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URSDames & MooreURS Greiner Woodward Clyde

August 15,2001Project 49-FOK96217.02

CommanderU.S. Army Engineer District, Kansas CityATTN: CENWK-EC-EC (Ms. Vicki Murt)700 Federal Building601 East 12th StreetKansas City, Missouri 64106-2896

Re: Draft Final Explanation of Significant DifferencesOperable Unit No. 2 (Groundwater)Former Nebraska Ordnance Plant, Mead, NebraskaContract No. DACW41-96-D-8014Task Order No. 0017, WAD 2

Dear Ms. Murt:

We are hereby transmitting five copies of the subject document. Distribution of the remainingcopies has been made in accordance with the attached distribution list.

The ESD will be made available to the public at the Public Availability Session on Thursday,August 30, 2001. Following the public comment period, the document will be revised toinclude a responsiveness summary. An announcement will be placed in local newspapersnotifying the public of the comment period duration and the availability of the document.Please call Curt Elmore at 913/344-1154 if you require additional information.

Very truly yours,

URS Group, Inc.

Curt Elmore, Ph.D., P.E.OU2 Project Manager

Enclosures

latthew E. WilsonProject Geologist

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D R A F T F I N A l

EXPLANATION OFSIGNIFICANT DIFFERENCESOPERABLE UNIT NO. 2(GROUNDWATER)FORMER NEBRASKAORDNANCE PLANTMEAD, NEBRASKA

DACW41-96-D-8014TASK ORDER NO. 0017Prepared forDepartment of the ArmyU.S. Army Engineer DistrictKansas City District Corps of Engineersi\......-,as City, Missouri

August 2001

URSURS Group, Inc.10975 EL MONTE, SUITE 100OVERLAND PARK, KANSAS 66211(913)344-100049-FOK96217.02

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DISTRIBUTION LISTDRAFT FINAL EXPLANATION OF SIGNIFICANT DIFFERENCES

OPERABLE UNIT NO. 2 (GROUNDWATER)FORMER NEBRASKA ORDNANCE PLANT

MEAD, NEBRASKA

Organization

U.S. Army Corps of EngineersKansas City DistrictATTN: CENWK-EC-EC (Vicki Murt)U.S. Army Corps of EngineersHTRW Center of ExpertiseATTN: HTRW Document Distribution (Ric Hines)Nebraska Department of Environmental QualityATTN: Mr. Ralph MartinUniversity of Nebraska LincolnAgricultural Research and Development CenterATTN: Mr. Daniel J. DuncanU.S. Environmental Protection Agency Region VFIWaste Management DivisionATTN: Mr. Craig BernsteinNatural Resources DistrictATTN: Mr. Larry AngleNebraska Department of HealthATTN: Mr. Howard IsaacsLincoln Water SystemATTN: Mr. Jerry ObristUniversity of Nebraska Hazardous Materials Safety OfficerATTN: Mr. Del Weed

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OU2 Explanation of Significant DifferencesFanner Nebraska Ordnance Plant

LEAD AND SUPPORT AGENCY ACCEPTANCEOF THE EXPLANATION OF SIGNIFICANT DIFFERENCES

FORMER NEBRASKA ORDNANCE PLANT SITEOPERABLE UNIT 2

Signature sheet for the following Explanation of Significant Differences for Operable Unit 2:contaminated groundwater, explosives-contaminated soil which could act as a source ofexplosives contamination of groundwater and which does not meet the OU1 excavation criteria,and soil contaminated with VOCs, f inal action at the Former Nebraska Ordnance Plant site bythe U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency.

The principal topic addressed by this Explanation of Significant Differences is the replacementof the focused extraction of contaminated groundwater with focused remediation usinggroundwater circulation well systems. The motivation for the change in remedial systems is thedesire to conserve the site groundwater supply.

District Engineer DateU.S. Army Engineer DistrictKansas City District Corps of Engineers

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OU2 Explanation of Significant DifferencesFormer Nebraska Ordnance Plant

LEAD AND SUPPORT AGENCY ACCEPTANCEOF THE EXPLANATION OF SIGNIFICANT DIFFERENCES

FORMER NEBRASKA ORDNANCE PLANT SITEOPERABLE UNIT 2

Signature sheet for the following Explanation of Significant Differences for Operable Unit 2;contaminated groundwater, explosives-contaminated soil which could act as a source ofexplosives contamination of groundwater and which does not meet the OU1 excavation criteria,and soil contaminated with VOCs, final action at the Former Nebraska Ordnance Plant site bythe U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency.

The principal topic addressed by this Explanation of Significant Differences is the replacementof the focused extraction of contaminated groundwater with focused remediation usinggroundwater circulation well systems. The motivation for the change in remedial systems is thedesire to conserve the site groundwater supply.

Regional Administrator DateEPA Region VII

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SUPERFUND PROGRAM - EXPLANATION OF SIGNIFICANT DIFFERENCES

Former Nebraska Ordnance PlantOperable Unit No. 2 SEPA

MeadSaunders County, Nebraska

United States Army Corps of EngineersKansas Citv District

August 16,2001

INTRODUCTION TO THE SITE

Site Name and LocationFormer Nebraska Ordnance Plant, Mead. Nebraska

Operable Unit 2 (OU2): Contaminated groundwater,explosives-contaminated soil which could act as a sourceof explosives contamination of groundwater and whichdoes not meet the Operable Unit 1 (OU1) excavationcriteria, and soil contaminated with volatile organiccompounds (VOCs).

Section 2.1 of the Record of Decision (ROD) which isincluded in Attachment 1 provides additionalinformation regarding the site location and description.

Identification of Lead and Support AgenciesAn Interagency Agreement (LAG) has been executed forthis site between the EPA, the Department of the Army,and the Nebraska Department of Environmental Quality(NDEQ). The U.S. Army Corps of Engineers representsthe Department of the Army anu is performing theenvironmental restoration at the site with input fromRegion VII EPA. The State of Nebraska is representedby the NDEQ as a party to the LAG.

All three parties to the IAG acknowledge that thepost-ROD changes to the selected remedy are notfundamental in nature and therefore it is appropriate toexecute an Explanat ion of Significant Differences (ESD)instead of more formally amending the ROD.

STATEMENT OF PURPOSE

Statutory ComplianceThis ESD documents signif icant changes to the remedyselected by the OU2 ROD, and USAGE is complyingwith CERCLA § 117(c) and National Contingency Plan(NCP) §§300.435(c)(2)(i) and 300.825(a)(2) bydescribing to the public the nature of the signif icantchanges, summarizing the information that led to makingthe changes, and affirming that the revised remedycomplies with the NCP and the statutory requirements ofCERCLA.

ROD Signature DatesThe OU2 ROD was signed by the RegionalAdministrator for EPA Region VII on April 7, 1997 andby the Deputy Assistant Secretary of the Army;Environment, Safety and Occupational Health on March21. 1997.

Circumstances Leading to the ESDThe ROD Responsiveness Summary section documentedthe following public input with regard to the potentialimpact of the selected remedy on the site groundwatersupply:

• What actions w i l l be taken to prevent shortages ofgroundwater at irrigation and domestic wells '? Whataction wil l be taken if irrigation and domestic wellsgo dry?

• Potentially, future development of groundwaterresources w i l l be limited.

• The treated groundwater should be reinjected intothe aquifer .

The public inpu t formally recorded in the ROD wasoccasionally repeated informal ly during subsequent

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Technical Review Committee (TRC) meetings andRestoration Advisory Board (RAB) meetings.

Pilot testing of an innovative groundwater remediationtechnology using a system known as a groundwatercirculation well (GCW) was undertaken as a result of thepublic input. The technology involves the extraction ofcontaminated groundwater from one depth interval in awell , t reatment, and recharge of the treated groundwaterinto the same formation at a second depth interval in thesame well. The application of a GCW results in no netgroundwater loss or aquifer drawdown. The results ofthe pilot study indicate that it is technically andeconomically feasible to replace a portion of the pump-and-treat groundwater extraction wells specified by theROD wi th GCW systems. The purpose of this ESD is todocument the use of several GCW systems to replaceselected traditional high volume pump-and-treat wells.

Attachment 2 includes a fact sheet about the pilot study.The fact sheet includes several illustrations which helpexplain how a groundwater circulation well functions.

Inclusion of the ESO in the Administrative RecordThis document w i l l be added to the OU2 Administrat iveRecord.

Administrative Record Location and AvailabilityThe information repository for the site has beenestablished at the following address:

Mead Public Library316 South Vine StreetMead, Nebraska 68041

(402) 624-6605

Library hours:

Wednesday: 3:00 - 7:00 pm(3:00 - 8:00 pm, June - August)

Thursday: 9:30-11:30 am and3:00-7:00 pm(3:00 - 7:00 pm, June - August)

Saturday: 10:00 am - 3:00 pm

The information repository contains the adminis t ra t iverecord inc lud ing the remedial investigation report,feasibility study report, the ROD, and other documentsrelevant to the former NOP site.

SITE HISTORY, CONTAMINATION, ANDSELECTED REMEDY

BRIEF SUMMARY OF CONTAMINATIONPROBLEMS AND SITE HISTORYOperable Uni t 2 includes an estimated 23 b i l l i on gallonsof contaminated groundwater under ly ing approximately6,000 acres of primari ly agr icu l tura l property. Thepredominant groundwater contaminants aretrichloroethene (TCE), which may have been released idur ing the construction of an Atlas Missile faci l i ty anddur ing other act ivi t ies; and hexahydro-1.3,5-trinitro-1.3,5-triazine (RDX) which was released during formerNOP ordnance production operations. Attachment 1includes Section 2.2 of the ROD which providesadditional site history and environmental invest igat iondetails. :

SELECTED REMEDYThe following text has been excerpted from the RODDeclaration:

The OU2 remedial action addresses one of the principalthreats at the site, contaminated groundwater, bycontaining, extracting, and treating the contaminatedgroundwater on-site. The major components of theselected remedy include:

• Hydraulical ly contain contaminated groundwaterexceeding the Final Target Groundwater CleanupGoals.

• Focused extraction of groundwater in areas wi th .'re la t ively high concentrations of TCh ui idexplosives.

• Treat all groundwater using granular activatedcarbon (GAC) adsorption, advanced oxidationprocesses (AOPs), and air stripping. GACadsorption and AOP may be applied i n d i v i d u a l l y orin combination, while air stripping must be appliedin combination with one of the other technologies tceffectively treat explosives. ^

•- Dispose of treated groundwater by beneficially £-* nreusing it or through surface discharge. The treated O ^groundwater w i l l also be avai lable for other uses \O r>such as fire suppression, but the water may not be O §acceptable for human consumption without {§_addi t ional treatment.

• Provide a potable water supply to local groundwaterusers whose water supply contains RDX exceeding

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the Lifetime Health Advisory and/or TCE exceedingihe Maximum Contaminant Level (MCL).

• Monitor the groundwater elevations and waterqual i ty .

• Excavate and treat explosives-contaminated soilwhich could act as a source of explosivescontamination of groundwater and which does notmeet OU1 excavation criteria.

The Final Target Groundwater Cleanup Goals for thechemicals of concern are:

Methylene chloride - 51,2-dichloropropane - 5TCE - 5 Mg/L1,3,5-trinitrobenzene - 0.778 /ig/L2.4,6-trinitrotoluene - 2 ^g/L2,4-dinitrotoluene - 1.24 figfLRDX - 2

The following text describes the implementation of theremedy to date:

• Hydraulic containment of the TCE plumes wasinit iated in 1998 using two extraction wells. Theconstruction of nine additional extraction wells isunderway, and all eleven wells are expected to be inoperation in late 2001 thereby hydraulical lycontaining both the TCE and explosives plumes.The hydraulic containment system is known as thePhase I Remedial Action, and is shown on Figure 1.

• The groundwater extracted for hydrauliccontainment has been and w i l l be treated using GAC

; at a single treatment facility.

• Currently, treated groundwater is being sui facedischarged to Clear Creek, but the expansion of thehydraulic containment system under constructionincludes transmitting treated groundwater to bothClear Creek and Wahoo Creek for discharge. Thesystem currently under construction also includesprovisions for the agricultural use of some or all ofthe treated groundwater.

• Local groundwater users whose wells containunacceptable levels of RDX and/or TCE arereceiving bottled water and/or their water suppliesare being treated using GAC units. On-goingconstruction of two pipelines on University ofNebraska Agricultural Research and DevelopmentCenter (ARDC) property wil l permit potentiallycontaminated wells to be taken out of potableservice. Five GAC treatment units will be removedfrom service upon completion of the pipeline.

• Groundwater elevations and water quality have beenand are being monitored on a regular basis.

• The OU2 soils were excavated and treated during theOU1 remedial action d u r i i m 1997 and 1998.

BASIS FOR THE DOCUMENT

MOTIVATION FOR CONSIDERING REMEDYDIFFERENCES

The ROD Responsiveness Summary contains thefollowing input regarding the perceived impact of theselected remedy on the groundwater supply and thereuse of treated groundwater:

• What actions wil l be taken to prevent shortages ofgroundwater at irrigation and domestic wells? Whataction wi l l be taken if irrigation and domestic wellsgo dry?

• Potentially, future development of groundwaterresources w i l l be l imited.

• A beneficial reuse for the treated groundwatershould be developed.so that the water is not solelydischarged to a surface stream.

• Discharging 4 m i l l i o n gallons of water a day toClear Creek dur ing flooding w i l l cause a negativepublic reaction.

• A rural water district should be developed. Whatarea would the rural water district serve?

• The treated water should be reinjected into theaquifer.

Subsequent public input during Restoration AdvisoryBoard meetings, Technical Review Committee meetings,and .other public meetings reinforced the need toconsider groundwater conservation measures and thedevelopment of beneficial reuse options.

Three initiatives were undertaken as a result of thepublic input. The first in i t ia t ive formalized a three-stepapproach to balance efforts to clean up groundwater wi ththe need for continued use of the groundwater during theclean-up. The process was designated "WaterAvai lab i l i ty Characterization", and a report and a factsheet were generated for public information and review,two public avai labi l i ty sessions were conducted, and aresponsiveness summary to the public input wasprepared. The information gathered during the process

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was used as a basis of design when selecting extractionwell flowrates and locations. This effort is documentedin the Draft Water A v a i l a b i l i t y CharacterizationTechnical Memorandum (WCFS, 1997).

The second in i t i a t i ve involves the addition of a pipelineto carry treated groundwater from the treatment plant toa Wahoo Creek discharge point on the west side of thesite. This pipel ine, which has been constructed and w i l lsoon be ready for service, provides for treatedgroundwater discharge to creeks on both the east andwest sides of the site. The new pipeline wi l l serve twopurposes. It w i l l mitigate concerns regarding theflooding of Clear Creek, the access points have beenconstructed so that beneficial reusers may obtain thetreated groundwater for agricultural and other purposes.

The third i n i t i a t i v e was the consideration of aninnovative process called groundwater circulation wellsto replace the focused extraction component of theselected remedy. The executive summary from the pilotstudy report (URS, 2001) is presented in Attachments.The results of the pilot indicate that it is technically andeconomically feasible to replace the focused extractionwells with GCW systems.

ADMINISTRATIVE FILE REFERENCE

The administrative record contains the OU2 Record ofDecision, the pilot study report, and the WaterAvailabili ty Characterization Technical Memorandum.

DESCRIPTION OF SIGNIFICANTDIFFERENCES

SIGNIFICANT DIFFERENCE DESCRIPTION

The significant difference in the remedy relative to theremedy selected in the ROD is the use of groundwatercirculation wells to provide focused remediation ofgroundwater hot spots instead of a more typical high-volume pump-and-treat system. Although GCWsystems constitute an innovative technology, essentiallyevery element of a GCW system was considered in theROD. Figure 2 shows the remedy contemplated in theROD, and Figure 3 shows the remedy with GCWfocused remediation.

A GCW system extracts contaminated groundwaterusing the same type of equipment that would be used ina focused extraction well.

A GCW system w i l l treat TCE-contaminatedgroundwater using an air stripper. A GCW system w i l ltreat RDX-contaminated groundwater using an advancedoxidation process known as ultra-violet photolysis. Bothof these treatment technologies were listed in the ROD.However, it may be feasible to treat only TCE at a GCWthat is located in an area where TCE and RDX plumesare also co-located. This concept of selective treatmentwas not considered in the ROD because the previouslyconsidered remedial al ternatives included p ip inggroundwater from mul t ip le wells to one or two largetreatment p lan t s . "Total" treatment was necessary toprevent both the migration of contamination above theclean up goals to areas down gradient from the area ofattainment as well as to prevent the disposal ofgroundwater with concentrations above clean up goals.The GCW systems w i l l return the treated groundwater tothe aquifer at the point of extraction, and all of the GCWlocations w i l l be up gradient from the hydraul iccontainment system. Any contamination not reduced toclean up goals w i l l eventual ly be attenuated or capturedby the hydraulic containment system. Therefore,selective treatment and/or treatment to concentrationsabove the clean up goals is acceptable.

The ROD lists the following types of beneficial reusethat may be considered during remedial design:

• Reinjection into the aquifer.

• Agr icu l tu ra l use inc lud ing livestock watering,processing, or other use.

• Drinking water supply inc lud ing supply to apotential rural water district, the ARDC. a nearbycommunity or munic ipa l i ty , or some combination ofthese potential water users.

• The recharge element of a GCW system may beconsidered equivalent to reinjection into the aquifer .

The remaining elements of the selected remedy:hydraul ic containment of the leading edge ofcontamination, provision of an alternative water supplyto impacted users, groundwater monitoring, and OU2soils, remediation, are not effected by the replacement offocused extraction wells by GCW systems.

It is estimated that approximately 14 GCW systemsoperating at 50 gallons per minute (gpm) each w i l lreplace three focused extraction wells which wouldoperate at a combined flowrate of 800 gpm.' The three *-focused extraction wells would discharge more than 420 £

, mi l l ion gallons of treated groundwater each year to v, nearby surface streams. It is possible that a small £

fraction of that water could be used for purposes such as

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irrigation, but the vast majority of the treatedgroundwater would be discharged to streams. However,there w i l l not be any surface discharge from any of theGCW systems, and the groundwater resource w i l l beconserved for potential use by local property owners.Today, the two pilot GCW systems continue to removecontamination from the aquifer.

The estimate cost for constructing a focused extractionsystem consisting of three extraction wells isSI.9 mi l l i on . It was estimated in the GCW pilot studytechnical memorandum that twelve more GCW systemscan be constructed for the same cost. It was estimatedthat the annua l operation and maintenance cost for thetwo existing GCW systems combined with twelve new

: GCW systems is approximately $41,000. This is lessthan the annua l operation and maintenance costs of thethree-well focused extraction system, which wasestimated as 5100,000.

CHANGES IN EXPECTED OUTCOMESGroundwater flow modeling and mass transportmodeling were performed during the GCW pilot studyreporting phase. An analytical method was applied toestimate groundwater restoration times with thefollowing results:

• Estimated restoration time for existing focusedextraction well-based altemative-650 years with atotal extraction flowrate of 850 gpm and a maximumassumed TCE concentration of 8,100 pig/L

• Estimated restoration time for GCW-basedalternative-330 years wi th a total GCW flowrate of550 gpm, a total hydraulic containment extractionflowrate of 350 gpm, and a maximum assumed TCEconcentration of 8,100

A restoration time estimate for a focused extraction well-based alternative were calculated in the Feasibility Study

, (WCC, 1995) and were subsequently presented in the1 Record of Decision. The Atlas Missile Area Plume

restoration time estimate presented in the Record ofi Decision was 130 years wi th a total extraction flowrate: of 1,170 gpm and a maximum assumed TCE

concentration of 4,800 (ig/L. The current restorationtime estimates are much larger because the currentflowrates are lower and much higher TCE concentrationshave been measured since the Record of Decision wasissued. The total extraction flowrate was decreased fromthe Feasibil i ty Study estimates to the current values as aresult of publ ic input regarding the perceived impacts ofthe remedy on the groundwater supply.

The relative comparison of restoration times for theentire Atlas Missile Area TCE plume indicates that theestimated restoration t ime for the GCW-basedalternative is s ignif icant ly lower than the restorationtime estimate for the ex i s t ing focused extractionalternative.

Likewise, the ana ly t i ca l model was applied to the LoadLines 2, 3. and 4 RDX plume w i t h the fol lowing results:

• Estimated restoration t ime for existing focusedextraction well-based a l ternat ive-52 years wi th atotal extraction flowrate of 2.150 gpm and amaximum assumed RDX concentration of 530 |ig/L

• Estimated restoration t ime for GCW-basedaltemative-52 years wi th a total GCW flowrate of150 gpm, a total hydraul ic containment extractionflowrate of 1,850 gpm, and a maximum assumedRDX concentration of 530 fig/L

The restoration time estimate developed in theFeasibility Study was 77 years wi th a total extractionflowrate of 1,770 gpm and a maximum assumed RDXconcentration of 530 u,g/L. The current restoration timeestimates are roughly equivalent to the feasibility studyestimates.

The modeling results predict that the groundwaterrestoration time fora GCW-based remedial alternative isequal to or less than the estimated groundwaterrestoration t ime fora focused extraction well-basedremedial alternative. The estimated capital cost of theGCW-based alternative was the same as the estimatedcost of the focused extraction well-based alternative.However, the GCW restoration time estimate calculatedusing an analyt ical model was approximately three timesthe restoration t ime presented in the ROD. The primaryfactors which account for the differences in the currentestimates and the ROD estimate are:

• The lower extraction flowrates that have beendeveloped as a result of public input concerning theperceived impacts of the remedy on groundwatersupply

• The higher TCE concentrations that have beenmeasured since the ROD was issued

The most significant change in the expected outcome isthe ratio of contaminant mass removed to the quant i ty oftreated groundwater surface discharged. Duringapproximately 9 months of operation, the TCE pilot u n i tremoved approximately 24 gallons of TCE from 13m i l l i o n gallons of groundwater which was returned tothe aquifer. The RDX pilot u n i t removed approximately

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240 grams of RDX from 5 mi l l ion gallons ofgroundwater tha't was returned to the aquifer. Thequanti ty of contaminant mass that would be removed ifthe focused extraction alternative was operating isunknown, but more than 300 mill ion gallons ofgroundwater would not be returned to the aquifer dur inga nine^month period.

In summary, the modified remedy w i l l :

• Continue to provide protection of down gradientareas using 11 high volume extraction wells

• Provide treated groundwater for agr icu l tura l andother uses

• Remediate contamination hot spot areas whi leconserving the groundwater in those areas

• Restore groundwater as qu ick ly or more quick lythan the remedy selected in the ROD

• Cost approximately the same to construct as theremedy selected in the ROD while potentiallycosting less to operate.

SUPPORT AGENCY COMMENTS

SUMMARY OF COMMENTS

In 1999, the Army proposed to divide the remedialaction into two phases to accommodate consideration ofGCW-based focused remediation as a replacement forhigh volume pump-and-treat focused extraction. TheEPA and NDEQ expressed support for the considerationof GCW systems by approving a revised remedial actionimplementation schedule. The corresponding approvalletters dated March 30. 1999 are included inAttachment 4.

The State has determined that Nebraska AdministrativeCode (NAC) Title 122 - Rules and Regulations forUnderground Injection and Mineral Production Wells isapplicable to GCW systems although Title 122 was notidentified as an applicable or relevant and appropriaterequirement (ARAR) in the ROD. Attachment 4contains a letter from the State dated April 23, 2001which establishes provisions for the construction andoperation of GCW systems at the former NOP site. AnEPA memorandum dated December 27, 2000 regardingreinjection of groundwater as a part of a CERCLAremedial action is also included in Attachment 4.

[The remainder of this section w i l l be completedsubsequent to the receipt of comments on the ESDfol lowing the public comment periodl.

STATUTORY DETERMINATIONS

COMPLIANCE WITH CERCLA §121

The modified remedy is protective of human health andthe environment , complies w i th Federal and Staterequirements that are applicable or relevant andappropriate to the remedial action, is cost-effective, anduses permanent solutions and alternative treatment andresource recovery technologies to the maximum ex ten tpossible.

This modified remedy also satisfies the statutorypreference for treatment as a principal element of theremedy. That is, it reduces the toxicity. mobility, andvolume of contaminants as a principal element throughtreatment.

Because th i s remedy w i l l result in contaminantsremaining on-site above levels that allow for un l imi teduse and unrestricted exposure, a statutory review w i l l beconducted wi th in five years after the in i t ia t ion of theremedial action to ensure that the remedy is, or w i l l be.protective of human health and the environment.

PUBLIC PARTICIPATION COMPLIANCE

COMPLIANCE WITH NCP §300.435(c)(2)(ii)

A notice of ava i lab i l i ty and a brief description of th isESD was published in [name to be completed] which is amajor local newspaper of general circulat ion on [date tobe completed].

A public availability session for the ESD was conductedon August 30, 2001. The ESD was made available topublic by placing it in the Administrative Record file onAugust 30, 2001. Although the NCP does not require aformal public comment period, a public comment periocwas conducted from August 30, 2001 to October 1.2001. ,

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REFERENCES

URS Group, Inc. (URS). 2001. Draft FinalGroundwater Circulation Well Pilot Study TechnicalMemorandum. Operable Unit No. 2 (Groundwater),Former Nebraska Ordnance Plant, Mead, Nebraska.Prepared for the Kansas City District Corps ofEngineers under Contract No. DACW41-96-D-8014,Task Order No. 0017, WAD 1. April .

U.S. Environmental Protection Agency (EPA). 1999. AGuide to Preparing Superfund Proposed Plans,Records of Decision, and other remedy selectiondecision documents. EPA 540-R-98-031. July .

Woodward-Clyde Consultants (WCC). 1995. DraftFinal (Revision 2) Feasibility Study Report.Operable Unit No. 2 (Groundwater), FormerNebraska Ordnance Plant, Mead, Nebraska.Prepared for the Kansas City District Corps ofEngineers under Contract DACA41-92-C-0023.May.

Woodward-Clyde Consultant (WCC). 1997. FinalRecord of Decision, Operable Unit 2, FormerNebraska Ordnance Plant Site, Mead, Nebraska.Prepared for the Kansas City District Corps ofEngineers under Contract No. DACA41-92-C-0023.Signed in April .

Woodward-Clyde Federal Services (WCFS). 1997.Draft Final Water Ava i l ab i l i t y CharacterizationTechnical Memorandum Operable Unit No. 2(Groundwater), Former Nebraska Ordnance Plant,Mead, Nebraska. Contract No. DACW41-96-D-8014. Prepared for U.S. Army Corps of Engineers.Kansas City District. March.

LISTOFACROYNMS: AOPs Advanced Oxidation Processes

ARAR Applicable or Relevant and AppropriateRequirement

ARDC Agricultural Research and DevelopmentCenter

: CENWK Kansas City DistrictCERCLA Comprehensive Environmental Response,

Compensation, and Liability ActEPA Environmental Protection Agency

i ESD Explanation of Significant Differences: GAC Granular Activated Carbon! GCW Groundwater Circulation Well' gpm gallons per minute! IAG Interagency Agreement: MCL Maximum Contaminant Level| NAC Nebraska Administrative Codei NCP National Contingency Plan: NDEQ Nebraska Department of Environmental! Qualityj NOP Nebraska Ordnance Plant, OU1 Operable Unit No. 1| OU2 Operable Unit No. 2i RAB Restoration Advisory Boardi RDX Hexahydro-1,3,5-trinitro-1,3,5-triazine! ROD Record of Decision1 TCE Trichloroethene' TRC Technical Review Committee

URS URS Group, Inc.; USAGE U.S. Army Corps of Engineers; VOCs Volatile Organic Compounds

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,.J °" '-SCALE IN MILES

URS GfOUO Inc. u s ARMY ENGINEER DISTRICTUfiu uiuufj iiiif. CORPS OF ENGINEERS10975 El Monte. Suite 100 lfAN<5A% rlTY UIQQrtllBIOverland Port.. Karoos M211 KANSAS CITY, MISSOURI

Deiigned by:

A.C.E.

Drawn by:

RAD.

Checked by:

M.E.W.

Submitted by:

A.C.E.

gn^grm EXPLANATION OF SIGNIFICANT DIFFERENCESl.n.l OPERABLE UNIT 2 - GROUNDWATER

FMR. NEBRASKA ORDNANCE PLANT - MEAD. NE.

U.S. Army Corpsof Engineers PHASE I

REMEDIAL ACTION

* 1 IN. - 1 MILE rtHmter:

Oota: AUGUST. 2001

f??31)

8 7^i / >-•i—.

FORMER ATLAS 'MISSLE AREA •>-

FORMER NIKEMAINTENANCE AREA

AFBMD TECH. AREA

FORMER NOPLANDFILL AREA

FORMERNOP LOAD'*--'UK.

.N " < »,>—< .X.....

rpriTrn r.aoUNDWATER PIPELINE

U.S. HIGHWAY 63

FORMER NOP BOUNDARY

EW -10300gpm

TREATEDGROUNDWATERPIPLINE

LEGEND:

APPROXIMATE AREA OF EXPLOSIVES - CONTAMINATED GROUNDWATER(CONCENTRATIONS OF RDX GREATER THAN OR EQUAL TO THE HEALTHADVISORY OF 2pg/L).

APPROXIMATE AREA OF TCE - CONTAMINATED GROUNDWATER(CONCENTRATIONS OF TCE GREATER THAN OR EQUAL TO THE MAXIMUMCONTAMINANT LEVEL OF 5pg/L).

APPROXIMATE AREA OF COMBINED TCE AND EXPLOSIVES - CONTAMINATEDGROUNDWATER (TCE AND EXPLOSIVES CONCENTRATIONS GREATER THAN OREQUAL TO 5/jg/L AND 2pg/L RESPECTIVELY).

N

I0 1/2

SCALE IN MILES

of59ro Q-

URS Group Inc.10975 El Mont., Suit* 100Ovorland Park. Konm 66211

Designed by:

A.C.E.

Drawn by:

RAD.

Checked by:

M.E.W.

Submitted by:

A.C.E.

mU.S. ARMY ENGINEER DISTRICT

CORPS OF ENGINEERSKANSAS CITY, MISSOURI

EXPLANATION OF SIGNIFICANT DIFFERENCESOPERABLE UNIT 2 - GROUNDWATER

FMR. NEBRASKA ORDNANCE PLANT - MEAD. NE.

of Engineers PHASE I

REMEDIAL ACTIONWITH FOCUSED EXTRACTION ALTERNATIVE

"-"I IN. =

Dat<l: AUGUST

1 MILE

2001

SS- 2

Sheetnumber:

4

1

FORMER ATLAS 'MISSLE AREA

FORMER NIKEMAINTENANCE AREA

TREATED GROUNDWATER PIPELINE

TREATEDGROUNDWATERPIPUNE

LEGEND:

APPROXIMATE AREA OF EXPLOSIVES - CONTAMINATED GROUNDWATER(CONCENTRATIONS OF RDX GREATER THAN OR EQUAL TO THE HEALTHADVISORY OF 2pg/L).

APPROXIMATE AREA OF TCE - CONTAMINATED GROUNDWATER(CONCENTRATIONS OF TCE GREATER THAN OR EQUAL TO THE MAXIMUMCONTAMINANT LEVEL OF 5/jg/L).

N m

8-

ro Q-

fAPPROXIMATE AREA OF COMBINED TCE AND EXPLOSIVESGROUNDWATER (TCE AND EXPLOSIVES CONCENTRATIONSEQUAL TO Spg/L AND 2>ig/L RESPECTIVELY).

-̂ - GROUNDWATER CIRCULATION WELL SYSTEMS

- CONTAMINATEDGREATER THAN OR

URS Group Inc.10975 El Mont*. Suit. 100Overland Pork. Koran 68211

Deeigned by:

A.C.E.

Drown by:

RAD.

Checked by:

M.E.W.

Submitted by:

A.C.E.

ESI FMR

U.S. Army Corpsof Engineers

S<X"*: 1 IN. - 1 M

Datt: AUGUST. 2C

Dwg. 0No)! O

0 1/2 1

SCALE IN MILES

U.S. ARMY ENGINEER DISTRICTCORPS OF ENGINEERS

KANSAS CITY, MISSOURI

REMEDIAL DESIGNOPERABLE UNIT 2 - GROUNDWATERNEBRASKA ORDNANCE PLANT - MEAD. NE.

PHASE I AND PHASE IIREMEDIAL ACTION

ILE number:

01

1

• ATTACHMENT 1 Relevant ROD Sections

II

II

III

I

II

IIIIII

i-r-

IFormer NOP - Mead - Saunders County, Nebraska

-- -

re

PO a.

h-i O

n

OU2 Record of DecisionFormer Nebraska Ordnance Plan!

2.0 DECISION SUMMARY

2.1 SITE NAME, LOCATION, AND DESCRIPTION

The former NOP site occupies approximately 17,250 acres located one-half mile south of the townof Mead, Saunders County, Nebraska as shown on Figure 1. During World War II and the KoreanConflict, bombs, shells, and rockets were assembled at the site. The site includes four load lines,where bombs, shells, and rockets, were assembled; the Burning/Proving Grounds, where fuses weretested and materials were destroyed by burning; a Bomb Booster Assembly Area, where boostersthat amplify the effect of the detonators and assure the complete detonation of the main explosivewere assembled; Administrative Area, which included offices, residences, and a laundry; an AirForce Ballistic Missile Division (AFBMD) Technical Area, where historical information suggeststhat parts were cleaned; and an Atlas Missile Area. The locations of these. features_are..sho_wn onFigure 2. According to reports, wastewater from both the load line plant operations and the laundrywas discharged into a series of sumps, ditches, and underground pipes. Historical information alsosuggests that TCE was released at the AFBMD Technical Area and the Atlas Missile Area.

The former NOP site is located in the Todd Valley, an abandoned alluvial valley of the ancestralPlatte River. The thickness of unconsolidated material above bedrock in the Todd Valley at the siteranges from approximately 81 feet to 157 feet. The unconsolidated material consists of topsoil,loess, sand, and gravel. The uppermost bedrock unit is the Omadi Shale in the northwest and theOmadi Sandstone in the southeast portions of the site.

Three aquifers are present at the site: the Omadi Sandstone aquifer, the Todd Valley aquifer, andthe Plane River alluvial aquifer. Three aquitards are present: the Pennsylvanian shales, the OmadiShale, and the Plane River aquitards. Where the Omadi Shale is absent, the Todd Valley aquifersand the Plane River alluvial aquifer are in hydraulic communication with the Omadi Sandstone andbehave as single aquifers without hydraulic barriers.

The water-bearing portions of the unconsolidated material in the Todd Valley are divided into twounits, an upper fine sand unit and a lower sand and gravel unit. During the OU2 RemedialInvestigation (RI), the sand and gravel unit was found to range from 17.5 to 72 feet thick and thefine sand unit was found to range from 12 to 77 feet thick. The upper fine sand unit is overlain by 4 ~~to 23 feet of the Peoria Loess.

The unconsolidated material in the Platte River Valley, which ranges from 39 to 49 feet thick.Overbank silts and clays ranging from 10 to 17 feet thick overlie the Platte River alluvial sands andgravels.

The water table surface of the Todd Valley slopes toward the south-southeast with depths togroundwater table in the Todd Valley ranging from 6.6 feet to 58.0 feet. A local zone of r> &•groundwater discharge is located along the western side of the Platte River floodplain in the O 9southeastern portion of the site. East of Johnson Creek, the water table surface of the Platte River rvi Q-

r\> §O g

GL

E:\92030\OU2ROD3.ACE 2~-l October 1996

WYOMING

Figure 1General Site Location Map

FORMER NEBRASKAORDNANCE PLANT

KANSAS

vo £no it—' 3

ACAD ritf 92=R-lT.RJ. SC: 1-1

F i g u r e 2Si te Map

W.MM._s.\\:i. A S I A I / BDj-NIf.-T- j'

FORMER NOP S I T E BOUNDARY

OU2 Record of DecisionFormer Nebraska Ordnance Plant

alluvial aquifer slopes to the south, paralleling the Plane River Valley with depths to groundwatertable in the Plane Valley ranging from 0.0 to 10.2 feet.

The site is nearly flat, with a few gentle slopes. Surface water drainage in the eastern portion of thesite is generally to the southeast, toward Johnson Creek and the Natural Resources District (NRD)Reservoir. In the western portion of the site, surface water drains to the southwest, toward SilverCreek.

According to the draft National Wetlands Inventory Map for the Mead Quadrangle, a number ofwetland types occur in the vicinity of the site, however, these areas will not be influenced by theactivities addressed in OU2.

Most of the site is owned by the University of Nebraska, which operates an agricultural experimentstation called the Agricultural Research and Development Center (ARDC) on the premises. Crop,hog, dairy, and cattle research take place on site. Other portions are owned by the NebraskaNational Guard, United States Air Force, and Army Reserves. Some private pasture and cropproduction also take place on site, and some private light industry exists near the northern end ofthe site. Adjacent land use is primarily agricultural, except for the Village of Mead which is locatednorth of the site.

2.2 SITE HISTORY AND PREVIOUS INVESTIGATIONS

2.2.1 Site History

The former NOP was a load, assemble, and pack facility which produced bombs, boosters, andshells. The NOP included four bomb load lines, a Bomb Booster Assembly plant, an ammoniumnitrate plant, two explosives burning areas, a proving range, a landfill, a wastewater treatment plant,analytical laboratories, and storage and administration facilities. Most of the raw materials used tomanufacture the weapons were produced at other locations and shipped to the NOP facility forassembly. However, ammonium nitrate was produced at the Ammonium Nitrate Plant during thefirst months of operation. Finished munitions, bulk explosives, and related ordnance materials andcomponents were stored and demilitarized at the site.

Routine plant operations included washout of explosive materials prior to bomb loading andassembly, and bomb washing following assembly. Wash water was discharged to sumps and inopen ditches.

The production facilities were active during both World War II and the Korean Conflict. TheNebraska Defense Corporation operated the NOP for the Army from 1942 until 1945 and producedmunitions which were loaded with trinitrotoluene (TNT), amatol (TNT and ammonium nitrate),tritonal (TNT and aluminum), and Composition B (RDX and TNT). Tetryl boosters were zassembled for bombs in the Bomb Booster Assembly Area. In 1945, ordnance production £_ croperations were terminated, and the facilities and operations were placed on inactive status. r O ?

\O o,ro iCO 3

^ v^w t/1

E:\92030\OU2ROD3 A C E ? - 2 O c t o t x r l 9 9 6 —

OLJ2 Record of DecisionFormer Nebraska Ordnance Plant

During the interim period (1945 through 1949), the NOP was decontaminated and used primarilyfor storage and disposal of bulk explosives and munitions, and production of ammonium nitrate foruse as fertilizer. Decontamination consisted of flushing and sweeping buildings that were not beingused for storage. After decontamination operations were completed, explosives residues in thesumps, settling basins, pipelines leading to the drainage ditches, and an unspecified quantity ofcontaminated soil and sludge from the drainage ditches were removed and reportedly taken to theBurning/Proving Grounds. In some instances, portions of the tile pipe composing the drainagesystem from the sump to the open ditches were removed and disposed.

In 1950, the plant was temporarily reactivated and produced an assortment of weapons for use inthe Korean Conflict. The NOP was placed on standby status in 1956 and declared excess to Armyneeds in 1959.

After the NOP was declared excess in 1959, it was transferred to the General ServicesAdministration for disposition. Approximately 1,000 acres were retained by the Army for NationalGuard and Army Reserve training, 12 acres were retained by the Army for use as a Nike Missilemaintenance area, 2,000 acres were transferred to the U.S. Air Force to build the Offutt Air ForceBase Atlas Missile Site, and 40 acres were transferred to the Department of Commerce. From 1959

.to 1960, the Offutt Air Force Base Missile Site S-l launch area (Atlas Missile Area) was built on1,185 acres north of Load Line 4. TCE was used during construction to degrease and cleanpipelines used to carry liquid oxygen fuel for missiles. Historical information suggests that TCEwas released as ground spills and/or discharged into surface drainage features during theconstruction activities. The exact locations, quantities, and dates of TCE disposal are not known.The missile facilities were abandoned in 1964, and the Atlas Missile Area and the Nike Area weretransferred to the Nebraska National Guard. The U.S. Air Force also occupied 34 acres of thenorthern portion of Load Line 1 for use as the AFBMD Technical Area. The purpose of theAFBMD Technical Area is unclear, but historical site information suggests that parts were cleanedwith TCE in a laboratory, and the spent TCE was discharged into the sewer. The potential TCEsoil contamination is not located in the areas contaminated with explosives. In 1962, approximately9,600 acres of the former NOP site were purchased by the University of Nebraska for use as anagricultural research farm which is now the ARDC, and an additional 600 acres were obtained in1964. The remaining 5,250 acres were eventually purchased by private individuals andcorporations.

Since NOP closure, the property has been used primarily for agricultural production and research.In addition to these land uses, several commercial operations were conducted on former NOP Zproperty. Apollo Fireworks operated for a period of approximately 20 years until 1989 in the C* °"Bomb Booster Assembly Area, At the former administration buildings, various commercial O T^

.enterprises were in operation including insulation board manufacturing and expanded styrene foam \Q r>packing material processing. Property was leased for these and other purposes by private [^ §individuals. —

Several environmental investigations (discussed below) resulted in the listing of the former NOPsite on the National Priorities List (NPL) under Section 105 of CERCLA on August 30, 1990. In !

September 1991, USAGE, USEPA, and NDEQ entered into an Interagency Agreement (TAG)

E:\92030\OU2ROD3 A C E 2 o October 1996

OU2 Record of DecisionFormer Nebraska Ordnance Plan!

under Section 120 of CERCLA to investigate and control environmental contamination at theformer NOP site.

2.2.2 Previous Investigations

Soil

Previous investigations include an archives search for the U.S. Army Toxic and HazardousMaterials Agency (USATHAMA, now called Army Environmental Center) in 1983;Polychlorinated Biphenyl (PCB) investigations by the University of Nebraska in 1984 and 1985,USEPA in 1988, and USAGE in 1993; a soil, sediment, surface water, and groundwater.investigation by USAGE in 1989; a shallow soil gas investigation in 1990; a soil investigation bythe USAGE in 1991; an unexploded ordnance (UXO) survey and soil investigation by USAGE in1991; a preliminary health assessment by the Agency of Toxic Substances and Disease Registry(ATSDR) in 1991; and a Supplemental Soil RI for OU1 by USAGE in 1991.

The 1983 archives search was conducted to assess the potential for contamination at the NOP sitefrom Army operations. Findings of the Archive Search Report were based primarily on the U.S.Army Ordnance Ammunition Command's 1959 Survey of Explosives Contamination. Areasrecognized in the Archives Search Report as having the greatest potential for explosives-contamination were the four load lines, the Bomb Booster Assembly Area, and theBurning/Proving Grounds.

In. 1989, USAGE conducted a confirmation study to determine if past Army activities at the NOPsite resulted in environmental contamination. A. geophysical survey was conducted to screenboring locations and locate buried materials. The study concluded that explosive residues arepresent in soil around three of the load lines.

In 1991, USAGE identified and assessed potential sources of explosives contamination and UXO.USAGE performed a records review and site inspection which included excavation of two test pitsand collection of 18 soil samples. Locations potentially requiring remedial action were identifiedas those where solid pieces of TNT were visibly present or where TNT was found in soil atconcentrations greater than 2 percent by weight. The areas identified based on these criteria were atthree of the load lines and parts of the Burning/Proving Grounds.

ATSDR completed its Preliminary Health Assessment in 1991. ATSDR concluded that potentialhuman exposure to hazardous substances at the former NOP may result in adverse health effects. Itwas concluded that the public could be exposed to the explosive compounds RDX and TNT viaskin contact or soil ingestion.

In 1991 and 1992, USAGE conducted an OU1 RI to evaluate the extent (area and depth) ofexplosives-contaminated soil at the former NOP site. Most sampling was based on historical Nwashwater disposal practices during the ordnance production process. Explosives compounds were g Qdetected in soil in all four load lines, the Bomb Booster Assembly Area, and the Burning/Proving po Q-

ro goi g

E.\92030\OU2ROD3.ACE 2~̂ 3 October 1996 —

OU2 'Record of DecisionFormer Nebraska Ordnance Plant

Grounds. No significant explosives contamination was identified in the Administration Area. Nolive ordnance was found on-site.

OU1 RJ results indicate that explosives contamination in soil is mostly limited to soils in and underdrainage ditches and sumps in the load lines and the Bomb Booster Area. It is believed that thiscontamination originated from the discharge of water used to wash away explosives dust andresidue which resulted from the ordnance load, assemble, and pack process. In theBurning/Proving Grounds, testing and burning activities probably contributed to soilcontamination. The majority of the explosives contamination was detected in shallow soil. Atsome locations, however, explosives compounds were detected at depths of approximately 30 feetbelow the surface. Explosives contaminant concentrations in the ditches generally decreaseddownstream from collection sumps. TNT, RDX, and 1,3,5-trinitrobenzene (TNB) were theexplosives contaminants most often detected. The OU1 results are presented in the SupplementalRJ Report for OU1.

Based on the PCB investigations, PCB-contaminated soil was identified in locations associatedwith former transformer pads and subsequently removed by the University in 1985 and USAGE in1994 and 1995. Removal of remaining PCB-contamination is ongoing. Unexploded ordnance hasnot been found on-site, but some internal components of ordnance (booster adapters, fuses,propellants, and bulk TNT) were found and disposed. Investigation of unexploded ordnance isongoing at the site. Documents related to the site are available for review in the informationrepository at the Ashland Public Library.

Groundwater

Groundwater sampling was initiated by USAGE during the 1989 Confirmation Sampling whensamples were collected from monitoring wells and water supply wells. RDX, TNT, and TCE wereidentified in the groundwater samples. Some of the TCE concentrations exceeded the MCL of5 micrograms per liter (ug/L). As a result of the Confirmation Study, carbon filtration systemswere installed at two residences southeast of the_former NOP, a carbon filtration system wasinstalled at the AJIDC Agronomy Building, and two ARDC water supply wells were removed fromservice. Subsequently, the water supply well sampling was continued on a periodic basis.Additional residences were identified where the TCE concentrations exceeded the MCL or theRDX concentrations exceeded the HA of 2 (ig/L. Currently, water is" being treated and/or bottledwater is being supplied at four private residences which are all southeast of the former NOP. Inaddition, water is being treated with GAC adsorption at 26 ARDC locations.

ZIn late 1989 and early 1990, a soil gas survey was conducted by USAGE to evaluate areas of soil pj §-that may be contributing TCE contamination to groundwater. TCE and other VOCs were detected o 9in some samples; however, source areas were not definitively identified. ^ ^

USAGE installed and sampled additional monitoring wells prior to the OU2 RJ. {§

E:\92030\OU2ROD3ACE - ^ October 1996

OU2 Record of DecisionFormer Nebraska Ordnance Plant

2.2.3 Summary of OU2 RI Results

USAGE conducted an OLJ2 RJ in 1992 to evaluate the nature and extent of potential chemicals ofconcern (COCs) in the groundwater at the former NOP site attributable to past Department ofDefense (DoD) activities. The secondary objective was to evaluate the potential nature and extentof VOC contamination in soils at three areas (Administration Area, Atlas Missile Area, and theAFBMD Technical Area) to assess whether or not these contaminated areas are possible continuingsources of VOCs in the groundwater. Groundwater samples were also collected from 136monitoring wells and were analyzed for VOCs, explosives compounds, and general water qualityparameters. Selected monitoring wells were also analyzed for semi-volatile organic compounds(SVOCs) and metals. Soil and soil gas samples were collected and analyzed for VOCs. Field datawere also collected to characterize the geology at the former NOP site, and to estimate the directionand rate of groundwater flow. Groundwater samples were collected from every monitoring well ona quarterly basis beginning during the OU2 RI (August 1992) and continuing for one year.Subsequent sampling has been performed periodically at selected monitoring wells, and themonitoring program is ongoing.

The OU2 RJ identified four groundwater contamination plumes with separate source locationidentified for each plume. Two of the plumes consist of explosives contaminated groundwater(primarily RDX) and two of the plumes consist of primarily TCE-contaminated groundwater. Theplumes overlap in two areas where both TCE and RDX are in the groundwater in the same location.Both the TCE plume with its source at the Atlas Missile Area and the explosives plume with itssource at Load Lines 2, 3 and 4 extend past the eastern boundary of the former NOP.

Higher groundwater contamination was found in the upper fine sand units than in the sand andgravel units below. Generally, lower contamination was found in the deepest of the three aquiferswhich is the Omadi Sandstone aquifer. Table 1 lists the ranges of the COCs detected ingroundwater.

The OU2 RJ data indicated that the Administration Area was not a continuing source ofgroundwater contamination. However, data did not conclusively indicate whether the Atlas MissileArea or the AFBMD Technical Area are, or are not, continuing sources of TCE to groundwater.The data do indicate TCE groundwater contamination did originate in those areas.

Subsequent to the OU2 RI, a Groundwater Containment Removal Action was developed to stop thespread of the TCE plumes. The implementation of that removal action awaits acquisition ofnecessary easements for property access. If the containment of the TCE plumes is notaccomplished by this removal action, it will be conducted as a part of the remedial action instead.Section 2.6 contains more details regarding the Groundwater Containment Removal Action.

E.\92030\OU2ROD3.ACE October 1996

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IIIIIIIIIIIIIIIIIIi

Table 1Range of COC Concentrations Detected in Monitoring Well Samples

Contaminant of Concern

Methylene chloride1 ,2-dichloropropane

TCETNBTNTRDX

2,4-DNT

Range of Detected Concentrations on M\VsMaximum (jig/L)

61027

48004395341.9

Minimum (ug/L)0.5 JB0.7J0.6J0.1

0.100.080.13

Notes:

1)2)3)4)5)6)7)

J = Below Quantitation Limit (estimated)B= Compound also detected in laboratory blankTCE = TrichloroetheneTNB = 1,3,5-trinitrobenzeneTNT = 2,4,6-trinitrotolueneRDX = Hexahydro-l,3,5-trinitro-l,3,5-triazine2,4-DNT = 2,4-dinitrotoluene

~O Oro Q.vo nno goo §

in

E:\92030\OU2ROD3 ACE October 1996

* ATTACHMENT 2 Pilot Study Factsheet

IIIIIIIiiiiiiiiii_ Former NOP - Mead - Saunders County, Nebraska

O ft^ o-O Of>0 5.

Army Corpsif Engineers

isas City District

PILOT STUDY FACT SHEETFORMER NEBRASKA ORDNANCE PLANT

Summer 2000

GCW-2 WELLHEADAND UV CONTACTOR

This factsheetdescribes thegroundwatcrcirculationwell (GCW)pilot studies

, that arcbeingconducted asa part ofgroundwatcrremediation at theformer NebraskaOrdnance Plant(NOP) site. The pilot studies are being conducted bythe Kansas City District Corps of Engineers whoshare the responsibility for site activities along withthe U.S. Environmental Protection Agency and theNebraska Department of Environmental Quality.Another fact sheet provides an overview ofgroundwater remediation activities at the site.

What is a pilot study?A pilot study is an engineering study that providessite-specific data about a specific technology ortechnique by implementing that technology on-siteusing portable or non-permanent equipment.Typically, the pilot study is conducted over apredetermined period of time. One of the primaryobjectives of the pilot study data gatherinp nrocess isto provide engineers with the right kind ofinformation for designing full-time, permanentinstallations should the technology prove to befeasible.. Pilot studies are very valuable forevaluating:

• New technologies

• Sites with complex physical characteristics

• Very large projects where the cost of the pilotstudies are relatively small compared to the cost ofthe permanent installation and the pilot study datamay prevent costly failures

What is GCW?Groundwatcr circulation well technology is anexciting approach for remediating contaminatedgroundwatcr. GCW includes the following basicelements:

1. Contaminated groundwatcr is pumped into a GCW.2. The groundwatcr is treated on the spot in the well

casing or in a buried vaul t at the well head. Ourpilot studies use vaults to hold the treatmentequipment.

3. The treated groundwatcr is returned to the aquiferthrough an interval of the same well which isphysically separated from the extraction interval.Depending on the geology at the GCW site, someof the treated groundwatcr wi l l probably traveldown stream away from the influence GCW andsome of the treated groundwater may mix withuntreated groundwatcr and enter the GCW againfor treatment another time. This is illustrated onthe cross-sectional flow pattern drawing on thenext page. The amount of groundwatcr that isrecirculatcd and the size of the aquifer that istreated by a GCW is very dependent on thegeology at the GCW location. Because it is verydifficult to characterize precise geologic detailsover large areas, pi lot studies are very useful forevaluating GCW projects.

iRMER NEBRASKA ORDNANCE PLANT OPERABLE UNIT 2 - GROUNDWATER

UPGflACIfcNr GCV, G3CUNU S^R OCWNGPADIENT

-EXTRACTION W

CROSS-SECTIONAL FLOW PATTERN

GCW BenefitsThe following aspects of GCW make it attractive atthe site:•/ Treated groundwater is conserved through

recharge to the aquifer.

•/ It may not be necessary to acquire as much realestate relative to the pump and treat groundwatercleanup method because there is no need for longpipelines.

•/ Very high treatment efficiency and/orrecirculation are not required because the focus ofthe action is to remove large masses ofcontaminants. The down stream hydrauliccontainment wells provide a safeguard againstcontamination of currently "clean" areas.

GCW-2 WELLHEAD

GCW-1 PACKER

GCW-1 WELLHEAD ANDSHALLOW TRAY AIR STRIPPER

Oil

59PO Q-\O £00 g

U

' low does GCW fit intoine overallsmediation?

uroundwatCi remediation at the formerNOP site consists of two major( Imponents:• Containment pumping and treating

^roundwatcr at the leading edge of the:ontaminant plumes so that the forward

progress of the contamination is'mpedcd.

« Creating the most contaminatedgroundwater which occurs miles from'he leading edges of the plumes (focusedextraction). One option is to use

additional pump and treat wells for this^nction, and another;0ption is to use}CW instead.

If the results of the pilot studies indicatet it the technology is viable for the formerf DP site, an engineering design may beperformed so that the most contaminated

'= ;as of groundwater arc remediated byf "W units. The pilot study systems havebeen designed and constructed so that theyr ty be converted to regular, full-time,f 1-scale, permanent use if so desired. Inaddition, the construction of the wells iss .:h that they may be converted to: ditional pump and treat wells if GCW isnot viable.

[iFocuse. Extraction

vn

FORMER NOPLOAD LINE 4'

Details of the pilot studiesWe are currently conducting two GCW pilot studiesat the former NOR One pilot system is installed atthe location where the highest concentrations of TCEhave been measured, and the second system has beeninstalled near the location where the highestconcentrations of RJDX have been measured. Severalmonitoring wells have been installed at both pilotstudy locations upgradicnt and downgradicnt of thetreatment systems. Samples from these groundwatermonitoring wells arc collected to measure how wellthe treatment system is cleaning up the groundwaterwithin the aquifer. The groundwater samples areanalyzed on site using TCE and RDX field analysiskits. The field analysis kits provide real-timeinformation as to the concentrations in thegroundwater and the effectiveness of the treatmentsystems. Additional groundwater samples areperiodically sent to off site laboratories to confirm thefield analysis results. In addition to the overallperformance of each system, we are especiallyinterested in the performance of the treatment unitwhich uses ultra-violet light to destroy RDX and theperformance of the shallow-tray stripper which isused to treat TCE because it is the first time that theseparticular treatment technologies have been used inGCW systems. The following diagrams provideadditional details about the individual TCE and RDXpilot systems.

For more information or any questionsconcerning this project, please contact:

Tom GraffU.S. Army Corps of Engineers

Kansas City District601 E. 12th Street

Kansas City, Missouri 64106

Phone: (816)983-3894Or Collect (816) 983-3486

GCW-1(TCE Pilot Study Site)

Ground Surfacerou

Well locationconsists of a24-inch bonngwith a 12-inchcasing.

Extraction Zone• Between 60 - 70 ft below ground

surface (bgs)1 Will extract groundwater somewhere

between 30 - 50 gpm1 Concentration of approximately

4.000 ug/1 TCE

Recnaroe Zone• Between 89-108 ft bgs

GCW-2(RDX Pilot Study Site)

Ground Surface

Well locationconsists of a14-inch boring witha 6-inch casing.

Recharge Zone• Between 14 - 40 ft below

ground surface (bgs)

Extraction Zone• Between 50 - 60 ft bgs• Will extract groundwater

somewhere between 1 5 - 2 0 gpm• Concentrations of approximately

50 ug/1 RDX

oono a.VO o>CO °CO §

ro

' 10975 El Monte, Suite 100Overland Park, Kansas 66211

IATTACHMENT 3 Pilot Study Executive Summary

III

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Former NOP - Mead - Saunders County, Nebraska

SECTIOHZERO Executive Summary

The Operable Uni t 2 Record of Decision defined a remedy that included two dif ferentapplications of pump-and-treat aquifer restoration. The first application consists of installing11 extraction wells that wi l l hydraul ica l ly contain the leading edge of contaminant plumes bypumping groundwater at a total flowrate of 2,650 gpm. Subsequent to treatment, that water wil lbe surfaced discharged or beneficially reused. Two of the eleven wells are currently in place andoperating, and the construction of the remaining nine wells is on-going. The secondpump-and-treat application defined in the Record of Decision included three focused extractionwells located at or near hot spots so that contaminant mass wil l be more rapidly removed fromthe aquifer relative to hydraulic containment alone. Project stakeholder's interest in conservinggroundwater supply avai lab i l i ty provided the mot iva t ion to consider groundwater circulationwells as an innovative replacement for the three focused extraction wells because groundwatercirculation wells are a zero discharge technology. The purpose of the groundwater circulationwell pilot study was to characterize the technical feasibil i ty of using groundwater circulationwells to remediate relatively high concentrations of RDX and TCE. Secondary objectives of thepilot study were to collect cost and design data.

Two groundwater circulation well systems were constructed for the pilot study. The TCE systemconsists of the extraction, treatment, and recharge of groundwater at 50 gpm. A shallow tray airstripper installed in a vault is used to treat groundwater below the ground surface. Dedicatedbladder pumps have been installed in 2 existing and 14 new monitoring wells. Groundwatersamples collected from those wells as well as samples collected from the air stripper inf luent andeffluent sampling ports were analyzed with colorimetric field kits, and selected samples weretransmitted to an off-site laboratory for confirmatory analysis. These data and the results ofnumerical groundwater flow modeling were used to estimate the effective treatment area in theaquifer. In addition, data were collected from the monitoring wells to identify potentiallyapplicable bioenhancement technologies, and data gaps associated with the evaluation of suchtechnologies.

The RDX system consists of the extraction, t rea tment , and recharge of groundwater at more than20 gpm. The groundwater is treated below the ground surface using a 3.5 kW medium pressureul t ra -v io le t l ight commercial dis infect ion u n i t . Groundwater samples collected from 10 new-monitoring wells as well as treatment system i n f l u e n t and eff luent samples were analyzed wi thimmunoassay field kits, and selected samples were transmitted to an off-site laboratory forconfirmatory analysis.

Both systems operated as designed. The treated water discharge pump failed twice at GCW-1, C> S-and the system is sometimes shut down due to regional electrical power fluctuations. The o 9treatment efficiency of the air stripper ranges between 96 and 99 percent, with influent (^ £•concentrations ranging between 970 ua/L and 7,300 ug/L and effluent concentrations ranging ^ §between 13 ug/L to 150 |-ig/L. Approximately 24 gallons of TCE have been removed from !§_1 3 mi l l ion gallons of water treated by the system. It is estimated that the effective aquifertreatment area is between 80 ft and 240 ft wide.

A surface flooding event related to poor drainage conditions at GCW-2 caused the system to beshut down for several days. I n i t i a l l y the t reatment system was rented, and that rental u n i teven tua l ly fai led and was replaced wi th a purchased u n i t . F i n a l l y , the GCW-2 recharge intervalfailed to accept all of the treated groundwater, and the wel l was successfully redeveloped. Thecause of the recharge fa i lure was not i den t i f i ed , but damage from s i l t - laden flood water enteringthe system cannot be eliminated. The pilot study location RDX concentrations are lower than

«OvP3-'.PROJECTS'.K962l7.0HDRAFT FINAL PS TMVTEXT DOC\19-APR-01\\ 0- 1

SECTIOHZERO Executive Summary

desired, but even so, in f luen t concentrations have ranged from around 5 ug/L to 78 ug/L. Thetreatment system reduced RDX concentrations in effluent samples to less than the detectionlimits of 5 p.g/L or 1 ug/L. Approximately 240 grams of RDX have been removed from5 mi l l ion gallons of water treated by the system. It is estimated that the effective treatment areais between 60 ft and 180 ft wide.

The bioenhancement evaluation at the TCE site indicated that due to the presence of high levelsof dissolved oxygen in the aquifer a co-metabolism option may be feasible but the same oxygenlevels-make reductive dechlorination not feasible. Overall, bioenhancement opt ions at the RJDXsite do not appear feasible because the ultraviolet light treatment system would k i l l any bacteriain the groundwater extracted by the well.

Given that the pilot study results indicate that groundwaler c i rcu la t ion well technology istechnically feasible at the site, a cost comparison was developed between the existing focusedextraction alternative and a groundwater circulation well focused remediation alternative. It wasestimated that the construction of a groundwater circulation alternative consist ing of the twopilot systems and twelve new pilot systems was the cost equivalent to the ex i s t ing focusedextraction alternative. The annual operation costs were estimated to be lower for thegroundwater circulation well alternative.

Numerical and analytical modeling was performed to compare the predicted performance of thetwo alternatives for the former Atlas Missile Area TCE plume. The estimated TCE plumerestoration times developed using the analytical evaluation showed that the groundwatercirculation well restoration time was approximately one-half of the value estimated for thecurrent focused extraction alternative, and the results of the numerical modeling were s imilarbetween the two alternatives. However, the GCW value estimated using the analytical modelwas approximately three times the restoration t ime estimate presented in the Record of Decision.The primary factors which account for the differences in the es t imates is the :

• The lower extraction flowrates that have been developed as a resul t of p u b l i c i npu tconcerning the perceived impacts of the remedy on the groundwater supply

•" The higher TCE concentrations that have been measured since the Record of Decision wasissued

An analy t ica l evaluat ion of the Load Lines 2, 3, and 4 RDX p l u m e indica ted that the estimatedrestoration times for the groundwater circulat ion well a l ternat ive and the ex i s t ing focusedextraction alternative are equivalent .

The modeling estimated that, i n i t i a l l y , TCE mass would be removed at a greater rate for thegroundwater circulation well alternative, although the exist ing focused extraction a l te rna t ivewould eventually remove more mass. However, the exis t ing focused extract ion al ternat ive mayresult in the discharge of more than 300 mi l l ion gallons of treated g roundwate r a n n u a l l ycompared to zero discharge for the groundwater circulation well a l te rna t ive . Given thesignif icant and relat ively consistent record of publ ic concern regarding the conservation of thelocal groundwater supply, which is cr i t ica l for local agricul ture , and the conclusion that agroundwater c i rcu la t ion well alternative is approximately equ iva len t to focused extract ion in ^ g_terms of cost and effectiveness, it is concluded that the groundwater c i r cu la t ion well shou ld be o °considered for implementa t ion as the second phase of remedial ac t ion . PO Q-

S i——'0-2 «OVP3\PROJECTS\K96217.0UDRAFT FINAL PS TM\TEXT.DOCU9-APR-OU\

ATTACHMENT 4 Support Agency Comments

recr

59PO CL.

Former NOP - Mead - Saunders County, Nebraska

STATE OF NEBRASKADEPARTMENT OF ENVIRONMENTAL QUALITY

Suite 400. The Atrium1200 'N1 Streel

P.O. Box 98922Lincoln, Nebraska 68509-8922

March 30, 1999 phone (4021471-2186

Mike JohannsGovernor

Mr. Steven K. IversonU.S. Army Corps of Engineers Kansas City District700 Federal Building601 East 12th StreetKansas City, MO 64106-2896

Re: NOP OU-2 Phase II Schedule Extension Request

Dear Mr. Iverson:

The Nebraska Department of Environmental Quality has considered your request forrevising the OU-2, ground water remedial action schedule. As indicated in your letter,the OU-2 ground water remediation action will be split into phases as follows:

• Phase I - Containment Remedial Action / Pump and Treat• Phase II -- Focused Remedial Action / In-situ Pilot Study

A separate schedule was developed and proposed for the phase II pilot study.

In December 1998, the Department sent the Army Corps of Engineers a lettersupporting the proposed innovative approach to ground water remediation at the Meadsite. Therefore, the proposed schedule for the pilot study, and remedial Design /remedial action is acceptable to the Department.

If you have any questions, please call Ken Maas at (402) 471-2988.

Sincerely,

Richard SchlenkerSuperfund Section SupervisorAir and Waste Management Division

cc: Craig Bernstein, EPA Region VIIoctore

An Equal OpponentDrinhaH uiim «

I • UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

*'«< MOI* REGION VII726 MINNESOTA AVENUE

KANSAS CITY, KANSAS 66101

Mr. Steven K. IversonProject ManagerHTRW Project Management BranchU.S. Army Corps of Engineers, Kansas City District601 East 12th StreetKansas City, Missouri 64106

Dear Mr. Iverson:

SUBJECT: Approval of Schedule of the Remedial Design and Remedial Action ofOperable Unit No. 2 at the Former Nebraska Ordnance Plant Near Mead, Nebraska,Proposed In Your Letter dated March 18, 1999

The United States Environmental Protection Agency - Region YE (EPA) has received •your letter dated March 18, 1999, proposing a phased approach and schedule for completion ofthe Remedial Design and Remedial Action activities necessary to implement Phase It ofOperable Unit No. 2 at the Former Nebraska Ordnance Plant near Mead, Nebraska. The EPAapproves the phased approach and the schedule proposed in your letter.

Pilot Study:Submit Draft Work Plans November 30, 1999Submit Draft Final Work Plans February 11, 2000Submit Draft Pilot Study Report January 31, 2001

Explanation of Significant Differences (ESD) (if required):Submit Draft ESD ~ March 19,2001 j£Public Availability Session May 16, 2001 DQSubmit Draft-Final ESD July, 18, 2001 ^ o.Approved ESD September 19,2001 g g»

vo tRemedial Design Phase II: —

Submit Draft Remedial Design Phase JJ April 19, 2001Submit Draft-Final Remedial Design Phase 13 July 18, 2001Approved Remedial Design Phase JJ September 19, 2001

RECYCLE

Remedial Action Phase II Contract Acquisition:Issue Request for Proposal October 17, 2001Award Remedial Action Contract January 9, 2002

Remedial Action Phase II:Notice to Proceed February 6, 2002Submit Draft Remedial Action Work Plans March 19, 2002Construction Complete / O&M Start November 6, 2002Submit Draft Remedial Action Report April 3, 2003

As far as Phase I, there are no changes proposed to the schedule as it now exists.

Should you have any questions, please call me at (913) 551-7688.

Sincerely,

Craig BernsteinRemedial Project ManagerFederal Facilities/Special Emphasis BranchSuperfund Division

cc: Ken Maas, NDEQ

50PO Q-VO £-^ g

O ^

STATE OF NEBRASKADEPARTMENT OF ENVIRONMENTAL QUALITY

Suite 400. The Airiuin1200 -N- Street

P.O. Box 98922Lincoln, Nebraska 68509-8922

Phone (402) 471-2186

MlkeJohanns April 23, 2001Governor

Commander U.S. Army District, Kansas CityAttn: CENWK-EC-EC (Thomas Graff, P.E.)700 Federal Building601 East 12'h StreetKansas City, Missouri 64106-2896

RE: Ground Water Circulation Well TechnologyFormer Nebraska Ordnance Plant, Operable Unit No. 2IIS No. 67479, Program No. NE6211890011, Superfund

Dear Mr. Graff:

The Department has reviewed the information provided by URS regarding thepilot study at the former Nebraska Ordnance Plant near Mead, Nebraska. The departmenthas determined that Title 122 - Rules and Regulations for Underground Injection andMineral Production Wells is applicable to the ground water circulation wells (GCWs)used in this pilot study. These wells are injecting treated ground water into anunderground source of drinking water.

Title 122, Chapter 4, Section 001, prohibits construction and operation of anyinjection well or other injection activity in a manner that allows the movement of fluidcontaining any contaminant into underground sources of drinking water, if the presenceof that contaminant may cause a violation of any primary drinking water regulation or theNebraska Groundwater Protection Standards, or may otherwise adversely affect thehealth of persons, unless authorized by a permit under Chapter 3.

The department recognizes that the Nebraska Ordnance Plant is a site on theNational Priorities List and subject to the waiver provision in Section 121(e)(l) of theComprehensive Environmental Response, Compensation, and Liability Act (CERCLA). z

The substantive requirements of Title 122, which would otherwise have been included in Ci §•a permit, are still applicable. The department understands that long-term remedial action O Ogoal is to achieve compliance with the Nebraska Groundwater Protection Standards.

§In addition, the department also appreciates and supports the use of this

innovative technology to treat contaminated groundwater while ensuring the groundwateris beneficially returned to the aquifer rather than discharged. The public support of thisbeneficial reuse option is one of the principal reasons this innovative technology wasdeveloped and proposed. ' •

An Equal QppoTlunl(y/Aff\rmal\ve Action Employer

Printed with »cv ink on recvcktd oanef

The Department approves proposed injection of the treated ground water via theGCWs at the Nebraska Ordnance Plant Superfund Site, provided that:

1. The ground water must be treated prior to injection,

2. The ground water must be injected into the formation, from which it wasextracted via the same well,

3. The contaminant levels being injected do not classify it as a hazardous waste,

4. The permittee must demonstrate hydraulic control at the site,

5. All monitoring and reporting requirements in Title 122, Chapters 18 and 19 aremet, and

6. The injection does not adversely affect the health and safety of persons.

If you have any questions concerning this letter, please contact David Miesbachof my staff at (402) 471-4982. Your cooperation is appreciated.

Sincerely,

Jay D. RingenbergDeputy Director

xc: Craig Bernstein, EPA Region VII/Curt Elmore, URS

Dave Miesbach, NDEQRalph Martin, NDEQ Remediation Section

of5?PO Q-

ia

December 27, 2000

MEMORANDUM

SUBJECT: Appl icab i l i ty of RCRA Section 3020 to In-Situ Treatment of Ground Water

FROM: Elizabeth Cotsworth, Director /S/Office of Solid Waste

TO: RCRA Senior Policy AdvisorsRCRA Enforcement ManagersSuperfund Regional Policy Managers

We have recently received several questions on how the Resource Conservation andRecovery Act (RCRA) applies to the reinjection of ground water contaminated with hazardouswaste during cleanups, and particularly on the applicability of section 3020(b) of RCRA toground-water remedies involving in-situ bioremediation and other forms of in-situ treatment.This memorandum clarifies that reinjection of treated ground water to promote in-situ treatmentis allowed under section 3020(b) as long as certain conditions are met. Specifically, the groundwater must be treated prior to reinjection; the treatment must be intended to substantially reducehazardous consti tuents in the ground water - either before or after reinjection; the cleanup mustbe protective of human heal th and the environment; and the inject ion must be part of a responseaction under CERCLA section 104 or 106 or a RCRA corrective action intended to clean up thecontamination.

Background

Section 3020 of RCRA addresses the underground injection of hazardous waste in thecontext of RCRA and CERCLA cleanups. RCRA section 3020(a) bans hazardous waste disposalby underground injection into a formation which contains an underground source of drinkingwater (within one-quarter mile of the well), or above such a formation. However. RCRA section3020(b) exempts from the ban-reinjection of treated contaminated ground water withdrawn froman aquifer, if the fol lowing criteria are met: (1) the reinjection is a CERCLA section 104 or 106response action or part of a RCRA corrective action intended to clean up the con tamina t ion , (2) $the contaminated ground water is treated to substant ia l ly reduce hazardous consti tuents prior to

g-

o

such re in jec t ion, and (3) the response action or corrective action is sufficient to protect humanhealth and the environment upon completion. ' -

In the past, EPA and state regulators have expressed concern that the RCRA land disposalrestrictions (LDRs) might add further limitations on ground-water reinjection conducted as partof a RCRA or CERCLA action. The LDR requirements, found in RCRA sections 3004(f), (g),and (m) and codified at 40 CFR Part 268, establish specific treatment standards that restrictedhazardous waste must meet before it may be disposed of in a land disposal unit. Ground waterbeing reinjected may contain a restricted waste, and injection of hazardous waste intounderground injection wells is land disposal under LDR. To address concerns that thesetreatment requirements might limit the scope of the section 3020(b) exemption, EPA issued aclarifying memorandum on December 27, 1989. The memorandum stated that contaminatedground water reinjected during the course of RCRA or CERCLA cleanups in a manner consistentwith the RCRA section 3020(b) exemption is not subject to RCRA land disposal restrictions. Asthe memorandum summarized, "EPA construes the provisions of RCRA section 3020 to beappl icable instead of the LDR provisions at RCRA sections 3004(f), (g), and (m). to remjectionsof contaminated ground water into an underground source of drinking water (LJSDVV), which arepart of a CERCLA response action or RCRA corrective action." (emphasis added) (See Don R.Clay, Assistant Adminis t ra tor for Solid Waste and Emergency Response, to EPA Waste

'Prior to the 1984 amendments to RCRA that included section 3020, EPA promulgatedvery s imilar requirements in the implementing regulations for the Underground Injection Control(UIC) Program at 40 CFR 144.13. Additional clarification for injection wells at section144.13(d) provides exemptions from the prohibi t ion on Class IV wells (wells involving theinject ion of hazardous waste) in cases where the aquifer has been exempted pursuant to specificcriteria, or where no underground source of drinking water (USDW) source exists w i th in onequarter mi le of the injection well .

a£o ono Q.\o o

Management Division Directors and Regional Counsels, OSWER Directive #9234.1-06; a copyof the memorandum is attached.)2

EPA's December 27, 1989 memorandum, therefore, clarified the relationship betweenRCRA section 3020 and the LDR requirements. Since that memorandum, EPA has receivedadditional inquiries on the scope of section 3020, particularly as it applies to ground-waterremedies involving in-situ bioremediation and other in-situ treatment. The remainder of thismemorandum addresses those inquiries.

Application of Section 3020(b) to In-situ Treatment

•Questions have been raised as to whether the Corrective Action Management Unit(CAMU) rule superseded this 1989 directive. EPA emphasizes that the CAMU requirements donot supercede the 1989 memo. In addition, questions have been raised as to whether MinimumTechnological Requirements (MTRs) apply to reinjection. MTRs apply to landf i l l s , surfaceimpoundments, and waste piles and therefore are not relevant to reinjection.

2"o-

ro a.-07 §

COft

As the December 27,1989 memorandum stated, the RCRA section 3020(b) exemptionfrom the ban on hazardous waste injection applies to reinjected ground water only if the groundwater "is treated to substantially reduce hazardous constituents prior to such injection", and theinjection meets the other requirements for exemption. The memorandum further stated that"steps necessary to 'substantially reduce' hazardous constituents should be decided on a case-by-case basis," unt i l further guidance is developed. Today's memorandum clarifies one element ofthe requirement for substantial treatment."

EPA interprets section 3020(b)(2) to require that contaminated ground water withdrawnfrom an aquifer be treated prior to reinjection and that the treatment be intended to "substantiallyreduce" hazardous constituents in the ground water. But the "substantial reduction" may occureither before or after reinjection. To be more specific, the reduction may occur "in-situ" afterreinjection of the ground water into the aquifer (that is, within the formation that is the targetzone for the injected f luid) . The intended treatment must reasonably be expected to reduce levelsof contamination and must be part of a legitimate effort to achieve cleanup of suchcontamination. As long as the reinjection meets these conditions (and the other conditions ofsection 3020(b)), it may occur wi thout triggering the section 3020(a) prohibi t ion on undergroundinjection of hazardous wastes or the RCRA land disposal restrictions.

This memorandum also does not address what degree of treatment would be considered"substantial", which is a determination made on a case-bv-case basis.

o of\> Q.

This clarification is particularly relevant to in-situ ground-water bioremediation. Overthe last decade, government, academic, and industrial researchers have investigated and pilotedremedial systems that rely on "enhanced" or "engineered" in-situ bioremediation of contaminatedground water to promote treatment or increase biodegradation of hazardous constituents. Theseremedial systems can be used to clean up ground water contaminated with petroleumhydrocarbons, chlorinated aromatics, chlorinated solvents, and other common pollutants. Inthese systems, remediators stimulate the biodegradation of pollutants by manipulating subsurfaceconditions (for example, by adding nutrients) and in some cases by adding naturally-occurring ornonindigenous microorganisms. In many cases, contaminated ground water is extracted duringthe course of the remedy, amended to promote in-situ bioremediation, and reinjected. These"amendments" or "treatment agents" might include addition of microorganisms'"bioaugmentation"), nutrients (for example, phosphate or ammonium nitrate), electron donors(for example, oxygen, hydrogen peroxide, or specifically-designed commercial products), orsubstrates to promote microbial growth (for example, lactic acid, various alcohols, propane, orother chemical products). Amending the extracted contaminated ground water in any of theseways clearly constitutes "treatment" under RCRA (see section 1004(34)). Therefore, EPAconsiders these systems to be consistent with RCRA section 3020(b)(2) treatment requirement,as long as extracted ground water contaminated wi th hazardous waste is amended (or otherwise"treated") before reinjection, and as long as the treatment is intended to achieve a substantialreduction of hazardous constituents after reinjection."1

EPA emphasizes that the general principle described above - that under section3020(b)(2) "treatment" must occur prior to reinjection, but the "substantial reduction" ofhazardous const i tuents in the ground water may occur after reinjection - applies to other in-situtreatment systems besides biotreatment, as long as they too comply with the conditions of section3020(b). For example, it would potent ia l ly apply where ground water contaminated withhazardous waste is reinjected in the course of in-situ f lushing or in-s i tu chemical oxidation. In-situ f lushing is a ground-water cleanup method that involves the injection or inf i l t ra t ion of af lushing so lu t ion into a zone of contaminated soil and ground water, followed by downgradientextraction of ground water and elutriate ( f lushing solution mixed wi th contaminants) . Flushingso lu t ions t y p i c a l l y include p l a i n water, augmented by surfactants, co-solvents, or oiner treatmentagents. The extracted ground water/elutriate mixture is treated above-ground to remove most ofthe contaminant , and then remjecied to repeat the f lushing procedure.

I n - s i t u chemical ox ida t ion is another subsurface treatment method, i nvo lv ing thein t roduc t ion of oxidizing agents into contaminated aquifers. Typical oxidants inc lude hydrogen ^peroxide, potassium permanganate, and ozone. Delivery methods van-1, but the oxidants are Ci S-sometimes mixed wi th extracted ground water , which is then reinjected and recirculated. This O 9method p o t e n t i a l l y can destroy or deerade an extensive variety of hazardous wastes, inc lud ing vo p,

~ " Is. O

" S i m i l a r l y . EPA considers these systems cons is tent wi th the UIC regulat ions at 40 CFRsection 144 .1 3.

§l/l

volatile organic compounds (such as trichloroethylene and benzene) and semivolatile organiccontaminants (such as certain pesticides, polycyclic aromatic hydrocarbons, and polychlorinatedbiphenyls) in ground water sediment, and soil. These advanced technologies show greatpromise in addressing ground-water contamination.

In both of the systems described above, the addition of treatment agents to extractedcontaminated ground water prior to reinjection constitutes "treatment," and therefore thereinjection would be a l lowable under section 3020(b), as long as the other condi t ions of thatsection were met.

EPA has occasionally been asked how RCRA applies to a commercial chemical orchemical product that is injected into ground water for in-situ treatment where no ground water iswithdrawn and reinjected. RCRA subtitle C, including section 3020 (a), does not regulatematerial that is not a hazardous waste and thus does not prohibit the injection of a material intoground water during in-s i tu treatment if the material is not a hazardous waste. Therefore, as longas the injected materials are not hazardous wastes, the exemption in 3020(b) is not needed toallow the injection into ground water of flushing solution, oxidants, or other treatment agentswi thout mixing wi th extracted ground water. If any of these substances qua l i fy as a "hazardouswaste," then its injection is subject to RCRA subtit le C regulation, and, if that injection is into orabove a formation that conta ins an underground source of drinking water, it is prohibited byRCRA section 3020(a).

Under RCRA. a material is regulated under RCRA subtitle C only if it is a "hazardouswaste" as defined in 40 CFR. section 261.3, and a material is only a "hazardous waste" if itmeets the defini t ion of "solid waste" in 40 CFR. section 261.2. A "solid waste" is defined insection 261.2 as a "discarded material." Commercial chemicals or chemical products generallyare not "discarded," even when their use results in deposit on the land, if they are being used fortheir ordinary or original intended purpose. See section 261.2(c) ( i i ) (commercial chemicalproducts are not solid wastes when applied to the land and that is "their ordinary manner of use")and section 261.33 i n t r o d u c t i o n (enumerated commercial chemical products are solid wasteswhen "applied to the land m lieu of thei r original intended use"). For example, a pesticideapplied on the land for the purpose of ki l l ing pests is not considered "discarded," and thus is notsolid or hazardous waste subject to RCRA regulatory requirements. S imi la r ly a commercialchemical or chemical product that is specially formulated to treat contamination and then is —injected into ground water to treat that type of contaminat ion is not considered discarded and isnot subject to RCRA regulatory requirements.

A commercial chemical or chemical product injected into ground water also would not besubject to RCRA s u b t i t l e C regulations when it is injected into ground water to treat a type ofcontaminat ion if it had been proved successful elsewhere in treating such contamination, or if ithad been commonly used in other forms of treatment of such contaminat ion, or if it had chemicalproperties that could l e g i t i m a t e l y be expected to promote in-si tu treatment of that con tamina t ion . 2TSee Self v. United S t a t e s . 2 F. 3d 1071, 1079-81 ( 1 0 l h C i r . 1993) (broadlv construing ordinary £ o-

00i ro Q.

£PA °00 §

mariner of use/original intended purpose test to include uses furthering a generic rather thanhighly specific act ivi ty) .

Eligible Cleanup Authorities

RCRA sections 3020(b)(l)(A) and 3020(b)(l)(B) limit the section 3020(b) exemption to"response actions" taken under CERCLA section 104 or 106 and to "corrective action" requiredunder RCRA. EPA has frequently been asked to clarify its views on the scope of this limitation.First, the exemption of course applies to any CERCLA action under section 104 or 106,

including actions where federal agencies other than EPA are the lead agency. Second, theexemption would apply to any actions taken at RCRA treatment, storage, or disposal facilities(TSDs) under RCRA "corrective action" authorities, including (but not l imited to) sections3004(u): 3004(v), and 3008(h). It would also apply to injections that occur as part of a remedyunder an authorized state corrective action program, as long as these injections met the otherexemption requirements of RCRA section 3020(b).5

Other Considerations When Selecting Groundwater Reinjection as a Cleanup Remedy

EPA supports the types of activities described in this memorandum because they canoften provide effective treatment in otherwise intractable situations. In approving ground-waterremedies, regulators should consider the current and potential beneficial uses of the groundwater, and the t ime it w i l l take different remedies to achieve remedial goals, including whetherthe "substantial treatment" consistent with section 3020(b)(2) wi l l occur within a reasonableperiod of time. The treatment timeframe should be consistent with the remedial goals for thesite. Regulators should also be careful when selecting ground-water reinjection remedies toensure tha t activit ies intended to remediate contamination, such as flushing, do not inadvertentlyresult in any unacceptable migration of contaminants or treatment agents beyond the zone oftreatment. To assure the action is sufficiently protective of human health and the environment,regulators should review methods for monitoring the proposed ground-water reinjection. andmay want to consider hydraul ic containment measures.

Conclusion

'Simply qua l i fy ing for the e l ig ible cleanup authorities under section 3020(b) does notaffect other regulatory obl igat ions, whether federal, state, or local. For example, it does not p^ g.obviate the need for operators of these inject ion systems to provide inventory informat ion , or O °meet other specific requirements imposed by the UIC Program Director in direct implementation J^ °-°-or primacy programs. Therefore, operators should coordinate wi th thei r state regulators to 4^ob ta in , as necessary, variances, waivers, construct ion permits, approvals , etc.. prior to re in jec t ion Jgunder 3020(b) of the federal RCRA statute. ~

IIIIIIIiIIIIIIIIIII

8

I trust these clarifications will facilitate the use of enhanced in-situ bioremediation andother ground-water remedies at sites where ground water is contaminated with RCRA hazardouswaste. If you have any specific questions about these issues, contact Robert Hall, DeputyDirector, Permits and State Programs Division, at 703-308-8432.

cc: Bruce Kobelski, OWLarry Reed, OERRWalter Kovalick, TIOBarry Breen, OSREBetsy Devlin, ORE/REDTom Kennedy, ASTSWMO

Attachments

PO O.vo n01 go|