-------
known to capture approximately 90% of the groiindwater flowing from Elmendorf AFB,
including all of the areas shown on Figure 2-3.
Upgradient source areas are being studied as part of the remedial investigations
of each individual OU and as part of State/Elmendorf Restoration Agreement (SERA) site
studies. However, the impacts of the upgradient sources on OU 5 were evaluated in a
groundwater model. The results of the model (discussed later) were used to predict future
groundwater quality at OU 5 and to select a remedial action to treat future conditions at
OU 5.
2.2 Regulatory and Enforcement History
Based on the results of environmental investigations, Elmendorf AFB was
listed on the National Priorities List by the U.S. Environmental Protection Agency (U.S.
EPA) in August 1990. This listing designated the facility as a federal site subject to the
remedial response requirements of CERCLA, as amended by the Superfund Amendments and
Reauthorization Act of 1986. On 22 November 1991, the USAF, U.S. EPA, and the Alaska
Department of Environmental Conservation (ADEC) signed the Federal Facilities Agreement
(FFA) for Elmendorf AFB. The contaminated areas of Elmendorf AFB were divided into
seven OUs, each to be managed as a separate region and investigated according to varying
schedules. There are six RCRA source areas along the upgradient edge of the western and
central portions of OU 5. All six of these source areas are currently going through RCRA
clean closure. However, if contamination has reached the groundwater, it will be addressed
under CERCLA and handled as part of the action at OU 5.
In accordance with the FrA, a Remedial Investigation (RI) of OU 5 was
conducted in the summer of 1992. The RI determined the nature and extent of the
contamination, and the potential risks to public health and the environment. The results were
compiled and.analyzed in the RI report. The RI concluded that fuel, fuel constituents, and
low levels of solvents were found in soil and groundwater in OU 5. Fuel constituents were
Elmendorf AFB OU 5 Record of Decision 2-7
-------
also detected at relatively low concentrations in surface water ditches and in the beaver pond
wetland area. The impacts to soil were found in the areas where impacted ground water
seeped from the bluff. Impacts in the soil at the source areas (location of the leaks) were
low and did not pose a threat to human health or the environment.
Based on the RI results, No Further Action (NFA) Decision Documents were
prepared, signed, and approved in August 1994 for the soil in the potential source areas in
OU 5 except ST37, the western area diesel leak. The NFA sites are ST-38, SS-42, SS-53,
SD-40, and ST-46.
Two investigations were conducted while completing the FS. One study
investigated the extent of PCB contamination in the snowmelt pond "water and sediment. The
other study assessed the capacity of the beaver pond wetland area to naturally attenuate
contamination. The Final RI/FS was submitted in March, 1994. A Proposed Plan was
distributed to the public on 6 June 1994, and a public meeting to discuss the plan was held
on 23 June 1994. A Draft OU 5 Groundwater Modeling Report (GMR) was issued on
4 August 1994.
2.3 Role of Response Action
The CERCLA process described above is intended to identify solutions to
contamination issues where they exist. The remedial action described in this ROD addresses
threats to human health and the environment posed by contamination at OU 5. The RI/FS
and the Groundwater Modeling Reports define these threats as primarily groundwater
contaminants. The OU 5 GMR was used to further document the appropriateness of the
decisions made in this ROD. At this time, grouncr-ater will be monitored. Further response
actions, coordinated with regulatory agencies, could be considered if monitoring finds
concentrations of contaminants greater than predicted by the GMR.
Elmendorf AFB OU 5 Record of Decision 2-8
-------
2.4 Community Participation
Public participation has been an important component of the CERCLA process
at Elmendorf AFB. Activities aimed at informing and soliciting public input regarding base
environmental programs include:
Environmental Update. Environmental Update is a newsletter
distributed to the community and interested parties. It discusses the
progress that has been made on OUs and advises the public about
opportunities to provide input concerning decisions to address
contaminated areas of the base. Aspects of the OU 5 CERCLA
progress have been published in this update.
Community Relations Plan. The base environmental personnel
maintain and regularly update a Community Relations Plan. It
describes how the base will both inform the public of base
environmental issues and solicit public comment on base environmental
programs.
The Technical Review Committee. Base personnel meet quarterly
with representatives of the community to discuss base environmental
programs and solicit their comments.
Public Workshops. On 5 February 1992, approximately 75 people
attended a public workshop where base personnel discussed base
environmental programs and encouraged public participation.
Videotape. Base personnel made a videotape describing base
environmental activities. The tape is used with both internal (to the
base) and external audiences.
Community Council Briefs. The Air Force regularly provides briefs
to the community council on the progress of the Installation Restoration
Program (IRP). Specific presentations were made regarding the
progress at OU 5 and on the planned remediation.
Speakers Bureau. The 3rd Wing Public Affairs Office maintains a
speakers bureau capable of providing speakers versed in a variety of
environmental subjects to military and civic groups.
Elm-Jiidorf AF3 Of 5 Record of Decision 2-9
-------
Newspaper Releases. News releases were published on significant
events during the IRP. News releases were made announcing all public
meetings that were held to discuss proposed remedial actions.
Information Repositories. Public access to technical documents was
provided through information repositories located at the Bureau of Land
Management's Alaska Resources Library and the University of Alaska
at Anchorage's Consortium Library. The information in the
repositories was also maintained in the administrative record. The
remedial action was selected based on the information held in the
administrative record.
Display Board. During public functions, a display board, showing key
elements and progress of the Elmendorf IRP, was used to communicate
technical issues to the public. It was used during both on-base and off-
base events.
Proposed Plan. The proposed plan was distributed to the public on 6
June 1994, a public meeting was held 23 June 1994, and the public
review period was from 6 June to 6 July 1994. The plan was approved
on 7 July 1994.
Public Notice. Public notices have been issued prior to all significant
decision points in the IRP. For OU 5, public notice was issued for the
proposed plan in the Anchorage Daily News (6/1/94) and the Sourdough
Sentinel (6/3/94).
Mailing List. A mailing list of parties interested in the restoration
program is maintained by the base. Notices and publications (news
releases including the OU 5 proposed plan meeting) was released via
the mailing list.
Responsiveness Summary. Public comments were received on the
proposed plan. The Air Force maintained a record of all comments
and has published responses to the comments in this Record of
Decision.
All decisions made for OU 5 were based on information contained in the Administrative
Record.
Elmendorf AFB OU 5 Record of Decision 2-10
-------
3.0 SITE CONTAMINATION, RISKS, AND AREAS REQUIRING
RESPONSE ACTIONS
This section identifies the areas which may require remedial action. These
areas were chosen based on the risk that contaminants pose to human health and the
environment. The basis of this analysis is the data collected during the Remedial
Investigation (RJ) which identified the nature and extent of contamination in OU 5.
3.1 Nature and Extent of Contamination
During the RI, samples of soil, soil gas, groundwater, sediment, and surface
water were collected and analyzed for organic and inorganic constituents. Significant levels
of organic contaminants were detected in the soil, sediment, seeps, and groundwater. The
contaminants include: fuel products (benzene), volatile organic compounds (VOCs),
inorganic compounds, and semivolatile organic compounds (SVOCs). Tables 3-1, 3-2, and
3-3 show the contaminants detected and the frequency of detections. Figures are referenced
below that show the location of detected constituents.
In the upper aquifer and in some seeps, fuels were the most frequently
detected contaminants in OU 5. Concentrations of diesel (ranging from not detected [ND] to
290 ng/L), gasoline (ND to 700 /zg/L) and jet fuel (ND to 760 /zg/L) were found. VOCs
were also found in groundwater samples at the eastern and western portions of the OU.
Trichloroethylene (TCE) was the most commonly detected VOC (ranging from ND to 52
Mg/L). Figures 3-1 and 3-2 show the distribution of organic compounds in groundwater.
Inorganics were detected in a few groundwater samples above background. Barium and
manganese were the metals most often detected above background concentrations. However,
only one manganese detection was significantly above background (one order of magnitude).
The source identification efforts, operational history of the base, and the RI revealed no
source of manganese contamination in OU 5. Therefore, the results are thought to be
Elmendorf AFB OU 5 Record of Decision 3- 1
-------
Table 3-1
Potential Contaminants of Concern Water
Contaminant
Maximum
Concentration
MCLs
Frequency
(Detections//?
Samples)
Groundwater (Maximum Concentration and MCLs - pg/L)
1 , 1 , 1-Trichloroethane
1 , 1 ,2,2-Tetrachloroethane
Benzene
Ethylbenzene
JP-4
TFH Diesel
TFHGas
Toluene
Trichloroethylene (TCE)
Xylenes, total
bis(2-ethylhexyl) phthalate
tert-butyl methyl ether
Di-n-butyl phthalate
Diethyl phthalate
N-nitrosodiphenylamine
1,1-Dichloroethane
2-Methylnaphthalene
Aluminum1"
Barium
Calcium"
Chloroethane
Iron"
Manganeseh
Naphthalene
Potassium6
Seleniumh
Vanadium*1
9.4
8
8.5
16
760
290
700
1.4
52
39
20'
0.56
1
1
5
1.3
9
68
103
94,700
1.3
12,600
4,280
13
2,070
2.5
5
200
5
700
1,000
5
10,000
6
50-200
2,000
300
50
50
1/7
1/7
4/16
2/10
4/23
7/28
3/17
2/8
6/14
2/10
5/26
1/7
3/13
3/25
2/15
1/3
1/3
2/3
4/6
1/5
1/3
3/4
3/6
1/3
1/5
2/5
2/5
Elmendorf AFB OU 5 Record of Decision
3-2
-------
Table 3-1
(Continued)
Contaminant
Maximum
Concentration
;7MCLs."---;;-
Frequency
(Detections/*
Samples)
Surface Water (Maximum Concentration and MCLs - /ig/L)
1,1,1 -Trichloroethane
1,1-Dichloroethane
1 ,2-Dichloroethane
4-Methylphenbl (p-cresol)
Benzene
Bromomethane
Ethylbenzene
JP-4
Naphthalene
TFH Gas .
Toluene
Trichloroethylene (TCE)
Xylenes, total
trans- 1 ,2-Dichloroethene
1 , 1 ,2,2-Tetrachloroethane
1.9
2.3
2.6
7
1.5
13
12
770
1
400
27
6.6
19
1.9
4.3
200
5
5
700
1,000
5
10,000
100
2/5
1/5
1/5
1/4
2/10
1/5
1/5
1/5
1/3
1/3
3/9
4/10
1/5
1/3
2/5
a Resampling of groundwater showed no Bis(2-ethylhexyl) phthalate at well OU 5 MW-11, the site of the 20
detection.
Only those metals detected above background listed.
Elmendorf AFB OU 5 Record of Decision
5-3
-------
Table 3-2
Potential Contaminants of Concern Sediment
Contaminant ; .
Maximum
Concentration
; Frequency
/J(Detexiti^fjff:^-
.'.;:.:Samjples)"-"::'v' :";'''
Sediment (Maximum Concentration - pg/kg)
2-Methy 1 naphthalene
4-MethylphenoI (p-cresol)
Anthracene
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Chrysene
Ethylbenzene
Fluoranthene
PCB-1260 (Arochlor 1260)
Phenanthrene
Pyrene
TFH Diesel
TFH Gas
Toluene
Xyleries, total
bis(2-ethylhexyl) phthalate
JP^
Naphthalene
100
89
230
59
91
58
63
120
930
130
1,600
270
150
7,400,000
700,000
26
6,200
240
100,000
69
2/10
1/5
1/5
1/5
1/5
1/5
1/5
2/5
3/10
1/5
4/6
3/10
1/5
2/5
2/3
1/5
2/5
1/5
1/5
1/5
Elmemlorf AFB OU 5 Record of Decision
3-4
-------
Table 3-3
Potential Contaminants of Concern Soil
" : "' -Contairiinant
; Maxim um . v :.
Concentration
Maximum
Background
Concentration8
Frequency
(Detections/;;
# Samples);
Soil (Maximum Concentration - /tg/kg, regardless of depth)
4-Nitrophenol
Diethyl phthalate
Pyrene
Di-n-butyl phthalate
Ethylbenzene
JP-4
TFH Gas
Toluene
Xylenes, total
bis(2-Ethylhexyl) phthalate
Benzo(k)fluoranthene
Fluoranthene
Phenanthrene
TFH Diesel
Benzene
2-Methylnaphthalene
Anthracene
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(g,h , i)pery lene
Chrysene
Indeno(l ,2,3-c,d)pyrene
4-Methylphenol (p-cresol)
100
49
280
39
202
14,000
310,000
64
3,940
180
180
300
240
1,160,000
14.9
48
63
200
330
160
100
240
98
51
1/5
2/6
3/8
1/1
3/12
2/11
5/18
3/18
4/12
3/3
2/2
2/2
2/2
11/26
2/6
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
Elniendorf AFB OU 5 Record of Decision
3-5
-------
Table 3-3
(Continued)
Contaminant :
. Maximum
Concentration
Maximum
Background
Concentration3
Frequency^: '.
(Peietxumstt
Samples) ?
Soil (Maximum Concentration - mg/kg) (Continued)
Aluminum
Arsenic
Barium
Beryllium
Calcium
Copper
Cadmium
Chromium (Total)
Lead
Manganese
Mercury
Potassium
Sodium
Selenium
Silver
Thallium
Zinc
19, 100 mg/kg
28.2 mg/kg
3,650 mg/kg
1.3 mg/kg
35,300 mg/kg
38 mg/kg
3.1 mg/kg
64 mg/kg
206 mg/kg
199,000 mg/kg
0.31 mg/kg
1,440 mg/kg
1,430 mg/kg
3.1 mg/kg
22 mg/kg
0.59 mg/kg
159 mg/kg
19,211
9.0
131.4
0.47
4,021
183
1.46
25.5
18.3
459.4
0.11
508.5
364.9
0.37
0.91
NE
49.9
1/38
1/38
10/38
3/38
10/38
4/38
1/38
1/38
21/38
8/38
2/38
1/38
14/38
3/38
1/38
5/26
3/38
a Background value was 99% confidence limit for the mean for surface soil.
NE = Not established.
= Background concentrations provided for inorganic analytes.
ElmencJorf AFB OU 5 Record of Decision
3-6
-------
g.
o
>
3
O
c
o
8
WAST
PAINT
TANK
CORRIDR
?--"'i ---. - ; la -'
LOWER ,;BLUFF ARfe^
(B SOil «XTIM3
0 w«fn sur«.r wfu
A CALOfNC S'Af JOM
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*n£rtf HO DMA ARf POSrfO.
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FIGURE 3-1
ORGANIC CONTAMINANTS
DETECTED IN UPPER
' AQUIFER GROUNDWATER
o no «o 500.
ELWMX3BF Ate
ANCHORAGE. ALASKA
-------
n
oo
O
73
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00
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FIGURE 3-2
OftOANIC CONTAMINANIS
DETECTED IN UPPER
UIFEH onOUNDWAIEfl
<00 flop
. wu wvALfFES >*f Pf ue n
*Mf/?£ NO DATA A/If POS
-------
naturally occurring and are the result of geological variability typical of glacial outwash
plains.
Surface water (ditch water, the snowmelt pond, and the beaver pond wetlands)
has been impacted by volatile organics. Seeps are not considered surface water but
discharges from groundwater. However, most concentrations are low (see Table 3-1) and the
compounds were generally detected in 20% of the samples. The exception is TCE which
was detected in 4 of 10 samples. A single detection of JP-4 (770 /ig/L) was found on a
puddle formed by seep water. The puddle is technically surface water, but is not a body of
water like the beaver pond wetland area or the snowmelt pond. Figures 3-3 and 3-4 show
the distribution of organics in surface water.
Sediment has been impacted in the beaver pond and snowmelt pond.
Semivolatile compounds are found in 20% of the samples tested with anthracene having the
highest concentration (230 pig/kg) (see Table 3-2). PCBs were detected in 4 of 6 sediment
samples taken at the snowmelt pond with a maximum concentration of 1,600 /ig/kg. Volatile
organics and fuel hydrocarbons were also detected with xylene being the most prevalent VOC
and TFH-diesel being the most prevalent fuel hydrocarbon. The distribution of organics
found in sediment are shown on Figures 3-3 and 3-4.
Soil at different depths has been impacted by VOCs, semivolatiles, fuel
hydrocarbons, and metals (Table 3-3). The VOCs, toluene, xylene, and ethylbenzene were
detected in approximately 20% to 25% of the samples. Most of the semivolatile compounds
are found in a single sample set. Otherwise semivolatile organics are found sporadically.
The distribution and depth of organic compounds in soil are shown on Figures 3-5 and 3-6.
Metals were found above background in soil (see Table 3-3). Manganese had
the highest concentration at one location. Most of the metals that exceeded background are
naturally found at high concentrations. Very few concentrations of contaminants detected at
OU 5 were above background. Lead and sodium exceeded background the greatest number
Elmendurf AFU OU 5 Record of Decision 3-9
-------
LfGCNO
fACe DrtA/NACf DlfCW
HACE CULVERT
A SUflf ACf WAff« ISW OR SfDIMFN
SAMPLING LOCATION
NA M3f APPLICABLE INOT DETECTED IN SAMPLE/
NOrf: DAfA WPOnfEO fOfl SUHf ACf WATCH
ARE TOTAi UCTALS.
DATA SHOWN ARE THC HIGHEST OBSfOVEO
FROM TWO SOUNDS Of SAMPLING.
FIGURE 3-3
ORGANIC CONSTITUENTS
DETECTED IN SURFACE WATER
AND SEDIMENT
CLMCM3ORF AfB
ANOIOHAOE. ALASKA
-------
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-------
of times. Figures 3-7 and 3-8 show the distribution of inorganics in soil. Generally, higher
concentrations of the metals were found in organic rich soil. Organic soils can adsorb and
concentrate metals so it is reasonable to conclude that the elevated concentrations are due to
natural accumulation through adsorption and not through impacts from base operations. This
conclusion is further supported by there being no historical evidence of sources that would
discharge metals.
Detailed studies were performed at the beaver pond wetland and snowmelt
pond to determine if the impacts identified during the RI were, or could, affect the
environment. Samples were taken of the sediment and water in the beaver pond and were
tested for microbial potential, adsorption, and chemistry. The retention time and flow rate in
the wetland also was determined. This study concluded that the beaver pond was currently
treating the contaminant load entering the wetland via groundwater discharge and has treated
water contamination for many years without a significant degradation of the wetland. The
study estimated that the pond is 18 times larger than necessary to treat the current
contaminant load by natural processes.
The snowmelt pond was studied to determine the extent of PCB contamination
in the pond's water and sediment. PCBs were not detected in any water samples. Total
organic carbon (TOC) was also measured at sediment sampling locations because PCB
sediment standards vary according to accompanying TOC concentrations. TOC binds the
PCBs to sediment material, reducing its ability to migrate. PCB concentrations are below
standards at three locations but above standards at two locations where TOC is high. There
was no geographical pattern to the locations where TOC is not sufficient to bind the PCBs
(reflected in lower standards at these locations).
AFB OU 5 Record of Decision 3-14
-------
CORRIDOR SP?/80lS'
^r.o, .^^
-^a' :;"^^:;:-^3^ ' A^^
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POST''ROAD, CO'RRIDOR"'"^'-1^"^
INDlj^TRIAL Alfi'A
FIGURE 3-7
INORGANIC ELEMENTS
DETECTED IN SOIL ABOVE
BACKGROUND LEVELS
o xo
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.
-------
3.2 Risk Evaluation
Based on the concentrations of contaminants detected during the RI, human
health and environmental risk assessments were performed to determine if areas should be
considered for remedial action. All concentrations of contaminants, including all potential
contaminants of concern, whether exceeding Applicable or Relevant and Appropriate
Requirements (ARARs) (discussed later) or not, were included in the risk assessments.
Human Health Risk Assessment (HRA)
By determining under what land use conditions people are potentially exposed
to what chemicals, for how long, and by what pathways of exposure, the cancer and
noncancer risks were determined in the RI/FS.
Exposed Populations and Exposure PathwaysListed below are four possi-
ble exposure pathways to contamination. Details on the parameters used in the Health Risk
Assessment are shown on Table 3-4.
Residential (Current and Future Potential). The HRA evaluated
exposure of residents to contaminated surface soil through direct
contact (incidental ingestion and dermal absorption) and inhalation of
dusts. Their exposure to lower and upper aquifer groundwater through
inhalation (showering), ingestion, and dermal contact (showering) was
also evaluated.
Current and Future Short-Term Workers. The HRA evaluated
exposure of workers to contaminated subsurface soil through direct
contact (dermal absorption and incidental ingestion) and inhalation of
vapors from the soil.
Exposure of Current and Future Recreationalists (Children).
Exposure of children was evaluated with respect to contaminated
sediment (ingestion and dermal absorption) and contaminated surface
water (ingestion, dermal absorption, and inhalation of volatiles from
surface water).
ElmiMidorf AFB OU 5 Record of Decision 3-17
-------
Table 3-4
Parameters Used in the Risk Assessment
'"' '" ' ' ''; . ''''}'.' '''\'^--'^'- \-\ "'!: '"
:' :y ' -' :" -:. '? -vi''-y:-:: ":":*::"" - > '' '-''.
' - ' :''-. ' ' ....."-.-- '.:;;". ' ^ .:$:'#: 'roS ':'.-: '::^'.
..; |- ^^^:ExIwsure :Parainet(ew|||^s^;::ia-:
' :.' '.:;:,;: -.' .; ; ::"!:'-": ' !:; b|ll;;:;:;l|:;s-:C:l>::
Exposed Individual V ".'*' ' f ;:?ll|ill?%?:?-: '
Body Weight (kg)
Soil Ingestion Rate (mg/day)
Exposed Skin Surface Area (cm2)
Adherence to Skin Factor (ing/cm2)
Days/year exposed (Inhalation and Ingestion)
Years exposed
Days/year exposed
Dust inhalation rate (mVday)
Paniculate concentration (/*g/m3)
Water Ingestion Rate (L/day)
Time in Water (min/day)
Sediment Ingestion Rate (mg/day)
^libsurfaci§:-S6ii;l;:-::
'- French -W§!ii|:f::;-
70
480
5,000
1.0
24
5
NA
NA
NA
NA
NA
NA
If:. ;'. !' : '^ 4 '.-.vV £ ':'
iPll!:i:^i^c^
;:x: ..:;:.:;.;.- -.- .:...:v>-...;:.:.::.:y.;v:/ ,-.. : - . -.
l:iil^iE:i;:;;iii
IX;2!PI:lResiicSfe
15 (0-6 yr)
70(>6yr)
200 (0-6 yr)
100(>6yr)
5,800
1.0
'350
30
350
20
50,30
NA
NA
NA
Pathway
iiilillp
.-- x- . -:;-.::;.::-:.:::.v:: w-'x-.v.-
;:|;A;yierag||:
70
100
5,000
0.2
275
9
40
20
50, 30
NA
NA
NA
!i;|(G}rbi§i
. :-.: :-. . . :-:::.-:-.-.-.-. : :- . .
70
NA
23,000
NA
NA
30
350
15
NA
2
15
NA
>;..-- .:;H::-:: '.*:-;«
diwaW'lH I
||A^eriij|e 1
||:||i|:||y
lehtf ;-.;;:;||| 1
70
NA
20,000
NA
NA
9
275
15
NA
1.4 '
10
NA
lM:::ttlii:::-,5::
m:?w&trir}
.. - - ;-......;. . :. .-. . .- .... ..; -.-. . .
& Recreational
glSIUlerliy..;--
35
NA
3,900
Sediment
10,000 Water
1.0
NA
5
26
NA
NA
0.05
60
100
-------
Exposure of Recreationalists. The HRA evaluated recreationalists'
exposure to contaminants through the consumption of fish caught in
Ship Creek.
Exposure AssumptionsRisk can be calculated both for the average exposure
and the reasonable maximum exposure (RME) of the population. All chemicals detected
during sampling were evaluated as potential sources of cancer and noncancer health risks. In
the case of metals, risks were only calculated if the metals concentrations exceeded
background concentrations. Average exposure risks were assessed using the arithmetic
average concentration at the site. RME risks were assessed using the 95% upper confidence
limit of the arithmetic mean concentration in soil, sediment, surface water, or ground water in
subareas such as the beaver pond wetland area.
Conservative assumptions were used to avoid underestimating risk. For
example, the HRA assumed that future residents would live where the contaminants are
located and they would drink and shower with the contaminated, upper aquifer ground water.
This is a highly conservative assumption since the topography of the bluff and wetlands at
the base of the bluff would not allow for construction of residences along the bluff where
contamination is greatest. In addition, the upper aquifer is unlikely to be used as a water
supply because of its poor yield relative to the lower, confined aquifer.
Using exposure levels and standard values for the toxicity of contaminants,
excess lifetime cancer risks (ELCRs) and hazard indices (His) were calculated to describe
cancer and noncancer risks, respectively. The ELCR is the additional chance that an
individual exposed to site contamination will develop cancer during his/her lifetime. It is
expressed as a probability such as 1 x 10"6 (one in a million).
The HI estimates the likelihood that exposure to the contamination will cause
some negative health effect. An HI score above one indicates that some people exposed to
the contamination may experience at least one negative health effect.
Elmendorf AFB OU 5 Record of Decision 3-19
-------
ELCRs and His were calculated using Reference Doses (RfDs) and Cancer
Slope Factors (CSFs) which represent the relative potential of compounds to cause adverse
noncancer and cancer effects, respectively.
Two sources of RfDs and CSFs were used for this assessment. The primary
source was Integrated Risk Information System (IRIS) database, the U.S. EPA repository of
agency-wide verified toxicity values. If a toxicity value was not available through IRIS, then
the latest available quarterly update of the Health Effects Assessment Summary Tables
(HEAST) issued by the U.S. EPA's Office of Research and Development was used as a
secondary source. For some chemicals detected at OU 5, no toxicity value from IRIS or
HEAST was available, and toxicity values were provided by the U.S. EPA Region X as
provisional RfDs and cancer slope factors.
Table 3-5 summarizes the highest human health risks discovered in the HRA.
The risks are based on exposure to soil and groundwater. Locations where the risk exceeds
10"6 (i.e., 10"*, 10"5) are shown on Figure 3-9. At two locations in the central part of the OU
groundwater quality exceeds standards, but risk was less than 10~5. The only scenario that
generates a noncancer HI value exceeding one, or total excess lifetime cancer risks greater
than 1 x 10^, is when future residents ingest the upper aquifer groundwater in the western
area of OU 5 for 70 years. For ingestion of upper aquifer groundwater extracted along the
base of the bluff, the estimated risks are largely due to arsenic and manganese which are
thought to naturally occur at elevated concentrations.
Elmendorf AFB OU 5 Record of Decision 3-20
-------
Western
Seeps
CORPS OF
ENGINEERS
BLDG.
Groundwpter
R.SK o j- i. /Exceeding
^pgic Sediment ^standards
, 1 X 10-4 \ W /
RISK IN SOIL
4.7 x 10-5
Areos Considered for
Remediol Action Legend:
@ SOILS
Central
RISK IN SOIL
9 x 10-5
Eastern
?SVO
RISK IN PLUME
? 4 X 10-5
~'\
Surface
Water
Soils
SEEP AREA
GROUNDWATER PLUME
[77] SURFACE WATER AND/OR SEDIMENTS
(SNOWWELT AND BEAVER PONDS)
O GROUNDWATER SAMPLE EXCEEDING STANDARD
( /
\--/;
1200
SCALE IN FEET
Figure 3-9. Human Health Risk in OU 5
-------
Table 3-5. Human Health Risks
Media
Soil
Groundwater
Location
Western Area
Central Area
Western
Plume
Eastern
Plume
Cumulative Risk
4.7 x 10* ELCRa, HI < 1
9 x 10'5 ELCRa, HI < 1
1 x 104 ELCRa, HI = 3
4 x 10 5 ELCRb, HI < 1
Chemical(s) Driving the Risk
Arsenic, PAHs
Arsenic
Arsenic, gasoline, manganese, diesel
fuel, and benzene
Gasoline, TCE
a Excess lifetime cancer risk, assumed future resident, 70 years of exposure by ingest ion.
b Assumed future resident, 70 years if inhaling vapors while showering.
The risk was calculated using assumptions regarding exposure pathways and
the time receptors, including humans and animals, were exposed to the contaminants.
Constant exposure was assumed over a lifetime. This is a conservative approach that may
overestimate the actual risk. Risk management decisions were made considering the
uncertainty in the assumptions used in the risk assessment. At OU 5 the shallow
groundwater is not used and is not expected to be used in the future, so existing risks and
potential risks are significantly less than the worst-case risk.
Environmental Risk Assessment (ERA)
The ERA did not link particular contaminants to specific ecological impacts.
However, it identified potential risks to the environment and environmental receptors which
may have been affected by contaminants. The risk is calculated using an equivalency factor
and specific risk numbers are not calculated. Detected concentrations are compared to
critical concentrations published in the literature.
The ecological risk at the snowmelt pond was determined by comparing PCB
concentrations and associated TOC data with sediment quality criteria for the protection of
aquatic life. The PCB standard is variable, depending on the TOC. The higher the TOC,
the more the PCBs are bound to the sediment, and are not available for uptake by receptors.
Elmeixiorf AFB OU 5 Record of Decision
3-22
-------
The most specific correlation between environmental risk and particular
contamination is at the snowmelt pond. Waterfowl such as dabblers are the only potential
receptors. Sediment contaminated with PCBs at 1.16 mg/kg (the highest concentration
found) could pose a risk to ducks if they dig with their beaks in thie pond sediments: Fish
are not found in the snowmelt pond.
In general, animals could be exposed to contaminants through the soil gas they
breathe while burrowing, the plants they eat, and the dermal contact they have with media
contaminated by fuels. Plants could potentially be affected by contamination. The RI/FS
determined that plant stress exists in OU 5, but was probably not caused by identified
contaminants in the OU. The stress is probably due to natural conditions. The ERA did not
discover any impacted endangered species or endangered species habitat.
Uncertainties Associated with the Risk Assessment
Risk assessments involve calculations based on a number of factors, some of
which are uncertain. The effects of the assumptions and the uncertainty factors may not be
known. Usually, the effect is difficult to quantify numerically, so the effect is discussed
qualitatively. Some of the major assumptions and uncertainty factors associated with the risk
assessment are the following:
The assessment used EPA Region 10 default exposure parameters for
most calculations. Some of these parameters are not realistic for a
subarctic climate (May overestimate risk).
Existing concentrations are assumed to be the concentrations in the
future. No reduction through natural degradation and attenuation over
time is r?.ken into account (May overestimate risk).
No increase through additional contamination is assumed (May
underestimate risk).
Potential degradation products of existing organic contaminants are not
considered (May overestimate or underestimate risk).
ElmemJorf AFB OU 5 Record of Decision 3-23
-------
3.3 Established Final Contaminants of Concern (COCs) and Cleanup Levels
. Final COCs were developed from the results of the risk assessment and by
considering regulatory standards. The final COCs are shown on Table "3-6 along with the
maximum detected result. The basis for identifying the COC (risk or regulatory standard) is
identified. The cleanup levels that will be achieved by the remedial action at OU 5 are also
shown on Table 3-6.
3.4 Summary
Actual or threatened releases of hazardous substances from OU 5, if not
addressed by implementing the response action selected in this ROD, may present an
imminent and substantial endangerment to public health, welfare, or the environment.
Elmcndorf AFB OU 5 Record of Decision 3-24
-------
o
3,
>
3
o
D
8
Table 3-6
Final Contaminants of Concern and Cleanup Levels
Contaminant
Maximum Concentration
BasisforfOG
Clean Up Level
Basis for Clean Up Level
Groundwatcr . ' .'.'.. ..
TCE
Benzene
TFH Diesel
TFH-Gas
52 /ig/L
8.5 ng/L
290 itg/L
700 ng/L
Contributes to a risk > 10'5
Contributes to a risk > 10'5
Contributes to a risk > 10'5
Contributes to a risk > 10s
5/ig/L
5/ig/L
10 ng/L
10 ftg/L
MCLa ' '
MCLa
Alaska Water Quality Standards'5
Alaska Water Quality Standardsb
Surface Water .
Sheen
TFH-Gas
JP-4
Sheens exists
400 ng/L
770 /zg/L
Water Quality Standard
Water Quality Standard
Water Quality Standard
No sheen
10 /xg/L
10 /zg/L
Alaska Water Duality Standardsb
Alaska Water Quality Standards1*
Alaska Water Quality Standards'5
Soil ...-'-. ;-'v
TFH-Diesel
1,160 mg/kg
Threat to groundwater
1,000 mg/kg
Alaska Cleanup .Matrix Level Cc
N>
L/i
a 40 CFR Part 131, and 18 ACC Chapter 70.010a and d, 70.015 through 70.110, 18 AAC 80.070.
b 18 AAC 70.020. Based on ecological risk (protective of aquatic resources).
c 18 AAC 78.315.
-------
4.0 REMEDIAL ACTION OBJECTIVES, ALTERNATIVES, AND
COMPARATIVE ANALYSIS
4.1 Remedial Action Objectives
Specific remediation alternatives were developed and evaluated for the areas
with potential risk and that exceeded the cleanup levels identified in Section 3.3. Specific
remedial action objectives are:
Protect human health and the environment by preventing ingestion and
contact with contaminated groundwater by people and preventing
animal contact with contaminated seep water;
Use treatment techniques whenever practicable;
Implement a solution that is capable of managing impacts from
upgradient sources as the contaminants reach OU 5; and
Implement a cost effective solution that can achieve the cleanup levels
for the final COCs.
4.2 Alternatives
Beaver Pond Wetland Area and Snowmelt Pond Remedial Alternatives
The sediment and surface water in the beaver pond wetland area have few
treatment options available that would be practical and feasible.
Natural attenuation and institutional controls would be the only response
actions that would be both effective and implementable for the beaver pond wetland area.
Any attempt to either contain, extract and treat ex situ, or treat surface water in situ would
negatively affect the wetlands area. For example, physically removing visible sheens,
dredging sediments, or processing wetland water through a treatment facility would all upset
ecological balances, disturb the water flow, and/or violate potential ARARs that specify
Elmendorf AFB OU 5 Record of Decision 4-1
-------
minimal disturbance of wetlands. It has been demonstrated in previous studies that the
beaver pond wetland area is a viable natural wetland that can remediate contaminants
entering into it.
The constructed wetland will be made by partially filling the snowmelt pond so
that its average depth is 6 to 12 inches. This partial filling will isolate the PCBs in the
sediments. The constructed (enhanced) wetland will expand the dimensions of the existing
snowmelt pond to treat low volumes of impacted water collected from groundwater seeps at
OU 5. Impacts to the existing snowmelt pond area will be minimized by the use of sediment
nets. Mitigation will be accomplished by increasing the area of the snowmelt pond and by
the planting of additional wetland vegetation.
The remedial alternative for the beaver pond wetlands is appropriate if the
following is true:
1. The beaver pond wetland continues to actively remediate groundwater
that discharges into the pond.
2. Concentrations of the COCs found at OU 5 today will not increase in
the future due to upgradient impacts.
The second assumption deals with the migration of contaminants from
upgradient sources.
Impacts at OU 5 from upgradient sources were evaluated in a three
dimensional flow and transport model. The purpose of the model was to predict the future
concentrations of benzene and TCE in OU 5. These two compounds are the primary risk
drivers at OU 5 and each has sources upgradient of OU 5. Figures 4-1 and 4-2 show
benzene concentrations across Elmendorf AFB currently and in 10 years. Figures 4-3 and
4-4 show TCE concentrations currently and in 10 years over the same geographical area.
These figures show that the concentrations of benzene and TCE in the groundwater that come
from upgradient sources are predicted to decrease in OU 5 over time.
Elmendorf AFB OU 5 Record of Decision 4-2
-------
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Figure 4-2. Elmendorf' AFB TCE Concentrations at the Water Table (Present)
-------
Elmendorf ;AFB
t-
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Figure 4-3. Elmenciorf AFB Benzene Concentrations at the Water Table (10 Years)
-------
Elmendorf AF'B
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igure 4-4. Elincudorr AFB TCE Concentrations at (he Water Table (10 Years)
-------
The concentration contours on the year 10 figures show lower concentrations
than in figures for earlier years; however, the areas affected appear larger than the plumes
shown on the current year figures. Some of the increase in affected area is due to migration,
but the apparent increase in plume size is also due to the method used to develop the plume
contours. The current year plume contours were drawn by hand, interpreting the extent of
contamination based on the distribution of concentrations. The year 10 contours are
computer generated using the model output. Data are plotted on a much tighter grid using
the model output. Also the model interpolates data and projects migration from a source to a
model grid node. These two factors associated with the model make a plume look larger
than if drawn using professional experience and judgment.
A sensitivity analysis was run on the model to determine if changes in the
model assumptions could result in a different conclusion. For example, if no natural
degradation of TCE occurs, could conditions possibly degrade at OU 5? The model was run
with no TCE degradation and the results show that, in the 5- to 10-year horizon, the
concentration of TCE increases and impacts OU 5. Thereafter, TCE concentrations will
decline. This finding is not realistic because the TCE was released 10 to 20 years ago. If
there were no natural attenuation the concentrations of the COCs would be higher at OU 5
than revealed by the RI. Another sensitivity analysis run on the model was to determine the
effect on OU 5 if the source areas contribute contaminants for 30 years. With this change in
assumptions, the model predicted that conditions at OU 5 would not degrade in the future.
Concentrations of TCE would slowly attenuate over 15 to 20 years, a longer period than if
sources ceased contributing contaminants in 5 years.
The model results show that the assumption that impacts will not increase at
OU 5 is reasonable.
Elmcndorf A KB OU 5 Record of Decision 4-7
-------
Identification of Remedial Action Alternatives
To identify a remedial action alternative that could best achieve the objectives,
ten media specific options were identified. These options included no action, excavation,
pumping, passive extraction, treatment (e.g., granular activated carbon), bioventing,
biological treatment, institutional controls, air sparging, and wetland treatment. These
options were combined in the FS into 32 multimedia alternatives. Each alternative was
evaluated against the first seven CERCLA evaluation criteria. Though there are 32
alternatives, many are only slightly different from each other. To simplify the comparative
analysis, the 32 alternatives were grouped into four alternatives that represent the primary
actions that could be taken.
Except for the no action and natural attenuation alternatives, the cost of each
alternative includes 30 years of monitoring groundwater and surface water, including Ship
Creek, the beaver pond wetland area, and influent and effluent of treatment systems, for the
contaminants of concern. This monitoring assumption is worst case and includes the cost for
a hypothetical monitoring program. The actual monitoring program will be developed as
part of the design of the selected alternatives. The actual number of locations that will be
monitored could be less than the worst case hypothetical assumption and actual costs would
probably be lower than those presented in this ROD. However, any changes in costs would
affect all alternatives and would not affect the alternative selection process. A 7% discount
rate was assumed in calculating present worth cost. Any expense of using or acquiring land
not owned by the Air Force is not included in the cost estimates. The four alternatives are
as follows:
Elmendorf AFB Ob' 5 Record of Decision 4-8
-------
1. No Action
No Cost
Evaluation of this alternative is required by CERCLA as a baseline reflecting
current conditions without any clean up. This alternative is used for comparison with each
of the alternatives. While natural processes should degrade and reduce the concentrations of
the chemicals of concern to acceptable levels, this alternative does not include any long-term
monitoring. There are no costs associated with this alternative. Time frame until cleanup
goals are achieved cannot be determined.
2. Natural Attenuation with Institutional Controls for Groundwater and Beaver Pond
Wetlands Area/Passive Extraction with a Constructed Wetland for Groundwater
Seeps/Isolation of Snowmelt Pond Sediments/Excavation, Biopiling, and Backfilling for Soil
Estimated Capital Costs: $0.8 million
Annual Cost: $0.08 million
Present Worth Cost: $1.6 million
Time to Complete Clean Up: 20 years
Discount Rate: 7%
Cost Accuracy: -30 to +50%
Groundwater would be remediated by natural processes that break down and
dilute contaminants. In addition, institutional controls in the form of deed restrictions would
prevent future use of the contaminated water. The Air Force would continue to monitor
groundwater quality and would regularly update off-base land owners of the monitoring
results. If there is any indication that contamination is getting worse, the remedial actions
would be reevaluated and additional action would be taken if necessary.
Elniendorf AFB OU 5 Record of Decision 4-9
-------
Seep water would be passively extracted by natural flow with passive
extraction wells and collection systems from the upper aquifer before it reaches the
groundwater seeps. Thus, the groundwater seeps would be eliminated. The contaminated
water would be channeled to the snowmek pond where engineered wetlands would be
constructed. Biological processes would remove most of the contaminants from the water.
The treated water would flow from the constructed wetlands into a drainage ditch. Tests to
determine treatment effectiveness would be necessary. The engineered wetland would also
isolate the snowmelt pond sediments. This alternative would treat all the contaminated seep
water except the seep water flowing into beaver pond wetland area. Treatment of those
groundwater seeps must rely on natural attenuation to avoid damaging the wetland habitat.
About 1,500 cubic yards of soil would be excavated from both of the areas
with surface soil contamination (see Figure 3-9). Much of this soil would have to be
removed to install the passive extraction wells. The holes would be backfilled with treated
soil or clean soil. The contaminated soil would be transported to the eastern end of the base
to the existing biopiling system.
Biopiling involves supplying air and required nutrients to a soil pile to
maximize natural degradation. Degradation of contaminants would be monitored to
document the breakdown rate and confirm that cleanup levels are being met. The treated soil
would be used on base for fill after cleanup levels are achieved. It would take approximately
4 months to remove the contaminants from the excavated soil by biopiling.
3. Active Extraction for Groundwater and Groundwater Seeps/Natural Attenuation for
Beaver Pond Wetlands Area/Natural Degradation with Institutional Controls for Soil/Isolation
for Snown-sk Pond Sediments
Capital Costs: $2.5 million
Annual Cost: $2.1 million
Present Worth Cost: $28.4 millon
Elmendorf AFB OU 5 Record of Decision 4-10
-------
Time to Complete Clean Up: 30 years
Discount Rate: 7%
Cost Accuracy: -30 to +50%
Water would be pumped from the aquifer and near the groundwater seeps
through wells that would be installed. The water would flow into an air stripper (system to
volatilize contaminants) where the contaminants would be transferred to the air. The air
carrying the contaminants would then be filtered by an activated carbon system. Activated
carbon would be disposed at an U.S. EPA-approved RCRA facility. Finally, the water
would be discharged into the aquifer at the base of the bluff. Separate systems could be used
in different areas. This system would remove more water than passive extraction, which
allows it to treat both the groundwater seeps and the groundwater.
Natural degradation would remediate the soil contamination and institutional
controls would restrict access by humans.
4. Air Sparging with Soil Vapor Extraction for Groundwater and Groundwater
Seeps/Natural Attenuation for Beaver Pond Wetland Area/Bioventing for Soil/Isolation for
Snowmelt Pond Sediments
Capital Costs: $2.9 million
Annual Cost: $1.8 million
Present Worth Cost: $24.8 million
Time to Complete Clean Up: 30 years
Discount Rate: 7%
Cost Accuracy: -30 to +50%
This system would volatilize the groundwater contaminants while they are in
the ground. Compressed air would be pumped into the areas with contaminated groundwater
through wells that would be installed. The bubbling air would separate contaminants from
Elmendorf AFB OU 5 ReconJ of Decision 4-11
-------
the groundwater by volatilizing them into the soil vapor. A soil vapor extraction system
would then remove the contaminant-carrying vapors from the soil, so that the contaminants
can be adsorbed by activated carbon. Finally, the activated carbon is disposed at an U.S.
EPA-approved RCRA facility. Breakthroughs (leaks of contaminant-carrying air) are
possible in the lower bluff area and near the bluff face. Tests to determine treatment
effectiveness would be needed. The Air Force might need to get permission from
landowners to install this system on privately owned land below the bluffs.
Soil would be treated by bio venting. This process would add oxygen into the
soil to enhance the growth of natural microbial populations that feed on the organic
contaminants. A blower would force air into contaminated soil via wells. Nitrogen and
phosphorous could be added to stimulate bacterial growth and contaminant destruction. Soil
sampling would be needed to ensure that cleanup levels were being achieved. It is uncertain
how long it would take to clean up the contamination. Bioventing may require pumping out
groundwater to lower the water table near the contaminants if the water table is too close to
the contaminated soil.
4.3 Summary of Comparative Analysis of Alternatives
The comparative analysis describes how each of the four alternatives meet the
CERCLA evaluation criteria relative to each other. Because the beaver pond wetland area
and snowmelt pond remedial alternatives will be included in any selected alternative, the
comparative analysis focuses on areas which are not addressed by these remedies.
4.3.1 Threshold Criteria
Overall Protection of Human Health and the Environment. Alternative 4
would provide the greatest protection of human health and the environment because
groundwater, groundwater seeps, and soil would all be actively treated to acceptable cleanup
levels. Alternative 3 is slightly less protective since soil is not actively treated.
Elmendorf AFB OU 5 Record of Decision 4-12
-------
Environmental receptors would continue to be exposed to surface soil contamination until it
is remediated by natural degradation.
Alternative 2 would provide nearly as much protection as Alternatives 3 and 4
by actively treating groundwater seeps and soil, the contamination most likely to impact
human health and the environment. Currently, there are no environmental or human
receptors of upper aquifer groundwater. Institutional controls for groundwater in
Alternative 2 would ensure that people will not be exposed to upper aquifer groundwater in
the future.
Alternative 1 would not be as protective because people and environmental
receptors would continue to be exposed to contaminated soils and groundwater seeps until
contaminants in these media degrade to acceptable levels.
Natural processes would take longer to remediate the soil and, without
monitoring, the progress of the natural attenuation and accompanying reduction in risk could
not be assessed. In addition, Alternative 1 leaves open the possibility that future base
personnel and residents might use contaminated upper aquifer groundwater.
Compliance with ARARs. Compliance with ARARs would be achieved for
Alternatives 3 and 4 which actively treat contaminants in all impacted media. The time to
achieve cleanup levels is uncertain but is predicted to be less than 15 years. Alternatives 1
and 2 would comply with applicable cleanup regulations for groundwater and would likely
achieve cleanup levels within 15 to 20 years, based on the groundwater model.
Alternative 1, the no action alternative, would not comply with ARARs for
soil. In addition, without monitoring, there would be no way to determine when, or if,
cleanup levels had been achieved in either soil or groundwater.
ElnieivJorf AFB OU 5 Record of Decision 4-13
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4.3.2 Primary Balancing Criteria
Long-Term Effectiveness and Permanence. All alternatives could be
effective in the long term. The model predicts that natural attenuation would be effective and
will remediate to the cleanup levels. Once cleanup levels are met, remediation will be
permanent. None of the alternatives would be expected to produce toxic by-products.
Reduction in Toxicity, Mobility, and Volume through Treatment.
Treatment for this criteria is assumed to mean processes other than those which would
naturally occur. Alternative 4 would reduce the volume of contaminants through treatment to
a greater degree than other alternatives because it would actively treat contaminated soil,
groundwater, and groundwater seeps. Alternatives 2 and 3, both of which employ active
treatment on two media, would provide slightly less reduction through treatment.
Alternative 1, which would not actively treat any media, would not meet this criteria.
Short-Term Effectiveness. Short-term effectiveness is primarily affected by
whether alternatives would reduce risk in the short term and the degree to which alternatives
can be implemented immediately without causing negative side effects on the environment.
Alternatives which actively treat water or restrict its use reduce risk faster than alternatives
which solely rely on natural attenuation.
Alternatives that negatively impact the environment during implementation are
not effective in the short term. This is the case with remedial alternatives that affect the
beaver pond wetlands. Pumping water from the pond or interception of groundwater that
feeds the wetland would ruin the existing natural habitat. For this reason, natural attenuation
is the selected remedy for the wetlands. Natural attenuation is relatively effective in the
short term since implementing natural attenuation is the only alternative which causes no
impact to the wetland while providing monitoring necessary to be sure cleanup levels are
being met. The study of the beaver pond wetlands showed that it is a healthy functioning
Elmendorf AFB OU 5 Record of Decision . 4-14
-------
system, and is currently managing contaminants entering the wetland through groundwater
flow, by natural physical, chemical, and biological processes.
Alternative 2 would be the most effective in the short term. Groundwater use
restrictions and soil and seep treatment would immediately reduce risk to humans and the
environment. Soil treatment could be completed within a year.
Alternative 4 would be fairly effective in the short term. Once implemented,
soil treatment could be completed within a year and its active extraction of groundwater
could expedite contaminant removal compared to natural attenuation. A treatability study for
bioventing would be necessary. More important, to implement bioventing in shallow soil
below the bluff some of the shallow aquifer might have to be dewatered. This would cause
short-term damage to wetland environment in the area.
Similarly, the short-term effectiveness of Alternative 3 would be reduced
because active extraction of groundwater would negatively affect the wetland environments.
In addition, this alternative would rely on natural attenuation of soil which would not reduce
the impact of soil contaminants on environmental receptors.
Alternative 1 would be the least effective alternative in the short term because
it would not take immediate steps to reduce risks and would require the longest time to
achieve cleanup levels.
Implementability. As discussed above, Alternatives 2, 3, and 4 would
require treatability studies before they could be implemented. Alternative 2 also requires
access to non-Air Force property to construct a wetland in the snowmelt pond. Alternative 3
would be the most difficult to implement because treated water could not be easily discharged
into the shallow groundwater in the area below the bluff. Alternative 4's implementability
would also be limited by the need to dispose of or regenerate activated carbon. Alternative 2
would be simpler to implement than Alternative 3 and 4; since the technology is not
ElmcnJorf AFB OU 5 Record of Decision 4-15
-------
complex, the treatment options do not involve discharges of large volumes of water, disposal
of captured contaminants, or other technical obstacles to implementation. Alternative 1
would be the easiest alternative to implement since no actions are involved.
Cost. Estimated capital costs, and annual operational and maintenance (O&M)
cost, are shown in the description of alternatives. The present worth is the capital and O&M
cost over a 30-year period using a discount rate of 7 percent. The costs are accurate to
within -30% to +50% of the actual costs. Alternative 1 has no cost while active alternatives
(Alternatives 3 and 4) have the highest costs. Alternative 2 has a relatively moderate cost.
4.3.3 Modifying Criteria
State Acceptance. The State of Alaska concurs with the Air Force and U.S.
EPA in the selection of Alternative 2.
Community Acceptance. Based on the comments received during the public
comment period, the public has no preference of alternatives. Qne letter raised concern
about implementing alternatives on land not owned by the Air Force. Locating the wetland
in the snowmelt pond is the current engineering concept because of its location and existing
water balance conditions. There is also the beneficial result of isolating the PCBs in the
sediment of the pond if the wetland is built at this location. Another comment described
using electromagnetic/radio frequency technology to treat soil. The technology described
would be a viable solution comparable to the alternatives with active treatment (Alternatives
3 and 4). These alternatives have high cost to benefit ratios (high cost for the incremental
benefit). The third comment supported Alternative 2.
ElmeiKlorf AFB OU 5 Record of Decision 4-16
-------
5.0 SELECTED REMEDY
The selected remedy is Alternative 2 because it best meets the nine CERCLA
criteria. It protects human health and the environment and complies with ARARs. It is
effective at reducing contamination both in the short term and long term, and is
implementable, cost-effective, and acceptable to the public and the State of Alaska.
Alternative 2 provides an appropriate level of treatment to reduce risks and comply with
ARARs. Other alternatives do not meet the CERCLA criteria as well as Alternative 2.
Alternatives 3 and 4 provide little additional environmental benefit, especially relative to risk
reduction in Alternative 2, which is the most cost effective of the four alternatives.
Alternative 2 was selected because it best provides the following specific
benefits at OU 5:
Existing habitat in the beaver pond wetlands area is preserved. The
monitoring will ensure that the current health state of the wetlands is
being maintained and improved as contaminant concentration levels are
decreasing.
The habitat in the snowmelt pond will be improved from an open pond
to a vegetated wetlands system. This alternative is consistent with the
city of Anchorage's land-use plan that calls for the snowmelt pond to
be a greenbelt preservation area.
The pathway for PCBs found in the snowmelt pond sediment is broken
by constructing the wetland in this off-base location.
The impacts from seep water are isolated, thus protecting wildlife and
plants. Collecting the water protects surface water bodies. This action
prevents the spread of contaminants on the land surface.
Shallow contaminated soil source areas potentially contributing
contaminants to ground water are removed.
Institutional controls will eliminate risk to human health by ensuring
that contaminated upper aquifer groundwater will not be consumed by
people until cleanup levels (MCLs for benzene and TCE, see Section
3.3) are met.
ElmenJorf AFB OU 5 Record of Decision 5-1
-------
The remedy is appropriate because fuel pipes are regularly maintained.
The pipelines and tanks are hydrostatically tested annually and pressure
tested under higher pressures triannually.
Specific components of the selected remedy are illustrated in Figure 5-1 and
consist of the following:
Groundwater
(1) Institutional controls on land use and water use restrictions will restrict
access to the contaminated groundwater throughout OU 5 until cleanup
levels listed in Table 3-6 have been achieved.
(2) Groundwater will be monitored to estimate the rate of natural
attenuation, to provide an early warning of potential off-site
contaminant migration, and to ensure protection of human health and
the environment.
Seeps
(1) . Seep water will be passively extracted from areas of contamination
along the western and central bluffs. The water will be drained to the
constructed wetland where enhanced natural chemical, physical and
biological processes will reduce contamination to below cleanup levels.
The location of the constructed wetland will be determined in the
Remedial Design phase. If it is located at the snowmelt pond, the
recommended site, a layer of permeable material will be placed over
pond sediment. Baffles would be installed to control the flow of water
and maintain retention time and native vegetation will be put in place to
help degrade contaminants.
(2) Water will be monitored near the exit of the constructed wetland to
ensure that the wetland is reducing concentrations to below the Alaska
water quality standards specified in Table 3-6.
(3) Natural attenuation will be relied upon to treat seep and surface water
in the beaver pond wetland area.
Elmendorf AFB OU 5 Record of Decision 5-2
-------
SOUTH
NOT TO SCALE
T,
C3
Vi
Monitoring and
Natural Attenuation
for Groundwater
NORTH
Excavate Contaminated
Soil and Biopile
Deed Restrictions/
Institutional Controls
for Contaminated Areas
Horizontal
Drain Wells
Contaminated
Groundwater
Seeps Collected and Discharged to
Constructed Wetland in Snowmelt Pond
Isolate Impacted Sediment
in Constructed Wetland
Monitoring and Natural Attenuation
for Beaver Pond Wetlands
Ship
Creek
Figure 5-1. Selected Remedy
-------
(4) Water from the seeps and beaver pond wetland areas will be monitored
to estimate the rate of natural attenuation and make sure that
contamination does not reach Ship Creek.
Soil
(1) Approximately 3,000 cubic yards of contamination soil near the ground
surface will be excavated in the western and central areas and
transported to an on-base treatment facility. The treatment facility will
be selected in the Remedial Design phase; biopiling is currently being
considered.
(2) Soil removed from the areas of contamination will be replaced by
treated soil or clean fill from on base.
(3) Soil in the treatment facility will be monitored for contaminant
concentration reduction. When the concentrations are below cleanup
levels, the soil will be removed and used as fill around the base.
The remedy will be implemented after the Remedial Design has been
completed. The Remedial Design is currently in progress. It is expected that the remedy
will be implemented for 30 years, or until cleanup levels have been achieved. The actual
time frame for remediation is not known but the groundwater model predicts cleanup levels
will be achieved in 10 to 15 years. A 30-year planning horizon specified in U.S. EPA
guidance documents is being used. Monitoring data will be regularly reviewed to assess the
progress made by the selected remedy toward the cleanup levels. If problems are identified,
further remedial action will be considered. The public, the State of Alaska, and the U.S.
EPA will be consulted before further remedial actions are chosen.
Because the remedy will result in hazardous substances remaining on-site
above health based levels, a review will be conducted within five years after commencement
of remedial action. The review will ensure that the remedy continues to provide adequate
protection of human health and the environment.
Elmendorf AFB OU 5 Record of Decision 5-4
-------
5.1 Statutory Determinations
The selected remedy satisfies the requirements under Section 121 of CERCLA
to:
Protect human health and the environment;
Comply with ARARs;
Be cost effective; and
Utilize permanent solutions and alternative treatment technologies to the
maximum extent practicable.
5.1.1 Protective of Human Health and the Environment
The selected remedy is protective of human health and the environment. The
current points of exposure include surface soil, seeps, surface water, and sediment.
Treatment will eliminate contamination in surface soil and seeps. An additional benefit of
constructing the wetland in the snowmelt pond is that doing so would protect environmental
receptors by isolating PCBs in the sediments. Natural attenuation will treat the beaver pond
wetland area surface water. The Beaver Pond study showed natural attenuation would be
effective and any other treatment method would pose a significant threat of doing more harm
than good to the wetland environment.
There are no direct current receptors of groundwater in OU 5. Institutional .
controls will eliminate the risk to human health by ensuring that contaminated upper aquifer
groundwater will not be consumed by people until cleanup levels (MCLs for benzene and
TCE) are met. The time required to achieve MCLs is not known, but could be as short as
10 to 15 years based on the groundwater model. The three dimensional model of
contaminant flow at Elmendorf AFB showed that conditions are not expected to degrade at
OU 5 from sources within the OU and from sources upgradient. Over time, conditions will
improve and the model predicts that cleanup objectives can be met by natural attenuation
Elmendorf AFB OU 5 Record of Decision 5-5
-------
processes. Therefore, the model further substantiates that the selected alternative is
protective of human health and the environment. A remediation period of 10 to 15 years is
reasonable given current land use at the site.
5.1.2 Applicable or Relevant and Appropriate Requirements (ARARs)
Chemical-Specific ARARChemical-specific cleanup levels for OU 5 are
identified in Table 5-1. The Maximum Contaminant Levels (MCLs) established for drinking
water under State and Federal laws are relevant and appropriate to groundwater contaminants
of concern at OU 5 as a chemical-specific regulation. For petroleum contaminated soil that
will be removed and remediated, it is relevant and appropriate to apply soil cleanup level C
from Table D of 18 Alaska Administrative Code (AAC) 78.315.
Location-Specific ARARsRequirements which must be met due to the
location of the contamination and remedial actions are identified in Table 5-2. For OU 5
there are location-specific requirements for the wetland areas between the bluffs and Ship
Creek. Current studies indicate that portions of OU 5 between the bluffs and Ship Creek
meet the legal criteria for waters of the United States under 33 CFR Part 328.3. Although
formal permits are not required, the substantive requirements under the Clean Water Act
Section 404 are applicable.
Action-Specific ARARsThe selected remedy will comply with those ARARs
applicable to construction of the wetlands and extraction system and to the excavation of the
contaminated soil. Complying with the substantive requirements of National Pollution
Discharge Elimination System (NPDES) and Alaska wastewater provisions will be necessary
to allow water treated by the constructed wetlands to discharge into a drainage ditch
Action-specific ARARs are shown in Tables 5-3 and 5-4. Treated water discharged from
wetlands into Alaska surface waters will be controlled to ensure that the quality of the
receiving waters meets the organic standards for fresh water set forth under 18 AAC 70.020.
Groundwater and groundwater seeps located at OU 5 contain naturally occurring high
Elmendorf AFB OU 5 Record of Decision 5-6
-------
g.
o
n
'CD
O
o
a
o
Table 5-1
Chemical-Specific Applicable or Relevant and Appropriate Requirements
Contaminant
Maximum Concentration
Cleanup Level
Established by ARAR
" . '-' " ': ' '-.'. .: ' ::":''' '. . " ". ..'
;;- :-..-.-. . ; :- - ; ; . T .; .'---.. ..:!" ' " . :.
-.". ' ' ''V'. '- '.':'' '-' -' '"jSSx .-:'' : ';- .-.' -.:.;" "J
; ,:; -:'-;-.; ".;.;. . . Source of Requirement : ; : -,';
Groundwater
TCE
Benzene
TFH Diesel
TFH-Gas
52 /tg/L
8.5 /xg/L
290 ligIL
700 ng/L
5/xg/L
5/ig/L
10 Mg/L
10/ig/L
MCLa
MCLa
Alaska Water Quality Standards'5
Alaska Water Quality Standardsb
Surface Water
Sheen
TFH-Gas
JP-4
Sheens exists
400 ng/L
770 /*g/L
No sheen
10 /zg/L
10 //g/L
Alaska Water Quality Standards'5
Alaska Water Quality Standards'5
Alaska Water Quality Standards'5
Soil
TFH-Diescl
l,160mg/kg
1 ,000 mg/kg
Alaska Cleanup Matrix Level Cc
a 40 CFR Part 131, and 18 ACC Chapter 70.0lOa and d, 70.015 through 70.110. 18 AAC 80.070.
b 18 AAC 70.020.
c 18 AAC 78.315.
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Table 5-2
Location-Specific ARARs
Statutory,
Regulatory Basis
Resource
Conservation and
Recovery Act
Clean Water Act,
Section 404
Citation
40 CFR Sec. 264.18
18 AAC Sec. 63.040
33 USC 1251 et seq. Sec. 404
40 CFR Pan 230
33 CFR Parts 320-330
Description
Prohibits or restricts siting of hazardous waste
management units in certain sensitive areas (100-
year floodplain, active seismic area, wetlands).
Prohibits discharge of dredged or fill material into
wetlands without a permit.
Elmendorf AFB OU 5 Record of Decision
5-8
-------
Table 5-3
o.
a
s
o
Action-Specific Federal ARARs
Operable Unit 5
Elmendorf Air Force Base, Alaska
c.
o
1
D
Standard, Requirement, Criteria, or Limitation
Citation
Description
Comments/
Applicability
Clean Water Act
EPA-Administered Permit Programs: The
National Pollutant Discharge Elimination
System
Criteria and Standards for the National
Pollutant Discharge Elimination System
33 USC Sec. 1251-1376
40 CFR Part 122
40 CFR Part 125
Requirements for the discharge of
pollutants from any point source into
waters of the U.S. (surface waters)
Provides discharge criteria, chemical
standards, and permit forms for
existing industrial operations.
Applicable if remedial
action requires outfall
discharge
Applicable to remedial
actions which cause
discharge to waters of
the U.S.
Occupational Safety and Health Act of 1970
Occupational Safety and Health Standards
Safety and Health Regulations for .
Construction
Safety and Health Standards for Federal
Service Contracts
29 USC Sec. 657 and 667
29 CFR Part 1910
29 CFR Part 1926
29 CFR Part 1925
Sets standards for safety in the work
environment.
Sets standards for safety in the
construction work environment.
States that safety and health
standards are applicable to work
performed under Federal Service
Contracts.
Applicable to all
remedial actions
Clean Air Act
National Primary and Secondary Ambient Air
Quality Standards
40 CFR Part 50
Establishes standards for ambient air
quality to protect public health and
welfare.
-------
i
g.
o
3,
>
3
o
8
o
a
Table 5-4
Action-Specific State ARARs and TBCs
Operable Unit 5
Elmendorf Air Force Base, Alaska
Standard, Requirement, Criicria',>:pr
Limitation :
Alaska Air Quality Control Regulations
Alaska Wastewater Disposal Regulations
Alaska Water Quality Use Classes and Criteria
Citation
18 AACCh. 50
18 AAC 72.500 - 72.600
18 AAC 70.020
Description
Establishes emission standards for classes of air pollution sources.
Provides for disposal of nondomestic wastewater into or onto the land,
surface water, or groundwater.
Provides water quality standards for freshwater uses.
-------
background levels of inorganic substances. In determining compliance with NPDES and
Alaska Wastewater provisions, additional treatment will not be required to reduce
concentration in the effluent below the background concentrations set forth in Table 5-5.
5.1.3 Cost Effectiveness
The remedy is the most cost effective of the alternatives because it affords
overall effectiveness proportional to its costs. The additional protection that can be achieved
by actively treating groundwater in Alternatives 3 and 4 provides only marginal increases in
protection of human health and the environment with a cost several times higher than the
selected remedy.
5.1.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
to the Maximum Extent Practicable
The U.S. Air Force, the State of Alaska, and EPA have determined that the
selected remedy represents the maximum extent to which permanent solutions and treatment
technologies can be used in a cost-effective manner at OU 5. Of those alternatives that are
protective of human health and the environment and comply with ARARs, the U.S. Air
Force, the State of Alaska, and EPA have determined that the selected remedy provides the
best balance of tradeoffs in terms of long-term effectiveness and permanence, reduction in
toxicity, mobility, or volume achieved through treatment, short-term effectiveness,
implementability, cost (as discussed in the preceding section), and the statutory preference
for treatment as a principal element and considering State and community acceptance.
All alternatives would use readily available technologies and would be feasible
to construct. Alternatives 1 and 2 would be readily implementable; they require no
additional remedial action beyond construction of an engineered wetland. The technologies
involved in Alternatives 3 are effective and use treatment technologies, but are less
implementable due to environment impacts caused by the alternatives.
Elmendorf AFB OU 5 Record of Decision 5-11
-------
Table 5-5
Maximum Allowable Effluent Discharge Based on Background
Concentrations of Metals in Groundwater
^P4^ ; ' ,.. ..'. ;,.:,;: ..,' .^
Antimony
Arsenic
Beryllium
Cadmium
Chromium
Copper
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Thallium
Zinc
-|^ii;li|i;Si^^noebtration
Sl:rSSSSmg'L) ,,-,.,,
0.05
0.1
0.01
0.005
0.05
0.2
0.5
30
0.005
0.2
0.1
0.01
0.2
0.5
Elmendorf AFB OU 5 Draft Record of Decision
5-12
-------
The most decisive factors in the selection decision were long-term
effectiveness and implementability. Alternative 2 provides the best option for cost effective
and practical remediation of OU 5, because the benzene and TCE concentrations will return
to background conditions in time. Alternatives 3 and 4 would reduce the concentrations of
these compounds in the aquifer; however, given the fragile nature of the geochemical
environment, Alternatives 3 and 4 present considerable risk of damaging the natural wetlands
in OU 5. Active extraction and air sparging will affect the water chemistry and water
balance of the wetlands, most likely negatively impacting the habitat in the wetlands.
5.1.5 Preference for Treatment as a Principal Element
The selected remedy satisfies this statutory preference by using a constructed
wetland to remediate seeps and by on-base treatment of contaminated soils. Because of the
substantial additional cost of actively treating groundwater, its potential negative effects on
OU 5 hydrology, and the fact that there are no current receptors of groundwater, institutional
controls and monitoring are a better way of addressing groundwater contamination than
active treatment. Natural attenuation and isolation are used in areas where active treatment is
impractical.
5.2 Documentation of Significant Changes
The selected remedy was the preferred alternative presented in the proposed
plan. No significant changes have been made.
ElmemJorf AFB OU 5 Record of Decision 5-13
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PART ffl. RESPONSIVENESS SUMMARY
Public Input in the QU 5 Selected Remedy
The primary avenues of public input have been through the Proposed Plan and
public comment period. The Proposed Plan for OU 5 was issued to the public on 6 June
1994. This began a public comment period that ended on 6 July 1994. To encourage public
comment, the USAF inserted a pre-addressed, written comment form in distributed copies of
the Proposed Plan. The comment forms were also distributed at the 23 June 1994 public
meeting, held at the Federal Building in Anchorage.
The public meeting to receive comments on the Proposed Plan was attended by
26 people including nine community members. Oral comments were received from two
people: one representative from Physicians for Social Responsibility, and one citizen
representing himself. Following the public meeting, and prior to the conclusion of the public
comment period, written comments were submitted by four individuals.
All comments received are documented in the administrative record file for the
site. A transcript of the public meeting is available for public review at the site information
repositories. The repositories are located at the Bureau of Land Management's Alaska
Resources Library and the University of Alaska at Anchorage's Consortium Library. Public
comments, relevant to OU 5 and/or the environmental restoration program at Elmendorf, are
presented below and have been paraphrased for greater clarity. This ROD is based on the
documents in the Administrative Record and comments received from the public.
Response to ruoiic Comments
Public Comment 1: There was a concern that biopile technology and intrinsic remediation
may not work in this climate.
Elmendorf AFB OU 5 Record of Decision 6-1
-------
USAF Response: A study by Cold Regions Research Labs indicates that biopile
technology will work in this climate. ADEC has observed a number
of bioremediation projects in the Anchorage area which have been
effective at remediating petroleum-contaminated sites. Some
bioremediation projects in the Anchorage area have achieved ADEC
Alaska Cleanup Matrix Level A cleanup standards for petroleum-
contaminated soils. Level A cleanup standards require restoring the
formerly contaminated soil to a point where the soil can be reused
without any restrictions, limitations, or potential harmful effects to
human health and the environment.
The Air Force Center for Environmental Excellence and the EPA's
Kerr Laboratory are cooperatively conducting a treatability study to
validate intrinsic remediation at OU 5. If the ongoing treatability
study does not validate the feasibility of intrinsic remediation, then a
more active remedial action will be implemented.
Also, a detailed intrinsic remediation study on the beaver pond
wetland area was done in 1993 to determine if natural physical,
chemical, and biological processes destroy the contaminants and clean
up the environment. The study at the beaver pond did show that
intrinsic remediation is working. There are high levels of
contaminants at the back of the pond near where groundwater
discharges into the pond. No contaminants were detected in the water
leaving the pond. The study concludes that microorganisms play a
cr:*1""1 role in contamination breakdown and reduction.
To determine if a plume contaminated primarily with fuel products
and, in particular, benzene would naturally degrade in this climate, a
mathematical model was used to estimate migration and breakdown of
Elmendorf AFB OU 5 Record of Decision 6-2
-------
contaminants. The climate was considered in choosing appropriate
model parameters, and the model results showed effective reduction of
contamination through intrinsic remediation. The proposed
alternatives also include monitoring. If the monitoring shows that our
assumptions were not correct, the proposed alternative will be
reevaluated and, if necessary, a more aggressive approach to clean up
will be taken.
Public Comment 2: Is the Base suggesting alternatives before they are proven to work?
USAF Response: The proposed plan addresses the primary components of the remedial
action; specific techniques will be developed in the remedial design.
The components of the Proposed Plan (monitoring, wetland treatment,
soil treatment, and restrictions on the use of groundwater) will meet
the remedial action objectives. If a specific design feature such as
natural attenuation does not operate as predicted, the other remedial
actions discussed in the proposed plan are contingent alternatives that
can be reevaluated in the future.
Public Comment 3: A concern was raised that since the releases occurred up to 50 years
ago and contamination is still found, that intrinsic remediation occurs
slowly.
USAF Response: The tanks and leaks were not drained of fuel product and repaired
until a few years ago. There could have been a continuous fuel leak
for some liL..: -jnd data show the plumes have not migrated far in 50
years. The limited migration suggests relatively quick and effective
natural attenuation.
Elmendorf AFB OU 5 Record of Decision 6-3
-------
Public Comment 4: Is the rate of plume migration currently being monitored?
USAF Response: Yes. The rate of migration is tracked and is well documented in a
remedial investigation report. Data and the groundwater model show
that detectable contamination does not migrate far from the source.
Public Comment 5: The USAF was asked to clarify whether intrinsic remediation means
groundwater quality is only being monitored.
USAF Response: Yes. There will be up to 19 monitoring wells in OU 5. The
monitoring will be used to document that intrinsic remediation is
remediating groundwater and that there is no threat to human health
and the environment. If the monitoring data show that cleanup levels
are not being achieved, additional remedial action may be needed and
would be coordinated through the U.S. EPA and ADEC.
Public Comment 6: When will the plumes with contamination reach Ship Creek?
USAF Response: On a site-wide basis, it does not appear that contaminants will reach
and impact Ship Creek. The model of groundwater flow and
contaminant transport showed that in the future contaminant
concentrations in groundwater will decline and that Ship Creek will
not be affected.
Public Comment 7: A concern was raised about how remedial action will be affected if
Elmendorf AFB were ,^ -Jose.
USAF Response: Before any property is conveyed outside the base, there are
procedures to make sure it's not contaminated. Before property can
be legally conveyed, all remedies necessary to protect human health
Elmendorf AFB OU 5 Record of Decision 6-4
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and the environment must be in place. In the event property is
conveyed, by law the United States must specifically retain the right
to enter the property for remediation purposes should additional
remediation activities be necessary. When a base reaches the Base
Realignment and Closure Committee, and they have decided to close
that installation, one of the first major decisions is how to clean that
property up as fast as possible to convey that property to the private
sector. At that time, more expensive alternatives that would expedite
remediation could be selected. Therefore, if the base were to close,
remedial action would continue.
Public Comment 8: Does the Proposed Plan consider the cumulative effects from the
combination of contaminants?
USAF Response: Yes. In the residential-use risk assessment scenario, the Air Force
looked at cumulative risk and made decisions on that basis, despite the
fact that the risk assessment is very conservative. The greatest
potential risk is from using the shallow aquifer. That aquifer is not
being used at the Base, so the likelihood of drinking water being
drawn from that aquifer is very unlikely.
Public Comment 9: The Proposed Plan for Remedial Action for Operable Unit 5 (OU 5)
includes a wetland planned on property owned by the Alaska Railroad
Corporation. The action could render the land permanently unusable.
USAF Response: Elmendorf AFB will be working v.-l:l. ;he Alaska Railroad Corporation
to gain access to the snowmelt pond area beneath the OU 5 bluff area
where pipes and lift stations will be located. The access agreement
will provide for monitoring for the duration of the remediation effort;
possibly up to 30 years.
Elmcndorf AFB OU 5 Record of Decision 6-5
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Public Comment 10: The comment was made that the remedial action should be
implemented cost effectively.
USAF Response: Elmendorf AFB will implement the remedial response cost effectively,
remaining in compliance with all regulatory and engineering
requirements.
Public Comment 11: In situ soil remediation using electromagnetic/radio frequency
technology has been thoroughly tested and evaluated. Could this
technique be used at OU 5?
USAF Response: The preferred remedial action was selected after a review of
technologies shown to be effective at the time the Feasibility Study
was conducted. Contaminated soil is limited to small areas with
relatively low concentrations of the contaminants of concern. Given
these conditions, and since the impacted soil is easily removed, in situ
methods of remediation did not have favorable scores in the evaluation
of alternatives.
Public Comment 12: The concern was raised that it has taken a long time for action at
OU5.
USAF Response: The evaluation of impacts and developing remedial alternatives for
OU 5 was conducted following approved U.S. EPA guidance on
conducting Remedial Investigations and Feasibility Studies. All work
and decision making was done according u, Jvj schedule and
requirements in the Federal Facilities Agree n'»e.T;i.
Elmendorf AFB OU 5 Record of Decision 6-6
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Public Comment 13: Is the lower aquifer contaminated?
USAF Response: No, wells have been installed into the lower aquifer and analytical
data have shown that the aquifer is not impacted.
Public Comment 14: Are contaminants migrating into Ship Creek and the Knik Arm?
USAF Response: Ship Creek has been sampled and data have shown that it has not been
impacted. Monitoring of Ship Creek indicates that no measurable
amounts of contaminants are migrating from OU 5 into Ship Creek
and the Knik Arm. Monitoring will continue to be conducted in the
future as part of the selected alternative. If monitoring indicates that
Ship Creek could be impacted in the future, corrective action will be
taken in cooperation with the regulatory agencies.
Public Comment 15: Will covering snowmelt pond sediment with a layer of gravel isolate
PCBs?
USAF Response: PCBs adhere strongly to sediment and have a very low solubility.
The primary transport mechanism is through sediment transport. By
covering the sediment with a layer of gravel, the transport mechanism
will no longer exist. Because of the very low solubility of PCBs, no
detectable concentrations of PCBs are expected in the water overlying
the gravel. The pond water will be monitored.
Public Comment 16: Will intrinsic remediation effectively work at OU 5?
USAF Response: Intrinsic remediation has been an effective process at the base to date.
The Beaver Pond Study (RI/FS, Appendix R) showed that the beaver
pond wetland area could effectively attenuate contaminants that enter
Elmendorf AFB OU 5 Record of Decision 6-7
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it. The contaminant plumes are relatively small and have not shown
signs of widespread migration. The intrinsic remediation alternative
for ground water is preferred because it is presently working, is shown
to be effective, and is the most cost effective alternative. The
alternative was selected after evaluating all alternatives against the
nine U.S. EPA evaluation criteria, and the alternative was found to
comply with applicable, relevant, and appropriate requirements.
Groundwater and surface water will be monitored. If the monitoring
data indicate that intrinsic remediation is riot functioning as predicted,
Elmendorf AFB will work with the regulatory agencies to take
corrective action.
Elmendorf AFB OU 5 Record of Decision 6-8
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APPENDIX A
OU 5 ADMINISTRATIVE RECORD INDEX
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Appendix A
Index to OU 5 Documents in Administrative Record
Date Submitted
7/01/94
3/04/94
11/17/93
11/17/93
11/17/93
12/08/93
6/01/94
6/03/94
5/01/94
5/01/94
Document Number
017830-018519
031679-033304
025778-025778
025779-025779
025780-025780
025788-025788
040264
040265
040268-040283
040284-040321
(confidential)
A>:;::;-.;; Title/Mjiject r;.f i-
Management Plan, Operable Unit 5, Elmendorf Air
Force Base, Alaska
Operable Unit 5 Remedial Investigation/Feasibility
Study
Letter from USAF to U.S. EPA requesting comments
on OU 5 Draft RI/FS and identification of ARARs
Letter from USAF to U.S. EPA requesting comments
on OU 5 Draft RI/FS and identification of ARARs
Letter from USAF to Alaska Department of
Environmental Conservation requesting comments on
OU 5 Draft RI/FS and identification of ARARs
Letter from Alaska Department of Environmental
Conservation requesting 20 day extension for comments
on the Draft RI/FS
News release in the Anchorage Daily News announcing
public comment period and public meeting for the OU
5 Proposed Plan
News release in the Sourdough Sentinel announcing
public comment period and public meeting for the OU
5 Proposed Plan
Elmendorf Air Force Base, OU 5, The Proposed Plan
for Remedial Action
Mailing list: May 1994 OU 5 Proposed Plan Fact
Sheet
Author
EMO/Battelle/CH2M Hill
USAF-Elmendorf AFB
Sharon Stone,
USAF-3 SPTG/CEVR
Sharon Stone,
USAF-3 SPTG/CEVR
Sharon Stone,
USAF-3 STTG/CEVR
Jennifer Roberts,
Alaska Department of
Environmental Conservation
USAF-Elmendorf AFB
USAF-Elmendorf AFB
USAF-Elmendorf AFB
USAF-Elmendorf AFB
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Appendix A
Index to OU 5 Documents in Administrative Record (Continued)
Date Submitted
12/94
11/18/94
11/17/94
12/94
Document Number
Unassigned
Unassigned
Unassigned
Unassigned
Title/Subject
Transcript of Public Meeting Written Public Comments
State Comments OU 5 ROD
U.S. EPA Comments OU 5 ROD
Ground water Modeling Report
Author
USAF-Elmendorf AFB.
ADEC
U.S. EPA .
Radian Corporation
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