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SUBJECT: Amended Record of Decision (ROD) for Mid
Superfund Site
America Tanning Company
FROM: Michael I Sanderson .Director, Superfund Division
Dennis Grams, P.E. Regional Administrator
Attached is an Mended operated as a hideCompany Superfimd Site.
During ated8 wastewater stream which contaminated thetanning
facility. The tanning operat .8 ., . mium jhe U.S.
Environmentalonsite treatment system and Decision jn 1991 which
called for the solidificationProtection Agency (EPA) issued * ^
soil capping. The EPAof contaminated sludges, sediments _ J . (rd)
in 1993. Data obtained during the subsequently went on to complete
a Renje 8 t > revealed that the clay-linedRD and a Potentially
Responsewhen they were disturbed. Air impoundment areas on-site
wereSere to be remediated as originally
heptane >eve,s of hydrogen su.hde gas wouM be leased
during the solidification process.
remedy which is outlined in the amendment t ... . re
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MEMORANDUM
SUBJECT: Amended Record of Decision (ROD) for Mid-America
Tanning CompanySuperfund Site
FROM: Michael J. SandersonDirector, Superfund Division
TO: Dennis Grams, P.E.Regional Administrator
Attached is an amended Record of Decision (ROD) for the
Mid-America Tanning Company Superfund Site. During the 1970s and
80s, Mid-America Tanning operated as a hide tanning facility. The
tanning operations generated a wastewater stream which contaminated
the On-site treatment system and surrounding soils with chromium.
The U.S. Environmental Protection Agency (EPA) issued a Record of
Decision in 1991 which called for the solidification of
contaminated sludges, sediments and soils on-site followed by soil
capping. The EPA subsequently went on to complete a Remedial Design
(RD) in 1993. Data obtained during the RD and a Potentially
Responsible Party-lead Removal in 1994, revealed that the
clay-lined impoundment areas on-site were releasing hydrogen
sulfide gas when they were disturbed. Air sampling and modeling
data indicated that if the site were to be remediated as originally
recommended in the ROD, that unacceptable levels of hydrogen
sulfide gas would be released during the solidification
process.
In response to this concern, the EPA evaluated the remedy and
identified an alternative remedy which is outlined in the amendment
to the ROD. The amended remedy is equally as protective of human
health and the environment and will also reduce the potential for
hydrogen sulfide gas emissions. In addition, the amendment to the
ROD addresses some areas of the site which were not included in the
original remedy, but which will need to be remediated. These areas
include the wet well area, aeration basin, final clarifier, filter
press building and miscellaneous soils and debris.
The EPA held a public comment period to allow the community to
comment on the proposed plan. In addition, the EPA offered to hold
a public availability session to address comments on the proposed
plan. No comments were received regarding the proposed ROD
amendment nor were there any requests to hold a public availability
session.
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SUPRSANDERSON
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In summary, the amended remedy addresses the health and safety
concern raised by the presence and potential for hydrogen sulfide
emissions, addresses all areas of the site requiring remediation,
is equally as protective of human health and the environment, and
will provide a more cost-effective remedy for the site.
Please let me know if you have any questions or would like
additional clarification.
Attachment
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DECLARATIONRECORD OF DECISION AMENDMENT FOR THE
MID-AMERICA TANNING COMPANY SUPERFUND SITE WOODBURY COUNTY,
IOWA
JULY 1996
SITE NAME AND LOCATION
Mid-America Tanning Company Superfund Site Woodbuiy County,
Iowa
INTRODUCTION
The United States Environmental Protection Agency (EPA) is
amending the Record of Decision (ROD) for the Mid-America Tanning
Company Superfund Site. On September 24, 1991, a ROD was issued for
the Mid-America Tanning Company Site located in Woodbuiy County,
Iowa. The ROD presented the remedy selected by the EPA for this
site, which called for in-situ immobilization of the
densely-contaminated sediments in the east and west aeration
lagoons and the northeast field in conjunction with the placement
of soil-clay caps over the less densely-contaminated source areas.
Impoundment waters were to be treated as necessary and either
discharged to the nearby oxbow lake or transported off site to a
Publicly Owned Treatment Works (POTW). As a result of information
which has been developed subsequent to the issuance of the ROD, the
EPA has determined that fundamental changes to the remedy were
necessary. The amendment to the ROD describes and summarizes the
basis for these changes as well as documenting changes in the
remedy at the site.
The EPA is the lead agency for the site, and the Iowa Department
of Natural Resources (IDNR) has been designated the support agency.
The amendment to the ROD is being issued by the EPA with
concurrence by the state of Iowa.
The ROD amendment together with the original ROD presents the
selected remedial action for the site. This action was chosen in
accordance with the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 (CERCLA), as amended by the
Superfund Amendments and Reauthorization Act of 1986 (SARA), and
the National Contingency Plan (NCP). Section 117(c) of CERCLA
provides that after the adoption of a final remedial action plan,
if any remedial action is taken, or if any enforcement action under
section 106 or 122 is entered into, and such action, settlement or
decree differs in any fundamental respect from such final plans,
the lead agency shall publish an amendment to the ROD with the
reasons such changes were made. The ROD amendment will explain
these changes to the remedy. In accordance with the NCP, 40 C.F.R.
300.825 (a)(c)(21), this
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amendment and the information supporting these decisions are
part of the administrative record file and are available for public
review and comment. The administrative record file is available for
review at the the Sergeant Bluff City Hall, Sergeant Bluff, Iowa
and the EPA Region VH Office, Kansas City, Kansas.
DESCRIPTION OF THE AMENDED SELECTED REMEDY
The major components of the selected remedy, as amended,
include:
• Contaminated soils in the northeast Held will be consolidated
and/or excavated and consolidated with the Polishing Basin
sediments and covered with a soil/clay cap or geosynthetic cap such
as high-density polyethylene (HDPE) that achieves the same level of
performance;
• Sediments in the polishing basin and east and west aeration
lagoons will be dewatered. The dewatered sediments will then be
covered with a clay/soil cover or comparable geosynthetic cap;
• On-site treatment and discharge of impoundment water to the
nearby oxbow lake;
• Excavation of the burial trench material followed by on-site
stabilization and consolidation with the northeast field soils
prior to capping;
• Excavation of the contaminated soil areas, other than the
northeast field, and consolidation of this material with the
aeration lagoon sediments and/or polishing basin sediments prior to
capping;
• Removal of the sediments in the wet well, aeration basin, and
final clarifier and consolidation of this material with the
sediments in the aeration lagoons prior to capping. The emptied
basins will be decontaminated with high-pressure steam and
backfilled with clean soil;
• The filter press building along with other miscellaneous
contaminated debris will be decontaminated by washing these items
with a high-pressure steam cleaner. Wash water will be treated
on-site and discharged to the oxbow lake. Floor scrapings and
building residue will be disposed of in accordance with the
Resource Conservation and Recovery Act (RCRA); and
• Land use restrictions in the form of deed restrictions will be
instituted to limit future use of the property.
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STATUTORY DETERMINATIONS
The selected remedy as amended remains protective of human
health and the environment, complies with federal and state
requirements that were identified in the ROD as applicable or
relevant and appropriate to this remedial action and is cost
effective. In addition, the remedy, as revised, utilizes permanent
solutions and alternative treatment technologies to the maximum
extent practicable for this site. These changes to the remedy will
increase protectiveness of human health and environment, both short
term and long term.
Dennis Grams, P.E. DateRegional Administrator Environmental
Protection Agency Region VII
Attachment:
Decision SummaryResponsiveness Summary-Attachment A
t
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AMENDMENT TO THE
RECORD OF DECISION FOR THE
MID-AMERICA TANNING COMPANY SUPERFUND SITE
WOODBURY COUNTY, IOWA
Prepared by:
U.S. Environmental Protection Agency
Region VII
Kansas City, Kansas
July 1996
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Amended Record of Decision
Decision Summary
Contents
l.
Introduction........................................................................
......... . 1
n. Community
Relations.......................................................................
2m. Reasons for Issuing the ROD
Amendment..................................... 2
IV. Description of the New
Alternatives............................................... 3
V. Evaluation of
Alternatives...............................................................
5
VI. Statutory
Determinations................................................................
13
Responsiveness
Summary...............................................................
Attachment A
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DECISION SUMMARYRECORD OF DECISION AMENDMENT for the
MID-AMERICA TANNING COMPANY SUPERFUND SITE WOODBURY COUNTY,
IOWA
L INTRODUCTION
The Mid-America Tanning (MAI) Company Superfund Site is located
in Woodbury County, Iowa, approximately seven miles south of Sioux
City and four miles south of the town of Sergeant Bluff. The MAT
site occupies 98.7 acres of land in an industrial area known as the
Port Neal Industrial District. The site is bordered on the north by
Kind & Knox, a gelatin manufacturer, on the east by a Chicago
and Northwestern railroad right-of-way, and on the west and south
by agricultural land and public-use hunting grounds. The nearest
stretch of the Missouri River is approximately l.S miles to the
southwest.
The MAT Site operated as a hide tanning processor under several
different ownerships from 1970 until 1989. The tanning process
included fleshing,, brine curing and trimming of hides as well as
brine and chrome tanning. The tanning operations generated a
wastewater stream that contained dirt, brine, flesh, detergents,
hair, sulfides, ammonia, lime, grease and chromium. During a period
of the operation, contaminated sludges were buried in trenches and
land fanned on the site. The Environmental Protection Agency (EPA)
completed an Remedial Investigation/Feasibility Study (RI/FS) in
July 1991 and issued a Record of Decision (ROD) in September 1991.
The selected remedy in the ROD consisted of in-situ immobilization
of the densely-contaminated sediments in the east and west aeration
lagoons and the northeast field, placement of a soil-clay cap over
the less densely-contaminated source areas, and treatment and
discharge of contaminated impoundment waters. The EPA completed a
Remedial Design (RD) in 1993, and in 1994 the Foxley Cattle Company
was ordered to conduct a removal action at the site. Foxley
complied with the Order and completed the removal action in May
1995. While conducting the RD and subsequent removal action, EPA
determined that the sediments found in the clay-lined impoundment
areas were generating hydrogen sulfide gas at concentrations posing
significant health risks. Air sampling and modeling indicated that
unacceptable levels of hydrogen sulfide gas would be released
during the solidification process. In response to this concern, EPA
is amending the remediation to minimize disruption of the waste and
the release of hydrogen sulfide gas. The ROD amendment recommends
dewatering the impoundment areas using a system of wick drains and
then applying an improved cap to the area. In addition, the ROD
amendment addresses the need to remediate the sediments in the wet
well area, aeration basin and final clarifier. These sediments will
be consolidated with the aeration lagoon sludges and/or polishing
basin sediments and capped. The ROD amendment also provides for
decontamination of the filter press building and other debris on
site.
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U. COMMUNITY RELATIONS
The EPA is issuing this ROD Amendment to meet the public
participation provisions mandated under Section 117(a) of the
Comprehensive Environmental Response,Compensation, and Liability
Act (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act (SARA) of 1986, and Section 300.435 (c)(2)(II)
of the National Oil and Hazardous Substances Pollution Contingency
Plan (NCP).
The proposed plan for this ROD amendment was made available to
the public in the administrative record file located at the Sioux
City Public Library, 529 Pierce Street, Sioux City, Iowa and the
EPA Region VII Office, Kansas City, Kansas. A public notice was
published in the Sinnx ri«y Journal announcing the commencement and
length of the public comment period and the availability of the
administrative record file. The EPA offered to hold a public
meeting to discuss the ROD Amendment if requested; however, no
requests were received. Comments received during the public comment
period are addressed in the Responsiveness Summary. The EPA
received no comments to the proposed plan for this ROD
Amendment.
m. REASON FOR ISSUING THE ROD AMENDMENT
During the Remedial Design and subsequent Removal Actions at the
site, the EPA determined that the sediments found in the clay-lined
impoundments were generating hydrogen sulfide gas at concentrations
posing significant health risks. Air sampling indicated that the
levels of hydrogen sulfide gas released would significantly
increase when the impoundment sediments were disturbed.
The selected remedy in the ROD for the impoundment sediments is
in-situ stabilization followed by a 2-foot soil cap. In-situ
solidification requires disturbing the impoundment sediments with a
large-scale auger. Based on air sampling and modeling, the levels
of hydrogen sulfide released during the mixing of impoundment
sediments with solidification agents are projected to exceed worker
permissible exposure limits as defined by the National Institute
for Occupational Safety and Health (NIOSH) and the Occupational
Safety and Health Administration (OSHA). Air dispersion modeling
also indicates a reasonable likelihood that hydrogen sulfide
emissions at the site perimeter would exceed the permissible
exposure levels for hydrogen sulfide established by the Agency for
Toxic Substances and Disease Registry (ATSDR).
An alternate remedy of dewatering the sediments would
substantially reduce the disturbance of the impoundment sediments.
Therefore, significantly less hydrogen sulfide gas
emissions would be generated as compared to implementation of
the in-situ solidification. A geosynthetic cap or an improved clay
Cap would be placed over the dewatered sediments
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forming an infiltration barrier that can resist leaching from
deformations caused by settling and drying, thereby, potentially
reducing long-term cap maintenance costs.
IV. DESCRIPTION OF THE NEW ALTERNATIVES
The original remedy for remediation of the contaminated soil,
sediment and impoundment water included the following major
components:
• Treatment followed by discharge or off-site disposal of
impoundment waters;
• In-situ stabilization/solidification of contaminated sediments
and soils in the east aeration lagoon, west aeration lagoon, and
northeast Held, followed by a 2-foot soil cap;
• Soil/clay capping of the polishing basin sediments and
miscellaneous contaminated surface soils;
• Stabilization/solidification of contaminated sludges removed
from burial trenches followed by either onsite or off-site
disposal;
• Semi-annual monitoring and maintenance of soil/clay caps and
immobilized materials; and
• Annual long-term ground water monitoring.
The amended remedy will be as protective of human health and the
environment, be more implementable and decrease the cost of the
remedial action. The changes include the replacement of the in-situ
solidification of impoundment sediments and northeast field soils
with innovative dewatering technology followed by an improved cover
design; inclusion of additional site contaminated areas at the site
into the remedy; and documentation of the final decisions on waste
disposal options identified in the original ROD. The amended remedy
will fully meet the remedial action objectives identified in the
Feasibility Study identified as prevention of direct contact and
contaminant migration to the ground water.
The major changes in the amended remedy include:
• Contaminated noitheast field soils would not undergo in-situ
stabilization, but rather would be consolidated and/or excavated
and consolidated with the Polishing Basin sediments and covered
with an improved soil/clay cap meeting specified performance
criteria or geosynthetic cap such as high-density
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polyethylene (HDPE) that would achieve similar performance
criteria. Depth of the contamination in the northeast Held ranges
from 1 to 1.5 feet, and a redesigned cap will continue to provide
an implementable, cost-effective, and equally protective
remedy. Contamination from this area may also be excavated and
consolidation with the Polishing Basin sediments. This would be
equally protective and may be even more cost-effective.
• Sediments in the east and west aeration lagoons would not
undergo stabilization/solidification. Instead, the impoundment
areas would be dewatered and capped. The impoundment covers would
be redesigned to incorporate an improved soil/clay cap meeting the
performance criteria or comparable geosynthetic cap such as
high-density polyethylene. Post-ROD sampling indicated the presence
of hydrogen sulfide gas production from the impoundment sediments.
Air sampling and modeling indicates that dangerous levels of
hydrogen sulfide gas would be emitted should the impoundment
sediments be disturbed which would occur under the original remedy.
This change will provide a more cost effective remedy that greatly
reduces the potential for releases of hydrogen sulfide gas, thereby
reducing the health risk to on-site workers and the nearby public.
The amended remedy is also protective due to the improved cover
design.
• Contaminated soil areas, other than the northeast field, will
be excavated and consolidated with the aeration lagoon sediments
and/or polishing basin sediments prior to capping. The original
remedy had these areas capped in place; however, by consolidating
these soils, the costs associated with cap construction will be
significantly reduced while maintaining equal protection to the
public health and the environment.
The following are the areas where the original remedy contained
options:
• The original remedy indicated that impoundment waters were to
be treated as necessary and either discharged to the nearby oxbow
lake or transported off site to a POTW. All impoundment water will
be treated on-site if necessary and discharged to the nearby oxbow
lake. The EPA has determined that on-site treatment would be most
cost-effective due to the quantity of water potentially needing to
be treated. This is not a change from the original remedy and just
serves to document EPA’s preference for treating the water
on-site.
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• The original remedy indicated that contaminated sludges
excavated from the burial trenches were to be stabilized and
disposed of either on-site or off-site. Based on preliminary
calculations, on-site stabilization and consolidation with the
northeast field soils followed by capping will be the most
cost-effective way to remedy this area of the site. This is not a
change from the original remedy and just serves to document EPA’s
preference for treating the burial trench material on-site.
The following are the areas that the original remedy did not
address.
• The original remedy did not address the sediments remaining in
the wet well, aeration basin, and final clarifier. This ROD
amendment addresses the removal of the contaminated material and
consolidation of it with the sediments in the aeration lagoons
and/or polishing basin. These sediments would then be capped. The
emptied basins will be decontaminated with high-pressure steam and
backfilled with clean soil. These actions will further reduce the
risk of direct contact to site contaminants and the potential
threat of contaminant releases to the environment.
• The original remedy did not address the decontamination of the
filter press building and miscellaneous contaminated debris. This
ROD amendment addresses decontamination of these areas by washing
with a high-pressure steam cleaner. Wash water will be treated
on-site and discharged to the oxbow lake. Floor scrapings and
building residue will be disposed of in accordance with the
Resource Conservation and Recovery Act (RCRA). These actions will
provide additional protection of human health and the
environment.
V. EVALUATION OF ALTERNATIVES
The NCP sets forth nine evaluation criteria which serve as a
basis for comparing the remedial alternatives for final actions.
The nine criteria are divided into three categories: Threshold
Criteria, Primary Balancing Criteria, and Modifying Criteria. If
any remedial alternatives identified during the Feasibility Study
do not meet the Threshold Criteria (Criteria 1 and 2), EPA will not
consider them as possible final remedies. If the alternatives
satisfy the Threshold Criteria, they then are evaluated against the
next rive criteria, called the Primary Balancing Criteria. These
criteria are used to compare the remedial alternatives against each
other in terms of effectiveness, implementability, and cost. The
final two criteria, state acceptance and community acceptance, are
called Modifying Criteria. The alternatives are compared against
the Modifying Criteria after the state and community have reviewed
and commented on die Proposed Plan and the other alternatives
considered by EPA.
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The following is a discussion of the nine criteria used by EPA
for remedy selection.
A. Threshold Criteria:
1. Overall Protection of Human Health and the Environment
The EPA assesses the degree to which the alternatives would
eliminate, reduce, or control threats to public health and the
environment through removal, containment, and/or institutional
controls. An alternative is
normally considered to be protective of human health if the
excess cancer risk is reduced to less than 1 in 1,000,000 (10-6)
and risks do not pose non-carcinogenic health risks {Hazardous
Index (HI) < 1}.
Based on the results of the risk assessment performed at MAT,
current and/or future contact to sediment in the east and west
aeration lagoons, the polishing basin, and the soils in the
northeast field, pose a potential human health risk. The original
remedy reduced the threat of exposure of the contaminants by
in-situ stabilization and capping of the soils and sediments and
the removal and discharge of contaminated impoundment waters. The
amended remedy would adequately protect human health because it
addresses the principal threat of exposure by treating and
discharging impoundment waters and by capping the associated
contaminants and preventing direct contact. The amended remedy
would also reduce the likelihood of all exposure of ecological
receptors to the contaminated areas. The amended remedy also
provides greater protection as compared to the original remedy by
reducing the likelihood of hydrogen sulfide gas emissions at levels
above worker threshold standards during the remedial action. In
this case, the amended remedy is more protective. The amended
remedy also includes an improved capping system which will help
ensure and minimize contaminant migration into the groundwater in
the future. Institutional controls in the form of deed restrictions
limiting building of structures on site will supplement the
containment measures and help to ensure that exposures in these
areas will not increase to the extent that the carcinogenic risks
would be unacceptable.
2. Compliance with all Applicable or Relevant and Appropriate
State And Federal Environmental Regulations
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%The amended remedy will comply with all federal and state
applicable or relevant and appropriate requirements (ARARs).
Applicable requirements are those state or federal requirements
legally applicable to the release or remedial action contemplated
that specifically address a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance found
at the site. If it is determined that a requirement is not
applicable, it may still be relevant and appropriate to the
circumstances of the release. Requirements are relevant and
appropriate if they address problems or situations sufficiently
similar to the circumstances of the release or remedial action
contemplated, and are well-suited to the site.
The majority of the ARARs which applied for the originally
selected alternative also apply to the amended alternative. The
chemical-specific ARARs that are relevant and appropriate at the
site include Ambient Water Quality Criteria (AWQC) and National
Pollution Discharge Elimination System (NPDES) standards. As with
the original remedy, the amended remedy involves removal of surface
water in the polishing basin and east and west aeration lagoons
followed by treatment and discharge to an on-site surface water
(oxbow lake). Soils and sediments will be capped in place. Capping
includes provisions for drainage and runoff control. The
substantive requirements include AWQC, effluent limitations and
monitoring requirements and will be met by the amended remedy.
The state of Iowa promulgated regulations pursuant to Iowa Code
Section 455E.5 will apply to cleanup actions at the site where
significant amounts of soil contamination are present and
groundwater contamination is Occurring. These regulations, set
forth in 567 LAC 133, are applicable since groundwater
contamination has been observed at the site. As with the original
ROD, groundwater contamination and long term monitoring will be
addressed in a separate action.
The federal and state action-specific ARARs include all OSHA,
all Hazardous Materials Transportation Act (HMTA) regulations, and
the Clean Water Act (CWA) regulations applicable to discharge to
POTWs. The RCRA regulations would only be considered applicable for
the trench material because of the TCLP test results. Trench
materials will be treated through ih-situ stabilization prior to
consolidation and capping. The RCRA regulations are not relevant
and appropriate to the chromium contaminated soils and sediments
since they do not fail TCLP.
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• •
In addition, RCRA regulations may be considered as relevant and
appropriate for materials which may be generated such as floor
scrapings. Floor scrapings which might be generated as part of the
decontamination process will be tested. Based on the results of
these tests, the materials will either be consolidated with the
soils and sediments and capped or consolidated with the trench
materials prior to in-situ stabilization and capping.
B. Primary Balancing Criteria
1. Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of
a remedy to maintain reliable protection of human health and the
environment over time once clean up goals have been met.
Institutional controls, including local zoning regulations which
limit the uses of the property and deed restrictions prohibiting
the construction of buildings or other structures on the capped
areas of the site, would prevent damage or deterioration of the
capped areas and exposure of the contaminants present at the site.
These restrictions will apply to this property regardless of any
subsequent change in ownership, thereby offering long-term
effectiveness and permanence of the selected amended remedy.
Evidence indicates that the levels of contamination in several
areas of the site potentially pose a current and/or future risk to
human health or the environment. The implementation of the amended
remedy will result in a reduction in the risk in all areas where
contamination was found to pose a risk through direct contact or
inhalation. The amended remedy provides more protection by
including additional areas in the remediation.
The amended alternative includes treatment of contaminants and
engineering controls. Surface waters will be treated if necessary
prior to discharge. Although contaminated soils and sediments will
be left in place and capped, potential for direct exposure will
significantly be reduced. Mobility of the contaminants will be
reduced through dewatering and an improved capping system. The
improved cap will limit the ability of surface water runoff to
cause contaminants to migrate into the groundwater. Both the
original remedy and the amended remedy rely on groundwater
monitoring to ensure that the remedy continues to provide effective
long-term protection of human health and
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the environment. The improved cap contained in the amended
remedy will be constructed and maintained in a manner that provides
long term effectiveness and permanence. Groundwater will be
monitored to ensure that the remedy is operating as designed.
2. Reduction of Toxicity, Mobility, or Volume Through
Treatment
Section 121(b) of CERCLA states that remedial actions involving
treatment which permanently and significantly reduce the volume,
mobility or toxicity of the hazardous materials, are to be
preferred over those not involving such treatment. This evaluation
criteria relates to the ability of a remedial alternative to
control or eliminate risks caused by the mobility, toxicity or
volume of hazardous wastes.
The amended alternative will reduce the toxicity of the surface
waters of the polishing basin and east and west aeration lagoons by
treating these waters prior to discharge. Neither the original nor
the amended remedy reduce the toxicity of the hazardous
constituents in the contaminated soils and sediments.
The original remedy employed in-situ stabilization to reduce the
mobility of the contaminants. The amended alternative will employ
capping and engineering controls to reduce the mobility of the
hazardous constituents. The amended remedy will reduce mobility of
the contaminants through the use of the clay-lined impoundment
system. An improved cap will further reduce the likelihood of
infiltration of surface water causing the contaminants to
migrate.
The original remedy’s use of in-situ stabilization would have
increased the volume of material significantly. The amended
alternative is an improvement in that the volume of contamination
will actually be decreased through the dewatering of the polishing
basin and impoundment areas.
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3. Short-Term Effectiveness
Short-term effectiveness evaluates the length of time needed to
implement each segment of the alternatives. The EPA considers the
risks that a particular activity may pose to site workers, nearby
residents, or the local environment. Short-term effectiveness
involves the period of time needed to achieve protection and
considers any adverse impacts on human health and the environment
that may be posed during the construction and implementation period
until clean up goals are achieved.
The amended remedy requires less disturbance of the contaminated
sediments in the impoundment areas, thereby, reducing their
agitation and potential for release of emissions of hydrogen
sulfide gas which may affect on-site workers and nearby residents.
The previously selected remedy anticipated the use of a large-scale
auger which would have significantly disturbed the sediments and
resulted in releases of high levels of hydrogen sulfide gas into
the air. Based on air sampling and modeling, the levels of hydrogen
sulfide released during the action of mixing impoundment sediments
with solidification agents as specified in the original ROD would
exceed worker permissible exposure limits as defined by NIOSH and
OSHA. In addition, air dispersion modeling indicates that when
conducting the original ROD there would be a reasonable likelihood
that hydrogen sulfide emissions at the site perimeter would exceed
the permissible exposure levels for hydrogen sulfide established by
ATSDR.
4. Implementability
The EPA considers how difficult the alternative is to construct
and operate, how other government agencies and EPA will coordinate
monitoring programs and the availability of goods and services and
personnel needed to implement and manage the alternative.
Implementability addresses the technical and administrative
feasibility of a remedy, including the availability of materials
and services needed to implement the chosen solution.
Given the potential for releases of high levels of hydrogen
sulfide gas into the atmosphere, the original remedy is no longer
as readily implementable. Higher levels of worker protection would
be necessary. This would increase the time necessary to implement
the remedy and add
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an additional risk factor which must be accounted for in
completing the effoit. The amended remedy is readily implementable
in that dewatering the impoundment areas can be implemented more
easily than dewatering followed by solidification. In addition, the
amended remedy minimizes the disturbance of the areas lowering the
threat of hydrogen sulfide gas releases. Therefore, special
provisions for dealing with these releases can be eliminated.
Because of the increased concern over the releases of hydrogen
sulfide gas, the original remedy would have taken longer to
complete; however, the amended remedy should be able to be
completed in the original time frame (44 weeks).
5. Cost
The HPA considers capital costs, operation and maintenance
costs, and present worth, which is the cost of the activities that
will take place until the remedial action is completed. Capital
costs apply to activities such as construction, land and site
development, and disposal of waste materials. Annual operation and
maintenance costs are spent on activities such as on-going
operation of equipment, insurance and periodic site reviews.
The CERCLA requires that the EPA select a cost-effective
alternative that protects human health and the environment and
meets other requirements of the law. The EPA has determined that
the selected remedy is as protective and in some cases more
protective of human health and is more
cost effective to implement. The estimated capital cost for the
original remedy was $4,621,300 and Operation & Maintenance cost
for 30 years of $21,000 per year. Costs are estimated to have
increased through inflation to approximately $5,574,000 using
today’s pricing data for the same remedy. The original remedy’s
cost estimate did not include the cost for remediating the wet
well, aeration basin, final clarifier, filter press building or
miscellaneous contaminated soils nor did it include dewatering and
treatment of the total volume of water now contained in the
impoundment areas. The potential for hydrogen sulfide emission
would also increase the cost of implementing the original remedy in
that a higher level of worker protection would be needed during
construction activities. This higher level of protection would
cause work to proceed at a slower pace increasing the overall time
needed to complete the remediation. The increased time on-site
would increase the labor costs
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r.
associated with the construction causing the overall costs to be
even higher than the estimate above.
The preliminary cost estimate to implement the amended remedy is
$2,661,593 depending on the amount of consolidation of the
contamination that is possible. This estimate also includes
remediation of all areas identified in the original remedy plus the
wet well, aeration basin, final clarifier, filter press building
and miscellaneous contaminated soils. This estimate prices out the
remediation of the northeast field as a separate containment cell,
but does assume that a moderate amount of consolidation of the
contaminated areas is possible. When these factors are taken into
consideration, the cost to implement the amended remedy is
significantly less than the cost to implement the original remedy.
In addition, if a geosynthetic cap is utilized, Operation &
Maintenance (O&M) costs could be reduced since there are
minimal costs associated with long term maintenance of synthetic
caps. Overall, the amended remedy is seen to be a more cost
effective remedy providing equivalent or greater protection to
human health and the environment.
C. Modifying Criteria:
1. State Acceptance
The state of Iowa, through the Iowa Department of Natural
Resources (IDNR), is supportive of the amended remedy for this site
and prefers this remedy to the originally selected remedy.
2. Community Acceptance
The EPA held a public comment period to allow the community to
comment on the preferred alternative as set forth in the proposed
plan and supported by the administrative record. In addition, the
EPA notified the public regarding its willingness to conduct a
public availability session on the proposed plan. The EPA did not
receive any comments regarding the proposed ROD Amendment at the
site nor requests to conduct a public meeting.
In comparing the original remedy with the amended remedy, the
EPA has determined that the original and amended remedy meet the
threshold criteria, overall protection of human
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.health and the environment, and compliance with state and
federal requirements.
The amended remedy presents the better balance of tradeoffs,
with respect to the primary balancing criteria, in particular with
respect to implementability and cost. In addition, the amended
remedy continues to be protective of human health and reduces
mobility of the contamination by providing an improved capping
system. For the modifying criteria of state and community
acceptance, the amended alternative is preferred. In the tradeoff
and balancing of all nine criteria, the amended remedy is EPA’s
preferred remedy.
VL STATUTORY DETERMINATIONS
The EPA has determined, and the state of Iowa concurs, that the
selected amended remedy herein satisfies the statutory requirements
specified in CERCLA Section 121 which state that the selected
remedy must protect human health and the environment and comply
with applicable or relevant and appropriate federal and state
requirements. In addition, the remedy, as amended, utilizes
permanent solutions and alternative treatment technologies to the
maximum extent practicable for this site. These changes to the
remedy will increase protectiveness of human health and
environment, both short term and long term.
(
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ATTACHMENT A
RESPONSIVENESS SUMMARY RECORD OF DECISION AMENDMENT
MID-AMERICA TANNING COMPANY SUPERFUND SITE
In accordance with CERCLA Section 117, a public comment period
was held from May 13, 1996 to June 11, 1996, to receive comments
from interested parties on the EPA’s proposed plan for the Record
of Decision Amendment for the Mid America Tanning Company Superfimd
Site, Sergeant Bluff, Iowa. The EPA received no written comments on
the proposed plan.
The EPA offered to hold a public meeting if requested. No
requests for a public meeting were received.