Volume 1 Record of Decision EPA Superfund Casmalia Resources Superfund Site Santa Barbara County California


SEMS-RM DOCID # 100008710

Volume 1:
RECORD OF DECISION

EPA Superfund

CASMALIA RESOURCES SUPERFUND SITE
SANTA BARBARA COUNTY, CALIFORNIA

U.S. Environmental Protection Agency
Region IX
San Francisco, California

EPA 10: CAD 020743125

June 2018

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RECORD OF DECISION

for

CASMALIA RESOURCES SUPERFUND SITE,
SANTA BARBARA COUNTY, CALIFORNIA

U.S. Environmental Protection Agency
Region IX
San Francisco, California

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June 2018

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Table of Contents

Section	Page

ACRONYMS AND ABBREVIATIONS	vii

PART 1:	IILARATIION	1

1.1	Site Name and Location	1

1.2	Statement of Basis and Purpose	1

1.3	Assessment of Site	2

1.4	Description of Selected Remedy	2

1.5	Statutory Determinations	6

1.6	ROD Data Certification Checklist	7

1.7	Authorizing Signatures	8

IIISIION SUMMARY	9

2.1	Site Name, Location, and Brief Description	9

2.2	Site History and Enforcement Activities	10

2.3	Community Participation	15

2.4	See. " Role of Operable Unit or Response Action	16

2.5	Site Characteristics	16

2.6	Current and Potential IFu ;e and Resource Uses	35

2.7	Summary of Site Risks	37

2.8	Remedial Action Objectives	53

2.9	Description of Alternatives	57

2.10	Comparative Analysis of Alternatives	69

2.11	Principal Threat Wastes	74

2.12	Selected Remedy	75

2.13	Statutory Determinations	93

PART 3: RESPONSIVENESS SUMMARY	99

3.1	Stakeholder Comments and	isponses	99

3.2	Techni " " Legal Issues	99

Works Cited	101

Appendix A	Groundwater Monitoring Network

Appendix B	Nature and Extent of Contamination Figures

Appendix C	Risk Assessment Supporting Details

Appendix D	Applicable or Relevant and Appropriate Requirements (ARARs)

Appendix E	Cost Estimate Detail for Selected Remedy

Appendix F	Administrative Record Index (forthcoming)

Appendix G	Responsiveness Summary for Proposed Plan Comments

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TABLE OIF CONTENTS

List of Tables

No. Title

2-1 Contaminated Liquids, Extraction, Treatment, and Disposal

2-2 Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

2-3 Summary of Risk-Based Concentration Exceedances by Media, Location, and
Constituents

2-4 Chemicals of Concern in Surface Soil - Terrestrial Birds, Soil Invertebrates, and Plants

2-5 Chemicals of Concern in Shallow Soil - Terrestrial Mammals, Soil Invertebrates, and
Plants

2-6 Chemicals of Concern in Sediment Based on Aquatic Wildlife and Sediment
Invertebrates

2-7 Dissolved Chemicals in Groundwater that Exceed Maximum Contaminant Levels

2-8 Medium-Specific EPCs for Each Chemical of Concern

2-9 Cumulative Risk and Hazard, Potential Exposures to Onsite Soil

2-10 Cumulative Risk and Hazard, Potential Exposures to Offsite Soil and Offsite Sediment

2-11 Cumulative Risk and Hazard, Potential Exposures to Onsite Sediment

2-12 Cumulative Risk and Hazard, Potential Exposures to Onsite Surface Water

2-13 Cumulative Risk and Hazard, Potential Outdoor Air Exposures to Onsite Soil Vapor

2-14 Cumulative Risk and Hazard, Administration Building - Potential Indoor Air Exposures to
Vapors Emanating from Soil

2-15 Cumulative Risk and Hazard, Potential Exposures to Onsite Soil, Offsite Sediment, and
Offsite Soil Vapor, Hypothetical Offsite Resident

2-16	Remediation Levels for Chemicals of Concern in Soil

2-17	Sitewide Remedial Alternatives Components

2-18	Summary of Sitewide Remedial Alternatives Evaluation

2-19	Estimated Groundwater Cleanup Times and Costs for Sitewide Alternatives 1 through 6

2-20	Description and Cost Estimate Summary for the Selected Remedy

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TABLE OIF CONTENTS

List of Figures

No.	Title

2-1	Site Location Map

2-2	Historical Site Layout

2-3	Current Site Layout

2-4	Selected Site Aerial Photographs (1970-2016)

2-5	Site Chronology and Milestones

2-6	Conceptual Site Model Block Diagram

2-7	Conceptual Site Model, Baseline Human Health Risk Assessment, Uncapped Areas

2-8	Conceptual Site Model, Baseline Human Health Risk Assessment, Surface Water

2-9	Conceptual Site Model, Ecological Risk Assessment, Terrestrial Uncapped Areas

2-10	Conceptual Site Model, Ecological Risk Assessment, Terrestrial Capped Areas

2-11	Conceptual Site Model, Ecological Risk Assessment, Freshwater Habitat Areas

2-12	Local Groundwater Basins

2-13	Parcel Ownership in Site Vicinity

2-14	Feasibility Study Areas 1 through 4

2-15	Feasibility Study Area 5

2-16	Closure Status of Former Surface Impoundments

2-17	Water Table Potentiometric Surface, December 2015

2-18	Summary of Chemical Detections and Exceedances - All Media

2-19	Soil Hotspot Locations with Exceedances

2-20	LNAPL, DNAPL, and Total VOCs in Upper HSU

2-21	LNAPL, DNAPL, and Metals in Upper HSU

2-22	DNAPL and Total VOCs in Lower HSU

2-23	DNAPL and Metals in Lower HSU

2-24	Co-Located Risks to Ecological Communities Assuming Barium is Not Toxic

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TABLE OIF CONTENTS

2-25 Co-Located Risks to Wildlife Receptors Assuming Barium is Not Toxic
2-26 Caps Considered in Remedial Alternatives

2-27 Location of Waste Management Area, Technical Impracticability Zone, and Point of
Compliance

2-28 Sitewide Remedial Alternative 2 - Capping, Liquids Extraction, Large Evaporation Pond

2-29 Sitewide Remedial Alternative 3 (Selected Remedy) - Capping, Liquids Extraction,

Small Evaporation Pond

2-30 Sitewide Remedial Alternative 4 - Capping, Liquids Extraction, Offsite Discharge

2-31 Sitewide Remedial Alternative 5 - Capping, Liquids Extraction, P/S Landfill Dewatering,
Small Evaporation Pond

2-32 Sitewide Remedial Alternative 6 - Capping, Liquids Extraction, P/S Landfill Dewatering,
Groundwater Extraction, Offsite Discharge

2-33 Selected Remedy - Process Flow Diagram for NAPL and Groundwater

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Acronyms and Abbreviations

Hg/L	microgram per liter

amsl	above mean sea level

ARAR	applicable or relevant and appropriate requirements

ASTM	ASTM International (formerly the American Society for Testing and

Materials)

BAF	bioaccumulation factor

Basin Plan	2011 Water Quality Control Plan for the Central Coast Basin

BERA	baseline ecological risk assessment

BMP	best management practice

BO	biological opinion

BTA	Burial Trench Area

CA	cost analysis

CD	Consent Decree

CDA	Central Drainage Area

CDFW	California Department of Fish and Wildlife

CDI	chronic daily intake

CERCLA	Comprehensive Environmental Response, Compensation, and Liability
Act of 1980

CERCLIS	Comprehensive Environmental Response, Compensation, and Liability

Information System

CFR	Code of Federal Regulations

CNS	Casmalia Neutralization System

COC	chemical of concern

COPC	chemical of potential concern

COPEC	chemical of potential ecological concern

CR	Casmalia Resources

CSC	Casmalia Steering Committee

CSM	conceptual Site model

CTAC	community technical assistance consultant

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ACRONYMS AND ABBREVIATIONS

DCE	dichloroethene

DNAPL	dense nonaqueous phase liquid

DTSC	Department of Toxic Substances Control

EE/CA	Engineering Evaluation/Cost Analysis

EPA	U.S. Environmental Protection Agency

EPC	exposure point concentration

ERA	ecological risk assessment

ESA	Endangered Species Act

ESD	Explanation of Significant Differences

ET	evapotranspiration

FPP	Former Ponds and Pads Area

FR	Federal Register

FS	Feasibility Study

GAC	granular activated carbon

GCL	geosynthetic clay layer

HDPE	high-density polyethylene

HHRA	human health risk assessment

HI	hazard index

HQ	hazard quotient

HS	hotspot

HSU	hydrostratigraphic unit

IAC	Interagency Committee

IC	institutional control

LLTW	low-level threat waste

LNAPL	light nonaqueous phase liquid

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ACRONYMS AND ABBREVIATIONS

LOAEL	lowest observed adverse effect level

LTE	long-term effectiveness

MCL	maximum contaminant level

MCPP	2-(2-chloro-4-methylphenoxyl) propionic acid

mg/kg	milligram(s) per kilogram

MNA	monitored natural attenuation

MSA	Maintenance Shed Area

NAPL	nonaqueous phase liquid

NCP	National Oil and Hazardous Substances Pollution Contingency Plan

NOAEL	no observed adverse effects level

NPDES	National Pollutant Discharge Elimination System

NPL	National Priorities List

O&M	operation and maintenance

OM&M	operations, maintenance, and monitoring

OSWER	Office of Solid Waste and Emergency Response

OU	operable unit

P/S	Pesticide/Solvent (Landfill)

PCB	polychlorinated biphenyl

PCE	tetrachloroethene

PCT	Perimeter Control Trench

POC	Point of Compliance

PRP	potentially responsible party

PSCT	Perimeter Source Control Trench

PTW	principal threat waste

RAO	remedial action objective

RCF	Runoff Control Facility (Pond)

RCRA	Resource Conservation and Recovery Act

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ACRONYMS AND ABBREVIATIONS

RfC	reference concentration

RfD	reference dose

Rl	Remedial Investigation

RL	remediation level

ROD	Record of Decision

RWQCB	Regional Water Quality Control Board

SF	slope factor

Site	Casmalia Resources Superfund Site

SOW	Statement of Work

State	State of California

STE	short-term effectiveness

SVOC	semivolatile organic compound

TBD	to be determined criteria

TCE	trichloroethene

TDS	total dissolved solids

Tl	Technical Impracticability

TIE	Technical Impracticability Evaluation

TRV	toxicity reference value

TSD	treatment, storage, and disposal

USC	United States Code

USDW	underground source of drinking water

USFWS	U.S. Fish and Wildlife Service

VOC	volatile organic compound

WCSA	West Canyon Spray Area

WMA	Waste Management Area

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iCLA RATION

1.1 Site Name ar atioin

Casmalia Resources Superfund Site (Site), Santa Barbara County, California, Comprehensive
Environmental Response, Compensation, and Liability Information System (CERCLIS)
identification number CAD020748125.

The Site is an inactive, 252-acre, Class I hazardous waste management facility that lies in the
northwestern corner of Santa Barbara County, California. The Site is situated 10 miles
southwest of Santa Maria, 4 miles from the Pacific Coast, and 1.5 miles north of the
unincorporated town of Casmalia. Nearby off-property land uses are primarily ranching and
grazing, with some oil and natural gas development. Vandenberg Air Force Base lies 8 miles
southeast of the Site.

The Site was owned and formerly operated by Casmalia Resources (CR). It accepted over 5.6
billion pounds of solid and liquid wastes from over 10,000 generators between 1972 and 1989.
The facility stopped accepting wastes in 1989 after CR was unsuccessful in obtaining a Resource
Conservation and Recovery Act (RCRA) Part B permit to treat, store, and dispose of hazardous
wastes. The facility ceased operations in 1991.

Waste management operations were conducted within the 252-acre facility boundary,
designated as Zone 1. Waste management units included numerous landfills, surface
impoundments, evaporation pads, oil field waste spreading areas, treatment units, injection
wells, and disposal trenches. The former waste disposal facility (Zone 1) is surrounded by
adjacent properties, designated as Zone 2. The multiple Zone 2 parcels were all formerly owned
by the owner/operator, CR, and are now owned by several different entities, including a land
acquisition company formed by the Casmalia Steering Committee (CSC), the primary potentially
responsible party (PRP) group, and several other local landowners. The CSC acquired several
Zone 2 parcels and established institutional controls (ICs) to help create a partial buffer zone
around Zone 1. This Record of Decision (ROD) addresses both Zone 1 and Zone 2.

1.2 Statemen isis and Purpose

This decision document presents the U.S. Environmental Protection Agency's (EPA's) Selected
Remedy for the Casmalia Resources Superfund Site, including both Zone 1 and Zone 2. The
remedy was chosen in accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA), 42 United States Code (USC) Section 9601 etseq., as
amended, and, to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP), 40 Code of Federal Regulations (CFR) Part 300. This decision is based
on EPA's Administrative Record file for this Site. The Proposed Plan (EPA, 2017) and ROD
address the community involvement requirements of CERCLA.

The Department of Toxic Substances Control (DTSC) is the lead support agency for the State of
California (State), and has been the primary support agency during the Remedial Investigation

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PART 1: THE DEC LA RAT II ON

(Rl) and Feasibility Study (FS) process for the Site. In addition, EPA has consulted with the U.S.
Fish and Wildlife Service (USFWS), the Central Water Quality Control Board (RWQCB), and the
California Department of Fish and Wildlife (CDFW) for many years during ongoing Site
investigations and development of the Selected Remedy. In accordance with 40 CFR § 300.430,
the State has actively participated in the decision-making process, and has provided EPA with
invaluable input. DTSC, as the support agency, reviewed a pre-final version of this ROD and
concurred with the Selected Remedy in a letter to EPA dated May 7, 2018.

1.3 iessment of Site

Releases of hazardous substances have contaminated soil, sediment, soil vapor, surface water,
and groundwater as a result of past hazardous waste treatment, storage, and disposal activities
at the former Class I hazardous waste management facility. The response actions selected in
this ROD are necessary to protect public health or the environment from actual or threatened
releases of hazardous substances and contaminants into the environment.

1.4 scription of Selected Remedy

The Selected Remedy and the major components are summarized in this section. The Selected
Remedy will provide the best approach for cost-effective risk reduction. It will protect human
health and the environment by either removing hazardous substances and contaminants from
the Site, thereby reducing any residual risk, or by limiting exposure to human receptors and/or
ecological receptors by implementing the actions described later in this section.

The Selected Remedy will be the final remedy for the entire Site, comprised of Zones 1 and 2
(Figure 2-1). The remediation strategy incorporates actions for five different principal study
areas (designated Areas 1 through 5) and multiple impacted media into a comprehensive
remedy (Figures 2-14 and 2-15). Areas 1 through 4 include the primary source areas and
associated soil, sediment, and surface water. Area 5 includes onsite (Zone 1) groundwater and
is further divided into three subareas (Area 5 North, Area 5 South, and Area 5 West).

Consistent with EPA's presumptive remedy for municipal solid waste landfills and common
practice at many large legacy hazardous waste landfill sites, the Selected Remedy is a combined
containment and treatment remedy. The remedy will include engineering controls, institutional
controls (ICs), contaminant source reduction and treatment, monitored natural attenuation
(MNA), perimeter control, long-term operations and maintenance (O&M), long-term
monitoring, and contingency measures.

Principal threat wastes (PTWs) for the Site are high-concentration waste materials that occur
within the northeastern portion of the Site and underlying groundwater. The PTWs include
waste materials within the five landfills and the adjacent disposal areas, and the highly
contaminated free-phase nonaqueous phase liquid (NAPL) between and underlying these areas.
The PTWs contain numerous organic and inorganic chemicals at high concentrations across
multiple chemical classes (volatile organic compounds [VOCs], semivolatile organic compounds
[SVOCs], herbicides, pesticides, dioxins/furans, metals, and cyanide). The Selected Remedy

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PART 1: THE DEC LA RAT II ON

addresses PTWs through NAPL source reduction, extraction and treatment of contaminated Site
liquids, and containment of waste materials in landfills, soil, and groundwater.

The Selected Remedy includes many different components based on Site areas. The primary
remedial actions for each of the five study areas are as follows:

• Area 1 (Capped Landfills Area. Burial Trench Area [BTA1. and Central Drainage Area [CPA]):
The Selected Remedy includes continued use of the existing RCRA Subtitle C capping
systems for the landfills area, plus expansion of the caps in selected areas. These RCRA-
compliant caps (RCRA caps) were constructed on four of the landfills (Pesticide/Solvent
[P/S] Landfill, Heavy Metals Landfill, Caustics/Cyanide Landfill, and Acids Landfill) between
1999 and 2002. The capped area will be expanded to cover the uncapped polychlorinated
biphenyl (PCB) Landfill, interstitial areas with former waste management units between the
landfills, the BTA west of the landfills, and the CDA south of the landfills. Capping will
contain waste materials and contaminated soil and minimize infiltration and potential
migration of contamination to groundwater.

• Area 2 (RCRA Canyon and West Canyon Spray Area [WCSAD: The Selected Remedy includes
installation of either an evapotranspiration (ET) cap or a RCRA hybrid cap. A RCRA cap
meets Subtitle C performance standards, and selection of the cap configuration will be
finalized during the remedial design phase and is subject to EPA approval.

• Area 3 (Former Ponds & Pads Area [FPPD: The Selected Remedy includes excavation of four
soil hotspots (Hotspot-1 [HS-1] through Hotspot-4 [HS-4]), which are discrete areas with
elevated concentrations of metals, VOCs, and other organic compounds. Excavated soil will
be consolidated into the existing PCB Landfill prior to capping. Subject to EPA approval
during remedial design, all or a portion of HS-1 in the Liquids Treatment Area alternatively
may be covered with an asphalt cap, and Hotspot-3 (HS-3) in the FPP Area may be covered
with the RCRA cap extended from Area 1. The final remedial approach for these hotspots
will be selected during the remedial design phase. A fifth soil hotspot (Hotspot-10 [HS-10]),
consisting of contaminated soil in the Maintenance Shed Area (MSA), will be covered with
the RCRA cap extended from Area 1.

• Area 4 (Stormwater Ponds and Treated Liquid Impoundments): The Selected Remedy
includes removal of all liquids, placement of clean soil, and installation of engineered caps
over Pond 18, Pond A-5, Pond 13, A-Series Pond, and the Runoff Control Facility (RCF) Pond.
Pond 18 will be closed, Ponds A-5 and 13 will be closed and converted into lined stormwater
retention basins, and a lined stormwater channel will be constructed over the former
footprint of the RCF Pond (after it is capped). Surface water systems for treated liquids and
clean stormwater will continue to be managed separately. These improvements will allow
for more offsite discharge of clean stormwater to the B-Drainage and Casmalia Creek.

Finally, one or more new, lined, RCRA-compliant evaporation ponds will be constructed
over the former footprint of the A Series Pond.

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PART 1: THE DEC LA RAT II ON

• Area 5 (Sitewide Groundwater). Area 5 includes three subareas:

-	Area 5 North: The Selected Remedy includes subsurface liquids extraction and
treatment from existing and new facilities in the source areas (source reduction).
Extraction will continue from the existing Gallery Well, Sump 9B, and the Perimeter
Source Control Trench (PSCT) to contain and prevent groundwater from migrating
vertically and laterally to the south. Approximately 16 new NAPL extraction wells will be
installed in the P/S Landfill to capture as much pooled product as possible and reduce
the driving head that may contribute to downward and lateral migration. The area that
is circumscribed by the boundaries of the five hazardous waste landfills is designated as
a Waste Management Area (WMA) because waste materials are being left in place and
removal is not practicable. Groundwater cleanup levels do not apply within the WMA;
and groundwater below the area circumscribing the five landfills will not be remediated
pursuant to the NCP and EPA guidance on WMAs (EPA, 1993a; EPA, 1996; EPA, 2009a).

-	The Selected Remedy also includes a Technical Impracticability (Tl) Zone designated
pursuant to the NCP and EPA guidance (EPA, 1993c). A comprehensive Technical
Impracticability Evaluation (TIE) evaluation was documented in the Rl Report (CSC,
2011) and the FS Report (CSC, 2016), which examined: (1) hydrogeologic factors;

(2) contaminant-related factors; and (3) technology constraints on remediation system
design and implementation. The TIE concluded that full restoration of groundwater to
MCLs within a limited portion of the Site, designated as Area 5 North, is technically
impracticable from an engineering perspective [40 CFR 300.430(f)(l)(ii)(C)(3)]. ATI
waiver is appropriate for Area 5 North because the presence of large volumes of light
nonaqueous phase liquid (LNAPL), dense nonaqueous phase liquid (DNAPL), and
dissolved-phase organic and inorganic contamination in low-permeability fractured
bedrock, both within and south of the P/S Landfill, make it technically impracticable to
meet drinking water standards in this area. The presence of LNAPL and/or DNAPL is
observed up to 500 feet south of the P/S Landfill in the CDA; there is no expectation that
groundwater within this area can be remediated for beneficial use.

The WMA is within the boundaries of the Tl Zone. A Point of Compliance (POC) will
encompass both the WMA and the Tl Zone, and will be located at the Area 5 North
boundary to ensure that groundwater quality is not further degraded outside this area.
Because the Tl Zone includes the WMA, and because the POC is the boundary of the Tl
Zone, this ROD may refer to the Tl Zone to mean both the Tl Zone and the WMA.
Groundwater cleanup levels apply beyond the POC boundary circumscribing the Tl Zone
(Area 5 North). Approximately 12 new Lower Hydrostratigraphic Unit (HSU) monitoring
wells will be installed to verify that dissolved-phase contaminants and NAPL are not
migrating southward underneath the PSCT outside of Area 5 North. A rigorous
compliance monitoring program will also be implemented.

Under the Selected Remedy, highly contaminated liquids and NAPL from the Gallery
Well, Sump 9B, and new source area extraction wells in the P/S Landfill will be stored

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PART 1: THE DEC LA RAT II ON

onsite and then transported to an EPA-approved offsite treatment, storage, and disposal
facility. Less-contaminated liquids from the PSCT and perimeter control trenches (PCT)-
A, PCT-B, and PCT-C will be treated onsite using a treatment system upgraded pursuant
to the ROD, and the treated effluent will be sent to one or more new onsite evaporation
ponds.

- Area 5 South and Area 5 West: The Selected Remedy includes liquids extraction and
onsite treatment from the existing PCT-A, PCT-B, and PCT-C to contain and prevent
contaminated groundwater from migrating southward down the adjacent drainages.
The Selected Remedy also includes MNA to both treat and help contain groundwater
contamination onsite (within Zone 1). MNA is a passive, in situ method whereby
contaminant concentrations are reduced in place through existing physical, chemical, or
biological processes.

•	Stormwater Discharge: Fresh sitewide stormwater, consisting of runoff generated from rain
events, will be managed following remedy implementation using new, lined, stormwater
retention basins, and discharged to the B-Drainage and Casmalia Creek under National
Pollutant Discharge Elimination System (NPDES) permit substantive requirements.

•	Institutional Controls (ICs): The ICs include environmental covenants that place restrictions
on both land use and water use within the boundaries of the former waste disposal area
(Zone 1) and surrounding land parcels (Zone 2). These restrictions include land or water
disturbing activities such as excavation, construction, demolition, groundwater pumping,
and any activity that affects habitat, open space, or wetlands, which cannot be
implemented without EPA approval. ICs are already established for six parcels, in the form
of legal covenants that provide for land and water use restrictions and allow access for CSC
(and successor landowners) to perform response actions and long-term operations,
maintenance, and monitoring activities. EPA is also included as a third-party beneficiary to
these covenants, allowing it access to the Site and the ability under the law to enforce the
terms of the covenants. As needed, additional ICs will be implemented as part of the
remedial design and remedial action phases of work.

•	Long-Term Operations and Maintenance (O&M): Long-term O&M will be conducted to
ensure that all Site components and systems are functioning effectively throughout the
duration of the remedial action. Long-term O&M will address multiple media and systems,
including, but not limited to, capping systems, liquids collection, treatment, and disposal
systems, surface water management, and all monitoring systems. Long-term O&M will
incorporate modern, integrated, and upgradeable automated process control systems and
instrumentation to ensure that all Site systems function safely, reliably, and effectively;
these will include, but not be limited to, alarms, automatic shut-off systems, video
surveillance systems, data recorders, and flow controllers. Long-term O&M will be
performed based on optimization studies, and a long-term O&M plan that will be subject to
EPA review and approval.

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PART 1: THE DEC LA RAT II ON

•	Long-term Monitoring: Long-term performance and compliance monitoring will be
conducted to ensure that remedial systems are functioning effectively and remain in
compliance with performance standards. Long-term monitoring will include compliance
monitoring of groundwater both laterally and vertically, surface water, soil vapor and
ambient air, and performance monitoring of remedial systems. Long-term monitoring will
also include ongoing evaluation of ICs. Long-term monitoring will incorporate modern,
integrated, and upgradable automated data collection systems and instrumentation to
ensure that Site monitoring systems function effectively, including, but not limited to, data
loggers for new monitoring wells. Long-term groundwater monitoring will be performed
based on optimization studies and subject to a long-term monitoring plan that will require
EPA review and approval. EPA may require additional monitoring, if determined necessary
based on the results of monitoring data, to ensure protection of human health and the
environment.

•	Contingency Measures: Contingency measures will be performed if groundwater monitoring
data indicate that contamination is migrating beyond area boundaries, including the POC
and the perimeter boundary of the former disposal facility (Zone 1). Contingency measures
will be initiated if groundwater monitoring data show that migration is occurring at
statistically representative concentrations that cause, or are likely to cause, exceedances of
performance standards. These contingency measures will be performed to ensure adequate
containment. Contingency measures may include any or all the following: (1) additional
monitoring from existing wells; (2) installation of additional monitoring wells to further
characterize potential migration; and (3) installation of a limited number of extraction wells
within a localized area to maintain hydraulic containment. These extraction wells would
supplement the area and perimeter containment provided by existing perimeter control
trenches, extraction wells, and natural attenuation. Installation of additional extraction
wells outside the POC or Zone 1 perimeter boundary as part of contingency measures may
require an Explanation of Significant Differences (ESD).

1.5 Statut terminations

The Selected Remedy is protective of human health and the environment, complies with
federal and State requirements that are applicable or relevant and appropriate to the remedial
action (unless justified by a waiver), is cost-effective, and utilizes permanent solutions and
alternative treatment (or resource recovery) to the maximum extent practicable. The Selected
Remedy complies with the offsite disposal requirements of CERCLA and the NCP.

The Selected Remedy also satisfies the statutory preference for treatment as a principal
element of the remedy (that is, reduces the toxicity, mobility, or volume of hazardous
substances, pollutants, or contaminants as a principal element through treatment) for the
contaminated media.

Because the Selected Remedy will result in hazardous substances, pollutants, or contaminants
remaining onsite above levels that would allow for unlimited use and unrestricted exposure, a

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PART 1: THE DEC LA RAT II ON

statutory review will be conducted within 5 years after initiation of remedial action, and every 5
years thereafter, to ensure that the remedy is, or will be, protective of human health and the
environment. If it is determined that components of the Selected Remedy are not protective,
EPA will evaluate corrective actions and implement the preferred action to ensure continued
protectiveness.

1.6	D Data Certification Checklist

Specific certification information is included in Part 2, the Decision Summary, of this ROD.
Additional information can be found in the Administrative Record file for this Site. Part 2
information is organized in the following sections:

•	Chemicals of concern (COCs) and their respective concentrations (Section 2.5.6)

•	Baseline risk represented by the COCs (Section 2.7)

•	Performance standards (cleanup or containment levels) established for the COCs and the
basis for these levels (Section 2.8.7)

•	How source materials constituting principal threats are addressed (Section 2.11)

•	Current and reasonably anticipated future land use assumptions, and current and potential
future beneficial uses of groundwater used in the baseline risk assessment and ROD
(Section 2.6)

•	Potential land and groundwater use that will be available at the Site as a result of the
Selected Remedy (Section 2.6)

•	Estimated capital, annual operations and maintenance (O&M), and total present value
costs, discount rate, and the number of years over which the Selected Remedy cost
estimates are projected (Section 2.12.15)

•	Key factors that led to selecting the remedy (Section 2.13)

This ROD was prepared consistently with guidance published by EPA for preparation of RODs
(EPA, 1999b).

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PART 1: THE DECLARATION

Authorizi , ; jnalures

Administrator

U.S. Environmental Protection Agency

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PART 2:

CISION SUMMARY

2.1 Site Name, Location, ai ef Description

Casmalia Resources Superfund Site (Site), Santa Barbara County, California, CERCLIS
Identification Number CAD020748125.

The Site is an inactive Class I hazardous waste management facility located in the northwestern
corner of Santa Barbara County, California (Figure 2-1). The Site lies in a rural setting,
approximately 4 miles from the Pacific Ocean and about 10 miles southwest of the city of Santa
Maria. The small, unincorporated town of Casmalia is located approximately 1.5 miles south-
southeast of the Site and has a population of about 300. Nearby land uses surrounding the Site
include agriculture, cattle grazing, and oil field development.

EPA is the lead agency for the Site, and has worked collaboratively with numerous public
agency stakeholders throughout the history of the Site. DTSC, the Central Coast RWQCB, and
CDFW have participated actively for many years in Site planning, oversight, and decision
making. DTSC is the lead support agency for the State and provided formal concurrence of the
Selected Remedy in a letter to EPA dated May 7, 2018. In addition, EPA has consulted with the
USFWS.

The source of cleanup monies will be a fund established by EPA based on settlement funds
received from PRPs, and work funded and performed by other PRPs (see Section 2.2.4). The
former Class I hazardous waste management facility, owned and formerly operated by CR,
accepted over 5.6 billion pounds of solid and liquid wastes between 1972 and 1989. More than
10,000 businesses and government entities sent waste to the Site. Wastes received at the Site
included (in part): petroleum wastes, acids, bases, organic chemical solvents, petroleum
solvents, paint sludge, pesticides, infectious wastes, septic tank pumpings, and sewage sludge.
The facility stopped accepting wastes in 1989, after CR was unsuccessful in obtaining a permit
under RCRA to treat, store, and dispose of hazardous wastes; it then closed in 1991.

Waste management operations were conducted within the 252-acre facility boundary,
designated as Zone 1. Former waste management units included:

• 6 landfills

• 43 surface impoundments

• 15 evaporation pads

• 2 nonhazardous waste spreading areas

• 6 oil field waste spreading areas

• 11 shallow injection wells

• 7 disposal trenches

• 1 drum burial unit

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PART 2: THE DECISION SUMMARY

The historical Site layout is shown in Figure 2-2. The former waste management facility (Zone 1)
of the Site is secured by perimeter fencing and an access gate. Zone 2 extends outward from
Zone 1 and encompasses adjacent properties, owned by the CSC and other local landowners.
The CSC acquired several Zone 2 parcels to help create a partial buffer zone around Zone 1.

This ROD addresses both Zone 1 and Zone 2.

2.2 Site History and Enforcement Activities

EPA has been engaged with the Site for many years, first in reviewing the application for a RCRA
permit and then in an environmental response mode under the Superfund Program. CR was
operated as a limited partnership. CR's general partner, Kenneth Hunter, Jr., later Hunter
Resources Inc., operated the Site from 1972 to 1991 as a Class I hazardous waste disposal
facility. CR coordinated with EPA and State regulators in the 1980s, implementing phased Site
improvements and seeking to obtain a RCRA Part B permit. The facility ultimately experienced
operational, regulatory, and financial challenges, however, that led to increased regulatory and
community concerns. The Site stopped accepting wastes in 1989, after CR was unsuccessful in
obtaining a RCRA permit; it ceased operations in 1991.

At that time, conditions at the Site presented imminent and substantial endangerment to
human health and the environment. EPA temporarily began conducting critical Site stabilization
activities in 1992 under Superfund emergency response authorities, and continued those
activities through 1996. EPA and the CSC finalized a Consent Decree (CD) in 1997 that provided
for the CSC to conduct Site characterization and response actions. Work under the CD is
planned to continue through implementation of the Selected Remedy in this ROD.

The Site was placed on the National Priorities List (NPL) on September 13, 2001.

2.2.1 Casimalia Resources Operations (1972 - 1991)

The CR facility began operations in 1972 in accordance with California RWQCB Waste Discharge
Permit No. 72-28, which allowed a 61-acre hazardous waste disposal facility, including 15
surface impoundments and one landfill area. The permit was amended twice (Permit No. 75-73;
Permit No. 80-43) to gradually expand the Site to its ultimate size of 252 acres. The facility
accepted a diverse array of solid and liquid hazardous waste materials during its lifespan, but
stopped accepting liquids in July 1987 and solid wastes in November 1989.

During CR operations, the Site also had five waste treatment units: (1) an acid/alkaline
neutralization facility, identified as the Casmalia Neutralization System (CNS); (2) a hydrogen
peroxide treatment system; (3) a wet air oxidation unit; (4) a temporary pilot-scale powder-
activated carbon treatment unit; and (5) oil recovery tanks. None of these waste treatment
units are currently in place.

Federal, State, and local environmental and health agencies closely scrutinized the Site during
the 1980s. Potential environmental concerns were showcased in the local media, and
community complaints in the mid- to late-1980s noted odors emanating from the Site, and

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alleged surface water and groundwater contamination. Despite some operational
improvements implemented by CR, it became clear by 1988 that a RCRA Part B permit would
not be forthcoming. The Site operator stopped accepting waste in 1989, substantially ramped
down Site activities, and effectively abandoned the Site in 1991.

Various measures were taken to limit Site-related impacts. During early Site operations,
subsurface clay barriers were installed in the B- and C-Drainages in 1972-1973 and in 1982. CR
installed subsurface compacted clay barrier walls downgradient of the P/S Landfill and PCB
Landfill in 1980. The P/S Landfill barrier includes a liquids extraction point called the "Gallery
Well," which also was installed in 1980. A subsurface barrier near Pond 20 was constructed in
1981-1982, and a subsurface barrier was installed at the base of RCRA Canyon in 1984. A
relatively shallow liquid extraction point, Sump 9B, was constructed in response to evidence of
contamination observed during closure of the former Pad 9B waste pad in 1988.

Groundwater extraction has been ongoing since 1980, when the Gallery Well began operating
as a groundwater collection facility. CR installed several perimeter collection and extraction
facilities, including three collection trenches and five extraction wells in 1989. These features,
located along the A-, B-, and C-Drainages, were originally called plume capture and control
trenches, but are now commonly referred to as the "perimeter control trenches" (PCT-A, PCT-B,
and PCT-C). Extraction wells installed within these trenches are completed to depths of
approximately 35 to 70 feet bgs.

CR installed the PSCT downgradient of the landfills in 1990 (see Figure 2-3). The PSCT is a 3-feet
wide gravel-filled collection trench that extends over a linear distance of about 2,650 feet
across most of the central portion of the Site, downgradient of the five landfills, the CDA, and
the BTA (CSC, 2011). The PSCT extends to depths of between approximately 13 and 65 feet,
depending on the depth at which unweathered claystone bedrock was encountered during
construction. The PSCT is designed to intercept subsurface liquids migrating from north to
south across the Site.

In 1998, the CSC installed an additional shallow liquid extraction point (Road Sump) south of
Sump 9B to intercept groundwater potentially migrating downgradient from Sump 9B.

2.2.2 EPA Emergency Response Operations (1992-1996)

EPA invoked Superfund removal authority to conduct emergency response operations and
stabilize the Site from 1992 through 1996. EPA maintained essential Site operations, including:
collection, treatment, and disposal of contaminated liquids; management of surface water;
groundwater monitoring; and stabilization of the landfills. EPA then entered into enforcement
negotiations with the CSC that led to the Casmalia CD in 1997 and the CSC taking over
stabilization and maintenance activities.

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PART 2: THE DECISION SUMMARY

2.2.3 CSC Response Actions under Consent Decree (1997-Present)

Under the 1997 CD, the CSC is obligated to fund and perform specific Site cleanup activities.
The CSC has been performing response actions under EPA oversight as required by the CD and
CERCLA processes. These requirements define specific, phased elements of work that include
Site operations, monitoring, RIs, and development of an FS. The CSC's work has included
continued Site stabilization activities, including ongoing extraction, treatment, and disposal of
contaminated subsurface liquids, monitoring, and routine maintenance.

Consistent with the CD, the CSC installed an engineered capping system for the P/S Landfill in
1999. The CSC also implemented non-time critical removal actions, including performing an
Engineering Evaluation/Cost Analysis (EE/CA) that led to an EE/CA report in 2000, as well as
capping of an area encompassing three landfills (Heavy Metals, Caustics/Cyanide, and Acids
landfills) and areas between these landfills in 2001 and 2002. The CSC intentionally left the fifth
landfill (PCB Landfill) uncapped, with the plan of placing future remediation soils there and then
installing a RCRA cap. Figure 2-3 presents current Site conditions, which includes the former
and current landfills, current extraction trenches and extraction wells, former ponds and
evaporation pads, and configuration of the five ponds.

The CSC has continued to operate and maintain groundwater collection facilities (Gallery Well,
Sump 9-B, PSCT, PCT-A, PCT B, and PCT-C) under EPA's oversight through the requirements of
the CD. Table 2-1 presents a summary of the operations of these systems, including total
volumes extracted through mid-2016. The CSC also initiated a routine groundwater and surface
water monitoring program pursuant to the CD, which consists of semiannual collection of water
level and water quality data.

Figure 2-4 presents aerial photographs showing the progression of Site conditions from 1970
(prior to landfill development), through various years of Site operations and stabilization
activities, to current conditions (2016). Figure 2-5 presents a timeline of key operational,
investigation, response, and enforcement activities since 1972 when Site operations began.

Key Accomplishments: To date, EPA oversight of CR and the CSC has resulted in completion of
many significant projects to stabilize the Site, remove and contain contamination, control risks,
conduct characterization, evaluate remedial alternatives, and set the stage for final Site
remediation. Key enforcement and source stabilization and control activities have included the
following.

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PART 2: THE DECISION SUMMARY

•	Completed negotiations that resulted in the Casmalia CD and NPL listing

•	Proposed and then completed listing of the Site on the NPL in 2001

•	Performed response actions at most former waste surface impoundments and evaporation
pads in the southern area of the Site, and placed contaminated soils into the existing
landfills (prior to capping)

•	Removed the former RCRA Landfill waste and placed the contents into the existing landfills
(prior to capping)

•	Installed subsurface compacted clay barrier walls in the B- and C-Drainages, downgradient
of the P/S and PCB landfills, at the base of RCRA Canyon, and near former Pond 20, to limit
lateral subsurface fluid migration in these areas

•	Capped four existing landfills (P/S, Heavy Metals, Caustics/Cyanide, and Acids)

•	Installed the Gallery Well extraction system in the P/S Landfill, with extraction and
treatment/disposal of approximately 11,000,000 gallons of liquid since operations began

•	Constructed an onsite liquids treatment system for water from the PSCT

•	Installed the PSCT at the foot of the P/S Landfill, with extraction and onsite treatment of
approximately 87,000,000 gallons of liquid since operations began

•	Installed the Sump 9B liquids extraction system between the P/S Landfill and the PSCT, with
extraction and treatment/disposal of approximately 7,000,000 gallons of liquid since
operations began

•	Installed three PCTs (PCT-A, PCT-B, and PCT-C) near the southern Site boundary

•	Installed approximately 400 monitoring wells and piezometers in onsite and offsite areas

•	Constructed an improved stormwater collection and storage system, including three
stormwater retention ponds (RCF Pond, A-Series Pond, and Pond 13) and two treated
liquids evaporation ponds (Pond A-5 and Pond 18)

•	Constructed an engineered wetland (B-Drainage wetland) to address habitat restoration for
special-status amphibians

•	Completed extensive Site investigations, an Rl report, and an FS report

•	Provided ongoing routine Site maintenance, including: collection, treatment, and disposal of
contaminated liquids; landfill cap maintenance; routine water level, groundwater, surface
water, and biological monitoring; reporting; and related activities

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2.2.4 Summary of Enforcement Activities

EPA has entered into numerous CDs and Administrative Orders on Consent with PRPs in order
to require these PRPs to implement and/or fund ongoing Site work. Under the 1997 CD, the CSC
is required to fund and conduct the Phase I work (such as, fund and perform the Rl and FS), and
to conduct Site work funded from EPA settlements.

Through 2017, based upon EPA's initial cost estimate using Site records to develop a settlement
formula, EPA settled with over 2,000 parties. Over 1,900 PRPs, referred to as de minimis
contributors because they sent relatively small amounts of waste to the Site, resolved their
liability and contributed over $63 million for Site-related response actions. The remaining
parties include the former owner and operator and customers referred to as "major" waste
generators, who have collectively paid over $56 million. Altogether, these settlements have
recovered over $119 million to help fund response actions at the Site. EPA continues to pursue
additional PRP settlements and may take further enforcement action against non-settled PRPs
in order to raise funds for Site-related response action and to reimburse EPA for Site-related
costs.

2.2.5 Casmalia Consent Decree

The 1997 CD and Statement of Work (SOW) define discrete elements of work, sequencing and
phasing of major work activities, and specific projects, activities, and deliverables. The CD
further establishes a process for funding response actions through third-party recoveries. The
work covered by the CD and SOW are described in terms of four phases, as follows:

Phase I: Phase I work includes: performance of early response actions (such as, Site

stabilization, critical Site operations, and liquids management) and routine Site
maintenance; design and capping of the P/S Landfill; cap design for the other
landfills; Site characterization; and preparation of the Rl report and FS report. Phase
I work is funded directly by the CSC member companies.

Phase II: Phase II work includes: specified Site activities not covered under Phase I, including
cap construction for the other landfills (except the PCB Landfill); ongoing, routine
Site operations after 2000; ongoing, routine groundwater monitoring; community
relations activities; collection, treatment, and disposal of Site liquids; stormwater
management; and Site monitoring.

Phase II also includes design and construction of the Selected Remedy, along with
the first 5 years of operations, maintenance, and monitoring (OM&M). Although the
CSC is obligated to perform the Phase II work under the CD, the work must be
funded by cashout settlements from other parties or other sources.

Phase III: Phase III work includes the first 30 years of long-term OM&M.

Phase IV: Phase IV work entails the post 30-year OM&M work after Phase III.

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PART 2: THE DECISION SUMMARY

The CSC has completed Phase I work, is currently performing Phase II work, and is required to
complete Phase II obligations, including design and construction of the Selected Remedy and
the first 5 years of OM&M. The party or parties that will perform Phases III and IV, which may
include the CSC, are to be determined.

2.3 Community Participation

EPA's outreach goal is to educate the community about work being done at the Site and
collaborate with stakeholders to successfully engage the public. EPA relies on community input
to understand local priorities and concerns during remedy decision making. The Site has
historically been a focus of community concern during and since the time it was an active, Class
I, hazardous waste management facility. EPA began holding community meetings at the town of
Casmalia when it temporarily took over critical Site stabilization activities in 1992, under
emergency response authorities. EPA continued to hold community meetings as it conducted
emergency response operations from 1992 through 1996, and developed and finalized the CD
in 1997. For the past two decades, EPA has hosted regular Interagency Committee (IAC)
meetings with the DTSC, RWQCB, CDFW, and USFWS to coordinate work, solicit input, and
communicate the status of ongoing activities with public stakeholders.

EPA has also helped support a Community Technical Assistance Consultant (CTAC) to review
and provide community input on technical initiatives and Site response work. The CTAC role
provides an opportunity for community members to learn about the Site and share community
needs and concerns. The CTAC provides input and feedback to EPA and the State so that
community perspectives can be considered in the remedy selection process. Particularly in the
last few years, the CTAC has played an active role in the ongoing IAC meetings, representing the
viewpoints of the local community.

The Proposed Plan for the Site was made available to the public on November 22, 2017. The
Proposed Plan and other Site documents (including the Rl report and FS report) can be found:
on the EPA website, in the Administrative Record file of the information repositories
maintained at the EPA Region IX Superfund Records Center at 95 Hawthorne Street in
San Francisco, California; and at the Santa Maria Public Library, 2nd Floor, Reference
Department, 421 S. McClelland Street, Santa Maria, California. The notice of the availability of
the Proposed Plan, including the date and location for the public meeting and public comment
period, was published the week prior to the start of the public comment period in the Santa
Maria Times newspaper and sent to the Site mailing list. A public comment period was held
from November 22, 2017, to January 22, 2018.

A public meeting was held December 6, 2017, to present the Proposed Plan to the community
audience and accept public comments. The meeting was attended by about 60 people. EPA
presented an overview of the Proposed Plan and formal public comments were accepted at the
meeting. Transcripts of the public meeting are part of the Administrative Record file at the
information repositories. EPA's response to comments received at the public meeting and

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otherwise during the public comment period are included in the Responsiveness Summary,
which is part of this ROD (see Section 3.0 and Appendix G).

2.4 Scope and Role of Operable Unit or Response Action

The Site is a large facility with many legacy waste management units and extensive soil,
sediment, surface water, and groundwater contamination. Although the Site has been
stabilized and there are no current risks of exposure to the public, remediation and long-term
OM&M at the Site are necessary for long-term protection of human health and the
environment. The Site has not been organized into multiple operable units (OUs). The Selected
Remedy presents the final response action for the entire Site. The Selected Remedy addresses
PTWs at the Site through the containment of waste within the landfills and removal of NAPL
source material.

The remediation strategy incorporates actions for five different Site areas and multiple
impacted media into a comprehensive remedy. The study areas are described in further detail
in Section 2.5.3. Areas 1 through 4 include the primary source areas, soil, sediment, and surface
water. Area 5 includes onsite groundwater. The five areas are defined within the former facility
boundary (Zone 1) to facilitate cleanup evaluation and implementation, based on each area's
unique hazardous waste operations during the operational era, ongoing response actions,
physical characteristics, and Site-related contaminants. The Selected Remedy addresses PTWs
at the Site through containment of the waste within the landfills, and the removal of NAPL
source material in Area 1. Long-term monitoring, based on optimization studies, will be
required to verify that contaminants are not migrating beyond the POC boundary in Area 5
North, or beyond the Zone 1 boundary.

2.5 Site Characteristics

The CSC conducted Rl activities (planning, fieldwork, and reporting) from 2002 through 2011 to
characterize the nature and extent of contamination, fate and transport of contamination, and
human health and ecological risk. The Rl work included the installation and sampling of
monitoring wells and piezometers in Zone 1 and Zone 2 areas, highly complex groundwater
modeling and geophysical surveys, and extensive sampling of soil, sediment, soil vapor, surface
water, and groundwater. The FS was completed from 2011 to 2016 to evaluate a range of
remedial alternatives to address soil, soil vapor, surface water, sediment, and groundwater
contamination in accordance with the NCP and CERCLA RI/FS guidance. The CSC completed the
final Rl report in January 2011 (CSC, 2011) and the final FS report in February 2016 (CSC, 2016).
Concurrent with the Rl and FS work (2002 to 2016), important interim actions were also
completed, including extraction and treatment and/or disposal of contaminated Site liquids
(NAPL and groundwater). The Site conditions are documented in the Rl report and FS report.
Key features of the Site are described in Section 2.5.2.

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2.5.1 Conceptual Site Model

The conceptual Site model (CSM) presents an understanding of the sources of chemicals
released to the environment, how they were released and transported within and among
media, and the exposure pathways and routes by which both human and ecological receptors
may contact them. Receptors that may be potentially exposed to Site-related chemicals are
identified, and the likelihood of their potential exposures is assessed through consideration of
the current and the anticipated future use of the Site.

The former hazardous waste management facility accepted a full range of listed and
characteristic RCRA wastes. As a result of these activities, contamination occurs pervasively
throughout the Site. The primary contaminant sources include existing landfill areas, former
waste disposal areas and facilities that have not previously undergone cleanup, and residual
contamination from prior Site cleanup activities. Of these, the existing landfill areas and former
disposal areas not addressed through prior interim response actions represent the most
significant continuing sources of contamination.

Based on extensive Site characterization, chemicals of potential concern (COPCs) consist of
numerous VOCs, SVOCs, polycyclic aromatic hydrocarbons, pesticides, herbicides, PCBs, dioxins,
furans, and metals. Over 300 chemicals of interest, which are commingled and dispersed
throughout various Site areas and multiple media, have been detected. The chemicals are
adsorbed to soil and claystone, mixed within soil gas, dissolved in surface water and
groundwater, and accumulated as free-phase and residual LNAPL and DNAPL.

Figure 2-6 presents a 3-dimensional CSM geological block diagram for the Site.

From a risk assessment perspective, there must be a complete exposure pathway from the
source to receptors for chemical intake to occur. The CSM identifies potentially complete
exposure pathways and potential receptors. The human health CSM diagrams for uncapped
areas and surface water at the Site are presented in Figures 2-7 and 2-8. The ecological CSM
diagrams for terrestrial uncapped areas, terrestrial capped areas, and freshwater habitat areas
at the Site are in Figure 2-9, Figure 2-10, and Figure 2-11, respectively.

2.5.2 Site Features and Physiography

The 252-acre Site is in the northwestern corner of Santa Barbara County, California. The area
near the Site is sparsely settled, and land uses consist primarily of agriculture, cattle grazing,
and oil field development. The Site is located on the south-flanking slope of the gently rolling
Casmalia Hills, and bounded by the North Ridge to the north; it generally slopes from north to
south. Casmalia Creek flanks the Site on the west/southwest and merges with Shuman Creek
approximately 2 miles south of the Site and approximately 1 mile west of the town of Casmalia.
Shuman Creek empties into the Pacific Ocean, approximately 4 miles west of the confluence
with Casmalia Creek. An ephemeral drainage is located to the north/northeast of the Site and is
referred to as the "North Drainage." Three surface drainages exit the southern facility boundary
and are identified, from east to west, as the A-Drainage (southeastern corner), B-Drainage

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PART 2: THE DECISION SUMMARY

(south-central boundary), and C-Drainage (southwestern corner). The North Drainage and A-
Drainage are tributaries to Shuman Creek, while the B-Drainage and C-Drainage are tributaries
to the perennial Casmalia Creek immediately west of the Site (see Figure 2-1).

Surface elevations range from 835 feet above mean sea level (amsl) at the north to 375 feet
amsl at the southern boundary. The A-, B-, and C-Drainages play crucial roles in EPA's remedial
actions with respect to: (1) the management and controlled discharge of surface water; and (2)
implementation of habitat restoration projects, including constructed wetlands for threatened
and endangered species.

The CSC constructed the wetlands habitat in the B-Drainage in 2008 to serve as mitigation of
potential harm to special-status species, primarily from the anticipated closure of surface water
ponds, in accordance with a 2007 consultation with USFWS and subsequent USFWS Biological
Opinion (BO). The wetlands are located immediately south of Zone 1 (Figure 2-1). The BO was
issued to cover ongoing Site operations and anticipated future cleanup and closure of all five
existing surface water ponds (RCF, A-Series Pond, Pond A-5, Pond 18, and Pond 13). Special-
status species at the Site include the federally threatened California Red-legged Frog and the
federally endangered California Tiger Salamander.

The Casmalia Hills form a topographic high location, separating two groundwater basins. The
Santa Maria Valley groundwater basin is located to the north and east of the Site, and the San
Antonio Valley Creek groundwater basin is located south of the Site (Figure 2-12). The Site lies
in an upland area between these two basins, but drains to the Shuman Creek watershed;
therefore, drainage is formally associated with the San Antonio Valley Creek basin. Although
groundwater is present, the Site is not located within a California-designated groundwater
basin. Groundwater beneath the Site does not serve as a source of drinking water for the town
of Casmalia or other communities. The town of Casmalia receives its water supply via a pipeline
connection from Casmite Well No. 1, located about 2.7 miles northeast of the Site in the
separate Santa Maria Valley basin. Parcel ownership near the Site is depicted on Figure 2-13.

2.5.3 Study Areas and Sampling Strategy

The Site has been thoroughly studied, beginning with CR Site investigations and response
actions in the 1980s, followed by EPA's Site stabilization and monitoring activities from 1992
through 1996. Since 1997, studies continued with the CD work that required the CSC to
complete the RI/FS, conduct response actions, and perform ongoing O&M.

Numerous detailed study areas were identified during the Rl to facilitate: assessing Site
characteristics, nature and extent of contaminants, and fate and transport of contaminants;
and conducting risk assessments. The media subject to characterization and monitoring have
included soil, soil vapor, groundwater, surface water, and sediment.

The Rl study areas were identified based on historical use and waste management and disposal
practices, and included those listed as follows.

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REMEDIAL INVESTIGATION STUDY AREAS

Soil and Sediment
Study Areas

Capped Landfills

PCB Landfill

RCRA Canyon Area

West Canyon Spray Area

Burial Trench Area (BTA)

Central Drainage Area (CDA)

Liquids Treatment Area

Maintenance Shed Area

Administration Building Area

Roadways

Remaining On-Site Area

Former Ponds and Pads Areas (FPP)

Stormwater Ponds

Treated Liquids Impoundments

Offsite Area (areas outside the Site boundary, that is, Zone 2)

Surface Water and
Groundwater
Study Areas

Stormwater Ponds

Treated Liquids Impoundments

Northern Groundwater Area

Southern Groundwater Area

Offsite Area (surface water and groundwater outside the Site boundary, that is, Zone 2)

Based on the Rl results, the many detailed Rl study areas were consolidated and five main study
areas were designated for the purposes of conducting the FS. Four areas (Areas 1 through 4)
include surface features and systems, and a fifth area (Area 5) includes all onsite groundwater.
Area 5 is further divided into three subareas (Area 5 North, Area 5 South, and Area 5 West),
based on topography, subsurface structure, groundwater flow patterns, and contaminant
distribution. Area 5 addresses onsite groundwater because contamination that could contribute
to exceedances of remediation levels has been contained within the Zone 1 boundary. The five
FS study areas were established and evaluated based on geographical features, surface or
subsurface structure, and/or similar impacted media.

The five study areas include:

• Area 1 (Capped Landfills Area, BTA, and CDA)

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• Area 2 (RCRA Canyon and WCSA)

• Area 3 (FPP Area)

• Area 4 (Stormwater Ponds and Treated Liquid Impoundments)

• Area 5 (Groundwater)

- Area 5 North

- Area 5 South

- Area 5 West

Figure 2-14 shows the location of Areas 1 through 4, addressing surface features. Figure 2-15
shows the location of Area 5, addressing groundwater.

2.5.4 Oinsite Sources and Features

A large number of sources of contamination, numerous engineering systems and components,
and multiple impacted media are present at the Site. The historical waste management units
and current Site features are summarized in the following subsections.

2.5.4.1 Waste Management Units and Facilities

The six landfill disposal areas were located along the northern portions of the Site. One of the
landfills, the former RCRA landfill, was excavated and partially closed between 1989 and 1990.
Surface impoundments (used for evaporation and treatment of liquid wastes or for storing
stormwater) and evaporation pads (used to evaporate liquid wastes and Site stormwater
runoff) primarily occupied the southern and central portions of the Site. Some surface
impoundments and evaporation pads were also present in the northern portion of the Site,
between the landfills (Figure 2-2).

Five Existing Inactive Landfills

CR operated the five existing landfills (P/S, Heavy Metals, Caustics/Cyanide, Acids, and PCB) in
the 1970s and 1980s. In the late 1980s, CR graded the existing landfills (with the exception of
the PCB Landfill) in accordance with closure plans prepared for each landfill. To achieve the
desired grades, CR placed approximately 20 to 60 feet of stabilized soils excavated as part of
the pond and pad closure activities. CR placed a minimal thickness of cover soil over the PCB
Landfill because this landfill was never filled to capacity; it was to be left uncapped and
reserved for future remediation soils.

Following negotiation of the CD in 1997, the CSC improved the P/S Landfill clay buttress in 1998
to provide additional stability and enhance containment, and constructed a RCRA cap in 1999.
Following completion of the EE/CA report in 2000, CSC placed a RCRA cap over the Heavy
Metals Landfill and the interstitial areas on either side of that landfill in 2001, and capped the
remainder of the EE/CA Area (Caustics/Cyanides and Acids landfills, along with the interstitial
areas) in 2002. The CSC constructed a buttress for the Caustics/Cyanides Landfill as part of the

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EE/CA Area capping project. Except for the PCB Landfill, the five inactive Site landfills have now
been capped.

Former RCRA Landfill, RCRA Canyon, and West Canyon Spray Area

The former RCRA Landfill is in a natural canyon (currently referred to as "RCRA Canyon," and
historically sometimes referred to as "West Canyon") on the northwestern side of the Site. This
area was at one time intended to be lined in preparation for receiving RCRA-regulated waste
from the McColl Superfund Site. However, when it became apparent that McColl wastes would
not be delivered to the Site, in 1989 to 1990, CR excavated the limited amount of RCRA Canyon
wastes that had been placed in late 1983 to early 1984 and transferred the wastes to the P/S
Landfill.

RCRA Canyon was also the location of the oil-field-waste spreading areas, referred to as "the
WCSA." The north and west slopes of this area received oil field wastes (primarily drilling mud),
winery wastes, spray irrigation of leachate, and surface stormwater runoff collected from other
portions of the Site. Dried wastes were reported to have been periodically removed and used as
daily cover in the landfills.

Burial Trenches and Shallow Disposal Wells

Waste disposal in the BTA, also historically referred to as "the Burial Cells Unit," began in the
early 1970s with disposal in seven trenches directly south of the PCB Landfill and west of the
P/S Landfill (Figure 2-2). The disposal trenches were constructed by excavating a series of cells
15 to 40 feet square and approximately 15 feet deep. Cells were constructed in seven rows and
assigned numerical designations, with the individual cells in a given row assigned alphabetical
designations.

Waste disposal in the BTA also included liquids disposal in 11 shallow wells constructed
between December 1977 and September 1982. Available information indicates two of these
wells (wells 10 and 11) were between trenches 4 and 5, and the remaining nine wells were
between trenches 3 and 4.

Former Surface Impoundments and Spreading Areas

CR used a total of 43 ponds and 15 evaporation pads, collectively referred to as "surface
impoundments." Construction of the surface impoundments began in 1972, and new
impoundments were added or enlarged through 1985. These facilities were used for the
receipt, treatment, storage, and evaporative disposal of acid and alkaline wastes, oil field
wastes, industrial wastewater, and Site stormwater runoff. Although contaminated liquids were
eventually transferred to most Site ponds, only a few Site ponds directly received wastes. In
addition to the hazardous waste ponds and pads, two waste ponds (Sludges 1 and 2) were used
for disposal of non-hazardous wastes, such as sewage sludge, and six areas were used for
spreading and drying oil field wastes and drilling mud. Disposal of liquids to the ponds ceased
by 1988.

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CR conducted surface impoundment closure activities from 1988 to 1991. The overall objective
of the closure activities was to remove hazardous constituents to background or other cleanup
levels approved by the RWQCB. Surface impoundment closure was undertaken in three stages:
liquids removal, bottom sludge removal, and contaminated subgrade removal. Removed liquids
and bottom sludges were either evaporated or solidified for disposal into the Site's landfill
areas. Contaminated subgrade materials were also relocated to the Site's landfill areas for
disposal.

Based on available information, it appears that 40 out of the 58 former surface impoundments
were recommended for closure at the time. Four entire impoundments (Pad 9A, Pad 9B, Pond
R, and Pond 23) and limited portions of two others (the western portion of Pond 6 and the
southern berm area of Pond 19) were recommended for closure as landfills through capping.
Impoundments recommended for closure as landfills are restricted to the area lying north of
the PSCT, and either overlie or are near known existing contamination sources, including the
BTA, CDA, and the toe area of the P/S Landfill. The closure status of the former surface
impoundments is shown on Figure 2-16. Some of the former ponds and pads contain significant
hotspots of contaminated soils because CR did not complete response actions.

Disposal of drums occurred on an experimental basis in the area of former Pond 19 (Figure 2-2).
Wastes once deposited in this former Drum Burial Area were removed and redeposited into
one of the existing inactive landfill areas, beginning in about December 1979 until early 1980.

Former Waste Treatment Units

The Site had five waste treatment units: (1) the acid/alkaline CNS; (2) a temporary pilot-scale
PACT unit; a wet air oxidation unit; a hydrogen peroxide treatment system; and oil recovery and
treatment tanks (Figure 2-2). These treatment units no longer exist, but the former treatment
unit areas were evaluated during the RI/FS process.

2.5.4.2 Current Containment and Extraction Facilities

Several structures and facilities have been installed to limit contaminant migration and treat
impacted or potentially impacted liquids.

Subsurface Barriers and Extraction Facilities

CR installed subsurface compacted clay barrier walls downgradient of the P/S Landfill in 1980,
along with the Gallery Well located immediately upgradient of this barrier. Subsurface barriers
were also installed at the base of the PCB Landfill in 1980, near Pond 20 in 1981 to 1982, and at
the base of RCRA Canyon in 1984. As part of early Site operations, subsurface clay barriers with
extraction facilities were also installed in the B- and C-Drainages in 1972 to 1973 and 1982,
respectively (Figure 2-2).

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PART 2: THE DECISION SUMMARY

The Gallery Well began operating in 1980 as a groundwater extraction facility. A relatively
shallow liquid extraction point, Sump 9B, was constructed in the CDA in 1988, in response to
evidence of contamination observed during the closure of the former Pad 9B waste pad.

CR installed several perimeter collection and extraction facilities, including three collection
trenches and five extraction wells, in 1989. These features, located along the A-, B-, and
C-Drainages, are referred to as the "perimeter control trenches" (PCTs, or PCT-A, PCT-B, and
PCT-C). CR installed the PSCT downgradient of the landfills in 1990 (see Figure 2-3). In 1998, the
CSC installed an additional shallow liquid extraction point (Road Sump) to intercept
groundwater potentially migrating downgradient from Sump 9B.

Stormwater Runoff Collection Ponds and Treated Liquids Ponds

Five existing unlined ponds were created by CR as a result of excavating waste and
contaminated soils from the former surface impoundments in the late 1980s. Three of these
ponds are currently used for stormwater collection along the south-central Site boundary:

• RCF Pond. The RCF Pond is in the area once occupied by portions of former Ponds 3, 4, 9,
10, and 11. It currently receives untreated water from PCT-A for evaporation. Stormwater
from the central and eastern part of the Site also flows to the RCF Pond.

• A-Series Pond. The A-Series Pond is in the area once occupied by portions of former Ponds
A-l, A-2, A-3, and A-4. It currently receives untreated water from PCT-B and PCT-C for
evaporation.

• Pond 13. Pond 13 is the most southerly (downgradient) of the original stormwater runoff
containment ponds. It is still used for its original purpose of stormwater runoff control.

Two of these ponds have been used for treated liquids disposal, and are located near former
ponds of the same designation in the southwestern portion of the Site. These are:

• Pond A-5. Pond A-5 previously received treated liquids extracted from Sump 9B and the
Gallery Well; this pond does not currently receive any liquids.

• Pond 18. Pond 18 currently receives treated effluent from the PSCT granular activated
carbon (GAC)-treatment system for evaporation.

The five existing ponds all contain total dissolved solids (TDS) concentrations that approach or
exceed the concentration of seawater due to evaporation from the extracted groundwater.
Pond water contains metals at concentrations that may present an increased risk to ecological
receptors. Pond sediments contain concentrations of metals that may serve as an ongoing
source of groundwater contamination. The ponds also have become "attractive nuisances" for
several special-status species, including the California Red-legged Frog, the California Tiger
Salamander, and the Western Spadefoot toad. For the purposes of the Superfund Program, an
attractive nuisance refers to an area, habitat, or feature that is attractive to wildlife and has, or

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has the potential to have, waste or contaminants left on site that are harmful to plants or
animals after a completed remedial action (EPA, 2007). For the Site, the contaminants consist of
elevated TDS levels that will be present in the new lined evaporation pond system, resulting
from treated groundwater discharged to the ponds that evaporates over time.

The CSC constructed another small, unlined surface water runoff collection basin during 2003 in
a portion of the CDA (Figure 2-3). Clean stormwater runoff from the P/S Landfill cap and EE/CA
Area cap is directed via constructed drainage swales into this basin, and a pipeline from the
basin allows stormwater to be directed into the RCF Pond or the upper reaches of the
B-Drainage for discharge outside the Site's boundary, bypassing uncapped areas of the Site.

This pipeline is equipped with valves and flow meters to control the location and rate of
discharge. Discharges from this pond comply with the substantive provisions of the General
NPDES permit.

Subsurface Site Liquids Management

The Gallery Well, Sump 9B, the PSCT, and the PCTs are currently used to control subsurface
liquids migration under requirements of the 1997 CD. Liquids have been extracted from these
features since they were each installed, although the method for treating and/or disposing of
these liquids has changed over time. Liquids from the Gallery Well and Sump 9B, which also
contain LNAPL and DNAPL, are temporarily stored in tanks at the liquids treatment area and
then disposed at an offsite treatment, storage, and disposal (TSD) facility. Liquids from the PSCT
are treated onsite using GAC and discharged to Pond 18 for evaporation. Liquids from the PCTs
are discharged directly to the RCF and A-Series ponds for evaporation without treatment.

The groundwater collection facilities are operated to maintain water levels at or below specific
criteria elevations. Criteria water level elevations are described by water level depths measured
from a datum, such as top of the casing of the collection facility; they have been historically
referred to as "action levels." Periodic liquid level measurements document compliance with
the specific action levels established for each applicable extraction point. Routine Site
maintenance, wetlands monitoring, and groundwater monitoring activities are also conducted.
The CSC submits quarterly progress reports to EPA to document the significant work in the
following main CD elements or components of work at the Site:

• Interim Collection/Treatment/Disposal of Contaminated Liquids Component of Work

• Routine Site Maintenance Element of Work, including Wetlands Operations/Monitoring

• Routine Groundwater Monitoring Element of Work

2.5.5 Geology and Hydrogeology

In the vicinity of the Site, the Todos Santos Claystone Member (claystone) of the Sisquoc
Formation overlies the Monterey (Shale) Formation. The Monterey Formation is up to
5,000 feet thick and is composed of interbedded shale, chert, limestone, and diatomite.

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The claystone underlying the Site is massive to faintly bedded, and has been informally divided
into an upper weathered stratigraphic unit and a lower unweathered stratigraphic unit. The
weathered claystone ranges in thickness from about 15 to 100 feet, and in most places is 30 to
60 feet thick (CSC, 2011). The unweathered claystone is below the weathered claystone, is up
to 1,300 feet thick, and conformably overlies the Monterey Formation. The unweathered
claystone is significantly less fractured than the overlying weathered claystone.

Two hydrostratigraphic units have been defined, identified as: the Upper Hydrostratigraphic
Unit (Upper HSU), associated with the shallow weathered claystone; and the Lower
Hydrostratigraphic Unit (Lower HSU) associated with the underlying deeper unweathered
claystone. Groundwater flow at the Site is quite restricted in both the Upper HSU and Lower
HSU. Most groundwater flow occurs in fractures in the Upper HSU, with a minor component of
flow in the less fractured Lower HSU. Although groundwater flow occurs through fractures in
the Upper and Lower HSUs, most groundwater is stored within the matrix porosity. Given the
thickness of the unweathered claystone (>1,000 feet), the generally small aperture of fractures,
and the lack of interconnectivity between fractures on a Site-wide scale, significant movement
of dissolved-phase contaminants or NAPL to at any appreciable rate is unlikely. The overall
decrease of fracture density with depth and apparent limited fracture connectivity suggest that
the majority of fractures likely terminate at depth and act as areas of dead-zone storage (CSC,
2016).

Groundwater flow conditions have been evaluated through numerous field investigations and
numerical groundwater flow modeling. Over 400 groundwater monitoring wells and
piezometers have been installed across the Site. A natural groundwater flow divide occurs at
the North Ridge. Groundwater north of this divide flows northward toward the North Drainage.
Groundwater south of the ridge flows southward beneath the Site. Groundwater flow direction
is controlled by topography, the geologic structure of the contact between the two HSUs, and
the liquids extraction facilities operated to control the migration of landfill leachate and
contaminated groundwater. The water table contour map on Figure 2-17 presents typical
horizontal groundwater flow patterns and gradients at the Site. Appendix A presents a Site plan
with the well locations and a table of well construction details.

Groundwater modeling specialists spent over 5 years developing and applying a simulation
model to depict onsite groundwater flow patterns. The Rl report provides a detailed discussion
on the development, calibration, use, and results of the groundwater modeling work. The
results of the groundwater elevation data and the numerical flow modeling showed the
following:

• The North Ridge is a groundwater flow divide, and contaminants in groundwater are not
present north of the divide. Contaminants dissolved in groundwater flow southward from
this divide, beneath the primary source areas (landfills, CDA, and BTA) and toward the PSCT.

• The Gallery Well extracts liquids (aqueous phase, LNAPL, and DNAPL) from the P/S Landfill,
which contributes to containment of these liquids within the landfill area. NAPL and
dissolved-phase constituents are contained within the P/S Landfill area from the

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combination of the underlying unweathered claystone, clay barrier, and extraction from the
Gallery Well. DNAPL may not be completely contained at the actual base of the landfill;
however, because the potential exists for it to migrate a short distance downward and
laterally through fractures in the underlying claystone (based on the observed presence of
DNAPL in downgradient wells including Sump 9B and RGPZ-7D). Nevertheless, as described
above, significant movement of NAPL beyond this area at any appreciable rate is unlikely.

• Sump 9B extracts liquids between the P/S Landfill and the PSCT, which contributes to a
localized capture zone of liquids and mitigation of a surface seep that historically formed
during wet winters.

• The PSCT extracts and contains contaminated liquids moving southward beneath the
primary source areas and through the Upper HSU. Liquids flowing through the Lower HSU
are either captured by the PSCT or some may move beneath the PSCT as indicated by
particle tracking. Based on the specific compounds detected and their concentrations
relative to the wells within and upgradient of the PSCT, these compounds are believed to be
related to previously existing ponds and pads and/or to contaminants present in these areas
prior to construction of the PSCT (CSC, 2011).

• The lack of extensive continuity between fractures may limit the extent of potential fluid
pathways on a Site-wide scale (CSC, 2011).

In summary, there are two water-bearing units (Upper HSU and Lower HSU) beneath the Site
area where NAPL is present. There has been extensive monitoring of these two water bearing
units, and groundwater contaminants are limited in horizontal and vertical extent (as described
further in Section 2.5.6.5). These water-bearing units have discontinuous fractures and low
hydraulic conductivity which limit contaminant migration. Perimeter groundwater extraction
systems are installed downgradient of the primary source areas (i.e., landfills, CDA, BTA) to
capture contaminant migration in the Upper HSU. In addition, groundwater monitoring data
show that contaminant concentrations in the Lower HSU are at or below MCLs at the Zone 1
boundary. There are no current drinking water aquifers that could be impacted by the
dissolved-phase constituents or NAPL. The Lower HSU is up to 1,300 feet thick and is underlain
by the Monterey Formation which is up to 5,000 feet thick, and these impede contaminant
migration. Horizontal and vertical contaminant migration from the discontinuous fractures in
the water bearing zones is very slow and is also limited by diffusion into the claystone matrix.
The capping and extraction systems which are part of the Selected Remedy will reduce the
hydraulic driving force and further limit contaminant migration into the fractures.

2.5.6 Nature and Extent of Contamination

The nature and extent of contamination at the Site includes VOCs, SVOCs, and metals in soils,
surface water and sediment, and groundwater (with VOCs present to a limited degree in soil
vapor). Over 300 COPCs have been detected, many of which exceed human health and
ecological risk-based levels. These chemicals are also commingled and dispersed within the
various media across the Site. The nature and extent of contamination by media for each area

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are summarized in the following subsections. Figure 2-18 presents a plan view summary of the
chemical detections and exceedances for each media. Table 2-2 presents the COPCs in each
media based on the Rl results. Table 2-3 presents the constituents detected above risk-based
concentrations in each media. Appendix B contains selected figures that depict the nature and
extent of key constituents in the various media.

2,5,6,1 Soils

Soil contamination occurs pervasively throughout Areas 1 and 2, and variably within Area 3.
Contamination includes many COPCs (metals, VOCs, SVOCs, and other organic compounds), as
follows:

•	In Area 1, surface and subsurface soils represent the most contaminated soils at the Site.
Soils north of the PSCT in the CDA and BTA are primarily contaminated with metals and
organic compounds, many of which increase in concentration with depth and serve as
groundwater contamination sources via infiltration.

•	In Area 2, COPCs were identified in RCRA Canyon/WCSA and included elevated
concentrations of metals (copper, chromium, and zinc) that remain from areawide spraying
of oil field and other wastes during disposal operations. The elevated concentrations of
these metals occur in the top several feet of soil and diminish with depth.

•	In Area 3, several discrete soil hotspot areas contain elevated concentrations of metals,
VOCs, and other organic compounds. These hotspot areas include the following (see
Figure 2-19):

-	Hotspot 1 (HS-1) - shallow soil contamination in the Liquid Treatment Area (metals,
organics)

-	Hotspot 2 (HS-2) - shallow soil contamination in the former MSA (metals, organics)

-	Hotspot 3 (HS-3) - shallow and deeper soil contamination from former Ponds A and B
(organics)

-	Hotspot 4 (HS-4) - shallow soil contamination south of PSCT-1 (metals, organics)

-	Hotspot 5 (HS-5) - shallow soil contamination north of RCF Pond (metals, organics)

-	Hotspot 6 (Hs-6) - shallow soil contamination northwest of RCF Pond (organics)

-	Hotspot 7 (HS-7) - shallow soil contamination due east of Pond 18 (metals)

-	Hotspot 8 (HS-8) - shallow soil contamination further east of Pond 18 (metals)

-	Hotspot 9 (HS-9) - shallow soil contamination between Pond 18 and RCF Pond (metals,
organics)

27

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- Hotspot 10 (HS-10) - deeper soil contamination southwest of RCF Pond, from a former
waste pond discovered while drilling soil boring RISBON-59 (organics)

The maximum depth of soil impacts was encountered in the BTA where former deep waste
disposal operations resulted in elevated inorganic concentrations at depths of up to 44.75 feet
bgs, and elevated organic concentrations at depths of up to 77.5 feet bgs.

For VOCs, the constituent found in soils at the highest concentration was tetrachloroethene
(PCE) at 46 milligrams per kilogram (mg/kg) in the FPP Area (Area 3). This concentration is
approximately 4 times the preliminary remediation goal of 11 mg/kg (CSC, 2011).

Soil sampling indicates that soil contamination only occurs onsite within the historical facility
boundary (Zone 1). Soils in Zone 2 did not show evidence of impacts from former facility
operations.

2,5,6,2. Soil Vapor

Soil vapor containing VOCs and limited amounts of methane has been found in various
sampling locations across the Site. Although many COPCs have been detected at low
concentrations, some high concentrations have been found in relatively discrete areas, such as
the former waste disposal areas that serve as sources of soil vapor.

A total of 43 individual VOCs was detected at the various soil vapor sampling locations around
the perimeter of the landfills, the CDA, and the BTA, and represent COPCs in soil vapor. The
VOCs that exceeded risk-based concentrations were PCE, trichloroethene (TCE), and
1,3-butadiene. The highest soil vapor concentrations occur primarily in association with the
most extensive buried waste materials in Area 1. These VOCs are likely the result of
contamination from the landfills and residual contamination in the BTA and CDA.
Concentrations tend to decrease away from the source areas, to below risk-based cleanup
levels at the Site's boundaries.

Localized soil vapor concentrations in the North Drainage are subject to continued study and
are being monitored by a cluster of three soil gas probes along the North Ridge. Results from
monitoring during the period between 2009 and 2014 show that soil vapor concentrations in
the North Drainage probes are relatively low (below risk-based concentrations), and are
consistent or decreasing over time.

The generation of landfill gas as methane is relatively insignificant because organic rich
municipal solid waste was not disposed of in the landfills. Gas flux testing of the interim soil
caps was conducted in 1997, and results indicated there was no substantial movement of
methane and other VOCs through these interim soil caps and into ambient air. Based on these
findings, it was concluded that the landfill cap, as constructed over the P/S Landfill in 1999,
would effectively eliminate the very low gas fluxes observed, and installation of a gas mitigation
system was not needed. The construction materials selected for the final caps included fine-

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grained soils and high-density polyethylene (HDPE) geomembranes to restrict transport of soil
vapor.

2.5.6.3 Surface Water and Sediment

Until remedial action is implemented, the five surface water storage ponds in Zone 1 play a
critical, but temporary, role in collecting, storing, and evaporating stormwater and treated
liquids to prevent uncontrolled discharges. The TDS and metals concentrations in the five ponds
have been generally increasing over time due to a high concentration of salts and metals from
both surface water and extracted groundwater discharged to the ponds and subject to
evaporation. Low levels of organic compounds also are occasionally detected in some ponds.
The TDS and metals exceed ecological risk screening levels, including those for the California
red-legged Frog, a special-status species that formerly inhabited the ponds in the 1990s and
early 2000s until the ponds became too salty. The underlying pond sediments also contain
elevated levels of metals, VOCs, and other organic compounds, and serve as potential sources
of contamination to shallow groundwater.

Surface water and sediment in Zone 2 (along Casmalia Creek, North Drainage, and the A-, B-,
and C-Drainages) did not show evidence of impacts from former Site operations.

2.5.6.4 Surface Seeps

Based on extensive studies, surface seeps have been identified in two main areas within Zone 1,
as follows:

• RCRA Canyon Seep. This seep forms seasonally at the southern end of RCRA Canyon in the
winter. The seep forms in response to a shallow water table and upward groundwater
gradients at the canyon bottom that are greater in the winter, in response to rainfall
infiltrating over the canyon. The seep is elevated in TDS and metals, which could result in
risks to amphibians if water is allowed to pond. The seep reveals the shallow depth of
groundwater in this area, and points to a need to install low-permeability capping systems
to contain and lower groundwater levels.

• Sump 9B Seep. This seep periodically forms between the P/S Landfill and the PSCT due to a
shallow water table that will intersect the ground surface in response to rainfall infiltrating
over the area. This seep will not form if the water table is pumped down by Sump 9B. When
it forms, however, the seep is highly contaminated and has an LNAPL sheen. This seep also
points to the need to install low-permeability capping systems to contain and lower
groundwater levels.

2.5.6.5 Groundwater

Groundwater has been impacted by a wide range of organic and inorganic contaminants,
including LNAPL and DNAPL. Figures 2-20 and 2-21 show the lateral distribution of total VOCs
and metals (along with LNAPL and DNAPL), respectively, for the Upper HSU. Figures 2-22 and 2-

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23 show the lateral distribution of total VOCs and metals (along with DNAPL) in the Lower HSU.
Other classes of organic contaminants (such as, SVOCs, herbicides, pesticides, and PCBs) are
distributed within the aerial extent covered by the total VOCs. Appendix B provides figures that
show the lateral distribution of key metals (arsenic, nickel, cadmium, and selenium) in the
Upper HSU and Lower HSU. The lateral extent of exceedances of maximum contaminant levels
(MCLs) has been contained within the Site's geographic boundaries (Zone 1) by a combination
of engineered containment systems (such as, barrier trenches, sumps, and liquids extraction
systems) and MNA. The lateral extent of measurable LNAPL and DNAPL in both the Upper HSU
and Lower HSU is limited to Area 5 North. The PSCT, completed to the base of the Upper HSU to
a maximum depth of 65 feet, was designed to capture Upper HSU groundwater migrating to the
south.

The vertical extent of dissolved-phase constituents and DNAPL is greatest in the area south of
the P/S Landfill. The highest concentrations of dissolved-phase constituents and the greatest
DNAPL thickness are generally found in Upper HSU monitoring wells in this area, completed at
depths of up to about 100 feet bgs. At monitoring wells near the toe of the P/S Landfill, such as
RIPZ-13 and RGPZ-5D, DNAPL was found to accumulate near the contact between the more
permeable Upper HSU and the less permeable Lower HSU. However, based on drilling and
sampling of several wells (including RGPZ-6D, RGPZ-7C, and RGPS-7D) about 500 feet south of
the Gallery Well, dissolved-phase constituents above MCLs, and observable DNAPL, are present
within the Lower HSU at depths of up to about 150 feet bgs.

The VOCs detected in groundwater in the greatest number of wells and at relatively high
concentrations compared to other constituents include PCE, TCE, cis-l,2-dichloroethene (DCE),
vinyl chloride, and benzene. The maximum concentration detected in groundwater for PCE
(140,000 micrograms per liter [|_ig/L]) is 24,000 times greater than the MCL of 5 |ag/L. Similarly,
the maximum concentration detected in groundwater for TCE (120,000 |ag/L) is 22,000 times
greater than the MCL of 5 |ag/L.

Area 5 North

Area 5 North presents obstacles to full remediation because of the presence of multiple source
areas and complex hydrogeology. Area 5 North encompasses the major landfills and burial
areas. The P/S Landfill was a disposal Site for many drums and containers of liquid wastes.
Shallow groundwater generally flows horizontally through preferential pathways in the
heterogeneous and fractured Upper HSU. Groundwater flows at slower rates in the less
fractured Lower HSU. Contamination resides both in fractures and as residual contamination in
the matrix of the claystone, which is characterized by very low permeability and high porosity,
preventing effective long-term removal or treatment.

As described, DNAPL has been detected in Lower HSU piezometers (RGPZ-7C and RGPZ-7D) in
the CDA, approximately 500 feet south of the P/S Landfill and north of the PSCT, indicating a
potential for density-driven mobile DNAPL to flow through Lower HSU fractures. Geologic cross-
sections prepared during construction of the P/S Landfill indicate the presence of a "low spot"
at the base of the landfill where DNAPL could accumulate. As part of the Rl, the CSC conducted

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geophysical surveys to further delineate the base of the landfill. The geophysical surveys
provided images of the base of the landfill, and support the presence of the low area. The CSC
later installed four piezometers directly into the landfill, one of which (RIPZ-13) documented a
DNAPL thickness of 14 feet.

Based on laboratory analysis, the DNAPL contains over 100 constituents, including VOCs,

SVOCs, and a host of other compounds. Some key constituents include TCE, PCE,
1,2-dichlorobenzene, 1,2,3-trimethylbenzene, ethylbenzene, xylenes, pentane, toluene, and
diphenyl ether, among many others.

Area 5 North includes a designated WMA where the former landfills are located. Area 5 North
also includes many technical complexities that warranted an evaluation of Tl for groundwater
restoration in the area surrounding the WMA. EPA guidance was followed in preparing a TIE
report, which was included in the Rl report and summarized in the FS report. The evaluation
assessed the potential to achieve full restoration of groundwater to MCLs in all three
groundwater study areas (Area 5 North, Area 5 South, and Area 5 West). The evaluation
identified several factors that supported Tl with respect to groundwater restoration for Area 5
North, including:

•	Ongoing sources of contaminants that are encapsulated within capped landfills, such as
solvents and pesticides within the P/S Landfill

•	High volumes of NAPL, including up to 100,000 gallons of LNAPL, and up to 100,000 gallons
of pooled DNAPL that have accumulated at the base of the P/S Landfill and serve as an
ongoing source of contamination

•	Migration of NAPL and dissolved-phase groundwater constituents into low-permeability
fractured bedrock that are difficult to access and treat

•	Numerous chemical constituents (such as, hydrocarbons, solvents, metals, and PCBs) that
are difficult or impossible to treat by in situ and/or ex situ technologies

The TIE concluded that full restoration of groundwater to MCLs in Area 5 North, within a
reasonable timeframe, was not technically practicable from an engineering perspective.
Specifically, groundwater modeling showed that it would take several thousand years to restore
groundwater to MCLs, even with aggressive pump-and-treat technologies and after removal of
NAPL source material. In situ technologies, such as bioremediation or chemical oxidation, would
also have very limited effectiveness because of the difficulty in achieving widespread contact
between the injected remedial amendments and the contaminants. Area 5 North is
characterized by conditions that contribute to Tl, including large volumes of residual wastes,
large volumes of pooled DNAPL, fractured and low-permeability claystone, and the occurrence
of matrix diffusion.

Area 5 South

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South of the PSCT in Area 5 South, groundwater moves generally southward at a relatively slow
rate. The flow rate and direction are controlled primarily by Site topography, hydraulic
conductivity of the Upper and Lower HSUs, and unpredictable fracture patterns. The presence
of ponds influences the shallow groundwater flow paths. The concentrations of dissolved-phase
contamination are much lower than in Area 5 North, and no NAPL has been detected. The PSCT
captures groundwater and contaminants in the Upper HSU and restricts contaminant migration
from Area 5 North to Area 5 South. VOC and metals concentrations are near or below MCLs in
the Lower HSU beneath the PSCT (based on monitoring wells completed at depths of up to
about 200 feet; see Figures 2-22 and 2-23). MNA processes slow contaminant mass migration in
Area 5 South (south of the PSCT), as described in Section 2.5.8. PCT-A and PCT-B intercept
groundwater in the Upper HSU at the southern perimeter of the Site and prevent it from
moving offsite down these drainages.

Area 5 West

Groundwater contamination in Area 5 West is influenced by shallow wastes that were buried or
sprayed in the RCRA Canyon area and WCSA. Shallow contaminated soils are present in RCRA
Canyon, and represent a source of contaminants to groundwater. Groundwater flow in the
Upper HSU in RCRA Canyon is largely influenced by topography and surface water elevations in
the ponds. MNA processes help slow contaminant mass migration in Area 5 West, as described
in Section 2.5.8. PCT-C intercepts groundwater in the Upper HSU at the southern perimeter of
the Site and restricts it from moving offsite down this drainage. Similar to Area 5 South, VOC
and metals concentrations are near or below MCLs in the Lower HSU across Area 5 West (based
on monitoring wells completed at depths of up to about 200 feet; see Figures 2-22 and 2-23).

A prominent seasonal surface seep forms at the southern end of RCRA Canyon in the winter.
The seep forms in response to a shallow water table and upward groundwater gradients at the
canyon bottom that are greater in the winter in response to rainfall infiltration. Based on
laboratory sampling, this seep has elevated metals and TDS concentrations, and may represent
a potential risk to wildlife if allowed to accumulate.

2.5.7 Distribution of Nonaqueous Phase Liquid

The presence of detectable NAPL is limited to the area underlying Area 1 and within Area 5
North. The P/S Landfill and CDA are the only areas of the Site where both free-phase (mobile)
LNAPL and DNAPL in the Upper HSU were observed during drilling, gauged in routine liquid
level monitoring, or implied based on dissolved chemistry results. Results of extensive Site
investigations document the presence of substantial volumes of NAPL in and south of the
P/S Landfill within Area 5 North. Up to 100,000 gallons of pooled DNAPL has accumulated at the
base of the P/S Landfill, and a similar amount of pooled LNAPL also occurs on top of the

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aqueous phase liquids. In addition, free-phase DNAPL is known to exist at the following
locations:

• DNAPL pool overlying Lower HSU fractured claystone within the southern area of the P/S
Landfill. Measurable thicknesses are present in the Gallery Well, RIPZ-27 immediately north
of the Gallery Well, and RIPZ-13 approximately 150 feet north of the Gallery Well.

• Within fractures of the Lower HSU claystone in the CPA between the P/S Landfill and the
PSCT. Measurable thicknesses are present within Lower HSU piezometers RGPZ-7C and
RGPZ-7D, approximately 500 feet south of the clay barrier and 150 feet north of the PSCT.

The distribution of LNAPL and/or DNAPL within the Upper and Lower HSUs, as observed in
monitoring locations or interpreted from groundwater concentrations, is depicted on
Figures 2-20 through 2-23.

Within the P/S Landfill, approximately 3,000 to 4,000 gallons of DNAPL (and minor volumes of
LNAPL) were historically extracted and continue to be extracted from the Gallery Well annually.
The annual rate of DNAPL extraction has been relatively stable for over 10 years, indicating a
significant volume of free-phase DNAPL occurs in the P/S Landfill. Where present, DNAPL
thicknesses range from approximately 5 to 14 feet in piezometers within the southern end of
the P/S Landfill.

The CDA (located downgradient of the P/S Landfill and upgradient of the PSCT) is the only other
area of the Site where DNAPL was gauged in routine monitoring, and implied based on
dissolved chemistry within Lower HSU monitoring wells. Former Pads 9A and 9B in the CDA
were used for landfill runoff and leachate control, and may also be sources of DNAPL because
of observed DNAPL in this area.

The BTA was also investigated for the presence of NAPL because of the significant extent of
groundwater contamination in this area. Although dissolved VOC concentrations are relatively
high in this area, no wells or piezometers in the BTA were observed to contain NAPL during
liquid level monitoring.

2.5.8 Monitored Natural Attenuation

Natural attenuation refers to naturally occurring processes that reduce contamination in soil or
groundwater without human intervention. These processes can reduce the mass, toxicity,
mobility, volume, or concentration of contaminants. The reduction of contamination can
happen as a result of a variety of biological, chemical, and physical processes, such as
biodegradation, volatilization, dispersion, dilution, and sorption. Biodegradation and
volatilization can result in significant reductions of total contaminant mass from soil and
groundwater. The other natural attenuation processes can result in a reduction of
concentration, but not an actual reduction of contaminant mass, because the contamination is
either spread over a larger area (dispersion, dilution) or removed from the aqueous phase
(sorption). MNA refers to the ongoing evaluation and verification of natural attenuation

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processes. While MNA is a passive remediation approach, it does not preclude the use of active
remediation, and is often used in combination with active remedies.

The MNA processes play a critical role at the Site, effectively contributing to the reduction in
contaminant concentrations and limiting the nature and extent of groundwater contamination.
Groundwater data demonstrate the occurrence of significant natural attenuation processes in
all three groundwater areas (Area 5 North, Area 5 South, and Area 5 West). Natural attenuation
helps to contain and prevent offsite migration of contaminants in the Upper HSU, and to
generally contain contaminants in the Lower HSU within Area 5 North.

Extensive groundwater monitoring data, collected between 1998 and 2008, provide strong
evidence that natural attenuation processes reduce contaminant concentrations and contribute
to the effective containment of groundwater contamination within the boundaries of Zone 1.
The Rl and FS reports include detailed MNA evaluations that address organic and inorganic
chemicals in groundwater in a manner consistent with EPA policy and guidance. The natural
attenuation evaluation specifically considered EPA's guidance on the use of MNA as a remedy
component at Superfund sites (EPA, 1999a). The CSC collected and analyzed data along three
lines of evidence to demonstrate the occurrence of MNA processes, consistent with the Office
of Solid Waste and Emergency Response (OSWER) directive (EPA, 1999a) and further described
as follows:

(1) Groundwater Concentrations over Time. Concentrations of organic and inorganic
constituents are declining in Area 5 South and Area 5 West, as shown in an extensive set of
time series concentration charts. Concentrations of organic and inorganic constituents are
also declining in some wells in Area 5 North. Biodegradation is one of the most important
natural attenuation processes observed at the Site, particularly for chlorinated solvent
compounds, which are the most widespread dissolved-phase constituents in groundwater.
For inorganic compounds, sorption to aquifer solids provides the primary means for
attenuation of the groundwater plume. Dilution (rainfall recharge) and dispersion are also
important attenuation processes for both organic and inorganic constituents.

(2) Geochemical Data. The biodegradation of solvent-class, fuel-derived hydrocarbons was
evaluated using geochemical data focused on the following four lines of evidence:

- Concentrations of dissolved-phase organic contaminants (for example, PCE and TCE)
decrease along flow paths from high concentrations at source areas, to low
concentrations or nondetectable levels in downgradient portions of plumes.
Corresponding increases in degradation products (such as cis-l,2-DCE, ethene and
ethane) relative to PCE and TCE were also observed. Cis-1,2-DCE represents 80 to
100 percent of the total DCE, further suggesting reductive dechlorination. Evaluation of
benzene concentrations over time and along flow paths similarly reveals biodegradation
into its breakdown products.

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- Dissolved hydrogen concentrations, in conjunction with other indicators, suggest
metabolic breakdown of organic constituents consistent with reductive dechlorination
processes.

- The spatial distribution and concentrations of electron donors and acceptors (dissolved
oxygen, nitrate, iron, manganese, sulfate, and sulfide) were evaluated; changes in
concentrations spatially and temporally within contaminated groundwater are
consistent with degradation processes.

- Metabolic end products (for example, methane) were evaluated as indicators of
biodegradation. Increasing concentrations of dissolved methane and ethane in
downgradient, contaminated areas are consistent with reductive dechlorination
processes. The redox potential, alkalinity, and chloride concentrations also indicate
reductive dechlorination processes.

(3) Microcosm Studies. Dehaloccocoides bacteria, a known degrader of chlorinated solvents,
were detected in groundwater samples. The presence of Dehaloccocoides is consistent with
the biodegradation of chlorinated solvent compounds.

2.6 Current and Potential Future Site and Resource Uses

2.6.1 Land Use

The County of Santa Barbara has applied agricultural land use zoning in the area that includes
and surrounds the Site. Local land use generally entails agricultural and grazing activities. Parcel
ownership near the Site is depicted on Figure 2-13. The Site is located within a group of land
parcels comprising approximately 4,500 acres that, during the time the facility operated, were
all owned by Kenneth Hunter, Jr., or CR. The 252-acre facility (Zone 1) is located within portions
of three land parcels that are still owned by CR:

• Parcel 113-260-002 (397.82 acres)

• Parcel 113-260-003 (158.67 acres)

• Parcel 113-260-004 (38.21 acres)

Based on the CD, Zone 2 is the area that encompasses the extent of Site-related contamination
or potential contamination outside the CR facility boundary (Zone 1); the Zone 2 outer
boundary remains undetermined (unbounded) at this time. The CSC formed a real estate
holding company, the Casmalia Resources Acquisition Property Company, which acquired three
additional parcels immediately north of Zone 1:

• Parcel 113-260-001 (91.94 acres)

• Parcel 113-220-012 (118.32 acres)

• Parcel 113-220-010 (442.29 acres) immediately north of Zone 1

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The CSC's control over these six parcels (total of 1,247.25 acres) allows it to manage access and
provide a substantial buffer zone around the facility. In 2011, ICs were established for the six
parcels previously listed, in the form of legal covenants that provide for land and water use
restrictions, and allow access for CSC to perform response actions and long-term OM&M
activities. The covenants run with the land pursuant to California Civil Code Section 1471, and
successive owners of the property are bound to such restrictions. EPA is also included as a
third-party beneficiary to these covenants, allowing it access to the Site and the ability under
the law to enforce the terms of the covenants.

EPA anticipates that Site remediation and OM&M activities will continue throughout the long-
term future. For Zone 1, other land uses such as cattle grazing are restricted by perimeter
fencing and ICs. Stakeholders expect the land use for the adjacent parcels in Zone 2, outside the
former waste management facility boundary, to continue, consistent with agricultural zoning,
including oil and gas development.

2.6.2 Groundwater and Surface Water Use

The Site is underlain by low-permeability rocks that are generally considered to be non-water-
bearing compared to the unconsolidated sediments found within the nearby alluvial valleys and
basins. Although groundwater is present, the Site is not located within a California-designated
groundwater basin, and groundwater beneath the Site does not serve as a source of drinking
water for the town of Casmalia or other communities. The town of Casmalia receives its water
supply via a pipeline connection from Casmite Well No. 1, located approximately 2.7 miles
northeast of the Site in the separate Santa Maria Valley basin. There is an extensive
groundwater monitoring network along the southern boundary of the former facility. After
many years of investigations, there has been no indication that Site-related contaminants
above screening levels have migrated in groundwater past the southern perimeter containment
trenches at the southern Zone 1 boundary toward the town of Casmalia (see Figure 2-18 and
figures in Appendix B).

Groundwater within Zone 1 is not extracted for beneficial use. Groundwater surrounding
Zone 1 is used to support ranching, livestock, and similar nonpotable use activities. Nearby
groundwater has not been developed for drinking water purposes because of the high
concentrations of TDS. Four shallow water supply wells are located along Casmalia Creek, just
west of Zone 1; only one of these wells is used. The active well (WS-2) is situated on CSC-
controlled property, and is used on a limited basis for nonpotable purposes related to Site
operations and environmental response activities.

Based on federal groundwater classification, groundwater at the Site qualifies as an
underground source of drinking water (USDW). A USDW is defined as an aquifer or portion of
an aquifer that: (1) is currently used as a drinking water source or may be used as a drinking
water source in the future; (2) contains TDS levels below 10,000 milligrams per liter; (3) meets
the sufficient yield criterion of 150 gallons per day, and (4) is not an exempted aquifer (40 CFR
144.3). In addition, groundwater at the Site is classified as a potential source of drinking water
(Subclass MB; EPA, 1986).

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Beneficial uses for groundwater and surface water are defined in the Water Quality Control
Plan for the Central Coast Basin (Basin Plan, RWQCB, 2017). The Central Coast RWQCB develops
and periodically updates the Basin Plan to outline how water quality should be managed to
provide the highest water quality reasonably available. The Basin Plan identifies several
beneficial uses for the surface water and groundwater of the Shuman and Casmalia Creek
watersheds in the San Antonio hydrologic unit.

Surface water beneficial uses for the Casmalia Canyon Creek subunit within the Shuman Canyon
Creek watershed (the nearest to the Site) include municipal or domestic water supply,
agricultural supply, recreational, wildlife and warm water aquatic habitats, spawning,
reproduction, and/or early development offish, and commercial sport fishing. Beneficial uses
for groundwater throughout the Central Coastal Basin are considered suitable for agricultural
water supply, municipal and domestic water supply, and industrial use.

The ICs established in 2011 for the six parcels listed in Section 2.6.1 are legal covenants that
provide for land and water use restrictions. As noted above, EPA anticipates that Site
remediation and long-term OM&M activities will continue throughout the future, and there will
be no beneficial use of groundwater and surface water within Zone 1 of the Site.

2.7 Summary of Site Risks

In risk management decision-making for the Site, EPA considered the following factors when
assessing the need for remediation:

• There are multiple COCs present at the Site. In the event of uncontrolled exposure(s), some
COCs pose carcinogenic risks and/or noncancer hazards for various human populations,
while some pose risks to various plant and animal populations.

• Multiple contaminants are present at the Site at concentrations that exceed established
ARARs. For example, 81 constituents found in groundwater exceed MCLs (see Table 2-7).

• There are multiple former waste management units and contaminated media at the Site.
Contamination is present in soils, sediments, surface water, groundwater, and subsurface
soil gas, all potentially creating uncontrolled exposures to various current and future human
populations, as well as to various plant and animal populations.

• There are multiple exposure pathways by which various human, plant, and/or animal
populations may experience current or future uncontrolled exposures to contamination at
the Site. Potential human exposure pathways include direct ingestion, dermal contact, and
inhalation.

• Remediation to ARARs, as required by the NCP, will leave potential residual human cancer
risks on the order of 1 x 10"5 for some potentially exposed current and future populations
via some uncontrolled pathways. For example, attainment of MCLs for TCE and PCE will
achieve protectiveness to approximately 1 x 10"5 in the event groundwater becomes a

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source of domestic tap water (a long-term eventuality recognized by the State of California,
per State water policy).

•	There is general agreement among major stakeholders (e.g., representatives of State
agencies, potentially responsible parties, and community representatives) on the need for
Site remediation.

A comprehensive risk assessment was conducted as part of the RI/FS process to identify and
estimate potential risk to people and the environment from contaminated soil, soil vapor,
sediment, and surface water. The risk assessment is detailed in the Rl report (CSC, 2011) and
summarized in the FS report (CSC, 2016). Consistent with EPA guidance and policy, the risk
assessment included a human health risk assessment (HHRA) and an ecological risk assessment
(ERA). The HHRA included a baseline risk assessment that evaluated cancer and noncancer risks
for existing Site conditions, and current land and water uses; it also included an evaluation of
risk for reasonably anticipated future land use scenarios. The ERA included a quantitative
evaluation of Site risks to a wide range of plant and wildlife species, for current and future use
scenarios.

Together, the HHRA and ERA are used to identify an initial list of COPCs, followed by a shorter
list of chemicals of concern (COCs), or those chemicals that exceed risk-based concentrations
and must be addressed by the Selected Remedy.

The HHRA and ERA also accounted for prior completion of several interim environmental
response actions. The P/S Landfill and EE/CA Area (Heavy Metals, Caustics/Cyanides and Acids
landfills, and the areas between these landfills) have already been capped. In the HHRA and
ERA, it was presumed that the PCB Landfill would be capped in the future, and that the CDA and
BTA areas would also be capped. It was also presumed that the two treated liquids
impoundments (Pond A-5 and Pond 18) and three stormwater ponds (RCF, A-Series, and Pond
13) would be drained of contents and capped prior to reconfiguration in support of long-term
operations.

The study areas for exposure calculations included the following:

•	Areas 1 to 3: The terrestrial, uncapped Areas in Areas 1 to 3, including the CDA, BTA, Liquids
Treatment Area, RCRA Canyon, WCSA, MSA, Administration Building Area, Roadway Areas,
Remaining Onsite Areas, and FPP Area south of the PSCT

•	Area 4 (Stormwater Ponds and Treated Liquids Impoundments): A-Series Pond, RCF Pond,
Pond A-5, Pond 13, and Pond 18

•	Offsite Drainages: North Drainage, A-Drainage, B-Drainage, and C-Drainage

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2.7.1 Background Concentration Evaluation

The HHRA and ERA both included a background analysis of naturally occurring constituents,
selection of COPCs, and calculations of exposure point concentrations (EPCs). A statistical
analysis was performed on the chemical concentration data to calculate upper-bound
concentration estimates of metals and dioxins in background soils. COPCs were selected for
each environmental medium (soil, sediment, surface water, and soil vapor). Chemicals were
identified as a COPC on a per-medium basis if: the frequency of detection was greater than
5 percent, the chemical was not considered an essential nutrient (calcium, magnesium,
potassium, iron, and sodium), and was greater than background.

2.7.2 Human Health Risk Assessment

The baseline risk assessment estimates what risks the Site poses if no actions were taken. It
provides the basis for taking action and identifies the contaminants and exposure pathways
that need to be addressed by the remedial action. This section of the ROD summarizes the
results of the baseline risk assessment for this Site.

For purposes of the HHRA, the Site included both Zones 1 and 2. Zone 1 includes the inactive
hazardous waste management facility and comprises approximately 252 acres. Zone 2 includes
the area encompassing the extent of Site-related contamination or potential contamination
outside the Zone 1 boundary.

Consistent with EPA guidance, the HHRA process included: (1) data review and evaluation;
(2) exposure assessment; (3) toxicity assessment; (4) risk characterization; and (5) uncertainty
analysis. The key steps are described in the following subsections, along with a description of
the COCs identified from the HHRA.

la Review and Evaluation

A thorough data evaluation was conducted to develop a risk assessment dataset, identify
media-specific COPCs, and calculate EPCs for evaluation in the HHRA. The risk assessment
prepared as part of the Rl (CSC, 2011, Appendix T), along with summaries in Section 8 of the Rl
Report, include extensive detail concerning cancer and non-cancer health risks for individual
Site areas and features, receptors, and exposure scenarios. Condensed, summary level tables
provide a general indication of health risks, receptors, and exposure pathways associated with
different Site areas and features. These tables did not intend to provide quantitative risk data
for small scale portions of the Site or every individual Site feature.

EPA guidance discusses Site-specific considerations that can affect risk-based selection of
remedial actions. Although EPA may consider 1 x 10"4 as an upper bound in terms of cancer risk,
EPA also uses a discretionary range of risk of 1 x 10~6 to 1 x 10~4 as a basis for remedial actions,
particularly in combination with other risks and Site-specific factors. EPA also evaluates
chemical-specific ARARs (e.g., exceedances of MCLs for groundwater), non-cancer risk (e.g.,
HQ>1), ecological risks, and Site management and remedy implementability considerations to

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develop a basis for action. The Rl Report followed EPA guidance in terms of calculating human
and ecological risks. Moreover, some summary level health risk tables used 10~5 as a mid-range
proxy to indicate general Site areas and major features where cumulative cancer risks were
calculated between the 1 x 10~6 and 1 x 10~4 range.

2.7.2.2 Expost fssmentforHHRM

The objectives of the exposure assessment were to identify potential receptors (populations)
that may be exposed to chemicals in impacted media, the exposure pathways, and the route of
potential intake. The end product of the exposure assessment is a measure of chemical intake
as an average daily dose that integrates the exposure parameters for the receptors of concern
(such as, contact rates, exposure frequency, and duration) with the EPC for the media of
concern. These average daily doses are then used with chemical-specific toxicity values (such
as, reference doses and cancer slope factors), to arrive at an estimate of potential health risks
for the potential receptors of concern.

The CSM identifies potential chemical sources, release mechanisms, transport media, routes of
chemical migration through the environment, exposure media, and potential receptors.
Receptors that may be potentially exposed to Site-related chemicals are identified and the
likelihood of their potential exposures assessed through consideration of the current and the
anticipated future use of the Site. Figures 2-7 and 2-8 provide the HHRA-related CSMs for the
terrestrial (uncapped) and surface water areas, respectively.

The following receptors may be potentially exposed to Site-related chemicals within Zone 1:

•	Site commercial/industrial workers maintaining the liquids treatment area, surface
impoundments, and landfill covers and drainage structures

•	Trespassers

•	Ranchers using NTU Road to access their lands

The following receptors were also evaluated in the HHRA because they may be potentially
exposed to Site-related chemicals within Zone 2:

•	Ranchers working the fields along the southwestern border of Zone 1

•	Consumers of beef raised in the fields near Zone 1

•	Recreational users of the drainage areas

•	Hypothetical residents living near the Site

EPCs are the concentrations of chemicals in environmental media to which receptors may be
exposed through defined exposure pathways. EPCs were estimated for each environmental
media associated with complete and potentially complete pathways identified in the CSM.
These media and pathways include the following:

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• Surface (0 to 6 inches bgs) and shallow (0 to 5.5 feet bgs) soil considered for incidental
ingestion, dermal contact, and inhalation of fugitive dust and vapor pathways, as well as
ingestion of beef

• Surface (0 to 6 inches bgs) and shallow sediment (0 to approximately 5 feet bgs) considered
for incidental ingestion, dermal contact, and inhalation of fugitive dust and vapor pathways

• Soil vapor considered for the vapor inhalation pathway

• Surface water considered for incidental ingestion, dermal contact, and inhalation pathways

EPCs were derived using the same statistical methodology for soil, sediment, and surface water.
EPCs for the outdoor and indoor air exposure pathways in the HHRA were further developed
using fate-and-transport modeling, as described in Appendix T of the final Rl report (CSC, 2011).
The EPC tables for each medium are presented in Appendix C. The medium-specific EPCs for
each COC are presented in Table 2-8.

Finally, the exposure assessment quantified the magnitude, frequency, and duration of
chemical intake (daily intake) by the potential receptor populations.

2.7.2.3 Toxicity Assessment for HHRA

The toxicity assessment characterized the relationship between the magnitude of exposure to a
COPC and the nature and magnitude of adverse health effects that may result from such
exposure. Adverse health effects are classified into two broad categories: noncarcinogenic and
carcinogenic. Toxicity criteria are generally developed based on a threshold approach for
noncancer effects and a non-threshold approach for cancer effects.

Potential effects resulting from human exposure to noncarcinogens were estimated
quantitatively using chronic reference doses (RfDs) for ingestion or dermal contact with
chemicals and reference concentrations (RfCs) for inhaled chemicals. The RfD is an estimate of
the maximum human exposure level that can be present without an appreciable risk of
deleterious effects during a designated time. The RfC is an estimate of the maximum air
concentration that can be present without an appreciable risk of deleterious effects. In
addition, CalEPA (2000, 2003) has developed chronic reference exposure levels for the Air
Toxics Hot Spots program, which were used if they were more conservative than the RfCs.

Potential cancer effects resulting from human exposure to carcinogens are generally estimated
quantitatively using oral cancer slope factors or inhalation unit risk factors.

2.7.2.4 Risk Characterization and Identification of COCs for HHRA

Risk characterization integrates the results of the exposure assessment and toxicity assessment
to estimate potential cancer risks and adverse noncancer health effects associated with
exposure to chemicals detected at the Site. This integration provides quantitative estimates of
cancer risk and noncancer hazard that are then compared to regulatory risk thresholds. The risk

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characterization led to the identification of COCs, which are those COPCs exceeding a risk
threshold. For groundwater, COCs include chemicals which exceed, or may be reasonably
expected to exceed, MCLs.

For carcinogens, risks are generally expressed as the incremental probability of an individual
developing cancer over a lifetime as a result of exposure to the carcinogen. Excess lifetime
cancer risk is calculated from the following equation:

Risk = CDI x SF

where:

Risk = a unitless probability (such as, 2 x 10"5) of an individual developing cancer
CDI = chronic daily intake, averaged over 70 years (mg/kg per day)

SF = slope factor, expressed as (mg/kg per day)1

These risks are probabilities that usually are expressed in scientific notation (such as, 1 x 10"6).
An excess lifetime cancer risk of 1 x 10"6 indicates that an individual experiencing the
reasonable maximum exposure estimate has a 1 in 1,000,000 chance of developing cancer as a
result of Site-related exposure. This is referred to as an "excess lifetime cancer risk" because
the risk would be in addition to the risks of cancer individuals face from other causes, such as
smoking or excessive sun exposure. The chance of an individual developing cancer from all
other causes has been estimated to be as high as one in three. EPA's discretionary risk
management range for Site-related exposures is 1 x 10"6 to 1 x 10"4.

The potential for noncarcinogenic effects is evaluated by comparing an exposure level over a
specified time period (such as a lifetime), with a RfD derived for a similar exposure period. An
RfD represents a level that an individual may be exposed to that is not expected to cause any
deleterious effect. The ratio of exposure to toxicity is called a hazard quotient (HQ). An HQ of
less than or equal to 1 indicates that a receptor's dose does not exceed the RfD, and that toxic
noncarcinogenic effects from that chemical are unlikely. The HI is generated by adding the HQs
for all COCs that affect the same target organ (such as, liver) or that act through the same
mechanism of action within a medium or across all media to which a given individual may
reasonably be exposed. An HI of less than or equal to 1 indicates that, based on the sum of all
HQs from different contaminants and exposure routes, toxic noncarcinogenic effects from all
contaminants are unlikely. An HI of greater than 1 indicates that Site-related exposures may
present a risk to human health.

The HQ is calculated as follows:

Non-cancer HQ = CDI/RfD

where:

CDI = chronic daily intake
RfD = reference dose

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CDI and RfD are expressed in the same units and represent the same exposure period (that is,
chronic, subchronic, or short term).

For the purposes of the HHRA, a cumulative cancer risk of 1 x 10~5 (mid-range proxy to indicate
where cumulative cancer risks were calculated between the 1 x 10~6 to 1 x 10~4 range) and
noncancer HI of 1 were used to compare Site commercial/industrial worker risk estimates. For
all other potential exposures, a cancer risk level of 1 x 10~6 and noncancer HI of 1 were used.
These risk levels are used to provide context to the risk results and support the following
discussion, which focuses on those pathways and chemicals that contribute the majority to the
risk estimates. Additional considerations, such as technical feasibility, economic, social,
political, and legal factors, may be part of the final risk management decision.

The risk results are summarized in Tables 2-9 through 2-15 for onsite soil, offsite soil and
sediment, onsite sediment, onsite surface water, outdoor air, indoor air, and potential
exposures to various media by a hypothetical offsite resident. The results show the following:

• For potential exposures to Site soils and sediments via direct contact (ingestion and dermal
contact) and outdoor inhalation, only the FPP Area and Liquid Treatment Study Areas
exhibited elevated risk for Site commercial/industrial worker exposures, with a cumulative
risk of 5 x 10~5 and a noncancer HI of 2, respectively. PCE in shallow soil was the primary risk
driver for the FPP Study Area and MCPP was the primary risk driver for both surface and
shallow soils at the Liquid Treatment Study Area. In addition, risk estimates for trespasser
exposures to FPP soils were slightly elevated (2 x 10"6) because of the presence of PCE in
subsurface soils. The sample locations that contributed the majority to these risk estimates
were RISBON-37, RISBON-41, and RISBON-63 in the FPP Study Area just south of the PSCT
and RISBLT-02 in the Liquid Treatment Study Area.

• For soils/sediments outside the Site's boundary, cancer risk and noncancer hazard
estimates for recreational and rancher exposures were below a cancer risk level of 1 x 10~6
and a noncancer HI of 1.

• For Site surface water, Ponds A-Series, Pond 13, and RCF Pond cancer risk estimates were
elevated for Site commercial/industrial worker exposures (maximum cumulative risk of 8 x
10"5) and trespassers (maximum cumulative risk of 3 x 10~6), with arsenic as the primary risk
driver. All noncancer His were below 1.

• For the hypothetical resident living near the Site, the BTA, CDA, and FPP Study Areas
exhibited elevated risk resulting from exposures from transport of Site vapors to locations
outside the Site's boundary, with a maximum cumulative BTA risk estimate of 1 x 10~5. The
primary risk drivers were PCE and TCE. The sample locations that contributed the majority
to these risk estimates were RISBON-37, RISBON-41, and RISBON-63 in the FPP Study Area
just south of the PSCT; RISBCD-07 in the CDA; and RISSBC-05 in the BTA. It should be noted
that the hypothetical resident evaluation is overly conservative in that modeling assumes
the resident is located adjacent to the study area being evaluated. In reality, the resident

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would be located some distance from the study area boundary, which would result in lower
estimates of exposure.

• For the hypothetical residential exposures, only the vapor intrusion pathway resulted in a
marginally elevated risk estimate, with a cumulative risk estimate of 2 x 10~6. The primary
risk driver for this pathway was 1,3-butadiene. When considering more recent soil vapor
data, this risk estimate would be even lower and similar to the target risk level of 1 x 10~6.

In summary, the HHRA results indicated that several COPCs are primary risk drivers and are,
therefore, identified as COCs. Several COCs were identified for the Site, based on those that
exceeded the 10~5 cancer risk (or midway within the EPA risk management range of 1 x 10~6 to 1
x 10"4) or had a noncancer hazard quotient greater than 1 (HQ>1). EPA selected 1 x 10~5 as the
basis for identification of risk drivers to ensure protectiveness above the minimum level of 1 x
lO-4.

• Soils (CDA, BTA, Liquids Treatments Area, FPP Area):

- 2-(2-chloro-4-methylphenoxyl) propionic acid (MCPP)

- PCE

- TCE

These areas exhibited elevated risk from dermal contact, incidental ingestion, and outdoor
inhalation for Site commercial/industrial worker exposures (cumulative risk estimate of 5 x 10~5
and a noncancer hazard index [HI] of 2), with PCE and MCPP as the primary risk drivers. The
CDA and BTA exhibited elevated risk from outdoor inhalation for a hypothetical resident
assumed to be living adjacent to the Site's boundary (maximum cumulative risk estimate of 1 x
10"5), with PCE, TCE, and benzene as the primary risk drivers. The hypothetical resident
evaluation is conservative, in that the modeling assumes the resident is located adjacent to the
study area being evaluated. In reality, the resident would be located some distance from the
study area, thereby resulting in lower estimates of exposure.

• Surface Water (Ponds):

- Arsenic

The A-Series Pond, RCF Pond, and Pond 13 surface water exhibited elevated risk (within EPA's
discretionary risk range of 1 x 10"6 to 1 x 10"4) for commercial/industrial worker exposures
(maximum cumulative risk of 8 x 10"5) and trespasser exposures (maximum cumulative risk of 3
x 10"6), with arsenic as the primary risk driver. All noncancer His were below 1. The HHRA
identified no COCs for sediment. Tables 2-4, 2-5, 2-9, and 2-12 present the HHRA-related COCs
in surface soil, shallow soil, and sediment, respectively. As described in the summary of the
ecological risks in Section 2.7.3, EPA has determined that it is appropriate to close all the
existing ponds to prevent exposure of special status species to contaminated pond water and to
prevent attractive nuisances.

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•	Site Groundwater:

-	Dissolved chemicals in groundwater that exceed MCLs (81 chemicals; see Table 2-7 for
the full list)

The State of California classifies essentially all groundwater within the State as a potential
source of drinking water. Thus, even though at present there are no known complete exposure
pathways for groundwater, and no current or reasonably anticipated future reuse scenarios
that include exposure pathways or receptor populations for groundwater within Zone 1,
remedial action is being chosen based on the presence of multiple COCs at concentrations
above MCLs.

The HHRA did not include detailed risk calculations of cancer and non-cancer risk for
groundwater because there are no reasonably anticipated future uses that include residential
or commercial reuse of groundwater within the footprint of the former waste disposal Site. The
HHRA identified and evaluated future use scenarios that include only onsite workers and
unauthorized trespassers as potential receptors. All remedial alternatives include ICs to prohibit
residential and commercial reuse. However, the Selected Remedy addresses remediation of
groundwater, except in the designated WMA and Tl Zone, based on the presence of multiple
COCs that exceed MCLs.

•	Soil Vapor:

-	1,3-butadiene

-	PCE

-	TCE

For the hypothetical residential exposure, the vapor intrusion pathway for indoor air resulted in a
marginally elevated risk estimate (cumulative risk estimate of 2 x 10"6), with 1,3-butadiene as the
primary risk driver. In addition, PCE and TCE are COCs based on potential outdoor inhalation
exposure by a hypothetical resident assumed to be living near the Site's boundary (see Table 2-3).

Table 2-8 presents the COCs and associated medium-specific EPCs.

2.7,2,5 Uncertainty Analysis

The methodology used in the HHRA is consistent with EPA and State risk assessment guidance.
However, the procedures used in any quantitative HHRA are conditional estimates, given the
many assumptions that must be made about exposure and toxicity. Major sources of
uncertainty in risk assessment include: (1) natural variability (such as, differences in body
weight or sensitivity in a group of people); (2) incomplete knowledge of basic physical,
chemical, and biological processes (such as, the affinity of a chemical for soil, degradation
rates); (3) model assumptions used to estimate key inputs (such as, exposure, dose response
models, and fate-and-transport models); and (4) measurement error, primarily with respect to
sampling and laboratory analysis.

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Site-specific factors, which the HHRA incorporated, decrease uncertainty, although uncertainty
may persist in even the most Site-specific HHRAs because of the inherent uncertainty in the
process. However, because the assumptions used tend to be protective of health and
conservative in nature, the estimated risks are likely to exceed the most probable risk posed to
potential receptors at the Site, and actual risks would be much lower.

2.7.3 Ecological Risk Assessment

The objective of the ERA was to conduct a sitewide assessment using a tiered approach that
would provide information for the RI/FS. To achieve this objective, the ERA assessed whether
Site-related chemicals in Site media have adversely affected resident flora (plants) and resident
fauna (animals).

The ERA was conducted in an iterative (or tiered) manner, with greater detail and refinement
included in each successive tier. In the screening-level ERA, chemicals of potential ecological
concern (COPECs), defined as chemicals that are potentially Site related, were identified. In the
Tier 1 ERA, risks were estimated for all the COPECs. Finally, the Tier 2 ERA used Site-specific
biota uptake values and ecological benchmarks to identify COCs (COCs are those COPECs that
exceed a risk threshold).

The ERA considered potential exposure pathways for the terrestrial uncapped areas and
freshwater aquatic areas. The capped landfills and interstitial areas were not included in the
ERA. The surface seeps were not evaluated beyond Tier 1 because they are currently dry,
facilities (for example, Sump 9B) are in place to control the seeps, and they were not expected
to be sources of exposure to amphibians, aquatic life, or aquatic plants. Multiple exposure
pathways were evaluated, including direct contact and uptake by plants and invertebrates, as
well as inhalation and ingestion by animals.

EPA has determined that it is necessary and appropriate to close all the surface water ponds to
prevent: exposures of special-status species (threatened and endangered amphibians) to
contaminated pond water, and attractive nuisances. In terms of ecological risk, all five ponds
contain very high concentrations of TDS and metals that exceed Tier 1 ecological screening
levels (HQ>1) for multiple constituents in both pond water and pond sediments. The TDS
concentrations in the ponds approach the levels found in seawater (20,000 - 40,000 ppm).
Consistent with EPA guidance, the ecological risk assessment examined risks to aquatic plants,
sediment invertebrates, amphibians, and other aquatic wildlife from exposure to pond
sediments. Tier 1 exceedences were identified for pond sediment, primarily for metals such as
cadmium, chromium, manganese, mercury, molybdenum, selenium, vanadium, and zinc (see
Table 2-6). A Tier 2 ERA was not conducted on the ponds, because it had already been
determined appropriate to close the ponds based on the results of the Tier 1 evaluation.
Therefore, the Tier 2 ERA focused on the remaining exposure areas and risk-driving COPECs
from the Tier 1 ERA, which included:

• Administration Building Area

• RCRA Canyon

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•	WCSA

•	Roadway areas

•	Remaining Site areas

•	FPP Area south of the PSCT

Consistent with EPA guidance, the ERA process included: (1) data review and evaluation; (2)
exposure assessment; (3) toxicity assessment; (4) risk characterization; and (5) uncertainty
analysis. These process components, including identification of ecological COCs, are described
in the following subsections.

la Review and Evaluation and Identification of COPECs

A thorough data evaluation was conducted to develop a risk assessment dataset and identify
chemicals of potential ecological concern (COPECs). In the ERA, COPECs were selected following
appropriate guidance, as described in the Rl Report (2011). COPECs were selected for sitewide
areas as well as individual study areas. Data for each medium were used in the COPEC selection
process. Briefly, the steps included:

•	Evaluation of frequency of detection, where chemicals were selected as sitewide COPECs if
the chemical was positively detected in 5 percent or more of the samples)

•	Identification of essential nutrients

•	Comparison of Site data with background data (for metals in soil and sediment only), where
the maximum detected concentration of metals was compared to the 95 percent UTL, as
described in the Rl Report (2011)

For estimating exposures to ecological receptors at the Site, the following Site media data were
evaluated:

•	Surface soil (0 to 6 inches bgs)

•	Shallow soil (0 to 5.5 feet bgs)

•	Deep soil (0 to 10 feet bgs; only for the deep burrowing receptor)

•	Sediment (0 to 6 inches bgs)

•	Surface water (from ponds and runoff)

•	Soil vapor

2.7.3.2 Expost issment for the ERA

The objectives of the exposure assessment were to identify potential receptors (populations)
that may be exposed to chemicals in impacted media, the exposure pathways, and the route of
potential intake. For the ERA, the CSMs were developed on the basis of existing information
regarding the nature and extent of chemical contamination, habitat types, and flora and fauna
at the Site. The exposure media evaluated included soils, sediment, surface water, and soil gas.
The ecological receptors evaluated included terrestrial ecological communities (plants and soil

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invertebrates), freshwater ecological communities (sediment-dwelling invertebrates, aquatic
life, and aquatic plants), terrestrial wildlife (reptiles, amphibians, mammals, birds, and deep
burrowing mammals), and freshwater wildlife (amphibians, mammals, and birds). Figures 2-9,
2-10, and 2-11 provide the CSMs for terrestrial uncapped, terrestrial capped, and aquatic areas,
respectively.

Identification of Ecological Receptors and Indicator Species

General classes of ecological receptors were identified to represent different trophic levels to
characterize potential ecological risks associated with the Site. Representative species were
used, as appropriate, to represent a wide range of receptors within each functional group, as
follows.

•	Terrestrial Ecological Communities:

-	Terrestrial plants: general category (not species specific)

-	Soil invertebrates: general category (not species specific)

•	Terrestrial Wildlife:

-	Amphibians: general category (not species specific)

-	Reptiles: western fence lizard (Sceloporus occidentalis)

-	Mammals:

¦	Herbivorous small mammals: California vole (Microtus californicus)

¦	Invertivorous small mammals: ornate shrew (Sorex ornatus)

¦	Carnivorous mammals: striped skunk (Mephitis mephitis)

•	Birds:

-	Invertivorous ground-feeding birds: western meadowlark (Sturnella neglecta) (breeding)

-	Herbivorous ground-feeding birds: western meadowlark (Sturnella neglecta) (non-
breeding)

-	Carnivorous birds (raptors): American kestrel (Falco sparverius)

-	Deep-burrowing Mammals: represented by the American badger (Taxidea taxus)

•	Freshwater Aquatic Ecological Communities:

-	Sediment-dwelling Invertebrates: general (not species specific)

-	Aquatic life: general (not species specific)

-	Aquatic plants: general (not species specific)

•	Freshwater Aquatic Wildlife:

-	Amphibians: general (not species specific)

-	Mammals:

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¦ Omnivorous/invertivorous small mammals: raccoon (Procyon lotor)

•	Birds:

-	Invertivorous wading birds: killdeer (Charadrius vociferous)

-	Invertivorous (breeding) diving birds (ducks): mallard duck (Anas platyrhynchos)

The Site also contains several listed special-status species, including the California red-legged
frog (federally listed as threatened, and a State species of special concern), the California tiger
salamander (federally listed as endangered, and State listed as threatened), and the western
spadefoot toad (State species of special concern). As described elsewhere in the ROD, EPA
continues to work with the USFWS and CDFW through the Site's interagency committee to
address habitat mitigation and protection of these species.

The exposure scenarios evaluated for the ecological receptors include the following:

•	The terrestrial uncapped areas evaluated included the following exposure units: RCRA
Canyon, Liquid Treatment Area, WCSA, Burial Trench Area, Maintenance Shed Area, Central
Drainage Area, Administration Building Area, Roadway Areas, Remaining Site Areas, FPP
Area, A-Series Pond, RCF Ponds, Pond A-5, Pond 13, and Pond 18. The treated liquid
impoundments (Pond A-5 and Pond 18) and the stormwater ponds (A-Series Pond, RCF
Pond, and Pond 13) are anticipated to be closed as part of the Selected Remedy. Therefore,
the treated liquid impoundments and the stormwater ponds were evaluated similarly to
terrestrial areas. For terrestrial receptors, exposures were estimated for each of these units,
and also for the two following sitewide scenarios: (1) sitewide (that is, all terrestrial
uncapped units) with Pond A-5 and Pond 18; and (2) sitewide without ponds (that is, all
terrestrial uncapped units only).

•	The freshwater aquatic areas evaluated included the following exposure units: Site
freshwater aquatic areas (A-Series Pond, RCF Pond, Pond A-5, Pond 13, and Pond 18),
freshwater aquatic areas outside the Site's boundaries (North Drainage, A-Drainage, B-
Drainage, upper C-Drainage, lower C-Drainage), runoff in RCRA Canyon, Site freshwater
seeps (qualitatively only; A-series seep Caustic/Cyanide and Acid Landfill seep, Caustic
Landfill seep, Seep 9B). For Site freshwater aquatic receptors, exposures were estimated for
each of the units listed, and also for the following two sitewide scenarios: pondwide (that is,
all Site ponds) and stormwater impoundments (A-Series pond, RCF Pond, and Pond 13).

Ecological community exposures are expressed in terms of Site media concentrations, whereas
wildlife exposures are expressed in terms of daily doses. For wildlife receptors, numerous
exposure assumptions, such as food and water ingestion rates, body weights, and absorption
factors, are defined in the ERA for estimation of the exposure doses for each wildlife receptor.
These exposure parameters were obtained from literature sources and used in all tiers of the
ERA. In contrast, bioaccumulation factors (BAFs) for the screening-level and Tier 1 ERA were
primarily obtained from guidance documents or other commonly used literature sources, but
were developed from Site-specific uptake data for the Tier 2 ERA.

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2.7.3.3 Ecological Effects Assessment for the ERA

The effects assessment includes the identification and development of toxicity values for
ecological receptors. Following California Environmental Protection Agency guidance (Cal-EPA
1996), toxicity values were based on "no-effect" levels. The no-effect level is the concentration
or dose at, or below which, no adverse effects on the test organism are observed. However, to
evaluate a range of risk estimates for ecological receptors in all the tiers of the baseline
ecological risk assessment "lowest observable effects" data or other alternate "upper bound"
toxicity values were also developed.

For ecological communities and amphibians, effects are assessed using toxicity values referred
to as "screening values." Screening values are threshold concentrations expressed in mg/kg or
milligrams per liter /L that are effect levels or benchmarks for organisms inhabiting/exposed to
that matrix (soil, sediment, surface water). For terrestrial plants, soil invertebrate ecological
communities and amphibians, single screening values were developed; for sediment-dwelling
invertebrates and aquatic life, low and high screening values were developed; and for aquatic
plant ecological communities and amphibians, single screening values were developed.

For wildlife (mammals and birds), effects are assessed using toxicity values referred to as
"toxicity reference values" (TRVs). A TRV is defined as a daily dose of a chemical expressed in
milligrams of chemical per kilogram of body weight per day and represents a dose associated
with no-effect, lowest-effect, or mid-range-effects for ecologically relevant endpoints. For
wildlife, a range of low and high TRVs were developed. Low TRVs were based on no observed
adverse effects levels (NOAELs) and high TRVs were based on the lowest observed adverse
effect level (LOAEL) or mid-range effect levels. TRVs could not be developed for reptiles
because of limited toxicity data. Both NOAELs and LOAELs represent doses affecting receptors
at the individual level. If risks (that is, HQs over 1) are predicted at this level (that is, when the
estimated exposure dose exceeds the LOAEL), effects may be evident at the population level.
Because there is a higher level of concern, NOAEL-based TRVs are considered when making risk
management decisions for protected (threatened and endangered) species.

2.7.3.4 Ecological Risk Characterization and Ecological COCs

The Tier 2 ERA was conducted to further evaluate pathways, receptors, and risk-driving COPECs
from the Tier 1 ERA. The Tier 2 ERA included additional studies and evaluations designed to
make the ecological risk assessment more Site-specific and less generic.

The Tier 2 ERA included the following additional efforts to further refine the ecological risks at
the Site:

• Tissue sampling (plants, soil invertebrates, and/or small mammals)

• Refinement of ecological benchmarks, including developing tissue TRVs to use as additional
weight-of-evidence in the risk characterization

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The ERA anticipated that all the remedial alternatives being considered will include closure of
all the ponds and remediation to prevent known exposures from surface impoundments (pond
water and sediment), as well as the CDA, BTA, MSA, and Liquids Treatment Area. Therefore, the
Tier 2 ERA focused on the remaining exposure areas and risk-driving COPECs from the Tier 1
ERA, which included the following: Administration Building Area; RCRA Canyon; WCSA;

Roadway Areas; remaining Site areas; and FPP Area south of the PSCT.

The Tier 2 ERA identified that ecological risks at the Site are driven mainly by the following COCs
for terrestrial birds (Table 2-4):

•	Chromium, copper, and zinc in the RCRA Canyon Area

•	Chromium, copper, and zinc in the WCSA

•	Chromium and copper in the Roadway area

The invertivorous bird (based on the invertivorous meadowlark) is predicted to be the most
sensitive terrestrial bird to potential adverse effects from exposure to these chemicals in
surface soil (0 to 0.5 foot bgs).

For terrestrial mammals, a comparison of Site-specific tissue data to tissue-based TRVs
developed for kidney and liver tissue indicates that cadmium, chromium, copper, lead, and zinc
are not expected to accumulate in target tissues at levels that would result in potential adverse
risks. Tier 2 risks to terrestrial mammals at the Site are driven mainly by barium in RCRA
Canyon. However, historical activities indicated that drilling mud containing barium sulfate was
spread in RCRA Canyon and the WCSA. Barium toxicity to ecological receptors (wildlife) results
from free barium ions, which can be absorbed into lungs and intestines. Barium sulfate, which
is insoluble, does not cause significant toxicity because free barium ions are not released. The
toxicity values used in the baseline ecological risk assessment were all based on soluble forms
of barium, and therefore the calculated ecological risk from exposure to barium reported in the
Rl was overestimated. Considering that barium at RCRA Canyon and the WCSA is barium sulfate
and, therefore, not toxic to ecological receptors, barium was excluded as an ecological COC.

Figures 2-24 and 2-25 depict the co-located risks to ecological communities and wildlife
receptors, respectively, assuming that barium is not toxic.

2.7.3.5 Uncertainty Analysis

The methodology used in the ERA is consistent with EPA and State risk assessment guidance.
However, the procedures used in any quantitative ERA are conditional estimates, given the
many assumptions that must be made about exposure and toxicity.

Site-specific factors, which the ERA incorporated, decrease uncertainty, although uncertainty
may persist in even the most Site-specific ERAs due to the inherent uncertainty in the process.
However, because the assumptions used tend to be protective of the environment and
conservative in nature, the estimated risks are likely to exceed the most probable risk posed to
potential ecological receptors at the Site, and actual risks would be much lower.

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k Assessment Conclusions

The Selected Remedy in this ROD is necessary to protect public health or welfare or the
environment from actual or threatened releases of hazardous substances, pollutants, or
contaminants into the environment.

2.7.5 Basis for Action

The basis for action considers the nature and extent of contamination in waste materials and
impacted media, risk assessments, Site-specific conditions and characteristics, and remediation
technologies. The Site contains many different waste materials, along with multiple impacted
media. Waste materials and impacted media include: (1) surface and shallow waste materials
and contaminated soil, (2) contaminated surface water, (3) extracted contaminated subsurface
liquids, (4) contaminated pond sediments, (5) soil vapor, (6) large-volume sources of NAPL
(DNAPL and LNAPL), and (7) contaminated groundwater with multiple commingled
constituents, many of which exceed MCLs.

Many factors were considered in developing and evaluating remedial alternatives for the Site.
The alternatives are evaluated against both human health cancer/noncancer risk-based
screening levels and ecological risk screening levels. Additional considerations included:

•	Consistency with EPA and State policies, including CERCLA's preference for treatment and
NAPL source reduction

•	EPA's presumptive remedy for municipal solid waste landfills and common practice for large
legacy hazardous waste landfills

•	The State's policies directed toward achieving the highest water quality consistent with the
maximum benefits to the people of the State (e.g., groundwater considered suitable for
agricultural water supply, municipal and domestic water supply, and industrial use)

(RWQCB, 2017)

•	The State's anti-degradation policies for groundwater

•	Overall constructability

•	Compatibility and integration with other Site systems

•	Reduction of infiltration in areas where waste remains in place

•	Control of hydraulic gradients to prevent surface outflow and seeps
The basis for action for different Site media is summarized as follows:

•	Waste Materials and Contaminated Soil: The Site contains large volumes of waste materials
(and PTW) and contaminated soils that pose risks to receptor populations through direct

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physical contact and outdoor inhalation of vapors in some portions of the specified Site
areas. The waste materials are primarily within Area 1 (PCB Landfill, CDA, and BTA), while
contaminated soils are located within Areas 1, 2, and 3. The receptor population primarily
includes Site workers, trespassers, and ecological receptors. Waste materials and
contaminated soils also serve as contamination sources for Site groundwater.

• Large-Volume Sources of NAPL: Despite the Gallery Well and Sump 9B providing ongoing
NAPL removal for many years, large volumes of NAPL (including LNAPL and DNAPL) are
present in Area 5 North. Monitoring has documented the presence of an estimated 100,000
gallons of pooled DNAPL at the base of the P/S Landfill; a similar amount of pooled LNAPL
also occurs at the water table surface in the P/S Landfill area. In addition, DNAPL has been
detected in fractured bedrock underlying the P/S Landfill and CDA. The NAPL is a PTW and a
major source of contamination of groundwater. Per the NCP, EPA expects to use treatment
to address PTW (EPA, 1991), including the reduction of NAPL to limit the spread of
groundwater contamination.

• Contaminated Groundwater: Groundwater underlying the Site would pose an unacceptable
risk, if it were to be used for domestic purposes, because it contains a large number of
dissolved constituents at concentrations that exceed MCLs. Although there is no reasonable
anticipation that Site groundwater would be used for domestic purposes, EPA has
determined that MCLs apply as applicable or relevant and appropriate requirements
(ARARs) for Site groundwater (unless a waiver is applied). This approach aligns with State of
California policies directed toward achieving the highest water quality consistent with the
maximum benefits to the people of the State.

• Contaminated Surface Water and Pond Sediment: The Site contains five ponds (Area 4) that
were designed and constructed as temporary surface water storage facilities. All five ponds
contain very high levels of TDS that approach or exceed the concentration of seawater.
Remedial action to address the ponds is necessary for a combination of reasons, including:
(1) pond water contains actionable human health risk levels and exceeds Tier 1 ecological
risk screening levels; (2) underlying TDS-contaminated pond sediments are present; (3)
pond water and pond sediments are sources of groundwater contamination; and (4) the five
ponds are attractive nuisances that can create risks to threatened and endangered species
at the Site. The temporary need for the ponds will likely be eliminated during
implementation of the Selected Remedy that includes other new stormwater and liquids
management systems.

2.8 nediali Action Objectives

Remedial action objectives (RAOs) describe, in general terms, what a remedial action should
accomplish to be protective of human health and the environment. RAOs are statements that
specify the environmental media of concern, contaminant type, potential exposure pathways to
be addressed by remedial actions, receptors to be protected, and remediation goals or cleanup
levels (40 CFR Section 300.430[e][2][i]).

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Section 300.430 of the NCP (40 CFR 300.430) directs EPA to focus on an excess upper-bound
lifetime cancer risk to an individual of between 1 x 10~4 and 1 x 10~6 when deciding on remedial
action objectives to be protective for known or suspected carcinogens. The NCP further notes
that the 1 x 10~6 risk level should be considered as a point of departure for such decisions, and
that RAOs be consistent with existing ARARs. At the Site, RAOs are a mix of ARARs, chiefly
MCLs, and risk-based cleanup levels (CLs). The RAOs identified in the ROD are intended to meet
ARARs and/or be protective of human health at a 1 x 10~5 excess cancer risk or noncancer risk
hazard quotient of 1.0. These health protective goals were chosen to be consistent with the
threshold criteria set forth in 40 CFR § 300.430 (protection of human health and compliance
with ARARs). They are also consistent with the primary balancing criteria (long-term
effectiveness, reduction of toxicity, mobility or volume of contamination, short term
effectiveness, implementability, and cost-effectiveness) and modifying criteria (state and
community acceptance) in 40 CFR § 300.400.

For known or suspected carcinogens that do not have established MCLs (for example, soils),
risk-based CLs were chosen to be protective of human health as 1 x 10"5 excess cancer risk. The
remediation of 1 x 10"5 was chosen to be consistent with the threshold criteria set forth in 40
CFR § 300.430 and to be consistent with the protectiveness achieved by attainment of MCLs for
those contaminants for which MCLs have been established.

The RAOs are summarized in Sections 2.8.1 through 2.8.6.

2.8.1 Soil (Areas 1, 2, and 3)

The RAOs for soil are as follows:

•	Prevent direct physical human exposure (e.g., dermal exposure and incidental ingestion) to
risk-driving chemicals in soil and waste materials, such that total carcinogenic risks are
below the risk level of 1 x 10"5, and noncancer His are less than or equal to 1 (see human
health CLs for soil in Table 2-16).

•	Provide containment and minimize infiltration and vertical and lateral migration of
contamination into groundwater.

•	Prevent ecological exposure to risk-driving chemicals in soil, such that risks are below the
acceptable target levels (LOAEL, HQ less than or equal to 1) (see ecological CLs for soil in
Table 2-16).

•	Reduce sources of contamination in soil to minimize the vertical downward migration of
contaminants to groundwater, such that infiltration does not contribute to additional
exceedances of MCLs in groundwater.

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2.8.2	Pond Sediments (Area 4)

The RAOs for pond sediments are as follows:

•	Prevent direct physical contact (that is, dermal exposure and incidental ingestion) to pond
sediments, such that total carcinogenic risks are below the risk level of 1 x 10~5, and
noncancer His are less than or equal to 1.

•	Prevent ecological exposure to risk-driving chemicals in pond sediments, such that risks are
below the acceptable target levels (LOAEL, HQ less than or equal to 1).

2.8.3	Surface Water (Area 3ugh 4, and Adjacent Wetlands)

The RAOs for surface water are as follows:

•	Prevent human exposures (that is, dermal exposure or incidental ingestion) to risk-driving
chemicals (primarily metals) in surface water, such that total carcinogenic risks are below
the risk level of 1 x 10"5, and noncancer His are less than or equal to 1.

•	Prevent off-property discharges of surface water with concentrations of contaminants in
excess of appropriate permit limits and discharge requirements that are protective of public
health and the environment.

•	Prevent ecological exposures to risk-driving chemicals in surface water, such that exposures
are below acceptable target levels (HQs less than or equal to 1).

•	Achieve target treatment standards, to be defined during the remedial design phase, for
effluent from the new groundwater treatment system prior to discharge to the onsite lined
evaporation pond(s).

2.8.4	NAPL (Aire id 5)

The RAOs for NAPL are as follows:

•	Reduce DNAPL sources of groundwater contamination that contribute to exceedances of
MCLs by removing DNAPL source material from the base of the P/S Landfill in Area 1 and
other areas where present, to the extent practicable.

•	Reduce LNAPL sources of groundwater contamination that contribute to exceedances of
MCLs by removing LNAPL source material, to the extent practicable, from the P/S Landfill in
Area 1 and other areas where present.

•	Contain NAPL within the Zone 1 subarea (Area 5 North) to prevent further groundwater
impacts beyond this area.

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2.8.5 Groundwater (Area 5)

The RAOs for groundwater are as follows:

• Where technically practicable (Area 5 South and Area 5 West), restore the beneficial use of
groundwater by achieving MCLs, or other applicable cleanup goals for chemicals without
MCLs.

• Contain groundwater contamination within the Zone 1 subarea (Area 5 North) where
groundwater restoration to applicable standards is not technically practicable.

• Prevent potential off-property migration of groundwater contamination beyond the Zone 1
perimeter boundary.

2.8.6 Wetland Habitat for Threatened and Endangered Species (Are rough 4, and

Adjacent Wetland)

As described previously, the Site contains contaminated surface water and sediment that
exceed Tier 1 ecological risk levels and which pose unacceptable risks to federal threatened and
endangered species that have been documented at the Site. Surface water at the Site, such as
the ponds, can also create an attractive nuisance.

The RAOs for wetland habitats for threatened and endangered species in Areas 1 through 4,
and the adjacent wetlands, are as follows:

• Maintain or provide soil, sediment, vegetation, and water quality capable of supporting a
functioning ecosystem for the aquatic and terrestrial plant and animal populations at the
Site.

• Maintain or provide soil, sediment, vegetation, and water quality supportive of individuals
of special-status species, which are protected under the Endangered Species Act (ESA).

2.8.7 Cleanup Levels

The CLs, also referred to as "remediation levels" or "remediation standards" in various EPA
documents, apply to the remediation and containment within the various impacted media. The
preliminary remediation goals identified in the Proposed Plan are established as CLs in the ROD.
The CLs apply to the RAOs presented in Sections 2.8.1 through 2.8.6.

The CLs have been identified for the Site based on the results of the HHRA and ERA. Table 2-16
presents soil CLs for the human health COCs (MCPP, TCE, and PCE) and the ecological COCs
(chromium, copper, and zinc).

For groundwater, concentrations of dissolved-phase constituents will be required to meet MCLs
in Area 5 South and Area 5 West, which are beyond the designated Tl Zone of Area 5 North (see
Table 2-7). There is no expectation that groundwater impacted by the high volumes of

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heterogeneous waste materials within the Tl Zone will be cleaned up to MCLs, in the area
within the Tl Zone. EPA is not establishing alternative groundwater cleanup levels due to:
(1) the technical challenges of designating an appropriate alternative level based on the large
number of COCs; and (2) the Tl of achieving MCLs, let alone potentially more stringent
alternative cleanup levels. However, EPA will continue to evaluate groundwater remediation
during long-term groundwater monitoring and the five-year review process.

Existing pond surface water will be removed during implementation of the Selected Remedy.
The existing surface water will be removed, and the pond bottoms will be capped, thereby
eliminating unacceptable risk to ecological receptors. Therefore, CLs are not required for these
media.

In summary, the media-specific CLs are as follows:

• Soil (including hotspots): Risk-based concentrations (Table 2-16)

• Groundwater: MCLs (Table 2-7), except in the designated Tl Zone in Area 5 North

• Pond Surface Water and Sediment: None (the Selected Remedy will eliminate exposure to
existing pond surface water and sediment)

• Soil Vapor: None (the Selected Remedy will provide for capping of the CDA and BTA in Area
1, and excavation and/or capping of soil hotspots in the FPP Area in Area 3)

• Seep Surface Water: None (The Selected Remedy will provide for capping and will eliminate
seeps)

• Surface Water Discharge: The applicable, substantive, NPDES permit limits and discharge
requirements will apply to offsite surface water discharge.

2.9 scription of Alternatives

The six sitewide remedial alternatives were developed and presented in the FS report, and are
summarized in this section.

The FS process began with an evaluation of General Response Actions, based on the various
environmental media and contaminant types, to address RAOs and potential ARARs. General
Response Actions considered included containment, in situ treatment, removal, ex situ
treatment, disposal, reuse, and ICs. Several cap types were also considered. A wide range of
remedial technologies was then reviewed, with the goal of selecting a set of potentially
effective technologies as components in the remedial alternatives. The technologies considered
inappropriate were screened out in the initial evaluation. The next step was to combine the
technologies retained from the screening evaluation, along with results of the TIE for
groundwater in Area 5 North, to develop a range of remedial alternatives for each study area. A
second screening evaluation of those remedial alternatives was then conducted, based on the

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PART 2: THE DECISION SUMMARY

three screening criteria from CERCLA guidance (effectiveness, implementability, and cost). This
evaluation screened out remedial alternatives that did not rate well on these criteria, resulting
in a list of compiled, sitewide, remedial alternatives that are subject to detailed evaluation
described in this section.

Six sitewide remedial alternatives were developed following technology screening and
evaluation of alternatives for individual areas. Each alternative is a combination of the remedial
components from the area-specific detailed evaluation. The alternatives range from least
aggressive (no further action), to more aggressive (P/S Landfill dewatering), to most aggressive
(P/S Landfill dewatering and groundwater extraction and treatment). The six alternatives have
several common components, as well as distinguishing features.

2.9.1 Common Elements
The following are common elements for each remedial alternative (except Alternative 1):

• Engineered RCRA Capping Systems: Each alternative includes engineered capping systems.
The engineering designs of the various capping configurations vary spatially throughout the
Site and between different alternatives. The various types of caps evaluated during the
development of remedial alternatives are illustrated on Figure 2-26.

• ICs: Each alternative includes ICs, which are administrative and legal controls to help
minimize the potential for human exposure to contamination and/or protect the integrity of
the response action. Land use covenants have been established for six parcels, including
and surrounding the Zone 1 portion of the Site.

• Soil Hotspot Remediation: Each alternative includes remediation of the soil hotspots in Area
3 to reduce the residual human health and ecological risks to acceptable levels. The
hotspots would be addressed by excavation (with disposal of soils in the PCB Landfill prior
to capping of that landfill) and/or capping.

• Liquids Extraction and Onsite/Offsite treatment: Each alternative includes continued
extraction of liquids from the Gallery Well and Sump 9B, with disposal at an approved,
offsite facility. Each alternative also includes continued liquids extraction from the PSCT and
PCT-A, PCT-B, and PCT-C, with the treatment and effluent disposal requirements differing
among the various alternatives.

• Habitat Mitigation: Each alternative includes habitat mitigation, which may include
improvement of existing habitat and/or potential construction of additional habitat. The
scope of habitat mitigation will be based on coordination with the USFWS during the
remedial design phase.

• A WMA and Tl Zone Encompassed by a POC: Each alternative includes both a WMA and Tl
Zone encompassed by a POC. The POC is located at the Tl Zone (Area 5 North) boundary to
ensure that groundwater quality is not further degraded outside this area (see Figure 2-27).

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PART 2: THE DECISION SUMMARY

• MNA: Each alternative includes MNA that contributes to the reduction in contaminant
concentrations, and limits the nature and extent of groundwater contaminant migration at
the Site.

• Long-term OM&M with Optimization of Monitoring. Extraction, and Treatment
Components: Each alternative includes a long-term OM&M program to monitor treatment
system performance, contain groundwater impacts, and ensure compliance with
performance standards at the POC.

2.9.2 Distinguishing Features

Several features and technologies, such as the size and type of lined evaporation ponds and
extraction systems, clearly differentiate the alternatives.

The distinguishing feature of Alternative 1 (No Further Action) is that no additional remedial
action would take place. There is no cost estimate associated with this alternative.

The distinguishing feature of Alternative 2 (Capping, Liquids Extraction, Large Evaporation
Pond) is the use of a larger evaporation pond system (about 11 acres) for treatment of
extracted liquids and a portion of stormwater runoff from the uncapped eastern slope of RCRA
Canyon.

The distinguishing feature of Alternative 3 (Capping, Liquids Extraction, Small Evaporation
Pond), the Selected Remedy, is the use of a smaller evaporation pond system (about 6 acres)
for treated extracted liquids, while all of RCRA Canyon will be capped. Stormwater from the
entire RCRA Canyon area will have acceptable ecological risks (HQ less than 1) and allow offsite
discharge to the B-Drainage.

The distinguishing feature of Alternative 4 (Capping, Liquids Extraction, Offsite Discharge) is the
elimination of evaporation ponds by adding a treatment plant at the Site for PSCT and PCT
liquids that treat constituents to meet NPDES permit requirements. The treated liquids would
be discharged offsite to Casmalia Creek, rather than managed in an evaporation pond.

The distinguishing feature of Alternative 5 (Capping, Liquids Extraction, P/S Landfill Dewatering,
Small Evaporation Pond) is aggressive dewatering of the P/S Landfill by constructing
approximately five horizontal wells drilled underneath and into the landfill using horizontal
directional drilling (HDD).

The distinguishing features of Alternative 6 (Capping, Liquids Extraction, P/S Landfill
Dewatering, Groundwater Extraction, Offsite Discharge) are P/S Landfill dewatering (as in
Alternative 5), combined with construction and operation of approximately 80 new
groundwater extraction wells in Area 5 South and Area 5 West. The extracted liquids would be
treated to meet NPDES requirements and discharged offsite to the C-Drainage, rather than
managed in an evaporation pond.

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PART 2: THE DECISION SUMMARY

2.9.3 Remedial Alternatives
Table 2-17 summarizes the components for the six alternatives.

2.9.3.1 Alternative 1-No Further Action

Alternative 1 is included for completeness and assumes that no additional remediation will take
place, other than the response actions that were already completed (that is, the installation of
RCRA caps on the P/S Landfill and the EE/CA area) and are ongoing (that is, groundwater
extraction and treatment/management from the existing Gallery Well, Sump 9B, PSCT, and PCT
features). Liquids from the Gallery Well and Sump 9B are disposed at an approved, offsite
facility. The PSCT liquids are treated onsite using GAC and discharged to Pond 18. The PCT
liquids are discharged to the RCF and A-Series Pond. Stormwater is retained in onsite ponds for
evaporation, except for fresh stormwater from the capped landfill area that is discharged
offsite to the B-Drainage and Casmalia Creek. This alternative neither protects human health
and the environment nor achieves ARARs because of contaminants that are either not
contained or result in unacceptable exposure. Therefore, it does not meet CERCLA's threshold
criteria for remedy selection.

2.9.3.2 Alternativ ipping, Liquids Extraction, Large Evaporation Pond

Alternative 2 would use a large evaporation pond (11 acres) for treated extracted liquids and a
portion of stormwater from RCRA Canyon (see Figure 2-28). Among other objectives, this
alternative remediates RCRA Canyon (Area 2) to meet all RAOs that do not by themselves
require that all of the RCRA Canyon area be covered with some sort of cap. In doing so, this
alternative assumes that some stormwater runoff from RCRA Canyon would be directed to the
new evaporation pond to be constructed in the footprint of the existing A-Series Pond. Further
remediation details for each area are described as follows:

• Area 1 - PCB Landfill. BTA. and CPA: Area 1 would be covered with a RCRA cap over
approximately 28.8 acres. The cap will be similar in design to the existing P/S Landfill cap
and the EE/CA Area cap and will tie into these caps. The RCRA cap would also extend to
cover the maintenance shed area. Stormwater from Area 1 would be discharged offsite to
the B-Drainage and Casmalia Creek under a General Permit.

• Area 2 - RCRA Canyon and WCSA: Area 2 would be remediated by constructing a RCRA ET
cap that is approximately 5 feet thick over the western portion of RCRA Canyon (about 8.4
acres), excavating the relatively shallow contaminated soils of the WCSA, and then
backfilling the excavations with clean soil (about 5.5 acres). The ET cap would serve to
reduce surface water infiltration in this area of the Site, thereby lowering the level of the
water table and eliminating the surface seeps at the southern end of RCRA Canyon.
Stormwater from the capped western slope would be discharged offsite down the B-
Drainage and Casmalia Creek under a General Permit. Stormwater best management
practices (BMPs) will be used over the eastern slope of the RCRA Canyon (about 19.3 acres).
Stormwater from the uncapped eastern slope of RCRA Canyon will not be discharged offsite

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PART 2: THE DECISION SUMMARY

because of low-level (HQ less than 1) residual soil contamination. Instead, this stormwater
would be retained in the new 11-acre, lined, evaporation pond that would be constructed in
the footprint of the closed A-Series Pond and/or RCF Pond.

• Area 3 - FPP Area. Remaining Onsite Areas: Area 3 would be remediated by addressing the
five soil hotspot locations, which would reduce the residual human health and ecological
risks to acceptable levels. The hotspots would be addressed as follows:

- HS-1: The shallow soil hotspot in the Liquids Treatment Area would be excavated to CLs
for soil (Table 2-16) and placed under the RCRA cap of the PCB Landfill, and/or covered
with an asphalt cap as shown on Figure 2-26.

- HS-2: The shallow soil hotspot(s) in the MSA would be covered with the RCRA cap
extended from Area 1.

- HS-3: The shallow and deep soil hotspot in the former Ponds A/B area would either be:

(1) excavated to CLs for soil and placed under the RCRA cap of the PCB Landfill; or

(2) covered with the RCRA cap extended from Area 1 (based on an implementability and
engineering evaluation during remedial design).

- HS-4: The shallow soil hotspot south of PSCT-1 would be excavated to CLs for soil and
placed under the RCRA cap of the PCB Landfill.

- HS-10: Because there are no unacceptable human health or ecological risks for the deep
soil hotspot at RISBON-59, the proposed action is long-term groundwater monitoring.
Two additional downgradient monitoring wells will be installed to verify that there are
no unacceptable impacts to groundwater. Stormwater from Area 3 would be discharged
to the B-Drainage and Casmalia Creek under a General Permit.

• Area 4 - Stormwater Ponds and Treated Liquid Impoundments: Area 4 would be
remediated as follows:

- Pond 18 - Remove all liquids, place clean soil within the pond footprint to regrade it to
match adjacent Site topography, and install a RCRA cap to close the pond.

- Pond A-5 - Remove all liquids, place excavated soil from the WCSA within the pond
footprint to raise the bottom of the former pond, and install a lined cap retention basin.
The basin will be constructed with a double liner consisting of an HDPE layer and a
geosynthetic clay later (GCL) (HDPE/GCL liner) liner, and converted into a new retention
basin used as part of the RCRA Canyon stormwater management system.

- Pond 13 - Remove all liquids, place a clean soil cover over the pond, construct an
HDPE/GCL liner as an engineered cap for the contaminated sediments in the pond, and
convert into a new retention basin.

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PART 2: THE DECISION SUMMARY

-	A-Series Pond - Remove all liquids, regrade the northeastern corner of the pond to
increase the pond size to approximately 11 acres, add soil fill to raise the pond bottom
above the water table, and construct a double-lined (such as, dual HDPE liner) RCRA
evaporation pond system. The double-lined system would include leak detection, and a
leachate collection and removal system. The new evaporation pond would also receive
any liquids remaining prior to remedial construction at the other existing ponds, and
future treated PSCT and PCT liquids. The design configuration and total number of
individual evaporation ponds would be finalized during the remedial design phase, but
the total area would remain at approximately 11 acres. The evaporation pond system
would be designed with biological controls (such as, netting, fencing, screening, and
hazing) and biological monitoring to minimize adverse impacts to special-status species
based on coordination with USFWS. Habitat mitigation would be performed as
necessary based on coordination with USFWS during the remedial design phase.

-	RCF Pond - Remove all liquids, place clean soil throughout the bottom of the pond to
raise the pond bottom to prevent groundwater intrusion, construct a soil cap (or "eco-
cap"), and construct a new lined stormwater channel through the middle of former
pond footprint to the B-Drainage to convey stormwater runoff from the CDA and other
capped portions of the Site.

• Area 5 North: Area 5 North would be addressed through liquids extraction from existing and
new facilities to control and contain contaminant sources within the designated Tl Zone.
However, Area 5 North would not be remediated to meet MCLs because the presence of
LNAPL, DNAPL, residual NAPL, and dissolved-phase organic and inorganic contamination in
low-permeability fractured bedrock generally makes it technically impracticable to
remediate the groundwater to meet MCLs in this area. Extraction would continue from the
existing Gallery Well and from approximately 16 "NAPL-only" (LNAPL and DNAPL) extraction
wells to be installed in the southern portion of the P/S Landfill. Increased extraction from
the P/S Landfill should reduce the driving head of the DNAPL that is likely causing it to
spread into the Lower HSU beneath the P/S Landfill and CDA.

Within the Upper HSU, extraction would continue from the PSCT to prohibit groundwater
from migrating southward outside of the designated Tl Zone. Extraction will also be
performed from Sump 9B if the water table remains unacceptably high after capping in
Area 1.

Finally, approximately 12 new Lower HSU monitoring wells would be installed and
monitored upgradient of PSCT-1 and PSCT-4 (three at each location with each location
monitoring two depths) to verify that dissolved-phase contaminants and NAPL are not
migrating southward underneath the PSCT and outside the Tl Zone.

The liquids extracted from the Gallery Well and approximately 16 new NAPL-only wells in
the P/S Landfill would be stored and shipped for treatment and disposal at an approved
facility. The extracted liquids from the PSCT would be treated at the Site using an upgraded
treatment system that would likely include, but not be limited to, solids removal and

62

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PART 2: THE DECISION SUMMARY

activated carbon; the treated effluent would then be transferred to the new 11-acre
evaporation pond. The treatment system design details will be determined during remedial
design.

• Area 5 South: Within the Upper HSU, extraction would continue from the PCT-A and PCT-B
facilities to contain and prevent contaminated groundwater from migrating through the A-
and B-Drainages. The current concentrations of dissolved-phase organic and inorganic
contaminants within the Upper HSU exceed MCLs. These concentrations are expected to
decrease over many decades as a result of naturally occurring conditions, including dilution
and flushing from infiltrating rainfall and natural degradation of organic compounds. The
flushed contaminants would be extracted at the PCT-A and PCT-B facilities as long as
contaminants exceed MCLs. This approach is referred to as "MNA with perimeter
containment." The Lower HSU does not require remediation because the concentrations of
organic and inorganic compounds in groundwater are below MCLs in this area.

The liquids extracted from the PCT-A and PCT-B facilities would be treated at the Site, using
an upgraded liquids treatment system that would likely include, but not be limited to, solids
removal and activated carbon; the treated effluent would then be transferred to the new
11-acre evaporation pond. The treatment system selected will be determined during
remedial design.

• Area 5 West: Within the Upper HSU, extraction would continue from the PCT-C facility to
contain and prevent contaminated groundwater from migrating through RCRA Canyon and
the C-Drainage. Concentrations of the dissolved-phase inorganic contaminants within the
Upper HSU currently exceed MCLs. A significant source of this contamination is likely from
the metals in the overlying soils in RCRA Canyon and the WCSA, and infiltration of surface
water high in metals from Pond A-5 and the A-Series Pond. Once these sources are
eliminated, the metals concentrations in Area 5 West will decrease over many decades as a
result of naturally occurring conditions, including dilution and flushing from infiltrating
rainfall. The flushed contaminants would be extracted at the PCT-C facility as long as
contaminant levels exceed MCLs (MNA with perimeter containment).

The Lower HSU of Area 5 West does not require remediation because the concentrations of
organic and inorganic compounds in groundwater are below MCLs in this area.

The liquids extracted from PCT-C would be treated at the Site using an upgraded liquids
treatment system that would likely include, but not be limited to, solids removal and
activated carbon. The treated effluent would then be transferred to the new 11-acre
evaporation pond.

The time to construct for Alternative 2 is estimated to be 5 years. The estimated
remediation timeframes for groundwater in Area 5 South to reach remediation goals (MCLs)
would range from 80 years (nickel) to 260 years (arsenic) after complete source removal.
Based on model simulations, the estimated remediation timeframes for groundwater in
Area 5 West to reach MCLs would range from 90 years (nickel) to 220 years (arsenic) after

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PART 2: THE DECISION SUMMARY

complete source removal. There is uncertainty in the actual timeframes to achieve cleanup
standards, and the actual timeframe may range from several decades to centuries.

• Long-Term O&M: Long-term O&M will be conducted to ensure that all Site components and
systems are functioning effectively throughout the duration of the remedial action. Long-
term O&M will address multiple media and systems, including, but not limited to, capping
systems, liquids collection, treatment, and disposal systems, surface water management,
and all monitoring systems. Long-term O&M will be performed based on optimization
studies, and a long-term O&M plan that will be subject to EPA review and approval.

• Long-term Monitoring: Long-term performance and compliance monitoring will be
conducted to ensure that remedial systems are functioning effectively and remain in
compliance with performance standards. Long-term monitoring will include compliance
monitoring of groundwater both laterally and vertically, surface water, soil vapor, and
ambient air, and performance monitoring of remedial systems. Long-term monitoring will
also include ongoing evaluation of ICs. Long-term groundwater monitoring will be
performed based on optimization studies and subject to a long-term monitoring plan that
will require EPA review and approval. EPA may require additional monitoring, if determined
necessary based on the results of monitoring data, to ensure protection of human health
and the environment.

• Contingency Measures: Contingency measures will be performed if groundwater monitoring
data indicate that contamination is migrating beyond area boundaries, including the POC
and the perimeter boundary of the former disposal facility (Zone 1). Contingency measures
will be initiated if groundwater monitoring data show that migration is occurring at
statistically representative concentrations that cause, or are likely to cause, exceedances of
performance standards. These contingency measures will be performed to ensure adequate
containment. Contingency measures may include any or all of the following: (1) additional
monitoring from existing wells; (2) installation of additional monitoring wells to further
characterize potential migration; and (3) installation of a limited number of extraction wells
within a localized area to maintain hydraulic containment. These extraction wells would
supplement the area and perimeter containment provided by existing perimeter control
trenches, extraction wells, and natural attenuation.

2.9.3 , ernativ ipping, Liquids Extraction, Small Evaporation Pond (Selected

Remedy)

Alternative 3 is a variation of Alternative 2 and is the Selected Remedy in this ROD.

Alternative 3 will use landfill capping, liquids extraction, and a smaller (approximately 6 acres)
evaporation pond(s) instead of the larger (11 acres) pond (see Figure 2-29). The primary
difference in this alternative is additional capping in Area 2 to ensure that all stormwater runoff
from the RCRA Canyon area can be discharged to the B-Drainage and Casmalia Creek via the
General Permit, rather than managed in the evaporation pond.

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PART 2: THE DECISION SUMMARY

The remediation details for each area are described as follows:

• Area 1 - PCB Landfill. BTA. and CPA: Area 1 remediation would be the same as described for
Alternative 2.

• Area 2 - RCRA Canyon and WCSA: Area 2 would be capped with either an ET cap or a RCRA-
equivalent hybrid cap that covers the western and eastern slopes of RCRA Canyon and the
WCSA. As shown on Figure 2-26, an ET cap will include a foundation later and a vegetative
layer approximately 4 feet in thickness; the hybrid cap will include a foundation layer, HDPE
liner, geotextile drainage later, biotic barrier, and a vegetative layer about 2 feet in
thickness. The cap type for the different subareas would be selected during remedial
design. With this capping, stormwater from the entire area will have acceptable ecological
risks (that is, HQ less than 1) and allow discharge to the B-Drainage and Casmalia Creek. In
addition, the larger cap will significantly reduce surface water infiltration in this area,
further lowering the level of the water table and helping to eliminate the contaminated
surface seep at the southern end of the RCRA Canyon.

• Area 3 - FPP Area. Remaining Onsite Areas: Area 3 remediation would be the same as
described for Alternative 2.

• Area 4 - Stormwater Ponds and Treated Liquid Impoundments: Area 4 remediation would
be the same as for Alternative 2, except that this alternative would use a smaller
(approximately 6 acres) evaporation pond(s) within the former footprint of the A-Series
Pond and/or RCF Pond, instead of the larger 11-acre pond because no stormwater from
RCRA Canyon would be discharged into it. The design configuration and total number of
individual evaporation ponds will be finalized during the remedial design phase, but the
total area will remain at about 6 acres. The evaporation ponds will be designed with
biological controls (such as, netting and fencing) and biological monitoring to minimize
adverse impacts to special-status species. Habitat mitigation will be performed as necessary
based on coordination with USFWS and CDFW during the remedial design phase.

The remainder of the A-Series Pond area would be capped with an eco-cap.

• Area 5 North. Area 5 South, and Area 5 West - Groundwater: Area 5 remediation would be
the same as described for Alternative 2, except that treated water would be directed to a
smaller (approximately 6 acres) evaporation pond(s), instead of the larger (11 acres) pond.

The time to construct for Alternative 3 is estimated to be 5 years. Based on model simulations,
the estimated remediation timeframes for groundwater in Area 5 South to reach MCLs are
similar to those presented for Alternative 2. The estimated remediation timeframes for
groundwater in Area 5 West to reach MCLs would be faster than those presented for
Alternative 2, because the source of metals over the entire RCRA Canyon area would be capped
under Alternative 3 compared to a partial cap under Alternative 2. However, the predicted
difference in timeframes between Alternatives 2 and 3 is likely within the range of accuracy of
the analysis; therefore, it is not quantified.

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PART 2: THE DECISION SUMMARY

2.9.3 - , ernativ - ipping, Liquids Extraction, Offsite Discharge

Alternative 4 is a variation of Alternative 3 that would include landfill capping, liquids
extraction, and offsite discharge without an evaporation pond (see Figure 2-30). The pond
would be eliminated by adding a treatment plant at the Site for PSCT and PCT liquids that treats
both organic and inorganic constituents to meet substantive NPDES permit requirements. The
treated liquids would then be discharged offsite to Casmalia Creek, rather than managed in an
evaporation pond. This alternative may also involve a process to obtain approval from the
RWQCB to allow for offsite discharge of treated liquids to Casmalia Creek, which is located
within the Antonio Creek Valley Creek basin.

The remediation details for each area are described as follows:

• Area 1 - PCB Landfill. BTA. and CPA: Area 1 remediation would be the same as described for
Alternative 2.

• Area 2 - RCRA Canyon and Western Canyon Spray Area: Area 2 remediation would be the
same as described for Alternative 3.

• Area 3 - FPP Area. Remaining Onsite Areas: Area 3 remediation would be the same as
described for Alternative 2.

• Area 4 - Stormwater Ponds and Treated Liquid Impoundments: Area 4 remediation would
be the same as described for Alternative 3, except that no RCRA evaporation pond would be
constructed for management of stormwater or extracted liquids. All stormwater would be
discharged to the B-Drainage and Casmalia Creek. Additional treatment would be added to
treat PSCT and PCT liquids to meet NPDES substantive permit requirements prior to
discharge to the C-Drainage west of the Site. The bottom of the A-Series Pond would be
partially filled to raise the pond bottom above anticipated groundwater levels; it would then
be capped with an eco-cap similar to the cap proposed for the RCF Pond.

• Area 5 (Groundwater) - Area 5 North. Area 5 South, and Area 5 West: Area 5 remediation
would be similar to Alternative 2, except liquids extracted from the PSCT and PCTs would be
treated to meet NPDES substantive requirements prior to discharge to the C-Drainage west
of the Site.

The time to construct for Alternative 4 is estimated to be 5 years. The estimated remediation
timeframes for groundwater in Area 5 South and Area 5 West to reach MCLs would be similar
to those presented for Alternative 2, given the range of accuracy of the analysis.

2.9.3 , ernativ • ¦ jpping, Liquids Extraction, P/S Landfill Dewatering, Small
Evaporation Pond

Alternative 5 is a variation of Alternative 3 that would include landfill capping, liquids
extraction, and aggressive dewatering of the P/S Landfill using horizontal extraction wells at the

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PART 2: THE DECISION SUMMARY

base of the landfill (see Figure 2-31). Alternative 5 would use horizontal wells to drain up to 10
million gallons of contaminated liquids, including up to 100,000 gallons of pooled DNAPL, from
the base of the P/S Landfill over a period of several years. The wells would be installed along
the base of the landfill using horizontal direction drilling (HDD) technology. As with Alternative
3, the treated PSCT and PCT liquids would be discharged to a new, 6-acre evaporation pond
constructed in the footprint of the A-Series Pond, and all stormwater would be discharged to
the B-Drainage and Casmalia Creek.

The remediation details for each area are described as follows:

• Area 1 - PCB Landfill. BTA. and CPA: Area 1 remediation would be the same as described for
Alternative 2.

• Area 2 - RCRA Canyon and WCSA: Area 2 remediation would be the same as described for
Alternative 3.

• Area 3 - FPP Area. Remaining Onsite Areas: Area 3 remediation would be the same as
described for Alternative 2, with one exception: The RISBON-59 hotspot (HS-10) would be
excavated and the contaminated soil would be moved to the PCB Landfill prior to capping of
that landfill.

• Area 4 - Stormwater Ponds and Treated Liquid Impoundments: Area 4 remediation would
be the same as described for Alternative 3.

• Area 5 (Groundwater) - Area North. Area 5 South, and Area 5 West: Area 5 remediation
would be the same as described for Alternative 2 for Area 5 South and Area 5 West.
However, for Area 5 North, aggressive dewatering of the P/S Landfill would be conducted by
constructing approximately five horizontal wells drilled underneath and into the landfill
using HDD. Alternative 5 also includes the conversion of four existing CDA monitoring wells
into LNAPL skimming wells. The Gallery Well would remain in operation, but this alternative
does not include the 16 "NAPL only" wells in the P/S Landfill. The Gallery Well liquids, NAPL,
and other aqueous phase liquids drained from the P/S Landfill would be sent offsite to a
permitted facility for disposal.

The time to construct for Alternative 5 is estimated to be 5 years. The estimated remediation
timeframes for groundwater in Area 5 South and Area 5 West to reach MCLs would be similar
to those presented for Alternative 2, given the range of accuracy of the analysis.

2.9.3 ernativ < • ¦ .jpping, Liquids Extraction, P/S Landfill Dewatering, Groundwater
Extraction, Offsite Discharge

Alternative 6 is a variation of Alternative 5 that also includes landfill capping, liquids extraction,
P/S Landfill dewatering, and construction and operation of approximately 80 new groundwater
extraction wells in Area 5 South and Area 5 West to help decrease the timeframe to achieve
MCLs (see Figure 2-32). In addition, Alternative 6 proposes that extracted liquids would be

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PART 2: THE DECISION SUMMARY

treated sufficiently and discharged to the C-Drainage west of the Site, in accordance with

NPDES substantive permit requirements, such that no evaporation pond would be needed.

The remediation details for each area are described as follows:

• Area 1 - PCB Landfill. BTA. and CPA: Area 1 remediation would be the same as described for
Alternative 2.

• Area 2 - RCRA Canyon and WCSA: Area 2 remediation would be the same as described for
Alternative 3.

• Area 3 - FPP Area. Remaining Onsite Areas: Area 3 remediation would be the same as
described for Alternative 5.

• Area 4 - Stormwater Ponds and Treated Liquid Impoundments: Area 4 remediation would
be the same as described for Alternative 4.

• Area 5 Groundwater (Area 5 North): Area 5 North remediation would be the same as
described for Alternative 5, with the following additions:

- Approximately a dozen new LNAPL skimming wells would be installed in the CDA. The
extracted LNAPL would be stored and shipped to a permitted facility for disposal.

- Extraction would occur immediately from 4 of the 12 new monitoring wells that would
be installed and monitored within the Lower HSU upgradient of PSCT-1 and PSCT-4 to
ensure that dissolved-phase contaminants and NAPL are not migrating southward
underneath the PSCT outside of the designated Tl Zone. These liquids would be
combined with the liquids extracted from the PSCT and PCTs for treatment and disposal.

- Liquids extracted from the PSCT and PCTs would be treated to meet NPDES substantive
permit requirements and discharged to the C-Drainage west of the Site rather than
being managed in an evaporation pond. The Gallery Well liquids, NAPL, and other
aqueous phase liquids drained from the P/S Landfill would be sent offsite to a permitted
facility for disposal.

• Area 5 Groundwater (Area 5 South and Area 5 West): Area 5 South and Area 5 West
remediation would be the same as described for Alternative 2, except that approximately
80 new groundwater extraction wells would be located throughout the two areas to
decrease the timeframe to achieve MCLs. The liquids from the PCTs and the 80 new
extraction wells would be treated to meet NPDES substantive permit requirements, and
then discharged to the C-Drainage west of the Site, rather than being managed in an
evaporation pond.

The time to construct for Alternative 6 is estimated to be 5 years. The estimated
remediation timeframes for groundwater in Area 5 South and Area 5 West to reach MCLs

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would be faster than those for Alternative 3 because of the aggressive extraction from the
80 new wells. However, there is uncertainty in the timeframes to achieve cleanup
standards; and the estimated time to achieve CLs is still expected to be several decades and
potentially over a century.

2.10 Comparative Analysis of Alternatives

The alternatives were evaluated based on the CERCLA criteria identified in the NCP. The nine
CERCLA criteria include the following:

•	Threshold Criteria:

1.	Overall Protection of Human Health and the Environment

2.	Compliance with ARARs

•	Balancing Criteria:

1.	Long-Term Effectiveness (LTE)

2.	Reduction of Toxicity, Mobility, or Volume through Treatment

3.	Short-Term Effectiveness (STE)

4.	Implementability

5.	Cost

•	Modifying Criteria:

1.	State Agency Acceptance

2.	Community Acceptance

Table 2-18 presents a graphical summary of the comparative evaluation of the sitewide
alternatives against the CERCLA 9-point criteria. The following narrative provides a detailed
comparison of the sitewide alternatives. For additional comparison, Table 2-19 provides a
summary of the estimated groundwater cleanup times for Area 5 North, South, and West, along
with projected capital and O&M costs for each alternative.

1,	Overall Protection of Human Health and the Environment

Overall protection of human health and the environment addresses whether each alternative
provides adequate protection of human health and the environment, and describes how risks
posed through each exposure pathway are eliminated, reduced, or controlled, through
treatment, engineering controls, and/or ICs.

With the exception of the No Further Action alternative (Alternative 1), all remedial alternatives
achieve the RAOs and are protective of human health and the environment.

2.	Compliance with ARARs

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Section 121(d) of CERCLA and NCP Section 300.430(f)(l)(ii)(B) require that remedial actions at
CERCLA sites attain standards legally referred to as "ARARs," unless such ARARs are waived
under CERCLA section 121(d)(4).

Applicable requirements are those cleanup standards, standards of control, and other
substantive requirements, criteria, or limitations promulgated under federal or State
environmental, or facility siting laws that specifically address a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance found at a CERCLA Site. State
standards that a state identifies in a timely manner and that are more stringent than federal
requirements may be applicable. Relevant and appropriate requirements are those cleanup
standards, standards of control, and other substantive requirements that, while not
"applicable" to a hazardous substance, pollutant, contaminant, remedial action, location, or
other circumstance at a CERCLA Site, address problems or situations sufficiently similar to those
encountered at a CERCLA Site that their use is well-suited to the particular Site. Only those
State standards that are identified in a timely manner and are more stringent than federal
requirements may be relevant and appropriate. The ARARs for the Site are presented in
Appendix D.

Compliance with ARARs addresses whether a remedy will meet all of the ARARs of other federal
and State environmental statutes or provides a basis for invoking a waiver.

With the exception of the No Further Action alternative (Alternative 1), all alternatives comply
with the proposed ARARs. For example, chemical-specific ARARs include MCLs, which would
apply across the Site, except for the Tl Zone in Area 5 North. EPA's approach to groundwater at
the Site is to apply the selected groundwater cleanup ARARs (MCLs) throughout the plume,
except for the designated Tl Zone within Area 5 North where it is not technically practicable to
meet ARARs. The Selected Remedy (Alternative 3) incorporates a waiver of the groundwater
cleanup ARARs within the designated Tl Zone (including the WMA) within Area 5 North. This
approach complies with CERCLA Section 121(d)(4), is consistent with EPA's presumptive remedy
approach to groundwater at landfill sites, and is protective of human health and the
environment.

3. Lo. n Effectiveness

LTE refers to expected residual risk and the ability of a remedy to maintain reliable protection
of human health and the environment over time, once cleanup levels have been met. This
criterion includes the consideration of residual risk that will remain onsite following
remediation and the adequacy and reliability of controls.

Overall, Alternatives 3 through 6 are reasonably comparable in achieving LTE, although
Alternatives 4 through 6 more aggressively address Site liquids and could potentially provide
improved LTE. Alternatives 2-3 make use of similar remedial components, but differ in scale,
such as the size of evaporation ponds and liquids treatment systems. Alternative 4 uses
additional liquids treatment and excludes evaporation ponds. Alternatives 5 and 6 are more
aggressive, utilizing P/S Landfill dewatering with horizontal wells for Alternative 5 and

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aggressive liquids extraction. Alternative 6 includes aggressive pump-and-treat extraction to
accelerate cleanup times for on-property (Zone 1) groundwater in Area 5 South and Area 5
West. However, both Alternatives 5 and 6 involve additional project complexity, risk, and cost.
Alternative 5 involves significant project risk, which is described below under implementability.

Alternative 3 is ranked above Alternative 2 because it provides more widespread and effective
capping systems, more effective treatment systems, and less reliance on evaporation ponds.
The Alternative 3 capping system would cover the entire RCRA Canyon/WCSA area, better limit
infiltration, and increase the potential to meet NPDES substantive permit requirements.
Alternative 3 would also eliminate a seep at the southern part of the RCRA Canyon that
contains elevated TDS and metals. Alternative 3 uses a smaller 6-acre evaporation pond, which
would provide less artificial habitat and, therefore, better protection of ecological species, as
well as easier dredging and maintenance, compared to the larger 11-acre pond for Alternative
2.

Alternative 4 does not include an evaporation pond and, therefore, provides better protection
of ecological species compared to those alternatives with ponds. Also, Alternative 4 provides
more aggressive liquids treatment prior to discharge to Casmalia Creek, but increases project
risk and technical complexity. Alternatives 5 and 6 provide even more aggressive liquids
extraction and treatment through horizontal wells (Alternative 5) and vertical wells (Alternative
6), but are also more vulnerable to increased project risk and technical complexity. The risks
and complexities associated with Alternative 5 include challenges in installing horizontal wells
in heterogeneous materials, and at the proper depths and spacing to capture sufficient DNAPL.
Both Alternatives 5 and 6 include risks and complexities with long-term handling and offsite
shipment and disposal of large volumes of hazardous liquids.

The FS report includes a thorough evaluation of the benefits and weaknesses (project risks)
associated with the use of HDD and horizontal wells in the context of this specific Site
application. For Alternative 5, these risks include the possibility of uncontrolled releases of large
volumes of contaminated liquids. The FS concludes that there are difficult technical challenges
and unacceptable project risks associated with the use of horizontal wells. Moreover, the use of
horizontal wells to dewater the P/S Landfill would merely serve to accelerate a dewatering
process that has been occurring gradually over time since the installation of the landfill caps in
1999 through 2002. The FS included groundwater modeling (MODFLOW) that estimated the
horizontal wells, used in Alternatives 5 and 6, would take roughly 4 or 9 years, respectively;
whereas dewatering without horizontal wells would take on the order of 10 or 11 years,
respectively, following construction of the remedial action. The FS concluded that the technical
challenges, risks, and costs associated with the use of horizontal wells outweigh any potential
incremental benefits.

Reviews at least every 5 years, as required, would be necessary to evaluate the effectiveness of
any of these alternatives because hazardous substances would remain onsite in concentrations
above health-based levels.

4. Reduction of Toxicity, Mobility, or Wolume Through Treatment

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Reduction of toxicity, mobility, or volume through treatment refers to the anticipated
performance of the treatment technologies that may be included as part of a remedy.

Alternatives 2 through 4 are generally equivalent in achieving reduction of toxicity, mobility, or
volume through treatment. These three alternatives include source reduction to extract pooled
NAPL from the P/S Landfill, and liquids extraction from the PSCT and three PCTs for
containment. Alternative 4 includes additional treatment of liquids to allow for discharge to
Casmalia Creek instead of evaporation in ponds. Alternatives 5 and 6 provide even more
aggressive liquids extraction and treatment through horizontal wells (Alternative 5) and vertical
wells (Alternative 6), but are also more vulnerable to increased project safety risk and technical
complexity from long-term operations and offsite waste transportation and disposal. In
addition, Alternatives 5 and 6 would limit the potential for further migration of contaminants,
but would not substantially increase protectiveness compared to Alternative 3, despite the
considerably greater cost. Groundwater is effectively contained within Site boundaries, and EPA
has no reason to believe that future property use will rely on onsite groundwater.

All alternatives, except for the No Further Action alternative (Alternative 1), are equivalent in
terms of using containment to address PTWs in Area 1, where the former landfills and burial
areas are located.

5.	Sli	?ness

Short-term effectiveness addresses the period of time needed to implement the remedy and
any adverse impacts that may be posed to workers, the community, and the environment
during construction and operation of the remedy, until cleanup levels are achieved.

Alternative 3 is top ranked in achieving STE because it provides remedial effectiveness in the
short term, with less project risk (complexity and uncertainty) associated with horizontal well
drilling (Alternative 5) or more aggressive pump-and-treat systems (Alternative 6). Alternative 3
is ranked higher than Alternative 2 because the smaller evaporation ponds would provide
better protection of ecological species. Although Alternative 4 has the advantage of not
including an evaporation pond, Alternative 3 is ranked higher because Alternative 4 is
vulnerable to additional project risk and technical complexity associated with construction of a
more robust treatment plant to meet offsite discharge requirements.

6.	tmplemeniabitity

Implementability addresses the technical and administrative feasibility of a remedy from design
through construction and operation. Factors, such as availability of services and materials,
administrative feasibility, and coordination with other governmental entities, are also
considered.

Alternative 3 is the top-ranked alternative in achieving implementability, because it is readily
implementable and would not face the same risk and technical challenges associated with
meeting NPDES discharge requirements (Alternative 4), horizontal wells (Alternative 5), or
vertical wells with more aggressive pump-and-treat systems (Alternative 6). Alternative 5 is

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ranked lower than Alternative 3 for implementability because of challenges in installing
horizontal wells in heterogeneous materials and at the proper depths and spacing to capture
sufficient DNAPL, challenges in maintaining wells and collection equipment in effective working
order over an extended OM&M period, and increased potential for unintended releases.
Alternative 6 is ranked lowest for implementability because of technical complexity associated
with the aggressive pump-and-treat systems, including installation, optimization, and
monitoring of an 80-well extraction system, construction of additional liquids treatment
systems, and long-term transport of large volumes of hazardous liquids. Alternative 3 is ranked
above Alternative 2 because of reduced OM&M requirements for a smaller lined evaporation
pond system.

7. Cost

Table 2-19 summarizes the estimated capital, annual O&M, total present value costs, discount
rate, and the number of years over which the Selected Remedy would occur. A breakdown of
the costs, by area, for the Selected Remedy is provided in Table 2-20. The detailed costs
associated with the Selected Remedy are presented in Appendix E. For the Selected Remedy,
capital costs are estimated at $60 million, and annual O&M costs are estimated at $4 million.

Present value cost estimates were developed for each alternative using a 3 percent and
7 percent net discount rate. EPA guidance (EPA, 2000) and Office of Management and Budget
Circular A-94 require use of a 7 percent discount rate for the evaluation of alternatives for
federal projects. Present value costs were also calculated using a 3 percent discount rate. The
estimates also included both a commonly used 30-year O&M period, consistent with EPA
guidance, and an extended 100-year O&M period. The extended 100-year O&M period
provides a more realistic, long-term, cost estimate because long-term O&M is anticipated to
extend substantially past an initial 30-year O&M period, essentially in perpetuity.

Costs generally increase from Alternatives 2 through 6 corresponding to an increase in technical
complexity (see Table 2-19). Significant cost drivers include liquids treatment, horizontal drilling
(Alternative 5), vertical drilling at up to 80 locations (Alternative 6), and the collection,
treatment, and disposal of hazardous liquids over extended durations. For Alternative 5, costs
associated with the extraction and offsite treatment of roughly 10 million gallons of
contaminated liquids over several (e.g., 3 to 5) years would be substantial, nearly doubling the
annual O&M costs. Alternative 6 provides more aggressive liquids extraction and treatment
compared to Alternative 3 along with accelerated on-property groundwater cleanup times in
Area 5 South and Area 5 West, although at much higher cost. Construction costs for Alternative
6 are about 1.5 times the construction costs for Alternative 3. More significantly, annual O&M
costs for Alternative 6 are nearly four times higher than those for Alternative 3 due to high
costs associated with liquids extraction, treatment, and disposal.

8. State Agency Acceptance

The State has been actively involved at the Site with EPA through the IAC. During the public
hearing for the Proposed Plan, State agencies submitted comment letters supporting the RI/FS
process and the Proposed Plan for Site remediation. DTSC, in its role as lead State support

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agency for the Site, has expressed its support for, and formally concurred on, the Selected
Remedy based on a review of the pre-final ROD as described in a May 7, 2018, letter to EPA.

9. Community Acceptance

The key Site documents (including the Rl report, FS report, and Proposed Plan) were made
available by EPA for public review, and can be found on the EPA website and in the
Administrative Record file (see Appendix F for the Administrative Record index).

During the public comment period held from November 22, 2017, through January 22, 2018,
the community generally expressed its support for the Preferred Alternative (Alternative 3).
Comments received during the public comment period are addressed in the Responsiveness
Summary (Section 3.0 and Appendix G).

Green Remediation

In the Superfund program, green remediation is the practice of considering all environmental
effects of remedy implementation and incorporating options to minimize the environmental
footprint of cleanup actions. Although not one of the nine formal CERCLA/NCP criteria, the
green remediation aspects of the remedial alternatives were evaluated in the FS report. These
aspects provide useful information regarding the incorporation of sustainability concepts and
practices into remedy implementation. The green remediation aspects evaluated included
electricity, fuel usage, water usage, and air emissions for: (1) remedial construction activities;
(2) materials manufacturing and transport; and (3) OM&M activities, including treatment and
offsite disposal of liquids.

As summarized in Table 2-18, Alternative 3 is rated as having lower adverse impacts and costs
(that is, rated as better) than Alternatives 4 and 6 because they involve operation of a larger
liquids treatment plant to treat inorganic constituents prior to offsite discharge. Alternative 3 is
rated higher than Alternatives 5 and 6 because of the greater risks and potential impacts from
horizontal well installation, and the transport and offsite disposal of large volumes of hazardous
liquids. Overall, Alternatives 4 through 6 rank lower than Alternative 3 because they include
significantly more remedial construction and long-term OM&M, which would increase
electricity, fuel usage, water usage, and air emissions. Alternative 3 is rated nearly the same as
Alternative 2 because the additional impacts of the ET cap construction across the entire RCRA
Canyon/WCSA are balanced by the lower impacts from construction of a smaller evaporation
pond.

2.11 Principal Threat Wastes

The NCP establishes an expectation that EPA will use treatment to address the principal threats
posed by a Site wherever practicable (NCP Section 300.430(a)(l)(iii)(A)). The PTW concept is
applied to the characterization of "source materials" at a Superfund Site. A source material is
material that includes or contains hazardous substances, pollutants, or contaminants that act as
a reservoir for migration of contamination to groundwater, surface water, or air, or act as a

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source for direct exposure. As an example, NAPL in groundwater may be viewed as source
material. PTWs are those source materials considered to be highly toxic or highly mobile that
generally cannot be reliably contained, or would present a significant risk to human health or
the environment should exposure occur.

The PTWs at the Site are the high-concentration waste materials within the five landfills. PTWs
within Area 5 North include drummed waste and NAPL within the P/S Landfill, and NAPL within
the CDA. The PTWs contain numerous organic and inorganic chemicals at high concentrations
across multiple chemical classes (VOCs, SVOCs, herbicides, pesticides, PCBs, dioxins/furans,
metals, and cyanide).

Low-level threat wastes (LLTWs) are present within contaminated soil in Areas 2, 3, and 4.
LLTWs are those source materials that generally can be reliably contained and present lower
potential risk than PTWs. They include source materials that exhibit low toxicity, have low
mobility in the environment, or are near health-based levels.

The PTWs and LLTWs at the Site have been addressed by various response actions over time,
including excavations, pond closures, reconsolidation of pond bottoms and other materials into
the existing five landfills, capping of four landfills and interstitial areas between these landfills,
and extraction of NAPL and highly impacted groundwater for disposal at an offsite permitted
facility.

The Selected Remedy considers how PTWs and LLTWs can be managed in a manner that is
protective of human health and the environment, complies with CERCLA, and is consistent with
the NCP. According to the NCP and EPA guidance, EPA expects to use treatment to address
principal threats posed by a Site wherever practicable, and engineering controls, such as
containment, for waste that poses a relatively low long-term threat.

Based on an extensive technical evaluation conducted during the RI/FS process, EPA has
determined that it is not technically practicable to treat PTWs in landfills (Area 1), and in
groundwater within a portion of the Site (Area 5 North) where NAPL is present. Therefore, the
Selected Remedy includes designation of a WMA (for Area 1) and Tl Zone (for Area 5 North),
along with containment and source reduction through liquids extraction and treatment.

2.12 Selected Remedy

After careful study of the remedial alternatives developed for the Site, EPA has identified
Alternative 3 as the Selected Remedy. The Selected Remedy is a combined containment and
treatment remedy that includes NAPL source reduction, extraction, and treatment of
contaminated Site liquids, and containment of waste materials in landfills, soils, and
groundwater.

The Selected Remedy meets statutory requirements for protecting human health and the
environment, achieves ARARs (while incorporating a waiver for MCLs within the designated Tl

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Zone for Area 5 North), adopts permanent solutions, uses treatment where technically
practicable, and is cost-effective.

The Selected Remedy will achieve containment of both solids and liquids through use of
engineering controls, ICs, and MNA. The Selected Remedy will include NAPL source reduction and
treatment through existing and new extraction wells to provide focused DNAPL removal, thereby
reducing sources that contribute to groundwater contamination. Extracted NAPL will be pre-
treated (for example, subject to oil-water phase separation) prior to transport to an approved,
permitted facility for further treatment and disposal. The Selected Remedy will also expand the
current use of groundwater extraction systems (containment trenches, extraction wells, and
extraction sumps) to remove contaminated liquids, which are then treated and sent to the lined
evaporation ponds.

2.12.1 Key Components of Selected Remedy
The Selected Remedy includes the following key components:

• Area 1 (Capped Landfills Area. BTA. and CPA): The Selected Remedy includes continued use
of the existing RCRA capping systems for the landfills area, plus expansion of the caps in
selected areas. These RCRA caps were constructed on four of the landfills (P/S Landfill,
Heavy Metals Landfill, Caustics/Cyanide Landfill, and Acids Landfill) between 1999 and 2002.
The capped area will be increased to cover the uncapped PCB Landfill, interstitial areas with
former waste management units between the landfills, the BTA, and the CDA. The Area 1
cap will also be extended to cover soil hotspot HS-1 in the MSA, and may be extended to
cover HS-3 in the FPP Area based on an implementability and engineering evaluation during
remedial design.

• Area 2 (RCRA Canyon and WCSA): The Selected Remedy includes installation of either an ET
cap or RCRA hybrid cap (a RCRA cap meets RCRA Subtitle C performance standards; the cap
type will be selected based on an implementability and engineering evaluation during the
remedial design phase, subject to EPA review and approval).

• Area 3 (FPP Area): The Selected Remedy includes excavation and/or capping of four soil
"hotspots" (HS-1 through HS-4, discrete areas with elevated concentrations of metals,

VOCs, and other organic compounds) and consolidation of excavated soils into the existing
PCB Landfill prior to capping. The final remedial approach for these hotspots will be
selected during the remedial design phase. The extent of excavation and/or capping will be
based on confirmatory soil sampling to verify that cleanup to CLs for soil is achieved. In
summary, the hotspots will be addressed as follows:

- HS-1: The shallow soil hotspot in the Liquids Treatment Area will be excavated to CLs for
soil (Table 2-16) and placed under the RCRA cap of the PCB Landfill, and/or covered with
an asphalt cap, as shown on Figure 2-26.

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PART 2: THE DECISION SUMMARY

- HS-2: The shallow soil hotspot(s) in the MSA will be covered with the RCRA cap
extended from Area 1.

- HS-3: The shallow and deep soil hotspot in the former Ponds A/B area will either be:

(1) excavated to CLs for soil and placed under the RCRA cap of the PCB Landfill, or

(2) covered with the RCRA cap extended from Area 1.

- HS-4: The shallow soil hotspot south of PSCT-1 will be excavated to CLs for soil and
placed under the RCRA cap of the PCB Landfill.

- HS-10: Because there are no unacceptable human health or ecological risks for the deep
soil hotspot at RISBON-59, the selected action is long-term groundwater monitoring.
Two additional, downgradient monitoring wells will be installed to verify that there are
no unacceptable impacts to groundwater. Stormwater from Area 3 would be discharged
to the B-Drainage and Casmalia Creek under the substantive requirements of the
General Permit.

• Area 4 (Stormwater Ponds and Treated Liquids Impoundment): The Selected Remedy
includes removal of all liquids (with TDS concentrations that approach or exceed the
concentration of seawater), placement of clean soil, and installation of engineered caps
over Pond 18, Pond A-5, Pond 13, A-Series Pond, and RCF Pond. Pond 18 will be closed;
Ponds A-5 and 13 will be closed and converted into lined stormwater retention basins; and
a lined stormwater channel will be constructed over the former footprint of the RCF Pond
(after it is capped). Finally, one or more new, lined evaporation ponds will be constructed
over the former footprint of the A Series Pond.

• Area 5 (Sitewide Groundwater), which includes three subareas:

- Area 5 North: The Selected Remedy includes subsurface liquids extraction and
treatment from existing and new facilities in the source areas (source reduction).
Extraction will continue from the existing Gallery Well, Sump 9B, and the PSCT to
contain and prevent groundwater from migrating southward. Approximately 16 new
extraction wells will be installed in the P/S Landfill to capture as much pooled NAPL as
possible. The area that is circumscribed by the boundaries of the five hazardous waste
landfills is designated as a WMA because waste materials are being left in place. A Tl
waiver is necessary for Area 5 North because the presence of LNAPL, DNAPL, and
dissolved-phase organic and inorganic contamination in low-permeability fractured
bedrock that make it technically impracticable to remediate and meet drinking water
standards in this area. The POC will encompass the Tl Zone; it will be located at the Area
5 North boundary to ensure that groundwater quality is not further degraded outside
this area. Also, approximately 12 new Lower HSU monitoring wells will be installed to
verify that dissolved-phase contaminants and NAPL are not migrating southward,
underneath the PSCT outside of Area 5 North. Rigorous performance and compliance
monitoring programs will also be implemented.

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Under the Selected Remedy, highly contaminated liquids and NAPL from the Gallery
Well, Sump 9B, and new source area extraction wells in the P/S Landfill will be stored
onsite and transported to an EPA-approved offsite TSD facility for treatment. Liquids
from the PSCT and PCTs will be treated onsite in a new treatment system, and treated
effluent will be sent to one or more new onsite evaporation ponds.

- Area 5 South and Area 5 West: The Selected Remedy includes liquids extraction and
onsite treatment from the existing PCT-A, PCT-B, and PCT-Cto contain and prevent
contaminated groundwater from migrating southward down the adjacent drainages.
The Selected Remedy also includes MNA, a passive, in situ method whereby
contaminant concentrations are reduced in place through physical, chemical, or
biological processes.

• Collection/Treatment & Disposal of Liquids (Sitewide): Contaminated liquids and NAPL from
the Gallery Well and NAPL source reduction extraction wells completed in the P/S Landfill
would be stored onsite and then transported to an offsite TSD facility for treatment. Liquids
from the PSCT would be treated onsite using an upgraded treatment system, and treated
liquids would be sent to the evaporation ponds for volume reduction. Liquids from the PCTs
would be treated using an upgraded liquids treatment system and sent to the evaporation
ponds for volume reduction. Figure 2-33 presents preliminary process flow diagrams for
these systems; final design details will be confirmed during the remedial design phase.

• Stormwater Discharge: Fresh sitewide stormwater will be managed following remedy
implementation using new, lined, stormwater retention basins and discharged to the B-
Drainage and Casmalia Creek under NPDES substantive requirements.

• WMA. Tl Zone, and POC: A WMA is designated as circumscribing the surface footprints of
the five former landfills within Area 1 North. A Tl Zone is designated throughout Area 5
North. A POC is designated along the boundary of the Tl Zone (Area 5 North boundary).

• Institutional Controls: ICs, in the form of land use covenants and related restrictions, will
provide controls on land and water use to help prevent exposures to contamination. The
goal of ICs is to help ensure long-term protectiveness of the Selected Remedy because
waste materials will remain in place.

• Interim OM&M: Operations, maintenance, and monitoring will continue on an interim basis,
under work plans approved by EPA, throughout the construction of the Selected Remedy.

• Long-Term Operations & Maintenance (O&M): Long-term O&M will be conducted to ensure
that all Site components and systems are functioning effectively throughout the remedial
action. Long-term O&M will address multiple media and systems, including, but not limited
to, capping systems; liquids collection, treatment, and disposal systems; surface water
management; and all monitoring systems (including air, surface water, groundwater,
biological). Long-term O&M will incorporate modern, integrated, and upgradable
automated process control systems and instrumentation to ensure that all Site systems

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function safely, reliably, and effectively; these will include, but not be limited to, alarms,
automatic shut-off systems, video surveillance systems, data recorders, and flow
controllers. Long-term O&M will be performed based on optimization studies and a long-
term O&M plan that will be subject to EPA review and approval.

• Long Term Monitoring: Long-term performance and compliance monitoring will be
conducted to ensure that remedial systems are functioning effectively and remain in
compliance with performance standards. Long-term monitoring will include compliance
monitoring of groundwater both laterally and vertically, surface water, soil vapor and
ambient air, and performance monitoring of remedial systems. Long-term monitoring will
also include ongoing evaluation of ICs. Long-term monitoring will incorporate modern,
integrated, and upgradable automated data collection systems and instrumentation to
ensure that Site monitoring systems function effectively; these will include, but not be
limited to, data loggers for new monitoring wells. Long-term groundwater monitoring will
be performed based on optimization studies and subject to a long-term monitoring plan
that will require EPA review and approval. EPA may require additional monitoring, if
determined necessary based on the results of monitoring data, to ensure protection of
human health and the environment.

• Contingency Measures: Contingency measures will be performed if groundwater monitoring
data indicate that contamination is migrating beyond area boundaries, including the POC
and the perimeter boundary of the former disposal facility (Zone 1). Contingency measures
will be initiated if groundwater monitoring data show that migration is occurring at
statistically representative concentrations that cause, or are likely to cause, exceedances of
performance standards. These contingency measures will be performed to ensure adequate
containment. Contingency measures may include any or all the following: (1) additional
monitoring from existing wells; (2) installation of additional monitoring wells to further
characterize potential migration; and (3) installation of a limited number of extraction wells
within a localized area to maintain hydraulic containment. These extraction wells would
supplement the area and perimeter containment provided by existing perimeter control
trenches, extraction wells, and natural attenuation. Installation of additional extraction
wells outside the POC or Zone 1 perimeter boundary, as part of contingency measures,
could require an ESD.

• Five-Year Reviews: Because waste will remain at the Site, EPA will conduct statutory reviews
every 5 years to continue to evaluate and ensure the long-term protectiveness of the Selected
Remedy. The five-year reviews include evaluations of overall remedy protectiveness,
including the effectiveness of NAPL removal and the effectiveness of ICs. If it is determined
that components of the Selected Remedy are not protective, EPA will evaluate corrective
actions and implement the preferred action to ensure continued protectiveness.

The following graphic summarizes the key components of the Selected Remedy.

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Summary of Key Components of the Selected Remedy

•	RCRA Engineered Capping Systems: Use of RCRA capping to contain contaminated soil and waste materials, including
existing and new layered engineered capping systems (soils and geosynthetics) and RCRA ET covers, for Areas 1 and 2,
and limited portions of Area 3.

•	Soil Hotspot Removal and/or Capping: Focused excavation and reconsolidation of contaminated soil and waste
materials in isolated portions of Area 3 into the existing PCB Landfill, which will later be capped and closed, and/or
capping of the hotspots.

•	Stormwater and Treated Groundwater Removal/Existing Pond Closure: Removal of existing stormwater and treated
groundwater from the five existing ponds, which will be closed.

•	Long-Term Stormwater Management: Construction of two lined stormwater retention basins, with conveyance systems
(for example, V-ditches and channels) for off-property discharge to the B-Drainage.

•	Lined Evaporation Ponds for Treated Groundwater: Construction of a new evaporation pond system (approximately 6
acres), with liners and security fencing.

•	NAPL Source Reduction: Removal of an estimated 100,000 gallons each of pooled DNAPL and LNAPL sources from the
P/S Landfill, using existing extraction wells and about 16 new vertical NAPL-only extraction wells.

•	Qff-Propertv NAPL Treatment and Disposal: Transportation, treatment, and offsite disposal of NAPL at an EPA-approved
facility,

•	Perimeter Containment of Groundwater Contamination with Collection Trenches and MNA: Perimeter containment of
shallow (Upper HSU) and deep (Lower HSU) groundwater contamination within the former facility boundaries (Zone 1),
using several existing containment trenches, extraction wells, and MNA.

•	Groundwater Collection, Treatment, and Disposal/Optimization of Site Systems: Collection of groundwater from
existing containment trenches, on-property treatment, and transfer of treated effluent to the new 6-acre, lined,
evaporation pond system. A pre-design evaluation during remedial design/remedial action to help select optimized
extraction rates and improve OM&M. The improvements will likely include automation, instrumentation, and
integration, including installation and use of meters, sensors, transducers, continuous recording data loggers, leak
detection and notification systems, telemetry, and centralized control systems^

•	ICs: Land use controls and/or government controls to restrict access and establish controls on land and water use, to
limit or prevent exposures to contamination (extensive ICs for six parcels are already in place).

•	Designation of WMA and Tl Zone (within Area 5 North) with POC: The footprint of the former landfills within Area 5
North is designated as a WMA because waste materials are being left in place and there is no expectation that
groundwater in this area can be remediated for beneficial use. The area within the Area 5 North boundary is designated
as a Tl Zone for groundwater. This area contains multiple, closely spaced, waste management units, and large volumes of
LNAPL and DNAPL, which have accumulated at the base of the P/S Landfill and are observed up to 500 feet south of the
landfill in the CDA. A detailed TIE concluded that full restoration of groundwater to MCLs within Area 5 North was not
technically practicable from an engineering perspective. Designation of a POC that corresponds to, or is located just
outside of, the Area 5 North boundary to demonstrate groundwater quality is not further degraded outside the Tl Zone.

•	Long-term O&M/Long-Term Monitoring: Long-term O&M, including monitoring for overall performance and regulatory
compliance (for example, long-term compliance monitoring for groundwater at the Area 5 North boundary and
corresponding POC, and the Site [Zone 1] boundary).

•	Contingency Measures Contingency measures, such as additional monitoring and focused extraction in localized areas,
will be conducted if deemed necessary by EPA.

•	Ecological Habitat Mitigation: Mitigation of selected ecological habitat areas to address adverse impacts to threatened
or endangered species covered by the federal ESA,

•	Five-Year Reviews: Superfund law requires EPA to conduct a detailed review every 5 years when waste is left in place, to
confirm the Selected Remedy remains fully protective and meets intended goals. EPA will conduct five-year reviews to
assess ongoing protectiveness. If the remedy is found to be deficient or no longer protective, EPA will begin work to
evaluate and implement necessary corrective actions and improvements.

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2.12.2 Waste Management Area

The Selected Remedy includes a WMA coincident with the outer boundary of the five former
landfills in Area 1.

Consistent with the NCP preamble and with EPA guidance documents, EPA is designating the
footprint of the former landfills (P/S, Heavy Metals, Caustics/Cyanide, Acids, and PCB landfills)
within Area 5 North as a WMA for the Selected Remedy. In general, the term "waste left in
place" is used in the NCP to refer to landfill wastes that, at the completion of the remedy, will
be contained or otherwise controlled within a WMA (EPA, 1996). The NCP preamble sets forth
EPA's regulatory approach for groundwater as follows, "remediation levels generally should be
attained throughout the contaminated plume, or at and beyond the edge of the waste
management area when waste is left in place" (EPA, 2009a). Under this EPA regulatory
approach, CLs for groundwater do not apply within the WMA.

Where several, closely spaced, waste management units exist, EPA guidance (1993a) provides
for designation of a single WMA. EPA is designating the footprint of the five former landfills
within Area 5 North as a single WMA because waste materials are being left in place and there
is no expectation that groundwater under and between the landfills can be remediated for
beneficial use.

Area 5 North also contains large volumes of NAPL (both LNAPL and DNAPL), which have
accumulated at the base of the P/S Landfill and are observed up to 500 feet south of the landfill
in the CDA. Consistent with EPA guidance (EPA, 1996), NAPL is not included within the WMA
and EPA generally does not consider NAPL as "waste left in place." This is because the full
extent of NAPL contamination is often not known, and NAPL can continue to migrate in the
subsurface. Also, NAPL is considered a PTW and is, therefore, treated separately from
groundwater as a source of contamination. The Selected Remedy includes components to
reduce the NAPL sources of contamination in Area 5 North using NAPL extraction.

Although Area 5 North contains hazardous waste landfills rather than municipal waste landfills,
the use of a WMA is also generally consistent with EPA's guidance entitled, Presumptive
Remedy for CERCLA Municipal Landfill Sites (EPA, 1993b). The presumptive remedy guidance
states that, "... consistent with the [NCP], EPA's expectation was that containment technologies
generally would be appropriate for municipal landfill waste because the volume and
heterogeneity of waste generally make treatment impracticable." The guidance further states
that waste in landfills generally occurs in large volumes and is often co-disposed with industrial
and hazardous wastes; therefore, containment is generally an appropriate response action,
including capping, source area groundwater control, liquids collection and treatment, gas
collection (if appropriate), and ICs. The WMA within Area 5 North contains the five former
landfills, where waste materials will be left in place and treatment is not technically practicable.

Figure 2-27 presents the plan view layout of the WMA, located within a portion of Area 5 North
that coincides with the outer boundary of the five former landfills. Groundwater in this area
underlies the most highly contaminated parts of the Site, including the capped landfills and the

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PCB Landfill. A WMA is appropriate for both the Upper and Lower HSUs within this area for
both organic and inorganic compounds.

2.12.3 Technical Impracticability Zone

The Selected Remedy includes a Tl Zone coincident with the outer boundary of Area 5 North.
EPA conducted a TIE as part of the RI/FS process. The TIE concluded that it is technically
impracticable to clean up groundwater throughout Area 5 North to cleanup standards, namely
MCLs. According to the NCP, a Tl waiver may be appropriate, when compliance with an ARAR
"is technically impracticable from an engineering perspective" (40 CFR 300.430[f][l][ii][C][3]).
CERCLA Section 121(d)(4) provides that ARARs may be waived in certain limited circumstances,
as long as the remediation also ensures protection of human health and the environment.

The Rl and FS reports contain a comprehensive TIE section, including an assessment of the
potential to achieve full restoration of groundwater to MCLs in all three areas (Area 5 North,
Area 5 South, and Area 5 West). The TIE closely follows the Guidance for Evaluating Technical
Impracticability of Ground-Water Restoration (EPA, 1993c). Consistent with the guidance, the
TIE examined: (1) hydrogeologic factors; (2) contaminant-related factors; and (3) technology
constraints on remediation system design and implementation. The TIE concluded that full
restoration of groundwater to MCLs within a limited portion of the Site, designated as Area 5
North, is technically impracticable from an engineering perspective. Groundwater restoration in
the other two areas (Area 5 South and Area 5 West), while not strictly technically impracticable,
will require long-term remediation with MNA, on the order of decades to over 200 years,
depending on the contaminant. Although remediation costs are not a primary factor in a Tl
determination, the estimated cost for complete restoration of the capped landfills area
(including landfill removal) is in the tens of billions of dollars, based on the TIE.

Restoration to MCLs within Area 5 North is technically impracticable because: (1) large volumes
of pooled DNAPL have accumulated at the base of the P/S Landfill and extend south into the
CDA; (2) residual waste will be capped in place (but not removed) representing an ongoing
source of contamination; (3) DNAPL will be removed through additional extraction measures,
but residual DNAPL will remain as an ongoing source of contamination; (4) low-permeability,
fractured claystone with high matrix porosity is present resulting in significant matrix diffusion
and storage of contaminant mass; and (5) remediation technologies are ineffective in removing
contaminant mass in these types of environments. Further, groundwater contamination will be
effectively contained within the Area 5 North boundary through a combination of engineering
controls and MNA.

No in situ technology is capable of treating the diverse array of chemicals found in the Tl Zone
of Area 5 North. In addition to NAPL and organic constituents, this area contains many
inorganic constituents (for example, metals such as arsenic, cadmium, nickel, and selenium)
that significantly exceed MCLs in both the Upper and Lower HSUs. EPA also examined the
feasibility of pump-and-treat remediation in groundwater within this area; it concluded that
such actions would not be effective. Groundwater flow and contaminant transport modeling
demonstrated that, even after several thousands of years of operation, pump-and-treat

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remediation would not restore contaminated groundwater to MCLs. Buried waste within Area 5
North will continue to provide ongoing sources for groundwater contamination within the Tl
Zone. Furthermore, substantial contamination is contained within the matrix of the low-
permeability claystone (through matrix diffusion), and back diffusion processes would
contribute to long-term contaminant migration from the matrix into groundwater.
Consequently, pump-and-treat remediation could remove large volumes of contaminated
liquids from fractures, yet remain largely ineffective in addressing contaminants within the
claystone matrix, which would serve as a continuing source of groundwater contamination.

Figure 2-27 presents the plan view layout of the Tl Zone. The base of the Tl Zone is 200 feet
amsl. This elevation is about 100 feet below the deepest monitoring well where DNAPL was
found (RGPZ-7D, which has a total depth of 148.3 feet bgs and is screened between
approximately 328 and 315 feet amsl). The base of the Tl Zone at 200 feet amsl (or about 265
feet bgs at the RGPZ-7D well location) will fully encompass any known DNAPL impacts to
groundwater within Area 5 North.

The effects of both designations (the WMA and Tl Zone) are similar because there is no
expectation that waste materials will be removed or that groundwater throughout all of Area 5
North can be cleaned up to ARARs. The Tl Zone (including the WMA) will be subject to ICs and
rigorous performance and compliance monitoring programs.

EPA has established one POC that is coincident with the Area 5 North boundary. During the
remedial design phase, a rigorous groundwater monitoring program will be established to
demonstrate compliance with the designated Tl Zone. The groundwater monitoring program is
expected to consist of two key phases: (1) interim monitoring during remedial construction; and
2) long-term monitoring following construction completion. Monitoring wells will be installed at
strategic locations, based on optimization studies, to provide advance indication and detect
potential migration of contamination exceeding remediation levels beyond the POC. Monitoring
will be performed during construction and throughout the long-term OM&M period based on a
monitoring plan approved by EPA. Compliance at the POC will also be evaluated as part of
overall remedy protectiveness during regular five-year reviews.

2.12.4 Shi i it I \ i im and Long-Te :M

The O&M program is expected to consist of two key phases: (1) ongoing OM&M that will
continue to be performed on an interim basis, under work plans approved by EPA, throughout
the construction of the Selected Remedy; and (2) long-term O&M following construction
completion.

Interim O&M: Interim (short-term) O&M will continue throughout the construction of the
remedy to ensure that site systems function safely, effectively, and reliably. O&M will continue
under EPA-approved O&M plans that may be subject to modification to accommodate
construction activities.

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Long-Term O&M: Long-term O&M will be conducted to ensure that all Site components and
systems are functioning effectively throughout the duration of the remedial action. Long-term
O&M will address multiple media and systems, including, but not limited to, capping systems;
liquids collection, treatment, and disposal systems; surface water management; and all
monitoring systems (including air, surface water, groundwater, biological). Long-term O&M will
incorporate modern, integrated, and upgradeable automated process control systems and
instrumentation to ensure that all Site systems function safely, reliably, and effectively; these
will include but not be limited to alarms, automatic shut-off systems, video surveillance
systems, data recorders, and flow controllers. Long-term O&M will be performed based on
optimization studies and a long-term O&M plan that will be subject to EPA review and approval.

Other key components of the long-term O&M activities will include: (1) evaluation of the nature
and extent of NAPL and dissolved-phase groundwater COCs; (2) evaluation of overall plume
stability through trend analysis; (3) evaluation of individual well concentration trends over time
for target COCs; (4) development of sampling locations and frequency recommendations based
on statistical analysis; (5) evaluation of individual well analytical data for statistical sufficiency
and identify locations that have achieved RLs; (6) establishment of procedures to improve NAPL
extraction; (7) establishment and tracking of influent and effluent concentrations at the
upgraded groundwater treatment plant; (8) tracking of the rates and volumes of NAPL and
groundwater extraction; (9) evaluation of the estimated capture zone of the various
containment systems (such as wells and trenches); and (10) any additional activities as
requested by EPA. Section 2.12.11 presents additional details regarding NAPL extraction
activities.

2.12.5 Interim and Long-Term Monitoring

Interim monitoring will continue during construction of the Selected Remedy, followed by long-
term performance and compliance monitoring throughout the duration of the remedial action,
to ensure safe and effective operation of Site systems and compliance with performance
standards. Long-term monitoring will be based on optimization studies and will incorporate
integrated and upgradable automated data collection systems and instrumentation to ensure
reliable and accurate data collection.

Interim Monitoring: Interim monitoring for appropriate Site media will continue during
construction of the Selected Remedy under monitoring plans that are subject to EPA review and
approval. Interim monitoring will be replaced by long-long term monitoring upon approval of
long-term monitoring plans.

Long-Term Performance Monitoring: Performance monitoring will be conducted based on
monitoring plans that are subject to EPA review and approval. Performance monitoring will be
conducted for multiple media and Site facilities and systems to ensure that the Selected
Remedy is functioning effectively. Performance monitoring will include appropriate Site media,
such as groundwater, soil vapor, ambient air, surface water, and NAPL. Performance monitoring
will be conducted to ensure that Site facilities and systems are functioning in a safe, reliable,
and effective manner in conformance with design goals and parameters.

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Long-Term Compliance Monitoring: The compliance monitoring will be conducted based on
monitoring plans that are subject to EPA review and approval. Compliance monitoring will be
conducted for Site media, such as groundwater and surface water, to ensure that the Selected
Remedy is functioning in conformance with performance standards. Monitoring wells will be
designated to monitor containment for (1) the POC which is being designated for the Tl Zone
and (2) for the Zone 1 perimeter boundary. Surface water will be monitored to ensure
compliance with performance standards.

2.12.6 Capping and Pond Lining Technologies

The Selected Remedy includes several engineered cap and pond-lining technologies. The
capping configurations for the various Site areas will be confirmed during the remedial design
phase (subject to EPA review and approval), and include those listed as follows:

•	RCRA Cap (Area 1 - PCB Landfill, CDA, BTA, Maintenance Shed Area; Area 4 - Pond 18):

-	2 feet of vegetative layer

-	Biotic barrier, geocomposite drainage layer, geomembrane, geosynthetic clay liner

-	Foundation layer (variable thickness), to 90 percent compaction

•	ET Cap (Area 2 - RCRA Canyon/WCSA)1:

-	4 feet of vegetative layer

-	1 foot of foundation layer, to 90 percent compaction

•	RCRA-Equivalent Hybrid Cap (Area 2 - RCRA Canyon/WCSA)1:

-	2 feet of vegetative layer

-	Biotic barrier, geotextile drainage layer, and HDPE liner

-	Foundation layer (variable thickness), to 90 percent compaction

•	Ecological Cap (Area 4 - RCF Pond):

-	2 feet of vegetative layer

-	Foundation layer (variable thickness), to 90 percent compaction

•	Asphalt Cap (Area 3 - HS-1, Liquids Treatment Area):

-	4 inches of asphalt

-	4 inches of aggregate base

•	Lined Cap Retention Basin (Area 4 - Pond A-5, Pond 13 [clean storm water]):

-	1 foot of soil cover

-	Geonet geotextile, geocomposite liner, and HDPE liner

-	2 feet of foundation layer, to 90 percent compaction

•	RCRA Evaporation Pond (Area 4 - A-Series Pond [treated groundwater]):

1 The Selected Remedy includes an ET cap and/or RCRA-Equivalent hybrid cap for Area 2 (RCRA Canyon/WCSA),
and the specific design details will be developed during the remedial design phase.

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-	1 foot of soil cover

-	Primary HDPE geomembrane, geonet drainage layer, secondary HDPE geomembrane

-	Leachate collection and removal system (connected to geonet drainage layer, sump)

-	Vadose zone monitoring beneath secondary HDPE geomembrane

-	2 feet of foundation layer, to 90 percent compaction

instruction Water

The Selected Remedy will require a sufficient quantity of water that is of adequate quality for
construction purposes, including, but not limited to, soil conditioning, dust control, and
irrigation. Because of the potential for serious drought conditions in California, adequate
supplies of suitable quality water must be made available for construction. Potential water
sources to be considered may include potable or reclaimed water, to be delivered by pipeline
or truck, or onsite wells or ponds, subject to adequate supply and potentially requiring onsite
treatment.

EPA will set limits on TDS concentrations for construction water that will be used at the Site.
The TDS concentrations must be sufficiently low to promote vegetative growth, prevent
degradation to vegetation and the soil column, and reduce adverse impacts from stormwater
runoff to the nearby B-Drainage and Casmalia Creek. TDS limits will be established for the
entire soil thickness above caps containing geomembranes (such as, RCRA cap), and throughout
the entire thickness of caps without geomembranes (such as, ET cap). Construction water with
higher TDS levels can be used below the geomembrane layer only for caps constructed with
geomembranes.

2.12.8	Monitoring During Remedial Construction

An appropriate level of monitoring of construction activities will be conducted during remedial
construction. The monitoring protocol will be identified during the remedial design and
remedial action phases. Such monitoring will likely include air monitoring in active work areas,
along the Site's perimeter as determined necessary by EPA, soil erosion and sediment control,
third-party construction quality assurance (using current national standards that are acceptable
to EPA) for the engineered caps and other components of the Selected Remedy, construction
completion verification, and other related protocol.

2.12.9	Habitat Mitigation

The Selected Remedy includes habitat mitigation, which will be conducted based on
coordination with the USFWS and CDFW during the remedial design phase. For example, the
lined evaporation pond system will be designed with biological controls (such as, netting,
fencing, screening, and hazing) and biological monitoring to minimize adverse impacts to
special-status species based on coordination with USFWS. Habitat mitigation may also include
establishing appropriate nearby suitable habitat for ecological species of concern, and/or other
appropriate measures.

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istitutional Controls

EPA considers ICs to include "non-engineered instruments, such as administrative and legal
controls, that help to minimize the potential for human exposure to contamination and/or
protect the integrity of the response action" (EPA, 2011). ICs typically limit land or resource use,
or by providing information that helps modify or guide human behavior at a Site. Common
examples of ICs include zoning restrictions, building or excavation permits, well drilling
prohibitions, easements, and covenants. ICs are used to ensure that unacceptable exposure
from various Site media containing COCs does not occur.

The Selected Remedy will make use of ICs by including existing and future land use covenants
as part of the remedy. The goal is to help ensure protectiveness since waste materials will
remain in place. Covenants have been established for six parcels (Property), which include a
total of 1,247.25 acres in all of Zone 1 and portions of Zone 2 located to the north and south of
the Site (see Figure 2-13). These covenants include:

•	On May 31, 2011, a Covenant to Restrict Use of Property/Environmental Restrictions was
issued for the following parcels, which comprise all but the southeastern portion of Zone 1
and portions of adjacent land:

-	Parcel 113-260-002 (Parcel 2)

-	Parcel 113-260-003 (Parcel 3)

•	On June 1, 2011, a Covenant to Restrict Use of Property and Easement/Environmental
Restrictions was issued for the following parcels:

-	Parcel 113-260-004 (Parcel 4), which includes the southeastern portion of Zone 1 and
portions of adjacent land

-	Parcels 113-260-001 (Parcel 1), 113-220-010 (Parcel 10), and 113-220-012 (Parcel 12),
which are located adjacent to and north/northeast of Parcels 2 and 3

The covenants establish various provisions, restrictions, and conditions (collectively referred to
as "Environmental Restrictions"), to which the Property is subject, including how the Property is
used, occupied, leased, sold, and/or conveyed. The Environmental Restrictions run with the
land pursuant to California Civil Code Section 1471, and successive owners of the Property are
bound to such restrictions. The objectives of the Environmental Restrictions are to:

•	Prevent residential construction, and maintain control over any commercial, industrial,
agricultural or ranching, construction, or other activity that may interfere with response
actions taken or approved by EPA.

•	Provide space for potential construction of remedial systems and monitoring systems at the
Site.

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• Protect any measures taken or approved by EPA to protect wildlife habitat, open space, and
wetlands, including, but not limited to, habitat for endangered or threatened species.

• Mitigate risks that might be associated with unanticipated release of hazardous materials
from the Site.

The covenants require that the Property owner(s) grant access to those performing response
actions under regulatory oversight by EPA and/or the State, including their agents and
contractors. The covenants also require that the Property owner(s) not undertake any "land or
water disturbing activity" on the property that is not approved in writing by EPA. Land or water
disturbing activities include excavation, construction, demolition, groundwater pumping, and
any activity that affects habitat, open space, or wetlands. EPA is also included as a third-party
beneficiary to these covenants, allowing it full access to the Site and the ability under the law to
enforce the terms of the covenants.

Current and future landowners will give written notice of Site contamination to each buyer,
lessee, renter, and mortgagee of any of these lands. Also, every lease, deed, mortgage, or
instrument conveying any part of these lands will expressly provide that it is subject to these
Environmental Restrictions.

The long-term OM&M activities will include monitoring of the effectiveness and enforcement of
ICs. The ICs will also be evaluated as part of the five-year review process. Additional ICs for
other land parcels may be implemented if deemed necessary by EPA.

2.12.11 NAPL Extraction and Monitoring

The Selected Remedy includes the installation of approximately 16 NAPL extraction wells in the
southern portion of the P/S Landfill to provide additional source reduction.

As described in the FS report, the liquids in the P/S Landfill result in a "driving force" (head) that
facilitates: (1) downward migration of contaminated liquids and pooled DNAPL through source
areas and fractured bedrock; and (2) horizontal migration into weathered and unweathered
bedrock. This head contributes to the horizontal gradient that causes groundwater (and
contaminants dissolved in groundwater) to move southward through the Lower HSU and
potentially underneath the PSCT.

The objectives of the NAPL extraction wells are to reduce the overall volume of mobile NAPL
and decrease the thickness of pooled NAPL, which will also reduce the hydraulic head that
creates a driving force that can push NAPL (and dissolved constituents) into fractured bedrock.

The network of extraction wells (estimated to be 16, but potentially ranging from 15 to 20) will
be installed to a depth at or near the base of the P/S Landfill to extract as much NAPL, including
mobile pooled DNAPL and LNAPL, as technically practicable. The objective is to pump from a
large number of wells at low pumping rates to maximize extraction over the long-term and
avoid destabilization of the capture area due to over-pumping. The network of extraction wells

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will be installed in the early stages of remedy construction. The extraction goals, specific
performance standards, and operating protocol will be established during the remedial design
phase, and will considerthe total estimated volume of 100,000 gallons of DNAPL, and a similar
volume of LNAPL. Companion monitoring wells will also be installed near the extraction wells to
provide long-term monitoring of NAPL thickness. The extraction and monitoring wells will be
located in the low area of the P/S Landfill toe, where substantial thicknesses of pooled NAPL
has been observed in existing wells. The new wells will be installed with the goal of directly
intercepting the DNAPL pool and overcoming the barriers to DNAPL flow that would likely leave
DNAPL behind using only the Gallery Well. Various investigative approaches, such as membrane
interface probe, cone penetrometer testing, and/or ultraviolet optical screening tool, will be
considered to map the bottom of the landfill and evaluate NAPL distribution, so that the
optimal well locations are selected for the likely presence of recoverable LNAPL and DNAPL. The
scope of these investigation activities will be determined during the remedial design phase.

The new extraction and monitoring wells will be installed in a manner that recovers as much
NAPL volume as possible, using either: (1) a single screen across the entire saturated zone
(LNAPL, aqueous phase, and DNAPL) (the preferred approach); or (2) two screens across both
the upper LNAPL zone and lower DNAPL zone. EPA-approved well materials will be used. One or
more pumps will be placed in each extraction well where both measurable LNAPL and DNAPL
are present. The bottom pump will be placed at the top of the DNAPL zone and pumped slowly
(pulsed pumping only several times per day) to recover DNAPL that comes into the well by up
coning. The top pump will be placed within the LNAPL and pumped slowly to skim LNAPL that
comes into the well. The extraction rates of groundwater will be minimized so that the LNAPL
and DNAPL saturations and flow paths around each well are maintained at the maximum
possible level to increase LNAPL and DNAPL recovery. Some groundwater would be extracted,
as appropriate, to slightly enhance the inward gradients towards the extraction wells.

The extraction wells will be designed and operated based on optimization studies to maximize
the volume of extracted pooled LNAPL and DNAPL. The well operations will be detailed in the
O&M monitoring plan (as described in Section 2.12.4). Wells will be monitored for key
operating parameters, such as volume, extraction rates, DNAPL and LNAPL thickness, key
indicator constituents, and others, throughout the long-term OM&M period. If EPA determines
that NAPL extraction is negligible and does not continue to contribute to improved
protectiveness under those operating conditions, EPA may approve temporary discontinuation
of extraction in one or more extraction wells, pending further evaluation. Extraction may be
temporarily discontinued if, for example, EPA determines that continued extraction of liquids is
not resulting in substantial, or measurable, removal of NAPL constituents. In such a case,
extraction in one of more wells may be paused, for several months or even years, to allow for
additional evaluation and consideration of revised extraction procedures. The NAPL presence
will continue to be monitored throughout the OM&M period, and extraction will resume when,
and if, EPA determines that continued extraction will enhance protectiveness.

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Girt of Compliance and Compliance Monitoring Programs

Consistent with the NCP and EPA guidance, the POC for attaining CLs in groundwater is
established on a Site-specific basis. Final cleanup levels for contaminated groundwater
generally should be attained throughout the entire contaminant plume, except when remedies
involve areas where waste materials will be managed in place. In the latter case, cleanup levels
should be achieved "at and beyond the edge of the waste management area when waste is left
in place" (1990 NCP preamble at 55 FR 8713). Pursuant to the NCP (including NCP preamble), a
POC generally would be established at, or just outside of, the WMA.

However, based on the TIE, ARARs are not expected to be attained in groundwater within the Tl
Zone, which encompasses all of Area 5 North and includes the WMA. For this reason, EPA is
designating the POC to correspond to the Area 5 North boundary. Compliance monitoring at
the POC will be used to demonstrate that groundwater quality is not further degraded outside
the Tl Zone.

The Selected Remedy will incorporate a long-term groundwater performance and compliance
monitoring program to monitor system performance, containment of groundwater impacts,
and compliance with performance standards both at the POC (corresponding with the Area 5
North boundary) and at the Zone 1 property boundary. The long-term O&M and monitoring
program will include identification of groundwater and NAPL extraction protocol (including
optimization studies), groundwater monitoring networks, monitoring standards, and a
formalized POC. The Site already has a significant water monitoring network in place, which will
need to be supplemented to appropriately monitor the Selected Remedy following
implementation.

ontingency Measures

Contingency measures will be performed if groundwater monitoring data indicate that
contamination is migrating beyond area boundaries, including the POC and the perimeter
boundary of the former disposal facility (Zone 1). Contingency measures will be initiated if
groundwater monitoring data show that migration is occurring at statistically representative
concentrations that cause, or are likely to cause, exceedances of performance standards. These
contingency measures will be performed to ensure adequate containment. Contingency
measures may include any or all the following:

1.	Additional monitoring from existing wells

2.	Installation of additional monitoring wells to further characterize potential migration

3.	Installation of a limited number of extraction wells within a localized area to
maintain hydraulic containment

These extraction wells would supplement the area and perimeter containment provided by
existing perimeter control trenches, extraction wells, and natural attenuation. Installation of

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additional extraction wells outside the POC or Zone 1 perimeter boundary, as part of
contingency measures, could require an ESD.

The objectives of such extraction would be to provide improved hydraulic containment and
limit further migration beyond area boundaries. The Selected Remedy includes perimeter
control, using containment trenches and perimeter extraction wells, which have already been
in operation for many years. Installation of additional extraction wells in a localized area,
therefore, would provide incremental improvements to the existing perimeter control systems.
Further evaluation would be conducted to determine if additional measures are necessary.

Details of the compliance monitoring program and contingency measures for additional
monitoring and/or extraction in the vicinity of the Tl Zone within Area 5 North (and
corresponding POC) and the Site's boundary will be developed during the remedial design
phase. Design and operation of the monitoring program will be based on the results of
optimization studies.

reener Cleanups Considerations

Consistent with EPA Region IX's Greener Cleanups Policy (EPA, 2009c), the Selected Remedy will
incorporate greener cleanup practices. The Selected Remedy's remedial design phase will
evaluate a range of practices, strategies, and technologies to support the implementation of
greener cleanups. The greener cleanups approach should reflect the following core elements:

• Reduce total energy use and apply renewable energy sources.

• Reduce air pollutants and greenhouse gas emissions.

• Reduce water use and impacts to water resources.

• Reduce, reuse, and recycle materials and waste.

• Protect and restore land and ecosystems.

As part of the greener cleanups approach, a greener cleanups assessment will be submitted for
approval as part of the remedial design phase. This assessment will evaluate opportunities to
apply greener cleanup BMPs and reduce the environmental footprint throughout remedial
actions. The greener cleanups assessment will consider and outline, at a minimum, the
following touchstone practices:

• Renewable energy to power the cleanup remedy

• Clean diesel fuels and technologies for onsite equipment and transport

• Reuse or recycling of demolition debris

• Water from recycled sources and recycling of treated water

The assessment will use resources, such as EPA's Principles for Greener Cleanups (EPA, 2009b),
EPA's Green Remediation Strategy (EPA, 2010), the ASTM Greener Cleanups Standard Guide
(ASTM, 2013), the Greener Cleanups Policy - EPA Region 9 (EPA, 2009c), and resources on
cluin.org (EPA, 2018), in considering these practices and identifying any additional greener
cleanup BMPs at the Site.

-------
PART 2: THE DECISION SUMMARY

The implementation of these practices, or any additional greener cleanup BMPs, does not
change cleanup goals, or how and why cleanup decisions are made. Instead, such practices call
for more environmentally friendly methods of implementing the cleanup. The cleanup at the
Site must meet all statutory and regulatory requirements.

encing of Work

The Selected Remedy sequencing of work will be finalized during the remedial design phase,
subject to EPA review and approval. In general, the Selected Remedy will be constructed over a
period of about 5 years. The preliminary construction sequence is summarized as follows:

• After the ROD has been approved, expeditiously begin the remedial design field
investigations in the southern portion of the P/S Landfill to locate, design, construct, and
begin extraction from the NAPL-only wells. The network of approximately 16 (e.g., 15-20)
NAPL extraction wells will be installed in the early stages of the remedy construction
process. Expeditious recovery of NAPL, a principal threat waste, in the early stages of
remedial action is important in minimizing further migration of NAPL.

• Complete the Selected Remedy for RCRA Canyon and WCSA (Area 2), which would include
an ET cap and/or RCRA hybrid cap over the entire area. During that same timeframe, the
liquids from Pond A-5 would be transferred to the RCF Pond; the A-5 pond would be
backfilled with the WCSA excavated soils; and the new, lined, retention basin in the
footprint of the A-5 pond would be constructed. The proposed pipeline that conveys
stormwater runoff from the capped RCRA Canyon area would be built and put into service.
The stormwater runoff from the southern portion of RCRA Canyon would sheet flow to the
A-Series Pond and be monitored for a period of time (to be identified during remedial
design) to determine whether the stormwater meets the NPDES substantive requirements
and can be discharged.

• Complete the Selected Remedy for the CDA, PCB Landfill, BTA (Area 1), and the MSA and
FPP Area (Area 3), which will consist of a RCRA cap. The proposed concrete drainage
channel to convey clean stormwater runoff from the northern part of the Site through or
around the B-Drainage wetlands would be built and put into service at this time.

• Complete the pond closures of the A-Series Pond, Pond 18, and Pond 13 (Area 4). The A-
Series Pond will be emptied and the new lined evaporation pond system will be constructed
in the footprint of the A-Series Pond.

• Complete the Selected Remedy for the RCF Pond (Area 4), which involves adding an eco-cap
to the raised pond bottoms, and conduct grading and BMPs in the area south of the PSCT
(Area 3).

• Complete the recommended groundwater remedy (Area 5) by completing design and
construction of the upgraded groundwater treatment system.

-------
PART 2: THE DECISION SUMMARY

2.12.16 Cost Estimate for the Selected Remedy

The estimated capital, annual O&M, total present value costs, discount rate, and the number of
years over which the Selected Remedy occurs are summarized in Table 2-19. A breakdown of
the costs by area for the Selected Remedy is provided in Table 2-20. The detailed costs
associated with the Selected Remedy are presented in Appendix E.

For the Selected Remedy, the estimated capital costs, annual O&M, total present worth capital,
and O&M costs are summarized as follows:

Capital Costs (2014 $):	$59,967,000

Annual O&M Costs (2014 $):	$4,064,000

Total present worth capital and O&M costs,	$89,499,000
7 percent discount rate1, 30-year timeframe

Total present worth capital and O&M costs,	$96,218,000
7 percent discount rate1, 100-year timeframe

¦""The 7% discount rate is included per EPA guidance and OMB Circular A-94. Table 2-20 presents additional
cost details.

cted Outcomes of Selected Remedy

The expected outcome of the Selected Remedy is to achieve RAOs through the removal,
treatment, and/or containment of soil, groundwater, and surface water contamination to CLs,
and the protection of human and ecological receptors from unacceptable exposure, including
onsite (Zone 1) containment of impacted groundwater. The Selected Remedy will control and
monitor remaining onsite contamination. The Selected Remedy will be subject to ongoing
OM&M activities and five-year reviews to help verify protectiveness of human health and the
environment.

2.13 Statut terminations

Under CERCLA Section 121 and the NCP, the lead agency must select remedies that are
protective of human health and the environment, comply with ARARs (unless a statutory waiver
is justified), are cost-effective, and use permanent solutions and treatment or resource
recovery technologies to the maximum extent practicable. In addition, CERCLA includes a
preference for remedies that employ treatment that permanently and significantly reduces the
volume, toxicity, or mobility of hazardous wastes as a principal element, and includes a bias
against offsite disposal of untreated wastes. The following sections discuss how the Selected
Remedy meets these statutory requirements and explain the 5-year review requirements for
the Selected Remedy.

93

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PART 2: THE DECISION SUMMARY

>tection of Human Health and the Environment

Under its legal authorities, EPA's primary responsibility at Superfund sites is to undertake
remedial actions that achieve adequate protection of human health and the environment. The
Selected Remedy includes ICs, containment and engineering operation controls, and source
removal/reduction, to reduce or eliminate unacceptable human and ecological exposure to
contamination remaining onsite. If no action is taken, potential exposure would result in
unacceptable risk to human health and the environment.

2.13.2 Compliance with Applicable or Relevant and Appropriate Requirements and
Justification of a Waiver

Remedial actions selected under CERCLA must comply with all ARARs under federal
environmental laws or, where more stringent than the federal requirements, State
environmental or facility siting laws. Where a state has delegated authority to enforce a federal
statute, such as RCRA, the delegated portions of the statute are considered to be a federal
ARAR unless the state law is broader in scope than the federal law. ARARs are identified on a
Site-specific basis, from information about Site-specific chemicals, specific actions that are
being considered, and specific features of the Site's location. There are three categories of
ARARs:

• Chemical-specific ARARs are health- or risk-based numerical cleanup or containment values
or methodologies, which, when applied to Site-specific conditions, result in the
establishment of numerical values for COCs at the Site. These values establish the
acceptable amount or concentration of a COC that may be found in or discharged to the
ambient environment.

• Location-specific ARARs are restrictions placed on concentrations of hazardous substances
or the conduct of activities because of special locations, which have important geographical,
biological, or cultural features. Examples of special locations include wetlands, flood plains,
sensitive ecosystems, and seismic areas. Location-specific ARARs for the Site include
substantive requirements that address federally threatened and endangered species, and
migratory birds that have been found at the Site. Location-specific ARARs include the
substantive requirements of the ESA and Migratory Bird Treaty Act among other
requirements, based on the presence of species that may be exposed to Site-related risks.

• Action-specific ARARs are technology-based or activity-based requirements, or limitations
on actions, to be taken in handling hazardous wastes. They are triggered by the particular
remedial activities selected to accomplish a remedy. Action-specific ARARs for the Site
generally include requirements to address selection, design, operation, monitoring, and
closure of remedy systems and components.

Where no ARARs exist for a given chemical, action, or location, EPA may consider non-
promulgated federal or State advisories and guidance as "to be considered" criteria (TBC).

-------
PART 2: THE DECISION SUMMARY

Although consideration of a TBC is not required, if standards are selected based on TBC,
those standards are legally enforceable as performance standards.

EPA's approach to groundwater at the Site is to apply the selected groundwater cleanup ARARs
(MCLs) throughout the plume, except for the designated Tl Zone within Area 5 North where it is
not technically practicable to meet ARARs. The Selected Remedy incorporates a WMA where
ARARs do not apply, and a waiver of the groundwater cleanup ARARs within the designated Tl
Zone in Area 5 North. This approach complies with CERCLA Section 121(d)(4), is consistent with
EPA's presumptive remedy approach to groundwater at municipal waste landfill sites and
common practice for large hazardous waste landfill sites, and is protective of human health and
the environment. A Tl waiver is necessary for groundwater in Area 5 North because the presence
of LNAPL, DNAPL, residual NAPL, and dissolved-phase organic and inorganic contamination in
low-permeability fractured bedrock make it technically impracticable to remediate and meet the
drinking water standards in this area. The Selected Remedy complies with all other ARARs.

Appendix D provides a complete list of ARARs for the Site.

2.13.3 Cost-Effectiveness

CERCLA requires EPA to consider the cost-effectiveness of the Selected Remedy. The NCP
defines a cost-effective remedy as one where "costs are proportional to its overall
effectiveness." More than one remedial alternative can be cost-effective, and EPA is not
required to select the most cost-effective alternative. Overall, effectiveness is determined by
evaluating three of the balancing criteria: long-term effectiveness; reduction in toxicity,
mobility, and volume through treatment; and short-term effectiveness.

The costs associated with the Selected Remedy and the other sitewide alternatives are
summarized in Table 2-19. A breakdown of the costs by area for the Selected Remedy is
provided in Table 2-20. The detailed costs associated with the Selected Remedy are presented
in Appendix E.

EPA judges the No Action Alternative (Alternative 1) as neither protective of human health nor
cost-effective.

2.13.4 Utilization of Permanent Solutions and Treatment or Recovery 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 used in a practicable manner. Of those
alternatives that are protective of human health and the environment, and comply with ARARs,
EPA has determined that the Selected Remedy provides the best balance in terms of the five
balancing criteria, while also considering the statutory preference for treatment as a principal
element, in addition to state and community acceptance.

The Selected Remedy will maximize the extent to which permanent solutions and treatment or
recovery technologies can be used in a practicable manner. It consists of the following:

-------
PART 2: THE DECISION SUMMARY

• Area 5 North - Source Removal: Removing LNAPL and DNAPL will reduce the volume of
source material that is acting as a source of contamination to groundwater and reduce the
potential for LNAPL and DNAPL to further migrate. Transport of extracted source area
liquids (NAPL) to an offsite TSD facility will allow for treatment of this material.

• Area 5 North - Containment: Extracting liquids from the PSCT, treating the liquids, and
discharging them to the new lined evaporation pond system (footprint of A-Series Pond
and/or RCF Pond) will reduce the volume of highly contaminated groundwater and prevent
it from migrating toward Area 5 South. MNA processes will supplement these actions to
further reduce contaminant concentrations.

• Areas 5 South and Area 5 West - Restoration and Containment: Extracting liquids from the
three PCTs, treating the liquids, and discharging them to the new evaporation pond
(footprint of A-Series Pond and/or RCF Pond) will reduce the volume of moderately
contaminated groundwater and prevent it from migrating to the A-, B-, and C-Drainages.
MNA processes will supplement these actions to further reduce contaminant
concentrations.

2.13.5 Preference for Treatment as a Principal Element

Removing NAPL, a PTW, will reduce the volume of source material that is acting as a source of
contamination to groundwater and reduce the potential for NAPL to further migrate. Transport
of extracted source area liquids (NAPL) to an offsite TSD facility will allow for treatment of this
material.

Although not considered a PTW, extracting liquids from the PSCT and the PCTs (PCT-A, PCT-B,
and PCT-C), treating the liquids, and discharging them to the new lined evaporation pond
system (footprint of A-Series Pond and/or RCF Pond) will reduce the volume of contaminated
groundwater and prevent it from migrating. MNA processes will supplement these actions to
further reduce contaminant concentrations.

2.13.6 Five-Year Review Requirements

The NCP at 40 CFR Section 300.430 (f)(4)(ii) requires a five-year review if the remedial action
results in hazardous substances, pollutants, or contaminants remaining onsite above levels that
allow for unlimited use and unrestricted exposure. This review evaluates whether a remedy
currently is, or will be, protective of human health and the environment.

Because the Selected Remedy will result in hazardous substance, pollutants, or contaminants to
remain onsite above levels that allow for unrestricted use and unrestricted exposure, a
statutory five-year review will be required. A five-year review will be conducted within 5 years
after initiation of the remedial action, and every 5 years thereafter, to ensure that the remedy
is, or will be, protective of human health and the environment. The five-year review will also
include evaluation of the effectiveness of NAPL extraction, ICs, and other pertinent
requirements.

-------
PART 2: THE DECISION SUMMARY

cumentation of Significant Changes from Preferred Alternative of Proposed Plan

The Proposed Plan for the Casmalia Resources Superfund Site was released for public comment
on November 22, 2018, and the 60-day public comment period closed on January 22, 2018. The
Proposed Plan identified Alternative 3 (Capping, Liquids Extraction, Small Evaporation Pond) as
the Preferred Alternative for remediation. EPA reviewed all written and oral comments
submitted during the public comment period. It was determined that no significant changes to
the Selected Remedy, as originally identified in the Proposed Plan, were necessary or
appropriate.

97

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RESPONSIVENESS SUMMARY

3.1	Stakeholder Comments ai	»sponses

There was significant community response received at the public meeting and provided in
writing during the comment period. The comments and EPA responses are included in the
Responsiveness Summary as Appendix G of this document.

3.2	Technical and Legal Issues

The Selected Remedy includes many complex technical requirements that will be addressed
during the remedial design phase, subject to EPA review and approval.

The five-year review will reevaluate overall cleanup goals (including RLs) to ensure that the
Selected Remedy is protective of human health and the environment.

There are no outstanding legal issues.

99

-------
Works Cited

ASTM International (ASTM). 2013. Standard Guide for Greener Cleanups. ASTM E2893-13el.
November.

Casmalia Steering Committee (CSC). 2011. Final Remedial Investigation Report, Casmalia
Resources Superfund Site. January 25.

Casmalia Steering Committee (CSC). 2016. Final Feasibility Study Report, Casmalia Resources
Superfund Site. February 25

Regional Water Quality Control Board, Central Coast Region (RWQCB). 2017. Water Quality
Control Plan for the Central Coast Basin. State Water Resources Control Board/California
Environmental Protection Agency. March.

U.S. Environmental Protection Agency (EPA). 1986. Guidelines for Ground-Water Classification
under the EPA Ground-Water Protection Strategy, Final Draft. November.

U.S. Environmental Protection Agency (EPA). 1991. A Guide to Principal Threat and Low Level
Threat Wastes. OSWER Publication 9380.3-06FS. November.

U.S. Environmental Protection Agency (EPA). 1993a. Waste Management Area (WMA) and
Supplemental Well (SPW) Guidance. June.

U.S. Environmental Protection Agency (EPA). 1993b. Presumptive Remedy for CERCLA Municipal
Landfill Sites. OSWER Directive No. 9355.0-49FS. September.

U.S. Environmental Protection Agency (EPA). 1993c. Guidance for Evaluating Technical
Impracticability of Ground-Water Restoration. September

U.S. Environmental Protection Agency (EPA). 1996. Presumptive Response Strategy and Ex-Situ
Treatment Technologies for Contaminated Ground Water at CERCLA Sites. OSWER Directive No.
9283.1-12. October.

U.S. Environmental Protection Agency (EPA). 1999a. Use of Monitored Natural Attenuation at
Superfund, RCRA Corrective Action and Underground Storage Tanks Sites. OSWER Directive No.
9200.4-17P. April.

U.S. Environmental Protection Agency (EPA). 1999b. A Guide to Preparing Superfund Proposed
Plans, Records of Decision and Other Remedy Selection Decision Documents. OSWER Directive
No. 9200.1-23P. July.

U.S. Environmental Protection Agency (EPA). 2000. A Guide to Developing and Documenting
Cost Estimates during the Feasibility Study. OSWER Directive No. 9355.0-75. August.

101

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WORKS CITED

U.S. Environmental Protection Agency (EPA). 2007. Ecological Revitalization and Attractive
Nuisance Issues. Office of Superfund Remediation and Technology Development. EPA Publication No.
542-F-06-003. June.

U.S. Environmental Protection Agency (EPA). 2009a. Summary of Key Existing EPA CERCLA
Policies for Groundwater Restoration. OSWER Directive No. 9283.1-33. June 26.

U.S. Environmental Protection Agency (EPA). 2009b. Principles for Greener Cleanups. OSWER
Publication (unnumbered). August 27.

U.S. Environmental Protection Agency (EPA). 2009c. Greener Cleanups Policy - EPA Region 9.
September 14.

U.S. Environmental Protection Agency (EPA). 2018. Contaminated Site Clean-Up Information.
Link: https://clu-in.org/greenremediation/methodoloev/index.cfm

U.S. Environmental Protection Agency (EPA). 2010. Superfund Green Remediation Strategy.
September.

U.S. Environmental Protection Agency (EPA). 2011. Recommended Evaluation of Institutional
Controls: Supplement to the "Comprehensive Five-Year Review Guidance." OSWER Directive
9355.7-18. September.

U.S. Environmental Protection Agency (EPA). 2017. Proposed Plan, Casmalia Resources
Superfund Site, Santa Barbara County, California. November.

102

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es

-------
EPA RECORD OF DECISION

CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-1. Contaminated Liquids, Extraction, Treatment, and Disposal

Gallery Well	Sump9B	PSCT	PCTs

Entity

Year

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

O/O

1980

X

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1981

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1982

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1983

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1984

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1985

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1986

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1987

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1988

-

X

None

P/S LF

-

-

-

-

-

-

-

-

-

-

-

-

0/0

1989

-

-

-

-

X

X

Solidification

P/S LF

-

-

-

-

X

X

None

RCF, A-Series

0/0

1990

-

X

None

Offsite TSD, TX

-

X

Solidification

P/S LF

X

-

-

-

-

X

None

RCF, A-Series

0/0

1991

-

X

None

Offsite TSD, TX

-

-

-

-

-

-

-

-

-

X

None

RCF, A-Series

EPAa'b

1992

-

X

None

Offsite TSD, NJ

-

-

-

-

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

EPAa

1993

-

X

None

Offsite TSD, NJ

-

-

-

-

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

EPAa

1994

-

X

None

Offsite TSD, NJ

-

X

None

Offsite TSD, NJ

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

EPAa

1995

-

X

None

Offsite TSD, NJ

-

X

None

Offsite TSD, NJ

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

EPAa

1996

-

X

Bio/PACT

Pond A-5

-

X

Bio/PACT

Pond A-5

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSCC

1997

-

X

Bio/PACT

Pond A-5

-

X

Bio/PACT

Pond A-5

-

X

GAC

Pond 18/A5

-

X

None

RCF, A-Series

CSC

1998

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18/A5

-

X

None

RCF, A-Series

CSC

1999

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2000

-

X

None

Offsite TSD, CA

-

X

ATS/GAC

Pond 18

-

X

ATS/GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2001

-

X

None

Offsite TSD, CA

-

X

ATS/GAC

Pond 18

-

X

ATS/GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2002

-

X

None

Offsite TSD, CA

-

X

ATS/GAC

Pond 18

-

X

ATS/GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2003

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2004

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2005

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2006

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

1

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-1. Contaminated Liquids, Extraction, Treatment, and Disposal







Gallery Well



Sump9B





PSCT





PCTs



Entity

Year

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

Const

Ext

Tmt

Disposal

CSC

2007

X

None

Offsite TSD, CA

X

None

Offsite TSD, CA

X

GAC

Pond 18

X

None

RCF, A-Series

CSC

2008

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2009

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2010

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2011

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2012

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2013

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2014

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2015

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

CSC

2016

-

X

None

Offsite TSD, CA

-

X

None

Offsite TSD, CA

-

X

GAC

Pond 18

-

X

None

RCF, A-Series

Total Volume
Extracted (gallons)d

Gallery Well: 11,295,940

Sump 9B: 6,876,008

PSCT: 87,704,476

PCTs: 187,115,084

Notes:

Source: Modified from Table 2-4, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).
a The Owner/Operator controlled PCT extraction from 1992 through 1996
b EPA Emergency Response Section began operations at the site in August 1992
c The CSC took over site operations from EPA on September 17, 1997

d Total volumes are based on site records, but should be considered estimated values, and are through the end of September 2016.
- = did not occur or not applicable
ATS = Ameripure treatment system

Bio/PACT = biologically-activated/powdered-activated carbon treatment

Const = constructed

CSC = Casmalia Steering Committee

EPA = U.S. Environmental Protection Agency

Ext = extraction

GAC = granular activated carbon

0/0 = Owner/Operator

P/S LF = pesticide/solvent landfill

PCT = perimeter control trench

PSCT = perimeter source control trench

RCF = runoff containment facility (pond)

Tmt = treatment

X = implies the date that something occurred

TSD = treatment, storage, and disposal (CA - California; NJ - New Jersey; TX - Texas)

2

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Study Area- Specific Study Area- Specific

Parameter	SitewideSoil Soil Matrix COPC for Soil Matrix COPC for Sediment Surface Onsite Soil Offsite Soil

Class CAS_RN	Parameter	Matrix COPC	HHRA	ERA	COPC Water COPC Vapor COPC Vapor COPC

CYANIDE

A57-12-5

Amenable Cyanide

-

-

-

-

CYANIDE

57-12-5

Total Cyanide

X

-

-

-

DIOXIN

35822-46-9

1,2,3,4,6,7,8-HpCDD

-

-

-

-

DIOXIN

67562-39-4

1,2,3,4,6,7,8-HpCDF

-

-

-

-

DIOXIN

39227-28-6

1,2,3,4,7,8-HxCDD

-

-

-

-

DIOXIN

57653-85-7

1,2,3,6,7,8-HxCDD

-

-

-

-

DIOXIN

57117-44-9

1,2,3,6,7,8-HxCDF

-

-

-

-

DIOXIN

19408-74-3

1,2,3,7,8,9-HxCDD

-

-

-

-

DIOXIN

72918-21-9

1,2,3,7,8,9-HxCDF

-

-

-

-

DIOXIN

3268-87-9

OCDD

-

-

-

-

DIOXIN

39001-02-0

OCDF

-

-

-

-

DIOXIN

URS-TEQ-04

Total Avian Dioxin TEQ

X

-

X

X

DIOXIN

URS-TEQ-06

Total Fish Dioxin TEQ

X

-

X

X

DIOXIN

URS-TEQ-02

Total TEQ

X

-

X

X

HERB

93-72-1

2,4,5-TP (Silvex)

-

X

-

-

HERB

94-82-6

2,4-Dichlorophenoxybutyric
acid
(2,4-DB)

X



X



HERB

88-85-7

2-sec-Butyl-4,6-dinitrophenol
(Dinoseb)

-

X

-

-

HERB

75-99-0

Dalapon

X

-

-

-

HERB

120-36-5

Dichlorprop

-

-

X

-

HERB

94-74-6

MCPA

X

-

-

-

HERB

93-65-2

MCPP

X

-

X

-

3

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface
Water COPC

Onsite Soil
Vapor COPC

Offsite Soil
Vapor COPC

Metals

7429-90-5

Aluminum

*

-

-

-

-

-

-

Metals

7429-90-5

Aluminum (Dissolved)

-

-

-

-

-

-

-

Metals

7440-36-0

Antimony

-

-

-

-

X

-

-

Metals

7440-36-0

Antimony (Dissolved)

-

-

-

-

X

-

-

Metals

7440-38-2

Arsenic

-

-

-

-

X

-

-

Metals

7440-38-2

Arsenic (Dissolved)

-

-

-

-

X

-

-

Metals

7440-39-3

Barium

X

-

-

X

X

-

-

Metals

7440-39-3

Barium (Dissolved)

-

-

-

-

X

-

-

Metals

7440-41-7

Beryllium

X

-

-

-

X

-

-

Metals

7440-41-7

Beryllium (Dissolved)

-

-

-

-

X

-

-

Metals

7440-43-9

Cadmium

X

-

-

X

X

-

-

Metals

7440-43-9

Cadmium (Dissolved)

-

-

-

-

X

-

-

Metals

7440-70-2

Calcium

-

-

-

-

**

-

-

Metals

7440-70-2

Calcium (Dissolved)

-

-

-

-

**

-

-

Metals

7440-47-3

Chromium

X

-

-

X

X

-

-

Metals

7440-47-3

Chromium (Dissolved)

-

-

-

-

X

-

-

Metals

7440-48-4

Cobalt

X

-

-

-

X

-

-

Metals

7440-48-4

Cobalt (Dissolved)

-

-

-

-

X

-

-

Metals

7440-50-8

Copper

X

-

-

X

X

-

-

Metals

7440-50-8

Copper (Dissolved)

-

-

-

-

X

-

-

Metals

7439-89-6

Iron

-

-

-

-

**

-

-

Metals

7439-89-6

Iron (Dissolved)

-

-

-

-

**

-

-

Metals

7439-92-1

Lead

X

-

-

X

X

-

-

4

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface Onsite Soil
Water COPC Vapor COPC

Offsite Soil
Vapor COPC

Metals

7439-92-1

Lead (Dissolved)

-

-

-

-

X

-

Metals

7439-95-4

Magnesium

-

-

-

-

**

-

Metals

7439-95-4

Magnesium (Dissolved)

-

-

-

-

**

-

Metals

7439-96-5

Manganese

X

-

-

X

X

-

Metals

7439-96-5

Manganese (Dissolved)

-

-

-

-

X

-

Metals

7439-97-6

Mercury

X

-

-

X

X

-

Metals

7439-97-6

Mercury (Dissolved)

-

-

-

-

X

-

Metals

7439-98-7

Molybdenum

X

-

-

X

X

-

Metals

7439-98-7

Molybdenum (Dissolved)

-

-

-

-

X

-

Metals

7440-02-0

Nickel

X

-

-

X

X

-

Metals

7440-02-0

Nickel (Dissolved)

-

-

-

-

X

-

Metals

7440-09-7

Potassium

-

-

-

-

**

-

Metals

7440-09-7

Potassium (Dissolved)

-

-

-

-

**

-

Metals

7782-49-2

Selenium

X

-

-

X

X

-

Metals

7782-49-2

Selenium (Dissolved)

-

-

-

-

X

-

Metals

7440-22-4

Silver

-

-

-

-

X

-

Metals

7440-22-4

Silver (Dissolved)

-

-

-

-

X

-

Metals

7440-23-5

Sodium

-

-

-

-

**

-

Metals

7440-23-5

Sodium (Dissolved)

-

-

-

-

**

-

Metals

7440-28-0

Thallium

X

-

-

X

X

-

Metals

7440-28-0

Thallium (Dissolved)

-

-

-

-

X

-

Metals

7440-31-5

Tin

X

-

-

X

X

-

Metals

7440-62-2

Vanadium

X

-

-

-

X

-

5

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface Onsite Soil
Water COPC Vapor COPC

Offsite Soil
Vapor COPC

Metals

7440-62-2

Vanadium (Dissolved)

-

-

-

-

X

-

Metals

7440-66-6

Zinc

X

-

-

X

X

-

Metals

7440-66-6

Zinc (Dissolved)

-

-

-

-

X

-

PAH

91-57-6

2-Methylnaphthalene

-

-

-

X

-

-

PAH

83-32-9

Acenaphthene

X

-

-

-

-

-

PAH

208-96-8

Acenaphthylene

-

-

X

-

-

-

PAH

120-12-7

Anthracene

X

-

-

-

-

-

PAH

56-55-3

Benzo(a)anthracene

X

-

-

X

X

-

PAH

50-32-8

Benzo(a)pyrene

X

-

-

X

X

-

PAH

205-99-2

Benzo(b)fluoranthene

X

-

-

X

X

-

PAH

191-24-2

Benzo(g,h,i)perylene

X

-

-

X

X

-

PAH

207-08-9

Benzo(k)fluoranthene

X

-

-

-

-

-

PAH

218-01-9

Chrysene

X

-

-

X

-

-

PAH

53-70-3

Dibenzo(a,h)anthracene

-

-

-

-

X

-

PAH

206-44-0

Fluoranthene

X

-

-

X

-

-

PAH

86-73-7

Fluorene

X

-

-

X

-

-

PAH

193-39-5

lndeno(l,2,3-c,d)pyrene

X

-

-

X

-

-

PAH

91-20-3

Naphthalene

X

-

-

X

X

-

PAH

85-01-8

Phenanthrene

-

-

-

X

-

-

PAH

129-00-0

Pyrene

X

-

-

X

-

-

PCB

11096-82-5

Aroclor 1260

X

-

-

X

-

-

PCBConger

SUM-PCBC

Sum of PCB Congeners

X

-

-

X

-

-

PCBConger

SUM-PCBC

PCBConger-PCBC TEQ

X

-

-

X

-

-

6

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor







Study Area- Specific

Study Area- Specific









Parameter



Sitewide Soil

Soil Matrix COPC for

Soil Matrix COPC for

Sediment

Surface

Onsite Soil

Offsite Soil

Class CAS_RN

Parameter

Matrix COPC

HHRA

ERA

COPC

Water COPC

Vapor COPC

Vapor COPC

PCBConger SUM-PCBC PCBConger-Total Avian PCBC	X	-	-	X

TEQ

PCBConger

35065-29-3

2,2',3,4,4',5,5,-HpCB-180

X

-

X - -

PCBConger

35065-30-6

2,2'3,3'4,4',5-HpCB-170

X

-

X - -

PCBConger

39635-31-9

2,3,3',4,4',5,5'-HpCB-189

X

-

X - -

PCBConger

38380-08-4

2,3,3',4,4',5-HxCB-156

X

-

X - -

PCBConger

69782-90-7

2,3,3',4,4',5'-HxCB-157

X

-

X - -

PCBConger

32598-14-4

2,3,3',4,4'-PeCB-105

X

-

X - -

PCBConger

52663-72-6

2,3',4,4',5,5'-HxCB-167

X

-

X - -

PCBConger

74472-37-0

2,3,4,4',5-PeCB-114

X

-

X - -

PCBConger

31508-00-6

2,3',4,4',5-PeCB-118

X

-

X - -

PCBConger

65510-44-3

2',3,4,4',5-PeCB-123

X

-

X - -

PCBConger

32774-16-6

3,3',4,4',5,5'-HxCB-169

X

-

X - -

PCBConger

57465-28-8

3,3',4,4',5-PeCB-126

X

-

X - -

PCBConger

32598-13-3

3,3',4,4'-TeCB-77

X

-

X - -

PCBConger

70362-50-4

3,4,4',5-TeCB-81

X

-

X - -

PEST

72-54-8

4,4'-DDD

-

X

X - -

PEST

72-55-9

4,4'-DDE

X

-

X - -

PEST

50-29-3

4,4'-DDT

X

-

X - -

PEST

309-00-2

Aldrin

-

X

-

PEST

319-84-6

alpha-BHC

-

X

-

PEST

5103-71-9

Chlordane, alpha

-

-

X - -

PEST

12789-03-6

Chlordane, gamma

-

X

-

7

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment Surface
COPC Water COPC

Onsite Soil
Vapor COPC

Offsite Soil
Vapor COPC

PEST

319-86-8

delta-BHC

-

-

X

-

-

-

PEST

60-57-1

Dieldrin

-

-

X

-

-

-

PEST

959-98-8

Endosulfan 1

-

-

X

X

-

-

PEST

33213-65-9

Endosulfan II

-

-

-

X

-

-

PEST

1031-07-8

Endosulfan sulfate

-

-

-

X

-

-

PEST

72-20-8

Endrin

-

-

X

X

-

-

PEST

76-44-8

Heptachlor

-

-

-

X

-

-

PEST

1024-57-3

Heptachlor epoxide

-

X

X

-

-

-

PEST

118-74-1

Hexachlorobenzene

X

-

-

X

-

-

PEST

143-50-0

Kepone

-

-

-

X

-

-

PEST

72-43-5

Methoxychlor

X

-

-

-

-

-

PEST

2385-85-5

Mi rex

-

X

X

-

-

-

SVOC

65-85-0

Benzoic acid

-

-

X

-

-

-

SVOC

111-44-4

Bis(2-chloroethyl)ether

-

-

-

X

-

-

SVOC

117-81-7

Bis(2-ethylhexyl)phthalate

X

-

-

X

-

-

SVOC

84-66-2

Diethylphthalate

X

-

-

-

-

-

SVOC

84-74-2

Di-n-butylphthalate

-

-

X

-

-

-

SVOC

107-21-1

Ethylene glycol

-

-

-

0

-

-

SVOC

62-75-9

N-Nitrosodimethylamine

-

X

X

-

-

-

SVOC

55-18-5

N-Nitrosodiethylamine

-

-

-

X

-

-

SVOC

621-64-7

N-Nitrosodipropylamine

-

-

X

X

-

-

SVOC

10595-95-6

N-Nitrosomethylethylamine

-

-

X

-

-

-

SVOC

930-55-2

N-Nitrosopyrrolidine

-

X

X

X

-

-

8

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface
Water COPC

Onsite Soil
Vapor COPC

Offsite Soil
Vapor COPC

voc

71-55-6

1,1,1-Trichloroethane

X

-

-

-

-

X

-

voc

79-00-5

1,1,2-Trichloroethane

-

-

-

-

-

X

-

voc

75-34-3

1,1-Dichloroethane

X

-

-

X

X

X

-

voc

75-35-4

1,1-Dichloroethylene

X

-

-

-

-

X

-

voc

87-61-6

1,2,3-T richlorobenzene

-

-

-

-

-

-

-

voc

95-63-6

1,2,4-Trimethyl benzene

-

-

-

-

-

X

X

voc

106-93-4

1,2-Dibromoethane (EDB)

-

-

-

-

X

-

-

voc

95-50-1

1,2-Dichlorobenzene

-

-

-

-

-

-

-

voc

107-06-2

1,2-Dichloroethane

-

-

-

-

-

-

-

voc

540-59-0

1,2-Dichloroethene

X

-

-

X

-

-

-

voc

78-87-5

1,2-Dichloropropane

-

-

-

-

-

X

-

voc

108-67-8

1,3,5-T rimethylbenzene

-

-

-

-

-

X

X

voc

106-99-0

1,3-Butadiene

-

-

-

-

-

X

X

voc

541-73-1

1,3-Dichlorobenzene

-

-

-

-

-

-

-

voc

106-46-7

1,4-Dichlorobenzene

-

-

-

-

-

X

-

voc

123-91-1

1,4-Dioxane

-

-

-

-

-

-

X

voc

591-78-6

2-Hexanone

-

-

-

-

-

X

X

voc

622-96-8

4-Ethyltoluene

-

-

-

-

-

X

-

voc

67-64-1

Acetone

X

-

-

X

X

X

X

voc

75-05-8

Acetonitrile

X

-

-

-

X

-

-

voc

107-02-8

Acrolein

X

-

-

-

-

-

-

voc

71-43-2

Benzene

X

-

-

X

-

X

X

voc

75-25-2

Bromoform

-

-

-

-

-

-

-

9

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface
Water COPC

Onsite Soil
Vapor COPC

Offsite Soil
Vapor COPC

voc

74-83-9

Bromomethane

-

-

-

-

-

X

-

voc

75-15-0

Carbon disulfide

X

-

-

X

X

X

X

voc

56-23-5

Carbon tetrachloride

-

-

-

-

-

X

-

voc

75-00-3

Chloroethane

-

-

-

-

-

X

-

voc

67-66-3

Chloroform

-

X

-

-

-

X

X

voc

74-87-3

Chloromethane

-

-

-

-

-

X

X

voc

79-38-9

Chlorotrifluoroethene

-

-

-

-

-

-

-

voc

156-59-2

cis-l,2-Dichloroethene

-

-

-

-

-

X

-

voc

110-82-7

Cyclohexane

-

-

-

-

-

X

-

voc

60-29-7

Diethyl ether

-

-

-

-

-

-

-

voc

108-20-3

Diisopropyl ether

-

-

-

X

-

-

-

voc

64-17-5

Ethanol

-

-

-

-

-

X

X

voc

100-41-4

Ethylbenzene

-

-

-

X



X

X

voc

75-69-4

Freon 11
(Trichlorofluoromethane)

-

-

-

-

-

X

-

voc

76-12-0

Freon 112

-

-

-

-

-

-

-

voc

76-13-1

Freon 113 (1,1,2-trichloro-
1,2,2-trifluo)

X

-

-

X



X

-

voc

75-71-8

Freon 12
(Dichlorodifluoromethane)

-

-

-

-

-

-

-

voc

142-82-5

Heptane

-

-

-

-

-

X

X

voc

110-54-3

Hexane

-

-

-

-

-

X

X

voc

67-63-0

Isopropanol

X

-

-

-

-

X

X

voc

78-93-3

Methyl ethyl ketone

X

-

-

X

-

X

X

10

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-2. Chemicals of Potential Concern in Soil, Sediment, Surface Water, and Soil Vapor

Parameter
Class

CAS_RN

Parameter

Sitewide Soil
Matrix COPC

Study Area- Specific
Soil Matrix COPC for
HHRA

Study Area- Specific
Soil Matrix COPC for
ERA

Sediment
COPC

Surface
Water COPC

Onsite Soil
Vapor COPC

Offsite Soil
Vapor COPC

voc

108-10-1

Methyl isobutyl ketone (MIBK)

-

-

-

X

X

X

-

voc

96-37-7

Methylcyclopentane

-

-

-

X

-

-

-

voc

75-09-2

Methylene chloride

X

-

-

X

X

X

X

voc

124-19-6

Nonanal

-

-

-

-

0

-

-

voc

123-38-6

Propanal

X

-

-

X

X

-

-

voc

100-42-5

Styrene

-

-

-

-

-

X

X

voc

75-65-0

Tert-butyl alcohol (TBA)

X

-

-

-

-

-

-

voc

127-18-4

Tetrachloroethylene

X

-

-

-

-

X

X

voc

109-99-9

Tetrahydrofuran

X

-

-

X



X



voc

108-88-3

Toluene

X

-

-

-

-

X

X

voc

1330-20-7

Total xylenes

-

-

-

-

-

X

X

voc

156-60-5

trans-l,2-Dichloroethylene

-

-

-

-

-

-

-

voc

79-01-6

Trichloroethylene

X

-

-

X

X

X

X

voc

75-01-4

Vinyl chloride

-

X

-

-

-

X

-

Notes:

X = compound was selected as a COPC for that medium
- = not applicable

* = not selected as a COPC because site soil pH > 5.5 (EPA, 2003: Ecological Soil Screening Level for Aluminum. OSWER Directive 9285.7.60).
** = the compound was not selected as a COPC because it is an essential nutrient

0 = compound was detected only in offsite surface water (not in any onsite media); therefore, it was not selected as a COPC

CAS_RN = Chemical Abstracts Service Registry Number

COPC = chemical of potential concern

DDE = dichlorodiphenyldichloroethane

ERA = Ecological Risk Assessment

HHRA = Human Health Risk Assessment

MCPA = 2-methyl-4-chlorophenoxyacetic acid

MCPP = 2-(2-chloro-4-methylphenoxyl) propionic acid

OCDD = octachlorodibenzodioxin

OCDF = octachlorodibenzofuran

11

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

PAH = polycyclic aromatic hydrocarbon

PCB = polychlorinated biphenyl

PEST = pesticide

RA = risk assessment

SVOC = semivolatile organic compound

TEQ = toxicity equivalent

VOC = volatile organic compound

12

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-3. Summary of Risk-Based Concentration Exceedances by Media, Location, and Constituent

Media

Study Area

Constituent(s)

Exceedances

Soil

Capped Landfills Area

None

No unacceptable exposures



RCRA Canyon

Chromium, Copper, Zinc

Eco RBC exceedance



West Canyon Spray Area

Chromium, Copper, Zinc

Eco RBC exceedance



Burial Trench Area

Total DDT, Dioxin TEQ, TCE, Copper

Eco RBC exceedance



Central Drainage Area

Dioxin TEQ

HH RBC exceedance (one location)



Total DDT, TCE, Dioxin TEQ, Chromium

Eco RBC exceedance





MCPP

HH RBC exceedance (one Location)



Liquids Treatment Area (Hotspot 1)

Total DDT, MCPP, Chromium, Copper,
Zinc

Eco RBC exceedance





Dioxin TEQ

HH RBC exceedance (one location)



Maintenance Shed Area (Hotspot 2)

Total DDT, Dioxin TEQ, Chromium,
Copper, Zinc

Eco RBC exceedance



Administration Building Area

None

No unacceptable exposures



Roadways Area

Total DDT, PCB Congeners, Chromium,
Copper, Zinc

Eco RBC exceedance



Former Ponds and Pads and Remaining
Onsite Areas (Hotspots 3, 4, and 10)

PCE

HH RBC exceedance (one location)



Total DDT, PCE, TCE, Total PCB
congeners, Chromium, Copper

Eco RBC exceedance



Offsite Soils

None

No unacceptable exposures

Sediment

Stormwater Ponds

MCPP

Eco RBC exceedance



Treated Liquids Impoundments

MCPP

Eco RBC exceedance



Offsite Sediments

None

No unacceptable exposures

Soil Vapor

Central Drainage Area

PCE

No unacceptable exposures3



Former Ponds and Pads

PCE, TCE

No unacceptable exposures



Burial Trench Area

TCE

No unacceptable exposures3



North Drainage

1,3-Butadiene

HHRA exceedance - offsite resident (hypothetical)

13

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES





Table 2-3. Summary of Risk-Based Concentration Exceedances by Media, Location, and Constituent



1 Media

Study Area

Constituent(s)

Exceedances 1

Surface Water (Onsite Ponds)

Stormwater Ponds

Arsenic

HHRA exceedance - industrial workers



Arsenic, Barium, Nickel, Selenium

Eco Exceedance - aquatic plants, aquatic life



Treated Liquids Impoundments

None

No unacceptable exposures

Surface Water (Onsite drainages)

Onsite

None

No unacceptable exposures

Surface Water (Offsite drainages)

Offsite

None

No unacceptable exposures

Groundwater

On/Offsite

None

No unacceptable exposures'5

Notes:

Source: Modified from Table 5-3, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

a PCE and TCE were also identified as COCs for offsite exposures due to potential volatilization into outdoor air (per Table 7-2 from Final Feasibility Study Report, Casmalia Resources
Superfund Site [CSC, 2016]).

b Groundwater was evaluated during the risk assessment, but risks were not calculated for groundwater due to the lack of complete exposure pathways and receptor populations.

Although EPA has no reason to believe that future property use will rely on onsite groundwater, MCLs will apply as the cleanup goals for the chemicals found in groundwater outside of

Area 5 North. The results of the HHRA showed that PCE, TCE, and 90 other chemicals exceed drinking water standards (i.e., MCLs).

Eco RBC Exceedance = listed constituents exceed site-specific ecological risk-based concentration

HH RBC Exceedance = listed constituents exceed site-specific human health risk-based concentrations

HHRA Exceedance = chemical was identified as a risk-driver in the HHRA

Eco Exceedance = chemical was identified as a risk-driver in the ERA

Please note that while there may be a few individual samples in a Study Area that exceed an RBC, the Study Area as a whole may not pose a significant risk due to the use of the 95UCL

concentration in the ERA and HHRA. The 95UCL concentration better represents the concentration to which a receptor may be exposed regularly. The sample-specific comparison to the

RBCs presented in this section is to only provide context to the discussion of nature and extent of constituents across the Site. See Sections 5.2.3 and 5.3 for human health and ecological

chemicals of concern based on the outcome of the risk assessment.

95UCL = 95 percent upper confidence limit

COC = chemical of concern

DDT = dichlorodiphenyltrichloroethane

Eco = ecological

HH = human health

MCL = maximum contaminant level

PCE = tetrachloroethylene/tetrachloroethene

RBC = risk-based concentration

RCRA = Resource Conservation and Recovery Act

TCE = trichloroethylene/trichloroethene

14

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-4. Chemicals of Concern3 in Surface Soil - Terrestrial Birds, Soil Invertebrates, and Plants	

Exposure Area

Tier 1 ERA

Tier 2 ERAb

Human Healthc

RCRA Canyon Area

Risk-driving COPECs identified for further evaluation in the
Tier 2 ERA: Cadmium, Chromium, Lead, and Zinc

Chromium, Copper, and Zinc

None

West Canyon Spray Area

Risk-driving COPECs identified for further evaluation in the
Tier 2 ERA: Cadmium, Chromium, Copper, and Zinc

Chromium, Copper, and Zinc

None

Administration Building Area

None

None

None

Roadway Area

Risk-driving COPEC identified for further evaluation in the
Tier 2 ERA: Chromium

Chromium and Copper

None

Remaining Onsite Area

None

None

None

Former Ponds and Pads Areas

None

None

None

Liquids Treatment Aread

Cadmium, Chromium, Vanadium, MCPP, DDT, Total DDT,
and Hexachlorobenzene

-

MCPP

Burial Trench Aread

Chromium, Vanadium, and TCE

-

None

Maintenance Shed Aread

Cadmium, Chromium, Lead, Vanadium, and DDE, and
Total DDT

-

None

Central Drainage Aread

Chromium, Vanadium, Dioxin TEQ, Total TEQ, Bis
(2-ethylhexyl)phthalate, and Endrinc

-

None

A-Series Pondd

Cadmium and Selenium

-

None

RCFPondd

Chromium

-

None

Pond A-5d

Cadmium, Chromium, and Selenium

-

None

Pond 13d

Cadmium and Selenium

-

None

Pond 18d

Cadmium, Chromium, and Selenium

-

None

Notes:

Source: Modified from Table 7-1, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

a COCs are those chemicals of potential concern that have been identified in the quantitative risk assessment as exceeding a risk threshold and, therefore, warrant further evaluation in
the feasibility study. For areas with planned presumptive remedies, COCs are based on the results of the Tier 1 ERA. For areas with no planned presumptive remedies, COCs are based on
the results of the Tier 2 ERA and the HHRA. This applies to surface soil (0 to 6 inches below ground surface).
b COCs are based on terrestrial birds only.

c COCs are based on commercial/industrial worker exposures and target risk of > 1 x 10 5 and hazard quotient of > 1.
d The exposure area has an assumed presumptive remedy in place and was not evaluated in the Tier 2 ERA.

- = Exposure area was not evaluated in Tier 2 ERA.

COPEC = chemical of potential ecological concern

15

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-5. Chemicals of Concern3 in Shallow Soil - Terrestrial Mammals, Soil Invertebrates, and Plants

Exposure Area

Tier 1 ERA

Tier 2 ERAb

Human Healthc

RCRA Canyon Area

Risk-driving COPECs identified for further evaluation in
the Tier 2 ERA: Cadmium, Chromium, Copper, and Zinc

None

None

West Canyon Spray Area

Risk-driving COPECs identified for further evaluation in
the Tier 2 ERA: Cadmium, Chromium, Copper, and Zinc

None

None

Administration Building Area

None

None

None

Roadway Area

Risk-driving COPEC identified for further evaluation in the
Tier 2 ERA: Chromium and Zinc

None

None

Remaining Onsite Area

None

None

None

Former Ponds and Pads Areas

Risk-driving COPEC identified for further evaluation in the
Tier 2 ERA: Zinc

None

PCE

Liquids Treatment Aread

Cadmium, Molybdenum, Selenium, Zinc, DDT, Total DDT,
MCPP, Hexachlorobenzene, and Mirex

-

MCPP

Burial Trench Aread

Molybdenum, Selenium, and Zinc

-

TCE

Maintenance Shed Aread

Cadmium, Chromium, Lead, Lead, Zinc, Dioxin TEQ, and
Total TEQ

-

None

Central Drainage Aread

Molybdenum, Zinc, Dioxin TEQ, and Total TEQ

-

PCE

A-Series Pondd

Cadmium, Molybdenum, Selenium, and Zinc

-

None

RCFPondd

Molybdenum, Selenium, and Zinc

-

None

Pond A-5d

Barium, Cadmium, Molybdenum, Selenium, and Zinc

-

None

Pond 13d

Cadmium, Selenium, and Zinc

-

None

Pond 18d

Cadmium, Molybdenum, Selenium, and Zinc

-

None

Notes:

Source: Modified from Table 7-2, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).
a COCs are those chemicals of potential concern that have been identified in the quantitative risk assessment as exceeding a risk
threshold and, therefore, warranting further evaluation in the Feasibility Study. For areas with planned presumptive remedies,
COCs are based on the results of the Tier 1 ERA. For areas with no planned presumptive remedies, COCs are based on the
results of the Tier 2 ERA and the HHRA. This applies to shallow soils (0 to 5.5 feet bgs).
b COCs based on terrestrial mammals only.

c COCs based on commercial/industrial worker exposures and target risk of > 1 x 10-5 and hazard quotient of > 1.
d Exposure area has a presumptive remedy in place and was not evaluated in the Tier 2 ERA.

- = Exposure area not evaluated in Tier 2 ERA
bgs = below ground surface

16

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-6. Chemicals of Concern* in Sediment Based on Aquatic Wildlife and Sediment Invertebrates

Exposure Area

Tier 1 ERA

Tier 2 ERA

Human Health

A-Series Pond

Arsenic, Chromium, Manganese, Mercury,
Molybdenum, Selenium, Vanadium, and Zinc

-

None

RCF Pond

Chromium, Avian PCB TEQ, Total TEQ, and
MCPP

-

None

Pond A-5

Cadmium, Chromium, Selenium, and MCPP

--

None

Pond 13

None

-

None

Pond 18

Chromium, Selenium, and MCPP

-

None

Notes:

Source: Modified from Table 7-3, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

* No COCs were identified for sediment in the Tier 2 ERA because all of the ponds will have assumed presumptive remedies in
place as part of the EPA-approved closure plan for the site, and will be backfilled/graded to prevent accumulation of water;
they will be unavailable as a pathway for aquatic receptors, essentially eliminating the potential for adverse effects to aquatic
receptors.

- = Exposure area not evaluated in Tier 2 ERA

17

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-7. Dissolved Chemicals in Groundwater that Exceed Maximum Contaminant Levels

Chemical

MCL
(Hg/L)

Maximum Detected
Concentration (|Jg/L)
(Hg/L)

Location

Date

1,1,1-Trichloroethane

200

410,000

Gallery Well

9/30/1997

1,1,2,2-Tetrachloroethane

1

1,700

PSCT-1

5/23/2002

1,1,2-Trichloroethane

5

2,700

PSCT-1

5/23/2002

1,1-Dichloroethane

5

170,000

PSCT-1

5/23/2002

1,1-Dichloroethylene

6

38,000

PSCT-1

5/23/2002

1,2-Dichloroethane

0.5

110,000

PSCT-1

5/23/2002

1,2-Dichloropropane

5

4,400

PSCT-1

5/23/2002

1,4-dioxane

1e

1,000

RIMW-7

4/22/2008

1,2,3,4,6,7,8-HpCDD

0.00003

8.71

RIPZ-8

10/19/2006

1,2,3,4,6,7,8-HpCDF

0.00003

2.43

RIPZ-8

10/19/2006

1,2,3,4,7,8,9-HpCDF

0.00003

0.343

RIPZ-8

10/19/2006

1,2,3,4,7,8-HxCDD

0.00003

0.0162

RIPZ-8

10/19/2006

1,2,3,4,7,8-HxCDF

0.00003

1.01

RIPZ-8

10/19/2006

1,2,3,6,7,8-HxCDD

0.00003

0.491

RIPZ-8

10/19/2006

1,2,3,6,7,8-HxCDF

0.00003

0.401

RIPZ-8

10/19/2006

1,2,3,7,8,9-HxCDD

0.00003

0.0716

RIPZ-8

10/19/2006

1,2,3,7,8,9-HxCDF

0.00003

0.345

Gallery Well

11/15/2004

1,2,3,7,8-PeCDD

0.00003

0.0287

RIPZ-8

10/19/2006

1,2,3,7,8-PeCDF

0.00003

0.856

RIPZ-8

10/19/2006

2,3,4,6,7,8-HxCDF

0.00003

0.27

RIPZ-8

10/19/2006

2,3,4,7,8-PeCDF

0.00003

0.772

RIPZ-8

10/19/2006

2,3,7,8-TCDD

0.00003

0.000737

Sump 9B

4/14/2005

2,3,7,8-TCDF

0.00003

0.461

RIPZ-8

10/19/2006

Acenaphthylene

0.2 a'f

58

Gallery Well

12/15/2004

Aluminum-Dissolved

1,000

1,400

RGPZ-6D

4/6/2005

Aluminum-Total

1,000

150,000

RGPZ-6B

3/2/2005

Antimony-Dissolved

6

14

WP-3D

6/5/1998

Antimony-Total

6

25

RGPZ-12D

5/4/2006

Arsenic-Dissolved

50

710

Pond 13

10/28/2004

Arsenic-Total

50

330

Pond A-5

11/3/2004

Barium-Total

1,000

1,300

RG-8B

4/6/2004

Benzene

1

39,000

PSCT-1

5/23/2002

Benzo(a)anthracene

0.2 a'f

130

Gallery Well

12/15/2004

Benzo(a)Pyrene

0.2 a'f

34

SW-17

4/15/2005

Benzo(b)fluoranthene

0.2 a'f

33

Gallery Well

12/15/2004

Benzo(ghi)perylene

0.2 a'f

43

RGPZ-6B

3/2/2005

Benzo(k)fluoranthene

0.2 a'f

35

SW-17

4/15/2005

18

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-7. Dissolved Chemicals in Groundwater that Exceed Maximum Contaminant Levels

Chemical

MCL
(Hg/L)

Maximum Detected
Concentration (|Jg/L)
(Hg/L)

Location

Date

Beryllium-Dissolved

4

8

RP-98C

9/26/1997

Beryllium-Total

4

80

WS-4

5/3/2006

Bis(2-ethylhexyl) phthalate

4

19,000

Gallery Well

4/13/2005

Bromodichloromethane

100 b

5,400

Gallery Well

11/22/1999

Bromoform

100 b

15

Gallery Well

2/11/1998

Cadmium-Dissolved

5

150

MW-18C

4/14/2005

Cadmium-Total

5

422

B-5

12/31/1997

Carbon tetrachloride

0.5

19,000

Gallery Well

9/30/1997

Chlorobenzene

70

400

Gallery Well

11/17/2005

Chloroform

00

o

C"

180,000

PSCT-1

5/23/2002

Chromium-Dissolved

50

110

RIMW-9

5/1/2006

Chromium-Total

50

8,960

B-5

12/31/1997

Chrysene

0.2 a'f

150

Gallery Well

12/15/2004

cis-l,2-Dichloroethene

6

200,000

PSCT-1

5/23/2002

cis-l,3-Dichloropropene

0.5 c

7.1

RAP-3A

4/26/1999

Copper-Dissolved

1,000

3,330

B3B

10/29/1998

Copper-Total

1,000

5,010

B-5

12/31/1997

Dibenz(a,h)anthracene

0.2 a'f

15

SW-17

4/15/2005

Endrin

2

4,000

Gallery Well

7/18/2000

Ethylbenzene

300

34,000

PSCT-1

10/22/2003

Fluoranthene

0.2 a'f

210

Gallery Well

12/15/2004

Fluorene

0.2 a'f

430

Gallery Well

12/15/2004

Freon 11

(Trichlorofluoromethane)

150

20,000

Gallery Well

9/30/1997

Freon 113

1,200

52,000

Gallery Well

9/30/1997

Heptachlor

0.01

0.33

RG-7B

10/16/2003

Heptachlor epoxide

0.01

0.33

WP-3S

5/10/2001

Hexachlorobenzene

1

640

Gallery Well

11/22/1999

Lead-Dissolved

15

218

B3B

1/2/1998

Lead-Total

15

584

B-5

12/31/1997

Lindane (gamma-BHC)

0.2

0.83

RIMW-8

5/10/2006

Manganese-Dissolved

50f

44,000

Gallery Well

11/15/2004

Manganese-Total

50f

44,000

Gallery Well

4/13/2005

MTBE

13

7,000

Gallery Well

7/18/2000

Methylene Chloride

5

1,700,000

PSCT-1

5/23/2002

Naphthalene

0.2 a'f

150,000

SW-17

4/15/2005

Nickel-Dissolved

100

3,830

Gallery Well

11/5/1998

Nickel-Total

100

26,100

Gallery Well

11/22/1999

19

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-7. Dissolved Chemicals in Groundwater that Exceed Maximum Contaminant Levels

Chemical

MCL
(Hg/L)

Maximum Detected
Concentration (|Jg/L)
(Hg/L)

Location

Date

OCDD

0.00003

112

RIPZ-8

10/19/2006

OCDF

0.00003

16

RIPZ-8

10/19/2006

o-Xylene

1,750 d

29,000

PSCT-1

10/22/2003

PCBs

0.5

3,000

Gallery Well

4/13/2005

PCP

1

81

RGPZ-6B

4/18/2005

Pyrene

0.2 a'f

290

Gallery Well

12/15/2004

Selenium-Dissolved

50

2,900

Pond 13

10/28/2004

Selenium-Total

50

1,600

Pond 13

10/28/2004

Styrene

100

1,100

Rd Sump

7/20/2000

Tetrachloroethylene

5

140,000

Gallery Well

9/30/1997

Thallium-Dissolved

2

22

A2B

9/12/1997

Thallium-Total

2

86

A2B

9/12/1997

Toluene

150

98,000

Gallery Well

9/30/1997

trans-l,2-Dichloroethene

10

2,300

PSCT-1

5/23/2002

Trichloroethylene

5

120,000

PSCT-1

5/23/2002

Vinyl Chloride

0.5

20,000

SW-17

4/15/2005

Xylene (total)

1,750

160,000

PSCT-1

10/22/2003

Zinc-Dissolved

5,000

7,810

Gallery Well

11/5/1998

Zinc-Total

5,000

6,900

Gallery Well

9/30/1997

Notes:

Source: Modified from Appendix A, Table A-3, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

California MCLs are listed above, unless otherwise noted.

a The federal MCL for PAH compounds is based on benzo(a)pyrene.

b MCL based on trihalomethane.

CMCL based on total 1,2-dichloropropene.

d MCL based on total xylenes.

e A California/federal MCL is not established; the California Notification Level is listed.

f California MCL is not established; the federal MCL is listed.

Hg/L = microgram per liter (parts per billion)

HpCDD = heptachlorodibenzo-p-dioxin

HpCDF = heptachlorodibenzofuran

HxCDD = hexachlorodibenzo-p-dioxin

HxCDF = hexachlorodibenzofuran

MTBE = methyl tert-butyl ether

PCP = pentachlorophenol

PeCDD = pentachlorodibenzo-p-dioxin

PeCDF = pentachlorodibenzofuran

TCDD = tetrachlorodibenzo-p-dioxin

TCDF = tetrachlorodibenzofuran

20

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-8. Sitewide Medium-Specific EPCsfor Each COC

Media

COC

EPC -
Concentration

Units

Basis - Location/Depth

Basis -
Data

Soils

MCPP

118

mg/kg

Sitewide Surface Soils: 0-0.5 foot bgs

UCL

(HHRA)a



49.2

Mg/kg
mg/kg

Sitewide Shallow Soils: 0-5 feet bgs
Offsite B-Drainage Soils: 0-5 feet bgs

UCL
ND



PCE

0.1590

mg/kg

Sitewide Surface Soils: 0-0.5 feet bgs

UCL





11.28

mg/kg
mg/kg

Sitewide Shallow Soils: 0-5 feet bgs
Offsite B Drainage Soils: 0-5 feet bgs

UCL
ND



TCE

1.03

mg/kg

Sitewide Surface Soils: 0-0.5 feet bgs

UCL





1.22

mg/kg
mg/kg

Sitewide Shallow Soils: 0-5 feet bgs
Offsite B Drainage Soils: 0-5 feet bgs

UCL
ND

Soils

Chromium

66.0

mg/kg

Sitewide Surface Soils: 0-0.5 feet bgs

UCL

(ERA)b



49.9

mg/kg

Sitewide Shallow Soils: 0-5 feet bgs

UCL



Copper

42.3

mg/kg

Sitewide Surface Soils: 0-0.5 feet bgs

UCL





25.1

mg/kg

Sitewide Shallow Soils: 0-5 feet bgs

UCL



Zinc

103

mg/kg

Sitewide Surface Soils: 0-0.5 feet bgs

UCL





71.4

mg/kg

Sitewide Shallow Soils: 0-5 feet bgs

UCL

Surface

Arsenic (total)

220

Hg/L

Pondwide surface water

UCL

Waterc

Arsenic (dissolved)

390

Hg/L

Pondwide surface water

UCL

Soil

PCE-for HHRA

55,000

ppbv

Onsite soil vapor

Max

Vapord

PCE - for ERA

16,478

ppbv

Onsite soil vapor

UCL



PCE-for HHRA/ERA

1.1

ppbv

Offsite soil vapor

Max



TCE-for HHRA

150,000

ppbv

Onsite soil vapor

Max



TCE - for ERA

48,434

ppbv

Onsite soil vapor

UCL



TCE-for HHRA/ERA

0.69

ppbv

Offsite soil vapor

Max



1,3-Butadiene - for HHRA

54

ppbv

Onsite soil vapor

Max



1,3-Butadiene - for ERA

15

ppbv

Onsite soil vapor

UCL



1,3-Butadiene - for
HHRA/ERA

8.3

ppbv

Offsite soil vapor

Max

Notes:











a Based on Table 7-2c (Summary of EPCs for Onsite Soil Sitewide Without Ponds) and Table 7-3 (Summary of EPCs for Offsite

Soil); CSC, 2011











b Based on Table 7-2c (Summary of EPCs for Onsite Soil Sitewide Without Ponds); CSC, 2011.



c Based on Table 7-6 (Summary of EPCs for Onsite Surface Water); CSC, 2011





d Based on Table 7-8 (Summary of EPCs for Soil Vapor) and Table 7-9 (Summary of EPCs for Offsite Soil Vapor); CSC, 2011.

EPC = exposure point concentration
Max = maximum (concentration)
mg/kg = milligram per kilogram
ND = not detected
ppbv = part per billion by volume
UCL = upper confidence limit

21

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-9. Cumulative Risk and Hazard, Potential Exposures to Onsite Soil







Commercial/Industrial Worker





Trespasser



Rancher



(0

Surface Soil
- 0.5 feet bgs)

Shallow Soil
(0 to 5 feet bgs)

Surface Soil
(0 to 0.5 feet bgs)

Shallow Soil
(0 to 5 feet bgs)

Surface Soil
(0 to 0.5 foot bgs)

Shallow Soil
(0 to 5 feet bgs)

Study Area

Noncancer
Hazard

Cancer
Risk

Risk/Hazard Noncancer Cancer
Drivers Hazard Risk

Risk/Hazard
Drivers

Noncancer
Hazard

Cancer
Risk

Noncancer
Hazard

Cancer
Risk

Noncancer Cancer
Hazard Risk

Noncancer Cancer
Hazard Risk

Administration
Building

5E-02

2E-07

5E-02

2E-07



4E-03

5E-09

4E-03

5E-09

-

-

Burial Trench

4E-01

6E-06

4E-01

7E-06



4E-02

2E-07

4E-02

2E-07

-

-

Central Drainage

3E-01

9E-06

3E-01

1E-05



2E-02

2E-07

2E-02

2E-07

-

-

Former Ponds
and Pads

9E-02

8E-06

5E-01

5E-05

Tetrachloro-
ethylene

7E-03

2E-07

6E-02

2E-06

-

-

Liquid Treatment

2E+00

7E-06

MCPP 2E+00

6E-06

MCPP

1E-01

1E-07

1E-01

1E-07

-

-

Maintenance
Shed

1E-01

3E-06

1E-01

3E-06



7E-03

5E-08

7E-03

5E-08

-

-

RCRA Canyon

1E-01

5E-07

9E-02

4E-07



8E-03

1E-08

6E-03

8E-09

-

-

Roadways

2E-01

5E-06

2E-01

5E-06



1E-02

1E-07

1E-02

1E-07

3E-02 9E-07

3E-02 8E-07

Remaining Onsite

1E-01

5E-06

1E-01

4E-06



9E-03

1E-07

1E-02

9E-08

-

-

West Canyon
Spray

8E-02

5E-07

7E-02

6E-07



5E-03

1E-08

4E-03

1E-08

-

-

Notes:

Source: Modified from Table 8-1, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
surface soil = soil between 0 and 0.5 feet bgs
shallow soil = soil between 0 and 5 feet bgs
- = not applicable

22

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-10. Cumulative Risk and Hazard, Potential Exposures to Offsite Soil and Offsite Sediment





Recreator



Rancher



Surface
(0 to 0.5 foot bgs)

Shallow
(0 to 5 feet bgs)

Surface
(0 to 0.5 foot bgs)

Shallow
(0 to 5 feet bgs)

Study Area

Noncancer
Hazard

Cancer
Risk

Noncancer Cancer
Hazard Risk

Noncancer
Hazard

Cancer
Risk

Noncancer Cancer
Hazard Risk

Offsite Soil3

3E-03

7E-09

3E-03 7E-09

1E-02

3E-08

1E-02 3E-08

Offsite Sedimentb

7E-04

7E-09

--

3E-03

3E-08

--

Notes:

Source: Modified from Table 8-2, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
a Potential exposures to offsite soils are evaluated based on data collected from the B Drainage.

b Potential exposures to offsite sediment are evaluated based on data collected from North Drainage, A Drainage, and Lower
and Upper C Drainages. Exposure pathways evaluated for offsite soil/sediment include: incidental ingestion, dermal contact,
and outdoor inhalation.

In addition to the above pathways, ingestion of beef is also evaluated for a rancher.

- = not applicable

23

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-11. Cumulative Risk and Hazard, Potential Exposures to Onsite Sediment

Commercial/Industrial Worker

Trespasser

Surface Sediment
(0 to 0.5 foot bgs)

Shallow Sediment
(0 to 5 feet bgs)

Surface Sediment
(0 to 0.5 foot bgs)

Shallow Sediment
(0 to 5 feet bgs)

Noncancer Cancer
Study Area Hazard Risk

Noncancer Cancer
Hazard Risk

Noncancer Cancer
Hazard Risk

Noncancer Cancer
Hazard Risk

Pond 18

4E-02

2E-07

3E-02

2E-07

2E-03

3E-09

2E-03

3E-09

Pond A-5

7E-02

2E-07

7E-02

1E-07

5E-03

5E-09

4E-03

5E-09

Notes:

Source: Modified from Table 8-3, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
CSC and EPA agreed that two treated liquids impoundments, Pond A-5 and Pond 18, will be drained as part of site
remediation. Therefore, potential exposure to pond waters from these two areas were not considered in the HHRA.
However, pond sediments were evaluated as exposed surface soils because the ponds will be drained.

24

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-12. Cumulative Risk and Hazard, Potential Exposures to Onsite Surface Water

Commercial/Industrial Worker

Trespasser

Noncancer	Risk/Hazard Noncancer

Study Area	Hazard Cancer Risk	Drivers	Hazard Cancer Risk

A-Series Pond

7E-02

5E-05

Arsenic

8E-03

2E-06

Pond 13

1E-01

8E-05

Arsenic

1E-02

3E-06

RCF Pond

7E-02

5E-05

Arsenic

8E-03

2E-06

Notes:

Source: Modified from Table 8-4, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
CSC and EPA agreed that two treated liquids impoundments, Pond A-5 and Pond 18, will be drained as part of site
remediation. Therefore, potential exposure to pond waters from these two areas were not considered in the HHRA.
However, pond sediments were evaluated as exposed surface soils because the ponds will be drained.
- = not applicable

25

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-13. Cumulative Risk and Hazard, Potential Outdoor Air Exposures to Onsite Soil Vapor
(Commercial/Worker)	

CO PC

Noncancer Hazard

Cancer Risk

1,1,1-Trichloroethane

4E-04

—

1,1,2-Trichloroethane

2E-06

2E-10

1,1-Dichloroethane

4E-04

1E-07

1,1-Dichloroethylene

3E-03

--

1,2,4-Trimethylbenzene

7E-06

~

1,2-Dichloropropane

1E-04

2E-09

1,3,5-Trimethylbenzene

1E-06

~

1,3-Butadiene

8E-05

9E-09

1,4-Dichlorobenzene

2E-08

6E-11

2-Hexanone

1E-07

--

4-Ethyltoluene

2E-07

~

Acetone

1E-06

~

Benzene

1E-06

5E-10

Bromomethane

8E-07

--

Carbon disulfide

2E-08

~

Carbon tetrachloride

2E-03

1E-06

Chloroethane

7E-10

2E-12

Chloroform

6E-04

6E-08

Chloromethane

4E-07

--

cis-l,2-Dichloroethene

1E-03

~

Cyclohexane

2E-08

~

Ethanol

2E-07

~

Ethylbenzene

5E-08

~

Freon 11 (Trichlorofluoromethane)

2E-04

--

Freon 113 (l,l,2-trichloro-l,2,2-trifluo

1E-04

~

Heptane

6E-08

~

Hexane

3E-06

~

Isopropanol

4E-07

--

Methyl ethyl ketone

1E-06

--

Methyl isobutyl ketone (MIBK)

9E-09

~

26

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-13. Cumulative Risk and Hazard, Potential Outdoor Air Exposures to Onsite Soil Vapor
(Commercial/Worker)	

CO PC

Noncancer Hazard

Cancer Risk

Methylene chloride

1E-05

2E-09

Styrene

8E-10

--

Tetrachloroethylene

4E-03

3E-07

Tetrahydrofuran

3E-06

7E-10

Toluene

3E-07

--

Total Xylenes

2E-06

--

Trichloroethylene

9E-03

2E-07

Vinyl chloride

7E-05

2E-07

Cumulative Risk

2E-02

2E-06

Notes:

Source: Modified from Table 8-5, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
The soil vapor-to-outdoor air pathway was evaluated using onsite soil vapor data.

- = not applicable

27

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-14. Cumulative Risk and Hazard, Administration Building - Potential Indoor Air Exposures to Vapors Emanating
from Soil (Commercial/Industrial Worker)	

CO PC

Noncancer Hazard

Cancer Risk

1,2,3-Trichlorobenzene

2E-03

--

1,2-Dichlorobenzene

2E-04

--

1,2-Dichloroethene

3E-03

--

1-Butanol

2E-04

--

Acenaphthene

2E-06

--

Acetone

5E-05

--

Anthracene

2E-07

--

Benzene

3E-02

8E-06

Carbon disulfide

8E-03

--

Ethylbenzene

1E-04

--

Fluorene

8E-07

--

Methyl ethyl ketone

9E-06

--

Naphthalene

2E-03

7E-08

Pyrene

5E-08

--

Tert-Butyl Alcohol

1E-04

--

Tetrachloroethylene

2E-02

1E-06

Tetrahydrofuran

5E-05

1E-08

Toluene

6E-04

--

p-Xylene

5E-03

--

Cumulative Risk

6E-02

9E-06

Notes:

Source: Modified from Table 8-6, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).
The soil-to-indoor air pathway was evaluated using Administration Building soil data.

- = not applicable

28

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-15. Cumulative Risk and Hazard, Potential Exposures to Onsite Soil, Offsite Sediment, and Offsite Soil Vapor, Hypothetical Offsite Resident





Surface Soil
(0 to 0.5 foot bgs)





Shallow Soil
(0 to 5 foot bgs)



Offsite Soil Vapor





Noncancer
Hazard

Cancer Risk

Risk/Hazard
Drivers

Noncancer
Hazard

Cancer Risk

Risk/Hazard Drivers

Noncancer
Hazard

Cancer Risk

Risk/Hazard
Drivers

Administration
Building

3E-03

3E-08

-

2E-03

3E-08

-

-

-

-

Burial Trench

7E-01

1E-05

Trichloro-
ethylene

7E-01

1E-05

Trichloroethylene

-

-

-

Central Drainage

5E-02

1E-06

-

1E-01

4E-06

Benzene;
Tetrachloroethylene

-

-

-

Former Ponds and
Pads

4E-02

1E-07

-

1E+00

7E-05

Tetrachloroethylene;
Trichloroethylene

-

-

-

Liquids Treatment

1E-02

8E-08

-

1E-02

6E-08

-

-

-

-

Maintenance Shed

1E-03

8E-08

-

2E-03

8E-08

-

-

-

-

RCRA Canyon

5E-03

7E-08

-

4E-03

5E-08

-

-

-

-

Roadways

3E-02

7E-07

-

3E-02

6E-07

-

-

-

-

Remaining Onsite

1E-03

3E-08

-

1E-02

2E-07

-

-

-

-

West Canyon Spray

2E-03

2E-07

-

4E-03

2E-07

-

-

-

-

Offsite Sediment3'b

2E-01

8E-07

-

4E-03

2E-07

-

-

-

-

Offsite Soil3-c

7E-01

5E-07

-

7E-01

5E-07

-

-

-

-

Offsite Soil Vapord

7E-01

8E-07

-

7E-01

8E-07

-

3E-02

2E-06

1,3-Butadiene

Notes:

Source: Modified from Table 8-7, Final Remedial Investigation Report, Casmalia Resources Superfund Site (CSC, 2011).

Only the outdoor air pathway was evaluated for adjacent residents, assuming they are located next to the site.
aExposure pathways evaluated for offsite soil and sediment include: incidental ingestion, dermal contact, and outdoor inhalation.

Potential exposures to offsite sediment are evaluated based on data collected from North Drainage, A Drainage, and Lower and Upper C Drainages.
Potential exposures to offsite soils are evaluated based on data collected from the B Drainage.
dSoil vapor results collected offsite were used to evaluate the indoor air pathway.

- = not applicable

29

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-16. Cleanup Levels for Chemicals of Concern in Soil



Ecological RBC







Cleanup Levels

Chemicals of Concern

Surface Soil3
(mg/kg)

Subsurface Soilb
(mg/kg)

Human Health RBC
(mg/kg)

Background11
(mg/kg)

Surface Soil3 Subsurface Soilb
(mg/kg) (mg/kg)

Ecological

Chromium

74

204

—

47

74

204

Copper

25

14

—

19

25

19

Zinc

191

353

—

104

191

353

Human Health

MCPP

~

—

770d

NA

770

770

TCE

~

—

50e

NA

50

50

PCE

~

—

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-17. Sitewide Remedial Alternatives Components







Alternative 3



Alternative 5

Alternative 6





Alternative 2

Capping, Liquids Extraction, Small

Alternative 4

Capping, Liquids Extraction, P/S

Capping, Liquids Extraction, P/S Landfill



Alternative 1

Capping, Liquids Extraction, Large

Evaporation Pond

Capping, Liquids Extraction,

Landfill Dewatering, Small

Dewatering, Groundwater Extraction,

Feasibility Study Area

No Further Action

Evaporation Pond

SELECTED REMEDY

Offsite Discharge

Evaporation Pond

Offsite Discharge

Area 1 - Capped Landfills, PCB Landfill, BTA, and CDA













Capped Landfills (P/S, Heavy Metals,
Caustics/Cyanide, Acids)

RCRA Cap (existing)

RCRA Cap (existing)

RCRA Cap (existing)

RCRA Cap (existing)

RCRA Cap (existing)

RCRA Cap (existing)

PCB Landfill

-

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

BTA

-

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

CDA

-

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

Area 2 - RCRA Canyon/WCSA*













8.4-acre RCRA Canyon

-

ET Cap

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent Hybrid
Cap

5.5-acre WCSA

-

Excavate/Backfill

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent
Hybrid Cap

ET Cap and/or RCRA-Equivalent Hybrid
Cap

19.3-acre other areas

-

Stormwater BMPs

ET Cap

ET Cap

ET Cap

ET Cap

Area 3 - Former Ponds/Pads, Roadways, Remaining Onsite Areas, MSA, LTA











MSA (Location 2)

-

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

LTA (Location 1)

-

Excavate/Asphalt cap

Excavate/Asphalt cap

Excavate/Asphalt cap

Excavate/Asphalt cap

Excavate/Asphalt cap

Ponds A/B (Location 3)

-

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

South of PSCT-1 (Location 4)

-

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Excavate/PCB LF disposal

RISBON-59 (Location 10)

-

Groundwater Monitoring

Groundwater Monitoring

Groundwater Monitoring

Excavate/PCB LF disposal

Excavate/PCB LF disposal

Area 4 - Ponds













Pond 18

-

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

RCRA Cap

Pond A-5

-

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

Pond 13

-

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

Lined Cap Retention Basin

A-Series

-

RCRA Evaporation Pond

Eco-Cap/RCRA Evaporation Pond

Eco-Cap

Eco-Cap/RCRA Evaporation Pond

Eco-Cap

RCF

-

Eco-Cap

Eco-Cap

Eco-Cap

Eco-Cap

Eco-Cap

Area 5N - Groundwater - North













WMA and Tl Waiver

-

WMA and Tl Waiver

WMA and Tl Waiver

WMA and Tl Waiver

WMA and Tl Waiver

WMA and Tl Waiver

P/S Landfill













- Gallery Well

Gallery Well

Gallery Well

Gallery Well

Gallery Well

Gallery Well

Gallery Well

- DNAPL/LNAPL Ext Wells (w/ min. water)

-

DNAPL/LNAPL Extraction

DNAPL/LNAPL Extraction

DNAPL/LNAPL Extraction

-

-

- Landfill dewatering

-

-

-

-

P/S LF de-watering

P/S LF de-watering

Central Drainage Area

-	Sump 9B (contingency measure)

-	LNAPL Extraction Wells (skimming)

Sump 9B

Sump 9B

Sump 9B

Sump 9B

Sump 9B
Convert 4 existing monitoring
wells to LNAPL extraction wells

Sump 9B
Add 12 new LNAPL skimmer wells

Perimeter Containment

-	Upper HSU

-	Lower HSU

PSCT Ext

PSCT Ext
Monitor 12 new LHSU wells

PSCT Ext
Monitor 12 new LHSU wells

PSCT Ext (Offsite discharge)
Monitor 12 new LHSU wells

PSCT Ext
Monitor 12 new LHSU wells

PSCT Ext (Offsite discharge)
Extraction from 4 new LHSU wells

Monitor 8 new LHSU wells

Monitored Natural Attenuation	-	MNA	MNA	MNA	MNA	MNA

31

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EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-17. Sitewide Remedial Alternatives Components







Alternative 3



Alternative 5

Alternative 6





Alternative 2

Capping, Liquids Extraction, Small

Alternative 4

Capping, Liquids Extraction, P/S

Capping, Liquids Extraction, P/S Landfill



Alternative 1

Capping, Liquids Extraction, Large

Evaporation Pond

Capping, Liquids Extraction,

Landfill Dewatering, Small

Dewatering, Groundwater Extraction,

Feasibility Study Area

No Further Action

Evaporation Pond

SELECTED REMEDY

Offsite Discharge

Evaporation Pond

Offsite Discharge

Area 5S - Groundwater - South













Aggressive extraction

-

-

-

-

-

40 Ext wells

Perimeter Containment

PCT-A/B Extraction

PCT-A/B Extraction

PCT-A/B Extraction

PCT-A/B Extraction (Offsite
discharge)

PCT-A/B Extraction

PCT-A/B Extraction (Offsite Discharge)

Monitored Natural Attenuation

-

MNA

MNA

MNA

MNA

MNA

Area 5W - Groundwater - West













Aggressive extraction

-

-

-

-

-

40 Ext wells (Offsite discharge)

Perimeter Containment

PCT-C Extraction

PCT-C Extraction

PCT-C Extraction

PCT-C Extraction (Offsite
discharge)

PCT-C Extraction

PCT-C Extraction (Offsite discharge)

Monitored Natural Attenuation

-

MNA

MNA

MNA

MNA

MNA

Onsite Disposal to Evaporation Pond













Location

RCF, A-Series, A-5, 18, 13

A-Series (reconstructed, 11 acres)

A-Series and/or RCF
(reconstructed, 6 acres)

None

A-Series (reconstructed, 6 ac)

None

Groundwater

PSCT/PCT

PSCT/PCT

PSCT/PCT (after treatment)

-

PSCT/PCT

-

Stormwater

Sitewide, except capped
landfill area

Partial RCRA Canyon/WCSA

-

-

-

-

Offsite Disposal to TSDF













Groundwater/NAPL liquids

-

DNAPL/LNAPL, Gallery Well
liquids

DNAPL/LNAPL, Gallery Well
Liquids

DNAPL/LNAPL, Gallery Well
liquids

P/S LF liquids, Gallery Well
liquids

P/S LF liquids, Gallery Well
liquids

Offsite Disposal to Casmalia Creek













Groundwater (treated)

-

-

-

PSCT, PCT (treated)

-

PSCT/PCT, P/S LF, 80 (+/-) wells
(treated)

Stormwater

Capped Landfills

Entire site, except partial RCRA
Canvon/WCSA

Entire site

Entire site

Entire site

Entire site

Notes:

Source: Modified from Table 12-1, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

* For Area 2, Alternatives 3 through 6, the final cap may be an ET cap or RCRA-equivalent hybrid cap. The cap type and design for the three sub-areas in Area 2 will be determined during remedial design. The bold font is applied for the Selected Remedy.

BTA = Burial Trench Area

BMP = best management practice

CDA = Central Drainage Area

DNAPL = dense nonaqueous phase liquid

ET = evapotranspiration

HSU = hydrostratigraphic unit

LF = landfill

LHSU = lower hydrostratigraphic unit

LNAPL = light nonaqueous phase liquid

LTA = Liquids Treatment Area

MNA = monitored natural attenuation

MSA = maintenance shed area

NAPL = nonaqueous phase liquid

P/S = pesticides/solvent

Tl = technical impracticability

TSDF = treatment, storage, and disposal facility

WCSA =West Canyon Spray Area

WMA = Waste Management Area

32

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-18. Summary of Sitewide Remedial Alternatives Evaluation















Alternative 6













Alternative 5

Capping, Liquids







Alternative 2





Capping, Liquids

Extraction, P/S Landfill







Capping, Liquids

Alternative 3

Alternative 4

Extraction,

Dewatering,







Extraction, Large

Capping, Liquids Extraction,

Capping, Liquids

P/S Landfill

Groundwater





Alternative 1

Evaporation

Small Evaporation Pond

Extraction, Offsite Dewatering, Small

Extraction, Offsite



Evaluation Criteria

No Further Action

Pond

SELECTED REMEDY

Discharge

Evaporation Pond

Discharge

1

Overall Protection of Human Health















and the Environment

No

Yes

Yes

Yes

Yes

Yes















2

Compliance with ARARs

No

Yes

Yes

Yes

Yes

Yes

3

Long-term Effectiveness

N/A

3

9

9

9

9

4

Reduction of Toxicity, Mobility or

M /A

3

3

3

3

3



Volume through Treatment

IN/M











5

Short-term Effectiveness

N/A

3

9

3

3

O

6

Implementability

N/A

3

9

»

3

O

7

Cost

N/A

<5

3

O

O

o

8

State Acceptance

State agencies (with DTSC as the lead state agency) have expressed support for the Preferred Alternative)

9

Community Acceptance





Pending review after 60-day public comment period



Green Impacts Assessment

N/A

9



9

•

•



Capital Costs (2014 $)

$0

$53,987,000

$59,967,000

$65,737,000

$69,411,000

$93,245,000



Annual O&M Costs (2014$)

$2,724,000

$3,997,000

$4,065,000

$7,772,000

$8,464,000

$14,849,000



NPV: Capital + O&M, 30-year, 3%

$53,400,000

$115,445,000

$120,224,000

$195,733,000

$147,035,000

$291,069,000



NPV: Capital + O&M, 30-year, 7%

$33,807,000

$85,195,000

$89,499,000

$138,550,000

$113,814,000

$209,924,000

33

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES













Table 2-18. Summary of Sitewide Remedial Alternatives Evaluation





















Alternative 6











Alternative 5

Capping, Liquids





Alternative 2





Capping, Liquids

Extraction, P/S Landfill





Capping, Liquids

Alternative 3

Alternative 4

Extraction,

Dewatering,





Extraction, Large

Capping, Liquids Extraction,

Capping, Liquids

P/S Landfill

Groundwater



Alternative 1

Evaporation

Small Evaporation Pond

Extraction, Offsite Dewatering, Small

Extraction, Offsite

Evaluation Criteria

No Further Action

Pond

SELECTED REMEDY

Discharge

Evaporation Pond

Discharge

NPV: Capital + O&M, 100-year, 3%

$86,089,000

$159,052,000

$163,561,000

$282,661,000

$191,734,000

$412,474,000

NPV: Capital + O&M, 100-year, 7%

$38,875,000

$91,956,000

$96,218,000

$152,025,000

$120,744,000

$228,744,000

Balancing Criteria (Criteria Nos. 3 - 6)

Cost and Green Impacts Assessment









Q Poor

Q Low











© Poor to Moderate

© Low to Moderate









3 Moderate

3 Moderate











9 Moderate to good

9 Moderate to High









0 Good

0 High











Notes:

Source: Modified from Table 12-5, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

Green impacts assessment is not one of the nine CERCLA criteria for evaluation of alternatives; however, it is included as a consideration for selection of a remedial alternative.

NPV = net present value

O&M = operations and maintenance

34

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE

TABLES

Table 2-19. Estimated Groundwater Cleanup Times and Costs for Sitewide Alternatives 1 through 6

Area

Alternative 1
No Further Action

Alternative 2
Capping, Liquids Extraction, Large
Evaporation Pond

Alternative 3
Capping, Liquids Extraction, Small
Evaporation Pond

SELECTED REMEDY

Alternative 4
Capping, Liquids Extraction, Offsite
Discharge

Alternative 5
Capping, Liquids Extraction, P/S Landfill
Dewatering, Small Evaporation Pond

Alternative 6

Capping, Liquids Extraction, P/S Landfill Dewatering,
Groundwater Extraction, Offsite Discharge

Estimated Groundwater Cleanup Times (years)3

Area 5 Northb

N/A

>6,300

>6,300

>6,300

>6,300

>6,300

Area 5 Southc

N/A

>260

>260

>260

>260

>100

Area 5 Westc

N/A

>220

>220

>220

>220

>100

Estimated Sitewide Alternative Cleanup Costsd

Capital Costs

$0

$54.0M

$60.0M

$65.7M

$69.4M

$93.2M

O&M Costs (per year)

$2.7M

$4.0M

$4.1M

$7.8M

$8.5M

$15.0M

NPV (30 years, 7%)

$33.8M

$85.2M

$89.5M

$138.6M

$113.8M

$209.9M

NPV (30 years, 3%)

$53.4M

$115.5M

$120.2M

$195.7M

$147.0M

$291.1M

NPV (100 years, 7%)

$38.9M

$92.0M

$96.2M

$152.0M

$120.7M

$228.7M

NPV (100 years, 3%)

$86.1M

$159.1M

$163.6M

$282.7M

$191.7M

$412.5M

Notes:

a Estimated cleanup times are from Final Feasibility Study Report, Casmalia Resources Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016), including Appendix A-Technical Impracticability Evaluation. The timeframes are based on various analytical models and have considerable
uncertainty.

b The estimated cleanup time for Area 5 North is the time for PCE to diffuse out of the bedrock matrix and reach the groundwater cleanup level of 5 ng/L. This timeframe is after all DNAPL is removed from the fractures and assumes fractures are continually flushed with clean water. Given that the DNAPL
is unlikely to completely diffuse from the fractures, and the residual DNAPL cannot be completely removed by remediation, the groundwater concentrations at the site will remain above MCLs for an indeterminate length of time. These prolonged timeframes form a primary basis for EPA's proposed Tl
Zone and waiver of cleanup levels (i.e., MCLs) for groundwater in Area 5 North.

c The estimated cleanup times for Area 5 South and Area 5 West are timeframes after sources are removed, so actual timeframes will likely be longer.
d Estimated costs are from Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

Alternative 3 is EPA's Selected Remedy and is highlighted in bold.

M = million

N/A = not applicable (EPA will not be selecting Alternative 1, so cleanup times under this alternative are not provided).

35

-------
EPA RECORD OF DECISION, CASMALIA RESOURCES SUPERFUND SITE
TABLES

Table 2-20. Description and Cost Estimate Summary for the Selected Remedy

Feasibility
Study
Area

Description

Selected Remedy Component

Capital Costs
2014$

Annual
O&M Costs
2014$

Present Worth Capital + O&M Costs (2014 $)
Discount Rate

O&M

Timeframe 3% 7%



PCB Landfill, BTA, CDA, Capped Landfills Area - P/S

RCRA Cap (PCB Landfill, BTA, CDA) + Stormwater Controls + ICs + Monitoring

$14,018,000

$318,000

30-Year

$18,793,000

$14,749,000

1

Landfill, EE/CA Landfill Area

100-Year

$23,806,000

$15,526,000











30-Year

$23,301,000

$17,936,000

2

RCRA Canyon, WCSA

ET Cap (entire RCRA Canyon, WCSA) + Stormwater Controls + ICs + Monitoring

$15,655,000

$473,000

















100-Year

$30,322,000

$19,024,000



Former Ponds and Pads, Remaining Onsite Areas,

RCRA Cap (Location 2) + Excavate ([Location 3] [20']; [Location 4] [5']) + Excavate/New





30-Year

$9,888,000

$7,619,000

3

Roadways, Liquids Treatment Area, Maintenance

Asphalt Cap (Location 1) (5') + Groundwater Monitoring (Location 10) + Grading/BMPs

$6,681,000

$196,000









Shed Area

(Uncapped Areas) + Stormwater Controls + ICs + Monitoring





100-Year

$12,814,000

$8,072,000



Stormwater Ponds and Treated Liquid

Eco-Cap (RCF Pond, portion of A-Series Pond) + Construct 6-acre Lined Evaporation Pond





30-Year

$21,621,000

$16,287,000

4

Impoundments - A-Series Pond, RCF Pond,

(A-Series Pond) + RCRA Cap (Pond 18) + Lined Retention Basin (Ponds A-5,13) +

$13,131,000

$386,000









Pond A-5, Pond 13, Pond 18

Stormwater Controls + ICs + Monitoring





100-Year

$30,318,000

$17,636,000





Extraction (PSCT, Gallery Well) + Extraction (NAPL-only in P/S Landfill) + Extraction





30-Year

$31,445,000

$22,402,000

5N

Groundwater, Area 5 North

(NAPL-only in CDA, 4 wells) + Monitoring (12 new LHSU wells) + Treat and Discharge PSCT

$6,068,000

$2,128,000











Groundwater to Onsite Evaporation Pond + ICs + Monitoring (combined with Tl Waiver)





100-Year

$43,294,000

$24,240,000

5S

Groundwater, Area 5 South

Extraction (PCT-A, PCT-B) + Treat/Discharge to Onsite Evaporation Pond + MNA + ICs +

$1,781,000

$305,000

30-Year

$7,667,000

$5,216,000



Monitoring

100-Year

$11,863,000

$5,867,000



Groundwater, Area 5 West

Extraction (PCT-C) + Treat and Discharge to Onsite Evaporation Pond + MNA + ICs +

$2,633,000

$258,000

30-Year

$7,509,000

$5,290,000

5W









Monitoring

100-Year

$11,144,000

$5,853,000











30-Year

$120,224,000

$89,499,000





Total Present Worth Cost Estimate

$59,967,000

$4,064,000

















100-Year

$163,561,000

$96,218,000

Notes:

Source: Modified from Table 12-6, Final Feasibility Study Report, Casmalia Resources Superfund Site (CSC, 2016).

Present worth of capital costs are 2014 dollars, based on an average capital expenditure for each year of 5-year construction period using net discount rate of 3% and 7%. Total present worth of capital + O&M costs are 2014 dollars, based on 30- and 100-year timeframes and include 35% to 50%
contingencies.

Costs are presented using net discount rates of 3% and 7%, as suggested in EPA guidance; these are consistent with current expected inflation and return on investments. For FS Area 2, the Selected Remedy would use either an evapotranspiration or hybrid cap but cost estimate assumes an

evapotranspiration cap.

EE/CA = engineering evaluation/cost analysis

IC = institutional control

LHSU = lower hydrostratigraphic unit

36

-------
Figures

-------
BMJ

Shuman Jf

OiK' , 1

Water

ZONE 2

B-Drainage
Wetlands

GUADALUPE SANTA
MARIA

Water"

Qastnalia

/fBM 294)^./' #>*

CASMALIA

VANDENBERG

LOSCf
ALAMOS

MILITARY

LOMPOC

ROAD

A 0 2,000 4,000

A 1	1		J	=f

North Approximate scale in feet





Base Map: USGS 7.5' Topographic Quadrangles:

i" O

U.S EPA REGION IX

Casmalia, CA1959 (Photorevised 1982);

CASMALIA RESOURCES

Guadalupe, CA 1959 (Photorevised 1982)

SUPERFUND SITE



FIGURE 2-1





Site Location Map





Record of Decision



Source: Modified from Figure 1-1, Final Feasibility Study



Report, Casmalia Resources Superfund Site, Casmalia





Steering Committee, February 15, 2016 (CSC, 2016)





PR0602171402SCO ROD_Figure2-l Site Location Map.ai 2/18

-------
FORMER RCRA
LANDFILL

CAS MALI A
NEUTRALIZATION
SYSTEM (CNS)

PCB
LANDFILL

/BURIAL
CELLS UNIT

PESTICIDES/
SOLVENTS
» LANDFILL

IEAW METALS
LANDFILL

AIR OXIDATION
UNIT (WAO)

WCCB

POND 22

)AUSTICS/CYANIDES
LANDFILL

POND

POND

WASHOUT PADS

ACIDS
LANDFILL /}

POND D

POND

POND C

POND

IPOND A—5

POND

IL RECO

POND 17

POND S

POND L

POND A—4

POND 8

POND J

POND M

POND T

POND 5

POND A—3

POND 18

POND 2CT

POND
A-6

POND 9

POND A—2

POND 2

POND 101

POND 1

POND 3

POND 11

POND A—1

POND 4

POND 12

ADMINISTRATION
BUILDING AND
SCALES

POND 13

TRANSPORTATION
YARD

I #i ~l Burial Trenches, Taken From Figure A21—1—1
(Woodward—Clyde, 1988)

Injection Well Location, Taken From Figure A21—1—1
(Woodward—Clyde, 1988)

	

Former Pond or Pad
I	1 Landfills

Oil Field Waste Spreading Area
Non—RCRA Sludge Disposal Area
Former Drum Burial Area
Subsurface Clay Barrier

Clay Barrier/Extraction Trench
(Woodward—Clyde, 1988)

P/S Landfill Clay Barrier (1981 Photograph)

Notes

1.	Waste disposal unit locations taken from Figure A21—1—1
(Woodward—Clyde, 1988).

2.	Subsurface barriers and trenches taken from Figure 21—1
(Woodward—Clyde, 1988).

Approximate scale in feet

yltD5x

3 \

PROl4

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-2



Historical Site Layout



Record of Decision



Source: Modified from Figure 2-2, Final Feasibility Study Report, Casmaiia Resources
Superfund Site, Casmaiia Steering Committee, February 15, 2016 (CSC, 2016)



-------
¦





' //AJ\

^irp^lk

-s>\\

-OvC

^ v *»

¦ \M

J/^~{

Ijr—vyr^

-' \ !|j !\M£

ypi w

" aiVW ywS
! \

i

/ nmrnw.

¦ n\U'4*V

Source: Modified from Figure 2-1, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

LEGEND

c	Existing Pond

1 Former Ponds and Pads

	Landfill Limits

Capped Landfills
¦fi- Liquids Extraction Location

= = - Road Location, Dashed Where Unpaved
«Z2222J22> Central Drainage Area Collection Basin
Pipelines

Perimeter Source Control Trench (Brierly & Lyman, 1989a)

	 Perimeter Control Trench (Brierly & Lyman, 1989b)

P/S Landfill Clay Barrier (1981 Photograph)

0	500

	1	I	I	I	I

Approximate scale in feet

Topographic Source: Pacific Engineer
Associates, July 8 1998

yltD5x

\—
-------
1985-1986

12 FEBRUARY2002

Aerial image © Google Earth, 2016. Annotation by CH2M HILL, 2016.

1,000
J	I	I



U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

Approximate scale in feet

Source: Modified from Figure 2-6, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 201S (CSC, 2016)

FIGURE 2-4

Selected Site Aerial Photographs (1970-2016)
Record of Decision

H'- I	. • '	'I f. -*5 »>- "|8

-------
72 74 76 78 80 82

84 86

88

YEAR
92 94

96 98 00 02 04 06 08 10

12

14

'16

13

Site Operation Activities

EPA Response

CSC Site Work

o

1978: California Waste Hazardous Permit Issued
1978: TSCA Permit Issued for PCB Landfill

w c

§¦2
IS

ai w
°-'E
2 E

TO "O

a><

C T3
a) c
O TO

<>

i: Administrative Order on Consent
Issued. CSC Beings Work at Sit

01973: Ws

Operations Begin at Site

O* 1972:

Operational Permits Obtained

1980: RCRA Part A Notification to EPA
1980: Site Expanded to 252 Acres (Current Size)

I: RCRA Part B Permit Application and Revisions

1997: Consent Deer*

2003: General
Stormwater

Permit Issued

2004: Addendum
to General Stormwater
Permit

s. ijenerai a a	2008: B-Drainage.

Discharge \/ Wetlands Construction ®

1996-present: CSC's Ongoing Site Operation & Maintenance Activities

2004: Revised
Pondwater Management
Plan Issued



o

1992-1996: EPA Emergency Response Team On-Site	npqes

Permit Issued

O O1

2QQ3- ' 2004-2009: Rl Sampling Program
Central Drainage Area

Retention Basin Constructed

V)

a*

w .2
Q =
1989: RCRA Canyoj Landfill Waste Moved to OtherjLandfills
72-1988: Construction/Operation/Modification of Surface Impoundments

t

-------
Pesticide/Solvent Landfill (Capped)

t- Waste Management Area (WMA)

Proposed Technical
Impracticability (Tl) Zone

Landfill Cap

-Solid Waste

Caustics/Cyanide Landfill
(Capped)

Containerized
Liquid Waste

DNAPL

Central Drainage
Area

PCT-A Irench

Burial
Trench
Area

Clay —<
Barrier

Former Ponds and Pads
Subarea

PCT-B Trench

Impacted Groundwater
(Inorganics)

Clay
Barrier

PCT-C
Trench

LEGEND

Fractures

DNAPL-Filled Fractures

Proposed Technical Impracticability (Tl) Zone
¦¦¦¦ Waste Management Area (WMA)
| | Landfill Cap
~ Solid Waste
| 1 Containerized Liquid Waste
| DNAPL

••?	Extent of Dissolved Phase Organics or

DNAPL in Fractures is Uncertain

-?	 Extent of Dissolved Phase Metals is

Uncertain

Upper/Lower HSU Contact (Approximate)

	PSCT

	 PCT

	»— Groundwater Level

Area 5 North

Area 5 South

= Area 5 West

Note: Oblique graphic, not to scale, vertical
exaggeration is approximately 2 times.

<&)
¦*' PRO^

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-6



Conceptual Site Model Block Diagram

Record of Decision



Source: Modified from Figure 4-24, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

PR0602171402SCO ROD_Figure_2-6_Conceptual_Site_Model_Block_Diagram.ai 2/18

-------
Potentially Exposed Population

Past or Current	Chemical	Environmental	Potential	Potential

„ ^ ^	„ mjL mjL Current/Future Hypothetical

Sources of Release Transport Exposure Exposure Current/Future	Onsite Offsite offsite	Offsite

_ . .. mi.- ¦¦ j- r. ¦ i. I-. i. Onsite Workers	Trespasser Recreational _	_ .. .. .

Contamination Mechanisms Media Points Routes	Ranchers	Residential

Study
Area

I nf i I trati o n/Pe rco I ati o n
and Leaching

Groundwater
(shallow or deep)

Dust Generation via Wind
and During Former Facility
Operation

Ambient Air

particulate deposition

Direct contact by receptors

Surface Soils

Direct contact by receptors

Subsurface Soils



— Volatilization from Soil

Ambient Air



Vapor Inhalation



Indoor Air

Vapor Inhalation

— Volatilization from GW

Onsite
Wells (1)



Incidental Ingestion
and Dermal Contact

-













Offsite



Incidental Ingestion







Wells (2)



and Dermal Contact















Onsite



Inhalation















Offsite



Inhalation





















Onsite



Incidental Ingestion/Dermal Contact















Offsite



Incidental Ingestion/Dermal Contact















Onsite



Incidental Ingestion/Dermal Contact















Offsite



Incidental Ingestion/Dermal Contact













Ambient Air



Vapor Inhalation









Indoor Air

	~

Vapor Inhalation

—~



Wind Erosion of Soil



Locally-Raised



Offsite

-

Beef





and Surface Runoff



Beef



Ingestion





GW: groundwater

(1)	Onsite wells not used for Potable Water

(2)	Sample results collected from offsite monitoring wells do not indicate a significant impact

Potentially complete pathway will be quantitatively evaluated

Insignificant pathway: an exposure estimated to be 2 or more orders of magnitude less than by other pathways (for the same receptor), or if the likelihood of exposure by that pathway is very small (USEPA, 1989)
~ Incomplete Pathway

* Including Pond 18 and Pond A-5 Sediments assuming liquids are drained
Section 8

yt0SrX

3 \

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-7



Conceptual Site Model, Baseline Human Health Risk

Assessment, Uncapped Areas

Record of Decision



PR0602171402SCO ROD_Figure 2-7 Conceptual Site Model, Baseline Human Health Risk Assessment, Uncapped Areas.ai 2/18

-------
Potentially Exposed Population

Past or Current

Sources of
Contamination

Chemical
Release
Mechanisms

Environmental
Transport
Media

Potential
Exposure
Points

Potential
Exposure
Routes

Current/Future
Onsite
Workers

Onsite
Trespasser

Off site
Recreational

Current/Future
Off site
Ranchers

Hypothetical

Offsite
Residential

Study
Area

Infiltration/Percolation
and Leaching

Surface Runoff and
Direct Discharge

Groundwater
(shallow)

seepage

Surface Water
and Sediment

particulate deposition

volatilization

Dust Generation via
Wind and during
Former Facility Operation

Ambient
Air

Onsite
Water Bodies

Offsite
Drainages (1)

Incidental Ingestion
and Dermal Contact

Incidental Ingestion
and Dermal Contact

Inhalation







¦

mi

WiiSB









il§

S

m





IllB

(1) The Site is currently a zero discharge facility

Potentially complete pathway will be quantitatively evaluated

Insignificant pathway: an exposure estimated to be 2 or more orders of magnitude less than by other pathways (for the same receptor), or if the likelihood of exposure by that pathway is very small (USEPA, 1989)
Incomplete Pathway

~

mzj

% p„0i^

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-8



Conceptual Site Model, Baseline Human Health Risk

Assessment, Surface Water

Record of Decision



PR0602171402SCO ROD_Figure2-8 Conceptual Site Model, Baseline Human Health Risk Assessment, Surface Water.ai 2/18

-------
Source

Ecological Receptors

Primary
Media/Release
Mechanism

Secondary

Release
Mechanism

Potential
Exposure
Media

Potential
Exposure Route

Plants	Soil Invertebrates1 Reptiles2

Birds

Mammals

Chemicals in
Source Areas
Includes
T errestrial
Capped Areas
and Ponded
Areas as Dry

Notes:

Ingestion

Shallow Soil6 -r

Aiimal Uptake

Aiimal
T issue

Direct Contact
and Uptake

Ingestion

Plant Uptake



Plant Tissue



Ingestion









Surface Soil

Volatilization

Dust
Entrainment





Inhalation





Inhalation



| Ingestion |



Direct Contact

Leaching

Transport &
Migration

Groundwater5

Surface Water
Runoff

Surface Water

Ingestion

Direct Contact
and Uptake

See Freshwater Habitats
CSM (Figure 9-3)

1	The direct contact and uptake pathway quantifies for all pathways.

2	Some amphibians may be found in terrestrial areas and would have exposure pathways similar to those for reptiles.

3	Birds are assumed to be non-burrowing and therefore, exposed to surface soils only.

4	Mammals are assumed to be burrowing and therefore, exposed to surface and shallow soils.

6 Groundwater could contribute to the volatilization and inhalation pathways; inhalation of burrow air quantified using soil gas data. Groundwater-to-seeps are no longer a pathway (seeps currently dry).
6 Only ingestion of subsurface soil by burrowing mammals is a complete and significant pathway; direct contact by burrowing mammals is complete but not significant;

	and all other pathways for all receptors are incomplete.	

Explanation:

Pathway is not complete.

Pathway complete or potentially complete; exposure is considered insignificant at this time.
Pathway will be qualitatively evaluated unless found to be significant.

Pathway complete or potentially complete.

Pathway will be quantitatively evaluated.

PR0602171402SCO ROD Figure 2-9 Conceptual Site Model, Ecological Risk Assessment, Terrestrial Uncapped Areas.ai 2/18

^tDSX

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-9



Conceptual Site Model, Ecological Risk Assessment,

Terrestrial Uncapped Areas

Record of Decision



-------
Source

Release
Mechanism

Potential
Exposure
Media

Ecological Receptors

Potential Exposure
Route

Plants

Invertebrates

Reptiles4

Birds

Mammals

Chemicals in
Capped Areas

Volatilization

Leaching /

Notes:

Air

Groundwater

Inhalation

Direct Contact and
Uptake

Ingestion

Surface Water
Exchange**

* Some amphibians may be found in terrestrial areas and would have exposure pathways similar to those for reptiles.
** See Seeps under Terrestrial Uncapped and Freshwater Habitat CSMs.

Explanation:

Pathway is not complete.

Pathway complete or potentially complete; exposure is considered insignificant at this time.
Pathway will be qualitatively evaluated unless found to be significant.

Pathway complete or potentially complete.

Pathway will be quantitatively evaluated.

J""**

i A t,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-10

Conceptual Site Model, Ecological Risk Assessment,
Terrestrial Capped Areas
Record of Decision

PR0602171402SCO ROD_Figure 2-10 Conceptual Site Model, Ecological Risk Assessment, Terrestrial Capped Areas.ai 2/18

-------
Ecological Receptors

Source

Primary
Media/Release
Mechanism

Secondary

Release
Mechanism

Potential
Exposure
Medium

Potential Exposure
Route

Aquatic Plants Aquatic Life1 Amphibians

1,2

Birds

Mammals

Chemicals in
Ponded Areas
as Wet and

Offsite
Drainages

Volatilization

Ambient Air

Surtace Water

Sediment

Animal Uptake

Animal Tissue

r

Plant Uptake

Plant Tissue

Surface Water

Leaching

Transport &
Migration

Groundwater

Seeps4

Ingestion

Direct Contact or

Inhalation

J—

Ingestion

Ingestion

Ingestion

Direct Contact or
Uptake

Ingestion

Direct Contact or
Uptake

Inhalation of
volatiles3

Ingestion

Direct Contact or
Uptake

Notes: 1 The direct contact and uptake pathway quantifies for all pathways.

2	Some amphibians may be found in terrestrial areas (see Figures9-1 and 9-2).

3	Inhalation pathway quantified via soil gas; see terrestrial CSM (Figure 9-1).

4	Seeps are currently dry and therefore, no complete exposure pathways. Risk from seeps based on historical data are discussed qualitatively in the ERA.

Explanation:

Pathway is not complete.

Pathway complete or potentially complete; exposure is considered insignificant at this time.
Pathway will be qualitatively evaluated unless found to be significant.

Pathway complete or potentially complete.

Pathway will be quantitatively evaluated.

J""**

i A t,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-11

Conceptual Site Model, Ecological Risk Assessment,
Freshwater Habitat Areas
Record of Decision

PR0602171402SCO ROD_Figure 2-11 Conceptual Site Model, Ecological Risk Assessment, Freshwater Habitat Areas.ai 2/18

-------
Explanation

Approximate Boundary of Groundwater Basin
Casrialla Resources Facility
|	1 HMs

- — River/Creek
—Roads

Pacific Coast
— — Vandenbur© Air Force Base Boundary
—Groundwater Flow Direction

Source: Topographic base map provided by Pacific Engineering, Inc. from aerial survey dated March 4, 2004.

/ A "t,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

'*1 pho-^

Approximate scale in miles

SANTA MARIA VALLEY GROUNDWATER BASIN

~-V4

" \ i

Shuman Creek Drainage Area

Approximate scale in miles

SAN ANTONIO GROUNDWATER BASIN

SITE

Source: Modified from Figure 4-6, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

FIGURE 2-12

Local Groundwater Basins
Record of Decision

PR0602171402SCO ROD_Figure 2-12 Local Groundwater Basins.ai 2/18

-------
Oil Company Property

Casmalia Resources Aquisition
Property Company

Agricultural Property

Casmalia Resources Property

113-260-004,

Casmalia Resources
Aquisition Property
Company

Agricultural Property

Legend

Casmalia Disposal Site
Casmalia Resources Property
J Casmalia Resources Acquisition Property Company a
J Oil Company Property

Agricultural-Zoned Property (west/south of Site)	North

Agricultural-Zoned Property (east of Site)

| 1 Highlighted parcels with existing institutional
controls (land use covenants)

Source: Modified from Figure 7-3, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

County Assessor's Parcel Boundaries

2,400

J	I	L

4,800

Approximate scale in feet

/W!\

i o \
\W/

PRO"



U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-13

Parcel Ownership in Site Vicinity
Record of Decision

PR0602171402SCO ROD_Figure 2-13 Parcel Ownership in Site Vicinity.ai 2/18

-------
Remaining

On-Site

Area

Area 3

Maintenance Shed Area

Burial
Trench
Area

RCRA Canyon

PCB
Landfill

Former
Ponds
and Pads
Subarea

Liquid Treatment Area

Capped Landfills

Area 2

PONfil-i

Area 1

tPONP 2,

WpondiI

I West
j Canyon
/ Spray Area

jGal/erijf.WelJ

POND,

Area 4

Area 3

itjQNO'R

Central
Drainage
Area

PQNpl6

Remaining
On-Site
Area

SgtBjij,

-PQNtV

POND
| A-5 I

PON~B'6\

f },/ y j-A ''•? ¦

Ipqmde A v-.---1.	//~"s 	¦

Former Ponds and Pads Subarea

¦pAbjM,

Area 3

POND S

POfJDl'

Area 3

Remaining
I On-Site
i Area

pond j\ A p4^!4f\ j'

PAD ?a:

POND t

Area 4

A-SERIES
POND ,

'POND

lis 1

pdfyn-y



SQND ;V->

potmv

RCFPOND

Area 4

PONDi]

Administration
Building Area

Fotfn

POND

Remaining On-Site
Area —

POND
13 if

Area 4

Area 4

Explanation
FS Study Area Boundary

Area 1
LJ Area 2
Area 3
Area 4

Other Site Features

	 Casmalia Site Boundary

L _ I Rl Study Area
i	| Existing Extent of Capped Landfills

P/S Landfill Clay Barrier (1981 Photograph)

Perimeter Source Control Trench (Brierly & Lyman, 1989a)

Perimeter Control Trench (Brierly & Lyman, 1989b)

	 Buttress

Burial Trench Location (Figure A21-1-1 Woodward-Clyde, 1988)

Historical Natural Drainage

(Based on 1956 Photo, 1974 Topographic Maps,

and Figures 21-2 and 21-3 Woodward-Clyde, 1988)

Historical Feature

"	 Former Waste Burial Area

k * * Fence

Oil Field Waste Spreading Area (Based on 1983,1985/86 Photos)

Oil Field Waste Spreading Area
(Figure A21 -1-1 Woodward-Clyde, 1988)

1983 Spray Area

Stormwater Pond

Treated Liquid Impoundment

Source: Topographic base map provided by Pacific Engineering, Inc.
from aerial survey dated March 4, 2004.

0	440

	1	i	i	i	i

Approximate scale in feet

/ Q \

1321

v 
-------
Remaining

On-Site

Area

Maintenance Shed Area

Burial
Trench
Area

RCRA Canyon

Former
Ponds
and Pads
Subarea

Liquid Treatment Area

Capped Landfills

Area 5 North

Area 5 West

¦ v

| West
j Canyon
I Spray Area

.Gallery Well

Central
Drainage
Area



Remaining
On-Site
Area

¦m\ix

POND

) M A-5

4 v '

Former Ponds and Pads Subarea

PCT-C Extraction
Trench

POND

PO/VD S?

Remaining
I On-Site
I Area

POND J)

Ar ea 5 South

POND
: IS

POti&t

A-SERIES L
POND i

KSVDiZ

RCFPOND

Administration
Building Area

Remaining On-Site
Area

PCT-A Extraction
T rench

POND

13

PCT-B Extraction
Trench

Explanation

D Area 5 North
Area 5 West
Area 5 South
Other Site Features

	 Casmalia Site Boundary

L _ ] Rl Study Area
I __ _] Existing Extent of Capped Landfills
Piezometer
V Monitoring Well

Liquids Extraction Well

P/S Landfill Clay Barrier (1981 Photograph)

Perimeter Source Control Trench (Brierly & Lyman, 1989)

PCT Extraction Trench

Clay Barrier

	 Buttress

Burial Trench Location (Figure A21-1-1 Woodward-Clyde, 1988)

Historical Natural Drainage

(Based on 1956 Photo, 1974 Topographic Maps,

and Figures 21-2 and 21-3 Woodward-Clyde, 1988)

Historical Feature

	 Former Waste Burial Area

'"i Fence

Oil Field Waste Spreading Area (Based on 1983,1985/86 Photos)

Oil Field Waste Spreading Area
(Figure A21-1-1 Woodward-Clyde, 1988)

1983 Spray Area

t Stormwater Pond

Treated Liquid Impoundment

Source: Topographic base map provided by Pacific Engineering, Inc.
from aerial survey dated March 4, 2004.

-L

Approximate scale in feet

o \

Mj

t'RC)'*'



U S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-15

Feasibility Study Area 5
Record of Decision

Source: Modified from Figure 8-1B, Final Feasibility Study Report, Casmalia Resources Supeifurid Site,
Casmaiia Steering Committee, February 15, 2016 (CSC, 2016)

WFilFWWJWWirea 5-iK®I

-------
LEGEND

>	~3 Recommended for Closure

				mmi

Sources:

Brieriey & Lyman, Pond Closure Certification Report and
Casmalia Resources and RWQCB Status Reports

] Closure Process Incomplete: Constituents in
Excess of Target Cleanup Levels (TCLs)
Locally Left in Place

^ Recommended for Closure as Landfill by
Capping as Part of Selected Remedy

yltD5x
s \

USB/

\	
-------
LEGEND
Zone 1 Boundary
Ponds

Caustic Cyanide Landfill
Metals Landfill

Former RCRA Landfill
Pesticide Solvent Landfill
PCB Landfill
Acids Landfill

Pre-development paleo drainage
Water Table Flow Vectors

Water Table Elevation Contour
(ft-MSL)

Ground Surface Elevation

Note:

Zone 1 Boundary is
extrapolated from Figure 1
and is approximately located

/ A \	U.S EPA REGION IX

CASMALIA RESOURCES
\V|f-V	SUPERFUND SITE

Source: Modified from Figure 2-1, Final Feasibility Study Report, Casmaiia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)	

PR0602171402SCO ROD_Figure 2-17 Water Table Potentiometric Surface, December 2015.ai 2/18

FIGURE Figure 2-17

Water Table Potentiometric Surface, December 2015
Record of Decision

-------
RGRA
Tan d fill

Pesticide
Solvent
Landfill

Metals
Landfill

ibletLNAPL

. C a li sti c/Cy an id e

ible DNAPL

Potential DNAPL Zone

Landfill



.irnr

Acids
landfill

POND
A-5

P5.3 - 10.0 feet
>10 feet

Extent of metals in sediment in excess of RBCs
0-5.3 feet

Extent of metals in soil in excess of RBCs
0-5.3 feet
>5.3 - 10.0 feet
>10 feet

Indicates Elevated TDS in Existing Pond Water
and RCRA Canyon Storm Water Runoff

i A "t,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

Ar

p„o^

FIGURE 2-18

Summary of Chemical Detections and Exceedances -
All Media

Record of Decision

PR0602171402SCO ROD_Figure 2-18 Summary of Chemical Detections and Exceedances- All Media.ai 2/18

-------
Location 1

Location 2

RISSRS

11





Analyte

Depth

Resu1t

Uni ts

Zn

0

360

mg/kg

Cu

0

350

mg/kg

Cr

0

470

mg/kg

Cu

i

21

mg/kg



RISBON-

75





Analyte

Depth

Resu1t

Uni ts

Cu

5

150

mg/kg

Cr

5

130

mg/kg

J Cu

8

24

mg/kg



RISBON-

78





Analyte

Depth

Resu1t

Uni ts

Cu

5

27

mg/kg



RISBLT-02





Analyte

Depth

Resu1t

Units

1 Total DDT

0

3. 1

mg/kg

MCPP

0

1400

mg/kg



RISBLT-

07





Analyte

Depth

Resu1t

Uni ts

Zn

9

120

mg/kg



RISBLT

10





Analyte

Depth

Resu1t

Un i ts

Zn

0.5

280

mg/kg

Cu

0.5

96

mg/kg



RISBLT-

11





Analyte

Depth

Resu1t

Uni ts

J Cu

5

86

mg/kg



RISBLT

12





Analyte

Depth

Resu1t

Uni ts

I Cu

0

32

mg/kg

-

RISSUS-Ol

Analyte Depth	Result Units

Cu	0	30 mg/kg

RISSMS-02

Analyte Depth	Result Units

Zn	0	210 mg/kg

Cu	0	93 mg/kg

Ba	0	1100 mg/kg

Cr	0	83 mg/kg

RISBMS-

02







Analyte

Depth

Resu1t

Un

ts

TEQ

0

19.0521164 pg

/g











RISBMS-

04







Analyte

Depth

Resu1t

Units



Cu

0.5

51

mg/kg



Cr

0,5

300

mg/kg



Zn

6.5

330

mg/kg



Cr

6,5

130

mg/kg







RISBMS

11







Analyte

Depth

Resu1t

Uni ts



Zn

0

350

mg/kg



Cu

0

170

mg/kg

\

Ba

0

1300

mg/kg



V—-

Cr

0

180

mg/kg



RISBON-37





Analyte Depth

Result

Un its

PCE 5

560

mg/kg

PCE 10

1600

mg/kg



RISBON-63





Analyte Depth

Resu1t

Un its

TCE 0

0.074

mg/kg

RISS0N-02





Analyte Depth

Resu1t

Units

Cu 0

29

mg/kg



RISBON-27





Analyte Depth

Resu1t

Units

Cu 5

45

mg/kg

RISS0N-20





Analyte Depth

Result

Un i ts

PCBC 0

0.6430553

mg/kg

Cu. 0

48

mg/kg

Ba 0

2800

mg/kg

RISSON-27

Analyte Depth	Result Units

Total DDT 0	0.26	mg/kg

PCBC	0	0.5992564 mg/kg

RISSON-39

Analyte Depth Result Units
I Total DDT 0	0.12 mg/kg

RISS0N - 40

Analyte Depth	Result Units

Total DDT 0.5	0.14 mg/kg

Total DDT 4.5	0.15 mg/kg



RISB0N

72





Analyte

Depth

Resu1t

Uni ts

Cu.

0

59

mg/kg

Ba

0

3800

mg/kg

Explanation
Soil Sample Locations

A Surface Soil (Type 2)

Surface to Shallow Soil (Type 3)
Surface to Medium Soil (Type 4)
Surface to Deep Soil (Type 5)

O
0
~

©

Surface to Deep Soil - Groundwater
and/or Contact if Encountered (Type 6)

NAPL (Type 7)

Other Site Features

I® Approximate Hotspot Location 1

	Casmalia Site Boundary

[ 1 FS Study Area Boundary
l"' Rl Study Area Limits
Liquids Extraction Weil
P/S Landfill Clay Barrier (1981 Photograph)
¦ Perimeter Source Control Trench (Brierly & Lyman, 1989)
Perimeter Control Trench (Brierly & Lyman, 1989)

Historical Feature

	 Former Waste Burial Area

** - " Fence

S3 Stormwater Pond
Esza Treated Liquid Impoundment

Source: Topographic base map provided by Pacific Engineering, Inc.
from aerial survey dated March 4, 2004.

Note:

'Posted data grouped and labeled by hotspot location

©



| A \

\MU

RO^

420

Scale in Feet (1 inch = 420 feet)

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-19

Soil Hotspot Locations with Exceedences
Record of Decision

PR0602171402SCO ROD Figure 2-19 Soil Hotspot Locations with Exceedences.ai 2/18

-------
Former

tlla.v
Barrier

'^sticide/
Solvent

Metals
\ Landfill

-10% (Freon 113
only)

Vleasurab e LNAPL

easurable DNAPL

1% (Freon 113 only)

/

Clay Barrier -

Trench

Acids
^andfil

PCT-C Trench

ZONE

POND
18

A-SERIES
POND

POND

Clay Barrier

PCT-A Trench

POND
13

Clay Barrier-

PCT-B Trench

SCALE IN FEET

LEGEND

Burial Trench

Landfill Boundaries

Facility and Zone 1 Boundary

Perimeter Source Control Trench (PSCT)

Perimeter Control Trench (PCT)

Clay Barrier

Creek

Pond Outline

Total VOCs

Dissolved Concentration Contour of
LNAPL Constituents greater than 1%, 10%
of aqueous solubility

Measurable LNAPL (Free Phase)

Dissolved Concentration Contour of DNAPL
Constituents greater than 1%, 10% of
aqueous solubility

Measurable DNAPL (Free Phase)

Historical Natural Drainage

Note: Dissolved concentrations of DNAPL
inferred surrounding areas of measurable
DNAPL.

^tDSX

p A t,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

PRO""*9

FIGURE 2-20

LNAPL, DNAPL, and Total VOCs in Upper HSU
Record of Decision

PR0602171402SCO ROD_Figure 2-20 LNAPL, DNAPL, arid Total VOCs iri Upper HSU.ai 2/18

-------
Former

FCB
Landfill

""Oaj
Barrier

Pesticide/ >
'JSa! '

Metals
+jni{riTTl

Cau stic/Cyanide

^ 4 ¦ n '

Measurable DNAPL

1% (Freon 11? only)

ay Barrier

^French

Aci^ i
Landfill/
/ I/
/ /

PCTC Trench #

POhfD
A/5

POND

A-SERIES
POND

POND

Clay Barriei

PC.T-A Trench

Clay Barrier

PCT-B Trench

LEGEND

Burial Trench

Landfill Boundaries

Facility and Zone 1 Boundary

Perimeter Source Control Trench (PSCT)

Perimeter Control Trench (PCT)

Clay Barrier

Creek

Pond Outline



Anthropogenic Metals

Background Metals

Arsenic
. s"~\ Cadmium
. /" \ Nickel

Selenium

Dissolved Concentration Contour of
LNAPL Constituents greater than 1%, 10%
of aqueous solubility

Measurable LNAPL (Free Phase)

Dissolved Concentration Contour of DNAPL
Constituents greater than 1%, 10% of
aqueous solubility

Measurable DNAPL (Free Phase)



Historical Natural Drainage

Note: Dissolved concentrations of DNAPL
inferred surrounding areas of measurable
DNAPL.



\



U.S EPA REGION IX

CASMALIA RESOURCES

SUPERFUND SITE

N

FIGURE 2-21

LNAPL, DNAPL, and Metals in Upper HSU
Record of Decision

PS3»S1?M«5SK?	PSSWJs. IWWM itrUqiB-ifilfcu SlSH8

-------
-------
Former

PCB
Landfill

"Clay
Barrier

Potential DNATL «

Clay Barrier

PCT-C Trench

Meacur

JNAPL

ZONE 1

POND
18

A-SERIES
POND

POND

Clay Barrier'

PCT-A Trench

POND
13

Clay Barrier

PCT-B Trench

LEGEND

Burial Trench

Landfill Boundaries

Facility and Zone 1 Boundary

Perimeter Source Control Trench (PSCT)

Perimeter Control Trench (PCT)

Clay Barrier

Creek

Pond Outline

Anthropogenic Metals

Background Metals

V

V

Arsenic

\ Cadmium not detected above criteria
\ Nickel
Selenium

Dissolved Concentration Contour of DNAPL
Constituents greater than 1%, 10% of
aqueous solubility

Measurable DNAPL (Free Phase)

V	

Presence of DNAPL inferred by DNAPL at
Landfill/Lower HSU contact
Potential DNAPL Zone. Horizontal and Vertical
extent uncertain.

Historical Natural Drainage

i A	U.S EPA REGION IX

CASMALIA RESOURCES
\	SUPERFUND SITE

FIGURE 2-23

DNAPL and Metals in Lower HSU
Record of Decision

PR0602171402SCO ROD_Figure 2-23 DNAPL and Metals in Lower HSU.ai 2/18

-------
Burial Trench

RISKS TO SOIL INVERTEBRATES

Burial Trench

Maintenance
Shed

RISKS TO TERRESTRIAL PLANTS

Other Features
Presumptive Remedy Areas
Property Boundary

Roadway Samples Outside
Presumptive Remedy Area
Roadway Samples Inside
Presumptive Remedy Area

RISKS ASSOCIATED WITH SOIL INVERTEBRATES
OR TERRESTRIAL PLANTS

A.#OR *

O
O

SOIL CONCENTRATION <= UTL

OR HQLOWEST-EFFECT LEVEL < 1
COPPER HQ LOWE ST-EFFECT LEVEL >= 1
CHROMIUM HQ LOWE ST-EFFECT LEVEL >=
ZINC HQLO WEST-EFFECT LEVEL >= 1

GRAPHIC SCALE
325 650

I Feet

NOTES

BASE IMAGERY FROM STATE OF CALIFORNIA,

UNIVERSAL TRANSVERSE MERCATOR PROJECTION (UTM)
ON THE NORTH AMERICAN DATUM OF 1983. SOURCE
IMAGE DATE IS 1994.

California

/®s\

» o \

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-24



Co-Located Risks to Ecological Communities

Assuming Barium is Not Toxic

Record of Decision



PR0602171402SCO ROD_Figure 2-24 Co-Located Risks to Ecological Communities Assuming Barium is NotToxic.ai 2/18

-------
Burial Trench

Maintenance
Shed

RISKS TO ORNATE SHREW

Burial Trench

Maintenance
Shed

RISKS TO WESTERN MEADOWLARK (INVERTIVORE)

LEGEND

| | Landfills
I Ponds

I	

Other Features
Presumptive Remedy Areas
Property Boundary

Roadway Samples Outside
Presumptive Remedy Area
Roadway Samples Inside
Presumptive Remedy Area

A ,• OR *

RISKS ASSOCIATED WITH ORNATE SHREW OR
WESTERN MEADOWLARK (INVERTIVORE)

SOIL CONCENTRATION <= UTL

OR H Ql-0 WE ST- EFFECT LEVEL < 1
0 COPPER HQlOWEST-EFFECT LEVEL >= 1
O CHROMIUM HQ LOWEST-EFFECT LEVEL >= 1
ZINC HQLOWE ST- EFFECT LEVEL >= 1

GRAPHIC SCALE
325 650

I Feet

NOTES

O

BASE IMAGERY FROM STATE OF CALIFORNIA,

UNIVERSAL TRANSVERSE MERCATOR PROJECTION (UTM)
ON THE NORTH AMERICAN DATUM OF 1983. SOURCE
IMAGE DATE IS 1994.

California

/®s\

» o \

ISBI

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-25



Co-Located Risks to Wildlife Receptors

Assuming Barium is Not Toxic

Record of Decision



PR0602171402SCO ROD_Figure 2-25 Co-Located Risks to Wildlife Receptors Assuming Barium is NotToxic.ai 2/18

-------
2 FT

VARIABLE





VEGETATION COVER

W5ETATIVE LAYER
(EVAPOIRANSPIRAUVe)

A A A A A A A A A' A'

BIOTIC BARRIER
(GEONET)

GEOCOMPOSITE
DRAINAGE LAYER

- GEOMEMBRANE

GEOSYNTHETIC
CLAY LINER (GCL)

-VEGETATION COVER





VEGETATIVE LAVER

2 FT



(EVAPOTHANSPIRATIVE)

'V•'.* ~".*•'.* •*.

VARIABLE !





RCF Pond

FILL/LEVELING LAYER

DETAIL A - TYPICAL RCRA
CAP SECTION

NOT TO SCALE

PCB Landfill CDA, BTA, MSA

VEGETATION COVER
^

'1 FT

5 FT

DETAIL E - TYPICAL ECO-CAP - SOIL CAP
NOT TO SCAL£

STORMWATER

JTT

	1— MA.yr'myin flu itT.'.>.iT&r»rt*VrT.'rti ¦ iVwii>ni . it	If r

3

300 MIL GEONET
GEOTEXTILE

> GEOCOMPOSITE UNER
HOPE

Pond A-5, Pond 13

FILL/LEVELING LAYER

LEVELING LAYER

DETAIL B - TYPICAL ff RCRA-EQUIVALENT
MONO SOIL CAP SECTION

NOTES:

1.	CAPS A. B, C, AND D ARE USED IN APPLICATIONS THAT
PREVENT OR MINIMIZE RAINWATER INFILTRATION.

2.	CAP E IS USED TO PREVENT POTENTIAL EXPOSURE TO
ECOLOGICAL RECEPTORS.

3.	CAP F IS USED TO LINE THE STORMWATER RETENTION
BASINS.

4.	CAP G IS ONLY CONSIDERED IN THE LIQUID TREATMENT
AREA.

5.	CAP H IS USED TO LINE THE EVAPORATION POND AND
INCLUDES A LEACHATE COLLECTION AND RECOVERY
SYSTEM (LCRS) COMPOSED OF A 300 MIL GEONET
DRAINAGE LAYER THAT DRAINS TO A SUMP. THE POND
BOTTOM IS SLOPED AT 1% TO COLLECT ANY LEACHATE
THAT PENETRATES THE PRIMARY LINER.

6.	USE OF OFFSITC BORROW SOIL IS PROPOSED FOR THE
VEGETATIVE AND FOUNDATION LAYERS (SEE FIGURE 10-2)
BORROW SOIL IS A CLAYSTONE MATERIAL AND WILi NEED
SOME PRE-PROCESSING SUCH AS SCREENING AND
PULVERIZING TO REDUCE PARTICLE SIZE.

7.	FOUNDATION LAYERS WILL BE COMPACTED TO 90%
RELATIVE COMPACTION WHILE VEGETATIVE LAYERS WILL BE
TREATED WITH SOIL AMENDMENTS (E.G. BIOSOLIDS) AND
LIGHTLY COMPACTED (85% RELATIVE COMPACTION).

RCRA CanyonAA/CSA (Optional)

DETAIL F-LINED CAP
RETENTION BASIN

NOT TO SCAL£

DIVERSION
BERM

NOT TO SCALE

GROUND SURFACE

4 FT

1 FT

RCRA CanyonAA/CSA (Optional)

ASPHALT

AGGREGATE BASE

RUNOFF

Liquid Treatment Area

LEVELING LAYER

DETAIL C - TYPICAL EVAPOTHANSPIRATIVE

	CAP SECTION 	

NOT TO SCALE

VARIABLE

v ,i ¦, V t y i i. -v ¦_ .<.». ..

UC-rrrA-ntf I AVCD

VEGETATIVE LAYER

(EVAPOTHANSPIRATIVE)	M /—

~V A A A A /\	VS /

Si •	/

BIOTIC BARRIER
"(GEONET)

GEOTEXTILE
DRAINAGE LAYER

TO SUMP
(LEACHATE
COLLECTION
AND
REMOVAL
SYSTEM)

-LEVELING LAYER

DETAIL G - TYPICAL ASPHALT CAP
CROSS SECTION
NOT TO SCALE

1% EVAPORATION POND WATER

??•'.''s. '..ir;•. S !?¦¦¦¦'¦<¦"*¦. '
"s-';	SOL COVER ''-. '• i':	r

GEOCOMPOSITE
"DRAIN

LYSIMETER
GEOMEMBRANE

ROOT
BARRIER

DETAIL I - TYPICAL ACAP
TYPE LYSIMETER SECTION

NOT TO SCAL£

HDPE LINER

60 MIL HDPE GEOMEMBRANE (PRIMARY)
300 MIL GEONET DRAINAGE LAYER
60 MIL HDPE GEOMEMBRANE (SECONDARY)
VAOOSE ZONE LEAK DETECTION SYSTEM

FILL/LEVELING LAYER
VADOSE ZONE

FILL/LEVELING LAYER

DETAIL D - TYPICAL RCRA-EQUIVALENT

	HYBRID CAP SECTION 	

NOT TO SCALE

Source: Modified from Figure 10-1 A. Final Feasibility Study Report, Casmaiia Resources Superfund Site,
Casmaiia Steering Committee, February 15, 2016 (CSC, 2016)

RCRA Canyon (Optional)

DETAIL H TYPICAL RCRA
EVAPORATION POND SECTION
NOT TO SCALE

A-Series Pond



A

'<( <.»0^



U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-26

Caps Considered in Remedial Alternatives
Record of Decision

PR0602171402 SCO ROD_Figure 2-26 Caps Considered in Remedial Alternatives ,ai 2/18

-------
I v 'Area 5 North vjpr
(Technical Impracticability [Tl] Zone)

Point of Compliance
(around perimeter of
/ Tl Zone)

Area 5 South

r monitoring

bouncpSj'

jltD S>Vl,



Total Acreage of Area 5 North
= 92.90 acres

AO	500

i—i—i—i—i
North Approximate scale in feet

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-27

Location of Waste Management Area, Technical
Impracticability Zone, and Point of Compliance
Record of Decision

PR0602171402SCO ROD_Figure 2-27 Location of Waste Management Area, Technical Impracticability Zone, and Point of Compliance.ai 2/18

-------
NORTH RCRA
CANYON

CONCRETE-LINED CHANNEL
FOR UNCAPPED FLOW

SW FLOW DIVIDE

PERIMETER STORMWATER DITCH

///AREA 2

WEST RCRA
CANYON

PCB LANDFILI

GRADING
AND BMPs

CONCRETE-LINED
CHANNEL FOR
CAPPED FLOW

P/S LANDFILL

EXISTING CAPPED LANDFILLS

BURIAL TRENCH
AREA (BTA)

AREA 1

GALLERY
WELL

CENTRAL DRAINAGE
AREA (CDAi,—'

PSCT

PROPOSED LINED RETENTION
BASIN IN FOOTPRINT OF
POND A—5

MAINTENANCE
SHED AREA

SUMP 9B

POND
A-5

PCT-C EXTRACTION
TRENCH

GRADING
AND BMPs

PERIMETER
STORMWATER
DITCH

DRAINAGE CHANNEL

AREA 3

A-SERIES POND

POND 18

CLAY BARRIER

CONVEYANCE PIPE

PROPOSED
EVAPORATION POND
IN A-SERIES POND
FOOTPRINT

RCF POND

, RIP-RAP
CULVERT

^ PCT-B EXTRACTION TRENCH

CLAY BARRIER

PCT-A EXTRACTION TRENCH

POND 13

FIGURE 2-28

Sitewide Remedial Alternative 2 - Capping, Liquids
Extraction, Large Evaporation Pond
Record of Decision

Source: Modified from Figure 12-1 A, Final Feasibility Study Report, Casmalia Resources Superfund Site,
Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

LEGEND:

LIMITS OF STUDY AREA (AREAS 1-4)

PSCT TRENCH

PCT EXTRACTION TRENCH	^
	 CLAY BARRIER ©

EXISTING RCRA CAP
PROPOSED RCRA CAP

EXISTING MONITORING WELL

EXISTING EXTRACTION WELL

PCT AND PSCT EXTRACTION WELLS

NAPL-ONLY EXTRACTION WELL

EXISTING PIEZOMETER

PROPOSED UPPER HSU MONITORING WELL

LHSU MONITORING WELL

RIP RAP

CHANNELED STORMWATER FLOW
NATURAL STORMWATER FLOW

EVAPOTRANSPIRAT1VE (ET) CAP
ECO CAP - SOIL CAP (RCF POND) HS-11 SOILHOTSPOT1
UNED EVAPORATION POND (A-SERIES POND)

LINED RETENTION BASIN (POND A-5, POND 13)

EXCAVATION (5') AND BACKFILL

EXCAVATION (20*) AND BACKFILL OR COVER WITH CAP EXTENDED FROM AREA 1
EXCAVATION (5'), BACKFILL, AND ASPHALT COVER
PROPOSED ASPHALT COVER

5' EXCAVATION AND BACKFILL TO GRADE

UNCAPPED AREA INCLUDING GRADING AND BMPs

LNAPL IN UPPER HSU

DNAPL IN UPPER HSU

DNAPL IN LOWER HSU

POTENTIAL EXTENT OF DNAPL
IN LOWER HSU

NOTES:

1.	THE REMEDIAL ALTERNATIVE INCLUDES RCRA CAPS IN FS AREAS 1 AND 3, AN ET CAP IN FS AREA 2, EXCAVATION IN
FS AREA 3 AND AN ECO CAP IN AREA 4.THE EXCAVATED SOIL IN FS AREA 3 IS DISPOSED OF IN THE PCB LANDFILL
PRIOR TO CAP CONSTRUCTION.

2.	A NEW 11-ACRE UNED EVAPORATION POND IS PROPOSED IN THE FOOTPRINT OF THE A-SERIES POND.

3.	THE TREATED PSCT AND EXTRACTED PCT GROUNDWATER IS SENT TO THE EVAPORATION POND IN THE FOOTPRINT OF
A-SERIES POND.

4.	RCF POND WILL BE BACKFILLED TO RAISE THE MINIMUM BOTTOM ELEVATION TO APPROXIMATELY 415 FT MSL AND
ENSURE IT IS ABOVE THE GROUNDWATER LEVEL

5.	THIS REMEDIAL ALTERNATIVE FOR FS AREA 5 INCLUDES OPERATING THE EXISTING PSCT, GALLERY ML AND PCT
EXTRACTION SYSTEMS AND DNAPL/LNAPL-ONLY EXTRACTION FROM 16 WELLS IN THE SOUTHERN PART OF THE P/S
LANDFILL

6.	CAPPED AREA STORMWATER FLOW IS DIRECTED THROUGH POND 13. DISCHARGED THROUGH OR AROUND WETLANDS AND
ONTO THE OFFSITE B-DRAINAGE. UNCAPPED AREAS IN FS AREA 3 SOUTH OF THE PSCT AND EAST OF LTP ROAD WILL
INCLUDE GRADING AND BMPs TO MINIMIZE EROSION.





~no**-

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

| TO "B" DRAINAGE THROUGH OR AROUND THE WETLANDS

North

Approximate scale in feet

PR0602171402SCO ROD_Figure 2-28 Sitewide Remedial Alternative 2-Capping, Liquids Extraction, Large Evaporation Pond.ai 2/18

-------
NORTH RCRA
CANYON

SW FLOW DIVIDE

PERIMETER STORMWATER DITCH

-WASTE MANAGEMENT (WMA)

WEST RCRA
CANYON

PCB LANDFILL

P/S LANDFILL

EXISTING CAPPED LANDFILLS

BURIAL TRENCH
AREA (BTA)

AREA 1

GALLERY
WELL

CENTRAL DRAINAGE
AREA (CDM^

MAINTENANCE
SHED AREA

SUMP 9B

POND
A-5

GRADING
AND BMPs

PERIMETER
STORMWATER
DITCH

•DRAINAGE CHANNEL

AREA 3

A-SERIES POND

POND 18

CLAY BARRIER

CONVEYANCE PIPE

PROPOSED
EVAPORATION POND
IN A-SERIES POND
FOOTPRINT

RCF POND

k N— RIP-RAP
CULVERT

/ PCT-B EXTRACTION TRENCH

POND 13

UNED EVAPORATION POND (A-SERIES POND)

UNED RETENTION BASIN (POND A-5, POND 13)

5' EXCAVATION WITH ET CAP

EXCAVATION (5') AND BACKFILL

EXCAVATION (20") AND BACKFILL OR COVER WITH CAP EXTENDED FROM AREA 1

EXCAVATION (5'), BACKFILL, AND ASPHALT COVER

PROPOSED ASPHALT COVER

UNCAPPED AREA INCLUDING GRADING AND BMPs

LNAPL IN UPPER HSU

DNAPL IN UPPER HSU

DNAPL IN LOWER HSU

_9 	« _ POTENTIAL EXTENT OF DNAPL

IN LOWER HSU

¦¦¦¦¦¦ WASTE MANAGEMENT AREA (WMA)

TECHNICAL IMPRACTIBILITY (Tl) ZONE & POINT OF COMPLIANCE (POC)

NOTES:

THE REMEDIAL ALTERNATIVE ASSUMES AN ET CAP FOR FS AREA 2. BUT THE ACTUAL CAP TYPE AND DETAILS WILL BE DETERMINED DURING
REMEDIAL DESIGN. THIS REMEDIAL ALTERNATIVE ALSO INCLUDES RCRA CAPS IN FS AREAS 1 AND 3, AND AN ECO CAP AND UNED PONDS IN FS
AREA 4. THE EXCAVATED SOIL IN FS AREA 3 IS DISPOSED OF IN THE PCB LANDFILL PRIOR TO CAP CONSTRUCTION.

A NEW 6-ACRE EVAPORATION POND IS PROPOSED AS SIX 1-ACRE PONDS IN THE FOOTPRINT OF THE A-SERIES POND.

THE TREATED PSCT AND EXTRACTED PCT GROUNDWATER IS SENT TO THE EVAPORATION POND IN THE FOOTPRINT OF A-SERIES POND.

RCF POND WILL BE BACKFILLED TO RAISE THE MINIMUM BOTTOM ELEVATION TO APPROXIMATELY 415 FT MSL AND ENSURE IT IS ABOVE THE
GROUNDWATER LEVEL

THIS REMEDIAL ALTERNATIVE FOR FS AREA 5 INCLUDES OPERATING THE EXISTING PSCT, GALLERY WELL AND PCT EXTRACTION SYSTEMS AND
DNAPL/LNAPL-ONLY EXTRACTION FROM 16 WELLS IN THE SOUTHERN PART OF THE P/S LANDFILL

CAPPED AREA STORMWATER FLOW IS DIRECTED THROUGH POND 13, DISCHARGED THROUGH OR AROUND THE WETLANDS AND ONTO THE OFFSITE
B—DRAINAGE. UNCAPPED AREAS IN FS AREA 3 SOUTH OF THE PSCT AND EAST OF LTP ROAD WILL INCLUDE GRADING AND BMPs TO MINIMIZE
EROSION.

THE UNSHADED AREAS ("WHITE SPACE") BETWEEN SHADED AREAS REPRESENTS LAND WHERE SOIL/SOIL
GAS DO NOT EXCEED RISK-BASED LEVELS, AND WHERE SURFACE OR NEAR SURFACE REIlCDIATION IS
NOT REQUIRED BASED ON CURRENTLY AVAILABLE INFORMATION. THIS IS SUBJECT TO CHANGE BASED
ON FORTHCOMING REMEDIAL DESIGN PLANNING ACTIVITIES.

RACTION TRENCH

1,000
	I

Approximate scale in feet



U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-29

Sitewide Remedial Alternative 3 (Selected Remedy) -
Capping, Liquids Extraction, Small Evaporation Pond
Record of Decision

LEGEND:

WASTE MANAGEMENT AREA
LIMITS OF STUDY AREA (AREAS 1-4)
PSCT TRENCH
PCT EXTRACTION TRENCH
CLAY BARRIER

EXISTING RCRA CAP

PROPOSED RCRA CAP

EVAPOTRANSPIRATiVE (ET) CAP
AND/OR HYBRID CAP

ECO CAP - SOIL CAP (RCF POND)

EXISTING MONITORING WELL

EXISTING EXTRACTION WELL

PCT AND PSCT EXTRACTION WELLS

NAPL-ONLY EXTRACTION WELL

EXISTING PIEZOMETER

PROPOSED UPPER HSU MONITORING WELL

LHSU MONITORING WELL

RIP RAP

CHANNELED STORMWATER FLOW
NATURAL STORMWATER aOW

SOIL HOTSPOT 1

^TECHNICAL IMPRACTIBILITY (Tl) ZONE & POINT OF COMPLIANCE (POC)

PROPOSED LINED RETENTION
BASIN IN FOOTPRINT OF
POND A-5

PCT-C EXTRACTION
TRENCH

~

CLAY BARRIER

1.

2.

3.

4.

5.

6.

PCT—A EXT

J TO "B" DRAINAGE THROUGH OR AROUND THE WETLANDS

PR0602171402SCO ROD_Figure 2-29 Sitewide Remedial Alternative 3 (Selected Remedy) - Capping, Liquids Extraction, Small Evaporation Pond.ai 2/18

-------
NORTH RCRA
CANYON

SW FLOW DIVIDE

PERIMETER STORMWATER DITCH

WEST RCRA
CANYON

PCB LANDFILI

P/S LANDFILL

EXISTING CAPPED LANDFILLS

BURIAL TRENCH
AREA (BTA)

AREA 1

GALLERY
WELL

CENTRAL DRAINAGE
AREA

PSCT

PROPOSED LINED RETENTION
BASIN IN FOOTPRINT OF
POND A—5

MAINTENANCE
SHED AREA

SUMP 9B

POND
A-5

PCT-C EXTRACTION
TRENCH

GRADING
AND BMPs

PERIMETER
STORMWATER
DITCH

DRAINAGE CHANNEL

AREA 3

A-SERIES POND

POND 18

CLAY BARRIER

CONVEYANCE PIPE

RCF POND

, RIP-RAP
CULVERT

^ PCT-B EXTRACTION TRENCH

CLAY BARRIER

PCT-A EXTRACTION TRENCH

POND 13

FIGURE 2-30

Sitewide Remedial Alternative 4 - Capping,
Liquids Extraction, Offsite Discharge
Record of Decision

Source: Modified from Figure 12-3A, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

| TO "B" DRAINAGE THROUGH OR AROUND THE WETLANDS

AREA 4: Ponds
AREA 5: Groundwater

LEGEND:

LIMITS OF STUDY AREA (AREAS 1-4)
PSCT TRENCH
PCT EXTRACTION TRENCH
	 CLAY BARRIER

0
~
~

EXISTING RCRA CAP
PROPOSED RCRA CAP

EVAPOTRANSPIRATIVE (ET) CAP
AND/OR HYBRID CAP

ECO CAP - SOIL CAP	HS-11

(A-SERIES. RCF POND)

LINED RETENTION BASIN (POND A-5, POND 13)

EXISTING MONITORING WELL

EXISTING EXTRACTION WELL

PCT AND PSCT EXTRACTION WELLS

NAPL-ONLY EXTRACTION WELL

EXISTING PIEZOMETER

PROPOSED UPPER HSU MONITORING WELL

LHSU MONITORING WELL

RIP RAP

CHANNELED STORMWATER FLOW
NATURAL STORMWATER FLOW

SOIL HOTSPOT 1

5' EXCAVATION WITH ET CAP

EXCAVATION (5*) AND BACKFILL

EXCAVATION (20') AND BACKFILL OR COVER WITH CAP EXTENDED FROM AREA 1



U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

0	500

r A I	I	I

North

Approximate scale in feet

EXCAVATION (5'). BACKFILL, AND ASPHALT COVER

PROPOSED ASPHALT COVER

UNCAPPED AREA INCLUDING GRADING AND BMPs

LNAPL IN UPPER HSU
DNAPL IN UPPER HSU

DNAPL IN LOWER HSU

POTENTIAL EXTENT OF DNAPL
IN LOWER HSU

Z THE PSCT AND PCT GROUNDWATER IS TREATED FOR VOC's AND INORGANICS IN AN ONSITE UQUIDS TREATMENT
PLANT AND DISCHARGED OFFSITE TO CASMALIA CREEK UNDER A SITE-SPECIFIC NPDES PERMIT.

3. RCF POND WILL BE BACKFILLED TO RAISE THE MINIMUM BOTTOM ELEVATION TO APPROXIMATELY 415 FT MSL
AND ENSURE IT IS ABOVE THE GROUNDWATER LEVEL

4. THIS REMEDIAL ALTERNATIVE FOR FS AREA 5 INCLUDES OPERATING THE EXISTING PSCT. GALLERY WELL AND
PCT EXTRACTION SYSTEMS AND DNAPL/LNAPL-ONLY EXTRACTION FROM 16 WELLS IN THE SOUTHERN PART OF
THE P/S LANDFILL

6. CAPPED AREA STORMWATER FLOW IS DIRECTED THROUGH POND 13, TO DISCHARGED THROUGH OR AROUND THE
WETLANDS AND ONTO THE OFFSITE B—DRAINAGE. UNCAPPED AREAS IN FS AREA 3 SOUTH OF THE PSCT AND
EAST OF LTP ROAD WILL INCLUDE GRADING AND BMPs TO MINIMIZE EROSION.

NOTES:

THE REMEDIAL ALTERNATIVE ASSUMES AN ET CAP FOR FS AREA 2, BUT THE ACTUAL CAP TYPE AND DETAILS
WLL BE DETERMINED DURING REMEDIAL DESIGN. THIS REMEDIAL ALTERNATIVE ALSO INCLUDES RCRA CAPS IN
FS AREAS 1 AND 3, AND AN ECO CAP IN FS AREA 4. THE EXCAVATED SOIL IN FS AREA 3 IS DISPOSED OF IN
THE PCB LANDFILL PRIOR TO CAP CONSTRUCTION.

1.

PR0602171402SCO ROD_Figure 2-30 Sitewide Remedial Alternative 4-Capping, Liquids Extraction, Offsite Discharge.ai 2/18

-------
NORTH RCRA
CANYON

SW FLOW DIVIDE

PERIMETER STORMWATER DITCH



FIVE HORIZONTAL
EXTRACTION WELLS

WEST RCRA
CANYON

PCB LANDFILl

P/S LANDFILL

EXISTING CAPPED LANDFILLS

BURIAL TRENCH
AREA (BTA)

AREA 1

¦¦•¦•¦•¦•¦•.•.v.

GALLERY
WELL

[NTRAI

.INAGE

PROPOSED LINED RETENTION
BASIN IN FOOTPRINT OF
POND A—5

MAINTENANCE
SHED AREA

SUMP 9B

POND
A-5

PCT-C EXTRACTION
TRENCH

GRADING
AND BMPs

PSCT

PERIMETER
STORMWATER
DITCH

DRAINAGE CHANNEL

AREA 3

!IES POND

POND 18

CLAY BARRIER

CONVEYANCE PIPE

RCF POND

, RIP-RAP
CULVERT

/ PCT-B EXTRACTION TRENCH

CLAY BARRIER

PCT-A EXTRACTION TRENCH

POND 13

Source: Modified from Figure 12-4A, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

y TO "B" DRAINAGE THROUGH OR AROUND THE WETLANDS

V,	U.S EPA REGION IX

CASMALIA RESOURCES
SUPERFUND SITE

500	1,000

Approximate scale in feet

FIGURE 2-31

Sitewide Remedial Alternative 5 - Capping, Liquids
Extraction, P/S Landfill Dewatering, Small Evaporation Pond
Record of Decision

LEGEND:

	 LIMITS OF STUDY AREA (AREAS 1-4) +

PSCT TRENCH
PCT EXTRACTION TRENCH
CLAY BARRIER
HORIZONTAL WELL

EXISTING RCRA CAP

PROPOSED RCRA CAP

EVAPOTRANSPIRATVE (ET) CAP
AND/OR HYBRID CAP

ECO CAP - SOIL CAP
(A—SERIES, RCF POND)

*
~

— ? —

HS-11

EXISTING MONITORING WELL
FOR LNAPL SKIMMER

EXISTING MONITORING WELL

EXISTING EXTRACTION WELL

PCT AND PSCT EXTRACTION WELLS

EXISTING PIEZOMETER

LHSU MONITORING WELL

RIP RAP

CHANNELED STORMWATER FLOW
NATURAL STORMWATER FLOW

POTENTIAL EXTENT OF DNAPL
IN LOWER HSU

SOIL HOTSPOT 1

LINED RETENTION BASIN (POND A-5, POND 13)

5' EXCAVATION WITH ET CAP

EXCAVATION (5') AND BACKFILL

EXCAVATION (20') AND BACKFILL OR COVER WITH CAP EXTENDED FROM AREA 1

EXCAVATION (5'). BACKFILL, AND ASPHALT COVER

PROPOSED ASPHALT COVER

UNCAPPED AREA INCLUDING GRADING AND BMPs

EXCAVATION (50') AND BACKFILL

NOTES:

DNAPL IN LOWER HSU

1.	THE REMEDIAL ALTERNATIVE ASSUMES AN ET CAP FOR FS AREA 2, BUT THE ACTUAL CAP TYPE AND DETAILS WILL BE
DETERMINED DURING REMEDIAL DESIGN. THIS REMEDIAL ALTERNATIVE ALSO INCLUDES RCRA CAPS IN FS AREAS 1 AND
3. AND AN ECO CAP AND LINED PONDS IN FS AREA 4. THE EXCAVATED SOIL IN FS AREA 3 IS DISPOSED OF IN THE
PCB LANDFILL PRIOR TO CAP CONSTRUCTION.

2.	A NEW 6—ACRE EVAPORATION POND IS PROPOSED AS SIX 1-ACRE PONDS IN THE FOOTPRINT OF THE A-SERIES POND.

THE FOOTPRINT OF

THE TREATED PSCT AND EXTRACTED PCT GROUNDWATER IS SENT TO THE EVAPORATION POND I
A—SERIES POND.

RCF POND WILL BE BACKFILLED TO RAISE THE MINIMUM BOTTOM ELEVATION TO APPROXIMATELY 415 FT MSL AND
ENSURE IT IS ABOVE THE GROUNDWATER LEVEL

THIS REMEDIAL ALTERNATIVE FOR FS AREA 5 INCLUDES OPERATING THE EXISTING PSCT, GALLERY WELL AND PCT
EXTRACTION SYSTEMS AND P/S LANDFILL DE-WATERING WITH HORIZONTAL WELLS IN THE SOUTHERN PART OF THE
LANDFILL LIQUIDS FROM DE-WATERING P/S LANDFILL ARE SENT OFFSITE FOR DISPOSAL

CAPPED AREA STORMWATER FLOW IS DIRECTED THROUGH POND 13, DISCHARGED THOUGH OR AROUND THE WETLANDS
AND ONTO THE OFFSITE B—DRAINAGE. UNCAPPED AREAS IN FS AREA 3 SOUTH OF THE PSCT AND EAST OF LTP ROAD
WILL INCLUDE GRADING AND BMPs TO MINIMIZE EROSION.

PR0602171402SCO ROD_Figure 2-31 Sitewide Remedial Alternative^-Capping, Liquids Extraction?P_S Landfill Dewatering, Small Evaporatioiff Pond .ai 2/18

-------
NORTH RCRA
CANYON

SW FLOW DIVIDE

PERIMETER STORMWATER DITCH

RVE HORIZONTAL
EXTRACTION WELLS

AREA 2

WEST RCRA
CANYON

PCB LANDFILI

P/S LANDFILL

EXISTING CAPPED LANDFILLS

WEST CANYON
SPMAY AREA^v

BURIAL TRENCH
AREA (BTA)

AREA 1

GALLERY
WELL

CENTRAL DRAINAGE
AREA (CDA) ,
		SUMP 9B

BB

PROPOSED UNED RETENTION
BASIN IN FOOTPRINT OF
POND A—5

MAINTENANCE
SHED AREA

POND
A-5

PCT-C EXTRACTION
TRENCH

GRADING
AND BMPs

PERIMETER
STORMWATER
DITCH

DRAINAGE CHANNEL

AREA 3

A-SERIES POND

POND 18

CLAY BARRIER

IONVEYANCE PIPE

RCF POND

RCFPOND

, x— RIP-RAP
CULVERT

/ PCT-B EXTRACTION TRENCH

CLAY BARRIER

POND 13

TO "B" DRAINAGE THROUGH OR AROUND THE WETLANDS

FIGURE 2-32

Sitewide Remedial Alternative 6 - Capping, Liquids
Extraction, P/S Landfill Dewatering, Groundwater Extraction,
Offsite Discharge
Record of Decision

LEGEND:

	 LIMITS OF STUDY AREA (AREAS 1-4)

	 PSCT TRENCH

	 PCT EXTRACTION TRENCH

	 CLAY BARRIER

HORIZONTAL WELL

*

S3

EXISTING RCRA CAP

PROPOSED RCRA CAP

EVAP07RANSPIRA71VE (ET) CAP
AND/OR HYBRID CAP

ECO CAP - SOIL CAP
(A-SERIES. RCF POND)

NEW LNAPL SKIMMER WELL
EXISTING MONITORING WELL
EXISTING EXTRACTION WELL
PCT—A AND PSCT EXTRACTION WELLS
AGGRESSIVE EXTRACTION WELL
EXISTING PIEZOMETER
LHSU MONITORING WELL
LHSU EXTRACTION WELL
RIP RAP

	—- CHANNELED STORMWATER FLOW

	 NATURAL STORMWATER FLOW

HS-11 SOIL HOTSPOT 1

UNED RETENTION BASIN (POND A-5, POND 13)

5" EXCAVATION WITH ET CAP
EXCAVATION (5") AND BACKFILL

EXCAVATION (20') AND BACKFILL OR COVER WITH CAP EXTENDED FROM AREA 1

EXCAVATION (50') AND BACKFILL

EXCAVATION (5"). BACKFILL, AND ASPHALT COVER

PROPOSED ASPHALT COVER

UNCAPPED AREA INCLUDING GRADING AND BMPs

LNAPL IN UPPER HSU
DNAPL IN UPPER HSU
DNAPL IN LOWER HSU

_ POTENTIAL EXTENT OF DNAPL
IN LOWER HSU

NOTES:

1.	THE REMEDIAL ALTERNATIVE ASSUMES AN ET CAP FOR FS AREA 2, BUT THE ACTUAL CAP TYPE AND DETAILS WILL BE DETERMINED DURING REMEDIAL
DESIGN. THIS REMEDIAL ALTERNATIVE ALSO INCLUDES RCRA CAPS IN FS AREAS 1 AND 3, AND AN ECO CAP IN FS AREA 4. THE EXCAVATED SOIL IN
FS AREA 3 IS DISPOSED OF IN THE PCB LANDFILL PRIOR TO CAP CONSTRUCTION.

2.	THE AGGRESSIVE EXTRACTION FROM AREA 5 SOUTH AND 5 WEST AND THE PSCT AND PCT GROUNDWATER IS TREATED FOR VOCs AND INORGANICS IN
AN ON SITE LIQUIDS TREATMENT PLANT AND DISCHARGED OFFSITE TO CASMALIA CREEK UNDER A SITE-SPECIFIC NPDES PERMIT.

3.	RCF POND WILL BE BACKFILLED TO RAISE THE MINIMUM BOTTOM ELEVATION TO APPROXIMATELY 415 FT MSL AND ENSURE IT IS ABOVE THE
GROUNDWATER LEVEL

4.	THIS REMEDIAL ALTERNATIVE FOR FS AREA 5 INCLUDES OPERATING THE EXISTING PSCT. GALLERY WELL AND PCT EXTRACTION SYSTEMS AND P/S
LANDFILL DE-WATERING WITH HORIZONTAL VtELLS IN THE SOUTHERN PART OF THE LANDFILL UQUIDS FROM DE-WATERING P/S LANDFILL ARE SENT
OFFSITE FOR DISPOSAL

5.	CAPPED AND UNCAPPED AREA STORMWATER FLOW IS DIRECTED THROUGH POND 13, DISCHARGED THROUGH OR AROUND WETLANDS AND INTO THE
OFFSITE B-DRAINAGE. UNCAPPED AREAS IN FS AREA 3 SOUTH OF THE PSCT AND EAST OF LTP ROAD WILL INCLUDE GRADING AND BMPs TO MINIMIZE
EROSION.

Approximate scale in feet

PCT—A EXTRACTION TRENCH

/°s'\
§ \
I®/

Kny

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

Source: Modified from Figure 12-6A, Final Feasibility Study Report, Casmalia Resources
Superfund Site, Casmalia Steering Committee, February 15, 2016 (CSC, 2016)

PR0602171402SCO ROD_Figure 2-32 Sitewide Remedial Alternative 6-Capping, Liquids Extraction, P_S Landfill Dewatering, Groundwater Extraction, Offsite Discharge.ai 2/18

-------
FROM
GROUNDWATER
EXTRACTION WELLS f
IN PCT-A,
PCT-B, AND PCT-C



EQUALIZATION
TANK





TRANSFER

//



X

PUMP

FILTER

LPGAC VESSEL LPGAC VESSEL
2,000 LBS 2,000 LBS



X

DISCHARGE
TO

EVAPORATION
POND

LPGAC VESSEL LPGAC VESSEL
2,000 LBS 2,000 LBS

PCT-A, PCT-B, AND PCT-C PROCESS FLOW

NAPL-ONLY
EXTRACTION-
LIQUIDS

VPGAC
DRUM
200 LB

VPGAC
DRUM
200 LB

VAPOR

;LNAPL'

WATER
PHASE

DNAPL

. /	£—



i

^ WATER
'PHASE

1' NAPLPHASE

VPGAC
DRUM
200 LB
OFFSITE
»- TRUCK
STEEL WATER HAUL
PHASE TANK
13,000 GAL

VPGAC
DRUM
200 LB

STEEL SETTLING
TANK
13,000 GAL

OFFSITE

TRUCK

HAUL

FROM
EXTRACTION
PUMPS

>

PSCT-

2, 3, 4

NAPL-ONLY EXTRACTION PROCESS FLOW

PR0602171402SCO ROD_Figure 2-33 Selected Remedy - Process Flow Diagram for NAPL and Groundwater.ai 2/18

GALLERY
WELL

VPGAC
DRUM
200 LB

VAPOR



LNAPL

\ \ \ \ \

x \

\ \ \ \. \ \

\ \

\ WATER

\ \

\\ PHASE N

\
\ \

V\\\v

\ \ WW

\ \
,

- / / / / /



/V DNAPL /

//

// > , 3 ,



VAPOR

WATER
PHASE

WATER
PHASE

NAPL PHASE

STEEL SETTLING
TANK
13,000 GAL

VPGAC
DRUM
200 LB

VPGAC VPGAC
DRUM	DRUM

200 LB	200 LB

OFFSITE
TRUCK
STEEL WATER HAUL
PHASE TANK

13,000 GAL OFFSITE

	TRUCK

HAUL

GALLERY WELL PROCESS FLOW

VPGAC
DRUM
200 LB

VPGAC
DRUM
200 LB

STORAGE TANK
16,000 GAL

VAPOR

J

VPGAC
DRUM
200 LB

VPGAC
DRUM
200 LB

STORAGE TANK
16,000 GAL

VAPOR

















i







¥//
w

















X

X

2,000 LBS

2,000 LBS

X

X









X



U-



1

LPGAC VESSEL n
2,000 LBS









X









EFFLUENT
TO PROPOSED
EVAPORATION
POND

LPGAC VESSEL LPGAC VESSEL LPGAC VESSEL
2,000 LBS	2,000 LBS	2,000 LBS

TRANSFER PRE-FILTERS
PUMP

FINISH-FILTERS

PSCT PROCESS FLOW

^tDSX

*•; pho^

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-33

Selected Remedy - Process Flow Diagram for NAPL and

Groundwater

Record of Decision

-------
LEGEND:

XIST1NG BENCH
OAD 1

: \ \

EXISTING GALLERY
WELL ROAD

CENTRAL DRAINAGE AREA

g

STAINLESS STEEL

NAPL-ONLY EXTRACTION WELL
IN UPPER HSU - CONTINUOUS SCREEN

NOT TO SCALE

SOUTHERN PORTION OF P/S LANDFILL

N

(,	) NAPL EXTRACTION AREA

EXISTING EXTRACTION WELL
Q	NAPL-ONLY EXTRACTION WELL {16 WELLS)

BENCH ROAD

STAINLESS STEEL

NAPL-ONLY EXTRACTION WELL
IN UPPER HSU - TWO DISCRETE SCREENS

NOT TO SCALE

100'

GRAPHIC SCALE

PnCJl4

U.S EPA REGION IX
CASMALIA RESOURCES
SUPERFUND SITE

FIGURE 2-34

Selected Remedy - Preliminary Design Details for
NAPL-Only Extraction Wells
Record of Decision

PR0602171402SCO ROD_Figure 2-34 Selected Remedy - Preliminary Design Details for NAPL-Only Extraction Wells.ai 2/18

-------