*QS - US Environmental Protection Agency · protection of human health and the environment, compliance with other environmental requirements, Implementability, short-term effectiveness,

•Q•\*SRECORD OF DECISION

ROD DECISION SUMMARY

SUMMARY OF REMEDIAL ALTERNATIVE SELECTION

WILDCAT LANDFILL SITE

KENT COUNTY, DELAWARE

*5$9̂

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION III

PHILADELPHIA, PA

and

DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROLDOVER, DE

3AR3022II*

TAB^E OF CONTENTS

Page

I. Introduction,,,,.,.,,..,..,..,,,...,,.,.,,.,,.,,,..,,.,,,.,,....,,, 1II, Site Location and Description,,.,.,,,,,.,,.,,..,,,,,,,.,..,,,.,.,,, 1III. Site History,,,,,,.,,,.,,.,.,.,.,,,,,....,.,,...,,,,,..,,.,...,,.,, AIV, Current Site Status,.,,,,.,,,.,.,...,.,,,..,.......,,,.,,.,,....,,, 5

A, Geology.,,,,,,,,,,,,,,,.,,.,.,,,.,.,.,.,,...,,,,,,,,,,,,,,,,..,, 5B, Hydrology.,.,..................,.....,.,,,..,..,,,,,.,,......,., 8C, Extent of Contamination......,.,.,..,,..,.,.,.,.,,....,....,,.,, 13

1. Inorganic,,,.,,,,,,....,..,...,.....,,.,,.....,.,,.,.....,.,. 132. Organic,.......,.,..,,.,,,,...,.........,..,,.,.,,..,....,.,. 14

V. Biological Assessment.,....,,,,,,...,...,..,........,....,....,,.,. 15VI, Risk Assessment,.,,.,...,,.,.,,,,,..,......,,.,.,,,,,.,,,.,,..,,,,. 15

A, Groundwater--Current Offsite Residents,.,,,,..,.....,..,.,,,,,,, 19B, Oroundwater-•Future Offsite Residents....,.,..,.....,.....,.,,.. 19C, Groundwater--Future Onsite residents,....,....,.,...,.......,.,. 19D, Soil and Leachate--Occasional Si.te Users,,,,,,,,.,,,,,,,,,.,,,,, 19E, Surface Water--Occasional Site Vsera,,..,.,,.....,.11........... 20F, Fish Intake--Occasional Site Users.,,.........,..,..,.,...,,,,., 20

VII. Remedial Action Objectives....,.,...,.......,...,,..,,,,..,.....,,, 20VIII, Remedial Alternatives Evaluation,,..,..,....,,,..,.,,,,,,.,..,.,.,, 21

A. Description of Alternatives,,,...,.......,.,..,..,..,,,,..,,,,.. 21B, Evaluation of Alternatives...,...,...,,,,,,,,,,.....,..,,..,,.., 23

IX, Community Relations...,.........,...,....,..,,,....,....,..,..,,... 33X, Documentation of Significant Changes,....,,,,.,,,,.,,..,,..,,.,,.,. 34XI, Selected Remedial Alternative.,.....,.,........,,,.,,,.,,.....,,.,, 34

A, Description and Performance Goals,....,..,..,,..,,,.,,,,,..,,.,, 34B, Statutory Determinations,,,,.,...,.,..,.,,..,..,,,,,,,,.....,.,. 36

ATTACHMENTS

A • Administrative Record IndexB • Responsiveness Summary

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FIGURES

Page

Figure 1, Site Location Hap,.,,,..,.,,.,,.,,,,,,.,,..,,,,,,,.,..,.....,,, 2Figure 2, Site Hap,.,,.,,,.....,....,,.........,,,,..,..,,,,....,.....,.. 3Figure 3, Borehole and Monitor Well Locations....,.....,.,.,......,...,., 6Figure 4, Trench Locations,,.,,.,...,,,.,.,...,,.,,......,.,.,,..,,.,..,, 7Figure 5, Groundwater-level Elevations In Columbia Formation.,,.,.,.,.,., 10Figure 6, Groundwater-level Elevations In Waste and Heander Channel,,..., 11Figure 7, Schematic Hydrodynamlc Cross Section.,.......,...,.,..,.,.,.,., 12Figure 8, Organic Compounds in Groundwater Samples,......,.,....,.,.,.,,. 16Figure 9, Domestic Well Sample Locations,..,...,..,......,...,..,.,....., 28Figure 10. Offsite Groundwater Restricted Areas in Columbia Formation.... 29

TABLES

Table 1, Suonary of Risk Assessment,,,.,,..,,.,,,,,,.,,,,,.,.,.,.,,.,... 18Table 2. Recommended Alternatives: Summary of Detailed Analysis.,,,.,.., 24

.o

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SUMMARY OF REMEDIAL ALTERNATIVE SELECTIONWildcat Landfill SiteKent County. Delaware

I, Introduction

This Record of Decision addresses the first of two operable units for theWildcat Landfill site and is made up of the landfill proper and the adjacentareas, The second operable unit consists only of the pond that is locatedalong the northwestern border of the landfill, This ROD Involves selection ofa remedial alternative which addresses the contamination source by preventingexisting and future direct contact where a direct contact threat is posed bythe site, by reducing the potential for future direct contact risks off thesite, and by prohibiting well Installations in areas of known or suspectedcontamination, The remedial investigation/feasibility study (RI/FS) will becontinued in order to address the impacts the landfill on the adjacent pond andthe wildlife found there,

A remedial investigation was conducted to determine the extent of contaminationresulting from the site and to determine the potential risks posed to humanhealth and the environment on and adjacent to the site, The remedialinvestigation report addresses the onsite risks posed by the site, the offslteground water contamination risks, and the stream and wetland systems on andadjacent to the site, The accompanying feasibility study report screenedvarious response actions which could be used to mitigate effects of the siteand to compare a number of alternatives which address the problems posed by thesite, The alternatives have been evaluated using the following criteria fromthe Superfund Amendments and Reauthorlzatlon Act (SARA) Section 121:protection of human health and the environment, compliance with otherenvironmental requirements, Implementability, short-term effectiveness, long-term effectiveness and permanence, reduction in toxlclty, mobility and volume,cost effectiveness, and community acceptance, The public was given anopportunity to comment upon the Proposed Remedial Action Plan and theAdministrative Record which includes the RI/FS, The comments and concerns madeby the public are considered in the alternative evaluation and are specificallyaddressed in the attached responsiveness summary (Appendix B).

Finally, this Record of Decision documents the selection of the final remedyby DNREC and EPA and is based upon the contents of the Administrative Record,

II, Site Location and Description

The Wildcat Landfill site is approximately 44 acres in area located in KentCounty, Delaware, 2 1/2 miles southeast of Dover (See Figure 1), itie site liesalong the west bank of the St, Jones River and la bordered to the north andeast by the river and associated marshlands, and to the south and west byresidential and commercial establishments (See Figure 2), A pond which wascreated by construction of the landfill is located directly adjacent to theitte along the northwestern edge, Portions of the site lie within the 100-yearfloodplaln of the St, Jones River,

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to

LOCATION MAPWildcat Landfill, Dover, Dilawaro

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BARDEN PLUMBING &0. B. WILLIAMS

ELECTRICAL COMPANY

LIBERTOI— CONSTRUCTIO

ABANDONEDRACE TRACK

HUNNRESIDENCE WASTE

RECYCLINGFACILITY

Finn 2FEATURES ADJOINING

..»' APPROXIMATE LANDFILL BOUNDARY LANDFILL !4

Widest Lan0 800 CTp̂ ttOO 2000 DOV8T, DittWWO

SCALE r • wor"

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o

Much of che alee Is situated upon low-lying wetland sediments. However, thearea to the southwest was backfilled with wastes following excavation of soiland sand material; consequently, In that area of the landfill, wastes are Indirect contact with the surflclal sand aquifer, The entire site was coveredwith sands excavatud from this area and from a second excavation area nearbyalthough this second area was not used for landfllllng, Much of the site Ispresently well vegetated with a number of plant communities established,Leachate seeps are present In a few areas of the site, particularly In the areaof che adjacent pond, Exposed trash Is evident In Isolated areas across theentire area of the site and Includes empty or partially empty drums, tires,solid latex, and assorted municipal trash,

The St. Jones River and its associated marshlands provide natural barriers tohuman access along the north, east, and part of the southeast boundaries of thesite, Access along the northwest area of the site is not restricted but ismade somewhat difficult by the adjacent pond and associated marshy areas, Thesite Is easily accessed along the southwest perimeter both by vehicle and onfoot in the area of the Hunn house and behind the businesses located adjacentto the site. As shown in Figure 2, the only residential property locateddirectly adjacent to the site is the Hunn residence who are the propertyowners,

The Wildcat Landfill site is situated in the Atlantic Coastal PlainPhysiographic Province, Host of the site is below about 20 feet mean sealevel (HSL), within the natural meander channel of the St. Jones River, Thislow-lying part of the landfill was created by dumping and spreading wastedirectly into the wetlands of the river, The southwestern corner of thelandfill lies at elevations of 20 to 30 feet HSL and is apparently beyond themeander channel, Wastes in this upland portion were disposed within a man-madeexcavation,

The predominant surface hydrologlc feature of the area is the St. Jones Riverand its tributary, Tldbury Creek, Both are tidal with a normal tide range of2 feet in the vicinity of the site. Much of the site lies within the 100-yearfloodplaln, Two other surface hydrologlc features of the area are the pondand a small dralnageway (which conveys water from Route 10 to the St. JonesRiver along the northwestern border of the site), The dralnageway appears tohave been man-made and is separated from the landfill by a low but continuousridge extending along the.pond and landfill,

The geohydrologic units of major Importance in the area are the surficlalColumbia Formation and two major sand beds within the Calvert Formation of theChesapeake Group, namely, the Frederlca Aquifiir and the underlying CheswoldAquifer. All residents of the study area draw their water from wells withinone of these three units.

HI. Site History

The site was operated as a permitted sanitary landfill between 1962 and 1973,accepting both municipal and industrial wastes, Liquid and solid wastes werereportedly mixed together, compacted, and covered; drums of waste werereportedly emptied onsite and the empty drums recycled, Industrial wastessuspected to have been disposed include latex waste and paint sludges,

AR302220

However, there are no known existing records of the actual quantity of wasteswhich were disposed In the landfill,

The facility was permitted as a solid waste landfill by the Delaware StateBoard of Health In 1962, The site was later pernltted by the Delaware Waterand Air Resources Commission (WARC) and then by DNREG, However, throughout Itseleven years of operation, the facility appears to have routinely violatedoperating and other permits Issued by the regulating agencies, In August of1973 the facility was ordered by DNREC to cease operations for falling tocomply with permit conditions, The site operators were ordered to cover withsoil and revegetace the site, The entire regulatory history Is discussed Inthe EPA Remedial Action Master Plan (RAMP) which la available In theAdministrative Record,

The site was Investigated by the EPA In June 1982 for possible inclusion onthe National Priority List (NPL) of hazardous waste sites. The site wassubsequently listed In December 1983 and the RAMP published that same month,The Delaware DNREC requested and the EPA agreed to allow the state toperform a remedial Investigation and feasibility study, DNREC began theInvestigation In September 1985 and the feasibility study In November 1987,The RI/F5 report was drafted and released for public comment in May 1988,

IV, Current Site Status

Through a Cooperative Agreement with the EPA, the Delaware DNREC completed theRI/FS for the Wildcat Landfill site through ltd contractor, CH2M HillSoutheast, Inc. The RI report describes the geology and hydrogeology, onslteand off site chamlcal characteristics, onslte and off site biological assessment,wetlands assessment, and suspected risks within the study area, The geology,hydrology, and types and concentrations of contaminants found onslte andoffslte will be described in this section, The biological assessment and therisk assessment will be described in the next two sections, respectively, Asummary of all chemical data generated during the remedial investigation isincluded in Remedial Investigation Report.

A, Geology

The geology of the study area was Interpreted from monitor well borings drilledonslte and offslte, The monitor well locations are found on Figure 3,Trenches were dug onslte both for sample collection and for Interpreting thegeology and hydrology of the study area (See Figure 4), Other informationsources were cuttings from nearby residential wells, logs of nearby wells fromthe Delaware Geological Survey, logs of borings from the Delaware Departmentof Transportation at the Route 10 bridge, historical areal photographs, UnitedStates Geological Survey (USGS) topographical maps, Delaware Geological Surveygeologic and hydrogeologlc reports, and reconnaissance of the area,

There are three kinds of surflclal deposits in the study area. The twonaturally occurring deposits are sands interpreted to be of the ColumbiaFormation and the meander channel organic silts and sands of the St, JonesRiver, The third surflclal material are the landfill wastes associated withthe landfill and a small area on the eastern side of the river which appearsto be construction material,

AR30222I

9 3 WASTE BOREHOLEOJ1B MONITORING MU. BORPHQLP

PONO ««TER tEVEt MONUMENT MONITORING WELLPROXIMATE LAMflU. B()WCAflY SAMPUINQ LOCATIONS '

MO 800 WWcat Landfll,— D o v e r , Delsware

IR3022212

,\14 TRENCH LOCATION/«•' , AITflOXIMATE LANOFIU BOUNOAflY FigUti

. , LOCATIONS OF TRENCHESNOT£«TRENCHES 1-14 EXCAVWEO l2/H3/Hj swr.«4-. ii —;,...---,•-. T*IM>TRENCHES W-23 EXCAVATED U/Z-6/B7 REMEDIAL INVESTIGATION»——- m—J" WILDCAT LANDFILL,

DOVER, — ———Ul* RMKII MIIM, fKOTIlalKWn R.OKK ON I/Ml |i _______

Tho general stratigraphy of Che study area Is detailed In the RI report and isdescribed hnre In ascending order:

(1) The Cheswold aquifer Is a sandy zone within the Chesapeake Groupconsisting of medium to coarse sand and shells, The top of Che Cheswoldaquifer In the study area Is at approxlnatley 200 feet below ground surface,These sands underlie the entire study and are separated from the overlyingFrederica sands by confining silts and clays, The Cheswold sands were notevaluated In the remedial Investigation but will be used In the remedialaction;

(2) The Frederica sands are Interpreted as members of the upper ChesapeakeGroup, These sands underlie the entire study area and generally grade fromfine alley sand In che southern part of the study area to coarse sand withgravel In the central and eastern portions of the study area;

(3) The clay sen!-confining layer found above the Frederica sands extendsthroughout Che study area although Its extent and Integrity beneath themeander channel was not defined, These clays are generally plastic and Insome places contain a trace of silt and fine sand;

(4) The Columbia Formation directly overlies the clay semi-confining layer Inall locations outside of the meander channel of Che St. Jones River. Thisformation Is composed primarily of fine Co coarse sands with a crace of mediumgravel, Sands of the Columbia underlie portions of Che landfill outside ofthe meander channel, Within the meander channel, however, distribution ofColumbia sands is uncertain although sand deposlCs were found there, Thesecould either be extensions of the Columbia or channel deposits;

(5) The meander channel deposits of the St. Jones River are exposed along Chenorch, east, and southeast of the boundaries of che landfill, Slmlllardeposits are found exposed In and around the pond on the west side of Chelandfill, The uppermost unit of these deposits is composed of organic siltsand some clay1, root fibers, and wood fragments, These deposlCs were alsofound beneath the landfill In Che meander channel, Beneath these organicdeposits are sands which may either be undisturbed Columbia sands 6v reworkedchannel deposits;

(6) The landfill materials are in direct contact with sands of the ColumbiaFormation in the southeast corner of the landfill, This Is referred to asArea 1 In the risk assessment, Wastes within the meander channel are indirect contact with meander channel organic silts, The typical wastesencountered during Che remedial investigation included municipal refuse (glassbottles, waste paper, Crash, and decomposed garbage), latex in strips'andsheets, scattered crushed, empCy, and some intacc drums, and manufacturedplastic Items, Wastes ranged Co 20 feet deep across Che sice with the thickestand highest area outside the meander channel, Within the meander channel thewastes have compressed and otherwise displaced the meander channel silts,

B, Hydrology

The hydrology of the study area Is strongly Influenced by the St. Jones Riverand che tidal action of the river. The hydrogeology was determined with the 27monitor wells installed at 15 locations on and near the landfill. Wells were

AR30222I*

u

330 ftz/day for

screened within the Columbia Formation, Frederics sands, landfill materials,meander channel silts, and meander channel sands,

The hydraulic properties of natural materials In the study area weredetermined through variable-head (slug) testa at Individual wells, and by ahaquifer test conducted for 48 hours in the Frederlca sands at MW-16A. Singlewater-level measurements were taken In all the monitor wells and In the pondadjacent to the site In April and June 1986, Continuous water-levelmeasurements were taken between September 1986 and January 1987 at variousmonitor wells and from the St, Jones River, Figure 5 and Figure 6 representthe offslte and onslce surface water table configuration, respectively, Thehydraulic conductivity of the Columbia wells ranged from 2,5 x 10"3 to3,3 x 10*̂ cm/sec which is typical of sands and silty sands, The hydraulicconductivity of the meander channel organic silts were 9.9 x 10 and1,9 x 10, Many of the tests conducted In the meander channel silts andsands were abnormal which may indicate a limited areal extent of those sands,The hydraulic properties of the Fredrrlca sands were 412 totransmisslvlty, 3 x 10 "j and 1.3 x li"zcra/sec for hydraulicconductivity, and 9.6 x 10"* and 2.7 x 10"3 for storativlty. Thesevalues are typical of semiconfined sands and silty sands.

Patterns of groundwater flow are generally toward the St. Jones River althoughvery localized flow directions are more varied because of local topographicfeatures and tidal fluctuations of the river. Measurements from wells whichare tidally Influenced are difficult to Interpret because the tidal influencevaries both spatially and temporally depending on the location of the monitorwell with respect to the river,

The hydrodynamic setting is depicted in Figure 7 and as fallows:

(1) The Columbia Formation is unconfirmed and the water table mimics thetopography, Flow is from topographic highs to topographic lows, Groundwaterfrom the Columbia discharges into the various surface features found withinthe meander channel, Discharge from the area of the Wildcat Archery Range iseither into the St. Jones River directly or into the dralnageway that existsnorthwest of both the pond and the site. Discharge from the Columbia in thearea directly west of the site is toward the pond, the landfill, and TldburyCreek, Discharge may also occur Into the meander channel sands If they aredirectly connected to the Columbia sands, The southwestern corner of thelandfill rests directly upon Columbia sands and horizontal flow continues fromthis area of the landfill toward both the St, Jones River and Tldbury Creek;

(2) The semlconflning clays found atop the i Frederlca sands allow verticalflow. Within the meander channel this flowj is vertically upward while outsideof the mecnder channel the flow is downward;

(3) The Frederlca sands are semiconfined with the overlying confining claysrelatively thin beneath parts of the meander channel. Horizontal flow isgenerally from west to east, Vertical flow Is controlled by reohargeoccurring from the Columbia Formation through the confining clays and into theFrederlca sands outside of the meander channel, and upward discharge from theFrederlca sands into the meander channel and the St. Jones River occurring

AR302225

INTEflPRETED WATER-LgVEL CONTOUR IR MSUCOLUMBIA/MEANDER CHANNEL CONTACT LINE ' Flgvir* 5QflOUNOWATER DIVIDE INTCRPRETIVE MAP OF

8,36«15 MONITOR WELL AND WATER LEVEL REAOINQ IFT MSU WATER-LEVEL E A T IAPPROXIMATE LANDFILL BOUNDARY

AWIU 1CH1, 19

SKiSS,

INTERPRETED WATER-LEVEL CONTOUR IFT MSU ..Figuti 6COLUMBIA/MEANDER CHANNEL CONTACT LINE > INTERPRETIVE MAP OP

<"•../ QROUNDWATER DIVIDE WATER-LEVEL ELEVATIONS IN6.9M15 MONITOR WELL AND WATER LEVEL READING IFT ,MSL) , WASTE AND IN MEANDER

CHANAnilUWldoat Lanolll,

. , ,h ~"") APPROXIMATE LANOFILL BOUNDARY CHANNEL ORGANIC SOILS,\̂ ^

SCALE \" '

RR302227

ioIoi

SiHit

12

vj

within the neander channel. All wells within the Frederics were Influenced byCidal action from the elver; ,,

(A) Horizontal flow direction within the neander channel sands Is poorlydefined although flow directions are undoubtedly toward the St, Jones River,All wells were influenced by the tidal action of the river. These sands arebeing recharged by overlying deposits near the center of the landfill and awayfrom the center of the neander channel, and discharging upward Into overlyingdeposits within the neander channel;

(5) Horizontal flow directions within the landfill wastes is poorly definedwithin the neander channel. However, flow is expected to follow topographyand be consistent with flow fron Columbia sands outside of the landfill.Generally, horizontal flow will be radial fron topographic highs within thelandfill with discharge occurring Into the adjacent pond and neander channeldeposits. Within Area 1, horizontal flow will continue offslte into Columbiasands with subsequent discharge Into the St. Jones River and Tldbury Creek.

(6) The nean tidal variation In the St, Jones River Is approximately 2 feet.The nean elevation was 1 foot nean sea level (MSL) with a total range of -1 to3 feet MSL, Water levels In nany wells showed slnlllar fluctuations In level,Generally, the water levels were higher In April and lower in June and October.The average linear velocity of flow in the Columbia Fornatlon was calculated at49 to 91 feet per year, The average linear velocity of groundwater flow In theFrederlca sands is between S.6 and 26 feet per year,

C, Extent of Contamination

Two rounds of sampling and chemical analysos were performed In the renedialInvestigation and the table summaries are found In the RI Report.Simples of soil, water, and landfill contents were collected throughout thestudy area, This Includes samples collected by the EPA Emergency Response leanfron wetlands and stream channel locations.

1, Inorganic Characterization and Contamination

The najor ion and bulk chemistry Interpretations ware used to classify thevarious waters in the study area and to Interpret the likelihood of inorganicnetal concentrations and distribution, Based upon the total dissolved solidsconcentration, the waters of the study area are of three types:

•less than 200 parts per million (ppm)•-Columbia Fornatlon, all donestlcwells, and Frederlca sands;•SOO to 2000 ppm--meander channel silts, landfill leachate; and•greater than 2000 ppm--surfnee water fron St. Jones River and Its tributaries,

The ion chemistry (namely the cations:calcium, magnesium, potassium, sodium;and anlons:carbonate, chloride, sulfat«) suggest that the pond and MW-12 watershave been affected by the landfill, that the meander channel silt water hasbeen affected by the St, Jones River, and that the neander channel sand watersare affected by the Frederlca aquifer waters, There appears to be no affect ofeither the St. Jones River nor the landfill on the neander channel sands, Thisdata supports the hydrogeologlc understanding that there exists an upwardgradient from the Frederlca aquifer Into the neander channel, or i:hat the

13

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meander channel organic sllcs have beta an effective buffer for contaminantsleaving the landfill and entering those organic deposits, or both. Both HW-15and MW-16B are almlllar to the Fredertca aquifer water. HU6B nay be affectedby the landfill but the results are anomalous. f\

The trace element chemistry (aluminum, antimony, arsenic, barium, cadmium, \<ichromium, cobalt, copper, Iron, lead, manganese, mercury, nickel, selenium,silver, tin, vanadium, zinc) of waste trenches were slmillar to the bottomsediments of the St. Jones River and generally within the range ofnaturally-occurring concentrations, The concentrations from soils takenfrom borings, primarily of Columbia Formation sands outside the landfill, wereslightly below the river and landfill sediments,

The extraction procedure analyses performed on landfill wastes were almost allbelow the detection limits although barium at 2400 ppb occurred In Trench 6;lead at 10,5 ppb In trench 1, 20.5 ppb In Trench 3, 19,5 ppb In Trench 7, and1940 ppb In Trench 17; mercury at 0.3 ppb In Trench 16, 1,4 ppb In Trench 18,and 0,2 ppb In Trench 24; and selenium at 10 ppb In Trench 10.

The mean concentration of trace elements In water samples were primarilyreflective of the St. Jones River, as most were taken from the river. Station6 In wetlands adjacent to the southeast of the landfill had relatively highconcentrations of aluminum, arsenic, birlum, chromium, Iron, lead, manganese,vanadium, and zinc. Station 16 In the; pond and the leachaiie seep near thesouth end of the pond also had higher concentrations of these elements ascompared to the St. Jones River, Groundwater and leachate samples taken withinthe landfill contained elevated levels all trace elements except arsenic andmanganese when compared with groundwater samples taken outside the landfill.In addition, cadmium, cobalt, nickel, and vanadium were consistently present inthe landfill waters but rare or absent In other groundwater samples includingboth domestic and commercial, and monitor wells,

2. Organic Characterization and Contamination

Vlth few exceptions, samples taken from the study area contained concentrationsof organic constituents in the low ppb range, Further, there was nodiscernible pattern to their distribution,

The highest concentrations up to a total of 70 ppm were found In drumsexcavated during the second trenching operation. Most of this Is accounted forwith styrene at 69 ppm. Other common constituents were ethylbenzena (from afew to 900 ppb), methylene chloride (slmillar range), and phthalates (generally10 to 40 ppb).

Trench samples typically contained totals of a few hundred ppb of organicconstituents. Of the 43 organic compounds detected In Round 2 sampling,only acetone (6 to 43 ppb), benzene (4 to 15 ppb), chlorobenzene (16 to 110ppb), ethylbenzene (1 to 300 ppb), methylene chloride (1 to 5 ppb),xylenes (7 to 150 ppb), and naphthalene (5 to 32 ppb) were common. Thehighest single concentration for phthalate was 8500 ppb In Trench 24,

The water and sediment samples collected from the wetlands and surface waterby the EPA Emergency Response Team were generally free of organic constituents,Phthalates were found from some sediments In the study area In the low ppb

I : I !

14

to

range,

Both groundwater and surface water samples generally contained low levels oforganic contamination, But as seen In Figure 8, benzene conpounds, toluene,and xylenes (BTX) were cannon contanlnants in the low ppb range, Certain ofthese contaainants also occurred In wells upgradlent of the landfill, such asMH 13A, IB and C, and 14A, In fact, the highest concentration of BTX conpoundsoccurred In HW-16B which Is screened across the river In the ColumbiaFormation.

V. Biological Assessment

The biological assessmtmt documented a productive and diverse ecosystem withinthe Wildcat Landfill site boundary, Five species of plants were Identifiedwhich are listed on the Delaware Natural Heritage Inventory draft list of rareor leldom seen plants, Hlstopathology on white-footed nice andbioaccuaulatlon studies of snail mammals did not indicate adverse effects toterrestrial wildlife,

Comprehensive sediment toxicity testing did not Indicate any adverse effectson the St. Jones River and the marshlands adjacent to the site, However, ofthe fish that were collected fron the river, two fish contained PCS levels inexcels of the Food and Drug Administration action level of 2 ppm, Theavailable nonltor well water data, surface water data, and sediment data donot indicate that the landfill is a source of the FCBs.

Several Impacts from the landfill were found in the pond adjacent to the site,These impacts Included levels of acute toxicity in the southwest portion of thepond, leachate entering the pond from the site having concentrations of certainmetals above water quality criteria, and bioaccunulation of several metalswithin turtles and munmichog fishes collected from the pond,

I1In order to fully assess the Impact of bioaccumulation in the fish uponmigratory birds which may be feeding on these fish, the pond has been made aseparate operable unit and will be addressed in a continuation of theremedial investigation and feasibility study. Remediation of the pond is notaddressed in this record of decision.

VI, Risk Assessment

The purpose of the risk assessment is to provide a mechanism for documentingthe hazards or potential hazards posed by the site for the support of renedialactions under Section 106 of CERCLA, The general elenents of the riskassessment include a toxlcitv assessment of chemicals identified at thesite, exposure assessment for identifying the major potential routes ofhuman exposure, and the risk characterization which conblnes the potentialexposure pathways and Information on the toxicity assessment to estlnate thepotential effects of the site on human health,

The current and future exposure pathways examined for this site in the riskassessment are (1) exposure in groundwater for residents downgradlent ofthe site who use groundwater as a source of drinking water, (2) exposure to

IS

HR30223I

n».r.iwjt,,t».'.'w

1. Benzena2, ChloniMnzena3. EUiylbanzana4, Total Xytones5. Toluem6. Chloreattiaiw(Conctntradonilnppti)

Compound Concantratlons NotShown Ware Below DatectaCWUrrtts

<M Xyftnti

MonltortnoWallApproxhun* Undflll Bourtfwy

Figure 8 . . '"*''SIGNIFICANT ORGANIC COMPOUNDSIN GROUNDWATER SAMPLES, ROUND 2

16 AR302232

contaminants In groundwater for future onsite residents who use groundwater asa source of drinking water, (3) exposure of contaminants In the St. Jones Riverfron incidental Ingestlon of surface water by occasional site users,(4) exposure through Ingestlon of fish fron the St. Jones River by occasionalsite users, (5) exposure to contaminants in soil and leachate through directcontact by occasional site users, and (6) exposure to contaminants in the soiland leachate through direct contact by future onsite residents.

The Ingestlon of fish in the St, Jones River is reported here but is not asubject for this decision. The Information has been given to the federal andstate agencies responsible for this public health concern, This pathway Isnot considered here because of the following! (1) the landfill could not beidentified as a source of the FCBs although PCBa were found in certain wastenaterlals, (2) PCBs were not found offslte in either sediments or watersamples, and (3) the fish sampled in the St, Jones River travel well beyond thelength of river near the site, including possibly beyond the St, Jones Riverwatershed,

The risk characterization Includes comparisons between estimated Intakes andreference doses (RfDs) for noncarcinogenlc chemicals and estimates of excesslifetime cancer risk for exposure to carcinogens, These comparisons and riskestimates must be Interpreted carefully because, for each exposure setting,assumptions as to chemical concentrations, exposure durations, andcharacteristics of the potentially exposed population are made, Further,quantitative assessment is possible only for those chemicals for which EPA hasdeveloped numerical criteria. Chemicals which have no criteria are excludedfrom the risk analysis, Table 1 summarizes the risk assessment withsummaries of existing or future exposed populations, routes of exposure, excesslifetime cancer risks, comparisons to reference doses for noncarclnogens, andchemicals of concern,

Over 80 chemicals were detected in samples analyzed for the Rl and over 60were considered in the risk assessment, These chemicals can be separated intotwo categories according to their health effects, namely, carcinogens and otherchronic toxicants that are noncarcinogenlc, The carcinogenic effects areexpressed as the excess lifetime cancer risk from exposure to individualchemicals, '•

The excess lifetime cancer risk Is the incremental increase in the probabilityof developing a cancer from exposure to contaminants at the site, For example,a 1 x 10"° excess lifetime cancer risk is an Increase In the risk of cancerIncidence of one case per million people exposed, The acceptable risk rangeadopted by EPA is 10'* to 10'7.

The exposure to noncarclnogens is assessed by comparing estimated dailyIntakes of contaminants to reference doses (RfDs). RfDs are established belowthe threshold dose, that is, below the dose at which effects are expected tooccur, A simple additive risk model is used to assess the overall potentialfor noncarclnogenic effects from a mixture of chemicals, The estimated dallyIntake for each chemical is divided by the RfD for that chemical and theresulting quotients for each chemical of the mixture is added resulting in thehazard index (HI), If the HI exceeds 1,0, the potential hazard isunacceptable and the chemicals are further evaluated,

17

AR-302233

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A. Croundwater • Current Offsite Residents

There is no evidence of contamination from the landfill In any of thedomestic wells sampled near the site, All well* within the immediate vicinityof the landfill were sampled in the RI. The domestic wells DW-8 and DW-10exist in close proximity to the landfill and could potentially be affected bylandfill contaminants should they be overpumped or if groundwater flowdirections change near these wells, A risk assessment was performed on thesewells because of their close proximity to the site. No RfDs were exceeded andthe HI equals 1,0, The chemicals which contributed to the HI were barium,cadmium, copper, and lead, These are natural trace elements, The potentialexcess lifetime cancer risk was determined from maximum concentrationsreported in residential and commercial wells and is 1 x 10"° because of thepresence of benzene and methylene chloride,

B, Groundwater--Future Offslte Residents

There are no existing users of water downgradlent of the site whereoffsite migration of contaminants has been documented, The risk assessment isbased upon data from HU-12A and B, and HW-6B, The estimated dally Intake formanganese was exceeded in KM-12, and the HI equals 2,9, However, manganese isan essential nutrient and the RfD is based upon Inhalation exposures ratherthan Ingestlon, The potential excess lifetime cancer risk through ingestlonof offslte groundwater Is 6 x 10"° due to the presence of benzene at 4 ug/1In MH-12, No other carcinogens were detected in these wells,

C. Groundwater--Future Onslte Residents

The toxlclcy effects of onslte chemicals were used In the risk assessment toevaluate their effects on future onslte residents. Data from HU-2 and aqueoustrench samples from Area 1 were used in the evaluation. The RfDs weresubstantially exceeded for antimony, cadmium, lead, mercury, barium, andchromium, and the HI was 104. The potential excess lifetime cancer risk was4 x 10. Arsenic, FCBs, and chrysene contributed most to this value,Concentrations of arsenic, however, are below the maximum contaminant level(MCL), Of the eleven samples used in this assessment, six contained arsenic,four contained FCBs, and one contained chrysene,

D. Soil and Leachate--Occasional Site Users

Both current and future occasional site users such as recreational users andworkers could be exposed to contaminants,in soil and leachate, The values forsoils are extrapolated from chemical concentrations found in buried landfillwastes and from leachate from the trenches. Values from a leachate seepsampled near the potad were also used, Only ingestion Is quantitativelyassessed and is compared to acute (10-day) exposure to chemicals in theleachate. The RfDs for adults and children were not exceeded and the HIvalues were negligible. The excess lifetime cancer risk from the ingestlon ofsoils is 1 x 10"J with arsenic, FCBs, and chrysene contributing most tothat risk level, This level is very conservative with a number of Importantassumptions, The chemical concentration levels in the surflcial leachateseeps is assumed to be the same as the levels found In leachate from thetrenches even though the concentrations for the leachate seep.near the pondwere considerably lower than the trench samples, and with no FCBs found at thesurface seep. • •

19 !

l i HR302235

E, Surface Water--Occasional Site Users

The RfDs for surface water were not exceeded and are negligible. The excesslifetime cancer risk of 8 x 10° Is based on arsenic (which was below the HCL)and chlordane (detected In one sample).

F, Fish Intake--Occasional Site Users

Three fish collected from the St, Jones River were found to contain FOB levelsin excess of the Food and Drug Administration (PDA) action level of 2.0 ppb.The excess lifetime cancer risk Is 3 x 10 , The remedial investigationwas unable to detect any FCBs beyond the landfill wastes In either sediments,groundwater, or surface water samples. The fish that were analyzed are able tomove considerably within the St, Jones River and its tributaries and arebottom feeders. For these reasons, the Information on the FOB levels in thefish samples has been given to the appropriate state and federal agencies andis not addressed as a site-specific issue in this decision.

VII. Remedial Alternative Objectives

The remedial action objectives were developed to respond to the site hazards(summarized previously in this document) which are discussed In the RemedialInvestigation Report, Remedial action objectives address the media of concern,which, for the Wildcat Landfill site are the offslte biota and the'landfillcontents.

The remedial investigation found that the major areas of contamination are theleachate within the landfill contents, leachate seeps near the pond, andgroundwater contamination of the shallow surface aquifer in a limited area,The risk assessment performed for the Wildcat Landfill Indicates thatcontaminants leaving the landfill do not currently pose a threat to humanhealth, However, people coning onto the landfill may be exposed tocontaminants at levels of concern in leachate seeps or from exposed landfillcontent*, The potential risks associated with future releases of contaminantsfrom the landfill Into the groundwater and, subsequently, into surface waterare also considered.

As stated previously in the Biological Assessment (Section V of this document),biota on the landfill have not been adversely affected, However, onsite biotacould become contaminated In the future, Therefore, the objective is tominimize the Ingestlon of contaminated biota by humans by limiting theexposure of biota to landfill contents, The impact of the landfillcontaminants on small fish and turtles in the adjacent pond is not a humanhealth concern since neither the turtles nor the snail fish are consumed byhumans, However, the fish may be a concern for migratory birds which use thepond for feeding. This will be addressed as a separate operable unit withan extended RI/FS report,

There are a number of concerns regarding the landfill contents: (1) theSt, Jones River could cause some erosion of the landfill contents througheither flooding of the river or through migration of the river channel;

20

AR302236

(2) there Are leachate seeps aC Isolated areas along the periphery of thelandfill, particularly notable in the area of the pond; and (3) protection ofthe pond and wetlands adjacent to the site from runoff during any remedialaction activities.

Future direct contact with wastes is also a concern should residential orcomnerclal development occur upon the landfill. Therefore, the future risksassociated with onslte water wells was evaluated.

There is a future risk associated with future releases to the groundwater ofcontaminants originating from the landfill. These groundwaters, however,occur only as the water table aquifer, are of very United area, contain noexisting users, contain little available groundwater, have naturally high ironcontent, and discharge to the St, Jones River and Tldbury Creek, a few hundredyards away from the landfill,

In conclusion, the remedial action objectives for the Wildcat LandfillFeasibility Study are:

1. Minimize the ingestlon of potentially contaminated biota taken from thesite.

2. Prevent direct public contact with landfill wastes,3, Limit the erosion of the landfill contents by the St. Jones River.4. Minimize the environmental impacts of the landfill contents on biota,5, Identify future Impacts of releases of landfill contents to groundwater

and, subsequently, to surface water. Any releases must be addressed,

VIII, Remedial Alternatives Evaluation

A, Description of Alternatives

The alternative development process combines technologies and correspondingprocess options for each medium which form the remedial actions for the siteas a whole. The resulting alternatives include a range of remedies and levelof effort which satisfy all or some of the remedial action objectives. Inaccordance with recent EFA guidance, none of the alternatives In the detailedanalysis Include treatment due to the size of the landfill (approximately 44acres) and the absence of hot spots on the site, These site specific factorsmake treatment impracticable, The purpose of the alternative analysis is toprovide the lead agency with a list of potential alternatives which providethe best balanoe among the evaluation criteria and meets the statutory findingof protection of human health and the environment, attains ARARs, Is costeffective, and utll-lzes alternate treatment technologies to the maximum extentpracticable, The no action alternative is Included as the baseline and shouldonly be used when the risk assessment Indicates there are no present or futurethreats to public health or the environment,

Alternative 1; No Action

The no action alternative requires no remedial action, therefore, the existingsite conditions would remain unchanged, The existing vegetative coverprovides for a large degree of erosion control, maintains the existinghydrologlc system, provides wildlife habitat, and limits direct contact by

21

8R302237

B, Evaluation of Alternatives

The five alternatives assembled above are evaluated to develop a more completeanalysis of their relative advantages and disadvantages, The evaluation isbased upon the following eight criteria developed in accordance with Section121 of SARA (See Table 2):

short-term effectiveness!long-tern effectiveness and permanence;reduction of toxic!ty, nobility, and volume;implementablllty;compliance with ARARs;overall protection of human health and the environment;cost; andcommunity acceptance,

State acceptance Is also a criteria developed by EPA for the analysis ofalternatives but since the state is a co-selector of the remedy along withEPA, that criteria is not pertinent since the state acceptance Is reflected inselection of the final remedy,

The short-term effectiveness pertains to the potential impacts on thecommunity and to workers during the remedial action activities, the potentialenvironmental impacts of the remedial action, and the effectiveness andreliability of nitlgative and protective measures, The protection of thecommunity and workers during implementation of the remedial action refers tothe onslte risks and offslte risks of implementing the alternative, At thissite, three of the four alternatives have transportation of drums to aRCRA incinerator as the only offslte component, There would also be IncreasesIn dust levels during construction activities, Therefore, there is littlerisk to the community from Implementation of any of the alternatives, There'may be risk to workers onslte; therefore, worker protection would be needed toprevent direct contact with the landfill contents and Inhalation of dust andvolatile emissions, •',

•\\The landfill is currently affecting only the shallow groundwater aquifer andthe offslte pond adjacent to the site, As was mentioned previously,' theeffects on the pond will be addressed In an extended RI/FS report, There are,however, several other environmental Impacts resulting from the implementationof alternatives,

The fence In Alternative 2 would deter large terrestrial animals fromfeeding on the landfill and would deter transient populations from coming incontact with exposed waste and leachate on the site, The grading and cappingactivities In Alternatives 3, 4A, and 4B would prevent any potential risk toterrestrial animals from direct contact with landfill contents, However, Itwould also involve the removal of trees and shrubs used as nesting habitat bybirds, In addition, these alternatives would also eliminate 7.9 acresof wetland within the landfill and 1,8 acres of wetland around the perimeterof the landfill as a result of cap overlap, However, the cap overlap in thevicinity of the pond could minimize the Impact of the leachate seeps on thepond, There are also five plants found on the site listed on the DelawareNatursl Heritage Inventory that would be eliminated from the landfill byAlternatives 3, 4A, and 4B,

23

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nThe long-term effectiveness and permanence refers to the magnitude of totalresidual risk in terns of untreated waste, the adequacy and suitability ofcontrols used to manage untreated waste, and the reliability of these controlsover time, In terns of total risk of the residual waste, only Alternatives 3,4A, and AB constitute any waste reduction, namely, the removal of any drumsfound on the surface or through grading operations. The fact that landfillwaste will remain onsite for all the alternatives means that there Is apotential for future contaminant releases fron known and unknown waste In thelandfill, although the potential and rate of release Is small. This appliesto all the alternatives, including the No Action Alternative, Because thepotential for direct contact exists on the site, the No Action alternative(which Included no controls) is not reliable, Groundwater monitoring isIncluded in all alternatives except the No Action and should prove reliable inreporting any future releases to the groundwater, and hence, potentialreleases to surface waters, Alternative 2 would rely entirely on the fence asthe control against direct contact, The grading and capping options wouldprovide additional protection against direct contact and thus supply the bestdirect contact protection. The grading and capping options would require themost maintenance. All of the alternatives except Alternative 1 containinstitutional controls to prohibit all well drilling onslte and in the shallowaquifer to the southeast of the site and along the extreme southwest edge, asdelineated In Figure 10, Since these restrictions are to be administered bythe statA, it is considered a long-tern remedial action. Finally, since wastewill remain onslte, a review of the effectiveness of the final remedial actionwill be done in five years,

Reduction of toxlcity. mobility, and volume refers to the amount of materialto be treated, the amount of hazardous materials that will be destroyed orreduced, and the degree of expected reduction, Also, this evaluationaddresses the statutory preference for selecting a remedial action that •employs treatment to significantly reduce the toxlcity, mobility, and voluma'of hazardous substances, Volume would be reduced depending on the number ofdrums encountered during the remedial action and disposed of offsite, Otherthan the potential for treatment of drum contents, none of the alternativescompletely treat all of the waste found onsite,

The analysis of impleraentabiUtv addresses the technical and administrativefeasibility of implementing the alternatives as well as the availability ofservices and materials associated with each alternative, The alternatives donot require unusual equipment or materials although the volumes of soil andclay are considerable, However, sources of soil and clay exist within theStnte of Delaware, Uith the exception of the offslte drum disposal, onlyonslte technologies are Included, Monitoring of groundwater Is essential fordetecting any future releases of contaminants, The only significant

i implementabillty issue will be construction requirements for the grading andi capping In Alternatives 3, 4A, and AB, Since the landfill is located in'' wetland areas, settlement of the cap would need to be Investigated beforeconstruction, Also, a more detailed analysis of the potential floodvelocities In the event of the 100-year scorn of 24-hour duration should bedone targeting some of the assumptions made in the preliminary analysisIncluded in the Feasibility Study, This should be done for the grading andcapping options of Alternatives 3, 4A, and 4B, Implementation of stateimposed restrictions on well development both onsite and in the previouslydescribed shallow aquifer area Is not considered a problem because Delaware

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475000 477500 478000 1Approximate Undflll BoundaryArea of Known or Probable Groundwater ContaminationArea Potentially Susceptible to Groundwater Contamination {

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presently has this authority under the state well permitting program,Further, this shallow aquifer has very low water yielding capacity andcontains naturally high levels of Iron,

The evaluation of ARAR compliance by alternatives includes a review of thestate and federal applicable or relevant and appropriate chemical-specific,action-specific, and location-specific requirements, and other concernsidentified as to-be-considered (TEC), The TBCs do not meet the regulatoryprerequisites of ARARs, These are nonpromulgated advisories or guidanceIssued by state or federal agencies. In this section, the alternatives willbe evaluated as to how each meets the major ARARs for the site. A completelist of the ARARs Is found in the Feasibility Study report and TechnicalMemorandum Number 1, found In the Administrative Record, The ARARs used inthis analysis Include the action-specific requirements of the Delaware RiverBasin Commission (DRBC), the Executive Orders pertaining to wetlands andfloodplalns, 40 CFR 264.310, and the effluent limitations of the NationalPollution and Discharge Elimination System (NPDES) pursuant to Section 402 ofthe Clean Water Act (CWA). Any construction activities affecting greater than2,5 acres of wetland must be approved by the DRBC, This is applicable to thegrading and capping alternatives, A statement of findings regarding thewetlands Is included In this record of decision under statutory determinations,Discharge Into the offslte stream from the temporary diversion ditches inAlternatives 3, 4A, and 4B would require an NPDES permit. A CWA Section 404permit Issued by the US Army Corps,of Engineers is also required for theplacement of fill material within the offsite navigable;waters, Including thewetlands, '

The DNREC Wetland Regulations and Wetlands Act are state ARARs. Permitsfor any construction activity within offslte wetlands Is required regardless ofthe area affected. Wetlands over the surface of the landfill and around theperimeter of the landfill would be lost during the construction activities forAlternatives 3, 4A, and 4B. Permits are not required for any remedial actionactivities on the site in accordance with SARA.

The Delaware Regulations Governing the Construction of Water Wells would applyto the installation of monitor wells or other wells associated with theremedial actions,

The location-specific rules governing floodplalns applies to remedial actionsat this site, All portions of the remedial activity must be designed,constructed, and maintained to avoid washout by the 100-year flood. Also,remedial activity should avoid adverse effects, and restore and preservenatural and beneficial values. Since the landfill Is partially within the100-year floodplaln, this would apply to all alternatives except the no-actionalternative,

The State of Delaware Solid Waste Disposal Regulations of 1974 and federalRCRA closure and capping requirements (40 CFR 264,310) are relevant andappropriate, The state solid waste disposal regulations require a cap with aminimum 2-feet of compacted soil with a minimum 2 per cent slope on the finalgrade. Alternatives 3, 4A, and 4B satisfy the slope requirement but none ofthem satisfy the 2 feet of compacted soil requirement. However, the soil andsoil/clay caps are both 1,5 feet thick with an added thickness provided by thegrading fill that ranges from 0 to 4 feet,

30

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The loll requirements of the Delaware solid waste regulations nay notpracticable at the Wildcat Landfill sice for three reasons: (1) the weight ofsuch a cap would likely alter the existing site dynamics by causing subsidenceof the landfill materials deeper into the underlying wetland sediments,(2) the intent of the two feet of compacted cover material is to reduceInfiltration Into the waste materials but at the Wildcat Landfill site this isnot a concern since the landfill is already located within a wetlands area anddecreasing infiltrating water will not alter that hydrologlc feature, and(3) the onslte risks associated with the site are from direct contact withexposed wastes and this risk would be more cost-effectively reduced by a soilcap,

The relevant and practicable Intents of the capping option at the WildcatLandfill site would be better accomplished by a soil cap containing 1,5 feetof compacted soil and 0,5 feet of topsail, The essential 2 foot coverrequirement is, thus, net,

Closure of the landfill will be accomplished in accordance with the relevantportions of Subtitle C of RCRA. The RCRA requirements are not applicable tothis situation because there are no site records indicating that RCRA wastewas disposed of at the site and because no RCRA characteristic waste wasidentified in the study, However, in order to address the contaminationencountered at the Wildcat Landfill, the requirements of RCRA are consideredrelevant.

Since the intent of RCRA closure is generally not appropriate for largemunicipal landfills where waste Is generally of low toxlclty, EPA has proposedrequirements for alternate closure options under RCRA (52 Fed. Reg, 8712, March19, 1987) which nay only be used where closure is not applicable, but isrelevant and appropriate, The alternate closure options combine the elementsof clean closure and the closure in place options,

The',1 alternate closure is considered the correct closure method for the WildcatLandfill site because the pathways of potential exposure of contaminants isUnited and the contamination remaining onslte has both low nobility and lowtoxlcity, The alternate landfill closure consists of the partial removal ofwastes (in this case, the renoval of drums containing wastes encounteredeither on the landfill surface or during the grading operation), stabilizationand containment with a soil cap (that will be permeable) to address the directcontact threat, and long-tern management controls, The long-tern managementcontrols consist of maintenance of the site and the cap, onslte land userestrictions, and ground water monitoring, Although the alternate landfillclosure should be used when there is not significant threat to ground water,the Implementation of the state Imposed institutional controls on welldevelopment in the very limited area of concern is considered sufficient forthis situation,

Alternatives 1, 2, and 3 do not meet the alternate landfill closurerequirements because none contain a landfill cover, Alternatives 4A satisfiesthis ARAR because it consists of a soil cover over the entire site,Alternative 4B exceeds the alternate landfill closure requirements because Itconsists of an Impermeable clay cap with a soil cover,

31

flR3022l»7

The Delaware Natural Heritage Inventory draft list of rare or seldom seenplanes Is a TEC since five plants from that list have been Identified onthe site, Impacts of any remedial action affecting these plants are to beminimized, however, this does not preclude Implementation of the remedial _.action, Since Alternatives 3, 4A, and 4B Involve earthwork on the site, this ; • )TBC would apply to all three of these alternatives, _

Section IV of this ROD summarized the contamination In the groundwater nearthe site, This section showed that certain chemical-specific criteria (HCLs)are presently exceeded in the ground water, The point of human exposure tothe contaminated ground water should normally be set at the facility boundaryunless specific criteria set forth in Section 121 (d)(2)(B)(li) of SARA aremet. Maximum contaminant levels are not considered relevant and appropriateat the Wildcat Landfill site since the site conditions meet the exceptionsoutlined in Section 121 (d)(2)(B)(ll), For the Wildcat Landfill site it hasbeen determined water quality criteria In the St, Jones River are theappropriate levels to achieve because the ground water discharges directlyinto the rlvor and there is no statistical increase in the levels above waterquality criteria, In addition, institutional controls are a part of theselected remedy in the limited distance between the site and the points ofground water discharge, Finally, current and projected risk levels andreference doses (RfD's) for offsite ground water ingestion is within the riskrange considered acceptable by EPA,

Alternative 1 does not meet this ARAR because it is a no action withoutinstitutional controls and monitoring, However, Alternatives 2, 3, 4A, and 4Bmeet this requirement since they all contain .institutional and monitoringcontrols in the distance between the site and the points of ground waterdischarge to the St, Jones River,

The overall protection of human health and the environment criterion refers tohow each alternative eliminates, reduces, or controls existing and potentialrisks to human health and the environment through treatment, engineeringcontrols, and/or institutional controls, All alternatives, exceptAlternative 1, control the Ingestion of contaminated groundwater byadministrative restrictions and monitoring for future releases, Alternative 2reduces only the risk of direct contact, Alternatives 3, 4A, and 4B reducethe risk of direct contact and erosion of the landfill contents and couldreduce the Impact of the leachate seeps into the offsite pond,

All of the final alternatives are also evaluated on a cost basis, The costestimates are within +50% to -301 cost ran(;e in accordance with EPA policy,They represent the best estimation of the capital, operation and maintenance,and total present worth costs, Costs will only be updated at the pre-deslgnand final design stage, Since the capital costs are the highest for thesoil/clay cap alternative, that alternative has the highest present worth ofapproximately $8,5 million. The costs for the alternatives from the detailedanalysis is as follows: Alternative 1- $0,00; Alternative 2- $350,000;Alternative 3- $6,3 M; Alternative 4A- $7.5 M; Alternative 4B- $8,53 H, Thecost for the preferred alternative is $5,4 H.

There are uncertainties Involved with the cost estimates that are Important tonote, The level of personal protection required during the grading andcapping alternatives Is uncertain, Landfill gas and vapors could be emitted

,32Q

SR3022W

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with disturbance of che landfill concents. Since the composition of thelandfill gases has not been characterized, Level B protection would berequired. However, future monitoring and sampling nay prove that the landfillgases do not present any danger which would lower the dugree of personalprotection for workers, Should this be the case only Level D protection wouldbe necessary, In order to provide a conservative cost estimate it was assumedthat Level B and Level D personal protection would be used 501 of the timeduring grading and cap construction, Another uncertainty Involves thesampling, removal, excavation, and treatment of the drums in an offslte RCRA

, Incinerator, The number and contents of drums on and in the landfill isunknown, Based on estimates made from visual Inspection of the landfill andthe excavated trenches, a number of 160 drums was used for the drum count asthe number of drums containing hazardous waste requiring offsite incineration,that are currently on or could be uncovered, during the grading operation.

The community acceptance criterion Indicates Chose features of thealternatives the community supports, those for which they have reservations,and those for which they strongly oppose. This evaluation is based uponcomments submitted to either the state or EPA as well as Chose made at thepublic meeting,

IX. Community Relations

The Wildcat Landfill site is located In a moderately populated area 2 1/2miles southeast of Dover in Kent County, Delaware, Private residences arefound along Route 10 to the north and west of the site, The site owner'sresidence is located directly adjacent to the site to the south, A numberof snail businesses are located directly adjacent to the site to the southwest.An archery range is situated on property presently owned by the landfill ownerand ii situated between Route 10 and the northwestern edge of the landfill,Dover Air Force Base housing is located directly across the St. Jones Riverfrom the landfill.

Local officials were briefed by DNREC prior to initiation of the remedialinvestigation in 1985 and again following completion of the Proposed Plan inJune 1988, A fact sheet was prepared and distributed to the local residencesand businesses prior to the remedial investigation which described the RI/FSprocess and discussed the site-specific problems. Press conferences were heldat the site prior Co Che Initiation of field activities during both the firstand second rounds of sample collection. Press releases were also Issued byDNREC Co Che news media during Che Investigation and when the proposed planwas Issued,

A public meeting was held on June 16, 1988 to discuss the proposed plan and toobtain public comment on Chat plan, Letters were sent to the businesses andresidences located very near to the site inviting them to the public meeting,A 30-day public comment period was held by DNREC and EPA from Hay 26, 1988 toJune 24, 1988, The administrative record was made available for public reviewboth near the site and at EPA Region III offices.

DNREC and EPA have attempted to respond to all public comments in the attachedresponslveness summary (Appendix B),

X, DocufflflnCatlon of Significant Changes

No significant changes Co the preferred alternative presented In the proposedplan have occurred. ., ^_^

XI. Recommended Alternative

The selected remedy chosen by the lead agency must a cost-effective remedywhich effectively mitigates and minimizes threats to and providesadequate protection of human health and the environment, Both CERCIA and SARArequire selection of a remedy which provides protection of human health andthe environment which Is cost-effective and utilizes permanent solutions andalternative treatment technologies or resource recovery options to the maximumextent practlclble, and that attains federal and state ARARs unless otherwisewaived, In addition, treatment of the principal threat at the site to reducethe nobility, toxlclty, and volume of the hazardous substance Is preferred,The remedy selected for the Wildcat Landfill site, excluding final decision onaddressing the adjacent pond, Is discussed below.

A, Description of the Selected Remedial Alternative and Performance Coals

A modified version of Alternative 4A, Containment With a Soil Cap, has beenchosen to mitigate the existing and future risks posed by the site and whichmeet the goals and objectives, and federal and state ARARs, This alternativeIncludes the institutional controls and monitoring requirements detailed inAlternative 2 and Included in Alternative 4A, The major difference betweenthe chosen modified alternative and Alternative 4A is that only those areas onthe site which pose a direct contact risk will be capped and that the cap willmeet the Intent of the Delaware solid waste regulations, As was mentionedpreviously, the two-foot compacted soil requirement may not be practicable forthe reasons previously detailed, Chapter 6 of the Feasibility Study describesthe chosen alternative and estimates the total cost for that alternative,

i iThis preferred alternative would require all the Institutional controlsdescrlUjrln Alternative 2 onslte and in offslte areas identified as potentialprob):.«'n .peas, The purpose of these restrictions is to prevent direct contact(primarily through ingestlon) with landfill contents or contaminantsoriginating from the landfill, Fencing is not chosen for inclusion inthis alternative for the following reasons; (1) the United soil cap waschosen as the more long-term remedy for reducing the future onslte risks,(2)' difficulty in constructing a fence because of the number of property ownerswho^would be effected, and (3) access to the site Is limited by thesurrounding land-use and terraine features, A very llmitiid soil cap (botharenUy and physically) sinillar In design to that described in Alternative 4Awill lie placed on areas of the landfill where wastes are exposed or whereleach; e seeps or pools are found, These areas will be graded, covered withsoil and seeded. Further, any drums exposed on the landfill surface or fromthe graded areas will be disposed of offslte in either a solid waste landfill,or In a RCRA incinerator if the contents are determined to be hazardous,Hazardous wastes will not be disposed of at RCRA landfills in deference to theland ban on disposal of hazardous waste, However, no RCRA characteristichazardous wastes were encountered during the remedial Investigation,

IAR302250

''•3

The general features of the preferred alternative Is as follows:

1. Institutional controls will be Implemented by Che state In areas adjacent tothe site to prevent the Installation of water wells In the surface aquifer thatIs downgradlent of the southwestern edge of the site, These controls will beImplemented by the state using the existing water well permitting program.This area discharges Into the St. Jones River and Tldbury Creek, The ARARassociated with this aspect of the chosen alternative Is the DelawareRapulaclons Governing the Construction of Water Wells.

2. Institutional controls will be Implemented by the state which precludeonsite Installation of water wells for domestic or commercial purposes,Construction activities which would disturb the Integrity of the soil cap onthe site will be discouraged, The existing state well permit program willpreclude onsite water well construction under the Regulations Governing theConstruction of Hater Wells. The Delaware Solid Haste Regulations will be theARAR used to discourage onsite development which would disturb the integrity ofthe site. Also, the atate will work toward Including language in the deeds ofsite owners, or other legal means, at least describing the landfill locationon the property,

3. Two commercial wells, DW-8 and DW-10, located adjacent to the site in anarea of concern will be replaced. The shallow wells presently existing wouldbe replaced by single-cased wells to approximately 200 feet below groundsurface. The installation of these wells would be according to the DelawareRegulations Governing the Construction of Hater Wells.

4, Exposed landfill wastes, barren areas, and leachate pools or seeps will becovered according to the Intent of the Delaware Solid Waste Regulations of 1974which includes 1.5 feet of unconpacted and 0.5 feet of topsoil cover, minimum2 per cent slope, and revegetatlon, Consideration will be given to the otherTBC'i identified such as the DNHI draft list and to the existing natural usesof the site such as areas of Important wildlife habitat value, The RCRAalternate landfill closure policy will also be used to meet the RCRA relevantand appropriate requirements, Also, should the volume of cover required tomeet the ARAR's be impracticable because of site-specific concerns, such assubsidence because of excessive weight, DNREC and EPA will decide on theactual cover requirements to be met.

5, Offsite disposal of drums containing wastes to either a solid wastelandfill or a RCRA incinerator depending on whether the waste is hazardous ornot, The RCRA requirements will be the appropriate ARARs for offsltetransportation and disposal of hazardous! wastes. Disposal of non-hazardouswastes will done in-accordance with the Delaware Solid Haste Regulations,

6, Signposting to discourage disruption of the soil cap,

7. Monitoring of groundwater downgradlent of the site will be done incompliance to RCRA, Subpart F to identify changes in the release ofcontaminants from the site, This is particularly Important in the southeasternarea near the owner's residence,

8, Shallow monitor wells will be Installed in the groundwater discharge areaof the southwestern corner of the landfill along Tldbury Creek to Insure that

35 ;I !

li AR30225

the Federal Water Quality Criteria are not exceeded above background levels atthe discharge point, Monitor well construction will be done In accordencewith the Delaware Regulations Governing the Construction of Water Wells,Sampling will be done along with the other monitoring activities at the site, ^-^The Clean Water Act is the appropriate federal ARAR, ( , )

Since much of the site Is well vegetated with limited cover material In place,the existing direct contact risk is only associated with those areas where 1waste materials are exposed or where leachate seeps or pools are found,Institutional controls taken by the state will be Imposed to prevent thefuture direct contact risks identified in the risk assessment,

The performance goals are met where the Intent of the Delaware Solid WasteRegulations and the RCRA alternate landfill closure requirements are achievedon the site, The Federal Water Quality Criteria standards will be monitoredoffslte at surface water discharge points and within the groundwater monitoringwells between the landfill and the surface water discharge area. Theinstitutional restrictions will be placed by the state to Insure that theonslte and offslte restrictions are placed upon the property, This willinclude water well installation restrictions and declarations in property deedsthat landfilling has occurred within the property boundary.

The following statement of findings regarding the wetlands Is also consideredas a TBC. (1) The RI/FS for the Wildcat Landfill site has determined thatwetlands onslte and adjacent to the site may be graded and covered In order toeliminate the existing leachate seeps and provide cover to exposed wastes inareas that constitute an unacceptable risk to public health and theenvironment. All remedial alternatives except the No Action Alternative willrequire grading and covering of certain of these areas. (2) The grading andfilling activities shall be conducted in a manner conslstant with provisionsof Appendix A of 40 CFR Part 6, The subject regulations have been entitled"Statement of Procedures on Floodplaln Management and Wetland Protection,"These procedures constitute policy and guidance for carrying out provisions ofExecutive Order 11990 which addresses Protection of Wetlands. (3) Theremedial design of the remedial action shall be developed in a mannerconslstant with Appendix A of 40 CFR Part 6 to assure that potential harm andadverse effects to the wetlands Is minimized, The remedial design has notbeen initiated at this time. Therefore, specific steps to minimize impactshave not yet been Identified, In addition, the effect of the remedial actionon the wetlands cannot be accurately assessed at this time. (4) While allremedial measures shall be designed to minimize harm to the wetlands, It ispossible that some adverse effects may be unavoidable, Should remedialactivity be expected to create such effects, restorative or mitigatlve measuresshall be developed during the remedial design and reviewed by DNRCC and EPA,If anticipated adverse effects occur, restorative or mitigatlve measures maybe implemented as part of the remedial action,

B, Statutory Determinations

The purpose of this section is to describe the ability of the selected remedyto be conslstant with the statutory requirements of Section 121 of CERCLA andwill describe the adequacy of the remedy to be protective of human health andthe environment, attain ARARs, be cost-effective, utilize permanent solutions

36

flR302252

«nd alternative technologies or resource recovery technologies to the maximumextent practicable, and address the preferance for reduction In toxlclty,nobility, or volume.

'^ Protection of Human Health and the Environment

The selected renedy Is adequately protective of human health and theenvironment through the alternate closure engineering of the landfill surface,removal and treatment of drums containing wastes, and the onslte and offslteInstitutional controls to be Imposed by the state, The existing directcontact risks from exposed waste, leachate seeps and pools found onslte willbe eliminated by the alternate closure soil capping to be placed In areas ofthe site where direct contact exists, Stabilization of the surface eliminatesthe human exposure to the wastes and also reduces the exposure of thebiological community to waste materials. The future direct contact risks tohumans will be minimized by the Institutional controls to be placed on the sitefor water well drilling and construction activities. Signposting will alsodiscourage onslte exposure,

The selected alternative will not pose unacceptable short-term risks althoughthe grading and the offslte disposal of drums have low short-term risksassociated with then, There should be no cross-media impacts from theselected media since all waste materials will remain In place except the drumswhich are to be disposed of offsiste,

bAttainment of the Applicable or Relevant and Appropriate Requirements

The selected remedy for addressing the problems posed by the Wildcat Landfillsite meets the intent of the applicable or relevant and appropriate'requirements of both Federal and any more stringent State environmental andpublic health requirements, A number of Federal and State to be considered(TBC's) have also been Identified and are Included in this discussion, TheMOL requirement In ground water at the facility boundary has been waivedbecause of the special conditions present at the site. These specialconditions Include the very United aquifer area, lack of receptors, closeproximity to the surface discharge, and low yield and quality of the sectionof aquifer in question, The intent of the Delaware Solid Waste DisposalRegulations will be met by meeting the state closure requirements found in theDelaware Sanitary Code, Fart 38, under which the site was originally to beclosed,

The complete listing of State and Federal ARAR's and TBC's are found In theFeasibility Study report and Technical Hemorandun #1, both found in theAdministrative Record.

The chemical-specific requirements are;

1, 40 CFR 122 (Clean Water Act) • This is a relevant and appropriaterequirement which Includes the acute and chronic ambient water qualitycriteria (WQC) for protection of freshwater aquatic life, At the WildcatLandfill site these requirements are to be met at the ground waterdischarge point along Tidbury Creek,

37

I AR302Z53

2. 40 CFR 122 (Clean Hater Act) • The Federal Pollution Discharge EliminationStandards are applicable for the discharge from the landfill duringlandfill capping activities,

3, The State of Delaware Regulations Governing the Control of Water Pollution •The applicable requirements Involve the discharge of waters to surfacewater and this applies to the onslte landfill capping action duringconstruction, A permit would be required since water would be dischargedoff site,

4, The State of Delaware Water Quality Standards for Streams • This Is anapplicable state requirement for discharges to surface waters from pointsources, These requirements are enforced under the Delaware RegulationsGoverning the Control of Water Pollution,

The location. specific requirements are:

1, State of Delaware Regulations Governing the Construction of Water Veils-This Is an action-specific requirement concerning the construction andsiting of water wells, These requirements are applicable to remedialactions for both monitor well construction and replacement of domesticwells,

2, Stat« of Delaware Wetland Regulations and the Wetlands Act (Chapter 66) •These location-specific requirements are applicable to all remedial actionswhich impact the existing tidal wetlands, The capping actions at theWildcat Landfill site will impact both onslte and offsite wetlands andmeasures must be taken to minimize these Impacts. A permit is required.

3, Delaware River Basin Commission (DRBC) Rules of Practice and Procedure •This applicable requirement applies to actions where 2.5 or more acres ofwetlands are drained, filled, or otherwise altered, An environmental

• Impact analysis is required, jI : '

4, 40 CFR 264.18(b) • Actions within the ; 100-year floodplaln must be designed,constructed, operated, and maintained ; to avoid washout,

5. Executive Order 11988, Protection of Floodplains (40 CFR 6, Appendix A) •This applicable requirement requires actions to avoid adverse effects,minimize potential harm, and restore and preserve natural and beneficialvalues .

6, Executive Order 11990, Protection of Wetlands (40 CFR 6, Appendix A) •Measures must be. taken to minimize the destruction, loss, or degradation ofwetlands,

7, Clean Water Act, Section 404<(40 CFR Parts 230, 231) • Action must be takento prohibit discharge of dredged or fill material Into wetlands without apermit,

The action-specific requirements are!

1, State of Delaware Solid Waste Disposal Regulations (1974) and the StateSanitary Code Part 38 • Section 6.03(g)(l) of the solid waste

38

AR3Q225l»

:o

P

regulations requires a final slope of at least 2 per cent which precludeserosion. A nlnlmum of two feet of compacted cover is also required InSection 6.03(g)(4)(b). The actual cover requirements will be a two footsoil cover but the compaction requirements will be modified as describedpreviously with 1.5 feet of compacted and 0,5 feet of uncompacted topsoll.

2, 40 CFR 264.310 • The RCRA closure requirements will be met undex the EPAalternate landfill closure policy allowing the site to be suitably covered,This is a relevant and appropriate requirement.

3, 40 CFR 264 • The RCRA hazardous waste requirements will also be applicableto the transportation and disposal of any hazardous wastes found in drumseither on the landfill surface or during the grading actions,

The to be considered (TBC's) are!

1, Delaware Natural Heritage Inventory • This is a draft list of rare orseldom seen plants which have been found on the site, These plants will beconsidered during the onsite grading and capping activities.

2. Integrated Risk Information System dat* base • This Information is.used Indetermining the concentration of carcinogenic compounds at the 10"brisk level and the concentration of non-carcinogens for the reference doselevel,

3. 45 FR 79318-79379 (November 28, 1980) • These are levels for contaminantsin water for the protection of human health.

Cost-Effectiveness

The selected remedy attains ARARs and mitigates the onsite and offsite risksto hunan health and the environment while the cost Is less than the otherremedies (3, 4A, and 4B) that include the onsite soil capping option. Theselected remedy is also much more sensitive to the other to-be-consideredrequlrenents such as the rare plants than the other remedies,

The selected renedy is considerably more costly than the no action alternativeand Alternative 2. However, these alternatives are not effective inaddressing the Identified risks over the long-term nor do they meet thefederal and state ARAR's,

Utilization of Ptrnanent Solutions and Alternative Treatment Technologies

The final feasibility study report describes the modified alternative chosento renedy problems posed by the site. This selected remedy differs from thedetailed alternatives 3, 4A, and 4B by reducing the area of the landfill to becovered with a soil cap. This was done for two reasons: (1) certain areas ofthe site are already covered and very well vegetated with adequate slopes and(2) sensitive wetland and open water environments are directly adjacent to thesite with certain areas of the site having reverted to wetland-likeconditions. Any grading, capping and revegetatlon would not Improve over theexisting site conditions,

39

AR302255

The selected remedy la as protective of hunan health as Alternatives 3, 4A,and 4B because the sane existing and future direct contact risks are mitigatedbut at a lower cost. Further, the selected remedy Is note protective of theenvironment since the area* of the site which are stable and already provide /m.value to the biological community are left intact and because encrouchment of r )the cap near the wetlands and the pond is reduced considerably. Both the -̂ ,short-tern and long-term effectiveness of the selected remedy both for thesoil capping and the institutional controls are as good as the otheralternatives where capping Is detailed. Further, the replacement: of certainwells adjacent to the site Is very effective and precludes the need formonitoring in that area and Is thus more cost-effective, The Implementabilltyof the institutional controls, particularly for restricting water welldevelopment, will be straightforward as the state well permitting program is inplace with the state authority to approve or deny water well development, Theplacement of deed restrictions is less straightforward but would beaccomplished by the state through mechanisms recently developed by the DNRECSolid Waste Branch for active landfill facilities. Although authority does notexist at the itate level to specifically preclude all activities on thelandfill, language either placed In deeds or as declarations to the deed whichstate the presence of the landfill will preclude activities on the landfill,These institutional controls would be permanent controls as would the onsltecapping and offsite water well replacement, The toxlclty of contaminantswithin the landfill will not be reduced as no treatment of landfill contentswill occur (except for drum wastes found to be hazardous). The nobility ofcontaminants offsite is presently reduced considerably by the presence of theorganic silts beneath much of the landfill ard the hydrologlc groundwaterregime existing in the vicinity of the river, The short-term effectiveness ofthe cap In reducing infiltration and altering the existing evapotransporationregime will not be as good as the existing site conditions since areas to begraded, covered with soil, and revegatated are presently vegetated with a widevariety of flora, However, this will likely not Increase the mobility of theonslte contaminants since surface drainage controls will be In place during thegrading activities.

Summarily, the selected remedy is found to be the more cost-effective while atthe same time addressing the onslte and offsite risks identified in theremedial Investigation. Further, the remedy Is as effective both in theshort-term and the long-term as the other alternatives which Include soilcapping.

Preference for Treatment as a Principal Element

The selected remedy will be using incineration as the only permanent treatmentand this will apply only to the contents of drums found either on the surfaceof during the grading of certain areaii of the landfill where these contentsare determined to be hazardous wastes. The remedial Investigation did notidentify areas of the landfill which would require special treatmentexcept where drums are found nor did the risk assessment identify existingunacceptable offsite risks to human health which would be associated with thelandfill, Finally, the very large area and volume of the landfill precludedany practicable treatment of all the landfill wastes,

HR302256

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APPENDIX A: AdBtnlstntlve Record Index

flR302257

LANPPIU. SITEAEHINISTRATIVE RECORD *

SITE IDENTIFICATIONPreliminary Assessment'and Site Investigation Reports1) Memorandum to Mr. Jeffrey Haas, U.S. EPA, from Mr. James L. Bailey, U.S. EPA,

re: Trip Report of Wildcat Landfill, 5/13/60. P. 1-4. Two site maps areattached to the memorandum.

2) Report: A Resampling Trip Report of Wildcat landfill, TCP No. F3-B20S-01,prepared Dy Ecology and Environment, 8/9/82. P. 5-169.

3) Report: A Hydrogeoloqic Study For Wildcat landfill. TCP Ho. F3-8209-10A,prepared by Ecology and Enviroment, U/a/82. p. 170-195. Reterences-arelisted on P. 182.

4) Letter to Mr. Alan 0. Thompson, Kent County Planning Office, fron Mr. Chriajatcnari, U.S. EPA, re: Site Inspection Reports, 3/25/83. P. 196-214.The following are attached to the letter:

a) Identification and Preliminary Assessment Report>b) Site Inspection Report;c) Tentative Dispositionsd) Final Strategy Determination.

Correspondence

1) Letter to Mr. John Harsch, U.S. EPA, from Mr. Robert J. Touhey, DelawareDepartment of Natural Resources and Environmental Control, re: publichealth risk at Wildcat Landfill, 6/29/83. P. 1-1.

* Administrative Record available 5/23/88, updated 5/3V88.(kite: Coipany or organizational affiliation is identified in the index onlywhen it appears in the record.

ftR302258

REMEDIAL RESPONSE PLANNINGWork Plans •.

1) Report; Remedial Action Master Plan. Wildcat Landfill Site, Rent County,' Delaware, prepared by sw Associates, Inc.. 12/83. P. 1-145. References

'ace listed on P. 103-108.

2) Letter to Mr. Thomas toltaggio, U.S. EPA, fron Hr. John T. Barndt, DelawareDepartment of Natural Resources and Environmental Control, re: transmittalof the Final Site Specific Quality Assurance Project Plan, 11/1/85. P. 146-408.The following are attached to the letter:

a) a memorandum regarding ccmnenta on the Wildcat Landfill RemedialInvestigation/Feasibility Study Quality Assurance Project Plan;

b) a report entitled "Site Specific Quality Assurance Project Plan*;o) a memorandum regarding Wildcat Landfill Remedial Investigation/

Feasibility Study Quality Assurance Project Plan;d) a memorandum regarding XSS Minimum Detection Limits for Acid and

Base-Neutral Bxtractable Organic Compounds;e) a memorandum regarding Trace Organica Detection Units;f) a letter regarding written approval of the Wildcat Landfill Site

Specific Quality Assurance Plan;g) a letter regarding written approval of the Quality Assurance Plan

for Wildcat Remedial Investigation/Feasibility Study;h) a memorandum regarding the review of the evidence control log*

3) Report: Sample Plan, Remedial Investigation/Feasibility'Study. WildcatLandfill,'Paver, Delaware, prepared by CH2M Hill, U/Z7/B5. P. 409-478.The following are attached to the report:

a) a memorandum regarding changes to the Wildcat Sampling Plan;b) a letter regarding changes to the Wildcat Sampling Plan;c) a letter regarding modification to the sampling plan;d) a letter regarding changes and additions to the sampling plan;e) a letter regarding changes in the sampling plan;f) a memorandum regarding Final Revisions to the Wildcat Project

Sampling Plan, dated November 1, 1985;g) a letter regarding water wall construction;h) a memorandum regarding Sampling Plan Discussions for Wildcat Project;i) a letter regarding comments and racaimendationa on the Wildcat_-tandfilt,Sam?ling Plan; ' , «. >

j) a memorandum regarding clarification of changes to Wildcat ProjectSampling Plan, Cost Estimates, Deportment Contract, and WildcatState Date;

It) a letter regarding final changes to the November 1, 1985 Sampling Planat Wildcat Landfill;

1) a letter regarding approval of the Sampling Plan and Health andSafety Plan for the Wildcat Project;

m) a memorandum regarding Specific Gravity Tost for Wildcat Landfilln) a memorandum regarding Specific Gravity for Wildcat Superfund Project;o) a memorandum regarding Specific Gravity and Oxidation-Reduction

Potential (Eh); .

aR3Q2259

p) a letter regarding changes to the Wildcat Sampling Plan pertainingto the residential well sampling?

q) a memorandum regarding changes to the Wildcat Sampling Plan pertaininto the residential well sampling.i

4) Letter to Mr, John Bamdt, Delaware Department of Natural Resources andEnvironmental Control, fron Ms. Sadia Kissoon, CH2M Hill, ret transmittalof the Revised Work Plan for Wildcat Feasibility Study, 3/4/88. P. 479-492.The Revised Work Plan is attached to the letter.

Remedial Investigation/Feasibility Study reports

1) Report: Agenda, General Information Meetings, Submission of 254 form andSupporting References, Wildcat Landfill Remedial Investigation andFeasibility Study, (no author cited), 2/13/85. P. 1-32.

2) Letter to Mr. Benjamin Coaton, Delaware Department of Natural Resourcesand Environmental Control, frctn Mr. Henry Harris, CH2M Hill, Inc., re:transmittal of revised scope of work and cost estimates for the RemedialInvestigation and Feasibility Study of the Wildcat Landfill, 6/6/65.P. 33-68. A Proposed Scope of Services is attached to the letter.

3) Report: Progress Report, Wildcat Landfill Remedial Investigation andFeasibility Study, prepared by CHZH Hill, Inc., 6/3.7/85-12/6/85. P. 69-165.

4) Contract for Personal Services by and between CH2M Hill Southeast, Inc.,and the Department of Natural Resources and Environmental Control, 7/3/85.P. 166-213. Hie following are attached to the contract:

a) Attachment A, Scope of Services, Wildcat Landfill RemedialInvestigation and Feasibility Study;

b) Aiwndment Number 1 to Contract for Personal Services;c) Amendment Number 2 to Contract for Personal Services.

5) Report: Remedial Investigation/Feasibility Study Scope of Work (no author cited),(undated). P. 214-223.

6) Report: Super-fund Program Proposed Plan, Wildcat Landfill Site, KentCounty. DE, prepared by Department ot Natural Resources and EnvironmentalControl and Environmental Protection Agency, Region III, 5/88. P. 229-234.

-" ' Lf - * '7) Report: Technical Memorandum No. 1, Initial Identification of FederalApplicable or Relevant and Appropriate Requirements for the Wildcat Site,prepared by CB2M Hill, Inc., 5/88. P. 235-284.

8) Report: Draft Feasibility Study Report for Public Cement, prepared byCH2M Hill, Inc., 5/85. P. 285-396.

9) Report: Remedial Investigation Report, Tfolume I, prepared by CB2M Hill,Inc., 5/88. P. 397-698,

flR302260

-x. 10) Report! Remedial Investigation Report. Volume II, Appendices to thei Remedial Investigation Report, prepared by CHZM Hill, Inc., 5/B8.

-• • P. 699-874.

11) Report: Remedial Investigation Report, Volume'III. Chemical'AnalyticalData, prepared by CH2M Hill, Inc., 5/88. P. 875-1177.

12) Report! >Remedial Investigation Report, Voluire_IV> Appendices to theBiglogicansaessment, prepared by CH2M Kill, Inc.) 5/88. P. 1178-1367.References are listed on P. 1204.

Correspondence1) Memorandum to Mr. Robert J. Touhey from Mr. Michael A. Apgar and Ms. Marlin

P. LaRiccia, re: potential health threat and possible fencing needs of theWildcat Landfill, 5/20/83. P. 1-3. A Proposed Outline For FieldInvestigation and Evaluation of Wildcat Landfill is attached to thememorandum.

2) Memorandum to Mr. Robert J., Touhey, Mr. Gerard L. Esposito and Mr. MichaelA. Apgar, Delaware Departmer t of Natural Resources and EnvironmentalControl, from Mr. John Barndt, Delaware Department of Natural Resourcesand Environmental Control, re: Initial Meeting For Wildcat LandfillRemedial Investigation/Feasibility Study Between CHZM Hill and DelawareDepartment of Natural Resources and Environmental Control, 7/30/85.P. 4-4.3 3) Memorandum to the Wildcat File from Mr. John Barndt, Delaware Departmentof Natural Resources and Environmental Control, re: Work Plan Modifications,9/11/85. P. 5-9.

4) Memorandum to Ms. Catherine A. Hast ropier i, U.S. EPA, from Mr. EdnundSkernolis, U.S. EPA, re: time extention [sic] for Wildcat Cooperative Agreement,3/26/86. P. 10-11. A letter requesting an extension of tine is attached tothe memorandum.

5) Letter to Mr. Thomas C. Voltaggio, U.S. EPA, from Mr. G«y A. Molchan,Delaware Department of Natural Resources and Environmental Control, re:identifying State Applicable or Relevant and Appropriate Requirements (ARAR's),6/30/87. P. 12-13. A li.it of potential ARAR's is attached to the letter.

6) Letter to Ms. Sadia Kissoon-Parker, CH2M Hill, from Mr. Andrew Palestini,U.S. EPA, re: Federal ARAR's to be used in Feasibility Study, 1/21/88.P. 14-16.

7) Letter to Mr. Henry Harris, CH2M Hill, Inc., from Mr. Joseph J. Hardman,Delaware Department of Natural Resources and Environmental Control, re:Approval of Scope of Work Change for Federal ARAR Development, 2/5/88.PT17-17. ^̂

J9R30226I

8) Letter to Mr. Andrew Palestini, U.S. E.P.A., from Mr. Joseph.J. Hardman,Delaware Department of Natural Resources and Environmental Control, re:Wildcat Landfill Feasibility Study Scope of Work Change for Federal ARARDevelopment, 2/5/88. P. 18-18.

9) Letter to Mr. John T. Brandt, Delaware Department of Natural Resourcesand Environmental Control, fran Andrew Palestini, U.S. EPA, resdeveloping of the Federal ARA'a for the Remedial Investigation/FeasibilityStudy report, 3/9/88. P. 19-19.

10) Letter to Mr. Andrew Palestini, U.S. EPA, from Mr. Joseph o, Hardman,Delaware Department of Natural Resources and Environmental Control, re:extension of Wildcat Landfill grants, 3/15/88. P. 20-20.

Work Assignments1) Letter to Mr. Thomas P. 'Eichler, U.S. EPA, from Mr. John E. Wilson,

Delaware Department of Natural Resources and Environmental Control, re:application for Federal Assistance, 9/19/84. P. 1-38. The application isattached to the letter.

2) Letter to Mr. Steve Goodbred, united States Fish and Wildlife Services,fran Mr. Daninic Digiulio, U.S. EPA, re: biological assessment at andaround the site, 10/8/85. P. 39-63. A letter regarding the scope ofwork for the Wildcat Bioassessment Study and a report entitled "ProposedSampling Plan to Assess Impacts of Wildcat Landfill, Dover, Delaware, OnFish And Wildlife Resources* ore attached to the letter.

^3) Memorandum to Mr. John E. Wilson fran Mr. John T. Bamdt re: Wildcat l̂Supertund Project Grant Amendment Application, 2/6/86. P. 64-80. TheGrant Amendment Application is attached to the memorandum.

4) Memorandum to the Wildcat Files fron Mr. John T. Brandt ret WildcatRemedial Investigation/Feasibility Study Grant Amendment Cert Estimate,2/10/86. P. 81-82.

5) Letter to Mr. Roy Schrock, U.S. EPA, fron Mr. John T. Brandt, DelawareDepartment of Natural Resources and Environmental Control, re: extendingWildcat Landfill grant period, 3/5/86. P. 83-83.

6) Memorandum to Mr. John; E. Wilson, Delaware Department of NaturalResources and Environmental Control, from Mr. John Brandt, DelawareDepartment of Rajbural Resources and Environmental Control, re:; WildcatGrant'Amendment Application, 3/6/86. P. 84-118. The Grant AmendmentApplication is attached to the memorandum.

7) Letter to Honorable John E. Wilson, Delaware Department of NaturalResources and Environmental Control, fran Mr. William T. Wisniewski,U.S. EPA, re: approval of the assistance amendment to extend the budgetand project periods , 4/15/86. P. 119-120. The assistance amendnntapplication is attached to the letter.

8) Memorandum to Mr. Roy Schrock, U.S. EPA, fran Mr. Jim Butch, U.S. EPA, retWetlands Determination, 4/21/86. P. 121-121. !' ,T| .

! QRR302262

J

9) Letter to' Honorable John E. Wilson, Delaware Department of NaturalResources and Environmental Control, fron Mr. Stephen T. Golding, DelawareOffice of Budget Director, re: approval of request for additional federalfunds, 4/23/86. P. 122-122.

10) Letter to Ms. Catherine Hastropieri, U.S. EPA, from Mr. John E. Wilson,Delaware Department of Natural Resources and Environmental Control, re:transmittal of the assistance amendment application for the Wildcat Landfill,6/17/86. P. 123-125. The assistance amendment application is attached tothe betteri

11) Memorandum to Mr. David W. Charters, U.S. EPA, from Mr. Andy Palestini,U.S. EPA, re: transmittal of the final report on Environmental ResponseTeam's Assessment at the Wildcat Landfill, 7/20/87. P. 126-130. The finalreport is attached. .

12) Memorandum to Mr. John E. Wilson, Delaware Department of Natural Resourcesand Environmental Control, frcm Mr. John T. Brandt, Delaware Departmentof Natural Resources and Environmental Control, ret Wildcat SuperfundProject Grant Amendment No. 3 Application, 9/17/87. P. 131-146. TheGrant Amendment No. 3 Application is attached to the mnorandun.

13) Letter to Honorable John E. Wilson, Delaware Department of NaturalResources and Environmental Control, from Mrs. Francine Booth, DelawareOffice of Budget Director, re: review of Wildcat Landfill RemedialInvestigation and Feasibility Study/tamdment, 9/29/87. P. 147-147.

14) Memorandum to Mr. John E. Wilson, Delaware Department of NaturalResources and Environmental Control, fron Mr. John T. Brandt, DelawareDepartment of Natural Resources and Environmental Control, ret WildcatLandfill Superfund Grant Antndnent No. 5 Application, 3/4/88. P. 148-170.The Grant Amendment No. 5 Application is attached to the nenrandun. .

15) Letter to Honorable John E. Wilson, Delaware Dipartment of NaturalResources and Environmental Control, fron Mr. James M. Seif, U.S. EPA,re; approval of the assistance amendment to extend the budget and projectperiods, 4/1/88. P. 171-172. The assistance amendment is attached to theletter.

AR302263

Calamity RalatlonaTlan1) Repoeti QiminitvBalationa Ply-'Wildcat Uhdfill 3it«/tohfc Qxntv.

Dover, •frlawara, prBpatad ly MB corporation, VIU. P. i-23.2) Report: Coiiiiinitv RBlaticm Plan Uxtote/Hildcat landfill Sita. tent

County, l&ver. Eniaware, prepared byfi. ttaan H. httgmld, bKparnmnt of Natural tteaources and Bwironraental Control* 9/85.P, 24-33.

o

b

"V--' CPBML cuip/aa DocDmirM *

I) "Promotion of Sle» ttn flpd«t«i I-*," Ftd>nl iMiie.r. d«cid 4/10/86.

2) "PropoMl of updict 4," Fidtnl tulmr. lUttd 9/18/83.

3) Miaonndua co IT. S. IPA frn Mr. G«n« Luciro r«|irdtn| cowuUty ctltcioai•c Suptrfund Znforc«»«t ileti, dacid 8/28/83.

4) OronndmtBr ConttaiMClon «nd Frocictlan. uadictd by Mr. Dauld V.rcllcUao on 8/28/83, " "

3) Mnoriadui to Toile Wtic« hUuintac Dlvliion Dtrieeon Itflani I-X (ro«Mr, WUHw H«d«Ma tad Mr, G«M Lue«a tit Policy on FloodpUlu tad

AtiiiMinti for CZKCU ActloM, 8/6/83.

6) Oaidaact of Ktudlil InT«itli«tloni ond«r CHCLA. d«c«d 6/83.

7) Guldaaei oa fMitbility Studlta andir CCTCLA. dtcid 6/83.

8) "Propoitl of Opdttt 3," Ptd«r»l Htjlitir. d4ttd 4/10/83.

9) Mnonndia to Mr. Jack MeGrw tncttlid "ComitUtr blatloai AetlTicii«C Suptrfuod Sleii - Inctrii Guidtaei,' ditid 3/22/13.

10) "Propoul of Op<Utt 2,' Pidinl Ujlitir. dicid 10/13/84

11) EPA Crouadwtir Piotietioa 5ent«ty. d«tid 9/84,

12) MnoriadM to 0.8. RPA fro* Mr. Htllla Itclain, Jr. MitcUd"Tnntattul u 8up«rfuad Inoral Proctdurii - Uvlilon 2,' dat*4 1/20/84,

13) "Propoitl of Opd*C« 1,' P«dir«l Utlitit. d«Cid 9/8/83.

14) CflynltT UUtloni la SuMrfundt A Hindbook (JBt«rt» mtloa). d«tid9/83.

13) •Ptopo«4l of Mi« iMloul Prlorltr UK," Pidinl Ittiicir. <Ucid12/30/«. *- :! *̂

'l

16) "Eipaadtd UlilbUlty Lilt,* Fidoril Ittlitir. dicid 7/23/62.

17) 'lae.rl. Priatleiti Hit.' Pid>nl iMJUir. (Utld 10/23/81.

18) OneantroUid Hitirdoui Ifnti 8tci Unklni incai A gut'i JUmul(und««d). '

19) Flild itindird Omnctni froeidurit - Air 8urr«illiBe« (ondttid).

20) Pt»ld 3tind«rd OpintiM froetdurn - ilti 5ifit? Plin (und*Cid),

* Loeicid, to EPA S«|ion III offte*. RR302265

APPENDIX B; Retfponfllvencfls Sunoary

O

Wildcat Landfill • Responslveness Summary

Section 117 CERCLA, as amended by SARA, requires that a proposed plan be madeavailable for public review, DNREC and EFA have accepted comments on theProposed Flan and the draft Remedial Investigation/Feasibility Study reportsbeginning May 26, 1988, and ending June 24, 1988. A public meeting was held onJune 16, 1988, at the DNREC building auditorium in Dover (Kent County),Delaware to discuss the findings of the remedial investigation, present thealternatives developed to mitigate the problems posed by the site, and presentthe preferred alternative of DNREC and EFA,

During the public comment period, comments were submitted by Playtex, Inc.This Responsiveness Summary summarizes their comments by topic, followed bythe DNREC and EPA response to these concerns and comments,

Written comments received from Playtex Inc. (received by DNREC and EPA on June23, 1988):

1, Comment:

The 30-day public comment period does not meet the Section 117(a) CERCLArequirement that a reasonable opportunity for public comment be provided bythe agency since the study had lasted 8 years, Also, the preferredalternative was not announced until one week before the expiration of thepublic comment period,

Response:

First, the National Contingency Plan (NCP) presently requires a 21-daycomment period for remedial action plans, The revised NCP, not yetadopted by EPA, has proposed a 30-day public, comment period, Thus, the30-day comment period chosen by DNREC and EFA for the Wildcat Landfillpublic comment period exceeds the requirements of the existing NCP. Thisdecision is also consistent with EPA Region III policy. The 30-day commentperiod is regarded by DNREC and EPA as "providing reasonable opportunity"for public comment on the Administrative Record and the Proposed Plan,

Second, the Proposed Plan, which outlines the preferred alternative, wasmade available to the public at the beginning of the 30-day comment periodas part of the Administrative Record, not one week before the close of thepublic comment period. Notice in the local newspaper and other mediaoutlined the preferred alternative and provided notice of the publicmeeting. Copies of the Proposed Plan were also available at the DoverPublic Library and the offices of DNREC and EPA Region III, The ProposedPlan provided a brief analysis of the preferred alternative as required byCERCLA Section 117(a)(1),

Third, the remedial investigation field work was Initiated in December1985 and the Proposed Flan was made available in May 1988. The RI/FS andProposed Plan were completed in 2-1/2 years and It was primarily thesefindings that were used by DNREC and EPA In developing the preferredalternative found in the Proposed Plan and the Record of Decision.

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2. Comment:

The remedial plan Is expensive and noc erst-effective when compared to therisks that are posed by the site, The reports and studies are speculative,particularly where risks are evaluated. The Institutional control andmonitoring plan would be a cost-effective solution In accordance withSection 121<b) of CERCLA with respect to the risks found at the site.Covering rather than capping would better Unit contact by unauthorizedpersons,

Response;

First, the preferred alternative and the evaluation of all the alternativesfound In the RI/FS, Proposed Flan, and Record of Decision, oust considereight criteria when evaluating alternatives, namely, short-terneffectiveness, long-term effectiveness and permanence, reduction intoxicity and mobility and volume, Implementablllty, compliance withapplicable or relevant and appropriate Federal and State requirements,overall protection of human health and the environment, cost, and communityand acceptance, The preferred alternative was chosen by DNREC and EFA toprovide a remedy which gives the best balance possible among the eightcriteria.

Second, risk assessments oust Include nany assumptions as to the exposureand effects of exposure on hunans, The approach utilized for the WildcatLandfill risk analysis Is generally a worst-case scenario which is veryprotective of human health. Because of the assumptions that must be takenin risk analyses, very definitive statements cannot be nade, Rather,probabilities oust be used resulting in the need for words such as "could"and "nay".

Third, the monitoring and institutional controls alternative was notselected because It did not meet the requirements for long-terneffectiveness and permanence, and compliance with applicable or relevant andappropriate requirements. Nor were the existing direct contact risks andfuture direct contact risks addressed solely by that alternative, However,aspects of that alternative are part of the preferred remedy.

Fourth, the preferred alternative proposed a soil cover in lieu of the soilcaps in alternatives 4A and 4B. The soil cover proposed consists of i1.5 feet of compacted soil and 0,5 feet of uncompacted soil for vegetation,The purpose of the soil cover is to (1) limit the direct contact risksidentified In the risk assessment, (2) prevent erosion fron a 100-yearstorm event, (3) provide for stable vegetative cover, and (4) meet theminimum applicable or relevant and appropriate state and federalrequirements. The soil cover that has been chosen is necessary to meetthese requirements,

18302268

b

3. Comment::

The projected overhead and administrative coats are disproportionately highand therefore not cost-effective,

Response:

The high contingencies Included In the Feasibility Study are based on theuncertainties associated In developing an alternative without doing theactual design. These contingency costs are actually lower In the preferredalternative as more detailed Information was given to the contractor Inestlnatlng the cost of the preferred alternative. These costs are detailedIn Chapter 6 of the final Feasibility Study report,

4. Comment:

Alternatives 3, 4A, and 4B are extrene In neetlng the problems posed by thesite,

Response:

The primary objective of the Feasibility Study li to develop a range ofwatte management options that protect human health and the environment,These are to Include the no-action alternative, The list of alternativesare developed coincident with the Remedial Investigation while the problemsand risks posed by the site are being evaluated, Consequently, the agenciesrequire a range of alternatives which will be able to address those problemsand risks posed by the site, In the case of the Wildcat Landfill preferredremedy, a modified version of Alternative 4A was chosen, DNREC and EFAagreed that to grade and cap the entire surface of the landfill was notwarranted and that to do so would cause unacceptable environmentaldegradation by destroying the established vegetative cover; especially the7,9 acres of onslte wetlands and the 1,9 acres of offslte wetlandscontingent with the landfill, The .Intent of the preferred remedy Is tograde and cover with soil those arena of the landfill which are presentlybarren, contain leachate seeps, or allow water to pond on the surface,

S. Comment:

The decision to study further the pond Is unwise and Inconsistent with thegoals of CERCLA.

Response;

CERCLA Investigations and actions must consider environmental Impacts ofsites which nay not Include purely human health concerns, The decisionto separate the pond Into a separate operable unit was done to allow theU,S, Fish and Wildlife Service to (1) determine the Impacts of elevatedlevels of certain metals In fish upon migratory birds feeding In the pond,and (2) determine whether the metal accumulations found In turtles In thepond are a concern. Rather, It will be an extension of the original RI/FSand with a very limited scope, This study will not Include a new RI/FS,Both EFA and DNREC will be working toward a quick turnaround for thisdetermination.

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