United States
          Environmental Protection
          Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R09-93/102
September 1993
f/EPA   Superfund
         Record of Decision:
         San Gabriel Valley Area 1
         (Operable Unit 4)
         (Amendment), CA

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4.
50272-101
REPORT DOCUMENTAT10N 11. REPORT NO.
PAGE EPA/ROD/R09-93/102
TItle and Subtitle
SUPERFUND RECORD OF DECISION
San Gabriel Valley Area 1 (Operable Unit 4)
First Remedial Action
A~hor(.)
1
3. Recipient'. Acc888lon No.
5.
Report Dat8
09/22/93
(Amendment), CA 6.
7.
8.
Perfonnlng Organization Rep(. No.
8.
Performing Organization Name .nd Add-
10
Project TuklWork Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
12. SponsorIng Organization Name and Add-
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type o' Report' PwIod Cov8I'8CI
Agency
800/800
14.
15. Supplementary Nola
PB94-964525
18. Abetract (Umlt: 200 wona)
The San Gabriel Valley Area 1 (Operable Unit 4) site is one of four Superfund sites
located approximately 10 to 20 miles east of Los Angeles, Los Angeles County,
California. Land use in the area is mixed industrial, commercial, residential, and
undeveloped. The site includes four broad areas of ground water contamination
under!ying significant portions of the cities of Azusa, Baldwin Park, La Puente,
Industry, West Covina, El Monte, South El Monte, Monrovia, Arcadia, Rosemead, Alhambra,
and other municipalities. In 1983, VOC contamination in. ground water was detected by
Aerojet Electrosystems in Azusa. Samples taken from a nearby well, owned by the Valley
County Water District, identified elevated levels of TCE to 1,800 ug/l. Subsequent
State investigations revealed over 50 wells throughout the San Gabriel Basin that were
contaminated with TCE, PCE, and/or carbon tetrachloride, and computer modeling
predicted that contaminant levels would exceed SDWA MCLs within several years. A 1988
ROD addressed the potential threat to human health posed by contaminated ground water
beneath the Suburban Water System's (SWS) Bortolo Well Field, as OU4. The well field
consists of four public supply wells located along the east side of the San Gabriel
River in the Whittier Narrows area, south of the city of South El Monte. An estimated
51,200 people and approximately 17,000 commercial and residential water connections use
(See Attached Page)
17. Document Analysis L D88crfptora
Record of Decision - San Gabriel Valley Area 1 (Operable Unit 4)
First Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (PCE, TCE)
(Amendment), CA
b.
Id8ntlfl8~nd8d Terms
c.
COSAl1 FiaIci'Group
18. Availability Statement
19. Sacurfty Clau (Thi. Report)
None
:10. Sacurlty CIas. (This Pllga)
None
21. No. o' Pagea
30
2'l. PrIca
(Sea ANSl-Z38.18)
s.. m.tlUCl/OIJ8 on R..,.,..
OPTIONAL FORM 272 (4-77)
fFormerly NTI8-35)
Department o' Commen:e

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EPA/ROD/R09-93/102
San Gabriel Valley Area 1 (Operable Unit 4)
First Remedial Action
(Amendment), CA
Abstract (Continued)
these four wells as a water supply. The 1988 ROD also provided for extraction and
treatment of ground water onsite using an air stripping system to a level of 1 ug/l, with
discharge of the treated water into the SWS's existing water"distribution system and
installing a granular activated carbon offgas treatment system to control VOC emissions.
However, recent investigations have shown that, due to factors such as natural
attenuation, dilution and flow patterns, contaminant levels have not risen as expected in
the ground water beneath the well field. This ROD amends the 1988 selected remedy for
ground water. The primary contaminants of concern affecting the ground water are VOCs,
including PCE and TCE.
The amended remedial action for this site includes continuing ground water monitoring for
the next five years to evaluate contaminant levels; delaying the construction of the
ground water treatment system until such time that monitoring data demonstrates steadily
increasing levels of contamination above MCLs for at least 4 months; not treating ground
water if contaminant levels remain the same or diminish, or treating ground water, if
necessary, using the specified treatment system documented in the 1988 ROD, if
appropriate. The estimated present worth cost for this amended remedial action is
$24,000,000. This cost change is due to the fact that the original design accounted for
less stringent air emissions controls than are now required, and also that the current
estimate was based on more detail.
PERFORMANCE STANDARDS OR GOALS:
Subsequent to issuance of the 1988 ROD, EPA and the State developed a new drinking water
standard for PCE; therefore, the chemical-specific ground water cleanup goal for PCE is 5
ug/l. Additionally, newly developed State air quality standards for emissions control of
the treatment system are considered applicable and will be adhered to during operat~on of
the- remedy. "

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SFUND RECORDS eTR
1851-05662
AR0277
Record of Decision Amendment
Suburban Water systems/Bartolo Well Field Operable
San Gabriel Valley Superfund site Areas 1-4
Declaration
Unit
statement of Basis and Purpose
This decision document presents the Amendment to the Record of
Decision (ROD) for the Suburban Water Systems (SWS)/Bartolo Well
Field Operable Unit, in the San Gabriel Valley Superfund Si tes
Areas 1-4. This decision was made in accordance with the
Comprehensive Environmental Response,' Compensation, And Liability
Act of 1980 (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA), and the National Contingency
Plan (NCP). This decision is based on the Administrative Record
file for this Operable Unit (OU). The State of California concurs
with this decision.
Description of the Amendment
The remedy selected in the September 29, 1988, ROD for the
SWS' Bartolo Well Field OU consisted of the installation of a
groundwatE~r treatment system at the SWS' Bartolo, Well Field to
treat water contaminated with perchloroethene (PCE) to 1 part per
billion (ppb). At the time of the 1988 ROD, there was no state or
federal standard for PCE. Subsequent to the original ROD, EPA and
the State of California have established a new drinking water
standard of 5 ppb for PCE. This Amendment sets the treatment level
. for all' contamination at the federal or state drinking water
standard, whichever is lower. This Amendment also considers
Southern California Air Quality Management' District Regulation 13
and Rule 1401 as ARARs for the' emissions control system of the
treatment plant. Because contaminant levels have not increased in
the SWS' Bartolo Well Field (contrary to computer modeling
predictions), this Amendment also delays the building of the
treatment system until certain conditions are met as described
below. EPA will instead evaluate, for at least a 5 year period,
water quality sampling results from the SWS' Bartolo Wells in
conjunction with sampling results obtained from the Whittier
Narrows monitoring network.
If groundwater conditions change to where monitoring data from
the three "low" capacity wells or monitoring data from the "high"
capacity well and one" low" capacity well, in the SWS' Bartolo Well
Field, demonstrate a trend of steadily increasing contamination
levels above MCLs for at least a four (4) month period, EPA will
begin evaluating optimal locations for a treatment system and begin
reevaluating the existing treatment system design or begin
evaluating a new treatment system, under the observed groundwater
conditions. If the trend above MCLs in the wells mentioned above
continues for an additional two (2) month period, EPA will either

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begin construction of the current treatment system design, if
appropriate, or complete design of a new treatment system and
implement the design. In the interim, while the treatment system is
being designed or constructed, EPA will evaluate the use of, and if
feasible, implement mobile or temporary treatment systems.
Declaration
CUrrent groundwater conditions at the SWS' Bartolo Well Field
pose no public health threat, therefore, no remedial action is
necessary at this time. However, future groundwater conditions
cannot be accurately predicted and may change over time. EPA will
therefore monitor and evaluate groundwater data from the SWS'
Bartolo Well Field over a five-year period, to ensure continued
protection of public health. The five-year period to be used for
the review will start when field work (monitoring well.
installation) for the Whittier Narrows ROD commences.
~ .
C. W~
John. Wise, Acting Reg10nal
Administrator
~. 22- 93
Date

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RECORD OF DECISION AMENDMENT
SUBURBAN WATER SYSTEMS / BARTOLO WELL FIELD OPERABLE UNIT"
SAN GABRIEL VALLEY SUPERFUND SITE AREAS 1-4
September
1993
L.
INTRODUCTION
On
september
29,
1988,
the
United
states
Environmental
Protection Agency (EPA) signed a Record of Decision (ROD) for the
Suburban Water Systems' (SWS') Bartolo Well Field Operable unit for
the San Gabriel Valley Superfund Sites, Areas 1-4.
The purpose of
this ROD Amendment is to explain the differences between the
remedial action originally selected in the 1988 ROD,
and the
remedial action which will be implemented at the SWS' Bartolo Well
Field Operable Unit.
Under section 117 of the Comprehensive Environmental Response,
Compensation,
and
Liability Act
of
1980,
as
amended
by the
Superfund Amendment and Reauthorization Act of 1986 (CERCLA), and
pursuant to 40 C.F.R. S 300.435(c) (2) (ii) (55 Fed.Reg. 8666, 8852
(March 8, 1990», EPA is required to prepare a ROD Amendment when
fundamental changes are made to a final remedial action plan as
described in a ROD.
This document provides a brief background of the SWS' Bartolo
Well Field, a summary of the remedy selected in the original ROD,
a description of the changes to the ROD that EPA is making, and an
explanation of why EPA is making changes to the ROD.
1

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EPA is
issuing
this ROD Amendment to take
into
account
additional
information obtained during project design and not
available when the 1988 ROD was signed; to reflect comments by
Potentially Responsible Parties (PRPs) who were not identified when
the original ROD was signed; and to reflect changes in the law
since the original ROD was signed.
The changes included in this
ROD Amendment are: (1) treating water to meet new federal drinking
water standards for perchloroethene;
(2)
revising overall cost
estimates for the treatment facility; (3) providing treatment for
air emissions from the treatment facility that will meet the South
Coast Air Quality Management District (SCAQMD) regulations for air
emissions without offsets; and (4) to delay the construction of the
treatment ~acility until such time as groundwater ~ontamination in
the eastern Whittier Narrows area is believed by EPA to pose a
threat to public health.
This ROD Amendment and the supporting documentation will
become
part
of
the
SWS'
Bartolo
Well
Field
Operable
Unit
Administrative Record.l
A copy of the Administrative Record has
been placed at the Whittier Central Public Library,
7344 South
1 EPA held a thirty day public comment period on this ROD
Amendment. All comments received during this time period and EPA's
responses to those comments have been included in the SWS' Bartolo
Well Field Operable unit Administrative Record in accordance with
40 C. F .R. ~ 300.825 (b) . In addition, EPA has also included
comments received after the close of this comment period and EPA's
responses to these late comments in the SWS' Bartolo Well Field
Operable Unit Administrative Record. Including these late comments
and EPA' s responses is not required. (See 40 C. F. R. S
300.825(2) (c».
2

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Washington Street, Whittier, California, as well as in the Records
Center
at
EPA Region
9,
75
Hawthorne
street,
San
Francisco,
California.
:I:I: .
BACKGROUND
The following section provides a brief background of the SWS'
Bartolo Well Field Operable Unit and a short summary
of the remedy
selected in the 1988 ROD.
Additional background information can be
found in the September 29, 1988, ROD, and in the SWS' Bartolo Well
Field Operable Unit Administrative Record.
&.
site Location and Historv
The San Gabriel Valley Superfund Site Areas 1 - 4
are located
in Los Angeles County approximately 10 - 20 miles east of Los
Angeles in southern California (Figure 1 inset).
The sites are
four
broad
areas
of
groundwater
contamination
underlying
significant portions
of the cities of Azusa,
Baldwin Park,
La
Puente, City of Industry, West Covina, EI Monte, South EI Monte,
Monrovia, Arcadia, Rosemead, Alhambra, and other municipalities or
unincorporated areas of the San Gabriel Valley.
The sites include
industrial, commercial, residential, as well as undeveloped areas.
To provide planning flexibility, the entire San Gabriel Valley has
been subdivided into seven Remedial Investigation (RI) areas as
shown in Figure 1.
Groundwater contamination by volatile organic compounds (VOCs)
was first detected in the valley when Aerojet Electrosystems in
Azusa sampled a nearby groundwater well owned by Valley county
Water
District
and
found
1800
parts
per
billion
(ppb)
of
3

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FIG U REI
THE SAN
GABRIEL
BASIN
RI
AREAS
Dr a It
..
LEGEND:
~
I'IIO~OCIC 10111 AI'
"...",
A~~I'IA~ AOI.rll 10IIIAI'
"...",
IAIOI IIAIS'OIIAIIOI
,."
II AlIAS
J}~~~J
UIIOCI
@
o
2
3
4
5
MIlES

Basinwide Technical .Plan

Son Gabriel Basin

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,.----
trichloroethene (TCE).2
The Maximum Contaminant Level (MCL) for
this substance in drinking water, as set by both EPA and the state
of California, is 5 parts per billion (ppb).
Subsequent sampling
by the California Department of Health Services (DHS) and the Los
Angeles County Department of Health Services identified over 50
wells throughout the San Gabriel Basin contaminated with TCE,
perchloroethene (also known as tetrachloroethene or PCE) , or carbon
tetrachloride
( CTC)
at concentrations above the action levels
established- by DHS.
In September 1983 ,
EPA evaluated the threat posed by the
contamination in the San Gabriel Valley, and proposed the area for
inclusion on the National Priorities List (NPL).
In May 1984, the
area was listed on the NPL as San Gabriel Valley Areas 1-4.
SWS'-Bartolo Well Field consists of four public water supply
wells located along the east side of the San Gabriel River in the
Whittier-Narrows area (Figure 2).
The contamination in this area
may be associated with sources in areas 1,2 and 4.
These four
wells provide about 55-60% of the water supply for approximately
17,000 commercial and residential water connections representing
approximately 51,200 persons in SWS's Whittier Service District.
In addition, the Bartolo Well Field provides a small percentage of
the water supply for the neighboring La Mirada Service District.
2 The Maximum Contaminant Level (MCL) for this contaminant is
5 ppb. As explained in more detail below, drinking water which
meets the MCL is considered to be protective of human health. In
this instance, the contaminant level is approximately 360 times
greater than the level permitted in drinking water.
4

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SOUTH
EL MONTE
~
co
o
rr
.:w:
u
GJ
Q.
~~
~o
~#l>
.~ .
~#l> .
cJ>
- PROJECT
LOCA TION
Pica
RIVERA
o'lJ.~
.~~
~'
~'lJ.~
~()~
Figure a.. Location 01 Bartolo
Well Field Operable Unit

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IL..
1988 RECORD OF DECISION
The 1988 Record of Decision selected a remedy to address a
potential public health threat posed by contamination of Suburban's
pUblic water supply wells.
This response action constituted the
second EPA remedial action in the San Gabriel Valley3 and was
designed to achieve two objectives:
(1) to partially control the
movement and spread of contaminants in the Whittier Narrows area of
the San Gabriel Valley, thereby contributing to contaminant removal
from the San Gabriel Valley Areas 1, 2, and 4 sites; and (2) to
address the potential public health threat posed by contamination
of SWS's Bartolo Well Field.
The remedial action selected in the original decision document
to achi~ve these objectives incorporated the following components:
...1.
Extraction of groundwater fro.m the existing
wells in SWS' Bartolo Well Field;
2.
Construction of a packed tower air stripping
system to
treat
contaminated groundwater.
The
treatment facility was to be built on SWS' property
at the Bartolo Well Field.
since this location is
within the IOO-year floodplain of the San Gabriel
River,
appropriate floodproofing measures were to
be incorporated into the treatment system design to
minimize the damage to the facility and to limit
3 The first response action. was taken at Richwood Mutual
Water Company in 1988 to supply drinking water. E~A expects
several additional actions to be taken in the San Gabr1el Valley
over the next five to ten years.
5

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the downtime after a flood event;
3.
Installation
of
a
vapor-phase
Granulated
Activated Carbon (GAC) off-gas treatment system to
control
Volatile
Organic
Compound
(VOC)
air
emissions from the air stripping system;
4.
Treatment of contaminated water to contaminant
concentrations
at
or
below maximum
contaminant
levels (MCLs) resulting in a cumulative cancer risk
level of 10-6 or less4; and
5.
Use of the treated groundwater as drinking
water supply for SWS's customers by feeding the
treated water directly into SWS' s existing water
distribution system.
At the time the original record of decision was signed, PCE
was recognized as a potential carcinogen in water even though no
MCL existed.
The treatment level for PCE was set at 1 ppb, which
corresponded
to
the
cumulative
cancer
risk
of
10-6.5
This
treatment level was calculated based upon projections of the
maximum levels of all contaminants that could possibly be expected
at the Bartolo Well Field over a 30-year period.
4 The cumulative cancer risk of 10-6 risk level was
established as "the point of departure for determining remediation
goals for alternatives when ARARs are not available or are not
sufficiently protective because of the presence of multiple
contaminants at a site or multiple pathways of exposure. II (See 40
C.F.R. S300.430(e) (2) (A) (2»
5 See footnote
cumulative cancer risk.
number
3
for
more
explanation
on the
6

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The original record of decision identified South Coast Air
Quality Management District (SCAQMD) Rule 1167 as the basis for
incorporating air emissions control.
At the time the ROD was
signed, this was a "to be considered" requirement rather than an
Applicable or Relevant and Appropriate Requirement (ARAR)6.
The Operable unit Feasibili ty study
(OUFS)
estimated the
present worth cost of the selected remedy at $15 Million, based on
a 30 year project life.
The response action is the first phase of a potential larger
response action initially planned for the Whittier Narrows area to
limit or control migration of contamination, if necessary, within
the Whittier Narrows area.
It also addresses a small part of the
overall groundwater contamination problem in the San Gabriel Valley
Superfund-Site, Areas 1-4.
Several additional operable units are
planned
to
address
other
aspects
of
the
San
Gabriel
sites'
contamination.
III. AMENDMENT TO THE 1988 RECORD OF DECISION
&-
Introduction
This Amendment to the "1988 ROD for the SWS' Bartolo Well Field
clarifies and modifies certain points set forth in EPA's 1988 SWS'
Bartolo Well Field ROD.
This Amendment to the 1988 ROD addresses the treatment level
6 In addition to ARARS, EPA may, as appropriate, "identify
other advisories, criteria, or guidance to be considered for a
particular release. The' to be considered' (TBC) category consists
of advisories, criteria, or guidance that were developed by EPA,
other federal agencies, or states that may be useful in developing
CERCLA remedies. II 40 C.F.R. ~300.400(9) (3)
7

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for PCE
in the water,
the air
emissions
levels,
the 30 year
estimated cost of the project, arid the "schedule" for construction
of the project.
The other features of the remedy selected in the
1988 ROD are otherwise unchanged.
Jh
Summary of ROD Amendments
The 1988 ROD established a target risk of 10-6
( one excess
cancer risk in one million people)
which corresponded to a cleanup
level of 1 part per billion
(ppb)
for PCE.
Subsequent to the
original ROD, a new MCL of 5 ppb was established for PCE by both
EPA and the California Department of Toxic Substances Control.
Treating drinking water to meet MCLs is considered protective of
human health by both agencies.
This Amendment sets the treatment
level for all contaminants at the Federal or State MCL, whichever
is lower.
-Meeting MCLs will result in a lower reduction of risk
compared to the treatment levels set in the 1988 ROD, however, the
new cleanup levels remain well within EPA's acceptable risk range
of 10-4 to 10-6, and will reduce total project costs by an estimated
six million dollars.
These cleanup levels will also help achieve
EPA's primary goal of containing groundwater contamination within
the San Gabriel Basin, with an added benefit of providing drinking
water that meets MCLs.
SCAQMD Rule 1167, although a "to be considered" rule in 1988,
was
not
an
ARAR .
SCAQMD
has
more
recently
identified
its
Regulation 13, Rule 1401, Rule 212, and Rule 402 as the potential
ARARs for this project.
Regulation 13 and Rule 1401 require air
emissions control that are more stringent than Rule 1167.
This.
8

-------
Amendment considers SCAQMD Regulation 13 and Rule 1401 as the ARARs
for the air emissions control system.
Cost estimates for this project have increased since the OUFS
estimate.
The 1988 OUFS projected a total present worth project
cost of $15 Million, based on a 30 year project life and
a 5%
interest rate.
The updated 60% design estimate in 1991 for this
project was $24 Million, also based on a 30 year project life and
a 5% interest rate.
The reasons for the difference are twofold:
1)
the design has accounted for the more stringent air emissions.
control required; and 2) the design estimate contains a much higher
level of detail than the OUFS estimate.
1.
Explanation of Siqnificant Chanqes
The
1988
Suburban
Feasibility
study
relied
on
computer
modeling that predicted contaminant levels would rise above MCLs
within several years.
There are many complex factors affecting
chemical
movement
and
chemical
concentrations
in
groundwater
including retardation and natural attenuation of contamination, as
well
as
remedial
activities
that
eliminate
sources
of
contamination.
EPA used very conservative assumptions (e.g., the
highest chemical concentrations analyzed in groundwater, chemicals
would move at the same rate as groundwater) in the model and did
not take into consideration such factors as natural attenuation,
dilution, retardation, complex groundwater flow patterns, and the
elimination of contaminant sources, when contamination levels at
the SWS' Bartolo Well Field were predicted.
During design of the treatment system, contaminant levels in
9

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the Bartolo Well Field
area
failed to reach levels that were
projected in the 1988 Feasibility study.
Contaminant levels at the
Bartolo Well Field and at virtually all nearby wells sampled by EPA
in 1991 and 1992, remain below MCLs.
The issue of low contaminant
levels that were not increasing was raised during the July, 1991
public comment period for the proposed amendment.
In light of
current data and public comments, EPA will postpone indefinitely
construction of the treatment facility until certain conditions are
met as described below.
The SWS' Bartolo Wells which are comprised of three (3) "low"
capacity wells and one (1)
"high" capacity well, are currently
being monitored monthly by Suburban Water Systems pursuant to the
requirements of Title 22, California Code of Regulations.
EPA will
evaluate
the
data
collected
by
Suburban Water
Systems
and
incorporate the data into the data base for the Whittier Narrows
Operable Unit.
In addition,
EPA may also collect groundwater
samples
from
the
SWS'
Bartolo
Well
Field
as
necessary,
to
supple~ent and/or verify the existing monitoring.
If monitoring data from the three low capacity wells or
monitoring data from the high capacity well and one low capacity
well demonstrate a trend of steadily increasing contamination
levels above MCLs for at least a four (4) month period, EPA will
then begin evaluating optimal locations for a treatment system and
begin reevaluating the existing treatment system design, or begin
evaluating a new treatment system, under the observed groundwater
conditions. If the trend above MCLs continues for an additional two.
10

-------
(2) month period, EPA will either begin construction of the current
treatment system design, if appropriate, or complete design of a
new treatment system and implement the design.
In the interim, while the treatment system is being designed
or constructed, EPA will evaluate the use of, and if feasible,
implement mobile or temporary treatment facilities.
If remedial
action is not undertaken by the end of the five-year monitoring
period, then EPA will proceed with the five-year review.
~
Evaluation of the Nine criteria
The National Contingency Plan (NCP), 40 C.F.R.
S 300.430(e) (9) (iii) establishes nine (9) criteria against which a
remedy must. be compared.
The nine criteria are as follows:
1.
compliance with applicable or relevant and appropriate
_requirements (ARARs);
overall protection of human health and the environment;
2.
3.
short-term effectiveness in protecting human health and
the environment;
4.
long-term effectiveness in protecting human health and
the environment;
5.
reduction
of
toxicity,
mobility,
and
volume
of
contaminants;
6.
technical
and
administrative
feasibility
of
implementation;
7.
capital and operation and maintenance costs;
8.
state acceptance; and
9.
community acceptance~
11

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This Amendment affects the original evaluation of only four of
the nine criteria:
compliance wi th applicable or relevant and
appropriate requirements
(ARARs);
overall protection of human
health and the environment; reduction of toxicity, mobility and
volume of contamination; and, capital and operation and maintenance
costs.
The
application
of
the
remaining
five
criteria
is
unaffected by this Amendment.
a.
compliance
with
applicable
or
relevant
and
appropriate requirements (ARARs):
Original ROD
Yes, complies with ARARs, with "offsets" for
excess air emissions
Amended ROD
Yes, complies with ARARs, without "offsets"
There are two new ARARs for this Operable Unit since the
original ROD was signed in 1988: (1) the establishment of Federal
and state MCLs for PCE; and (2) the SCAQMD rules and regulations
setting limits for air emissions.
Pursuant to the NCP, EPA is
required to meet new ARARs only when such ARARs are determined to

be necessary to be protective of human health and the environment,
as specified in 40 C. F .R.
S 300.430(f) (1) (ii) (B) (1).
For the
purposes of this ROD amendment, although not bound by law to do so,
EPA is electing to meet the new more stringent SCAQMD regulations,
as EPA had elected to meet the substantive requirements of Rule
1167.
Compliance with the new MCL for PCE is being met for reasons
other than those set forth in 40 C.F.R. S 300.430(f) (1) (ii) (B) (1).
These
reasons
include
EPA's
ability
to provide treatment
of
12
i .

-------
drinking water to levels protective of human health, while reducing
the costs of this project. These reasons are discussed later in
section III.C.(b),(c), and, (e) of this document.
ARARs can be grouped into three categories: chemical-specific
ARARSi action-specific ARARSi
and location-specific ARARs.
The
chemical-specific ARARs that apply to this response action are the
Safe Drinking Water Act (Federal) MCLs and the California MCLs,
whichever is the more stringent.
Table 1 lists the federal and
California MCLs for the site contaminants of concern from' the
Public Health Evaluation in the Suburban OUFS Report.
It should be
noted that no additional contaminants of concern have been detected
in subsequent sampling.
Table 1 also lists the Maximum contaminant
Level Goals (MCLGs) for these contaminants.
MCLGs, which are based
only
upon- health
criteria,
are
not
directly .applicable
as
chemical-specific requirements because they are not enforceable
standards.
The
primary
action-specific
requirements
affecting
this
response action are the SCAQMD's Regulation 13 and Rule 1401.
The
purpose of Regulation 13 is to control VOCs as precursor emissions
to ozone formation in the South Coast Air Basin.
Rule 1401
controls air emission of carcinogenic air contaminants.
The South
Coast Air Basin is currently in nonattainment status with respect
to the National Ambient Air Quality Standards (NAAQS) for ozone.
In
california,
authority
to
regulate
stationary
sources
of
emissions
has been delegated to
local
air quality management
districts.
Therefore, these rules, having been promulgated by
13

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Table 1
Bartolo Well Field
Chemicals of Concern
(ppb)
Chemical  Federal MCL MCLG California MCL
Carbon Tetrachloride 5 0 0.5
1,2 - Dichloroethene 70 70 6
1,1 - Dichloroethene 7 7 6
Methylene Chloride 5 0 
Perchloroethene (PCE) 5 0 5
Trichloroethene  5 0 5

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SCAQMD in 1990, constitute a promulgated state requirement under a
state environmental law, as set forth in CERCLA S 121(d), that is
generally applicable.
SCAQMD's Rule 1167 was a TBC (to be considered) that EPA
intended. to follow,
in the 1988 proposed plan.
Public comment
supported the inclusion of air emission controls, and therefore the
ROD included installation of air emission controls (off-gas vapor
phase GAC treatment) to comply with SCAQMD Rule 1167.
This rule is
no
longer .generally
applicable
to
existing
or
proposed
air
stripping systems operated by private parties within the South
Coast Basin, therefore, it is not a TBC.
The current applicable SCAQMD rules
require,
among other
things,
that
all
new
or
modified
facilities
emitting
ozone
precursors (Regulation 13), VOCs and toxic emissions (Rule 1401),
install Best Available Control Technology
(BACT)
to limit
air
emissions.
This is to limit excess cancer risk from toxic air
emissions to less than 1 x 10-6.
At the current contaminant levels
found in the Bartolo wells, an air stripping facility with BACT
would be expected to emit approximately one pound per day of total
VOCs.
The Projected future wellhead and depth-specific contaminant
concentrations that were expected to be extracted from the Bartolo

Well Field for treatment, and formed the basis for air stripper
design,
would
cause projected
air emissions
to
substantially
increase.
At the maximum projected water treatment capacity, the
air emissions, without BACT to limit such emissions, could reach
twenty pounds total VOC emissions per day.
The original ROD meets
14

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BACT under the SCAQMD regulations.
However, SCAQMD requires that
"offsets"
(as
defined under Regulation
13
and Rule
1401)
be
acquired by any facility emitting more than one pound of VOC
emissions per day. The facility, as designed under the original
ROD, included a boiler to preheat off-gases. This boiler would have
produced
nitrogen
oxides
and
sulfur
oxides
as
products
of
combustion. The current design has incorporated an electric pre-
heater
in
order
to
eliminate this
source
of
ozone precurser
emissions, as required under Regulation 13. The original facility
design utilized a carbon adsorption off-gas treatment system that
would have treated 90% of the maximum expected emissions.
The
current design has utilized changes in both the towers and the off-
gas treatment to remove 95% of the maximum expected emissions as
required by Rule 1401. Because the facility as designed under the
original ROD would have allowed approximately two pounds of VOCs
plus boiler emissions to be released to the air, "offsets" would

have been required for all air emissions in excess of one pound per
day.
The treatment system as modified under the ROD Amendment will
be limited to one pound or less per day; hence, no "offsets" are
required under the ROD Amendment.
!;k.
overall
nrotection
of
human
health
and
the
environment. short-term effectiveness and lona-term
effectiveness
Original ROD
Residual Risk
Water:
5 X 10-7
(Treat to 10-6 target risk)
Air: 5 x 10-7
(Assumes 90% removal)
15

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Amended ROD
Residual Risk
Water:
1 X 10-5
(Treat to MCLs )
Air: 2 x 10-8
(Assumes 95% removal)
These criteria were reevaluated in light of both the new MCL
for PCE and the SCAQMD regulations for air emissions control.
The ROD Amendment requires reevaluation of this
criteria
because compliance with the MCL for PCE will result in a residual
risk for the treated water that may be slightly higher than in the
original ROD, if the projected contaminant levels are ever reached.
The new residual risk of 1 x 10-5, resulting only if the maximum
projected contamination levels are realized, falls within the EPA
policy for a target residual risk range between 10-4 and 10-6.
These levels, projected by computer modeling may, in fact, never be
realized. -
Compliance with this new MCL is considered protective of human
health. Treatment of water to a quality meeting all federal and
state drinking water standards is consistent with EPA policy.
Treatment of water under the original ROD was set at a level
considerably lower than the drinking water standard for PCE because
there was no MCL calculated for PCE at the time.
The ROD Amendment
meets the new drinking water standard.
The design of the treatment
facility established a target treatment level lower than the "never
to exceed" level.
In so doing, the actual concentration of PCE in
the treated water will be somewhat lower than the MCL.
. Compliance with SCAQMD regulations is protective of both human
health and the environment. Regulation 13 limits ozone precursors
16

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within the Los Angeles air quality basin in order to reduce smog
formation.
Rule 1401 limits risk due from air toxics to less than
1 x
10-6.
Generally,
a risk assessment
is required of
all
facilities; those exceeding 1 x 10-6 risk are required to use BACT
to limit emissions.
Rule 1401 allows 5 years for environmental
remediation
projects
to
come
into
compliance
with
the
risk
requirements.
Because this facilitity was in design at the time of
promulgation, EPA decided full compliance with the regulation at
this time was preferable.
£.:..
reduction
of toxici tv.
mobilitv.
and volume of
contaminants
original ROD
Adequate for all media if carbon is
regenerated     
Adequate for all media. if carbon is
"Amended ROD
regenerated
Evaluation of this criterion for impacts on the groundwater
basin is unchanged from the original ROD.
There is potential for
slightly
less reduction of toxici ty ,
mobility,
and volume of
contaminants to receptors under this amendment,
if contaminant
levels ever reach the projected maximum.
However, the new cleanup
level is still within EPA's acceptable risk range.
d.
technical
and
administrative
feasibilitv
of
implementation
Original ROD
Feasible
Amended ROD
Feasible
Evaluation of this criterion is unchanged from the original
17

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ROD.
e.
caDital and operation and maintenance costs
Original ROD
Amended ROD
$15,266,000 (based on 5% interest rate
and 30-year project life. Cost estimate
from OUFS.)     
$24,662,000 (based on 5% interest rate
and 30-year project life.
from 60% design.)
Cost estimate
Cost-effectiveness of the selected remedy was reevaluated.
Costs
for the two
alternate
carbon adsorption configurations
described in the OUFS were updated to 1991 dollars by adding a
factor of 13% to the 1988 estimate.
Feasibility study estimates
are not based on detailed design work and may vary between -30% to
+50%.
Figure
3
shows
the
updated
cost
estimates
for
both
configurations of liquid phase carbon adsorption system along with
the cost estimate for the air stripping system.
The estimate for
the air stripping system was produced as ~art of the 60% design
package, and is expected to vary approximately 15%.° Treatment to
MCLs rather than to 1 ppb will save an estimated six million
dollars over the course of the project.
As design progresses,
the unknown variables that lead to
uncertainty in cost estimates decrease.
To properly compare cost
estimates, not only must the actual cost estimates be compared, but
the
uncertainty
associated
with
the
estimates
must
also
be
compared.
The uncertainty associated with the 60% design estimate
is considerably smaller than the uncertainty associated with the
18

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Figure 3
Current Design Cost Estimate for Air Stripping*

. Current cost estimate of Air Stripping* with vapor phase granular actIvated
carbon air emissions treatment system.
- Estimate reflects 60 percent design completion, less the estimated
savings due to implementation of recommendations made in a Value
Engineering Study. Estimate is expected to vary within 15 percent.
(Range = $20,963,000 to $28,361,000)

...... ..... ....... .... .....,... ..... ......... ..... .....,....... ....... $24,662,000

Updated Feasibility Study Estimates for

LGAC Systems*

. Suburban 1988 OUFS cost of "dual bed" liquid phase carbon adsorption
(series configuration of two carbon vessels) (OUFS Alternative G) .
Updated to 1991 dollars to account for inflation. Estimate is expected
to vary between -30percent to +50percent.
(Range = $17,866,000 to $38,284,000)
............... ....... ......... ...~..... .............................. $25,523,000

. Suburban 1988 OUFS cost of "single bed" liquid phase carbon adsorption
parallel configuration of carbon vessels) (OUFS Alternative H)
Updated to 1991 dollars to account for inflation. Estimate is expected
to vary between -30 percent to +50 percent.
(Range = $16,370,000 to $35,080,000)
........ ....... ..................... ............. ....... ... ...- ........
$23,387,000
*The present worth estimates above are based on a 30-year project life and a
5 percent interest factor.

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pre-design estimates.
The result of this decreased uncertainty is
that there is a high probability that the air stripping system will
cost less than the Granular Activated Carbon (GAC) alternatives
originally proposed.
f.
state acceptance of alternative
Original ROD
Yes
Amended ROD
Yes
Evaluation of this criteria is unchanged from the original
ROD.
g.:,.
community acceptance of alternative
Original ROD
Yes
Amended ROD
Yes
Evaluation of this criteria is unchanged from the original ROD
with resp~ct to the facility.
The decision to del~y construction
is based upon comments received during the public comment period
for this Amendment.
IV.
STATUTORY DETERMINATION
Considering the new information that has been developed and
the changes that have been made to the selected remedy,
EPA
believes that the remedy as revised by this Amendment remains
protecti ve of human heal th and the environment,
complies with
federal and state requirements that are applicable or relevant and
appropriate to this interim remedial action, and is cost effective.
Under the present conditions, this remedy will not result in
hazardous substances remaining on site above health based levels.
This remedy is protective of human health and the environment.
The
19

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five-year
review
will
apply to
this
action
to
evaluate
the
permanence of the remedy.
Under current conditions, there is no
contamination
remaining
on
site
above
health-based
levels,
therefore, the statutory requirements of CERCLA S121 for remedial
actions are not applicable.
v.
PUBLIC PARTICIPATION
EPA has presented these changes to the remedy in the form of
an Amendment to the original ROD.
EPA held a thirty day public
comment period on this Amendment.
All comments received and EPA's
responses
Record.'
to
them
have
been
included
in
the
Administrative
, See footnote number 1 for further information regarding the
public comment period and Administrative Record.
20

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Record of Decision Amendment
Responsiveness Summary
Suburban Water Systems/Bartolo Well Field Operable
San Gabriel. Valley superfund Site Areas 1-4
unit
A. Overview
At the time of the public comment period from June 25
through July 25, 1991, EPA had selected an amended alternative
for the Suburban Water Systems/Bartolo Well Field Operable Unit
(SWS' Bartolo Well Field OU). EPA's recommended amended
alternative addressed the treatment level for perchloroethene
(PCE) in the extracted groundwater, the 30 year estimated cost of
the project, and air emissions levels. Based on comments
received and groundwater data' showing contaminant levels have not
increased (contrary to modeling predictions), EPA has decided to
postpone construction of the treatment system. This decision
will be subject to a five year review to assure that the
monitoring continues to provide adequate protection of human
health and the environment.
The major issues or concerns expressed in the six letters
submitted to EPA during the public comment period questioned the
economics and scale of the proposed treatment system, the ability
of the model to accurately predict future concent~ations, and
even the need to build a treatment system, given current
groundwater trends of lower contaminant concentrations. Only one
commentor supported the construction of the Bartolo treatment
system. Two commentors stated that the necessary Remedial
Investigation information to evaluate the model (used by EPA) was
not released to the public. These same commentors were also
concerned about liability and who ultimately would be expected to
pay for the project. One commentor offered suggestions on
preventing future groundwater contamination by better regulating
underground tanks.

The major concerns expressed during the July 16, 1991,
public meeting were regarding treatment levels of extracted
groundwater from initially 1 part per billion (ppb) for PCE, to 5
ppb for PCE, following recently promulgated federal and state
drinking water standards. There were also comments and questions
on the accuracy of EPA's model and on the schedule of
specification contract awards for the proposed treatment system.
This responsiveness summary is divided into the following
sections:
.
.
EPA Activities Prior to the Public Meeting
Summary of Comments Received During the Public Comment"
Period and EPA Responses

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B. EPA Activities Prior to the Public Keeting
Prior to the beginning of the public comment period, EPA
published a public notice on June 19, 1991, in the San Gabriel
Valley Tribune. This notice described EPA's proposed changes to
the 1988 Suburban OU ROD and announced the public comment period
and the upcoming public meeting. The notice also announced
locations where the original ROD and Proposed Plan were available
at the Whittier Central Public Library and at the EPA information
repository in San Francisco.
EPA also prepared a 6-page fact sheet describing the
proposed changes to the original ROD. Copies of the fact sheet
were mailed on June 23, 1991, to the general mailing list for the
San Gabriel Valley Superfund site. This general mailing list of
over 1,00 names consisted of elected officials, media
representatives, representatives of local cities and local
districts, and PRPs.
C. Summary of comments Received During Public Comment Period
Comments received during the public comment period for the
SWS' Bartolo Well Field OU are briefly summarized below. The
comment period was held from June 25, to July 25, 1991.
1.
2.
-The San Gabriel Basin Industry Coalition. (the "Industry
Coalition") commented, there is an inadequate basis for
EPA to proceed with the project because the "community"
has been denied the necessary Remedial Investigation
(RI) information to review the modeling used by EPA.
Therefore, the project should be delayed pending review
of the data.
EPA Response - All of the data used for the Suburban
modeling has been available to the public in the
Administrative Record repositories located at the
Whittier Central. Public Library and the EPA information
repository in San Francisco.
The Industry Coalition commented that the design
capacity of the treatment system exceeds the volume of
water currently being pumped. They suggested
downsizing the treatment system or blending the water.

EPA Response - The treatment plant capacity was
designed for maximum capacity and variable flow to
account for a wide range of conditions. If groundwater
conditions change to the point where building a
treatment plant is necessary, EPA will reevaluate the
treatment plant design and reevaluate the current
SWS'Bartolo well locations under observed conditions.
2

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If they are not appropriate, EPA will evaluate new well
location(s) and new treatment system(s).
3.
The Industry Coalition also commented "there is no need
for remediation based on current circumstances," ....
EPA Response - Based on recent groundwater data which
show that contamination levels have not increased, EPA
will delay construction of the treatment plant until
there is an increase in contamination levels as
described in the ROD amendment.
4.
Munger, Tolles & Olsen commented that since PRPs were
not identified at the time of the original comment
period on the Suburban Proposed Plan, "... comments on
the proposed amendments provides no meaningful
opportunity to comment on the proposed remedy."

EPA Response - EPA published a notice of availability
of the 1988 Suburban Proposed Plan in the San Gabriel
Vallev Tribune and the Whittier Dailv News. EPA mailed
copies of the 1988 ProPQsed Plan to approximately 800
names, including private individuals, companies,and
elected officials. In addition, EPA mailed copies of
the 1991 Suburban Proposed ROD Amendment to over 1,000
names including approximately 300 PRPs. Furthermore,
_page 1 of the June 1991, Proposed Amend~ent Fact Sheet
for Suburban stated the opportunity to comment on the
recent proposed amendment, the alternatives on the
original Suburban/Bartolo Operable unit Feasibility
Study (OUFS), and the Administrative Record (AR). EPA
also announced twice at the July 16, 1991 public
meeting for the Suburban/Bartolo amendment that the
public was being given the opportunity to comment on
the AR, the proposed amendment, and the original OUFS.
Thus, EPA believes there has been ample opportunity for
the public to comment on .all aspects of the proposed
remedy.
5.
Munger, Tolles & Olson commented that the necessary RI
information was not released to the public and
therefore, ..."it is impossible to comment meaningfully
on the proposed remedy. II
EPA Response - See EPA response to comment #1.
6.
Munger, Tolles & Olson also commented that until the
need for the project is more fully justified, the
contracts should not be let.
EPA Response - Because construction of the treatment
system is being delayed, contracts have not been let. .
3

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. 7.
EPA assumes "contracts" are for construction of the
treatment system. Also, see EPA response to comment
#3.
The Upper San Gabriel Valley Municipal Water District
("the Water District") expressed its concern on the
economics of the project. The Water District also
asked for the modeling to be revised to reflect an
increase in population and therefore an increase in
pumping rates and the potential impacts of a lowered
water table, and reduced groundwater flow through the
Whittier Narrows.
EPA Response - Revising the model to reflect an
increase in population would be extremely difficult if
not impossible, as this would require predicting
demographic changes within a limited area of the San
Gabriel Valley which would be very difficult to do with
any degree of accuracy. The commenter also assumes an
increase in population would directly lead to an
increase in pumping of groundwater. It is possible that
water demands for an increaseing population could be
met by other means such as importation of water from
other sources, or by conservation of water.
4

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