PB94-964503
EPA/ROD/R09-94/107
July 1994
EPA Superfund
Record of Decision:
Aircraft Control and Warning Site,
Mather Air Force Base, CA
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SUPERFUND
RECORD OF DECISION:
AIRCRAFT CONTROL AND WARNING SITE
MATHER AIR FORCE BASE
SACRAMENTO COUNTY, CALIFORNIA
December 1993
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Table of Contents.
List of Tables v
List of Figures • • v
1.0 Declaration . . . . ... ... . .'..'............ 1-1
1.1 Site Name and Location . 1-1
1.2 Statement of Basis and Purpose 1-1
1.3 Assessment of the Site 1-1
1.4 Description of the Selected Remedy 1-2
1.5 Statutory Determinations 1-3
1.6 Signatures 1-4
2.0 Decision Summary 2-1
2.1 Site Name, Location, and Description 2-1
2.1.1 Land Use . 2-5
2.1.2 Surface Water Resources 2-5
2.1.3 Groundwater Resources 2-6
2.2 Site History and Enforcement Activities 2-6
2.3 Highlights of Community Participation 2-22
2.4 Scope and Role of Response Action 2-23
2.5 Summary of Site Characteristics 2-23
2.5.1 Summary of Hazardous Material Releases . :. .1 . . 2-23
2.5.2 Nature and Extent of Contamination ........ '. ......... 2-24
2.5.2.1 Soils . . . . 2-24
2.5.2.2 Groundwater 2-26
2.6 Summary of Site Risks 2-27
2.6.1 Human Health Risks 2-30
2.6.1.1 Contaminant Identification 2-30
2.6.1.2 Exposure Assessment 2-34
2.6.1.3 Toxicity Assessment 2-34
2.6.1.4 Risk Characterization . . 2-35
2.6.2 Environmental Risks 2-37
2.7 Description of Alternatives . . . 2-37
2.7.1 Alternative 1 - No Action 2-38
R1J12-93/EES/S170016.ROM U
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Table of Contents (Continued).
2.7.2 Alternative 2 - Institutional Controls . ................. 2-39
2.7.3 Alternative 3 - Extraction/Injection and Treatment ......... 2-39
2.7.4 Alternative 4 - Extraction/Treatment with Discharge to Mather Lake
or Sewer ..... ..... ;..... ..... .:........... 2-40
2.8 Summary of the Comparative Analysis of Alternatives ........... 2-41
2.8.1 Overall Protection of Human Health and the Environment ..... 2-42
2.8.2 Compliance with Applicable or Relevant and Appropriate
Requirements ................................ 2-44
2.8.2.1 Contaminant-Specific Applicable Relevant or
Appropriate Requirements ................... 2-46
2.8.2.2 Action-Specific Applicable or Relevant and Appropriate
Requirements .......................... 2-47
2.8.2.3 Location-Specific Applicable or Relevant and
Appropriate Requirements . . . . ............... 2-51
2.8.2.4 Compliance With Applicable or Relevant and
Appropriate Requirements ................... 2-51
2.8.3 Long-Term Effectiveness and Permanence ...... . ....... 2-52
2.8.4 Reduction of Toxicity, Mobility, or Volume ............. 2-52
2.8.5 Short-term Effectiveness ......................... 2-53
2.8.6 Implementability .............................. 2-54
2.8.7 Cost ..................... ........... ••.-.-• 2-54
. 2.8.8 State/Support Agency Acceptance ...'.. . . . . . . . ..... : . . v 2-55
2.8.9 Community Acceptance .......... .............. . 2-55
2.9 The Selected Remedy ................................ 2-56
2.9.1 Extraction Wells ...... . ......... .............. 2-58
2.9.1.1 Pre-Treatment Unit ....................... 2-58
2.9.1.2 Air Stripping Tower and Blower ............... 2-59
2.9.1.3 Post-Treatment Unit ...................... 2-60
2.9.1.4 Vapor Phase Carbon Adsorption System .......... 2-60
2.9.1.5 Injection Wells ......................... 2-61
2.9.2 Performance Evaluations ......................... 2-61
2.9.3 Estimated Costs . . .............. ........... .... 2-62
2.10 Statutory Determinations . . . . ........... ............... 2-66
2.10.1 Protection of Human Health and the Environment ......... 2-66
RLU2-93/EES/B1700I6.RQM
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Table of Contents (Continued).
2.10.2 Compliance with Applicable or Relevant and Appropriate
Requirements 2-67
2.10.3 Cost Effectiveness 2-67
2.10.4 Utilization of Permanent Solutions and Alternative Treatment (or
Resource Recovery) Technologies to the Maximum Extent
Practicable . :" 2-67
2.10.5 Preference for Treatment as a Principal Element 2-68
2.11 Documentation of Significant Changes 2-68
2.12 References 2-68
3.0 Responsiveness Summary 3-1
Appendix A - Administrative Record Index
RU12-93/EES/I1700I6.ROM . . jy
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List of Tables.
Table
2.2-1 Investigations at the AC&W Site 2-10
2.2-2 TCE Concentrations In AC&W Site Wells, Quarterly Sampling
fTT 1991d and IT 1993c] , 2-16
2.6-1 Groundwater -.Potential Future Residential Exposure 2-37
2.8-1 Summary of Comparative Analysis '..'..' 2-43
2.8-2 Estimated Excess Cancer Risks 2-44
2.8-3 Groundwater Discharge Treatment Standards 2-50
2.8-4 Present Worth Costs for All Alternatives 2-55
2.9-1 Selected Remedy Costs 2-62
2.9-2 Estimated Cost Summary, Present Worth Calculation 2-63
2.9-3 Estimated Cost Summary, Capital and O&M Cost Breakdowns . . 2-64
List of Figures.
Figure Title Page
2.1-1 Site Vicinity Map 2-2
2.1-2 AC&W Site Map 2-3
2.1-3 Site Maps and Soil Boring Locations, IRP Sites 12, 25, 30,
and 47 2-4
2.5-1 Dissolved TCE Concentrations in Groundwater at the Water Table,
October 1991 . . 2-28
2.5-2 Dissolved TCE Concentration in Groundwater at the Base of the
SWBZ, October 1991 2-29
RLU2-93/EES/S170016.ROM
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1.0 Declaration
Statutory Preference for Treatment as a
Principal Element is Met
and Five-Year Site Review is Required
1.1 Site Name and Location :
Aircraft Control and Warning (AC&W) Site
Mather Air Force Base, Sacramento County, CA
7.2 Statement of Basis and Purpose
This decision document, a Record of Decision (ROD), presents the selected remedial action
for the AC&W Site, Installation Restoration Program (IRP) Site 12, at Mather Air Force
Base (AFB), Sacramento County, California which was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments Reauthorization Act of 1986 (SARA)
and, to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the Administrative Record for the
AC&W Site. The content of this ROD is based on recommendations in the U.S. EPA's
Interim Final Guidance on Preparing Superfund Decision Documents [EPA 1989a]. The
Administrative Record Index, (Appendix A), identifies documents upon which the decision is
based.
The purpose of this ROD is to set forth the remedial action to be conducted at the AC&W
Site to remedy groundwater contamination associated with the AC&W Site. No further
action is planned for IRP sites 25, 30, and 47, where three underground storage tanks (USD
and associated contamination have been completely removed. The UST at Site 47 was
removed in January 1993.
The U.S. Environmental Protection Agency Region IX (EPA K) and the State of California
concur with the selected remedy.
7.3 Assessment of the Site
Reports indicate that from 1958 to 1966 waste solvents and transformer oils were disposed in
a waste disposal pipe in the AC&W area. Investigations conducted as part of the Air Force
Installation Restoration Program (IRP) foiled to locate the waste disposal pipe but did find
RL/12-93/EES/SI700I6.ROM 1-1
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trichloroethylene (TCE) contamination in the shallow water bearing zone (SWBZ) in the
AC&W area. The SWBZ is classified as a potential source of drinking water by the State of
California, although it is not currently used in the AC&W area. Actual or threatened -—
releases of hazardous substances from this site, specifically TCE in the SWBZ, if not
addressed by implementing the response action selected in this ROD, may present a current
or potential threat to public health, welfare, or the environment.
Two other releases of hazardous substances occurred at the AC&W Site. Diesel fuel leaked
from USTs at IRP Sites 25 and 30, and a UST containing unleaded gasoline at IRP Site 47
failed a tank integrity test and was assumed to have leaked. In 1987 the USTs and
contaminated materials at IRP Sites 25 and 30 were removed. Analyses of soil samples from
IRP Sites 25 and 30 has confirmed that no contamination remains. The UST at IRP Site 47
was removed in January 1993. Contaminated soil discovered during removal of the UST
was completely removed. Because no contaminated material is present at IRP Sites 25, 30,
and 47 there is no threat to public health, welfare, or the environment.
1.4 Description of the Selected Remedy
The selected remedy will address the potential threat to human health posed by TCE
contamination in groundwater (primarily in the SWBZ). The SWBZ, although not presently
used near the AC&W Site, is a potential source of drinking water, therefore the selected
remedy will reduce the maximum concentration throughout the AC&W Site groundwater
plume to the Federal drinking water standard of 5 parts per billion (ppb) for TCE.
The major components of the selected remedy include: . ' . .
• Extraction of contaminated groundwater by pumping;
• Treatment of extracted groundwater by air stripping;
• Vapor phase carbon adsorption of TCE from the stripped vapor, as necessary;
• Off-site regeneration of spent activated carbon, as necessary; and
• On-site injection of treated water into the SWBZ.
The effluent reinjected outside.of the contaminated plume and into clean groundwater will
have a discharge median monthly TCE concentration level of 0.5 micrograms per liter (jig/f)
or ppb. Reinjection of the effluent within the contaminated plume will have a median
RU12-W/EES/I170016.ROM 1-2
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monthly TCE concentration level not exceeding the concentration of TCE in the groundwater
at the point of reinjection. However, in no case will the maximum discharge concentration
level exceed 5.0 pg/l (ppb), the federal and state maximum contaminant level (MCL)
drinking water standard.
Additional discharge options for the treated groundwater will be evaluated in the future as
redevelopment and re-use of Mather AFB occurs and the Groundwater OU and Soil OU
Focused Feasibility Study is developed.
No further action is required at IRP sites 25, 30, or 47, former UST sites, to protect public
health, welfare, or the environment.
1.5 Statutory Determinations
The selected remedy satisfies the statutory requirements of Section 121 of CERCLA, as
amended by SARA, in that the following four mandates are attained:
• The selected remedy is protective of human health and the environment.
• The selected remedy complies with federal and state requirements that are
legally applicable or relevant and appropriate to the remedial action.
• The selected remedy is cost-effective.
• The selected remedy utilizes permanent solutions and alternative treatment
technologies or resource recovery technologies, to the maximum extent
practicable. ; . . ;
The selected remedy satisfies the statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume as a principal element. .Because this remedy will result
in hazardous substances remaining on-site above health-based levels during the remedial
action, Five-Year Site Reviews will apply to this action [55 FR 8730 and 40 CFR 300.430
RLU2-93/EES/I170016.ROM 1-3
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7.6 Signatures
<4.fl\.jU£- ^
^^i n
JohnlC. Wise • •• - - -- U • - ~ . . Date
Deputy Regional Administrator, Region DC
U.S. Environmental Protection Agency
Charles H. Smith, PhD, P.E. . Date
BRAC Environmental Coordinator
Remedial Project Manager - Mather
U.S. Air Force Base Conversion Agency :
X7 /[ /
Anthony J. Lanws (/ Date
DSMOA Technical Program Manager
Department of Toxic Substances Control .
California Environmental Protection Agency
RL/12-n/EES/S170016.ROM 1-4
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2.0 Decision Summary
2.1 Site Name, Location, and Description
Mather Air Force Base (AFB) is a formerly active military facility approximately 12 miles
east of Sacramento and due south of Rancho Cordova (unincorporated) in Sacramento County
.California, as shown in Figure 2.1-1. The Base is due south of U.S. Highway SO, a major
highway connecting Sacramento and South Lake Tahoe. The Base encompasses 5845 acres
(129 acres of easements) in an unsurveyed part of Township 8 North, Ranges 6 East and 7
East, as shown by Figure 2.1-2. Mather AFB was closed under the Base Closure and
Realignment Act (BCRA) on September 30, 1993. Environmental activities at the facility
continue under the management of the Air Force Base Disposal Agency, with oversight by
the U.S. Environmental Protection Agency and the California Environmental Protection
Agency.
The Aircraft Control and Warning (AC&W) Site is near the east central part of Mather AFB,
as shown in Figure 2.1-2. Access to the AC&W Site is via Security Road from Mather
Boulevard. Vegetation at the AC&W Site consists of annual grasses and a few trees.
Topography of the site consists of several low gentle hills. Surface elevations range from
about 107 to 134 feet above mean sea level. Surface water in the area drains directly into
Morrison Creek and into an unnamed tributary of Morrison Creek.
Surface features in the AC&W area include an enclosed radar dome operated by the Federal
Aviation Administration (FAA), about ten one-story buildings, at least eight small sheds and
storage units, above ground tanks containing water, fuel, and oil, electrical and.
heating/ventilation/air conditioning (HVAC) service units, paved driveways, and other
improvements, as shown in Figure 2.1-3. Subsurface features are also shown on
Figure 2.1-3 and include abandoned-in-place septic tanks and tile field, sites where fuel and
gasoline tanks were removed, and the location of the former AC&W water supply well;
which was destroyed and sealed on March 22 and 23, 1990. All of the underground fuel
tanks shown in Figure 2.1-3 have now been removed.
Natural resources are not utilized at the AC&W Site.
The nearest residential area, the Mather AFB Base Housing area, is 2700 feet from the
AC&W Site, as measured from the. former AC&W water supply well.
RLM2-93/EES/S17001«.ROM . 2-1
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MATHER
AIR FORCE
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SACRAMENTO. CALIFORNIA
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REFERENCE
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RU12-W/EES/8170016.ROM
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2-4 .
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2.1.1 Land Use
On Mather AFB near the AC&W Site, there are three current land use categories:
residential, administrative/occupational, and recreational. Land uses, both on-base and off-
base, have changed since Mather AFB closed on September 30, 1993. The nearest
residential area, currently unoccupied, is the Mather AFB Base Family Housing area, 2700
feet from the AC&W Site, as measured from the former AC&W water supply well.
Administrative/occupational personnel of the FAA currently occupy buildings/facilities at the
site. Recreational uses of land in the immediate vicinity include golfing and trap shooting.
Generalized current land use patterns off-base are as follows:
• North and Northwest: Mostly single family residential development, with
major retail centers and other business uses centered along Folsom Boulevard,
Mather Field Road, and Zinfandel Road; this area includes schools and
outdoor public recreation facilities;
• West and Southwest: Mostly open rural land with some fanning and pasture
land;
U Mostly industrial use, with some commercial agricultural
• South: Mostly agricultural use with some commercial or industrial areas.
2.1.2 Surface Water Resources
Morrison Creek is the surface water feature closest to the AC&W Site. The creek is an
ephemeral stream that runs through the southeast comer of the AC&W area and is about
700 feet southeast of the former AC&W water supply well, as shown by Figure 2.1-2. It is
commonly dry in summer and early fall. It flows onto the Base from the northeast via an
aqueduct into Mather Lake, flows out of the lake towards the AC&W Site, past the site and
flows off-base to the southwest. An artificial pond on Morrison Creek is about 1000 feet
southwest of the former AC&W water supply well. The pond covers about one-tenth of an
acre.
Mather Lake is the largest surface water feature near the AC&W Site. It encompasses 64
acres and is about 3000 feet northeast of the former AC&W water supply well. The lake is
an impoundment of Morrison Creek. It is an aquatic habitat and a recreational resource for
the Base. The lake is fed by two ephemeral streams that cross Folsom South Canal by
aqueducts and then flow into the lake. The lake level is maintained by surface water runoff,
RL/i:-93/EES/»I70016.ROM 2-5
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by water pumped from Folsom South Canal, and in 1991 by groundwater pumped into the
lake. Several siltation ponds associated with aggregate mining are about 6000 feet north of
the AC&W Site. They contain standing water throughout the year. The siltation ponds are
not part of Mather AFB property.
2.1.3 Groundwater Resources
Groundwater resources in the region of the AC&W Site occur in the Shallow Water Bearing
Zone (SWBZ), the Lower Water Bearing Zone (LWBZ) of the Laguna Formation, and in
underlying deeper aquifers in the Mehrten Formation.
The SWBZ is at least 60 feet in thickness. It has the water table as an upper surface, about
120 feet below land surface (bis), and the top of the LWBZ as a lower boundary.
Groundwater from the SWBZ is not currently utilized in the vicinity of the AC&W Site.
The top of the LWBZ occurs between 180 to 200 feet bis. The base of the LWBZ is defined
in Wells MAFB-68 and MAFB-78. At the MAFB-78 drilling locality, the base of the LWBZ
in the AC&W Site area may be defined by a clayey silt layer about 250 feet bis. The former
AC&W water supply well, destroyed and sealed on March 22 and 23, 1990, was completed
in the LWBZ. However, most of the groundwater pumped by Family Housing Area (FH)
water production Wells FH-1, FH-3, New FH-4, FH-5, and FH-6 is from depths greater
than 318 feet bis, i.e., from the deeper aquifers in the Mehrten Formation.
2.2 Site History and Enforcement Activities
Mather. AFB was constructed in 1918 and its primary mission was a flight training, school:
The Mather AFB AC&W Site was constructed in the late 1950s as part of the Air Defense
Command early warning system. The 668th AC&W Squadron, which operated the site
jointly with the FAA, left Mather AFB in 1966. The AC&W Site is currently occupied by
the FAA.
It has been reported that trichloroethylene (TCE), used as a solvent and degreaser in facility
operations, and waste transformer oil were commonly disposed into a waste disposal pipe in
the AC&W area during the period between 1958 and 1966. This pipe, the suspected main
source of contamination at the AC&W Site, Installation Restoration Program (IRP) Site 12,
was reported to be about 100 feet southwest of Building 10150. The existence of the waste
disposal pipe has never been verified, all attempts to locate the pipe have been unsuccessful.
Estimates suggest that about 1200 gallons of TCE, and 1400 gallons of transformer oil may
RLri2-93/EES/SITOOI6.ROM 2-6
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have been disposed in this manner. Three additional suspected releases occurred near the
AC&W Site involving underground storage tanks (UST). These releases were investigated as
part of the AC&W Remedial Investigation/Feasibility Study (RI/FS) [IT 199 la, 199 Ib] and-
included:
• Diesel fuel leaked from a 550-gallon steel UST which was installed in 1951
near Building 10100 (IRP Site 25). During the UST removal in November
1987, a small hole was found in the tank. Soil samples taken beneath the tank
contained diesel fuel at a concentration of 5738 parts per million (ppm).
Contaminated soil was removed from the UST excavation and replaced with
clean backfill. Samples collected during the RI and FS [IT 1991a and 1991b]
confirmed that no contamination remains in the soil.
• Diesel fuel leaked from an 8000-gallon UST which was installed in 1951 near
Building 10300 (IRP Site 30). The UST was last used in 1982, and was
removed in 1987. During the UST removal, in the excavation near the fill end
of the tank, soil eight feet bis was found to contain 2206 ppm of diesel fuel.
Contaminated soil was removed from the UST excavation and replaced with
clean backfill. No contamination was detected in soil samples collected at the
UST site during the RI and FS [IT 1991a and 1991b].
These UST removal and remediation actions were undertaken by the Mather
AFB Environmental Management (323 FTW/EM) and Civil Engineering
Squadrons (323 CES/DEV) squadrons [IT 199la]. The squadrons also took
similar action at 18 other USTs at Mather AFB. Soils removed from the UST
excavations were stockpiled, sampled, and analyzed for petroleum constituents.
All soils having concentrations of petroleum constituents greater than 100 ppm
were disposed in the Casmalia, Class I, landfill. Soils containing less than 100
ppm petroleum constituents were used as fill material on Mather AFB.
• A leak of unleaded gasoline occurred at a 4000-gallon UST located 250 feet
northwest of Building 10400 (IRP Site 47). The UST was installed in 1983
and has been out of service since 1989 [IT 1991a]. The UST failed an
integrity test and may have leaked as much as 10000 gallons but no
contamination was detected in soil samples collected at the UST site during the
RI and FS [IT 1991a and 19915]. Contaminated soil was discovered upon
removal of the UST in January 1993 [IT 1993a]. The contaminated soil was
removed and replaced with clean fill.
Since no contamination remains at these three UST sites, and there is no threat posed to
pubb'c health, welfare, or the environment posed by past releases, no further action is
required. .
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The AC&W Site was placed on the Superfund (CERCLA) National Priorities List (NPL) in
July, 1987 after TCE was detected in groundwater in concentrations ranging from 4 ppb to
790 ppb in shallow monitoring wells [AeroVironment 1988], and in concentrations of 112
ppb in the former AC&W water supply well [Weston 1986]. AeroVironment Inc. [1988]
performed the sampling in November and December of 1986. In July 1989, the U.S. Air
Force, the U.S. EPA and the State of California signed a Federal Facility Agreement (FFA)
under CERCLA Section 120 to ensure that environmental impacts from past and present
operations are thoroughly investigated and appropriate cleanup actions are taken to protect
public health, welfare, and the environment. The Air Force is the owner of the site, the
principal responsible party, and lead agency for conducting investigative and cleanup
activities. There have been no CERCLA enforcement actions at the AC&W Site.
Remedial investigations conducted at the AC&W Site are part of the U.S. Air Force IRP.
Ten investigations have been conducted at the AC&W Site and routine groundwater
monitoring is an ongoing activity. The dates, type of studies, and organizations involved in
these are summarized in Table 2.2-1 and include:
• Initial investigation, Mather AFB Bioenvironmental Engineering Staff,
November 1979 [Weston 1986];
• IRP Records Search for Mather AFB, Phase I, June 1982, [CH2M-HU1 Inc.
1982];
• IRP Phase II Confirmation/Quantification, Stage 1 Investigation, June 1986,
Roy F. Weston Inc., [Weston 1986];
•' IRP Phase II Confirmation/Quantification, Stage 3 Investigation, February
1988, AeroVironment Inc., [AeroVironment 1988];
• IRP Sampling and Analysis for Site Monitor Wells October/November 1988,
IT Corporation [IT 1990a];
• IRP Site Inspection Report, IT Corporation, August 1990 [IT 1990b];
• IRP Remedial Investigation, IT Corporation, March 1991 [IT 1991a];
• IRP Quarterly Routine Groundwater Monitoring, EA E, S and T Corporation
and FT Corporation, [EA 1990a, EA 1990b, EA 1990c, IT 1991c, IT 1991d,
IT 1992a, IT 1992b, IT 1992c, IT 1992d, IT 1993b, IT 1993c, and IT 1993d]
• IRP Feasibility Study, FT Corporation, August 1991 [IT 1991b];
RU12-93/EES/B170016.ROM 2-8
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• FS Preliminary Design Investigation, IT Corporation, [IT 1992e]; and
• Underground storage tank removal, IT Corporation [IT 1993a].
The Mather AFB Bioenvironmental Engineering Staff conducted the first investigation at the
AC&W Site during November 1979 in an attempt to locate the suspected waste disposal pipe
[Weston 1986]. They excavated an area about 30 feet long and 15 feet wide to depths of
four to six feet bis, south or southwest of Building 10150, the pump house for the AC&W.
well, and collected soil samples for analysis of TCE and polychlorinated biphehyls (PCBs).
The pipe was not located and no organic chemicals were detected in the soil [Weston 1986].
A groundwater sample collected on August 12, 1980 from the AC&W water supply well was
found to contain 112 ppb of TCE [Weston 1986].
In 1982 the Air Force Engineering and Services Center retained CH2M-HU1 to conduct a
Phase I on-base records search [CH2M-HU1 1982]. The search suggested that TCE, waste
engine oils, carbon tetrachloride, antifreeze, and transformer oil were reportedly disposed
into the pipe from 1958 to 1966. The pipe reportedly received about 120 gallons of TCE
and 130 gallons of transformer oil per year during that period. During the early 1960s an
additional 150 gallons of waste TCE were generated at the AC&W Site, and in 1966 an
additional 225 gallons of waste transformer oil were also generated. Estimates suggest that
about 1200 gallons of TCE, and 1400 gallons of transformer oil may have been disposed in
this manner. The records search also indicated detections of TCE in analyses of water from
the AC&W production well over the period of August 1979 to August 1981 [CH2M-HU1
1982].
The Phase 1 records search was followed by the-Phase II, Stage 1 investigation [Weston
1986]. As pan of this study in 1985, Roy F. Weston, Inc. installed three shallow
groundwater monitoring wells (MAFB-1, -2, and -3) down gradient of the AC&W Site and
began the sampling and analysis of groundwater for aromatic compounds (e.g., benzene,
etc.), halogenated organic compounds (e.g., TCE, etc.), oil and grease, and PCBs. The
major results of this study are summarized by Table 2.2-1.
The Phase II, Stage 2 Investigation of Mather AFB conducted by AeroVironment [1987] did
not address the AC&W Site. However, during March 1986 to March 1987, the Phase H,
Stage 3 investigation of the AC&W Site was conducted by AeroVironment [1988] which
included monitoring well installation, groundwater sampling, and a soil gas survey.
RLU2-93/EES/S1700I6.ROM 2-9
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Table 2.2-1 Investigations at the AC&W Site
to
o
Phase and
Investigator
Initial
Investigation -
Mither AFB
.BioenvironmenUl
Engineering Stiff
IRP Phise 1.
Records Search -
CH2M Hill
IRP Phase II,
Confirmation /
Quantification
Stage 1 -
Roy F. Wcslim Inc.
IRP Phase II
Slage 3
Investigation -
AeroVironmenl
Soil Investigation and
Significant Analytical
Result*
Excavation to find waste
disposal pipe, seven soil
samples analyzed for TCE
and PCBs: neither delected,
pipe not located
None
None
Soil gas survey found low
levels of TCE (0:02 jig/f).
PCE and TCA. Soil gas
volatile organic compound .
concentrations ranged from .
0.0002 pg/r to o.oo7 fig/r.
although the data are . •
considered suspect
(ITI991b). Soil
contamination levels not '
significant.
Monitoring
Wells
Constructed
None
None
Three shallow
wells:
MAFB-I
MAFB2
MAFB-3
Five shallow
wells:
MAFB-50
through
MAFB-54
Six deep
wells:
MAFB47
through
MAFB-72
Groundwater Investigation and
Significant Analytical Results
Water production wells sampled, TCE found in
AC&W water production well at a maximum of
1 12 fig/f in sample collected on August 12, 1980.
None
TCE found in MAFB-I, -2, and -3 (S.I to
460 fig/0- Oil and grease found in MAFB-I, -2,
and -3 (190 to 760 mg/f ). ' Toluene found in
MAFB-I and -2 (< lOOpg/f). PCBs were not
delected.
TCE found in MAFB-I, -2, -3 and -52 (4.1 to 790
pg/f ). No TCE found in MAFB-51, -S3. -54. or
in deep wells.
Benzene (22 jig/f ) and dichlorobenzene (1 .6 /ig/f )
were detected in MAFB-70. Xylene found in
MAFB-71 (23 ng/f).
Other
Articles
None
Base records
search .
None
Geophysical
surveys did
not locate
the reported
AC&W
waste
disposal pipe
References
fWeslon 1986)
(CH2M-HUI
1982]
(Weston 1986]
|AeroViron-
ment 1988]
AC&W = Aircraft Control and Warning AFB = A'ir Force Base IRP = U.S. Air Force Installation Restoration Program
PCE = perchloroelhylenc PCBs = polychlorinaled biphenyls TCA = Irichloroelhane TCE =» Irichloroethylene TPHD = total petroleum hydrocailions as diesel
VOCi = volatile organic compounds /ig/f = microgram per liter pph =• I part per billion mg/kg = milligram per kilogram ppm «= I part per million
-------
Table 2.2-1 Investigations at the AC&W Site (continued)
Phase and
Investigator
IRP Sampling
and Analysis
for Site
Monitor Wells
- IT Corp.
IRP
Phase IV-A,
Site Inspection
- IT Corp.
IRP
Remedial
Investigation
- IT Corp.
Soil Investigation and
Significant Analytical Results
None
Evaluated ill geologic and chemical
data relating to environmental
contamination at Mather AFB. No
sampling or analyses conducted.
VOCs and TPHD in soil gas at
two fuel spill areas, by -septic
leach Held, and area where waste
disposal pipe reported to be.
TCE less than 1 1 ppm. TPHD
less than 247 ppm.
In seven surface soil samples
PCBs and TCE not detected, 1
fig/kg PCE in one sample.
Five soil borings, SB-I through
SB-S. Organic lead found in
every sample from SB-4,- with a
maximum of 0.8 mg/kg.
although data are suspect.
Xylenes, 1 .0 fig/kg at 1 .5 feel,
and TCE, 5 and 4 ^g/kg at III
and 121 feet, found in SB5. .
Monitoring
Wells
Constructed
None
None
Seven
shallow
wells:
MAFB-74
MAFB-77
MAFB-79
MAFB-81
MAFB-82
MAFB-83
MAFB-84
Two deep
wells:
MAFB-78
MAFB-80
Groundwater Investigation and
Significant Analylkal Results
All AC&W wells umpled. TCE found in MAFB-
1. -2. -3. and -52 (6-560 pg/f), toluene in MAFB-
1 (58 fig/0, and phenol in MAFB-67. -69. and
-71 (48-540 fig/0
Evaluated all geologic and chemical data relating
to environmental contamination at Mather AFB.
Data from 1988 groundwaler sampling included,
but not data from Remedial Investigation [IT
I99lb|. Two rounds of water level measurements
conducted for all on-base monitoring wells. No
sampling or analyses of groundwater.
Aquifer testing, groundwater modeling,
groundwater sampling.
TCE in Shallow wells MAFB-I. -2,-3. -SO.
-SI, -52,1*53, -54. and -83. Maximum TCE
in MAFB-83 (520 /ig/f). TCE not found in
wells MAFB-79. -81, -82, and -84. Other
contaminants include toluene and xylenes.
In deep wells MAFB-67, -68. -69
contaminants included low concentrations of
benzene, xylenes, ethylbenzene, and
dichlorobenzene. TCE found in MAFB-67
and -68 at a maximum concentration of
9.6 fig/f.
Down gradient extent of plume not defined.
Other
Activities
All AC&W
wells
redeveloped
None
Geophysical
surveys
Aquifer
testing
AC&W
water
supply well
sealed and
destroyed
References
(IT I990a|
(IT I990b|
(IT 199UJ
,
AC&W a Aircraft Control and Warning AFB ••= Air Force Base IRP = U.S. Air Force Installation Restoration Program PCE = perchloroelhylene
PCBs = polychlorinated biphenyls TCE = Irichloroelhylene TPHD = total petroleum hydrocarbons as diesel VOCs = volatile organic compounds
microgram per liter ppb = I part per billion mg/kg = milligram per kilogram ppm = I part per million
-------
g
Kf
ft
Table 2.2-1 Investigations at the AC&W Sile (continued)
• Phase and
Investigator
IRP Quarterly
Routine
G round waler
Sampling -
IT Corp. unJ
EA E. S and T.
Inc.
IRP Feasibility
Study -
IT Corp.
Soil Investigation and .
Significant Analytical
Results
None
16 Surface soil samples.
Organic lead not
detected.
Monitoring
Wells
Constructed
None
Three
shallow
pumping
wells:
AT-I
AT-2
AT-3
One deep
pumping
well:
AT-4
Gmundwater Investigation and
Significant Analytical Results
All Mather AFB wells sampled, including
AC&W wells. AC&W Sile data for selected
constituents summarized in Quarterly
Groundwater Monitoring Report(s) from
second quarter 1991 |IT 199) through second
quarter 1993 (IT I993c). See ROD Table
2.2-2 for summary of quarterly AC&W Site
TCE data.
Aquifer testing, groundwater modeling,
groundwater sampling.
'Four aquifer tests (pump tests) completed.
Maximum concentrations of TCE noted in
report were found in well AT-2 (800 pglt)
and in MAFB-I and -83 (400-500 pg/f).
Other
Activities
None
None
References
IEA I990a|
|EA I990b]
IEA I990c|
(IT I99lc]
(IT I99ld|
(IT I992a|
(IT I992b]
(IT I992cj
(IT I992d|
(IT I993a|
(IT I993b]
(IT I99lb]
AT = Aquifer test wells, pumped only during aquifer testing IRP = U.S. Air Force Installation Restoration Program
TCE = Irichloroethylene /ig/f = microgram per liter ppb = I part per billion mg/kg = milligram per kilogram . ppm = 1 part per million
-------
Table 2.2-1 Investigations at the AC&W Site (continued)
Phase and
Investigator
IRP
Preliminary
Design
Investigation
- IT Corp.
UST
Removal
Project -
IT Corp.
Soil Investigation and
Significant Analytical
Results
None
UST and contaminated
soil removed from
IRP Site 47 (UST
I0400B)
Monitoring
W«lb
Constructed
Nine shallow
welts:
MAFB-190 -
MAFB-198
None ' •
Groundwater Investigation and
Significant Analytical Results
Groundwaler sampled during drilling in one to four depth
intervals and at screened interval after well completion and
purging. Wells were screened at the water table (MAFB-190,
-192. -197) or in the lower SWBZ near the SWBZ/LWBZ
interface (MAFB-I9I. -193, -194. -195, -196, -198).
In PDI well MAFB-196 the concentrations of TCE at the water
table was 390 jig/f . In all other PDI wells the concentrations of
TCE at the water table were less than 1 .3 jig/f or non
detectable.
In PDI wells MAFB-194 and MAFB-196, screened at or near
the base of the SWBZ, concentrations of TCE were 210 pg/f
and 180 |ig/f . In other PDI wells screened at or near the base
of the SWBZ TCE was not detectable.
Downgradient extent of plume established. Size and shape of
plume refined.
The calculated amount of pure TCE in the plume is IS gallons
or 180.6 pounds (81.94 kg) and adsorbed on SWBZ sediment*
is 16 gallons or 194.9 pounds (88.44 kg).
None
Other
Activities
Two
stratigraphic
borings
None
Reference*
(TT 19921
(IT I993s|
K>
IRP = U.S. Air Force Installation Restoration Program LWBZ = Lower water bearing zone
PDI = Preliminary Design Investigation SWBZ. = Shallow water bearing zone TCE = Irichlorocthylenc UST = underground tlorage lank
pg/f = microgrem per liter ppb = I part per billion mg/kg = milligram per kilogram ppm = I part per million
-------
Trichloroethylene was detected in groundwater samples collected during November and
December of 1986. The concentrations ranged from 4 ppb to 790 ppb in samples from
shallow monitoring wells [AeroVironment 1988]. These analytical results contributed to the
placement of the AC&W Site CERCLA NPL in July, 1987. Results of the Phase H, Stage 3
Investigation activities are summarized by Table 2.2-1.
In the fall of 1988, IT Corporation conducted a redevelopment and groundwater sampling
program for all useabie wells on Mather AFB, including those at the AC&W Site [TT 1990].
Results of the sampling are summarized in Table 2.2-1.
IT Corporation conducted field work for the Remedial Investigation (RI) at the AC&W Site,
from August 1989 through March 1990. This work consisted of:
• Soil gas surveys to assess vadose zone contamination;
• Installation of soil borings near the suspected AC&W waste disposal site, at
the fuel spill sites, and near the septic tank and leach fields to assess vadose
zone contamination and collect geologic data;
• Installation, monitoring, and sampling of nine monitoring wells;
• Aquifer testing; and
• Abandonment of the former AC&W production well.
The RI confirmed the presence of dissolved phase TCE near the water table in the SWBZ.
Non-aqueous phase liquids (NAPLs) were not found. Sampling data from Well MAFB-67
indicated that the TCE may have extended into the underlying LWBZ. However, as shown
in Table 2.2-2, TCE in Well MAFB-67 has not been detected since the August 1990
sampling round, suggesting the detection may not reflect significant aquifer contamination.
Significant contamination was not found in soils and sediments sampled from near the ground
surface to the water table. The low levels of organic lead (< 1 ppm) detected in samples
from soil borings are not considered significant since subsequent analyses showed no
detectable organic lead [IT 1991b]. Significant contamination was absent in samples
collected from soil borings at the three UST sites. This indicates that the removal of
contaminated soil during UST removal at IRP Sites 25 and 30 was successful for protection
of public health, welfare, and the environment. The results of the RI are summarized in
Table 2.2-1. A baseline risk assessment was also prepared as part of the RI.
RL/i:-9J/EESrtI7001«.ROM 2*14
-------
Quarterly sampling and analysis of groundwater of all Mather AFB monitoring wells began
in autumn of 1989 and has continued through the present as follows:
• IT Corporation performed sampling and analysis from October 1989 until
February of 1990;
• EA Engineering, Science and Technology performed sampling and analysis
from May 1990 until December 1990 [EA 1990a, EA 1990b, and EA 1990c];
and
• IT Corporation has been performing the sampling and analysis from December
1990 to the present.
The TCE concentrations found in all AC&W Site wells sampled during the quarterly
monitoring from October 1989 through May 1993 are shown in Table 2.2-2 [IT 199 Ic, IT
1993c]. The fluctuations in TCE concentrations in some wells are thought to be caused by
dynamic mechanisms of the plume, and by effects of sampling and analysis.
The AC&W Feasibility Study (FS) field work began in the summer of 1990. The FS field
investigations were conducted to provide data to support the specification of remedial
alternatives. In the summer and fall of 1990, four additional wells were drilled and aquifer
tests were performed at each well. These tests provided hydrologic data for determining
groundwater flow and transport within and between the SWBZ and LWBZ. Pumping the
LWBZ continuously for seven days at nearly 600 gallons per minute (gpm) during one
aquifer test failed to effect contaminant transport across the SWBZ/LWBZ interface; i.e.,
.from the SWBZ into the LWBZ. This limited hydraulic communication between the SWBZ
and LWBZ supports the predictions in computer-fate and transport modeling [IT 199la].
Samples collected during drilling also suggested that the plume extends further down gradient
as was suspected from the RI [IT 1991a].
In summer and fall of 1991 nine additional monitoring wells were installed and two
stratigraphic borings were also completed in the Preliminary Design Investigation (PDI), as
shown in Table 2.2-1. Purposes of the PDI were to:
• Characterize the vertical distribution of TCE in the SWBZ;
• Characterize the area! extent of TCE contamination;
• Collect data to refine the understanding of the stratigraphy of the SWBZ; and
• Reassess the remedial alternatives proposed in the FS [TT 1991b],
RU12-9VEES/S1700I6.ROM 2-15
-------
Table 2.2-2 TCE Concentrations In AC&W She Wells, Quarterly Sampling
{IT 1991d and IT 1993c]
WELL
NO.
MAFB-1
(shallow
well)
MAFB-2
(shallow
well)
MAFB-3
(shallow
well)
DATE SAMPLED
(quarterly sampling round)
10/89
02/90
06/90
08/90
12/90
03/91
05/91
08/91 - 11/92
(six sampling rounds)
02/93
04/93
10/89
02/90
06/90
08/90
12/90
03/91
05/91
08/91 - 11/92
(six sampling rounds)
02/93
04/93
10/89
02/90 .
06/90
08/90
12/90
03/91
05/91
08/91
11/91
03/92
04/92
07/92
11/92
02/93
04/93
TRICHLOROETHYLENE
(concentration in pg/f )
240
450 -..'•.-.
410
360
50.8
88
101
NA - Insufficient water volume in well
NS - Well not sampled
NA - Insufficient water volume in well
31
32
28
25
5.3
19
29
NA - Insufficient water volume in well
NS - Well not sampled
NA - Insufficient water volume in well
210 . '. . •
240
210
370
109
250
270
180
NA - Insufficient water volume in well
160
71
NA - Insufficient water volume in well
NA - Insufficient water volume in well
NS - Well not sampled
47
RLU2-9J/EES/81700I6.ROM
2-16
-------
Table 2.2-2 TCE Concentrations In AC&W Site Wells, Quarterly Sampling
[IT 1991d and IT 1993c] (continued)
WELL
NO.
MAFB-50
(shallow
well)
MAFB-51
(shallow
well)
MAFB-52
(shallow
well)
DATE SAMPLED ,
(quarterly sampling round)
10/89
02/90
06/90
08/90
12/90
03/91
05/91
08/91
11/91
02/92
04/92
07/92
10/92
02/93
04/93
10/89
02/90
06/90
08/90
12/90 - 10/92
(nine sampling rounds)
02/93
05/93
10/89
02/90
06/90
08/90
12/90
03/91
05/91
08/91
11/91
03/92
04/92
07/92
10/92
02/93 .
04/93
TRICHLOROETHYLENE
(concentration in pg/f)
4.7
10.0
9.6 . .
7.0
3.5
3.1
2.8
3.4 J - Concentration estimated
ND
1.8
3.1
2.8
2.7
NS - Well not sampled
3.5
0.7
0.9
0.6
0.2
ND
NS - Well not sampled
NP - Constituent not analyzed
27.0 '
26.0
22.0
16.0
6.4
15.0
20.0
17.0 J - Concentration estimated
12.0
16
18
13
15
NS - Well not sampled
-13 • - --
RU12-93/EES/SI700I6.ROM
2-17
-------
Table 2.2-2 TCE Concentrations In AC&W Site Wells, Quarterly Sampling
[IT 1991d and IT 1993c] (continued)
WELL
NO.
MAFB-53
(shallow
well)
MAFB-54
(shallow
well)
MAFB-67
(deep
well)
DATE SAMPLED
(quarterly sampling round)
10/89
02/90
06790
08/90
12/90
03/91
05/91
08/91
11/91
03/92
04/92
07/92
10/92
02/93'
04/93
10/89
02/90
06/90
08/90 - 03/92
(eight sampling rounds)
04/92
07/92
10/92
02/93
05/93
10/89
02/90
06/90
08/90
12/90 - 10/92
(nine sampling rounds)
02/93
05/93
TRICHLOROETHYLENE
(concentration in fig/t)
0.6
0.7
ND
0.4
ND
1.8
2.7
10.0 J = Concentration estimated
ND
4.6
4.4
6.4
9.2
NS • Well not sampled
7.5
0.5
0.4
0.3
ND
0.6
ND
ND ... . . • ...
NS - Well not sampled
ND
1.1
9.6
4.6
1.0
ND
NS - Well not sampled
ND
RL/I2-93/EES/SI700I6.ROM
2-18
-------
Table 2.2-2 TCE Concentrations In AC&W Site Wells, Quarterly Sampling
[IT 1991d and IT 1993c] (continued)
WELL
NO.
MAFB-68
(deep
well)
MAFB-69
(deep
well)
MAFB-70
(deep
well)
MAFB-71
(deep
well)
MAFB-72
(deep
well)
DATE SAMPLED
(quarterly sampling round)
10/89
02/90 - 10/92
(twelve sampling rounds)
02/93
04/93
10/89 - 10/92
(thirteen sampling rounds)
02/93
04/93
10/89 - 08/90
(four sampling rounds)
12/90
03/91 - 03/92
(five sampling rounds)
05/92 - 11/92
(three sampling rounds)
02/93
04/93
10/89 - 07/92
(twelve sampling rounds)
10/92
02/93
05/93
10/89 - 10/92
(thirteen sampling rounds)
02/93 - 05/93
(two sampling rounds)
TRICHLOROETHYLENE
(concentration in pgft)
2.0
ND
NS - Well not sampled
ND
ND
NS - Well not sampled
NP - Constituent not analyzed
ND
2.0
NA - Well obstructed
ND
NS - Well not sampled
ND
ND
1.7
NS - Well not sampled ,
NP - Constituent not analyzed
ND
NS - Well not sampled
RLH2-93/EES/SI70016.ROM
2-19
-------
Table 2.2-2 TCE Concentrations In AC&W She Wells, Quarterly Sampling
[IT 1991d and FT 1993c] (continued)
WELL
NO.
MAFB-74
(shallow
well)
MAFB-77
(shallow
well)
MAFB-78
(deep
well)
MAFB-79
(shallow
well)
DATE SAMPLED
(quarterly sampling round)
10/89
02/90
06790
08/90
12/90
02/91
05/91
08/91
11/91
03/92
04/92
07/92 - 10/92
(two sampling rounds)
02/93
05/93
10/89
02/90
06/90
08/90
12/90
03/91
05/91
08/91
11/91
03/92
04/92
07/92
10/92
02/93
04/93
10/89 - 10/92
(thirteen sampling rounds)
02/93
05/93
10/89 - 10/92
(thirteen sampling rounds)
02/93
04/93
TRICHLOROETHYLENE
(concentration in pg/f)
100
130
49.0
84.0
40.2
150
200
87.0
140
180
270
NA - Insufficient water volume in well
NS - Well not sampled
NA - Insufficient water volume in well
2.9
11.0
1.2
1.5
ND
2.3
1.1
0.6
0.8
' 5.2' -•'" •'.'
1.2
1.0
ND
9.6
7.1
ND
NS - Well not sampled
ND
ND
NS - Well not sampled
ND
RU12-93/EES/S170016.BOM
2-20
-------
Table 2.2-2 TCE Concentrations In AC&W Site Wells, Quarterly Sampling
[IT 1991d and IT 1993c] (continued)
WELL
NO.
MAFB-80
(deep
well)
MAFB-81
(shallow
well)
MAFB-82
(shallow
well)
MAFB-83
(shallow
well)
MAFB-84
(shallow
well)
DATE SAMPLED
(quarterly sampling round)
10/89 - 10/92
(thirteen sampling rounds)
02/93
04/93
10/89 - 10/92
(thirteen sampling rounds)
02/93
05/93
10/89 - 10/92
(thirteen sampling rounds)
02/93-04/93
(two sampling rounds)
10/89
02/90
06/90
08/90
12/90
02/91
05/91
08/91
11/91
03/92
04/92
07/92 .
10/92
02/93
04/93
10/89 - 10/92
(thirteen sampling rounds)
02/93
05/93
TRICHLOROETHYLENE
(concentration in uglt)
ND
NS - Well not sampled .
ND
ND
NS - Well not sampled
NP - Constituent not analyzed
ND
NS - Well not sampled
400
540
490
770
120
350
303
350
330 J - Concentration estimated
470
330 -
310
280
NS - Well not sampled
290
ND
NS - Well not sampled
NP - Constituent not analyzed
J = Concentration estimated
NA = Not available, dry well or insufficient well volume, or well obstructed
ND = Not detected at method detection limit, i.e., EPA Method 8010
NP = Constituent not an analyte per current Project Work Plans [IT 1993b].
NS = Well not scheduled to be sampled per current Project Work Plans [IT 1993b]
R1/12-93/EES/S170016.ROM
2-21
-------
In the PDI, groundwater samples were collected during drilling and after completion of the
monitoring wells to establish the vertical distribution of TCE in the SWBZ and to determine
the area! extent of the plume. Data from the analyses were used to estimate the amounts aL-
pure TCE present in the SWBZ plume, i.e., 15 gallons dissolved in SWBZ groundwater, and
16 gallons adsorbed onto SWBZ materials. Review of the new PDI data revealed no
conditions at the AC&W Site that are detrimental to the selected remedy.
In 1993 all remaining USTs at the AC&W Site were removed and closed under the U.S.
Army Corps of Engineers UST Removal Project. The UST northwest of building 10400
(IRP Site 47) was removed in January of 1993 [IT 1993a]. The removal of contaminated soil
during UST removal at IRP Site 47 was successful for protection of public health, welfare,
and the environment. The 50-gallon UST adjacent to building 10150 was removed in
January of 1993 and the abandoned 8500-gailon UST was removed in May of 1993.
2.3 Highlights of Community Participation
The Remedial Investigation Report for the AC&W Site was released to the public in April
1991. The Feasibility Study Report for the AC&W Site was released to the public in
September 1991. The Proposed Plan for the AC&W Site was released to the public in
September 1991. The Revised Proposed Plan for the AC&W Site was released to the public
in March 1992. These four documents were made available to the public in both the
Administrative Record file and in information repositories maintained at the following
locations:
The Environmental Management Office, Mather AFB;
The Mather AFB Library (now closed); , •
The Sacramento Central Library;
The Ranchp Cordova Community Library; and
The U.S. EPA Region IX Docket Room in San Francisco.
The notice of availability for the RI Report [IT 1991a], FS Report [IT 1991b], and the
Proposed Plan was published in the Sacramento Bee on September 23, 1991. The notice of
availability of the Revised Proposed Plan was published in the Sacramento Bee and
Sacramento Union on March 11 through March 15, 1992.
Two public comment periods were held; the first from October 1, 1991 to October 31, 1991,
and the second from March 16, 1992 to April 15, 1992. Two public meetings were held at
the Rancho Cordova Public Library; the first on October 1, 1991 and the second on April 1,
RL/J2-93/EES/SI70016.ROM . 2-22
-------
1992. The public comment periods and public meetings addressed the Proposed Plan and the
Revised Proposed Plan. Representatives from the U.S. Air Force (USAF), U.S. EPA-
Region IX, the California Regional Water Quality Control Board (RWQCB), and the
California Department of Toxic Substances Control (DTSQ were present at the meetings.
Representatives from the Air Force and regulatory agencies answered questions about the site
and the remedial alternatives under consideration.. The Responsiveness Summary, Section
3.0 of this ROD contains responses to questions from both meetings and also documents that
no comments were received during the public comment periods.
The public participation requirements of CERCLA Sections 113(k)(2)(B)(i-v) and 117 were
met in the remedy selection. This ROD presents the selected remedial action for the AC&W
Site, at Mather AFB, California, chosen in accordance with CERCLA (as amended by
SARA) and to the extent practicable, the National Contingency Plan. The decision for this
site is based on the Administrative Record.
2.4 Scope and Role of Response Action
This ROD addresses the planned response action to address the primary risk at the AC&W
Site posed by TCE in groundwater, primarily in the SWBZ, a potential source of drinking
water. If wells were to be installed in the SWBZ in the future at the AC&W Site area, the
water could contain TCE in concentrations above regulatory standards for drinking water.
The purpose of the response action is to prevent future exposure to contaminated
groundwater at the AC&W Site (principally in the SWBZ) by removal of the contaminants.
2.5 Summary of Site Characteristics
2.5.1 Summary of Hazardous Material Releases
Groundwater at the AC&W Site has been impacted by past waste disposal practices and is
the affected media at the AC&W Site. The primary risk at the AC&W Site is posed by
groundwater contamination, a finding supported by Sections 2.5.2.1 and 2.6.1 of this ROD.
Soil was impacted by fuel releases and waste disposal practices in the past. However,
contamination from fuel releases has been removed, and contamination from other sources
has not been confirmed. Therefore, soil is no longer an affected medium at this site.
It has been reported that TCE, used as a solvent and degreaser in facility operations, and
waste transformer oil were commonly disposed into a waste disposal pipe in the AC&W area
during the period between 1958 and 1966. This pipe, the suspected main source of
contamination at the AC&W Site (IRP Site 12) was reported to be about 100 feet southwest
RUI2-9J/EES/81700I6.ROM 2-23
-------
of Building 10150. The existence of die waste disposal pipe has never been verified, all
attempts to locate the pipe have been unsuccessful. Estimates suggest that about 1200 gallons
of TCE, and 1400 gallons of transformer oil may have been disposed in this manner.
Three additional suspected releases may have occurred near the AC&W Site involving USTs.
These releases were investigated as part of the AC&W Site RI/FS [TT 1991a and 1991b] and
as part of a subsequent UST removal project [IT 1993a] and are summarized in Section 2.2
of this ROD.
2.5.2 Nature and Extent of Contamination
2.5.2.1 Soils
The types of contaminants suspected to have been present in soils at the AC&W Site included
TCE, waste transformer oil, waste motor oil, diesel fuel, unleaded gasoline, carbon
tetrachloride, and antifreeze [IT 1990b, 199la]. These contaminants may have entered the
soil via the reported AC&W waste disposal pipe, and in the case of diesel fuel and unleaded
gasoline via leaks and releases from three USTs. The quantity of contaminants is not known
beyond the estimated volume potentially disposed into the AC&W waste disposal pipe as
reported above.
Significant contamination in the soil has only been found in excavations surrounding the two
USTs that leaked diesel fuel, i.e., at IRP Sites 25 and 30, and one UST that leaked unleaded
gasoline, i.e., at IRP Site 47. The contaminated soil at IRP Sites 25, 30, and 47 was
removed and replaced with clean backfill [IT.1991a, IT 1993a]. Results of soil sampling
conducted during the RI [IT 199la] showed little evidence of fuel components or
contaminants remaining in the soil in the study area. Results of soil samples collected from
five soil borings (SB-1 through SB-5) and analyzed during the RI [IT 199 la] showed the
following:
• Two of five soil borings showed very low levels of organic lead (< 1 ppm).
In boring (SB-3) adjacent to the UST northwest of Building 10400, IRP Site
47, (the suspected unleaded gasoline leak site) organic lead was detected in
four sampled intervals:
- 4 to 4.5 ft, 0.8 ppm,
- 101 to 101.5 ft, 0.9 ppm,
- 105.5 to 106 ft, 0.8 ppm, and
- 123.5 to 124 ft, 0.8 ppm.
RLH2-93/EES/S170016.ROM 2-24
-------
In boring (SB-4) at Site 25 (the diesel fuel spill site) organic lead was detected
in the following sampled intervals:
No leaded fuels were known to have been stored at the AC&W Site; and,
further investigations of organic lead contamination in surface soils indicated
non-detectable concentrations [IT 1991b].
• No petroleum hydrocarbons were detected in laboratory-analyzed samples
obtained from those sites.
• At two locations (boring SB-5 at 1.5 and 90.5 feet bis) xylenes were detected.
The concentrations, 1 and 2 ppb respectively, are estimated values since these
results were less than the quantitation limit The risk of adverse health effects
associated with this level of contamination is insignificant, i.e., less than two
in one billion (1.9 x 10*) [TT 1991a].
• Trichloroethylene in soils was detected in only two samples collected near the
water table at depths of 111 and 121 feet bis in boring SB-5, located near the
AC&W septic tank and leach field. Both TCE concentrations are estimated
values since the results were less than the sample quantitation limit of 6 ppb.
Concentrations of xylenes and TCE in the soil, each detected twice at levels less than the
quantitation limits, indicate that there is no significant soil contamination. This conclusion is
also supported by analyses of near surface soil samples, collected 2.0 to 3.0 feet bis, which
found no contamination [IT 199la]. Absence of significant contamination sources renders
the following ROD considerations of no consequence:
Lateral and vertical extent of contaminants;
Concentration of contaminants;
Mobility of contaminants;
Carcinogenicity or noncarcinogenicity of contaminants; and
Potential surface and subsurface pathways of migration.
RLM2-93/EES/8170016.ROM 2-25
-------
2.5.2.2 Groundwater
Results of RI/FS groundwater sampling and analysis confirmed a plume of dissolved-phase
TCE in groundwater in the SWBZ near the water table. Of the constituents detected, TCE is
the only consistently detected contaminant of concern in groundwater in the SWBZ. Other
results of this investigation are summarized as follows:
• Only one LWBZ well, MAFB-67, had repeated detections of TCE in past
quarterly monitoring rounds from October 1989 through August 1990 (see
Table 2.2-2). Trichloroethylene, however has not been detected in Well
MAFB-67 in the October 1990 round of sampling nor in the quarterly
sampling rounds since. The specific source and/or migratory pathway of TCE
into Well MAFB-67 is not known, however, results of the FS aquifer testing
indicate little hydraulic communication from the SWBZ and the LWBZ. The
vertical extent of contamination by Volatile Organic compounds (VOCs) below
the SWBZ is defined by the LWBZ monitoring wells.
• A maximum TCE concentration of 800 ppb was detected during the FS aquifer
testing from Well AT-2 [IT 199 lb]. One sample, collected by the RWQCB at
Well AT-2, showed about 1200 ppb of TCE.
• Organic constituents other than TCE were either not consistently detected or
were below concentrations in associated sample Quality Control (QC) blanks
with the exception of three wells in the LWBZ. These three wells, MAFB-68,
-70, and -71, showed detectable concentrations of toluene, ethylbenzene and
xylene in the last three sampling rounds of the RI, which ended in early 1990.
However, the maximum concentrations detected were less than IS ppb and
were below the U.S. EPA and California's MCLs or applied action levels
(AALs) for those constituents [IT 199 lb].
The U:S. EPA and California MCLs and California AALs are:
Analyte EPA MCL1 CA MCL (1990)" CA AAL (1991)°
Toluene 1000 ng/t 2000 ng/t 2000
Ethylbenzene 700 ng/l 680 ftg/l 2000
Xylenes- 10000 n%lt 1750 ng/t 2000
total
1 = Federal maximum contaminant level for drinking water, 40 CFR 141.32
b = California drinking water primary maximum contaminant level, 1990
c = California applied action level, 1991
Trichloroethylene is classified as a probable human carcinogen by the U.S. EPA. The
volume of TCE in the SWBZ was estimated in the FS [IT 1991b] to be 13 gallons dissolved
RJL/12-W/EES/SI70016.ROM 2-26
-------
in groundwater and 15 gallons adsorbed on saturated soil. Current estimates of the volumes
of TCE in the SWBZ, calculated from PDI data, are 15 gallons dissolved in groundwater and
16 gallons adsorbed on saturated soil [IT 1992e]. Trichloroethylene, as a dissolved phase in
SWBZ groundwater, forms a plume that is elliptical in shape and oriented to the southwest,
suggesting migration towards the family housing area. The SWBZ plume, defined using
monitoring well data obtained during the PDI in October 1991, is shown in Figures 2.5-1
and 2.5-2. Figure 2.5-1 shows the plume at the top of the SWBZ at the water table. Figure
2.5-2 depicts the plume at the base of the SWBZ, 50 feet below the water table. A
comparison of current (1993) data to those in Figure 2.5-1 and 2.5-2 has been made and it
was determined that the current data corroborates the contours shown in these figures. The
1991 data set used to generate Figures 2.5-1 and 2.5-2 is more complete than later data
because the 1991 data set includes screening data at depths that are not sampled by
monitoring wells, and because wells MAFB-1, MAFB-2, and occasionally MAFB-3 have
become dry or have insufficient water to sample because of water table drop.
Groundwater monitoring subsequent to the risk assessment have shown maximum values less
than the historical maxima listed.
No completed risk pathways exist for TCE. However, in an unrestricted land use, maximum
exposure scenario, a water well could be completed in the SWBZ in the future. If such a
well were installed, exposure of the public to contaminated groundwater would be possible
through ingestion of drinking water or inhalation of TCE that volatilized during showering,
or by absorption through the skin during showering.
2.6 Summary of Site Risks .
The RI [IT 199 la] included fate and transport modeling and a baseline risk assessment. The
modeling was performed using AT123D: Analytical Transient one-, two-, and three-
Dimensional Simulation of Waste Transport in the Aquifer System [Yeh 1981, IT 1991a].
The modeling predicted that the TCE plume is not expected to impact down-gradient drinking
water wells in the future. Also, the modeling predicted that, as the result of natural
attenuation processes, the reasonable maximum exposure (RME) concentration for TCE in
the plume may be reduced to 5 ppb within 20 years [IT 1991b]. The computer modeling
results were used to aid in comparative analysis during the FS, and not to justify a "no
further action" alternative. The data collected and utilized in the RI and FS were of U.S.
EPA quality level HI, IV, or V, or equivalent. Formal data validation of the RI- and FS-
generated data was performed to ensure that data were of the quality commensurate with
their intended use.
RL/12-93/EES/8I70016.ROM 2-27
-------
K>
Is)
00
51
(MOJ
LEGEND
©
X
—1—
SHALLOW MONITORING WELL
SCREENED AT WATER TABLE
DRY WELL
BASE WATER SUPPLY WELL
AC&W WATER SUPPLY WELL
(ABANDONED)
SCREENING SAMPLE
APPROXIMATE TCE PLUME
DETECTION LIMIT BOUNDARY
(9>) TCE CONCENTRATION IN ppc
NO NONE DETECTED
NOTES
II TCI CONCENTRATIONS FOR MY WfllS
WERE FROM TNE 6/91 SAMFUNO
RESULTS. WEILS ARE SCREENED AT
THE WATER TABLE.
21 CONTOURS ARE I, 10. AND 100 ppb TCE
31 A COMPARISON OF DATA FROM III]
AND 1891 CORROBORATES THE
CONTOURS SHOWN
FIOUflE S.»-1
DISSOLVED TCE
CONCENTRATION IN GROUNDWATER
AT THE WATER TABLE
OCTOBER 1991
MUPMtD ran
MATHER AIR FORCE BASE
SACRAMENTO. CALIFORNIA
INTCMNATinNAI.
Ttcimntor.Y
conroiuiioN
-------
i
N>
LEGEND
0
X
*
SHALLOW MONITORING WELL
SCREENED AT WATER TABLE
SHALLOW MONITORING WELL
SCREENED AT BASE OF SWBZ
DRY WELL
BASE WATER SUPPLY WELL
ACAW WATER SUPPLY WELL
(ABANDONED)
SCREENING SAMPLE
AQUIFER TEST WEU.
SCREENING SAMPLE
1 APPROXIMATE TCE PLUME
, DETECTION LIMIT BOUNDARY
<».») TCE CONCENTRATION IN ppb
HO NONE DETECTED
( )• ESTIMATED TCE CONCENTRATIONS
BASED ON VERTICAL DISTRIBUTION
OF TCE
NOTES
II AQUIFER TEST Will TCE CONCEN-
TRATIONS ARE BASED UPON OCT-NOV
1110 SCREENING SAMPLES
21 MV WILLS ARE SCREENED AT THE
WATER TABLE
31 CONTOURS ARE I. to. »nt 100 ex* TCE
41 A COMPARISON OF DATA FROM IMS
AND 1191 CORROBORATES THE
CONTOURS SHOWN
SCALE
400
BOO FEET
FIGURE S.I-}
DISSOLVED TCE
CONCENTRATION IN CROUNDWATER
BASE OF SWBZ
OCTOBER 1991
rMMMB rcN
MATHER AIR FORCE BASE
SACRAMENTO. CALIFORNIA
INTERNATIONAL
TECIINOIXN;V
-------
Although the site is currently controlled by the Air Force, Mather AFB was closed on
September 3.0, 1993. Future land use is currently undecided.
The RI baseline risk assessment showed the RME to groundwater contamination to occur in a
hypothetical residential land use scenario whereby new drinking water wells might be
installed in the SWBZ [TT 1991a]. Under these conditions, the RME concentration of TCE
would be about 146 ppb resulting in an excess cancer risk of 1.1 x 10~5, which is within the
acceptable risk range of 10* to 10*. The calculated RME concentration for the LWBZ is 1.2
ppb, which results in an excess cancer risk well below the 10"6 level.
The potential for contaminants to volatilize from groundwater, migrate through the vadose
zone, and accumulate in homes in the future is not a threat at the AC&W Site, although it
may pose a threat at other Superfund sites. This potential path of contaminant migration and
exposure was evaluated in Section 5.2.1 of the RI Report [IT 199 la] and was dismissed for
the following reasons:
• The RI soil gas survey indicated that vapor phase transport is occurring but the
vapor phase is not reaching the ground surface.
• The large volume of the TCE SWBZ plume relative to its surface area limits
the significance of the volatilization as a [TCE] loss mechanism.
• The shape of the TCE plume in the SWBZ is not indicative of a system in
which vapor phase transport followed by re-solution [into the groundwater] is
an important transport mechanism. Systems that have a large vapor phase
component tend to be less directional and more disperse. The TCE plume in
the SWBZ is directional, very narrow relative to its length.
Although soil is not an affected media, the RI baseline risk assessment included possible soil
contaminants since xylene was found in two samples. The baseline risk assessment indicated
the risk of adverse health effects from xylene was 1.9 x 10"', less than two in one billion,
which is a negligible risk.
2.6.1 Human Health Risks
2.6.1.1 Contaminant Identification
The RI baseline risk assessment identified eight constituents as chemicals of potential concern
in groundwater and two constituents as chemicals of potential concern in soils at the AC&W
RL/I2-9}/EES/S1700l6.ROM 2-30
-------
Site [IT 1991a]. These were benzene, chloroform, chloromethane, tis-l,2-dichloroethylene,
ethylbenzene, trichloroethylene, toluene, and xylene in the AC&W Site SWBZ groundwater
and organic lead and xylene in AC&W Site soils. •—;
The constituents identified in the RI [IT 1991a], including the chemicals of potential concern,
were evaluated during the FS [TT 1991b] to determine the contaminants of concern for the FS
analysis of alternatives. These constituents were benzene, bis(2-ethylhexyl) phthalate, carbon
tetrachloride, chloroform, chlorbmethane, cis-l,2-dichloroethyiene, trans-1,2-
dichloroethylene, ethylbenzene, total lead, methylene chloride, toluene, 1,1,1 trichloroethane,
trichloroethylene, and xylenes in the AC&W Site SWBZ groundwater and organic lead and
xylene in AC&W Site soils. Most of the constituents were eliminated from the final list of
contaminants of concern [IT 1991b]. The evaluation was done to eliminate common
laboratory contaminants, constituents with concentrations below applicable or relevant and
appropriate requirements (ARARs), constituents which lack environmental prevalence, and
constituents which are within the range of background levels. This evaluation process of
potential contaminants of concern is in compliance with U.S. EPA guidance documents [EPA
1989b], and was presented and accepted in both the AC&W Remedial Investigation Report
[IT 1991a] and the Feasibility Study [IT 1991b]. On the basis of the evaluation, TCE in
groundwater is the single remaining contaminant of concern [IT 1991b]. The range of
detected TCE concentrations is as follows:
• From 0.3 ugll to 790 /*g/f as reported in the RI [IT 1991a].
• The three samples collected from Well AT-2 during the FS aquifer tests
contained 560 ugll, 800 /*g/f, and 1200 Mg/f of TCE [IT 1991b]. The
sample that contained 1200 ng/l of TCE was collected by the RWQCB:
• Since the FS aquifer testing performed in November of 1990, the maximum
concentration of TCE has been 470 jtg/f in groundwater from well MAFB-83.
The calculated 95% upper confidence limit of the arithmetic average for TCE is 146 ng/t in
the SWBZ and less than 1.2 ng/t in the LWBZ [IT 1991b]. These estimates were reported
in the FS [IT 1991b] and are based on data collected during the RI. The remainder of this
section provides additional information on the evaluation of the constituents that were
eliminated as contaminants of concern.
Constituents identified as potential contaminants of concern were eliminated from further
consideration if they were determined to be indicative of laboratory contamination. The U.S.
RU12-93/EES/8170016.ROM 2-31
-------
EPA guidance [EPA 1989b] states that for common laboratory contaminants (e.g., acetone,
methylene chloride, and phthalate esters), sample results should be considered as positive
results only if the concentrations in the sample exceed ten times the maximum amount
detected in any blank. For constituents other than common laboratory contaminants, sample
results should be considered as positive if the concentration of the chemical in the sample
exceeds five times the maximum amount detected in any blank.
The following constituents were determined to be artifacts of laboratory contamination:
• Bis(2-ethylhexyl) phthalate [IT 1990a];
• Chloromethane [IT 1991b]; and
• Methylene chloride [TT I991b].
Constituents were eliminated as contaminants of concern and from further consideration if
contaminant levels were below ARARs, or were below discretionary to-be-considered
materials (TBQ as defined in 40 Code of Federal Regulations (CFR) 300.400(g)(3) in the
absence of chemical-specific ARARs. Commonly used ARARs were the U.S. EPA and/or
California (CA) drinking water MCLs. Constituents that do not exceed an ARAR or TBC
value [IT 1991b], and therefore are not contaminants of concern in groundwater, include:
• Benzene: below 1 ppb ARAR (CA MCL);
• Carbon tetrachloride: below 0.5 ppb ARAR (CA MCL) and not
environmentally prevalent;
• Chloroform: below 100 ppb ARAR (U.S. EPA MCL for total
trihalomethanes); below 4.5 ppb TBC (derived Water Quality Criterion based
on 22 CCR 12711 exposure level per Regional Water Quality Control Board
guidance [RWQCB 1989]);
• Cis-1,2 dichloroethylene: below 6 ppb ARAR (CA MCL);
• Trans-1,2 dichloroethylene: below 10 ppb ARAR (CA MCL) and not
environmentally prevalent;
• Ethylbenzene: below 680 ppb ARAR (CA MCL);
• Toluene: below 40 ppb TBC (proposed secondary MCL);
• 1,1,1 Trichloroethane: below 200 ppb ARAR (CA MCL) and not
environmentally prevalent, and;
RL/12-93/EES/M70016.ROM 2-32
-------
• Xylenes: below 1750 ppb ARAR
-------
eliminated as a contaminant of concern in soils at the AC&W Site because it was detected
only twice and at concentrations estimated to be less than 2 ppb. The baseline risk
assessment indicated that the risk of adverse health effects from ingestion of soil containing^
ppb of xylene is 1.9 x 1O9, a negligible risk [IT 1991b].
2.6.1.2 Exposure Assessment
Although there are no residents currently in base housing, the area was used to house base
workers and their families until September 30, 1993, and is planned to be used again after
redevelopment. The water wells that supply the housing area draw water from the LWBZ or
deeper in the Mehrten Formation. Aquifer test data support the interpretation of only limited
hydraulic connection between the SWBZ and LWBZ [IT 199 lb]. Evaluation of monitoring
data and mathematical modeling, performed as part of the baseline risk assessment, predicted
that the groundwater plume of TCE has not and will not impact the water supply wells in
family housing area [IT 199la]. Therefore, the baseline risk assessment concluded that
groundwater at the AC&W Site does not currently present a completed pathway for
exposure. However, in an unrestricted land use, maximum exposure scenario, the possibility
exists for completion of a well in the SWBZ in the future. In the event a well of this nature
is installed, the possibility of exposure to contaminated groundwater could result in exposure
from dermal contact, ingestion of drinking water and inhalation of volatilized constituents
during showering.
2.6.1.3 Tox/cfty Assessment
The U.S. EPA classifies TCE as a probable human carcinogen (Group B2) [EPA 1990]. A
Group B2 carcinogen is known to produce cancer in laboratory animals, and lifetime
exposure to TCE by oral ingestion has been documented to produce liver tumors in several
strains of mice [EPA 1990]. Cancer Potency Factors (CPF) have been developed by the
U.S. EPA's Carcinogenic Assessment Group for estimating excess lifetime cancer risks
associated with exposure to potentially carcinogenic chemicals. The U.S. EPA has estimated
the TCE oral CPF as 1.1 x lO"2 (mg/kg-day)'1 [EPA 1990]. Cancer potency factors,
correction factors, and the estimated intake of the carcinogen, expressed in mg/kg-day, i.e.,
milligram of chemical for each kilogram weight of an individual per day, are used to
calculate an upper-bound estimate of the excess lifetime cancer risk associated with exposure
at the estimated intake level. Use of this approach makes underestimation of the actual
cancer risk highly unlikely.
RI/12-93/EES/S1700I6.ROM 2-34
-------
The potential for noncarcinogenic adverse health effects caused by exposure to chemical
contaminants is estimated through the use of Reference Doses (RfD) developed by the U.S.
EPA. Reference doses are estimates, for a specific chemical constituent, of the lifetime
human daily exposure level that is likely to be without an appreciable risk of adverse effects.
The calculation of a RfD includes methods to ensure that the RfD will not underestimate the
potential for adverse noncarcinogenic effects to occur. Reference doses are applicable to the
general population, including sensitive individuals. By comparing the RfDs with the
estimated intakes of chemicals present in environmental media, e.g., the amount of a
chemical ingested from drinking contaminated water, an assessment can be made of the
health risks posed by the chemicals present
As reported in the RI report [IT 1991a], noncarcinogenic effects produced by oral ingestion
of TCE are not well characterized, but have been estimated as follows:
• The estimated RfD is based on the U.S. EPA Lowest-Observable-Adverse-
Effect-Level (LOAEL). The LOAEL is the lowest exposure level at which
there are statistically or biologically significant increases in the number or
severity of adverse effects.
• The TCE LOAEL is 55 ppm, which corresponds to an estimated TCE
adsorbed dose of 7.34 mg/kg-day [EPA 1987],
• The U.S. EPA then divided the LOAEL dose by 100 to provide a conservative
estimate of the RfD, i.e., 7.34 x 10° mg/kg-day [IT 1991a].
The estimated TCE RfD is 7.34 x 10"2 mg/kg-day [IT 1991a]. A daily intake of more than
7.34 x 10'2 mg per kg of body weight would be likely to produce adverse, but
noncarcinogenic, health effects during an individual's lifetime, i.e., after 70 years of daily
TCE intake.
2.6.1.4 Risk Characterization
Excess lifetime cancer risks are calculated using the assumed contaminant intake level, other
exposure correction factors, and the CPF. These risks are probabilities that are generally
expressed in scientific notation (e.g., 1 x 10* or 1E-6). An excess lifetime cancer risk of
1 x 10^ indicates that, as a plausible upper bound, an individual has a one in one million
chance of developing cancer as a result of site-related exposure to a carcinogen over a 70-
year lifetime under specific exposure conditions at a site.
JU/12-9)/EES/8170016.ROM 2-35
-------
Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the Hazard Quotient (HQ) (or the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminant's reference dose). By
adding the HQs for all contaminants within a medium or across all media to which a given
population may reasonably be exposed, the Hazard Index (HI) can be generated. The HI
provides a useful reference point for gauging the potential significance of multiple
contaminant exposures within a single medium or across media. The HI provides a
numerical indicator of the nearness to acceptable limits of exposure or the degree to which
acceptable exposure levels are exceeded. As the HI increases towards unity (i.e., 1), so does
concern for the potential hazard posed by the constituent
For the final AC&W Site baseline risk assessment, a residential unrestricted land use,
maximum exposure scenario was assumed. The potential risk posed by exposure to
contaminants was estimated by quantifying potential human intake and identifying toxicity
characteristics for the contaminants of concern in the exposure pathways. Trichloroethylene
is the only contaminant of concern in SWBZ groundwater.
Trichloroethylene is a probable human carcinogen. The excess lifetime cancer risk for TCE
is obtained by multiplying the intake of TCE by the TCE CPF. The ingestion intake for
TCE is calculated by assuming an ingestion rate of 1.4 liters of water/day containing a
contaminant amount equal to the 95% upper confidence limit of the arithmetic average [IT
1991b]. The inhalation intake is calculated as the amount of TCE which would volatilize
from the water source during showering. The resulting risk level represents the probability
that an individual could contract cancer due to exposure to TCE from SWBZ groundwater if
used for drinking or while showering. The calculated risk level for TCE under the
residential/unrestricted land use scenario was 1.1 x 10*5; i.e., the risk level represents the
probability of one person in one hundred thousand contracting cancer from the exposure.
This calculated risk levels is within the acceptable range of 10"* and 10"*, as defined in 40
CFR 300.430(e)(2)(i)(A)(2).
The results of the risk characterization process for groundwater beneath the AC&W Site are
summarized in Table 2.6-1.
RL/12-93/EES/SI70016.ROM 2-36
-------
Table 2.6-1 Groundwater - Potential Future Residential Exposure
Constituent
TCE
Ingestion
Intake
(mg/kg/day)
8.3 x Iff4
Ingestion
Toxicity - CPF
(mg/kg/dayX1
1.1 x 10-J
Inhalation
Intake
(mg/kg/day)
1.2 x 10*
Inhalation
Toxicity - CPF
(mg/kg/day)-1
1.7 x 1(TJ
Total —
Risk
1.1 x 10*
2.5.2 Environmental Risks
There are no environmental risks associated with contaminants at the AC&W Site as reported
in the RI/FS Site Inspection report [IT I990b] and RI/FS reports [IT 1991a, and 1991b]
because:
• There are no critical habitats affected by AC&W Site contamination; and
• There are no endangered species or habitats of endangered species affected by
contamination at the AC&W Site.
However, actual or threatened releases of TCE in the groundwater, if not addressed by
implementing the response action selected in this ROD, may present potential threat to public
health, welfare, or the environment.
These conclusions are based on Section 8.4 'FLORA and FAUNA" of the Site Inspection
Report [IT 1990b] and Section 6.3.1.2 'Receptor Assessment' of the RI Report [IT 1991a],
Because there are no completed risk pathways at the AC&W Site a site-specific ecological ,
risk assessment has not been performed. However, the Basewide Comprehensive Risk
Assessment, will include an ecological risk assessment, and the assessment will be completed
before issuance of the final ROD for Mather AFB.
2.7 Description of Alternatives
Seven remedial alternatives (four primary alternatives with respective sub-alternatives) were
developed for detailed analysis in the FS Report for the AC&W Site [IT 1991b],
Groundwater, primarily in the SWBZ, is the affected media at the AC&W Site. Soils are
not an affected media and are not considered in the remedial alternatives. The remediation
goal of each of these alternatives is to reduce the concentration of TCE in groundwater at the
AC&W Site to the Safe Drinking Water Act (SDWA) MCL of 5 ppb.
RUI2-93/EES/SI700I6.ROM
2-37
-------
All alternatives include a groundwater monitoring program consistent with ARARs and
compatible with the site-wide groundwater monitoring program (IT 1993e], as approved by
the Air Force, U.S. EPA, and State of California in accordance with the FFA for
Mather AFB.
The seven remedial alternatives are as follows:
• Alternative 1 - No Action
• Alternative 2 - Institutional Controls
Alternative 2a - Access Restrictions
Alternative 2b - Alternate Water Supply
• Alternative 3 - Extraction/Injection and Treatment
Alternative 3a - Extraction/Injection with Ultraviolet/Oxidation
(UV/OX) Treatment
- Alternative 3b • Extraction/Injection with Air Stripping/Vapor Phase
Carbon Adsorption Treatment
• Alternative 4 - Extraction/Treatment with Discharge to Mather Lake or
Sanitary Sewer
Alternative 4a - Extraction/Treatment with UV/OX and Discharge to
Mather Lake or Sanitary Sewer
Alternative 4b - Extraction/Treatment with Air Stripping/Vapor Phase
Carbon Adsorption and Discharge to Mather Lake or Sanitary Sewer
2.7.1 Alternative 1 - No Action
This alternative assumes current site conditions plus implementation of a groundwater
monitoring program to assess characteristics of the plume. This alternative considers taking
no active cleanup measures, such as groundwater pumping or removal of contamination. The
CERCLA/Superfund program requires that the No Action Alternative be evaluated to provide
a baseline for comparison purposes. The No Action Alternative relies on natural degradation
and dispersion processes to eventually eliminate the contamination. Computer modeling
predicted that the RME concentration for TCE may be reduced to 5 ppb within twenty years
in this alternative [IT 1991b). The modeling was performed using GWFL3D code [Walton
1989] and interactive version of the PLASM code [Prickett and Longquist 1971], and the
RLM2-93/EES/S170016.ROM 2-38
-------
GWTR3D code [Walton 1989] to simulate transport of TCE in the SWBZ. The modeling
also utilized predicted TCE concentrations generated using AT123D: Analytical Transient
one-, two-, and three-Dimensional Simulation of Waste Transport in the Aquifer System [Yen
1981, IT 1991a].
The time required to achieve remediation, i.e., to reduce the concentration of TCE to 5 ppb
throughout the AC&W Site SWBZ plume, is expected to be greater than 20 years.
2.7.2 Alternative 2 - Institutional Controls
Remedial Alternatives 2a and 2b rely, to the maximum extent possible, on institutional and
access restrictions to prevent the possibility of exposure to the contaminated groundwater.
Continued groundwater monitoring is applied until the TCE concentration is reduced via
natural degradation and dispersion to 5 ppb. Achievement of full remediation is expected to
require greater than 20 years, although the RME concentration is predicted to drop to 5 ppb
within 20 years [IT 1991a].
In Alternative 2a, two types of restrictions are evaluated, as described below:
• Requirements in the property deed to restrict land use by prohibiting
installation of wells in the contaminated portion of the SWBZ; or
• Continued Air Force control of the site to prevent public use of the site,
thereby eliminating the possibility of installing a water supply well in the
contaminated area.
Alternative 2b provides two possible sources of alternate drinking water supplies which .
include:
• Connecting the Base to the city water supply; or
• Decommissioning the current Base family housing wells located nearest to the
plume and relying on increased production from the other family housing wells
which are located even further away from the contaminated zone.
2.7.3 Alternative 3 • Extraction/Injection and Treatment
Remedial Alternatives 3a and 3b rely on active cleanup of the plume. The time required to
achieve remediation pursuant to this alternative is estimated by computer modeling to be 10
years [IT 1991b]. The modeling was performed using GWFL3D code [Walton 1989] and
RL/12-93/EES/I1700I6.ROM 2-39
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interactive version of the PLASM code [Prickett and Longquist 1971], and the GWTR3D
code [Walton 1989] to simulate transport of TCE in the SWBZ. The modeling also utilized
predicted TCE concentrations generated using AT123D: Analytical Transient one-, two-, and
three-Dimensional Simulation of Waste Transport in the Aquifer System [Yen 1981, IT
1991a]. In these alternatives, water is modeled to be pumped at a total of 200 gpm from
specifically located pumping wells, is treated to remove the contamination, and is then
injected into an array of injection wells up-gradient of the plume to direct the flow of
contamination toward the capture wells. Continued groundwater monitoring is also included
in Alternatives 3a and 3b.
For Alternatives 3a and 3b, the goal is to reduce the concentration of the plume to 5 pg/l
(ppb) to meet the MCL ARAR. The treated water will be injected into the SWBZ. Best
available control technology (BACT) will be used for the treatment system off-gasses if
required to meet Sacramento Metropolitan Air Quality Management District (SMAQMD) air
rules ARAR.
Alternative 3a evaluates using UV and ozone or hydrogen peroxide to oxidize and degrade
the TCE in the removed groundwater. The end-products of the UV/OX process are chiefly
carbon dioxide and water. Alternative 3b evaluates the combination of two industry standard
cleanup processes to remove the TCE from the extracted groundwater. Air stripping uses a
stream of air to separate the TCE from the water. Once the TCE volatilizes and becomes a
part of the air stream, the air stream is filtered with activated carbon to remove the TCE
vapor from the air. As the filter becomes saturated with TCE, it is exchanged for a fresh
filter. The spent filter is shipped to a carbon regeneration facility where the TCE is
thermally destroyed. Alternative 3b, with injection of treated .effluent into the SWBZ, is the
selected remedy (see Section 2.9) for this ROD.
2.7.4 Alternative 4 - Extraction/Treatment with Discharge to Mather Lake or Sewer
Alternatives 4a and 4b rely on active cleanup of the plume. The time required to achieve
remediation pursuant to this alternative is estimated by numerical computer modeling to be
more than 10 years [IT 1991b]. The modeling was performed using GWFL3D code [Walton
1989] and interactive version of the PLASM code [Prickett and Longquist 1971], and the
GWTR3D code [Walton 1989] to simulate transport of TCE in the SWBZ. The modeling
also utilized predicted TCE concentrations generated using AT123D: Analytical Transient
one-, two-, and three-Dimensional Simulation of Waste Transport in the Aquifer System [Yeh
1981, IT 1991a]. '
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The treatment portion of Alternative 4a is the same as Alternative 3a in that groundwater is
extracted via pumping and treated with UV/OX. The difference between Alternatives 3a and
4a is that in Alternative 4a the treated water will either be:
• Discharged to Mather Lake, thereby reducing the need to supply .Mather Lake
with water from other sources (i.e., Folsom South Canal); or
• Discharged to the sanitary sewer line for disposal by the Sacramento County
Sewage Treatment Plant
The treatment portion of Alternative 4b is the same as Alternative 3b. Groundwater is
extracted via pumping and treated with air stripping and a vapor phase carbon adsorption
system if necessary. The treated water is discharged via one of the two options described in
Alternative 4a above, i.e., to Mather Lake or to the sanitary sewer.
Continued groundwater monitoring is also included in Alternatives 4a and 4b.
2.8 Summary of the Comparative Analysis of Alternatives
The remedial alternatives developed in the Feasibility Study were analyzed in detail using the
nine evaluation criteria required by the NCP (Section 300.430(e)(7)). These criteria are
classified as threshold criteria, primary balancing criteria, and modifying criteria. Threshold
criteria are:
(1) Overall protection of human health and the environment; and
(2) Compliance with ARARs.
Primary balancing criteria are:
(3) Long-term effectiveness and permanence;
(4) Reduction of toxicity, mobility, or volume through treatment;
(5) Short-term effectiveness;
(6) Implementability; and
(7) Cost.
Modifying criteria are:
(8) State/support agency acceptance; and
(9) Community acceptance.
RUI2-93/EES/8I700I6.ROM 2-41
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The resulting strengths and weaknesses of the alternatives were then weighed to identify the
alternative providing the best balance among the nine criteria. Table 2.8-1 summarizes this
comparison.
2.8.1 Overall Protection of Human Health and the Environment
Overall protection of human health and the environment addresses whether a remedy
provides adequate protection and describes how risks posed through each pathway are
eliminated, reduced, or controlled through treatment, engineering controls, or institutional
controls. The RI baseline risk assessment determined the excess cancer risk of the TCE
plume to a human receptor as 1.1 x 10^ [TT 1991a]. Therefore, implementation of the no-
action (Alternative 1) or either of the two institutional control alternatives (Alternatives 2a
and 2b) would result in risk within the acceptable limits, i.e., between 10"* and 10"4. For
these alternatives and using exposure concentrations predicted by the AT123D analytical
computer model [Yeh 1981], calculated risk would decrease from 1.1 x 10~s at present to less
than 1.0 x Itf7 by year twenty [TT 1991a].
Implementation of an extraction/treatment system (Alternatives 3a, 3b, 4a, or 4b) decreases
risk from the plume at a more rapid rate. The risks presented below are estimated to
represent risks due to the remaining TCE, as predicted by computer modeling, at the end of
that particular year [IT 1991b]. The modeling was performed using GWFL3D code [Walton
1989] and interactive version of the PLASM code [Prickett and Longquist 1971], and the
GWTR3D code [Walton 1989] to simulate transport of TCE in the SWBZ. The modeling
also utilized predicted TCE concentrations generated using AT123D: Analytical Transient
one-, r\vo-, and three-Dimensional Simulation of Waste Transport in the Aquifer System [Yeh
1981, IT 199la]. The estimates are exceedingly conservative in that they do not allow for
any losses due to degradation, dispersion, natural attenuation, etc., over the entire assumed
human exposure period of 30 years. The average concentration of the remaining TCE as
predicted by the computer fate and transport modeling at one, five, and ten years are
assumed to be representative of the long-term exposure contamination [TT 1991a].
The estimated excess cancer risks (using the RME concentration, i.e., the 95% upper
confidence arithmetic average of modeling projections [IT 1991b]> from the TCE remaining
RU12-93/EES/S170016.ROM 2-42
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£
Table 2.8-1 Summary of Comparative Analysis
ALTERNATIVES
CRITERIA
Overall Protectlveness of
Human Health &
Environment
Compliance with ARARs
Long-Term Effectiveness
and Permanence
Reduction of Toxlclty,
Mobility, or Volume
Short-Term Effectiveness
Implementablllty
Present
Cost Worth
(millions)
1
Baseline
Risk Is
1. IE-OS
2a
2b
Institutional controls
prevent exposure by
eliminating pathway
3a
3b
Active remediation
reduces risk to
4.0E-07 In year 6.
4a
4b
Active remediation
reduces risk to
4.0E-07 In year 7.
All alternatives will reduce TCE levels to below 5 ppb.
However, the time-frames over which the reduction occurs differ as follows:
2O years
20 years
2O years
1O years
1O years
> 1O years
>10 years
All alternatives offer the same degree of long-term effectiveness.
No residual risk will remain to threaten human health and the
environment once the cleanup goals have been met.
No Induced reduction. •
Reduction occurs only via
natural attentuatlon.
TCE levels are reduced
below 5 ppb In 1 0
years.
TCE levels are reduced
below 5 ppb 1O-20
years. :
'• I
All alternatives offer a high degree of short-term effectiveness. .
No adverse community, worker, or environmental Impacts anticipated.
• • . : " ; i ' ".
All alternatives are considered' to be readily Implementable;
however, Implementablllty Is rated as follows:
Highest j Very High! Highest 1 Very High; Very High) High
$0.4
Deed
$0.4
Security
$0.7
City Water
$3.1
Modify
$1.0
$4.5
$3.5
Lake
$5,3
Sewer
$5.7
| High
Lake
$4.3
Sewer
$4.8
-------
in the groundwater at 1, 5, and 10 years (assuming an operating life of ten years) are shown
in Table 2.8-2.
Table 2.8-2 Estimated Excess Cancer Risks
Alternative
Pumping With Injection
Pumping Only
Year 1
8.0 x 106
9.4 x 10*
Year?
4.9x10?
1.3 x 10*
Year 10
9.6X104
1.6 x 1C"7
2.8.2 Compliance with Applicable or Relevant and Appropriate Requirements
Pursuant to section 121(d) (1) of CERCLA [42 USC Section 962 l(d)], remedial actions must
attain a degree of clean-up which assures protection of human health and the environment.
Additionally, remedial actions that leave hazardous substances, pollutants, or contaminants on-
site must meet standards, requirements, limitations, or criteria that are ARARs. Federal ARARs
for any site may include requirements under any federal environmental laws. State ARARs
include promulgated requirements under state environmental or facility-siting laws that are more
stringent than any Federal ARARs and that have been identified to the U.S. EPA by the state
in a timely manner.
Applicable requirements are those cleanup standards, control standards, and other substantive
environmental protection requirements, criteria, or limitations promulgated under Federal or
State law that specifically address a hazardous substance, pollutant, contaminant, remedial
action, location or other circumstances at a CERCLA sitel '
Relevant and appropriate requirements are defined as those cleanup standards of control and
other substantive environmental protection requirements, criteria, or limitations promulgated
under Federal or State law that, while not "applicable" to a hazardous substance, pollutant,
contaminant, remedial action, location or other circumstance at a CERCLA site, nevertheless
address problems or situations sufficiently similar to those encountered at the CERCLA site to
indicate their use is well-suited to the particular site. If no ARAR addresses a particular
situation, or if an ARAR is insufficient to protect human health or the environment, then non-
promulgated standards, criteria, guidance, and TBC advisories may be used to provide a
protective remedy.
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The regulatory framework associated with the cleanup of groundwater at the AC&W Site is
driven by the potential beneficial use of local groundwater. "The goal of EPA's Superfund
approach is to return useable groundwater to their beneficial uses within a timeframe thatjs
reasonable" [Federal Register page 51433, December 21, 1988]. Drinking water is considered
to be the highest beneficial use and remediation to drinking water standards affords the greatest
level of protection and cleanup. As required by the California Porter-Cologne Water Quality
Act, the Regional Water Quality Control Board - Central Valley Region defines the beneficial
uses of various water bodies for the Sacramento River Bask. Water bodies and their beneficial
uses are presented in the Central Valley Basin Plan. The Basin Plan classifies aquifers in the
AC&W Site area to have "existing or potential beneficial uses as sources of drinking water".
This regional plan has been promulgated and is an ARAR for the AC&W Site.
Section 121(e) of CERCLA, USC Section 962 l(e), states that no federal, state or local permit
is required for remedial actions conducted entirely on-site. Therefore, action conducted entirely
on-site must meet only the substantive, not the administrative, requirement of the ARAR. Any
action which takes place off-site is subject to the full requirements of the federal, state, and local
regulations.
CERCLA Section 121 states that, at the completion of a remedial action, a level or standard of
control required by an ARAR will be attained for wastes that remain on-site. In addition, the
NCP, 40 CFR Section 300.435(b)(2) requires compliance with ARARs during the course of the
Remedial Design/Remedial Action.
Applicable or relevant and appropriate requirements are identified on a site-specific .basis from
information about specific chemicals at the site, specific actions that are being considered as
remedies, and specific features of the site location. There are the three types of ARARs:
• Contaminant-specific requirements are ARARs that set limits on concentrations
of specific hazardous substances, pollutants, and contaminants in the environment
such as ambient water quality criteria and drinking water standards.
• Action-specific requirements are ARARs that set technology-based restrictions
which are triggered by the type of action under consideration. Examples of
action-specific ARARs are Resource Conservation and Recovery Act (RCRA)
regulations of waste treatment, storage, and disposal.
• Location-specific requirements are ARARs that set restrictions on certain types
of activities based on site characteristics such as restrictions on activities in
wetlands, floodplains, and historic sites.
RLU2-93/EES/S170016.ROM 2-45
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The following sections outline the ARARs and other information that U.S. EPA considered for
the AC&W Site.
2.5.2. 1 Contaminant-Specific Applicable Relevant or Appropriate Requirements
The contaminant-specific ARARs for the AC&W Site are federal drinking water standards and
promulgated State of California drinking water standards which are more stringent than federal
standards. Cleanup levels are set at health-based levels, reflecting current and potential use and
exposure. Each is relevant and appropriate to set cleanup standards at the site. For systemic
(noncarcinogenic) toxicants, cleanup levels represent that amount to which humans could be
exposed on a daily basis without appreciable adverse effects occurring during their lifetime. For
carcinogens, cleanup levels must fall within a 104 to 10* risk range [NCP, 40 CFR §300.430
Potential drinking water regulations include MCLs for specific contaminants [Section 1412 of
the SDWA, 42 USC §300g-l "National Drinking Water Regulations"; National Primary
Drinking Water Regulations, 40 CFR Part 141]. Maximum contaminant levels are enforceable
standards which apply to specified contaminants which U.S. EPA has determined have an
adverse effect on human health. The MCL for TCE is 5 ppb. Maximum contaminant levels
are set at level that are protective of human health and set close to Maximum Contaminant
Levels Goals (MCLGs).
Under the authority of the NCP [40 CFR §300.430(f)(5)], MCLGs set at levels above zero must
be attained by remedial actions for ground or surface Water that is currently or potentially a
source of drinking water, where the MCLGs are relevant and appropriate under the
circumstances based on the factors in the NCP [40 CFR .§300.400(g)(2)]. The MCLGs are
applicable to the site if the MCLGs are less stringent than or equal to the federal MCL.
California has promulgated MCL for primary volatile organic compounds, however, the U.S.
EPA has chosen the Federal MCL for TCE, i.e., 5 ppb (/ig/0, as the groundwater cleanup
standard for the AC&W Site because the California MCL for TCE, i.e., 0.005 mg/f (5 /ig/0
[22 CCR Section 64444.5] is equal to the Federal MCL.
2.8.2.2 Action-Specific Applicable or Relevant and Appropriate Requirements
2.8.2.2.1 Air Stripping - Alternatives 3b and 4b. Alternatives 3b and 4b utilize air
stripping to remove TCE from the groundwater followed by vapor phase carbon adsorption to
Rl/i:-93/EES/S1700I6.ROM 2-46
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remove TCE from the air stream. The SMAQMD requires that new source that emits toxic
chemicals to the atmosphere must have authorization for construction and operation. Although
on-site treatment facilities are exempted by CERCLA from administrative requirements of the
permit, emission limits and monitoring requirements imposed by the SMAQMD permit must be
met. These requirements include SMAQMD Rule 202 Section 301, and Rule 402 Section 301,
et seq.:
• SMAQMD Rule 202, Section 301, "Best Available Control Technology" (BACT)
Section 301 is considered to be relevant and appropriate to the air emissions from
the air stripper. BACT is required for emissions of reactive organic compounds.
The SMAQMD requires that a risk assessment for air emissions be performed to
support the remedial design phase. System-specific requirements include ability
of the carbon adsorption system to perform at a minimum control efficiency of
90%, and that daily emissions will be quantified and not exceed SMAQMD
limitations.
• SMAQMD Rule 402, Section 301, "Nuisance"
Section 301 is considered to applicable to the remedial action. Discharges of air
contaminants will not be in such quantities as to cause injury, detriment, nuisance
or annoyance to any considerable number of persons or the public, or endanger
the comfort, repose, health or safety of any such persons or the public, or cause
injury or damage to business or property.
The OSWER Directive 9355.0-28, "Control of Air Emissions from Air Strippers at Superfund
Groundwater Sites" will be considered. This TBC covers all Superfund sites with potential air
stripper emissions. ' = " . . .
2.8.2.2.2 Off-Site Thermal Regeneration .of Spent Activated Carbon -
Alternatives 3b and 4b. Use of activated carbon for remediation of VOCs under Alternatives
3b and 4b could trigger requirements associated with regeneration or disposal of the spent
carbon. If the spent carbon is a listed waste or a characteristic waste then it is regulated as a
hazardous waste under RCRA [42 USC S9601. et seq.1 and California's Hazardous Waste
Management (HWM) regulations [22 CCR 66262.10 - 66262.57].
Movement of contaminants to new locations and placement in or on land will trigger land
disposal restrictions for the waste [RCRA 40 CFR §263 Subpart D]. Additionally, closure for
units which store hazardous waste for more than 90 days must be met [RCRA 40 CFR §264.110
-264.120].
RLU2-93/EES/S170016.ROM 2-47
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Containers used for storage of contaminated carbon that is classified as a listed or characteristic
waste must comply with California HWM regulations [22 CCR 66262.30 - 66262.33].
Accumulation of hazardous waste on-site for more than 90 days may trigger the requirements
set forth in RCRA [40 CFR Part 264] and California HWM regulations [22 CCR 66264].
On-site storage of contaminated carbon can trigger state requirements such as California HWM
regulations [22 CCR 66262.10 - 66262.43, and 66264] and municipal or county hazardous
material ordinances. If the spent carbon is a hazardous waste, construction and monitoring
requirements for storage facilities may also apply.
Disposal of contaminants can trigger RCRA land disposal restrictions for disposal. If land
disposal restrictions are triggered, spent carbon would need to meet treatment standards and
RCRA off-site Subtitle C disposal restrictions would also apply.
The selected remedy will utilize, if necessary, the off-site thermal regeneration of the spent
carbon. Regeneration of activated carbon, using high-temperature thermal process, is considered
"recycling" under both Federal RCRA regulations, and California hazardous waste regulations.
Transportation, storage, and generation of hazardous waste for recycling must comply with
requirements of RCRA and California HWM regulations [22 CCR Sections 66262.10 -
66262.57). Performance standards for hazardous waste incinerators can also be requirements
for on-site carbon reactivation.
2.8.2.2.3 Discharge to Surface Waters • Alternatives 4a-1 and 46-7. Substantive
National Pollutant Discharge Elimination System (NPDES) permit requirements [NPDES, Clean
Water Act §402; 40 CFR Parts 122-125] would apply under Alternatives 4a-l and 4b-l to
discharge of treated effluent to surface waters. These requirements would primarily be effluent
limitations and monitoring requirements. Ambient Water Quality Criteria are used by the State
of California to set Water Quality Standards in the California Inland Surface Waters Plan.
Standards in the plan are used by the RWQCB to set NPDES effluent discharge limitations.
RL/12-M/EES/81700I6.ROM 2-48
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2.8.2.2.4 Underground Injection - Alternatives 3a and 3b. Alternatives 3a and 3b
include groundwater extraction, treatment of the groundwater, and injection of treated effluent
into the SWBZ. Effluent from the groundwater treatment system that is injected into the aquifer
at the AC&W Site, i.e., the SWBZ, must meet the following ARARs:
• "The Water Quality Control Plan (Basin Plan) for the Central Valley Regional
Water Quality Control Board (Region 5): The Sacramento River Basin (Basin
5A), The Sacramento-San Joaquin Delta Basin (Basin SB), and the San Joaquin
River Basin (Basin 5Q" fRWQCB 1990];
• The State Water Resources Control Board Resolution No. 68-16 (Antidegradation
Policy) "Statement of Policy with Respect to Maintaining High Quality of Waters
in California,";
• The State Water Resources Control Board Resolution No. 88-63 (Policy on
Sources of Drinking Water),";
• Section 3020 of RCRA; and
• The federal Underground Injection Control (UIC) Program for class V wells set
forth in 40 CFR Part 144.
The SWRCB Resolution 68-16 requires maintenance of existing State water quality unless it is
demonstrated that a change will benefit the people of California, will not unreasonably affect
present or potential uses, and will not result in water quality less than that prescribed by other
State policies.
According to the decision of the U.S. EPA Administrator, Resolution 68-16, the water anti-
degradation policy, is a State ARAR for the establishment of numerical limits for the reinjection
of treated ground water into clean areas (i.e., high quality waters) of the aquifer, i.e., outside
of the contaminated plume. The numerical limits established on a monthly median and on a
daily maximum basis to meet the requirements of Resolution 68-16 are set forth in Table 2.8-3
With respect to the reinjection of treated ground water within the contaminated plume, treatment
shall be at most the concentration level of the trichloroethylene (TCE) in the ground water at the
point of reinjection measured on a monthly median basis, but not greater than 5 /tg/1, the Federal
and State primary MCL. With respect to reinjection of treated groundwater outside the
contaminated plume, the effluent is required to attain a discharge level for TCE of 0.5 pg/1
measured on a monthly median basis, with the maximum inforceable discharge standard not to
exceed 5.0 jtg/1. To meet the requirement that the selected remedy be protective of human
RLU2-9J/EES/8I700I6.ROM 2-49
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Table 2.8-3 Groundwaler Discharge Treatment Standards
Groundwaler
Constituent
TrichloitMlhylenc (TCE)1
Toul Volilile Organic Constituents (VOCi)'
pH
Discharge Treatment Standards . •
Standards for Injection into Non-Contaminated Portions of the
Aquifer Based on Stale Board Resolution 61-16
(Concentrationi in ug/f)
30 Day Median1
O.I
1.0
6.5 < pH < 8.5
Daily Maximum1
5.0
5.0
Standards for Injection In the Contaminated
Portions of the Aquifer Baaed on UK mote)
atrinfem of (a) MCLa (SlaU or Federal
which ever ia more stringent) as • Daily
Maximum (aee below) or (b) In Situ Oroundwaler
Concentrations at the Point of Injection aa 30 Day Median
(Concentrations In pg/f)
SUM or Federal MCLa Daily Maximum
5.0
1. EPA iMlhod 601 and 602 with • detection limit of 0.5 jig/f.br ten. Iflhe daily maximum ii exceeded in additional ssmple(s) must b« collected and analyzed within the time month lo
demonstrate dial the monthly median haa not been exceeded.
2. Carclnofena.
3. Toul VOCa will be the turn of all EPA Method 601 and 602 analyiii constituents including TCE.
K>
6.
o
-------
health and the environment, the U.S. Air Force shall maintain hydraulic control of the plume
while extracting contaminated ground water, and reinjecting treated ground water into the
contaminant plume or the clean portion of the aquifer.
Section 3020 of RCRA prohibits disposal of hazardous waste above or into a formation which
contains a source of drinking water. This prohibition does not apply to injection of treated
contaminated groundwater into an aquifer if: ' - .
• Such injection is pan of a response action under Section 104 or 106 of CERCLA;
•
• The contaminated groundwater is treated to substantially reduce hazardous
substances prior to such injection; and
• The response action will, upon completion, be adequate to protect human health
and the environment.
The federal UIC Program requires that injection wells such as .those that would be located at the
Site:
• Not cause a violation of the primary MCL in the receiving aquifer, and
• Not adversely affect the health of persons [40 CFR Section 144.12].
The effluent reinjected outside of the contaminated plume and into clean groundwater will have
a discharge median monthly TCE concentration level of 0.5 micrograms per liter (pg/l or ppb).
Reinjection of the effluent within the contaminated plume will have a median monthly TCE
concentration level not exceeding the concentration of TCE in the groundwater at the point of
reinjection. However, in no case will the maximum discharge concentration level exceed 5.0
fig/1 (ppb), the federal and state MCL drinking water standard.
2.8.2.3 Location-Specific Applicable or Relevant and Appropriate Requirements
The Air Force has not identified any location-specific ARARs for the AC&W Site.
2.8.2.4 Compliance With Applicable or Relevant and Appropriate Requirements
All of the alternatives considered in the FS [IT 1991b] will comply with the ARARs. None of
the proposed alternatives will require waivers to be issued. The point in time at which ARARs
are satisfied, however, differs significantly among the alternatives. Alternatives 3a and 3b are
predicted to achieve ARARs about 10 years after start-up by increasing capture efficiency as a
result of injecting the treated effluent. Alternatives 4a and 4b, which rely on extraction only to
RUI2-93/EES/S1700I6.ROM 2-51
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capture and contain the plume, are predicted to require more than 10 years of operation to
achieve ARARs.
Alternatives 1, 2a, and 2b; however, rely on natural attenuation and degradation processes to
reduce contaminant levels. For these alternatives, the rate and transport modeling effort
predicted natural phenomena will require at least 20 years to adequately reduce TCE and achieve
the MCL of 5 ppb [IT 1991a]. The modeling was performed using ATJ23D: Analytical
Transient one-, two-, and three-Dimensional Simulation of Waste Transport'" d* Aquifer System
[Yeh 1981, IT 1991a].
•
2.8.3 Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a remedy to maintain reliable
protection of human health and the environment over time. The criterion includes the
consideration of residual risk and the adequacy and reliability of controls. Long-term
effectiveness and permanence is essentially the same for all seven of the alternatives. The only
long-term activity is groundwater monitoring, and this activity is common to all alternatives,
including no-action.
However, the transition point from short-term to long-term, i.e., the end of the remedial action
implementation period, varies between the alternatives. Long-term is considered to begin when
ARARs are achieved: at least year 20 for Alternatives 1, 2a, and 2b; in about 10 years for
Alternatives 3a and 3b; and in excess of 10 years for Alternatives 4a and 4b.
2.8.4 Reduction of Toxicfty, Mobility, or Volume
Reduction of toxicity, mobility, or volume through treatment refers to the preference for a
remedy that uses treatment to reduce health hazards, contaminant migration, or quantity of
contaminants at the site. Alternatives 3a, 3b, 4a, and 4b (pump and treat alternatives) offer
significant advantages in reduction of toxicity, mobility, and volume relative to Alternatives 1
and 2, i.e., alternatives which do not employ active treatment. In addition, the pump and treat
alternatives fully meet the statutory preference for treatment technologies that permanently
destroy the principal hazardous constituents: Alternatives 3b and 4b resulting in the on-site
destruction of TCE via UV/OX reactions; and Alternatives 3a and 4a resulting in the off-site
destruction of TCE during carbon regeneration. Alternatives 3a and 4a will not meet the
statutory preference for treatment technologies that permanently destroy the principal hazardous
constituents if vapor-phase carbon adsorption is not required to comply with SMAQMD ARARs.
RL/12-93/EES/S170016.ROM 2-52
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The time required to reduce the absolute concentration of TCE to a maximum of 5 ppb
throughout the AC&W Site groundwater plume has not been established definitively, but will
be modeled as part of the remedial design. Modeling results presented in the FS (see Appendix
E, Table E-6 [IT 199 lb]) indicate that Alternatives 3a and 3b may reduce TCE concentration
to maximum of 4 ppb after 10 years of operation while Alternatives 4a and 4b may reduce TCE
concentration to a maximum of 6 ppb in 10 years [IT 1991b]. The modeling was performed
using GWFL3D code [Walton 1989] and interactive version of the PLASM code [Prickett and
Longquist 1971], and the GWTR3D code [Walton 1989] to simulate transport of TCE in the
SWBZ. The modeling also utilized predicted TCE concentrations generated using AT123D:
Analytical Transient one-, two-, and three-Dimensional Simulation of Waste Transport in the
Aquifer System [Yeh 1981, IT 199la]. Thus Alternatives 4a and 4b will probably require more
than 10 years to reduce the AC&W Site SWBZ plume TCE concentration to 5 ppb.
Alternatives 1, 2a, and 2b contribute.no induced reduction of toxicity, mobility, or volume and
rely solely on natural attenuation to reduce the TCE plume to the S ppb level over a period
predicted by the baseline fate and transport modeling to be at least 20 years.
2.8.5 Short-term Effectiveness
Short-term effectiveness refers to the period of time needed to complete the remedy and to any
adverse impacts on human health and the environment that may be posed during the construction
and implementation of the remedy. All of the alternatives are judged to offer a high degree of
short-term effectiveness because of the lack of risk posed to the community and/or workers
during the construction and implementation phase.
The pump and treat alternatives (Alternatives 3a, 3b, 4a, and 4b) are the only alternatives which
could potentially expose the community/workers by bringing TCE to the surface for treatment
However, any potential threat can be readily controlled. The treated groundwater effluent will
be sampled on a regular basis and the Off-gas emissions will be continuously monitored. The
pump and treat system would be de-activated in the event that unacceptable discharges occur.
No adverse environmental impacts are anticipated from the construction and implementation of
any of the pump and treat alternatives. Alternatives 3a and 3b return the treated effluent to the
SWBZ so that the aquifer will not be depleted by extraction of the groundwater.
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2.8.6 Implementabitity
Implementability refers to the technical and administrative feasibility of a remedy, including
availability of materials and services needed to implement the selected remedy. It also includes
coordination of federal, state, and local governments in cleanup of the site. Although all of the
alternatives considered in the detailed analysis are readily implementable, Alternatives 1 and 2b
offer the highest degree of implementability. For obvious reasons, Alternative 1 (no action) is
easily implementable, requiring only monitoring of the groundwater, and Alternative 2b
(alternate water supply) requires only the abandonment of wells, such as Well FH-3, or the
extension of the city water supply.
Alternative 2a (deed restrictions/continued Air Force control) also presents minimal
implementability problems; however, specific actions proposed for this alternative are sensitive
to the future land use. If this alternative were ultimately chosen for implementation, the
possibility exists that at some time into the institutional action (if the AC&W Site were allowed
public access), a change from continued Air Force security to deed restrictions and/or other site
security would be necessary. Therefore, base closure would not preclude implementation of this
alternative.
Of the pump and treat alternatives, Alternatives 3a and 3b are judged more implementable than
Alternatives 4a and 4b because it may be easier to mitigate potential injection well plugging by
biologic growths, metallic precipitants, silt particles, or by other effects than to meet the
requirements governing the discharge of effluent to Mather Lake.
2.8.7 Cost
This criteria examines the estimated cost for each remedial alternative. For comparison, capital
costs and annual O&M costs are used to calculate a present-worth cost for each alternative. A
detailed cost analysis was performed for each of the alternatives proposed in the FS Report (and
sub-options where applicable) [IT 199Ib]. These cost estimates, presented in the FS Report [TT
19916] and Proposed Plan, were calculated assuming a clean up standard of a 5 ppb TCE RME
concentration, however, based on guidance from regulatory agencies, this assumption has been
changed to an absolute TCE concentration of 5 ppb. The revised present worth cost estimates
of each alternative, assuming zero equipment salvage value, zero percent inflation, and a five
percent discount rate, are shown for comparison in Table 2.8-4 in order of least expensive
(Alternative 1) to most expensive (Alternative 4a-2).
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Table 2.8-4 Present Worth Costs for All Alternatives
Alternative
1 No-action
2a-l Deed Restrictions
2a-2 Continue Site Security
2b-2 Modify Well Field
2b-l City Water Supply
3b Air Stripping/Vapor Phase Carbon Adsorption
and Injection
4b-l Air Stripping/ Vapor Phase Carbon Adsorption
and Discharge to Mather Lake
3a Ultraviolet Light/Oxidation and Injection
4b-2 Air Stripping/Vapor Phase Carbon Adsorption
and Discharge to Sanitary Sewer
4a-l Ultraviolet Light/Oxidation and Discharge to
Mather Lake
4a-2 Ultraviolet Light/Oxidation and Discharge to
Sanitary Sewer
Present Worth Costs
$0.4 million
$0.4 million
$0.7 million
$1.0 million
$3.1 million
$3.5 million
$4.3 million
$4.5 million
$4.8 million
$5.3 million
$5.7 million
2.8.8 State/Support Agency Acceptance
State acceptance.indicates whether, based on its review of the RI, FS, and Proposed Plan, the
state in which the site resides agrees with the preferred alternative. The Air Force, as the lead
agency, has involved the State of California Department of Toxic Substances Control, and the
State of California Regional Water Quality Control Board. The Air Force has responded to all
state regulatory agency comments received during their reviews of the Feasibility Study Report
and the Proposed Plans. The state regulators support the selection of Alternative 3b as the
preferred remedy.
2.8.9 Community Acceptance
Community acceptance indicates the public support of a given alternative. Section 3.0 of this
Record of Decision documents the community acceptance of the selected remedy, as presented
in the Proposed Plan.
RL/12-93/EES/JI70016.ROM
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2.3 The Selected Remedy
The U.S. EPA has selected Alternative 3b as the remedy for the AC&W Site. The selected
remedy for contaminated groundwater at the AC&W Site consists of groundwater extraction,
treatment via air stripping and injection of treated effluent into the SWBZ. If necessary to meet
ARARs, the treatment system off-gasses will be collected by activated carbon adsorption. The
effluent limit for TCE (see Table 2.8-3) is 0.5 pg/l as a monthly median for reinjection outside
of the contaminant plume, and variable up to the lesser of 5 pgft .or the concentration in
groundwater at the point of injection, and in both cases will have a daily maximum concentration
of 5 pg/l. The remedial action is intended to restore the AC&W Site groundwater to its
beneficial use, which is a potential source of drinking water. The remediation will be achieved
when the TCE concentration throughout groundwater of the AC&W Site has been reduced to
the ARAR-based SDWA MCL of 5 ngft (ppb). As discussed in Section 2.8.1 above, the TCE
concentration in the groundwater at the conclusion of the remediation will be within or below
the cancer risk range considered to be acceptable, i.e., within the range of 10"* to 10*.
Based on information obtained during the remedial investigation and on a careful analysis of all
remedial alternatives, the U.S. EPA and the State of California believe that the selected remedy
will achieve this objective.
Moreover, the selected remedy (1) does not contemplate discharge to surface waters, and such
discharge is prohibited, (2) prohibits the bypass or overflow of untreated or partially treated
waste, (3) requires that the discharge shall be limited to approved on-site land disposal using
injection wells, and (4) that the pH of the treated ground water shall be between a pH of 6.5 and
8.5 or equivalent to the pH of the receiving water. The Remedial Design (RD) and the
Remedial Action (RA) Work Plan will provide.for alternative discharge options in the event the
reinjection capacity becomes insufficient to handle the treated effluent. These alternative
discharge options will be used only on a temporary basis.
The selection of this remedy is based on a comparative analysis of the alternatives presented
above and provides the best of trade-offs with respect to the nine evaluation criteria. The
selected remedy provides the best route towards achieving the cleanup standards and restoring
the groundwater to full beneficial use.
This section is a description of the conceptual engineering features and operation of the selected
remedy. The initial conceptual design parameters listed below were developed from RI/FS
modeling [IT 1991a, IT 199Ib, and IT 1992e]. The current design parameters being used for
RL/12-93/EES/S1700I6.ROM 2-56
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initial modeling during the remedial design are more reflective of current conditions at the site,
and are indicated in parentheses below the RI/FS model parameters. These parameters are
provided for indication purposes. The specific design details will be determined during^the
remedial design phase in order to meet the performance objective of complete capture of the
contaminant plume to the aquifer cleanup level, and therefore may be different than those listed
and discussed below:
• Influent TCE Concentration = variable, possibly as much as 500 ppb at start-up
(Current design estimates predict an average of about 100 ppb with a maximum
of about 200 ppb.)
• Effluent TCE Concentration = 5 ppb (maximum)
• Groundwater Flow Rate (combined) = 200 gpm
(Current design estimates a combined flow of about 270 gpm)
• Air Flow Rate = 670 cubic feet per minute (cfm)
(Current design estimates 900 cfm)
• Volumetric Air/Water Ratio = 25:1.
The detailed implementation of the selected remedial action will be performed by the U.S. Air
Force in consultation with the regulatory agencies during the RD/RA phase, at which time the
U.S. Air Force will develop reporting, notification and monitoring programs. The monitoring
program shall include sufficient monitoring (both in terms of frequency and test methods
employed) to evaluate the effectiveness of the RA and ensure that the effluent reinjection
standards adopted herein are being met. The U.S. Air Force shall, at a minimum, -include the
following in the RD/RA phase: Locations of the extraction, injection, and performance
monitoring wells, estimated extraction and injection rates, proposed operational procedures,
proposed contingency plan for the extraction, treatment and injection system in the event of
power outage and/or mechanical failure, geologic well logs and well development data sheets
for all newly installed extraction, injection and performance monitoring wells proposed for the
AC&W Site ground water treatment system. The operational procedures shall reflect that the
ground water treatment system will not be operated in excess of its design capacity without the
prior approval of the regulatory agencies.
Since the selected remedy does not contemplate on-site disposal of hazardous or remedial action
derived wastes, no such action specific ARARs were selected. Hazardous and remedial action
derived wastes could consist of wastewater, screenings, sludges and other solids generated during
RL/12-93/EES/1I70016.ROM 2-57
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construction, operation and maintenance of die treatment system. Off-site disposal of such
wastes will be performed in accordance with applicable federal, state and local laws, regulations
and ordinances. However, these requirements would not be considered ARARs under Jhe
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as
ARARs apply only to on-site activities.
2.9.1 Extraction We/Is
The contaminated groundwater would be pumped from the SWBZ from production wells using
down-hole submersible pumps. It is estimated that these wells would have a combined
production rate of 270 gpm. The influent water would flow through buried polyvinyl chloride
(PVQ piping to a pre-treatment filtration unit
Initial background concentration of all potential pollutants shall be determined for each water-
bearing zone in which reinjection will occur.
The U.S. Air Force will perform metals and minerals monitoring before and during the remedial
action. If the results necessitate the establishment of reinjection standards for additional
constituents in order to meet Applicable or Relevant and Appropriate Requirements (ARARs),
an amendment to the ROD, inclusion in the Groundwater/Comprehensive OU ROD, or other
appropriate procedural mechanisms will be considered by the U.S. Air Force, U.S. EPA, and
CalEPA.
2.9.1.1 Pro-Treatment Unit
The pre-treatment unit would consist of a bag-type filter. The filter bag would be capable of
removing particles from the influent water that are as small as 1 micron. Actual specifications
for the pre-treatment unit will be developed during the remedial design phase. Because heavy
solid loads are not anticipated, it should be only necessary to change the filter bag once or twice
per year. Actual maintenance intervals would be dictated by field conditions.
After passing through the pre-treatment unit, the influent would be pumped to the top of the air
stripping tower(s). A description of the major components of the air stripping treatment unit is
presented below.
RI/I2-93/EES/S170016.ROM 2-58
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2.9.1.2 Air Stripping Tower and Blower
The air stripping tower(s) would be of a cylindrical, vertical design which will allow air flow
countercurrent to the liquid flow through packing. Components of a typical air stripping tower
include:
Spray Nozzles
Spray nozzles are used to uniformly distribute the liquid influent over the packing to
avoid channelling and dry spots.
Mist Eliminator
The mist eliminator is a relatively thin bed of packing or wire mesh material. It is
situated above the main packing and spray nozzles and is used to remove entrained water
droplets from the exiting air stream.
Packing System
Within the column of polypropylene packing material, the liquid and countercurrent air
contact each other, stripping contaminants from the liquid. In time, the packing material
can become encrusted with solids precipitated from the liquid influent or can be fouled
with biological growth, necessitating removal and disposal. This fouling would cause
gradual reduced efficiency in the removal of contaminants, as well as increasing the
pressure drop through the packing resulting in decreased air flow from the blower. It
is anticipated that the removal and refill of the packing material would need to be carried
out only once per year. The used packing would be classified as non-hazardous waste
and could be disposed in a sanitary landfill. The treated water would exit the tower and
be forced by an effluent pump along the effluent line to the post-treatment filtration unit
Blower :
The supply air for the air stripping tower is provided by a blower. After contacting the
liquid, the air flows out the top of the stripping tower. Here the off-gas is wanned by
a heater. The heater is used to reduce the relative humidity in the air stream which
increases the effectiveness of the vapor phase carbon adsorption process and reduces
carbon consumption. A heater will not be necessary if activated carbon adsorption of the
vapor phase is not required to comply with SMAQMD ARARs.
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2.9.1.3 Post-Treatment Unit
Specifications of any post-treatment unit (PTU) will be developed during the remedial design
phase. Purposes of the PTU will be to remove any particulates which may have formed in the
treatment process, and to maintain effluent chemical properties to mitigate potential chemical,
physical, or biological fouling of the aquifer and injection wells. The effluent will be pumped
from the PTU to the injection wells through buried PVC pipelines.
2.9.7.4 Vapor Phase Carbon Adsorption System
Vapor-phase carbon-adsorption treatment will be used if required to meet SMAQMD ARARs.
The vapor phase carbon adsorption is included as part of the selected remedy to prevent negative
cross-media impacts and maintain 90% capture efficiency. There are two main types of vapor
phase carbon adsorption systems which may be used in conjunction with the air stripper to
remove contaminants from the off-gas stream. The first type consists of self-contained, portable
activated carbon canisters. These canisters are filled with regenerated granular carbon which
removes impurities from the stripper off-gas. Approximately 2000 to 3000 Ibs of activated
carbon would be needed for the anticipated TCE concentrations and air flow rates. These units
are designed for installation on a concrete pad. The only installation needed is to connect the
inlet from the stripper tower and outlet ports. The canisters can be connected in a series lead-
lag configuration for increased contact times, or parallel configuration for high flow rates. The
useful life of the carbon is dependent upon the concentration of the organic compounds in the
gas stream, flow rate, and temperature. With the AC&W Site treatment system, it is estimated
that the carbon would initially require replacement once per month, with less frequent
replacement as influent TCE concentration decreases. When the carbon becomes saturated with
contaminants, the canister is detached, sealed, and shipped for regeneration. The carbon vendor
would provide shipping and regeneration as a service.
The second type of carbon system is a permanent skid-mounted structure in which single or dual
beds of granular activated carbon are arranged. The system employs the same principles as the
carbon canisters, however, maintenance is more involved. Maintenance consists of removal and
transport of the spent carbon to a regeneration facility, cleaning the vessel and filling the vessel
with regenerated carbon. The shipping and regeneration service would be provided by the
carbon vendor.
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After carbon treatment, the treated vapor would be discharged to the atmosphere. The off-gas
would be analyzed continuously with an in-line monitor to prevent unacceptable releases of
organic gases to the atmosphere. --;
Selection of the type of carbon system will be made after further analysis in the design phase.
2.3.1.5 injection Wells
Detailed specifications for the injection wells will be developed during the remedial design
phase. The location of the injection wells and selection of injection well screen intervals will
be established during the remedial design phase. The treated effluent will be injected into the
SWBZ using wells screened in the SWBZ. These wells will have a combined injection rate of
about 270 gpm, or equal to the extraction rate.
2.9.2 Performance Evaluations
In addition to operational monitoring of influent, effluent, arid air emissions, routine sampling
of the site groundwater (both SWBZ and LWBZ) will be conducted to monitor the migration of
the TCE plume and the decrease in the concentration. Specific sampling, analysis, and
monitoring requirements will be established during the remedial design. This data will be
utilized both as a part of institutional control and as pan of periodic performance evaluations of
the remedial system.
Periodic performance evaluation reports will present groundwater monitoring data. The
evaluation report shall demonstrate that the capture zones of the extraction wells are adequate
to provide complete capture of the plume exceeding the aquifer cleanup standard of 5 /ig/l (ppb)
TCE, and shall demonstrate that the injection of treated groundwater does not degrade the
receiving water quality.
Five-Year Site Reviews and periodic performance evaluations, as recommended by the U.S.
EPA, are to be included as a component of the selected remedy. The specific schedule for
periodic performance evaluations will be determined during the remedial design phase.
However, the U.S. EPA recommends an initial evaluation be conducted one to two years after
the remedy is operational and functional, in order to determine whether modifications to the
restoration action are necessary. The U.S. EPA also recommends that more extensive
performance evaluations be conducted at least every five years [55 FR 8740]. The purpose of
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the evaluations is to determine whether cleanup levels have been, or will be, achieved in the
desired timeframe. After the evaluations are completed, the following options should be
considered:
• Discontinue operation;
» Upgrade or replace the remedial action to achieve the original remedial action
objectives or modified remedial action objectives; and/of
• Modify the remedial action objectives and continue remediation, if appropriate
[55 FR 8740].
2.9.3 Estimated Costs
Major costs associated with the selected remedy were estimated during the FS [IT 1991b]. The
cost estimates have been revised to incorporate the longer period of remediation (10 years versus
6 years) and are summarized in Tables 2.9-1, 2.9-2 and 2.9-3, below. Cost estimates will be
refined and finalized during the remedial design phase.
Table 2.9-1 Selected Remedy Costs - Alternative 3b
Cost Component
Capital
Operation and Maintenance*
Total Costs
Total Dollars x 1000
$1605
$2521
$4126
Present Worth' x 1000
$1602
$2032
$3634
Calculated over a 10 year life, 5% discount rate
RLU2-93/EES/SI70016.ROM
2-62
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K)
8
Selected Remedy: Alternative 3b
Extraction / Injection
Air Stripper with Vapor Phase Carbon Adsorption (200 gpm)
Annual Discount Rate 5%
. Cost / Year (x 1000)
I. Year 0 I 23456789 10 II Totals
2. Capital Costs ******* . .$2.3 $2.3 $2.3 $2.3 $2.3 $1,604.9
3. O&M Costs $0 MM*- ***** ***** HUM* MM* MM* MM* MM* MM* MM* MM .$2,521.2
4. Discount 1.000 0.952 0.907 0.864 0.823 0.784 0.746 0.711 0.677 0.645 0.6140.585
Factor
5. Annual MMM* MM* MM* MM* MM* ***** ***** MM* ***** MM* MM* MM $4.126.1
Expenditures . .
6. Present Worth MMM* ***** ***** MM* MM* ***** ***** MM* ***** *MM MM* MM $3.549.0
Total Cost $3,434
O St M = Operations and Maintenance '
-------
Table 2.9-3 Estimated Cost Summary, Capital and O & M Cost Breakdowns
Selected Remedy: Alternative 3b
Extraction / Injection
Air Stripper with Vapor Phase Carbon Adsorption (200 gpm)
Capital Costs
Construction Costs:
Extraction Wells
Treatment Plant
Auxiliary Components
Injection Wells
Sub-Total Construction Costs
Bid Contingency of 15%
Scope Contingency of 15%
Regulatory Negotiations and Submittals
Total Construction Costs
FS Report
Appendix G
Element No.
$127,020 -3, 167% of 4,
10, 40% of 11
$363,660 , 13, 14, 15, 16
$5,604 5,6,7
$117,000 8, 9, 60% of 11
$613,284
$91,993
$91,993
$23,355
$820,624
Management and Engineering Costs:
CERCLA Documentation
$256,209
Remedial Design $198,783
Construction Management and System Start-Up $317,810
Total Management and Engineering Cost $772,802
Total Capital Cost $1,593,426
O & M = Operations and Mainti
FS Report
Appendix Cl
Dement No.
1, 2, 3
RL/12-93/EES/S170016.ROM
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Table 2.9-3 Estimated Cost Summary, Capital and O & M Cost Breakdowns
(continued)
O&MCosts: Cost/Year
1. Sampling
Yearl $70,110
Year 2-10 $39,840
Year 11 $7,568
2. Labor
Year 1 $108,312
Year 2-10 $90,712
Year 11 $38,096
3. Air Stripper / Carbon Adsorption O & M
Year 1-10 $83,053
4. Miscellaneous O & M
Year 1-10 $30,081
Year 11 $3,249
Total O & M Costs / Year
Year 1 $291,556
Year 2 - 10 $243,686
Year 11 $48,913
TotalO&MCost $2,533,643
O & M = Operations and Maintenance
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2.10 Statutory Determinations
The selected remedy satisfies the statutory requirements of Section 121 of CERCLA, as amended
by SARA, in that the following four mandates are attained:
• The selected remedy is protective of human health and the environment, will
decrease site risks, and will not create short term risks nor have cross-media
consequences;
• The selected remedy complies with federal and state requirements that are
applicable or relevant and appropriate to the remedial action such as chemical-
specific ARARs, chemical-specific cleanup standards, and action-specific ARARs
for discharge of treated effluent by underground injection;
• The selected remedy is cost-effective in its fulfillment of the nine CERCLA
evaluation criteria through remediation of the contaminated groundwater in a
reasonable period of time; and
• The selected remedy M^KM* permanent solutions and alternative treatment
technologies or resource recovery technologies, to the maximum extent
practicable while concurrently satisfying the statutory preference for remedies that
employ treatments which reduce toxicity, mobility, and/or volume.
The following sections describe how the selected remedy satisfies each of the statutory
requirements and the preference for treatment.
2. 10. 1 Protection of Human Health and the Environment
As reported in the RI Report [IT 1991a], current on-site health risks are calculated to be within
the range considered to be acceptable by the U.S. EPA (i.e., within the 10"4 to 10"6 carcinogenic
risk range [55 FR 8716]). Active treatment of the groundwater will further reduce the risk, as
indicated in Section 2.8.1. Five- Year Site Reviews will apply to the selected remedy
[55 FR 8730] since during the period of remediation, hazardous substances will remain on-site
possibly in concentrations above health-based levels.
Section 2.8.5 discussed the short-term effectiveness of the evaluated alternatives. The selected
remedy will not pose unacceptable short-term risks to human health or to environment during
implementation. Section 2.6.2 discussed the current on-site risks to the environment. Control
measures have been incorporated into the conceptual design of the remedy, including off-gas
monitoring, treatment unit security (e.g., fencing), effluent monitoring, and possibly the
implementation of BACT for. the air emissions.
RL/12-93/EES/1I70016.ROM 2-66
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2.70.2 Compliance with Applicable or Relevant and Appropriate Requirements
The selected remedy, when complete, will have reduced the concentrations of contaminants in
groundwater to clean up standards thereby satisfying the chemical-specific ARARs (Federal_o.r
State MCL, whichever is more stringent for the site). In addition, during remediation, this
remedy will meet action-specific ARARs for discharge of treated groundwater into the aquifer
by injection. For any waste carbon that is generated during treatment, the applicable RCRA and
more stringent California HWCA requirements will be met No waiver will be necessary.
2.10.3 Cost Effectiveness
As discussed previously, all alternatives evaluated in the FS were equally effective as all will
eventually achieve the SDWA MCL. Alternatives 3a and 4a, however, satisfy the regulatory
preference for active treatment, when practicable (see 40 CFR 300.430 (a)(l)(iii)(D)).
Alternatives 3b and 4b also satisfy the required preference for active treatment, when
practicable, only if vapor phase carbon adsorption is required. As shown in Section 2.8.7, the
selected remedy is less costly than a similar alternative involving the use of UV/OX for
treatment (Alternative 3a).
2.10.4 Utilization of Permanent Solutions and Alternative Treatment (or
Resource Recovery) Technologies to the Maximum Extent Practicable
Table 2.8-1 summarizes the detailed analysis of the alternatives with respect to the CERCLA
mandated evaluation criteria and identifies the major trade-offs of the selected remedy. The
selected remedy, Alternative 3b, by actively treating the groundwater, satisfies the statutory
preference to utilize permanent solutions and treatment technologies to the maximum extent
practicable. The trade-offs in the evaluation criteria of the selected remedy, as compared to the
other alternatives, is as follows. The selected remedy'offers potentially greater implementability
than Alternative 4a by avoiding discharge of treated effluent to Mather Lake. It also offers the
advantage that the extraction and treatment of the groundwater will not deplete the SWBZ. Air
stripping/vapor phase carbon adsorption is preferred over UV/OX because the technology is:
• More developed and proven in similar applications;
• More capable of handling variable flow rates and/or TCE concentration;
• Considered more reliable, less complex, and subject to less complicated operation
and maintenance requirements; and
• More cost-effective.
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2.10.5 Preference for Treatment as a Principal Element
The primary risk potentially posed by the AC&W Site is from a hypothetical exposure to TCE
contaminated groundwater. The hypothetical exposure scenario requires a drinking water
supply well to be installed in the plume. The selected remedy employs active treatment of the
groundwater, via air stripping, to mitigate the potential threat to human health. Therefore, the
CERCLA preference for treatment is satisfied by the selected remedy.
2.11 Documentation of Significant Changes
The Proposed Plan for the AC&W Site was released for public comment in October 1991. The
Proposed Plan identified Alternative 4b (i.e., extraction, treatment by air stripping and vapor
phase carbon adsorption, and discharge to Mather Lake) as the preferred alternative. The Air
Force, as lead agency, reviewed all written and verbal comments submitted during the public
comment period.
However, after realization of ARARs by the regulatory agencies, it was determined that
Alternative 3b (i.e., extraction, treatment by air stripping and vapor phase carbon adsorption,
and injection of treated effluent into the SWBZ) is more cost effective than Alternative 4b. The
Air Force released a Revised Proposed Plan for public comment in March 1992, which identified
Alternative 3b as the preferred alternative. The Air Force, as lead agency, reviewed all written
and verbal comments submitted during the public comment period. After comment review, it
was determined that no significant changes to the remedy outlined in the Revised Proposed Plan
were necessary.
2.72 References : .
Aero- Installation Restoration Program Phase II Stage 2 Final Report. September
Vironment 1985 to June 1987. Volumes 1 and 2. Prepared by AeroVironment Inc.,
1987 Monrovia, California.
Aero- Installation Restoration Program Phase II. Confirmation/Quantification Stage 3
Vironment Final Report. July 1986 to March 1987. Volumes 1 and 2. Prepared by
1988 AeroVironment Inc., Monrovia, California.
R1J12-93/EES/SI70016.ROM 2-68
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CH2M- Installation Restoration Program Records Starch for Mather Air Force Base.
Hill, Inc. California. Phase I. June 1982. Contract No. F0863780-G0010-0013,
1982 Gainesville, Florida. •—;
EA 1990a Quarterly Ground Water Sampling at Mather Air For?? Pare, May- June 1990.
Prepared by EA Engineering, Science and Technology Corporation, Lafayette,
California. .
EA 1990b QuaifTly Ground Water Sampling at Mather Air Force Base. August 1990.
Prepared by EA Engineering, Science and Technology Corporation, Lafayette,
California.
EA 1990c Quarterly Ground Water Sampling at Mather Air Force Base. November.
December 1990. Prepared by EA Engineering, Science and Technology
Corporation, Lafayette, California.
EPA 1987 Trichloroethylene. in Health Advisories for 25 Organics. Office of Drinking
Water, NTTS Document No. PB87-235578.
EPA 1988a CERCLA Compliance with Other Laws Manual: Interim Final. August 1988,
EPA/540/G-89/006, U.S. Environmental Protection Agency, Washington, D.C.
EPA 1988b Guidance on Remedial Actions for Contaminated Ground Water at Superfund
Sites. December 1988, EPA/540/G-88/003, U.S. Environmental. Protection
Agency, Washington D.C. .
EPA 1989a Interim Final Guidance On Preparing Superfund Decision Documents: The
Proposed Plan. The Record of Decision. Explanation of Significant Differences,
The Record of Decision Amendment. June 1989, OSWER Directive 9355.3-02,
Office of Emergency and Remedial Response, U.S. Environmental Protection
Agency, Washington, D.C.
EPA 1989b Risk Assessment Guidance for Suoerfund. Volume I. Human Health Evaluation
Manual. Interim Final. December, 1989, EPA/540/1-89/002, U.S. Environmental
Protection Agency, Washington, D.C.
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EPA 1990 Health Effects Assessment Summary Tables: First and Second Quarters. FY
1990. Office of Solid Waste and Emergency Response, OSWER 9200.6-303-(89-
4) —
IT 1990a Sampling and Analysis Report for Site Monitor Wells October/November 1988
Mather Air Force Base. California. Prepared by IT Corporation forHAZWRAP.
IT 19905 U.S. Air Force Installation Restoration Program. RI/FS Activities for Mather Air
Force Base. California. Final Site Inspection Report. August 1990, Prepared by
IT Corporation for HAZWRAP.
IT 199la U.S. Air Force Installation Restoration Program. Final Remedial Investigation
Report of the AC&W Site for Mather Air Force Base. California. March 1991,
Prepared by IT Corporation for HAZWRAP.
IT 1991b U.S. Air Force Installation Restoration Program. Feasibility Study for Mather Air
Force Base. California. AC&W Site. Final Report. August 1991, Prepared by IT
Corporation for Battelle Environmental Management Operations (EMO).
IT 1991c U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. June 1991. Mather Air Force Base. California. July 1991.
Prepared by IT Corporation for Battelle Environmental Management Operations
(EMO).
IT 1991d U.S: Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Third Quarter 1991. Mather Air Force Base. California.
September 1991. Prepared by IT Corporation for Battelle Environmental
Management Operations (EMO).
IT 1992a U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Fourth Quarter 1991. Mather Air Force Base. California.
January 1992. Prepared by IT Corporation for Battelle Environmental
Management Operations (EMO).
RU12-93/EES/S1700J6.ROM
2-70
-------
IT 1992b U.S. Air Force Installation Restoration Program, Quarterly Groundwater
Monitoring Report. First Quarter 1991. Mather Air Force Base. California. June
1991. Prepared by IT Corporation for Battelle Environmental Management
Operations (EMO).
IT 1992c U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Second Qy?rfn' i°92. Mather Air Force Base. California.
August 1992. Prepared by FT Corporation for Battelle Environmental
Management Operations (EMO).
IT 1992d U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Third Quarter 1992. Mather Air Force Base. California.
November 1992r Prepared by IT Corporation for Battelle Environmental
Management Operations (EMO).
IT 1992e U.S. Air Force Installation Restoration Program. Preliminary Design
Investigation. Mather Air Force Base. California. AC&W Site. Final Report
June 1992, Prepared by IT Corporation for Battelle Environmental Management
Operations (EMO).
IT 1993a Closure Report. Building 10400. UST 10400B. Underground Storage Tank
Removal Project. Mather Air Force Base. California, September 1993. Prepared
for U.S. Army Corps of Engineers, Sacramento, California.
IT 19935 U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Fourth Quarter 1992. Mather Air Force Base. California.
February 1993. Prepared by IT Corporation for Battelle Environmental
Management Operations (EMO).
IT 1993c U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. First Quarter 1993. Mather Air Force Base. California. June
1993. Prepared by IT Corporation for Battelle Environmental Management
Operations (EMO).
RUI2-93/EES/SI70016.ROM 2-71
-------
IT 1993d U.S. Air Force Installation Restoration Program. Quarterly Groundwater
Monitoring Report. Second Quarter 1993. Mather Air Force Base. California.
August 1993. Prepared by IT Corporation for the Air Force Center for
Environmental Excellence (AFCEE).
IT 1993e IRP 1993 Draft Groundwater Monitoring Program Project Plans for Mather Air
Force Base. California. Vol. I - Sampling and Analysis Plan. Vol. 2 - Quality
Assurance Project Plan. Vol. 3 - Health and Safety Plan. IT Corporation,
Martinez, California, March 1993.
Prickett and Selected Digital Computer Techniques for Groundwater Resource Evaluation.
Longquist Prickett, T.A., and C.G. Longquist, 1971, Bulletin 55, Illinois State Water
1971 Survey, Champaign, Illinois.
RWQCB Staff Report of the California Regional Water Quality Control Board. Central
1989 Vallev Region. "A Compilation of Water Quality Goals", November 1989,
Prepared by Marshack, J.B.
RWQCB The Water Control Plan (Basin Plan) for the Central Valley Regional Water
1990 Quality Control Board (Region 5): The Sacramento River Basin (Basin 5A), The
Sacramento-San Joaquin Delta Basin (Basin 5B), and The San Joaquin River
Basin (Basin 5Q, Second Edition, March 1990, California Regional Water
Quality Control Board • Central Valley Region, Sacramento, California.
SWRCB California Inland Surface Waters Plan: Water Quality Control Plan for Inland
1991 Surface Waters of California. 199.1, California State Water Resources-Control
Board, Sacramento, California.
Walton 1989 Numerical Groundwater Modeling: Flow and Contaminant Migration. Walton,
William C., 1989, Lewis Publishers, Inc., Chelsea, Michigan.
Weston Installation Restoration Program Phase II - Confirmation/Quantification Stage I
1986 Final Report. Volumes 1 and 2. September 1983 to June 1986. June 1986,
Prepared by Roy F. Weston, Inc., West Chester, Pennsylvania.
R1V12-93/EES/81700IS.ROM
2-72
-------
Yeh, G.T. AT123D: Analytical Transient one-, two-, and three-Dimensional Simulation
1981 Waste Transport in the Aquifer System. ORNL-5602.
22 CCR Maximum Contaminant Levels. California Code of Regulations, Title 22,
64444.5 Section 64444.5.
22 CCR
66262.10-
66262.57
Standards Applicable to Generators, Of Hfl'flTv'PV? Waste. California Code of
Regulations, Title 22, Sections 66262.10 - 66262.57.
22 CCR
66262.30 -
66262.33
Pre-Transport Requirements. California Code of Regulations, Title 22,
Sections 66262.30 - 66262.33.
22 CCR Standards for Owners and Operators of Hazardous Waste Transfer. Treatment.
66264 Storage, and Disposal Facilities. California Code of Regulations, Title 22, Section
66264.
40 CFR 122 EPA Administered Permit Programs: The National Pollutant Discharge
Elimination System. Code of Federal Regulations, Title 40, Part 122, U.S.
Environmental Protection Agency, Government Printing Office, Washington,
D.C.
40 CFR 136 Guidelines for Establishing Test Procedures for the; Analysis of Pollutants Code
of Federal Regulations, Tide 40, Part .136, U.S. Environmental Protection
Agency, Government Printing Office, Washington, D.C.
40 CFR 300 National Oil and Hazardous Substances Pollution Contingency Plan. Code of
Federal Regulations, Title 40, Part 300, U.S. Environmental Protection Agency,
Government Printing Office, Washington, D.C.
53 FR 53194 Federal Register. Volume 53, December 21, 1988, page 51394 etseq.. EPA's fi
SSU Preamble to the Proposed Rule of the "National Oil and Hazardous
Substances Pollution Contingency Plan", 40 CFR Part 300, U.S. Environmental
Protection Agency, Government Printing Office, Washington D.C.
RL/12-9J/EES/JI70016.ROM
2-73
-------
55 FR 8666 Federal Register. Volume 55, March 8, 1990, page 8666 etseq.r EPA's et seq.
Preamble to the Final Rule of the "National Oil and Hazardous Substances
Pollution Contingency Plan", 40 CFR Pan 300, U.S. Environmental Protection
Agency, Government Printing Office, Washington, D.C.
RU12-9J/EES/8170016.ROM 2-74
-------
3.0 Responsiveness Summary
The public comment period for the Proposed Plan at the AC&W Site, Mather AFB, began on
October 1, 1991 and expired on October 31, 1991 without any comments being received by the
base or regulatory agencies. The public meeting presenting the Proposed Plan occurred on
October 1, 1991. The transcript from the public meeting is included in die Administrative
Record. While one comment was made during the October 1, 1991 public meeting presenting
the Proposed Plan, it related more to base closure than the AC&W Site remediation. The
comment is found on page 16 of the transcript from the October 1, 1991 meeting. Note that on
page 10 line 10 of the transcript Lt Col. Blank used the word "below" when he meant 'above".
His statement should have been, "None of the wells in the current round of sampling show any
contamination above detection limits in that deeper water bearing zone."
The public comment period for the Revised Proposed Plan at the AC&W Site, Mather AFB,
began on March 16, 1992 and expired on April IS, 1992 without any comments being received
by the base or regulatory agencies. The public meeting presenting the Revised Proposed Plan
occurred on April 1, 1992. The transcript from the public meeting is included in the
Administrative Record. The transcript contains all public comments and responses from
representatives from Mather Air Force Base, EPA, and California regulatory agencies. The
public made 18 comments during the public meeting on April 1, 1992. Twelve comments were
directly applicable to the selected remedy in the Revised Proposed Plan. These comments and
the U.S. Air Force Air Training Command responses are provided below. The other comments
were of a more general nature. .
1. Why are we concerned with TCE (trichloroethylene)? What are the real effects? Why
are we so concerned? (Mr. Flaming)
Trichloroethylene (TCE) is a suspected human carcinogen, for which a Safe Drinking
Water Act maximum contaminant level (MCL) of five parts per billion has been
established. The MCL is set at that level to ensure no more than one person in one
million who consistently consumes water containing that amount of TCE will contract
cancer from that exposure. Because the groundwater underlying Mather AFB is
classified by the State of California as a potential drinking water source, the water must
be treated to a level that meets the MCL of five parts per billion.
RI/12-93/EES/8170016.ROM
-------
2. Has any of the water on the (AC&W) site been treated yet? (Ms. Rogers)
No permanent treatment has been initiated at the AC&W Site. An aquifer pumping test
was performed in 1990; this test removed sufficient contaminated groundwater to reduce
the maximum TCE level in the groundwater, but the water was not treated on site.
Untreated groundwater was discharged to the regional sewer where it was treated by
Sacramento County.
3. How long would that treatment take before you got it to the five parts per billion? (Ms.
Rogers)
Reducing the TCE concentration in the plume to an average of five parts per billion has
been projected to take six years of operation of the groundwater extraction, treatment and
reinfection system. The Air Force has not calculated the time required to reduce the
TCE concentration to a maximum of five parts per billion everywhere in the plume.
This calculation will be performed during design of the treatment system.
4. Do you know that (the treatment system proposed for the AC&W Site) to be effective
from other locations? (Mr. Flaming)
Groundwater extraction, treatment and reinjection systems have been shown to be
effective for reduction of total mass of contaminants in groundwater systems and for
capture and containment of contaminated groundwater. Experience with these systems
has shown that reducing contamination to acceptable limits can take longer than predicted
through groundwater modelling. However, since groundwater extraction is effective at
containment and mass reduction, it is the method of remediation most often chosen for
sites with contaminated groundwater.
5. "Are (civilians) going to be allowed to go onto the (AC&W) Site? Is there a risk to the
civilian tenant coming on-base within the six-year time frame (calculated for treatment
system operation)? (Mr. Flaming)
Civilian use of the AC&W Site is a possibility. Reuse options for base property are still
being pursued.
The calculated risk from the AC&W Site is to persons drinking contaminated
groundwater from the shallow aquifer. If someone drilled a well into the most
contaminated portion of the shallow aquifer within the six-year time the groundwater is
being treated, the water from that well would contain TCE in concentrations above the
maximum contaminant level (MCL). The MCL is calculated based on a lifetime (70-
year) excess cancer risk of one in a million.
6. Is Mather Air Force Base responsible for the original contamination? (Ms. Rogers)
Yes, it is most probable the contamination at the AC&W Site originated from Air Force
operations at that site.
R1/I2-93/EES/J170016.ROM 3-2
-------
7. Is that (source of contamination) the pipe that they can't find? Is that where they think
the contamination is coming from? (Ms. Rogers) _
Yes. The disposal pipe that was referenced in the Installation Restoration Program Phase
I Report (Preliminary Assessment) is still thought to be the likely source of contamination
at the AC&W Site.
8. What year do you think (Lt Col Blank) (that) there was dumping into the pipe? (Ms.
Rogers) ,
Records indicate the pipe was used from about 1958 to 1966.
9. Was it (dumping into the pipe) just forgotten about until 1979? (Ms. Rogers)
The disposal into the pipe was standard practice at the time. It was not until 1979, when
TCE contamination was discovered in groundwater at other locations in the Central
Valley, that anyone thought further about this disposal activity.
10. What's TCE used for? Is it a by-product of some sort? (Mr. Gray)
TCE is a chlorinated solvent used widely in the 1950s through 1970s for cleaning and
degreasing. It was brought onto the base as a primary product, not a by-product
11. (Are) federal monies being used to do this clean-up? (Ms. Rogers)
Yes. Monies used for environmental clean-ups at Mather AFB come from a special
account within the Department of Defense budget (the Base Realignment and Closure
Account).
12. Is there an estimate how much (the remediation will cost) for this six-year period? (Ms.
Rogers)
The current estimate for construction of the remediation system at the AC&W Site is
$2.9 million.
RJL/I2-9J/EES/M700I6.ROM 3.3
-------
Attmlnlilriilv* Record Indtit, Aircraft Control MM! Warning SH*
ID
82001
87002
•2003
83001
8)002
•3003 10/3/83
83004 I2WN
83005 12/20/93
84001 8/IT/84
04002
94003
•4004
•4005
•3001
•5002
vim
10/24/14
12/4*4
2/16*5
VIMS
twos
MOOI
IO/I/M
I2/IM5
2AM
DAT!
8/1/82
10/4/82
10/20/82
1/18/83
tint
kntataKon Rattorakon Program Raoortf) Saatch to Maftiat A» Foeea Baw. Phata I. Slaga I
Itntt Commani on InMalalnn Radwakon Program Raconta Baarcn lor Malhar AFB
laHai Raport: MartmSlaha kiipaction Report to Maltw AFB
PmuHff Raport • InaMaMn RaMotaaon Program Pnata HA. Mamei AFB
LalMf Sunmary ol Maakng Ragantng Phn. IIB SlDamanl ol Worti.
Laltar CommanI on IflP Phata HB SMarnan) of Word
MFR: IRP Coordkiakon Maakng (OrKuiiion ol Phaia II MrJ acMvttln)
MnulM ol MAFB IRP Uaakng 2 Aug 84
Mntai ol «P Technical Working Oreia> Maakng. 20 Aug 84
MnvkH ol IRP TacMcal Working Oroup MaaHng.«Ort 84
LamvCommani Phaaal Raport. Phaaa»A Praama? RaportaPhntHBSOW
Jlaa ol IRP Taot>*al Working Orata; Maakng. 28 Oo) 84
MnrJaa at mp Ftaaunay Maakng to Phaaa «. Slaga 2.22 Jut B».
MnrJM of WP WortJng Qnup MaaHng. 18 Apr M
latiiii Commini on *»P. phaaa «. Staga 3 Dcopa ol Wo* to Mainat AFB
LaM> Commani on IBF-. ph*M H. Slaga 3 Scojio ol wo* tor Uaihar AFB
lanar Commanl on mf. FtiM* «. Slaga I C«»>iin4lun>0uanllfc«»on bra* Baport
LMat Commani on IRf. Phijaa (i. Suga i ConamiallrjnrTluaniricaltaOrallFlapoil
AUTHOR _
CH2Mrta.oinaivia.rT.
,A Caniral ValayRajtonal Walai auaMy Cortroi Board
CA Dap), ol HaaHh SanteM.' Toiiea SubMancM Cortrt* C
naaring • Sdanea. AroirJa. CA
Cap). Oaf^Koryc^, Horn. Cno^Matiar AFB " '_"
Capl. Darrtt KordnjU. Bkwnv. Engr. Mafwr AFB
CA Cam al Vday Ragional Waiai OuaHy Cortrd BoaW
CaplJamaaCunanlBloanviingr, Mafiat AFB
MS^falridaSpartiiBES^BPe.UaihaiAre
MSgl Par/Ida Spaita.BCSVSOPB, Mafjat AFB
US ErfAwmantiPirtaalon Agancy. Ragion IX"
MSgl Parrlda 8pa>k>. BESVSOPB. Ma«m AFB
Hl WMM
u*j Control Bavtl
CACartralValafBat
CA Oapi ol Maa» Santoaa. iiic B^iatewaa Control OMitan
CA Cantrai Vaaay Waotonai Wai Ouattf Conkoj Brii^_^_
CA Oapi oi Haaiiti Oaivtcaa. froac Subatanoaa Comrd Mi lilun "
!CIF«flT_ _
HQATC.BanoollAFB.TX
>apuly Ragkmal CMI EnjkiMr, DapMnant ol Ih* Ah FOR*
W.J^C«artiatw^3CJ8n^.MiiriaiAFa
ec<^ajl<^*lmlrorYnanWHa«aJiLatora^,Bnx)MAFB
Cat.MarMandruJAFHOATO80P8 " ™~ "_ __"
id SUughiac, Baaa'canmandai. Uaihat AFB" "" ..~.
Maaur^.^Cmiirtar.UalhaiAfB"
wfTabvn mxl MHROttft
wraMft vv AllMOvM
Hntm *wid AaMnHM • •
MBaiig^.BiMeonwm^/aMiarAFB
" WaandAiiiiidni __
iipl Jamaa Cunao. U8AF HO6P Matiii/BOPB
M Bruc» Jotinaorv •?>»• ciniiiindar. Mainar AFB
Capi Jamaa Cumin. USAF MOW MaiharfSOPB
ColBf^Jonnao^Baa«Cornmaiirlat.i4alh»AF8
3/iy»»
LaMf Commani on •)»>. Phaaa I. Slaga I Cot*malrc«>Ouan)rlcatlonf>all Raport
nix
WOO)
VI/M
•7007
BTOOt
VI2/I7
•VJT/tf
U«« Commani on B»>. Phaaa ». Suga I ConarmaaoyQuartrtcaaon Or all Raport
rRP.PJya ». Slag* I Cuiiaijiiaa^»6uan>«c«»on Final Baport,'yd I i 2
:•. oj Sacramanlo Haajh Daft, Mm
*y F.WaaK»i.lnc.'waaToolmt»to>5>uaBil«arilonfcallFttpi«.*inf7
CADaptolHaa»i8arYtaaa.Too>\ BB^M Co
Caj« Jamaa Curran, U8AFH08P >taiioi«OPB ~
aftiationjloir. Braojo) AFB_
Oont>ntonalt6i«*i
KM7
t2r2!M7
.•Mr ComnM Wf. Plm* «. Sua> 3 Cor*m«»i)rtauin««e««on DrM R4p«1. Jun 17
US ErwkonmnW PrKaaanAoancr, Radon M
dADapiolHaaitiSarvteaa.PubfcWalatSnipff Branch'
Col Don Koaone. J23 FTW/EM,~Uatiir AFB
Capl Jamaa Cumn, USAF HOSP Matiar/OOPB _
iolBtuoaJohnaon, Baaa Commantfar. tialnaf AFB
iapTJamaa Cutan, USAF HOSP MajhatjiiOFV^
•ft Jam* Cunan. USAF Mcj? MatfiatnaPB
•8007
4/1IM
4/I4VM
MraOi ot T»dria< B»vt«w Cuii»i*ll Muling on It Jut M .
88011 8/ttJM
88012 VJM8
jDai
-------
Admlnlittdlv* flacof d hidti, Aircraft ConUol end Warning SHt
9}
90007
99009
•9010
99011
9MI3
99014
9MI9
99019
90001
90002
90003
90004
90009
90012
90014
90019
90017
90018
90019
90021
90022
90023
90029
90021
90027
90O28
•0029
91001
91003
•1009
91007
91008
91009
9J010
91011
91012
91013
91014
91019
•1019
DATC
W9/99
IO/I/W
10/1*9
IO/i/19
II/I3W
11/29/M
II/29M
I2/I/M
2/14/90
2001*0
J7fl»
4/1/90
i(l/90
tntao
7/1/90
7/2W90
8/I/9O
8/3/90
•WOO
9/IMO
10/l/M
IOH/W
It/1/90
lt/19/90
11/26/M
11/29/90
MAW
2/1/91 •
2/14/91
4/ISnll
S/I9/9I
S/I9/II
9/23/91
0/19/91
7/2/91
7/29/91
rai/ii .
tit/at
•/Ml
Tim
Final AC»W SiM RVF8 Sampfng t Anatyti. Plan (Vd «». Metier AFB
Final ACIW 8*. WF8 OuaNy Aiauanca Projad Plan (Vd W). WWW AFB
Find AC*W M. mF8 Final HUM t Safely PUn (Vd IV), Metier AFB
Unum ot Teofretel na»lar» Comma Una, 13 Mo» M
lee* Comma* on Oil* Final AC4W 84. RVF8 Work Plan
LMUT Comma* on Dial Final ACIW See f*F8 Wo* Plan
UM> Comma* on IBP Communty Retaftm Plan to Metier AFB. Dae 88
Bamplng 4 Andy* Rapoit tor 8aa Mentor We*, OoM*» M
Dial On!*; Aaaurenee Plan to Quarterly Orourid»td.r Sanding
taniM.olT*D>^RwWComnWMMMing.ioMa|r80 '
Ouanarly brouidedej Bamplng, Matiac AFB. MayUuna 90. Vd l.». AM
RUF8 to MAFB • 8*. Mpadkn Rapoct
VakMad Data Sunmary Report Addandum • Forth Ouarw 1 989 Watt
OuailanyOnwndMlatSamjAng. MAFB. Auj 1990. Vd 1. », am) M ,
Valdatod Oau Sunmaiy Rjparl • FM Ott 1990
FaatMWy Study lor UAFB, ACIW 8Ja- Final Work Plan
MJnmaaolina Projad Managa?. M.i»«na, 23 OolM
laiw Commint. en bira Final Saa" mapadkn Raporl and ACtW 8>a F.8 Work Pan
l*nuto.oi»»IRCUM«ngUMov90" • ,
Mnaaa ol BPM Uwkng 8 Uar M
Quartan* OnMndMMr Bamdjng. MAFB. Nov-Dao 1999. Vd 1. i, and M
«nu*M ol •• Piajad UarxoM'i UMNng 30 Jan 91
MM Commanl an Romkia Ground Watar Honaortng ProgiMi Projad Plana
LMM Commart on Rouan. Grand Walar MoniMna Program PnffH Plant
L««CoB^Bar*V»3FTWniM.lwhafAFB
HO ATODEEV. Randolph AFB, TX
Ak Fora. Siatami Command. WitdK PaBanon AFB, OH
HOATC/DeEy,Handak
-------
Administrative Record Index, Aircraft Control «nd Warning Site
Mather, California
ID
91017
91018
91019
91020
91021
91022
91023
91024
91025
91026
91028
91029
91030
92005
92008
92007
92008
92010
92010
92013
92014
no."
92020
92021
92023
92024
92025
92026
92027
92026
92030
92031
92032
92033
92034
92035
92036
92037
92038
92041
92047
92057
R062
92063
DATE
9/1/91
9/9/91
9/17/91
9/17/91
9/23/91
10/1/91
1 0/1/91
10/16/91 •
10/24/91
1272/91
12/3/91
12/3/91
1/1/92
1/1/92.
1/14/92
2/11792
2/25/92
2/25/92
3/1/92
1/23792
373792
3/18/92
177/92
3/27/92
4/1/92
5/1/92
5/22/92
5726792
5728792
6/12792
6/1/92 _
a/4/92
7/6/92
7/13/92
7/20792
7/20/92
7/27/92 .
8/7/92
900792
1*3792
2/18/92
/1 7/92
4/20/92
6/4792
TITLE
Letter Commeni on ihe Final Proposed Plan lor Groundwater Cleanup al Ihe ACSW Sile
Quarterly Oioundwaler Monitoring Report lor Third Oualer. daled Sepl 1991
Preliminary Design Investigation tor Ihe ACSW Site. Final Work Plan
Summary ol Stale S Local ARARS
Minutes ol Technical Review Committee Meeting . 20 Aug 91
Notice ol Availability ol Proposed Plan and Notice ol Intent lo Adopt a Negative Declaration
Letter Commeni on Preliminary Design Investigation for Ihe ACSW Sile, Draft Final Work Plan
Public Meeting Minutes on Proposed Plan lor Ground Water Treatment al Ihe ACSW Srte
Letter Commeni on Quarterly Qroundwaler Monitoring Report for May 1991
Minutes of the Project Manager's Meeting 25-26 September, 1991
toffee of Determination • Approval of Negative Declaration tor 'Proposed Plan for Oroundwatar (
Minutes of Technical Review Committee Meeting, 21 November 1992
.elter Commeni on Third Quarter 1991 Qroundwaler Monitoring Report tor May 1991
Draft Final Installation Restoration Program Community Plan tor Mather AFB. Jan 1992
Quarterly Qroundwaler Monitoring Report for Fourth Quarter 1991, Mather AFB
Letter Commeni on Draft Record of Decision tor the ACSW Site. Mather AFB
Letter ResokcHating a Request for ARARS for the ACSW Site
Letter Comment on Draft Record oi Derision lor the AC«W SHe
.etler Commeni on Drift Record of Decision tor Ihe AC4W SHe .
Revised Proposed Plan tor Qroundwaler Cleanup el Ihe. ACSW SHe
Minutes of the Remedial Project Manager's Meeting. 9 Jan 92
.etler Commeni on Draft Record ol Decision tor ACSW SHe
ARARS for ACSW Oroundwater Treatment System
Minuteiol Ihe Protect Manager's Meeting. It Mai 92 . .
Minutes of Technical Review Commfttee Meeting. 11 Mar 92 • '
Public Meeting Minutes on the Revised Proposed Plan tor tie ACSW Site
Oroundwaier Monitoring Project Plane for 1992 ' ..' .
Letter Commeni on Superfund Record of Decision tor Ihe ACSW SHe' and Discharge ReqiCreme
.etler Commeni on Supertund Record of Decision tor Ihe ACSW SHe '
Letter Commeni on Suparfund Record oi Decision, AC* W SHe
Superfund Record of Decision: Aircraft Control A Warning SHe (FJnl Issue)
Draft Final Prekrenary Design Investigation Report for Ihe ACSW SHe.
Letter Comments on the Superfund Record of Decision tor the ACSW SHe.
Quarterly Oroundwater Monitoring Report - First Quarter 1992 •
Minutes of Technical Review Committee Meeting. 3 Jun 92
Letter Commeni on Draft Final ACSW SHe Preliminary Design Investigation Report
Letter Commeni on 1992 Qroundwaler MonHorlng Program Project Plans
.liter Commeni on First Quarter 1992 Qroundwaler Monitoring Report
Letter Commeni on 1992 Groundwater MonHorlng Program Project Plant
Quarterly Oroundwater Monitoring Report • Second Quarter 1992
Letter Commeni on Second Quarter 1992 Qroundwater MonHorlng Report
Quarterly Oroundwaier MonHorlng Report • Third Quarter 1992 ' . • •
Letter Commeni on Third Quarter 1992 Oroundwaier MonHorlng Report •
Reevafualing Alternatives tor Disposal of Treated Water at ACSW SHet
Comments of Draft Watte Discharge Raqukemenii tor ACSW SHes
Litter Commeni on Effluent Discharge for ARARS il AC4W SHe
AUTHOR
CA Central Valley Regional Water Quality Control Board
nlemational Technology Corporation
nternational Technology Corporation
CA Department ol Toxic Substance Control
LI Col Richard Blank, 323 FTW/EM. Mather AFB
CA Department ol Toxic Substance Control
*A Department oi Toxic Substance Control
Peter's Shorthand Reporting Corpor alien
US Environmental Protection Agency. Region IX
LI Col Richard Blank. 323 FTW/EM, Mather AFB
CA Department ol Toxic Substance Control
LI Cot Richard Blank. 323 FTW/EM. Mather AFB
US Environmental Protection Agency. Region IX
nlemational Technology Corporation
International Technology Corporation
Sacramento Metropolitan Air Quality Management Orslrtct
CA Department ol Toxic Substance Control
US Envkoomental Protection Agency. Region IX
CA Department of Toxic Subslance Control
O ATC/DEVR. Ramtotph AFB. TX
U Col Richard Blank. 323 FTW/EM. Mather AFB
CA Central Valley Regional Water Quality Control Board
CA Central VaNey Regional Water QuaMy Control Board
Lf Col Richard Blank. 323 FTW/EM. Mather AFB
LI Coi Richard Blank. 323 FTW/EM, Mather AFB
Certified Shorthand Reporter
International Technology Corporation
CA Central VaJtay Regional Water Quality Control Board
CA Department ol Toxic Substance Control
US Environmental Protection Agency, Region IX
International Technology Corporation
US Environmental Protection Agency. Region IX
International Technology Corporation
U Cot Richard Bank, 323 FTW/EM. Mather AFB
CA Department ol Toxic Substance Control
US Environmental Protection Agency, Region IX
US Environmental Protection Agency, Region IX
CA Department ol Toxic Substance Control
International Technology Corporation
US Environmental Protection Agency, Region IX
International Technology Corporation . . ._
US Environmental Protection Agency. Region IX
WMiam PhMvanlan. HO ATC/DEEV, Randolph AFB, TX
HO ATC/DEEV, Ranrjotoh AFB. TX
Mi Katharine Moore. US EPA, Region IX
RECIPIENT
1 Col Richard Blank, 323 FTW/EM, Mather AFB
HO ATC/DEEV. Randolph AFB. TX
HO ATC.DEEV, Randolph AFB. TX
1 Col Richard Blank. 323 FTW/EM, Mather AFB
lembers and Attendee!
o Whom H May Concern
LI Coi Richard Blanki 323 FTW/EM, Mather AFB
Administrative Record tor ACSW, MAFB
U Col Richard Blank, 323 FTW/EM. Mather AFB
'oniborv mo Alt 000009
CAOftoe of Planting A Research
lumbers and Attendees
1 Col Richard Blank, 323 FTW/EM. Mather AFB
HO ATC/DEEV. Randolph AFB. TX
HO ATC/DEEV, Ranrjotoh AFB. TX
.1 Col Richard Blank. 323 FTW/EM, Mather AFB
U Cot Richard Blank. 323 FTW/EM, Mather AFB
U Col Richard Blank. 323 FTW/EM. Mather AFB
U Col Richard Bank. 323 FTW/EM, Mather AFB
Pubic
etanbora tmrf Att0nd0M
J Col Richard Blank, 323 FTW/EM. Mather AFB
CA Department of Toxic Subetanee Control
Members) end Attendee*
AdrnHslreUve Record for the AWW SHe
HQ ATC/DEEV, Randojph AFB, TX
U Col Rk*ard uier*.ltt3 rrW/EM, Mather AFB
LI Col Richard Blank. 323 FTW/EM. Mather AFB
U Col Richard Blank. 323 FTW/EM. Mather AFB
AdmWstreUve Record Fie tor Mather AFB
HQ ATC/DEEV^ Randolph AFB. TX
U Cot Richard Blank. 323 FTW/EM. Mather AFB
HQ ATC/DEEV, Randolph AFB. TX
MmrOetiH find At10no00t
U Col Richard Blank. 323 FTW/EM. Mather AFB
LI Col Richard Blank. 323 FTW/EM, Mather AFB
LI Col Richard Blank, 323 FTW/EM, Mather AFB
U Col Richard Blank, 323 FTW/EM. Mather AFB
HO ATC/DEEV. Ranrjotoh AFB. TX
U Col Richard Blank, 323 FTW/EM. Mather AFB*
HQ ATC/DEEV, Ranrjotoh AFB. TX
LI Col Richard Hank. 323 FTW/EM, Mather AFB
Ml Trade Biejngton. CA EPA. DT8C
Mr Michael Mosbacher, CA Water OuaMy Control Board
HQ ATC/DEEV, Randolph AFB, TX
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Adrrilnlitratlve. Record Index, Aircraft Control ind Warning 8He
Mather. CeWomle
ID
92064
92065
92066
92067
<206t
92069
92070
92071
92072
92073
92074
9207}
92076
92077
92078
92079
93003
93004
03005
93006
93011
93012
93013
93014
93016
93017
93016
93019
93020
93021
93024
93028
93029
93033
93034
93055
93056
83057
DATE
6/10*2
6/11/92
6/11/92
6/11/92
6/11/92
6/12/92
6/1442
6/18/92
6/19/92
6/19/92
70/92
7/6/92
7/13/92
641/92
9/3/92
9/11/92
2/32/83
2/8/93
2/12/93
2/16/93
3/8/93
3/15/93
1/19/93
3/19/93
4/2/93
4/22/93
4/22/93
5/21/93
S/24/93
64/93
6/1543
7/9/93
7/9/93
8/20/93
8/20/93
2/22/93
S/!J<93
5/13/93
TITtE
Letter Commenll on Drill ROD AC»W Site!
letter Retponte lo Mt VonlWi Hi, ROD ACtW Silei did 6//IO/92
letter Comment! on Retrlted ROD tor ACtW Site!
L«t1tf Commenll on Reviled BOO lor ACtW Sil«
Letter Comnwnlt on Reviled ROD lor ACIW Site!
Otipule fleioliXioo letter. ACtW SUM
B«pul« Reiotutton Authority. AC»W 6*n (Federel)
MMtm AFB Dhpute Concerning Appacallon of SIM* Water Boaid Rttolulion
Mather Olspult Resolution • ACtW Silt
Mather Diipuie Resolution • AC* W SMe
Dispute Reiotullon Authority (Slate)
Dispute HeiduHon Committee Meeting Report
Elevation ol Dispute lo Senior Eieculive Comriflee
Dispute Fotow-Up. TCE Rtmovil *t Varioui Siln
letter Response to Dispute tor ACtW Site
Response to Dispute Letter From Air Force
Superlund Record ol Decision, ACIW Site. Drill Final
Quarter^ Oroundwater Monitoring Report • Fourth Quarter 1992
Letter Retjxmse lo EPA Region IX t ACtW Olipule Dedllon
Letter Requesting ACtW Dispute Elevation lo the AdmWstrelor ol the US EPA
Letter Comment on the Fourth Quarter 1992 Qroundwater MonHortng. Report
Letter Comment on ACtW Site Record ol OecMon
Lettei Comment on ACtW 8Ne Record ol Dedtlon
Letter Comment on Fourth Quarter 1992 Oroundwaler Monitoring Report
Minutes ol RemedM Project! Manager* Meeting 25 February 1993 '
Letter ol Final Decision on tie ACtW Oiipule
Mlnulee ol Ch« Technical Review Commmee Meeting 26 Mar 93 • ' •
Letter Comment on 1993 Qroundwaler Monitoring Program Project Plan* lor Mather AFB
Letter Comment on 1993 Oroundwater Monitoring Program Project Plant tor Mlthei AFB
Quarterly Oroundwaler MonHortng Report • FkM Quarter 1993
Minutei ol Remeolal Protect Manager Moellng 2 1 May 93
US EPA ^Region IX Oedrtin lor ine ACtW Site Dispute
Letter Comment on First Quarter 1993 Qroundwater Monitoring Report lor MAFB
Letter Comment on AC*W Silt February 1993 Record ol DtcMon
Mtaulet ol Remedial Protect Manager1! Meeting. 27 Jury 1993
Revfted ROD lor ACtW Silt
Coil EtlJmate lot Otipute
CA Retporae to EPA Final Dedtlon
AUTHOR
Mt Antonla Vonter, CA Regional Water OuaWy Control Board
AFCEE. Regional Count*. U Col Simmon. 8.F., CA
Capl Mr(«, HQ ATC/DEEV, Randolph AFB. TX
Cyt Milei. HQ ATODEEV. Randolph AFB. TX
Cap) Milei. HO AICA)EEV. Randolph AFB, TX
CA EPA. Dept ol Toric Subtlano* Control
US EPA. Region IX
CA Water He*ourcei Cortrol Board. ChM Counol
CdPowen.MQATCAOEEV. Randolph AFB. TX
Col Pomn. HQ ATODEEV. RandoMi AFB. TX
CA EPA, Oepl ol Toito Bubetanw Control
US EPA. Region IX
CA EPA. Depl Toric Subtlanot Control
CA Regional Water OuaMy Control Board
Mr Oary Vxt, SAF/MtQ
CA Slate Waler Retourcet Board
US Ak Force
rtitfnuoruH TMlnioloov CofpofVtkvi
Mr Gary Vetl. 8AF/MKJ
CA Department ol To* Subtlance Control
US Environmental Protection Agency, Region IX
CA Central Vieey Regional Water OuaMtContral Board
CA Departmenl ol Tonic Subtlance Control
CA Central Valley Region*) Water OuaMy Control Board
It Col Riohwd BUM*. 323 FTW/EM, MJieSer AFB
Mi Carol Browner. US EPA AdmM*trator
LI Coi Richard Blank. 323 FTW/EM, Matfier AFB
CA Department ol Tonfc Subttance Control
CA Centre) Vaaty Regional Wiler OuiWy Control Board
International Teohnolopy Corporation
Or Charlei Smith, AFBOAAJL-D(EM)
Mr John Wita, US EPA AoYnHtlrator. Region IX
US Environmental Protection- Agency, Region IX
CA Central Va«ey Regional Water OuaWy Control Board
Or Charm Smith, AFBOVOMXEM). Mather
HQ ATCfflEEV, Rendoin AFB. TX
8AF/MK),
State Water Control Board
ECIPIEMT
U Col aank, 323 FTW/EM, MAFB
Mi Antoria Vortter, CA Repjonel Water Oualty Control Board
Ml rUthertne Moore, US EPA, Region IX
Mr Mkhaal MotbechertCA Water OuaMy Control Board
Mt Trade BiNnglon. CAA EPA. Depl Toilo Subttanoe Control
M Poweri, HQ ATC. Randolph AFB. TX t US EPA. Region IX
Col Poweri. HQ ATC, Randolph AFB, TX t CA EPA, DT8C
Memo to CVRWQCB]LwryPearton
Mr Antony Landrt^CA EPA. Dept ol Tonto Subttance Control
ik Kttti Tekale, US EPA. Region IX
Mr Keiiri Tekata, US iPA. Region IX
HQ ATC, Rendolph AFB, TX t DavU Wang. CA EPA, DTSC
Mr Verjt.SAF/VIQ.Mr McOovem.US EPA; Mr 8m Hoo.CA EPA
ik Vett,8AF/MIO:Mr McOovem.US EPA: Mr Boo Hoo.CA EPA
Mr McOovem, US EPA; Mr Soo Moo. CA EPA
Mr V.rt.9AF/MIQ;Mr McOovem.U8 EPA; Mr Soo Hoo.CA EPA
AdminltlraiiVe Record File tor Mather AFB
HO ATC/DEEV, Randolph AFB. TX
US EPA Region IX ArMnMretor end DkectorCA OT8C
lit Carol Browner. US EPA, AdmWKralor
U Col Richard Blank, 323 FTW/EM. Mather AFB
LI Col Richard Blank. 323 FTW/EM, Mather AFB
.1 Col Richard Blank. 323 FTW/EM. Mather AFB
Li Col Richard Blank. 323 FTW/EM. Mather AFB
Membeii end Attendee!
Dtp. Sec. ol tie AF tor Em.. Safety, t Occupational HafNh
Member* and Attendee!
Dr Chartei Smth. AFBOA/Ot D (EM) Mather
Or Chartei Smith. AFBOA/OL-D (EM) Matner
HQ ATODEEV, Ranfcpi AFB, TX
Member! end Attendee!
brChirte.Srrtth.AFBO/wlo (EM) Mather {
DrCnarlet Smith. AFBDA/DL-DiEM) Metier .
Dr Chartei SrrMi. Af BOAAX 0 (EM) Mather
M6fTn4fB md Altsndeiai
US EPA. CA DTSC. CA ROCB
USEPA.negtonlX
US EPA Region IX •
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