UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION VII

901 NORTH 5TH STREETKANSAS CITY KANSAS 66101

/

JAN

MEMORANDUM

SUBJECT Aluminum Company of America (Alcoa) Site - Approval Memorandum toperform an Engineering Evaluation/Cost Analysis for a Non Time CriticalRemoval Action

FROM James Colbert RPMIANE/SUPR

THRU GlennCurtis ChiefIANE/SUPR

TO Michael J Sanderson, DirectorSuperfund Division

Subject

40110583

SUPERFUND RECORDS

The U S Environmental Protection Agency (EPA) has determined that there has been arelease and/or there is a substantial threat of a release of hazardous substances to the environmentat the Aluminum Company of America (Alcoa) Davenport Works Site in Riverdale, Iowa Thismemorandum documents the decision to proceed with an Engineering Evaluation/Cost Analysis(EE/CA) for a non-tune critical removal action (NTCRA) at specific areas of the Alcoa Site TheEE/CA will evaluate the cleanup alternatives for reducing or eliminating the potential for arelease from the Eastern Historical Disposal Site (EHDS), Wetland #2, and Outfall 002 TheEE/CA will be prepared by MFG Inc a contractor for Alcoa (responsible party) The EPA willprovide oversight

The decision to proceed with this EE/CA is consistent with EPA guidance regardingNTCRAs and the long-term remedial strategy for this site This memorandum is not a final EPAdecision regarding the selection of the NTCRA

II Background

A Site Description and History

The Alcoa Davenport Works is one of the world's largest aluminum rolling mills Thesite is located in Scott county in east-central Iowa in the town of Riverdale, Iowa, adjacent to

RECYCLE^

Bettendorf, Iowa one of the Iowa-Illinois Quad cities Since the original construction and startof operations in 1948, the facility has undergone a variety of expansion and update programsThe facility is more than one mile m length with over 100 acres of the 445 acre site under roofThe site is bounded to the south by the Mississippi River, to the north by state route 67 to theeast by the Riverside Power Plant and industrial property, and to the west by residentialindustrial, and undeveloped property

In 1956 Alcoa began utilization of an unhned waste oil surface impoundment at theAlcoa-Davenport Works primarily for the storage of oil wastes from manufacturing operationsBetween 1956 and 1979, Alcoa also placed a variety of other solid wastes into the impoundmentincluding grease solvents, pickle liquors and paint coating wastes Between 1979 and 1981Alcoa, having discovered that waste oil in the surface impoundment contained polychlonnatedbiphenyls (PCBs), voluntarily removed all pumpable waste oil and sludge from theimpoundment and solidified a portion of the remaining unpumpable sludge with cement kiln dustto aid in preventing leaching of PCBs from said sludge Shallow groundwater monitoring andsampling activities conducted by Alcoa between 1980 and 1984 indicated that PCBs and volatileorganic compounds (VOCs) were present in the alluvial aquifer in the vicinity of the surfaceimpoundment

In July 1990 Alcoa and EPA entered into an Administrative Order on Consent, DocketNo 90 F-0027 (1990 AOC) pursuant to Section 106(a) of the Comprehensive EnvironmentalResponse, Compensation and Liability Act of 1980 (CERCLA), as amended 42 U S C Section9606(a) One of Alcoa's requirements in the 1990 AOC was to conduct a Facility SiteAssessment (FSA) to identify potentially contaminated areas at the Alcoa Davenport WorksThe FSA was completed in early 1992, and the initial FSA Report was submitted to EPA in April1992 Comments and conditional approval of the Initial FSA Report were issued by EPA in aletter dated February 10 1993 The FSA identified over 75 potentially contaminated areas (FSAunits) where documented releases and possible releases of hazardous substances may haveoccurred as a result of current and historical production and waste management activities InAugust 1995 Alcoa and EPA entered into a 1995 AOC Docket No VII 95-F 0026 thatprovides for the evaluation of and if necessary, the performance of removal actions at the FSAunits The FSA units that will be affected by this NTCRA are the EHDS and Outfall 002 Asignificant portion of the EHDS has been identified as a wetland and is referred to as Wetland #2

B Nature and Extent of Contamination

Surface water and groundwater contamination has been observed within the EHDS Thisinformation, collected during Phase I and Phase II of the ongoing site wide GroundwaterRemedial Investigation (RI), indicates that there is a potential for release of site relatedcontaminants from the EHDS to Outfall 002, which can occasionally discharge off site to theMississippi River

-2-

In 1997, during Phase I of the Groundwater RI, nonaqueous phase liquid (NAPL) wasdiscovered in an unconsohdated zone well (EDS-5) located near Outfall 002 in the EHDS In1998, analysis of a NAPL sample obtained from piezometer 002-P01U during Phase n of theGroundwater RI indicated concentrations of tetrachloroethene (PCE) at 382,000 mg/1, PCBArochlor 1248 at 341 mg/1, and a total concentration of polycychc aromatic hydrocarbons(PAHs) at 5 819 3 mg/1 In addition to the NAPL sample surface water and groundwatersamples were also collected m the vicinity of Outfall 002 and Wetland #2 during Phase II of theGroundwater RJ Elevated concentrations of PCE, tnchloroethene (TCE), total 1 2-dichloroethene (DCE) and vinyl chloride were detected in surface water samples collected atthree locations along Outfall 002 The surface water sample collected adjacent to piezometer002-P01U had the highest total chlorinated solvent concentration (132 mg/1) The upstreamsample had the second highest total (235 mg/1) and the downstream sample had the lowest total(0 79 mg/1) The chlorinated solvent concentrations in these Outfall 002 surface water sampleswere three to five orders of magnitude higher than the concentrations detected in groundwatersamples obtained from unconsohdated zone monitoring wells located adjacent to the westernedge of the outfall

In addition, Wetland #2 was evaluated in conjunction with the ecological risk assessmentprocess for the FSA Units Results of the evaluation based on surface water samples andsediment samples mdicate that PCBs are sufficiently elevated to pose a risk to the semi-aquatichabitat of Wetland #2 An Environmental Effects Quotient (EEQ), or the ratio of exposureconcentration/dose to toxicity reference values, can be calculated for both the no observedadverse effects level (NOAEL) and the lowest observed adverse effects level (LOAEL)Specifically both the EEQNOAFL and the EEQLOAcL exceeded 1 (the level of concern) for the greatblue heron, mallard duck, and little brown bat The EEQ, OAFI also exceeded 1 for mallard ducksbased upon concentrations of polycychc aromatic hydrocarbons (PAHs), copper and manganese

In summary, the location and extent of contamination appears to be related to theinteraction between unconsohdated zone groundwater soils/sediments m the EHDS, includingWetland #2 and contaminated surface water in Outfall 002 and Wetland #2 During a sustainedprecipitation event water may enter Outfall 002 and its tributary from surface runoff and directprecipitation Water may also enter the mam branch of Outfall 002 as a result of lift stationoverflow during heavy precipitation events Observation and water level data indicate thatsurface water in Outfall 002 normally discharges to groundwater, however during a heavyprecipitation event the increased surface water flow and elevated groundwater condition leads toadditional surface water in Outfall 002 that may discharge to the Mississippi River Also thelevels of PCBs in sediments and surface water of Wetland #2 pose a potential ecological risk to anumber of different receptors

m Threat to Public Health, Welfare, or the Environment

The National Contingency Plan (NCP) provides that the lead agency, EPA, shall considerthe factors listed m 40 CFR Section 300 415(b)(2) to determine the appropnateness of a removal

3-

action based on a threat to human health or welfare or the environment The factors whichjustify a removal action within the area of the site associated with the EDHS (including Wetland#2) and Outfall 002 are outlined below

A 300 415(b)(2)(i) - Actual or potential exposure to nearby humanpopulations, animals, or the food chain from hazardous substances orpollutants, or contaminants

Potential exposure of nearby animal populations and the food chain toelevated concentrations of PCBs PAHs copper and manganese has been documented in theecological risk characterization of Wetland #2 Analytical results also demonstrate elevatedconcentrations of chlorinated solvents (i e, PCE TCE, DCE, and vinyl chloride) inunconsohdated zone groundwater and surface water in Outfall 002

B 300 415(b)(2)(n) - Actual or potential contamination of drinking watersupplies or sensitive ecosystems

Potential exposure of nearby animal populations and the food chain toelevated concentrations of PCBs, PAHs, copper and manganese has been documented in theecological nsk characterization of Wetland #2 (i e, a sensitive ecosystem)

C 300415(b)(2)(v) - Weather conditions that may cause ha/ardoussubstances or pollutants or contaminants to migrate or be released

During a heavy precipitation event, the increased surface water flow andelevated groundwater condition leads to additional surface water in Outfall 002 and Wetland #2These conditions may cause the contaminated surface water in Outfall 002 and Wetland #2 tomigrate or be released to the Mississippi River

D 300415(b)(2)(vn) The availability of other appropriate federal or stateresponse mechanisms to respond to the release

The EPA has entered into the 1995 AOC with Alcoa and is the leadagency for addressing this site under CERCLA authority

IV Additional Factors Demonstrating Appropriateness of Removal Action

In addition to considering Section 300 415(b)(2) factors the Agency considers thefollowing additional factors in determining whether to employ a NTCRA or a remedial action ina particular situation

(1) Tune Sensitivity of the Response - During periods of heavy precipitation theincreased surface water flow and elevated groundwater condition leads to additional surface

4-

water in Outfall 002 and Wetland #2 These conditions may cause the contaminated surfacewater m Outfall 002 and Wetland #2 to migrate or be released to the Mississippi River Aremoval action alternative needs to be implemented to abate this situation

(2) Complexity of Both the Problems to be Addressed and the Action to be Taken TheEE/CA will more fully develop the removal action alternatives from which a NTCRA will beselected to address the direct contact risks associated with surface water and soils in this area ofthe Alcoa facility and dimmish the likelihood of an overland release of contaminants to theMississippi River It appears that the contamination and thieats to human health and theenvironment caused by historic contamination at the EWDS near Outfall 002 and Wetland #2 canbe partially addressed by using the implementable and proven technology offilhng/regrading/covenng

(3) Comprehensiveness of the Proposed Action - Following the NTCRA, a more complexand complimentary remedial action will be selected to address site-wide groundwatercontamination based upon the findings of the ongoing Groundwater RemedialInvestigation/Feasibility Study (RI/FS) The risk due to groundwater contamination associatedwith the EHDS will necessarily be addressed during the groundwater RI/FS process AnyNTCRA that is selected will be consistent with any future remedial action

(4) Likely Cost of the Action - The purpose of an EE/CA is to develop and evaluateremoval action alternatives Therefore the alternatives and associated costs are not known at thistime However, Alcoa has outlined a preliminary removal action alternative that would involvethe enclosure or re-routing of Outfall 002 and the filhng/re-grading of the EHDS, includingWetland #2 A preliminary estimate of the cost associated with the removal action alternativediscussed above is between one million and three million dollars

V Endangerment Determination

The actual and/or threat of a release of hazardous substances from Outfall 002 andWetland #2 presents an imminent and substantial endangerment to the public health or welfareor the environment A non time critical removal action is therefore necessary and appropriate toabate, prevent minimize, stabilize, mitigate, or eliminate such threats

VI Enforcement Strategy

In July 1990, Alcoa entered an Administrative Order on Consent with EPA, Docket No90 F-0027 (1990 AOC) One of the requirements in the 1990 AOC was to conduct a FacilitySite Assessment (FSA) to identify potentially contaminated areas at the Alcoa-Davenport WorksThe EHDS (including Wetland #2) and Outfall 002 were evaluated after being identified as FSAunits In letters dated October 12 1999 and May 11 2000 Alcoa recommends and requestsEPA approval to proceed with the NTCRA process and develop an EE/CA to present response

5-

action alternatives pursuant to the requirements of the 1995 AOC The EE/CA will be submittedto EPA for review and approval

VII Proposed Project/Oversight and Cost

The purpose of the EE/CA will be to evaluate alternatives for reducing or eliminating thepotential for exposure of nearby animal populations and the food chain to elevatedconcentrations of contaminants in the EHDS, Wetland #2, and Outfall 002 as well as thepotential for a release of contaminants to the Mississippi River from the EHDS Wetland #2 andOutfall 002

As required by the 1995 AOC, the EE/CA shall present response action alternatives inaccordance with relevant sections of EPA' s Guidance on Conducting Non-Time CriticalRemoval Actions Under CERCLA dated August 1993 The general format of the EE/CA shallbe m accordance with Exhibit 5 (EE/CA Outline) of the August 1993 guidance document

Alcoa has outlined a preliminary response action alternative that would involve theenclosure or re-routing of Outfall 002 and the fillmg/re-grading of the EHDS including Wetland#2 To offset the loss of Wetland #2 Alcoa is in the process of restoring and creating newwetlands near Pnnceton Iowa with the assistance of the Iowa Department of Natural Resources(IDNR) The wetland mitigation process is being conducted in accordance with an Off SiteWetland Mitigation Plan that was developed by Alcoa and reviewed by EPA, IDNR, and theUS Army Corps of Engineers

A preliminary estimate of the cost associated with the response action alternativediscussed above is between one million and three million dollars All costs associated with thedevelopment of the EE/CA and the implementation of the selected response action alternativewill be paid by Alcoa Costs incurred by EPA during the oversight of the EE/CA andimplementation of the selected response alternative will also be paid by Alcoa pursuant to the1995 AOC

VIII Recommendation

Based upon the information provided in Sections I through V of this EE/CA ApprovalMemorandum we recommend your signature to allow Alcoa to perform an EE/CA for responseactivities at the EHDS, Wetland #2, and Outfall 002 areas of the Alcoa-Davenport Works Site

Approved

Michael J Safjoerson, DirectorSuperfund Division

Date

-6

JAN 9 2001

MEMORANDUM

SUBJECT Aluminum Company of America (Alcoa) Site - Approval Memorandum toperform an Engineering Evaluation/Cost Analysis for a Non Time CriticalRemoval Action

FROM James Colbert RPMIANE/SUPR

THRU GlennCurtis ChiefIANE/SUPR

TO Michael J Sanderson, DirectorSuperfund Division

I Subject

The U S Environmental Protection Agency (EPA) has determined that there has been arelease and/or there is a substantial threat of a release of hazardous substances to the environmentat the Aluminum Company of America (Alcoa)- Davenport Works Site in Riverdale Iowa Thismemorandum documents the decision to proceed with an Engineering Evaluation/Cost Analysis(EE/CA) for a non-time critical removal action (NTCRA) at specific areas of the Alcoa Site TheEE/CA will evaluate the cleanup alternatives for reducing or eliminating the potential for arelease from the Eastern Historical Disposal Site (EHDS) Wetland #2 and Outfall 002 TheEE/CA will be prepared by MFG Inc a contractor for Alcoa (responsible party) The EPA willprovide oversight

The decision to proceed with this EE/CA is consistent with EPA guidance regardingNTCRAs and the long-term remedial strategy for this site This memorandum is not a final EPAdecision regarding the selection of the NTCRA

II Background

A Site Description and History

The Alcoa-Davenport Works is one of the world s largest aluminum rolling nulls Thesite is located in Scott county in east-central Iowa m the town of Riverdale Iowa adjacent to

&SUPRIANE COLBERT RHARRINGTON X7875 G IANE EECAApproval MemoALCOAWetland 2 01 04 2001

IANE CNSL IANEColbert Pemberton Curtis

4.1

Bettendorf, Iowa, one of the Iowa Illinois Quad cities Since the original construction and startof operations in 1948 the facility has undergone a variety of expansion and update programsThe facility is more than one mile in length with over 100 acres of the 445 acre site under roofThe site is bounded to the south by the Mississippi River, to the north by state route 67, to theeast by the Riverside Power Plant and industrial property and to the west by residential,industrial, and undeveloped property

In 1956, Alcoa began utilization of an unhned waste oil surface impoundment at theAlcoa-Davenport Works primarily for the storage of oil wastes from manufacturing operationsBetween 1956 and 1979 Alcoa also placed a variety of other solid wastes into the impoundmentincluding grease, solvents pickle liquors, and paint coating wastes Between 1979 and 1981,Alcoa having discovered that waste oil m the surface impoundment contained polychlonnatedbiphenyls (PCBs), voluntarily removed all pumpable waste oil and sludge from theimpoundment and solidified a portion of the remaining unpumpable sludge with cement kiln dustto aid in preventing leaching of PCBs from said sludge Shallow groundwater monitoring andsampling activities conducted by Alcoa between 1980 and 1984 indicated that PCBs and volatileorganic compounds (VOCs) were present in the alluvial aquifer in the vicinity of the surfaceimpoundment

In July 1990, Alcoa and EPA entered into an Administrative Order on Consent DocketNo 90 F-0027 (1990 AOC) pursuant to Section 106(a) of the Comprehensive EnvironmentalResponse, Compensation and Liability Act of 1980 (CERCLA) as amended, 42 U S C Section9606(a) One of Alcoa's requirements m the 1990 AOC was to conduct a Facility SiteAssessment (FSA) to identify potentially contaminated areas at the Alcoa-Davenport WorksThe FSA was completed in early 1992, and the initial FSA Report was submitted to EPA in April1992 Comments and conditional approval of the Initial FSA Report were issued by EPA in aletter dated February 10,1993 The FSA identified over 75 potentially contaminated areas (FSAunits) where documented releases and possible releases of hazardous substances may haveoccurred as a result of current and histoncal production and waste management activities InAugust 1995 Alcoa and EPA entered into a 1995 AOC Docket No VII-95 F-0026 thatprovides for the evaluation of and, if necessary, the performance of removal actions at the FSAunits The FSA units that will be affected by this NTCRA are the EHDS and Outfall 002 Asignificant portion of the EHDS has been identified as a wetland and is referred to as Wetland #2

B Nature and Extent of Contamination

Surface water and groundwater contamination has been observed within the EHDS Thisinformation collected during Phase I and Phase II of the ongoing site wide GroundwaterRemedial Investigation (RI), indicates that there is a potential for release of site relatedcontaminants from the EHDS to Outfall 002, which can occasionally discharge off site to theMississippi River

-2-

In 1997 during Phase I of the Groundwater RI nonaqueous phase liquid (NAPL) wasdiscovered in an unconsohdated zone well (EDS-5) located near Outfall 002 in the EHDS In1998, analysis of a NAPL sample obtained from piezometer 002 P01U during Phase II of theGroundwater RI indicated concentrations of tetrachloroethene (PCE) at 382 000 mg/1, PCBArochlor 1248 at 341 mg/1 and a total concentration of polycyclic aromatic hydrocarbons(PAHs) at 5,819 3 mg/1 In addition to the NAPL sample, surface water and groundwatersamples were also collected in the vicinity of Outfall 002 and Wetland #2 during Phase n of theGroundwater RI Elevated concentrations of PCE tnchloroethene (TCE), total 1,2dichloroethene (DCE) and vinyl chlonde were detected in surface water samples collected atthree locations along Outfall 002 The surface water sample collected adjacent to piezometer002-P01U had the highest total chlorinated solvent concentration (132 mg/1) The upstreamsample had the second highest total (235 mg/1) and the downstream sample had the lowest total(0 79 mg/1) The chlorinated solvent concentrations in these Outfall 002 surface water sampleswere three to five orders of magnitude higher than the concentrations detected in groundwatersamples obtained from unconsohdated zone monitoring wells located adjacent to the westernedge of the outfall

In addition, Wetland #2 was evaluated m conjunction with the ecological risk assessmentprocess for the FSA Units Results of the evaluation based on surface water samples andsediment samples indicate that PCBs are sufficiently elevated to pose a risk to the semi-aquatichabitat of Wetland #2 An Environmental Effects Quotient (EEQ), or the ratio of exposureconcentration/dose to toxicity reference values, can be calculated for both the no observedadverse effects level (NOAEL) and the lowest observed adverse effects level (LOAEL)Specifically, both the EEQNOAEL and the EEQLOAEL exceeded 1 (the level of concern) for the greatblue heron, mallard duck, and httle brown bat The EEQLOAEL als° exceeded 1 for mallard ducksbased upon concentrations of polycychc aromatic hydrocarbons (PAHs), copper, and manganese

In summary, the location and extent of contamination appears to be related to theinteraction between unconsohdated zone groundwater, soils/sediments in the EHDS includingWetland #2 and contaminated surface water m Outfall 002 and Wetland #2 During a sustainedprecipitation event water may enter Outfall 002 and its tributary from surface runoff and directprecipitation Water may also enter the main branch of Outfall 002 as a result of lift stationoverflow during heavy precipitation events Observation and water level data indicate thatsurface water in Outfall 002 normally discharges to groundwater, however during a heavyprecipitation event the increased surface water flow and elevated groundwater condition leads toadditional surface water in Outfall 002 that may discharge to the Mississippi River Also, thelevels of PCBs in sediments and surface water of Wetland #2 pose a potential ecological nsk to anumber of different receptors

III Threat to Public Health, Welfare, or the Environment

The National Contingency Plan (NCP) provides that the lead agency, EPA shall considerthe factors listed m 40 CFR, Section 300 415(b)(2) to determine the appropnateness of a removal

-3-

action based on a threat to human health or welfare or the environment The factors whichjustify a removal action within the area of the site associated with the EDHS (including Wetland#2) and Outfall 002 are outlined below

A 300 415(b)(2)(i) - Actual or potential exposure to nearby humanpopulations, animals or the food chain from hazardous substances, orpollutants, or contaminants

Potential exposure of nearby animal populations and the food chain toelevated concentrations of PCBs, PAHs copper, and manganese has been documented in theecological risk characterization of Wetland #2 Analytical results also demonstrate elevatedconcentrations of chlorinated solvents (i e, PCE TCE DCE, and vinyl chloride) inunconsohdated zone groundwater and surface water in Outfall 002

B 300 415(b)(2)(n) - Actual or potential contamination of drinking watersupplies or sensitive ecosystems

Potential exposure of nearby animal populations and the food chain toelevated concentrations of PCBs, PAHs copper, and manganese has been documented in theecological risk characterization of Wetland #2 (i e, a sensitive ecosystem)

C 300415(b)(2)(v)- Weather conditions that may cause hazardoussubstances or pollutants or contaminants to migrate or be released

Dunng a heavy precipitation event the increased surface water flow andelevated groundwater condition leads to additional surface water in Outfall 002 and Wetland #2These conditions may cause the contaminated surface water in Outfall 002 and Wetland #2 tomigrate or be released to the Mississippi River

D 300 415(b)(2)(vn) — The availability of other appropriate federal or stateresponse mechanisms to respond to the release

The EPA has entered into the 1995 AOC with Alcoa and is the leadagency for addressing this site under CERCLA authority

IV Additional Factors Demonstrating Appropriateness of Removal Action

In addition to considering Section 300 415(b)(2) factors the Agency considers thefollowing additional factors in determining whether to employ a NTCRA or a remedial action ina particular situation

(1) Time Sensitivity of the Response Dunng penods of heavy precipitation theincreased surface water flow and elevated groundwater condition leads to additional surface

-4

water in Outfall 002 and Wetland #2 These conditions may cause the contaminated surfacewater in Outfall 002 and Wetland #2 to migrate or be released to the Mississippi River Aremoval action alternative needs to be implemented to abate this situation

(2) Complexity of Both the Problems to be Addressed and the Action to be Taken - TheEE/CA will more fully develop the removal action alternatives from which a NTCRA will beselected to address the direct contact risks associated with surface water and soils in this area ofthe Alcoa facility and diminish the likelihood of an overland release of contaminants to theMississippi River It appears that the contamination and threats to human health and theenvironment caused by historic contamination at the EWDS near Outfall 002 and Wetland #2 canbe partially addressed by using the implementable and proven technology offilling/regradmg/covenng

(3) Comprehensiveness of the Proposed Action - Following the NTCRA, a more complexand complimentary remedial action will be selected to address site-wide groundwatercontamination based upon the findings of the ongoing Groundwater RemedialInvestigation/Feasibility Study (RI/FS) The risk due to groundwater contamination associatedwith the EHDS will necessarily be addressed during the groundwater RI/FS process AnyNTCRA that is selected will be consistent with any future remedial action

(4) Likely Cost of the Action - The purpose of an EE/CA is to develop and evaluateremoval action alternatives Therefore, the alternatives and associated costs are not known at thistime However Alcoa has outlined a preliminary removal action alternative that would involvethe enclosure or re routing of Outfall 002 and the filling/re-gradmg of the EHDS, includingWetland #2 A preliminary estimate of the cost associated with the removal action alternativediscussed above is between one million and three million dollars

V Endangerment Determination

The actual and/or threat of a release of hazardous substances from Outfall 002 andWetland #2 presents an imminent and substantial endangerment to the public health, or welfareor the environment A non tune critical removal action is therefore necessary and appropriate toabate prevent, minimize, stabilize, mitigate or eliminate such threats

VI Enforcement Strategy

In July 1990 Alcoa entered an Administrative Order on Consent with EPA Docket No90-F 0027 (1990 AOC) One of the requirements in the 1990 AOC was to conduct a FacilitySite Assessment (FSA) to identify potentially contaminated areas at the Alcoa-Davenport WorksThe EHDS (including Wetland #2) and Outfall 002 were evaluated after being identified as FSAunits In letters dated October 12,1999, and May 11,2000, Alcoa recommends and requestsEPA approval to proceed with the NTCRA process and develop an EE/CA to present response

—J**

action alternatives pursuant to the requirements of the 1995 AOC The EE/CA will be submittedto EPA for review and approval

VII Proposed Project/Oversight and Cost

The purpose of the EE/CA will be to evaluate alternatives for reducing or eliminating thepotential for exposure of nearby animal populations and the food chain to elevatedconcentrations of contaminants m the EHDS Wetland #2, and Outfall 002 as well as thepotential for a release of contaminants to the Mississippi River from the EHDS Wetland #2 andOutfall 002

As required by the 1995 AOC the EE/CA shall present response action alternatives inaccordance with relevant sections of EPA's Guidance on Conducting Non-Time CriticalRemoval Actions Under CERCLA, dated August 1993 The general format of the EE/CA shallbe in accordance with Exhibit 5 (EE/CA Outline) of the August 1993 guidance document

Alcoa has outlined a preliminary response action alternative that would involve theenclosure or re-routing of Outfall 002 and the filhng/re-grading of the EHDS including Wetland#2 To offset the loss of Wetland #2 Alcoa is in the process of restoring and creating newwetlands near Pnnceton, Iowa with the assistance of the Iowa Department of Natural Resources(IDNR) The wetland mitigation process is being conducted in accordance with an Off-SiteWetland Mitigation Plan that was developed by Alcoa and reviewed by EPA IDNR, and theUS Army Corps of Engineers

A preliminary estimate of the cost associated with the response action alternativediscussed above is between one million and three million dollars All costs associated with thedevelopment of the EE/CA and the implementation of the selected response action alternativewill be paid by Alcoa Costs incurred by EPA during the oversight of the EE/CA andimplementation of the selected response alternative will also be paid by Alcoa pursuant to the1995 AOC

VIII Recommendation

Based upon the information provided in Sections I through V of this EE/CA ApprovalMemorandum, we recommend your signature to allow Alcoa to perform an EE/CA for responseactivities at the EHDS Wetland #2, and Outfall 002 areas of the Alcoa-Davenport Works Site

Approved

Michael J Sanderson, DirectorSuperfund Division

Date

-6