United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R10-92/044
September 1992
SEPA Superfund
Record of Decision:
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NOTICE.
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement. but adds no further applicable information to
the content of the document. All supplemental material is, however, contained in the administrative record
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50272.101
REPORT DOCUMENTATION 11. REPORT NO. I 2. 3. Redplenh Acce8810n No.
PAGE EPA/ROD/R10-92/044
4. TIlle - Subtitle 5. Report 0.18
SUPERFUND RECORD OF DECISION 09/01/92
Elmendorf Air Force Base, AK 6.
First Remedial Action - Interim
7. Aulhor(a) 8. P_nnlng Organization Rapt. No'
8. P"onnlng Org8lnlzatlon ""'e and AcIdr- 10. ProjectIT..k/Work Untt No.
11. ContrIlCl(C) or Granl(G) No.
(C)
(G)
12. Sponaorfng Organization Name and Addr.a 13. Type 0' Report & PerIod Covered
U.S. Environmental Protection Agency 800/000
401 M Street, s.w.
Washington, D.C. 20460 14.
15. Supplementary No...
PB93-964604
16. Abatrect (Uml!: 200 worde)
The 13 ,DO-acre Elmendorf Air Force Base (AFB) site is located adjacent to the
municipality of Anchorage, Alaska. Land use on the base includes airfield and base
support operations, personnel housing, and recreational facilities. Approximately
1. Smiles south of the base, land use is residential and industrial. Wetlands, lakes,
and ponds cover about 1,416 acres of the site. The estimated 8,600 people who reside
on the base do not use the shallow aquifer as their drinking water supply. From 1940
to 1991, Elmendorf AFB used a 20-acre portion of the site, referred to as source area
ST41, to store the fuel product JP-4 and aviation gasoline in four 1-million gallon
underground tanks. As a result of numerous leaks and above-ground spills since the
tanks were installed in the 1940s, USAF conducted investigations through its
Installation Restoration Program (IRP). These investigations revealed several hundred
thousand gallons of fuel in the ground water and soil. Remedial investigation
activities in 1988 and 1989 included installing monitoring wells and test trenches.
During that time, a concrete dam was installed in an effort to recover fuel from the
south seeps. Additional studies conducted in 1990 and 1991 indicated that groundwater
within an approximate SOO-foot radius around ST41 is contaminated. In January 1991,
(See Attached Page)
17. Document An8ly8la .. D88crlptora
Record of Decision - Elmendorf Air Force Base, AK
First Remedial Action - Interim
Contaminated Medium:GW
Key Contaminants:VOCs (benzene, toluene, xylenes)
b. IdentifleralOpen-Endecl Tenna
c. COSA TI Fleki'Group
18. Availability Statement 19. Security Cia.. (Thla Report) 21. No. 0' P-
None 30
20. Security CIa.. (Thla Page) 22. PrIce
Nnnp
18 See InatrucUona on Rell8lS11 272 (4.77)
(See ANSI-Z39. )
(Formorty NTlS-35)
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EPA/ROD/Rl0-92/044
Elmendorf Air Force Base, AK
First Remedial Action - Interim
Abstract (Continued)
the four tanks and piping were pumped dry and taken out of service. This ROD addresses
an interim remedy at Elmendorf AFB. This actionis needed to reduce further spread of
fuel constituents through the recovery of floating product on the ground water surface,
and containment of seeps. Future RODs will include a final remedy for ground water and
soil at ST41, as OU2, and will address the other six OUs at the site. The primary
contaminants of concern affecting the ground water at ST41 are the compounds in JP-4,
especially VOCs such as benzene, toluene, and xylenes.
The selected interim remedial action for this site includes seep containment to collect
the floating fuel and contaminated ground water, followed by introduction to a sump
designed to separate the fuel and water. Fuel from the sump would be recycled, whereas
the water would be filtered and pt~ped to an air stripper, and discharged to the
Anchorage Municipal Wastewater system. Air emissions from the air stripper would be
treated by carbon adsorption, and the spent carbon filters subsequently disposed of
offsite. Ground water monitoring will be implemented to evaluate the performance of the
interim remedial action. The esti.mated present worth cost for this remedial action is
$467,300, which includes an annual O&M cost of $27,500.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific ground water clean-up goals are based
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DECLARATION STATEMENT
for
RECORD OF DECISION
ELMENDORF AIR FORCE BASE
ANCHORAGE, ALASKA
OPERABLE UNIT ~., SOURCE AREA ST41 - INTERIM REMEDIAL ACTION
SEPTEMBER 1992
SITE NAME AND LOCATION
Elmendorf Air Force Base
Operable Unit 2, Source Area ST41 , Interim Remedial Action
Anchorage, Alaska
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim remedial action for Operable Unit 2,
Source Area ST41 (Four-Million Gallon Hill) at Elmendorf Air Force Base, a National Priorities
Ust site located in Anchorage!, Alaska. The interim remedy was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Uability Act of 1980 (CERCLA),
as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), the
Federal Facility Agreement entered into by the l)nited States Environmental Protection Agency
(USEPA), the United States Air Force (USAF), and the State of Alaska on November 14, 1991,
and, to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the administrative record for this site and
is summarized in the attached Decision Summary.
The USAF is the lead agency for this decision. The USEPA approves of this decision and,
along with the Alaska Department of Environmental Conservation (ADEC), has participated in
the scoping of site investigations and evaluation of interim remedial action alternatives. The
State of Alaska concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from Operable Unit 2, Source Area
ST41, if not addressed by implementing the interim response action selected in this Record of
Decision, may present an imminent and substantial endangerment to public health, welfare, or
the environment.
DESCRIPTION OF THE SELECTED REMEDY
This interim remedial action addresses contamination at one of seven operable units at \
Elmendorf Air Force Base. ST41 is one of two source areas in Operable Unit 2. The purpose
of this interim remedial action is to initiate recovery of product floating on the groundwater
surface, which poses the principaJ threat to human health and the environment This action will
also reduce further movement of contaminated groundwater through containment. of seeps,
thus eliminating a pathway of contamination to humans, wildlife, and plants from surface water.
and groundwater. The interim remedy is expected to be consistent with the final remedy that
al\elmllofOd4\Oc:IOber 20. 1992
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will be selected for Operable Unit 2 following completion of the remedial investigation/feasibility
study. .
The major components of the selected remedy include:
.
Extraction 01 fuel product from the groundwater surface in the shallow aquifer to minimize
further migration;
Containment of seeps using collection systems and subsequent product recycling and
water treatment;
.
.
Treatment of water collected from seeps and wells by an air stripping process to meet
federal, state, and local regulations;
.
Treatment of the emissions from the air stripping process to meet state regulations and
existing base permit requirements;
Disposal 01 the treated groundwater in accordance with federal, state, and local
regulations by discharge to the municipal wastewater system; and
.
.
Monitoring of the effectiveness of the groundwater containment and treatment process to
provide design information for the final remedy.
DECLARATION
The selected remedy is protective of human-health and the environment, complies with federal
and state requirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. Although this interim remedial action is not intended to fully
address the statutory mandate for permanence and treatment to the maximum extent
practicable, this interim remedial action does utilize treatment and thus is in furtherance of that
statutory mandate. Because this action does not constitute the final remedy for the operable
unit,- the statutory preference for remedies that employ treatment that reduces toxicity, mobility,
o( volume as the principal element. although partially addressed in this remedy. will be
addressed by the final response action. Subsequent actions may be necessary to fully
address the risks posed by the conditions at this operable unit.
Because this remedy will result in hazardous substances remaining on site above health-based
levels. a review will be conducted within five years after commencement 01 the remedial action
to ensure that this action continues to reduce the threat to human health and the environment
Review 01 this interim actio", will be conducted under the remedial investigation/feasibility study
being performed for this operable unit.
JUl I 3 Igg~
Date
- --8I\eIo:n1!~~ 10. '892..
ii
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DECLARATION OF THE RECORD OF DECISION
. DECISION SUMMARY
RESPONSIVENESS SUMMARY
FOR
INTERIM REMEDIAL ACTION
OPERABLE UNIT 2
SOURCE AREA ST41
ELMENDORF AIR FORCE BASE
ANCHORAGE,ALASKA
JULY 1992
.
F,
..
1:;.
~
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Signature sheet for the foregoing Operable Unit 2, Source Area ST41,.'Elmendorf Air Force
Base Interim Remedial Action, Record of Decision between the United States Air Force and the
United States Environmental Protection Agency, Region 10, with concurrence by the Alaska
Department of Environmental Conservation.
~/k
1-/-?2--
Date
~RegiOnal Administrator, Region 10
r ~nited States Environmental Protection Agency
"...., ..
1II\eIm\f-f'0d4\Ju1y 10. 1992
iii
100'J1. Recyded
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Signature sheet for the foregoing Operable Unit 2, Source Area ST 41. Elmendorf Air Force
Base Interim Remedial Action, Record of Decision between the United States Air Force and the
United States Environmental Protection Agency, Region 10, with concurrence by the Alaska
Department of Environmenr~co servation.
/ // ~/%.
~~J//,"7~ I~ A-.j-:J-~ /1;2
DatIĄ' /
South Central Regional Administrator
Alaska Department of Environmental Conservation
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TABLE OF CONTENTS
Page
DECISION SUMMARY,
1.0 SITE NAME, LOCATION, AND DESCRIPTION
2.0 SITE HISTORY AND ENFORCEMENT ACTlYmES
2.1 History of Operations
2.2 History of Site Investigations
2.3 History of Enforcement Actions
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
4.0 SCOPE AND ROLE OF OPERABLE UNIT AND RESPONSE ACTION
5.0 SUMMARY OF SOURCE AREA CHARACTERISTICS
5.1 Geology and Hydrology
5.2 Sources and Types of Contaminants
6.0 SUMMARY OF SOURCE AREA RISKS
7.0 DESCRIPTION OF ALTERNATIVES
7.1 Alternative 1 - No Action
7.2 Alternative 2 - Product Removal Using Existing Storage
Tanks And Seep Containment
7.3 Alternative 3 - Product Removal Using Recovery Wells and
Seep Containment
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
1
3
3
3
4
4
5
5
5
7
7
8
8
9
10
11
I
8.1 Criterion 1 - Overall Protection of Human Health and the Environment- 11
8.2 Criterion 2 - Compliance with Applicable or Relevant and Appropriate
Requirements
8.3 Criterion 3 - Long-Term Effectiveness and Permanence
8.4 Criterion 4 - Reduction of Toxicity, Mobility, or Volume
Through Treatment
8.5 Criterion 5 - Short-Term Effectiveness
8.6 Criterion 6 - Implementability
8.7 Criterion 7 - Cost
8.8 Criterion 8 - State Acceptance
8.9 Criterion 9 - Community Acceptance
12
12
12
13
13
13
13
14
..
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""""of,'Od4\Ju1y 10, 191r2
vii
, 00% A8c:yCI8d
...... .-. - ~.... ~ -
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TABLE OF CONTENTS
Page
. 9.0 SELECTED REMEDY
9.1 Recovery System Approach
9.2 Effectiveness of Treatment Technology
9.3 Treated Water Disposal
9.4 Cost
9.5 Summary
10.0 STATUTORY DETERMINATIONS
1 0.1 Protection of Human Health and the Environment
10.2 Compliance with Applicable or Relevant and Appropriate
Requirements
10.2.1 Action-$pecific ARARs
10.2.2 Location-$pecific ARARs
10.3 Cost Effectiveness
10.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to
the Maximum Extent Practicable
10.5 Preference for Treatment as a Principal Element
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
14
14
15
15
15
17
17
17
18
18
18
18
19
19
19
Ust of Figures
Figure 1 Base Location Map
Figure 2 Source Area ST 41 Location Map
1
2
Ust of Tables
Table 1 Groundwater/Surface Water Sampling Results
Table 2 Estimated Costs
3
16
Ust of Attachments
ATTACHMENT A Responsiveness Summary
ATTACHMENT B Community Relations Activities at Elmendorf AFB
81\81m\kQd4\Ju1y 10. 1982
viii
100.. ~
""'._._'-----~. '''''',.-.-.----
. .
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DECISION SUMMARY
. for
RECORD OF DECISION
ELMENDORF AIR FORCE BASE
ANCHORAGE, ALASKA
OPERABLE UNIT 2, SOURCE AREA ST41 - INTERIM REMEDIAL ACTION
JULY 1992
1.0 SITE NAME, LOCATJON, AND DESCRIPTJON
Elmendorf Air Force Base (AFB), a National Priorities Ust (NPL) site. is located within the
northern border of the Municipality of Anchorage, Alaska. The base is bordered on the east
. by the U.S. Army's Fort Richardson, on the south by the city of Anchorage, and on the
north and west by the Knik Arm of Cook Inlet (Figure 1). The base encompasses
approximately 13.130 acres. of which 7,077 acres are essentially undevefoped. Wetlands,
lakes. and ponds cover approximately 1.416 acr:es. The approximately 6.053 acres
remaining have been developed for airfield operations. base support operations. personnel
housing, and recreational facilities. The base population is approximately 8.600 military
personnel and dependents. Approxima1e1y 6,100 military personnel and 1 ,600 civilians
work on base. .
~
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,~::Elmendorf
Air Force Base \
C
1 Eagle River
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City of ~
Anchorage '\.,
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Smendorf AFB
Anchorage
Intemational
Airport
Figure 1
Location Map
Elmendorf Air Force Base
Anchorage, Alaska
~.
L
8II8ImllofOd4\Ju1y 10. 1992
100% A8cyaed
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The interim remedial action for Operable Unit 2 (OU2) will occur at Source Area ST 41
(ST41), also known as Four-Million Gallon Hill. ST41 is apprQximately 20 acres in size and
is located near the western edge of the base, north of Loop Road, west of Brown Road, and
approximately 2,200 feet east of the Knik Arm of Cook Inlet (Figure 2).
'J.!.S
,~
';.JS
,~
'~
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.
LEGEND
. Approxi",.t. Seep LOC8tionS
GroundwUlr /
0Mde/
/
L ... Groundwater Flow Direction
\).1; Wetlands Area
Not to Sc8I.
~
)
.
LOOQ Road .
To End 01 East - West R~.,-
Figure 2
Source Area ST41 Location Map
Elmendorf Air Force Base
Anchorage, Alaska
N
W~E
S
ST41 includes four one-million gallon, underground JP-4 and aviation gasoline storage
tanks and ancillary piping constructed In the early 1940s. Reports indicate that the tankS
are 5t881 and may have an outer concrete lining. ST 41 also includes an area of
approximately one acre located west of the tanka which is described as a tank sludge burial
area. The sludge burial area will be investigated in the ongoing remedial
investigationJfeasibility study (RIIF5) for OU2.
5T 41 is situated on the glacially deposited Elmendorf Moraine. Elevations range from 225
to 275 feet above mean sea level on the northeast-southwest trending moraine.
Groundwater levels range from approximately 34 feet below ground surface on top of the
moraine. to less than one foot below ground surface north and south of the moraine.
Groundwater seeps are evident along the south side of the moraine. A similar seep is
located on the north side of the moraine, where shallow groundwater is discharging to a
wetlands area.
5T41 is located about 1,000 feet from the west end of the base airfield. Land in the vicinity
01 5T 41 is . basically undeveloped except for an abandoned underground tank complex to
the east Residences and residentiaJ support services occupy much of the southwest
corner 01 the base about one-half mile south of 5T 41. Approximately one and one-half
miles south of ST 41. and just beyond the Government Hill Gate at the southwest comer of
the base, is an Anchorage residential area commonly referred to as Government Hill.
IndustriaJ land uses beyond the southwest boundary of the base include railroad yards. a
fuel storage tank farm. and marine facilities.
~\IuIIf 10. 1182
2
1~ A8cyCII8d
" ~-. -. --_.~ - ." -.'.. .->-.
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it.
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..
2.0 SITE HISTORY AND ENFORCEMENT ACTMnES
2.1 History of Operations
. .
Since installation in the early 1940s, the four tanks at ST 41 reportedly have been subject to
numerous leaks and above-ground spills estimated to total several hundred thousand
gallons. .
In the 19705, an oil/Water separator was installed in response to fuel seeping out of the
south side of the Elmendorf moraine, north 01 Loop Road. During an inspection in May
1983. an additional fuel seep on the south side was discovered. In 1989, a concrete dam
was installed In an effort to recover fuel from the south seeps. During RVFS work In 1991, a
fuel seep was discovered on the north side 01 the Elmendorf moraine, discharging into a
wetlands area.
Fuel product has been observed floating on the groundwater in monitoring wells located
downgradient 01 the tanks. Leak tests conducted in late 1990 indicated that aU four tanks
and piping were leaking. In January 1991, the tanks and piping were pumped dry and
taken out of service.
Fuel-related contaminants, including benzene, have been detected in the groundwater and
the surface water seeps downgradient 01 the tanks at levels above the maximum
contaminant levels (MOLs) established by the Safe Drinking Water Act and the Alas~a
Water Quality Standards (Table 1).
TABLE 1
GROUNDWATER/SURFACE WATER SAMPUNG RESULTS
Type
Contaminant
Concentration (Range)
Standard
Groundwater
Benzene
10.0 to 15.000.0
5.0 MOL.
5.0 AWQS"
Surface Water
Benzene
400.0
All values in micrograms per liter.
*MCL - Maximum Contaminant Level.
**AWQS- Alaska Water Quality Standards.
2.2 History of Site Inveatlg8tlon8
In 1983, the U~F began studies of Elmendorf AFB through its Installation Restoration
Program (IRP). Source Area ST41 was identified through a records search conducted in
1983 which indicated that numerous leaks and above-ground fuel spills had occurred since
the tanks were installed in the 1940s. Two groundwater monitoring wells were installed
II\8Im\kocMWuIy 10. 1882
3
100.. R8c:ycIed
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downgradient 01 the seeps in 1984. AnalyticaJ results 01 groundwater samples indicated no
water quality problems downgradlent of the seeps.
Remedial investigation activities performed in 1988 and 1989 included the drilling of twenty-
six borings, seventeen 01 which were completed as. monitoring wells. Two test trenches
were dug on the south side of the moraine, a terrain conductMty survey was conduded in
the tank sludge burial area, and soil-gas samples were collected. Results 01 the
investigation indicated that the soil and water samples collected at the site were
contaminated with fuel and with the soluble components 01 fuel.
In August 1990 and May 1991, addltionaJ investigative activities were conduded including
collection 01 surface water (seep) samples, subsurface soil samples, groundwater probe
samples, and product probe samples; installation of nine monitoring wells; and sampling of
monitoring wells. Evaluation of the data from these sampling efforts serves as the basis for
this interim action. .
Groundwater data indicate that groundwater within an approximate 500-foot radius around
ST 41 is contaminated and ftoating product exists downgradient of both the north and south
tanks. In addition, soil and surface water contamination exist at ST 41.
2.3 History of Enforcement ActIon8
In 1989, Elmendorf AFB was proposed for placement on the NPL The facility was placed
on the NPL in August 1990. A Federal Facilities Agreement (FFA) for Elmendorf AFB was .
signed on November 14,1991 by the USAF, USEPA, and ADEC. The FFA documents and
facilitates cooperation and information exchange between the USAF, USEPA and ADEC
during development, implementation, and monitoring of appropriate. response actions at
the base. These actions must be in accordance with the Comprehensive Environmental
Response, Compensation, and Uability Ad of 1980 (CERCLA) and the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP). The FFA also establishes
requirements for the performance of remedial investigations and interim remedial actions at
the base, including ST41.
3.0 HIGHUGHTS OF COMMUNITY PARnCIPA110N
Prior to conducting community relations activities for ST 41, a public workshop was held to
discuss the various environmental cleanup programs underway at Elmendorf AFB. On
January 28, 1992, the date and location 01 the workshop were advertised in the Anchorage
Daily News and Anchorage Times. On January 29, 1992, the USAF issued a press release
announcing the public workshop which was held on February 5, 1992 at the Government
Hill Elementary School. Approximately 75 individuals attended the workshop.
The Proposed Plan for ST 41 was released to the public for comment on February 17, 1992.
The document was mailed to approximately 240 individuals on the Elmendorf AFB mailing
list. This document was also made available to the public in the administrative record
maintained in Anchorage at the Bureau 01 Land Management's Alaska Resources Ubrary in
the Federal Building and at the Consortium Ubrary of the University of Alaska at Anchorage.
A notice 01 the public comment period and the availability of this document was published
in the Elmendorf AFa newspaper, the Sourdough Sentinel, on February 13, 1992, and in the
. Anchorage Times and the Anchorage Daily News on February 16, 1992. A. public comment
period on the Proposed Plan was held from February 17, 1992 to March 17,1992.
""""'''-
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A public meeting was held on February 'Zl, 1992 at the Wilda Marston Theater at the z.J.
Loussac Ubrary in Anchorage to present the. Proposed Plan. Approximately 30 Individuals
. attended the public meeting. At this meeting, USAF, USEPA, and ADEC representatives
discussed the project, an.c;wered questions, and received public comments. A verbatim
transcript of the meeting was prepared by a court reporter. Written comment forms were
distributed at the public meeting.
Seven sets of written comments were received during the public comment period.
Aesponses to the comments received during the public comment period and at the public
meeting are included in the Aesponslveness SUmmary, Attachment A to this Record of
Decision (ROD).
In February 1992. the first issue of Environmental Update, a quarterty newstetter aimed at
keeping the public informed of the status of environmental cleanup programs at 8mendorf
AFB, was distributed to workshop attendees and individuals on the mailing list. The second
issue of Environmental Update was distributed In May 1992 to indMduais on the mailing list
4.0 SCOPE AND ROLE OF OPERABlE UNIT AND RESPONSE ACTION
Operable Unit 2. which contains ST41, Is one of seven operable units comprised of 32
known and/or suspected hazardous waste sites located at Elmendorf AFB. Existing site
characterization data indicated OU2 source areas presented substantial threats to hum8[\
health and the environment This ROD for OU2 addresses the first Interim remedial actJon
at 8mendorf AFB.
The interim remedial action Is needed to reduce the further spread of fuet constituents, and
thereby reduce the potential risk of impact to existing and future groundwater users located
downgradient of the site, and initiate a strategy expected to be consistent with the finaJ
remedy. This action Is limited to addressing floating product and seep contamination,
whereas the final remedy will also consider groundwater and soil cleanup. The selected
.interim action includes product extraction, containment of seeps, treatment of collected
water, and disposal. These elements will likely become major components of the final
remediation at the site. .
Aemedial investigation field work is currently underway at OU2. Prior to completion 01 the
AI report, data collected will be used to prepare a baseline risk ass999ment Under the
Federal Facilities Agreement. the draft RVFS is to be submitted to USEPA by January 15,
1994. The draft ROD 10r OU2 is scheduled to be submitted to USEPA by July 15, 1994.
5.0 SUMMARY OF SOURCE AREA CHARACTERISTICS
5.1 Geology and Hydrology
Geologic units of concem at and near ST41 include the Elmendorf Moraine, the Anchorage
Plain alluvium, the Bootlegger Cove Formation, and unnamed sediments that underlie the
Bootl~ger Cove Formation.
ST41 is situated 'on the glacially deposited Elmendorf Moraine. The moraine consists of
. laterally and vertically discontinuous, unconsolidated, glacial till with poorly sorted
. - boulders, gravel, sand, silt, and clay. The Bootlegger Cove Formation, a low permeability
clay layer, is believed to underiie ST41, although the borings to date have not been drilled
deep enough to confirm this.
rhJIfN fOd4\Ju1y 10. 1111r2
5
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The Anchorage Plain alluvium, often called the o&.nwash plain, is present approximately one-
quarter mile south of the Elmendorf Moraine. The deposits of this unit are characterized by
gravel and sand with minor amounts of silt. In general, the outwash plain deposits mantle
the base from Ship Creek to the Elmendorf MoraIne. These deposits are undertaln at
variable depth by the Bootlegger Cove Formation, which in turn is undertain by unnamed
sediments similar to the outwash plain sediments. The stratigraphic relationship of the
sediments of the outwash plain to the Elmendorf Moraine at ST 41 is currently unknown.
Groundwater is present in all four of the geologic units described above. However,
significant quantities of water are only obtainable from the outwash plain deposits and the
deposits which underlie the Bootlegger CcMA Formation. The shallow water table aquifer
of the outwash ptain is believed to be separated from a deeper confined aquifer in the
unnamed sediments by the Bootlegger Cove Formation. This clay layer Is expected to act
as a barrier that significantly retards movement of grounCfwater and contaminants between
these aquifers.
At ST41 , groundwater is found in the sediments of the Elmendorf Moraine. Because of the
lateral and vertical heterogeneity of these deposits, groundwater is typically found in
perched systems and is in greatest abundance in sand and gravel lenses within the
moraine. Evidence of perched groundwater is Indicated by the presence of groundwater
seeps along the south and north sides of the. moraine.
Groundwater level measurements in existing monitoring wells at ST 41 indicate that a
groundwater dMde is present at the crestllne of the moraine. In general, groundwater on
the north side of ST 41 flows northwest and groundwater on the south side of the moraine
flows southeast. Water levels at ST41 are highly variable, ranging from 34 feet below
ground surface on top of the moraine to approximately one foot below ground surface
south of the moraine. L:' .
The hydraulic interaction between groundwater found In the Elmendorf Moraine sediments
at ST 41, the shallow wat~ table aquifer, and the ~eeper confined aquifer is not fully
understood. Numerous borings and monitoring wells have been drilled on and around
ST 41. However, the depth of these borings was Insufllclent to determine and characterize
the hydrogeolo~ic environment below ST 41.
As part of ongoing RI activities, borings will be drilled at and near ST 41 to more fully
characterize the geologiC'" and hydrogeologic environment This effort will provide
information useful in understanding and defining the potential for contaminant migration to
the shallow water table aquifer and the deeper confined aquifer.
No Elmendorf AFB supply wells in the immediate vicinity of ST 41 obtain water from the
shallow groundwater aquifer. In general, the deeper confined aquifer at Elmendorf AFB
serves currentty only as a stand-by water supply when surface water supplies cannot meet
demand. The area surrounding Elmendorf AFB uses surface water for various services,
including industrial, commercial, domestic, and public supply. The nearest wells using the
shallow aquifer are private water wells located in the Government Hill residential area south
of and adjacent to the base. These wells are located over one and one-half miles away and
not directly downgradient of the site; thus, the wells are not expected to be in danger of
contamination from ST 41.
oI\8Im\kod4\Ju11t 10. 111G1:Z
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5.2 Sourcea and Types of Contaminants
The source 01 contamination at ST 41 was periodic surface spills and subsurface leaks in
the tanks. Leaking valves and pipes may also have contributed. The volume 01 fuel
released is estimated to have been several hundred thousand gallons. The spills and
subsurface leaks have resulted in fuel product floating on the groundwater and seeping
from locations on the north and south sides 01 the hill. Dissolved constituents of the fuel
product have also contaminated the groundwater.
The primary contaminant at ST 41 is the fuel product JP-4, although other types of fuel
products may also have been stored in the tanks. The main compounds 01 concern in JP-4
are benzene, toluene, ethylbenzene, and xylenes (BTEX). Benzene, a known human
carcinogen, is the most toxic and mobile of the BTEX compounds.
Although the ongoing RVFS will determine the full extent 01 contamination at 5T 41, the
. following information has been obtained from previous investigations. SubsurfaCe soil
samples contain elevated levels 01 BTEX, lead, and total petroleum hydrocarbons. Free
product was observed floating on top 01 the groundwater in two monitoring wells
down gradient of the tanks. In one well 125 feet south of the tanks, 0.30 feet 01 product was
encountered at 14.5 1eet below ground surface. In a well 25 feet north of the tanks, 1.62
feet of product was encountered at 18.21 feet below ground surface.
Benzene concentrations in groundwater range from 10 micrograms per liter (pg/L) to 15;0Q0
#Jg/L south 01 the tanks and were measured at 1,600 #Jg/L at one location north 01 the tanks.
. TPH contamination exhibits a similar distribution, ranging from 0.3 milligrams per liter (mg/L)
to 730 mg/L south of the tanks, and 120 milligrams per liter (mg/L) north of the tanks.
Trichloroethene (TCE) was detected at 12 #JglL in groundwater from one monitoring well
located northeast of the tanks, and will be addressed in the ongoing RifFS.
A surface water (seep) sample was collected on the nortt't 'side 01 the moraine in the
wetlands approximately 200 feet northwest of the tanks. The sample contained BTEX
concentrations of 1,670 jUgiL with benzene at 400 #JglL Total arsenic was also slightly
elevated at 0.07 mglL; the MCL is 0.05 mglL Visible petroleum contamination was
observed at the two seeps approximately 200 feet south 01 the tanks on the south side of
the mors!ne.
Antimony, arsenic, cadmium, chromium, lead, nickel, selenium, and thallium have been
detected above MCLs in groundwater from monitoring wells located near the tanks and the
tank sludge disposal area. The highest metals contamination was evident in groundwater
collected from a monitoring well located north and hydrogeologically downgradient of the
sludge disposal area we!lt of the tanks. Future RI activities will attempt to determine if the
metal concentrations can be attributed to Elmendorf AFB operations or if the observed
concentrations are representative of natural background conditions. .
6.0 SUMMARY OF SOURCE AREA RISKS
I
L.
The continued release 01 contaminants into groundwater currently poses the most
significant human health risk at ST 41 . This contamination could potentially affect base
standby water supplies. The north surface seep discharges into an adjacent wetlands,
posing an ecological risk at ST 41. The south seeps discharge into a drainage ditch
adjacent to the road, posing risks to human and ecological receptors.
..
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1
. 1to8In\\I-focM\JuIy 10. 11182
7
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Before a dear understanding of the risks posed by ST 41 can be determined, more
information must be collected and a quantitative risk assessment must be performed. The
. risk assessment will be conducted during the ongoing RVFS.
Contaminants have consistently been observed beneath ST 41 in the shallow aquifer. Data
collected from monitoring wells indicate that contaminants, inctuding benzene, toluene,
ethylbenzene, TCE. and metals are present at levels above MCls. A surface water sample
from the north seep indicates that benzene is present above the Alaska Water Quality
Standards. Table 1 summarizes this information. .
Existing data indicate that benzene is present in the groundwater as far as 400 feet to the
south and 250 feet to the north of ST41, although the actual boundary of the contamination
is uncertain.
7.0 DESCRIPTION OF AlTERNATIVES
The USAF, USEPA, and ADEC Initially screened a range of alternatives that would achieve
significant risk reduction while the final remedy for ST41 is being developed. The list was
narrowed to the following three alternatives for evaluation in the Proposed Plan:
.
Alternative 1 - No Action;
Alternative 2 - Product Removal Using Existing Storage Tanks and Seep Containment;
and
.
Alternative 3 - Product Removal Using Recovery Wells and Seep Containment.
The no-action alternative was evaluated consistent with the requirements of the NCP and
serves primarily as a point of comparison for other alternatives. The other two alternatives
were selected for more detailed evaluation because they could be readily implemented
using commonly available technologies and equipment. If effective, the two alternatives
would reduce risk by controlling further migration 01 contaminants from the seep(s) and by
initiating removal of a source of contamination through extraction of the fuel product
floating on the groundwater. .
.
A description of the three alternatives follows.
7.1 Alternative 1 . No Action
Under this alternative, no interim remediaJ actions would be implemented at ST41. The
condition of the buried tanks would be unchanged with groundwater or surface water
possibly entering the tanks until an equilibrium of inflow and outflow was reached. The
floating product would remain on the shaJlow groundwater surlace and continue to dissolve
in the groundwater and migrate away from the tanks. The discharge at the seep areas
would continue and the amount and extent 01 ftoating product would remain undefined until
the RI/FS was completed and a final remedy selected. No costs are associated with the no
action alternative other than monitoring, which is part of the remedial investigative costs
under all alternative,. .
III\tIImlf-f0d4\Ju1'f 10. 1992
8
1~ A8c:yc:Ied
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. -. ""'"-0.
. "'.' ~ .
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7.2 Alternative 2. Product Removal Using Existing Storage TankaAnd Seep
Containment .
Under this alternative,the four existing storage tanks would be utilized for product
collection. The tanks would be cleaned to remove any existing product, water, and/or
sludge. Floating 'product would be removed and recycled. Water in the tanks would be
pumped and sent to tho collection sumps. Sludge would be removed, treated with an
emulsion-breaking chemical, and piped to the collection sumps. The tank walls would be
perforated. as necessary" to allow larger quantities of fuel product and groundwater to flow
back into the tanks for collection. A metered float control system would be used to pump
the fluid from the tanks. The fuel/water mixture collected from the tanks would be
processed through collection sumps to separate the fuel product from the contaminated
water, thus allowing the fuel to be recovered and recycled. Waste water from the collection
sumps would be sent to an air stripper for treatment. When the system was no longer
effectively extracting fuel, all remaining liquids and sludge would be removed from the
tanks. Final tank closure would be addressed in the final remedy for ST 41.
The elements described below, seep containment, air stripping, and groundwater
monitoring, are common to both Alternative 2 and Alternative 3.
Seep containment would occur through the instaJlation of a perforated pipe or an infiltration
trench to collect the floating fuel and contaminated groundwater discharging at the two
seeps on the south side of the moraine and one seep on the north side. The collected
fuellwater mixture would be gravity-fed to a collection sump, which would allow the lighter
fuel to separate to the top of the water. A collection sump would be placed near the seep
containment system on the north side and another between the two seep containment
systems on the south side of ST 41. If geological conditions are found to be favorable
during construction of the groundwater collection syst.,m, the system might be expanded
laterally to collect more free product and contaminated water. Gravity collection systems
would be used, where possible, to limit pumping requirements and to minimize mixing of
the fuel with the water. If it was determined that the collection sumps were not providing
adequate separation, an clil/water separator would be placed in the collection sumps. Fuel
from the collection sumps would be recycled or recovered for its heating value.
Contaminated soils removed during installation of seep containment systems and collection
sumps ~uld be stored on base with other fuel-contaminated soil. The contaminated soil
would be acfdressecf in the final remedial action for ST 41.
1!J
.(,
Water from the collection sumps would be pumped to an air stripper for treatment. This air
stripper would be located in the immediate vicinity of ST41. Air stripping is the best
demonstrated available technology (BOAT) for removing volatile organics, such as BTEX
compounds, from contaminated groundwater. In the air stripping process, volatile organics
would be transferred from the water phase to the air phase. Iron/biological pretreatment
would be included because of the high iron content of the groundwater. This treatment
could be expanded to include some other metals, as necessary. Design of the
pretreatment unit would take into account other parameters,. such as temperature, and
suspended and dissolved solids. which could affect the efficiency of the air stripper. Air
emissions from the air stripper would be treated by carbon adsorption to remove any
volatile organics such as benzene, toluene, ethyl benzene, and xylene. Carbon adsorption
units would be placed on the air stripper to provide maximum control and minimum release
of the volatile. organics back into the environment. Discharge air from the carbon
adsorption unit would be periodically sampled to ensure that no organics were being
emitted in excess of allowable standards. If the air did not meet discharge requirements,
enhancements to the carbon adsorption unit or other treatment systems would be
1:'
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5
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81\81m\l-rod4~ 10. 11182
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evaluated. The spent carbon filters from the air stripping process would 'be disposed of in
accordance with federal and state regulations. .
Effluent water from the air strfpping process would be discharged to the Anchorage
municipal wastewater system through the Elmendorf AFB collection system. Sampling and
analysis would be performed. to ensure that effluent meets the requirements for discharge
into the system. Effluent water would be sampled for BTEX and other organic compounds,
and for heavy metals. If air stripping treatment did not meet the effluent requirements 10r
discharge of water into the base sewer system, other water treatment systems would be
evaluated.
Groundwater monitoring during the remedial activities would be used to evaluate
performance and success of the interim remedial action and aid in the selection of the
ultimate remedy 10r the source area.. Monitoring points would be located downgradient,
within, and at the edges of the plume as determined by the soil gas survey conducted as
part of the OU2 RI/FS field program. Existing monitoring wells, and possibly additional
monitoring wells or piezometers, would be used. Monitoring would occur at least three
times annually, in early spring, late summer, and late fall, as part of the RI/FS activities.
Climatic conditions make winter sampling events unfeasible. The groundwater would be
monitored 10r BTEX. other volatile organic compounds. and heavy metals. Gradients and
product thickness would be measured to determine the movement 01 product and the
effectiveness 01 the action.
The success 01 this alternative in terms 01 the quantity of product and groundwater which'
could be recovered and treated is directly related to the position of the water table with
respect to the tanks. It is unclear whether any or all 01 the tanks are in contact with
groundwater. whether the groundwater gradient could be reversed, and whether any of the
fuel product is at a higher elevation than the leaking portions 01 the tanks.
Engineering design 01 Alternative 2 would take approximately 6 months. Actual
construction would take approximately 30 days but would not occur during winter months.
The amount 01 time required for product to flow back into the tanks is highly uncertain as is
the amount 01 product and water which would be recovered.
The estimated capital cost 01 Alternative 2 is $300,800, and estimated operation and
maintenance (O&M) costs are $27,500 per year. The total present worth of Alternative 2 is
estimated to be $438,300 assuming a 5-year period 01 operation and a 10 percent interest
rate.
7.3 Alternative 3. Product Removal Using Recovery Wells and Seep Containment
In this altemative, a minimum of four 1 Q..inch diameter extraction wells would be installed to
a depth 01 approximately 40 188t to remove floating product from the groundwater surface
on both the north and south sides of the moraine. Two recovery wells would be installed at
both the north and south side of ST 41 near each 01 the two monitoring wells in which
product has been found. The wells would be pumped to draw down the water table and
enhance the collection of the product. The collected fuel/water mixture would be separated
and handled as described previously in the Alternative 2 description. The collected water
would be'treated by air stripping.
- . The-lateral extent of the floating product would be assessed using product probes or soil
gas measurements downgradient 01 the tanks and in wells with known floating product. If
the fuel product extends a long distance from the tanks, additional wells might need to be
added to increase product recovery. Information gathered from the performance of these
"""'''~'.IuIY 10. 11182
10
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wells would be used to determine the need for additional wells or the need to evaluate
other product extraction technologies. '
Seep control, air stripping, and groundwater monitoring would be as described previously
in the Alternative 2 description.
Engineering design of Alternative 3 would take approximately 6 months. Actual
construction would take approximately 30 days but would not occur during winter months.
The actual flow rate and quantities 01 fuel and groundwater expected to be recovered are
uncertain. This is because the extent 01 the product plume is not well defined, and
hydrogeologic characteristics 01 the soil are highly variable.
The estimated capital cost 01 Alternative 3 is $329,800, and estimated O&M costs are
$27,500 per year. The total present worth 01 Alternative 3 is estimated to be $467,300
assuming a S-year period 01 operation and a 10 percent interest rate.
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The National Contingenc.."y Plan identifies nine criteria to be used to evaluate remedial
alternatives. These criteria are described below as they apply to an interim action. The first
two listed criteria represent threshold criteria that must be met by the interim action
alternatives. The criterion 10r long-term effectiveness and permanence was not considered
relevant, because an "interim" action is, by definition, a short-term remedy. The three
interim action alternatives were evaluated against the other eight criteria to select a remedy.
8.1 Criterion 1: Overall Protection of Human Health and the Environment
Overall protection 01 human health and the environment addresses whether a remedy
provides adequate protection and describes how risks posed through each pathway are
eliminated, reduced, or controlled.
.,
Based on the preliminary findings, floating product and fuek:ontaminated groundwater
appear to be restricted to the shallow aquifer, which is not presenUy used as an on-base
drinking water supply. However, Mure risks to possible downgradlent groundwater users
might occur if groundwater contaminants continue to migrate away from ST 41 and
eventually, off base. For this reason, protection 01 human health and the environment was
assessed relative to the ability of each alternative to remove floating product and contain
contaminated groundwater coming to the surface at the seeps.
Alternatives 2 and 3 are both protective of human health and the environment. Both would
remove floating fuel product, the primary source 01 contamination, and are protective of
Mure groundwater uses. The proven extraction technology 01 Alternative 3 may be more
reliable than Alternative 2 in collecting floating product. The effectiveness of Alternative 2
involves some measure of uncertainty with changing the groundwater gradient to induce
flow 01 product and contaminated groundwater back into the perforated tanks. Both
Alternatives 2 and 3 involve final off-site treatment or disposal 01 the spent carbon from the
air stripper. Under Alternative 1 (no action), the migration and spread 01 floating product
and cOntaminated groundwater discharging at the seeps would continue until the final
remedy was imp1emented. .
!
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~\IUIĄ 10. 11182
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8.2 Criterion 2: Compliance with Applicable or Relevant and Appropriirte
Requirements .
The purpose of the interim remedial action is to remove floating product, a known source of
contamination from the groundwater surface, and to contain contaminated groundwater
where it comes to the surface at the seeps until the final remedy is implemented. This
interim action is neither intended to restore the aquifer to drinking water conditions, nor to
attain all federal and state ARARs relating to deanup of the aquifer. The USAF, USEPA, and
ADEC expect that such ARARs will b9 met by the final remedy to be selected for the site.
The ARARs for this interim remedy relate to the treatment and disposal of groundwater that
is collected and treated during implementation of the interim remedial action and for air
emissions resulting from the treatment.
Alternatives 2 and 3 involve the discharge of processed wastewater to the Anchorage
municipal wastewater system through the Elmendorf AFB collection system in accordance
with Anchorage Water and Wastewater Utility (AWNU) requirements of 100 parts per billion
(ppb) for BTEX and 10 mg/I for TPH. State and fed8nI1- ernJssion standards would be
met through the use of carbon adsorption units on the air stripper.- . .The used air stripper
carbon would be disposed of In accordance with federal and state regulations. All work in
nearby weUands would be conducted in accordance with the substantive requirements of
the Clean Water Act, Section 404. No chemical-specific ARARs exist for the limited scope
of this interitn remedial action. No ARARs are identified for Alternative 1 since no action is ~
involved.
8.3 Criterion 3: Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to expected residual risk and the ability of
a remedy to maintain reliable protection of human health and the environment over time
once clean-up goals have been met.
For this interim action, this criterion was not considered due to the limited scope of the
interim remedial action. The final remedy at ST 41 is expected to provide both long-term
effectiveness and permanence. However, all contaminants extracted would be permanently
removed as a source of groundwater contamination.
8.4 Criterion 4: Reduction of ToxJclty, MobUlty, or Volume Through Treatment
Reduction of toxicity, mobility, or votume through treatment refers to the preference for a
remedy that uses treatment to reduce health hazards, contaminant migration, or the
quantity of contaminants at the site.
Alternatives 2 and 3 would reduce the toxidty, mobility, and volume of groundwater
contaminants through the extraction and treatment of fuel product and small amounts of
contaminated groundwater. Both Alternatives 2 and 3 would reduce toxicity through
treatment of extracted groundwater and seep water. Alternative 3 would actively remove
floating product and therefore reduce mobility and volume sooner than Alternative 2.
Alternative 2 may be less effective due to the unproven extraction technology and unknown
length of time required to draw product back into the perforated tanks. Under Alternatives
2 and 3, spent carbon filters would be disposed of off-site for further treatment. Alternative
1 (no action) would not achieve any of these goals.
~\JuIy 10. 1992
12
1~ A8cyd8d
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. ~-""--"'.:..:.-_'-.':.,-':',-,:".,---...,..'..)~ .C.-.._.
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8.5 Criterion 5: Short.Term Effectiveness
Short-term effectiveness refers to the period of time needed to complete the remedy and
any adverse impacts on human heatth and the environment that may be posed during the
construction and implemontation of the remedy.
Alternatives 2 and 3 can be designed and installed in less than one year with minimal
impact to human heaJth. Floating product containment can be effected within a short
period of time following initiation of pumping. Construction may involve some temporary
adverse impacts due to disturbance of adjacent wetlands. However, actions will be taken
to minimize and mitigate adverse impacts. Construction is not expected to increase the
current site risk to on-site workers, base personnel, or the surrounding communities.
During construction, no noise impact to base residential communities or surrounding
communities is anticipated given the large distance (approximately 1.8 miles) to the nearest
off-base community and the nature of the construction involved In implementing either of
these alternatives. Air emissions and water and solid residual disposal will be regulated by
ARARs. Alternative 1 has no short-term effectiveness.
8.6 Criterion 6: ImplementabUlty
Implementability refers to the technical and administrative feasibility of a remedy, including
the availability of materials and services needed to implement the chosen solution. It also
includes coordination of federal, state, and local governments to clean up the site.
Implementation of Alternatives 2 or 3 would be relatively straight-forward with few
administrative requirements that would cause delays. Both alternatives could be expanded
and used as part of the final remedial action. Alternative 2 would utilize existing tanks,
possibly making it easier to initiate. Alternative 3 would require more time for the
installation of new recovery wells. For either alternative, steep grades and the freezelthaw
cycle will be taken into account during design of the system. The system will not be
designed for winter operation when temperatures are consistently below 32 of. For either
alternative, contractor and equipment requirements would be easily obtainable locally.
8.7 Criterion 7: Coat
. .
This criterion examines the estimated costs for each remedial atternative. For Comparison,
capital and annual O&M costs are used to calculate a present worth cost for each
alternative.
Alternative 1 does not meet threshold criteria. Alternative 2 has a slightly lower estimated
capital cost ($300,800) U,an Alternative 3 ($329,800). The higher cost of Alternative 3 is
associated with mobilizing a drilling crew for recovery well installation. Estimated O&M
costs ($27,500 yearly) for Alternatives 2 and 3 are the same. Estimated present worth is
$438,300 for Alternative 2 and $467,300 for Alternative 3, assuming a 5-year period of
operation and a 10 percent interest rate for each alternative.
~.
8.8 Criterion 8: State Acceptance
The State of Alaska Department of Environmental Conservation has been involved in the
selection of the 1nterim remedial action and concurs with the selection of the remedy as
described in Section 9.0.
"
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8.9 Criterion 9: Community Acceptance
BaSed on comments received during the public comment period and at the public meeting,
the public generally supports the selected remedy. Comments received are described in
the attached Responsiveness Summary. The major concern of the community in relation to
the interim remedial action was that contamination in all media at ST 41 be fully aadressed
in the final remedy.
9.0 SELECTED REMEDY
The selected interim remedial action for this Operable Unit is Alternative 3, Product Removal
Using Recovery Wells and Seep Containment This remedy calls for the design and
implementation of an interim remedial action to protect human health and the environment.
The goal of this remedial action is to initiate removal of floating product from the shallow
groundwater surface, reduce further movement of contaminated groundwater, and eliminate
a pathway of contamination to humans, wildlife, and plants from surface water and
groundwater. The ultimate level of remediation to be attained for this source area will be
determined in the final remedy for ST 41 .
Alternative 3 Indudes the following key elements:
...
. . ~ ".
..~ Product extraction from the groundwater surface in the shallow aquifer to minimize
further migration of floating fuel;
.
Seep containment using collection systems and subsequent product recycJlng and
water treatment;
.
Treating the water collected from seeps and wells by an air stripping process to meet
federal, state, and local regulations;
Treating the emissions from the air stripping process to meet state regulations and
existing base permit requirements;
.
.
Disposing of the treated groundwater in accordance with federal, state, and local
regulations by discharge to the municipal wastewater system; and
Monitoring of the effectiveness of the groundwater containment and treatment process
to provide design information for the final remedy. .
.
9.1 Recovery System Approach.
The selected remedy indudes the installation of four extraction wells to remove floating
product from the shallow groundwater surface. Two extraction wells will be located in
proximity of each monitoring well in which floating fuel product had been observed during
past sampling events. The wells will be pumped to draw down the water table and enhance
the collection of the product. Additional recovery wells may be installed to increase
product recovery, as necessary. Seeps on the north and south sides of the moraine will be
controlled through tQe installation of perforated pipes or infiltration trenches to collect the
fuel/water mixture. .
The extent of the fuel plume is not well defined, and hydrogeological characteristics of the
soil are highly variable. Thus, the actual flow rate and quantities of fuel and groundwater
. expected to be recovered are uncertain. An initial engineering estimate has been made
8I\8Im\f-f'o04\Ju1y 10. 1II1II2
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that the contamlnateC! groundwater flow at the recovlry wells wlQ be 1.0 gallons per minute
(gpm) and the ftow re~ 8t 8ach seep Will avorage 2.0 gpm. Some chang.. may be m.de
to the recovery ey8tem .. II result of the detailed dl.lgn and construction proC888C18, Such
chang8., In general, reflect modlftcatlon. resulting from thl 8nglnlorlng dMlOn process.
9.2 EfteOtlven... 0' Treatment Technologv
Air .trlpplng Is the selected treatment prool... It 18 . prov8r"l technology for the extraction
of organlo oontamlnanta from groundwater. Prior to Ilr sltlpplng, the Nel/water mlxtule
reoovered from the groundwater and seeps will be procel.ed through collection lumps.
Fuel from the lumps wUI be recycled or recovered for It. heating value. Contaminated
water will be pumped from the sumps .10 the air stripper for treatment. A pretreatment
system will bl Included, as nece..ary, to reduce dissolved and suspended elolldl and
microorganIsm. that might Inhibit thl operation of the air strtpper. Fllt.ra and/or residual
materials from the pretreatment Iyatem will bo disposed of In accordance with the federal
off..lte disposal policy (OSWER 9834.11) and ltate regulatlonl.
It I. expected that the air stripper wtll remove 99.6% to 99,8% of thl organl08 In tho
contamlnatod groundwater. An Inltiar .,Umat. of JP-4 lolublllty In water 18 60.80 mgll.
Benzin., the primary OOtItamlnant 01 concern, make. up approximately K by walght of
JP-4. Thus the maximum benzene concentration In the contaminated wat.r ,. 8xpectod to
be 1 eoo ppb. Based on th.., oalouletlont and assumptions, the air strlpp.r should ~
pr~lc:te removal of benzene to . conctntratlon of 1.8 ppb In the effluent weter which 13
below the 5.0 ppb MCL for benzene.
Emission. from the 8/r atrlpper will contain the volatile organic compound. romov~d from
tho oontamlnatld groundwater. Prior to dl8charge to the atmosphere, the .Ir emle810"I will
be trt.tod by carbOn adsorption to remove the vdlatlle organic.. Th, spent oarbon will be
disposed 0' In aocordanQo with the federal Off-Iltl 'dl8lpoeal policy (OSWER 9834.11) and
8tat8 regulations. Preliminary risk O8Ioulations based on an estimated bernene
conoentratlon In the discharge air of O.oooa parts por million (ppm) Indicate that 8 risk of
10-6 at the point of discharge exJltt. Thl8 rllk II expected to be further reduced In the
breathing zon., 18 oonsldered 800eptable, and roprl"nt; an overall roduotlon 01 rlak at
ST41. Thl. ..Umat. 888umU m8xlmum B'(peetld concentration. 01 benzone In the
groundwater, maximum oroundwater flow. minimum air flows. complet. vclatUlzr.tlon 01
benzene, and a 96 percent removal 01 benzene by carbon adsorption. The actual expected
dl8charg. valu88 w1Il be determlnod during design 01 the Interim remedial action treatment
system. Durtng the design phi", ADEC will review and establish .Ir monitoring criteria. .
8.3 Treated W8ter Dl8po.al
The IMIlooted dlsc:harge method for the treated WAter 18 to discharge to the Anchorage
municipal wastewater eystem through the Elmendorf AFB collactJon 8ystem. Organlc8
conc.ntraUona would be w'" below the AWNU allowable atand81d for BTEX of 100 ppb
and 10r TPH of 10.0 mg/l. .
8.4 Coat
The e.Umated present worth for the eelected remedy II $487,300 a'8umlng.a &-year period
~era110n and 8 10 percent Interest ra1. (Table 2). Th8 esUlnated total capital cost Is
,GOO. Annual O&M 001" are eetlmated to be $27.500.
~'\Alleullt1. '881
15
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TABLE 2
ESTIMATED COSTS
PRODUCT REMOVAL USING RECOVERY WELLS AND SEEP CONTAINMENT
Four large-aiameler. rue' recovery wells Will be Installed to collect the floating prOduct. Some grounawater will be
removed to creale a fuel gradient toward Ih. Well. Fuel ana water will be separated. the fuel recycled. and the water
trealed by air StflPOing ana caroon adSOrption. The treated water will be CliscNrged to the municipal sewer system
through the base Collection system. Contaminated water seeoing nonh ana south of the tanks will be Collected. separated
ana treated in the same manner as th. fluid recovered from the WellS.
Item
No.
Quantity I Units
Desaiption
Unit
Price
TotaJ
Cacital Cost
Fuel Recoverv
Fuel Recovery Wells
Tanks Pump and Piping
Observation WeHs
4.
5. .
6.
7.
8.
9.
10.
11.
12.
1.
2.
3.
4 each $15.000 $60.000
2 each $7.500 $15.000
12 each $2.000 $24,000
1 each $4.000 $4 .000
1 each $3.500 $3.500
1 each $4,000 $4.000
1 each $2.000 $2.000
1 lump sum $4.000 $4.000
1 lump sum $4.500 $4,500
2300 feet $46 $105.800
1 25 feet S56 $7,000
2 each $10.000 S20.000
$253.800
S51.000
$25.000
$329.800
$1,000
$1,000
$4.500
$5.000
S15.000
$1,000
$27.500
$467,300
Water Treatment
. 10 GPM Air Stripper
Vapor Phase Carbon Unit
Pretreatment Unit
Surge Tank
Mobilization
Installation
Sewer
SeeD Control
Interceptor Trenches
ColleCtion Sumps/Separators
Subtotal.
Contingencies @ 20%
Engineering @ 10%
Total Capital Cost:
Annual Oceration and Maintenance Costs
1 . ColleCtion Sump Pumps
2. Air Stripper
3. Carbon Disposal
4. Monitoring and Reporting
5. Analytical Laborato.ry
6. Tank Pumping and Piping
Total O&M Costs:
Present Worth:
(assuming 10% interest and 5-year duration)
16
. - .' -. . ''0.- -". - ~- . -.-,
-. -. ., ..',".:.'-. ...~.. ~, .- '. .
-~~ '.. -:~ ~.. -, ".-' :~-", :. ....'
.. '.. ", - '". .-
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9.5 Summary
The selected alternative calls for the design and implementation of an interim remedial
action to protect human health and the environment. The goaJ of this interim remedial
action is to initiate removal of floating fuel product from the shallow groundwater surface,
reduce further movement of contaminated groundwater, and eliminate a pathway of
contamination to humans, wildlife, and plants from surface water and groundwater. The
ultimate level of remediation to be attained at ST 41 will be determined in a finaJ remedial
action for this source area. This interim remediaJ action will be monitored carefully to
determine the feasibility of achieving aquifer restoration with this method and to ensure that
hydraulic control of the contaminated plume is maintained.. After the period of time
necessary to complete the RifFS and arrive at a final decision for ST 41, a flnaJ ROO for OU2
will be prepared that will specify the ultimate goal, remedy, and anticipated time-frame.
Upon completion of this RifFS, the interim system may be incorporated into the design of
the remedy specified In the final remedlaJ action ROO.
10.0 STATUTORY DETERMINATIONS
The USAF's and USEPA's primary responsibility under their legaJ CERCLA authority is to
select interim remediaJ actions that are protective of human health and the environment. In
addition, Section 121 of CERCLA. as amended by SARA. provides severaJ statutory
requirements and preferences. The selected remedy must be cost-effectfve and utilize
permanent treatment technologies or resource recovery technologies to the maximum
extent practicable. The statute also contains a preference for remedies that permanently or
. significantly reduce the volume, toxicity, or mobility of hazardous substances through
treatment. CERCLA also roquires that the selected remedlaJ action for the site must comply
with ARARs established under federal and state environmentaJ laws, unless a waiver is
granted.
,.
,,,-,,,
The selected alternative for this interim remedial action is protective of human health and
the environment. It meets ARARs within the limited scope of the action and is cost effective.
The preferred alternative is consistent with the statutory mandate for treatment to the
maximum extent practicable. It represents the best balance of trade-offs among the
alternatives with respect to pertinent criteria given the limited scope of the action.. Because
this is an interim action, review of this remedy will be ongoing as the USAF continues to
develop final remedial alternatives for the site.
10.1 Protection of Human Health and the Environment
'"
~
The selected interim remedial action will protect human health and the environment by
initiating removal of the source of contamination through extraction of the product floating
on the shallow groundwater. and also by reducing the further migration of fuel constituents
in groundwater discharging at the seeps. The selected remedy thus reduces the threat to
future potential drinking water supplies located beyond the current site boundaries.
The treatment of contaminated water will be to a level that meets ARARs and is protective of
human health and the environment. The contaminants will be permanently removed from
the groundwater through the treatment process which includes air stripping. As necessary,
pre-treatment and post-treatment processing will be employed to ensure the disposed
water and treatmQflt residues do not constitute an unacceptable risk to human health or the
environment.
aI\elmllofOd4\Augus112. 1992
17
100'!10 Recycled
. ._. ." --'-"
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1 0.2 Compliance with Applicable or Relevant and Appropriate Requirements
The selected remedy will comply with all applicable or relevant and appropriate action- and
location-specific requirements (ARARs). No chemical-specific ARARs exist 10r the limited
scope of this interim remedial action. In addition, USEPA, the State, and USAF have agreed
to consider USEPA guidance governing the control of air emissions from air strippers
(OSWER Directive 9355.0-28, Control of Air Emissions from Superfund Air Stripoers at
Superfund Groundwater Sites. issued June 15, 1989).
10.2.1 ActJon-Speclfic ARARs
.
To the extent hazardous waste, as defined by the Resource Conservation and
Recovery Act, 42 U.S.C. ~S 6901 et. sea.. is extracted from the groundwater, air
emissions resulting from operations of an air stripper shall comply with the
requirements 01 40 CFR 264 Subparts AA & BB. Spent carbon from the carbon
adsorption unit and filters and/or residual materials from the pretreatment system will
be stored and disposed of or recycled at a RCRA-approved facility in accordance with
the USEPA policy on offsite disposal 01 CERCLA waste.
.
Processed wastewater will be discharged into the Anchorage municipal wastewater
system through the Elmendorf AFB collection system in accordance with 40 CFR 403.5
and the Anchorage Water and Wastewater Utility requirements of 100 ppb for BTEX
and 10 mg/l for TPH.
To the extent wastewater will be discharged into the waters of the United States, such
. discharge shall comply with the substantive requirements of 40 CFR Part 125 and the
Alaska Wastewater Disposal regulations set forth in 18AAC62.
.
.
40 CFR Part 230 sets forth guidelines pursuant to Section 404 of the Federal Water
. Pollution Control Act, 33 U.S.C. ~ 1344, to control discharges 01 dredged or fill material
into the waters 01 the United States, including special aquatic sites such as wetlands.
.
State of Alaska Air Quality Control regulations (18AAC50) establish criteria for ambient
air quality from sources such as air strippers.
1 0.2.2 Location-Specific ARARs
.
40 CFR Part 6, Appendix A, requires that federal agencies conduct activities to avoid,
to the extent possible, the long and short-term adverse impacts associated with the
destruction or modification of wetlands.
1 0.3 Cost Effectiveness
The selected interim remedial action is cost-effective, because it protects human health and
the environment, attains ARARs, and meets the objectives established for the interim action
in a way that is proportional to its cost. The cost of the selected remedy is slightly higher
than Alternative 2; however, there are concerns about the effectiveness of Alternative 2 for
the purposes 01 this interim action. Alternative 1 is the least expensive, but does not
achieve the objectives of the interim action.
.
.
aI\elmllofOd4\August 12. 1992
18
1 ()()'% Recycled
- ~ .- ---. . . - .-
. . -'"., --~-- -" -'~' .-."-'
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10.4 Utilization of Permanent Solutions and AlternatJve Treatm'ent Technologies or
Resource Recovery Technologies to the Maximum Extent Practicable
Although the selected interim remedial action has certain features of a permanent solution
because of its use of a treatment technology, this is a limited scope action and is not
intended to provide a final remedy for this site. Product extraction and treatment of
collected water will minimize further significant contaminant spread in the groundwater and
will permanently reduce the toxicity, volume, and mobility of contaminants by collection on
activated carbon for off-site recycling or destruction. The treatment process for the
extracted groundwater and collected surface water will be designed to meet or exceed
state and federaJ standards for the protection of human heaJth and the environment prior to
discharge.
"10.5 Preference for Treatment aa a Principal Element
This action is being undertaken primarily to remove the source of contamination and limit
the spread of contaminants in the groundwater in the shallow aquifer beneath ST 41. While
this interim action does employ treatment. the statutory preference for "remedies employing
treatments that permanentJy and significantJy reduce the toxicity, mobility, or volume of the
hazardous substances, pollutants, or contaminants as a principaJ element will be more fully
addressed in the fin.al decision document for this operable unit.
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
The selected interim remedial action is the preferred alternative presented in the Proposed
Plan and during the pUblic meeting. No changes to the components of the preferred
alternative have been made.
~
.
II
III\8Iml/ofOd4\.h!IY 10, 1992
19
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