untied states environmental protection agency …

UNTIED STATES ENVIRONMENTAL PROTECTION AGENCYREGION III

841 Chestnut BuidingPhiladelphia, Pennsylvania 19107

SUBJECT: DU Pont-Newport Superfund Site DATE: 2/26/93South Landfill

FROM: Randy Sturgeon, RPMDE/MD Section, Regij

TO: Joan Colson, RRELEPA-Cincinnati

THRU: G Peter Ludzia, ChiefDE/MD Section, Region 3

I am requesting your review of portions of EPA's proposedremedy at the Du Font-Newport Superfund Site (Site). Inparticular, I need help addressing some concerns the PRP hasabout the proposed remedy for the south landfill. EPA's proposedremedy called for in-situ stabilization of the landfill and thencapping with a geosynthetic clay liner (GCL). The stabilizationwould tie up the heavy metal contamination which is especiallynecessary since some of the waste is in the water table. The capwas proposed as additional protection to keep rain water frominfiltrating the waste material. The landfill is triangular inshape with wetlands and a pond being immediately adjacent on oneside, the Christina River being immediately adjacent on thesecond side, and several roads being adjacent on the third side.

The PRP has responded during the public comment period thatthe cap of the stabilized waste was overly protective andtherefore not a cost-effective solution and that thestabilization would not necessarily bind up all the metals (infact, the PRP is stating that some might become more mobile).

I need help answering the following questions:

1. Is stabilization a viable technology for thislandfill? Will it prevent or minimize to the maximum extentpracticable the migration of metals the ground water and then theriver and the wetlands?

2. What is the most appropriate test for theperformance of the stabilization? Is the TCLP test appropriateor some other leach test using de-ionized water or ground waterfrom the Site7 RR32I063

3. Is a cap necessary on top of the stabilizedmaterial? Is a soil cover or single membrane liner adequate?

The goal of the remedial action at the south landfill is toprevent migration of the metals to the adjacent river andwetlands where impacts have been observed and remediation is alsobeing called for (although the PRP also disputes the extent ofEPA's proposed remedies in these areas also). The south landfillis one of the principle threats at the Site and as such treatmentis preferred.

I have attached the pertinent parts of the draft ROD andother useful information. I have discussed this verbally withFrank Freestone and CarIton Wiles on 2/24/93. Due to the timedeadlines for this ROD, I would like a report by March 15, 1993with a verbal report ASAP. Thank you for your help.

RR32I06U

DRAFT—ENFORCEMENT CONFIDENTIAL

DECISION SUMMARY

SITE DESCRIPTION AND BACKGROUND

The E.I. Du Pont, Newport Superfund Site (commonly known asthe Du Font-Newport Site and referred to throughout this documentas the "Site") is located partially in Newport, New CastleCounty, Delaware and partially in unincorporated New CastleCounty, Delaware. It is an approximately 120-acre site locatedat James and Water Streets in Newport, Delaware near the 1-95,1-495, and Delaware State 141 interchange (see Figure 1). TheSite includes land currently occupied by a paint pigmentproduction facility (the CIBA-GEIGY plant), a chromium dioxideproduction facility (the Du Pont Holly Run plant), two industriallandfills separated by the Christina River, and a baseballdiamond (owned by Du Pont and referred to as the ballpark)located just northwest of the CIBA-GEIGY plant across the Amtrakrailroad (see Figure 2).

The pigment plant, originally built during the period from1900 to 1902, was owned and operated by Henrik J. Krebs andmanufactured Lithopone, a white, zinc- and barium-based inorganicpaint pigment. In 1929, E.I. du Pont de Nemours & Company(Du Pont) purchased the plant and continued to produce Lithopone.Due to a decline in popularity, Lithopone production ceased in1952. By this time, however, Du Pont had begun to producedifferent organic and inorganic pigments, as well as othermiscellaneous products. Some of these included purified titaniumdioxide (the titanium dioxide was produced elsewhere), titaniummetal, blue and green copper phthalocyanine pigments (CPC), redquinacridone pigment (QA), high purity silicon, thoriated nickel,and chromium dioxide. In order to expand the production ofchromium dioxide, Du Pont constructed the Holly Run plant duringthe 1970's. In 1984, Du Pont sold the pigment manufacturingoperations to CIBA-GEIGY Corporation, but retained the chromiumdioxide production operations.

The Holly Run plant and the CIBA-GEIGY plant were built onfill material placed over low-lying farmland. Most of the fillmaterial underneath the CIBA-GEIGY plant and a small portion atthe Du Pont plant is contaminated with heavy metals such ascadmium, lead, barium, and zinc. This is a result of disposaloperations and poor storage and handling practices of rawmaterials. As part of the CIBA-GEIGY pigment plant operations

1Known locally by some as the Christiana River. It is asecondary contact recreational river and used for boating, waterskiing, and fishing.

AR32I065


(although prior to CIBA-GEIGY's ownership), waste and off-specification products were disposed of in the north and southlandfills. The north landfill was used for the disposal ofLithopone wastes, other organic pigment wastes, chromium wastes,and other miscellaneous wastes including off-spec thoriatednickel. Wastes were disposed of in the north landfill from 1902to 1974. The south landfill was used for the disposal of largequantities of Lithopone wastes. The south landfill operated fromapproximately 1902 to 1953.2 A small portion of the ballparkappears to have become contaminated when contaminated soil fromthe pigment plant was used to groom the field.

2Note that all on-Site disposal activities stopped prior tothe enactment of the Resource Conservation and Recovery Act(RCRA, 42 U.S.C.SS6901 et seq.). Therefore, none of thecontaminated media being remediated at this Site is or contains alisted-RCRA hazardous waste (unless it is found that waste existsat the Site caused by post-1980 activities that qualifies as alisted-RCRA hazardous waste). However, if on-site or off-sitedisposal occurs (as defined when "placement" occurs), RCRA may bean applicable or relevant and appropriate requirement (ARAR) ifthe waste is a characteristic-RCRA hazardous waste. Whennecessary, the determination of whether or not RCRA is an ARAR isdiscussed for each area of the Site under the "Description ofAlternatives and Summary of the Comparative Analysis ofAlternatives" section and in the "Compliance With Applicable orRelevant and Appropriate Requirements" section of this ROD.

RR321066


SOILS

The RI determined that high concentrations of certain metalsexist in soils in the north landfill, in the south landfill, andunderneath the CIBA-GEIGY and the Du Pont Holly Run plants.Elevated levels of metals were also found in the ballpark.Background metal concentrations for soils in the vicinity of theSite were difficult to establish due to the generally disturbednature of the soils in the area. For this reason, metalsdetected in the soils at the Site were compared to reportedbackground soil concentrations in a northern Delaware ste in theU.S. Geogical survey's "Element Concentrations in Soils and OtherSurficial Materials of the Conterminous United States" (seeTable 1) which EPA has determined are adequate for this RI.Figure 3 shows the location of soil samples collected during theRI and where metals levels exceeded background (i.e., wherecontamination is present). It also lists contaminant levels atvarious locations. At many of these sampling locations, a numberof samples were collected at different depths.

Barium, zinc, cadmium, arsenic, lead, mercury, silver,antimony, cobalt, copper, selenium, and vanadium were alldetected above background levels. Of these metals barium, zinc,cadmium, and lead were the most prevalent. Contaminant levelsunderneath the CIBA-GEIGY plant are as high as 0.6% arsenic, 13%lead, 9% barium, and 6% zinc. The north landfill has levels ashigh as 4% barium, 5% zinc, and 5% lead. The south landfill haslevels as high as 7% barium, 1.6% lead, and 1% zinc.3

As indicated above, the north and south landfills areheavily contaminated. See Table 2 for a list of estimatedquantities of materials that were disposed of in the northlandfill. One of the largest waste streams at the Site came fromthe Lithopone process where raw zinc and barium ores were refinedto make a paint pigment. This waste stream consisted insolubleresidues from the zinc and barium refining process. This residuecontained all of the heavy metal contaminants present in the rawmaterial ore as well as zinc and barium. Some of this wasteappears to have been disposed of in the north landfill althoughmost of it went to the south landfill.

310,000 parts per million (ppm) are equivalent to onepercent. Therefore, soil containing 5% lead is equivalent tosoil containing 50,000 ppm lead.

SR32I067


To get to the south landfill, this Lithopone waste streamwas pumped as a slurry through a pipeline to the south side ofthe Christina River and discharged into a wetland area. Dikeshad been built to control the movement of the sludge (whichhardened upon exposure to air, forming the south landfill),however aerial photographs show that at times, the dikes werebreached, and the sludge flowed into areas of which some arestill wetlands today.

The south landfill was covered in the early 1970's with soilexcavated from the area which is now part of the DelawareRoute 141 Christina River bridge approach ramp. This was done bythe Delaware Department of Transportation (DelDOT) as part of thebridge construction. In order to construct this bridge, BasinRoad (or South James Street) was moved west onto the southlandfill. Historical aerial photographs show the south landfillextended to the edge of the original Basin Road. DelDOT soilborings taken in the early 1970's confirmed this when one of thestratigraphic units in several borings located between the newand old Basin Road was characterized as "chemical fill" (seeFigures 4 and 5).

RR32I068


From the results of the RI/FS, EPA has determined thatcontaminated soil or sediments in several areas of the Site areprincipal threats. The principle threats include thecontaminated soil beneath the CIBA-GEIGY plant, the contaminatedwaste in the north and south landfills, and the contaminatedsediments in the north drainage way (adjacent to the northlandfill). The sediments in the north drainage way havecontaminant levels as high as 3% lead and 2% zinc.

Section 300.430(a)(1)(iii) of the NCP states that "EPAexpects to use treatment to address the principal threats posedby a site, wherever practicable," that "EPA expects to useengineering controls, such as containment, for waste that poses arelatively low, long-term threat or where treatment isimpracticable," and that "EPA expects to use a combination ofmethods, as appropriate, to achieve protection of human healthand the environment." It also states that "EPA expects to useinstitutional controls.........to supplement engineering controlsas appropriate.......," and that institutional controls may beused "where necessary, as a component of the completed remedy."However, the NCP also states that institutional controls "shallnot substitute for active response measures........as the soleremedy unless such active measures are determined not to bepracticable........."

After giving careful consideration to available technologiesand Site characteristics, EPA has determined that treatment ofthe contaminated soil in the south landfill is practicable.

11 AR32I069


SUMMARY OF AREAS REQUIRING REMEDIATION

In summary, based on the potential impacts to human healthand the environment, EPA has determined that the following areasof the Site warrant remediation:

1. Ballpark: This area has surface soils above EPA'sclean-up criteria of 500 ppm that create an unacceptable risk tohuman health.

2. North landfill including the drainage way: This areacontinually releases contaminants to the ground water in the filland/or Columbia aquifers which affects shallow ground water inthe direction of migration and ground-water discharge areas. Oneof the discharge points that is affected is the Christina Riverwhich has Ambient Water Quality Criteria (AWQC) exceedances andsome sediments which exhibit unacceptable environmental impacts.Another discharge point is the north drainage way, parts of whichexhibit extreme impacts to ecological receptors.

3. South landfill: This area continually releasescontaminants to the ground water in the fill zone and/or Columbiaaquifers which affects shallow ground water in the direction ofmigration and ground-water discharge areas. The two discharge

22 ftR3ZI070'


points are the river and the south wetlands which have AWQCexceedances and some sediments which exhibit unacceptableenvironmental impacts. Any subsurface maintenance orconstruction activities would result in unacceptable risks tohumans.

ftft32IQ7l23


SOUTH LANDFILL

ALTERNATIVE #2: This alternative would involveinstitutional controls, access road improvements on the berm inthe south wetlands, excavation and backfilling of the portion ofthe landfill underneath and to the east of Basin Road (i.e., allof the landfill currently on Delaware Department ofTransportation (DelDOT) property) with consolidation in the restof the landfill, and installation of a low-permeability coverover the portion of the landfill on Du Pont property (see Figure28). Also, in order to provide better Site security to controltrespassing, additional fencing and a barrier of plants (perhapsthorny plants) would be installed around the entire southlandfill area including the landfill and the adjacent wetlandarea. The institutional controls would include a notification inthe deed regarding past land use, and restrictions on future landuse. Access road improvements would involve regrading thesouthern berm, installing erosion control matting, adding crushedstone on top of the berm and installing a culvert through theexisting breach. The low permeability cover would be of the sameconstruction as on the north landfill. The present worth cost ofthis alternative is $7,000,000. ^

AR32I0720


ALTERNATIVE #3: This alternative is the same as Alternative#2 with the addition of a physical barrier wall that extends tothe base of the Columbia aquifer (technology to be chosen duringremedial design from deep soil mixing, soil/bentonite slurry,sheet piles, or geosynthetic membrane) along the river and groundwater recovery and treatment similar to that described inAlternative #2 for the north landfill. The present worth cost ofthis alternative is $16,000,000.

ALTERNATIVE #4: This alternative is the same as Alternative#2 except that the waste in the south landfill will be stabilizedin-situ prior to capping. By stabilizing the waste, the abilityof the metals to be leached by the ground water will be greatlyreduced.16 Currently the water table is in the waste materialand even after capping, about two feet of waste will still be inthe water table. For the purposes of the feasibility study,Portland Cement Type I was used as the stabilization agentalthough a design optimization study would have to be done todetermine the appropriate agent to be used during the remedialaction. The present worth cost of this alternative is$15,300,000.

COMPARATIVE ANALYSIS OF ALTERNATIVES: The "no action"alternative does not meet the threshold criteria of overallprotection of the environment because of continued contaminantrelease to the ground water which discharges to the adjacentwetlands and contaminates the sediments and the surface water.Alternatives #2, #3, and #4 call for capping the landfill whichwould greatly reduce the release of contaminants to the groundwater thereby protecting the wetlands and the river andcontributing to a reduction in ground-water contaminant levels(which exceed MCLs) and to a reduction in surface watercontaminant levels (which exceed AWQCs in the south wetlands andthe river). Also, by consolidating the landfill, all of thelandfill could be capped, and potential worker exposure duringany future subsurface work along Basin Road would be eliminated.

Currently, much of the waste in the south landfill is belowthe water table. Capping the landfill would reduce the ground-water mound, but approximately two feet of waste would still bein the water table even after the mound dissipates. By

16If the material to be stabilized fails the TCLP test, RCRAland disposal regulations would be considered ARARs. Althoughthe regulations would not be applicable because no placementwould occur (because the treatment would be done in-situ), theregulations would be relevant and appropriate because the wastewould be similar to RCRA hazardous waste and the regulationswould be well-suited to the remedial action. IB'39 I D 7*3

30


stabilizing the waste before it is capped (as called for inAlternative #4), the amount the of contaminants that could beleached out by natural ground-water flow would be limited to themaximum extent practicable, thereby contributing to theprotection of the ground water and the surface water.17

Most of the major ARARs for this part of the Site arerelated to the protection of wetlands (see Table 12).Alternatives #2, #3, and #4 all meet their respective ARARs.Care would be taken during the design and construction to preventany adverse affects in the south wetlands and the ChristinaRiver. Any wetlands that would be destroyed during remedialaction would be replaced on a one-to-one area ratio. ForAlternative #4, if the waste material fails the TCLP test,compliance with the RCRA land disposal regulations would beaccomplished by making sure the stabilized material passes theTCLP test.

RCRA Subtitle C landfill ARARs (in particular those relatedto closure) are not ARARs for the south landfill. Although thereis currently waste material in the south landfill that could beclassified as RCRA-hazardous waste, disposal occurred before 1980so these regulations are not applicable. These regulations wouldbe relevant for Alternatives #2 and #3 since the waste beingcapped would be a RCRA-hazardous waste. However, forAlternatives #2 and #3, they are not appropriate because they arenot well suited for this area. One of the major closurerequirements is for a cap to be installed that is less permeablethan the liner or natural subsoils underneath the waste (toprevent a bathtub effect). This is an inadequate requirement forthis area it would allow a cap that would not adequately controlinfiltration. For Alternative #4, since the waste is beingstabilized to the point of no longer being a hazardous wasteprior to capping, these regulations would not be relevant.

17Although in wastes with a large number of metalcontaminants, stabilization has been shown in some studies tocause the leachability of some contaminants to increase whiledecreasing others, stabilization has been determined by EPA to bethe best demonstrated available technology (BOAT) for soils andsludges with heavy metal contamination. A design optimizationstudy would have to be done during remedial design to determinethe proper type and amount of stabilization agent. It shouldalso be noted that stabilization decreases mobility by not onlydecreasing the leachability, but also greatly decreasing thepermeability of the waste and therefore reducing the ability ofthe leaching agent (in this case ground water or infiltratingrain water) from coming into contact with the waste. AR32 I 07U*

31

DRAFT—ENFORCEMENT CONFIDENTIAL4- &

Alternative #4 offers the greatest degree of long-termeffectiveness although the difference from Alternative #3 issmall. By stabilizing the waste material (as in Alternative #4),the leachability of the metals would be greatly reduced therebyminimizing the ability of the contaminants from the southlandfill to migrate to the wetlands and cause an impact toenvironmental receptors. While in Alternative #3, any groundwater that comes into contact with waste material, would beextracted before it enters the river (and by pumping, this groundwater could not enter the south wetlands), the extremely highamount of operations and maintenance (that would probably berequired forever) greatly decreases (in comparison to Alternative#4) the ability to maintain reliable protection of theenvironment.

Stabilizing the waste would greatly reduce its mobility butwould increase its volume by about 25%. Alternatives #2 and #3offer no reduction of toxicity, mobility, or volume throughtreatment. Alternative #2 is the best in terms of short-terraeffectiveness (with Alternative #4 being the worst) because ithas the least number of major components. However, in all thealternatives (except the "no action" alternative), traffic alongBasin Road, which is the only easy access to a number of salvageyards, would be greatly restricted and possibly halted duringpart of the construction. Alternatives #2, #3, and #4 are allimplementable with Alternative #2 being the easiest andAlterative #4 being the most difficult. The net present worthcost of Alternative #2 is significantly less than the other two,with Alternative #4 being slightly less than Alternative #3.

EPA has determined that Alternative #4 (consolidation,stabilization, and capping) is the preferred remedy because itprovides the greatest degree of overall protection of humanhealth and the environment, will contribute the most to loweringthe ground-water MCL exceedances and the surface-water AWQCexceedances, meets EPA's preference for treatment, and has thehighest degree of permanence and long-term effectiveness amongthe compared alternatives.

The State supports the selection of Alternative #4. Thepublic supports capping or possibly stabilizing the waste but notboth. Also, strong objections have been expressed to anytemporary complete closing of Basin Road or South James Street.To alleviate the concerns, the performance standards state thatthe excavation must be done in such a way as to allow sometraffic through this area during daily business hours.

32 AR32I075


3. SOUTH LANDFILL

3.1. DESCRIPTION: The portion of the landfill underneathand to the east of Basin Road (i.e., all of the landfillcurrently on DelDOT property) shall be excavated and backfilledwith clean fill, with the excavated soil being consolidated inthe rest of the south landfill.

PERFORMANCE STANDARDS:

3.1.1. A statistically significant number of samples (to beanalyzed for TAL metals) shall be collected to determine theextent (lateral and vertical) of the contamination at the southlandfill on DelDOT property underneath and to the east of BasinRoad (or South James Street).

3.1.2. A task of the remedial design shall be to determinesoil clean-up goals that protect human health and the environment

52 AR32I076

for this excavated area of the south landfill. EPA shall approvethese levels.

3.1.3. Soils above the clean-up criteria on DelDOTproperty, and on whatever Du Pont property necessary to allowconstruction of the cap and to provide unlimited access to theboat ramp at the west side of the James Street bridge, shall beexcavated and consolidated to the remaining portion of the southlandfill.

3.1.4. The excavation activities (and potentially otherremedial action tasks at the south landfill and south wetlands)will require temporary restrictions or re-routing of traffic.Nearby residents and business shall be notified in a timelymanner of any inconveniences. The scheduling of work shall doneis such a way as to allow limited road access through this areaduring normal daily business hours for vehicles which do not havean alternate route.

3.1.5. A statistically significant number of confirmationsamples shall be collected to determine whether or not the soilremaining in the excavation is below the clean-up criteria.

3.1.6. Once the excavation passes the confirmatorysampling, it shall be backfilled with clean fill from an EPA-approved off-site source. Backfilling shall be done in such away as to minimize settlement and provide an adequate base forBasin Road.

3.1.7. After the excavation is backfilled, Basin Road shallrepaved in accordance with DelDOT road construction requirements.

3.2. DESCRIPTION: The waste in the south landfill shall bestabilized in-situ prior to capping. By stabilizing the waste,the ability of the metals to be leached by the ground water willbe greatly reduced. A design optimization study shall beperformed to determine the appropriate stabilization agent to beused.


3.2.1. Prior to stabilization, corings shall be collectedto adequately determine the depth of the waste material (TALmetals analysis may be necessary).

3.2.2. After excavation and consolidation of thesoils/waste from the east portion of the south landfill and thesediments from the south wetlands into the remaining part of thesouth landfill, the soil/waste material in the south landfillshall be stabilized in-sltu. Stabilization shall involve

53 ftR32!077


thoroughly mixing a cementitious or pozzolanic reagent mixturewithout removing the soil from the landfill. All of theunexcavated portion of the south landfill shall be stabilized.

3.2.3. Prior to stabilization, design optimization testsshall be done in order to determine the proper nature andquantity of the stabilization agent. A task of the remedialdesign shall be to develop a work plan (for EPA approval) for thedesign optimization tests. EPA shall approve the choice ofstabilization agents.

3.2.4. Stabilization shall continue until the soil/wastematerial passes the TCLP test (RCRA land disposal regulations areARARs).

3.3. DESCRIPTION: A low permeability cover (of similarconstruction to the north landfill) shall -be installed over theportion of the landfill on Du Pont property (see Figure 28).


3.3.1. The landfill cap shall completely cover thestabilized portion of the south landfill.

3.3.2. The landfill cap shall designed and constructed insuch a way as to limit to the maximum extent practicable anyencroachment on the south wetlands, the south pond, or theChristina River.

3.3.3. The landfill cap shall have a permeability of 10~7cm/sec or less.

3.3.4. The landfill cap shall have at least two layers oflow permeability material, one of which shall be a geosyntheticmembrane.

3.3.5. The landfill cap shall be designed and constructed:to function with minimum maintenance; to promote drainage andminimize erosion or abrasion of the cover; to accommodatesettling so that the cover's integrity is maintained; and toprovide adequate freeze protection for the liner.

3.3.6. The landfill cap shall be re-vegetated in such a wayas to provide a high quality wildlife habitat to the maximumextent practicable (without endangering the liner). The types ofvegetation shall be determined during the remedial design andapproved by EPA.

3.4. DESCRIPTION: Institutional controls shall be placedon the Du Pont property south of the Christina River to restrict

54 &R32I078


future land use and to notify the public of past land use.Improvements shall be made to the access road on the berm in thesouth wetlands (including adding a culvert through the existingbreach) to allow easier access for equipment and to preventerosion. Also, in order to provide better Site security tocontrol trespassing, additional fencing and a barrier of rosebushes or other thorny plants shall be installed around theentire south landfill area including the landfill and theadjacent wetland area.


3.4.1. Institutional controls shall include the following(help Walter!11!1!1!!!1 I!!1!!!!)

3.4.2. Improvements to the south berm shall be made in sucha way as to allow easy access for equipment. This shall involveimproving the road bed, installing a culvert in the existingbreach (the invert elevation of which shall be approved by EPA),and taking erosion control measures to limit, to the maximumextent practicable, the banks from eroding into the wetlands.

3.4.3. Human access to the Site shall be limited to themaximum extent practicable, without severely limiting themigration of terrestrial animals into this area. This shall beaccomplished by using a combination of fencing and thorny bushes.EPA shall approve the locations of the fences and the bushes (seeFigure 28 for the approximate location of the fences and bushes).

3.5. DESCRIPTION: The present worth cost of thisalternative is $15,300,000. See Table 16 for details of the costestimate including the capital cost and annual operations andmaintenance costs.

55 &R32I079


COST-EFFECTIVENESS

Of the alternatives that offer protection of human healthand the environment, the selected remedy is the least costly. Italso meets all other requirements of CERCLA and affords overalleffectiveness proportionate to the cost. Also, the net presentworth of $48.7 million is much less expensive than the estimatedcost of $750 million for complete removal of the contamination.For several areas of the Site, cost had little to do with theselection of the remedy for that area of the Site because onlyone alternative passed the threshold criteria of overallprotection of human health and the environment and compliance ofARARs. However, there are several issues relating to the cost-effectiveness of the selected alternative which do merit furtherdiscussion.

In the north landfill area, two alternatives met thethreshold criteria. The alternative that provided the greatestdegree of overall protection to human health and the environment

25The clean-up criteria for the sediments were set toprotect aquatic life only since there was not expected to be anyhuman exposure by direct contact to the sediments. However,sediment contaminant levels that are protective of aquatic lifemay, as potentially in this circumstance, not be protective ofhuman health through ingest ion of ground water.

73

AR32I080

also happened to be the less costly of the two alternatives by$400,000.

In the south landfill area, the stabilization and capalternative is $8 million wore expensive than the cap onlyalternative. However, since the waste material is in the watertable (and will continue to be even after the localized ground-water mounding dissipates after capping), EPA determined the costwas worth the extra degree of protection of the environmentbecause stabilization will limit to the maximum extentpracticable the migration of heavy metals to the river and thesouth wetlands. Also, stabilization and capping meet thestatutory preference for treatpont as a principal element.

74 AR32I08I

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AR32I087

TABLES

SUMMARY OF HAZARDOUS SUBSTANCE LBT COMPOUNDS AND METALSDETECTED IN TEST PfT SAMPLES "ETALSSOUTH DBPOSAL SITE FELL

.!•»«•- CHfiL Pj, jjSSm. tiSke B&, L.SL uSL ™

ND = Not detectedCRDL = Contract Required Detection LimitB = Compound was detected in the QC BlankJ = Reported value is less than detection limit

Note; Test pit TP-1 samples were not analyzed for HSL compounds. • n O O IAnOd1

1 s •'M-28

". r •• < •» " HO™D »860 HD ND

660 KD NO ND ™ 2 J "D" » » » » »' ™ S(mg/kg) (mg/k:

rr ^ r. T T T T I4-6M "'9°:••: s «- r r r i „::" 183osmium :;.;: ?; ™ « 4-79° M« *'•• 70515 4S 102 33 47 33 32

M ± "! "321 324 i Q?n ia

s- ;: Z = I SF = :? T' ™ ' 1'820 3,580 835

s: • • • " = " -rr s ' s H r = = r r"••* ND 9.0 59 •> < ...SodiUm 1-90 48 ll 281 " °*48 2'°Vanadium 0.27Zinc 69 39 56

°'48 49 14'200 l.«0 2,810 16,000 1,080 283

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