United States
          Environmental Protection
          Agency
Off ice of
Emergency and
Remedial Response
EPA/ROD/R09-93/088
March 1993
£EPA    Superfund
          Record of Decision:
          San Gabriel Valley Area 1
          (Operable Unit 2), CA

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50272-101
 REPORT DOCUMENTATION 11. REPORT NO.      2.     3. Reclplenf. Ac:c88.lon No.  
  PAGE   EPA/ROD/R09-93/088              
4. Thle and Subth18                  5. Report Date   
 SUPERFUND RECORD OF DECISION               03/31/93 
 San Gabriel Valley Area 1 (Operable Unit 2), CA     6.      
 Third Remedial Action                    
7. Author(.)                  8. Performing Organization R.pt. No.
9. Performing Org.nlzatlon Name .nd Addr...             10 ProJ.ct Ta.klWork Unh No. 
                      11. Contract(C) or Grant(G) No. 
                      (C)      
                      (G)      
12. Sponsoring Organization Narne and Add,...             13. Type of Report & Period Cov.red 
 U.S. Environmental Protection Agency               
 401 M Street, S.W.               800/800   
 Washington, D.C. 20460              14.      
15. Supplementary Note.                      
       PB94-964524                 
16. Abstract (Llmh: 200 word.)                      
 The San Gabriel Valley Area 1 (Operable Unit 2) site is part of a larger area of ground
 water contamination located near the San Bernadino Border, in Los Angeles County, 
 California. This site is situated to the south of the Pomona Freeway and to the west
 of the San Gabriel Freeway, and consists of low lying hills.  Much of the OU is  
 utilized for flood control, and the Whittier Narrows Flood Control Dam serves as a 
 boundary between the adjacent San Gabriel and Central Basins. Two major rivers located
 within the OU boundaries are the San Gabriel and Rio Hondo Rivers. Land use in the 
 area is mixed residential,  commercial, recreational, and light industrial. The nearest
 residential areas are South El Monte and South San Gabriel to the north and Montebello
 and pico Rivera to the south. Currently, ground water from onsite production wells is
 used for domestic, industrial, and agricultural purposes. In 1984, EPA investigations
 detected VOC contamination and determined it was a direct result of past manufacturing,
 cleaning, and degreasing operations in the area, in both ground water and surface water
 in the San Gabriel Basin.  Since impacted ground water must flow through the Whittier
 Narrows before exiting the San Gabriel Basin, EPA designated the Whittier Narrows area
 as one of six OUs for this site. 1988 and 1989 RODs addressed contamination at the 
 Richwood and Suburban OUs,  respectively. This ROD focuses on evaluation of ground 
 (See Attached Page)                    
17. Document Analyala e. Dacrlptora                    
 Record of Decision - San Gabriel Valley Area 1 (Operable Unit 2), CA    
 Third Remedial Action                    
 Contaminated Medium: None                   
 Key Contaminants: None                    
 b. Identlfl.rsIOpen-Ended Term8                    
 c. COSATI Field/Group                      
18. Avallabllhy Statement           19. Sacurhy Class (ThIs Report)  21. No. of Pages 
                   None     44 
                 20. Sacurhy Claes (Thl. Page)   22. Price  
                   None       
(See ANSI-Z39.18)
SNlnstructlons on RIVlrB6
OPTIONAL FORM 272 (4-77)
(Form.rly NTI5-35)
Department of Comm.rce

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EPA/ROD/R09-93/088
San Gabriel Valley Area 1 (Operable Unit 2), CA
Third Remedial Action
Abstract (Continued)
water contamination potentially flowing from within the San Gabriel (Areas 1-4) Superfund
site into the Whittier Narrows Area, and subsequently into the Central Basin, as OU2.
Future RODs will address the remaining three OUs, which all are located upgradient of this
site, and include the Baldwin Park OU, Puente Valley OU, and South El Monte OU. Based on
monitoring data and risk assessments conducted as part of the RI/FS, EPA has determined
that the risk level of the contaminants in the OU falls well within EPA's acceptable risk
range; therefore there are no contaminants of concern affecting this site.
The selected remedial action for this site is no action, with ground water monitoring.
Site investigations have confirmed that contaminants within OU2 currently pose no risk to
human health and the environment. The estimated present worth cost for this remedial
action is $5,200,000.
PERFORMANCE STANDARDS OR GOALS:
Not applicable.

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                        .RECORD OF  DECISION
       "MONITORING ONLY" (NO ACTION)  ALTERNATIVE SELECTION
                           DECLARATION

SI-TE NAME AND LOCATION

Whittier Narrows Operable Unit
San Gabriel Valley Superfund Site, Areas 1 through 4
Los Angeles County, California

STATEMENT OF BASIS AND PURPOSE

This decision document represents  the selection of the "Monitoring
Only" Alternative  for the Whittier Narrows Operable  Unit in Los
Angeles County, California, one of six operable units for the San
Gabriel Valley Superfund Site,  Areas 1  through  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.

The State of California concurs with this.decision.

DESCRIPTION'OF THE "MONITORING ONLY" (NO ACTION) ALTERNATIVE

The "Monitoring Only"  Alternative  selected for the Whittier Narrows
Operable  Unit  will  include  the installation of   up   to  nine
additional multiport  or cluster groundwater monitoring wells plus
approximately eight single point wells.   The installation  of these
additional wells will enhance the existing groundwater monitoring
network at the operable unit.  Sampling and analysis of groundwater
from the new monitoring wells will be conducted quarterly for one
year, then adjusted upon review of validated analytical results and
seasonal fluctuations.  The current sampling and  analysis  schedule
will be  followed  for  the existing groundwater monitoring network
(and will also be adjusted pursuant to validated  analytical results
and  seasonal  fluctuations  as  necessary).    In addition  to the
installation  of new  monitoring  wells,  well  logging  and depth-
specific sampling will be performed at approximately ten production
wells located  within  the Whittier Narrows area.  Additional well
logging  and  depth  specific sampling  may be required depending on
the  results of the   depth specific  sampling  of the  initial ten
wells.   New groundwater monitoring  wells  will be  installed using
a phased approach.  The "A" priority multiport wells and the single
point wells will be installed as  a first phase,  most of which are
located along the northern boundary of the operable unit.  The "B"
priority multiport wells, if needed,  will be installed as  a second
phase, after monitoring results are evaluated from the "A"  priority
multiport  wells,  the single depth  wells  and  local  water  level
measurements:

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DECLARATION

Based  on the  currently available  data, no  remedial  action is
necessary to ensure protection of human health  and the environment.
Because future groundwater conditions within the operable unit may
change as groundwater flows through  the area,  the groundwater will
continue  tb be  monitored and  results  evaluated,  in  an  annual
summary report, to verify continued  protection of human health and
the environment.   A five-year  review will be performed  for the
Whittier Narrows Operable Unit, at which time more information on
factors affecting the groundwater quality within the operable unit
will be available,  and EPA's decision will be revisited.  The five-
year period to be used for the review will start when field work
(installation of monitoring wells)  commences.
       John^Wise,  Acting Regional Administrator

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1.0
RECORD 01' DECISION
''KOHrlORDIG ONLY" (BO AC'.rIOB) ALTERDTrvB SELBCTION
DBCISION SUHHARY
OPERABLE UNIT NAME. LOCATION. AND DESCRIPTION
1.1
OPERABLE UNIT NAME
Whittier Narrows Operable Unit
San Gabriel Valley Superfund site, Areas 1 through 4
Los Angeles County, California
1.2
OPERABLE UNIT LOCATION
The Whittier Narrows Operable Unit (OU) is located in Southern
.-- ." - California in eastern Los Angeles County near the San
Bernardino County border as shown in Figure 1. The OU area is
situated primarily to the south of State Route 60 (the Pomona
Freeway) and mostly to the west of Interstate Route 605 (the
San Gabriel River Freeway). The OU is bisected by Rosemead
Boulevard. The nearest residential areas are South El Monte
and South San Gabriel to the north and Montebello and Pico
Rivera to the south.
. .
1.3
OPERABLE UNIT DESCRIPTION
The San Gabriel Valley Superfund Site, Areas 1-4, consists of
large areas of groundwater contamination from many sources.
The groundwater is contaminated mainly with various volatile
organic compounds, such as trichloroethene (TCE) and
tetrachloroethene (PCE) that have been used in manufacturing
processes and in cleaning and deqreasing operations.

The OU consists of the area between the 1-1/2-mile-wide gap in
the low lying hills, that serves as the boundary between the
.San Gabriel Basin and the Central Basin. This area
constitutes the southernmost portion of the San Gabriel Valley
Superfund site, Areas 1 through 4, to the Pomona Freeway (see
Figure 2). The OU is bordered on the west and northwest by
the Montebello Hills and on the east and southeast by the
Puente Hills. .
The San Gabriel River and Rio Hondo River are two major rivers
located within the OU boundaries. Much of the OU is used for
flood control, with compatible secondary uses such as golf
courses, equestrian areas, camp grounds, and recreational
parks. The Whittier Narrows Flood Control Dam is the
designated boundary between the San Gabriel Basin and Central
Basin (see Figure 2). Other land use in the OU consists of
residential, commercial, or light industrial. Most of the

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                              RAYMOND
                                  BASIN
                                                 u
                                         SAN GABRIEL BASIN
                                                                                          UPPER   SAf>
                                            WHITTIER NARROWS
                      LOS
                     ANGELES
            QROUNDWATER
            RECHARGE AREAS -
                                                                                         NOT TO SCALE
                CENTRAL
                 BASIN
WEST COAST
BASIN    *.
MONTEBELLO
FOREBAY AREA
                                                                         L-_ _%£< ^ _ _c_ _ _~L:
                                              ORANGE COUNTY
                                              GROUNDWATER
                                                                         ALLUVIUM AND ASSOCIATED OCPOSlTS
                                                                         OF RECENT OR PLEISTOCENE ACE
                                                                         SEDIMENTARY ROCKS OF  MARINE ORIGIN,
                                                                         MAINLY TERTIARY WITH SOME CRETACEOUS
                                                                  m ....... fc "'U   CRYSTALLINE  AND METAMORPHIC ROCKS,
                                                                  I j _. » J   JURASSIC OR  OLDER; SOME TERTIARY ROCKS
                                       FIGURE   1
                                       LOCATION MAP
                                       WHITTIER NARROWS OPERABLE UNIT
                                       FEASIBILITY STUDY
          (SOURCE: CDWR, 1966)

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U)
                   \T^   E;
                    .   ARpR
                    S  SI*E
                    V  GROU
XWHITTIER NARROWS OPERABLE UNIT
  AND SURROUNDING AREA ,-"^ "    "
  OPERABLE UNIT FEASIBILITY
  STUDY REPORT  /i
                                                                new- Y ,>^\:J   » i*;--
                                                                                                  ^-l:.^'  -r B'nStfr-t)
   WHITTIER NARROWS
  •i$f  i  ri
   L/kO69126.tV01

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area that is not restricted to flood control or recreation is
fully  developed  (these  areas  are  limited  to the  extreme
northeast portion of the OU.

Groundwater, from 14 production wells, is currently used for
domestic, industrial, and agricultural purposes.

     1.3.1      Geolocry

     Whittier Narrows was  formed by  erosion,  faulting,  and
     subsequent filling with  alluvium of a gap between the
     Montebello Hills to the west and  the Puente Hills to the
     east.

     The San Gabriel Mountains form the northern boundary of
     the San Gabriel Basin and range from 900 feet at the base
     to  over 10,000  feet  above mean  sea  level  (msl)  in
     elevation.    The San  Gabriel  Mountains are  comprised
     primarily of Cretaceous and older rocks including quartz
     diorite, granite, gneiss,  schist,  and associated dikes
     and inclusions. The Repetto, Merced, Puente, Montebello,
     and San Jose Hills bound the basin along the  southwest
     and southeast.   These hills are composed  of  primarily
     Tertiary   marine  sedimentary   rocks  consisting   of
     sandstone,  siltstone,  and shale locally interbedded with
     conglomerate and cut by volcanic dikes.

     The San Gabriel Basin is a broad piedmont plain with an
     average slope of about 65 feet per mile.   Ground surface
     elevations range front about 900 feet above msl  in the
     north to about 200 feet above msl  at Whittier  Narrows
     Dam.  The basin contains alluvium and assorted deposits
     of Recent and Pleistocene age.  The  San Gabriel Mountains
     and, to a lesser extent,  the flanking low hills are the
     sources  of  the basin-fill  sediments,   which  reach  a
     maximum  depth  of  approximately  4,000  feet  in  the
     southwestern portion of the basin.

     Sedimentary  rocks  of the  Quaternary and Tertiary age
     occur in the northeastern  portion  of the Central Basin
     (the area referred  to  as  the Montebello Forebay) .  These
     rocks are  categorized  as either alluvium,  sediments of
     the Upper and Lower Pleistocene age,  or sediments of the
     Tertiary age.  The alluvium is primarily unconsolidated
     gravel, sand,  and  silt deposited by streams.   Alluvium
     generally occurs from the ground surface to about 100 to
     200  feet below  ground  surface  (bgs).    The  sediments
     underlying the alluvium consist of the Lakewood and San
     Pedro  Formations  and   are  of  the  Upper  and  Lower
     Pleistocene  Age.   The Lakewood  Formation is  generally
     comprised  of gravel,  sand, silt,  and clay,  and occurs
     from about 100  feet bgs  to  250 feet bgs.  The San Pedro

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--- .--
Formation is composed of stratified sand with some beds
of fine gravel, silty sand, and silt. The San Pedro
Formation occurs from about 200 feet bgs to about 900
feet bgs. Sediments in the San Pedro Formation are
offset more by faults than in the Lakewood Formation
sedimen"ts. Except for the geologic faults, which offset
these formations, the stratigraphy within the OU is
generally ~lat lying.
Tertiary rocks in the Whittier Narrows are divided into
the P ico and Repetto Formations, older sediments and
volcanic rocks, and other undifferentiated rocks. The
Pico Formation is composed of sand, silt, and clay of .
marine origin, interbedded with gravels. Layers of
gravel and sand range in thickness from 20 to 100 feet
and are interbedded with micaceous siltstone and clay.
The Repetto Formation is generally composed of siltstone
with layers of sandstone and conglomerate. The older
sedimentary rocks include the Puente Formation, which
contains mostly siltstone and shale, with lesser amounts
of sandstone and conglomerate. The Topanga Formation
also occurs in the Central Basin area and consists of
shale, sandstone, and conglomerate. Volcanic rocks
include calcic andesite flows, tuffs, and volcanic
breccias. The volcan~c rocks are interbedded wi th
se~inientary rocks of the Topanga Formation in some areas.
Compared to the rest of the San Gabriel Basin, the
geology of the Whittier Narrows is relatively well
characterized to depths of at least 400 feet because of
the density of well logs. oil wells to the west and
water wells to the east are particularly abundant in the
vicinity of the Whittier Narrows Dam, and water wells are
somewhat abundant a1ong"the San Gabriel River and Rio
Hondo River below the dam. At greater depths,." the
geology is generalized and well logs must be examined
individually for local details. Several very thick
(several hundred feet) clay and gravel layers occur
. locally at depths greater than 400 to 500 feet bgs, based
on data from a limited number of very deep wells.
1.3.2 Hvdroqeoloqy
The San Gabriel Basin aquifer consists of the alluvial
sediments deposited in the San Gabriel Basin. Over 300
production wells pump over 200,000 acre-feet per year of
groundwater from the San Gabriel Basin.
In the Central Basin, the aquifers of the Lakewood and
San Pedro Formations are in places separated by low-
permeability materials. In stratigraphic order, these
aquifers are: the Gaspur-Ballona, Exposition-Artesian,
5

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Gardena-Gage, Hollydale, Jefferson. Lynwood, Silverado,
and Sunnyside.   The lateral and vertical extent of clay,
silt, and sandy-clay layers is poorly defined.  In some
areas, individual aquifers  in  the Lakewood arid San Pedro
Formations   are   not  separated   by   low-permeability
materials and may directly overlie each other.  However,
between the Silverado and Sunnyside aquifers of the San
Pedro Formation,  a  layer of  low-permeability materials
exists that  is laterally continuous  over much  of  the
Whittier Narrows area and the northeastern portion of the
Central Basin.

Aquifers in the Whittier Narrows occur in the alluvium in
addition to the Lakewood and San Pedro Formations.  The
formations older than the San Pedro Formation typically
have very few production wells.

Available well logs indicate  that  Whittier  Narrows and
the adjacent  part of the Montebello Forebay have the same
general characteristics of the San Gabriel aquifer (i.e.,
discontinuous inter finger ing lenses of alluvial deposits)
with typical  yields of 500 gallons per  minute or greater.
Zones producing groundwater to wells in Whittier Narrows
are generally composed of sand and gravel.  These zones
may be laterally continuous with aquifers of the Lakewood
and San  Pedro  Formations  in the Central  Basin.   These
aquifers are generally  flat-lying, except for the area
adjacent to the Rio Hondo and Pico fault systems.

The geologic  materials in the  Whittier Narrows vary from
clay to  gravel over short  distances,  and  the hydraulic
conductivity is  expected  to vary by  several  orders of
magnitude within  the vertical interval that a well may
penetrate. Hydraulic  conductivity values estimated from
aquifer tests in the Whittier Narrows range from near one
feet per day to over 1,000 feet per day.

In the  San Gabriel Basin,  estimates  of  specific yield
based  on  well logs,  range  from  3  percent near  the
peripheral areas of  the  basin  to 24  percent  in  the
central portion of the basin.  Values of specific yield
are greater near the mountains and in the center of the
basin where  the clay  content  of  the alluvium is small.
This analysis  indicates that  the specific yield within
the Whittier Narrows ranges from 10 to 20 percent.

Groundwater pumping in Whittier Narrows for potable water
uses occurs  at the City of Whittier and Suburban Water
Systems  well  fields.   These wells  have  produced an
average of 16,000 acre-feet per year of groundwater from
1977 to  1990.

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2.0
OPERABLE UNIT HISTORY AND ENFORCEMENT ACTIVITIES
The u.S. Environmental Protection Agency (EPA) identified the San
Gabriel Valley as a Superfund site due to the detection of a
variety of:'volatile organic contaminants in' the groundwater and
surface waters in'the San Gabr~el Basin and the risk or potential
risk to people consuming the water. EPA listed this site as the
San Gabriel Valley Superfund Site, Areas 1 through 4, on the
National Priorities List in 1984.
Since impacted groundwater from sources within the San' Gabriel
Valley Superfund Site, Areas 1 through 4, must first flow through
the Whittier Narrows before exiting the San Gabriel Basin, EPA
identified the Whittier Narrows as an operable unit to address
groundwater contamination potentially flowing into the Central
Basin. EPA evaluated .groundwater quality data within the OU to
de..termine what risks are posed by groundwater conditions within the
OU to determine if it is necessary to limit or control the
migration of impacted groundwater through the Whittier Narrows.
Whi ttier Narrows is one of six OUs (see page 8) that EPA has
designated for investigation in the San Gabriel Valley.
EPA is pursuing overall remediation of the San Gabriel Valley
Superfund Site, Areas 1 through 4, at, two levels: 1) via a
Superfund ~~operative Agreement with the-Los Angeles Regional Water
Quality Control Board (LARWQCB). The LARWQCB is the lead agency for
investigations and 'remediation of soil and shallow groundwater at
individual facilities (source investigations) throughout the San
Gabriel Basin, and 2) EPA-lead investigations and remediation of
deeper, regional groundwater contamination potentially originating
from multiple facilities. These two elements are being implemented
concurrently within the San Gabriel Basin.
To date,. Qver 300 General Notice letters have been issued, by EPA,
to potentially responsible parties throughout the San Gabriel
Valley. special Notice letters will be issued for the Baldwin Park
and Puente Valley OUs in 1993.

EPA had previously prepared a Feasibility Study for Whi ttier
Narrows in 1989 which evaluated various remedial alternatives,
based on computer modeling predictions of increasing contamination
levels in Whittier Narrows. Subsequent groundwater monitoring did
not support these modeling predictions. Based on the groundwater
monitoring data and the hydrogeologic complexity of the area, EPA
has decided that it will no longer rely on. computer modeling for
predicting future contamination levels in this OU. (See EPA
response to general comment #11 in Responsiveness summary)
7

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3.0  HIGHLIGHTS OF COMMUNITY PARTICIPATION

The Feasibility  Study  Report and Proposed Plan for  the Whittier
Narrows  Operable  Unit  were released to  the public  in  September
1992.   These  two documents were made available to the  public in
both the administrative record file and an information repository
maintained at the EPA Docket Room in Region 9 and at the Whittier
Central Public Library.  The notice of  availability for these two
documents was published in the Los Angeles Times on September 15,
1992.   A public  comment period was held from September 16,  1992
through November 16,  1992.   In  addition, a public meeting was held
on September 23,  1992.   At this meeting,  representatives from the
U.S. Environmental Protection Agency, Region 9 answered questions
about   the  OU   and  the   "monitoring  only"  alternative  under
consideration.    Following the  meeting,  written  comments  were
received from state and local agencies only, not private citizens.
A response to the comments  received during this period is included
in_ the  Responsiveness  Summary, which is  part of this  Record of
Decision.  This  decision document presents  the  "monitoring only"
alternative selected  for the Whittier Narrows Operable Unit, in Los
Angeles County,  California,  chosen in accordance with CERCLA, as
amended by SARA,  and  the NCP.  The decision for this OU is based on
the administrative record.
4.0  SCOPE AND ROLE OF THE OPERABLE UNIT

The term "Operable Unit" is used to define a discrete action that
is  an  incremental  step  toward  a  comprehensive  site  remedy.
Operable Units  may address certain geographical  areas,  specific
site problems, initial phases of a remedy, or a set of actions over
time.

This operable unit was identified, in accordance with the NCP, to
address groundwater contamination  in the Whittier Narrows area and
potentially flowing  from the San Gabriel Valley  Superfund Site,
Areas l through 4, through Whittier Narrows, and into the Central
Basin.   Source  identification  and control investigations  are
currently being performed by the State of California and are not a
part of this Record of Decision.

The objective of  this OU is to evaluate groundwater quality data
within the Whittier Narrows Operable Unit to determine what risks,
if any,  are posed by groundwater conditions and,  if necessary,
limit or  control the migration of impacted groundwater through
Whittier Narrows.

As with many Superfund sites,  the  investigation at the San Gabriel
Valley Superfund Site, Areas 1  through 4, is complex.  As a result,
EPA has organized the groundwater investigation into six distinct
operable units to date: Whittier Narrows OU,  Richwood OU, Suburban
OU, Baldwin Park OU,  Puente Valley OU, and South El Monte OU.  The

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Suburban OU  is adjacent  to the Whittier  Narrows OU,  while the
remaining OUs  are  hydraulically upgradient of  Whittier Narrows.
Records of Decision were signed for the Richwood and Suburban OUs
in 1988 and 1989, respectively.  The Suburban OU  Record of Decision
is  currently  being   amended   to   reflect  current  groundwater
conditions of  low-level  contamination  in  Whittier  Narrows.   A
Record  of Decision for the Baldwin Park  OU  is scheduled  to be
signed by EPA in 1993.


5.0  SUMMARY OF OPERABLE UNIT CHARACTERISTICS

Table 1 lists the  chemicals of  potential concern,  identified for
the groundwater within the Whittier Narrows OU.   Groundwater within
the Whittier Narrows OU appears  to  be impacted mainly from sources
located hydraulically upgradient from the OU. The LARWQCB however,
has identified some potential sources within the Whittier Narrows
OU and is currently investigating them.  Potential routes of human
exposure include the use of groundwater for domestic, industrial,
and  agricultural  purposes,  and  volatilization  through  soil.
Potential routes of environmental exposure include groundwater from
production wells used  for  irrigation and other nondrinking water
purposes.


6.0  SUMMARY OF RISKS

The information  presented  in this section is  a summary  of the
Screening Baseline Risk  Assessment performed  for  the Whittier
Narrows OU and can  be found, in  its entirety, in the Public Review
Draft.  Whittier  Narrows  Operable  Unit  Feasibility Study.  San
Gabriel  Basin,  Los  Angeles  County  California  located at  the
information repositories at EPA Region 9 and the Whittier Central
Public Library.

     6.1  HUMAN HEALTH RISKS

     The media of  concern  for  this OU is  groundwater.   Table 2
     lists the contaminants of  potential  concern  along with the
     mean,  maximum,   and   minimum  concentrations  detected  in
     groundwater samples obtained  at  the wellhead for production
     wells screened over  multiple intervals  and  from discrete
     intervals in the aquifer from two multiport monitoring wells
     and four single point monitoring wells.

     Exposure to contaminants in  groundwater  could occur through
     the use of groundwater for  domestic purposes.  In residences,
     people can be  exposed to contaminants from  ingestion of water
     used for  drinking and cooking.    They can  also  be exposed
     through dermal  absorption  of  contaminants, primarily during
     bathing  and  showering, and  inhalation of volatile organic
     compounds (VOCs)  released  from the water  into the  household

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   Table 1 
  CheD1icals of Potential Concern in Groundwater
   Whittier Narrows Operable Unit.
-    
   Chemical Name 
   Chloroform 
   1,1- Dichloroethane 
   1,1- Dichloroethene 
   cis-1,2- Dichloroethene 
   Ethylbenzene 
   Styrene 
   T etrachloroethene 
   Toluene 
   1,1,1- Trichloroethane 
   Trichloroethene ..
--  -  
- - - . Xylene 
10
.;\
. .

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Table 2
Chemicals of Potential Concern in Groundwater
Mean, Maximum, and Minimum Concentrations Detected
- Whittier Narrows Operable Unit
Chemical Name
Chloroform
1, 1-Dichloroethane
1, 1-Dichloroethene
cis-1,2-
Dichloroethene
Ethylbenzene
Styrene
Tetrachloroethene.
Toluene
1,1,1-
Trichloroethane
Trichloroethene
Xylene
# Detected/
# Sampled*
1/49
14/51
11/56
23/29
4/49
2/37
43/67
4/49
5/53
37/63
2/49
Concentration (ug/1)
Arithmetic
Mean*
0.4
0.4
0.4
2.5
0.9
0.5
1.1
0.9
0.5
1.4
1.4
Maximum
Detected
0.3
0.6
1.0
6.1
20.0
0.6
7.0
2.8
2.2
7.0
22.0
Minimum
Detected
0.3
0.2
0.2
0.5
0.3
0.5
0.3
0.3
0.2
0.2
4.0
Drinking
Water
Standard
100
5
6
6
680
100
5
1,000
200
5
1,750
' Duplicate/split samples were averaged before summary statistics were calculated.
" The arithmetic mean was calculated using actual detected values and 1/2 the
detection limit for those sampling events where the chemical was not detected.
11

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air d~ring showering, bathing, cooking, or by use of household
appliances such as dishwashers. Exposure to contaminants in
groundwater could also occur through use of groundwater for
industrial purposes. Workers could be exposed through dermal
absorption of contaminants or inhalation of VOCs.
Residents and workers could also be exposed to contaminants in
groundwater through transport of VOCs from groundwater through
soil and into ambient air or into the foundation of a
building.
Additionally, groundwater from two production wells within the
OU is used to fill three manmade lakes in the Whittier Narrows
Recreation Area. Individuals may be exposed to contaminants
in the surface water through inhalation of VOCs or through
ingestion of fish. Because swimming is not allowed in these
lakes, ingestion of lake water by individuals was not
._- .-.-considered. .
Based on potential exposure frequency, duration, and estimated
intake exposures, residents exposed to contaminated
groundwater used for domestic purposes are expected to be the
maximally exposed population.
The estimated size of the exposedp.opulation in the Whittier
NarrotfS-OU is 99,400, based. on the number of individuals
. provided drinking water from production wells located within
the OU. .
Table 3 presents the intake assumptions used to estimate the
average and reasonable maximum exposure to chemicals in
groundwater used for domestic purposes.
6.2
TOXICITY ASSESSMENT
Toxic response depends on the dose or concentration of the
substance. Toxicity values are a quantitative expression of
the dose-response relationship for a chemical. Toxicity
values 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.
RfDs have been developed by the EPA for indicating the
potential for adverse health effects from exposure to
chemicals exhibiting noncarcinogenic effects. RfDs, which are
usually expressed in units of milligrams per kilogram per day
(mg/kg-day), are estimates of lifetime daily exposure levels
that should not pose an adverse health effect for humans,
including sensitive individuals. Estimated intakes of
chemicals from environmental media (e. g., the amount of
chemical ingested from contaminated drinking water) can be
12

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compared  to   the  Rf D.     Rf Ds  are   derived  from  human
epidemiological studies or animal studies to which uncertainty
factors have  been applied  (e.g.,  to account  for  the use of
animal data to predict effects on humans).  These uncertainty
factors help  ensure  that  RfDs will  riot  underestimate  the
potential for adverse noncarcinogenic effects to occur.

The dose-response relationship for carcinogens is expressed as
a CSF. Generally, the slope factor is a plausible upper-bound
estimate of a  response per unit intake  of a chemical over a
lifetime.   The approach used to estimate  the slope factor from
animal  studies   or   human  data   assumes  a  dose-response
relationship  with  no threshold  (i.e.,  even the  smallest
exposure may  produce  a  carcinogenic response).    There is
uncertainty and conservatism built into the risk extrapolation
approach  (where  results  of animal  and  human studies  are
applied to the human population).   Cancer risks estimated by
this  method produce an estimate  that provides a  rough  but
plausible upper limit of risk (i.e., it is not likely that the
true risk would be much more than the estimated risk, but it
could be considerably lower).

Table 4 presents  the RfDs  and CSFs for the contaminants of
potential concern.

6.3  RISK-CHARACTERIZATION            •
     * • ^

Excess lifetime cancer risks are determined by multiplying the
intake level with the CSF.  These risks are probabilities that
are generally  expressed in scientific notation (e.g., IxlO"6).
An excess lifetime cancer risk of  IxlO"6  indicates that, as a
plausible upper bound, an individual  has a one in a million
chance of  developing cancer as a result  of a site-related
exposure to a carcinogen over a  70-year lifetime under the
specific exposure conditions of a  site.  EPA's  acceptable risk
range is 10~4  to 10~6, meaning 1  in 10,000 to  1 in  1,000,000
chance of excess cancer.

Potential  concern for noncarcinogenic  effects of  a single
contaminant in a  single medium  is  expressed as  a hazard
quotient (HQ)   (or the ratio of the estimated  intake derived
from  the contaminant concentration  in a given medium to the
contaminant's RfD).   By  adding the HQs  for all contaminants
within  a  medium  or across  all  media  to  which  a  given
population may  reasonably be  exposed, the Hazard Index  (HI)
can be generated.   The HI  provides a useful  reference point
for gauging the potential significance of multiple contaminant
exposures within a single medium or across media.

A  summary  of  estimated risks for residential  exposure to
groundwater from the Whittier Narrows OU is presented in Table
5  for noncarcinogenic effects and Table 6 for carcinogenic

                           13

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  Table 3   
 Intake Assumptions Used In Future-Use Scenarios 
.. Whittier Narrows Operable Unit  
  Intake Value (Adult) 
    Reasonable 
 Parameter 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
. .    
. The dose from inhalation of VOCs is assumed to be equivalent to the dose from 
ingestion of 2 liters/day.    
. -..
14

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TihU«
DoM-RapooM VuUbla for Ckokab of Cooun
WUtthrNuTawiOpfnbUUuit
Cboaiul
Chloroform
l.t'Dichloroctninc
LI-DIchloroctbenc
ci»- 1 .2-Dichloroeih.ne
Einylbciucne
Slyrene
Tdnchlonxlh.rtt
TolutM
I.l.l-Trichloraillitn.
TrichlorocUum
XyleM
Srdfink Toricity '• ,
(mf^i/dir)
CfWulEffvl
Ljv«r
Ljv«r
Liv.r
Blood
Livtr, Kidney
Blood/Li v.r
Liv.r
CHI. l>«. Now, U«tr. Kldnty
Uvir
-
Liv.r. MOM, Taiott. CNS, Ftuuilclly
Onl
UD
0.01
O.I
0.0009
0.01
O.I
0.]
0.01
0.1
0.09
0.006
2.0
Sourtt
BUS
HEAST
EPA
HBAST
BUS
DUS
DIU
out
HEAST
ECAO
BUS
Ukiladoi
RfD
-
O.I
-
-
0.)
-
-
o.«
0.1
-
0.09
Soon*
DUS
HEAST
urn
ous
QUS
DU1
nu
HEAST
HEAST
OUS
HEAST •
Cuxinogmic rottnty •'•
(miWW
Tatar 9ti
Liv.r, KidMy
Mamnury, Uvtr
Kidney, Adnnil
-
-
Lunf, Bronchi, Uuk.mii
Uvir. Ltuktmlt
^
-
Lunf, Llv«r
-
Oral
Sop.
Factor
0.0061
-
-
-
•^. •
0.0)
0.051
-
-
O.'OII
-
Wdthlor
Efidaca*
Bl
C
C
O
0
B7
tl
0
D
B2
D
Soma
DUS
DUS
EPA
OUS
DUS
HEAST
HEA1T
DUS
OUS
HEAST
OUS
InKalflfjoQ
Soot
Factor
0.011
-
-
-
-
0.002
0.002
-
-
0.017
-
Wafhlof
Cridmct'
B2
C
C
D
O
B2
n
D
D
B2
D
Soarct
DUS
HEAST
EPA
PUS
' IRIS
HEAST
HEAST
out
DUS
HEAST
OUS
Hour.
HE AST • Hulih EffMU Autumnl Summiry Ttblti.
DtlS - InUf raud Riik InlbmuUoa Syium.
EPA • 1 , 1-DichloroclhCM it iviliuud tccordioj to t nud!fi«d-R(D tppro^d: Group C circlnof.ru which ixhibll wuk nUialt of utvino|iaiciljr in co Croopi: A It Humia Clrcli»t4o; B jl Prohibit Humu Ctrtioofto (Bl -limiUd tvidtnct of ctn!ao|cnkiiy la humicu. BJ-MilTKUM lt with budcqutu or lick of ividtnct in hunuiu): C it
Pouibli humia Cixinofin; D ii Not CUnifUblt it lo Humia Ctreinotiaiciljr.

-------
Table 5
Estimated Noncancer Hazard Quotients from !
Domestic Use of Groundwater*
Whittier Narrows Operable Unit
Chemical
Chloroform
1, 1-Dichloroelhane
1, 1-Dichloroelhene
cis-l ,2-Dichloroethene
Ethylbenzene
Styrene
Tetrachloroethene
Toluene
1,1,1-Trichloroethane
Trichloroethene
Xylene
//Detected/
^Sampled
1/49
14/51
11/56
23/29
4/49
2/37
43/67
4/49
5/53
37/63
2/49
Concentration (/tg/1)
*
Arithmetic
Mean
0.4
0.4
0.4
2.5
0,9
0.5
1.1
0.9
0.5
1.4
1.4
95 Percent
UCLk
0.4
0.4
0.5
3.2
1.3
0.5
1.3
1.2
0.6
1.8
2.3
Total Hazard Index
Average Exposure
Ingestion
0.001
0.0001
0.01
0.007
0.0002
0.00007
0.003
0.0001
0.0002
0.006
0.00002
0.03
Inhalation
0.001
0.0001
0.01
0.007
0.00008
0.00007
0.003
0.00004
0.00005
0.006
0.0004
0.03
Reasonable Maximum
Exposure • .
Ingestion
0.001
0.0001
0.02
0.009
0.0004
0.00007
0.004
0.0002
0.0002
0.008
0.00003
0.04
Inhalation
0.001
0.0001
0.02
0.009
0.0001
0.00007
0.004
0.00005
0.00005
0.008
0.0007
0.04
' Exposure assumptions used are shown in Table 3. .
b 95 Percent Upper Confidence Limit.

-------
Table 6
Estimated Excess Lifetime Cancer Risk from '
Domestic Use of Groundwater*
YVhittier Narrows Operable Unit
Chemical
Chloroform
1,1-Dichloroethane
1 , 1 -Dichloroelhene
cis-l,2-Dichloroethene
Eihylbcnz<;ne
Styrene
Telrachloroethene
Toluene
1,1,1 -Trichloroelhane
Trichloroelhene
Xylene
^Detected/
^Sampled
1/49
14/51
11/56
23/29
4/49
2/37
43/67
4/49
5/53
37/63
2/49
Concentration (jig/1)
Arithmetic
Mean
0.4
0.4
0.4
2.5
0.9
0.5
1.1
0.9
0.5
1.4
1.4
95
Percent
UCL>
0.4
0.4
0.5
3.2
1.3
0.5
1.3
1.2
0.6
1.8
2.3
Total Cancer Risk
' . Average Exposure
Ingestion
9x 10-'
*«
--
--
--
5 x 10'
2 x 10'r
--
-- •
5 x 10*
«
3 x 10'7
Inhalation
1 x 1
-------
risk.
For average ingestion and inhalation exposures from the
domestic use of tap water, the sum of the noncancer HQs is
0.Q3 for each route. The HI, based on an average exposure
scenario, is.0.06. For the reasonable maximum exposure (RME)
to groundwater from the domestic use of .tap water, the sum of
the noncancer HQs is 0.04 for each route. The overall
noncancer HI from RME to groundwater in the Whittier Narrows
is 0.09, well below the level of concern for potential
noncancer health effects. When the HI exceeds 1 (i.e., intake
exceeds RfD), there is a potential for health concern.
The estimated excess lifetime cancer risks for average
ingestion and inhalation exposures to tap water are 3x10-7 and
2xlO-7 , respectively. The total estimated excess lifetime
cancer risk for average residential exposure through domestic
--- _--use of groundwater is 5X10-7. The estimate lifetime cancer
risk for RME from tap water are 1x10-6 for ingestion exposures
and 8X10-7 for inhalation exposures. The total estimated
excess lifetime cancer risk for the residential RME through
domestic use of groundwater is 2X10-6 which is at the lower
end of EPA's acceptable risk "target range" of 10-4 - 10-6.
~:-.._~.~ ]:,
uncertainties
uncertainties associated with this screening are due to
uncertainties in the risk assessment process in general
(i.e., the toxicological data base), specific
uncertainties in characterizing the site, and
uncertainties associated with describing exposures.
EPA's risk assessment is conservative in nature and
attempts to account for concentrations by typically
overestimatinq rather than underestimating risks in order
to ensure adequate protection of public health.
Therefore, actual risks are likely to be lower (if they
exist at all) than estimated risks. This screening risk
assessment is subject to uncertainty from a variety of
sources including:
.
.
Sampling and Analysis
Fate and transport .
Exposure estimation
Toxicological data
.
.
Uncertainty associated with sampling and analysis include
the inherent variability (standard error) in the
analysis , representativeness of the samples, sampling
errors, and heterogeneity of the sample matrix.
This
screening
risk
assessment
makes
simplifying
18

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assumptions about the environmental fate and transport of
the site contaminants, specifically, that no contaminant
loss  or  transformation  occurred.   The assessment  also
assumes  that  the chemical  concentrations detected  in
groundwater remain constant during the assessed exposure
duration.  The choice of data to represent exposure point
concentrations  is  an  additional  source  of  potential
error.

In addition, the screening risk assessment focuses only
on VOCs detected in groundwater in the Whittier Narrows
OU. Other chemicals present in the groundwater, such as
inorganics, may  present an additional health  risk not
addressed in the assessment.

The estimation of exposure requires numerous assumptions
to describe potential exposure situations.  There are a
number  of  uncertainties  regarding the  likelihood  of
exposure, frequency of contact with contaminated media,
the concentration of contaminants at exposure points, and
the time period exposure.  Assumptions used in this risk
assessment tend to simplify and approximate actual site
conditions.

The  toxicological  data  base  is  also  a  source  of
Uncertainty.  These uncertainties include, extrapolation
from  high to  low doses  and from  animals to humans;
species, gender, age, and strain differences in uptake,
metabolism,   organ   distribution,  and   target   site
susceptibility;  and  human population  variability  with
respect  to diet, environment,  activity  patterns,  and
cultural factors.

6.3.2     Summary of Risks

Eleven VOCs were detected in  groundwater from production
and monitoring wells located  within the Whittier Narrows
OU.    Human populations  potentially   exposed  to  VOCs
present in the groundwater include individuals using the
groundwater for  domestic,  industrial,  and recreational
purposes.   The  exposure  scenario evaluated assumes a
resident would come in contact with groundwater through
domestic  use  of  tap water.   Based  on  potential for
exposure  frequency,  duration,  and  estimated  intake,
residents  exposed to  contaminated  groundwater  used for
domestic  purposes  are  expected  to  be   the  maximally
exposed population.

The  groundwater  exposure  scenario  was  evaluated  by
estimating  the noncarcinogenic and carcinogenic risks
associated with it.   The noncarcinogenic exposure levels
do  not  exceed  the corresponding  RfDs  for  individual

                      19

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     contaminants  of  potential  concern.  The  sum  of  the
     noncancer HQs for the contaminants of potential concern
     is 0.06  for  the  average  exposure  scenario  and 0.08 for
     the RME  scenario,  both below the  level  of concern for
     noncancer health effects.  The estimated excess lifetime
     cancer risk for residential domestic use of groundwater
     is 5xlO~7 for the  average  exposure scenario and 2xlO~6
     for the RME scenario.  In general, EPA uses 10~6 to  10"4
     as its "target range" within  which EPA strives to manage
     risks as part of a Superfund cleanup.  Estimated excess
     lifetime cancer  risks  for residential domestic  use of
     groundwater  fall  below this  range  for  the  average
     exposure scenario  and  at  the  lower end of  the  target
     range for the RME scenario.

6.4  ENVIRONMENTAL RISKS

Six VOCs were  detected in groundwater from production wells in
the Whittier  Narrows  Nature Center and Rose  Hills Memorial
Park.  Groundwater from these production wells  is currently
being  used  for  irrigation  and  other  nondrinking  water
purposes.  Potential environmental receptors include vegetation
and wildlife  exposed to  groundwater  in  these  areas.   The
detected  VOCs  will   be  removed  from water  primarily  by
volatilization to the  atmosphere.  These VOCs are not expected
to significantly bioconcentrate  in aquatic organisms or adsorb
to sediment.   A comparison of concentrations detected in these
production wells to the  corresponding chemical-specific acute
and chronic National  Ambient Water Quality  Criteria  (AWQC)
shows that the AWQC are  considerably higher (greater than 400
times)  than the detected concentrations.

National Ambient Water Quality Criteria  (AWQC) are published
by  EPA under the Clean Water  Act.    If not exceeded,  the
appropriate AWQC should  protect most aquatic life and its uses
(Federal Register, Vol.  45,  No.  231, November  28,  1980).  The
freshwater AWQC for acute effects  is 11,600 ug/1 for toluene.
There is no freshwater AWQC for acute effects for 1,1-DCA. The
freshwater AWQC for chronic effects is 20,000 ug/1  for 1,2-DCA
and 840 ug/1 for PCE. There is no chronic AWQC for
1,1-DCA,  1,1-DCE,  TCE,  or  toluene.   The acute and chronic
chemical-specific  AWQC  are  considerably higher than  the
concentrations  detected in production wells in  Rose Hills
Memorial Park in 1991 (maximum of  3 ug/1)  and  in the Whittier
Narrows Nature Center in 1987-1988 (less than 1 ug/1).
                           20

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7.0
DESCRIPTION OF THE "MONITORING ONLY" (NO ACTION)
ALTERNATIVE
As a general policy, EPA uses the results of the risk assessment to
establish .the need or basis for taking a' remedial action and
compares a "no action" alternative to several remedial (action)
alternatives. For this OU, the risk assessment established there
are currently no unaccepable risks present, therefore, no remedial
action and no comparison of remedial alternatives is necessary at
this time. .
Although the risk assessment has demonstrated that current risk at
the OU is well within EPA's acceptable risk range, EPA recognizes
that there is some degree of uncertainty as to the future
conditions at the OU. Therefore, EPA will continue the currently
operating groundwater monitoring network and supplement this
monitoring program with the instal~ation of up to nine additional
multiport or cluster - groundwater monitoring wells, plus
approximately eight single point wells, to gather groundwater data
where currently none exists. The new wells will be sampled for
inorganic and organic compounds. Design and construction of the
new monitoring wells will be consistent with current and potential
future remedial action goals of the basinwide Superfund project.

The approximate locations of the poten~~~l additional monitoring
wells are shown, in Figure 3. New well locations were selected to
fill data gaps in Whittier Narrows, to evaluate groundwater quality
entering Whittier Narrows, to evaluate local groundwater levels and
flow directions, and to serve as early warning wells for some
drinking water wells. Each new well will be a multiport well (if
more than three or four zones will be sampled, a cluster well (if
less than three or four zones are sampled), or a single depth well.
Figure 3 shows the approxiInate locations of the new wells. The
multiport wells have been designated as "A" priority and "B"
priority wells. The "A" wells, and the si,ngle point wells (at the
"B" priority locations) will be installed as a first phase in order
to fill data gaps downgradient of potential contaminant sources and
to establish some localized groundwater flow gradients. The "B"
wells, if needed, will be installed the following year, pending the
resul ts of local water level measurements and monitoring results of
the "A" wells and single point wells. The well logging and depth
specific sampling will be conducted concurrently (if technically
feasible) with the installation of the '''A'' priority wells and
single point wells.
In addition to the new monitoring wells, EPA will provide well
logging and depth-specific sampling of approximately ten existing
wells in the OU area. The locations of these wells are also shown
in Figure 3.

Validated monitoring data. will be shared with all interested
pat:ties. In addition, EPA will prepare an annual report summarizing
21

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the monitoring data collected from the expanded monitoring network.
This report will also be made  available to all interested parties.

Should  future  conditions change  to where an unacceptable risk is
present within the  OU  (i.e., a risk  greater  than  10~4,  or if
operating" drinking  water wells  are threatened  or  impacted by
groundwater contamination from the San Gabriel Valley) then EPA is
prepared to take the appropriate response(s).  Such response (s) may
include  an  accelerated  feasibility   study   to  determine  an
appropriate remedial action and/or the need to install additional
monitoring  wells,  or,  if response  time is critical,  a removal
action.  CERCLA Section  104 authorizes removal responses whenever
any  hazardous  substance  is  released or there  is  a substantial
threat  of such a release into the environment of any pollutant or
contaminant which may present an imminent and substantial danger to
the public health or welfare. In addition to  requirements of CERCLA
and  the NCP,  EPA  removal actions  will be  guided  by,  Superfund
Removal  Procedures   -   Action   Memorandum   Guidance.   dated
December,1990, and Interim Final Guidance on  Numeric Removal Action
Levels  at  Contaminated  Drinking  Water  Sites,   OSWER  Directive
9360.1-10, dated October 6, 1987.  Also,  removal action  levels for
some chemicals have  been revised  in a (Draft)  Final Guidance on
Numeric Removal Action  Levels at Contaminated Drinking Water Sites.
that  EPA is  currently  evaluating. This  "Final" guidance  will
replace the 1987 guidance once the evaluation has been completed.

If groundwater' data in  the Whittier Narrows OU show an unacceptable
risk or a" trend towards an unacceptable risk,  EPA  will begin to
evaluate the appropriate location(s) for extraction and treatment
systems.  For  operating drinking water  wells in  the San Gabriel
Valley  or  the  Central Basin  that  are unable to  meet federal or
state   drinking  water  standards   due  to   San  Gabriel  Valley
contamination, EPA may determine that well head  treatment or an
alternative  drinking water supply is necessary. Depending upon
contamination  levels,   EPA may  use  its removal authority for
drinking water wells threatened or  impacted by San Gabriel Valley
contamination because of the much quicker response time compared to
EPA's remedial authority.

The type of treatment will depend upon the contaminants present and
the  pumping rates  of  the  wells.    However,  based  on  treatment
systems in operation in  the San Gabriel Valley and Central Basin,
liquid-phase Granular Activated Carbon  (GAG) or air stripping may
be used.  Air  stripping systems  may require off-gas treatment to
meet air quality standards.  All treatment systems will be designed
to  meet  applicable  or  relevant   and  appropriate   requirements
(ARARs).

Water  reuse or  disposal from  new extraction  systems  will be
evaluated, and will  largely depend upon extraction rates and the
location of the extraction system relative to the point(s) of use.
                                22

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The total present worth cost associated with the implementation and
operation  and  maintenance  of phases  A  and B  of the  expanded
monitoring network,  plus the cost  of monitoring  the  existing,
network  is approximately $  5,200,000.  This  cost assumes a phased
installation approach with incremental costs discounted 5 percent
to  the  base  year.   Well installation  is scheduled to  begin in
fiscal year  (FY)  93.   The  period to  be used for  the  five-year
review will start when monitoring well installation begins.
                                23

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                      RECORD OF DECISION
       "MONITORING ONLY11 (NO ACTION) ALTERNATIVE SELECTION
                      RESPONSIVENESS SUMMARY

                  Whittier  Narrows Operable Unit
       San.Gabriel Valley superfund Site/  Areas 1  through 4
                  Los Angeles  County/  California

A.   OVERVIEW

At the time of  the  public comment period, the  US Environmental
Protection Agency (EPA)  had identified a preferred alternative for
the Whittier Narrows  Operable Unit, Los Angeles County, California.
EPA's  recommended alternative ("monitoring only")  addresses- the
need  to expand  the  existing  groundwater monitoring network  at
Whittier Narrows to enhance the continued monitoring of groundwater
quality within the operable unit area.  The preferred "monitoring
only" alternative, as specified in the Record of Decision, involves
the  installation of  additional  multiport or cluster  monitoring
wells and single point wells within the operable unit area, as well
as, additional depth-specific  sampling and well logging of existing
production wells.  EPA  recommended the  Whittier  Narrows Operable
Unit for a five  year review.

Additional monitoring work  will also be performed by local agencies
of the San Gabriel and Central Basins.  EPA is working with these
agencies to. coordinate field activities, and. to share and evaluate
monitoring-'data.

Judging from the comments  received during the  public meeting and
the  public comment  .period,  concerned  state  and  local agencies
strongly agreed with the need for an expanded monitoring  network at
Whittier  Narrows.   Of  major   concern to  these agencies  was the
number  and  location of  new  monitoring  wells   proposed to  be
installed  and  the  proposed   time  frame  recommended   for  their
installation.  Many agencies expressed a desire to be more involved
in the design and implementation of the  new monitoring network. In
addition,  the  agencies  recommended  that  a contingency plan for
groundwater  treatment be  part  of  any Record  of  Decision.  The
California Department of Toxic Substances  Control  (DTSC) expressed
the concern that EPA did not have sufficient data to characterize
the risk or to conclude that no remedial action was needed at this
time.  DTSC was also concerned that the  proposed monitoring system
may not provide early detection of contamination entering the OU
because of the large  distances  between the wells.   DTSC recommended
that all field work be completed  within a two year time frame.  EPA
also received  one comment  letter (from  a state agency)  after the
close  of  the  comment period.  Since the letter was received after
the
close of the comment period, EPA is not  required  to respond in the
responsiveness summary.  However, the  main comment expressed in the
letter was a general agreement with the comments  contained in the
comment  letter  submitted  by  the California Department of Toxic
Substances Control.

  No written  comments were received  from private citizens during

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the public comment period. Oral comments received from private
citizens attending the public meeting concerned drinking water
quality at'the tap (i.e., color, turbidity, etc.) and were not
considered significant to the low-level volatile organic compound
groundwater contamination at this operable unit. These citizens
were referred to their local water purveyor.'
These sections follow:
.
Background on community Involvement.
.
Summary of Comments Received During PUblic Comment Period
and EPA Responses.
B.
BACKGROUND ON COMMUNITY INVOLVEMENT.
EPA identified the San Gabriel Valley as a Superfund site due to
the detection of a variety of organic contaminants in the
groundwater and surface waters in the San Gabriel Basin. The EPA
listed this srte as the San Gabriel Valley Superfund Site, Areas 1
through 4, on the National Priorities List in 1984. Because of the
large size and complexity of the San Gabriel Basin, EPA has
organized the groundwater investigation into six distinct Operable
Units (aU): Whittier Narrows OU, Richwood au, Suburban au, Baldwin
Park au, Puente Valley OU, and the Sout~ El Monte OU.

Contaminate"d groundwater from sources within the San Gabriel Valley
Superfund Site, Areas 1 through 4, must first flow through the
Whittier Narrows before exiting the San Gabriel Basin. EPA
identified the Whittier Narrows as an operable unit to evaluate
groundwater quality data within the OU to determine what risks are
posed by groundwater conditions within the OU and, if necessary,
limit or control the migration of impacted groundwater through the
Whittier Narrows.
EPA is pursuing overall remediation of the San Gabriel Valley
Superfund, site, Areas 1 through 4, at two levels: 1) in
cooperation with the Los Angeles Regional Water Quality Control
Board (LARWQCB), LARWQCB-lead investigations and remediation of
soil and shallow groundwater at individual facilities (source
investigations), and 2) EPA-lead investigation and remediation of
deeper, regional groundwater contamination potentially originating
from mUltiple facilities. These two elements are being implemented
concurrently within the San Gabriel Basin.
To date, over 300 General Notice letters have been issued, by EPA,
to potentially responsible parties throughout the San Gabriel
Valley. special Notice letters will be issued for the Baldwin Park
and Puente Valley OUs in 1993.

EPA had previously prepared a Feasibility Study for Whittier
Narrows in 1989, which evaluated various remedial alternatives,
based on computer modeling predictions of increasing contamination
2

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levels in Whittier Narrows. Subsequent groundwater monitoring did
not support these modeling predictions. Based on the groundwater
monitoring data and the hydrogeologic complexity of the area, EPA
had decided that is will no longer rely' on computer modeling for
predicting future contamination levels in this OU. (See EPA
response tc'~'general comment #11.) .
The Feasibility study Report and Proposed Plan for the Whittier
Narrows Operable Unit were released to the public in September
1992. These two documents were made available to the public in the
administrative record file at an information repository maintained
at the EPA Docket Room in Region 9 and at the Whittier Central
Public Library. The notice of availability for these two documents
was published in the Los Angeles Times on September 15, 1992.

This notice briefly described the proposed alternative and
announced the public comment period and the upcoming public
meeting. The notice also announced locations where the Whittier
N~~~QWS Operable Unit Feasibility Study (OUFS) report could be
reviewed. The OUFS report was located in the Whittier Central
Public Library and the EPA Region IX office in San Francisco.
EPA also prepared a 7-page fact sheet describing the Whittier
Narrows OUFS report and EPA's recommended alternative. Copies of
the fact sheet were mailed on September 14, 1992 to the general
mailing list for the San Gabriel Vall~y. Superfund site. This
general mail.ipg'list consisted, at the time, of approximately 1,955
names, inciuding elected officials, Potentially Responsible Parties
(PRPs), media representatives, and repres~ntatives of various
cities and water districts in the Central and San Gabriel Basins.
A public comment period was held from September 16, 1992 through
November 16, 1992. In addition, a public meeting was held on
September 23, 1992. At this meeting, representatives from the u.S.
Environmental Protection Agency, Region 9 answered questions about
the au and the "monitoring only" alternative under consideration.
A response to the comments received during this period is included
in this document, which is part of this Record of Decision. The
Record of Decision presents the "monitoring only" (no action)
alternative selected for the Whittier Narrows Operable unit, in Los
Angeles County, California, chosen in accordance with CERCLA, as
amended by SARA, and the NCP. The decision for this OU is based on
the administrative record.
3

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C.
SUMMARY OF COMMENTS RECEIVED DURING PUBLIC COMMENT PERIOD
Comments received during the Whittier Narrows Operable unit public
comment period for the Feasibility Study Report and Proposed Plan
are summar.ized briefly below. The comment'period was held from
September 16 to November 16, 1992. The comments are divided into
two categories: General Comments are those comments that pertain
to the general proj ect approach and were common to most of the
agencies submitting comments, unless otherwise stated; and Specific
Comments are comments that pertain to specific technical issues of
the Feasibility study or Proposed Plan.
GENERAL COMMENTS
1.
Most of the local agencies located in the San Gabriel and
Central Basins stated that EPA should continue to solicit
input from them regarding remedial acti vi ties in the
Whittier Narrows area. Many agencies suggested that EPA
designate one local agency to take the lead for
developing the design and implementation of new
monitoring wells. Many of these agencies also
recommended a second public meeting, to be located in the
Central Basin, to provide private citizens and local
agencies, within the Central Basin, a better forum for
~.~essing their comments and,"concerns.

EPA Response EPA considers one public meeting
,sufficient. Should the need arise, there will be other
opportunities for public input as described in EPA's
response to comment #2 below. Also, EPA is willing to
meet with interested parties to discuss the proposed
expanded monitoring network, and to meet and, discuss
monitoring results and potential modifications to the
monitoring network. EPA will retain the lead for the
design and installation of new monitoring wells and for
any remedial actions as part of the Whittier Narrows
Operable unit.
2.
Many of the agencies submitting comments recommended that
a contingency plan be included in the Proposed Plan for
the Whittier Narrows Operable Unit, since no remedial
actions have been identified. '
EPA Response - Based on the results of the continuing
groundwater monitoring effort and :the risk assessment for
the Whittier Narrows Operable unit, EPA has determined
that no remedial action is necessary at this time for the
continued protection of human health and the environment.
EPA rec6gnizes however, that there is some degree of
uncertainty as to the current condition in the au. In
the event that future groundwater monitoring results
within the operable unit change to where an unacceptable
4

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risk' (e.g. greater than 10-4) is present within the
operable unit, EPA is prepared to take the appropriate
response (s) . Potential response actions (such as an
accelerated feasibility study, additional monitoring well
installation, drinking water well-head treatment, or use
af EPA's removal authority) are described in the Record
of Decision for the Whittier Narrows Operable Unit. EPA
has met with the state and local agencies and has agreed
to continued discussions of trigger criteria and
potential contingency actions, outside of the framework
of the Record of Decision. However, the conunenters
should recognize that developing trigger criteria and
contingency actions will be very difficult because of
lack of information regarding where contamination sources
originated and where contamination may be found, the
specific contaminations that may be found, where
extraction systems will be located, what extraction rates
should be, and what to do with the treated groundwater.
EPA believes that there are too many uncertainties to
developing a contingency plan with any measureable degree
of accuracy. Before any remedial or non-time critical
removal actions are undertaken by EPA, there will be a
minimum of 30 days allowed for the general public to
comment on EPA's proposed actions.
3.
Water generated from Whittie:r;' Narrows project-related
activities (i.e., spinner logging,' groundwater sampling,
etc.) should be put to the maximum beneficial use
possible.
4.
EPA Response - EPA concurs and will do so whenever it is
practicable. It should be noted that water from spinner
logging, if disposed of on the ground will recharge the
aquifer to a certain degree as the water percolates
through the ground into the aquifer.

Many of the agencies submitting comments stated that the
cost of assistance from local agencies or the costs
associated with treatment plants required on production
wells because of contamination from the San Gabriel
Valley should be reimbursable from the Superfund.
EPA Response - Unless there i.s a formal cooperati ve
Agreement between EPA and another agency, assistance
(including well-head treatment) provided by local
agencies is typically not reimbursed from Superfund. EPA
does however appreciate the cooperative efforts of the
local agencies, and may be able to provide guidance in
future to the local agencies on how to recover costs from
PRPs.
5.
Many of .the agencies submitting comments noted that
treatment of groundwater should consider both Federal and
State of California requirements and regulations.
5

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     EPA Response - Any removal actions taken by EPA involving
     treatment  of groundwater,  will comply  with  Federal,
     state, and local applicable or relevant and appropriate
     requirements (ARARs)  to the  extent  practicable.   Any
     remedial actions involving treatment of groundwater will
     comply  with ARARs  unless a  formal  waiver is  deemed
     necessary  and  justified by  EPA.   It should be  noted
     however, groundwater treatment was not  formally evaluated
     in  the  OUFS and   Proposed  Plan  because  groundwater
     conditions and EPA's risk  assessment do not indicate any
     significant risks to human health or the environment.

6.   The Proposed Plan does  not provide  sufficient security
     that a remedial action will be undertaken in the Whittier
     Narrows Operable Unit when warranted.

     EPA  Response  - Although a  remedial  action  is  not
     warranted at this time, EPA remains committed to take the
     appropriate  remedial  or  removal action,  if and  when
     necessary.  EPA intends to exercise its removal authority
     if  appropriate,  if a  situation arises  that does  not
     permit  the time required  to adequately  implement  the
     remedial action process.  The removal action process is
     described  in the Record  of  Decision for  the Whittier
     Narrows Operable Unit  and in the National Contingency
     Plan  (NCP).  All EPA monitoring data  from the Whittier
     Narrows monitoring network will  be made available to all
     Interested parties. In addition, EPA is willing to meet
     with interested parties to  discuss groundwater quality
     data and potential  contingency  measures.   EPA believes
     its remedial and removal authorities under CERCLA and the
     NCP,  combined with  its commitment to share monitoring
     data and to meet with interested parties, is sufficient
     security that remedial action will be taken if warranted.

7.   Many agencies commented that  the technical basis for the
     phased installation of the proposed new monitoring wells
     has not been adequately described.

     EPA Response -  EPA feels it is not  prudent to install
     all the monitoring wells at this time,  because installing
     all of the proposed new monitoring wells right away may
     lead to well locations that are  not ideal. This approach
     may lead  to an inefficient monitoring network  and may
     lead to the placement of previously unneeded additional
     wells, thereby  increasing monitoring costs.  On the other
     hand,  a phased  installation approach  allows for  the
     optimum  placement  of   any  succeeding wells once  the
     priority wells have  been installed and  analytical results
     from  these  wells   have been  assessed.     EPA  has  in
     cooperation  with state  and local agencies, prioritized
     the installation of the multiport wells as  "A" and "B".
     The "A" wells plus approximately eight single point wells
     will be installed first. The  "B" wells will  be installed

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8.
after water level measurements have been taken
monitoring from the "A" wells has been evaluated.
anticipates both phases of the new wells will
installed in approximately a 2 year period.

Many' agencies commented that the approach described in
the proposed plan does not offer a 5-year early warning
system, as stated, but perhaps as little as 2-years.
and
EPA
be
9.
EPA Response - EPA believes there is at least a 5 year
warning period for groundwater contamination entering
Whi ttier Narrows from areas north of Highway 60. Of
course contamination already within Whittier Narrows
could reduce contamination travel time to the Central
Basin. The monitoring network, however, should be able
to detect this contamination and provide sufficient early
warning to take appropriate actions. The travel time
estimates are based on approximate continuous groundwater
flow times. Conservative groundwater flows were used in
these approximations. Furthermore, 'given EPA's removal
authority and its commitment to accelerate its remedial
process, EPA is confident that even a two year warning
will be sufficient to respond.

Many local agencies commented that a data gap is present
in the western segment of'the..Whittier Narrows that was
~~~'. c,onsidered in the proposed new monitoring network.
BPA Response - EPA has been meeting with and will
continue to meet with interested parties (e.g. ,state and
local agencies) to refine monitoring well locations. The
"final" monitoring well locations and prioritization of
the placement of the wells (shown in figure 3 of the ROD)
. were chosen by BPA and were based on comments received by
EPA. Actual field conditions and future monitoring
results however, may cause some monitoring wells to be
relocated from the locations depicted on figure 3 of the
ROD.
10.
Several local agencies stated that it is their
preliminary opinion that the source of contamination
(present above state, and federal maximum contaminant
levels) found in one well loca~ed in Pico Rivera is the
San Gabriel Valley.
EPA Response - The source of this contamination is not
clear. There are' potential source areas wi thin the
Central Basin which need to be evaluated. EPA is
currently working with a local agency to' investigate
potential sources in the pico Rivera area. Placement of
new monitoring wells, as part of the Whittier Narrows
Operable Unit Proposed Plan, may also assist in
evaluating the source of this contamination.
7

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11.  Several agencies commented that the Feasibility Study for
     the Whittier Narrows Operable Unit makes no attempt to
     -forecast  future  groundwater  conditions  within   the
     Narrows.   The  study  assumes that  concentrations  of
     contaminants remain constant and, therefore, the health
     risks remain constant.  The technical basis for assuming
     constant contamination concentrations in the  future is
     not  adequately described.    Past  EPA  analyses  have
     forecast rising contaminant levels  in the Narrows.

     EPA Response - Current monitoring results  collected by
     EPA  have  shown  that  contaminant  levels  within  the
     Whittier Narrows area have not risen  according to  past
     predictions.   Instead of  an  increase  in  contaminant
     levels, there  appears  to  be a decrease  in contaminant
     levels.  Changing groundwater conditions may be affected
     by  many  complex  factors,  including  retardation  and
     natural  attenuation  of  contamination,   as   well  as
     upgradient remedial  activities  and the  elimination of
     sources.    EPA  used  groundwater   modeling  (computer
     modeling) in an  attempt  to predict  future groundwater
     chemical contaminations.   In order to be protective of
     public health,  very conservative assumptions were used in
     the model (e.g. the highest chemical concentrations found
     In groundwater were used,  and chemicals  would move at
     the same  rate  as groundwater) , and  did not  take  into
     consideration  such  factors  as natural  attenuation,
     retardation, and the ongoing elimination of contamination
     sources.  In addition,  other factors affecting chemical
     movement in groundwater such  as hydraulic conductivity
     and   hydraulic   gradients   were    areally   averaged
     (simplified) to take into account  variations  in those
     parameters.  However,  local (as opposed to the larger
     areal)  variations   in  these  parameters  could  affect
     groundwater  flow  and  therefore contaminant  movement.
     Because it now appears  the assumptions used in the model
     were too conservative,  EPA expects from now on to rely on
     field data for indicating trends in contaminant levels
     rather  than using  modeling  to  predict  contamination
     levels in the Whittier  Narrows.  Plus, the complexity of
     groundwater  conditions there  makes  it unlikely  that
     modeling  can  be   used to  accurately  predict  future
     groundwater chemical concentrations.

12.  Many  agencies  commented  that,  in  accordance  with the
     Montebello Forebay protection  strategy, the installation
     of  well  head treatment   systems   is   essential  for
     protection  of  the  drinking water  within the Central
     Basin.

     EPA Response - Generally,  EPA  agrees that for production
     wells  that  cannot  meet drinking water  standards,  well
     head treatment may  be appropriate.   EPA will evaluate any
     such problems which appear to  be caused by contamination

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. .-.- .~..-
from the San Gabriel Superfund sites and determine, in
consultation with state and local authorities, what, if
any, action is warranted. .
SPECIFIC COMMENTS
1.
The California Department of Toxic Substances Control
(DTSC) commented that a screening risk assessment is
inappropriate at the level of an OUFS. Such a risk
assessment should be thorough and quantitative, per U.S.
EPA guidance. DTSC also questioned the existence of a
Remedial Investigation Report.

EPA Response - The EPA refers the-DTSC to OSWER Directive
9355.0-30. contained within this document is the
following: "Early and interim action RODs do not require
a completed baseline risk assessment, although enough
information must be available to demonstrate the
potential for risk and the need to take action. Data
sufficient to support the interim action decision can be
extracted from the ongoing RIfFS for the site and set out
in a focused feasibility. study or other appropriate
dQcUltlent that includes a short analysis of a limited
number of alternatives (55 Fed. Reg. at 8704)." Because
the Whittier Narrows ROD is for an interim action, the
criteria for a screening risk assessment has thus been
satisfied. A basinwide Remedial Investigation Report is
available at the Whittier Central Public Library and in
the EPA Region IX information repository.
2.
The DTSC commented that this OUFS addresses only volatile
contaminants in groundwater. If other organic chemicals
were sought, these data are absent and not mentioned.
Inorganic contaminants are surely present at this site at
levels above background. Therefore, it seems highly
probable that potential health risks are underestimated
in the documents reviewed. At the very least, estimates
of risk are made greatly more uncertain by the exclusion
of these classes of chemicals,. but such uncertainty is
not reflected in Table 6-9 of the Feasibility Study
Report.
EPA Response - All organic chemicals that were positively
detected in at least one sample were included as
contaminants of potential concern (COPCs). Admittedly,
inorganics were not the focus of the RIfFS or the risk
assessment. The risk assessment acknowledges that
inorganics present in the groundwater may present
additional risk (p. 6-31). EPA cannot respond to the
statement that II inorganic contaminants are surely present
at this site above background," since, as far as we know,
background levels have not been established for this
9

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     area.   New monitoring wells  installed  as part  of  the
     Whittier Narrows monitoring network will be sampled for
     inorganics.

3.   The DTSC commented that for exposure pathways, residents
     could be exposed to contaminants of potential concern via
     volatilization from underground sources,  but this pathway
     is apparently dismissed.   Given that groundwater is the
     only contaminated media,  please construct a  matrix of
     possible  exposure  routes, as  shown in U.S. EPA  risk
     guidance, Exhibit 6-7.

     EPA Response - We disagree that the universe of possible
     exposure pathways should be quantitatively evaluated in
     a screening baseline risk  assessment.  Dominant pathways
     of   exposure   were   addressed  in  the  interim  risk
     assessment.   Because  dominant pathways did  not  show a
     significant   risk,   it   is  extremely   unlikely  that
     additional  pathways,   such  as  volatilization  from
     underground sources,  would pose a significant risk.

4.   The DTSC commented that on Page 6-10, Table 6-24 of the
     Feasibility Study  Report, they  do  not  understand  the
     meaning of the "P" data qualifier, which is stated to be
     used  for data  for  which both  the "J"  and "U"  data
     qualifier  apply.    According  to  U.S.  EPA  guidance
     documents on data validation and risk assessment, the "J"
     and "U" categories are mutually exclusive.  If an analyte
     is not detected, its concentration cannot be estimated.

     EPA Response  -  "U" and  "J"  categories  are not mutually
     exclusive.    A  "UJ"  qualifier  indicates  an estimated
     quantitation  limit.   The compound was analyzed for,  but
     not  considered  non-detected.    Because  of  analytical
     problems,   the  quantitation  limit   is  approximated
     (estimated).  The "P" qualifier means that both the "J"
     and "U" qualifiers apply.

5.   The DTSC commented on Page 6-18 of the Feasibility Study
     Report,  for Tables  6-4 and  6-7, the 95 percent upper
     confidence  limit (UCL)  on the  mean concentration is
     incorrectly referred  to  as  an "upper 95th percentile."
     These  terms are not  synonymous.   The  95th percentile
     values for chemical concentrations would be considerably
     higher  than the 95  percent UCLs, which are the values
     correctly shown on the tables.  Please correct the use of
     these terms.

     EPA  Response  -  We acknowledge this  error.  However, it
     does not affect the outcome of the risk assessment.

6.   The  DTSC   commented  on  Page   6-4  and   6-76  of  the
     Feasibility Study Report,  Frequency  of Detection  - Based
     on Table 6-2,  we tallied the ratio of the number of tiroes


                           10

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a chemical was detected to the number of samples analyzed
for that chemical. Data qualified with a IIJII" "L", or
~P" were scored as detections. These data, especially'
the denominators, disagree with the ratios shown in
Tables 6-5 and 6-7. Since these denominators are used in
the calculation of the 95 percent UCLs on mean chemical
concentrations (mean.:!: s.d. /nl/2), these discrepancies
should be resolved.
EPA Response - Monitoring Wells EPAMW011, EPAMW012,
X11TMA01, and X11TMAG1 did not contain detectable levels
of VOCs. As the risk assessment states (p. 6-18), these
wells have not been included in the evaluation of '
groundwater exposures. This likely explains the
inconsistency wi th respect to the denominators.
Regarding the numerator, the inclusion of the "P"
qualifier as a detection is not appropriate (see above).
7.
The DTSC commented on the Dermal Exposure portion of the
Feasibility study Report. Risks from dermal exposures to
volatile organic chemicals in domestic water can be
greater than portrayed in this section. DTSC believes
risks due to dermal exposure to volatiles in domestic
wat~r. should be quantified.' ,"The. most recent guidance
from U. S. EPA on the subj ect of dermal exposure to
volatiles is "Relevant Contribution of Dermal Exposure to
Total Absorbed Dose," which is Chapter 9 in Interim
Guidance for Dermal Exposure Assessment. The
contribution of the dermal pathway for, ethylbenzene,
tetrachloroethene, and trichloroethene in domestic water
is estimated to be between 2 and 20 percent of total
exposure via ingestion, inhalation, and dermal exposure.
Therefore, addition of the dermal route might be expected
to increase estimates of risk by less than a factor of
two. This is strikingly different from statements in the
OUFS which dismisses risks from the dermal route as being
several orders of magnitude less than those from
ingestion and inhalation.

EPA Response - The risk assessment did not discount the
dermal route based on the risks 'being "several orders of
magnitude less than those from ingestion and inhalation"
as is implied in the comment. Rather (p. 6-22), the
"screening assessment does not quantitatively estimate
dermal absorption from household water use because of the
uncertainty associated with making a quantitative
estimate of such an exposure." The risk assessment does
state that the absorbed dose through dermal exposure
could be several orders of magnitude less than through
ingestion of tap water. We also acknowledge that the
exposure could be 2 to 20 percent of the ingestion dose.
Even if one were to assume these latter estimates
provided by the reviewer, the conclusions of the interim
risk assessment would not be affected.
11

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10.
8.
The Water Replenishment District (WRD) of Southern
California commented that the Feasibility study Report
fails in its water quality assessment of impacts to the
Montebello Forebay of the Central Basin by neglecting to
account for existing TCE and PCE contamination already
existing in the Central Basin. The screening baseline
risk assessment provided in Section 6 of the report does
not take into account potential health impacts to
Montebello Forebay consumers which are already receiving
a background or baseline level of PCE contamination in
drinking water supplies. Therefore, an assessment should
be made of potential health impacts and water quality
treatment requirements for Montebello Forebay wells
receiving the incremental contamination from Whittier
Narrows.
EPA Response - We found the risks to be insignificant in
the Whittier Narrows. The risks would still be
insignificant when added to the Montebello Forebay of the
Central Basin. Not knowing the background or baseline
level of PCE contamination in drinking water supplies at
the Montebello Forebay let us assume two different
scenarios. The first scenario assumes that no other
sources of contamination besides Whittier Narrows would
be responsible for contamination in the Central Basin.
In this case, the concehtrations present in the
MQn~ebello Forebay would be predicted to be similar to
concentrations in Whittier Narrows (barring the presence
of an isolated spot of contamination that has already
moved through Whittier Narrows) and no additic;mal risk is
predicted. For the second scenario, let us assume that
the contamination is rather high in the Montebello
Forebay (close to 1 in 10,000 excess cancer risk) due'to
other sources. In this case, the incremental risk from
Whittier Narrows (assuming no dilution) would still be
insignificant relative to the preexisting risk and no
additional water quality treatment requirements would be
necessary. '
9.
The WRD commented that the proposed revised Record of
Decision for the Bortollo (Suburban) Well Field Operable
Unit should be developed in conjunction with the Record
of Decision for the Whittier Narrows Operable Unit.
EPA Response - The monitoring of groundwater quality
within the Whittier Narrows will take into account the
groundwater affecting the Suburban Operable Unit. After
the Records of Decision for both the Suburban and
Whittier Narrows Operable Units are signed, EPA will
manage these operable units together as one area.
Suburban wells will also be part of the Whittier Narrows
monitoring network.
The WRD commented that
even
though the average blended
12

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water quality for subsurface flow coming through the
Whittier Narrows into the Central Basin meets drinking
water standards for trace ,organic compounds, water
flowing through the Narrows at specific depths is in
excess of standards for both ,TCE and PCE. The
?easibility Study Report should address potential
remedial action at specific depth intervals for both TCE
and PCE. Depth-specific production and treatment would
be very effective in significantly reducing the mass
transport of these industrial solvents of concern into
the Central Basin.
. .
EPA Response - The residents of Whittier Narrows and the
Central Basin are exposed to groundwater that is blended
from multiple aquifer zones o.r intervals. Discrete
intervals of production wells are not points of exposure
for residents. At such low concentrations (barely above
MCLs) , it would be premature and it would not be cost
effective to initiate remedial activities for these
discrete intervals. However, depth specific production
and treatment may be appropriate if future data show
increased contamination levels, and EPA will certainly
evaluate this method if a remedial action is warranted.
11.
The City of Pico Rivera. requested that 'the City be
incl~ded in the FeasibilitX.'st\,ldy. for the Whittier
Narrows Operable Unit so that its wells may serve as an
early warning system for the Central Basin.

EPA Response - Selected wells in the City of Pico Rivera
(see figure 3 of the Record of Decision) will be included
in EPA' s expanded monitoring network for the Whittier
Narrows Operable Unit to determine the extent that
contaminants from the San Gabriel Basin are impacting the
Central Basin. EPA believes that the monitoring wells
currently in place and the proposed new wells to be
placed north of the whittier Narrows Dam are better
suited as early warning wells for the Central Basin.
*12. The California State Water Resources Control Board
(SWRCB) requested clarification on, (a) how' hydraulic
conductivity was estimated from specific gravity tests,
(b) how aquifer tests were used to determine hydraulic
conductivity.
EPA Response - (a) - For specific capacity test data
that included information on the duration of pumping, the
transmissiVity was estimated using the Cooper - Jacob
approximation (1946). This methodology assumes that the
drawdown is small compared to the initial saturated
thickness (additional assumptions are listed in Cooper
and Jacob (1946) and Bear (1979). For specific capacity
test data that did not include information on the
duration of pumping, the transmissivity was estimated
13

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     from  the  Theim  equation  (Bear,  1979).     Hydraulic
     conductivity   was  estimated   from   the   values   of
     transmissivity by dividing the  transmissivity  by  the
     length  of  the  well  in the  saturated  alluvium.    As
    .mentioned in  the OUFS,  additional discussion  of  this
    •methodology is presented in the San Gabriel Supplemental
     Sampling Program Report  (EPA,  1986)

     (b) -  Some of the aquifer test data were from tests
     analyzed by the California  Department of Water Resources
     (CDWR,  1966)  in  their  Bulletin  104-2.   CDWR  used  the
     methods of Theis  (1935)  and Chow (1952).   Aquifer test
     data  from  the  monitoring wells installed  by  EPA  in
     Whittier Narrows  were  evaluated  using  the  Cooper-Jacob
     approximation  (1946).   These  analyses assume  that  the
     well  penetrates   an   aquifer   that   is  homogeneous,
     isotropic,  and of  infinite horizontal extent.  Additional
     assumptions are discussed in Bear (1979).

13.   The  SWRCB  also commented  that  the equation  used  for
     calculating groundwater velocity  on  page  A-2  of  the
     Whittier Narrows OUFS, yields only an average velocity.

     EPA Response - We agree with  the comment made that the
     equation V=Ki/ne  yields  only  an  average  velocity.   The
     velocity calculated with this equation would represent
    .the average velocity over the  volume of the aquifer that
     the parameters were measured  in.   For example,  if the
     gradient "i", hydraulic conductivity  "K",  and porosity
     "ne" were  estimated at  two  wells, the  velocity would
     represent  average  velocity  between  the  two  wells.
     However, because hydrogeologic properties and groundwater
     discharge/recharge may  vary between the  two wells,  the
     actual  velocity at any point in  space between the two
     wells may vary from the estimated average velocity.

     In Whittier Narrows, hydrogeologic data from wells (i.e.,
     individual,  discrete   points  in  space)  are  the  only
     available data for estimating the groundwater velocity.
     It  is thus  necessary to utilize estimates of "average
     velocity" based  on data from wells,  even  though  the
     velocity may  vary between the wells.   Because  another
     draft of the OUFS report will not be  produced,  we will
     unfortunately not be able to add more text to further
     clarify this point.  The average velocity  estimated could
     be used  to estimate the average velocity for transport of
     a contaminant  if  the  contaminant travelled at the same
     velocity as the groundwater.
                           14

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*References
Bear, J.
HYdraulics of Groundwater.
MCGraw-Hill, New York.
1979.
California Department of Water Resources. Planned Utilization of
Ground Water Basins. San Gabriel ValleY. ADDendix A: GeohYdroloqy.
Bulletin 104-2. 1966.
Chow, V. T. On the Determination of Transmissivity and Storage
Coefficients from Pumping Test Data. Transactions American
GeoDhysical Union. 33:397-404. 1952.
Cooper, H. H., Jr. and C. E. Jacob. A Generalized Graphical Method
for Evaluating Formation Constants and Summarizing Well Field
History. Transactions American Geophysical Union. 27: 526-534.
1946
EPt\;- see United States Environmental Protection Agency.
Theis, C. V. The ~elationship Between the Lowering of the
Piezometric Surface and Rate and Duration of Discharge of a Well
Using Groundwater Storage. Transactions American Geophvsical
Union. 16: 519-524. 1935.
United States Environmental Protection Agency, Draft San Gabriel
Supplement~l Samplinq Proqram ReDort. Volume 2. Prepared by CH2M
Hill, May -19.;. 1986.
15

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MAILING LIST FOR WHITTIER NARROWS OUFS
Jim Goodrich
Main San Gabriel Basin Water
425 East Huntington Drive
Monrovia, CA 91016
Quality Authority
Tim Jochem
Upper San Gabriel Valley
11410 E. Valley Blvd.
El Monte, CA 91731
Municipal Water District
Tim Hampton
Metropolitan Water
1111 Sunset Blvd.
P.O. Box 54153
Los Angeles, CA 90054-0153
District of Southern California
Mike Sorensen
California Department of Toxic Substances Control
P.O. Box 806
400 P Street, 4th Floor
Sacramento, CA 95812-0806
Jon Bishop
California Regional Water
101 Centre Plaza Drive
Monterey Park, CA 91754
Quality Control Board, Los Angeles
John Maulding
Main San Gabriel Basin Watermaster
425 E. Huntington Drive, suite 200
Monrovia, CA 91016
Ken Harris
State Water Resources
901 P Street
Sacramento, CA 95814
Control Board
~ob Stalling
San Gabriel Valley Municipal
549 E. Sierra Madre Ave.
P.O. Box 1299
Azusa, CA 91702
Water District
Richard Atwater
General Manager
Central Basin Municipal
7439 East Florence Ave.
Downey, CA -90240-3699
Water District

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jeff Helsley
District Engineer
central and West Basin Water Replenishment District
1261 East 166th Street
Cerritos, CA  90701

John Norman
General Manager
Central and West Basin Water Replenishment District
1261 East 166th Street
Cerritos, CA  90701

Robert Wagner
Chairperson
Southeast Water Coalition
12700 Norwalk Blvd.
Norwalk, CA  90651-1030

Mike Stover
Assistant City Manager
City of Lakewood
5050 Clark Ave.
Lakewood, CA  90712

Thomas M. Regan
Bookman - Edmonston Engineering, Inc.
100 North Bravo Blvd., Suite 600
Glendale, CA  91203-  2699

Fran McPoland
c/o Rep. Esteban Torres
U.S. House of Representatives
1740 Longworth House  Office Bldg.
Washington, D.C.  20515

Richard Powers
City Manager
Norwalk City Hall
12700 Norwalk Blvd.
Norwalk, CA  90650
                                           Engineer

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PROPOSEO UON I TOR I NG
PLAN - WHITTIER NARROWS
. RECORD or DECISION
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