PB99-964503
EPA541-R99-043
1999
EPA Superfund
Record of Decision:
San Gabriel Valley Site (Area 1)
El Monte OU
Los Angeles, CA
6/23/1999
-------
-------
SFUHO fteCCROS CTK
49056
INTERIM RECORD OF DECISION
SAN GABRIEL VALLEY SUPERFUND SITE
EL MONTE OPERABLE UNIT
LOS ANGELES COUNTY, CALIFORNIA
June 1999
United States Environmental Protection Agency
Region IX - San Francisco, California
-------
-------
Contents
Page
Part I - Declaration 1-1
1.1 Site Name and Location I-l
1.2 Statement of Basis and Purpose I-l
1.3 Assessment of the Site .. I-l
1.4 Description of the Selected Remedy I-l
1.5 Statutory Determinations 1-2
1.6 ROD Data Certification Checklist 1-2
Part II - Decision Summary II-l-l
1 Site Name, Location and Description II-l-l
1.1 Site Description II-l-l
2 Site History and Enforcement Activities II-2-1
2.1 Site History H-2-1
2.2 Remedial Investigation Activities II-2-1
2.3 Enforcement Activities II-2-2
3 Community Participation II-3-1
4 Scope and Role of Operable Unit II-4-1
5 Site Characteristics 11-5-1
5.1 Location and Topography II-5-1
5.2 Surface Water [1-5-1
5.3 Geology 11-5-2
5.3.1 San Gabriel Basin II-5-2
5.3.2 El Monte OU II-5-2
5.4 Hydrogeology II-5-3
5.4.1 San Gabriel Basin II-5-3
5.4.2 El Monte OU II-5-3
5.5 Groundwater Management II-5-4
5.5.1 San Gabriel Basin Judgment II-5-4
5.5.2 Long Beach Judgment II-5-5
5.6 Groundwater Contamination II-5-5
EM ROD.DOC
-------
Contents
Page
8
0-2 Groundwater Uses \\ • II-6-1
7 Summary of Site Risks II~6"1
7.1 Summary of Human Health Risk Assessment n~7^
/.I.I Identification of Chemicals of Concern "-7-1
7.1.2 Exposure Assessment H-7-1
7.1.3 Toxicity Assessment H-7-2
7.1.4 Risk Characterization 11-1-2
7.2 Summary of Ecological Risk Assessment''.".'.'.'.'.'.".'.'.' IJ-7-3
7.3 Conclusion l1'7'5
Remediation Objectives H-7-5
9 Description of Alternatives ' Ir"8"1
9.1 Alternative I -No Action .' H-9-1
9.2 Alternative 2 - Groundwater Monitoring n'9-l
y.2.1 Monitoring . II-9-I
0*7 * *. . ° *"*"•••*••»».«___.
9.3.2 Treatment ........... ' " .................... • ................. II-9-2
9.3.3 Conveyance and Discharge ...................................... ll~9-2
9.3.4 Monitoring ____ ...................................... II-9-2
. and
9.4.1 Extraction ____ ........................................... II-9-3
9.4.2 Treatment ....... ' ." .' ......................................... II-9-3
?onveyance. Discharge and Monitorine ............................ n"9'3
9.5.1 Extraction ........ ............................. II-9-4
9.5.2 Treatment ........ .".".'.' ....................................... II-9-4
9.5.3 Conveyance and Discharge .............. ........................ • H'9'4
9.5.4 Monitoring ............. ............................. - ...... II-9-4
10 Comparative Analysis of Alternatives .............................. ^'^
Threshold Criteria ....... .............. * ................... II-IO-l
Primary Balancing Criteria ..." ...................... .................. II-IO-l
Modifying Criteria . . ................................... ..... II-IO-l
' ?o"n" OvS P° °f "'""'"' kea'"h and ilie E«vironraen, ................... H'!?-]
............
.................................. IMO-2
EM_ROD.DOC
-------
Contents
Page
10.2 Compliance with ARARs II-l0-2
10.2.1 Compliance with ARARs: Evaluation of Alternatives II-10-2
10.3 Long-Term Effectiveness II-10-3
10.3.1 Long-Tenn Effectiveness and Permanence: Evaluation of
Alternatives II-10-3
10.4 Reduction of Toxicity, Mobility, and Volume Through Treatment II-10-3
10.4.1 Reduction of Toxicity, Mobility, or Volume Through Treatment:
Evaluation of Alternatives 11-10-4
10.5 Short-Term Effectiveness II-10-4
10.5.1 Short-Term Effectiveness: Evaluation of Alternatives II-10-5
10.6 Implementability II-10-5
10.6.1 Implementability: Evaluation of Alternatives ... . II-10-5
10-7 cost ;;;;;;; n.10.6
10.7.1 Cost: Evaluation of Alternatives II-10-7
10.7.2 Cost: Comparison of Alternatives II-10-7
10.8 State Acceptance II-10-7
10.9 Community Acceptance II-10-7
11 Selected Remedy jj.j ^
11.1 Description of the Selected Remedy II-! 1 -1
1 l.l.l Performance Criteria . . H-l 1-1
11.1.2 Compliance with Performance Criteria II-l 1-2
11.1.3 Supplemental Explanation of Performance Criteria IT-11-3
11.2 Summary of the Estimated Remedy Costs II-l 1-5
11.3 Expected Outcomes of the Selected Remedy II-l 1-5
12 Applicable or Relevant and Appropriate Requirements (ARARs) II-12-1
12.1 Chemical-specific ARARs II-12-2
12.1.1 Federal Drinking Water Standards II-12-2
12.1.2 California Drinking Water Standards II-12-3
12.2 Location-specific ARARs II-12-3
12.2.1 Location Standards forTSD Facilities II-12-3
12.2.2 Endangered Species Ace II-12-3
12.2.3 California Fish and Game Code II-12-3
12.2.4 National Historic Preservation Act II-12-4
12.2.5 Archaeological and Historic Preservation Act II-I2-4
12.2.6 Historic Sites, Buildings, and Antiquities Act II-I2-4
12.3 Action-specific ARARs II-12-4
12.3.1 Local Air Quality Management II-12-4
12.3.2 Federal Clean Water Act and California Porter-Cologne Water
Quality Act II-12-5
12.3.3 California Hazardous Waste Management Protrram 11-12-6
12.4 ARARs Waivers ". ". '..'.'.'. 11-12-7
EM ROD.DOC
III
-------
Contents
Page
13 Statutory Determinations II-13-1
13.1 Protection of Human Health and the Environment ' ' n-13-1
13.2 Compliance with ARARs 11-13 1
13.3 Cost-Effectiveness II-13-1
13.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies to the Maximum Extent Practicable ' II-13-2
13.5 Preference for Treatment as a Principal Element '.'.'.'.'.'.'.'.'.'.'.'. II-13-2
13.6 Five-Year Reviews II-13-2
14 Documentation of Significant Changes II-14-1
Part in - Responsiveness Summary III-l-l
1 Responses to Written Comments OI-l-l
1.1 Responses to Comments from Mr. Glen E. Powell III-l-l
1.2 Responses to Comments from San Gabriel Valley Water Company Ill-1-2
1.3 Responses to Comments from the Northwest El Monte Community
Task Force (NEMCTF) Ill-1-3
2 Responses to Oral Comments III-2-1
2.1 Response to Comments from Ken Russo of the NEMCTF III-2-1
2.2 Response to Comments from David Chamberlin of CDM, representing
the NEMCTF . _ 111-2-3
2.3 Response to Comments from Tom Schmidt representing Hermetic Seal
and the NEMCTF III-2-4
References 1
EM_ROD.DOC
IV
1
•
-------
Contents
Page
Tables
I Summary of Chemicals of Concern and Exposure Point Concentrations
in Groundwater
2 Estimated Total Excess Lifetime Cancer Risk from Domestic Use of
Groundwater
3 Estimated Total Noncancer Hazard Index from Domestic Use of Groundwater
4 Cost Comparison of Alternatives
5 Chemicals of Potential Concern
6 Detailed Cost Estimates for the Selected Remedy
Figures
1 Location Map of El Monte Operable Unit
2 1997 Shallow VOC Contamination
3 1997 Deep VOC Contamination
4 Comparison of Alternatives
EM_ROD.DOC V
-------
-------
Parti
Declaration
-------
-------
1
Part I - Declaration
1.1 Site Name and Location
This Interim Record of Decision (ROD) addresses groundwater contamination at the El Monte Operable
Unit (El Monte OU) located within the San Gabriel Valley Superfund Site Area 1 in Los Angeles
County, California.
1.2 Statement of Basis and Purpose
This ROD presents the selected interim remedial action for the El Monte OU of the San Gabriel Valley
Superfund Site in accordance with the Comprehensive Environmental Response, Compensation and
Liability Act of 1980, 42 U.S.C. §§ 9601 et. seq., as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA) (collectively referred to herein as CERCLA) and to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan, 40 C.F.R. Part 300
(NCP). This decision is based on the Administrative Record for this site.
The State of California, acting through the California Department of Toxic Substances Control (DTSC)
and the Los Angeles Regional Water Quality Control Board (RWQCB), concur with the selected remedy.
1.3 Assessment of the Site
EPA has determined that volatile organic compounds (VOCs) have been released into groundwater
within the El Monte OU, and that a substantial threat of release to groundwater still exists. The response
action selected in this ROD is necessary to protect the public health or welfare or the environment from
actual or threatened releases of hazardous substances into the environment.
1.4 Description of the Selected Remedy
This interim action ROD addresses groundwater contaminated with VOCs. EPA's objective is to protect
human health and the environment. The selected remedy is containment of groundwater contaminated
with VOCs in the shallow and deep zones in the El Monte OU to prevent further migration of existing
groundwater contamination. This remedy includes performance criteria that will require extraction and
treatment of contaminated groundwater at certain locations along the downgradient edge of the
contamination and will require continued monitoring and evaluation at other locations. Most likely, the
treated groundwater will be discharged to Eaton Wash (more probable for shallow groundwater) or
provided to local water purveyors (more probable for deep groundwater). Other discharge options may
be evaluated. In addition, this remedy includes monitoring in the shallow and deep groundwater zones in
the El Monte OU. This remedy is one of five interim remedial actions that are under evaluation or have
been selected to contain contaminated groundwater plumes within the San Gabriel Valley Superfund
6M_ROD.DOC 1-1
-------
PART I - DECLARATION
EL MONTE OU INTERIM ROD
Sites.
1.5 Statutory Determinations
The selected interim action remedy is protective of human health and the environment, complies with
federal and state requirements that are applicable or relevant and appropriate to the interim remedial
action, is cost effective, and utilizes permanent solutions to the maximum extent practicable. This
remedy also satisfies the statutory preference for treatment as a principal element of the remedy (i.e.
reduces the toxicity, mobility, or volume of materials through treatment).
Because this interim remedy will result in hazardous substances remaining onsite above health-based
levels and does not limit groundwater use or restrict exposure, a review will be conducted at least once
every five years after commencement of the interim remedial action to ensure that the remedy continues
to provide adequate protection of human health and the environment.
1.6 ROD Data Certification Checklist
The following information is presented in the Decision Summary section of this ROD. Additional
information can be found in the Administrative Record file for this site.
Chemicals of concern (COCs) and their respective concentrations
Baseline risk represented fay the COCs
Current and future groundwater use assumptions used in the baseline risk assessment and ROD
Groundwater use that will be available at the site as a result of the selected remedy
Estimated capital, operation and maintenance (O&M), and total present worth costs; discount rate;
and the number of years over which the remedy cost estimates are projected
Decisive factors that led to selecting the remedy (i.e., how the selected remedy provides the best
balance of tradeoffs with respect to the balancing and modifying criteria)
Cleanup levels in the aquifer are not included in this interim action ROD because this is an interim action
remedy focused on groundwater containment.
Keith A. Takata
Director of Superfund Division
U.S. Environmental Protection Agency, Region IX
Date
EM_ROD.DOC
1-2
-------
Part II
Decision Summary
-------
-------
Part II - Decision Summary
This Decision Summary portion of the interim Record of Decision (ROD) summarizes the information
and approaches that the U.S. Environmental Protection Agency (EPA) used to reach a decision on this
remedy. It also establishes the remedy that EPA has selected.
1 Site Name, Location and Description
This ROD presents EPA's selected remedial action to address groundwater contamination at the El
Monte Operable Unit (El Monte OU) located within the San Gabriel Valley Superfund Site Area 1 in Los
Angeles County, California.
1.1 Site Description
The El Monte OU is part of the San Gabriel Valley Superfund Site Area 1, located in eastern Los
Angeles County, California (Figure 1). The term "Operable Unit" (OU) is used to define a discrete
action that is an incremental step toward a comprehensive site remedy. Operable units may address
certain geographic areas, specific site problems, initial phases of a remedy, or a set of actions over time
In addition to the El Monte OU, EPA has identified other OUs at the San Gabriel Valley Superfund Site
These are the Baldwin Park OU, Alhambra OU, Puente Valley OU, Richwood OU, South El Monte Ou'
Suburban OU. and WhiUier Narrows OU. EPA is the lead regulatory agency overseeing the cleanup at'
the San Gabriel Valley Superfund Site. The San Gabriel Valley Superfund Site Area 1 has a CERCLIS
ID CAD980677355.
The San Gabriel Valley encompasses a basin that is approximately 170 square miles. Groundwater in the
ban Gabriel Basin is the primary drinking water source for more than one million people Regional
groundwater contamination by volatile organic compounds (VOCs) prompted EPA to place the San
Gabriel Valley on the National Priorities List (NPL) in 1984. This list identifies the highest priority
hazardous waste sites in the United States for investigation and cleanup.
The El Monte OU covers approximately 10 square miles in the south central portion of the San Gabriel
Basin. The El Monte OU is generally bounded by the San Bernardino Freeway (Interstate 10) on the
south, Rosemead Boulevard on the west, and Santa Anita Avenue and the Rio Hondo on the east The El
Monte OU IS highly developed and lies within the cities of El Monte, Rosemead, and Temple City Most
of the area is zoned for residential use and is likely to remain residential. Industrial activity in the El
Monte OU is primarily concentrated in the central portion of the OU.
Groundwater flow in the El Monte OU is principally from east to west. However, there is also a
southerly component of groimdwater flow in the eastern portion of the OU. Both of the aquifer zones
(shallow and deep) in the El Monte OU are considered to be drinking water sources by the State of
California and the deep zone is currently used for drinking water. VOCs are the primary organic
contammants found above state and federal drinking water standards (maximum contaminant levels or
MCLs) tn the El Monte OU. Tetrachloroethene (PCE) and trichloroethene (TCE) are the VOCs that have
EM ROD.DOC
H-l-l
-------
PART II -DECISION SUMMARV
6L MONTE OU INTERIM ROD
been detected most often in groundwater, although other VOCs, including 1,2-dichloroethane (1,2-DCA),
1,1-dichloroethane (1,1-DCA), cis-l,2-dichloroethene (cis-l,2-DCE), l,l-dichloroethene (1,1-DCE), and
carbon tetrachloride (CC14) have also been detected above drinking water standards in the El Monte OU.
In general, VOC concentrations are highest in the shallow groundwater in the vicinity of industrial
facility source areas where releases have occurred. VOCs have also spread downward into the deep zone
beneath the shallow zone, then migrated downgradient in the deep zone towards drinking water
production wells. Several drinking water wells in the El Monte OU have been impacted by VOC
contamination. These wells have had to be shut down or equipped with wellhead treatment to reduce
contaminant levels. To address the industrial areas that contain the sources of groundwater
contamination, the Los Angeles Regional Water Quality Control Board (RWQCB), with funding from
EPA, oversees site-specific investigations and cleanups at facilities where releases have occurred.
Figures 2 and 3 show 1997 VOC concentrations in the shallow and deep zones.
EM_ROD.DOC [1-1-2
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
2 Site History and Enforcement
Activities
2.1 Site History
The San Gabriel Valley has been the subject of environmental investigation since 1979 when
groundwater contaminated with VOCs was first identified. In May 1984, four broad areas of
contamination within the basin were listed as San Gabriel Areas 1 through 4 on EPA's NPL. EPA
subsequently divided the basin into eight operable units (OUs) to provide a means of describing
hydrogeology and contaminant distribution, and planning remedial activities in the basin. The source of
groundwaier contamination in the basin is from industrial facilities.
In 1986, data were compiled and reviewed to develop a preliminary conceptual hydrogeologic model of
the San Gabriel Valley, as described in the Supplemental Sampling Program (SSP) Report (EPA, 1986).
The results of the SSP investigations provided much of the basis for planning the remedial investigations
that have been performed in the San Gabriel Valley since 1986. The Interim San Gabriel Basin
Remedial Investigation Report (EPA, 1992a) describes these investigations and incorporates their results
into an integrated discussion of EPA's understanding of hydrogeologic conditions in the basin.
EPA issued a draft Statement of Work (SOW) for a remedial investigation and feasibility study (RI/FS)
to address the El Monte OU. On March 16. 1995. EPA entered into an Administrative Order on Consent
(AOC) with the Northwest El Monte Community Task Force (NEMCTF), a group of PRPs in the El
Monte OU, in which the NEMCTF agreed to perform the investigation detailed in the final SOW.
Sources of groundwater contamination in the El Monte OU include industrial facilities engaged in the
manufacture of electronic, aviation, navigational, and vibration analysis equipment, aircraft flooring,
glass container, generators, high precision instruments, precision sheet metals, spring coils, nails,
industrial paint, flow meters, name plates, gazebos, and patio furniture; paper printing; metal plating;
chemical handling and transfer; and dry cleaning.
2.2 Remedial Investigation Activities
EPA developed the RI/FS process for conducting environmental investigations under Superfund. The
RI/FS approach is the methodology that the Superfund program has established for characterizing the
nature and extent of risks posed by uncontrolled hazardous waste sites to evaluate potential remedial
options. The RI serves as a mechanism to collect data for site characterization. The FS serves as the
mechanism for development, screening, and evaluation of potential remedial alternatives.
As stated in the Statement of Work, the RI/FS was designed to meet the following goals:
Assess aquifer characteristics and characterize the vertical and lateral distribution of
concentrations of VOCs in groundwater in the El Monte OU area to support a focused FS and the
selection ol'one of more interim actions lor the HI Mome OU area.
EM_ROD.DOC II-2-1
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
Develop and analyze alternatives for appropriate interim remedial actions to control the vertical
and horizontal migration of groundwater with relatively higher concentrations of VOCs to areas
in the El Monte OU with relatively lower concentrations of VOCs.
An RI field program was conducted for the El Monte OU during the period from September 1996
through November 1997. In addition, a production wells investigation was conducted from mid-1995
through early-1996 by the NEMCTF. The RI field program consisted of shallow and deep (multi-port)
monitoring well installation, groundwater monitoring and aquifer testing. The final RI Report was
submitted to EPA in April 1998.
An FS was performed for the El Monte OU in 1997 and 1998. The FS identified remedial action
objectives, assembled remedial action alternatives, and provided an evaluation of the remedial action
alternatives using the nine Superfund evaluation criteria established by EPA. The final FS Report was
submitted to EPA in July 1998.
2.3 Enforcement Activities
EPA began its enforcement efforts in the El Monte OU in 1985 by searching historical federal, state and
local records for evidence of chemical usage, handling, and disposal in the El Monte OU area At
approximately the same time, the RWQCB initiated its Well Investigation Program (WIP) to identify
sources of groundwater contamination. In 1989, EPA entered into a cooperative agreement with the
RWQCB to expand the WIP program, to assist EPA in determining the nature and extent of the sources
of groundwater contamination in the San Gabriel Valley, and to identify responsible parties. The
RWQCB directly oversees facility-specific investigations in the El Monte OU area; EPA helps fund
these activities and, when necessary, uses its enforcement authority to obtain information and ensure that
facility investigations are promptly completed.
As of March 1999, the RWQCB has sent chemical use questionnaires to approximately 231 facilities in
the El Monte OU area; inspected approximately 228 of these facilities; and directed approximately 73
facilities to perform soil, soil gas, and/or groundwater investigations. EPA has concurrently used its
authority under Section 104(e) of the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) to request information from more than 110 current and former owners and
operators in the El Monte OU. From these investigations, EPA has identified 20 facilities as sources of
groundwater contamination for the El Monte OU.
From 1990 through 1994, EPA sent General Notice of Liability letters to approximately 40 entities in and
around the El Monte OU area. On October 7, 1994, EPA sent Special Notice letters to 17 potentially
responsible parties (PRPs), requesting that these parties present a good faith offer to perform the RI/FS
for the El Monte OU. Fifteen of these PRPs formed the NEMCTF and in March 1995 entered into an
AOC with EPA to conduct the RI/FS. In May 1995, EPA issued a Unilateral Administrative Order
(UAO) to one PRP. Crown City Plating, that failed to present a good faith offer. Crown City Plating
completed the activities that the UAO required in 1997, and the NEMCTF completed the RI/FS in Julv
1998.
Since 1995, EPA and the RWQCB have continued to investigate potential sources of contamination. In
August and October 1997, EPA notified 4 additional entities that they had been identified as PRPs. EPA
is now in the process of identifying a final group of PRPs for the El Monte OU. EPA anticipates issuing
Special Notice letters to the El Monte OU PRPs after the ROD is issued; however, EPA may offer to
settle with some of the smaller PRPs in lieu of issuing Special Notice letters.
EPA and the RWQCB have undertaken enforcement activities elsewhere in the San Gabriel Valley,
including facility investigations, issuance of CERCLA section 104(e) requests for information, issuance
EM_ROD.DOC TI_2_2
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
of General and Special Notice letters, and filing of cost recovery litigation. PRPs in the Puente Valley
and South El Monte OUs have entered into Administrative Consent Orders to perform the RI/FS
activities for their respective OUs. EPA also issued a UAO to two parties in the Puente Valley OU. In
the Baldwin Park OU, EPA issued a ROD in March 1993, and in May 1997 sent Special Notice letters to
19 PRPs seeking performance of the remedial design and remedial action (RD/RA). Soon thereafter,
perchlorate contamination was discovered in the Baldwin Park OU, leading EPA to extend the deadline
for the submission of a good faith offer to July 1999.
EM_ROD.DOC . H-2-3
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
3 Community Participation
The Proposed Plan for this remedy, in the form of a fact sheet, was distributed to the parties on EPA's
mailing list for the El Monte OU in October 1998. The Proposed Plan, together with the Final El Monte
OU RI (COM, 1998a) and FS (COM, 1998b) reports and other pertinent documents, were also included
in the Administrative Record file available at EPA's Superfund Records Center at EPA's Regional
Office in San Francisco, and locally at two information repositories: the West Covina Library and the
Rosemead Library. The Administrative Record for the El Monte OU was placed in CD-ROM format in
each repository.
In addition, EPA held a public meeting to present the Proposed Plan and EPA's preferred alternative on
November 18, 1998, at the South El Monte High School in South El Monte, California. At this meeting,
EPA answered questions and accepted oral comments pertaining to the El Monte OU and the preferred
alternative. A transcript of this meeting is available at the EPA's Superfund Records Center and at the
two information repositories.
Notice of EPA's public meetings, availability of the Proposed Plan, and the announcement of a 60-day
public comment period was published in the following newspaper:
• San Gabriel Valley Daily Tribune October 26, 1998
The public comment period ran from October 26 to December 26, 1998. EPA received several sets of
written comments during the public comment period. These comments and the significant oral
comments are addressed in the Responsiveness Summary, included as Part III of this ROD.
EM_ROD.DOC ' j[.3_l
-------
-------
PART II-DECISION SUMMARY
EL MONTE OU INTERIM ROD
4 Scope and Role of Operable Unit
There are four areas of groundwater contamination in the San Gabriel Basin aquifer listed on the NPL as
San Gabriel Valley Areas I through 4. Groundwater contamination in the San Gabriel Valley extends
over very large areas (approximately 30 square miles). In the valley, there are a number of different
areas of contamination with distinct conditions and contaminant sources. To facilitate implementation of
remedial actions, EPA has divided the site into eight different OUs (Figure 1):
• Alhambra OU- RI/FS underway
• Baldwin Park OU- ROD signed, EPA is negotiating with PRPs to implement remedy
• El Monte OU- Subject of this ROD
• South El Monte OU-Nearing completion of the RI/FS process
« Whittier Narrows OU- Previous groundwater monitoring only ROD, EPA is currently preparing a
ROD Amendment
• Suburban OU- No action remedy selected in ROD.
Richwood OU- State has taken the lead on implementing the water supply remedy
• Puente Valley OU- ROD signed, EPA is negotiating with PRPs to implement remedy
The El Monte OU remedial action selected in this ROD is classified as an interim action because it is
intended to control the migration of contamination. Additional remediation may be needed to clean up
VOC contamination remaining in the groundwater. EPA will use information collected during operation
of the selected remedy to help determine the need for additional actions and the nature of the final
remedy. The final remedy may include additional remedial actions at or in the vicinity of industrial
facilities identified as groundwater contamination sources in the El Monte OU. This interim action will
neither be inconsistent with, nor preclude, implementation of the final remedy. The OU-specific actions
currently being undertaken in the San Gabriel Valley are primarily interim actions. It is anticipated that a
final ROD will be issued for the entire San Gabriel Valley Superfund site once remedial design/remedial
action (RD/RA) implementation has been initiated at all of the individual OUs.
EM_ROD.DOC ri-4-l
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
5 Site Characteristics
5.1 Location and Topography
The El Monte OU lies in the central portion of the San Gabriel Valley (Figure 1), approximately 25 miles
from the Pacific Ocean, in eastern Los Angeles County. Located within the San Gabriel Valley is the San
Gabriel Basin, a broad piedmont plain that slopes gradually to the southwest at a gradient of
approximately 65 feet per mile (California Department of Water Resources {CDWR}, 1966). This
structural basin is a natural ground-water reservoir that collects rainfall on the valley floor and run-off
from the surrounding highlands, recharging the groundwater aquifer.
The San Gabriel Basin is bounded to the north by the San Gabriel Mountains and to the southwest, south,
and southeast by a crescent-shaped system of low hills. The hills making up the system, from west to
east, are the Repetto, Merced, Puente, and San Jose Hills. The only significant break along this boundary
falls between the Merced and Puente Hills at Whittier Narrows. Whittier Narrows is the lowest point in
the San Gabriel Valley and is the exit for the San Gabriel and Rio Hondo Rivers and their tributaries,
which serve as the drainage system for the valley.
The El Monte OU covers a surface area of approximately 10 square miles. The OU is not defined by any
significant physiographic features, though the eastern boundary is roughly adjacent to the Rio Hondo.
The El Monte OU varies from approximately 340 feet mean above sea level (MSL) in the northeast to
260 feet above MSL in the southeast.
Santa Anita Avenue defines the eastern boundary of the El Monte OU. The western and southern
boundaries coincide with Rosemead Boulevard and the San Bernardino Freeway (Interstate 10),
respectively. Several streets that traverse a residential area between Lower Azusa Road and Live Oak
define the northern boundary.
Most of the annual precipitation in the El Monte OU occurs intermittently during the winter months of
December through March. The long-term average precipitation for the San Gabriel Basin is about 18
inches per year. Temperatures are usually moderate; the average annual temperature in the San Gabriel
Valley is about 62 degrees Fahrenheit (°F). January and July are the coldest and warmest months of the
year, respectively.
5.2 Surface Water
Two major stream systems carry surface flow from the San Gabriel Valley: the San Gabriel River and the
Rio Hondo and their tributaries. The headwaters for these two systems are in the San Gabriel Mountains.
The systems transverse the San Gabriel Valley in a southwesterly direction and exit the valley at Whittier
Narrows. Except in the case of significant storms, these channels do not carry much natural run-off.
There is considerable non-natural flow from wastewater plant discharge, imported surface water intended
for groundwater recharge.
Nearly all of the stream channels comprising the surface water drainage of the San Gabriel Valley have
been modified and concrete-lined (including the Rio Hondo and its tributaries in the £1 Monle OU
EM ROD.DOC II-5-1
-------
PART II-DECISION SUMMARY
EL MONTE OU INTERIM ROD
vicinity). This lining minimizes recharge of the aquifer by surface water flow.
The Rio Hondo and Eaton Wash are the major surface water features crossing the El Monte OU and
vicinity areas. The Rio Hondo drains the northwest portion of the San Gabriel Valley The Rio Hondo
EST Th ^ntCw Uhfr°m "* "^^ t0 *" S°Uth and iS ™^ adJ'acent tofce eastern
boundary The Eaton Wash crosses the western portion of the El Monte OU from the north to the south
where It joins the Rio Hondo beyond the southern boundary of the OU. Most ome flowTn helio
fiZ I*?"? "? ^ Pe? R°ad Spreading Grounds J'ust north of the a Monte OU, so significant
flow m the Rio Hondo through the El Monte OU is limited to substantial storm events. ^mca^
5.3 Geology
5.3.1 San Gabriel Basin
The San Gabriel Basin is filledwith alluvial deposits, primarily of Quaternary age, which overlie
Datively impermeable rock. These deposits are 2,000 to 4,000 feet thick over the center of the basin
and range between approximately 250 to 800 feet thick at the basin outlet in Whittier Narrows
distinct sources of sediment in the basin: the coarse-grained crystalline rocks of the San
S^ y POSltT rdatlVe t0 riVCr and """a"* courses' * Particular; coarse-grained
sediments are prevalent m the San Gabriel River proximity. Most of the San Gabriel Basin is
Jlurv'CJT >y ff!11! 1CnSCS °f allUVial deposits (e'S- cobbles' Sravel' sil<> and clay) and the
alluvial depos.ts show a high degree of variability in sediment type, both vertically and laterally.
Major structural features controlling regional ground-water How in the San Gabriel Basin include the
topographic highs (i.e., San Gabriel Mountains and southern hills) and topographic lows (i e Whittie
Madrel u.t IvstT^f5 ™ ^ **f*?* Bashl P°^tially impact ^ JeT^JSe
Madre Fault System, the Raymond Fault, the Lone Hill- Way Hill Fault, and the Workman Hill Fault.
5.3.2 El Monte OU
Most of the El Monte OU is located west of the Rio Hondo, where the alluvial deposits are more
* P0rtl°n °U fS lOCatCd CaSt °f the Ri°.Hondo in an «« with coarser river
to K n°ted at a number of lpcations in the £1 Monte
the locanons of deeper monitoring wells installed during the El Monte OU RI The
?££ SnSr??13 .'Jcou?lfd dUring thC W C°nSiSted of interbedded gravels, sands, silts and clays.
The majority of the silts and clays were encountered in the upper 100 feet below grade.
There do not appear to be any anally extensive uniform aquitards, however, there are considerable finer-
SSSf 52!"^ PrCSent m thc,general dePths of 90 to 12° fe«t bgs. The sediments in the eastern
portion of the OU area proximal to the Rio Hondo, are coarser-grained, consisting predominantly of
be^tr V WUh !nte[bedded silts "* clavs- Coward the western edge of the OU, the material
become less coarse, with silty sands and sands predominating. Because of the fluvial nature of the
depositional environment, the lithologic logs do not correlate well, even over short distances
EM ROD.DOC
n-5-2
»
-------
PART If - DECISION SUMMARY
EL MONTE OU INTERIM ROD
5.4 Hydrogeology
5.4.1 San Gabriel Basin
The San Gabriel Groundwater Basin comprises approximately 167 square miles of water-bearing valley
land (CDWR, 1966). The maximum depth of alluvial fill within the main basin is unknown, though
CDWR (1966) shows an alluvial depth of more than 4,000 feet at a location north of Whittier Narrows
(CDWR, 1966).
Natural features that control the regional pattern of groundwater movement in the San Gabriel Basin
include topographic highs (San Gabriel Mountains and southern hills) and lows (the valley floor,
especially Whittier Narrows), and to some extent faults. Generally, groundwater in the basin flows from
topographically high to low areas in the absence of groundwater pumping. In addition, groundwater flow
is also controlled by the locations of significant recharge, such as undeveloped alluvial fans, riverbeds
and spreading basins. Recharged groundwater moves away from these areas, generally towards
topographically lower areas. Under natural groundwater flow conditions, such as those encountered in
the first half of this century, groundwater generally flowed away from the margins of the basin towards
the center of the alluvial valley, and then towards Whittier Narrows (EPA, 1992a).
In parts of the basin, concentrated groundwater withdrawal by pumping significantly affects the direction
and rate of groundwater flow. With the increased use of wells to extract groundwater from the basin, the
pattern of groundwater flow in the basin has changed over time (EPA, 1992a). About 80 percent of the
groundwater discharge from the San Gabriel Basin is now to production wells (EPA, 1992a). The
remaining groundwater discharge consists of subsurface outflow through Whittier Narrows and minimal
discharge to surface water in Whittier Narrows and Puente Valley.
5.4.2 El Monte OU
As noted above, there do not appear to be any areally extensive aquitards in the El Monte OU area, but
there are considerable fine-grained sequences present, particularly in the general depths between 90 and
120 feet bgs. The unconsolidated deposits in the El Monte OU are of fluvial origin and consist of
interbedded sediments comprised of gravel, sand, silt, and clay and mixtures of these materials.
Depth-to-water in the El Monte OU at the end of the RI was between 50 and 60 feet below ground
surface (bgs) in the eastern portion of the OU, approximately 110 feet fags along the western boundary of
the OU and less than 40 feet near the southern OU boundary.
Based on the lithologic, water-level, and contamination data generated during the RI, the aquifer in the
El Monte OU area has been divided into a shallow zone (representing approximately the upper 50 to 100
feet of the aquifer) and a deeper zone (representing the interval from base of the shallow zone down to
approximately 400 feet bgs).
5.4.2.1 Hydraulic Conductivity
Hydraulic conductivity is a measure of how easily fluids can flow through porous media. The geologic
materials in the El Monte OU vary from clay to gravel over short distances, thus estimates of hydraulic
conductivity in the area are very location- and scale-dependent. During the RI, aquifer tests were
performed at deeper production wells and shallow monitoring wells. j
Average conductivity estimates for the deep production wells tested ranged from 11 to 22 feet/day for the j
EM_ROD.DOC H-5-3
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
wells west of the Rio Hondo and 71 ft/day for the one well located east of the Rio Hondo Tests of three
shallow sue assessment wells in the El Monte OU yielded conductivity estimates ranging froS *3 to 106
The aquifer testing performed during the RI indicates that hydraulic conductivity values are similar in the
shallow and deep zones and are generally less than 50 ft/day.
5.4.2.2 Groundwater Flow Conditions
rf?™ fl°W 'S teSCribed b«°W * teiTOS °f fl°W directi°n and P**1*** both in 'he horizontal and
co T Tl°n? fl°W 1S diSCUSSCd f°r ** Shallow zone' wherc hiSher levels of VOC
contammation occur, and the deep zone, where lower levels of VOC contamination occur.
Within the river deposits generally east of the Rio Hondo (and east of the El Monte OU), the direction of
d^r±f * I n ^ Shall°W zone is ^rally southwestward towards Whittier Narrows. T^e flow
direction in the shallow zone m the western portion of the El Monte OU is predominantly from east to
S*^
of the OU just west of the RK> Hondo, groundwater flow directions in the shallow zone vary
considerably, but the net flow direction is towards the south. The hydraulic gradient towards the west in
the sha ow zone ranged from 0.0028 to 0.0036 feet per feet during L RI. Usmg awn^dtaS
above for the shaiiow z°ne resuits
^
The groundwater flow direction in the deeper zone in both eastern and western portions of the El Monte
2 AftSS! H LT eaSlt0,T^ 7* WCStem trend iS the result of deePer °
H ,
-^ H°Te3( Pa*' Grad'entS in the de£P zone are sirailar to th°se listed above for the
v The hydraulic heads m the deeper aquifer are .about 15 to 20 feet lower than those in the
3,T- fT^J" fl°W VelOCity b the deePer *>ne is estimated at about 1 10 feet per
, which is generally higher than the estimates for the shallow zone.
3 34
feet
erVnStalled I T1 the E1 Monte OU area d»ring the RI. These multi-port
., intervals and Provide information on water levels and water quality
aquifer Pronounced head differences are present at all four locations. The
^m y ^ 5^ bCTeen thC Shallowest and de«P«t intervals ranged from 20.65
associated downward vertical gradients ranged from 0.0836 to 0. 1396 feet per
resistance
webv nnnr uer an ressance to vert
flow caused by the mterbedded fine-grained strata in the aquifer. These large vertical gradients indicate
that there is some degree of separation between the shallow and deep zones
5.5 Groundwater Management
o /•» j. • i rj —.. ~—-..>-. ^uoiii. The rights to pump groundwater from the
Jsan oabnel Basin is adjudicated (i.e., assigned to specified users in accordance with a court judgment)
There are two judgments that govern groundwater management in the El Monte OU vicinity
5.5.1 San Gabriel Basin Judgment
fS!rtrnfgThtS ^ the,Maln San Gabriel Basin were adjudicated in a stipulated judgment by the Superior
Court of Los Angeles County m 1973 (amended in 1989). This adjudication resulted in assigning water
EM ROD.DOC
ir-s-4
-------
PART II - DeCISIOH SUMMARY
EL MONTE OU INTERIM ROD
rights to approximately 50 parties that each hold rights to greater than one percent of the natural safe
yield of the basin (152,700 acre-feet per year, established in the judgment), and approximately 100
parties that each hold rights to less than 1 percent of the natural safe yield. Also, according to the
judgment, only selected parties have the right to export groundwater out of the Main San Gabriel Basin.
The judgment also establishes the duties of a Watermaster, which include annually determining an
operating safe yield for the basin, monitoring pumpers' compliance with the judgment, issuing permits
for all new and increased pumping in the basin, and preparing an annual report that includes details of
pumping activities in the basin. The amount of groundwater that each water rights holder can pump in
any year is adjusted by prorating the pumper's prescriptive rights (percentage of natural safe yield) by the
operating safe yield, as established by the Watermaster.
The majority of the groundwater pumped from the Main San Gabriel Basin is used for drinking water,
supplied to the public by purveyors that are regulated as public water supply systems. Annually,
pumping typically equals or exceeds the operating safe yield of the basin. When excess extraction
occurs, the judgment has established provisions for assessing pumpers the cost of importing replacement
water to replenish the excess amount extracted. Replacement water is imported water purchased by the
Upper San Gabriel Valley Municipal Water District and artificially recharged within the basin. The
1997-98 replacement water assessment is $246.65 per acre-foot.
5.5.2 Long Beach Judgment
The Long Beach Judgment is the 1964 settlement of a lawsuit between parties in the Central and San
Gabriel Basins. This judgment mandates that an average of 98,415 acre-feet of useable water will be
delivered to the Central Basin each year. This water consists of: (1) surface flow that passes through
Whittier Narrows, (2) subsurface (groundwater) flow through Whittier Narrows, and (3) a portion of the
water exported (piped) from the San Gabriel Basin to the Central Basin.
Although the Long Beach Judgment specifies an average entitlement of 98,415 acre-feet per year, the
actual entitlement is calculated yearly by the court-appointed San Gabriel River Watermaster. The San
Gabriel River Watermaster tabulates the water discharge through Whittier Narrows. If more than 98,415
acre-feet are delivered to the Central Basin from the San Gabriel Basin in a year, then the San Gabriel
Basin is credited with the excess. Conversely, if less is delivered, the San Gabriel Basin is required to
make up the difference either from past credits or, if that is not sufficient, through delivery of imported
surface water as makeup water to the Central Basin.
5.6 Groundwater Contamination
VOCs are the primary organic contaminants found in groundwater above state and federal drinking water
standards in the El Monte OU. PCE and TCE are the VOCs that have been detected most often in
groundwater, although other VOCs, including 1,2-DCA, I,l-DCA,cis-l,2-DCE, 1,1-DCE, and CC14
have also been detected above drinking water standards in the El Monte OU. Jji general, VOC
concentrations are highest in the shallow groundwater in the vicinity of industrial facility source areas
where releases have occurred. Figure 2 shows the extent of VOC contamination in the El Monte OU in
the shallow zone. As shown in this figure, there are fairly large areas where VOC concentrations exceed
10 times the drinking water standards (or 50 ug/L) and isolated smaller areas where concentrations
exceed 100 times drinking water standards (or 500 ug/L). In these areas, concentrations of PCE and
TCE detected during the last round of sampling for the El Monte OU RI range from about 81 to 2,200
ug/L and 70 to 1,000 ug/L, respectively.
TCE and PCE concentrations in the deeper zone in the El Monte OU are much lower, generally less than
EM_ROD.DOC II-5-5
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
20 ug/L with a maximum of just over 50 ug/L. TCE is detected at higher concentrations than PCE in the
deep zone. The extent of deep zone contamination is shown in Figure 3. Only one area had
concentrations that exceeded 10 times the drinking water standards. Depth-specific samples collected
from a production well indicated TCE exceedances down to 550 feet bgs, but in general the PCE and
TCE exceedances in the deep zone occur above 350 feet bgs. In both the shallow and deep zones, VOC
concentrations at the El Monte OU boundary are below drinking water standards. This indicates that at
present groundwater contamination has not substantially migrated beyond the boundaries of the El
Monte OU.
As described above, EPA has identified a number of industrial facilities in the El Monte OU as
contaminant sources where releases have impacted groundwater quality. To address the industrial areas
that contain these sources, the RWQCB, with funding from EPA, oversees site-specific investigations
and cleanups.
Within the El Monte OU, EPA's RI efforts focused on regional groundwater contamination and EPA has
not yet identified any specific areas of principal threat wastes. At some of the individual industrial
facilities, where elevated concentrations of contaminants have been identified in the vadose zone and
shallow groundwater, the RWQCB is overseeing facility-specific remedial actions. These focused
actions should address the more highly-contaminated source areas.
EM_ROD.DOC n_5_6
-------
PART II - DECISION SUMMARY
e. MONTE OU INTERIM ROD
6 Current and Potential Future Site and
Resource Uses
6.1 Land Uses
Most of the El Monte OU is densely populated residential communities, with some commercial and light
and heavy industrial areas. The area is essentially fully developed with very limited undeveloped or
open areas. In the portions of the El Monte OU where the shallow groundwater contamination addressed
in this ROD is found, land use is primarily light and heavy industrial. Residential areas are found
adjacent to these industrial areas.
The El Monte OU is located in the cities of El Monte, Rosemead and Temple City. Eighty-three percent
of the City of El Monte is zoned for residential use, seven percent is zoned for professional office
purposes, five percent is zoned for industrial use, and five percent is zoned for commercial use. The city
population was estimated at 136,938 in 1994. According to a demographic profile provided by the City
of El Monte Planning Division, the population is expected to grow at a moderate rate during the late
1990s. The population in the City of Rosemead was estimated at 51,638 in 1990. The City of Rosemead
is zoned primarily residential and commercial, with some light manufacturing. The population of
Temple City was estimated at 32,000 in 1995. Temple City is zoned primarily residential, with some
commercial and heavy industrial. Land, use in the El Monte OU area is not expected to change
significantly over time.
6.2 Groundwater Uses
The State of California has designated all portions of the San Gabriel Basin aquifer as either a current or
potential source of drinking water. Currently, groundwater extracted in the vicinity of the El Monte OU
is used as municipal water supply for residential, commercial and industrial purposes. As discussed
previously, water rights in the Main San Gabriel Basin are fully adjudicated. Thus, the Main San Gabriel
Basin Watermaster monitors all extraction. The producers that extract groundwater from within the El
Monte OU are: California American Water Company, Clayton Manufacturing .Company (industrial user),
Crown City Plating Company (industrial user), City of El Monte, Driftwood Dairy (agricultural user),
and Southern California Water Company. VOCs are detected in all production wells in the El Monte OU
area. California American Water Company and the City of El Monte have had to shut down wells
because of contamination and both the City of El Monte and Southern California Water Company have
installed wellhead treatment systems to address VOC contamination in production wells.
Production from the shallow zone is limited as most of the production wells are perforated in the deeper
zone. There are currently no drinking water supply wells that draw water from the shallow, highly .
contaminated zones in the vicinity of industrial facilities. Future groundwater use in the OU vicinity is
expected to be similar to current use, with active extraction occurring in many portions of the OU.
Future extraction will likely be primarily from the deeper zones.
EM_ROD.DOC _-
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
7 Summary of Site Risks
EPA completed a Preliminary Baseline Risk Assessment (RA) for the El Monte OU in 1997 (EPA
1997a). The baseline risk assessment estimates the human health and environmental risks that the site
could pose if no action were taken. It is one of the factors that EPA considers in deciding whether to
take action at a site. In the El Monte OU, EPA's decision to take action is based principally on the
presence of contamination in groundwater at levels that exceed drinking water standards, evidence that
contamination will continue to migrate into groundwater areas that are presently clean or less
contaminated, and the current and potential use of groundwater in and around the El Monte OU as a
source of drinking water. The risk assessment is also used to identify the contaminants and exposure
pathways that need to be addressed by the remedial action. This section of the ROD summarizes the
results of the Preliminary Baseline RA for the El Monte OU.
7.1 Summary of Human Health Risk Assessment
This summary of human health risk includes sections on the identification of chemicals of concern
(COCs), exposure assessment, toxicity assessment, and risk characterization.
7.1.1 Identification of Chemicals of Concern
In the two-year period between January 1993 and January 1995, 25 VOCs were detected in groundwater
irom the El Monte OU area. Sampling data were available from 16 production wells and 52 site
assessment monitoring wells during this period. All 25 VOCs were considered chemicals of potential
concern (COPCs) for evaluation in the Preliminary Baseline RA. Of these 25 COPCs only three
contributed significantly to the estimated risks and are discussed as chemicals of concern (COCs) in this
RA summary. Table 1 provides information on these COCs in each of two well groupings and three
individual production wells considered in the RA.
As shown in Table 1, the three primary COCs found in groundwater in the El Monte OU were
tnchloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride. All of the COCs are
VOCs and all are present in the most contaminated portion of the shallow zone. Only two of the COCs
PCE and TCE, were also found in the deeper production wells. The table also shows that frequency of '
detection (i.e., the number of times the chemical was detected in the samples collected from each well
grouping or production well during 1993 through 1995 groundwater sampling). The table indicates that
PCE and TCE are the most frequently detected COCs in the El Monte OU and represent the extent of
contamination in groundwater at the site shown in Figures 2 and 3.
Table I presents the exposure point concentration for each of the COCs detected in each of the well
groupings and production wells evaluated. In all cases, the highest exposure point concentrations were
from either TCE or PCE. The 95th percentile (95%) upper confidence limit (UCL) on the arithmetic
mean concentration was used as the exposure point concentration for all of the COCs in the well
groupings and production wells.
EM_ROD.DOC
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
7.1.2 Exposure Assessment
Exposure refers to the potential contact on an individual (or receptor) with a chemical. Exposure
assessment is the determination or estimation of the magnitude, frequency, duration, and route of
potential exposure. This section briefly summarizes the potentially exposed populations, the exposure
pathways evaluated, and the exposure quantification from the preliminary baseline RA performed for the
El Monte OU.
Land use in the El Monte OU is primarily residential, commercial and industrial. There are nine active
production wells in the El Monte OU. Of these, six are drinking water wells used for domestic purposes,
one is an industrial well also used for drinking water, one is used for industrial purposes only and one is
used for irrigation. Exposure to contaminants in groundwater could occur through the use of groundwater
for domestic purposes, such as ingestion of tap water, inhalation of contaminants from water used for
bathing, cooking and laundering, and dermal contact with the water. In the baseline RA, EPA evaluated
two scenarios under which individuals might be exposed to contaminated groundwater:
1. Potential for a current resident to be exposed to contamination in groundwater through domestic use
2. Potential for a future resident to be exposed to contamination in groundwater through domestic use
It should be noted that the assumption that residents could be exposed to untreated groundwater from the
well groupings or production wells evaluated is conservative. There are not currently any wells
producing water for public drinking water supply from the highly contaminated shallow groundwater
areas in the western or eastern portions of the El Monte OU, Further, regulations, such as the Safe
Drinking Water Act, currently prohibit water purveyors from serving water contaminated in excess of
drinking water standards to consumers. 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.
7.1.3 Toxicity Assessment
Table 1 shows the three COCs that are the major risk contributors for the El Monte OU. Based on data
from various animal studies, all three of the compounds (carbon tetrachloride, PCE and TCE) are
classified as probable human carcinogens (EPA weight of evidence class B2) and have the following oral
carcinogenic slope factors (toxicity values) :
• Carbon Tetrachloride - 0.13 (mg/kg/day)'1 (Source: Integrated Risk Information System (IRIS), EPA,
1995a).
• PCE - 0.052 (mg/kg/day)'1 (Source: Environmental Criteria and Assessment Office, EPA, 1995b).
• TCE - 0.011 (mg/kg/day)'1 (Source: Environmental Criteria and Assessment Office, EPA, 1995b).
AH three of the above compounds are also considered carcinogenic through the inhalation route. Based
on data from various animal studies, the inhalation carcinogenic slope factors are:
• Carbon Tetrachloride - 0.053 (mg/kg/day)*1 (Source: Integrated Risk Information System (IRIS),
EPA, 1995a).
• PCE - 0.002 (mg/kg/day)'1 (Source: Environmental Criteria and Assessment Office, EPA, 1995b).
• TCE - 0.006 (mg/kg/day)'1 (Source: Environmental Criteria and Assessment Office, EPA, 1995b).
EM_ROD.DOC H-7-2
-------
PART II - DECISION SUMWARV
EL MONTE OU INTERIM ROD
The dermal route of exposure was incorporated into the preliminary baseline RA using an equation that
incorporates the exposure point concentration and a dermal permeability constant (in centimeters/hour
[cm/hr]). The dermal permeability constants for the three compounds are:
• Carbon Tetrachloride - 0.022 cm/hr.
• PCE - 0 .048 cm/hr.
• TCE - 0.016 cm/hr.
In addition to their classification as probable human carcinogens, the three compounds have toxicity data
indicating their potential for adverse noncarcinogenic health effects in humans. The available toxicity
data indicate that all three of the compounds primarily affect the liver. The chronic toxicity data
available for these compounds have been used to develop oral reference doses (RfDs). An RfD
represents a level that an individual may be exposed to that is not expected to cause any deleterious
effect. The oral RfDs are:
• Carbon Tetrachloride - 0.0007 mg/kg/day (Source: Integrated Risk Information System (IRIS), EPA,
I995a).
• PCE - 0.01 mg/kg/day (Source: Integrated Risk Information System (IRIS), EPA, 1995a).
• TCE - 0.006 mg/kg/day (Source: Environmental Criteria and Assessment Office, EPA, 1995b).
Carbon tetrachloride is also considered to have noncarcinogenic effects via inhalation. The inhalation
reference dose for carbon tetrachloride is 0.00057 milligrams per kilogram per day (mg/kg/day) (Source:
Environmental Criteria and Assessment Office, EPA, 1995b).
7.1.4 Risk Characterization
This section presents the results of the evaluation of the potential risks to human health associated with
exposure to contaminated groundwater in the El Monte OU. Exposure scenarios are evaluated by
estimating the noncarcinogenic and carcinogenic risks associated with them.
For carcinogens, risks are generally expressed as the incremental probability of an individual developing
cancer over a lifetime as a result of exposure to the carcinogen. These risks are probabilities that usually
are expressed in scientific notation (e.g., 1 x 10"*). An excess lifetime cancer risk of 1 x 10"* indicates
that an individual has a 1 in 1,000,000 chance of developing cancer as a result of site-related exposure.
This is referred to as an "excess lifetime cancer risk" because it would be in addition to the risks of
cancer individuals face from other causes such as smoking or exposure to too much sun. The chance of
an individual developing cancer from all other causes has been estimated to be as high as one in three.
EPA's generally acceptable risk range for site-related exposures is 10"* to IO"6. An excess lifetime
cancer risk of greater than one in ten thousand (1 x 10"*) is the point at which action is generally required
at a site (EPA, 199la).
The potential for noncarcinogenic effects is evaluated by comparing an exposure level over a specified
time period (e.g., a life-time) with a reference dose (RfD) derived for a similar exposure period. The
ratio of exposure to toxicity is called a hazard quotient (HQ). An HQ less than one indicates that a
receptor's dose of a single contaminant is less than the RfD and that toxic noncarcinogenic effects from
exposure to that chemical are unlikely. HQs for all COCs that affect the same target organ (e.g., liver) are
added together to generate the Hazard Index (HI). An HI less than one indicates that noncarcinogenic
effects from all the contaminants are unlikely. Conversely, an HI greater than one indicates that site-
related exposures may present a risk to human health.
EM_ROD.DOC [1.7.3
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
7.1.4.1 Conclusions
Tables 2 and 3 present the risk characterization summaries for carcinogenic and noncarcinogenic effects,
respectively. The risk estimates presented in Tables 2 and 3 are based on average and reasonable
maximum exposure (RME) and were developed by taking into account various conservative assumptions
about the frequency and duration of exposure to groundwater, as wells as the toxicity of the primary
COCs. v y
To assess potential current residential exposure to groundwater through domestic use, data from all
active drinking water wells sampled from January 1993 through January 1995 that had positive
detections of VOCs were used (wells 01900918,01902948, and 08000101 on Tables 2 and 3). The
cumulative estimated hazard index was less than one for the average exposure and RME scenarios (see
the production wells on Table 3). The estimated excess lifetime cancer risk ranged from IxlO'8 to 9xlO-8
for the average exposure scenario and IxlO'7 to IxlO* for the RME scenario (see the production wells on
Table 2). The estimated excess lifetime cancer risks based on exposure to groundwater from the
production wells that are currently active are less than the 10" to 10"* acceptable risk range used by EPA
to manage risks at Superfund sites. In addition, the estimated risks for these production wells are
conservative because they do not take into account treatment of groundwater or the blending of
groundwater from these wells with other production wells.
To assess potential future residential exposure to contamination in groundwater through domestic use,
the preliminary RA focused on two areas within the OU that had groundwater concentrations exceeding
10 times the primary drinking water standards (i.e., MCLs). These two areas are represented by Well
Group 1 (western El Monte OU) and Well Group 2 (eastern El Monte OU) on Tables 2 and 3. The two
well groups consist primarily of shallow monitoring wells at or near industrial facilities and include those
wells with the highest VOC concentrations in the OU area. The shallow intervals monitored by these
wells are not currently used for drinking water supply. Use of these well groups to evaluate potential
future risk is a conservative approach. The estimated hazard index ranged from 2 to 3 for the average
residential exposure scenario and 6 to 10 for the RME residential scenario (see Well Groups 1 and 2 on
Table 3). Major chemical contributors to the estimated hazard indices include carbon tetrachloride, PCE
and TCE. The estimated excess lifetime cancer risk ranged from 7\IQ~S to 2x10" for the average
exposure scenario and 5x10" to 2xlO"J for the RME (see Well Groups 1 and 2 on Table 2). Major
chemical contributors to the estimated excess lifetime cancer risk include PCE and TCE. The estimated
hazard indexes and excess lifetime cancer risks based on potential future exposure to groundwater from
Well Groups 1 and 2 exceed the acceptable risk range used by the EPA to manage risks at Superfund
sites. Based on these estimated risks, the areas around Well Groups 1 and 2 should be considered for
remediation.
The industrial/irrigation exposure to contamination in groundwater from production wells 01901055 and
01902924 was evaluated qualitatively in the preliminary RA. Concentrations of TCE in both wells
exceeded the MCL, however, only limited data from these wells are available and neither well is used for
drinking water purposes. The maximum concentration of VOCs in Wells 01901055 and 01902924 are
well below the concentrations found in Well Groups 1 and 2. Therefore, worker risks from exposure to
water from Wells 01901055 and 01902924 are expected to be less than those calculated for domestic use
of Well Group 1 and 2 (described above). Further, in general, worker exposure is less than residential
exposure.
Based on this risk characterization summary, actual or threatened releases of hazardous substances at this
site, if not addressed by implementing the response action selected in this ROD, may present a potential
threat to public health, welfare, or the environment. As described in the preceding paragraphs, the
groundwater contamination does not represent a current threat to public health or welfare.
EM_ROD.DOC n.7.4
-------
PART It - DECISION SUMMARY
H. MONTE OU INTERIM ROD
7.2 Summary of Ecological Risk Assessment
An evaluation was conducted as part of the El Monte OU Preliminary Baseline RA to determine whether
there are any potential ecological exposure pathways in the El Monte OU. The potential for exposure to
ecological receptors is related to the extent that groundwater contaminants migrate to or are discharged
to surface water habitat. The environmental evaluation indicated that there are two plausible means for
ecological receptors to be exposed to groundwater contaminants in the El Monte OU:
Extraction and discharge of contaminated groundwater into surface water bodies containing
ecological receptors.
* Natural discharge of contaminated groundwater into surface water bodies that contain ecological
receptors.
The surface water bodies present in the El Monte OU area include the Rio Hondo (running northeast to
southwest along the eastern boundary of the OU area) and Eaton Wash (running generally north to south
in the western portion of the OU area). Both of these channels are concrete-lined in the OU area
limiting potential ecological habitat. '
Outside of periodic, short-duration discharge associated with well testing activities, there is no known
surface-water discharge of groundwater extracted in the El Monte OU. Based on the very limited
frequency and duration of this Rl-related type of discharge, no additional evaluation is warranted for this
potential pathway.
The depth-to-water in the El Monte OU generally ranges between approximately 35 and 100 feet below
ground surface. Given these groundwater depths, it is extremely unlikely that groundwater discharge to
surface water would occur in the El Monte OU. EPA's Interim San Gabriel Basin RI Report (EPA,
1992a), confirms that natural discharge of groundwater to surface water (caused by shallow groundwater
levels intersecting stream channel bottoms) is not expected in the Rio Hondo north of the Whittier
Narrows area. Based on the depth-to-water in the El Monte OU, potential exposure pathways for aquatic
and terrestrial organisms do not appear possible.
Based on this brief environmental evaluation, there do not appear to be any complete ecological exposure
pathways in the El Monte OU.
7.3 Conclusion
In addition to the risk assessment, EPA has considered the state and federal drinking water standards
(MCLs and MCLGs) that have been established for contaminants found in the El Monte OU. MCLs and
MCLGs are set at levels, including an adequate margin of safety, where no known or anticipated adverse
health effects are expected to occur. Even if the cumulative carcinogenic site risk to an individual based
on reasonable maximum exposure is less than lO'4 and the non-carcinogenic hazard quotient is less than
1, remedial action will generally be warranted if MCLs or non-zero MCLGs are exceeded. "Role of the
Baseline Risk Assessment in Superfund Remedy Selection Decisions," OSWER Directive 9355 0-30
April 22, 1991. '
Contaminant concentrations exceed MCLs throughout a significant portion of the El Monte OU,
including groundwater regions that are currently used as sources of drinking water. In some areas,
contamination levels exceed 100 times MCLs. Based on the risk characterization, the presence of
widespread contamination in excess of MCLs, the use of groundwater in the El Monte OU as a source of
drinking water, and evidence that the contamination is migrating, EPA has determined that actual or
EM_ROD.DOC __
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
threatened releases of hazardous substances at this site, if not addressed by implementing the response
action selected in this ROD, may present an imminent and substantial endangerment to public health,
welfare, or the environment.
4
EM_ROD.DOC n_7_5
-------
PART [I - DECISION SUMMARY
EL. MONTE OU INTERIM FtOO
8 Remediation Objectives
EPA's Remedial Action Objectives (RAOs) for the El Monte OU are to:
• Prevent exposure of the public to contaminated groundwater above MCLs;
• Inhibit contaminant migration from more highly contaminated portions of the aquifer to less
contaminated areas or depths;
• Reduce the impact of continued contaminant migration on downgradient water supply wells, and;
« Protect future uses of less contaminated and uncontaminated areas.
These objectives reflect EPA's regulatory goal of restoring usable groundwater to its beneficial uses
wherever practicable, within a time frame that is reasonable, or, if restoration is deemed impracticable, to
prevent further migration of the plume, prevent exposure to the contaminated groundwater, and evaluate
further risk reduction (40 C.F.R. Section 300.430[a][l][iii][FJ). The RAOs address the risks associated
with exposure to contaminated groundwater in the El Monte OU (described above in Section 7) by
significantly limiting the potential for future exposure.
To meet the RAOs, migration control will be required in the El Monte OU as long as VOC
concentrations in migrating groundwater exceed state or federal drinking water standards. The RAOs for
the El Monte OU do not include numeric, chemical-specific objectives in the aquifer or a time frame for
restoration because this is an interim action to contain contamination. Although this interim remedial
action is not focused on mass removal, the proposed remedy will remove significant contaminant mass
from the aquifer, in effect beginning the restoration process.
EM ROD.DOC II-8-1
-------
-------
PART II -DECISION SUMMARY
EL MONTE OU INTERIM ROD
9 Description of Alternatives
EPA evaluated five alternatives in the FS for the El Monte OU:
• Alternative 1- No-Action
• Alternative 2- Groundwater Monitoring
• Alternative 3- Shallow Groundwater Control in Western El Monte OU
• Alternative 4- Shallow Groundwater Control in Western and Eastern El Monte OU
• Alternative 5- Shallow Groundwater Control in Western and Eastern El Monte OU Plus Deep
Groundwater Control
A brief description of the five remedial alternatives is presented below.
9.1 Alternative 1 - No Action
The NCP requires EPA to consider a no action alternative and to evaluate the risk to the public if no
action were taken. The No-Action Alternative provides a baseline for comparison with other remedial
alternatives under consideration. In this alternative, no remedial actions are taken to control contaminant
migration from or within the El Monte OU. This alternative does not include any groundwater
monitoring, extraction, or treatment, so there is no cost associated with this alternative
The No-Action Alternative allows continued, uncontrolled migration of contamination. This alternative
does not meet EPA's RAOs and does not comply with state and federal requirements.
9.2 Alternative 2 - Groundwater Monitoring
The only remedial action incorporated into Alternative 2 is groundwater monitoring to monitor VOC
plume migration in the shallow and deep zones in the El Monte OU. Alternative 2 does not have any
extraction, treatment, conveyance, or discharge components. This alternative would rely solely on
passive mechanisms such as dilution or dispersion to address contaminant migration. This alternative
also assumes that the groundwater management activities described in Section 5.5 continue to limit
human exposure to groundwater contamination. This alternative includes implementing a monitoring
program using new and existing wells to monitor contaminant migration and compliance with the El
Monte OU remedial action objectives in the shallow and deep zones.
9.2.1 Monitoring
For cost estimation and evaluation of the alternative, installation of 9 new monitoring wells and semi-
annual sampling of new and existing wells are assumed. These new wells would include 7 shallow wells
and. 2 multi-port wells.
EM_ROD.DOC
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
•
9.3 Alternative 3 - Shallow Groundwater Control in
Western El Monte OU
Alternative 3 includes the monitoring program from Alternative 2, plus shallow zone groundwater
extraction and treatment components in the western portion of the El Monte OU to inhibit migration of
contaminated groundwater. Alternative 3 does not include any active measures to address deep zone
contamination. The system would be designed to contain shallow groundwater in the western portion of
the OU that has VOC concentrations exceeding 10 times the primary drinking water standards (i.e.,
MCLs). The key components of the alternative are described below.
9.3.1 Extraction
The groundwater extraction in Alternative 3 would generally occur west of Temple City Boulevard
(Figure 2). The shallow extraction would control migration of high-level contamination towards the
west. This alternative would inhibit migration of contamination into downgradient shallow zones that
are currently less contaminated or uncontaminated. Although the primary objective of the extraction
wells is containment, to the extent possible, they would also be sited to maximize mass removal. The
total extraction rate assumed for cost estimation purposes is 150 gallons per minute (gpm). The actual
extraction well locations and rates would be determined during remedial design based on additional
evaluation of the extent of contamination during the remedial design investigation.
9.3.2 Treatment
Either air stripping with off-gas treatment or liquid-phase carbon adsorption would be used to remove
VOCs from the extracted groundwater prior to discharge. For cost estimation purposes, this alternative
assumes a treatment system consisting of air stripping with carbon adsorption of VOCs in the off-gas. [
Other treatment processes could be evaluated during remedial design. 4t|
Treatment for nitrate and total dissolved solids (TDS) present in the shallow groundwater is not included
in the cost estimates presented in Table 4. However, treatment for elevated nitrate and TDS may be
necessary to meet requirements for discharge of the treated groundwater to surface water. For cost
estimation purposes, a reverse osmosis process was assumed to treat elevated nitrate and TDS. If I
required, the addition of reverse osmosis treatment would increase total costs for Alternative 3 by about
25 percent.
9.3.3 Conveyance and Discharge
The assumed end use of the treated groundwater is discharge to Eaton Wash, although other options,
such as reuse of the treated water in industrial processes or landscaping, may be evaluated. In the
assumed scenario, the treated water would be conveyed from the treatment plant to Eaton Wash for
discharge.
9.3.4 Monitoring
Alternative 3 includes a monitoring system to ensure compliance with RAOs and the performance
criteria (discussed in Section 11) in the shallow zone in the Western El Monte OU. In addition, selected
monitoring wells maybe used to provide an early warning system that would provide sufficient time to
prevent noncompliance. Less contaminated groundwater not contained by the remedial action would be
subject to natural attenuation processes as it migrates downgradient. The effectiveness of natural
attenuation processes would be verified by groundwater sampling. For cost estimation and evaluation of
the alternative, installation of 9 new monitoring wells and semi-annual sampling of new and existing
EM_ROD.DOC • - u_9_2
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
wells are assumed. These new wells would include 7 shallow wells and 2 multi-port wells.
9.4 Alternative 4 - Shallow Groundwater Control in
Western and Eastern El Monte OU
Alternative 4 includes all of the components of Alternative 3 described above, plus groundwater
extraction and treatment in the shallow zone in ,the eastern portion of the El Monte OU to inhibit
migration of contaminated groundwater. As in Alternative 3, Alternative 4 does not include any active
measures to address deep zone contamination. This system would be designed to contain shallow
groundwater in both the western and eastern portions of the OU that have VOC concentrations exceeding
10 times the primary drinking water standards (i.e., MCLs). The key components of the alternative are
described below.
9.4.1 Extraction
The additional groundwater extraction in Alternative 4 would generally occur west of Arden Drive and
north of Valley Boulevard (Figure 2). The additional extraction would be intended to control westerly
and southerly migration of high-level shallow zone contamination that is located well to the east of the
Alternative 3 extraction. This alternative would inhibit migration of contamination into downgradient
shallow zones that are currently less contaminated or uncontaminated. Although the primary objective of
the extraction wells is containment, they would also be sited to maximize the removal of contaminants
from the groundwater. The additional extraction rate assumed for cost estimation purposes is 180 gpm.
This would bring the total extraction rate to 330 gpm. The actual extraction well locations and rates
would be determined during remedial design based on additional evaluation of the extent of
contamination during the remedial design investigation.
9.4.2 Treatment
The treatment assumed for Alternative 4 is the same as that described above for Alternative 3. Separate
treatment facilities would be located in the eastern portion of the OU under Alternative 4.
Treatment for nitrate and total dissolved solids (TDS) present in the shallow groundwater is not included
in the cost estimates presented in Table 4. However, treatment for elevated nitrate and TDS may be
necessary to meet requirements for discharge of the treated groundwater to surface water. For cost
estimation purposes, a reverse osmosis process was assumed to treat elevated nitrate and TDS. If
required, the addition of reverse osmosis treatment would increase total costs for Alternative 4 by about
35 percent.
9.4.3 Conveyance, Discharge and Monitoring
Assumptions for each of these components are the same as described above for Alternative 3.
EM_ROD.DOC H-9-3
-------
PART II -DECISION SUMMARY
SL MONTH OU INTERIM ROO
9.5 Alternative 5 - Shallow Groundwater Control in
Western and Eastern El Monte OU Plus Deep
Groundwater Control
Alternative 5 includes all of the components described above for Alternative 4, plus groundwater control
in two areas of deep zone contamination. One area of deep zone control is in the northwestern portion of
the OU in the vicinity of the active Encinitas wellfield (Figure 3). The second area is in the southern
portion of the OU. Drinking water wells completed in the deep zone in both of these areas have been
impacted by VOC contamination. The deep extraction would be designed to control migration of
groundwater containing VOC contamination in excess of primary drinking water standards (MCLs) The
key components of the alternative are described below.
9.5.1 Extraction
The additional groundwater extraction in Alternative 5 would generally occur in two separate locations
In the northern portion of the OU, the extraction would occur at, or in the vicinity of the Encinitas
wellfield (Figure 3). In the southern portion of the OU, extraction would be near the downgradient
extent of contamination. The additional extraction would be intended to control deep zone
contamination exceeding drinking water standards that is migrating northwest and west-southwest
towards existing production wells beyond the OU boundaries. The total deep zone extraction rate
assumed for cost estimation purposes is 1,325 gpm. This would bring the total extraction rate assumed
for Alternative 5 (deep zone plus shallow zone) to 1,655 gpm. The actual extraction well locations and
rates would be determined during remedial design based on additional evaluation of the extent of
contamination during the remedial design investigation.
9.5.2 Treatment
Extracted water would be treated for VOC removal by either air stripping with off-gas treatment or
liquid-phase carbon adsorption. For cost estimation purposes, this alternative assumes a treatment
system consisting of air stripping with carbon adsorption of VOCs in the off-gas. Other treatment
processes could be evaluated during remedial design.
Treatment for nitrate and total dissolved solids (TDS) would not likely be required for the deep
groundwater because the deep water contains lower concentrations of these constituents
9.5.3 Conveyance and Discharge
The assumed end use option for the treated deep groundwater is delivery to a municipal water supply
system. As in Alternatives 3 and 4, it is assumed that the treated shallow water would be discharged to
Eaton Wash, although other options, such reuse of the treated water in industrial processes or
landscaping, may be evaluated.
9.5.4 Monitoring
Alternative 5 includes a monitoring system to ensure compliance with RAOs and performance criteria in
the shallow and deep zones in the El Monte OU. In addition, selected monitoring wells maybe used to
EM_ROD.DOC n_9_4
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
provide an early warning system that would provide sufficient time to prevent noncompliance. Less
contaminated groundwater not contained by the remedial action would be subject to natural attenuation
processes as it migrates downgradient. The effectiveness of natural attenuation processes would be
verified by groundwater sampling. For cost estimation and evaluation of the alternative, installation of 9
new monitoring wells and semi-annual sampling of new and existing wells are assumed. These new
wells would include 7 shallow wells and 2 multi-port wells.
EM_ROD.DOC H.9.5
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
10 Comparative Analysis of Alternatives
The five remedial ahematives described in Section 9 are evaluated using the nine Superfund evaluation
cntena hsted in 40 C.F.R. Section 300.430. The comparative analysis provides the basis for determining
which alternative presents the best balance of the criteria. The first two evaluation criteria are considered
threshold criteria that the selected remedial action must meet. The five primary balancing criteria are
balanced to achieve the best overall solution. The two modifying criteria, state and community
acceptance, are also considered in remedy selection.
Threshold Criteria
• Overall Protection of Human Health and the Environment addresses whether each alternative
provides adequate protection of human health and the environment, and describes how risks posed
through each exposure pathway are eliminated, reduced, or controlled through treatment, engineering
controls, and/or institutional controls. 6
• Compliance with ARARs addresses the requirement of Section 121(d) of CERCLA that remedial
actions at least attain legally applicable or relevant and appropriate federal and state requirements
standards, cntena, and limitations, which are collectively referred to as "ARARs " unless such '
ARARs are waived under CERCLA Section 12l(d)(4).
Primary Balancing Criteria
• Long-term Effectiveness and Permauence refers to the ability of a remedy to maintain reliable
protection of human health and the environment over time.
• Reduction of Toxiciry, Mobility, or Volume Through Treatment refers to the anticipated
performance of the treatment technologies that may be included as part of a remedy.
• Short-term Effectiveness addresses the period of time needed to implement the remedy and any
adverse impacts that may be posed to workers and the community during construction and operation
of the remedy until cleanup goals are achieved.
• Implementability addresses the technical and administrative feasibility of a remedy from design
through construction and operation. Factors such as availability of services and materials
administrative feasibility, and coordination with other governmental entities are also considered.
• Cost evaluates the estimated capital, operation and maintenance (O&M), and indirect costs of each
alternative in comparison to other equally protective alternatives.
Modifying Criteria
• State Acceptance indicates whether the state agrees with, opposes, or has concerns about the
preferred alternative.
• Community Acceptance includes determining which components of the alternatives interested
persons in the community support, have reservations about, or oppose.
EM.ROD.DOC
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
This section describes each threshold and primary balancing criterion, evaluates each alternative in
relation to each criterion, and identifies advantages and disadvantages among the alternatives in relation
to each criterion. Figure 4 presents a comparative matrix in which the five alternatives are ranked for
each of the evaluation criterion. The details of how the rankings have been assigned for each criterion
are provided below.
10.1 Overall Protection of Human Health and the
Environment
The NCP requires that all alternatives be assessed to determine whether they can adequately protect
human health and the environment from unacceptable risks from site contamination. These risks can be
mitigated by eliminating, reducing, or controlling exposure to hazardous substances, pollutants, or
contaminants.
10.1.1 Overall Protection of Human Health and the Environment:
Evaluation of Alternatives
Alternatives 1 and 2 provide the least overall protection of human health and the environment. Neither
alternative has an active remedy component that provides migration control or containment of the
contaminated groundwater. Only the existing groundwater management activities discussed in Section
5.5 would be available to control public exposure to the contaminated groundwater. Limitations of
Alternative 1 include increased long-term potential for human exposure; leaving the burden of
constructing treatment facilities to water purveyors; and increased cost, difficulty, and time required for
containment. As long as existing government controls remain in effect, there should be no increase in
long-term potential for human exposure with Alternative 2. The burden and cost of constructing
treatment facilities, if required, would be borne by the water purveyors. Alternative 2 includes
groundwater monitoring that would provide early warning of increases in contaminant concentrations at
downgradient drinking water sources. An advantage of Alternatives 1 and 2 is that there are no risks
associated with treatment residuals because none are created.
Alternatives 3 through 5 would reduce long-term risks to human health and the environment by
containing contaminated groundwater and preventing migration from more highly contaminated areas to
less contaminated areas. However, Alternatives 3 and 4 are not considered fully protective because they
do not address deep zone contamination. Portions of the deep zone are currently in use as a drinking
water supply. The treatment technologies employed by these alternatives are effective at meeting federal
and state MCLs. Alternative 4 is ranked higher than Alternative 3 because it includes additional shallow
extraction and discrete containment in the eastern portion of the El Monte OU. Alternative 4 extraction
also provides additional mass removal in the eastern portion of the OU. Alternative 5 is ranked higher
than Alternatives 3 and 4 because it addresses both shallow and deep groundwater contamination in the
El Monte OU.
10.2 Compliance with ARARs
This evaluation criterion is also a threshold requirement and is used to determine if each alternative
would attain federal and state ARARs, or whether there is adequate justification for invoking waivers for
specific ARARs.
10.2.1 Compliance with ARARs: Evaluation of Alternatives
Alternatives I and 2 do not meet ARARs. Both alternatives allow for continued migration of
contaminants above MCLs into less contaminated and uncontaminated portions of the groundwater.
EM ROD.DOC • II-10-2
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
Alternatives 3 through 5 were designed to meet the ARARs described in Section 12 of this ROD. These
alternatives provide containment as well as protection of existing production wells and significant
portions of the aquifer that are currently less contaminated or uncontaminated. The recent discovery of
deep groundwater contamination at the Encinitas Well Field, however, indicates that Alternatives 3 and 4
may not meet drinking water ARARs for the deep groundwater zone. Alternative 5 is ranked higher than
Alternatives 3 and 4 because it addresses both shallow and deep groundwater contamination.
10.3 Long-Term Effectiveness
This evaluation criterion assesses the extent to which each remedial alternative reduces risk after the
remedial action objectives are met. Residual risk can result from exposure to untreated waste or
treatment residuals. The magnitude of the risk depends on the magnitude of the wastes and the adequacy
and reliability of controls, if any, that are used to manage untreated waste and treatment residuals. For
this interim action, untreated waste refers to any contaminated groundwater not removed from the
aquifer.
The performance of the alternatives in relation to this criterion is evaluated primarily by estimating the
extent to which each alternative prevents the migration of contamination into less contaminated and
uncontaminated areas. Preventing or reducing contaminant migration reduces contaminant
concentrations in downgradient areas» reducing risk by reducing the likelihood of exposure. Because this
is an interim remedy to contain contaminant migration, untreated wastes will remain in the groundwater.
10.3.1 Long-Term Effectiveness and Permanence: Evaluation of
Alternatives
Alternatives 1 and 2 are ranked low for this criterion because neither alternative has an active remedy
component that provides migration control or containment of the contaminated groundwater.
Contaminated groundwater would continue to migrate downgradient. Although natural attenuation
processes (adsorption, dilution, dispersion) would likely decrease the concentration of contaminants in
the plumes, downgradient water supply wells would be vulnerable to VOC contamination. Alternatives 1
and 2 would not generate any treatment residuals.
Alternatives 3 through 5 provide containment and treatment of contaminated groundwater as indicated
by groundwater modeling. Alternatives 3 and 4 are assigned a lower ranking than Alternative 5 because
they only address the shallow groundwater contamination and provide containment at 10 times drinking
water standards. Alternative 5 addresses both the shallow and deep contamination and provides
containment of water above drinking water standards in the deep zone. Less contaminated groundwater
not contained by the remedial actions in Alternatives 3 through 5 would be subject to natural attenuation
processes as it migrates downgradient. The effectiveness of natural attenuation processes would be
verified by groundwater sampling.
In Alternatives 3 through 5 the residual generated from treatment of contaminated groundwater would be
spent granular activated carbon. This spent granular activated carbon would be reactivated offsite. The
transportation and reactivation of this residual would be conducted in accordance with applicable
regulations and would present minimal long-term risks because contaminants adsorbed to the granular
activated carbon would be destroyed during the reactivation process.
10.4 Reduction of Toxicity, Mobility, and Volume
Through Treatment
This criterion addresses the preference, as stated in the NCP, for selecting remedial actions employing
treatment technologies that permanently and significantly reduce toxicity, mobility, or volume of the
EM ROD.DOC n-10-3
-------
PART Jl - DECISION SUMMA«y
EL MONTE OU INTERIM ROD
hazardous substances asa principal element of the action. This preference is satisfied when treatment is
used to reduce the principal threats at a site through destruction of toxic contaminants, reduction of total
mass of toxic contaminants, irreversible reduction in contaminant mobility, or reduction of total volume
of contaminated media.
This evaluation focuses on the following factors for each remedial alternative:
• Whether the alternative satisfies the statutory preference for treatment as a principal element
- The treatment process employed, including the amount of hazardous materials that will be destroyed
or treated and the degree of expected reduction in toxicity, mobility, or volume
• The degree to which treatment is irreversible
• The type and quantity of treatment residuals that will remain following treatment
10.4.1 Reduction of Toxicity, Mobility, or Volume Through
Treatment: Evaluation of Alternatives
Alternatives 1 and 2 do not provide any increased reduction in toxicity, mobility, or volume over existing
conditions and do not satisfy the statutory preference for treatment. Alternatives 3 through 5 satisfy the
statutory preference for treatment. These alternatives would significantly reduce the volume and
mobility of contamination by inhibiting further contaminant migration. The treatment technologies
considered for Alternatives 3 through 4, air stripping with off-gas controls and liquid-phase carbon
adsorption, would irreversibly reduce the toxicity and volume of contaminants in the extracted
groundwater and result in an effluent stream that meets drinking water standards for VOCs Both
treatment technologies would result in the destruction of VOCs when the granular activated carbon is I
regenerated.
Alternative 3 would provide removal of an estimated 21,400 pounds of VOCs over a 30-year period of WT
operation, while Alternative 4 would provide removal of an estimated 40,000 pounds Alternative 5
provides the highest amount of mass removal with an estimated 45,900 pounds of VOCs removed
Although the VOC mass removed by Alternative 5 is larger than the VOC mass removed by Alternatives
3 and 4, a substantially greater amount of water must be pumped for a relatively small increase in VOC
mass removed. The extraction rate for Alternative 5 is approximately 5 times that of Alternative 4, while
the VOC mass removed is only about 15 percent greater. It should be noted that these VOC mass
removal estimates are very approximate and actual operation of the extraction and treatment systems in
Alternatives 3 through 5 could yield lower or higher values.
10.5 Short-Term Effectiveness
This criterion evaluates the effects of each remedial alternative on human health and the environment
auring the construction and implementation phase until remedial action objectives are met The
following factors are addressed for each alternative:
Protection of workers and the community during construction and implementation phases.
This factor qualitatively examines risk that results from implementation of the proposed remedial
action and the effectiveness and reliability of protective measures.
Environmental impacts. This factor addresses the potential adverse environmental impacts that
may result from the construction and implementation of an alternative. This factor also evaluates the
reliability of the available mitigation measures to prevent or reduce potential impacts.
Time until RAOs are achieved.
EM_ROD.DOC
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
10.5.1 Short-Term Effectiveness: Evaluation of Alternatives
Alternative 1 is not evaluated for this criterion because there is no construction or implementation phase
and RAOs would not be met. None of the alternatives pose unmitigable risks to the community during
construction and implementation. Nor do any of the alternatives pose unmitigable risks to workers
beyond general construction hazards associated with large construction projects. No unmitigable
negative environmental impacts are anticipated in the areas in which facilities would be constructed.
For Alternative 2, the RAOs would not be met as long as contaminant migration continues, which would
likely be a considerable length of time. For Alternatives 3 through 5, containment of contaminated
groundwater would be achieved within a few days of system startup. However, Alternatives 3 and 4 do
not provide containment in all contaminated areas. Alternative 3 would meet the RAOs in the shallow
zone in the western portion of the El Monte OU. Alternative 4 would meet the RAOs in both the western
and eastern portions of the shallow zone, but would not achieve RAOs in the deep zone. Alternative 5 is
the only alternative that would meet the RAOs in both the shallow and deep zones. Alternative 5 may
take slightly longer to meet RAOs because of the additional construction required.
10.6 Implementability
This criterion addresses the technical and administrative feasibility of implementing an alternative and
the availability of various services and materials required during its implementation. The following
factors are considered:
• Technical Feasibility
Ability to construct and operate: addresses any technical difficulties and unknowns
associated with construction or operation of the technology
Reliability of technology: focuses on the likelihood that technical problems associated
with implementation will lead to schedule delays
Ease of undertaking additional remedial action: includes a discussion of what, if any,
future remedial actions may need to be undertaken and how the remedial action would
interfere with, or facilitate, the implementation of future actions
• Administrative Feasibility
Coordination with other agencies, including the need for agreements with parties other
than EPA required for construction and operation of the remedy.
• Availability of Services and Materials
Availability of necessary equipment, specialists, and provisions to assure any necessary
resources
Availability of services and materials, plus the potential for obtaining competitive bids
10.6.1 Implementability: Evaluation of Alternatives
Alternative 1 is not evaluated for this criterion because no action is implemented. As described above,
the implementability evaluation incorporates several factors. Each of these is discussed separately in the
following text. -
Technical Feasibility: Ability to Construct and Operate. The extraction, treatment, and conveyance
technologies included in Alternatives 3 through 5 and the monitoring technologies included in
Alternatives 2 through 5 are widely used. No significant difficulties are expected in construction and
operation of these technologies.
EM_ROD.DOC II-10-5
-------
PART (I - DECISION SUMMARY
EL MONTE OU INTERIM ROD
Technical Feasibility: Reliability of Technology. The extraction, treatment, conveyance, and
monitoring technologies in Alternatives 2 through 5 are generally known to be proven and reliable.
Technical Feasibility: Ease of Undertaking Additional Remedial Actions. The alternatives would
not interfere with the implementation of future response actions to further contain contamination or
restore groundwater in the El Monte OU area.
Administrative Feasibility. There are not likely to be any significant administrative feasibility issues
associated with implementation of Alternative 2, other than obtaining access agreements for monitoring
well installation. Implementation of Alternatives 3 through 5 would require acquisition of property
and/or easements for the construction of extraction wells, treatment facilities, and conveyance facilities.
In addition, implementing Alternatives 3 through 5 would require resolution of the following
administrative issues associated with groundwater extraction and discharge of treated water to local
water purveyors or to Eaton Wash:
• Agreements may need to be made with the Watermaster or with a water purveyor to account for
extraction from the basin by the parties implementing the selected remedy because these parties may
not have water rights.
• An agreement with the Watermaster may be required regarding the potential need to pay
replenishment fees for treated water discharged to Eaton Wash.
• Agreements would need to be reached with water purveyors that would receive treated water from
the groundwater treatment facilities specifying the amount of water each purveyor would accept; the
treated water delivery location; responsibility for any necessary capital improvements to purveyor
systems; and to determine operational, liability, financial, and other arrangements,
• Water purveyors would need to obtain approval for modifications to their water supply permits.
• If treated water is discharged to Eaton Wash, RWQCB Basin Plan water quality objectives for Eaton
Wash would need to be met. If the discharge exceeds Basin Plan inorganic water quality objectives,
it may be necessary to conduct an evaluation of the impact of the discharge on downgradient surface
water and groundwater, as well as an evaluation of reuse alternatives for the VOC-treated
groundwater. If water quality impacts are minimal and reuse alternatives infeasible, the discharge
may be allowed. If the water quality impacts are unacceptable and no other method of disposal is
identified, a treatment system for the inorganics would need to be included as part of the remedial
action. Reverse osmosis treatment is one such system that is generally known to be proven and
reliable.
Availability of Services and Materials. Implementation of Alternatives 3 through 5 would require
fabrication of treatment plant equipment. Required services and materials are believed to be available,
including qualified contractors for construction and operation of the necessary facilities.
Alternative 2 is assigned a higher ranking in Figure 4 because there are no significant issues that could
impact implementability of this monitoring-only alternative. Alternatives 3, 4 and 5 are ranked lower
because of the administrative issues associated with groundwater extraction and treated water discharge.
Alternatives 4 and 5 require construction of additional facilities that could lead to more
construction/schedule delays.
10.7 Cost
This criterion addresses the total cost of each alternative. This includes short- and long-term costs, and
capital and O&M costs. The following cost elements are considered for each alternative:
• Capital Cost. Direct capital cost includes the cost of construction, labor, equipment, land, site
development, and service. Indirect capital cost includes engineering fees, license and permit cost,
EM_ROD.DOC II-10-6
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
startup and shakedown costs, and contingencies.
• O&M Cost. Annual O&M cost includes operating labor cost, maintenance materials and labor
pumping and treatment energy costs, monitoring costs, and all other post-construction costs
necessary to ensure continuous effective operation of the alternative.
• Total Present Worth. The total present worth of each alternative is calculated at a discount rate of
5 percent and a time period of 30 years. Total present worth for each alternative includes capital cost
plus the present worth of the annual O&M costs.
The cost estimates are considered order-of-magmtude level estimates (i.e., the cost estimates have an
expected accuracy of+50 to -30 percent). The assumption of a 30-year operating period is based on EPA
guidance and does not reflect any specific finding regarding the duration of the selected remedy.
10.7.1 Cost: Evaluation of Alternatives
Although there is no cost presented for the no-action alternative (Alternative 1), there have been and
would continue to be substantial financial impacts on local water purveyors or their rate payers because
of the continued migration of contamination to their production wells. Table 4 summarizes the estimated
costs for Alternatives 2 through 5, respectively.
10.7.2 Cost: Comparison of Alternatives
Table 4 compares the cost of each alternative for capital costs, long-term O&M costs, and present worth
The short-term capital costs range from $1,250,000 for Alternative 2 to $7,930,000 for Alternative 5
The annual O&M costs range from $200,000 for Alternative 2 to $960,000 for Alternative 5.
10.8 State Acceptance
The State of California has provided comments and feedback to EPA throughout the RI/FS process for
the El Monte OU. In a letter dated April 12, 1999, the California Department of Toxic Substance
Control (DTSQ, as lead agency for the state, concurred with EPA's selected remedy. In addition the
RWQCB concurred with EPA's selected remedy in a letter dated March 10, 1999.
10.9 Community Acceptance
EPA received written comments from one individual and two organizations on the Proposed Plan for this
interim action in the El Monte OU. In addition, EPA received limited oral comments and questions at
the public meeting held in November 1998 to discuss EPA's plans. EPA responded directly to the oral
questions at the public meeting. All of the written comments received during the 60-day public comment
period , along with EPA's responses to them, are presented in the Responsiveness Summary in Part HI of
this ROD. The transcript for the public meeting is available at EPA's Superfund Records Center at
EPA's Regional Office in San Francisco, and locally at two information repositories- the West Covina
Library and the Rosemead Library.
One commenter did not believe that the information collected and evaluations performed to date
provided sufficient justification to demonstrate that the remedy selected (Alternative 5) was necessary.
This commenter requested that EPA perform additional evaluations and incorporate these into the
remedy selection process. EPA has determined that sufficient data have been collected and evaluated to
conclude that the preferred alternative presented in the Proposed Plan represents the most appropriate
interim remedy for the El Monte OU. None of the comments received warranted a change to the overall
remedy that EPA selected.
EM_ROD.DOC . , IMO_7
-------
-------
PART II -DECISION SUMMARY
EL MONTE OU INTERfM ROD
11 Selected Remedy
After considering CERCLA's statutory requirements, the detailed comparison of the alternatives using
the nine evaluation criteria, and public comments, EPA, in consultation with the State of California has
determined that the most appropriate remedy for this site is Alternative 5: shallow groundwater '
control in western and eastern El Monte OU plus deep groundwater control. Alternatives 1 and 2
provide the least overall protection of human health and the environment and do not comply with
ARARs. Alternative 3 addresses only a portion of the shallow zone in the El Monte OU Although
Alternative 4 adequately addresses all of the shallow contamination in the OU, it does not include
remedial actions that provide containment of the deep zone contamination. Deep zone contamination has
impacted several production wells in the El Monte OU and EPA believes that controlling further
contaminant migration in the deep zone is critical. Because it addresses contaminant migration in both
the shallow and the deep zone, Alternative 5 is the only alternative that meets EPA's remedial action
objectives in both the shallow and deep zones and satisfactorily meets the threshold criteria of overall
protection of human health and the environment and compliance with ARARs. Although Alternative 5
costs more than the other alternatives, the additional benefits provided from the deep zone containment
far outweigh the additional cost. Overall, Alternative 5 provides the best balance in tradeoffs between
the evaluation criteria. EPA expects that this interim remedy will provide the basis for the final remedv
for the El Monte OU. , y
11.1 Description of the Selected Remedy
The selected remedy will be implemented using a performance-based approach. The performance-based
approach specifies criteria ("performance criteria") that must be met while allowing flexibility in
implementation. The performance criteria are designed to attain the RAOs for the El Monte OU and are
described below. These performance criteria have been refined since they were first presented in the
proposed plan for the El Monte OU.
11.1.1 Performance Criteria
Performance Criterion for the Shallow Zone:
The remedial action shall prevent groundwater in the shallow zone with VOC contamination above 10
times the ARARs listed in Table 5 front migrating beyond its current lateral and vertical extent.
Compliance with this criterion will be monitored at wells described as follows:
• Located laterally and vertically downgradient of shallow groundwater contamination exceeding
10 times the relevant ARAR, but generally within areas where VOC concentrations exceed the
ARARs listed in Table 5.
• Completed with screen lengths generally of 20 feet or less between the water table and 130 feet bgs.
Longer screened intervals may be appropriate in limited situations and will be evaluated on a case-
by-case basis
Extracted groundwater will be treated by air stripping (with off-gas controls) or liquid-phase carbon
adsorption. If alternative treatment technologies are identified, EPA will evaluate the alternative
EM_ROD.DOC II-1J-]
1
-------
PART u - DECISION SUMMARY
EL MONTE O(J INTERIM ROO
technologies in accordance with the criteria specified in 40 C.F.R. Section 300.430 during remedial
Performance Criterion for the Deep Zone, .\orthwestern Area
The'remedialaction shall provide sufficient hydraulic control to prevent deep zone groundwater with
ralSSTT rt™*!"?1"**listed™ ™* 5 from migrating into or beyond the EncMtas
Well Field Area (described in Section 1LL3.2) in the northwestern portion oftheOU.
Compliance with this criterion will be monitored at compliance wells described as follows:
• Located within 2,000 feet of a production well in the Encinitas Well Field.
• Located generally west to northwest of the current extent of deep zone groundwater contamination
within the area with detectable VOC concentrations in the deep zone. contaminate,
" Sv hl?d ^ SCree"lenS*s of 20 feet or Iess w»Wn the deep zone. Larger screened intervals
may be appropriate m limited situations and will be evaluated on a case-by-case basis.
Performance Criterion for the Deep Zone, Southern Area
The remedial action shall apply measures necessary to prevent deep zone groundwater with VOC
contam nation above the ARARs listed in Table 5 from migrating Lyondls current"aland
vertical extent, as described in the RI/FS for the El Monte OU, in the southern portion oftheOU.
Compliance with this criterion will be monitored at compliance wells described as follows:
Located within 2,000 feet of the current extent of groundwater contaminated with any VOC
cxcecdmg its ARAR. Because the downgradient extent of deep zone contamination in the
southern area is not well defined, additional data collection during remedial design may be
necessary in this area. 5 y
Located generally west to southwest of the current extent of deep zone groundwater
contamination, within the area with detectable VOC concentrations in the deep zone
™v Eleaed WUh 5?™Snr1
-------
PART II - DECISfON SUMMARY
EL MONTE OU INTERIM ROD
compliance EPA also anticipates that additional monitoring wells will be installed, or existing wells
within this buffer zone will be used to provide an early warning system, and therefore provide sufficient
time to address and prevent noncompliance. . u««,icm
Imminent exceedance of the performance criteria at compliance wells indicates that groundwater
contamination is migrating, and hydraulic containment is required. Any actual or imminent exceedance
of the performance catena at the compliance wells will require groundwater extraction and treatment to
achieve hydraulic containment. Actual exceedance of performance criteria at compliance wells will
result in the initiation of enforcement actions.
11.1.3 Supplemental Explanation of Performance Criteria
^L^v^h^r^r0^^ addi[ional "^nation of the performance criteria, their meaning and
objectives to help clarify the intent of the criteria.
11.1.3.1 The "Shallow" and "Deep" Zones
The shallow zone generally encompasses the upper 100 feet of the saturated aquifer including the
interval between the water table and approximately 150 feet below ground surface The deep zone
generally includes the somewhat coarser-grained interval beneath the shallow zone that is used for
groundwater production. Both terms are used in a manner consistent with their usage in the El Monte OU
Final Remedial Investigation and Feasibility Study Reports (COM, 1998a and 1998b, respectively).
^IrSfniT" mdJdeePr^S ^ termS intCnded t0 deSCribe general horizons within «« aquifer(s)
underlying the El Monte OU. During the course of the RI and development of the FS, the complex
stratigraphy was simplified with generalizing assumptions about vertical intervals that appear to have
similar characteristics throughout the area. However, actual subsurface conditions are not accurately
described by terms that imply a well-layered system. The alluvial materials that underlie the El Monte
OU are very heterogeneous, and are made up of interfmgering lenses of variable hydraulic properties.
The shallow zone represents the upper portion of the saturated sediments at and under the water table
contaminant concentrations, transport rates and groundwater flow directions in the shallow zone varv
considerably across the El Monte OU. Remediation of migrating contamination in the shallow zone
requires careful analysis of this variability and an adequate understanding of the extent nature and
sources of contamination. ' '
The deep zone incorporates the entire portion of the aquifer beneath the shallow zone. In the context of
this remedy the deep zone extends to the deepest depths where groundwater exceeds ARARs standards
In general, this ,s the upper 400 feet below ground surface. However, depth-specific sampling indicates
that isolated occurrences of deeper ARARs exceedances are possible. Contamination appears to travel
faster within the deep zone because of the coarser sediments and associated higher hydraulic
conductivity values. Numerous drinking water production wells extract water from the deep zone in the
El Monte OU vicinity. Containing contaminant migration within the deep zone is considered essential to
avoiding further adverse impacts to downgradient drinking water wells in the future.
11.1.3.2 Encinitas Well Field Area
The Encinitas Well Field contains production wells owned by Southern California Water Company The
current extent of deep zone groundwater contamination extends into the Encinitas Well Field EPA's
objective in this portion of the deep zone is to ensure that contamination does not migrate beyond the
Encmitas Well Field Area. For the purposes of this remedial action, the Encinitas Well Field Area is
?«n^ 3S: (l) the three Southem California Water Company Encinitas wells (wells 01902024
10902035 and 08000073) and (2) the downgradient extent of contamination above ARARs in the
vicinity of these wells. The intent of defining the zone in this manner is to provide an adequate basis for
designing a remedial acUon that does not allow contamination to spread away from its current extent.
EM_ROD.DOC
-------
PART II _ DECISION SUMMARY
EL MONTE OU INTERIM ROD
2toSS^C" Fn ^ ^ is °onsider!d to be a genera"y eIIiP^*I or circular area that encompasses
both the Encmitas wells and any downgradient extent of contamination.
WeFedr,rfr * accomPIish the deeP 2one <*jectivts in the Encinitas
well Field Area. The first relies exclusively on installation of new extraction wells upgradient of the
production wells. These new wells must provide sufficient hydraulic control to cap Je conSminatJon
migrating into the production field. The second approach incorporates the production we?ls imo tK
rernedwl action. If this approach is used, it must be demonstrated that pumping from the production
wells alone, or in combination with new wells, provides sufficient hydraulic control. For the production
wells to be considered part of the remedial action, the responsible parties will have to provide acceptable
assurances to EPA that the wells will operate in a manner that ensures compliance with the peSance
criteria If other approaches for achieving containment are identified, EPA will evaluate those methods
in accordance with the criteria specified in 40 C.F.R. Section 300.430. mcmoos
mACdial ^pr0a°h> """Plfe** will be monitored at wells located downgradient of the Encinitas
Area. If a new extraction system is used, monitoring wells must also be placed to measure
the effectiveness of the system at preventing migration of contaminants into the Encinitas Well Field
Area. The remedial action must, by itself, provide sufficient capture and be monitored to ensure that the
performance criteria are not exceeded.
11.1.3.3 Compliance Wells
Compliance wells in the shallow zone will be located to ensure adequate monitoring of contaminant
migration both laterally and vertically. Wells must provide sufficient information to assess whether the
ofThei llSS^f rVenti^ fUrther migrati°n °f contaminants- Tl* Dumber, location, and monitoring
of these wells must ensure that contamination is not spreading laterally away from areas that are already
contaminated, or vertically into deeper zones.
SlnSf^8 °Tntly Condu?iinS ** 'tEarlv Response Action Program" (ERAP) that includes the
installation of 7 shallow momtonng wells along the edges of the shallow groundwater plumes. Data
collected from this program will be used together with data collected during the RI to determine the
current lateral and vertical extent of shallow groundwater contamination.
Compliance wells in the deep zone, southern portion of the OU, must be located within 2 000 feet of the
^t™™^ Ter contamination exceeding ARARs or, in the northwestern portion of the OU
wtthin2000 feet of the Encinitas Well Field Area, yet within areas of detectable contamination, as'
described in the performance criteria, and further described below. The intent of locating these wells in
this manner is to provide compliance points that are sufficiently distant from existing contamination
above ARARs to provide enough time to ensure that additional actions can be taken before threshold
concentrations are exceeded. The wells must also be sufficient in number and adequately located to
ensure that contamination above ARARs does not migrate away from the Encinitas Well Field Area or
the current extent of contamination in the southern area. As described above, the downgradient extent of
contamination m the southern deep zone has not been fully characterized. The downgradient extent of
contamination will be more fully characterized using data from up to two ERAP mtilti- port wells in the
southern area of the El Monte OU.
Locations of all compliance wells are subject to EPA approval. Well screens will generally be of 20 feet
or ess. Concentrations in wells vary as a function of screen length because of blending Therefore
wells with screens longer than 20 feet are not generally considered appropriate for monitoring
compliance. However, based on conditions encountered during installation of these wells it may be
appropriate to consider longer screens to ensure monitoring of several high-permeability zones
Installation of wells with screens exceeding 20 feet will be considered on a case-by-case basis subject to
er A approval. J
EM_ROD.DOC
II-11-4
-------
PART II - DECISION SUIWMAR V
cL MONTS OU INTERIM ROD
11.1.3.4 Adverse Effects
The term "adverse effects" is included in the performance criteria to prevent the design and installation
of a hydraulic control system that maintains concentrations at compliance wells below specified
thresholds at the expense of production wells that are not part of the remedy. The principal adverse
effect of concern is implementation of the remedial action in a manner that results in increased
contaminant concentrations in wells that are not part of the remedial action. This requirement prevents,
for example, the installation of new extraction wells immediately upgradient of the compliance wells and
downgradient of production wells that are not part of the remedial action. The remedial action must be
protective of the environment and not result in adverse effects, either on production wells, or on the
overall extent of contamination.
11.2 Summary of the Estimated Remedy Costs
A detailed breakdown of the estimated capital, operating and maintenance (O&M), and present worth
costs associated with the selected remedy is included in Table 6. The present worth costs assume a 5%
discount rate and a 30 year project duration. These cost estimates are expected to be accurate within +50
to -30%. The total estimated capital costs are $7.93 million. The estimated annual O&M costs are $0.96
million and the total present worth cost estimate is $22.67 million.
11.3 Expected Outcomes of the Selected Remedy
Once implemented, this interim remedy will protect the existing beneficial uses of the currently
uncontaminated aquifer downgradient of the compliance wells. The remedy will allow for continued use
of these areas, particularly the deep zone, as a source of drinking water supply.
Because the interim remedial action selected in this ROD is for containment and not restoration, no final
cleanup standards have been established for restoration of groundwater. This means that at least a
portion of the shallow and deep zones upgradient of the compliance wells and any associated extraction
systems will likely remain contaminated and unusable for a considerable length of time.
EM_ROD.DOC 11-11-5
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU fNTERIM ROD
12 Applicable or Relevant and
Appropriate Requirements (ARARs)
Section 121(d) of CERCLA, 42 U.S.C. § 9621(d) requires that remedial actions at CERCLA sites attain
(or justify the waiver of) any federal or state environmental standards, requirements, criteria, or
limitations that are determined to be legally applicable or relevant and appropriate. These applicable or
relevant and appropriate requirements are referred to as "ARARs." Federal ARARs may include
requirements promulgated under any federal environmental laws. State ARARs may only include
promulgated, enforceable environmental or facility-siting laws of general application that are more
stringent or broader in scope than federal requirements and that are identified by the state in a timely
manner.
An ARAR may be either "applicable," or "relevant and appropriate," but not both. If there is no specific
federal or state ARAR for a particular chemical or remedial action, or if the existing ARARs are not
considered sufficiently protective, then other guidance or criteria to be considered (TBCs) may be
identified and used to ensure the protection of public health and the environment. The NCP, 40 C.F.R.
Part 300, defines "applicable," "relevant and appropriate," and "to be considered" as follows:
Applicable requirements are those cleanup standards, standards of control, or other substantive
requirements, criteria, or limitations promulgated under federal environmental or state environmental
or facility siting laws that specifically address a hazardous substance, pollutant, contaminant,
remedial action, location, or other circumstances found at a CERCLA site. Only those state
standards that are identified by a state in a timely manner and that are more stringent than federal
requirements may be applicable.
• Relevant and appropriate requirements are those cleanup standards, standards of control, and
other substantive requirements, criteria, or limitations promulgated under federal environmental or
state environmental or facility siting laws that, while not "applicable" to a hazardous substance,
pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA site, address
problems or situations sufficiently similar to those encountered at the CERCLA site that their use is
well suited to the particular site. Only those state standards that are identified in a timely manner
and that are more stringent than federal requirements may be relevant and appropriate.
TBCs consist of advisories, criteria, or guidance that EPA, other federal agencies, or states
developed that may be useful in developing CERCLA remedies. The TBC values and guidelines
may be used as EPA deems appropriate.
ARARs are identified on a site-specific basis from information about the chemicals at the site, the
remedial actions contemplated, the physical characteristics of the site, and other appropriate factors.
ARARs include only substantive, not administrative, requirements, and pertain only to onsite activities.
Offsite activities must comply with all applicable federal, state, and local laws, including both
substantive and administrative requirements, that are in effect when the activity takes place. There are
three general categories of ARARs:
EM_ROD.DOC II-12-1
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
• Chemical-specific ARARs are health- or risk-based concentration limits, numerical values, or
methodologies for various environmental media (i.e., groundwater, surface water, air, and soil) that
are established for a specific chemical that may be present in a specific media at the site, or that may
be discharged to the site during remedial activities. Thuse ARARs set limits on concentrations of
specific hazardous substances, pollutants, and contaminants in the environment. Examples of this
type of ARAR include state and federal drinking water standards.
• Location-specific ARARs set restrictions on certain types of activities based on site characteristics.
Federal and state location-specific ARARs are restrictions placed on the concentration of a
contaminant or the activities to be conducted because they are in a specific location. Examples of
special locations possibly requiring ARARs may include floodplains, wetlands, historic places, and
sensitive ecosystems or habitats.
• Action-specific ARARs are technology- or activity-based requirements that are triggered by the type
of remedial activities under consideration. Examples of this type of ARAR are RCRA regulations
for waste treatment, storage, or disposal.
EPA has evaluated and identified the ARARs for the selected remedy in accordance with CERCLA, the
NCP, and EPA guidance, including the CERCLA Compliance with Other Laws Manual. Part I (Interim
Final). OSWER Directive 9234.1-01 (EPA, 1988a) and CERCLA Compliance with Other Laws Manual
Part II. OSWER Directive 9234.1-02 (EPA, 1989).
12.1 Chemical-specific ARARs
The chemicals of potential concern for the El Monte OU are VOCs that have been detected in
groundwater in the El Monte OU. Table 5 lists these VOCs and their chemical-specific ARARs. I
12.1.1 Federal Drinking Water Standards (•
EPA has established MCLs, 40 C.F.R. Part 141, under the Safe Drinking Water Act (SDWA), 42 U.S.C.
§§ 300f-j, to protect public health from contaminants that may be found in drinking water sources.
MCLs are applicable at the tap for water that is delivered directly to 25 or more people or to 15 or more
service connections.
Under the SDWA, EPA has also designated Maximum Contaminant Level Goals (MCLGs), 40 C.F.R.
Part 141, which are health-based goals that may be more stringent than MCLs. MCLGs are set at levels,
including an adequate margin of safety, where no known or anticipated adverse health effects would
occur. MCLGs greater than zero are relevant and appropriate where multiple contaminants in
groundwater or multiple pathways of exposure present unacceptable health risks (EPA, 1988b). One
chemical detected in the El Monte OU groundwater, 1,1,2-trichloroethane, has an MCLG that is more
stringent than its MCL.
Under Section 300.43 0(f)(5) of the NCP, remedial actions must generally attain MCLs and nonzero
MCLGs if the contaminated water is a current or potential source of drinking water. The 1995 Water
Quality Control Plan for the Los Angeles Region (Basin Plan) designates all of the contaminated
groundwater in the El Monte OU as current and potential sources of drinking water. However, since this
ROD selects an interim remedial action to contain contaminant migration, no final cleanup standards are
established for the restoration of groundwater. Final cleanup standards will be established in a Final
ROD. For this Interim ROD, EPA has determined that the federal MCLs and nonzero MCLGs listed in
Table 5 are ARARs for any groundwater that is extracted and used for domestic, municipal, industrial, or
agricultural purposes, and for any groundwater that is discharged to the environment. In addition, these
MCLs and MCLGs are ARARs for currently uncontaminated groundwater in the deep zone
downgradient of the existing compliance wells established by the remedial action (EPA, 1988a).
EM_ROD.DOC II-12-2
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
If treated groundwater is to be delivered into a public water supply, all legal requirements for drinking
water in existence at the time that the water is served will have to be met because EPA considers the
service of water to the public to be an offsite activity.
12.1.2 California Drinking Water Standards
California has established state MCLs for sources of public drinking water, under the California Safe
Drinking Water Act of 1976, Health and Safety Code (H&SC) §§ 4010.1 and 4026(c), California Code of
Regulations (CCR) Title 22, §§ 64431 and 64444. Some state MCLs are more stringent than the
corresponding federal MCLs. EPA has determined that the more stringent state MCLs are relevant and
appropriate for the El Monte OU. There are also some chemicals that lack federal MCLs. Where state
MCLs exist for chemicals that lack federal MCLs, EPA has determined that the state MCLs are relevant
and appropriate for the El Monte OU. State MCLs apply to remedial actions in the El Monte OU in the
same manner as federal MCLs. Table 5 identifies the state MCLs that are ARARs for this remedial
action.
12.2 Location-specific ARARs
This ROD specifies performance criteria for the remedy. As such, the locations of remediation facilities
(e.g., wells, treatment plant, and pipelines) are not specifically identified herein. Locations of
remediation facilities will be determined during the remedial design, and will conform to the location-
specific ARARs identified below.
12.2.1 Location Standards for TSD Facilities
California Code of Regulations, Title 22, Section 66264.18 establishes location standards for Hazardous
Waste Treatment, Storage, and Disposal Facilities (TSDFs). Subsection 66264.18(a) prohibits the
placement of TSDFs within 200 feet of a fault displaced during the Holocene epoch.
Subsection 66264.18(b) requires that TSDFs located within a 100-year floodplain be capable of
withstanding a 100-year flood. These standards are applicable to the construction of any new
groundwater extraction and treatment-facilities used as part of this remedial action.
12.2.2 Endangered Species Act
The Endangered Species Act, 15 U.S.C. §§ 1531-1544, and implementing regulations, 40 C.F.R. §
6.302(h), 50 C.F.R. Parts 17, 222 and 402, are applicable to any remedial actions that impact a proposed
or listed threatened or endangered species or destroy or adversely modify the critical habitat of a listed
species. No endangered species are known or suspected to occur in the locations where remedial action
facilities might be constructed. If, however, it appears during the implementation of the remedial action
that construction activities or the discharge of treated groundwater might adversely affect a proposed or
listed species, EPA will consult with the U.S. Fish and Wildlife Service (FWS) in accordance with
50 C.F.R. Part 402 and ensure that regulatory requirements are followed so that adverse impacts are
avoided or mitigated.
12.2.3 California Fish and Game Code
California Fish and Game Code sections 2080,5650(a), (b), and (f), 12015, and 12016 prohibit the
discharge of harmful quantities of hazardous materials into places that may deleteriously affect fish,
wildlife, or plant life. These provisions are applicable if the remedial action will result in the discharge
of treated groundwater to surface waters.
EM_ROD.DOC II-12-3
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
12.2.4 National Historic Preservation Act
The National Historic Preservation Act and implementing regulations (16 U.S.C. § 470,40 C.F.R.
Part 6.30l(b), 36 C.F.R. Part 800) require federal agencies or federal projects to take into account the
effect of any federally assisted undertaking or licensing on any district, site, building, structure, or object
that is included in, or eligible for, the Register of Historic Places. If remedial action is likely to have an
adverse effect on any cultural resources that are on or near the El Monte OU, EPA will examine whether
feasible alternatives exist that would avoid such effects. If effects cannot reasonably be avoided,
measures will be implemented to minimize or mitigate the potential effect.
No cultural resources are anticipated in the vicinity of facilities for this remedial action. However, during
preliminary design, a complete review of all impacted areas will be made.
12.2.5 Archaeological and Historic Preservation Act
This statute and implementing regulations, 16 U.S.C. § 469, 40 C.F.R. Part 6.30l(c), establish
requirements for the evaluation and preservation of historical and archaeological data that may be
destroyed through alteration of terrain as a result of a federal construction project or a federally licensed
activity or program. No sites of historical interest are anticipated in the vicinity of facilities for this
remedial action. However, during preliminary design, a complete review will be made of impacted
areas.
12,2.6 Historic Sites, Buildings, and Antiquities Act
The Historic Sites, Buildings, and Antiquities Act, 16 U.S.C. §§ 461-467, 40 C.F.R. Part 6.30 l(a),
requires federal agencies to consider the existence and location of landmarks on the National Registry of
Natural Landmarks to avoid undesirable impacts on such landmarks. The remedial action is not
anticipated to affect any of the facilities regulated under the act. However, during preliminary design, a
complete review will be made of impacted areas.
12.3 Action-specific ARARs
12.3.1 Local Air Quality Management
One VOC treatment technology that may be used is air stripping. Air emissions from air strippers are
regulated by the California Air Resources Board, which implements the federal Clean Air Act (CAA), as
well as the air pollution control requirements of the California H&SC, through local air quality I
management districts. Local districts may impose additional regulations to address local air emission
concerns. The local air district for the El Monte OU is the South Coast Air Quality Management District
(SCAQMD). The SCAQMD has adopted several rules that are ARARs for air stripper emissions and
construction activities.
SCAQMD Regulation XIII, comprising Rules 1301 through 1313, establishes new source review
requirements. Rule 1303 requires that all new sources of air pollution in the district use best available
control technology (BACT) and meet appropriate offset requirements. Emissions offsets are required for
all new sources that emit in excess of one pound per day.
SCAQMD Rule 1401 requires that best available control technology for toxics (T-BACT) be employed
for new stationary operating equipment, so that the cumulative carcinogenic impact from air toxics does
not exceed the maximum individual cancer risk limit of 10 in 1 million (1 x 10'5). Many of the
contaminants found in the El Monte OU groundwater are air toxics subject to Rule 1401.
ENf_ROD.DOC II-12-4
-------
PART II _ DECISION SUMMARY
SL MONTE OU /MTER/M «OO
_
ARARs for construction and operation of remedial action
le em,ssions from a point source.' Rule 402P™Sts
', nuisance, or annoyance to the public. Rule 403
Water
<**»
• Municipal and domestic supp]y (potential beneficial use)
• Groundwater recharge Cintennittent beneficial use)
- Water contact recreation (intermittent beneficial use)
' Noncontact water recreation (existing beneficial use)
• Wann freshwater habitat (potentia,/intennittent beneficial use)
- Wildlife habitat (existing beneficial use)
relevant segment of the Rio Hondo: Basm PIan are ARARs for Eaton Wash and the
• Total Dissolved Solids: 750 mg/L
• Sulfate: 300 mg/L
• Chloride: 150 mg/L
• Boron: 1. 0 mg/L
• Nitrogen (NO3-N -<- NO2-N)- 8 mg/L
EM_ROD.DOC
II- 12-5
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
concentration of a waste discharged to surface or groundwater is required to use the "best practicable
treatment or control."
Resolution 68-16 is applicable to discharges of treated groundwater. If treated water is to be discharged
to Eaton Wash, the RWQCB may require an evaluation of the potential impact of nitrate and TDS
contained in treated groundwater on receiving waters and investigate alternative discharge options. If
water quality impacts are minimal and alternative discharge options infeasible, the RWQCB may allow
the discharge to Eaton Wash.
12.3.2.3 State Water Resources Control Board Resolution 92-49
. Subsection III.G of the SWRCB's "Policies and Procedures for Investigation and Cleanup and
Abatement of Discharges under Water Code Section 13304" (Resolution 92-49) requires attainment of
background water quality or, if background levels cannot be restored, the best quality of water that is
reasonable. Resolution 92-49 is not an ARAR because this is an interim remedial action to contain the
spread of contamination, rather than a final action to restore groundwater in the El Monte OU.
12.3.2.4 Standards Applicable to CERCLA Section 104(b) Discharges to Surface
Waters
Site investigation activities undertaken pursuant to CERCLA § 104(b) are considered to be removal
actions. It is EPA policy that removal actions "comply with ARARs to the extent practicable,
considering the exigencies of the circumstances." (55 Fed. Reg. 8756).
It is possible that certain site investigation activities will take place during remedial design, which will
result in temporary high-flow, high-volume discharges of contaminated groundwater (e.g., discharges
from aquifer testing of extraction wells). EPA has considered the best available technology
economically achievable (BAT) for treatment and disposal of these discharges. The three disposal
options that EPA considered are: (1) onsite storage and disposal at a Resource Conservation and
Recovery Act (RCRA)-approved hazardous waste facility, (2) discharge to a sanitary sewer for treatment
at a wastewater treatment plant, and (3) onsite treatment and discharge to surface water channels. EPA
has concluded that compliance with chemical-specific ARARs is not practicable, considering the
exigencies of the circumstances, for many temporary high-flow, high-volume discharges.
EPA has determined that compliance with chemical-specific ARARs is practicable and necessary for
CERCLA § 104(b) activities that do not result in temporary high-flow, high-volume discharges. EPA
will determine the application of chemical-specific ARARs to CERCLA § 104(b) activities on a case-by-
case basis. Where practicable, these discharges must comply with ARARs.
12.3.3 California Hazardous Waste Management Program
The federal RCRA establishes requirements for the management and disposal of hazardous wastes. In
lieu of the federal RCRA program, the State of California is authorized to enforce its Hazardous Waste
Control Act, and implement regulations (CCR Title 22, Division 4.5), subject to the authority retained by
EPA in accordance with the Hazardous and Solid Waste Amendments of 1984 (HSWA). California is
responsible for permitting treatment, storage, and disposal facilities within its borders and carrying out
other aspects of the RCRA program. Some of the Title 22 regulations are applicable to the generation
and disposal of hazardous wastes in the El Monte OU.
12.3.3.1 Hazardous Waste Generator Requirements
CCR Title 22 establishes requirements applicable to generators of hazardous waste. Implementation of
the remedial action may generate hazardous waste as a result of ground-water monitoring and well
installation (e.g., contaminated soil and groundwater and used personal protective equipment).
Hazardous waste may also be generated as a result of ground-water treatment to remove VOCs (e.g.,
EM_ROD.DOC II-12-6
-------
ST^0eC'SION SUMMAKY
SL MONTE OU INTERIM ROD
.
12.3.3.2 Land Disposal Restrictions
Section 66264. 14: Security Requirements
'
12.4 ARARs Waivers
EM_ROD.DOC
II-12-7
-------
-------
PART II - DECISION SUMMARY
EL MONTE OU INTERIM ROD
13 Statutory Determinations
Under CERCLA Section 121, EPA must select remedies that are protective of human health and the
^ST;^ * 7htaPPliCfe f r relCVant ^ aPPr°P™
-------
PART II _ DECISION SUMMARY
EL MONTE Oil INTERIM ROD
13.4 Utilization of Permanent Solutions and
Alternative Treatment Technologies to the
Maximum Extent Practicable
As an interim remedial action, EPA has determined that the selected remedy represents the maximum
?*!?«« Permanent solutions and treatment technologies can be utilized in a practicable manner •
in the El Monte OU EPA has also determined that the selected remedy provides the best balance of
tradeoffs in terms of the five balancing criteria, while also considering the statutory preference for
treatment as a principal element and considering state and community acceptance.
The selected remedy satisfies the long-term effectiveness criterion by removing VOC contamination
from the groundwater and destroying the VOCs during carbon regeneration. Groundwater containment
through extraction effectively reduces the mobility and volume qf and potential for exposure to site-
related contamination. The selected remedy does not present any short-term risks that can not be readily
mitigated and EPA expects that the implementability issues associated with the selected remedy can be
resolved in a timely manner.
13.5 Preference for Treatment as a Principal Element
By treating the contaminated groundwater through air stripping or liquid-phase carbon adsorption the
selected remedy addresses the site contamination through the use of treatment technologies By using
treatment as a significant portion of the remedy, the statutory preference for remedies that employ
treatment as a principal element is satisfied.
13.6 Five-Year Reviews
Because the remedy will result in hazardous substances remaining onsite above levels that allow for
unlimited use and unrestricted exposure, EPA shall conduct a review of the remedy at least once every
5 years after initiation of remedial action. The review will assess whether the remedy continues to
provide adequate protection of human health and the environment. If it is determined that the remedy is
no longer protective of human health and the environment, then modifications to the remedy will be
evaluated and implemented as necessary.
EM_ROD.DOC
-------
PART II -DECISION SUMMARY
EL MONTE OU INTERIM ROO
14 Documentation of Significant
Changes
The Proposed Plan for the El Monte OU was released for public comment in October 1998 The
Proposed Plan identified Alternative 5, Shallow Groundwater Control in Western and Eastern El Monte
OU Plus Deep Groundwater Control, as the Preferred Alternative for addressing groundwater
contamination in the El Monte OU. EPA reviewed written and verbal comments submitted during the
public comment period. It was determined that no significant changes to the remedy, as originally
identified m the Proposed Plan, were necessary.
EM ROD.DOC
II-14-1
-------
-------
Part III
Responsiveness Summary
-------
.*- *•
-------
Part HI - Responsiveness Summary
This Responsiveness Summary portion of the interim Record of Decision (ROD) presents the U.S
Environmental Protection Agency's (EPA) responses to the written and significant oral comments
received at the public meeting and during the public comment period. Comments were received from
one individual, one water purveyor, and the Northwest El Monte Community Task Force (NEMCTF) a
group of potentially responsible parties in the El Monte OU who conducted the Interim RI/FS for the El
Monte OU. The section is divided into responses to written comments and responses to oral comments
Comments are expressed in italics, EPA's responses in plain text.
1 Responses to Written Comments
This section provides responses to written comments received by EPA during the public comment
period. Written comments were received from Mr. Glen E. Powell; CPM; the San Gabriel Valley Water
Company (SGVWC); and the NEMCTF.
1.1 Responses to Comments from Mr. Glen E. Powell
Powell Comment. EPA Fact Sheet which is seeking WRITTEN AND VERBAL COMMENTS from the
Public on its plan of remediation of the El Monte Operable Unit ground water. EPA prefers the most
expensive alternative without consideration of Nature's Natural Process of cleansing itself.
I believe that it is not in the best interest of our Government and out Nation to press jbr a liarsli
punishment on OWNERSHIP of PROPERTY which Congress has discouraged on Real Estate
Investments of properties located in the San Gabriel Valley. They have pronounced without ANY
consideration of PUBLIC LAND FILLS commonly known as PUBLIC DUMPS, which are ALL a matter
of PUBLIC RECORDS located in this El Monte Area, should be taken into consideration for minor
pollution found on ALL properties located in the line of flow of our natural underground surface water
flow (maps attached).
Since ALL PROPERTIES IN THE SAN GABRIEL VALLEY are guilty of using these PUBLIC DUMPS in
the past, our present PROBLEM should be treated on the same basis as our aging sewer problem with a
reasonable tax on ALL PROPERTIES using this ground water based upon the amount used. There is an
increase use of this ground water today (with the increase in our San Gabriel Valley population), which is
being drawn from this underground water supply. This increase volume of water used, will free up '
capital, which is now being demanded (by the EPA) from those, who may not have owned the property
being named as a major polluter, which they now hold and have capital investment interest in the
property, but did not have at the time of the supposed claim of pollution. This will help to free up capital
which builds factories, multifamily and office buildings and shopping centers that in turn produce jobs.
EM_ROD.DOC m-l-l
-------
PART III - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
increased income and wealth.
A bill has been introduced to facilitate larger quantities of run-off water to flow into the vallev to heh
clean existing ^r supplies and allow for more water storage for use during drought years^ been
^^
^l^^^S00""^ imPaCtmg ^^ areas Comment. San Gabriel Valley Water Company ("San
) is a public utility providing water service to all or portions of 18 cities in LosAnlete Tcounto
*''0 ™erned that VOCsfrom the El Monte OU could be a source of the
r I Plant N? 8 ^ might CmtSe the c°™™™
-------
PART in - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
flow directions in the deeper zone in this area are from east to west. Available data indicate that the
SGVWC s Plant No. 8 wellfield is more likely coming from sources in the SoS S Monte OU.
°nte °U JS lntended t0 C0ntain deeP ^amination in the southern
1.3 Responses to Comments from the Northwest El
Monte Community Task Force (NEMCTF)
NEMCTF Comment No. 1. USEPA 's Proposed Plan states that the shallow aquifer within the EMOU n
considered a drinking water source by the State of California. We point out that USEPA fails to
acknowledge the fact that the shallow aquifer is not usable for drinking water purpose* flue ohizh
concentrates of Total Dissolved Solids and Nitrate. These two compounds may be natural y occurring
M° COmP°U,ndS ^ n0t relMedt° the operations of the businesses thacompr^he
reC°f'Zet,hat theState '* Agnation of potential drinking water sources inches
ma have limitations on
* , na rnng water sources inchs
aquifers whtch may have limitations on their use as a result of pre-existing water quality constraints It
£3£2 h°Ter'!hal suct signiflcant water quality limila« -
aquifer be taken into consideration in determining the remedy
ackn°wIedSes th/1 P°rtions of *e shallow aquifer in the El Monte OU area
srr^r^
rs^^^
e fS C°nSlderable ^amination in the deep Zone in the El Monte OU and vicinity, Seating
of vertical migration pathways from the shallow zone to the deeper zone. The larger the
extent of contamination in the shallow zone, the greater the potential for vertica. migrationlnSThe deeper
Second, EPA's performance criterion for the shallow groundwater zone reflects the current absence of
±^ndwar ninthatZOne' (SeePart"' Section 11.1). The performance criteria £ The Sp
groundwater zone require contamment of contamination above MCLs because the deep zone is an existing
I
T6"* N0' 2\YS?PA 'S Pr°P°sedPl™ describes USEPA 's summary of site risks. USEPA
una A/ /" r,eaS°,nable t0 ^P*" that ^public will be exposed to contaminated groundwater
at unacceptable levels unless a very costly remedy is implemented. We point out that USEPA ~s
contemplated scenario is highly unlikely to occur; and. would in fact nlcessHaetheoc^rence of a
series of unlawful acts. USEPA 's Proposed Plan assumes that someone would install a potable water
supply well, without obtaining a permit, into the shallow aquifer in an area containing L l^ighelt levels
of contamination and located directly beneath an industrial facility. This USEPA scenario assumes the
EM ROD.DOC
III-1-3
-------
.
vfotatoi of easily Itsalatton enacted and promulgated to preclude such
PART III - RESPONSIVENESS SUMMARY
H-MONTE OU INTERIM ROD
an outcome.
groundwater in a potential drinking water aquifer are consistSfwifh EPA^ucT
"risk-based" interim remedy. The primary goal of this interim
considered in deciding whether to take action at the El Monte OU. The remedial des L wil no?L T™^
K°rat
concentrations averaged over a five year, or greater, period of time. We request thatUSEPA
the constable uncertainties and potential inaccuracies reflected in these Zo maps
EPA's Response. EPA generally concurs with the comment regarding the
°-di°*™i°'»' <"Pi«'i«» of =ontamu»,ion fa, actually
EM ROD.DOC
III- 1-4
•
-------
PART in - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
The figure shows only regional variability in contamination. In much of the basin, distances between
data points are in the 1,000s effect. Thus, there is significant uncertainty in the true locations of the
concentration contours."
NEMCTF Comment No. 4. In its analysis of (he various remedial Alternatives USEPA notes that
Alternatives ! and 2 do not meet several of their criteria. Given that these two Alternatives were crafted
by USEPA to include the previously described unlawful acts associated with supplying untreated highly
contaminated groundwater as a potable water supply over time, it is presupposed by USEPA that
Remedial Alternatives I and 2 would not comply with state or federal requirements
EPA's Response. The comment incorrectly interprets the analysis of Alternatives 1 and 2 in relation to
the evaluation criteria. The reasons that these alternatives do not meet several of the criteria are not
related tothe potential long-term use of the shallow, highly contaminated groundwater as a potablTwater
supply. The following text, summarized from the El Monte OU Final FS, describes why these alternatives
do not meet or are ranked low for the various criteria:
Overall Protection of Human Health and the Environment- Alternatives 1 and 2 provide the least
overall protection of human health and the environment. Neither alternative has an active remedy
component that provides migration control or containment of the contaminated groundwater other than
groundwater management actions which regulate groundwater pumping in the San Gabriel Basin.
ARARs" T11656 alternatives do not meet the ARARs criteria because both alternatives allow continued
migration of contaminants and also may not ensure compliance with MCLs established by the federal or
state Safe Drinking Water Acts.
Long-Term Effectiveness- Alternatives 1 and 2 are ranked low for this criterion because neither
alternative has an active remedy component that provides migration control or containment of the
contaminated groundwater. Contaminated groundwater would continue to migrate downgradient.
Reduction in Toxicity, Mobility and Volume- Alternatives I and 2 do not provide any increased
reduction in toxicity, mobility, or volume over existing conditions and do not satisfy the statutory
preference for treatment.
NEMCTF Comment No. 5. In describing Remedial Alternatives 3 and 4, USEPA notes the purported
value of these alternatives in "inhibiting " the migration of contaminants from the shallow to the deep
aquifer. However, USEPA fails to point out that this assumed potential migration is already significantly
inhibited by the natural subsurface materials. The San Gabriel Basin Watermaster has stated that existing
shallow and deep data "appear to confirm the effectiveness of clay layers in controlling the vertical
migration of contaminants in the study area. " Prior to making a final selection of a remedy in the Record
of Decision, the NEMCTF group of companies requests that USEPA quantitatively analyze whether the
remedy actually provides any further substantive benefit in inhibiting vertical migration into the deep
aquifer when compared to naturally occurring impediments to such migration, as well as facility-specific
source control actions.
EPA's Response. The comment fails to acknowledge the considerable extent of deep contamination that
currently exists in the El Monte OU, indicating that vertical migration from shallow to deep zones does
occur in the El Monte OU. Although EPA agrees that the presence of fine-grained materials does act to
reduce the magnitude of vertical migration, we do not concur with the Watermaster's conclusion that clay
layers are effective in "controlling the vertical migration of contaminants."
There are insufficient data available to "quantitatively analyze" the difference between vertical migration
under the remedy compared to vertical migration without the remedy. However, given the current
occurrence of deep contamination extending over a large area and the potential presence of numerous
man-made conduits (i.e., old production wells), it is reasonable to expect that inhibiting further migration
ot shallow contamination will reduce the potential for additional vertical migration into the deep zone.
EM_ROD.DOC
-------
PART III - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
NEMCTF Comment No. 6. USEPA states a preference for Remedial Alternative 5. This is far and away
the most costly remedial alternative. USEPA notes that their approach "provides for flexibility in
implementation. " Yet, elsewhere in the Proposed Plan there are several references to USEPA intending to
"extract and treat" groundwater. USEPA appears to be ignoring its own policy and guidance. USEPA
policy and guidance documents state that USEPA should evaluate the effectiveness of focused source
control actions coupled to Monitored Natural Attenuation. Aggressive source control actions are already
underway at several of the NEMCTF facilities located within the EMOU. USEPA has failed to factor the
effectiveness of such actions into their Proposed Plan. We request that USEPA (a) clearly and fully
evaluate the beneficial effects of on-going facility-specific actions before selecting the remedy, and (b)
coordinate closely with the LARWQCB to identify any additional facilities where remedial actions are
appropriate. Where such additional actions would increase the effectiveness or reduce the costs of the
CERCLA remedy, USEPA should both ensure that the LARWQCB mandates the implementation of such
actions, and incorporate the resulting benefits into the selection of the remedy.
EPA's Response. EPA disagrees with the assertion that it is "ignoring its own policy and guidance." In
accordance with the performance-based remedy described in this ROD, if source control actions and
natural attenuation are sufficient to inhibit further contaminant migration, then active pumping will not be
necessary in the shallow groundwater zone and pumping may be limited in the deep zone. However, EPA
believes that it is very likely that extraction and treatment will be needed at least in portions of both the
shallow and deep zones to meet the remedial objectives and performance requirements developed for this
remedy.
Aggressive source control actions undertaken at individual facilities certainly have the potential to reduce
the magnitude of shallow zone extraction and treatment that may be required to meet the performance-
based requirements of this remedy. There is no need to evaluate the beneficial effects of on-going
facility-specific actions before selecting a remedy. If they are adequate to inhibit contaminant migration,
this will be apparent in the monitoring to be performed at the "early-warning" and compliance monitoring
wells that will be used to monitor this remedy.
EPA is continuing to work with the Los Angeles Regional Water Quality Control Board regarding
appropriate site-specific actions at facilities in the El Monte OU.
NEMCTF Comment No. 7. As USEPA is aware, the NEMCTF. in cooperation with the San Gabriel
Basin Water Quality Authority (WQA), is voluntarily implementing an aggressive field program to collect
additional data that will be helpful in selecting and designing the remedy. We believe that it is presently
premature and inappropriate for USEPA to select the remedy for the EMOU without considering the
additional data in progress and incorporating these essential data and related analyses into the final
remedy selection process. We look forward to continuing the cooperative working relationships between
the NEMCTF and USEPA to ensure that all necessary information has been collected and evaluated prior
to remedy decisions.
EPA's Response. EPA has reviewed the initial results generated from the shallow monitoring wells
installed as part of the Early Response Action Program (ERAP) referred to in this comment. Those
results were taken into consideration in developing this ROD. EPA agrees that the additional data to be
collected as part of the ERAP will be very helpful in designing the El Monte OU interim remedy and in
ultimately monitoring performance of the remedy. However, this ROD describes a performance-based
remedy and does not specify specific remedy components. EPA does not believe that any additional data
to be generated through the ERAP after the ROD is signed will affect the performance-based requirements
of the remedy described in this ROD.
EM_ROD.DOC HI-1-6
-------
PART III - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
EM_ROD.DOC
III-1-7
-------
-------
PARTI1I -RESPONSIVENESS SUMMARY
ec MONTE OU INTERIM ROD
2 Responses to Oral Comments
In this section, EPA provides responses to oral comments received at the public meeting held on
November 18 1998. EPA responded to a number of questions directly at the public meeting TOs
section provides responses only to formal oral comments that were not fully addressed at the meeting
formal oral comments were received from three parties: Mr. Ken Russo, representing the Northwest El
Monte Community Task Force (NEMCTF); Mr. David Chamberlin of Camp Dresser & McKe
S^SST •*. J*VT«n Schmidt, representing H^SeJ^t
NEMCTF. The full transcript of the pubhc meeting is available at EPA's Superfund Records
* " ^ ^^ "*
the Rse Liy
2.1 Response to Comments from Ken Russo of the
NEMCTF
This section presents excerpts from Mr. Russo's oral comments and provides EPA's responses to those
bSSnp"0 f,f -£r°t;s rrente- ™e entire tcxt °f Mr- R'SS°*S ^^ ™£i™*
Degmning on Page 33 of the attached meeting transcript.
Mr Russo's Comments, Transcript Page 35, Line 15 through Page 36, Line 22. Let '3 talk about the
£ShC,rnaTiatl°n t thfHS ^ mai" iSSUe ^ a''e here t0 talk abmlt toni^ * did not come from
t^Z? ?/T7 0jJ°lventS int° the soil' and • W3Ste St0rage areas' chemical handIi"S and Borage areas,
it areas, paint booth areas, processing areas, drain pipes, and drainage sumps.
EPA's Response. Although broad sub-regional remedial actions have not been initiated in the El Monte
Sin H ST±fur Cf ",UP haS °CCUITed in the °U area" RWQCB investigations, funded by and
?« S A? W ' C l° a ^omdv/atcr remediation system being installed at the Hermetic Seal
facility. Also, water purveyors have installed wellhead treatment to remove contaminants from
groundwater extracted from contaminated portions of the deeper aquifer.
Mr. Russo's Comments, Transcript Page 38, Line 23 through Page 39, Line 2. Yet today under the
Superfund process, we are still not viewed as having sufficient information to proceed with actual
cleanup. We will be expected to spend hundreds of thousands more dollars to continue studying the
Sr s RefP°nse- Th'5 statement is not correct. Sufficient information has been collected in the El
Monte OU to proceed with the cleanup. Field activities that the NEMCTF has recently initiated are
intended as a component of the remedial design to help refine design parameters and provide data points
tor monitoring remedy compliance with performance standards.
EM ROD.DOC
III-2-1
-------
PART III - RESPONSIVENESS SUMMARV
EL MONTE OU INTERIM ROD
If the NEMCTF would like to accelerate implementation of the remedy in the El Monte OU FPA ,.,
^^
work with the NEMCTF as ^cleanup ^^TrkTinl f°rW"
-------
PART III - RESPONSIVENESS SUMMARY
EL MONTE OUINTERfM ROD
treated for VOC contamination ?
treated grounds, ,o any
IKS
"iro"h '
°s'= of groundwater that is
'°
process win take a considerabenpre
addition, there is already a considerable ° '
addressed, re8a,d,ess of the
2One- However- this
mign"iO11 wi" ocour- "°
" "'
component of the remedial action. • aavantageous to incorporate the existing wells as a
^^
2'2
™ *° Comments from David Chamberlin
CDIW, representing the NEMCTF
can be
on
S responses «o
EPA's Response. See response to NEMCTF written Comment No. 1
Mr. Chamberlin's Comments, Transcript Page 43 Lines
n ofsUe risk as being rea
EM_ROD.DOC
III-2-3
-------
PART III - RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
EPA's Response. The Proposed Plan does not describe the site risk as being reasonably expected to
occur. The Proposed Plan presents risks that are the maximum risks that could reasonably be expected if
the future exposure occurs. The likelihood that these potential future exposures will occur is not
discussed. The first paragraph of the Summary of Site Risks section of the Proposed Plan does note that
the exposure scenarios evaluated assume the absence of regulatory controls (existing regulatory controls
limit the potential for exposure).
Mr. Chamberlin's Comments, Transcript Page 43, Lines 16 through 20. We 're. concerned that the
depiction of the plume on page 3 of the proposed plan and on the wall behind me this evening that
oversimplified and overstated the actual true conditions in the subsurface.
EPA's Response. Although EPA agrees that the depictions of contamination in the El Monte OU
presented in the Proposed Plan are simplified, we do not believe the maps significantly overstate the
extent of contamination in the OU. These interpreted maps are based on data generated during the RJ
along with additional site assessment and production well data collected during a similar time frame.
Mr. Chamberlin's Comments, Transcript Page 43, Lines 21 through 25. We're concerned about the
overstatement of the potential risk for the contaminants to migrate from the shallow aquifer into the
deeper aquifer. The data suggests that they have not to any degree of significance.
EPA's Response. EPA disagrees with the conclusion that contaminants have not migrated from the
shallow zone to the deep zone "to any degree of significance." This statement fails to acknowledge the
considerable extent of deep contamination that currently exists in the El Monte OU, indicating that
vertical migration from shallow to deep zones has and does occur in the El Monte OU. Although EPA
agrees that the presence of fine-grained materials does act to reduce the magnitude of vertical migration,
the large areas of deep zone contamination confirm that the physical conditions are not sufficient to stop
vertical migration.
Mr. Chamberlin's Comments, Transcript Page 44, Lines 1 through 4. And lastly we're concerned
about the need for flexibility in meeting EPA's performance criteria by means other than the installation
of new and costly extraction wells.
EPA's Response. As described in this ROD, the performance standards for the selected remedy provide
considerable flexibility for implementation of this remedy. New groundwater extraction wells will be
needed only in areas where data indicate potential contaminant migration towards compliance monitoring
wells.
2.3 Response to Comments from Tom Schmidt
representing Hermetic Seal and the NEMCTF
This section presents excerpts from Mr. Schmidt's oral comments and provides EPA's responses to those
specific portions of Mr. Schmidt's comments. The entire text of Mr. Schmidt's statement can be found
beginning on Page 44 of the attached meeting transcript.
Mr. Schmidt's Comments, Transcript Page 45, Lines 1 through 11. / must also say that I feel that
[the members of the Northwest El Monte Community Task Force have] been unfairly picked out of all of
the potentially responsible parties in the Valley and in the El Monte Operable Unit because they have
voluntarily stepped to the plate.
There are parties who are out there who have basically laid in the grass and have been allowed to do so
by the regulatory agencies because they have garnered what they call - what we call. I should say, the
critical mass for getting the job done that the agencies want.
EM_ROO.DOC ' IH-2-4
-------
PART III-RESPONSIVENESS SUMMARY
EL MONTE OU INTERIM ROD
th!t time APH h r* >l ofDnt S?eC?' N°tlCe LetterS t0 a1' °f the PRPs that had bee" ^entified at
unlS' tt R T M -PRPS J°med t0gCther SS the Northwest El Monte Community Task Force to
undertake the Remedial Investigation and Feasibility Study for the El Monte OU. EPA issued a Unilateral
Administrative Order to the one remaining PRP, Crown City Plating, which complied with the
requirements of the Order. EPA identified four additional PRPs in 1 997. EPA and the NEMCTF met
with these PRPs and two of the four subsequently joined the NEMCTF. EPA is now making PRP
6'611 n™°nl "al ^"P °f facilities to be investigated in the El Monte OU. EPA will require
PRPs share responsibility for implementation of the El Monte remedy.
,, CommentsV rranscript Page 46, Lines 3 through 12. 1 believe that there is an essential
that ,s missing You cannot dean up the groundwater until all sources of soil contamination
have been e^mnated And. I would urge all of the jurisdictions involved, especially the Regional Board
to move ahead and address a fashion to deal with those sources and to deal with parties who have either
condition ^ l° C°me t0 'ke tableln tSrmS °ftaking °n resP°^ilityfor their site
EPA's Response. EPA concurs with the comment regarding the need to eliminate sources of soil
oemtamination. The remedy selected in this ROD is an interim action intended to provide containment of
the existing groundwater contamination. As this remedy is being implemented to ensure that future
contaminant migration is limited, EPA will continue to work with the LA RWQCB to require appropriate
facility-specific remedial actions that reduce future contaminant loading
EM_ROD.DOC
III-2-5
-------
-------
REFERENCES
EL MONTE OU INTERIM ROD
References
Camp Dresser & McKee, Inc. El Monte Operable Unit Interim Remedial Investigation/Feasibility Study,
Final Remedial Investigation Report, San Gabriel Valley. Los Angeles County, California. Prepared for
the Northwest El Monte Community Task Force. April 1998a.
. El Monte Operable Unit Interim Remedial Investigation/Feasibility Study, Final Feasibility
Study Report, San Gabriel Valley, Los Angeles County, California. Prepared for the Northwest El Monte
Community Task Force. July 31, 1998b.
CDM. See Camp Dresser & McKee, Inc.
EPA. See U.S. Environmental Protection Agency.
U.S. Environmental Protection Agency. Supplemental Sampling Program Report, San Gabriel Basin Los
Angeles. California. Prepared by CH2M HILL. 1986.
•. CERCLA Compliance with Other Laws Manual, Part I (Interim Final). OS WER Directive
9234.1-01. 1988a.
. Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites OSWER
Directive 9283.1-2. 1988b.
-. CERCLA Compliance with Other Laws Manual, Part II. OSWER Directive 9234.1-02.
1989.
. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions. OSWER
Directive 9355.0-30. April 22, 199la.
fnterim San Gabriel Basin Remedial Investigation Report, Los Angeles County, California
Prepared by CH2M HILL. July 1992a.
. Integrated Risk Information System. Chemical Files. U.S. EPA Integrated Risk Information
System Database. Office of Research and Development. Cincinnati, Ohio. 1995a.
—. El Monte Operable Unit, Preliminary Baseline Risk, San Gabriel Basin, Los Angeles County,
California. Prepared by CH2M HILL. October 1997a.
EM ROD.DOC
-------
-------
Tables
-------
-------
Table 1
Summary of Chemicals of Concern and Exposure Point Concentrations in Groundwater
El Monte Operable Unit
Groundwater Area
Well Group 1 (Western El Monte OU)
Well Group 2 (Eastern El Monte OU)
Production Well 01900918
Production Well 01 902948
Production Well 08000101
Chemical of
Concern
PCE
TCE
Carbon Tetrachloride
PCE
TCE
PCE
TCE
TCE
TCE
Frequency of
Detection
33/53
49/53
30/66
61/66
62/66
2/5
2/5
2/9
4/8
Minimum
Concentration
(ppb)
ND
ND
ND
ND
ND
ND
ND
ND
ND
Maximum
Concentration
(Ppb)
24,000
1,500
59
1.510
4,600
1
2.5
12
1.2
Exposure Point
Concentration
(PPb)
2,659
352
6.6
344
841
0.8
2.0
0.6
0.8
Statistical
Measure
95% UCL
95% UCL
95% UCL
95% UCL
95% UCL
95% UCL
95% UCL
95% UCL
95% UCL
Notes:
ND = non-detect
ppb = parts per billion or ug/L (mlcrograms per liter)
95% UCL = 95 per cent upper confidence limit on the arithmetic mean groundwater concentration.
SCO/982710001. DOC-97/EMRODTBS.DOC
-------
Table 2
Estimated Total Excess Lifetime Cancer Risk from Domestic Use of Groundwater
El Monte Operable Unit
Average Exposure
Re sonable Maximum Exposure
Ingestion Inhalation Dermal
Major Chemical
Contributors
Production Well
01900918
Production Well
0.1902948'
Production Well
08000101 '
Data from these three active production wells were used to evaluate potential current risks in the El Monte OU area
1™^^^^
SCCW982710001.DOC.97/EMRODTBS.DOC
-------
Table 3
Estimated Total Noncancer Hazard Index from Domestic Use of Groundwater
El Monte Operable Unit
Wells
Production Well
01900918 '
Production Well
01902948 '
Production Well
08000101 1
Well Group 1 2
Well Group 2 2
Average Exposure
Ingestlon
0.003
0.001
0.001
3
2
Inhalation
NA
NA
NA
0.04
0.1
Dermal
0.0002
0.00004
0.00006
0.3
0.1
All
Routes
0.003
0.001
0.002
3
2
Reasonable Maximum Exposure
Ingestion
0.01
0.003
0.004
9
5
Inhalation
NA
NA
NA
0.09
0.3
Dermal
0.0007
0.0001
0.0002
1
0.3
All
Routes
0.01
0.003
0.004
10
6
Major Chemical
Contributors
None
None
None
PCE, TCE
Carbon tetrachloride,
PCE, TCE
' Data from these three active production wells were used to evaluate potential current risks in the El Monte OU area.
2 Data from Well Group 1 (representing the highly contaminated portions of western El Monte OU) and Well Group 2 (representing the
highly contaminated portions of eastern El Monte OU) were used to evaluate potential future risks in the El Monte OU area.
SCO/982710001.DOC-97/EMRODTBS.DOC
-------
Table 4
Cost Comparison of Alternatives1
Alternative
3
4
5
Capital Costs
$1,250
$2,990
$4,830
$7.930
SI.OOOs)
Annual O&M Costs
$200
$430
$570
$960
Net Present Worth
(30-years @ 5%)
$4.340
$9.620
$13,560
$22.670
1 Net Present Worth is based on treatment for VOCs only. '
SCO/982710001.DOC-97/EMRODTBS.DOC
-------
Table 5
Chemicals of Potential Concern
Compound
1.1-Dichloroethane
1,1-Dichloroelhene
1.1,1-Trichloroethane
1 .1 ,2-Trichloro-1 ,2,2-trifluoroethane
1,1.2-Trichloroethane
1,2-Dichtoroethane
1 ,2,3-Trichtorobenzene
1 ,2,4-Trimethylbenzene
1 ,3-Dichlorobenzene
2-Propanone
2-Hexanone (methyl n-butyl ketone)
Benzene
Bromoform1
Carbon Oisulflde
Carbon Tetrachloride
Chloroethane
Chloroform'
cis-1 ,2-Dichloroethene
Dibromochloromelhane1
Methylene Chloride
Tetrachloroethene
Trichloroethene
Trichlorofluoromethane
Toluene
Xylenes, total
ARAR
(ug/L)
5
6
200
1.200
3
0.5
-
.
-
-
1
100
-
0.5
.
100
6
100
5
5
5
150
150
1,750
Source
California MCL
California MCL
Federal MCL
California MCL
Federal MCLG
California MCL
-
.
.
.
-
California MCL
Federal MCL
.
California MCL
.
Federal MCL
California MCL
Federal MCL
Federal MCL
Federal MCL
Federal MCL
California MCL
California MCL
California MCL
'These chemicals are trihalomethanes (THMs); the MCL listed is for all four THMs: •
chloroform, bromodichloromethane, dibromocnloromethane, and bromoform.
Note: "-" indicates "no MCL has been established or proposed."
SCO/982710001 .OOC-97/EMRODTBS.DOC
-------
Table 6
Detailed Costs Estimates for the Selected Remedy
El Monte OU - Interim ROD
Extraction Wells (Includes well pumps)
100ft. @ 30 gpm 11 ea
•300ft. ® 100 gpm 1 ea
300 ft. © 125 gpm i ea|
300ft. @ 150 gpm 2 ea.
Treatment Unite (Air Stripping w/VG AC Off-Gas Treatment, includes discharge
100 gpm System 1 &,
150 gpm System 1 |g.
180 gpm System 1 (g
425 gpm System i (5.
800 gpm System 1
Conveyance Systems (Pipelines)
1 .5-inch Diameter Pipelines 5,000
2-Inch Diameter Pipelines 3.950
2,5-inch Diameter Pipelines 1 ,800
3-inch Diameter Pipelines 3.OOO
4-inch Diarnaier Pipelines 6.980
6-Inch Diameter Pipelines 4,000
8-Inch Diameter Pipelines 800
Monitoring Program
Shallow Monitoring Wells 7
Daep Monitoring Wells 2
Well Abandonment 1
Total Capital Costs
Is.
If.
If.
if.
If.
If.
If.
If.
ea.
ea.
(3.
$202.000
$318.000
$384,000
S388.0OO
pumps)
$256,000
$557,000
S359.OOO
S468.000
5469,000
SIS
£20
$25
S30
$40
S60
S80
$71.000
5349,000
- SSO.OOO
Annual Operations & Maintenance Costs (Including Engineering and Contingencies) »
Capital Costa
S 2,222,000
S 318,000
S 384,000
S 776,000
S 256,000
S SS7,000
S 359,000
S 468,000
S 463,000
S 73,000
C 70 nnn
S 45 000
S 90,000
$ 279,000
S 240,000
S 64,000
S 497,000
$608,000
S 50.000
Present
Extraction Wells (including pumping costs)
100ft. ©30 gpm
300ft. ® 100 gpm
300 ft. @ 125 gpm
300ft. © 150 gpm
300 ft. @ 800 gpm
Treatment Units (including pumping, power, labor,
100 gpm System
150 gpm System
180 gpm System
425 gpm System
800 gpm System
MonHorino Program
Shallow Monitoring Wells
Deep Monitoring Wells
Monitoring Program - Existing Wells
Unit Cost Annual Cost^ Worth Costsl
n S4.000
i S6.000
1 S6.000
2 S7.000
i 322^000
and carbon costs)
i $65,000
1 $210,000
i $113,000
, Si 15,000
i S1 63.000
7
2
i
S5.000
$12,'ooo
51 42.000
$44,000
$6.000
56,000
SI 4,000
S22.000
$65,000
S210,000
S113.000
S115,000
$163,000
$35,OOO
$24.000
S142.000
S 676,000
S 92,000
S 92,000
S 215,000
$ 338,000
S 999,000
$ 3,229,000
S 1,737,000
S 1,768,000
$ 2,606,000
S 538,000
$ 369,000
S 2,183,000
Total Annual O&M Costs
Total Discounted O&M Costs'
S 959,000
Total Capital Costs
! 14,742,000
Total Present Worth Costs
S 7,926,000
$ 22,668,000
Uotas
(1) Based on 30-year project and S'A discount rate.
CS?ltal c°**'*amMes ara "«°3*coun«ed because ihe construction work wiH ba performed in the earl/ staaes of iho
project O&M costs are reported .. pr«^nt worth estimates qlvon a 5% discount rate for a 30 year duration Cost
estimates are based on extraction rates and Influent quality estimates that may be refined during remedial design Cost
estimates are expected to be whnln a +50 to -30% accuracy range. 8icn.wraiae.ion. i-os<
Is. m tump sum
If. a linear foot
•a. = each
emrod_5tab.xls
I
4
-------
Figures
-------
-------
EL MONTE
OPERABLE UNIT
ALHAMBRA ;
N OU !
BALDWIN
PARK
OU /
RICHWOOD
SOUTH
EL MONTE
OU
PUENTE
VALLEY
OU
WHITTIER
NARROW
OU
San Gabriel
Basin
234
mm
Scale In Miles
Figure 1
^ Vicinity Map
El Monte Operable Unit
-------
eck Road
Spreading
Basin
ENCINITAS
WELLx.
LEGEND
VOC Contamination
Laboratory detection limits
to Drinking Water Standards
(DWS)
DWStolOxDWS
10xDWSto100xDWS
Greater than 100x DWS
BERNARDINO FWY.
Figure 2
1997 Shallow VOC Contamination
El Monte Operable Unit
This figure Is Intendtd to prcvU* a conoaolual depletion ol lh« VOC distribution In th* Shalow Zone.
Stcausi of Itw gwunHztd nttura o( Itw Figure, which was oompossd uslna dtla tpannhg >
lv»-y««r pflrtod ind obukiad (torn dWerani data IOUKM, actual VOC concentniloni «l sptdfic
locations wihln Iho El Monl> OU mty dovlale from IhOM shown on DM Figure.
-------
LEGEND
VOC Contamination
Laboratory detection limits
to Drinking Water Standards
(DWS)
DWS to lOx DWS
10xDWSto100xDWS
0 0,5 1
Scale in Miles
Figure 3
1997 Deep VOC Contamination
El Monte Operable Unit
-------
Evaluation
Criteria
.
.
Overall
Protectiveness
Compliance
with ARARs
Long-term
Effectiveness
& Permanence
implement-
ability
Short-term
Effectiveness
Reduction of
Toxicity,
Mobility or
Volume by
Treatment
Capital Cost
O&M
PWC
State Agency
Acceptance
Community
Acceptance
Alternative 1
No Action
o
0
o
not applicable
not applicable
O
$0
$0
$0
o
o
Alternative 2
Groundwater
Monitoring
O
o
o
•
9
o
•
$1.25 million
$0.20 million
$4.34 million
O
0
Alternative 3
Shallow
Groundwa-
ter Control
in Western
EMOU
9
9
9
9
9
.9
$2.99 million
$0.43 million
$9.62 million
O
®
Alternative 4
Shallow
Groundwater
Control in
Western and
Eastern
EMOU
9
9
9
9
9
9
$4.83 million
$0.57 million
$13.56 million
O
a
Alternative 5
Shallow
Groundwater
Control in
Western and
Eastern EMOU
plus Deep
Groundwater
Control
*
•
•
9.
*
*
$7.93 million
$0.96 million
$22.67 million
•
e
0 « High Q . Medium Q = Low Figure 4
* O&M = Annual Operations and Maintenance Cost Alternative Evaluation Matrix
PWC = Present Worth Cost: 5% Discount Rate, 30 Years El Monte Operable Unit
•I
-------
STARS/SCAT ACCOMPLISHMENTS
DOCUMENTATION APPROVAL FORM
&
__ _ ROUTE SLIP
To: Superfund Records Center / SFD-7-C
Attention: Diane White
Site Name: 3rt/*£*\dL*I oti
Occurrence: CA
Activity Date:
Event/Activity
SRC Doc No.:
Seq
Please check all appropriate boxes:
(Make sure document is dated & authorship indicated)
3 Please index D Retain in Records Center
^ STARS/SCAP Accomplishment D Return to Sender
Comments:
CBI? Yes d No D
D FOIA Exemption 5 & 7
Cl Attorney-Work Product
D Attorney Client Privilege
D Deliberative Process
I have reviewed the supporting documentation for the noted
accomplishment and it supports the Superrund Program
Implementation Manual definition.
( \SecaonChicQ
i Phone: Y~?J f^ I Mail Code:
«vlnd 04/04/97 - J:\PM\HTESUPS\STABS.PM4
-------
-------
-------
-------
Reproduced by NTIS
(0
•-
£ C
ESi.o
E5='5
0) U O
0£.So
8-0 -S05
0 c m *
TJ c ® e
^ 3T5 C
National Technical Information Service
Springfield, VA 22161
This report was printed specifically for your order
from nearly 3 million titles available in our collection.
For economy and efficiency, NTIS does not maintain stock of its vast
collection of technical reports. Rather, most documents are printed for
each order. Documents that are not in electronic format are reproduced
from master archival copies and are the best possible reproductions
available. If you have any questions concerning this document or any
order you have placed with NTIS, please call our Customer Service
Department at (703) 605-6050.
About NTIS
NTIS collects scientific, technical, engineering, and business related
information — then organizes, maintains, and disseminates that
information in a variety of formats — from microfiche to online services.
The NTIS collection of nearly 3 million titles includes reports describing
research conducted or sponsored by federal agencies and their
contractors; statistical and business information; U.S. military
publications; multimedia/training products; computer software and
electronic databases developed by federal agencies; training tools; and
technical reports prepared by research organizations worldwide.
Approximately 100,000 new titles are added and indexed into the NTIS
collection annually.
For more information about NTIS products and services, call NTIS
at 1-800-553-NTIS (6847) or (703) 605-6000 and request the free
NTIS Products Catalog, PR-827LPG, or visit the NTIS Web site
http://www.ntis.gov.
NTIS
Your indispensable resource for government-sponsored
information—U.S. and worldwide
-------
------- |