-
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