PB94-964502
EPA/ROD/R09-94/106
July 1994
EPA Superfund
Record of Decision:
Baldwin Park San Gabriel Valley
Area Site, CA
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RECORD OF DECISION
BALDWIN PARK OPERABLE UNIT
SAN GABRIEL VALLEY SUPERFUND SITES
LOS ANGELES COUNTY, CALIFORNIA
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United States Environmental Protection Agency
Region 9 - San Francisco, California
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BALDWIN PARK RECORD OF DECISION
TABLE OF CONTENTS
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PAGE=.~. . .
... NIJ-MIJRR:.~~:
Pan I. Declaration
3
Pan II. Decision Summmy
1.
2.
3.
4.
5.
6.
Site Location and Description
Site History
Enforcement Activities
Highlights of Community Participation
Scope and Role of the Operable Unit
Summary of Baldwin Park Operable Unit
Characteristics
Summary of Site Risks
Description of Alternatives.
Summary of Comparative Analysis
of Alternatives
Applicable or Relevant and Appropriate
Requirements (ARARs)
The Selected Remedy
Statutory. .Determinations
Documentation of Significant Changes
40
50
62
64
6
10
14
15
17
7.
8.
9.
18
19
26
32
10.
11.
12
13.
Figures and Tables
65
Pan III. Responsiveness Summmy
Table Of Contents and Introduction
Responses A-F
Responses to Individual Comments
Responses to Written Comments
Responses to Oral Comments at Public Meeting
Held May 20, 1993
89
93
143
289
Figures and Tables
293
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Baldwin Park ROD
PART I.
DECLARATION
SITE !lAKE AND LOCATION
Baldwin Park Operable Unit
San Gabriel Valley Area 2 Superfund Site
Los Angeles County, California
STATEKENT OP BASIS AND PURPOSE
This decision document presents the selected remedial action
for the Baldwin Park Operable Unit (OU), San Gabriel Valley
Superfund sites, chosen in accordance with CERCLA as amended by
SARA and, to the extent practicable, the National Contingency
Plan. This decision is based on the administrative record for
this operable unit.
In a letter from Margaret Felts, Deputy Director, Site
Mitigation Program, Department of Toxic Substances Control, the.
State of California concurred with EPA's' selected remedy.
ASSESSHENT OP THB SITE
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response action
selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare or the environment.
DESCRIPTION OP THE REHEDY
The Baldwin Park Operable Unit addresses a large area of
groundwater contamination in the San Gabriel Valley. Volatile
organic compounds (VOCs) are present in the groundwater
throughout a several mile long area, extending beneath the
of Azusa, Irwindale, and Baldwin Park. Six other operable
address contamination in other portions of the San Gabriel
(see Figure ROD-4).
cities
units
Basin
The remedy will limit further migration of contaminated
groundwater to areas and depths that would benefit most from
additional protection, remove a significant mass of contamination
from the aquifer, and collect data necessary to determine final
clean up standards for the Baldwin Park area. The Baldwin Park
Operable Unit is classified as an interim action.
The selected remedy includes extraction of contaminated
groundwater at the downgradient end of two broad subareas of
contamination. The first of the two subareas is the lower area,
where concentrations of trichloroethene (TCE), tetrachloroethene
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Baldwin Park ROD
(PCE), carbon tetrachloride (CTC), or other'contaminants are five
to 10 times Federal or state drinking water standards, and where
downgradient portions of the aquifer are significantly less
contaminated. The second area is the upper area, where
concentrations of PCE or TCE exceed 200 times drinking water
standards, indicating the presence of non-aqueous phase,
contamination or other surface or subsurface sources of TCE, PCE,
CTC, or other contaminants that are acting as continuing sources
of dissolved-phase groundwater contamination.
The remedy includes extraction of contaminated groundwater
at locations and rates sufficient to capture contaminated
groundwater moving from the upper'and lower areas of '
contamination during all anticipated recharge conditions. EPA's
analyses indicate that its remedial objectives will be
efficiently met by extracting approximately 19,000 gallons per
minute of contaminated groundwater as continuously as feasible.
The final decision on precise extraction rates and locations will
be made during remedial design. One or more existing groundwater
extraction wells may be used in the remedy.
The remedy includes treatment facilities needed to remove
TCE, PCE, CTC, and other contaminants from the extracted
groundwater by either or both of two proven treatment
technologies: liquid-phase granular activated carbon filtration
and air stripping (with offgas controls). Treatment technologies
will be determined during remedial design after additional
groundwater quality data are obtained. One or more existing
treatment facilities may be incorporated into the remedy.
The remedy includes pipelines, pump stations, and other
conveyance facilities needed to deliver the treated groundwater
to one or more uses or users. EPA's preference is that treated
water be supplied to one or more water purveyors, possibly
including Metropolitan Water District of Southern California, for
distribution to their residential and business customers. The
final decision will be made after completion of the ROD depending
on the outcome of additional negotiations with potential
recipients of the treated water to identify recipients that can
be supplied at least cost with the fewest institutional
obstacles.
If water purveyors can accept water for most, but not all,
of the year, excess water may be piped to spreading basins and
flood control channels operated by the Los Angeles County
Department of Public Works for recharge into the aquifer. If
agreements cannot be reached with water purveyors, water may be
recharged year-round. If necessary, recharge location(s) will be
determined during remedial design.
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Baldwin Park ROD
The remedy includes the installation and sampling of
groundwater monitoring wells, the sampling of existing monitoring
wells, measurement of groundwater elevations at monitoring and
production wells, and the measurement of other aquifer properties
to verify or refine plume boundaries, predict treatment facility
influent concentrations, and evaluate the effectiveness of the
. remedy.
EPA will review this action every five years throughout the
interim remedy period.
EPA is the lead agency for this project and the Department
of Toxic Substances Control of the State of California
Environmental Protection Agency is the support agency.
DECLARATION
This interim action is protective of human health and the
environment, complies with Federal and. State applicable or
relevant and appropriate requirements directly associated with
this action and is cost effective. This action utilizes
permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable for this
interim action. The statutory preference for remedies that
employ treatment that reduces toxicity, mobility, or volume as a
principal element will be addressed at the time of the final
response action. Subsequent actions are planned to fully address
the principal threats at the site.
Because this remedy will result in hazardous substances
remaining on-site above health-based levels, EPA shall conduct a
review, pursuant to CERCLA Section 121, 42 U.S.C. ~ection 9621,
at least once every five years after commencement of remedial
action to ensure that the remedy continues to provide adequate
protection of human health and the environment.
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Baldwin Park ROD
PART II.
DECISION SUMMARY
This Decision Summary summarizes site-specific information
and analyses relevant to the selection of an interim remedy for
the Baldwin Park Operable Unit of the San Gabriel Valley Area 2
Superfund Site. The Decision Summary includes a description of
the nature and extent of contamination, a comparative analysis of
remedial alternatives (i.e., clean up options), a description of
the selected remedial alternative, and the rationale for the
selected remedy. The Decision Summary presents some of the same
information included in the Declaration (Part I), but in
significantly greater detail.
1.
SITE LOCATION AND DESCRIPTION
Section 1.1 briefly describes the location and physical
characteristics of the San Gabriel'Valley, including its
topography, geology, hydrology, land use, and water management
practices. section 1.2 describes the Baldwin Park area in more
detail. '
1.1 The San ,Gabriel Valley: Location, Physical
Characteristics, and Water Management Practices
1.1.1
Location and Topography
The San Gabriel Valley is a suburban, largely developed
portion of Los Angeles County covering more than 170 square miles
(see Figure ROD-1). More than one million residents live in the
Valley, alongside a variety of commercial and industrial
operations. '
The San Gabriel Mountains are a major geologic feature of
the region. They form the northern boundary of the San Gabriel
Valley, rising up to 10,000 feet in elevation. The Valley
surface is a broad piedmont plain, which slopes from the San
Gabriel Mountains southward towards a gap in the southern hills
known as the Whittier Narrows. The average slope of the valley
floor is about 65 feet .per mile. Figure ROD-2 shows major
features of the area.
1.1.2
Surface Water, Groundwater, and Water Management
Major surface water features in the San Gabriel Valley
include the San Gabriel River, tributaries to the San Gabriel
River, and spreading basins located to the river channels. The
San Gabriel River system drains a portion of the San Gabriel
Mountains. Surface flow in much of the San Gabriel River is
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Baldwin Park ROD
intermittent; the river channel is often dry, except during
significant storm events and spring runoff.
Tributaries to the San Gabriel River present in the Baldwin
Park area include Big Dalton Wash, Little Dalton Wash, and Walnut
Creek. Much of the length of these tributaries has been lined
with concrete. As in the San Gabriel River, flow in the
tributaries is intermittent, limited to storm events or when the
channels are being used to transport water to recharge
facilities.
Los Angeles County operates two spreading basins in the
Baldwin Park area to increase recharge of the aquifer.
Groundwater producers in the San Gabriel Valley typically extract
more water than is "naturally" replenished; the overdraft is
replaced by "artificially" recharging water in the spreading
basins. The recharged water originates as local storm runoff or
is imported surface water transported from Northern California
and the Colorado River. The two spreading basins are the large
Santa Fe Spreading Grounds, located in the northern part of the
Baldwin Park area along the San Gabriel River, and the smaller
Irwindale spreading Grounds (ISG), located in the eastern portion
of the Baldwin Park area adjacent to Big Dalton Wash.
1.1.3
Water Rights and Water Hanagement Institutions
The San Gabriel Basin a~ifer underlies most of the San
Gabriel Valley. It stores an estimated three trillion qallons of
water and is the primary source of water for most of the Basin's
one million residents. In the last 20 years, annual groundwater
extraction (pumping) in the Basin has ranged from approximately
59 to 78 billion gallons per year. A typical household uses 150
to 250 gallons per day.
Water resource management iri the San Gabriel Basin is
governed by two court decisions resulting from intra- and inter-
basin conflicts over the use of water.
The first lawsuit, settled in 1964 as the Long Beach
Judgment, requires that the water users in the San Gabriel Basin
deliver an average of 98,415 acre-feet/year of usable water to
the downstream Central Basin. (One acre-foot equals 325,829
gallons.) The San Gabriel River Watermaster administers the
interbasin aqreement.
The second lawsuit, settled in 1973 as the Alhambra
Judgment, allocates water rights within the San Gabriel Basin.
The Main San Gabriel Basin Watermaster was established to
administer the Alhambra Judgment. This Judgment includes a
monetary assessment on those water purveyors pumping more than
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Baldwin Park ROD
their annual share of the operating Safe Yield, as set by the
Watermaster. Assessment fees are used to buy imported water for
basin replenishment.
Agencies which use or manage water in the Basin currently
includes 3 watermasters, 3 municipal water districts, the .
Metropolitan Water District, the San Gabriel Basin Water Quality
Authority, 45 water purveyors, and 105 individual water-rights
holders. The role of the municipal districts is mainly to
provide supplemental water supplies from Metropolitan Water
District of Southern California (Metropolitan) or the State Water
Project (SWP). The water purveyors vary in size and type and
include investor-owned utilities, special districts, city water
departments, and small mutual water companies.
Water purveyors in the Baldwin Park area include the: City
of Azusa, California Domestic Water Company, City of Glendora,
La Puente Valley County Water District, San Gabriel Valley Water
Company (SGVWC), Suburban Water Systems (Suburban), Valley County
Water District (VCWD), and others.
Purveyors in the basin have, for the most part, acted
independently in deciding where, when, or in what quantities they
pump groundwater. In 1991, due in large part to EPA and State
efforts, the Watermaster adopted rules to regulate water supply
actions that may affect the movement of contaminated groundwater
in the San Gabriel Basin. There is not yet a consensus on the
adequacy of Watermaster's efforts to regulate water supply
actions in the Basin.
1.2
The Baldwin Park Area
The Baldwin Park Operable Unit (OU) addresses groundwater
contamination in and near the cities of Azusa, Irwindale, and
Baldwin Park, in the area EPA has designated as Remedial
Investigation (RI) Area 5 (Figure ROD-2). The approximate
location of this multiple square-mile area, referred to as the
"OU area" or "Baldwin Park area," is west of Azusa Avenue
(Highway 39), south of the San Gabriel Mountains, east of the San
Gabriel River, and north of Walnut Creek.
Nearly all of the Baldwin Park area is fully developed for
residential, commercial, and industrial use. The largest parcels
of open land are active and inactive gravel pits and the Santa Fe
Flood Control Basin.
The Sierra Madre Fault system passes through the northern
portion of the Baldwin Park area, generally east/west, near the
base of the San Gabriel Mountains. The system presents a low-
permeability barrier that limits groundwater movement southward
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Baldwin Park ROD
from the San Gabriel ,Mountains. In the OU area, groundwater
levels north of the fault system are substantially higher than
those to the south.
The surficial geoloqy of the Baldwin Park area is composed
of alluvial materials deposited by the San Gabriel River and its
tributaries. Braided stream deposits occur along River channels;
outcrops of stream channel deposits also occur along River
channels and major tributaries. Floodplain deposits and
undifferentiated alluvium cover the area between the stream
channels. The underlying sediments are derived from the
dominantly crystalline San Gabriel Mountains and are typically
coarse-grained (e.g., sand, gravel, and boulders). These
sediments are unconsolidated to partially consolidated non-marine
sediments of Recent and Pleistocene Age. They were deposited by
fluvial and geomorphic processes associated with the San Gabriel
River and its tributaries. Marine sediments, probably of
Pleistocene and Pliocene Age, underlie some of the non-marine
sediments and are included within the groundwater system.
The northern and central portions of the Baldwin Park area
consist almost entirely of massive gravel deposits. Lithologic
evaluations of well logs indicate gravel deposits greater than
500 feet in thickness in the northern portions of the Baldwin
Park area, mixed with 10- to 30-foot-thick layers of clay and
gravelly clay further south. The thickness of alluvial sediments
is believed to range from a few hundred feet in the north to over
2,000 feet in the south.
Hydraulic conductivity estimates in the Baldwin Park area
are some of the highest in the basin. Aquifer test results from
seven locations yield hydraulic conductivity estimates between
about 270 and 5,000 ft/day. The highest estimates are for the
northern and central portion of the basin; lower values are
observed toward the southwestern and southeastern margins. .
These high hydraulic conductivity estimates indicate that very
large extraction volumes are required to create significant
changes in the flow of groundwater. Estimates of specific yield
are 0.1 to 0.2, reflecting the coarse-grained materials in the
area.
Figure ROD-3 reprints a map prepared by the Los Angeles
County Department of Public Works (LACDPW) illustrating water
levels during fall 1990. The figure shows water level contours
drawn using data from 150 to 200 wells. (Groundwater flows in a
direction perpendicular to groundwater level contours.) The'
figure provides a snapshot of regional flow, but does not show
local-scale variations in groundwater flow caused by pumping,
recharge, or geologic faults.
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Baldwin Park ROD
Figure ROD-3 indicates that groundwater flow in the OU area
is generally towards the Whittier Narrows to the southwest. The
direction of flow can vary significantly from Figure ROD-3 (by
more than ninety degrees), however, particularly in the vicinity
of the Santa Fe Spreading Grounds during periods of significant
recharge.
An estimate of the average horizontal gradient in the
Baldwin Park area in the fall 1990 is approximately 0.002 foot
per foot (ft/ft), which is among the lowest in the basin
(estimate derived from Figure ROD-3). Deviations from this
regional estimate are expected to be greatest in the vicinity of
pumping wells, recharge areas, and faults. Vertical gradients
are not well known. At one location in the middle of the Baldwin
Park area where data are available on vertical gradients across
1300' of the aquifer, gradients are low « 0.004 ft/ft in
September 1991). Vertical gradients may be locally higher,
however, near pumping wells, geologic faults, and zones of
recharge, such as spreading basins.
The elevation of the water table in the Baldwin Park area
can vary significantly year to year, decreasing during dry years
and rapidly increasing during periods of above-average rainfall.
In the period 1982-1992, the groundwater level at the "Baldwin
Park Key Well" (identified in the Alhambra Judgment) began 1982
at approximately 240', declined during subsequent drought years
to just under 200' in 1991, then rebounded to over 250' after the
two relatively wet years of 1991/92 and 1992/93. This
variability in water levels influences the movement of
contaminants and complicates the installation of shallow
monitoring wells (e.g., requiring relatively long-screened
intervals).
2. SITE HISTORY: origins, Discovery, and Local Response to tbe
Groundwater contamination
2.1
origins and Discovery of the contamination
Volatile Organic Compounds (VOCs), the contaminants
responsible for placement of portions of the San Gabriel Basin on
the National Priorities List (NFL), were apparently used in large
quantities at industrial facilities as early as the 1940s.
Throughout the 1940s, 50s, 60s, 70s, and 80s, carbon
tetrachloride (CTC), tetrachloroethene (PCE), trichloroethene
(TCE) and other VOCs were used by hundreds of businesses in the
OU area for degreasing, as raw materials for automotive products,
by a solvent recycler, for chemical extractions, and for other
purposes. VOCs have probably been released to the ground by a
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Baldwin Park ROD
combination of intentional disposal, careless handling during
loading and unloading, leaking tanks and piping, and other means.
The significant depth to water in most of the OU area (100
to 400' below ground surface) provides some sorptive capacity for
VOCs released to the soil. More importantly, however, the
absence of extensive fine-grained layers (e.g., clay or silt
layers) in the OU area increases the likelihood that contaminants
released to the subsurface will reach groundwater. Fine-grained
materials inhibit the downward movement of contaminants due to
their lower permeability and higher sorptive capacity.
VOCs may have reached the groundwater as early as the 1940s
or 1950s, but were not detected in groundwater until 1979 during
environmental monitoring activities conducted by Aerojet
Electrosystems near its facility in Azusa. In May 1984, four
areas of contamination were listed as San Gabriel Valley Areas
1-4 on EPA's National Priorities List based on water quality
information available at the time of listing. Subsequent
investigation by EPA and others revealed widespread VOC
contamination. During the past 12'years, more than two-thirds of
the 366 water supply wells (also known as production wells) for
which VOC data are available have shown detectable concentrations
of VOCs; .about one-quarter of the 366 wells have shown
concentrations exceeding drinking water standards.
2.2
Remedial Investigation
EPA's Remedial Investigation of the San Gabriel Basin began
in 1985 with a basinwide groundwater sampling program known as
the Supplemental Sampling Program. In subsequent years, EPA
completed additional field sampling efforts, which have included
sampling of inactive water supply wells, depth-specific sampling
of water supply wells, and monitoring well installation and
sampling. The results of EPA's sampling efforts are summarized
in numerous EPA documents:
Draft Technical Memorandum, Well Logging and Depth-Specific
Sampling, San Gabriel Area 5 Remedial Investigation... May
22, 1990.
Technical Memorandum, Sampling of Existing Wells, San
Gabriel Area 5 Remedial Investigation. June 25, 19~1.
Technical Memorandum, Well Logging and Depth-Specific
sampling, San Gabriel Area 5 Remedial Investigation.
December 2, 1991.
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Interim Report of Remedial Investigations, San Gabriel
Basin... July 1992. (This report summarizes sampling
activities up through 1989.)
Technical Memorandum, sampling of Existing Wells--Second
Round, San Gabriel Area 5 Remedial Investigation. July
1992.
Technic~l Memorandum, Area 5 Monitoring Well Installation
and sampling, San Gabriel Area 5 Remedial Investigation...
October 26, 1992.
EPA's Remedial Investigation has included the compilation
and analysis of data collected by individual water purveyors,
business and property owners, and the Main San Gabriel Basin
Watermaster. Individual water purveyors regularly sample more
than 50 wat~r supply wells in the Baldwin Park area in accordance
with Federal and State drinking water requirements. Individual
businesses and property owners have installed and sampled more
than 25 groundwater monitoring wells in. facility-specific
investigations in the Baldwin Park area, most of which are
overseen by the California Regional Water Quality Control Board
(Regional Board). EPA works cooperatively with the Regional
Board to set investigation priorities and provide assistance at
individual sites as needed. The Main San Gabriel Basin
Watermaster has also sampled several inactive water supply wells
in the Baldwin Park area.
EPA has summarized and analyzed the results of the Remedial
Investigation, making use of data collected by EPA and others, in
the Baldwin Park Operable Unit Feasibility Study Report, dated
April 2, 1993.
2.3
Local Response to the contamination
EPA has not implemented any remedial actions in the Baldwin
Park area, but water purveyors and local agencies have
implemented or plan to implement projects that contribute or will
contribute to EPA's remedial objectives.
As the contaminated groundwater has spread and existing
water supply wells have become contaminated, water purveyors have
installed treatment facilities and responded in a variety of
other ways to satisfy their obligations to supply water meeting
State and Federal drinking water standards. Some purveyors have
shut down wells. In other cases .they have been able to continue
to operate contaminated wells by pumping wells intermittently, at
reduced rates, or by blending contaminated water with better
quality water from other wells. In other cases, they have
drilled wells deeper or installed new wells in search of cleaner
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Baldwin Park ROD
water, acquired water from other San Gabriel Basin water
purveyors, or purchased imported water. More recently, as other
options become less feasible and more costly, purveyors have
installed wellhead treatment systems.
In the au area, purveyors have made use of all of these
options to respond to the contamination. The Valley County Water
District (VCWD) has shut down four wells and installed wellhead
treatment facilities at three others; the San Gabriel Valley
Water Company (SGVWC) has shut down wells, deepened existing
, wells, drilled new deep wells, used blending, and installed
wellhead treatment; Suburban Water Systems has blended and
installed new deeper wells; and the City of Glendora has
purchased additional imported water. Although more than 12
existing water supply wells have become contaminated in the area,
the Baldwin Park area continues to serve as a significant source
of drinking water. Periodic monitoring ensures that drinking
water supplied to consumers meets EPA and State drinking water
standards. .
Three water purveyors (VCWD, SGVWC, and La Puente Valley
County Water District) have funded treatment projects in the
Baldwin Park area. The State Water Resources Control Board and
the California Department of Toxic Substances Control have
contributed funding for two other treatment facilities. State
funding has been provided to the San Gabriel Basin Water Quality
Authority, which has overseen the construction of a second Valley
County Water District treatment facility (at the Arrow Highway
well) and, as of March 1994, is preparing to begin construction
of another treatment project at the Big Dalton well. If
constructed and operated as planned, the project at the Big
Dalton well site may partially satisfy EPA's remedial objectives
in. the Baldwin Park area. The Authority's planned project would
result in the extraction and treatment of 2,000 to 3,000 gallons
per minute (gpm) of contaminated groundwater, a small but
significant portion of the approximately 19,000 gpm of extraction
that EPA's studies indicate may be needed.
Water purveyors' response to the contamination has been
driven by their need to supply safe drinking water to their
customers~ Initi~lly, some purveyor actions (e.g., relocating
wells from contaminated to clean areas) may have marginally
contributed to the spread of contamination in the aquifer, but
more recent actions (e.g., the installation of treatment)
contribute to the cleanup. Still, EPA does not believe that
actions by water purveyors provide an adequate, cumulative
response to the contamination. The limitations of installing
treatment only at existing water supply wells after the
contamination has spread (occasionally termed wellhead treatment)
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are described further in Section 7 of this document (Summary of
si te Risks).
3.
ENFORCEMENT ACTIVITIES
EPA began its enforcement efforts in the Baldwin Park area
in approximately 1985 with searches ,for and evaluations of
historical Federal, state, and local records on chemical usage,
handling, and disposal.
In 1985, the California Regional Water Quality Control Board
(Regional Board) began its Well Investigation Program (WIP) to
identify the sources of groundwater contamination detected in
water supply wells. In 1989,. EPA entered into a cooperative
agreement with the Regional Board to expand the WIP program, in
order to assist EPA in determining the nature and extent of the
sources of the groundwater contamination in the Baldwin Park area
and other portions of the San Gabriel Valley, and to identify
responsible parties. The cooperative agreement has been renewed
annually. Regional Board staff directly oversee facility-
specific investigations in the Baldwin Park area; EPA's role has
been to help fund the Regional Board, help set priorities, and,
as needed, to intervene in individual investigations to obtain
information, evaluate claims of inability to pay, and threaten or
use Federal enforcement authority to ensure that necessary
investigation work is promptly completed.
As of October 1993, the Regional Board has, in the Baldwin
Park area, sent chemical use questionnaires to more than 1,600
facilities; inspected more than 600 of these facilities; directed
more than 70 facilities to investigate potential soil or soil gas
contamination; and directed approximately 17 facilities to
investigate groundwater contamination. EPA has used its
authority to request information (CERCLA section 104(e» to
supplement the Regional Board's efforts by sending information
requests and evaluating responses from more than 150 current and
historical property owners and businesses.
Concurrent with source identification efforts, EPA carried
out a fund-lead Remedial Investigation and Feasibility Study
(RIfFS) (i.e., using funding from the Superfund trust fund),
rather than through enforcement action. In the RIfFS, EPA
supplemented data generated d~ring facility-specific
investigations with regional information on the nature and extent
of contamination.
A subset of the 70+ facilities investigating contamination
in the Baldwin Park area are believed to be contributors to the
groundwater contamination. EPA has sent General Notice of
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Baldwin Park ROD
Liability for the Baldwin Park Operable Unit to approximately 110
owners and/or operators, representing 20 to 25 contaminated
parcels. Most of the General Notice letters were sent in three
mailings: in May 1990, September 1990, and August 1993.
EPA anticipates issuing special notice for the Baldwin Park
Operable unit in 1994 to a subset of recipients of General
Notice. EPA has begun discussions with individual Potentially
Responsible Parties (PRPs) and the San Gabriel Basin Industry
Coalition (representing multiple PRPs) in an effort to speed the
start of clean up work in the Baldwin Park area. To date,
however, no Administrative Orders on Consent or Consent Decrees
have been attempted or reached, and no Unilateral Administrative
Orders (UAOs) have been issued, to or with PRPs in the Baldwin
Park area. One Baldwin Park area PRP, the Aerojet Gencorp, .
agreed in 1990 to pay $554,678.59 associated with investigating
Aerojet's Azusa, California facility in partial settlement of EPA
past costs. .
Enforcement efforts in other parts of the San Gabriel Valley
Superfund Sites include a Consent Order reached in September 1993
with 42 PRPs for the Puente Valley operable Unit (see Figure ROD-
4). In addition, as of March 1994, four parties in the Puente
Valley and EI Monte Operable units of the San Gabriel valley have
been issued UAOs for Remedial Investigation. Work required by
one of the UAOs is complete; work required by two of the UAOs ,is
in progress; and work required by the fourth UAO is expected to
begin soon.
4.
HIGHLIGHTS OF COHKtJNITY PARTICIPATIOIl
The Proposed Plan for the Baldwin Park Operable unit, in the
form of a fact sheet, was distributed in May ~993 to more than
2,000 parties on EPA's mailing list for the San Gabriel Valley
Superfund Sites. Additional copies of the Proposed Plan were
distributed to water purveyors and to Baldwin Park area
businesses known to have subsurface contamination. The Proposed
Plan, together with the Baldwin Park Operable unit Feasibility
Study, were also made available in the San Gabriel Valley at the
West Covina Public Library, the office of the Upper San Gabriel
Valley Municipal Water District in El Monte, and the office of
the San Gabriel valley Municipal Water District in Azusa,
California. The entire Administrative Record File, containing
these two documents and other documents considered or relied upon
in developing the Proposed Plan, is available at the West Covina
Public Library and at EPA's Regional Office in San Francisco.
Notice of a public meeting, availability of the Proposed
Plan and Feasibility Study, and the announcement of a 30 day
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Baldwin Park ROD
public comment period were published in the San Gabriel Valley
Tribune newspaper on May 7, 1993. EPA also issued a press
release announcing the Proposed Plan on May 7, 1993. In
addition, the Los Angeles Times and San Gabriel Valley Tribune
newspapers published articles about the remedial investigation,
feasibility study, and Proposed Plan.
A public meeting was held on May 20, 1993 in the Baldwin
Park City Council Chambers to discuss EPA's clean up plans. At
this meeting, EPA representatives made a brief presentation of
the Proposed Plan, answered questions, and solicited comments
from members of the public. A response to comments received
during the public meeting is included in the Baldwin Park au
Responsiveness Summary, which is included as Part III of this
Record of Decision (ROD).
EPA extended the public comment period twice in response to
requests for extensions from members of the public. A public
notice printed in the San Gabriel Valley Tribune on June 12, 1993
extended the original 30 day public comment period to 60 days.
Another notice printed in the San Gabriel Valley Tribune on July
15, 1993 extended the public comment period to 91 days. The
public comment period closed on August 12, 1993. EPA received
more than 400 written comments from 26 individuals or entities,
as well as a three hour videotape. These comments and EPA's
responses to these comments are summarized in Part III of this
ROD.
Other community relations activities have included extensive
consultation with local water purveyors, State and local
agencies, and local groups and individuals potentially affected
by EPA's planned action in the Baldwin Park area, including
participation at numerous public meetings attended by
representatives of more than a dozen state and local agencies and
members of the public. These public meetings have typically been
held bimonthly or quarterly, from 1990 through late 1993. EPA
representatives have also made presentations to interested
groups, includinq the San Gabriel Basin Water Quality Authority
Public Advisory Group and the Superfund Working Information Group
(SWIG). In addition to the Baldwin Park Proposed Plan fact
sheet, EPA has issued fourteen fact sheets between 1986 and 1993
describing investigation and clean up activities throughout the
San Gabriel Valley. .
This decision document presents the selected remedial action
for the Baldwin Park Operable Unit in Los Angeles County,
California, chosen in accordance with CERCLA, as amended by SARA,
and, to the extent practicable, the National Contingency Plan.
The decision for this site is based on the Administrative Record.
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Baldwin Park ROD
5.
SCOPE AND ROLE OF THE OPERABLE UNIT
There are four areas of groundwater contamination in the San
Gabriel Basin listed on the National Priorities List (NPL). They
are San Gabriel Valley Area 1, San Gabriel Valley Area 2, San
Gabriel Valley Area 3, and San Gabriel Valley Area 4.
The Baldwin Park Operable unit is one of seven operable
units initiated by EPA to date (see Figure ROD-4). The OU
addresses groundwater contamination extending across the cities
of Azusa, Irwindale, and Baldwin Park, corresponding to the San
Gabriel Valley Area 2 NPL site. Other OUs address groundwater
.contamination in one or more of the other three NPL areas of the
Basin.
The available data indicate the presence of groundwater
contamination in the Baldwin Park area far in excess of drinking
water standards (demonstrating a.need for action) and are
sufficient to determine the approximate size and locations of the
needed action (allowing specification of the remedy). EPA
believes that the available data are sufficient to select a
remedy that will meet EPA's remedial objectives, described in
Section Eight of this ROD. EPA is confident that the OU
represents a significant step toward complete clean up of the
area and will not be inconsistent with, or preclude
implementation of, a final remedy. EPA has not yet selected a
final remedy for the San Gabriel Valley Superfund sites, but the
final remedy is expected to include, at a minimum, limiting
contaminant migration in and/or from the Baldwin Park area, the
Puente Valley, and other highly contaminated areas of the basin.
The Baldwin Park OU is classified as an interim action to .
reflect the possibility that additional projects in the Baldwin
Park area may be needed. EPA will use information collected
during operation of ~e selected remedy to help determine the
need for additional actions and the nature of the final remedy.
Among the critical decisions to be made are: the need for and
extent of cleanup of soil contamination in the vadose zone (i.e.,
above the water table); how to address lower levels of
groundwater contamination which may remain after the remedy is
implemented; and the feasibility of complete restoration of all
or portions of the site.
EPA has initiated six other operable units in the San
Gabriel Valley in. addition to the Baldwin Park OU. Three of the
six projects, the Richwood, Whittier Narrows, and Suburban Water
Systems Bartolo Wellfield Operable Units, resulted in the
construction of a carbon adsorption treatment facility for the
Richwood Mutual Water Company and installation of monitoring
wells in the Whittier Narrows/Suburban Water Systems area. The
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Baldwin Park ROD
other projects are in the planning or investigation stages. They
are the Puente Valley Operable Unit (addressing groundwater
contamination in the cities of Industry and La Puente), the El
Monte Operable Unit, and the South EI Monte Operable Unit.
Record of Decision (ROD) documents were signed for the
Richwood and Suburban Water Systems Operable Units in 1984, 1987,
1988, and 1993. The ROD for the Whittier Narrows Operable Unit
was signed in March 1993. The Whittier Narrows OU ROD and the
Suburban Water Systems OU Amended ROD both conclude that
treatment facilities are not now needed, but call for continued
monitoring.
As of February, 1994, ROD documents have not been signed for
the Puente Valley, EI Monte, or South EI Monte areas. In
september 1993, EPA reached an agreement with Puente Valley area
PRPs to complete a detailed investigation and evaluation of
cleanup options for groundwater contamination in the Puente
Valley. EPA is currently evaluating existing water quality data
in the EI Monte and South EI Monte areas to determine the need
for additional remedial investigation in these areas
6.
SUJlMARY OP BALDWJ:N PARK OPERABLB maT CHARACTER:IST:ICS
Figure ROD-5 presents a simplified, smoo~hed picture of the
extent of groundwater contamination in 1993 in the OU area and in
other areas of the San Gabriel Basin. The most prevalent
contaminants in the Baldwin Park area are the solvents TCE, PCE,
and CTC.
TCE, PCE, or CTC have been detected in more than one dozen
water supply wells in the Baldwin Park area at concentrations
exceeding Federal and State drinking water standards. The
contaminated wells are scattered across a five to 10 square mile
area. EPA and the State have set safe levels for TCE and PCE in
drinking water at 5 parts per billion (ppb)i the State standard
for CTC is 0.5 ppb. Other VOCs detected above state and/or
Federal standards in the Baldwin Park area include: 1,2-
dichloroethane (1,2-DCA)i 1,1-dichloroethene (1,1-DCE)i 1~1~
dichloroethane (1,1-DCA), cis-1,2-dichloroethene (cis-1,2-DCE),
trans-1,2-dichloroethene (trans-1,2-DCE), 1,1,1-trichloroethane
(1,1,1-TCA), and chloroform. Table ROD-1 presents a list of VOCs
detected in soil, soil gas, or groundwater in the Baldwin Park
area. VOCs include contaminants detectable with EPA analytical
methods 502.1, 503.1, 524.1, or 524.2. In addition, nitrate, an
inorganic contaminant, has been detected at significant
concentrations in groundwater at or near the proposed extraction
areas, approaching the drinking water standard of 45 milligrams
per liter (mg/l). Nitrate concentrations upgradient of proposed
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Baldwin Park ROD
extraction areas are significantly higher, exceeding 45 mgjl over
a large area and exceeding 90 mgjl northeast of the Baldwin Park
area.
Figures ROD-6, ROD-7, and ROD-8 illustrate the lateral
extent of groundwater contamination for TCE, CTC, and nitrate.
Assumptions and simplifications made in preparing Figures ROD-6
and ROD-7 include: the figures aggregate data over a 15 month
period; they aggregate data collected from over 100 wells that
vary in the number and depth of perforated intervals; contaminant
contours included in the figures are interpreted in areas where
no wells are present; and the figures do not delineate individual
plumes that may be present within the areas of contamination
shown in the figure. Figure ROD-8 aggregates nitrate.data over a
3 year period (nitrate has been sampled less frequently than
VOCs) .
Figure ROD-9 presents one of several possible
interpretations of the vertical extent of TCE contamination,
based on depth-specific sampling data.
The groundwater contamination appears to be the result of
multiple sources, located mostly in the city of Azusa. Also see
Section 11. 2 .
7.
SUMMARY OF SITE RISKS
As part of its evaluation of the need for action, EPA has
completed a preliminary assessment of the risks that could result
if no action is taken to address the groundwater contamination in
the Baldwin Park area (the baseline risk assessment). Interim
remedial actions do not require a completed baseline risk
assessment, although enough information must be available to
demonstrate that action is necessary to stabilize the site,
prevent further degradation, or achieve significant risk
reduction quickly (Preamble to the NCP Final Rule, 55 Federal
Register 8704).
The preliminary risk assessment estimates potential, not
actual, risk. The risk estimates are based on the unlikely
assumption that Federal and state drinking water standards are
not enforced, in which case residents of the Baldwin Park area
could be served contaminated groundwater extracted from within or
near the OU area of contamination without treatment. This is
only an assumption; groundwater served to consumers is currently
believed to satisfy all enforceable drinking water standards.
The risk assessment estimates human health and environmental
risks that could result from exposure to contaminated ground-
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Baldwin Park ROD
water. Vadose zone remediation is not a goal of the interim
action, therefore, exposure to contaminated soil or soil gas are
not addressed in this preliminary risk assessment.
The risk assessment includes four steps:
7.1
(COPC):
Xdenti~ication of Chemicals of Potential Concern
This step involves the identification of the chemicals found
in the groundwater in the au area whose presence may contribute
to risk. EPA selected as COPC contaminants detected in
groundwater during EPA-sponsored sampling of two monitoring wells
and 14 production wells in the Baldwin Park OU area between
September 1990 and September 1991. Seventeen VOCs were detected
in groundwater from the OU area. The contaminants, average
concentrations, and upper 95th confidence limits are presented in
Table ROD-2.
7.2
Exposure Assessment:
Two exposure pathways (routes by which the contamination can
enter the body) are considered in the risk assessment: ingestion
of contaminated groundwater and inhalation of VOCs released from
the water into the household air during showering, bathing,
cooking, or other routes. Exposure could also occur through the
transport of VOCs from groundwater through soil and into ambient
air or into the foundation of a building. Any exposure through
soil is assumed to be insignificant because the depth to
groundwater is greater than 100 feet. Dermal absorption (through
skin contact) of contaminants was also considered but is believed
to present a zero or insignificant risk.
The potentially exposed populations are residents and
workers in the OU area and individuals visiting the Santa Fe Dam
Recreation Lake. The maximally exposed population is assumed to
be residents exposed to contaminated groundwater used for
domestic purposes.
The monitoring data and assumptions used to characterize
exposure point concentrations are analytical results from EPA-
sponsored sampling of 15 of 16 wells in the Baldwin Park area
between September 1990 and September 1991. Arithmetic mean
chemical concentration are calculated to evaluate groundwater
exposures for the average exposure scenario; the 95 percent upper
confidence limit on the arithmetic mean of the data set is used
for the reasonable maximum exposure scenario. These calculations
assume complete blending of groundwater from the 15 wells. The
blended concentration estimates are significantly less than the
average or maximum concentrations measured at selected wells.
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Baldwin Park ROD
For example, the blended arithmetic mean and upper 95th
confidence limit concentrations for TCE are 55.1 and 96.9
microgram/liter, respectively. The average and maximum
concentrations at one well (well no. 01902169) are 335 and 450
microgram/liter.
If a chemical is not detected in a particular sample, but is
detected in other groundwater samples in the same well or in
another well in the OU area, a value equal to 1/2 the detection
limit is used to estimate the exposure concentration. In cases
where duplicate samples have been taken, the sample and duplicate
results are averaged before summary statistics are calculated.
It is assumed that the concentration remains constant for the
duration of the exposure period. .
Major exposure assumptions are summarized below. The dose
from inhalation of VOCs is assumed to be equivalent to the dose
from ingestion of 2 liters/day. .
Exposure Pac1:ors
In1:ake Value (Adul1:)
Reasonable
parame1:er Average Maximum
Ingestion Rate 2 liter/day 2 liter/day
Body weight 70 kg 70 kg
Exposure Frequency 350 days/year 350 days/year
Exposure Duration 9 years 30 years
Years in Lifetime 70 years 70 years
7.3
Toxici1:y Assess.~D1::
An individual's response to a contaminant depends on the
dose and the contaminant's toxicity. The risk assessment makes
use of quantitative information on the toxicity (i.e., the dose-
response relationship) of each of the contaminants of concern.
Table ROD-3 presents the toxicity factors, which take the'form of
reference doses (RfDs) for noncarcinogenic effects and cancer
slope factors (CSFs) for carcinogenic effects. Both RfDs and
CSFs are specific to the exposure route.
Cancer slope factors have been developed by EPA's
Carcinogenic Assessment Group for estimating excess lifetime
cancer risks associated with exposure to potential carcinogenic
chemicals. CSFs, which are expressed in units of (mg/kg-day)-l,
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Baldwin Park ROD
are multiplied by the estimated intake of a potential carcinogen,
in mg/kg-day, to provide a conservative, upper-bound estimate of
the excess lifetime cancer risk associated with the exposure.
Underestimation of the actual cancer risk is highly unlikely.
Cancer slope factors incorporate uncertainty factors to account
for the use of animal data to predict effects on humans and other
uncertainties.
Reference doses (RfDs) have been developed by EPA for
indicating the potential for adverse health effects from exposure
to chemicals exhibiting noncarcinogenic effects (e.g., harm to
the liver). RfDs, which are expressed in units of mg/kg-day, are
estimates of lifetime daily exposure levels for humans, including
sensitive individuals, which are likely to be without an
appreciable risk of deleterious effects during a lifetime.-
Estimated intakes of chemicals from environmental media (e.g.,
the amount of a chemical ingested from contaminated drinking
water) can be compared to the RfD. As with CSFs, RfDs
incorporate uncertainty factors and are unlikely to underestimate
the potential for adverse effects.
A modified RfD approach is used~to estimate the cancer risk
potential from oral exposure to 1,1-DCE due to its weak evidence
of carcinogenicity. The modified RfD is estimated by dividing
the oral RfD by an additional safety factor of 10.
7.4
Human Heal~h Risk Characteriza~ion
The last portion of the risk assessment integrates the
toxicity and exposure assessments to estimate the potential risks
to human health from exposure to site chemicals. The risk
assessment examines three measures of human health risk: cancer
risk, non-cancer effects, and groundwater concentrations in
relation to drinking water standards. Also included is a summary
of limitations of the data and methodology used in the risk
. assessment
7.4.1
Potential carcinogenic Effects
The potential for carcinogenic effects is evaluated by
estimating excess lifetime cancer risk, which is the probability
of developing cancer during one's lifetime over the background
probability of developing cancer (i.e., if no exposure to site
contaminants occurred). Excess lifetime cancer risks are
determined by mUltiplying the intake level by the cancer potency
factor. These risks are probabilities that are generally
expressed in scientific notation (e.g., 1x10-6 or 1E-6). An
excess lifetime cancer risk of 1x10-6 indicates that, as a
plausible upper bound, an individual has a one in one million
chance of developing cancer as a result of site-related exposure
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Baldwin Park ROD
to a carcinogen over a 70 year lifetime under the specific
exposure conditions at a site. The probability of developing
cancer from all causes in California is approximately 250,000 out
of 1,000,000 people (1 in 4). A risk of lout of 1,000,000 means
that one additional person out of a group of 1,000,000 people
could develop cancer as a result of the chemical exposure.
Because of the methods used to estimate CSFs, the excess
lifetime cancer risks estimated in this preliminary risk
assessment should be regarded as upper bounds on the potential
cancer risks rather than an accurate representation of the true
cancer risk. The actual risk could be as low as zero.
carcinogenic risks are assumed to be additive within a route of
exposure. Any synergistic or antagonistic interactions are not
considered. .
In the Baldwin Park Risk Assessment, EPA predicts that if
contaminated groundwater were used as a drinking water source
without treatment, as many as 60 out of 1,000,000 (6 x 10-5)
persons may develop cancer during their lifetimes (based on the
Reasonable Maximum Exposure). The risk was incorrectly reported
as 30 out of 1,000,000 (3X 10-5) in the Proposed Plan. The
excess lifetime cancer risk for average residential exposure
through domestic use of groundwater is estimated as 10 out of
1,000,000 (1 x 10-5). EPA generally considers excess cancer
risks greater than 100 out of a million to be unacceptable.
Table ROD-4 shows carcinogenic risks associated with each
contaminant of concern and each exposure pathway. The estimated
excess lifetime cancer risk for reasonable maximum exposure from
tap water is 3 x 10-5 for ingestion exposures (incorrectly
reported as 4 x 10-5 in Table ROD-4) and 3 x 10-5 for inhalation
exposures.
Since completion of the risk assessment, the inhalation
slope factor for TCE has been revised downward from 0.017
mg/kg/day-l to 0.006 mg/kg/day-l. Use of the revised slope factor
would reduce the estimated excess lifetime cancer risk for
reasonable maximum exposure from 6 x 10-5 to 5 X 10-5.
The major chemical contributors to the estimated lifetime
cancer risk based on reasonable maximum exposure are PCE and TCE.,.
with estimated risks of 1 x 10-5 and 2 x 10-5 (assuming the
revised TCE slope factor).
7.4..2
Potential Noncanc~ Effects
Potential concern for noncarcinogenic effects of a single
contaminant in a single medium is expressed as the Hazard
Quo~ien~ (HQ), the ratio of the estimated intake derived from the
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Baldwin Park ROD
contaminant concentration in a given medium to the contaminant's
reference dose. When the hazard quotient significantly exceeds
one (i.e., intake significantly exceeds RfD), there is potential
for health concern. A Hazard Index (HI) can be generated by
adding the HQs for all contaminants within a medium or across all
media to which a given population may reasonably be exposed, The
HI provides a useful reference point for gauging the potential
significance of multiple contaminant exposures within a single
medium or across media. The method assumes dose additivity.
When the HI exceeds one, there is a potential for health
risk. If a single HQ exceeds one, the HI will exceed one. The
HI can also exceed one even if no single chemical intake exceeds
its RfD.
In the Baldwin Park Risk Assessment, EPA estimates the non-
cancer Hazard Index from reasonable maximum exposure to
groundwater in the Baldwin Park OU area as 1.8, assuming that
contaminated groundwater will be served to consumers without
treatment (incorrectly reported as 0.9 in the Proposed Plan).
The total HI, based on an average exposure scenario, is 1.
Non-cancer effects associated with each contaminant of
concern and each exposure pathway are summarized in Table ROD-5.
Noncarcinogen exposure levels do not exceed the RfDs for
individual COPC. The major chemical contributors to the overall
noncancer Hazard Index based on reasonable maximum ingestion and
inhalation exposures are TCE with an estimated Hazard Index of
0.8, 1,1-DCE with an estimated Hazard Index of 0.4, and carbon
tetrachloride with an estimated Hazard Index of 0.2.
7.4.3 cOD~amiDaD~ CODceD~ra~ioDs iD Rela~ioD ~o
Drinking .a~er S~andards
The third measure of risk examined in the risk assessment is
contaminant concentrations in groundwater in the Baldwin Park
area in relation to drinking water standards (the lower of the
state or Federal Maximum contaminant Level (MCL) for each
contaminant). The comparison assumes that the contaminated water
is delivered directly to local residents without treatment. The
comparison shows unacceptably high concentrations of TCE, PCE,
erc, 1,1-DCE, 1,2-DCA, and cis-l,2-DCE. The highest TCE
concentrations at Baldwin Park area wells are more than 100 times
safe levels; the average TCE concentration for recent sampling of
15 Baldwin Park area wells is approximately 10 times safe levels.
The bases for EPA's decision to take action are the amount
by which groundwater co~centrations in the Baldwin Park area
exceed acceptable levels, migration of the contamination into
clean and less contaminated areas, and the importance of the San
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Baldwin Park ROD
Gabriel Basin as a source of drinking water. EPA believes that
remedial action is necessary even though the carcinogenic risk
levels do not exceed 100 in a million.
Table ROD-6 summarizes uncertainties associated with this
preliminary risk assessment. One critical assumption is the use
of average. (i.e., blended) chemical concentrations measured at 15
different wells. A risk estimate that assumes exposure to
groundwater produced at the more highly contaminated wells
(rather than the blended concentrations assumed in the risk
assessment) would be higher.
In conclusion, actual or threatened releases of hazardous
substances from this site, if not addressed by implementing the
response action selected in this ROD, may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
7.5
Health Risk Characterization, Environmental Risks
The risk assessment also includes an evaluation of
ecological (non human-health) impacts.
Significant impacts to potential environmental receptors are
unlikely since most of the Baldwin Park area is developed (i.e.,
paved) and the primary exposure pathway is via contaminated
groundwater. There are few environmental receptors present since
urbanization has destroyed most wildlife habitat.
One of the only possible environmental exposure pathways is
if significant VOC contamination reached the Santa Fe Dam
Recreation Lake. PCE and TCE have been detected at production
well 08000070 used to fill the man-made lake, although at low
concentrations of less than 1 microgram/liter. No effects are
expected since concentrations which may affect aquatic life are
significantly higher. The National Ambient Water Quality
Criterion (AWQC) for chronic effects resulting from exposure to
PCE is 840 microgram/liter. There is no chronic AWQC for TCE.
Of greater potential significance is the presence of
riparian and upland vegetation around the lake, and any
construction or operating impacts on the vegetation. One plant
community, Riversidian sage scrub, is considered to be a
sensitive biological resource. The Riversidian sage scrub plant
community is dominated by plant species that potentially provide
habitat for a variety of animal species. Two special-status
species, the California gnatcatcher and San Diego horned lizard,
potentially occur in this habitat type.
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Baldwin Park ROD
8.
DBSCR:IPT:IOlf OF ALTBRlfATIVES
The remedial objectives of the Baldwin Park OU, which guided
the development and evaluation of the remedial alternatives, are:
... to prevent future increases in, and begin to reduce,
concentrations of all VOCs in groundwater in the Baldwin
Park area by limiting further migration of contaminated
groundwater into clean and less contaminated areas or depths
that would benefit most from additional protection and by
removing contamination from the aquifer.
The Baldwin Park au is an interim action. Accordingly, the
remedy does not include in situ (i.e., in the aqUifer)
remediation standards or a restoration timeframe.
Portions of the aquifer that would benefit most from
additional protection include: (i) areas downgradient of
residual subsurface contamination (e.g., dense non-aqueous phase
liquids (DNAPLs) or other non-aqueous phase contamination) that
are clean or contaminated only by dissolved-phase contamination;
and (ii) clean or less contaminated areas with active water
supply wells, downgradient of more highly contaminated areas.
EPA interpreted the remedial objectives to require, at a
minimum, groundwater extraction in two areas. Each of the four
cleanup alternatives (Alternatives 1-4) evaluated in the Baldwin
Park Operable Unit Feasibility Study includes the construction
and operation of new groundwater extraction wells in two or three
areas, treatment facilities to remove VOCs from groundwater
(assumed, in the FS, to be air stripping with vapor pbase
granular activated carbon), pipelines and related conveyance
facilities to deliver the treated water, and groundwater
monitoring. Selected existing facilities may also be used. The
differences between cleanup alternatives are in project size and
recipient of the treated water. EPA also evaluated a no action
alternative.
Existing beneficial uses of the San Gabriel Basin aquifer
include municipal and domestic supply (defined in California
water quality standards as ."uses of water for community,
military, or individual water supply systems including, but not
limited to, drinking water supply").
The following sections describe the No Action Alternative
and the four action alternatives.
8.1
The No Action Alternative
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Baldwin Park ROD
A No Action Alternative (more accurately described as a No
Active Response Alternative since it includes installation and
sampling of monitoring wells) provides a baseline for comparison
of other cleanup alternatives. In a No Action Alternative, no
action is taken to limit contaminant migration beyond actions
already taken by water purveyors or local agencies such as the
San Gabriel Basin Water Quality Authority. The No Action
Alternative would include a monitoring program to provide early
warning of increasing contaminant concentrations at existing,
active water supply wells downgradient of the Baldwin Park area
of contamination. Three clusters of production wells are active
within approximately 1 mile of the downgradient end of the au
area of contamination (San Gabriel Valley Water Company's B4 and
B6 well clusters and La Puente Valley County Water District's
well cluster), but two of the three clusters are located within
several hundred feet of each other. For cost-estimating
purposes, it is assumed that three new monitoring wells would be
required to meet the objectives of the monitoring program. The
cost of constructing the monitoring wells would be approximately
$ 0.4 million in initial, capital costs and less than $ 0.1
million in annual sampling costs.
The monitoring program would provide data to help predict
when contaminants in downgradient production wells may increase
to levels requiring installation of new wellhead treatment or
modification of existing wellhead treatment facilities.
8.2 Remedial Alternative No.1: Extract, Treat, and
Distribute Approximately 19,000 gpm of Groundwater to San Gabriel
Valley Water Purveyors
8.2.1
Extraction Locations and Rates
Alternative 1 calls for extraction of groundwater from two
broad areas of contamination (referred to as the upper and lower
areas). Figure ROD-I0 shows the two areas marked approximate
ex'traction well locations. The precise locations of the new
extraction wells and treatment facilities would be determined
during the remedial design phase of the project, after the
installation and interpretation of data from new groundwater
monitoring wells. The remedy may use two existing groundwater
extraction wells and a planned wellhead treatment system if,
during remedial design, EPA determines that they are suitably
located, if agreements can be reached for their use, and if ,they
meet other requirements of this Record of Decision.
EPA's computer simulations of groundwater flow and particle
movement indicate that approximately 19,000 gpm of water must be
extracted to meet EPA's objectives of controlling contaminant
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Baldwin Park ROD
migration. EPA's analyses indicate that approximately 10,~00 qpm
of groundwater must be extracted more or less continuously in the
lower area; approximately 8,500 qpm of groundwater must be
extracted in the upper area. These extraction rates would limit
contaminant migration out of the upper and lower areas of
contamination (i.e., to capture or contain the areas of
contamination).
Extraction in the lower area would limit further migration
of groundwater contaminated with VOCs at concentrations
approximately five to 10 times drinking water standards.
Sampling results from two locations in 1989 - 1992 show average
TCE concentrations between 40 and 50 ppb (the MCL for TCE is 5
ppb). Actual concentrations vary month to month and year to
year. EPA sampling at a third location-has shown average CTC
concentrations of 12 ppb (the MCL for CTC is 0.5 ppb).
Concentrations of TCE and CTC downgradient of the lower area are
significantly lower.
Extraction in the upper area would limit further migration
of groundwater containing VOCs at concentrations more than 200
times safe levels (e.g., more than 1,000 ppb TCE or PCE, or more
than 100 ppb 1,2-DCA). The highest concentration measured at a
monitoring well in the upper area exceeds 30,000 ppb PCE.
Extraction in the upper area would help prevent highly
contaminated areas adjacent to the likely sources of the
groundwater contamination from moving into less contaminated
downgradient areas, increasing the likelihood that downgradient
areas could eventually be restored. Extraction in both the upper
and lower areas would significantly reduce contaminant
concentrations throughout the Baldwin Park area, although the
rate and magnitude of the reduction are difficult to predict.
8.2.2
Treatment
After the contaminated groundwater is pumped above-ground,
it would be piped to treatment facilities capable of removing
VOCs from groundwater. contaminant concentrations in the treated
water would meet State or Federal Maximum contaminant Levels for
VOCs, whichever are more stringent. Initial studies completed by
EPA indicate that the most efficient, proven treatment
technologies will be air stripping (with offgas controls) or
liquid phase granular activated carbon (LGAC). EPA's analyses
indicate that both technologies are effective for most mixes of
contaminants, but differ in cost depending on the VOC influent
concentrations expected at the treatment facilities, which are
dependent on precise extraction locations and whether groundwater
from multiple extraction locations are blended and treated at a
centralized facility. The two technologies may also be combined
into a treatment train.
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Baldwin Park ROD
Liquid phase granular activated carbon transfers the
contaminants from water to a charcoal-like material. Air
stripping transfers volatile contaminants (e.g., VOCs) from water
to air; vapor phase granular activated carbon transfers the
contaminants from air to a charcoal-like material. If air
stripping is used, it would include vapor phase granular .
activated carbon or other offgas controls to meet air emission
requirements of the South Coast Air Quality Management District.
EPA also evaluated the cost, effectiveness, and feasibility
of advanced oxidation processes. Advanced oxidation processes
are innovative treatment methods capable of destroying
contaminants. EPA's initial studies indicate that advanced
oxidation processes would be considerably more expensive than
either air stripping or LGAC.
The extracted groundwater would be treated for VOCs at one
or more locations to be determined during remedial design. If
treated water is supplied for local use, the most cost-effective
arrangement would probably be to construct multiple treatment
facilities (possibly four separate facilities).
8.2.3
Distribution/Use of Treated Water
If the necessary agreements are reached, the treated water
will be supplied to agencies that directly or indirectly supply
drinking water to San Gabriel Valley residents and businesses
(water purveyors). Excess water would be piped to spreading
basins, the San Gabriel River channel, or tributary flood control
channels operated by the Los Angeles County Department of Public
Works for recharge into the aquifer when water purveyors are not
able to use all of the treated water.
EPA expressed a preference to supply treated water to
purveyors, rather than for recharge, due to lower pumping costs
(although higher initial capital costs) and the risk that
existing recharge areas may not offer enough recharge capacity
during winter and spring rainy season. There is excess capacity
in recharge areas for much, but not all of the year. In each of
the last two years, existing users of Baldwin Park area spreading
grounds used all of the available capacity for several
consecutive months. In contrast, supplying treated water to
purveyors has the advantage that purveyors should be able to
accept water close to year-round, minimizing the risk of not
being able to distribute extracted water during winter and spring
months.
In the FS it is assumed that water would be supplied to San
Gabriel Valley Water Company, Suburban Water Systems, Covina
Irrigating Company, and the city of Glendora, although other
29
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Baldwin Park ROD
,
purveyors could substitute. There are pros and cons to supplying
each purveyor which could potentially accept treated water. Some
purveyors could distribute large quantities of water year-round;
others could distribute less water for only part of the year.
Some purveyors are located near likely treatment plant locations
(requiring minimal pipeline); others are located further away or
at higher elevations (requiring more pumping). Purveyors also
vary in how much they are willing to pay for additional supplies,
in whether they could accept water without first resolving water
rights issues (e.g., exporting water from the basin), and in
their expertise in operating treatment facilities.
8.2.4
Project Duration, Cost, and Evaluation
The project would operate for an initial period of five
years, after which EPA will conduct a formal assessment of the
project's effectiveness. The results of the assessment may lead
to continued operation of the project as is, or recommended
modifications in the extraction rates and locations or other
project components. The project would be expected to operate
until contaminant concentrations decrease sufficiently that
continued efforts to limit the migration of contaminated
groundwater or remove contaminant mass are no longer necessary.
The assessment will include an evaluation of the effects of the
operation of nearby public water supply wells on the attainment
of EPA's remedial objectives.
It is estimated that implementation of Alternative 1 would
require approximately 36 months from the date the ROD is signed.
During this period, EPA intends to negotiate an agreement for
funding of the selected remedy, and then proceed with design,
construction, and initial testing of the equipment to make sure
it functions properly.
The estimated cost of Alternative 1 is $47 million in
capital costs and $4 million in annual operation and maintenance
costs. More than half of the capital costs would be for
construction of treatment facilities; the remainder of the costs
would be for well systems, pipelines, and land acquisition. The
estimate assumes that new treatment facilities must be
constructed, although one or more existing or planned facilities
may be used. The biggest contributor to the operating costs
would be the cost of regenerating or replacing the granular
activated carbon used in the treatment process. The cost
estimates for Alternatives 1-4 each include an added 35% to
account for the risk of higher than expected labor or material
costs, unforeseen delays, and other factors that may increase
costs.
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Baldwin Park ROD.
~
8.3 Remedial Alternative Ho. 2: Extract, Treat, and
Distribute Approximately 29,000 qp8 of Groundwater to San Gabriel
Valley Water Purveyors and Recharge Areas
Alternative 2 differs from Alternative 1 in that it involves
the extraction of groundwater from three (rather than two) broad
areas of contamination (the lower, middle and upper areas). See
Figure ROD-10. Extraction in the lower and upper areas would be
the same as described for Alternative 1. Alternative 2 would add
extraction in the middle area to prevent further degradation of
the area in between the upper and lower extraction areas and
remove additional contaminants. Approximately 10,000 gpm of
water would need to be extracted in the middle area to provide
the additional migration control. The additional 10,000 gpm
would be distributed in part to water purveyors and in part to
the San Gabriel River channel and the Irwindale Spreading
Grounds. In the FS it is assumed that water would be supplied to
San Gabriel Valley Water Company, Suburban Water Systems, Covina
Irrigating Company, the city of Glendora, and the city of Azusa,
although other purveyors could substitute.
The estimated cost of Alternative 2 is $65 million in
initial, capital costs and $7 million in annual operation and
maintenance costs. Implementation may take longer than
Alternative 1 due to the need to construct additional facilities
and reach agreements to distribute approximately an additional
10,000 gpm of treated water.
8.4 Remedial Alternative Ho. 3: Extract, Treat, and
Distribute Approximately 29,000 qp8 of Groundwater to San Gabriel
Valley Water Purveyors and Ketropolitan Water District of
Southern California
Alternative 3 shares the same extraction component as
Alternative 2, and the same water use option for groundwater
extracted from the lower area, but differs in the disposition of
extracted groundwater from the upper and. middle areas. Instead
of supplying treated water to local purveyors, treated water
would be piped from the treatment facilities to Metropolitan's
Middle Feeder pipeline, which passes through the city of Baldwin
Park. Metropolitan would export the treated water to its member
agencies located in the northeastern and south central sections
of Los Angeles County during summer months or drought years.
Because Metropolitan possesses only negligible pumping rights in
the San Gabriel Basin, Metropolitan would be required to replace
every gallon of exported water by recharging an equivalent amount
of imported water during the winter or spring offpeak months when
imported water is relatively abundant. This type of operation is
often described as a conjunctive use operation.
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Baldwin Park ROD
,
Metropolitan may distribute the treated water to secondary
recipients during offpeak winter and spring months. Possible
arrangements include direct recharge from the treatment.
facilities, or discharge of the treated water into Metropolitan's
existing conveyance facilities for distribution .(wheeling) to
local water purveyors. The local water purv~yors would use the
treated groundwater in lieu of pumping clean groundwater.
The estimated cost of Alternative 3 is approximately $76
million in capital costs and $9 million in annual operation and
maintenance costs, higher than for Alternatives 1 or 2. The
actual cost to EPA is assumed to be equal to the cost of
Alternative 2, however. Metropolitan would be expected to fund
the difference in cost, referred to. as an enhancement cost.
8.5 Remedial Alternative Ho. 4: Extract, Treat, and
Distribute Approximately 29,000 gpm of Groundwater to
Metropolitan Water District of Southern california
Alternative 4 shares the same extraction component as
Alternatives 2 and 3, but differs in the disposition of the
treated water from the upper and middle areas. All treated water
would be piped from a treatment facility to Metropolitan's Middle
Feeder pipeline.
The estimated cost of Alternative 4 is approximately $78
million in capital costs and $10 million in annual operation and
maintenance costs, higher than for Alternatives 1, 2, or 3. The
actual cost is assumed to be equal to the cost of Alternative 2,
however. Metropolitan would be expected to fund the difference
in cost, referred to as an enhancement cost.
9. SUMMARY OF COMPARATrvE ANALYSIS OF ALTERNATIVES
This section ranks the five remedial alternatives in
relation to the nine Superfund evaluation criteria listed in 40
CFR Part 300.430.
9.1
OVerall Protection of Human Health and the Environment
Remedial Alternatives 1-4 protect human health and the
environment without substantial negative impacts. Alternatives
2, 3, and 4 would include additional extraction in a middle
portion of the aquifer not included in Alternative 1. The
additional extraction would provide additional protection for the
area in between the upper and lower extraction areas and remove
additional contaminant mass. Negative impacts associated with
Alternatives 1-4 include the disruption that would result from
32
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Baldwin Park ROD
.
installation of pipelines and other components of the remedy and
the impacts of handling, treating, and disposing of treatment
residuals (e.g., air emissions and spent carbon).
Alternative 1 (and Alternatives 2, 3, and 4) would reduce
short- and long-term risks to human health and the environment by
inhibiting contaminant migration from two hiqhly contaminated
portions of the aquifer (the upper and lower areas) to less
contaminated areas or depths to reduce the impact of continued
contaminant migration on downgradient water supply wells and to
protect future uses of less contaminated and uncontaminated
areas. Alternatives 1-4 would reduce the toxicity, mobility, and
volume of the contaminants and remove siqnificant contaminant
mass from the aquifer. The voc treatment technoloqies that would
be used are effective in meeting Federal and state drinking water
standards for VOCs. '
Alternative 1 (and Alternatives 2 and 3, but not Alternative
4) also offer the benefit of providing treated water to purveyors
whose wells are threatened by continued contaminant migration,
providing the vulnerable purveyors with an alternative water
supply.
The no-action alternative provides the least overall
protection of human health and the environment. It would not
provide any additional migration control beyond-that provided by
projects that may be built by parties other than EPA (e.g., by
local water purveyors or local water agencies). contaminant
concentrations in ,a significant portion of the a~ifer exceed
State or Federal drinking water standards.
Limitations of the no-action alternative include: the
increased potential for human exposure; leavinq the burden of
constructing treatment facilities to water purveyors; the
increased cost and difficulty of operating existing treatment
facilities if more highly contaminated groundwater reaches
existing facilities; the increased likelihood that future
increases in contaminant concentrations at active water supply
wells would result in emergencies requiring immediate actions not
consistent with long-term remediation goals (e.g., pumping in
relatively clean portions of the aquifer, potentially spreading
the contamination); and the increased eventual cost, difficulty,
and time required for containment or restoration of the aquifer.
(If no action is taken, continued contaminant migration would
result in the need to treat larger volumes of contaminated water
and may result in the increased presence of vinyl chloride or
other VOC degradation products that are more difficult to treat
or more toxic than the parent compounds.)
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Baldwin Park ROD
. ~
Alternatives 1-4 may not achieve final cleanup levels for
the groundwater. MCLs/MCLGs in situ are not ARARs for this
action because they are beyond the scope of this interim action.
9.2
compliance with ARARs
Each of Alternatives 1-4 is confiqured to comply with the
ARARs described in Section 10 of this ROD. No differences are
expected among these remedial alternatives in compliance with
ARARs. No ARARs waivers are expected to be needed.
9.3
Long-Term Effectiveness and Permanence
This evaluation criterion assesses the extent to which each
remedial alternative reduces risk after the remedial response
objectives are met. Residual risks in this interim remedy could
result from exposure to contaminated groundwater not removed from
the aquifer, or exposure to used granular activated carbon or
other treatment residuals. The performance of the alternatives
in relation to this criterion is evaluated by estimating the
extent to which each alternative prevents the migration of
contamination into less contaminated areas and the rate of
contaminant removal.
Alternatives 2, 3, and 4 would provide the greatest long
term effectiveness because they include additional extraction in
three subareas, which would limit downgradient and vertical.
migration in and beyond the upper, middle, and lower subareas and
remove significant contaminant mass from all three subareas.
Alternative 1 would provide the same protection in and
downqradient of the upper and lower subareas, but lacks the
additional benefits of extraction in the middle subarea. These
benefits are added protection for the area in between the upper
and lower extraction areas and removal of additional contaminant
mass.
The no-action alternative would not limit further
downgradient contaminant plume migration, or remove contaminant
mass, beyond that provided by projects that may be built by
parties other than EPA.
Fiqures ROD-11 and ROD-12 depict the results of computer
simulations that provide a measure of the effect of the no-action
alternative and the remedial alternatives on the movement of the
contamination in the OU area. The figures depict the movement of
particles representing selected drops of contaminated '
groundwater. Particles that terminate at black dots indicating
extraction well locations are captured, representing contaminant
molecules that are removed from the aquifer. Particles that
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Baldwin Park ROD
..
extend past extraction well locations represent an increase in
downgradient contaminant concentrations or a downgradient
expansion of the area of contamination. .
Figure ROD-12 illustrates the effectiveness of Alternatives
2, 3, and 4. The effectiveness of Alternative 1 would be similar
to that shown in the figure, except that particles originating in
Subarea 2 (the middle subarea) would be captured in Subarea 3
rather than Subarea 2. In each of Alternatives 1-4, most of the
particles shown in the figure are captured by OUwells in
Subareas 1 and 3. A few particles continue beyond the
downgradient margin of the OU area of contamination, although the
downgradient distances traveled are much shorter than shown for
the no-action alternative. .
There are some other minor differences in effectiveness
between Alternatives. Alternatives 1, 2, and 3 may be slightly
more effective than Alternative 4 because of reductions in
pumping at existing water supply wells at the periphery of
Subarea 3. Alternative 1 may also be slightly more effective
than Alternatives 2, 3, and 4 if Alternatives 2, 3, or 4 include
significant recharge in areas that increases the rate of
contaminant migration downgradient of recharge areas.
Alternative 1 assumes no recharge of treated groundwater and
Alternative 2 assumes recharge of 6,500 gpm of treated water.
Alternatives 3 and 4 assume no recharge, a project in which
treated water is supplied to Metropolitan could result in
recharge during offpeak periods.
Figure ROD-11 depicts the extent and degree of contaminant
migration for the no-action alternative. The figure shows that
some contaminated groundwater is extracted by an existing well.
cluster in the OU area, but much of the contaminated groundwater
continues to migrate unimpeded. This effect is illustrated by
the number of particles moving beyond the current downgradient
extent of contamination and the distances that these particles
travel. .
Alternatives 1-4 may result in air emissions (if air
stripping is used) and generate spent carbon or other treatment
residuals. Air emissions and risks associated with treatment
residuals are expected to be within acceptable levels. The
magnitude of the residual risks from treatment residuals for
Alternative 1 would be less than for Alternatives 2, 3, and 4
because of the lower extraction rate.
9.4
Treatment
Reduction of Toxicity, Mobility, or Volume Throuqh
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Baldwin Park ROD
This criterion addresses the statutory preference for
selecting remedial actions employing treatment technologies that
permanently and significantly reduce toxicity, mobility, or
volume of the hazardous substances as a principal element of the
action.
Alternatives 1, 2, 3, and 4 all satisfy the statutory
preference for treatment. Each of these four alternatives would
employ treatment processes that would significantly reduce the
volume of hazardous contaminants by inhibiting contaminant
migration, and reduce the toxicity and volume of hazardous
contaminants by treating the groundwater so that it meets MCLs
for VOCs.
The VOC treatment technologies assumed in Alternatives 1-4,
LGAC or air stripping with offgas controls, are technically
feasible and effective in meeting ARARs for VOCs in the extracted
and treated groundwater. Treatment of the contaminated
groundwater with LGAC or air stripping with carbon offgas
controls would substantially reduce the volume of contaminated
media and mobility of the contaminants by transferring
contaminants from groundwater to the GAC. This contaminated GAC
would require disposal or regeneration.
The Alternatives are similar in their capability to satisfy
this criterion. The major difference is the omission of
groundwater extraction in the middle area in Alternative 1. This
difference among alternatives is described in the long-term
effectiveness and permanence criterion and is not duplicated
here.
9.5
Short-Term Bffectiveness
This criterion evaluates the effects of each remedial
alternative on human health and the environment during the
construction and start-up of the remedy. It also addresses the
time elapsed during construction and start-up.
Alternative 1 may be designed and built more quickly than
Alternatives 2-4 because of its smaller size, although any of the
alternatives could be built in phases to minimize delay. There
may also be differences in the number or severity of
institutional obstacles, but these differences are taken into
account in the implementability criterion and not duplicated
here. We conclude that Alternatives 1-4 are similar in short-
term effectiveness and do not present unmitigable risks to the
community, workers, or the environment during construction and
implementation.
9.6
Xmplementability
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Baldwin Park ROD
.
This criterion addresses the technical and administrative
feasibility of implementing an alternative and the availability
of various services and materials required during its
implementation. Of particular importance in the Baldwin Park OU
is the administrative feasibility of the Alternatives, especially
the need for agreements with parties other than EPA to distribute
treated water. -
The technical feasibility of Alternatives 1-4 is similar.
The extraction, treatment, and conveyance technologies included
in all of the Alternatives are widely used and are generally
known to be proven and reliable. All of the Alternatives share
some risk that higher than estimated contaminant concentrations
could interfere with the ability of the treatment facility to
attain treatment objectives. .
Numerous administrative obstacles must be overcome to
implement any of the alternatives, but Alternative 1 is
potentially more feasible than Alternatives 2-4 due to the lower
amount of treated water that needs to be distributed
(approximately 10,000 gpm less water - 1/3 less). This would
result in the need to reach agreements with fewer parties that
would receive treated water from an OUi acquisition of less
property and/or fewer easements for the construction of
extraction wells, treatment facilities, and conveyance facilities
(and resolving other issues associated with a large construction
project in a developed area); and acquisition of fewer offsets
for air emissions if air stripping is used. Agreements with
recipients of treated water will need to specify the amount of
treated water to be delivered, the delivery location,
responsibility for any necessary capital improvements"to the
recipient's distribution system to accept the water, and
operational, liability, financial, and other arrangements.
Resolving these issues could potentially delay implementation of
the project.
If water purveyors accept treated water, they will be
responsible for obtaining approval for modifications to their
water supply permits. If treated water is recharged,
arrangements would need to be made with the Los Angeles County
Department of Public Works for use of its spreading grounds. An
agreement may not guarantee the required amount of spreading
capacity because of competition for use of available spreading
capacity.
In addition, for Alternatives 3 and 4, the following
administrative feasibility issues associated with the involvement
of Metropolitan would need to be resolved.
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Baldwin Park ROD
. Arrangements may need to be made with secondary recipients
for distribution of treated water during offpeak periods
(i.e., winter and spring months);
. Arrangements would need to be made with the LACDPW for
recharge of imported water. Although imported surface water
is already recharged for replenishment and cyclic storage,
significant additional amounts would increase the risk that
there may insufficient capacity in existing recharge areas.
. Metropolitan would need to reach agreement with the
Watermaster (and/or obtain court approval) for export of
additional water from the basin and the storage of imported
water recharged in the basin. The existing water rights
, agreement (the Alhambra Judgment) currently prohibits any
additional export of extracted groundwater from the basin
without Watermaster and/or court approval. Metropolitan and
, Watermaster are in their second year of negotiations over
the terms of an agre,ement.
. Before accepting treated water, Metropolitan may need to
reach agreement with the Watermaster (and/or obtain court
approval) to increase the available storage capacity in the
basin by modifying the operating criteria in the Alhambra
Judgment. Metropolitan may also need to mitigate adverse
effects of higher or lower water levels.
. Metropolitan staff have stated the possibility that
Metropolitan would impose more stringent treatment
requirements, which would require the construction of
additional treatment facilities.
. Financial agreements with Metropolitan for funding of
system enhancements would be necessary. Enhancement costs
are capital or operating costs that are not necessary for
attainment of remedial objectives. state or Metropolitan
funding may trigger the need for Metropolitan to prepare an
Environmental Impact Report to comply with the California
Environmental Quality Act (CEQA).
. Financial and operation agreements (including staffing,
maintenance schedules) may be needed to arrange for seasonal
changes in the operating scenario if the level of treatment
required by recipients of treated water during offpeak
periods differs from Metropolitan's requirements.
. Acquisition of property for a treatment facility could be
more difficult because of Metropolitan's likely requirement
that a single centralized treatment facility be constructed.
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Baldwin Park ROD
These disadvantages may be partially offset by
Metropolitan's expertise in constructing large water supply
projects, and by eliminating the need to reach agreements with
local water purveyors if arrangements for distribution of treated
water during offpeak periods do not involve local purveyors.
9.7
Cost
The following table presents estimated capital costs, O&M
costs, and the estimated present worth of each remedial
alternative. The present worth is estimated using discount rates
of 3, 5, and 10 percent, and a base period of 30 years. The
assumption of a 30-year project life reflects EPA Superfund
guidance; it does not reflect any specific finding regarding the
duration of the remedy. The costs are considered order-of-
magnitude level estimates (i.e., the true project cost may be 50%
higher or 30% lower than the estimated cost).
Estimated Costs of Remedial AItematives
(millions of doUan)
Net Present Worth at 3, 5, and 100/. Discount Rates
Short-Term (assuming 30 year lifetime)
Capital Annual O&M
Altemative Costs Costsl 3 Pereent 5 Pereent 10 Pereent
No-Action2 0.4 less than 0.1 1 0.9 0.8
8 1 47 3.5 to 5.0 116-145-- 101::124 - - 80--94---
2 65 5.9 to 7.8 182-217 156-184 121-138
33 65 5.9 to 7.8 182-217 156-184 121-138
43 65 5.9 to 7.8 182-217 156-184 121-138
J A range of O&M costs is provided to account for the range of potential purveyor reimbursement rates for
treated water from $25 to $75/acre-foot
2-fhe No-action alternative costs include only those costs associated with the no-action monitoring program.
Additionallong-term fmancial impacts of this alternative have not been estimated.
3 Actual project costs for Alternatives 3 and 4 would be greater than indicated due to requirements associated
f-~th the involvement of Metropolitan. It is assumed that Metropolitan would-pay.. for- 6Dy-cost~l-fesu1ting-"
from water supply or other requirements that are not necessary for attainment of remedial objectives
(enhancement costs). making the net project cost to EPA or PRPs the same as for Alternative 2.
9.8
state Acceptance.
In a letter dated August 12, 1993, the State of California
(Cal-EPA Department of Toxic Substances Control) concurred with
EPA's proposed remedy for the Baldwin Park OU. In a second
letter from Margaret Felts, Deputy Director, site Mitigation
39
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Baldwin Park ROD
"
Program, Department of Toxic Substances Control, the State of
California concurred with EPA's selected remedy.
t.t
Public Acceptance.
In addition to the State, twenty-five individuals and
organizations submitted over 400 comments on EPA's Remedial
Investigation, Feasibility Study, and Proposed Plan for the
Baldwin Park OU. These comments, and EPA's responses, are
presented in the Part III of this ROD (the Responsiveness
Summary). Most commenters submitted between one and ten
comments. One commentor, a recipient of General Notice of
Liability for the Baldwin Park OU, submitted approximately 250
comments.
Several comments expressed support for EPA's proposed
remedy; others did not. Most commented upon were two aspects of
the Alternatives: the size of the project (i.e., the amount or
rate of contaminated groundwater extracted from the aquifer); and
the disposition of the treated water. EPA's Proposed Plan calls
for extraction of approximately 19,000 qpm of contaminated
groundwater from two Subareas, as in Alternative L Several
individuals and two water agencies recommended that EPA select
the larger project included in Alternatives 2, 3, and 4
(extraction of approximately 29,000 qpm of contaminated
groundwater from three Subareas). Several businesses and.
business organizations recommended that EPA select a smaller
project.
Several individuals, local organizations, and water agencies
also recommended that EPA select Metropolitan as the recipient of
the treated water (a component of Alternatives 3 and 4), often on
the assumption that doing so would increase the extent or
decrease the cost of the clean up. .
10.
APPLICABLE OR RELEVANT AND APPROPR:IATE REQUIRBKENTS (DARs)
This section discusses Applicable or Relevant and
Appropriate Requirements (ARARs) for the Baldwin Park OU. Under
Section 121(d) (1) of the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 as amended by the
Superfund Amendments and Reauthorization Act of 1986
(collectively, CERCLA), 42U.S.C. section 9621(d), remedial
actions must attain a level or standard of control of hazardous.
substances which complies with ARARs of Federal environmental
laws and more stringent State environmental and facility siting
laws. Only State requirements that are more stringent than
Federal ARARs, are legally enforceable and consistently enforced,
and identified in a timely manner may be ARARs. The California
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Baldwin Park ROD
Department of Toxic Substance Control ("DTSC") is the lead state
agency for CERCLA matters. In accord with a directive by
Margaret C. Felts, Deputy Director site Mitigation Program, EPA
has communicated with DTSC with regards to ARARs and has relied
on DTSC for identification of state ARARs.
Pursuant to section 121(d) of CERCLA, the on-site portion of
a remedial action selected for a Superfund site must comply with
all ARARs. Any portion of a remedial action which takes place
off-site must comply with all laws legally applicable at the time
the off-site activity occurs, both administrative and
substantive.
An ARAR may be either "applicable," or "relevant and
appropriate," but not both. According to the National oil and
Hazardous Substances POllution contingency Plan (NCP) (40 CPR
Part 300), "applicable" and "relevant and appropriate" are
defined as follows:
. Applicable requirements are those cleanup standards,
standards of control, or other substantive environmental
protection requirements, criteria, or limitations
promulgated under Federal or State environmental or facility
siting laws that specifically address a hazardous substance,
pollutant, contaminant, remedial action, location, or other
circumstance found at a CERCLA site. only those State
standards that are identified by a State in a timely manner
"and that are more stringent than Federal requirements may be
applicable. "Applicability" implies that the remedial
action or the circumstances at the site satisfy all of the
jurisdictional prerequisites of a requirement.
. Relevant and appropriate requirements are those cleanup
standards, standard of control, and other substantive
environmental protection requirements, criteria, or
limitations promulgated under Federal environmental or State
environmental or facility siting laws that, while not
"applicable" to a hazardous substance, pollutant,
contaminant, remedial action, location, or other
circumstance at a CERCLA site, address problems or
situations sufficiently similar to those encountered at the
CERCLA site that their use is well suited to the particular
site. Only those State standards that are identified in a
timely manner and that are more stringent than Federal
requirements may be relevant and appropriate. .
Requirements are also classified as chemical-sPecific, location-
specific, or action-specific.
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Baldwin Park ROD
. Chemical-specific ARARs are health- or risk-based
concentration limits, numerical values, or methodologies for
various environmental media (i.e., groundwater, surface
water, air, and soil) that are established for a specific
chemical that may be present in a specific media at the
site, or that may be discharged to the site during remedial
activities. These ARARs set limits on concentrations of
specific hazardous substances, pollutants, and contaminants
in the environment. Examples of this type of ARAR are
ambient water quality criteria and drinking water standards.
. Location-specific requirements set restrictions on certain
types of activities based on site characteristics. Federal
and state location-specific ARARs are restrictions placed on
the concentration of a contaminant or the activities to be
conducted because they are in a specific location. Examples
of special locations possibly requiring ARARs include flood
plains, wetlands, historic places, and sensitive ecosystems
or habitats.
. Action-specific requirements are technology- or activity-
based requirements which are triggered by the type of
remedial activity. Examples are Resource, Conservation and
Recovery Act (RCRA) regulations for waste treatment, storage
or disposal.
Neither CERCLA nor the National oil and Hazardous Substances
Pollution contingency Plan (NCP) (400 C.F.R. Part 300) provides
across-the-board standards for determining whether a particular
remedy will result in an adequate cleanup at a particular site.
Rather, the process recognizes that each site will have unique
characteristics that must be evaluated and compared to those
requirements that apply under the given circumstances.
Therefore, ARARs are identified on a site-specific basis from
information about specific chemicals at the site, specific
features of the site location, and actions that are being
considered as remedies.
The following section outlines the ARARs that apply to this
site.
10.1' Chemical-Specific ARARs
10.1.1
Pederal Drinking Water standards
Section 1412 of the Safe Drinkina Water Act (SDWA). 42
U.S.C. Section 300a-1. "National Water ReCtUlations":
National primarv Drinkina Water ReCtUlations. 40 CFR
Part 141. -
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Baldwin Park ROD
EPA has established Maximum contaminant Levels (MCLs) (40
CFR Part 141) under the Safe Drinking Water Act (SDWA) to protect
public health from contaminants that may be found in drinking
water sources. These requirements are applicable at the tap for
water provided directly to 25 or more people or which will be
supplied to 15 or more service connections. The MCLs are.
applicable to any water that would be served as drinking water.
Under NCP section 300.430(f) (5), remedial actions must generally
attain MCLs and non-zero Maximum contaminant Level Goals (MCLGs)
for remedial actions where the groundwater is a current or
potential source of drinking water.
The groundwater. at the Baldwin Park OU is an existing and
potential source of drinking water. However, since the Baldwin
Park OU remedial action is an interim action, chemical-specific
cleanup requirements for the aquifer such as attaining MCLs and
non-zero MCLGS, which would be ARARs.for a final remedy, are not
ARARs for this interim action. (See NCP, 55 Fed. Reg. 8755.)
Nevertheless, EPA has determined that for the treatment plant
effluent from the Baldwin Park OU, the Federal Primary and any
Secondary Maximum contaminant Levels (MCLs) for VOCs and any more
stringent state of California Primary MCLs for VOCs are relevant
and appropriate and must be attained regardless of the end use or
discharge method for the treated water. In addition, treated
water that is discharged to surface water shall meet National
pollutant Discharge Elimination System (NPDES) discharge
requirements.
For treated 'water which will be put into a public water
supply, all legal requirements for drinking water in existence at
the time that the water is served will have to be met because EPA
considers serving of the water to the public (at the tap) to be
off-site. complying with all applicable requirements for
drinking water at the tap will also require attainment. of the MCL
for nitrate prior to serving the water to the public. Since
these are not ARARs, these requirements are not "frozen" or fixed
as of the date of the ROD. Rather, they can change over time as
new laws and regulations applicable to drinking water change.
-See NCP, 55 Fed. Reg. 8758 (March 8, 1990).
10.1.2
state Drinking Water standards
California Safe Drinkina Water Act. Health and Safety
Code. Division 5. Part 1. ChaDter 7. section 4010 et
sea.. California Domestic Water Oualitv Monitorina
reaulations. CCR Title 22. Division 4. ChaDter 15.
section 64401 et sea.
California has also established drinking water standards for
sources of public drinking water, under the California Safe
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Baldwin Park ROD
Drinking Water Act of 1976, Health and Safety Code sections"
4010.1(b) and 4026(c). California has promulgated primary MCLs
for VOCs. Several of the State MCLs are more stringent than
Federal MCLs. In these cases, EPA has determined that the more
stringent State MCLs for VOCs are relevant and appropriate for
the treatment plant effluent from the Baldwin Park OU interim
remedy. VOCs for which there are more stringent State standards
include: benzene; carbon tetrachloride; chlorobenzenej 1,2-
dibromoethane; 1,2-dichloroethane (1,2-DCA); 1,1-dichloroethene
(l,l-DCE); cis-1,2-DCE; trans-1,2-DCE; vinyl chloride; and
xylenes. There are also some chemicals where State MCLs exist
but there are no Federal KCLs. EPA has determined that these
state MCLs are relevant and appropriate for the treated water
prior to discharge or delivery to the water purveyor. VOCs for
which there are no Federal MCLs but for which State MCLs exist
are: 1,1-DCA; trichloroflouromethane (Freon 11); and 1,1,2-
trichloro-1,2,2-triflouroethane (Freon 113). The Federal and
State Primary KCLs for these compounds are listed in Table ROD-1.
Water served as drinking water is required to meet KCLs at
the tap, not MCLGs. However, EPA does retain the authority to
require changes in the remedy if necessary to protect human
health and the environment, including changes to previously
selected ARARs. See, 40 CFR Sections 300.430(f) (1) (ii) (B) (1) and
300.430(f) (5) (iii) (C). If EPA receives new information indicating
the remedy is not protective of public health and the
environment, EPA would review the remedy and make any changes
necessary to ensure protectiveness.
10.2
Location-Speci~ic ARARs
No location-specific ARARs were identified for the Baldwin
Park ou.
10.3
Action-speci~ic ARARs
10.3.1
Clean Air Act, 42 D.S.C. section 7401 et seq.
Rules and Regulations of the South Coast Air Oualitv
Manaqement District'
The Baldwin Park OU remedy may include air stripping,
triggering action-specific ARARs with respect to air quality.
The Clean Air Act requlates air emissions to protect human
health and the environment, 'and is the enabling statute for air
quality programs and standards. The substantive requirements of
proqrams provided under the Clean Air Act are implemented
primarily through Air POllution Control Districts. The South
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Baldwin Park ROD
,
.coast Air Quality Management District (SCAQMD) regulates air
quality in the San Gabriel Valley.
The SCAQMD has adopted rules that limit air emissions of
identified toxics and contaminants. The SCAQMD Regulation XIV,
comprising Rule 1401, on new source review of carcinogenic air
contaminants, is applicable for the Baldwin Park QU. SCAQMD Rule
1401 requires that best available control technology (BACT) be
employed for new stationary operating equipment, so the
cumulative carcinogenic impact from air toxics does not exceed
the maximum individual cancer risk limit of ten in one million (1
x 10-5). EPA has determined that Rule 1401 is applicable for the
Baldwin Park QU because compounds such as PCE and TCE are present
in groundwater, and release of these compounds to the atmosphere
exceeding SCAQMD requirements unless controls are implemented.
The substantive portions of SCAQMD Regulation XIII,
comprising Rules 1301 through 1313, on new source review are also
ARARs for the Baldwin Park QU.
The SCAQMD also has rules to limit the visible emissions
from a point source (Rule 401), to prohibit discharge of material
that is odorous or causes injury, nuisance or annoyance to the
public (Rule 402), and to limit downwind particulate.
concentrations (Rule 403). EPA has determined that these rules
are also ARARs for the Baldwin Park OU interim remedy.
10.3.2 Water Quality standards for Discharges of
Treated Water to Surface Waters or Land
state standards
For any discharge to land, including recharge at a spreading
basin, or discharge to surface water, that occurs on-site, the
discharged water must meet all action-specific ARARs for such
discharge. The ARAR applicable to the discharged water is:
.
The Los Angeles Regional Water Quality Control Board's
Water Quality Control Plan for the Los Angeles River
Basin (the "Basin Plan"), which incorporates state
Water Resources Control Board Resolution No. 68-16,
"statement of POlicy with Respect to Maintaining High
Quality of Waters in California." Resolution No. 68-16
requires maintenance of existing State water quality
unless it is demonstrated that a change will benefit
the people of California, will not unreasonably affect
) present or potential uses, and will not result in water
quality less than that prescribed by other State
policies.
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Baldwin Park ROD
state Standards - Discharaes to Land
In order to comply with the Basin Plan, any treated
groundwater that is discharged to land will be treated to
concentrations below Federal MCLs or State MCLs for VOCs,
whichever is more stringent. In addition, any nitrate.
concentrations in the water to be recharged will have to be
similar to or lower than the levels of these substances in the
portion of the aquifer where the recharge will occur. The
quality, quantity, and duration of the discharge will be
considered with respect to the existing water quality.
"
state Standards - Discharaes to Surface Water
CERCLA section 104lb) Activities
During the time period of RD/RA activities at the Baldwin
Park OU, additional CERCLA section 104(b) activities will be
taking place. During these additional CERCLA section 104(b)
activities, EPA anticipates that there may be temporary
discharges of treated water to the San Gabriel River and its
tributaries (collectively the San Gabriel River)., The ARAR for
any treated water that is generated and discharged to the San
Gabriel River as part of a CERCLA section 104(b) activity would
be the NPDES program, which is implemented by the Regional Board.
In establishing effluent limitations for such discharges, the
Regional Board considers the Basin Plan, which incorporates
Resolution 68-16, and the best available technology economically
achievable (BAT). See. Cal. Water Code section 13263.
Since the Regional Board did not identify specific
substantive discharge requirements or technology standards for
discharges resulting from CERCLA section 104(b) activities, EPA
has reviewed the Basin Plan and considered BAT and has made
certain determinations for the discharge of water generated by
CERCLA section l04(b) activities to the San Gabriel River. In
order to comply with this ARAR, any treated groundwater that
would be discharged pursuant to CERCLA section 104(b) activities
to the San Gabriel River would be treated to meet Federal MCLs or
State MCLs for VOCs, whichever is more stringent.
The treated water may also contain nitrate. The Basin Plan
states that the level of nitrate shall not exceed 36 mg/l (as
N03) in water designated for use as domestic or municipal supply.
According to the Basin Plan, the San Gabriel River is designated
for municipal or domestic~water supply. Therefore, 36 mg/l
nitrate would be an ARAR for CERCLA section 104(b) activities
resulting in discharges associated with the ou.
EPA has stated that "studies and investigations unde"rtaken
pursuant to CERCLA section 104(b), such as activities conducted
46
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Baldwin Park ROD
during RI/FS, are considered removal actions." (55 Fed. Reg.
8756) It is EPA's policy that removal actions "will comply with
ARARs to the extent practicable, considering the exigencies of
the circumstances." (55 Fed. Reg. 8756).
Some CERCLA section 104(b) activities that will occur during
the time of RD/RA are temporary high flow, high volume discharges
(e.g., discharges resulting from spinner logging/depth specific
sampling of water supply wells and aquifer testing). EPA has
considered BAT for these CERCLA section 104(b) activities. For
CERCLA section 104(b) activities that result in temporary high
flow, high volume discharges, EPA evaluated four options for
meeting the primary Federal and state MCLs for VOCs and nitrate:
(i) direct discharge to an existing drinking water distribution
system; (ii) on-site storage, then disposal at a RCRA-approved
hazardous waste facility; (iii) discharge into a sanitary sewer
for treatment at a wastewater treatment plant; and (iv) on-site
treatment, then discharge into flood control channels.
For reasons similar to those faced and addressed during
previous spinner logging/depth specific sampling, EPA reached the
conclusion that compliance with ARARs was not practicable
considering the exigencies of the' circumstances for CERCLA 104(b)
activities resulting in temporary high flow, high volume
discharges of water. EPA has determined that for CERCLA 104(b)
activities not resulting in temporary high flow, high volume,
discharges of water compliance with ARARs ie practicable
considering the exigencies of the circumstances.
state standards - Discharae to surface Water
RD/RA Activities
RD/RA activities may also include the discharge of treated
water to surface waters. Unlike the CERCLA section 104(b)
activities, the RD/RA activities shall be undertaken in
compliance with ARARs unless a waiver is attained. Because no
ARAR waivers are contemplated for the RD/RA for the Baldwin Park
OU, all RD/RA activities shall be undertaken in compliance with
ARARs.
As noted above, the ARAR for any treated water that is
discharged to surface waters is the NPDES Program which is
implemented by the Regional Board. In establishing effluent
limitations for such discharges, the Regional Board considers the
Basin plan, which incorporates Resolution 68-16, the Inland
Surface Water Plan and Temperature Plan for Surface Waters, and
the best available technology economically achievable (BAT).
See. Cal. Water Code section 13263.
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Baldwin Park ROD
Since the Regional Board did not identify specific
substantive discharge requirements or technology standards for
such discharges, EPA has reviewed the Basin Plan (with related
documents) and considered BAT and has made certain determinations
for the RD/RA discharges to 'surface waters. In order to comply
with this ARAR, any groundwater that will be discharged to
surface waters on-site must be treated to meet primary Federal
MCLs or State MCLs for VOCs, whichever is more stringent.
The treated water will also contain nitrate. The Basin Plan
states that the level of nitrate shall not exceed 36 mg/l in
water designated for use as domestic or municipal supply.
According to the Basin Plan, the San Gabriel River is designated
for municipal or domestic water supply. Therefore, the 36 mg/l
is an ARAR for the RD/RA discharges associated with the ou.
10.3.3
California Hazardous Waste Control Act
RCRA, passed by Congress in 1976 and amended by the
Hazardous and Solid Waste Amendments of 1984, contains several
provisions that are ARARs for the Baldwin Park ou. The State of
California has been authorized to enforce its own hazardous waste
regulations (California Hazardous Waste Control Act) in lieu of
the Federal RCRA Program administered by the EPA. Therefore,
State regulations in the California Code of Regulations (CCR),
Title 22, Division 4.5, Environmental Health Standards for the
management of Hazardous Wastes (hereinafter the State HWCA
Regulations), are now cited as ARARs instead of the Federal RCRA
Regulations. state regulations under Federally authorized
programs are considered Federal requirements, i.e., Federal
ARARs.
The contaminated groundwater is not a listed RCRA waste.
However, the contaminants are sufficiently similar to RCRA wastes
that EPA has determined that portions of the State's HWCA
Regulations are relevant and appropriate.
An air stripper or GAC contactor would qualify as a RCRA
miscellaneous unit if the contaminated water constitutes RCRA
hazardous waste. EPA has determined that the substantive
requirements for miscellaneous units set forth in sections
66264.601 -.603 and related substantive closure requirements set
forth in 66264.111-.115 are relevant and appropriate for the air
stripper or GAC contactor. The miscellaneous unit and related
closure requirements are relevant and appropriate because the
water is similar to RCRA hazardous waste, the air stripper or GAC
contactor appear to qualify as a miscellaneous unit, and the air
stripper or GAC contactor should be designed, operated,
maintained and closed in a manner that will ensure the protection
of human health or the environment.
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Baldwin Park ROD
The land disposal restrictions (LDR), 22 CCR Section 66268
are relevant and appropriate to discharges of contaminated or
treated groundwater to land, including the discharge of treated
water to spreading basins. The remedial alternatives presented
do not include land disposal of untreated groundwater. Because
of the uncertainty in the levels of contamination and volumes of
water to be derived from monitoring and extraction wells at this
site, these waters must be treated to meet Federal and State
Primary MCLs for VOCs, whichever is more stringent, prior to
discharge to land. By meeting the Federal and State MCLs for
VOCs before discharge, the remedy will satisfy the RCRA LDRs.
The container storage requirements in 22 CCR Sections
66264.170 -.178 are relevant and appropriate for the storage of
contaminated groundwater over 90 days.
On-site storage or disposal of the spent carbon from the
treatment system for more than ninety (90) days could trigger the
State HWCA requirements for storage and disposal if the spent
carbon contains sufficient quantities of hazardous constituents
that cause the spent carbon to be classified as a characteristic
hazardous waste. If the spent carbon is determined to be a
hazardous wast~ under HWCA (Sections 66261 and 66262), the
requirements for handling such waste set forth in Sections 66262
and 66268 are applicable.
10.4
Additional Hatters
10.4.1
Calirornia water. Well standards
Substantive standards for construction of public water
supply wells have been published by the State as the California
Water Well Standards. While these standards have not been
specifically promulgated as an enforceable regulation and are
therefore not ARARs, all groundwater facilities designed, located
and constructed to produce drinking water must be constructed in
accordance with these standards. Since the remedy involves
delivery of the treated water to the public supply system, EPA
has determined that the action shall comply with substantive
Water Well Standards for construction of water supply wells, such
as sealing the upper annular space to prevent surface
contaminants from entering the water supply. Wells constructed
solely for treatment and reinjection with no delivery to the
public supply system would not be subject to these water well
construction standards.
10.4.2
OSHA Requirements
Requirements of nonenvironmental laws, such as California
OSHA regulations (8 CCR 5192) are not considered as ARARs and all
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Baldwin Park ROD
such requirements applicable at the time of the activity would
have to be satisfied.
11.
THE SBLBCTED REKEDY
The remedial objectives of the Baldwin Park OU are to
prevent future increases in, and begin to reduce, concentrations
of trichloroethene, tetrachloroethene, carbon tetrachloride, and
other VOCs in groundwater in the Baldwin Park area (hereafter
referred to as contaminants or contaminated groundwater) by
limiting further migration of contaminated groundwater into clean
and less contaminated areas or depths that would benefit most
from additional protection, and by removing contaminants from the
aquifer.
An additional objective of this remedy is to collect and
analyze groundwater quality, groundwater flow, and other data
during operation of the remedy to determine final in situ clean
up standards for the Baldwin Park area. Among the critical
decisions to be made are the extent to which, and the timeframe
in which, to address lower levels of contamination which may
remain in the aquifer after construction and initial operation of
the remedy. The final ROD will include in situ restoration
standards, which may differ for different portions of the OU
area, and may call for additional remedial actions in the area.
EPA expects that this interim remedy will provide the basis for
the final remedy for the Baldwin Park area.
At a minimum, EPA will formally evaluate the performance of
the remedy every five years.
EPA's selected remedy includes the extraction rates and
locations included in Alternative 1 and the option of
distributing treated water to local purveyors (as described in
Alternative 1) or to Metropolitan (as described in Alternatives 3
and 4). These components of the remedy are identical to the
Proposed Plan. The extraction, treatment, water use, and
monitoring components of the remedy are described further below.
Also noted are project details that may change during the
remedial design and construction processes (e.g., number and type
of monitoring wells).
11.1
ExtractioD LocatioDS
The selected remedy shall include extraction of contaminated
groundwater at the downgradient end of two broad areas of
50
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Baldwin Park ROD
contamination to limit contaminant migration and remove
contaminant mass. The two areas are:
. The Lower Area: the portion of the aquifer in the
vicinity of the San Bernardino Freeway (I-10), east of the
San Gabriel River and west of Azusa Avenue (Highway 39),
where concentrations of contaminants listed in Table ROD-1
or other VOCs are approximately 10 times Federal or state
drinking water standards, and where downgradient portions of
the aquifer are significantly less contaminated, between ND
(non-detectable) and two times drinking water standards.
Extraction wells shall be located to maximize protection of
downgradient water supply wells. The areas are described by
ranges of concentrations because actual concentrations vary
month to month and year to year. Approximate boundaries of
this area are shown in Figure ROD-10 as the Lower Area.
. The Opper Area: the portion of the aquifer north of Arrow
Highway, immediately east of the Santa Fe Dam, containing a
significant mass of non-aqueous phase contamination or other
known or suspected surface or subsurface sources of
contaminants listed in Table ROD-lor other VOCs that are
acting as continuing sources of dissolved-phase groundwater
contamination. Available data indicate the presence of
sources of contamination upgradient of wells W10WOMW1,
V10VCMW1, VIOVCMW2, OSCOMW2-5, Aerojet MW3-4, and Wl1AZW-03
and -09. Concentrations of PCE or TCE at most of these
wells have exceeded 200 times drinking water standards. If
additional investigation work indicates the presence of
additional sources, the pumping confiquration should be
modified to the extent feasible to capture the additional
sources. Approximate boundaries of this area are shown in
Figure ROD-IO as the Upper Area.
EPA's analyses indicate that its remedial objectives can be
efficiently met by extracting contaminated groundwater from the
upper 400 - 500 feet of the. aquifer; from three wells in the
lower area and two wells in the upper area. Fiqure ROD-13 shows
approximate extraction locations as well locations 13, 10, 5, 6,
and 4. EPA recognizes that other pumping configurations,
increasing the number of extraction wells but reducing rates, or
decreasing the number of wells but increasing rates, may be
equally efficient. If supplemental analyses demonstrate that
alternative pumping configurations are equally efficient, they
may be substituted for EPA's recommended locations. The phrase
pumping configuration refers to precise extraction locations and
rates within the upper and lower areas of contamination.
EPA believes that it is premature to select the number of
wells or make a final decision on extraction locations at this
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Baldwin Park ROD
time. Final decisions on extraction locations, and
decisions on whether existing wells in the vicinity
selected locations will satisfy these requirements,
during remedial design.
final
of EPA's
will be made
11.2
Extraction Rates
The selected remedy shall include extraction of contaminated
groundwater at locations and rates sufficient to capture or
contain particles (representing contaminants dissolved in the
groundwater) moving from the upper and lower areas of
contamination. Extraction shall result in capture zones that
include the two subareas during all anticipated recharge
conditions. 1 The capture zones shall also include all
significant depth intervals where contaminant concentrations
exceed MCLs for contaminants listed in Table ROD-lor for other
VOCs. The extraction system may be designed to allow
contaminated groundwater to temporarily move past the extraction
locations during periods of high recharge at the Santa Fe
Spreading Grounds or elsewhere if the system can recapture,
during subsequent periods of lower recharge, any contaminated
groundwater that has moved beyond the extraction locations.
EPA's analyses indicate that its remedial objectives will be
efficiently met by extracting 19,000 qpm of contaminated
groundwater. EPA's analyses indicate that approximately 10,500
qpm of groundwater must be extracted more or less continuously in
the lower area; approximately 8,500 qpm of groundwater must be
extracted in the upper area. EPA's analyses indicate that these
rates' will intercept and captUre contaminated groundwater during
recharge and pumping conditions similar to those occurring.
between October '1977 and June 1990. During recharge conditions
similar to the exceptionally rainy spring of 1983, contaminated
groundwater may temporarily move beyond the extraction locations,
but, in particle tracking simulations, appears to be subsequently
recaptured.
If supplemental data and analyses justify modifications to
EPA assumptions about the extent of contamination, hydraulic
conductivity, regional flow gradients (which vary significantly
depending on the amount and timing of precipitation and
artificial recharge) or other factors that influence groundwater
flow and contaminant transport, EPA will consider revised rates.
EPA will also consider seasonally-variable rates that meet the
requirements of this section.
lThe amount and timing of precipitation and artificial
recharge vary month to month and year to year, as do the
resulting regional flow gradients.
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Baldwin Park ROD
~
Extraction shall occur as continuously as feasible.
Feasibility may be temporarily limited by insufficient capacity
to accept or distribute treated water by the recipient of the
treated water, resulting from low customer demand (e.g., during
rainy winter days) or competition for use of recharge areas.
11.3
Treatment
The extracted contaminated groundwater shall be treated to
remove contaminants listed in Table ROD-1 and other VOCs by
either or both of two proven treatment technologies: liquid-
phase granular activated carbon (LGAC) filtration and air.
stripping. The treated groundwater exiting the treatment
facilities shall meet Federal and state primary MCLs for
contaminants listed in Table ROD-1 and for other VOCs. In
addition, the treated groundwater shall meet proposed Federal
secondary MCLs for ethylbenzene and toluene. If air stripping is
used, offgas controls (e.g., vapor phase granular activated
carbon) shall be used to reduce air emissions in accordance with
ARARs promulgated by the South Coast Air Quality Management
District. EPA believes that if properly designed, these proven
treatment technologies (LGAC and air stripping) are equally
effective at removing VOCs for most mixes of contaminants. One
technology may be used at one location and the other at a
different location, or both technologies may be used in a
trea~men~ train at a single location.
Existing treatment facilities (e.g., planned treatment at
Valley County Water District's Big Dalton well) may be
incorporated into the remedy if, during remedial design,
agreements can be reached for their use and they meet other
requirements of this Record of Decision. The San Gabriel Basin
Water Quality Authority (the project's sponsor) expects.
construction to be completed in late 1994. One or more new
treatment facilities shall be constructed to provide the
remaining treatment capacity.
An Advanced Oxidation Process may be used for pretreatment
in combination with LGAC treatment if proven to be effective and
economical during design phase testing and analysis. The VOC
treatment technology or combination of technologies which best
meet the objectives of the remedy for the Baldwin Park OU will be
determined during the remedial design phase, when more detailed
and up to date information will be available to assess
effectiveness and cost. Final decisions on the locations of the
treatment facilities will also be made during remedial design.
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Baldwin Park ROD
11.4
Water Distribution and Use
The selected remedy shall include pipelines, pump stations,
and other conveyance facilities needed to transport the treated
. groundwater to one or more delivery locations. If treated water
is supplied to one or more water purveyors, the delivery location
or locations shall be at a pipeline, storage reservoir, or other
portion of the purveyors' distribution systems. The purveyors
would be responsible for distributing the water to their
residential and business customers through their existing
distribution systems. The selected remedy may also include
improvements to the recipient's existing distribution system if
the improvements are needed to allow the recipient to accept
treated groundwater at extraction rates required by Section 11.2
of this ROD.
EPA's preference is that treated water be delivered to water
purveyors. The advantages of supplying water to purveyors,
rather than recharge, are: reduced pumping costs; the lower risk
of inadequate distribution during and after rainy months; and
purveyors downgradient of Subarea 3 could reduce extraction at
existing water supply wells located outside of the highly
contaminated areas that may be pulling contaminated groundwater
into less contaminated areas or depths. .
Initial discussions with water purveyors indicate that
purveyors in best position to accept treated water are San
Gabriel Valley Water Company, Suburban Water Systems, Covina .
Irrigating Company (CIC), the cities of Azusa and Glendora, and
Metropolitan. CIC and Metropolitan are wholesalers of water that
would in turn supply retail water companies; the other four
companies supply businesses and residents directly. CIC's
potential customers include the City of Covina, the City of West
Covina, Suburban Water Systems, and others. Metropolitan's
customers include a large number of water agencies both within
and outside of the San Gabriel Valley.
EPA would actively support supplying treated water to
Metropolitan if it would decrease the cost of the project and
reduce institutional barriers. Supplying water to Metropolitan
would provide water users throughout Southern California with a
new source of water during peak demand periods, and probably
benefit from Metropolitan expertise in building and operating
large water supply projects. If Metropolitan receives treated
water, they would probably playa significant role in the design,
construction, and/or operation of the remedy to ensure that the
project meets their water supply requirements. Metropolitan has
reportedly budgeted $25 million for a conjunctive use project in
the San Gabriel Basin.
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Baldwin Park ROD
EPA believes that it is premature to specify anyone or a
combination of recipients of the treated water. The final
decision will be made after completion of the ROD depending on
the outcome of additional negotiations with potential recipients
of the treated water to identify recipients that can be supplied
at least cost with the fewest institutional obstacles. .
Arrangements must be made with recipients to address EPA and
purveyor financial obligations (see footnote, page 60);
responsibility for design, construction, operation, and
. maintenance; timing and dependability of the supplied water;
water rights issues; and other issues.
The potential for funding through the Reclamation Projects
Authorization and Adjustment Act of ~992 (P.L. ~02-575) will also
be considered. The Act authorizes Federal funding of up to 25%
for "the design, planning and construction of a conjunctive-use
facility designed to improve the water quality in the San Gabriel
groundwater basin and allow the utilization of the basin as a
water storage facility." .
If water purveyors can accept water for most, but not all,
of the year, excess water shall be delivered to a location or
locations from which it can flow into spreading basins and flood
control channels operated by the Los Angeles County Department of
Public Works for recharge into the aquifer. If agreements cannot
be reached with San Gabriel Basin water purveyors, water shall be
recharged year-round. If recharge is necessary, recharge
location(s) will be determined during remedial design. If
treated water is recharged, the state anti-degradation
requirement is an additional ARAR that may influence the level of
treatment. If treated water is recharged, the remedy may include
activities to maintain or improve the infiltration capacity of
the spreading grounds, or to acquire or develop new recharge
facilities. If treated water is discharged to a surface water,
the discharge shall meet NPDES requirements.
11.5
Monitoring program
The remedy shall include the installation and sampling of
groundwater monitoring wells, the sampling of existing monitoring
wells, measurement of groundwater elevations at monitoring and
production wells, and the measurement of other aquifer properties
to:
.
verify or refine the boundaries of upper and lower areas to
help determine final pumping configurations. -
Verify or refine the efficiency of EPA'S recommended pumping
configurations.
.
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Baldwin Park ROD
.
Verify or revise contaminant influent concentration
estimates that will be used in the design of the au
treatment facilities.
.
Provide an early warning network so that changes in the
groundwater flow regime or contaminant concentrations that
may require modifications in extraction rates, well
locations, or treatment methods are identified in time to
institute the necessary facility and operational changes.
Evaluate the presence and approximate location of non-
aqueous phase contamination or other subsurface sources of
groundwater contamination to supplement site assessments of
individual facilities or properties.
.
.
Evaluate the effectiveness of the remedy in satisfying the
remedial objectives of limiting the vertical and lateral
migration of contaminated groundwater and removing
contaminant mass in and downgradient of the upper and lower
areas. The evaluation may include plotting and
interpretation of temporal trends in water quality, analysis
of changes in groundwater flow induced by the extraction
wells, and computer simulations of groundwater flow,
including the estimation and evaluation of caprure zones.
Help determine the need for additional remedial actions in
the Baldwin Park area and the nature of the final remedy
(e.g., the extent to which and timeframe in which aquifer
restoration is feasible). satisfying this objective may
include lab or field testing to estimate parameters that
govern sorption, biogical degradation, or other processes
that affect contaminant transport in the aquifer (e.g.,
concentrations of total organic carbon, dissolved oxygen or
other gases, nutrients, indigenous microbial populations).
.
satisfying one or more of the monitoring objectives may also
require ancillary data, including information on pumping and
recharge rates and volumes, lithology, measurements of hydraulic
conductivity, and measurements of other aquifer properties.
These data are needed to allow for accurate determinations of the
direction and magnitude of horizontal and vertical flow in the
vicinity of the remedial action; discern significant temporal
variation in flow gradients; and simulate the effects of recharge
and pumping on groundwater flow. These data are also needed to
refine the understanding of the geology in the Baldwin Park area,
including the occurrence and extent of highly permeable or fine-
grained deposits which could affect groundwater flow paths.
Groundwater monitoring shall begin during the time of
remedial design to provide data necessary to complete the final
56
-------
Baldwin Park ROD
\
design and to establish pre-implementation, baseline conditions.
Initially, collection and analysis of groundwater quality samples
shall occur no less frequently than bimonthly for VOCs and
quarterly for other parameters (except for less frequent depth-
specific sampling of extraction wells). Initially, measurement
of water levels shall occur no less frequently than monthly.
Monitoring frequency may decrease if EPA determines that
conditions warrant such a decrease. Frequency may vary by
parameter. Water quality parameters to be quantified will
include VOCs, semivolatile organic compounds, general minerals,
nitrate (N03), radon, and physical parameters required for
treatment purposes (e.g., color, turbidity, and odor).
EPA's preliminary recommendations, which rely as much as
possible on existing wells, are to include the following numbers
and types of wells in the monitoring program:
.
Water quality and water level data at twenty-four
existing inactive and active production wells,
including two existing wells that may be used as
extraction wells. Some of these wells are currently
sampled as part of the Title 22 monitoring program, but
it may be necessary to increase the number and
frequency of parameters analyzed;
.
Water quality and water level data at five existing
standard monitoring wells and one existing MP
monitoring well, which include the Baldwin Park Key
Well and the U.S. Environmental Protection Agency's
deep multiple port (MP) monitoring well (MWS-l). Also,
continued sampling of selected facility site assessment
wells. Although most site assessment wells penetrate a
relatively small portion of the saturated zone, their
location upgradient of likely extraction well clusters
make selected wells favorable monitoring points for
assessing future water quality at the clusters;
.
Water quality and water level data at two new MP
monitoring wells (or equivalent.conventional well
clusters);
Water quality and water level data at two new two-well
monitoring well clusters (These wells were added in
response to public comments on the FS and Proposed Plan
- See Part III of this ROD.);
.
.
Water quality and water level data at eight new three-
well monitoring well clusters (One three-well cluster
was added in response to public comments on the FS and
Proposed Plan - see Part III of this ROD.);
57
-------
Baldwin Park ROD
.
.
Three new piezometer clusters, each containing three
wells (one set near each extraction well in Subarea 3)
to provide more detailed data on water level changes
near the extraction wells and evaluate the effective
capture zone of the extraction wells; and
Wellhead water quality data, depth-specific water
quality data, spinner logging, and water level data at
or adjacent to the five new extraction wells2 - to
evaluate the effectiveness of contaminant removal.
.
Locations and construction information on existing
production and monitoring wells are shown in Table ROD-7 and
Figure ROD-14. The purpose and location of the new wells are
described in Table ROD-8 and Figure ROD-14. The depth and number
of sampling zones are based, in part, on estimates of the
vertical extent of groundwater contamination.
Additional monitoring wells or piezometers shall be
installed to replace existing wells if significant vertical
gradients complicate the interpretation of water level data
collected from production wells; or if existing wells currently
planned for inclusion in the program are abandoned.
Locations shown in Figure ROD-14 may be revised, or
locations added or eliminated, if extraction locations change, if
EPA's interpretation of the lateral or vertical extent of
contamination changes, if influent concentrations to the
treatment facilities vary unexpectedly (requiring installing
additional wells to evaluate the magnitude and cause of the
observed deviation); if source investigations identify previously
unknown sources requiring characterization; or if individual
facility or property owners install new wells that should be
included in the monitoring program.
The remedy shall also include sampling of influent and
effluent water quality, into and exiting the treatment
facilities, and other collection and analysis of interpretive
data needed to meet the monitoring objectives outlined in this
section. EPA also recommends one-time geophysical logging of
new-well pilot holes and aquifer testing at new wells to provide
information on aquifer parameters and characteristics.
2 A cost-effective means of obtaining this data is to
install a permanent access pipe in at least one well at each
extraction well cluster. This allows for spinner logging and
collection of depth-specific water samples during operation.
58
-------
Baldwin Park ROD
"
11.6
Project Costs
The following two tables present estimates of the capital
costs, and operation and maintenance costs, for the remedy. The
estimated construction cost subtotal, which includes the
extraction, treatment, conveyance, and monitoring hardware, is
$25 million3. An additional $22 million is added to account for
engineering design, construction services, legal and
administrative costs, contingencies, and land acquisition. The
majority of the estimated construction costs of the remedy (more
than 75%) are associated with the treatment and conveyance
components. The majority of the estimated operating costs of the
remedy is for the purchase of electricity and carbon.
3 This estimate does not include the costs of the three
monitoring well clusters added to the remedy in response to
public comments. The estimated capital cost of the three wells
is less than $0.4 million; the estimated operating cost is less
than $0.1 million.
59
-------
Baldwin Park ROD
. . .' .... . .
=~;~~~~=:ijl~;j~:~;~t~~il~~,. ....... ",.' ........ . ....
. ". .....
"'"'' ~~~~.;~:r8.
Extraction System: New Groundwater 4. 13
Extraction Wells and Monitoring Wells
Treatment System for VOC Removal 10.7
Conveyance System: Pipelines, Pump 8.5
stations, and Other Conveyance System
Hardware
Other Construction Costs 1.6
"Bid and Scope" Contingencies . 8.8
(estimated at 35% of extraction,
treatment, . conveyance, and other
construction costs)
Construction Services (estimated at 1.0% 3.4
of extraction, treatment, conveyance,
other construction, and contingency
costs)
Land Acquisition 1..5
Engineering Design, Legal, and 8.5
Administrative Costs (estimated at 22%
of extraction, treatment, conveyance,
other construction, contingency, and
land acquisition costs)
TOTAL CAPITAL COSTS: 47.13
60
-------
Baldwin Park ROD
..
Ji~'~~Sf(.tl'II[i:~~t1jl':~~.
.. ......."" . .....":...."" .....:I~~~i~~~i
Electrical Costs for Extraction Wells
Electrical Costs for Pump Stations
Electrical Costs for Treatment System
1.5
0.7
Carbon Replacement
Other Treatment Plant Costs
Monitoring Well sampling
Maintenance (estimated as 2% of capital
cost estimate)
Purveyor Reimbursement Costs
(estimated at $50/acre-foot)4
0.4
0.9
0.8
0.73
0.7
- 1.5
TOTAL OPERATION AND MAINTENANCE COSTS:
4.23
The net present value of the remedy, assuming 30 years of
operation, a discount rate of 7%, and purveyor reimbursement of
$50/acre-foot, is $99.7 million3.
Three major assumptions made in developing the cost estimates are
described below.
Availability of Existing Wells: The cost estimate assumes
that two inactive existing water supply wells in the au
area, owned by local purveyors, can. be used as part of the
remedy. If additional existing wells are used, costs would
decrease slightly. If, instead, new wells must be
constructed, capital costs would increase slightly.
4 EPA expects that water purveyors that accepted and
distributed treated water would contribute to project operating
costs to offset any .savings resulting from not using other
sources of water. These avoided costs range from $30 per acre-
foot for purveyors that pump clean groundwater to more than $300
per acre-foot for purchases of imported water. One acre-foot
equals 325,829 gallons.
61
-------
Baldwin Park ROD
"
Bstimated contaminant concentrations: If actual contaminant
concentrations differ from the estimated concentrations, or
if new contaminants are detected, operating costs will
change. If the-deviations are large, capital modifications
may be necessary. The largest impact would be if increasing
nitrate (NO) concentrations in the groundwater make.
installation of NO) treatment necessary. The cost of N03
treatment is not included because of limitations in EPA's
ability to predict the timing and magnitude of future
increases in NO) concentration in groundwater, and
uncertainty about NO) treatment requirements of the
recipients of the treated water.
Availability of Existing Treatment Facilities: The cost
estimate assumes that new treatment facilities, with a
capacity of 19,000 gpm, must be built. One or more planned
or existing treatment facilities may be available and offset
the need for new treatment capacity, reducing the capital
costs of new treatment facilities.
1.2.
STATUTORY DETBRHINATIONS
As required under section 121 of CERCLA, the selected
interim remedy is protective of human health and the environment,
complies with Federal and State requirements that are legally
applicable or relevant and appropriate to the interim remedial
action, and is cost effective. The selected remedy utilizes
permanent solutions and alternative treatment technologies ~o the
maximum extent practicable and satisfies the statutory preference
for remedies that employ treatment to reduce toxicity, mobility,
and volume as a principal element.
12.1
Protection of Human Health and the Environment
The selected remedy will protect human health and the
environment by limiting further downgradient and vertical
migration of contaminated groundwater and removing significant
contaminant mass from the aquifer. The remedy will reduce
potential risks by decreasing the likelihood and magnitude of
future exposure to contaminated groundwater. contaminant
concentrations in the groundwater in the areas to be addressed by
the remedy are currently tens to ,thousands of times acceptable
levels. The selected treatment technologies are technically.
feasible and proven effective at meeting ARARs for VOCs in the
treated groundwater and air. Implementation of the remedy will
not pose unacceptable short-term risks. In addition, no adverse
cross-media impacts are expected.
62
-------
Baldwin Park ROD
12.2
compliance with ARARs
The selected remedy shall comply with all ARARs, which are
listed in Section 10 of this ROD. No ARARs waivers are expected
to be needed. Because the selected remedy is an interim remedy,
it may not achieve final cleanup levels for the groundwater and
no chemical-specific ARARs for aquifer cleanup are included. In
Alternatives 1-4, chemical-specific ARARs for the treated water
from the VOC treatment plant are Federal MCLs and more stringent
State MCLs for VOCs.
12.3 cost-Effectiveness and utilization of Permanent
solutions and Alternative Treatment Technologies to the Maximum
Extent Practicable
EPA believes that the selected remedy is cost-effective and
utilizes permanent solutions and treatment technologies to the
maximum extent practicable for an interim remedy. The selected
remedy will reduce the mobility of the contaminants in two
critical portions of the aquifer and will permanently reduce the
volume of contamination by limiting the spread of the
contamination and removing contaminant mass. The likelihood that
the remedy will operate for as many years as needed will be
increased if, as recommended, the treated water becomes a
dependable source of potable water. If the treated groundwater
becomes a dependable source of potable water, it would provide an
incentive for recipients of the treated water to support the
project's continued operation. The remedy calls for the
construction of conveyance systems and negotiation of agreements
needed to supply treated water to water purveyors for
distribution to their customers.
Extraction of contaminated groundwater in a third portion of
the aquifer would increase the effectiveness of the remedy and
reduce the mobility and volume of contaminants by further
limiting migration within the area of contamination and removing
additional contaminant mass~ Costs would increase, however, by
approximately 50%. (The area of contamination addressed in the
Baldwin Park OU is large, making it infeasible to limit migration
throughout the entire area of contamination. Any realistic
remedy must select the area or areas. of contamination that would
benefit most from additional protection.) EPA does not believe
that the incremental benefits of groundwater extraction in a
third subarea warrant the additional costs at present, given that
the selected remedy is an interim remedy. Adding a third area
may also decrease the implementability of the remedy due to the
need to distribute 50% more treated water, possibly delaying
implementation of the project. Implementability issues include
the need to reach agreements with additional parties that would
receive treated water from an OU, resolution 'of water rights
63
-------
Baldwin Park ROD
.
issues, and acquisition of additional property and/or easements
for 'the construction of extraction wells, treatment facilities,
and conveyance facilities.
EPA evaluated comments from the state, which concurred with
EPA's proposed remedy, and comments from the community, which are
mixed in their recommendations. The community offered comments
on a variety of topics, including the size of the remedy and the
disposition of the treated water. Some commenters recommended a
larger remedy; others recommended a smaller remedy. The more
than 400 public comments received during the public comment
period, along with EPA's responses, are presented in Part III of
this ROD.
The most significant factors in the selection of the remedy
are the interim status of the remedy, uncertainty about the cost-
effectiveness of the alternatives not selected, and
implementability. The Superfund evaluation criteria that were
the most important in selecting the remedy were long-term
effectiveness; reduction of toxicity, mobility, or volume;
implementability; and cost.
12.4
Preference for Treatment as a principal Element
This interim remedy will use treatment (air stripping and/or
LGAC) to address the principal threat posed by the site:
exposure to contaminated groundwater. Future actions may be
needed, however, to completely reduce the threat to acceptable
levels.
Because this remedy will result in hazardous substances
remaining on-site above health-based levels, EPA shall conduct a
review, pursuant to CERCLA Section 121, 42 U.S.C. section 9621,
at least once every five years after commencement of remedial
action to ensure that the remedy continues to provide adequate
protection of human health and the environment.
13.
DOCtJJIDTATION OF SIGNIFICANT CBAHGES
The Proposed Plan was released for public comment in May
1993. The Proposed Plan called for groundwater extraction and
treatment in the upper and lower areas (as identified in
Alternative 1). The Proposed Plan differed from the description
of Alternative 1 in the FS in one aspect: it identified local
water purveyors and Metropolitan as potential recipients of the
treated water. EPA reviewed all written and verbal comments
submitted during the public comment period. Upon review of these
comments, it was determined that no significant changes to the
remedy, as it was originally identified in the Proposed Plan,
were necessary.
64
-------
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-------
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NOTE:
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LEGEND
--------
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;;;
g--- WELL 10 NUMBER
'"
a
J~ WELLHEAD TCE CONCENTRATION
..
8LANK CASING
2> PERFORATED CASING
DEPTH-SPECIFIC TCE
CONCEN TR A TlON
41
-- 100--
ESTIMA TED LINE OF EOUAL TCE
CONCENTRA TION (uq/I)
NO
~
1. SEE FIGURE 110,5 FOR CROSS SECTION LOCA liON
2. WELLS PROJECTED INTO CROSS SECTION
3. BASED ON DATA COLLECTED BETWEEN
JUNE 1989 ANO DECEM8ER 1991
4. TCE MCL = 5 ug/I
FIGURE ROD-9
POSSIBLE VERTICAL DISTRIBUTION OF TCE
RI AREA 5
BAt DWIN PARI< OPERABLE UNIT
SAIl GABRIR !jA~IN
-------
210
o
.
0.5
1
MILES
'Q
TCE
Concentrations
generally between g:
100 and 1,000 ppb '<
<
CJ)
::>
~
TCE Concentration
generally between
40 and 100 ppb or CTC
. between 5 and 20 ppb
Figure
ROD-10
. Approximate Extraction Well locations
-------
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BALDWIN PARK OPERABLE UNIT
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PARTICLE TRACKING RESULTS
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--. '11'1([ '''11111
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BALOIIN PARK OPERABLE UN11
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LEGEND
,,,
RAW WATER PIPELINE
@
TREATED WATER PIPELINE
PURVEYOR CONNI;CTION POINT
.E
.4 EXTRACTION WELL CLUSTER
. TP4 TREATMENT PLANT LOCATION
o 2500 5000
! I I
SCALE IN FEET
FIGURE ROD-I3
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GROUNOWATER MONITORING
PROGRAI/
8ALDWIN PARK O'ERABLE UNIT
S'" Gabrl.1 Bui",
-------
Table ROD-l Partial List of Contaminants Detected in Groundwater in the
Baldwin Park area
Contaminant
Trichloroethylene (TCE)
l,l-Dichloroethane (I, I-DCA)
I, I-Dichloroethene (1, I-DCE)
cis-I,2-Dichloroethene
trans-I,2-Dichloroethene
1,2-Dichloroethane (1,2-DCA)
Acetone
Methy lene Chloride
Vinyl Chloride
. Trichlorofluoromethane (TCFM)
T etrachloroethene (PCE)
Carbon Tetrachloride (CTC)
l,l,l-Trichloroethane (l,l,l-TCA)
Benzene
Toluene
Bromodichloromethane (BDCM)
Chloroform
Chlorobenzene
I, 1,1,2- Tetrachloroethane
1,2,3- Trichloropropane
Freon 113
1,2- Di bromoethane
-------
Table ROD-2 .
Chemicals of Potential Concern in Groundwater
Concentration~
(pg/l)
Maximum
#Detectl Aritlunetic Standard Upper 95th Contaminant
Chemical #Sampled' Mean Deviation Percentile LevelJ
1,1,1- Trichloroethane 6/28 2.1 4.6 3.9 200
1,1- Dichloroethane 7/28 0.7 0.5 0.8 5
1,l-Dichloroethene 8/28 3.5 9.5 7.1 6
l,2-Dichloroethane 11/28 2.0 3.1 3.2 0.5
Acetone 2/28 4.9 13.9 10.3 -
Benzene 2/28 0.5 0.06 0.5 1
Carbon Disulfide 2/28 0.6 0.2 0.6 -
Carbon Tetrachloride 1l/28 1.8 2.8 2.9 0.5
Chloroform 13/28 2.2 3.1 3.4 100
cis-l,2-Dichloroethene 8/20 6.7 15.7 14.0 6
Ethylbenzene 1/28 0.5 0.003 0.5 680
Methylene Chloride 1/28 0.5 0.02 0.5 5
T etrachloroethene , 21/28 12.7 30.5 24.6 5
Toluene 2/28 0.5 0.07 0.5 1000
trans-l,2-Dichloroethene 3/8 0.6 0.2 0.8 10
Trichloroethylene 22/28 55.1 107.8 96.9 5
Xylene 1/28 0.5 0.01 0.5 1750
'Duplicate samples are averaged before sununary statistics are calculated.
~ata taken from BPOU FS Includes all wells except VI0AMMW1.
3State or federal Maximum Contaminant Level (MCL), whichever is lower.
Note:
- Indicates no available MCL.
IOOIOCII.LAO
-------
Table ROD-3
I)ose-Respon.u Variables 'or Cbemicals 0' Concern
Systemic Toxicity CarcinognUc Potftl(y
(mg/kg/day) (mg/kg/day)"
Oral Inhalation
Oral Inhnlation Slope Wt'ight 0' Slope Weight 0'
Chemical Ol'JlaD Arrected Rm Suurce Rm Sonrce Tumor Site Factor Evidence' Snurce I'actor EvidnlCe' Source
I,I,I-Tricbloro.:lhane Liver 0.09 "EAST 0.3 "EAST .. .. D IRIS .- D IRIS
I,I-Dichloro.:lhane Liver 0.1 "EAST 0.1 "EAST Mammary, Liver -- C IRIS -- C "EAST
I,I-Dichloro.:lhene Liver 0.0009 EPA .. IRIS Kidney, Adrenal .. C EPA -- C EPA
1,2-Dichloroethane .. -- IRIS -- IRIS Stomach, 0.091 82 IRIS 0.091 82 IRIS
Mammary, Liver
Acetone Liver, Kidney 0.1 IRIS -- IRIS -- -- D IRIS .- D IRIS
Benzene -- -- IRIS -- IRIS Blood 0.029 A IRIS 0.029 A IRIS
Felal Toxicity/Malformation .
Carbon Disulfide 0.1 IRIS 0.003 HEAST -- -- -- IRIS -- -- IRIS
Carbon Tetrachloride Liver 0.0007 IRIS .. IRIS Liver 0.13 82 IRIS 0.13 82 IRIS
Chloroform Liver 0.01 IRIS -- IRIS Liver, Kidney 0.0061 82 IRIS 0.081 B2 IRIS
cis-I,2-Dichloro.:thene 8100d 0.01 HEAST -- IRIS -. -- D IRIS -- D IRIS
Elhylbenzene Liver, Kidney 0.1 IRIS 0.3 IRIS -. .. D IRIS -- D IRIS
Methylene Chloride Liver 0.06 IRIS 0.9 "EAST Lung, Liver 0.0075 82 IRIS 0.0016 82 IRIS
Tetrachloroethene Liver 0.01 IRIS -- IRIS Liver, Leukemia 0.051 82 "EAST 0.002 82 HEAST
Toluene CNS, Eyes, Nose, Liver, 0.2 IRIS 0.6 HEAST -- -- D IRIS -- D IRIS
Kidney
trans-I,2-Dichloroethene 8100d 0.02 IRIS -- IRIS -- -- -- IRIS -- -- IRIS
Trichloroethylene - 0.006 ECAO -- IRIS Lung, Liver 0.011 82 HEAST 0.017 82 HEAST
Xylene Liver, Nose, Throat, CNS, 2 IRIS 0.09 "EAST -- -- D IRIS -- D IRIS
Fetotoxicity
HEAST ... Health Effecll Alacllmcnt Summary Tablca, EPA, 1991h.
IRIS co Inlegraled Risle Informalion SYllem, EPA, I 992f.
EPA co I,I-Dichlorocthene is ev.lu.ted Iccording 10 I modified-RID approach: Group C carcinogcns which exhibit weak evidcncc of carcinogcnicity arc comparcd to the oral RID/IO, EPA, I 990f.
ECAO ... Environmenlal Crileril Ind Assellrnent Office, EPA, 1992e.
- = Informalion nol Ivailable.
CNS ... Cenlral Nervoul Syalem.
'Weight of Evidence Groupl: A il Human Clrcinogen; 8 ia Probable Human Clrcinogen (BI-limited evidence of carcinogenicity in humans, BZ-sufficient evidencc of carcinogenicity in animals wilh inadcquatc or
lacle of evidence in humanl); C is POllible Human Clrclnogen; D is Not CI,"ifiable al to Human Carcinogenicity.
DA file name
-------
Table ROD-4
Estimated Excess Lifetime Cancer Risk from
Domestic Use of Groundwater
Average Exposure Reasonable Maximum Exposure
Chemical Ingestion Inhalation Ingestion Inhalation
I , I , I-Trichloroethane -- -- -- --
I,I-Dichloroethane -- -- -- --
I,I-Dichloroethene -- -- -- --
I ,2-Dichloroethane 6 x 1007 6 X 10-7 3 X 10-6 3 X 10-6
Acetone -- -- -- --
Benzene 5 x 10-8 5xlO-8. 2 X 10-7 2 X 10-7
Carbon Disulfide -- -- -- --
Carbon Tetrachloride 8 x 10-7 8 X 10-7 4 X 10-6 4 X 10-6
Chlorofonn 5 x 10-8 6 X 1007 2 X 10-7 3 x 10-6
cis-I,2-Dichloroethene -- -- -- --
Ethylbenzene -- -- -- --
Methylene Chloride 1 ~ 10-8 3 X 10-9 4 X 10-8 9 X 10-9
Tetrachloroethene 2 x 10-6 9 X 10-8 1 X 10-5 6 X 10-7
Toluene -- -- -- --
trans-I,2-Dichloroethene -- -- -- --
Trichloroethylene 2 x 10-6 3 X 10-6 I X 10-5 2 X 10-5
Xylene -- -- -- --
Total Risk 6 x 10"' 6 x 10"' 4 x 10~ 3 X 1005
~
-
IOOIID83.LAO
-------
Table ROD-5
Estimated Noncaneer Hazard Quotients rrom
Domestic Use or Groundwater
Average Exposure Reasonable Maximum Exposure
Chemical Ingestion Inhalation Ingestion Inhalation
1,1, t -Trichloroethane 0.0006 0.0002 0.001 0.0004
I,I-Dichloroethane 0.0002 0.0002 0.0002 0.0002
1,l-Dichloroethene 0.1 0.1 0.2 0.2
1,2-Dichloroethane -- -- -- --
Acetone 0.001 0.001 0.003 0.003
Benzene -- -- -- --
Carbon Disulfide 0.0002 0.005 0.0002 0.005
Carbon Tetrachloride 0.07 0.07 0.1 0.1
Chloroform ~ 0.006 0.006 0.009 0.009
cis-I,2-Dichloroethene 0.02 0.02 0.04 0.04
Ethylbenzene 0.0001 0.00005 0.0001 0.00005
Methylene Chloride 0.0002 0.00002 0.0002 0.00002
Tetrachloroethene 0.03 0.03 0.07 0.07
Toluene 0.00007 0.00002 0.00007 0.00002
trans-I,2-Dichloroethene 0.0008 0.0008 0.001 0.001
Trichloroethylene 0.3 0.3 0.4 0.4
Xylene 0.000007 0.0002 0.000007 0.0002
Total Hazard Index 0.5 0.5 0.9 0.9
-
IOOIOCI4.LAO
-------
I Table ROD-6 " I
UacertaiDties Associated With Risk Estimatioas
UacertaiDty Factor Effects of UacertaiDty Commeat
I. Exposure AssessmeDt
Exposure assumptions May over- or underestimalC risle Assumptions regarding media inlalee,
population characlCristics (e.g., body
weight. life span, etc:.), and exposure
paacrna may not characlCrizc actual
exposures.
Conc:entratioll8 are assumed 10 be COnsl8nt May over- or underestimalC risk: Docs not account for environmental falC,
transport, or transfer, which may reduce
chemical concentration. Docs not
acccum for future degradation 10
pocentiaUy more IOxic chemicals (e.g.,
PCE and TCE 10 vinyl chloride).
Contaminaat loss during sampling May underestimalC risle May ulldcrestimalC VOCs present.
Estimating iahalation expoaure. for released May over- or undercstimalC rislc Several variables affect the degree of
VOC. from lap walCr expoaure, including walCr ICmperature,
etc:.
Exlent of sampling effort May over- or undercstimalC risk: Sampling may not accuralCly characlCrizc
the medium being evaluated.
Chemical analy.ia proc:cdurca May over- or undercstimalC rislc Systematic or random erron may occur
during chemical analysis.
Intake May underestimalC rislt Assumes aU inlake of contaminants is
from the exposure medium being
evaluated (no relative source
contribution).
U. Toxicity Assessmeat
Cancer slope faclOr May overestimalC rislc Slope faclOra are upper 95th percent
confidence limiu derived from a
lillC8rizcd model. Considered unlileely
10 und:restimalC rille, especially for low
doscs.
Toxicity valuel derived from 8Jlimal atudica May over- or undercstimalC rislt Exuapolation from animal 10 humans
for carcinogenic aDd ooac:arcinogeDic effecu may induce error because of differencea
in absorption, pharmacoltincticl,larget
organa, eazymca, and population
variability.
Toxicity values derived primarily from high May over- or undercstimalC rislc Assumes IillC8r dose response
doaca, - expoaurca arc at low doaca relationship at low dosci. Posaibility
that some thresholds do exillt.
Toxicity Values May over- or uodercstimalC risk: Not all values known with the same
degree of certainty. May change u new
evidence becomes available.
Toxicity values derived from homogeneous May over- or undercstimalC rislt Human pOpulation may have a wide
8Jlima1 populatiOIl8 range of scnsitivitiellO a chemical.
lOOllDF5.LAO
-------
Table ROD-7
Groundwater Monitoring Program-Existing Wells
Sheet I of 2
Perforatt'd Intervals (rt) Quarterly
Total Sampling
Well Depth 1st 2nd Jrd 4th 5th 6th 7th 8th Through Other
Number (n) Programs Status
11900038 630 3S0-614 x Active
01900028 600 2S0-S80 x Active
01900831 SOO 2S2-474 Inactive
01900029 61S 264-S82 Inactive
01900882 SOO 199-2S2 280-48S Inactive
01902920 SOO 238-314 366-384 Active
01903012 NA NA Inactive, capped
78000098 1,078 760-769 824-836 8SS-938 942-9S2 980-992 1,024-1,032 x Active
019000311 600 300-S8S Active
0190003S' 600 2S4-S87 Inactive
019021691 280 120-280 Inactive
71903093 S06 272-421 440-466 477-497 Inactive, capped
08000039 622 S40-S82 S94-602 Inactive
08000060 600 300-600 x Active
SI9028S8 SOO 174-214 240-264 312-346 390-474 x Active
01901460 947 600-947 x Active
019028S9 400 ISS-179 18S-203 210-323 3SS-390 x Active
z
08000062 743 SS0-743 x Active
01901611 240 120-IS2 23S-24O 204-220 Inactive:
IOOIOCJD.LAO
-------
Table ROD- 7
Groundwater Monitoring Program-Existing Wells
Sheet 2 of 2
Perforated Intervals (n) Quarterly
Total Sampling
Well Depth ht 2nd 3rd 4th 5th 6th 7th 8th Through Other
Number (n) Programs Status
08000095 NA NA. x Active
08000069 846 566-642 679-695 787-825 x Active
01901600 300 NA Inactive
01901598 400 120-349 x Active
08000070 451 290-435 Active
MW5-012 1,521' 216-226 287-297 . 335-345 430-440 523-533 640-650 765-775 875-885 Monitoring well
Z I 000006 300 75-175 180-195 200-300 Monitoring well
WIONCMWI NA NA x Site assess. well
WI 1 AZWO I 354 148-354 x Site assess. well
WIIAZW03 385 180-385 x Site assess. well
WIIAZW09 NA NA x Site assess. well
NA-Infonnation not available..
'Proposed extraction well.
2EPAW5101-EPAW5113.
'Other perforated intervals = 1,030-1,040; 1,123-1,133; 1,256-1,266; 1,387-1,397; 1,496-1,505 feet.
IOOIOCJD.LAO
-------
Table ROD-8 (page 1 of 2)
Groundwater Monitoring Program- New Wells
(Proposed Plan Alternative)
Wen No. Total Perforated Intervals (ft)t
Depth
(ft) 1st 2nd 3rd 4th 5th 6th 7th Monitoring Wen Purpose
MW5-02 1,8002 200-210 300-310 400-410 500-510 600-610 700-710 800-810 Monitoring for most of the aquifer downgradient of Subarea 3 to fill a data
gap for remedial design and to monitor remedial effectiveness
MW5-03 1,200' 300-310 400-410 500-510 600-610 700-710 800-810 900-910 Monitoring across the entire aquifer downgradient of Subarea 1 to fill a data
gap for remedial design and to monitor remedial effectiveness
MW5-04P (3) 250 180-240 Three piezometers located around Cluster 4 to evaluate remedial effectiveness
of extraction, not needed for remedial design
MW5-054 600 190-200 390-400 580-590 Monitoring at Cluster 5 to provide contaminant data for remedial design prior
to installation of the extraction wen
MW-05P (3) 250 180-240 Three piezometers located around Cluster 5 to evaluate remedial effectiveness
of extraction, not needed for remedial design
MW5-06P (3) 250 180-240 Three piezometers located around Cluster 6 to evaluate remedial effectiveness
of extraction, not need for remedial design
MW5-07 600 190-200 390-400 580-590 Fill data gap for remedial design and provide upgradient early warning
monitoring for Cluster 5 during implementation
MW5-114 700 290-300 490-500 680-690 Monitoring at Cluster 13 to provide contaminant data for remedial design
prior to installation of the extraction wen
MW5-12 650 250-260 450-460 630-640 Upgradient early warning monitoring for Cluster 4 during implementation,
not needed for remedial design
MW5-13 700 340-350 510-520 680-690 Fill data gap for remedial design and provide upgradient early warning
monitoring for Clusters 10 and 13 during implementation
MW5-14 650 250-260 450-460 630-640 Fill data gap for remedial design and provide upgradient early warning
monitoring for Cluster 4 during implementation
MW5-15 700 190-200 450-460 680-690 Fill data gap for remedial design and provide upgradient early warning
monitoring for Cluster 6 during implementation
MW5-16 600 340-350 460-470 590-600 Provide additonal data on vertical distribution of contamination at location of
known shallow contamination
-------
Table (page 2 of 2)
Groundwater Monitoring Program- New Wells
(Proposed Plan Alternative)
Well No. Total Perforated Intervals (R)\
Depth
(rt) 1st 2nd 3rd 4th 5th 6th 7th - Monitoring Well Purpose
MW5-17 700 500-510 680-690 Provide additional data on the lateral and vertical extent of contamination
away from facilities in Subarea 1
MW5-1S4 600 450-460 5S0-590 Monitoring at Cluster 10 to provide deeper contaminant data for remedial
design prior to installation of the extraction wells
'Subject to revision/change.
2MP monitoring well- other perforated intervals = 1,000-1,010; 1,200-1,210; 1,400-1,410; 1,600-1,610; 1,7S0-1790
3MP monitoring well- other perforated intervals = 1,000-1,010; 1,100-1,110; 1,IS0-1,190
"'0 be located at corresponding extraction well cluster site.
-------
PART ID. RESPONSIVENESS SUMMARY FOR
PUBLIC COMMENTS ON THE BALDWIN PARK .
OPERABLE UNIT
TABLE OF CONTENTS
Comments Requiring Lengthy Responses
Response A:
Response B:
Response C:
Response D:
Response E:
Response F:
. EPA response to the "no migration/plume equilibrium"
hypothesis presented by the San Gabriel Basin
Industry Coalition.. ....... .......... """""'''''''''' ....... ....... .................... 93
The rationale for the scope, size, and pumping configuration
of the selected remedy...... """""""""""""""""""'''''''''''''''''' 1 08 .
The role of computer modeling in EPA's remedy........................... 119
The role of the Metropolitan Water District of Southern
California in the Baldwin Park Operable Unit (OU)....................... 127
The feasibility of "air sparging" and "soil vapor extraction"
as an alternative to groundwater extraction and treatment.......... 130
Are the data and technical analyses obtained and completed
as part of the Baldwin Park OU adequate to support the
selection of remedy? [[[ 138
Responses to Other Comments (Comments are grouped into six categories and
organized alphabetically within each category)
...Responses to Comments from Individuals and Interest Groups
1
!L.
J11
IV.
V.
VI
VII.
VIII.
Allan Hill (AH) ........ .........,.. ""'"'' '''''''''''''''''' ............."...... "'"'''''''''''''' 143
Alton J. Amdahl..... ....... ........ ..... "'''''''''''''''''''''''' """""""'''''''''''''''''''' 145
Bill Robinson (BR) ..... ...... .............................................,... ................".... 145
East Valleys Oraanization (EVO), submitted by John Korey and
Carol Montano, Toxies Task Force .... ...... ......................... ...................... 148
Friends of San Gabriel River (FSG), submitted by R. Brown,
Chairman ........., ............ ............... [[[ 149
Rayall K. Brown (RB) .. "'''''''' ...... ............. ............. ............. .................... 150
Sierra Club (SC), Angeles Chapter, submitted by Maxine Leichter............ 153
-------
...Responses to Comments from Federal and State Legislative Representatives
IX.
X.
"
Hilda Solis, Assemblywoman, 57th District, State of California (Sol) ........ 157
Esteban Torres, Member of Congress, 34th District, United States
House of Representatives (Tor) ..... ..... ......... ............................................ 157
...Responses to Comments from The California Department of Toxic Substances
Control
XI.
California Department of Toxic Substances Control (DTS), submitted
by Mike Sorensen, San Gabriel Project Manager...................................... 162
...Responses to Comments from Water Purveyors, Water Districts, and the
Watermaster
XII.
XIII.
XIV.
XV.
Main San Gabriel Basin Watermaster (WM), submitted by John
Maulding, Executive Director ...................... ............ "'''''''''''''''''''''''''''''' 165
Metropolitan Water District of Southern California (MWD), submitted
by Duane L. Georgeson, Assistant General Manager............................... 165
Southern California Water Company (SoC), submitted by Floyd
Wicks, President .... ........ .... ....... """""'" ....... ..:... '''''''''''''''''''' ............. 168
Three Vallevs Municipal Water District (TV), submitted by Muriel
F. O'Brien, President ..... ....~.. ................... ............. '"'''''''''''''''''''''''''''''' 170
...Responses to Comments from San Gabriel Valley Businesses and Business
Representatives .
XVI.
XVII.
XVIII.
IX.
Advanced Environmental Controls Consultina and Enaineerina
Services (AEC), submitted by Viji C. Sadasivan, Senior
Operations Manager ...... ....... ..... ..................... ....................................... 172
Aeroiet Gencoro (Aj), submitted by Suzanne Phinney,
Vice-President, Environmental (submitted summary
comments, comments on Proposed Plan, comments
on Baldwin Park Operable Unit Feasibility Study Report,
Proposal for Technical Modifications, Addendum to
Proposal for Technical Modifications, and two videotapes........................ 174
Azusa Land Reclamation (ALR), submitted by Gregory R.
McClintock, Attorney, McClintock, Weston, et. al.
(submitted summary comments and joined Aerojet
on comments on Proposed Plan, Feasibility Study,
Proposal for Technical Modifications, and Addendum
to Proposal for Technical Modifications) [[[ 269
Azusa Pipe and Tube Bendina (APTB), submitted by Ronald
-------
XX.
XXI.
XXII.
XX III.
XXIV.
XXV.
XXVI.
XXVII.
Chemical Waste Manaaement. Inc (CWM), submitted by Marc
Yalom, R. G., Hydrogeologist ................................,.............. ............. ~..... 271
John Glass and Associates (GI), submitted by John Glass '"''.'''''''.''''''''' 272
Greene Comcanv (Gr), submitted by Richard Greene............................... 272
San Gabriel Basin Industrv Coalition (IC), submitted by
Gregory R. McClintock, Treasu~er ...... ..............~ ..... .......................... ....... 273
San Gabriel Vallev Economic Council (EC), submitted by Will .
Lee, Executive Director .... .... .""".""". ....................................... '.""..'." 285
Trail Chemical Corporation (Tr), submitted by William J.
Peters, President...... .... ....... ...... ...... ............................ ......................... 286
Wvnn Oil (Wyn), submitted by Steven G. Miller, P.E., Erler
& Kalinowski (also joined in IC comments) .............................................. 288
Oral Comments (Oral) Presented May 20, 1993.........................................289
- Jeanne-Marie Bruno, Metropolitan Water District of Southern California
- Greg McClintock, San Gabriel Basin Industry Coalition
- Carol Montano, East Valleys Organization (EVO)
- Rufus Young, Attorney, Burke, Williams and Sorensen
- Royal Brown, speaking as an individual
- Mary Johnson, speaking as an individual
- Larry La Combe, Sierra Club National Water Resources Committee
- Bill Robinson, speaking as an individual
Fiaures and Tables ."""".' ....... ....... '''''' ............................................. ~..................... 293
91
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INTRODUCTION
The Responsiveness Summary summarizes and responds to all
significant comments received during the public comment period
for the Remedial Investigation, Feasibility Study, and Proposed
Plan for the Baldwin Park Operable Unit (OU) of the San Gabriel
Valley Superfund Sites in Los Angeles County, Californial. The
public comments period ran from May 13 through August 12, 1993.
Twenty-six individuals and organizations submitted more than 400
comments. Most commentors submitted between one and ten
comments; one commentor submitted approximately 250 comments.
This summary is divided into two sections. The first
section provides responses to comments that were submitted
multiple times or which require lengthy responses. These
responses are labeled Responses A through F. The second section
of the Responsiveness Summary presents a restatement (in
quotation marks) or paraphrased version of each significant
comment received, and EPA's response. The majority of the
comments were submitted in writing; oral comments made during the
EPA-sponsored public meeting held in Baldwin Park on May 20, 1993
are included last.
Some comments, and EPA's responses, refer to a page,
Figure, Table, or section number. If not noted otherwise, these
numbers refer to the two-volume Baldwin Park Operable Unit
Feasibility Study, included in the Baldwin Park Operable unit
Administrative Record as AR Numbers 394 and 395.
copies of all written comments received by EPA are
included in the Baldwin Park OU Administrative Record, available
for review at EPA's regional office in San Francisco and at the
West Covina Public Library in West covina, CA. The transcript of
the public meeting, including all of the questions, comments and
responses made during the meeting, is also included in the
Record.
lOne set of comments submitted by Aerojet General Corporation,
Azusa Land Reclamation Company, and Oil Solvent Process Company
after the close of the public comment period are also addressed.
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Baldwin Park ROD
..
BALDWIN PAlUt OU RESPONSIVENESS StJJDIARy
RESPONSE A. DE NEED POR ACTION IN SUBAREA 3: RESPONSE TO THE
PLUME STABILIZATION/PLUME EQUILIBRIUM HYPOTHESIS
In their Comments on the Feasibility Study Report and Proposed
Plan for the Baldwin Park Operable Unit, dated August I993, the
San Gabriel Basin Industry Coalition (the Coalition) opposes
EPA's proposed remedial action in Subarea 3. The Coalition
asserts that "sufficient data exist to suggest that the
contaminant plume has "stabilized" and may be at or reaching
equilibrium." They argue that "additional data need to be
gathered and analyzed to confirm or refute" their hypothesis that
plume equilibrium has been achieved.
We first present a summary of our response.
follows.
A detailed respo~se
.
.
.
.
StJHHARY OF RESPONSE
There is evidence of continued contaminant migration in
and immediately downgradient of Subarea 3. The Coalition
ignores this evidence in their comments.
The Coalition claim of "plume oscillation and retraction"
results from a misinterpretation of water quality data.
The Coalition claim of "plume stabilization/equilibrium"
is at odds with the widely-accepted belief that advective
forces dominate contaminant transport in high-velocity
sand and gravel aquifers such as in the Baldwin Park area.
The Coalition lists processes known to resist advective
forces or remove contaminant mass and then speculates that
the identified processes cOllectively could stabilize the
plume. The Coalition does not offer site-specific or
quantitative evidence that the listed processes will do so
and ignores site-specific evidence that the listed
processes are not significant in Subarea 3 and do not
contribute to plume equilibrium. The Coaltion fails to
support their unfounded, unconventional hypothesis.
The field investigations proposed by the Coalition are
unlikely to prove or disprove the Coalition hypothesis.
much more extensive and costly investigation would be
needed to prove or disprove that the plumes have
stabilized and to monitor indefinitely for any further
contaminant movement. Enough wells would be needed to
delineate and then detect changes in the size and
composition of individual contaminant plumes. EPA
A
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Baldwin Park ROD
"
believes that additional field investigations are needed
to support the design of the proposed remedy, but not to
establish the need for remedial action in Subarea 3. The
millions of dollars that would be spent on exhaustive site
characterization to evaluate the Coalition hypothesis
would be better directed toward clean up.
.
The objectives of EPA's remedy are to limit contaminant
migration and remove contaminant mass. The Coalition does
not disagree that EPA's proposed remedy would remove
significant contaminant mass in Subarea 3.
We conclude that the Coalition comment does not lessen the need
for remedial action in Subarea 3.
The detailed response that follows includes a presentation of
site-specific evidence that clearly indicates the continued
migration of contamination, followed by an evaluation of the
effect of each of the processes or factors identified by the
Coalition as potentially contributing to plume equilibrium.
Finally, we explore the scope and types of investigations that
would be required to demonstrate plume equilibrium.
DETAILED RESPONSE
A.l Evi4eDce of cODtiDue4 cODtamiDaDt HigratioD
In part A.1 of this response, we evaluate three important
indicators of continued migration of the groundwater
contamination in Subarea 3:
. increasing contaminant concentrations at wells within or
just downgradient of the Subarea;
. increasing areal extent of contaminant plumes; and
. favorable hydraulic conditions for advective contaminant
transport. .
Increasina Contaminant Concentrations
The Coalition comments imply that if the groundwater
contamination is spreading, contaminant concentrations should be
uniformly rising in existing downgradient wells. We believe that
this is an unreasonable test of continued contaminant migration
for reasons described in part A.2 of this response. The absence
of increasing concentration trends in existing wells would not
prove or disprove the continued migration of the groundwater
contamination.
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Baldwin Park ROD
Documentation of increasing concentration trends at wells located
near the downgradient end of the Subarea must, however, be viewed
as an indicator of continuing contaminant migration. There are
10 wells located either within the downgradient portion of
Subarea 3 or just downgradient of the Subarea that have been
sampled over the last 4 to 5 years. sampling results since 1988
(see Figures RS-9, 10, 11) show increasing concentrations at six
of these wells for either trichloroethylene (TCE) or carbon
tetrachloride (CTC). The six wells, and the contaminant showing
the increase, are:
Paddy Lane (01900031)- TCE
La Puente No.2 (01901469)- TCE
La Puente No.3 (01902859)- TCE
La Puente No.4 (08000062)- TCE
San Gabriel valley B4B (51902858)- CTC
San Gabriel Valley B4C (51902947)- CTC
These data provide a.very strong indicator of continuing
contaminant migration in the area. In fact, concentrations of
TCE in the Paddy Lane well (within Subarea 3) and the La Puente
wells (just downgradient of Subarea 3) have reached all-time
highs within the last year. Also in the last year or so,
increasing contaminant concentrations have forced La Puente
Valley County Water District, San Gabriel Valley Water Company,
and Cal Domestic Water Company to install wellhead treatment at
their Baldwin Park area wells.
Increasinq Areal Extent of Contaminant Plumes
Increasing areal extent of contaminant plumes is another prime
indicator of contaminant migration in the subsurface. It is
difficult, however, to measure increases or decreases in areal
extent in Subarea 3 because individual plumes have not been
delineated. Uniform movement of the broadly-defined "area of
contamination'O would not be expected and, further, could not be
detected with the available downgradient monitoring points.
A key point in the Coalition plume equilibrium theory is their
assertion that there has been an "oscillation" of the
downgradient extent of contamination in the vicinity of the 1-10
freeway. They state that evidence exists to indicate
downgradient movement of the "plume" between 1980 and 1985 and an
apparent "retraction of the Subarea 3 TCE plume" during 1985 to
1990. This interpretation is unsupported; data are not available
to support either the "oscillation" or "retraction" claim. The
downgradient wells apparently used to support their claim (as
shown in the figure in Appendix E of the Coalition's comments)
are San Gabriel Valley's B4 wells (well nos. 51902858 and
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Baldwin Park ROD
.'
51902947). These"wells were deepened in the late 1980s and the
screened intervals were changed from approximately 175 to 475
feet below ground surface (bgs) to approximately 900 to 1100 feet
bgs.- Thus, the post-1988 sampling data are not comparable to the
earlier data and cannot in any way be used to claim "plume
oscillation."
There are no other data available to support the claim of plume
"retraction" or "oscillation". There are no monitoring locations
in the upper several hundred feet of the aquifer at this location
or for nearly a mile downgradient.
Hvdroaeoloaic Conditions in Subarea 3
Hydrogeologic conditions in Subarea 3 are favorable for advective
transport of contaminants in the aquifer. Using a range of
hydraulic conductivity values (150 to 300 feet/day), an effective
porosity of 0.25, and a range of horizontal" gradients (0.001 to
0.025) for Subarea 3, the estimated average linear groundwater
flow velocity in Subarea 3 ranges from approximately 200 to 1,000
feet/year. And, as illustrated in Figure 2-3 and Plates 2, 3,
and 5 of the Feasibility Study, the lithology of Subarea 3 is
predominantly coarse-grained deposits, with relatively small
percentages of fine-grained, organic-rich sediments such as silt
and clay. In this type of coarse-grained, high-velocity
groundwater flow environment it is widely-accepted that advection
is the primary contaminant transport process. In the absence of
site-specific, quantitative data to the contrary, it is
reasonable to assume that contaminant migration will continue
within and out of the Subarea. Very high retardation rates and
active degradation mechanisms would be required to offset the
large advective influence. The presumption must be that the
contaminated groundwater will continue to migrate.
A.2
ABSENCB OF SITB-SPBCIFIC EVIDENCB FOR "PLUKB BQUILIBRItrX"
In "their comments, the Coalition selectively present evidence and
arguments in support of their hypothesis. In this section, we
examine the Coalition claims and identify significant
deficiencies in the Coalition evaluation. We examine and respond
to three claims:
.
Are contaminant concentration trends stagnant or declining?
Is there site-specific evidence that contaminant fate and
transport mechanisms are at work at rates to stop migration?
Do conditions in Subarea 3 differ significantly from
conditions in Subareas 1 and 2 where the Coalition
acknowledges that migration is occurring?
.
.
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Baldwin Park ROD
,
We believe that the answer to each of these questions is no.
Are contaminant Concentration Trends Staqnant or Declininq?
Answer: No.
If plume equilibrium has been reached in Subarea 3, then
contaminant concentrations throughout and downgradient of the
Subarea should be stagnant or declining. The only concentrations
potentially increasing would be those of degradation "daughter"
products, and these should be associated with a corresponding
decline in the "parent" products.
Contaminant concentrations are not, as asserted by the Coalition,
uniformly stagnant or declining in and downgradient of Subarea 3.
As described in part A.1 of this response (and shown in Figures
RS-9 to 11), concentrations of the primary contaminants TCE and
CTC have increased at 6 of the 10 wells in the area over the last
4 years. This indicates that contamination is continuing to
migrate within and downgradient of Subarea 3. Three other 'wells
show decreasing trends of the primary contaminant (either TCE or
CTC) .
The reasons that the increasing concentration trends are
accompanied by some declininq concentration trends are difficult
to determine due to the complexity of the contaminant sources and
variability in groundwater flow conditions. One likely cause of
of the trends is the variability in groundwater flow direction
due to changes in the location, amount, timing, and duration of
pumping and recharge. Accepting the Coalition's tenuous "plume
equilibrium" hypothesis would require rejection of this more
likely explanation. Chanqes in flow direction can cause wells
that formerly sampled "middle-of-the-plume" concentrations to
later sample lower "plume fringe" concentrations. The only way
to dismiss this explanation would be the installation and lonq-
term sampling of a large number of monitoring wells in the hope
of delineating individual plumes, installation of wells known to
be at or near the "centerline" of each plume, and then samplinq
long enough to show that contaminant concentrations remain stable
or decline. The feasibility of such an effort is discussed in
part A.3 of this response.
Another possible explanation for the declininq concentrations
observed in selected wells is variability in the timinq,
duration, and magnitude of the oriqinal sources of contamination.
Uncertainty about the sources of contamination makes it difficult
to determine if observed decreases in concentrations are
temporary, reflecting temporary decreases in the amount of
contaminants originally released into the subsurface, or are
evidence of plume equilibrium.
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Baldwin Park ROD
.'
Is There Site-sDecific Evidence that contaminant Fate and
TransDort Mechanisms are at Work at Rates to StOD Miaration?
Answer: No.
As organic contaminants come into contact with groundwater, they
dissolve and become solute. There are a number of physical and
chemical processes that affect the transport of solute in
groundwater. These include: advection, molecular diffusion,
mechanical dispersion, retardation, and degradation. Advection,
the transport of a contaminant by bulk groundwater flow (i.e., as
groundwater moves, so do the dissolved contaminants), is the
primary process by which contaminants migrate downgradient.
Retardation and degradation act to slow, not stop, the movement
of contaminants relative to the movement of the groundwater.
Although it is widely accepted that in high-velocity sand and
gravel aquifers (e.g., Subarea 3) advective forces dominate
contaminant transport, the Coalition claims just the opposite is
occurring in Subarea 3. The Coaltion has failed to support this
hypothesis.
The Coalition has listed and described the general nature of
contaminant fate processes that may influence contaminant
movement in Subarea 3, but has not presented any site-specific
evaluations of conditions in the Subarea.
The Coalition cites mechanisms that can contribute to plume
equilibrium in Subarea 3 by either reducing the contaminant mass
entering the Subarea (source reduction), reducing contaminant
concentrations in groundwater within the Subarea (retardation,
dilution, biological degradation), or removing contaminant mass
from the aquifer within the Subarea (contaminant removal,
vOlatilization). Each of these mechanisms may have some effect,
but we believe it extremely unlikely that their combined
magnitude could completely stop contaminant migration. Each
mechanism is discussed in more detail below.
Contaminant Removal
Contaminant removal by active groundwater production wells within
and just downgradient of Subarea 3 is minimal. The average
contaminant removal rate is estimated below for the period
between July 1987 and June 1992 using the average extraction rate
over this five-year period for all of the active production wells
in Subarea 3 and the average total concentration of chlorinated
volatile organic compounds (CVOCs) in each well or well cluster:
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Baldwin Park ROD
..
Well
Extraction Rate
acre-feet/dav
Average Cone.
!!Sll
Removal Rate
noundslday
Palm Ave. (08000039) 0.0005
Paddy Lane (01900031) 0.005
Big Dalton (01900035) 0.0
B6B,B6C (71903093, 71900721) 0.0
B6D (78000098) 8.35
La Puente Cluster 4.7
(01901460,01902859,08000062)
17
62
64
28
2.8
8.5
0.00002
0.0008
0.0
0.0
0.064
0.11
Total:
0.175
Although this average removal rate of 0.175 pounds per day
certainly helps in the remediation of contamination in the
Subarea, it is not a significant number given the contaminant
mass already in-place in Subarea 3 (in the 1,000s of pounds range
given the average CVOC concentrations detected in the Subarea and
the estimated size of the contaminated area), and the upgradient
contaminant mass in Subarea 2 that will eventually migrate into
Subarea 3.
Source Reduction
The Coalition argues that "better management practices by users
of chlorinated solvents in the 1960s and 1970s" resulted in
reduced contaminant releases.
Although neither the Coalition nor individual potentially
Responsible Parties (PRPs) have provided EPA with any data to
verify their claim (e.g., data comparing the volume of
contaminants released pre-1960 to the volume released since
1960), it is indeed likely that the magnitude of surface sources
has declined over the years. However, given the considerable
extent of groundwater contamination already present in Subareas 2
and 3, the large number of industrial sources located upgradient
where significant contamination has been detected in the vadose
(unsaturated) zone, it is quite likely that sizable, residual
subsurface sources exist that will continue to be a source of
dissolved contamination for many years to come.
Dilution
Dilution of contaminated groundwater from recharge or
infiltration of uncontaminated water acts to reduce the mass per
unit area or volume in the aquifer by spreading the contamination
into a larger volume of water, but does not reduce the mass of
contamination present in the aquifer. Dilution of contaminant
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Baldwin Park ROD
.
concentrations by recharge/infiltration within Subarea 3 is
unlikely to be significant. The Subarea is mostly paved, with
little opportunity for substantial infiltration and no facilities
for artificial recharge. Thus, it is unclear how dilution has
any impact on contributing to "plume equilibrium" in Subarea 3,
as the Coalition claims.
The large volumes of water recharged to the aquifer in spreading
facilities upgradient of Subarea 3 do indeed affect the
. contaminant concentrations observed entering the Subarea, both by
dilution and by influencing groundwater flow directions and
rates. However, these upgradient impacts do not contribute to
"plume equilibrium" within Subarea 3. Instead, it is probable
that the net effect of the large-scale recharge at the Santa Fe
Spreading Grounds is to periodically increase the local gradient,
thereby disrupting any equilibrium that might have been achieved,
by either sorption (retardation) or biological degradation,
discussed further below.
Retardation
Sorption and desorption of organic solute (e.g., CVOCs) by the
organic component of the aquifer material, commonly referred to
as retardation, decreases the velocity of solutes in groundwater.
The amount of sorption of solutes onto the aquifer material is
primarily a function of: 1) the organic content of the aquifer;
2) the mineralogy of the aquifer material, particularly the clay
content; and 3) the chemical characteristics of the so1ute.
In general, the primary factor controlling the retardation rate
in the aquifer is the organic carbon content 'of the aquifer
materials. Although we do not have any total organic carbon
measurements from the aquifer in Subarea 3, the occurrence of
organic carbon is typically associated with the clay content of
an aquifer. As discussed above, and in the Feasibility Study and
Interim Remedial Investigation Reports, the-aquifer in Subarea 3
is very coarse-grained. Although there is a slightly higher
percentage of fine-grained materials in Subarea 3 than further
upqradient in Subareas 1 and 2, the aquifer still consists of an
overwhelming majority of sand and gravel. This implies that
retardation rates in the Subarea are quite low.
The amounts of contamination sorbed onto aquifer materials and
dissolved in groundwater are related. Over time, if contaminant
concentrations in groundwater decline, any contaminants that have
sorbed will dissolve. Thus, even if retardation rates were high,
without some type of contaminant removal or active degradation
(discussed below), retardation alone will only affect the rate of
contaminant movement between different portions of the aquifer,
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Baldwin Park ROD
not contribute to the long-term containment and remediation of
contamination.
Biological Dearadation
The Coalition points to degradation as another "plume attenuation
mechanism" contributing to plume equilibrium in Subarea 3. The
Coalition claims that "there is evidence of significant
degradation of chlorinated ethenes (as evidenced by the presence
of daughter products in increasing ratios) as one moves
downgradient in the plume". Although there is a higher ratio of
daughter products in some downgradient wells, there are also
wells (both upgradient and downgradient) where this
generalization doesn't hold true. In fact, in Subarea 3, TCE is
still the primary contaminant detected in groundwater samples.
In general, aromatic compounds such as benzene, toluene, and
xylene, can degrade fairly rapidly under both aerobic or
anaerobic conditions. However, for halogenated aliphatic
compounds such as the chlorinated ethenes (PCE, TCE, DCE, etc.),
anaerobic conditions are necessary .for significant degradation to
occur (except where high concentrations of more readily degraded
compounds allow the co-metabolism of halogenated compounds).
Although site-specific data are not available, there is no
evidence to suggest that widespread anaerobic conditions are
present in Subarea 3.
Degradation or "daughter" products, such as dichloroethenes and
dichloroethanes, are present in most of the wells monitored
within the Subarea, but concentrations of these compounds are
much lower than the concentrations of TCE (TCE is typically
detected at concentrations 3 to 5 times higher than all of the
potential degradation products combined). This implies that,
although it is likely that some degradation is occurring, it is
not "significant." In addition, there is the possibility that
dichloroethenes and dichloroethanes themselves could have been
released at some sites. Even if there were "significant"
degradation occurring, the daughter products, some of which
(e.g., vinyl chloride) are more carcinogenic than the parent
products, .would continue to migrate downgradient. Only the rate
would be affected. Only complete degradation, leaving no
hazardous constituents, will stop contaminant migration and
assist in aquifer remediation. The presence of vinyl chloride
would be a good indicator of active degradation proceeding
towarqs completion, however, vinyl chloride has not been detected
in the Subarea.
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Baldwin Park ROD
~
Volatilization
The Coalition defines volatilization as the "transfer of
contaminant mass from the aqueous phase to the vapor phase,
enhanced by water table fluctuations, reducing the aqueous phase
concentrations." The Coalition further states that "it is not
clear at this point whether volatilization is a significant.
factor or not... As illustrated in Section 3 of the Feasibility
Study, in Subarea 3, high levels of contaminants are spread
across the upper several hundred feet of the aquifer. Therefore,
any volatilization that does occur will impact only a very small
percentage of the overall contaminant mass. The remainder of the
contaminated water can continue to migrate. In addition,
transfer of contaminants to the vadose zone is, in part, a
reversible process. contaminants that do transfer to the vadose
zone can be transferred back to the saturated zone with
infiltrating water or by desorption during the next water level
rise. Some contaminants could potentially volatilize and move
into the shallow vadose zone or atmosphere by diffusion, but the
considerable depth to water would limit this (average depth to
groundwater in the Subarea exceeds 100 feet). It is unlikely
that volatilization plays a significant role in reducing
contaminant migration in Subarea 3.
Do Conditions in Subarea 3 Differ Sianificantly from Subareas 1
and 2?
Answer: No.
For plume equilibrium to occur in Subarea 3, but not in Subareas
1 and 2, physical, chemical, and biological conditions in Subarea
3 (e.g., lithology, hydraulic conductivity, groundwater
extraction) must be significantly different than those in other
subareas.
The Coalition offers some generalizations about conditions
processes that they claim contribute to plume equilibrium,
they do not offer any specifics that differentiate Subarea
the upgradient areas where the Coalition acknowledges that
migration is occurring. A comparison of key parameters is
provided below:
Litholoav: Comments from both the Coalition and Aerojet
Gencorp (Aerojet) describe significant changes in lithology
moving downgradient through the Baldwin Park area. The purported
increase in fine-grained sediments in Subarea 3 is used to
justify reducing hydraulic conductivity estimates (see below) and
claim increased retardation resulting from higher total organic
carbon (TOC) levels. Although there is indeed a slight increase
in finer-grained materials and a decrease in cobbles toward the
and
oot
3 from
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Baldwin Park ROD
..
downgradient end of Subarea 3, the available lithologic logs
(Plates 1 though 6 in the FS) show that the aquifer materials are
still predominantly sand and gravel. The more dramatic increase
in fine-grained materials occurs further downgradient, well
beyond the Subarea (FS, Figure 2-3 and Plate 1).
Hydraulic Conductivity. Comments from the Coalition and
Aerojet also both claim that hydraulic conductivity values are
significantly lower in Subarea 3 than in the other Subareas.
Again, this claim is not supported by actual estimates from field
measurements. As shown in the Table below, there is not a trend
of decreasing hydraulic conductivity estimates towards the
downgradient end of Subarea 3.
Groundwater Extraction. Again, the Coalition and Aerojet
both cite groundwater extraction's effect on groundwater flow
conditions in Subarea 3 as another condition contributing to
"plume equilibrium." However, as shown above in the discussion
of contaminant removal, there is virtually no groundwater
extraction occurring in Subarea 3. The pumping wells that the
Coalition and Aerojet are apparently referring to are found in
four well clusters located between 1,200 and 4,800 feet
downgradient or cross gradient from the lower boundary of the
Subarea. Thus, they cannot contribute to plume equilibrium
within the Subarea; rather their presence reinforces the need to
contain higher levels of CVOCs in Subarea 3. In addition, all of
the extraction at two of the clusters (San Gabriel Valley's B4
and B6 clusters) is from greater than 750 feet below ground
surface. At a third cluster (Suburban's cross-gradient 139
cluster), over half of the production is from more than 550 feet
below ground surface. Extraction at these depths has little
impact on the primary contaminated interval in Subarea 3 located
between approximately 150 and 650 feet below ground surface.
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.,
Baldwin Park Area Hydraulic Conductivity Estimates
Well Agency Subarea Hydraulic Condo Data Point
(ftlday)
Morada- 01900029 EPA upgrad.2 345 pumping well
Lante- 08000060 EPA mid. 2 5,062 pumping well
Baldwin 3- 01900882 EPA downgrad.2 300-706 observ. wells
Baldwin 3- 01900882 Watermaster downgrad. 2 414 pumping well
Big Dalton- 01900035 EPA mid. 3 297 pumping well
Paddy Ln.- 0190003i EPA downgrad. 3 668-809 pumping well
B6B- 71900721 Watermaster downgrad. 3 263 pumping well
B6C- 71903093 EPA downgrad. 3 520-559 observ. well
140W4- 08000093 EPA downgrad. of 3 267-298 observ. well
A.3 Coali~ion Proposed Xnves~iqa~ions and cri~eria ~o Evalua~e
~he Plume Bquilibrium Bypo~hesis
The Coalition offers an unconventional hypothesis. To prove
this unconventional hypothesis, the Coalition would need to
obtain and properly interpret a large amount of site-specific
data.
The Coalition has proposed a "Characterization study" to
satisfy the need for site-specific data. EPA does not oppose
independent data collection efforts, but we disagree with the
Coalition claim that these data would be useful to "evaluate
the need for remedial action in Subarea 3" or to "demonstrate
whether the plume is migrating and should be contained or has
reached equilibrium and containment actions are not necessary. II
The Coalition proposed study includes installation of six
monitoring well clusters, monthly collection of water quality
samples for one year, groundwater modeling of contaminant
transport processes and quantification of contaminant mass
balance. In addition, the Coalition has outlined factors to be
used as a basis for development of criteria to determine the
need for containment. These factors are:
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..
.
"Whether monitoring points established downgradient
of the current plume show contaminant levels which
remain below a specified threshold concentration."
.
"Whether monitoring points established along the
centerline of the current plume in Subarea 3 show a
statistically significant increase in
concentrations."
.
"Whether variations in the observed trends in both
sets of monitoring points reflect downgradient
changes in contaminant mass."
"Whether observed current and historical trends can
be accurately reproduced by modeling so that future
changes can be accurat~ly predicted."
We believe that the Coalition proposed characterization study
and potential criteria are unlikely to prove or disprove the
Coalition hypotheses. We do not believe that they represent a .
reasonable indicator of or test for contaminant migration, and
that they reflect a misconception of conditions in Subarea 3.
There are a number of complicating circumstances that make it
unlikely that continuous, statistically significant trends will
be observed along the "plume centerline" described by the
Coalition or in most other locations within Subarea 3. To
truly perform a characterization study to evaluate potential
plume equilibrium in Subarea 3, a thorough understanding of
both the nature and extent of contamin~tion, and the detailed,
exact nature of lithologic heterogeneity in the Subarea are
required.
The Coalition description of a "plume centerline" incorrectly
represents the area of contamination delineated in Subarea 3 as
a single contaminant plume. In its Feasibility Study and
Proposed Plan, EPA shows approximate areas of groundwater
contamination, rather than multiple plumes with well-defined
boundaries, but this representation does not imply that there
is a single plume; instead it reflects the lack of enough water
quality data to delineate individual contaminant plumes.
The area of contamination most likely contains numerous
individual or commingled plumes that originated at multiple
sources from contaminant releases varying in magnitude, timing,
and duration. In addition, neither the initial surface
releases nor residual subsurface sources have been fully
characterized, nor are the highly transient nature of the
recharge and discharge stresses affecting groundwater flow and
contaminant migration, or the presence of preferential pathways
along "corridors" of higher hydraulic conductivity, likely to
.
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Baldwin Park ROD
,
be characterized to the extent needed to prove or disprove the
Coalition hypotheses.
Although the lithology in the area is predominantly sand and
gravel, the presence of preferential pathways along individual
zones of very high conductivity (i.e., buried river channels)
further complicates the distribution of contamination and our
ability to prove either absolute equilibrium or complete
control of migration. In addition, the highly-variable pumping
and recharge conditions in the Baldwin Park area have
significant impacts on the direction and rate of groundwater
flow and, thus, contaminant movement, in Subarea 3. All of
these factors contribute to what is likely a complex
distribution of contamination in the Subarea. EPA believes
that it is unnecessary to more precisely define the exact
location and extent of the individual plumes in the Baldwin
Park area before proceeding with its proposed interim remedy.
The Coalition proposal would require that individual
contaminant plumes be located and characterized before any
detailed field investigation could detect contaminant migration
downgradient of or along the centerline of plumes. Th~
investigation would need to include information of sufficient
detail to establish that no zones of higher hydraulic
conductivity exist throughout the lateral and vertical extent
of the "equilibrium boundary." These zones.could be anywhere
from 10s to 100s of feet wide and thick. (See Response C for
further description of lithologic variability. Essentially,
contamination is known to preferentially migrate within zones
of higher hydraulic conductivitYiSUch zones are likely in this
depositional environment and would need to be identified.)
Furthermore, to "prove" that containment is not now and will
never in the future be necessary in Subarea 3, a monitoring
program near the downgradient end of each individual plume.
would be needed. To take the first step alone and identify the
individual plumes would require literally dozens of monitoring
well clusters (not just the six wells proposed by the
Coalition). Subarea 3 covers an area approximately two miles
long by one mile wide. The second step of the investigation
(monitoring for contaminant migration) would require
additional, more focused monitoring at the end of each
contaminant plume identified.
The second part of the Coalition proposed "Characterization
Study" involves contaminant transport modeling and quantifying
the mass balance of contaminants in the Subarea. Because of
the lack of data and numerous assumptions that would be
required, neither of these efforts is likely to provide any
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firm, reliable conclusions. Perhaps the key parameter in both
of these tasks is information on the location, magnitude,
duration, a~d timing of contaminant sources. At the present
time, there is little or no information available on
contaminant sources throughout the Baldwin Park area (including
the likely presence of residual subsurface sources such as
dense non-aqueous phase liquids [DNAPLs]). Given the number of
potential sources present and the long period over which
releases may have occurred, it is unlikely that adequate
information will ever be available to adequately estimate these
parameters. Combine this with the numerous additional
assumptions on contaminant fate parameters required to perform
contaminant transport modeling, and it is likely that investina
substantial resources into modelina will only lead to disputes
over model inputs and results, not to "accurate predictions of
future changes" in contaminant conditions.
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"
BALD.:Ili PAlUt OU RESPONS:IVENESS SUMMARY
RESPONSE B: THE RAT:IONALE FOR THE SCOPE, S:IZE, AND POHP:ING
CONF:IGURAT:ION OF THE SELECTED REHEDY
B.1
Philosophy for Remediatinq contaminated Groundwater Sites
Remedial actions at sites with contaminated groundwater almost
always try to stop or limit further movement of the
contaminated groundwater into downgradient areas. Typically,
these groundwater "migration control" or "containment" actions
are implemented at the downgradient "leading edge" of the
contaminant plume or plumes. And, in most cases, containment
is achieved through groundwater extraction. At sites where the
contaminated area is large or extends deep into the aquifer,
groundwater extraction is currently the only feasible option
for providing adequate containment. This type of remedial
action inhibits contaminant migration beyond the extraction
locations, protects downgradient areas that are clean or less
contaminated, and can remove a significant mass of
contamination. EPA regulations and guidance, and experience at
countless other Superfund sites, highlight the importance of
limiting the spread of contamination at contaminated
groundwater sites.
There is a drawback associated with using groundwater
extraction to inhibit downgradient migration of contamination,
particularly if the area of contamination is large. The
drawback is increased contaminant concentrations in the portion
of the aquifer between the source and the extraction locations.
Groundwater extraction actually increases the hydraulic
gradient and accelerates the movement of groundwater located
upgradient of the extraction wells. The upgradient
groundwater, which is closer to the source of contaminants and
will generally have higher contaminant concentrations, will be
pulled towards the extraction wells through the less
contaminated portion of the plume. Thus, extraction at the
leading edge of the plume, while protecting downgradient areas,
will often degrade groundwater quality in the portion of the
plume between the source area and the extraction location(s),
at least temporarily. This drawback is usually considered to
be of much less significance than the remedial benefits
associated with providing protection to the uncontaminated or
less contaminated areas downgradient.
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.,
B.2 Rationa1e for EPA's Proposed Extraction Areas (the
Subareas)
Remedial abiectives for the Baldwin Park au
As stated in the FS, EPA's remedial objectives for the Baldwin
Park au are to:
. inhibit contaminant migration from more highly
contaminated portions of the aquifer to less contaminated
areas or depths to reduce the impact of continued
contaminant migration on downgradient water supply wells,
and to protect future uses of less contaminated and
uncontaminated areas; and
. to remove contaminant mass.
EPA's remedial objectives, and the remedy described in the FS,
Proposed Plan, and ROD, are consistent with the philosophy for
remediating contaminated groundwater sites described above.
Extraction is proposed in areas where there is a significant
decrease in contaminant concentrations in order to protect
downgradient, less-contaminated areas from the more
contaminated groundwater present upgradient.
Aerojet/ALR submitted several comments on the relative
importance of the migration control and mass removal
objectives. The comments vary in wording, but all argue that
mass removal should be given greater weight. The comments
include:
... the two objectives should be equally weighted...
... EPA must consider the mass of contaminant removed per
acre-foot of water extracted...
.... "source control or maximizing mass removal should be
considered objectives equivalent to migration control"...
EPA presents migration control as the primary objective and
mass removal as a secondary objective of the Baldwin Park au
because the migration control objective dictates the size of
the remedy (the minimum rate of groundwater extraction in each
significant subarea of contamination) and the need to locate,
extraction wells near the downgradient boundary of each
Subarea. This ranking of objectives is consistent with EPA
guidance. EPA does not believe that mass removal should
replace migration control as the primary objective, or that
additional extraction above that needed for migration control
is necessary in tbis interim action. Future remedial actions
in the Baldwin Park area may, however, emphasize mass removal
(see sections B.3 and B.5 of this response).
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"
Nor does EPA believe that maximizing mass removal or maximizing
the mass removed per acre-foot extracted are appropriate
objectives in this interim action, since doing so would
conflict with EPA's migration control objective (if recommended
extraction locations are moved to more highly contaminated
areas) or require additional extraction beyond what EPA
believes is necessary at present (if additional extraction
locations are added).
ProDosed Extraction in Subareas 1 and 3 (the upoer and lower
areas)
EPA's selected remedy calls for extraction of contaminated
groundwater in two portions of the aquifer (two Subareas) where
limiting the migration of contaminated groundwater appears to
offer the greatest benefit. In the upper area (Subarea 1),
remedial action can protect downgradient areas from the impact
of continuing surface and/or subsurface sources of
contamination; in the lower area (Subarea 3), remedial action
can offer some protection to active water supply wells and less
contaminated downgradient portions of the aquifer.
EPA proposed extraction in the Subarea ~, at its downgradient
end, as a source control action to limit the continued movement
of contaminant mass to downgradient areas and to remove
significant contaminant mass. Virtually all of Subarea 1 is
zoned for industrial use. Investigation results from soil,
soil vapor, and groundwater sampling at suspected source
locations in Subarea 1 confirm the presence of multiple sources
of contamination above and most likely beneath the water table.
Unless they are removed or contained, high-level contamination
in Subarea 1, continually fed by residual sources, will
continue to contaminate clean or less contaminated groundwater
in downgradient areas, increasing the timeframe for and
reducing the likelihood of cleaning up downgradient portions of
the aquifer. EPA's strategy is to install and operate
extraction wells to provide a barrier that prevents
contaminated groundwater from moving out of Subarea 1 into
d6wngradient areas. The selected remedy will cut off the
sources from downgradient areas.
contaminant levels in portions of Subarea 1 are in the 1,000s
of p.gll (parts per billion [ppb]); contaminant levels
downgradient of Subarea 1 are in the 100s of ppb.
EPA proposed extraction in the SUbarea 3, at its downgradient
end, to limit the movement of more highly contaminated
groundwater into less contaminated downgradient areas and to
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Baldwin Park ROD
"
remove contaminant mass. Benefits of containment include
preservation of the resource as a vital water supply and
underground storage reservoir, and preventing the spread of
contamination toward and beyond the Whittier Narrows. EPA's
proposed extraction should also benefit operators of active
water supply wells downgradient of Subarea 3 by limiting the
impacts of additional contaminant migration on their wells,
eliminating the need for wellhead treatment or reducing the
operating costs of existing treatment systems by minimizing
future increases in contaminant levels. contaminant levels
change from the 10s of ppb in Subarea 3 to near Maximum
contaminant Levels (MCLs) downgradient of the Subarea.
Research and experience at other contaminated groundwater sites
indicate that the presence of non aqueous phase contamination
or other subsurface sources will have a significant influence
on the time frame required for or likelihood of achieving
cleanup. If it is confirmed that all or most of the
significant sources of the groundwater contamination are
present in Subarea 1, then EPA's strategy of containing or
cutting off Subarea 1 from downgradient portions of the aquifer
will greatly increase the chances of and lessen the time
required to clean up downgradient areas.
B.3 Extraction in Subarea 2 (the "middle" area) and Other
possible Extraction Areas
In the FS, EPA also considered the benefits of extracting
contaminated groundwater in a third, "middle" area (labeled as
Subarea 2). contaminant concentrations in Subarea 2 are in the
100s of ppb; contaminant concentrations downgradient of this
area are in the 10s of ppb. The selected in~erim remedy does
not include extraction in this area because additional. .
extraction in Subarea 2 or in additional areas would offer
fewer or less certain remedial benefits at considerable added
cost. Additional extraction would also require the
distribution of greater volumes of. treated water, increasing
the institutional complexity of the project. EPA will
reconsider the merits of additional extraction in Subarea 2 if
significant sources of contamination are determined to be
present in this Subarea.
If significant sources of contamination are not identified in
Subarea 2, then the primary benefit of additional extraction in
Subarea 2 would be to more rapidly reduce contaminant
concentrations in the Subarea, but by an unknown amount. Our
ability to quantify the benefits of additional pumping is
limited by uncertainty in the precise extent of contamination,
in the relative masses of contamination in different portions
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Baldwin Park ROD
.
of the aquifer, and in the presence of preferential flow
pathways and other local-scale aquifer phenomena that affect
the time required for clean up. EPA will re-evaluate the
merits of additional extraction after the selected remedy is
implemented and evaluated. At that time, EPA will be able to
calculate rates of contaminant removal, the rate at which
contaminant concentrations in the aquifer are decreasing,
estimate the timeframe for future decreases and perhaps for
complete clean up, and evaluate the costs and benefits of
additional extraction.
The selected remedy, or variations of it that include a
realistic, finite number of extraction areas will inhibit
contaminant migration in certain areas, but not in others.,
There are probably other locations (in addition to the upper,
middle, and lower extraction areas evaluated in the FS) where
there are changes in contaminant concentrations that could
conceivably warrant groundwater extraction to protect
downgradient, less-contaminated portions of the aquifer and
remove additional contaminant mass. The extent of
contamination in the OU area is simply too large and variable
to propose extraction in every individual area where
contaminant concentrations may be higher upgradient than
downgradient. '
B."
"Approximate Extraction Areas" and "Pumping Configuration"
The preceding section describes the two approximate extraction
areas (Subareas 1 and 3) in which EPA's selected remedy calls
for remedial action. The next two sections describe EPA's
recommendations for precise extraction locations and rates in
each of the two Subareas. We refer to these recommended
extraction rates and locations as pumping configurations. The
recommended pumping configurations are based on the Subarea
boundaries and on computer simulations using EPA's groundwater
flow model to identify the most efficient combination of
extraction rates and locations that will minimize the movement
of contaminated groundwater out of the Subarea. EPA's
recommended pumping configurations are not necessarily the only
efficient arrangements. Other configurations calling for a
greater number of extraction wells but at lower rates, or fewer
wells at higher rates, may be equally efficient. See Response
C for additional details'on EPA modeling efforts.
EPA expects that the pumping configurations described in the
ROD will be refined during remedial design after additional
monitoring wells are installed and sampled and additional data
on hydrogeologic properties of the aquifer are obtained. These
data will be used to verify assumptions and refine EPA's
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interpretation of the lateral and vertical extent of
contamination (i.e., the Subarea boundaries), which are used to
determine the portions of the aquifer requiring cap~ure, which
in turn affect the pumping configuration.
PumDinq Confiquration in Subarea 1
EPA believes that ,within Subarea 1 there'are multiple sources
of groundwater contamination, and multiple plumes of
contamination separated by less contaminated areas. This
interpretation is based on information on the m~gnitude and
duration of chemical usage, handling, and disposal, and on the
magnitude, extent, and pattern of contaminant concentrations in
soil, soil gas, and groundwater at numerous facilities in the
Baldwin Park area. EPA believes that groundwater
concentrations at several locations in Subarea 1 reflect the
presence of more than one current or historical source. See
Figure RS-1. It is likely that additional sources will be
identified at additional locations as individual site
investigations progress. '
To achieve its remedial objectives in light of the presence of
multiple sources, EPA considered two differing approaches.
The first aDproach is to install mUltiple groundwater
extraction and treatment facilities, one at or near the
facility boundary of each and every significant source. If
numerous sources are confirmed, numerous groundwater
extraction, treatment, and distribution systems would need to
be installed and operated, increasing the total cost and
institutional complexity of the remedy. Groundwater extraction
and treatment systems may also be needed downgradient of
facility boundaries to contain and remove high-level
contamination that has migrated some distance from the sources.
Several comments suggest that only the one or two monitoring
wells where the highest concentrations have been measured
represent sources of groundwater contamination (e.g., WIOWOMWl,
V10VCMW1) and that the concentrations detected at other wells,
including OSCOMW2, Aerojet MW3, and W1~Z03, do not represent
sources. We disagree with this interpretation. Groundwater
concentrations alone should not be used to determine the
presence or absence of a source; other data on chemical usage,
soil contamination, and soil gas contamination must also be
considered. The lower, but still significant groundwater
concentrations measured at wells such as OSCOMW2, Aerojet MW3,
and W1lAZ03 may reflect differences in the spatial relationship
between the well and the original spill or release, or
differences in well screen length. A well located at the
centerline of a plume will show a higher concentration than a
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Baldwin Park ROD
.'
well located at the fringes of the plume, but the exact spatial
relationship of most monitoring wells in the Baldwin Park area
to the original release is unknown. Also, wells W11AZW01
through W11AZW09 have much longer screen lengths than the
Aerojet wells and well W10WOMW1. The screen lengths for wells
W11AZW01 through W11AZW09 exceed 200 feet; the screen lengths
for the Aerojet wells and well W10WOMW1 are 50 and 30 feet
respectively.
The second aDDroach is to install one groundwater extraction
and treatment system (which may include more than one well)
immediately downgradient of all of the known and suspected
sources designed to capture contaminated groundwater
originating from all of the sources. The advantages of the
second approach are reduced cost and reduced need for
investigation work to identify and determine the nature and
extent of each source and delineate the boundaries of each
resulting plume. Because of the number of suspected sources,
the large area across which they are located, and the depth of
the contamination, the cost of fully characterizing all
potential sources of high-level contamination and delineating
separate and distinct areas of contamination in Subarea 1 would
be high. Fully characterizing all suspected sources would
require a significantly greater number of monitoring wells and
other characterization work than has been completed to date to
determine both the lateral and vertical extent of
contamination. Even with much additional investigation, there
is a risk that some high-level contamination or hot spots,
especially residual sources, would remain undetected.
A disadvantage of the second approach is that it may allow
additional degradation of the interval between the more distant
sources and the extraction locations. In the Baldwin Park
area, data from well W10WOMW1 indicate the presence of a source
adjacent to or upgradient of this well. The distance between
well W10WOMWl and EPA's recommended extraction locations is
over 1 mile; the distance between well Vl0VCMWl and EPA's
recommended extraction locations is greater. The amount or
significance of this additional degradation is difficult to
measure because too few monitoring wells have been installed to
determine the precise distribution of contaminants in this
portion of the Subarea.
EPA chose the second approach in its proposed. plan. EPA
therefore defined Subarea 1 to address much of the industrial
area north of Arrow Highway where sources of the groundwater
contamination appear to be present and EPA proposed extraction
at the downgradient end of the Subarea.
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Baldwin Park ROD
.,
Aerojet, ALR, and oseo appear, in part, to favor the first
approach. They submitted numerous comments on the pumping
configuration in Subarea 1 which vary in wording but make the
same argument: that EPA should supplement its recommended
pumping configuration with additional extraction of .
contaminated groundwater in the vicinity of well W10WOMW1
(and/or well V10VCMW1) because concentrations of several CVOCs
measured in groundwater samples collected from these wells are
higher than in downgradient wells. They emphasize that the
highest contaminant concentrations measured in the Baldwin Park
area are at well W10WOMW1; that EPA's highest priority should
be to control these high concentrations; that EPA has ignored
the presence of "separate and distinct source areas" in Subarea
1; that EPA should redefine Subarea 1 to include only "small
hot spots"; that concentrations in Subarea 1 and 2 are similar
except for two small locations where they are anomolously high;
and that this error or omission will "further degrade aquifer
conditions and increase the cost and time necessary (for
remediation]."
EPA's response to these comments is that additional extraction
in highly contaminated areas beyond that proposed by EPA is
. beneficial (it would remove additional contaminant mass and
increase the ratio of contaminant mass to volume of pumped
groundwater), but that it is not necessary to meet the
objectives of this interim action. Extraction at W10WOMW1
would not contribute to EPA's objective of limiting the
migration of contaminated groundwater out of Subarea 1. And
the benefits of addressing one source (e.g., in the vicinity of
W10WOMW1) are limited if other significant sources are present,
particularly if other sources go ~naddressed. If any
significant subsurface sources are present, it is uncertain in
what timeframe portions of the aquifer impacted by the sources
will be cleaned up. If EPA applied this policy consistently
and demanded additional extraction at other .'hot spots wi thin
hot spots," it would greatly increase the cost of the remedy.
In its comments, Aerojet/ALR refer to the additional
degradation that would result from failing to address the
contamination present at W10WOMW1 closer to its source as
causing "further damage to the groundwater resource and
increas(ing] the time and cost required for effective
remediation." EPA believes that "damage" is a misleading
description of this limitation in that it fails to recognize
that this area is already highly contaminated and that
degradation of the area immediately upgradient of the
extraction locations is inherent in all groundwater extraction
and treatment remedies. EPA believes that in the absence of
significant additional data demonstrating that W10WOMW1
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"
represents the only significant source, an extraction scenario
similar to that outlined in the Proposed Plan is the most cost-
effective way to address contamination present at W10WOMW1 and
elsewhere in Subarea 1, and best balances EPA's "migration
control" and mass removal objectives for the OU.
Makina Use of the Arrow Hiahwav/Lante Well Cluster in Subarea 1
Aerojet, ALR, and OSCO also submitted comments in their
"Addendum to Proposal for Technical Modifications..." that EPA
should rely on 4000 gallons per minute (gpm) of extraction at
the existing Arrow/Lante cluster to limit the migration of
contaminated groundwater from Subarea 1 in place of EPA's
recommended Subarea 1 extraction rates and locations. The
Arrow/Lante locations are approximately 3/4 mile downgradient
of EPA's recommended locations (wells 10 and 13). Moving the
extraction locations downgradient, further from known and
suspected source locations, would reduce the effectiveness of
the remedy by allowing additional degradation of the interval
between EPA's recommended extraction locations and the
Arrow/Lante well cluster. If, as it now appears, this interval
does not include any significant sources of contamination, then
moving the extraction locations downgradient would eliminate or
indefinitely delay the cleanup of this interval.
Aerjet/ALR have failed to explain the conflict between their
suggestion to permit additional degradation of water upgradient
of the Arrow/Lante wells and their assertion that EPA's
recommended extraction locations in Subarea 1 would result in
degradation of the portion of the aquifer between well W10WOMW1
and EPA's recommended extraction locations.
Because the Record of Decision recommends, but does not
prescribe, groundwater extraction rates and locations, EPA has
not completed a detailed review of the computer modeling or
other analyses carried out in support of the proposal to
replace EPA's recommended extraction rates and locations with
. less extraction at the Arrow/Lante well cluster. Commentor is
proposing to substitute 4,000 gpm of extraction at Arrow/Lante
in place of the 8,500 gpm that EPA's evaluations indicate is
necessary. In their submittal, commentor does not identify
what differences in hydraulic conductivity, differences in
interpretation of the extent of contamination, or other
differences justify their assertion that they can extract
approximately 50% less groundwater and still satisfy EPA's
migration control objective. .
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n
PumDina Confiauration in Subarea 3
Comments were also received regarding the proposed extraction
scenario in the lower area. These comments primarily address
the possibility of focusing extraction in the lower area. on
individual contaminant plumes, rather than on the entire
'Subarea. EPA may support an extraction scenario that contains
and captures individual plumes rather than the entire width of
the contaminated area shown in the FS, if additional data
become available to more definitively characterize the nature
and extent of the multiple plumes that are likely present in
Subarea 3. However, given the size of the Subarea and the
depth of contamination detected, the data collection efforts
(monitoring well installation and sampling) that would be
required to adequately characterize all plumes potentially
present in the Subarea would probably be cost prohibitive (see
Response A for additional detail on the investigations that
would be required for this effort). This detailed
characterization would not only be extremely expensive and
cause undesirable delays in implementation of the migration
control action, but the investigation would not likely result
in a significantly different project cost (i.e., the total
extraction rate required would probably not be substantially
reduced).
8.5
When EPA May Support or Propose Additional Extraction
EPA supports additional groundwater extraction and treatment in
contaminated areas if consistent with EPA's remedial objectives
and shown to not significantly increase the vertical/lateral
extent of contamination, as might occur through pumping of
wells in relatively clean areas adjacent to more highly
contaminated areas or at wells screened deeper than the
contamination.
EPA may, in the future, propose additional groundwater
extraction in areas other than identified in the selected
remedy. EPA may propose additional extraction if additional
investigation work indicates the presence of additional sources
outside of Subarea 1 and distant from existing extraction and
treatment locations, and if there would be significant benefits
in protecting the less-contaminated region between the source
and the extraction locations. EPA may also propose additional
extraction if data collected during design, operation or
evaluation of the remedial action indicate that additional
extraction would significantly more quickly, or more
completely, achieve clean up.
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Baldwin Park ROD
Data that will be collected to evaluate the need for future
actions include additional investigation of the lateral and
vertical extent of contamination, sampling of groundwater in
deeper portions of the aquifer to evaluate the presence of
DNAPLs, refined estimates of the total mass of contamination
present in the au area, and the distribution of contamination
between the various phases.
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BALDWIN PAlUt OU RESPONSIVENESS SUMMARY
RESPONSE 0: EPA KODELING OF GROUNDWATER FLOW IN 'l'RE SAN
GABRIEL BASIN
This response addresses comments on groundwater modeling
provided by the San Gabriel Basin Industry Coalition, Aerojet
Gencorp, and Azusa Land Reclamation. AI though many of these
comments are repeated in several forms in several places, they
generally refer to similar issues regarding modeling performed
by EPA, both in support of the FS, and indirectly, to all
modeling performed by EPA to date. Thus, for simplicity,
responses to all of these comments are consolidated below.
In several places, the comments appear to confuse the CFEST
computer code with the CFEST model of the San Gabriel Basin
prepared by EPA. For clarity, this response assumes that
"CFEST code" refers to the generic CFEST software package,
whereas the "CFEST model" refers to the set of input parameters
and corresponding output of calculated results used to simulate
conditions within the San Gabriel Basin. The discussion that
follows is divided into an initial section responding to
comments on the CFEST code, followed by a section describing
EPA's general approach to modeling the San Gabriel Basin.
These are followed by a section that specifically addresses
comments regarding assumed parameters in the CFEST model of the
basin. The last portion of this response describes how the
model was used in the Baldwin Park FS.
0.1
OFEST Modeling software.
Numerous comments refer directly to the suitability of the
CFEST code for simulating conditions in the San Gabriel Basin.
Initial modeling of San Gabriel by EPA was performed using the
well-known MODFLOW code (EPA, 1986). However, the MOD FLOW
model could not accurately reproduce relatively local-scale
fluctuations in the water table in response to groundwater
pumping, nor could it simulate the migration of contaminants.
Given the complex geometry of the basin, and the need to refine
portions of the model in the future as more local analysis
would require, finite-difference codes were considered
generally inadequate. To select a new code and refine this
model, EPA undertook an evaluation of available finite-element
codes. The selection of codes was based on the following
requirements, among others:
1.
Ability to represent complex, irregular geometries.
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2.
Ability to simulate contaminant transport, including the
effects of dispersivity, degradation, retardation, and
time-varying sources.
High-level display capabilities and flexible input.
requirements that could easily be integrated with a
Geographic Information System (GIS) data base.
3.
4.
A code in the public domain.
A well-known code that had been extensively and
successfully verified and benchmarked with widespread
acceptance and credibility in the scientific and
engineering community. .
5.
Using these criteria, the selection was narrowed to three codes
available at the time: CFEST, Princeton, and SWIFT II. CFEST
was selected because, in addition to meeting the above
requirements, it was developed by the U.S. Government, approved
for use by the Nuclear Requlatory Commission, and verified and
benchmarked as part of one of the most exhaustive international
efforts ever undertaken (HYDROCOIN). In addition, because it
is used by governments, companies, and academic institutions
allover the world, it is widely accepted and its use is well
documented in the literature. CFEST is well suited to the
simulation of contaminant transport, considers coupled
groundwater flow and solute transport (including coupled
consideration of density effects), and supports the latest
display and graphical technologies available. Proprietary
codes have not gained this type of exposure and testing.
C.2
General Approach to San Gabriel Modeling
Re~ional- and Local-Scale Modeling.
The original version of the CFEST model of the San Gabriel
Basin was developed in 1988. As stated in numerous EPA
reports, the objective of this model was, and continues to be,
primarily the simulation of the regional behavior of the
groundwater system. As EPA's focus has moved into specific
portions of the basin, including Baldwin Park, this original
model has been updated, and most importantly, refined in the
areas of interest. In performing these refinements, parameters
have been updated to reflect new data as they become available
on a local scale. However, given the paucity of detailed
information from throughout the aquifer thickness and
throughout the extent of these local areas, (e.g., Baldwin
Park), the model is still considered to be primarily a regional
one, as stated in the Baldwin Park FS Report.
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In most cases, current hardware and software technology no
longer require development of separate regional- and local-
scale models. In the past, the use of direct solvers and the
memory limitations of computers dictated the need to develop
independent local-scale models with boundary conditions. based
on the results of regional models. simulation of local-scale
conditions in this manner was limited in that boundary
conditions were fixed to the behavior of the regional model,
and would generally not vary as a function of changing
conditions on a local scale. However, it is no longer
infeasible to continue to add local-scale complexity to
regional models to refine simulation of local behavior. This
is the approach taken by EPA with the San Gabriel model.
Thus, although it is not yet possible to gain a high level of
local-scale accuracy in areas like Baldwin Park, it is possible
to locally refine the regional model to better simulate the
effects of individual wells and recharge on a local scale.
This was done in the Baldwin Park portion of the regional
model, and as documented in the FS, the three-dimensional
simulations reproduce, as a baseline, observed historical
conditions. The effects of Santa Fe Spreading Grounds (SFSG)
recharge and Baldwin Park area groundwater extraction are
clearly reproduced in the modeling figures included in section
7 of the FS Report. The generally low gradients in the area
are also clearly represented in these simulations.
Nonetheless, the model does not account for local heterogeneity
of aquifer materials.
For example, the alluvial depositional system responsible for
the high degree of local variability in grain size and
hydraulic conductivity is not completely reflected in the
current zonation of hydraulic conductivity and other
parameters. It is likely that the pattern of buried river
channels has resulted in a complex of braided and meandering
stream deposits, overbank deposits, flood basins, levees, and
point bar sequences. Evidence of this includes the very high
measurements of hydraulic conductivity seen in some aquifer
tests. The current model simply attempts to reproduce the
regional, composite behavior of the system. The logging and
testing of new, deep monitoring wells should allow the system
to be somewhat more accurately represented numerically. As
remediation proceeds, further fine tuning of the model based on
ongoing monitoring from the new well network will allow
additional refinement.
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"
Solute Transcort Modelina.
EPA acknowledges the complexity of solute transport modeling as
highlighted by the comments. The nature of migration of CVOCs
in the San Gabriel Basin is a function of the chemistry of the
individual contaminants, the physical and chemical nature of
the aquifer materials (which is complicated further by its
heterogeneity), as well as the hydraulic behavior of the
groundwater system. EPA has already attempted to characterize
the parameters that define these variables, as documented in
the Basinwide Technical Plan (BTP) and Interim San Gabriel
Basin Remedial Investigation Report (RI Report) (EPA, 1990 and
1992). An additional variable, perhaps the most difficult to
estimate, is the location, timing, and magnitude of the
hundreds of historical and ongoing sources of contamination.
These include both primary sources at the surface and residual
sources in the subsurface.
Given the uncertainty in all of these variables, EPA has never
attempted to undertake the simulation of contaminant migration
in any but a regional, comparative manner. In theBTP, for
example, solute transport was simulated to evaluate the
potential effects of no action on a basinwide scale, and to
comparatively evaluate conceptual alternatives on a local
scale. Wherever these simulations are documented, there is
substantial explanation of the uncertainty involved and of the
comparative (versus absolute) objective of this modeling. The
sources of contamination used in this modeling were identified
in the course of calibrating simulation results. to the
available record of contamination in the basin. Unfortunately,
the record is limited to data since 1980; it is thus not
possible to fully recreate the patterns of migration that have
occurred since contamination probably began to be introduced
forty to fifty years ago.
In the Baldwin Park-area, the uncertainty regarding the nature
of contaminant sources is very high. There will never be an
exact, complete understanding of the timing, location, and
magnitude of the original sources of contamination. The
distribution of contamination in groundwater is directly
related to the nature of these sources; although much mingling
and coalescing of contamination has undoubtedly occurred,
individual "slugs" of contaminants clearly continue to migrate
through the system. The variability of contaminant
concentrations at individual wells results from the effects of
these sources, as well as from the effects of pumping and
recharge, both artificial and natural. There is also evidence
of the presence of non-aqueous phase contamination in the
subsurface. This contamination is likely to have migrated as
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free product, and will continue to behave as ongoing
supersaturated sources of contamination in several locations in
the subsurface. The current and future extent of contamination
in Baldwin Park is, and will be, strongly influenced by the
effects of these ongoing residual sources.
Given all this uncertainty, and the virtual fact that it will'
never be eliminated, EPA does not consider simulation of
contaminant transport in the Baldwin Park area to be useful as
anYthing but a tool to evaluate the relative merits of remedial
alternatives. Accurate, local-scale predictions of the future
nature and extent of contamination can only be approximate
estimates. Nonetheless, as explained previously, it should be
possible, in time, to use ongoing, detailed data from
monitoring wells to better identify locations and magnitudes of
residual sources and better approximate the local-scale fate
and transport of contaminants.
C.3
The SaD Gabriel Basin Hodel
Hvdraulic Conductivity
The zones of hydraulic conductivity used in the current CFEST
model of the San Gabriel Basin are based on estimates of the
areally-averaged nature and behavior of the system. There is
no question that individual measurements at wells differ (as
they would be expected to) from these areally-averaged values.
The issue of the relationship between essentially point
measurements of parameters versus the behavior of the system on
a larger scale has been extensively studied and documented.
Consideration of the effects of scale and the size of the truly
representative elemental volume is a large part of the
development of conceptual and numerical models of groundwater
and other natural systems. In essence, as much data as
possible must be considered, in conjunction with the observed
behavior of the system, in the definition of parameters. There
can be just as much error or uncertainty in relying exclusively
on a single data set from a limited number of sampling points,
as it is to overly simplify and average spatially-varying
parameters.
For the San Gabriel Basin model, months of effort were spent
compiling and evaluating data from previous investigations and
from wells located throughout the basin. CDWR's previous work
in the basin (CDWR, 1966) was considered an outstanding
evaluation of the nature of the groundwater system on which to
base EPA's initial efforts. The geologic complexity of the
aquifer was further evaluated by an analysis of over 700
individual well logs. Estimates of hydraulic conductivity were
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.'
based on (1) the lithology identified at individual wells, (2)
specific capacity tests, and (3) aquifer tests. All of this
information was brought together to develop initial estimates
of individual zones of hydraulic conductivity, which were then
refined throughout the process of calibrating the model..
During more recent updates of the model, these initial
estimates have been further validated. The fact that
individual aquifer tests have yielded values both above and
below these estimates is considered further evidence of their
relative accuracy.
In the course of reviewing well logs, considerable effort was
made to identify layering or any systematic pattern of
lithologic variability with depth. . The results of this work
have been extensively documented (EPA, 1986, and 1992). The
apparent consistency of material properties with depth has more
recently been verified in some areas (including Baldwin Park)
by the d~tailed geophysical and lithologic data acquired in the
course of installing deep monitoring wells. Clearly, in some
areas, layering has been established to various degrees;
overall, however, there still appears to be only limited
lateral continuity associated with individual variations in
aquifer materials. The third dimension of the San Gabriel
Basin model thus considers no change in lithology and hydraulic
conductivity. (The. effects of p~ping from different depths in
the basin is, however, a very important variable that is
discretely represented in the third dimension of the numerical
model. )
The apparent lack of well-developed layering throughout much of
the San Gabriel Basin does not necessarily imply that the
system is entirely isotropic. Indeed, anisotropy in the
vertical direction can be inferred to exist as a function of
the vertical stress. As mentioned above, there may also be a
regional anisotropy in hydraulic conductivity in the horizontal
plane, given the likelihood of preferential pathways along
buried river channels. However, there is no direct evidence of
the geometry of these channels, nor of their degree of
continuity in one direction over another. Thus, this regional
horizontal anisotropy has been accounted for in the shape and
location of the various zones of hydraulic conductivity, and a
global anisotropy has only been established in the vertical
direction. Vertical anisotropy results in a greater resistance
to flow in the vertical direction than in the horizontal
direction. The adequacy of these assumptions is reflected in
the model's calibration.
A wide range of values of anisotropy was experimented with
during model development and calibration. The ratio of 1:10
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(Kz:Kxy) resulted in the best match between simulated and
obserVed conditions. The sensitivity of the model to this
parameter was tested by varying this value by orders of
magnitude in both directions, and was found to be relatively
small (EPA, 1992).
Boundary Conditions
Comments regarding boundary conditions and their effect on
simulation of groundwater flow in the Baldwin Park area appear
to refer to the manner in which the Sierra Madre and Duarte
fault systems are represented rather than to the actual
boundaries of the model. As described in the many EPA
documents describing this model (e.g., EPA 1986, 1990, 1992,
and 1993), the boundaries of the finite-element grid extend to
the margins of the alluvial aquifer. These boundaries,
depending on their location, are defined by conditions of no
flow, prescribed head, or prescribed flux. None of these are
near the Baldwin Park area, and do not directly affect flow in
that portion of the model. The Duarte fault system lies
between the northern boundary of the model and the Baldwin Park
area. The Duarte and Sierra Madre systems represent
significant boundaries to flow across them, as evidenced by
differences of up to several hundred feet in water levels on
either side of individual faults. In the San Gabriel model,
the effects of these faults are represented by individual rows
of elements of low hydraulic conductivity. This discrete
representation of the faults is consistent with observed
conditions, as evidenced by the model's calibration.
C.4.
Baldwin Park PS Modeling
Based on the number of comments received from the Coalition and
Aerojet/ALR regarding the San Gabriel Basin CFEST model
discussed above, it appears that the readers believe that the
modeling performed to date (as described in the FS Report)
played a significant role in the development of the Proposed
Plan for the Baldwin Park OU. However, for the FS, simulations
using the San Gabriel Basin CFEST model had just two primary
purposes: .
.
Modeling was used to estimate preliminary locations
and rates of groundwater extraction (the pumping
configuration) for a remedial action in the OU.
These data were needed to evaluate water use and
distribution options and to develop cost estimates
for the remedial alternatives. As described in the
Proposed Plan for the Baldwin Park OU, EPA will
verify or refine its preliminary groundwater
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extraction locations and rates during remedial
design, after interpretation of additional data that
will be generated during installation and sampling of
new groundwater monitoring wells. See Response B for
additional discussion of the distinction between
approximate extraction areas and pumping
configurations.
The model was also used to perform particle tracking
simulations of the "base case" scenario and the
pumping configuration described in the FS Report.
The particle tracking simulation, using particles
originating from near the Subarea boundaries
delineated in the FS Report, verified the remedial
effectiveness of the preliminary configuration over
an extended period of time (12.75 years). Additional
simulations may be required to evaluate the
effectiveness of any revised pumping configurations.
Thus, the modeling performed to date for the Baldwin Park QU
using the San Gabriel basinwide CFEST model was not a critical
element in the development of the ultimate configuration of a
remedial action for this QU.
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BALDW:IN PAlUt OU RESPONS:IVENESS StJJlllr.RY
RESPONSE D: The Role of the .etropolitan Water District of
Southern california in the Baldwin Park OU
Several commentors advocated a significant role for tbe
Metropolitan Water District of Soutbern California
(Metropolitan) in tbe clean up, in some cases asserting tbat
Metropolitan involvement would reduce costs or speed clean up.
Some comments expressed disappointment tbat EPA did not select
conjunctive use as its remedy. Tbis response clarifies EPA's
position on tbe role of Metropolitan in its remedy.
D.1 The ROD Allows But Does Not Prescribe Ketropolitan
:Involvement
In its Feasibility study, EPA evaluates the advantages and
limitations of several options for distributing treated
groundwater extracted as part of the remedy. The options are:
(i) to supply treated water to "local water purveyors; (ii) to
supply treated water to Metropolitan for export from the San
Gabriel Basin; and (iii) to recharge the treated water in
existing spreading basins, the San Gabriel River channel, or
tributary flood control channels. The FS and Proposed Plan
describe pros and cons associated with each water distribution
option." "
In the Proposed Plan, EPA expresses a preference for supplying
treated water to one or a combination of water purveyors in the
San Gabriel valley for distribution to their customers. EPA
identifies six purveyors in position to accept treated water,
including Metropolitan. The Proposed Plan and ROD do not,
however, commit EPA to supply all or part of the treated water
to Metropolitan, or to anyone or combination of purveyors.
The ROD allows treated water to be distributed locally ~ to be
exported from the Basin by Metropolitan depending on the
outcome of additional negotiations expected to occur in 1994.
In the ROD, EPA does not commit to supply treated water to
Metropolitan due to uncertainty about whether Metropolitan
involvement would increase or decrease project cost, and
uncertainty whether institutional issues associated with
Metropolitan involvement would delay the project. EPA
recognizes several potential benefits of Metropolitan
involvement including the benefits associated with providing
water users throughout Southern California with a new source of
water during peak demand periods and Metropolitan expertise in
building and operating large water supply projects, but these
potential benefits do not, as yet, outweigh potential cost and
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Baldwin Park ROD
"
institutional issues. EPA would enthusiastically support
Metropolitan involvement if it is demonstrated that doing so
will decrease the cost of the project and reduce institutional
barriers.
The impacts of Metropolitan involvement on project cost are
discussed further below. Institutional issues associated with
Metropolitan involvement are described in the Proposed Plan and
Feasibility study.
D.2
xmpact o~ Ketropolitan Xnvolvement on project Funding
Some comments assert or assume that Metropolitan is prepared to
pay a portion of the groundwater clean up costs in the Baldwin
Park area, and conclude that a project in which Metropolitan is
involved would cost less to EPA or PRPs than one in which they
are not involved. EPA does not believe that this conclusion is
warranted. Metropolitan staff have indicated the possibility
that Metropolitan would contribute to cleanup costs, but to
date has committed only to fund "enhancement costs."
Enhancement costs are costs in excess of the costs of clean up
that would result from Metropolitan imposing more stringent or
more costly requirements (e.g., additional pipelines or pumping
stations needed to deliver water to Metropolitan's existing
facilities, additional treatment 'costs resulting from
imposition of treatment requirements exceeding Federal and
State standards).
Metropolitan staff have publicly stated that Metropolitan may
be willing to contribute $25 million to a joint .
EPA/Metropolitan project in the Baldwin Park area. In their
written comments, Metropolitan states that "Metropolitan's
Board has supported, in conceDt, providing 25 percent cost
sharing for a conjunctive use cleanup project...to cover the
water supply benefits resulting from the more stringent
drinking water objectives as well as increased surface pumping
costs required to convey treated water to Metropolitan's
distribution system. II Metropolitan and EPA are conducting cost
studies to determine how much of the $25 million, if any, would
remain after paYment of enhancement costs. To date, EPA has
received no firm commitments from Metropolitan or others for
funding of clean up costs.
More than one commentor mentioned the potential for securing
outside sources of funding to pay for construction of a
project, through the Reclamation Projects Authorization and
Adjustment Act of 1992 (P.L. 102-575), which authorizes federal
funding of up to 25% for lithe design, planning and construction
of a conjunctive-use facility designed to improve the water
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Baldwin Park ROD
quality in the
utilization of
FY94 , Congress
this purpose.
It is our understanding, however, that this funding would most
likely reduce Metropolitan's contribution and not offset either
EPA or Potentially Responsible Party (PRP) funding. EPA is
seeking clarification on the use of the funding. We also note
that additional appropriations for FY95 and beyond ar~
uncertain.
San Gabriel groundwater basin and allow the
the basin as a water storage facility." In
appropriated $5 million through P.L. 103-126 for
D.3
x.pact of Metropolitan Xnvolvement on Project Size
Some commentors assert that Metropolitan involvement would make
it possible to carry out a more extensive clean up. EPA has
discussed the potential for Metropolitan or other parties to
increase the size of the remedy, but has not received any
commitment to do so. EPA will, however, consider any new or
more specific commitments before selecting a water distribution
option.
D.4
Xmpact of project Size on Metropolitan Xnvolvement
Metropolitan has expressed concern that there may be a
threshold flow rate below which they are not interested in
receiving treated water. In recent discussions, EPA and
Metropolitan staff have also examined the potential for a
"local conjunctive use" arrangement in which treated water
would be supplied to selected local purveyors who are now
dependent on imported supplies. Metropolitan may support such
arrangements even though they may not involve pumping treated
groundwater into Metropolitan's distribution system. Several
of the local purveyors identified as potential recipients of
treated water in Appendix D of the FS and Proposed Plan could
be supplied in a "local conjunctive use" arrangement.
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Baldwin Park ROD
,
BALDWIN PARK OU RESPONSIVDBSB BUHMARY
RESPONSE E: THB FEASIBILITY OF AIR SPARGIHG/SOIL VAPOR
BXTRACTION AT THE BALDWIN PARK OU
EPA received two comments recommending :further evaluation o:f
the :feasibility o:f employing air sparging and soil vapor
extraction technologies (AS/SVE) :for the Baldwin Park OU. As
described in the :following text, AS/SVE has not been used at a
site where the groundwater contamination is as large or deep,
or speci:fically to provide containment o:f a groundwater plume,
leaving signi:ficant technical uncertainties regarding the
e:f:fectiveness o:f AS/SVE in place o:f groundwater extraction and
treatment at the Baldwin Park OU. Due to these uncertainties,
and the cost o:f resolving these uncertainties, EPA has not
selected AS/SVE as a treatment technology :for this interim
remedy. .
B.l Backqround
AS/SVE is a relatively new technology in which air is sparged
(i.e., pumped) into the saturated zone either within or below
the contaminated portion of the aquifer. The contaminants are
transferred from the aquifer to the vadose zone by stripping or
volatilization, and/or transformed or destroyed through
enhanced biodegradation. Air and contaminants are subsequently
removed from the vadose zone by soil vapor extraction wells,
treated, and discharged. To date, air sparging applications
have been limited to fairly shallow contamination (typically
the upper 30 feet of the water table), in locations near
contaminant sources. Air sparging has not previously been
applied at a site where the contamination extends as deep as in
the Baldwin Park area (450 to 650 feet below ground surface,
200 to 500 feet below the water table). Nor has it been
applied across an area as large as the required QU containment
areas (up to about 5,000 feet wide). In addition, AS/SVE is
not typically used to provide containment of a groundwater
plume or plumes, the primary objective of the QU.
B.2
Technical Considerations
The following evaluation of the feasibility of using AS/SVE in
the Baldwin Park QU was focused on Subarea 1. Therefore, the
discussions that follow describe conditions specifically in
Subarea 1 (the upper area) of the Baldwin Park QU, but similar
considerations would apply to the use of AS/SVE in Subarea 3
(the lower area). As described below, there are several
technical problems associated with using AS/SVE to meet Baldwin
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Baldwin Park ROD
Park au objectives. These are related to the zone of influence
of the air sparging wells, contaminant removal rate, and the
impact of air flow patterns.
Zone of Influence
An objective of EPA's remedy is to contain an area of
contaminated groundwater in Subarea 1 that is approximately
5,000 feet across. Although specific data on the vertical
extent of contamination in this containment area are not yet
available, based on downgradient data, it is likely that
contamination extends across at least the upper 200 feet of the
aquifer. An air sparging well influences a cone-shaped portion
of the aquifer that extends from the sparging point up to the
water table. The angle of distribution of this cone in coarse
gravels is typically about 15 degrees (Nyer, E. and S.
Suthersan, 1993). Assuming this angle, along with a well depth
of 250 feet below the water table (500 feet total depth), and a
well spacing of 50 feet, would yield a radius of influence at
the water table of about 67 feet. The cones of influence
between adjacent injection wells would overlap, but would still
result in an overall zone of influence that does not provide
complete coverage of the contaminated area (i.e., a
considerable portion of the lower 30 to 40 feet of the
contaminated area would not be impacted by sparging). Further,
given the developed, urban conditions present across most of
the containment area and that there will need to be
approximately one SVE well for each injection well, it is not
likely that injection wells could be spaced closer than 50 feet
apart (this would help close the gap between adjacent cones in
the lower portions of the contaminated interval). In fact,
even the assumed 50-foot spacing may not be feasible. Thus,
the AS/SVE system that could feasibly be installed will not
likely be able to remove contaminants across the entire
contaminated interval.
contaminant Removal Rate
A typical AS/SVE system for a fairly aggressive remediation
project would attempt to sparge about one pore volume of air
into the contaminated zone every three to four days (personal
communication, Billings, 1993). Depending on site conditions
(type of contaminant, magnitude of contamination, soil
characterist~cs, etc.) this type of exchange rate could
potentially achieve clean-up goals in one to several years.
Given the injection well characteristics described above (250
feet below the water table and a 67-foot radius of influence),
the pore volume in each weil's cone of influence is
approximately 294,000 ft3. To inject one pore volume every 4
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Baldwin Park ROD
~
days would require a flow rate of more than 50 cubic feet per
minute (cfm) per well. Although the permeability of the
formation in Subarea 1 is quite high, injection rates this
large may not be achievable at a single depth. Nested
injection zones could help facilitate this high rate, but would
actually reduce the pore volume exchange rate in the outer
portions of the cone (because shallower injection would not
send air out to as large of a radius).
Assuming that the 50 cfm flow rate could be achieved, the
system still may not be able to meet the containment objectives
for the QU. As stated in the FS Report, a primary objective of
this QU is to inhibit migration of contamination into
uncontaminated or less-contaminated areas. To achieve this
objective, AS/SVE system will have to remove the contamination
from the groundwater as it travels through the system's zone of
influence. Assuming a radius of influence for each injection
well of 67 feet, the total width of the zone of influence is
about 134 feet. Groundwater flow rates in this area are
typically in the 3 feet/day range, so the travel time through
the zone of influence will be approximately 45 days. During
this time, only 11 pore volumes will have been sparged
(assuming 1 pore volume every 4 days). It is highly
questionable whether the AS/SVE system could remove a majority
of the contaminants from the groundwater given this total
sparging volume.
Air Flow Patterns
. .
Although questions remain regarding the way injected air
actually travels through the aquifer, the most widely accepted
theory is that the injected air travels vertically through
discrete air channels (Nyer, E. and S. Suthers an , 1993).
Recent laboratory studies also point towards the discrete
channel method of travel being dominant under most conditions,
but also indicate that flow of air as discrete bubbles is
possible in coarse-grained gravels (Ji et aI, 1993).
Regardless of the method of travel, there are likely to be
areas unaffected by sparging within the zone of influence. If
the air is travelling as bubbles, heterogeneities in the
subsurface environment are going to divert the bubbles, leaving
voids where bubbles do not travel.' And, if air travels
predominantly in discrete air channels, which are likely quite
narrow, there are certain to be significant portions of the
zone of influence unaffected by the channeling air flow.
Generally, an AS/SVE system should be operated in a pulsed
fashion to help minimize the reduction in removal efficiency
associated with the formation of permanent air channels.
However, in the QU area, pulsing the system will reduce further
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the number of pore volumes exchanged during the time the
contaminated groundwater is flowing through the AS/SVE zone of
influence. Thus, for the Baldwin Park OU, either the air
channelling or subsurface heterogeneities (by reducing the
effective area of sparging) or the pulsed operating scenario
(by reducing the number of pore volumes exchanged) will reduce
the removal efficiency of the AS/SVE system and limit the
ability of an AS/SVE system to provide contaminant containment.
B.3
cost Comparison
Despite the unfavorable technical considerations for use of
AS/SVE in the OU area, EPA has completed a rough, preliminary
cost estimate for an assumed AS/SVE system in Subarea 1 of the
Baldwin Park ou. This cost estimate is described below and
compared to the estimated cost of the pump and treat system for
Subarea 1, described in the FS Report.
The AS/SVE system cost estimates are based on data provided in
the EPA publication A Technology Assessment of Soil Vapor
Extraction and Air Sparging (EPA/600/R-92/173, September, 1992)
and on 'cost estimates provided in the FS Report.
Table RS-1 summarizes the air sparging versus pump and treat
cost comparison performed for Subarea 1. The costs associated
with the groundwater monitoring program are not included in the
Table, because the specific vapor and groundwater monitoring
program that would need to be implemented for the AS/SVE
program was not developed. As shown in the Table, if
assumptions made in the comparison hold true, total costs for
an AS/SVE system would be less than costs for the pump and
treat system proposed.
PumP and Treat Costs
The costs for the pump and treat action in Subarea 1 were taken
from the various cost tables provided in Appendix H of the FS
Report, primarily Tables H.6-13 and H.6-14 in Appendix H.6, and
Appendix H.3 (costs for "Treatment Plant 10 - 8,500 gpm").
Air SDaraing
The capital and O&M costs for an AS/SVE system in Subarea 1
have been estimated by assuming the number, depth, and capacity
of injection wells as described above: injection wells that
are 500 feet deep, with an injection well spacing of 50 feet
(100 total injection wells), and an injection rate of 50
cfm/well (5,000 cfm total flow rate). It is assumed that the
extraction wells will also be spaced 50 feet apart (100 total
133
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Baldwin Park ROD
.,
extraction wells) and be 200 feet deep. The total extraction
rate is assumed to be 6,000 cfm (for an AS/SVE system, the
extraction rate must exceed the injection rate).
Wells. Based on previous EPA drilling experience, the
extraction and injection well installation cost is assumed
to be about $80/foot drilled. Total drilling footage for
injection wells is 50,000 feet (500 feet deep times 100
wells) and for extraction wells is 20,000 feet (200 feet
deep times 100 wells). This results in a total well
installation cost of $5,600,000.
Treatment Facility. The air treatment facility costs are
based on the extracted air flow rate of 6,000 cfm.
Comparing this air flow rate to the off-gas flow rates
developed in the FS indicates that one of the large vapor-
phase granular activated carbon units described in the FS
Report would be sufficient to treat the extracted air.
other treatment facility costs (based on Appendix H of the
FS Report) include an air heater, GAC storage, a small
operations building, radiation monitoring equipment, and
site work. Based on costs presented in the FS Report, the
total cost for this treatment facility is assumed to be
$300,000. .
pipelines, Meters, Pump, and Blower. The injected and
extracted air pipelines are assumed to be the equivalent
of a single 8-inch diameter pipeline. using similar,
pipeline costs to those described in the FS Report, the
pipelines would cost about $7/diameter-inch/foot. For the
5,000 foot pipeline length, this results in a total
pipeline cost of $280,000. The cost of valves and meters
is assumed to be $700/well, based on EPA (1992), for a
total of $140,000.
The blower (air compressor) required for the assumed
AS/SVE system is quite large. The required discharge
pressure is at least 150 psi. This is based on a 250-foot
head of water (109 psi) and a release pressure of about 50
psi (to overcome frictional losses in the system and the
capillary entry resistance to displace the pore water).
This release pressure is estimated based on approximately
1 psi for every 5 feet of water depth in coarse gravels
(Nyer, E. and S. Suthersan, 1993). Based on a
manufacturers' quote, the required compressor would be
about 1,000 hp and would cost approximately $385,000,
including the electrical and mechanical appurtenances.
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Baldwin Park ROD
The vacuum pump for the SVE wells is sized at 375 hp to
provide a flow rate of 6,000 cfm with a 5 psi vacuum. The
estimated $70,000 cost for this pump and appurtenances is
extrapolated from information provided in EPA, 1992.
Air/water separation equipment is required prior to the
treatment facility. Costs for this equipment are about
$25,000, based on EPA, 1992.
The total cost for all equipment listed in this category
is $900,000.
O'K. The electrical costs for the AS/SVE system are based
on similar electrical rates as assumed for the extraction
wells in the FS Report ,($0.11/kw-hr). The blower and
vacuum pump (total of 1,375 hp or 1,030 kw), if operated
continuously, will cost approximately $993,000/year. The
estimated electrical costs for the treatment facility are
$7,200 based on a fraction of the costs presented in
Appendix H.3 for Treatment Plant 10.
Treatment facility O&M costs include carbon replacement,
off-gas air sampling, natural gas costs and operating
labor. Because contaminant concentrations in the
extracted air are unknown, carbon replacement cost
estimates are based on a percentage of the Treatment Plant
10 carbon replacement costs presented in Appendix H.3 of
the FS Report. There are 12 vapor phase granular
activated carbon (VGAC) units in the assumed Treatment
Plant 10 configuration versus 1 in the AS/SVE system
treatment plant, thus, carbon costs for the AS/SVE
facility are estimated to be 1/12 of the Treatment Plant
10 costs, or $65,000. Air sampling costs are estimated to
be $200/sample and one sample per week (total cost of
$10,400).
Natural gas costs, for the air heater, are estimated to be
$6,800, 1/6 of the Treatment Plant 10 gas costs. System
operating labor, including the treatment plant and all
other system components, is estimated at 1.5 hours/day at
$35/hour for a total cost of $19,000/year.
The total treatment facility O&M costs are $101,200/year.
Annual AS/SVE system maintenance costs are estimated at 2
percent of the construction costs, or $136,000.
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Baldwin Park ROD
,
E." SWIIJI18.ry
The potential for cost savings is interesting, but significant
uncertainty about the ability of AS/SVE to satisfy the remedial
objectives of the Baldwin Park au, and the cost of reducing the
uncertainty, make it inappropriate to select AS/SVE in this
interim remedy. Reducing or resolving the technical
uncertainties would require additional evaluations of the costs
and effectiveness of AS/SVE, including extensive pilot testing
to determine operating parameters, evaluate areas of influence,
evaluate other measures of effectiveness, and refine cost
estimates.
In their written
several apparent
and treat system
below:
comments, Chemical Waste Management mentioned
advantages of the AS/SVE system over the pump
proposed by EPA. Each of these is addressed
.
"Reduced energy expenditures by eliminating
groundwater/treated water pumping." Estimated O&M
costs for AS/SVE are less than for pump and treat due
to decreased carbon usage, although the total energy
expenditures between the two systems are actually
fairly similar. As shown in Table RS-1, the
electrical costs for the pump and treat system are
approximately $400,000Iyear greater than for the
AS/SVE system. However, this does not consider the
purveyor reimbursement portion of the pump and treat
system. Reduced energy expenditures by the purveyors
may offset a large percentage of the $400,000Iyear
difference.
.
"Eliminated capital construction costs of pipelines
and distribution facilities to deliver treated water
to purveyors and of ex-situ air-stripping towers. II
Although it is correct that all of the listed
facilities will be eliminated, it should also be
noted that considerable additional capital
construction costs will be required to install the
200 AS/SVE system wells (compared to the three
extraction wells needed in the pump and treat
system).
"Eliminate potential need for scarce recharge
capacity in the winter months." As described in the
Proposed Plan, the preferred distribution alternative
for this action is to deliver the treated water to
purveyors for local use. In this scenario, the
additional recharge capacity required would be
.
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Baldwin Park ROD
c-
minimal. In addition, as described in the FS Report,
during most periods (including winter) there should
be adequate excess recharge capacity available in the
area to accept treated water.
.
"Shortened remediation time frame over typical
groundwater pump and treat systems." AS/SVE has been
shown to shorten remediation time in many existing
cases, but these applications are typically in source
areas with shallow contamination. In the au area,
the AS/SVE system would be used to contain
contamination originating from multiple sources, but
the sparging wells would be distant from the residual
sources. Unless additional AS/SVE systems are
implemented at each source, the use of AS/SVE would
not likely shorten remediation time. In fact, as
described above, the AS/SVE system may not be able to
remove the contamination from the water that passes
through the system's zone of influence.
References tor Response E:
Ji, Wei,. et ale Laboratory study of Air Sparging: Air Flow
Visualization. Groundwater Monitoring and Remediation, Volume
13, No.4. Fall 1993.
Nyer, Evan K. and Suthan S. Sutheran. Air Sparging: Savior of
Ground Water Remediations or just Blowing Bubbles in tbe Batb
Tub? Groundwater Monitoring and Remediation, Volume 13, No.
4. Fall 1993.
u.s. Environmental Protection Agency. A Technology Assessment
of Soil Vapor Extraction and Air Sparging. EPA/600/R-92/173.
September 1992.
Personal communications
Billings, Gale.
Billings and Associates.
December 1993.
137
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Baldwin Park ROD
BALDWIN PARK OU RESPONSIVENESS SUHKARY
RESPONSE P: ARE 'l'JIE DATA AND TECBNICAL AHALYSES OBTAINED AND
COMPLETED AS PART OF 'l'JIE BALDWIN PARK OU FEASIBILITY STUDY
ADEQUATE TO SUPPORT 'l'JIE SELECTION OF A REMEDY?
In their joint submittal, Aerojet Gencorp (Aerojet) and Azusa
Land Reclamation (ALR) make numerous comments about the adequacy
of the data collection and analysis efforts completed as part of
the Baldwin Park FS. Some of these comments offer specific
criticisms. Dozens of other comments simply repeat claims that
EPA's data collection and analysis efforts are inadequate without
offering any specific criticisms. 'l'his response summarizes most
of the specific criticisms and identifies the location of EPA's
response. We do not respond to the dozens of claims that are not
accompanied by specific criticisms.
F.1 EPA Believes That Data are Adequate to Support the Selection
of Remedy
EPA strongly believes that the water quality, hydrogeologic, and
other data collected and analyzed as part of the Baldwin Park FS
are adequate to support the selection of a remedy. During the
RIfFS, EPA deliberately carried out the minimum amount of site
characterization work needed to support remedy selection,
deferring to the time of remedial design some sampling and
analysis work that could have been, and at other Superfund sites
often is, completed prior to remedy selection. The Baldwin Park
RIfFS included sampling and analysis efforts by EPA, water
companies, the Main San Gabriel Basin Watermaster, individual
businesses and property owners, and others over the past 10
years. See Section 3 of the FS for a description of RI efforts,
and Section 2.2 of the ROD for a list of EPA documents
summarizing RI work in the Baldwin Park area.
During the Baldwin Park RIfFS, EPA believes that it collected and
analyzed data adequate to:
. justify the need for remedial action in the Baldwin Park
area;
. specify remedial action objectives;
. specify approximate extraction areas;
. suggest preliminary extraction rates and locations (and
allow modifications to these rates and locations if
additional analyses warrant a change);
. identify the least costly treatment technologies capable
of removing contaminants from groundwater and aChieving
treatment goals;
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Baldwin Park ROD
"
. identify alternative pipeline alignments and potential
recipients of the treated water; and
. estimate project costs consistent with EPA guidelines.
In our response to specific Aerojet/ALR comments on the Baldwin
Park Feasibility Study (elsewhere in this Responsiveness.
Summary), we respond to and in many cases rebut specific
criticisms asserting errors .or omissions in EPA's data collection
or analysis efforts. In other cases, we agree with comments that
point out the need for additional data collection and analysis to
support the desian of the remedy (as opposed to the selection of
the remedy). The following table summarizes many of the specific
criticisms that EPA's data collection and analysis efforts are
inadequate and identifies the location of EPA's response.
";. .",..".,' '.".'."';::.';"';":'.'.".:-.::.-::;:..;.;:;.::::";:.:::;:-.':";.;'.::::';':-:::::::;:::.:-::::-".::;,;".;:;:;:;>:;:;:::::;:;.::;:;:;.::;:;::.;.:.;::::.;.:-:.;::-::;:;:;:;:;:;::-::;:::::;:::::::;.<::.:::::;::
...~~~~~~ig~~z4milll!!~f~~i~I!!!.I'llil!::::::...........
....ZHADEQUATB}......................\:::\}... .... .............;;>i... ... ... . ... H. ...
EPA's proposal does not address a
portion of the aquifer exhibiting the
highest concentrations of chemicals
in groundwater (in the vicinity of
well #W10WOMW1).
Plumes in Subarea 3 have stabilized
or reached equilibrium, and
additio~al study is needed to justify
remedial action in Subarea 3
EPA's modeling efforts, using the
CFEST model, did not or cannot
account for "baseline" conditions
(e.g., effects of production
wells/pumping, recharge at Santa Fe
spreading Grounds, other local-scale
details) and are therefore "invalid"
and "technically inappropriate."
EPA did not examine the potential
remedial effects of recharge, and did
not consider the effects of existing
wells/wellhead treatment. "High
volumes of recharge at the SFSG
and/or ISG resulting from the
alternatives presented in the OUFS
could further negatively impact a
poorly developed remedial action..."
139
EPA's remedy does
address contamination
at well IW10WOMW1.
See Response B
The preponderance of
evidence indicate
otherwise. See
Response A.
EPA's modeling does
account for baseline
conditions. See
response to comments
Aj#143, Aj#144, and
Response C.
EPA did evaluate the
impacts of recharge
and consider the
effects of existing
wells/wellhead
treatment. See
responses to comments
Aj#145 and Aj#179.
-------
Recharge at the SFSG changes the
groundwater flow direction from
southwesterly to easterly, not "more
southerly toward the recommended OU
extraction locations" as stated by
EPA.
"On the basis of the very sketchy
information regarding the use of
aquifer recharge as an independent
general response action in the OUFS,
it is apparent that EPA has not
conducted a complete technical
evaluation of remedial alternative
options..."
The CFEST model is not sufficiently
calibrated on a localized scale to
provide the degree of detail
necessary for evaluating OU
alternatives. ...[F]ailure to
recognize such deficiencies of the
CFEST model will result in
technically limited simulation
results if applied to localized OU
scale decisions."
"EPA's statement that "computer
simulations do not indicate that the
choice of water use option results in
a significant difference in remedial
effectiveness" demonstrates EPA's
limited evaluation of remedial
alternatives considered for the BP
OUFS."
No data exists on the vertical
distribution of contamination in
Subarea 1.
140
Baldwin Park ROD
.,
EPA apologizes for an
editing error. See
response to comment
Aj#181.
EPA did evaluate the
impacts of aquifer
recharge. See
responses to comments
Aj#145 and Aj#179.
We disagree. See
response to Aj#143 and
Response C.
We disagree. See
responses to Aj#179
and 190.
Data on the vertical
extent of
contamination are
sufficient to select a
remedy, although
additional data are
needed for design.
See response to Aj#58.
-------
.There is only one monitoring well in
Subarea 2 and no monitoring wells in
Subarea 3. Remedial action in
Subarea 3 is based on "an almost
total absence of characterization
information"
"A contaminant mass balance/transport
analysis ...is needed to determine
whether further remedial measures are
required [in) Subarea 3."
EPA's proposed remedy will allow more
highly contaminated groundwater
located north of the 210 freeway to
spread into less contaminated areas.
EPA failed to complete a Remedial
Investigation.
Baldwin Park ROD
Data from production
wells in and down-
gradient of Subareas 2
and 3 are adequate to
specify a remedy.
Additional monitoring
wells will be
installed during the
time of remedial
design. See response
to comment Aj#14.
Mass balance/transport
analysis is not needed
to justify action.
See Responses A and C.
Movement of more
highly contaminated
groundwater into less
contaminated areas is
a limitation in the
cleanup of large areas
of groundwater
contamination. See
Response B.
This claim. is without
merit. See response
to Aj#259
P.2 Additional Data Collection and Analyses are Heeded During
the Time of Remedial Design
There is an important difference in purpose between the ROD and
remedial design phases of the Superfund process. The ROD
specifies the general nature of the remedy, but does not, and
should not, specify project design details. EPA regulations
state that the Record of Decision should identify and summarize
the major "technical aspects of the selected remedy that are
later refined into design specifications" in the remedial design
phase of the. Superfund process. EPA guidance advises that the
ROD should be limited to describing "major treatment components"
and "engineering controls" that will be part of the remedy, as
well as any "performance standard that the remedial action is
expected to achieve."
Completing investigation work pre-ROD to specify design details,
and specifying design details in the ROD, is neither legally
141
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I
[
I-
I
Baldwin Park ROD
required nor sensible. The time lag between completion of the
ROD and completion of remedial design for a project the size of
the Baldwin Park OU remedy is typically 12 to 24 months. Design-
related investigation work completed pre-ROD may prove obsolete
by the time the design is prepared, minimizing its value.
Completing work pre-ROD that may need to be redone post-ROD would
be inconsistent with good engineering judgment and common sense.
Nor does it make sense to "lock in" project details in a ROD when
additional data collected post-ROD may suggest refinements to
those details. If EPA specified a design detail in the ROD such
as which of the several potential recipients will receive treated
groundwater from the remedy, implementation of the project could
be delayed if data or discussions post-ROD suggest it would be
cheaper or quicker to supply water to a different recipient.
F.3 BPA Record of Decision for the Baldwin Park au Includes
Recommendations for Additional Data Collection and ADalyses
Durinq the Time of Remedial Desiqn
As described in the Baldwin Park Feasibility study, Proposed
Plan, and elsewhere in this Responsiveness Summary, EPA believes
that additional data collection is required during the time of
remedial design. The FS includes recommendations for a
monitoring program to be completed as the first step during the
time of remedial design; this Responsiveness includes revised
recommendations. See response to comment Aj#58.
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Baldwin Park ROD
......INDIVIDUALS AND INTEREST GROUPS...
I. Comments by Allan Hill (AH)
AB/l. COaaentor notes that the FS states that the 29,000 gpa (rather than
19,000 gpa) extraction scenario appears to be the "optimua scenario" for use
with the reaecUal alterzaatives (page 7-12). Be asks for docWDentation that a
19,000-gpa project stops aigratioD of the cODtaaiDatioD and further
explanation why BPA proposed a 19,000-gpa plan.
EPA ReSDonse: section 7 identifies three Subareas of groundwater
contamination in which remedial action may be warranted. Section
7 also includes a statement that extraction of 29,000 gpm is
"optimum" if the goal is to limit the migration of contaminated
groundwater in all three Subareas (and if modeling assumptions
remain valid). . (The "optimal II rate for extraction in two
Subareas is 19,000 gpm.) In this statement, EPA did not intend
to imply that extraction in the three Subareas is necessarily the
optimum remedy.
In subsequent evaluations, described in sections 11 and 12 and in
Response B included in this Responsiveness Summary, EPA compared
the advantages and limitations of extracting and treating
contaminated groundwater in two, three, or greater than three
Subareas. EPA concluded that remedial action in two Subareas was
the best option because it offered significant and relatively
certain benefits, will significantly limit the migration of
contaminated groundwater in and beyond the Baldwin Park area,
will remove significant amounts of contaminant mass, appears to
be implementable, and is technically defensible. This
Alternative was presented in EPA's Proposed Plan and selected in
this Record of Decision. We have prepared and included as
Response B a detailed explanation of the benefits and limitations
of EPA's remedy. We do not repeat that discussion here, but
instead refer the reader to. Response B of this Responsiveness
Summary .
We see, in hindsight, that EPA's decision to propose and select
the smaller of the remedies evaluated in the Feasibility Study,
and the use of the word optimal to describe the pumping
configuration of the larger remedy, has left some reviewers with
the impression that the selected remedy is less than adequate.
We hope that the explanation offered in this response and in
Response B better explains the rationale for EPA's decision.
AB/2. eommentor suggests that BPA proposed the 19,000 gpm project to satisfy
"the Watermaster group." eommentor writes: "I understand the watermaster
group believes they can _only dispose of 19,000 gpID within the adjudicated
area. Thus to avoid the question of export they. will agree to switch from
143
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Baldwin Park ROD
.
using ..lls ~t yield that much fro. the clean areas of the valley to accept
only that aaount of processed water fro. ..lls within the cont-mipation zone.
I have the understanding this is the fix ~t watermaster hopes to use to
prevent Conjunctive Use by Metropolitan or any other group from outside the
adjudicated area. ~ere are areas in the watershed of the San Gabriel River
~t must deP8Dd upon :imported water today that would be logical users of
10,000 918 of processed water from the operable unit. A good example is Puente
Valley."
EPA ReSDOnSe: Commentor is incorrect in assuming that EPA
developed its proposal primarily to satisfy the Main San Gabriel
Basin Watermaster, local water purveyors, or other local
interests. EPA has consulted extensively with local agencies,
purveyors, and interest groups, but the decision to propose
approximately 19,000 gpm of extraction represents current EPA
policy emphasizing containment, experience gained at numerous
other groundwater sites about the capabilities and limitations of
"pump and treat" technology, and the distribution of contaminated
groundwater in the Baldwin Park area. See Response B for a more
detailed explanation of the rationale behind EPA's proposed
pumping configuration.
Potential recipients of treated water include users that would be
supplied through export, in the Puente Valley and elsewhere. See
section 9 and appendix D for a list of potential recipients, and
an evaluation of the feasibility of supplying treated water to
users in the Puente Valley and other portions of the San Gabriel
Basin.
AB#3. Co8aentor requests that "SPA adopt a two phase iaplementation of the
29,000 918 extraction scenario where the first phase would be the 19,000 gp8
to be utiliaed br the ..atenaaster group. ~e second phase would be a 10,000
918 scenario ~t would be water for export by anr group other than the
existing local puapers. It could be part of a much larger conjunctive use
project or the existing crclic storage program of ~ee valleys M.W.D. or
Metropolitan Water District. If the institutional problems of the
adjudication provision prevent.ing new exports could not be overcome, the
10,000 gpa of processed wat.er could be discharged into the river for capture
br exist.ing downst.re.. facilities and eventual use br the cit.ies downst.ream of
the watenaaster extractors service areas. ~e watenaaster has such an
arrangement with the industrial firms cleaning up contamination in Puente
Valley."
EPA ResDonse: Comment or raises three issues: the size of the
remedy, the recipients of treated water from the remedy, and the
potential. for future EPA projects after implementation of the
selected remedy.
See AH#l and Response B for additional discussion of the size of
the selected remedy. See Section 9 for a discussion of water use
options, including the feasibility of discharging water into the
river or other surface water channels. We note that any
significant discharge of water into surface water channels must
consider the requirements and implementation history of the Long
144
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Baldwin Park ROD
.,
Beach Judgment. The Long Beach Judgment declares that users
downstream of the San Gabriel Basin (the "Upper Area" defined in
the Judgment) are entitled to an annual average of 98,415 acre-
feet of "usable water." The majority of this entitlement has,
however, been supplied historically through "natural" surface and
subsurface flow (resulting from precipitation and to a lesser
extent, discharge of treated sewage effluent). A minority of the
entitlement, termed "make-up water," has been met through the
purchase and transfer of imported water. Between the 1979-80 and
1991-92 water years, users in the San Gabriel Basin supplied an
average of 8,213 acre-feet of make-up water to downstream users.
The range in this period was 0 to 28,279 acre-feet/year. See
Twenty-ninth Annual ReDort of the San Gabriel River Watermaster
for 1991-92, City of Long Beach, et al., vs. San Gabriel Valley
Water Co., et al., Case No. 722647 - Los Angeles County.
There is the potential for future EPA projects in the Baldwin
Park area. EPA's selected remedy is an "interim action" that may
be supplemented or modified if information collected during
implementation of the project indicates the need for additional
groundwater extraction. EPA's project includes a comprehensive
groundwater monitoring program (see response to comment Aj#58)
that will generate data to evaluate the project's effectiveness.
II. Comments by Alton J. Amdahl
The comments submitted by Alton J. Amdahl are identical to
comments submitted by Allan Hill. See comments AH#1 to AH#3 and
EPA responses.
III. Comments by Bill Robinson (BR)
BR# 1a. "I C8DJ1ot support BPA' & proposeci interim "cont;.aiDJDent;." proj ect Opt;.ion
#1." "Recommendation: Option #3 Large Scale 29,000 GPN COnjunctive Use
Alt;.ernat;.ive combined with clean-up and regional export."
EPA ResDonse:
Comments noted.
BR#1b. "BPA .ust exert beavier influence to force a coaproaise bet;.ween local
and regional int;.ere8t;.s, rather than follow the local lead by accepi;.ing
inst;.it;.ut;.iona1 problems and locally inspired doubt;.s about;. wat;.er end use as a
penaanent obstacle to clean up of the basin. "COntaiDaent;." options are of
lit;.tle wort;.b to the public, but;. allows local purveyors, utilit;.ies who already
aonopoliae the aanagement;. of the basin, t;.o monopolize the BPA clean up by
145
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Baldwin Park ROD
pushing their cODtaiDmen~ O~iOD #1. ~e basin is a public resource DO~ a
priva~e lake (reservoir).-
EPA ResDonse: We disagree with comment or that EPA's Proposed
Plan is "of little worth to the public," that the clean up is
"monopolized" by local interests, or that "water end use is a
permanent obstacle to clean up." The decision to emphasize
containment and mass removal reflects current EPA policy and the
experience gained at sites with groundwater contamination
throughout the countrY. See response to AH#2 and Response B,
which further describe the rationale behind EPA's proposal.
BR#2. -BCODoaics of scale aD4 the stark reali~y of peraaDen~ wa~er shortages
in So. california in the Den decades argue tha~ all clean waur prociucecl by
the larges~ cleanup plan~ BPA can build will SOOD fiDei a beneficial end use.
~e wa~er indus~ry rou~inely uses paper ~rades and crecli~s ~o even ou~ the
peaks and valleys of annual wa~er usage. ~e8e ~echDiques can be appliecl ~o
wa~er prociucecl w keep a large scale plan~ opera~ing 12 8IODths per year a~
full capaci~y. ~e BPA goal should be both ~o enhance COIlllDOD local rou~ine
cyclic swrage (pu~ &Dei ~ake) prograa. ~ether with incr.ased regional export
opportUDi~i.s. -
EPA ResDonse: We agree that there is no fundamental reason that
19,000 gpm, 29,000 gpm, or greater amounts of water could not be
put to a beneficial end use. We wish to correct any
misconception that difficulties in distributing treated water are
the primary factor considered in determining the size of EPA's
proposal. The primary considerations are technical, as discussed
in AH#l and 2, and Response B.
We agree that "paper trades" may help in the distribution of
water from EPA's proposed project. EPA representatives have met
with water purveyors in the Baldwin Park area and the Main San
Gabriel Basin Watermaster to discuss possible trades, and will
continue discussions in the hope of reaching agreements to
distribute water from EPA's proposed project.
EPA's responsibility is to develop and implement remedial actions
needed for cleanup. EPA supports improvements in the use of San
Gabriel Basin's water resources, as long as it does not increase
the cost of or interfere with cleanup.
BR#3. -~e 8IOs~ likely problem tha~ could defea~ the cODjUD~ive use O~iOD or
aDV Op~iOD is DO~ UDders~aDding the width, leDgth and de~h aDd dire~ioD of
8IOvemeD~ of the plume and ai8s-si~ing the plan~ or D~ designing enough
flexibili~y of plan~/flexibili~y of cOD~aaiDa~ed wa~er feeder pipe to keep ~e
facili~y suppliecl wi~h cODtaaiDa~ed wa~er during i~s en~ire prociu~ive life.
Facili~y si~ing decisioDS .us~ be based UPOD ~rough programs of wa~er
~es~ing, analysis &Dei flow 8Od.eling. ~ese Drocrrams aus~ be cOD~rolled bv
Public aaeDcies guidecl by public in~eres~ goals DO~ priva~e 8ODopolisecl local
ageDcies with DOD public in~eres~ ax.s to grind. Locally, well ~es~ing is
cOD~rolled by the Alhaabra judgemeD~ Wa~enaas~er, an ara of L.A. 's Superior
Court, an ageDcy realis~ically cOD~rolled by ~e five larges~ wa~er u~ili~ies
existen~ in. the basin, an organizatioD wi~ apparen~ly enough influence to
146
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Baldwin Park ROD
drive ~e proposed projects to ~e detriment of ~e public interest, i.e. a
cleaner basiD."
EPA ResDonse: We agree that extraction locations should be based
on "water testing, analysis, and flow modeling." EPA will
consult with local agencies and others, public and private,
interested in and affected by the contamination and EPA's
.selected remedy, but EPA will remain responsible for making final
decisions on extraction locations and other project details.
BR#4. .SPA authority can overcoae opposition of ~e local water purveyor
8ODOpoly if SPA properly sites a facility, ~en exports part of ~e excess
production froa a proposed 29,000 GPII .Clean up. operable unit. Export rules
. under ~e LoDg Beach judgemeDt River Watermaster has beeD routine in ~e basin
transferring to Central basill cUrreDtly 85,000 A.P. a year in orderly, stable
and lODg-institutionalized fashion. ~e local monopoly interest has been
blowing s.oke at SPA apparently iIlcreasing SPA's export BDXiety in order to
selfishly aaiDtain ~eir nearly total cODtrol over ~e water resources of ~e
valley..
EPA ReSDonse: EPA disagrees that its "export anxiety" exceeds
its level of anxiety about any other distribution options. EPA
will select the distribution option that meets its remedial
objectives and to the extent feasible, minimizes cost, minimizes
institutional barriers that might delay or preclude
implementation, and satisfies state and local preferences.
We note that most of the 85,000 acre-feet (af)/yr of water
supplied to downstream users in the central basin to meet
obligations of the Long Beach Judgment has been met by natural
subsurface and surface flow. The increment actually purchased to
meet obligations of the Judgment ("Make-up.Water") has averaged
8,213 acre-feet over the last twelve years. Also see response to
AH#3.
BR#5. .~e San Gabriel Valley cODtains Dearly all built out communities wi~
liaited, well understood, stable demands for water. DemaDd increases about 1
percent per year. ~e proposed interim-containment solutioD - damages ~e
public interest by delayillg cleanup while furthering ~e private interest
control of ~e public basin resources. SPA funds and all public funds aust
serve public heal~ and safety, which demands ~e quickest feasible cleanup
solution. ~e S.G. basill as ~e .private lake. sceDBrio can be subordiDBted to
an improved proposal; a dual purpose approach that allows: 1. protection for
local water iIlterest for ~e beneficial use of water of ~e basin and; 2. ~e
regional beneficial interest ~rough orderly plBDDed exports of produced
excesses.
~e past decade. have brought broad beDefits ~rough ~e provisioDs of ~e
Long Beach judgemeDt (see comment #4). Future wider opportunities and beDefits
to ~e region 881' occur through support and sponsorship of SPA SuperfUDd.
Metropolitan Water District and Pederal Bureau of Reclamation fUDding and
federal legislatioD sponsorship of Cong. B. ~rres."
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Baldwin Park ROD
EPA ResDonse: EPA's proposal does not delay cleanup; it
represents the most significant step toward clean up made to
date. Nor does it represent any shift in control from public to
private interests. Also see responses to comments BR#1-4.
BR#6. -~e BPA propo.ed .01u~~oD O~~OD 1 damage. the publ~c ~~ere.~'by DO~
prov~d~g for opportua~~~e. for reg~oDal beDef~c~al ~~ere.~, hobb1.e. the
cleaa up goal, aad lo.e. the projec~ possible fua~g from Ne~ropo1.~taa Wa~er
D~.~r~ct, Bureau of Recl"'~~oD, ~ee Valleys M~c~pal Wa~er D~str~c~ aDd
CeD~ral Ba.~ Nua~c~pal Wa~er D~s~rict.-
EPA ReSDonse: This comment largely duplicates comments 1-5. EPA
is unclear how its proposal "loses ... possible funding" from
Metropolitan or others. EPA has received no firm commitments
from any of these agencies for funding of clean up costs. Nor
has EPA ruled out or in any way limited the possible involvement
of Metropolitan or others. Distributing water to Metropolitan
remains an option if it is demonstrated that supplying water to
Metropolitan will increase the extent of clean up, lessen costs,
speed implementation, or otherwise benefit clean up. There mav
be benefits if Metropolitan is involved, but at present, it is
unclear if Metropolitan involvement would provide a net benefit.
Also see response to Tor#l and Response D.
BR#7. Large .ca1.e cODjuactive use be~~er .erves both the local ~~eres~, because 8Or-
COD~aaiDa~ed wa~er i. cleaaed up aad removed fas~er, 8I1d eahaDce. the regioDal
~~ere.~ through ~crea.ed wa~er .upply froa export. ~e export UDder O~iOD #3 ala
iDclude. preferred ---ller $200-$300 per A.P. cle8l1 up eo.~.. ~e l.arge projee~
O~iOD o~iai..e. per A.P. cleaa up co.~., whi1.e ...1.1 .ca1.e project. Op~iOD. alao.~
double trea~8D~ cos~.. ~e ...1.1 projec~s oDly d~scerDable advaa~age: i~ ..~~a~s
the cODtrol of the 1.ocal parochial ~~eres~s of the wa~er purveyor cartel. S.G. bas~
export. a1.ready occur aDDually through ~~tier Darrow. iD aa orderly
~s~itutioDa1.i.ed fashioD ~ CeD~ral Bas~ by pipel~es, uadergrouad and occasioDal
surface f1.o... . .
EPA ReSDonse: This comment largely duplicates comments BR#1-6. We
agree that larger projects could limit migration of contaminated
groundwater in additional areas and increase the amount of
contamination removed, but again note that the size of the project has
been determined based primarily on technical considerations, as
discussed in AH#l and AH#2, and Response B.
IV. Comments by the East Valleys Organization, Toxics Task Force
(EVO)
DOll. ComID8D~or -supports ~he plaa, bu~ [does] DO~ thi.Dk tha~ i~ goes far enough."
Vie.. BPA's proposal a. overly cau~ious "a~ a ~iae .hen bold act~oD and ~g~tive
801.u~~OD. are requi.red..." Bxpresse. UDder.~8DdiD9 of "CODeerD. by so.e ~ ~he local
.ater e088UD~~y of lo.~g authori~y ~ IIWD," bu~ be1.ieve. tha~ "a greater threa~ ha.
come from the opposi~e ~end8Dcy: a balkaJLized poli~~cal structure and a parochial is.
148
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Baldwin Park ROD
in attitudes that have hampered decisive action and a comprehensive approach to the
vise us. of scarce resources."
EPA ResDonse: Comments noted. EPA does not view its proposal, whose
estimated "30 year present value" exceeds $100 million, as a "cautious"
or "unimaginative" step in the cleanup. See Response B for a more
detailed discussion of EPA's rationale for the scope of its remedy.
BV0#2. Rec0888l1ds that "EPA shou1.d support conjUDctive use vith the Metropolitan
Water District... to aake it possible to carry out a 80re extensive clean up, ...
help ensure Federal Bureau of Reclamation and IIWD participation in fUDding for the
facility, [aDd to aake) the San Gabriel Basin aquifer... [a) resource that vill help
all of Southern California cope vith its critical vater aanagement problems."
EPAResDonse: EPA remains interested in increasing the involvement of
Metropolitan Water District if it is demonstrated that Metropolitan's
involvement would increase the extent of clean up, lessen costs, speed
implementation, or otherwise benefit clean up. At present, it is
unclear if Metropolitan involvement would provide these benefits. See
response to Torl1 and Response D.
V. Comments by Friends of San Gabriel River (FSG)
FSQ#1. Co888Dtor [does) "not agree the proposed project of extraction of 19,000 gpa
at Baldvin Park Operable Unit vill achieve the objective of compliance vith the
requirements of federal law." ColIIIDentor recOllllRends that EPA adopt Alternative 3
(described in the Proposed Plan), favoring extraction of 29,000 918 (rather than
19,000 gpa) and involvement of Metropolitan Water District of Southern California.
ColIIIDeDtor asserts that extracting 29,000 gpa would speed clean up, reduce costs,
allow EPA's remedial objectives "to be achieved before the first effects of a 19,000
gpa prograa could even be detected," [and that) "it is the duty of EPA to achieve as
auch cleanup as those who are involved will finance on there [sic) own."
EPA ResDonse: As stated in the Proposed Plan and the ROD, EPA believes
that its selected remedy, calling for extraction and treatment of
approximately 19,000 gpm of contaminated groundwater, satisfies the
statutory requirements of Section 121 of the Superfund law and best
satisfies the Superfund evaluation criteria. The remedy is protective
of human health and the environment, cost-effective, complies with all
applicable or relevant and appropriate requirements, utilizes permanent
solutions to the maximum extent practicable, and satisfies the
statutory preference for treatment.
Commentor's assertion that extracting 29,000 gpm would allow EPA's
remedial objectives "to be achieved before the first effects of a
19,000 gpm program could even be detected" is unfounded. See Response
B for a detailed discussion of EPA's rationale for proposing extraction
of approximately 19,000 gpm, rather than 29,000 gpm, of contaminated
groundwater.
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Baldwin Park ROD
#
It would be senseless and irresponsible for EPA to determine extraction
rates based on the ability of EPA or others to fund the project, as
comment or suggests, rather than on technical analyses.
See Response B for a discussion of the rationale for the size of the
selected remedy and Response D for a discussion of the role of
Metropolitan Water District. .
FSG#2. C08aentor believes that treated groundwater that is not distributed to water
purveyors could be piped to spreading basins and flood control ch8l1Dels, eliaiDating
the risk that extraction of contaaiDated groundwater would need to cease due ~o
iDadequa~e deaand by w.~er company customers.
EPA ReSDonse: Recharging treated groundwater remains an option in the
Record of Decision. Recharge is not specified as the only acceptable
method of water distribution or disposal due to its potential .
disadvantages, which include inadequate spreading basin capacity, and
loss of usable water to the Central Basin. See Section 9 and the
response to comment AH#3 for a more detailed discussion of the
limitations and disadvantages of recharge.
FSG#3. Co8aentor also advises tha~ EPA -include conjunc~ive use by DO~ only
Me~ropoli~ Wa~er District but by any other group ~a~ will supply financing."
EPA ResDonse: EPA's plan allows for the supply of treated groundwater
to purveyors now dependent on supplemental sources of water, which may
result in increased conjunctive use of local and imported water
resources.
VI. Comments by Rayall Brown [presumed to be Royall Brown]
(RB)
RBll. Comaen~or found the microfila version of ~he AdmiDis~ra~ive Record a~ the Wes~
Covina Library -unreviewable. - Comaentor believed tha~ ~he library' s viewing
equipmen~ could only handle 3S ma fila, rather than ~e 16 ma forma~ used to
aicrofila the AdmiDis~ra~ive Record. .
EPA ResDonse: We regret the difficulty which the commentor had
reviewing the microfilmed version of the Administrative Record.
commentor's difficulty may have resulted from his unfamiliarity
the microfilm reader.
in
The
with
Commentor first informed EPA staff of his difficulty in reviewing the
microfilm (located at the West Covina Public Library) at an EPA public
meeting held on 5/20/93. After the meeting, EPA staff contacted Mr.
Bruce Guter, the documents. librarian. Mr. Guter viewed the microfilm,
including a frame identified by the commentor as unreadable (film 4,
frame 1710). Mr. Guter had no problem reading it. Mr. Guter noted
that there are two different lenses available - one for regular forma+
150
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Baldwin Park ROD
documents and the other for maps and other oversized documents.
Commentor may have used the wrong lens. We are confident of library
staff's willingness to help any members of the public having difficulty
reviewing the Administrative Record; we have found staff at the West
Covina Public Library extremely cooperative. No other commentor has
expressed any problem in reading the microfilm; to EPA or, as far as
the head librarian knows, to library staff.
At the public meeting, EPA staff offered to place a paper copy of the
Baldwin Park Feasibility study at the library to facilitate its review.
(The Feasibility study was the document of greatest interest.) The
Feasibility Study was mailed to the library on May 25th, 1993.
RBl2. Co_8D~or id8D~ifies several wells be~W88D ~e San Bernardino PreewaJ' (1-10)
and ~e railroad ~racks aloDg ValleI' Blvd where COD~._4n.n~ levels have exceeded
MCLs. Co_eD~or Do~es ~~ ~e Proposed Plan does DO~ address cOD~aaiDa~ioD .~ ~ese
wells, and ~~ cOD~..iDa~ioD sou~ of ~e freewaJ' will cOD~inue ~o spread.
eo-eD~or cODcludes ~.~ ~e proposed projec~ will Dot meet BPA' s aigratioD control
objectives.
EPA ResDonse: We agree that there is contaminated groundwater
downgradient of the proposed extraction in the "lower area." We make
this observation on page 7-5:
"Contamination has been detected downgradient of Subarea 3 (the
lower area] at concentrations at or near MCLs ..."
The comment highlights an important limitation of EPA's proposal. No
realistic cleanup proposal can completely stop migration of all
contaminated groundwater across an area as large as the Baldwin Park
area; any proposal that includes a realistic, finite number of
extraction locations will limit migration in some areas but not in
others. If the proposed extraction locations were moved some distance
south to address lower levels of contamination, more highly
contaminated groundwater upgradient of the extraction locations would
migrate unimpeded. As discussed in greater detail in Response B, EPA
believes that its proposal best meets its remedial objectives by
limiting migration and removing contaminant mass from areas in which
remediation will provide the greatest benefit.
Finally, we note that EPA's proposed project is an interim action which
may be supplemented in the future.
0#3. COmaeD~or Dotes ~t a treatmeDt f~ilitJ' has been installed bJ' La Puente
ValleI' CountJ' Water District at wells liated for poteDtial shutdown in the PS, ~able
7-3. COmaenwr rec~eDds ~t this and other treatment facili~ies cODtinue to
operate as long as the wells served bJ' the equipa8D~ show contaainatioD, pointing out
that i~ would "not be econoaical" to discoDtinue the use of insulled clean up
facilities in order to build other facilities.
EPA Response: EPA is aware of the installation and operation of a
treatment facility at the La Puente Valley County Water District's
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Baldwin Park ROD
..
wells. Water quality data available through 1992 indicate that
groundwater at the District's wells is less contaminated than
groundwater at the Big Dalton well and other locations to the north.
EPA included the District's wells in a list of "Wells for Potential
Shutdown or Reduced Extraction" as a reflection of our preference that
extraction in clean or less contaminated areas be minimized. EPA
recognizes, however, the District's need to extract water to meet its
water supply responsibilities.
EPA has no plans to limit operation of the District's wells or
treatment facility.
RBl4. C08aeDi:or Do~es i;ha~1 ".. .the Peasibi.li.~y 8~udy i.DcUca~es the "optiawa"
enra~i.oD scenari.o i.s 29,000 gpID a~ specific areas and if other wells are used a
larger 88Oun~ Deeds i:o be enra~ed i:o si:op the spread of COD~aainati.OD. CurreD~ly
at two well fields south of the 1-10 freeway the San Gabriel Wa~er eompaDY also has
:installed treatmeD~ facilities. ~e u.e of the clean up equi.pmeD~ south of the
free.ay :indi.cates a ..jor probl_. A~ preseD~ there are more .ell. south of the
free.ay connected ~o clean up facili~i.es than there are :in the Baldw:in Park Operable
UDit DOrth of the freeway. ~e ID~eria Plan Deeds i:o be al~ered ~o reflec~ the
exi.steDce of :installed clean up faci.li.~i.es south of the freeway. As a re.ul~ I
request ~he EPA adopt an :in~eria plan i;ha~ enra~s 29,000 gpa or more from wells :in
the Baldw:in Park Operable UDi~."
EPA ResDonse: EPA acknowledges the existence of several existing and
planned treatment facilities. The extent to which continued operatior
of any of the existing facilities will satisfy EPA's remedial
objectives will be determined during the design phase of the project,
making use of the most up-to-date water quality data. See response to
comment AH#1 and Response B for a detailed description of EPA's
rationale for proposing extraction of 19,000 gpm of contaminated
groundwater, rather than 29,000 gpm.
RBIS. Co_eDi:or "oppose[s) the recommended plan of 19,000 gpa enrac~ioD a. i.~ does
Dot ref1ec~ the :infras~ru~ure of the San Gabri.e1 River Bas:in." CommeD~or reports
i;hat an und~~ed San Gabri.el River Wa~eraa.~er Annual Report show. the 10wer area .i.~h
an annual eD~i.tl..eD~ of 85,600 Acre Peet of wa~er from the upper area, and i;ha~
10,000 gpa CODt:inUOUS pwap:ing equals 16,133 Acre feet per year. eo...eD~or concludes:
"~us if 10,000 gpID of the 29,000 gpID under alterDa~ives 2 or 3 was discharged down
the drai.Dage sys~.., the lower area could capture it and it would become groundwater
:in the 10wer basin. It could in future years be part of the .usable water docuaeDted
aDDually by the river .a~erlD8s~er. As a resu1~, ..., the :infra.~ru~ure exi.s~s ~o
dispose of all of the 29,000 918 enrac~i.oD a1~erna~ive wi~hou~ u~i.liz:ing any of the
exist:ing local pwapers efforts ~hat oDly can dispose of 19,000 gpa."
EPA ReSDonse: In the Proposed Plan, EPA expresses a preference that
treated groundwater be distributed to water purveyors for direct use,
but includes recharge as a backup water use option in case agreements
to distribute water to purveyors cannot be reached.
We agree with commentor that infrastructure exists to dispose of
treated water into local flood control channels, but there is a
significant disadvantage of this method of "disposal." See response to
AH#3.
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Baldwin Park ROD
..
RBl6. eo_entor notes that the Watermaster: "has aade arrangeaents to allow
Responsible Part~es in the Puente Valley who extract polluted water and to clean ~t
up and to d~scharge ~t to the drainage systea. ~is water becomes part of the usable
water under the rules of ease #722647. 1n Baldwin Park the wateraaster should not be
allowed to claia no infrastructure or capability to dispose of IIOre than 19,000 gpa
as they have aade accomaodations for the clean up of cont-miDaDts in Puente Valley
that is part of the San Gabriel River Systea."
BPA ResDonse:
Watermaster has made no such claim.
RBl7 . Co8aentor' s concluding recOlDl8endation is that BPA adopt..... a staged approach
to well head clean up that would allow for a future project that would involve
conjunctive u.e of well. in the Baldwin Park Operable Unit by Metropolitan Water
District or others such as ~ree Valleys llUDicipal Water District that is within the
San Gabriel River watershed."
BPA ResDonse: We encourage additional clean up projects by parties
other than EPA that are consistent with our remedial objectives.
VII. Comments by Sierra Club (SC)
(The Sierra Club submitted comments dated June 20, 1993 and August 9,
1993. The August comments include the Sierra Club's testimony
presented on August 6 at the public hearing conducted by the California
Assembly Committee on Groundwater Contamination and Landfill Leakage.)
June 20. 1993 comments
SCI1. "Representatives of the Sierra Club... are pleased that BPA has come forward
with a specific plan to begin cleanup. However considering the analysis presented in
the Baldwin Park Operable Unit Feasibility Study, we would reco-end selection of
alternative 3 as the preferred plan for several reasons."
BPA ResDonse:
Comment noted.
SC#2. "pirstly, Figure 12-1 clearly shows that options 2, 3 or 4 all provide a higher
degree of long-t~ra effectiveness than Opt~on 1. ~e study states that extracting
29,000 gpm total from three subareas within the Baldwin Park/1rwindale/Azusa area is
the "optiaua" scenario. We urge BPA to select the opt.ion which will best serve the
long tera interests of San Gabriel Valley residents. Achieving the IIOst effective
solution is worth the effort of overcoming difficulties in impleaentation."
BPA ResDonse: We agree that the higher pumping rates included in
Alternatives 2, 3, and 4 would provide a higher degree of long-term
effectiveness, but do not believe that their implementation is
warranted at present. See response to AH/1 on the use of the word
optimum and Response B on the rationale for the size of the remedy.
Difficulties in implementation are not the primary reason for selecting
a project calling for the extraction of approximately 19,000 qpm
(rather than 29,000 qpm) of contaminated groundwater.
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Baldwin Park ROD
.,
sel3. -If nece..ary BPA could request the court, which oversees the San Gabriel Basin
adjudication, to allow 10,000 gpa to be exported froa the basin under the condition
that the Metropolitan Water District of Southern California (NWD) recharge a like
880unt of iaported water to replace it. It would .e.. that there is a rea.onable
likelihood that the court would approve such a arrangement since it will provide the
.ost efficient and co.t effective cleanup of the San Gabriel Basin.-
EPA ResDonse: See Response D for a discussion of the role of
Metropolitan Water District in the remedy.
sel4. -Option 3 has the additional advantage of including NWD in the cleanup process.
~e entire clean-up effort would benefit fro. NWD's water quality technical expertise
and fiDaDcial resources. ~e availability of these resource. to assist in the cleanup
of the San Gabriel Basin is certainly in the long tera be.t interest. of the citizen.
of the SaD Gabriel Valley. Option 3 would, in addition to providing water to those
areas which have water rights iD the MaiD San Gabriel Basin, would also provide water
to comaUDities in the greater San Gabriel Valley who do not have such rights.-
EPA ResDonse: We agree that Metropolitan would bring water quality
expertise but are uncertain whether they will contribute financial
resources to the cleanup. See Response D.
Sel5. -Lastly Option 3 is preferable because it would place EPA in a stronger
negotiating position with Potentially Re.ponsible Partie. (Peps). ~e Peps are
already asking BPA to reduce the amount of water extracted to less than 19,000 gpa.
Selecting the option with a higher extraction rate will give EPA more room to
negotiate.-
EPA ResDonse: EPA is legally-required to select the remedial
that best meets the nine superfund evaluation criteria (e.g.,
maximizing effectiveness, minimizing cost). Improving one's
negotiating position is not among the nine criteria.
option
Auaust 9. ~993 comments
sel6. -...~e Sierra Club strongly favor....a joint contamination cleanup-conjunctive
u.e prograa ... ~e benefits of integrated.. .88D8gement of all local surface aDd
groundwater...are becoming increasingly obvious to progressive water managers aDd the
general public in SOuthern California. It i. understandable that BPA CBDDOt take the
lead in plBDDing for the use of groundwater stored under a conjunctive use program.
As I understand it, one of your main concerns is that you have not yet received a
fira comaitment from either the Metropolitan Water District of SOuthern California
(NWD) Or a local San Gabriel Basin water agency for a larger trea1:ment prograa
(29,000gpa as coapared to 19,000gpm) iD the Baldwin Park area. We would urge that
BPA work with NWD and local water agencies to address this is.ue. As you bow, the
San Gabriel Basin is aD adjudicated basin in which numerous water rights holders
claia the exclusive right to manage local resources as they see fit, and it will take
tiae to work out a solution that is ultimately beneficial to all parties. I believe
BPA would be reaiss iD adoptiDg the attitude that it should merely seek the simplest
short-tera solution and then walk away froa the situation. Although it may not have
been iDtended, your co_ents at the August 6 heariDg gave that i.8pres.ion [co_ents
by Jeff aoseDblooa]. I therefore urge that you give further consideration to a .ore
comprehensive cleanup-conjunctive use plan for the San Gabriel Basin.-
EPA ResDonse:
Comments noted.
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Baldwin Park ROD
Bel7. Are "concerned first and foremost that the health of the residents and workers
of the BasiD be protected by :i.Dsur:i.Dg that dr.i.Dk:i.Dg water provided by public and
private retailers to consumers meet all current and prospective Federal and State
standards. Secondly, we are concerned that the existiDg groundwater contaai.Dation not
be peraitted to eXPand beyond its present boundaries, thereby contaaiDatiDg
additional areas. !rI1irdly, we waut to see that further cont...iDetion does not occur
through discharge of additional toxics iDto the groundwater, and that those parties
who were respoDsible for past COD~-..i D-tion be held liable for their actioDs. ADd we
want to ensure that the abundant groundwater resources of this BasiD are effectively
aanaged so this area can be relatively self-reliaut for its water Deeds rather than
rely on large quautities of costly iaported water froa Northern California and the
Colorado Ili. ver.
For these reasonB the Sierra Club favors the adoption of the comprehensive plan
prepared by the Pederal Environmental Protection Agency to extract and treat 29,000
gallons per ai.Du~e (gpa) of groundwater froa three subareas withiD the BaldwiD
Park/IrwiDdale/Azusa superfund ContaaiDation Site. BPA has presented scientific data
iDdicating that this would be the optimum level of treatment to effectuate systeaatic
cleanup of existiDg cODtaaiDation and prevention of cont..:i.DatioD migration to
additional areas." .
EPA ResDOnse:
See response to comment AH#l and Response B.
Bela".. .!rI1e Metropolitan Water District of Southern California is prepared to
participate on a 25% cost-sharing basis. (See IIWD Board Letter of Jauuary 28, 1993)
!rI1e participation of IIWD is likely to be crucial to the success of this project, both
because of lIWD.s strong financial position and of that agency's acknowledged
expertise in addressing complex problem. of water treatment proces.es neces.ary to
aeet Federal and State drinking water standards.
Addition [al] funding up to.an additional 25% is also available from the UB Bureau of
Reclamation pursuant to Section 1614 of the Public Law 102-575 (Reclamation projects
Authorisation and Adjustment Act of 1992) for "the design, plann:i.Dg and constructioD
of a conjunctive-use facility designed to improve the water quality in the San
Gabriel groundwater basiD and allow the utilisation of the bas:i.D as a water storage
facility." Given the difficulty of obtainiDg local aud state fund. to clean up
cODtaaiDated groundwater iD the San Gabriel Basin, it only makes sense to aake use of
this additional Federal fund:i.Dg. II
EPA ResDonse: As described in response to comment Tor/1 and in
Response D, the magnitude and use of any funding provided by
Metropolitan Water District or P.L. 102-575 remain uncertain.
Sel9. "It is our understanding that because of limited sUpPOrt from local water
purveyors and objection froa some responsible parties, BPA is recommending that
treatment facilities for cleanup of the BeldwiD park/Irw:i.Ddale/Azusa area be limited
to producing only 19,000 gpa. ~he Sierra Club believes this level of treatment would
not aeet the long-tera objective of cleaning up existing contamination, nor would it
be the most cost-effective. Furthermore, it is doubtful that IIWD or the Bureau of
Reclamation would participate :i.D a smaller-scale project, since the conjunctive use
benefits of storing imported groundwater in the Bes:i.D would be significantly reduced.
Without lIWD's financial and technical support, and without Bureau of Reclaaation
fund:i.Dg, the prospect. of effective action in the near tera to accomplish both
groundwater contaaiDation reaediation and conjunctive use objective. will be
significantly diaiDished."
EPA ResDOnse: EPA's decision to select a remedy calling for the
extraction of approximately 19,000 qpm is based primarily on technical
155
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considerations; it is not due to limited support from water purveyors
or Peps. See Response B for an explanation of the size of EPA's
remedy. .
seilO. " .. .ne Sierra Club would like t:o .ee a .ore .eaningful role played by the
califoroia .BDviroD8en~al Pro~ec~ion Agency and the Regional Wa~er Ouali~r Board in
addre..ing the San Gabriel BasiD' s grouudwa~er cont:..., n.~ion. ne Regional Board has
been chronically uuderfuuded aDd uuders~affed in recen~ years and a. a resul~,
although i~ has dedica~ed suff, has beeD uuable t:o be as effec~ive a. i~ should be
iD developiDg aD uuders~aDding of the D8~ure 8Dd exten~ of grouudwa~er cont.-'n.~ion
in the Basin, ideD~ifying sources of this contamina~ion, and ~aking effec~ive
eDforc888D~ a~ion agains~ the responsible parties. I~ is essen~ial ~~ fuuding for
this agency be increased t:o en.ure tha~ remaining sources of con~aai.na~ion are
brough~ under full con~rol and tha~ pas~ source. of contamina~ion are held
responsible for their a~ion...
EPA ReSDonSe:
Comment noted.
VIII. Comments by the Superfund Working Information Group
(SWIG)
SWIQ#I. "..a commendable effort has been ..de by SPA ~o develop a cleanup projec~ 1
addre.s the problea of grouudwa~er [in the Baldwin Park area]..., [and tha~ on the
whole], ... SPA'. presen~ plans for r..edia~ion of the Baldwin Park-Azusa-Irwindale
contamiDaD~ plume se... ~o be going in the righ~ di.rec~ion, ~oward a final .olu~ion
of cleanup and con~rol of the VOC con~aai.na~ion in .the Main San Gabriel Basin."
EPA ResDonse:
Comment noted.
SWIQ#2. COIIIID8D~or also asks tha~ SPA consider "the prac~icali~ie. of enlarging the
ou~pu~ of the projec~, if feasible."
EPA ResDonse: EPA refers to the selected remedy as an interim action,
to reflect the possibility that additional projects may be needed in
the Baldwin Park area. EPAwill use information collected after
construction and operation of the selected remedy to help determine the
need to enlarge or in other ways modify the project. EPA's decision to
select a project extracting and treating approximately 19,000 qpm
rather than a larger project is discussed in Response B.
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.,
...FEDERAL AND STATE LEGISLATIVE REPRESENTATIVES...
IX. Comments by Hilda Solis, Assemblywoman, 57th District,
California Legislature
80111. Coaaen1;or urges BPA -to consider t;he .erits of a conjunctive U8e prograa as a
.eans to remedy bot;h VOC and Ditrate contamination... - Commentor argues t;hat
conjunctive use would offer t;he -potential 1;0 cleanup t;he contaaination in t;he Basin
while at t;he sliae tiae bot;h providing aD environaentally-soUDd _t;hod for storing
water and offering a fiDaDcial package which ought to prove beDeficial to all
affected parties.-
EPA ResDonse:
See Response D.
X. Comments by Esteban Torres, Representative, 34th District, U.S.
Congress
~rl1. -I aa struck by t;he fact that t;he alt.ernat.ive BPA prefers (Alt.ernat.ive ODe) is
t;he least. environaent.ally aoUDd alt.ernat.ive of the four. ... Alt.ernat.ive One would
pump 19,000 gpa ... 1;0 be used on1v b)' t;he local wat.er purveyors... Alt.ernat.ives
T.bree and Pour would pump 29,000 gpa... T.be fundament.al difference between t;hese t.wo
a1t.ernatives [one and four) is that. the t;hird and fourth alt.ernat.ives provide a
conjunct.ive use eleaent. and would pot.ent.ially remove one-t.hird .ore cont.aminant.s froa
t;he wat.er basin.
OD t;he surface, Alt.ernat.ive Four appears t.o cost t;he taxpayer significantl)' aore t.haD
Alternative ODe. However, last year Congress authorised funding 25' of t;he SaD
Gabriel Basin Project in Section 1614 of t;he aeclaaation Projects Authorizat.ion and
Adjust.aent. Act. of 1992 (Public Law 101-575). ADd as a result., t;he Board of Directors
of t;he Met.ropolit.an Wat.er Dist.rict (1PtD) c088it.t.ed significant. resources t.o t;his
worthwhile project..
If )'ou review Alt.ernat.ive One, (capit.al cost.: $47 81llion, t.o be ent.irely funded b)'
local businesses which are held respon8ible for t.he cont.aminat.ion) and compare it. t.o
Alt.ernat.ive Four (capit.al cost.s: $78 million wit;h only $39 million (50') funded by
local businesses and 50' by Sect.ion 1614 funds and MWD funds) I trust you will
conclude t;hat. Alt.ernative Four i8 bett.er fro. every perspect.ive. Alt.ernative Four
will give us t;he capacit.y t.o remove .ore cont-minaat.s froa the groundwater and will
8ave t;he local business community $8 million.
Even if BPA were 1;0 select a clean-up t.echnology that. goes beyond' air stripping' to
somet;hiDg like t;he 'liquid granular activated carbon' process recommended by IIWD, t;he
total cost of Alternat.ive Four would be $100 81llion, wit;h $50 81llion coming froa
t;he local business coaaunit.y and $50 million coming froa MWD and Section 1614. ~e
additional $3 81llion in local cost.s is a ...11 price t.o pay to achieve a 33 percent.
increase in cont_.inaat. reaoval. I suggest. that. t;he st.andard aeasure of cost.-
effect.iveness (Cost./t.on reaoval) should be t;horoughl)' analyzed in light. of t;he above.
Addit.ionall)', I want. you 1;0 know that., at. 8)' urging, the California COngressional
Delegat.ion has been actively pursuing a $5 million FY '94 appropriat.ion for t.he
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.'
iapleaentation of Section 1614 because the conjunctive use project is excellent
PUblic policy. Southern California gets an enhanced supply of water which reduces
pressure on the Colorado River and Northern California, and, .ore iaportautly, the
citiaens in the San Gabriel Valley get a cleaner supply of water.
If the reason that SPA has recolIIRended Alternative ODe is based on what has been
called the 'institutional probl..., associated with Conjunctive Use, I strongly
recolIIRend that the Agency take another look at its rationale. While I realiae that
BPA doesn't want to be "water broker" in Southern California, it can certainly assist
negotiations so that other, and perhaps .ore appropriate agencies, aanage our water
resources. Bowever, I don't believe that any 'institutional problea' justifies
.electing a clean-up alternative which accomplishes le.s clean-up at greater cost to
area busines.es and residents." '
BFA ResDonse: Internal EPA policy required an immediate response to
Congressman Torres. EPA's response (without the enclosed table),
delivered in a letter dated September 9, 1993, is reprinted here. Also
see Response D.
Honorable Esteban E. Torres
U.S House of Representatives
1740 Longworth House Office Building
Washington, D.C. 20515
Dear Mr. Torres:
Thank you for your letter of August 10, 1993 to Wayne Praskins,
one of our Superfund Project Managers, concerning the u.S.
Environmental Protection Agency's (EPA) Proposed Plan for the Baldwin
Park Operable Unit of the San Gabriel Valley superfund Sites. We
appreciate your continued support for efforts to clean up the soil and
groundwater contamination in the.San Gabriel Basin and your specific
comments on the Feasibility Study and Proposed Plan. We will, as
always, seriously consider your views in reaching a decision on how to
proceed with the clean up.
As you know, EPA's primary responsibility is to clean up the soil
and groundwater contamination. We share your goal, however, of also
identifying and supporting clean up projects that would improve the use
of California's limited water resources. We have been working with
staff of the Metropolitan water District of Southern California
(Metropolitan) and other local water agencies for more than three years
to evaluate and work out potential arrangements for a joint clean-
up/conjunctive use project.
I believe that we are in agreement on most aspects of the cleanup.
In the remainder of this letter, we wish to explain the rationale for
our position and respond to your comments on the involvement of
Metropolitan and the size of the proposed project.
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7nvo1vement of MetroDo1itan Water District
In the formal Superfund feasibility study prepared for the Baldwin
Park Operable Unit, we evaluate four clean up options (i.e.,
"Alternatives"). Alternatives One and Two assume distribution of
treated water to local water purveyors; Alternatives Three and Four
"provide a conjunctive use element" (i.e., assume the distribution of
treated water to Metropolitan).
EPA's Proposed Plan incorporates elements of each of these
Alternatives, including the potential for conjunctive use. (Your letter
mistakenly asserts that EPA's proposal is identical to Alternative
One). EPA's Proposed Plan recommends that treated water be distributed
to anyone or a combination of six water purveyors, including
Metropolitan. (See pages 7 and 11 of Proposed Plan.) Our proposal
does not specify Metropolitan or any other single purveyor as the one
and only recipient of treated water, because of the many unresolved
cost and institutional issues that make it uncertain whether
Metropolitan involvement would in fact reduce costs or speed clean up.
We believe that it would be unwise for EPA to commit to distributing
water only to Metropolitan or any other recipient at this time.
Metropolitan involvement does offer potential advantages to the
Baldwin Park Operable Unit such as their expertise in building and
operating large water supply projects and the benefits associated with
providing consumers throughout Southern California with a new source of
water during peak demand periods.
EPA would in fact wholeheartedly support Metropolitan involvement
if it would decrease the cost of the project and reduce institutional
barriers. Unfortunately, neither advantage has been demonstrated.
Metropolitan is attempting to better define project costs and resolve
institutional issues, but there remains the risk that Metropolitan
involvement could increase the cost or delay implementation of the
project. The impacts of Metropolitan involvement on project cost and
institutional complexity are discussed further below. Issues
associated with Metropolitan involvement are described in more detail
in the Proposed Plan and Feasibility Study. . .
KetroDo1itan FuDdinq contribution
Your letter presumes that one-half of the cost of a project in
which Metropolitan is involved would be funded in part by Metropolitan
and in part by a Federal appropriation authorized by Public Law 102-
575. You use this assumption to conclude that a project in which
Metropolitan is involved would be less expensive than one in which they
are not involved. Our understanding differs. Metropolitan staff have
stated their intent only to fund "enhancement costs." Enhancement
costs are costs in excess of the costs of clean up due solely to
Metropolitan's water supply requirements (e.g., additional pipelines or
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Baldwin Park ROD
.
pumping stations needed to deliver water to Metropolitan's existing
facilities, additional treatment costs resulting from imposition of
treatment requirements exceeding Federal and state standards).
Metropolitan has committed significant resources to studying the
feasibility of a conjunctive use project, and to securing outside
sources of funding to pay for construction of a project, but to date,
Metropolitan has not provided any commitment to fund clean up costs.
In addition, our understanding is that any funding from P.L. 102-
575 would reduce Metropolitan's contribution and not offset either EPA
or Potentially Responsible Party (PRP) funding. Our conclusion is that
the costs borne by EPA or the local business community would not change
whether or not Metropolitan is involved. Please let us know if our
understanding is incorrect.
Institutional ComDlexitv Associated with MetroDolitan Involvement
As described in more detail in the Feasibility study, there are
other potential complications associated with supplying water to
Metropolitan that could delay clean up. They include the need for an
agreement to store and export water in and from the Basin, Metropolitan
compliance with the California Environmental Quality Act, and
Metropolitan concerns about liability resulting from involvement at a
Federal Superfund Site. Perhaps the most significant complication is
that Metropolitan can benefit from receiving treated water only durin
the spring and summer peak demand months (probably May to September,
but the actual tim~ng would vary year to year). If treated water is
supplied to Metropolitan for use only during peak periods, it would be
necessary to develop arrangements to supply treated water to one or
more secondary recipients during fall and winter offpeak months. EPA-
and Metropolitan are investigating the feasibility of such
arrangements, but they remain uncertain.
Pro;ect size
In your letter, you recommend that EPA select the larger project
evaluated in Alternatives Three and Four, rather than the project
evaluated in Alternative One. Alternatives Three and Four evaluate a
project involving the extraction and treatment of contaminated
groundwater from three areas (the upper, middle, and lower areas);
Alternative One evaluates a project involving the extraction and
treatment of contaminated groundwater from two areas (the upper and
lower areas)'. Alternatives Two and Three would result in extraction
of approximately 29,000 gallons per minute (gpm); Alternative One would
result in extraction of approximately 19,000 gpm. '
Our decision to propose a 19,000 gpm project, rather than a 29,000
gpm project, is due primarily to uncertainty about the benefits of
extracting in a third area (the "middle area"). Additional extraction
in the middle area would more rapidly reduce contaminant concentratio--
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Baldwin Park ROD
in portions of the San Gabriel Basin aquifer, but by an unknown amount.
Our ability to quantify the benefits of additional pumping is limited
by uncertainty in the precise extent of contamination, in the relative
masses of contamination in different portions of the aquifer, and in
the presence of preferential flow pathways and other local-scale
aquifer phenomena that will affect the time required for clean up. Our
decision to propose extraction in two rather than three areas reflects
these physical uncertainties, the cost of the proposed clean up, and
the fact that EPA's proposal is an interim action which may be
supplemented in the future. A secondary reason for proposing 19,000
gpm rather than 29,000 gpm is the added complexity of distributing an
additional 10,000 gpm of treated water.
We are still evaluating other comments on our proposal. Some
comments call for the 29,000 gpm project, others call for a smaller
project of approximately 8,500 gpm. We should note that conjunctive
use remains an option in either a 19,000 gpm or 29,000 gpm project.
We thank you again for your continued support for the clean up of
the San Gabriel Basin. I hope that this letter addresses the concerns
expressed in your letter and better explains the rationale behind our
proposal.
Enclosed is a table summarizing comments submitted to EPA on the
Baldwin Park Operable Unit Feasibility Study and Proposed Plan, as you
requested in your letter of August 16, 1993. If I can be of further
assistance, please call me or my Congressional Liaison Officer, Sunny
Nelson, at (415) 744-1562.
Sincerely,
[Original signed by]
John c. Wise
Acting Regional Administrator
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.,
...THE CALIFORNIA DEPARTMENT OF TOXIC SUBSTANCES
CONTROL.. .
XI. Comments by The California Department of Toxic Substances
Control (DTS)
MSII. -We concur with the United State. BDviroD8ental Protection Agency' s (US BPA)
.elected reaedy...-
EPA ResDonse:
Comment noted.
MS#2. MSC does DOt believe that BPA' s proposed remedy will be iaplemented in a
tiaely lI&DDer using the BPA'. -enforcement first" approach. Foresees operation of
BPA'. .elected remedy no earlier than 1997 and note. that by this tiae the
contaaiDation in the lower sone could move al80st three quarter. of a aile
dOWDgradient. R.co..end. that BPA iDitiat. inve.tigation. needed for remedial de.ign
independent of and concurrent with negotiation. to .peed project iapl..entation.
Al.o rec0888Dd. that BPA expand/augment the current Big Dalton Wellhead ~reataent
Plant project to include the inve.tigations, well., and trea'bDent facilities needed
for contaiDaent of the .outhern end of the :&one of contaaiDation.
EPA ResDonse: Comments noted. EPA intends to initiate negotiations as
planned in 1994 and will consider steps to begin investigation work
needed for remedial design early in the negotiation process.
MS#3. Ask. that -flexibility [be) written into the Record of Deci.ion (ROD) to. allow
alternative 3 or 4 (or a variation of the.e conjunctive use alternatives) to be
iaplemented if the institutional arrangements can be completed so as not to delay
project implementation."
EPA ResDonse: EPA's Record of Decision includes flexibility to supply
treated water to purveyors for local use or export, or for recharge.
MS#4 (submitted as comment 1a). In this cOlIIIDent and the two subsequent co_ents,
MSC states ita belief that "the objectives stated in appendix E for the groundwater
8Onitoring program do not adequately describe all the information needed for the
design, for 8ODitoring of the effectiveness of the alternatives, or for determining
if aquifer restoration i. feasible."
MSC .tates the groundwater 8OnitoriDg program should "provide accurate
deteraiDation. of ground water flow direction. and seasonal variation of the flow
direction. ~i. will include 1) characterisation of both hori:&onal 8Dd vertical
gradient. within the au area, 2) the extent of the capture :&one aroUDci each
extraction well, 3) the effect of recharge in the nearby spreac1iDg grounds, and 4)
the effect: of ground water production on the periphery of the operable unit
boundaries. Our concern is that the proposed monitoring system will not provide
accurate ground water level information due to the predominant use of production
wells with aultiple .creened interval.. Water level. froa the.e well. can be bia.ed
by vertical gradient.. ~e propo.ed 8Onitoring .y.tea .hould be e.tabli.hed by fir.t
evaluating the existing well. for their suitability based on screened interval and
presence of vertical gradient.. We believe a much larger number of pie:&ometer
clu.ter. will be needed to accurately depict the ground water flow directions than
currently indicated in appendix E."
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Baldwin Park ROD
EPA ResDonse: We agree that water level data should be collected to
allow for accurate determinations of horizontal and vertical gradients
in the vicinity of .the remedial action. We agree that the data should
depict significant temporal variation in gradients and reflect any
effects of nearby recharge or pumping.
We recognize the limitation of production wells noted in your comment:
that water levels measured in production wells reflect average
pressures across the screened interval. Because relatively little
information in available to determine vertical gradients, we intend to
first sample existing wells and install and sample fifteen new
monitoring well clusters (we have increased the recommended number of
wells - see response to Aj#58), which will provide information on the
magnitude of any vertical gradients. If significant vertical gradients
are detected in the new wells, complicating the interpretation of water
level data collected from production wells, we agree that additional
monitoring wells or piezometers may be needed to replace existing
wells. .
MS#S (subai~~ecl as commen~ lb). "Provide addi~ional dau on ~he properties of ~e
. aquifer in ~e operable unit area. !rhese data include de~ of a11uvium, 1i~01ogic
characteri:&a~ion, organic material content of ~e alluvium, and ~e hydrau1ic
conductivity and storativity data obtainecl from pumping tests "i~ observation wells
or slug tests."
EPA ResDonse: We agree that the monitoring program may include
measurements of hydraulic conductivity and other aquifer properties.
needed to more accurately simulate groundwater flow in the Baldwin Park
area. Additional flow modeling may be completed to refine extraction
rates and locations, and to evaluate the performance of the remedy
after installation. We are uncertain, however, of the intended use of
data on soil organic content or other properties that are typically
used to simulate contaminant transport, rather than groundwater flow.
We remain open to collecting additional data, however, if their use is
clarified.
MS#6 (subaitted as comment 1c). "Provide additional dau on ~e attenuation
aechani..s which are affecting ~e rate of con~aminan~ IIOvement. !rhis wou1d include
characteri:&a~ion of 1) ~e effect of sorption and dilution ~rough ~e use of tracer
studies "i~ compounds which are not biodegradable, and have similar sorptive
properties as ~e v01atile organic compounds, 2) ~e natural aicrobial populations in
~e aquifer, and 3) ~e stoichiometry of electron donors and acceptors."
EPA ResDonse: As in the previous comment, we are uncertain of the
intended use of data that are typically used to simulate contaminant
transport, rather than groundwater flow. We remain open to collecting
additional data, however, if their use is clarified.
MS#7 (subai ~ted as coaaent 2). "!rhe proposecl plan aentions ~e exis~ing wellhead
treatment plants (~s) being operatecl by ~e Valley COunty Water District and ~e La
Puente Va11ey COunty Water Dis~rict. Xt does not however sute tha~ ~ey wi11 be
considerecl as part of ~e remedy. !rhese exis~ing treatment plants could fora an
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Baldwin Park ROD
t'
integral part: the reaedy and ..y provide considerab1.e savings since there is no need
for connecting piping to distribute treated water t:o the purveyors. At a a:iD:iaua, the
decision on whether to incorporate these treat:ment plants in the reaedy should be
based on an evaluation conducted during the reaedial design phase.-
EPA ResDonse: We agree with the comment. The contribution of existing
projects in the Baldwin Park area to EPA's remedial objectives will be
determined during remedial design.
DTS#8 (suba:itted a. c08llDent 3). -The FS rec08llDend. ertraction of ground water in the
upper 400-500 feet of the aquifer. Figure 3-9 indicates that high concentrations of
VOC'. are present between 400-600 feet deep in the aquifer. Brtraction should be
conducted in the upper 600 feet in the aquifer. Brtraction over a greater depth
interval wi1.l require increases extraction rate. to achieve the s... capture zone..-
. .
EPA ResDonse: We agree that high levels of contamination may be
present across the upper 600 feet of the aquifer in portions of the au
area. Extraction wells will need to capture water from across the
. entire extent of high-level contamination, and the FS should have
stated that extraction would be necessary from the upper 400 to 600
feet of the aquifer. The preliminary extraction well configurations
included in the FS extend approximately 400 to 550 feet into the
aquifer, and their influence likely extends beyond the base of the
well. However, as stated in the Proposed Plan, actual extraction rates
will be determined during remedial design. At that time, additional.
data will be available on the depth of contamination and the actual
extraction wells will be designed accordingly.
DTSI9 (.ubmitted a. comment 4). -On table 5.5: cancer Slope Factors 1.isted for
benzene, carbon tetrachloride, chlorofora, .ethylene chloride, aDd
tetrachloroethy1.ene are les. t:han the cancer slope factor. listed by the Ca1.ifornia
EDvironaental Protection Agency (Cal/EPA). The Cal EPA s1.ope factors are AHARs
and should be used in the toxicity assess.ent. Regarding cross-route extrapolation,
if only an oral RfD has been deteraiDed for a chea:ical, as a defau1.t, the oral am
should a1.so be used for ca1.culating risks via the :inhalation and dermal routes of
exposure.-
EPA ReSDonse:
slope factors.
Responsiveness
significantly.
We have recalculated excess cancer risk using Cal EPA
As presented in Table RS-2 included in this
Summary, the risk estimate does not change
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-
...WATER PURVEYORS, WATER DISTRICTS, AND THE
WATERMASTER...
XII. Comments by the Main San Gabriel Basin Watermaster (WM)
WIIIIO. fte Main San Gabriel Basin Watenua.ter (Watenaaster) states that -In general,
we concur with the concept described in the Proposed Plan including the use of
existing wells for extraction and treataent, and the us. of treated water to supply
drinking .ater to the Basin residents [rather than recharge]. - Watenuaster offers to
work with BPA to locate extraction aDd 8Onitoring .ells, aDd to aake arrang_ents for
distribution of treated water. Wateraaster also DOt.S that a portion of the
Wateraaster ~echDical Plan for BasiD Ground-Water Cleanup closely re.emble. BPA's
Proposed Plan.
EPA Response:
Comments noted.
XIII. Comments by Metropolitan Water District of Southern
California (MWD) .
NWD#1. -Metropolitan supports your efforts to address contaaiDation iD that area's
vital groUDdwat~r supply. Bowever, the Proposed Plan fails to recognize the
importance of preserving the Main San Gabriel Basin (BasiD) as a natural public
resource..., [and] fails to include cleanup effort. or a conjunctive use element that
could optiai.e the Basin'. .torage potential. Metropolitan, in sbort, is
disappoiDted that your preferred remedial alternative is local pump-and-treat
facilities .ith the single objective of controlling ~gration.-
EPA Response: EPA believes that its remedy does reflect the importance
of the San Gabriel Basin as a resource for present and future residents
and businesses in the Valley. See Response B for supplemental
information on the rationale for the scope and size of EPA's remedy.
We believe that the characterization of EPA's proposed remedy as
"local" and "single-objective" is misleading. We presume that the word
"local" refers to the disposition of treated water from the remedy.
EPA's proposal, and the Record of Decision, both allow treated water to
be distributed locally ~ to be exported from the Basin by
Metropolitan. EPA's actions in no way preclude or favor either option.
The comment appears to express disappointment that EPA is not
prescriptive in requiring treated water to be exported by Metropolitan.
See Response D for a discussion of reasons that EPA has not specified
Metropolitan as the recipient of the treated water.
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Baldwin Park ROD
We also wish to emphasize that the objectives of EPA's remedy are to
limit miqration and to remove contaminant mass from the aquifer (see
page 1-6).
NNDl2. Metropo1itan'. 1i.t. the benefit. of a conjunctive u.e project:
a) provide c1ean iaported vater to the basiD;
b) reliably treat contuaiDated groundvater to driDkiDg vater standards that are
.tricter th&D the State and Federal requirement.;
c) iapro"e vater .upply reliability for the region;
d) a..ure beneficia1 u.e of the treated groundvater year round, even vhen 10cal
purveyor. are not ab1. to use the vater.
EPA ResDonse: We note that benefits b) and d) are speculative.
Metropolitan has stated that if it participates in the remedy it may
wish to reduce contaminant concentration to below Federal or state
standards, but has not committed to this action (item b). Nor has
Metropolitan explained in detail the conditions that would need to be
met, particularly the costs, to assure beneficial use of the water
year-round (item d).
1IWD#3. Metropo1itan note. that SPA's propo.ed remedy i. "down-siaeel" iD relation to
reaedial alternati"e. under con.ideration early iD the RI/FS proce... A..ert. that a
larger 100 aillion gallon. per day project (four tiae. the .i.e of SPA'. propo.al)
would "optiai.e" the 8IIOunt of contaaiDant removal.
EPA ResDonse: As described in the FS (page 11-2), EPA initially
studied but screened out larger projects. Projects larger than
proposed by EPA would increase, but not "optimize," the amount of
contamination removed.
MWD#4. Argue. that SPA'. propo.al vill not satisfy SPA's remedial objective. by
failiDg to reduce VOC concentrations iD the lower area "to the masiaum enent
possible" or prevent future iDcreases. Hotes that "VOCs vill contiDue to aigrate
froa the aiclclle area iDto the lover area, thus iDcreasiDg the concentrations i..a the
lover area" aDd that project. larger than proposed by SPA are feasible.
EPA Response: Comment or is correct that EPA's proposal will not
completely stop contaminant miqration throughout the area of
contamination. No realistic proposal, whether it included pumping in
two, three, or more subareas, can stop all migration. We agree that
projects larger than proposed by EPA are feasible, but do not warrant
selection at this time. See Response B for additional discussion of
the benefits and limitations of EPA's remedy.
MWD#5. Bxpre..e. concern that air strippiDg vill not reliably remove 1,2-
dichloroethane (1,2 DCA) froa groundwater. Hote. that staff at the C&liforDia
Departaent of .ealth Service., Office of DrinkiDg Water (DJIS-ODW) have iDdicated that
a liquid pha.. granular acti"ated carbon treauent process may be required if the
influent vater i. ezpectecl tocontaiD organic co.pound. vith lov .enry'. con.tant.,
.uch a. 1,2 DCA.
EPA ResDonse: EPA agrees that air stripping may not be the preferred
technology for all or part of the remedy, particularly if individual
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Baldwin Park ROD
"wellhead" treatment facilities are installed at locations where
contaminants that are resistant to air stripping are present at
relatively high concentrations. Final decisions on treatment
technoloqy will be made during remedial desiqn, in cooperation with the
Department of Health Services. The suitability of air stripping
depends on future contaminant concentrations, treatment confiquration
(i.e., whether groundwater from multiple extraction locations is
blended at centralized treatment facilities), siting limitations, and
other factors.
NWD#6. IletropolitaD expresses dissatisfaction that the Proposed PlaD "does not
address the issuea of nitrate concentration, which over the life of the project will
exceed _xiaua contaaiDaDt levels and require treataent."
.EPA Response: EPA a~ticipates that nitrate levels at one or more
extraction locations may exceed the Maximum contaminant Level during
the life of the project. The need for treatment, and its timing if
needed is, however, difficult to predict. It depends on future
contaminant concentrations at extraction locations, the extent to which
groundwater from multiple extraction locations is blended at
centralized treatment facilities, the use of the treated water, and,
for some uses, the ability to blend high-nitrate water with low-nitrate
water to meet the nitrate standard.
NND#7. Believes that "assumptions used in selec~ing the ~reata8Dt processes and
extraction rates...have led to low capital and operation and ..inteDaDce cost
estiaates..[aDd that] this could lead to insufficient land acquisition and
inefficient use of public funds therefore jeopardizing the ultima~e success of the
project. MetropolitaD believes that liquid granular activated carbon and ion
exchange, or an alternative strategy for Ditrate control, should be included in the
east estimates."
EPA Response: Comment or does not explain how assumptions used in
selecting the extraction rates may have led to low cost estimates.
Comment or expresses the concern that the remedy may require additional
treatment beyond that assumed in the FS, but as noted in the FS and in
the previous two responses, the need for supplemental VOC or nitrate
treatment is difficult to predict. EPA therefore chose not to include
the costs of supplemental treatment in its costs estimates. We note
that EPA's cost estimates include an added 35% for "scope" and "bid"
contingencies - i.e., to account for the risk of higher than expected
labor or material costs and other factors that may increase costs.
Furthermore, EPA's goal in estimating costs in a Superfund feasibility
study is that the true cost be no more than 50% higher or 30% lower
than EPA's estimate. We believe that our estimates meet this goal.
NND#8. Rates that .Me~ropolitan' s Board has supported, in coneeut, proviciiDg 25
perceDt east sharing for a eODjunctive use cleanup project to cover the water supply
benefits resultiDg froa the 80re stringent drinking water objective. and increased
surface pumping costs required to cODvey ~reated water to Metropolitan's distribution
syst_. In addition, Metropolitan has succe.sfully worked with aember agencies,
Congressman Bsteban Torres, and others to secure 25 percent federal cost sharing from
the Bureau of Recl...~ion for the conjunctive use project. Claias that BPA has
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jeopardised ..etropolitan'. :involvement and the potential for other federal fund:ing
for a conjunctive use project."
EPA ResDonse: As the comment notes, any funding contributed by
Metropolitan would be earmarked first for "enhancement costs" resulting
from more stringent or more expensive requirements resulting from
Metropolitan involvement. The magnitude of any Metropolitan financial
contribution in excess of these enhancement costs (i.e., funding that
would reduce EPA or PRP costs) remains uncertain. Also see response
to Tor#l and Response D.
1IWD#9. "Iletropo1itan requires a co88:itaent fro. BPA to undertake a cooperative
conjunctive use project of approx:iaately 25-30 8gd capacity."
EPA ResDonse: EPA is committed to a project of approximately 27 MGD.
As noted in the Proposed Plan and in response to comment MWD#l, .
however, EPA does not believe it is prudent at this time to commit to
supply all or part of the treated water to Metropolitan. .
XIV. Comments by Southern California Water Company (SoC)
SoCII. "Southern ca1ifornia Water ComP&DY is concerned about be:iDg charged,
:indirect1y, for a project that 88Y be short-lived."
EPA ResDonse:
See response to comment SoC#4 below..
SoCl2. Bas a source of fund:ing, other than water revenues, been secured?
EPA ResDonse: As stated in the Proposed Plan, EPAintends to negotiate
with San Gabriel Valley property owners and businesses responsible for
the. contamination to secure funding for the construction and operation
of the selected project. . The only water revenues that are expected to
be used to fund the project are payments by water companies that agree
to accept and distribute treated water. The payments would offset any
water company savings resulting from not using other sources of water.
SoCl3. "Is there any guarantee that the "p1wae" of contam:ination wi11 sti11 be :in the
...e 1ocation at the time the proposed water treatment faci1ity i. p1aced :iDto
.ervice?"
EPA ResDonse: There is no absolute guarantee that contaminant
concentrations will not change at any given location with time. The
likelihood of changes is perhaps highest along the periphery of the
plume or plumes of contamination (e.g., at the Covina Irrigating
Company wells). EPA has, however, proposed extraction at or near
locations that have shown high, sustained levels of contamination, in
most cases for over a decade. Inves~igation work has also confirmed
the presence of significant continuing subsurface sources of
contamination that will continue to contribute to the need for
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groundwater treatment for years to come. EPA believes that there is
little likelihood that contaminant concentrations will rapidly decrease
at these locations.
SoC#4. "If the fiDaAcial "life" of the proposed projec1; is 30 1;0 40 year., who
cOD1;inue. 1;0 pay for a projec1; which aay DO l.oDger be Deeded, i.e. if the
cOD1;..ina1;ed "pluae. 8Ove. beyoDd the propo.ed groundwa1;er enrac1;ioD facili1;ie.?"
EPA Response: No one will pay; the project will be shut down after it
is no longer needed. We believe it is highly unlikely that the plume
or plumes will move beyond the proposed extraction facilities in the
near future. See response to SoC'3.
8oC#5. "I. BPA aware 1;ha1; approxiaa1;elJ' 60' of the eD1;i.re popula1;ioD of the San
Gabriel ValleJ' ill .erved by Private water u1;ili1;ie., IlADJ' of which are regula1;ed by
1;he California Public U1;ili1;ie. Comai..ioD (CPUC)?.. .
EPA ResDonse: EPA is aware that some companies affected by
contamination in the Baldwin Park area are private, investor-owned
utilities. EPA staff have consulted regularly with these companies
about its clean up plans.
SoC#6. "Will. BPA agree 1;0 seek CPUC "approval." of the proposed projec1;, Prior 1;0
awarding anI' CODIJ1;ruc1;ioD cOD1;rac1;s?
EPA Response: EPA will not seek CPUC approval of its proposed
project. EPA will, however, work with the CPUC to facilitate water
utility participation if private water utilities need to consult with
or obtain approval from the CPUC before accepting treated water from
EPA's selected remedy.
SoC#7. "Ba. BPA giveD serious cODsidera1;ioD 1;0 the wa1;er u1;ili1;ies' respoDse 1;0
groundwa1;er coDtaaiDatioD cleanup, i.e. individual well-head treatmeDt unit.,
designed 1;0 be aoved to an alternate site, as the Deed arises?"
EPA Response: Yes, EPA has considered plans by water utilities in
formulating its proposal. EPA is aware of treatment facilities in
operation or planned for Valley County Water District's Arrow/Lante,
Main, and Big Dalton wells, La Puente Valley County Water Districts
wells, and San Gabriel Valley Water Company's B6 wells. continued
operation of some of these facilities may offset a portion of the
extraction and treatment called for in EPA's proposal, but EPA does not
believe that extraction at these facilities is sufficient to meet its
remedial objectives. .
Soc#a. "Bow will BPA pwap fr08 basin and keep basin operated/aanaged properly?"
EPA ResDonse: EPA does not plan to increase its involvement in the
operation or management of the basin beyond the efforts needed to
implement its selected remedy. We expect all increases or decreases in
the extraction, transport, or recharge of the basin's water resources
to be consistent with the Alhambra judgment.
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..
SOC#9. "Bow will this affect opera'tioD of Dearby wells of o'ther producers? ~
EPA ResDonse: EPA or Peps may attempt to reach agreements with water
purveyors for use of inactive wells or the continued operation of
active wells whose operation contributes to EPA's remedial objectives.
Extraction at new wells may also cause limited drawdown at existing
wells, but there are few active water supply wells in the vicinity of
likely extraction locations and the magnitude of any effects are
expected to be small. .
soClI0. "Is plaD't capable of baDdliDg proposed ArseDi.c regula'tioDs? Iscos't es'ti.aa'te
reasoDable, addressiDg iDcreases iD opera'tioD due 'to regu1.a'tioDs?"
EPA ResDonSe: EPA does not anticipate treating groundwater for arsenic,
unless doing so allowed the water to be distributed more cheaply than
would otherwise be possible. If water is supplied to purveyors, water
producers will be expected to pay for any treatment that would be
required in the absence of the VOC contamination.
SoCill. "Please le't me kDow wha't SPA'. 't~e'table is..."
EPA ReSDOnse: EPA expects to begin formal negotiations with PEPS for
design, construction, and operation of its selected remedy in Spring
1994.
XV. Comments by Three Valleys Municipal Water District (TV)
'NIl. CoIameD'tor .. support [S] 'the SPA's efforts 'to address cOD'tamiDa'tioD iD 'this key
wa'ter supply source."
EPA ResDonse:
Comment noted.
'N12. COmaeD'tor believes 'tha't SPA's "~plied posi'tioD" is tha't iDs'titutioDal issues
associated with distribu'tiDg water to local purveyors or exportiDg wa'ter fro. the SaD
Gabriel BasiD are iDsur8lOUDtable. COma8Dtor disagrees with this positioD,
eaphasiaiDg 'that Netropoli'taD Wa'ter District aDd other ageDcies have beguD
discussioDS 'to resolve various iDsti'tutioDal issues. COmaeD'tor recomaeDds ..that the
report should weigh 8cieDtific evideDce aore heavily thaD iDstitutioDal issues iD
arriviDg at its prefereDce for actioD.-
EPA ResDonse: Comment or incorrectly infers EPA's position. EPA does
not believe that institutional issues associated with distributing
water are insurmountable, but does believe that institutional issues
should be considered in selecting the remedy. During the last several
years, EPA has led efforts to identify and resolve institutional issues
associated with distributing large amounts of treated water in the .
Azusa/IrwindalelBaldwin Park area. EPA has worked with Metropolitan
Water District, Watermaster, staff of your Water District, other local
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agencies, and individual water companies to identify potential amounts
and delivery locations for treated water. Section 9 and Appendix D
describe the results of EPA's discussions and evaluations.
TV13. Co8aent:.or no1;e. 'tha1; BPA refer. t:.o 'the 29,000 918 op1;ion a. "op1;:isal" and
believe. 'tha1; BPA has no1; adequa1;ely evalua1;ed 'the proposed 19,000-918 op1;ion.
Co_en1;or a.k.: "... i. 'there any difference in benefi1; be1;ween ei'ther of 'the
29,000-gpa op1;ion. and 'the 19,000-gpa op1;ion?"
EPA ReSDOnse:
See response to AH#l and Response D.
TV14. Co_ent:.or believe. 'tha1; if SPA could be 8IOre. op1;iai.1;ic abou1; 'the re.olu1;ion of
iD.1;i1;u1;ional i..ue., and would propo.e ez1;rac1;ion aDd 1;reataen1; of 29,000 gpa
(ra'ther 1:han 19,000 918), i1; "would have boosted 'the probability of resolving 'the
iD.titu1;ional i.sue., iD.1;ead of UDdenaiDing 'the effortll already underway by NND and
o'ther. . " Finally, C088ent:.or urge. SPA and o'ther agencie. t:.o proceed wi'thout delay t:.o
iapl..en1; 'the 8Os1; ~xpedi1;iou. and technically .ound remedial alterna1;ive.
EPA ResDonse: EPA does not believe that it has "undermined" efforts by
Metropolitan or others. EPA believes that its responsibility is to
identify both advantages and disadvantages of working with Metropolitan
and other project alternatives, and to work to identify and implement
the most effective, most easily implemented, most widely supported, and
least cost alternative.
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XVI. Comments by Advanced Environmental Gontrols
Consulting and Engineering Services
ABel 1. Co_en1;or bel.ieves 'tha1;: "Overal.l., 'the EPA' s approach is a reasonabl.e
one [al.'though] more clarifica1;ion is necessary on 'the liabili1;y and financial
issues."
EPA ResDonse:
Comment noted.
ABel2 . "Bow is 1;he :£ItA planning on narrowing down 'the lis1; of Po1;en1;ia1ly
aesponsibl.. Parties ( "PRPs") 1;ha1; will. be financially accoun1;able for 'the
cleanup of 'the Basin?"
EPA ResDonse: EPA is evaluating information on chemical usage
and handling, type of industrial operation, length of occupancy,
and presence of soil, soil gas, and groundwater contamination to
identify contributors to the groundwater contamination. EPA will
attempt to reach an agreement with contributors to the
groundwater contamination to finance the cleanup.
ABC#3. "Since 1;housands of businesses are 'though1; 1;0 have used chemicals 1;ha1;
could have caused 'the groundwa1;er con1;aaiDa1;ion, who is responsibl.e and 1;0
wha1; degree is 'the company financially responsible?" .
EPA ReSDonse: Hundreds or
the chemicals found in the
these businesses appear to
groundwater contamination.
companies in spring 1994.
thousands of businesses may have used
groundwater, but only a fraction of
be significant contributors to the
EPA expects to identify these
Also see response to AEC#2 and AEC#4.
ABel4. "Will facili1;ies wi'th deaiDiaus concen1;ra1;ions of VOCs, 1,1,1-
1;richloroe1;hane, me1;hy1ene chl.oride, and 1;01;a1 pe1;roleua hydrocarbon in onsi1;e
soil samples be expec1;ed 1;0 con1;ribu1;e 1;0 'the cleanup? Where will 'the EPA draw
'the line for whe1;her or no~ a facili1;y is financially responsible? Is 'there
any way 1;0 have a facili1;y removed from 'the PRP lis1; based on Con1;amina1;ion
Soil Reports?"
EPA ResDonse: EPA has not completed its evaluation of
Potentially Responsible Parties; EPA expects to complete its
evaluation in early 1994. The evaluation will include a review
of facilities eligible for de minimis settlements. We anticipate
that some facilities initially identified as possible
contributors through General Notice of Liability letters may be
eligible for de minimis settlements. .
ABelS. "Will 'the EPA consider Phase I and Phase II BDvironmen1;al Si1;e
Assessaen1;s 1;0 evalua1;e 1;he po1;en1;ial of si1;e con1;aaiDa1;ion due 1;0 on-si1;e and
neighboring sources from ei'ther pas~ or presen1; land use ac1;ivi1;ies? Since
soil con1;aaiDa1;ion was firs1; discovered in 'the Basin in 1979, his1;orical
inforaa1;ion is iaportan~ 1;0 de1;eraine 'the erten1; of 'the liabili1;y and who is
responsible for 'the con1;aaina1;ion."
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..
BPA ResDonse: EPA will consider current and historical
information in its efforts to identify contributors to the
groundwater contamination.
UCI6. -What percentage of the cleanup will consumers have to contribute? Will
it be $20 per year per household maximum raised from the San Gabriel Basin
Water Quality Authority?"
EPA ReSDonse: EPA does not plan to ask consumers to directly pay
for any portion of the cleanup.
Uel7. -What percentage of the $7.5 billion superfund will be allocated as a
loan grantor for qualified bus.iDes.es?"
EPA ReSDonse: section 111 of CERCLA authorizes use of the
Superfund trust fund for payment of selected governmental
response costs and for other purposes. section 111 does not
authorize use of the trust fund for your proposed purpose.
UeiS. -In .ome areas with.iD the bas.iD, the water table is at a depth of 20 to
30 feet. Several companies will have soil cont-m;uation due to the
contam.iDation travell.iDg onsite froa nearby facilities. Bow is the SPA go.iDg
to address this i.sue?"
EPA ResDOnse: EPA considers all information relevant to the'
identification of sources of contamination, including any
information that suggests that contamination detected at or
beneath a facility originates from adjacent facilities or
properties. Relevant information includes present and past
chemical usage and handling at the facility of interest and at
neighboring facilities, and contaminant concentration gradients
observed in soil gas, soil, and groundwater (i.e., spatial and
temporal patterns of contamination).
Depth to groundwater in the Azusa/Irwindale/Baldwin Park area is
typically one hundred to three hundred feet.
ABel' ~ "I. the EPA plaDD.iDg on implement.iDg soil standards' and threshold
values for companies to determ.iDe the degree of contamination?"
BPA ResDonse: EPA is carrying out literature reviews,
evaluations of methodologies used at other Superfund sites,
computer modeling, and other activities to help refine soil
contamination "action levels" and cleanup goals. These
activities are separate from the Baldwin Park Operable unit and
will not be included in the Baldwin Park Operable Unit Record of
Decision.
ABellO. "S.iDce banks and lend.iDg companies will not issue loans for clean.iDg
up contaa.iDated waste, how are the PRPs suppose to pay for the cleanup? Either
new regulations or reorganization of the f.iDaDc.iDg structure aust be
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iapleaented to insure proper cleanup, protect hWlUUl health, and contain the
contaainat~on £roa spreading out o£ the s~te area.-
EPA ResDonse: EPA will use authority provided by CERCLA to
evaluate the ability of responsible parties to pay for cleanup,
as well as consider other financing mechanisms allowed by law.
ABClll. -A£ter rev~ewing the Baldwin Park Operable Un~t Feasib~l~ty Study
Report, the actual costs could eas~ly exceed the projected budget cost of $47
aill~on to bu~ld the treatment fac~l~t~e8 and $4 aill~on ..~ntenance and
operating costs. What cost containment strategies will be used to assure that
the costs remain at or below these projected levels?-
EPA ResDonse: EPA's goal in a feasibility study is for the true
cost to be no more than 50% greater or 30% less than the
estimated cost. We note that EPA's cost estimate of $47 million
in capital costs already includes an added 35% to account for
unforeseen factors that may increase costs. If EPA funds the
project, EPA will use sound engineering and construction
principles to ensure that the remedy is properly designed and
built at reasonable cost.
XVII.
Comments by Aerojet Gencorp
Aerojet Gencorp (Aerojet) submitted three sets of comments
jointly with Azusa Land Reclamation (ALR) during the public
comment period:
o "Review Comments,
study Report, April
o "Review Comments,
operable Unit"
o "Proposal for Technical Modifications Optimization of
EPA Region IX Subarea 1 Proposed Project, Baldwin Park
Operable Unit," August 12, 1993
Aerojet also submitted:
Baldwin Park Operable Unit Feasibility
2, 1993"
Proposed Plan, May 1993, Baldwin Park
U.s.
o an 18 page letter with "general comments on and legal
analysis of the Baldwin Park OU FS and Proposed Plan," dated
August 10, 1993, and
o two videotapes titled "Aerojet Submission of Nicholas
Pogencheff Testimony, August 4, 1993 [Edited]."
Finally, Aerojet/ALR jointly submitted an addendum to their
"Proposal for Technical Modifications Optimization of U.s. EPA
Region IX Subarea 1 Proposed Project, Baldwin Park Operable Unit"
dated November 29, 1993. The oil and Solvent Process Company
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..
(OSCO) also joined in rhese commenrs, which were submirred afrer
rhe close of rhe formal public commenr period.
Many of rhese sers of comments are inrernally redundanr and
duplicare each orher; in some cases rhe same commenr is presenred
~o ro ~5 rimes. We presenr derailed responses ro rhe mosr
derailed ser of Aerojer/ALR commenrs, which are rhe "Review
Commenrs, Baldwin Park Operable Unir Feasibiliry Srudy Reporr,
April 2, ~993," followed by briefer responses ro rhe other sets
of commenrs.
XVII. 1. Response to "Review Comments, Baldwin Park Operable Unit
Feasibility Study Report, April 2, 1993"
General Comments (pp. 1-7)
Aj#l. Aerojet criticiaes EPA's Proposed Plan as based on a "preponderance of
assumptions and simplifications"; as not technically defensible or effective;
not supported by adequate water quality or hydrogeological data; as
unjustified without a higher level of detailed technical analysis; as based on
inadequate aodeling; proaising exaggerated or unsubstantiated benefits; a.
inconsistent with acceptable engineering practices and principles; as
inconsistent with the National COntingenq Plan; and as schedule- rather than
exposure-driven. Aerojet asserts that there is a substantial risk that
implementation of the remedy will damage the groundwater resource and increase
the time and cost required for remediation. Finally, Aerojet concludes that
the remedy should be limited to wellhead treatment at existing production
wells, and the removal of chemicals fro. groundwater at identified "hot spot"
areas.
EPA ResDonse: We do not believe that any of these complaints,
criticisms, or assertions warrant a change in the proposed
remedy. We summarize our response to these general comments
here. More detailed responses follow to more than 250 specific
comments that repeat the same complaints, criticisms, and
assertions.
- Adequate hydrogeologic and contaminant data are currently
available to select an appropriate response action. See
Response F.
- Assertions that EPA's proposal does not address a portion
of the aquifer exhibiting the highest concentrations of
chemicals in groundwater are incorrect (the Wynn Oil well).
EPA's proposed extraction and treatment in the upper area
will address contamination detected at the Wynn oil
monitoring well in a cost-effective manner. See Response B.
- Speculation that the plumes in Subarea 3 have srabilized
or reached equilibrium, and arguments that additional study
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.
is needed to justify remedial action in Subarea 3, are based
on misinterpretations of data (e.g., mistakenly alleging
oscillation and retraction of the plumes) and failure to
consider site-specific evidence warranting action (e.g.,
increasing trends in contaminant concentrations). See
Response A for a detailed explanation of the need for action
in Subarea 3.
- Assertions that EPA's modeling efforts did not or cannot
account for effects of pumping, recharge, or other local-
scale details are incorrect. Computer simulations completed
by EPA account for recharge and pumping in the Baldwin Park
area, including at the Santa Fe Spreading Grounds and the
Arrow/Lante well cluster/wellhead treatment facility. The
statement by EPA that its CFEST model "cannot discern local-
scale effects" refers to the limitation of the model to
predict the exact location of a cone of depression of a
pumping well or the impact of other perturbations on local
water levels. This. limitation results in part because the
"nodes" in EPA's model do not always coincide with actual
pumping locations. This limitation does not, however,
affect the accuracy of predictions of the regional impact of
existing or new extraction or recharge locations (e.g., the
results presented in Figures 7-4 to 7-8) or significantly
affect EPA's recommended extraction rates or locations. See
response to comments Aj#143, Aj#144, and Response C.
- Assertions that EPA did not examine the potential remedial
effects of recharge, and did not consider the effects of
existing wells/wellhead treatment, are incorrect. See
responses to comments Aj#145 and Aj#179.
- The assertion that EPA's proposed remedy will damage the
groundwater resource is unfounded. Aerojet/ALR correctly
point out that EPA's proposed remedy will allow more highly
contaminated groundwater located north of the 210 freeway to
spread into less contaminated areas, but fail to explain
that the movement of more highly contaminated groundwater
into less contaminated areas on its way to being drawn into
extraction wells is a common limitation of groundwater
cleanups, particularly when the area of contamination is
large as in th~ Baldwin Park area. See Response B for
additional details.
- Ignoring more than ten years of investigation efforts that
began in earnest with EPA's Supplemental Sampling Program in
1985, Aerojet claims that EPA is moving too quickly to
implement a remedy in the Baldwin Park area. Aerojet
asserts that EPA's actions are schedule-driven rather than
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Baldwin Park ROD
exposure-driven. More often, EPA has been criticized for
moving too slowly, for studying rather than cleaning up the
contamination.
Appendix (pp"o_I-32)
Aj#2. "Figure 1-2 pre.eAts a aisleadiDg represenution of t;he e%'teAt of
groundwater contamination by VOCs. Cont;...~ naat conceAtration cont;ouriDg at a
s..ller scale shows separate and distinct plumes in t;h. Baldwin Park Area. In
addit;ion, t;he cOlIDposit;e nature of t;he ..p artificially increases t;he enent of
contaaiDation by including isolated occurrences of chea.icals (ere) unrelated
t;o t;he pr.iaary source ch8llD.icals (PCB and ~). A response action based on
t;his represeAtation of contamiDant distribution will not efficient;ly achieve
stat;ed project objectives."
EPA Response: We agree that the illustrated area of
contamination may include, or at one time may have included,
separate and distinct plumes. We disagree, however, with the
assertion that EPA's decision not to show individual plumes
results in a "misleading representation." As its title
indicates, the purpose of Figure 1-2 is to show "Approximate
Areas of Groundwater contamination in the San Gabriel Basin." We
further state that the Figure shows "only regional variability in
contamination" (page 1-3) and a "simplified, smoothed" depiction
of the extent of contamination" (page 3-9). Its purpose is not
to show the precise locations of sources of contamination, nor to
conclusively show whether the areas of contamination consist of
one, two, or ten distinct plumes.
We disagree with the comment that the composite nature of the map
artificially increases the extent of contamination. We see no
reason to arbitrarily exclude from the Figure or give less
attention to portions of the aquifer contaminated with carbon
tetrachloride (CTC) above Federal or state drinking water
standards. The remedial objectives of the Baldwin Park Operable
unit are to address the presence of all of the volatile organic
compounds (VOCs) in the groundwater, not just the most prevalent
contaminants TCE and PCE.
Limitations of the data available to prepare Figure 1-2, and
guidelines to assist in its interpretation, are described in the
caption on page 1-3 and in great detail on pages 3-9 through 3-
23. The Figure is misleading only if interpreted in ways
explicitly discouraged.
We agree with commentor that response actions should be based on
an "understanding and evaluation of raw or actual water quality
and hydrogeological data; not on the interpreted representation
provided in Figure 1-2 or any other figure.
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.
Aj#3. "All three primary objectives as we1l as the secondary objective would
best be accomp1ished by controlling plume aigration in the source area of
highest concentrations. ~is is not proposed in any of the alternatives."
EPA ResDonse: We agree that containment is needed in source
areas; the primary objective of groundwater extraction in Subarea
1 is source control. See Response B for a more detailed
explanation of EPA's rationale for proposing groundwater
extraction and treatment in both Subareas 1 and 3.
Aj#4. "Xt is aisleading for the u.s. SPA to imply that implementation of the
interia operab1e unit response action based on currently avai1able data and
interpretations will accomplish the stated objectives. Due to the significant
hydrogeologic aDd water quality data deficiencies in the OU, there is serious
risk that iaplementation of a premature response action would resu1t in
further damage to the groundwater resource and increase the time and cost
required for effective remediation."
EPA ResDonse: We disagree. The evaluations completed as part of
the feasibility study indicate that EPA's selected remedy will
not result in the types of neg~tive impacts listed in the
comment. This comment does not identify any specific data
deficiencies; see Response F for a detailed response to
assertions that EPA's proposal is not supported by adequate data
or technical analysis.
Aj#S. "~ere is DO description of "the limitations of wellhead treatment" in
Section 6.1 as indicated. ~e only mention of wellhead treatment is in Table
6-2 where the few sentences in Section 1.2 are re-stated. Please elaborate."
Text included in Table 6-2 describes wellhead treatment as
extracting groundwater and installing treatment only as needed to
meet water supply needs.
The limitations of wellhead treatment are that, if left to
themselves, well owners are likely to install treatment only at
wells with contaminant concentrations just at or above Federal or
State drinking water standards - five micrograms per liter (ug/l)
for PCE and TCE; one-half ug/l for carbon tetrachloride. EPA's
proposal calls for extraction of groundwater from areas where
contaminant concentrations are higher: tens, hundreds, or
thousands of micrograms per liter. Well owners are unlikely to
install treatment and operate wells that are located in highly
contaminated areas without EPA or other external involvement. In
the FS, EPA therefore screened out wellhead treatment because it
was incapable of fully satisfying EPA's remedial objectives.
There are existing wells in the Baldwin Park area where treatment
has been installed or is planned. EPA expects that installation
and operation of treatment at existing wells will contribute to,
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Baldwin Park ROD
but not fully satisfy, EPA's remedial objectives for the Baldwin
Park area.
Ajl6. "Since the LARWgCB is focusing on surface source con~rol and vadose zone
characteriza~ion, SPA is lef~ with very li~tle groundwater data to
characterize the upgradien~ portion of ~he plume. ~ere were only ~hree
aonitoring wells in the en~ire OU prior ~o 1991."
EPA ResDonse: As of September 1992, the date on which data were
last reviewed during preparation of the Baldwin Park Operable
Unit Feasibility study, water quality data were available from
approximately 22 monitoring wells ins~alled in the Baldwin Park
area. The well numbers are: V10AMMW1, V10VCMW1, V10VCMW2,
VIOVCMW3, W10NCMW1, WllAZW01, WllAZW02, WllAZW03, WIIAZW05,
WIIAZW06, W11AZW08, W11AZW09, V10CAMW1, W10WOMW1, VIOPIEW1,
EPAMW611-619, EPAMW5101-5113, OSCOMW1, OSCOMW2, OSCOMW3, OSCOMW4,
OSCOMW5. All but one or two of these wells are located in the
upgradient portion of the plume. Comment or in fact notes the
existence of slightly "less than 25 [monitoring wells]" in
comment Aj#15. Additional data were obtained from water supply
wells in the area.
The comment that only three monitoring wells were available in
1990 is misleading, since EPA's analysis is based on data through
september 1992. Furthermore, the comment is incorrect. As of
December 31, 1990, at least eight of the 22 listed wells had been
installed: V10AMMW1, V10VCMW1, V10VCMW2, V10VCMW3, W1lAZW01,
W11AZW02, W11AZW03, V10CAMW1.
Ajl'. "I~ is .ta~ed tha~ a purpose of ~he OD.rSi. "~o evalua~e remedial
al~erDa~ives in sufficient detail to allow for the iden~ifica~ion of a
preferred r_edial alterDa~ive. ~i. study provides infonaation that will be
used in, bu~ doe. no~ describe the resul ~s of, ~he decision-making process."
In order for the public ~o conduct an independen~ evalua~:i.on of the 0'07S, i~
is importan~ tha~ SPA describe the decision-making process which led ~o
development of the al~erDa~ive. considered in the oars. ~e description of
this process in greater detail, is necessary to es~ablish that a proper range
of al~erD8~ives has been evalua~ed." .
EPA ReSDonse: section 11, pages 11-1 through 11-22, describes
the logic behind, and evaluations made, in the development of the
four alternatives evaluated in the feasibility study. Response B
further describes the rationale behind the decision to propose
groundwater extraction in two broad areas. Commentor asks for
additional description of the decision-making process, but does
not specify what details he/she wants.
Aj#S. "Although i~ is s~a~ed "I~ is no~ a goal of this oars, nor i. i~ a
reali.~ic goal of any CERCLA PS to r~ve all unce~in~y abou~ si~e
condi~ion. or the performance of po~en~ial remedial actions", the reported
siaplifica~ion. regarding the current exten~ of groundwater contam:i.Da~ion and
absence of data regarding the response of contamination to changing pumping
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Baldwin Park ROD
.
and recharge patterns both historically and as a result of the proposed
response action is significant, and can not be ignored. Failure to properly
consider these factors prior to selection of a preferred response alternative
will foster decisions that could exacerbate adverse impacts to the groundwater
resource and present serious obstacles to effective ..nagement of the OU and
developaent of effective remedial actions."
EPA ReSDOnSe:
See Response F.
Aj#9. "~e tiaing of the selection of a remedial alternative appears
pr8818ture. Within the last year, data from new wells have revealed a
different interpretation of contaminant distribution in the upgradient area of
the plwae. ~is information is mentioned in soae sections of the report but
have been largely ignored in many of the evaluations and development of
alternatives. ~ese recent interpretations are key to optimizing remedial
. actions, especially in Subarea 1."
EPA ResDonse: We disagree that "new" data imply a different
remedy than proposed by EPA. The so-called "new" data have not
been ignored in the development or evaluation of remedial
alternatives. The data were incorporated into the development of
the subarea boundaries defined in Section 7. The subarea
boundaries were used to determine approximate extraction
locations, which form the basis for the remedial alternatives.
See Response B for additional explanation of the extraction
scenario in Subarea 1 (particularly on advantages and
disadvantages of moving extraction locations closer to known or
apparent sources).
Aj#10. .~e first sentence implies that .no action is occurring presently and
that there is an immediate need to "reduce hazards". ~is is a misstatement
since current activities are achieving aaDJ' of £PA's objectives. ~ pwaping
well. with wellhead treataent facilities in the upgradient portion of the OU
have assisted in plwae containment and cont...i 1'\ant reaoval in Subarea 2. Xn
addition, production wells in the southwestern half of the OU have pwaped more
than 20,000 AF/YR resulting in additional plwae containment."
EPA ResDonse: We presume that the first part of this comment
refers to Valley County Water District's Arrow/Lante well.
cluster. We are unclear how our statement of the need to "reduce
hazards" implies that no action is occurring, but in any case we
agree that operation of these wells does remove contamination
from the aquifer. Operation of these wells was assumed in EPA's
computer simulations used to develop recommended extraction rates
and locations. See Appendix I and Response B.
Apparently, the production wells extracting 20,000 af/yr that are
referred to in the comment are the active wells located
downaradient of the more highly contaminated area; extraction
within the more contaminated area is, as of December 1993,
negligible. The 20,000 acre-feet per year of groundwater
extraction apparently refers primarily to extraction from clean
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Baldwin Park ROD
"
or relatively clean portions of the aquifer. As described on
page 6-14 and in Response B, EPA's remedial objectives can only
.be satisfied by extraction from relatively contaminated portions
of the aquifer.
In fact, as stated in the FS, there are remedial benefits to
reducing production at existing water supply wells outside of th~
more contaminated areas, thereby reducing the hydraulic gradient.
Ajill. MOD the bas~s of the s~9D~f~cant and cr~t~cal data that are aiss~g and
necessary to effect~vely character~ze the bas~c hydrogeolog~c cond~t~on5 ~n
the Baldw~ Park area and d~str~ut~on of chemicals w~th~ the local aqU~fer,
there appears to be a h~gh degree of r~sk that EPA will implement an uterim
action that w~ll not be cons~stent with effect~ve long-term remediat~on
actions for the au. Impl_eDtat~on of an improperly scoped and premature
uteria action is l~kely to ucrease both the time and cost necessary for a
long-term and fual response action for the au. In fact, EPA' sown strategy
with respect to the Superfund Accelerated Cleanup Model (SCAM) [s~c] ~s to
con.~der groundwater r_ed~at~on to be a long-term act~v~ty and not a
candidate for early action.M
EPA Response: We disagree; see Response F for a detailed
explanation. Comment or does not explain the basis for the
assertion that EPA's remedy will interfere with or not be
consistent with long-term remediation and incorrectly interprets
EPA's Superfund Accelerated Cleanup Model (SACM). The SACK calls
for greater emphasis and public awareness for "removal actions"
intended to address immediate threats to human health and the
environment. The SACK encourages a streamlined RIfFS and in no
way lessens the importance of or encourages unnecessary delays in
addressing areas of significant groundwater contamination such as
Baldwin Park.
Ajll2. Mne statement MGroUDClwater contamination u the au area is known to be
spreadug uto less-contaminated and uncontaminated port~ons of the aquiferM
is not substantiated based on the data and Msimplified picturesM presented by
EPA u both the mz and 0U1fS. Data are sparse dOWDgrad~eDt and ava~lable only
froa production wells w~th varyug puap~g histor~es and screen depths. No
aon~torug wells exist u Subarea 3.
In fact, ava~lable data udicates that the d~str~ution of contaaiuauts
characterized to date is s~9D~f~cantly ufluenced by groundwa~er puapug
patterns that appear ~o be prov~dUg a coaponent of hydraul~c conta~en~
throughout the au, and thereby controllug the aigrat~on of contaauants.
Data udicate that DO syst...t~c ucreases u contaaUant concentration are
occurrug downgradient of Subarea 3. EPA has failed to address this very
fundaaen~al rela~~onship as i~ appl~es to characterizat~on of the aqu~fer
system and the developaent of cand~date response act~ons.M
EPA Response: We disagree with the first and last part of this
comment which states that the data do not substantiate that
contaminated groundwater continues to spread into less
contaminated areas. Response A presents clear evidence of
increasing trends in contaminant concentrations at selected
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Baldwin Park ROD
..
downgradient wells and offers a detailed explanation of the need
for action in Subarea 3.
We agree that the "simplified pictures" included in the FS do not
justify remedial action. See response to comment Aj#2 and Aj#43.
We also agree that pumping wells influence groundwater movement,
but again note that existing wells are not suitably located to
fully satisfy EPA's remedial objectives.
Finally, the comment that EPA has failed to account for the
effects of pumping is incorrect. See response to comment Aj#
144.
Aj#13. -~e statements ~t the avai1ab1e data -are sufficient to determine
the approxiaate size and 1ocations of the actions" aDd that -this interim
action wi11 not be inconsistent- with a fiDa1 remedy, are premature and are
not supported by a sufficient 1eve1 of technica1 interpretations. Without a
more thorough understandiDg of the complex hydrogeologic system and the
present distribution of contamiDants, anyone of the candidate remedies could
be iDconsistent or adversely impact a final remedy."
EPA ReSDonse: This comment duplicates other comments.
disagree. See Response F.
Aga1n, we
Aj#14. "~though BPA has performed three additional field investigations since
mid-l,a" these more recent groundwater investigations have s..pled, with one
exception (MWS-l), production wells. Water quality samples collected from
production wells often produce results ~t are not characteristic of water
quality at a particu1ar 1ocation and depth due to the influences of prolonged
extraction of large volumes of water."
EPA ResDonse: We agree that production wells typically sample a
larger volume of the aquifer than do monitoring wells, and are
therefore representative of conditions in a larger portion of the
aquifer than are samples collected from monitoring wells. This
difference does not, however, preclude their use for determining
the approximate extent of groundwater contamination. 'It in fact
offers one advantage - a highly contaminated sample from a
production well suggests that a significant vertical interval of
the aquifer is contaminated.
It should be noted that a sample collected from a monitoring well
also represents average water quality across the screened
interval, and is not "characteristic of a particular location and
depth." Monitoring wells in the Baldwin Park area typically have
40 - 75' screens.
EPA has also collected depth-specific samples from several
production wells in the Baldwin Park area to provide more
discrete information on vertical variations in contamination.
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. ,:
Baldwin Park ROD
.
Section 3.2.2 and Figure 3-9 present some of this depth-specific
data.
Aj115. "Three wells shown on Pigure 1-4 were apparently sampled by EPA yet no
sampling results are included in Attachment A. These wells, 01900831,
Z1000066, aDd 01902971 SpaD the length of the plume aDd are important wells to
consider for plume definition."
EPA Response: We did intend to include these data; they were
inadvertently omitted from Attachment A. We apologize for any
inconvenience. A printout of these results is included in the
updated Attachment A included in the Administrative Record.
Aj116. "The reference that to date only 15 facilities have been directed to
investigate growndwater contamination in the OU is aD example of the liaited
amount of detailed data available fro. aD area that represents such a large
portion of the basin. Of the more than 500 specific groundwater monitoring
wells that exist in San Gabriel Basin, less than 25 are located within the OU
aDd only one monitoring well exists outside of Subarea 1. A significantly
greater level of detailed characterization will be necessary to support
effective decision making in the Baldwin Park OU."
EPA Response:
the selection
of the FS for
Response F.
We believe that the data are adequate to support
of remedy for the Baldwin Park area. See Section 3
a description of the available data. Also see
Aj117. "If lithologic well logs were used to estimate hydraulic conductivities
within the basin, why were data represented on Plates 1 through 6 not used to
establish areal trends in hydraulic conductivity? A cursory review of well
logs would suggest that higher hydraulic conductivities are present in the
northern portion of the basin with decreasing values towards Whittier Harrows
(south). This trend would be expected considering the depositional
environment. The net effect of this discrepancy would significaDtly influence
EPAts analyses regarding Subarea 3 conditions."
EPA Response: As described in EPA's Interim San Gabriel Basin
Remedial Investigation Report (July 1992, included in the
Administrative Record), the lithologic well logs ~ used to
establish areal trends in hydraulic conductivity. And, as
correctly stated in the comment, conductivity values do decrease
towards Whittier Narrows. These decreases are accounted for in
the San Gabriel Basin CFEST model. It is unclear what
"discrepancy" is referred to in the comment that would influence
EPA's analyses in Subarea 3. See Response C for additional
detail on this topic.
Aj118. "Aquifer tests at the Azusa Western Landfill were Dot specific capacity
tests. Data froD the pumping well are Dot available. The aquifer tests at
the Azusa Western Landfill produced inconclusive results. A reliable
hydraulic conductivity value cannot be determined fro. the data."
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Baldwin Park ROD
..
EPA ResDonse: Commentor is correct that the Azusa Western
Landfill tests were aquifer tests. Although EPA does not state
that the Azusa Western Landfill tests were specific capacity
tests, the organization of the text does leave that unintended
impression. Although the results of these aquifer tests were
inconclusive, they can be used to provide a rough estimate of the
hydraulic conductivity in the area. In fact, the landfill's
consultant (Law Environmental, Inc.) used aquifer test data to
estimate hydraulic conductivity values of 5,000 ft/day in a
north/south direction and 1,000 ft/day in an east/west direction
(n~990 Annual Report, Waste Disposal and Ground Water Monitoring,
Azusa Land Reclamation Landfill, Azusa, california", prepared by
Law Environmental, Inc., January 28, 1991).
Aj#19. "SPA has not ..de avai1ab1e for pub1ic review the resu1ts of the
"aquifer teats that yie1ded hydrau1ic conductivity estimates of 5,000
feet/day". It is our understanding that these tests were typica11y 1ess than
a few hours 10ng and wou1d therefore have produced resu1ts that are
questionable. ~is information should be provided to permit an independent
review of the "aquifer test" analysis and relative qua1ity of the data."
EPA ResDonse: Comment or refers to seven aquifer tests that
yielded hydraulic conductivity estimates between about 270 and
5,000 ft/day.
We agree that there are limitations in how some of these data
should be used. These data are from the initial round of well
logging and depth-specific sampling conducted by EPA in the
Baldwin Park area. The report summarizing these results is
available for review; it is referenced in the Baldwin Park
Feasibility Study (p.1-10) and included in the Administrative
Record. The title of this report is "Draft Technical Memorandum,
Well Logging and Depth-Specific Sampling, San Gabriel Area 5
Remedial Investigation, San Gabriel Basin, Los Angeles County,
California, May 1990."
Aj#20. "Were the hydraulic conductivity values corrected for partial
penetration? Were observation wells used in the tests? Bow do the resu1ts
compare with recent Watermaster aquifer tests? When will the results from
Watermaster tests be available to the public and for SPA to incorPOrate into
their analyses?"
EPA ReSDonse: The estimated hydraulic conductivity values were
not corrected for partial penetration. Some estimates were based
on data obtained from observation wells; others were not. The
lack of observation wells or. correction for partial penetration
do limit the accuracy of the results, but the error in the
hydraulic conductivity estimates is likely to be less than a
factor of two. The results have not been compared directly to
recent Watermaster aquifer tests; the Watermaster should be
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Baldwin Park ROD
contacted for information regarding the public release of their
report. \
Aj121. -Why ~t the CDWR aquifer tests from the discussion? CDWR conducted
several pumping tests with observation wells in the ou. ~e paragraph implies
that CDWR hydraulic conductivity estimates were based on lithology alone."
EPA ResDonSe: CDWR aquifer tests ~ considered in developing
the hydraulic conductivity zones for the San Gabriel Basin CFEST
model. (The paragraph was not intended to imply that CDWR
estimates were based on lithology alone.) See Response C for
additional detail on this topic.
Aj122. "Groundwater flow directions assaaed on the basinwide interpretations
presented on Figure 2-4 and references to those provided in the .DU' using
eFBST are inappropriate for evaluating groundwater flow conditions on a
localized scale such as for the Baldwin Park ou. Both of SPA's references
fail to identify localized flow variations that are evident in the OU due to
the effect. of recharge, pumping patterns and seasonal influence.. Failure to
-sufficiently characterize localized flow conditions in the OU limits SPA..
ability to develop and evaluate cost-effective and technically-sound respon.e
action.. Significant localized and regional flow components that have been
identified in the OU are not even generalized on Figure 2-4 of the ours.
Water level contours are open-ended or not represented in the most critical
area, Subarea 1."
EPA ResDonse: As discussed in Response C, and shown in Figures
7-4 through 7-8, the CFEST model can and does identify local flow
variations in the Baldwin Park area.
As stated in the text, Figure 2-4 is a reprint of water level
contour maps prepared by Los Angeles County Department of Public
Works (LACDPW) presented to illustrate regional flow conditions.
As discussed on page 2-10, we agree that the LACDPW contour maps
are of limited accuracy and lack detail on local conditions.
Among the limitations of Figure 2-4 listed on page 2-10 is that
"the map does not necessarily show local variability in water
levels caused by pumping, recharge, or geologic faults... [and]
aggregates measurements made over a 1- to 2-month period."
Aj#23. -~e statement "no cones of depression appear in the ou area because of
the relatively low pumping volumes and high hydraulic conductivity of the
aquifer- is incorrect. Figure 2-4 contours water table elevations in
increments of 25 feet, and in Subarea 1, 100-foot increments. Cones of
depression would not be evident at this scale. Detailed groundwater contour
..ps of the OU prepared by Harding Lawson Associates (&LA) and others show
that water supply production effects are prominent and can be readily
depicted. ~e above statement also contradicts SPA's Table 7-3 (p. 7-28) that
identifies averag- production from 1988 through 1991 for 16 wells operating in
the OU at a total pumping rate over 35,000 acre feet per year. Other well.
operating at similar pumping rates are a180 located in the OU. Please explain
this wide disparity in the interpretation of groundwater flow influence. in
the Ou."
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Baldwin Park ROD
,
EPA ReSDonse: The EPA statement should refer to significant
cones of depression in the OU area. All pumping we~ls create
cones of depression, but there are no significant cones of
depression caused by large pumping centers such as those found
.near the mouth of Puente Valley and in the western portion of the
San Gabriel Valley. In Figures 7-4 through 7-8, which show
groundwater contours at increments ofl foot, cones of depression
. for existing pumping wells are evident.
Aj124. -~e statement -Because the LACDPW contour maps are based on relatively
widely spaced data, gradients estimated from these contour maps are uncertaiD
estimates of the regional gradients. Local gradients are even less well
defiDed-, represents the significant lack of data on which SPA has based their
OU decisions. In order to develop an effective response action, SPA will need
to iDcorporate into their analysis the localized variations iD horizontal
hydraulic gradients that exist iD the OU. BLA has identified that some of the
steepest gradients in the basiD exist in the au due to recharge events at the
Santa Pe Plood Control Basin.-
EPA ResDOnse: EPA has incorporated localized variations in
horizontal hydraulic gradients into its analyses. This result
can be seen in Figures 7-4 through 7-8, which present the results
of EPA's modeling performed to develop approximate extraction
rates and locations for the remedy. Figures 7-4 through 7-8 also
show steep gradients caused by recharge at SFSG.
Aj125. -Seasonal variations iD vertical gradient apPear comparable iD
aagnitude to typical absolute values of vertical gradient, implyiDg a
significant likelihood of vertical gradient reversal. To what extent has the
eleaent of seasonal variations iD vertical groundwater gradients been further
characterized in the OU, and was this component factored iDto the decision to
justify the need for an iDterim response action?-
EPA ReSDonse: Seasonal variation in vertical groundwater
gradients have not been further characterized in the Baldwin Park
area. We do not know of any reasons why uncertainty about the
precise magnitude of vertical gradients might lessen the
justification for EPA's selected remedy.
Aj#26. -vertical gradients in the Whittier Harrows area may not apply to this
ou. Lithologic logs suggest a significant increase in the distribution of
fiDe-graiD sediments which can affect vertical gradients.-
EPA ResDonse: We agree that vertical gradients from Whittier
Narrows would not likely be applicable to the Baldwin Park area.
The text merely states that best sources of data in the San
Gabriel Basin are from EPA monitoring wells in Whittier Narrows
and Irwindale. vertical gradients measured in Whittier Narrows
are not provided or discussed on the page referenced in this
comment (p.2-14).
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Baldwin Park ROD
..
Aj#27. "Wou1.d additional recharge along the unlined ai.le of Walnut Creek
provide contaiJuDent at the downgradient edge of the plume? Does the SPA
groundwater aodel account for recharge in this area?"
EPA Response: Additional recharge along the unlined portion of
Walnut Creek could reduce the gradient somewhat in Subarea 3.
However, because this stretch is located more than one mile
downgradient of Subarea 3, the effect will likely be fairly
limited.. In addition, recharge in this area would increase the
groundwater flow velocity downgradient of this reach, thereby
increasing the rate of contaminant migration towards Whittier
Narrows.
The EPA San Gabriel Basin CFEST model does not account for
recharge in this area. Typically, surface water flow rates and
associated recharge are quite low in this reach.
Aj#2S. "Recharge at the Irwindale spreading Grounds (ISG) and other recharge
basins drastically changes local flow patterns. SPA's CFES~ simulations in
Section 7 demonstrate the groundwater mounding at ISG during both dry and wet
periods. Bow will an increase in recharge at the ISG affect contaminant
concentrations and movement?"
EPA Response: An increase in recharge at Irwindale Spreading
Grounds (ISG) will reduce gradients upgradient of the facility
and increase gradients downgradient of the facility. The effect
on contaminant movement would be similar (decreasing movement
upgradient of the facility and increasing movement downgradient
of the facility). As commentor notes, the results of CFEST
simulations presented in Figures 7-4 through 7-8 show the impacts
of recharge at the ISG for four specific clean up options.
Aj#29. "~s is an important institutional chauge that can provide purveyor
assistance in remedial actions."
EPA Response:
Comment noted.
Aj#30. "What are the specific results of the modeling that suggest that
purveyor practices ..y have caused only" a slll8ll fraction" of the increase in
the areal enent of the pluae and that "a continuation of past water
..nagement practices will increase the spread of contamination"? The.e
statements suggest a continuation of past practices will be more damaging than
past practices themselves. Why? Were remedial benefits resulting from some
of the previous pumping patterns also identified during the modeling
simulations? The results of these groundwater flow and transport simulations
should be ..de available in order to permit the public to conduct aD
independent evaluation of the ODF.S, aDd to justify SPA's decisions regarding
the type of interim response actions that are proposed for the OU."
EPA Response: The simulations that suggest that a small fraction
of the overall increase in the extent of contamination may
potentially be attributed to purveyor practices are described in
EPA's Basinwide Technical Plan (April 1990). The exact fraction
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Baldwin Park ROD
,
attributable to purveyor practices is
at 10% for the period 1980 to 1989).
Plan is referenced in the Feasibility
Administrative Record.
highly uncertain (estimated
The Basinwide Technical
study and included in the
The statements referenced in the comment both say essentially the
same thing - that purveyor practices have and will, if unchanged,
continue to contribute to the spread of contamination. It is
unclear how these statements suggest that "a continuation of past
practices will be more damaging than the past practices
themselves."
Aj#31. "Well 08000076 appears to be approximately 200 feet deeper than the
CDWR aquifer bottoa yet doesn't penetrate bedrock. This discrepancy doesn't
appear to be due to a cross-section projection problea since the well is very
close to the line of section. Is this evidence that the aquifer bottom is at
least 200 feet deeper than previously aapped?"
EPA ReSDonse: This well log may indeed be evidence that the
aquifer is thicker than estimated by CDWR at this location. As
shown on the cross-section, according to CDWR's contours, the
alluvial aquifer thickens rapidly in the vicinity of this well
and our understanding is that CDWR's contour map was based on
fairly widely-spaced data points. Thus, it would not be
surprising if CDWR's contour locations were somewhat off.
Aj#32. "Since sparse groundwater data are available from this OU, shouldn't
non-CLP data be used to assist in the delineation of the subareas? Hon-CLP
concentrations are used very specifically in estimating influent chemistry yet
not used in plume refinement. Further discussion on page 3-3 suggests that
non-CLP data are reliable; what is the justification for its exclusion?"
EPA ResDonse: Non-CLP data ~ used in preparing Figure 7-1.
They were used to verify the Subarea boundaries. The "ALL DATA"
listing in the Figure represents the average of CLP data and
available non-CLP data.
The comment that non-CLP data are "not used in plume refinement"
is incorrect. As stated on page 3-2, the area of contamination
figures presented in Section 3 do incorporate non-CLP data.
Aj#33. "It is stated that "non-CLP chemical data from both LARWQCB aDd AB 1803
programs were used to describe the nature and extent of contamination and to
estimate treatment plant influent chemistry, which in turn is used to develop
treataent technologies and to estimate treatment costs for the remedial
alternatives. For this use, the data do not have to be very precise because
influent estimates froa a single well have a relatively 8111811 impact on the
treatment cost for a remedial alternative and would not likely result in a
significant impact on the estimated bottom line cost of the remedial
alternatives". It is particularly important that data which has undergone a
high level of QA be used to identify and confirm the presence of contaminants
of concern. Identified concentrations that will be used as influent to a
treatment plant (design parameters) must be equally well scrutinized, as cost
1.88
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Baldwin Park ROD
impac'ts 881' be significan't. These s'ta'temen'ts are, supported by 'the fac't 'tha't
the compound vinyl chloride is lis'ted in ~able 8-1 (p. 8-8) as a con'trolling
compound ~'t is defined (p. 8-9) as "a compound tha't 881' con'trol cos't or
l.ild't the use of the reco_ended 'treaben't method". x't should be no'ted that
vinyl chloride was not de'tected in any of the CLP dau, and tha't it was only
detec'ted in one well specifically loca'ted in the OU (Wl1AZW01). The only
reported occurrence of vinyl chloride in 'the OU is froa non-CLP data available
for one well in which vinyl chloride vas detected sporadically frea 1985
through 1989, and not detected again since tha't t.iae. Xt is conceivable that
a remediation systea designed 'to 'treat vinyl chloride could be subs'tantially
over designed."
EPA ResDonse: Comment noted. Commentor is correct that vinyl
chloride has not been detected in CLP analyses, but there is no
reason to doubt its presence. Vinyl chloride has been detected
repeatedly at well W1LAZWOl and in vadose zone samples elsewhere
in Azusa. Part of the explanation for its absence in CLP
analyses is that most samples collected from monitoring wells in
the Baldwin Park area have not been analyzed through the CLP.
Instead, they have been analyzed in accordance with Regional
Board QA/QC requirements which, as noted on, pages 3-2 and 3-3,
are similar to EPA CLP requirements. Elevated detection limits
in samples with high concentrations of other compounds may also
mask its presence. '
Aj#34. "The s'tat_ent tha't "the data do DOt have to be very precise because
influent es't.iaates from a single well have a relatively small impac't on the.
'treabent cos't for a remedial al'terna'tive" is misleading. Under the
considered remedial alternatives water from only 1 or 2 wells would become
influent to a treabent plant. xt is critical that influent concentrations be
predicted 'to the highest level of certain'ty using dau of known quali'ty."
We agree with commentor that the cited statement could be
misleading. The statement is better rewritten as:
liThe data do not need to be as precise if groundwater
from multiple extraction locations is blended at a
centralized treatment facility, in which case water
quality at a single well would have less impact on the
treatment cost, and total cost, of a remedial
alternative II
The conclusions made in the text remains valid, however (pages 3-
3 and 3-4). The non-CLP data are believed to be of sufficient
quality for use in estimating influent concentrations and
verifying the contaminant subareas described in section 7.
Aj#35. "~e da'ta and statistics presen'ted in ~able 3-2 represent 'thos. for 'the
,entire San Gabriel Basin and are no't specific for 'the Baldwin Park OU. Table
3-2 does not provide any purpose for decision making with respect to the OU.
Xnstead, the public is required to sort 'through over 550 pages of laboratory
data provided in Attacbaent A and search for similar comparisons of data for
the Baldwin Park OU. Please reformat ~a1:)le 3-2 or provide a supplemental
189
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Baldwin Park ROD
table to represent data and statistics that can be referenced specifically for
. the OU.-
EPA ReSDonse: Table 3-2 was prepared for a previous EPA project,
and is reprinted in the Feasibility study to "give an indication
of the widespread and varied nature of the contamination present
in the San Gabriel Basin." Commentor's repulsion to this Table
is noted. Summary statistics, including average and peak values,
describing the nature and extent of contamination ~n the Baldwin
Park area are provided in Table 7-4. Actual water quality data
are included as Attachment A.
Aj136. -~e exclusion of data collected after August 1991 ignores data that
are important to the characterization of the contamination in the OU.-
EPA ResDonse: Data collected after August 1991 were considered.
Data up through September 1992 (the most up-to-date data
available at the time an interagency draft Feasibility Study was
completed) were used for the delineation of Subareas, as is shown
on Figure 7-1. More recent data confirm the distribution of
contamination shown in the Figures in the FS.
Aj#37. -While it aay not be practical to collect data on a tight grid as at
other Superfund sites, it is important to have sufficient data to characterize
the contamination prior to remedy selection. Additional monitoring wells may
suggest alternative remedial actions.-
EPA ResDonse: We believe that the data are adequate to specify a
remedy. See Response F.
Aj138. -Groundwater plumes are depicted on Pigure 3-1 -assuming groundwater
flow directions are fairly ..11 understood-, and inferring the direction and
aagnitude of groundwater flow without being -directly constrained by data-.
Because Pigure 2-4 clearly represents a lack of understanding of groundwater
flow patterns in the OU area, the depiction represented in Pigure 3-1 that is
unconstrained by water quality data is DOt technically defensible. ~e
iaplications resulting from £PA's alternatives based on -assumed- flow
directions -unconstrained by data- appears to be in violation with
requirements set forth under the Rational Contingency-Plan.-
EPA ReSDOnSe: EPA believes that its remedy is technically
defensible and meets all requirements of the National Contingency
Plan, which calls for EPA to "assess site conditions and evaluate
alternatives to the extent necessary to select a remedy." The
NCP and common sense discourage unnecessary data collection.
Neither of the limitations identified by commentor limit EPA's
ability to develop or select a remedy. Commentor offers the
conclusion that the data are inadequate without specifying how
the data limit EPA's ability to select an appropriate remedial
action.
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Baldwin Park ROD
As described in Response C and in response to numerous specific
comments, EPA possesses and has used knowledge of local flow
conditions in the development and evaluation of remedial
alternatives (see response to Aj#143). Figure 2-4 is a reprint
of water level contour maps prepared by LADPW presented to
illustrate regional flow conditions and does not represent any
interpretation by EPA of groundwater flow conditions. The Figure
is not used directly in the development or specification of the
remedy.
As for the extent of contamination, comment or overstates the
uncertainty and its impact on remedy selection. We acknowledge
uncertainty about the precise extent of contamination, but
believe that the data are sufficient to delineate areas of
significant contamination warranting remedial action. As
illustrated in Figure 7-1, the lateral boundaries of the Subareas
identified for the au ~ fairly well constrained by groundwater
quality data.
Aj#39. "EPA's continued use of a multi-chemical composite contour map has
created and is still creating a aisleading impression regarding the continuity
and interrelationships of areas containing chemicals in groundwater. Figure
3-1 should be deleted or replaced by a simple detected/not-detected boundary
..p. "
EPAResDonse: This comment duplicates a previous comment.
response to comment Aj #2 . '.
See
We also note that there are numerous ways to present
illustrate the extent of groundwater contamination.
commentor to prepare "detected/non-detected boundary
he/she prefers that method of presentation.
data to
We encourage
maps" if
Aj#40. "Hone of the iso-concentration ..ps include data collected over the
last year. Recent data at several facilities in the upgradient portion of the
plume significantly alter the iso-concentration lines shown on Pigures 3-1
thru 3-6. As stated in paragraph 1, "relatively few 8IODitoring wells have
been installed aDd s..pled in the OU area". Because so few data are
available, all data from recent wel18 should be incorporated into this
report."
EPA ResDonse: Commentor is correct that some data collected
after a cutoff date of fall 1991 were not incorporated into the
"iso-concentration" maps presented as Figures 3-1 through 3-6,
and Figure 11-8. Because new data are added to EPA's database on
a continuous basis, cut-off dates had to be selected for various
FS evaluations. The more recent data provide additional local-
scale detail on the distribution of contamination but do not.
alter the generalized areas of contamination shown in the
figures. Accordingly, EPA chose not to revise the figures in the
final draft of the FS.
191
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Baldwin Park ROD
I
Data collected after fall 1991 (such as from a well installed at
the Wynn oil facility) were, however, considered in the
development and evaluation of the remedial alternatives. The
Wynn oil data are included in the final draft of the feasibility
study (Attachment A, VOC Sampling Results, ..., Site Assessment
Wells) and were considered in the delineation of contaminant
Subareas, identification of proposed extraction locations, and
preparation of the Proposed Plan. The rationale for EPA's
proposal to extract and treat groundwater in the "upper area" (as
described in the Proposed Plan), rather than at the Wynn Oil
facility or other possible source areas, is discussed in detail
in Response B.
Aj#41. "If ~e ~ime period Kay 31, 1990 to Augus~ 31, 1991 applies ~o all
figures, ~en the ~~ value for SPA MW-5 is outside this period and should be
i~alici:&ed on ~e figure (see legend). ~is should be ~he same for Figures
3-3 ~rough 3-5."
EPA ResDonse: Commentor is correct that data collected at well
EPA MW-5 were collected in September 1991, after .the stated
cutoff date of August 31, 1991. The time periods noted in the
captions to the Figures should be revised accordingly.
Aj#42. "If dab fro. SPA 1CW-5 were incorporated on ~e figure but fall ou~side
~e tiae period, why weren't 1992 data also incorpOrated in~o ~he figures?"
EPA ReSDonse: The cutoff date of September 1991 was imposed to
allow for preparation of the Figures in time for issuance of the
first interagency draft of the Feasibility Study. EPA chose not
to revise the Figures in the final draft since the generalized
areas of contamination has not changed significantly.
Aj#43. "It is in~eres~ing ~o no~e [in figures 3-1 ~o 3-6] ~ha~ ~he highes~
value of ere occurs downgradient along a different flowpath ~an compounds
shown in ~e o~er plume figures. ~i8 indica~es a differen~ source area/time
and may suggest source loca~ions outside of Subarea 1."
EPA ResDonse: Not necessarily. CTC concentrations in
groundwater in the 10 to 30 ug/l range have been detected at
wells in all three Subareas, indicating the possibility of a
source of CTC within Subarea 1.
We caution reviewers not to use the Figures 3-1 to 3-6 to reach
conclusions about sources of contamination. As explained in
response to Aj#2, Figures 3-1 through 3-6 provide a "simplified,
smoothed" depiction of the extent of contamination"; they were
not prepared to show sources of contamination, nor to .
conclusively show whether the areas of contamination consist of
one relatively homogeneous area of contamination or distinct
plumes.
192
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Baldwin Park ROD
~
Aj#44. -~e statement -~e shape and size of the dOWl1gradient extent of
individual zones of contamination are typically inferred from the estimated
direction and aagnitude of groundwater flow and are in only a few cases
directly constrained by data from wells- indicates the high level of
uncertainty and lack of data regarding the distribution of chemicals in
groundwater and the significant limitations of Figures 3-1 through 3-6.-
EPA ReSDonse: This comment duplicates a previous comment.
response to comment Aj#38.
See
Aj#45. -Data used to construct Figures 3-1 through 3-6 represent aaximum
contaminant concentrations over a 15-month to 5-year period. Monitoring of
individual wells in the OU area has shown substantial seasonal variations of
VOC concentrations. ~e depictions, therefore, have limited accuracy.-
EPA Response: We agree that there is often significant temporal
variability in observed contaminant concentrations. This
variability does not imply any lack of accuracy in the Figures;
it implies only that the depiction of variability is not a
purpose or proper use of the Figures. Numerous figures in
Appendix B show how concentrations vary over time (see Figures B-
2 through B-1.5).
Aj#46. -~e total number of data points on Figure 3-1 are estimated, by EPA,
to represent approximately -100 wells-. ~e distribution of data points is
too sparse to aake the interpretations for an approximate 'a-square-mile ° area
of ItI Area 5. Based on the liaited number of data points per square aile, and
total absence of data points for several square aile areas within ItI Area 5
and the Baldwin Park OU, it is misleading for EPA to present the -simplified
or smoothed over- depictions of large continuous areas of groundwater
containing chemicals. Failure to recognize the separate and distinct areas of
contamination within these large areas of groundwater contamination will
foster the development and selection of inappropriate OU remediation
alternatives.-
EPA ReSDonse: This comment duplicates other comments. See
response to comment Aj#2 on the use of Figure 3-1.. See Response
B on the extent to which the presence of separate and distinct
areas of contamination would affect the remedy.
Aj#47. -Why were two different scales used
the purpose of comparing these two figures
s... scale for each figure, and to utilize
figures.-
for Figure 03-2 and Figure 3-1? For
it would be beneficial to use the
a common scale for all siailar
EPA ResDonse: Commentor is
prepared at different times
regret any inconvenience.
correct: the two Figures were
with slightly different scales.
We
Aj#4S. -Comparison of the distribution of concentrations posted for Figures 3-
2 through 3-5 indicate separate and distinct source areas between Subareas 1
and 2 of the OU, however EPA has depicted one large continuous area of
groundwater containing chemicals. ~e figures should identify the well
recordation number along with the posted chemical concentration in order to
facilitate an independent review of the data. Please substantiate the
1.93
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Baldwin Park ROD
..
rationale £or grouping cbemical concentrations togetber wben tbey are
interspersed between distances o£ over a aile in several locations on all of
these £igures? A clear set o£ guidelines used to construct these ..ps would
£acilitate review.-
EPA ReSDonse: This comment largely duplicates other comments.
See response to comments Aj#2 on the preparation and proper use
of Figure 3-1-
We have prepared a revised figure (included as Figure RS-2) that
includes well recordation numbers.
Aj149. "Please discuss tbe aerits of Pigures 3-2 througb 3-5 and their use in
decision aaking for the 0U1I"S. SPA bas repeatedly referred to these figures as
-cartoons and simplified approxiaations", and they are described as depicting
"substantial uncertainty in the true location of the, concentration contours.
~e boundaries between individual areas of contamination will probably change
as new data are obtained and interpreted-, (Figure 3-3 presents as few ,as 20
data points for the entire RI Areas, and £ewer than 15 data points £or the
OU). ~ese types of statements empbasize the necessity to obtain additional
data in order to make cost-e££ective and technically defensible OU decisions.
However, SPA sbowcases tbese £igures in the or:J7S as a priaary tool on wbicb to
make decisions regarding the extent and distribution o£ cbemical
concentrations in groundwater, thereby directly in£luencing the development
and selection o£ remediation alternatives.-
EPA ReSDonse: This comment largely duplicates previous
comments. See response to comment Aj#2. We emphasize again that
these figures are presented to show "regional variability in
contamination" (page 1-3) and a "simplified, smoothed" depiction
of the extent of contamination" (page 3-9). They are not
"showcased" or used as a basis for decision-making.
See Response F for a rebuttal to assertions that additional data
are needed before remedy selection.
Aj150. -It is stated that -no map of PCB contamination has been prepared
because PCB concentrations are generally somewhat less than ~CE
concentrations. " ~is stat-ent is incorrect and again ignores the importance
of identi£ying separate and distinct areas o£ contamination witbin the broad
continuous area of groundwater depicted by BPA as containing cbemicals in the
OU. ~e higbest concentration o£ all CVOCs detected in the OU was for tbe
compound PCB (18,000 ug/l), in Well W10WOMW1 north o£ the 210 Freeway. ~e
failure to identify tbese types of separate and distinct source areas witbin
the OU, and £ailure to develop and select remedial alternatives to optimize
the removal of cbemical mass from this distinct area, will result in furtber
daaage to the groundwater resource and increase the time and cost required for
ef£ective remediation."
EPA ReSDonse: This comment largely duplicates previous comments.
See Response B for an explanation of the rationale for EPA's
proposal to extract and treat groundwater in the "upper area" (as
described in the Proposed Plan), rather than at or near well
W10WOMW1 or other possible source areas.
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Baldwin Park ROD
We agree that the local-scale distribution of PCE differs from
other contaminants, but again emphasize that Figures 3-1 to 3-6
are presented to show generalized areas of contamination; they
are not the basis for EPA's decision-making.
Aj#51. "ID refer8ll1ce ~o the s~a~emeD~S ~ Pigures 3-7 &D.d 3-8 tha~ "the da~a
provide a aeasure of the degree of variahili~y iD cOD~aaiDaD~ cODceu~ratioDs
iD ~he au", &I1d "coDceD~ra~ioDs have chaDged by several hundred ppb iD a
aatter of a few moDths"; Bas SPA evalua~ed factors such as recharge eveDts,
pumpiDg pa~terDs, &I1d/or seasoDal effec~s that are likely respoDsible for the
refereDced chaDges? Please provide this iDformation for the time periods
shown on Pigures 3-7 and 3-8 (e.g., the respective pwapiDg rates for Well
08000060)."
EPA ResDonse: EPA has evaluated "factors such as recharge
events, pumping patterns, and/or seasonal effects." Although
there does appear to be some correlation between certain factors,
especially large recharge events, and contaminant levels at these
wells during specific periods, there does not appear to be
consistent, easily discernible patterns between any of the
factors and. contaminant levels. The large number of variables
impacting these wells (e.g., pumping, recharge, spatial and
temporal source variability) makes identification of specific
relationships very difficult.
Amounts of groundwater pumped in each quarter are
annual Watermaster reports, included by reference
Administrative Record (AR#404) and available from
Gabriel Basin Watermaster.
reported in
in the
the Main San
Aj#52. "Bas the sampliDg techDique for these wells ch&D.ged over ~ime.
to what exteut has this iDflueDced measured cODcentrations."
If so,
EPA ResDonse: The sampling technique for 08000060 has not
changed over time. EPA is not familiar enough with the sampling
techniques for ALR's monitoring well #1 (W11AZW01) to know if
they have changed. Regardless, it is unlikely that any changes
in sampling techniques would cause the types of variations
apparent on Figure 3-7.
Aj#53. "T.be discussion on contamin&l1t distribution changes implies ~ha~ these
changes could no~ be documen~ed until the SPA 1991-92 sampling data. However,
these shifts also can be seen iD the 1985 data as well."
EPA ResDonse: Comment or misinterprets the discussion on page 3-
23. EPA neither believes nor implies that these changes could
not be documented before 1991-92.
Aj#54. "T.be explana~ion of the plume shif~ emphasizes ~he cOD~rolliDg effects
of pumpiDg OD the groundwater flow regime &I1d COD~."'; ft.1II~ cODceD~ra~ioDs. I~
also sugges~s that the plume would be iD a differeut 10catioD aDd may be much
Darrower if DO pumpiDg occurred."
195
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Baldwin Park ROD
..
EPA ResDonse: We agree that the movement of some areas of
contaminated qroundwater have been affected by pumping. We have
seen no evidence, and commentor offers no evidence, that the area
of contamination would be much narrower if no pumping occurred.
AjISS. "Plea.e de.cribe the .ampliDg procedures and protocol that were used to
conduct the depth-specific sampling of the groundwater production wells. What
wa. done to ensure .ample isolation during depth-specific sampling of the
production .ells? Bow was it determined that no vertical flow was occurring?"
EPA ResDonse: The technique does not involve isolating depth
intervals but does require vertical flow. Sampling procedures
are described in detail in Sampling and Analysis Plan for Well
Logging and Depth-specific Sampling of Wells, November 9, 1990
(included in the Administrative Record as AR#181)
Aj156. "It i. not true that only seven wells iD the OU penetrate below the
upper 500 feet of the aquifer. According to various well construction tables
publi.hed by the Main San Gabriel Basin Watermaster an additional 10 to 12
wells in the OU are screened below the upper 500 feet. ODe of these deep
well. (08000076) is located Dear the northwest edge of the groundwater
contamination 8S shown on Figure 3-1. Apparently this well has been sampled
only once (1985). Data from this deep well and a shallow productioD well OD
the .ame facility to the southeast could provide northwesterly limits of
contamination".
EPA Response: The comment is correct: there are more than
seven wells. The text in the FS (p.3-26) should state that there
are only seven deep wells in or adjacent to the more highly
contaminated areas (where contaminant concentrations exceed 10
times MCLs).
EPA has obtained data from the listed industrial-use production
wells, 08000076 and 08000075, but the submitter of the data has
claimed that the data are confidential business information,
attorney-client communication, and attorney work product that
should not be publicly released. EPA is currently reviewing this
claim (as of February 1994). If and when allowed by law, EPA
will make this data available for public review.
Aj157. "Depictions shown in Figure 3-9, although based on verJ' limited
vertical profile concentrations, emphasize the complex nature of vertical
cont-.'DaDt distribution. AD incomplete understandiDg of vertical contaminant
distribution could result in a remecly that exacerbates contaminant transport
on the OU."
EPA ResDonse:
See response to comment Aj#58.
AjIS8. "Why has there been DO attempt to define the vertical extent of
contamination iD the northern portion of the plume? The vertical distribution
directly affects the reaedial reaedy."
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Baldwin Park ROD
EPA ResDonse: EPA believes that data on the vertical
distribution of contamination are sufficient to select a remedy,
although additional data are needed for design. The FS includes
recommendations for two new monitoring well clusters in the
northern portion of the area of contamination to help further
define both the lateral and vertical distribution of
contamination (see Appendix E). Data obtained from these new
wells will be used to determine precise extraction well
locations, rates, and depths.
In response to this and other comments on the need for additional
characterization of the extent of contamination in Subarea 1
(especially the vertical extent), EPA has reevaluated the
recommended monitoring program. We recommend three additional
monitoring locations in Subarea 1 as shown on the attached figure
(Figure RS-3). These include a third monitoring well cluster and
deeper monitoring wells installed adjacent to two existing
monitoring wells in the area (W11AZW01 and W11AZW03).
Aj159. "~e interpretation of vertical distribution of contaminants on Figure
3-9 suggests that there are at least two separate plumes of ~CE. ~e
identification of aicropl1l8les is an .important concept to remedr selection and
"I' affect the location and depths at which groundwater is pumped. Can other
aicropl1l8le. be defined?"
EPA ResDonse: The depiction of contamination illustrated in
Figure 3-9 is just one of several interpretations that fit the
available data. As discussed in response to previous comments,
there are probably multiple groundwater plumes in the OUarea.
As discussed in Responses B, EPA does not believe that it is
necessary or appropriate to define all of the "microplumes"
before remedy selection. If additional data collected during the
time of remedial design indicate the presence of specific plumes,
these data will be considered in the determination of precise
extraction locations and depths.
Aj160. "~e vertical distribution of contamination i. UDkDown in both the deep
and shallow (upper 500 feet) portions of the aquifer in large areas of the
ou. Although EPA does not consider deep vertical characterization of the
aquifer "essential to this interim action", the shallow vertical
characterization is critical and should be addressed in more detail."
EPA ReSDonse: Significant characterization of the shallow
groundwater has been carried out in Subarea 1. As of December
1993, more than 25 groundwater monitoring wells have been
installed and sampled in Subarea 1. Most of these wells are
currently sampled quarterly. Also see response to comments Aj#58.
Aj161. "~e oaFS speculates that four possible subsurface sources exist in the
ou . ~ese types of source. include dense non-aqueous phase liquid (DHAPL).
~ere is no tabulation or interpretation of data used to support these
conclusions. If such important conclusions are to be drawn substantiating
197
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Baldwin Park ROD
.
data shou~d be provided. Based on data co~~ected north of the 1-210 Freeway,
at ~east one "hot spot" has been identified. There is the potentia~ for more
groundwater to become contaai.Dated from this source area. Groundwater
extraction at the 10 and 13 c~uster., aore than l-ai~e dOWDgradient from this
source are., wi~~ increase this po.sibi~ity. If groundwater extraction is
appropriate for an interia action in Subarea I, it shou~d occur at identified
"hot spots"."
EPA ResDonse: We refer the reader to EPA guidance listed in the
Administrative Record (e.g., AR#403, EPA/600/R-92/030), or to
books or professional journal articles on contaminant fate and
transport, for more information. It is widely-accepted that if
released into the subsurface, relatively volatile contaminants
such as trichloroethylene will exist in the gaseous, aqueous, and
solid (sorbed) phases. As discussed in the FS, there is
circumstantial evidence that residual contamination is also
present in the subsurface in the Baldwin Park area as a pure,
non-aqueous phase liquid (a "NAPL").
We assume that the "hot spot" north of the I-210 freeway referred
to in the last part of this comment is well W10WOMW1, in which
case the comment duplicates previous comments. See Response B
for a discussion of the advantages and disadvantages of moving
extraction locations to the vicinity of well W10WOMW1.
Aj162. .~though a discussion of PCB, ~CA, and ~CB degradation is presented,
no interpretation of Ba~dwin Park au data is provided. Such interpretations
are necessary to support the contention that degradation processes are both
active and predictab~e. This "textbook" discussion is not referenced to site
specific data and therefore is of little usefulness in conceptualizing or
evaluating remedial a~terDatives."
EPA ReSDonse: The "textbook" discussion. is presented for readers
unfamiliar with degradation processes. As commentor's subsequent
comments note, the FS includes a discussion of site-specific data
beginning on page 3-35.
Aj163. "P~ease provide the specific data that supports the speculation
regarding the presence of anaerobic conditions in the au."
EPA ResDonse: EPA does not have specific data that support the
presence of anaerobic conditions in the au area. We note,
however, the presence of the Azusa Land Reclamation Landfill in
Azusa (ALR) and that anaerobic conditions are fairly common in
the vicinity of landfills. ALR's consultant also believes, as
stated in its "1990 Annual Report, Waste Disposal and Ground
Water Monitoring, Azusa Land Reclamation Landfill, Azusa,
California" (prepared by Law Environmental, Inc., January 28,
1991), that landfill gas is present in the vicinity of one of its
monitoring wells (MW-l) and that degradation of TCE to l,l-DCE is
likely occurring.
198
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Baldwin Park ROD
"
Aj#64. "Please provide the specific da~a tha~ supports the specula~ion
regarding the presence of aerobic condi~ions in ~he OU."
EPA ResDOnse: EPA does not have specific data that support the
presence of aerobic conditions in the OU area. However, given
the physical conditions present in the OU area (alluvial aquifer
with an overwhelming majority of coarse-grained materials,
unconfined conditions, high permeability, relatively high
groundwater-flow rates, and recharge of large volumes of surface
water in the vicinity), it is very likely that aerobic conditions
are prevalent at least in the upper portions of the aquifer
throughout most of the OU area.
Aj#65. "~e explana~ions should include the fa~ tha~ these produc~s are or
were historically used in consumer produ~s, too."
EPA ResDonse: We agree that some chlorinated solvents have and
continue to be used in consumer products, but note that the
amounts used in consumer products have typically been much less,
and often insignificant, in comparison to the amounts known to
have been used by industrial facilities in the OU area.
Aj166. "~e discussion of the Wynn Oil facili~y reveals contaminant
concen~rations orders of "gni~ude higher than seen in other OU wells. Why
were these da~a ignored in the discussion of chemical distributions, remedy
selection, and on Figures 3-1 through 3-61"
EPA ReSDonse: This comment duplicates previous comments. As
stated in response to comment Aj#40, the data were not ignored.
Aj#67. "Another possibility for the increase of 1,1-DeE is the dOWDgradi8D~
movement froa sources to the northeast. An upgradient well east of the
facility [ALa] dete~ed the highest concentration of 1,l-DeE in the area."
EPA ResDonse: It is true that upgradient sources of ~,~-DCE
could possibly be the cause for the increasing ~,~-DCE. However,
based on the timing of the increase and associated decline in
TCE, degradation may be a more likely scenario. A combination of
the two factors is also possible. As discussed in the response
to comment Aj#63, ALRls consultant believes that it is likely
that TCE is degrading to ~,l-DCE at this location (1I~990 Annual
Report, Waste Disposal and Ground Water Monitoring, Azusa Land
Reclamation Landfill, Azusa, California", prepared by Law
Environmental, Inc., January 28, 1991.
Aj#6S. "When conc8D~ra~ions of 1,1-DeB began to increase in this well
(W1lAIWD1), concen~ra~ions of PCB also increa.ed dr...~ically. Since PCB i. a
more chlorinated .olven~ than TCB, this increase is incon8is~ent with the
hypo~he.i. of biodegradation." J
EPA ReSDonse: The increase in PCE is much less "dramatic" than
the increase in ~,l-DCE, and PCE concentrations subsequently
199
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Baldwin Park ROD
.,
decreased. An increase in PCE concentrations is not necessarily
"inconsistent" with the hypothesis of degradation. There are
many factors that impact the concentrations observed at the
wells, including the location and nature of (particularly
variability in) the contaminant source.
Aj#69. -It is unclear why discussioRs of facilities that are Rot withiR the
geographic boundaries of the OU are iRcluded iR the text. ~ese discussioRB
provide little or RO assistaRce iR quaRtifyug degradatioR of chloruated
solveRts.-
EPA Response: The purpose of the discussion is to briefly
examine whether biological degradation of cvacs may be occurring
in the au area; not to quantify its rate. To accomplish this
task, we selected facilities where deep vadose zone and
groundwater investigation work had been completed and where the
investigation had verified the presence of potential degradation
products (dichloroethane, dichloroethene, or vinyl chloride). We
knew of only two facilities in the OU area which met these
criteria (as of mid 1992); therefore the evaluation was expanded
to include three other facilities in the San Gabriel Basin.
Subsurface conditions do differ in different portions of the
Basin, but evidence of degradation outside of the au area is
relevant to its potential in the au area.
Aj#70. -Figures 3-11 and 3-12 udicate that Ritrate cORceRtratioRs greater
thaR the MCL are probably already preseRt U portioRs of the OU.-
EPA Response:
Comment noted.
Aj#71. -IR what wells did depth-specific ...plug of Ritrate occur?
complete eRough to ideRtify a poteRtial high-nitrate Bone?-
Were data
EPA Response: Figure 1-4 in the FS lists the wells in the au
area where depth-specific sampling occurred. Depth-specific
nitrate samples were collected from all of these wells. As
stated on page 3-44, nitrate concentrations appeared to be fairly
uniform across the upper 400 to 500 feet of the aquifer.
Aj#72. -RadOR is Rot listed u ~able 4-2, however it is ucluded u ~ables 11-
5 aRd 11-6. ~e exclusion of radon from ~able 4-2 implies that there are RO .
chemical-specific -applicable- requiremeRts for this chemical. A TBC level of
1.5 pCi/L for radoR is listed OR ~able 4-3, however a -treataeRt objective- of
300 pCi/L is listed on ~able. 11-5 ADd 11-6. It is assumed that this
objective is based OR the proposed IICL~ this value is therefore cORsidered to
be a DC. ~e basis of the number used as the treataeRt objective should be
discussed u SectioR 4, ADd clearly identified as a TBC.-
EPA Response: Comment or is correct that the basis of the 300
pCi/L treatment objective for radon is the proposed MCL (as
stated on page 8-10 as part of the discussion of treatment
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Baldwin Park ROD
process options) and that until completion of the Record of
Decision this objective is a "To Be Considered" (TBC).
Aj173. "Bow wa. the water from SPA pumping tests discharged? Was the water
from spinDer logging aDd depth s&lllpling discharged to a storm sewer, recharge
basin, or discharged directly to the surface?"
EPA Response: Groundwater pumped during EPA-sponsored spinner
logging and depth-specific sampling of wells in the Baldwin Park
area was discharged either to a local water distribution system
(well numbers 08000060 and 01900031) or to nearby flood control
channels either by pipe or through storm drains (well numbers
01900882,71903093, 01900029, 01900035, and 08000093). The
pumping rates, volumes, and quality of water discharged are
described in the following two documents:
"Sampling and Analysis Plan for Well Logging and Depth-
Specific Sampling of Wells, San Gabriel Area 5 Remedial
Investigation. Prepared for EPA Region IX by CH2M HILL.
September 5, 1990."
"Technical Memorandum, Well Logging and Depth-Specific
sampling, San Gabriel Area 5 Remedial Investigation.
Prepared for EPA Region IX by CH2M HILL. December 2, 1991."
The rationale used to select the method of discharge is described
in:
"Draft Technical Memorandum, Disposal Alternatives for Water
Generated During Well Logging, Depth-Specific Sampling, and
Wellhead Sampling, Area 5 Remedial Investigation, San
Gabriel Basin. Prepared for EPA Region IX by CH2M HILL.
January 28, 1991."
All three of these documents are included in the Baldwin Park
Operable Unit Administrative Record (Administrative Record
Numbers 181, 203, and 276).
Aj174. "~e requirements for aesthetic qualities of treated water should be
siailar to those for uncontaminated water that currently 90es into the
purveyor's distribution system."
EPA ResDOnse:
Comment noted.
AjI7S. "Sufficient inforaation in Subarea 3 are not available to "demonstrate
that action i.nece..ary to stabili2e the site.."
EPA ResDonse: We disagree. See Response A for a detailed
response to the plume s~abiliza~ion and plume equilibrium
hypotheses offered by the San Gabriel Basin Industry Coalition as
reasons for delaying action in Subarea 3.
201
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Baldwin Park ROD
~
Aj176. "All chemicals reported as detected in the au have been included as
cheaicals of potential concern (COPCs) in the risk assessment. BPA has
outlined specific suggestions for selecting COPCs in the ~k ~...8m8DC
Qa;i.cUzac:e ~o:z: ~ (BaGS; BPA, 1989); none of the BPA approaches to
identify COPC. were incorporated in this oars. nese include, but are not
liaited to the following: a. Blimination of chemicals that were detected
infrequently (e.g., less than 5 percent); b. Comparison of co_on laboratory
cont-.,naDts (e.g., aethylene chloride, acetone) in site-specific samples to
laboratory &Del field blanks. nese chemicals would be retained as COPCs only
if the concentration in the site s..ple ezceed. 10 tiaes the maziaua
concentration detected in any corresponding blank ...ple.
Applying the above rules would eliaiDate at least ethylbenzene, .ethylene
chloride, aDd zylene(s) as COPCs. Insufficient infor8ation is available on
blank data to assess whether acetone would also be eliainated as a COPC.
Please ezplain the rationale for not following the BaGS protocol?"
EPA ReSDonse: The methodology used in the Baldwin Park
Feasibility study to select COPCs is consistent with EPA
guidance. The "specific suggestions" referred to in EPA's Risk
Assessment Guidance (RAGs) are oDtional aDDroaches offered if the
number of COPCs is so large as to make the risk assessment
unreasonably burdensome (see RAGS, page 5-20). The number of
chemicals evaluated in the risk assessment was reasonable and
manageable; nothing would be gained by eliminating any of the
chemicals.
Also, there is no justification for eliminating methylene
chloride or acetone as COPCs. These chemicals can result from
laboratory contamination during sample analysis, but in the
Baldwin Park area both acetone and methylene chloride are known
to have been widely used by industry as raw materials and
solvents.
Aj#77. "ne data set chosen for analysis in the risk assessment included only
the CLP data, even though other data also ezist for the OU. ne uSe of a data
set of only 1 year's duration can .sometimes significantly chaDge the estimated
ezposure concentrations, the COPCs selected for BDBlysis (because additional
data can allow elimination of 8IOre chemicals as COPCs, based on frequency of
detection), aDd resultiDg risks, compared with for ezample the use of a data
.et for. 3-year duration. ne uncertainties associated with use of a
selected data set should be discussed iD further detail."
EPA ReSDonse: Only CLP data were used in the risk assessment
because these data are of known, high quality. Inclusion of non-
CLP data would not, however, significantly change the risk
estimate. Inspection of Figure 7-1, which summarizes both CLP and
non-CLP data, indicates that the chemicals detected and their
average concentrations during the specified time period do not
differ significantly. .
Aj178. "It is unclear why "nondetects- from upgradient wells were removed from
the data set prior to conducting the statistical analysis. Removal of these
data results in the prediction of higher average and 95 percent upper
202
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Baldwin Park ROD
"
confidence limit (UCL) estimate. in the OU.
approach. "
Please substantiate this
EPA ResDonse: "Nondetects" from one well (V10AMMW1) and the
lower depth intervals of a second well (EPA 5-1) were not used to
estimate exposure to contaminated groundwater. The use of
nondetects from these two wells or from any of the hundreds of
other wells located in clean areas of the San Gabriel Basin would
misleadingly decrease the exposure estimate, in effect diluting
the known areas of contamination. The purpose of the risk
analysis is to estimate the risk resulting from exposure to
contaminated groundwater, not to estimate the obviously
insignificant risk from clean portions of the aquifer.
Aj179. "Additional specific information is needed to assess the approach used
in estimating exposure point concentration. for the risk assessment. It is
stated in RAGS that a well-by-well analysis should be conducted to estimate
chemical concentrations in groundwater for the purposes of the risk
assessment. It is stated in the OOPS that the data evaluation conducted for
the risk a.sessment .ignificantly reduced the estimated exposure,point
concentrations used in the analysis; it is unclear without additional
information and a detailed data evaluation whether or not this is actually the
ca.e. Plea.e provide the information necessary to conduct an independent
analysi. of the aethod. used."
EPA ReSDOnse: EPA guidance explicitly recommends using average
values for the concentration term in Superfund risk assessments
(see OSWER 9285.7-081, May 1992, included in the Administrative
Record). Commentor is incorrect in stating that RAGS requires a
well by well analysis.
We are unclear what additional information the commentor
requires; we believe that the FS provides all data needed to
estimate exposure concentrations and explains the methodology
clearly. Table 5-2 lists individual water quality results; text
on page 5-9 explains how the analytical results were analyzed;
and Table 5-3 presents the results of the analysis.
AjIBO. It ,i. unclear whether the statistical analyses were conducted with
proper regard to elevated detection limit. (if applicable; no discus. ion was
found in the text). The BPA default approach of applying one-half the CRQL
for all noDdetects was used in the analysis. Use of one-half aD elevated CRQL
can sometimes increase the exposure point concentration estimates
significantly, and, with very potent carcinogens, can aake an iaportaDt
difference in the results of the risk asses.ment.
EPA ReSDonse: Inspection of Table 5-2 (which lists detection.
limits for all samples) indicates that detection limits were not
elevated. They are less than or equal to 1 ug/l for all
analyses.
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Baldwin Park ROD
..
Also, the approach used in the risk assessment was to assume one-
half the detection Iimit (not one-half of the CRQL) if a chemical
was not detected in a particular sample.
Aj#81. "Plea.. prov~de detailed informat~on on the .tatistical approach used
in the analy.i., .0 that an independent rev~ew of the assessment can be
conducted. Some of the results of the stat~stical analysis appear to be of
concern. For example, a. shown on Tables A-l through A-4 (Appendix A),
concentrat~ons for many of the COPCs were predicted to be the ~ for both
the average and 95 VCL concentration, rais~g questions about the use of
elevated detection liait., robustness of the data set, etc. In addition, as
.hown in Table 5-3, the s~rd c:leviat~on for TCB is qu~te high (e.g.,
av.rage concentration of 55.1 - 107.8 89/1), in~cating high variability in
the data .et for th~. cheai.cal. Th~s standard deviat~on .e... to ~c:licate
high uncertainty in the "actual" average and 95 UCL concentration.. Since TCE
~. the r~.k "c:lriver" for the OU, a change in the concentration data, and/or
the a.sumpt~ons used to develop these concentration. could dramatically affect
the results of the risk assessment."
EPA ReSDonse: The expression of "concern" for the results of
the statistical analysis is unfounded. As described in response
to the previous comment, detection limits are not elevated. Nor
is the absence of a "normal" distribution or the level of
variability in the data unusual for environmental sampling; we
believe that it does not warrant additional or more sophisticated
analyses.
We agree that a higher concentration estimate, particularly for
TCE, would change the risk estimate. The impact-of assuming a
higher TCE concentration is easily predicted, however. If the
peak TCE concentration from all of the sampled water supply wells
(450 ug/l) were used in the risk estimate rather than the 95th
UCL (96.9 ug/l), the RME risk estimate would increase from
7 x 10-5 to approximately 2 x 10-4.
Aj#82. "SPA (1989) indicates that the lower of the max~um concentration and
the 95 VCL should be used to represent the exposure point concentrat~on for
the reasonable maxiaum exposure (RME) scenario. 110 discussion was found in
the text concerning this; more information (i. e., maxiaum detected chemical
concentrations) is needed to ensure that the lower of the two values was used
in a11 cases."
EPA ReSDonse: Maximum concentrations are easily determined from.
a visual inspection of Table 5-2. A comparison of Tables 5-2 and
5-3 shows that the 95th UCL is lower than the maximum '
concentration for all contaminants, with three exceptions. The
exceptions are benzene (UCL=0.5; maximum=0.5J), ethylbenzene
(UCL=0.5; maximum=0.4J), and methylene chloride (UCL=0.5;
maximum=0.2J). The risk resulting from exposure to the three
contaminants listed as exceptions does not contribute measurably
to the total risk estimate.' .
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Baldwin Park ROD
Aj#83. "~e lower of the state aDd federal NCLs for each COPC i. listed in
~able 5-3; these values include proposed NCLs in several ca.es. ~e document
should clearly outline which of the.e cheaical. are considered T.BCs, and which
are con.idered to be "applicable" ARAR8. In addition, existing MCLs for each
of the chemicals with a proposed MCL should be presented, if available."
EPA Response:
Federal MCLs.
Table 4-2 for
The values listed in Table
All are ARARs. No proposed
a complete list of State and
5-3 are State or
MCLs are listed.
Federal MCLs.
See
Aj#84. "Because the lower of the chemical-specific state and/or federal NCLs
is considered to be an ARAR for that chemical in groundwater in the Baldwin
Park OU, it was wmecessary to retain all chemicals as COPCs for evaluation in
the risk as.essm8l1t. Using a preli.miDary screening of 95 UCL chemical
concentrations against the lower of the state and/or federal MCLs listed on
~able 5-3, the following ch..icals could be dropPed fro. the risk ...e...ent,
as they are le.. than the NCL: l,l,l-~CA, l,l-DCA, benzene, chloroform,
ethylbenaene, methylene chloride, toluene, trans-l,2-DCB, and zylene(s)."
'EPA Response: This comment duplicates a previous comment.
response to comment Aj#76.
See
Aj#85. "Exposure point concentrations were estimated assuming that the data
set was normally distributed. JIore often than not, environmental data are
lognormally distributed, indicating that use of the arithmetic mean and the
upper 95 percent confidence limit of the arithmetic mean <95 UCL) may not
appropriately represent the data 8et. Rather, the U8e of the geometric aean
and its corresponding 95 UCL 88Y be more appropriate to represent groundwater
concentrations in the OU. Depending on the methods used in data compilation,
statistics, and data evaluation, the use of the geometric aean can reduce
"assumed" average and RMB chemical concentrations by up to several orders of
88gnitude. Dis reduction can dramatically decrease risks predicted in a risk
assesslDent. Methods to assess the normality of the data set are readily
available, and are commonly applied at HPL sites. ~ese methods should be
used for assessing the normality of the data set, and the results of this
analysis should be used in estimating exposure point concentrations for use in
the risk assessment."
EPA Response: We disagree that additional analyses of the
distribution of the data are needed (i.e., normal, log-normal) or
that the risk estimate should make use of a geometric mean. EPA
guidance (see OSWER 9285.7-081, May 1992, included in the
Administrative Record) specifically recommends use of the
arithmetic mean "regardless of ... the type of statistical
distribution that might best describe the sampling data." The
guidance further states "The qeometric mean ... bears no logical
connection to the cumulative intake that would result from long-
term contact with site contaminants..."
Aj#86. "Iii estimating exposure point concentrations, groundwater data from the
entire OU was used, without regard to the location of existing aunicipal or
water purveyor wells. Alternative methods for use in a risk assessment
include estimating potential health effect. on an area-specific basis (e.g.;
generating health risk isopleths for the entire area, to reflect the
significant differences in chemical concentrations distributed throughout the
205
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Baldwin Park ROD
"
OU; conducting the risk asses.ment with consideration of current weJ.J.head
concentrations, rather than an estimated average or 95 UCL; use of welJ.-by-
weJ.J. data, as stated above), etc. Risk as.essments conducted on an OU basis
increase the uncertainty of the assessment, and oversimpJ.ify the compJ.ez
conditions in the di.tribution of groundwater cont-.iq.nts. A risk assess.ant
considering the differing concentrations throughout the OU could be useful in
both defining the "actual" risk (e.g., froa weJ.lheads currentJ.y in use), would
aore appropriately define the potential future risk in each area, and would be
useful in helping define specific areas possibly needing remediation."
EPA ResDonse: We agree that more complicated methodologies
could be used to estimate concentrations, but believe that they
are unnecessary. The conclusion of the risk assessment, that
remedial action is warranted in portions of the aquifer
contaminated above drinking water standards, would not change.
Aj#87. "~e risk asses.ment used an average daily drinking water intake value
of 2 L/day; this value should be 1.4 L/day, based on 50th percentile adult
ingestion rates provided in the Exposure Pactors Bandbook (BPA, 1990)."
EPA ResDonse: Use of 2 L/day is consistent with u.s. EPA Region
IX recommendations. Page 9 of the Risk Assessment Guidance for
superfund Human Health Risk Assessment, u.s. EPA Region IX
Recommendations (Interim Final, 12/15/89) states: "The
traditional default values of 2 L/day water ingestion ... should
be used for both "Average" and "Reasonable Maximum" scenarios in
Region IX risk assessments. This deserves special notice since
national guidance is to use intake assumptions from the Exposure
Factors Handbook, which presents different average values." The
guidance is included by reference in the Baldwin Park
Administrative Record (AR#403).
Aj#88. .~e inhalation slope factor for ~ has recently been reduced from
0.017 to 0.006 mg/kg/day-1 a. recommended by BPA's Office of Bealth and
BDvironmental Assessment (BPA, 1992). Although the tert indicates that the
new slope factor was used in the analysis, ~ables 5-5, A-1 and A-2 indicate
that the old sJ.ope factor of 0.017 was actuaJ.J.y u.ed. ~e!rCB risks shouJ.d be
recalculated using the new slope factor, and the PS and community relations
fact sheet should be updated to reflect this change."
EPA ResDonse: The first statement, that the inhalation slope
factor for TCE has been revised, is correct.. The revised,
provisional value, 0.006, was not used in the Baldwin Park OU
risk assessment since it was published after the risk assessment
was completed.
The second sentence in the comment is incorrect. The text (p.5-
17) and the Tables all indicate that the old, unrevised value,
0.017, was used.
Use of the revised slope factor would not affect EPA's decision
to take action or the scope of the action. Commentor presents
the impact of this change in comment Aj#92.
206
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Baldwin Park ROD
Aj#89. "In addition, TCB (which "1' be on a continuum between a possib~e and
probab~e huaan carcinogen (SPA, 1992]) has not been assigned either an
iDha~ation or ingestion reference dose (Rm) on IRIS. Thus, the infoZ'IIAtion
on Tab~es 5-5, A-3, and A-4, which present an Rm and the ca~cu~ations of
noncarcinogeDic hea~th effects froll exposure to TCB, ahou~d be corrected. A
va~ue of 0.006 was erroneous~y ~isted on these Tab~es a. an Rm, rather than
as the s~ope factor for the cheaica~."
EPA ResDonse: . The RfD of 0.006 listed for TCE is correct. This
provisional oral RfD value was derived by EPA's Environmental
criteria and Assessment Office. A copy of an EPA memorandum
documenting the RfD is included in the Administrative Record.
The memo is from Joan Dollarhide to stan Smucker, dated 4/13/92.
Aj#90. "In the characteriaation of potentia~ health risk, chemicals considered
to be known or potential carcinogens should be combined using the carcinogenic
weight of evidence (WOB). SPA (1989) recommends that Group A carcinogens
shou~d be sWlUlled separately fro. Bl, B2, and C carcinogens. Thus, risk
characteriaation results shou~d be separately presented for each of the four
WOB categories, rather than sWIIIIIiDg all. four categories. In the risk
assess.ent, all carcinogens were .WlUlled as if they were all "known" hWlUU1
carcinogens, without consideration, of the WOB. Please revise the risk
assess.ent accordingly to follow SPA's protocol for risk characteriaation
(ZP.&, 1.989)." ' ,
EPA ReSDonse: The method used in the Baldwin Park OU
assessment is consistent with and explicitly described
guidance (RAGs). RAGs states:
risk
in EPA
"The cancer
carcinogens
as to class
risk equation for multiple substances sums all
equally, giving as much weight to class B or C
A carcinogens."
Aj#91. "Based on the erroneous Rm used for risk characterization, the
resulting haaard quotients (Tables 5-6, A-3, and A-4) of 0.25 and 0.44 for
average and RME cases (for both ingestion and inhalation exposures),
respectively, should be deleted and replaced with aeros in each case. In
addition, the resu~ting hazard index is changed significantly by this aistake;
previous results indicated total noncarcinogenic hazard indices of 1.0 and 1.8
for average and RME scenarios, respectively (Tables A-3 and A-4). Hew haaard
indices of 0.5 and 0.92 for average and RME, respectively, are calculated when
this aistake is corrected. While the initial results indicated that there may
be a concern for toxic effects from the noncarcinogenic chemical. in
groundwater, the results of this change indicate that noncarcinogenic health
effects are HOT expected from the presence of these chemicals (using the
a..umption that a haaard index greater than 1.0 indicates that adverse ilDpacts
"1' occur; ZP.&, 1.989). ..
EPA ReSDOnSe: Comment or is incorrect in asserting that EPA used
an erroneous RfD. As noted in response to comment Aj#89, EPA
properly assumed an RfD of 0.006 for TCE. The hazard quotients
of 1.0 and 1.8 remain valid.
Aj#92. "Similarly, the risk characterization results for hypothetical cancer
risks from exposure to TCB were also calculated incorrectly. As indicated
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Baldwin Park ROD
. .
above, the revised slope factor of 0.006 .g/kg/day~ should have been used in
the analysis; when this change is ..de, currently listed TCB risks are reduced
to 1 x 10-6 and 7 x 10-6 for average and RHB exposure scenarios , respectively."
EPA ResDonSe: Commentor is correct that the slope factor for TCE
has been revised downward from 0.017 to 0.006 mg/kg/day-l. Use
of the revised slope factor would not affect EPA's decision to
take action or the scope of the action.
Aj,93. "Although the text has a detailed discussion of the environmental
. species that are present in the Santa Fe Daa area (pp.5-22 to 5-27 ), only one
statement liDking potential environmental exposures with groundwater
concentrations was found. This sole reference cited aD average concentration
of less than 1 ug/l PCB and TCB in Well 08000070, used to fill the recreation
lake. 110 surface water data are presented in the O'C16'S, and therefore
considering the volatile nature of PCB aDd TCB, there is a strong possibility
that no environmental exposures are occurring."
EPA ResDonSe:
We agree.
Aj'94. "Groundwater injection wells and aquifer recharge via surface discharge
should be incorporated into Table 6-1 as general response actions to control
contaaiDant aigration (hydraulic containment)."
EPA ReSDOnSe:
Comment noted.
Aj'95. "Table 6-2 Table 6-2 contains a cOllllllOn aistake. In Situ Treatment and
Water Use are not really GRAs that address the response objective. They are
just parts of potential groundwater extraction alternatives; analogous to
choosing a turbine versus a submersible pump. That is, they are just process
options. Similarly, aquifer recharge should be separated from water use
because it is most commonly combined with groundwater extraction to affect
hydraulic containment, a "general response action".
EPA ResDonse: In situ treatment is presented as a General
Response Action since many in situ treatment methods (e.g.,
passive funnel and gate systems) do not involve groundwater
extraction. still, we appreciate the suggestions on alternative
ways to present the results of the response action/technology
screening process.
Aj'96. "In-Situ Treatment - The comment in the applicability column on
by-products suggests that the only in-situ method considered was
biotreatment. Was air sparging considered? The aquifer and vadose zone are
sufficiently permeable and the predomiDBDt chemicals are volatile. Since the
constituents of concern do not biodegrade easily under aerobic conditions, by-
products are not a concern. The problems with groundwater extraction,
including water disposal issues, warrant. a more detailed evaluation of other
options."
EPA ResDonse:
sparging.
See Response E for a detailed evaluation of air
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Baldwin Park ROD
Aj#97. "Groundwater Extract~on - Although extract~on 88Y remove h~gh ~eve~s of
vocs, the effect~veness ~s ~ocat~on dependent. If the -remedy ~s focused
.o~e~y on aigrat~on contro~, the ~ab~e shows that a downgrad~ent ~ocat1on ~s
preferab~e. Bowever, ~f the we~~ ~. downgrad~ent, the "yes" ~n the remova~
co~umn change. to a "no"."
EPA Response: We agree that effectiveness is location-dependent.
We note that a well located at and within the downgradient end of
contamination could achieve both objectives of migration control
and removal of high-level of contamination.
Aj#98. "When a re~at~ve~y .ma~~ area of very ugh concentrat~ons are known to
ex~.t a. u th~a OU, extract~on ~. 8IOre log~ca~~y ~ocated there to remove the
ugh ~ev.~. and prevent the~r aigrat~on dOWDgra~ent. OD~y then .hou~d both
co~umn. on ~ab~e 6-2 [for the "groundwater extraction entry] contau a "yes"
response."
EPA ResDonse: We are unsure of the "relatively small area of
very high concentrations" to which comment or refers. As pointed
out in response to other comments, the number of monitoring wells
are too few to define individuals plumes. See Response B for a
discussion of the alternative approaches for locating extraction
wells in areas with multiple sources.
Aj#99. "Groundwater Extraction - Accordug to the tab~e, groundwater
extraction w~th the we~~head treatment option ~s not capab~e of removug high
~eve~s of cont:....;n.tion or providug a degree of migration contro~. !rh~s is
incorrect. A we~~head treatment system on a production we~~ with relative~y
ugh concentrations will remove high ~eve~s of contamination. If pumping ~s
sufficient, ~t may a~so provide a degree of contaiDment. A we~l doe. not have
to pump contuuous~y to assist u migrat~on contro~. Contudnanta that begin
to aigrate past the uf~uence of a pumping we~~ 88Y be "recaptured" when
pumping resumes."
EPA ResDonse: We agree that treatment systems installed on
production wells with relatively high concentrations will remove
high levels of contamination and will, if suitably located,
contribute to migration control. We also agree that intermittent
pumping can contribute to migration control.
Aj#lOO. "The note in the applicabi~ity column states that "(B)xisting
dOWDgra~ent wells are not opt~lly ~ocated for aigrat~on control".
2 of the 3 proposed extraction ~ocation. u Subarea 3 are ex~stug
downgradient wel~s."
Bowever,
EPA Response: We agree. The text in the FS should state that.
existing wells are not suitably located to fully satisfy EPA's
migration control objective.
Aj#lOl. "Please provide the rat~ona~e to support EPA's decision to not include
optimizing mass removal of chemica~s from the aquifer to cOlDp~iment the OU
"migration control" object~ve. Current data udicates the presence of
separate and d~stinct source areas of chemicals u the OU that ~f continued to
be ignored, w~ll further degrade aquifer cond~t~ons and ucrease the cost and
time necessary to imp~ement effective migrat~on control and aqu~fer
209
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Baldwin Park ROD
"
reaed~at~on aea.ures. BLA'. ~dependent &Da1y.~. o£ aqu~£er cond~t~on.
~d~cates that a 80urce contro1 act~on wh~ch ..xi8izea ..as remova1 action
cou1d compli8eDt lli.gration control, aDd thereby further optimize the remedial
response objective for the OU."
EPA ReSDonse: Mass removal is an objective of the Baldwin Park
QU. See Response B for additional details on how the remedial
objectives of migration control and mass removal will be
translated into extraction rates, locations, and other project
details.
See Response B for additional explanation of EPA's strategy for
addressing known or suspected source areas.
Ajll02. "SPA's primary re.ponse objective ia stated to be -lIi.gration control",
with -...s reaova1" a. a secondary objective. ~e LARWQCB has a para11el
responsibility to a££ect -source control". Based on the goal o£ se1ecting a
reaedial . alteruative that i. compatible with the final remedy, and based on
the fact that lli.gration control may at least be in place through production,
the aost effective way to control lli.gration ..y be to reduce the source tera.
~erefore -source control" or ..xiaizing "..s. removal" should be considered
objectives equivalent to "migration control" or should be combined into a
single response objective for the QU."
EPA ResDonse: We agree that the remedy for the Baldwin Park area
should address the sources of the contamination. The extraction
and treatment facilities included in Subarea 1 in the selected
remedy will "reduce the source term" by limiting the impact of
any residual surface or subsurface contamination on portions of
the aquifer downgradient'of the Subarea.
We are unclear of the impact, if any, of restating or re-ranking
the two remedial objectives of migration control and mass removal
as suggested in the comment. Instead, we present in Response B
guidelines for translating the remedial objectives into
extraction rates, locations, and other project details.
Ajl103. "~e remedial response objective of inhibiting contaaiDant lli.gration
fro. highly contaaiDated areas is currently being achieved through production
well pU8p~g in Subarea 3. ~is objective could also be achieved in Subarea 1
by groundwater extraction fro. the most highly contaaiDated area upgradient
from the proposed extraction wells. Proposed extraction clusters are more
than I-mile dowDgradient from these high concentrations."
EPA ReSDonse: There is no evidence to support the assertion that
production well pumping in Subarea 3 is achieving EPA's remedial
objectives in the Subarea. See Response A for a detailed
response to this plume stabilization or no migration hypothesis.
Also see Response B for explanation of EPA's proposed pumping
configuration.
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Baldwin Park ROD
..
Aj#104. "Plea.e provide the rationale to conclude that "the remedy will be
optimized in .izo and configuration for aigration control rather that mass
removal". The optimiaation process should balance aigration control and ..s.
removal objectivos. A "balanced" response objective that would opti8iae the
"tiae- and cost-savings" provided by an au interia action should be
incorporated."
EPA ReSDonse: The decision to make migration control the primary
objective of the Baldwin Park OU is consistent with EPA
regulations and guidance and experience at other contaminated
groundwater sites. See pp. 6-1 through 6-13 for references to
relevant EPA regulations and guidance. Also see response to
comment Aj#102 and Response B which presents guidelines for
translating the remedial objectives into extraction rates,
locations, and other project details.
Aj#10S. "It is implied that BPA's interia action will resolve the items cited
as "aeasons Rot to Delay Action". Please explain how the interim action will
resolve each of the five item. discussed on pages 6-11 through 6-12."
As stated in the Proposed Plan, EPA's selected
EPA ReSDonse:
remedy would:
Limit further migration of highly contaminated groundwater
into less contaminated and uncontaminated portions of the
aquifer [reducing the potential for human exposure];
Reduce, but not necessarily eliminate, the need for water
purveyors with wells in the Baldwin Park area to install
treatment
Reduce the cost and difficulty of operating existing
treatment facilities by preventing highly contaminated
groundwater from reaching existing facilities
Reduce the likelihood that future increases in contaminant
concentrations at active water supply wells will result in
"emergencies" requiring immediate actions such as relocating
wells to clean areas .
Reduce the eventual cost, difficulty, and time required for
complete cleanup of all or portions of the aquifer. (If no
action is taken, continued contaminant migration would
result in the need to treat larger volumes of contaminated
water and may result in the increased presence of vinyl
chloride or other CVOC degradation products that are more
difficult to treat or more toxic than the parent compounds)
.
.
.
.
.
Aj#106. "The statement "Groundwater contamination in the au area is known to
be spreading into less contaminated and uncontaminated portions of the
aquifer", has' Dot been substantiated by a technical evaluation of available
data commensurato with the importance of this conclusion."
EPA ReSDOnSe:
We disagree.
See Response A.
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Baldwin Park ROD
"
Aj#107. "A. Do~ed iD previous .ec~ioD. iD ~is documen~, ~e dOWDgradien~
of ~e plume i. DO~ well defiDed. Curr8D~ pumpiDg aDd wellhead ~reabaeD~
provide a aea.ure of cOD~aimaeD~ dOWDgradien~ aDd perai~ ~ime ~o cOD~iDue
Deeded iDve.~iga~ioD. iD ~i. area. ~is would ensure ~a~ ~e area i.
proper17 chara~eri8ed before 8ODe7 is .P8D~ UDDeces.ari17."
part
will
EPA ResDonse: CUrrent pumping is inadequate to meet EPA's
remedial objectives. This conclusion is supported by the
evaluation of the "no action" alternative included in Section 12
of the FS. Also see Response A for discussion of the (limited)
value of conducting additional investigations before selection of
a remedy.
Aj#108. "Plea.e explaiD BPA'. cODclusioD ~~ "~e parti~ioDiDg of aore
COD~.-~ft.D~ ...s froa ~e dissolved ~ ~. sorbed phase" would occur iD ~he
aquifer [p.6-l2]. SiDce parti~ioDiDg is aD equilibrium driveD process i~ is
unclear how ~ime will iDcrease COD~._ift.Q~. .orbed ~ aquifer ..~erial.."
EPA ResDonse: As contaminated groundwater moves into clean or
less contaminated areas, additional contaminant mass would
partition from the dissolved into the sorbed phase.
Aj#109. "Af~er reviewiDg BPA wa~er quali~7 da~a aDd LARWQCB files, DO facili~7
iD ~e ou has been fouad where cODcen~ra~ioDs of DeB, DCA aDd viD7l chloride
iDcrease wi~ ~iae. ViD7l chloride has oD17 been de~e~ed iD a few wells iD
~e en~ire ou. 1Io.~ of ~e de~ec~ioD. were raDdom, oDe-~ime hi~s a~ low
cODcen~ra~ioD.."
EPA ResDonse: As stated in the FS, the text does not refer
specifically to facilities in the au area.. (The last paragraph
on p.6-12 reads: "At numerous facilities in the San Gabriel
Valley...") In addition, the text does not state that DCE, DCA,
and vinyl chloride are increasing. It states that concentrations
of "DCE, DCA, .QI: vinyl chloride increase with time."
There is only one facility in the au area with a long enough data
record to evaluate changes in vinyl chloride concentrations with
time. At this facility (the ALR landfill), trends at one well do
indicate that landfill-influenced degradation may be occurring.
Aj#110. "ID order ~o evalua~e ~he issue of biodegrada~ioD, exis~iDg ~reDd.
should be examined. !rhe len~7 discussioD iD Sec~ioD 3 oD17 explaiDs ~he
cODce~ aDd preseD~s sWlllD8~ da~a OD po~eD~ial degrada~ioD produc~s from ~wo
OU facili~ies. Wa~er quali~7 da~a should be aDa17zed over ~ime ~o see wha~
CODclusioDS CaD be ..de regardiDg ~he regional groundwa~er flow regime."
EPA ResDonse: We agree that additional evaluations are possible.
Also see response to comment Aj#69.
Aj#lll. "A cur80~ review of all of ~e de~e~ioD. pre8en~ed OD EPA'.
cODceD~ra~ioD maps of po~.D~ial degrada~ioD compounds iD Se~ioD 3 reveals
~~ aD overall iDcrease in degrada~ioD produc~s is DO~ occurring. Of ~he 15
wells ~~ have receD~17 de~ec~ed 1,2 DCA or 1,1 DeE (Figures 3-4 aDd 3-5),
~ere are DO wells ~ha~ have iDcreasiDg ~rends. of bo~ compounds over ~e las~
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Baldwin Park ROD
S-years. Le.. than 20 percent of the well. contaiD iDcrea.iDg trend. for
either of the two compounds. Attachment A data indicate that there has been
only one detection of viDyl chloride (2 ppb) iD the OU area iD the last few
years."
EPA ReSDOnSe: An overall increase in all degradation products
would not necessarily be expected even if biodegradation is
occurring. Given the complex contaminant distribution in the
area (probably numerous sources and plumes), degradation may be
occurring at different rates along different degradation pathways
in different areas depending on local conditions (both source-
related conditions and physical conditions).
It is not clear how the determination that both 1,2-DCA and 1,1-
DCE are not increasing at any wells impacts an evaluation of
degradation. As shown in Figure 3-10, these two compounds are
not in the same degradation sequence and would not be expected to
both be increasing for degradation of a given plume or
contaminant source.
Ajlll2. "In the case of this OU, additional mDnitoriDg may be necessary in
order to orooose a remedial action."
EPA ReSDonse: This comment duplicates previous comments. As
stated previously, we do not believe that additional monitoring
is needed before remedy selection. See Response A for additional
details.
Aj1113. "Continued pumping or increased pumping at selected water supply wells
can also inhibit contaminant migration.Watermaster's iDstitutional authority
can assist in achieving EPA objectives."
EPA ResDOnSe:
We agree.
Aj1114. "~is paragraph [p.6-14, paragraph 2] very effectively describes the
concept that should be applied to groundwater extraction in the OU. Both ..ss
reaoval and aigration control can be achieved through extraction at the source
area (.) where concentrations are the highest. Why not propose extraction
north of 1-210 Preeway where concentrations of some compounds are orders of
aagnitude higher than other wells in the OU."
EPA ReSDonse: This comment duplicates previous comments. See
Response B for a detailed response. We note that concentrations
of some contaminants in the Baldwin Park area south of the I 210
freeway are the same order of magnitude as concentrations north
of the I210 freeway. For example, 9,800 ug/l PCE was measured at
MW-3 at the Aerojet facility (5/93), versus concentrations as
high as 32,000 PCE at W10WOMW1 (8/93). The difference is a
factor of three, not "orders of magnitude."
Aj111S. "Please provide the documentation and describe the results of the
"bench-.cale oaone/hydrogen peroxide study that wa. completed using
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Baldwin Park ROD
-
groundwater from the au area and Whittier .arrows.-
.hould be available for public review~-
~i. important study
EPA ReSDonse: The results of this work can be found in two
papers referenced in the FS, both by Bellamy, William, et al
(1989 and March/April 1991). The 1991 article is available in
the Research Journal, Water Pollution Control Federation, Volume
63, Number 2.
Aj1116. -Please provide the definition and siguificance of use of the term
- a..iai.lable - organic compounds.-
EPA ReSDonse: The term "assimilable" is defined as "capable of
being assimilated." Assimilable organic compounds (AOC) are
compounds that can be converted by microorganisms into protoplasm
and assimilate into their cell mass. The amount of these
compounds present in the ozonated water is higher than in the
untreated water.
Aj1117. -~e last senteace of this page [p6-2S] is unclear.
-GAC filter [~?) through biological ~egradation-?-
Should it read
EPA ReSDonse: The referenced sentence is correct as written.
some extent, the granular activated carbon (GAC) filter will
become biologically active. Because the listed compounds are
readily biodegradable, they can be effectively removed by even
this limited biological activity.
To
Aj1118. -Aquifer recharge can help control contAminaDt migration only if
recharge occur. at a desirable location.-
EPA ResDonse:
We agree.
Also see response to comment Aj#179.
Aj#119. -~e effects of increased spreading on contaminant transport must be
fully evaluated prior to remedy implementation.-
EPA ReSDOnSe: EPA believes that it has completed adequate
evaluations of the impacts of recharge to support the selection
of remedy. Also see response to comments Aj#179
Aj1120. -As stated in the document, a combiDation of treatment processes "I'
be the 80st cost effective. Where are techDology combinations evaluated in
this document?-
EPA ResDonse: See Section 8 for an evaluation of two
combinations of treatment technologies (treatment technology
trains): air stripping followed by liquid phase carbon, and
Advanced Oxidation Processes followed by liquid phase carbon.
Section 8 also includes a discussion of the potential merits of
two-stage air stripping (p.8-41).
Aj1121. -!freabeat facilities currently exist in the basin. ~e Main San
Gabriel Basin Wateraester and the San Gabriel Water Quality Authority, as well
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Baldwin Park ROD
as individual water purveyors have been active in the design and installation
of wellhead treatment facilities in this OU. Data from these installations
would provide practical inforaation on specific treatment technologies,
operating problems, aDd costs. Were these data used in the develop8ent of
reaedial action.? Why were they not referenced in the section on technology
screening? Were they considered in the cost development?"
EPA ReSDonse: The experience of water purveyors and the San
Gabriel Basin Water Quality Authority were considered during the
development of remedial alternatives. They confirm EPA's
conclusions that either air stripping or liquid phase carbon may
be effective technologies depending on the precise mix on
contaminants. Data from existing San Gabriel Basin treatment
facilities were not used in the cost evaluation since contaminant
concentrations differ from those expected in EPA's selected
remedy. contaminant concentrations influence carbon usage, which
is one of the biggest contributors to operating costs. Nor were.
local data used to "identify specific designs or O&M problems."
It may be worthwhile to complete an up-to-date evaluation of the
performance of existing treatment facilities in the San Gabriel
Basin during remedial design, but it is not necessary or
appropriate as part of the remedy evaluation and selection
process.
Aj#122. "Please provide the details of the evaluation referenced in the
stat..ent "~rough an evaluation of the available groundwater quality data in
the OU area, three subareas within the larger OU area have been identified
betweeD which there appear. to be a significant change iD contaminant
concentrations.""
EPA ReSDonse: This statement is further explained in the
descriptions of each of the three Subareas on pp. 7-2 through 7-
6. Also see Response B for additional discussion of the
importance of the Subareas.
Aj#123. "~e dividiDg liDe between Subarea 1 and 2 is arbitrary. A more
precise representation would be to identify small hot spots as Subarea 1 and
iDclude the other Subarea 1 wells iD an expanded Subarea 2. Over time, Well
WllAZW03 (Subarea 1) and Well 1900034 (Subarea 2) have had very similar total
VOC concentrations. Similarly, data frol8 other wells iD Subarea 1 (omitted
from Figure 7-1) demonstrate that total VOC concentrations do not change
significantly from Subarea 1 to Subarea 2. For example, the average total
VOCs for all data pre.ented iD Subarea 2 on Figure 7-1 i. 450 ppb. ~. ia
very siailar to other wells iD Subarea 1 that are oaitted fro. the ..p yet
have .iailar LARWQCB data (WllAZWOl = 387 ppb, WI0HCMWI = 446 ppb)."
EPA ResDonse: The primary distinction between Subareas 1 and 2
is that within the boundaries of Subarea 1 there appear to be
significant and multiple sources of the groundwater
contamination. This interpretation is based on information on
the magnitude and duration of chemical usage, handling, and
disposal, and on the magnitude, extent, and pattern of
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Baldwin Park ROD
contaminant concentrations in soil, soil gas, and groundwater at
industrial facilities in the Subarea.
In their comment, Aerojet/ALR compare Subareas 1 and 2 based on
average CVOC concentration. This comparison does not, as
claimed, demonstrate that CVOC concentrations do not change from
Subarea 1 to Subarea 2. Data presented in Section 7 and other
comments submitted by Aerojet/ALR demonstrate significantly
higher concentrations in Subarea 1 than in Subarea 2 (although in
comment Aj#125, Aerojet/ALR prefer to label the higher
concentrations as anomalous). Instead, the comment highlights
the important point that Subarea 1 probably includes multiple
sources and plumes of contamination separated by less
contaminated areas, and is not a homogeneous area of
contamination~ We also note that comparisons of concentrations
between wells must account for differences between wells in their
spatial relationship to the original spill or release, and
differences in construction. A well located at the centerline of
a plume will show a higher concentration than a well located at
the fringes of the plume. Differences in construction are
evident in a comparison of wells installed at three different
facilities. Wells W11AZWOl through W11AZW09, for example, have
much longer screen lengths than the Aerojet wells or well
WIOWOMW1. The screen lengths for wells Wl1AZWOl through Wl1AZW09
exceed 200 feet; the screen lengths for the Aerojet wells and
well W10WOMW1 are 50 and 30 feet respectively.
Comment or also recommends redefining Subarea 1 to include "small
hot spots." See Response B for a more detailed response to this
and other comments on the delineation and use of the Subareas.
Aj1124. "There are more than five facili~ies being inves~iga~ed in Subarea 1."
EPA ResDonse: We agree,' and do not state or imply otherwise.
The FS mentions five facilities with groundwater monitoring wells
located in the area of contamination (as of 9/92).
Ajl125. "There were 20 aoni~oring wells in Subarea 1 a~ ~he ~i.ae of report
publica~ion. In con~ras~, there are only four wells in Subarea 2. Bxce~ for
2 ...11 areas iD Subarea 1 where conc8D~ra~ions are anomalously high, ~o~al
VOC concen~ra~ions are s~lar throughou~ both subareas."
EPA ReSDonse: This comment largely duplicates a previous
comment. See response to Aj#123 and Response B.
Aj1126. "The i8plica~ioD tha~ 1,2 DCA and 1,1 DeB cODc8D~ra~ioD. are higher in
Subarea 1 is incorrect. Approxima~ely 90 percen~ of the areal eneD~ of 1,2
DCA as shown OD Figure 3-4 is in Subarea 2 with the maximum conceD~ra~ion near
the Subarea 3 boundary. AI though the higher cODcen~rat.ioDS of 1,1 DeB are in
the downgradien~ portion of Subarea 1, the ..jori~y of ~he plume is loca~ed in
Subarea 2 (Figure 3-5)."
216
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Baldwin Park ROD
.
EPA ReSDonse: The first sentence of this comment contends that
1,2-DCA and 1,1-DCE concentrations are not higher in Subarea 1
than in the other Subareas. However, the third sentence of the
comment contradicts this by correctly pointing out that the
highest concentrations of 1,1-DCE ~ found in Subarea 1. Recent
sampling of monitoring wells at the Aerojet and Wynn Oil
facilities has confirmed that the highest concentrations of 1,2-
DCA present in the OU area are found in Subarea 1.
The second and third sentences of this comment discuss the extent
of contamination in the Subareas. It is unclear how these
statements are related to the maanitude of contamination being
discussed in the referenced text from the FS.
Aj1127. "Contradi~ing the statement that "Subarea 2 is located downgradient
of the ..in susDe~ed source area", review of the chemical data on Figure 7-1
indicates that the highest concentrations of chemicals in the OU have been
detected in Well. W10WOJIWl and VI0VCMWl, north of the Foothill Freeway (210).
The southern terminus of Subarea 1 .hown on Figure 7-1 i. 1.5- to 2-aile.
downgradient of these identified "hot soot.", re.pe~ively. Plea.e explain
why the area north of the Poothill Preeway was not identified a. a .eparate
Subarea." .
EPA ResDonse: This comment largely duplicates previous comments.
See Response B for additional explanation of EPA's recommended
extraction scenario in Subarea 1, particularly on the advantages
and disadvantages of delineating additional subareas (i.e.,
adding or moving extraction locations closer to wells W10WOMW1
and V1 OVCMW1) .
We also note that contaminant concentrations indicative of
residual subsurface sources are present not only at the two wells
mentioned in the comment, but extend to within about one-half
mile of the southern boundary of Subarea 1 (as far south as well
OSCOMW2). .
Aj1128. "It is al.o probable that chemical concentrations in Subarea 2 are the
result of "local" .ource. le.. "favorably" located with respe~ to ezi.ting
well. that have been s..pled. Why are so few monitoring wells shown on Pigure
7-1?"
EPA ReSDonse: The small number of monitoring wells in Subarea 2
reflects the small number of possible sources of contamination in
the Subarea. It is possible that there are significant sources
of groundwater contamination located in Subarea 2, but
investigation efforts to date indicate that most, and perhaps
all, of the significant sources are located in Subarea 1. Source
identification efforts have been extensive; the Regional Water
Quality Control Board has sent chemical use questionnaires to
more than 1,600 facilities and inspected more than 600 facilities
throughout the Azusa/Irwindale/Baldwin Park area.
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Baldwin Park ROD
.'
Aj#129. -A1though it is stated that -available data do not show any
significant change in contaminant levels from just downgradient of Subarea 3
to as far south to Whittier .arrows-, unsubstantiated contradictions regarding
chemicals aigrating downgradient of. Subarea 3 are ..de throughout the oars.
:rhis unsubstantiated contradiction also serves as SPA' s basis for a response
action in Subarea 3. Please explain this tisparity. :rhe paragraph also
iaplies (incorrectly) continuous cheai.cal concentrations all the way to
Whittier .arrows.-
EPA ResDonse:
statements:
We see not contradiction between these two
statement. (i): there is not a significant change in
contaminant levels from iust downaradient of Subarea 3 to as
far south as Whittier Narrows
statement (ii): contaminated groundwater continues to
spread into less contaminated areas
statement (i) results from the observation that contaminant
concentrations at various wells in the interval from ;ust
downaradient of Subarea 3 to the Whittier Narrows area are
generally at or near MCLs. No significant changes in contaminant
concentration are apparent within this interval, in contrast to
the difference between contaminant concentrations in Subarea 3
and concentrations downgradient of the Subarea. We agree with
commentor that the concentrations in this interval are not
necessarily "continuous."
statement (ii) results from a variety of evidence discussed in
detail in Response A.
We also note that EPA is planning remedial action in Subarea 3 to
satisfy two objectives: migration control and mass removal.
Aj#130. -:rhe vertical extent of contamination in Subarea 1 is UDkDown.
Available groundwater data confirm VOCs in the 400- to SOO-foot depth range at
one location in Subarea 2 onlv. If the contamination is shallower at
extraction locations then groundwater need not be extracted fro8 such a deep
interval. :rhis could result in fewer wells and/or lower pumping rates which
would lower costs substantially.-
EPA ResDonse: We agree that extraction wells should be designed
to remove contaminated groundwater only from contaminated
vertical intervals.
Aj#131. -A1though it is stated that -Extraction near wells with existing data
ensures that, at a aiDiaum, aigration of known high-level contaaiDation will
be inhibited-, review of Pigure 7-2 does not show the location of an
extraction well cluster at the data points shown on Pigure 7-1 where the
highest concentrations of chemicals in the OU have been detected (in Subarea 1
at Wells W10WOMW1, Vl0VCMW1, and OSCOMW2). ~e closest extraction well
clusters (10 and 13) to these two data points are located 1- to 2-ailes
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Baldwin Park ROD
.
downgradient. ~e concentrations of PCB and TCB detected in WIOWOMWl
represent the presence of the most significant 80urce o~ chemicals identified
to date in the OU. Pailure to addres8 the removal of VOCs from this location
during the interia action will result in further degradation of the aquifer,
further complicate, and increase the time and cost for long-term aquifer
reaediation in Subarea 1."
EPA ResDonse:
Response B.
This comment duplicates other comments.
See
Aj#132. "~i. figure [7-2] shows seven recommended groundwater extraction well
locations. ~ese, locations were selected on "downgradient margins of the
three subareas", and at "locations where existing water quality data are
available". Ro further rationale is given to support selection of well
locations. ~ese two selection criteria are inappropriate measures to achieve
an optimal extraction array and to substantiate the high magnitude of cost for
such a large-scale response action. Wells should not be located at the
margins of geographically defined subareas or any other artificially conceived
boundary. Additionally, extraction locations should be selected based on an
interpretation of available data, using a well defined groundwater model, not
at locations of groundwater quality. A considerable amount of additional
analysis and thought should go into the selection of these well locations."
EPA ResDonse: We agree with the latter part of this comment that
extraction locations should be based on water quality data and
modeling. They are. (See Section 7.1.1.) As the comment notes,
EPA has located approximate extraction areas at the downgradient
margins of the Subareas. The Subareas were delineated primarily
based on water quality data. (Other information that helps
identify sources of contamination were also used - see Response
B.) Logically, it follows that extraction areas are based on
water quality data. These approximate extraction areas have been
identified without the use of computer modeling.
EPA's recommendations for precise extraction locations and rates
(in contrast to the approximate extraction areas delineated using
water quality data) are based on the Subarea boundaries and on
computer simulations using EPA's groundwater flow model to
identify the most efficient combination of extraction rates and
locations within the approximate area of extraction. A specific
combination of extraction rates and locations is referred to as a
pumping con:tiguration. There are an unliml.ted number of possible
pumping configurations that could be implemented in each
approximate exaction areas. See Response C for additional
details onEPA modeling efforts.
It is therefore difficult to understand why the commentor refers
to the Subareas as "artificially conceived boundaries" and
criticizes EPA's selection criteria as inappropriate. Also see
Response B for additional explanation on the delineation and use
of the Subareas.
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Baldwin Park ROD
Aj#133. "Data from Well V10WONWl (sic] with the highest concentrations in the
OU (>1000x KCLs) are omitted from Figure 7-2 and the discussion on extraction
locations. These data are listed on Figure 7-1. The areal extent of
contaaiDation would have been interpreted differently if these data were
considered and should have influenced the location of the proposed
extraction."
EPA ResDonse: We disagree. (We presume the comment refers to
well W10WOMW1, not to V10WOMW1.) Data from well W10WOMW1 are
included in Figure 7-1 and were considered in the our
interpretation of the extent of contamination, and in determining
Subareas boundaries and approximate extraction areas. The
omission of well W10WOMW1 from Figure 7-2 is irrelevant; Figure
7-2 was not used for these purposes.
Aj#134. Reference is made to the statement "to the extent possible, the
remedial alternative will aake use of existing water supply wells. However,
there are at aost, onl!, three existiDg production wells in or near the OU area
of cont88liDation that are optimally located. ~able 7-1 describes these three
existing wells." (p.7-8) Please describe and provide the results of the
evaluation that was completed to make tbi.s conclusion.
EPA ResDonse: EPA's information on well locations in the San
Gabriel Basin has been obtained from the Main San Gabriel Basin
Watermaster and individual water purveyors. The three wells
listed in Table 7-1 are those wells optimally located at the
downgradient end of the three Subareas to satisfy EPA's migration
control objective.
There are other water supply wells located in the OU area, but in
less than optimal locations. These wells, which include the
Arrow/Lante and San Gabriel Valley B6 wells, are shown in Figures
7-1 and 7-2.
As noted in Appendix I, the continued operation of the
Arrow/Lante wells (on which wellhead treatment has been
installed) was assumed in EPA's computer simulations completed to
determine extraction rates and locations. The impact of these
wells is visible in Figure 12-2 (in Subarea 2) and described on
p.12-8.
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Baldwin Park ROD
-
Aj1135. "Why are existing production Wells 08000060 and 01900034 (presented on
Figure 7-1 with accomPanying chemical data) not identified in Table 7-l?
~ese existing wellhead treataent facilities that are strategically located in
the OU are already contributing to the remedy. These wells provide a degree
of aigration control while reaoving soae level of con~.._i nant ..ss. Were
these wells considered in the evaluation of extraction location and
quantities?"
EPA Response:
See response to previous comment.
Aj1136. The statement
computer s~ulations"
groundwater aaodeling.
"extraction locations
that "The n~er and capacity of new wells are based on
implies that extraction locations are based on
This statement contradicts BPA'. insistence that
are not based on groundwater modeling." Please explain.
EPA Response: There is no contradiction, but some additional
explanation of the distinction made in the FS between approximate
areas of extraction and precise extraction rates and locations is
necessary. See response to comment Aj#132.
Aj1137. "As implied earlier in the report, the BPA groundwater model may not
be an appropriate tool for conducting these evaluations. On the top of page
7-6, EPA states that "the extraction locations...could be optimized using a
IIIOre discrete model of the OU area...". Since the extraction locations,
influent chemistry, interval to be screened, and quantities pWllped are yet to
be optimized, how can reasonable costs be generated aDd compared with
alternative remedies?"
EPA Response: The goal in a Superfund feasibility study is to
prepare costs estimates that are no more than 50% above or 30%
below true costs. EPA believes that the uncertainty in these
parameters is low enough to allow this goal to be met.
Aj1138. "Please provide the results of the evaluation referenced in the
statement "In addition to the simulations, a hydrogeologic evaluation of the
aquifer ha. been performed to help estimate maximWII extraction rates for
individual clusters (p7-11)."
EPA Response:
which states:
The evaluation is summarized in the text on p.7-11
"Typical specific capacity values from existing wells in
the OU area range between 100 and 450 gallons per
minute/foot (gpm/ft). This indicates that, assuming a
drawdown of 50 feet, between 5,000 and 22,000 gpm could be
extracted from a single well or well cluster."
We are unclear as to what additional details commentor seeks.
Aj1139. "What was the basis for "assuming a drawdoWD of 50 feet"?"
EPA Response: Fifty feet of drawdown was assumed as a reasonable
maximum drawdown value that would not result in excessive pumping
costs.
221
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Baldwin Park ROD
"
Aj#140. "Bow was an ini~ial extrac~ion ra~e of 38,500 gallons per aiDu~e (gpa)
derived? Wba~ ra~ioDale was used ~o sele~ ~is ra~e and o~her ra~es
presen~ed in ~able 7-2? Bow was ~e aone of influBDce determined?"
EPA ReSDonse: The initial extraction rate of 38,500 gpm was
simply an "educated guess" based on previous simulations
performed during the initial development of remedial
alternatives. Rates for the subsequent simulations were based on
a review of the groundwater contour maps shown in Figures 7-5
through 7-8 of the FS. The zone of influence was manually
approximated by drawing capture zones for each well based on the
simulated groundwater contours (as shown in Figure 7-5 of the
FS).
Aj#141. "Because capture aones are no~ shown on all ~e figures, and for all
~iae periods, i~ is DO~ possible for ~e reader = comprehend how varied
extra~ion ra~es affe~ groundwa~er ca~ure. Addi~ionally, i~ is sore
cli.fficul~ = comprehend seasonal (temporal) variations in ~he flow regiae."
EPA ResDonse: We have added capture zones to Figures 7-5 through
7-8. They are included in this Responsiveness Summary as Figures
RS-4 through RS-7. We have also added capture zones to Figure
12-2; the revised Figure is included as Figure RS-8.
Aj#142. "~e .e~od of es~ablishing extraction ra~es for ~e ~ree subareas is
based on the need ~o provide ca~ure for ~e entire geographical area of all
subareas coabined. Based on discussions in Se~ion 7.1, ~ese Subarea
boundaries were es~ablished as a geographical convenience, and concen~ra~ions
are "DO~ uniform" within the subarea. ~e.e Subarea boundaries are no~ linked
~o a specific wa~er quali~y cri~eria or conc8D~ra~ion. I~ is therefore
inappropria~e to use ~hese geographical boundaries as required l~ts of
groundwa~er cap~ure."
EPA ReSDonse: This assertion in this comment that the Subareas
are geographic conveniences not linked to water quality
concentrations is incorrect, and duplicates previous comments.
See response to comment Aj#132.
Aj#143. "Review of ~he "Base Case" siaula~ions presen~ed on Figure 7-4 show
~he influence of recharge from the ISG and the associa~ed effec~s on ~he
groundwa~er regiae, however, all siaulations fail = quan~ify the .
si9Difican~ly grea~er influence of recharge from the San~a Pe Spreading
Grounds (SPSG). ~e influence of recharge from the SPSG has a dramatic effe~
on gradien~. and flow direc~ions in Subarea 1 and Subarea 2 far grea~er than
effec~s froll the ISG. Pailure ~o incorpora~e this con~rolling and proainen~
hydraulic fea~ure of Subarea 1 in £PA'. evalua~ion. will. con~inue = handicap
£PA'. abili~y ~o conduc~ valid modeling for the OU."
EPA ResDonse: Contrary to what is stated in this comment,
current recharge practices at SFSG ~ incorporated into all of
EPA's simulations. Recharge at SFSG is incorporated in the model
in the northern portion of RI Area 3 (see Figure 7-4 and Section
7.2.1 in the FS). Of the four quarters included on Figure 7-4,
only the Spring 1983 quarter had substantial recharge volumes at
SFSG. As shown in the figure, the high recharge rates at SFSG
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Ba~dwin Park ROD
cause significant changes in the magnitude and direction of
groundwater flow throughout the OU area (compared to the
"average" groundwater flow conditions shown for the Fall 1986 and
Spring 1987 quarters). Also, as shown in Figure 7-4, although
there is a large "mound" created by recharge at ISG (recharge at
ISG is entered as a nodal value, while recharge at SFSG is a
elemental value spread over four nodes), the groundwater flow
changes attributable to ISG impact a much smaller area than the
more regional impacts caused by SFSG.
Aj1144. "~e "Base Ca.e" simulations also fail to include the capture
influence fr08 existiAg production wells operating withiA the OU.. Several
production wells operate withiA the OU that have a "positive" effect ou
liaitiAg coutaminaDt aigratiou. ~is compouent will need to be evaluated iA
order to conduct. proper &Daly.is of the ".0 Actiou" Alternative. Ple..e
incorporate this cOlllpoueut into the "Base ease" simulations aDd make these
results available to the public for review. ~o.e wells that have a
"positive" effect ou limiting conta.iqant aigratiou should be summarized
similar to the way that BPA has summarized those wells with a "negative"
effect as identified in ~able 7-3 aDd Pigure 7-2."
EPA ResDonse: The "Base Case" simulations do include the
influence of existing production wells operating within the OU
area. For example, as is recognized in the next comment and in
subsequent comments, the Lante/Arrow Highway production well
cluster in the middle of Subarea 2 does cause deflections in the
groundwater contours shown in two of the four water level maps
included in Figure 7-4.
In reviewing Figures 7-4 through 7-8 to respond to this comment,
we noticed that the effects of the Lante/Arrow Highway well
cluster are obvious iri the spring 1983 and Fall 1989 maps, but
difficult to detect in the Fall 1986 and Spring 1987 maps. We
therefore reviewed the model input files to confirm that
operation of this well cluster was simulated throughout the
12 and 3/4 year modeling period as intended. We discovered that
in the 51 quarters simulated, significant pumping at Lante/Arrow
(at 3,000 qpm) was simulated in 47 of the 51 quarters. Of the
four quarters in which pumping was inadvertently not simulated,
two are the Fall 1986 and Spring 1987 quarters presented in
Figures 7-4 to 7-8. This error has negligible impact on the
modeling results (i.e., EPA's recommended extraction rates and
locations) since the zone of drawdown resulting from extraction
at this cluster does not extend into either Subarea 1 or 3, and
no impact on any aspects of the remedy, but we apologize for the
error.
We also note that this error would not affect the particle
tracking results presented in Figure 7-9 or 12-2 since the error
is less than 8%. (Extraction at this cluster was assumed in 47
of 51, or more than 92%, of the quarters.)
223
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Baldwin Park ROD
.'
Aj1145. -~e production well in the center of Subarea 2 in the Fall 1989
saulation appears to provide conu.iDment of a large percentage of the
cont8Jll..iDation area. What is the pumping rate of this well? What level of
conta.iDment to Subarea 1 is already being provided by this well?"
EPA ReSDonse: The simulated pumping rate for this well (the
Arrow/Lante well cluster) is 3,000 gpDi. The "level of
containment" can be interpreted from Figures 7-4 and 12-2. In
Figure 12-2, it is apparent that the cluster can extract and
contain some of the contaminated groundwater originating in
Subarea 1.
Two limitations of relying on extraction at this cluster are:
(i) The cluster can extract and contain some, but not all,
of the contaminated groundwater originating in Subarea 1.
The capability of the cluster to contain known areas of
contamination is greatest during dry periods with little
recharge and a flat gradient (e.g., Fall 1989), and most
limited during periods of high rainfall or significant
artificial recharge.
(ii) The Arrow/Lante cluster is located further away from
the known source areas than EPA's recommended extraction
locations, allowing further degradation of the interval
between EPA's recommended locations and the Arrow/Lante
cluster. contaminant concentrations are significantly
higher upgradient of EPA's recommended extraction locations
than immediately upgradient of the Arrow/Lante cluster.
See Response B for additional discussion of the advantages and
limitations of alternative extraction configurations in Subarea
1.
Aj1146. -As shown in the simulation, recharge at ISG has a significant impact
on the groundwater flow regae. ~e lDOund, which is located on the eastern
edge of Subarea 2, is especially prevalent during the Spring 1987 simulation.
If ext.raction in Subarea 1 (13,000 Ar/YR) is recharged at ISG, acreased
aouncI.iDg would be expected with potential large impacts on groundwater flow.
Bow would this affect contaaiDant transporl and concen1:ra1:ioDs a Subareas 2
and 3?" .
EPA ResDonse: As described in section 7.2.1 of the text,
additional spreading at ISG would likely increase the groundwater
gradient and change groundwater flow directions slightly in lower
Subarea 2 and upper Subarea 3. However, as shown in Figure 7-4,
the mound created by ISG does not significantly impact the
orientation of groundwater contours within the subareas. Thus,
the overall impact of increased spreading at ISG on contaminant
migration may not be substantial. Due to uncertainty about the
precise distribution of historical or existing contaminant
concentrations in groundwater, it is not possible to predict the
224
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Baldwin Park ROD
effect of additional recharge at the ISG on the precise
distribution of contaminants.
Aj#147. -Bxtraction well locations on Figure 7-5 do not agree wi~ extractiol1
well locations shown 011 Figure 7-2. ~is disparity is 808t evident in Subarea
1. ~e progressiol1 of 8Oc!ifying extractioD 10catioDs and rates is Dot
sufficiently described or documented froa a technical perspective.-
EPA ResDonse: We cannot identify any disparity.
can tell, the two figures do agree.
We believe that we have adequately described and documented our
efforts to determine extraction rates and locations. We cannot
respond to this comment in more detail, since commentor expresses
general dissatisfaction with the text without offering any
specific criticisms.
As far as we
Aj1148. -As 88ntioned in ~e text, ~e extraction rate of 38,500 gpa is much
larger ~ Decessary. In addition, it appear. ~e ~ree wells 011 ~e
southern edge of Subarea 3 are pumping at inefficiently high rate. and are
pulling in a lot of uncoDtaminated water. 2!hree wells may Dot be Decessary to
accomplish the Objectives.-
EPA ResDonse: As described in the FS, we agree that an
extraction rate of 38,500 gpm is larger than necessary to satisfy
our remedial objectives.
Aj#149. -What i. the northernmost extraction well in Subarea 3? What is the
pumping rate? It does not appear to be contributing to ~e effectiveness of
the sYlltea.-
EPA ReSDonse: In Figure 7-5, the northernmost extraction cluster
in Subarea 3 is Cluster 3, pumping at a rate of 2,000 gpm. As
described in the FS, this well cluster was evaluated and
eliminated during the development of the most efficient
extraction configuration. It is not included in EPA's
recommended extraction configuration.
Aj1150. -~e extraction well clusters need labels on Figure 7-5 to allow ~e
reader to determine ~e corresponding pumping rate at each cluster from Table
7-2.-
EPA ReSDonse:
Figure 7-2.
Locations of extraction well clusters are shown in
Aj#151. -The production well in ~e center of Subarea 2 is pumping at a
sufficient rate to capture ~e wid~ of ~e upgradient portion of ~e plume in
the Fall 198' simulatioD. nis simulatioD indicates that extractioD Clusters
10 and 13 are redundant and UDDecessary to provide contaiDment.-
EPA ResDonse: We disagree with the comment that clusters 10 and
13 are redundant. See response to comment Aj#145 and Response B.
We also note that potential remedies should not be evaluated
solely in relation to conditions in the Fall 1989 quarter shown
225
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Baldwin Park ROD
in Figure 7-6, which was an unrepresentative, extremely dry
period in the middle of a prolonged drought. More typically,
average rainfall, recharge, and groundwater flow gradients are
higher. . EPA's evaluations of potential extraction configurations
described in Section 7 look at effectiveness during dry, average,
and wet conditions (see p. 7-11).
Aj#152. WWhy is ertraction Well 13 not puaped in 'thi.s siaulaU.on?W
EPA ReSDonse: The simulations were performed sequentially and
Cluster 13 was not added to the extraction scenario until it
became apparent that Cluster 10 alone could not effectively
contain the entire width of Subarea 1.
Aj1153. Brtrac'tion WellS in the sou'thwest portion of Subarea 3 appears to be
pumping a lot of water outside of 'the cont:-...h..tion area. ~is is especially
true during 'the two . spring siaulations. ~is water will dilute 'the
contaaiDated groundwater. Was 'this considered in 'the influent chemistry
estimates? Xs 'this aD efficient use of resource.?
EPA ResDonse: As shown in Table 7-4 of the FS, the influent
estimate for Cluster 5 was assumed as a 50/50 mix of the
chemistry found in Clusters 3 and 6. Water quality data are not
currently available in the immediate vicinity of Cluster 5.
As described in the text and figures in Section 7 of the FS,
groundwater flow conditions (direction and rate) in the OU area
vary considerably over time. The zone of influence of the
simulated extraction well locations and rates will extend further
beyond the subarea boundaries under certain flow conditions.
Thus, the preliminary extraction rates identified for the various
clusters may not be the "optimum" rates for all times of year
(i.e., for all groundwater flow scenarios).
Aj1154. wIt appears 'that 'the eastern ertraction well in Subarea 2 will be
pumping cleaD water 80ving downgradient from 'the ISG. W
EPA ResDonse: Because the ISG are located very near the eastern
boundary of Subarea 2, under some. flow conditions, a portion of
the capture zone from the referenced well will extend into the
mound created by spreading at ISG.
Aj1155. WAgain, a production well in the center of Subarea 2 appears 'to be
pumping at a rate sufficient to achieve the containment objective in 'the Pall
1'8' simulation. What pwaping rate is used for 'this well in 'the si8lulations?
Is it less 'th8D ertrac'tion rates proposed for Clusters 10 aDd 131 If 'they are
less, could 'these proposed ertrac'tion rates be reduced during dry years and
still achieve coata1Daeat?W
EPA ResDonse: See responses to comments Aj#145 and Aj#151 for
the initial two questions in this comment.
226
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Baldwin Park ROD
.'
The extraction rates proposed in the FS are "average" rates that
satisfy the remedial objectives under most flow scenarios.
However, as stated apove, they are not the optimum rates during
all flow scenarios. Lower extraction rates would likely still
meet the remedial objectives during extended dry periods. .
Conversely, higher rates could potentially be needed if
significant increases in recharge of imported water or extended
wet periods occur.
Aj#l56. wIt is unclear why Pigure 7-8 presents the opt~ua well arrangement
and rate for the OD. 80 selection criteria were establiohed prior to
discussion of simulation results, no capture zones are shown on the figure,
the Subarea boundaries are not concentration related, and how each simulation
arrangements achieves selection criteria is not discussed. ~ independently
validate the selection of well locations and pumping rates, a significantly
aore detailed discussion on the modeling and selection procedure is needed.W
EPA ReSDonse: At least one of the assertions in this comment
duplicates (and is rebutted) in previous comments. See response
to comment Aj#132 which describes the use of water quality data
in delineating Subarea boundaries.
See p. 7-11 for a description of the selection criteria for the
optimum flow rate and pp. 7-11 and 7-12 for a brief discussion of
the extent to which the extraction configuration assumed in each
simulation meets the criteria. Page 7-11 describes the optimum
rate as "that rate at which the zone of influence from the
extraction wells extends to just beyond the subarea boundary
during a majority of the model period."
Capture zones were not drawn on the referenced figure (or the
rest of these groundwater contour figures) so that the reader can
have an unobscured picture of the simulated groundwater contours
resulting from the extraction scenario. As stated on page 7-12
of the FS, the zone of influence for each extraction well can be
added to the figure for each quarter "by drawing lines
perpendicular to the contours and noting whether they terminate
at one of the potential extraction locations." However, revised
figures are attached (Figure RS-4 to 8) that include approximate
capture zones.
Aj#l57. WContrary to the strategy of reducing pumping rates to not influence
capture outside Subarea boundaries, Figure 7-9 clearly shows that capture
zones include areas outside the Subarea boundaries.W
EPA ResDonse: To account for the uncertainties inherent in the
simulations and to provide a "margin of safety", the objective
was for the capture zones to extend "just beyond" the subarea
boundaries. Thus, the capture zones are intended to include some
areas outside of the subarea boundaries.
227
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Baldwin Park ROD
Aj1158. "Because of the shifting groundwater gradieuts, the eastern wells are
1ess effective during dry periods and the western wells are less effective
during wet periods. In addition, during dry periods. significantly lower
pumping rate. are necessary to achieve the objectives. COuld pumping rates be
alternately reduced on either side to optimize the syst..? ~is would reduce
the aaount of clean water that would be pumped and treated."
EPA ResDonse: Yes, pumping rates could vary over time.
Constant, continuous extraction was assumed in the FS to simplify
the development, costing, anQ evaluation of remedial
alternatives. Specific operating scenarios will be determined
during remedial design, and the "optimization" discussed. in the
comments could be evaluated at that time. It should be noted.
~at periodically shifting the extraction between different wells
would significantly complicate distribution of the treated water
and would likely result in higher capital costs because the
facilities on either side would need to be upsized to be able to
handle a larger fraction of the total extraction rate required.
Aj1159. "~e production well not identified in Subarea 2 is capable of
containing the plume. ~erefore, well clusters to the north in Subarea 1 and
to the south in Subarea 2 are redundant."
EPA ReSDonse: . This comment duplicates previous comments.
responses to comments #Aj145 and Aj#151.
See
Aj1160. "Why were additional simulations not conducted that evaluate lower
quantities of pumping? GiVeD the shifting groundwater flow directions aDd the
problea. of water disposal, it is important to establish the lowest pumping
quantities possible that achieve EPA objectives. Why were no simulations
conducted that examine varying pumping rates for varying groundwater flow
directions?"
EPA ReSDonse: Multiple simulations ~ conducted to evaluate
the performance of a variety of pumping rates for varying
groundwater flow directions. The results are presented in
Figures 7-5 through 7-8 and summarized in Table 7-2. We believe
that the recommended rates do represent the minimum acceptable
extraction rates given currently available data.
Also see response to Aj#l58 on the feasibility of varying
extraction rates over time.
Aj1161. "MaDy of these adverse effects such as pulling HOs toward extraction
well. could be avoided if pumping rates were balanced. When water is pumped
fro. the east where Has conceutrations are high, the well is also pumping
s..ller conceutrations of VOCs. ~erefore, the pumping rate of this well
could be drastically reduced while other wells in more optimal locations are
still pumping."
EPA ResDonse: We assume that the first sentence of this comment
is again referring to an operating scenario where extraction is
moved between eastern and western clusters depending on whether a'
wet or a dry cycle is occurring. It is not correct to state that
228
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Baldwin Park ROD
.
"pulling nitrate toward extraction wells could be avoided if
pumping rates were balanced." Because nitrate contamination is
already present within the subareas, any extraction scheme
intended to contain migration out of the subareas will increase
migration of nitrate toward the extraction wells. However, we
agree that minimizing capture of water from beyond the eastern
boundary of the subareas will help restrict the increase in
nitrate migration.
The second and third sentences of this comment appear to be
referring to a specific well cluster but do not identify the
cluster. Regardless of the cluster number, we do not think that
there are any clusters where the pumping rate could be
"drastically reduced." Also see responses to previous comments
on extraction rates and locations.
Aj#162. -Although it is true that the ISO are presently located on the eastern
edge of the contaai.nated area, they were located well within the contamination
area in the early 1980s. Will increased recharge at SFSG during wet years
-push- the plume !Jack 1;0 the southwest again? If so, recharge at the ISG
could spread contamination into currently clean areas to the south and
southeast.-
EPA ResDonse: See response #Aj146 for a brief discussion of the
effects of recharge at the ISG.
Aj#163. -!rb. foo'tDot. at the bot1;oa of the 'ta!Jl. ineUeat.s 'that VCWD intends
to increase procluction at the Arrow ...11. !rbis well is centrally located in
SUbarea 2 and is caP&!Jle of providing. significant degree of aigration
control. !rbis makes extraction Clusters 10 and 13 redundant. Why not cancel
one of the two extraction locations and aove the other up to the source area
north of 1-210 to op't~8e ..ss removal and aigration control?-
EPA ReSDonse: This comment duplicates previous comments.
responses to comments Aj#145 and Aj#151.
Also, see Response B for a more detailed discussion of the
rationale for the proposed Subarea 1 extraction scenario.
See
Aj#164. -!rbe selection of -potentially controlling VOC contaminants- should
have !Jeen accompanied !Jy an evaluation and tabulation of the frequency of
occurrence, mean or median concentration and concentration range. Estimated
concentrations mt the extraction wellhead can then be deterai.Ded.-
EPA ResDonse: EPA identified a list of potentially controlling
compounds to assist in the prediction of future contaminant
concentrations. For compounds that are not potentially
controlling, EPA simply assumed that the maximum historical
concentrations of each compound detected at each well could occur
in the future. For compounds that are potentially controlling,
EPA devoted more effort toward evaluating past variability in
concentration and predicting future concentrations.
229
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Baldwin Park ROD
The need for summary statistics or the relevance of the summary
statistics mentioned in the comment to this effort is unclear.
However, the information requested in the comment is tabulated
for the influent estimates described in Appendix B, including
frequency of occurrence, mean concentrat.ion, maximum
concentration, and the date of the most recent data available.
Aj116S. "Bow CaD viDyl chloride be select.ed as a "cont.rolliDg" compound when
concent.rat.ions at. all clust.ers except. 10 aDd 13 were est.imat.ed at. 0.0 ug/l?
It. is iDconceivable t.hat. 11 paramet.ers (chemicals) will direct.ly cont.rol
design of the t.reat.ment. syst.em."
EPA ResDonse: We agree that labeling the eleven compounds in
Table 7-4 as "controlling" is confusing; the compounds are better
labeled (and described in the text) as "potentially controlling"
compounds." Regardless of how they are labeled, the eleven are
"compounds that may control cost or limit use of a treatment
methods" (as explained in the footnote to the Table). These are
compounds whose presence may impact the design or operation of
the treatment facility if their concentration in the influent to
a treatment facility increases by a factor of ten or more above
the estimated concentration listed in the Table.
EPA could have used a simpler method and identified only one
controlling compound based on the estimated influent
concentrations. This method would have been less informative,
however, since historical variation in concentrations leads us to
expect future influent concentrations to vary from the estimates.
Because future variations cannot be predicted with 100%
certainty, we list all of those compounds that may become
controlling compounds if their concentrations rise sufficiently.
Aj1166. "~e discussion of peak concent.rat.ions discount.s t.he possibilit.y t.hat.
higher upgradient. concent.rat.ions iD Subarea 1 will aigrat.e dOWDgradient. t.o t.he
proposed ext.ract.ion wells because of the absence of long-t.erm iDcreasing VOC
t.rends. In fact., overall long-t.erm increasiDg t.rends are generally absent.
throughout. the ent.ire OU."
EPA ResDonse: We agree that increasing trends are not evident
for all contaminants at all wells, and do not expect to see such
trends at all wells. As discussed in Response A, however,
.increasing trends have been documented at a number of locations.
Aj1167. "Groundwat.er wi.th VOC concent.rat.ions orders of magnit.ude higher t.haD
the proposed influent. cheaist.ry at. the proposed extraction locat.ions exist.s a
lit.t.le over 1-aile upgradient.. Cont.rolling t.hese high concent.rat.ions should
be t.he highest. priorit.y when consideriDg a remedial action."
EPA ResDonse:
Response B.
This comment duplicates previous comments.
See
230
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Baldwin Park ROD
Aj1168. -~e .ecoRd paragraph aRd the footDote for Table 8-1 are cORfuaiRg.
Why are there two dj,ffereJIt allocatj,oRs of flow cORtrihutj,oR perceRtageS?
Please clarj,fy thj,a dj,acrePaRCY.-
EPA Response:
As explained in the footnote to Table 8-1,
"Estimated concentrations and required reductions listed in
this Table [8-1] are based on a preliminary estimate of the
blended contaminant concentrations expected in the influent
to a treatment facility. The estimates were subsequently
revised. The revised estimates are listed in Table 7-5 and
used in the description and evaluation of remedial
alternatives in Sections 11 and 12."
EPA chose not to repeat the evaluation presented in Section 8
using the revised concentrations because the cost of repeating
the analysis would have been greater than any benefits of doing
so. Revising the analysis would not change the ranking of the
remedial alternatives or significantly affect the estimated cost
of the alternatives.
Aj1169. -~e documemt should provide a ratiouale for siziRg treatmaDt plaRts
at 35,000 gpa, wnch is 21 perc8J1t over the required 29,000 gpa. ~e 29,000
gpa already acludes a backup tower with approxiaately 2,900 gpa capacity, or
approxia&tely 10 perceRt over-capacity capabilj,ty.-
EPA Response: The remedial alternatives are not sized at 35,000
gpm. Remedial alternatives 2, 3, and 4 are assumed to have a
capacity of 29,000 gpm, not 35,000 gpm.
The 35,000 gpm rate is assumed in the evaluation of treatment
technologies included in section 8, but this evaluation was not
used to define the size of or estimate the cost of the remedial
alternatives. There was no need to repeat the treatment
technology evaluation with a different rate since the conclusion
was not expected to change. As stated on page 8-11:
"The relative ranking of treatment technology costs of the
candidate treatment technologies is believed to be
independent of flow rate within the range of 5,000 to 70,000
gpm. "
Aj1170. "ease 3 (LGAC oRly) j,s stated to be le.. attractj,ve for several
reaSORa aclu~g the fact that this techRology would DOt be able to reduce
es~ia&ted peak vayl chlorj,de concentration.. Vayl chlorj,de has not beeR
detected except a a fe. i.olated .ell. aRd haa not beeR consisteRtly
detected. nerefore, this CORCerR is URfoURded.-
EPA Response: We disagree that our concern about the presence of
vinyl chloride is "unfounded." Vinyl chloride was detected in 14
of 40 samples collected from a monitoring well in the "upper
area" between 1984 and 1993, at an average concentration of 1.2
231
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Baldwin Park ROD
ug/l (well #W11AZW01). The California Maximum Contaminant Level
for vinyl chloride is 0.5 ug/l. Peak concentration in the same
period was 10 ug/l. The potential presence of vinyl chloride in
EPA's proposed treatment facilities is an important consideration
in the selection of a treatment technoloqy.
Aj#171. "Bstimating the cost of the four treatment options using "peak" VOC
concentrations and a required treatment capacitr of 35,000 gpm is overlr
conservative and rielda unrealisticallr high capital coats. It ia unclear whr
capital costs were estimated using "peak" concentrations, while operation and
aaint8D8J1ce (O&M) costs were estimated using "average" concentrations."
EPA ReSDonse: As explained in the response to comment Aj#169,
the estimated capital costs of Remedial Alternatives 2,3, and 4
are based on as assumed capacity of 29,000 qpm, not 35,000 qpm.
The simplest method of estimating project costs would have been
to predict a single influent concentration. To increase the
accuracy of the cost estimates, however, EPA predicted both peak
and average concentrations to estimate capital and operating
costs, respectively. Estimating peak and average concentration
increases accuracy because a treatment facility must be designed
to handle the highest concentration expected (i.e., peak
concentrations), but the cost of operation will reflect actual
day to day contaminant loadings (best estimated with average
concentrations). As described on page 8-7:
"The estimated Deak contaminant concentrations listed in
Table 8-1 are used to estimate and compare the size,
configuration, and capital cost of four VOC treatment
options. The estimated averaqe contaminant concentrations
are used to estimate contaminant loadings, carbon and .
oxidant usage, and other operating costs."
Aj#172. "Bow i. a IS-rear equipment life resolved with a 30-rear project
life? ~is discrepancr would suggest that O&M include at least one set of
equipment replacement costs for blowers, pumps, and air stripper lower
packing. "
EPA ReSDonse: The costs for a one-time equipment replacement
(after 15 years of operation) are included in the O&M cost
estimates prepared for the comparison of alternate treatment
process options. However, these equipment replacement costs were
inadvertently omitted from the remedial alternative cost
estimates included in Section 12. The impact of treatment
equipment replacement costs on the total cost of the alternatives
is not large. For Alternative 1, the estimated equipment
replacement cost is approximately $1,100,000. Using an interest
rate of 5 percent and assuming that the replacement equipment
would be purchased in 15 years, the present worth value of this
cost is about $540,000 (less than 1 percent of the estimated
present worth of the alternative). For Alternatives 2 through 4,
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..
the estimated replacement cost would be about $1,750,000. The
present worth of this cost is approximately $840,000 (also less
than 1 percent of the total present worth of these alternatives).
Aj#173. -~e fact that -influent concentration- has the largest effect on
costs contradicts stateaents ..de in earlier chapters that accurate
deterai.Dat~on/estiaation of influent concentrations is not necessary, and non-
CLP data that has undergone limited QA is sufficient.- .
EPA ResDonse: We see no contradiction. Commentor misstates
EPA's position, then applies flawed logic to reach an incorrect
conclusion. First, EPA does not state that influent
concentration has the largest effect on costs. EPA merely lists
"influent concentrations" as one of several assumptions that
affects the estimated treatment cost (page 8-23). Second, the
ranking of this assumption in relation to other assumptions does
not imply the need for any particular level of precision or
accuracy. Nor does EPA state that accurate
determination/estimation of influent concentrations is
unnecessary. On pages 3-1 to 3-5 and in the response to comments
Aj#32-34, we describe the quality of non-CLP data and the level
of accuracy appropriate to the estimation of influent
concentrations. We conclude that non-CLP data are adequate for
use in estimating influent concentrations.
Aj1174. -It should be noted again that influent concentrations may change
significantly if pumping locations are changed. ~~s is especially true for
the controlling compounds such as 1,2 DCA and 1, 1 DCB.-
EPA ResDonse:
We agree.
Ajl17S. -~is table [8-9] presents four compounds that will control design of
the three considered treatment options. ~is conclusion conflicts with the
ten compounds presented as controlling VOCs in Table 8-1. Please resolve this
discrepancy.-
EPA ResDonse: Table 8-9 lists eight compounds (four
"controlling" and four "potentially controlling"). Table 8-1
presents a list of ten "controlling" compounds, which includes
the same eight compounds identified in Table 8-9 and two
additional compounds identified later in the development of
remedial alternatives. Compounds in both tables are potentially
controlling - i.e., if their concentrations rise by factors of
five or so above historical peak concentrations they could
control the design, limit the operation, or significantly affect
the operational cost of the treatment facilities.
Aj#176. -~ere are several treatment plants currently in operation in the
basin; two are located in this OU. Why are these operations not discussed and
evaluated in Section 8? Did BPA compare cost estimates to actual costs, and
identify specific designs or 0&11 probleas 8IOre accurately through an
evaluation of this data? If not, why not?-
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EPA ReSDonse: This comment duplicates a previous comment.
response to Aj#121.
See
Aj1177. "According to ~able 4-3 (p. 4-14) the SPA lifetime adult health
advisory concentration for radon is 1.5 picoCuries per liter (pCi/l).
1I0wever, it i. st:ated in Section. 8 t:hat "radon is . naturally occurring
radioactive gas present in .ost groundwater and has been aea.urad in
groundwater s..ples collected in the OU at concentrations between 213 and 430
pCi/l, and in other portions of the San Gabriel Basin at concentrations in the
500 to 1,000 pCi/l range". ~e stat_ent in the ornrs that "radon is of .
concern since concentrations in portions of the OU area exceed the proposed RD
KCL and becau.e of potential treataent facility operator exposure" (p 8-10)
!.plies that residents and aunicipal worker. have always been exposed to
unacceptable level. of radon. ~e implications of an on the configuration and
operation of the OU should significantly affect cost allocation for treataent
costs. lIow will these costs be allocated?"
EPA ResDonse: EPA'sstatement that "radon is of concern" does
not necessarily imply past or current exposure to unacceptable
levels. The full statement is:
"Radon [Rn] is of concern since Rn concentrations in
portions of the OU area exceed the proposed Rn MCL and
because of potential treatment facility operator exposure.
If, however, air stripping or LGAC are the selected
treatment technology for VOC removal, additional treatment
for Rn will probably not be required since both of these
technologies remove Rn. The implications of Rn on the
configuration and operation of the OU are discussed in
section 8.4.3."
EPA's preliminary evaluation (described on pages 8-33 to 8-41)
indicates that the presence of radon will not significantly
affect the cost of the remedy. The most likely costs, if any,
would be associated with efforts to limit operator radiation
. exposure. EPA would most likely view any costs associated with
limiting operator exposure to radon or its decay products as part
of the cost of cleanup.
Aj1178. "Aquifer recharge should be considered as an independent general
response action, not solely as a means for disposal of treated water."
We agree that any remedial effects of aquifer recharge should be
considered in selecting the method or methods of disposing of
treated water. EPA's evaluations described in the FS indicates
that the differences in remedial effectiveness are likely to be
less significant than differences in cost. See response to
comment Aj#179.
Aj1179. "It is stated that "recharge at existing facilities CaD provide some
r-edial benefit", however, this compoDent is Dot included into any of the
reaedial alternative OptiODS."
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EPA ResDonse: EPA did consider the remedial effects of recharge
in the development of the remedial alternatives.
As discussed in Section 9, there are potentially positive and
negative remedial impacts associated with spreading at both ISG
and SFSG. Impacts of recharge in the San Gabriel River are
likely to be limited, because recharge in the River occurs over a
4-mile stretch, most of which is located more than one mile cross
gradient and downgradient from the au area of contamination (see
Figure 9-1).
Recharge at the three locations (SFSG, ISG, the River channel)
was assumed in computer simulations during the development of the
remedial alternatives. The results of one of these simulations
is shown in Figure 11-2 and described on p.11-6 for recharge
primarily at ISG [86 percent], with the remainder recharged in
the river channel [14 percent]. The results do not indicate that
recharge of treated water produces significant remedial benefits
in relation to the remedial benefits of properly located
groundwater extraction wells. EPA therefore chose not to
prescribe recharge as the preferred treated water distribution
option in any of the remedial alternatives.
Aj#180. "Infiltration of water in the SaD Gabriel River could be used as a
beDeficial cOJDponent ~ reduce CODt.....i "..nt aigratioD iD the OU. !rhis
cOJDponent should be iDcorporated iD~ at least one set of the modeliDg
.iaulation. used to evaluate reaedial alternative.."
EPA ResDOnse:
See response to previous comment, Aj#179.
Aj#181. "As previously stated, SPA's aodeling siaulations fail to identify the
detailed effects of recharge fro. the SFSG on the localized groundwater flow
regiae. IDdeP8DdeDt aodeling siaulations and actual water level .easureaents
conducted by IILA indicate that recharge at the SPSG changes the groundwater
flow direction from southwesterly to easterly, not "aare southerly toward the
recomaendedOU extraction locatioDs" as stated by SPA. !rhis makes it aor8
difficult for the proposed extraction wells to capture contaminants from the
upgradieDt portion of the ou. Pailure to recognize the changes iD flow
directions and gradients may result in negative impact. to the OU rather than
beneficial results. !rhese COmpDDeDts of SPA'. reaedial alternative selectioD
process warrant further consideration aDd technical iaproveaent."
EPA ResDonse: The first sentence in this comment is incorrect.
See response to Aj#143.
In response to the second sentence, we agree that recharge at the
SFSG changes the flow directions to a more southeasterly
direction, rather than to a more southerly direction. This
effect is shown in Figure 7-4. As stated several times in tbe
text, including in the paragraph referenced in the comment (p.9-
10, 3rd paragraph), EPA acknowledges that recharge at SFSG has
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Baldwin Park ROD
"
potentially negative remedial impacts and could increase the
amount of extraction necessary to attain remedial objectives.
Aj#182. "A1though the discussion focuses on the potential capacity of the
SFSG, the ability of the aquifer to receive this additional water is not
evaluated. Rising water levels have a variety of negative impacts, including
flooding of gravel operations. Average yearly spreading quantities of 40,000
AF/YR will be increased 50 percent with the possible 20,000 AF/YR added by
USGVMWD. An additional 14,000 AF/YR from Subarea 1 extraction (A1ternative
1, 8500 gpa) could create significant iapa~s on groundwater levels. ~e
iapa~s are compounded during wet years when precipitation, and runoff are
higher."
EPA ResDonse: EPA has completed an evaluation of the impact of
additional recharge on water levels and on the movement of
groundwater in the vicinity of the spreading basin. See pages
11-6 to 11-9, which presents the results of a computer simulation
in which 24,000 af/yr was assumed to be recharged at the SFSG.
EPA's preference is for treated water to be distributed to water
purveyors for direct use, but even if a majority of the treated
water is recharged, the amount recharged will be small in
relation to volumes already recharged. EPA does not expect its
remedy to result in water levels exceeding the opera ring limirs
allowed by the Alhambra Judgment. EPA expects that any
additional impacts on water levels resulting from the actions of
the Metropolitan Water District will be mitigated through
agreements between Metropolitan and the Watermaster or individual
water purveyors. In any case, section 9 includes a discussion of
potential adverse effects of lower or higher water levels,
including flooding of gravel quarries (pages 9-26 to 9-27).
Commentor is apparently dissatisfied with EPA's evaluation, but
does not specify what additional evaluations should be completed.
Comment or mistakenly asserts that average yearly spreading by
USGVMWD will increase 50 percent. Representatives of the USGVMWD
have stated that they do not plan to increase their net usage of
the SFSG. Their plans are to supply reclaimed water for direct
use or to recharge reclaimed water in place of imported water,
resulting in no net change in the amount recharged. See 11/5/93
letter from Timothy Jochem of the USGVMWD, included in the
Administrative Record.
Aj#183. "Recharge effects of this alternative [export by Metropolitan] must
also be evaluated. Recharge at SFSG would be significantly increased if ~
recharged a similar amount in the winter months that they bought in summer
.onths. SPA would still have to find a discharge point for water pumped in
winter months. If ~ and purveyor demands were low and ~ used additional
capacity at SFSG, where could the winter extra~ion volumes be discharged?"
As described in the response to the previous comment, EPA has
completed an evaluation of the impact of additional recharge at
the SFSG on the movement of groundwater in the vicinity of the
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Baldwin Park ROD
spreading basin. Additional evaluations may be completed if
recharge is determined to be a preferred method of distribution,
and as recharge scenarios are better defined.
"winter extraction volumes" may be delivered to one or a
combination of the three distribution options described in the
Feasibility Study: delivery to water purveyors for local use;
delivery to Metropolitan Water District for export; and recharge.
EPA's evaluations indicate that it should be feasible to
distribute the proposed 19,000 gpm to one of a combination of
options. The comment highlights the fact that distribution of
treated water may be more difficult in winter months than in
summer months, due to decreased consumer demand for water and
increased competition for use of existing recharge areas.
Aj#184. -DeClining water table conditions can result iD decreased purveyor
yields and the dewatering of monitoriDg and production wells.-
We agree.
This comment restates text on page 9-27:
"Potential adverse effects of lower water levels
include...decreased yield of existing wells (possibly
to zero)..."
Aj#18S. -Extraction locations should be selected based on technical reasons
ra~er ~811 site availability. ~e highest contaaiDant concentrations are
over a aile to the north. Was a parcel review conducted there?"
Extraction locations are based on technical reasons. Pages 10-12
to 10-14 include a discussion of site availability and other
factors to be considered in selecting parcels for new extraction
wells, but clearly state that "proximity to the preferred
extraction locations [is] the primary consideration in siting the
wells." The next paragraph on page 10-12 notes that the
rationale for selecting preferred [extraction] locations is
explained in section 7.
The Feasibility Study offers criteria to help guide the selection
of specific parcels, but does not include an evaluation of the
tens or hundreds of potential extraction well sites.
Aj#186. .~e ours contains significant techAical uncertainties in addition to
the institutional and logistical uncertaiDties summariaed in this discussion.
!rhere is only one 8OnitoriDg well outside of Subarea 1. .0 data exists on the
vertical distribution of cont-Bloi ftation iD Subarea 1. Upgradient li.aits and
downgradient liDits of the cont:-mif'-tion are poorly characterized. ~e.e
techAical uncertaiDties could have a large i8pact on costs and aay complicate
the design of an effective reaedial action.-
EPA ReSDonse: This comment duplicates previous comments. See
Response F for a detailed response. We do not believe that
uncertainty in the extent of contamination will interfere with
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Baldwin Park ROD
.,
remedy selection, have a "large impact on costs," or unreasonably
"complicate the design of an effective 'remedial action.
Aj1187. ",On the basis of the significant dat.a gaps regarding the distribution
of cheaical. in groundwater and hydrogeologic conditions in the OU, and EPA' s
inability to correctly identify "baseline" conditions in modeling simulations
(e.g., historical and current production well influences, recharge effects
fro. the SrSG), there exist significant obstacles that need to be resolved
prior to the development of effective remedial action alternatives. Failure
to properly characterize these controlling elements prior to remedial
alternative development (Section 11 of the ourS) ..y result in adverse impacts
to the OU and further complicate long-tera remedial actions."
EPA ReSDonse: The statement regarding "EPA's inability to
correctly identify "baseline" conditions in modeling simulations"
is incorrect. EPA's model is able to simulate past and present
production well influences, as well as the effects of recharge at
SFSG (see response to comment Aj#143). We also disagree that
current data gaps present obstacles that need to be resolved
before remedy selection or "may result in adverse impacts to the
au and further complicate long-term remedial actions." See
Response F for a more detailed response.
Aj1188. "~is chapter does not adequately develop a "range" of reaedial
alternatives for the OU. Four "remedial alternatives" are presented, however,
with few a.iDor exceptions these alternatives are "airror images" of each
other. ~is does not allow EPA or the reviewer to select from a true range of
alternatives. Differences between alternatives are primarily in the option
selected for use of the treated water (e.g., recharge, export, and local
use). ~ree alternatives contain identical extraction schemes (29,000 gpm)
with the fourth alternative lacking only extraction in Subarea 2 (19,000 gpm
tot.al) . "
EPA ResDonse: We believe that the four remedial alternatives
represent an appropriate range of cleanup options. The comment
expresses dissatisfaction with the range of alternatives included
in the Feasibility Study, but does not identify any flaws in
logic or in the specific analyses completed during development
and screening of the alternatives. Nor does the comment specify
other alternatives that should be considered.
We also disagree with the comment that the choice of alternatives
limits a reviewer's ability to offer comments on EPA's proposal.
In the Baldwin Park Proposed Plan, EPA welcomed comments on all'
aspects of the Feasibility Study, including the screening process
completed to develop remedial alternatives. The range and volume
of comments provided by Aerojet/ALR indicates recognition of the
opportunity to comment on all aspects of EPA's proposal.
We wish to emphasize that the purpose of much of the Feasibility
Study is to explain the methodology used to screen out the less-
promising alternatives, and to describe the results of each
screening step (e.g., sections 6, 7, 8, 9, and 11). section 6
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..
explains the rationale behind, and defines, EPA's remedial
objectives. section 7 describes the extent of contamination and
the results of computer modeling completed to determine
approximate extraction rates and locations. Section 8 describes
cost estimates completed to identify and estimate the costs of
treatment technologies. Sections 9 and 11 include evaluations
of existing water purveyor systems, evaluations and projections
of spreading basin capacity, and comparisons of pipeline
alignments to identify promising distribution options.
Aj1189. "~e 12 "wa~er.use options" all £ocus on disposal o£ the ~rea~ed wa~er
. rather 1:.han a. a coapon8D~ W enhance remedial e£fe~iv8De.s. Why i. this
iaportaD~ and beneficial aspe~ for al~erna~ive developaen~ excluded froathe
ours?" '
EPA Response: We assume that the comment is referring to using
recharge to enhance remedial effectiveness as previous comments
have. As described in the response to comment Aj#179 and in the
subsequent comment (which reprints text from page 11-6), recharge
at the three available facilities does not significantly enhance
remedial effectiveness as is implied by the comment.
Aj1190. "~e s~atement that -the analyses of the 12 wa~er use options
cost, rather than on the other Superfund evaluation criteria (such as
effec~iv8Des.), becau.e compu~er .imula~ion. do not Uadica~e ~ha~ the
of.a~er u.e option result. in a .igui£icant 4i£ference in remedial
effec~iv8De.s" deaon.~ra~e. SPA-. liai~ed evalua~ion of remedial al~erna~ives
considered for the 51 0f11I'S...
focus on
remedial
choice
EPA Response: We disagree, and commentor merely asserts that
EPA's conclusions are inadequate without offering evidence to the
contrary. As described in response to Aj#179, EPAls evaluations
did not indicate that recharge would significantly enhance
remedial effectiveness at any of the three facilities, and, at
ISG and SFSG, the potential negative remedial impacts may
actually outweigh any benefits of recharge.
Aj1191. "Recharge of ~rea~ed groUDdwa~er should have been considered as a
general response action ~hat would enhance the remedy or combined into a
broader response action (e.g_, hydraulic con~ainment). For example, recharge
of ~rea~ed wa~er along .e91Den~. of the San Gabriel River can be used ~o
enhance the remedial effe~iv8Dess of the response ac~ioD in the ou. On the
basis of the very ske~chy information regarding the use of aquifer recharge as
an independen~ general response action in ~he 0f11I'S, it is apparent ~hat EPA
has not cODduc~ed a comple~e ~echDical evaluation of reaedial al~erDa~ive .
op~ioD8, bu~ focu.ed on ODe remedial al~erDa~ive wi~h a range of enra~ion
rates and two water disposal o~ioDs."
EPA Response: We disagree with the conclusions included in this
comment, .which .duplicates previous comments. See responses to
comments Aj#94, Aj#179, and Aj#190.
Aj1192. -~e us. of the CFBST 804el for the purpose of evalua~ing au decisions
(as implied in ~he .~atement "Section 7 provide. reco..enda~ion. on the ra~e
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-
and locations of groundwater extraction based on the results of computer
80deling siaulating the effects of various extraction configurations on the
8Ov_ent of groundwater and contamination in the 011 area" [po 11-1]) is
considered techDicallr inappropriate. ~e CFBS~ 80del is not sufficientlr
calibrated on a localised scale to provide the degree of detail necessarr for
evaluatiDg 011 alternatives. As previouslr stated in comments submitted to the
SPA dated Jauuarr 20, 1993, failure to recognize 8uch deficiencies of the
CFB~ 80del .ill result in techDicallr limited simulation results if applied
to localised OU 8cale deci8ions."
EPA ResDonse: We disagree with the conclusions included in this
comment, which duplicates previous comments. See response to
comments Ajl143 and Response C.
Ajl193. "SPA'. own conclu.ion of their CFB~ 80del i. summarised as "SPA's
ground.ater flow model i. a regional 80del intended to simulate ground.ater
flow over relativelr large area., using regionallr averaged condition.. SPA' s
ground.ater flow model i. not, however, designed to discern local-scale
effects". aegardle.s of this statement, the CFB~ aodel is used extensivelr
br SPA a. the priaarr basis for remediation alternative development and
evaluation that require detailed, local-scale analrsis (e.g., Section 7.0)."
EPA ReSDonse: This comment duplicates previous comments. See
response to comment Aj#132 and Response C for a description of
the use of the CFEST model in the Baldwin Park au.
Ajl194. "Pigure 11-2 also demonstrates that anr pumping in Subarea 2 would
pull clean .ater outside of the Subarea a. a result, in part of groundwater
80undiDg at ISG. ~i. results in a decrease of reaedial effectiveness and mar
have an impact on con~.m;D.Dt transport."
EPA ResDonse: The first sentence is not correct in claiming
that "any pumping in Subarea 2 would pull clean water outside of
the subarea." Only extraction above a certain rate, during
specific flow scenarios, captures water from outside of the
subarea. As stated in response to comment Aj#156, the objective
of au extraction is to capture water from just beyond the subarea
boundaries under most flow conditions. Because the ISG are
located fairly close to the subarea boundary, part of the capture
zone does intersect the mound created by spreading at ISG.
We agree that spreading at ISG does result in some negative
"remedial impacts downgradient of the facility, as described in
Section 9 of the FS.
Ajl19S. "Option 1A appears to be a more efficient option than the enormous
amounts of puaping recoaaended in the proposed plan. It should be pursued if
it is deteZ'8iDed that puaping in Subarea 3 i. necessarr. If properlr located,
one well alone could provide a .ubstantial amount of migration control."
EPA ReSDonse: Option lA alone cannot meet the migration control
objective for Subarea 3. Option lA and other Subarea 3 options
were evaluated individually to identify the most cost effective
water distribution option for each individual well cluster, and
are not intended as remedial alternatives.
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Baldwin Park ROD
We aqree that one well alone can provide a substantial
miqration control. As shown in the FS, relatively few
well clusters are needed to provide containment across
areas of contamination.
amount of
wells or
larqe
Aj1196. .~e iAclusion of Cluster 5 iAto ~e Subarea 3 response action is
inappropriate. ~e only benefit fro. ~is location is to address a siAgle and
distiAct localized source of carbon tetrachloride ~at is not connected with
~e regional distribution of TCB/PCB. Please explaiA the ratioDale for.
iAcludiAg Cluster 5 iDto ~e regional Subarea 3 response action?
EPA Response: Carbon tetrachloride has been detected
consistently over time at multiple locations, not at a
and distinct location." Even if no other contaminants
present, the concentrations of carbon tetrachloride in
qroundwater would warrant remedial action.
We are unsure of the meaninq or implication of the comment that
the carbon tetrachloride is not connected with the reqional
PCE/TCE contamination. Commentor offers no evidence of the
source of any of the contamination, whether PCE, TCE, CTC, or any
of the other contaminants. It is interestinq to contrast this
assertion of a CTC "microplume" with previous comments that the
available water quality data are insufficient to adequately
characterize the extent of contamination.
"sinqle
were
Aj1197. .PuttiAg the treated water iAto liAed Big Dalton Wash and allowiAg
iAfiltration along ~e unliAed aile of Walnut Creek 88' provide contaiDaent
for the localiaed aicropluae of carboD tetrachloride. Cluster 5 is
UDDece..azy.~
EPA Response: We disaqree that cluster 5 is unnecessary.
response to comment Aj#179 reqardinq the remedial effects of
recharqe in this stretch of Walnut Creek.
See
Aj#19S. .Bas the impact of the additional 13,000 AF/YR. recharge iA SFSG been
evaluated iA teras of cont-III' ftant transport and concentrations? As described
earlier, additional recharge at SFSG will have a significant impact on
groundwater flow and contaaiDant transport..
EPA Response: As part of alternative development, recharqe of
various amounts of water at SFSG was simulated to evaluate the
impacts on qroundwater flow and contaminant transport. These
simulations included a ranqe of recharqe volumes, most of which
were larqer than the 13,000 aC-ft/yr value discussed here. See
response to comment Aj#179 for a description of a computer
simulation which assumed recharqe of approximately 25,000 qpm at
the SFSG. The effects of recharqe at the SFSG on the
distribution of contaminant concentrations in the OU area were
not evaluated.
Aj1199. .SiAce the other water options, such as artificial recharge or
.upplyiAg water to purveyors iA lieu of puapiAg, do not result iA a net 10..
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Baldwin Park ROD
.'
of groundwa~er s~orage, MET should be required ~o replace wa~er ~~ is
exported. However, ~is would significan~ly increase ~e amoun~ of wa~er ~hat
MET would need to recharge in ~e SPSG, causing locally rising groundwater
levels and additional deaand on SPSG capacity. ~is could also impact
groundw.~er con~._ift.u~ concen~ra~ions and ~r8D.port."
EPA Response: Restrictions on, and impacts of, increased
Metropolitan involvement in the San Gabriel Basin are being
addressed in negotiations between Metropolitan and the Main San
Gabriel Basin Watermaster. We suggest you contact these parties
for additional information on the need for replacement of
exported water or other water resource issues. These issues are
also discussed in Section 9 of the FS.
Potential effects of increased recharge at the SFSG are also
described in the FS.
Aj#200. "Dia~ribu~ion of ~rea~ed water ~o Li~~le Dal~OD Wash has ~e advan~age
of adding a degree of aigra~ion con~rol in Subarea 3. ~i. recharge would
flow fro. l:i.Ded cluumels of Li.~~le Dal~n Waah and Big Dal~on Wash ~o unlined
Walnu~ Creek, loca~ed i.aaedia~ely dOWDgradien~ of Subarea 3."
EPA Response: See response to Aj#27 regarding recharge in this
stretch of Walnut creek.
Aj#20l. "I~ appears ~a~ capi~al cos~s are higher wi~ local use ~8D wi~
recharge. However, 0&11 could be higher with recharge depending on cos~
offse~s by purveyors."
EPA Response:
Proposed Plan:
"Recharge would probably be less expensive initially, but
more expensive over the life of the project due to higher
pumping costs."
We agree.
A similar comment is included in the
Ajl202. "~e no-a~~ion al~erna~ive or "Base Case" condi~ions are no~ correctly
identified for ~e OU. A~ a lDiDimum, it is mown and stated in other sections
of ~he OUPS ~ha~ existing production Wells 1900034 and 8000060 are loca~ed in
the OU and already have wellhead ~rea~en~ equipmen~ in operation. Please
explain why ~ese important wells have been excluded from "Base Case"
simulations and evaluations."
EPA Response: As stated in
extraction at these wells is
simulations and evaluations.
and Aj#151.
numerous previous responses,
included in the base case
See responses to comments Aj#144
Aj#203. "Due ~ ~e significan~ da~a deficiencies ~~ are presen~ in ~e OU,
~e large number of aoDi.~ring well. ~t are planned for ins~allation a~ ~e
pluae fringes to es~ablish an "early warning .ys~.." would be bet~er used as
8ODi~or:i.Dg wells ~ support sy.~.. design. Wells should be placed in bo~ ~e
center of ~e plume a. well as some plume ..rgin areas ~ quantify plume
aov_8D~. " .
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EPA ReSDonse: Proposed monitoring wells ~ placed in both the
center of the areas of contamination, as well as along the
margins of the contaminated areas. A revised table and figure
are included (Table RS-J and Figure RS-J) that further defines
the purpose of each monitoring well cluster.
Aj#204. "ODce agau, clata 'that are ustrua8n'ta1.u characteri:aug
contaai.Dation u 'the upgracUent portion of 'the p1.uae are ollli.tted.
refue 'the iso-concentration 1.ues and are 1.ocated u a portion of
'that is ignored u 'the proposed aoni'torug prograa."
EPA ResDonse: Once again, we respond to the same comment. See
response to comment Aj#40. Revised iso-concentration lines in
the upgradient portion of Subarea 1 would not impact the proposed
monitoring program.
~ese data
the p1.uae
Aj#205. "Because 'the p1.uae is u.dequately characteri:aed in Subarea 3, 'the
proposed new wells shou1.d be used priaari1.y for characteri:aation and
IIOnitorug Drior to 'the selection of a remedia1. action u Subarea 3."
EPA ResDonse: We disagree with the assertion that additional
characterization work is needed prior to remedy selection. See
Response F.
Aj#206. "~ere are no availab1.e data to determine 'the vertical distribution of
con'taauants in Subarea 1.."
EPA ReSDonse: This comment duplicates previous comments.
responses to comments Aj#57- Aj#60.
See
Aj#207. "~ese tables list treatment objectives 'that are in a1.1. case. 'the
1.owest NCL of 'those 1.isted u Tab1.e 4-2 (i.e., the lower of 'the federa1. and
,state JlCLs, inc1.uding proposed JlCLs). ~is list includes bo'th "applicable"
and me ARARs; 'those MCLs not currently promulgated shou1.d not be used as
treatment objective., un1.es. DO o'ther app1.icab1.e or relevant aDd appropriate
concentration 1.i.m.its are avai1.ab1.e. ~e text shou1.d c1.early discuss which of
'these objectives are based on applicab1.e aDd which are based on me ARARs."
EPA ResDonse: As stated on page 8-10 and in response to comment
Aj#72, the basis for the treatment objective for radon is the
proposed MCL. Because the proposed radon MCL is not a final MCL,
it is referred to as a "To Be Considered (TBC)." All other
treatment objectives listed in Tables 11-5 and 11-6 are ARARs
(with the exception of acetone, as noted in the Tables).
Ajl208. "Simulations in Section 7 demonstrate 'that higher extraction rate. are
not remedially effective. Section 9 amplifies the logistical problem. of
discharging treated water. Why are 'these higher-extraction alternatives being
further discussed and evaluated?"
EPA ReSDonse: This comment is not correct in stating that
"higher" extraction rates are not remedially effective. As shown
on the figures in Section 7, extraction in Subarea 2 is effective
at controlling migration within and downgradient of the Subarea
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Baldwin Park ROD
"
and would remove significant contaminant mass. However, as
explained in Response B, EPA chose not to propose or select
extraction in this area.
Aj#209. -Although i~ is s~a~ed -Figure 12-1 illus~ra~es the major advan~ages
and dis.dvan~ages among the al~erna~ives-, review of Figure 12-1 indicates
~~ .11 .l~erna~ives (with the exception of Ro Ac~ion) received the same
le"el of ranking. ~is supports the abo"e claim ~~ BPA has failed ~o
de"elop IIOre than one remedial option. BPA has focused on varia~ions of one
remedial al~erna~ive with a range of e~rac~ion ra~es and ~wo options for
water disposal/usage. Please elabora~e on the reference ~o the -..jor
.d"an~ages and disad"an~ages presen~ed in Figure 12-1- so ~~ the reader may
discriaina~e be~ween differences, if presen~.-
EPA ReSDonse: This comment duplicates a previous comment.
response to comment Aj#188.
See
Aj#210. -Due ~ the significan~ lack of da~ ~o charac~eri8e the actual
dis~ribu~ion of cheaicals in groundwa~er in the OU and BPA' s inabili~y ~o
conduc~ valid groundwa~er 80deling for the OU using the CFEBr model, i~ is
pr...~ure for BPA ~ s~~e tha~ -none of the remedial ac~ions would exacerba~e
si~e condi~ions-. Failure ~ focus on the e~raction of groundwa~er a~
loca~ions where the hi9hes~ concen~ra~ions of cheaicals ha"e been iden~ified
in the OU, and ins~e.d ~ e~ract high volumes of groundwa~er more than I-aile
downgradien~ of this source area is likely ~o resul~ in exacerba~ing the
dis~ribu~ion of cheaicals in Subarea 1, and further complica~e and increase
the ~ime and cos~ for long-~era aquifer remedia~ioD in the OU. Siailarly,
there is sufficien~ e"idence ~o support the fac~ ~~ high volumes of recharge
.~ the SFSO and/or ISO resu1~in9 fro. the al~erna~i"es presen~ed in ~he OUPS
could further neg.~ively impact. poorly de"eloped remedial ac~ion which may
be implemen~ed withou~ the necessary ~echnical analyses.-
EPA ResDonse: We disagree with this comment, which duplicates
previous comments. See Response F.
Aj#2l1. ~Wha~ is the ra~ionale for conduc~ing groundwa~er modeling for 12.75-
years?-
EPA ResDonse: EPA developed its original computer model
simulating groundwater flow in the San Gabriel Basin using a
groundwater budget analysis that included data starting with the
1977-78 water year (beginning October 1, 1977) continuing through
June 1984 (the most recently available pumpage data at that
time). This 6.75-year period was selected to include a
reasonable range of the hydrologic conditions encountered over
the longer period of record. Subsequent model updates extended
the model period through June 1990, for a total of 12.75 years.
Because the annual San Gabriel Basin Watermaster Reports, which
compile groundwater pumpage data, are completed for a period
running from July through June of each year (and not the standard
October through September water year), the model updates have
always included a period that ends with 0.75 years.
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Baldwin Park ROD
See Appendix A of the Supplemental sampling Program (SSP) Report
for additional discussion of EPA's initial modeling efforts (EPA,
1986).
Aj1212. -Because the -Ho-Action- simul.ation was conducted with a groundwater
flow lIOdel and not a cont....h'.pt transport aodel, it is incorrect to assuae
that cont.-~ftant concentration levels would increase in the particle tracked
directions. Although s..ll amounts of con~.-~ "ants -y be 8IOving, processes
such as dispersion and retardation coul.d keep concentrations wel.l below MCLs
during that entire distance.-
EPA ResDonse: We disagree. The widely-accepted presumption is
that contaminants move with groundwater. See Response A for a
detailed response to the Dno-migration" hypothesis.
Aj1213. -pigure 12-2 fails to adequatel.y represent -Base CAse- conditions in
the au. In contrast to BPA' s simul.ations, independent groundwater model.ing
and particle tracking conducted using a local.-scale groundwater model.
developed specifically for evaluating remedial al.ternatives in the au indicate
that the operatiOD of VCWD' s Arrow Highway and LaDte wel.1 cluster do provide a
considerable containment component for Subarea 1. In fact, modeling
simulations conducted by others prior to the construction of wellhead
treataent equipment at these locations support this independent conclusion.-
EPA ResDonse: EPA has simulated base case conditions, including
operation of the Arrow/Lante well cluster. See response to
comment Aj#145
Aj1214. -Please provide
extraction continues at
the remedial objectives
vicinity of Subarea 3.
Al.ternative. -
the data to support BPA' s assumption -that significant
only one existing well cl.uster that coul.d help meet
of this au-. Other well clusters exist in the
~ese wells have not been included in BPA's Ho-Action
EPA ReSDonse: The quoted statement refers to the Arrow /Lante
cluster, which is the only cluster currently extracting
significant amounts of water within the au Subareas. We agree
that other well clusters exist in the vicinity of the Subarea
that may be contributing, or may in the future contribute, to
EPA's remedial objectives.
The last portion of the comment is incorrect. Wells located
downaradient of Subarea 3 ~ included in the no-action
alternative simulations.
Aj1215. -Pl.ea.e show the approximate l.imit of capture on Pigure 12-2 similar
to the aethod used for Figure 12-3.-
EPA ResDonse: A revised figure is attached (Figure RS-8)
showing the approximate limits of capture for the no-action
alternative.
Aj1216. -Please expl.ain why the Arrow and Lante well cluster was not included
with the computer simulations for the other Al.ternative scenarios presented in
245
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Baldwin Park ROD
the OUFS. ~e Arrow and LaD~e clu8~er should be ~corpora~ed ~~o all
scenarios considered for Subareas 1 and 2."
EPA Res~onse: The comment is incorrect. This cluster is
included in all computer simulations presented in the FS.
response to Aj#145.
See
Aj1217. "In con~ras~ ~o £PA's broad conclusioD "all of the remedial
al~erDa~ives would be effec~ive in .ee~ing the reaedial objec~ives of this au
~cludiDg reduc~g the eV8D~ual cos~, difficul~y, and ~iae required for
cOD~aiDaen~ or res~ora~ion of the aquifer" there exis~s serious risk tha~
CoapoD8I1~S of the Subarea 1 respoDse ac~ioD could further exacerba~e both the
areal and ve~ical dis~ribu~ioD of cODtaaiDan~s and increase the complexi~y,
even~ual cos~ and ~iae Decessary for reaedia~ioD."
EPA ReSDonse: This comment appears to duplicate previous
comments, which refer to the proposed extraction scenario in
Subarea 1. See Response F.
Aj121S. "LoDg-~era effec~iveness and permanence of remedial measures could be
~creased if ertra"iOD were proposed a~ "ho~-spo~S" where COD~A...il:lan~s are
orders of "gDi~ude higher than elsewhere in the au. ~s also applies ~o the
redU"iOD of ~oxici~y, aobili~y, aad volume."
EPA ResDonse: We agree that additional extraction in Subarea 1
(beyond that proposed by EPA) would speed the removal of
contaminant mass from the aquifer. Any additional extraction in
highly contaminated areas will remove contaminant mass. At
issue, however, is whether additional extraction beyond that
proposed by EPA is warranted given the significant cost of. each
incremental amount extracted.
See Response B for a more detailed explanation of tradeoffs of
additional extraction beyond that proposed by EPA.
Aj1219. "Bave addi~ioD&l simula~ioDs such as those pres8D~ed in Se"iOD 7
cODfiraecl tha~ smaller ertrac~ioD volumes are UDacce~able? Why were these
evalua~ioDs DO~ shown and discussed?"
EPA ResDonse: We believe that simulations shown and discussed
in section 7 demonstrate that smaller extraction volumes are
unacceptable. As explained in section 7, lower extraction rates
would not be able to adequately meet EPA's remedial objectives
for the presently-defined subarea boundaries and expected range
of groundwater flow conditions. Results of simulations are shown
in Sections 7 and 11.
Aj1220. "Po~8D~ial financial impac~s due ~o COD~~Ued aigra~ion are
UDsubsUU1~ia~ed due m the UDce~in~ies of coD~amiDan~ ~r8Dspo~."
EPA ResDonse:
We disagree.
See Response A.
Aj1221. "Why is the assumed flow ra~e used in ~he assessmeD~ of air emiSSiODS
2 m 30 ~imes larger 'Uuu1 the flow ra~e assumed for BI1Y of the ~rea~8D~
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Baldwin Park ROD
..
facilities !Deluded !D the reaediation alternative? ~e.e number. .hould
..tch the £10" rate a.sumptions u.ed in de.igniDg the treat:aent sy.tea., for a
.ore appropriate asses..ent of potential air -.i.sion..-
EPA ReSDonse: The evaluation of incremental risk from air
emissions assumed a higher flow rate (70,000 gpm) than the
remedial alternatives (19,000 to 29,000 gpm) because the air risk
evaluation was completed before the development of the remedial
alternatives. Because the sizes of the remedial alternatives
were uncertain, the evaluation was completed assuming the largest
size project under consideration (70,000 gpm), based on the logic
that if there are insignificant risks associated with a 70,000
gpm project, there will be insignificant risks associated with
any of the likely (smaller) project sizes.
The results of the evaluation are stated on page A.l-ll:
"The sum of the noncancer hazard quotients for the COPC is
0.05, below the level of concern for noncancer health
effects. The estimated excess lifetime cancer risk for
residential inhalation exposure is 3 x 10-6, which meets the
requirements of EPA and the SCAQMD."
The relatively low risk implies that repeating the evaluation
with lower flow rates is unnecessary and would not be an
efficient use of resources (unless other assumptions such as
influent concentrations change significantly).
Commentor is concerned that readers may misinterpret the results
of the air risk evaluation. The text clearly notes in the
introduction and in the discussion of results that the assumed
project size was "2 to 30 times larger than the flow rate assumed
for any of the treatment facilities included in the remedial
alternatives" (see pages A.l-l and A.l-ll).
Aj1222. -~e text iDdicate. tha~ the chemical conc8D~ra~ions used in the air
ri.k evalua~ion -differ soaewhat- from the concen~ra~ioDs assumed in the
evalua~ion of Alterna~ive 4. Please discuss the effe~s of this inconsis~ency
on the results of the predi~ecl iDhala~ion risks.-
EPA ReSDonse: The effect of the difference is insignificant,
particularly in relation to other factors affecting the risk
estimate. (See A.I-11 for a discussion of these factors). This,
conclusion is obvious from a comparison of concentrations in
Tables A.l-l and 8-1. using the concentrations from Table 8-1
instead of A.l-l does not change the cancer risk estimate of 3 x
10-6, rounding off to one significant figure.
Aj1223. -The SCREEN aodel used ~ coDdu~ the air risk evalua~ion is a very
conserva~ive aodel tha~ uses defaul~ me~eorological da~a, rather than site-
specific data. In addi~ion, the conse~ative a.sumption ",as ..de that
-.i.sions froa all 24 air s~rippers would originate frem ODe -representa~ive
247
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Baldwin Park ROD
stack", thereby significant1y over.sti8ating the emissions that wou1d be
expected to occur from a sing1e stack or s..11 group of stacks. Although the
docuaent does point out that the assessment is conservative, neverthe1ess,
elevated concentrations of carcinogenic and noncarcinogenic cheaica1s have
been estiaated at an offsite MEI location. Bypothetica1 hea1th risks at this
1ocation were predicted to be in excess of 1 x 10-6, suggesting that ~-BACT
would be necessary to control the emisaions (based on the bu11ets 1isted on
p.A.1-10). It is unclear whether the reau1ts of this screening aasessment
wi11 be used to require !r-BACT for the proj ect . fte resu1 ts of the air risk
eva1uation indicate on1y that the e.tiaated risk of 3 x 10-6 "meets the
requireaents of SPA and the SCAQMD". C1ear1y, based on the conservative
assuaptions used in the assessment, the "actua1" hea1th risk. associated with
the air stripPer eaissions are eXPected to be we11 be10w 10-6, indicating that
!r-BACT wou1d not be necessary for the protection of huaan hea1th in the area.-
EPA ResDonse: As stated on page A.l-ll, the project, when
constructed, is likely to differ in flow rate and treatment
facility configuration from assumptions made in the air risk
evaluation. If these or other parameters differ significantly
from assumptions made in the air risk evaluation, the evaluation
may not be directly applicable to the project as constructed.
Aj1224. "fte 0D.F.5 shou1d acre thorough1y discuss the overestimations and
highly conservative assumptions ..de in the asses..ent, and clearly spe11 out
to the public that there will 1fC1.r be 24 stacks located together, that people
do RC1.r live at one location for 'O-years (SPA indicates for health risk
as.essments that the 90th percentile duration of residence is 30-years; this
value should be used in the risk assessment), that the VOCs are readily
degraded in the atmosphere, and that the flow rate used in the analysis is up
to 30 times acre conservative than the eXPected flow rate of any of the
proposed the stripper sy.tem(s). Overall, the public should be informed that
this assessment is extremely conservative, and that if a refined analysis were
. conducted, the predicted health risks would likely be lowered by several
orders of aagnitude."
EPA ReSDonse: These assumptions are noted in Appendix A, as is
the conservative nature of the air risk evaluation.
Aj1225. "Conducting a screening assessment of this nature unnecessarily raises
public concerns, and can result in increased project costs due to the use of
unnecessary po11ution contro1s, as we11 as increased risk coaaunication to
ease public concerns. fte document should clear1y discuss and interpret the
resu1ts of the risk assessaent, and c1ear1y indicate that additional pollution
controls (i.e., ~-BACf) are 1fC1.r expected to be necessary for the protection of
huaan health in the project area."
EPA ReSDonse: This comment duplicates previous comments.
response to comments Aj#22l-224.
See
Aj1226. "SPA has indicated that route-to-route extrapo1ation should not be
conducted for chemicals without toxicity data for a specific pathway. Because
of the significant uncertainties associated with this approach, SPA haa
deve10ped RfCs for aany chemica1s (.0 that route-to-route extrapolation vi11
not be necessary). In the air risk evaluation, route-to-route extrapo1ation
vas conducted for all chemical. without RfCs; using this approach, toxicity
data for 8 of the 14 chemicals eva1uated in the air risk evaluation waa
extrapo1ated on the baai. of ora1 toxicity. fte document shou1d clear1y
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Baldwin Park ROD
discuss the basis of the extrapolation for each cheaical, and the toxicity
data used to e.tiaate inhalation toxicity values.-
EPA ResDonse: Route to route extrapolations were used when
there were no noncancer toxicity values available for the
inhalation route (i.e., oral reference doses (RIDs] were used for
inhaled exposures for organic compounds that lack inhalation
reference concentrations [RfCs]). This methodology is consistent
with EPA Region IX guidance (see USEPA. Region IX Preliminary
Remediation Goals (PRGs), Fourth Quarter 1993, 11/1/93).
Although this methodology may introduce additional conservatism
in the risk assessment, the estimated noncancer hazard index for
exposure to air stripper emissions is well below the EPA's target
hazard index of 1.
Aj#227. -nere is currently no RfD for 'rCB; both 'rable A.l-S and p. A.1.2-1
list an afD of 0.006; this value actually represents the new ECAO inhalation
slope factor for the chemical. orbe afD should be deleted, and the results of
the analysis should be changed acco~gly.-
EFA ResDonse:
Aj#89.
The comment is incorrect.
See response to comment
&jI228. -ne air ri.k asse.s.ent use. different toxicity value. (e.g., afC)
and iDtake assumptions (e.g., duration of residency of 70-years) for .ost
chemical. than those assuaptions used in the health risk assess.ent in Section
4. It is unclear why two different approaches for assessing potential health
risks were used.-
EPA ResDonse: Comment or is incorrect. The inhalation
values used in the Appendix A and Section 5 are exactly
[We presume that comment or intended to refer to Section
"Preliminary Baseline Risk Assessment," not Section 4,
"Identification of Applicable or Relevant and Appropriate
Requirements."] However, in Appendix A, inhalation values are
expressed in units of mg/m3 and in Section 5 inhalation toxicity
values are e~ressed in units of mg/kg/day. To convert from
units of mg/m to mg/kg/day, a breathing rate of 20 m3/day and a
bodyweight of 70 kg is assumed.
To calculate inhalation cancer risks for exposure to air stripper
emissions, the inhalation cancer slope factors were multiplied by
the estimated air concentrations. This is a conservative
calculation in that it does not take into account an exposure
duration of less than a lifetime. To estimate excess lifetime
cancer risks for an exposure duration of 30 years, the estimated
cancer risks presented in Appendix A may be multiplied by 0.43
(30/70).
toxicity
the same.
5,
Aj#229. -orbe air risk evaluation should clearly state that if all cancer risks
were auaaed considering the cancer WOE, that predict.ed health risks (even
under the wor.e-case assumptions used) would not significantly exceed 10-'.
SuaaiDg all known, probable, and possible huaan carcinogens together as if
249
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Baldwin Park ROD
[
~hey are all "known" human carcinogen8 i8 no~ con8is~en~ wi~ s~andard risk
assess.en~ prac~ices. Xi summa~ion of all carcinogenic chemicals was done
because a "screening" risk aBBeBBmen~ was conduc~ed, i~ should be clearly
poin~ed ou~ ~ ~e public tha~ ~iB prac~ice will reBul~ in an overeB~iaa~ion
of predic~ed heal~h risks."
I
EPA ResDonse: EPA's method is consistent with standard risk
assessment practices. EPA guidance recommends calculating a
pathway-specific cancer risk estimate and hazard index by summing
the contributions of each chemical in the pathway (see EPA "RAGs"
guidance (EPA/540/1-89/002) and EPA Region IX supplement
(December 15, 1989». This method of estimating risk includes
the assumption of independence of action by the compounds
involved (i.e., no synergistic or antagonistic chemical
interactions) and gives equal weight to all classes of
carcinogens. The summation of upper bound estimates of excess
lifetime cancer risk can introduce additional conservatism in the
risk assessment, this conservatism is acknowledged in the risk
assessment in section A.1.3.3, Risk Characterization. In
addition, the weight of evidence classification for all
carcinogens is listed in Table A.1-5.
AjI230." X~ is unclear why heal~ risks for VOCs and radon were conduc~ed in a
differen~ 88DDer. X~ appears tha~ an exposure dura~ion of 70-years was used
for ~e VOCs, while a dura~ion of 30-years waB uBed for ~e radon. niB
inconsis~ency should be correc~ed; a value of 30-years exposure dura~ion
should be u8ed for all chemicals."
EPA ResDonse:
See response to comment Aj#228.
Aj1231. "A "Resul~s" se~ion should be added ~o ~e air risk evalua~ion, tha~
clearly poin~s ou~ tha~ ~e risks predi~ed from iDbala~ion of each si~e-
rela~ed me are le8s ~han 10-'; only risks from l18~urally occurring radon
equals ~hiB value."
EPA ReSDonse: Risk estimates for each compound are clearly
summarized in Table A.1-6.
Aj#232. "~e risk assessmen~ for radon should be removed from ~e asseBBmen~
of 8i~e-rela~ed risks. Radon is na~urally occurring, and i8 no~ Bi~e-
rela~ed. I~ is inappropria~e ~o sua riskB from bo~ si~e-rela~ed and
naturally occurring chemicals in ~e assessment, wi~hout clearly explaining ~o
~e public tha~ ri~ks from exposure ~ radon are rela~ed ~ background
condi~ions in ~e area. By presen~ing ~e risks associa~ed wi~ radon
Bepara~ely from risks aBBocia~ed wi~ Bi~e-rela~ed chemicalB, ~e public can
be informed tha~ ~he riBks from ~is chemical have been considered, however,
do 11O~ have a dire~ bearing on ~e r...dia~ion proposed for ~e ou."
EPA ResDonse: We disagree with commentor's recommendation that
risk resulting from radon be ignored or hidden in the risk
assessment. Radon is naturally-occurring and "site-related" in
that its presence contributes to the risk that would be
experienced by those exposed to air emissions from the selected
remedy. All risks resulting from implementation of a remedial
action in the Baldwin Park area "have a direct bearing" on EPA's
250
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Baldwin Park ROD
proposal, regardless of the contaminant's origin. Table A.1-6
allows interested readers to discern the risk contribution from
radon and other individual compounds of concern.
Aj#233. "fte Polopolus well has a very shallow screen depth. Was this
considered in the evaluation? fte well is only 0.5-aile upgradient of the SPA
.ulti-port aonitoring well which detected the higher contaminant.
concentrations several hundred feet below the equivalent Polopolus well
intake. . Why wasn' t this well s..pled 8IOre often in the last I3-years? It is
located in the center of the ..iD area of VOC contamiDation."
EPA Response: The contaminant data from the Po1opoluswe11 were
not adjusted in any way to account for the relatively shallow
depth of this well. It should be noted that, as shown in Figure
3-9, depth-specific sampling indicated that contaminant
concentrations were fairly uniform across the upper several
hundred feet of the aquifer upgradient of the Polopo1us well.
Although it is certainly possible that higher concentrations are
present deeper into the aquifer at the Polopolus well location,
EPA's monitoring well MW5-1 is not directly downgradient of .the
Polopolus well (it is more cross gradient). Thus, the
distribution of contamination at the two locations would not
necessarily be expected to be similar.
Unlike most of the production wells in the basin, because the
Po1opo1us well is a privately-owned irrigation well, state-
mandated sampling under Title 22 is not required. EPA bgg
sampled the well during each EPA-sponsored sampling event in the
basin (1985, 1987, 1990, and 1991).
Ai#234. "Attach8ent A contains water quality data fro. some wells through
Hovember 18, 1991, DOt HoveJDber 7, 1990 as indicated in the text. Are all
data froa Hovember 1990 to HoveJDber 1991 included?"
EPA Response: November 7, 1990 is the cutoff date for sampling
data used to develop influent water quality estimates. November
18, 1991 is the cutoff date for data included in the original
Attachment A (an updated Attachment A containing data through
10/93 has been added to the Administrative Record). The cutoff
dates differ because, as stated in Attachment A and elsewhere in
these responses, as the FS progressed, different cut-off dates
were used for the water-quality data incorporated into various
evaluations (based on available data at the time the evaluation
was performed).
Aj#235. "ftese two wells [SGVWc B6] are located at the downgradient portion of
Subarea 3. !rIae docuael1t comments [in Appendix B) that pumping rates and
durations ..y control the VOC concentrations in those wells, suggesting that
pumping is pulling cont....... "ant.s dOWDgradient. Decreases in pumping might
result iD a rec~dingplume."
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Baldwin Park ROD
~
EPA ResDonse: We agree that production at the B6 wells
influences the local groundwater flow gradient. (It should be
noted that these two wells have been inactive for approximately
four years.) However, it is unclear how the conclusion could be
drawn that reduced pumping might result in a "receding plume."
Even with no pumping from these wells, regional groundwater flow
directions (and thus, contaminant migration) are towards this
well cluster from upgradient in the au area. consequently,
reduced pumping would not cause contaminant migration to change
directions or "recede" in the upgradient direction.
Aj#236. .Were the relatively high concentrations of other inorganics, such as
ms, factored into the treat:aent costs? Background inorganic water quality
for the San Gabriel Basin is characteriaed as .hard" water 8Dcl 88Y result in
added costs."
EPA ReSDonse: The inorganic quality of groundwater in the au
area ~ considered in the treatment evaluations.
Aj1237. "Because of the risk of pulling nitrates from the east with high
pumping rates, it is essential to conduct detailed analyses to recommend the
lowest possible extraction rate that will accomplish all of the objectives."
EPA ResDonse:
We agree.
Aj#238. "If the proposed extraction location in Subarea 1 was moved to the
area of highest contamination, (north of the I-210 freeway), the predicted
ground surface elevation at the we11 would increase more than 50 feet. ~is
additional elevation 88Y facilitate the surface conveyance to the city of
Aausa reservoirs."
EPA ResDonse:
Comment noted.
Aj#239. "Additional cont-.inant characterisation should be included as an
objective. CUrrent characterization is incomplete in all areas of the OU:
o Vertical distribution is unknown in Subarea 1.
o Subarea 2 is defined only by four wells, three production wells and
one monitoring well.
o ~ere are no monitoring wells in Subarea 3. Vertical and areal
distributions of contaminants are uncertain.
Much of this characterization is necessary Drior to selec't.ing a remedy."
EPA ResDonse: We agree that additional contaminant
characterization is a key objective of the monitoring program.
This was one of the criteria used in identifying the recommended
monitoring well locations and should have been included in this
list. An updated table is included in this Responsiveness
Summary (Table RS-3) to provide additional information on the
purpose of each new monitoring well cluster.
We agree that the monitoring program must be one of the first
steps during the time of remedial desian. We do not, however,
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Baldwin Park ROD
agree that the monitoring program must precede remedv selection.
As stated previously, adequate information has been collected and
is presently available to select a remedy for the Baldwin Park
QU. See Response F for additional details.
Ajl240. -KW-S-07 and 08000039 appear redundant.
early warning for Cluster 5.-
Well 0800039 can be used as
EPA ReSDonse: Production well 08000039 is located over 3,600
feet upgradient of the assumed Cluster 5 extraction location.
This was considered too far upgradient to provide reliable early
warning data for changes in contaminant conditions. In addition,
monitoring well clusters, rather than production wells, are
preferred for the early warning clusters to provide better data
on the vertical distribution of contaminants.
Ajl241. -MWS-D2 should be located farther downgradient and used to supp~..ent
the other dOWDgradient we~ls that have varying screen depths.-
EPA ReSDonse: The purpose of MWS-2 is to help monitor the
remedial effectiveness of Subarea 3 extraction by observing
changes in contaminant conditions iust downaradient of the
Subarea. The downgradient production wells referred to in the
comment will provide additional information to sUpplement data
from MWS-2, but. are a bit further downgradient than desired for
monitoring remedial effectiveness in Subarea 3.
Ajl242. -~e timing and purpose of the proposed monitoring wells should be
revised. Several of these wells should be installed initially, monitored, and
used to revise the cont"lII~n..nt characterization. OI1ly then should extraction
location and pumping be finalized.-
EPA ResDonse: We agree that the new monitoring wells should be
used to update our understanding of the extent of contamination
in the QU area. And, as described previously, the extraction
locations and rates will not be finalized until data have been
gathered from the monitoring program.
Ajl243. -~is discussion (p.B-9) amplifies the need for additional data from
the aonitoring program, yet none of these program wells bave the stated
purpose of additional aquifer characterization.-
EPA ResDonse: The FS recommends approximate type, number, and
location of wells, but it is not its purpose to serve as a
workplan for the installation or sampling of wells. After the
Record of Decision is completed, EPA or Potentially Responsible
Parties will prepare a detailed workplan for the installation and
operation of the monitoring network. Data on aquifer properties
will certainly be collected during monitoring well installation.
Ajl244. -.ow doe. the role of the San Gabriel Basin Water Quality Authority
blend or overlap with agency responsibilities? Since they are involved in
253
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Baldwin Park ROD
groUDdwa~er qua1i~y proje~. in the basin, their role and reBpoD.ibi1i~ies
shou1d be included."
EPA and staff of the San Gabriel Basin Water Quality Authority
periodically meet to coordinate investigation and clean up
actions in the Baldwin Park area and in other parts of the Basin.
The Authority, however, as an independent agency established by
State legislation, reaches its own decisions on how to contribute
to the cleanup. Our current. understanding is that the Authority
intends to complete installation of wellhead treatment at the Big
Dalton well. We suggest that you contact the Authority directly
for more detailed information about their planned activities.
Aj1245. "Are both the Arrow and LaD~e well. pumped a~ capaci~y during ~he
siau1a~ioDs? Siaula~ioDs in S.c~ioD 7 show the significance of this pumping."
EPA ReSDonse: The extraction rate assumed for these wells in
all simulations is 3,000 gpm, plus the existing pumping rate from
the Lante well during the three-year period of existing
extraction incorporated into the simulations. The 3,000 gpm flow
rate was based on discussions with the water purveyor regarding
the planned use of the new Arrow Highway treatment facility..
Aj1246. "Are any of the siau1a~ioDs with increased recharge shown or discussed
in this docWReD~? If Dot, why DO~?"
EPA ResDonse: Yes, see Figure 11-2 and accompanying text on
pages 11-6 and 11-9.
Ajl247. "Given the discussioD of the importance of secoDdary
liai~a~ioDs of particle tracking i:o evalua~e this cODdi~ioD,
the siau1a~ed ertra~ioD locatioDs in Subarea 1 80ved ~o ~he
cOD~aiDiDg secondary sources?"
source. and the
why .asD'~ ODe of
area suspec~ed of
EPA ReSDonse: This comment duplicates previous comments
recommending additional extraction upgradient of EPA's proposed
locations in the upper area. See Response B.
Aj1248. "~ere are references in the OOPS abou~ receD~ sampling in the Baldwin
Park key .ell (Z1000006), ye~ DO da~a from this .ell are included in
A~~achaeD~ A."
EPA ReSDonse: This. comment duplicates a previous comment.
response to comment Aj#15.
See
Aj1249. "Da~a from BPA Well MW611-19 are included in A~~achmeD~ A.
well in the OU?"
Is this
EPA ResDonse: Data included in Attachment A are from wells in or
in the vicinity of the areas of known contamination. EPA Well
MW611-19 meets this criterion.
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Ba~dwin Park ROD
Aj1250. -Figure 1-4 indicates that EPA has conducted recent groundwater
sampling at Wells 01900831 and 01902971. Bowever, data from these wells are
not included in Attachment A."
EPA Response: This comment duplicates a previous comment.
response to comment Aj#15.
See
XVII.2 Response to "Review Comments, Proposed Plan, May 1993, Baldwin
Park Operable Unit"
Aj1251. In this submittal, Aerojet/ALR repeat the same complaints, criticism.,
and a.sertions made in their comments on the Baldwin Park Operable Unit
Peasibility study. ~ey criticize BPA's Proposed Plan as -based on
simplifying assumptions that are not technically defensible.- ~ey assert
that BPA -fail[s) to consider local variations in the groundwater flow regime
and the effects of the proposed remedy on local groundwater flow and
cont.lll8j"ant transport"; -fails to incorporate strategic source control
aeasures"; -fails to recognise the benefits of existing wellhead treataent
facilities"; -fail. to adequately accurately [sic) describe -Base case-
hydraulic conditions...-; -fail[s] to opt~ze the effectiveness of proposed
project and theraby limited remediation objectives-; and, finally, thatEPA's
proposal risks "damage to the grOundwater resource.-
~ey continue, asserting that a "detailed review of the rationale provided and
the available data for the OU indicates that basis for the proposed response
action in unsubstantiated and appears to be driven by schedule..."; that
"EPA's groundwater modeling results are not sufficiently detailed to simulate
the effects of current aDd historic pumping and recharge patterns upon flow
conditions in Subareas 1 aDd 3 -; that "BPA has failed to demonstrate the need
for additional aigration control actions in dOWDgradient area. (Subarea3)...";
and includes "distorted" risk estimates and "exaggerated" claims of the costs
of not taking action.
EPA ReSDonse: These comments duplicate previous comments. See
summary response to Aerojet/ALR general comments on the Baldwin
Park Operable Unit Feasibility 'Study and responses to
approximately 250 specific comments that follow the general
comment. EPA believes that the majority of these comments make
incorrect assertions or reach unsupported conclusions, and do not
warrant any changes in EPA's proposed remedy.
Aj1252. In its comments on BPA's proposed remedial action in Subarea 3,
Aerojet/ALR assert that BPA has not demonstrated that the proposed remedial
action in Subarea 3 is needed to meet. EPA' s stated remedial objective. ~ey
cite "independent analyses" completed by camp Dresser ~ McKee, consultants to
the SaD Gabriel Basin Industry eoalit.ion, hypothesising that the plumes have
8t-8z,.-i H zed or zeac:hec:f eqn-i,.. "'2:1:-. ~ey also assert that "a broad DOn-
detectable area of !rCB and PCB exist. between the dOWDgradient. ..rgin of
Subarea 3 and Whitt.ier .arrows.- Lastly, they assert that EPA's remedial
objective for Subarea 3 contradicts a statement in the PS that "available data
do DOt show any significant change in cont-.inant levels dOWDgradient of
Subarea 3 to as far as Whittier .arrows."
255
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Baldwin Park ROD
"
EPA ReSDonse: The "independent analyses" completed by Camp
Dresser & McKee are speculative, largely unsupported by site-
specific data, based on misinterpretations of data (e.g.,
mistakenly alleging oscillation and retraction of the plumes) and
fail to consider site-specific evidence refuting their plume
equilibrium/no action hypothesis. See summary response to
Aerojet/ALR general comments. on the Baldwin Park OU Feasibility
Study and Response A for a detailed explanation of the need for
action in Subarea 3.
Also, we agree that neither TCE nor PCE have been detected at
some wells downgradient of Subarea 3, but would not characterize
the area of non-detects as broad due to the paucity of sampling
locations in this area. We also note the presence of other
contaminants at levels above MCLs (e.g., carbon tetrachloride) at
wells where neither PCE nor TCE have been detected.
Finally, we are unclear of any contradiction between EPA's stated
remedial objectives and the referenced statement. Contaminant
concentrations within Subarea 3 are higher than concentrations
downgradient of the subarea, indicating possible benefits of
remedial action to prevent the more contaminated groundwater from
migrating into less contaminated downgradient areas. The
referenced statement notes that there is not a "significant
change in contaminant levels from ;ust downqradient of Subarea 3
to as far south as Whittier Narrows." Contaminant
concentrations of different compounds at various wells in the
interval from ;ust downaradient of Subarea 3 to the Whittier
Narrows area are generally at or near MCLs. Thus, as stated in
the text, there is not a "significant change" in overall
contaminant levels within this stretch. Also see response to
. comment Aj#130.
Aj1253. %n its comments on SPA's proposed remedial action in Subarea 1,
Aerojet/ALR note the distance between well W10WOMWl and EPA' s recolIIIDended
extraction locations, and asserts that EPA's recommended extraction locations
in Subarea 1 8&Y "exacerbate the migration of chemicals from the highest
concentration source areas to less contaaiDated areas..."
EPA ResDOnSe: EPA believes that its recommended extraction
locations represent an effective strategy for limiting the
migration of contamination detected at well W10WOMW1. See
. Response B for a detailed explanation of the rationale for
recommended extraction locations.
EPA's
Aj1254. Aerojet/ALR also as.ert that SPA failed to identify the hydraulic
capture sones present fro. the operation of the Arrow and Lante wellhead
treatment facilities and did not adequately account for localize changes in
groundwater flow direction and gradients that have been documented in response
to recharge events at the Santa Fe Spreading Grounds.
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Baldwin Park ROD
EPA ReSDonse: These assertions is incorrect; EPA did assume
continued extraction at the Arrow/Lante wells and did account for
recharge at the Santa Fe Spreading Grounds. Aerojet/ALR in fact
acknowledge that EPA accounted for extraction at the Arrow/Lante
location. See response to comments Aj# 143 and Aj#145, and
Response B.
Aj1255. Aerojet/ALR recOJlllDend that the -Subarea 1 response action aust
consider })oth ..ss removal of chemicals per volume of water extracted and
aigratioD control, and optimi8e extraction, to achieve })oth objectives. Source
control is a prerequisite to optimi8e the effectiveness of groundwater
r_ecliation in Subarea 1.-
EPA ResDonse: We agree that migration control and mass removal
are both remedial objectives for the Baldwin Park QU. See
Response B for additional details on how these objectives will be
translated into extraction rates, locations, and other project
details. We also note that EPA's proposed extraction and
treatment in Subarea 1 would provide significant "source
control. II
XVII.3 Response to "Proposal for Technical Modifications Optimization of
U.S.EPA Region IX Subarea 1 Proposed Project, Baldwin Park Operable Unit"
Aj1256. Aerojet/ALR state that -Although data deficiencies also exist in
Subarea 1, an iDteria action that specifically targets source control appears
feasible at the present time. AerojetlALR state, however, that concentrations
of PCB and ~ in groundwater at well. OSCOMW2 and WI0WOMWl are -the highest
concentrations identified in Subarea 1 by at least an order of aagnitude, yet
BPA' closest extraction location, Cluster 10, is located up to l-aile
downgracUent of these evident hot spots.-
Aerojet/ALR assert that -BPA' s Subarea 1 proposed project... does not address
source control, and in fact will likely exacerbate the spread of cont....,nants
froa -hot spots- into less contaainated 80nes of the aquifer. - Aerojet/ALR
describe their'analysis of groundwater flow and water quality, their computer
aodeling efforts, and recOJlllDend that BPA relocate recOllllR8nded extraction
locations as shown in the submittal' (Plate 18) to -optimize the efficiency of
cont...., nant removal by at least an order of magnitude, while ..intaining BPA' s
goal for containment in Subarea 1.- ~e three recommended locations are:
. in the vicinity
. in the vicinity
. along Gladstone
(suggested rate =
of well WI0WOMWl (suggested rate = 3,000 gpm)
of well OSC0MW2 (suggested rate = 4,000 gpm)
Street northeast of BPA'. proposed 10 and 13
2,000 gpa)
clusters
~ey argue that their recOJlllDendations would -prevent
cont....in_ats from -hot spots- into le.s contaainated
and will ultimately decrease both the time and costs
not only [in] Subarea 1, but throughout the ou.-
the spread of
80nes of the aquifer ...
required for remediation
EPA ResDonse: See Response B for a detailed rebuttal to
criticisms of the pumping configuration in EPA's Subarea 1
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Baldwin Park ROD
proposed project, including the value of the additional
extraction in the vicinity of well W10WOMW1.
Because the Record of Decision recommends, but does not require,
groundwater extraction rates and locations, EPA has not completed
a detailed review of the computer modeling or other analyses
carried out in support of the proposal to replace EPA's
recommended extraction rates and locations with less extraction
in the vicinity of well OSCOMW2 and along Gladstone street. Our
own evaluations lead us to expect that extraction in the vicinity
of well W10WOMW1 will remove contaminant mass, but will not
contribute to EPA's objective of limiting migration of
contaminated groundwater out of Subarea 1. If so, then commentor
is proposing to substitute 6,000 gpm of extraction at well
OSCOMW2 and along Gladstone Street in place of the 8,500 gpm that
EPA's evaluations indicate is necessary. In their submittal,
comment or does not identify what differences in hydraulic
conductivity, differences in interpretation of the extent of
contamination, or other differences justify their assertion that
they can extract approximately 30% less groundwater and still
satisfy EPA's migration control objective. Also see response to
Aj#130.
Aj1257. Aerojet/ALR repeat their assertion that "Technical evaluations
strongly indicate that the proposed project in Subarea 3 is without technical
justification, and requires additional data collection and further analysis
prior to remedy selection."
EPA ReSDonse:
We disagree.
See Response A.
Aj1258. Aerojet/ALR claim that in their computer simulations "the magnitude
of simulated fluctuations is typically within 5 to 10 feet of measured
fluctuations, and only once varies as much as 18 feet." They claim that this
level of accuracy is "significantly greater than the 20- to 3D-foot range of
variations evident in BPA's calibration result. for the CFEST model." [p.21]
EPA ResDonse: EPA has not reviewed Aerojet/ALR's modeling
results in detail, but Plate B-3 in their submittal appears to
indicate that calibration results for the Key Well are in the 5
to 15 foot ranae. Contrary to Aeroj"et/ALR's claim, this result
is not significantly better than EPA's calibration results for
the Key Well (shown in Figure C-8 of the Interim RI' Report),
which generally range from 5 to 20 feet (not the 20 to 30 feet
claimed in the comment).
XVII.4 Response to 18 page letter with "General comments on and legal
analysis of the Baldwin Park au FS and Proposed Plan," dated August 10,
1993,
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Baldwin Park ROD
Aj1259. !rIae priBary 'theme of 'this se't of C088en'ts is 'the assertion 'tha't 'there
are "iDsufficien't da'ta 'to prepare, screen, evalua'te and .elec't appropria'te
reae4ial al'terna'tives." !rIais .e't of C0888D'tS also duplica'tes commen'ts
provided iD o'ther Aeroje't/ALR submi't'tals on 'the "plume s'tabiliza'tion"
hypo'thesis; on whe'ther £PA adequa'tely considered 'the effec'ts of an exis'tiDg
wellhead 'treauent projec't; on whe'ther £PA considered 'the impac'ts of recharge
a't 'the 8an'ta Fe SpreadiDg Grounds; aDd on the adequacy of £PA's computer
8OdeliDg. ODe apparen't difference be'tween 'this se't of commen'ts and o'ther
commsn'ts is an e.cala'tion of 'the rhe'toric used 'to cri'ticize £PA's proposal.
Among 'the comments direc'tec:l at £PA' s proposal are 'that i't is "discredi'ted" by
previous £PA iDac'tion; ra'tionalized by "dogma'tic assertion" ra'ther 'than
"exis'tiDg evidence or reasonable iDferences," based on "aisleadiDg"
predic'tions and analysis tha't is "fUDd8men'tally flawed"; and 'tha't i't "viola'tes
ba.ic 'tene'ts of ra'tional decision-aakiDg."
EPA ReSDonse: Despite the flamboyant rhetoric, these comments
duplicate comments made in other Aerojet submittals and responded
to in this Responsiveness Summary. See Response F for a summary
of EPA responses to Aerojet/ALR's assertion that EPA's selected
remedy is not supported by adequate data or technical analysis,
and responses to specific comments included in other Aerojet/ALR
submittals. .
Aj1260. Aeroje't asserts. repea'tedly that "~ere is no RJ[ for 'the BaldwiD Park
Operable Unit."
EPA ReSDonse: This claim is ridiculous. Comment or interprets
EPA's decision to omit the words remedial investigation from the
title of the Baldwin Park Operable Unit Feasibility Study as
implying that no remedial investigation was conducted. As
explained on page one of FS:
"The report also summarizes remedial investigation (RI)
activities completed in the OU area; more detailed
descriptions are available in separate reports (see Section
L 5) ."
As explained throughout the Feasibility Study and this
Responsiveness Summary, the remedial investigation for the
Baldwin Park OU included the collection and analysis of data from
hundreds of water supply and monitoring wells installed by water
purveyors and businesses; groundwater sampling performed as part
of EPA's Supplemental Sampling Program; four rounds of basinwide
groundwater sampling completed by EPA in 1988; two rounds of
wellhead sampling at existing wells in 1990-91; well logging and
depth-specific sampling of eight wells in the Baldwin Park area
byEPA in 1989-91; installation and initial sampling of a
1,540-foot-deep mUltiport (MF) monitoring well by EPA in Baldwin
Park in 1991; evaluations of the quality of EPA-collected and
other groundwater data; analyses of the hydrogeology, water
budget, water supply infrastructure, occurrence and movement of
VOCs, and occurrence of nitrate in the Baldwin Park area; the
development and use of a computer model of groundwater flow in
259
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Baldwin Park ROD
.'
the basin; as well as analyses of treatment technologies, water
distribution options, and other components of the Baldwin Park au
remedy.
XVII.S Response to two videotapes titled "Aerojet Submission of Nicholas
Pogencheff Testimony, August 4, 1993" [Edited, approximately 3 hours in
duration].
Aj1261. Aerojei; .ubaii;i;ecI i;hree hour. of ecUi;ecI videoi;apecl "i;e.i;iaony" 10
which Michola. Pog8Dcheff, con.ult'.aDi; i;o Aerojei; OeDcorp, i. appareni;ly
iDi;erviewecl by Pei;er ~afi;, an ai;i;orney repre.eni;iDg Aerojei;.
EPA ReSDonse: The videotapes largely duplicate written comments
provided by Aerojet Gencorp. They include minor errors in their
explanation of how the San Gabriel Basin is managed (e.g., they
incorrectly state that groundwater is not exported from the
Basin; they incorrectly identify the San Gabriel Basin operating
limits as 200 feet to 300 feet (actual limits are 200' to 250'»;
they include errors in their description of how contaminants move
from the surface to the groundwater (e.g., they comment at length
on the presence of surface sources of contamination,
hypothesizing that surface spills or releases have decreased over
time, but fail to acknowledge the continued presence of
significant subsurface sources of contamination); and they make
numerous errors in describing EPA modeling efforts. We repeat
here and respond to only selected comments from the videotapes.
. Aerojet correctly identifies ways in which EPA could have
increased the complexity and cost of its computer
simulations (e.g., increasing the number of nodes and cells
in the model), and offers hypothetical examples in which a
more complex model would be appropriate, but does not
demonstrate the need for a more complex model as part of the
Baldwin Park QU. See Response C for additional details.
. Aerojet criticizes simulations of groundwater flow and
contaminant transport completed by EPA in the 1980s and
presented in Appendix C of the Interim RI Report. These
simulations have no bearing on the Baldwin Park QU remedy.
In their criticism of past EPA simulations, Aerojet asserts
that there are no continuing surface or subsurface sources
of groundwater contamination in the Baldwin Park area. This
criticism is without merit. Significant evidence indicates
the presence of continuing subsurface sources in the Baldwin
Park area, in the vadose zone and as non-aqueous phase
contamination in the vadose and saturated zones. Aerojet
offers no data or analysis to the contrary. See Response B.
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Baldwin Park ROD
. Aerojet asserts repeatedly that their interpretation of
the hydraulic conductivity of the Baldwin Park area is more
accurate than EPA's assumed distribution of conductivity.
See Response A (Table of Baldwin Park Area Hydraulic
conductivity Estimates and accompanying text) and response
to comments Aj#17-21 for a rebuttal to this assertion.
. Aerojet.correctly notes that EPA used its computer model
to simulate the movement of groundwater in the Baldwin Park
area and did not attempt to simulate contaminant fate and
transport processes (e.g., dispersion and retardation). As
noted elsewhere in this Responsiveness Summary, EPA does not
believe that it is necessary to simulate contaminant fate
and transport to evaluate or select an interim remedy for
the Baldwin Park ou. EPA does not state, and did not intend
to imply, that contaminants move at the same rate as
groundwater. In its comments, Aerojet laments EPA's
decision to not simulate transport processes but does not
identify any ways in which EPA's decision affects the
selection of remedy.
. Aerojet discusses a "historical matching" exercise
completed during the development of their computer model in
which they acquired quarterly measurements of groundwater
levels in the Baldwin Park area over a 14 year period. They
also describe the resulting "good fit" between simulated and
actual water levels. EPA completed a similar effort, which
made use of quarterly water level data collected over a 12
year period and also resulted in a "good fit." Also see
response to Aj#258 and Response C.
. Aerojet states that "we have no idea what the areal extent
[of groundwater contamination] north of that high
concentration [detected at monitoring well W10WOMW1]." Data
are available, and were included in the Baldwin Park FS,
from at least half a dozen wells north of W10WOMW1. Also
see Response B for a detailed discussion of EPA's
interpretation of the distribution of contaminants in the
Baldwin Park area.
. Aerojet incorrectly asserts that EPA did not account for
the impacts of artificial recharge (spreading) at the Santa
Fe Spreading Grounds on the movement of groundwater in the
Baldwin Park area. Aerojet build~ on this incorrect
assertion in alleging that this deficiency results from the
"regional scale" of EPA's computer model.EPA considered
recharge at the Santa Fe Spreading Grounds in the
development of its remedy and depicts its effects in the FS.
EPA's recommended extraction rates and locations will limit
261
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"
Baldwin Park ROD
"
migration during periods of significant recharge at Santa Fe
Spreading Grounds. See response to comments Aj#143 and 179.
. Aerojet recommends extraction at or near well the Wynn oil
and OSCO "sources," criticizing EPA's recommended pumping
configuration for not maximizing mass removal and
accelerating the migration of potential "hot spots." We
disagree with ' this recommendation, which we discuss in
detail in Response B. Aerojet retracted this recommendation
in subsequent comments. See response to comments Aj#262-
271.
. Aerojet incorrectly asserts that EPA ignores the influence
of the Arrow/Lante projects on the movement of groundwater
and contaminants in the Baldwin Park area. See response to
comments Aj#144 and 145.
. Aerojet incorrectly asserts that the reclaimed water
project proposed by the Upper San Gabriel Valley Municipal
Water District would have a negative impact on the Baldwin
Park remedy. See response to comment Aj#182.
XVII.6 "Addendum to Proposal for Technical Modifications Optimization of
U.S. EPA Regional IX Subarea 1 Proposed Project Baldwin Park Operable
Unit, II November 29, 1993 and 4 page cover letter dated December 2, 1993
[SUBMITTED AFTER THE CLOSE OF THE PUBLIC COMMENT PERIOD]
In this submittal, Aerojet, ALR, and the oil and Solvent Process
Company (OSCO) change Aerojet/ALR'S previously suggested
locations and rates of groundwater extraction in Subarea 1. They
claim that "new data" available after the close of the public
comment period indicating a decrease in contaminant
concentrations in the vicinity of OSCOMW2 necessitate the change.
Ajl262. ODe of Aerojet/ALR/OSCO's arguments for chaDgiDg the~r prev~ously
recommended extract~on rates and locat~ons ~s that the "1992-93 wiDter was the
f~rst substantial wet period iD ten years."
EPA ReSDonse: This statement is incorrect. Rainfall, and
artificial spreading, in the previous winter of 1991-92 were also
sUbstantially higher than average.
Ajl263. Aerojet et. ale refer to 8On~toriDg well results fro. the Aerojet and
OSCO wells ,and other "DeW clau ava~lable only after the close of the publ~c
comment per~od" that imply the need to aod~fy prev~ously recommended
extract~on rates and locat~ons. ~ey state that the "early pattern [of water
quality data] suggested ~ source area ... [along] Motor Avenue near OSCO area"
262
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Baldwin Park ROD
hut that .ore recent data suggest that recharge .overwhel.a [s) the source or
sources..
EPA ResDonse: We disagree with the conclusion that recent
sampling data argue against extraction of contaminated
groundwater in the vicinity of the OSCO wells.
EPAts recommended pumping configuration includes extraction of
contaminated groundwater downgradient of the OSCO facility
because the available groundwater, vadose zone, and chemical
usage data indicate the presence of a continuing subsurface
source of contamination in the vicinity of the OSCO facility.
The Itnew data" cited by Aerojet/ALR/OSCO do not dispute this
view. The "new data" do show decreases in concentrations of some
contaminants at the OSCO wells, temporarily complicating the
interpretation of these water quality data, but the data do not
in any way indicate that the source or sources of contamination
have disappeared or even diminished. The observed decreases in
contaminant concentrations most likely reflect dilution of
contaminated water by clean recharge water, as varying
groundwater flow directions temporarily cause wells that were
downgradient of the contaminant source to be more cross-gradient.
The effect is likely to be temporary, however. We expect that
the wells will resume their downgradient relationship to the
source (and contaminant levels will rise) as recharge decreases
and groundwater flow direction resumes its more typical northeast
to southwest orientation.
Commentor refers to water quality data collected during May 1993.
These data reflect the influence of much higher than average
volumes of recharge at the Santa Fe Spreading Grounds during May
and the preceding several months, as summarized below. The
listed volumes were provided by Los Angeles County Department of
Public Works. .
Volumes of Water Recharged at the Santa Fe spreading Grounds in
1992-93
Month
Oct 92
Nov 92
Dec 92
Jan 93
Feb 93
Mar 93
Apr 93
May 93
Jun 93
Jul 93
Aug 93
Volume Recharged
133
5,560
1,670
6,700
6,.160
14,310
18 "010
~2.830
799
o
2,420
(acre-feet)
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Baldwin Park ROD
"
Sep 93
Oct 93
Nov 93
Dec 93
Jan 94
Feb 94
6,000
7,110
o
o
o
o
Aerojet/ALR/OSeo do not actually list or summarize any "new data"
and do not provide any clear statements as to how the "new data"
justify eliminating extraction in the vicinity of the oseo
facility. The closest the comment comes is in noting
fluctuations in contaminant concentrations at the oseo wells and
stating that recharge "overwhelms the source or sources." We
are unsure of the meaning of the word overwhelm in the comment.
We agree with the comment to the extent that it refers to more
recent data complicating, at least temporarily, our ability to
inrerprer water quality data from the oseo wells. We disagree
with the comment to the extent that it implies that recharge has
moved, diminished, or eliminated subsurface sources of
contamination in the area. .
Aj1264. In discussing ~eir aocIeling efforts, including Plate 3 of ~eir
submittal purporting to illustrate ~e impact of £PA' s recommended extraction
rates and locations, Aerojet et. al. claim ~at £PA's recommended extraction
rates and locations in Subarea 1 -results in accelerating ~e spread of
cont-lII;neDts from Well W10WOMW1 during wet cODditions, wi~ DO downgradieDt
containmeDt to inhibit cODt-lIIinaDt migratioD.- (p.4)
EPA Response: In response to the first portion of the comment
(asserting an accelerarion of the spread of contaminants), we
note that groundwater extraction always accelerates the movement
of groundwater and contaminants within its zone of drawdown,
regardless of regional flow conditions. In response to the
second portion of the comment (asserting the absence of
downgradienr conrainmenrto inhibit contaminant migration), we
offer EPA's particle tracking simulations which indicate that its
recommended extraction rates and locations will inhibit
contaminant migration from Subarea I during all expected flow
conditions. The simulation results presented by Aerojet et. al.
as Drawing 3 do not offer any evidence to the contrary. As
discussed in response to comment Aj#266, we do not believe that
the results presented in Plate 3 (as wells as Plates 1-6)
realistically simulate regional flow conditions in the Baldwin
Park area.
Aj1265. Aerojet et. a1. recommend ~e following changes (from ~eir August
1993 submittal) in extractioD rates aDd locations:
. reliance on 4000 gpa extraction at ~e existing Arrow/LaDte cluster to
limit ~e migration of contaminated groundwater from Subarea 1 in place
264
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Baldwin Park ROD
of a nev vell along Gladstone Avenue (and in place of £PA's reco..ended
pumping configuration).
. retraction of the proposal to install a nev extraction vell in the
vicinity of OSCOMW2
. reduction in the reco_ended extraction rate at the nev extraction
vell at WI0WOMWI to 2000 gpm
~ey assert that their 80deling establishes that 4,000 gpa of extraction at
the Arrow and Lente _lls vill -equal the contaiDaent component-of £PA' s
reco..ended extraction locations (#10 and 13), ..king BPA' s reco..ended
locations unnecessary. (p.4)
EPA ResDonse: See Response B for a discussion of the merits of
relying on extraction at Arrow/Lante and the value of extraction
at W10WOMW1. A significant disadvantage of moving extraction
locations from EPA's recommended locations to Arrow/Lante is that
it would permit additional degradation of the portion of the
aquifer between EPA's recommended extraction locations and the
Arrow/Lante wells.
Because the Record of Decision recommends, but does not
prescribe, specific groundwater extraction rates and locations,
EPA has not completed a detailed review of the computer modeling
or other analyses carried out in support of Aerojet's proposal to
replace EPA's recommended extraction rates and locations with
4,000 gpm at the Arrow/Lante cluster. Our own evaluations lead
us to expect that extraction in the vicinity of well W10WOMW1
will remove contaminant mass, but will not contribute to EPA's
objective of limiting migration of contaminated groundwater out
of Subarea 1. If so, then commentor is proposing to substitute
4,000 gpm of extraction at Arrow/Lante in place of the 8,500 gpm
that EPA's evaluations indicate is necessary. In their
submittal, commentor does not identify what differences in
hydraulic conductivity, differences in interpretation of the
extent of contamination, or other differences justify their
assertion that they can extract approximately 55% less
. groundwater and still satisfy EPA's migration control objective.
Also see response to Aj#122.
Aj#266. In the cover letter (p.3), Aerojet et. al. note that: (i) spreading
and recharge conditions resulting in the -vet condition- particle tracking
pattern is rarely in place for .ore than a fev .onths at a time; and (ii)
-zigs and zags- in cont.-~ftant movement result in the contamination 80viDg
-not as fast as a steady state aquifer would predict.-
EPA Response:
We agree with these two observations.
EPA's modeling efforts account for variability in rainfall and
recharge, and the atypical but expected occurrence of wet and dry
conditions, by using actual recharge volumes for each three month
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Baldwin Park ROD
"
period between October 1977 and June 1990 as input values into
the CFEST model.
EPA's modeling efforts account for varying regional flow
conditions, and "zigs and zags" in contaminant movement, in two
ways. First, EPA examined regional flow conditions, and the
performance of various remedies, at four different times (spring
1983, fall 1986, spring 1987 and fall 1989). These four times
correspond to one period of above average rainfall and spreading,
two average periods, and one dry period. See Figure 7-8 and
accompanying text for the results. Second, EPA used particle
tracking to examine the cumulative effects of alternating periods
of lower than average, average, and higher than average rainfall
and recharge. Zigs and zags are apparent in Figures 7-9 and 12-
2. As discussed in the FS, EPA uses a transient rather than
steady state model to account for variability in flow rates and
directions over time.
In contrast, Aerojet et. ale attempted to account for variable
rainfall and recharge by completing three different simulations,
but apparently repeat~ng the same rainfall/recharge assumptions
year after year in each of the three simulations. Aerojet's "dry
condition" simulation (Drawings 1 and 4) appears to assume
steady-state drought conditions every year for 14 consecutive
years. Aerojet's "wet condition" simulation (Drawings 3 and 6)
appears to assume extremely high rainfall conditions every year
for 14 consecutive years. We believe that this methodology is
unrealistic and inappropriate since we do not expect a 14 year
drought or 14 consecutive years of the extreme rainfall.
Designing a clean up project to perform in such conditions could
result in a significantly over- or under-designed project.
Aerojet et. ale also present the results of a transient computer
simulation which more realistically assumes varying
recharge/rainfall conditions over a 14 year period, but the
figure summarizing the results is extremely difficult to
interpret (Drawing 7). It appears to contradict EPA's results,
and Aerojet's own steady state results presented in Drawings 4-6,
in showing an average northwest to southeast direction of flow.
It also appears to show particle tracks making an abrupt right
turn on their way toward the Arrow/Lante wells. This behavior is
inconsistent with known hydrogeologic features of the area.
Aj1267. ID their cover letter (p.3), Aerojet et. ale claim that -all
extractioD system. will pull [groundwater] almost directly froa tbe Santa Fe
Spreacli.ng Grounds.-
EPA ResDonse: We believe that this conclusion is incorrect and
probably results from Aerojet's unrealistic recharge assumption
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Baldwin Park ROD
in which they assume extremely high rainfall conditions every
year for 14 consecutive years. See response to previous comment.
We also note that elsewhere in their submittal, Aerojet et. ale
appear to contradict this comment in asserting that their
proposal, in contrast to EPA's recommended extraction rates and
locations, "does provide hydraulic containment north of the 210
Foothill Freeway [when simulated for wet conditions] ... (p.5)"
Aj#26S. In the cover le~~er (p.3), Aeroje~ e~. ale also asse~ tha~ during
average or dry cODdi~ioDs the Arrow/LaD~e wells w1.ll reca~ure cOD~aai.Da~ed
groUDdwa~er 't.ha~ 1118}" bave passed the wells during we~~er per1.ods.
EPA ResDonse: As noted in the response to the comment Aj#265,
EPA's modeling indicates that approximately 8,500 gpm of
extraction, not 4,000 gpm, is needed to limit migration out of
Subarea 1 during all recharge conditions. We therefore doubt
that extraction of 4,000 qpm of contaminated groundwater at the
Arrow/Lante wells could satisfy EPA's migration control objective
during wet or average conditions, or recapture during average or
dry conditions contaminated groundwater that may have passed the
wells during wet conditions.
Aj#269. Aeroje~/ALR/OSCO clai.a tha~ £PA's reco..ended e~rac~1.oD well
loca~ion. would "unnecessar1.l}" increase the draw of wa~er fro. the Dortheas~,
pulling both VOC aDd n1.~ra~e con~..i.Da~1.on from DOrth of the 1-210."
EPA ResDonse: We disagree; EPA's computer simulations show that
EPA's recommended extraction rates and locations are at or near
the minimum needed to contain groundwater contamination in
Subarea 1. We have not reviewed Aerojet/ALR/OSCO's mOdeling
assumptions, but their conclusion that EPA's extraction rates are
unnecessarily high probably results from unrealistic modeling
assumptions. One unrealistic assumption, reflected in
unrealistic flow patterns in Aerojet/ALR/OSCO Drawings 1-6, is
described in response to comment Aj#266. EPA's modeling results
are presented in Figures 1-8 and 7-9.
Aj#270. Aeroje~/ALR/OSCO a180 repea~ maDY of the a8se~1.oD. made in other
8uba1.~~al.1 "tha~ £PA'. anal}"se. bave DO~ been 8uff1.c1.8D~1}" de~a1.led ~o
1.den~if}"...local-scale d1.8~Urb8Dces"; tha~ SPA d1.d DO~ cODs1.der the hydraul1.c
i.apac~8 of pumping a~ the Arrow/LaD~e wells; "£PA' s proposed reaed}" is DO~
effe~ive or ~ecbD1.c.lly defensible."
EPA ResDonse: EPA did consider extraction at the Arrow/Lante
wells and believes that its analyses are adequate to support the
selection of remedy. See Response B for a discussion of the
merits of relying on extraction at Arrow/Lante and the value of
extraction at W10WOMW1. See Response F for a rebuttal to the
assertion that data collection or analyses are inadequate to
support the selection of remedy.
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Baldwin Park ROD
AJ#27l. Aerojet/ALR/OSCO repeat their co_ent that SPA aust adequately
characterize the hydro1ogy and hydrogeology of the aquifer systea and basin
operations before issuance of a ROD for the Baldwin Park otJ. A1ternatively,
they recommend that SPA incorporate "a considerable element of flexibility" in
the ROD. .~e precise locations of wells and rates of groundwater extraction
can be adequate1y identified only after the interpretation of comprehensive
groundwater aonitoring data." .
EPA ResDonSe: As described in detail in Response F, EPA
disagrees with the assertion that additional data collection is
necessary before remedy selection.
We agree, however, that additional data collection is needed to
select precise extraction rates and locations.
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Baldwin Park ROD
XVIII.
Comments by Azusa Land Reclamation
ALRIl. ALR jointly suhai.tted co_ents on the Feasibility study and Proposed
Plan with Aerojet General COrporation and "endorses and includes by reference"
c~ents subaitted by the San Gabriel Basin Industry COalition.
EPA ResDonse: See EPA responses to comments by Aerojet General
corporation and the San Gabriel Basin Indu~try Coalition.
ALR#2. CO_entor expreases belief "that any iDteria remedy... will be on a
scale that ia deaigned aolely to achieve effective containment (while
hopefully ..xiaAsing ...s r880val)."
EPA ReSDonse: As explained in Response B, "containment" is one,
but not the sole remedial objective for the Baldwin Park area.
ALRI3. CO_entor atate. that "... [other than approximate extraction locations
and rates), virtually everything else about the project is left indefinite...
~e relatively undefined atate of the Proposed Plan precludes the level of
public participation in reaedy developIDent intended by CERCLA and the HCP by
leaving auch of the design detail, iDcludiDg the important issue of treated
water disposition, to poat-ROD and post co_ent refinement."
EPA ResDOnSe: Commentor asserts that a lack of detail in EPA's
proposal limits public participation but identifies only one
project detail missing from the Plan: the disposition of the
treated water. EPA did meet several times with potential
recipients of treated water, obtained specifications of purveyor
distribution systems, and completed detailed analyses of the cost
and feasibility of supplying water to potential recipients. In
the Feasibility Study and Proposed Plan, EPA presents the results
of its investigations: a list of potential recipients; flow
rates, pressures, and locations at which potential recipients
could accept treated water; and a discussion of the advantages
and disadvantages of supplying treated water to each potential
recipient. See pages 9-15 to 9-23, Appendix D, and pages 7-8 of
the Proposed Plan. EPA chose not to specify a single recipient
to allow the public'to comment on EPA's distribution options (the
disposition of the treated water has been an issue of significant
local concern) and also because of uncertainty about some project
details that affect the relative cost or feasibility of
transporting water to potential recipients. Nor did it appear
realistic to expect potential recipients to commit to accepting
treated water until EPA was in a position to make a reciprocal
commi tment.
We believe that the appropriate time to reach agreements on the
disposition of the treated water will be in the months after the
Record of Decision is signed. EPA expects to continue, and
perhaps complete, discussions with potential recipients of the
treated water in the next several months. We note that numerous
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Baldwin Park ROD
comments were received during the public comment period
expressing a preference to supply treated water to the
Metropolitan Water District of Southern California.
Lastly, we note that the commentor laments that EPA has left
"much of the desiqn detail" until after the ROD. In fact, the
NCP calls for "desiqn" to follow remedy selection; the usual
sequence is: remedial investigation => feasibility study =>
remedy selection => design => construction. It would be wasteful
and inefficient to complete "desiqn-level" studies pre-ROD that
are likely to be duplicated post-ROD. We have followed this
logic in the development of our proposed remedial action for the
Baldwin Park area.
ALRI4 . CoJllllleD=r poiDts out that the remedy is complicated by ..the elaborate
web of iDterrelated ageucies that adm.iDister its water supply aDd water
quality objectives," the use of the aquifer for driDkiDg water supply aDd
storage, aud siguificaut pumpage aDd recharge. .
EPA ResDonse: We agree. In its Baldwin Park Feasibility Study,
EPA considered and incorporated the effects of pumping and
recharge into the development and evaluation of remedial
alternatives. EPA has also consulted extensively with local
agencies with water supply or water management responsibilities
during the development of its Proposed Plan.
ALRI5 . CoJllllleu=r argues that EPA should complete a characterisatioD study iD
Subarea 3 = detenaiDe whether remedial actioD is warrauted.
EPA ResDonse: We disagree. See Response A, which explains in
detail the basis for EPA's conclusion that remedial action is
warranted in Subareas 1 and 3.
ALRI6. CoJllllleutor asserts that ..... siguificaut legal issues would be preseuted
hy auy attempt to JDOve forward at this time based OD the curreut
acIm.iDistrative record. Specifically a (1) the IICP precludes remedial action,
eveu interim action, based on inadequate data or, as in the case of Subarea 3,
au almost total abseuce of characterization infonaatioD; 811.d (2) the IICP
requireaeut that the remedial response selected be cost-effective would Dot be
satisfied. .. Comaen=r continues: .. . . . even if circWRstances where EPA' s "bias
for action" policy is triggered, a cODdition that does Dot exist here, the liCIt
aakes clear that remediaJ. actioD should not be taken UDtil .. site data" aud
informatioD make it possible = do so," (40 CFR 300.430(a)(l» aud ouy wheu
"information is sufficieut = support remedy selection (Preamble, 55 Fa
8704)". CoJIIIIIeu=r also cites other text: from the liCIt which calls for "a base
level of qualitative risk information" eveu at early or interim actions, aud
the Deed for EPA to demoustrate that &II. "actioD is Decessary to stabilise the
site, preveDt further degradatiOD, or achieve siguificaut risk reductioD
quickly." (55 Fa 8704-8705)
Lastly, COJllllleDtor cites liCIt requireaaeDts aud court decisions that remedy
selectiOD be cost-effective (p. 4-5).
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Baldwin Park ROD
EPA Response: Commentor does not identify any specific data
deficiencies in this comment. As discussed in Response F and
elsewhere in this Responsiveness Summary, EPA believes that its
data collection and analysis efforts are adequate to support the
selection of a remedy for the Baldwin Park au and that other
requirements of the NCP cited in the comment have been satisfied.
ALR#7. COIIIIDentor recolIIIDends the aodified extraetion configuration described
in the .Proposal for Technical Modifications Optimization of U.S.BPA Region XX
Subarea 1 Proposed Project, Baldwin Park Operable Unit. and asserts that this
8Odification aakes BPA's reco888Dded eztraction locations in Bubar.. 1 cost-
ineffeetive. COIIIIDentor also notes that if the .pluae equilibriua. hypothesis
advanced bl' the Coalition is confirmed, BPA' s recOllllDended remedl' for Bubarea 3
would be costs-ineffective.
BPA ResDonse: We disagree with commentor's claim that the
referenced report establishes that any portion of EPA's proposal
is cost-ineffective. See response to comment Aj#256, Response B
for EPA's response to the referenced report, and Response A on
the "plume equilibrium" hypothesis.
XIX.
Comments by Azusa Pipe & Tube Bending Corporation
APTB#l. COIIIIDentor describes his business's weak financial status, including
his difficultl' borrowing 8Onel'; expresses amazement that solvents could have
reached the subsurface at his Azusa facilitl'; expresses optillU... that the
business will be able to coaplete remedial investigation work requested bl' the
Regional Board; expresses concern over .the specter of additional costs of
undetermined amount.; and fiDal1l', fiDds it disconcerting and unfair that .we
find ourselves on a PRP list.-
.EPA ResDonse: Comments noted. We do not know of the PRP list
to which the comment or refers. Comment or has been directed to
investigate the extent of contamination at his Azusa facility by
the Regional Board, but Azusa Pipe & Tube Bending Corporation has
not, to date,. received General or Special Notice of Liability for
contamination at the San Gabriel Valley Superfund sites.
xx.
Comments by Chemical Waste Management, Inc.
CWM#1. COmmentor describes. potential advantages of air sparging combined with
soil vapor eztraction (AS/SVE), in relation to EPA' s proposed technology
(groundwater extraction, above-ground treatment, and distribution of treated
water). Recommends that BPA further investigate AS/BVB.
BPA Response:
See Response E.
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Baldwin Park ROD
XXI.
Comments by John R. Glass and Associates
1. co_entor, a real e.tate broker, de.cribe. a recently purcha.ed parcel of
land in a planned indu.trial park in Irwindale, CA, which appear. to be in the
.upper area. described in £PA'. Proposed Plan. CO_entor asks how he can help
the cleanup, and protect h.iaself, the owner, and any future tenants of the
Irwindale parcel fro. liability for the costs of BPA's proposed clean up.
EPA ReSDOnse: An EPA representative contacted the commentor by
telephone to explain CERCLA's liability provisions and to discuss
his concerns about the parcel.
XXII. Comments by Greene Company
Orll. ..z 'a glad to see that we are OD the way to cleaning up the ground water,
however, it se... that we are following that famous saying, we have the cart
before the horse!.
EPA ResDonse:
Comment noted.
Or12. .It's ay UDderstanding that it is illegal to dump toxic ..terial
(substances) on/in the ground, in the sewer or basically anywhere? Please just
a yes or DO answer..
EPA ResDonse: A simple yes or no answer would be misleading.
The wisdom and legality of dumping potentially toxic materials
depends on the material's constituents, its properties, the
amount disposed, and the method of disposal.
Or13. "Does your agency or any other ageDCY you know of have a count on the
amount of toxic drain cleaner that is dumped each year?
EPA ResDonse: No, although we note that if used as intended, all
household drain cleaner would end up in the sanitary sewer.
Or14. ....why is it illegal to dump toxic ..terial such as drain cleaners but
.it's ok to ..ke them?
EPA ResDonse: Many commonly-used materials such as drain
cleaner, bleach, glues, and gasoline are toxic if ingested or
inhaled in sufficiently large quantities, but are considered safe
if properly used and disposed of.
OrIS. Are the cODt...~ ftant. found in the groundwater the ...e ingredient. found
in toxic drain cleaners?
EPA ResDonSe: An EPA representative contacted the commentor to
clarify the comment. Commentor explained that he is concerned
that common household drain cleaners such as "Drano" or "Liquid
Plummer" may be contributing to the groundwater contamination.
EPA is not aware of any common drain cleaners that contain the
272
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Baldw~ Park ROD
chlorinated solvents or other contaminants found in the
groundwater.
XXIII. Comments by the San Gabriel Basin Industry
Coalition (I C)
Responses 1 through 7 address general c01l111Jents made by the
Industry Coalition (the Coalition) on pages 1-7 of their"
submittal that are not duplicated in the specific C01l111Jents
presented on pages 7-10. Responses 8 through 29 address the
specific C01l111Jents.
IC#l. Comaen~or wri~es tha~ - inpu~ files (supplied ~ 'the Coali~ion by EPA]
for aany of 'the aoni~oring and wa~er supply produc~ion wells lacked da~a on
wellhead and/or screened in~erval eleva~ions.- (p.l)
)
EPA ReSDOnse: EPA has supplied the Coalition with all requested
data in its possession, including elevation data. We note that
construction data for monitoring wells that are not in EPA's
electronic database are available in paper reports from EPA or
the Regional Board. We also note that EPA has not obtained
construction data for some from old, inactive production wells.
IC#2. Comaen~or wri~es tha~ -discussions wi'th EPA represenb~ives have
confiraed 'tha~ dab gaps wi'th re.pec~ ~o geographic loca~ion and comple~ioD
in~erval. for saae wa~er supply _lls con~inue ~o exist in 'the Basin,. tha~
da~a on 10ca~ioDs/comple~ion in~ervals ~ypically require a year or .ore ~o be
en~ered in~o EPA"' s elec~ronic da~abase, and ~ha~ -'the.e gaps and delays in
upda~ing 'the da~a have hampered modeling effo~s.- (p.2)
EPA ResDonse: See response to rCll. We also note that there
were delays in supplying data to the Coalition but that much of
the delay resulted from the Coalition's difficulties in
identifying which data they sought. These difficulties appeared
to result in large part from the Coalition's initial insistence
on communicating with EPA only through their legal
representatives who were not familiar with the types or uses of
the data and could not clearly communicate their needs to EPA
staff.
IC#3. ID i~s eKplanation of its deci.ion ~ develop a -parallel saulatioD
capabili~y. using i~. DYNSYS~ caaputer code, 'the Coali~ioD asse~. tha~
SPA's CFES~ computer code is -not sui ta):)le for cont...i DaD~ transpo~
replication or prediction..., cannot be used to depict OU specific
conditions..., and has le.s acceptability and credibility as a modeling tool-
'than the eoalition' s preferred caaputer code (DYNSYSTBM) because it is used
less frequently. Comaentor also claias that CPBS~cannot accurately saulate
effects of recharge and pumping, cannot account for -local variability in
aquifer hydraulic conditions,- critici.e. o~her 804el .ssump~ioDs, and finally
que.tion. the CPBST aodel's usefulness. (pp.2-5)
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Baldwin Park ROD
EPA Response: We believe that these criticisms of the CFEST code
are for the most part, untrue or misleading. The CFEST code, as
calibrated for the Baldwin Park area:
o is a useful and appropriate tool to support the
determination of approximate extraction rates and locations;
o is suitable for contaminant transport simulations;
o can be used to depict-OU-specific conditions;
o is an equally accepted and credible model (as DYNSYSTEM)
if properly developed and used;
o can accurately simulate recharge and pumping;
o can account for variability in hydraulic conditions;
o accurately simulates hydraulic conductivity;
o does not need to account for sorption or degradation to
justify the need for remedial action;
o makes reasonable assumptions about vertical
discretization, boundary conditions, and the ratio of
horizontal to vertical hydraulic conductivity, and other
input parameters.
See Response C for a detailed discussion of the role of modeling
in EPA's efforts. Also see Response A for a discussion of the
feasibility of using computer simulations of contaminant
transport in order to predict the rate of contaminant migration
in the Baldwin Park area. We doubt its feasibility.
IC#4. eommentor asserts ~t "current and historical pumpage for water supply
purposes have had a profound effect on groundwater conditions and contaminant
distribution in the Basin." (p. 3)
EPA Response: Comment or does not define "profound" or offer any
detailed support for this assertion, but we note, in contrast,
that our analyses suggest that pumping in the Baldwin Park area
accounts for only a fraction of the increase in the areal extent
of contamination. Also see response to comment Aj#54.
IcIS. eommentor ..kes a variety. of arguments that the aaount of data in
Subarea 3, or the analyse. of the data, are iDsufficient to justify remedy
selection. (e.g., see p.4)
EPA Response: We disagree. See Response F for a general
response to this comment. See Response A for an explanation of
EPA's view that additional data collection and analysis are
unlikely to alter the need for remedial action in Subarea 3 or
require any changes in the selected remedy.
IC#6. eommentor recommends that the extraction rates and locations be selected
to ..xiaize contam;neDt ..s. removal. (p.4)
EPA Response: contaminant mass removal is one, but not the sole,
remedial objective which should be used to guide the selection of
274
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'"
Baldwin Park ROD
extraction rates and locations. See Response B for a more
detailed explanation of factors to be considered in selecting
extraction rates and locations.
ICl7. Co8aentor IDentions (but does not inc1ude in its written comments) "very
preliaiDary" and "hypothetical" computer simulatio,ns which show a "plume or
plumes which demonstrate stability over time and eventua11y dissipate." The
results of the siau1atioD8 were brief1y presented 'to BPA represeDutives using
a series of slides at a public meeting he1d May 20, 1993. (p.S)
EPA ReSDOnSe: EPA cannot provide a complete response to this
comment since the Coalition does not identify assumptions made in
these simulations in its written submittal. We recall, however,
from the May 1993 presentation that one of the critical
assumptions in the computer simulations was a half-life for TCE
of approximately seven years and that this assumption was not
supported with any site-specific data. We believe that this
assumption is unrealistic, and suspect that it contributes
greatly to the stability and dissipation of the plume seen in the
computer simulations.
{The following 22 responses are to comments submitted as
"specific Comments on The Baldwin Park OUFS and Proposed Plan,"
Section 5 of the Coalition's submittal (pp. 7-10).]
ICiS. "The Coa1ition concurs with SPA's apparent decision 'to focus the
Proposed P1an on a remediation (conuiDaeDt) approach, rather than a
1arge-scale eDh&Dced water supp1y project. Bowever, a1though the se1ected
a1ternative is the 1east iDteDsive in teras of v01ume pumped of a11 of the
alternatives cODsidered in the OUFS, the OOPS proposes a significant
extraction program at the dOWDgradient end of the cODtam1DaDt p1ume(s) without
documentation 'that such action is Decessary 'to meet the stated reaedia1
objectives. The rationa1e stated OD p. 9 of the Proposed Plan for cessation of
operations when "contaaiDaDt cODcentratioDs decrease sufficient1y that
continued efforts 'to 1iait migration of contaminated groundwater are not
10nger necessary" aay app1y to Subarea 3 !!2!!. Furthermore, the OUf'S fai1s 'to
eva1uate and account for the potentia11y beDeficial impact of Subarea 1
pumpage on contaminant migration in Subareas 2 and 3.
aver balf of the proposed extraction rate (10,500 gpa of 19,000 gpa total) 18
from Subarea 3. lIode1ing/aoDitoring may deaoDstrate this is Dot Decessary
(especially with pumping from Subarea 1) resulting in a project with
considerably lower capital and O&M costs. COmplications resu1ting from
distribution of treated water to multiple purveyors would also be reduced.
The alternative of extraction only from Subarea 1 was apparently not evaluated
in the PS, although SPA aaterials distributed at the comaUDity .eeting on May
20 indicated that "extraction in one, rather than two broad contaaiDated
areas" was cODsidered."
EPA ResDonse: We disagree with the Coalition's comment that EPA
has not documented the need for remedial action at the
downgradient end of the contaminant plume(s) (the "lower area").
See Response A for a detailed response to this comment, including
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Baldwin Park ROD
a response to speculation by the Coalition on the importance of
various factors in resisting contaminant migration (sorption,
recharge-induced dilution, degradation, contaminant removal
through pumping, diminished releases to the subsurface).
Response A also explains how the Coalition's claim of "plume
oscillation and retraction" between 1980 and 1990 results from a
misinterpretation of water quality data, and the limited value of
the "Subarea 3 Characterization Study" proposed by the Coalition.
We also disagree with the assertion that action in Subarea 1
diminishes the need for action in Subar~a 3. Remedial action in
Subarea 1 will reduce the long-term influx of contaminants into
Subareas 2 and 3, but there is already a substantial area.
(several square miles) of high-level contamination present
downgradient of the proposed Subarea 1 extraction locations that
requires remediation. The proposed action in Subarea 1 will not
inhibit the continued migration of this existing contamination.
In addition, there may be subsurface sources of contamination in
Subarea 2 downgradient of the Subarea 1 extraction wells. And,
the fact that high-levels of contamination exist now and have
persisted in Subarea 2 for decades after improved management
practices likely reduced the input of surface sources indicates
that substantial residual sources may exist in the vadose zone
and aquifer wi thin Subarea 2. Furthermore, the existing
contamination is of sufficient extent that, even without any
continued additional influx of contaminants from Subarea 1 or
other surface or residual sources, contamination will continue to
move towards the Subarea 3 extraction wells for many years or
even decades.
Ielt. -~e OOPS recogD~zes and states (p. 7-5) that ava~lable data do not show
any s~gn~f~cant change ~ contaminant levels from just downgrad~ent of Subarea
3 to as far as Whi.tt~er Harrows, but unsubstant~ated statements regard~g
groundwater con~....iftat~n spread~g ~to less contaminated and uncontaminated
port~ons of the aquifer are made at several locat~ons ~ the text (such as on
p. 6-11).. On p. 7-38, it is noted that -dispersion, diffusion, or
retardation... are likely to cause contaminant levels to decl~e as
con~amina~ion 8igrates dOwngradien~.- ~ese cri~ical considerations were no~
utilized in any auumer in the evaluation of potential remedy options.-
EPA ReSDonse: There is substantial evidence that groundwater
contamination is spreading into less contaminated and
uncontaminated portions of the aquifer and that the listed
contaminant fate and transport processes (dispersion, diffusion,
and retardation) cannot stop contaminant migration. See Response
A for a detailed response to this comment.
Iel10. -Because the above two comments e.tabl~sh the necess~ty to collect da~a
to substant~ate a need for remedy ~ Subarea 3, remedy selection and design is
not appropriate until such subarea-specific data are collected. Pro~ect~on of
the publ~c health and the environment ~s currently be~g provided vu act~ve
and on-go~g wellhead treatment and cont~ued monitoring. Bence, there ~s no
276
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.'
Baldwin Park ROD
urgency U) iapl.eaentiDg any further remedy, and such action shoul.d be deferred
Wltil data are collected which demonstrate that such a need trul.y exists."
EPA ResDonse: We disagree that the above two comments "establish
the necessity" to collect additional data to justify the need for
action in Subarea 3. We also see no point in debating the
precise level of "urgency." We believe that the data support the
selection and implementation of a remedy for the Baldwin Park
area and, clearly, the sooner the remedy is implemented the less
the contamination will spread into clean or less contaminated
areas. See responses to the two previous comments and Response
A.
IC#ll. "The ours provides DO substaDtiation that the dOWDgradient puapage will
not confl.ict with the reaedial objective of inhibiting aigration fro. .ore
highly to less contaminated areas. In fact, this concern is stated on p.
7-26."
EPA ResDonse: We disagree. On page 7-26 of the FS, it is stated
that "the continued pumping of existing production wells located
outside of the highly contaminated areas can increase migration
into less contaminated areas, ... depend[ingJ on the location of
the existing well in relation to the contamination ..." This'
statement follows from basic hydraulic principles: that a
pumping well lowers the water table in the vicinity of the well
and that water flows from higher to lower elevations. The
implication of this statement is that extraction should not be
located in areas known to be clean or less contaminated than
nearby areas. Instead, extraction should be located in areas
known to be contaminated at higher concentration than nearby
areas. EPA's proposed project is consistent with this principle.
contaminant concentrations at or near proposed extraction
locations (Valley County Water District's Big Dalton and Paddy
Lane wells) have consistently remained significantly higher than
at downgradient wells (e.g., San Gabriel Valley Water Company's
B4 wells). The following table summarizes several years of data
for peak and average groundwater concentrations for these three
wells.
... .... ...
. . . . . . . . . . . . . '. . . . .. . . . . . .. . .. . . . . . . . . . .. ......... . . . ... .. . . . ... . . . . . . .
"'.. "'" "" .". "....,".. .... ......" ........ ..... """, . ..' .. -.- .. "........ . ... . ...
"', ..,"" ,,",""'.... .... ",'.".'.". .','.".",','.".',",".".","."'.",",.'.",',".".',".'.'.".".".",'.".",",".. ",",",.." .,".,".",'.".".."" ','.".", ..
,&~'J3~g/, f}jjg~:~:,g~~4.y::::<,,"";SGVWC'B4B"&". .....
?bii£6iitW'el1':: .. '::~~n~Ei))$:~/?:{\mm'.' i;i~4~.~i1:~~:ii;" .......
130 ug/l
42
5
1
9
5
85 nd
30 nd
14 nd
4 nd
16 4
7 1
277
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Baldwin Park ROD
PEAX AND AVERAGE GROtnmWATER CONCENTRATIONS FOR SELECTED WELLS
(1980 - 1991 for Big Dalton, Paddy Lane; 8/89 - 1991 for B4B
well; 7/88 - 1991 for B4C well).
We recognize that additional sampling planned as the first
step in the design of the project may change our understanding of
the precise extent of contamination. These additional data will
be used to select precise extraction locations that best meet
EPA's remedial objectives of limiting contaminant migration and
removing contaminant mass.
IC#12. "~he OOPS recogni.es and s~a~es (p. 11-9) ~~ ~e CFBS~ 80del is
appropria~e aDd applicable on a regional scale, and DO~ for local-scale use,
but accurate prediction/estimation o£ hydraulic conductivity has still not
been ..de, and ~ere is still too auch bias ~owards te8~8 exh:i.biting higher
values. ~e OOPS doe. recogni.e and s~ate that the hydraulic gradient in the
BPOU area is generally the lowest in the Basin (p. 2-13)."
EPA ResDonse: We believe that computer simulations completed by
EPA to support its proposed remedy are sUfficiently accurate for
their intended purpose. See Response C for additional
explanation of the role of computer modeling in the development
of EPA's proposed remedy. Also see response to comment Aj#1.
IClI3. "~e shape and size of the dOWDgradient extent o£ individual zones o£
contamination are ~y'pically inferred fro. the estimated direc~ion8 and
_gnitude o£ grou.Ddwater £10. and are in onlv a few £!.!.!!.£ direc~ly cons~rained
by da~a £roa wells" (eaphasis added)(p.3-10). Considerable u.Dcertain~y
con~inues ~o exis~, there£ore, regarding the dOWDgradien~ exten~ of the
plwae(s), precluding accura~e iden~ification o£ pluae/con~..in&D~ aigra~ion.
As a resul~, the curren~ PS viola~es the requir..en~s o£ the XCP in tha~ the
nature and exten~ of contamina~ion have DOt been es~ablished ~o the exten~
necessary ~o selec~ a reaedy."
EPA ResDonse: We agree with a portion of the comment in which
commentor emphasizes the uncertainty about the precise extent of
downgradient contamination, but disagree that this level of
uncertainty precludes the selection of an appropriate remedy or
violates the NCP.
The commentor's argument appears to be the same as presented in
its "General Comments" and in "specific Comments" 1, 2, 3, and 4
- that the only reasonable test of the need for remedial action
is the demonstration of statistically significant increasing
concentration trends. As described in Response A, EPA believes
that the preponderance of evidence shows that remedial action is
.needed to limit migration and remove contamination. We see no
significant evidence that the contamination will stop spreading
and disappear (Le., "naturally attenuate") without remedial
action.
.IC#14. "In S08e sections, the OUPS likely u.Dders~~es the effec~s of
hi.~orical pumpage on cont.m;ft.D~ aigra~ion (e.g., "a ...11 £rac~ion;" p.
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Baldwin Park ROD
2-19). ~i. con~radic~. o~her .ec~ion. where .hif~. in ~e en~ire 1ocation of
~e plume(s) are a~~ributed to pWllpage (p. 3-23). ~e absence of significan~
effec~s is allegedly suppo~ed by 8Ode1ing results, but there is no indication
where ~ese resul~s are pre.en~ed.-
EPA Response: We see no contradiction between the two
statements. The statement on page 2-19 that "purveyor practices
may have caused a small fraction of the increase in the areal
extent of contamination..." refers to the entire, multi-square
mile lateral extent of contamination. The statement on page 3-23
presents a hypothesis to explain decreases in contaminant
concentrations at two water supply wells along the eastern side
of the OU area. Reductions in contaminant concentration at these
two wells imply a small fractional decrease in the total lateral
extent of contamination.
The modeling results referred to on page 2-19 are discussed in
section two of the "Draft Basinwide Technical Plan" (EPA, 1990).
ICl15. -"xiaua cont.-'ftaD~ va1ues and, to a 1e..er e~en~ average value., are
.~ill used for plume delinea~ion purpo.e.. Such delineation should be baaed on
ao.~ recen~ value. for a consi.tent/concurrent period (i.e., not over a 15
8IOnU period). Figure 3-1 is clearly not a -snapshot in ~iae. - Table 3-2
include. a S\Ulllll8ry of data over a 12 vear period and ~erefore obscures any
con~aminan~ migra~ion or concentra~ion change ~rends.-
EPA Response: We believe that it is appropriate to illustrate
the extent of contamination using maximum or average values. In
the FS, figures 3-1 to 3-6 illustrate the extent of contamination
by combining data collected over the most recent 14 or 15 month
period. Despite the Coalition's criticism, the Coalition
apparently agrees with our view - a figure included i~ Appendix E
of the Coaltion's submittal (Changes in TCE Concentration With
Time) was also drawn by averaging data over a 12 month period.
EPA, and presumably the Coalition, believe that figures drawn
using data collected over a shorter period of time would provide
a less complete, less coherent, picture of conditions in the OU
area.
There is no single "right" way to illustrate the
contamination; assumptions must be made in order
figure. The "right" way to draw a figure is to
that are appropriate for the use of the figure.
extent of
to draw any
make assumptions
For example, illustrations of the geographic extent of
contamination (e.g., Figures 3-1 to 3-6 in the FS) are best drawn
by using data collected over a long enough time period to provide
good coverage of the area of interest. On the other hand,
illustrations of trends over time are best made by comparing
figures each constructed with data collected over a shorter
periods of time. We have included three new figures, Figures RS-
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Baldwin Park ROD
9 to 11, drawn to illustrate variations in contaminant
concentrations with time.
We agree that the data in Table 3-2 cannot be used to discern
contaminant trends. Identification of trends is not the purpose
of the table (see page 3-5).
ICl16. "~e statement that available data do not show large variations in
cont.m~n.Qt concentrations with depth (p. 7-6)(1) contradicts Figure 3-9, and
(2) ignores the fact that there are insufficient data to allow any 8ignificant
conclusions regarding the vertical distribution of contaminants beyond a
general characterization of vertical extent."
EPA ReSDonse: The statement on page 7-6 is that "the available
data do not show large enough variations in contaminant
concentration with depth to justify selectively extracting from
specific depth intervals ..." This statement does not contradict
the results of depth-specific sampling, which does show some
variation in concentration with depth (summarized and interpreted
in figure 3-9). Nor does this statement preclude selective
extraction if future water quality data demonstrate much higher
levels of contamination in selected depth intervals.
ICl17. "~e OOPS state. on page 9-4 that the "reaedial effects" of recharge of
extracted water via spreading are discussed. Bo such discussion could be
found."
EPA ReSDonse: Brief (sentence or two) qualitative discussions of
the remedial effects of recharge are included in each of
subsections 9.1.1, 9.1.2, and 9.1.3 of the FS. Also included in
section 11 is a comparison of computer simulations for two
scenarios: (i) extraction of 29,000 gpm of contaminated
groundwater; and (ii) extraction and recharge of 29,000 gpm,
primarily at the Irwindale Spreading Grounds (pages 11-6 to 11-
9). .
ICl18. "For five individual sites discussed (pp. 3-35 to 3-39) (only two of
which are located in or near the BPOU), the occurrence of TCE and daughter
compounds is attributed solely to degradation, ignoring potential (perhaps
probable) IDigration fro. upgradient areas."
EPA ResDonse:
Wyn#18.
Comment noted.
Also see response to comment
IC119. "~e OOPS appropriately recognizes the need for flexibility at this
tiae in teras of end u.e of extracted water, including both recharge and
distribution options, and flexibility for treatment unit size, cost, and
configuration. Bowever, the absence of . quantification of. costs and impacts
.ssociatecl with the distribution of extracted and treatecl groundwater,
although understandable at this time, precludes this FS from complying with
CERCLA guidance or the BCP. Because these cost. are li.kely to be significant
when compared to the total for each alternative, the FS presents an incomplete
analysis and comparison of the cost effectiveness of the alternatives."
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Baldwin Park ROD
EPA ResDonse: We disagree with the Coalition's comment that the
FS does not comply with the NCP or EPA guidance. The FS includes
a detailed evaluation of costs and institutional issues
associated with several distribution options. We believe that
our cost estimates are within the range called for in EPA
guidance (no more than 30% above or 50% below the true cost).
IC#20. "~e OOPS explicitly fails to acknowledge the impracticability of
aquifer restoration (p. 6-10). ~e "AHAR Waivers" .ection on p. 4-16 lists the
ca.e where "compliance with AHARs is technically impracticable from an
engineering perspective" as aD AHAR waiver conclition. Despite EPA guidance
regarding technical iapracticBility, thi.s is DOt 8entioned elsewhere in the
01JlPS. EPA' s proposed Plan refers to "complete cleanup of all or porlions of
the aquifer" (p. 4), despite EPA guidance aDd nUBerous ROD precedents
regarding the technical impracticability of aquifer restoration at comparable
groundwater contamination site.."
EPA ReSDonse: The comment is correct that EPA has not
acknowledged the impracticability of aquifer restoration. On
page.6-10 of the FS it is stated: "The remedial objectives do
not include restoration of the aquifer, not because it has been
concluded that restoration of all or a portion of the OU area is
impracticable, but because the Baldwin Park OU is a first,
interim (rather than final) remedial action."
We are aware of research and evaluations of other groundwater
contamination sites identifying factors that may prevent complete
restoration of all or portions of areas of groundwater
contamination. We do not believe it is appropriate to reach any
conclusions at this time, however, about the feasibility of
restoration of the Baldwin Park area. As stated on page 6-10 of
the FS, "Additional data obtained during design and
implementation of the remedial action will improve EPA's ability
to determine the nature of the final remedy (e.g., to determine
whether, or to what degree, restoration is practicable)." EPA's
position is consistent with current regulations and guidance.
The Coalition incorrectly asserts that EPA's use of the words
"complete cleanup of all or portions of the aquifer" in the
Proposed Plan is inconsistent with "EPA guidance and numerous ROD
precedents." The words are included as part of the statement
that "EPA is proposing this project in order to ... reduce the
eventual cost, difficulty, and time required for complete cleanup
of all or portions of the aquifer." This statement is consistent
with, and in fact advocated by, EPA guidance which calls for
interim actions at contaminated groundwater sites to limit
expansion of a contaminated area. The Coalition fails to provide
any EPA guidance or specific ROD precedents with which the
Baldwin Park au Proposed Plan is inconsistent.
IC#21. "~e 01JlPS recoguizes and states (p. 3-29) that significantly le.s
contaaiDant 88.S is entering the system than did historically. However, no
281
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Baldwin Park ROD
a~~emp~ i. ude ~o evalua~e 1;11e pro))able significan~ effec~B of bo1;11 1;11is
source redUC~iOD and 1;118 reduc~ioD of COD~..iDan~ ..ss by o1;11er _chanis.s OD
1;11e overall COD~._inaD~ ...s balance."
EPA ResDonse: On page 3-29 of the FS, EPA mentions the
likelihood that the number and magnitude of continuing surface
sources of groundwater contamination has decreased with time.
subsequent paragraphs on pages 3-29 and 3-30 discuss, however,
there remain significant subsurface sources of contamination.
The FS does not state, and we are not aware of any evidence
showing, that the rate at which contamination is entering the
groundwater (i.e., the "system") has significantly decreased.
The commentor merely speculates, without offering any site-
specific data, that the rate at which contaminant mass is
entering the groundwater has decreased.
EPA and the California Regional Water Quality Control Board have
worked with businesses in the Baldwin Park area to complete the
minimum amount of investigation work needed to locate releases of
hazardous substances, to determine the approximate extent of
contamination, and to determine if contamination has reached
groundwater. The data that have been generated in these
investigations can be used to very roughly estimate the magnitude
of contamination in the vadose zone. EPA does not, at present,
believe it prudent to spend, or to direct PRPs to spend, hundreds
of thousands or millions of dollars on additional investigation
work in order to better estimate the magnitude of contamination.
Furthermore, the absence of historical site characterization data
would probably preclude any identification of long-term trends in
the magnitude of sources until data had been collected for a
period of years.
As
The broader issue of whether additional effort put into a mass
balance estimate would prove useful in selecting a remedy is
discussed in Response A.
IC#22 (subai~~ed as COIDIDeD~ l5a). "Wi~h regard ~o 1;11e proposed 1DOni.~oriDg
progr.., as described :1D Appendix B. Iu wha~ever form i~ is ilDpl..eu~ed, 1;11e
8IODi~or:1Dg program 8U.~ Dreeede remedy sele~ioD and design."
EPA ResDonse: We do agree that the monitoring program must be
implemented during the time of remedial desian, however, we do
not agree that the monitoring program must precede remedy
selection. See Response F for additional explanation of EPA's
belief that adequate information has been collected and is
presently available to select a remedy.
IC#23 (sublDi~~ed a. COlDlD8D~ l5b) "~ere is DO discussioD of 1;11e eolle=ioD of
cri~ic.l da~a such .s soil. ch8lDis~ry (pa~icularly re~arda~ioD CO.poD8D~S)
and hyclraulic ~r..e~ers."
EPA ResDonse:
See response to DTSC comments #5 and 6.
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Baldwin Park ROD
IC#24 (sub.u.ttecl as comment 15c) "~e number of new 8Onitoring wells is
excessive for the purposes of reaedial design."
EPA ResDonse: We do not agree that the number of wells proposed
in the FS is excessive for the purposes of remedial design. In
response to other comments, EPA has increased the number of wells
in its recommended monitoring program. See response to comment
Aj#58, Table RS-3, and Figure RS-3.
It should be noted that not all of the monitoring wells presently
included in the monitoring program are exclusively intended for
remedial design. Some are intended for monitoring remedial
effectiveness, as listed in Table RS-3.
IC#25 (subaitted as comment 15d) "[~e] rationale for selection of 8IOnitor
well locations, as presented in ~able B-2, is not adequate to provide an
understanding or both the primary and secondary basis for each well."
EPA ResDonse: See Table RS-3 for a revised version of Table E-2,
which provides additional detail on the intended purpose of each
recommended new monitoring well cluster.
IC#26. (submitted.s comment 16) "Although risks are calculated in Section 5,
these numbers do not appear to be directly used to justify the need for
reaediation or to set cleanup goals. Calculated risks are within the range of
acceptable risk using CBRCLA guidance. ~e risk assessment failed to evaluate
the quantified risk of leaving con1:...iftants in place in the aquifer. At other
CBRCLA' sites,. natural attenuation has been accepted as a component of the
reaedy and ShOWD to result in acceptable risk. ~e purpose of the risk
assessment, therefore, is Unclear."
EPA ReSDonse: The purpose of the baseline risk assessment
completed for the Baldwin Park au is the same as for risk
assessments completed for numerous other Superfund sites - to
determine the need for remedial action by evaluating the
potential threat to human health and the environment in the
absence of any remedial action. In keeping with EPA guidance, it
is assumed in the risk assessment that contaminants are left in
place in the aquifer and that the contaminated groundwater is
served to consumers.
As described on pages 5-18 to 5-22 of the FS and pages 4-5
of the Proposed Plan, the risk assessment included in the Baldwin
Park OUFS examines three measures of risk: cancer risk, non-
cancer effects, and groundwater concentrations in relation to
drinking water standards (EPA and State maximum contaminant
levels, known as MCLs). The magnitude of the estimated non-
cancer effects and cancer risk are in the range in which EPA uses
discretion in deciding whether to take action, but the magnitude
of the groundwater concentrations (both mean and upper 95th
percentile concentrations) are sUfficiently high in relation to
drinking water standards (MCLs) to warrant action. EPA guidance
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Baldwin Park ROD
states that "action generally is warranted" if MCLs are exceeded
even if the estimated cancer risk is less than 10-4 and the non-
cancer hazard quotient is less than 1 (OSWER guidance 9355.0-30).
Because EPA's proposed project is an "interim," rather than
final remedy, EPA is not, at this time, proposing any final clean
up goals for the Baldwin Park area.
EPA agrees that "natural attenuation" (i.e., allowing nature
to take its course in place of any active remedial action) may be
an appropriate approach for meeting limited objectives at some
hazardous waste sites, particularly sites with more readily
degraded contaminants, but not at the Baldwin Park OU. EPA's
reasoning is described in Response A.
IC#27. (submi.ttecl as comaent 17) "~e comaent in ~able 6-2 that wellhead
trea1:aent is not applicable since "existing downgradient wells are not
opt.ilDall1' locatecl for ai.gration control" 881' not be relevant if pumping from
Subarea 3 is determi.ned not to be necessary."
EPA ResDonse: Comment noted. As described in Response A, we do
believe that pumping in Subarea 3 is needed, to limit further
migration of the groundwater contamination and to remove
contaminant mass.
ICI28.(suhmi.ttecl as comment 18) "Despite the potential cost and aesthetic
advantages of a two-stage air stripper process (p.8-41 to p.8-42) this
configuration vas not evaluatecl. We believe that it should be."
EPA ResDonse: We agree that a two-stage air stripper mav have
cost and aesthetic advantages, as described in the FS on pages 8-
41 and 8-42. The Proposed Plan and ROD allow the use of a two-
stage air stripper, or other variations on single stage packed
tower air stripping if shown to be equally effective, equally
implementable, and less costly. We did not carry out a detailed
cost comparison of one- versus two-stage air strippers because we
believe that such a comparison is more appropriately completed
during remedial design, making use of up-to-date water quality
data. A detailed evaluation completed now would most likely be
revised and superseded as final decisions are made on treatment
facility configuration (e.g., to what extent groundwater from
multiple extraction locations are treated at one or more
centralized locations) and as additional water quality data
become available.
IC#29. (suhmi.ttecl as comaent 19) "~e use of PVC pipe is assumed for pipes 18"
diameter and s..ller. ~s construction 88terial "1' not be appropriate for
conve1'ing untreatecl vater vith high VOC concentrations."
EPA ResDonse: The estimated average and peak influent
concentrations of VOCs are not expected to exceed 600 and 2,000
~g/l, respectively. These concentrations are not expected to
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Baldwin Park ROD
degrade the PVC pipe. However, additional evaluation can be
performed during remedial design to verify this assumption. The
type of material assumed for these smaller diameter pipes does
significantly impact the total costs estimated for the remedial
alternatives.
XXIV. Comments by the San Gabriel Valley Economic
Council
Bell. Co_ent;or "believes t;hat; t;bere i. enough t;echnical dat;a t;o just;ify t;be
r88lOval of VOC'. froa grouuelwat;er iD t;be BalelwiD Park, IrwiDclale aDd ABu.a
area, ... [aDd] t;bat; any groUDclw.~er cleanup plan au.~ have ,aea.urable resul~.
aDd be t;be 8Os~ cost; effe~ive.
EPA ResDonse:
Comment noted.
BC#2. "ConsieleriDg t;be number of curren~ PRP'. anel possible number of SNL's
[i.e., t;be ult;iaa~e number of PRPa - recipient;a of "Special Ho~ice" le~ters],
... it; ia not; economically feasible for [SPA's proposed project] to commence."
EPA ResDonse: EPA assumes that the comment refers to the ability
of PRPs to pay for EPA's proposed project. EPA has not completed
its evaluations of the ability of businesses currently under
investigation to fund EPA's proposed project, nor are we aware of
any independent evaluations of PRP's ability (or inability) to
pay. EPA will, however, complete its evaluations before formally
asking PRPs to fund the selected remedy.
Bel3. "Review and negotiat;e t;be $17 million San Gabriel Basin Watermas~er
Cleanup Plan [before any cleanup proje~. c~ence]."
EPA ResDonse: In comments on EPA's Proposed Plan, the Main San
Gabriel Basin Watermaster "generally concur[s]" with EPA's
Proposed Plan and notes that a portion of the Watermaster
Technical Plan for Basin Ground-Water Cleanup closely resembles
EPA's Proposed Plan (see Watermaster comments elsewhere in this
Responsiveness Summary). EPA therefore sees no value in delaying
action to allow for further review or discussion of the
Watermaster Plan.
Bel4. "Allow time for t;be Congressman B.t;eban Torre. "Deaon.~ra~ion Proje~"
bill ~o be heard [before any cleanup proj~. commence]."
EPA ReSDonse: Neither the Congressman nor his staff, in the bill
or in discussions of the bill, have recommended that EPA delay
currently planned projects such as proposed in the Baldwin Park
Proposed Plan. EPA sees no reasons to delay the selection or
implementation of remedy indefinitely while debate continues on
Congressman Torres' bill, nor does commentor offer any specific
reasons.
285
-------
Baldwin Park ROD
It should be noted that Congressman Torres' bill, H.R. 2853,
calls for remedial action "in the vicinity of Baldwin Park," as
does EPA's Proposed Plan.
BeiS. .~low ~ime for the development and administration of a guaranteed low
interest loan prograa to assist qualified businesses with hazardous waste
investigation and remediation [before any cleanup projects comaenceJ."
EPA ReSDonSe: EPA is willing to work with businesses to the
extent allowed by law to assist them in meeting their
investigation and clean up responsibilities. Commentor does not
mention any specific financing plans that would warrant delays in
the selection or implementation of remedial action in the Baldwin
Park area.
Bel'. .~low time for pap'. and SNL'. to formally organize to achieve
necessary negotiations with USEPA and to agree on allocation methodology
[before any cleanup projects comaence). Develop a aore cooperative, less
confrontational, relation.hip between the USEPA and the pap organization and
the pap'. th_selves as part of this organiaation process."
EPA ResDonse: EPA began to notify parties that they may be PRPs
for the Baldwin Park Operable Unit in 1990 through the issuance
of General Notice of Liability. EPA notified additional parties
of potential liability in August 1993.
EPA believes that it has made special efforts to work
cooperatively with PRPs. EPA invited PRPs to a series of
technical meetings to discuss potential remedies, has engaged in
continued dialogue with PRPs and their representatives, and has
encouraged the use of the services of a neutral third party to
help allocate responsibility. In recent General Notice of
Liability letters, EPA offered to supply facility-specific
information relevant to allocating responsibility; offered to
provide a list of experienced third-party mediators; and offered
to help arrange for a mediator. EPA has also expressed a
willingness to consider funding a portion of a mediator's cost.
xxv.
Comments by Trail Chemical Corporation
~#1. Comaentor thanks EPA staff for appearing at the May 20th public .eeting;
requests additional vi.its and presentations by EPA representatives to improve
community understanding of the proposed project.
EPA ResDonse: EPA staff periodically travel the San Gabriel
Valley to meet with representatives of local agencies, business
groups, and other interest groups. Please feel free to contact
EPA at the addresses or phone numbers listed on the Proposed Plan
fact sheet if you have questions or would like EPA
representatives to ~eet with an interested group.
286
-------
Baldwin Park ROD
Tr12. CO_entor wonders whether EPA' s proposed project is "inordinately .8811"
... [in. non-technical sense) "like two lonely straws in . big pool," but
.lso believes that estiaated cost of proposed project is "staggering."
EPA ResDonse: We suggest that the proposal be viewed as five (or
so) strategically-placed super straws whose presence will lessen
the need for a larger extended family of straws. EPA's rationale
for the proposed extraction scheme is described in detail in
section 7 and in Response B.
Tr13. CO..entor asks what studies have been completed by EPA of the economic
impact of the project on the co_unity; asks whether EPA has determined that
PRPs have the ability to pay; and asks whether there are "enviraumental
justice" issues concerning minority business owners and employees.
EPA ReSDOnse: EPA has completed evaluations of the ability of
many of the businesses currently under investigation to fund
EPA's proposed project. EPA has not, however, completed any
evaluations of the cumulative impact of the project, positive or
negative, on the community. You may wish to contact the Regional
Water Quality Control Board; we understand that the Regional
Board has completed a survey of the economic impact of its
investigation and clean up requirements on local businesses.
We are not aware of environmental justice issues raised by our
proposal.
Tr14. "Is EPA willing to consider an "intercept and remove" technique at
individual wells, treating the water prior to distribution, rather than a
large investment in a treatment plant?"
EPA ResDonse: EPA's plan can be viewed as an "intercept and
remove" technique in that it calls for limiting the migration
(i.e., interception) and removing contaminated groundwater from
two broad areas. A large investment in treatment plants is
inevitable as the contamination continues to spread, whether or
not EPA's proposal is implemented.
Tr#S. C088entor asks if "a team of community representatives [can) visit a
Treatment Plant of the type being proposed" and for details on the plants
location, type, costs, and effectiveness.
EPA ReSDOnSe: EPA can supply technical data on the performance
of VOC treatment systems installed in various locations in the
united states, but it may be of more interest to you to visit
treatment systems installed in your community. We suggest that
you contact the San Gabriel Basin Water Quality Authority, the
Valley County Water District in Baldwin Park, the La Puente
Valley County Water District in La Puente, or the San Gabriel
Valley Water Company in El Monte. All of these utilities and
agencies have constructed or operated VOC treatment facilities in
the Baldwin Park area.
287
-------
Baldwin Park ROD
XXVI. Comments by Wynn Oil
WyD#I. WynD Oil -joins in 'the co_ents ..de by 'the San Gabriel Basin Industry
Coalition, and hereby requests SPA to consider the comments submitted by the
Coalition to be submitted also by WynD Oil.-
EPA ReSDonse:
Comment noted.
WyD#2. WynD Oil objects to the inclusion of and conclusions of Section 3.4.4
of the PS. WyDD Oil particularly objects to Section 3.4. .4.1, which briefly
describes selected data fro. soil and groundwater sampling at the WynD Oil
facility and in Asusa, california and discusses the likelihood that S08e of
the cont-.i ~.nts observed in groundwater are degradation products.
specifically, WynD Oil states:
1) -it is wrong to select five out of sixt, isolated site investigations
for discussion in the Report-;
2) -'the discussion presented concerning the WyDD Oil site fails to take
all available data into account and presents a simplistic, speculative
and aisleading rationalization of the data discussed-;
3) -the discus.ion in section 3.4.4.1 either should be deleted from the
Report:. or l.i.8ited to a factual presentation of the groundwater quality
data fro. the WynD Oil 8IOnitoring well and the potential sources
identified by LARWQCB supervised site investigations in the vicinity of
the well.-
EPA ReSDonse: We agree that Section 3.4.4.1 should have provided
and discussed a third hypothesis: that the contaminants observed
in the Wynn Oil monitoring well may have originated offsite. The
text evaluates only two hypotheses: that the contaminants .
observed in the Wynn oil monitoring well were introduced directly
into the subsurface at the WYnn Oil facility, or are degradation
products of contaminants introduced into the subsurface at the
facility.
We also agree that the evaluations included in Section 3.4.4 are
simplistic and that some of. the "conclusions" are speculative.
The evaluations discuss possible sources of contaminants observed
in groundwater using phrases such as "may account for," "could
have been. present," or "the most likely explanation...is" to
indicate the speculative nature of the discussion.
Also, we should have included a statement that Section 3.4.4 does
not imply any conclusions about the liability of any parties for
the groundwater contamination. EPA believes that it is in
position to reach conclusions regarding the sources of the
groundwater contamination in the Baldwin Park area, but that was
not the intent of Section 3.4.4.
288
-------
Baldwin Park. ROD
We do not, however, believe that it is inappropriate or "wrong"
to discuss the five site investigations without discussing all of
the site investigations underway in the Baldwin Park area or in
the San Gabriel Valley. The purpose of the discussion in Section
3.4.4 is to briefly examine whether biological degradation of
vacs may be occurring in the au area; not to identify responsible
parties. To accomplish this task, we selected facilities where
deep vadose zone and groundwater investigation work had been
completed and where the investigation had verified the presence
of potential degradation products (dichloroethan~,
dichloroethene, or vinyl chloride). We knew of only two
facilities in the au area which met these criteria (as of mid
1992); we added three other facilities in the San Gabriel Basin
to provide a more representative evaluation.
XXVII. Oral Comments Presented During the EPA-Sponsored
Public Meeting on May 20, 1993
[Many of the oral comments duplicate written comments provided by
the same individuals or organizations.]
Oral Comments by Jeanne-Marie Bruno, Metropolitan .Water District of
Southern California
Oralil. COmmentor listed potential benefits of a "conjunctive use operation"
and expressed disappoinuent that EPA did not propose conjunctive use in the
. Proposed Plan.
EPA ReSDOnSe:
See Response D.
Orall2. Ms. Bruno "questions EPA' s treatment and technology selection of air
stripping and vapor pbaseGAC..."
. .
EPA ResDonse: EPA has not proposed or selected air stripping and
vapor phase GAC as the only acceptable technology. The Proposed
Plan and Record of Decision allow the use of air stripping and/or
liquid phase carbon. EPA expects to make a final decision on
treatment technology during remedial design.
Orall3. Ms. Bruno listed "significant co88iuents" to a conjunctive use
project in the San Gabriel Basin, near-coapletion of a comprehensive
feasibility study; plans to release a Notice of Preparation for an
BDvirolUDental Impact Report in JUDe 1993; bencb-scale testing on VOCs,
nitrate, and arsenic removal; negotiations for an agreement with the
Watermaster for storage, extraction, and treatment of water froa the Basin;
and the active pursuit of Federal funding.
289
-------
Baldwin Park ROD
EPA ResDonse:
Comments noted.
Oral Comments by Greg McClintock, San Gabriel Basin Indusny Coalition
Orall4. Mr. NcClatock expressed agreement with BPA' s proposal for
groundwater extraction and treatment a the "upper area.: but expressed
serious reservations about BPA's proposed action a the "lower area."
EPA ResDonse: See Response A for a detailed explanation of the
rationale for action in the lower area.
6>ral Comments by Carol Montano,. EasLValIeys .Organization.(EVO)
OrallS. Ns. Montano expressed frustration with the length of time it has taken
to develop the Proposed Plan for the Baldwa Park area but expresses full
support for the Plan. Commentor also expresses support for federal
legislation sponsored bJ' Esteban Torres and hope that BPA and PRPs will reach
agreement to fund the Plan.
EPA ResDonse:
Comments noted.
Oral Comments by Rufus Young, Attorney, Burke, Williams and Sorensen
Orall'. Mr. Young noted his avolvement a the case of United states vs.
Montrose Chemical, and in litigation connected with the Operating %ndustries
superfund Site. Commentor expresses concern that local cities 8&1' be dragged
iDto Superfund litigation and asks that BPA work with local governments to
prevent the costs of Superfund cleanup from beag passed on to local
taxpaJ'ers.
EPA ResDonse:
Comments noted.
Oral Comments by Royall Brown, speaking as an individual
Orall7. Commentor presented BPA with a list of water supplJ' wells and water
qualitJ' results and describec:l variations iD water qualitJ' among the listed
wells. Commentor noted that S08e wells south of the freewaJ' show cont-III' ftant
levels similar to the LaDte well, and concludes that BPA's operable unit
should address contamination at wells south of the freewaJ', as far south as
ValleI' Blvd.
EPA ReSDonse: This comment duplicates a written comment provided
by Rayall Brown (presumed to be Royall Brown). See response to
RB#2 and Response B. .
OrallS. Commentor criticizes the Proposed Plan for failing to address
contamination in the El Monte area.
290
-------
Baldwin Park ROD
EPA Response: Comment or is correct that the Proposed Plan for
the Baldwin Park area does not address contamination in the EI
Monte area. Due to the large extent of groundwater contamination
in San Gabriel Basin, EPA must prioritize its efforts. Remedial
action in the Baldwin Park area is EPA's current priority. EPA's
second and third priorities are to address the' contamination in
the Puente Valley and El Monte areas respectively. EPA recently
reached an agreement with local businesses which calls for the
businesses to complete a remedial investigation and feasibility
study in the Puente Valley. EPA is also developing a plan for a
remedial investigation and feasibility study in the El Monte
area. The Baldwin Park Proposed Plan further describes the
status of EPA projects in each area of the Basin.
orall9. CoIIIIDen~or believe. 'tha~ EPA's -con~aiDaen~- obje~ive is -wanaed
over- imd -all wrong. - CoJaIIIeD~r does noi: believe ~~ any of 'the remedial
al~erna~ive. evalua~ed in 'the Peasibili~y S~udy achieve real cleanup.
CoIIIIDeni:or believes 'tha~ EPA should emphasize -~~al pore i:onnage of 'the,
coni:ami.Dan~.- and revi.e i~s plan ~o achieve -real cleanup.-
EPA Response: We disagree that EPA's emphasis on "containment"
(i.e., migration control) will result in a meek or inappropriate
remedial response. EPA's remedy will limit the spread of the
contamination and remove a significant amount (whether measured
in pounds, kilograms or tons) of contaminant mass. See Response
B for additional explanation of the rationale for EPA's
recommended extraction rates and locations.
OralllO . CO_en~or reques~ed i:hai: EPA place addii:ional paper copies of i:he
Peasibilii:y S~udy ai: public libraries. Comaeni:or also reques~ed ~~ copies
of 'the Responsiveness SWlllllary be provided ~o all parties offering co_en~fi.
EPA Response: After the public meeting, EPA placed an additional
paper copy of the Feasibility Study in the West Covina PUblic
Library to supplement the paper copies previously provided to the
Upper San Gabriel Valley Municipal Water District in El Monte and
the San Gabriel Valley Municipal Water District in Azusa. The
water district offices are open to the public. EPA staff did
speak with a representative of the Baldwin Park library to
determine their interest in making a copy of the Study available.
The library representative expressed no interest in receiving a
copy and was not sent one. Also see response to comment RB#1.
EPA will provide copies of all or part of the Responsiveness
Summary to all parties requesting a copy.
291
-------
Baldwin Park ROD
Oral Comments by Mary Johnson, speaking as an individual
Oralili. Ms. Johnson expressed support for £PAts proposal, no~ing ~~ £PA
has clearly explained ~e reasoning behind i~s Proposed Plan. Ms. Johnson
expressed hope ~~ ~e review aDd approval process would con~inue, mallow
~e C088UDi~y ~o evalua~e and support wise wa~er quali~y decisions and
ac~!.ons.
EPA ReSDOnse:
Comments noted.
Oral Comments by Lany La Combe, Sierra Club National Water Resources
Committee
Oral#12. Kr. LaCOmbe expressed concern over ~e difference in es~.iaat:ed
be~ween £PAts proposed remedy ($47 million in capi~al cos~s) aDd for a
-conjUDc~ive use- projec~ proposed by Me~ropoli~aD Wa~er Dis~ric~ ($100
ai.llion in capi~al cos~.). Kr. La COmbe also expressed support for
conjUDc~ive use and concern abou~ wbo will finance ~be clean up.
co.~.
EPA ResDonse: EPA believes that $47 million is an accurate
feasibility study-level estimate for the capital cost of its
proposed remedy. EPA's goal in a Superfund feasibility study is
for the true cost to be no more than 50% above or 30% below the
estimated cost.
EPA staff have not reviewed Metropolitan's cost estimate, but
understand that it assumes additional treatment and distribution
facilities not necessary for cleanup.
Oral Comments by Bill Robinson, speaking as an individual
Orall13. Mr. Robinson expressed bis view ~at ~be £PAapproacb is "bes~ for
local bo~ spo~.," but: ~a~ conjUDc~ive use i. superior due ~o is "wa~er
conserva~!.on, wa~er supply, aDd also wa~er cleanup elements."
EPA ReSDonse: This comment duplicates written comments provided
by Mr. Robinson and others. See response to BR#1-7 and Response
D.
292
-------
. . . .
I: "./l~rf} !'jJ i!.[!:-,uJ[~--~:.--rli'n '.dNA'.OR IN tttE VIOt-nY OF,
n-IE ~ lOCAnoNS SHOWN IN THE FKJt.H
FIGURE Rs-l
INDICATORS OF MULTIPLE
SUBSURFACE SOURCES OF VOC
CONTAMINATION IN THE BALDWIN
PARK OU AREA
BAlDWIN PARK OPERABLE UNIT
Rea>rd of Oodsbn
Son GobrWBuIn
-------
4)
9)
Information Sources for FIgUre RS-l
1)
Initial Results of Shallow Zone Soil Matrix and. Vapor Monitoring Well Sampling.
AzusalIrwindale Study Area, San Gabriel Valley. November 19, 1993. (submitted by
Aerojet)
2)
Sile Assessment Report for Companion Soil Sampling and Installation and Sampling of
Nested Soil Gas Probes. Fonner Hartwell Corporation Site, 701 West Foothill
Boulevard, Azusa, California. November 9, 1992.
3)
Report for Contaminated Soil Excavation and Removal. California Portland Cement,
Azusa Facility. April 1992.
Supplemental A Soil Gas Survey. Conducted at Davidson Optronics, 223 Ramona
Boulevard, West Covina, California. December 7, 1993 (submittal was misdated 1992).
5)
Preliminary Soil Investigation and Tank Closure Report. Dri-Powr Company, Inc., 735
North Georgia Avenue, Azusa, California. April 1991.
6)
Vapor Monitoring Field Resulrs. Third Episode. Noram Site, 204 South Motor Avenue,
Azusa, California. February 23, 1993.
7)
Installation and Sampling of Soil Gas Vapor Test Wells. Pacific Precision Metals Facility
(AKA Tubing Seal Cap), 601 South Vincent Avenue, Azusa, California, 91702. July 24,
1992.
8)
Vapor Monitoring Well Field Results. Third Episode. RPM-Merit, 145 South Irwindale
Avenue, Azusa California. January 29, 1993. .
Report of Supplementary Subsurface Investigation. Rubber Urethanes, Inc., 968 West
Foothill Boulevard, Azusa, California. December 23, 1992. .
10)
11)
U.S. EPA's San Gabriel Basin Groundwater Quality Data Base. March 24, 1994.
Preliminary August 1993 Soil Vapor Sampling Analytical Results. Oil and Solvent
Process Company, Azusa, California. (Submittal from Chemical Waste Management to
U.S. EPA). September 7, 1993. .
-------
BALDWIN
PARK STUDY AREA
SAN GABRIEL VALLEY r CALIFORNIA
"
1992 VOC Plume
Three levels
Stream
-=::.0 Major Road
o
-
BALDWIN PARK OPERABLE UNIT RECORD OF DECISION
Figure RS-2
-------
.. . For Figure RS-3,
see Figure ROD-14
-------
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-------
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-------
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-------
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-------
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10/19/89
BALDWIN PARK OPERABLE UNIT RESPONSIVENESS SUMMARY
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-------
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BALDWIN PARK OPERABLE UNIT RESPONSIVENESS SUMMARY
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-------
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BALDWIN PARK OPERABLE UNIT RESPONSIVENESS SUMMARY
Figure RS-ll
-------
Table RS- 1
BALDWIN PARK RESPONSIVENESS SUMMARY
SUBAREA 1 COST COMPARISON: AIR SPARGING VS. PUMP AND TREAT
Description/Cost Item
Construction Elements
Well Systems
Treatment Facility
Pipelines/Pumping/Blowers
Construction Subtotal
Bid & Scope Contingencies
Construction Total
Services During Construction
Land Acquisition
Total Implementation Cost
Engineering, Legal & Admin Cost
TOTAL CAPITAL COST
Purveyor Reimbursement ($50/ac-ft)
Electrical Cost - Wells
Electrical Cost - Pump Stations
Electrical Cost - Treatment Facility
Treatment Plant Operations
Maintenance
TOTAL ANNUAL O&M COST
Net Present Worth of 0 & M Cost
@ 3 Percent
@ 5 Percent
@ 10 Percent
TOTAL NET PRESENT WORTH
@ 3 Percent
@ 5 Percent
@ 10 Percent
Estimated Cost
($1 ,000's)
PumplTreat Air Sparging
$912 $ 5,600
$4,415 $300
$3,465 $900
---------------------- -----------.----------
$8,792 $6,800
$3,077 $2,380
---------------------- ----------------------
$11,869 $9,180
$1,187 $918
$650 $1,100
---------------------- ----------------------
$13,706 $11 ,1 98
$3,015 $2,464
---------------------- ----------------------
$16.721 $13.662
( $686) $0
$864 Elect- Blowers $723
$380 Elect.-Vac. Pump $270
$173 $7
$1 , 1 63 $101
$176 $136
---------------------- ----------------------
$2.070 $1.238
$40.570
$31,819
$19,512
$24.256
$19,023
$11.666
$57,291
$48,540
$36,234
$40,977
$35,745
$28.387
-------
TABLE RS-2. ESTIMATED EXCESS LIFETIME CANCER RISKS USING CAL EPA CANCER SLOPE FACTORS (in
place of the slope factors assumed in the Baldwin Park Operable unit Feasibility Study)
.. .
CONTAMINANT
I . . .. . .
... . ...,,,.,,,,,
.. . .. . ....
. .. ." '....'...
... 0..""
.qALp:J:'~u CANqE.Ru
... ...SWTI22:.jjj-i.S80i,iiiir
inqest inhale
(oral)
1,2-dichloroethane
benzene
(1) (1)
0.1 0.1
0.15 0.15
0.03 0.02
0.014 0.0035
0.05 0.05
(1) (1)
--- -----
carbon tetrachloride
chloroform
methylene chloride
tetrachloroethylene
trichloroethylene
TOTAL RISK (using CAL EPA cancer
slope factors)
TOTAL RISK REPORTED IN BALDWIN
PARK OUFS (4/2/93)
---
-----
~iii~;i;l~~~mi\iliW~~~{~~;.
ave, ave,
inqest inhal
6E-7 6E-7
2E-7 2E-7
9E-7 9E-7
3E-7 lE-7
2E-B 7E-9
2E-6 2E,...6
2E-6 3E-6
6E-6 7E-6
6E-6
6E-6
RME, RME,
inqest inhal
3E-6 3E-6
7E-7 7E-7
5E-6 5E-6
lE-6 7E-7
7E-B 2E-B
lE-5 lE-5
lE-5 2E-5
3E-5 4E-5
3E-5 (2) 3E-5
(1) Cancer slope factors listed in Table 5-7 of Baldwin Park OU Feasibility
study are assumed since comment did not disagree with cancer slope factors used
for these compounds.
(2) Estimate incorrectly reported in Baldwin Park FS as 4E-5
NOTES:
-------
For Table RS-3, .
see Table ROD-8
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