PB94-964513
EPA/ROD/R09-94/115
July 1994
EPA Superfund
Record of Decision;
George Air Force Base
(O.U. 1) Site, CA,
3/8/1994
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INSTALLATION RESTORATION PROGRAM
FINAL
RECORD OF DECISION
OPERABLE UNIT 1
GEORGE AIR FORCE BASE
CALIFORNIA
Prepared For:
U.S. Army Corps of Engineers
Sacramento District
Sacramento, California
Prepared By
Montgomery Watson
365 Lennon Lane
Walnut Creek, CA 94598
File No. 1868.0654
March 1994
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2.0
,=
RECORD OF DECISION
OPERABLE UNIT 1
GEORGE AIR FORCE BASE
TABLE OF CONTENTS
Section
1.0
I>~C~lrI()N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 SITE NAM~ ANI> LOCAlrION '':''''''''''''''''''
1.2 STATEMENT OF BASIS ANI> PURP()SE . . . . . . . . . . . . . .
1.3 ASSESSMENT ()F THE SITE ..................,..
1.4 I>ESCRIPTION ()F THE SELECTEI> REMEI>Y . . . . . . . . . .
1.5 STATUT()RY I>ETERMINAlrIONS . . . . . . . . . . . . . . . . . .
1.6 SIGNATURES................' . . . . . . . . . . . . . . .
I>~CISION S~Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 SITE NAME, LOCAlrI()N, ANI> I>ESCRIPTION """'"
2.1.1 Regional Physiography. . . . . . . . . .. . . . . . . . . . . .
2.1.2 Meteorology. . . .-. . . . . . . . . . . . . . . . . . . . . . . .
2.1.3 I>emography and Land Use ................,..
2.1.4 Hydrogeology........... . . . . . . . . . . .' . . . . .
2.1.5 Surface Water Hydrology. . . . . . . . . . . . . . . . . . . .
2.1.6 Water Use ..........,. '. . . . . . . . . . . . . . . . .
2.1.7 Plant Life. . . . . . . : . . . . . . . . . . . . . . " . . . . . . .
2.1.8 Animal Life. . . . . . . . . . : . . . . . . . . . . . . . . . ..
SITE mSTORY ANI> ~NF()RCEMENT ACTIVITIES """
mGHUGHTS ()F COMMUNITY PARlrICIPATI()N .......
SCOP~ AND ROLE ()F ()PERABLE UNIT WITHIN THE
SITE STRATEGY . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 SUMMARY OF SITE CHARACTERISlrICS . . . . . . . . . . . . .
2.5.1 NortheastI>isposalArea .....................
2.5.2 Industrial/Storm Drain and C>utfall I>itch ...'....... .
2.5.3 STP Percolation Ponds. . . . . . . . . . . . . " . . . . . . .
2.6 SUMMARY OF SITE RISKS. . . . . . . . . . . . . . . . . . . . . .
2.6.1 NortheastI>isposalArea ..................,..
2.6.2 Industrial/Storm I>rain and C>utfall I>itch ..... . . . . . .
2.6.3 STP Percolation Ponds.. . . . . . . . . . . . . . .. . . . . .
2.7 I>ESCRIPTI()N ()F ALTERNATIVES. . . . . . . . . . . . . . . . .
2.7. i Alternative 1 - No Action with Groundwater Monitoring .
2.7.2 Alternative 2 - Groundwater Extraction, Air Stripping,
and Percolation. . . . . . . . . . . . . . . . . . . . . . . . . .
2.7.3 Alternative 3 - Groundwater Extraction, Air Stripping'
with Emission Controls, and Percolation. . . . . . . . . . .
2.2
2.3
2.4
. i
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Section
3.0
TABLE OF CONTENTS
(Continued)
2.8 SUMMARY OF COMPARATIVES ANALYSIS ALTERNATIVES
2.8.1 Overall Protection of Human Health and the Environment.
2.8.2 Compliance with ARARs . . . . . . . . . . . . . . . . . . : . .
2.8.2.1 Chemical-Specific ARARs ....,.........
2.8.2.2 Location-Specific ~ . . . . . . . . . . . . . . .
2.8.2.3 Action-Specific ARAks .. . . . . . . . . . . . . . .
2.8.2.4 Compliance with ARARs ...............
2.8.3 Long- Term Effectiveness and Permanence. . . . . . . . . .
2.8.4 Reduction of Toxicity, Mobility, and Volume through
Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8.5 Short-Term Effectiveness. . . . . . . . . . . . . . . . . . . . .
2.8.6 Implementability .'. . . . . . . . . . . . . . . ; . . . . . . . . .
2.8.7 Cost..... . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8.8 State Acceptance. . . . . " . . . . . . . . . . . . . . . . . . .
2.8.9 Community Acceptance. . . . . . . . . . . . . . . . . . . . .
2.9 THE SELECTED REMEDY . . . ; . . . . . . . . . . . . . . . . . . .
2.9.1 Selection of the Preferred Alternative. . . . . . . . . . . . .
2.9.2 Detailed Description of the Preferred Alternative. . . . . .
2.9.2.1 Extraction and Monitoring Well System. . . . . .
2.9.2~2 Air Stripping System. . . . . . . . . . . . . . . . . .
2.9.2.3 Effluent Disposal System. . . . . . . . . . . . . . .
2.9.3 Cost Analysis. . . . . . . . . . . . . . . . . . . . . . . .. . . .
2.9.4 System Implementation. . . . . . . . . . . . . . .. . . . . . .
2.10 STATUTORY DETERMINATIONS. . . . . . . . . . . . . . . . . .
. 2.10.1 Protection of Human Health and the Environment. . . . .
2.10.2 Compliance with ARARs . . . . . . . . . . . . . . . . . . . .
2.10.3 Cost Effectiveness. . . . . . . . . . . . . . . . . . '. . . . . .
2.10.4 'Utilization of Permanent Solution and Alternative
Treatment (or Resource Recovery) Technologies to the
Maximum Extent Possible. . . . . . . . . . . . . . . . . . .
2.10.5 Preference for Treatment as a Principle Element. . . . . .
2.11 DOCUMENTATION OF SIGNIFICANT CHANGES. . . . . . .
2.12 CURRENT INVESTIGATION STATUS. . . . . . . . . . . . . . .
2.12.1 Additional Investigations. . . . . . . . . . . . . . . .. . . . .
2.12.2 Investigation in Support of RD/RA . . . . . . . . . . . . . .
RESPONSfVENESSS~Y........... "."",.",.
3.1 OVERVIEW................................
3.2 BACKGROUND ON COMMUNITY INVOLVEMENT. . . . . .
ii
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Section
, 3.3
3.4
REFERENCES
APPENDICES
-;;..,.:;;;- .
TABLE OF CONTENTS
(Continued)
SUMMARY OF COMMENTS RECEIVED DURING THE PUBUC
COMMENT PERIOD. . . . . . . . . . '. . . . . . . . . . . . . . . . .
REMAINING CONCERNS. . . . . . . . . . . . . . . . . . . . . . .
-
A - ADMINISTRATIVE RECORD INDEX
B - RESPONSES TO AGENCY COMMENTS
iii
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3-2
3-5
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Figure
No.
3
4
5
6
7
8
9
10
11
LIST OF FIGURES
1
Vicinity Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
IRP Sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Location of the Industrial/Storm Drain and Outfall Ditch Site
SD-25 (S-20) and STP Percolation- Ponds Site WP-26 (S-21) ..
Schematic Representation of Piping in the Industrial/Stonn
Drain Site SD-25 (S-20) .........................
Regional Fault Map. . . . . . . . . . . . . . . . . . . . . . . . . . .
Regio~ Geology. . . . . . . . . . . . .. . . . . . . . . . . . . . .
Approximate Locations of Known Municipal and Domestic
Water-Supply Wells, GAFB Vicinity. . . . . . . . . . . . . . . . .
1987 Distribution of TCE in Groundwater at 5 Ilgll (Federal
MCL)................................... .
Conceptual Design of Phase I of the Extraction and Monitoring
Well Systems - Alternatives 2 and 3 .........,.......
Conceptual Design of Effluent Disposal System -
Alternatives 2 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . .
TCE Contamination in the Upper and Regional Aquifers,
July 1993 .................................
iv
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2-2
2-2
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2-11
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2-39
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Table
No.
1
2
. 3
4
5
6
7
8
9
10
LIST OF TABLES
Groundwater Data Summary, Northeast Disposal Area .... . . .
Summary of Cancer Risks and Hazard Indices for Operable
Unit 1 .............,......................
Summary of Detailed Analysis of Remedial Alternatives. . . . . .
Identification of Federal Chemical-Specific ARARs
.. .. .. .. .. .. .. .. ..
Identification of Federal Location-Specific ARARs
.. .. .. .. .. .. .. .. ..
Identific~tion of Federal Action-Specific ARARs . . . . . . . . . . .
Identification of State Acti
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AFBCA
APCD
AQMD
ARARs
ARB
bgs
CAO
CCR
CERCLA
CEQA
CESA
.cfs
CMP
CRP
DHS
DTSC
DWR
EIS
ESA
ET
FFA
FS
GAC
GAPB
gpd/ft
gpd
gpm
HWM
IRP
LF
MCL
MCLG
. mph
msl
NCP
NEDA
NPL
OAQPS
OSWER
OU
PID
PPE
RAB
RCP
RCRA
ACRONYMS AND ABBREVIATIONS
Air Force Base Conversion Agency
Air Pollution Control District
Mojave Air Quality Management District
applicable or relevant and appropriate requirements
Air Resources Board
. below ground surface
Cleanup and Abatement Order
California Code of Regulations
Comprehensive Environmental RespQnse, Compensation, and Liability Act
California Environmental Quality Act
California Endangered Species Act
cubic feet per seCond
corrugated metal pipe
Community Relations Plan
Department of Health Services
Department of Toxic Substances Control
California Department of Water Resources
Environmental Impact Statement
Endangered Species Act.
evapotranspiration
Federal Facility Agreement
Feasibility Study
granular activated carbon
George Air Force Base
gallons per day per foot
gallons per day
gallons per minute
Hazardous Waste Management
Installation Restoration Program
linear feet
maximum contaminant level
maximumcont~minant level goals
miles per hour
mean sea level
National Oil and Hazardous Substances Pollution Contingency Plan
Northeast Disposal Area
National Priorities List
Office of Air Quality Planning and Standards
Office of Solid Waste and Emergency Response
Operable Unit
photoionization detector
personal protective equipment
Restoration Advisory Board
. reinforced concrete pipe .
Resource Conservation and Recovery Act of 1976
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RD/RA
RME
ROD
RSA
RWQCB
SAL
SARA
sefiD
SDWS
SlIMP
SIP
SMCL
STP
TBC
TCE
TM
TMV
TPY
TRC
USAF .
USEPA
USFWS
USGS
VOC
VVWRA
ACRONYMS AND ABBREVIATIONS
(Continued)
Remedial Design/Remedial Action
reasonable maximum exposure
Record of Decision
regional statistical area
Regional Water Quality Control Board
State Action Levels
Superfund Amendments and ReauthQrization Act
standard cubic feet per minute -
secondary Drinldng Water Standards
sodium bexamethaphospbate
State Implementation Plans .
secondary maximum contaminant level
Sewage Treatment Plant
to-be-considered
trichloroethene
Technical Memorandum
toxicity, mobility, and volume
tons per year
Technical Review Committee
U.S. Air Force
U.S. Environmental Protection Agency
U.S. Fish and Wildlife Service
U.S. Geological Survey
volatile organic compound
Victor Valley Wastewater Reclamation Authority
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1.0 DECLARATION
1.1
SITE NAME AND LOCATION
George Air Force Base
Operable Unit 1
San Bernardino County, California
1.2
STATEMENT OF BASIS AND PURPOSE
This decision document, a Record of Decision (ROP), presents the selected remedial action for
Operable Unit (OU) 1 at George Air Force Base (GAFB), which was chosen in accordance with
the Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986
(SARA), and, to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). au 1 includes groundwater beneath the northeastern portion of GAFB
(Northeast Disposal Area [NEDA]) and adjacent off-base areas, the Industrial/Storm Drain (site
SD-25[S-20]), and the .Sewage Treatment Plant (STP) Percolation Ponds (site WP-26[S-21]).
This decision is based on the administrative record for this site and complies with 40 Code of
Federal Regulations (CPR), Part 300. ..
The purpose of this ROD is to set forth the remedial action to be conducted to remediate
groundwater contaminated by trichloroethene (TCE) beneath the NEDA and adjacent off-base
areas. No further action is planned for sites SD-25 (S-20), the Industrial/Storm Drain, and WP-
26 (S-21), the STP Percolation Ponds, which are also included in OU 1, as these sites were
within acceptable risk levels based upon the risk assessment performed as part of the remedial
investigation (IMM, 1992a).
The U.S. Air Force (USAF), Environmental Protection Agency (USEPA) Region IX, and the
State of California concur with the selected remedy.
1.3
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the remedial action presented in this ROD, may present a risk to public health,
welfare, or the environment.
1.4
DESCRIPI10N OF THE SELECTED REMEDY
Based on alternatives evaluated in the Feasibility Study (FS) (JMM, 1993a), the USAF, the
USEP A, and the State of California have selected Alternative 2 as the remedy for the TCE-
contaminated groundwater beneath and adjacent to the NEDA at GAFB, OU 1. The selected
remedy, designed to be implemented in two phases (phase I has been completed), consists of:
1-1
-------
.
installation of an estimated 19 groundwater extraction wells, the exact number to
be determined based on Phase I system efficiency;
.
groundwater treatment using two air stripping towers with direct discharge of
emissions to the atmosphere; .
.
discharge of treated water to the Upper Aquifer using the former STP Percolation
Ponds;
.
temporary discharge of treated water to an arroyo during the treatability study and
potential future discharge to the base golf course;
.
installation and quarterly sampling of an estimated eight new monitoring wells in
conjunction with basewide groundwater monitoring, the exact number to be.
determined based on Phase I system efficiency; and
.
implementation of deed restrictions as appropriate to prohibit use of groundwater
until grQundwater cleanup levels have been achieved.
No further action is required for the Industrial/Storm Drain and STP Percolation Ponds to
protect public health, welfare, or the environment.
1.5
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with federal
and state requirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. This remedy utilizes permanent solutions and alternative treatment
technology to the maximum extent practicable, and satisfies the stawtory preference for remedies
that employ treatment that reduces toxicity, mobility, and volume (TMV) as a principal element.
The estimated restoration time frame for the selectCcl remedy is 30 years. A review of this ROD
will be conducted every 5 years to ensure that the remedy continues to provide adeqUate
protection of human health and the environment.
1-2
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1.6
SIGNATURES
JA lAJ ~
John Wise
Deputy Regional Administrator
Environmental Protection Agency
Region IX
Alan K. Olsen
Director
Air Force Base Conversion Agency
Anthony J. Landis.
DSMOA TechDical Program Manager
State of California
Department of Toxic Substances Control
Harold Singer
Executive Officer
California Regional Water Quality Control Board
Lahontan Region
1-3
3. B.t;y
Date
Date
Date
Date
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1.6
SIGNATURES
John Wise
Deputy Regional Administrator
Environmental Protection Agency
{;1n ~ za
~ ~A~-./
DCite
- -
YhJ~ 19ff
Alan K. Olsen
Director
Air Force Base Conversion Agency
Date
Anthony 1. Landis. .
DSMOA Technical Program Manager -
State of California
Depanment of Toxic Substances Control
Date
Harold Singer
Executive Officer
California Regional Water Quality Control Board
Lahontan Region
Date
1-3
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1.6
SIGNATURES
John Wise
. Deputy Regional Administrator
Environmental Protection Agency
Region IX
Alan K. Olsen
Director
Air Force Base Convers' n Agency
r7
Anthony J,
DSMOA Technical Program Manager
State of California
Department of Toxic Substances Control
Harold Singer
Executive Officer
California Regional Water Quality Control Board
Lahontan Region
1-3
Date
-
Date
'3--7 11
Date
Date
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1.6
SIGNATURES
John Wise
Deputy Regional Administrator
Environmental Protection Agency
Region IX
Alan K. Olsen
Director
.Air Force Base Conversion Agency
Control
'"
..f--t.. Harold Singer
Executive Officer .
California Regional Water Quality Control Board
Lahontan Region
1-3
Date
Date
Date
-?J1aAcA 7..
JC( 'If
Date
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2.0 DECISION SUMMARY
This decision summary provides a description of au 1 including the regional sening,
physiography, meteorology, demography and land use, hydrology, hydrogeology, and water use.
This section also summarizes the problems posed by the conditions at au 1, the remedial
alternatives, and the rationale for the selection and how the selected remedy satisfies statutory
requirements.
2.1
SITE NAME, LOCATION, AND DESCRIPTION
GAFB encompasses an area of approximately 5,347. acres and is located in the western Mojave
Desert in the area of Victorville, California and adjacent to the City of Adelanto, California.
Victorville is located on Interstate 15, approximately 35 miles north of San Bernardino and 31
miles south of Barstow (Figure 1).
au 1 consists of the TCE plume beneath the NEDA and areas north of the base, the STP
Percolation Ponds, and the Industrial/Storm Drain. Figure 2 shows the location of the aus at
GAFB. Within OU 1,. the only concern is groundwater contamination. Several waste disposal
sites within the NEDA were identified as potential sources of TCE contamination in the
groundwater. These sites consist of burial sites, landf1l1 disposal sites, and spill or liquid
disposal sites. Characterization of potential soil contamination at these sites is being addressed
with ongoing activities at OU 3.
The STP Percolation Ponds, Site WP-26 (S-21), consists of five wastewater treatment plant
percolation ponds that were used from the early 1950s to 1980. The site consisted of the three
large main ponds and two smaller ponds that may not have been used. The percolation ponds
were used primarily for discharge of treated sanitary wastes, but also may have received waste
oils and solvents from industriaIshops that discharged to the sanitary system. Contaminants of
concern for the percolation ponds include heavy metals, solvents, and nitrate. The location of
the STP Percolation Ponds is shown on Figure 3. Investigation at the STP Percolation Ponds
indicate that the concentration of contaminants of concern are within background concentrations
for desert soils, with the possible exception of nitrates (JMM, 1992a). Elevated concentrations
of nitrates are limited to the upper 46 feet of soil.
The Industrial/Storm Drain, Site SD-25 (S-20), is located within the central and northeastern
portions of GAFB as shown on Figure 3. The Industrial/Storm Drain has been in operation
since the early 194Os. The Industrial/Storm Drain consists of the storm drain southeast of the
operational apron (East Storm Drain) and the stonn drain between the operational apron and the
Crosswind (Secondary) Runway (West Storm Drain), as well as the outfall ditch downgradient
from the storm drains (Figure 3). As shown, the East Storm Drain is parallel to and just east
of the operational apron. The East Storm Drain was constructed of various piping materials
includ~g reinforced concrete pipe (RCP) and corrugated metal pipe (CMP), but the pipe is
predominantly CMF. Pipe sizes range from 4 to 24 inches in diameter. Overall length of the
east pipe, including all laterals, is 10,235 linear feet (LF). Of this length, over 3,800 LF of the
CMP section was perforated pipe. Figure 4 shows schematically the location of the piping for
2-1
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01:0
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-:ICD
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e: -
-------
EL MIRAGE ROAD
.-----,
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I .
I---~ l_-
1
I
1
I.SD-le
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II
I~ 50.18 .
Ir
I;
I; OT-51 55-59
: CO
~ ~LF-ae
i1) LF-371
I
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CRIPPEN AVENUE
.,
AIR BASE RO"D
,.
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J:lz
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:II
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....
LEGEND
L..2:11
. QU-1
@ 0lJ-2
. OlJ-a
o OlJ-a RIIFS Sites
DP-10
RANCHO ROAD
J
@ QU-a Accelerated
Ac1ion Sites
@ OlJ.a No Further
Action Sites
o
2500
5000
Approximate Scale in Feet
IRP SITES
Note: Poorly defined. multiple location, or non-point source sites in OlJ-a .,. not shown
(Sites ST-31 , OT-61. OT-62, WP-63, OT064, OT-65, anclOT-66).
AGURE 2
1M3.0E
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o
t
1600
Sewa~ Treatment
Plant (STP)
i Percolation Ponds
.
I
.
L___",\
,
\
.
J
.
I
.
1.
. I
I .
. I
I I
. I
.
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.
I
.
I
.
I
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I
.
I
------,
IndustriaUStor:m
Drain Outfalll:>ltch
I
.
I
.
IndustriallStorm
. Drain (lSD)
AIR BASE ROAD
LOCATION OF THE INDUSTRIAU
STORM DRAIN AND OUTFALL DITCH
SITE SD-25 (S-20)
AND STP PERCOLATION PONDS
SITE WP-26 (S-21)
3200
.
Approximate Scale in Feel
f1I.G-12
FIGURE 3
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both storm drain pipelines. Investigations indicated that the sediments within the stonn d~in
were potentially hazardous. Consequently, the West Storm Drain was cleaned in place.
Sections of the East Stonn Drain were cleaned, and the perforated sections were replaced with
nonperforated piping. Soils underlying the perforated piping were also excavated and disposed
of appropriately. Subsequent confmnation sampling of soils underneath the Industrial/Storm
Drain indicated the chemical concentrations were at background levels. Hence, the
Industrial/Storm Drain appears to be free of contamination by hazardous materials.
2~1.1
Regional Physiography
GAFB is located in San Bernardino County, Califorpia, approximately 70 miles northeast of the
City of Los Angeles. The base is located in the Victor Valley in the western Mojave Desen,
a roughly triangular-shaped tectonic block bounded by the Garlock Fault Zone on the northwest,
the Lockhan and Helendale faults on the northeast, and the San Andreas Fault on the southwest
(Figure 5). This western portion of the Mojave Desert is flanked by the Sierra Nevada
Mountains to the northwest; the Fry, Radman, and Cady mountains to the northeast; and the San
Bernardino Mountains to the southwest. The Victor Valley is comprised of alluvial fan deposits
derived from the surrounding mountains, river deposits associated with the Mojave River system,
and lacustrine deposits from former lakes (Figure 6). The headwaters of the Mojave River are
located in the San Gabriel Mountains near Silverwood Lake at an elevation greater than 3,355
feet above mean sea level (msl). The Mojave River flows to Soda Dry Lake Bed, south of
Baker, at an elevation of approximately 923 feet above msl. Valley elevations in the vicinity
of GAFB range from 2,650 feet above IDSI at the northeast corner of GAFB to 2,920 feet above
msl at the southwest comer of the base, south of Air Base Road. The average elevation of the
Mojave River floodplain immediately east of the base is approximately 2,580 feet above msl.
The average elevation at GAFB is approximately 2,750 feet above msl, with an average
topographic gradient of 2 percent to the northeast.
The Mojave River flows along the east side of GAFB in a northwesterly direction. Communities
within the Victor Valley area include the town ofAdelanto, directly west and adjacent to GAFB,
the City of Victorville, directly southeast, and Silver Lakes, Apple Valley, and Hesperia. The
Victor Valley Wastewater Reclamation Authority (VVWRA) treatment plant is located
approximately 0.5 ~le northeast of the northern border of GAFB.
2.1.2
Meteorology
The climate in the GAFB area is typical of the high desert region of California and Nevada.
The summers are extremely hot and dry while the winters are cool and dry. The annual average
temperature is 62 of. July and August are the hottest months with maximum daily temperatures
often exceeding 100°F. Temperatures in December and January are the coldest, with nighttime
temperatures often falling below freezing. Based on records from 1942 to 1992, annual
. precipitation at GAFB ranges from 0.77 to 11.22 inches, with an average annual precipitation
of 5.72 inches. Monthly precipitation ranges from 0.25 to 4.47 inches, with January, February,
and March being the wettest months. During storm events, daily precipitation has reached as
high as 2.93 inches. Snowfall is infrequent, but typically totals a few inches per year and has
2-2
-------
LEGEND
. Manhole Accessway
:-I
- ~/ Jl ~--- --,
~~;--II~_-=-
--->:,\11'1
J---'
--'
...~-
,
,
Norlll8l Flow
Pipe
"
-,"
,-----
.-
I
,
I
, I
\ ,
\ I
\ ,I
,I
\ "
I "
"
I ,,~ --' Outfall Ditch
\ ,"
'........._---,,,,,.;
I Z-
SCHEMATIC REPRESENTATION
OF PIPING IN THE
INDUSTRIAUSTORM DRAIN
SITE SD-25 (S-20)
o
r--.----
1000 2000
----------,
Approxlm.l. Sc.I. In F...
FIGURE 4
IM30E
-------
/"'- """" ...... /"'- /"'- ./'- /"- /"-
~ ......- ~ ~/' /' /"- /"-
;/' /'- ~ ;/' /'- /"- /'- /"-
/'- /'- /'- /' /'- /'-- /'-
/"'-
/'- /"'. /'- /'- ....:...,
/"'.'/ /';---- ......:::....
~ /'
/"'. ./ JI-~'" 7
... ~ G$~
......~~e /' ,;g"" -
G.,r -
. Los Angeles
.
~
o
25
50
,
SCAlE IN MILES
Source: Modified from Calif' ...
omra Division 01 Mines. 1972.
0-11
/'
c
/' ~
/' ./"'\.,,~
/' ".....
/' /' "q}.;.I'
/'
/'
/'/'
/'....
San /' /'
Bernardino /"-
Mountains /' ~
/\
REGIONAL FAULT MAP
RGURE 5
-------
LEGEND
D
Mojave River Allwium
G
E3J
PI8istacene Fan Deposi1s
! "..;;.1 Recent Fan Deposits
~
- Quaternary Lake DeposIlS
Mesozoic and Paleozoic
Basement CocnpIu
REGIONAL GEOLOGY
AGURE 6
Mod~ied frem Bonungo and Spittler, 1986.
G-t
-------
been as high as 17 inches per year. The potential evapotranspinition (ET) rate is about 71
inches during the summer and averages 83 inches for the entire year (Science Applications
International Corporation [SAlC], 1987).
Prevailing winds in the area of GAFB are from the south; however, the strongest gusts are
typically from the west. Westerly gusts of 50 miles 'per hour (mph) or more usually occur in
. the spring. In the summer evenings, strong southerly winds blow over the San Bernardino
Mountains through Cajon Pass. The occurrence of northerly winds increases in the fall and
winter months (SAlC, 1987).
2.1.3
Demography and Land Use
-
GAFB is located within Census Tract 91.02, Regional Statistical Area (RSA) 32B of San
Bernardino County. The major cities in RSA 32B include Adelanto and Victorville and the
unincorporated communities of Hesperia and Apple Valley. The estimated populations of these
cities and communities, according to the 1990 Census, are:
AdelantQ
Apple Valley
Hesperia
Victorville
8,517
46,079
50,418
40,674
The Victor Valley area has experienced significant groWth in the past decade. From 1980 to
1990, the populations of the major Victor Valley communities have increased as follows (USAF,
1992):
Adelanto
Apple Valley
Hesperia
V ictorville
14.7 percent
12.4 percent
14.1 percem
11.1 percem
The major land use activities of the Victor Valley area include residential development,
government and commercial services, cement manufacturing, railroad and highway
transportation, localized agricultural activities along the Mojave River, and industrial mining in
the outlying areas. A major fuels distribution pipeline parallels Air Base Road for half the
length of the base, and a high-voltage transmission utility corridor crosses the southeast comer
of the base.
2.1.4
Hydrogeology
GAFB is located in the Upper Mojave River Valley Groundwater Basin. Within the OU 1 area,
the basin is composed of alluvial sedimentS which consist of potentially water-bearing sands and'
gravels and low permeability silts and clays. The depth to bedrock is at least 1,350 feet. Water
level and lithology data have been used to identify two distinct water-bearing zones in the study
2-3
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area: a shallow "Upper Aquifer" and a deeper "Regional Aquifer," separated by a "Mid~le
Clay/Silt Aquitard."
The Upper Aquifer is a 40- to 6O-foot-thick zone of saturated, highly to moderately permeable,
interbedded silty sands, poorly sorted sands, silts, and clays. Pump test data indicate that these
materials have transmissivities ranging from 5,500 to 20,700 gallons per day per foot (gpd/ft).
Groundwater elevations within the study area range from approximately 2,724 to 2,704 feet
above msl and have a gradient to the northeast of approximately 0.003 ftlft.
The Middle Clay/Silt Aquitard, consisting of interbedded very low to low permeability clays and
silts, is present from approximately 2,670 to 2,64Q feet above msl and is approximately 20 to
40 feet thick. The aquitard hydraulically separates the Upper and Regional aquifers but is not
continuous north of the base and east of the snuly area along the Mojave River bluff. However,
the aquitard is continuous to the west and southwest as determined by activities at au 2 and au
3. The lack of hydraulic communication between the aquifers through the aquitard is supported
by a zone of unsaturated moderately permeable materials encountered below the aquitard in
regional wells and dry clays within the aquitard in several well borings. To the northeast
beyond the lateral edge. of the aquitard, however, the Upper Aquifer merges with the Regional'
Aquifer through downward migration. Groundwater gradients within the Upper Aquifer increase
to the east and northeast as the edge of the aquitard is approached.
The Regional Aquifer generally consists of interbedded sands, gravelly sands, and silts with
minor caliche beds. Groundwater elevations in the Regional Aquifer within the study area range
from 2,587 to 2,582 feet above msl, with a gradient of 0.001 ftlft to the northeast. The
Regional Aquifer is geographically extensive and is hydraulically associated with the Mojave
River Aquifer. Several production wells in the site vicinity are screened in the Regional
Aquifer. The Mojave River Aquifer is an informal designation for groundwater within
unconsolidated coarse sands and gravels spatially associated with the Mojave River. The Mojave
River deposits overlie and are interbedded with older Regional Aquifer soils. This unit is
relatively transmissive and provides good quality water to regional wells. Potentiometric
contours of the Regional Aquifer are perpendicular to the directions of flow in the Mojave River.
Groundwarer flow in the Mojave River and Regional aquifers are therefore parallel. Adjacent
to GAFB, the Mojave River Aquifer gains groundwater flow from the Regional Aquifer.
2.1.5
Surface Water Hydrology
The Mojave River is the major surface drainage of the Victor Valley. The river chaDnel is about
125 miles long, extending from the San Bernardino Movntain~ in the south to Soda Dry Lake
in the northeast. Surface flow occurs principally during heavy stonns. In the Upper Mojave
River Basin, perennial flow occurs in two locations: (1) approximately 1 mile below the Forks
due to the contribution of the perennially flowing Deep Creek; and (2) near Victorville, where
flow occurs through two restricted areas, known as the Upper and Lower Narrows. The
narrows are formed by a bedrock ridge, which creates a sub~ace flow barrier, causing river.
underflow to rise to the surface. U.S. Geological Survey (USGS) topographic maps and aerial
photographs indicate that historically, surface flow continued downstream as far as Bryman, 8
2-4
-------
miles north of GAFB. Today, surface flow persists approximately 1 mile below the Lower
Narrows, located approximately 2 miles east of GAFB, except during and shortly after heavy
rainfall. Regional withdrawal of groundwater apparently has lowered the Mojave River
underflow in the vicinity of GAFB.
Daily mean discharge values of the Mojave River through the Lower Narrows during 1990
ranged from 1.6 to 373 cubic feet per second (cfs) , with an average discharge of 14.3 cfs
(USGS, 1990). Discharge records maintained since 1899 indicate an average discharge of 75.2
cfs, with a maximum discharge of 70,600 cfs recorded March 2; 1938 (USGS, 1992).
Surface water from GAFB drains predominantly tP. the northeast aDd east. Runoff from the
flightline and the industrial and office areas (including most hazardous waste accumulation points
and the hazardous waste storage yard) is directed through roadways, storm drains, culverts, and
ditches to the Outfall Ditch on the northeast side of the base. Flow from this drainage ditch
reaches the Mojave River only during heaVy storms. Runoff from residential areas and the
eastern part of the base flows east directly into the Mojave River wash. Much of the southern
part of the base drains northward into the industrial and flightline runoff system. The western
edge of the base d~ .westward into the desert (USAF, 1989).
A large, southeast-trending arroyo bisects the northeast section of the base. The arroyo channel
is approximately 15 feet wide near the northern base boundary and 100 feet wide where the
arroyo discharges into the Mojave River wash. It is fed by the Outfall DitCh from the base,
numerous gullies, and a smaller drainage ditCh originating from the Fire Training Area. Because
they cut through the desert pavement, the arroyos and gullies on the western side of the Mojave
River wash collect runoff water and may promote recharge to the subsurface along their
channels. Near GAFB the Mojave River has cut a wash approximately 1 mile wide and 200 feet
deep into the alluvial fan deposits (JMM, 1988d).
2.1.6
Water Use
Because of the arid conditions of the Upper Mojave River Valley Groundwater Basin in general,
and the GAFB area in particular, there are no surface water bodies available for reliable
utilization. As a result, water usage analyses conducted by the Mojave Water Agency focus on
groundwater withdrawals.
The Mojave Water Agency divides water usage into four categories: domestic, lake-type,
agriculture, and miscellaneous. The per capita rate of water demand is currently estimated to
be 200 to 285 gallons per day (gpd). Approximately 50 percent of this amount is believed to
be consumed and not returned to groundwater storage (SAlC, 1987). .
Lake-type water use refers to the region's ponds, lakes, and fIsh-culture farms, all of which are
fed by pumped groundwater. An estimated 751085 percent of this water percolates downward
to return to the water table. Evaporation is the most common form of water loss in this '
category, with a lake evaporation rate of 78 inches per year considered representative for the
Upper Mojave River Basin (SAlC, 1987). .
2-5
-------
Agricultural crops receive water through precipitation or applied water. Alfalfa is the primary
agricultural plant in the study area. Consumptive use of applied water (primarily through
evapotranspiration) is estimated to range from 3 to 5 acre-feet per year. Other additional water
demands in the GAFB and Victorville areas include water use by golf courses, cemeteries, and
cement plantS or other heavy industry. Within this category, an estimated 50 percent of all
groundwater pumped from storage is consumed.
The VVWRA, located northeast of the base, also has two supply wells used for industrial and
potable water supplies, although bottled water is supplied for workers at the plant. The
VVWRA wells are reported to be screened at 100 to 150 feet below ground surface (bgs) and
have pumping capacities of 500 gallons per ~te (gpm). The log from a soil boring
constructed near. the water supply wells shows the top 65 feet of alluvium to consist of silty
sands with stteaks of sand, silt, and gravel. The groundwater table was measured at 36 feet bgs.
According to the records of the California Department of Water Resources (DWR), fou,r
production wells exist southeast of the base. Production capacities of these wells range from 100
to 1,200 gpm. Wells are screened to depths ranging from 500 to 610 feet bgs and may be
screened in a deeper ~d possibly different aquifer system than the monitoring wells installed
at GAFB under Phase IT of the InstaJ.lation Restoration Program (IRP). .
Eight GAFB municipal water supply wells are located along Turner Road, near the Mojave
River below the base golf course and beyond the eastern base boundary. These wells are located
on the west side of the Mojave River in Section 30, T6N, R4W, just north of the Lower
Narrows. The GAFB wells are 101 to 442 feet deep. Three additional City of Adelanto wells
are located on Raccon Avenue west of the base and are 231 to 363 feet deep. GAFB and
Adelanto have received licenses from the California DWR to extract a total of 8.34 cfs of
groundwater.
Three additional wells located northeast of and across the Mojave River from the GAFB
production wells supply water to the town of Oro Grande. All 14 wells are believed to be
screened in a deeper aquifer system than that penetrated by the monitoring wells installed at
GAFB (Boyle, 1987). At least four wells are also maintained by the Riverside Cement Company
in Oro Grande. These wells are 100 to 152 feet deep and are primarily used for industrial
applications, although one well is reportedly also used for domestic purposes. There are
numerous privately owned domestic, agricultural, and industrial wells along the Mojave River.
The approximate locations of known municipal and domestic. water-supply wells in the GAFB
vicinity are shown on Figure 7.
2.1.7
Plant Life
The most predominant type of vegetation is the creosote bush scrub community which includes
creosote bush, cheesebush, burroweed, ricegrass, and Mormon tea. This type of vegetation is
typically found ih the undeveloped areas of the base. Russian thistle or tumbleweed is often
found in the disturbed areas (CH2M Hill, 1982). Riparian vegetation communities, including
2-6
-------
.0 m ffi
~ 3: 00
m lit
0 ~ % t
o ,.... 0
~ 0 Q ~ 0
D 0
COLUSA RD. ~ (11
UJ 0 ~
0
01( 0 ~ ~
"0 '"
~ g
!!!.
~ ....
C VVWRA iiI
II: a9 Well. U;
DESOTO AVE. w I ':t
-'.
il
.
~. I-
El MIRAGE ROAD at
RANCHO ROAD
<0
CRIPPEN AVENUE
City 01 Adelanto
Wella
~
AIR BASE ROAD
W
:J
ffi
?<
RANCHO ROAD
~
~
a
II:
II:
W
Iii
c(
C
II:
II:
~
Ii
-'
-'
w
m
HOllY ROAD
m
,....
~
8
~
o
VilLAGE DR.
~ Municipal Water Supply Well
o Domestic Water Supply Well
6 Surface Spring
/'
Approximate Direction of
Groundwater Flow
o 1/2 1
~~.. ..... ..,
APPROXIMATE SCALE IN MilES
APPROXIMATE LOCATIONS OF
KNOWN MUNICIPAL AND
DOMESTIC WATER-SUPPLY WELLS,
GAFB VICINITY
LEGEND
FIGURE 7
Wells ere approxlmetely located based on Calilomia Department Weter Rasources records
0:/194.0
-------
cottonwoods, willows, cattail rushes, and sedges, are found along the Mojave River channel,
near the golf course and near the old GAFB STP Percolation Ponds.
A biological assessment was conducted in 1989 in the northern ponion of the base and an off-
base section just north of the northern base boundary. This assessment was done as part of the
initial FS for the NEDA (JMM, 1988a). The dominant species found were creosote bush,
sweetbush, cheesebush, paperbag bush, and indigo bush, all Mojave Desert creosote bush scrub.
Golden cholla cactus, beavertail cactus, and pencil cholla were also found scattered throughout
the site. Herbaceous plants included introduced grasses such as abu-mashi and red brome. as
well as native grasses and herbs such as Indian ricegrass, spurge, chia, and fiddleneck. Joshua
trees occur along the base of the steep slopes in the.area (LSA, 1989).
Several sensitive plant species may occur in the area of GAFB. Good habitat exists for several
of the plant species; however, only Joshua trees were actually observed during the survey of the
area' (LSA, 1989). Additionally, the U. S. Fish and Wildlife Service (USFWS) lists three
Category-2 speCies that may be present on GAFB. These are the alkali mariposa lily, barstow
woody sunflower, and the desert cymoperus. Category-2 species are those for which existing
information is insufficie~t to warrant listing as endangered or threatened species (USAF, 1989).
2.1.8
Animal Life
Wildlife in the vicinity of GAFB includes both desen and riparian species such as black-tail
jackrabbit. cottontail rabbit, and antelope ground $QUirrel (CH2M Hill, 1982). Seventy-five bird
species have been identified in the area, including ravens, hawks, owls, quail, flycatchers, larks,
warblers, sparrows, and blackbirds. Other wildlife includes lizards, snakes, pocket mice, and
raccoons. .There are no fish species known to occur at GAFB. Generally, animal activity is
highest in the northern and southern portions of the base where native plants are leaSt disturbed.
Animal activity is lowest in the high traffic areas ,of the base, such as the housing and industrial
complex, recreation areas, and the runways (USAF, 1989). ' , '
The desert tonoise is the only animal species found on the base that is listed by the USFWS as
a threatened or endangered species. Two Category-2 animal species may be present on GAFB:
the ferruginous hawk and Mojave ground squirrel (USAF, 1989).
2.2
SITE HISTORY AND ENFORCEMENT ACTIVITIES
The Industrial/Storm Drain and the STP Percolation Ponds were identified in an IRP Phase I .
Records Search (CH2M Hill, 1982). The TCE plume was first identified during a subsequent
Phase IT investigation (SAlC, 1985, 1987). '
On January 16, 1986, the California Lahontan Regional Water Quality Control Board (RWQCB)
adopted the Cleanup and Abatement Order (CAO). The CAO required the USAF to define the
extent of TCE contamination in the groundwater beneath the NEDA, submit a plan for
remediation, and begin cleanup of the groundwater.
2-7
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Phase IIi and Phase IV IRP investigations were conducted for the Industrial/Stonn Drain and
the TCE plume beneath the NEDA (JMM, 1988a,b,c,d,e,f, 1989, 1990). These investigatic1ns
included separate FSs for the Industrial/Storm Drain and TCE plume in groundwater beneath
the NEDA.
The 1988 FS performed for the NEDA identified a preferred alternative for the remediation of
groundwater contamination (predominantly TCE). This alternative included nine extraction
wells, an air stripping facility, and reinjection of the treated water into the Regional Aquifer
(JMM, 1988a). This alternative was selected using a USGS-developed three-dimensional
groundwater model, and analytical data collected by SAIC during the Stage 1 and Stage 2
investigations. However, additional data needs were identified during the performance of the
1988 FS, and funher investigation was recommended. A Supplemental Site Characterization
was subsequently performed by JMM in 1987 to collect these data (JMM, 1988b).
GAFB was placed on the National Priorities List (NPL) in February 1990. In October 1990,
the USAF signed a Federal Facility Agreement (FFA) with the USEPA (Region IX), California
Department of Health Services (DHS) (now the Department of Toxic Substances Control
[DTSC]), and the RWQCB. The CAO was rescinded and operable units were created with the
signing of the FF A."
Investigations were also performed for the Industrial/Storm Drain to identify potential removal
and replacement options. Based on the analytical data gathered during the Phase IT
Investigations conducted by SAlC, as well as the findings presented as part of the Predesign
Technical Memorandum (TM) (JMM, 1988t),'a stoIID drain replacement project was planned
for the Industrial/Storm Drain. This project would consist of removal and replacement of the
East Storm Drain and a portion of the Upper West Storm Drain, abandonment of two sections
of the Industrial/Storm Drain system known as the "normal flow" and "high flow" bypass lines,
and rerouting of all flow to an existing oil/water separator. As part of the replacement project,
the normal and high flow bypass lines were to be cleaned and filled with concrete. Initially, the
entire length of the East Storm Drain and Upper West Storm Drain was to be replaced in
conjunction with the installation of a basewide pretreabnent system. However, because the base
was closed in 1992, constrUction of the basewide pretreatment system was canceled. As a result,
the storm drain removal project was altered to include cleaning, rather than removal, of the
upper West Storm Drain. The remainder of the. West Storm Drain was to be cleaned in place
and continue in use as a storm drain. .
To ensure. the condition of selected portions of the storm drains were such that they could be
cleaned rather than removed, a second investigation was perfonned in June 1989. Portions of
the stonn drains were videotaped to test the pipe integrity, and sediment samples were collected
to verify previously reported results and further define contamination in areas that had exhibited
high photoionization detector (PID) readings.
A third field investigation was perfonned as part of a second TM prepared for Site SD-25 (S-20)
(]MM, 1990). This investigation was performed to define the extent of contamination initially
detected as part of the sampling conducted for the Predesign TM (JMM, 1988f) in the high flow
2-8
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bypass and the normal flow ponions of the East Storm Drain and ponions of the West Storm
Drain, and to confIrm conclusions based on soil sampling results for which SAIC had missed
holding times.
Using the results of all three fIeld investigations at Site SD-25 (S-20), the fInal storm drain
removal project was initiated between October 1989 and May 1991. As part of this project, both
the high flow bypass and the normal flow ponions of the East Stonn Drain were cleaned and
fIlled with concrete, and the removed sediments were handled as designated wastes and disposed
off site. The normal flow bypass was rerouted from manhole 199 to manhole 202. The
perforated portions of the East Storm Drain were removed and replaced with nonperforated pipe.
Approximately 1,500 cubic yards of soil were gene~ted during excavation when the East Storm
Drain was removed. All excavated materials, including soil, sediments, and pipe, were disposed
off site. Videotapes showed the upper ponions of the West Storm Drain to be in good
condition; therefore, those sections were cleaned and left in place. The results of the Outfall
Ditch sampling were similar to SAiC's fmdings (JMM, 1990); therefore, it was again
determined that no further action was warranted for the Outfall Ditch.
In 1992, seven soil borings were drilled immediately adjacent to the East Industrial/Storm Drain
and the Outfall Ditch. This activity confIrmed that soil and sediment previously present in the
storm drain had been adequately remediated during the pipeline cleaning, removal, and
construction of the new reinforced concrete pipe. This activity also confIrmed that
contamination did not exist below depths previously sampled.
Investigations were performed at the STP Percolation Ponds to evaluate if contamination exists
at this site. Sampling of groundwater from monitoring wells located near the percolation ponds
occurred in 1985 and 1986 during Phase n of the IRP (SAlC, 1987). Also, two soil borings
were drilled (0 evaluate the condition of the vad~se zone. In 1987, an additional investigation
was performed including groundwater monitoring and drilling of two additional borings (JMM,
1992a).
In 1992, a third investigation was performed at the STP Percolation Ponds (JMM, 19913). This
investigation was conducted to (1) assess soils within and beneath the STP Percolation Ponds as
a potential source area for contaminants, (2) assess the potential for contaminant migration and
exposure pathways, including the surface exposure pathway and the potentW subsurface
migration pathway to groundwater, and (3) provide a means to monitor the effects of effluent
discharge (0 the percolation ponds. This investigation included the installation of four
groundwater monitoring wells and the drilling of 11 soil borings. Investigations at the STP
Percolation Ponds indicate that the contamjnant~ of concern in the soil are within background
concentrations for desert soils, except for elevated nittate concenttations that are in the top 46
feet of soil. .
As a result of a USEP A assessment, and subsequent placement of GAFB on the NFL in
February 1990, a new FS (JMM, 1993a) was prepared (1) to summarize and reassess the earlier
FS activities performed prior to . GAFB being placed on the NFL and (2) to update the
documentation of this investigation ~ current USEPA guidance published in 1988. The USEPA
2-9
-------
guidance (Guidance for Conduction Remedial Investigations and FeasibilitY Studies Under
CERCLA) was developed to reflect the new emphasis and provisions of SARA and incorporates
aspects of new or revised guidance on technical and management initiatives designed to
streamline the RIfFS process (USEPA, 1988a).
The fmdings and conclusions of this ROD are based on the analysis of OU 1 presented in the
final FS Repon (JMM, 1993a) and the accompanying Proposed Plan (JMM, 1993b). The
technical information supponing each alternative is included in these reports and the RI Repon
(JMM, 1992a).
2.3
lfiGHLIGHTS OF COMMUNITY _PARTICIPATION
The Community Relations Plan (CRP) was completed in 1991 for GAFB by International
Technologies Corporation following USEPA guidance (IT, 1991). Consistent with the CRP, the
USAF established a Technical Review Committee (TRC) which was composed of the USEP A,
DTSC, RWQCB, and representatives from adjacent communities. The TRC met on a quarterly
basis to provide community representatives with up-to-date information on recent milestone
events. In January 1994, GAFB established the Restoration Advisory Board (RAB) which
replaced the TRC. The RAB meets C?n a quarterly basis and the meetings are open to the public.
The RAB is designed to act as a focal point for environmental exchange between G~ and the
public.
The RI Repon (JMM, 1992a) , FS Repon (JMM, 1993a), and Proposed Plan (JMM, 1993b)
were released. to the public and were made available in both the Administrative Record File and
in information repositories maintained at the following locations:
.
The OL-Cf AFBCA Office at GAFB
The Victorville Branch of the San Bernardino County Library
The Adelanto Branch of the San Bernardino County Library
.
.
The availability of these documents and announcement of the pUblic. meeting and public comment
period were published in the Victor Valley Daily Press, the Los Angeles Times, the Orange
County Register, and the San Bernardino Sun in September 1993. A press release was sent. to
20 local newspaper, radio, and television organizations announcing the public meeting and public
comment period.
The Proposed Plan was mailed in September 1993 to all parties identified in the CRP, including
government officials, media, private organizations, and interested members of the community.
A public comment period was held from September 20 to October 19, 1993. A public meeting
was held on October 6, 1993 at GAFB. Representatives from the USAF, USEPA, DTSC, and
RWQCB were present at the meeting. The Responsiveness Summary, Section 3.0 of this ROD,
contains responses to questions from the meeting and comments submitted by mail.
2-10
-------
~ ---~----~~-- .
2.4
SCOPE AND ROLE OF OPERABLE UNIT WITHIN THE SITE
STRATEGY
The suspected hazardous waste sites present at GAFB were grouped into three 0t>erable unitS
based on the type of waste present and the geographical location (Figure 8). au 1 consistS of
three sites: (1) Site SD-25 (S-20), an Industrial/Storm Drain which in the past received industrial
waste; (2) Site WP-26 (S-21), the fonner STP Percolation Ponds; and (3) groundwater beneath
and adjacent to the NEDA contaminated with TCE. As no further action has been determined
for Site SD-25 and Site WP-26, the remaining role for au 1 is for treatment of the TCE plume
beneath and adjacent to the NEDA.
au 2 consists of the entire Liquid Fuel Distribution System, including five aboveground tanks,
two major pipelines, seven fuel pits, and distribution lines. Contamination at au 2 has resulted
from jet fuel (JP-4) releases. au 3 consists of the S8 remaining IRP sites located throughout
GAFB. Contamination potentially found at au 3 sites relates' to activities associated with
equipment maintenance; fire training; fuel use and storage; pest control; laboratory, shop, and
hospital operations; and old landfIll and solid waste disposal. au 3 includes several sites located.
in the NEDA, above tb.,e TCE plume.
2.5
SUMMARY OF SITE CHARACTERISTICS
This section summarizes the site characteristics at au 1. Due to the distinct nature of the three
sites that comprise au ~ (groundwater beneath the NEDA, the Industrial/Stonn Drain and
Outfall Ditch, and the STP Percolation Ponds), the discussions of the sites are presented
separately.
2.5.1
Northeast Disposal Area
Based on available data, groundwater beneath the NEDA has been found to exist in two separate
aquifers, the Upper Aquifer and the Regional Aquifer. The Upper Aquifer is a 40- to 6O-foot-
thick zone of saturated, moderately permeable materials interspersed with zones of low-
permeability materials. The depth to water in the aquifer varies between 60 and 120 feet bgs.
Groundwater elevations in the Upper Aquifer beneath the NEDA range from 2,737 feet msl to
the south to 2,711 feet msl north of GAFB. Generally, water levels did not change appreciably
in most wells over the period during which water levels were taken (June to December 1987)
with the exception of five wells (NZ-07, NZ-08, NZ-ll, NZ-31, and NZ-32). Water level.
changes in these five wells were as much as 3 to 20 feet over the period of the measurements.
The reason for these variations is presently not' known. The groundwater gradient within the
northeast portion of the base is approximately 0.003 ftlit to the northeast. North of the base,
two groundwater flow directions are indicated. The first is towards the northeast with a gradient
of 0.007 ftlit, and the second is towards the east with a gradient of 0.02 ftlit. Aquifer pump
tests conducted in the Upper Aquifer indicate the transmissivity ranges from 5,500 to 20,700
gpd/ft. with a storativity of about 5xlo-3. Slug test data indicate the hydraulic conductivity
ranges from 1.20 to 291.72 gpdIft2 (JMM, 1992a). .
. 2-11
-------
t
NZ-50 D
NZ-38
o
C NZ-47
SLUDGE
DRYING
$ LA~S
PERCOLATION
.. PONDS
I
I
I
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1
I
I
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---.-.
GEORGE AIR FORCE
BASE BOUNDARY
r'-'-'-'-'-'1
I I
. .
I I
. .
I
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I. .
I NZ-25/NZ-31
I NZ.24 NZ.29
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~-i2 NZ-19 J .
. I NZ~~-';' . --'or' Nt;;;
I NZ... IJ NZ.3Q
I NZ.23 Ie NZ-
-------
Groundwater in the Regional Aquifer is present at depths below 2,590 feet msl and. is
geographically extensive. Groundwater flow in the Regional Aquifer is to the northeast with a
gradient of 0.001 ftlft. This aquifer appears to be hydraulically connected to the Mojave River
underflow. Within GAFB and immediately north of the base, the Upper and Regional aquifers
are separate unitS, divided by a clay unit whose top elevation ranges from 2,640 to 2,670 feet
ms!. Three wells installed within GAFB below this clay unit indicated the existence of dry soil
zone between the Upper and Regional aquifers. However, this clay layer disappears north and
east of the base and the groundwater merges into one aquifer. A slug test performed in a well
screened in the Regional Aquifer indicated the hydraulic conductivity to be about 8.98 gpd/tr
(JMM, 1992a).
The investigations conducted at NEDA were primarily to characterize groundwater contamination
beneath the site. The groundwater investigations revealed the presence of volatile organic
compounds (VaCs). TCE is the primary contaminant of concern, being the most persistent and
widespread. A summary of the maximum concenttations of the contaminantS detected in the
groundwater beneath this site is presented in Table 1. TCE was detected in the Upper Aquifer
and in the Regional Aquifer northeast of where the two aquifers merge (Figure 8). Based on
this data, contamination of the Regional Aquifer above the MCL appeared to be limited to the
northeast off-site area near the Mojave River where groundwater from the Upper Aquifer merges
into the Regional Aquifer.
Based on an average concentration of TCE (47.3 ",g/l), the contaminated groundwater in au 1
is not a RCRA hazardous waste as dermed in 22 CCR Section 66261. The source of the TCE
contamination is currently unknown. Several waste disposal sites within the NEDA, being
characterized separately as part of au 3 investigations, were identified as potential sources. The
au 3 site primarily suspected is FT-19 (S-5); however, this has not been confirmed.
Within GAFB boundaries, TCE contamination of the Regional Aquifer was confirmed in three
wells (NZ-02, NZ-03, and NZ-13), all located in the eastern portion of the base. The TCE
concentrations in these wells were, however, below state and federal MCLs. Water level
measurementS in December 1987 in well NZ-02 indicate the water table is as much as 34 feet
above the top of the screen. Since the aquifer does not appear to be confmed near this well, it
is possible that potential contamination in the well is underestimated.
A large portion of the TCE plume has migrated off site beneath the northern boundary of GAFB.
TCE concentrations within most parts of GAFB boundaries are decreasing. Lateral migration
of the TCE appears to be toward the north within GAFB boundaries. Off site, two migration
pathways, consistent with hydrogeologic fmdings, are indicated. The first pathway is to the
northeast along the arroyo leading towards the Mojave River and the second is to the east
immediately north of the base. Because. of this lateral migration, TCE concentrations are
increasing off site, particularly in the northeast. It is also possible that teE concentrations are
increasing to the east of well NZ-40. However, this cannot be confirmed since there are no
monitoring wells in that area. Additional investigations to determine the extent of TCE
contamination in this area are planned as part of the Investigation in Suppon of RDIRA (Section
2.12.2).
2-12
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TABLE 1
GROUNDWATER DATA SUMMARY, NORTHEAST DISPOSAL AREA
Detection Maximum Average Standard Upper-Bound
Number Number Percent Limits Concentration Concentration Deviation . Concentration
Compound Analyzed Detected Detects (pg/l) (pg/l) (pg/l) (pg/l) (pg/l)
Acetone 128 2 1.54 80 46.00 NC NC
Benzene 130 1 0.77 0.1 0.1 0.10 NC NC
Carbon Disulfide 53 8 14.81 5 1.05 1.64 1.69
Carbon Tetrachloride 130 1 0.77 0.1 0.08 0.02 0.09
Chlorofonn 130 32 24.62 0.1 0.6 0.18 0.13 0.23
Dibromochloromethane 130 1 0.77 0.1 1 1.00 NC NC .
I,I-Dichloroethane 130 5 3.85 0.1 1 0.44 0.40 0.57
1,2-Dichlorobenzene 129 1 0.79 0 0.90 NC NC
1,2-Dichloropropane 130 1 0.17 0.1 0.1 0.10. NC NC
1,2-Dichloroethane 130 2 1.54 0.1 0.1 0.10 0.00 0.10
c-I,2-Dichloroethene 130 6 4.62 0.1 8.1 0.62 1.82 1.23
t-l,2-Dichloroethene 130 4 3.08 0.1 0.1 0.08 0.02 0.09
MEK 129 1 0.77 1.4 1.~0 NC NC
Methylene Chloride 130 4 3.08 5 0.9 0:36 0.34 0.47
Tetrachloroethene 130 24 18.46 0.1 1.1 0.38 0.71 0.61
Tetrahydrofuran 130 2 1.54 2.3 1.65 NC NC
Toluene 130 28 21.54 0.5 9 1.41 1.87 2.03
Trichlorobenzene 126 0 0.00 0 NC NC NC
1,1,2- Trichloroethane 130 0 0.00 0.1 0 NC NC NC
Trichloroethene 130 117 90.00 0.1 310 47.31 69.74 70.42
1,1,2- Trichloro-I,2,2-trifluorethane 1 1 100.00 3 3.00 NC NC
Trichlorofluoromethane 130 3 2.31 1.7 1.43 0.38 1.56
TRPH 32 II 34.38 1.4 0.74 0.29 0.84
Xylenes 130 2 1.54 0.1 0.1 0.08 0.02 0.09
-------
An evaluation of the rate and extent of TCE plume movement was conducted as pan of the 1988
RI (JMM, 1988d) as summarized in the 1992 R1 (JMM, 1992a). The results of groundwater
modeling indicated that the center of the TCE plume would move approximately 1 mile from
the northern boundary of the base in 30 years. The plume would move northeasterly around a
mound created by the VVWRA Percolation Ponds and discharge into the Mojave River in about
15 years, with a maximum estimated TCE concentration of 10 micrograms per liter (Ilg/l). The
model predicted that the existing VVWRA wells would be slightly impacted by the plume,
although concentrations were predicted to remain below 5 Ilg/l. These wells were, but are not
currently used for potable water; therefore, the projected impact was not anticipated to be
significant. Recent sampling events that have occurred at the VVWRA wells are discussed in
Section 2.12 of this document and the associated r~ferences. No other water supply wells are
known to exist in the path of the plume.
Based on the 1987 data, the mass of TCE present in the aquifer, within the 5 Ilgll
isoconcentration contour, was estimated to be approximately 430 pounds. The volume of
contaminated water was estimated to be 1.83xlQ9 gallons. The apparent area encompassed by
the plume has increased since 1986, while the peak concentration has decreased, possibly
indicating the occurren~e of dispersal and downgradient migration (JMM, 1992a). This portion
will continue to attenuate by adsorbing (0 soil surfaces. The mass that is not removed from the
groundwater by attenuation will eventually discharge to the Mojave River.
2.5.2
IndustriallStorm Drain and Outfall Ditch
The remedial actions that have taken place for this site include removal of all contaminated
sediments and replacement of the perforated portion of the pipe with nonperforated pipe, as
discussed in detail in Section 2.2. Subsequent sampling of soil beJ;1eath the East Storm Drain
indicated that the concentrations of contaminants were within background levels for GAFB soils
as determined through the available data in conjunction with typical desert soil values presented
in literature. Therefore, the soils beneath the Industrial/Storm Drain are not considered
haz2rdous. .
2.5.3
STP Percolation Ponds
The results of the soil sampling program conducted to evaluate the STP Percolation Ponds have
indicated that, with the possible exception of nitrate, the concentrations of the contaminants of
concern are within background concentrations for desert soils. Elevated nitrate concentrations
are expected since the ponds were previously used for disposal of the STP effluent. These
elevated concentrations are limited to the upper 46 feet of soils beneath the ponds. Elevated
nitrate concentrations have previously been a subject of concern because the selected remedy for
cleanup of the TCE in the groundwater beneath the NEDA includes discharge of treated
groundwater to the STP Percolation Ponds (see Section 1.4). Studies of wastewater discharge
to the soils of the Upper Mojave River Basin' have shown that the potential for transport of
nitrates to groundwater is low (USGS, 1993). This may be the result of low mobility in the soils
in this area, denitrification in the unsaturated zone, or dilution by vertical mixing with
groundwater. The STP Percolation Ponds have not been used since 1980 (JMM, 1992a). Based
2-13
-------
on this infonnation, discharge of the treated groundwater to the STP Percolation Ponds is not
expected to impact groundwater. However, existing wells around the STP Percolation Ponds
will be monitored for nitrates on a quarterly basis.
2.6
SUMMARY OF SITE RISKS
As in Section 2.5, discussion of site risks for the three sites that comprise au 1 are presented
separately. This risk assessment includes both a human health risk assessment and an
environmental risk assessment. The purpose of the risk assessment was to provide an evaluation
of the risks (both current and future) to human health and the environment posed by present site
conditions, assuming no attempt to mitigate or prey~nt potential exposure. A swmriary of the
carcinogenic risk and hazard indices calculated - for au 1 is presented in Table 2.
The au 1 risk assessment was-performed prior to validation of the available data. The data
used for this risk assessment could not all be validated as reported in the Validation Suminary
Report (JMM, 1993c); however, validated data will be collected to support the conclusions of
this risk assessment as part of the ongoing Investigation in Support of Remedial Design/Remedial
Action (RD/RA) (Sec~~n 2.12).
2.6.1
Northeast - Disposal Area
A baseline carcinogenic risk assessment associated with TCE was performed. The highest
human carcinogenic risk to the future resident using the groundwater beneath the NEDA is
estimated at 9xl0.s for the combination of water ingestion, dermal contact, and inhalation of
volatiles from the groundwater. Since there are no current, completed exposure pathways,
cancer risks have not been estimated for current exposure scenarios. This risk level is within
the lxl~ to lxl~ (1:10,000 to 1:1,000,(00) range established by the NCPbut above the lxl~
level set by the State of California (JMM, 1992a). -
Hazard index calculations for noncancer risks indicate the benchmark of 1.0 was exceeded at the
NEDA for the scenario of future child RME (2.9). However, the probability that an adverse
human health effect would occur is quite low given conservative exposure assumptions and the
potential toxicity of the vacs to humans (JMM, 1992a).
An environmental assessment was conducted to assess the potential risks to plants and animals
due to the presence of TCE in groundwater beneath the NEDA. Since groundwater beneath the
NEDA currently does not reach the surface, surface water is not a current route of exposure to
environmental receptors. However, potential construction activities associated with future
groundwater remediation could adversely affect plants and animals at the NEDA. Potential
environmental receptors include birds, mammals, reptiles, and plants. The Mojave ground
squirrel and the desert tonoise are considered to be the most sensitive species identified at
GAFB. The desen tortoise is on the Federal Eodaneered Species List and the Mojave ground
squirrel is on the California Endangered-Species List.
2-14
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TABLE 2
SUMMARY OF CANCER RISKS AND HAZARD INDICES FOR OPERABLE UNIT 1
Cancer Risk Hazard Index
Site
Receptor
Pathway Average RME Average RME
Nonheast Disposal Area
On-and Off-Site Adult Residents. Future
Ingestion 9 x 1()'6 1 x 10.5 1.9 X 10-1 2.9 'x 10-1
Inhalation 2 x 10-5 8 x 10-5 4.5 X 10.2 4.1 X 10-1
Dermal 1 x 10.7 4 X 10-7 3.5 X 10.3 1.1 X 10.2
Total 3 x 10-5 9 X 10-5 2.4 X 10-1 7.1 X 10-1
On- an~ Off-Site Child Residents. FutUre
Ingestion NC NC 3.5 X 10.1 5.5 X 10-2
Inhalation 1 x lO"5 3 x IO-S 9.6 X 10"1 2.80
Dermal 3 x 10"7 . 4 X 10"7 1.7 X 10"2 2.5 X 10.2
Total I X 10-5 3 x 10-5 1.3 2.9
Percolation Ponds
Casual Visitor. Current
Ingestion 9 x 10"' 9 x 10"' 1.0 x 1(t4 1.2 x 1004
Total 9 x I"" 9 x I"" 1.0 x I~ 1.2 x 1~
Constnlction Worker. FUtUre
Ingestion 2 x lO.7 2 X 10"7 3.0 X 10"2 3.3 X 10.2
Inhalation 9 X 10"7 4 x 1()'6 3.8 x 10"2 1.8 x 10.1
Total I x I~ 4xUr 6.8 x l~ 2.1 X 10-1
On-Site Adult Residents, Future
Ingestion 2 x 1()'6 2 x 1()'6 6.4 x 10"3 7.4 X 10-3
Inhalation 6 x 10-- 8 x 10-- 3.1 x 1(t4 1.6 x lO-3
Total 2 x lit' 2 x lit' 6.7 x Ir 9.0 x lr
On-Site Children Residents, FutUre
Ingestion NC NC 6.0 X 10"2 6.9 X 10"2
Inhalation NC NC 6.6 x 1(t4 9.2 x 1(t4
Total NC NC 6.0 x l~ 7.0 x 1~
Industrial/Storm Drain
Outfall Ditch, Future
Dermal 1 x 10"' 2 x 10"' 5.5 x 1()'6 1.0 x lO.5
Total I x I"" 2 x I"" 5.5 x lit' " 1.0 x lr
Contnlction Worker, Future
Ingestion 3 x 10"7 4 X 10"7 1.6 X 10"2 1.9 X lO.2
Inhalation 2 x 1()'6 2 x 1()'6 3.9 x 10"2 4.8 x 10"2
Total 2 x lit' 2 x lit' 5.5 x I~ 6.7 x 1~
RME - 95 percent upper bound concentration
-------
2.6.2
Industrial/Storm Drain and Outfall Ditch
The highest human carcinogenic risk, 2xl0~, is associated with a futUre construction worker
scenario for incidental ingestion of soil and inhalation of fugitive dust conraining metals.
Although the calculated carcinogenic risk is slightly above the level established by the State of
California, the detected metal concentrations are within native, background concentrations
(JMM, 1992a).
The risk to potential environmental receptors at the Industrial/Storm Drain and Outfall Ditch was
estimated to be low due to the low concentration of metals in surface and subsurface soils at the
site. The site was not considered suitable habitat f~r most species (JMM 1992a).
Based on the risk assessment, it was determined that risks for the Industrial/Storm Drain and
Outfall Ditch are within acceptable levels; therefore, remediation of this site would not be
required.
2.6.3
STP Percolation Ponds
The highest human carcinogenic risk, 4x1
-------
5) , Discharge of Emissions to the Atmosphere
6) Implementation' of Appropriate Deed Restrictions
Alternative 3
1)
2)
3)
4)
5)
Groundwater Monitoring
Groundwater Extraction
Treatment by Air Stripping with Emission Controls
Discharge Treated Water to STP Percolation Ponds
Implementation of Appropriate Deed Restrictions
2.7.1
Alternative 1 . No Action with Groundwater Monitoring
The no action alternative serves as a baseline against which other alternatives are compared, as
required by the NCP for Superfund sites. Under this no action alternative, the TCE plume will
be handled in a passive manner. Eight additional monitoring wells will be installed around the
perimeter of the plume, and will be sampled quarterly to determine its movement and evaluate
potential future impacts on any downgradient supply wells. Eight new monitoring wells will be
located in pairs (one shallow [approximately 100 to 120 feet] and one deep [approximately 150
to 180 feet]) along th~ boundary of the plume, as determined from the latest results of the
current quarterly monitoring program.
These eight monitoring wells will be sampled on a quarterly basis and samples will be analyzed
for VOCs (USEPA Methods 601 and 602), including both chlorinated hydrocarbons and
aromatic hydrocarbons. These analyses were specified on the basis of previous results of
groundwater sampling and analysis at the site. Costs of sampling existing wells are not included
in this alternative because such sampling is part of an existing program. If future investigations
at GAFB indicate the presence of other contaminants at significant levels in the groundwater,
the analytical parameters included in the monitoring program will be expanded accordingly. The
groundwater monitoring component of Alternative 1 is also included in Alternatives 2 and' 3. '
The no action alternative will not reduce, the risks to human health posed by VOCs in the
groundwater beneath the NEDA, and. provides no additional protection of human health or the
environment.
Alternative 2 . Groundwater Extraction, Air Stripping, and Percolation
Alternative 2 consists of an estimated 19 extraction wells located on and off base, followed by
treatment of extracted groundwater using tWo packed-tower air stripPers in series for removal
of the VOCs (primarily TCE), and disposal of the treated groundwater to the STP Percolation
Ponds. Packed towers are a proven technology and have been selected for this analysis for the
purposes of alternative comparison and relative cost analysis; however, other low-profile air
stripping processes (such as rotostrippers) are available and would be considered prior to
installation of the fInal system. Quarterly groundwater monitoring would be implemented, as
for the no action alternative, to assess the effectiveness of the proposed remediation system.
This active plume control alternative is designed to mitigate the advance of the TCE plume
towards potential downgradient receptors, while reducing the mass of TCE retained in the
2.7.2
2-16
-------
aquifer. The extraction system will ensure that VOC concentrations are reduced to
concentrations below the federal MCL for TCE (currently 5 #J.gll) and all other contaminants of
concern. The groundwater from the extraction wells would be piped to the air stripping facility
where TCE concentrations would be reduced to below 2.5 #J.g/l. The treated water, in turn,
would be piped to the STP Percolation Ponds for recharge into the Upper Aquifer. The use of
a ponion of the treated groundwater for golf course irrigation may be considered in the furore.
As a temporary measure during startup and shakedown of the treatment facility, treated
groundwater would initially be discharged to an arroyo (shown on Figure 9) near the treatment
facility .
This alternative would be implemented in two phases. Phase I includes the installation of three
on-base and six off-base extraction wells, four on-base and four off-base monitoring wells,
gravity collection piping; and an air stripping treatment system. During this phase, the treated
groundwater (approximately 260 gpm) will temporarily (approximately 6 months) be discharged
to an existing wash near the tteatment system. Appropriate precautions will be taken to avoid
or minimize the impacts of erosion. Temporary discharge of the tteated water will allow for
testing and operation of the. treatment system while the construction of a permanent
. recharge/reuse system is being completed. Phase I will also include the installation of an
effluent clear well, coiJstruction of an effluent transmission pipeline, and rehabilitation of the
existing percolation ponds to receive treated groundwater for. recharge. Rehabilitation of the
percolation ponds may include debris removal, repair of existing pavement and drainage.
regrading, and installation of any appropriate fences. The proposed locations of the system
components for Phase I are shown on Figure 9. The conceptual design for the effluent disposal
system at the STP Percolation Ponds is shown on Figure 10.
The second phase (Phase ll) would occur in about 2 years and would include the installation of
an estimated 10 additional extraction wells (nine off-base wells), additional pipeline and
roadway, and local power distribution to new wells. The exact number and location of the
additional wells would be determined based on the efficiency of the Phase I system. and,
therefore, are not shown on Figure 9.
Additionally, this alternative would include implementation of deed restrictions. as appropriate.
to prohibit use of groundwater until groundwater cleanup levels have been achieved. Prior to
sale or transfer of any GAFB propeny overlying contaminated groundwater beneath the NEDA,
the USAF will record any appropriate land use restrictions in accordance with California Health
and Safety Code Section 25230 as an institutional control.
2.7.3
Alternative 3 - Groundwater Extraction, Air Strippmg with Emission
Controls, and Percolation
Alternative 3 is the same as Alternative 2, with the addition of an emissions control system for
air stripper off-gas. .
The results of an air emissions health risk assessment indicate that the VQC air emissions from
the operation of the strippers for Alternative 2 do not warrant the use of emissions conttol
2-17
-------
. MoniIDring WeH
Q Ex1rac:tion WeI~pper Aquifer
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EXPLANATION
e Exndion Weil-RegionaJ Aquifer
o SOO 1000
~ I
Scale in Feet
CONCEPTUAL DESIGN OF PHASE I
OF THE EXTRACTION AND MONITORING
WELL SYSTEMS
ALTERNATIVES 2 AND 3
Topographic base III8pI modified from U.S. Geological Survey,
Adelanto and Victorville 7.5' quadrangle mlll)S.
FIGURE 9
Q.'2
-------
r-----,
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Clear Well and
Supply Pumping
New 8" PVC
Waterline
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SCALE IN FEET
FS.G-12
Northeast Disposal
Area (NEDA)
Sewage Treatment
Plant (STP)
. Percolation Ponds
I
L_-I
CONCEPTUAL DESIGN OF
EFFLUENT DISPOSAL SYSTEM
ALTERNATIVES 2 AND 3
FIGURE 10
-------
devices. This conclusion was based on the maximum (worst-case) total population excess cancer
burden risk of approximately lxl()-6 and the maximum individual lifetime excess cancer risk of
approximately 6xlO-9 estimated for the air stripper without emissions control. Alternative 2
meets the "threshold" criteria (overall protection of human health and the environment and
compliance with applicable or relevant and appropriate requirements [ARARs]); however, the
addition of emission controls would provide an additional degree of protection and will be
compared to Alternatives 1 and 2 with regard to the "primary balancing" criteria. A detailed
discussion of this comparison is presented in Section 2.8.
2.8
SUMMARY OF COMPARATIVE ANALYSIS ALTERNATIVES
The remedial alternatives developed were analyzed - in detail using the nine evaluation criteria
required by the NCP. These criteria are classified as threshold criteria, primary balancing
criteria, and modifying criteria. Threshold criteria are:
(1)
(2)
Overall protection of human health and the environment
Compliance with ARARs .
Primary balancing criteria are:
(3)
(4)
(5)
(6)
(7)
Long-term effectiveness and permanence
Reduction of toxicity, mobility, or volume through treatment
Short-term effectiveness .
Implementability
Cost
Modifying criteria are:
(8)
(9)
State! support agency acceptance
Community acceptance
The resulting strengths and weaknesses of the alternatives were then weighed to identify the
alternative providing the best balance among the nine criteria. Table 3 summarizes this
comparison.
2.8.1
Overall Protection of Human Health and the Environment
This criterion is an overall assessment of whether each alternative provides adequate protection
of human health and the environment. The evaluation focuses on a determination of the degree
to which a specific alternative achieves adequate protection and describes the manner in which
site risks are eliminated, reduced, or controlled through treatment, engineering, or institutional
measures. The potential for cross-media impacts is also assessed.
Alternative 1: The results of computer modeling for the no action scenario show that the center
of the TCE plume will move approximately 1 mile from the northern GAFB boundary in
2-18
-------
TABLE 3
SUMMARY OF DETAILED ANALYSIS OF REMEDIAL ALTERNATIVES
Reduction 01 Toxicity, Compliance with State,
Technical Mobility, or Volume Federal, and Local Health Assessment
Alternative Total Cost 8 Effectiveness Feasibility (TMV) Regulations
1. No Action with $631,900 Not Effective No Technical No Reduction in TMV Does not Comply Potential for Future
continued groundwater Limitations Exposure Remains
monitoring
2. Groundwater Extraction, $7,864,300 Effective Easily Implemented Significant Reduction in Compliance is Achievable Potential for Future
Air Stripping, and TMV for Groundwater Exposure
Percolation Significantly
Reduced
3. Groundwater Extraction, $9,999,100 Effective Easily Implemented Significant Reduction in Compli:mce is Achievable Potential for Future
Air Stripping, Emission TMV for Groundwater and , Exposure
Controls, and Percolation Air Significantly
Reduced
8 Shown in 1992 Dollars.
-------
approximately 30 years. This plume is expected to move northeasterly around the mound
created by the VVWRA percolation ponds and begin discharging into the Mojave River Aquifer
after approximately 15 years at an expected maximum concentration of 10 ~g/l. The resultS of
the health risk assessment conducted as pan of the R1 show potential unacceptable future risk
if the plume is not remediated. If a future residential exposure scenario is assumed whereby a
water supply production well is placed at the center of the TCE plume, the upper-bound excess
cancer risk is estimated to be 3.1x10-s, which is higher than acceptable levels of risk (10-6)
established by the California Environmental Protection Agency (Cal-EPA). This calculation
assumes consumption of 2 liters per day of TCE-contaminated water by a 70-kg adult, and
inhalation of TCE vapors and dermal contact during daily showers for 30 years (exposure from
other contaminants was assumed to be negligible, _~ased on a statistical analysis of sampling
results). Under the conditions of this hypothetical future residential exposure, the no action
alternative does not provide adequate protection of human health and the environment. Because
contaminated groundwater would not be available except through future installation of a supply
well, the risk to environmental receptors is minimal at this time. .
Alternative 2: The extraction and treabnent of the contaminated groundwater provides
protection to public h~lth and the environment by eliminating the potential for ingestion or
inhalation of TCE above acceptable levels from future water supplies. Although results of the
conservative groundwater modeling, which assumed no evaporative losses during recharge,
indicated that some TCE leakage through the extraction system could occur within 15 years,
continued groundwater monitoring will be employed and an appropriate enhancement of the
treabnent system will be developed as necessary to ensure proper containment of the plume.
Therefore, no excess cancer risk via the groundwater pathway is associated with this alternative.
As for Alternative 1, the environmental impacts of this alternative are expected to be minor
because there would be no contact of wildlife with the extracted groundwater prior to treabnent.
A second potential exposure pathway for this alternative is the uncontrolled emission of TCE
in stripper off-gas. This route was originally assessed as part of the initial FS, based on an
. influent TCE concentration of 150 ILg/l and a groundwater flow rate of 500 gpm. "Worst-case"
and "most probable" estimates of the rate of TCE air emissions were calculated for the proposed
air stripping operations at this concentration. These two scenarios were defIned as follows
(Appendix F, JMM, 1988a):
.
The "worst-case" scenario is the highest mass emission rate of contaminants
expected during the initial operation of the stripping facility. This rate is assumed
to extend for the duration of air stripper operations.
.
The "most probable" scenario is the expected emission rate of contaminants from
the stripper facility, if the total mass of contaminant.') emitted from operations are
prorated over the life of the facility. .
The resulting calculated worst-case and most probable TCE emission rates (based on a 150-ILg/I
influent) were 4.73xlO-3 g/sec (0.90 Ibs/day) and 1.58xlO-3 g/sec (0.30 lbs/day), respectively.
These emission rates were then used to estimate the risk to the surrounding population based
2-19
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on an analysis of the long-tenn average concentration patterns in the atmosphere and the
equivalently long-tenn patterns of the local population disnibution. The connibution of benzene
and 1,2-dichloroethane (l,2-DCA) was also included in the analysis (JMM, 1988a).
Four categories of risk were considered in this analysis:
.
Potential risk to an individual located at the most exposed point (Le., point of
highest ground level concentrations). Maximum concentrations were found to
occur at two points 200 meters north and east, respectively, of the proposed
stripper location. No residences are located in these areas.
.
Potential risk to an individual located- at the most exposed existing residence.
.
Potential community excess cancer burden. based on consideration of the
combined risk to the 43,244 people estimated to live within a 20-kilometer (Ian)
radius of the stripper location (JMM, 1988a).
.
Mean individual excess cancer burden for each of the 43,244 individuals living
within 2tl Ian of the stripper location. .
.
The results of this analysis, conducted for- emissions of TCE, benzene, and 1,2-DCA over a
simulated 10-year period, are presented in the 1988 FS report (JMM, 1988a). On the basis of
theSe results, it was concluded that both the maximum individual lifetime cancer risk and the
total surrounding excess cancer burden were insignificant and it was not necessary to control
VOC emissions from the proposed air stripping system.
Since the 1988 FS analysis, several of the factors considered in the air emission risk analysis
have changed, as listed below:
.
The inhalation unit risk factor for TCE has increased from 1.3x1()"6 to 2xl()"6
(p.g/m3)"1.
.
The estimated average TCE concentration snipper influent has decreased from
150 to 47 p.g/l, based on more recent groundwater monitoring results.
.
Additionally, the levels and frequency of detection of benzene, 1,2-DCA, and
other VOCs decreased to the point where they were not considered statistically
reliable for risk assessment purposes.
.
The period of groundwater remediation (and stripper operation) was increased
from 10 to 30 years. .
Based on these considerations and changes, the original risk calculations were updated to reflect
the current understanding of the conditions at the site and the potential treatment scenario.
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Based on this reassessment, the maximum lifetime cancer risk for the most exposed individual
was estimated to be less than 6xlO-9. Stated another way, the risk to the most highly exposed
individual is less than one chance in one hundred million that an individual would develop cancer
due to the inhalation exposure of TCE in the ambient air if the individual were to reside at the
point of maximum exposure. for a 70-year lifetime. The point of maximum exposure is 200
meters east or nonh of the stripper facility. For comparison, the risk level of concern for the
DTSC and the Mojave Air Quality Management District (AQMD) (formerly San Bernardino
County Air Pollution Control District [APCD]), which is under the jurisdiction of the California
Air Resources Board (ARB), is lxlO-6 or less than one in one million. The estimated lifetime
cancer risk for individuals residing at the "most exposed residence" was found to be two orders
of magnitude lower than the risk for the maximum .exposure point. The estimated risk for the
average residence in the area was an additional two orders of magnitude lower than the "most
exposed residence."
The worst-case community excess cancer burden was estimated based on the community
population of 43,244 individuals. The excess cancer burden is defmed as the number of excess
tumors per one million exposed individuals due to exposure to a specified compound. The
estimated excess lifetime cancer burden for an individual in the maximum exposed area would
be approximately 2xlo-il. (cancer risk per million times the exposed population). The Cal- EP A
DTSC has established a benchmark of one- excess cancer developmem in one million exposed
individuals as an acceptable risk and the Mojave AQMD has no established benchmark value for
an excess cancer burden. The excess cancer. burden is well below background levels and should
not present an excess risk to any potemially exposed individuals.
Based on the above calculations, the use of gas-phase granular activated carbon (GAC) or
catalytic oxidation technologies to control TCE emissions from the proposed air stripper is not
considered necessary to protect human health. Additionally, the emission rate of TCE is
estimated to be 0.28 lbs/day, based on an influent concentration of 47 ,.,.g/l. (Based on expected
stripper influent concentrations, the contribution of other VOCs to overall einissions is expected
to be negligible.)
Alternative 3: This alternative is as protective as Alternative 2. Although unwarranted by risk
assessment considerations, the inclusion of emissions control in the form of gas-phase GAC
provides an additional degree of overall protection. In this alternative, TCE groundwater is
transferred to GAC which must then be regenerated or properly disposed.
2.8.2
Compliance with ARARs
Pursuant to Section 121 (d) CERCLA, as amended, the remedial acti~ns must attain a degree
of cleanup which assures protection of human health and the environment. In addition CERCLA
requires that remedial actions meet standards, requirements, limitations, or criteria that are
applicable or relevant and appropriate requirements (ARARs). ARARs are of three types:
chemical-, action-, and location-specific. Identification and consideration of potential ARARs
associated with a- site - and its remedial action is an ongoing process throughout site,
characterization and remediation. .
2-21
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An ARAR may be either "applicable" or "relevant and appropriate," but not both. The NC;P
defines "applicable" and "relevant and appropriate requirements" as follows:
Applicable requirements means those cleanup standards, standards of control, and other
substantive requirements, criteria, or limitations promulgated under federal environmental
or state environmental, or facility siting laws that specifically' address a hazardous
substance, 'pollutant, contaminant, remedial action, location, or other circumstance at a
CERCLA site. Only those state standards that are identified by a state in a timely
manner, and that are more stringent than federal requirements, may be applicable.
Relevant and appropriate requirements meaJ1S those cleanup standards, standards of
control, and other substantive requirements, criteria, or limitations promulgated under
federal environmental or state environmental, or facility siting laws that, while not
, "applicable" to a hazardous substance, pollutant, contaminant, remedial action, location,
or other circumstance at a CERCLA site, address problems or situations sufficiently
similar to those encountered at the CERCLA site that their use is well suited to the
particular site. Only those state standards that are identified by a state in a timely
manner, and that are more stringent than federal requirements, may be applicable.
In other words, a requirement is "applicable" .when the remedial action or the circumstances at
the site satisfy all of the jurisdictional prerequisites of that requirement. Maximum Contaminant
Levels (MCLs) and nonzero Maximum Contaminant Level Goals (MCLGs) established for
drinking water, while not directly applicable to groundwater cleanups, are potential ARARs
when they are relevant and appropriate under thC terms of the release. Relevant and appropriate
requirements must be complied with to the same degree as if they were applicable, but there is
more discretion in this determination and it is possible for only part of a requirement to be
considered relevant and appropriate in a given case.
Where no promulgated standards exist for a given chemical or situation, nonpromulgated
advisories and guidance ("to-be-considered" materials [TBCs]) issued by federal or state
government may be used in determini1'lg the necessary level of cleanup for protection of h~
health or the environment. TBCs do not have the status of potential ARARs; however, in many
circumstances they will be considered along with ARARs as part of the site risk assessment and
may be used in determining the necessary level of cleanup.
. .
Identification of ARARs and TBCs must be done on a site-specific basis. Neither CERCLA nor
the NCP provides across-the-board standards for determining whether a particular remedy will
effect an adequate cleanup at a panicular site. Rather, the process recognizes that each site will
have unique characteristics that must be evaluated and compared to those requirements that apply
under the given circumstances.
The contaminant specific ARARs for au 1 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.
. For systemic (noncarcinogenic) toxicants, cleanup levels represent that amount to which humans
2-22
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could be exposed on a daily basis without appreciable adverse effects occurring during their
lifetime. For carcinogens, cleanup levels must fall within a 10-8 to 1~ risk range. (NCP. 40.
CFR ~300.430.[e][2][i][A][2]).
Potential drinking water regulations include MCLs for specific contaminants (Section 14i2 of
the Safe Drinking Water Act, 42 USC ~300g-1, National Primary Drinking Water Regulations,
. 40. CPR Part 141). Maximum contaminant levels are enforceable standards which apply to
specified contaminants which the USEP A has determined have an adverse effect on human
health. The MCL for TCE is 5 p.g/l. Maximum contaminant levels are set at levels that are
protective of human health and set close to MCLGs.
A listing of federal and state laws and regulations- that are ARARs is provided in Tables 4
through 7. .
2.8.2.1 Chemical-Specific ARARs. Chemical-specific ARARs include those
environmental laws and regulations that regulate the release to the environment of materials
possessing certain chemical or physical characteristics or containing specified chemical
compounds. These re.quirements generally set health- or risk-based concentration limits or
discharge limits for specific hazardous substances (USEP A, 1989).
Chemical-specific ARARs are determined by identifying federal and state environmental statutes
that are potentially applicable or relevant and appropriate to chemicals found at a particular site.
Both ARARs and TBCs are subject to a site-specific risk assessment to ensure exposure levels
are within acceptable limits for the protection of human health and other environmental
receptors. In some cases, such as multiple exposure pathways or multiple contaminants, a risk
.assessment may indicate that an ARAR alone is not sufficiently protective and TBC:;, including
risk-based limits, will be used to establish more stringent clean-up requirements.
Gro~ndwater, included in au 1, has been impacted by vac contamination. Specifically, TCE
is the contaminant of concern for the groundwater beneath the NEDA. A list of all chemicals
found in groundwater at the NEDA is presented in Table 1.
Nonzero MCLGs and MCLs are relevant and appropriate requirements in cases where surface
water or groundwater is or may be directly used for drinking ~ater, in which case the
MCLs/MCLGs should be met in the surface water or groundwater itself.
Additionally, the Cal-EPA has established numerical criteria (State Action Levels [SALsD for
selected chemicals in drinking water for which state MCLs have not yet been established. While
SALs are considered "technically nonenforceable standards," Cal-EPA has established a policy
by which any water system not meeting the SALs is required to take corrective action. Although
SALs are not promulgated, they could qualify as TBCs under appropriate circumstances..
California has promulgated MCLs for primary VOCs; however, the USEPA has chosen the
federal MCL for TCE as the groundwater cleanup standard for au 1 because the California
MCL for TCE is equal to the federal MCL. Accordingly, the ARAR for the final aquifer
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TABLE 4
IDENTIFICATION OF FEDERAL CHEMICAL-SPECII<'IC ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Appllcablel
Relevant
and
Appropriate
Comment
Associated
Remedial
Alternative
Safe Drinking Water Act
Nalional Primary Drinking
Water Standards
42 USC Sec. 300g
40 CFR Part 141
Establishes Maximum
Contaminant Levels (MCLs) and
Maximum Contaminant Level
Goals (MCLOs) for contaminants
in public water systems, based on
health, technological, and
economic considerations. MCLs
and non-zero MCLGs are
enforceable standards under the
NCP.
NolVes
Relevant and appropriate for aquifers which are
deemed to be potential drinking water
supplies. Cleanup standards for OU 1 ground
water within the aquifer are the federd! and
state MCLs (e.g., TeE = 5 ppb).
1.2,3
,
o
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TABLE S
IDENTIFICATION OF FEDERAL LOCATION-SPECII<'IC ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Appllcablel
Relevant
and
Appropriate
Comment
Associated
Remedial
Alternative
Endangered Species Act
1,2.3
16 USC Sec. 1531-1543
40 CFR 6-302(h)
50 CFR Part 200
50 CFR Part 402
Requires that Federal agencies
ensure that any action authorized,
funded, or carried by the agency is
not likely \0 jeopardize the
continued existence of any
threatened or endangered species or
destroy or adversely modify critical
habitat.
YefII._-
Critical habitats of threatened or endangered
species (e.g., the desert tortoise) exist in the
vicinity of GAFB, but these habitats would
not be adversely affected by any remedial
actions for au I.
.'
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TABLE 6
IDENTIFICATION OF FEDERAL ACTION-SPECIFIC ARARs
Appllcablel
Relevant Associated
Standard, Requirement, and Remedial
Criteria, or Limitation Citation Description Appropriate Comment Alternative
Sulld Waste Disposal Act 42 USC Sec. 6901.6987
Standards Applicable to 40 CFR Part 262 Establishes standards for generators Yes/n. Potentially applicable to remedial alternatives 3
Generators of Hazardous. of hazardous waste. involving treatment facilities which generate
Waste hazardous waste (e.g., spent activated carbon).
Standards Applicable to 40 CPR Part 263 Establisbes standards which apply Yes/.n Potentially applicable to remedial alternatives 3
'Ihutsporters of Hazarwus to persons transporting bazardous involving the transport of hazardous waste
Waste waste within the U.S. if the (e.g., spent activated carbon).
transportation requires a manifest
under 40 CFR Part 262.
Standards for Owners and 40 CFR Part 264 Establishes minimum national Yes/-. Potentially applicable to remedial alternatives 2,3
Operators of Hazarwus Waste standards whicb derme the involving the use or" activated carbon and its
Treatment, Stomge, and acceptable management of subsequent handling and disposal, as well as
Disposal Facilities hazardous waste for owners and air strippers and oll\er miscellaneous facilities
opemtors of facilities which treat, whicb treat, store, or dispose of hazardous
store, or dispose of hazardous waste.
waste.
Interim Standards for Owners 40 CFR Part 265 Establishes minimum national Yes/.-. Potentially applicable to remedial alternatives 3
and Operators of Hazardous standards that define the acceptable involving the use of activated carbon and its
Waste Treatment, Stomge, and management of hazardous waste subsequent handling and disposal, as well as
Disposal Facilities during the period of interim status air strippers and other miscellaneous facilities
and until certification of final which treat, store, or dispose of hazarduus
closure, or if the facility is subject waste.
tu post-closure requirements,
untial post-closure responsibilities
are fuUilled.
Land Disposal Restrictions 40 CFR Part 268 Establishes criteria and timetables Yes/n- Potentially applicable to remedial alternatives 3
for the restriction of land disposal involving the hUtd dispusal uf h8Z
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TABLE 7
IDENTIFICATION OF STATE ACTION-SPECIFIC ARARs
(Page I of 2)
Applicable/
Relevant Associated
Standard, Requirement, and Remedial
Criteria, or Limitation Citation Description Appropriate Comment Alternative
State Water Resources State Water Resources Establishes the State Board's YesI-- Applicable to remedial alternatives involving 2,3
Control Board's Control Board Resolution policy on maintaining the high ' the discharge of treated water which would
Nondegradatlon Polley No. 68-16 quality of California's waters. eventually reach the ground water. This
policy was used, together with the federal and
state MCLs. in selting the OU I-specific
cleanup standard for TeE in the treatment
effluent discharge.
Hazardous Waste 22 CCR, Div. 4.5, Sec. Establishes state regulations Yes/-n Potentially applicable to remedial alternatives 2, 3
Management Regulations 66260 et seq. governing hazardous waste control; involving the use of activated carbon and its
management and control of subsequent handling and disposal, as well as
hazardous waste facilities air strippers and other miscellaneous facilities
transportation; laboratories; which treal, store, or dispose of hazardous
classification of extremely waste.
bazardous,hazardous,and
nonhazardous waste.
Mojave Air Quality Pursuant to Mulford-Carrell Will not require emission controls Yes/--- Applicable to remedial alternatives which 2
Management District Air Resources Act (Health on air strippers as long as TeE discbarge emissions directly to the atmosphere
Guideline and Safety Code Sections emissions remain below lib/day. (i.e., airs trippers with no emission controls).
39000-44563; 17 CCR.
Part m)
Water Quality Control Plan Page 1-5-3. item d Prohibits the discharge of waste Yes/--- Applicable to remedial altematives involving 2, 3
ror tbe Labontan Region water except to the designated the discharge of treated or partially treated
(Basin Plan) disposal sites water.
Water Quality Control Plan Page 1-5-3. item f Requires the collection, transport. Yes/--: Applicable to remedial alternatives with 2, 3
ror tbe Labontan Region treatmenl or disposal facilities 10 treatment facilities.
(Basin Plan) be adequately protected from a 100-
year flood.
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TABLE 7
IDENTIFICATION OF STATE ACTION-SPECIFIC ARARs
(Page 2 01 2)
Appllcablel
Relevant Associated
Standard, Requirement, and Remedial
Criteria, or Limitation Citation Description Appropriate Comment Alternative
Sources 01 Drinking Water State Water Resources Dermes all ground and surface Yest--- The identification of the au I aquifers affected \, 2, 3
Policy Control Board Resolution water as existing or potential by TeE as potential drinking water sources
88-63 sources of drinking water unless forms the basis fur selection of MCls und
total dissolved solids are greater SWRCB Resolution 68-16 as specific
than 3,000 ppm, the well yield is ARARs to maintain existing high quality
less than 200. gpd from a single waters.
well, or ground water is reasonable
to treat using best manageinent
practices or best economically
achievable treatment practices.
Water Quality Control Plan Table 2-1, Beneficial Uses Dermes beneficial uses for ground Yest--- 1,2,3
ror the Lahontan Region of Ground Waters in Upper waters beneath GAFB as:
(Basin Plan) Mojave Hydrologic Unit municipal, agricultural, industrial 0 '
(628.20) service and fresbwater
replenishment.
Porter-Cologne Water California Water Code Requires any person discharging. Yes/--- Provides the basis for development of 2, 3
Quality Control Act Section 13267 waste to submit technical and reporting, notification, and monitoring
monitoring reports, considering programs during the RDIRA phase.
the need and benefits to be
obtained.
Water Quality Control Plan Page 1-76, item 2 Requires any person discharging Provides the basis for development of 2. 3
ror the Lahontan. Region waste to submit technical and Yest--- reporting, notification, and monitoring
(Basin Plan) monitoring reports, considering programs during the RDIRA phase.
the need and benefits to be
obtained.
-------
cleanup level will be the federal MCL for TCE. Therefore, the fInal aquifer cleanup level will
be 5.0 JLgll TCE.
Soil in the unsaturated zone is not impacted as a result of groundwater contamination in the
Northeast Disposal Area. Therefore, chemical-specifIc ARARs have not been identifIed for this
medium. . .
2.8.2.2
1988):
Locatioo.Specific ARARs. As defmed in the USEPA draft guidance (USEPA,
"Location-specifIc AAARs are resttictions. placed on the concentration of
hazardous substances or the c,onduct of activities solely because they are in
specifIc locations. Some examples of special locations include floodplains,
wetlands, historic places, and sensitive ecosystems or habitats."
Endangered species and their habitats are protected by the Endangered Species Act (ESA) (16
USC Sections 1531-1543). The desert tortoise.and the Mojave ground squirrel are potentially
sensiti:ve, rare, or threatened species within the vicinity of au 1 which are protected by the
ESA. Therefore, the ESA is an ARAR for on-site actions. The proposed remedial actions could
affect these species or their critical habitat during invasive installation. The mitigation efforts
that would be performed prior to installation of any remediation system would entail inspection
of the proposed location (i.e., extraction well or monitoring well location) for endangered
species by qualifIed personnel, and selection of an alternative to eliminate or minimize impacts
to these species if their presence is detected.
2.8.2.3 Action.Spedfic ARARs. Action-specifIc ARARs are resttictions that defme
acceptable treatment and disposal procedures for hazardous substances. These ARARs generally
set performance. design, or other similar action-specific controls or restrictions on particular
kinds of activities related to management of hazardous substances or pollutants, such as Resource
Conservation and Recovery Act of 1976 (RCRA) regulations for waste treatment, storage, and
disposal. These requirements are triggered by the particular remedial activities that are selected
to accomplish a remedy. The type and nawre of these requirements is dependent upon the
particular remedial or removal action taken at a site. Therefore, different actions or technologies
are often subject to different action-specifIc ARARs.
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 Lahonton RWQCB defines the beneficial uses of various
water bodies for the Mojave River Basin. Water bodies and their beneficial uses are presented
in the Lahonton Basin Plan. The Basin Plan classifies aquifers in the au 1 area to have
"existing or potential beneficial uses as sources of drinking water. II This regional plan has.been
promulgated and portions thereof are ARARs with respect to au 1. The identification of the
beneficial uses of the groundwater at au 1 serves as the basis for selection of the federal MCL
for TCE for the groundwater cleanup and the selection of m~um TCE concentrations for
2-24
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discharges of effluents into the percolation ponds pursuant to Resolution 68-16 as detennined
by the dispute resolution process discussed below (Discharge ARARs).
Treatment ARARs:
Use of activated carbon for remediation of VOCs under Alternative 3 could trigger requirements
associated with regeneration or disposal of the spent carbon. If the spent carbon is listed waste
or a characteristic waste then it is regulated as a hazardous waste under RCRA (42 USC ~9601,
et seq.) and California's Hazardous Waste Management (HWM) regulations (22 CCR 66262.10 -
66262.57). .
Movement of contaminants to new locations would trigger standards applicable to transporters
of hazardous waste (RCRA 40 CPR ~263). Placement in or on land would trigger land disposal
- restrictions for the waste (RCRA 40 CFR ~268). Additionally, closure for units which store
hazardous waste for more than 90 days mustbe met (RCRA 40 CFR ~264.110 - 264.120).
Containers used for storage of contaminated carbon that is classified as a listed or characteristic
waste must comply w.ith 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 [4
-------
directly for drinking water. However, because of the intermittent nature of this runoff area.
with surface flow occurring only during heavy storms, the arroyo has not been considered a
surface water.
On October 2, 1992, the RWQCB invoked dispute resolution regarding, in part, effluent
discharge levels for TCE at the NEDA. On April 22, 1993, the USEPA Administrator issued
a decision fmding that the California State Water Quality Control Board's anti-degradation policy
(Resolution 68-16) is an ARAR with respect to discharges of TCE at OU 1, and returned the
matter to the USEPA . Region IX Acting Regional Administrator (Regional Administrator) to
determine an appropriate standard for discharges intO the percolation ponds at OU 1. Based
upon negotiations between the USAF, the State of C~ifomia, and the USEP A, on July 9. 1993,
the Regional AdministratOr issued a fmal dispute resolution decision which set the effluent level
to be measured from the sampling port at 2.5 pg/l TCE on a median basis with a stated
maximum discharge level of 5 pg/l TCE. The decision further stated that the USAF will seek
to treat the discharge to attain a level of 0.5 p.g/l TCE as measured at the percolation ponds,
although such efforts do not constitute an enforceable discharge standard.
The USEPA's Office of Solid Waste and Emergency Response (OSWER) has issued a directive,
"Control of Air Emissions from Superfund Air Strippers at Superfund Groundwater Sites, II
which contains a Statement of Policy regarding the need for emissions controls at such facilities
(USEP A, 1989). This directive states that, for strippers located in areas that are nonattainment
for ozone, regions should:
. .. be guided by the emission limit goals in the document entitled, "Issues
Relating to VOC Regulations CutpOints, Deficiencies, and Deviations," issued in
May 1988 by the Office of Air Quality Planning and Standards (OAQPS) to aid
States in revising their State Implementation Plans (SIPs) to incorporate post-1987
ozone attainment strategies. The OAQPS guidance indicates that the sources most
in need of controls are those with an actUal emissions rate in excess of 3 pounds
per hour (lbs/hr) or 15 Ibs/day or a potential (Le., calculated) rate of 10 tons per
year (TPY) of tOtal VOCs. The calculated rate assumes 24-hour operation, 365
days per year.
The Mojave AQMD has stated that they will not require emissions controls on the air strippers
as long as TCE emissions remain below lIb/day. The AQMD has the authority to set this level
based on the Mulford-Carrell Air Resources Act (Health and Safety Code Sections 39000-44563;
CCR Title 17, Pan Ill).
2.8.2.4
Compliance with ARARs
Alternative 1: The no action alternative does not comply with ARARs. TCE, the contaminant
of concern, in the groundwater at concentrations above MCLs would be left unaddressed in this
alternati~. .
2-26
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Alternative 2: This alternative provides for treatment of groundwater using an air stripper
system and discharging treated groundwater to the percolation ponds. ARARs for aquifer clean-
up and discharge would be met. The air emission ARAR of lib/day would also be met.
Alternative 3: This alternative meets all of the ARARs that Alternative 2 meets. In addition,
ARARs pertaining to the use of GAC would also be met.
2.8.3
Long-Term Effectiveness and Permanence
The purpose of this criterion is to assess the residual risk and the adequacy and reliability of
controls associated with a particular alternative. - The magnitude of risk resulting from the
presence of untreated waste or treatment residuals is assessed with respect to the volume or
concentration of residual contaminants.
The second component, adequacy and reliability of controls, assesses the containment systems
and institutional controls in place to determine if they are sufficient to ensure that both human
and environmental exposure is within protective levels. The long-term reliability of management
controls to provide co~tinued protection from residuals is also addressed with regard to (1) the
potential need to replace- technical components of the alternative, and (2) the potential exposure
pathway and resulting risks should the remedial action need replacement.
Alternative 1: Although the current TCE contamination in the groundwater is expected to be
below ARARs before it reaches existing production wells, this alternative does not control
exposure to contaminated groundwater under an unlimited future land use scenario, nor does it
provide a long-term management measure.
Alternative 2: Because this alternative will remove and treat contaminated groundwater to
below ARARs, as discussed above, it provides effective and permanent remediation of
groundwater. To ensure the successful performance of the extraction system, groundwater will
be monitored on a quarterly basis. System enhancement may be employed as necessary if any
leakage of TCE from the extraction system capture zone is anticipated. Effluent from the air
stripper will be analyzed for VOCs on a monthly basis (based on mass balance calculations using
treatment system influent and effluent concentrations), and more frequently during the initial
startup and shakedown period. .
No treatment residuals, other than the air emissions, are expected for this alternative. Operation
of the alternative components is expected to be reliable because they are proven technologies.
Effective management will include frequent inspections and maintenance to avoid component
failure.
Alternative 3: This evaluation factor is the same as for Alternative 2. All technologies used
in this alternative are proven and reliable. Effective management and operation of the facility
will ensure that necessary maintenance is provided to prevent component failure. Residual risk
is minimal as long as spent carbon is properly handled.
2-27
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2.8~4
Reduction of Toxicity, Mobility, and Volume through Treatment
Alternatives are assessed to detennine the extent to which they pennanently reduce toxicity,
mobility, and volume (TMV) of the contaminants posing the principal threats at a site. The
specific factors considered in this assessment include:
.
treatment or recycling process( es) of associated target contaminants and the
amount of contaminants to be destroyed or treated;
.
degree of expected reduction in the TMV and the degree to which treatment or
recycling will be irreversible; --
.
type and quantity of treatment residuals expected to remain following treatment;
and
.
whether or not the alternative satisfies the stannory preference for treatment as
a principal element.
Alternative 1: This alternative provides no active reduction, of the TMV of contaniinated
groundwater.
Alternative 2: Treatment of contaminated groundwater by air stripping results in the
irreversible tranSfer of contaminant.~ from one media (groundwater) to another (air). However,
this transfer reduces the effective toxicity of the stripped TCE by lowering the relative media-
related risk. Exposure to TCE at 47 J.£gIl in the public water supply was determined to pose an
unacceptable risk to human health. Although the same mass of contaminant in stripper off-gas
did not pose such a risk, the mobility and volume of contaminants in air is actually increased.
In summary, this alternative reduces the TMV of contaminants in the media with the potential
for greatest risk (groundwater) but does not address the TMV of CODtamination in the air stripper
off-gas.
Alternative 3: This alternative provides a reduction in mobility and volume of TCE by
transferring it to a small volume of solid material. The adsorbed TCE can then be destroyed
when the carbon is thermally regenerated. Other disposal methods may result in eventual release
of the contaminants if improperly implemented. By destroying the CODtaminants, this treatment
method is irreversible.
2.8.5
Sbort- Term Effectiveness
Alternatives are evaluated with respect to their effects on human health and the environment
during implementation of the remedial action. This evaluation addresses protection of site
workers and the community during remedial actions, potential environmental impactS, and the
time until remedial action objectives are achieved.
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Alternative 1: This alternative is expected (0 take 3 to 4 months to implement (install and
sample wells and obtain results of first quaner's sampling). Implementation of the technologies
involved would pose no risks (0 the community. Worker exposure is also expected to be
minimal, although potential exposure could occur during installation of monitoring wells: .To
minimize such exposure, installation and sampling of monitoring wells will be conducted under
a site-specific Health and Safety Plan, with appropriate air monitoring and personal protective
equipment (PPE). Potential environmental impaCtS would be related to physical destruction of
habitat (e.g., desen tonoise and Mojave ground squirrel burrows) through the use of vehicles
and other equipment, during the. installation and sampling of monitoring wells.
. .
Alternative 2: Implementation of this alternativ~ is not expected to generate any adverse
impacts on the surrounding community and the environment, other thari the general nuisances
associated with any type of construction. Erosion will be kept to a minimum using appropriate
grading and other controls. Given the relatively remote location of the extraction and treatment
system, such impacts are expected to be minimal. Worker exposure is also expected to be
minimal; although potential exposure could occur during installation 9f the extraction wells. To
minimize such exposure, installation and sampling of extraction and monitoring wells will be
conducted under a site-specific Health and Safety Plan, with appropriate air monitoring and PPE.
With the exception of physical impacts, as described for Alternative 1, environmental impacts
are expected to be negligible because wildlife will not contact contaminated groundwater prior
to treatment and air emissions are low. The system is proposed assuming a 30-year duration.
Alternative 3: This evaluation factor is the same as for Alternative. 2.
2.8.6
Implementability
This criterion has three components: (1) technical feasibility, (2) administrative feasibility, and
(3) availability of services and materials. Each alternative is assessed on the basis of factors
within these three categories.
The assessment of the administrative feasibility of a particular remedial alternative is based on
the number and complexity of activities needed to coordinate with other offices and regulatory
agencies during preparation and implementation of the alternative. Factors that are considered
in the assessment of technical feasibility include:
.
potential for problems associated with construction and operation of an
alternative;
.
reliability of an alternative and its components;
.
ease of undertaking additional remedial action, if needed; and
.
ability to monitor the effectiveness of the remedy and evaluate the risks of
exposure should monitoring be insufficient to detect a failure.
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The availability of services and materials is to be considered. . This includes such items as off-
site treatment, storage or disposal capacity, equipment, and specialists.
Alternative 1: Installation of monitoring wells in the Upper Aquifer and collection and analysis
of groundwater samples are standard, proven technologies which readily comply with the criteria
for implementability. These criteria include ability to construct and operate the technology;
reliability of the technology; ease of undertaking additional remedial actions; ability to monitor
effectiveness of the remedy; ability to obtain approval from other agencies; coordination with
other agencies; availability of off-site treatment, storage, and disposal services; availability of
necessary equipment and specialists; and availability of prospective technologies. Since the
technologies are generally availabie and sufficiently ~monstrated, difficulties with construction,
technical problems, or availability of equipment are expected to be minimal. Only minimal
disposal services would be required. The installed monitoring wells would provide data that
would be valuable to any additional remedial actions that may be required. However, close
coordination with the three major regulatory agencies (USEPA. Lahontan RWQCB, and DTSC)
will be required because of the unique and overlapping interests and mandates of each agency.
Alternative 2: Installation of extraction wells and an ajr snipping system for this alternative
are standard, proven teChnologies which readily comply with the criteria for implementability.
These criteria include ability to construct and operate the technology; reliability of the
technology; ease of undertaking additional remedial actions; ability to monitor effectiveness of
the remedy; ability to obtain approval from other agencies; coordination with other agencies;
availability of off-site treatment, storage, and disposal services; availability of necessary .
equipment and specialists; and availability of prospective technologies. Since the technologies
are generally available and sufficiently demonstrated, difficulties with consauction, technical
problems, or availability of equipment are expected to be minimal. Only minimal disposal
services would be required. Discharge of treated groundwater is expected to be achieved on.
. base. Enhancing the system through additional extraction wells or retrofitting the system with
emission controls would be easily accomplished.
Alternative 3: This evaluation factor is the same as for Alternative 2.
2.8.7
Cost
Both capital costs and operation and maintenance costs are considered for each alternative, with
a target accuracy of -30 to +50 percent. Capital costs include both direct (e.g., equipment) and
indirect (e.g., contingency allowances) costs. Costs are presented on a present-worth basis over
a period of 30 years, with a discount rate of 10 percent. Detailed cost analysis is presented in
the FS (JMM, 1993a). .
Alternative 1: Costs of this alternative are limited to installation and development (eight wells), '
and 30 years of quarterly sampling and analysis, report preparation, and minor maintenance, for
a total present worth of $631,900, in 1992 dollars (assuming a discount rate of 10 percent).
2-30.
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Alternative 2: The 30-year present wonh in 1992 dollars of Alternative 3 (Phases I and II) is
$7,864,300. This assumes a discount rate of 10 percent.
Alternative 3: The 30-year present wonh in 1992 dollars of Alternative 3 (phases I and II),
including emissions control (GAC), is $9,999,100. This assumes a discount rate of 10 percent.
2.8.8
State Acceptance
This assessment considers the technic3J and administrative issues and concerns the state or
support agency may have regarding each of the alternatives. Final application of this criterion
will occur in the approved ROD. --
, ,
Alternative 1: It is likely that the state and community would not accept this alternative because
it does not actively control existing groundwater contamination.
Alternative 2:' This alternative provides for cleanup of the groundwater to below drinking water
standards. This state has conditionally approved this alternative pending the submittal of a work
plan for an Investigation in Support of RD/RA to fully defme the dimensions of the TCE plume
beneath the NEDA. Details of the ongoing Investigation in Support of RD/RA study and the
proposed schedule of activities is presented in Section 2.12.
Alternative 3: This alternative would be at least as acceptable to the regulatory agencies as
Alternative 2, due to the inclusion of an added level of protection in the form of emissions
control. '
2.8.9
Community Acceptance
This assessment evaluates the issues and concerns of the public regarding the proposed
alternatives. A Community Relations Plan (CRP) was prepared to address community concerns
and provide a forum for the exchange of information on OU 1 and other sites (IT, 1991). As
part of this plan, public participation is encouraged throughout all phases of design and
remediation.
Alternative 1: It is likely that the community would not accept this alternative because it does
not actively control existing groundwater contamination.
Alternative 2: This alternative provides for cleanup of the groundwater to below drinking water
standards. One potential area of concern may be with respect to stripper emissions, despite the
expected low VOC emission rates. Alternative 3, which includes emissions controls, may be
viewed by some individuals as providing a desired additional measure of security and more
adequately addresses the reduction in TMV.of contaminants. After the release of the Proposed
Plan, which presented Alternative 2 as the preferred remedy, the community'did not express any
significant objection during the public meeting or public comment period discussed in Section
2.3.
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Alternative 3: This alternative would be at least as acceptable to the community as Alternative
2, due to the inclusion of an added level of protection in the form of emissions control. .
2.9
THE SELECTED REMEDY
This section provides a description of the preferred alternative for remediation of groundwater
contamination at the NEDA based on the detailed evaluation of alternatives presented in the FS
(JMM. 1993a). This section includes the basis fo~ selection of a preferred alternative, a
description of the preferred alternative, and a cost analysis.
2.9.1
Selection of the Preferred Alternati!e
The objectives of the selected remedial action for the TCE plume in the Upper Aquifer beneath
the NEDA at GAFB are as follows:
.
To prevent exposure to contaminated groundwater that poses a risk of greater than
lx1()"6.
.
To reduce the TCE contamination in the groundwater beneath the NEDA to
below the federal MCL of 5 Ilg/l.
.
To reduce the TCE in treated groundwater effluent to meet the enforceable levels
of 2.5 Ilg/l TCE on a median basis with a maximum discharge level of 5 Ilgll
TCE, as measured at the effluent sampling pon of the treatment system (Table 8).
Furthermore, seek to treat the discharge to attain a level of 0.5 Ilg/l TCE as
measured at the percolation ponds. Although such efforts do not constitute an
enforceable discharge standard, the USAF may make minor modifications, as
necessary. in an effort to reach this goal.
.
To eliminate or reduce the potential for further migration of the existing TCE
plume in the groundwater.
.
To provide a conceptual design for a preferred alternative which will be
expandable to remediate an aquifer volume greater than that assumed for this
study, if required. based on the results of future monitoring.
The preferred alternative that best meets these objectives is Alternative 2, which consists of on-
and off-base Upper Aquifer groundwater extraction with an estimated 19 wells, followed by
treatment of extracted groundwater by two packed-tOwer air strippers, discharge of emissions
directly into the atmosphere, and recharge of the treated extracted groundwater to the Upper
Aquifer via percolation. Additionally, this alternative would include implementation of deed
restrictions as appropriate, prior to sale or transfer of land overlying contaminated groundwater,
to prohibit use of the groundwater until groundwater cleanup levels have been achieved.
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TABLE 8
GROUNDWATER DISCHARGE TREATMENT STANDARDS
Constituent
Standard for Discharge into STP Percolation
. Ponds Based on State Board Resolution 68-16
(Concentrations in pg/l)8
Standard for Aquifer Cleanup
is the Federal MCL
Median
Maximum.
Trichlorethylene (TCE)
pH
2.5
6.5 < pH < 8.5
- 5.0
Federal MCL
5.0 .
a
The USAF will seek to treat the discharge to attain a level of 0.5 IlglI TCE as measured at the percolation ponds. This level
is a nonenforceable goal. The USAF may make minor modifications, as necessary, to operate the treatment system at the
maximum efficiency in an effort to reach the goal.
-------
The extraction system will be implemented in tWo phases; the performance of the nine wells
installed as pan of the first phase will be used to determine the location and. operation of an
estimated 10 additional wells. This phased approach will allow the necessary flexibility to
implement and complete remediation in an effective manner. The initial nine wells will extract
the majority of the plume and will slow the advance of the rest of the plume. Additional wells
will then extract the remaining ponion of the plume. The estimated number of additional wells
. is based on assumptions made during the feasibility study and the actual number and placement
of additional wells will be c~cided based on the performance of the Phase I system and the
results of the Investigation in Support of RD/RA (see Section 2.12.2). Additional wells will be
added as needed up to a total extraction rate of 500 gpm.
Removal of TCE from the contaminated groundwater-and simultaneous removal of other detected
VOCs will be achieved by the packed tower air stripping process. Because the treated water will
be recharged to the Upper Aquifer, stringent treatment goals must be met by the air stripping
process. Therefore, tWo packed towers will be operated in series to ensure attainment of the
required removal efficiency, with a substantial safety factor. Recharge of treated groundwater
will occur at the STP Percolation Ponds, upgradient of the plume. A sprinkler irrigation system
will be used to ensure ~ven distribution of treated groundwater. However, the USAF may opt
to store the effluent in an open top tank at the STP Percolation Ponds and use a portion of the
effluent for irrigation of the golf .course. If the effluent is used for irrigation, the TCE
concentration must meet the discharge levels stated above.
This proposed combination of control measures. should capture all of the currently estimated
TCE plume having concentrations above MCLs (currently 5 p.g/l for TCE) in the Upper Aquifer.
The air stripping process will be ~pable of removing TCE to below 2.5 p.g/l (the enforceable
discharge level) even if the peak influent concentration of TCE combined from all extraction
wells is the highest concentration detected during monitoring (310 "g/l), an unlikely occurrence.
The preferred alternative will satisfy the remedial action objectives (RAOs). The concentrations
of TCE in stripper effluent are projected to be well below expected regulatory requirements for
recharge of treated groundwater. VOC air emissions are projected to be well within the AQMD
required action levels. Quarterly groundwater monitoring will be performed to assess the
performance of the overall extraction, treatment, and discharge system.
Since the selected remedy does not contemplate on-site disposal of hazardous wastes, no such
action-specific ARARs were selected. Hazardous wastes could consist of screenings, sludges,
and other solids generated during construction, operation, and maintenance of the treatment
system. Off-site disposal of such wastes will be performed in accordance with federal, state,
and local laws, regulations, and ordinances. However, these requirements would not be
considered ARARs under CERCLA, as ARARs apply only to on-site activities. .
The USEP A and the RWQCB have scheduled discussions to resolve whether sections arising
under Chapter 15 of Title 23 of the California Code of Regulations ("Chapter 15") are ARARs
and, if so, the scope and interpretation of Chapter 15. Consequently, the parties have not
determined whether or not Chapter 15 is an ARAR for the purpoSes of this ROD. The USAF,
2-33
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USEPA, and the RWQCB have agreed, however, that the USACE will sample drillings,
cuttings, and similar wastes to determine whether such wastes are hazardous wastes as defined
in 22 CCR Section 66300 or designated wastes as defmed in 23 CCR Section 2522. If such
sampling indicates that the wastes are hazardous wastes, the hazardous wastes will be discharged
only to Class I waste management units. If such sampling indicates that the wastes are
designated wastes, such designated wastes will be discharged only to Class I or Class II waste
management units.
Moreover, the selec~ remedy (1) does not contemplate discharge to surface waters, and such
discharge is prohibited, and (2) prohibits the bypass or overflow of untreated or partially treated
waste. The RD/RA Work Plan will provide for alternative discharge options in the event the
discharge capacity becomes insufficient to handle the treated effluent. These alternative options
will be used only on a temporary basis.
The detailed implementation of the selected remediaI action will be performed by the USAF in
consultation with the regulatory agencies during the RD/RA phase, at which time the USAF will
develop reporting, notification, and monitoring programs. The monitoring program shall include
sufficient monitoring (!>oth in terms of frequency and test methods employed) to evaluate the
effectiveness of the reniedial action and ensure that the effluent discharge standards adopted
herein are being met.. The USAF shall, at ~ minimum, include the following in the RD/RA
phase: locations of the extraction and performance monitoring wells, estimated extraction and
discharge rates, proposed operational procedures, proposed contingency plan for the extraction,
treatment and discharge system in the event of power outage and/or mechanical failure, geologic
well logs and well development data shee~ for all available extraction, and performance
monitoring wells proposed for the OU 1 groundwater treatment system. The operational
procedures shall reflect that the groundwater treatment system will not be operated in excess of
its design capacity without the prior approval of the regulatory agencies. The OU 1 groundwater
treatment system will be designed for contaminant removal and hydrologic control of the TCE
plume.
2.9.2
Detailed Description of the Preferred Alternative
The selected remedy consists of an estimated 19 groundwater extraction wells installed in the
Upper and Regional aquifers, followed by treatment of the extracted groundwater using two air
stripping towers in series, and recharge of treated groundwater at the fonner STP Percolation
Poruh. .
2.9.2.1 . Extraction and Monitoring Well System. The extraction and monitoring system
was designed to be implemented in two phases. The flISt phase, already implemented, includes
installation of three on-base and six off-base extraction wells. Extraction wells are consttucted
of carbon steel casing and slotted stainless steel screen. Submersible pumps are consttucted of
stainless steel with flow capacities ranging from 25 to 30 gpm and total dynamic head capacities
ranging from 110 to 330 feet. .
2-34
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If the monitoring results indicate the need, up to 10 additional extraction wells of similar design
will be installed for a potential total of 19 extraction wells. Installation of the additional wells
will be dependent on the monitoring results obtained during the implementation of the first
phase. The responsible consultant will make recommendations to GAFB regarding the need for,
and location of, any additional extraction wells. Final decisions will require approval from the
appropriate regulatory agencies.
The nine wells installed in the first phase are located along the shoulder area of an existing
unimproved roadway that follows the western slope of the desert arroyo. Because the total
distance between all extraction wells will exceed 6,000 linear feet (LF), the existing roadway
was improved to provide all-weather access to the ~ells for maintenance purposes.
The extracted water from the wells is pumped through a transmission pipeline buried adjacent
to the improved roadway to the air stripping treatment plant located on the base. The PVC
transmission pipeline varies in diameter from 2 inches furthest from the treatment plant to 8
inches entering the treatment plant. All piping is buried in a shallow trench (3 feet) to avoid
freezing problems during the winter and to avoid possible disruption due to vandalism or
accidental collisions wi~ vehicles on or off the base. The submersible pumps are stainless steel
and will be used as dediCated pumps for the duration of the remediation. These pumps are sized
to provide sufficient total dynamic head (hydraulic head) to deliver the groundwater to the
treatment plant.
Process controls are installed on all extraction wells, including a one-way valve on the well head
and an automatic shutoff switch for the pump. This switch is wired to the main control center,
located in close proximity to the air stripping facility. The automatic shutoff is wired into the
process control in a manner such that the failure of the air blower (which provides forced air
to the packed towers) will cause the pumps in each extraction well to shut off automatically.
Eight monitoring wells have been installed at locations with existing access or locations where
access was gained for the extraction well system. . Therefore, no additional improvements were
required for installation of the monitoring wells. In subsequent phases of the remediation,
existing monitoring wells will be identified that will aid in monitoring the progress of the
remediation as the size of the plume decreases. A monitoring plan will be included as part of
the RD/RA.
2.9.2.2 Air Stripping System. A contractor-designed and constructed air stripping
system was installed at the bottom of a drainage gully approximately 585 feet east of an existing
north! south roadway leading from the new fIre training area oil/water separator and 30 feet south
of the property boundary. This site provides a base elevation for each tower of approximately
2,808 feet above msl. This site reduces the visibility of the treatment system, but required good
site grading and drainage to prevent erosion of the loose soils in this area.
The treatment system includes two fiberglass towers that may be operated in series or in parallel,
depending on the magnitUde of influent concentrations. Each tower has a height of 30 feet and
2-35
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I~-
contains approximately 20 feet of polyethylene packing material. Water is introduced at the top
of the tower and is allowed to triclde down through the packing at a maximum rate of 500 gpm.
Additional facilities were also installed to provide an operational air stripping tower system. The
ancillary equipment includes a power transformer, motor control center, 500-gpm centrifugal
pump, 2,OOO-standard cubic feet per minute (scfm) blowers, buried 8-inch-diameter influent yard
piping, buried power distribution conduits, buried stormwater culverts, and flexible pavement
for all-weather access around the treatment facilities. A chemical feed system was installed for
the addition of sodium hexametaphosphate (SliMP) and a sodium hypochlorite solution. (The
addition of SHMP will alleviate clogging by preventing precipitation of carbonates and iron
oxides inside the tower, while the addition of soOium hypochlorite will prevent clogging by
biological growth.) Continuous chlorination will ~ monitored to minimize residue chlorine in
the treated water. The specific monitoring program will be included as part of the RD/RA.
Other accessories such as inlet piping, outlet piping, air ducring, access manholes, nozzles, air
louvers, doors, lights, and platforms have been included to provide a complete operational unit.
2.9.2.3 Emuent Disposal System. The present conceptual design for the effluent disposal
system includes a new pump station at the treatment facility and transmission pipeline to connect
the treatment plant to the abandoned STP Percolation Ponds (Figure 10). During design, a
percolation test will be performed in the ponds to determine how much acreage is required for
percolation. The results of this test will form the basis for detailed design criteria.
Residual nitrates are present beneath the percolation ponds at levels that could potentially impact
groundwater. Therefore, a groundwater monitoring plan is being prepared that will monitor and
assess the potential impacts of the nitrates present in the percolation ponds. Background water
quality, including nitrates, will be established prior to use of the ponds by sampling from
existing monitoring wells located along the perimeter of the ponds. After use of the percolation
ponds begins, wells will be sampled regularly to determine if recharge to the percolation ponds
adversely affects nitrate concentrations in the groundwater. If groundwater is impacted by the
nitrates present, the treatment 'system would be temporarily discharged to a nearby arroyo until
another suitable recharge method has been selected. A future discharge location may be the golf
course as a portion to the treated groundwater may be used for irrigation.
2.9.3
Cost Analysis
A preliminary detailed cost estimate has been prepared for Alternative 2 (Table 9). The
estimated capital cost for all items required for implementation of the alternative is
approximately $3,255,100. Yearly O&M costs, which include general maintenance, materials,
labor, energy, and chemicals, and monitoring, are estimated to be $394,300 per year. Using
the expected lifetime of the remediation system of 30 years and an interest rate of 10 percent,
the estimated present wonh of Alternative 2 is approximately $7,864,300. .
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TABLE 9
PRELIMINARY COST ESTIMATE, PREFERRED ALTERNATIVE
"
ItemlDescriptlon
Cost (1992 DoDars)
Goundwater Treatment System
Extraction WeDs (19)
Piping From Wells 10 Stripper
Tower. Blower. Process Piping
SHMP Feed SystemlConttol Building
Concrete Pad .
Utilities .
Controls and Panel
MOnitoring Wells (8)
Dedicated Bailers (8)
..
Percolation Pond Recharge
Clear WeD
Supply ~ps
Venturi Meter
Control Valve
Backflow Valve
Cinder Block Building
Valve Pit
MiscellaneouS
Instruments and Controls
Telemetry
E1ectrical
Paving. Grading. Fencing
Connection to Existing Pipe
Surge Tank
Transmission Pipe
Item Subtotal
Contingency @ 2S % of subtotal
Contractor's OH&P @ 2S % of subtotal
Total ColIStrUctkm Costs
Subtotal
Engineering at @ 9 '10 of construction costs
Engineering During Construction @ 9 % of construction costs
GAFB General and Administration (assumed at @ 9 % of capital costs)
GAFB Community Relations (lump sum)
Total Initial System Costs
Tota130 year Operations and MalDtenaDce Costs
TOTAL ESTIMATED 30 YEAR PROJECT BUDGET COSTS (a)
$626.010
$190.990
$111.690
513.960
$2.230
$97.480
$2.230
$199,300
$1.790
$22,340
517.870
$5.030
$4,470
$2,790
522,520
$5,580
$8.940
$8.940
$37.970
510.050
$16.750
58,380
$20.100
5732,670
$2,l70,080
SS42,S20
$542,520
$3,155,120
5292.960
5292.960
$292.960
$13.400
$4,147,400
$3.716.920
$7,864,320
. (a) Assuming a discount rate of 10%.
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2.9.4
System Implementation
To date, Phase I of the installation of Alternative 2 at the NEDA has been completed. This
phase of construction consisted of the installation of nine extraction wells, eight monitoring
wells, transmission piping, an influent wet well, an air snipping system (two packed towers in
series), an effluent clearwell, and a pipeline with a disnibution system for treated groundwater
to the STP Percolation Ponds. A treatability study is currently being performed to assess the
performance of the system in different operating modes and to determine the best long-term
operating mode. The treatability study was initiated in December 1991 and has been conducted
intermittently since that time. During the treatability study, effluent water is temporarily being
discharged to the arroyo. The nine individual pumps are pumping at rates between 5 and 45
gpm. The combined flow rate from the extraction wells averaged approximately 200 gpm when
all the wells were operational. A portion of the treated water is returned to the influent wet well
to maintain a steady flow at 500 gpm into the air snipper tower(s). Average influent
concentrations vary from 12 to 37 #4g/l. However, influent samples were collected from the
influent wet well and therefore include recycled effluent water, because an influent sampling pon
was not installed by the contractor. Installation of an influent sampling pon is currently planned
to enable accurate influent concentration measurements. Effluent concentrations from the
treatment system, run with one tower and some recycled water, have beeIi below detection
limits, with the exception of a one time detected concentration of 15 #4g/1 TCE in January 1993.
This occurred just prior-to the system being shut down to correct a biofouling problem.
A groundwater monitoring plan is being prepared to assess any impacts of recharging treatment
system effluent via the STP Percolation Ponds. If any negative impacts resulting from discharge
to the percolation ponds are observed, treated groundwater will be temporarily discharged to the
arroyo until funher recharge methods can be assessed. The futUre (phase ll) system
implementation will include installation of an estimated 10 additional extraction wells, additional
pipelines, access roadways, and power disnibution to new wells.
2.10
STATUTORY DETERMINATIONS
The selected remedy satisfies the statutory requirements of Section 121 of CERCLA, as amended
by SARA, in that the following five mandates are attained:
.
The selected remedy is protective of human health and the environment, will
decrease site risks, and will not create shon-term risk 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 clean-up standards, and action-specific
ARARs' .
,
2-37
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.
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;
.
The selected remedy utilizes permanent solutions and alternative treatment.
technologies or resource recovery technologies, to the maximum extent practical;
.
The selected remedy satisfies the preference for treatment as a principle element.
,
2.10.1
Protection of Human Health and the Environment
. -
Attainment of clean-up levels will assure that the levels of the contamjnant~ of concern in the
groundwater at OU 1 will not exceed drinking water standards. Alternative 2 uses engineering
controls in the form of a groundwater extraction and treatment system to remove contaminated
groundwater form the aquifer. The exuaction of cotttaminated groundwater will significantly
reduce the threat of exposure to residents. The implementation of this remedy will not create
any shon-te.rm risk nor any negative cross-media aspects.
2.10.2
Compwmce with ARABs
All ARARs will be met by the selected remedy. The remedy will achieve compliance will
chemical-specific clean-up standards. Action-specific ARARs will be met for the discharge of
groundwater. None of the anticipated actions or construction is expected to have a detrimental
impact on endangered species.
2.10.3
Cost Effectiveness
The USEP A, the USAF, and the State of California -believe that the selected remedy fulfills the
nine criteria of the NCP and provides overall effectiveness in relation to its cost. Alternative
2 has a total capital cost of approximately $3,255,100 and an approximate annual O&M cost of
$394,300. The total net present worth is $7,864,300, based on a 30-year estimate for the time
required to cleanup OU 1.
2.10.4
Utilization of Permanent Solution and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Possible
The selected remedy represents, to the maximum extent to whichpermanem solutions and
treatment technologies can be used, a cost-effective manner for remediating OU 1. The remedy
selected provides the best balance of long-term effectiveness and permanence; reduction of TMV
through treatment; shon-term effectiveness; implementability and cost-effectiveness. . By
discharging the neated water to the percolation ponds, the groundwater resource is conserved.
2-38
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2.10.5
Preference for Treatment as a Principle Element
Contaminants of concern in the groundwater will be extracted and treated using air-stripping.
Therefore, this remedy satisfies the statutory preference for remedies that employ treatment
which permanently and significantly reduces the TMV of hazardous substances as a principle
element.
2.11
DOCUMENTATION OF SIGNIFICANT CHANGES
There are no significant changes in this ROD from the Proposed Plan.
2.12
CURRENT INVESTIGATION STATUS
As mentioned, as a result of a USEP A assessment and subsequent placement of GAFB on the
NPL in February 1990, a new FS (JMM, 1993a) was prepared to snmm9rize and reassess the
earlier FS activities performed prior to GAFB being placed on the NPL and to update the
documentation of this investigation to current USEPA guidance (USEPA, 1988).
The preferred alternative described in this ROD is based on meeting the RAOs identified during
the 1988 FS (JMM, 1988b), as summarized in the 1993 FS (JMM 1993a). The findings of the
fmal FS report and the accompanying proposed plan (JMM, 1992b) were used to develop this
ROD. The technical information supporting each alternative is included in these reports and the
RI (JMM, 1992a). Data gaps identified in the RI report were used to develop a work plan for
an Investigation in Support of RDIRA at OU 1.
2.12.1
Additional Investigations
Subsequent to the installation of Phase I of the selected remedy (Alternative 2), additional
investigations have taken place at OU 1. These investigations include the following:
.
Baseline groundwater sampling (rounds 1 and 2) (JMM, 1992b,c)
Treatability Study' (in progress)
.
.
Installation of foUr groundwater monitoring wells around the STP Percolation
Ponds and four rounds of sampling (Montgomery Watson, 1994a)
.
Installation and sampling of 30 wells as part of RI investigations for au 3
(Montgomery Watson, 1994b)
.,
Interim groundwater sampling of 13 wells (Montgomery Watson, 1994c)
Figure 11 presents the base map showing the TCE plume beneath the NEDA using the most
recent groundwater data, collected in July 1993 (Momgomery Watson, 1994c). Thirteen wells
were sampled during this interim groundwater monitoring event. The maximum concentration
2-39
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NZ-50 D
NZ-38
D
OW-6
D
LEGEND
.
-5-
120
(2.6)
ND
NZ-47
D
GEORGE AIR FORCE BASE
MONITORING WELL SCREENED IN UPPER AQUIFER
IJ
MONITORING WELL SCREENED IN REGIONAL AQUIFER
UNE OF EQUAL TeE CONCENTRATION (~L)
DASHED WHERE APPROXIMATE
t
TCE CONCENTRATION (1JgIL); WELL SAMPLED DURING
1993 EVENT
DUPUCATE SAMPLE RESULT (1JgIL)
TCE NOT DETECTED; DETECTION UMIT .. O.511gIL
o 1000 2000
, ,
Appraxin.- Scale in F881
.
APPROXIMATE LATERAL EDGE OF AQUITARD
THE TeE IN WELL LW.2 IS NOT INTERPRETED TO BE
PART OF THE 001 TeE PLUME
THE TeE CONCENTRATION IN WELL NZ-19 APPEARS TO BE
ANOMALOUS AND WAS NOT USED IN CONTOURING- THE
TCE OCCURRENCE IS BEING FURTHER INVESTIGATED.
NORTHEAST DISPOSAL AREA
TCE CONCENTRATIONS IN THE
UPPER AND REGIONAL AQUIFERS
JULY 1993
..
a,-oe
RGURE 11
r
~'~
-:-
"
-:-
-:-
II
II
II
II
1\
"
-------
detected was 140 J.Lgll in well NZ-25. The configuration of the plume beneath OU 1 remained
similar to that observed during the 1987 sampling and that of the February 1992 baseline
sampling (JMM, 1992c). TCE appeared to be present in the Regional Aquifer only beyond the
edge of the aquitard where groundwater from the two water-bearing zones merge (northeast of
the base) (Montgomery, 1994c).
2.12.2
Investigation in Support of RD/RA
An ongoing Investigation in Support ofRD/RA has been underway at OU 1 since October 1993.
The focuses of this study are to bener defme of the site hydrogeology and groundwater
contamination to expedite cleanup activities for th~ dissolved TCE plume in the groundwater
beneath the NEDA, and to address the data gaps identified during the OU 1 RI. Additionally,
the study will reassess the RAOs in consideration of risk based cleanup levels, MCLGs, and the
results of the recent dispute resolution detennining cleanup and discharge levels. Specific
activities associated with this investigation are summarized as follows:
.
Well Evaluation. Evaluation of base-owned monitoring wells will be performed
including a literature search, physical inspection, and down-hole geophysical
logging of questionable wells.
.
.-
Well Abandonment. . Based on the well evaluation, approximately 25 wells will
be abandoned, to optimize the number of wells to be used for long-term
groundwater monitoring.
.
Well Installation. An additional 12 groundwater monitoring wells will be
installed to fill data gaps determined during previous OU 1 investigation
activities, including the well evaluation.
.
Aauifer Testinsz. Aquifer tests will be performed to gain a better understanding
of the aquifer parameters in both the Upper and Regional aquifers for subsequent
modeling input.
.
Groundwater Modeling. .Existing geotechnical data and data collected during the
Investigation in Support of RDIRA field effort will be used in a groundwater
flow/fate and transport model to predict the fate and transport of TCE in the
groundwater beneath the NEDA. .
.
Lonsz-tenn Monitorinsz Plan. A long-term groundwater monitoring plan will be
prepared, including any new wells, and will recommend the frequency of
sampling for each well.
.
Groundwater Samplinsz. The long-term groundwater monitoring program will be
initiated by conducting sampling as specified in the plan. A total of 50 wells
(including newly installed wells) will initially be sampled.
2-40
-------
.
Investig:ation in SUDport of RD/RA Report. An Investigation in Support of
RD/RA Report will be prepared to present the results of the Investigation in
Support of RD/RA field effort.
.
Risk Assessment. A baseline risk assessment will be performed, based on all
existing data, to characterize the risks to receptor populations. Results will be
presented in the Investigation in Support of RDIRA Report.
.
. .
Alternative Evaluation ReJ>Ort. Using the results of the baseline risk assessment
and the Investigation in Support of RDIRA Report, an Alternative Evaluation
Report will be prepared to address ~e TCE contamination beneath the NEDA.
This report will present a detailed screening of alternatives for continued remedial
action for the TCE plume beneath the NEDA to ensure capture of the plume.
A current schedule for document submittal for the Investigation in Support of RD/RA is
presented in Table 10. The results of this investigation, in conjunction with the results of the
Phase I Treatability Study and future groundwater monitoring will be used to determine if further
system enhancement ~ill be required to ensure that the final au 1 RAOs for reducing the
concentrations of contaIirinants in the groundwater beneath the NEDA are achieved.
2-41
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TABLE 10
DOCUMENT SUBMITTAL SCHEDULE
Investigation in Support of
RD/RA Documents
Draft
Comment
Due
Draft
Final
Final
Investigation in Support of RD/RA Report
Alternatives Evaluation Report
16-Jan-95
16-Jan-95
15-Feb-95
15-Feb-95
15-Apr-95
15-Apr-95
15-May~95
15-May-95
I
I
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3.0 RESPONSIVENESS SUMMARY
3.1
OVERVIEW
The public comment period for the proposed plan began on September 20, 1993 and ended
on October 19, 1993. A public notice summarizing the Proposed Plan, and announcing the
public comment period and public meeting was printed in the Victor Valley Daily Press, the
Los Angeles Times, the Orange County Register, and the San Bernardino Sun at the stan of
the public comment period. . A press release was sent to 20.local newspapers, radio, and
television organizations also summarizing the Proposed Plan and announcing the public
meeting.
-
At the public meeting, which was held on October 6, 1993 at GAFB, questions and
comments were received from the audience related to the Proposed Plan. A transcript of the
pUblic meeting minutes bas been included in the Admini!;trative Record. During the public
comment period, written comments were received from the State of California Deparnnent of
Fish and Game.
Judging from the comments received, the community accepts the USAF's preferred remedial
alternative for addressing the groundwater contamination beneath the NEDA and adjacent
off-base areas.
3.2
BACKGROUND ON COMMUNITY INVOLVEMENT
In an effort to involve nearby communities, GAFB has held press conferences and provided
press releases following meetings with regulatory agencies regarding au 1. Additionally, a
member of the VictorvilleCity Council was a member of the teChnical review panel during
select meetings about key issues of the au 1. project.
In November 1987, GAFB provided information about environmental concerns at the base as
part of the "GAFB c:ommunity Days" activities. In 1988, a repository of information for
public review was established at the GAFB library. In early 1990, similar repositories were
established at the Adelanto and Victorville public libraries. Administrative files for the
project are maintained at the GAFB Air Force Base Conversion Agency located in Building
321. In October 1992, GAFB held an informational open house to discuss the environmental
cleanup program and visit the potentially contaminated sites. .
In July 1991, GAFB established a TRC that consisted of members of the community and
local agencies and governmentS. The TRC met on a quarterly basis. In January 1994,
GAFB established the Restoration Advisory Board (RAB) which replaced the TRC. The
RAB is designed to act as a focaJ point for environmental information exchange between.
GAFB and the public. The RAB will meet quarterly and meetings are open to the public.
3-1
-------
3.3
SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC
COMMENT PERIOD
Comments received during the GAFB OU 1 public comment period on the fInal FS and
Proposed Plan are summarized below. The comment period was held from September 20,
1993 to October 19, 1993. The comments are presented in the order in which they were
received.
Public Meeting
1.
A citizen would like to know what was the maximum concentration of TCE
detected in the plume.
Air Force Resoonse: The maximum concentration detected in the TCE plume
was 580 #tg/l in monitoring well NZ40 that was sampled in February 1992.
2.
A citizen would like to know how the decisions were made regarding the use
of air ~ppers related to air emissions.
Air Force Re$ponse: As stated in the ROD and the FS, the decision not to
provide for emission controls are based on a risk assessment. It was
determined that emission from the air strippers would not present an excess
risk to any potential exposed individuals. The Mojave AQMD bas provided
guidance that allow for the lack of emission controls if the estimated emission
rate of TCE is below 1.0 lbs/day. The estimated emission rate of TCE for the
au 1 air stripper is 0.28 lbs/day.
3.
A citizen questioned the selection of -air strippers as the best available
technology and suggested charcoal filters.
Air Force Response: Based on the detailed analysis performed in the FS, it
bas been determined that the best available technology for the project is air
stripping. Air stripping is a proven technology and treatability stUdies at
GAFB indicate that this technology effectively remediatC TCE at these levels.
4.
A citizen suggested the use of a slurry wall to prevent plume migration.
Air Force Response: The depth of the TCE plume is greater than 100 feet
below ground surface, therefore the use of a slurry wall is deemed infeasible
for this project.
5.
A citizen would like to know whether the plume has migrated to the VVWRA
facility north of the base.
3-2
-------
Air Force Response: TCE has been detected in samples collected from wells
at the VVWRA facility. Based on interpretation of the most recent
groundwater data collected at OU 1, it is interpreted that the. TCE detected at
the VVWRA facility is not pan of the OU 1 plume. However, this .
interpretation in not conclusive. This question is being addressed as pan of
the ongoing Investigation in Suppon of RD/RA.
6.
. A citizen questioned the knowledge of the extent of the aquitard that separated
the Upper and Regional aquifers.
7.
'. Air Force Response: The current in~rpretation of the areal extent of the
aquitard that separates the Upper and Regional aquifers is that the aquitard
hydraulically separates the aquifers but is not continuous north of the base and
east of the study area along the Mojave River bluff. However, the aquitard is
continuous to the west and southwest as determined by activities at OU 2 and
OU 3. This question is also being addressed as part of the ongoing
Investigation in Suppon of RDIRA.
Mary Sc3.rpa, Mayor of Adelanto would like to know why the STP percolation
ponds were selected for effluent discharge.
Air Force Response: The percolation ponds were selected as the effluent
discharge point because the ponds will provide excellent inflltration of water
that would aid in aquifer recharge.
8.
A citizen would lilce to know 'the extent to nitrate contamination at the
percolation ponds and the potential for nitrate leaching.
Air Force ReSDonse: As stated it the RI and ROD, elevated concentrations of
nitrates exist at the percolation ponds to a depth of 46 feet below ground
surface. Groundwater in this area is in excess of 100 feet below ground
surface. Elevated concentrations of nitrates are expected because the ponds
were previously used for the STP effluent. Based in a study of the wastewater
discharge to the soils of the Upper Mojave River Basin (USGS, 1993),
discharge of treated groundwater to the percolation ponds is not expected to
impact groundwater. However, existing wells around th~ percolation ponds
will be monit0rc:d for nitrates on a quarterly basis.
9.
A citizen would lilce to know the volume of effluent to be discharged to the
STP percolation ponds.
Air Force Response: The current design for the remediation system at OU 1
would produce effluent discharge rate at a of 500 gallons per minute.
3-3
-------
10.
A citizen questioned the use of data collected at Site 21, the Industrial/Stonn
Drain, by SAIC.
Air Force ReSDonse: The data that was used in decision making and the
conclusions presented in the ROD are based on data collected subsequent to
the collected by SAIC. The West Storm Drain was cleaned in place. Sections
of the East Storm Drain were cleaned, and the perforated piping were replaced
with nonperforated pipe. Soils underlying the perforated piping were also
excavated and disposed of appropriately. Subsequent confIrmation sampling of
the soil beneath the Industrial/Storm Drain indicated that the chemical
concentrations were at background le~els. All of these activities occurred
after the collection of data by SAIC.
Written Comments
1.
The State of California Department of Fish and Game is concerned about the
effect this project may have on nearby ecosystems. The Department of Fish
and Game has commented that this project meet guidelines set forth in the
California Environmental Quality Act (CEQA). The Department of Fish and
Game has suggested that the Final Environmental Impact Statement (ElS) for
this project address specific issues that are summarized as follows:
a)
The effect that this project would have on overdraft of the Mojave
River;
b)
An assessment of the flora and fauna within and adjacent to the project
area;
c)
A discussion of impacts expected to adversely affect biological
resources, with specific measures to offset such impacts; and
d)
A range of alternatives to ensure a complete evaluation including those
that would minimi~ impacts to sensitive biological resources including
alternative locations.
The Department of Fish and Game also commented that if the project has the
potential to adversely affect species of plants or animal~ listed under the
California F,J1da'1gered Species Act (CESA), a CESA-Memorandum of
Understanding must be obtained. The Department commented that they
oppose the elimination of watercourses and lor the channelization or
conversion to subsurface drains.
Air Force Response: The DTSC conducted an initial Study and has determine
that no potential significant environmental impacts are likely to occur form
implementation of the proposed project. The potential minor effects have been
3-4
-------
identified and mitigation measures have been provided to reduce them to
insignificant levels. In September 1992, the DTSC issued a Mitigated
Negative Declaration (Cal EPA, 1991) for this project. Therefore, this project
does not fall under CEQA guidelines.
In March 1992, the USAF issued a BIS on the entitled "Disposal and Reuse of
George Air Force Base, California." . Included in this EIS is a discussion of
potentially affected environments including biological and water resources.
Several other studies have been performed including a 1991 repon entitled
"Biological Survey of George Air Force Base" (SAlC, 1991) that provides
baseline biological conditions in particular for federally or state protected
species. Prior to activities that might impact sensitive biological resources, a
biological survey is conducted and activities are modified to minimize any
adverse impact. For.example, prior to construction of the now operating
remediation system at au 1 a biological assessment was performed (LSA,
1989) that identified impacted vegetation and wildlife. Mitigation measures
were recommended and implemented during the construction phase. All
ARARs, including those related to the proteCtion of the biological resources,
will be complied with at the appropriate time. This project does not effect
watercourses, surface drains, or wetlands.
3.4
REMAINING CONCERNS
Concerns that the USAF was unable to address during remedial planning activities include
the following:
.
What is the nature or the aquitard separating the Upper and Regional
aquifers?
.
Can the fate and transpon model better predict plume movement?
.
Can the eastern edge of the plume be better defined for its lateral extent?
To address these concerns, the USAF has begun an investigation to better define the site
hydrology and groundwater col\tamination and to expedite cleanup activities for the
dissolved TCE plume. Specific activities associated with the above concerns include:
.
Installation of 12 groundwater monitoring wells to fill data gaps;
.
Aquifer testing to gain a better understanding of the aquifer parameter for
both the Upper and Regional aquifers; and
.
Developing a new groundwater model to better understand the nature of
groundwater movement, the fate and transpon of TCE in the groundwater,
and the risks associated with OU 1.
3-5
-------
REFERENCES
Boyle'Engineering Corporation (Boyle), 1987. "Alter Base Water Supply, George Air Force
Base, Victorville, California. . Well Field Analysis." San Bernardino, California.
California Environmental Protection Agency (Cal EPA), 1991. "Mitigated Negative
Declaration, Groundwater Pump and Treat Facility, Northeast Disposal Area, George Air
Force Base." Long Beach, California; September 1991.
CH2M Hill, 1982. "Installation Restoration Program Phase I Search for George Air Force
Base, California." Gainesville, Florida.
International Technologies Corporation (IT), 1991. "Community Relations Plan for the
Installation RestOration Program at George Air Force Base, California, " San Bernardino,
California, April 1991.
James M. Montgomery, Consulting Engineers, Inc. (JMM), 1988a. "Installation Restoration
Program, Phase. IV -A Feasibility Study. Northeast Disposal Area, Upper Aquifer
Remediation. George Air Force Base, California." Pasadena, California, Apri11988.
- . .
JMM, 1988b. "Installation Restoration Program IV-A, Feasibility Study, Site Investigation
Report; Northeast Disposal Area, Upper Aquifer Remediation. George Air Force Base,
California." Pasadena, California; August 1988.
JMM, 1988c. "Installation Restoration Program, Phase IV -A, Feasibility Study. Site S-20 -
IndUstrial Storm Drain. George Air Force Base, California." Pasadena, California;
September 1988.
JMM, 1988d. "Installation Restoration Program, Remedial Investigation Report, Volume ffi-
Appendices. George Air Force Base, California." Pasadena, California; June 1988.
JMM, 1988e. "Installation Restoration Program, Final Design Analysis, Northeast Disposal
Area Upper Aquifer Remediation~ FY 1988. George Air Force Base, California."
Pasadena, California; May 1988.
JMM, 1988f. "Pre-design Remedial Investigation Technical Memorandum, Site S-20 -
indUstrial Storm Drain. George Air Force Base, California." Pasadena,' California; July
1988.
JMM, 1989. ."Final Design Analysis, Site S-20, East Storm Drain, Installation Restoration
Program FY88, George Air Force Base, California." Pasadena, California; February
1989.
R":l
-------
JMM, 1990. "Technical Memorandum for Site 20, Site S-26, and the Northeast Disposal Ar.ea.
George Air Force Base, California." Pasadena, California; May 1990.
JMM, 1992a. "Remedial Investigation, for Operable Unit 1, George Air Force Base,
California." Walnut Creek, California; August 1992.
JMM, 1992b. "Baseline Groundwater Sampling Repon, Round 1, George Air Force Base,
California." Walnut Creek, California; June 1992.
JMM, 1992c. "Baseline Groundwater Sampling Repon, Round 2, George Air Force Base,
California." Walnut Creek, California; December 1992.
JMM, 1993a. "Feasibility Study for Operable Unit 1, George Air Force Base, California."
, Walnut Creek. California; September 1993.
JMM, 1993b. "Proposed Plan for Operable Unit 1, George Air Force Base, California. It
Walnut Creek. California; September 1993.
JMM, 1993c. "Technical Memorandum, Data Validation Summary Repon for Data Used in the
OU 1 Remedial Investigation Repon, George Air Force Base, California." Walnut
Creek, California; August 1993., '
LSA, 1989. "Biological Assessment of the Montgomery Engineers Groundwater Contamination
Remediation System;" July 1989.
Montgomery Watson. 1994a. "Groundwater Monitoring Report, STP Percolation Ponds,
Operable Unit 1, George Air Force Base. California." Walnut Creek, California; In,
Progress.
. Montgomery Watson, 1994b. "Remedial Investigation for Operable Unit 3, George Air Force
Base. California." Walnut Creek. California; In Progress.
Montgomery Watson 1994c. "Interim Groundwater Sampling Repon, George Air Force Base,
California." Walnut Creek, California; In Progress.
Science ApplicatiODS International Corporation (SAlC) , 1985. "Installation Restoration
Program. Phase n Confirmation/Quantification Stage I Investigation at George Air Force
Base." Bellevue, Washington.
SAlC, 1987. "Installation Restoration Program - Phase n - Stage 2 Confirmation/Quantification
. (Final Report), George Air Force Base, California." Bellevue, Washington; January 8,
1987.
SAIC. 1991. "Biological Survey of George Air Force Base." February 1991.
R-2
-------
U.S. Air Force (USAF), 1989. "Closure of George Air Force Base, San Bernardino County,
California, Draft Environmental Impact Statement." December 1989.
USAF, 1992. "Environmental Impact Statement, Disposal and Reuse of George Air Force Base,
California." March 1992.
U.S. Environmental ProteCtion Agency (USEPA), 1988. Guidance for Conducting: Remedial
Investi~ations and Feasibilitv Studies Under CERCLA. Interim Final. Office of
Emergency and Remedial Response, Washington, D.C., EPA/540/G-89/004, October
1988.
-
USEPA, 1989. Risk Assessment Guidance for Superfund. Vol. 1: Human Health Evaluation
Manual. Part A, Region IX Recommendations, Office of Solid Waste and Emergency
Response, December 1989.
USEPA, 1992. Region 9 USEPA, Drinking Water Standards and Health Advisories Table.
Drinking Water and Groundwater ProteCtion Branch, Public Water Supply Section.
December 1992.
U.S. Geological Surv~ (USGS), 1990. "Water Resources Data, California, Water Year 1990,
Volume I, Southern Great Basin from Mexican Border to Mono Lake Basin, and Pacific
Slope Basin from Tijuana River to Santa Maria River." USGS Water-Data Report CA-
90-1.
USGS, 1992. "Steamflow Reports for the Mojave River, 1905 through 1992." Published and
unpublished records. .
USGS, 1993. "Potential for Groundwater Contamination from Movement of Wastewater
Through the UnsatUrated Zone, Upper Mojave River Basin, California." USGS Water-
Resources Investigations Report 93-4137.
R-3
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--
APPENDIX A
ADMINISTRATIVE RECORD
(On fde at GAFB Environmental Programs Office
Contact: Air Force Base Conversion Agency
Department of the Air Force
OL-CI AFBCA, Bullding 321
George AFB, California 92394-50(0)
-------
I .
- -
APPENDIX B
RESPONSE TO AGENCY COMMENTS
- -
-------
--
DRAFT ROD COMMENTSIRESPONSES
.0
-------
.~'lf.O ST4~#".
:ftTt
\S'
"'.. ~l
~4L lIIIC1't
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
75 Hawthorne Street
San Francisco, Ca. 94105-3901
December 7, 1993
Ms. Denise Caron
Chief, Environmental Programs
AFBDA/OL-C, Building 321
George Air Force Base, CA 92394-S0ao.
Dear Ms. Caron:
We have reviewed the draft Record of Decision (ROD) for
Operable Unit 1 and are providing the following comments.
If you have. any questions please contact me at (~15) 744-
2409.
I
Brian Swarthout
Remedial Project Manager
cc:
Jay Cass, RWQCB'
Emad Yemut, DTSC
Greg Little, MW
Sarabjit singh,
URS
Prinrrd on Rrcydrd Paprr
-------
~.s. Environmen~al Pro~ec~ion Agency
commen~s on the
draft Record of Decision
for aper&ble unit 1
General comments
1. The selected remedy should not be limited to "up to 19"
extraction or eight new monitoring wells. These numbers can be
given as estimates based on a concep~ual design, however the .
Remedial Design will need to give a more detailed justification
of the number of wells necessary to-remediate the plume and
monitor its effectiveness. The cleanup standard of 5 ug/l is the
main factor that will determine the number of wells needed.
During design implementation of the groundwater cleanup it may be
concluded that more wells are needed to ensure that the cleanup
standard is effectively achieved. The ROD can not put an upper
limit on the number of wells that will be necessary for
groundwater remediation.
2. The ARARs section should include a tabular presentation of
the state and Federal ARARs. This table can be used as the
foundation for developing an-agreement on ARARs. An example
table is attached at the back of the comments.
3. The responsiveness summary must be included in the draft
final ROD. In order to allow for sufficient review of the
comments and Air Force responses, EPA would prefer that the
summary be submitted for review in draft form prior to submittal
of the draft final ROD.
Specific Comments.
1. Section 1.4 DescriDtion of the Remedy
The selected r~medy should not be limited to "up to 19"
extraction or eight new monitoring wells. These nuwbers can be
given as estimates based on a conceptual design, however the
Remedial Design will need to give a more detailed justification
of the number of wells necessary to remediate the plume and
monitor its effectiveness. The cleanup standard of 5 ug/l is the
main factor that will determine the number of wells needed.
During design implementation of the groundwater cleanup it may be
concluded that more wells are needed to ensure that the cleanup
standard is effectively achieved. The ROD can not put an upper
limit on the number of wells that will be necessary for
groundwater remediation. .
2. Section 2.1 Site Name. Location~ and Descrintion
Paragraph 3. State the contaminants of concern for the STP
Percolation Ponds.
-------
3. Section 2.1.6 Water Use
Paragraph 7 says that seven GAFB wells and three Adelanto wells
are located along Turner Road. What type of wells are these?,
drinking water supply, industrial water supply, etc. .
4. section 2.5.1 Northeast DisDosal Area
This section should describe all known or suspected sources of
contamination if any are known. If none are known .than say so.
5. Section 2.5.1 Northeast DisDosal Area
Paragraph 3. The fourth sentence begins with'" wi thin the deep.
portion of the Upper Aquifer,..". Since this is the first
reference of the deep portion of the Upper Aquifer, the document
should. explain how it is defined. This information should also
be presented in Section 2.1.4 Hydrogeology.
6. section 2.5.1 Northeast DisDosal Area
Paragraph 3. The last sentence in this paragraph say that
contamination from the North East Disposal Area does not pose an
immediate threat to any potential receptors. This statement is
incorrect since the groundwater contamination of in this area has
already threatened the supply wells at VVWRA. Please make the .
appropriate changes.
7. Section 2.5.1 Northeast DisDosal Area
Paragraph 4. The first sentence is confusing. It first states
that the three wells are "within GAFB boundaries" and than states
that they are "all located to the east of the base." This
sentence should be corrected so that it more clearly describes
the location of the wells.
8. Section 2.5.1 Northeast DisDosal Area
Paragraph 4. The last sentence of this paragrapn states that'"TCE
measured in the Regional Aquifer is unrelated to the TCE plume
observed in the Upper Aquifer" in the area of NZ-02, HZ-OJ, and
NZ-13 . This statement is vague and should be expanded upon. If
it is not related to the Upper Aquifer than to what is the TCE in
the Regional Aquifer related.
9. Section 2.5.2 Industrial/Storm Drain and Outfall Ditch
Since no further action are expected at this site, the first
sentence of this section should be expanded to briefly explain
what remedial actions were taken.
10. Section 2.5.3 STP Sewaae Treatment Ponds
The Air Force should expandPthe rationale for no further action
-------
at this site, by statinq that based on the levels of
contamination in the soil, qroundwater is not expected to be
impacted by nitrates.
11. Section 2.7 DescriDtion of Alternatives
This section should describe the portions of the treatment system
. that have already been installed.
12. Section 2.7.2 Alternative 2 - Groundwater Extraction. Air
striDDina and Percolation
The second half. of the paraqraph sta~es that if portions of the
plume escape, "it is expected that VOC concentrations reachinq
downqradient receptors would decrease through dispersion..." The
approach described in this sentence is not acceptable. The
purpose of the cleanup is to capture the entire plume and not to
allow it to escape. The mechanisms contributing to "dispersion"
have not been demonstrated and should not be considered part of
the remedial action. .
13. section 2.7.j Section 2.7.2 Alternative 2 - Groundwater
Extraction. Air StriDDina with Emission controls... and Percolation
The question of whether air emission controls will be needed
should be expanded~ Other factors beside risk may.contribute to
the need to install air emission controls. For example, the San
Bernadino County Air Pollution Control District (AFCD)
requirement of 1 Ib/day (cited on page 2-34) may drive the
decision. Compliance with this ARAR should be discussed.
14. section 2.8.2.3 Action SDecific ARARs
Discharge ARARs. Last Sentence. The discussion on complying
with San Bernadino County APCD ARARs should be expanded to cite
the specific regulation that limits emissions and how the Air
Force will ensure that it will be complying with these ARARs.
15. Section 2.9.1 Selection of the Preferred Ramedv
This section should include a discussion of. the no
decisions for Sites S-20 and 5-21. The discussion
should include mention of the soil removal actions
taken at these sites.
action
of Site S-20
that have been
-------
~-_..I._- - -.-
Attachment A
The followinq comments were provided by Danita Yocom,
Assistant Reqional Council, USEPA Reqion9 for the draft Record
of Decision for Operable Unit 1, Georqe Air For~e Base,
California
1. section 2.8.2 ComDliance with ARARs.
Delete the first sentence in the paraqraph and substitute with
the followinq:
"Pursuant to Section 121(d) CERCLA, as 'amended, remedial actions
must attain a deqree of cleanup whicb assures protection of'human
health and the environment. In addition, CERCLA requires that
remedial actions meat standards, requirements, limitati~ns or
criteria that are applicable or relevant and appropriate
(ARARs)."
Delete the second sentence in the second paraqraph (re USEPA
draft quidance and the "proposed" RCP) and substitute with the
followinq: -
"The RCP defines "applicable requirements" and "relevant and
appropriate requirements" as follows:"
In the second line of each definition (i.e. "applicable
requirements" and "relevant and appropriate requirements"),
delete the phrase "environmental protection." In the third line
of each definition, delete "federal or state law" and substitute
with "federal environmental or state environmental or facility
sitinq laws". At the end of each definition add the followinq:
"Only those state standards that are identified by a state in a
timely manner and that are more strinqent than federal
requirements may be applicable."
2. Section 2.8.2.1 Chemical-SDecific ARARs.
The ROD should spacify 1Ithich re~Jj,r~ents are the chemical-
specific AJU~ for the contaminants of concern in OU-l. Here,
the State standard for TCE (the State MCL) is not more strinqent
than the federal standard, and therefore we are selectinq the
federal standard. .
With respect to Secondary Drinkinq Water Standards (SDWS),
the State established how the SDWS are enforceable? 'Also,
is the point of compliance? If the point of compliance is
tap, the SDWS are probably not ARABs.
At an appropriate place prior to the discussion of the specific
ARARs, add the followinq:
has
what
at the
"The contaminant specific ARARs for OU-1 are federal drinkinq
water standards and promulqated State of California drinkinq
-------
water standards which are more stringent than federal standards.
Cleanup levels are set at health-based levels reflecting current
and potential use and exposure. For sys~emic (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 10 -4 to 10 -6 risk range.
[NCP, 40 CFR S300.430(e)(2)(i)(A)(2)]"
"potential drinking water regulations include MCLs for specific
contaminants [Section 1412 of the Safe Drinking Water Act, 42 USC
S300g-1, 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 levels that are
protective of human health and set close to Maximum contaminant
Level Goals (MCLGs)."
"California has promulgated MCLs for primary volatile organic
compounds, howev~r, the u.S. EPA has chosen the federal MCL for
TCE as the groundwater cleanup standard for OU-1 because the
California MCL for TCE is' equal to the federa+ MCL."
Delete the first sentence in the third full paragraph on page 2-
30, as it is not relevant to the remedy. Delete the last
sentence in the third paragraph.
Delete the first and second sentences in the fourth full
paragraph on page 2-30, unless the State establishes that its
Secondary Drinking Water Standards are enforceable for
groundwater.
Delete the first full paragraph on page 2-31. As the portion of
the dispute regarding final aquifer cleanup levels under 92-49
was withdrawn by the State, the decision did not establish the
final aquifer cleanup level. The dispute established a cleanup
level for discharges to percolation ponds, which should be
discussed under t.~e s~ctiun regnr~ing action-s~ecific A-~.
, . .
3. section 2.8.2.2 Location-SDecific ARARs.
I recall that the FS for OU-3 stated that the Endangered Species
Act (ESA) was not an ARAR at the site. An ARAR determination for
the ESA would be the same for all operable units. Has the Air
Force consulted with the u.S. Fish and Wildlife Service (FWS) as
proposed by CERCLA Compliance with Other Laws Manual II (1989)?
If the FWS determines that the endangered species is not present,
then the ESA is not an ARAR. If a determination is made that the
endangered species'or its habitat will not be affected, the ROD
should so state. If the endangered species or its habitat will
be affected, the ROD must state what mitigation measures will be
taken. Therefore, the discussion of the ESA needs to be revised
pending further consultation.
-------
Revise the last paragraph on page 2-31. If the desert tortoise
and/or its habitat is in the vicinity of OU-1, the paragraph
should read as follows:
"Endangered species and their habitats are protected by the
Endangered species Act [16 U.S.C. Sections 1531-1543). The
desert tortoise is a potentially sensitive, rare, or threatened
species within the vicinity of the operable unit which is .
protected by the ESA. Therefore, the ESA is an ARAR for on-site
actions. The proposed remedial actions would not [would?) affect
the species or its critical habitat. [If the remedial actions
would affect the species or its critical habitat,: "The
following mitigation measures will be taken:" The mitigation
measures also should be described briefly in the description of
the selected remedy. '] " '
4. Section 2.8.2.3 Action-SDecific ARARs.
Treatment ARARs.
Delete the third full paragraph on page 2-33 as it is a location
specific ARAR which has already been addressed in Section
2.8.2.2.
Discharae ARARs.
As the discussion of the dispute will have been deleted under the
chemical-specific ARARs section, the background of, the dispute
should be moved to the section regarding the discharge to the
percolation'ponds. The paragraph should read as follows:
"On October 2, 1992 the Regional Water Quality Control Board,
Lahontan Region (RWQCB) invoked dispute resolution regarding, in
part, effluent discharge levels for TCE into the percolation
ponds in the HEDA. On April 22, 1993 the USEPA Administrator
issued a decision finding that the California State Water Quality
Control Board's anti-degradation policy (Resolution 68-16) is an
ARAR with resp~ct to discharges of TCE at OU 1, and returned the
matter to th~ USEPA Reqion IX ~ctinq Regional Administrator
(Regional Administrator) to det&rmine anappropriat6 standard for
discharges into the percolation ponds at OU 1. Based upon
negotiations between the USAF, the State of California and USEPA,
on July 9 1993 the Regional Administrator issued a final dispute
resolution decision which set the effluent level to be measured
from the sampling port at 2.5 mg/l TCE on a median basis with a
maximum discharge level ,of 5 mg/l TCE. The decision further
stated that the USAF will seek to treat the discharge to attain a
level of 0.5 mg/l TCE as measured at the percolation ponds,
although such efforts do not constitute an enforceable discharge
standard."
5. Section 2.8.4 Reduction of Toxicitv. Mobilitv and Volume
throuah Treatment.
-------
In the first sentence of the first paragraph, insert the word
"permanently" before the word "significantly".
6. section 2.8.6 Short-term Effectiveness.
Are there any proposals to mitigate potential impacts on habitat.
Also, are the Mojave ground squirrels an endangered species? If
so, they should be mentioned in the ARARs discussion of the
Endangered Species Act.
7. section 2'.9.1 Community Acce'Dtance.
In the first full paragraph on page_2-44, delete the word "goal"
and substitute with "standard". This change should be made in
any other place in the text where an enforceable cleanup level is
described. The word goal should only be I.lsed if i.l1e numi;er is
not enforceable, as with the discharge into the percolation
ponds. .
8. Section 2.10 StatutorY Determinations.
In the second bu~let, delete "for discharge of treated effluent
to the former STP percolation ponds" as that is not a statutory
mandate.
-------
. ---... ... -- ~
IdC6-vt::-l'-l c...) , -
Memorandum
',,-..
.......,
To:
Emad Yemut
Site Mitigation Branch. Base Closure Unit
Department of Toxic SubStanCeS Control'
24S West Broadway, Ste 350
Long Beach, CA 90802
Date Pee. 1, 1993
From:
. ~. ~ ~ IZ"-/.Ji J .
~&~Ional Water Quality Control ~ 241.7408
hontan Region
Ictorvu18 Braneh Office
, 542B Civic Drive, SUite 100
Vlctorvll\e, CA 82392-2351
Fax (619) 241-7308
Subjecs: REGIONAL BOARD STAFF COMMENTS - DRAFT RECORD OF DECISION (ROD).
OPERABLE UNIT ONE (OU-I), GEORGE AIR FORCE BASE (GAFB), SAN
BERNARDINO COUNTY .
Introduction
. .
Regional Board staff have reviewed the Draft QU-I ROD a11d have a number of comments.
. The ROD must address a number of Regional Board concerns.
.
Subswuive waste discharge requirements and an outline of futUre actions must be
iDc1uded. as agreed by the parties. There must be a time schedule for submittal of
doc~ relating to TCE plume defmition. plume containment and Phase n
extIiICtiOl1 wells.
.
The ROD must reflect current site conditions, even if the most recent ground water
infomwion was not used in developing the selected TCmedy.
The section discassing ARARs mUSt be clarified to clearly show what are potential
ARAR.s and what ARARs will apply [0 the selected mnedy.
.
.
The ROD should clearly indicate in the opening sections that Phase I of the selected
remedy is ~~:ll]y complete using the 1988 FS conclusioDS.
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Page 2.
Yemut
December 1, 1993
COMMENTS - ~. FT OU -1 ROD
'_.'
, .
-
General Comments
1.
Include I..anlnuure A2!'eed to Durin, RPM Conference Call
The ROD mUSt be wriaen in aa:ordaDce with &he agreemem made during the
Remedial Project Manager (RPM) conference can of September 13. 1993. The RPMs
agreed that tbe Substantive Waste Discharge Requi~~ for OU-I. ROD
. 'Addendum. dated September I, 1993. prepared by. ReJional Board sW'f would DOt be
included with the ROD.
The RPMs agtccd that the c1rafi ROD would comain substantive waste disCharge
requirements and an outline of actions to be performed as a part of the Remedial
Design/RemcdiaI Action process. A time schcduIc (or document submiuals must be
included. For iDstaDcc. data gaps in the TCE plume definition aDd Phase n extraction
wells for plume conWnmcnt must be resolved as described in the Rancdial
InvestigationIFeasibility Saidy (RIIFS).
Regional Board staff are aware that US EPA. Region IX. the Deparanent of Toxic
Subsranccs CODtrOl. me State Water Rc:somces ContrOl Boud. rile Central Valley
Regional Water Quality CODttol Bomf, and the Air Force 3M developing language for
i Castle APB ROD that may apply, in part. to GAFB. This Regional Board suff
have DOt been involved in specific: cfiv!1ssicms for Castle APB. however we will
favorably consider .specific language as it may apply to GAFB. .
Please refer to the following for specific substantive waste discharge requirement
items to be included in the ROD:
.
ItemS A.I - A.S.I. B.l - B.4. C.2. C.4. D.2, D.6, D.9 - D.12 from a
RegionaI Board handout (RPM meedDg. September 1.-1993) entitled
Substandve Waste DiscbarJc Rcqu4emems for Land Disposal. Operable Unit
ODe (OU-I). George Air Force Base.
Items 1. (all) and 3. (aU) from RcgioDal Board letter dated October 2. 1992
entitled Specific S1ate Applicable or RclcvlDC a114 Approprlare RequirementS
(ARARS) for Operable UDit One (OU-1). George Air Force Base (GAFB). In
addition. iDclude refereaces from enclosure 1 or mat Jea=r to the followiDg:
!be Basin Plan, SWRCB 68-16. Article S, Chapter IS. Title 23. Cal. Code or
Regs, aDd DWR Bulletin 74-90 aDd 74-81.
.
~c Comments
2.
PaRe 1-2. Section 1-4. Descriotion of Selected Remedv
Please add to the founh buJler that temporary discharge is now occurriDg to the
arroyo and future dist-h."ge to the golf course is allowed..
-------
. '
w~w-~.-.~~~ .~.~~
COMMENTS - D~-F'I' OtJ-l ROD
..."'''''', "'WUI,",~ ~u....., 0::;
;:,....:J...Q~::I=
IU
....0::;':'
Page 3
Yemut
December 1, 1993
3.
4.
S.,
'_i
. '
-
:pasze 2-11. Section 2.2. Site Hisrorv and Enforcement ACtivities
This section should indicate that Cleanup and Abatement Order (CAO) No 6-86-3 was
adopted by the Regional Boafd on Ianuary 16., 1986. It required the Air Fo~ to
define the extent of tricbloroethene (TeE) contamination in the ground water beneath
1he northeast disposal area (NEDA), submit a plan for remf'1JiSirion and begin cleanup
of the ground water. This CAO was the impetus for the 1988 Feasibility Study.
CAO ~86-3 was rescinded when the Federal Facilities Agreement was signed.
Fi~re 8. Distribution of TCE in Ground}Vl!tcr
Please revise this figure as follows:
a.
show the most recent (1992) ground water iDformation for each well.
b.
revise the plume configuration to reflect thc most recent data;
c.
show the monitoring wells instaUcd around the percolation pondS.
4.
show the soUtheastern plume edge with a notation to mciicatc it is undefined.
show the approximate edge of the aquiurd separating thc'upper and regional
aquifers. .
e.
f.
show data from each aquifer zone (upper and lower).
Puc 2-17. Section 2.5.1. Nonheast Disj)osaJ Area
a.
2nd paragraph, The text stateS that .(VOCs) are the major COIIta~iMnts of
concern, with TCE being the most persistent and widespread". The text
should specifically state what the ContamiDants of Couccm are. We suggest
that TCB be listed as being over the remed~on goal. nitrate be listed as
potcnrl:'l1y affecting groundwater quality downgradieDt of the disposal location,
anc1 an otbcr compouuds ~twere detectccf be listed but indicate they are at
iDsignif1C3nt concemrations. - Refer to the fmal ~~edhd Investigation IepOrt.
page 5-6 for the other constituents deteeted. '
Terms should be consistent throughout the document. The term "chemicals of
concern- is Used on page 2-51, Section 2.10.5. '
b.
2nd paragraph, rIgUre 8 does not show w~ the tWo aquifers merge as
~~. '
c.
2Dd parapph. Please deiete or reword the last sentence in tbis paragraph;
"CoftbmiMtion at this location currently does not pose an immediate threat to
, any potential receptor". This is in conflict with the State's policy to view
ground water as a resource to proteCt. preserve and r~tOte for present and
potential future users, rather than a pathway of poteDtia1 exposure to existing
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.' Page 4
Yemut
December 1, 1993'
6.
7.
8.
",-,*,'
COMMENTS - 'C' FT OU-l ROD
--
receptors. The existing TCE cormamimtion is a violation of the Basin Plan.
. AdditiODally, domestic water production wells at the Victor Valley Waste '
Water R~,JSlm2tion Authority (VVWRA) may have dercctable conceattations of
TCE from the 1eac1iDg edge of the OU-1 plume. Because of this reason,
VVWRA purcbascs bottled ~ for employees. Water from dJese wells arc
used for operations at VVWRA. The well drawdown will Still iDfluence the
TCE plume movement. .
Pal!e 2-17. Secrlon 2.5.1. NortheaSt DisposaJ Area. 3rd para2I'mh
The last sentence, which states that "it is believed that the TeE measurec1 in the
Regional Aquifer is umelated to the TCE plume obscrvc:d in the Upper Aquifer" is
puzzling. The TCE CODCCDtratiODS measured in the regional aquifer along the main
advance of the plume (NZ-48, MW.I07) is related to the TCE in the upper aquifer.
The highest TCE coDCeDttation measured in tile NEDA grouDd water to dare is 580
ugll in MW-40. This well is slightly down gradicDt, but predomiml~ly cross-gradient
of NZ-02, NZ-03 and NZ.13. Because the TCE plume is undcfiDcd in the area to
the cast of MW-40, it would be prematUre to state the conclusions made in the text.
.
Pal!e 2-18. Section 2.5.1. NortheaSt Dimosat Area. 2rd 1)ara~h
i.
The text states that the rate and extent of TCE plume movement was evaluated
as part of the 1992 RI report. This is mcorr=:t. The 1 m RI repeated the
results of work peIfoImed in the 1988 RI.
b.
The ROD should state that the r=sults of the traDSpOrt model will have to be
verified as part of the iemPJij-t Design. The lithology'.and ground water flow
assumptions used in the 1988 aDaIysis should be revised to include c:urTem
information.
Th= ~ states that the esrim~ted mass of TCE in me aquifer is 430 pounds.
Th= actual mass is probably greater. The Statement sbould be,removed from
the ROD or qualified to indicate that the mass estimates were made ~g
isocomcurs gECater man s lJCf./l. Conccmratiom = than 5 ugI1 were
discountc4. Add.itionally. the cunemly observed higbcst TCE concenttaIiOD.
(MW~) was 110t used to esdmate me mass of TCB.
The text states that me peak concentration of TCE has decreased. This is
incorrect. We UDd=rstaDd tbe peak observed TCE ccmcemration to be 580 ugll
(NZ~, 1992); the last time wells in the NEDA ~ sampled.
Pa2e 2.19. Section 2.S.3. STP Sewa,e Treatment Ponds '
c.
d.
The text n:fers to a nitrate migration StUdy being conducted by the' USGS. Under
separate cover, a copy of the final report was sent to GArB. Please refer to it for
spec;itic conclusions. The repon title is Potential for Ground-Wuet Contamimttion ,
From Movement of Wastewater Throu2h the Unsaturated Zone. uDDer Moiave RIver
Basin. Ca1ifo~, Water Resources Investigation Repon 93~137. ,. , '
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--. -. ---- ----
. ..-- -- . "-- . -. --
-------_..._~..;.,
. . c...=-
Page 5
Yemut
December 1., 1993
COMMENTS - D-'FT OU-l ROD
"'-". "
"-"
9.
Paee 2-22. Alternative 2-Groundwater Extracrion. Air Stritmin2. and Percolation. 1St
oaralmlDh " "
The teXt States MShould portions of the plume escape captUre by the extraction systcm,
it is expected that voc conccnuations leaChing down gradient receptOrs would
decrca.sc through dispersion to concentrationS below the federal MCL for TCEM. The
=xt should ~ revised. The ROD must include a requirement to t!\~;"tain hydraulic
control of the plume in accordance with SWRCS Resolution 68-16 to prevent further
spread of pollution. Allowing portions of the plume to migrate beyond the existing
conflgUI'ltion is unacceptable aM would be a violation of State policy.
10.
Page 2-22. Alternative 2-Groundwater EXtraction. Air Stritmini. and Percolation. 2nd
parammh "
This paragraph is misleading. Most of the components referred to as part of Phase I
are iDstalled now. Temporary discharge has occurred to the arroyo since December"
1991, about tWo years. The text should describe me operadng system realistically.
Definite dat~ for submittal of the Phase II work plans should be iDcluded. The last.
sentence indicates that proposed locations of Phase I componentS arc shown on Figure
10. The components shoWD. on Figure 10 arc cxisW1&, not proposed.
11.
~re 9. ConceDtUal Desim of Extraction and Monitorinll WeUs
This . figure is misleading. It should be revised to note what facilities are completed as
part of Phase I and what facilities are proposed (or DCCCSsary) for .Phase n. To better
illUStrate the proposed remedy, we suggest another figure be included to show all
proposed Phase IT well locations (see fiDa1 FS, Figure S-l).Thc figure should clearly
indicate that the locations may be modified as ~sary to maximize plume
comaimnent and captUre, based upon a future capture ZODe analysis and review of
Phase I treatability study data.
12.
" Table 1. Summary of Derailed AnA1m!; of Remedial Alternatives
The proposed remedy cost for a1tcmative 2 is projected at $7,864,300. Projected
remedial costs for Operable Unit 2 scenarios arc much higher. Cost is a faCtor in
choosing a rcmcciy. Please provide a cost comparison amlysis Statement that would
indicate what confidence should be placed in the COSt esamates. This is an impol'Wlt
. task becauR the ultimare choice of remedial options fer all GAFB siteS will involve
considerable public cxpendiNre.
13.
Table 2. Chemical-Specific ARARs :anti TBCs For Detected Ccmmounds. Northeast
DiSDOsal Area .
This table, refereDCCd on Page 2-30, second paragraph, last sentence is confusing and
misleading. The referenc:c StateS "A list of all chemicals found in groundwater at the
NEDA is prcscmed in Table 2, ~ong with their rcspcctive potential ARARs".
a. The ROD CODCCmS itself primarily with TCE (page 2-17, second paragraph).
The text and table must indicate the DlaXmmm concentrations and extent of all
"detected compounds" in the NEDA. This information is ~s:ary to
-------
. w_-'w. ---- .c.~-
j~....... I'\~,-~ ~u.I..;.I'" Q~ ~
::I....J"'';':>::>()-;::I~
II.J
r-.I:.J,
" Page 6
Yemut
December 1, 1993
14.
c.
d.
COMMENTS - rr f1' au -1 ROD
. ,-"..~
'-
conclude that TCE is the primary Contaminant of Concern. RegiOnal Board
staff agree tbat TCE is the primary Contaminant of Concern.
b.
The table must indicate if the values are for in-sitn aquifer cleanup levels.
tteared water effluent levels or bOth. "
c.
The table must iDclude natural background water quality for both the area
affected by the TeE plume and the receiviDg watets beneath the percolation
ponds. 1bis iDfomwion is DeCeSSary for determining how to incolpOrate
SWRCB ResolUtion 68-16 criteria..
d.
-
The table must include values that would reflect taste and odor values as
required by the Basin Plan.
e.
The table must indicate which of the values will apply to the site. We suggest
tbat the table be modified to show all potcutial ARARs aDd clearly labeled to
indicate that the list is for "potential- ARARs only. the teXt should have two
~oul sections, following section 2.8.1 for ground watl:r cleanup and
treated water effluent chemical-specific ARARs. "The reader then will not be
COJIfusecI to think that the values shown in tile table are chosen to apply to QU-
I. See comment no's. 14.c. aDd 14.d., below. .
f.
!be table must "include Dittate (see COmment S. above) m1 the results of the
dispute resolution process (see comment 14, below).
Pue 2-31. section 2.8.1. Chemical Soecijic ARARs. 1st paramlDh
a.
The text discusses the dispute reSolution process and specifIC values resulting
from the process. . We sugest that S=OI1 2.8.1 be. limited to generic
discussions regming potential ARARs, iDCluding the dispute resolution
process. Table 2 should be mooified to include specific values that resulted
from the dispute reSolUlion process. The last ~ of paragraph 1 should
be moved as ;nd;~.ated below.
b.
This section must iDclud~ reference to the Warer QuaJity Comrol Plan for the
Lahoman Basin (Basin P!in). The beDeficial uses of groUDd water in the
atfected area must be listed (Basin Plan page 1-2-4. uea 628.20. Upper
Mojave). "
New Section 2.8.2.1.1. Chemical-Specific ARARs for F'maI Aquifer Cleanup.
should be added. 'Ibis section would cliscuss wbat the fiDal aquifer cleazmp
values must be. The last sem=ce of the 1St paragraph. Page 2.-31 should be
movec1 !)ere.
New Section 2.8.2.1.2. Chemical-Specific ARARs for Treareci Effluent. should
be added. This section would discuss what the treated waIer effluent values
must be. The last paragraph of Page 2-33 and 1st full paragraph of Page 2-34
should be movec1 to here.
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Page 7
Yemut
'.. December "1,'.1"993
19.
20.
COMMENTS - D- FT OU-l ROD
"-
'-
- -.- _00..
15.
. .
Page 2-32. Section 2.8.2.3. Action-Specific ARARs. Treatment ARARs:. 2nd
paramtDh on pare
The text refers to Alternatives 3b and 4b. There arc only alternatives 1. 2. and 3
under consideration.
16.
Page 2-33. Section 2.8.2.3. Action.Soecific ARARs. Treatment ARARs:. 2nd full
para2r3Dh on pa~e .
The teXt States that the "sclected remedy will.1Uilize off-site thennal regeneration of
spent carbon". This is incorTCCt. The selected remedy uses air Stripping.
The ROD mUSt State that "designated" waste must be disposed in a manner that
complies with Water Code Section 13173 aDd Section ZS22. Title 23, Ca!. Code of
Regs. W1ulc federal CERCLA rcquimnems regulate only "hazardous" subStances,
California regulates other waste that could affect water quality including "designated"
waste.
17.
Pue 2-33. Section 2.8.2.3. Action-SDeCific ARARs. Dischar2e ARARs
See Commem 14. above.
18.
Pa2'e 2-43. Section' 2.9. L Selection of the Preferred Alternative. second to last
sentence o~l Dara~raph
Please modify the following scn1eDCe to include:
" The estima~ number of additional wells is based on assumptiODS made during the
FS and the adual number and placement of additional wells wij1 be decided based on
the performance of tbe Phase I system
-."
~~ .,::::~~~2...1='. '~';:;:r;"'/'.""'r':."'~tir;~~;::--'~".'."a"1".~."~.~
..;.J/'.:-';,Q~;'.~::::-~.~... -.....~ l"- ~-..........
Pa2e 2-43. Section 2.9.1. Selection of the Preferred Alternative. last sentence on Daie
The sentence "This recbarge will ~h,.n~e operation of the extraction syStem, as it
will prcvcm excessive drawdown and will act to flush adsorbed TCE from aquifer
materials- should be removed or qualified. During the dispute resolution process,
Regional Boald staff questioned to what degree recharge to the Old Sewage Trearment
Plam Percolation Ponds would affect the TeE plume. For additional infonnation see
items numbered 3.b and S. atraehment 11 to the May 13. 1993 letter from the State .
Water Resources Control Board to US EPA. Region 9.
Pa2'e 2-46. Section 2.9.2.2. Air St:rin1)inr Svstem. last para2l'2t3h
The text indicates that sodium hexamethaphospbate is added to prevent precipitation
and sodium hypochlorite is added to prevent biologicaJ groWth in the air stripping
towers. These compounds arc to be continuously monitored to "min;m~" residual
chlorine in the treated Water.
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~age 8
Yemut
December 1, 1993
'-
COMMENTS - D- oFT. OU-l ROD
-'
Please indicate what minimum chlorine levels will remain to prevent formation of
aihalometbanes (THMs) in the ground water.
21.
Pa,e 2--48. Section 2.9.4. SyStem. I.nmlementatioD. last 1)ara2I'aph
The text states that -Data gaps identified in the RI repon (]MM. 1992) will be used
to develop a work pIan for supplemeuta.l investigations at au.1.. The ROD must
incJude a S11mmt")' of the data gaps idemified and include a schedule for conducting
additional investigations. This work has been verbally agt=1 to by the Air Force for
some time. however no foanal schedules have been proposed.
22.
PIJe 2-51. Section 2.10.S. Preference for Treatment as a Principle Element
See comment S, above.
If you have any questions please call lehiel Cass at (619)241-7408 or Cindi Mitton at
(619)241-7413.
jcl21ouldrod.mem
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-
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STATE OF CALIFORNIA - ENVIRONMENTAL PROTEC'nON AGENCY
1~6r.06'10/ 6.3./0
Pf!re WILSON. G-.-
DEPARTMENT OF TOXIC SUBSTANCES CONTROL
Region .
2., w.! 1tra8cM8y. SuiI8 350
L.ang188dl. CA 80102......
. 1318) ,...
€i
December 2. 1993
Ms. Denise Caron
Air Force Base Disposal Agency
OL-ClAFBDA, Building 321
George Air Force Base. California 92394-5000
Dear Ms. Caron:
DRAFT RECORD OF DECISION (ROD). OPERABLE UNIT 1~ GEORGE AIR FORCE BASE
(GAFB). CALIFORNIA.
The Department of Toxic Substances Control (Department) has completed the review of the
above subject document. dated October 1993.
The Air Force should incorporate the State's comments into the ROD. Enclosed are the
Department's and the U\hontan Regional Water Quality Control Board's general and specific
comments.
If you have any questions orconcenis. please contact me at (310) 590-4915.
Emad B. Yemut
Region 4 Base Qosure Unif-
Base Cosure Branch
Enclosures
cc:
Mr. Bob Butler
Department of the Air Force
HQ AFBDAISP
1211 South Fern St., St. DI70
Arli'ngton. Virginia 22202-20808
-
Mr. Fred Mueller (CESPK-ED-EC)
U.S. Army Engineering District. Sacramento
Corps of Engineers
1325 J Street .
Sacramento. California 95814
ft.
~.
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Ms. Denise Caron
December 2, 1993
Page 2 .
Mr. Gerald Saulnier
Depanment of the Air Force
. AFCEE-ESRB
Brooks AFB, Texas 78235
Ms. Donna Grubb-Hewlett
The Mitre Corp/Center for Civil Systems
7525 Colshire Drive
McLean, Virginia 22101-3481
Mr. Greg Little
Montgomery Watson
365 Lennon Lane
Walnut Creek. California 94598
Mr. Brian Swarthout
U.S. Environmental Protection Agency
Mail Stop H-9-1
75 Hawthorne Street
San Francisco, California 94105
Mr. Emad Yemut
Region 4 Base Qosure Unit
Base Qosure Branch
California Environmental Protection Agency
Depanment of Toxic Substances Control
245 West Broadway, Suite 350
Long Beach. California 90802-4444
Mr. Jehiel Cass
California Regional Water Quality Control Board
Lahonton Regional Office
15428 Civic Drive, Suite 100
Victorville, California 93292
Mr. Jeff Hubbard
U.S. Army of Corps of Engineers
Omaha District CEMRO-ED-EA
215 17th Street .
Omaha, Nebraska 68102
Mr. Sarabjit Singh
URS Consultants, Inc.
2710 Gateway Oaks Drive, Suite 250 North
Sac:ramento, California 95833
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If6~. ~o/6' 5.10
GEORGE AIR FORCE BASE
Record Of Decision, Operable Unit 1
GENERAL COMMENTS
1.
. All parties involved in the cleanup of George Air Force Base (C3AFB) acknowledge that
certain significant portions of the TCE plume remain undefined both in the North and
Northeast where the Upper and Regional Aquifers merge. The State's position is that
without the knowledge of the gross dimensions of the plume, both in the Upper and
Regional Aquifers, the preferred alternative constructed and operational since December
1991 will not ensure the complete, capture of the plume and expedite the cleanup.
A language should be included in the Operable Unit 1 (OU1) RecorcI of Decision (ROD)
that reflects the situation and identifies the data gaps. THe Air Force (AF) should include
a deadline for the submittal of the Workplan lor implemeriting the additional investigation
at OU1 to completely defining the TCE plume and filling the data gaps identified during
the RllFs study. . .
2.
The AFshould clarity that Deed Restrictions will be part 01 the preferred alternative. The
State believes that prior to sale or transfer of any of GAFB property overlying the
contaminated groundwater plume, the AFshou/d record a land use restriction in .;;
accordance with California Health and Safety Code Section 25230 as an institutional
control to prohibit installation 01 wells until the groundwater standards have been
achieved. The AF should provide notice of this restriction in any purchase, lease, or other
agreement relating to that property.
3.
.
The ARARs section is confusing and incomplete. The AF should identity the ARARs for
each alternative in a tabulated form. The AF should conduct a comparative analysis of
compliance with chemical-specific ARARs, location-specific ARARs, and action-specific
ARARs for each alternative. then, the text will highlight the major ARARs. .
-
1
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SPECIFICS COMMENTS
1.
Section 1.2. St8tement of Basi8 .nd Purpose
page 1-1
2.
Provide the year when CERCLA and SARA were enacted; 1980 for CERCLA and 1986 for
SARA. Also. include the section of CFR that complies with this action: . 40 Code of
. Federal Regulations. (CFR) Part 300-.,
Deacriptlon of The Selected Remedy, SectIon 1.4
pIIge 1-2
The State believes 1hat the selected groundwater remedy should include 8 Deed
reatrictiona8 as one of the major com~ of the selected remedy.
The text also states that" groundwater treatment using two air stripping towers.. The AF
should also ctarify that there will be direct discharge of emissions from the air strippers to
the atmosphere. because the emissions are in compliance with 8ir quality ARARs.
3.
St8tutory Detenninationa, Section 1.5
page 1-2
-
The Air Force should inctude an estimate of the remedy duration 10 achieve cteanup
standards. The Air force should also state that the 5 year review will be conducted on an
ongoing basis 10 ensure 1hat the remedy continues 10 provide adequate protection of
human health and the environment. because the groundwater remedy WIll result in'
hazardous substances remaining onsite until the cleanup standards are met.
4.
Signatures, Section 1.6
. p.ge 1.3
Please change the signature block for the Department of Toxic Substances Control to the
following:
Anthony J. Landis
DSMOA Technicat Program Manager
State of California
Department of Toxic Substances Control
s.
Distribution 01 TCE in Groundwater .t 5 ppb, Figure 8
The figure shows the boundary of TeE plume (5ppb) based on 1987 data; the TCE plume
boundary should be based on current available data. This figure should show that the
plume has impacted the VVWRA wells. The figure should also show the data gaps 10 the
north and northeast It should differentiate between wells screened in the upper aquifer
and wells screened in the regional aquifer.
2
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6.
Northeast Disposal Area, Section 2.5.1
page 2-16
The third paragraph of page 2-17 states that. given the easterly directior:l of groundwater
flow near wells NZ-02. NZ-03; and NZ-13,it is believed that the TCE measured in the
Regional Aquifer is unrelated to the TCE plume observed in the Upper Aquifer". This
statement is not adequate and should be deleted. The State's understanding 01 this
. matter which is based on Remedial Investigation documents provided by the Air Force. is
that the contamination has migrated off base in a north-easterly direction and has.
impacted the Regional Aquifer. The Upper and Regional Aquifers merge in the vicinity 01
well NZ-40 which is screened in the regional aquifer with a 580 ppb TCE.
It is our understanding that the Air Force agreed to characteriZe the full extent of TCE
contamination in the regional aquifer emanating from George AFB. The AF agreed on
conducting additional investigations to fill the data gaps identified in the operable unit 1
Remedial Investigation. The AF should provide the State with a submittal date for the
additional investigations Workplan, and should clarify this issue in the ROD.
7.
Northeast Disposal Area, Section 2.5.1
page 2-18
The second paragraph states that" It is expected that the existing ~A wells will be
slightly impacted by the plume, although concentrations are predicted to remain below 5
ppb". We already know that some 01 V\f\NRA wells are impacted by the plume, please
correct this paragraph to reflect that. .
8.
STP Sewage Treatment Ponds, Section 2.5.3
page 2-19
This section should include a clarification that the AF will monitor the groundwater
quarterly for nitrate from existing wells around the STP peres ponds.
9.
Summary Of Site Risks, Section 2.6
page 2-19
Even though the primary contaminant 01 concern at OU1 is TCE. the AF should include
the 9 additional compounds that are also present and detected at OU1: Benzene. Carbon
Tetrachloride, Chloroform. 1.1-dichloroethane(1,1-DCA), 1,2-dichloroethane(1,2-DCA), cis-
1,2-dichloroethane, 1-2-dichloropropane, methylene chloride, and tetrachloroethene(PCE).
Furthermore, 1,1-DCA and 1,2-CCA. in. anaerobic conditions, will undergo
dehydrohalogenation to form Vinyl Chloride. Vinyl Chloride. like benzene is a known
human carcinogen. and has a maximum concentration level of 0.5 ppb per State 01
California MCLs. The MCL for benzene is 1 ppb. .
The AF should include these chemicals 01 concern in a tabulated form. Information on
, frequency of detection. maximum concentration, and mean concentration should also be
included in this table. The State believ~s that the AF should monitor for these
compounds and for Vinyl chloride in addition to TCE.
3
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10.
Summary of Site Risks, Section 2.6
page 2.19
The AF should include a clarification that the data used to prepare the baseline risk
assessment was collected during the OU1 RI, that all the RI data have been validated,
and that the quality is acceptable to support the recommendation of this ROD.
. Northeast Disposa' Area, Section 2.6.1
, page 2.19
11.
Include a summary table of carcinogenic and noncarcinogenic risk. and indicate if the risk
is acceptable for the different sceJ:larios considered.
--
12.
Northeast Disposal Area, Section 2.6 .
page 2.19
Even though section 2.6, summary of site risks states that the risk assessment includes
both human health risk assessment and an ecological risk assessment, no ecological
risk is presented in the subsections. Please include a section on ecological risks and
identify any State or Federal threatened or endangered plant species or other ecological
receptors.
13.
Description of. Alternatives, Section 2.7
page 2.20
The AF should clarify that the technical information supporting each alternative and the
future risk assessment associated with implementation of a remedial action is included in
the final OU 1 FS.
This section should also include an estimate of the volume of contaminated groundwater
in the upper aquifer. The cumulative carcinogenic risk to human health from groundwater
from ingestion. and inhalation of airborne VOCs while showering should be included.
14.
Description of Alternatives, Section 2.7
page 2.20
The AF should states and clarifies if . the contaminated groundwater is either a Resource
Conservation and Recovery Act (RCRA) listed waste or RCRA characteristic waste as
defined in Title 22 California Code of Regulations (CCR) Section 66261; or whether
. groundwater contaminants are listed wastes or. if the groundwater exhibit corrosivity,
ignitability, reactivity, or toxicity characteristics ( Title 22 CCR Section 66261,.24).
15.
Alternative 1, No Action With Groundwater Monitoring, Section 2.7.1, page 2-21
Please clarify that this alternative is required for consideration by the NCP. that this,
alternative will not comply with relevant and appropriate federal and state MCLs
established in the National Primary Drinking Water Standards [40 CFR section 141.61 (a)]
and Drinking Water Primary Standards (Title 22 CCR Division 4 section 64444.5], and that
this no action alternative will not reduce the risk to human health posed by the VOCs in
groundwater.
4
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20.
16.
Alternative 2- Groundwater Extraction, Air Stripping, and Percolation, Section 2.7.2,
page 2-21 .
The AF should include Deed Restrictions as part 01 this alternative. The State believes
that prior to sale or transfer of any of George AFB property overlying the contaminated
groundwater plume, the AF should record a land use restriction in accordance with
California Health and Safety Code Section 25230 as an institutional control to prohibit
. installation of wells until the groundwater standards have been achieved. The AF should
provide notice of this restriction in any purchase, lease, or o1her agreement relating to
that property. A clarification of this matter should be included as part of this section.
17.
Alternative 2. Groundwater Extraction, Air Stripping, and Percolation, Section 2.7.2,
page 2.21
The main components of this alternative should be presented in a tabulated form. This
alternative's main components consists of : 1) Deed restriction. 2) Groundwater
monitoring. 3) Groundwater extraction, 4) Treatment by air stripping, 5) Direct discharge
of emission to atmosphere. if emissions are in compliance with air quality ARARs, 6)
Discharge of treated water to STP peres ponds for recharge into the Upper Aquifer.
18.
Alternative 2- Groundwater Extraction, Air Stripping, and Percolation, Section 2.7.2,
page 2.21
The State believes that the AF should compare the air stripping alternative 2 to a different
alternative such as Carbon Adsorption, because the only difference between alternative 2
and alternative 3 is the addition of the Air emission control system which the AF should
include as part 01 alternative 2, if they are not in compliance with air quality ARARs.
, .
19.
Alternative 2. Groundwater Extraction, Air Stripping, and Percolation, Section 2.7.2,
page 2.22
The text states that "The second phase would occur in about 2 years and would include
the installation of up to 10 additional wells (nine off-base wells). additional pipeline and
roadway, and local power distribution to new wells.. We believe that the locations and
number of wells should be based on the additional investigation that the AF agreed to
implement to define the full dimensions 01 the plume in the Upper and Regional Aquifers.
Alternative 2. Groundwater Extraction, Air Stripping, and Percolation, Section 2.7.2,
page 2.22
The AF should identify the ARARs for each alternative in a tabulated form and include
them in this section. The AF should include a comparative analysis 01 compliance with
chemical-specific ARARs, location-specific ARARs, and action-specific ARARs for each
alternative. Then the text should highlight the major ARARs.
5
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21.
Overall Protection 01 Human Health and the Environment
page 2-26
The Text states that' The estimated average TCE concentration stripper .influenthas
decreased from 150 to 47 ppb, based on more recent groundwater monitoring results";
however. a clarification to this matter should be added. The TCE plume is moving'
outside the base boundary; as such the TCE concentration is decreasing inside the base
. boundary and increasing outside the base boundary. Therefore. the average influent
concentration may increase when the additional investigation is conducted to characterize
the full extent of the plume in the upper and regional aquifers, and when the additional 10
or more extraction wells are installed.
22.
Overall Protection 01 Human Health and th.e Environment
page 2-27
The text states that" Additionally, the levels and frequency of detection of benzene. 1.2-
DCA. and other VOCs decreased to the point where they were not considered statistically
reliable for risk assessment purposes'. this may be true for the present conditions;
however, when the additional investigation is implemented and the full dimensions of
contamination is characterized this may change. As such. the AF should monitor for
these products. (see comment number 9). and for byproduct of degradation since the
remediation will take an estimated 30 years to complete.
23.
Compliance with.ARARs, Chemical-specific ARARs, Section 2.8.2.1 page 2-29
The AF should consider the . National Emission Standards for hazardous Air
Pollutants-NESHAPs(40 CFR Section 61.63, Section 61.92, Section 6.1.102, and
Section 61.348). The air stripping remedial alternative should comply with this relevant
and appropriate ARAR. If. at the present time. NESHAPs are not applicable because
groundwater is not at least '10% volatile hazardous air pollutants by weigbt": the AF
should comply with the substantive requirements 01 this ARAR.
24.
Location -specific ARARs, Section 2.8.2.2
page 2-31
. The State believes that" RCRA Location Standards (Title 22 CCR Chapter 14 Section
66264.18)" is 8 relevant and appropriate ARAR. The facility should not be constructed
within 200 ft of an earthquake fault and. if it is located within the 100-year floodplain. it
should be designed. constructed. operated and maintained to prevent washout 01 waste.
25.
Action-specific ARARs, Section 2.8.2.3
page 2.32
The State believes that: Tank Systems (Title 22 CCR Section 66264.190 - 66264.199) is
a relevant and appropriate substantive requirements that should be incorporated into the
design and operation of the tanks used to store groundwater.
6
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Miscellaneous Units (Title 22 CCR Section 66264.600 - 66264.603). The air stripping
towers should be located. designed. constructed. operated. maintained. and closed in a
manner that ensures protection 01 human health and the environment (e.g.. prevention of
releases) and should comply with the relevant and substantive requirements for
miscellaneous treatment unit. . .
Transportable Treatment Unit (title 22 CCR Section 67450). the air stripping tower is
considered a 1ixed treatment unit. The State believes that the operation of the air
. stripping tower should comply with applicable substantive requirements for fixed
treatment units. including discharge of treated effluent and treatment at site of waste
generated.
26.
State Acceptance, Section 2.8.8
page 2-41
The SUite conditionally approved the OU#1 FS. This approval was conditioned on the AF
submittal 01 a workplan for the additional investigation to define the 1ull dimensions 01 the
TCE plume. This ROD should incorporate a statement to that fact. it should also include
a submittal date for the phase II additional investigation study.
The State believes that the AF should monitor 10r any increase in VOCs emission from the
air stripper that may cause an unacceptable risk to human health and the environment.
Documentation should be provided to the State. USEPA and the local APCD on a yearly
basis.
27.
Community Acceptance, Section 2.8.9
page 2-41
The AF should state that the Proposed Plan was presented to the community and
discussed at a public meeting, and provide a brief summary of the community concerns.
The AF should clearly state if the community accepted this alternative in general. or if
they have major concerns.
28.
The Selected Remedy, Section 2.9
page 2-42
This section should state that the selected remedy was completed based on the 1988 FS
conclusion.
29.
Selection of the Preferred Alternative, Section 2.9.1
page 2-43
The text states that. The preferred alternative that best meets these objectives is
alternative 2. which consists 01 on and off-base Upper Aquifer groundwater extraction with
19 wells. followed by treatment of extracted groundwater by two packed-tower air
strippers. and recharge 01 the treated extracted groundwater to the Upper Aquifer via
percolation..
7
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The AF should also state that Deed Restriction will be part 01 the selected remedy. Deed
restrictions should be placed on any George AFB property that overlies the VOC plume
prior to sale or transfer to prohibit the installation of water wells in areas that still contain
VOCs above cleanup standards.
The AF should also state that the emissions from the air stripping towers will be
discharged directly to the atmosphere. if emissions are in compliance with air quality
ARARs,
30.
Selection of the Preferred Alternative, Section 2.9.1
page 2-43
The Te~ states that" The estimated number of additional wells is based on assumptions
made during the feasibility study and the actual number and placement of additional wells
will be decided based on the performance of the phase I system,", The text should clarify
that additional investigation will be implemented at OU1 to define the full extent 01
contamination in the upper and regional aquifers. and based on this study the locations
and number of additional extraction wells will be determined.
31.
Cost Analysis, Section 2.9.3
page 2-47
The AF should present the estimated total cost in a tabulated 10rm. The total cost should
include a breakdown 01 the direct/indirect capital cost, annual/periodic cost (life 01 30
years). and a cost summary.
8
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. 8.
RESPONSE TO USEPA COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
General Comments
1.
The text has been modified as appropriate to indicate that the 19 extraction wells
and 8 monitoring wells are estimates; however, the exact number will be based on
system (Phase I) efficiency.
Potential ARARs and TBCs have been presented in tabular form (Tables 4
through 10). .
2.
3.
The Responsiveness Summary has been included in the Draft Final ROD as
Section 3.0.
Specific Comments
1.
Section 1 4 Description of Alternatives
See response to General Comment 1 above. The text has been modified
accordingly. .
2.
Section 2.1 Site Name
3.
The text has been modified accordingly. Additionally, the RI (JMM, 1992) has
been cited where appropriate.
Section 2.1.6 Water Use
The text has been modified to indicate that the wells referenced are municipal
supply wells.
4.
SeCtion 2.5.1 Northeast DiSJ)Osal Area
The text has been revised to state that the source of TCE is currently unknown;
however, several au 3 sites have been identified as potential sources.
5.
Section 2.5.1 Northeast Disposal Area
References to the deep portion of the Upper Aquifer have been removed from the
text.
6.
Section 2.5.1 Northeast Di~posal Area
The sentence referenced has been removed from the text.
7.
Section 2.5 1 Northeast Disposal Area.
The text has been modified to clarify that the wells referenced are located in the
eastern portion of the base.
Section 2.5.1 Northeast Disposal Area
The sentence referenced has been removed from the text
BI-I
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RESPONSE TO USEPA COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
9.
Section 2.5.2 IndustrialJStonn Drain and Outfan Ditch
The text has been modified to state that the remedial actions that have taken place
have included removal of all contaminated sediments and replacement of the
perforated portion of the pipe with nonperforated pipe as detailed in Section 2.2
(Site History and Enforcement Activities).
10.
Section 2.5.3 STP Percolation Ponds
Section 2.5.3 has been revised substantially to clarify that groundwater is not
expected to be impacted by nitrate and that quanerly monitoring of the wells
around the STP percolation ponds will be-performed.
11.
Section 2.7 Description of Alternatives
12.
This section is intended to provide a brief description of potential alternatives
which were evaluated during the FS process (JMM, 1993). However, Section
2.9.2 (Detailed Description of the Preferred Alternative) presents details of the
portion of the system (Phase I) which has already been installed.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippin~. and
Percolation
13
The text has been modified to state that the extraction system will ensure that
VOC concentrations are reduced to below federal MCLs. The reference to
dispersion has been removed.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippin~. and
Percolation .
14.
Section 2.7 is intended to summarize the alternatives that were evaluated in the FS
(JMM, 1993). The text has been modified to reference Section 2.8. where a
detailed comparison of the alternatives is presented. including compliance with
ARARs as presented in Section 2.8.2. Additionally, Section 2.8.1 presents a
discussion of calculations showing that with a 47 Jig/l influent concentration
.(expected to be less) the emission rate ofTCE is estimated to be O.28Ibslday.
Section 2.8.2.3 Action-Specific ARARs
. ,
The reference to San Bernardino County APCD has been changed to cite the
Mulford-Carrell Air Resources Act (Health and Safety Code Sections 3900-
44563) as regulated by the Air Resources Board and enforced under CAC, Title
17, Part m. The text in Section 2.8.3 (Long-tenn Effectiveness and Pennanence)
has been expanded to clearly state that VQC emissions will be monitored based on
influent and effluent concentrations from the treannent system. Note that this
monitoring has been occurring for the ongoing Treatability Study and the
calculated mass of VOCs emitted has been well below the San Bernardino County
APCD stated limit of 1 lb/day. Emissions will continue to be monitored in this
manor.
15.
Section 2.9.1 Selection of the Preferred Remedy
BI-2
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.,' ".,,''''
RESPONSE TO USEPA COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
This section presents a discussion of the preferred remedy for the groundwater'
beneath the NEDA at GAFB; however, Section 2.5.2 has been modified to state
that the remedial actions that have taken place have included removal of all
contaminated sediments and replacement of the perforated portion of the pipe as
detailed in Section 2.2 (Site History and Enforce~ent Activities). Section 2.6 has
also been expanded to state that the risk assessment supports the conclusion of no
further action for the Industrial/Storm Drain and Outfall Ditch, and the STP
percolation ponds. Additionally, Section 2.2 has been expanded to clarify that the
technical information supporting the conclusions presented in this ROD is
included in the RI (JMM, 1992) and FS (JMM, 1993a) reports.
Attachment A, Reviewer: Danita Yocom, Assis~t Regional Council, USEPA Region 9
L
Section 2.8.2 Compliance with ARARs
The text has been modified accordingly.
2.
Section 2.8 2.1 Chemical Specific ARARs
All changes recommended in this comment have been made to the text.
-. ,
3.
Section 2.8.2.2 Location-Specific ARARs
The text has been modified accordingly, including a discussion the mitigation
efforts would include inspection of the proposed installation location (i.e.,
extraction well or monitoring well location) for endangered species by qualified
personnel and selection of an alternate location if the presence of these species is
detected.
4.
Section 2.8.2.3 Action-Specific ARARs
Treatment ARARs. The referenced paragraph has been removed from the, text.
5.
Disch~e ARARs. The text has been modified accordingly.
Section 2.8.4 Reduction of Toxicitv. Mobility and Volume throu~h Treatment
The text has been modified accordingly.
6.
Section 2 8 5 Short-term Effectivenes.c;
7.
See response to Attachment A. Comment 3. Discussion of mitigation of potential
impacts on sensitive habitat are now presented in Section 2.8.2.2. The Mojave
ground squirrel is also included in this discussion.
Section 2.9.1 CommunitY Acceptance
8.
The text has been modified accordingly.
Section 2.10 Statutory Determinations
The text has been modified accordingly.
Bl-3
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, RESPONSE TO LRWQCB COMMENTS.
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
General Comments
1.
Section 2.12 has been added to the text of the ROD which presents an outline of
activities to be performed. as well as a schedule of submittals. for the
Investigation in Suppon ofRDIRA currently underway.
Specific substantive discharge requirements will be included in the Remedial
Design. However, language from the ROD prepared for Castle AFB which
addresses this issue has as been included as appropriate in Section 2.9.1 (Selection
of Preferred Remedy).
Specific Comments
2.
Section 1.4 Description of Selected Remedy
3.
The text has been modified accordingly.
Section 2.2 Site History and Enforcement Activities
4.
The text has been modified accordingly.
Fiiure 8
a. Although Figure 8 is included to present the data that was available when
the 1988 FS analysis was performed, an additional figure (Figure 11) has been
added to the document to present the most recent information regarding TCE
distribution in the groundwater. The title of Figure 8 has been revised to clarify
that it presents 1987 data.
b.
See response to Comment 4 (a) above.
c. See response to Comment 4 (a) above. Only the wells available during the
1987 sampling events are presented on this figure; however, the wells around the
percolation ponds are presented on Figure 11.
d. See response to Comment 4 (a) above. Section 2.12 has been added to the
text which discusses the data gaps and presents the most current groundwater data
(Figure 11) with an indication that the southeastern edge of the plume is
undefined.
e.
The figure has been revised accordingly.
f. Discussion of separate "zones" within the Upper Aquifer has been
removed from the text. .
5.
Section 2.5.1 Northeast Di&posal Area
a. The text has been modified to clearly state that TCE is primary
contaminant of concern. Discussion of the "significance" of other detected
compounds is presented in subsequent sections (Le., based on the risk
assessment). A list of the maximum concentrations of the contaminants of
concern detected in the groundwater at the NEDA are now presented in Table 1.
Bl-4
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RESPONSE TO LRWQCB COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
Nitrate has not proven to be a contaminant of concern for the groundwater beneath
the NEDA. Concern over nitrate has arisen as a result of proposed use of the STP
percolation for discharge of treated groundwater as part of the preferred
alternative. ' Therefore, the discussion of the STP percolation ponds (Section
2.5.3) has been revised substantially to clarify the rationale that nitrate is not
expected to pose a threat to human health. Additionally, the monitoring wells
around the percolation ponds will be monitored on a quanerly basis. Discharge
can be discontinued if it is deemed that elevated nitrates are occurring due to this
discharge.
The text has been revised to consistently use the terminology of "contaminants of
concern. "
b. Figure 8 has been revised to show the approximate location of the lateral
edge of he Upper Aquifer. .
c.
The sentence referenced has been removed from the text.
6.
Section 2.5 1 Northeast Disposal Area
. The sentence referenced I)as been removed from the text.
7.
Section 2 5 1 Northeast Disposal Area
a. The appropriate reference has been cited and the text has been modified to
indicate that the 1992 RI summarizes previous work.
b. The intent of this section. and this ROD, is to summarize the conclusions
of the 1992 RI and 1993 FS reports which summarized previous work (Le., 1988
RIlFS) and were based on previous data. As agreed upon in the RPM meetings
and presented in the approved Final 1993 FS. new data will not be incorporated
here and will be presented separately as pan of the ongoing Investigation in
Support of RDIRA. Section 2.12 (Current Investigation Status) has been added to
the text of the ROD which summarizes activities that have occurred to date, as
well as the scope of the Investigation in Support of RDIRA, which includes
additional modeling. The text in has been revised to reference appropriate
previous documents and clarify that the results are based on these 'earlier modeling
efforts. .
c. See Comment 7 (b). The intent of this section, and this ROD. is to
summarize the conclusions of the 1992 RI and 1993 FS reports which summarized
previous work (Le., 1988 RIlFS) and were based on previous data. As agreed
upon in the RPM meetings and presented in the approved Final 1993 FS, new data
will not be incorporated here and will be presented separately as part of the
ongoing Investigation in Support of RDIRA. Section 2.12 (Current Investigation
Status) has been added to the text of the ROD to clearly state what activities have
occurred to date. .
d.
See response to Comment 7 (b) and (c).
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8.
Section 2 5.3 STP Percolation Ponds
USGS Water-Resources Investigations Report 93-4137 has been referenced in the
ROD and referred to as appropriate in Section 2.5.3. .'
9.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippine. and
Percolation'
The text has been modified to state that the extraction system will ensure that
VOC concentrations are reduced to below federal MCLs. The reference to
dispersion has been removed. Discussions regarding SWRCB Resolution 68-16
are presented in Section 2.8.2.3 (Action-5pecific ARARs).
10.
Section 2.7.2
Percolation
Alternative 2-Groundwater Extraction. Air Strippine. and
Section 2.9.2 (Detailed Description of the Preferred Alternative) presentS a
discussion of the system that has been installed to date. Section 2.7 (Description
of Alternatives) is intended to summarize the Alternatives evaluated in the in the
1988 RIIFS. as summarized in the 1993 Final FS which conformed to the
guidance set 'forth in the Guidance for Conductine Remedial Investi~ations and
Feasibili~ Studies UnderCERCLA (USEPA. 1988).'
11.
Fi~ure 9
See response to comment 10. This figure. and the section in which it is presented.
is intended to show the system proposed for the Alternatives 2 and 3 that were
presented in. the 1993 Final FS. However. Section 2.9.2 presentS a detailed
discussion of the system which has been installed to date. Additionally. Section
2.1.2 (Current Investigation Status) has been added to the document to summarize
the investigation activities that have occurred since the installation of Phase I of
the treaunent system and the ongoing Investigation in Support of RDIRA the
focus of which is to provide data to modify Phase II to maximize plume
containment and capture. Sufficient data is not available at this time to present
locations of Phase II well locations with any accuracy. The text throughout the
document has been modified to clarify that the 1993 FS presentS technical backup
for alternatives evaluated. which presented the referenced figure showing best
guess Phase n well locations based on data available at that time.
12.
Tahle 1 Summaty of Detailed Analvsis of Remedial Alternatives
13.
More detailed cost estimation will be performed as part of the Remedial Design.
Table 1 (now Table 3). and the section in which it is presented. is intended to
summarize the comparison of alternatives presented in the 1993 Final FS which
conformed to the guidance set forth in the Guidance for Conductine Remedial
Investieations and Feasibility Studies Under CERCLA (USEPA. 1988). Costs
presented were not intended as a remedial design but as best estimates for
comparison of proposed alternatives.
Table 2 (now Tahle 11)
a. The maximum detected concentrations for all compounds have been added
to the table. as reported in the RI (JMM. 1992). Additionally. Table 1 has been
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added to the document to give a detailed summary of groundwater data available
for the 1988 RI/FS.
b. A footnote has been added to Table 2 (now Table 11) which states that the
federal MCL of 5 ~gIl is the chemical-specific ARAR for the final aquifer cleanup
level and the action-specific ARAR for treated effluent discharge is 2.5 ~g/l TCE
on a median basis. with a maximum discharge level of 5 ~gIl.
c. Section 2.12 has been added to the text of this ROD to clearly state what
activities have occurred since the 1988 RI/FS. Background water quality data is
currently being assessed as part of the STP percolation pond monitoring activities
(discharge to the ponds has not begun)-, -additionally, background water quality
data is being assessed as part of the ongoing OU 3 investigations as well as the
Investigation in Support of RDIRA. However, the intent of this ROD is to present
the conclusions summarized in the 1992 RI and 1993 FS reports which
summarized previous work (Le.. 1988 RIIFS) and were based on previous data.
As agreed upon in the RPM meetings. this new data will not be incorporated here
and will be presented separately as part of the Investigation in Support of RDIRA.
d. Taste. and odor values are secondary drinking water standards which are
not ARARs in this case.
e. The table has been modified to clarify it presents potential chemical-
specific ARARs. Tables 4 through 10 have been added to the document which list
all potential federal and state ARARs for the compounds detected at the NEDA.
The text has been modified to clearly state that the federal MCL for TCE is the
ARAR fodinal aquifer cleanup.
See response to Comments 13 (b) above. The discussion of the results of the
dispute resolution process, which affected the discharge ARARs, is now located in
Section 2.8.2.3 (Action-Specific ARARs) where it is most appropriate. Section
2.8.2.1 has been simplified to clearly state the final aquifer cleanup value of 5 J.lg/l
as a chemical-specific ARAR. .
f. The table presents the contaminants of concern for the groundwater
contamination beneath the NEDA Nitrate has not proven to be one of these
contaminants. Concern over nitrate has arisen asa result of proposed use of the
STP percolation for discharge of treated groundwater as part of the preferred
alternative. Therefore, the discussion of the STP percolation ponds (Section
2.5.3) has been revised substantially to present the rationale that nitrate is not
expected to pose a threat to groundwater. Additionally, the monitoring wells
around the percolation ponds will be monitored on a quarterly basis. Discharge
can be discontinued if it is deemed that elevated nitrates are occurring due to this
discharge.
The table has been footnoted to present the results of the dispute resolution
process (see Comment 13 [b] above). .
14.
Section 2.8 2.1 Chemical Specific ARARs
a.' The text in Section 2.8.2.1 has been modified as to be more generic. The
dispute resolution discussion. which resulted in 2.5 J.lg/l discharge levels on a
median basis. is now presented in 2.8.2.3 (Action-Specific ARARs). Table 2
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. 18.
20.
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(now Table 11) has been footnoted to present the results of the dispute resolution
process (see Comment 13 [b] and [0 above).
b. The Basin Plan is now presented in Table 7 (Identification of Potential
State Chemical-Specific ARARs). This table states that use of MCLs as a
remedial standard would cleanup groundwater to its highest beneficial use (Le..
drinking water).
c. The discussion of the results of the dispute resolution process. which
affected the discharge ARARs. is now located in Section 2.8.2.3 (Action-Specific
ARARs) where it is most appropriate. Section 2.8.2.1 has been simplified to
clearly state the final aquifer cleanup- 'Value of 5 ~gIl as a chemical-specific
ARAR.
15.
d. See response to 14 (c) above. The discussion of the results of the dispute
resolution process has been clarified; however, it is an action-specific ARAR and
is presented in Section 2.8.2.3 as such. . .
Section 2.8 2 3 Action-Specific ARARs
- -
The text has been corrected to state Alternative 3.
16.
Section 2.8.2 3 Action-Specific ARARs
The text has been revised to state the Alternative 3, which includes emission
controls using GAC, could use off-site thennal regeneration of spent carbon.
17.
Additionally, a paragraph has been added to state that although contaminated
groundwater is not classified as a RCRA hazardous waste, subsequent disposal
without treatment may impact groundwater; therefore, it is considered a California
"designated" waste, as defmed by Title 23 CCR. Consequently, the remedial
alternative must treat contaminated water to minimize impacts to beneficial uses
of groundwater prior. to discharge. The au. 1 dispute resolution process
determined appropriate treatment and discharge levels.
Section 2.8.2 3 Action-Specific ARARs
See response to Comment 14 above.
Section 2.9.1 Selection of the Preferred Alternative
The text has been modified accordingly..
19.
Section 2.9.1 Selection of Prefen-ed Alternative
The sentence in question has been removed from the text
Section 2.9.2.2 Air Strippin~ System
The text has been modified to indicate that specific details of the monitoring'
program will be included in the RDIRA. .
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DRAFT RECORD OF DECISION, OPERABLE UNIT 1
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21.
Section 2 9.4 System Implementation
The schedule of additional investigations and a summary of ongoing Investigation
in Support of RDIRA activities is now presented in Section 2.12 (Current
Investigation Status).
Section 2.10 5 Preference for Treatment a.<; a Principle Element
The text has been revised accordingly.
--
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General Comments
1.
The schedule of additional investigations and a summary of ongoing Investigation
in Support of RDIRA activities is now presented in Section 2.12 (Current
Investigation Status).
The text of this ROD has been modified where appropriate to clarify that deed
restrictions will be part of the preferred alternative.
2.
3.
Tables 4 through 10 have been added to the document which present potential
federal and state ARARs. The text throughout the section has been revised to
clarify which ARARs will apply.
Specific Comments
1.
Section 1.2 Statement of Basis and Puq>ose
2.
The text has been modified ac,?ordingly.
Section 1 4. Description of the Selected Remedy
The text has been modified accordingly.
3.
Section 1.5 Statutor:y Determinations
4.
The text has been modified accordingly.
Section 1.6 Si~atures
5.
The text has been modified accordingly.
Fi~ure 8
6.
The approximate location of the lateral edge of the Upper Aquifer has been added
to the figure. A distinction has been made between wells screened in Upper and
Regional Aquifers. The intent of this section, and this ROD, is to summarize the
conclusions of the 1992 RI and 1993 FS reports which summarized previous work
(i.e., 1988 RJ/FS) and were based on previous data. As indicated in the legend of
Figure 8, the plume presented is based on 1987 data. Presentation of current data
in Figure 8 would be misleading. However, Section 2.12 has been added to the
text of this ROD which summarizes activities which have occurred to date as well
as the scope of the ongoing Investigation in Support of RDIRA which includes
installation of 12 wells to address the data gaps to the north and northeast. Figure
11 has been included in this Section 2.12 which presents the most recent
groundwater sampling results in light of recent activities.
Section 2.5.1 Nonheast Disposal Area
The sentence referenced has been removed from the text. See response to
Comment 5 above. Section 2.12 has been added to the text which discusses the
scope of the ongoing Investigation in Suppon of RDIRA and presents a schedule
these activities.
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7.
Section 2.5.1 Northeast Disposal Area
The text has been modified to clearly state that the discussion is presenting the
predictions of the model performed for the 1988 FS analysis. The reader is
directed to Section 2.12 and associated references which discuss the recent
sampling eventS that have occurred at the VVWRA.
8.
Section 2.5.3 STP Percolation Ponds
The text has been modified accordingly.
9.
Section 2 6 Summary of Site Risks
A table (Table 1) has been added to Section 2.5.1 of the document which listS the
maximum concentrations. frequency of deteCtion. and mean concentration of
detected compounds based on the data available for the 1988 RIIFS. A
monitoring plan will be included as part of the RDIRA.
10.
Section 2.6 SummaI)' of Site Risks
A statement has been added to the text to state that the OU 1 risk assessment was
performed.prior to validation of the available data. The data used for this risk
assessment could not all be validated. as reported in a Validation Summary Report
(JMM. 1993c); however. validated date will be collected to support the
conclusions of this risk assessment as part of the ongoing Investigation in Support
of RDIRA (Section 2.12). .
11.
Section 2.6.1 Northeast Di&posal Area
A summary table (Table 2) has been added to the document which presentS the
cancer risk and hazed index calculations.
12.
Section 2.6.1 Northeast Disposal Area
A discussion of the environmental risk assessment. identifying endangered species
that may be affected. has been added to the text.
13
Section 2.7 Description of Alternatives
The text in Section 2.2 (Site History and Enforcement Activities) has been
modified to clarify that technical information supporting each alternative is
presented in RI (JMM. 1992) and the FS (JMM. 1993). A summary table (Table
2) has been added to the document which presentS the cancer risk and hazed index
calculations including ingestion. inhalation. and dermal exposure to contaminantS.
The estimated volume of contaminated water has been added to Section 2.5.1
(Northeast Disposal Area).
Section 2.7 is intended to summarize the alternatives that were evaluated in the
Final FS (JMM. 1993). However. Section 2.6 (Summary of Site Risks) discusses
the risks associated with OU 1. .
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14
Section 2.7 Description of Alternatives
The text in Section 2.5.1 has been modified to state that the contaminated
groundwater in OU 1 is not a RCRA hazardous waste as defined in 22 CCR
Section 66261. Based on the reponed average TCE concentration of 47 I!gIl. the
contamination is well below the Maximum Concentration of Contaminants for
the Toxicity Characteristic (using TCLP procedure) of 0.5 mg/l. Additionally,
this value is well below the soluble threshold limit concentration (STLC) of 204
mgll for TCE.
15.
Section 2 7.1 No Action With Groundwater Monitorine
The text has been- modified to state the No Action alternative is included, as
required by the NCP. for comparison against other alternatives and will provide
no additional proteCtion of human health or the environment. Section 2.8.1
(Overall ProteCtion of Human Health and the Environment) provides additional
discussion of this issue.
16.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippin~. and
Percolation. " .
A discussion of appropriate deed restrictions has been added to Section 2.7.2.
17.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippine. and'
Percolation
The main components of each alternative has been presented in tabular fonn at the
beginning of Section 2.7. Deed restrictions have been included in this list
18 " Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippin~. and
Percolation
The intent of this ROD is to present the conclusions of the 1992 RI and 1993 FS
reportS which summarized previous work (i.e.. 1988 RIlFS) and were based on
previous data. The Final 1993 FS. which confonned to the guidance set forth in
the Guidance for Conductine Remedial Investieations and FeasibilitY Studies.
Under CERCLA (USEP A. 1988), arid provides technical support for these" .
alternatives, was approved by the regulatory agencies. Comparison of additional
alternatives at this juncture would mean perfonning a new FS. However, different
treatment alternatives may be considered as a result of the fmdings of the ongoing
Investigation in Suppon ofRDIRA now presented in Section 2.12.
Section 2.7.2 Alternative 2 - Groundwater Extraction. Air Strippine. and
Percolation
The text has been modified to indicate that the proposed 10 wells is an estimate,
the exact number and location to be detennined based on the efficiency of the
Phase I system.
BI-12
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26.
27.
RESPONSE TO DTSC COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
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20.
Section 2 7.2 Alternative 2 - Groundwater Extraction. Air Strippin~. and
Percolation
Tables 4 through 9 have been added to the document which present potential
federal and state ARARs. The text throughout the section has been revised to
clarify which ARARs will apply. .
21.
Section 2 8.1 Overall Protection of Human Health and the Environment
The intent of the discussion is to present the conclusions of the 1992 RI and 1993
FS reports which summarized previous work (i.e., 1988 RIJFS) and were based on
previous data. The text throughout the document has been modified where
appropriate to clarify this point Section 2.12 (Current Investigation Status) has
been added to the document which describes the scope of ongoing Investigation in
Support of RDIRA. Part of the focus of this study is to reassess the RAOs and
determine if system enhancement would be required. Additionally, a monitoring
plan will be included as part of the RDIRA. .
22.
Section 2.8.1 Overall Protection of Human Health and the Environment
23.
See response to Comment 21 above.
Section 2.8.2.1 Chemical-SpeCific ARARs
24.
Under NESHAPS, there are no emission standards for TCE or air strippers;
therefore, this would not be ARAR.
Section 2.8.2.2 Location-Specific ARARs
25.
This ARAR has been incorporated into Table 8 (Identification of Potential State
Location-Specific ARARs). .
Section 2.8.2.3 Action-Specific ARARs
Requirements for Tank Systems, Miscellaneous Units, and Fixed Treatment Units
are covered under 22 CCR Section 66260 et seq.. which is summarized in Table 9
(Identification of Potential State Action-Specific ARARs).
Section 2.8.8 State Acceptance
The text has been modified to reflect the state's conditional._approval of
Alternative 2. Additionally, it references Section 2.12 (Current Investigation
Status) which provides a schedule for the Investigation in Support of RDIRA.
The text in Section 2.8.3 (Long-term Effectiveness and Permanence) has been
expanded to clearly state that VOC emissions will be monitored based on influent
and effluent concentrations from the treatment system. Note that this monitoring
has been occurring for the ongoing Treatability Study and the calculated mass of
VOCs emitted has been well below the San Bernardino County APeD stated limit
of lib/day. Emissions will continue to be monitored in this manor.
Section 2.8.9 Community Acceptance
BI-13
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29.
30
31.
RESPONSE TO DTSC COMMENTS
DRAFT RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR-FORCE BASE
28.
The text has been modified to reflect the current status that after the release of the
Proposed Plan, which presented Alternative 2 as the preferred remedy. the
community did not express any significant objection during the public meeting or
public comment period.
Section 2.9 The Selected Remedy
The text has been modified to indicate that the detailed evaluations of alternatives
are presented in the FS (JMM, 1993) (which brought the 1988 RIIFS up (0 date
with current CERCLA guidance and summarized previous work). Terminology
which implied that recent monitoring data was incorporated in this analysis has
been removed.
Section 2 9.1 Selection of the Preferred Alternative
The text has been modified accordingly.
Section 2.9.1 Selection of the Preferred Alternative
The text has been modified accordingly.
Section 2.9.3 Cost Analysis
The tabulated costs for the preferred alternative have been presented as Table 12.
Section 2.8.7 now references the FS (JMM, 1993) for detailed cost analysis.
BI-14
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DRAFf FINAL ROD COMMENTS /RESPONSES
-------
~1IT..'f;
-T - iI'.
i A,
\Sf
~..( ~';I
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
. REGION IX
. 75 Hlwthorne Street
Sin Francisco, CI. 94105-3901
February 17, 1994
Ms. Denise Caron
Chief, Environmental Programs
AFBDA/OL-C, Building 321
George Air Force Base, CA 92394-5000
Dear Ms . Caron:'
We have reviewed the draft final Record of Decision for
Operable Unit 1 and are providing the attached comments. These
comments were pr~pared by Danita Yocom of EPA's Office of
Regional Council~ .
If you have any questions please contact me' at (415) 744-
2409.
Sincerely,
. '.-.
. ~ ..\
~_/
Brian SWarthout
Remedial Project Manager
cc:
Jay Cass, . RWQCB
Emad Yemut, DTSC
Greg Little,JMM
Prinrftl on RrcydId Prqwr
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
75 Hawthorne Street
San Francisco, CA 94105
February 17, 1994
MEMORANDUK
Subject:
Draft Final Record of Decision ("ROD") for OU-1 at
George Air Force Base ("GAFB")
Danita D. Yocom, Assistant Regional Counsel
Prom:
To:
Brian Swarthout, Regional Project Manager
This memorandum summarizes my comments on the above-
referenced draft final ROD.
I have a few general comments with respect to applicable or
relevant and appropriate requirements ("ARARs") in the. ROD.
First, the tables which identify ARARs for the alternative
remedies should correspond to the narrative portion of the ROD
which describes why such environmental laws are ARARs with
respect to the alternative. remedies discussed in the ROD. The
tables are not a substitute for a narrative discussion of the
ARARs. I understand that there may have been some confusion as
to what Tables 4 through 10 were to include, and that therefore,
the tables show potential ARARs from the RIfFS. The tables for
. the final ROD should only reflect ARARs which apply to the three'
alternatives considered in the ROD. Enclosed as attachment A is
a list which summarizes the ABARs discussed in the narrative.
This leads to my second comment which regards the inclusion
of additional ARARs in the draft final ROD. As any ARARs
analysis requires specific consideration of the manner in which a
proposed ARAR applies to the particular circumstances at a site,
the NCP requires that ARARs be identified in a timely manner.
Given that federal facilities are under considerable time
pressure to complete decision documents for cleanup, it is
inappropriate to raise additional ARARs for inclusion at this
time as ARARs often raise complex, and sometimes conten~ious,
issues regarding interpretat~on of the law in question.
For example the draft final ROD (in section 2.8.2.3, at page
2-37) adds Title 23 as an ARAR with respect to contaminated
groundwater. I understand that EPA and the State are discussing
whether Chapter 15 of Title 23 is an ARAR at other fed.eral
facilities, and that such discussion also includes issues
regarding the scope and interpretation of 23 CCR .S2511(d). In
-------
particular, the Regional Board is asserting, inter slig, that if
the limitations on the exclusion in S2511(d) are present, all
requirements of Chapter 15 must be implemented; this would
include cleanup to background. Naturally, the results of these
discussions would affect the implementation of Chapter 15 at OU-
1. .
Additional information is needed in order to determine (i)
whether a designated waste is present at OU-1, (ii) whether the
exclusion in S2511(d) applies, and (iii) if the circumstances at
OU 1 come within either section, the interpretation of the
requirements imposed by either section. For example, what
constitutes a "designated waste"? ~s it groundwater or extracted
groundwater? If extracted groundwater is a designated waste,
does it remain a designated waste after treatment? If there is a
designated waste, how will 23 CCR 52522(b) (the requirement that
designated waste be discharged into Class I or Class II waste
management units) affect the remedial alternatives? (E.g. would
new percolation ponds be constructed?) Would such designation
have any other impacts on the way in which the al ternati ves are
implemented? How is the classification of certain media as
designated waste-to be read in conjunction with 23 CCR S2511(d}?
In light of the numerous issues which must be addressed, we
do not have sufficient time to adequately address this issue. I
, suggest deleting the language at page 2-37 and adding at the end
of the ARARs section the following language:
"In its comments to the draft ROD, the state requested that
the Air Force include 23 CCR 52522, which relates to designated
wastes, as an ARAR in the ROD. The , Air Force, EPA and the state
acknowledge that EPA and the state have scheduled discussions to
resolve whether sections arising under Title 23 of the California
Code of Regulations are ARABs and, if so, the interpretation of
such sections. . The Air Force, EPA and the state agree that while
23 CCR 52522 will not be listed as an ARAR in the ROD for reasons
relating to timeliness, the Air Force agrees to implement the
remedy in conformance with the determinations made in .such forum
in order to meet assure that ~e remedy is protective.
Finally, please be advised that, while I referred to the
State's comments in interpreting additions to the text, I did not
respond to the State's comments which were attached as .
appendices. Consequently, my. comments do not address issues that
the state raised in their comments which were not addressed in
the text of the ROD. .
-------
Attachment A
ARARs Identified in the Narrative portion of the ROD.
(A)
Chemical Soecific ARARs.
( 1)
Federal:
Safe Drinking Water Act/Federal MCLs/MCLGs (42 usc 53009;
40 CFR Part 141). Relevant and appropriate.
(B)
Location Soecific ARARs.
(1)
Federal:
Endangered species Act.
Applicable. .
(C)
Action Soecific ARARs.
(1) Federal:
RCRA 40 cn- 263.
Relevant and appropriate.
RCRA 40 cn 264.110 -264.120.
Relevant and appropriate.
RCRA Subtitle C (off-site disposal).
appropriate.
Relevant and
(2)
state:
22 CCR 66262.30 - 66262.33.
Relevant and appropriate.
22 CCR 66264.
Relevant and appropriate.
22 CCR 66262.10 - 66262.57
Relevant and appropriate.
Resolution 68-16. Relevant and Appropriate~ While the
Porter-Cologne Act is not the AllAR, it could be listed in
the citation to Resolution 68-16 as the authorizing statute.
The Basin Plan may also be added as a citation to this ARAR.
Mojave AQMD Rules enacted pursuant to the Mulford-Carrell
Air Resources Act (Health and Safety Code 539000-44563;
Title 17, part III). Relevant and Apropriate. There should
be a cite to the Mojave AQMD rule that exempts air strippers
from emission controls so long as the TCE- emission remain
below llb. per day. '!'he rule is the ARAR and the Act is the
authorizing statute. '!'he Rule (with citation) should appear
in the standard column and Mulford-Carrell may appear in the
in the citation section as the authorizing statute.
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FEB-17-1994 16:56
F!U1 RLD:E REG I ~ 6E
TO
9151097S3412
P.B2
Statp of California
Mernorandum
To:
Emad Yemut
Department of Toxic Substances Control
Date: Feb. 17. 1994
~4~kr
Jehiel Cass, Associate WRCE
CaJifomia Realon.' Water Quality Centrol Beard
LahOntan Region
Vietorville Branch Office
16428 Civic Drive. Suite 100
Victorville. CA 92392.2359
(619) 241-6683
Subj.ct~OMMENTS ON DRAFT FINAL RECORD OF DECISION (ROD) t OPERABLE UNIT ONE (OU-l) t
GEORGE AIR FORCE BASE, SAN BERNARDINO COUNTY
From:
Regional Board staff has completed review of the draft final ROD. Montgomery
Watson, consu1tants to George AFB. did an excellent job in addressing our
comments on the draft ROD.
Attached you willf1nd a short list of items that Board staff beHave are
necessary to make the ROD technically correct and adequately incorporate State
Applicable or Relevant and Appropriate Requirements. .
ene: Attachment A
cc:
Gordon Hannings, Montgomery Watson
Denise Carort, .GAFB
Brian Swarthout, US EPA
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FEB-17-1994 16:$
FIU1 RI...OCB REG I (}.I 6B
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9151097S3412
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A.ttachment A
: Draft Fina1 Record o( Decision, OU-l .
Reg;onal Board Staff Comments
Annotated Edition Page References
1.
. ',r~~~'~:?~'j.'~~':;~b"'.'..'~'~?i~-i~'" '~'.r:".-'~"~"~..
are not. used
Page 2-19, 3rd par, RThese well$
for potable waterA
This is necessary to indicate to the reader that the production wells at
Vi ctar Val 1.y Waste Water Treatment Pl ant are intended to be potable water
wells. Board staff understand that bottled water i$ currently purchased
for employees.
2.
~:.~:[~~JltI~ji:!F'~~'~'~','.~t~"-;,;,:,'~:;-j~~-'..'.:'
3.
2-}9, 4th par, -TCE present in the a.quife
II1II was estimatedM
This is necessary for the reader to understand that the total
TCE mass in the aquifer may be greater.
Figure 9, add to Title box:
estimate of
..&~~f~L.-~.~';.
4;
. -
Tne reader should understand that more extraction wells are planned, but
not shown. .
Tabl. 9, add to reflect page 2-37 statement:
W81t. Of.poeal to
Land a88Ul.tf~
25 CCR, See.
2510 et Rq.
btlbLf Ihn atat.
r...,llclona ~h.
dltPOUL of ..ft. to
land, fneludla criteria
for "'.nned VIae.
~lIcable to any
_CI CStspoeecS ~o
Land 8UdI .. weL I
cuutngs etc.
5.
The potential list of Applicable or Rehvant and Appropriate Requirements
(ARARs) should reflect the document. See page 2-37 and comment 9, below.
Table 10, reverse the last two items in the description ca1umn.
6.
These two statements are in reverse order from what was intended.
Table 11, add to footnote 9. the following sentence (or something like
it):
r.ij.~..~...~.ii~;~f~I~~l~~lIi~~lj~l«tfl~.~'!~ltall~t
The ROD must' indicate that part of the US EPA Regional Administrators
decision regarding the dispute was that the system must be operated to the
MaXimum ext.~ feasable without adding ne. treatment equipment to achieve
the goal. : .
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~1'7-1994 16:57
AD1 RL..OCE REG I (t.I 68
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915109'753412
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7.
8.
I
Table 12, see item 6, above. Add the same footnote.
I
Page 2-49, second bullet. add something like: "minor modifications may be
necessary if ~the goal can not be met. a .
I
Page 2-51, add after 1st par.:
9.
I
This is necessary to fully address our comments on the draft document that
all non-hazardous waste disposed, resu1ting from either investigAtions or
remediation will be disposed in accordance with State requirements.
Add to the appropri ate section that receiving water qual1ty wi 11 be
determined for the permanent disposal sit8 prior to permanent disposa1.
,10.
This requirement was previously agreed to by the Air Force.
jc13/rodcDm.not
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TCTA... P. 04
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. FEB-25-1994 17:31
FIU'1 R!..OCE REG! CN' 6B
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9151B9'i'53412
P.02
MEMORANDUM
To:
Denise Caron, George AFB
Brian Swarthout, US EP A IX
Emad Yemut. DTSC
Gordon Manning, Montgomery Watson
Jehle! Cass. Regional Board ~
Febnwy 25. 1994
George Air Force Base. Operable Unit One ROD
From:
Date:
Subject:
US EPA, Region IX and Lahontan RegionaJ Board staff have completed discussions
regarding appropriate language for the £inaJ OU-! ROD.
We believe that the attached changes should be made to the ROD. Page numbers refer to
the annotated version of the draft final ROD. The ROD should be finalized for signature.
If necessary, a conference call may be arranged on Monday to discuss the changes.
jc13/oulroda
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Additions to Record of Decision, Table 7, (Revised 2/25/94)
Standard, Criteria, etc. Citation Description
Comment
Water Quality Control Plan for the
LabontAn Region (Basin Plan)
Water Quality Control Plan for Ibe
Lahontan Region (Basin Plan)
Sources of Drinking Water Policy
Water Quality Control Plan for the
Lahontan Region (Basin Plan)
Porter-Cologne Water Quality
Control Act
Water Quality Control Plan for the
Lahontan Region (Basin Plan)
Page 1-5-3, item d
Page 1-5-3, Item f
Slate Water
Resources Control
Board Resolution 88-
63
Table 2-1, Beneficial
Uses of Ground
Waters fn Upper
Mojave Hydrotogic
Unit (628.20)
California Water
Code Section 13267
Page 1-7-4, hem 2
Prohibits the discharge of waste water except to the
designated disposal sites.
Requires the collection, transport, treatment or
disposal facilities to be adequately protected from a
100-year flood.
Defines all ground and surface water as existing or
potential sources of drinking water unless total
dissolved solids are greater than 3,000 ppm, the
well yield fe less than 200 gpd from a single well, or
ground water Is unreasonable to treat wing best
management practices or best economically
achievable treatment practices.
Defines beneficial uses for ground waters beneath
George AFB as: municipal, agricultural, industrial
service and freshwater replenishment
Requires any person discharging waste to submit
technical and monitoring reports, considering the
need and benefits to be obtained.
Applicable to remedial
alternatives involving the
discharge of treated or
partially treated water.
Applicable to remedial
alternatives with treatment
facilities.
The Identification of the OU-
1 aquifers affected by TCE as
potential drinking water
source* forms the basis for
•election of MCLs and
SWRCB Resolution 68-16 as
specific ARARs lo maintain
existing high quality waters.
Provides the basis for
development of reporting,
notification and monitoring
programs during the RD/RA
phase.
1
5
jc!3/oulrodta
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FEB-25-1994 17:32
FIU1 R!.OCB REG I Ct.J 6B
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915112197S3412
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~ -.
Lzusert ~ 1:11.. sect:ton 2.8.2.:1 at 1:be -OJ)
Drink.1ng .ater i. caas1Otu:e4 1:0 be -. Idgbest ~ total ase a~
r888diat:iOD ~ dZ'~ va~ 8tand8rda arto=- the ~.ate8t '
level of protecticm aDd cleanup. A8 required ~ 1:!1e Col1r0ftl1a
Port.er-COlGCJQ8 .&~ Qwll1~ Act, 1:.he Mglanal QQaJ.ity Control
Board LahOl1ton Region def1D88 the beD8ficial ~ ~ various
water :bodiea tor the Naja... 3U.ver _sin. Va1:8r bOC11e8 ID1d tbeir
ba'aaficdal U888 ... pr888J1tec1 in t:I18 IJabCmton Ba81D Plan. The
hain Pl.aD c1a88.1~~. aquirera in tile 00-1 area t:o haw .WItRDCJ
or ~lAl bezaericial '1'" as 8CII12"C.. of drinking' vater-. '1'h1s
N9!0JI41 plan hA. be- p:'CIIInIlptecl ad ponic:nm 1:b8reot' are AKARs
wii:h reapeot. to CO 1. 'lb. iAeMU:l.aaUon o~ the bCef~1&1 uses
of tbe ~0IIDdwat:c' at OC' 1 ..,.es. u th8 JMBis. tOI: ..leat:ion of
t:h. federal MCL for. 'rCB tor tb8 ~n1;R cleanup aDd the
..lection Df ..xi8ua ~ G~t:1cma for.di8C:ba.rgea ~
.~fJ.Q...t8 ~ 1obo pc:'CI01Art1.oD pcm118 purllUaDt1:O "Ol~on 68"16
.. d.~in.a by i:be d.i8pu1;e resolutJ.on prooesa. .
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. FEB-25-1994 17:33
FR:t1 ~ REGIc:N 6B
915109?S3412
TO
Remove ~e ~!rat: pu-aFapb i.n Sec:tJ.OJl a. 8.2.3 WIder troat:lleDt
ABA8IJ wb1c:b. beIJ.1na "UthoWJh ttIe aani:&JI.1nat8d ~ur &1: 00-1,
is not c1...1tied...-
%n..ne .. t:!ia8 :eil:8t: CICIIp:J.8bt ~graph em pa98 ~-!S1.
Z!'A aud t.btt 5'ta't. bllY8 lICbada1.eG G18CQ8810D8 -eo resc~ ve Whethcr
88Ci:ion. .r~. undN' a:aap1;a" 115 ot ~J.t;1. 23af =- caLUarn.1A
Code ot IWt9Ulat1ans (.CbII~.. 15") an ARAIt.C u4, ~ 80, tbe
8Cop8 aad intezpz:'e~:l.OD o~ Cba~ 15. c:ou.,u~YI Oe
partiea ha..,e Dot d8tel:II1Aed wb8~ Dr not Cba.P~ 25. 18 an'.ARAIC
for ~ puz'pOIiI88 o£ w.. JitOI). :ra. au 1'aI:v8, 8PA 8IIcI 1:110 State
bav. .~884f bowe¥8Z", ~~ t:ba Air .oroe ,,1.11. 888))1. csrU11Dp.
ClQ.t:~J.n.sJ. aDd 1Wd.~ vaat:88 ~~iQ8 wIaetIa8Ir 1lUClava8t:- are
luLzucloWl v.ate8 .. cht1Ded in 22 CCR ~On' ."00 or. 4es:l.gnat:e4
wa.bt8 .. detined 111 23 cca S8Gtoioa 2N2. U 811= saap1.1ftf
inticet:08 't:hat i;JaI ...-te8 are laa8&rdoua .asc., ~. ba8&J:~~. '
1II'a.~" w:Ul .. cU..~ =1)' 1:0 C1u8 .1 vaa1:8 ...pmant ~t8.
%f 8Uah 8IIIIP11D9 1DdJ.aatea 'tAB 1:b8 .aRes are de814N1te4 w&Ste8,
ouob cie81g'J1&toecl ..... rill be ItI...ceargad 01111 'to CJ.... I or
C1- U: vaaa I18ft898118At \lD1t8.
P.es
TDTR. P. as
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RESPONSE TO USEPA COMMENTS
DRAFT FINAL RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
General Comments
Tables presenting potential ARARs have been revised such that only specific
ARARs mentioned in the text have been included.
The USEPA and the Lahontan RWQCB have not resolved whether sections
arising under Title 23 CCR are ARAR for au 1. Therefore, the paragraph in
question (Section 2.8.2.8, first paragraph in Treatment ARARs) has been removed
from the text and the language presented by the Lahontan RWQCB (February 25,
1994) has been incorporated.
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B2-1
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I
RESPONSE TO LRWQCB COMMENTS
DRAFI' FINAL RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
1.
The text has been modified to state that the wells "were, but are not currently used'
for potable water."
The text has been modified accordingly.
2.
3.
The title of Figure 9 has been modified to clarify that it shows Phase I of the
extractionltreattnent system. The text now states that because the exact number
and location of extraction wells for Phase n is pending determination of Phase I
efficiency, they are not shown on Figure 9.
Table 9 has been removed from the ROD. Potential ARARs are no longer
presented. The USEPA and the Lahontan RWQCB have not resolved whether
this is an ARAR for OU 1. (See Additional Comments [February 25, 1994]
below)
4.
5.
Table 10 has been removed from the ROD. Potential ARARs are no longer
presented.
Table II has been removed from the ROD. Potential ARARs are no longer
presented. -However, a similar footnote has been added to Table 8 (previously
Table 12, see Comment 7)
6.
7.
A footnote has been added to Table 8 (previously Table 12) to state that "'The
USAF will seek to treat the discharge to attain a level of 0.5 ~gIl TCE as
measured at the percolation ponds. This level is a nonenforceable goal. The
USAF may make minor modifications, as necessary, to operate the treabnent
system at the maximum efficiency in an effort to reach the goal." This is
consistent with the language used in the text. .
The text has been modified to state that ""the USAF may make minor
modifications, as necessary, in an effort to reach this goal." This is consistent
with the language used in response to Comment 7.
8.
9.
This comment has been addressed by an additional inset provided by the Lahontan
RWQCB on February 25. 1994 (see below).
Section 2.12.1 (Additional Investigations) currently states that four rounds of
groundwater monitOring has occurred at the four wells ins~d around the STP
Percolation Ponds. Additionally, Section 2.5.3 (STP Percolation Ponds) states
that the STP Percolation Ponds will continue to be monitored for nitrates on a
quarterly basis.
10.
Additional Comments (Dated FehrnaQ' 25. 1994)
The three inserts provided by the Lahontan RWQCB (two inserts for Section
. 2.8.2.3 and one for Table 7 [previously Table 6]) have been added as suggested
with minor editOrial revisions. .
B2-2
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RESPONSE TODTSC COMMENTS
DRAFI' FINAL RECORD OF DECISION, OPERABLE UNIT 1
GEORGE AIR FORCE BASE
General Comments
DTSC had no comments for revision to the Draft Final ROD.
B2-3
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