PB96-964509
                                 EPA/ROD/R09-96/152
                                 December 1996
EPA  Superfund
       Record of Decision:
       Operating Industries, Inc., Landfill,
       Monterey Park, CA
        9/30/1996

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                      FINAL
               RECORD OF DECISION
                       FOR
            OPERATING INDUSTRIES, INC.
                 SUPERFUND SITE
           MONTEREY PARK, CALIFORNIA

                     Volume 1

                   September 1996
SCO100192D1.DOC

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                                  Declaration
                             Site Name and Location
 Operating Industries, Inc. (OH)
 Monterey Park, California
                        Statement of Basis and Purpose

 This decision document presents the selected remedial action for the Operating Industries,
 Inc. (OH) Site, in Monterey Park, California, chosen in accordance with the Comprehensive
 Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended
 by the Superfund Amendments and Reauthorization Act of 1986 (SARA) and, to the extent
 practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).
 This decision is based on the Administrative Record for this site.

 The State of California concurs with the selected remedy.
                             Assessment of the Site

Actual or threatened releases of  hazardous substances from this site, if not addressed by
implementing the response action  selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.
                           Description of the Remedy

This ROD addresses liquids control and contaminated groundwater as well as  long-term
operation and maintenance of all environmental control facilities at the landfill, excluding those
facilities  covered under the Gas Migration  Control and Landfill Cover ROD,  as amended
(EPA,  1990a; originally the Gas Migration Control ROD [EPA, 1988b]).  Liquids will be
controlled at the landfill  perimeter to  prevent migration of  contaminants to groundwater.
Contaminated groundwater currently beyond the landfill perimeter will be allowed to naturally
attenuate over  time.  The U.S. Environmental Protection Agency  (EPA) has signed three
previous  RODs for the OH Site.   These  cover Site Control and  Monitoring, Leachate
Management, and Gas Migration Control and Landfill Cover. The RODs for Site Control and
Monitoring and Leachate Management were interim in nature and not  considered permanent.
These RODs  are no longer applicable beginning  with the signing of this  ROD, although
activities required under those RODs will continue as  part of this ROD.  The ROD for Gas
Migration Control  and Landfill Cover selected a final  remedial action  that represents a
SCO100192D2.DOC

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 significant component of the permanent site cleanup, but is not included in, or modified by, this
 ROD.

 The major components of the selected remedy for this action include:

 •      Installation  of a perimeter liquids  control system in areas where  contaminants are
        migrating from the landfill at levels that cause groundwater to exceed performance
        standards.  Contaminated groundwater beyond the landfill perimeter would be reduced
        to below cleanup standards through natural attenuation.

 •      Conveyance of the collected liquids to the onsite treatment plant.

 •      Onsite  treatment of  collected  liquids  using the existing  leachate treatment plant,
        modified as necessary to handle the new liquids. Discharge of treated liquids to the
        County Sanitation Districts of Los Angeles County sanitary sewer system.

 •      Implementation  of a monitoring  and  evaluation program to  ensure  that natural
        attenuation of the contaminated groundwater is  progressing as anticipated, to detect
        future releases of contaminants from the  landfill, and to ensure that perimeter liquids
        control system performance standards are being met.

 •      Establishment of institutional  controls to ensure appropriate future use of the On Site
        and to  restrict groundwater  use in the  immediate  vicinity of  the  OH Site.   The
        institutional controls  will supplement  the engineering  controls  to  prevent or limit
        exposure to hazardous substances.

 •      Interim operation and maintenance of existing site activities (gas  extraction and air dike,
        leachate collection, leachate treatment,  irrigation, access roads, stormwater drainage,
        site  security, slope repair, and erosion  control), except to the extent that they are
        addressed under the Gas Migration Control and Landfill Cover ROD.

 •      Long-term  operation  and maintenance  of all  facilities  and  environmental  control
        components at the OH Site, excluding those covered under the Gas Migration Control
        and Landfill Cover ROD.
                            Statutory Determinations

The selected remedy is protective of human health and the environment, complies with
federal and state requirements that are legally applicable or relevant and appropriate to the
remedial action,  and  is  cost-effective.   This  remedy  utilizes  permanent  solutions  and
alternative treatment technologies  to the maximum extent practicable.  Components of the
selected final remedy satisfy the statutory preference for remedies  that employ treatment that
reduces toxicity, mobility, or volume as a principal element.  The size  of the landfill mass
precludes a remedy in which all contaminants could be excavated and effectively treated.
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 Therefore, consistent with the NCP and EPA guidance, including Guidance for Conducting
 Remedial Investigations/Feasibility Studies for  CERCLA Municipal Landfill Sites (EPA
 OSWER Directive 9355.3-11, February 1991a), the remedy uses containment to address the
 low-level threat from the landfill.

 Because this remedy will result in hazardous substances remaining onsite above health-based
 levels,  a review will  be conducted at least once every  5 years  after commencement of
 remedial action to ensure that the remedy continues to provide adequate protection of human
 health and the environment.
lam
                                                                          y
 Keith A. Takata                                             Date
 Director of Superfund Division
 U.S. Environmental Protection Agency, Region IX
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                                   Contents

Section                                                                     Page
Declaration	i
Site Name and Location	i
Statement of Basis and Purpose	i
Assessment of the Site	i
Description of the Remedy	i
Statutory Determinations	ii

Part I    Decision Summary	1-1
           1.0    Site Summary	1-1
                 1.1     Site Location and Description	1-1
                 1.2     Physiography and Topography	1-1
                 1.3     Land Use	1-3
                        1.3.1  Historic Land Use	1-3
                        1.3.2  Current Land Use	1-3
                 1.4     Demographics	1-7
                 1.5     Surface Water Hydrology	1-7
                        1.5.1  Regional Hydrology	1-7
                        1.5.2  Surface Water Drainage at the OH Site	1-8
                 1.6     Geologic Setting Summary	1-8
                 1.7     Hydrogeologic Setting Summary	1-9

          2.0    OH Site History and Enforcement Activities	1-10
                 2.1     Landfill History	1-10
                        2.1.1  Historical Waste Disposal and Landfill Operations.. I-11
                        2.1.2  Landfill Development and Thickness	1-12
                        2.1.3  Waste Types and Quantities	1-12
OH Site Final Record of Decision                                               Page v
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                 2.2    Field Investigations	1-12
                        2.2.1  Hydrogeologic Investigations	1-15
                        2.2.2  Geologic and Geotechnical Investigations	1-15
                        2.2.3  Air Quality Investigations	1-16
                        2.2.4  Surface Water Sampling	1-16
                        2.2.5  Leachate Investigations	1-16
                        2.2.6  Landfill Gas Investigations	1-21
                 2.3    Summary of EPA Actions at the Oil Site	1-22
                        2.3.1  Summary of Enforcement Activities	1-22
                        2.3.2  OH Site Operable Units	1-24
                        2.3.3  OH Site Consent Decrees and Administrative
                               Orders	1-25

          3.0    Highlights of Community Participation	1-25

          4.0    Summary of Site Characteristics	1-26
                 4.1    Air	1-27
                        4.1.1  Ambient Air	1-27
                        4.1.2  In-Home Air	1-27
                 4.2    Soil	1-27
                        4.2.1  Surface Soil	1-28
                        4.2.2  Subsurface Soil	1-28
                 4.3    Surface Water	1-28
                 4.4    Groundwater	1-28
                        4.4.1  Northwest Area	1-33
                        4.4.2  Southwest Area—Groundwater Contamination	1-34
                        4.4.3  Eastern Area—Groundwater Contamination	1-35
                        4.4.4  West and South Aquifer Systems—Groundwater
                               Contamination	1-36
Page vi                                                OH Site Final Record of Decision
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          5.0    Summary of Site Risks	1-37
                 5.1    Baseline Human Health Risk Assessment Summary	1-37
                        5.1.1   Identification of Contaminants of Potential
                               Concern	1-38
                        5.1.2   Exposure Assessment	1-38
                        5.1.3   Toxicity Assessment	1-45
                        5.1.4   Risk Characterization Summary	1-48
                        5.1.5   Baseline Human Health Risk Assessment
                               Conclusion	1-56
                 5.2    Baseline Ecological Risk Assessment Summary	1-69

          6.0    Description of Remedial Alternatives	1-70
                 6.1    Alternative No. 1—No Further Action	1-70
                 6.2    Alternative No. 2—Perimeter Liquids Control (EPA's
                        Selected Remedy)	1-76
                 6.3    Alternative No. 3—Perimeter Liquids Control Plus
                        Source Control	1-80
                 6.4    Alternative No. 4—Perimeter Liquids Control Plus
                        Groundwater Control or Remediation	1-83

          7.0    Summary of the Comparative Analysis of Alternatives	1-88
                 7.1    Overall Protection of Human Health and the
                        Environment	1-89
                        7.1.1   Alternative No. 1	1-89
                        7.1.2   Alternative No. 2	1-91
                        7.1.3   Alternative No. 3	1-91
                        7.1.4   Alternative No. 4	1-92
                 7.2    Compliance with ARARs	1-92
                 7.3    Long-term Effectiveness and Permanence	1-93
Oil Site Final Record of Decision                                               Page vii
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                        7.3.1  Magnitude of Residual Risk	1-93
                        7.3.2  Adequacy and Reliability of Controls	1-95
                 7.4    Reduction of Toxicity, Mobility, and Volume Through
                        Treatment	1-97
                 7.5    Short-term Effectiveness	1-98
                 7.6    Implementability	1-102
                 7.7    Cost	1-104
                 7.8    State Acceptance	1-106
                 7.9    Community Acceptance	1-106

          8.0    Selected Remedy	1-107
                 8.1    Perimeter Liquids Control Component	1-108
                        8.1.1  Performance Standards and Point of
                              Compliance	1-108
                        8.1.2  Contingency Measures	1-112
                 8.2    Liquids Treatment Component	1-112
                        8.2.1  Performance Standards and Point of
                              Compliance	1-113
                        8.2.2  Contingency Measures	1-113
                 8.3    Groundwater	1-113
                        8.3.1  Performance Standards and Point of Compliance... I-113
                        8.3.2  Contingency Measures	1-117
                 8.4    Environmental Monitoring	1-117
                        8.4.1  Detection Monitoring	1-118
                        8.4.2  Compliance/Performance Monitoring	1-118
                 8.5    Additional Components	1-118
                        8.5.1  Institutional Controls....	1-118
                        8.5.2  Site Administration	1-120
                        8.5.3  Operation and Maintenance of Facilities and
                              Environmental Control Systems	1-120
Page viii                                               OH Site Final Record of Decision
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                 8.6   Cost of the Selected Remedy	1-121

          9.0    Applicable or Relevant and Appropriate Requirements (ARARs) .1-121
                 9.1    Chemical-Specific ARARs	1-129
                 9.2   Location-Specific ARARs	1-130
                 9.3   Action-Specific ARARs	1-131

          10.0   Documentation of Significant Changes	1-132

          11.0   Statutory Determinations	1-132
                 11.1   Protection of Human Health and the Environment	1-133
                 11.2   Compliance with ARARs	1-133
                 11.3   Cost-Effectiveness	1-133
                 11.4   Utilization of Permanent Solutions and Alternative Treatment
                       Technologies to the Maximum Extent Practicable	1-134
                 11.5   Preference for Treatment as a Principal Element	1-135

          References	R-l

Tables
1      Examples of Generic Wastes Permitted for Disposal at OH Landfill	1-13
2      Examples of Liquid Wastes Reportedly Disposed at Oil Landfill
       from 1976 to 1984	1-14
3      Selected Chemicals of Potential Concern for Air, Groundwater, and Soil	1-39
4      Exposure Parameters for Estimating Exposure for Residential Intake
       of Ambient Air	1-43
5      Parameters for Estimating Residential Exposures from Ingestion
       of Groundwater Contaminants	1-43
Oil Site Final Record of Decision                                               Page ix
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6      Parameters for Estimating Chemical Intake for an Adult Resident
       from Inhalation of Groundwater Volatiles 	1-44
7      Parameters for Estimating Chemical Absorption from Dermal Contact
       with Groundwater	1-44
8      Parameters for Estimating Intake for Residents and Workers Via Dermal,
       Inhalation, and Ingestion Exposure to Soil 	1-46
9      Toxicity Values and Chemical-Specific Parameters for Chemicals
       of Potential Concern	1-49
10     Summary of Leachate Extraction by Strategic Area 	1-90
11     Approximate Time to Reach Chemical-Specific ARARs in Groundwater	1-94
12     Comparisons of Contaminants Removed Through Liquids Collection/Extraction
       Reduction in Toxicity, Mobility, and Volume of Contaminants
       Through Treatment	1-99
13     Comparisons of Treatment Residuals Generated Reduction in Toxicity,
       Mobility, and Volume of Contaminants Through Treatment	I-100
14     Comparison of Costs	1-105
15     Perimeter Liquids Control Chemical Performance Standards and Groundwater
       Cleanup Standards	I-110
16     Effluent Discharge Limits	1-114
17     Approximate Time and Migration Distances to Reach Cleanup Standards
       in Groundwater Under the Selected Remedy	1-116
18     Selected Remedy Cost Estimate Summary	1-122
19     Summary of Chemical-Specific ARARs	1-124
20     Summary of Location-Specific ARARs	1-125
21     Action-Specific ARARs.....	1-126

Figures
1      Landfill Location Map	1-2
2      Property Ownership/Usage Adjacent to OH Landfill	1-5
3      Monitoring Well Locations	1-17
Page x                                              OH Site Final Record of Decision
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4      Compounds with Average Ambient Air Concentrations
       Exceeding Background	1-19
5      S ampling Network for the In-Home Air Monitoring Program	1-20
6      Landfill Gas Monitoring Well Locations	1-23
7      1992/1993 MCL Exceedance Contours in Shallow or Unconfined Flow
       Systems	1-29
8      1992/1993 MCL Exceedance Contours in Deep or Confined Flow Systems	1-31
9A    Total Cancer Risk for Ambient Air Monitoring Station Locations—Residential
       Adult Reasonable Maximum Exposure Conditions	1-53
9B    Total Noncancer Hazard Index for Ambient Air Monitoring Station
       Locations—Residential Adult Reasonable Maximum Exposure Conditions	1-55
10    Total Cancer Risk for Surface Soil/Sediment by Area Residential
       Child Reasonable Maximum Exposure Conditions	1-57
11     Total Noncancer Hazard Index for Surface Soil/Sediment by Area
       Residential Child Reasonable Maximum Exposure Conditions	1-59
12    Total Cancer Risk for Individual Shallow Groundwater Wells Using
       Chemicals of Potential Concern by Well - Residential Adult Reasonable
       Maximum Exposure Conditions	1-61
13     Total Cancer Risk for Individual Deep Groundwater Wells Using
       Chemicals of Potential Concern by Well - Residential Adult Reasonable
       Maximum Exposure Conditions	1-63
14    Total Noncancer Hazard Index for Individual Shallow Groundwater Wells
       Using Chemicals of Potential Concern by Well - Residential Adult
       Reasonable Maximum Exposure Conditions	1-65
15     Total Noncancer Hazard Index for Individual Deep Groundwater Wells
       Using Chemicals of Potential Concern by Well - Residential Adult
       Reasonable Maximum Exposure Conditions	1-67
16     Alternative No. 1: No Further Action	1-71
17     Miscellaneous Existing Landfill Features Included in Alternative No. 1	1-73
Oil Site Final Record of Decision                                             Page xi
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 18    Alternative No. 2: Perimeter Liquids Control	1-77
 19    Alternative No. 3: Perimeter Liquids Control plus Source Control	1-81
20    Alternative No. 4: Perimeter Liquids Control plus Groundwater Control	1-85
Page xii                                                On Site Final Record of Decision
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                               Acronym List

ARARs      applicable or relevant and appropriate requirements
BTEX       benzene, toluene, ethylbenzene, and xylene
Caltrans      California Department of Transportation
CCR        California Code of Regulations
CERCLA    Comprehensive Environmental Response, Compensation and Liability
             Act of 1980
DTSC       California Department of Toxic Substances Control
EPA         Environmental Protection Agency
ft/day        feet per day
ft/yr         feet per year
gpm         gallons per minute
HELP       Hydrologic Evaluation of Landfill Performance model
hp           horsepower
MCL        maximum contaminant level
MCLG       maximum contaminant level goal
mg/L        milligrams per liter
MOC        USGS Method-of-Characteristics code
NCP         National Oil and Hazardous Substances Pollution Contingency Plan
On          Operating Industries, Inc.
OSWER      Office of Solid Waste and Emergency Response
PCB         polychlorinated biphenyl
PCE         perchloroethylene
ppm         parts per million
RCRA       Resource Conservation and Recovery Act of 1976
ROD        Record of Decision
SCAQMD    South Coast Air Quality Management District
TBC         to be considered
TCE         trichloroethylene
\ig/L         micrograms per liter
     3
[ag/m        micrograms per cubic meter
USGS       U.S. Geological Survey
OH Site Final Record of Decision
Contents
     Page xiii
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                                       Parti
                              Decision Summary



                               1.0  Site Summary


                        1.1  Site Location and Description

 The Operating Industries, Inc. (OH) Site is located at 900 Potrero Grande Drive in the City of
 Monterey Park, approximately  10 miles east of  downtown Los Angeles (Figure 1).  The
 landfill property covers 190 acres  and  is divided by  California Highway 60  (Pomona
 Freeway).  The 45 acres to the north of the freeway are referred to as the North Parcel, and
 the 145 acres to the south of the freeway are called the South Parcel. The neighboring City of
 Montebello borders the South Parcel and portions of the North Parcel.


                       1.2  Physiography and Topography

 This section discusses major physiographic and topographic features in the area surrounding
 the Oil Site and within the landfill boundary itself.

 The OH Site is located in central Los Angeles County, California, on the northwestern flank
 of the Montebello Hills (also known as the La Merced Hills).  The Montebello Hills are one
 of a series of low-lying hills that separate the Los Angeles Coastal Plain from the San Gabriel
 Valley. The elevation of the crest of the Montebello Hills is approximately 570 feet above
 mean sea level.  The San Gabriel Mountains, located approximately 12 miles to the north  of
 the landfill, form the northern boundary of the San Gabriel Valley. Elevations in the San
 Gabriel Mountains exceed 10,000 feet mean sea level.

 The Los Angeles Coastal Plain, to the south of the landfill, is a coastal plain sloping toward
 the Pacific Ocean,  approximately 20 miles away.  The Montebello Plain lies within the Los
 Angeles Coastal Plain just south of the Montebello Hills (and therefore just south of the OH
 Site) between the Los Angeles River and the Rio Hondo, and is  considered by California
 Department of Water Resources to be a source of groundwater recharge to the Los Angeles
 Basin (CDWR, 1961).

 The landfill was constructed by filling a former quarry pit that was cut into the side and top  of
 a portion of the Montebello Hills. The landfill was ultimately constructed to a height higher
 than the adjacent Montebello Hills.  Elevations  at the landfill range from approximately
Oil Site Final Record of Decision                                             Page 1-1
Part I - Decision Summary                                            scoiooi92D3.DOC

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 380 feet above mean sea level at the North Parcel to 640 feet above mean sea level at the top
 deck of the South Parcel. The top of the South Parcel is about 150 to 250 feet above the
 surrounding natural grade, and the maximum depth of the landfill  bottom is about  200 feet
 below the surrounding natural grade (EPA, 1987a).

 The South Parcel landfill side slopes are quite steep:  the north side of the South Parcel,
 directly adjacent to Pomona Freeway, is at a slope of about 2 (horizontal) to 1  (vertical) (an
 angle of approximately 27 degrees). The slopes on the east and south sides of the landfill are
 at approximately 3 to 1 (an 18-degree angle).  The west slope is at approximately 4 to 1 (a
 14-degree angle).
                                   1.3.  Land Use

 This section presents a description of historic and current land use in the vicinity of the OH
 Site.

 1.3.1  Historic Land Use

 The Montebello Hills oil field, located to the southeast of the landfill, was developed in the
 early 1900s. The oil field has provided an abundant source of petroleum and natural gas
 reserves from petroleum exploration  oil wells drilled in the vicinity of the landfill, including
 some within the current landfill  boundary.  Throughout  its producing history, a significant
 percentage of the production  from the Montebello Hills oil field has been a sodium-chloride
 brine.  Historic maps of the oil field  show the locations of apparent "brine ponds" associated
 with oil field activities in the area south and southeast of the landfill, including along the current
 southern boundary of the landfill.  Later, oil field wastes are reported to have been disposed into
 the landfill.

 Older aerial photographs (pre-1960) show little residential or commercial development near the
 landfill. By 1968, residential development had moved closer to the landfill; and by the mid-
 1970s, considerable residential and commercial development had taken place adjacent to the
 landfill boundary.

 1.3.2  Current Land Use

 The  area  surrounding  the  OH  Site  is  heavily   developed  with  mixed  general
 commercial/industrial and residential land use, with small pockets of open space (Figure 2).
 Specific land use at and around the landfill is presented below as follows, beginning north of
 the North  Parcel, and progressing clockwise around the landfill. Figure 2 shows approximate
 property boundaries and ownership/usage of properties adjacent to the landfill.
Oil Site Final Record of Decision                                              Page 1-3
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              A Southern California Edison substation complex occupies a portion of the
              property to the northwest of the North Parcel.  The remainder of the property
              north of the North Parcel is occupied  by two plant nurseries  that share a
              common border with the North Parcel.

              Resurrection Cemetery is located north/northeast of the North Parcel.

              The North Parcel is partially occupied by the following businesses: Recycled
              Wood Products; Ecology Auto Wrecking; Manhole Adjusting, Inc.; and Aman
              Brothers Pavement Crushing.

              In addition, the OH Site  leachate treatment plant  is located on the North
              Parcel, as are  the Environmental  Protection Agency (EPA) and  OH Landfill
              Work Defendants'  office trailers.  Aside  from  remediation  activities and
              landfill investigations, there is no active land use on the South Parcel.

              The Montebello Town Square, a  large shopping complex, occupies the land
              east of the South Parcel. A small strip on the east end of the landfill contains
              a landfill gas collection system installed as part of the development to reduce
              migration of landfill gas toward the shopping complex.

              The Montebello Hills  oil  field, which contains  many  active oil production
              wells, is located to the southeast of the South Parcel.

              On the southeast  and south  side of the  landfill,  adjacent land use is mostly
              low-density residential with pockets of medium-density residential and open
              space.  Many  homes  in this area are located immediately adjacent to  the
              landfill boundary and share a common property line with the landfill.

              A small piece of property adjacent to the southwest corner of the South Parcel
              is currently vacant.

              The surface  facilities  for a Southern  California Gas Company underground
              natural gas storage reservoir adjoin the southwest portion of the South Parcel.

              The remainder of the western boundary of the South Parcel is bordered by
              residential development, similar  to the residential areas south of the South
              Parcel.
Page 1-4                                              Oil Site Final Record of Decision
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                                                                                                                                                                                                          Approximate Scale in Feet
                                                                                                                                                                                                          . — Approximate Location of
                                                                                                                                                                                                              Fence/Property Boundary
m\109994.l6.0t Iig2 8/96
                                                                                                                                                                                                        Figure 2
                                                                                                                                                                                                        Property Ownership/Usage
                                                                                                                                                                                                        Adjacent to Oil Landfill
                                                                                                                                                                                                        Oil Site Final Record of Decision
                                                                                                                                                                                                                  Page 1-5

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                                 1.4.  Demographics

 Demography, as presented in this section, is combined with discussions  of land  use to
 identify potential receptor populations for the assessment of health risks associated with the
 landfill. Population demographics in the census tracts that extend to an approximate 1-mile
 radius of the landfill boundary are presented. Additionally, there are several subpopulations
 within the overall population who may be more sensitive to, or receive more exposure to,
 environmental contamination. These subpopulations  are  termed "sensitive  populations."
 Sensitive populations in the vicinity of the OH Site include young children, elderly persons,
 people who spend a significant portion  of time in  homes in the vicinity of the landfill, and
 people who work near the landfill.

 As reported in the 1990 census, the total population contained within the tracts surrounding
 the landfill is 35,101 persons (U.S. Department of  Commerce,  1990b).  The total population
 of the Cities of Monterey Park and Montebello is 59,570 and 60,740 persons, respectively.

 There are  two age groups  within  the overall  population  of particular  sensitivity  to
 environmental conditions:   children under 5 years and adults 65 years or greater.  The
 population  of children under 5 years  (2,307 persons) and  adults  65 years  or  greater
 (4,047 persons)  together  comprise  6,354 persons,  or  approximately  18 percent  of  the
 population in the tracts surrounding the landfill.

 Also of importance are persons who are likely to spend a significant portion of time at home
 in the tracts surrounding the landfill.  This number was estimated from the 1990 census to be
 13,863 persons, or approximately 39 percent of the population in the tracts surrounding the
 landfill (U.S. Department of Commerce,  1990b).
                          1.5 Surface Water Hydrology

This discussion of regional surface water hydrology includes major rivers, drainage patterns,
and sources of infiltration such as spreading basins and irrigation.  Surface water drainage at
the landfill is also discussed.

1.5.1  Regional Hydrology

The regional drainage divide, as reported by the California Department of Water Resources
(CDWR, 1966), that separates the Central Basin from the San Gabriel Basin runs directly
through the northeast corner of the landfill. The San Gabriel Valley is drained by two major
rivers,  the Rio Hondo and San Gabriel River.  Almost all natural surface water outflow from
the San Gabriel Valley,  including the Rio Hondo and San Gabriel River, passes through
Whittier Narrows, located approximately 2 miles east of the landfill. After passing through
Oil Site Final Record of Decision                                              Page 1-7
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 Whittier Narrows, both rivers extend southerly across the Los Angeles Coastal Plain to the
 Pacific Ocean.

 There are numerous dams and spreading basins in the general vicinity of the OH Site that
 serve as locations for groundwater recharge.  Whittier Narrows Dam lies on both the Rio
 Hondo and San Gabriel River. The area upstream of the dam is a wildlife refuge.  Two major
 spreading grounds lie approximately  1 mile  downstream  of the  Whittier Narrows  dam,
 including the Rio Hondo  Spreading Ground  (on the Rio  Hondo) and San Gabriel River
 Spreading Ground (on the San Gabriel River).  Additional spreading  grounds  are  located
 several miles upstream in the San Gabriel Valley.

 1.5.2  Surface Water Drainage at the Oil Site

 Surface water present on and in the vicinity of the OH Site  is limited to storm water runoff
 following substantial rainfall events.   There are no  natural streams  on or adjacent to the
 landfill. Surface water (storm water) runoff from the South Parcel flows to lined swales on
 the inboard side of each terraced bench road on the landfill side slopes, where it is diverted to
 the storm water drainage system.  Most runoff from the top deck and east, north, and west
 slopes  drains through four main  storm drains to concrete, trapezoidal  drainage  ditches
 paralleling the Pomona Freeway.   Runoff from the south slopes flows through a series  of
 smaller drains into the City of Montebello storm drainage  system.  All of the  runoff gets
 routed through Los Angeles County storm drains to the rivers and ultimately discharges to the
 Pacific  Ocean (LACDPW, 1987).
                         1.6  Geologic Setting Summary

Detailed discussions of the regional and site-specific geology  are presented in the Draft
Remedial Investigation Report (EPA, 1994c). The geologic units in the immediate vicinity of
the OH Site are described briefly below.

The Pico  Unit, the San Pedro Formation, the Lakewood Formation, and the younger
(Holocene) fluvial/alluvial sediments are the geologic units present around the OH Site. The
Lakewood  and San Pedro Formations have been grouped together because of their similar
hydrologic properties and difficulty in distinguishing them in the field.

In the OH Site area, the Pico Unit consists of siltstone; silty sandstone; and very fine-grained
sandstone with interbedded medium- to coarse-grained sandstone, fine-grained conglomerate,
and occasional marine limestone beds. The siltstone intervals are greater than 500 feet thick
at some  locations  around the landfill; however, these intervals are probably made up  of
numerous siltstone layers, not one massive unit.  The sandstone and conglomerate intervals
range in thickness from a few inches to over 200 feet.
Page 1-8                                              Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

-------
 The Lakewood/San Pedro Formation unconformably overlies the Pico Unit in the OH Site
 vicinity. Within the landfill vicinity, the Lakewood/San Pedro Formation consists largely of
 poorly consolidated sandstones and  conglomerates,  with lesser amounts  of siltstone.
 Generally,  Lakewood/San Pedro sandstones are in  contact  with  Pico  Unit siltstones.
 However, in the eastern portion of the area, Lakewood/San Pedro Formation sandstones are
 in contact with Pico Unit sandstones.  In other areas, such as the western portion of the
 landfill, Lakewood/San Pedro siltstone may be in contact with Pico siltstone.

 The Holocene alluvium consists of unconsolidated sediments ranging in size from clay to
 cobbles and boulders.  The  alluvium  typically  occurs  surficially  and  occupies  the
 topographically low portions of the Oil Site vicinity.
                      1.7  Hydrogeologic Setting Summary

Detailed discussions of the regional and site-specific hydrogeology are presented in the Draft
Remedial Investigation Report (EPA, 1994c).  Significant hydrogeologic units in the local
vicinity  of the On  Site include: Pico Unit  deep siltstone,  Pico Unit  sandstones and
conglomerates, Pico Unit shallow siltstone (termed the Shallow Silt Flow System in the area
southwest  of the South Parcel), and  Lakewood/San  Pedro Formation sandstone.  The
complex geologic conditions present in  the OH Site vicinity  (i.e., depositional environment,
folding,  faulting) have resulted  in  similarly  complex  hydrogeologic conditions.  The
hydrogeologic units and groundwater flow conditions vary considerably in different portions
of the landfill.

Two deeper Pico Unit sandstone aquifer systems have been  delineated: the South Aquifer
and the West Aquifer.  The South and West Aquifer Systems are confined beneath Pico Unit
shallow  siltstone at  the  western  end  of  the  South  Parcel. The  South  Aquifer  trends
approximately northeast-southwest in  a narrow elongated band along the southern boundary
of the landfill, and does not appear to be laterally extensive in the northwest-southeast
direction. It is unconfined to semiconfined along the southeastern and eastern boundaries of
the South Parcel.

The West Aquifer has been  detected only along the western  boundary of the South Parcel.
Although the downgradient extent  of this unit is uncertain, it does not appear to be laterally
extensive to the west.

Other semiconfined to confined Pico Unit sandstones and conglomerates occur in the vicinity
of the North Parcel.  These sediments do not appear to correlate with either the South or West
Aquifers.

Pico Unit siltstone is generally referred to as Pico Unit deep siltstone when present below the
South or West Aquifers.  It is referred to as Pico Unit shallow siltstone near the water table
Oil Site Final Record of Decision                                              Page 1-9
Part I - Decision Summary                                            scoiooi92D3.DOC

-------
 and above the West Aquifer. The Pico Unit shallow siltstone is described as the Shallow Silt
 Flow System along the western and southern boundaries of the South Parcel for discussions
 of groundwater occurrence and groundwater flow conditions.

 The depth to water in the landfill vicinity varies greatly, and ranges from about 15 to 20 feet
 at the southwestern corner of the South Parcel to over 200 feet at the southeastern corner of
 the landfill.  In the western portion of the South Parcel, the groundwater table  is near (or
 potentially in contact with) the waste prism.  Under the center of the eastern end of the South
 Parcel, a boring drilled through the waste prism indicated water about 13 feet beneath the
 waste (Oil Landfill Work Defendants, 1995b).

 The estimated horizontal groundwater flow velocity in the shallow  systems varies greatly in
 different units, ranging from approximately 0.3 to  1,810 feet per  year (ft/yr).  The higher
 estimated velocities are in the unconfined aquifer to the north of the South Parcel.  These
 numbers may be artificially high if other factors such as restrictions in the shallow units are
 affecting the gradients. The lower velocity estimates are generally for flow in the shallow silt
 around the southwestern perimeter of the South Parcel. Flow in the silt may be several orders
 of magnitude higher in preferential flow paths such as fractures or more permeable lenses.

 Water level measurements  in wells located around the southwestern corner of the South
 Parcel indicate the presence of a groundwater mound. Because of the low permeability of the
 siltstone surrounding this area, recharge does not readily flow  away from  the landfill and
 therefore creates a localized groundwater mound. Groundwater flow in this area is generally
 radial, away from the  landfill.  It also appears that a groundwater mound has  developed
 northeast of the landfill, probably due to irrigation at the Resurrection Cemetery and nurseries
 surrounding the northern boundary of the North Parcel. Recharge probably infiltrates through
 the thin Lakewood/San Pedro Formation but cannot readily  infiltrate  into the  lower-
 permeability Pico Unit  siltstones, thereby causing a mound to form.

 There is no known use of groundwater within approximately 1.5 miles of the OH Site.


            2.0  Oil Site History and Enforcement Activities


                              2.1    Landfill History

 This section presents a  brief summary of information describing the  historical waste disposal
 and landfill operations,  landfill development and  thickness,  waste types and  quantities
 disposed at the landfill, and landfill development.
Page I-10                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

-------
 2.1.1 Historical Waste Disposal and Landfill Operations

 Prior to  1946, the OH property was a sand and gravel quarry. Waste disposal operations at
 the landfill began on  14 acres in  October 1948 by Monterey Park Disposal Company.  In
 January  1952, Operating Industries, Inc. assumed ownership of the landfill; and, by 1958, the
 landfill had expanded to 218 acres. The size was later reduced to 190 acres when the State of
 California purchased 28 acres for construction of the Pomona Freeway.

 In October 1954, the California Regional Water Pollution Control Board No. 4, Los Angeles
 Region,  first  permitted  disposal of liquids at the landfill (Resolution  54-15) (CRWPCB,
 1954). In March  1976,  the Los Angeles Regional Water Quality  Control Board (formerly
 California Regional Water Pollution Control Board No. 4) limited disposal of liquids to a
 32-acre  area in the western portion of the South Parcel  (Order No. 76-30) (LARWQCB,
 1976a).  This order allowed Operating Industries, Inc. to mix liquids with solid refuse at a
 ratio of 10 gallons per cubic yard of refuse. In September 1976, Order 76-133 (LARWQCB,
 1976b) increased the allowable ratio to 20 gallons per cubic yard.

 In 1982, leachate  was observed seeping offsite (LARWQCB, 1984). Operating Industries,
 Inc. stopped accepting hazardous liquid waste in January 1983 and all liquid waste in April
 1983.  A leachate collection system was installed to collect leachate  seeping from the landfill.
 Leachate generated  at the landfill was collected  and redisposed  by  combining  it with
 incoming refuse that  was mixed back onto the working face of the landfill (LARWQCB,
 1984). This practice  continued  until September 1984, when the California Department  of
 Health Services classified leachate generated at  the landfill as hazardous  and prohibited
 redisposal, effective October 1984.  At that time, Operating Industries, Inc. began shipping all
 leachate offsite for treatment and disposal.

 Prior to 1984, Operating Industries, Inc., the landfill operator and owner, performed several
 landfill control  measures. This included installation  of the leachate collection system,
 development of an air-dike air injection system on the  west side of the landfill to  control
 subsurface gas migration, installation of gas extraction wells around the perimeter  of the
 landfill,  installation  of a gas flaring  station to burn  landfill gas,  site contouring,  slope
 terracing and vegetation,  and covering of refuse with fill.

 Operating Industries, Inc.'s control of the environmental problems and maintenance  of the
 control systems began to diminish  significantly in late 1984.  In this same time period, EPA
 began initial site investigations. On May 19,  1986, Operating Industries, Inc. notified the
 state of its intent to discontinue all site control and monitoring activities except irrigation. By
 the end of May 1986, the OU  Site was added to the National Priorities List. EPA assumed
 responsibility for site activities on May 20, 1986.
Oil Site Final Record of Decision                                             Page 1-11
Part I - Decision Summary                                             scoiooi92D3.DOC

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 2.1.2 Landfill Development and Thickness

 Landfilling operations began in 1948 by filling an existing natural canyon currently occupied
 by a portion of the Pomona Freeway and north-central portions of the South Parcel. Cut-and-
 cover filling operations began in the early 1950s.  Additional areas were quarried and filled.
 From the 1950s through the  1970s, the waste disposal activities expanded to cover the current
 landfilled area. During this time, the height of the landfill was also increased several times,
 ultimately reaching the current elevation of approximately 640 feet above mean sea level.
 The thickness of solid waste in the South Parcel ranges from approximately 200 to 325 feet.
 The North Parcel contains approximately  11 acres of solid waste, ranging in thickness up to
 55 feet.

 2.1.3 Waste Types  and Quantities

 Examples  of  the types of  wastes  permitted for disposal  at the  landfill (Monterey Park
 Resolution 60-58) are listed in Table 1.  Table 2 lists  examples of liquid wastes reportedly
 disposed at the OH Site between  1976 and 1984 (EPA, 1987e).  A total estimated refuse
 volume of 38 million  cubic yards weighing 22 to 31 million tons was disposed at the landfill
 over its operating life (EPA,  1988g).  More than three-fourths  of  the refuse was disposed
 before 1974, before records were maintained for truck counts and delivered weight.

 Liquids are excluded from the refuse mass calculations  discussed in the preceding paragraph.
 Liquid wastes were disposed at  the landfill throughout its history,  until April 1983. More
 than 300 million gallons of liquids are recorded as having been disposed between 1976 and
 1983 (EPA, 1988d). Liquid  wastes were reportedly disposed at the landfill prior to 1976, but
 records were not kept  by landfill operators.
                            2.2    Field Investigations

A large number of field investigations have been performed at, and in the vicinity of, the OH
Site over approximately the  last 20 years. This section provides an accounting and brief
description of the field investigations and monitoring programs that provided data used in
geologic,  hydrogeologic, and contaminant analyses and  interpretations in the Remedial
Investigation.   Detailed  discussions of these investigations are presented in  the  Draft
Remedial Investigation Report (EPA, 1994c).

Section 2.2.1 discusses major hydrogeologic investigations.  Section 2.2.2 briefly describes
major  geologic and geotechnical investigations that have been performed  at the landfill.
Page I-12                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

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                                         Table 1
            Examples of Generic Wastes Permitted for Disposal at Oil Landfill
                            (Monterey Park Resolution 60-58)
                            Oil Site Final Record of Decision
   Natural earth
   Rock, sand,  and gravel
   Paving fragments
   Concrete
   Brick
   Plastic and plaster products
   Steel mill slag
   Clay base rotary mud
   Mud cake from oil field sumps
   Street sweepings
   Glass
   Asbestos fiber and products therefrom
   Metals and metal products except magnesium and its alloys
   Paper and paper products including roofing and tar paper
   Cloth and clothing
   Wood and wood products
   Lawn clippings, sod, and shrubbery
   Cold ashes
   Manufactured rubber products
   Solid plastic products
   Paint sludge received from  water-circulating paint spray booths not transported in
    vacuum tanks
   Rotary drilling mud from oil field drilling operations
   Cleanings from production tanks
   Acetylene sludge
   Sludge from automobile wash racks and steam-cleaning products
   Mud and water from laundries
   Liquid latex waste
   Ceramic, pottery, and glaze wastes
  Lime and soda water
  Paint sludge recovered  from water circulated in paint spray
  Water containing not more than 0.5 percent molasses
  Market refuse (in limited quantities)
  Not permitted for disposal (Monterey Park Resolution 60-58):  spent acid waste, spent
  caustic waste, and common  chemically stable salts from manufacturing or industrial
  processes.	
  Reference:     EPA (1987e)
scoiooi9i6B.wp5                                                                Page 1-13

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Examples of Liquid Wastes
01
(Percent figures are approximate
Reports to the LARWQCB)
Mud and water
Mud water and oil
Drilling mud
Tank bottom . .
Latex wastes 	
Paint sludge 	
Coolant . 	
Carbon black and water 	
Remaining generic types 	
Alkaline solution
Aluminum sludge and flocculent
Animal fat and water
Asbestos pulp and water
Asphalt and water
Brake fluid
Brine
Burnishing media
Burner (baghouse) dust
Carpet material and water
CAT CR catalyst
Caustic soda
Caustic solution
Cement and water
Ceramic glaze
Cleaning compound
Coconut
Corn syrup
Creosote
Dairy wastes
Diamogion silica
Dough and water
r^CC fines and water
fiberglass
Film gelatin
Filter clay
Fish and water
Food-processing wastes
Glass dust and water
Glue and water
Grease waste and water
nk and water
_jme and water
Reference: EPA (1987e)
Table 2
Reportedly Disposed at Oil Landfill from 1976 to
I Site Final Record of Decision
values based on general descriptions appearing on Oil










Lint and water
Liquor
Metal dust and water
Mineral water
Molasses and water
Nickel, copper, and water
Oxides (Al, Pb, Si, Zr)
Organic wastes
Perlite
Petroleum industry sludge
Plastic dust
Polymer sludge
Rain water
Resin, PVC, and water
Rouge and water
Rust sludge
Sand and water
Sawdust and water
Settling basin sludge
Slurry
Soap and water
Sodium silicate
Starch and water
Stretford solution
Sulfur fines in water
Tank sludge
Tar pit sludge
Tile glaze
Waste paper
Wastewater
Wax (polishing compound) and water
Welding flux



1984

Monthly

60%
12%
4%
6%
2%
2%
1 5%
1%
11.5%


































 Page 1-14
SCO1001916C.WP5

-------
 Section 2.2.3 summarizes  two air quality investigations  performed in the vicinity of the
 landfill.  Section 2.2.4 briefly summarizes surface water sampling at the landfill.  Finally,
 Sections 2.2.5  and 2.2.6 describe investigation and  sampling of leachate and  landfill gas,
 respectively.

 2.2.1 Hydrogeologic Investigations

 EPA performed six major hydrogeologic investigations at the OH Site between 1975 and
 1993, resulting in the installation of 75 groundwater monitoring wells.  Monitoring well
 locations are shown in Figure 3. Activities conducted as part of these investigations include:
 drilling and monitoring well installation, formation testing, surface  and subsurface soil
 sampling,  groundwater  sampling and  analysis,  and  aquifer  testing.    Data  from  the
 hydrogeologic investigations were used extensively throughout the Remedial Investigation.

 2.2.2 Geologic and Geotechnical Investigations

 EPA performed  several geologic and geotechnical  investigations  that provide  additional
 information regarding the subsurface conditions at or  near the OH Site.  A brief  summary of
 these follows.

 Geologic Mapping and Investigations.  There  are several published papers  and reports
 pertaining  to the  geologic conditions  in the vicinity of the OH Site.  Additionally, EPA
 conducted focused geological mapping at the OH Site  and the surrounding area during several
 investigations.  Also, the OH Landfill Work Defendants have performed geologic mapping of
 the OH Site and vicinity.

 Geotechnical Investigations.  EPA performed numerous geotechnical  studies related  to
 landfill  development,  residential  and  commercial  property  development,   petroleum
 exploration, and the underground storage of imported natural gas in the vicinity of the OH
 Site.  Geotechnical investigations within the landfill boundary have typically been related to
 landfill development and  construction;  these investigations primarily include geologic
 mapping,  material testing,  and  landfill characterization  relative to  slope  stability and
 foundation investigations. EPA drilled numerous borings  to define the limits of the waste
 prism and to investigate the type and extent of contamination or landfill gas migration. Since
 1987, EPA has conducted geotechnical monitoring of  slope  stability, including measurements
 of inclinometers and surveying of surface monuments.

 North Parcel Site Characterization. In 1987, EPA performed a surface and subsurface soil
 investigation at the North Parcel to identify the vertical and  lateral soil contamination and the
 extent of waste on the North Parcel (EPA, 1988i).  EPA collected surface soil samples from
 throughout the auto salvage yard and drilled borings for waste characterization. Shallow and
 deep soil samples were obtained from all of the borings.
Oil Site Final Record of Decision                                             Page 1-15
Part I - Decision Summary                                            scoiooi92D3.DOC

-------
 2.2.3 Air Quality Investigations

 EPA conducted two air quality investigations as part of the Remedial Investigation for the OH
 Site. One investigation focused on ambient air in the vicinity of the landfill, and the other
 investigation focused on air quality in the homes surrounding the landfill.

 24-Hour Ambient Air Monitoring.  EPA conducted an investigation to collect and analyze
 ambient outdoor air  samples in  the  vicinity  of the landfill (EPA,  1991c).  Ambient air
 sampling was conducted for  one year, from  September 1989  to  September  1990.  EPA
 installed nine air monitoring stations for the study; seven were located along the perimeter of
 the  landfill,  and  two were  located  some distance away  from the landfill to serve as
 background locations. Sampling locations are shown in Figure 4.

 In-Home Air Monitoring.   Between November 1992  and July 1993,  EPA conducted an
 in-home air monitoring program to evaluate whether potentially harmful landfill gas from the
 OH  Site was entering nearby homes  (EPA, 1993a). EPA  recommended the in-home air
 monitoring program  at the conclusion of the year-long  ambient  air study described above.
 EPA used existing methane data from monitoring of water meter  boxes  and probes to
 establish the target area for residential sampling.  The sampling program included homes
 along the streets adjacent to the southern boundary of the landfill as well as a small area west
 of the landfill. EPA took air samples from a total of 197  homes; the locations of these homes
 are identified in Figure 5.

 2.2.4 Surface Water Sampling

 Surface water in the form of runoff from the landfill is sampled routinely as  part of the site
 control and monitoring activities at the landfill.  In addition, EPA  collected two surface water
 runoff samples from  the North Parcel in 1987  as part of a  field reconnaissance to identify
 surface drainage features.

 Routine surface water sampling began in February 1990 and continues through the present.  For
 the first three (or more, in some instances) storms of  the  rainy season, EPA performs surface
 water sampling within several hours after the start of a storm at designated sampling locations.
 The  majority of  the  surface water sampling  results are included in OH  Landfill  Work
 Defendants monthly reports (OH Landfill Work Defendants, 1990 to 1994).

 2.2.5 Leachate Investigations

 This section provides a brief overview of investigations that have been performed to delineate
 and characterize leachate at the OH Site.
Page 1-16                                            Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

-------
                                                                                                                                                                                               ©  Converse, Davis, Oixon
                                                                                                                                                                                                   Wells (CDD. 1975)
                                                                                                                                                                                               -{B- Initial Monitoring Well
                                                                                                                                                                                                '   Installation (EPA, 1985)
                                                                                                                                                                                                A  North Parcel Hydrogeology
                                                                                                                                                                                                   Investigation (EPA. 1988c)
                                                                                                                                                                                                D  Phase i Hydrogeology
                                                                                                                                                                                                   Investigation (EPA, 1990b)
                                                                                                                                                                                                ©  Phase II Hydrogeological
                                                                                                                                                                                                   Investigation (EPA. 1992a)
                                                                                                                                                                                                A  Hydraulic Testing Program
                                                                                                                                                                                                   (USAGE, 1993)
                                                                                                                                                                                                    Approximate Location of
                                                                                                                                                                                                    FenceXProperty Boundary
                                      \V           y/       >/
                        Q     n      —' ^^     //

                                            I          £o~   n.
                                                                                                                                                                                                Figure 3
                                                                                                                                                                                                Monitoring Well Locations
I:\PROJECTS\109994.16\109994-1.0WG
                                                                                                                                                                                                          Page 1-17

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Oq
ft
                                                                           0    1,000  2,000


                                                                                  Seal* In Feet
  -/-U \
^IT^^T
1. ^,1  >cu
*                                                                                 24-Hour Ambient Air Background
                                                                                 Monitoring Stations
                                                                                 24-Hour Ambient Air Monitoring
                                                                                 Stations
                                                           Station 4
                                                           Ethylbenzene
                                                             PCE
                                                            Toluene
                                                  Station 1 or
                                                    1,1-DCA
                                                   Ethylbemene
                                                   Vinyl CHoride J
                                                                          Figure 4
                                                                          Compounds With Average
                                                                          Ambient Air Concentrations
                                                                          Exceeding Background
                                                                          (at the 85 percent significance level)
                                                                          OH Site Final Record of Decision
   m11009W. 18.01 oompi 8/ee

-------
                                        *f<**£^:
                                        W -Bb^>.  wWiv-»s^
*w*
                      1&' <<£
                     '/S,"S^


                                                                             250  500


                                                                              SCALE M FEET
                                                                                        1000
                                                                         Features:


                                                                         /\/ Approximate Location of
                                                                            Fence/Property Boundary

                                                                         A/ Road Boundary

                                                                         *"* Homes Included in the
                                                                            Sampling Network
                                                                         Figure 5
                                                                         Sampling Network
                                                                         for the In-Home
                                                                         Air Monitoring Program

                                                                         OH Site Final
                                                                         Record of Decision

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 Leachate Seeps Sampling and Analysis. EPA collected leachate samples from leachate seeps
 in Iguala Park after heavy rains in January 1993. The OH Landfill Work Defendants performed
 a survey of onsite landfill seeps after the  1992/1993 rainy season to prioritize seepage areas for
 potential remediation prior to installation of the landfill cover (OH Landfill Work Defendants,
 1993a).

 Leachate Sampling and Analysis.  Since 1983, EPA has periodically collected and analyzed
 leachate to characterize its chemical composition and source areas.  EPA performed its first
 comprehensive analyses  of leachate  chemistry in  1986 (EPA,  1986a), and conducted several
 leachate sampling programs between 1986 and 1989.   Liquid samples were collected from
 various locations  in  the leachate and landfill  gas  collection  systems  on the South Parcel,
 including sumps, wells, tanks, and two deep interior landfill gas extraction wells. EPA also
 measured liquid levels in 17 landfill gas extraction wells on the top deck of the landfill.

 During soil boring drilling at the North Parcel  (EPA, 1988i), EPA collected perched liquids
 from two borings located in the southwest portion of the North Parcel landfill area.  These
 liquids were encountered at the transition between waste and the underlying native soil.

 Since  1990, the OH Landfill Work Defendants have performed several leachate sampling events
 associated with evaluations of leachate quantity and quality for the leachate treatment plant.
 Samples have been collected primarily from gas collection and leachate wells, as  well as the
 sumps associated with the leachate collection system.

 2.2.6 Landfill  Gas Investigations

 EPA has collected a large amount of landfill gas data at the OH Site since the mid-1970s. This
 section provides a brief overview of the major sources of data most relevant to analyses in the
 Remedial Investigation and Feasibility Study.

 Landfill Gas Probes and Wells.  Operating Industries,  Inc. installed landfill gas  monitoring
 probes along the west, south, and east borders of the South Parcel in 1976 and 1981  and around
 the North Parcel in 1981. Operating Industries, Inc. installed perimeter gas extraction wells in
 various phases from  1982  through 1984.  Many  of the landfill gas probes continue to be
 monitored routinely for methane  and  other constituents as part of the ongoing site control and
 monitoring activities.

 Air Dike Wells.  In response to  a Los Angeles  County Health Department order (January 23,
 1981), Operating Industries, Inc. installed an air dike system in native material along the south
 and west borders of the landfill to control landfill-generated methane gas emissions  beyond the
 landfill boundary.  EPA installed 26 wells in 1981  to create the air dike.  Additional wells and
 monitoring probes were installed in October 1982. EPA constructed eight gas migration test
 wells (GMTW-1 through -8) to a maximum depth of 101 feet as part of a testing program for
 the existing air dike system (OH Landfill Work Defendants, 1992b).
Oil Site Final Record of Decision                                              Page 1-21
Part I - Decision Summary                                             scoiooi92D3.DOC

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 South and North Parcel Landfill Gas Monitoring Wells.  EPA installed 15 landfill gas
 monitoring wells along the western and southern boundaries of the South Parcel in  1987 and
 1988 (EPA, 1988h).  EPA also installed multiple gas probes in each borehole at various depths,
 with bentonite seals between the probe levels.

 EPA installed 13 landfill gas monitoring wells on the North Parcel in June/July 1987 (EPA,
 1987d).  Each well  contains either two or three  probes at depths between 6 and 64 feet.
 Locations and probe  depths for both North and South Parcel landfill gas monitoring  wells are
 shown in Figure  6.
                  2.3 Summary of EPA Actions at the OH Site

 EPA has performed a variety of emergency actions in response to environmental problems at
 the landfill, including erosion control improvements, installation of a toe buttress for slope
 stability, surface runoff and drainage improvements, rehabilitation  of the main flare station,
 site  security, placement  of vented  water meter box covers in the areas  surrounding  the
 landfill, and installation of control systems in nearby affected residences.

 EPA formally began the Remedial  Investigation/Feasibility  Study  at the OH Site  in  1986,
 although field investigations had been initiated in 1984.  To efficiently manage the problems at
 the OH Site and to address the most apparent environmental problems prior to implementation
 of the final remedy, EPA divided the work into three operable units,  as described below. EPA
 has successfully negotiated five Consent Decrees with various potentially  responsible party
 groups to perform and fund portions of the work specified in the previous RODs for  the
 operable units.  In addition, some of the funds from  the last two Consent Decrees are to go
 towards final remedy.

 2.3.1  Summary of Enforcement Activities

 Prior to EPA involvement, various state and local agencies reported that Operating Industries,
 Inc.  frequently violated  waste  disposal regulations during the operations at  the  landfill
 between 1952 and 1984.  Operating Industries, Inc. was  notified and/or cited for several of
 these violations.   EPA sent Resource Conservation and Recovery Act of 1976  (RCRA)
 Section 3007/Comprehensive Environmental Response, Compensation  and Liability Act of
 1980 (CERCLA)  Section 104(e) notice letters and  information requests to Operating
 Industries, Inc. and individual owners in 1984.

 There are  approximately  3,950 potentially responsible  parties at the OH Site.  Since 1984,
 EPA has sent combined general notice and CERCLA 104(e) letters to potentially responsible
Page 1-22                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

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                                     NGMW-03

                                      NGMW-09
                                               NGMW-13,

                                             NGMW-11
                                          031
"8
                                                                NORTH PARCEL
                                                          ^ INGMW-05
                                                                                    SGMW-H
                                                                SGMW-11I_SGMW-12    ,SGMW_13
                                                                                                                                LEGEND/NOTES
	Approximate Location of
     Fence\Property Boundary


—I—  Landfill Gas Monitoring
     Well Locations

  *  Correspondence  between as-
    built designation and current
    field designation is uncertain
    or unknown.
                                                                                                                             0      400     800
                                                                                                                           APPROXIMATE SCALE IN FEET
                                                                                                                      Figure 6
                                                                                                                      Landfill Gas Monitoring
                                                                                                                      Well Locations
                                                                                                                      Oil Site Final Record of Decision
     I:\,PROJECTS\I09994.16\109994-2.0WG   09-23-96

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 parties that generated approximately 87 percent (by volume) of the manifested liquid waste
 for  which  EPA has records.   Various groups  of these  potentially  responsible parties
 participated in the Consent Decrees described below.  The  remaining 13 percent of the
 manifested liquid wastes, reflected in EPA's records, was generated by approximately 3,600
 de minimis generators.

 2.3.2 Oil Site Operable Units

 The term "operable unit" refers to a discrete action taken at a Superfund site to address specific
 site  problems.  At the OH Site, Operable Unit No. 1 pertains to site control and monitoring
 activities; Operable Unit No. 2  pertains to leachate management; and Operable Unit No. 3
 pertains  to landfill gas control and landfill cover.  EPA has completed individual feasibility
 studies and signed RODs for each of the three operable units.

 Operable  Unit No. 1:  Site Control and Monitoring. This operable unit  addressed the
 seven major interim environmental control systems and activities at the OH Site that require
 operation, maintenance, inspection, and monitoring on a continuous basis:  gas extraction and
 air dike  systems, leachate collection system,  irrigation system, access road system,  storm
 water drainage system, site security, and slope repair and erosion control.  In the ROD for
 Site Control and Monitoring (EPA, 1987a),  EPA decided  that full-time site control  and
 monitoring  should be  undertaken,  providing  daily  operation, repair and replacement of
 control system components when necessary, and system  improvements.  The  ROD for Site
 Control and Monitoring is interim and ends at the signing of this ROD, although activities
 required  under the  Site Control and Monitoring ROD will  continue as part of this ROD.

 Operable  Unit No. 2:   Leachate  Management.   EPA's  interim  selected remedy for
 management of leachate collected at the OH Site, as presented in the  ROD for the Leachate
 Management Operable Unit (EPA, 1987b), was treatment of the leachate at a treatment plant
 located at the landfill. This plant has been built on the North Parcel  and consists of a Remote
 Oil Separation Facility (on  the  South Parcel),  influent storage and equalization,  biological
 reactors,  chemical precipitation,  sand filtration, granular activated carbon adsorption, effluent
 storage and discharge, a foul air system, a storm water holding system, and a sludge disposal
 system.  The ROD specified that treated  leachate be disposed in facilities operated by the
 County Sanitation Districts of Los Angeles County. The  ROD for Leachate Management is
 interim and ends at the signing of this ROD, although activities required under the Leachate
 Management ROD will continue as part of this  ROD.

 Operable Unit No. 3: Gas Migration Control and Landfill Cover.  The Gas  Migration
 Control and Landfill Cover ROD, as amended (EPA,  1990a;  originally  the Gas  Migration
 Control ROD [EPA, 1988b]), defines a final  landfill cover and  landfill gas migration control
 remedy to collect and destroy landfill gas that would otherwise  be released from the landfill.
 (The Gas Migration Control  and Landfill  Cover ROD is referred to as the Gas Control and
Cover ROD throughout this document.) In  general, the work  specified in the Gas Control
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 and Cover ROD includes design, construction, operation, maintenance, and monitoring of a
 landfill gas control system; a landfill cover system; and a surface water management system
 for the OH Site. The new landfill gas system will likely supplement, partially incorporate,
 and partially replace the existing landfill gas system.  The amendment to the ROD also
 includes design and construction of a landfill cover to reduce surface emissions of landfill
 gas, reduce oxygen intrusion into the refuse, reduce surface water infiltration, minimize slope
 erosion, and improve aesthetics.  The Gas Control and Cover ROD is a final ROD and,  as
 such, is a significant component of the final site cleanup, but is not included in or modified
 by this ROD.

 2.3.3 Oil Site Consent Decrees and Administrative Orders

 Five Consent Decrees have been successfully negotiated with various potentially responsible
 party groups for performance and funding of various portions of the site cleanup. The first
 Partial Consent Decree was negotiated for work on Operable Units No. 1 and 2. The Second
 Partial Consent Decree was negotiated with additional potentially  responsible parties  to
 provide funding for the same scope of work as the first Partial Consent Decree.  The Third
 Partial Consent Decree was negotiated for the design and implementation of a major portion
 of Operable Unit No. 3.  The Fourth and Fifth Partial Consent Decrees provide additional
 funding for ongoing or planned work at the site.

 In addition to the Consent Decrees, site cleanup work has been performed under a Unilateral
 Administrative Order (Unilateral Administrative Order No. 94-01) that EPA issued to three
 of the previously nonsettling potentially responsible parties.   The order required  these
 potentially responsible parties to participate in the collection and treatment/disposal of wastes
 associated with the OH Site in cooperation with the potentially responsible parties performing
 work at the site under the Consent Decrees. These three parties subsequently joined the Fifth
 Partial Consent Decree. Parties responsible for performing work under a Consent Decree are
 collectively referred to as  Oil Landfill Work Defendants throughout this ROD.
               3.0  Highlights of Community Participation
The Proposed  Plan  for  this remedy,  in  the  form of  a fact  sheet, was  distributed to
approximately 3,000 parties on EPA's  mailing list for the OH Site.  The Proposed Plan,
together with the Feasibility Study Report (EPA, 1996) and the Draft Remedial Investigation
Report (EPA, 1994c),  were also  made  available  in the site vicinity at the Bruggemeyer
Memorial Library in Monterey Park, the Montebello Regional Library in Montebello, and the
Chet Holifield Library in Montebello.  Microfilm of the entire Administrative Record File,
containing  these  three documents and other  documents considered or relied  upon in
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 developing the Proposed Plan, is available at the Bruggemeyer Memorial Library. The file is
 also available at EPA's Regional Office in San Francisco.

 Notice of public meeting, availability of the Proposed Plan, and the announcement of  a
 30-day public comment period were published in the Los Angeles Times newspaper, San
 Gabriel edition, on May 31, 1996, and the Monterey Park Progress and Montebello News
 newspapers on May 30, 1996.

 EPA held a public meeting on June 12, 1996, near the site to discuss its cleanup plan.  At this
 meeting, EPA representatives made  a brief presentation  of  the Proposed Plan, answered
 questions,  and solicited comments from members of the public.  A transcript of the public
 meeting, including oral comments  and responses, is included as Appendix A of this ROD.

 EPA extended the public  comment period in response to a request from members of the
 public. A public notice mailed to the entire EPA mailing list extended the original  30-day
 public comment period to 60 days.  EPA received several sets of written  comments during
 the public comment period. These comments are addressed in the Responsiveness Summary,
 included as Part II of this ROD.

 EPA has also held frequent meetings with the public, the state, and local agencies to discuss
 ongoing activities at the landfill. In addition to the Proposed Plan fact sheet for this remedy,
 EPA has issued numerous fact sheets between 1985 and  1996 describing investigation and
 cleanup activities at the Oil Site.

 This decision document presents the selected remedial action  for the OH Site, in Monterey
 Park,  California,  chosen  in  accordance  with  CERCLA,  as amended  by  Superfund
 Amendments and Reauthorization Act of 1986 (SARA), and, to the extent practicable, the
 National Oil and Hazardous Substances Pollution Contingency  Plan (NCP). The decision for
 this site is based on the Administrative Record.
                   4.0  Summary of Site Characteristics
This section  summarizes results from environmental sampling conducted at the OH  Site
during the Remedial Investigation. The nature and extent of landfill-related contamination in
air, soil, surface water, and groundwater are discussed.
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                                      4.1  Air

 EPA conducted a year-long outdoor ambient air study at the OH Site in 1989 and 1990. In
 1992 and 1993, EPA implemented an in-home air monitoring program at homes near the OH
 Site. Results of these programs are summarized below.

 4.1.1 Ambient Air

 EPA installed nine air monitoring stations for the ambient air study (Figure 4). Seven of the
 stations were  set up to collect samples from air near the boundary of the landfill, and two
 stations were installed away from the landfill for comparisons to background air.

 A statistical evaluation of the results indicated that average concentrations of selected volatile
 organic compounds  adjacent to  the landfill exceeded average background  concentrations
 (Figure 4).  The stations where at least one volatile organic compound exceeded background
 are shown in Figure 4. These data indicate that the landfill is  impacting air adjacent to the
 landfill boundary.

 4.1.2 In-Home Air

 Based on the results of the ambient air study, EPA implemented an in-home air monitoring
 program to estimate the levels  of landfill gas in air inside and outside (ambient) homes near
 the OH Site. The primary focus  of the in-home air monitoring program was to determine
 whether  landfill gas was entering homes through their foundations.   EPA measured vinyl
 chloride  in the in-home air study to evaluate landfill gas impacts. EPA collected samples
 from 197 homes in the neighborhoods surrounding the landfill.  Locations of these homes are
 shown in Figure 5.   Vinyl chloride was detected in about 20 percent of the 197 homes
 sampled, and was only near or exceeded the OH Site-specific action level of 1 part  per billion
 in approximately 4 percent of the homes.  Seven homes were determined to require interim
 gas control measures, which EPA subsequently installed.  Supplemental sampling  confirmed
 the effectiveness of the interim gas control systems.
                                     4.2 Soil

EPA collected samples of both surface and  subsurface soil at and in the vicinity of the OH
Site during several field efforts conducted during the remedial investigation.

The primary soil investigations were conducted on the North Parcel and along the perimeter
of the  South Parcel. The surface  soil investigation along the South Parcel perimeter also
included collection of sediment samples from drainages leading away from the landfill.
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 4.2.1  Surface Soil

 Along the perimeter of the South Parcel and on the North Parcel, EPA found isolated, low-
 level contaminant  concentrations  in  surface soil  and sediment.  In  three areas of limited
 extent, the  concentrations  exceeded both  preliminary  remediation  goals (health-based
 concentrations that are used for risk screening purposes  as possible "triggers" for further
 evaluation) and background concentrations.  However, the baseline risk assessment results
 (summarized in Section 5) indicate that risks associated with this surface soil/sediment are
 not sufficiently elevated to warrant action for the protection of human health.

 4.2.2  Subsurface Soil

 In  general, only isolated occurrences of  contaminants were detected in subsurface soil
 samples. Along the perimeter of the South Parcel, results indicate that the higher contaminant
 levels  found in  subsurface  soil samples are  in areas  where  shallow  groundwater
 contamination has  also been detected. These areas  include the western and southwestern
 perimeters of the South  Parcel and  the northeastern corner of the South Parcel.  These
 subsurface samples were collected from greater than  10 feet below ground surface, which is
 typically the maximum depth evaluated in human health risk assessments.
                                4.3  Surface Water

Surface water present on and in the vicinity of the OH Site is limited to storm water runoff
following substantial rainfall events and  periodic irrigation  runoff. Storm water  runoff
samples are routinely collected from all drainages leaving the OH Site. Detections of organic
and inorganic constituents in surface water  samples occur only sporadically and at generally
low concentrations. The surface water management systems to be implemented under the Gas
Control  and  Cover ROD  will  virtually  eliminate  the potential  for  surface  water
contamination.
                                4.4 Groundwater

This  section  provides  a  summary  of  pertinent information  regarding  groundwater
contamination  originating from  the OH  Site.   The following  nature  and  extent  of
contamination discussions are  divided  by general  geographic areas  and/or aquifers (see
Figures 7 and 8).
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                                                                                                                                   T     *«r5-44A
                                                                                                                                             	 —350

                                                                                                                                              __ —3WQ EASTERN  AREA
                                                                                                                                                                                   Approximate Location of
                                                                                                                                                                                   Fence\Property Boundary
                                                                                                                                                                             OI-30A
                                                                                                                                                                               (3)

                                                                                                                                                                                *— Number of Compounds
                                                                                                                                                                                   Exceeding MCLs In
                                                                                                                                                                                   1992/1993
                              .  ,'\    .                \oi-j.
                              V   \   \    \  „,>03
                                                                                                                                                                              Figure 7
                                                                                                                                                                              1992/1993 MCL
                                                                                                                                                                              Exceedance Contours in
                                                                                                                                                                              Shallow or Unconfined
                                                                                                                                                                              Flow Systems
                                                                                                                                                                              Oil Site Final Record of Decision
h \PHajECT5\1DW94.1SVUM94-3.0m  09-13-99
                                                                                                                                                                                      Page 1-29

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                                                                                                                                                                                                          LEGEND/NOTES
                                                                                                                                                                                                      0 Eastern Area
                                                                                                                                                                                                         Deep Wells

                                                                                                                                                                                                      A West Aquifer Wells

                                                                                                                                                                                                      * South Aquifer Wells

                                                                                                                                                                                                         Northwest Area Deep Wells

                                                                                                                                                                                                         Approximate Location of
                                                                                                                                                                                                         Fence\Property Boundary

                                                                                                                                                                                                         Well Number


                                                                                                                                                                                                  OI-21B
                                                                                                                                                                                                      0)

                                                                                                                                                                                                      *— Number of Compounds
                                                                                                                                                                                                         Exceeding MCLs
                                                                                                                                                                                                         in 1992/1993
                                                                                                                                                                                                  -- Approximate
                                                                                                                                                                                                          1§§2/1993 MCL
                                                                                                                                                                                                          Exceedance Contours

                                                                                                                                                                                                  - - Potentlometric Surface
                                                                                                                                                                                                         Contours- South
                                                                                                                                                                                                         Aquifer
                                                                                                                                                                                                         Fault (Inferred)
                                                                                                                                                                                                        0    200  400  600

                                                                                                                                                                                                       APPROXIMATE SCALE IN FEET
                                                                                                                                                                                                   Figure 8
                                                                                                                                                                                                   1992/1993 MCL
                                                                                                                                                                                                   Exceedance Contours in
                                                                                                                                                                                                   Deep or Confined Flow
                                                                                                                                                                                                   Systems
                                                                                                                                                                                                   OH Site Final Record of Decision
r:\PR(X*CTSVW99«.16V09994-4.0l«; 9-23-96
                                                                                                                                                                                                               Page 1-31

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 The discussion of the nature and extent of groundwater contamination presented below is
 summarized from the Draft Remedial Investigation Report (EPA, 1994c) and is based on data
 from the 1992/1993 monitoring  period.   The  Draft Remedial Investigation  Report also
 provides an in-depth evaluation of all groundwater data collected from 1984 to 1993. For the
 Feasibility Study  Report  (EPA,  1996), groundwater quality data from  1994 were also
 evaluated to identify areas of concern for groundwater and to see if any significant changes
 had occurred.

 4.4.1 Northwest Area

 The Northwest Area encompasses the western portion of the North Parcel, the  northwest
 portion of the South Parcel,  and the area downgradient (northwest  and  west) of the two
 parcels.

 Nature and  Extent of Groundwater  Contamination.  EPA evaluated the groundwater
 contamination in the Northwest Area using the 1992-1993  maximum contaminant level
 (MCL) exceedances, shown in Figures 7 (shallow or unconfined flow systems) and 8 (deep or
 confined flow systems).

 •      1992-1993 maximum contaminant level exceedances (Figure 7) indicate the presence
       of one contaminant  plume  moving  approximately due west along the  northern
       boundary of the South Parcel and a second area of contamination on and  north of the
       North Parcel.

 •      It appears that contaminants exiting the landfill near Wells CDD-13  and OI-19B enter
       groundwater, which then migrates  toward Well OI-46A.  This westerly  plume is
       consistent with the groundwater flow directions presented in Figure 7.

 •      Data from the deeper units in this same area (primarily Wells OI-19A and OI-24B),
       shown in Figure 8, also  show maximum contaminant level exceedances indicating
       deeper groundwater contamination in the vicinity of the shallow plume source areas.

 Contaminant Fate and Transport.  Conclusions regarding contaminant transport from the
 landfill into and through groundwater in the Northwest Area are summarized below.

 •      The potential physical pathways for contaminants to migrate from the landfill and into
       the  groundwater  in this  area may be  through  several small canyons that  were
       excavated  prior to  the establishment of the landfill and subsequently  filled with
       refuse.  These canyons  were located approximately  along  the  present  northern
       boundary of the South Parcel. The lithology of basal rock in  these canyons is silty
       sandstone and siltstones that are probably less permeable than the overlying waste or
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        fill material. This permeability contrast can direct flow from the interior sections of
        the landfill outward towards the north-northwest.

 •      While most of the contaminant transport will likely be through the unconfined aquifer
        system, some migration also occurs through siltstones and deeper, confined units.

 4.4.2  Southwest Area—Groundwater Contamination

 The Southwest Area refers to the  area  around  the  western, southwestern,  southern, and
 southeastern boundaries of the  southwestern corner of the South Parcel.

 Nature and  Extent  of Groundwater  Contamination.    EPA evaluated groundwater
 contamination in the Southwest Area  using the 1992/1993 MCL exceedances, as shown  in
 Figures 7 and 8.  As shown in  these figures, the perimeter wells exhibit numerous maximum
 contaminant level exceedances.  These data indicate at least two shallow plumes migrating from
 the Southwest Area of the landfill (Figure 7).  The following  observations have  been made
 regarding the groundwater plumes.

 •      The contaminant levels at the fringes of the monitoring well network indicate that
        impacted water is not likely present considerable distances further downgradient (i.e.,
        less than a few hundred feet beyond the current monitoring wells).

 •     The west-southwest plume extends at least to Well OI-35A, located about 1,800 feet
       from the  landfill boundary.  Contamination present  this  far downgradient in the
       Shallow  Silt Flow System  is  not  consistent  with  the  horizontal flow velocities
       calculated for the Shallow Silt Flow System, and is likely indicative of preferential
       flow through higher-velocity features  in the siltstone matrix (such as fractures or
       sandier intervals) or along the contact  between the Lakewood/San Pedro and Pico
       Units.

 •      The primary source of contamination in the Southwest Area appears to be subsurface
       releases along the borders of the landfill.

 Contaminant Fate and Transport.  Conclusions regarding contaminant transport from the
 landfill into and through groundwater in the Southwest Area are summarized below:

 •      The primary pathway for contaminant transport from the landfill into the surrounding
       regions of the Southwest Area is subsurface releases along the borders of the landfill
       and subsequent horizontal migration of contaminants through the siltstone, fractures,
       and sandier  intervals in the Shallow Silt Flow System. Additionally, contaminants
       can migrate directly into groundwater in  the  Lakewood/San Pedro/Fill unit at the
       southwest corner of the landfill.
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 •     Following wet periods, contaminated groundwater flow is possible along the contact
       between the Lakewood/San Pedro Formation (or the Lakewood/San Pedro/Fill unit)
       and the Shallow Silt Flow System, given the permeability contrast between the two.

 •     Although there are high contaminant concentrations near the landfill perimeter in the
       Southwest Area (particularly of organic constituents), migration through the siltstone
       causes organic constituents to be retarded and concentrations to decrease considerably
       with distance from the perimeter of the landfill.

 •     Migration through  the  siltstone causes  organic constituents to be retarded and
       concentrations to decrease considerably  with distance  from  the perimeter of the
       landfill.  The semivolatile organic compounds are even more retarded that the volatile
       organic compounds  and are not expected to transport  as quickly away  from the
       landfill because of their generally high retardation rates.  Outside Well OI-35A, there
       are very few organic compounds detected at the fringes of the shallow plumes in the
       Southwest Area.

 4.4.3 Eastern Area—Groundwater Contamination

 The Eastern Area comprises the area to the north, east, and south of the eastern portion of the
 South Parcel and the area to the north and east of the North Parcel.

 Nature and Extent of Groundwater Contamination.  The 1992/1993 combined maximum
 contaminant level exceedances, shown in Figures 7 and 8,  indicate one anomalous well and one
 shallow  plume.  The  following  observations  have been made regarding groundwater
 contamination in this area:

 •      The anomalous well is Well OI-44A, which has three maximum contaminant level
       exceedances.  (This well is anomalous because it appears to have contamination of the
       type associated with the landfill, but is located upgradient of the landfill according to
       the available  groundwater data.)  However, the hydraulic relationship between this
       well and other wells closer to the landfill in the Eastern Area is not well understood.

 •      The contaminant plume appears to be small and shallow, moving to the east from the
       northeast  corner   of  the  South  Parcel  toward  Well OI-30A  and  potentially
       Well OI-12C.  This  plume  is primarily  organic, but  does  contain  inorganic
       constituents as well. The lack of organic  compounds in the other unconfined wells
       outside  Wells OI-20A and  OI-30A  (located  about 400 feet   downgradient  of
       Well OI-20A) indicates that the extent of organic contamination in  the Eastern Area is
       limited.
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 •     Based on the suite of contaminants detected in Well OI-20A, it is apparent that liquid-
       borne contaminants in the northeast corner of the South Parcel are the source of the
       Well OI-20A plume. However, there are few data regarding the occurrence of liquids
       on the eastern end of the landfill.

 Contaminant Fate and  Transport.  Conclusions regarding contaminant transport from the
 landfill into and through groundwater in the Eastern Area are summarized below.

 •     Coarse-grained aquifer materials in the Unconfined Aquifer System appear to be in
       contact  with the base  of the  landfill along  the  eastern  end.   The most  likely
       contaminant pathways  in  the  Eastern  Area   are  through these coarse-grained,
       permeable units of the unconfined aquifer that are contacting the waste prism.

 •     The  majority of the contamination emanating from  the eastern portion of the  South
       Parcel will  migrate into the Unconfined Aquifer System;  lesser  amounts  and
       concentrations will be transported in the deeper units.

 4.4.4 West and South Aquifer Systems—Groundwater Contamination

 The South Aquifer trends approximately northeast-southwest  in  a  narrow elongated band
 along the southern boundary of the landfill, and does not appear to be laterally extensive in
 the northwest-southeast direction. EPA has detected the West Aquifer only along the western
 boundary of the South Parcel; it does not appear to be laterally extensive to the west.

 Nature and Extent of Contamination.  Based on maximum contaminant level exceedances,
 it appears that fairly isolated, low-level areas of contamination are present in the South  and
 West Aquifers (Figure 8).

 In the West Aquifer, organic contamination has been increasing in  Well OI-18B and exceeds
 maximum contaminant levels  for three constituents.  The extent of  the West  Aquifer
 downgradient of the landfill perimeter is not well defined.  The source of the West Aquifer
 contamination could be either direct communication with  the  landfill beneath the central
 portion of the South Parcel or vertical transport through the Shallow Silt Flow System.

 In  the South  Aquifer,  three wells show  maximum contaminant  level  exceedances
 (Wells OI-06, OI-29B  and OI-15B) (Figure 8). In  the South Aquifer, the source could either
 be contaminants migrating through the vadose zone in the unconfined portions of the unit (at
 the eastern end of the landfill and in the vicinity of Well OI-6), through vertical migration of
 contamination through the Shallow Silt Flow System, or through hydraulic connection with
 the base of the landfill  itself (towards the eastern end).
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 Contaminant Fate and Transport.  Groundwater in the South and West Aquifers ultimately
 flows toward the Central Basin (EPA, 1994c).  The Pico Unit South Aquifer System is likely
 below the Central Basin's Sunnyside Aquifer (the deepest San Pedro Formation drinking
 water source in the Central Basin) and may represent the lowest fresh-water-bearing unit in
 the Central Basin.  The Pico Unit South Aquifer could potentially be used in the future as a
 drinking water source, although it is not currently used as such. If the West Aquifer System
 were continuous across the entire area south and west of the landfill, it appears that it would
 correspond to an upper portion of the Sunnyside Aquifer.  However, the limited available
 data indicate that the West Aquifer is continuous throughout this area.
                         5.0  Summary of Site Risks
 EPA performed a Baseline Ecological Risk Assessment and a Baseline Human Health Risk
 Assessment to evaluate whether there are unacceptable human health or ecological risks from
 potential exposure to chemicals associated with the OH Site.  This section summarizes the
 key components  and findings  of  the  Baseline Risk Assessments.   The Baseline  Risk
 Assessments  are  included  as  Appendixes A (ecological)  and B  (human health) in the
 Feasibility Study Report (EPA, 1996). The primary objectives of the risk assessment were:

 •      To identify the primary causes and  relative magnitude of risks to human health or the
       environment associated with existing or potential contaminant exposure

 •      To evaluate whether remedial actions are  needed to  protect  human health or the
       environment

 •      To support development of the Feasibility Study through preparation of preliminary
       cleanup goals and providing risk estimates for decisionmaking processes in selecting
       a remedial alternative
           5.1 Baseline Human Health Risk Assessment Summary

In accordance with the streamlined approach for Baseline Risk Assessments at CERCLA
municipal landfills, EPA focused the Baseline Risk Assessment for the OH Site on those
media beyond the source area:  ambient air, groundwater, and offsite soils/sediment. EPA
intended the Baseline Risk Assessment to identify those contaminants and media requiring
remedial action based on unacceptable risks.  The media, pathways, and chemicals addressed
under the streamlined approach are discussed briefly below.
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 Modified No-Action Scenario.  For the OH Site, under the modified no-action scenario,
 rather than a typical no-action  scenario, EPA evaluated  risks  of exposure assuming that
 currently existing and operating control systems remain  in place; and that no additional
 remedial actions would be constructed or operated.  The modified no-action scenario was
 selected as the basis for the Risk Assessment because the data collected during the remedial
 investigation  were collected while existing  systems  were operating.   Thus,  current site
 conditions (baseline) are best represented by the modified scenario.

 5.1.1 Identification of Contaminants of Potential Concern

 EPA selected chemicals of potential concern  from validated environmental monitoring data
 collected between 1989 and 1990 for ambient air,  1989 and 1993 for groundwater, and 1987
 and 1992 for North Parcel and near-site soil, respectively.  For purposes of the Baseline Risk
 Assessment,  these data were assumed  to represent current conditions and to  reflect an
 adequate time period to incorporate seasonal or annual variations.  Table 3 lists the chemicals
 of potential concern used in the baseline risk assessment.

 5.1.2 Exposure Assessment

 This section briefly summarizes the potentially exposed populations, the exposure pathways,
 and the exposure quantification from the Baseline Human Health Risk Assessment.

 5.1.2.1 Potentially Exposed Populations

 Potential receptors on the landfill property include  authorized workers within the fenced area
 (the South Parcel  and the landfilled portion  of the North Parcel) and employees and
 customers of the commercial  operations  on  the remainder of the North Parcel.  Potential
 receptors in the area surrounding the landfill  include workers in the surrounding industrial
 and commercial facilities and children and adults in the residential areas.

 5.1.2.2 Chemical Exposure Pathways

 An exposure pathway describes how a receptor could be exposed to contaminants present at a
 site or released from a site. A complete exposure pathway requires the following elements: a
 source, a mechanism for release and migration, an exposure medium, a point of potential
 human contact, and a route of exposure.

Under the streamlined approach, only those exposure scenarios associated with contaminated
media beyond the source area (waste prism and its components) were quantitatively evaluated
in the Baseline Risk Assessment. The retained exposure pathways include:  (1) inhalation of
contaminants  in ambient air by residents; (2) potential ingestion, dermal contact  with, and
inhalation of contaminated groundwater by adult residents; and (3)  ingestion, dermal contact
Page 1-38                                             Oil Site Final Record of Decision
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Table 3
Selected Chemicals of Potential Concern for Air, Groundwater, and Soil
OH Site Final Record of Decision
Page 1 of 3
Chemical Name Air Groundwater Soil
Organic Constituents
1,1,1,2-Tetrachloroethane
1 ,1 ,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
1,1-Dichloroethane
1 ,1-Dichloroethylene
1 ,2,4-Trichlorobenzene
1 ,2-Dibromoethane
1 ,2-Dichlorobenzene
1 ,2-Dichloroethane
1 ,2-Dichloroethylene (Total)
1 ,2-Dichloroethylene, trans-
1 ,2-Dichloropropane
1 ,3-Dichlorobenzene
1,3-Dichloropropene, trans-
1 ,4-Chlorotoluene
1 ,4-Dichlorobenzene
1 ,4-Dioxane
2 ,4-Dimethylphenol
2-Butanone
2-Hexanone
2-Methylnaphthalene
2-Methylphenol
3,3'-Dichlorobenzidine
4,4'-DDD
4,4'-DDE
4,4'-DDT
4-Methyl-2-pentanone
4-Methylphenol
4-Nitroaniline
Acenaphthene
Acetone
Aldrin
Anthracene
Benzene
Benzo(a)anthracene
Benzo(a)pyrene
3enzo(b)fluoranthene
3enzo(g,h,i)perylene
Benzo(k)fluoranthene
tenzoic acid
Jenzyl alcohol
3enzyl chloride
Beta-BHC
BHC, alpha-
BHC, delta-
BHC, gamma- (Lindane)
bis(2-Ethylhexyl)phthalate
Butylbenzylphthalate
Carbazole
Carbon disulfide
Carbon tetrachloride
Chlordane
Chlordane, gamma-

X

X




X
























X
















X


X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X
X

X
X
X
X
X





X
X
X
X
X
X
X
X
X
X
X
X
X
X



X




X
X


X





X

X

X



X
X
X
X
X

X
X
X
X
X
X
X
X






X
X

X



CHMDTNW2.XLS
                                                                                      Page 1-39

-------
Table 3
Selected Chemicals of Potential Concern for Air, Groundwater, and Soil
OH Site Final Record of Decision
Page 2 of 3
Chemical Name
Chlorobenzene
Chloroethane
Chloroform
Chloromethane
Chrysene
cis-1 ,2-Dichloroethylene
cis-1 ,3-Dichloropropene
Di-n-butylphthalate
Di-n-octylphthalate
Dibenzofuran
Dibromochloromethane
Dichlorodifluoromethane
Dieldrin
Diethylphthalate
3imethylphthalate
Endosulfan I
Endosulfan II
Endosulfan sulfate
Endrin
Endrin aldehyde
Ethylbenzene
:luoranthene
Fluorene
teptachlor
Heptachlor epoxide
Hexachlorobutadiene
sophorone
i/lethoxychlor
Vlethylene chloride
vl-Nitrosodiphenylamine
Naphthalene
'entachlorophenol
^henanthrene
'henol
'urgeable organic halogens
"yrene
Styrene
"etrachloroethylene
Toluene
"otal Organic halogens
"richloroethylene
"richlorofluoromethane (Freon 11)
Vinyl actetate
Vinyl chloride
Xylene, m,p,-
Xylene, m-
Xylene, o-
Xylenes, p-
Xylenes, total-
Air Groundwater
X

X

















X
















X
X

X


X





X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X
X

X
X
b
X
X
X
X
b
X
X

X
X
X
X
X
X
Soil
X



X
X

X
X
X










X
X



X


X
X
X
X
X
X

X
X

X

X

X
X
X



X
         Page 1-40
CHMDTNW2.XLS

-------
Table 3
Selected Chemicals of Potential Concern for Air, Groundwater, and Soil
ON Site Final Record of Decision
Page 3 of 3
Chemical Name
Air Groundwater
Soil
Inorganic Constituents
Aluminum
Ammonia nitrogen (as N)
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chloride
Chromium (Total)
Cobalt
Copper
Cyanide
ron
_ead
Magnesium
Manganese
Mercury
Nickel
Nitrate
Nitrite (as N)
3otassium
Selenium
Silver
Sodium
Sulfate
Sulfide
Thallium
in
Vanadium
Zinc































X
X
X
X
X
X
X
a
b
X
X
X
X
a
X
a
X
X
X
X
X
a
X
X
a
b
b
X

X
X
X

X
X
X
X
X
a

X
X
X
X
a
X
a
X
X
X


a
X
X
a


X
X
X
X
Key:
a: Essential Nutrients
b: Major cation/anion, or other water quality parameter
x: Chemical of Potential Concern
CHMDTNW2.XLS
Page 1-41

-------
 with, and inhalation of contaminated soil/sediments by workers (North Parcel soil only) and
 residents. Ambient air and soil/ sediment exposure pathways are currently complete exposure
 pathways;  the groundwater  exposure pathway is  not  currently complete  because nearby
 groundwater is not being used, but could be at some point in the future.

 EPA estimated ambient air and soil/sediment exposures for adult and child residents. EPA also
 evaluated soil from the North Parcel for worker exposure and groundwater for adult residential
 exposure.

 5.1.2.3  Exposure Quantification

 Exposure, defined as contact with a chemical or physical agent, is estimated using  six factors:
 chemical concentration  at the point of exposure,  contact rate,  exposure frequency, exposure
 duration, body weight, and averaging time, as described by the following general equation:

       Intake = Concentration x Contact Rate x Exposure Frequency x Exposure Duration
                                Body Weight x Averaging Time

 Exposure, or intake, is expressed as milligrams  of chemical per kilogram of body  weight per
 day (mg/kg-day) to normalize for time and body weight. The following presents the  parameters
 and methods used in estimating exposure for each of the selected exposure pathways.

 Ambient Air. EPA used air concentrations from the 24-hour  ambient air study to calculate
 chemical intake by inhalation (mg/kg-day) for  residential exposures to adults and children.
 Key exposure parameters are shown in Table 4.

 Groundwater. Residents could be exposed to contaminants in groundwater through ingestion,
 inhalation of volatile organic compounds, or dermal contact with groundwater if  used for a
 water supply.

 Ingestion.   The parameters used  to  calculate  the  intake associated with the  ingestion of
 contaminants in groundwater are shown in Table 5.

 Inhalation.  Residents could also be exposed to chemicals transferred from tap water to the air
 from showers, baths, toilets, dishwashers, washing machines, and during cooking. Inhalation of
 chemicals from groundwater is applicable only for volatile compounds.  EPA evaluated risks
 due to inhalation of volatile organic compounds from groundwater according to the approach
 that Andelman et al. developed (Andelman et al., 1987). EPA selected the highest volatilization
 factor of 0.0005 from the Andelman et al. approach. Using the EPA volatilization factor of
 0.0005 to convert groundwater  concentrations  to a corresponding  air  concentration, EPA
 calculated the intake associated with the inhalation of chemicals volatilized from groundwater
 using the parameters presented in Table 6.
Page 1-42                                              Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

-------
Table 4
Exposure Parameters for Estimating Exposure for Residential Intake of Ambient Air
On Site Final Record of Decision
Description (units)
Exposure point concentration for air (mg/m3)
Body weight (kg)
Inhalation rate (m3/day)
Exposure frequency (days/year)
Exposure duration (years)
Averaging Time (years) - Cancer
Averaging Time (years) - Noncancer
Reasonable J
Child
95% UCL
18"
10C
350
9
70
9
Maximum
Adult"
95% UCL
70
20
350
30
70
30
Averaee Value
Adult"
95% UCL
70
20
350
9
70
9
"EPA, 1991f, unless otherwise noted.
bEPA, 1989h.
CEPA, 1994d.
Table 5
Parameters for Estimating Residential
Exposures from Ingestion of Groundwater Contaminants
On Site Final Record of Decision
Description (units)
Exposure point concentration for groundwater (mg/L)
Daily water ingestion rate (L/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging Time (years) - Cancer
Averaging Time (years) - Noncancer
Value"
Arithmetic mean
2
350
30
70
70
30
Average Value
Arithmetic mean
1.4
350
9
70
70
9
aEPA, 1991e.
''EPA, 1992f.
SCO1001916D.DOC
Page 1-43

-------
Table 6
Parameters for Estimating Chemical Intake for an Adult Resident
from Inhalation of Groundwater Volatiles
On Site Final Record of Decision
Description (units)
Exposure point concentration in air (mg/m3)
Exposure point concentration in water (mg/L)
Body weight (kg)
Averaging Time (years) - Cancer
Averaging Time (years) - Noncancer
Exposure frequency (days/year)
Exposure duration (years)
Daily inhalation rate (mVday)
Reasonable Maximum
Exposure Value8
Cwx0.5
Arithmetic mean
70
70
30
350
30
15
Average Value1*
Cwx0.5
Arithmetic mean
70
70
9
350
9
15
"EPA, 1991e.
''EPA, 1992f.
Table?
Parameters for Estimating Chemical Absorption from Dermal Contact with Groundwater
On Site Final Record of Decision
Description
(units)
Exposure point concentration in water (mg/L)
Exposed skin surface area (cm /event)
Dermal permeability coefficient (cm/hour)
Exposure time (hour/day)
Exposure frequency (event/year)
Exposure duration (years)
Body weight (kg)
Averaging time (years)
Cancer effects
Noncancer effects
Reasonable Maximum
Exposure Value8
Arithmetic mean
23,000
Chemical-Specificc
0.25
350
30
70
70 .
30
Average Valueb
Arithmetic mean
20,000
Chemical-Specific0
0.17
350
9
70
70
9
aCal-EPA, 1992.
"EPA, 1992g.
CEPA, 1992J.
Page 1-44
SCO1001916D.DOC

-------
 Dermal Contact.  Dermal absorption is typically an insignificant route of exposure in the
 residential groundwater use setting. However, EPA estimates dermal absorption for chemical
 contaminants to assure that any potential risks from this exposure pathway are addressed. The
 magnitude of potential exposure by this pathway is related to the concentration in water, surface
 area of exposed skin, the dermal penetrability of the contaminant, and frequency and duration
 of exposure. The parameters in Table 7 were used to estimate exposure through dermal contact.

 Soils/Sediments

 Ingestion.  Exposure through ingestion  of contaminants  in  soil/sediments depends on the
 concentration in soil, the amount ingested, and the frequency and duration of exposure.

 EPA evaluated average and reasonable maximum exposures for both a toddler (0-6 years)
 and an adult, using the parameters presented in Table 8.

 Inhalation.  EPA calculated exposure via inhalation of dust  and  vapors from contaminated
 surface soil using soil  concentration, the soil volatilization factor, the paniculate emission
 factor describing the amount  of soil entrained in the air as dust, inhalation rate,  and the
 frequency and duration  of  exposure.    The paniculate emission  factor  expresses  the
 relationship  of chemical  concentrations adsorbed  to  soil and concentrations of airborne
 respirable dust particles and  is estimated  using EPA default values (EPA,  1991e).  The
 parameters  used to  estimate  intake from inhaling both  contaminated  dust from soil and
 volatile compounds from soil are presented in Table 8.

 Dermal Contact. Dermal absorption of contaminants in soil/sediments is a function of the
 concentration in soil, the surface  area of exposed skin, the ability of the  contaminant to
 penetrate through the skin, and frequency  and duration of exposure.

 EPA estimated the absorbed dose from reasonable maximum and average exposure by dermal
 contact with contaminants in soil using the parameters presented in Table 8.  Toddler (0 to
 6 years) and adult exposures were calculated for reasonable maximum and average exposure.

 5.1.3  Toxicity Assessment

 Chemical contaminants  may be divided into two groups according to their effects on human
 health.  Contaminants may have carcinogenic effects  or noncarcinogenic/systemic  effects.
 Exposure to some of the chemicals detected at the OH Site could potentially result in both
 types of effects. Carcinogenic  effects result in, or are suspected to result in, the development
 of cancer.
Oil Site Final Record of Decision                                              Page 1-45
Part I - Decision Summary                                             scoiooi92D3.DOC

-------
Table 8
Parameters for Estimating Intake for Residents and Workers Via Dermal, Inhalation, and Ingestion Exposure to Soil
On Site Final Record of Decision
Description
Exposure Point Concentration in Soil
Body Weight (kg):
Toddler (0-6 years)
Adult
Soil Ingestion Rate (mg/day)
Toddler (0-6 years)
Adult
nhalation Rate (m3/day)
Toddler (0-6 years)
Adult
Soil- Volatilization Factor (m3/kg)
'articulate Emission Factor (m3/kg)
Skin Surface Area (cm2)
Toddler
Adult
Absorption Factor (fraction)
Soil-to-Skin Adherence Factor (mg/cm2)
ixposure Frequency (days/year)
ixposure Duration (years)
Cancer (adult)
Noncancer (adult)
Child
Averaging Time
Cancer (adult)
Noncancer (adult)
Cancer (child)
Noncancer (child)
Residents
RME Value"
Lessor of the maximum 01
95% UCL values
15
70
200
100
16
20
Chemical-
specific0
4.63xl09
2,400d
5,800"
0.10(organics)c
0.01 (inorganics)
0.2"
350
30
30
6
70
30
70
6
Average Value1"
Arithmetic mean
15
70
200
100
16
20
Chemical-
specific0
4.63x1 09
2,100d
5,000d
0.10(organics)e
0.01 (inorganics)
0.2d
350
9
9
6
70
9
70
6
Workers
RME Value"
Lesser of the maximum or
95% UCL values
70
50
20
Chemical-
specific0
4.63x1 09
5,800"
0.10(organics)e
0.01 (inorganics)
0.2"
250
25
25
70
25
Average Value6
Arithmetic mean
70
50
20
Chemical-
specific0
4.63xl09
5,000"
0.10organics)e
0.01 (inorganics)
0.2"
250
9
9
70
9
*EPA, 1991e, unless otherwise noted.
'EPA, 1992g, unless otherwise noted.
:Inhalation of volatilized chemicals for all COPC with a Henry's Law Constant (HLC) greater than or equal to IxlO"5 atm-m"3/mole and a
molecular weight (MW) less than or equal to 200 g/mole.
•EPA, 1992.
2SCAQMD, 1988.
 Page 1-46
SCO1001916D.DOC

-------
 EPA has developed a carcinogen classification system using weight-of-evidence to classify
 the likelihood that a chemical is a human carcinogen.  Definitions for the weight-of-evidence
 classifications are presented below.
EPA Weight-of-Evidence
Classification System for Carcinogenicity
Group
A
BlorB2
C
D
E
Description
Human carcinogen, based on evidence from epidemiological studies.
Probable human carcinogen.
B 1 indicates that limited human data are available.
B2 indicates sufficient evidence in animals and inadequate or no evidence in humans.
Possible human carcinogen, based on limited evidence in animals.
Not classifiable as to human Carcinogenicity.
Evidence of noncarcinogenicity for humans.
Source: EPA, 1986b.
 Noncarcinogenic or systemic effects include a variety of toxicological end points  and may
 include effects on specific organs or systems, such as the kidney, liver, and lungs.

 EPA's  Carcinogenic  Assessment  Group  has  developed cancer slope factors for estimating
 excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals of
 potential concern.  Cancer slope factor(s), which are expressed in units of (mg/kg-day)"1, are
 multiplied by the estimated intake of a potential carcinogen, in mg/kg-day, to provide an upper-
 bound estimate of the excess lifetime cancer risk associated with exposure at that intake level.
 The term "upper bound" reflects  the conservative estimate of the risks calculated  from the
 cancer slope factor(s). Use of this approach  makes underestimation of the actual cancer risk
 highly unlikely. Cancer slope factor(s) are derived from the results of human epidemiological
 studies or chronic animal bioassays to which animal-to-human extrapolation and uncertainty
 factors have been applied (for example, to account for the use of animal data to predict effects
 on humans).

 EPA has developed reference doses to indicate the potential for adverse health effects from
 exposure to  chemicals of potential concern  exhibiting noncarcinogenic  effects.  Reference
 doses, which are expressed in units of mg/kg-day, are  estimated threshold levels  for daily
 exposure  above  which  exposure  is  considered  unsafe  for  humans,  including  sensitive
 individuals.   Estimated intakes of chemicals  of potential concern from environmental media
 (e.g., the amount of a chemical ingested from contaminated drinking water) can be compared to
 the reference doses. Reference doses are derived from the results of human epidemiological
 studies  or animal studies to which uncertainty factors have been applied  (for example,  to
Oil Site Final Record of Decision                                              Page 1-47
Part I - Decision Summary                                              scoiooi92D3.DOC

-------
 account for the use of animal data to predict effects on humans).  These uncertainty factors help
 ensure that the reference doses will not underestimate the potential for adverse noncarcinogenic
 effects to occur.

 Table 9 presents toxicity values for chemicals of potential concern for both carcinogenic and
 noncarcinogenic effects.   Slope factors  and reference  doses  are specific to the route of
 exposure.  For example, oral  slope factors are used to evaluate risk through  ingestion of
 carcinogenic chemicals of potential  concern.   In  cases where route-specific cancer slope
 factors or reference doses were not available (for example, for the inhalation and dermal
 routes), oral cancer slope factors or reference doses were used.

 5.1.4 Risk Characterization Summary

 Information presented in the exposure assessment and the toxicity assessment is integrated in
 this section to  characterize risk to human health from chemicals of potential concern at the
 Oil Site.

 For carcinogens, risks are estimated 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 are generally expressed in scientific notation (e.g.,  1 x 10~6  or 1E-6).  An
 excess lifetime cancer of 1 x 10~6 indicates that as a reasonable maximum estimate, an
 individual has  a one in one million  chance of developing cancer as result of site-related
 exposure to a carcinogen over a 70-year lifetime under specific exposure conditions at the OH
 Site; similarly, an excess lifetime cancer risk of 1  x 10"4  refers to a reasonable maximum
 estimate of a one in ten thousand chance of developing cancer as a result of the exposure.

 EPA uses the general 10"4 to 10"6 risk range as a "target range" within which EPA strives to
 manage risks as part of a  Superfund  cleanup.  Although the EPA risk manager may deem
 acceptable the  waste  management strategies achieving reductions  in site risks  anywhere
 within the risk range,  EPA has expressed a preference for cleanups achieving  the more
 protective end of the range  (for example, 10~6).

 The potential for noncarcinogenic health effects is evaluated by  comparing an exposure level
 over a specified time period (for example, a lifetime) with a reference doses derived for a
 similar exposure period. The ratio of exposure to toxicity is called a hazard quotient. If the
 estimated intake (exposure) is  greater than the reference doses, the hazard quotient will be
 greater than one. A hazard quotient greater than one indicates the potential  for an adverse
 noncarcinogenic health effect from exposure to the chemical.

 A hazard  index is generated by adding the hazard quotients for all chemicals of potential
 concern within  a medium or across all media to which a given population may reasonably be
exposed.    A  hazard  index  exceeding  one  indicates  the   potential   for  an  adverse
Page 1-48                                              Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

-------
Table 9
Toxicity Values and Chemical-Specific Parameters
for Chemicals of Potential Concern
Oil Site Final Record of Decision
Page 1 of 3
Chemical Name
Oral RfDa
mg/kg-day
Inhalation
RfDa
mg/kg-day
Weight-of-
Evidence
Classification
Oral Slope
Factor
kg-day/mg
Inhalation
Slope
Factor
kg-day/mg
Kp"
cm/hr
ABSC
VFd
Organic Compounds
acenaphthene
acetone
aldrin
anthracene
benzene
benzo(a)anthracene
benzo(a)pyrene
benzo(b)fluoranthene
benzo(g,h,i)perylene
benzo(k)fluoranthene
benzoic acid
benzyl alcohol
Denzyl chloride
bis(2-ethylhexyl)phthalate
butanone, 2-
butylbenzyl phthalate, n-
carbazole
carbon disulfide
carbon tetrachloride
chlordane
chlorobenzene
chloroethane
chloroform
chloromethane
chlorotoluene, p-
chrysene
ddd, 4,4'-
dde, 4,4'-
ddt, 4,4'-
di-n-butyl-phthalate
di-n-octyl-phthalate
dibenzofuran
dibromochloromethane
dibromoethane, 1,2-
dichlorobenzene, 1,2-
dichlorobenzene, 1,3-
dichlorobenzene, 1,4-
dichlorobenzidine, 3,3-
dichlorodifluoromethane
dichloroethane, 1,1-
dichloroethane, 1,2-
dichloroethene, 1,1-
isomers)
dichloroethene, cis-1,2-
0.06
0.1
0.00003
0.3
-
-
-
-
-
-
4
0.3

0.02
0.6
0.2
-
0.1
0.0007
0.00006
0.02
-
0.01
0.0036
0.02
-
-
-
0.0005
0.1
0.02
0.004
0.02
-
0.09
0.089
0.22856
-
0.2
0.1
-
0.009
0.009
0.01
0.06
0.1
0.00003
0.3
-
.
-
-
-
-
4
0.3
-
0.02
0.2857
0.2

0.002857
0.00057
-
0.005714
2.857
0.01
-
-
-
-
-
0.0005
0.1
0.02
-
0.02
0.00005714
0.05714
-
0.22856
-
0.05714
0.14285
-
0.009
0.009
0.01
NA
D
B2
D
A
B2
B2
B2
D
B2
D
NA
B2
B2
D
C
B2
NA
B2
B2
D
NA
B2
C
D
B2
B2
B2
B2
D
NA
D
C
B2
D
D
B2
B2
D
C
B2
C
NA
D
-
-
17
-
0.029
0.73
7.3
0.73
-
0.073
-

0.17
0.014


0.02
-
0.13
1.3
-
~
0.0061
0.013
-
0.0073
0.24
0.34
0.34
-
-
-
0.084
85
-
-
0.024
0.45
-
-
0.091
0.6
-
-
-
-
17.15
-
0.02905
0.73

0.73

0.073
-
-
0.17
0.014
-
-
0.02
-
0.0525
1.3
-
-
0.0805
0.0063
-
0.0073
0.24
0.34
0.3395
-
-
-
0.084
0.77
-
-
0.024
0.45
-
-
0.091
0.175
-
-
0.15
0.0012
0.0016
0.2258
0.11
0.81
1.2
-
0.107
0.033
0.0073
0.0025
0.0138
0.033
0.005
0.073
0.07967
0.5
0.022
0.046
0.041
0.008
0.13
0.0042

0.81
0.28
0.24
0.43
0.033
26.88
0.107
0.0039

0.061
0.087
0.062
0.017
0.012
0.0089
0.0053
0.016
0.001
0.001
0.1
0.1
0.1
0.1
0.1
0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0
0.1
0.1
2.11E+05
2.70E+04
-
2.18E+06
9.60E+03
-

-
-
-
-
-
1.00E+05
-
3.68E+04
-
-
5.10E+03
6.10E+03
-
2.90E+04
2.70E+03
9.10E+03
2.80E+03
2.10E+04
5.53E+07
-
-
-
-
-
-
-
2.90E+04
5.70E+04
5.70E+04
6.30E+04
-
1 .80E+03
6.20E+03
9.30E+03
1.50E+03
8.80E+03
5.90E+03
MASTRTO2.XLS
                                                                                   Page 1-49

-------
Table 9
Toxicity Values and Chemical-Specific Parameters
for Chemicals of Potential Concern
Oil Site Final Record of Decision _ „ .
Page 2 of 3
Chemical Name
dichloroethene, trans-1,2-
dichloropropane, 1,2-
dichloropropene, 1,3-
dieldrin
diethylphthalate
dimethylphenol, 2,4-
dimethylphthalate
dioxane, 1,4-
endosulfan
endrin
ethylbenzene
fluoranthene
fluorene
heptachlor
heptachlor epoxide
hexachlorobutadiene
hexachlorocyclohexane, alpha-
hexachlorocyclohexane, beta-
hexachlorocyclohexane, delta-
hexachlorocyclohexane, gamma-
hexanone, 2-
indeno(1 ,2,3-cd)pyrene
isophorone
methoxychlor
methyl-2-pentanone, 4-
methylene chloride
methylphenol, 2-
methylphenol, 4-
naphthalene
nitroaniline, p-
nitrosodiphenylamine, n-
pentachlorophenol
)henanthrene
phenol
pyrene
styrene
tetrachloroethane, 1,1,1,2-
tetrachloroethene
toluene
Irichlorobenzene, 1 ,2,4-
trichloroethane, 1,1,1-
trichloroethane, 1,1,2-
trichloroethene
richlorofluoromethane
vanadium
Oral RfDa
mg/kg-day
0.02
0.0011
0.0003
0.00005
0.8
0.02
10
-
0.00005
0.0003
0.1
0.04
0.04
0.0005
0.000013
0.002

-
-
0.0003
-
-
0.2
0.005
0.05
0.06
0.05
0.005
0.04
-
-
0.03
-
0.6
0.03
0.2
0.03
0.01
0.2
0.01
0.09
0.004
0.006
0.3
0.007
Inhalation
RfDa
mg/kg-day
0.02
0.0011428
0.005714
0.00005
0.8
0.02
10
-
0.00005
0.0003
0.2857
0.04
0.04
0.0005
0.000013
0.002

-
-
0.0003
-
-
0.2
0.005
0.022856
0.8571
0.05
0.005
0.04
-
-
-
-
0.6
0.03
0.2
-
0.01
0.11428
0.0025713
0.2857
0.004
0.006
0.19999
-
Weight-of-
Evidence
Classification
D
B2
B2
B2
D
NA
D
B2
NA
D
D
D
D
B2
B2
C
B2
C
D
B2-C
NA
B2
C
D
NA
B2
C
C
D
NA
B2
B2
D
D
D
C
C
C-B2
D
D
D
C
B2
D
NA
Oral Slope
Factor
kg-day/mc

0.068
0.18
16
-
-
-
0.011
-
-
-
-
-
4.5
9.1
0.078
6.3
1.8

1.3
-
0.73
0.0010
-

0.0075
-
-
-
-
0.0049
0.12
-
-
-

0.0260
0.052
-
-
-
0.0570
0.0110
-
-
Inhalation
Slope
Factor
kg-day/mc
-
0.068
0.1295
16.1
-
-
-
0.011
-
-
-
-
-
4.55
9.1
0.077
6.3
1.855
-
1.3
-
0.73
0.0010
-
-
0.0016
-
-
-
-
0.0049
0.12
-
-
-

0.0259
0.002
-
-
-
0.0560
0.0060
-
-
Kpb
cm/hr
0.01
0.01
0.0055
0.016
0.0048
0.0015
0.0016
0.0004
0.002
0.003
1
0.36
0.358
0.011
0.055
0.12
0.019
0.016
0.028
0.014
0.005
1.9
0.0042
0.04328
0.0015
0.0045
0.016
0.01
0.069
0.014
0.0079
0.65
0.23
0.0082
0.3255
0.67
0.0256
0.37
1
0.1
0.017
0.0084
0.2300
0.017
0.001
ABSC
0
0.1
0.1
0.1
0.1
0.1
0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0
VFd
8.70E+03
1.10E+04
1.80E+04
-
-
-
-
5.20E+04
-
-
1.60E+04
-
1.12E+06
-
-
-
-
-
-
-
-
-
-
-
6.40E+04
4.77E+03
-
-
1 .05E+05
-
4.31 E+03
-
2.11E+06
-
-
4.03E+04
3.79E+04
1.71E+04
1.91E+04
2.18E+05
2.25E+04
2.11E+04
1.12E+04
3.44E+03
-
        Page 1-50
MASTRTO2.XLS

-------
Table 9
Toxicity Values and Chemical-Specific Parameters
for Chemicals of Potential Concern
OH Site Final Record of Decision _ „ , „
Page 3 of 3
Chemical Name
vinyl acetate
vinyl chloride
xylene, m-
xylene, mixture
xylene, o-
xylene, p-
Oral RfDa
mg/kg-day
1
-
2
2
2
2
Inhalation
RfDa
mg/kg-day
0.05714
-
0.2
0.2
0.2
0.2
Weight-of-
Evidence
Classification
NA
A
NA
D
NA
NA
Oral Slope
Factor
kg-day/mg
-
1.9
-
-
-
-
Inhalation
Slope
Factor
kg-day/mg
-
0.294
-
-
-
-
Kpb
cm/hr

0.0073
0.08
0.08
0.08
0.08
ABSC
0.1
0.1
0.1
0.1
0.1
0.1
VF"
-
3.46E+03
6.07E+04
6.89E+04
8.55E+04
5.99E+04
Inorganic Compounds
aluminum
ammonia
antimony
arsenic
barium
jeryllium
cadmium (food)
cadmium (water)
chromium (hexavalent)
chromium (trivalent)
iron
manganese (food)
manganese (water)
mercury
nickel, soluble salts
nitrate
nitrite
selenium
silver
thallium
tin
zinc
1
0.97
0.0004
0.0003
0.07
0.005
0.001
0.0005
0.005
1
-
0.14
0.005
0.0003
0.02
1.6
0.1
0.005
0.005
-
0.6
0.3
-
0.02857
-
-
0.00014285
-

-
-
-
-
0.0000142
0.0000142
0.00008571
-
-
-
-
-
-
-
-
NA
D
D
A
D
B2
B1
B1
A
D
NA
D
D
D
D
D
D
D
D
D
NA
D
-
-
-
1.75
-
4.3

-
-
-
-

-
-
-
-
-
-
-
-
NA
-
-
-
-
15.05
-
8.4
6.3
6.3
42
-
-

-
-
-
-
-
-
-
-
-
-
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.1
0
0
0
0
0
- .
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
a - Reference Dose
b - Dermal Permeability Coefficient
c - Absorption Factor
d - Volatilization Factor
MASTRTO2.XLS
                                                                                    Page 1-51

-------
 noncarcinogenic health effect from exposure to the medium or media.  The hazard index
 provides  a  useful  reference point for  gauging the potential  significance  of  multiple
 contaminant exposures within a single medium or across media.

 Noncancer hazard indexes and cancer risks were estimated for ambient air, groundwater, and
 surface soil.

 Summary of Estimated Ambient Air Risks.  EPA calculated ambient air risk estimates for
 residential exposure via inhalation.   EPA also calculated estimated  cancer  risks  and
 noncancer hazard indexes for each monitoring station,  as shown in Figures 9a  and 9b,
 respectively.

 Ambient air was found to present an elevated risk to human health at the monitoring stations
 around the OH Site.  Stations 1, 2, and 7 had the highest cancer risks, exceeding 3 x 10"4,
 primarily due to the presence of vinyl chloride, a known landfill contaminant. Other stations
 had cancer risks falling in the 5.1 x 10"5 to 1.8 x 10"4 range.  Excluding the influence of
 background pollutants, risks  at Stations 1, 2, and 7 still  exceed 1  x 10~4 under reasonable
 maximum exposure conditions and Stations 3,4, and 6 exceed 1 x 10~5.

 Summary of Estimated Soils/Sediment Risks.   As recommended for the streamlined
 approach to conducting remedial investigations at CERCLA municipal landfills, EPA did not
 sample soils directly overlying the waste prism because these soils will be under the landfill
 cover after implementation of a final remedy. The cover will prevent future releases of waste
 and soil from the landfill. EPA used data, from soil samples collected at locations outside the
 area to be covered, for the Baseline Risk Assessment.  EPA collected these samples as part of
 the near-site surface soil/sediment investigation  and the North  Parcel  investigation soil
 sampling programs.

 EPA evaluated soils and sediments from the North Parcel and near-site sampling areas for
 child and adult exposure scenarios.  Figures 10 and 11  present sample locations  and risk
 assessment results for total cancer risk and total noncancer hazard index, respectively. Under
 the most  health-protective  scenario (child reasonable maximum exposure) and the least
 protective (adult average exposure), all  near-site sampled areas but one (Area B under
 average adult exposure) exceeded a cancer risk of 1 x 10"6, including the  background areas
 (Pico  Background,   Lakewood/San   Pedro  Background,  and  Freeway  Control  Area
 Background).  Cancer risks  for the  Area D, Iguala Park,  and Southern  California Gas
 Company sample areas were  only slightly greater than background at 1.87 x 10~5 or higher
 under child reasonable maximum exposure conditions.  These compare to background area
 cancer risks of 1.30x 10~5 to 1.74x  10~5 under the same conditions.  Noncancer hazard
 indexes exceeded one for only some areas under the child reasonable maximum exposure
 scenario (Southern California Gas Facility,  Iguala Park,  Pico Background, and Area D).
Page 1-52                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

-------
                                                                                  Montebello
                                                                                  Town Center
                                                                                                                                 4000
•    24-Hour Ambient Air
      Monitoring Station


if    24-Hour Ambient Air
      Background Monitoring
      Station
                                                                                                       Total Cancer Risk

                                                                                                       RED     1.00E-4 - 1.00E-3

                                                                                                       GREEN  1.00E-5-1.00E-4
                                                                                                       Figure 9A
                                                                                                       Total Cancer Risk for
                                                                                                       Ambient Air Monitoring Station
                                                                                                       Locations - Residential
                                                                                                       Adult Reasonable Maximum
                                                                                                       Exposure Conditions

                                                                                                       Oil SH« Final ftecord of DacMon
24 Gap 981836:59 Tlutday
/BIS4/OII/PLOTS/FI09A.AML

-------
"d
t»
•8
                                                                                       Montebello
                                                                                       Town Center
0     1000    2000          4000

         SCALE IN FEET

 Legend:


 •    24-Hour Ambient Air
      Monitoring Station


 if    24-Hour Ambient Air
      Background Monitoring
      Station
Figure 9B
Total Noncancer Hazard Index
for Ambient Air Monitoring
Station Locations -
Residential Adult Reasonable
Maximum Exposure Conditions

OH Sit* Rnal Record of Decision
    20 Sap 9611:57:59 Friday
    /GIS4/OII/PLOTE/FIQ9B.AML

-------
 Noncancer hazard indexes for the Southern California Gas Company Facility and Iguala Park,
 1.68 and 1.76, respectively,  were only slightly greater than Pico Background,  1.34, under
 child reasonable maximum exposure conditions.

 Summary  of Estimated  Groundwater Risks.   Groundwater  data are available from
 monitoring wells  installed on or near the  landfill. Figures 7  (shallow wells) and 8 (deep
 wells) show the locations of these groundwater monitoring wells.   Groundwater  sample
 results  from  January  1989  through  October 1993 were  used to calculate groundwater
 exposure risks on a well-specific  basis.   Adult residential receptors were evaluated for
 potential groundwater exposure via ingestion, volatile inhalation, and dermal contact.  Risks
 were calculated  using the  reasonable maximum  exposure conditions  for each  of  the
 72 monitoring wells at the landfill.

 For  chemicals of concern detected  in individual wells, 27 wells exceeded a cancer risk of
 1 x 10"4  under reasonable maximum exposure conditions (Figures 12 and 13).  Fifty out of
 72 wells had  associated hazard index  values exceeding one (Figures 14  and 15).  Twelve
 wells had hazard index values exceeding 10. The wells with the highest estimated cancer and
 noncancer risks are generally those wells along the landfill perimeter at the southwest corner
 of the South  Parcel, an area with extensive leachate in the  waste prism and numerous
 exceedances of drinking water standards in the shallow groundwater monitoring wells.

 The  presence of naturally occurring arsenic, beryllium, and manganese in the OH Site vicinity
 affects the cancer risk and noncancer hazard index estimates for the groundwater monitoring
 wells.  As discussed in the Feasibility Study Report (EPA, 1996), the estimated  cancer risk
 for arsenic and beryllium is 1.5 x 10~4 using the baseline concentrations presented in the Draft
 Remedial Investigation Report (EPA, 1994c).  Similarly, the hazard quotient for the baseline
 concentration  of manganese is 0.7. Although the estimated "baseline" concentrations  are
 likely somewhat higher than true background, these estimates show how naturally occurring
 inorganic constituents in the  OH Site area complicate the evaluation of site-related  risks in
 groundwater.  However, taking these baseline concentrations into consideration, data from
 19 wells still indicate site-related risks exceeding 1 x 10"4.

 5.1.5  Baseline Human Health Risk Assessment Conclusion

 Actual or threatened releases  of hazardous substances from the OH 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.
Page 1-56                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

-------
                                                                               North Parcel
                                                                                 1.38E-05
                      Pico Background
                         1.74E-05
                                                                                                                                      Freeway Control
                                                                                                                                     Area Background
Lakewood/§an
Background>Iiof
                                                                                                        Iguala Park Area
                                                                                                             5.33f-05

Legend:


A/  Approximate Location of Oil
     Fence/Property Boundary

A/  Road Boundary
                                                                                                                                                           Surface Soil/Sediment Sampling Location
                                                                                                                                                            +   Near Site

                                                                                                                                                            •   North Parcel
Total Cancer Risk

 RED      1.00E-5-1.00E-4

 GREEN   1.00E-6-1.00E-B
                                                                                                                                                           Figure 10
                                                                                                                                                           Total Cancer Risk for
                                                                                                                                                           Surface Soil/Sediment by Area
                                                                                                                                                           Residential Child Reasonable
                                                                                                                                                           Maximum Exposure Conditions

                                                                                                                                                           Oil Sita Final R.cord of Dtdilon
                                                                                                                                                                           Page 1-57

-------
                                                                           North Parcel
                                                                             0.886
                      Pico Background
                         1.340
                                                                                                                                                  A/ Approximate Location of Oil
                                                                                                                                                      Fence/Property Boundary
\V Note: BG-04, BG-05Cand'BG^06  \
 {•V-I I	Mated approi-WOO ft to     }
        ~
Surface Soll/Sedlmant Sampling Location
 +  Near Site
                                                                                                                               Freeway Control
                                                                                                                              Area Background
                                                                                                                                   0.660
                                        ern'California Gas
                                  Facility Area   16w   x  '
                                  ;>'      3V-
                                                                                                                                                   Figure 11
                                                                                                                                                   Total Noncancer Hazard Index for
                                                                                                                                                   Surface Soil/Sediment by Area
                                                                                                                                                   Residential Child Reasonable
                                                                                                                                                   Maximum Exposure Conditions
                                                                                                                                                                    Page 1-59

-------
     0    250    500	WOO

             SCALE N FEET

Legend:


/V  Approximate Location of Oil
     Fence/Property Boundary

/V  Road Boundary
Cancer Risk

 PURPLE  *   > 1.00E-4

 RED     *   1.00E-5 - 1.00E-4

 GREEN   +   1.00E-6 - 1.00E-5

 BLUE    o   < = 1.00E-6
NOTE:  Risk estimates based on
       data collected between
       1989 and 1993
 Figure 12
 Total Cancer Risk for Individual
 Shallow Groundwater Wells Using
 Chemicals of Potential Concern
 by Well - Residential Adult
 Reasonable Maximum
 Exposure Conditions

 Oil Sit. Final Rncord of Didilon
                    Page 1-61

-------
                                                                                                                                                                                   0    250    500
                                                                                                                                                                              Legend:
                                                                                                                                                                              A/  Approximate Location of Oil
                                                                                                                                                                                   Fence/Property Boundary

                                                                                                                                                                              A/  Road Boundary
                                                                                                                                                                              Well Groupings
                                                                                                                                                                              Cancer Risk
                                                                                                                                                                               PURPLE  *   > 1.00E-4

                                                                                                                                                                               RED     *   1.00E-5 - 1.00E-4

                                                                                                                                                                               GREEN   +   1.00E-8 - 1.00E-5
                                                                                                                                                                              NOTE: Risk estimates based on
                                                                                                                                                                                     data collected between
                                                                                                                                                                                     1989 and 1993
                                                                                                                                                                               Figure 13
                                                                                                                                                                               Total Cancer Risk for Individual
                                                                                                                                                                               Deep  Groundwater Wells Using
                                                                                                                                                                               Chemicals of Potential Concern
                                                                                                                                                                               by Well - Residential Adult
                                                                                                                                                                               Reasonable Maximum
                                                                                                                                                                               Exposure Conditions

                                                                                                                                                                               Oil SK. Final lUcord of D.d.lon
fQl S4/OIWUJTS/FIQ13 JIML
                                                                                                                                                                                                  Page 1-63

-------
     0    250   500	TOO

            SCALE N FEET

Legend:
     Approximate Location of Oil
     Fence/Property Boundary
A/  Road Boundary



Noncancer Hazard Risk

 RED     *  > 10

 GREEN   +  1-10

 BLUE    o  < = i
NOTE: Hazard index estimates based
      on data collected between
      1989 and 1993
 Figure 14
 Total Noncancer Hazard Index for
 Individual Shallow Groundwater
 Wells Using Chemicals of Potential
 Concern by Well - Residential
 Adult Reasonable Maximum
 Exposure Conditions

 Oil Srt« Final R«cord of CXdsion

                  Page 1-65

-------
                                                                                                                                                                              0    250    500
                                                                                                                                                                                      SCALE N FEET
                                                                                                                                                                         Legend:
                                                                                                                                                                         /V Approximate Location of Oil
                                                                                                                                                                              Fence/Property Boundary

                                                                                                                                                                         A/ Road Boundary
                                                                                                                                                                         Noncancer Hazard Risk

                                                                                                                                                                           GREEN   +    1-10

                                                                                                                                                                           BLUE    o    < = i
                                                                                                                                                                          NOTE: Hazard Index estimates based
                                                                                                                                                                                on data collected between
                                                                                                                                                                                1989 and 1993
                                                                                                                                                                          Figure 15
                                                                                                                                                                          Total Noncancer Hazard Index for
                                                                                                                                                                          Individual Deep Groundwater
                                                                                                                                                                          Wells Using Chemicals of Potential
                                                                                                                                                                          Concern by Well - Residential
                                                                                                                                                                          Adult Reasonable Maximum
                                                                                                                                                                          Exposure Conditions

                                                                                                                                                                          Oil Sit. Final R.cord of D.dtlon
/QIS4/OI I/PLOTS J /Fl Q15 .AML
                                                                                                                                                                                           Page 1-67

-------
               5.2 Baseline Ecological Risk Assessment Summary

 The area surrounding the landfill is heavily developed for mixed general commercial and
 industrial use, and residential use, with pockets of open space. Potential wildlife corridors
 between the landfill property and undeveloped areas exist, although they have been reduced
 and fragmented by development of adjacent lands.  The primary wildlife corridor between the
 South Parcel and the undeveloped Montebello Hills oil field located southeast of the landfill
 is limited and broken by Montebello Boulevard.

 Urban and industrial development around the landfill has  replaced most native plants with
 disturbed or landscaped habitats supporting non-native  and ornamental plants.  Disturbed
 areas  that  are not  landscaped support  grasses and  weedy, ruderal  plants.  During  a
 reconnaissance visit in February 1994, an observer noted signs of plant stress in limited areas
 adjacent to the landfill  at the Southern California Gas facility and in Iguala Park. Signs of
 plant stress in non-native plants were observed that included discoloration and deformation in
 actively growing plant tissues including leaf tips and buds, as well as older leaves and stems.
 The source of the observed plant stress is not known, but observed plant  stress was near
 historical leachate seeps and areas of recent heavy construction activities.

 Wildlife observed at the landfill includes lizards, red-tailed hawks, American kestrels, white-
 throated swifts, Say's phoebe, California towhee, western meadowlarks, loggerhead shrikes,
 and American  goldfinch.  Mobile wildlife such as hawks,  kestrels, shrikes,  and other birds
 can easily move to and  from the landfill using the scattered trees and vegetation for shelter.
 Other wildlife  expected to occur at the landfill include owls, raccoons, and  coyotes. These
 species may move at night and may be less reliant on intact corridors for movement.

 Species of special concern that  have been observed at the landfill  site include white-tailed
 kite, Cooper's  hawk,  blue-grey gnatcatcher, and loggerhead  shrike (CDM Federal,  1994).
 The only special-status  species observed during the February 24, 1994, reconnaissance visit
 was a loggerhead shrike (a federal Category 2 Candidate species).

 EPA  evaluated ecological exposure pathways  assuming a "modified  no action"  scenario.
 This scenario assumed continued operation of the existing control systems.  As part of the
 streamlining process,  exposure to the landfill contents and landfill contaminant sources were
 not considered complete pathways  because the landfill gas  migration control  and landfill
 cover systems called for in the Gas Control and Cover ROD will eliminate this pathway.

 Ecological pathways  of exposure to contaminants released to ambient air were considered
 incomplete for onsite  emissions because of planned installation  of the landfill gas  collection
 system and the landfill  cover. Offsite exposure to air emissions by terrestrial wildlife and
 plants was limited to dust emissions from areas that  would not be included in the landfill
 cover.
Oil Site Final Record of Decision                                              Page 1-69
Part I - Decision Summary                                             scoiooi92D3.DOC

-------
 Exposure of plants to contaminants in groundwater via root uptake is considered incomplete
 in all areas except in a limited area at the southwestern corner of the South Parcel near the
 Southern California Gas facility.  In this area, groundwater is approximately  15 feet below
 ground surface  adjacent to the site, dropping to more  than  75 feet below ground surface
 approximately 400 feet away from the waste prism. Groundwater levels in all other areas
 around the OH Site are generally more than 40 feet below ground surface.

 Ecological pathways of exposure to contaminants in surface  water  runoff were considered
 incomplete for onsite and offsite areas.  Surface water runoff in  the area is primarily from
 irrigation, although storm water runoff occurs with significant precipitation events. Surface
 water transport  of contaminants from the site to the surface water/storm water collection
 systems will be  limited or prevented by installation of the landfill cover, thus making offsite
 exposure unlikely.

 Under the modified no-action scenario, ecological exposure to contaminants in leachate seeps
 through direct contact are incomplete for both onsite and offsite areas.
                6.0  Description of Remedial Alternatives
                   6.1 Alternative No. 1—No Further Action

Alternative  No. 1 consists  of implementing  remedial  measures  similar to the leachate
management,  site  control,  and  monitoring  activities  currently  performed at  the  site.
Alternative No.  1  assumes implementation of  the remedial measures stipulated in the Gas
Control and Cover ROD.  The objective of Alternative No. 1 is  to provide an increased
degree of protectiveness of human health and the environment than is currently present at the
site by continuing to operate; maintain; and, as necessary, improve or replace existing landfill
systems. Because the existing system does not control migration of landfill contaminants to
groundwater, it would continue to occur in Alternative No. 1. Alternative No. 1 satisfies the
NCP requirement for inclusion of a no-action or no-further-action alternative.

Alternative No. 1 Description. Alternative No.  1 includes operation and maintenance of
existing site activities (gas extraction and air dike, leachate collection, leachate treatment,
irrigation, access roads, stormwater drainage, site security, slope repair, and erosion control),
except to the extent that they are addressed under the Gas Control and Cover ROD. Landfill
gas and landfill cover components were selected as part of the Gas Control and Cover ROD
and  are not reselected or modified in this ROD.  Implementation  of the Gas Control and
Cover  ROD is assumed in the  analysis of this alternative.  Major remedial components of
Alternative No. 1  are presented in Figures 16  and 17, and are described below.  Specific
Page 1-70                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                            Part I - Decision Summary

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                                                                                                                         Thermal Destruction Facility
                                                                                                                            (location to be determined)
                                                                                  Existing Leachate
                                                                                   Treatment Plant

                                   Existing Remote OH I
                                    Separation Facility I
                                                                                                                                    Existing Toe
                                                                                                                                 Buttress
                                                                                                                             Limit of Landfill
                                                                                                                             Gas Extraction
                                                                                                                                 System
                                                          I Existing Sump A
Existing iguala Park
Leachate Extraction
 Trench and Wells
                                                           Existing Sump B  |    \ \ / f
                                                                                                  Existing GMTW-
                                                                                                  Series Leachate
                                                                                                  Extraction Wells
                                                                            0   200  400  600
                                                                        APPROXIMATE SCALE IN FEET
                                                                                                                                                                             Legend:
                                                                            Approximate Location of Oil
                                                                            Landfill Fence/Property
                                                                            Boundary
                                                                            Road Boundary

                                                                            Existing Leachate
                                                                            Extraction Location

                                                                            Landfill Cover and Storm
                                                                            Water Management System

                                                                            Limit of Landfill Gas
                                                                            Extraction System
Notes:
(1) Remedial components and locations
   shown are conceptual. Specific
   components and locations are
   assumed for cost estimating and
   alternative comparisons only; other
   options are possible.
(2) Other Alternative No. 1 components
   are assumed to be similar to existing
   features shown on Figure 17.
(3) Landfill gas, landfill cover, and storm
   water management systems shown
   for reference only.
                                                                                                                                                                           Figure 16
                                                                                                                                                                           Alternative No. 1:
                                                                                                                                                                           No Further Action
                                                                                                                                                                           ON Site Final Record of Decision
m100004.10.01 41102000
                                                                                                                                                                                            Page 1-71

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                                                                Security Gate
                                                            Greenwood
                                                            Entrance
                                                    EPA Support Area
                                      Leachate
                                      Treatment Plant
                               Access Road

                   Flare
                   Station 1 (FS-1)
         Flare
         Station 2 (FS-2)
  Personnel
  Decontamination
  Trailers
     Decontamination
     Facility
             0      300     600


           Approximate Scale in Feet
                                                                                       Legend:

                                                                                       	OH Landfill Fence

                                                                                       • • • i  Caltrans Fence

                                                                                         (§)   Gate (Vehicle Access)

                                                                                         (MG)  Gate (Manway Only)
Figure 17
Miscellaneous Existing Landfill
Features Included in Alternative
No.1
Oil Site Final Record of Decision
m109994.16.01 site layout 8/96

-------
 remedial alternative components or technologies presented in this section are intended only to
 serve as representative examples of possible measures that could be taken to achieve the
 objectives of Alternative No. 1 and to estimate costs. Other viable remedial measures may
 be evaluated as part of the remedial design activities for the site.

 Leachate  Collection, Conveyance,  and Landfill Liquids Treatment.   The objective of
 leachate management for Alternative No. 1 is to control and prevent leachate from migrating
 offsite as  surface  seeps.  Leachate  management for Alternative No. 1  would consist of
 operation  and maintenance  of  the existing leachate collection system and,  if necessary,
 upgrades or replacement to improve operability, maintainability, and reliability of the system.
 Leachate management is currently performed in select areas of the South Parcel  only; there is
 no leachate management on the North Parcel.

 The existing South Parcel leachate collection and conveyance system is intended primarily to
 capture leachate  on the  landfill slopes and near the  landfill boundary (EPA,  1994c).  The
 existing system would be operated and maintained until  the landfill cover is operational.
 Active near-surface leachate  collection may cease if the completed landfill cover is adequate
 to manage liquids  that are currently  collected in those systems and if surface seeps cease.
 Leachate is currently, and would continue to be, collected  from existing extraction wells in
 the interior portions of the South Parcel. Leachate would also continue to be collected from
 other existing perimeter leachate collection systems such as  the Iguala Trench.

 Leachate, condensate, and other  liquids collected would be  conveyed to the existing leachate
 treatment plant (Figure 16).   Operation and maintenance of the leachate treatment  plant
 should be required  under Alternative No. 1.  Constituent concentrations would be reduced to
 below discharge limits so that the treated landfill liquids could be discharged to the County
 Sanitation  Districts of Los Angeles County sanitary sewer system.  After discharge to  the
 County Sanitation Districts of Los Angeles County system, the landfill liquids would undergo
 additional  treatment downstream in the municipal  sewer treatment system.   The total
 treatment plant influent flow  rate for  Alternative  No. 1  is  estimated  at approximately
 5.5 gallons per minute (7,850 gallons per day).

 The Alternative  No. 1  treatment  process would consist  largely  of  the existing OH Site
 leachate treatment  plant with some minor process enhancements  (polymer addition to  the
 sequential batch reactors).  However, these treatment processes serve only as  examples of
 processes that could be appropriate to treat landfill liquids.

 Limited  initial leachate  treatment system operating data suggest that effluent  from the
 sequential  batch  reactors would meet discharge requirements  without further treatment.
 However, pesticides are  capable of passing through biological  processes,  such  as the
 sequential batch reactors.  Because current operating data are limited, and because  there is a
 potential for pesticide pass-through, use of the existing sand filtration and carbon adsorption
units has been assumed for cost definition of Alternative No. 1.
Page 1-74                                              Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

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Administration, Institutional Controls, Site Security, and Facility Maintenance.  This
section addresses a broad range of remedy components not specifically covered by other
control activities.   Many of the  administration, site security,  and facility maintenance
activities described in this section are similar to activities currently performed as part of site
control and monitoring activities.

Administration.  The purpose of administrative activities would be to manage  staff, order
equipment, and perform other administrative functions to ensure that performance standards
are  met.   Health  and safety monitoring  and  enforcement, employee  training,  budget
administration, administration building operation and maintenance, performance reporting, and
payment of  applicable  taxes  would also be included in this remedial  activity.   Other
miscellaneous activities are included in this section, including meteorological monitoring and
collection and conveyance of decontamination water to the leachate treatment plant.

Institutional Controls.   Institutional controls would be used as appropriate to supplement
engineering controls for short- and long-term management to prevent or limit exposure to
hazardous substances, pollutants, or contaminants, and to ensure the effectiveness of remedial
actions.  The primary objectives of institutional controls are to (1) limit human exposure to
potentially contaminated materials onsite (e.g., leachate, landfill contents, and groundwater);
(2) prevent trespassing onto the landfill; and (3) protect the integrity of the landfill closure
and remedial action components.

North Parcel Areas Not Used as a Landfill or for Site-Related Facilities.  EPA  determined
that no landfill-related risks are posed by soils in the areas of the North Parcel not containing
landfill-related wastes nor used for site facilities (the  "nonlandfill areas").  Therefore, no
further action  is required for soils in the  nonlandfill  areas.   Institutional controls and,
potentially, engineering controls will be  required for  contaminated  groundwater  and,
potentially, liquids control on the North Parcel.

Site Security.  The purpose of site security activities at the OH Site is to limit access to the
site and protect the integrity and operation of the implemented control systems.  This activity
would be accomplished through use of guards, fences, gates, lighting, and alarms.

Facilities Maintenance. Facilities at the OH Site included in this section are:  access roads,
road  and identification  signs, buildings, utilities,  aesthetic  landscaping, equipment,  and
trucks.  Activities associated with these facilities would include routine maintenance  and
operation.  These activities would be in addition to  operation and maintenance  of specific
landfill components described above.

Postconstruction Environmental Monitoring.  The  objective  of the Alternative  No. 1
environmental  monitoring program would be to collect sufficient information to assess the
degree of protectiveness provided by the environmental control systems and to determine
Oil Site Final Record of Decision                                              Page 1-75
Part I - Decision Summary                                              scoiooi92D3.DOC

-------
 whether performance standards are being met.  Additionally, routine monitoring would be
 performed  to  facilitate  efficient operation  and  maintenance  of the  landfill  control
 components.   The objective  of long-term  groundwater monitoring would be to evaluate
 changes to groundwater contaminant concentrations  and to the lateral and vertical extent of
 groundwater contaminant migration.
               6.2 Alternative No. 2—Perimeter Liquids Control
                             (EPA's Selected Remedy)

 Alternative No. 2 includes construction of new liquids control systems along the perimeter of
 the  landfill in areas  of known  or suspected landfill liquids migration, and treatment and
 discharge  of  liquids collected  in  these systems.   Alternative  No. 2 incorporates all
 components  of Alternative No. 1, except for portions of the existing leachate  collection
 systems after the perimeter liquids control system is operational.

 The objective of Alternative No. 2 is to provide control of liquids at the landfill perimeter, as
 well as to attain the objectives of Alternative No. 1. This alternative would prevent migration
 of contaminants from the landfill to groundwater at the landfill perimeter at levels that impair
 water quality and/or represent a threat to  human health and the environment.  By preventing
 further offsite landfill liquids migration, this alternative minimizes  further groundwater
 contamination  from landfill liquids.  Perimeter  liquids control would also protect  human
 health  and the environment by  minimizing offsite  exposure to  landfill  contaminants,
 minimizing volatilization of landfill contaminants into air, and preventing additional near-site
 soil  contamination. Contaminant concentrations in groundwater beyond the landfill boundary
 would be reduced to below  cleanup standards through natural attenuation.   Groundwater
 would  be  monitored to  ensure that natural attenuation  is   progressing  as anticipated.
 Institutional controls would be used to prevent exposure to contaminated groundwater.

 Alternative No. 2 Description.  EPA assessed available monitoring data to determine areas
 in which perimeter liquids control may be needed. The areas of concern include the western
 perimeter of the South Parcel; the northwest corner of the South  Parcel; and, to a more limited
 extent, the far eastern perimeter of the South Parcel.

 A representative conceptual design for Alternative No. 2 is  illustrated in Figure 18.  Other
 technologies and extraction configurations are possible and may be explored during remedial
 design.  This section presents a description of the conceptual design of Alternative No.  2 used
 for evaluations in the Feasibility Study.

Applicable Components of Alternative No. 1. All of the components from Alternative No. 1
would  be included  in Alternative No. 2.   The perimeter liquids control system may make
portions of the leachate collection system included under Alternative No. 1 unnecessary.
Page 1-76                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

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Existing Remote OH
 Separation Facility
                                                                                             Umlt of Landfill
                                                                                             Gas Extraction
                                                                                                                                                        0   200  WO 600

                                                                                                                                                    APPROXIMATE SCALE \N FEET
         Approximate Location of Oil
         Landfill Fence/Property
         Boundaiy
         Road Boundaiy

         Landfill Cover and Storm Water
         Management System
   	Limit of Landfill Gas
         Extraction System

   —•  Area of Perimeter Landfill
         Liquids Control by Extraction
         Trench

         Shallow Extraction Well with
         Well Number

         Shallow Two-Well Cluster
         with Well Numbers

         Deep Extraction Well with
         Well Number

         Uquld Pipeline

         Compressed-Air Pipeline

   •    Air Compressor
         Building/Repump Station

Notes:
(1) Remedial components and locations
   shown are conceptual. Specific
   components and locations are
   assumed for cost estimating and
   alternative comparisons only; other
   options are possible.
(2) Other Alternative No. 1 components
   included In this alternative are assumed
   to be similar to selected existing
   features shown on Figures 16 and 17.
(3) Landfill gas, landfill cover, and storm
   water management systems shown for
   reference only.
                                                                                                                                              Figure 18
                                                                                                                                              Alternative No. 2:
                                                                                                                                              Perimeter Liquid* Control
                                                                                                                                              Oil Slto Final RKOrd ol frdtfon
                                                                                                                                                                 Page 1-77

-------
 Perimeter  Liquids Control, Conveyance, and Treatment.  A perimeter liquids control
 system  would  be installed in  areas  where  contaminant levels  in groundwater exceed
 performance standards.

 The  conceptual  design  of the  perimeter liquids control  system at  the  OH Site includes
 95 extraction wells (shallow and deep) in addition to an extraction trench system along the
 western and southwestern boundary of the South Parcel. Landfill  liquids collected under this
 alternative  would be pumped  to the  existing leachate treatment plant for treatment. The
 estimated perimeter liquids extraction  rate for this alternative would be 190,100 gallons per
 day (132 gallons per minute).   In addition, about  3,750 gallons per day  (2.6 gallons  per
 minute) of landfill liquids (including condensate and other liquids) would be collected.

 EPA's evaluations indicate that the existing leachate treatment plant, with some modifications
 as necessary, would be adequate to treat liquids in Alternative No. 2. The treated liquids would
 be  discharged to the County Sanitation Districts of Los Angeles County sanitary sewer system.
 After discharge to the County Sanitation Districts of Los Angeles County sanitary sewer
 system,  the liquids would undergo additional  treatment in the municipal  sewer treatment
 system.

 Remedial Design Investigation.  Prior to final design of a perimeter liquids control system, a
 remedial design investigation would be performed to better characterize both the actual  areas
 where contaminants are migrating beyond the landfill perimeter and the hydraulic properties
 of the various aquifers or formations at the landfill perimeter. In addition, some additional
 delineation of the contaminated groundwater areas would be required.  The conceptual remedial
 design investigation would consist primarily of installation and testing of new monitoring  wells
 and collection of liquids samples.

 Postconstruction Environmental Monitoring Program. As in Alternative No. 1, EPA would
 implement a long-term, postconstruction environmental monitoring program with this alterna-
 tive to collect sufficient  information to assess the degree  of protectiveness provided by the
 environmental control systems and to determine whether performance  standards were being
 met.  In  addition to the monitoring described in Alternative No. 1,  the two main objectives of
 Alternative  No. 2 environmental monitoring are  (1)  to  evaluate  the  effectiveness  and
 performance of the Alternative No. 2 perimeter landfill liquids control system by monitoring
 liquid levels and contaminant concentrations downgradient of the control systems and (2) to
 evaluate changes to groundwater contaminant concentrations through natural attenuation and to
 the  lateral and vertical extent of groundwater contamination after placement  of the remedial
 measures.
Oil Site Final Record of Decision                                              Page 1-79
Part I - Decision Summary                                             scoiooi92D3.DOC

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   6.3  Alternative No. 3—Perimeter Liquids Control Plus Source Control

 Alternative No. 3 includes new leachate extraction and conveyance systems located within
 the  interior of the waste prism and treatment and discharge of the collected  leachate, and
 incorporates all components of Alternative No. 2.

 The objective of Alternative No. 3 is to provide enhanced control of landfill liquids over that
 presented  in Alternative No. 2; to provide additional reduction in toxicity,  mobility, and
 volume; and to potentially reduce the long-term management of liquids, as well as to attain
 the objectives of Alternative No. 2. In Alternative No. 3, leachate extraction within the waste
 prism would remove some of the liquids that are currently migrating or  that may  migrate
 towards the perimeter of the  landfill.   One potential benefit of interior leachate extraction
 would be  to provide additional assurances that landfill contaminants would  be contained,
 especially  for any areas where perimeter liquids control would be technically challenging.
 Extracting leachate from the interior of the landfill may reduce the period of time required to
 operate the perimeter liquids control system, and it may reduce the long-term  flow rate into
 the perimeter system.  Extracting interior leachate would also potentially  reduce long-term
 management of liquids at the site, potentially satisfying the NCP goal of reducing the need
 for  long-term  management  through  removal and  destruction  of  toxic and/or  mobile
 contaminants to a greater extent than Alternative No. 2.

 Alternative No. 3 Description. EPA interpreted various landfill data  to provide a basis for
 estimating the  location of potentially saturated zones, the volume of leachate present and
 potentially extractable, its ability to  migrate, potential migration  pathways,  and potential
 impacts to groundwater.  EPA targeted potentially saturated zones for leachate extraction that
 were considered a potential threat to groundwater. The total volume of leachate targeted for
 extraction is approximately 113 million gallons. This  represents about 76 percent of the total
 potentially extractable leachate (estimated at 145 million gallons), but only about 13  percent
 of the estimated total volume of leachate in the waste prism (871 million gallons).

 Figure 19  illustrates  a  representative conceptual design for Alternative No. 3.   Other
 technologies and extraction configurations are possible.  A description of the conceptual design
 of Alternative No. 3 follows.

 Interior Leachate  Extraction, Conveyance,  and Landfill Liquids Treatment.  Vertical
 extraction  wells  are  assumed to  be the most effective technology  for  interior leachate
 extraction  in Alternative No. 3.   The number of wells assumed  for a particular  area is
 influenced  by the saturated thickness, geometry of the bottom of the extraction  area,  and the
 anticipated well yield and targeted extraction volume (i.e., the quantity  of leachate each well
 is anticipated to produce compared to the total volume  to be extracted).
Page 1-80                                              Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

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Existing Leachate
 Treatment Plant
                                                                                                                                     Thermal Destruction Facility
                                                                                                                                        (location to be determined)
                                     Interior Waste Prism
                                  Uachate Extraction Well
                            Existing Remote Oil
                            Separation Facility:
                                                                                                                               Limit of Landfill
                                                                                                                               Gas Extraction
                                                                                                                                   System
                                           Perimeter Landfill
                                          Liquids Control and
                                           Extraction System
                                                                                               0   200  400  600

                                                                                            APPROXIMATE SCALE IN FEET
                                                                                                                                                                                Legend:
                                                                                                Approximate Location of Oil
                                                                                                Landfill Fence/Property
                                                                                                Boundary

                                                                                                Road Boundary

                                                                                                Leachate Collection
                                                                                                Pipeline
                                                                                                Landfill Cover and Storm
                                                                                                Water Management System

                                                                                                Limit of Landfill Gas
                                                                                                Extraction System

                                                                                                Perimeter Landfill Liquids
                                                                                                Control System
                                                                                                 Interior Leachate
                                                                                                 Extraction Well

                                                                                                 Air Compressor Building/
                                                                                                 Repump Station

                                                                                                 Compressed-Air Pipeline
n10M04.18.01 (xWiZ W8
                                                                                        Notes:
                                                                                        (1)  Remedial components and locations
                                                                                            are conceptual. Specific components
                                                                                            and locations are assumed for cost
                                                                                            estimating and alternative
                                                                                            comparisons only; other options are
                                                                                            possible.
                                                                                        (2)  All components in Alternative No. 2
                                                                                            (Figure 18) are assumed to be
                                                                                            included herein. Other features are
                                                                                            assumed to be similar to selected
                                                                                            existing features shown in Figures
                                                                                            16 and 17.
                                                                                        (3) Landfill gas, landfill cover, and storm
                                                                                           water management systems shown
                                                                                           for reference only.


                                                                                      Figure 19
                                                                                      Alternative No. 3:
                                                                                      Perimeter Liquids Control
                                                                                      plus Source Control
                                                                                      Oil Site Final Record of Decision
                                                                                                                                                                                               Page 1-81

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 Alternative No. 3 would involve collection and treatment of both interior leachate (estimated
 to be approximately  20.5 gallons per minute initially) and perimeter liquids (estimated at
 about 135 gallons per minute).  The existing leachate treatment system would be augmented
 with new process  equipment for perimeter liquids  (Alternative  No. 2) because separate
 treatment of the more concentrated interior leachate would almost fully utilize the existing
 process equipment. The two treatment streams would be combined into the existing outfall
 and discharged to  the County  Sanitation Districts of Los  Angeles  County  sanitary  sewer
 system.  After discharge to the County Sanitation Districts  of Los Angeles County sanitary
 sewer system, all of the liquids would undergo additional treatment  in the municipal  sewer
 treatment system.

 Remedial Design Investigation. Implementation of Alternative No. 3 would require additional
 field investigations  of the extent of extractable leachate,  hydraulic properties of the  waste
 prism, and sustainable yields of extraction wells because of the inherent complexity of the
 waste prism.

 Postconstruction Environmental  Monitoring.  The objective  of  the Alternative  No. 3
 postconstruction  environmental  monitoring program   would  be   to collect  sufficient
 information to assess the degree of protectiveness provided by the  environmental control
 systems and to determine whether remedial objectives and performance standards are met.
    6.4 Alternative No. 4—Perimeter Liquids Control Plus Groundwater
                             Control or Remediation

Alternative  No. 4  includes control of contaminated  groundwater,  and,  as an  option,
remediation of contaminated groundwater.  It also incorporates all components of Alternative
No. 2, or, as an  option, Alternative  No. 3.   The objective of Alternative No. 4 is to control
areas of contaminated groundwater exceeding cleanup standards, as well as to attain the
objectives of Alternative No. 2, or,  as an option, Alternative No. 3.  Alternative No. 4A is
intended to contain and prevent further migration of contaminated groundwater. Alternative
No. 4B is intended to contain and, where feasible, remediate or restore groundwater within a
shorter time period through more aggressive groundwater collection.

Alternative No. 4 Description. EPA used data from existing shallow and deep monitoring
wells at the  OH Site to define the areas of concern potentially requiring groundwater control
at the downgradient boundary.
Oil Site Final Record of Decision                                             Page 1-83
Part I - Decision Summary                                            scoiooi92D3.DOC

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 A conceptual design for Alternative No. 4 is illustrated in Figure 20.  Other technologies and
 extraction configurations are possible.  A description of the conceptual design of Alternative
 No. 4 follows.

 All Components  of  Alternative No. 2  or Alternative  No. 3.    As  discussed  above,
 Alternative No. 2 includes  perimeter liquids control. Alternative No. 3  adds extraction of
 leachate from the interior of the landfill.  For purposes  of discussion herein, it has been
 assumed  that Alternative No. 4 would include all remedial components from  Alternative
 No. 2.  However, if Alternative No. 4 were selected for this remedy, it  could also include
 leachate extraction from some or all of the Alternative No. 3 extraction areas.

 Control or  Control/Remediation of Contaminated  Groundwater. Alternative No. 4A
 includes control  of  contaminated groundwater in the following locations: northwest and
 west of the northwestern corner of the South Parcel, north of the North Parcel, west  of the
 western perimeter of the South Parcel, south and southeast of the southwestern corner of the
 South Parcel, and east  of the northeastern corner of the South  Parcel. Alternative No. 4B
 consists of groundwater control at all of the above areas plus additional extraction  in the
 Northwest Area to more aggressively collect and possibly restore contaminated groundwater
 within a  shorter time period.  Assumed  depths of collection  are based upon  known or
 suspected  depths of  contamination, recent depth-to-water  measurements, and  interpreted
 thickness  of confined units.

 EPA used groundwater extraction  from  vertical  extraction wells  as  the  representative
 technology for groundwater containment  in the Feasibility Study.   The purpose  of the
 extraction  wells  would be  to prevent contaminated liquids from  migrating  beyond (i.e.,
 downgradient of) the control boundary.  Assumed extraction well locations are shown in
 Figure 20.   The  estimated  groundwater  extraction rate  for Alternative No. 4A  is  about
 526,600 gallons per day (366 gallons per minute); and for Alternative No. 4B, it is estimated
 to be 892,900 gallons per day (620 gallons per minute).

Disposal Options for Treated Groundwater.  The Feasibility Study evaluated five different
 options for discharge of the extracted  and treated groundwater.  These are sanitary  sewer
 discharge, aquifer injection discharge, surface water discharge, irrigation reuse discharge, and
 deep well injection discharge. The deep well injection discharge option was eliminated as a
feasible discharge option in the Feasibility Study. The remaining four discharge options were
incorporated  into Alternative No. 4.  The total  flow rates for discharge under Alternatives
No. 4A and 4B would be 501 and 755 gallons per minute, respectively. This would include
the perimeter liquids (135 gallons per minute) and the groundwater (366 gallons per minute
in Alternative No. 4A and  620 gallons per minute in  Alternative No. 4B).  It has been
assumed in all discharge options  that the perimeter liquids portion of  Alternative  No. 4
(135 gallons per minute) would be discharged to the sanitary sewer.
Page 1-84                                             Oil Site Final Record of Decision
scoiooi92D3.DOC                                             Part I - Decision Summary

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                                                                                                                                                                            j>g«nd:
                                                                 Existing Leachate
                                                                  Treatment Plant
                                                                        I Landfill Cover]
                           ®   ^NORTHWEST AREA
  .--"   ,--"1       H41B    .«»               ...
>"\                     •-        -
Existing Remote Oil
 Separation Facility \   c\*-$/
                                                                                                                                                                          0   200  400  600
                                                                                                                                                                      APPROXIMATE SCALE IN FEET


                                                                                                                                                                    Approximate Location of Oil Landfill
                                                                                                                                                                    Fence/Property Boundwy

                                                                                                                                                                    Road Boundary

                                                                                                                                                                    Landfill Cover and Storm Water
                                                                                                                                                                    Management System

                                                                                                                                                                    Limit of Landfill Gas
                                                                                                                                                                    Extraction System

                                                                                                                                                                    Perimeter Landfill Liquids
                                                                                                                                                                    Control Area

                                                                                                                                                                    Area of Concern for
                                                                                                                                                                    Groundwater Control

                                                                                                                                                                    Shallow Extraction Well

                                                                                                                                                                    Shallow Two-Well Cluster

                                                                                                                                                                    Deep Extraction Well

                                                                                                                                                                    Extraction Wells Included In
                                                                                                                                                                    Alternatives 4A and 4B

                                                                                                                                                                    Extraction Wells Included In
                                                                                                                                                                    Alternative 4B Only
                                                                                                                                                                                I Graundwitar Extracdon Art* Und tel I
                                                                                                                                                                                | Flow Rrt» and Qually Ertnatu    I

                                                                                                                                                                             Existing Monitoring Will Grouping*:

                                                                                                                                                                               •   Northwest Area Unconfined Aquifer
                                                                                                                                                                                   Northwest Area Deep
                                                                                                                                                                                   Southwest Area Perimeter
                                                                                                                                                                               &   Southwest Area Downgradlent
                                                                                                                                                                               o   Eastern Area Unconfined Aquifer
                                                                                                                                                                               v   Eastern Area Deep
                                                                                                                                                                               o   South Aquifer
                                                                                                                                                                                   West Aquifer
                                                                                                                                                                            Not»«:
                                                                                                                                                                            (1) Remedial components and location! ihown am
                                                                                                                                                                               conceptual. Specific components and locations are
                                                                                                                                                                               assumed for cost ssttmating and aftemative
                                                                                                                                                                               comparisons only, other options are possible.
                                                                                                                                                                            (2) AI components In Alternative No. 2 (Figure 16) «
                                                                                                                                                                               assumed to be Included herein. Other features are
                                                                                                                                                                               assumed to be sknllar to selected existing  fsatires
                                                                                                                                                                               shown on Figures 16 and 17.
                                                                                                                                                                            (3) Landfill gas, landfil cover, and storm water
                                                                                                                                                                               management systems shown for reference only.

                                                                                                                                                                             Figure 20
                                                                                                                                                                             Alternative No. 4:
                                                                                                                                                                             Perimeter Liquids Control
                                                                                                                                                                             plus Groundwater Control
                                                                                                                                                                             Oil Site Final Record of DeoMon  '
                                                                                                                                                                                                   Page 1-85

-------
Conveyance.   The purpose of the Alternative No. 4 groundwater extraction conveyance
system is to transport groundwater from the collection systems to the treatment plant. The
conveyance system for Alternative No. 4 extraction would begin at each well and extend to
the connection at the treatment plant.

Additionally,  a conveyance system would be needed  to transport treated  liquids  from the
treatment plant to facilities  for each of the four discharge options considered.  For sanitary
sewer discharge, an additional pipeline would be needed to transport the treatment plant
discharge to the County Sanitation  Districts of Los Angeles County system at Wilcox
Avenue.  In addition, in Alternative No. 4B, a pipeline would be needed downstream of the
Wilcox Avenue connection to provide additional capacity.   Injection wells (likely located
northwest of the North Parcel) and associated pipelines  would be needed for the  aquifer
injection discharge option. Discharge under the surface water discharge option would likely
be into a  drainage in the nursery adjacent to the North Parcel, or potentially  into the drainage
channel on the south side of the Pomona Freeway. For the  irrigation reuse discharge option, a
pump station would be required to supply the treated groundwater to the potential recipients of
treated water at an appropriate pressure for use in their system. Potential recipients include the
surrounding nurseries, cemetery, golf course, and the landfill itself.

Groundwater   Treatment.  Because  discharge  standards  vary between various  discharge
options, EPA  assumed and evaluated a treatment system  for each discharge option.  EPA
added representative unit processes  as required to meet the differing discharge requirements.
The perimeter  liquids  treatment component of Alternative No. 4 would be identical to that
presented for Alternative No. 2, so this component is not discussed again in this section.

The conceptual groundwater treatment system consists primarily of new units located at or
adjacent to the existing plant because the perimeter liquids would use much of the existing
leachate treatment plant capacity.

Remedial Design Investigation. The objective of the remedial design investigation for
Alternative No. 4 would be to collect hydrogeologic and lithologic data to refine the design of
the proposed groundwater control or remediation systems  prior to implementation.  For the
conceptual remedial design investigation, the types of data that would need to be collected (in
addition to those addressed by the Alternative No. 2 remedial design  investigation) include
the  lateral  and  vertical  extent  of contamination,  hydraulic properties  of the affected
hydrogeologic units in the offsite areas, potential migration  pathways to offsite areas, and
long-term sustainable yields of extraction wells.

Postconstruction Environmental Monitoring.  Alternative No. 4 incorporates all of the
monitoring discussed in Alternative No. 2, except that the offsite groundwater monitoring
component would be modified. The objectives of groundwater monitoring in the offsite areas
under Alternative No. 4 are to evaluate the effectiveness and performance of the groundwater
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 control/restoration  systems  and to assess  groundwater contaminant  migration  after the
 placement of these systems.
      7.0  Summary of the Comparative Analysis of Alternatives

 This section compares the remedial  alternatives described in Section 6.  The comparative
 analysis provides the basis for determining which alternative presents the best balance of
 EPA's  nine  Superfund evaluation criteria provided in  40 Code of Federal  Regulations
 Part 300.430 (listed below).    The first two  cleanup 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

        1.     Overall Protection of Human  Health and the Environment addresses
              whether an alternative provides adequate protection from unacceptable risks
              posed by the site.

       2.     Compliance with Applicable or Relevant and Appropriate Requirements
              (ARARs) addresses whether an  alternative attains specific federal and state
              environmental requirements  and  state facility siting requirements or provides
              grounds for a waiver.

 Primary Balancing Criteria

       3.      Long-term Effectiveness and Permanence refers to the degree to which an
              alternative provides reliable protection of human health and the environment
              over time.

       4.      Reduction of Toxicity, Mobility, or Volume Through Treatment refers to
              the degree to which an alternative uses treatment to reduce the health hazards
              of  contaminants,  the movement of contaminants,  or  the quantity  of
              contaminants at the site.

       5.      Short-term Effectiveness addresses the degree to which human  health and
             the  environment  will  be  adversely  impacted during  construction  and
              implementation of an alternative.

       6.     Implementability refers to the technical and administrative feasibility of an
             alternative.   This includes technical difficulties and uncertainties and the
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              availability of materials and services.  It also includes coordination of federal,
              state, and local government efforts.

        7.     Cost evaluates the estimated capital, operation and maintenance, and indirect
              costs of each alternative in comparison to other equally protective alternatives.

 Modifying Criteria

        8.     State Acceptance indicates whether  the state agrees with, opposes, or has
              concerns about the preferred alternative.

        9.     Community Acceptance includes determining which components  of the
              alternatives interested persons in the community support,  have reservations
              about, or oppose.

 The strengths and  weaknesses  of the  alternatives were weighed to identify the alternative
 providing the best balance with respect to the nine evaluation criteria.
       7.1 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, in  both the short term and long term, from
unacceptable risks.  These risks  can be mitigated by eliminating, reducing, or controlling
exposure to hazardous substances, pollutants, or  contaminants. Overall protection of human
health and the environment draws on the assessments of other evaluation criteria, especially
long-term  effectiveness  and permanence,  short-term  effectiveness,  and  compliance with
ARARs.  Reduction of toxicity, mobility, and volume is another important criterion for this
overall evaluation.  An overall summary of the  criteria, as they relate to protectiveness  of
human health and the environment, is presented in  Table 10.

7.1.1 Alternative No. 1

Of all the alternatives,  Alternative No. 1  is  the least protective of  human  health  and the
environment. Because landfill contaminants would continue to migrate into the groundwater,
Alternative No. 1 would not protect groundwater resources nor adequately protect future human
exposure to contaminated groundwater. Alternative No. 1 would not comply with ARARs for
landfill closure and groundwater protection, which require that landfill contaminants not escape
from the landfill  into groundwater and other media and require cleanup of groundwater  to
acceptable levels.  Also, Alternative No. 1  would also fail to meet CERCLA Section 121(d),
which generally requires  groundwater remedies affecting potential  drinking water sources  to
attain drinking water standards.
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Table 10
Comparison of Overall Protection of Human Health and the Environment
OH Site Final Record of Decision
Evaluation Criteria
Alternative No. 1
Alternative No. 2
Alternative No. 3
L*flg*T&;jh:Effectiveness and Permanence
Magnitude of Residual Risk
Leachate
Groundwater
Adequacy and Reliability of Controls
Engineering Controls
Institutional Controls/Monitoring

Med.
Med.

Med.
Low/Med.

Med.
Med.

Med./High
Med.

Low
Med.

Med./High
Med.
Alternatives No. 4A and 4B


Med.
Med.

Med./High
Med./High
Reduction in Toxicity, Mobility, and Volume Through Treatment
Estimated Volume of Constituents Removed Through Collection/Extraction
Inorganic Constituents (tons)
Organic Materials (tons)
Volatile and Semivolatile Organic
Constituents (tons)
Treatment Residuals Generated (tons)
2,700
1,290
40
610

4,800
2,370
11
160

11,450
4,780
63
1,080
(4A) (4B)
10,500 30,900
2,430 2,460
12 16
160 - 760 840 - 1,660
Short-Term Effectiveness
Risk to Community During Implementation
Protection of Workers
Time Until Remedial Objectives Achieved3
Environmental Impacts
Med.
Med.
4 to 6 years
Low
Med.
Med.
5 to 7 years
Low
Med.
Med.
5 to 7 years
Low
High
Med.
5 to 7 years
Low
Compliance with ARARs
Chemical-Specific ARARs
Time Until Chemical-Specific Remedial
Goals Achieved- Inorganics
Time Until Chemical-Specific Remedial
Goals Achieved- Organics
Location-Specific ARARs
Action-Specific ARARs
No
Unknown (many tens of years
longer than Alt. No. 2)
Unknown (many tens of years
longer than Alt. No. 2)
Yes
No
Yes"
Estimated to range from about 50
years in some areas up to 150 years
+/- 50 years in other areas
Estimated to be less than 50 years
Yes
Yes
Yesb
Estimated to range from about 50
years in some areas up to 150 years
+/- 50 years in other areas
Estimated to be less than 50 years
Yes
Yes
Yesb
Estimated to range from about 20
years in some areas up to 60 years
+/- 20 years in other areas
Estimated to be less than 50 years
Yes
Yes
a For groundwater, the times listed only represent the time until remedial objectives are partially met, through institutional controls and perimeter control (except for Alternative No. 1,
which does not have perimeter control); remedial objectives would not be fully met until cleanup goals are achieved (cleanup times are given under chemical-specific ARARs).
b There is a potential that inorganics in the Southwest Area may not meet ARARs in a reasonable time (the estimated range of cleanup times is provided above and in Table 11).
SCO/10019173.XLS

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 Each of the alternatives incorporates institutional controls to protect human health.  Alternative
 No. 1  relies on institutional controls to protect human health from exposure to constituents in
 groundwater for the longest amount of time and over the largest  area.  This is because the
 source would not be controlled and would continue to contaminate groundwater.  Due to the
 lack of perimeter liquids control, the extent of the area that would require institutional controls
 cannot be reliably predicted, nor can the length of time that institutional controls would be
 required.  These uncertainties make implementation of institutional controls for this alternative
 more difficult than for any other alternative. Accordingly, Alternative No. 1 is less protective of
 human health and the environment for groundwater than the other alternatives.

 7.1.2 Alternative No. 2

 Alternative No. 2 would be significantly more protective of human health and the environment
 than Alternative  No.  1 because,  by containing contaminants at the landfill perimeter, there
 would be no further impact to groundwater. Alternative No. 2 would meet landfill closure and
 chemical-specific ARARs pertaining to the offsite migration of landfill contaminants and to
 groundwater cleanup (which are not met by Alternative No. 1).  The period of time over which
 institutional controls would be required is substantially less than Alternative No. 1.  The area
 over which  institutional controls would  be  needed would also be  substantially less than
 Alternative No.  1, although it could potentially extend an  additional 600 feet up  to 1,000
 ±500 feet beyond the current extent of contamination.  Alternative No. 2 would comply with all
 ARARs, although there is a potential that groundwater cleanup for inorganic constituents in the
 Southwest Area may take an excessive  amount of time to reach cleanup standards (because of
 the complex subsurface conditions).

 7.1.3  Alternative No. 3

 Alternative No. 3 would have similar protectiveness of human health  and the  environment as
 Alternative No. 2.  For  groundwater, Alternative No. 3 would be almost identical to Alternative
 No. 2 because the perimeter liquids control system will prevent migration of contaminants to
 groundwater. Institutional controls would be required for the same amount of time and over the
 same area as Alternative No. 2. Extracting and treating interior leachate may achieve a slightly
 higher degree of long-term protectiveness and may reduce the magnitude of residual risk from
 leachate contained within the landfill. However, the large majority of leachate (approximately
 87 percent) would remain onsite under this alternative. Removing a portion of the contaminant
 source may also slightly enhance  the effectiveness of the perimeter liquids control system in
 preventing migration  of contaminants to groundwater,  because  the amount of  leachate
 migrating  to  the perimeter may be reduced.   Therefore,  from  a  contaminant migration
 perspective, Alternative No. 3 may be slightly more protective  of  the environment than
 Alternative No. 2. Alternative No. 3 would comply  with  all ARARs, except potentially for
 groundwater cleanup of inorganics in the Southwest Area (as described above for Alternative
No. 2).
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7.1.4 Alternative No. 4

Alternative No. 4  would provide the same  level of long-term protection from exposure  to
contaminated  groundwater as Alternatives No. 2 and No.  3, except for inorganic contami-
nation.  It would  be  more protective overall  than  the other alternatives because inorganic
contamination would  not spread and because extraction of  contaminated groundwater would
enhance natural attenuation of the inorganic contamination.  Alternative No. 4 would have the
least  reliance  on  groundwater monitoring and institutional  controls because its groundwater
control  component would minimize the size  of the contaminated area (and  thus the  area
required for institutional controls).  Active extraction of contamination would achieve cleanup
standards for inorganic constituents sooner than other alternatives and therefore minimizes the
time required  for institutional controls (although institutional controls would still be required
for up to 60 years +/- 20 years).

Alternative No. 4 would cause significantly increased impacts on the community surrounding
the landfill during remedy implementation because of the large-scale construction activities  in
the adjacent neighborhoods.   These include installation of numerous extraction wells and
conveyance systems in residential streets.  These construction activities would cause significant
noise and disrupt traffic patterns. The alternative would also have long-term adverse impacts,
including potential leaks or spills of contaminated groundwater,  significant ongoing operation
and maintenance activities, and ongoing traffic disruptions.

Alternative No. 4 would comply with all ARARs, although,  as with Alternatives No. 2 and  3,
there  is  the potential that groundwater cleanup of inorganic constituents in the Southwest Area
may take an excessive amount of time (because of the complex subsurface conditions).

As discussed previously, it is possible that  all or portions  of the Alternative No. 3  interior
leachate extraction systems could be incorporated into Alternative No. 4.  The combination of
interior  leachate extraction plus groundwater control/remediation (Alternative No. 4B) would
provide the highest degree of protectiveness of human health  and the environment of all the
alternatives.
                          7.2 Compliance with ARARs

This section presents a comparison of alternatives with respect to compliance with chemical-
specific, location-specific, and action-specific ARARs.

Chemical-Specific ARARs.  Chemical-specific ARARs  are health-  or risk-based numeric
values  or  methodologies  that, when  applied  to site-specific  conditions, result  in the
establishment of numeric values of the acceptable amount, or concentration, of a chemical that
may be found in, or discharged to, the ambient environment.  Alternative No. 1 would not meet
chemical-specific ARARs pertaining to groundwater cleanup.  This is because the  landfill
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 source would not be contained and natural  attenuation would not effectively  reduce  either
 organic or inorganic constituents  to cleanup  standards within an  acceptable  time frame.
 Alternatives No. 2, 3, and 4 would meet chemical-specific ARARs, with the possible exception
 of inorganic constituents in  groundwater in  the Southwest Area.  Because of the complex
 groundwater flow conditions  and low-permeability formation, there is a potential that inorganic
 constituents in the Southwest Area may take an excessive amount of time to meet cleanup
 standards (cleanup of inorganics could require up to 150 +/- 50 years under Alternatives No. 2
 and 3 and 60 +/- 20 years in Alternative No. 4). The estimated cleanup times for both organic
 and inorganic constituents are shown in Table  11 for each of the alternatives.

 Location-Specific ARARs.  Location-specific ARARs are restraints placed on activities in or
 impacts on specific areas. It is expected that all  of the  alternatives would comply with all
 location-specific ARARs.

 Action-Specific  ARARs.    Action-specific  ARARs  are  technology-  or  activity-based
 requirements or standards that apply to specific remedial activities that are conducted as part of
 the selected remedy. Actions related to the OH Site include construction activities, such as the
 extraction trench or groundwater extraction wells and leachate collection and treatment systems,
 and landfill closure requirements.  All alternatives  involve operation and maintenance of site
 control systems, and discharges from the treatment systems.  With the exception of Alternative
 No. 1, site control systems in all alternatives could be designed, constructed, and operated to
 meet federal and state action-specific ARARs.  Alternative No. 1 would not meet the federal
 and state ARARs pertaining to landfill closure, such as the prevention of contaminant migration
 away from the landfill and protection of groundwater.
                 7.3  Long-term Effectiveness and Permanence

Long-term effectiveness is evaluated through two criteria:  the magnitude of the residual risk
remaining after the remedy is implemented and the adequacy and reliability of engineering and
institutional controls.

7.3.1  Magnitude of Residual Risk

The magnitude of residual risk is typically gauged by the risks remaining from untreated waste
at the conclusion of  remedial  activities.  EPA's guidance  on streamlining the remedial
investigation/feasibility study for CERCLA municipal  landfills  recognizes  that containment
technologies are  generally appropriate  for landfills containing  municipal  waste, and  that
complete treatment of all hazardous constituents (including the landfill contents) is generally
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"d
f»
Oq
ft
                              Table 11
Approximate Time to Reach Chemical-Specific ARARs in Groundwater
                  Oil Site Final Record of Decision
                                 Area
                      Alternative No. 1
   Alternative No. 2
(and Alternative No. 3)a
Alternative No. 4
         Organic Constituents
Northwest Area
Southwest Area - Western LW/SP
Southwest Area - Western Shallow Siltstone
Southwest Area - Southeast
Eastern Area
Unknown*
Unknownd
Unknown
Unknown*1
Unknown*
12
25
33
43
18
12
25
33
43
18
         Inorganic Constituents*
Northwest Area
Southwest Areaf
Eastern Area
Unknown*
Unknown*
NAg
56
About 150 years +/- 50 years
NA8
20"
About 60 years +/- 20 years
NAg
         aFor natural attenuation modeling purposes, Alternatives No. 2 and 3 are assumed to have essentially the same impacts on groundwater.
         b Alternatives No. 4A and 4B are the same except for inorganic constituents hi the Northwest Area, where the tune to MCLs
          hi Alternative No. 4B would be less than 20 years.
         cUsing vinyl chloride hi modeling.
         *Contaminant levels would not reach MCLs until the landfill source is depleted (many decades). Once the source is gone, the time to reach MCLs
          would be similar to Alternative No. 2.
         "Using antimony hi modeling. Note that the inorganic modeling was fairly conservative and the times presented may be closer to upper-bound estimates.
         Anorganic model results were obtained from the southeast segment of the Southwest Area. These results are also assumed to be representative
          of inorganic transport hi the other two segments hi the Southwest Area.  Note that uncertainty in the distribution of inorganic contamination and complexities
          hi the groundwater flow conditions (especially over longer times and with greater distances from the landfill) leads to uncertainty in the
          simulation results, thus a range of years is shown for inorganic constituents in the Southwest Area.
         glnorganic constituent modeling not performed; primarily organic contamination hi the area.                                               	
       SCO/10019174.XLS

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 impracticable.  None of the remedial alternatives include removal of the landfill contents, and
 all of the alternatives use a containment technology to prevent exposure to the contents.

 Groundwater Contamination. For Alternatives No. 2, 3, and 4, it has been estimated that the
 magnitude of residual site-related risk in groundwater will be significantly reduced  through
 perimeter liquids control; natural attenuation; and, for Alternative No. 4, control of groundwater
 beyond the landfill  perimeter.  Alternative No. 3 could slightly reduce the residual risk to
 groundwater over Alternative No. 2 by enhancing effectiveness of the perimeter liquids control
 system.  The potential reduction is only considered slight, because the perimeter liquids control
 system would still inhibit migration of mobile contaminants to groundwater even if they were
 not actively extracted from the waste prism. Because the cleanup standards would be met in a
 shorter time-frame under Alternative No. 4, the risk reduction would be realized  sooner.
 However,  the  eventual  risk  reduction  would be the  same for all  three alternatives.   In
 Alternative No. 1, the magnitude of site-related  risk would initially  increase because there
 would be additional influx of contaminants from the landfill to groundwater. Eventually, the
 site-related risk in groundwater would diminish in a similar fashion as the other alternatives;
 however, it is estimated that this  would take many  additional decades  under  Alternative
 No. 1.

 Even with the  site-related  contaminants  reduced to their cleanup standards, the estimated
 overall risks in groundwater could still exceed 10"4 because of naturally occurring levels  of
 inorganic constituents, primarily arsenic,  in the OH  Site vicinity.  However,  Alternatives
 No. 2, 3, and 4 would reduce the site-related risks in an acceptable time frame (with the
 possible  exception of the Southwest Area).   Alternatives No. 2, 3,  and 4 would be  more
 protective of any future use of or exposure to groundwater in the OH Site vicinity, although
 there is no currently known use of this groundwater.

 Leachate. Varying degrees  of residual risk associated with leachate will remain at the landfill,
 depending on the alternative.   Over the 30-year evaluation period, Alternative No. 3 would
 provide a slightly higher reduction in residual risk from leachate than the other three alternatives
 because an estimated 13 percent of the total leachate present in the landfill would be actively
 extracted.   The  reduction  in residual risk would be only slightly  higher than the  other
 alternatives because  a considerable volume of leachate (about 87 percent of the total) would
 remain onsite.

 7.3.2 Adequacy and Reliability of Controls

 This evaluation criterion pertains to the adequacy and  suitability of controls that  are used to
 manage treatment residuals or untreated wastes that remain at the site. The main controls used
 in the alternatives for the OH Site consist  of containment or control systems and institutional
 controls.
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 Containment, Conveyance, and Treatment Technologies.   The technologies included in
 Alternatives  No. 1  through  4  (e.g.,  perimeter liquids  control,  leachate  extraction,  and
 groundwater extraction) are generally considered adequate and reliable, if properly designed,
 constructed, monitored, operated, and maintained.

 Institutional Controls.  All of the alternatives would rely on institutional controls  to limit
 human exposure to potentially contaminated materials, prevent trespassing, and protect the
 integrity of the landfill closure and remedial action components within the landfill boundary.
 All  of the  alternatives would rely on groundwater monitoring and institutional controls to
 ensure that groundwater is not used until cleanup standards  are met.   (Again, no current
 groundwater use is known  to occur in the landfill vicinity.)  The adequacy and reliability of
 institutional controls are highly dependent on enforcement and maintenance by state and local
 regulators and adequate definition  of the area of contamination over which institutional controls
 are required.  Institutional controls can be subject to changes in the political jurisdiction, legal
 interpretations, and the  level of enforcement, as well as to changes in the need for water
 resources. Institutional controls would only be effective with a high degree of certainty in the
 short term,  because regulators of  the institutional controls cannot ensure the effectiveness or
 enforceability beyond a number of years.  Therefore, alternatives that rely on institutional
 controls for shorter time frames and smaller, well-defined areas are generally considered more
 reliable than those with long time frames and larger, less well-defined areas.

 Duration of Institutional Controls. For institutional controls,  the primary difference between
 the alternatives is the duration that the controls would be relied upon, the area over which they
 would be required, and the degree to which the area can be defined.  Table 11 presents a
 comparison of the time to reach cleanup standards (after which time institutional controls are
 not necessary).  Institutional controls would be required for the longest time in Alternative
 No.  1 (likely for many tens of years longer than Alternatives No.  2 and 3).  For Alternatives
 No. 2  and 3, the  maximum time required for institutional controls  could  be as  high as 150
 ±50 years (for inorganic contaminants in  the Southwest  Area).   For  Alternative No. 4,
 institutional controls would be required in the Southwest Area for up to about 60 +/- 20 years.

Area of Institutional Controls. Inorganic exceedances of cleanup  standards define  the area
 required for institutional controls, because inorganic constituents have migrated further than
 organic constituents in the  OH  Site vicinity.   Simulation  results  used to estimate inorganic
 contaminant transport  are  summarized  in  the  following paragraph. Inorganic  transport
 simulation results are somewhat uncertain because of complex transport conditions at the OH
 Site  that are difficult to model and because of uncertainties in the distribution  of inorganic
 contamination.

For  Alternative No. 4, groundwater  with inorganic contaminants above cleanup standards
 would be contained at the approximate downgradient extent of currently known contamination.
This would define the area requiring institutional controls for Alternative No. 4. In Alternatives
No. 2 and 3, the inorganic constituents could potentially travel up to 600 feet (Northwest Area)
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 or 1,000 +/- 500 feet (Southwest Area) further than the current extent of contamination. This
 maximum extent would define the area requiring institutional controls for Alternatives No. 2
 and 3.  In Alternative No. 1, inorganic constituents would  not  reach  equilibrium and stop
 migrating until after the landfill source was depleted (likely to be many decades).  After  the
 landfill source is depleted, the time  to reach cleanup  standards would be similar to  that
 presented for Alternative No. 2.  Because the time until the source is depleted is unknown,  the
 maximum extent of the area requiring institutional controls is not known and cannot be reliably
 projected.  This would create significant challenges in administration of institutional controls
 under Alternative No.  1.  For any of the alternatives,  monitoring  data  could indicate  that
 institutional controls would be required over a larger or smaller area than currently estimated.

 Monitoring. All of the alternatives would rely on groundwater monitoring to varying degrees
 to  ensure that institutional  controls are  adequate  to  prevent  exposure  and that engineering
 control systems  are  working  properly.  The OH Site is  in a  highly complex geologic
 environment. As a result, detecting contaminant migration  may be  difficult in some  areas.
 Alternative No. 4 relies on groundwater monitoring the least. Alternatives No. 2 and 3 rely on
 monitoring considerably more than Alternative  No. 4 because of the need to closely monitor  the
 extent of contamination and the progress of natural attenuation.  Alternative No. 1 relies  on
 groundwater monitoring much  more than the other  alternatives for  two reasons.  First,  the
 magnitude of additional releases from the landfill would need to be monitored to determine if
 offsite conditions were deteriorating  significantly.  Second,  extensive  offsite  groundwater
 monitoring  would  be  needed to  determine  how far  that  the uncontrolled  groundwater
 contamination was migrating for implementation of institutional controls.
   7.4 Reduction of Toxicity, Mobility, and Volume Through Treatment

This evaluation criterion addresses the statutory preference for selecting remedial actions that
permanently  and significantly reduce toxicity, mobility, or volume through treatment.  This
criterion is evaluated through treatment processes used and materials treated; the amount of
hazardous materials destroyed or treated; expected reductions in the toxicity, mobility, and
volume; irreversibility of the treatment; and the type and quantity of treatment residuals.

Because of uncertainties in the location, quantity, and flow characteristics of leachate within the
landfill, it is not possible to estimate with certainty the total (or percentage) volume of leachate
removed from the landfill for each of the alternatives. It is also not possible, primarily due to
uncertainties  in the distribution  of groundwater  contamination, to  precisely  evaluate the
percentage of contaminants removed from the aquifer. However, based on estimated treatment
plant  influent flow rates and concentrations,  quantities  of constituents removed through
collection/extraction can be estimated.
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 Table 12  presents  the  anticipated  mass  of  organics  and  inorganics  removed  through
 collection/extraction of liquids in each alternative.  Similarly, Table 13 presents .the estimated
 mass of treatment residuals generated at the onsite treatment facilities.  These numbers are
 adequate for comparative purposes, although they likely overestimate the  total magnitude of
 mass removed and residuals generated over the 30-year period. EPA assumed, in estimating
 these mass values, that the quantity and quality of inflow to the treatment plant would remain
 constant over the 30-year treatment period.  However, it is likely that the quantity of liquids and
 the influent concentrations would eventually decrease over time in the perimeter liquids control
 system (Alternatives No. 2,  3, and 4), interior leachate extraction wells (Alternatives No. 1
 and 3), and groundwater extraction system (Alternative No. 4).

 As shown in Table 12, Alternative No. 3 would remove significantly larger volumes of volatile
 organic compounds and semivolatile organic compounds (1.5 to 6 times more) than the other
 alternatives due to interior leachate extraction. Alternative No. 4B would  remove the largest
 volume of inorganic constituents (2.7 to  11 times more than  the other alternatives). If the
 option  that incorporates Alternative No. 3 into Alternative No. 4 were  considered, it would
 result in the largest volume of constituents removed (this option is not represented in Table 12).

 Alternatives No. 2 and 4A with the  sanitary sewer discharge option generate the least treatment
 residuals  (Table 13). Alternatives  No. 2 and 4A generate between 3.8 times less treatment
 residuals (than Alternative No. 1) and 10.3 times less treatment residuals (than Alternative No.
 4B aquifer injection, irrigation, or surface water discharge options).

 All of the alternatives would use the existing leachate treatment plant to treat landfill liquids to
 County Sanitation Districts of Los Angeles County discharge  standards.   The treatment
 processes would not remove all  landfill liquid contaminants,  as this  is not required by the
 discharge standards. However, those constituents remaining in the treated  water would be
 further treated at County Sanitation Districts of Los Angeles County sanitary sewer treatment
 facilities using an activated sludge process. This treatment would remove most of  the organic
 and inorganic constituents.  The treatment performed at both the onsite leachate treatment plant
 and the County Sanitation Districts of Los Angeles County sanitary sewer facilities would be
 irreversible.
                           7.5  Short-term Effectiveness

Several factors are addressed in evaluating short-term effectiveness of the remedial alternatives,
including potential short-term risk to the community during implementation, threats to workers
during remedial actions, and potential adverse  environmental  impacts from construction and
implementation.
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Table 12
Comparisons of Contaminants Removed Through Liquids Collection/Extraction
Reduction in Toxicity, Mobility, and Volume of Contaminants Through Treatment
On Site Final Record of Decision
Alternative
1
2
3C
4AC
4BC
Total
Flow Rate
(gpm)
5.5
135
155
501
755
Alternative-Specific
Flow Rate
(gpm)
5.5
135
20.5
366
620
Volatile and Semivolatile
Organic Constituents
Annual
(tons/yr)
1.3
0.4
4.6
0.4
0.5
30-Year Totalb
(tons)
40
11
63
12
16
Total Organic Materials8
Annual
(tons/yr)
43
79
230
81
82
30-Year Totalb
(tons)
1,290
2,370
4,780
2,430
2,460
Total Inorganic Constituents"
Annual
(tons/yr)
93
160
620
350
1,030
30-Year Totalb
(tons)
2,790
4,800
11,450
10,500
30,900
'Organic (humic) materials removal was calculated based on the influent TOC. Inorganic constituent removal was calculated based on the estimated influent
TDS (for Alternatives No. 2 and 4 an assumed baseline TDS of 500 mg/L was subtracted from the influent TDS in the calculation).
b Assumes that the estimated flow rates and influent concentrations remain constant throughout the 30-year period, except for Alternative No. 3 where the
assumed flow rate decreases over tune in the same manner as described for the costing (5 years at 20.5 gpm, 10 years at 10.25 gpm, and 15 years at 2 gpm).
= The Alternatives No. 3 and 4 annual and 30-year totals incorporate the Alternative No. 2 values.
SCO10019175.XLS

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Table 13
Comparisons of Treatment Residuals Generated"
Reduction in Toxicity, Mobility, and Volume of Contaminants Through Treatment
Oil Site Final Record of Decision
Alternative
1
2
3C
4A - Sewer Discharge0
4A - Aquifer Discharge0
4A - Surface Water/Irrigation Discharge0
4B - Sewer Discharge0
4B - Aquifer Discharge0
4B - Surface Water/Irrigation Discharge0
Total
Flow Rate
(gpm)
5.5
135
155
501
501
501
755
755
755
Alternative-Specific
Flow Rate
(gpm)
5.5
135
20.5
366
366
366
620
620
620
Waste Sludge
Annual
(tons/yr)
17
2.0
72
2.0
17
17
15
42
42
30-Year Total"
(tons)
510
60
880
60
510
510
450
1,260
1,260
Waste Granular Activated Carbon
Annual
(tons/yr)
3.3
3.3
9.5
3.3
8.3
8.3
13
13
13
30-Year Total"
(tons)
100
100
200
100
250
250
390
400
400
a The treatment residuals generated are primarily from organic material.
Assumes that the estimated flow rates and influent concentrations remain constant diroughout the 30-year period, except for Alternative No. 3 where the
assumed flow rate decreases over time in the same manner as described for the costing. (5 years at 20.5 gpm, 10 years at 10.25 gpm, and 15 years at 2 gpm).
c The Alternatives No. 3 and 4 annual and 30-year totals incorporate the Alternative No. 2 values.
SCO10019176.XLS

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 Risk to Community During Remedial Action Implementation. Effects on the community
 during remedial actions are related to risks that result from implementation, such as dust during
 excavation or construction, increased vehicular traffic, air quality impacts from the release of
 gas, and noise.

 Because there are no significant components to construct, Alternative No. 1  would have the
 fewest short-term, construction-related impacts.  Installation of the perimeter liquids control
 system in  Alternative No. 2  would slightly increase noise, dust, and vehicular traffic.
 Construction activities would primarily be onsite.  Releases of landfill gas to the atmosphere
 could occur during excavation of the extraction trench but should not  pose a risk to  the
 community due to monitoring and implementation of mitigation measures to reduce emissions,
 as necessary.  Effects to the community under Alternative No. 3 would be similar to, or slightly
 increased over, Alternative No. 2 because of installation of extraction wells within the waste
 prism.

 Alternative No. 4 would present significantly greater impacts to the community because of the
 large-scale construction activities associated with installation of numerous extraction wells and
 conveyance systems throughout the surrounding neighborhoods. The greatest impacts would be
 in residential neighborhoods in the Southwest Area, where construction activities  would occur
 in streets, sidewalks, and driveways.  These activities are expected to cause significant increases
 in noise and dust from drilling and trenching operations, as well as significant disruptions to
 traffic flow patterns. There is also the potential for spills or leaks of contaminated  groundwater
 in the neighborhoods under this alternative.

 Protection of Workers During Remedial  Action.  There is a potential for adverse health
 effects on  workers from exposure to hazardous substances during construction of any of the
 alternatives.  If activities  adhere to the site-specific health and safety plan and all regulatory
 requirements, this potential is minimized.  Alternative No. 3 has a greater risk of exposure than
 the other alternatives because of the extensive installation of leachate  extraction wells into  the
 waste prism.

 Construction-related accidents and injuries would likely increase in proportion to the amount of
 activities. As such, Alternative No. 4 has the most construction activities and thus would have
 the highest potential for accidents and injuries.  Alternative No. 1 has  the least construction of
 the alternatives and  therefore would  likely result in  the  fewest  accidents and  injuries.
 Alternatives  No. 2  and 3  are  fairly  similar in  the  magnitude  of construction,  although
 Alternative No. 3 does add extraction wells and  conveyance systems  for interior leachate
 extraction. These two alternatives have significantly more construction than Alternative No. 1
 and significantly less construction than Alternative No. 4.

 Time Until Remedial  Action Objectives Are Achieved.  In general,  the remedial action
 objectives relate to protection of human health and the environment by preventing exposure to
Oil Site Final Record of Decision                                              Page 1-101
Part I - Decision Summary                                              scoiooi92D3.DOC

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 landfill-related contaminants and preventing the release of landfill-related contaminants to the
 media of concern.

 Short-term remedial action objectives  for groundwater would be  met when  institutional
 controls, which reduce the potential for exposure, were activated.

 Long-term  (permanent)  remedial action objectives  for  groundwater would be met when
 groundwater contaminant levels, through a combination of natural attenuation, perimeter liquids
 control, and control of groundwater beyond the landfill boundary (depending on the alternative),
 reach cleanup standards and institutional  controls are no longer necessary. EPA used modeling
 of contaminant transport and the natural attenuation processes to estimate the approximate time
 to reach cleanup standards and the distance contamination would travel during that time.  These
 results should be viewed only as tools for comparing and contrasting the relative merits of each
 alternative.  In general, the modeling is somewhat conservative and likely gives values that are
 closer to upperbound estimates for times and distances (especially for inorganic constituents).
 Local variability in the landfill source or hydrogeologic parameters may result in contaminants
 actually reaching cleanup standards sooner or later and migrating shorter or longer distances
 than predicted by the model.

 Table 11  shows the  estimated  times until cleanup  standards  are achieved based on the
 simulation results.  As shown in the table, the time to reach cleanup standards in Alternative
 No. 1 is unknown.  However, the time will likely be many decades longer than the times
 estimated for Alternatives No. 2, 3, or 4.  There is a considerable reduction in the time to meet
 cleanup standards for inorganic constituents in groundwater in Alternative No. 4 (ranging from
 20 to 60 +/- 20 years)  compared to Alternatives No. 2 and 3 (ranging from 56 to 150 ±50 years).
 EPA's  modeling indicates that  there would be no difference in the  time  to meet cleanup
 standards among Alternatives No. 2, 3, and 4 for organic constituents.

 Environmental  Impacts.   Potential  environmental   impacts associated  with   remedy
 implementation include releases of landfill gas to the air, soil erosion and silt buildup, and loss
 of wildlife habitat. Potential landfill gas releases and erosion and siltation impacts can be
 mitigated through proper  placement  of control  measures  and regular inspection  during
 construction to maintain their effectiveness.  Overall, all the alternatives are considered to have
 equal construction-related environmental impacts.
                               7.6 Implementability

This evaluation criterion addresses the technical feasibility,  the availability of services and
materials, and the administrative feasibility of each of the alternatives. The technical feasibility
includes the ability to construct and operate the technology and the relative ease of undertaking
the remedial action and the ability to monitor its effectiveness. The availability of services and
materials  addresses the availability of the necessary equipment,  technologies, services, and
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 other resources to construct the remedial action. The administrative feasibility considers the
 activities needed to coordinate and obtain approvals from other agencies.

 Technical Feasibility.  All of the alternatives are technically feasible and implementable.
 Fairly  standard and proven  construction techniques could  be used  to install the  remedial
 components  associated  with  the   alternatives.    The  remedial measures  could  employ
 technologies, services, and materials  that are proven, reliable, and  generally available; no
 significant technical difficulties are  anticipated for construction of the remedial components.
 The analysis of individual alternatives, described below, identifies some issues to be clarified.

 Alternative No. 1  would be the easiest to implement because it requires the fewest construction
 and operational elements. Alternatives No. 2, 3, and 4 all include the installation of a perimeter
 liquids control system around portions of the landfill.  Construction of an extraction trench and
 installation of extraction wells may be difficult because of existing belowgrade utilities, buried
 refuse along the trench alignment, and limited access between the landfill and the perimeter of
 the site. These difficulties may increase costs; however, the cost increase would be the same for
 all three alternatives.

 Alternative  No. 3  includes  installation  of  extraction  wells  within  the  landfill.  Some
 construction difficulties are anticipated, but wells are implementable. Landfill gas and leachate
 extraction wells have previously been installed into the landfill and pumped at the OH Site. It
 may  be difficult  to locate the extraction wells in the desired locations  because of access
 difficulties.  Because of the increased construction and operation issues associated with these
 wells, Alternative No. 3 is considered to be slightly less implementable than Alternative No. 2.

 Alternatives No. 4A and 4B  are considered the most  difficult to  implement,  given  the
 significant construction and operational requirements associated with the offsite extraction and
 conveyance systems. Construction in the residential areas adjacent to the landfill would require
 considerable  more accommodation and coordination with local residents.   Anticipated
 significant construction difficulties include access and availability of rights-of-way, presence of
 buried utilities, proximity to homes, and extensive disruption to the community.

 Availability of Services and Materials. All alternatives could employ technologies that have
 proven reliable either at the OH Site or other sites.  The equipment and personnel necessary to
 design  and construct the alternatives are  considered  generally available for  projects of this
 magnitude from a number of contractors, although some specialty contractors  would likely be
 needed.  All alternatives are considered approximately equal when considering the availability
 of services and materials.

Administrative Feasibility.   All alternatives would require administrative effort, including
implementation  of institutional controls and  coordination with other offices and  agencies.
Institutional controls are discussed above. In summary, institutional controls would be the most
difficult to implement  in Alternative No. 1  because the maximum extent of the inorganic
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 contamination (and  thus the area  requiring institutional  controls)  is  unknown,  and the
 institutional controls would be required for the longest time. The institutional controls would
 be the easiest to implement in Alternative No. 4 because the area requiring institutional controls
 matches the current extent of contamination, and the controls would be needed for the shortest
 time.  Institutional controls would be slightly more difficult to administer under Alternatives
 No. 2 and 3 than under Alternative No. 4.

 Outside of institutional controls, Alternative No. 1 is considered the easiest to administratively
 implement. The existing leachate treatment  plant already has a discharge permit, and the
 remaining permits or approvals are not anticipated to require significant coordination among the
 approval agencies.

 Alternatives No. 2 and 3 would use the existing treatment plant to treat additional quantities of
 landfill liquids collected at the perimeter or from within the landfill.  These alternatives also
 assume discharge to the sewer. A revision to the existing discharge permit would be needed to
 address the increased volume of liquids to be discharged.

 Alternatives No. 4A and 4B would require the construction of extraction wells and conveyance
 systems in off site areas. Gaining  access and approval for the  construction  may  prove
 problematic and cause significant delays.  In the event voluntary access could not be  acquired,
 access to the private properties would be sought through legal mechanisms, potentially a time-
 consuming and relatively unpredictable process. In addition, these alternatives would require
 extraction and discharge of significant amounts of groundwater. Acquisition of the necessary
 permits to pump and discharge  the  groundwater may be difficult.  These activities would
 require considerable coordination with the Regional Water Quality Control Board and  the water
 districts that oversee water rights. Because of these reasons, Alternatives No. 4A and 4B would
 be the most difficult to implement administratively.
                                       7.7  Cost

A summary of estimated costs for the four alternatives is presented in Table 14.  The table
breaks down the capital, operation and maintenance, and net present worth cost estimates by
costs common to all alternatives (interim operations and maintenance) and those costs that are
alternative-specific.  An overview  of the cost analysis performed,  as  well as detailed cost
breakdowns for each alternative, are presented in the Feasibility Study Report (EPA, 1996).

A cost component common to all alternatives is the interim operation and maintenance costs to
operate the site  for an estimated 5 years while the systems required by the Gas Control and
Cover  ROD and new systems required by this ROD are being implemented.  This component
totals $46,350,000.  The Feasibility Study Report (EPA, 1996) provides additional detail on the
derivation of this cost.
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I
Table 14
Comparison of Costs
(in thousands)
OH Site Final Record of Decision
Alternative
1
2
3
4A - Sewer Discharge
4A - Aquifer Discharge
4A - Surface Water Discharge
4A - Irrigation Discharge
4B - Sewer Discharge
4B - Aquifer Discharge
4B - Surface Water Discharge
4B - Irrigation Discharge
Capital Cost
$ 2,800
$ 17,600
$ 25,500
$ 30,100
$ 35,600
$ 35,000
$ 35,600
$ 34,900
$ 46,200
$ 43,700
$ 44,300
Annual O&M
$ 6,030
$ 6,360
$ 7,850
$ 8,680
$ 10,360
$ 10,550
$ 10,590
$ 9,510
$ 12,210
$ 12,190
$ 12,230
Net Present Worth
Interim
O&M
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
$ 46,350
Capital
Cost
$ 2,800
$ 17,600
$ 25,500
$ 30,100
$ 35,600
$ 35,000
$ 35,600
$ 34,900
$ 46,200
$ 43,700
$ 44,300
Present
Worth
O&M
$ 92,700
$ 97,800
$ 120,700
$ 133,400
$ 159,300
$ 162,200
$ 162,800
$ 146,200
$ 187,700
$ 187,400
$ 188,000
Total
Net Present
Worth
$ 142,000
$ 162,000
$ 193,000
$ 210,000
$ 241,000
$ 244,000
$ 245,000
$ 227,000
$ 280,000
$ 277,000
$ 279,000
     SCO100192EB.XLS

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 As shown in Table 14, the operation and maintenance costs are by far the largest portion of
 the estimated costs for each alternative.  As would be expected, Alternative No. 4 has the
 highest  alternative-specific capital  cost, annual operation and maintenance costs, and net
 present  worth costs.  The estimated Alternative No. 4 net present worth costs range from
 $210  to $279  million,  depending on  the  extraction and discharge  option (Table 14).
 Alternative No.  1  has the  lowest  estimated  total net present worth cost,  $142 million.
 Alternative No. 2, at $162 million, costs an additional $20 million over  Alternative No. 1.
 Alternative No. 3 costs an estimated $193 million, an additional $31 million over Alternative
 No. 2.  As  described throughout Section 7, significant additional benefits would be realized
 in choosing Alternative  No.  2 over Alternative No. 1,  at an additional cost  of around
 $20 million (a 14 percent  increase).  On the other hand, substantial additional benefits are not
 apparent in choosing either Alternative  No. 3 or 4 over Alternative No.  2, at an estimated
 increase in costs of between $31 and $119 million.

 Certain components of the cost estimates may include overlap with costs associated with the
 Gas Control and Cover ROD.  As implementation of both this remedy and landfill gas control
 and landfill  cover systems progresses, there would likely be opportunities to realize cost savings
 over the estimates  presented  herein, particularly if the same entity  is implementing both
 components and the design and implementation of both is occurring concurrently.
                               7.8 State Acceptance

In a letter dated September 6, 1996, the State of California (Cal-EPA Department of Toxic
Substances Control) concurred with EPA's selected remedy for the OH Site.
                           7.9 Community Acceptance

EPA received 10 sets of comments from individuals, organizations, and agencies on EPA's
Remedial Investigation, Feasibility Study, and Proposed Plan for this remedy at the On Site.
These comments, and EPA's responses to the comments, are presented in the Responsiveness
Summary in Part II of this ROD.

Some of the comments received from the community expressed support for EPA's proposed
remedy; others did not.  Several of the commentors recommended that EPA select remedial
Alternative No.  3.   EPA has determined  that the preferred alternative presented in the
Proposed Plan (Alternative No. 2 ) is the most appropriate remedy and provides responses to
those commentors that preferred other alternatives in the attached Responsiveness Summary.
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                              8.0 Selected Remedy

 After considering CERCLA's statutory  requirements,  the  detailed  comparison  of  the
 alternatives using the nine criteria, and public comments, EPA, in consultation with the State
 of California, has determined that the most appropriate remedy for the Oil Site is Alternative
 No.  2:  Perimeter Liquids  Control.  The selected  remedy addresses liquids control and
 contaminated groundwater as well as long-term operation and maintenance of environmental
 control facilities at the landfill. Liquids will be controlled at the landfill perimeter to prevent
 migration of contaminants to groundwater.  Contaminated groundwater currently beyond the
 landfill perimeter will be allowed to naturally attenuate over time.  This remedy meets the two
 Superfund threshold evaluating criteria, overall protection of human health and the environment
 and compliance with ARARs, and  provides the best balance of the  remaining  Superfund
 evaluation criteria. The major components of the selected remedy for this action include:

 •       Installation of a  perimeter liquids control system in areas  where contaminants  are
        migrating from the landfill at levels that  cause groundwater to exceed performance
        standards.  Contaminated groundwater currently beyond the landfill perimeter would
        be reduced to below cleanup standards through natural attenuation.

 •       Conveyance of the collected liquids to the existing onsite treatment plant.

 •       Onsite treatment of collected liquids  using the existing leachate treatment plant,
        modified as necessary, to handle the new liquids. Discharge of treated liquids to the
        County Sanitation Districts of Los Angeles County sanitary sewer system.

 •       Implementation  of a  monitoring  and evaluation program to ensure  that  natural
        attenuation of the contaminated groundwater is progressing  as anticipated,  to ensure
        that perimeter liquids control system performance standards are being met, and to
        detect future releases of contaminants from the landfill.

 •      Establishment of institutional controls to ensure appropriate future use of the OH Site
       and to restrict groundwater  use  in  the  immediate vicinity of the  OH Site.  The
       institutional controls  will supplement the engineering controls  to prevent or  limit
       exposure to hazardous substances.

 •      Interim operation and maintenance of existing site activities (gas extraction and air dike,
       leachate collection, leachate  treatment, irrigation,  access roads, stormwater  drainage,
       site security, slope repair, and erosion control),  except to the extent that they are
       addressed under the Gas Control and Cover ROD.
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 •     Long-term operation and  maintenance  of all facilities and environmental control
       components at the OH Site, excluding those covered under the Gas Control and Cover
       ROD.

 Figure 18 shows some of the conceptual components of the selected remedy.

 These measures are in addition to EPA's previous decision to build and operate a landfill gas
 migration control system, landfill  cover, and surface water management system, as outlined
 in the Gas Control and Cover ROD.  These components are not reselected or modified in this
 ROD, and remedial design of these  systems is  already underway.  The selected remedy,  in
 conjunction with  the Gas Control  and Cover ROD, addresses all contaminated media at the
 Oil Site.

 EPA will review  the selected remedy no less often than  every 5 years  after the initiation  of
 the remedial action to ensure that  human health and the environment are being protected by
 the implemented remedy. As part  of the review, EPA will evaluate whether the performance
 standards specified in this  ROD remain protective of human health and the environment.
 EPA will continue reviews until no hazardous substances, pollutants, or contaminants remain
 at the Oil Site above levels of concern for human health and the environment.

 The following sections describe the  remedial objectives  and performance standards for the
 various  components of the selected remedy.  Using performance  standards, rather  than
 specifying particular technologies or actions,  allows  for more flexibility during remedial
 design and remedial action. This approach can be much  more efficient and cost-effective  in
 instances where  uncertain or  variable conditions are present,  such as the subsurface
 conditions around portions of the Oil Site.
                  8.1 Perimeter Liquids Control Component

The remedial action objective of the perimeter liquids control component of the selected
remedy is to prevent migration of contaminants from the landfill to groundwater at levels that
impair water quality and/or represent a potential threat to human health and the environment.
The technologies necessary  to  achieve this  objective  and comply with the  performance
standards described below will be selected during remedial design.

8.1.1  Performance Standards and Point of Compliance

Perimeter liquids control will be required  in areas where contaminants migrate from the
landfill at levels causing groundwater  to  exceed chemical  performance standards.   The
chemical performance  standards for  perimeter  liquids control for each contaminant of
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 concern are shown in Table 15. The list of contaminants of concern presented in Table 15
 has been selected from the list of chemicals of potential concern from the Baseline Risk
 Assessment  (Table 3),   based on additional evaluation  of groundwater monitoring  data.
 These standards have been set based on ARARs (state or federal drinking water MCLs, to the
 extent that they are above baseline), as available.  If an MCL is not currently available for a
 specific contaminant of concern, health-based criteria have been used for the performance
 standards.  Compound-specific health-based criteria are  based on either a  cancer risk of
 1 x 10~6 or a noncancer hazard index of 1.

 There are several  segments around  the  landfill perimeter where available groundwater
 monitoring  data indicate that  performance standards  are  being  exceeded.  These  areas
 include:

 •     Along the northwestern perimeter of the South Parcel in the vicinity of Well CDD-13,
       to a depth of approximately 70 feet

 •     Along the northwestern perimeter of the South Parcel in the vicinity of Well OI-24B,
       at a depth of approximately 130 to 150 feet

 •     Along the northwestern perimeter of the South Parcel in the vicinity of Wells OI-19A
       and OI-19C, to a depth of approximately 180 feet

 •     Along the northeastern perimeter of the South Parcel in the vicinity of Well OI-20A,
       to a depth of approximately 170 feet

 •     Along the western perimeter of the  South  Parcel between Wells PE-3 and PE-7, to a
       depth of approximately 200 feet

 •     Along the western perimeter of the South Parcel in the West Aquifer in the vicinity of
       Well OI-18B, at a depth of approximately 280 to 300 feet

 •     At the southwestern corner of the South Parcel between Wells OI-53P and OI-50A to
       a depth of approximately 80 feet

 •     Along the southern boundary of the South Parcel between Wells OI-16A and PE-13 to
       a depth of approximately 175 feet

Perimeter liquids control is  required in  each area where  groundwater  exceedances  of
performance standards have been confirmed or are confirmed in the future.  At a minimum,
perimeter liquids control is  required  in the aforementioned areas.   The remedial design
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Table 15
Perimeter Liquids Control Chemical Performance Standards and Groundwater Cleanup Standards
ON Site Final Record of Decision
Contaminant of Concern
State or Federal
ARARd
(ug/L)
Health-Based
Concentration
(ug/L)
Selected Performance
Standard and Cleanup
Standard
(ug/L)
ORGANICS
1,1,1-Trichloroethane
1 ,1 ,2-Trichloroethane
1,1-Dichloroethane
1,1-Dichloroethylene
1 ,2,4-Trichlorobenzene
1 ,2-Dichlorobenzene
1 ,2-Dichloroethane
1 ,2-Dichloroethylene, cis-
1 ,2-Dichloroethylene, trans-
1 ,2-Dichloropropane
1 ,3-Dichloropropene, cis-
1 ,3-Dichloropropene, trans-
1 ,4-Dichlorobenzene
1 ,4-Dioxane
2-Butanone
4-Methyl-2-pentanone
Acetone
Aldrin
3enzene
BHC, beta-
BHC, gamma- (Lindane)
bis(2-Ethylhexyl)phthalate
Butylbenzylphthalate
Carbon tetrachloride
Chlordane
Chlorobenzene
Chloroform
Di-n-octylphthalate
Dibromochloromethane
Endrin
Ethylbenzene
Heptachlor
Heptachlor epoxide
Methoxychlor
Methylene chloride
Pentachlorophenol
Styrene
Tetrachloroethylene
Toluene
Trichloroethylene
rrichlorofluoromethane
Vinyl chloride
Xylenes, total
200
c
c
6
70
600
0.5
6
10
c
0.5
0.5
c





1

0.2
4
100
0.5
0.1
70
100

100
2
700
0.01
0.01
40
5
1
100
5
150
5
150
0.5
1,750
1,473
0.32
1,000
0.07
23
464
0.2
77
153
0.26
0.13
0.13
0.72
1.6
2,464
198
768
0.0005
57.89
0.05
0.06
5.6
6,034
0.25
0.06
51
0.27
9.3
1.0
10
704
0.02
0.01
162
6.2

0.01
0.74
683
2.1
1,641
0.03
1,885
200
t
i
6
70
600
0.5
6
10
i
0.5
0.5
c
1.6
2,464
198
768
0.00053
<
0.05
0.2
i.
100
0.5
0.1
70
100
9.3
100
2
700
0.01
0.01
40
5
1
100
5
150
5
150
0.5
1,750
INORGANICS
Aluminum
Ammonia
1,000

36,500
35,405
1,000
35,405
        PageI-110
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Table 15
Perimeter Liquids Control Chemical Performance Standards and Groundwater Cleanup Standards
OH Site Final Record of Decision

Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium VI
Chromium III
Copper
Cyanide
Fluoride
Lead
Manganese
Mercury
vlickel
Nitrate (As NOs)
Nitrite (as N)
Selenium
Thallium
Vanadium
Zinc
State or Federal
ARARd
6
50
1,000
4
5
50
50
1,300
200
1,990°
15

2
100
10,000
1,000
50
4°


Health-Based
Concentration
15
0.05
2,555
0.02
18
183
36,500
1,351
730
2,190

1830°
11
730
58,400
3,650
183

256
10,950
Selected Performance
Standard and Cleanup
Standard
6
50
1,000
t
c
«
50
50
1,300
200
1,990°
15
1830°
4
100
10,000
1,000
50
4°
256
10,950
"Present analytical techniques are limited to 0.05 ug/l. This value may need to be adjusted in the future if
analytical techniques do not improve.
'These values are baseline concentrations as presented in the Draft Remedial Investigation Report (EPA, 1994c).
These baseline concentrations are higher than their respective MCLs. Therefore, in accordance with Title 22,
CCR, Section 66264.94, the baseline concentrations are used.
This value has been adjusted from the one presented in the Risk Assessment appendix (Appendix B) of the
Feasibility Study Report (EPA, 1996) because of newer reference dose data.
dThe most stringent of either the state or Federal MCL is listed.
SCO1001916E.XLS
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 investigation must be sufficient to identify any additional areas where groundwater exceeds
 performance standards.

 In accordance with the ARARs (presented in Section 9), the point of compliance is at the
 downgradient boundary of the waste management unit.  The monitoring points to be used to
 determine compliance shall  be identified  during remedial design.   Hydraulic control, or
 potentially other measures acceptable to EPA, must be used to demonstrate that the perimeter
 liquids control system is complying with the remedial action objective.  In areas that do not
 have groundwater  contaminant concentrations  in  excess of the  chemical  performance
 standards, compliance will be demonstrated by continued detection monitoring to ensure that
 future releases resulting in  groundwater concentrations  above the chemical  performance
 standards do not occur.

 The perimeter  liquids control system will need to operate until releases  are  no longer
 occurring that cause  groundwater concentrations in exceedance of chemical  performance
 standards or, if the perimeter control system uses hydraulic control, until liquids are no longer
 present in the perimeter liquids control system.  If portions of the perimeter  liquids control
 system meet these requirements, those portions could  be shut down  while  other portions
 continue to operate.

 8.1.2 Contingency Measures

 If the perimeter  liquids control system  is not  demonstrated  to be  effective, appropriate
 measures shall be taken to bring the system into compliance. Examples of such measure may
 include, but are not  limited to, any of the following, subject  to approval by EPA:  more
 closely spaced extraction wells to facilitate perimeter liquids control, higher extraction rates
 to increase hydraulic  control, installation of a cutoff well or extraction trench in place of
 wells, or extraction from inside the waste prism to enhance control. EPA may  also determine
 that  more extensive  groundwater  monitoring  is  required to ensure that  concentrations in
 groundwater are not increasing.
                       8.2 Liquids Treatment Component

The existing leachate treatment plant, modified as necessary, shall be used to treat the liquids
collected as part of the selected remedy.  The treated liquids shall be discharged to County
Sanitation  Districts of  Los Angeles  County sanitary sewer system.   Based  on existing
monitoring data collected from the landfill perimeter and the existing industrial wastewater
discharge permit issued by County Sanitation Districts of Los Angeles County (CSDLAC,
1994), only minor modifications to  the treatment plant would be required.   In  addition,
mitigation  measures  shall be designed to improve treatment plant aesthetics. However,
because the selected remedy will result in increased discharge volumes, the existing permit
will need to be modified. If County Sanitation Districts of Los Angeles County changes the
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 wastewater discharge requirements, more extensive treatment plant modifications may be
 necessary.

 Off-gas or air emissions from the treatment plant shall be conveyed through the existing or a
 modified foul-air  system to  the existing flare  or  the  thermal destruction facility (to be
 constructed under the Gas Control and Cover ROD) for treatment.

 8.2.1 Performance Standards and Point of Compliance

 The performance standards  for effluent from the  treatment plant shall be the discharge
 requirements outlined in the existing discharge permit (Table 16).  If County Sanitation
 Districts of Los Angeles County revises the discharge limits, the new discharge limits shall
 supersede the performance standards listed in Table 16.

 County Sanitation Districts of Los Angeles County shall determine the point of compliance
 as part of the  industrial wastewater discharge  permit.  Currently, all effluent from the
 treatment plant is held for batch discharge following testing; the point of compliance is the
 effluent discharge tank.  If continuous discharge is allowed in the revised permit, the point of
 compliance will likely be the discharge weir.

 8.2.2 Contingency Measures

 If performance standards cannot be met by the existing plant, additional  treatment processes
 shall be installed, as necessary, to ensure compliance with the performance standards.
                                8.3 Groundwater

The remedial action objectives for groundwater cleanup  under the selected remedy are to
reduce contaminant  concentrations  in groundwater to below  cleanup  standards through
perimeter liquids control and natural attenuation and to prevent exposure to contaminated
groundwater through implementation of institutional controls.  Institutional controls are
discussed below in  Section 8.5.1.  EPA believes that perimeter liquids control and natural
attenuation will be sufficient to reduce concentrations to cleanup standards. However, if that
is not the case, EPA will implement contingency measures  (described below).

8.3.1  Performance Standards and Point of Compliance

The key element of the groundwater component of the selected remedy is the ability of the
groundwater contamination to naturally attenuate. As part  of the Feasibility Study, EPA used
Oil S ite Final Record of Decision                                            Page 1-113
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Table 16
Effluent Discharge Limits
OH Site Final Record of Decision
Conventional Pollutants
PH
Dissolved Sulfides
Temperature
Discharge Limit (mg/L)
>6 pH units
0.1
140°F
Heavy Metals and Cyanide (Total)
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Silver
Zinc
Cyanide
3
0.69
2.77
3.38
0.69
2
3.98
0.43
2.61
1.20
Priority Organics (Total)
Oil and Grease (per Method 5520B)
Volatile Total Toxic Organics
Semivolatile Total Toxic Organics
Total Identifiable Chlorinated Hydrocarbons (TICH)a
75
1.0
1.0
Essentially None
Radioactivity
Title 17, CCR, Section 30287: Concentration of any radionuclide: 400 picoCuries per liter above
>ackground; Total: 1 curie per year.
aTICH are comprised of: aldrin, dieldrin, chlordane (cis & trans), trans-nonarochlor, oxychlordane,
leptachlor, and heptachlor epoxide, DDT and derivatives (p, p', and o, p' isomers of DDT, DDD and DDE),
endrin, HCH (sum of a, b, g, d, isomers of hexachlorocyclohexane), toxaphene, polychlorinated biphenyls.
 Page 1-114
SCO10019172.DOC

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 an analytical  model to evaluate the effect of natural attenuation on reducing groundwater
 contaminant concentrations.  Although the numbers generated by the model are not expected
 to  be extremely precise, they do provide a rough  guideline with which to evaluate  the
 progress  of natural attenuation.   Thus, the performance  standard  for  the groundwater
 component of the selected remedy is for contaminant concentrations  in groundwater to be
 reduced to below the cleanup standards (Table 15) through natural attenuation in accordance
 with the approximate times and distances provided in Table 17.

 Table 17 provides estimates of approximate natural attenuation times and migration distances
 for both organic and inorganic constituents in different areas and units around the OH Site.
 Table 17 indicates areas that were not specifically modeled by EPA; the values presented are
 extrapolated from other areas that were modeled. In these cases, additional evaluation during
 remedial design may be warranted. Additional definition of some of the groundwater plumes
 may also be necessary during remedial design.

 In accordance with the ARARs (presented in Section 9), the point of compliance is at the
 downgradient boundary of the  waste management unit.  EPA shall identify the monitoring
 points to  be used to determine compliance during remedial design.  Groundwater cleanup
 standards identified in Table 15 shall be attained in groundwater at the point of compliance.

 Groundwater  monitoring  and evaluation  shall  be  performed  to  determine  if  natural
 attenuation is  progressing approximately as predicted. The specifics of the monitoring and
 evaluation program will be determined during remedial design; at a minimum, this program
 shall include procedures for well-by-well and plumewide evaluation, as described below.

 For groundwater that is currently contaminated above cleanup standards, statistical methods
 shall be used to evaluate monitoring data on both a well-by-well basis and a plumewide basis.
 If the well-by-well  analysis indicates significantly  increasing  concentrations,  additional
 evaluation will be required and additional monitoring  may be necessary in the vicinity of the
 well.

 The plumewide analysis will be compared to the times and distances provided in Table 17 to
 ensure that concentrations in the overall plume are reducing as expected and that higher-than-
 expected downgradient contaminant migration is not occurring. If either of these criteria are
 not  met,  more  detailed  evaluation will be required and contingency measures shall  be
 implemented, if EPA determines that they are necessary. General contingency measures are
 discussed  below.

 Any concentration increases in  groundwater downgradient of existing contamination should
 not exceed the time  and  distance expectations listed  in Table 17. Increases that are  not in
 accordance with Table 17 will warrant additional evaluation.  Contingency measures shall be
 implemented if EPA determines that they are necessary.
Oil Site Final Record of Decision                                            Page 1-115
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OQ
 O>
Table 17
Approximate Time and Migration Distances to Reach Cleanup Standards in Groundwater Under the Selected Remedy
Oil Site Final Record of Decision
Area
Northwest Area - Shallow Units
Northwest Area - Deeper Units
Southwest Area - Shallow Units
Southwest Area - West Aquifer
Eastern Area
Organic Constituents8
Years
12
12b
34 (average0)
34b
18
Distance (feet)
0
0
200
200
0
Inorganic Constituents3
Years
56
56b
About 1 50 years +/- 50 yearsd
Not Applicable
56b
Distance (feet)
600
600
About 1 ,000 feet +/- 500 feetd
Not Applicable
600b
aThese approximate times and distances should be considered as general guidelines for evaluating the progress of natural attenuation and should not be considered
as precise time frames for remediation, additional evaluation during remedial design may be warranted. The distances listed refer to distances beyond the current areas
of contamination (shown in Figure 20).
bModeling of natural attenuation was not performed specifically for this area; estimated times are extrapolated from other areas. Additional
evaluation may be warranted during remedial design in these areas.
"Simulations were performed in different portions of the Southwest Area and 34 years represents the average of these simulations.
"Note that uncertainty in the distribution of inorganic contamination and complex groundwater flow conditions (especially over longer times and with greater distances
from the landfill) leads to uncertainty in the simulation results, thus a range of years and distances is shown for inorganic constituents in the Southwest Area.
        SCO1001916F.XLS

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 For groundwater that is currently not contaminated and not immediately downgradient of
 existing contamination, cleanup standards should not be exceeded.  Confirmed exceedances
 of cleanup standards in such areas will warrant additional evaluation. Contingency measures
 shall be implemented if EPA determines that they are necessary.

 8.3.2  Contingency Measures

 If, during implementation of the selected remedy, it is demonstrated that natural attenuation is
 not progressing as expected or additional  exceedances of cleanup standards are confirmed in
 previously clean  areas,  appropriate actions  will  be  required  to  meet  the performance
 standards. Examples of contingency measures include, but are not limited to, the following,
 subject to approval by EPA:

 •      Additional groundwater monitoring to evaluate the significance of further migration
 •      Enhanced perimeter liquids control in the area(s) of concern
 •      Expanded institutional controls over a larger area
 •      Active groundwater remediation measures (e.g., focused groundwater pumping)

 If contingency  measures  represent a significant departure from the selected remedy, a ROD
 amendment or Explanation of Significant Differences may be appropriate.
                         8.4 Environmental Monitoring

To ensure that the performance standards are met for all components of the selected remedy
for as long as contamination remains  onsite, a  long-term monitoring  program shall  be
designed and implemented. The monitoring program is intended to meet several objectives,
including:

•      Assess compliance with the chemical performance standards and cleanup standards
•      Monitor the effectiveness of the perimeter liquids control system
•      Detect additional releases of contaminants from the landfill
•      Monitor the progress of natural attenuation in groundwater
•      Monitor effluent chemical concentrations from the treatment plant

Details of the monitoring program shall be described in a monitoring plan to be submitted for
EPA approval during remedial design. Additional information on various components of the
monitoring program is included above in Sections 8.1  and 8.3, as well as in the following
sections.
Oil Site Final Record of Decision                                           Page 1-117
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 8.4.1 Detection Monitoring

 As described in the ARARs section below (Section 9), a detection monitoring program shall
 be applied to areas at the landfill perimeter that are currently unaffected by releases.   A
 monitoring plan shall be developed that outlines the list of parameters to be monitored (this
 list shall, at a minimum, include the contaminants of concern presented in Table 15), and the
 frequencies for collecting samples and conducting statistical analyses.  Sampling shall be
 scheduled to include the times of expected highest and lowest elevation of the potentiometric
 surface.  The list of parameters shall be selected to provide reliable indication of a release
 from the landfill.

 Perimeter liquids control will be necessary in any area in which groundwater concentrations
 exceed chemical performance standards.  Detection monitoring can be re-established after
 perimeter liquids control is no longer necessary in that area.  Detection  monitoring shall
 continue until  the groundwater  has been in  continuous compliance with  the  chemical
 performance standards for a period of 3 consecutive years.

 8.4.2 Compliance/Performance Monitoring

 Four types of compliance or performance monitoring will be needed as part of the selected
 remedy.  For the perimeter liquids control system, the types of monitoring include:

 •      Monitoring contaminant concentrations downgradient of the perimeter liquids control
       system to determine compliance

 •      Monitoring physical conditions downgradient of the perimeter liquids control system
       to determine compliance

 For natural attenuation, the types of monitoring include:

 •      Monitoring of the groundwater contamination to  evaluate the progress of natural
       attenuation (as described above in Section 8.3.1)

 •      Monitoring downgradient of the existing areas of groundwater contamination  to
       ensure that contaminants  are  not moving  at  faster  rates   than  predicted  (see
       Section 8.3.1).

A monitoring plan shall be prepared that  outlines how each of these  types of compliance
monitoring will be performed. The monitoring plan shall comply with the ARARs identified
in Section 9.3.   The monitoring plan shall  detail the locations  of  the  monitoring,  the
frequency of the monitoring, the constituents to be  monitored,  the types  of statistical
Page 1-118                                            Oil Site Final Record of Decision
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 evaluations to be performed, and how the monitoring and evaluation results will be used to
 determine compliance with performance standards.
                            8.5 Additional Components

 This section describes additional components of the selected remedy, including institutional
 controls,  site administration, site security, and operation and maintenance of facilities and
 environmental control systems.

 8.5.1 Institutional Controls

 Institutional controls are nonengineering methods that federal, state, local governments, or
 private parties can use to prevent or limit exposure to hazardous substances, pollutants, or
 contaminants, to ensure the effectiveness of remedial actions.  The selected remedy requires
 institutional controls both on the landfill and in certain areas beyond the landfill boundary.

 Institutional Controls  Within the Landfill Boundary.  The  primary objectives of
 institutional controls within  the  landfill  boundary  are to (1) limit human exposure to
 potentially contaminated materials, (2) prevent trespassing, and (3) protect the integrity of the
 landfill closure  and remedial action components.   Institutional  controls within the landfill
 boundary may include, but are not limited to, deed notices  and  restrictions on construction
 that run with the land; access restrictions including, but not limited to, fencing and warning
 signs; zoning controls;  and well restrictions.   Institutional controls within the landfill
 boundary must prohibit all  activities and uses that EPA determines would  interfere or be
 incompatible with,  or  that  would  in any way  reduce or  impair  the effectiveness or
 protectiveness of this remedy.   Institutional controls shall also  be required for  site-related
 facilities outside of the landfill boundary.

 Institutional Controls Beyond the Landfill Boundary. Institutional controls must also be
 implemented to prevent use of contaminated groundwater as a drinking water supply for the
 duration of the remedy.  Institutional  controls are required in areas where contaminant
 concentrations exceed the chemical performance standards or where they are anticipated to
 exceed performance standards in the future. The exact area where institutional controls  will
 need to be implemented shall be determined during remedial design, as approved by EPA.
 There are currently no known groundwater wells in use within the areas of groundwater
 contamination; all residences, businesses, and industrial facilities within the expected area of
 institutional controls are currently connected to municipal water systems.

Implementation  of institutional  controls  will  need  to be  coordinated with  the  local
Watermasters in the San Gabriel and Central Basins to conform  with existing regulations
governing groundwater use in both groundwater basins in the OH Site vicinity as both basins
Oil Site Final Record of Decision                                             Page 1-119
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are adjudicated. The strict control on groundwater use should help to implement institutional
controls.   Coordination  with  Los Angeles County,  which requires  permits for  well
installation, shall also be required. If deemed necessary, local ordinances may also be used to
limit installation of drinking water wells.

North  Parcel Areas Not  Used as a  Landfill or for Site-Related  Facilities.   EPA
determined that no landfill-related risks are posed by soils in the areas of the North Parcel not
containing landfill-related wastes, nor used for site-related facilities (the "nonlandfill areas").
Therefore, no further  action is required for soils  in the nonlandfill areas.  The Baseline Risk
Assessment (presented as Appendix B in EPA, 1996) did identify potential risks associated
with nonlandfill-related businesses present  on the North Parcel and/or  with the adjacent
Pomona Freeway. State and local authorities may wish to consider such potential risks when
evaluating appropriate use of the nonlandfill areas.  Institutional controls  and, potentially,
engineering controls will be required for contaminated groundwater and, potentially, liquids
control on the North Parcel.

8.5.2  Site Administration

The selected remedy incorporates long-term administration  of site  activities,  including
management of staff, ordering equipment, and performing other administrative functions to
ensure that performance objectives are met.  Specific activities shall be  determined during
remedial design.

8.5.3  Operation and Maintenance of Facilities and  Environmental Control
Systems

The selected remedy includes operation  and maintenance of all facilities and environmental
control systems at the OH Site,  except for those systems covered by the Gas Control and
Cover  ROD.  These  activities,  facilities, and environmental  control  systems include:  the
perimeter liquids control system, groundwater monitoring system, leachate treatment plant,
leachate collection system, gas extraction and air dike system, irrigation system, access roads,
stormwater drainage system, site security, slope repair,  erosion control,  and  site operation
facilities, except to the extent that these activities, facilities, and systems are addressed by the
Gas Control and Cover ROD.

In accordance with ARARs (as presented  in Section 9), the existing leachate collection
system  (or equivalent) will  need to be operated until leachate is no longer generated and
detected or until it is no longer feasible to operate.
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                         8.6 Cost of the Selected Remedy

 The selected remedy was evaluated for cost in terms of capital costs, annual or operation and
 maintenance, and net present worth cost. Capital costs include the sum of direct capital costs
 (such  as construction materials and labor, equipment, sewer connection fees) and indirect
 capital costs (such as engineering, legal, construction management).  Annual costs  include the
 cost for labor, materials, maintenance, energy, and equipment replacement. Net present worth
 costs  include capital costs plus  operation  and maintenance costs over a 30-year period.
 Table  18 summarizes the capital,  annual operation and maintenance, and net present worth
 costs for the selected remedy.

 A cost component common to all alternatives is the interim operation and maintenance costs to
 operate the  site for an estimated 5 years while the systems required by  the Gas Control and
 Cover ROD and new systems required by this ROD are being implemented.  This  component
 totals $46,350,000.  The Feasibility Study Report (EPA, 1996) provides additional detail on the
 derivation of this cost.
     9.0  Applicable or Relevant and Appropriate Requirements
                                    (ARARs)

Section 121(d) of CERCLA, 42 U.S.C. § 9621(d), requires remedial actions on CERCLA
sites to attain (or justify  the waiver of) applicable, or relevant and appropriate, federal and
state environmental or state facility siting requirements.  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 ARARs and that are identified by the
state in a timely manner.  The California Department of Toxic Substances Control, the lead
state agency for the OH  Site, provided potential State ARARs to the EPA as part of this
process.

Applicable  requirements  are those cleanup standards,  standards of control,  criteria, or
limitations that specifically address conditions, circumstances, or activities  at a CERCLA
site. Relevant and appropriate requirements are  those cleanup standards, standards of control,
criteria, or limitations that,  while not directly "applicable" to conditions, circumstances, or
activities at a CERCLA  site, address problems or situations sufficiently similar  to those
encountered at the site that their use is well suited to the site.  A requirement that is not
directly applicable must be both relevant and appropriate, based on site-specific factors, to be
an ARAR.  The criteria for determining relevance and appropriateness are listed in the NCP,
40 CFR § 300.400(g)(2).
Oil Site Final Record of Decision                                           Page 1-121
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Table 18
Selected Remedy Cost Estimate Summary
Oil Site Final Record of Decision
DESCRIPTION
CAPITAL COSTS:
Administration, Institutional Controls, Site Security, and Facility Maintenance:
Perimeter Control System
Landfill Liquids Treatment Capital Costs
Sewer Connection Fees
Postconstruction Environmental Monitoring
Subtotal
Bid and Scope Contingencies @ 30%
TOTAL DIRECT COST
Indirect Costs @ 38.5%
Alternative No. 2 Remedial Design Investigation
TOTAL INDIRECT COST
TOTAL CAPITAL COST
ANNUAL O & M
Administration, Inst. Controls, Site Security, and Fac. Maint.
Perimeter Control System Maintenance
Landfill Liquids Treatment Operation and Maintenance
Postconstruction Environmental Monitoring
Subtotal
Contingencies @ 30%
TOTAL ANNUAL O & M
Capital Costs
Present Worth of O&M (30 yrs @ 5%)
Site Operations During Remedy Implementation (5 years assumed)
TOTAL SELECTED REMEDY NET PRESENT VALUE
Total Cost
$953,000
$6,089,000
$496,000
$301,000
$435,000
$8,274,000
$2,480,000
$10,754,000
$4,160,000
$2,679,000
$6,840,000
$17,590,000
$2,712,000
$720,000
$802,000
$656,000
$4,890,000
$1,470,000
$6,360,000
$17,600,000
$97,800,000
$46,350,000
$161,800,000
       Page I-122
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 Nonpromulgated advisories or guidance issued by federal or state government do not have
 the status of potential ARARs.   Such advisories or guidance, which are  termed  "To-be-
 Considered Material,"  may  be  used during the cleanup process to further the goal of
 protecting human health and the environment.

 ARARs only include substantive, not administrative, requirements, and pertain only to on-
 site matters. Any offsite activities must comply with all  applicable federal, state, and local
 laws, including both substantive and administrative requirements.

 ARARs are identified on a site-specific basis from information about the  chemicals  at the
 site, the actions that may take place at the site, and the features of the site location. There are
 three general categories of ARARs:

 •  Chemical-specific ARARs are numerical values or methodologies that, when  applied to
    site-specific conditions, result in the establishment of numerical values.  They are used to
    determine acceptable concentrations of specific hazardous substances, pollutants, and
    contaminants in the environment. If a chemical is  subject to more than one  numerical
    value or methodology, the most stringent is generally selected.

 •  Location-specific  ARARs are restrictions placed on the concentration of  hazardous
    substances, pollutants, or contaminants  or the conduct of activities solely because they are
    in specific locations, such as wetlands or floodplains.

 •  Action-specific  ARARs are technology- or activity-based requirements or limitations on
    actions taken with respect to hazardous  substances, pollutants, or contaminants.

 EPA's analysis and identification of chemical-specific, location-specific, and action-specific
 ARARs for the selected remedy for the  OH Site followed EPA guidance, including the
 CERCLA Compliance with Other Laws Manual (Interim Final), EPA Office of Solid Waste
 and Emergency Response (OSWER) Directive 9234.1-01, August 1988 (EPA,  1988k), and
 the CERCLA Compliance with Other Laws Manual:  Part n, Clean Air  Act and Other
 Environmental Statues and State Requirements (Interim Final), OSWER Directive 9234.1-02,
 August 1989 (EPA, 1989f).

 The following sections present  the federal and state ARARs identified for  this remedy.
 Federal and state chemical-specific ARARs are discussed in Section 9.1, and are listed in
 Table 19.  Federal and state location-specific ARARs are discussed below in Section 9.2, and
 are listed in Table  20.  Federal and state action-specific ARARs are discussed below in
 Section 9.3, and are listed in Table 21.
Oil Site Final Record of Decision                                            Page 1-123
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T)
I
Table 19
Summary of Chemical-Specific ARARs
Oil Site Final Record of Decision
Citation
Description of Requirement
ARAR
Determination
Comments
FEDERAL ARARs
40CFR§ 141,Subparts
BandG
22 CCR § 66264.94 (c)
Establishes national primary drinking water standards for public
drinking water supply systems (Maximum Contaminant Levels,
or "MCLs").
Requires establishment of groundwater protection standards for
waste management units where releases have occurred;
concentration limits may be set greater than background (up to
the MCL) if it is technically or economically infeasible to
achieve background and the proposed limit will not pose a
substantial hazard to human health or the environment.
Relevant and
appropriate
Applicable
MCLs are relevant and appropriate for groundwater designated as a current or
potential source of drinking water where the more stringent maximum
contaminant level goals ("MCLGs") are not relevant or appropriate. MCLGs are
not appropriate due to the complex hydrogeological setting at the Oil Site, the
minimal risks of exposure, and the limited potential use of the resource. MCLs
for contaminants of concern are listed in Table 15.
EPA selected MCLs that exceed baseline (or health-based limits where no MCLs
are set) as the groundwater protection standard, due to the complex
hydrogeological setting at the Oil Site, the minimal risks of exposure, and the
limited potential use of the resource. The groundwater protection standards are
listed in Table 15. This requirement is applicable (by reference from 22 CCR §
66265.99) to interim status facilities at which groundwater remediation is
necessary.
STATE ARARs
22 CCR §§6443 1,64444
State Water Resources
Control Board Resolution 92-
49 III. G
Porter-Cologne Water Quality
Control Act § 13370.5;
California Government Code
§ 54739
Establishes California primary drinking water standards for
public drinking water supply systems (also known as "MCLs").
Requires cleanup and abatement of discharges to background
water quality, or the best water quality which is reasonable if
background levels cannot be restored.
Pursuant to these authorities, the Los Angeles County Sanitation
District issues Industrial Wastewater Discharge permits setting
discharge limits for concentration of contaminants, temperature,
and volume.
Relevant and
appropriate
where more
stringent than
federal standard
Applicable
Off-site
discharge
requirement
Specific California MCLs are relevant and appropriate where they are more
stringent than federal MCLs. California MCLs that are more stringent than
federal MCLs for contaminants of concern are listed in Table 15.
Applicable to wastes discharged to waters of the state. EPA selected MCLs that
exceed baseline (or health-based limits where no MCLs are set) as the
groundwater protection standard, due to the complex hydrogeological setting at
the OH Site, the minimal risks of exposure, and the limited potential use of the
resource.
Permits are required for discharges to the sanitary sewer, because it is an off-site
activity. Discharges must meet pretreatment standards, presented in Table 16.
Changes to pretreatment standards, or additional flows over the current permit
limit of 24,000 gpd, will require modification of the current permit.
    SC0100192D4.DOC

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Table 20
Summary of Location-Specific ARARs
OH Site Final Record of Decision
Location
Within 200 ft of a
fault displaced in
Holocene time
Seismic Zone
Migratory bird area
Citation
22CCR
§ 66264.18(a)
23 CCR § 2547
16 U.S.C. § 703
Description of Requirement
Prohibits construction of new
hazardous waste treatment, storage,
or disposal facilities.
Requires waste management units to
be designed to withstand the
maximum credible earthquake
without damage to the foundation or
to structures that control leachate.
Protects species of native birds in the
U.S. from unregulated "take," which
can include poisoning at hazardous
waste sites.
ARAR
Determination
Applicable
Relevant and
appropriate for
existing units;
applicable for
new units
Applicable
Comments
Several faults have been identified in the area that may have been
displaced during the Holocene period (EPA, 1994c).
Appropriate seismic protection measures are required for existing
leachate collection and treatment units at the Oil Landfill. Any new
waste management units must be designed to withstand the maximum
credible earthquake.
Oil Landfill provides habitat for protected bird species. The remedial
design process will identify any measures necessary to prevent an
unregulated "take" of protected bird species.
SCO100192D6.DOC

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•8
Table 21
Action-Specific ARARs
Oil Site Final Record of Decision
Citation
Description of Requirement
ARAR Determination
Comments
Landfill Maintenance, Closure and Postclosure
22 CCR§ 66265.31
22CCR§§ 66265.32,
66265.33, 66264.34,
66265.37(a), 66265.55,
66265.56(a)-(c), (e)-(h)
22CCR§66265.14
14CCR§17767(c)
14 CCR§ 17701
14 CCR § 17706
14CCR§ 17707
14 CCR § 17713
22 CCR §66265.1 11
(a),(b)
22 CCR §66265.3 10
(b)(l), and (b)(3) except
references to §§ 66265.1 18
-120.
22 CCR § 66265.95
22 CCR § 66265.96
22 CCR § 66264.96(c)
Requires maintenance and operation of facilities to minimize fire,
explosion, or release of hazardous substances.
Specifies emergency and communications systems for hazardous waste
facilities, testing of equipment, and arrangements for emergency
support services.
Requires security measures sufficient to prevent unknowing or
unauthorized entry onto hazardous waste facilities.
Requires security measures to prevent unauthorized access to closed
landfills and monitoring, control, and recovery systems.
Requires operation and maintenance of landfills to prevent public
nuisance.
Requires operation and maintenance of landfills to minimize dust
creation.
Requires operation and maintenance of landfills to control vectors
(insects, rodents, etc.).
Requires operation and maintenance of landfills to control odors.
Requires closure to minimize need for further maintenance and to
protect human health and the environment from releases of hazardous
substances.
Requires facility closure to minimize chance of postclosure release of
hazardous waste; facilitate postclosure maintenance, monitoring and
emergency response.
Establishes the point of compliance for groundwater protection
standards as a vertical surface located at the hydraulically
downgradient limit of the waste management area.
Defines the compliance period for groundwater quality as the number
of years equal to the active life of the waste management unit.
Requires restarting the compliance period if evaluation monitoring is
initiated.
Extends groundwater quality compliance period until groundwater
protection standard has been met for three consecutive years.
Applicable
Applicable
Applicable
Relevant and appropriate
Relevant and appropriate
Relevant and appropriate
Relevant and appropriate
Relevant and appropriate
Applicable
Applicable
Applicable
Applicable
Applicable
fhe remedial design process will identify appropriate measures
consistent with the provisions of this requirement.
Che remedial design process will specify appropriate
communication and emergency systems consistent with the
substantive provisions of these requirements.
Substantive provisions are pertinent to Oil Site security.
Appropriate security measures could include existing or upgraded
systems.
Substantive provisions are pertinent to OH Site security.
Appropriate security measures could include existing or upgraded
systems.
The remedial design process will identify appropriate measures to
prevent public nuisance.
The remedial design process will identify appropriate measures to
minimize dust creation.
The remedial design process will identify appropriate measures to
maintain vector control.
The remedial design process will identify appropriate measures to
maintain odor control.
The remedial design process will identify measures to reduce
maintenance and prevent releases consistent with the provisions of
this requirement.
The remedial design process will identify specific post-closure care
measures consistent with the provisions of this requirement.
The remedial design process will identify well locations to monitor
compliance with the groundwater protection standards consistent
with the provisions of this requirement.
The remedial design process will specify the compliance period for
specified areas consistent with the provisions of this requirement.
This requirement would extend the compliance period if
groundwater performance standards are not met by the end of the
period specified by 22 CCR § 66265.96. Applicable (by reference
from 22 CCR § 66265.99) when groundwater remediation is
required at interim status facilities.
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Table 21
Action-Specific ARARs
Oil Site Final Record of Decision
Citation
22 CCR § 66265.98
(a) - (1)
22 CCR § 66265.99(a), (b),
(e)(l)-(4)and(6)except
for references to surface
water
22 CCR § 66264. 100(d)
22 CCR §66265.1 17 (b)-
(d) except references to
66265. 11 8, 119 and 120.
Los Angeles Regional
Water Quality Control
Board Order WDR 96-054
NPDES # CAS6 14001
Description of Requirement
Requires release detection monitoring in areas unaffected by prior
releases.
Requires evaluation monitoring to assess the nature and extent of any
exceedances of groundwater performance standards.
Requires water quality monitoring program to measure effectiveness of
remediation.
Requires post-closure care for 30 years after completion of closure of
the interim status hazardous waste management facilities.
Establishes requirements for stormwater discharges from hazardous
waste treatment, storage and disposal facilities
ARAR Determination
Applicable
Applicable
Applicable
Applicable
Applicable to on-site
discharges; otherwise off-
site discharge requirement
Comments
The remedial design will specify the elements of a monitoring
program consistent with the substantive provisions of this
requirement to detect new groundwater performance standard
exceedances in areas where no exceedances of groundwater
performance standards previously occurred.
The remedial design will specify the elements of a monitoring
program consistent with the substantive provisions of this
requirement to evaluate the nature and extent of exceedances of
groundwater protection standards in groundwater.
The remedial design process will identify the measures necessary to
monitor the effectiveness of groundwater remediation. Applicable
(by reference from 22 CCR § 66265.99) when groundwater
remediation is required at interim status facilities.
Post-closure care includes monitoring and maintenance of waste
containment systems. EPA may determine that the length of the
period may be modified.
Stormwater discharges from the site fall within the scope of the
general permit. Stormwater discharges to the sanitary sewer are not
included, but are addressed in the Sanitary District permit for the
Leachate Treatment Plant.
Landfill Liquids Treatment arid Disposal
22 CCR § 66264.601
22 CCR §§66264.192,
66264. 193(c)-(f),
66264.194,66264.195,
66264.197
23 CCR § 2581(c)(2) and
(c)(3) except references to
surface water
22 CCR § 66265.3 10(e)(2)
22 CCR §§66264. 1050-
1063
Requires location, design, construction, operation, and maintenance of
miscellaneous units that treat hazardous waste to ensure protection of
human health and the environment.
Requires construction, operation, and closure of hazardous waste
treatment in tanks to comply specified standards, including secondary
containment, inspections, and operating limits.
Requires operation of leachate collection and removal systems as long
as leachate is generated and detected throughout the post-closure care
period.
Requires maintenance and operation of leachate collection, removal
and treatment system to prevent excess accumulation of leachate during
post-closure care period.
Sets air emission standards for equipment leaks for units from facilities
that contain or contact hazardous wastes with organic concentrations of
at least 10 percent by weight.
Applicable to new units;
portions applicable or
relevant and appropriate to
existing units
Applicable to new units;
portions applicable or
relevant and appropriate to
existing units
Applicable
Applicable
Applicable
New units that treat leachate, a listed hazardous waste (F039), must
meet these requirements. Requirements for operation, maintenance
and closure are relevant and appropriate to existing leachate
treatment units.
New treatment tanks that treat leachate, a listed hazardous waste
(F039), must meet the substantive provisions of these requirements.
Substantive requirements for operation, maintenance and closure
are relevant and appropriate to existing leachate treatment tanks.
Existing leachate collection systems, or functional equivalents,
must be operated to the extent feasible (pursuant to 23 CCR
§2511(d».
The remedial design process will identify appropriate measures to
prevent excess accumulation of leachate.
Substantive provisions may be applicable to specified equipment.
SC0100192D7.DOC
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fa
era
to
oo
Table 21
Action-Specific ARARs
Oil Site Final Record of Decision
Citation
22CCR§§ 66264.32,
66264.33, 66264.34,
66265.37(a), 66265.55,
66265.56(a)-(c), (e)-(h)
Description of Requirement
Specifies emergency and communications systems for hazardous waste
facilities, testing of equipment, and arrangements for emergency
support services.
ARAR Determination
Applicable
Comments
The remedial design process will specify appropriate
communication and emergency systems for the leachate treatment
plant consistent with the provisions of these requirements.
Excavation, Construction and Disposal
22 CCR§ 66265. 114
22 CCR§ 66265.13
22 CCR § 66262.34
22 CCR§§ 66264. 171 -
66264.175,66264.178.
22 CCR § 66264.552
(e)(D - (4)
22 CCR § 66264.553
(b),(c)
SCAQMD Rule 402
SCAQMD Rule 403
SCAQMD Rule 11 50
Requires equipment, structures and soils to be properly disposed of or
decontaminated during closure.
Requires analysis of hazardous waste before transfer, treatment, storage
or disposal.
Allows storage of hazardous waste onsite in containers for up to 90
days.
Requires storage of waste in appropriate containers, and appropriate
management and closure of containment areas.
Allows redisposal of hazardous wastes generated as part of remediation
in designated units
Allows establishment of temporary tanks and container storage areas
for treatment or storage of remediation wastes
Limits discharge of any air contaminant or material that causes injury,
detriment, nuisance, or annoyance, or that endangers the comfort,
repose, or safety of the public, property, or business.
Limits downwind concentration of PM-10 from fugitive dust to 100
g/m^ above upwind concentration, averaged over 5 hours.
Requires mitigation measures that ensure a nuisance does not occur
when buried waste is exposed.
Applicable
Applicable
Applicable
Applicable to new units,
relevant and appropriate for
existing units
Applicable to new units,
relevant and appropriate for
existing units
Applicable to new units,
relevant and appropriate for
existing units
Applicable
Applicable
Applicable
The remedial design process will identify procedures to comply
with this requirement.
Excavation or other management of wastes must meet these
requirements.
Applicable to wastes managed during implementation or
maintenance.
Applicable to wastes managed in containers during implementation
or maintenance.
Designated onsite units may receive redisposed wastes from the
landfill.
Temporary tanks and container storage areas may be established
during remediation consistent with this requirement.
Applies to any activities conducted that generate air contaminants
or materials.
Applies to activities generating fugitive dust (i.e. earth-moving,
construction/ demolition, or vehicular movement).
Potentially applicable to construction or maintenance activities.
     SCO100192D7.DOC
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                          9.1 Chemical-Specific ARARs

 The only chemical-specific ARARs that pertain to the selected remedy are those that address
 water quality.  Chemical-specific soil requirements are not pertinent to the selected remedy,
 as the remedy does not select any response for soil (although action-specific ARARs would
 apply to management of contaminated soils and wastes necessitated by implementation of the
 remedy  or  site maintenance).  Chemical-specific surface water and air  requirements  are
 addressed in the Gas Control and Cover ROD.  Chemical-specific ARARs are listed in
 Table 19.

 Drinking Water Standards.   Section 121(d)(2) of  CERCLA, 42 U.S.C. § 9621 (d)(2),
 requires  CERCLA cleanups  to  attain  water quality  criteria established  under the Safe
 Drinking Water Act if those criteria are relevant and appropriate, considering, among other
 factors,  the designated or potential  use of  the water resource.   The  1995 Water  Quality
 Control  Plan  for the  Los Angeles  Region (known as the  "Basin  Plan")  designates  the
 groundwater surrounding  the OH Site as potential drinking water.  EPA  has identified  the
 drinking  water  standards  referred to as "Maximum Contaminant Levels" for site-related
 contaminants as an ARAR, using the more stringent of federally- or state-designated MCLs.
 Due to the complex hydrogeological setting at the OH Site, the minimal risks of exposure,
 and  the  limited potential use of the resource, EPA did not identify the more stringent
 standards known as "Maximum  Contaminant Level Goals."  MCLs for contaminants of
 concern at the Oil Site are listed in Table 15.

 Water Quality Standards for Landfill Closure. Landfill closure requirements under both
 federal and State law prescribe water quality protection standards.  The OH Site is an "interim
 status" hazardous waste landfill, having received hazardous wastes after November 19, 1980,
 the effective date of the Resource Conservation and Recovery Act of 1978, 42 U.S.C. § 6901,
 and having  never obtained a final permit. Regulations governing closure  of interim status
 landfills  are applicable to the OH  Site.  The California hazardous waste program is federally
 authorized to operate in lieu of the federal program; therefore, the California interim status
 regulations  are  considered federal  ARARs.   Federal  and state regulations  applicable to
 permitted facilities may be,  as a  general matter, relevant and appropriate  to  interim status
 facilities; however,  with regard to  chemical-specific  water  quality protection,  those
 regulations that are both relevant and appropriate are no more stringent than the interim status
 regulations.  However, certain regulations applicable to groundwater protection standards at
 permitted facilities where releases have taken place are applicable to interim status facilities
 by reference from the interim status regulations.  These regulations  are also considered
 federal ARARs.

 The  OH  Site also accepted  municipal  solid waste (such as household trash), but stopped
 accepting these wastes prior  to  the effective date  of federal  and state regulations for
 municipal solid waste landfills. These regulations may be, as a general matter, relevant and
 appropriate  to older  landfills that accepted  municipal solid wastes;  however, as with the
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 regulations for permitted hazardous waste facilities, those solid waste regulations pertaining
 to chemical-specific water quality protection that are both relevant and appropriate are no
 more stringent than the interim status regulations.

 The applicable regulations allow a water quality protection standard greater than background,
 if it is technically or economically impracticable to attain  background levels, provided that
 the standard is protective of human health and the environment and is no higher than MCLs.
 Due  to the complex hydrogeological setting at the  OH Site, the minimal risks of exposure,
 and the limited potential use of the resource, EPA selected MCLs that exceed baseline levels,
 and health-based levels for contaminants that have no MCLs, as the ARAR.  The MCLs and
 health-based levels are listed on Table 15.

 Offsite Discharge to the Sanitary Sewer. The Leachate Treatment Plant discharges effluent
 to  the sanitary  sewer.   This  effluent  subsequently undergoes further treatment at  County
 Sanitation Districts of Los Angeles County facilities.  This discharge is considered an
 "offsite" activity; therefore, the activity is not subject to ARARs and must meet not only
 substantive,  but also administrative, requirements.  The substantive requirements  include
 chemical-specific criteria for the effluent. The requirement for a permit is listed in Table 19
 solely for informational purposes.
                           9.2 Location-Specific ARARs

The OH Site presents two location-specific issues: seismic (earthquake-related) requirements
and a requirement related to protected bird species.  The location-specific ARARs are listed
in Table 20.

Seismic Requirements.  The  OH Site is located near several faults that may have  been
displaced during the Holocene period. New hazardous waste treatment, storage, or disposal
facilities  may  not be built within 200  feet of such a  fault.   In addition,  regulations
promulgated by the State Water Resources Control Board require waste management units to
be  designed to withstand  the  maximum credible  earthquake for  their  location.   This
requirement is applicable for new facilities, and relevant and appropriate to existing facilities
(to the extent  that existing facilities can be made  to  withstand the maximum credible
earthquake).

Migratory Bird Area. The OH Site provides habitat to several species of migratory birds
protected  under federal law. The prohibition against "taking"  such migratory birds, which
can include poisoning at hazardous waste sites, is applicable.
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                            9.3 Action-Specific ARARs

 Federal and/or state environmental requirements address numerous activities required by the
 selected remedy.  These activities include landfill maintenance, closure, and postclosure;
 landfill liquids treatment and  disposal;  and excavation, construction, and disposal.  The
 action-specific ARARs are listed in Table 21.

 Landfill Maintenance, Closure, and Postclosure. The interim status regulations pertinent
 to landfill  maintenance (such as emergency prevention and security) and to landfill closure
 and postclosure are  applicable to the  OH  Site.   Certain  permitted facility regulations
 pertaining  to  monitoring the effectiveness of water quality  remediation and to the water
 quality compliance period for facilities undergoing water quality remediation  are applicable
 by reference to interim status facilities.  Certain state standards for nuisance-related controls
 at municipal solid waste facilities are more stringent than interim status regulations, and are
 relevant  and  appropriate to the selected  remedy.   In addition,  stormwater discharge
 requirements are applicable for  onsite discharges not addressed in the Gas Control and Cover
 ROD  (offsite  discharges must meet both  administrative  and  substantive requirements).
 Stormwater discharges that  will be addressed under the  Gas Control and Cover ROD are
 subject to the ARARs identified in that ROD.

 The Gas Control and Cover ROD, which is a final ROD, identified ARARs for landfill gas
 collection  and destruction.   Gas  collection  and destruction activities undertaken as site
 control measures (termed the "gas extraction and air dike system") prior to their inclusion as
 activities under the Gas Control and Cover operable unit are subject to the ARARs identified
 in the Gas Control and  Cover  ROD.   To the extent that these  interim gas collection and
 destruction activities cannot meet specific ARARs, such ARARs are waived for the interim
 measures, as implementation of the Gas Control and Cover ROD will achieve the ARARs.

 Landfill Liquids Treatment and Disposal.  The interim status regulations,  which require
 leachate collection and removal to prevent excess accumulation, are applicable  to  the OH
 Site.   The State Water  Resources Control Board regulation for leachate collection  and
 removal is  different in scope and also applicable, requiring leachate collection and  removal
 through the postclosure period.  However, as the OH Site is undergoing remediation under the
 oversight of a public agency, the State Water Resources Control Board regulation is only
 applicable to the extent feasible.

 Design and construction requirements for permitted facilities are applicable to any new units
 implemented under this  remedy.  Operation, maintenance, and closure requirements are
 applicable to new units and either applicable  or relevant and appropriate to  existing units
 (depending on when they were constructed).
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 Off-gas from the leachate treatment plant is collected and sent through the existing "foul air"
 system to the landfill gas control system for destruction.  ARARs for the landfill gas control
 system are included in the Gas Control and Cover ROD.

 Regulation  of  air emissions from equipment leaks  is  applicable  if specified  equipment
 contains hazardous wastes with organic concentrations of 10 percent or more.

 Excavation, Construction and Disposal. The interim status regulations, which  require
 analysis of hazardous wastes prior to management and proper disposal or decontamination of
 equipment,  structures and soils  during closure, are applicable. Requirements for permitted
 facilities for storage of waste, temporary tanks, and containers, and redisposal of remediation
 wastes are applicable to new remediation units and  relevant and appropriate for  existing
 units.  In addition, South Coast Air Quality Management District (SCAQMD) regulations
 pertinent to construction, excavation, and maintenance of systems other than those addressed
 by the Gas Control and Cover ROD are applicable.
               10.0 Documentation of Significant Changes

EPA issued the Proposed Plan for this remedy at the OH Site for public comment in June
1996.  The Proposed Plan identified Alternative No. 2, Perimeter Liquids Control, as the
preferred alternative.  EPA reviewed all written and verbal comments submitted during the
public comment period. After reviewing these comments, EPA  has determined that no
significant changes  to  the  remedy, as originally identified in the Proposed  Plan,  are
necessary.
                       11.0 Statutory Determinations

EPA's primary responsibility at Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment.   In addition, Section 121  of
CERCLA establishes several  other statutory requirements and preferences.  These specify
that when complete, the selected remedial action for a site must  comply with applicable or
relevant  and  appropriate  environmental standards  established under federal  and state
environmental requirements and state facility siting requirements (unless a statutory waiver is
justified). The selected remedy must also be cost-effective and utilize permanent solutions
and alternative treatment technologies or resource recovery technologies to the  maximum
extent  practicable.  Finally, the statute includes a  preference for remedies that  employ
treatment that permanently and significantly reduces the volume,  toxicity, or mobility  of
hazardous wastes as their principal element. The following sections discuss how the selected
remedy at the OH Site meets these statutory requirements.
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            11.1  Protection of Human Health and the Environment

 The selected remedy protects human health and the environment by eliminating, reducing, or
 controlling site-related risk  through  perimeter  liquids control  and treatment of landfill
 contaminants, natural attenuation of groundwater contaminants beyond the landfill boundary,
 and implementation of institutional controls to  significantly reduce the potential for future
 exposure to landfill-related  contaminants and  contaminated groundwater.   The selected
 remedy further protects human health and the  environment by providing  for groundwater
 monitoring that will track movement of the groundwater contamination and detect any
 potential adverse impacts. This will allow for ongoing evaluation of groundwater quality and
 implementation  of contingency measures, if necessary (e.g., if  natural attenuation is not
 progressing as anticipated [see Table 17]).   There  is  no current use of,  or exposure to,
 groundwater in the OH Site vicinity.

 Site security and institutional  controls on the landfill will provide protection of human health
 and the environment from landfill contents.

 There are no short-term threats associated with  implementation of the selected remedy that
 cannot be readily mitigated.  Further, no adverse cross-media impacts are expected from the
 remedy.
                         11.2 Compliance with ARARs

The selected remedy of perimeter liquids control, liquids collection and treatment, natural
attenuation of groundwater, groundwater monitoring, and institutional controls will comply
with all federal and state applicable  or relevant and appropriate  chemical-, action-, and
location-specific requirements (ARARs). Federal and state ARARs  pertinent to the selected
remedy are discussed  in  Section 9.  The  specific ARARs for the selected remedy are
presented in Tables 19, 20, and 21.

As discussed in the comparison of remedial alternatives section (Section 7.2), there is a slight
potential that because  of  the complex groundwater flow conditions and low-permeability
formation, natural  attenuation may take an excessive  amount of time to reduce inorganic
constituents in groundwater southwest of the landfill to cleanup standards.
                             11.3  Cost-Effectiveness

EPA  has  determined that  the selected remedy  is cost-effective  because it will provide
increased protectiveness at  a reasonable cost in comparison to the other alternatives.  The
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 estimated total net present worth of the selected remedy is $162 million. This represents an
 increase of only 14 percent over Alternative No. 1 (No Further Action), yet it would be more
 protective  of human health  and the environment than Alternative No.  1.  Further,  unlike
 Alternative No. 1, the selected remedy meets ARARs.  The selected remedy is the least costly
 alternative that is fully protective of human health  and the environment and that  meets
 ARARs.  Alternatives  No. 3 and 4 do not offer additional benefits commensurate with the
 associated increases in  cost and would therefore not be cost-effective.
     11.4  Utilization of Permanent Solutions and Alternative Treatment
               Technologies to the Maximum Extent Practicable

 EPA has determined that the selected remedy represents the maximum extent to which
 permanent solutions and treatment technologies can be utilized in a cost-effective manner.

 Of those alternatives that meet the two threshold  criteria of overall protection of human
 health and the environment and compliance  with  ARARs, EPA has  determined  that the
 selected remedy  provides the best balance of long-term effectiveness and permanence;
 reduction in toxicity, mobility, or volume through treatment;  short-term effectiveness;
 implementability; costs; and state and community acceptance.

 The selected remedy  is in part a containment-based remedy and  is consistent with EPA's
 Presumptive Remedy for CERCLA Municipal Landfill Sites (EPA, 1993c).  The remedy also
 includes considerable  collection, removal, and treatment of landfill contaminants through the
 perimeter liquids control system.   The perimeter liquids  control  system  addresses the
 principal threats  posed by landfill contaminants through inhibiting further migration  of
 contaminants to groundwater.  The other principal threats, landfill contents and landfill gas,
 were previously addressed through the Gas Control and Cover ROD.

 The component of the selected remedy for groundwater beyond the landfill perimeter offers a
 high degree of long-term effectiveness through natural  attenuation enhanced by perimeter
 liquids  control, groundwater monitoring to ensure  that contamination does  not spread to
 potential receptors, and implementation of institutional controls to prevent future exposure to
 contaminated groundwater.  (As noted above, there  is no current use of or  exposure  to
 groundwater in the vicinity of the Oil Site.)

 Although the Alternative No.  3  (Source Control plus Perimeter  Control) and Alternative
 No. 4 (Groundwater Control plus Perimeter Control) alternatives may offer slightly increased
 protection of human  health and the environment, these slight increases would only be
 realized at significantly higher costs.  In addition, Alternative No. 4 has substantially higher
 community impacts than the selected remedy.
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             11.5  Preference for Treatment as a Principal Element

 By treating the landfill contaminants collected in the perimeter liquids control system at the
 onsite treatment plant, the selected remedy addresses one of the principal threats posed by the
 site through the use of treatment technologies.   Therefore,  the  statutory  preference for
 remedies that employ treatment as a principal element is at least partially  satisfied.  The
 selected remedy does not use active treatment as a principal element for existing groundwater
 contamination.  However, the combination of perimeter liquids control, natural attenuation,
 groundwater monitoring, and institutional controls prevents exposure and offers a permanent
 solution to the groundwater contamination.
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                                  References
 Andelman, J. B., L. C. Wilder and S. M. Myer.  "Indoor Air Pollution  from Volatile
 Chemicals in Water" INDOOR AIR '87,  Vol. I, Proceedings of the 4th International
 Conference on Indoor Air Quality and Climate.  Institute for Water, Soil and Air Hygiene.
 Berlin.  1987.

 California Department  of  Water Resources.  Planned  Utilization  of the Ground  Water
 Basins of the Coastal Plain of Los Angeles County, Appendix A, Ground Water Geology.
 Bulletin of the California Division of Water Resources, 104. 1961.
	. Planned Utilization of Ground Water Basins, San Gabriel Valley, Appendix
A, Geohydrology. Bulletin of the California Division of Water Resources, 104-2. 1966.

California Regional Water Pollution Control Board No. 4, Los Angeles Region. Resolution
No.  54-15, Prescribing Requirements  for  Disposal of Refuse at Monterey  Disposal
Company Dump, 900 Potrero Grande Road, Monterey Park. October 6,1954.

CDM Federal.  Personal communication between Roderick J. Higbie, P.E., CDM Federal
Programs, and Gary Santolo, CH2M HILL. February 24, 1994.

Cogliano, V. J., J. C. Parker, and W. E. Pepelko. "Vinyl Chloride:  Another Look." The
Toxicologist. 10:349. 1990.

Cogliano,  V.  J.  and  J.   C.   Parker.    "Some  Implications  of  Toxicology  and
Pharmacokinetics for Exposure Assessment."   Journal  of Exposure  Analysis and
Environmental Epidemiology. Supplement 1. 1992.
On Site Final Record of Decision                                              Page R-l
References                                                          scoiooi92ED.DOC

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 Cogliano, V. J., G. F. S. Hiatt, and A. R. Den.  "A Quantitative Risk Assessment for
 Vinyl Chloride—Indications of Early-Life Sensitivity." Toxicology,  (in press).

 County Sanitation  Districts of Los Angeles County.   Industrial  Wastewater Discharge
 Permit No. 13196.  June 21,1994.

 Hiatt, G.  F. S.,  V.  J. Cogliano, R. A. Becker, et al.  Vinyl Chloride—Indoor Air Action
 Levels at a  Superfund Site.  Hazardous Waste and  Public Health:  The  International
 Conference on the  Health Effects of Hazardous Waste.  Princeton Scientific Publishing.
 1994.

 Los Angeles County Department of Public Works. Drains and Facilities. 1987.

 	.  Coastal Plain Deep Aquifer Groundwater Contour Map. Fall, 199la.

 Los Angeles Regional Water Quality Control  Board.  Order No.  76-30, Revised Waste
 Discharge Requirements for Operating Industries, Inc. March 22,1976a.
	.  Order No. 76-133, Revised Waste Discharge Requirements for Operating
Industries, Inc. September 27,1976b.
	.  Order No. 84-119, Amended Waste Discharge Requirements for Operating
Industries Landfill. November 19,1984.

OH Landfill Work Defendants.  Report of Recommendations, Evaluate and Design LFG
Migration System for the Southwestern and Western Boundaries of the Oil Landfill.
Prepared by Bryan A. Stirrat & Associates, Inc. for CURE, Inc. August 19, 1992b.
Page R-2                                               OH Site Final Record of Decision
SCO100192ED.DOC                                                           References

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 	.  Seep Mitigation Field Examination & Evaluation.  Prepared by Bryan A.
 Stirrat & Associates for CURE, Inc. December 6,1993a.
 	.   Oil SCM/LMS  Monthly Progress  Reports.  Prepared by  CURE,  Inc.;
 Contributions by Environmental  Solutions, Inc.;  Bryan A.  Stirrat & Associates;  and
 James M. Montgomery, Inc., and New Cure, Inc. January 1990 to December 1994.
 	.  Draft Data Synthesis Report for Seismicity,  Settlement, and Slope Stability,
 Oil Landfill  CD-3 Activities.  Prepared by Environmental Solutions, Inc. for New Cure,
 Inc. February 1994a.
	.   Technical  Memorandum  No. 14,  Report  of  Findings,   Geophysical
Measurement  for Seismic Analysis.    OH  Landfill  CD-3 Activities.   Prepared by
Environmental Solutions, Inc. for New Cure, Inc. January 17,1995b.

U.S. Department of Commerce. 1990 Census. Summary Tape Files 1A and 3A.  1990b.

U.S. Environmental Protection Agency.  Analysis Results for the July, 1986  Operating
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          -. Guideline for Carcinogen Risk Assessment.  1986b.
	. Record of Decision, Operating Industries, Inc., Monterey Park,  California,
Site Control and Monitoring Operable Unit.  July 31, 1987a.
	. Record of Decision, Operating Industries, Inc. Monterey Park, California,
Leachate Management Operable Unit.  November 16,1987b.
OH Site Final Record of Decision                                             Page R-3
References                                                          scoiooi92ED.DOC

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 	.  Draft Technical Memorandum, Site  Characterization  and Installation of
 Landfill Gas Monitoring Wells, North Parcel, Operating Industries, Inc., Monterey Park,
 California. Prepared by CH2M HILL and Black and Veatch. October 1987d.
 	.  Leachate Management Feasibility Study, Operating Industries, Inc. Landfill
 Site.  Prepared by Camp Dresser & McKee Inc. December 30,1987e.
 	.  Record of Decision, Operating Industries,  Inc., Monterey Park, California,
 Gas Migration Control Operable Unit.  September 30, 1988b.
	.   South Parcel  Hydrogeology  Existing  Data  Technical  Memorandum,
Operating  Industries,  Inc.,  Monterey  Park,  California.  Prepared  by CH2M  HILL.
October 12,1988d.
	.  Operable  Unit Feasibility Study for Landfill  Gas  Migration Control,
Operating Industries, Inc., Monterey Park,  California. Public Comment Draft.  Prepared
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	.  South Parcel Landfill Gas Monitoring Wells, Including Soil Borings Logs,
Geophysical Logs, Cross Sections, and Monitoring Results.  Prepared by CH2M HILL.
March 21,1988h.
	. Preliminary North Parcel Site Characterization, Operating Industries, Inc.,
Monterey Park, California. Prepared by CH2M HILL. March 4, 1988i.
	. CERCLA Compliance with Other Laws Manual: (Interim Final).  OSWER
Directive 9234.1-01. August 1988k.
Page R-4                                              OH Site Final Record of Decision
SCO100192ED.DOC                                                          References

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 	.   Risk  Assessment Guidance for  Superfund.  Volume I.  Human Health
 Evaluation Manual (Part A). Interim Final. EPA/540/1-89/002. December 1989d.
 	.  CERCLA Compliance with Other Laws Manual: Part II. Clear Air Act and
 Other Environmental Statutes and State Requirements (Interim Final).  OSWER Directive
 9234.1-02. August 1989f.
 	. Record of Decision, Amendment to Decision Summary, Operating Industries,
 Inc., Monterey Park, California, Gas Migration Control Operable Unit.  September 28,
 1990a.
 	.  Guidance for Conducting Remedial Investigations/Feasibility Studies for
 CERCLA Municipal Landfill Sites.  OSWER Directive No. 9355.3-11. February 1991a.
	. Draft Report for 24-Hour Ambient Air Sampling at the Operating Industries,
Inc. Landfill Monterey Park, California.  Prepared  by Science Applications International
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	.  Risk Assessment Guidance for Superfund.   Volume  I.  Human  Health
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	.   Role of Baseline Risk  Assessment in Superfund  Remedy Selection
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OH Site Final Record of Decision                                             Page R-5
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 	.  Public Comment Draft,  In-Home Air  Monitoring  Report,  Operating
 Industries,  Inc.  Landfill,  Monterey  Park,   CA.  Prepared by Science  Applications
 International Corporation.  November 16,1993a.
 	.  Presumptive Remedy for CERCLA Municipal Landfill Sites. Quick Reference
 Fact Sheet. EPA 540-F-93-035. September 1993c.
 	-.  Draft Remedial Investigation Report, Operating Industries, Inc., Monterey
 Park, California.  Prepared by CH2M HILL. October 25,1994c.
 	.  Feasibility Study Report for Operating Industries, Inc.  Landfill Superfund
 Site, Monterey Park, California. Prepared by CH2M HILL. March 1996.
Page R-6                                              OH Site Final Record of Decision
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