PB97-964404
EPA/541/R-97/194
January 1998
EPA Superfund
Record of Decision:
F E Warren Air Force Base, OU 2
Cheyenne, WY
9/30/1997
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I. RECORD OF DECISION DECLARATION
INTERIM REMEDIAL ACTION
OPERABLE UNIT 2,
Shallow Groundwater at Spill Site 7
F.E. WARREN AIR FORCE BASE
1.0 SITE NAME AND LOCATION
The site name is F.E. Warren Air Force Base (FEW), and it is located in Cheyenne, Wyoming. This site
was placed on the National Priorities List (NPL) in February 1990. This Record of Decision (ROD)
addresses the interim remedial action (IRA) at Operable Unit (OU) 2. Shallow groundwater. The only
portion of OU2 addressed by this IRA ROD is the shallow groundwater located within the upper 15 feet
of the aquifer contaminated from Spill Site 7 (SS7). The only contaminants addressed by this IRA ROD
are trichloroethene (TCE), vinyl chloride, cis 1,2-dichloroethene. trans 1.2-dichloroethene. and total 1,2-
dichloroethene.
2.0 STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected IRA for the top 15 feet of groundwater beneath SS7 at
FEW. This IRA was chosen in accordance with Comprehensive Environmental Response, Compensation
and Liability Act (CERCLA). as amended by the Superfund Amendments and Reauthorization Act of
1986 (SARA), and the National Oil and Hazardous Substances Pollution Contingency Plan fNCP). This
decision is based on the Administrative Record for this site.
The selected IRA for OU2 at SS7 includes an IN SITU PASSIVE TREATMENT WALL. This IRA
addresses only TCE, vinyl chloride, trans-1,2-DCE, cis-l,2-DCE. and total 1,2-DCE in the upper 15 feet
of groundwater at SS7. which, in turn, should minimize flow of these contaminants from SS7 into
Diamond Creek. The United States Environmental Protection Agency (EPA) and State of Wyoming
Department of Environmental Quality (WDEQ), as oversight agencies, concur with the selected IRA.
The United States Air Force (USAF) is the lead agency for the site.
The in situ passive treatment wall will not address all of the contamination at OU2 SS7. The selected
IRA addresses only TCE and other volatile organic compounds (VOCs) in the top 15 feet of groundwater
beneath SS7. Other site contaminants detected at SS7 in shallow groundwater, other environmental
media, and the deeper portions of the aquifer, are not addressed by the selected IRA. Alternatives for a
final remedy will be proposed in a feasibility study after all Rl data are available and evaluated. The
selected IRA will not affect or interfere with other IRAs currently planned at FEW, and it will be
consistent with any future actions, to the extent possible.
3.0 ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by implementing
the IRA selected in this ROD. may present an imminent and substantial endangennent to public health.
welfare, or the environment.
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4.0 DESCRIPTION OF THE SELECTED IRA
The selected IRA for the top 15 feet of groundwater at SS7 is an IN SITU PASSIVE TREATMENT
WALL. OU2 is one of 10 OUs that will be investigated under terms of the Federal Facility Agreement
(FFA). The IN SITU PASSIVE TREATMENT WALL will address SS7 contaminants in groundwater at
and downgradient of SS7 using an iron filings passive treatment wall technology. Groundwater beneath
SS7 is only a portion of the groundwater identified for OU2. OU2 also includes facility groundwater
beneath other sites included in OU1 and also beneath sites in OUs 4, 5. 9 and 10. Groundwater beneath
these OUs will be addressed by the final OU2 remedial action.
The function of the IRA is to reduce groundwater contamination in the top 15 feet of the aquifer beneath
the SS7 site, and thereby, reduce the risks associated with exposure to contaminated groundwater.
Groundwater contaminants addressed by the IRA include trichloroethene (TCE). vinyl chloride, 1,2-
dichloroethene (total) (1,2-DCE), trans 1.2-DCE and cis-l,2-DCE. While the IRA addresses one of the
principal threats at the site (i.e.. indicator contaminants of concern [ICOCs] in the top 15 feet of
groundwater) the final remedial alternative will address remediation of other environmental media, in
addition to the remainder of groundwater. and other types of contaminants that pose an unacceptable risk
at the site.
The selected IRA will meet the remedial action objectives by directing groundwater through the in-situ
passive treatment wall. Although the selected IRA is an innovative technology, it is expected to degrade
the target contaminants to acceptable levels. The in-situ passive treatment wall is constructed of a
treatment medium that degrades ICOCs and other volatile organic compounds (VOCs) to nontoxic by-
products. ICOCs identified as posing an unacceptable risk in the top 15 feet of groundwater are TCE,
vinyl chloride, total 1.2-DCE. cis-l,2-DCE, and trans 1,2-DCE. Concentrations of ICOCs will be
permanently reduced to Safe Drinking Water Act (SDWA) maximum contaminant levels (MCLs). Thus,
groundwater contaminant concentrations are permanently reduced to acceptable levels, there are minimal
impacts to the site after construction, there are no treatment residuals, and the selected IRA is consistent
with future remedial actions planned for the remainder of OUI and OU2.
5.0 STATUTORY DETERMINATIONS
USAF has determined, with the concurrence of EPA and WDEQ. that this IRA is protective of human
health and the environment, complies with federal and state applicable or relevant and appropriate
requirements (ARARs) directly associated with this action, satisfies the requirements for an interim
measures waiver of any standards that are not addressed by this remedy and is cost effective. For the
scope of this IRA, the statutory mandate for permanence and treatment to the maximum extent
practicable is met because this IRA does use treatment and thus is in furtherance of that statutory
mandate. Because this IRA does not constitute the final remedy for OUI. SS7 or OU2, the statutory
preference for remedies that employ treatment that reduces toxicity, mobility, or volume as a principal
element (although partially addressed for groundwater contaminants) will be addressed by the final
action. Subsequent actions are planned to fully address the principal threats posed by current conditions
at OU 1. SS7 and the remainder of OU2.
CERCLA Section I21(c). 42 U.S.C. Section 962l(c). requires five-year reviews in the event that
hazardous substances, pollutants, or contaminants remain on site. USAF will conduct reviews every 5
\ears after commencement of the remedial action to ensure that the IRA continues to provide protection
of human health and the environment. Because this is an IRA ROD. review of this site and of this IRA
will be ongoing as USAF continues to develop final remedial alternatives for OL: I and OU2.
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6.0 SIGNATURE OF AGENCY ACCEPTANCE OF REMEDY (EPA)
The undersigned representative concurs \\ith the Record of Decision for the Interim Remedial Action.
Operable Unit 2: Shallow groundwater beneath Spill Site 7 at F.E. Warren Air Force Base. Wyoming.
MAX H. DODSON DATE
ASSISTANT REGIONAL ADMINISTRATOR
ECOSYSTEMS PROTECTION AND REMEDIATION
U.S. ENVIRONMENTAL PROTECTION AGENCY - REGION 8
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6.0 SIGNATURE OF AGENCY ACCEPTANCE OF REMEDY (WDEQ)
The undersigned representative concurs with the Record of Decision for the Interim Remedial Action.
Operable Unit 2: Shallow groundwater beneath Spill Site 7 at F.E. Warren Air Force Base. Wyoming.
4^4
DENNIS HAMMER ' " [/
DIRECTOR, WYOMING DEPARTMENT
OF ENV/RONMENTAL QUALITY
/[?- 10 -
DATE
J
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6.0 SIGNATURE OF AGENCY ACCEPTANCE OF REMEDY (L'SAF)
The undersigned representative concurs with the Record of Decision for the Interim Remedial Action.
Operable Unit 2: Shallow groundwater beneath Spill Site 7 at F.E. Warren Air Force Base. Wyoming.
LANCE W. LORD, LIEUTENANT GENERAL
VICE COMMANDER
AIR FORCE SPACE COMMAND
DATE
23 SfoTuit
'
1197
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II. DECISION SUMMARY FOR THE RECORD OF DECISION
INTERIM REMEDIAL ACTION AT OPERABLE UNIT 2,
Shallow Groundwater at Spill Site 7
F. E. WARREN AIR FORCE BASE
1.0 SITE NAME, LOCATION, AND DESCRIPTION
FEW occupies 5,866 acres immediately adjacent to and hydrogeologically upgradient of the west side of
the City of Cheyenne. Wyoming (Figure I). FEW was placed on the National Priorities List on
February 21, 1990. Historically. FEW has served a number of military functions, including cavalry
outpost, quartermaster depot, and intercontinental ballistic missile (ICBM) operations base. Operations
began at the U.S. Army outpost named Fort D.A. Russell in 1867. The name was changed to Fort F.E.
Warren in 1930. The Fort was a major training facility during and after World War II. Fort F.E. Warren
was transferred to the newly formed U.S. Air Force in 1947. FEW underwent extensive renovation after
World War II. The majority of the Army training facilities were torn down and not replaced.
Construction since that time has centered on facilities for USAF operations. Beginning in 1958. FEW
became a Strategic Air Command base. Since then, FEW has served as an operations center for (1) the
Atlas ICBM, (2) the Minuteman I and III, and (3) the Peacekeeper (MX) ICBMs. FEW was part of Air
Combat Command from 1992 to 1993, and in July 1993. became part of Space Command.
FEW is bordered by agricultural land and rural or suburban residential areas. FEW contains 831
residential housing units and several unaccompanied personnel housing units (barracks), along with the
services required by residents. The nearest residences to SS7 are off-base, approximately 0.5 miles to the
west, upgradient from the site. SS7 is in an area of gently rolling terrain overlooking a relatively sharp
drop in elevation lo Diamond Creek. SS7 is located within a stream meander, and the terrain generally
slopes to the northeast toward Diamond Creek. Building 1294 is at the topographic high point at the site.
The location of SS7 is shown on Figure 2.
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
On September 26. 1991, a Federal Facility Agreement (FFA) was signed among USAF, EPA. and
WDEQ. The FFA is required by Section 120 of CERCLA. The FFA provides the framework for EPA
and WDEQ oversight of continuing remedial investigations at FEW and further identifies USAF
investigation activities and schedules. USAF provides documents to EPA and WDEQ for review and
concurrence, in accordance with the FFA. USAF is the lead agency for implementing CERCLA
requirements at FEW.
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FIGURE 1
Location Map
F.E. Warren AFB
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FIGURE 2
Operable Unit 2
Spill Site No. 7
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In April 1995. USAF implemented a treatability study at SS7. The treatability study was designed to
remove TCE and its degradation products from groundwater through the use of a collection and treatment
system. The collection s\stem consisted of horizontal drains installed below the ground surface: air-
stripping towers to remove TCE and its degradation products from the groundwater; and a granular-
activated-carbon filter to treat the gases from the air stripping towers. The treated groundwater was
reinjected into the aquifer upgradient of the collection drains. The treatability study was operated for a
period of 12 months. Although TCE concentrations in some monitor wells within the influence of the
treatability study showed decreases. TCE concentrations between the collector drains and Diamond
Creek remained elevated and actually increased. Additionally, contaminated groundwater was bypassing
the collector drains and reaching Diamond Creek.
OU2 groundwater beneath and downgradient of SS7 contains significant concentrations of TCE and its
degradation products. Through the results of the completed remedial investigation (Rl) activities. USAF
has determined the grease trap at SS7 was a source of the TCE groundwater contamination. To control
TCE contamination in shallow groundwater beneath and downgradient of SS7, an IRA has been selected.
As remedial investigations are completed, remedies will be selected for contaminated groundwater at
F.E. Warren Air Force Base.
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
USAF has prepared and implemented a community relations plan (CRP) in accordance with CERCLA
requirements and the FFA. The CRP describes community involvement activities that USAF will
undertake during remedial activities at FEW. USAF has followed the requirements of the CRP,
including issuing periodic fact sheets, holding public meetings, and providing the opportunity for public
comment throughout the IRA process.
The Administrative Record has been filed at two locations: FEW and the Laramie County Public
Library. USAF has prepared and distributed fact sheets to all persons or groups identified on the CRP
mailing list. Currently, the mailing list has approximately 550 listings.
The announcement of commencement of the public comment period and public meeting for this ROD
was made on July 13, 1997 through notices in the Wyoming Tribune-Eagle and in the Casper Star-
Tribune. The original public comment period was July 26. 1997 through August 25, 1997. A public
meeting to discuss this ROD was held in Cheyenne, Wyoming on August 19. 1997.
Due to a delay in distribution of the Proposed Plan to persons or groups on the mailing list. USAF
extended the closure of the original public comment period from August 25. 1997 to September 9. 1997.
An additional public meeting uas held in Cheyenne. Wyoming on September 4. 1997. The extension of
the public comment period and the additional public meeting were announced on August 24. 1997
through notices in the Wyoming Tribune-Eagle and in the Casper Star-Tribune. Moreover, a notice was
mailed to persons or groups on the mailing list in order to announce the extension of the public comment
period and the additional public meeting.
In addition to the newspaper notices. USAF issued press releases, and an article appeared in the FEW
Sentinel newspaper on August 29. 1997. An article describing the original public meeting was published
in the Casper Star-Tribune on August 20. 1997.
Official transcripts of the public meetings were prepared and placed in the Administrative Record.
Responses to all comments on the Proposed Plan are presented in the Responsiveness Summary of this
ROD.
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4.0 SCOPE AND ROLE OF OPERABLE UNIT
Groundwater contamination from SS7 \\iil be addressed under OU2. The selected IRA for OU2 at SS7 is
an action to treat contaminated groundwater by installing an in situ passive treatment wall. OU2 is one
often operable units that will be addressed under the terms of the FFA. The operable units identified at
FEW are:
OU1 Spill Sites 1 through 7
OU2 Facility Groundwater, with the exception of groundwater at OUs 3, 6. 7. and 8
OU3 Landfills 3 and 6
OU4 Acid Dry Wells
OU5 Fire Protection Training Area 2
OU6 Opening Burning/Open Detonation Area
OU7 Firing Ranges
OU8 Landfill 5
OU9 Landfills 2 and 4
OU10 Landfill 7 and Fire Protection Training Area No. 1.
The groundwater contamination associated with OUs 3. 6, 7, and 8 will be investigated and remediated as
part of those OUs, separate from OU2. All of the investigations are being conducted in accordance with
the FFA. It is anticipated that the final remedial action ROD for OU2 will be issued after the Rl has been
completed for the other OUs.
The in situ passive treatment wall will not address all of the contamination at OU2 or at OU1, SS7. The
selected IRA addresses only TCE and other volatile organic compounds (VOCs) in the top 15 feet of
groundwater beneath SS7. Other contamination detected at SS7 is not addressed by the selected IRA.
Alternatives for a final remedy will be proposed in a feasibility study after all RI data are available and
evaluated. The selected IRA will not affect or interfere with other IRAs currently planned at FEW, and it
will be consistent with any future actions, to the extent possible.
The purpose of this IRA is to:
• Minimize the potential for ingestion, inhalation, and dermal exposure to groundwater ICOCs by
reducing levels to MCLs in the first 15 feet of the water table.
• Minimize contaminant loading to Diamond Creek from the SS7 shallow groundwater by reducing
groundwater ICOC levels to MCLs in the first 15 feet of the aquifer.
Descriptions of remedies selected for other FEW sites are described in the Administrative Record.
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5.0 SITE CHARACTERISTICS
The primary source of groundwater contamination at SS7 is the former grease trap that was located about
150 feet northeast of Building 1294.
Samples of soils, groundwater. and surface water have been collected from the site.
Groundwater has been shown to be contaminated by various organic contaminants but
predominantly by TCE and cis-1.2-DCE. Groundwater samples from 26 monitor wells at SS7
were collected and analyzed during September and October 1992 and August and September
1993 for the OU1 Rl. The groundwater samples were analyzed for VOCs. semivolatile organic
compounds (SVOCs), and metals. 1,2-Dichloroethene (1,2-DCE) was detected in 1 of 29
samples. TCE was detected in 19 of 29 samples collected at concentrations ranging from 1.0 to
9,900 micrograms per liter (ug/L). The highest TCE concentration was detected in a monitor
well near the former location of the grease trap. Based on laboratory analytical results, the
highest TCE concentration in groundwater at SS7 was detected in MW069 at 12.000 ug/L in
August 1993.
Collection and analyses of samples from Spill Site 7 have been conducted on an on-going basis. The
results are presented in the Focused Remedial Investigation for Operable Unit 2: Spill Site 7 at F.E.
Warren Air Force Base. Wyoming; the Remedial Investigation for Operable Unit I at F.E. Warren Air
Force Base. Wyoming; the Spill Site 7 Final Treatabilitv Study Report. F.E. Warren Air Force Base.
Wyoming; the Spill Site 7 Shutdown Monitoring (9/18/96, 10/2/96 and 10/3/96); and the Spill Site 7 -
Field Activities Report Surface Water Sampling (4/17/97 and 6/16/97). These reports may be found in
the Administrative Record.
6.0 SUMMARY OF SITE RISKS
A streamlined risk assessment (SRA) was prepared to characterize the potential human health exposure
and risks, under baseline conditions, associated with ICOCs in groundwater at SS7. An ecological SRA
was not performed for SS7. The following paragraphs describe the SRA calculations and input criteria.
Cancer potency factors (CPFs) have been developed by EPA for the purpose of estimating lifetime cancer
risks associated with exposure to potentially carcinogenic chemicals. CPFs are expressed in units of
mg/kg-day"1 and are multiplied by the estimated intake of a potential carcinogen (in mg/kg-day) to
provide an upper-bound estimate of the excess lifetime cancer risk associated with exposure at that intake
level. The term "upper bound" reflects the conservative estimate of the risks calculated from the CPF.
Use of this approach makes underestimation of the actual cancer risk highly unlikeK. CPFs are derived
from the results of human epidemiological studies or chronic animal bioassays to which animal-to-human
extrapolation and uncertainty factors have been applied.
Reference doses (RfDs) have been developed by F.PA for indicating the potential for adverse health
effects from exposure to chemicals exhibiting noncarcinogenic effects. RfDs are expressed in mg/kg-day
and are estimates of lifetime daily exposure levels for humans, including sensitive individuals. Estimated
intakes of chemicals from environmental media (i.e.. the amount of a chemical ingested from
contaminated drinking water) can be compared to the RfD. RfDs are derived from human
epidemiological studies or animal studies to which uncertainty factors have been applied (e.g.. to account
for the use of animal data to predict effects on humans). These uncertainty factors help ensure that the
RfDs \\ill not underestimate the potential for adverse noncarcinogenic effects to occur.
Groundwater ICOCs included in the SS7 SRA were selected by USAF, VVDEQ and EPA. Contaminants
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selected as ICOCs \\ere the most likely to present unacceptable risks to human health and the
environment at present concentrations. The ICOCs for the SS7 SRA included TCE: 1.2-DCE (total):
isomers of 1.2-DCE. including cis and trans 1.2-DCE: and vinyl chloride. The only potential exposure
pathways characterized by the land-use scenario for future adult and child residents include ingestion and
dermal contact with contaminated groundvvater and inhalation of volatile chemicals. The exposure
scenarios considered in the SRA were the future child and future adult residents. The residential risk
assessment scenario is the most conservative risk assessment scenario, and there are no current
residential areas or current plans for creation of any residential areas at or near SS7.
Lifetime cancer risks resulting from exposures to contaminants are determined by multiplying the intake
level with the CPF. These risks are probabilities that are generally expressed in scientific notation (e.g.,
1x10' or I.OE-6). An excess lifetime cancer risk of l.OE-06 indicates that, as a plausible upper bound.
an individual has a one in a million chance of developing cancer as a result of site-related exposure to a
carcinogen over a 70-year lifetime under the specific exposure conditions at a site.
Potential concern for noncarcinogenic effects of a single contaminant in a single medium is expressed as
the hazard quotient. The hazard quotient is the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminant's reference dose. By adding the hazard
quotients for all contaminants within the groundwater medium to which a given future population may
reasonably be exposed, the hazard index can be generated. The hazard index provides a useful reference
point for gauging the potential significance of multiple contaminant exposures to groundwater at SS7.
Contaminant-specific preliminary remediation goals (PRGs) were calculated for groundwater for the
future land-use scenario using information from the toxicity assessment and risk characterization
calculations. For carcinogenic contaminants, a target risk level of l.OE-06 was used. For
noncarcinogenic contaminants, a total hazard quotient of 1.0 was used. The SRA risk characterization
compared the contaminant concentration term for each of the ICOCs with the corresponding groundwater
PRGs for each exposure scenario. Carcinogenic risks associated with TCE consistently exceeded the
target risk level. Also, hazard indices determined to indicate potential noncarcinogenic health effects
were greater than 1.0 for both TCE and 1,2-DCE.
Based on the results of the SRA, USAF determined that SS7 groundwater presents both carcinogenic and
noncarcinogenic unacceptable human health risks to future populations living at SS7. TCE presents an
unacceptable carcinogenic risk and both total 1.2-DCE and TCE present an unacceptable
noncarcinogenic risk. Risk assessment summary tables from the FS have been included as Attachment B
to this IRA ROD. To minimize these potential risks until a final remedy is developed for all of OU2. an
IRA for groundwater is necessary at SS7. The complete streamlined risk assessment is contained in
Appendix E to the Focused Remedial Investigation for Operable Unit 2: Spill Site 7 at F.E. Warren Air
Force Base. Wyoming. This report is filed with the Administrative Record.
Actual or threatened releases of hazardous substances from this site, if not addressed by implementing
the IRA selected in this ROD. may present an imminent and substantial endangerment to public health.
welfare, or the environment.
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7.0 DESCRIPTION OF ALTERNATIVES
Three alternatives have been evaluated for the IRA for OU2 at SS7. The three alternatives are
summarized in the following paragraphs. None of these three remedial alternatives are expected to be the
final remedy for OU2.
Alternative No. I is no action. Evaluation of the no-action alternative is required by the NCR to be used
as a baseline comparison for other alternatives. Under Alternative No. I. USAF would take no action at
SS7 to prevent migration or exposure to the TCE contamination.
Alternative No. 2 is an in situ passive treatment wall. This remediation technology includes a permeable
treatment wall installed vertically below ground surface and perpendicular to the direction of
groundwater flow. Segments of highly permeable material are installed adjacent to the reactive treatment
medium. As contaminated groundwater flows through the wall and into the selected treatment medium,
the contaminants are degraded to nontoxic by-products. A long-term monitoring program will be
implemented to monitor both the effectiveness of the treatment wall and groundwater movement. The
treated groundwater is expected to meet the maximum contaminant levels provided in the Safe Drinking
Water Act regulations and the Wyoming Water Quality Rules and Regulations for groundwater (Chapter
VIII) with respect to ICOCs. Soil spoils from installation of the treatment wall will require
characterization to determine if they meet the definition of a hazardous waste. If so, the soil spoils will
be managed in accordance with the Wyoming Hazardous Waste Rules and Regulations.
Alternative No. 3 includes modifications to the treatability study. The treatability study was conducted
from April, 1995 until March, 1996. The treatability study system consists of horizontal drains that
collect contaminated groundwater, an above-ground water treatment system, and injection drains to
return the treated groundwater to the aquifer. Alternative No. 3 replaces the horizontal drains with
vertical extraction wells and incorporates other modifications to treat larger volumes of groundwater.
After the groundwater is extracted, it is treated using air stripping towers that remove TCE and other
volatile organic contaminants. A long-term monitoring program will be implemented to monitor both the
effectiveness of the collection and treatment systems and groundwater movement. To the extent
hazardous waste is extracted from groundwater. air emissions from the air stripper will comply with the
requirements of the Resource Conservation and Recovery Act. Clean Air Act and Wyoming air quality
standards and regulations. Contaminant levels in treated groundwater are expected to comply with the
requirements of the Safe Drinking Water Act and Wyoming water quality rules and regulations for
groundwater (Chapter VIII) with respect to ICOCs. If the treated groundwater is discharged to an off-site
publicly owned treatment works (POTW). a discharge permit will be required: if it is discharged to on-
site surface water, the substantive requirements of a National Pollutant Discharge Elimination System
(NPDES) permit will be met.
8.0 MONITORING WELL CONSTRUCTION
The State and USAF disagree on whether USAF is required to obtain permits from the State Engineer's
Office pursuant to state Ian. whether USAF has a federal reserved water right covering groundwater at
FEW. and whether Wyoming statutes, rules, and regulations pertaining to groundwater appropriation are
ARARs. Despite these disagreements, however, the parties believe that the procedures described below
will enable USAF to appropriate uater for the required monitor wells, \\hile preserving the parties' legal
and jurisdictional positions. By employing these procedures, the parties intend to avoid the necessity for
protracted dispute resolution and/or legal action to resolve their legal and jurisdictional differences. The
parties do not anticipate that the legal and jurisdictional issues will need to be resolved in the context of
this IRA for groundwater cleanup at SS7 or in the context of the CERCLA clean-up at FEW. Consistent
with this background, the purpose of these procedures is to effectuate the parties' desire that progress at
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SS7 continue, while ensuring that the legal and jurisdictional positions of the State and USAF are
preserved in the event of a future dispute relating to appropriation of groundwater at SS7 or other
cleanup actions at FEW.
These procedures, and the reservation of jurisdictional and legal arguments, are only applicable within
the context of water appropriation incident to construction, operation, and abandonment of monitor wells
at FEW for USAF's on-base CERCLA cleanup activities. The procedures set forth herein shall not be
relied upon as precedent for any activities or water use or development outside the narrow context of the
USAF's CERCLA cleanup, unless otherwise agreed to in writing by the parties.
By employing these procedures, the parties are not waiving any arguments they may raise concerning the
legal applicability of State law permitting requirements, or the designation of State law requirements as
ARARs. In particular, but not by way of limitation, the parties each preserve their legal positions
concerning: (1) whether USAF has a federal reserved water right covering use of water at FEW; (2)
whether Wyoming Statutes and the Regulations and Instructions of the State Engineer's Office are
ARARs: and (3) whether the permitting exemption contained in Section 9621(e)( I) of CERCLA applies
to State permits for the appropriation of groundwater. In the event that a dispute or disagreement arises
between the parties in the implementation of the procedures described herein, the parties expressly agree
that any and all legal arguments and/or defenses are fully preserved and may be raised in any proceeding
relating to the disputed issue.
USAF and the State agree to the following procedures relating to the appropriation of groundwater
incident to the construction, operation, and abandonment of monitor wells at FEW during the CERCLA
cleanup:
A. Prior to the construction of any wells. USAF will complete and submit to the State Engineer's
Office, the State's standard form. "Application for Permit to Appropriate Groundwater."
B. USAF will comply with all requirements for appropriating groundwater contained in Wyoming
Statutes and Parts 2 and 3 of the Regulations and Instructions of the State Engineer. USAF
further agrees to submit a "Statement of Completion" on the standard State form, providing the
information required therein.
C. USAF maintains that in providing information to the State on the State's forms and complying
with State law procedures that it is not making application for a permit under State law, and
further, that it is not required to follow State law for the appropriation of federally reserved
groundwater. It is USAF's position that it is only providing information to the State in the most
usable and efficient format to enable the State to properly maintain its uater records system, and
cooperating with the State as a matter of comity. As provided above, by submitting information
on the State's forms and otherwise complying with State law. USAF does not waive its right to
claim that no State permit is necessary or that USAF is not bound to follow State law in
appropriating groundwater for the CERCLA cleanup at FEW.
D. The State Engineer will treat the forms and information received from USAF as a permit
application, and will issue permits in the name of USAF. The State Engineer will, in all respects.
and in the same manner as for any private water appropriator. maintain its records and administer
the permits in accordance with all applicable State law. As provided above, by following these
procedures, the State does not waive its right to claim that USAF is required to obtain State
permits and follow State law in the appropriation of groundwater at FEW.
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E. The parties agree to work in good faith to resolve any disputes or disagreements that may arise in
the implementation of these procedures.
In the event that a dispute or disagreement arises from these procedures, and the parties are unable to
resolve the matter through informal negotiation, the parties agree that an action to resolve the underlying
jurisdictional and legal issues pertinent to appropriations of groundwater at SS7 may be maintained
pursuant to the FFA. Section 962l(e)(2) of CERCLA. or through any other applicable remedy provided
for by law.
9.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
Alternative Nos. 1.2, and 3 were compared with the nine EPA criteria established to evaluate remedial
alternatives. The following paragraphs describe this evaluation.
I. Overall Protection of Human Health and the Environment. Alternative No. 1 provides no
mechanism for reducing or monitoring aquifer contaminant levels. Human health and the
environment are not protected. Alternatives No. 2 and 3 provide adequate protection by reducing
contaminant levels in groundwater to below MCLs. Alternative No. 3 requires additional
monitoring of treatment residuals before they are discharged to the Publicly Owned Treatment
Works (POTW) or Diamond Creek and the atmosphere.
No unacceptable short-term or cross-media impacts are expected for Alternative No. 2.
Treatment would be required to mitigate any potential cross-media impacts of Alternative No. 3.
No unacceptable short-term impacts are expected for Alternative No. 3.
2. Compliance with ARARs. Alternative No. I, No Action, does not comply with ARARs.
Contaminants in groundwater at SS7 will not be reduced or remediated.
Treated groundwater resulting from Alternatives No. 2 and 3 would comply with the Safe
Drinking Water Act regulations and Wyoming Water Quality Rules and Regulations. Chapter
VIII for ICOCs. Soil spoils from installation of the Alternative No. 2 treatment wall will require
characterization, as will soil spoils generated during well installation associated with Alternative
No. 3. to determine if they meet the definition of a hazardous waste. If so, the soil spoils will be
managed in accordance with Wyoming Hazardous Waste Rules and Regulations.
Alternative No. 3 would require a discharge permit if treated groundwater is discharged to an off-
site publicly owned treatment works (POTW), or the substantive requirements of an NPDES
permit will be met if treated groundwater is discharged to surface water. Alternative No. 2 does
not generate effluent that requires discharge to a POTW or the environment. Alternative No. 3
would generate air emissions from the air stripper that will comply with requirements of 40 CFR
Part 264. Subpart AA. Process Vents, the Clean Air Act. and Wyoming Air Quality Standards
and Regulations. Section 21. The complete list of ARARs for the IRA at SS7 is included as
Attachment A.
3. Long-Term Effectiveness and Permanence. Alternative No. 1 does not provide an effective
long-term remedy for groundwater. because it does not manage or reduce risk to groundwater.
Alternatives No. 2 and 3 meet remedial action objectives and use adequate and reliable controls
to evaluate the system performance. Alternative No. 2 does not produce treatment residuals. No
operation and maintenance activities other than periodic groundwater and surface water
monitoring would be required for Alternative No. 2. Alternative No. 3 would require routine
monitoring to ensure compliance with discharge permits or substantive NPDES requirements.
I''.warren .ou2 ss7dccdi>cs'ss7lVnd.di)c „ , ,.
Page 15
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Alternative No. 3 would further require extensive operation and maintenance activities. Controls
and wall width would be used to manage the treatment residuals and untreated waste from
Alternative No. 2. The effluent water on the downgradient side of the treatment wall would be
sampled regularly to ensure that contaminant concentrations remain at or below MCLs.
Alternatives No. 2 and No. 3 provide an effective and permanent long-term remedial action.
4. Reduction of Toxicirv. Mobility, and Volume through Treatment. Alternative No. 1 would
not reduce toxicity, mobility, and volume of contaminants in groundwater at SS7. Given
sufficient time, both Alternatives No. 2 and 3 could reduce ICOC levels to their respective
MCLs. Degradation products may be present downgradient of Alternative No. 2, but are
anticipated to be at concentrations below regulatory limits. Degradation products resulting from
Alternative No. 2 would not pose an unacceptable risk to human health and the environment.
The chemical treatment process associated with Alternative No. 2 uses destructive techniques to
reduce contaminant concentrations, and the reductions are permanent. Alternative No. 3 uses
physical separation techniques to reduce contaminants, and therefore, treatment residuals are
produced. Treatment residuals from Alternative No. 3 would require additional management and
disposal, in accordance with regulatory requirements.
Alternative No. 2 reduces mobility, toxicity. and volume of contaminants. Alternative No. 3
would reduce mobility and volume but not toxicity of contaminants. Alternative No. 2 provides
the most effective treatment for SS7 ICOCs in the upper 15 feet of the groundwater aquifer.
5. Short-Term Effectiveness. Alternative No. 1 is not effective in the short-term because no
action would be taken. Alternatives 2 and 3 will be effective immediately upon completion of
construction in that they will begin to reduce contamination in groundwater and reduce the flow
of contaminated groundwater from the site. Alternative No. 2 would require approximately 39
years to meet the remedial action objective cleanup goals. Alternative No. 3 would require
approximately 30 years to meet the remedial action objective cleanup goals.
Alternatives No. 2 and 3 would pose some potential environmental impacts and worker risks
during trench and monitor well installation. No increased risk to workers or the community and
no environmental impacts would occur with Alternative No. 2 after construction and
implementation. During construction of Alternatives No. 2 and 3, dust may be generated that
may pose a minor, but temporary, risk to both workers and the surrounding community. These
risks would be minimized by following health and safety procedures. Air monitoring will be
used to assess the requirement for temporary control measures during construction. Monitoring
would be performed to ensure that treated groundwater meets the cleanup goal. Monitoring
would be performed to also ensure that workers are not affected during extensive operation and
maintenance activities for Alternative No. 3.
6. Imnlementabilitv. Alternative No. I is easily implemented because no action is taken.
Alternatives 2 and 3 would be easily implemented because traditional and proven construction
technologies would be used. Neither Alternative 2 nor 3 is anticipated to be inconsistent with or
preclude implementation of subsequent remedies. The equipment, specialists, and services
required to implement a long-term monitoring program are available, and monitoring is easily
performed to measure system performance. The operation and maintenance activities necessary
for Alternative No. 3 are extensive in comparison to Alternative No. 2.
Administrative implementability concerns for Alternative No. 2 are expected to be minimal and
I::\«arremou2ss7'decdocs ss~lrod.doc p .,
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consist of coordination of the FEW engineering department and the regulatory approval of the
long-term monitoring program. Alternative No. 3 requires a POTW discharge permit or
compliance with the substantive portions of the NPDES permit regulations. There may be
administrative difficulties with obtaining a POTW discharge permit based on past performance.
Alternative No. 2 and No. 3 can be implemented at SS7 using common construction and
engineering practices. Because Alternative No. 3 may require a permit for off-site discharge of
treated water. Alternative No. 2 provides the most easily implemented remedy.
7. Cost The cost to implement Alternative No. 1 is $0. The capital cost for Alternative No. 2 is
$1.619,000. The capital cost for Alternative No.3 is $375.000. Long-term monitoring is the only
operation and maintenance cost required for Alternative No. 2 and is expected to be S85.000 for
the first year. Operation and maintenance costs for Alternative No. 3 are estimated to be
$247,000 for the first year. The total 30-year present worth for Alternative No. 2 is $2,131,000.
The total 30-year present worth for Alternative No. 3 is $2,639.000. Because of fewer operation
and maintenance requirements. Alternative No. 2, compared with Alternative No. 3 (which
achieves the same cleanup standard), has the lowest 30-year cost.
8. State/Support Agency Acceptance. EPA concurs with the selection of Alternative No. 2 for the
groundwater IRA at SS7. The State of Wyoming, Department of Environmental Quality agrees
with the Air Force's selection of the iron filings wall as the preferred alternative to be used for
shallow groundwater treatment at Spill Site 7. The agency has expressed some concerns
regarding the proposed configuration for the wall and its ability to treat shallow groundwater
contamination across the site, particularly groundwater associated with the source area for much
of the contamination noted at the site. It is the state's position that groundwater flow at the site.
especially relative to the area where the grease trap was located, has not been well characterized
and appears to be moving in a radial direction which would result in incomplete interception by
the treatment wall. The wall is planned to be located on the northern portion of the site, as
proposed in the FS. Additionally, the state would like to see, as an immediate benefit of the
wall's installation, a decrease of discharge of contaminants to the creek such that water quality
criteria for TCE and related contaminants are met. However, it is not known at this time whether
the wall will intercept an adequate zone of groundwater to accomplish this. Additionally, data
collected to date suggests that the greater mass of contamination at the site is located deeper in
the aquifer than the wall will extend. The construction of the preferred alternative will not
preclude the incorporation, at a later date, of a remedy designed to address deeper zone
contamination. The state has agreed to the preferred alternative with the understanding that the
performance of the remedial action will be monitored to determine both the horizontal and
vertical extent of contaminant reduction resulting from the implementation of the remedy.
9. Community Acceptance. Both oral and written comments were received from the community
during the public comment period and public meeting described in Section 3.0. Based on these
comments, the general community consisting of the residents of the City of Cheyenne. Laramie
County, and FEW have not expressed any comments or concerns about the technical aspects of
the selected alternative.
10.0 THE SELECTED INTERIM REMEDIAL ACTION
Based on consideration of the requirements of CERCLA. the detailed analysis of the three remedial
alternatives, agency comments, and public comments. USAF has determined that Alternative No. 2:
INSITU PASSIVE TREATMENT WALL is the most appropriate IRA for OU2 groundwater at SS7. The
purpose of this response action is to control unacceptable carcinogenic and noncarcinogenic risks posed
I •waircn'iou2\.ss7\(kcdocs.ss7l'rod.dnc „ , -.
Pa«e 17
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by the upper 15 feet of the ground water aquifer from TCE. total 1,2-DCE. trans 1.2-DCE. cis 1.2-DCE.
and vinyl chloride and minimize contaminant loading from SS7 to Diamond Creek. This IRA does not
address the remainder of groundwater. other environmental media, or other site contaminants. The final
remedy will address all of the contaminants detected above the target risk levels. Performance standards
for the ICOCs are based on the National Primary Drinking Water Regulations that identify MCLs. The
groundwater will be treated by an iron filings passive treatment wall technology described in the Focused
FS. Based on the comparative analysis presented in Section 9.0 above. Alternative No. 2 will provide the
greatest benefits when evaluated against the nine criteria. Alternative No. 2 was selected as the IRA at
SS7 because of the following advantages:
• Low operation and maintenance requirements
• Minimal impacts to the site after construction
• No effluent, therefore no effluent discharge permits or requirements
• No treatment residuals to recycle and dispose
• Cost effectiveness.
In situ passive treatment wall technology is considered innovative; a patent for this technology has been
issued to EnviroMetals Technologies. Inc. for the reductive dephlorination of chlorinated aliphatic
hydrocarbons by zero-valent iron. Implementation of this alternative will require registration,
notification, conceptual design approval, and payment of fees to EnviroMetals Technologies. Inc. These
costs are included in the capital cost presented in Section 9.0. During the design process, the actual
length, width, and depth of the wall will be designed to optimize the treatment potential. The treatment
wall is composed of more permeable materials than the surrounding groundwater aquifer. Contaminants
passing beneath the treatment wall will not be treated.
The long-term monitoring program would assess the effectiveness of the performance of Alternative
No 2. Alternatives No. 1, 2, and 3 are described in detail in the Focused Feasibility Study. This report is
filed in the Administrative Record.
The point of compliance, to determine if the selected interim remedial action is meeting its remedial
action objectives, is established to be between Diamond Creek and the iron filings wall. Monitor wells
will be used as the point of compliance. The monitor wells will be screened to approximately between
2 feet above the water table and 2 to 2.5 feet above the base of the wall. The monitor wells will be
located downgradient of Manhole 0+00. one near either end of the wall and at intermediate locations
along the length of the wall, due to heterogeniety of the aquifer. Exact locations will be determined by
joint agreement of the EPA. WDEQ- and USAF during the design of the remedial alternative and will be
identified in a compliance monitoring plan.
Compliance monitoring will begin thirty days after installation of the iron filings wall. However, due to
the uncertainty of groundwater velocity between the iron filings wall and monitoring wells, regulatory
compliance will not be determined until stabilization of ICOC concentrations have been established
through agreement among EPA. WDEQ. and USAF.
I warren ou2 ss7\dccdocs\ss7lrod doc „ ,.,
Page 18
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Alternative No. 2 will reduce TCE. vinyl chloride, total 1.2-DCE. trans 1.2-DCE, and cis-l.2-DCE to
concentrations below the corresponding regulator, limits. These limits are presented in Table I. Limits
for the contaminants listed in Table I are based on VICLs set forth in the National Primary Drinking
Water Regulations. 40 CFR Part 141 for public drinking water systems. Although the total present worth
costs are comparable for Alternatives No. 2 and 3. Alternative No. 2 requires lower operation and
maintenance costs. Figure 3 shows the proposed location of the treatment wall.
TABLE 1
Performance Standards For ICOCs
Spill Site 7 Groundwater
ICOC
TCE
total 1.2-DCE
trans 1.2-DCE
cis- 1.2-DCE
vinyl chloride
Maximum Concentration
Detected
12.000
See 1 below
440
610
ND
Rtgalatory Limit
(IUJ/L)
5
3002
100
70
2
Notes:
Regulatory Limits arc Maximum Contaminant Levels found in 40 CFR Part 141.
The reported maximum concentrations detected are based on laboratory analytical results.
'Total 1.2-DCE was not included in groundwater analyses. Total 1.2-DCE is comprised ot"trans and cis 1.2-DCE
:WDEQ standard for mixed isomcrs of 1.2-DCE.
ug/L
Micrograms per Liter
F 'warren ou2 ss7 dccdocs.ss7lrixl.doc
Pane 19
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11.0 STATUTORY DETERMINATIONS
USAF's selected IRA for Operable Unit 2, SS7 is Alternative No. 2. The selected IRA meets the
statutory requirements of Section 121 of CERCLA. as amended by SARA. These statutory requirements
include protecting human health and the environment, complying with ARARs, assuring cost
effectiveness, using permanent solutions and alternative treatment technologies to the maximum extent
practicable, and assuring preference for treatment as a principal element. The selected IRA uses
permanent solutions and treatment technologies to the maximum extent practicable. This IRA is not
designed or expected to be the final remedy for OU2; however, the selected IRA represents the best
balance of trade offs among the two remedial alternatives with respect to pertinent criteria given the
limited scope of the action.
The selected IRA will reduce TCE and other ICOCs and VOCs in SS7 groundwater. The in situ passive
treatment wall results in permanent destruction of TCE and related compounds to allowable
concentrations. Alternative No. 2 reduces the potential for exposure to site contaminants. Installation of
the system components will cause minimal short-term effects to the community. There will be no cross-
media impacts from the installation or operation of the in situ passive treatment wall. As discussed in
Section 9.0, the selected IRA for SS7 will comply with ARARs.
The following paragraphs summarize how the selected IRA meets the statutory requirements.
Protection of Human Health and the Environment
Alternative No. 2 protects human health and the environment by passively treating the contaminated
groundwater in place via reductive dehalogenation processes as groundwater flows through the wall. The
IRA will reduce ICOC concentrations in groundwater to MCLs as groundwater flows through the wall.
Currently, groundwater at SS7 is not being used. There will be minimal risk to human health and the
environment during construction, operation, and maintenance of the treatment wall. Strict adherence to
health and safety protocols and monitoring will minimize risk from VOCS, dust, and noise. Erosion
control barriers will be used to prevent surface run-off to Diamond Creek.
Compliance with ARARs
The in situ passive treatment wall will comply with all potential action-specific and location-specific
ARARs. The treated groundwater is expected to meet MCLs set forth in the National Primary Drinking
Water Regulations for ICOCs that pose an unacceptable risk in groundwater in the upper 15 feet of the
groundwater aquifer. Pursuant to the remedial action objectives. ARARs will not be met for groundwater
located beneath the upper 15 feet of the aquifer or for contaminants other than TCE, total 1.2-DCE. trans
1,2-DCE, cis 1.2-DCE. and vinyl chloride. Soil spoils classified as hazardous waste will be managed in
accordance with the Wyoming Hazardous Waste Rules and Regulations.
Cost Effectiveness
The cost for Alternative No. 2 is slightly lower for the total 30-year present worth. The capital cost for
Alternative No. 2 is SI.619.000 and $375.000 for Alternative No. 3. Long-term monitoring is the only
operation and maintenance cost required for Alternative No. 2 and would result in a cost of S85.000 for
the first year. The operation and maintenance cost for Alternative No. 3. including long-term monitoring.
filter replacement, and GAC regeneration would be S247.000 for the first year. The total 30-year present
worth for Alternative No. 2 is S2.131.000 and S2.639.000 for Alternative No. 3. Alternative No. 2
achieves the same performance standards as Alternative No. 3. with the lowest overall cost.
F:\warren\ou2'.ss7''decduei ss/l'rod doc p -,,,
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Utilization of Permanent Solutions and Alternative Treatment Technologies to the Maximum
Extent Practicable
USAF has determined that the selected IRA represents the maximum extent to which permanent
solutions and treatment technologies can be utilized in a cost-effective manner for the interim source
control action for site-specific ICOCs in the upper 15 feet of the aquifer. Alternatives 2 and 3 are
protective of human health and the environment and comply with ARARs. USAF has determined that
Alternative No. 2 fulfills the remaining criteria (described in Section 9) better than Alternative No. 3.
The relative benefits of the selected remedy are lower operations and maintenance requirements, fewer
administrative requirements, and permanent destruction of ICOCs. The selected remedy can be
implemented using common engineering and construction practices and readily available materials. The
in situ passive treatment \vall technology is considered to be innovative. Information obtained from
monitoring during operation will be used to assess the effectiveness of the selected remedy.
Preference for Treatment as a Principal Element
The selected remedy treats contaminated groundwater by dechlorinating volatile halogenated
contaminants. Therefore, the statutory preference for remedies that employ treatment as a principal
element is satisfied.
12.0 EXPLANATION OF SIGNIFICANT CHANGES
The Proposed Plan for the ROD was released for public comment in July 1997. The preferred alternative
identified in the Proposed Plan was an in situ passive treatment wall, \\hich was determined to be
protective of human health and the environment. USAF, EPA, and WDEQ reviewed all written and
verbal comments submitted during the public comment period. There were no significant changes to the
preferred alternative.
I .vvarren'OuJ.ss7\dccdocs'.>s7lrod.di>i: .,
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III. RESPONSIVENESS SUMMARY
FOR THE RECORD OF DECISION
INTERIM REMEDIAL ACTION AT OPERABLE UNIT 2,
Shallow Groundwater at Spill Site 7
F.E. WARREN AIR FORCE BASE
INTRODUCTION
The responsiveness summary for the ROD is organized into sections as follows:
A. Overview
B. Background on Community Involvement
C. Summary of Comments Received
D. State Concerns
E. Community Relations
A. OVERVIEW
At the time of the ROD public comment period, the preferred alternative for the IRA at OU2, SS7 had
been selected by USAF, with EPA and WDEQ concurrence The preferred IRA. IN SITU PASSIVE
TREATMENT WALL, was presented in the Proposed Plan. Based on the public's response and
comments received during the public comment period for the ROD, there were no significant objections
to the preferred alternative as presented.
B. BACKGROUND ON COMMUNITY INVOLVEMENT
Community interest in CERCLA and Installation Restoration Program (IRP) activities at FEW has
fluctuated over the years since the initial record search and personnel interviews conducted for USAF in
September 1985. No specific individuals or organizations have been consistently involved over this
period, although many groups and individuals have been involved during the life of the project. There
were no concerns expressed during the SS7 Rl or on the Focused Feasibility Study before the public
comment period for the ROD.
C. SUMMARY OF COMMENTS RECEIVED
The public comment period on the Proposed Plan for the OU2, SS7 IRA at FEW was held from July 26
to September 9. 1997. Comments received during the public comment period are summarized below.
Similar comments have been combined where possible to prevent duplication of responses.
1. Is the selected interim remedial alternative the best technology available to address
specific SS7 issues at the present time?
Response. The iron filings wall is considered an innovative and relatively new
technology. This technology is well suited to the type of contaminants to be
addressed by the interim remedial action at SS7. The iron filings wall technology is
designed to reduce concentrations of chlorinated hydrocarbons found in
groundwater in the upper 15 feet of the aquifer below the SS7 area. Based on
current research and field tests, the technology appears to be very appropriate and
!•' «arrcn.ou2 si7\dcc<]ocsvss7lrod.d(X n ,-,
Paae 22
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very promising in reducing contaminants of concern at SS7. In addition, the
technology is not the final remedy for the site.
2. Will the construction of the iron filings wall create more pollution than it is
designed to correct?
Response. Although there will be some additional potential for dust, noise, and
traffic during the construction phase, measures will be taken to keep these
nuisances to a minimum. Construction will be completed only during certain hours
of the day, and dust control measures will be implemented in accordance with
federal, state, and United States Air Force (USAF) regulations. The trench for the
iron filings wall will require common construction equipment, such as track-
mounted backhoes. If no action is taken to reduce contaminant concentrations in
the upper 15 feet of the groundwater aquifer at SS7, the contaminants will continue
to migrate toward Diamond Creek. Based on the results of the streamlined risk
assessment, this unchecked release may affect any future populations living in the
SS7 area.
3. How did USAF determine that the interim remedial action at SS7 will only address
the upper 15 feet of the groundwater aquifer?
Response. The depth of 15 feet was based on initial studies indicating that the
majority of the TCE contaminated groundwater beneath SS7is between 0 and 15
feet below the groundwater surface. Because these studies have not been
completed, USAF, EPA, and WDEQ agreed to use this depth to implement an
interim remedial action at SS7. Once the studies have been completed and more
information about the characteristics of the site is known, a final remedy will be
selected to address any additional contaminants of concern in groundwater at
depths greater than 15 feet and contaminants of concern in other environmental
media.
4. Based on initial studies at the site, have the concentrations of TCE been increasing,
and if so, why?
Response. The source of the TCE, a grease trap associated with Building 1294, has
been removed; therefore, the potential for additional contamination of the
groundwater by this source has been removed. Although higher concentrations of
TCE were noted during the treatability study in downgradient monitor wells,
subsequent sampling events indicate the TCE concentrations are not increasing.
5. How much heat does it take to chemically break down TCE?
Response. The reductive dechlorination of TCE does not require an outside energy source.
The breakdown of TCE is caused by an electron transfer process.
I 'AxarrcmiHi2 •>*7 dccdocs ss7l'i
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D. STATE CONCERNS
The State of Wyoming. Department of Environmental Quality agrees with the Air Force's selection of
the iron filings wall as the preferred alternative to be used for shallow groundwater treatment at Spill
Site 7. The agency has expressed some concerns regarding the proposed configuration for the wall and
its ability to treat shallow groundwater contamination across the site, particularly groundwater associated
with the source area for much of the contamination noted at the site. It is the state's position that
groundwater flow at the site, especially relative to the area where the grease trap was located, has not
been well characterized and appears to be moving in a radial direction which would result in incomplete
interception by the treatment wall. The wall is planned to be located on the northern portion of the site.
as proposed in the FS. Additionally, the state would like to see. as an immediate benefit of the wall's
installation, a decrease of discharge of contaminants to the creek such that water quality criteria for TCE
and related contaminants are met. However, it is not known at this time whether the wall will intercept
an adequate zone of groundwater to accomplish this. Additionally, data collected to date suggests that
the greater mass of contamination at the site is located deeper in the aquifer than the wall will extend.
The construction of the preferred alternative will not preclude the incorporation, at a later date, of a
remedy designed to address deeper zone contamination. The state has agreed to the preferred alternative
with the understanding that the performance of the remedial action will be monitored to determine both
the horizontal and vertical extent of contaminant reduction resulting from the implementation of the
remedy.
The state does not agree with the methods used to estimate the length of time needed for Alternatives 2
and 3 to achieve the objectives of this interim action. Estimates suggest that cleanup may be achieved
more quickly with Alternative No. 3 than Alternative No. 2; however, there is considerable difficulty in
accurately predicting the length of time until cleanup is achieved for either option and the potential
margin of error is not necessarily consistent for both alternatives.
E. COMMUNITY RELATIONS
The Proposed Plan for the ROD was published in July 1997. Display advertisement providing notice of
the Proposed Plan and the public meeting were published on July 13, 1997 in the Wyoming Tribune-
Eagle and in the Casper Star-Tribune. A copy of the Proposed Plan was placed in the Administrative
Record on July 24, 1997. The Administrative Record locations are:
Laramie County Library 90 CESNCEVR
Reference Section Environmental Restoration Section
2800 Central Avenue 6203 15th Cavalry Avenue. Building 367
Cheyenne, WY 82001 F.E. Warren AFB. WY 82005-2788
Phone: (307)634-3561 Phone: (307)773-3468
Due to a delay in distribution of the Proposed Plan to persons or groups on the mailing list, USAF
extended the closure of the original public comment period and held an additional public meeting. The
extension of the public comment period and the additional public meeting were announced on August 24.
1997 through notices in the Wyoming Tribune-Eagle and in the Casper Star-Tribune. A copy of the
Proposed Plan was sent to all persons or groups on the mailing list.
All of the newspaper advertisements and mailings were coordinated among USAF. EPA. and WDEQ
before publication or distribution. In addition to the paid advertisements. USAF issued press releases.
An article describing the public meeting was published in the Casper Star-Tribune on August 20. 1997.
and an article appeared in the FEW Si'Hlini'l newspaper on August 29. 1997.
I::;.wanvmou2\ss7'.deod
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ATTACHMENT A
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS
INTERIM REMEDIAL ACTION
OPERABLE UNIT 2
Shallow groundwater at Spill Site 7
F.E. WARREN AIR FORCE BASE
-------
TABLE A-l
Chemical-Specific ARARs
Operable Unit 2, Spill Site 7
•<^$t«dinl,'Rt<1.lrt«Mt,>CrittH«,''-!^^
; .;1^^:.'::'- '#&iu$m£ *$*)&*•;•• \ ••
'ii. I1/- I ' '• »-*J.f . , .!;••'•.-• - .•••:• '.i •••
SAFE DRINKING WATER ACT
National Primary Drinking Water Regulations
Maximum Contaminant Level Goals
CLEAN AIR ACT
National Emission Standards for Hazardous Air
Pollutants
^*§&'*r##$fe
:-^S*«?fi«
42 USC Sec. 300G
40CFRI4l,Subparts
B and G
40CFR Hl.Subpart
F
42 USC See. 7401-
7642
40 CFR 60 and 61,
Subpart A
WYOMING ENVIRONMENTAL
QUALITY ACT
W.S. 35-11-101 to
35-11-1428
Article 2, W.S.
35-11-201
Article 3. W.S.
35-11-301
FEDERAL
-
Establish health-based standards for
the public water systems (maximum
contaminant levels)
Establish drinking water quality
goals set at levels of no known or
anticipated adverse health affects,
with an adequate margin of safety.
-
Establish regulatory standards for
specific hazardous air pollutants
STATE OF WYOMING
-
Addresses discharge or emission of
air contaminants
Prohibits certain acts without a
permit
-
No/Yes
No/Yes
-
No/Yes
-
Yes/NA
Yes/NA
TOHBaKMHHB
-
Groundwater is a potential or actual source of drinking
water. This IRA is due to groundwater contamination
from particular ICOCs. MCI ^ for these ICOCs and
contaminants or constituents that are specifically
attributable to the remedial action alternatives are
relevant and appropriate at the agreed point of
compliance.
Groundwater is a potential or actual source of drinking
water. This IRA is due to groundwater contamination.
However, there are no MCLGs that are relevant for the
ICOCs in this IRA.
-
Relevant and appropriate during construction or
maintenance of the selected IRA and operation of
Alternative No. 3, if it is the selected remedial alternative.
Applicable under those circumstances if the source meets
the definition of a major source of hazardous air
pollutants.
-
Compliance with state air quality numeric and other
substantive requirements identified as ARARs satisfies
all requirements of this provision.
Compliance with state water quality substantive
requirements (permits are not required) identified as
ARARs satisfies all requirements of this provision.
F:\warrenVou2\ss7\decdocs\ss7frod.doc
Page 26
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TABLE A-l (Continued)
Chemical-Specific ARARs
Operable Unit 2, Spill Site 7
• Standard, Requirement, Criteria, "'"'f'
•'•• •"•' •••;• or umitatio* ' :«, :-i'-; -'. ;
WYOMING WATER QUALITY RULES AND
REGULATIONS
V "..itViv. •
Citations ';: •-,:
Chapter 1, Section 13
Chapter 1, Section 21 (a,
c)
Chapter 1, Section 22
Chapter 1, Section 24
Chapter 1. Section 26
Chapter 1, Section 29
Chapter VIII
Chapter XVII,
Appendix A, Sections
III, IX
••• ' •'•• ••• '•' ''(.'^SJAi,
• :..- :vR"^^'>Y,fJJ;4
Toxic Materials
Protection of aquatic life
Radioactive Material
Dissolved Oxygen
pll
Oil and grease
Quality Standards for Wyoming
Groundwaters
Establishes standards for LUST
remediation actions
} « A'**"tf«*f#W/MVW&l&''n
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Ycs/NA
Yes/NA
Yes/NA
No/Yes
siffSKilHiSl
Applicable to those contaminants and/or constituents
that are specifically attributable to the selected IRA,
but not the ICOCs. Compliance with other state water
quality substantive requirements satisfies all
requirements of this provision.
Ammonia is not anticipated and monitoring is not
required. Applicable to those contaminants and or
constituents that are specifically attributable to the
selected IRA.
Radioactive materials are not anticipated and
monitoring is not required. Applicable to
contaminants and or constituents that are specifically
attributable to the selected IRA.
Not applicable unless affected waters upgraded to class
2.
Primarily applicable during construction. Although
discharges aft not anticipated, miy be applicable
during any maintenance.
Groundwater is a potential or actual source of drinking
water. This IRA is due to groundwater contamination.
Regarding Section I, compliance with other state
water quality substantive requirements (permits are not
required) identified as ARARs satisfies all
requirements of this provision. Applicable to those
contaminants and or constituents that are specifically
attributable to the selected IRA and the ICOCs at the
agreed point of compliance.
This IRA is being conducted as a result of groundwaler
contamination. Compliance with Federal Safe
Drinking Water Program Maximum Contaminant
Levels for ICOCs satisfies relevant and appropriate
requirements of these provisions.
F:\warren\ou2\ss7\decdocs\ss71rod.doc
Page 27
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TABLE A-l (Continued)
Chemical-Specific ARARs
Operable Unit 2, Spill Site 7
WYOMING HAZARDOUS WASTE
RULES AND REGULATIONS
Chapter I
Overview and definitions
Yes/NA
If hazardous waste is generated, (his chapter would
apply. Applicable as necessary to implement other
substantive requirements.
Chapter 2
Identification and Listing of
Hazardous Waste
Yes/NA
If hazardous waste is generated, this chapter would
apply. Applicable in identifying listed or characteristic
hazardous waste subject to other substantive
requirements.
Notes:
ARARs = Applicable or relevant and appropriate requirements
CFR = Code of Federal Regulations
EPA = U.S. Environmental Protection Agency
ICOC = Indicator contaminants of concern
LUST = Leaking Underground Storage Tank
MCL = Maximum contaminant level
MCLGs *° Maximum contaminant level goals
NA " Not applicable
Sec. = Section
USC = U.S.Code
W.S. = Wyoming Statute
F:\warren\ou2\ss7\decdocs\ss7frod.doc
Page 28
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TABLE A-2
Chemical-Specific ARAR Standards
Operable Unit 2, Spill Site 7
Notts:
WDEQ Drinking Water Equivalent Level standards have not been listed because alt analytes listed above hold a respective federal
MCL that takes precedence (as per WDEQ Chapter XVII, Appendix I)
Contaminants listed are considered indicator contaminants of concern in the OU2, SS7 Focused Remedial Investigation, 1996.
None listed
MCL " Maximum contaminant level
mg/L = Milligrams per liter
WDEQ = Wyoming Department of Environmental Quality
F\warren\ou2\ss7\decdocs\ss7frod.doc
Page 29
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TABLE A-3
Action-Specific ARARs
Operable Unit 2, Spill Site 7
< .^.^i^ReqBlrtijMil, CriterU, »•$•&'
,-;":..". H*-iir'U«ltail6i5')f----;-"v^'
CLEAN WATER ACT
NPOES Storm Water Regulations
Criteria and Standards Tor the National
Pollutant Discharge System
National Prctrcatmcnl Standards:
Prohibited Discharges
CLEAN AIR ACT
National Emissions Standards for
Hazardous Air Pollutants
National Primary and Secondary
Ambient Air Quality Standards
RESOURCE CONSERVATION AND
RECOVERY ACT
Air Emissions Standards for Process
Vents
>.. 1'.-,.V->.ftVv-Nj-<>M
^-> CMittojii : ;-
33 USC Sec. 125 1-1376
40CFRPart 122
40 CFR Part 125
40 CFR 403.5
42 USC 740 1-7642
40 CFR Part 60 and 61,
Subpart A
40 CFR Part 50
42 USC Sec. 6901, et.
seq.
40 CFR 264, Subpart
AA
•'•^';?i j#?»^- J^#^fe*B
.:•' ;»• •' '•: Desirlptioh " "V|/^.
FEDERAL
-
Establishes requirements for discharge of
storm waters
Provides discharge criteria, chemical
standards, and permit forms for existing
industrial operations
Establishes National Pretreatment
Standards to control pollutants that pass
through POTWs
-
Establishes emissions standards for
specific hazardous air pollutants
Establishes standards for ambient air
quality to protect public health and welfare
Including standards for participate matter
and lead)
••
•stablishes air emission requirements for
>rocess units
WMfift
>•> v«-.. -Tu'. r-«KIH . .
-
Yes/NA
Yes/NA
Yes/NA
-
No/Yes
Yes/NA
""
No/Yes
-
Storm water may occur from the site making substantive
requirements applicable.
Although permits are not required, substantive provisions are
applicable to remedial actions (Alternative No. 3) that cause
discharge to waters of the U.S.
Applicable if Alternative No. 3 is selected and the option to
discharge treated water to the POTW is selected.
-
Relevant and appropriate during construction or maintenance of
the selected IRA and operation of Alternative No. 3. if it is the
selected IRA. Applicable under those circumstances if the source
meets the definition of a major source of hazardous air pollutants.
Emissions from IRA process will be subject to NAAQS unless
state standards are more stringent.
—
Relevant and appropriate if Alternative No. 3 is selected.
Although hazardous waste is not anticipated to exceed the
threshold, applicable if air stripping operations treat hazardous
wastes that have a total organic* concentration of 10 parts per
million by weight or greater.
STATE OF WYOMING
WYOMING ENVIRONMENTAL
QUALITY ACT
Article 2. WS. 35-1 1-
2011035-11-212
Discharge or emission of air contaminants
Yes/NA
Compliance with state air quality numeric and other substantive
requirements identified as ARARs satisfies all requirements of
this provision.
F:\warrtn\ou2\ss7\decdocs\ss7froddoc
Page 30
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TABLE A-3 (Continued)
Action-Specific ARARs
Operable Unit 2, Spill Site 7
. jjtMdard, Reqilreneal* Criteria, • ••
_••••« -H or LlaltatkHr • • .•-%.;.
WYOMING WATER QUALITY
RULES AND REGULATIONS
3*?.3^ ***«$&
. CiUdoni /
Articles. WS. 35-11-
301
Chapter 1, Section 10
Chapter 1, Section 1 l(a,
b)
Chapter 1. Section 12
Chapter 1, Section 14
Chapter I, Sections 15,
16, 17(a-c)
Chapter 1, Section 23(a,
b)
Chapter 1, Section 28
Chapter 111, Section
4(e),6(d),7(c),8(a-0
Chapter IV, Sections
1
Chapter VIII
Chapter XI, Part G
!#^-?;#> ,.••*: ^Vi$*tli-
• •!•-.-» ':• • Jf'JJWy!?? ' ? ;?;•;•/£'!#
Prohibits certain acts without a permit.
Testing Procedures
Flow conditions
Protection of Wetlands
Dead animals and solid waste
Settleable solids; floating and suspended
solids; and taste, odor and color.
Turbidity
Jndesirable aquatic life
Construction, installation or modification
of facilities capable of causing or
contributing to pollution
Releases of oil and hazardous substances
Water Quality Standards for Wyoming
Groundwater.
Standards for the Design and Construction
and for the Abandonment of Monitor Wells
^.AbpUcaM^tley^W
i$?W*PrJY!,!?8?K
Yes/NA
Ycs/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
|ftjdH|jl[JI StlSW^M^Mi^'M
^*
-------
TABLE A-3 (Continued)
Action-Specific ARARs
Operable Unit 2, Spill Site 7
•^S£s&®Sfc?
WYOMING AIR QUALITY
STANDARDS AND REGULATIONS
WYOMING HAZARDOUS WASTE
RULES AND REGULATIONS
••t&ij ! ^"V^.'^ffcw
'<'•' dufloru ;
Section 14
Section 16(a), (c)
Section 19
Section 2 l(c)(v) and 0)
Chapter 1
Chapter 8
Chapter 9
Chapter 10
Chapter II, Sections
4-.-- ' '" ;««.? :
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Yes/NA
Primarily applicable during construction and any maintenance of
IRA.
Applicable if Alternative No. 3 is selected. No monitoring is
required.
Primarily applicable during construction and any maintenance of
IRA.
If hazardous waste is generated, this chapter would apply.
Applicable as necessary to implement other substantive
requirements.
If hazardous waste is generated, this chapter would apply.
If hazardous waste is generated, this chapter would apply.
Applicable if hazardous waste is treated on site, except when
treated in a container, or if hazardous waste is accumulated on
site for more than 90 days. Storage of hazardous waste longer
than 90 days is not anticipated.
f hazardous waste is generated, these provisions would apply.
Chapter 8, Section 3(e) refers to these requirements for a
generator that accumulates hazardous waste on site for 90 days or
ess.
f hazardous waste is generated, these provisions would apply.
F:\wan-en\ou2\ss7\decdocs\ss7frod.doc
Page 32
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TABLE A-3 (Continued)
Action-Specific ARARs
Operable Unit 2, Spill Site 7
.
CltattoM
$W^^*!W^$
'•••*•:", •' '.Ml.lDrtWiJinQBv^;1?.?'r;f-
LOCAL
ORDINANCES RELATED TO THE
DISCHARGE OF UNSANITARY OR
CONTAMINATED WASTES
City of Cheyenne
Code, Chapter 45
Discharge of effluent water
Yes/NA
If Alternative No. 3 is selected and wastewater is discharged to
the CBPU POTW, local pretreatment standards and requirements
will be applicable.
Notts:
ARARs - Applicable or relevant and appropriate requirements
BACT = Best available control technology
CAMU = Corrective action management unit
CFR = Code of Federal Regulations
EPA = U.S. Environmental Protection Agency
FR = Federal regulation
GAC - Granular activated carbon
ICOCs = Indicator contaminants of concern
NA = Not applicable
NES1IAPS= National Emission Standards for Hazardous Air Pollutants
NPDES = National Pollution Discharge Elimination System
POTW = Publicly Owned Treatment Works
RCRA <• Resource Conservation and Recovery Act
Stat = Statute
USC = U.S.Code
UST = Underground Storage Tank
W.S. = Wyoming Statute
F:\warren\ou2\ss7\decdocs\ss7frod.doc
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Table A-4
Location-Specific ARARs
Operable Unit 2, Spill Site 7
^ :Cri«H«,orLI«lrafloiJ
•tgijv cj&iion : v •
. : ' .~v; •;,;•.-. :• ; Description £?•; i ••'• . ' '*""> \-,
ISS^S^S!SI^
FEDERAL— NA
STATE OF WYOMING
WYOMING WATER
QUALITY RULES AND
REGULATIONS
Chapter 1, Appendix
A
Chapter VIII
Classifications for Diamond and Crow Creek
Quality Standards for Wyoming
Groundwaters
Yes/NA
Yes/NA
If affected waters are upgraded, ARARs as listed
herein for the upgraded stream classifications
would be applicable to those contaminants and/or
constituents that are specifically attributable to the
selected IRA. but not the ICOCs.
Groundwater is a potential or actual source of
drinking water. Applicable to those contaminants
and or constituents that are specifically attributable
to the selected IRA and the ICOCs at the agreed
point of compliance.
Notes:
ARARS = Applicable or relevant and appropriate requirements
ICOCs • Indicator contaminants of concern
NA = Not applicable
F:\warren\ou2\ss7\decdocsVss7frod.doc
Page 34
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TABLE A-5
Temporarily Waived Federal and Wyoming State ARARs
Operable Unit 2, Spill Site 7
•**£fc*&&$9*V>-
Criteria, or Limitation
SAFE DRINKING WATER ACT
National Primary Drinking Water
Regulations
Maximum Contaminant Level Coals
WYOMING WATER QUALITY
RULES AND REGULATIONS
•• •: *':;'*.<.\..-;>.?i&%t$&&»
Glutton '•'••' V
42 USC. Section 300G
40CFRI4I,
Subparts B and G
40CFR 141,
Subpart F
•%*??* -wwfaii&frStei&w.
•''• ••' ' DtKripHon •"•'? ^-';l*'' -
FEDERAL
Maximum Contaminant Levels
Establish drinking water quality goals
STATE OF WYOMING
Chapter 1, Section 13
Chapter 1. Section 18
Chapter 1,
Section 21 (a-c)
Chapter 1, Section 22
Chapter VIII
Toxic Materials
Human Health
Protection of Aquatic Life
Radioactive Material
Water Quality Standards for Wyoming
Groundwater
iiiiis?s?!^siifiisi
Interim measures waiver for contaminants and/or constituents that are not
specifically attributable to the remedial alternatives and are not ICOCs.
Interim waiver for contaminants and/or constituents that are not
specifically attributable to the remedial alternatives and are not ICOCs.
Interim waiver for those contaminants or constituents that are not
specifically attributable to the selected IRA and the ICOCs.
Not applicable unless the affected waters are upgraded to Class 2.
Interim waiver for those contaminants and/or constituents that are not
specifically attributable to the selected IRA and the ICOCs.
Although radioactive materials are not anticipated and monitoring is not
required, an interim waiver applies for those contaminants and/or
constituents that are not specifically attributable to the selected IRA.
Interim waiver for those contaminants or constituents that are not
specifically attributable to the selected IRA.
Notes:
ARARS
ICOCs
Applicable or relevant and appropriate requirements
Indicator contaminants of concern
F:\warren\ou2\ss7\decdocs\ss7frod.doc
35
-------
ATTACHMENT B
RISK ASSESSMENT SUMMARY TABLES
INTERIM REMEDIAL ACTION
OPERABLE UNIT 2
Shallow Groundwater at Spill Site 7
F.E. WARREN AIR FORCE BASE
-------
TABLE B-l
Groundwater Preliminary Remediation Goals
Operable Unit 2, Spill Site 7
-, ... .^ .-.
Indicator Contaminant of Concern
' '-
Carcinogenic Effect
Trichloroethene
1.54ng/L
Noncarcinogenk Effect
1.2-dichlorocthene (total)
328ng/L
1,820
Trichloroethene
210ng/L
Notes:
RME
Reasonable Maximum Exposure
Micrograms per Liter
Source: USAF 1996a.
F: \warren\ou2 \ss7\decdocs\ss7frod.doc
Page 37
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TABLE B-2
Carcinogenic Risk Analysis Summary
Operable Unit 2, Spill Site 7
GW-129
Trichloroethene
1.6
1.2E-07
I.OE-06
GW-I7IA
Trichloroethene
4.5
3.3E-07
2.9E-06
GW-17IB
Trichloroethene
380.0
2.8E-05
2.5E-04
GW-I72C
Trichloroethene
86.0
6.3E-06
5.5E-05
GW-I73A
Trichloroethene
74.0
5.4E-06
4.8E-05
GW-I73A-A
Trichloroethene
71.0
5.2E-06
4.6E-05
GW-I73B
Trichloroethene
750.0
5.5E-05
4.8E-04
GW-173SS
Trichloroethene
1,000.0
7.3E-05
6.5E-04
GW-174
Trichloroethene
1.0
7.3E-08
6.5E-07
GW-174 A
Trichloroethene
2.0
1.5E-07
1.3E-06
GW-174C
Trichloroethene
310.0
2.3E-05
2.0E-04
GW-27
Trichloroethene
180.0
1.3E-05
1.2E-04
GW-43
Trichloroethene
5.3
3.9E-07
3.4E-06
GW-67
Trichloroethene
76.0
5.5E-06
4.9E-05
GW-68
Trichloroethene
9,900.0
7.2E-04
6.4E-03
GW-69
Trichloroethene
9,700.0
7.1E-04
6.3E-03
Notes:
RME
Source: USAF J996a
Micrograms per Liter
Reasonable Maximum Exposure
F:\warremou2\ss7\decdocs\ss7frod.doc
Page 38
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TABLE B-3
Noncarcinogenic Hazard Analysis Summary
Operable Unit 2, Spill Site 7
GW-129
Trichloroethene
0.0013
0.0073
GW-I71A
Trichloroethene
4.5
0.0037
0.02!
GW-171B
1,2-dichloroethene (total)
Trichloroethene
Cumulative hazard for well 17IB
8.6
380.0
0.0047
0.31
0.32
0.026
1.7
1.8
GW-172C
1,2-dichloroethene (total)
Trichloroethene
Cumulative hazard for well I72C
73.0
86.0
0.04
0.07
0.11
0.22
0.39
0.62
GW-173SS
Trichloroethene
1,000.0
0.82
4.6
GW-174
Trichloroethene
1.0
0.00082
0.0046
GW-174A
Trichloroethene
2.0
0.0016
0.0091
GW-174C
Trichloroethene
310.0
0.25
1.4
GW-27
1,2-dichloroethene
Trichloroethene
Cumulative hazard for well 27
28.0
180.0
0.015
0.15
0.16.
0.085
0.82
0.91
GW-43
1,2-dichloroethene (total)
Trichloroethene
Cumulative hazard for well 43
1.8
5.3
0.00099
0.0043
0.0053
0.0055
0.024
0.03
GW-67
Trichloroethene
76.0
0.062
0.35
GW-68
Trichloroethene
9,900.0
8.1
45.0
GW-69
1,2-dichloroethene
Trichloroethene
Cumulative hazard for well GW-69
400.0
9,700.0
0.22
8.0
8.22
1.2
44.0
45.2
Notes:
(ig/L = Micrograms per Liter
RME = Reasonable Maximum Exposure
Source: USAF J996a.
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Page 39
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