SEMS-RM DOCID # 5412
San Gabriel Valley Areas 1, 2,
Los Angeles County,
RECORD OF
for
SUBURBAN W A T E
BARTOLO WEL
OPERABLE
SFUND RECORDS CTR
1851-00717
XR0198
and 4 Superfund Sites
California
DECISION
R SYSTEMS
L FIELD
UNIT
United States Environmental Protection Agency
Region 9 -- San Francisco, California
September 1988
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San Gabriel Valley Areas 1, 2, and 4 Sites
RECORD OF DECISION FOR SUBURBAN WATER SYSTEMS
BARTOLO WELL FIELD OPERABLE UNIT
Concurrence — Superfund Program
Neil Ziemba r
Remedial Project Manager
State Programs Section (T-4-1)
9 /zsr/v?
Date '
ill.
Paula Bisson
Chief
State Programs Section (T-4-1)
9-
Date
Chief
Superfund Remedial Branch (T-4-A)
//et/M-
Date
As^ista^t Director for Superfund
Toxics & Waste Management Division (T-4)
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San Gabriel Valley Areas 1, 2, and 4 Sites
RECORD OF DECISION FOR SUBURBAN WATER SYSTEMS
BARTOLO WELL FIELD OPERABLE UNIT
Concurrence — Toxics & Waste Management Division
1-Zf-ft
Dffredtor
Toxics & Waste Management Division
Date
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 Fremont Street
San Francisco, Ca. 94105
2 6 SEP 1989
MEMORANDUM
SUBJECT: San Gabriel Valley Areas 1, 2, and 4 Sites, Suburban
Water Systems Bartolo Well Field Operable Unit Record
of Decision •
nt Division
TO: Nancy J. Marvel, Regional Counsel
Office of Regional Counsel
Please find enclosed for your concurrence the Final Record
of Decision (ROD) for the San Gabriel Valley Area 1, 2, and 4
sites, Suburban Water Systems Bartolo Well Field Operable Unit in
Los Angeles County, California. This document was submitted for
review by your staff and we know of no unresolved issues. If you
have any questions about this ROD, please contact Jon Wactor
(ORC) at 4-8042 or Neil Ziemba (T-4-1) at 4-7174. Neil would
appreciate receiving this concurrence sheet by COB Tuesday,
September 27, or Wednesday morning, September 27 at the latest,
so that the ROD can be transmitted to the RA for signature as
scheduled on September 27. Please contact Lynn Trujillo,
secretary of the Superfund Remedial Branch, at 4-8910 so that
your concurrence sheet can be collected after you have signed it.
Please sign below if you are in agreement with the following
statement:
The enclosed Record of Decision package for the San Gabriel
Valley Areas 1, 2, and 4 sites, Suburban Water Systems Bartolo
Well Field Operable Unit in Los Angeles County, California has
been reviewed and I concur with the contents.
FROM:
Regional Counsel
Office of Regional Counsel
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 Fremont Street
San Francisco, Ca. 94105
2 6 SEP 19M
MEMORANDUM
SUBJECT: San Gabriel Valley Areas 1, 2, and 4 Sites, Suburban
Water Systems Bartolo Well Field Operable Unit Record
rtf /-* i e i An %
nt Division
TO: Harry Seraydarian, Director
Water Management Division
Please find enclosed for your concurrence the Final Record
of Decision (ROD) for the San Gabriel Valley Area 1, 2, and 4
sites, Suburban Water Systems Bartolo Well Field Operable Unit in
Los Angeles County, California. This document was submitted for
review by your staff and we know of no unresolved issues. If you
have any questions about this ROD, please contact Jon Wactor
(ORC) at 4-8042 or Neil Ziemba (T-4-1) at 4-7174. Neil would
appreciate receiving this concurrence sheet by COB Tuesday,
September 27, or Wednesday morning, September 27 at the latest,
so that the ROD can be transmitted to the RA for signature as
scheduled on September 27. Please contact Lynn Trujillo,
secretary of the Superfund Remedial Branch, at 4-8910 so that
your concurrence sheet can be collected after you have signed it.
Please sign below if you are in agreement with the following
statement:
The enclosed Record of Decision package for the San Gabriel
Valley Areas 1, 2, and 4 sites, Suburban Water Systems Bartolo
Well Field Operable Unit in Los Angeles County, California has
been reviewed and I concur with the contents.
FROM:
-t1ai-bL,~fa\ca
Date
Harry Seraydarian
-fC^irector
Water Management Division
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 Fremont Street
San Francisco, Ca. 94105
[fcr6 SEP 1*
MEMORANDUM
SUBJECT: San Gabriel Valley Areas 1, 2, and 4 Sites, Suburban
Water Systems Bartolo Well Field Operable Unit Record
TO: David Howekamp, Director
Air Management Division
Please find enclosed for your concurrence the Final Record
of Decision (ROD) for the San Gabriel Valley Area 1, 2, and 4
sites, Suburban Water Systems Bartolo Well Field Operable Unit in
Los Angeles County, California. This document was submitted for
review by your staff and we know of no unresolved issues. If you
have any questions about this ROD, please contact Jon Wactor
(ORC) at 4-8042 or Neil Ziemba (T-4-1) at 4-7174. Neil would
appreciate receiving this concurrence sheet by COB Tuesday,
September 27, or Wednesday morning, September 27 at the latest,
so that the ROD can be transmitted to the RA for signature as
scheduled on September 27. Please contact Lynn Trujillo,
secretary of the Superfund Remedial Branch, at 4-8910 so that
your concurrence sheet can be collected after you have signed it.
Please sign below if you are in agreement with the following
statement:
The enclosed Record of Decision package for the San Gabriel
Valley Areas 1, 2, and 4 sites, Suburban Water Systems Bartolo
Well Field Operable Unit in Los Angeles County, California has
been reviewed and I concur with the contents.
FROM:
Date
Director
Air Management Division
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 Fremont Street
San Francisco, Ca. 94105
2 6 SFP I*00
MEMORANDUM
SUBJECT: San Gabriel Valley Areas 1, 2, and 4 Sites, Suburban
Water Systems Bartolo Well Field Operable Unit Record
r\*F nor»i ci nn •
TO: Nora McGee, Assistant Regional Administrator
Office of Policy and Management
Please find enclosed for your concurrence the Final Record
of Decision (ROD) for the San Gabriel Valley Area 1, 2, and 4
sites, Suburban Water Systems Bartolo Well Field Operable Unit in
Los Angeles County, California. This document was submitted for
review by your staff and we know of no unresolved issues. If you
have any questions about this ROD, please contact Jon Wactor
(ORC) at 4-8042 or Neil Ziemba (T-4-1) at 4-7174. Neil would
appreciate receiving this concurrence sheet by COB Tuesday,
September 27, or Wednesday morning, September 27 at the latest,
so that the ROD can be transmitted to the RA for signature as
scheduled on September 27. Please contact Lynn Trujillo,
secretary of the Superfund Remedial Branch, at 4-8910 so that
your concurrence sheet can be collected after you have signed it.
Please sign below if you are in agreement with the following
statement:
The enclosed Record of Decision package for the San Gabriel
Valley Areas 1, 2, and 4 sites, Suburban Water Systems Bartolo
Well Field Operable Unit in Los Angeles County, California has
FROM:
Toxics & Waete Management Division
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 Fremont Street
San Francisco, Ca. 94105
2 6 SEP 1988
MEMORANDUM
SUBJECT: San Gabriel Valley Areas 1, 2, and 4 Sites, Suburban
Water Systems Bartolo Well Field Operable Unit Record
Division
TO: John Wise
Deputy Regional Administrator
Please find enclosed for your concurrence the Final Record
of Decision (ROD) for the San Gabriel Valley Area 1, 2, and 4
sites, Suburban Water Systems Bartolo Well Field Operable Unit in
Los Angeles County, California. We would appreciate receiving
your concurrence by COB Tuesday, September 27, or Wednesday
morning, September 27 at the latest, so that the ROD can be
transmitted to the RA for signature as scheduled on September 27.
Please have your secretary contact Lynn Trujillo, secretary of
the Superfund Remedial Branch, at 4-8910 so that your concurrence
sheet can be collected after you have signed it.
Please sign below if you are in agreement with the following
statement:
The enclosed Record of Decision package for the San Gabriel
Valley Areas 1, 2, and 4 sites, Suburban Water Systems Bartolo
Well Field Operable Unit in Los Angeles County, California has
been reviewed and I concur with the contents.
FROM
Date
T-2-&86
Deputy Regional Administrator
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RECORD OF DECISION
TABLE OF CONTENTS
SECTION PAGE
DECLARATION iii
DECISION SUMMARY
1.0 Site Location and Description 1
2.0 Site History 2
3.0 Enforcement 6
4.0 Community Relations 7
5.0 Decision Scope 8
6.0 Nature and Extent of Contamination 9
7.0 Baseline Site Risks 11
8.0 Changes to the Proposed Plan 12
9.0 Description of Alternatives 14
10.0 Applicable and Relevant and
Appropriate Requirements (ARARs) 17
11.0 Floodplain Assessment 20
12.0 Summary of Alternatives Analysis 2 3
13.0 The Selected Remedy 2 6
14.0 Statutory Determinations 28
— Attachments —
ADMINISTRATIVE RECORD INDEX
RESPONSIVENESS SUMMARY
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RECORD OF DECISION
TABLE OF CONTENTS
— Figures —
FIGURE/TABLE FOLLOWING PAGE
1 — Location & General Geology of San Gabriel Basin 1
2 — Extent of Volatile Organic Compound Groundwater
Contamination in the San Gabriel Valley 1
3 — Location of Suburban Water Systems Bartolo Well Field 2
4 — Maximum Historical Concentrations of PCE and TCE
in Wells in the Vicinity of Whittier Narrows 10
5 — Approximated Areas with TCE and PCE Contamination
in the Vicinity of Whittier Narrows 10
6 — Historic TCE and PCE Concentrations
in Bartolo Well 201W2 10
7 — Historic TCE and PCE Concentrations
in Bartolo Well 201W4 10
8 — Interpreted Geologic Cross-Section in the Vicinity
of the Bartolo Well Field, with Well Logging and
Depth-Specific Sampling Results 10
9 — Alternatives For Remedial Action at the
Bartolo Well Field 14
10 — Well Pumping Without Well Modification 16
11 — Well Pumping With Well Modification 16
12 — Alternative Treatment Site Locations 2 0
— Tables —
1 — Maximum Concentrations of Organic Contaminants
Found in Suburban Water Systems Bartolo Well Field 10
2 — Cost Comparison of Assembled Alternatives 17
3 — MCLs, MCLGs, & State Action Levels for Primary Organic
Contaminants Detected in the Whittier Narrows Area 18
4 — Analysis of Alternatives 2 3
5 — Cost Summary for Selected Remedy 2 8
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RECORD OF DECISION
DECLARATION
SITE NAME AND LOCATION
San Gabriel Valley Areas 1, 2, and 4
Los Angeles County, California
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the San Gabriel Valley Areas 1, 2, and 4 sites, in Los
Angeles County, California, developed in accordance with
CERCLA, as amended by SARA, and the National Contingency
Plan. This decision is based on the administrative record
for these sites. The attached index identifies the items
that comprise the administrative record upon which the
selection of the remedial action is based.
The State of California concurs on the selected remedy.
DESCRIPTION OF THE SELECTED REMEDY
This remedial action is the second to be taken at the site.
In a May 1984 Record of Decision (ROD) and a subsequent September
1987 ROD Amendment, EPA selected a remedy to address the public
health threat posed by volatile organic compound (VOC)
contamination of the public water supply wells of three small
mutual water companies in El Monte. The first remedial action is
currently in the construction phase. The remedial action
selected in this decision document—the Suburban Water Systems
Bartolo Well Field Operable Unit—is designed to achieve two
objectives: (1) to partially control the movement and spread of
contaminants in the Whittier Narrows area of the San Gabriel
Valley, thereby contributing to aquifer restoration at the San
Gabriel Valley Areas 1, 2, and 4 sites; and (2) to address the
potential public health threat posed by contamination of SWS's
Bartolo Well Field.
This remedial action is the first phase of a larger remedial
action planned for the Whittier Narrows area to control the
migration of contamination into Central Basin to the south, where
additional public water supply wells are threatened by
contamination. A RI/FS is currently being conducted to develop
an overall Whittier Narrows Operable Unit and is expected to be
released for public comment in 1989, leading to a Record of
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Decision by January 1990. The remedial action selected in this
decision document will be incorporated into the remedial action
for the entire Whittier Narrows area.
This remedial action addresses a small part of the overall
groundwater contamination problem in the San Gabriel Valley Areas
1, 2, and 4 sites. It is expected that several additional
operable units will be planned to address other aspects of the
San Gabriel sites' contamination problems; identification of
future operable units is currently underway.
The remedial action selected in this decision document
incorporates the following components:
o extraction of groundwater from the existing wells in
Suburban Water Systems' Bartolo Well Field and, if
feasible, modification of the existing wells and/or
installation of new production wells to selectively
extract groundwater from the most highly contaminated
zones of the underlying aquifer;
o construction of a packed tower air stripping system to
treat contaminated groundwater on Suburban Water Systems
property at the Bartolo Well Field. Since this location
is within the 100-year floodplain of the San Gabriel
River, appropriate floodproofing measures will be
incorporated into the treatment system design to minimize
the damage to the facilities in the event of flooding and
to limit the downtime necessary after a flood event to
prepare the system to return to operation;
o installation of a vapor-phase GAC off-gas treatment system
to control VOC air emissions from the air stripping
system;
o treatment of contaminated water to contaminant
concentrations below MCLs that results in a cumulative
cancer risk level of 10-6 or less; and
o use of the treated groundwater as water supply for SWS's
customers by feeding the treated water directly into SWS's
water distribution system.
DECLARATION
The selected remedy is protective of human health and the
environment, attains Federal and State requirements that are
applicable or relevant and appropriate for this remedial action,
and is cost-effective. This remedy satisfies the statutory
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V
preference for remedies that employ treatment that reduces
toxicity, mobility, or volume as a principal element and utilizes
permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable. As
part of the remedy, groundwater monitoring will be conducted to
track contaminant levels in the Bartolo Well Field and to monitor
the performance of the treatment system to ensure adequate
protection of human health and the environment.
Date
Regional Administrator
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RECORD OF DECISION
DECISION SUMMARY
1.0 SITE LOCATION AND DESCRIPTION
The San Gabriel Valley Areas 1-4 sites are located
approximately 10-20 miles east of Los Angeles in Los Angeles
County in southern California (Figure 1). The sites are four
large areas of groundwater contamination that underlie
significant portions of the cities of Azusa, Baldwin Park, La
Puente, City of Industry, West Covina, El Monte, South El Monte,
Monrovia, Arcadia, Rosemead, Alhambra, and other municipalities
or unincorporated areas of the San Gabriel Valley. The general
areas of contamination associated with the four San Gabriel Sites
are shown in Figure 2. The sites include industrial, commercial,
residential, as well as undeveloped areas.
The San Gabriel Valley is an alluvial basin bounded by the
San Gabriel Mountains, which rise up to 10,000 feet in the north,
and to the east, southeast, southwest, and west by a series of
low-level (under 1000 feet) sedimentary hills—the San Jose,
Puente, Merced, and Repetto Hills. The major surface water
drainage in the San Gabriel Valley is the San Gabriel and Rio
Hondo Rivers which flow from the northeast to the southeast where
they flow from the valley through the Whittier Narrows, a
two-mile gap between the Merced and Puente Hills. There is
typically no flow in the rivers during the summer dry season
except near the Whittier Narrows area, where the flow is
primarily a combination of sewage treatment plant effluent and
groundwater discharge. The valley is a broad plain that slopes
at an average of 65 feet per mile from the foot of the San
Gabriel Mountains toward Whittier Narrows.
The Main San Gabriel Groundwater Basin, which underlies the
San Gabriel Valley, consists primarily of highly permeable gravel
and cobble deposits. Numerous interbedded lenses of clays also
occur, particularly in the southern portion of the basin and near
the surrounding hills. Regional groundwater flow velocities
range as high as 1000 feet per year. Groundwater flows generally
in the same pattern as the surface water drainage with subsurface
drainage flowing out of the San Gabriel Basin through the
Whittier Narrows area into Central Basin to the south. In some
areas of the valley, however, such as in the west valley near San
Gabriel, large-scale groundwater pumping has resulted in a
reversal of the historical groundwater flow direction.
Groundwater also discharges to surface water along San Jose Creek
in the southeast portion of the valley and in the San Gabriel and
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FIGURE 1
LOCATION AND GENERAL GEOLOGY
OF SAN GABRIEL BASIN
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Rio Hondo Rivers near Whittier Narrows. Substantial recharge of
groundwater occurs in the unlined San Gabriel river bed and in
spreading basins located in the northern portion of the valley.
The San Gabriel Basin provides over 90% of the water supply
for a population of over 1 million people. Forty-five different
water purveyors extract groundwater from the basin, as well as
additional commercial/industrial users. Water rights within the
basin have been adjudicated. Water rights for the basin's
pumpers have been determined as a percentage of the Operating
Safe Yield, which is established annually by the Main San Gabriel
Basin Watermaster based on water level measurements within the
basin. The location and quantity of groundwater pumped is not
controlled, however, an assessment fee is charged for any pumping
in excess of water rights. The assessment fee is essentially a
charge for the purchase of imported surface water to be
artificially recharged in the basin to replace the excess
groundwater pumped.
In addition to the intrabasin adjudication, there is also an
adjudication of water rights between users of the Main San
Gabriel Basin and Central Basin to the south (see Figure 1).
This interbasin adjudication guarantees an average annual usable
flow (groundwater plus surface water) into Central Basin through
Whittier Narrows. If the guaranteed flow requirement is not met,
the Main San Gabriel water users must pay for the purchase of
replacement surface water that is used for artificial recharge of
Central Basin just south of Whittier Narrows.
The subject of this Record of Decision, Suburban Water
Systems'(SWS) Bartolo Well Field, consists of four public water
supply wells located along the east side of the San Gabriel River
in the Whittier Narrows area (Figure 3). The contamination in
this area may be associated with either the San Gabriel Valley
Areas 1, 2, or 4 sites (see § 6.0, page 9) or some combination
thereof. These four wells provide about 55-60% of the water
supply for approximately 17,000 commercial and residential water
customers in SWS's Whittier Service District. In addition, the
Bartolo Well Field provides a small percentage of the water
supply for the neighboring La Mirada Service District. SWS is a
private water utility with numerous groundwater wells in the San
Gabriel Valley.
2.0 SITE HISTORY
Prior to World War II, the San Gabriel Valley was primarily
an agricultural area. During the war, several industries that
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S*A/
*4
'*1
1f0
A"vs
WHITTIER
NARROWS
SCALE IN MILES
BEDROCK OUTCROPS
FIGURE 3
LOCATION OF SUBURBAN WATER SYSTEMS
BARTOLO WELL FIELD
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used large amounts of industrial solvents were located in the
valley. This was followed by the rapid development of
industrial/commercial and residential areas in the valley during
the postwar period. Today, many different industries in the
valley are large users of the chlorinated solvents that have
contaminated groundwater in the basin. Given this history of
industrial development, in all likelihood the contamination of
the groundwater basin began as early as the increase in
industrial activity during the war. Recent investigations of
potential sources of groundwater contamination by the Los Angeles
Regional Water Quality Control Board have indicated that the
basin's contamination is the cumulative result of the solvent and
waste handling and disposal practices of dozens of different
industrial/commercial facilities located throughout the valley.
Groundwater contamination by volatile organic compounds
(VOC) was first detected in the valley when Aerojet
Electrosystems in Azusa sampled a nearby groundwater well owned
by Valley County Water District and found 1800 parts per billion
(ppb) of trichloroethylene (TCE). Subsequent sampling by the
California Department of Health Services (DHS) and the Los
Angeles County Department of Health Services identified over 50
wells contaminated with TCE, perchloroethylene (also known as
tetrachloroethylene or PCE), or carbon tetrachloride (CTC) at
concentrations above the action levels established by DHS. The
action levels are those concentrations above which DHS recommends
that public water suppliers take action to reduce the level of
contamination in drinking water supplies; they have been set at
5, 4, and 5 ppb, respectively, for TCE, PCE, and CTC. All water
purveyors in the San Gabriel Valley, except for three small
mutual water companies in El Monte, were able to supply water
that met the DHS action levels by a combination of shutting down
the most highly contaminated wells, blending water from
contaminated wells with water from clean wells, or using simple
aeration systems for treatment of water contaminated with low
levels of VOCs.
Four areas of groundwater contamination in the San Gabriel
Valley, designated as San Gabriel Valley Areas 1-4, were proposed
for inclusion on the National Priorities List in September 1983,
attaining final NPL status in May 1984. A San Gabriel Management
Committee was established by DHS in 1983 for the purposes of
coordinating remedial action in the San Gabriel Valley. The
committee, which consisted of representatives of EPA, state and
local regulatory agencies, water purveyors, and a public interest
group, agreed on three primary goals: (1) take immediate action
to supply the three mutual water companies in El Monte with a
clean water supply that meets DHS action levels; (2) identify the
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sources of groundwater contamination and take action to control
existing sources; and (3) develop a long-term strategy for
remedial action in the San Gabriel Basin.
To address the first goal, EPA prepared a focused
feasibility study (FFS) to evaluate interim remedial measures
(IRM) to solve the water quality problems of the three mutuals in
El Monte. The FFS was released for public comment in December
1983 and a Record of Decision (ROD) selecting air stripping
treatment as the IRM action was signed in May 1984. Subsequent
to the May 1984 ROD, a pre-design study was initiated that led to
substantial revisions to the cost estimates for the alternatives
considered in the FFS. Based on the revised cost estimates, EPA
proposed in October 1986 to revise its remedy selection for the
IRM and instead select installation of carbon adsorption
treatment systems for the three mutuals. After a public comment
period, an amendment to the 1984 ROD changing the remedy selected
to carbon adsorption was signed in September 1987. Construction
of a treatment system for one of the mutual water
companies—Richwood Mutual Water Company—is currently underway.
Design of a treatment system for a second mutual water
company—Rurban Homes—was completed, but construction was put on
hold as VOC levels in their wells have dropped below DHS action
levels. The third mutual water company
involved—Hemlock—declined EPA assistance and has installed a
carbon adsorption treatment system on its own.
To address the second management committee goal, EPA and
state agencies have conducted several activities to identify
potential sources of VOC contamination within the basin (see
§ 3.0, Enforcement, for further discussion). The third
management committee goal is the focus of the San Gabriel sites
remedial investigation/feasibility study (RI/FS). An overall
RI/FS for all of the San Gabriel sites is being conducted rather
than a separate RI/FS for each site. EPA is managing the sites
through one large basinwide study because all of the areas of
contamination are located in one hydraulically-connected basin,
where actions to address the contamination in one area may have a
significant effect on the contamination in nearby areas.
The RI/FS for the San Gabriel sites was initiated by EPA in
1984 with a preliminary investigation termed the Supplemental
Sampling Program (SSP). This investigation, which was completed
in May 1986 with the release of a draft report, included the
sampling of 70 existing groundwater wells for a full range of
organic chemical contamination, collection and evaluation of
existing data, and regional groundwater flow modeling. The EPA
sampling was coordinated with sampling conducted by water
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purveyors under a new state law (Assembly Bill 1803) and by DHS,
so that a total of 195 existing wells were sampled in 1985. The
primary findings of the SSP were:
o VOCs were the only major organic contaminants affecting
public water supply wells in the basin;
o the areas of contamination were much larger than
previously thought based on sampling data obtained prior
to 1985;
o the potential for significant migration of contamination
was great and a large number of currently clean wells were
threatened by contamination;
o contamination may potentially migrate through Whittier
Narrows into Central Basin, thereby threatening additional
wells; and
o use of an alternative water supply (imported surface
water) to replace the contaminated groundwater supply in
the San Gabriel basin was not feasible on a regional
basis.
The modeling results from the SSP showed that 36 wells were
potentially threatened by contamination above DHS action levels
and EPA proposed Maximum Contaminant Levels (MCL) within 5 years
if the contamination migrated at the same velocity and direction
as regional groundwater flow. In planning for the next phase of
the RI/FS, EPA considered whether any operable units should be
planned to address the water guality problems of specific water
companies, as the IRM had done for the three mutuals. The owners
of the 36 wells were invited to a meeting in April 1987 to inform
them of their potential problem and to obtain information on the
potential public health threat if these wells became
contaminated.
Prior to that meeting, in the fall of 1986, SWS contacted
EPA concerning contamination at its Bartolo Well Field in
Whittier Narrows. VOC levels had recently increased in these
wells, which were located directly downgradient of contaminated
wells (the Bartolo wells were included on the list of 36
potentially threatened wells). The Bartolo wells provide the
major portion of the water supply (over 55 percent) for a
population of approximately 70,000 residents of the City of
Whittier. In addition, as a center of large capacity pumping in
the Whittier Narrows area, the pumping has a potentially large
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effect on the migration of contaminants through the Whittier
Narrows area into Central Basin. The current pumping capacity of
the Bartolo Well Field is approximately 9,300 gallons per minute.
When SWS contacted EPA, they had completed a study evaluating
various options to provide clean water in the event contaminant
levels increased above DHS action levels. After discussions with
SWS regarding the Bartolo well field contamination, EPA initiated
the Suburban Water Systems Bartolo Well Field Operable Unit
Feasibility Study (OUFS) in March 1987 with the goal of
evaluating alternatives to address the public health threat posed
by contamination of the Bartolo well field, as well as evaluating
the role that extraction at the Bartolo Well Field could play in
controlling contaminant migration in the Whittier Narrows area.
On June 22, 1988, the draft SWS Bartolo Well Field OUFS was
released for public comment.
3.0 ENFORCEMENT
The San Gabriel sites were first discovered based on
contamination of public supply wells. At the time of listing,
the sources of contamination were unknown. EPA and the Los
Angeles Regional Water Quality Control Board have conducted
numerous activities over the last several years to identify the
sources of groundwater contamination in the San Gabriel Valley.
In August 1983 and January 1984, EPA issued 88 RCRA Section
3007/CERCLA Section 104 information request letters to facilities
suspected of being major users of chlorinated solvents in the San
Gabriel Valley. Federal, state, and local agency files
pertaining to 49 facilities (including 29 major solvent users as
identified by the information request letter responses and 19
landfills in the San Gabriel Valley) were reviewed in 1986-87.
Site inspections were also conducted for 6 facilities in the San
Gabriel Valley. In 1987 and 1988, EPA issued information request
letters to an additional 208 facilities in the Baldwin Park/Azusa
area, as well as follow-up information request letters to 12 high
priority sites out of the original 88 letter recipients.
The RWQCB began source investigation activities in 1980 with
an industrial survey to determine major solvent users in the San
Gabriel Valley. The results of this investigation were used to
develop EPA's list of the first 88 information request letter
recipients. More recently, in 1986, the RWQCB began a major
source investigation program called the AB 1803 Followup Program.
Under this program, an area (typically one square mile)
surrounding contaminated public supply wells was established
within which a door-to-door industrial survey would be completed.
Inspections are conducted at all facilities potentially using
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solvents. Facilities that may have had a release due to their
handling or storage practices are requested to conduct a leak
detection program for their facility. If soil contamination is
found, an expanded soil and groundwater investigation is
required. As of this time, the RWQCB is currently involved in
investigations in the El Monte, La Puente, and City of Industry
areas. Approximately 60 facilities have reached the groundwater
investigation phase. EPA plans to provide funding to the RWQCB
through a Cooperative Agreement to expand their AB 1803 Followup
Program into additional areas of the San Gabriel Valley.
EPA is currently reviewing the RWQCB files to determine
which facilities are potential sources of groundwater
contamination and should receive general notice letters.
Although EPA plans to issue general notice letters in the near
future, the investigation is not yet sufficiently advanced to
issue special notice letters for implementation of the SWS
Bartolo Well Field Operable Unit.
4.0 COMMUNITY RELATIONS
The public comment period for the OUFS and the proposed plan
opened on June 22nd and continued through July 22, 1988. A
public meeting was held on July 13th at the Whittier Community
Center Theatre in Whittier and was attended by approximately 60
people.
Prior to the beginning of the public comment period, EPA
published a notice on June 19th in both the San Gabriel Valley
Tribune and Whittier Daily News. The notice briefly described
the proposed plan and announced the public comment period and the
public meeting. The notice also announced the availability of
the proposed plan and the draft OUFS for review at the
information repositories established at the Whittier Public
Library, the La Puente Public Library, the Upper San Gabriel
Valley Municipal Water District offices in El Monte, and the EPA
Region 9 office in San Francisco.
A fact sheet describing the proposed plan was delivered to
all of the information repositories on June 22nd. Copies of the
fact sheet were mailed on June 24th to the EPA general mailing
list for the San Gabriel sites, which included about 800 names of
members of the general public, elected officials, and media
representatives. In addition, EPA sent a letter notifying the
City Manager of Whittier of the proposed plan and upcoming public
meeting. Copies of the proposed plan and draft OUFS report were
also provided to the state and local agencies on the San Gabriel
-------
-8-
Valley Superfund Project Technical Advisory Committee, the
Central and West Basin Replenishment District, and Suburban Water
Systems. Intergovernmental review was initiated in a letter of
July 22nd through the Governor's Office of Planning and
Research/State Clearinghouse.
The OUFS evaluated two different locations for siting of a
new water treatment facility. To solicit comment from the
community on locating the treatment facility remote from the
Bartolo Well Field at the Bartolo Transmission Main High Point
alternative site, EPA delivered notices door-to-door in the
vicinity of the High Point site. The notices included the
proposed plan fact sheet, a map of the Bartolo Well Field/north
Whittier area showing the High Point location, and a cover letter
encouraging public comment regarding the alternative locations.
The delivery was made in two phases. On July 9th, the notices
were delivered to about 800 homes in the residential area near
the High Point location who were thought to be in visual range of
the potential site. On July 13th, notices were delivered to
about 2,400 homes located somewhat further from the High Point
location.
In addition to EPA's community relations activities, SWS
cooperated in notifying their customers of EPA's proposed plan.
A notice was mailed on June 22nd to all of their approximately
34,000 customers in the Whittier and La Mirada service districts
(who would potentially receive drinking water from the proposed
treatment plant). The notice briefly described the OUFS,
announced the public comment period and public meeting, and
invited SWS's customers to contact SWS to obtain a copy of the
proposed plan fact sheet. EPA provided about 800 copies of the
fact sheet to SWS that were distributed to customers who called
in a request. SWS also sent letters to the City Managers of
Whittier and La Mirada notifying them of the proposed plan and
the public meeting.
EPA has prepared the attached responsiveness summary, which
provides responses to the comments submitted in writing during
the public comment period, as well as comments made by attendees
at the July 13th public meeting.
5.0 DECISION SCOPE
As discussed in the Site History (page 4), EPA has
previously selected a remedy to address the public health threat
posed by contamination of the public water supply wells of the
three mutual water companies in El Monte. The response action
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-9-
that is the subject of this decision document constitutes the
second EPA remedial action in the San Gabriel Valley and is
designed to achieve two objectives:
o to partially control the movement and spread of
contaminants in the Whittier Narrows area of the San
Gabriel Valley, thereby contributing to aquifer
restoration at the San Gabriel Valley Areas 1, 2, and 4
sites; and
o to address the potential public health threat posed by
contamination of SWS's Bartolo Well Field.
This response action is the first phase of a larger response
action planned for the Whittier Narrows area to control the
migration of contamination into Central Basin to the south, where
additional public supply wells are potentially threatened by
contamination. EPA is currently conducting a Whittier Narrows
operable unit RI/FS that is scheduled to be released for public
comment in 1989, leading to a Record of Decision by January 1990.
The response action selected in this decision document will be
incorporated into the EPA response action for the entire Whittier
Narrows area.
This response action addresses a small part of the overall
groundwater contamination problem in the San Gabriel Valley Areas
1,2,and 4 sites. It is expected that several additional operable
units will be planned to address other aspects of the the San
Gabriel sites' contamination problems. EPA is currently working
to identify and set priorities for future operable units that are
necessary to address the public health threat posed by the San
Gabriel Valley sites.
6.0 NATURE AND EXTENT OF CONTAMINATION
Large areas of the San Gabriel Valley have groundwater
contaminated with volatile organic compounds at concentrations
that exceed EPA MCLs or DHS action levels (Figure 2). Although
there are substantial gaps of data concerning the extent of
contamination in the San Gabriel Valley (including areas as large
as a mile across for which no groundwater quality data exists),
it is known that the regional groundwater flow from the Area 1,
2, and 4 sites is toward the Whittier Narrows area. The areas of
contamination shown in Figure 2, which is based on current
available groundwater quality data in the San Gabriel Valley,
have been drawn conservatively in that if no data is available,
the area is assumed to be uncontaminated. Based on regional
-------
-10-
groundwater flow patterns and limited available data regarding
the vertical extent of contamination (see discussion below), it
is highly probable that the "clean" areas separating the
contamination in the Whittier Narrows area from the major plume
areas in the Area 1, 2, and/or 4 sites are actually contaminated.
Figure 4 shows the maximum historical concentrations of the
two primary contaminants of concern, PCE and TCE, in wellhead
samples from production wells in the Whittier Narrows area,
including the Bartolo Well Field. Based on this data, a map of
the areas of groundwater contamination in the Whittier Narrows
area has been prepared (Figure 5). The Bartolo Well Field is
located near the western edge of the main area of contamination
in the Whittier Narrows area. Table 1 shows the maximum
concentrations found in SWS's wells in the Bartolo well field,
along with EPA MCLs and DHS action levels for the contaminants
detected. As of this date, only one contaminant has been
detected at levels above EPA's MCLs or DHS action levels: Well
201W4 (Recordation No. 01901433) has recently showed TCE
concentrations above the MCL of 5 ppb (6.3 ppb). The
concentration of contaminants in SWS's wells has been increasing
over the last two years. Figures 6 and 7 show the increasing
trend of historic TCE and PCE concentrations for Wells 201W2 and
201W4. The trend for the other two SWS wells is more equivocal,
showing no clear increasing trend. Simple analytical modeling of
the zone of capture of the Bartolo wells was completed and showed
that Well 201W4 may be pulling much of its water from the
contaminated area to the east.
Limited testing of production wells has also been conducted
to determine the vertical extent of contamination in the vicinity
of the Bartolo well field. The special testing was completed for
one of SWS's wells (201W4) and the nearest well upgradient to the
Bartolo wells, San Gabriel Valley Water Company Well B2. The
testing procedure, referred to as "well logging and depth
specific sampling," utilizes existing production wells with
multiple perforated intervals to determine the quantity of water
produced from each interval, and the depth-specific water
quality. The results of this testing are shown, along with a
representation of the local geologic conditions based on
available well logs, in Figure 8. The limited data shows that
the most contaminated water may occur within the zones of
intermediate depth (200-350 feet). The shallower zones are
contaminated at lower levels, and the deepest zones are even less
contaminated. This suggests that sources of contamination far
upgradient of the Bartolo well field may contribute a significant
portion of the groundwater contamination found in this area,
since if local sources were the primary source of contamination,
-------
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-------
TABLE 1
MAXIMUM CONCENTRATIONS OF ORGANIC CONTAMINANTS FOUND
IN SUBURBAN WATER SYSTEMS BARTOLO WELL FIELD*
Max imum
Historical Number of
Concentration Samples Number of
Chemical (ug/1 ) Analyzed Detections
1,1,1-Trichloroethane 1.0 61 11
1,1-Dichloroethane 0.4 5 7 3
1.1-Dichloroethylene 1.8 132 9 2
1.2-0ichIoroethane 0.1° 63 4
c i s-1,2-Dichloroethylene 4.2 14 8
Carbon Tetrachloride (CTC) 0.1° 72 3
Dibromochloromethanea(THM) 0.6 55 1
Methylene Chloride 1.0 59 5
TetrachIoroethyIene (PCE) 3.9C 115 94
Pentane8 3.0b 1 1
trans-1,2-Dichloroethylene 3.5k 59 8
TrichIoroethyIene (TCE) 5.8C 136 121
Concentration ranges and numbers of detections represent data collected
by EPA, DHS, Suburban Water Systems, and the Upper San Gabriel Valley
Municipal Water District (AB 1803 Program monitoring) from January 1980
through April 1, 1988.
a Compound has been detected in only one sample.
k The reported concentration was estimated.
c Excluding anomalous sample results reported by Thermo Analytical.
-------
8ART0L0 WELL 201W2 (01901430)
~ TRICHLOROETHYLENE A TETRACHLOROETHENE CPCE)
FIGURE 6
HISTORIC TCE AND PCE CONCENTRATIONS
IN BARTOLO WELL 201 W2 (1901430)
-------
BARTOLO WELL 201W4 (01901433)
~ TRICHLOROETHYLENE A TETRACHLOROETHENE CPCE)
FIGURE 7
HISTORIC TCE AND PCE CONCENTRATIONS
IN BARTOLO WELL 201 W4( 1901433)
-------
SOUTH
WEST
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200 •
LEGEND
150
10.9/13.1/27.5
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DEPTH-SPECIFIC
TCE/PCE/TRANS-1,2- 100-
DCE CONCENTRATION
(ug/l)
RELATIVE WATER 50 H
PRODUCTION (%) FROM
THAT PARTICULAR ZONE
PERFORATED INTERVAL
WELL USED FOR WELL
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FIGURE 8
INTERPRETED GEOLOGIC CROSS-SECTION
IN THE VICINITY OF THE BARTOLO WELL
FIELD, WITH WELL LOGGING AND DEPTH-
SPECIFIC SAMPLING RESULTS
-------
-li-
the shallower zones would be expected to have the highest
contamination concentrations.
7.0 BASELINE SITE RISKS
To determine the baseline site risk posed by contamination
at the Bartolo Well Field, estimates were made of the future
water quality at the wellhead of the SWS wells. The estimates of
future wellhead water quality were based on the mean and maximum
historical wellhead concentrations observed in production wells
located upgradient of the Bartolo Well Field. Regional
groundwater flow velocities were used to determine travel times
from upgradient wells to the Bartolo Well Field. For the
purposes of estimating future water quality for the baseline site
risk assessment, wells were grouped in approximate 5-year
intervals based on the estimated travel time. The mean and
maximum historical concentrations of all wells within a 5-year
travel time of the Bartolo Well Field were used as the estimate
of the concentration of the Bartolo wells over this 5-year
period. For the short-term (0-5 years), wellhead concentrations
of the two primary contaminants, TCE and PCE, are estimated to
continue to rise and reach a maximum of 17 and 18.5 ppb,
respectively. This is based on the historical contaminant
concentrations that have been detected in the nearest upgradient
well, San Gabriel Valley Water Company Well B2.
This method for estimating future water quality suffers (as
would any other method) from the limited detailed data available
regarding water quality and local groundwater flow velocities.
For example, there are no wells within the 5-20 year travel time
interval. Therefore, data from the 4 wells found within the
20-25 year travel time interval were used to represent the entire
5-25 year travel time interval.
The future concentration estimates extended out 60 years.
Although 70 years is normally used for a cancer risk assessment,
there are no upgradient wells with travel times between 60 and 7 0
years. Using the estimates of future water quality at the
Bartolo Well Field, the no action risk baseline for cancer risks
was calculated in the Public Health Evaluation to be
approximately 6-8 x 10~6, or just under 10 . This number
represents the risk of contracting cancer due to exposure to
contaminated groundwater from the Bartolo Well Field. While SWS
by law cannot serve water that exceeds MCLs, the public health
evaluation hypothetically removes this institutional control and
assumes exposure to the contaminated groundwater via SWS's water
supply system.
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-12-
Although more than 2 0 organic chemical contaminants have
been detected in SWS's Bartolo well field or in upgradient wells
in the Whittier Narrows area, many of these did not enter into
the calculation of the baseline site cancer risk. Only TCE, PCE,
carbon tetrachloride, chloroform, 1,1 -dichloroethylene,
1,2-dichloroethane, methylene chloride, and
1,1,2,2-tetrachloroethane are considered potential carcinogens in
water. In addition, because of equivocal evidence of
carcinogenicity, 1,1-dichloroethylene and 1,1,2,2-tetrachloethane
were not considered a carcinogen in the Public Health Evaluation
calculations for this site.
At sufficiently high exposure levels, the noncarcinogens,
along with some of the carcinogens, have chronic
(noncarcinogenic) or subchronic (short-term) health effects
associated with them. The contaminant concentrations currently
found or estimated to be found in the future in the Bartolo Well
Field are all below levels believed to have the potential to
cause noncarcinogenic health effects.
The primary exposure pathway is ingestion of groundwater.
Other exposure pathways of concern for contaminated groundwater
used for domestic purposes include absorption through the skin
(dermal exposure route) and inhalation of volatilized chemicals,
which could occur during showering, cooking, or other water uses
in the home. These exposures would tend to increase the baseline
risk from ingestion. While there is no scientific consensus on
the significance of these pathways, some current literature
suggests that these pathways may be equal to or greater than the
exposure due to ingestion. The risk from these pathways,
however, are not currently quantifiable.
8.0 CHANGES TO THE PROPOSED PLAN
This decision document selects the response action described
in the proposed plan. The only change that has been made is in
the determination of applicable or relevant and appropriate
requirements (ARAR) that would apply to the proposed action,
however, this does not change the selection of remedy. Some
uncertain aspects of the response action that were included in
the proposed plan are clarified in this section.
In the proposed plan, South Coast Air Quality Management
District (SCAQMD) Rule 1167 is identified as an ARAR. This ARAR
is presented as the rationale behind including activated carbon
adsorption treatment of the air stripper off-gas for control of
-------
-13-
air emissions. A recent court ruling has stayed enforcement of
this rule, so it is not legally considered an ARAR at this time,
but instead as a "to be considered" requirement (see ARARs—§
10.0 on page 18). In this decision document, the remedy selected
still incorporates the air emissions control despite the fact
that SCAQMD Rule 1167 is not considered an ARAR.
The rationale behind this is that SCAQMD fully intends to
pursue the procedural steps needed to establish Rule 1167 as a
legally enforceable promulgated regulation in the near future.
In addition, the South Coast Air Basin is considered
nonattainment for ozone under the Clean Air Act. As the intent
of Rule 1167 was to control the VOC precursor emissions to ozone,
it is reasonable to include air emissions control as part of this
response action to assist SCAQMD's efforts to reach attainment
status in the South Coast Basin. Finally, public comment
submitted to EPA in writing and made by attendees at the public
meeting was overwhelmingly in support of including air emissions
controls regardless of the legal status of SCAQMD Rule 1167.
The proposed plan included incorporation of well
modifications to selectively extract groundwater from the most
contaminated zones in the aquifer. This recommendation was based
on the limited data available that showed well modification may
be feasible. The actual extent of incorporating well
modification in the response action depends on whether additional
data collected during the design phase supports its feasibility.
During the design phase, well logging and depth-specific
sampling of wells in the Bartolo Well Field will be conducted,
and one or more groundwater monitoring well clusters may be
installed nearby and sampled to better determine the vertical
distribution of contamination. Based on the data obtained
through this testing, a determination of the feasibility of well
modification will be made. If well modification is determined to
be feasible, the actual modifications to SWS's wells will be
designed. In addition, the need or desirability of drilling new
extraction well(s) to extract the most highly contaminated
groundwater will be subsequently determined and new wells
designed if so indicated.
The proposed plan also described how, at a minimum, EPA will
incorporate floodproofing features into the design of the
treatment system at the Bartolo Well Field. During the design
phase, alternative floodproofing options will be identified. The
actual floodproofing measures incorporated into the design will
be selected at that time based on their potential to reduce flood
damage and their cost-effectiveness.
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-14-
9.0 DESCRIPTION OF ALTERNATIVES
As described in the Decision Scope section (page 8), EPA
established two primary remedial response objectives for the SWS
Bartolo Well Field response action:
o to control migration of contaminants from the San Gabriel
Basin through Whittier Narrows into the Central Basin,
thereby contributing to aquifer restoration at the San
Gabriel Valley Areas 1, 2, and 4 sites; and
o to address the potential public health threat posed by
contamination of SWS's Bartolo Well Field by providing
residents in SWS's Whittier District with a water supply
meeting federal and state drinking water standards.
General response actions that may be applicable to
groundwater contamination were screened based on two
criteria—the ability to meet the remedial response objectives
and the applicability of the technology to the site conditions.
Several technologies were dismissed from further consideration
based on these criteria. For instance, containment options
involving vertical barriers such as slurry walls were dismissed
because they are physically limited to about 2 00 feet in depth
and groundwater contamination has been detected to greater depths
in the Whittier Narrows area. Similarly, in situ treatment was
not evaluated further since the technology has not advanced to
the state where it could be reliably used in an aquifer such as
the San Gabriel Basin where the horizontal and vertical extent of
contamination is so large.
For response actions involving extraction and treatment of
contaminated groundwater, options for disposal of treated
groundwater that did not involve discharge to SWS's water supply
distribution system were eliminated from further consideration.
The reason for this is that direct discharge of treated water to
SWS's water supply system is the only way that the second
response objective can be met without supplying an alternative
water supply in addition to the groundwater response action at a
substantial additional cost.
Figure 9 shows the alternatives developed and evaluated in
the OUFS. One alternative (Alternative I) was developed—
alternative water supply—that would only meet one of the
remedial response objectives. This alternative would involve
replacing the water supply currently obtained from the Bartolo
Well Field with water purchased from the Metropolitan Water
-------
Figure 9
ALTERNATIVES FOR REMEDIAL ACTION AT THE
BARTOLO WELL FIELD
AIR STRIPPING
CARBON
ADSORPTION
Minimum
Air Stripping
Dual Bed
Single Bed
ALTERNATE WATER SUPPLY ALTERNATIVE
2
Maximum
Air Stripping
1
A Bartolo Main High Point Location
Q Bartolo Well Field Location
D Bartolo Main High Point Location
D with off gas carbon treatment
n Bartolo Well Field Location
p Bartolo Well Field Location
with off gas carbon treatment
Well Modification
. F Bartolo Main High Point Location
¦ G Bartolo Well Field Location
|-j Bartolo Well Field Location
Connect to MWD
NO ACTION ALTERNATIVE
Alternative E is the alternative proposed by EPA.
1 Well modification can be used in conjunction with either air stripping or carbon
adsorption. (See text for description). EPA proposes to use it in combination
with air stripping.
2 The No Action Alternative was used as a baseline for comparison to the
other alternatives (A-l above)
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-15-
District of Southern California (MWD) and conveyed through a new
pipeline. This alternative would meet the objective of supplying
SWS's customers with water that meets federal and state drinking
water quality standards. However, it would not meet the
objective of controlling the migration of contaminants through
the Whittier Narrows area. Under this alternative, response
action to meet the second objective would be deferred to the
future Whittier Narrows operable unit.
All of the other remedial alternatives considered (except
the no action alternative) involve extraction of groundwater from
the Bartolo Well Field (to meet the first remedial response
objective), treatment of the contaminated water, and use of the
treated water as water supply for SWS's customers (to meet the
second remedial response objective). The alternatives differed
in their choice of treatment technology, level of treatment,
treatment technology configuration, and location of the treatment
system.
Two treatment technologies, identified by EPA's Drinking
Water Office as the Best Available Technologies for treatment of
VOCs in drinking water applications, were evaluated in detail:
o Packed tower air stripping treatment (Alternatives A-E);
and
o Liquid phase granular activated carbon adsorption
(GAC) treatment (Alternatives F-H).
All of the treatment system alternatives were developed to treat
contaminated water at a rate of 10,000 gallons per minute, at
about the nominal production capacity of the wells in the Bartolo
Well Field. In addition, all of the treatment system
alternatives are assumed to operate over the expected design life
of the installed equipment (30 years). Whether the treatment
facilities would need to operate longer than 30 years depends on
the selected remedy for the Whittier Narrows Operable Unit and
other operable units at the San Gabriel Valley Areas 1, 2, and 4
sites.
Several alternative air stripping alternatives were
developed by using different combinations of three
components—level of treatment, control of emissions, and
location. Two different levels of treatment were evaluated. The
alternative termed "minimum air stripping" would treat the
contaminated water to a level where the contaminant
concentrations would meet EPA MCLs and DHS action levels
(Alternatives A & C). The "maximum air stripping" alternative
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-16-
would treat to levels below MCLs and action levels at which the
cumulative residual public health risk would be at or below the
10"6 level (Alternatives B, D, & E). Air stripping alternatives
were developed that did not incorporate any air emissions
controls (Alternatives A, C, & D), as well as alternatives that
did include gas phase GAC treatment of off-gas emissions
(Alternatives B & E). The alternatives with air emissions
controls would reduce expected VOC emission levels by an
estimated 90%. Air stripping alternatives were also developed
for two alternative treatment system locations. One location was
on SWS property at the Bartolo Well Field (Alternatives C-E).
Since this location is in the 100-year floodplain of the San
Gabriel River, an alternative site (termed the Bartolo Main high
point location) for the treatment system was considered that is
about one and one-half miles to the south along the transmission
main that carries water from the Bartolo Well Field to SWS's
Whittier Service District (Alternatives A & B).
Two configurations of carbon adsorption systems were
evaluated for consideration. Under one configuration (single
bed), water would flow through a single carbon vessel before
entering the treatment system (Alternative H), while under the
other configuration (dual bed), the water would flow through two
carbon vessels in a series combination (Alternatives F & G). The
dual bed configuration has a higher capital cost, but provides an
extra level of protection since if contamination "breaks through"
the first carbon bed there is still a second carbon bed to
provide treatment of the contaminated water. In addition to the
alternative treatment system configurations, carbon adsorption
alternatives were also developed for the two different locations
for the treatment system described above (Alternatives F & G at
the Bartolo Well Field site and Alternative H at the Bartolo Main
high point site).
An additional extraction alternative was developed as an
option that could be combined with any of the treatment system
alternatives—well modification. Based on the limited well
logging and depth-specific sampling that was conducted (see
§ 6.0, pp. 10), it appears that the contamination is more
prevalent in specific zones of the aquifer at the Bartolo Well
Field. Under the well modification alternative, the existing
Bartolo wells would be modified and/or new production wells would
be installed to selectively extract water from the depths where
the most contamination is found. In this way, the amount of
groundwater contamination removed from the aquifer by the
response action will be maximized, which will assist in the
control of migration of contaminants in the Bartolo Well Field
area. Figures 10 and 11 show conceptually how well modification
-------
Figure 10
WELL PUMPING WITHOUT
WELL MODIFICATION
-------
Figure 11
WELL PUMPING WITH
WELL MODIFICATION
20 ppb TCE ^
Well Casing
I ' nl'Unllm rUtltti'
-------
-17-
could increase the removal of groundwater contamination from the
aquifer.
Further testing during the design phase will have to be
conducted to determine what, if any, well modifications are
feasible. For the purposes of estimating the cost of this
alternative, it was assumed that the four existing wells are
modified so that only water from the upper two zones are
extracted and one new production well is installed to make up for
the lost production capacity.
Estimates have been made of the maximum potential
depth-specific contaminant concentrations, based on the results
of the depth-specific sampling conducted at San Gabriel Valley
Water Company Well B2, located upgradient of the Bartolo Well
Field. The estimates were obtained by multiplying the maximum
historical wellhead concentrations found in Well B2 by the ratio
between the maximum depth-specific concentration and the wellhead
concentration found during the depth-specific sampling of Well
B2. Since selective extraction of contaminated water may be
implemented with any treatment system alternative, the estimated
maximum potential depth-specific contaminant concentrations were
used in estimating influent concentrations for the treatment
system alternatives' conceptual designs.
Estimated total present worth costs for the treatment system
alternatives that were developed in detail range from about 6.6
to 26.1 million dollars. The estimated cost of the well
modification option (which would be in addition to the cost of
any of the treatment system alternatives) is about $2.6 million.
The alternative water supply alternative alone would have an
estimated total cost of $42.1 million. Table 2 gives a summary
of the capital and operations and maintenance costs for the
alternatives.
10.0 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARs)
Applicable or relevant and appropriate requirements (ARARs)
can be grouped into three categories: chemical-specific ARARs;
action-specific ARARs; and location-specific ARARs. The
chemical-specific ARARs that apply to this response action are
the Safe Drinking Water Act MCLs. California DHS has set action
levels for VOCs, a few of which are more stringent than the MCLs
or for which no MCL has been established. While the DHS action
levels are not promulgated standards and are not, therefore,
ARARs, they have been taken into consideration during development
of remedial action alternatives. In addition, DHS has recently
-------
Table 2
COST COMPARISON OF ASSEMBLED ALTERNATIVES
($l,000's)
Incremental Met Present Worth
Short-Term Long-Term at Discount Rate
Alternative Capital Cost OSM Cost 3 Percent 5 Percent 10 Percent
A:
Minimum Air Stripping at
Bartolo Main High Point
1,640
324
7,991
6,621
4,694
B:
Maximum Air Stripping at
Bartolo Main High Point
with Off-gas Carbon
Treatment
4,342
707
18,198
15,209
11,006
C:
Minimum Air Stripping at
Bartolo Well Field
1,739
326
8,129
6,750
4,812
D:
Maximum Air Stripping at
Well Field
2,363
393
10,056
8,397
6,063
E:
Maximum Air Stripping at
Bartolo Well Field with
Off-Gas Carbon Treatment
4,387
708
18,258
15,266
11,058
F:
Dual Bed Carbon Adsorption
at Bartolo Main High Point
10,693
1,003
30,358
26,116
20,151
G:
Dual Bed Carbon Adsorption
at Bartolo Well Field
10,221
994
29,700
25,498
19,589
H:
Single Bed Carbon
Adsorption at Bartolo
Well Field
7,433
1,052
28,059
23,609
17,353
I:
Replace Bartolo Well
Field Supply with
Water from MWD
6,388
2,326
51,973
42,140
28,312
Additional Option for All
Treatment
Alternatives:
Well Modification 1
,042
101
3,022
2,595
1,994
-------
-18-
proposed MCLs for a number of VOCs. Of particular significance,
the proposed MCL for PCE is 2 ppb, which is lower than the
current DHS action level of 4 ppb. Although the proposed MCLs
are not yet promulgated, they have been taken into consideration
during the remedy selection process. Table 3 lists the MCLs and
DHS action levels for the primary contaminants from the Public
Health Evaluation.
Table 3 also lists the Maximum Contaminant Level Goals
(MCLGs) for the primary contaminants. MCLGs, which are based
only upon health criteria, are not directly applicable as
chemical-specific requirements because they are not enforceable
standards. In accordance with the EPA "Interim Guidance on
Compliance with Applicable or Relevant and Appropriate
Requirements (OSWER Directive 9234.0-05)," the MCLs are
considered the chemical-specific ARARs because they are (1) the
enforceable drinking water standards, (2) required to be set as
close to the MCLGs as is feasible, taking into consideration the
best technology, treatment techniques and other factors
(including cost), and (3) protective of public health to within
EPA's acceptable carcinogen risk range of 10-4 to 10~7.
The primary action-specific requirement affecting this
response action is the South Coast Air Quality Management
District's (SCAQMD) Rule 1167. The purpose of Rule 1167 was to
control VOCs as precursor emissions to ozone formation in the
South Coast Air Basin. The South Coast Air Basin is currently in
nonattainment status with respect to the National Ambient Air
Quality Standards (NAAQS) for ozone. In California, authority to
regulate stationary sources of emissions has been delegated to
local air quality management districts. Therefore, this rule,
having been duly promulgated by SCAQMD in early 1988, constituted
a promulgated state requirement under a state environmental
law—as set forth in section 121(d) of the Superfund Amendments
and Reauthorization Act of 1986 (SARA)—that is generally
applicable.
This rule requires that all air stripping facilities
treating contaminated groundwater that emit more than one pound
per day of total VOC emissions install air emission controls
capable of reducing air emissions by 90%. At the current
contaminant levels found in the Bartolo wells, an air stripping
facility would be expected to emit just below one pound per day
of total VOCs; however, with the projected future wellhead and
depth-specific contaminant concentrations that are expected to be
extracted from the Bartolo Well Field for treatment in the near
future, the air emissions will exceed the one pound per day
limit.
-------
TABLE 3
MCLS, MCLGs & STATE ACTION LEVELS
FOR PRIMARY ORGANIC CONTAMINANTS
DETECTED IN THE WHITTIER NARROWS AREA
(Mg/i)
CHEMICAL
MCL OR
PROPOSED
MCL
MCLG OR
PROPOSED
MCLG
STATE
ACTION
LEVEL*
trichloroethylene (TCE)
tetrachIoroethyIene (PCE)
1,1-dichloroethylene
trans-1,2-dichloroethylene -
70
16'
cis-1,2-dichloroethylene
70
16'
carbon tetrachloride (CTC) 5
State Action Levels are set by the California Department of Health Services,
a DHS has recently proposed establishing State MCLs for PCE and CTC of 2 and
0.5 ppb, respectively.
15 Action level is for each 1,2-dichloroethylene isomer individual concentre
tion or the some of the concentrations of both isomers.
-------
-19-
Rule 1167 was considered an ARAR in the proposed plan since
the rule was promulgated on January 8, 1988 and scheduled to take
effect before installation of a treatment system at the Bartolo
Well Field. Therefore, the proposed plan included the
installation of air emission controls (off-gas vapor phase GAC
treatment) to comply with SCAQMD Rule 1167. Subsequent to the
release of the proposed plan, a state court ruled on a lawsuit
filed by the Upper San Gabriel Valley Municipal Water District
challenging the adoption of Rule 1167 without preparation of an
Environmental Impact Report (EIR) as required under the
California Environmental Quality Act (CEQA). The court's
decision ordered SCAQMD to rescind its adoption of the rule and
refrain from re-adopting a rule governing emissions from air
stripping equipment pending completion by SCAQMD of an EIR
focused on the potential impact of the rule on groundwater
supplies, groundwater quality, and imported water supplies in the
SCAQMD area. Since the rule is no longer generally applicable to
existing or proposed air stripping systems operated by private
parties within the South Coast Basin, it is not legally an ARAR.
It has been taken into consideration during the remedy selection
process, however, since SCAQMD has indicated that it fully
intends to proceed to adopt Rule 1167 as a promulgated
requirement.
Several of the alternatives developed included construction
of treatment systems at the Bartolo Well Field. The Bartolo Well
Field is located within the flood retention basin of the Whittier
Narrows Dam. The proposed treatment system location is located
within the 100-year floodplain of the San Gabriel River. Two
location-specific ARARs apply to actions that would take place
within the floodplain. First, the Floodplain Management
Executive Order (E.O. 11988), directs EPA to avoid actions
located within or affecting the 100-year floodplain unless the
floodplain location is the only practicable alternative. In
addition, in the absence of a practicable alternative, actions
must be designed or modified in order to minimize potential harm
to or within the floodplain. Second, EPA drinking water
regulations adopted under the authority of the Safe Drinking
Water Act (40 CFR, 141.5) require that the construction or
modification of public water supply systems, to the extent
practicable, should not be located within the 100-year
floodplain. To determine compliance of potential alternatives
with these ARARs and to comply with the EPA implementing
regulations for E.O. 11988 (40 CFR Part 6, Appendix A, Statement
of Procedures on Floodplain Management and Wetland Protection), a
floodplain assessment was prepared as part of the OUFS. The next
section describes the findings of the floodplain assessment.
-------
-20-
11.0 FLOODPLAIN ASSESSMENT
The floodplain assessment, prepared as part of the OUFS,
included the following components: whether the action would be
located within or affect the 100-year floodplain; the
identification of alternatives to carrying out the action within
the floodplain; the impact of the action on the floodplain; the
identification of measures to minimize potential harm to the
action if the action must be carried out in the floodplain; and
the implications of loss of use of the treatment facility during
and after a flood event.
Five of the treatment system alternatives developed in the
OUFS include the construction of treatment alternatives at the
Bartolo Well Field site, which is located on 90 acres of land
owned by SWS inside the Whittier Narrows Dam impoundment area.
The proposed treatment facilities would be located at an
elevation approximately 13 feet below the 100-year flood
elevation, corresponding to the 30-year flood elevation that has
the probability of being flooded once every 30 years. Since the
design life of the treatment facilities is 30 years, at least one
flood event would be expected during the facilities' lifetime.
The highest probability of flooding would occur during the winter
storm season, which typically lasts from November through April.
The 3 0 year flood elevation is subject to frequent flooding,
sedimentation, and wave action. The warning for a 100-year flood
could be as little as 12 hours; for a 3 0-year flood, the warning
would be less.
An alternative location for the treatment system outside of
the floodplain was identified and retained for detailed
evaluation in the OUFS. This alternative site is located at the
high point of the Bartolo Transmission Main, which carries water
from the Bartolo Well Field to the Whittier Service District to
the south. The site is near the intersection of Workman Mill
Road and Strong Avenue (Figure 12). Though a specific property
has not been identified, several acres of vacant property are
adjacent to the high point location.
The primary advantage of the alternative high point site is
that it is not within the 100-year floodplain. In addition,
construction and operation of the treatment system is slightly
less costly at the high point site since the treated water can
return to the Bartolo Transmission Main by gravity without
repumping. This cost difference is less than 0.4 percent,
however, for the treatment system configuration included in the
proposed plan.
-------
WELL FIELD SSTE
BARTOLO WELL FIELD
W~2
* #W~6
WHiTTlER NARROWS QAM
# W-4
#W~S
V'
ROSE HillS MEMORIAL PARK
.-HIGH POINT SHE
/
^C,,; ^ ¦
%JS
¦>N
0 1000 2000
SCALE IN F£ET
FI&URE 12
ALTERNATIVE TREATMENT
SITE LOCATIONS
-------
-21-
The high point location has two serious disadvantages.
First, the high point site is located adjacent to residential
areas. Due to the potential visual, noise, and air quality
impacts, the acceptability of this location to the community is
questionable (see § 12.0, page 25 for a discussion of public
comment regarding this issue). Second, property at the high
point location would have to be identified and acquired. This
would require additional time and expense to complete the design
and construction of the action. To get an estimate of the
potential delay to construction, DHS was contacted regarding how
quickly they would be able to acquire property at the high point
location. [Note: Under EPA CERCLA policies, the state is
required to obtain site access for EPA response actions.] DHS
responded that they would obtain property either through purchase
of easements through negotiation or through eminent domain.
Either course of action would add a delay of at least one year to
the project because an Environmental Impact Report would be
required under CEQA before DHS could take action to obtain
property. If negotiations proved unsuccessful, the use of
eminent domain could result in substantial delays (2-5 years) due
to the mandatory notice and appeal process, as well as potential
lawsuits.
The Bartolo Transmission Main high point site is not
considered a practicable alternative due to the long delay in
implementation that would be incurred to allow for locating and
acquiring property for the treatment facility, and due to its
vicinity to adjacent residential areas and the lack of public
acceptance within the local community.
For the Bartolo Well Field location, the primary
disadvantage is its location in the floodplain and the
possibility of damage or loss of equipment or interruption of
operation of the system during and after a flood event. In
addition, as discussed above, the treatment system cost is
slightly higher due to the need for a booster pump station to
return the treated flow to the Bartolo Transmission Main. The
two primary advantages of the well field location are its
ownership by SWS, which allows for expedited construction, and
its location remote from any residential areas.
A treatment facility can be constructed in such a manner at
the Bartolo Well Field that it will not have any effect on the
floodplain. The treatment system can be designed to withstand
wave action in the dam impoundment area. In addition,
construction techniques can be used to secure or remove equipment
to prevent it from being carried away and becoming lodged in the
dam spillway and blocking the downstream flow of floodwater. The
-------
-22-
facility would be constructed so that there is no change in the
storage volume of the impoundment. Therefore, the facility will
have no effect on floodplain boundaries.
Numerous floodproofing techniques are available to minimize
damage to the facility during flooding if the treatment system is
located at the Bartolo Well Field site. The maximum flood
protection would be achieved by elevating the facility above the
100-year flood elevation on earth fill or piles. This would add
substantial capital cost to the project and require additional
time for design and construction. In addition, if earth fill was
used, Army Corps of Engineers requirements specify that an
equivalent amount of fill has to be removed from the same or
lower elevation within the dam impoundment (so the impoundment
storage volume stays the same). Removal of this amount of fill
may impact adjacent wetland areas.
Several partial floodproofing techniques that could be used
to minimize potential flood damage. These include: designing
major treatment equipment such as packed towers and carbon
vessels to be floodable; elevation of lightweight,
water-sensitive equipment on platforms above the 100-year flood
elevation; elevation on fill of the expensive, water-sensitive
equipment, such as electrical transformers; or trailer or skid
mounting major equipment, such as fans and motors, for removal
when floods are expected. Specific floodproofing measures to be
utilized would be determined during the design phase.
The intent of EPA drinking water regulations regarding the
siting of public water supply system facilities (40 CFR 141.5) is
to avoid an interruption of water supply during a natural
disaster such as a flood event. Locating the treatment facility
in the Bartolo Well Field would subject the system to loss of use
during a flooding episode. In addition, there could be a down
time of approximately 1-2 months (or more depending on the extent
of flood damage) after a flood event to prepare the system to
return to operations. In this event, SWS would have to rely on
other outside, more expensive sources of water. SWS currently
relies on California Domestic Water Company, the Metropolitan
Water District of Southern California, the City of Whittier, and
La Habra Heights to supply peak and emergency water supply.
These sources of water have been used in the past when the
Bartolo Transmission Main was totally out of service. Sufficient
excess capacity was available in the past and should be available
in the future if such a need arises, particularly during the wet
winter months (a period of low demand for water supply) when the
treatment facility is most likely to be out-of-service due to a
flood.
-------
-23-
12.0 SUMMARY OF ALTERNATIVES ANALYSIS
Table 4 provides a summary of the analyses of alternatives.
The alternatives were evaluated based on nine criteria: (1)
overall protection of human health and the environment, (2) short
term effectiveness in protecting human health and the
environment, (3) long-term effectiveness and permanence in
protecting human health and the environment, (4) compliance with
ARARs, (5) reduction of toxicity, mobility, or volume of
contaminants (this criteria is under the heading "performance of
technology" in Table 4), (6) technical and administrative
feasibility of implementation, (7) state acceptance, (8)
community acceptance, and (9) capital and operation and
maintenance costs.
Consideration of Alternative Water Supply
All of the alternatives that were evaluated in detail are
capable of meeting the objective of providing water to SWS's
customers that meets all federal and state drinking water
standards. The alternative water supply alternative, however,
does nothing to meet the second objective of helping to control
the migration of contaminants. It is also almost twice as costly
as any of the extraction and treatment alternatives. Therefore,
it has been ruled out based on its cost and its lower
effectiveness in protecting human health and the environment.
Treatment Technology
Both the packed tower air stripping and liquid-phase GAC
treatment system technologies can treat the contaminated water to
the desired levels. In addition, both technologies are virtually
equal in protection of human health in that both risks due to
exposure of contaminated water and air emissions can be reduced
to below the 10 cancer risk level, although the GAC system
would virtually eliminate ozone precursor emissions and exposure
to any air emissions in the South Coast Air Basin. All of the
GAC alternatives are at least 50% higher in cost than the most
costly air stripping alternative. Therefore, the GAC
alternatives were ruled out since there is no significant
difference in these technologies regarding effectiveness in
protecting public health.
-------
TABLE 4
ANALYSIS OF ALTERNATIVES
Alternative
PROTECTION OF
HEALTH AND ENVIRONMENT
COMPLIANCE
WITH ARARS
PERFORMANCE
OF TECHNOLOGY
FEASIBILITY OF
IMPLEMENTATION
ACCEPTANCE OF ALTERNATIVE
COST
C a p i t a I
+ 0 & M
Total
Short Term | Long Term
State
Commun i ty
A: Minimum
Air strip-
ping at Main
High Point
Site
Can Treat to MCLs
Residual Risk
Water: 1 x 10 7
Air: 6x10"'
Tes
Adequate for
Water;
Preference for
T reatment not
Met for Air
Land Must Be
A c q u i r e d ;
Likely Delay in
Implementation
No
S t rong
Public
Comment in
Opposition
1 ,640,000
4,981,000
6,621,000
B : M a x imum
Air strip-
ping at High
Point with
Emission
Controls
Can Treat Beyond MCLs
Residual Risk
Uater: 5 x 10 ~
Air: 5 x 10"°
(assumes 90% removal)
Ozone Precursor emis-
sions also reduced
Yes
Adequate for
all media if
carbon is
regenerated
Land Must Be
A c q u ired;
Likely Delay in
Imp I ement a t i on
Yes, but
add it i onaI
CEQA re-
qui rements
must be met
St rong
P u b I i c
Comment i n
Opposition
4,342,000
1 0 , 867,000
15,209,000
C : Minimum
Air strip-
ping at
U e I I Field
Site
Can Treat to MCLs
Residual Risk
Water : 1 x 10 7
Air: 2x10"'
Yes
Adequate for
Water;
Preference for
T reatment not
Met for Air
Feasible
No
Most Public
Comment i n
Opposition;
Central &
West Basin
Rep. D i s t r .
Supports
1,739,000
5,011 ,000
6,750,000
D : Maximum
Air strip-
ping at
Well Field
Site
Can Treat Beyond MCLs
Residual Risk
Water: 5 x 10 7
Air: 2 x 10
Yes
Adequate for
Water;
Preference for
T reatment not
Met for Air
Feasible
No
Strong
Public
Comment in
Oppos i t i on
2,363,000
6,034,000
8,397,000
E : Maximum
Air strip-
ping at Well
Field with
Emission
Controls
Can Treat Beyond MCLs
Residual Risk
Water: 5 x 10 _
Air: 2 x 10"0
(assumes 90% removal)
Ozone Precursor Emis-
sions also reduced
Yes
Adequate for
all media if
ca rbon i s
regenerated
Feasible
Yes
Yes
4,387,000
10,879,000
15,266,000
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
*
30-year present worth O&N cost calculated using a 5% discount factor
-------
TABLE 4
(continued)
ANALYSIS OF ALTERNATIVES
Alternative
PROTECTION OF
HEALTH AND ENVIRONMENT
COMPLIANCE
WITH ARARS
PERFORMANCE
OF TECHNOLOGY
FEASIBILITY OF
IMPLEMENTATION
ACCEPTANCE OF ALTERNATIVE
COST
Capi taj,
+ 0 £ M-
Total
Short Term | Long Term
State
Commun i ty
F: Dual Bed
Carbon Ad-
sorpt ion at
Main High
Point Site
Can treat beyond MCLs
to 10 risk level;
Completely eliminates
ozone precursor emis-
sions and exposure to
air toxics
Yes
Adequate;
Preference for
treatment met
if carbon is
regenerated
Land must be
acqu ired;
Likely delay in
implementation
No
No
P u b I i c
Comment
10,693,000
15,423,000
26,116,000
G : Dual Bed
Carbon Ad-
sorption at
Well Field
Site
Can treat beyond MCLs
to 10 risk level;
Completely eliminates
ozone precursor emis-
sions and exposure to
air toxics
Yes
Adequate;
Preference for
treatment met
if carbon is
regenerated
Feasible
No
No
P u b I f c
Comment
10,221,000
1 5 , 277, 000
25,498,000
H : Single
Bed Carbon
Adsorption
at We I I
Field Site
Can treat beyond MCLs
to 10 risk level;
Completely eliminates
ozone precursor emis-
sions and exposure to
air toxics
Yes
Adequate;
Preference for
t reatment met
if carbon is
regenerated
Feasible
No
No
P u b I i c
Comment
7,433,000
1 6, 1 76, 000
23,609,000
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
I : Replace
We I I Supply
With Water
From MWD
Will meet MCLs for
water supply;
Does nothing to
control migration of
contaminants
Yes for
ARARs
related to
water
suppIy
Adequate for
water supply;
Does not meet
preference
for treatment
Feasible
No
Little
P u b I i c
Comment;
P r obabIy
Acceptable
6,388,000
35,752,000
42,140,000
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Additional
Option For
T reatment
A I ternat i ves
Wei I
Modification
A I I ows for more
efficient use of
treatment for control
of contami nant
migration
Yes
Adequate
Well testing
required to
determine
feasibility
o f
implementation
Yes
Yes
1 , 042, 000
1 , 553 , 000
2,595,000
*
30-year present worth O&M cost calculated using a 5X discount factor
-------
-24-
Air Stripping Design Treatment Efficiency
The minimum air stripping design alternatives are capable of
providing water that meets all federal and state drinking water
standards. It is less protective of human health than the
maximum air stripping design alternatives since there are
multiple contaminants in the groundwater in the Whittier Narrows
area so that the residual cancer risk level is 10-5 for treated
water. For an increased cost of approximately 10-15% in the
proposed plan, the maximum air stripping design can reduce the
residual risk level by more than an order of magnitude. In
addition, the maximum air stripping design would be more
protective over the long-term if well modification is implemented
since water that is more highly contaminated will be selectively
extracted. The levels that may be obtained through selective
extraction will be uncertain due to lack of knowledge of the
overall sources and extent of contamination in the Whittier
Narrows area. A maximum air stripping design will provide better
protection in the event a slug of more highly contaminated water
reaches the Bartolo well field.
Control of Air Emissions from the Air Stripping System
The cost of including gas-phase GAC treatment of the air
stripper off-gas to achieve a 90% reduction of total VOC
emissions is approximately 80%. Although this expenditure would
reduce the cancer risk level associated with the air emissions by
an order of magnitude, uncontrolled emissions pose an estimated
risk of only about 5 x 10 , toward the low end of EPA's
acceptable risk range of 10-4 to 10 . Emission controls would
be needed, however, to comply with the requirements of SCAQMD
Rule 1167. Although this rule is not now considered an ARAR due
to a recent court decision (see §10.0, page 19), it has been
considered in the remedy selection process since SCAQMD fully
intends to meet the requirements set by the court judgment and
proceed toward adoption of this rule as a promulgated, legally
enforceable, generally applicable requirement in the near future.
It should be noted that the intent of this rule was to
control ozone precursor emissions and the South Coast Air Basin
is in nonattainment status with respect to the ozone NAAQS. In
fact, the South Coast Air Basin is acknowledged to have the worst
ambient air quality with respect to ozone in the nation.
Installation of an air stripping system with air emission
controls is more protective of the environment in that it will
reduce ozone precursor emissions to the atmosphere by 90% and
-------
-25-
will support efforts by SCAQMD to reach attainment status for
ozone in the South Coast Air Basin.
In addition, public comment submitted to EPA in writing and
made by attendees at the public meeting were overwhelmingly in
support of including air emission controls regardless of the
legal status of Rule 1167 due to the severe air pollution problem
already existing in the San Gabriel Valley.
Location of Treatment Facility
The relative advantages and disadvantages of the alternative
locations for siting of the treatment facility have been
discussed in detail in §11.0—Floodplain Assessment. There would
be a risk of flood damage and temporary interruption of service
if the the treatment facility is located at the Bartolo Well
Field, along with slightly higher costs due to the need to pump
the water uphill in the Bartolo Transmission Main. To locate the
facility at the high point site, however, would potentially add a
long delay to construction of the treatment facility (1-5 years)
to allow for acquisition of property. Therefore, its short term
effectiveness is substantially less than that for the Bartolo
Well Field site since it may not be operational before average
contaminant concentrations in the Bartolo Well Field exceed
federal and state drinking water standards. In addition, a large
amount of contamination may continue to migrate due to a delay in
implementing well modifications if the high point site is
selected.
The high point site is unacceptable to the community in the
vicinity of the proposed treatment plant location as evidenced by
the near unanimous public opposition to this location voiced at
the public meeting and in written comments submitted to EPA.
Well Modification
Well modification can be included as an option for any of
the treatment alternatives. By selectively extracting the most
highly contaminated water in the aquifer, the maximum amount of
contamination will be removed from the groundwater. This is more
protective of human health and the environment in that the amount
of contamination that could continue to migrate would be reduced
to a greater extent. This would result in a greater attainment
of the SARA preference for utilizing treatment for reduction of
toxicity, mobility, or volume of contaminants at the site. The
cost of well modification is estimated at approximately $2.6
million, which results in about a 17% increase in the cost of the
proposed plan.
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13.0 THE SELECTED REMEDY
The selected remedy for the SWS Bartolo Well Field Operable
Unit includes extraction of contaminated groundwater from the
Bartolo Well Field. The existing wells will be modified and/or
new production wells will be installed to selectively extract the
most highly contaminated groundwater, if further testing during
the design phase shows this to be feasible. The treatment
technology will be a packed tower air stripping system to be
constructed at the Bartolo Well Field site. The treatment system
will be equipped with an off-gas vapor-phase GAC treatment system
to control air emissions. The treated water will be fed directly
into SWS's water distribution system.
Continuation of the extraction of contaminated groundwater
from the Bartolo Well Field is chosen as a means of providing
water supply for SWS's customers, since it will help to control
the spread of contamination in the Whittier Narrows area, unlike
the option of using an alternative water supply. Implementation
of well modification, if feasible, will maximize the amount of
groundwater contamination removed from the Main San Gabriel
Groundwater Basin by this response action. This will assist in
the control of contaminant migration.
Packed tower air stripping is chosen as the treatment
technology because this treatment method provides virtually the
same human health protection as the other technology considered
with substantially less cost. Air emission controls will be used
to reduce the level of VOC emissions. The emission controls are
included in the selected remedy because (1) they would be
necessary to comply with SCAQMD Rule 1167, which was rescinded as
a result of a court judgment in a lawsuit, but for which SCAQMD
is fully intending to meet the procedural and substantive
requirements of the court judgment to allow promulgation of a
legally enforceable requirement, (2) they would reduce the ozone
precursor emissions in the most polluted air basin in the nation
with respect to ozone air quality, and (3) public comments
received were overwhelmingly in favor of including emission
controls due to the severe existing air pollution in the San
Gabriel Valley, regardless of the legal status of SCAQMD Rule
1167.
The target level of treatment chosen is to achieve a
cumulative 10 cancer risk level. This corresponds with the
maximum air stripping design alternative. This level of
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treatment, which will result in contaminant levels well below
MCLs and DHS action levels in the treated water, is more
protective of human health. The choice of an overall 10~6 risk
level versus treatment to MCLs was made because of: (1) the
multiple contaminants in the groundwater in the vicinity of the
Bartolo Well Field, (2) the fact that an approximately 10-15%
increase in cost could result in a reduction of risk level of
over an order of magnitude, and (3) the implementation of well
modification to selectively extract the most highly contaminated
water may lead to greater uncertainty in the contaminant
concentrations of influent water; in this situation, the
increased level of treatment will provide additional protection
of public health.
In practice, the target level of performance of the
treatment system will be to reduce the level of one of the
primary VOC contaminants detected in groundwater in the Whittier
Narrows area, PCE, to below 1.0 ppb. This corresponds to the
10 cancer risk level for PCE. In the Public Health Evaluation,
the majority of risk was determined to be associated with
potential exposure to PCE. Based on the estimated future
concentration of PCE and other VOCs in water extracted from the
Bartolo Well Field, and the predicted percent removal of
different contaminants in an air stripping system, meeting this
target level for PCE will reduce the risks associated with
exposure to the other contaminants to well below their 10-6
cancer risk levels. Therefore, the total cumulative
cancer risk level of the treated water will be approximately
10 . In addition, 1 ppb is a practical target level of
performance given the accuracy of current methods of laboratory
analysis for VOCs at low level concentrations. The target
level—1 ppb—is near the practical limit of detection and
quantification for PCE.
The Bartolo Well Field site for the treatment facility was
selected as there is no practicable alternative to locating the
treatment facility within the 100-year floodplain. The Bartolo
Transmission Main high point site is not considered a practicable
alternative due to the long delay in implementation that would be
incurred to allow for locating and acquiring property for the
treatment facility, and due to its vicinity to adjacent
residential areas and the lack of public acceptance within the
local community. The land acquisition process of DHS could take
up to 5 years. This is an unacceptable delay in implementation
of the project due to the expected increase in contaminant levels
at the Bartolo Well Field and the resulting greater threat to
human health and the environment. Public comment submitted in
writing to EPA and statements made by attendees at the public
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meeting were overwhelmingly against locating the treatment
facility at the high point site. Such opposition increases the
possibility of delays in DHS completing its land acquisition
process since it includes completion of an Environmental Impact
Report as part of the CEQA project review process.
Floodproofing measures will be incorporated within the
design of the treatment facility at the Bartolo Well Field to
minimize the potential damage to the treatment facility during
flooding, as well as to limit the downtime necessary after a
flood event to prepare the system to return to operations.
The selected remedy is expected to operate over the
estimated 3 0-year design life of the installed equipment.
Extraction of contaminated groundwater using the Bartolo wells
could be discontinued, however, as part of the Whittier Narrows
Operable Unit if it is determined that a more efficient
extraction system for the control of contaminant migration in the
Whittier Narrows Area should be installed at other locations. If
this occurred, treatment of contaminated groundwater would still
be conducted at the Bartolo Well Field treatment facility.
Whether a treatment system at the Bartolo Well Field will have to
operate for a period longer than 30 years will depend on the
selected remedy for the Whittier Narrows operable unit and other
operable units in San Gabriel Areas 1, 2, and 4. Groundwater
monitoring will be conducted as part of the remedy to track
contaminant levels at the Bartolo Well Field and to monitor the
performance of the treatment system.
The estimated cost of the selected remedy is given in detail
in Table 5. These costs reflect the conceptual design described
in the OUFS; the cost of the final design could vary, depending
on such variables as the specific well modification or
floodproofing measures eventually included.
14.0 STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment—as required by Section 121 of CERCLA—in that it
treats groundwater to an overall excess risk level of 10 or
less, below the MCLs for the contaminants of concern. In
addition, the remedy at least attains the requirements of all
ARARs, including the MCLs, the Floodplain Management Executive
Order (E.O. 11988), and Safe Drinking Water Act regulations
regarding modification of public water supply systems (40 CFR
141.5). The remedy is determined to meet the requirements of
E.O. 11988 and 4 0 CFR 141.5 because locating the treatment
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TABLE 5
COST SUMMARY FOR SELECTED REMEDY:
MAXIMUM AIR STRIPPING AT BARTOLO WELL FIELD SITE
WITH OFF-GAS CARBON TREATMENT AND WELL MODIFICATION
Cost Items
General
Mobilization, Bonds, and Insurance
Construction Admin. Trailer
Security Service
Community Relations
Health & Safety Program
Permits
Site Preparation and Construction
Earthwork
Structures and Equipment
Piping and Electrical
Construction Subtotal
Bid and Scope Contingencies
Construction Total
Services During Construction
Total Implementation Cost
Engineering, Legal, and Admin. Cost
Estimated Cost
515,000
2,375,000
2,890,000
1.156.000
4,046,000
404.000
4,450,000
979.000
TOTAL CAPITAL COST
5,429,000
INCREMENTAL ANNUAL O&M COST
809,000
NET PRESENT WORTH OF O&M
At 3 percent
At 5 percent
At 10 percent
15,851,000
12,432,000
7,623,000
TOTAL NET PRESENT WORTH
OF REMEDIAL ACTION
At 3 percent
At 5 percent
At 10 percent
21,280,000
17,861,000
13,052,000
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facility in the floodplain is the only practicable alternative
due to the need to take timely action to respond to the threat to
human health and the environment posed by groundwater
contamination at the Bartolo Well Field.
Packed tower air stripping has been shown to be the most
cost-effective technology for treating the VOC contaminants found
in the Bartolo Well Field. In addition, the use of well
modification is a cost-effective method of maximizing the removal
of contaminants from groundwater in the Bartolo Well Field while
still providing a water supply for SWS's customers that meets all
federal and state drinking water standards after treatment.
Although the addition of air emission controls will significantly
increase the cost of the selected remedy (by about 80%), it is
determined to be justified as a cost-effective measure for the
following three reasons: (1) to meet the requirements of SCAQMD
Rule 1167, which, although are not currently generally applicable
due to a recent court decision, are expected to be generally
applicable in the near future; (2) to reduce ozone precursor
emissions (the goal of Rule 1167) in a nonattainment area (the
South Coast Air Basin) that has the worst ozone air quality in
the nation; and (3) in response to overwhelming public comment to
incorporate air emissions to minimize the increase in existing
air quality problems regardless of legal requirements.
The selected remedy permanently and significantly reduces
the mobility and volume of hazardous substances with respect to
their presence in groundwater—the contaminants are removed from
the groundwater, thereby reducing contaminant migration in the
vicinity of the Bartolo Well Field. Packed tower air stripping
will result in a small increase in the toxicity, mobility, and
volume of hazardous substances with respect to their presence in
the air. PCE and TCE, the primary contaminants of concern, are
also toxic when inhaled, as well as when ingested. In addition,
VOCs are generally more mobile once they become airborne.
Finally, air stripping increases the volume of contamination in
the air by transferring the volume of contamination that was once
in the water into the air.
The inclusion of air emissions controls in the selected
remedy, however, reduces the impact of the air emissions in a
cost-effective manner to the maximum extent practicable. In
addition, the air emissions are estimated to add virtually no
risk to the project via airborne contaminants (<10 ). The
absence of added risk is due largely to (1) dilution of
contamination as it exits from the air stripping system, (2) the
air emissions controls that will remove about 90% of the
contaminants in the air, and (3) the remoteness of the proposed
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facility at -the Bartolo Well Field site with respect to populated
areas. The VOCs that will be emitted from the treatment system
are precursor emissions to the formation of ozone in the
atmosphere. With the addition of air emission controls, however,
the selected remedy reduces the potential for ozone formation to
the maximum extent practicable.
To meet the statutory preference for remedies that utilize
alternative treatment or resource recovery technologies to the
maximum extent practicable, the spent carbon from the GAC off-gas
treatment system will be regenerated, if feasible, instead of
disposed of in a landfill.
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ATTACHMENT A
PROJECTED WATER QUALITY AT SUBURBAN WATER SYSTEMS' BARTOLO WELL
FIELD OVER THE 30-YEAR PROJECT LIFE
Compound Concentration
(parts per billion)
Acetone
ND
Benzene
ND
- 4
Carbon Tetrachloride (CTC)
l -
3
Chloroform
1 -
3
1,1-Dichloroethane (1,1-DCA)
1 -
1
1,2-Dichloroethane (1,2-DCA)
l -
1
1#1-Dichloroethyiene (1,1-DCE)
1 -
4
1,2-Dichloroethylene (1,2-DCE)
1 -
10
cis-1,2-Dichloroethylene (cis-
3 -
28
1,2-DCE)
trans-1,2 Dichloroethylene
2 -
35
(trans-1,2-DCE)
Tetrachloroethylene (PCE)
2 -
36
Toluene
1 -
2
Total Trihalomethanes
1 -
8
1,1,1-Trichloroethane (1,1,1-
1 -
8
TCA)
Trichloroethylene (TCE)
2 -
21
Vinyl Chloride
ND
Xylenes
ND
- 1
6
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