United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R09-91/067
August 1991
&EPA Superfund
Record of Decision:
Castle Air Force Base, CA
-------
50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.'
EPA/ROD/-R09-91/067
3. Rociptonrs Accossion No.
4. Title and Subtitle
SUPERFUND RECORD OF DECISION
Castle Air Force Base, CA
First Remedial Action
5. Report Date
08/12/91
7. Author(s)
8. Performing Organization Rept No.
9. Performing Organization Name and Addreaa
10. ProjecVTaak/Work Unit No.
11. ContractfC) or Grant(G) No.
(C)
(G)
12. Sponsoring Organization Name and Addresa .
U.S.. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report ft Period Covered
800/000
14.
15. Supplementary Notes
16. Abstract (Limit: 200 words)
The 2,777-acre Castle Air Force Base is a Strategic Air Command training base 6 miles
northwest of the City of Merced in Merced County, California. Land use in the area
is predominantly agricultural. Several irrigation canals and laterals are located
within 1 mile of the base including Canal Creek, which borders the base on. its
southwest boundary and receives runoff from the base and'irrigated land downstream.
At least 20 agricultural wells are located within 3 to 4 miles of the site, and a
number of residential and municipal wells are located within 2 miles of the site.
Since 1941, the site has been used as a military air training base. Fire training
activities, as.well as aircraft and jet engine maintenance activities including metal
plating and processing, have occurred onsite. Both processes involve the.use of
fuels, solvents, and chemicals and have generated municipal and chemical wastes..
During routine well sampling, the State identified elevated TCE concentrations in
ground water in the shallow aquifer beneath and south of the site. In 1984, the base
was required not only to implement remedial measures to correct this identified
contamination but also to prevent future ground water degradation from waste
discharges. The site has been divided into operable units (OUs) for remediation.
(See Attached Page)
17. Document Analysis, a. Descriptors
Record of Decision - Castle Air Force Base, CA
First Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (benzene^ PCE, TCE)
b. Identifiers/Open-Ended Terms
c. COSATI Held/Group
18. Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
54
22. Price
(See ANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
-------
EPA/ROD/R09-91/067 ., ' . ,
Castle Air Force Base, CA- - . '.'.
First -Remedial Action - . . . ~
Abstract (Continued) . . . " , -
This Record of Decision (ROD) provides an interim remedy, for the main TCE plume, as OU1.
Future RODs will address remaining soil-and ground water contamination. The primary
contaminant's of concern affecting the ground water are VOCs including benzene, PCE, and
TCE. ; - . : :'',. " , " .. , ' -.
The selected, remedial action for this interim-remedy includes onsite .pumping and
treatment of ground water using air stripping, followed by natural biological enhancement
to accelerate the release and degradation of hazardous constituents in the saturated
zone; reinjecting the treated ground water -qnsite to maintain hydraulic control and avoid
depletion of the aquifer; treating emissions from the air_stripping process using ^
granular' activated carbon; and treating the emissions abatement.unit by onsite steam ,
regeneration, and disposing of the liquid condensate offsite. The estimated-present'
worth cost for this remedial action is $28,445,000, which 'includes an annual O&M cost of
$2,744,000. ' '' , - . . , '
PERFORMANCE STANDARDS OR GOALS: Ground water clean-up goals based on MCLs' and risk .
levels will be established in -a subsequent ROD. . * .- . - . .
-------
RECORD OF DECISION
INTERIM
OPERABLE UNIT No. 1
CASTLE AIR FORCE BASE
CALIFORNIA
August 7,1991
-------
! TABLE OF CONTENTS
* - .
( PAGE
LIST OF TABLES AND FIGURES '.. ii
| . 1.0 DECLARATION FOR THE RECORD OF DECISION 1-1
2.0 SITE DESCRIPTION, SITE HISTORY, COMMUNITY RELATIONS 2-1
[ 3.0 SCOPE AND ROLE OF THE OPERABLE UNIT 3-1
4.0 SUMMARY OF SITE CHARACTERISTICS . 4-1
| 5.0 SUMMARY OF SITE RISKS 5-1
6.0 DESCRIPTION OF ALTERNATIVES .. 6-1
| 7.0 COMPARATIVE ANALYSIS OF ALTERNATIVES 7-1
8.0 THE SELECTED REMEDY 8-1
9.0 STATUTORY DETERMINATIONS .... 9-1
10.0 RESPONSIVENESS SUMMARY 10-1
dA:ENG:9327-TOC/061991
-------
LIST OF TABLES
TABLE TITLE
.4-1 Summary of TCE Detected in Groundwater for Main TCE Plume
4-2 Organic Compounds Detected in MTP Groundwater Sampling Rounds 1, 2, 3, 4
4-3 Metals and Ions Detected in MTP Groundwater Sampling Rounds 1, 2, 3, 4
7-1 Comparison of Cleanup Alternatives . .
7-2 Estimated Maximum Annual Waste and Emissions for Remedial Alternatives
7-3 Potential Federal Applicable, or Relevant and Appropriate Requirements for the
Main TCE Plume (Operable Unit No. 1) .
7-4 Potential State Applicable, or Relevant and Appropriate Requirements for the ,
Main TCE Plume (Operable Unit No. 1) -
, 8-1 Alternative I - Present Worth Analysis
8-2 -Alternative I-Present Worth Values in 1990 Dollars
' * ' .," 1 *
'..-' LIST OF FIGURES ,
FIGURE . . TITLE
1-1 Main TCE Plume, Operable Unit Nq. 1
' »> ' .''''.
2-1 Major Population Centers Near Castle AFB
2-2 Regional Drainage Map
.^A:ENG:9327-TOC/061991
-------
t ' .
\ INTERIM OPERABLE UNIT NO. 1
CASTLE AIR FORCE BASE
> CALIFORNIA
1.0 DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Castle Air Force Base
Merced County, California
STATEMENT OF BASIS AND PURPOSE
This decision document represents the selected interim remedial action for Operable Unit
No. 1 at Castle Air Force Base, which was developed in full accordance with the National Oil
and Hazardous Substances Pollution Contingency Plan (NCR) as well as the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by
the Superfund Amendments and Reauthorization Act of 1986 (SARA).
This decision is based upon the Preliminary Site Characterization Report (PSCR) (IT
September 1990) and the Feasibility Study (FS) and the Proposed Plan (PP) for Interim
Operable Unit No. 1 (IT, December 1990). All of these documents are available in the
Administrative Record for Castle AFB.
The United States Environmental Protection Agency and the State of California agree on the
selected remedy.
ASSESSMENT OF THE SITE
The Main Trichtoroethytene (TCE) Plume, defined as TCE above the maximum contaminant
level (MCL) of 5 ppb in the shallow aquifer beneath the Base, contains TCE which, if not
addressed by implementing the selected interim remedy in this Record of Decision (ROD),
may present an imminent and substantial endangerment to public health and welfare. The
terms 'Main TCE Plume" and "MTP" are used throughout this document to designate a plume
that contains a variety of contaminants. TCE has been the most prevalent and mobile of the
contaminants and can thus be used to determine the extent of groundwater contamination.
1-1
vlA:ENG:9327-1/070191
-------
DESCRIPTION OF THE REMEDY
. ... . . ., ,, ..__ ^
The remedy described in Interim'Operable Unit No. 1 represents an early effort to extract and
treat the "contaminated groundwater under the Base. This operable unit will be succeeded by
subsequent operable units which will address groundwater contamination on and off Base
and, ultimately, an overall Base ROD which will assure that all contamination, including any
contaminated soils, is addressed. , '
*> ' v ' ' * *'* ' '
'*'" ,,"", ' 1, I' ' *"i . '-.
'--1. ..'=' ' ' V "' ". .'"'' ':" ' " '
The Main TCE Plume (MTP), is one of the sites currently being investigated at the Castle Air
Force Base. Operable Unit No. 1 (OU-1) addresses the principal MTP groundwater threat
..; .' '.'''.'*'
posed by TCE concentrations in the shallow aquifer groundwater beneath the central portion
"."> , * . ,".'. J
of Base or Main Sector of the Base and the contiguous areas to the south and southwest of
the Base (Figure 1-1). The shallow aquifer in which the plume occurs is also used as a ''
drinking/or irrigation water source for some off-base residents. -
' '"'-, ' ,- ' *~\
The interim remedy addresses the remediation of groundwater contamination by eliminating or
reducing the risks posed by the site, through treatment and engineering and institutional
controls. The final remedy will be selected in a subsequent ROD.
The major components of the selected interim remedy are:
- Pumping groundwater from a series of shallow aquifer extraction wells to maintain
hydraulic control of the plume and begin reducing residual TCE concentrations.
Surface treating the extracted groundwater by air stripping to allow the return of
water to beneficial use (resource recovery). . .< .'.
Reinjecting the treated groundwater back to the shallow aquifer to assist in
maintaining hydraulic control and to avoid depletion of the aquifer.
. Applying natural biological enhancement to accelerate the degradation of hazardous
- constituents in the saturated zone.
Abating the air stripper emissions with granular activated carbon to avoid degrading
ambient air quality. The abatement unit would be steam regenerated on site and
the liquid condensate would be disposed off site at an EPA-RCRA approved ''
recycling facility.
. ; . .. . 1-2
MA:ENG:9327-1/070191
-------
I DECLARATION
, This interim action is protective of human health and the environment, complies with Federal
i and State applicable or relevant and appropriate requirements for this limited-scope action and
. is cost effective. Although this interim action is not intended to address fully the statutory
i mandate for permanence and treatment to the maximum extent practicable, this interim action
does utilize treatment and thus is in furtherance of that statutory mandate. Because this
i action does not constitute the final remedy for the operable unit the statutory preference for
remedies that employ treatment that reduces toxidty, mobility, or. volume as a principal
I element, although partially addressed in this remedy, will be addressed by the final response
action. Subsequent actions are planned to address fully the threats posed by the conditions
\ at this operable unit. Because this remedy will result in hazardous substances remaining on
site above health-based levels, a review will be conducted to ensure that the remedy
continues to provide adequate protection of human health and the environment within five
years after commencement of the remedial action. Because this is an interim action ROD,
review of this site and of this remedy will be ongoing as Castle AFB continues to develop final
remedial alternatives for the Main TCE Plume operable unit and the overall Castle AFB site.
Colonel Michaeljy Kehoe
Chairman, Environmental Protection Committee
Castle Air Force Base
W. McGovem
Regional Administrator
United States Environmental Protection
Agency, Region DC
AUG 2 3 1991
^^^^^^^^^^^^^MV^^MV^^^H^^M
ValSiebal
Regional Administrator
California Department of Health Services
Toxic Substance Control Program, Region I
1-3
MA:ENG:9327-1/070191
-------
I I « 1
1314 *
\
CAS
BLOC. 1335 \ \ \
RQNJECT10N
E \M
STREET '(
PROPOSED OU-1 EXTRACTION WELL
PROPOSED OU-1 REINJECTION WELL
BLOC. 1260
BUILDING WHERE TCE WAS
HISTORICALLY USED
(ENGINEERING SCIENCE. 1983)
PROPOSED OU-1 PIPELINES (ARROW
INDICATES DIRECTION OF
-175-
?-
TOPOGRAPHIC CONTOUR (FT. MSL)
APPROXIMATE TCE MCL BOUNDARY; TCE
CONCENTRATION WITHIN BOUNDARY IS 25.0 ppb.
(QUESTION MARKS IMPLY UNCERTAINTY)
HISTORICAL DIRECTION OF CROUNDWATER
MOVEMENT. AUGUST. 1986
DIRECTION OF GROUNDWATER MOVEMENT.
JULY. 1989
SCALE
1000
2000
3000 FEET
REFERENCE: UCCS TOPOGRAPHIC QUADRANGLES:
ATWATER. CAUF. DATED: 1960. REVISED 1967
AND WINTON. CAUF. DATED: 1961. REVISED 1987.
FIGURE 1-1
MAIN TCE PLUME
OPERABLE UNIT N0.1 (OU-1)
PREPARED FOR
CASTLE AIR FORCE BASE
CALIFORNIA
INTERNATIONAL
TECHNOLOGY
CORPORATION
CA-UTPU2(CAC71
-------
2.0 SITE DESCRIPTION, SITE HISTORY, COMMUNITY RELATIONS
SITE NAME. LOCATION. AND DESCRIPTION
Castle AFB is a Strategic Air Command (SAC) Training Base located in Merced County,
California approximately six miles northwest of the City of Merced in the State of California.
Neighboring communities within six miles of the Base include Wirrton (Pop. 7,583), Atwater
(Pop. 22,585), Livingston (Pop. 7,103), and Merced (Pop. 50,000) (Figure 2-1). The Base
covers an area of 2,777 acres comprising runway and airfield operations, industrial areas,
housing, recreational facilities, and several noncontiguous parcels. In addition, two residential
off-Base housing annexes that total approximately 206 acres are located southwest of the
Base for housing of military personnel and their families. The site, the Main TCE Plume
(Operable Unit No. 1), consists of TCE concentrations above 5 ppb in the shallow aquifer
groundwater located beneath the central portion or main sector of Castle AFB and the
contiguous areas to the south and southwest of the Base (Figure 1-1).
The total relief across the Base is approximately 35 feet, ranging from 200 feet above mean
sea lev^l (MSL) at the northwestern comer to 165 feet above MSL at the southern boundary
comer. Relief within the Base boundaries is essentially flat
Land use within a two-mile radius of the Base is primarily agricultural. Crops grown in the
area consist primarily of almonds, peaches, and grapes. Several small dairies and a large
chicken farm are located to the east Open pasture lands are located to the north and east
Residential areas are located primarily west of the Base and include Base housing, trailer
parks, recently constructed residential suburban housing and rural farm residences.
There are no major surface water bodies (lakes or rivers) within five miles of the Base.
Domestic and agricultural water are supplied to the region by both groundwater wells and the
canals of the California Central Valley irrigation projects. A number of irrigation canals and
laterals (Black Rascal Creek) are located within one mile of the Base, the largest and most
significant is Canal Creek, which is controlled by the Merced Irrigation District Canal Creek
borders the Base proper on the southwest boundary (Figure 2-2). .In it's upper reaches
upstream from the Base, Canal Creek's flow is diverted for irrigation use. Downstream from
the Base, it receives runoff from the Base and irrigated land.
. >
I 2-1
[*w1A:ENG:9327-2/08p291
-------
The Merced Irrigation District operates at least 20 agricultural wells within three to four miles
of the Base. The City of Atwater, a number of private residences, and the Base operate
domestic water wells within two miles of the Base proper. A number of these wells were
abandoned due to TCE contamination. Under county code the residences were supplied with
bottled water or connected to new wells installed in the deeper confined aquifers. Other
residences whose wells were contaminated were furnished with granulated activated carbon
(GAC) filtration systems. The Base currently monitors approximately 18 off-Base private
residential wells on a regular basis.
* ' \
Wildlife in the area consists almost exclusively of jack rabbits, rodents, and birds (including
ducks and pheasants). The Base Is located in the historical range of three endangered
species. The Air force will have a biologist determine the presence or absence of these
species and also have a qualified agency determine the presence or absence of. wetlands.
Any surface area disturbance associated with the selected interim remedy is minimal and
should not have a significant impact on endangered species' habitats or wetland areas, should
they exist. There are no geologic faults identified below the Base. There are no historic
places located within three miles of the Base; nor does the Base lie within a designated
floodplain area. The average annual rainfall is approximately six inches.
The natural vegetation of the area consists primarily of salt-tolerant plants. Much of the soils
in the area contain.soluble salts and alkalis. The principal grass is salt grass (Distichlis
spicata). Trees such as the white oak, Fremont cottonwood. Oregon ash, box elder, and
willows are found along surface drainage areas.
The subsurface geology was Interpreted from over 150 monitoring wells and borings installed
during the remedial investigation and related to existing geologic literature. The following
generalizations about the geology beneath the Base were developed by relating cross-
sectional information and established stratigraphic units.
Sediments from about 0 to 95 feet below grade generally consist of complexly interbedded
sequences of alluvial deposits consisting of silty sand, silts, sands, and gravels. These
sediments are identified regionally as older alluvium. The gravels generally occur from about
70 to 95 feet below grade, and a high percentage of the gravels are concentrated in the Main
2-2
/A:ENG:9327-2/080291
-------
. ..
I Base Sector.. Hardpan, which is a thin layer of cemented soil, exists intermittently at depths
generally up to 10 feet below grade.
i ' . ','., " ' . "-.' ,''' . -
The older alluvium unconformably overlies a section composed predominantly of clay. This
I section was identified as the upper Turtock Lake formation. The contact between the clay
section and the overlying alluvial deposits appears to be erosional, and the thickest
I sequences of gravel in the older alluvium have accumulated in trough-like depressions into the
clay sequence. The clay sequence itself contains lenses of gravels, sands, and clayey sands
{ which are not correctable throughout the Base.
< . ^ i
{ The Turlock Lake formation is divided into an upper and lower unit. The upper unit contains
mostly finer-grained materials as described above; the lower contains sands. The lower
Turlock Lake,formation is a fairly continuous unit occurring from about 260 to 320 feet below
grade. These sands comprise the confined aquifer at the Base.
A deep regional aquifer occurs at about 650 feet below grade and is an important source of
water in the Modesto-Merced Area. The deep water-bearing unit is located in the upper part
of the Mehrten Formation. In the region of the Base, this formation consists of claystone,
siltstone, sandstone, and conglomerate. The vertical extent of the deep aquifer is unknown.
However, it would not be usable for beneficial purposes below the level where saline water
occurs, which is at about 1,200 feet below the ground surface.
SITE HISTORY AND ENFORCEMENT ACTIONS
Castle AFB was first used as a military air base in December 1941. The primary mission of
the Base through World War II was the training of Army air crews. The Strategic Air
Command assumed responsibility of the Base in 1946 and has occupied the Base with the
, . 93rd Bombardment Wing since 1947.
The construction of facilities at the Base has paralleled increases in the size of its mission and
the number of organizations in residence. Originally, the major industrial activities related to
aircraft maintenance centered in two hangers (Buildings 47 and 51} and the machine shop
(Building 52, later demolished in 1977), located on the southwestern side of Apron Avenue
(Figure 1-1). In 1955, an additional parking apron, hanger (Building 1550), and other
2-3
MA:ENG:9327-2/080291
-------
I
I
I
structures were added to support the newly arrived 456th Fighter Interceptor Squadron (Figure
1-1). Since 1955, Building 1550 has been used extensively for industrial activities. Buildings
1253 and 1260 were built in the late 1970s and assumed the majority of the industrial
activities previously performed in Building 52. These activities included metal plating and
processing, and jet engine maintenance.
Fuels (JP-4), solvents (TCE) and chemicals have been handled at the Base since the 1940s.
Municipal and chemical wastes have also been generated as a result of maintenance
operations, fuel management, fire training, and other Base activities. In the 1950s, expanded
industrial activities related to the SAC mission resulted in increased waste generation rates.
Prior to the current remedial investigation, several previous studies and investigations have
been performed to identify the historical use of chemicals, disposal, and/or leakage of these
chemicals to the soil, and the extent and impact of these chemicals on groundwater resources
in and around the Base. .
During the routine sampling of several Base and private wells in 1980, trace levels of TCE
were detected in the four Base water production wells. Seven test wells were then installed in
the shallow aquifer by the Base as part of the investigation. The results of this sampling
program prompted the Base to construct a new deep aquifer water supply well (PW-10) and
provided the impetus for the start of the Air Force's Installation Restoration Program (IRP) at
CastieAFB.
In 1981, Phase I of the IRP was conducted by Engineering Science. A total of 35 separate
sites were identified and organized into 26 sites or groups of sites having the potential for
environmental contamination. Recommendations for further investigative work called for 21 of
the 26 sites to be evaluated. The 21 sites were grouped into 15 investigation sites located in
the central part of the Base, the landfills, and the west and north flight line areas.
In March 1984, the California Regional Water Quality Control Board Central Valley Region
issued Cleanup and Abatement Order Number 84-027. This order required the Base to
provide users of the Base water supply and impacted off-Base wells with potable water
- 2-4
MA:ENG:9327-2/080291
-------
I
supplies. Also, the Base was required to implement remedial measures to correct identified
and future groundwater degradation from waste discharges.
In September 1984. the Phase II, Stage 1 field investigation was conducted by the Roy F.
Weston Company. This investigation included the installation of 27 monitoring wells and 11
unsaturated zone lysimeters into the shallow aquifer to sample for groundwater contamination
and to test for perched water zones. Two rounds of water quality sampling were conducted.
The Phase II, Stage 1 investigation determined that the soils and sediments at the Base had
not been significantly impacted at the majority of the sites investigated, but that the
groundwater needed further evaluation. This conclusion Is considered preliminary and will be
verified in the RI/FS for the overall Base. Significant TCE concentrations were detected in the
central or Main Base Sector. The Weston Phase II, Stage 1 Final Report recommended
additional investigations of the landfill, fire training areas, fuel spills, and disposal areas, and
for further evaluation of the TCE plume in the Main Base Sector.
Results of the Phase II, Stage 1 investigation and the Base's groundwater sampling program
indicated that TCE contamination may be present not only in the Main Base Sector, but also
in the South Base Sector and Disposal Areas Nos. 2 and 4. As a result of these findings,
Weston conducted a Phase II, Stage 2 investigation which included further evaluations of the
landfills; fuel spills and leaks, and selected disposal areas. The field investigation included
soil organic vapor (SOV) monitoring at 205 points, the drilling of 48 soil borings, the
installation of 27 monitoring wells and 5 lysimeters or perched wells, and conducting two
rounds of groundwater sampling. The Phase II, Stage 2 investigation was completed in April
1987, and the final report was issued in August 1988.
In 1986, the Air Force contracted Oak Ridge National Laboratory (ORNL), operated by Martin
Marietta Energy System, Inc., and their subcontractor, IT Corporation (IT), to support the
Phase IV-A IRP activities. These activities included conducting an SOV monitoring survey
and additional record searches. Approximately 374 SOV points on a 300-foot spacing were
sampled in the Main Base Sector to identify potential volatile organic contaminant source
areas.
2-5
MA:ENG:9327-2/080291
-------
Castle fell under the provisions of the Comprehensive Environmental Response Compensation
and Liability Act (CERCLA) when amended in 1986. Castle Air Force Base was then placed
on the National Priorities List (NPL) in 1987.
Results of all the above field investigations and data collection activities were used to develop
the current Remedial Investigation/Feasibility Study (RI/FS) program. The first phase of Rl
field activities was initiated by IT Corporation in August 1988. These activities included the
installation of 63 monitoring wells in the upper and lower zone of the shallow aquifer and 9
monitoring wells in the confined aquifer. In June 1989, the second phase of the Rl was
initiated and included conducting two rounds of quarterly groundwater sampling in 160 wells.
These wells included previously installed Base and Phase II wells, new Rl Base wells, and off-
Base private wells. In addition, 77 soil borings were drilled and sampled to assist in the future
characterization of various investigative sites. Two rounds of groundwater level
measurements were made, and 15 short-term (4-hour) pump tests were also conducted. The
second phase of the Rl field activities was completed in February 1990. The results of the
above field activities are described in the Preliminary Site Characterization Report, which is
the basjs for the Interim Operable Unit No. 1 Feasibility Study.
The third phase of Rl field activities began in March 1990 and continued through May 1991.
These activities included quarterly groundwater sampling rounds 3, 4, and 5, two 30-day .
aquifer pump tests, a preliminary site assessment of Castle Vista landfills, six water level snap
shots and development of work plan No. 2. Ongoing and near-term future Rl field activities
include the installation of approximately 50 VOC probes, continued quarterly groundwater
samplings, water level snap shots, and a sewer line TV camera survey.
In addition to Operable Unit No. 1 (OU-1), Operable Unit No. 2 (OU-2) will address remedial
actions on groundwater contamination in the Wallace Road and DA-4 areas while Operable
Unit No. 3 (OU-3) will address any remaining groundwater contamination not addressed by
OU-1 and OU-2. Operable Unit No. 3 will be implemented following additional Rl activities to
determine the remaining extent of groundwater contamination. A contaminant source
assessment task will be performed to identify and to characterize any remaining potential
waste sites at Castle AFB. Following this task, an Rl Work Plan for Existing Sites and
2-6
M:ENG:9327-2/080291
-------
Contaminant Source Assessment Sites will be prepared and implemented to complete the Rl.
An installation wide RI/FS report and ROD will conclude the RI/FS process at the Base.
Estimated dates for the completion of these activities are:
Draft Final ROD for Operable Unit No. 2 October 1992
(See Section 3.0)
Draft Final ROD for Operable Unit No. 3 February 1994
(See Section 3.0)
Work Plan for Existing Sites and Contaminant
Source Assessment Sites July 1992
Implementation of the Work Plan for Existing
Sites and Contaminant Source Assessment Sites April 1993
Installation-wide Remedial Investigation
Report (Rl) January 1994
Installation-wide Feasibility Study (FS) June 1994
Installation-wide Record of Decision (ROD) April 1995
HIGHLIGHTS OF COMMUNITY PARTICIPATION
A Community Relations Plan for the Base was finalized in June 1990. This Plan lists contacts
and interested parties throughout the Air Force, government, and local community. It also
established communication pathways to ensure timely dissemination of pertinent information
through mailings, public announcements in the local paper, and local information repositories.
The Interim Operable Unit No. 1 Feasibility Study was released for public comment in
December 1990.
A Proposed Plan announcement for Operable Unit No. 1 (OU-1) was mailed to interested
parties and an announcement of the OU-1 public comment period and community meeting
was placed in local papers. The public comment period began on December 20,1990 and a
community meeting was held on January 8.1991 in the City of Atwater, to discuss the
proposed TCE greundwater clean up alternatives. The public comment period was then
extended to February 21,1991, following a written request by a concerned member of the
community. AH comments were received during the public comment period and a
Responsiveness Summary was prepared by the Air Force addressing these comments
(Section 10).
2-7
,IAv 9327-2/080291
-------
j
3.0 SCOPE AND ROLE OF THE OPERABLE UNIT
Currently three operable units have been identified at the Base. They include: the Main TCE
Plume (Operable Unit No. 1), the Wallace Road/DA-4 TCE plumes (Operable Unit No. 2) and
the remaining groundwater cleanup on/and off-Base (Operable Unit No. 3). Current
investigations suggest that the groundwater contamination in the Wallace Road/DA-4 TCE
plumes stem from sources other than the Main TCE Plume. Operable Unit No. 3 will address
groundwater remediation for the remaining portions of groundwater contamination on and off-
Base not previously covered by Operable Units No. 1 and 2. Operable Unit No. 3 will proceed
following the completion of site characterization activities and will complete the defintion of
groundwater contamination at Castle AFB. the remaining contamination on Base will be
addressed in the overall RI/FS and ROD for the entire Base.
The principal risk to public health posed by Operable Unit No. 1 is the TCE plume to the south
and southwest of the Base which has the potential to impact off-Base residential water wells.
Delays in remediating the Main TCE Plume (MTP) could potentially affect additional wells and
a greater area, making remediation more difficult and costly.
The lateral area delineated by the MTP, defined as TCE at or above the drinking water MCL
of 5 parts per billion (ppb), exceeds 212 acres (Figure 1-1). The full extent of the plume
delineated at less than 5 ppb in all directions is not completely known at this time. Additional
off site investigations are planned. The two other operable units will address the remaining
problems of groundwater contamination both on and off the Base.
Since data has shown that Applicable or Relevant and Appropriate Requirements (ARARs)
have been exceeded in the groundwater under Castle AFB, this interim operable unit is
designed to initiate early action to mitigate potential threats to public health and the
environment Subsequent operable units and the overall Base ROD will define further actions
to mitigate potential threats. The selected interim remedy in this action is expected to be
consistent with subsequent remedies and planned future actions at the Base. Pursuant to
regulatory guidance for Interim remedial actions, the Interim Operable Unit No. 1 Feasibility
Study does not contain a baseline risk assessment. Risks to public health and the
environment will be assessed in a subsequent ROD.
3-1
MA:ENG:9327-3/070191
-------
4.0 SUMMARY OF SITE CHARACTERISTICS
In addition to the original investigative sites identified at the Base, the state has identified
further areas of potential contamination. Investigation of these sites is under way. The sites
include areas where disposal of wastes or known leaks or spills of significant amounts of fuels
or chemicals have occurred on the Base. During the remedial investigations, soil sampling (of
borings) and groundwater sampling were performed in order to characterize each site. Other
geophysical and investigative techniques were also used to identify potential buried drums,
unusual objects, levels of radioactivity, or high levels of significant volatile soil organic vapor.
!
The site investigation identified three groundwater plumes containing various chemicals but
primarily TCE (Figure 1-1). The largest plume, the Main TCE Plume (MTP) (Operable Unit
No. 1), consisted of a number of smaller plumes from different source areas which have
merged to form one large plume beneath the central portion of the Base. The MTP occurs in
the shallow aquifer which is used as a drinking/irrigation water source for some off-Base
residents. The soils, investigated thus far, were found to contain trace levels of volatile
organics (Rgure 4-2). A number of sites were found to contain potentially significant levels of
petroleum-type hydrocarbons as a result of former fuel leaks and spills. Remediation of soils
will be determined in a later ROD.
A number of chemicals have been identified in the groundwater within the MTP (Tables 4-1, 4-
2 and 4-3). Some of the chemicals have established Maximum Contaminant Levels (MCLs)
under the Federal and State Safe Drinking Water Act (Tables 4-2, 4-3). The remedial action
MTP chemicals of potential concern which exceed MCL's include:
Trichtoroethylene (TCE) :
Benzene ~
Tetrachtoroethytene (PCE)
ds-1,2-Dtehloroethylene (1,2-DCE).
Chloroform
1,2-Dichtoroethane (1,2-DCA)
1,1-Dichtoroethytene
Carbon Tetrachtoride
Chloromethane
1,1-Dichloroethane
4-1
MA:ENG:9327-4/070191
-------
Elevated levels of JP-4 (jet fuel) were also detected, but there are no regulatory cleanup
standards set for JP-4 since it consists of a diverse mixture of petroleum hydrocarbons.
However, there are MCLs established for individual components of JP-4 such as benzene,
toluene, xylene, ethy(benzene, etc., which may pose a health risk (Tables 4*2 and 4-3). Only
benzene has been detected above MCLs.
Rgure 1-1 shows the delineation of the TCE plume at the 5 parts per billion (ppb) boundary.
This level is the drinking water standard for TCE promulgated by the U.S. EPA under National
Primary Drinking Water Standards. The plume also delineates the extent of contamination of
the other constituents of concern described above. The selected interim remedy will remove
and treat the constituents listed in Tables 4-2 and 4-3 within the delineated area. Potential
groundwater users are the Air Force, nearby residents! and farmers.
' The highest level of TCE detected during the four rounds of quarterly Rl groundwater
sampling within the MTP was 1,200 ppb (Table 4-1). A number of TCE hot spots were also
identified which exceeded 100 ppb. The vast majority of groundwater within the MTP contains
TCE at levels less than 50 ppb. Benzene was detected at a maximum concentration of 660
ppb in a monitoring well located in the immediate vicinity of the petroleum, oils and lubricants
(POL) storage area (Table 4-2). The POL storage, area is the primary area of the Base where
fuels (which contain benzene) are handled.
The Main TCE Plume is in a relatively porous and transmissive formation. It is influenced by
off-Base pumping of irrigation and municipal wells indicating these wells may be screened
higher than well log reports indicate. It is expanding at a rate that is potentially significant to
water sources. .
4-2
,A:ENG:9327-4/070191
-------
TABLE 4-1
SUMMARY OF TCE DETECTED IN GROUNDWATER
FOR THE MAIN TCE PLUME
(PPb)
WELL NO/
MW-115
MW-120
MW-125
MW-210
MW-220
MW-245
MW-290
MW-300
MW-310
MW-509
MW-510
MW-511
MW-512
MW-513
MW-514
MW-515
MW-516
MW-517
MW-518
MW-519
MW-520
MW-521
MW-522 --
MW-523
MW-524
MW-525
MW-527
MW-528
MW-529
MW-530
MW-531
MW-532
MW-534
ROUND 1
20
(Free
product)
0.8
35
16
0.6
ND
8.7
150
0.9
25
2.6
16
ND
3.1
2.3
49
23
4.9
. 530
2.6
240
55
7.3
38
0.5
7.1
24
1,000
1.3
18
0.4
ND
ROUND 2
22
(Free
product)
0.8
39
25
ND
ND
6.4
94
0.8
39
ND
25
0.8
3.0
4.8
76.0
1.8
ND
730
1.3
390
310
14
45
120
8.4
26
1,144
ND
26
0.4
0.4
. ROUND 3
46
Dry
1.4
38
25
ND
ND
6.2
120
22
40
3
32
0.8
3.5
0.7
71
3.4
11
920
1.9
340
160
9.3.
70
140
12
23
1,200
2.1
120
ND
0.3
ROUND 4
Dry
Dry
1.2
43
49
Dry
0.9
0.8
83
2.2
61
5.9
35
0.3
3.5
ND
59
0.7
7.8
1000
1.4
610
330
15
48
170
10
9.5
1.100
1.4
63
0.4
1
MA:ENG:9327T4-1 .BM/061991
4-3
-------
TABLE 4-1
SUMMARY OF TCE DETECTED IN GROUND WATER
FOR THE MAIN TCE PLUME
(ppb)
MW-536
MW-543 ;
MW-544
MW-551
MW-552
MW-554
MW-556
MW-557
MW-602
MW-603
MW-606
MW-608
MW-711
MW-712
MW-752
MW-TW-13
MW-TW-14>
MW-TW-15 ,
MW-TW-16
MW-TW-17
MW-TW^18 ,
MW-PW-2
MW-PW-3 ..
MW-PW-4 -
MW-PW-9
MW-PW-10
MW-BOYLE2 -
MW-BOYLE4
MW-MI0228
MW-4781
MW-2679
0.3 "
46
23
16
0.4
29
30
9.9
ND
NO
ND
ND
ND
0.3
1.3
2.3
58
4.7
470
7.3
(Not
. functioning)
2.6
2.9
3.1
0.3
0.5
ND
ND
12
1-3
ND
0.3 ....
73
24
31
ND
47
36
6.6
12
ND
10
0.8
0.3
1.6
1.8
2.1
, 69
5.5
350
7.4
20
2.3
2.3
..
0.3
ND
ND
0.7
, 13
0.9
0.3
" ...ND
. 130
22
13
ND
61
150
16
ND :
30
15
0.5
ND
4.8
2.4
3.3
120
5.5
480
10
34
'. ~
~
"~-
0.3
^2
.:
~.
.
0.8
130
45
- 46
ND
.66
100
9.6
ND
51
5.6
ND
ND
2
3-' "...
1.1
~
6.1
.34
'
.
_-
ND
1.5
' ':.'--
* Well locations are shown on Figure 1-4 in the Interim Operable Unit No. 1
Feasibility Study for Castle AFB, December 1990
ND = None detected . -
MA:ENG:9327T4-1 .BM/061991
4-4
-------
TABLE 4-2
ORGANIC COMPOUNDS DETECTED IN MTP GROUNDWATER
SAMPLING ROUNDS 1, 2, 3, AND 4
f *
COMPOUND ,
Trichloroethylene*
Benzene*
fetrachloroethylene*
Cis-1 ,2-Dichloroethylene*
Methylene Chloride
Xylenes
Ethyjbenzene
Acetone
Toluene
1,1-Dichloroethylene*
1 ,2-Dichloroethane*
Carbon tetrachloride*
Chloroform*'
Dichlorbdifluoromethane
JP4
1,1-Dichloroethane*
Chloromethane*
Trichlorofluoromethane
Trans-1 ,2-Dichloroethylene
1,2-Dichloropropane
Chloroethane
Chlorobenzene
1 ,2-Dichlorobenzene
Bromoform
.HIGHEST
CONCENTRATION
DETECTED WITHIN
MAIN TCE PLUME
(Ppb)
1,200
660
180
140
44
43
38
26
17
17
16
15
12
7.5
7.4
5.5
5.0
2.3
2
1.2
1.1
0.4
0.4
0.4
MCL
(Ppb)
5
1
5
6
1750
680
~
6
0.5
0.5^
100
~
5
~
150
1°
5
30
~
.
SAMPLE LOCATION
MW-529
MW-531
MW-521
MW-531
MW-519
MW-531 - ' '.
MW-531
MW-608
MW-531
MW-529
MW-531
MW-525
MW-523
MW-Boyle-2
MW-609
MW-533
MW-521
MW-352
MW-522 .
MW-609
MW-709
MW-531/523/524/607
MW-608
MW-Boyle-4
* Contaminants of Concern
MA:ENG:9327T4^2.BM/061291
4-5
-------
TABLE 4-3
METALS AND IONS DETECTED IN MTP GROUNDWATER
SAMPLING ROUNDS 1, 2, 3 AND 4
' '-
Arsenic
Barium
Bromide
Cadmium
Calcium
Chloride
Chromium
Copper
Cyanide
Fluoride
Hardness
Iron
Lead
Magnesium
Manganese
Nitrate
Phosphate
Potassium
Selenium
Silver
Sodium
Specific Conductance
Sodium Sutfate
Total Dissolved Solids
Zinc
pH (low)
pH (high)
HIGHEST
CONCENTRATION
DETECTED WITHIN
MAIN TCE PLUME
(ppm)
ND
0.32
1
0.005
71
59
0.01
0.025
0.02
0.4
280
0.9
0.005
29
2.4
14
2.2
50
0.005
0.01
.68
790 umhos/cm
69
500
0.06
6.3 std units
9.7 std units
MCL
(ppm)
0.05
1
0.01
~
- ' i.
0.05
' -
-
~
-
0.05
.
45
-
. .
0.01
0.05
- .
-
-
'
, -
SAMPLE LOCATION
~ . , -
MW-536/TW-17
MW-525
MW-533/557
MW-TW-13
MW-559
MW-557
MW-557
MW-557
MW-608
MW-531/532
MW-115
MW-125
MW-115
MW-533
MW-TW-15
MW-513
MW-605
MW-557
MW-557
. MW-559
MW-115
MW-245
MW-536
MW-525
MW-Boyte-3
MW^05/607/TW-16
MA:ENG:9327T4-3.BM
4-6
-------
5.0 SUMMARY OF SITE RISKS
Site risks have not been fully characterized, however, ft is clear that MCLs have been
exceeded for several contaminants as discussed in Section 4 (Tables 4-2 and 4-3).
Therefore, ft is appropriate to initiate early cleanup action via an interim remedy. Ten organic
chemicals of potential concern were previously identified for the MTP area. The general goals
of this interim action are to prevent the further spread of contamination and initiate mass
removal of contamination from the aquifer. This action is designed to stabilize the spread of
contamination, prevent further degradation, and to achieve risk reduction quickly. Risks are
partially addressed by this interim remedy in that treatment actions will be expedited. More
specific findings on risk and ultimate target cleanup levels for the groundwater will be
established in a subsequent final action ROD. :
- 5-1
MA:ENG:9327-5/070191
-------
6.0 DESCRIPTION OF ALTERNATIVES
As discussed in Section 5.0, the goals of this interim action are to prevent the spread of
further contamination and to initiate removal of contamination from the aquifer. The cleanup
target for the aquifer will be established in a subsequent ROD. Any residual contaminants
resulting from the cleanup alternatives will be treated or disposed of in accordance with the
Resource Conservation and Recovery Act (RCRA). A description of the nine alternatives
developed and screened is provided below. For purposes of comparing the net present worth
of each alternative, a discount rate of seven percent and an annual inflation rate of six percent
were, assumed (Table 7-1). These rates were considered to be representative of the
economic conditions at the time the Operable Unit No. 1 Feasibility Study was prepared.
Alternatives 6 through I are based on pumping groundwater through extraction wells located in
the Main Base Sector. The pumping rate and optimum configuration of the wells will be
determined during the remedial design phase. Based on conceptual modeling, a total
pumping rate of 1250 gallons per minute from five extraction wells was used for the
preliminary design basis.
The air stripping towers, identified in Alternatives B, C, D, and I, were conceptually sized for
estimating purposes at 84 inches diameter, 25 foot packing depth, and a required air flow rate
of 3345 SCFM. The preliminary tower sizing is based on (worst case) high levels of detected
organic compounds in the Base groundwater sampling data from rounds one, two, three, and
found, and on achieving a removal concentration level to meet established MCLs for the
. chemicals of concern.
As noted in Section 5.0, this action does not set specific cleanup levels. All pump and treat
Alternatives (B through I) would initiate the remediation of groundwater to meet the objectives
of this action. As a part of this action, cleanup levels will be established for the treated
effluent and any possible air emissions from the air stripper. The treated groundwater will be
cleaned to the MCLs and/or ARAR listed on Tables 4-2 and 4-3.
ALTERNATIVE A .
Alternative A is the no-action alternative. This alternative was evaluated for baseline
comparison purposes. The alternative considers taking no active remedial measures such as
6-1
MA:ENG:9327-6/070191
-------
groundwater pumping or removal of contamination. There is no reduction of toxicity, mobility,
and volume through treatment. A site monitoring period of 30 years is used as the basis for
estimating a reasonable cost and present worth. A net present worth of $9,368,000 is
estimated for this alternative resulting from an estimated annual operating cost of $360,000
over a 30-year period.
ALTERNATIVE B .
Alternative B considers groundwater removal by pumping and surface treatment of the
" groundwater using air stripping. The emissions from the air stripper would be abated using a
gas fired thermal combustor. Burning the emissions would destroy contaminants and
eliminate the need to dispose of waste off-site. Treated groundwater would be reinjected into
the same aquifer, increasing the flushing rate of contaminants and avoiding aquifer depletion
caused by groundwater pumping.
This alternative is estimated to have a net present worth of $34,020,000, an initial capital cost
of $2,277,000, and an annual operational cost of $1,438,000. A remedial duration of 25 years
is estimated for this alternative.
ALTERNATIVE C
Alternative C considers groundwater removal by pumping and the same treatment and control
measures as Alternative B. In addition, in situ biological enhancement is included which
stimulates naturally occurring soil bacteria to accelerate the degradation of contaminants in
the groundwater and those adsorbed onto soil particles. Upon completion of the remediation,
the bacteria die off leaving no residuals. Treated groundwater would be reinjected, preventing
regional aquifer depletion. In some applications, the process reduces the clean up time by as
much as 90 percent . ......
This alternative is estimated to have a net present worth of $26,308,000, an initial capital cost
of $2,437,000, and annual operational costs of $2,530,000. A remedial duration of 10 years is
estimated .for this alternative. .
6-2
MA:ENG:9327-6/070191
-------
ALTERNATIVE D : .
Alternative D evaluates groundwater pumping and surface treatment using the same
equipment configuration and emission controls as Alternative B. Treated groundwater is
disposed through a surface outfall into an irrigation or drainage canal instead of reinjection
back into the aquifer. In situ biological enhancement is not considered as part of this
alternative. This alternative wouTd be expected to deplete the aquifer at a rate of up to 10 feet
per year if implemented. .... ,
This alternative is estimated to have a net present worth of $39,302.000, an initial capital cost
of $2,027,000, and annual operational costs of $1,438,000. A remedial duration of 30 years is
estimated for this alternative.
' ' '
; ALTERNATIVE E
^^^^^^^^^MHM^V^B . -V
Alternative E evaluates groundwater pumping and reinjection of treated groundwater. The
surface treatment technology for the pumped groundwater is liquid phase granular activated
carbon adsorption. The carbon would be regenerated on-site using medium pressure steam.
The regeneration process generates a condensate from the units which contains contaminants
removed from th'e groundwater. Regenerant condensate containing recovered contaminants
would be collected and taken off-site to an approved recycling facility. Treated groundwater
will be reinjected into the same aquifer. In situ biological enhancement is not considered as
part of this alternative. , " -
This alternative is estimated to have a net present worth of $39,330,000, an initial capital cost
of $3,484,000, and annual operational costs of $1,623,000. A remedial duration of 25 years is
__ estimated for this alternative. ._ V , -:-
ALTERNATIVE F . ., .
Alternative F considers the same removal, .surface treatment, and groundwater disposal
(reinjection) technologies as Alternative E. Similar to Alternative C, in situ biological
enhancement is also included. The alternative is unique in that on-site treatment of the
condensate generated from the granular activated carbon regeneration process is included.
The technology evaluated for on-site treatment of the regenerant is ultra-violet (UV) photolysis
which is considered an innovative technology. .
6-3
MA:ENG:9327-6/070191 '
-------
1
1 ' ''"'
J .
* This alternative is estimated to have a net .present worth of $26,752,000, an Initial capital cost
of $4,010,000, and annual operational costs of $2,411,000. A remedial duration of 10 years is
I estimated for this alternative. ,
I ALTERNATIVE G
. Alternative Q evaluates the potential advantages of smaller decentralized treatment units.
i This alternative considers the advantages of using individual granular activated carbon
treatment units at each groundwater extraction well location. After treatment, groundwater
| would be reinjected. The carbon units would be regenerated using a mobile skid mounted
boiler system. Regenerant condensate containing recovered contaminants would be collected
and taken off-site to an approved recycling facility. The primary disadvantage of decentralized
operation is the cost of system maintenance and monitoring.
'\ - . '
This alternative is estimated to have a net present worth of $65,240,000, an initial capital cost
of $4,333,000, and annual operational costs of $2,753,000. A remedial duration of 25 years is
estimated for this alternative.
ALTERNATIVE H' '
Alternative H evaluates'utilizing UV photolysis treatment for treating the entire groundwater
volume. Groundwater would be pumped to the surface and the contaminants broken down by
passing the groundwater past strong ultra-violet lights. In addition, hydrogen peroxide would
be added to accelerate decomposition. The technology is innovative and avoids some of the
problems associated with other alternatives such as waste generation and disposal. Following
treatment, the groundwater would be reinjected, minimizing aquifer depletion. In situ biological
enhancement is also included as a technology option with this alternative.
This alternative is estimated to have a net present worth of $44,013,000, an Initial capital cost
of $7,735,000. and annual operational costs, of $3,836,000. A remedial duration of 10 years is
estimated for this alternative.
..- - . " *>
ALTERNATIVE I '
Alternative I is identical to Alternative C except that the thermal combustor used for air
emission abatement under Alternative C is replaced with a vapor phase granular activated
", '. , 6-4' . ' ' .
MA:ENG:9327-6/070191 , . ,
-------
carbon (GAC) abatement unit Groundwater extraction, centralized air stripping treatment,
treated groundwater reinjection and in situ biological enhancement are technology options
included as part of Alternative I. The carbon would be regenerated on-site using medium
pressure steam. The regeneration process generates a condensate from the units which
contain contaminants removed from the groundwater. This condensate would be collected
and taken off-site to an EPA-RCRA approved recycling facility.
This alternative is estimated to have a net present worth of $28,445,000, an initial capital cost
of $2,541,000, and annual operational costs of $2,744,000. A remedial duration of 10 years is
estimated for this alternative.
6-5
MA:ENG:9327-6/070191
-------
7.0 COMPARATIVE ANALYSIS OF ALTERNATIVES
The nine alternatives were evaluated according to the nine National Contingency Plan (NCP)
evaluation criteria to determine the most appropriate or preferred alternative.
NCP EVALUATION CRITERIA .
The nine-point evaluation criteria includes the following:
Overall Protection of Human Health and the Environment
Compliance with ARARs
Long-Term Effectiveness and Permanence
Reduction of Toxicity, Mobility, or Volume
Short-Term Effectiveness
Implementability
Cost
State and/or Support Agency Acceptance
Community Acceptance.
EPA policy states that in the case of interim remedial actions, ARARs for aquifer restoration
do not apply. It is understood that the interim remedy will be followed up by a final remedy
which will establish cleanup levels based on ARARs and a risk assessment.
A summary comparison of cleanup Alternatives A through I is shown on Table 7-1. A
discussion of each of the evaluation criteria follows.
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternative A is least protective of human health and the environment due to the long
anticipated duration to achieve protective levels in the groundwater and the likelihood that
more wells would become contaminated. Under Alternatives B, C, D, F, and H destruction will
ideally reduce contaminants to simpler less toxic compounds. However, an assessment of
thermal abatement equipment for Alternatives B, C, and D will be performed to insure
7-1
MA:ENG:9327-7/070191
-------
4 incomplete combustion by-products are not formed. Risk due to media transfer of chemicals
to the air must be managed to insignificant levels under air stripper Alternatives B, C, D, and I.
i Monitoring of air emissions will be performed upon implementation of these alternatives in
order to assure adequate human health protection is being achieved. Waste transferred off
I site to a state approved recycling facility under Alternatives E, Q, and I (and to a lesser extent
T B, C, D, and F) have a residual risk associated with the proper control of the off site facility.
1 In-situ biological enhanced recovery under Alternatives C. F, H, and I is expected to achieve
better risk reduction and protection of human health and the environment than the remaining
treatment alternatives since it is expected to result in earlier cleanup. Alternative G is the
most responsive alternative for addressing hew areas of contamination in a short period of
\ . time, simply by installing additional units to add treatment capacity. .Under Alternative D,
discharging to surface water contributes to aquifer depletion. Alternatives C, F, H, and I are
the most effective alternatives in terms of overall protection of human health and the
environment, with Alternative H being the most protective.
COMPLIANCE WITH ARARs/TO BE CONSIDERED (TBCS1 MATERIALS
The Superfund Amendments and Reauthorization Act (SARA) requires that remedial actions
meet legally applicable or relevant and appropriate requirements (ARARs) of other
environmental laws. These laws may include: the Toxic Substances Control Act, the Safe
Drinking Water Act, the Clean Air Act, the Clean Water Act the Resource Conservation and
Recovery Act, and any state law which has stricter requirements than the corresponding
federal law. A list of potential Federal and State ARARs for the MTP are shown on Tables 7-
. 3 and 7-4, respectively.
A legally applicable" requirement is one which would legally apply to the response action if
that action were not taken pursuant to Sections 104,106 or 122 or CERCLA. A 'relevant and
appropriate* requirement is one that, while not "applicable" is designed to apply to problems
sufficiently similar that their application is appropriate.
Since this is an interim remedial action, it is not necessary to establish cleanup levels for the
groundwater. MCLs are therefore not ARARs for the groundwater. Grpundwater cleanup
levels based on MCLs and risks will .be established in a subsequent ROD. ARARs do apply
for treated water prior to disposal or reinjection. All alternatives, with the exception of -.
7-2
MA:ENG:9327-7/070191
-------
4
I
Alternative A, will comply with ARARs specific to this action to cleanup the treated water to
appropriate levels (as defined by discharge permit requirements) prior to reinjection and to
g i
i properly address air emissions (as defined with emission permit requirements).
\ -';
I Air emission limitations (ARARs) will be established by the more stringent of either (1) the
Merced County Air Pollution Control District permit to operate requirements (Rules 210.1
\ and/or 210.2) or (2) EPA's OSWER Directive 9355.O28 (Guidance to Control Air Emissions
From Air Strippers at Superfund Sites). Discharge/re-injection limitations (ARARs) will be
I established by the more stringent of either (1) the State's Porter-Cologne Water Quality Act
(Water Code, Division 7, Section 13000 et seq., CCR Title 23) or (2) the State's RWQCB
permit requirements. Additional ARARs may apply pending review of permit requirements,
remedial design documents and the outcome of the wetlands and endangered species
assessments.
Long-Term Effectiveness and Permanence
Alternative A, the no action alternative, has a high residual risk and poor control due to the
fact that residuals are left in place and natural attenuation may not occur for a significant
period of time. During this time the plume would be expected to continue expanding into
unaffected areas. This alternative is not considered to be long-term effective and permanent.
Alternatives C, F, H, arid I are expected to have the least residual risk due to the flushing
effect, of reinjection combined with the enhanced desorption of chemicals from the vadose
zone soils as a result of in-sltu biological enhancements. Carbon adsorption Alternatives E, F,
G, and I retain some risk due to possible mismanagement at an off-site location.
Alternatives C and H provide the most long-term effective and permanent solution due to the
utilization of on site destruction of chemical contaminants removed from the aquifer.
Alternatives with thermal abatement will destroy the contaminants on site, however extensive
testing would be required to ensure that incomplete combustion is not creating more
hazardous substances.
Reduction of Tbxicitv. Mobility and Volume bv Treatment
Under the Alternative A (no action), mobility and expansion of the plume would occur resulting
in an increase in the volume of affected groundwater. Under the active treatment Alternatives
7-3
MA:ENG:9327-7/070191 -
-------
i '
* B through G, treatment reduces the toxicity, mobility, and volume of chemicals in affected
groundwater. Under Alternatives B, C, D, and H (and to a lesser extent F), the chemicals of
concern are destroyed through thermal treatment, while Alternatives E, G, and I result in
( moving chemicals to an approved off site or recycling facility. Alternatives F and H destroy
contaminants on site through photolytic oxidation. Table 7-2 lists quantities of hazardous
j wastes and emissions that would be generated by Alternatives A through I and assumes no
' products of incomplete combustion will occur. Toxicity and exposure will be managed through
abatement and compliance with risk assessment-derived health protective limits on air
. emissions set by permit requirements.
Short-Term Effectiveness
Alternatives C, F, H, and I using in situ biological enhancement are expected to achieve
protection in the shortest time period. Under Alternative G, the ability to move and deploy
additional treatment systems rapidly upon discovering a new hot spot will be a short term
advantage over other treatment alternatives. Alternative D is expected to take the longest
period of time of all the active alternatives to achieve protection. Alternative A will not meet
NCP criteria for short-term effectiveness. Alternative B which utilizes incineration, has the
. ' ' i "-
potential for Incomplete combustion which may result in the production of highly toxic
compounds which could pose a threat to public health and the environment.
Wells known to be contaminated were either previously removed from service or had filtration
units placed on them to protect the community during remedial actions. Should additional
wells become contaminated, the Base will take prompt action to properly remove these wells
from service or install filtration units to provide a safe water supply. Any well taken out of
service will be abandoned through proper procedures or converted to a monitoring well in
order to monitor contamination levels.
Air exposure pathways generated from media transfer operations and a small level of
incomplete abatement will occur under the air stripper Alternatives B, C, D, and I. Alternatives
which use thermal abatement will take longer to implement due to the need to conduct
extensive testing to assure there are no highly toxic substances being produced via
incomplete combustion.
. 7-4
M:ENG:9327-7/080291
-------
* Compliance with standard operating procedures, the Occupational Safety and Health
: Administration (OSHA) requirements, and health and safety plans, if required, are expected to
» ...
i protect workers during remedial activities. ,
» . .
i Under Alternative A, relying on natural attenuation/dilution could environmentally impact the
: ^'
deeper aquifers and contaminate larger volumes of water. Under Alternative D, the discharge
j of treated groundwater to surface waters will result in groundwater depletion, possible
subsidence, wells drying out, and disturbance of an existing surface water regime could occur.
Implementabilitv
All alternatives are constructable and implementable. The use of ultraviolet (UV) photolytic
treatment under Alternatives F and H are innovative, however difficulties with technical
implementation are not expected. Reliance on material attenuation only renders Alternative A
technically ineffective. The decentralized GAC Alternative G Is the most flexible alternative in
terms of remediating new areas, but would also require the largest number of effluent
discharge monitoring stations. As a result, labor and maintenance costs would be higher. Air
emission monitoring will be required under Alternatives B, C, D, and 1. Test bum and air
dispersion modeling will be required for all alternatives that require thermal abatement. A
contract with an off site facility and/or disposal facility will be required for alternatives utilizing
GAC. .
Under Alternatives B, C, D, and I the substantive requirements of any necessary air permits
and air monitoring would have to be met by the Air Force upon implementation. Manifesting
of off site waste shipments is required under Alternatives B, C, D, E, F, G, and I. The
substantive requirements of the National Pollutant Discharge Elimination System (NPDES)
permitting and monitoring will have to be met for treated groundwater for Alternative D.
On a net present worth basis, Alternative A was the most economical alternative while
Alternative G costs the most A comparison of present worth cost for all nine alternatives is
shown on Table 7-1.
7-5
MA:ENG:9327-7/070191
-------
. ..
STATE AND COMMUNITY ACCEPTANCE
i U.S. Environmental Protection Agency (EPA) Region IX and the California Department of
I Health Services (DHS) and Regional Water Quality Control Board (RWQCB) have been
involved in the technical review of the Interim Operable Unit No. 1 Feasibility Study (OUFS)
t . and the development of the Proposed Plan and Record of Decision (ROD). The EPA and the
State agree with the preferred alternative as presented in this Record of Decision.
i
i - * .
Community acceptance of the interim remedial action has been positive. During the public
, comment period, only three written comments were received. The comments, along with
questions raised during the public meeting, were intelligent and pertinent. The community
' seemed most concerned about; the depletion in the groundwater supply caused by
remediation, the length of clean-up actions, and the possible production of additional
hazardous wastes during the clean-up. The Responsiveness Summary (Section 10.0)
provides a thorough review of the public comments received on the OUFS and Proposed
Plan, and the Air Force's responses to the comments received.
7-6
MA:ENG:9327-7/070191
-------
POOR QUALITY
ORIGINAL
TABLE 7-1
COMPARISON OF CLEANUP ALTERNATIVES
A
B
C
0
E
r
0
H
1
MM****
Mo Action
Contrasted thermally
abated air flrifpor.
CW rminjoclion
Controlled thermally
obotod air stripper. .
CW reinjection with «l-
situ biotreatment
Centrolnod thermally
abated air stirpper
surface water discharge
Centralized 6AC.
adsorption, steam
regeneration, OH
romjoction
Centralized GAC
adsorption, steam
rooenot udon. condonooto
photolysis and recycle.
CW reinfection with in-
situ biotreatment
Oecentrafied CDC
adsorption, steam
regeneration. CW
rejection
Centralized W
photolysis treatment.
CW nm/*caca mill in
situ biotreatment
Cfntrafiod air
ttrtppar with (MC
ODatomont, CW
nmjfCllon mttt in trtu
blotrtttmmt
OMDMU.
monn»M
Nat Protfctnm .
' (.«* protoctiv*
duo to lonoor
duration
Hail pral«cM«
Un pratoeUM
out to longor
duration
Lot* protoctiro
duo to .longar
auntlon
Uott prottctk*
Lon prottctiv*
duo to tonoor
duration
MM! fWQtfCtlM
Mod pntKUro
COMPLMMCC
Mm100 years
Potential air exposure
poth*ay Remedial
duration: 25 years
Potential air exposure
pothfoy Remedial
duration: 10 yoorm
Potential air exposure
pathway Remedial
duration: JO years
Limited interim
exposure Remedial
duration: 2S years
Very limited interim
exposure Remedial
duration: 10 yean
Limited interim
exposure Remedial
duration: 25 rears
Very limited interim
exposure Remedial
duration: 10 years
Potential air exposure
pathway Remedial
duration: 10 years
MUMCMMUnr
Eoiieit
to implement
knptemmlaM*
bnplomentablo
Impletnentable
tmplemontoHo
rniJamentoblo
Implementatle
Implomontoblo
rnphmentablo
*eosr
(pnoo* ***)
$ ».3t».000
$ J4.020.000
- $ 25.JO&000
1 M.XIOOO
$ J9.JJO.OOO
$ 2S.7i2.000
t 6S.240.000
$ 44.0IJ.OOO
1 28.445.000
svnt
.: ACctrtAMce
Not expected
to approve
May have
concern over
thermal abatement
Hay have
concern over
thermal abatement
Hoy hove concern
over aquifer depletion
and thermal abatement
fxpected to
approve
expected to
approve
expected to
approve
Hay have a
concern over
unwanted by-products
expected to
approve
COHUUHTT
Mxtrwete
Hot expected
to approve
concern over
thermal abatement
Hay have
concern over
thermal abatement
May have concern
aver oqui/or depletion
and thermal abatement
expected to
approve
fxpected to
approve
£>pected to
approve
Hoy have a
concern over
unwanted by-products
expected to
approve
co-ccl2(ca-97) 6/91
^ASSUMES A IX WfUIMN AMD 7X DISCOUNT RATE.
7-7
-------
TABLE 7-2
ESTIMATED MAXIMUM ANNUAL WASTE AMD EMISSONS FOR REMEDIAL ALTERNATIVES
(Pounds)
ALTERNATIVES
Hazardous Waste Solid'
Spent Carbon
Hazardous Waste.UaukT
Steam Regenerant w/organlcs
Chlorinated Organlcs
(free liquid) .
Spent Add
(from air stripper washing)
Priority Air Pollutants*
Parflculates
Sulfur Dioxide
Nitrogen Oxides
'Carbon Monoxide .
Organlcs (as Hydrocarbons)
Organlcs (as chlorinated
hydrocsftXMis)
Hydrochloric Add (gas)
A
None
None
None
None
None
None
None
None
None
None
None
8
>» i
wone
None
None
48.800
00.3
23.8
5.560
1.300
240
62
17,100
C
None
None
None
48,800
00.3
23.8
5.560
1.390
240
82
17,100
D
None
None
None
48.800
99.3
23.8
5.560
1.390
240
82
17,100
E
32.200
1,145.000
25,100
None
3.5
0.84
198
49
8.5
"
Trace
F
32.200
None
25.100
None
3.5
0.84
198
49
8.5
*
Trace
0
32,200
1.250.000
24,880
None
..
3.0
0.03
217
54
0:3
*"
Trace
H
None
None
None
None
None
None
None
None
"Trace
"5.5
"17.100
1
32.200
1,250.000
24,880
48,800
3.0
0.03
217
54
274
822
Trace
* A net reduction In overall base emissions would result since Ihese emissions would be offset by a 110 percent equta
required for meeting regulatkms to permit new sources.
" Not emitted as air pollutants, returned dissolved In treated groundwater. emission offsets do not apply. ,
*" Storage tank breathing and working losses only.
1 Residuals to be sent to EPA-RCRA Permitted Facility
1 Air pollutants win meet established ARAR's
nt reduction In emissions from existing sources as
1VN19WO
MA: ENG:9352-T/061991/3
-------
TABLE 7-3
PAGE 1 OF 5
POTENTIAL FEDERAL APPLICABLE, OR RELEVANT AND
APPROPRIATE REQUIREMENTS FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
CHEMICAL SPECIFIC ARARS
REQUIREMENT
APPLICATION TO THE MAIN TCE PLUME
Resource Conservation and
Recovery Act (RCRA) as amended
by Hazardous and Solid Waste
Amendments (HSWA) (42 USCA
7401-7642)
(40 CFR 260-280)
RCRA-related regulations are generally action
specific. However, RCRA provides Maximum
Concentration Limits (RCRA MCLs) as part of
groundwater protection standards (40 CFR
264.94).
(RELEVANT AND APPROPRIATE)
II. Safe Drinking Water Act (SDWA)
[42 USCA 300(f)]
(40 CFR Parts 141-149)
(54FR22Q64, Federal Register,
May 22,1989)
II. Established MCLs which are enforceable
standards for chemicals in public drinking
water supplies. They not only consider health
factors, but also economic and technical
feasibility of removing a chemical from a
water supply system.
(RELEVANT AND APPROPRIATE)
Clean Water Act, amended (CWA)
(33 USCA 1251-1376)
(40 CFR 100-149)
III. Ambient Water Quality Criteria (AWQC);
established under Section 304 of CWA (51
FR 43665), are based on effects on human
health and aquatic life that do not reflect
technological or economic considerations.
CWA AWOC's would be applicable to water,
to a sewer, or site runoff directed to a water
body (including a storm drain or flood
channel) with or without treatment.
(MUST MEET RELEVANT AND
APPROPRIATE DEFINITION)
MA:ENG:9327T7-3/061291
7-9
-------
TABLE 7-3
PAGE 2 OF 5
POTENTIAL FEDERAL APPLICABLE, OR RELEVANT AND
APPROPRIATE REQUIREMENTS FOR THE MAIN TCE PLUME (OPERABLE UNIT NO; 1)
IV. Clean Air Act (CAA)
(42 USCA 7401-7642)
(40 CFR 50-69)
IV. a. National Ambient Air Quality Standards
(CAA Sec. 109)
. National primary and secondary ambient air
quality standards (NAAQS) are required to be
met under Section 109 of the CAA and are
Bsted In 40 CFR 50. No air pollutants have
been measured at Castle Air Force Base.
(MAY BE RELEVANT AND APPROPRIATE-
AMBIENT AIR)
b. National Emission Standard for
Hazardous Air Pollutants
. National Emission Standards for Hazardous
Air Pollutants (NESHAPs) are process and
industry specific and must be industry
specific. They must be converted from point
source standards to area source standards in
order to be applied at CAFB. NESHAPs are
currently limited to very few chemicals (40
CFR 61).
(MAY BE RELEVANT AND APPROPRIATE-
AMBIENT AIR)
LOCATION SPECIFIC ARARS - FEDERAL
There are no location-specific ARARs associated with CAFB. The Base is located in the historical
range of three endangered species. The Air Force will have a biologist determine the presence or
absence of these species. Any surface area disturbance associated with the selected interim remedy
is minimal and should not have a significant impact on these species habitats, should they exist The.
Air Force will also have a qualified agency assess the Base to determine the presence or absence of
wetlands. Any surface area disturbance associated with the selected interim remedy will be minimal
and should not significantly impact any wetlands should they exist. The Base is not In a floodplain,
nor are there any known surface water bodies that are being affected. There are no geologic faults
below or near the base. No historic places are located within 3 miles. Consequently, the following
federal statutes are not "appropriate and relevant" to the Castle Air Force Base Operable Unit No. 1
(Main TCE Plume): . ;
National Historic Preservation Act (NHPA) 16 CFR Part 470, el seq. Endangered Species
Act (ESA) 50 CFR Sections 402.01 and 402.04. Protection of Wetlands Executive Order
11990 (40 CFR 6.302 (a). Wild and Scenic Rivers Act (WSRA) 36 CFR Section 297.4
Coastal Zone Management Act (CZMA) 15 CFR Section 930.30 and 930.34. Wilderness
Act (WA) 50 CFR Section 35.5.
7-10
MA:ENG:9327T7-3/080291
-------
TABLE 7-3
PAGE 3 OF 5
POTENTIAL FEDERAL APPLICABLE, OR RELEVANT AND
APPROPRIATE REQUIREMENTS FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
TO BE CONSIDERED MATERIAL - FEDERAL
REQUIREMENT
National Contingency Plan (NCP)
(55 FR 8666, Federal Register,
March 8,1990)
(40 CFR 300)
II. Toxic Substances Control Act
(TSCA) PCB Spill Cleanup Policy
(52 FR 10688, April 2, 1987)
(40 CFR Part 61, 'Suppart G)
III. Groundwater Protection Strategy of U.S.
EPA
IV. ^40 CFR 264.94
APPLICATION TO THE MAIN TCE PLUME
Baseline Risk Assessment will determine safe
levels for those chemicals w/o MCLs, and will
Judge whether MCLs are sufficiently health-
protective for the.chemical mixture found in the
plume.
While not potential ARARs, the requirements of
the PCB spill cleanup policy may by
"appropriate relevant" for CERCLA actions.
While not potential ARARs, the groundwater
classification guidelines are considered in the
Baseline Risk Assessment and Feasibility
Study.
Establishes three categories of groundwater
protection standards: background, RCRA
MCLs and Alternate Concentration Limits
(ACLs). CERCLA Sec. 121(d)(2)(B)(ii) list
three additional conditions limiting use of ACLs
at Superfund sites.
ACTION-SPECIFIC ARARS-FEDERAL
A. GROUNDWATER PUMP AND TREAT REMEDIATION ALTERNATIVE:
1. TREATMENT OF GROUNDWATER (DISCHARGES TO GROUNDWATER &
DISPOSAL OF RESIDUALS):
REQUIREMENTS
Resource Conservation and Recovery Act
(RCRA) as amended by Hazardous and
Solid Waste Amendments (HSWA)
(40 USCA 7401-7462)
(40 CFR 264-265)
APPLICATION TO THE MAIN TCE PLUME
Although RCRA was not In effect during active
waste disposal and is not strictly applicable, the
similarity between the historical disposal at
CAFB and RCRA regulated practices makes it
reasonable to judge RCRA requirements
generally relevant and appropriate. SARA
relieves the requirement of obtaining a permit,
but all RCRA requirements must be met
MA:ENG:9327T7-3/061291
7-11
-------
TABLE 7-3
PAGE 4 OF 5
POTENTIAL FEDERAL APPLICABLE, OR RELEVANT AND
APPROPRIATE REQUIREMENTS FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
II. Resource Conservation and Recovery Act
(RCRA) as amended by Hazardous and
Solid Waste Amendments (HSWA)
(40 CFR 264.90)
(40 CFR 264.94) Monitoring
III. Underground injection Control Regulations
(40 CFR Parts 144 through 147)
IV. Clean Water Act (CWA)
33 USCA 1251-1376
40 CFR 100-149
(1). National Pollutant Discharge
Elimination System (NPDES)
40 CFR 122-125
(2). Water Quality Standards
CWA402(a)(1j
Hazardous constituents entering groundwater
must not exceed concentration limits In the
aquifer underlying the waste management unit
(WMU). The groundwater monitoring program
must provide a reliable indication of
groundwater quality below the WMU.
Potentially applicable for alternatives utilizing a
groundwater injection option.
The Clean Water Act requires permitting if
effluent discharges under the NPDES permit
program and seeks to protect the existing and
attainable uses of waters of the U.S. Permit
may not be required, but all requirements must
be met.
NPDES permits contain applicable standards,
monitoring requirements, and standard and
special conditions for water discharges. Both
pn-site and off-site discharges from CERCLA
sites to surface waters are required to meet the
substantive CWA requirements, and best
management practices. Only off-site CERCLA
discharges must be permitted. The base
wastewater treatment facility has a NPDES
discharge permit.
Effluent limitations are required to achieve all
appropriate State water quality standards. EPA
Policy for the Development of Water Quality
Based Permit Limitations for Toxic Pollutants.
(49 FR 9016, March 9,1984) states that toxic
pollutants contained in direct discharges will be
controlled beyond Best Control
Technology/Best Available Technology
(BCT/BAT) equivalents in order to meet
applicable state water quality standards.
2. TREATMENT OF GROUNDWATER (DISCHARGE TO POTW)
REQUIREMENT
(1). Discharge to Publicly Owned Treatment
Works (POTWs)
(CWA 307)
APPLICATION TO THE MAIN TCE PLUME
Pretreatment regulations (40 CFR 403) control
the introduction of pollutants to POTWs.
,dA:ENG:9327T7-3/061291
7-12'
-------
TABLE 7-3
PAGE 5 OF 5
POTENTIAL FEDERAL APPLICABLE, OR RELEVANT AND
APPROPRIATE REQUIREMENTS FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
3. TREATMENT OF GROUNDWATER (DISCHARGE TO AMBIENT AIR):
REQUIREMENTS
APPLICATION TO THE MAIN TCE PLUME
(1). National Ambient Air Quality Standards
(CAASec. 109)
No air pollutants have been measured at
Castle Air Force Base.
(MAY BE RELEVANT AND APPROPRIATE-
AMBIENT AIR
(2). National Emission Standard for
Hazardous Air Pollutants
National Emission Standards for Hazardous Air
Pollutants (NESHAPs) are process and industry
specific and must be industry specific. They
must be converted from point source standards
to area source standards in order to be applied
at CAFB. NESHAPs are currently limited to
very few chemicals (40 CFR 61).
(3). EPA - OSWER Directive 9355.0-28,
"Guidance on the Control of Air Emissions
from Air Strippers at Superfund Sites."
Guidance seeks to incorporate air quality
concerns into the Superfund remedy
selection. Policy may set target levels
(TBCs) where ARARs do not exist. The
directive applies to future remedial
decisions at Superfund sites located in
ozone non-attainment areas. Such sites
are required by the directive to control
, total volatile organic compound emissions
from air stippers and soil vapor extraction
operators to fifteen pounds per day.
1) Requires FS to evaluate the impact of VOC
emissions in attainment and nonattainment
areas for ozone.
2) Requires consideration in the FS of health
risks from the execution of the remedy as well
as form the uncontrolled site.
3) Requires alternatives and their costs In FS
evaluation of control measures.
4) Requires FS to evaluate compliance wtth
Air ARARs with implementation of alternative.
5) Requires a determination in the FS of
estimated cumulative uncontrolled air emission
rate from all air strippers at the site.
7-13
MA:ENG:9327T7-3/061291
-------
TABLE 7-4
PAGE 1 OF 5
POTENTIAL STATE APPLICABLE, OR RELEVANT AND APPROPRIATE REQUIREMENTS
FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
CHEMICAL SPECIFIC ARARS - STATE
REQUIREMENT
I. State Drinking Water Act (SDWA)
Health and Safety Code, Division 7,
Part I, Chapter 7, Section 4010 et
seq.
Mulford-Carrell Air Resources Act
(Health and Safety Code Sections
39000-44563) as regulated by the Air
Resources-Board and enforced by
local Air Quality Management
Districts under CAC, Title 17, Part III.
APPLICATION TO THE MAIN TCE PLUME
SDWA establishes drinking water standards
for sources of public drinking water. Federal
MCLs are incorporated into State regulations,
and in some cases the State may promulgate
more stringent State MCLs. The DHS has
set MCLs for 10 of the constituents found in
the TCE plume at CAFB. Several of the
MCLs are at the same levels or more
stringent levels than PDWS-MCLs.
(RELEVANT AND APPROPRIATE)
Ambient Air Quality Standards are listed
under Section 70200/70200.5 of CAC Title
17. Benzene is identified as a toxic air
contaminant. However, no threshold value
has been determined. (MAY BE RELEVANT
& APPROPRIATE-AMBIENT AIR)
LOCATION SPECIFIC ARARS-STATE
There are no location-specific ARARs associated with CAFB. The Base is located in the
historical range of three endangered species. The Air Force will have a biologist
determine the presence or absence of these species. Any surface area disturbance
associated with the selected interim remedy is minimal and should not have a significant
impact on these species habitats, should they exist The Air Force will also have a
qualified agency assess the Base to determine the presence or absence of wetlands.
Any surface area disturbance associated with the selected interim remedy will be minimal
and should not significantly impact any wetlands should they exist. The Base is not in a
floodplaln, nor are there any known surface water bodies that are being affected. There
are no geologic faults below or near the base. No historic places are located within 3
miles. Consequently, the following state statutes are not 'appropriate and relevant" to
the Castle Air Force Base Operable Unit No. 1 (Main TCE Plume):
NOTE: California DHS will provide a Ust of pertinent statutes for location-specific
ARARs.
7-14
MA:ENG:9327T7-4/080291
-------
TABLE 7-4
PAGE 2 OF 5
POTENTIAL STATE APPLICABLE, OR RELEVANT AND APPROPRIATE REQUIREMENTS
FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
TO BE CONSIDERED MATERIAL - STATE
REQUIREMENT
APPLICATION TO THE MAIN TCE PLUME
1. DHS Applied Action Levels (AALs)
Applied action levels are exposure limits that
are pollutant-and receptor-specific and are used
as a point of departure for establishing cleanup
levels. They are similar to the levels
established by the Baseline Risk Assessment
to assure that MCLs are adequately health-
protective.
(MUST BE APPROPRIATE AND RELEVANT)
2. Central Valley RWQCB. A
compilation of Water Quality Goals.
(10/88)
This guidance document contains a compilation
of Water Quality Goals developed by CVWQCB
for various beneficial uses of groundwater.
3. Safe Drinking Water & Toxics
Enforcement Act (Proposition 65)
Reporting of hazardous materials
(developmental toxicants) releases will be
required if fisted substances are being
discharged to the environment at significant risk
levels given in the statute.
(MUST BE APPROPRIATE AND RELEVANT)
MA:ENG:9327T7-4/061291/2
7-1S
-------
TABLE 7-4
PAGE 3 OF 5
POTENTIAL STATE APPLICABLE, OR RELEVANT AND APPROPRIATE REQUIREMENTS
FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
ACTION-SPECIFIC ARARS - STATE
A. GROUNDWATER PUMP AND TREAT REMEDIATION ALTERNATIVE:
1. TREATMENT OF GROUND WATER (DISCHARGES TO GROUND WATER &
DISPOSAL OF RESIDUALS):
REQUIREMENT
APPLICATION TO THE MAIN TCE PLUME
Hazardous Waste Control Act (Health
& Safety Code Section 25100-25395)
as administered by the Department of
Health Services (DHS) under the
California Administrative Code Title 22,
Chapter 30; Minimum Standards for
Management of Hazardous and
Extremely Hazardous Wastes.
1: HWCA has many elements that are
intended to control hazardous wastes
from their point of generation through
accumulation, transportation, treatment,
storage, and ultimate disposal, ft is
implemented largely through regulations
under the CAC, Title 22, Division 4,
Chapter 30. Section 66300 of
Chapter 30 provides no RCRA-type
exemption for CERCLA sites; therefore
most regulations will be directly
applicable to CAFB alternatives.
(1) Criteria for identifying Hazardous
, Wastes (Title 22, 66693-66746)
Disposal of Residuals from
groundwater treatment
(1) Tests for identifying hazardous
characteristics are described in Title 22,
Article 11, Sections 66693-66746. If a
chemical is either listed or tested and
found hazardous, ft must comply with
the hazardous waste requirements
under TOe 22. While these standards
are not treatment or disposal limits, the
resulting classification as hazardous
waste results in efforts to meet the
standard, thereby making hazardous
designation methods a form of
treatment standard.
(2) Persistent and Biocumulative Toxic
Substances (66699) Disposal of
Residuals from groundwater treatment.
(1) Total Threshold Limit Concentrations
(TTLCs) and Soluble Threshold Limit
Concentrations (STLCs) have been
established for selected toxics.
MA:ENG:9327T7-4/061291/3
7-1&
-------
TABLE 7-4
PAGE 4 OF 5
POTENTIAL STATE APPLICABLE, OR RELEVANT AND APPROPRIATE REQUIREMENTS
FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
REQUIREMENT
(3) Porter-Cologne Water Quality Act
Water Code, Division 7, Section 13000
et seq., CCR Title 23, Chapter 3,
Subchapter 9 and Subchapter 15,
1050-2836
APPLICATION TO THE MAIN TCE PLUME
Similar to the Federal CWA, the Act and its
associated regulations apply to protection of
waters of the state. An NPDES permit is
required for off-site discharges, whereas,
only substantive requirements are required
for on-site discharges. Porter-Cologne
delegates standard
2. TREATMENT OF GROUNDWATER (DISCHARGE TO POTW)
REQUIREMENT
(1) Discharge to Publicly Owned
Treatment Works (POTWs) County
Sanitation District of Merced County
APPLICATION TO THE MAIN TCE PLUME
Pretreatment regulations (40 CFR 403)
control the introduction of pollutants to
POTWs
3. TREATMENT OF GROUNDWATER (DISCHARGES TO AMBIENT AIR)
REQUIREMENT
APPLICATION TO THE MAIN TCE PLUME
(4) Mulford-Carrell Air Resources Act,
Hearth and Safety Code, Division 26,
Section 39000 et seq. 17 CAS Part III
Chapter .1, Section 60000 et seq.
The State counterpart of the Federal CAA,
Murford-Carrell, establishes the California
Air Resources Board (CARB) and the local
Air Quality Management Districts (AQMDs).
Permitting authority is delegated in this act
While the treatment unit may not need a
federal permit, It is not relieved from the
requirements of this act. Allocation of
allowable air emissions are on an air basin
specific basis.
(5) Merced County Air Pollution Control
District Rule 210.1 Standards for
Authority to Construct and Rule 210.2
Standards for Permits to Operate.
There may be specific sections of the local
Air Pollution Control Board regulations that
must be met by the design and operation of
an air stripping unit. These may include:
Nuisances (including odors).
7-17
MA:ENG:9327T7-4/080291
-------
TABLE 7-4
PAGE 5 OF 5
POTENTIAL STATE APPLICABLE, OR RELEVANT AND APPROPRIATE REQUIREMENTS
FOR THE MAIN TCE PLUME (OPERABLE UNIT NO. 1)
REQUIREMENT
APPLICATION TO THE MAIN TCE PLUME
(6) Rute.1167-Air Stripping Operations
(Reg. Xl-Source Specific Stds)
This rule is designed to reduce volatile
organic compound (VOC) emissions from
new and existing air stripping equipment
used in the treatment of affected
groundwater.
MA:ENG:9327T7-4/061291/5
7-18
-------
8.0 THE SELECTED REMEDY
The selected interim remedy for this ROD is Alternative I, which consists of:
Pumping groundwater from a series of shallow aquifer extraction wells to maintain
hydraulic control of the TCE plume and begin removing residual TCE
concentrations.
Surface treating the extracted groundwater by air stripping to allow the return of
water to beneficial use (resource recovery).
-. Reinjecting the treated groundwater back to the shallow aquifer to assist in
maintaining hydraulic control and avoid depletion of the aquifer.
Applying natural biological enhancement to accelerate the release/ degradation of
hazardous constituents in the saturated zone.
Abating the air stripper emissions with granular activated carbon (GAC) to avoid
degrading ambient air quality. The abatement unit would be steam regenerated on
site and the liquid condensate would be disposed off site at a permitted recycling
facility.
CONCEPTUAL DESIGN OF SELECTED REMEDY
The selected interim remedy under Alternative I will conceptually consist of groundwater
extraction from an intercepting well field consisting of five wells, one well located at or near
each of the TCE hot spots or identified source locations within the Main TCE Plume. The
wells will tentatively be pumped at a rate of approximately 250 gallons per minute each.
Pumping tests, scheduled to be performed later in the Rl field program, will provide design
data on the number of extraction wells required, their location, and discharge rates.
The surface treatment facility will conceptually consist of a new centralized treatment plant in
an undeveloped area northeast of the POL/storage tank farm (Rgure 1-1). The remedial
treatment technology option will conceptually consist of twin air stripping towers operating in
series, equipped with three double bed vapor phase GAC abatement units with the double
beds operating in series flow. Two of the double bed units will be on-line continuously (one
pair for each of the two strippers), while the third pair of beds remain on standby. An on-site
oil or gas fired boiler will provide steam for the regeneration cycle. Regenerant steam will be
condensed using a Hastelloy alloy heat exchanger and collected in a holding tank pending off-
site disposal to an approved EPA-RCRA recycling facility. The third GAC unit is necessary for
. - . 8-1
MA:ENG:9327-8/061991
-------
continuous operation of the stripper, since the regeneration cycle will require approximately
eight hours. Each adsorber vessel will be sized to contain 6,000 pounds of GAC. A life of 20
I regeneration cycles for the GAC is assumed for estimating purposes. The steam requirement
. is estimated at 10,350 pounds for each single carbon bed.
1 ' .
The air stripping towers were conceptually sized for estimating purposes at 84 inches
( diameter, 25 foot packing depth, and a required air flow rate of 3345 SCFM. The preliminary
tower sizing was based on (worst case) high levels of detected organic compounds in Base
) groundwater sampling data from rounds one, two, three, and four, and on achieving a removal
concentration level to meet re-injection ARARs pursuant to the discharge permit
I
The treated groundwater effluent will be piped to a reinjection well field upgradient from the
extraction well field, with the exact locations to be specified after pumping tests are
conducted. Reinjection wells will be spaced to maximize plume capture and to minimize time
of cleanup.
In addition, nutrients and hydrogen peroxide will be reinjected with treated groundwater to
increase available oxygen in the contaminated aquifer. This action serves to stimulate growth
of natural indigenous bacteria, increase the release rate of contaminants from soil particles,
and degrade some of the contaminants In-sltu. A partial stream of 250 gallons per minute of
the treated groundwater will.be used as the carrier for the nutrients and returned to the aquifer
by a combination of reinjection wells and separate biotreatment injection wells.
Details of the selected interim remedy will be finalized during the remedial design phase.
; SUMMARY OF PRELIMINARY COST ESTIMATES
*
: The selected Interim remedy provides overall effectiveness proportionate to its costs, such that
1 ft represents a reasonable value. Tables 8-1 and 8-2 show the preliminary estimates of
i capital costs, operation and maintenance costs, and total net present value of the selected
remedy (Alternative I). Final cost estimates may vary from the estimates presented due to
changes that may occur as a result of hydraulic modeling, and difference in environmental
setting at the time of remedial design and construction. Such changes, in general, will reflect
modifications resulting from the engineering design process. The hydraulic gradient control
8-2
dA:ENG:9327-8/061991
-------
system and system performance evaluation and schedule will be developed during the
remedial action design process. . '
8-3
MA:ENG:9327-8/061991
-------
TABLE 8-1
ALTERNATIVE I - PRESENT WORTH ANALYSIS
Installed cost of 5 extraction welt-pumps
Installed cost of 5 hotspot extraction wells .
Installed cost of double contained groundwater transfer piping
Installed cost of air stripper treatment system with
GAC emission abatement system
Annual operating cost of air stripper treatment plant
Installed cost of treated water reinjection transfer piping
Installed cost of 8 reinjection wells
Installed cost of biotreatment nutrient feed system
Installed cost of biotreatment injection wells
Annual operating cost of biotreatment nutrient feed system
(assumes 250 GPM of 1250 GPM total groundwater extracted
treated for bio-reinjection)
Cost tQ abandon MID No. 228
Replacement cost of 8 reinjection wells (assume 5 year well
lifetime for present worth analysis)
"Annual maintenance cost
$ COST
96,000
110,000
214,000
1,548,000
1,567,000
149,000
176,000
100,000
60,000
1,092,000
88,000
176,000
50,000
Total estimated capital expenditure (1990 basis)
Total estimated annual operating and maintenance cost (1990 basis)
* Costs shown on 1990 dollar value basis
** Includes disposal costs for periodic stripper cleaning
4A:ENG:9352-T/061991/4
2,541,000
2,744,200
8-4
-------
TABLE 8-2
ALTERNATIVE I PRESENT WORTH VALUES N 1990 DOLLARS*
ANNUAL INFLATION RATE
DISCOUNT RATE
5%
7%
9%
11%
13%
4%
28,420
25,939
23,795
21,934
20,310
6%
31,263
28,445
26,004
23,890
22,049
8%
34,478
31,247
28,469
26,067
23,981
10%
38,065
34,382
32,220
28,492
26,128
12%
42,085
37,898
34,292
31,194
28,515
Values In thousands of dollars.
MA:ENG:9352-T/06199i/5
8-5
-------
9.0 STATUTORY DETERMINATIONS
' The Comprehensive Environmental Response Compensation and Liability Act (CERCLA) as
I amended has designated Federal Facilities as responsible for undertaking remedial actions.
I EPA has the responsibility to ensure that the selected response actions protect human health
/ . and the environment. In addition, Section 121 of CERCLA establishes several other statutory
I . . requirements and preferences. These specify that when complete, the selected remedy for
the site must comply with local, state and federal ARARs unless a waiver is justifiable (tables
I
7-3 and 7-4). ARARs will have to be established for ten contaminants of potential concern
(Section 4.0) for both the treated groundwater and any potential air emissions. ARARs apply
whether the groundwater is to be disposed of via re-injection or by another means. Similarly,
ARARs apply whether the air emissions from the air stripper are controlled or not controlled.
Potential ARARs may be identified by EPA, the California DHS, Water Board, Air Board or by
Merced County Health Department or any other agency with an applicable enforceable
standard.
The selected remedy also must be cost effective and utilize permanent solutions and
alternative treatment technologies to the maximum extent practicable. Remedies that employ
treatment that permanently and significantly reduce the volume, toxicity, or mobility of
hazardous wastes as a major part of the remedy are preferable. How the selected interim
remedy meets these requirements is discussed below.
The selected interim remedy represents the best balance of trade-offs among alternatives with
respect to pertinent criteria, given the limited scope of this action. An in-situ biotreatment
treatability study willbe performed prior to the final design. This study will not cause a delay
to the implementation of the remedy. Re-injection may begin without bio-enhancement should
the treatability study results not be available. Further, bio-enhancement can begin when ail
parameters controlling bio-enhancement are determined.
PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy protects human health and the environment through extraction of TCE
contaminated groundwater and removal/treatment of volatile organic contaminants by air
stripping. The volatile contaminants will be transferred to the gas phase, removed by granular
9-1
MA:ENG:9327-9/070191
-------
activated carton (QAC) adsorption; then recovered by steam regeneration. The condensed
steam containing contaminants adsorbed on the carbon will be collected for treatment or
disposal at an approved facility, as would any spent carbon generated by the treatment
process.
..- . '
Extraction of the groundwater will eventually eliminate the threat of exposure to the
contaminants from direct contact, from inhalation, and from ingestion. Once pumping begins
and hydraulic control is achieved, there are no short term threats associated with the selected
remedy. Wells (exposure routes) known to have been contaminated will have previously been
f ,'"-,'
removed from service or had filtration units placed on them prior to the start of remediation.
Any new wells which become contaminated will also be taken out of service (Section 7.0).
No adverse affects as a result of cross media transfer are expected. Control of emissions
using GAC will adequately control any potential exposure risk.
ATTAINMENT OF ARARs
The selected interim remedy will achieve ARARs (Tables 7-3 and 7-4) for the treated
groundwater and any potential air emissions (including TBCs such as EPA's OSWER Directive
9355.0-28 regarding the control of emissions from air strippers). ARARs for the groundwater
will be documented tn a subsequent ROD. .
ARARs for the treated groundwater will be determined by the California Regional Water
Quality Control Board in the permit requirements for the discharge water. ARARs for the air
emissions will be set by the Merced County Air Pollution Control District in the permit
requirement for the air emissions.
' ' - ' ' ' ' ' '."'"'-
COST EFFECTIVENESS
The selected remedy (Alternative I) was evaluated for cost effectiveness against the other
eight alternatives (A-H). The selected remedy was one of the least costly alternatives and
provides the same benefits and level of protection in the shortest period of time compared to
the other alternatives (Table 7-1). The interim remedy will provide effectiveness proportional
to the cost of the remedy given the operation and maintenance and present worth cost for the
protection of human hearth and the environment.
' 9-2
MA:ENG:3327-9/070191
-------
UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT
TECHNOLOGIES OR RESOURCE RECOVERY TECHNOLOGIES TO THE MAXIMUM
| EXTENT POSSIBLE
The selected interim remedy is not designed nor expected to be final but it represents the best
| tradeoffs among alternatives with respect to the pertinent criteria, especially the balancing
criteria of implementability, short-term effectiveness and cost. The permanent solution will be
| established in a subsequent ROD. Contaminants will be permanently removed and eliminated
by groundwater extraction and surface treatment Contaminants will be reclaimed in the
/ steam condensate and disposed off-site at an EPA-RCRA state approved recycling facility.
| Resources will be conserved to the maximum extent possible using the selected remedy.
Treated water will be reinjected back into the shallow aquifer. The fife of the carbon used for
abatement will be maximized by on site steam regeneration. Contaminant recovery will be
' implemented to the maximum extent possible without losing the removal efficiency of the
abatement unit. .
PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
' The requirement that treatment be a principal element of the remedy will be satisfied in the
final decision document for the site or final operable unit This operable unit action is
consistent with planned future actions, to the extent possible.
9-3
MA:ENG:9327-9/070191
------- |