Dft_EPA_Application_Plan_5-27-21_0002.pdf

DRAFT

PCB CLEANUP APPLICATION AND PLAN

Bureau of Indian Affairs San Carlos Irrigation Project Operation and Maintenance Yard Coolidge, Arizona

PREPARED FOR:

United States Environmental Protection Agency, Region 9

75 Hawthorne Street, San Francisco, CA 94105

ON BEHALF OF:

San Carlos Irrigation Project

13805 N. Arizona Boulevard, Coolidge, AZ 85128

PREPARED BY:

Bureau of Indian Affairs, Western Regional Office

Division of Environmental and Cultural Resources Management

2600 N. Central, Phoenix, AZ 85004

BIA CONTRACTOR:

Oneida Total Integrated Enterprises

317 E. Main Street, Ventura, CA 93001

Contract Number: 140A1119P0026

Project No: 2019076

May 2021

PCB Cleanup Application and Plan BIA SCIP PCB Site Coolidge, Arizona

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TABLE OF CONTENTS

1.0 INTRODUCTION

1.1. Site Description and Background

1.1.1. Current Conditions

1.1.2. Cultural Setting

1.1.3. Surrounding Land Use

1.1.4. Biological Survey

1.2. Purpose of this Cleanup Plan

2.0 SUMMARY OF SITE INVESTIGATIONS

2.1. Initial PCB Investigation

2.2. Follow-up PCB and Underground Storage Tank (UST) Investigations

2.3. Preliminary Assessment & Removal of Fuel Storage Tanks

2.3.1. Initial Assessment (2014)

2.3.2. Supplemental Assessment (2015)

2.4. Supplemental Site Investigation Work Plan and HHRA (2018)

2.5. Supplemental Site Investigation (2019)

2.6. Cumulative Analytical Results

2.6.1. PCB AOC Areas (Onsite)

2.6.2. Northern Maintenance Yard (Onsite)

2.6.3. Perimeter Area – North

2.6.4. Perimeter Area – Southwest

2.6.5. Perimeter Area – East

2.6.6. Perimeter Area – South

2.7. Updated HHRA

3.0 ADDITIONAL SITE INVESTIGATION

3.1. Pad Area Assessment

3.2. Retention Basin Area Assessment

3.3. Step-Out Sampling

3.4. Asphalt and Concrete Assessment

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4.0 SITE SPECIFIC REMEDIATION PLAN

4.1. Site Specific Remedial Approaches

4.1.1. PCB AOC-1 and Vicinity (Onsite)

4.1.2. PCB AOC-2 (Onsite)

4.1.3. PCB AOC-3 and Vicinity (Onsite)

4.1.4. PCB AOC-4 (Onsite)

4.1.5. PCB AOC-5 and Vicinity (Onsite)

4.1.6. Northern Maintenance Yard (Onsite)

4.1.7. Perimeter Area – North (Offsite)

4.1.8. Perimeter Area – Southwest (Offsite)

4.1.9. Perimeter Area – East (Offsite)

4.2. Permits and Plans

4.2.1. Access Agreements

4.2.2. Dust Control Plan

4.2.3. Health and Safety Plan

4.2.4. Stormwater Pollution Prevention Plan (SWPPP)

4.2.5. Excavation Plan

4.3. Archaeological Monitoring

4.4. Public Notification

4.5. Site Preparation and Security Measures

4.6. Delineation of Excavation Areas

4.7. Utility Clearance

4.8. Vegetation Removal

4.9. Asphalt Removal

4.10. Remedial Excavation

4.10.1. Soil Loading, Staging, and Storage Operations

4.10.2. Decontamination Area

4.10.3. Confirmation Sampling

4.10.4. Offsite Disposal

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4.10.5. Borrow Source Evaluation, Backfill, and Site Restoration

4.10.6. Grading

4.11. Storm Water Retention and Basin Installation

4.12. Project Schedule

5.0 LABORATORY PROCEDURES

5.1. Sampling Program

6.0 REPORTING

6.1. PCB Cleanup Report

6.2. Land Use Covenant

7.0 REFERENCES

FIGURES

Figure 1 Site Location

Figure 2 Site Features and Perimeter Areas

Figure 3 PCB Areas of Concern and Exclusion Areas

Figure 4 AOC-1 and Perimeter Area – East Soil Sample Results and Excavation Details

Figure 5 AOC-2 Soil Sample Results and Excavation Details

Figure 6 AOC-3 Soil Sample Results and Excavation Details

Figure 7 AOC-4 Soil Sample Results and Excavation Details

Figure 8 AOC-5 Additional Assessment and Excavation Details

Figure 9 Northern Maintenance Yard and Perimeter Area – East Soil Sample Results and Excavation Details

Figure 10A Primary Approach, Perimeter Area - North Soil Sample Results and Excavation Details

Figure 10B Option A, Perimeter Area - North Soil Sample Results and Excavation Details

Figure 11 Perimeter Area - Southwest Soil Sample Results and Excavation Details

Figure 12 Perimeter Area – South Soil Sample Results

Figure 13 Planned Concrete Pad Area – Soil Sampling Locations

Figure 14 North Retention Basin Details

Figure 15 Asphalt and Concrete Characterization Sample Locations and Asphalt Removal Areas

TABLES (IN-TEXT)

Table 3-1 Sampling and Analysis Summary for Additional Assessment

Table 4-1 Estimated Volumes of PCB-Impacted Soil

Table 4-2 Sample Quantities by Excavation Area

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APPENDICES

Appendix A Certification Statement (Completed by Selected Contractor)

Appendix B Project Schedule (Completed by Selected Contractor)

Appendix C Site-Specific SAP (Completed by Selected Contractor)

ACRONYMS AND ABBREVIATIONS

ADEQ Arizona Department of Environmental Quality

ADOT Arizona Department of Transportation

AOC area of concern

AST aboveground storage tank

BMP best management practice bgs below ground surface

BIA Bureau of Indian Affairs

CFR Code of Federal Regulations

CGP Construction General Permit

CSM conceptual site model

EA Exclusion Area

EPC exposure point concentration ft feet

HASP Health and Safety Plan

HHRA human health risk assessment

LUC land use covenant mg/kg milligrams per kilogram mph miles per hour

NELAP National Environmental Laboratory Accreditation Program

NOI Notice of Intent

NRHP National Registry of Historic Places

OAW Outstanding Arizona Water

O&M Operation and Maintenance

OSHA Occupational Safety and Health Administration

OTIE Oneida Total Integrated Enterprises, LLC

PA Preliminary Assessment

PAH polycyclic aromatic hydrocarbons

PCB polychlorinated biphenyl ppm parts per million

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QAPP Quality Assurance Project Plan

RSL Regional Screening Level

SAP Sampling and Analysis Plan

SCIP San Carlos Irrigation Project

SHPO State Historic Preservation Office

SSI Supplemental Site Investigation

SWPPP Stormwater Pollution Prevention Plan

TPH total petroleum hydrocarbon

TSCA Toxic Substances Control Act

USEPA United States Environmental Protection Agency

UST underground storage tank

Coolidge, Arizona

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1.0 INTRODUCTION

Soil containing polychlorinated biphenyl (PCB) concentrations above human-health risk-based screening levels are present at and around the perimeter of the Bureau of Indian Affairs (BIA) San Carlos Irrigation Project (SCIP) Operation & Maintenance (O&M) Facility Maintenance Yard (the “Site”), in Coolidge, Arizona. Data collected during a 2014-2016 Preliminary Assessment (PA) of PCBs (E W Wells Group, 2017) was used to perform a human health risk assessment (HHRA) and develop a human health risk conceptual site model (CSM) in the Supplemental Site Investigation (SSI) Work Plan (Helios Resources, 2018). HHRA results indicate PCB concentrations in surface soil pose an unacceptable risk to site workers based on United States Environmental Protection Agency (USEPA) Regional Screening Levels (RSLs). Data collected during the 2019 SSI (OTIE, 2020) was used to further refine the original CSM and HHRA.

Site characterization results indicate that data collected is sufficient to move forward with remedial action at the Site. In compliance with Toxic Substances Control Act (TSCA) of 1976, which regulates PCBs in the United States, this proposed PCB Cleanup Application and Plan (Cleanup Plan) summarizes the lateral vertical extent of PCB contamination at the Site and proposed details for remedial action to achieve cleanup objective.

The Cleanup Plan is organized by the following sections: Introduction, Summary of Investigations, Additional Site Investigation, Site Specific Remediation Plan, Laboratory Procedures, and Reporting.

Appendices A through C will be completed and submitted by the selected remedial contractor following interim approval of the Cleanup Plan by the USEPA. Remedial activities will commence upon completion and approval of Appendices A through C.

1.1. SITE DESCRIPTION AND BACKGROUND

The 20-acre SCIP Maintenance Yard and adjoining project offices are located at 13805 N. Arizona Boulevard, approximately two miles north of downtown Coolidge, Arizona at the junction of Highways 87 and 287 (Figure 1). The property includes SCIP offices, a large maintenance yard, maintenance shops, a former herbicide and possible pesticide storage area, and a former diesel-powered electric generating plant and metering building. Approximately one third of the Site is paved. An electrical substation is located inside a gravel-covered, fenced area near the center of the Maintenance Yard. Prior to removal in 2014, one 100,000-gallon diesel aboveground storage tank (AST), two 6,000-gallon lubricating oil product ASTs, one 1,000-gallon used motor oil AST, and one 2,000-gallon diesel pressure relief AST were located on Site. Site features are shown on Figure 2.

Transformers with oil containing PCBs were used and managed at the Site for many years prior to regulation by the USEPA. Between 1930s and 1970s, a standard practice of SCIP personnel included releases of used oil from decommissioned PCB and non-PCB containing transformers to mitigate dust from unpaved parking areas and roadways within the SCIP Maintenance Yard.

Site description details are presented in the PA (E W Wells Group, 2017) and SSI Work Plan (Helios Resources, 2018) and summarized below.

1.1.1. Current Conditions

Current SCIP operations include distribution and metering of electricity and irrigation water utilities;

storage and service of electrical transformers; fuel storage and fueling operations; and parking and maintenance of vehicles and heavy-duty electricity and irrigation equipment. SCIP does not currently generate electricity, but transmits and distributes purchased electricity, and distributes irrigation water

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for agricultural customers on the Gila River Indian Community lands and the San Carlos Irrigation and Drainage District lands located in central Pinal County.

1.1.2. Cultural Setting

The Site and adjacent properties are located within the National Registry of Historic Places (NRHP)-eligible prehistoric archaeological site known as the Grewe Site. The Grewe Site is culturally sensitive and several tribes consider it a traditional cultural property. Previous excavations at the Grewe Site have identified buried artifacts and features including canals, pit houses, communal earth ovens, and burials.

Due to the cultural sensitivity of the Site, future remediation plans will be coordinated with input from the Arizona State Historic Preservation Office (SHPO) and tribal representatives.

1.1.3. Surrounding Land Use

Land use around the Site is generally agricultural. The SCIP Maintenance Yard, which is owned by the BIA, is identified by the Pinal County Assessor’s Parcel Number 209-10-0110. Properties adjacent to the Site are shown on Figure 3 and include the following:

1. Union Pacific Railroad Parcel, a portion of which is identified as Perimeter Area–East, is directly east of the Yard and is a right-of-way for the rail line (Parcel Number 209-10-0200).

2. State of Arizona Parcel South, portions of which are identified as Perimeter Area–Southwest and Perimeter Area–South, is owned by the state (Parcel Number 209-10-0160). The southern part of the property is used by Arizona Department of Transportation (ADOT) as the right- of-way for Highway 287.

3. MLC Family Trust Parcel, a portion of which is identified as Perimeter Area–North, is owned by MLC Farms LLC (Parcel Number 209-10-0070).

4. The BIA owns the parcels to the west of the Yard (Parcel Numbers 209-10-010A and 10B).

1.1.4. Biological Survey

A preliminary ecological reconnaissance was completed in 2017 with a query of the United States Fish and Wildlife Service Information, Planning, and Conservation system and the Arizona Game and Fish Department’s Heritage Data Management System. Results were presented in a Biological Report included in the SSI Work Plan (Helios Resources, 2018). Three federally protected species, two with proposed critical habitat, are located within one 7.5-minute quadrangle of the project area, and four special status species have been documented 5 five miles of the project limits. A formal biological assessment to determine impacts to State and Federally protected species may be required prior to remediation activities at the Site. However, based on the Site setting, project limits and background, potential future effects on the identified species are not anticipated.

1.2. PURPOSE OF THIS CLEANUP PLAN

The purpose of this Cleanup Plan is to comply with the Toxic Substances Control Act (TSCA) of 1976, which regulates PCBs in the United States. This plan describes the proposed activities to remediate the Site to unrestricted use, under a risk-based cleanup approach as defined in TSCA [40 Code of Federal Regulations (CFR) § 761.61(c)]. This plan describes the planned extent and methods of remedial activities, and the sample collection and analysis procedures to be followed to verify the removal of soil exceeding the following USEPA-approved PCB cleanup goals in milligrams per kilogram (mg/kg) (Helios Resources, 2018):

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• Onsite Areas: 10 mg/kg;

• Perimeter Area–East: 2 mg/kg; and

• Perimeter Area–North and –Southwest: 0.23 mg/kg (USEPA residential RSLs [USEPA, 2020b]).

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2.0 SUMMARY OF SITE INVESTIGATIONS

2.1. INITIAL PCB INVESTIGATION

The BIA investigated the Yard for PCBs in 1982 and found concentrations above 50 parts per million (ppm) in near-surface and subsurface soil north of the old diesel building and at the northeast corner of the transformer storage area. The initially identified ground surfaces with elevated PCB concentrations were paved with asphaltic concrete pavement as an interim measure to limit PCB migration and to mitigate human health hazards (BIA RFP, 2013).

2.2. FOLLOW-UP PCB AND UNDERGROUND STORAGE TANK (UST) INVESTIGATIONS

The BIA conducted additional PCB soil sampling in 1991 (GPI, 1991) to delineate PCB contamination documented in the 1982 investigation. Five distinct areas of PCB contamination at the Site were identified with PCB concentrations above 50 ppm to a depth of 1 foot below ground surface (bgs); these were designated as PCB areas of concern (AOCs) 1 through 5 (Figure 3). Three of the AOCs had been previously paved. Additional sampling locations reportedly contained PCB concentrations of less than 50 ppm, although supporting data was not included in the report.

Total petroleum hydrocarbons (TPH) in soil were evaluated at two Site locations, including: (1) adjacent to the 100,000-gallon diesel AST and (2) at the former pump dispenser island area located near the southeast corner of Building 113. TPH was detected at up to 16,000 mg/kg at depths up to approximately 30 feet (ft) bgs.

2.3. PRELIMINARY ASSESSMENT & REMOVAL OF FUEL STORAGE TANKS

The PA was planned and implemented with technical support and direction provided by the USEPA Region 9 TSCA Program Office. Soil analytical results indicated localized and shallow areas of PCB contamination in the Yard and on adjacent, private properties. Project details are presented in the PA Report (E W Wells Group, 2017). The sections below provide a synopsis of the PA Report, with a focus on the PCB assessment activities.

2.3.1. Initial Assessment (2014)

The initial assessment, from October 14 through November 9, 2014, included subsurface investigations at AOCs 1 through 5. In preparation for the assessment, the Yard was divided into 40-foot grid squares to establish a reference grid for sampling locations. PCB assessment activities included drilling and sampling a total of 228 shallow borings (up to 3 ft bgs) using a direct-push geoprobe drill rig, as follows:

• The focus was on the initial five PCB AOCs; consequently, borings were drilled at a closer spacing of 10 to 15 ft in the AOCs; and

• The larger overall Yard grid samples were located using a 40-foot grid spacing pattern.

A 2.0-inch diameter macro sampler equipped with an acrylic sample liner was utilized to collect soil samples in unpaved areas. In paved areas, the upper sample was initiated from directly beneath the pavement to the desired depth. At the five AOCs, samples were collected at depths from 0 to 3 inches, 3 inches to 1 foot, and 1 foot to 2 ft bgs. Additional PCB grid locations were sampled at approximately 0 to 3 inches, and 3 inches to 1 foot bgs. The perimeter areas were sampled using hand tools from 0 to 3 inches and 3 to 12 inches.

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2.3.2. Supplemental Assessment (2015)

The supplemental assessment was completed from June 16 through 25, 2015 and included collecting soil samples to identify and characterize potential PCB contamination in near-surface soil in “perimeter area” properties located to the northwest, north, west, southwest and east of the Yard. These assessments were necessary for BIA to characterize contamination, both at the federally-owned SCIP property, and at adjacent parcels to determine the extent of PCB contamination in the soils. In addition, the supplemental assessment included collection of near-surface soil samples from each of three distinct areas within the Yard, designated as Exclusion Areas (EA) 2 through 4. Sampling and analysis of soil in the Exclusion Areas were necessary to evaluate whether these locations could be excluded from future remedial action.

Sampling density within the Perimeter and Exclusion Areas varied during the supplemental assessment phase of the work, between 10-foot and 20-foot grid spacing. A 20-foot grid spacing for samples was selected for Exclusion Area 2 (substation). A 10-foot grid sample spacing was selected for Exclusion Areas 3 and 4. Perimeter areas were sampled on a 20-foot grid spacing. Soil samples were collected by hand, using a small shovel and manual digging from a depth of 0 to 3 inches bgs.

2.4. SUPPLEMENTAL SITE INVESTIGATION WORK PLAN AND HHRA (2018)

Previous PCB investigations performed between 1982 and 2016 identified PCB concentrations above human-health risk-based screening levels in soils at and around the perimeter of the Site. Data collected during the 2014 – 2016 PA of PCBs (E W Wells Group, 2017) were used to perform the HHRA and develop a human health CSM in the SSI Work Plan (Helios Resources, 2018). The purpose of the SSI was to improve definition of the extent of PCBs in soil at and around the Site. Results of the HHRA were used in developing the SSI sampling plan. The HHRA results indicated PCB concentrations in established Site exposure areas posed risks within or below the USEPA risk range. The following are offsite exposure areas, identified as Perimeter Areas: Perimeter Area–Northwest, Perimeter Area–North, Perimeter Area–East, Perimeter Area–Southwest, Perimeter Area–South, and Perimeter Area–West. The following are onsite exposure areas: historical PCB Areas of Concern (AOCs) 1-5 (five separate exposure areas), exclusion areas 1-4, and the remainder of the sampling grid not included in the two onsite areas defined above, identified as “GRID.” Perimeter Area–Northwest and Perimeter Area–West were recommended for no further assessment and no action based on the SSI Work Plan HHRA. The remaining exposure areas were recommended for further evaluation, including collection of additional soil samples.

2.5. SUPPLEMENTAL SITE INVESTIGATION (2019)

The BIA conducted SSI field activities in October and November 2019 to improve characterization of the extent of PCBs in soil onsite and offsite at adjacent properties to refine the HHRA. Data collected during the SSI was used to develop a remediation approach to protect onsite and offsite commercial workers and future hypothetical offsite residents from PCB exposure, evaluate whether TPH has enhanced the vertical mobility of PCBs in soil, determine if perched groundwater is present beneath the Site at depths up to 120 feet bgs, and determine if perched groundwater is impacted by TPH, PCBs or polycyclic aromatic hydrocarbons (PAHs).

A total of 171 surface soil samples were collected at depths of 0 to 3 inches bgs from onsite and offsite areas. A total of 15 shallow subsurface soil samples from 3 to 12 inches bgs were collected from the Perimeter Area – North, Onsite Northeast Corner, and Onsite Former Transformer Areas 1 and 2.

Surface soils were collected using a hand trowel; shallow subsurface soil samples were collected from soil cores obtained from hand augers.

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2.6. CUMULATIVE ANALYTICAL RESULTS

2.6.1. PCB AOC Areas (Onsite)

During the PA, all five AOCs had PCB concentrations greater than 10 mg/kg at various sample depths.

Figures 4 through 8 show the assessment areas, and depths and concentrations of detected PCBs, as summarized below.

• AOC 1 had 20 boring locations, with a total of 60 samples collected at various depths. Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 25,000 mg/kg (Figure 4). A total of 27 of the 60 samples (45%) exceeded the cleanup goal of 10 mg/kg.

• AOC 2 had 16 boring locations, with a total of 48 samples collected at various depths. Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 700 mg/kg.

(Figure 5). A total of 18 of the 48 samples (37.5%) exceeded the 10 mg/kg cleanup goal.

• AOC 3 had 20 boring locations, with a total of 60 samples collected at various depths. Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 540 mg/kg (Figure 6). A total of 19 of the 60 samples (31.7%) exceeded the cleanup goal of 10 mg/kg.

• AOC 4 had 25 boring locations, with a total of 75 samples collected at various depths. Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 130 mg/kg (Figure 7). Highest concentrations were found in either the 0 to 3-inch interval or the 3 to 12-inch interval. In most cases, reported concentrations were below 1 mg/kg below 1 foot. A total of 32 of the 75 samples (42.7%) exceeded the cleanup goal of 10 mg/kg.

• AOC 5 had 15 boring locations, with a total of 45 samples collected at various depths. Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 380 mg/kg (Figure 8). Highest concentrations were found in either the 0 to 3-inch interval or the 3 to 12-inch interval. In most cases, reported concentrations were below 1 mg/kg below 1 foot. A total of 16 of the 45 samples (35.6%) exceeded the cleanup goal of 10 mg/kg.

2.6.2. Northern Maintenance Yard (Onsite)

During the SSI, a total of 23 soil samples were collected from 0 to 3 inches bgs in the Northern Maintenance Yard area. Aroclor 1260 was detected in each sample, ranging from 0.64 mg/kg to 230 mg/kg (Figure 9). A total of six samples (26.1%) exceeded the cleanup goal of 10 mg/kg.

2.6.3. Perimeter Area – North

During the PA, sampling in Perimeter Area-North consisted of the collection of 133 soil samples on 20-foot centers. During the SSI, an additional 22 soil samples were collected at the same 20-foot grid centers. The area is generally unpaved, with variable amounts of vegetation, some of which is very dense. This area likely received surface run-off from the northern end of the SCIP property, where initial assessment results indicated that PCBs were present at concentrations greater than 0.23 mg/kg.

Reported PCB concentrations during both the PA and SSI events ranged from not detected at the laboratory reporting limit, to 59 mg/kg. A total of 77 of the 133 samples (58%) contained PCB concentrations at or above the 0.23 mg/kg cleanup goal. In general, concentrations were highest along the southern end of the area (nearest the Yard northern fenceline), and moderated toward the north.

PCB results for Perimeter Area–North are presented on Figures 10A and 10B.

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2.6.4. Perimeter Area – Southwest

During the PA, sampling in the Perimeter Area–Southwest consisted of the collection of 32 soil samples on 20-foot centers. During the SSI, an additional 12 soil samples were collected. The area is asphalt-covered parking/storage and encompasses an area outside the SCIP fence, which is in an ADOT easement. The area is directly south and slightly east of the yard fence where initial assessment results indicated that PCBs were present at concentrations greater than 0.23 mg/kg. This area may have received surface run-off or windblown sand and silt from the Yard.

Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 6.2 mg/kg.

A total of 14 of the 44 samples (31.8%) exceeded the cleanup goal of 0.23 mg/kg. PCB results for the Perimeter Area–Southwest are presented on Figure 11.

2.6.5. Perimeter Area – East

During the PA, sampling in the Perimeter Area–East consisted of the collection of 99 soil samples on 20-foot centers. During the SSI, an additional 6 soil samples were collected. The area is a strip of dirt located east of the SCIP yard fence line, between the fence and an elevated railroad track, which is currently in use. Due to several previous soil samples collected along the eastern fence perimeter, additional information was required between the fence and the railroad tracks.

Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 19 mg/kg. A total of 7 of the 104 samples (7%) exceeded the cleanup goal of 2.0 mg/kg. PCB results for the Perimeter Area–East are presented on Figures 4 and 9.

2.6.6. Perimeter Area – South

During the PA, sampling in the Perimeter Area–South consisted of the collection of 26 soil samples from a total of 18 sample locations. During the SSI, an additional 43 soil samples were collected. BIA re-establish the Perimeter Area–South, to be bounded on the north by the property fence line (corrected in 2017), on the west by Perimeter Area–Southwest, and on the east by Union Pacific property. The southern boundary aligns with the Perimeter Area–Southwest southern boundary. Perimeter Areas- South and -Southwest represent the ADOT property between the site and highway.

Reported PCB concentrations ranged from not detected at the laboratory reporting limit, to 2.1 mg/kg.

A total of 1 of the 43 samples (7%) exceeded the cleanup goal of 0.23 mg/kg. PCB results for the Perimeter Area–South are presented on Figure 12.

2.7. UPDATED HHRA

An updated HHRA was completed pursuant to the goals of the SSI, to refine the HHRA presented in the SSI Work Plan, and determine what, if any, remediation is necessary under a risk-based cleanup approach defined in USEPA TSCA 40 CFR § 761.61(c). Each offsite and onsite exposure area was evaluated for risk to human health by developing an exposure point concentration (EPC) using the existing PCB concentration data combined with the 2019 SSI data set.

A 95% upper confidence limit of the mean (UCL) was the representative statistic used to obtain the EPC for exposure areas. The 95% UCL was developed with the latest version of USEPA ProUCL statistical software, version 5.1.002, using the program’s recommended UCL. Human health risk was calculated using the online USEPA RSL Calculator (USEPA, 2020a). Default inputs were used for risk calculation at the 1x10-6 risk level and 1.0 hazard quotient. Default residential receptor inputs were used for the calculation of risk in perimeter areas, and default composite worker inputs were used for calculation of

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risk onsite. Analytical results from the additional soil samples collected in November 2019 were combined with the existing PA soil data from 2014-2015 to calculate EPCs, given as the 95% UCL as recommended by the ProUCL software, and the associated cancer risk and non-cancer hazard.

In offsite exposure areas Perimeter Area – Southwest and Perimeter Area-North, the EPC was recalculated for hypothetical exposure mitigation to refine the planned removal areas. The resulting EPCs for both areas are below their respective USEPA-approved RSLs/PCB cleanup goals following removal action. For Perimeter Area – South, the EPC was calculated to be 0.213 mg/kg, which is below the respective USEPA-approved RSL/PCB cleanup goal, thus will require no further action. In onsite exposure areas, following the general removal of soil above the PCB cleanup goal of 10 mg/kg at AOCs 1 through 5 and the Northern Maintenance Yard values were within the USEPA risk management range.

Coolidge, Arizona

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3.0 ADDITIONAL SITE INVESTIGATION

Based on discussions with the USEPA and the results of the SSI, additional sampling is recommended prior to start of site remediation activities. PCB soil, concrete, and asphalt data gaps exist within the Yard. Assessment of a future concrete pad area and two future retention basins are proposed.

Additional PCB step-out soil sampling is recommended in the following areas: AOC-1, AOC-2, AOC-3, AOC-4, AOC-5, and the Northern Maintenance Yard. PCB asphalt sampling is recommended in the following areas: AOC-1, AOC-2, AOC-3, AOC-4, and AOC-5. PCB concrete sampling is recommended in one area, AOC-2.

The sections below detail the proposed additional site investigation activities.

3.1. PAD AREA ASSESSMENT

SCIP personnel removed the former onsite concrete pad in 2019 south of AOC-1 and north of AOC-2 (Figure 13). As such, the surface and near surface (up to 2 ft in depth) soils were never assessed in this area (Pad Area). The results of the assessment will be used to evaluate in-place soil for both the assessment of PCBs and to characterize prior to disposal upon installation of the concrete pad.

One hundred fourteen (114) samples will be collected at 38 proposed sampling locations within the Pad Area. They will be sampled at the surface (0-3 inches), subsurface (6-12 inches), and to 24 inches; and will be analyzed for Aroclors. The 24-inch samples will be held by the laboratory and only analyzed if the shallower samples are above the onsite cleanup goal. Figure 13 shows the proposed grid pattern and sample locations. Additional sampling details are provided in Table 3-1 below.

Following the Pad Area Assessment, soil will be excavated and disposed if results exceed the PCB cleanup goal of 10 mg/kg. Once excavated to the planned depth, confirmation soil samples will be collected in accordance with the requirements outlined in Section 4.10.3. Based on the results, additional excavation and confirmation sampling will be performed until PCBs in the confirmation samples are detected at or below the cleanup goals of 10 mg/kg.

3.2. RETENTION BASIN AREA ASSESSMENT

To manage stormwater runoff from the Yard to adjacent properties, two separate retention basins will be constructed. The first retention basin (North Retention Basin) is located in the northwest corner of the Yard and will have a footprint of approximately 30,246 square feet. The second retention basin (South Retention Basin) will be located on the western portion of the Yard and will have a footprint of approximately 13,100 square feet. The surface and subsurface soils shall be assessed for determining the use of soil (either re-use within the Yard or for off-site disposal).

For the North Retention Basin, the 30,246 square foot area will be overlain with a 50-ft x 45-ft sampling grid with 16 sampling locations (Figure 14). For the South Retention Basin, the 13,100 square foot area will be overlain with a 50-ft x 50-ft sampling grid with 4 sampling locations (Figure 8). For each of the sample locations, three sample depths will be collected from the surface (0-3 inches), subsurface (20-24 inches), and to 48 inches; and will be analyzed for Aroclors. The 48-inch deep samples will be held by the laboratory and analyzed if the subsurface samples (20-24 inches) are above the PCB cleanup goal of 10 mg/kg. Additional sampling details are provided in Table 3-1 below.

Following the Retention Basin Area Assessment and design, soil will be excavated according to the design plan.

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3.3. STEP-OUT SAMPLING

In discussion with the USEPA, additional step-out sampling was recommended to refine the remedial action footprint in AOCs 1 through 5, and the Northern Maintenance Yard. For each of the sample locations, three sample depths will be collected from the surface (0-3 inches), subsurface (6-12 inches), and to 24 inches; and will be analyzed for Aroclors. The 24-inch samples will be held by the laboratory and analyzed if the subsurface (20-24 inch) samples are above the onsite cleanup goal of 10 mg/kg.

Figures 4 through 9 show the proposed step-out sample locations. Additional sampling details are provided in Table 3-1 below.

Following the step-out sampling, soil will be excavated and disposed if results exceed the onsite PCB cleanup goal of 10 mg/kg. Once excavated to the planned depth, confirmation soil samples will be collected in accordance with the requirements outlined in Section 4.10.3. Based on the results, additional excavation and confirmation sampling will be performed until PCBs in the confirmation samples are detected at or below the respective cleanup goal.

3.4. ASPHALT AND CONCRETE ASSESSMENT

Asphalt and concrete exist in the onsite areas AOCs 1 through 5. Based on TSCA PCB Regulations, porous surfaces, which include asphalt and concrete, require characterization and remediation (if necessary).

The main source of PCBs was the spraying of transformer oil throughout the Yard to the surface. Upon discovery of elevated PCB concentrations in a 1982 PCB survey, driveways, roads, parking areas and work areas were paved with asphaltic concrete (asphalt) pavement as an interim measure to limit PCB migration (E.W. Wells, 2017). Since the asphalt was installed after the source of PCBs were discovered and practices stopped, the bottom layer of the asphalt or concrete thickness where the asphalt and soil surface meet could potentially contain the most elevated PCB concentrations. Therefore, sampling will be within ½-inch of the soil and asphalt interface. The samples will be collected using a core bit to drill to the appropriate depth for the collection of a uniform, finely ground powder for laboratory analysis. The samples will be collected in accordance with the Standard Operating Procedure for Sampling Porous Surfaces for PCBs (USEPA, 2011).

Asphalt samples are proposed for the areas where soil exceeded the cleanup goal and are proposed for removal. In addition, asphalt and concrete samples will be collected at each of the proposed step-out sampling locations (Section 3.3), if encountered above the soil. Eighty-three (83) asphalt samples and five (5) concrete samples will be collected at the soil and asphalt/concrete interface and analyzed for Aroclors. Sampling details are provided in Table 3-1 and sample locations are illustrated in Figure 15.

Table 3-1 – Sampling and Analysis Summary for Additional Assessment

Location Analytical Method

Depth (inches)

Proposed Samples Rationale

Pad Area (Figure 13)

8082 – Aroclors Soil: 0-3, 6- 12, and 24 (held)

114 soil samples Concrete area that was removed in 2019 but was not assessed for PCBs

North and South Retention Basins (Figures 8 & 14)

8082 – Aroclors Soil: 0-3, 20-24, and 48 (held)

60 soil samples

Additional soil samples for determining the use of excavated soil (either re-use onsite or offsite disposal)

OTIE 11

AOC-1

(Figures 4 & 15)

8082 - Aroclors

Soil: 0-3, 6- 12, and 24 (held) Asphalt:

Note 2

27 soil samples; 2 asphalt samples

Soil: additional step-out soil characterization around the perimeter of AOC-1 Asphalt: in-place sampling for waste characterization and disposal during removal action

AOC-2

(Figures 5 & 15)

8082 - Aroclors

Soil: 0-3, 6- 12, and 24 (held) Asphalt and Concrete:

Note 2

51 soil samples; 29 asphalt samples; 5 concrete samples

Soil: additional step-out soil characterization around the perimeter of AOC-2 Asphalt and concrete: in-place sampling for waste characterization and disposal during removal action

AOC-3

(Figures 6 & 15)

8082 - Aroclors

Soil: 0-3, 6- 12, and 24 (held) Asphalt:

Note 2

27 soil samples; 25 asphalt samples

Soil: additional step-out soil characterization around the perimeter of AOC-3 Asphalt: in-place sampling for waste characterization and disposal during removal action

AOC-4

(Figures 7 & 15)

8082 - Aroclors

Soil: 0-3, 6- 12, and 24 (held) Asphalt:

Note 2

18 soil samples; 25 asphalt samples

Soil: additional step-out soil characterization around the perimeter of AOC-4 Asphalt: in-place sampling for waste characterization and disposal during removal action

AOC-5

(Figures 8 & 15)

8082 - Aroclors

Soil: 0-3, 6- 12, and 24 (held) Asphalt:

Note 2

33 soil samples; 2 asphalt samples

Soil: additional step-out soil characterization around the perimeter of AOC-5 Asphalt: in-place sampling for waste characterization and disposal during removal action

Onsite Northern Maintenance Yard (Figure 9)

8082 - Aroclors Soil: 0-3, 6- 12, and 24 (held)

12 soil samples Additional step-out soil characterization in the onsite northern maintenance yard

Notes:

1) All samples will be collected into laboratory-provided sampling jars, which will be properly labeled and placed in a chilled cooler for transport to the laboratory under chain of-custody protocol. The samples will be analyzed for PCBs following USEPA Test Method 8082.

2) Depth of the asphalt and concrete samples to be within ½-inch of the soil and asphalt or concrete interface.

OTIE 12

4.0 SITE SPECIFIC REMEDIATION PLAN

The results of the SSI demonstrate that Site characterization is complete and that the data is of sufficient quality and quantity to move forward with remediation at the Site. The purpose of this PCB Cleanup Plan is to comply with the TSCA of 1976, which regulates PCBs in the United States. This plan describes the planned remedial activities at the Site to achieve unrestricted use under a risk-based cleanup approach as defined in TSCA [40 CFR § 761.61(c)]. The plan describes the extent and methods of remedial activities, and the sample collection and analysis procedures to be followed to verify the removal of soil exceeding the USEPA-approved PCB cleanup goals.

The BIA will contract the services of a remedial contractor to perform the remedial activities described in the following sections. The selected contractor will provide certification of this document using the certification form provided in Appendix A prior to start of work.

4.1. SITE SPECIFIC REMEDIAL APPROACHES

Excavation, transport, and off-site disposal have been selected to address the PCB impacted soils at the Site and perimeter areas. Mechanical excavating equipment will be used to remove the PCB impacted soils. The proposed onsite and offsite excavation areas are identified similarly to the established site assessment areas. An excavation grid pattern was established for each excavation area based on the combined historical sampling locations. The grid size varies by each proposed excavation area. Each proposed excavation area is separated by hazardous (greater than 50 mg/kg) and non-hazardous (between the cleanup goal and less than 50 mg/kg) excavation areas. The in-place soil sampling results will be used for applicable profiling prior to the start of excavation work (according to CFR 761.61(a)(5)(i)(B)(2)(i)). PCB soils are considered hazardous at results greater than 50 mg/kg and require special handling for disposal. Additional excavation and disposal details are provided in Section 4.10.

Following excavation, confirmation sampling will be completed as described in Section 4.10.3.

Site specific details are provided below. General requirements are presented in the subsequent sections.

Depending on the additional site investigation (Section 3.0), additional excavation may be warranted.

4.1.1. PCB AOC-1 and Vicinity (Onsite)

PCB concentrations in excess of the established cleanup goal (10 mg/kg) were detected in the vicinity of AOC-1 at various depths to 2 ft bgs. A 15-ft by 12-ft excavation grid was overlain on the AOC-1 boundary to coincide with the sampling pattern. A total of 13 of the 20 grid squares contained soil samples exceeding the PCB cleanup goal. The number of grid squares and planned excavation depths by waste category, as shown in Figure 4, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 1 grid square to 1-ft depth o 3 grid squares to 2-ft depth o 1 grid square to 3-ft depth o 2 grid squares to 4-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 1 grid square to 3-ft depth o 5 grid squares to 4-ft depth

OTIE 13

An additional area east of AOC-1 had elevated PCB soil concentrations above the cleanup goal. The 40-ft by 20-ft excavation area will be excavated to a depth of 1 ft bgs.

4.1.2. PCB AOC-2 (Onsite)

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected in the vicinity of AOC-2 at various depths to 1 ft bgs. A 12-ft by 12-ft excavation grid was overlain on the AOC-2 boundary to coincide with the sampling pattern. A total of 17 of 18 sampled grid squares contained soil samples exceeding the PCB cleanup goal. The number of grid squares and planned excavation depths by waste category, as shown in Figure 5, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 6 grid squares to 1-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 7 grid squares to 1-ft depth o 4 grid squares to 2-ft depth

4.1.3. PCB AOC-3 and Vicinity (Onsite)

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected in the vicinity of AOC-3 at various depths to 1 ft bgs. A 15-ft by 12-ft excavation grid was overlain on the AOC-3 boundary to coincide with the sample pattern. A total of 15 grid squares contained soil samples exceeding the cleanup goal. The number of grid squares and planned excavation depths by waste category, as shown in Figure 6, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 8 grid squares to 1-ft depth o 1 grid square to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 3 grid squares to 1-ft depth o 3 grid squares to 2-ft depth

Two sampling locations southwest of AOC-3 had elevated PCB concentrations. A 20-ft by 20-ft area will be excavated to a depth of 1 ft bgs.

4.1.4. PCB AOC-4 (Onsite)

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected in the vicinity of AOC-4 at various depths to 1 ft bgs. A 15-ft by 15-ft excavation grid was overlain on the AOC-4 boundary to coincide with the sampling pattern. A total of 20 of 27 grid squares contained soil samples exceeding the cleanup goal. The number of grid squares and planned excavation depths by waste category, as shown in Figure 7, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 8 grid squares to 1-ft depth o 6 grid squares to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 1 grid square to 1-ft depth

OTIE 14

o 5 grid squares to 2-ft depth

4.1.5. PCB AOC-5 and Vicinity (Onsite)

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected in the vicinity of AOC-5 at various depths down to 2 ft bgs. A 10-ft by 15-ft excavation grid was overlain on the AOC-5 boundary to coincide with the original sample pattern. A total of 14 grid squares contained soil samples exceeding the cleanup goal. The number of grid squares and planned excavation depths by waste category as shown in Figure 8, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 1 grid square to 1-ft depth o 3 grid squares to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 6 grid squares to 2-ft depth o 4 grid squares to 3-ft depth

An additional three 10-ft by 10-ft grids to the north and south; and an additional 15-ft by 15-ft grid to the west of AOC-5 were identified exceeding the cleanup goal. These areas will be excavated to a depth of 1 ft bgs.

4.1.6. Northern Maintenance Yard (Onsite)

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected in the northern portion of the Maintenance Yard at various depths down to 1 ft bgs. The planned excavation depths by waste category, as shown in Figure 9, are as follows:

• Soil in excess of 10 mg/kg (non-hazardous disposal) o one 15-ft by 20-ft rectangle to 1-ft depth o one 20-ft by 30-ft rectangle to 1-ft depth o one 30-ft by 60-ft (approximate) rectangle to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o one 15-ft by 25-ft rectangle to 1-ft depth o two 20-ft by 30-ft (approximate) rectangles to 3-ft depth

4.1.7. Perimeter Area – North (Offsite)

This section presents two separate disposal options for the Perimeter Area–North, which is currently owned by MLC Farms LLC (Parcel Number 209-10-0070). Option A outlines the details for the planned excavation if the property remains with the MLC Farms LLC, which would require clean-up to the residential RSL of 0.23 mg/kg. The primary approach outlines the details for the planned excavation if the property is acquired by the BIA, which would allow the On-Site cleanup goal of 10 mg/kg to be used.

Primary Approach

PCB concentrations in excess of the cleanup goal (10 mg/kg) were detected at various depths down to 2 ft bgs. A 20-ft by 20-ft excavation grid was overlain on the perimeter area boundary to coincide with the original sample pattern. A total of 5 grid squares contained soil samples exceeding the cleanup goal. The planned excavation depths by waste category, as shown in Figure 10A, are as follows:

OTIE 15

• Soil in excess of 10 mg/kg (non-hazardous disposal) o 4 grid squares to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 1 grid square to 2-ft depth

Option A

PCB concentrations in excess of the RSL/cleanup goal (0.23 mg/kg) were detected in the Perimeter Area –North at various depths to 1 ft bgs. The exposure point concentration (EPC) for Perimeter Area – North was separately recalculated for the hypothetical exposure mitigation (removal) of the area containing the detected concentrations of Aroclor above 0.6 mg/kg. The resulting EPC of 0.233 mg/kg corresponds with a carcinogenic risk of 9.7x10-7, which is below the de minimis risk value and would therefore require no further remedial action. A 10-ft by 10-ft excavation grid was overlain on the sample pattern. A 20-ft by 20-ft excavation grid was overlain on the perimeter area boundary to coincide with the original sample pattern. A total of 80 grid squares contained soil samples exceeding the cleanup goal. The number of grid squares and planned excavation depths by waste category, as shown in Figure 10B, are as follows:

• In-place soil in excess of 0.6 mg/kg (non-hazardous disposal) o 81 grid squares to 2-ft depth

• Soil in excess of 50 mg/kg (hazardous disposal) o 1 grid square to 2-ft depth

4.1.8. Perimeter Area – Southwest (Offsite)

PCB concentrations in excess of the RSL/cleanup goal (0.23 mg/kg) were detected in the Perimeter Area

– Southwest at various depths down to 1 ft bgs. The EPC for Perimeter Area – Southwest was separately recalculated for the hypothetical exposure mitigation (removal) of the area containing concentrations of Aroclor 1260 above 1.03 mg/kg. The resulting EPC of 0.234 mg/kg corresponds with a carcinogenic risk of 9.79 x 10-7, which is below the de minimis human health risk value of 1 x 10-6 and would therefore require no further remedial action. A 10-ft by 10-ft excavation grid was overlain on the sample pattern.

A total of 38 grid squares will be excavated to remove the soil required to achieve the resulting EPC. The number of grid squares and planned excavation depths by waste category, as presented on Figure 11, are as follows:

• In-place soil in excess of 1.03 mg/kg (non-hazardous disposal) o 38 grid squares to 2-ft depth

4.1.9. Perimeter Area – East (Offsite)

PCB concentrations in excess of the RSL/cleanup goal (2.0 mg/kg) were detected in the Perimeter Area – East at various depths down to 1 ft bgs. A 10-ft by 10-ft excavation grid was overlain on the scattered sample pattern. A total of 9 grid squares contained soil samples exceeding the cleanup goal. The number of grid squares and planned excavation depths by waste category, as presented on Figures 4 and 9, are as follows:

• In-place soil in excess of 2 mg/kg (non-hazardous disposal) o 8 grid squares to 1-ft depth

OTIE 16

o 1 grid squares to 2-ft depth

4.2. PERMITS AND PLANS

All necessary permits or approvals will be obtained prior to implementation of remediation activities.

4.2.1. Access Agreements

For all planned offsite work, access agreements will be required. Access agreements will be coordinated through the BIA real estate office. Any offsite work will not commence without the fully executed access agreements.

4.2.2. Dust Control Plan

All construction projects in Pinal County require a dust permit if the disturbance to surface is greater than one tenth acre (>0.1 acre or 4,356 square feet [ft2]). The Site will require a permit, as the anticipated workspace is equal to approximately 15.3 acres (662,112 ft2). There are four areas (Onsite [13 acres], North [1.5 acres], South [0.7 acres], and East [0.8 acres]) requiring earthwork activities. The following best management practices (BMPs) will be implemented for dust mitigation:

• Vehicle movement at the site area will not exceed 5 miles per hour (mph) at any time (permit requirements are less than 15 mph);

• During earthwork activities, potable water will be sprayed by hose or water truck;

• Water dispersion will be increased if visible dust is observed;

• Contaminated soil will be staged at a designated stockpile area;

• Stockpiled soil will require moisture conditioning and coverage by 10-mil plastic sheeting ballasted with sand/gravel bags (when not being worked); and

• In the event of transfer of soil from equipment, the soil will be moisture conditioned at the time of transfer.

4.2.3. Health and Safety Plan

The contractor will develop a Site-specific Health and Safety Plan (HASP) in accordance with current health and safety standards as specified by the Federal and Arizona Occupational Safety and Health Administration (OSHA). Since PCB concentrations in the excavation areas generally will range from non-detect to 200 mg/kg, emphasis of the HASP will involve the handling of these soils as it relates to excavation, soil sampling, equipment decontamination, archaeological testing, and data recovery. The provisions of the HASP are mandatory for all personnel at the Site. All onsite personnel will be required to read and sign the HASP prior to starting the field work.

4.2.4. Stormwater Pollution Prevention Plan (SWPPP)

A SWPPP is required on all construction sites per the Construction General Permit (CGP). The SCIP proximity to receiving waters listed under section 303(d) of the Clean Water Act and Outstanding Arizona Water (OAW) in A.A.C. R18-11-112(G) exceeds the minimum linear distance.