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These RODs are no longer applicable beginning with the signing of this ROD, although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
SC0100192D2.DOC jjj
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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
Contents scoiooi9ib3.doc
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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
Contents scoiooi9ib3.doc
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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
Contents scoiooi9ib3.doc
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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
scoiooi92D3.DOC Part I - Decision Summary
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.$? //'
o -.—..•..v..~i..r'evelopnieritbf ff .
V Californiajnc. and California *
AV^Bankers Trust Company '-, •*•/
0 300 600
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.
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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
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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
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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
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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
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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
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© 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
-------
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
-------
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
Page 1-24 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
Oil Site Final Record of Decision Page 1-25
Part I - Decision Summary scoiooi92D3.Doc
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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.
Page 1-26 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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.
Oil Site Final Record of Decision Page 1-27
Part I - Decision Summary scoiooi92D3.DOC
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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).
Page 1-28 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
-------
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
-------
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
Oil Site Final Record of Decision Page 1-33
Part I - Decision Summary scoiooi92D3.DOC
-------
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.
Page 1-34 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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.
Oil Site Final Record of Decision Page 1-35
Part I - Decision Summary scoiooi92D3.DOC
-------
• 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).
Page 1-36 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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.
Oil Site Final Record of Decision Page 1-37
Part I - Decision Summary scoiooi92D3.DOC
-------
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
scoiooi92D3.DOC Part I - Decision Summary
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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
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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
-------
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
-------
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
-------
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
-------
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
-------
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
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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
Oil Site Final Record of Decision Page 1-87
Part I - Decision Summary scoiooi92D3.DOC
-------
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
Page 1-88 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
-------
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.
Oil Site Final Record of Decision Page 1-89
Part I - Decision Summary scoiooi92D3.DOC
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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
-------
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).
Oil Site Final Record of Decision Page 1-91
Part I - Decision Summary scoiooi92D3.DOC
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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
Page 1-92 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
Oil Site Final Record of Decision Page 1-93
Part I - Decision Summary scoiooi92D3.DOC
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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
-------
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.
Oil Site Final Record of Decision Page 1-95
Part I - Decision Summary scoiooi92D3.DOC
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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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Part I - Decision Summary scoiooi92D3.DOC
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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
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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
Page I-102 Oil Site Final Record of Decision
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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
Oil Site Final Record of Decision Page 1-103
Part I - Decision Summary scoiooi92D3.DOC
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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.
Page I-104 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
-------
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.
Oil Site Final Record of Decision Page 1-107
Part I - Decision Summary scoiooi92D3.DOC
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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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scoiooi92D3.DOC Part I - Decision Summary
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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
Oil Site Final Record of Decision Page 1-109
Part I - Decision Summary scoiooi92D3.DOC
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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
SC01001916E.XLS
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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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Pagel-lll
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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
Page 1-112 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
Part I - Decision Summary scoiooi92D3.DOC
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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
Part I - Decision Summary scoiooi92D3.DOC
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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
Part I - Decision Summary scoiooi92D3.DOC
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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
scoiooi92D3.DOC Part I - Decision Summary
-------
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
Part I - Decision Summary scoiooi92D3.DOC
-------
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.
Page I-120 Oil Site Final Record of Decision
scoiooi92D3.DOC Part I - Decision Summary
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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
Part I - Decision Summary scoiooi92D3.DOC
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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
rod tl9.XLS
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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.
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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.
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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
-------
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
-------
. 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
Industries Site Samples, Los Angeles, CA - NEIC Project D24. Correspondence from Dr.
Joe Lowry, NEIC. September 16, 1986a.
-. 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
-------
. 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
by CH2M HILL. June 1988g.
. 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
-------
. 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
Corporation. February 1991c.
. Risk Assessment Guidance for Superfund. Volume I. Human Health
Evaluation Manual, PartB. Development of Risk-Based Preliminary Remediation Goals.
Interim Report. Publication 9285.7-01B. December 1991e.
. Risk Assessment Guidance for Superfund. Volume 1. Human Health
Evaluation Manual, Supplemental Guidance: "Standard Default Exposure Factors."
OSWER Directive 9285.6-03. March 25,1991f.
. Role of Baseline Risk Assessment in Superfund Remedy Selection
Decisions. OSWER Directive 9355.0.30. 1991k.
OH Site Final Record of Decision Page R-5
References scoiooi92ED.E>oc
-------
. 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
scoiooi92ED.DOC References
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