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UNITED STATES ENVIRONMENTAL PROTECTION AGENCYj '.':\-REGION VII726 MINNESOTA AVENUEKANSAS CITY, KANSAS 66101MEMORANDUMSUBJECT:Submittal of Five-Year Review for the DuPont/Todtz SiteFROM:Nancy J. Swyers, P.E.Iowa/Nebraska BranchTO:Michael J. Sanderson, DirectorSuperfund DivisionTHRU:Glenn Curtis, ChiefIowa/Nebraska\Attached is the Five-Year Report for the DuPont/Todtz site.This report concludes that the remedy selected at the time of theRecord of Decision (ROD) is still protective of human health andthe environment. Therefore, we recommend your approval of thisreport.However, we do recommend that the semiannual monitoringconducted to date continue on the same schedule. According tothe current provisions of the ROD and Consent Decree (CD),semiannual monitoring would revert to annual monitoring nextyear.If you have any questions concerning this Five-Year ReviewReport, please feel free to contact me at x7703.AttachmentS00013618SUPERFUND RECORDSRECYCLE

MEMORANDUMSUBJECT:Submittal of Five-Year Review for the DuPont/Todtz SiteFROM:Nancy J. Swyers, P.E.Iowa/Nebraska BranchTO:Michael J. Sanderson, DirectorSuperfund DivisionTHRU:Glenn Curtis, ChiefIowa/Nebraska BranchAttached is the Five-Year Report for the DuPont/Todtz site.This report concludes that the remedy selected at the time of theRecord of Decision (ROD) is still protective of human health andthe environment. Therefore, we recommend your approval of thisreport.However, we do recommend that the semiannual monitoringconducted to date continue on the same schedule. According tothe current provisions of the ROD and Consent Decree (CD),semiannual monitoring would revert to annual monitoring nextyear.If you have any questions concerning this Five-Year ReviewReport, please feel free to contact me er\share\covermem.5CNSL9/28/95IA/NECurti:-L(. 71

-1MEMORANDUMSUBJECT:Submittal of Five-Year Review for the DuPont/Todtz SiteFROM:Nancy J. Swyers, P.E.Iowa/Nebraska BranchTO:Michael J. Sanderson, DirectorSuperfund DivisionTHRU:Glenn Curtis, ChiefIowa/Nebraska BranchAttached is the Five-Year Report for the DuPont/Todtz site.This report concludes that the remedy selected at the time of theRecord of Decision (ROD) is still protective of human health andthe environment. Therefore, we recommend your approval of thisreport.However, we do recommend that the semiannual monitoringconducted to date continue on the same schedule. According tothe current provisions of the ROD and Consent Decree (CD),semiannual monitoring would revert to annual monitoring nextyear.If you have any questions concerning this Five-Year ReviewReport, please feel free to contact me at x7703.AttachmentSUPR:IANE:NSwyers:dulmer sBraeckelCurtis

FIVE-YEAR REVIEWDUPONT/TODTZ SITECAMANCHE, IOWAPrepared by:U.S. Environmental Protection AgencyRegion 7Kansas City, Kansas// a\ rii i ,)./MicTiael j . flanderso fSuperfund Division DirectorDate

TABLE OF CONTENTSSECTIONTITLE1.0INTRODUCTION2.0EASESITE BACKGROUND2.1Site Location and History2.22.3Community Relations ActivitiesSite Characteristics2.4Site Risks3.0REMEDIAL ACTION OBJECTIVES4.0SUMMARY OF RESPONSE ACTIONS4.1Non-Contingent RemedialConstruction Activities4.24.2.14.2.2Post-Construction ActivitiesGroundwater Monitoring Program RequirementsContingent Further Remedial ActionRequirements4.34.45.0Groundwater Monitoring ResultsFurther ActionsARARS REVIEW5.1Background5.2New Laws Since the ROD5.3Analysis of the Four Compounds Specified inthe ROD6.0SUMMARY OF SITE VISITS7.0AREAS OF NON-COMPLIANCE8.0STATEMENT OF PROTECTIVENESS8.1DuPont and EPA Data8.2University of Iowa Hygienics Laboratory Data9.0RECOMMENDATIONS10.0NEXT REVIEWFIGURESTABLESAPPENDIX

1.0INTRODUCTIONThis report documents the five-year review conducted by theU.S. Environmental Protection Agency (EPA) at the DuPont/TodtzSite in Camanche, Iowa, to determine if the remedial responseactions at that site remain protective of human health, welfare,and the environment. Section 121 of the ComprehensiveEnvironmental Response, Compensation, and Liability Act (CERCLA),as amended, and Section 300.430(f)(4)(ii) of the National Oil andHazardous Substances Pollution Contingency Plan (NCP) requirethat periodic (at least once every five years) reviews beconducted for sites where hazardous substances, pollutants, orcontaminants remain at the site above levels that allow forunlimited use or unrestricted exposure following the completionof all remedial actions for the site. The purpose of thesereviews is to determine the continued adequacy of the implementedremedial actions in providing protection of human health,welfare, and the environment.The five-year review is to be conducted by the lead agency,which is the EPA at the DuPont/Todtz Site. In general, five-yearreviews are to be started within four to five years of theinitiation of site cleanup.The EPA has established three levels of review. Level IIIrequires the most in-depth review and would be appropriate forsites where there is the greatest likelihood that the remedialactions implemented for the site are no longer protective. Level11 is a less intensive review, and Level I is appropriate forsites where it is least likely that the remedial actions are nolonger protective. This review of the DuPont/Todtz Site is aLevel I review because it is unlikely that the response actionsimplemented at the site are no longer protective of human health,welfare, and the environment.2.0SITE BACKGROUND2.1Site Location and HistoryThe 12 acre site is a former gravel pit that is located onthe 120 acre Todtz family farm. The site is locatedapproximately 1 1/4 miles from the City of Camanche, Iowa.Camanche is located along the Mississippi River about 2 milessouth of Clinton, Iowa. Refer to Figures 1-1 and 1-2 for sitelocation maps.From approximately 1958-1975, the 12 acre site was used bythe City of Camanche for disposal of their municipal refuse. Inthe early 1970s, E.I. DuPont de Nemours and Co., Inc. (DuPont)constructed an unlined 2.6 acre impoundment in the northwest

corner of the site for disposal of waste from their cellophanemanufacturing plant in Clinton, Iowa. An estimated 4,300 tons ofwet end cellophane process wastes from the Clinton plant weresubsequently disposed of in the DuPont impoundment from 1971until its closure in 1975.The site was identified as a potential uncontrolledhazardous waste site in 1979 and added to the final NationalPriorities List (NPL) in June 1986.On April 4, 1988, a CERCLA 104/122 Consent Order was signedby both EPA and DuPont which finalized the agreement for DuPontto conduct a Remedial Investigation/Feasibility Study (RI/FS),which focused on their impoundment. As a result of the RI/FS,EPA signed a Record of Decision (ROD) on November 5, 1988. Theremedy specified in the ROD includes a 2-foot soil cover over theimpoundment, a fence around the impoundment, deed restrictions,installation of the Bark residence drinking water well in thedeeper bedrock aquifer, an expanded groundwater monitoringsystem, and further remedial actions which will be required ifaction levels of target compounds are exceeded.DuPont conducted the Remedial Design/Remedial Action (RD/RA)required by the ROD pursuant to a Consent Decree (CD) which wassigned by EPA and DuPont on September 28, 1989 and lodged by theDepartment of Justice (DOJ) on December 28, 1989. After thepublic comment period, the CD was entered by the Judge onNovember 6, 1990.2.2Community Relations ActivitiesThis site is located within a mile of the Chemplex Site,which is another Superfund site, and Arcadian (formerly HawkeyeChemical), a fertilizer plant. There are also numerousindustries and resulting pollution from these industries in thenearby Cities of Clinton and Camanche. As a result of publicconcern for the two Superfund sites and industrial pollution,several environmental groups including the Coalition AgainstPollution (CAP) and Ducks Unlimited organized in the area.A community relations plan was prepared by EPA during theRI/FS. As part of the ROD process, the public was given anopportunity to comment on EPA's preferred remedy in the ProposedPlan and to request a public meeting. The public did not requesta public meeting or comment on the proposed remedy.The public, including environmental groups, became veryactive in environmental issues during the public comment periodfor the CD which commenced on December 28, 1989 and ended onFebruary 28, 1990. Three public meetings were held during thistime to discuss this site and other environmental issues in thecommunity. The United States received fourteen comment letters

regarding the proposed CD.The comments were addressed prior tothe entry of the CD.An EPA Fact Sheet was issued to concerned citizens,environmental groups, and the media prior to commencement ofconstruction of the soil cover and groundwater monitoring system.2.3Site CharacteristicsThe upper groundwater aquifer at the site generally flows ina southeast direction with the majority of the groundwaterrecharge occurring upgradient of the site. The impoundmentwastes are periodically in direct contact with the groundwater.The bedrock aquifer is separated from the upper aquifer by athick sequence of low permeable clays and silts that appear tobehave as an aquitard.Sampling and analysis of soil and shallow groundwaterconducted prior to and during the RI/FS concluded thatconcentrations of carbon disulfide, toluene, tetrahydrofuran(THF), arsenic, lead and benzene were present in the impoundmentabove background concentrations. The location of monitoringwells is as indicated on Figure 1-3. The maximum concentrationsidentified in the groundwater in the vicinity of the berm areaimmediately downgradient of the Dupont impoundment (in monitoringwells now referred to as DU-08-S, DU-09-S, and DU-10-S) prior toinitiation of the remedial action (RI/FS, 1988), are as follows:Concentrations are reported in ug/1 or ppb.-carbon ,5001,600400209Except for arsenic and benzene, these compounds are amongthose reported by DuPont as being used at the Clinton cellophaneplant and were disposed in the DuPont impoundment.In the monitoring wells located in the hydraulicallydowngradient south and southeastern direction from theimpoundment berm and the municipal landfill (in monitoring wellsDU-02-S, DU-03-S, DU-04-S, DU-05-S, DU-06-S, and DU-07-S), thegroundwater concentrations of organic and inorganic compoundshave in general been slightly above background but not abovehealth-based levels. The exception is the groundwater frompiezometer PZ-03 (PZ-03 was replaced by monitoring well DU-02-Sduring the Remedial Action) which contained concentrations ofarsenic at approximately 80 and 60 ug/1 in March of 1988 whichexceeds the Maximum Contaminant Level (MCL) for arsenic of 50ug/1.

2.4Site RisksThe Endangerment Assessment (EA) is included in the RIreport and presents an evaluation of the existing and potentialfuture impacts of contamination at the DuPont impoundment onhuman health and the environment. One of the major objectives ofthe assessment was to assist in identification of the principalroutes of human and environmental exposure to site contaminantsin order to focus the FS on remedial alternatives that would mosteffectively prevent or preclude adverse impacts.The following conclusions were reached based on the exposurescenarios evaluated in the EA.1.Risks to human health or the environment associatedwith direct contact and ingestion of surface soils orsurface water downgradient of the impoundment appear tobe below those used by EPA in determining whether humanhealth or the environment are protected.2.There would be an unacceptable risk to human health orthe environment through ingestion of ground waterwithin the impoundment and at the impoundment berm.3.Risks to human health or the environment throughingestion or direct contact with ground water from theshallow aquifer at or near the southern or southeasternboundaries of the Site perimeter, which is severalhundred feet downgradient from the DuPont impoundment,appear to be below those used by EPA in determiningwhether human health or the environment are protected.Concentrations of 60 and 80 ug/1 of arsenic have beendetected at PZ-03 on the eastern boundary of thelandfill. These concentrations exceed the MCL of 50ug/1. However, risks to human health or theenvironment in this portion of the Site would appear tobe acceptable because the aquifer would not beconsidered a viable drinking water supply at thislocation.The findings of the RI and the EA indicate that the DuPontimpoundment is the source of contamination for the Site.3.0REMEDIAL ACTION OBJECTIVESBased on the findings of the RI and EA, the following arethe remedial action objectives established in the 1988 FS for theDuPont impoundment:

Subsurface Soil and Waste"Protect human health and the environment by preventingdirect contact with and future releases of the contaminatedsubsurface soil and waste within the impoundment."Groundwater"Protect human health and the environment by preventingdirect contact with or ingestion of contaminatedgroundwater, minimizing further releases of groundwatercontaminated with DuPont- related constituents at levels thatpresent an unacceptable hazard to human health and theenvironment beyond the perimeter of the Todtz FarmLandfill."Based on these objectives, the focus of the FS was on thedevelopment of cost-effective remedial actions for controllingthe potential release of waste constituents from the impoundment.Remedial alternatives were screened based on effectiveness,implementability, operation and maintenance efforts and costs,and capital costs. Excavation of the impoundment wastes anddisposal at a RCRA landfill or treatment onsite usingincineration, stabilization or in-situ treatment technologieswere eliminated since they were not cost-effective based on therelatively low risk to public health and the environment and thelarge capital cost.EPA evaluated four basic alternatives and two variations forremediation of the DuPont impoundment. These alternatives were1) no action, 2} soil cover, 3) geomembrane multilayer cap, and4) geomembrane-clay multilayer cap with bentonite slurry wall.The alternative selected includes the following major components:- A 2-foot soil cover over the DuPont impoundment;- Access restrictions which include deed limitations andsite fencing;- Site maintenance which includes mowing the vegetativecover and repairing the fence;- A groundwater monitoring system which includesimplementation of further remedial actions if certainchemical specific action levels are exceeded;- Replacement of the Bark residence drinking water well inthe deeper bedrock aquifer.4.0SUMMARY OF RESPONSE ACTIONS4.1Non-Contingent Remedial Construction ActivitiesAt the request of the Bark residents, DuPont replaced theirdrinking water well prior to finalization of the CD. The well

was installed in September 1989 pursuant to a design that wasapproved by EPA.DuPont commenced construction of the 2-foot soil cover andgroundwater monitoring system in April 1991 and completedconstruction on July 29, 1991. The final inspection wasconducted on July 31, 1991. Representatives of EPA and DuPontwere present during the inspection.4.2Post-Construction ActivitiesIn addition to the construction activities summarized inSection 4.1, the Remedial Action includes an extensivegroundwater monitoring program to ensure protection of humanhealth and the environment with chemical - specific action levelsthat trigger further remedial actions if any action levels aremet or exceeded. Maintenance of the soil cover, fence, andmonitoring well network is also required. DuPont is in theprocess of conducting these activities pursuant to the CD withEPA oversight.4.2.1Groundwater Monitoring Program RequirementsMonitoring of both the shallow and deep bedrock aquifer isrequired pursuant to the CD. The location of the monitoringwells is as indicated on Figure 1-3. The list of analytes issummarized on Table 4-2. The specific monitoring requirementsare as follows:The deep monitoring wells (including the James Barkresidential well) are required to be sampled semiannually for twoyears following the completion of non-contingent remedial actionsin July 1991. If no DuPont-impoundment related constituents aredetected above background concentrations during this period, thewells were to be sampled every five years thereafter. Because nocontaminants were detected in deep wells during the two yearsfrom July 1991 to April 1993, the deep wells are not required tobe sampled again until April 1998.All shallow monitoring wells are required to be sampled atleast semiannually for the first five years and annuallythereafter for thirty years. The need to continue monitoringbeyond this point will be evaluated at that time and at thecorresponding statutory five year review. Sampling of theshallow wells began in July 1991 and is continuing. According tothe CD, the semiannual sampling will continue until April 1996.After that time frame, annual sampling will continue for thirtyyears.

4.2.2Contingent Further Remedial Action RequirementsFurther remedial actions will be triggered in the event thatan Action Level concentration for one or more trigger compoundsat specific shallow monitoring wells (specified in Table 4-3 andin Figure 1-3) is met or exceeded (which will be verified bystatistical analysis). If any of the Table 1 Action Levelconcentrations are met or exceeded, further remediation of theimpoundment will be performed. If any of the Table 2 ActionLevels are met or exceeded, remediation of the groundwater willbe performed. Once groundwater remediation is triggered,groundwater cleanup levels will consist of all applicable Stateor Federal cleanup standards for all DuPont- related constituentslisted in Table 4-4. If the impoundment remediation has not beentriggered at the time the Table 2 Action Level concentrations aremet or exceeded, both the remediation of the impoundment andremediation of the groundwater will be performed at the sametime.Intermediate trigger levels were also established in the CDin order to provide a mechanism for conducting the planning anddesign functions prior to an Action Level exceedance. Forexample, if 50% of any Table 1 Action Level is met or exceeded,quarterly monitoring (as opposed to the required semiannual orannual monitoring) for that particular compound at the exceededwell will be conducted. If 80% of any Table 1 Action Level ismet or exceeded, DuPont is required to submit a TreatmentEvaluation Study (TES) to evaluate remedial options consisting ofa slurry wall around the impoundment as compared to treatmentremedies. After completion of the TES, EPA is to decide whetherthe remedy will be a slurry wall or a treatment remedy. Theschedule in the CD provides for the pre-design of the selectedremedy in order for it to be complete prior to a 100% ActionLevel exceedance.4.3 Groundwater Monitoring ResultsGroundwater monitoring pursuant to the CD has been conductedby DuPont with EPA oversight since July 1991. Monitoring wasalso conducted prior to 1991 during the RI/FS in 1988, and in1989 and 1990. All of the analytical results from DuPont and EPAgroundwater samples are included in the Appendix. Someexceedances of 50% and 80% of the THF Action Level have occurredin at least one trigger well and the discussion of theseexceedances are as follows:THF was detected at a concentration of 42 ppb in monitoringwell DU-05-S during a routine semiannual groundwater samplingevent conducted in April 1993. This value constituted an 80%exceedance of the Table 1 Action Level for THF which is 50 ppb.Pursuant to the CD, verification of the 80% exceedance is thenext required step. The verification process consists of

obtaining quadruplicate samples from any wells that exceed 80% ofa Table 1 Action Level. The samples are to be collected as soonas practicable after realizing that the previous event yieldeddata that exceeded any established trigger levels.The 80% value of the 50 ppb THF Table 1 Action Level is 40ppb, thus the April 1993 value of 42 ppb exceeded the 80% triggerlevel. DuPont conducted the 80% verification sampling in June1993 and obtained the following quadruplicate results: 91 ppb;93 ppb; 110 ppb; and 110 ppb. The average value of thequadruplicate data was 101 ppb. The June 1993 sampling dataconclusively verified the 80% exceedance of the Table 1 ActionLevel for THF but also satisfied the 100% exceedance criteria.The 100% exceedance value is the actual trigger level which is 50ppb, thus an average of quadruplicate samples yielding 101 ppbclearly surpasses the 100% exceedance but did not verify the 100%exceedance. After obtaining an initial exceedance of a differentlarger percentage exceedance, the verification process must berepeated in order to verify the new larger percentage ofexceedance.DuPont collected quadruplicate samples in August 1993 inorder to verify the initial 100% exceedance of THF observedduring the June 1993 event. As mentioned previously, the June1993 event clearly verified the 80% exceedance but indicated thatthe exceedance might actually be in the 100% range. The DuPontquadruplicate THF results for the August 1993 sampling eventconsisted of the following: 48 ppb; 50 ppb; 51 ppb; and 51 ppb.The average value of the quadruplicate data was 50 ppb. TheAugust 1993 sample results indicated that the initial 100%exceedance was verified and that an 80% THF exceedance wasverified for a second time.EPA split samples were obtained by a contractor during theAugust 1993 sampling event. The EPA samples were analyzed by theRegion VII Laboratory and yielded the following THF results: 10ppb; and 15 ppb. The average value for the two EPA split sampleswas 12.5 ppb. The EPA split samples did not confirm the 100% THFexceedance nor the initial 80% exceedance. The average EPA THFvalue of 12.5 ppb was substantially less than the average DuPontconcentration of 50 ppb. The two data sets were statisticallyevaluated and it was determined that the two sets of values werestatistically different, or not from the same population. Thelarge data differences indicated that either the DuPont or EPAresults were not valid. The incompatibility of the DuPont andEPA data for the August 1993 event, as well as theincompatibility of the DuPont data when compared to June 1993DuPont results, clearly indicated that all data were erratic.The June 1993 DuPont data represented a two fold increase overthe prior April and subsequent August 1993 results.10

The erratic nature of the data, coupled with the fact thatonly one well (DU-05-S) was yielding elevated results, led to thedecision to again collect EPA split samples during an upcomingroutine semiannual sampling event in October 1993.Additionally,the observed exceedances occurred during the time period of theregional midwestern flooding events of 1993.A large portion ofthe DuPont/Todtz Site was flooded and certain wells, includingmonitoring well DU-05-S, were only accessible by boat. Since thesite is located on terrace and floodplain deposits and is inclose proximity to the Mississippi River, the wells in low lyingareas had been constructed on artificial soil berms in order toavoid overtopping during a flood event. An additional factor inthe decision to obtain more information by evaluating the October1993 sampling event, included the position of the static waterlevel in well DU-05-S. This was the only on-site monitoring wellwhich had a water level that directly corresponded to theelevation of the surrounding ponded water. This fact indicates amore direct hydraulic relationship of this well to the shallowsubsurface, which is in direct hydraulic communication with anyponded or surface water. This situation is most likely due tothe position of the DU-05-S well screen being located at a veryshallow depth.However, the shallow well screen depth would alsobe capable of more readily detecting any surface water influencessince surface water has a direct affect on, and is in hydrauliccommunication with, shallow groundwater.DuPont conducted a semiannual groundwater sampling event inOctober 1993 which included quadruplicate sampling at well DU-05S. EPA personnel collected groundwater split samples whichincluded a sample from monitoring well DU-05-S. The THF valuesfor the quadruplicate DuPont samples and the EPA split sample forwell DU-05-S were all at non-detect levels. The DuPont and EPAdata for the October 1993 event, including the comparison of datafrom the other split samples from different wells, were inagreement. The October 1993 data indicated that there was nogroundwater exceedance for any Action Level value mandated by theCD.Pursuant to the CD, DuPont was required to sample DU-05-S ona quarterly basis for THF because there was an exceedance of atleast 50%.The monitoring frequency for THF in that well willrevert back to a semiannual basis only after four consecutivequarterly samples from that well indicate that no Table 1compound is being found at 50% of the Table 1 Action Levelconcentrations.During the January 1994 sampling event, THF was again nondetect in DU-05-S. However, in April 1994, THF was detected atconcentrations of 34, 37, 38, and 42 ppb according to DuPont'sresults and at concentrations of 57 and 63 ppb according to EPA'sresults. These results indicated an 80% exceedance. However,when the verification sampling took place in June 1994, THF was11

detected in DU-05-S at concentrations of 6.8, 8.1, 9.3, and 12ppb according to DuPont's results and at concentrations of 14 and15 ppb according to EPA's results. In October 1994, THF was notdetected in DU-05-S according to DuPont's results and EPA'ssample result of 31 ppb was probably cross-contaminated andshould be considered unreliable. In January 1995, both DuPont'sand EPA's results for THF in DU-05-S were non-detect. On April25, 1995 another semiannual sampling event was conducted. BothEPA's and DuPont's results were again non-detect for THF. Sincefour consecutive quarterly samples from DU-05-S indicate that noTable 1 compound is being found at 50% of the Table 1 ActionLevel concentrations, the monitoring frequency for this well canrevert to semiannually.4.4 Further ActionsDue to the verified 80% exceedance of THF in monitoring wellDU-05-S in June 1993, DuPont was required by the Consent Decreeto provide a draft TES. The TES was submitted to EPA onSeptember 22, 1993. EPA provided comments to DuPont datedOctober 22, 1993. DuPont submitted a revised TES on December 6,1993.Since the elevated THF levels did not reoccur during theOctober 1993 and January 1994 sampling events, EPA halted theschedule that included finalization of the TES and predesignactivities. However, when elevated levels of THF recurred inApril 1994, EPA decided that these activities should resume. Ina letter to DuPont dated October 21, 1994, EPA requested thatDuPont submit a Draft Project Operations Plan for Pre-DesignStudy. In a letter to EPA dated December 2, 1994, DuPont agreedto submit the Draft Project Operations Plan. The Plan wassubmitted to EPA on April 12, 1995. EPA submitted comments onthe plan to DuPont dated May 17, 1995. According to the schedulein the CD, DuPont will conduct the predesign but will not berequired to conduct the design or implement the remedy untilthere is a verified 100% exceedance of a Table 1 Action Level.5.0ARARS REVIEW5.1 BackgroundThe Five Year Review includes a review of newly promulgatedor modified requirements of Federal and State environmental laws.These new laws are evaluated to determine whether they areapplicable or relevant and appropriate requirements (ARARs) andwhether they call into question the protectiveness of theresponse action selected in the Record of Decision (ROD). Theintent of the review is to evaluate whether the selected remedyremains protective of human health and the environment.AlthoughARARs are usually considered frozen as of the date of the ROD, ifan evaluation in the light of the new laws concludes that theremedy is no longer protective of human health and the12

environment, it would be necessary to change the remedy to meetthe new ARAR standards. The NCP provides:Requirements that are promulgated or modified after RODsignature must be attained (or waived) only when determinedto be applicable or relevant and appropriate and necessaryto ensure that the remedy is protective of human health andthe environment. NCP 40 CFR § 300.430(f)(1)(ii)(B)(1).In the DuPont/Todtz Site ROD, the selected remedy includedreplacement of a residential drinking water well, an impoundmentcover, monitoring, and two contingent operable units, oneinvolving further impoundment containment and the other involvinggroundwater cleanup remediation. The two contingent operableunits could be triggered by certain chemical concentration actionlevels of any of four designated trigger compounds found inmonitoring well samples: arsenic, chromium VI, THF and carbondisulfide. The ROD also specified the cleanup levels to beattained for the four compounds in the event that groundwaterremediation is ever implemented. Since the groundwater cleanupremediation has so far not been triggered and is not beingimplemented, it may seem premature to review cleanup levels whichestablish chemical concentrations at which groundwater extractionand treatment could be considered complete and terminated, ifever implemented. However, such numerical levels were defined inthe DuPont/Todtz Site ROD.A Consent Decree was negotiated for the performance of theremedial action at the site. The Consent Decree establishedcleanup levels for other chemical constituents in addition to thefour that had been specifically mentioned in the ROD. TheConsent Decree did not freeze the cleanup levels but recognizedthat MCLs and other cleanup standards might c

Pollution (CAP) and Ducks Unlimited organized in the area. A community relations plan was prepared by EPA during the RI/FS. As part of the ROD process, the public was given an opportunity to comment on EPA's preferred remedy in the Proposed Plan and to request a public meeting. The publ

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