 2.94

0.621 ................... ....... ...

1.561 ....... ..........

0.0230.00289000090000

682

35601 ............ 186

7.720E-07.................

38.1200000

4.290E-07..................

29.478

.......................... ... ...

............ 114.7

14.7

0.11775

0.0810.0230.081

........ 023....0.023

0.081............ ............... .....

14.71.24

7.80.159

14.77.8

0.0252

*0.15914.7

0.0069415

0.0069415

0.0069415

8.40.002850.002850.002850.002850.00285

0.00285.023.

0.023- 0.023

0.081......... 023.;.

i................

0.02.................0.01

0.000580.01

.......... ....0.1

0.0020.00015

.............5...0.0007

0.00046

0.000550.00046

0.060.2................10

0.1

........... .....

........... .....0.00005

0.000058

0.000081

0.000630.01

0.00020.0002

0.0020.01

0.00020.00003

0.0010.00026

0.0050.005

0.010.00003

0.0050.000040.00240.0001

0.000040.000060.000120.000120.00006

0.010.005

0.000410.01

0.00029

0.000040.0009

0.000690.00094

0.0000440.005

.................

.................104

9.7634.6

.................5.91

2150027400

2550

....... ..... ..

........ .......

............ ....

................

.................

0.00648

0.000936

0.00315

1.26

0 .055

5300

69

............. ...

0.0015500

69

16.92.452.4

0.076

14230.85

142......... 85...

30.85

142............. ............... ..69008.72

12101210

2.991

19.955

6900.................

0.194.................0.194.................0.194......... ....27400

3.93.93.93.93.9

.............9...

30.8530.85

142.................

30.85

........... ...

.................

i.................30.85

6008

0.0050.7

0.07580.7

0.50.0030.084

50.5

0.0350.0270.035

40.2..................107

................

................0.0012

................0.0006

0.0006

0.0230.7

0.010.010.010.7

0.010.084

0.70.0003

0.0050.005

0.050.0002

0.70.0001

0.1160.00520.00020.00010.0014

0.020.0006

0.70.3

0.0780.7

0.000

0.00010.00030.00030.00030.0006

0.005

.................

.................0.32

0.4760.00119

I.................

S.................

10803.23.2

0.32

...............................6

2800

0.0000623

0.0054

0.46

1............. ..

6.340E-07

0.000114

6.1

0.01080.00072

11.90.000060.000060.00018

0.641.12

0.18 ...................: ...... 6 .... .. 0.015

.6.........

0.00230.00085

115011500.54

..... ............

..................

..................

..................................

10.5

0.00025 4490 ............ 0.0221 54 ............................... 19.955. ........ .... 0.105

0.00780.05

0.000290.00064

2.470E-1"1.................

1.63

6900

1.66

13

0.06910.013

6.500E-08............ .....0.77

30

10.5

6.4

0.03170.015

0.0317................0.0150.015

0.0317

10.50.4165i...............6.2

0.10510.56.2

0.0083

0.10510.5

0.48

0.48

S................

0.48

3.20.00006610.00006610.00006610.00006610.0000661

0.0000661

0.0150.015

0.0317

0.015. 015......

0.02................. "0.01

0.000580.01

...............1.

0.0020.00015

.............5...0.0007

0.00046

0.000550.00046

0.060.2

.................

0.1

........... 666..

........ .. ..0.00005

0.000058

0.000081

0.000630.01

0.0010.00020.0002

0.010.0002

0.000030.001

0.00026

0.0050.0050.01

0.000030.005

0.000040.00240.0001

0.000040.000060.000120.000120.00006

0.010.005

0.000410.01

0.00029

0.000040.0009

0.000690.00094

0.0000440.005

0.00025

0.00780.05

•0.000290.00054




TABLE C-1.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING TOXICITY BENCHMARKS-Continued

WW totals (mgal) NWW totals (mg/kg) I NWW leach (mg/I)

CAS No. Name Multipath EGround-ate Ext I l Muipath Extrapo- NWW water I Extraclo- Eexiael oee leve modeled lated leach EOC modeled lel

modeled eled I WW EQC lee lel lated each EQCexitlvel extlee ,evel leac lee ,evel eac lee ,evel w

60-11-7 ......

119-93-7 ....57-97-6 ......

79-44-7 ......122-09-8 ....

105-67-9 ....119-90-4 ....84-74-2 ......99-65-0 ......100-25-4 ....534-52-1 ....51-28-5 ......121-14-2606-20-2 ....117-84-0 ....123-91-1 ....122-39-4 ....122-66-7 ....298-04-4 ....541-53-7 ....115-29-7 ....959-98-8 ....332-13-65-

9.1031-07-8145-73-3 ....72-20-8.7421-93-453494-70-5106-89-8 ....51-43-4.110-80-5 ....141-78-6 ....51-79-6 ......107-12-0 ....60-29-7 ......97-63-2 ......62-60-0 ......100-41-4 ....106-93-4 ....75-21-8 ......96-45-7.151-56-4 ....52-56-4 ......640-19-7 ....62-74-8 ......206-44-0 ....86-73-7 ......16984-48-850-00-0 ......64-18-6 ......765-34-4 ....319-86-8 ....76-44-8 ......1024-57-3 ..87-68-3 ......118-74-1 ....319-84-6 ....

319-85-7 ....

58-89-9 ......

77-47-4 ......67-72-1.70-30-4.1888-71-7757-58-4591-78-6302-01-2193-39-5

............. .................. 02762

0.000625 0.0000702 ..................3.820E-06 0.00464 ..................

Dimethylaminoazobenzene,p-.

Dimethylbenzidine, 3,3-.Dimethylbenz(a)anthracene,

7,12-.Dimethylcarbamoyl chloride..Dimethylphenethylamine,

alpha, alpha-.Dimethylphenol, 2,4- .............Dimethyoxybenzidine, 3,31- ..Di-n-butyl phthalate ...............Dinitrobenzene, 1,3- ..............Dinitrobenzene, 1,4- ..............Dinitro-o-cresol, 4,6- .............Dinitrophenol, 2,4- ................Dinitrotoluene, 2A4- ...............Dinitrotoluene, 2,6- ...............Di-n-octyl phthalate ...............Dioxane, 1,4- ........................Diphenylamine ......................Diphenylhydrazine, 1,2- .......Disulfoton ..............................Dithiobiuret ............................Endosulfan ............Endosulfan I ..........................Endosulfan II .........................

Endosulfan sulfate ................Endothall ...............................Endrin ....................................Endrin aldehyde ....................Endrin ketone .......................Epichlorohydrin .....................Epinephrine ...........................Ethoxyethanol, 2- .................Ethyl acetate .........................Ethyl carbamate ....................Ethyl cyanide (propionitrile) ..Ethyl ether .............................Ethyl methacrylate ................Ethyl methanesulfonate ........Ethylbenzene ........................Ethylene Dibromide ...............Ethylene oxide ......................Ethylene thiourea ..................Ethyleneimine (aziridine).Famphur ................................Fluoracetamide, 2- . ..............Flouracetic acid, sodium saltFluoranthene .........................Fluorene ................................Fluoride .................................Formaldehyde .......................Formic Acid ...........................Glycidylaldehyde ...................HCH, delta- ...........................Heptachlor .............................Heptachlor epoxide ...............Hexachloro-1,3-butadiene .....Hexachlorobenzene ..............Hexachlorocyclohexane,

alpha-(alpha-BHC).Hexachlorocyclohexane,

beta-(beta-BHC).Hexachlorocyclohexane,

gamma-(Undane).HexachlorocyclopentadieneHexachloroethane .................Hexachlorophene ..................Hexachloropropene ...............Hexaethyl tetraphosphate .....Hexanone, . ........................Hydrazine ..............................Indeno (1,2,3-cd) pyrene ......

1511.788831.28

50.210.712.9

0.002558

29

0.0131

6.62

0.0729

0.335

14.7

255000.0055

74.50.000928

17.7

15801310

0.0158

0.00002370.000528

0.007880.0004240.0001 42

0.000445

0.000783

0.005210.049

5.1 50E-06

0.00285

3.780.0336

2270.018

0.2730.2940.181260

0.042414.7

458

6

6550

414000

39........39

27.324

93000039

0.00036

0.00053

27.522.4

27... . 3..27.3

7.8

7830.08060.0226

21

0.0013

119

0.. . 212....0.212

0.0165

0.0810.159

0.02520.0252

0.. . 159....

006915

0.0069415

00.915

00.915

006915

0.0069415

0.0069415

006915

14.7

0.159

0.01

0.00330.00037

0.05

0.000470.0077

0.000330.00011.

0.040.05

0.000420.000020.00031

0.0000420.012

0.001510.01

0.00007

. 000.......0.000340.0004

0.0004

0.10.00039

0.00050.0005

0.06519

1.160.009

0.050.1

0.001530.003450.001060.000060.00006

0.001

0.02

0.0006210.00021

0.050.0232

0.2

.. 02...0.00024

0.00002

0.00010.00161

0.000035

0.000023

0.000025

0.00018I .600E-06

0.2070.01

0.005

0.000043

0.000620.00263

113000.236

900005.54

56.1213

86.3448013.2

11800

42.6

73.1

026

44

6900272000

412003420

00133550000

0.00745

0.51

89800

48.8301000

1210

7.790.0264

36.40.01160.0333

0.12

0.102

145080.6

0.0000241

..................0

..................

..................

..................0.194

..................

..................

..................

..................

..................

.................142

690C1210

19.95E

0.71 ...... ...........

0.7 0.00001E0.039 2.760E-0E

14219.955

2.9912.991

19..955.....

1945

0.194

195

195

195

0.194

0.194.............

3

0.0527

0.2490.25

33

0.030.260.25

0.1390.00050.041

0.70.0035

. 0005......0.00950.009

0.04

0.00360.020.03

0.0714

2.030.18

30.1

0.003190.00110.018

0.00020.000 1

0.07

10

0.080.08

0.4

0.07230.0008

0.0006

0.042

0.09230.02068

0.70

0.005

0.30.0748

0.00884

0.03170.105

0.008130.0083

0.. . 105.....

0.485

0.4

0.580.05

0.58

0.05

0.48

0.48

10

0.485

0.6931 .................

...............0.0313

0.0013E

0.0000241

0.031710.66.2

0.10E

1.190.0102

25.20.0064

0.1050.1120.064

0.10.0136

2.6

13

0.94

32

5400

15114

10.56.6

117008.1

0.000015

0.00017

1.743.4

10.. . 5....10.5

6.2

0.450.00691

0.0001130.11

0.00021

0.01

0.00330.00037

0.05

0.000470.0077

0.000330.00011

0.040.05

0.000420.000020.00031

0.0000420.012

0.001510.01

0.00007

0.000040.00030.0004

0.00040.1

0.000390.00050.0005

0.06519

1.160.0009

0.050.1

0.001530.003450.001060.000060.00006

0.001

0.02

0.000210.00021

0.050.0232

0,2

0.00020.00004

0.0000320.0001

0.001610.000035

0.000023

0.000025

0.000181.600E-06

0.2070.01

0.005

0.000043

5970I ..................




TABLE C-1.-SUMMARY OF CONSTITUENT-SPECIFIC ExIT LEVEL DEVELOPMENT USING ToxIcITY BENCHMARKS-Continued

WW totals (mg/I) NWW totals (mg/kg) NWW leach (mg/I)

AS.Name Mutipath war O itran - Mutipath Extrapo- ww Ground- Extrapo-CAS No. nd 1 water WEQC modeled latedleach --- w lated eacht WW EQexit level modeled level leach level level EO modeled level I

mdld exit level Iae ech ___ each level I____ ____

74-88-4 ......78-83-1 ......465-73-6 ....78-59-1 ......120-58-1143-50-0 ....303-43-4 ....7439-92-1 ..108-31-6 ....123--33-1109-77-3148-82-37439-97-6126-98-7 ....74-93-1 ......67-56-1 ......91-80-5 ......16752-77-572-43-5.74-83-9.

74-87-3.

78-93-3 ......1338-23-4 ..60-34-4 ......108-10-1 ....80-62-6.66-27-3.91-57-6.298-00-0 ....75-55-8 ......56-49-5 ......74-95-3 ......75-09-2.101-14-4

70-25-7 ......

56-04-2 ......50-07-7 ......7439-98-7 ..91-20-3 ......130-15-4 ....86-88-4 ......134-32-7 ....91-59-8 ......7440-02-054-11-5.88-74--4 ......99-09-2 ......100-01-6 ....99-95-3 ......55-86-7 ......51-75-2 ......

126-85-2 ....302-70-5 ....

55-63-0 ......99-55-8 ......88-75-5.100-02-779-46-9.56-57-5 ......55-18-5.62-75-9 ......924-16-3 ....10595-95-61116-54-7 ..621-64-7 ....86-30-6 ......4549-40-059-89-2.759-73-9 ....684-93-5 ....

.. . . 0.023180000 39 ............................................... 0.0069415

78.6 0.531 ..... .........

0.0000264

1250.0708

6.70'0. 3 7

0.00022

0.2960.0156

78

3.12

lodomethane .........................Isobutyl alcohol .....................Isodnn ...................................Isophorone ............................Isosafrole ...............................Kepone ..................................Lasiocarpine ..........................Lead ......................................Maleic anhydride ...................Maleic hydrazide ...................Malononitrile ..........................Melphalan ..............................Mercury .................................Methacrylonitnle ....................Methanethiol ..........................Methanol ...............................Methapyrilene ........................Methomyl ...... .......Methoxychlor..........Methyl bromide

(Bromomethane).Methyl chloride

(Chloromethane).Methyl ethyle ketone .............Mehtyl ethyl ketone peroxideMehty hydrazine ....................Methyl isobutyl ketone ..........Methyl methacrylate ..............Methyl methanesulfonate.Methyl naphthalene, 2-. ........Methyl paratyhion ..................Methylaziddine, 2-. ................Methylcholanthrene, 3- .........Methylene bromide ...............Methylene chloride ................Methylenebis, 4,4'-(2-

chloroaniline).Methyl-nitro-nitrosoguanidine

(MNNG).Methylthiouracil ....................Mitomycin C ........................Molybdenum ........................Naphthalene ........................Naphthoquinone, 1,4-.. ..........Naphthyl-2-thiourea, 1-. ........Naphthylamine, 1-. ................Naphthylamine, 2-. .................Nickel ....................................Nicotine and salts .................Nitroaniline, 2- .......................Nitroaniline, 3- .......................Nitroaniline, 4- .......................Nitrobenzene .........................Nitrogen mustard ..................Nitrogen mustard hydro-

chloride salt.Nitrogen mustard N-Oxide ....Nitrogen mustard N-Oxide,

HCl salt.Nitroglycerine ........................Nitro-o-toluidine, 5- ...............Nitrophenol, 2- . .....................Nitrophenol, 4- . .....................Nitropropane, 2-. ...................Nitroquinoline-1 -oxide, 4-. .....Nitrosodiethylamine ...............Nitrosodimethylamine ............Nitrosodi-n-butylamine ..........Nitrosomethylethylamine .......M-Nitrosodiethanolamine ......N-Nitrosodi-n-propylamine ....N-Nitrosodiphenylamine.N-Nitrosomethyl vinyl amine.N-Nitrosomorpholine .............N-Nitroso-N-ethylurea ...........N-Nitroso-N-methylurea.

141

6990C

0.662

9.8f0-01170C0.37f

121 00C38E

78

28.2

78

2.320.039

1.8314

.................. ..................

........... I ...... ................. I

.................. ..................5040 10.E

............... I .. ..................

.................. ..................

............ I ..... .................

................. * '*'*'**'****"**"0,345 0.084

.................. .................

.................. ..................

0.00019

0.00004060.0002680.000279

0. 129

0.06447.54

...... E....6

.0E0053

0.2

14.7

0.159

14.70.1590.159

14.7

0.11775

0.1590.0069415

7.80.159

0.117750.00285

0.159

.. 0. 762...

0.0050.011

0.020.010.01

0.016

0.01

0.050.1

0.000090.009

.....0.0210.1

0.050.000086

0.00011

0.00013

0.01

0.000810.0050.010.010.01

0.010.000240.00026

55200

743

0.000277

568

0.5988.91

19.4504

30.85

0.194

69009. 955....

19.9556900

19.66519.955

0.194

90.81 ...............

112000

1700C39S00

1.43

0.0001288400

30E

0.1591 ............. I ..................

0.1177514.7

14.70.11775

0.1590.159

0.1590.027620.027620.02762. 159......

0.159

0.0010.001E

0.010.. . 01...0.01

0.01

0.0540.050.02

0.0064

I .............................

11412000C

............. I ... I

..................

..................

..................10E

..................

..................

..................

................4

44.E.......... .........................

0.159 ......................0. 159 ...............

0.1590.02762

0.02520.0252

0.159

0.0000371

0.1590.1590.159

. 01...0.010.05

0.005770.04

0.0020.0006

0.060.028

0.010.026

0.05

0.05...... 0 .1.

0.12E

0.000640.00245

0.0940.00244

0.023W127C

121019.955

1.663.9

19.955

3.28

0.0050.0035

0.07190.7

0.097

20.07

30.5

0.10.0005

......0.4673

0.00570.02

0.02

0.00834

0.003150.0027

0.70.7

0.0691

0.0460.0001

0.02

15

0.162

0.000032

11.6

0.1380.006

30

0.92

0.015

0.46

10.5. 105......

0.10510.5

.400.105

0.4

I.................. ..................

8.1

23.4

1.410OE-.060.19

0.01E

19.9551 .................. I ............

1.686900

69001.66

19.95519.955

19.95E3.2E3.2E3.2E

19.95519.95E

0.30.0665

0.70... . 7.....0.7

0.0544

19.9551 .................. I..................19.9551 .................. I ..................

19.955,3.2E

2.9912.991

19.95!

0.01287E

19.95519.95Z19.95E

0... . 7.....0.7

0.0022

0.0740.03

0.0180.7

0.01440.084E

0.7

..................

..................I.K2.7

..................

..................

..................

................. I4.&

..................

..................

..................

.................0.032

..................

..................

1 .020E-063.400E-06

0.00003E6.800E-08

0.00001710.04E

.......6.20.105

0.0000661

0.105

0.00884

0.105

6 .410.5

10.56.4

0.1050.105

0.1050.008840.008840.00884. 105.....

0.1050.1050.105

0.1050.008840.00830.0083

0.105

0.0000119

0.10350.1050.105

0.0050.011

0.020.010.01

0.016

0.01

0.050.1

0.000090.009

0.0210.1

0.050.000086

0.00011

0.00013

0.01

0.000830.005

0.010.010.01

0.010.000240.00026

0.0010.0018

0.01

0.010.01

0.0050.020.050.050.02

0.0064

0.010.01

0.050.00577

0.040.002

0.00060.06

0.0280.01

0.0260.05

0.05

0.01

0.09591 ..................




TABLE C-1.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING TOXICITY BENCHMARKS-Continued

WW totals (mg/I) NWW totals (mg/kg) NW leach (mg)CAS No. Name rMuipath ound- Extrapo- Multipath [ Extrapo- IGround- I Extrapo- 1

water I xt ww watermodeled Water x 'IW EQC modeled lated leach ... watered lated each WW EQCmodeled lated el level O mcdl evel,exit level exit level level __laheellvl _1ahee~ level

615-53-216543-55-8100-75-4930-55-213256-22-9103-85-51615-80-1152-16-9 ....

20816-12-0

297-97-2

126-68-1 ....

123-63-756-38-2 ......608-93-5 ....76-01-7 ......82-68-8.

87-86-5.62-44-2 ......85-01-8 ......108-95-2 ....62-38-4 ......25265-76-3108-45-2 ....106-50-3298-02-2 ....298-06-6 ....

3288-58-2

2953-29-9

85-44-9 ......109-06-8 ....1336-36-3 ..23950-58-51120-71-4107-10-8 ....51-52-5 ......107-19-7 ....129-00-0110-86-1 ....50-55-5.108-46-3 ....81-07-2 ......94-59-7.7782-49-27440-22-418883-66-457-24-9 ......100-42-5 ....18496-25-81746-01-6 ..95-94-3 ......630-20-679-34-5 .....127-18-458-90-2 ......107-49-3 ....3689-24-5

7440-28-062-55-5 ......39196-18-4108-98-579-19-6 ......62-56-6.137-26-8 ....7440-31-5108-88-3584-84-9 ....95-80-7.823-40-5

0.101

7310

N-Nitroso-N-methylurethane.N-Nitrosonomicotine ..............N-Nitrosopiperidine ..............N-Nitrosopyrrolidine ..............N-Nitrososarcosine ................N-Phenylthiourea ..................N,N-Diethylihydrazine ..........Octamethyl- pyro-

phosphoramide.Osmium tetroxide ..................O,O-Diethyl 0-pyrazinyl

phosphorothioate.0,0,0-Tethylphosphorothioate.

Paraldehyde ..........................Parathion ...............................Pentachlorobenzene .............Pentachloroethane ................Pentachloronitrobenzene

(PCNB).Pentachlorophenol ................Phenacetin ............................Phenanthrene ........................Phenol ...................................Phenyl mercuric acetate.Phenylenediamines (N.O.S.)Phenylenediamine, m- . .........Phenylenediamine, p-.Phorate .........................Phosphorodithioic acid, o-o-

diethyl ester.Phosphorodithioic acid, o-o-

diethyl-s-methyl.Phosphorodithioic acid,

trimethyl ester.Phthalic anhydride ................Picoline, 2- . ...........................Polychlorinated biphenyls .....Pronamide .............................Propane sultone, 1,3- ...........Propylamine, n-. ....................Propylthiouracil ......................Propyn-1-ol, 2- . .....................Pyrene ...................................Pyridine .................................Reserpine ..............................Resorcinol ..............................Saccharin and salts ..............Safrole ...................................Selenium ...............................Silver .....................................Streptozotocin .......................Strychnine .............................Styrene ..................................Sulfide ...................................TCDD, 2,3,7,8- ......................Tetrachlorobenzene, 1,2,4,5-Tetrachloroethane, 1,1,1,2-...Tetrachloroethane, 1,1,2,2-...Tetrachloroethylene ..............Tetrachlorophenol, 2,3,4,6- ...Tetraethyl pyrophosphate .....Tetraethyldithiopyrophosphat-

e.Thallium (1) ............................Thioacetamide ...............Thiofanox ..............................Thiophenol ............................Thiosemicarbazide ................Thiourea ................................Thiram ...................................Tin .........................................Toluene .................................Toluene diisocyanate ............Toluenediamine, 2,4- ............Toluenediarnine, 2,6- ............

0.00028680.3

0.522

0.0829822199

3.3475.7

1 .050E-0914.8

0.02410.00371560C

2720

0.23

646

29... . 8..

0.. . 211....

0.00001060.000212

0.273

440000

5.15

0.081

0.00204

84

0.0117

0.78

0.0061421.3

0.156

0.00350.927

0.04563.7

1.8a0E-070.2340.0750.024

2.041.89

0.05

41... . 3..

.000159......

0.1590.159

0.1590.11775

0.159

1.240.11775

0.11775

7.8

0.023

14.70.00285

0.159

0.159

.................. 0.11775

0.001 350.0047

0.0053

30.02

0.05

0.00050.000038

0.0050.02

0.000080.02

0.0060.00028

0.010.0174

0.010.00004

0.002470.0534

................3

0.128

205

11.4

2.92

163000

0.00932

784

157

0.1 17 75 ................. -. . -0. 11775 ..................1 .........

1320.159

0.117750.159

0.1177539

0.00694150.159

14.7

0

14... . 1..

0.. . 159.....11775.......11775......

0.159

. 001......0.005

0.00145

0.0050.1

0.010.00027

0.0110.05

0.1

0.002 10.00060.0005

0.00840.0004

21 .OOOE-08

0.001410.00005

0.00020.000140.00062

0.000058

0.0007

0.050.02

0.058

0.00011

0.01340.02

0.00596438

15800814

10.51.94

0.134

0.0041629000

7.980E-06-168133

29.3133006150

2.81

19.95519.955

19.9551.66

19.955

8.72

1.866

1.66

1210

30.85

69003.9

19. 955

19.955

1.66 ................. I ..................

1.66 .................. ..................

2352.519.955

1.6619.955

1.6636700

19.9550.194

19.955

6900

5.121 ..................

........... .....

176000

0.0101

19.9551.661.661.661.66

0.1948.72

19,955......

19,955

0.0330.042

0.146

200

3

700.025

0.020.01

0.052

0.1222

0.70.2185

0.70.7

0.002

70.070.04

0.097

0.0057

0.050.0726

0.237

0.0155

0.3

30.004

21 .000E-06

0.0340.00010.00020.0007

0.043

0.0039

3

3

3500

0.00027

0.000068

0.. . 105....

11600.......

0 . 05..6 4i

0.054

0.00041

32

0.0045

0.3

4.810OE-065.7

1.690.06

0.000950.357

0.01615.4

1 .780E-1 00.03170.00780.0077

0.680.58

0.0192

12.... . 6...

.000051......

0.105

-0.105

6.4

0..1...05

0.41 656.4

6.4

6.2

0.015

10.50.0000661

0.105

0.105

6... . 4.....

6.4

6.4

27.6

0.105

6.40.105

6.415

0.1050.48

0.105

10.5

0.0.4165...

0.05

0.00135

0.0047

0.0053

3

0.02

0.05

1

0.00050.000038

0.0050.02

0.000080.02

0.0060.00028

0.010.0174

0.01

0.00004

0.0010.0005

0.00145

0.0050.1

0.010.00027

0.0110.05

0.1

0.00210.00060.0005

0.00840.00004

21.000E-08

0.001410.00005

0.00020.000140.00062

0.000058

0.00071

0.050.02

0.05

80.00011

0.01340.02

2.63

7.86

13.9

0.301

19300

0.506

5440

01 06




TABLE C-1.--SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING TOXICITY BENCHMARKS-Continued


CAS No. Name Multipath Ground- Extrapo Multipath Extrapo- Ground- Extrapo-modeled water lated exit WW EC modeled lated leach NWW water lated each WW EQCexit level modeled level leach level level EGC modeled levelexit level each level

496-72-0 .... Toluenediamine, 3,4- ........ .................................... 0.159 0.02 .................. 19.955 1 .................. 0.105 0.02636-21-5 .... Toluidine hydrochloride; o- ....................... 0.159 0,01 .................. 19.955 0.7 .................. 0.105 0.0195-53-4 ...... Toluidine, o- .......................... 0.441 0.00224 .................. 0.0121 2.35 .................. 0.029 0.00068 .................. 0.0121106-49-0 .... Toluidine, p- .......................... 0.703 0.00224 .................. 0.0168 0.128 .................. 0.043 0.0068 .................. 0.01688001-35-2 .. Toxaphene ............................ 0.000364 21.5 .................. 0.00127 0.000176 .................. 0.0295 0.11 .................. 0.0012776-13-1 ...... Trichloro-1,2,2- 2210 11000 .................. 0.00108 ..................................... 0.00114 2400 .................. 0.00108

trifluoroethane, 1,1,2-.120-82-1 .... Thchlorobenzene, 1,2,4-. ...... 0.685 9.31 .................. 0.0002 3450 .................. 0.574 1.3 .................. 0.000271-55-6 Trichloroethane, 1,1,1-. ......... 73.9 120 .................. 0.00008 48200 .................. 0.0002 0.0539 .................. 0.0000879-00-5 Trichloroethane, 1,1,2-. ......... 0.0117 0.007 .................. 0.0001 11.3 .................. 0.004 0.0018 .................. 0.000179-01-6 ...... Trichloroethylene ................... 138 0.0384 .................. 0.00019 567 .................. 0.0001 0.0128 ................. 0.0001976-69-4 ...... Trichlorofluoromethane ......... 51.4 48 .......... 0.00008 25800 ............ 0.001 16 .................. 0.0000875-70-7 . Trichloromethanethiol ................. .............................. 0.11775 .................................... 1.66 .................................... 6.4 ..................95-95-4 . Trichlorophenot, 2,4,5- .......... 38.8 18.1 .................. 0.00049 11500 .................. 0.0672 4.2 .................. 0.0004988-06-2. Trichlorophenol, 2,4,6- ........... 0.1 0.0536 .................. 0.0004 124 .................. 0.0785 0.0152 .................. 0.000493-76-5. Trichlorophenoxyacetic acid, 15.5 1.68 .................. 0.00008 63.2 .................. 0.0063 0.64 .................. 0.00008

2,4,5- (245-T).93-72-1 ...... Trichlorophenoxypropionic 9.72 1.26 .................. 0.00008 6.36 .................. 0.00028 0.48 .................. 0.00008

acid, 2,4,5- (Silvex).96-18-4. Trichloropropane, 1,2,3- ......... 707 1.1 .................. 0.00032 872 .................. 0.0009 0.34 .................. 0.0003299-35-4 Trinitrobenzene, sym- ........... 3 0.0078 .................. 0.00026 0.442 .................. 0.25 0.003 .................. 0.00026126-72-7 .... Tns (2,3-dibromopropyl) 0.000237 0.00252 .................. 0.0245 0.357 .................. 0.061 0.000099 .................. 0.0245

phosphate.52-24-4 . Tris (1-az dinyl) phosphine .................................... 0.11775 ... ..... ............. 1.66 .................................... 6.4 ..... .........

sulfide.72-57-1 Trypan blue ...................................................... . 14.7 ........ ............ 6900 ........ . ............ 1 0.5 ..................66-75-1 Uracil mustard .............. ....................... .............. . 0.159 ..................................... 19,955 .................................... 0.105 .................7440-62-2 .. Vanadium .............................. 15800 9.58 .................. 0.003 250 ................. 1 3.71 .................. 0.003108-05-4 .... Vinyl acetate ............... .................................... 14.7 0.005 .................. 6900 0.005 .................. 10.5 0.00575-01-4 ...... Vinyl chloride .............. 0.00199 0.000156 *...... 0.0017 1.23 ........... 0.0017 0.00006 .................. 0.0001781-81-2 ...... Warfarin ............................... 0.0069415 0.05 .................. 0.194 3 . 0.48 0.051330-20--7 .. Xylenes (total) ................. 22.4 859 .................. 0.002 172000 ........... 0.0002 147 .................. 0.0027440-66-6 .. Zinc ...................................... 23200 99 .................. 0.002 316 ............... 0.3 38.4 .................. 0.002

TABLE C-2.---SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING MCL-BASED NUMBERS

WW totals (mg/I) NWW totals (mg/kg) NWW leach (mg/)

CA Io ae utpt Ground- Ground- ExA NO. Name Muiath ater Extrapo- Multipath ItExtrapo- ,t Wmodeled evei lated exit W EQC modeled dlated it IeeWW wler Ia IW-moi lemo deled GO

t xi Wextlvl level level exit level level Leach level

83-32-9 ......20-96-8 ....67-64-1.75-05-8 ......98-86-2 ......75-36-5.591-08-2 ....53-96-3.107-02-8 ....79-06-1 ......107-13-1 ....1402-68-2116-06-3309-00-2 ....107-18-6 ....107-05-1 ....92-67-1.2763-96-4

504-24-5 ....61-82-5 ......62-53-3 ......120-12-77440-36-0140-57-8 ....7440-38-22465-27-2115-02-6 ....7440-39-3 ..71-43-2 ......92-87-5 ......

Acenaphthene ................... !.Acenaphthylene ..................Acetone ...............................Acetonitrile ..........................Acetophenone .....................Acetyl chloride .....................Acetyl-24hiourea, 1- . ..........Acetylaminofluorene, 2-. .....Acrolein ...............................Acrylam ide ..........................Acrylonitrile .........................Aflatoxins ............................Aldicarb ...............................Aldrin ...................................Allyl alcohol .........................Allyl chloride ........................Am inobiphenyl, 4-. ..............Aminomethyl-3-isoxazolol,

5-.Am inopyridine, 4-. ...............Amitrole ...............................Aniline .................................Anthracene ..........................Antimony .............................Aram ite ................................Arsenic ................................Auramine .............................Azaserine ............................Barium .................................Benzene ..............................Benzidine ............................

49.5......... ... ...232000

6.585960

0.002483.67

0.00428

.................

.................

5.640E-07

.................

0.0742

.......... .....0.444

8210

40.5

0.02090.00015

31.2...................15.60.7816.8

................

0.000260.0011

.......... ......

.................

.............. ....

............... ...0.053

.. ..... .......0.136

0.384

280.0295

2.2400E-06

.................0.00285

0.02410.117750.02762

..................14.7

0.0069415...............

39........ .. .. ..0.02762

0.159

0.027620.0069415

.................0.00285

............ -;14.7

........... .. .0.1590.159

0.00180.02

0.20.015

0.00158

0.020.013

0.010.008.................0.05

0.000034..............0.002

0.02

....... ... ..0.000230.007

0.00080.02

0.0005

0.0010.000040.0025

9480...........' ....17400

9231210

............. ;...2.63

0.004360.961

.................

.................

........... ....

258

.................

..............4.21

8.72

0.17

2080.109

0.0000298

................3.9

................30.85

1.663.28

...............6900

0.194........- .....,36700............ .....

3.2819.955

3.280.194..................

3.9.......... 6900......... .. ..

19.95519.955

0.07420.7

0.0270.014

0.03

............... .70

0.0750.10.7

..................

0.0006

0.002

0.01 320.5

2

0.3031

0.20.00010.042

4.9

60.36.4

0.0000380.00034

3.670E--06

... . 017....

0.017............

0.00119......... ... ............... .0.0115

6.40.00884

...............

............. '....

10.50.54

................

15

'0.008840.105

0.008840.54

0.00119

10.5

0.1050.105

0.00180.02

0.20.015

0.00158

.................0.02

0.0130.01

0.008

0.050.000034

................

0.0020.02

0.000230.007

0.00080.02

0.0005

0.0010.00004

0.0025




TABLE C-2.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING MCL-BASED NUMBERS-Continued


CASNo.Name Ground- ,Ground- ECSNo. Name Multipath Gaerond- Mulhipath Extrapo-. NWW water Elaed -odellwater mod- iWW EoC modeled a WW EOC

eilee eledvexi level exit level level Leach levellevelel

106-51-4 ....98-07-7.50-32-8 ......205-99-2 ....205-82-3 ....207-08-9191-24-2 ....100-51-6 ....100-44-7 ....56-55-3 ......225-51-4 ....7440-41-739838-32-9111-44-4 ....117-81-7542-88-1 ....598-31-2 ....75-27-4 ......75-25-2.

101-55-3

357-57-371-36-3 ......88-85-7 ......

85-68-7 ......7440-43--9 ..86-74-8 ......75-15-0 ......353-50-4 ....56-23-5 ......75-87-6 ......305-03-3 ....57-74-9 ......494-03-1126-99-8 ....

107-20-0 ....106-47-8 ....108-90-7 ....510-15-6124-48-1 ....75-00-3 ......

110-75-8 ....67-66-3.59-50-7.107-30-2 ....91-58-7 ......95-57-8 ......7005-72-3

5344-82-1542-76-77440-47-3218-01-9 ....6358-53-8.7440-48-47440-50-8108-39-4 ....95-48-7 ......106-44-5 ....4170-30-357-12-5.14901-08-7108-94-1 ....131-89-5 ....

50-18-0 ......20830-81-372-54-8 ......53-19-0 ......72-55-9 ......3424-82-6 ..

0.002310.000805

225001.13

0.0138

10.10.569

0.001410.00044

33.30.178

1.880.0164

393.9

0.000717

0.0008270.007

0.0006481280

0.008540.064

14.70.27

0.002850.00285

0.00285

.0.0241

0.0241

Benzoqulnone, p- ................Benzotdchloride ..................Benzo(a)pyrene ..................Benzo(b)fluoranthene .........Benzo(j)fluoranthene ...........Benzo(k)fluoranthene ..........Benzo[g,h,iperylene ...........Benzyl alochol .....................Benzyl chloride ... .....Benz(a)anthracene .............Benz(c)acridine ..................Beryllium .............................Bis (2-chloroisoproply) etherBis(2-chlorethyl)ether ..........Bis(2-ethylhexyl)phthalate ...Bis(chloromethyl) ether .......Bromoacetone .....................Bromodichoromethane.Bromoform

(Tribromomethane).Bromopheyni phenyl ether,

4-.Brucine ................................Butanol ................................Butyl-4,6-dinitrophenol, 2-

sec- (Dinoseb).Butylbenzylphthalate ...........Cadmium .............................Carbazole ............................Carbon disulfide ..................Carbon oxyfluodde ..............Carbon tetrachloride ...........Chloral .................................Chlorambucil .......................Chlordane ...........................Chlomaphazin .....................Chloro-1,3-butadiene, 2-

(Chloroprene).Chloroacetaldehyde ............Chloroaniline, p- ..................Chlorobenzene ....................Chlorobenzilate ...................Chlorodibromomethane ......Chloroethane (ethyl chlo-

ride).Chleroethyl vinyl ether, 2-Chloroform ..........................Chloro-m-cresol, p- .............Chloromethyl methyl ether ..Chloronaphthalene, 2- ........Chlorophenol, 2- . ................Chlorophenyl phenyl ether,

4-.Chlorophenyl thiourea, 1-o-Chloropropionitrile, 3- .........Chromium ...........................Chrysene .............................Citrus red No. 2 ..................Cobalt ..................................Copper ................................Cresol, m- ...........................Cresol, o- ............................Cresol, p- ............................Crotonaldehyde ...................Cyanide ...............................Cycasin ...............................Cyclohexanone ...................Cyclohexyl-4,6-

dinitrophenol, 2-.Cyclophosphamide .............Daunomycin ........................DDD ....................................DDD (o,p') ...........................DDE ....................................DDE (o,p') ...........................

1600

0.738

0.0115

0.000014

0.515

5171.5

0.073116.3

0.00759

134

13001.32

674615656

63.5

.000126......

.1....O...0.

0.038

18.4

0.1

24

0.420.68

0.0540.0066

0.057

0.9

0.6180.1

27908.48.4

0.84

913000..

0... .. 228....

0.159

0.0241

0.. . 27....0.270.27

0.27

0.. . 27....

0.0241

0.0241

0.27

0.18

7.87

0.0259

0.0252

0.59

14.7

00.6915

00.9159

0.01

0.0000230.000018

0.00020.00020.0008

0.000745.000E-06

0.0000130.00050.0003

0.001450.0003

0.00027

0.0050.00008

0.0002

D.2273.7

274037.5

0.1

0.05910.9440.115

225

19173

0.011 ..................

200.014

0.00029

0.0000420.00005

.. 12....1.

0.00121

,0.00021

0.00004

0.002

0.00007

0.000040.020

0.00007

0.002

0.00005

0.52

0.0140.00055

0.01

0.1

0.00075

0.00055

6900142

3.93.9

3.9

30.. ......... .. 8...

.. .. 8...

0.70.004

0.06210.0699

0.010.70.7

0.0340.00276

0.08260.03

0.10.05860.0651

0.143

0.030;0012

0.02

0.00360.0000661

1515

4.300E-0D6

0.000320.0019

0.000380.108

0.002520.018

0.71 ..................

10.50.033

0.001 190.00119

0.001 19

0.0115

0.01 15

................ I 19.9551 ............ ..I .. i 0.105182001 .................. .0231 6........772,1........, 0.042, 0.0112,...........

330

8.54

0.00978

288

14224706.8227.5

6.74

104

9.7634.6

5.912150027400

2550

0.........

.000936.....

19.955

30.85142........142

142

142

142........30.85

30.85

142

12

12

0.95

0.85

0.2

0.0002

0.02

0.0015

0.015..................6.4

0.0115

0.036

0.00099i...........

0.05920.0002

0.0690.00085

0.005

0.0050.002

0.0050.7

0.07580.7

0.50.0030.084

50.5

0.0350.0270.035

40.2

107

0.0012

0.0006

0.160.19

0.00570.0018

0.017

0.32

0.2380.00119

10803.23.2

0.32

2800.......

.000062......

0.105

0.0115

. 03.....0.0330.033

0.033. 033.....

0.0115

0.0115

0.033

0.530.0194

0.1053

0.0115

0.0150.53

10.50.194

0.01

0.0000230.000018

0.00020.00020.0008

0.000745.OOOE-06

0.0000130.00050.0003

0.001450.003

0.00027

0.0050.000080.0002

0.01

200.014

0.00029

0.0000420.00005

0.00121

0.00021

0.00004

0.002

0.000660.000040.005040.00007

0.005

0.000030.02

0.010.00058

0.01

0.10.002

0.00015

0.50.0007

0.000460.000550.00046

0.060.2

100.1

0.00005

0.000058

........ I I 0.159386 1 5.61............!!

15.41 0.033 1 ..................




TABLE 0-2.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING MCL-BASED NUMBERS-Continued

WW totals (mg/I) NWW totals (mg/kg) NWW leach (mg)I GrudI 1Gon-EtpCAS No. Name Multipath ra - Multipath Extrapo- NWW Grud

modledat water mod-wtrE

moelled evl -1 lated ex it WW EOC modeled lated exit I ,C modeled Leach WW EQCxt level, level exit level level Leach

50-29-3 ......789-02-62303-16-4132-64-9192-65-4 ....189-64-0 ....189-55-9 ....194-59-2 ....226-36-8 ....53-70-3 ......224-42-096-12-8 ......

864-41-0110-57-6 ....

96-23-1 ......95-50-1 ......541-73-1106-46-7 ....91-94-1 ......75-71-8 ......75-34-3 ......107-06-2 ....75-35-4 ......156-59-2156-60-5111-91-198-87-3 ......

120-83-287-65-0 ......94-75-7 ......

78-87-5 ......542-75-6 ....10061-91-510061-02-660-57-1 ......1464-53-5 ..

84-66-2 ......311-45-5

56-53-1 ......94-58-6 ......60-51-5 ......131-11-3 ....77-76-1 ......60-11-7.

119-93-7 ....57-97-6 ......

79-44-7 ......122-09-8....

105-67-9 ....119-90-4 ....84-74-2 ......99-65-0 ......100-25-4534-52-151-26-5 ......121-14-2 ....606-20-2 ....117-84-0 ....123-91-1122-39-4122-66-7298-04-4541-53-7 ....115-29-7 ....959-98-833213-65-9

DDT .....................................DDT (o,p') ...........................Diallate ................................Dibenzofuran .......................Dibenzo[a,e]pyrene .............Dibenzo[a,h]pyrene .............Dibenzo[a,ilpyrene ..............Dibenzo[c,g]carbazole, 7H-.Dibenz(a,h)acridine ..'...........Dibenz(a,h)anthracene.Dibenz[a,jjacridine ..............Dibromo-3-chloropropane,

1,2-.Dichloro-2-butene, 1,4- . ......Dichloro-2-butene, trans-1,4-.

Dichloro-2-propanol, 1,3-Dichlorobenzene, 1,2. ........Dichlorobenzene, 1,3- .........Dichlorobenzene, 1,4- .........Dichlorobenzidine, 3,3. ......Dichlorodiflouromethane .....Dichloroethane, 1,1 . ..........Dichloroethane, 1,2 . ..........Dichloroethylene, 1,1-. ........Dichloroethylene, cis-1,2- ...Dichloroethylene, trans-1,2-Dichloromethoxyethane ......Dichloromethylbenezene

(benzal chloride).Dichlorophenol, 2,4- ............Dichlorophenol, 2,6- ............Dichlorophenoxyacetic acid,

2,4- (2,4-D).Dichloropropane, 1,2 . ........Dichloropropene, 1,3- .........Dichloropropene, cis-1,3- ....Dichloropropene, trans-i,3-Dieldrin ................................Diepoxybutane, 1,2.3,4-

(2,2'43ioxirane.Diethl phthalate ...................Diethyl-p-nitrophenyl phos-

phate.Diethylstillbestrol .................Dihydrosafrole .....................Dimethoate ..........................Dimethyl phthalate ..............Dimethyl sulfate ..................Dimethylaminoazobenzene,

p-.Dimethylbenzidine, 3,3'- .....Dimethylbenz(a)anthracene,

7,12-.Dimethylcarbamoyl chlorideDimethylphenethylamine,

alpha, alpha-.Dimethylphenol,2,4- ............Dimethyloxybenzidine,3,3'- .Di-n-butyl phthalate .............Dinitrobenzene,1,3 .............Dinitrobenzene,1,4 .............Dinitro-o-cresol,4,6- ............Dinitrophenol,2,4- ................Dinitrotoluene,2,4- ...............Dinitrotoluene,2,6- ...............Di-n-octyl phthalate .............Dioxane,,1A .......................Diphenylamine ....................Diphenylhydrazine,1,2 . ......Disulfoton ............................Dithiobiuret ..........................Endosulfan ..........................Endosulfan I ........................Endosulfan II .......................

0.0000181

..................

0.26

.................8.440E-.06

0.003714.7

S 37.40.0698

.................

0.004

00008

0.0046

0.0049

0.00609

..... ..... 0.00008120.4

..................

.................

....................

....................

0.00176

0.0022

7.8

............. * ...

1.120.0042

35.70.00016

0.04750.0413

0.2940.42

0.62

0.273

0.1150.00289000090000

682

0.000630.01

0.0010.00020.0002

0.010.0002

0.000030.001

0.00026

3560. 1861 .. 5

7.710E-07............ I:38.1

200000.......... ..

0.0006253.820E-06

1511.78883

1.28............ ....50.210.712.9

0.00255829

0.0131

6.62

.. ..... ...

.................

4.2900E-07

29.478

.............14.7

............0.117750.02762

0.0000702 .........0.00464.........

3.780.0336

9000.0168

...................0.2730.2940.1681260

0.042414.7

458

6

0.270.159

0.02520.0252

0.. .... 5...9

00.9159

0.00315

1.26

.000155.....

000155

0.005 ..................0.005 ..................

8.40.002850.002850.002850.002850.00285

0.00285. 0241....

0.0241

0.0241

0.21.024...

0.0241

14... . 7.....

5000C

63.90.0524

807C24.2

6.12.5g.

540C1 380C

0.194

2740C3.93.93.93.G3.9

3.9

.. 0 . 85....

30.85

142

30.. . 8......

30.8530.. ........

769 .........30.85

3140 ........ .....

16.932.42.642.67

0.001 76

..................

..................I .....................................................

6900

0.0006

0.0230.70.7

0.010.01

0.70.01

0.0840.7

0.0001,

0.0054

0.4E

6.340E-07

0.0003E

0.005 .................0.005 .........

0.050.0002

0.70.0001

0.1160.00520,00020.00010.0014

0.020.0006

0.70.3

0.07880.7

0.00011

0.00010.00030.00030.00030.0006

0.005

1.62

0.2160.00072

11.90.00006

0.0090.0216

0.1120.16

0.54

1.80.001190.00 1190.001190.001190.00119

0.001190..0... 115...

0.0115

0.0115

0.015

0.0115

0.18. ....... ..0.105.........

0.01150.00085

115011500.54

..................

..................

..................

..................

..................10.5

4490 ........: . .0 022 54 .................... .... 19.951 ....... . .... .0

2.470E-1 1

1.63

........... I ...6900

.................1.663.28

0.010.00003

0.0050.00004

0.00240.0001

0.000040.000060.00012

000120.000(.

0.010.005

0.000410.0

0.00029

0.000040.0009

0.000690.00094

0.0000440.005

0.00025

0.00780.05

0.000290.00064

0.01

0.0033

0.00037

0.05

0.000470.0077

0.000330.00011

0.040.05

0.000420.000020.00031

0.0000420.012

0.0015 10.01

0.00007

. 00004......0.000340.0003

113000.23690000

5.54

56.1213

86.3448013.2

11800

42.6

73.1

14219.955

2.9912.991

19..........

195

30.0691

0.013.............7...

6.500E-08

0.7730

10.5

6.40.00884

0.7 0.000018 ..................0.039 2.760E-0 6 ..................

.3

0.0527

0.2490.25

33

0.030.260.25

0.1390.0005

0.0410.7

0.0035

.0. 5....0.00950.009

1.190.0102

1000.0064

0.1050.1120.064

0.10.0136

2.6

13

0.94

0.0330.105

0.00830.0083

0.. .. 105....

0.5

0.000081

0.000630.01

0.0010.00020.0002

0.010.0002

0.000030.001

0.00026

0.0050.05

0.010.00003

0.0050.00004

0.00240.00010.000040.000060.000120.000120.00006

0.010.005

0.000410.01

0.00029

0.000040.00090.000690.00094

0.0000440.005

0.00025

0.00780.05

0.000290.00064

600.01

0.00330.00037

0.05

0.000470.0077

0.000330.00011

0.040.05

0.000420.000020.00031

0.0000420.012

0.001510.01

0.000070.000040.00030.0004

0.00062 ..................0.00263 ..................





WW totals (mg/) NWW totals (mg/kg) NWW leach (mg/I)

Name M Ground Ground- ECAS No. Ni d Extrapo- Multipath Extrapo- NWW water a,,-Iwmodeled ar ii lated ex t WW EQC modeled mated exit I modeled a W EQC

exit level le el level I exit level level I I Leach le

__vo I I i level ev1031-07-8 ..145-73-3 ....72-20-8 ......7421-93-4 ..53494-70-5106-89-8 ....51-43-4 ......110-80-5 ....141-78-6 ....51-79-6 ......107-12-0 ....60-29-7.97-63-2 ......62-50-0 ......100-41-4 ....106-93-4 ....75-21-8 ......96-45-7 ......151-56-452-85-7 ......640-19-7 ....62-74-8.

206-44-0 ....86-73-7 ......16984-48-850-00-0 ......64-18-6 ......765-34-4319-86-8 ....76-44-8 ......1024-57-3 ..87-68-3 ......118-74-1 ....319-84-6 ....

319-85-7

58-89-9.

77-47-4.67-72-1 ......70-30-4 ......1888-71-7 ..757-58-4 ....591-78-6 ....302-01-2 ....193-39-5 ....74-88-4 ......78-83-1 ......465-73-6 ....78-59-1 ......120-58-1 ....143-50-0 ....303-43-4 ....7439-92-1 ..108-31-6 ....123-33-1 ....109-77-3 ....148-82-3 ....7439-97-6 ..126-98-7 ....74-93-1.67-56-1 ......91-80-5 ......16752-77-572-43-5 ......74-83-9 ......

74-87-3 ......

78-93-3 ......1338-23-4 ..

60-34-4 ......

Endosulfan sulfate ..............Endothall .............................Endrin ..................................Endrin aldehyde ..................Endrin ketone ......................Epichlorohydrin ...................Epinephrine .........................Ethoxyethanol,2-. ................Ethyl acetate .......................Ethyl carbamate ..................Ethyl cyanide (propionitrile)Ethyl ether ...........................Ethyl methacrylate ..............Ethyl methanesulfonate ......Ethylbenzene ......................Ethylene Dibromide ............Ethylene oxide ....................Ethylene thiourea ................Ethyleneimine (azirindine) ...Famphur ..............................Fluoracetamide, 2-. .............Fluoracetic acid, sodium

salt.Fluoranthene .......................Fluorene ..............................Fluoride ...............................Formaldehyde .....................Formic Acid .........................Glycidylaldehyde .................HCH, delta- .........................Heptachlor ...........................Heptachlor epoxide .............Hexachloro-1,3-butadiene ...Hexachlorobenzene ............Hexachlorocyclohexane,

alpha- (alpha-BHC).Hexachlorocyclohexane,

beta- (beta-BHC).Hexachlorocyclohexane,

gamma- (Lindane).HexachlorocyclopentadieneHexachloroethane ...............Hexachlorophene ................Hexachloropropene .............Hexaethyl tetraphosphateHexanone,2 . .....................Hydrazine ............................lndeno(1,2,3-cd) pyrene .....lodomethane .......................Isobutyl alcohol ...................Isodrin .................................Isophorone ..........................Isosafrole ............................Kepone ................................Lasiocarpine ........................Lead ....................................Maleic anhydride .................Maleic hydrazide .................Malononitrile ........................Melphalan ...........................Mercury ...............................Methacrylonitrile ..................Methanethiol .......................Methanol .............................Methapyrilene .....................Methomyl ............................Methoxychlor .......................Methyl bromide

(Bromomethane).Methyl chloride

(Chloromethane).Methyl ethyl ketone .............Methyl ethyl ketone perox-

ide.Methyl hydrazine .................

.......4800

414000

39.........39

390

27.324

9300008.4

0.018

0.00053

27.522.4

27.... . 3.27.3

174000.0806

3.621

0.0069415

00069415

0.159

14.7

0.159

7.87

0.0069415

0.0729

0.335

14.7

0.005574.5

0.000928

17.7

15801310

0.0158

0.00002370.000528

0.007880.0004240.000142

0.000445

0.000783

0.005210.049

5.150E-06

0.00285

180000

78.6

0.0000264

907000

1250.0708

6.730.37

0... . 212.....0.212

0.051

0.015

0.561

31

0.2714.7

7.80.159

0.0241

0.0069415

14.70.. . 159....0.159

14.7

0.175

0.159

006915

0.09591 ......... I............

781 ................

0.00040.1

0.000390.00050.0005

0.06519

1.160.009

0.050.1

0.001530.003450.001060.000060.00006

0.001

0.02

0.000210.00021

0.050.0232

0.2

. 0002......0.00024

0.00002

0.00010.00161

0.000035

0.000023

0.000025

0.000181 .600E-06

0.2070.01

0.005

0.0000430 .0050.0110.020.010.01

0.016

0.01

0.050.1

0.000090.009

0.02 10.1

0.050.000086.0.00011

0.00013

0.01

0.26

44

6900272000

412003420

0.00133550000

0.00745

0.51

597089800

48.8301000

0.026436.4

0.01160.0333

0.12

0.102

145080.8

0.0000241

3.9

55200

743

0.000277

568

0.5988.91

138000

19.4504

0.1940.194

0.. . 194....0.194

195

6900.......19.955

6900

19.955

60

0.194

69001210

19.955

30.85

0.194

69009. 955....

19.955

6900

19.665

19.955

1945

90.81 ..................

I 112000..... I 7.81 .................. I .............

0.1591 ........ I.............

0.04

0.020.03

0.0714

2.030.18

30.1

0.003190.0011

0.0180.00020.0001

0.07

1

0.080.08

0.4

0.0008

0.0008

0.0026

0.0920.026

0.70

0.0056

0.005

0.035

0.0719.7

0.7

0.075

0.5

0.140.005

0.463

07

30.05

0.2

540C

114

0.540.54

......0.5

0.54

0.105

10.50.105

10.51 ..................6.6

117001.75

0.00075

0.00017

1.743.4

10... . 5..10.5

660.00691

0.0180.11

010.5

0.540.01159

0.54

C

6.20.54

0.00021 .................

1. ..................

0.0330.00136

0.0000241

15

0.162

0.000032

'12

0.0230.006

30

0.92

0.03310.56.2

0.105

0.0115

0.54

10.50.. . 10..5.0.105

10.5

.4

0.10510.5

0.021 ......... I ..................

.......... 0 .............. 30120 .............. ....

19.9551 ......... I..... I

6........2

0.00040.1

0.000390.00050.0005

0.06519

1.160.009

0.050.1

0.001530.003450.001060.000060.00006

0.001

0.02

0.000210.00021

0.050.0232

0.2

0.00020.00004

0.000032

0.00010.00161

0.000035

0.000023

0.000025

0.000181.600E-06

0.2070.01

0.005

0.0000430.0050.011

0.020.010.01

0.016

0.01

0.05

0.1

0.000090.009

0.0210.1

0.050.000086

0.00011

0.00013

0.01

o.105 1 ..................

0.00131...........

340...........



66436 Federal Register / Vol. 60, No. 245 / Thursday, December 21, 1995 ./ Proposed Rules


WW totals (mgI) NWW totals (mg/kg) NWW leach (mg/i)

CAS No. Name Multpath wae mod- Extrapo- Multipath Extrapo- NWW Ground-waterGatrud- latwd laEeC

modeled lated exit WW EQC modeled lated exit modeled WW EQCexit level eled exit level exit level level EOC Leah Leachlevel level level

108-10-1 ....80-62-6.66-27-3.91-57-6.298-00-075-55-8 ......56-49-5 ......74-95-3.75-09-2.101-14-4 ....

70-25-7.

56-04-2.50-07-7.7439-98-791-20-3.130-15-4886-.4.134-32-791-59-8 ......7440-02-0 ..54-11-5 ......88-74-4 ......99-09-2.100-01-6 ....98-95-3.55-86-7.51-75-2.

126-85-2302-70-5 ....

55--63-0.99-55-8.88-75-5.100-02-7 ....79-46-9.56-57-5.55-18-5.62-75-9.924-16-3 ....10595-95-61116-54-7 .2621-64-786-30-6 ......4549-40-0 ..59-89-2 ......759-73-9684-93-5 ....615-53-2 ....16543-55-8100-75-4930-55-2 ....13256-22-9103-85-5 ....1615-80-1 ..152-16-9 ....

20816-12-0297-97-2

126-68-1

123-63-756-38-2 ......60-93-5 ....76-01-7 ......82-68-8.

87-86-5.62-44-2.85-01-8.108-95-262-38-4 ......

10.369900

......... 06 2 ................

9.880E-06117000.376

121000385

7.8 ..................282 ............ .

0.117750.00285.................

0.159

0.02762

0.01170.0290.039

1.8314

Methyl isobutyl ketone ........Methyl methacrylate ............Methyl methanesulfonate ....Methyl naphthalene, 2-. ......Methyl parathion .................Methylazinidine, 2-. .............Methylcholanthrene, 3- .......Methylene bromide .............Methylene chloride ..............Methylenegbis, 4,4'-(2-

chloraoniline).Methyl-nitro-

nitrosoguanidine (MNNG).Methylthiouracil ...................Mitomycin C ........................Molybdenum .......................Naphthalene ........................Naphthoquinone, 1,4- .........Naphthyl-2-thiourea, 1- . ......Naphthylamine, 1-. ..............Naphthylamine, 2- ...............Nickel ..................................Nicotine and salts ...............Nitroaniline, 2- .....................Nitroaniline, 3- .....................Nitroanlline, 4- ..............Nitrobenzene .......................Nitrogen mustard ................Nitrogen mustard hydro-

chloride salt.Nitrogen mustard N-Oxide..Nitrogen mustard N-Oxide,

HCI salt.Nitroglycerine ......................Nitro-o-toluidine, 5- .............Nitrophenol, 2- . ...................Nitrophenol, 4- ....................Nitropropane, 2-. .................Nitroquinoline-1 -oxide, 4- ....Nitrosodiethyamine ............Nitrosodimethylamine ..........Nitrosodi-n-butylamine ........Nitrosomethylethylamine.N-Nirtrosodlethanolamlne ...N-Nitrosodi-n-propylamlne ..N-Nitrosodiphenylamine ......N-Nitrosomethyl vinyl amineN-Nitrosomorpholine ...........N-Nitroso-N-ethylurea .........N-Nitroso-N-methylurea ......N-Nitroso-N-methylurethaneN-Nitrosonomicotine ...........N-Nitrosopiperidlne .............N-Nitrosopyrrolidine ............N-Ntrososarcosine ..............N-Phenylthiourea ................N,N-Diethylhydrazine ..........Octamethylpyrophosphora-

mide.Osmium tetroxide ................O,O-Diethyl 0-pyrazinyl

phosphorothioate.0,0,0-Triethyl

phosphorothiloate.Paraidehyde ........................Parathion .............................Pentachlorobenzene ...........Pentachloroethane ..............Pentachlorontrobenzene

(PCNB).Pentachlorophenol ..............Phenacetin ..........................Phenanthrene .....................Phenol .................................Phenyl mercuric acetate.

0.345

. ...... 0.................

0.00079

0.129

0.06447.54

0.084

.......00.E...........01.....

... 0...2..... 0.0..2...2.

. ...... 0......0..... ......

............. ....... ...0.0106 0.0000106

0.101 0.000212

7310 0.273

2.637.86

13.9

0.301

193000.506

0.27

0.00204

840.0117

0.000830.005

0.010.010.01............ ....0.01

0.000240.00026

1700039500

..............1.43

0.0001 288400306

0.1591 ....... I............0.11775

14.7

14.70.11775

0.1590.159

0.1590.027620.027620.02762..... 1... 9..

0.159

0.0010.0018

0.01

0.. . 01....0.01

0.05

0.020.050.050.02

0.0084

120000

106

44.8

0.159 .................. .............0.159 ..................

0.1590.02762

0.02520.0252

0.159

0.0000371

0003190.1590.159

0.1590.17590.159

0.1759

0.11775

7.8

0.0241

14.70.00285

. 01...0.01

0.050.00577

0.040.002

0.00060.06

0.0280.01

0.0260.05

0.128

0.000640.00245

0.0940.00244

0.02331270

.5................ ................0.01...........

0.001350.0047

0.0053

30.02

0,05

0.00050.000038

0.0050.02

0.000080.02

0.0060.00028

0.0534

3.........1

.............0.128

205.............11.4

2.92

163000

1.663.9

19.955

3.28

0.003150.0027

0.70.7

0.691

0.0460.0001

0.02

38.1

.................23.4

1 .410OE-060.0085

0.09

19.9551 ....... I............1.66

6900

69001.66

19.99519.955

19.9553.283.283.28

9. 955....19.95519.955

19.955

19.955

3.282.9912.991

19,955

0.012875

19.95519.955

19.95519.865

19.955

1.66

1210

30.85

69003.9

0.30.0665

0.7

0.. . 7.....0.7

3.

3

0.0544

0... . 7.....0.7

30.0022

3

0.0740.03

0.0160.7

0.01440.0846

* 3

0.7

0.0330.042

0.146

200

3

700.025

0.020.01

0.052

0.1222

2.7

2.04

0.032

1 .020E--063.400E--06

0.0000366.800E-06

0.0000170.046

... 0..E.....

.000-06

0.105

................116D00.0543

0.018

0.00041

0.7 ......... 32

0.009321 ......... I.............

6.40.00119

0.105

0.00884

0.000830.0050.010.010.01

0.010.000240.00026

0.1051 ..................

8.410.5

10.56.4

0.1050.105

0.1050.008840.008840.00884

0... 5..0.1050.105

0.105

0.1050.00884

0.00830.0083

0.105

0.0000119

0.001150.1050.105

0.105.40

0.105

0.1946.4

64

6.2

0.0115

10.50.00119

0.0010.0018

0.010.010.01

0.0050.020.050.050.02

0.0064

0.010.01

0.050.00577

0.040.002620.0006

0.060.028

0.010.026

0.05

0.05

0.01

0.001350.0047

0.0053

3002

0.05

1

0.00050.000038

0.0050.02

0.000080.02

0.0060.00028

0.00451 ........ I.............

5040. 4.38




TABLE 0-2.-SUMMARY OF CONSTITUENT-SPECIFIC EXIT LEVEL DEVELOPMENT USING MCL-BASED NUMBERS-Continued

WN totals (mg/i) _ NWW totals (mg/kg) NWW leach (mg/I)Nae• Ground- Grud h Ext

Nam Multi Mutipath Extrapo- NWW water 1arCAS No. Name modeled water mod- lae xtWW EQC modeled lated exit NWN modeled ',--- WEQexI roeI I 1 1 Grounve I ExLaci

exit level i level exit level level Leach level

25265-76-3108-45-2 ....106-50-3298-02-2298-06-6 ....

3288-58-2

2953-29-9

85-44-9 ......109-06-8 ....1336-36-323950-58-51120-71-4107-10-8 ....51-52-5 ......107-19-7129-00-0....110-86-1 ....50-55-5 ......108-46-3 ....81-07-2 ......94-59-7 ......7782-49-27440-22-418883-66-457-24-9 ......100-42-5 ....18496-25-81746-01-695-94-3 ......

630-20-6 ....79-34-5 ......127-18-458-90-2.107-49-3 ....3689-24-5

7440-28-062-55-5 ......39196--18-4108-98-5 ....79-19-6 ......62-56-6 ......137-26-87440-31-5108-88-3 ....584-84-9 ....95-80-7.823-40-5 ....496-72-0636-21-595-53-4 ......106-49-0 ....8001-35-2 ..76-13-1 ......

120-82-1 ....71-55-6 ......79-00-5 ......79-01-6.75-69-4.75-70-7 ......95-95-4 ......88-06-2.93-76-5 ......

93-72-1 ......

96-18-4 ......99-35-4 ......126-72-7

............544C

0.10E

Phenylenediamines (N.O.S.)Phenylenediamine, m- ........Phenylenediamine, p- .........Phorate ...............................Phosphorodithioic acid, 0-o-

diethyl ester.Phosphorodithioic acid, o-o-

diethyl-s-methyl.Phosphorodithioic acid,

trimethyl ester.Phthalic anhydride ..............Picoline, 2. .........................Polychlorinated biphenyls ...Pronamide ...........................Propane sultone, 1,3- .........Propylamine, n- ...................Propylthiouracil ...................Propyn-1-ol, 2 . ...................Pyrene .................................Pyridine ...............................Reserpine ............................Resorcinol ...........................Saccharin and salts ............Safrole .................................Selenium .............................Silver ...................................Streptozotocin .....................Strychnine ...........................Stryene ................................Sulfide .................................TCDD, 2,3,7,8- ....................Tetrachlorobenzene,

1,2,4,5-.Tetrachloroethane, 1,1,1,2-.Tetrachloroethane, 1,1,2,2-.Tetrachloroethylene ............Tetrachlorophenol, 2,3,4,6-.Tetraethyl pyrophosphate ...Tetraethydithiopyrophos-

phate.Thallium (I) .............Thioacetamide ....................Thiofanox ............................Thiophenol ..........................Thiosemicarbazide ..............Thiourea ..............................Thiram .................................Tin .......................................Toluene ...............................Toluene diisocyanate ..........Toluenediamine, 2,4- ..........Toluenediamine, 2,6- ..........Toluenediamine, 3,4- ..........Toluidine hydrochloride, o-Toluidine, o- ........................Toluidine, p- ........................Toxaphene ..........................Trichloro-1,2,2-

trifluoroethane, 1,1,2-.Tdchlorobenzele, 1,2,4- .....Trichloroethane, 1,1,1. .......Trichloroethane, 1,1,2-. .......Trichloroethylene ................Trichlorofluoromethane.Trichloromethanethiol .........Trichlorophenol, 2,4,5- ........Trichlorophenol, 2,4,6- ........Trichlorophenoxyacetic acid,

2,4,5- (245-T).Trichlorophenoxypropionic

acid, 2,4,5- (Silvex).Trichloropropane, 1,2,3- .....Trinitrobenzene, sym- .........Tris (2,3-dibromopropyl)

phosphate.

....................OJE

....................

................... I

....................

.......11.521.3

54.10.156

0.00350.232

0.0450.91

0.000570.234

0.0750.024

0.02551.89

0.0353

5.... . 9......0.... 159...

. 0. 2. 24...

0.002249

0.7722

9.31120

0.0350.024

48

18.10.0536

1.68

0.159................

0.15S

0.1 177E

0.010.0174

0.010.00004

784

157

0.11775...............

0.175.............

0.117750.159

0.1177539

0.1590.0069415

0.159

14.7

015.11775.......11775.......11775.......11775......

0.159

0.11775

0.00028680.3

30400.522

0.0829822199

3.3475.7

1 .050E-0914.8

0.02410.0037156002720

0.23

646

29... . 8..0.. . 211....

0.. . 441....0.. . 703....

0.117

0.1

.723

720

730.01127

0.0010.0005

0.00145

0.0050.1

0.010.00027

0.0110.050.1

0.002 10.00060.0005

0.00840.00004

21.000E-08

0.00141

0.000050.0002

0.000140.00062

0.000058

0.0007

0.050.02

0.058

0.00011

0.01340.020.020.01

0.01210.0168

0.001270.001 08

0.00020.00008

0.000 10.000190.00008

.00049......0.000490.0008

0.00008

0.000320.000260.0245

0.00596438

15800814

10.51.94

1.134

0.0041629000

7.80E-06168

13329.3

133006150

2.81

5.12

176000....... 0101......

4800

1.3

357

25800

11500124

63.2

6.36

8720.4420.357

19.955..............

19.955

1.66

0.70.70.7

0.002

0.10................................................

4

1.661 ....... I.................1.68

2352.519.955

1.6619.955

1.6636700

19.9550.194

19.955

0

6900.......

9.955.....1... . 66...1... . 66...

19.955

1.66

...............07770.070.04

0.097

0.0057

0.050.0726

0.237

0.0155

0.3

0.0042

1.000E-060.034

0.00010.00020.0007

0.043

0.0039

3

3

3500

0.00027

0.70.0290.043

0.029150.00114

0.05740.0002

0.0040.0001

0.001

0.06720.07850.0063

0.00028

0.061

........................

0.0095.7

..............1.690.06

0.000950.0892

0.22

5.400E-070.0317

0.105

0.105

6.4

8.4

8.4

42

0.105

6.40.105

6.415

0.1050.54

0.105

0

0.0078 .......0.0077 .......0.0085 ..................

0.010.0174

0.010.00004

.................

0.0010.0005

0.00145..............0.005

0.10.01

0.000270.011

0.050.1

...........i ....0.00210.00060.0005

...............0.0084

0.000042

1.000E-080.00141

0.000050.0002

0.00014

0.58 ........... 0.000621............... 0.5. .... ...

......................................................... 0.000058

0.014

...............

0.00680.008'

016

...........i

0.0080.00068

016

4.20.0529

0.6490.08

0.4

0.03

0.000099

0.594..............0.105

0.5

0.0007

0.050.02

........... 6 6 58

0.00011......... .. ..0.0134

0.020.020.01

.0.01210.0168

0.001270.00108

0.00020.000080.0001

0.000190.00008

0.00040.000080.00008

0.000320.00026

0.0245

0.21 ..................

1.1 ........0.0078 ...........

0.00252 ...........





WW totals (mg/I) NWW totals (mg/kg) NWW leach (mg/)

CAS No. Name Multipath Ground- E -Muiph Extpo- NW Grund-m o d e l e d w a te r m o d - E xlra -a

po eled xt lated exit WW EQC m lated exit EQC modeled e WWEC

exit level eled exit level exit level level Leach Levellevel level level

52-24-4 ...... Tis(1-azridinyl) phosphine ...................................... 0.11775 .................. ................. 1.66 ............ 6.4 ..................sulfide.

72-57-1 ...... Trypan blue ....................................... ............... . 14.7 .................................... 6900 .................................... 10.5 ..................66-75--1 ...... Uracil m ustard ..................... ...................................... 0.159 .................................... 19.955 ..................................... 0.105 ..................7440-62-2 .. Vanadium ............................ 15800 9.58 .................. 0.003 250 .................. 1 3.71 ............. 0.003108-05-4 .... Vinyl acetate ............. .................... 14.7 0.005 .................. 6900 0.005 ................. . 10.5 0.00575-01-4 ...... Vinyl chloride ..................... 0.00199 0.0078 .................. 0.00017 1.23 .................. 0.0017 0.003 .................. 0.0001781-81-2 ...... Warfarin ................... 0.0069415 0.05 ....... 0.194 3 .................. 0.54 0.051330-20-7 .. Xylenes (total)..........22.4 88............ 0.002 1 0.0002 21 .................. 0.0027440-66-6 .. Zinc ................................ 99 0.002 316 .................. 0.3 38.4 .................. 0.002

Appendix D

TABLE D-1.-COMPARISON BETWEEN MODELED EXIT LEVELS AND UNIVERSAL TREATMENT STANDARDS

Wastewater NonwastewaterCAS Name Exit level r UTS Exit level UTS Exit level UTS

(mg/I) (mg/I) (mg/kg) I (mg/kg) (mg/I) (mg/I)

83-32-9 ............ Acenaphthene .............................................................67-64-1 ............ Acetone ........................................................................75-05-8 ............ Acetonitnle .........................................................................98-86-2 ............ Acetophenone ....................................................................107-02-8 .......... Acrolein ..............................................................................107-13-1 .......... Acrylonitrle ...................................................................... ..107-05-1 .......... Allyl chloride ................................... . .............................62-53-3 ............ Aniline ................................................................................7440-36-0 ........ Antimony ............................................................................7440-38-2 ........ Arsenic ...............................................................................7440-39-3 ........ Barium ................................................................................56-55-3 ............ Benz(a)anthracene .............................................................71-43-2 ............ Benzene .............................................................................50-32-8 ............ Benzo(a)pyrene ..................................................................205-99-2 .......... Benzo(b)fluoranthene .........................................................7440-41-7 ........ Beryllium ............................................................................39638-32-9 ...... Bis (2-chloroisopropyl) ether ..............................................111-44-4 .......... Bis(2-chlorethyl)ether .........................................................117-81-7 .......... Bis(2-ethylhexyl)phthalate ..................................................75-27-4 ............ Bromodichloromethane ......................................................75-25-2 ............ Bromoform (Tribromomethane) .........................................71-36-3 ............ Butanol ...............................................................................88-85-7 ............ Butyl-4,6-dinitrophenol, 2-sec- (Dinoseb) ..........................85-68-7 ............ Butylbenzylphthalate ..........................................................7440-43-9 ........ Cadm ium ............................................................................75-15-0 ............ Carbon disulfide .................................................................56-23-5 ............ Carbon tetrachloride ..........................................................57-74-9 ............ Chlordane ..........................................................................126-99-8 .......... Chloro-1,3-butadiene, 2-(Chloroprene) ..............................106-47-8 .......... Chloroaniline, p- .................................................................108-90-7 .......... Chlorobenzene ...................................................................510-15-6 .......... Chlorobenzilate ..................................................................124-48-1 .......... Chlorodibromomethane ......................................................67-66-3 ............ Chloroform .........................................................................95-57-8 ............ Chlorophenol, 2- ................................................................7440-47-3 ........ Chromium ...........................................................................218-01-9 .......... Chrysene ............................................................................108-39-4 .......... Cresol, m-. .........................................................................95-48-7 ............ Cresol, o- ...........................................................................106-44-5 .......... Cresol, p- ...........................................................................72-54-8 ............ DDD ...................................................................................72-55-9 ............ DDE ..............................................................................50-29-3 ............ DDT ....................................................................................84-74-2 ............ Di-n-butyl phthalate .... ... . . . ............117-84-0 .......... Di-n-octyl phthalate ............................................................96-12-8 ............ Dibromo-3-choloropropane, 1,2. .......................................95-50-1 ............ Dichlorobenzene, 1,2-. .......................................................106-46-7 .......... Dichlorobenzene, 1,4-. .......................................................75-71-8 ............ Dichlorodifluoromethane ....................................................75-34-3 ............ Dichloroethane, 1,1-. ..........................................................107-06-2 .......... Dichloroethane, 1,2-. ..........................................................75-35-4 ............ Dichloroethylene, 1,1-. .......................................................156-60-5 .......... Dichloroethylene, trans-12 . ..............................................120-83-2 .......... Dichlorophenol, 2,4- ...........................................................

0.0740.053

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TABLE D-1 .- COMPARISON BETWEEN MODELED EXIT LEVELS AND UNIVERSAL TREATMENT STANDARDS-Continued

Wastewater NonwastewaterCAS Name Exit level UTS Exit level 1 UTS Exit level UTS

(mg/I) (mg/) (mg/kg) (mg/kg) (mg/I) I (mg/I)

94-75-7 ............78-87-5 ............10061-01-5 ......10061-02-6.60-57-1 ............84-66-2 ............131-11-3 ..........105-67-9 ..........51-28-5 ............121-14-2 ..........606-20-2 ..........123-91-1 ..........122-39-4 ..........298-04-4 ..........72-20-8 ............141-78-6 ..........60-29-7 ............97--63-2 ............100-41-4 ..........206-44-0 .......86-73-7 ............76-44-8- ..........1024-57-3 ........87-68-3 ............118-74-1 ..........319-84-6 ..........319-85-7 ..........58-89-9 ............77-47-4 ............67-72-1 ............193-39-5 ..........78-83-1 ............7439-92-1 ........7439-97-6 ........126-98-7 ..........67-56- * ...........72-43-5 ............74-83-9 ............74-87-3 ............78-93-3 ............108-10-1 ..........80-62-6 ............298-00-0 ..........74-95-3 ............75-09-2 ............86-30-6 ............930-55-2 ..........91-20-3 ............7440-02-0 ........98-95-3 ............924-16-3 ..........56-38-2 ............608-93-5 ..........82-68-8 ............87-86-5 ............108-95-2 ..........298-02-2 ..........1336-36-3 ........23950-58-5 ......129-00-0 ..........110-86-1 ..........94-59-7 ............7782-49-2 ..........7440-22-4 ..........1746-01-6 ..........95-94-3 ..............630-20-6 ............79-34-5 ..............127-18-4 ............58-90-2 ..............7440-28-0 ..........108-88-3 ............8001-35-2 ..........76-13-1 ........... ..120-82-1 ............71-55-6 ..............79-00-5 ..............79-01-6 ..............75-69-4 ..............

Dichlorophenoxyacetic acid, 2,4- (2,4-D) ..........................Dichloropropane, 1,2- . .......................................................Dichtoropropene, cis-1,3 . ..................................................Dichloropropene, trans-1,3 . ..............................................Dieldrin ...............................................................................Diethyl phthalate ................................................................Dimethyl phthalate .............................................................Dimethylphenol,2,4. ..........................................................Dintrophenol,2,4- ...............................................................Dinitrotoluene2,4- ..............................................................Dinitrotoluene2,6- ..............................................................Dioxane,1,4 . .....................................................................Diphenylamine ...................................................................Disulfoton ...........................................................................Enndrin ...............................................................................Ethyl acetate ......... /.....................Ethyl ether ..........................................................................Ethyl methacrylate .............................................................Ethylbenzene .....................................................................Flouranthene ......................................................................Flourene .......................................................................Heptachlor ..........................................................................Heptachlor epoxide ............................................................Hexachloro-1,3-butadiene ..................................................Hexachlorobenzene ...........................................................Hexachlorocyclohexane, alpha-(alpha-BHC) .....................Hexachlorocyclohexane, beta-(beta-BHC) ........................Hexachlorocyclohexane, gamma-(Lindane) ......................Hexachlorocyclopentadiene ...............................................Hexachloroethane ..............................................................Indeno(1,2,3-cod) pyrene .....................................................Isobutyl alcohol .............................................................Lead ...................................................................................Mercury ..............................................................................Methacrylonitrile .................................................................Methanol ............................................................................Methoxychlor ......................................................................Methyl bromide (Bromomethane) ......................................Methyl chloride (Chloromethane) .......................................Methyl ethyl ketone ............................................................Methyl isobutyl ketone .......................................................Methyl methacrylate ...........................................................Methyl parathion ................................................................Methylene bromide ............................................................Methylene chloride .............................................................N-Nitrosodiphenylam ine .....................................................N-Nitrosopyrrolidine ...........................................................Naphthalene .......................................................................Nickel .................................................................................Nitrobenzene ......................................................................Nitrosodi-n-butylam ine .......................................................Parathion ............................................................................Pentachlorobenzene ..........................................................Pentachloronitrobenzene (PCNB) ......................................Pentachlorophenol .............................................................Phenol ................................................................................Phorate ..............................................................................Polychlorinated biphenyls .............................................Pronam ide ..........................................................................Pyrene ................................................................................Pyridine ..............................................................................Safrole ................................................................................Selenium ............................................................................Silver ..................................................................................TCDD,2,3,7,8 .....................................................................Tetrachlorobenzene, 1,2,4,5- .............................................Tetrachloroethane, 1,1,1,2-. ...............................................Tetrachloroethane, 1,1,2,2-. ...............................................Tetrachloroethylene ...........................................................Tetrachlorophenol, 2,3,4,6- ................................................Thallium (I) .........................................................................Toluene ..............................................................................Toxaphene .........................................................................Trichloro-1.2.,2-tnfluoroethane, 1,1,2- . ...............................Trichlorobenzene, 1,2,4- ....................................................Trichloroethane, 1,10-. ......................................................Trichloroethane, 1,1,2-. ...................................... ; ...............Trichloroethylene ................................................................Trichlorofluoromethane ......................................................

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0.000059190

784

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0.0130.073

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0.000140.000440.00078

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0.30.016

787

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TABLE D-1.--COMPARISON BETWEEN MODELED EXIT LEVELS AND UNIVERSAL TREATMENT STANDARDS-Continued

Wastewater NonwastewaterCAS Name Exit level UTS Exit level UTS Exit level UTS

(mgI) (mg/) (mg/kg) (mg/kg) (mgI) (mg/I)

95-95-4 .............. Trichlorophenol, 2,4,5- ....................................................... 18 0.18 12000 7.4 4 ....................88-06-2 .............. Tnchlorophenol, 2,4,6. ...................................................... 0.054 0.035 120 7.4 0.015 ....................93-76-5 .............. Trichlorophenoxyacetic acid, 2,4,5- (245-T) ...................... 2 0.72 63 7.9 0.64 ....................93-72-1 .............. Trichlorophenoxypropionic acid, 2,4,5- (Silvex) ................. 1 0.72 6 7.9 0.48 ....................96-18-4 .............. Trichloropropane, 1,2,3- ..................................................... 1 0.85 870 30 0.34 ....................126-72-7 ............ Tris (2,3-dibromopropyl) phosphate ................................... eqc 0.11 0.36 0.1 eqc ..............7440-62-2 .......... Vanadium ........................................................................... 10 4.3 250 .................... 4 0.2375-01-4 .............. Vinyl chloride ...................................................................... eqc 0.27 1 6 eqc ....................1330-20-7 .......... Xylenes (total ..................................................................... 22 0.32 170000 30 150 ...................7440-66-6 .......... Zinc ........................................ ... 99 2.61 320 1...... 38 5.3

For the reasons set out in thepreamble, Chapter I of Title 40 of theCode of Federal Regulations is amendedas follows:

PART 260-HAZARDOUS WASTEMANAGEMENT SYSTEM: GENERAL

1. The authority citation for part 260continues to read as follows:

Authority: 42 U.S.C. 6905, 6912(a), 6921-6927, 6930, 6934, 6935, 6937, 6938, 6939,and 6974.

2. In § 260.10, add the followingdefinitions in alphabetical order:* * * * *

Director means the RegionalAdministrator or the State-Director, asthe context requires, or an authorizedrepresentative. When there is noapproved State program, and there is anEPA administered program, Directormeans the Regional Administrator.When there is an approved Stateprogram, Director normally means theState Director. In some circumstances,however, EPA retains the authority totake certain actions even when there isan approved State program. In suchcases, the term Director means theRegional Administrator and not theState Director.* * * * *

Monofill means a landfill where wasteof only one kind or type is placed in oron land and which is not a pile, a landtreatment facility, a surfaceimpoundment, an undergroundinjection well, a salt dome formation, asalt bed formation, an undergroundmine, a cave, or a corrective actionmanagement unit.

PART 261-IDENTIFICATION ANDLISTING OF HAZARDOUS WASTE

. 3. The authority citation for part 261continues to read as follows:

Authority: 42 U.S.C. 6905, 6912(a), 6921,and 6922.

4. Section 261.3 is amended byrevising the first sentence of paragraph

(a)(2)(iv) and the first sentence ofparagraph (c)(2)(i) to read as follows:

§ 261.3 Definition of hazardous waste.* * * * *

(a) * * *(2)* * *(iv) It is a mixture of solid waste and

one or more hazardous wastes listed insubpart D of this part and has not beenexcluded from paragraph (a)(2) of thissection under either §§ 260.20 and260.22, § 261.36, or § 261.37 of thischapter; however, the followingmixtures of solid wastes and hazardouswastes listed in subpart D of this partare not hazardous wastes (except byapplication of paragraph (a)(2) (i) or (ii)of this section) if the generator candemonstrate that the mixture consists ofwastewater the discharge of which issubject to regulation under eithersection 402 or section 307(b) of theclean water act (including wastewater atfacilities which have eliminated thedischarge of wastewater) and:* * * * *

(c) * * *(2) * * *(i) Except as otherwise provided in

paragraph (c)(2)(ii) of this section,§ 261.36, or § 261.37 of this chapter, anysolid waste generated from thetreatment, storage, or disposal of ahazardous waste, including any sludge,spill residue, ash, emission control dust,or leachate (but not includingprecipitation run-off) is a hazardouswaste. * * ** * * * *

5. A new § 261.36 is added to subpartD to read as follows:

§ 261.36 Exemption for listed hazardouswastes containing low concentrations ofhazardous constituents.

(a) Any hazardous waste listed underthis subpart, any mixture of such alisted waste with a solid waste, or anywaste derived from the treatment,storage, or disposal of a listed hazardouswaste that does not exhibit any of thecharacteristics of hazardous waste in

subpart C of this part 261 and that meetsall of the requirements in § 261.36(b)-(d) is exempt from all requirements ofparts 262-266 and part 270 of thischapter. Any such waste which alsomeets the requirements of § 261.36(e) isalso exempt from the requirements ofpart 268 of this chapter.

(b) Requirements for qualifying for anexemption.-(1) Testing. (i) For eachwaste for which an exemption isclaimed, the claimant must test for allof the constituents on appendix X tothis part 261 except those that theclaimant determines should not bepresent in the waste. The claimant isrequired to document the basis of eachdetermination that a constituent shouldnot be present. No claimant maydetermine that any of the followingcategories of constituents should not bepresent:

(A) Constituents identified inappendix VII to this part 261 as thebasis for listing the waste for whichexemption is sought;

(B) Constituents listed in the table to§ 268.40 of this chapter as regulatedhazardous constituents for LDRtreatment of the waste;

(C) Constituents detected in anyprevious analysis of the same wasteconducted by or on behalf of theclaimant;

(D) Constituents introduced into theprocess which generates the waste; and

(E) Constituents which the claimant'knows or has reason to believe arebyproducts or side reactions to theprocess that generates the waste.

Note: Any claim under this section must bevalid and accurate for all hazardousconstituents; a determination not to test fora hazardous constituent will not shield aclaimant from liability should thatconstituent later be found in the waste.

(ii) The claimant must develop asampling and analysis plan for eachwaste for which an exemption is sought.The plan must identify:

(A) Sampling procedures andlocations sufficient to characterize theentire waste for which the exemption is




claimed. Grab'sampling is acceptable forthis purpose.

(B) Analytical methods that theclaimant will use to determine, forwastewaters and nonwastewaters, thetotal concentration of each constituenton appendix X to this part except forthose constituents which the claimanthas determined should not be presentunder § 261.36(b)(1)(i).

(iii) The claimant must conductsampling and analysis in accordancewith the plan.

(iv) The results of the sampling andanalysis must show, for bothwastewaters and nonwastewaters, thatall total constituent concentrations inthe waste are at or below the exemptionlevels in appendix X to this part 26 1and, for nonwastewaters, that allleachable constituent concentrations areeither:

(A) At or below exemption levels inAppendix X to this part 261, asdetermined by testing an extract usingtest method 1311 (the ToxicityCharacteristic Leaching Procedure, setout in "Test Methods for EvaluatingSolid Waste,.Physical/ChemicalMethods" (SW-846)), or

(B) Estimated to be at or belowexemption levels using the equation{[(AxB)+(CxD)]/[B+(2OxD)J} leach exitlevel, where A=concentration of theanalyte in the liquid portion of thesample; B=Volume of the liquid portionof the sample; C=Concentration of theanalyte in the solid portion of thesample; D=Weight of the solid portionof the sample.

(2) Treatment requirements. Anywaste that exits using an exit level onTable B to appendix X to this part 261must meet the treatment standard forsuch a constituent under § 268.40 of thischapter, regardless of whether or not thewaste is intended for land disposal,unless the claimant meets theexemption requirements in § 261.36(e).

(3) Public Notice. The claimant mustsubmit for publication in a majornewspaper of general circulation, localto the claimant, a notice entitled"Notification of Exemption Claim forListed Hazardous Wastes ContainingLow Concentrations of HazardousConstituents Under the ResourceConservation and Recovery Act"containing the following information:

(i) The name, address, and RCRA IDnumber of the claimant's facility;

(ii) The applicable EPA HazardousWaste Code of the waste for which theexemption is claimed and the narrativedescription associated with the listingfrom this part 261 subpart D;

(iii) A brief, general description of themanufacturing, treatment, or other

process or operation producing thewaste;

(iv) An estimate of the average andmaximum monthly and annualquantities of the waste claimed to beexempt;

(v) The name and mailing address ofthe agency to which the claimant issubmitting the notification requiredunder § 261.36(b)(4).

(4) Notification to implementingagency. Prior to managing any waste asexempt under this section, the claimantmust-send to the Director via certifiedmail or other mail service that provideswritten confirmation of delivery anotification of the exemption claimmeeting the following requirements:

(i) The name, address, and RCRA IDnumber of the person claiming theexemption;

(ii) The applicable EPA HazardousWaste Codes;

(iii) A brief description of the processthat generated the waste;

(iv) An estimate of the average andmaximum monthly and annualquantities of each waste claimed to beexempt;

(v) Documentation for any claim thata constituent is not present as describedunder § 261.36 (b)(1)(i);

(vi) The results of all analyses andestimates of constituent concentrationsrequired under § 261.36(b)(1)(iv) and allquantitation limits achieved;

(vii) Documentation that any wastethat exits using a constituent exit levelfrom Table B to Appendix X to this parthas met the applicable treatmentstandards in § 268.40 of this chapter,unless the claimant is also claiming theexemption under § 261.36(e);

(viii) Evidence that the publicnotification requirements of§ 261.36(b)(3) have been satisfied; and

(ix) The following statement signed bythe person claiming the exemption orhis authorized representative:

"Under penalty of criminal and civilprosecution for making or submitting falsestatements, representations, or omissions, Icertify that the requirements of 40 CFR261.36(b) have been met for all wasteidentified in this notification. Copies of therecords and information required at 40 CFR261.36(d)(7) are available at the claimant'sfacility. Based upon my inquiry of theindividuals immediately responsible forobtaining the information, the information is,to the best of my knowledge and belief, true,accurate, and complete. I am aware that thereare significant penalties for submitting falseinformation, including the possibility of fineand imprisonment for knowing violations."

(c) Effectiveness of exemption. Noclaim shall take effect until the claimantreceives confirmation of delivery for thenotification required under § 261.36(b)(4).

(d) Conditions for maintaining theexemption. To maintain any exemptionclaimed pursuant to this section, theclaimant must satisfy the followingconditions:

(1) Changes in information. Theclaimant must submit to the Directorany change in any informationsubmitted under § 261.36(b)(4) withinten business days of the claimant's firstknowledge of the change.

(2) Schedule for retesting. Theclaimant must retest the waste for whichthe exemption was claimed on thefollowing schedule:

(i) For the first three years of theexemption, the claimant must:

(A) Test wastes generated at the timethe exemption is claimed in volumesgreater than 10,000 tons/year on aquarterly basis;

(B) Test wastes generated at the timethe exemption is claimed in volumesgreater than 1000 tons/year but less than10,000 tons/year must on a semi-annualbasis;

(C) Test wastes generated at the timethe volume is claimed in volumes lessthan 1000 tons/year on an annual basis.

(ii) After the first three years of anexemption, the claimant must retest thewaste for which the exemption wasclaimed on an annual basis.

(3) For every retest the claimant mustprepare and comply with a samplingand analysis plan meeting therequirements of § 261.36(b)(1)(ii) anddetermine the concentration of:

(i) Each constituent from Table A toappendix X to this part that wasdetected in the initial test within anorder of magnitude below either its totalor leachable exemption level and eachconstituent from Table B to appendix Xof this part that is identified as a basisfor listing the waste on appendix VII tothis part or is listed as a regulatedhazardous constituent for the waste inthe table of "Treatment Standards forHazardous Wastes" in § 268.40 of thischapter; and

(ii) Any other constituent that theclaimant has reason to believe may benewly present in the waste since themost recent test.

(4) Exemption levels. Theconcentrations of all constituents testedmust meet the criteria set out in§ 261.36(b)(1)(iv).

(5) Treatment requirements. Anywaste exiting by using an exit level fora hazardous constituent from Table B toappendix X to this part must meet thetreatment requirements for such aconstituent under § 268.40 of thischapter prior to exit regardless ofwhether or not the waste is intended forland disposal, unless the claimant meets

66441




the exemption requirements in§ 261.36(e).

(6) Records. The claimant mustmaintain records of the followinginformation in files en-site for threeyears after the date of the relevant test:

(i) For initial testing, all informationsubmitted under § 261.36(b)(4), allrevisions to such material submittedunder § 261.36(d)(1) and all informationrequired to be maintained under§ 261.36(d)(6)(iii);

(ii) For retests:(A) All volume determinations made

for the purpose of determining testingfrequency under § 261.36(d)(2);

(B) All sampling and analysis plansrequired under § 261.36(d)(3);

(C) All analytical results andestimates of leachable concentrations (ifany) for constituents required to beassessed under § 261.35(d)(3);

(D) Documentation showing that awaste exiting using any constituent exitlevel from Table B to appendix X to thispart and is required to be reassessedunder § 261.36(d)(3) has met applicabletreatment standards under § 268.40 ofthis chapter, unless the claimant alsoclaims the exemption under § 261.36(e);and

(iii) For both initial tests and retests,the claimant must also retain records of:

(A) The dates and times wastesamples were obtained, and, for totalconcentrations and leachableconcentrations that were analyzed, thedates of the analyses;

(B) The names and qualifications ofthe person(s) who obtained the samples;

(C) A description of the temporal andspatial locations of the samples;

(D) The name and address of thelaboratory facility at which analyses ofthe samples were performed;

(E) A description of the analyticalmethods used, including any clean-upand extraction methods;

(F) All quantitation limits achievedand all other quality control results(including any method blanks, duplicateanalyses, and matrix spikes), laboratoryquality assurance data, and adescription of any deviations frompublished analytical methods or fromthe plan which occurred; and

(G) All laboratory documentation thatsupports the analytical results, unless acontract between the claimant and thelaboratory provides for thedocumentation to be maintained by thelaboratory for the period specified in§ 261.36 (b)(2) and also provides for theavailability of the documentation to theclaimant upon request.

Note: Failure to satisfy any of theseconditions voids the exemption and requiresmanagement of the waste for which theexemption has been claimed as hazardous

waste. Submission of notification to theDirector that all waste conditions have beensatisfied re-establishes the exemption for allwaste generated after that date.

(e) Exemption from part 268requirements.-If all hazardousconstituent levels in a waste qualifyingfor exemption are at or below theappendix X to this part concentrationlevels at the waste's point of generation,prior to any mixing with other solid orhazardous wastes and prior to anytreatment, the waste is exempt from allrequirements of part 268 of this chapter.The claimant also must meet thefollowing documentation requirements:

(1) For initial tests, in place of thecertification required at § 261.36(b)(4)(ix), the claimant must submit thefollowing statement signed by theperson claiming the exemption or hisauthorized representative and, if theclaimant is not the generator of thewaste, also signed by the generator orhis authorized representative:

Under penalty of criminal and civilprosecution for making or submitting falsestatements, representations, or omissions, Icertify that, for the waste identified in thisnotification, the concentration of allconstituents assessed as required under§ 261.36 (b)(1)(iv) met the applicable levels inappendix X to this part 261 at the point ofgeneration and that all other requirements of40 CFR § 261.36 (b) have been met. Copies ofthe records and information required at 40CFR § 261.36 (d)(4) are available at theclaimant's facility. Based upon my inquiry ofthe individuals immediately responsible forobtaining the information, the information is,to the best of my knowledge and belief, true,accurate, and complete. I am aware that thereare significant penalties for submitting falseinformation, including the possibility of fineand imprisonment for knowing violations.";or

(2) For every retest required under§ 261.36(d)(2), the claimant mustdocument that the concentrations of allconstituents retested as required under§.261.36(d)(3) met the applicable levelsin appendix X to this part 261 at thewaste's point of generation, mustinclude information supporting thisclaim from the waste's generator if thegenerator is not the person asserting theclaim, and must retain suchdocumentation in files on-site for threeyears after the date of the relevant test.

(f) Nothing in this paragraphpreempts, overrides, or otherwisenegates the provision in § 262.11 of thischapter, which requires any person whogenerates a solid waste to determine ifthat waste is a hazardous waste.

(g) In an enforcement action, theburden of proof to establishconformance with the exemptioncriteria shall be on the claimant.

6. A new § 261.37 is added to read asfollows:

§ 261.37 Exemption for listed hazardouswastes containing low concentrations ofhazardous constituents and managed Inlandfills and monofills.

(a) Any hazardous waste listed underthis subpart, any mixture of such alisted waste with a solid waste, or anywaste derived from the treatment,storage or disposal of such a listed wasteis exempt from regulation as ahazardous waste under parts 262-266and 270 of this chapter if it meets therequirements in § 261.37(b) and (d)(including the requirement that allhazardous constituents present in thewaste be at or below the levels listed inappendix XI to this part and that thewaste be disposed in a landfill ormonofill, but not a land applicationunit). To maintain the exemption, thewaste must satisfy the conditions in§ 261.37(e). Any such waste which alsomeets the requirements of 261.37(f) isalso exempt from the requirements ofpart 268 of this chapter.

(b) Requirements for qualifying for anexemption-(1) Testing. (i) For eachwaste for which an exemption isclaimed, the claimant must test for allof the constituents on appendix XI tothis part 261 except those that theclaimant determines should not bepresent in the waste. The claimant isrequired to document the basis of eachdetermination that a constituent shouldnot be present. No claimant maydetermine that any of the followingcategories of constituents should not bepresent:

(A) Constituents identified inappendix VII to this part 261 as thebasis for listing the waste for whichexemption is sought;

(B) Constituents listed in the table to§ 268.40 as regulated hazardousconstituents for LDR treatment of thewaste;

(C) Constituents detected in anyprevious analysis of the same wasteconducted by or on behalf of theclaimant;

(D) Constituents introduced into theprocess which generates the waste; and

rE) Constituents which the claimantknows or has reason to believe arebyproducts or side reactions to theprocess that generates the waste.'

Note: Any claim under this section must bevalid and accurate for all hazardousconstituents; a determination not to test fora hazardous constituent will not shield aclaimant from liability should thatconstituent later be found in the waste.

(ii) The claimant must develop asampling and analysis plan for each




waste for which an exemption is sought.The plan must identify:

(A) Sampling procedures andlocations sufficient to characterize theentire waste for which the exemption isclaimed. Grab sampling is acceptable foithis purpose.

(B) Analytical methods that theclaimant will use to determine, forwastewaters and nonwastewaters, thetotal concentration of each constituenton appendix XI to this part except forthose constituents which the claimanthas determined should not be presentunder § 261.37(b)(1)(i).

(iii) The claimant must conductsampling and analysis in accordancewith the plan.

(iv) The results of the sampling andanalysis must show, for bothwastewaters and nonwastewaters, thatall total constituent concentrations inthe waste are at or below the exemptionlevels in appendix XI to this part 261and, for nonwastewaters, that allleachable constituent concentrations areeither:

(A) At or below exemption levels inappendix XI to this Part 261, asdetermined by testing an extract usingtest method 1311 (the ToxicityCharacteristic Leaching Procedure, setout in "Test Methods for EvaluatingSolid Waste, Physical/ChemicalMethods" (SW-846)), or

(B) Estimated to be at or belowexemption levels using the equation{(AxB)+(CxD)}/{B+(ZOxD)} < leach exitlevel, where A=concentration of theanalyte in the liquid portion of thesample; B = Volume of the liquidportion of the sample; C=Concentrationof the analyte in the solid portion of thesample; D = Weight of the solid portionof the sample.

(2) Treatment requirements. Anywaste that exits using an exit level onTable B to appendix XI to this Part 261must meet the treatment standard forsuch a constituent under § 268.40 of thi,chapter, regardless of whether or not thewaste is intended for land disposal,unless the claimant meets theexemption requirements in § 261.37(0.

(3) Public Notice. The claimant mustsubmit for publication in a majornewspaper of general circulation, localto the claimant, a notice entitled"Notification of Exemption Claim forListed Hazardous Wastes ContainingLow Concentrations of HazardousConstituents and Managed in Landfillsand Monofills Under the ResourceConservation and Recovery Act"containing the following information:

(i) The name, address, and RCRA IDnumber of the claimant's facility;

(ii) The applicable EPA HazardousWaste Code of the waste for which the

• exemption is claimed and the narrativedescription associated with the listingfrom this part 261 subpart D;

(iii) A brief, general description of themanufacturing, treatment, or otherprocess or operation producing thewaste;

(iv) An estimate of the average andmaximum monthly and annualquantities of the waste claimed to beexempt;

(v) The name and mailing address ofthe agency to which the claimant issubmitting the notification requiredunder § 261.37(b)(4);

(vi) The following statement:The exemption for this waste from the

hazardous waste regulatory scheme isconditioned disposing of the waste in alandfill or monofill (and not a landapplication unit.)

(4) Notification to implementingagency. Prior to managing any waste asexempt under this section, the claimantmust send to the Director via certifiedmail or other mail service that provideswritten confirmation of delivery anotification of the exemption claimmeeting the following requirements:

(i) The name, address, and RCRA IDnumber of the person claiming theexemption;

(ii) The applicable EPA HazardousWaste Codes;

(iii) A brief description of the processthat generated the waste;

(iv) An estimate of the average andmaximum monthly and annualquantities of each waste claimed to beexempt;

(v) Documentation for any claim thata constituent is not present as describedunder § 261.37(b)(1)(i);

(vi) The results of all analyses andestimates of constituent concentrationsrequired under § 261.37(b)(1)(iv) and allquantitation limits achieved;

(vii) Documentation that any wastethat exits using a constituent exit levelfrom Table B to appendix XI to this parthave met the applicable treatmentstandards in § 268.40, of this chapter,unless the claimant is also claiming theexemption under § 261.37(0;

(viii) Evidence that the publicnotification requirements of§ 261.37(b)(3) have been satisfied; and

(ix) The following statement signed bythe person claiming the exemption orhis authorized representative:

Undes penalty of criminal and civilprosecution for making or submitting falsestatements, representations, or omissions, Icertify that the requirements of § 261.37(b)have been met, including the requirementthat all hazardous constituents present in thewaste are at or below the levels listed onappendix XI to this part, for all listed wastesidentified in this notification. I also certify

that arrangements have been made to disposeof the waste in a landfill or monofill (and nota land application unit). Copies of therecords and information required at § 261.37(e)(7) are available) at the claimant's facility.Based upon my inquiry of the individualsimmediately responsible for obtaining theinformation, the information is, to the best ofmy knowledge and belief, true, accurate, andcomplete. I am aware that there aresignificant penalties for submitting falseinformation, including the possibility of fineand imprisonment for knowing violations.

(5) The claimant must receiveconfirmation of delivery for thenotification required under § 261.37(b)(4).

(c) Tracking, storage, treatment andother management prior to disposal.Until a listed hazardous waste meetingthe requirements of § 261.37(b) is placedin a landfill or monofill, it remainssubject to all requirements of parts 262-266 and 270 of this chapter. The wasteis also subject to the requirements ofpart 268 of this chapter unless itqualifies for an exemption under§ 261.37(0.

(d) Disposal in a landfill or monofill.The claimant must ensure that anylisted waste meeting the requirements of§ 261.37(b) for which an exemption issought is disposed of in either a landfillor monofill (and not a land applicationunit). The landfill or monofill need notbe subject to regulation as a hazardouswaste management unit. The wastebecomes exempt as soon as it is placedin a landfill or monofill unit.

(e) Conditions for maintaining theexemption. To maintain any exemptionclaimed pursuant to this section, theclaimant must satisfy the followingconditions:

(1) Compliance with modifiedhazardous waste manifest system. If thelandfill or monofill in which the wasteis disposed is not a hazardous wastedisposal unit subject to part § 264.71-264.72 or § 265.71-265.72 of thischapter, the claimant must:

(i) Ensure that the manifest form isreturned from the disposal facility, and

(ii) Obtain information showing thatthe disposal facility designated on themanifest received the waste for whichthe exemption is sought and placed it ineither a landfill or monofill (and not aland treatment unit).

(2) Changes in information. Theclaimant must submit to the Directorany change in any informationsubmitted under § 261.37(b)(4) withinten business days of the claimant's firstknowledge of the change.

(3) Schedule for retesting. Theclaimant must retest the waste for whichthe exemption was claimed on thefollowing schedule:

66443




(i) For the first three years of theexemption, the claimant must:

(A) Test wastes generated at the timethe exemption is claimed in volumesgreater than 10,000 tons/year on aquarterly basis;

(B) Test wastes generated at the timethe exemption is claimed in volumesgreater than 1000 tons/year but less than10,000 tons/year must on a semi-annualbasis;

(C) Test wastes generated at the timethe volume is claimed in volumes lessthan 1000 tons/year on an annual basis.

(ii) After the first three years of anexemption, the claimant must retest thewaste for which the exemption wasclaimed on an annual basis.

(4) For every retest the claimant mustprepare and comply with a samplingand analysis plan meeting therequirements of § 261.37(b)(1)(ii) anddetermine the concentration of:

(i) Each constituent from Table A toappendix XI to this part that wasdetected in the initial test within anorder of magnitude below either its totalor leachable exemption level and eachconstituent from Table B to appendix XIto this part that is identified as a basisfor listing the waste on appendix VII tothis part or is listed as a regulatedhazardous constituent for the waste inthe table of "Treatment Standards forHazardous Wastes" in § 268.40 of thischapter; and

(ii) Any other constituent that theclaimant has reason to believe may benewly present in the waste since themost recent test.

(5) Exemption levels.-Theconcentrations of all constituents testedmust meet the criteria set out in§ 261.37(b)(1)(iv).

(6) Treatment requirements.-Anywaste exiting by using an exit level fora hazardous constituent from Table B toAppendix XI to this part must meet thetreatment requirements for such aconstituent under § 268.40 of thischapter prior to exit regardless ofwhether or not the waste is intended forland disposal, unless the claimant meetsthe exemption requirements in§ 261.37(f).

(7) Records.-The claimant mustmaintain records of the followinginformation in files on-site for threeyears after the date of the relevant test:

(i) For initial testing, all informationsubmitted under § 261.37(b)(4) and allrevisions to such material submittedunder § 261.37(e)(2), all informationobtained under § 261.37(e)(1), and allinformation required to be maintainedunder § 261.37(e)(7)(iii);

(ii) For retests:(A) All volume determinations made

for the purpose of determining testingfrequency under § 261.37(e)(3);

(B) All sampling and analysis plansrequired under § 261.37(e)(4);

(C) All analytical results andestimates of leachable concentrations (ifany) for constituents required to beassessed under § 261.37 (e)(5);

(D) Documentation showing that awaste exiting using any constituent exitlevel from Table B to Appendix XI tothis part has met applicable treatmentstandards under § 268.40 of this chapter,unless the claimant also claims theexemption under § 261.37(0; and

(iii) For both initial tests and retests,the claimant must also retain records of:

(A) The dates and times Wastesamples were obtained, and, for totalconcentrations and leachableconcentrations that were analyzed, thedates of the analyses;

(B) The names and qualifications ofthe person(s) who obtained the samples;

(C) A description of the temporal andspatial locations of the samples;

(D) The name and address of thelaboratory facility at which analyses ofthe samples were performed;

(E) A description of the analyticalmethods used, including any clean-upand extraction methods;

(F) All quantitation limits achievedand all other quality control results(including any method blanks, duplicateanalyses, and matrix spikes), laboratoryquality assurance data, and adescription of any deviations frompublished analytical methods or fromthe plan which occurred; and .

(G) All laboratory documentation thatsupports the analytical results, unless acontract between the claimant and thelaboratory provides for thedocumentation to be maintained by thelaboratory for the period specified in§ 261.37 (b)(2) and also provides for theavailability of the documentation to theclaimant upon request. Failure to satisfyany of these conditions voids theexemption and requires management ofthe waste for which the exemption hasbeen claimed as hazardous waste.Submission of notification to theDirector that all waste conditions havebeen satisfied re-establishes theexemption for all waste generated afterthat date.

(f) Exemption from part 268requirements.-If all hazardousconstituent levels in a waste qualifyingfor exemption are at or below theappendix XI to this part concentrationlevels at the waste's point of generation,

prior to any mixing with other solid orhazardous wastes and prior to anytreatment, the waste is exempt from allrequirements of part 268 of this chapter.The claimant also must meet thefollowing documentation requirements:

(1) For initial tests, in place of thecertification required at § 261.37(b)(4)(ix), the claimant must submit thefollowing statement signed by theperson claiming the exemption or hisauthorized representative and, if theclaimant is not the generator of thewaste, also signed by the generator orhis authorized representative:

Under penalty of criminal and civilprosecution for making or submitting falsestatements, representations, or omissions, Icertify that, for the waste identified in thisnotification, the concentration of allconstituents assessed as required under§ 261.37 (b){1)(iv) met the applicable levels inappendix XI to this part 261 at the point ofgeneration and that all other requirements of40 CFR 261.37 (b) have been met. I alsocertify that arrangements have been made todispose of the waste in a landfill or monofill(and not a land application unit). Copies ofthe records and information required at 40CFR 261.37 (e)(7) are available at theclaimant's facility. Based upon my inquiry ofthe individuals immediately responsible forobtaining the information, the information is,to the best of my knowledge and belief, true,accurate, and complete. I am aware that thereare significant penalties for submitting falseinformation, including the possibility of fineand imprisonment for knowing violations.";and

(2) For every retest required under§ 261.37(e)(3), the claimant mustdocument that the concentrations of allconstituents retested as required under§ 261.37(e)(4) met the applicable levelsin appendix XI to this part 261 at thewaste's point of generation, mustinclude information supporting thisclaim from the waste's generator if thegenerator is not the person asserting theclaim, and must retain suchdocumentation in files on-site for threeyears after the date of the relevant test.

(g) Nothing in this paragraphpreempts, overrides, or otherwisenegates the provision in § 262.11 of thischapter, which requires any person who

.generates a solid waste to determine ifthat waste is a hazardous waste.

(h) In an enforcement action, theburden of proof to establishconformance with the exemptioncriteria shall be on the claimant.

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66458 Federal Register / Vol. 60, No. 245' / Thursday, December 21, 1995 / Proposed Rules

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Federal Register / Vol. 60, No. 245 / Thursday) December 21, 1995 / Proposed Rules 66459

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TABLE B.-QUANTITATION-BASED CONDITIONAL EXIT LEVELS

MCL benchmark option Toxicity benchmark option

CAS No. Name Wastewater Nonwastewater Wastewater NonwastewaterTotals Totals Leach Totals Totals Leachmg/(mg/) (mg/kg) I (mg/I) (mg/) (mg/kg) (mg/I)

208-96-8.75-36-5 ..........591-08-2 ........107-02-8 ........79-06-1 ..........107-13-1.1402-68-2.116-06-3 ........309-00-2 ........107-18-6 ........2763-96-4.

504-24-5 ........61-82-5 ..........120-12-7 ........7440-38-2.2465-27-2 ......115-02-6 ........92-87-5 ..........98-07-7 ..........50-32-8 ..........205-82-3.207-0-9.191-24-2 ........56-55-3 ..........225-51-4 ........542-88-1.

357-57-3.86-74-8 ..........353-50-4 ........75-87-6 ..........305-03-3.57-74-9 ..........494-03-1.107-20-0 ........110-75-8 ........

107-30-2 ........

5344-82-1.

542-76-7.

6358-53-8.7440-48-4.57-12-5 ..........14901-08-7 ....108-94-1 ........131-89-5 ........

50-18-0 ..........20830-81-353-19-0 ..........72-55-9 ..........3424-82-6 ......50-29-3 ..........789-02-6 ........192-65-4 ........

189--64-0 ........189-64-9 ........194-59-2 ........

226-36-8 ........53-70-3 ..........

224-42-0.311-45-5.

56-53-1 ..........77-78-1 ..........119-93-7 ........

57-97-6 ..........

Acenaphthylene.Acetyl chloride .........Acetyl-2-thiourea ......Acrolein ....................Acrylamide ...............Acrylonitrile ..............Aflatoxins .................Aldicarb ....................Aldrin ..................Allyl alcohol .........Aminomethyl-3-

isoxazolol, 5-.Aminopyridine, 4-. ....Amitrole ....................Anthracene ...............Arsenic .....................Auramine ..................Azaserine .................Benzidine .............Benzotrichloride.Benzo(a)pyrene.Benzo(j)fluorantheneBenzo(k)fluorantheneBenzo[gh,i]peryleneBenz(a)anthraceneBenz[cjacidine ........Bis(chloromethyl)

ether.Brucine .........Carbazole .................Carbon oxytluorideChloral ......................Chlorambucil ............Chlordane ................Chlornaphazin ..........Chloroacetaldehyde.Chloroethyl vinyle

ether, 2-.Chloromethyl methyl

ether.Chlorophenyl thio-

urea, 1-o-.Chloropropionitrile,

3-.Citrus red No. 2 .......Cobalt .......................Cyanida ....................Cycasin ....................Cyclohexanone ........Cyclohexyl-4,6-

dinitrophenol, 2-.CyclophosphamideDaunomycin .............DDD (o,p') ................DDE .........................DDE (o,p') ................DDT ..........................DDT (o,p') ................Dibenzo-

[a,elypyrene.Dibenzo- [a,hlpyreneDibenzo- [a,i]pyrene.Dibenzo-

[c,g]carbazole,7H-.

Dibenz- (a,h)acridineDibenz- (ah)ant,

hracene.Dibenz[a,j] acridineDiethyl-p-nitrophenyl

phosphate.Diethylstibestrol ........Dimethyl sulfate .......Dimethybenzidine,

3,3'-.Dimethyl- benz(a)-

anthracene, 7,12-.

0.02(1)

0.0130.010.008

(1)0.050.000034

(1)(1)

( )(I)

0.007

(I)(1)

0.0025(1)

(1)

20(1)(1)(I)(1)0.00004

(1)(1)(I)

(1)

(1)

(1)

0.2(1)100.1

(1)(1)(,)

0.000058(1)

0.000081(1)

.............................. i

(1)

0.1

(1)

(1)(,)

(,)(1,)

(1)(I)

0.042(1)

S .............................. i

! .............................. i

(1)

(I)(1)I')(U)(1)

(1)(I)(1)

(1)

(,)

(1)

(1)

(,)

(1)(,)(,)

(1)

(1) ()

0.02(1)

S ..............................

0.010.008

(1)

0.000034(1)(1)

(,)

(,)

0.007

(1)(. )

0.0025(1)

S..............................

i ..............................

0.000013

(1)

20(1)

()

(1)

.)(1)(1)

(1)

(1)

0.1

(1)

S 0.5

(1)

0.1

(I)(1)

(I)

(I)

.... ... ... ... ... . : ... .. .. ... ... ............... . .............................. i .............................. i ............................... . . . . . . . . . . . . . . I .. . . . . . . . . . . . . . . I . . . . . .................. I................. . . . . . . ................................ ............... ............... .... ..... 0 .0 1 ...... I ....... 0 .0 .1 . ..... I ..............................

0.00003

(1)

0.0078(1)

0.0033

0.00037

0.02(1)

0.0130.01

(1)0.050.000034

(1)(1)

(1)

()0.0070.0005

(1)(1)0.0025

(I)

.............................. i

..............................

(1)

20(1)(1)(,)(,)

0.00004()(1)(1)

(1)

(1)

0.1

(1). ............. .............

0.210

0.1

(,)(1)(1)

0.000058(1)0.000081

(1)..............................

................. ........ ................ .... ....................... .0.084 0.00003 0 .000030.084

(1)

1

0.7

0.039

( ) (,.

0.0078(1)0.0033

0.00037

0.0078(1)0.0033

0.00037

(1)

(1)

0.7

0.039

(1)

0.10.008

(1)

(,)(,)

(1)(I)

(,)(1)

0.042(1)

(1)......

i ..............................

S ..............................

(1)(1)(1)(1)(I)

(1)(I)

(1)

(1)

(1)

(1)

(,)

(,)

(1)(1)(I

(1)

(')

i ..............................

(1)

0.01

(1)0.000034

(1)(1)

(1)(1)

0.007

(I)(. )

0.0025(1)0.0000230.00020.00020.00080.0000130.0005

(1)

20(,)(1)(1)(1)

(1)(1)(1)

(1)

(,)

0.1

(I)

(1)(1)

0.1

('1(1)

(1)(,)

(1)

0.001

0.00020.00020.01

0.00020.00003

0.001(1)

0.0078(1)0.0033

0.00037




TABLE B.--QUANTITATION-BASED CONDITIONAL EXIT LEVELS-Continued


CAS No. Name Wastewater Nonwastewater Wastewater Nonwastewater

Totals Totals Leach Totals Totals Leach(mg/) (mg/kg) I (mg/) (mg/I) (mg/kg) I (mg/I)

79-44-7 ..........

119-90-4 ........

100-25-4 ........534-52-1 ........541-53-7 ........145-73-3.51-43-4 ..........62-50-0 ..........

96-45-7 ..........151-56-4 ........

52--85-7 ..........640-19-7 ........62-74-8 ..........

16984-48-8 ....50-00-0 ..........765-34-4 ........76-44-_ .........118-74-1 ........70-30-4 ..........757-58-4 ........

302-01-2.193-39-5 ........

465-73-6 ........143-50-0 ........303-43-4 ........108-31-6.148-82-3.74-93-1 ..........16752-77-5 ....1338-23-4 ......

60-34-4 ..........91-57-6 ..........

75-55-8 ..........56-49-5 ..........

101-14-4 ........

70-25-7 ..........

56-04-2 ..........50-07-7 ..........86-88-4....

88-74-4 ..........99-09-2 ..........55-86-7 ..........51-75-2 ..........

126-85-2 ........

302-70-5.

55-63-0 ..........110-02-7 ........79-46-9 ..........55-18-5 ..........62-75-9 ..........924-16-3.

10595-95-6 ....

1116-54-7 ......

621-64-7 ........

Dimethylcarbamoylchloride.

Dimethy- oxyben-zidine, 3,3'-.

Dinitrobenzene, 1,4-Dinitro-o-cresol, 4,6-Dithiobiuret ...............Endothall ..................Epinephrine .............Ethyl

methanesulfonate.Ethylene thiourea .....Ethyleneimine

(aziddine).Famphur ...................Fluoracetamide, 2- ...Fluoracetic acid, so-

dium salt.Fluoride ....................Formaldehyde ..........Glycidylaldehyde ......Heptachlor ................Hexachlorobenzene .Hexachlorophene .....Hexaethyl

tetraphosphate.Hydrazine .................indeno(1,2,3-

cde)pyrene.Isodrin ......................Kepone .....................Lasiocarpine .............Maleic anhydride.Melphalan .......Methanethiol ............Methomyl .................Methyl ethyl ketone

peroxide.Methyl hydrazine ......Methyl naphthalene,

2-.Methylazindine, 2-Methylcholanthrene,

3-.Methylenebis, 4,4'-

(2-chloroaniline).Methyl-nitro-

nitrosoguanidine(MNNG).

Methylthiouracil ........Mitomycin C .............Naphthyl-2-thiourea,

1-.Nitroaniline, 2-. .........Nitroaniline, 3- ..........Nitrogen mustard .....Nitrogen mustard hy-

drochloride salt.Nitrogen mustard N-

Oxide.Nitrogen mustard N-

Oxide, HCI salt.Nitroglycerine ...........Nitrophenol, 4- .........Nitropropane, 2-. ......Nitrosodiethylamine .NitrosodimethylamineNitrosodi-n-butyl-

amine.Nitrosomethylethyla-

mine.N-

Nitrosodiethanola-mine.

N-Nitrosodi-n-propyamine.

(,)(1)(1)

0.018

(I)(1)

0.040.05

(1)..............................

(1)

(. )(1)

(1) (1)

.............................. ..............................(1) (1)

0.040.05

(1)0.1

(t)

(I)(1)

0.02(1)(1)

..............................

0.023(1)0.000040.00160.21

(1)

(1)

0.020.016

(1)(1)()()

0.05(I)

(1)

0.01

(I)

0.01

(1).

(1)

(1)(1)(,)

0.050.05

()(,)

(1)

(1)

(,)

0.050.00580.0020.00060.06

0.028

0.01

0.026

0.21(1)

(1)

0.000043

0.016

..............................

(1)

(I)

0.01

(,)

(1)(1)

0.01(1)

(1)

(1)

0.050.05

.()(1)

(I)

(1)

(1)0.05

0.0020.00060.06

0.028

0.01

0.026

0.040.05

(1)0.1

(1)

0.02(I)(I)

i ..............................

0.023(1) f0.000040.00160.21

(1)

(1)

0.020.016

(I)

()(1)(,)0.05

(1)

(1)

0.01

(1)0

0.01

(I)

(I)

(1)(I)(I)

0.050.05

(1)()(I)

(1)

(I)0.050.00580.0020.00060.06

0.028

0.01

0.026

(I)(I)(1)

0.018

(I)(1)

(1)(I)i .............................. i

(1)

2(1)

0.097(1)

(1)(,)

(1)

(1)

(1)0.046

(1)

(1)

(1)(1)(1)

(,)(1)

(I)

(1)

(1)

0.074

0.040.05

(1)(. )

(1)

(1)

0.00160.21

(1)

(1)

0.000043

0.016(I)(I)(1)

(1)

(1)

(1)

0.01

(1)

0.01

(1)

(I)

(1)(1)(I)

0.050.05

(1)

(1)

(I)

(1)

0.05

0.0020.0006

0.06

0.028

0.01

0.026

2(1)

0.097(1)

(I)(1)

(1)

(I)

(1)

0.046

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)0.074

0.7



66464 Federal Register / Vol. 60, No. 245 / Thursday, liecember 21, 1995 / Proposed Rules

TABLE B.--QUANTITATION-BASED CONDITIONAL EXIT LEVELS-Continued


CAS No. Name Wastewater Nonwastewater Wastewater Nonwastewater

Totals Totals Leach Totals Totals Leach(mg/I) (mg/kg) (mg/I) (mg/I) (mg/kg) (mg/I)

4549-40-0 ......

759-73-9 ........

615-53-2 ........

16543-55-8 ....100-75-4 ........930-55-2 ........13256-22-9 ....103-85-5 ........1615-80-1 ......20816-12-082-68-8 ..........

85-01-8 ..........62-38-4 ..........

298-06-6 ........

3288-58-2 ......

2953-29-9 ......

85-44-9 ..........1336-36-3 ......

1120-71-4 ......

108-46-3.81-07-2 ..........18883-66-4 ....57-24-9 ..........1746-01-6 ......107-49-3 ........

62-55-5 ..........79-19-6 ..........62-56-6 ..........137-26-8.7440-31-5 ......584-84-9 ........95-80-7 .........95-53-4 ..........106-49-0.8001-35-2.75-70-7 ..........126-72-7.

52-24-4 ..........

72-57-1 ..........66-75-1 ..........75-01-4 ..........81-81-2 ..........

N-Nitrosomethy vinylamine.

N-Nitroso-N-ethylurea.

N-Nitroso-N-methylurethane.

N-NitrosonomicotineN-NitrosopiperidineN-NitrosopyrrolidineN-NitrososarcosineN-Phenylthiourea .....N,N-DiethylhydrazineOsmium tetroxide.Pentachloronitroben-

zene (PCNB).Phenanthrene ..........Phenyl mercuric ace-

tate.Phosphorodithioic

acid,dimethylethylester.

Phosphorodithioicacid, o-o-diethylester.

Phosphorodithioicacid, o-o-diethyl-s-methlyl.

Pyhosphorodithioicacid, tnmethylester.

Phthalic anhydride ...Polychlorinated

biphenyls.Propane sultone,

1,3-.Resorcinol ................Saccharin and salts .Streptozotocin ..........Strychnine ................TCDD, 2, 3, 7.8- ......Tetraethyl

pyrophosphate.Thioacetamide.Thiosemicarbazide ...Thiourea ...................Thiram ......................T in ............................Toluene diisocyanateToluenediamine, 2,4-Toluidine, 0- .............Toluidine, p-- .............Toxaphene ...............TrichloromethanethiolTris (2, 3-

dibromopropyl)phosphate.

Tris (1-azridinyl)phosphine sulfide.

Trypan blue ..............Uracil mustard ..........Vinyl chloride ...........W arfarin ...................

(1)

(I)

(I)

0.00140.0047

(1)(I)(1)

3

0.006(1)

(1)

(1)

(1)

(1)

(1)0.0005

(1)

0.1(,)(I)

1 .012E-08(1)

0.17

(1)(1)0.058

(I)0.0130.0120.0170.0013

(1)

0.025

(1)

(1)(1)

0.05

1No testing required; additional LDR requirements apply.

(1)

(1)

(1)

(,)

0.033(I)(1)(I)

200

(I)

(1)

(1)

(1)

(1)

' (1)

7(1)(1)

3

(1)

(1)

500

1

0.03

(1)

(1)

(1)(I)

(1)

(1)

(I)

(1)0.00140.0047

(I)(,)(1)

30.02

0.006(. )

(1)

(1)

(1)

(I)

(1)

(,)

(1)

(1)

(1)

(I)

8(1)

0.0130.0120.017

(1)0.025

(1)

(1)(1)

(1)

(1)

(1)

(1)0.00140.0047

(1)(I)(1)

3

0. 006(t)

(I)

()

(1)

(1)

(1)

0.0005

(I)

0.1(1)(1)

1.OOOE-08(1)

0.13

(I)(I)

0.058

(1)0.0130.0120.0170.0013

(1)0.025

(1)

(1)(1)

0.000170.05

(1) D(')

(1)

(I)

(I)

0.033

(1)(1)(I)

200

(1)

(I)

(1)

(1)

(1)

(1)(1)(,)

500

1

0.03(1)

(I)

(1)

(1)0.00140.0047

(,)(I)(1)30.02

0.006()

(1)

(I)

(1)

(1)0.0005

(I)

(I)(I)

1.OOOE-08(1)

(1)(1)

8(I)

0.0130.0120.017

(1)0.025

(1)

(,)(1)

PART 266-STANDARDS FOR THEMANAGEMENT OF SPECIFICHAZARDOUS WASTES AND SPECIFICTYPES OF HAZARDOUS WASTEFACILITIES

Authority: 42 U.S.C. 6905, 6912(a), 6924,and 6934.

10. Section 266.20 is amended by

revising the first sentence of paragraph(b) to read as follows:

9. The authority citation for part 266* * * *

continues to read as follows:

(b) Products produced for the generalpublic's use that are used in a mannerthat constitutes disposal and thatcontain recyclable materials are notpresently subject to regulation if, foreach hazardous constituent in eachrecyclable material (i.e., hazardouswaste) that they contain, they meet the



Federal Register./ Vol. 60, No. 245 / Thursday, December 21, 1995 / Proposed Rules

applicable exit levels in appendix X toPart 261 of this chapter. * * *

PART 268-LAND DISPOSALRESTRICTIONS

11. The authority citation for part 268continues to read as follows:

Authority: 42 U.S.C. 6905, 6912(a) 6921,and 6924.

12. Section 268.2 is amended byadding paragraph (j) to read asfollows:* * * * *

(j) Land treatment means waste isapplied onto or incorporated into thesoil surface.

13. Section 268.40 is amended byrevising the first sentence of paragraph(a), revising paragraph (e), and addingparagraph (g) to read as follows:

§ 268.41 Applicability of treatmentstandards

(a) Except as provided in paragraph(g) of this section, a waste identified inthe table "Treatment Standards forHazardous Wastes" may be landdisposed only if it meets therequirements found in the table. **** * * * *

(e) Except as provided in paragraph(g) of this section, for all characteristic

wastes (DO01, D002, and D012-D043)that are subject to treatment standardsin the following table "TreatmentStandards for Hazardous Wastes," allunderlying constituents (as defined in§ 268.20(i)) must meet UniversalTreatment Standards, found in § 268.48,Table UTS, prior to land disposal.* * * * *

(g) Wastes subject to either thetreatment standards described inparagraph (a)(1) or (a)(2) of this sectionorithe Universal Treatment Standardsdescribed in paragraph (e) of thissection may be land.disposed if theymeet either of the alternative, risk-basedstandards found in subpart F and G ofthis part and representing levels atwhich threats to human health or theenvironment are minimized.

14. Part 268 is amended by addingSubpart F consisting of § 268.60 to readas follows:

Subpart F-Minimize Threat LevelsWithout Management Requirements

§268.60 Minimize threat levels.(a) Table "Minimize Threat Levels"

identifies risk-based standardsrepresenting levels at which threats to

human health and the environment areminimized. These levels may be used asalternatives to waste-specific treatmentstandards in the table to § 268.40 and tothe Universal Treatment Standards inthe table to § 268.48. Nonwastewatersmust meet both the total and wasteextract levels contained in the table of"Minimize Threat Levels".

(b) Wastes identified in the Table to§ 268.40 may be land disposed if theymeet either the requirements in thatTable or the standards in the MinimizeThreat Table for all constituents.Characteristic wastes that are subject tothe requirement for meeting UniversalTreatment Standards under § 268.40(e)must also meet the requirements ofTable UTS or the Minimize Threat Tablefor all underlying hazardousconstituents as defined in § 268.2(i).

(c) Wastes containing either regulatedhazardous constituents under the Tableto § 268.40 or UTS constituents whichdo not have treatment standards listedin the Minimize Threat Table mustcontinue to comply with treatmentstandards for these constituents in thetables to § 268.40 or § 268.48 prior toland disposal.

268.60 TABLE 1.-MINIMIZE THREAT LEVELS

WW standard NWW standard NWW standardCAS Constituent name (mg/I) (mg/kg) (mg/I)

Acenaphthene .................................................................................Acetone .......... ...................................................................... .Acetonitrile .......................................................................................Acetophenone .................................................................................Allyl chloride ....................................................................................Barium .............................................................................................Benzene ..........................................................................................Bis(2-ethylhexyl)phthalate ...............................................................Bromodichloromethane ...................................................................Bromoform (Tribromomethane) .......................................................Butanol ............................................................................................Butyl-4.6-dinitrophenol, 2-sec- (Dinoseb) .......................................Butylbenzylphthalate .......................................................................Carbon disulfide ..............................................................................Carbon tetrachloride ........................................................................Chloro-1,3-butadiene, 2- (Chloroprene) ..........................................Chloroaniline, p- ..............................................................................Chlorobenzene ................................................................................Chlorodibromomethane ...................................................................Chloroform ............................................................................. .Chlorophenol, 2-. .............................................................................Chrysene .........................................................................................Cresol, m- ........................................................................................Cresol, o- .........................................................................................Cresol, p- .........................................................................................Di-n-butyl phthalate .........................................................................Di-n-octyl phthalate .........................................................................Dichlorobenzene, 1,2-. ....................................................................Dichlorobenzene, 1,4- .....................................................................Dichlorodifluoromethane .................................................................Dichloroethane, 1,1-. .......................................................................Dichloroethylene, trans-1,2- ............................................................Dichlorophenol, 2,4- ...................................................................Dichlorophenoxyacetic acid, 2,4- (2,4-D) ........................................Diethyl phthalate .............................................................................Dimethyl phthalate ..........................................................................

3116

17

33

..............................

..............................

160.19

240,..............................

0.52S..............................

2

|..............................

0.90.1880.84

23015

15

30.622

19078

950017000

9201200260

210011023019

17018000

77087

3309

290140

250028

7100

3522000270002600

900004500

5000064

810024

14000770

31004500

560.36

160.00540.00110.00250.01860.064

6460.0016

..............................

0.1610.00180.0170.320.0012330.32

250.160.011

120.000061

0.180.6

54

83-32-9 .......67-64-1 .......75-05-8 .......98-86-2 .......107-05-1 .....7440-39-3 ...71-43-2 .......117-81-7 .....75-27-4 .......75-25-2 .......71-36-3 .......88-85-7 .......85-68-7 .......75-15-0 .......56-23-5 .......126-99-8 .....106-47-8 .....108-90-7 .....124-48-1 .....67-66-3 .......95-57-8 .......218-01-9 .....108-39-4 .....95-48-7 .......106-44-5 .....84-74-2 .......117-84-0 .....95-50-1 .......106-46-7 .....75-71-8 .......75-34-3 .......156-60-5 .....120--83-2 .....94-75-7 .......84-66-2 .......131-11-3 .....

66465



'66466 Federal Register / Vol. 60, No. 245 /'Thursday, December 21, 1995 f prqposed Rules

268.60 TABLE 1.-MINIMIZE THREAT LEVELS-Continued

CAS Constituent name WW standard NWW standard NWW standard

I (mg/I) (mglkg) I (mg/)

105-67-9 .....51-28-5 .......121-14-2 .....606-20-2 .....1.22-39-4 .....298-04-4 .....72-20-8 .......141-78-6 .....60-29-7 .......97-63-2 .......100-41-4 .....206-44-0 .....86-73-7 .......76-44-8 .......87-68-3 .......319-85-7 .....58-89-9 .......77-47-4 .......67-72-1 .......78-83-1 .......7439-92-1 ...7439-97-6 ...67-56-1 .......72-43-5 .......74-83-9 .......74-87-3 .......78-93-3 .......108-10-1 .....80-62-6 .......298-00-0 .....74-95-3 .......75-09-2 .......91-20-3 ....7440-02--098-95-3 .......56-38-2 .......608-93-5 .....82-68-8 .......108-95-2 .....298-02-2 .....23950-58-5.129-00-0 .....110-86-1 .....7782-49-2 ...7440-22-4 ...95-94-3 .......630-20-6 .....79-34-5 .......127-18-4 .....58-90-2 .......7440-28-0 ...108-88-3 .....76-13-1 .......120-82-1 .....71-55-6 .......79-00-5 .......79-01-6 .......75-69-4 .......95-95-4 .......88-06-2 .......93-76-5 .......93-72-1 .......96-18-4 .......7440-62-2 ...1330-20-7 ...7440-66-6 ...

Dimethylphenol, 2,4- .................................................................Dinitrophenol, 2,4- ..........................................................Dinitrotoluene, 2,4-. .........................................................................Dinitrotoluene, 2,6-. .........................................................................Diphanylamine .................................................................................Disulloton ........................................................................................Endrin ..............................................................................................Ethyl acetate ...................................................................................Ethyl ether .......................................................................................Ethyl methacrylate .......................... * ...........................................Ethylbenzene ...................................................................................Fluoranthene ...................................................... : ............................Fluorene ..........................................................................................Heptachlor .......................................................................................Hexachloro-1,3-butadiene ...............................................................Hexachlorocyclohexane, beta- (beta-BHC) ....................................Hexachlorocyclohexane, gamma- (Lindane) ...................................Hexachlorocyclopentadiene ...........................................................Hexachloroethane ...........................................................................Isobutyl alcohol ...............................................................................Lead ................................................................................................Mercury .......................................................................................Methanol .........................................................................................Methoxychlor ...................................................................................Methyl bromide (Bromomethane) ...................................................Methyl chloride (Chloromethane) ....................................................Methyl ethyl ketone .........................................................................Methyl isobutyl ketone ....................................................................Methyl methacrylate ........................................................................Methyl parathion ..............................................................................Methylene bromide ...........................................................................Methylene chloride ..........................................................................Naphthalene ....................................................................................Nickel ..........................................................................................Nitrobenzene ...................................................................................Parathion .........................................................................................Pentachlorobenzene .......................................................................Pentachloronitrobenzene (PCNB) .......... : ........................................Phenol .............................................................................................Phorate ............................................................................................Pronamide .......................................................................................Pyrene ......................... ...... ............. ..............Pyridine ..........................................................................................Selenium ........................... ...... .......... .... .........Silver ...............................................................................................Tetrachlorobenzene, 1,2,4,5- ..........................................................Tetrachloroethane, 1,1,1,2-. ............................................................Tetrachloroethane, 1,1,2,2-. ............................................................Tetrachloroethylene .................... ................................................Tetrachlorophenol, 2,3,4,6- ..... .................................................Thallium (I) ............................... ................................................Toluene ...........................................................................................Trichloro-1,2,2,-trifluoroethane, 1,1,2-. ............................................Trichlorobenzene, 1,2,4- .................................................................Trichloroethane, 1,1,1- .....................................................................Trichloroethane, 1,1,2- ....................................................................Trichloroethylene .............................................................................Trichlorofluoromethane ...................................................................Trichlorophenol, 2,4,5- ....................................................................Trichlorophenol, 2,4,6- ....................................................................Trichlorophenoxyacetic acid, 2,4,5- (245-T) ..................................Trichlorophenoxypropionic acid, 2,4,5- (Silvex) ..............................Trichloropropane, 1,2,3-. .................................................................Vanadium ........................................................................................Xylenes (total) .................................................................................Zinc .................................................................................................

.40.27

15

0.073

39027-24392822

0.00044

3930

0.37870.37

788

28

0.662

14110.084350.081

840.11

2154

0.160.93

2000;23

22

30.2200

0.6974

48180.05421110

2299

11000

21086

1200043

0.2627600041000

3400550000

600090000

836

0.120.1

150081

55000570

0.6140000

19500

911100001700040000

8400310

120000110

45

160000160440

16000810

170

13029

130006200

5180000

350048000

11570

2600012000

12063

870250

170000320

1

0.110.0643

1332

110117823

0.00690.000210.69

0.0331512

0.1430

0.92303

8

0.190.015350.032

32

620.06

0.0320.00780.00770.680.580.019

13

10.0540.00180.013

1640.0150.64

0.344

15038




15. Part 268 is amended by addingsubpart G consisting of §§ 268.70 and268.71 to read as follows:

Subpart G-Cenditioned MinimizeThreat Levels with ManagementRequirements

§2W.70 Conditioned Minimize ThreatLevels.

(a) Table "Conditioned MinimizeThreat Levels" identifies risk-basedstandards representing levels at whichthreats to human health and theenvironment are minimized for wasteswhich are placed in landfills ormonofills (but not land applicationunits). These l3vels may be used asalternatives to waste-specific treatment

standards in the table to § 268.40 and tothe Universal Treatment Standards inthe table to § 268.48 for wastes whichcomply with the requirements of§ 268.71. Nonwastewaters must meetboth the total and waste extract levelscontained in the table of "MinimizeThreat Levels".

(b) Wastes identified in the Table to§ 268.40 may be land disposed if theymeet, for all hazardous constituentsidentified in the table to § 268.40, eitherthe requirements in that table, thestandards in the Minimize Threat Tablein subpart F, or, if they meet therequirements in § 268.71, the standardsin the Conditioned Minimize ThreatTable. Characteristic wastes that aresubject to the requirement for meeting

Universal Treatment Standards under§ 268.40(e) must also meet therequirements of Table UTS, theMinimize Threat Table, or, if they meetthe requirements of § 268.71, theConditioned Minimize Threat Table, forall underlying hazardous constituents asdefined in § 268.2(i).

(c) Wastes containing either regulatedhazardous constituents under the Tableto § 268.40 or UTS constituents whichdo not have treatment standards listedin the Minimize Threat Table mustcontinue to comply with treatmentstandards for these constituents in thetables to § 268.40, § 268.48, or theMinimize Threat Table to Subpart Fprior to land disposal.

268.70 TABLE 1.-CONDITIONAL MINIMIZE THREAT LEVELS

CAS Constituent name WW standard NWW standard NWW standard

I (mg/I) (mg/kg) (mg/I)

Acenaphthene ....................................................................... .Acetone ...........................................................................................Acetonitrile .......................................................................................Acetophenone .................................................................................Allyl chloride ....................................................................................Aniline ..............................................................................................Barium .............................................................................................Benzene ............................................Bis (2-chloroisopropyl) ether ...............................Bis(2-ethylhexyl)phthalate ...............................................................Bromodichloromethane ...................................................................Bromoform (Tribromomethane) .......................................................Butanol ............................................................................................Buthl-4,6-dinitrophenol, 2-sec- (Dinoseb) .......................................Butylbenzylphthalate .......................................................................Cadmium .........................................................................................Carbon disulfide .............................................................................Carbon tetrachloride ........................................................................Chloro-1,3-butadiene, 2-(Chloroprene) ...........................................Chloroaniline, p- ...............................................................................Chlorobenzene ................................................................................Chlorodi- bromomethane ..............................................................Chloroform ...................................................................................Chlorophenol, 2-. .............................................................................Chromium ........................................................................................Chrysene .........................................................................................Cresol, m- ........................................................................................Cresol, o- .........................................................................................Cresol, p- .........................................................................................DDD .................................................................................................DDT ....................................................................................... .Di-n-butyl phthalate .........................................................................Di-n-octyl phthalate .........................................................................Dichlorobenzene, 1,2-. ....................................................................Dichlorobenzene, 1,4- . ....................................................................Dichloro- difluoro- methane .............................................................Dichloroethane, 1,1-. ................................. ............................ .Dichloroethane, 1,2-. .......................................................................Dichloro- ethylene, trans-i,2-. ........................................ : ................Dichlorophenol, 2,4- . .....................................................................Dichlorophen- oxyacetic acid, 2,4- (2,4-D) .....................................Dichloropropane, 1,2-. ....................................................................Dichloropropene, cis-1,3- ................................................................Dichloropro- pene, trans-1,3- ................................... t ......................Diethyl phthalate .............................................................................Dimethyl phthalate ..........................................................................Dimethylphenol, 2,4- . ......................................................................Dinitrophenot, 2,4-. ..........................................................................Dinitrotoluene, 2,4-. .........................................................................

3116

17

331 .-...........................

160.19

240

0.52S..............................

2

0.9

0.1880.84

230

15

15

30.622

19078

40.27

63000390002200

75000260170

34000250

97740240

1600410006000

87110

3800130

17005800

4100Q200

768500

1635

3000046000

29000.260.11

9000021000530000

6508400

11059

130000770

120001806562

19000

24000450

1400

1321

122

0.07245

0.0230.00880.00110.0110.081

210.24

670.32

240.0077

0.5660.00790.075120.0012

11111

68000.0054

250.1

320.06

450.000210.0002140.7620.011

1000010000

220

50.370.39

83-32-9 .......67-64-1 .......75-05-8 .......98-86-2 .......107-05-1 .....62-53-3 .......7440-39-3 ...71-43-2 .......39638-32-9 .117-81-7 .....75-27-4 .......75-25-2 .......71-36-3 .......88-85-7 .......85-68-7 .......7440-43-9 ...75-15-0 .......56-23-5 ...;...126-99-8 .....106-47-8 .....108-90-7 .....124-48-1 .....67-66-3 .......95-57-8 .......7440-47-3 ...218-01-9 .....108-39-4 .....95-48-7 .......106-44-5 .....72-54-8 .... *.50-29-3 .......84-74-2 .......117-84-0 .....95-50-1 .......106-46-7 .....75-71-8 .......75-34-3 .......107--06-2 .....156--60-5 .....120-83-2 .....94-75-7 .......78-87-5 .......10061-01-510061-02-684-66-2 .......131-11-3 .....105-67-9 .....51-28-5 .......121-14-2 .....

66467




268.70 TABLE 1.-CONDITIONAL MINIMIZE THREAT LEVELS-Continued

CAS Constituent name WW standard NWW standard NWW standard(mg/) (mg/kg) (mg/I)

606-20-2 .....122-39-4 .....298--04-4 .....72-20-8 .......141-78-6 .....60-29-7 .......97-63-2 .......100-41-4 .....206-44-0 .....86-73-7 .......76-44-8 .......1024-57-3 ...87-68-3 .......319-84-6 .....319--85-7 .....58-89-9 .......77-47-4 .......67-72-1 .......78-83-1 .......7439-92-1 ...7439-97-6 ...67-56-1 .......72-43-5 .......74-83-9 .......74-87-3 .......78-93-3 .......108-10-1 .....80-62-6 .......298-00-0 .....74-95-3 .......75-09-2 .......86-30-6 .......91-20-3 .......7440-02-0 ...98-95-3 .......152-16--9 .....56-38-2" .......608-93-5 .....82-68-8 .......87-86-5 .......108-95-2 .....298-02-2 .....23959-58-5 .129-00-0 .....110-86-1 .....94-59-7 .......7782-49-2 ...7440-22-4 ...95-94-3 .......630.20-6 ......79-34-5 .......127-18-4 .....53-90-2 .......7440-28-0 ...108-88-3 .....76-13-1 .......120-82-1 .....71-55-6 .......79-01-6 .......75-69-4 .......95-95-4 .......88-06-2 .......93-76-5 .......93-72-1 .......96-18-4 .......7440-62-2 ...1330-20-7 ...7440-66-6 ...

Dinitrotoluene, 2,6-. .........................................................................Diphenyla- mine ..............................................................................Disulfoton ........................................................................................Endrin ..............................................................................................Ethyl acetate ...................................................................................Ethyl ether .......................................................................................Ethyl methacrylate ...........................................................................Ethylbenzene ...................................................................................Fluoranthene ...................................................................................Fluorene ..........................................................................................Heptachlor ......................... .......................................................Heptachlor epoxide .........................................................................Hexachloro-1,3-butadiene ...............................................................Hexachloro- cyclohex- ane, alpha- (alpha-BHC) ............................Hexachloro- cyclohex- ane, beta- (beta-BHC) ................................Hexachloro- cyclohex- ane, gamma- (Lindane) ..............................Hexachloro- cyclopent- adiene .......................................................Hexachloroethane ...........................................................................Isobutyl alcohol ...............................................................................Lead ................................................................................................Mercury ...........................................................................................Methanol ..........................................................................................Methoxychlor ...................................................................................Methyl bromide (Bromo- methane) .................................................Methyl chloride (Chloro- methane) .................................................Methyl ethyl ketone .....................................Methyl isobutyl ketone ....................................................................Methyl methacrylate ........................................................................Methyl parathion ..............................................................................Methylene brom ide ..........................................................................Methylene chloride ................................................... : ......................N-Nitrosodi- phenylamine ................................................................Naphthalene ....................................................................................Nickel ........................................................................................Nitrobenzene ...................................................................................Octamethyl- pyrophos- phoramide ...................... ...........................Parathion .........................................................................................Pentachlorobenzene .......................................................................Pentachloro- nitrobenzene (PCNB) ................................................Pentachlorophenol .........................................................................Phenol .............................................................................................Phorate ............................................................................................Pronamide .......................................................................................Pyrene .............................................................................................Pyridine ...........................................................................................Safrole .............................................................................................Selenium .........................................................................................Silver ...............................................................................................Tetrachloro- benzene, 1,2,4,5-. .......................................................Tetrachloro- ethane, 1,1,1,2- . .........................................................Tetrachloro- ethane, 1,1,2,2- ..................................................Tetrachloro- ethylene ......................................................................Tetrachloro- phenol, 2,3,4,6- ......................................................Thallium (I) ......................................................................................Toluene ...........................................................................................Trichloro-1,2,2,-trifluoroethane, 1,1,2-. ............................................Trichlorobenzene, 1,2,4- . ................................................................Trichloroeth- ane, 1,1,1-.. . .............................................................Trichloroeth- ylene .........................................................................Trichlorofluo- romethane .................................................................Trichlorophenol, 2,4,5- . ...................................................................Trichlorophenol, 2,4,6- ....................................................................Trichlorophenoxyacetic acid, 2,4,5-(245-T) ....................................Triclorophen- oxypropionic acid, 2,4,5- (Silvex) .............................Trichloropro- pane, 1,2,3- ...............................................................Vanadium ....................................... . .................. ..................Xylenes (total) .................................................................................Zinc ..................................................................................................

15

0,0733902724392822

0.00044

39300.37870.3778828

0.662

14110.084

3.5

0.081

840.11

2154

0.16

0.93200

0.23

22

302200

0.69

48180.0542111"0

2299

42012000

5827

600000260000100000

2100090000

.8

0.56290

0.180.640.75

1500890

1200001600

39310000

280

85091

25000038000

1000006

21000'720

3600430000

86005203119

22390000

510230000

16000930

28

160037070

10000035000

. 33560000

62000190

3200170000

55000160150520

140002700

71000051000

0.2215

120770 10510

37274227

.................... ........

100.006920.00099

0.115341

0.4110

4

11011

33110

0.190.0530.24

1514

0.110.37

160000

0.0022110252

0.210.0044

0.032'0.0420.0077320.071

5112000

30.00770.049

61220.068221

13

700130




§ 268.71 Associated ManagementRequirements.

Waste may meet the standards set outin the Conditional Minimize ThreatTable as an alternative to the treatmentstandards in the tables to Subpart D of

this part or the Minimize Threat Table set forth in subpart F of this part or theto subpart F of this part only if they are treatment standards set forth in subpartplaced in a landfill or a monofill as D of this part.defined in 40 CFR 260.10. Waste that is [FR Doc. 95-29458 Filed 12-20-95; 8:45 am]placed in land application units mustcomply with the minimize threat levels BILLING CODE 6560-60-P

66469

