3. FIO-GFI-EastElliot_DecisionDocument.pdf

DECISION DOCUMENT

CAMP ELLIOTT

EAST ELLIOTT-MUNITIONS RESPONSE SITE (MRS) 01C, 01D,

and 01F

PROJECT NUMBER – J09CA006706

SAN DIEGO COUNTY, CALIFORNIA

U.S. Army Corps of Engineers Los Angeles District

915 Wilshire Boulevard Los Angeles, California 90017

July 2019 l1pmmama Text Box

1200C PERM

J09CA006706_05.09_0002_a

(Intentionally blank)

Decision Document East Elliott-MRS 01C, 01D, and 01F San Diego County, California i

TABLE OF CONTENTS

PART 1: DECLARATION

1.1 SITE NAME AND LOCATION

1.2 STATEMENT OF BASIS AND PURPOSE

1.3 ASSESSMENT OF EAST ELLIOTT-MRS 01CDF

1.4 DESCRIPTION OF SELECTED REMEDY

1.5 STATUTORY DETERMINATIONS

1.6 DATA CERTIFICATION CHECKLIST

1.7 AUTHORIZING SIGNATURE

PART 2: DECISION SUMMARY

2.1 NAME, LOCATION, AND BRIEF DESCRIPTION

2.2 EAST ELLIOTT-MRS 01CDF HISTORY

2.2.1 Site Investigation History

2.2.2 Enforcement History

2.3 COMMUNITY PARTICIPATION

2.4 SCOPE AND ROLE OF RESPONSE ACTION

2.5 EAST ELLIOTT-MRS 01CDF SITE CHARACTERISTICS

2.5.1 Conceptual Site Model (CSM)

2.5.2 East Elliott-MRS 01CDF Site Features

2.5.3 Soil

2.5.4 Investigation and Sampling Strategy

2.6 CURRENT AND POTENTIAL FUTURE LAND AND RESOURCE USES ... 15

2.6.1 Current Land Use

2.6.2 Future Land Use

2.6.3 Surface Water and Groundwater Use

2.7 SUMMARY OF SITE POTENTIAL RISKS/HAZARDS

2.7.1 Human Health Risks/Hazards

2.7.2 Biological Resource Analysis

2.8 REMEDIAL ACTION OBJECTIVES

2.9 DESCRIPTION OF ALTERNATIVES

2.9.1 Alternative 1 – No Further Action

2.9.2 Alternative 2 – Institutional Controls to Protect Current and Future Site Users ii

2.9.3 Alternative 3 – Removal of DoD Military Munitions from the Surface with ICs to Protect Current and Future Site Users

2.9.4 Alternative 4 – Digital Geophysical Mapping and Surface and Subsurface Removal of DoD Military Munitions to a depth of 12 inches bgs, with ICs to Protect Current and Future Site Users

2.9.5 Alternative 6 – DGM and Surface and Subsurface Removal of DoD Military Munitions to a depth of 12 inches bgs, with ICs to Protect Current and Future Site Users with Implementation in Delineated Response Areas

2.9.6 Alternative 7 – Excavation, Sifting, Removal of DoD Military Munitions, and Restoration

2.9.7 Five-Year Reviews

2.10 COMPARATIVE ANALYSIS OF ALTERNATIVES

2.10.1 Overall Protection of Human Health and the Environment

2.10.2 Compliance with Applicable or Relevant and Appropriate Requirements (ARAR)

2.10.3 Long-term Effectiveness and Permanence

2.10.4 Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment

2.10.5 Short-term Effectiveness

2.10.6 Implementability

2.10.7 Cost

2.10.8 State/Support Agency Acceptance

2.10.9 Community Acceptance

2.11 TREATMENT TO ADDRESS THE POTENTIAL FOR MUNITIONS TO BE

PRESENT

2.12 SELECTED REMEDY

2.12.1 Summary and Description

2.12.2 Cost Estimate

2.12.3 Estimated Outcomes

2.13 STATUTORY DETERMINATIONS

2.14 DOCUMENTATION OF SIGNIFICANT CHANGES

PART 3: RESPONSIVENESS SUMMARY

3.1 STAKEHOLDER COMMENTS AND LEAD AGENCY RESPONSES

3.1.1 DTSC and CDFW Comment/Response

3.1.2 Stakeholder Comment/Response

iii

3.2 TECHNICAL AND LEGAL ISSUES

REFERENCES

LIST OF TABLES

Table 1 – East Elliott-MRS 01CDF Selected Remedy Table 2 – Potential MEC Summary for East Elliott-MRS 01CDF Table 3 – East Elliott-MRS 01CDF Selected Remedy Costs Table 4 – Relevant Considerations for Cost-Effectiveness Determination

LIST OF ATTACHMENTS

Attachment 1 – Documentation of California Department of Toxic Substances Control Concurrence on East Elliott-MRS 01CDF Selected Remedy Attachment 2 – Site Figures

Figure 1 – Location Map Figure 2 – Site Layout Figure 3 – Results of Previous Investigations at East Elliott-MRS 01C, 01D, and 01F Figure 3a – Results of Remedial Investigation at East Elliott-MRS 01C, 01D, and 01F Figure 4 – Current Landowner Map Figure 5 – Delineated Response Areas Figure 6 – Exposure Pathway Diagram - East Elliott-MRS 01C, 01D, and 01F

Attachment 3 – Administrative Record Index Attachment 4 – Newspaper Publications Attachment 5 – East Elliott MRS 01 Public Meeting Transcript iv

LIST OF ACRONYMS AND ABBREVIATIONS

AGC Advanced Geophysical Classification APC Armor-piercing, Capped ARAR Applicable or Relevant and Appropriate Requirements ASR Archives Search Report bgs below ground surface CDFW California Department of Fish and Wildlife CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations COPC contaminants of potential concern CSM Conceptual Site Model DDESB Department of Defense Explosive Safety Board DERP Defense Environmental Restoration Program DGM Digital Geophysical Mapping DoD United States Department of Defense DTSC State of California Department of Toxic Substances Control EE/CA Engineering Evaluation/Cost Analysis ESA Endangered Species Act FS Feasibility Study FUDS Formerly Used Defense Sites GSA General Services Administration HA Hazard Assessment HE high explosive IC Institutional Controls MBTA Migratory Bird Treaty Act MC Munitions Constituents MD Munitions Debris MDAS material documented as safe MEC Munitions and Explosives of Concern MOU Memorandum of Understanding mm millimeter MMRP Military Munitions Response Program MRS Munitions Response Site MTRP Mission Trails Regional Park NCP National Oil and Hazardous Substances Pollution Contingency Plan RAO Remedial Action Objectives RCRA Resource Conservation and Recovery Act RI Remedial Investigation SARA Superfund Amendment and Reauthorization Act TCRA Time Critical Removal Action v

TNT Trinitrotoluene USACE United States Army Corps of Engineers USC United States Code USEPA United States Environmental Protection Agency USMC United States Marine Corps UU/UE Unlimited Use/Unrestricted Exposure UXO Unexploded Ordnance VSP Visual Sample Plan vi

PART 1: DECLARATION

1.1 SITE NAME AND LOCATION

Site Name: Camp Elliott East Elliott-MRS 01C, 01D, and 01F

Formerly Used Defense Site (FUDS) Project Number: J09CA006706

Federal Facility Identifier: CA99799F527500

Camp Elliott East Elliott-MRS 01C, 01D, and 01F (hereinafter referred to as East Elliott-MRS 01CDF) is a merged MRS, comprising three of seven sub-areas encompassed by the Former East Elliott MRS 01 Remedial Investigation (RI)/Feasibility Study (FS) project. East Elliott-MRS 01CDF is located approximately 12 miles northeast of downtown San Diego. It is comprised of approximately 2,244 acres, and is a sub-area of East Elliott MRS 01, which is comprised of approximately 3,035.5 acres. East Elliott-MRS 01CDF’s location is depicted on Figure 1 – East Elliott-MRS 01CDF Location Map and Figure 2 – East Elliott-MRS 01CDF Site Layout. (Note:

Referenced figures throughout this document are included as Attachment 2.)

The United States Marine Corps (USMC) used Camp Elliott, including East Elliott-MRS 01CDF, from 1940 until the end of World War II for live-fire training exercises. At its largest, Camp Elliott was comprised of 30,500 acres. East Elliott (3,035.5 acres, later identified as Former East Elliott MRS01) was a designated training area associated with Camp Elliott in which training exercises were conducted. These exercises included the use of artillery and machine guns, and anti-tank training using artillery, mortars, bazooka rockets, and trip flares. Following World War II and up until 1953, the United States Navy Training and Redistribution Center used Camp Elliott, but, reportedly, did not conduct live-fire training. The Department of Defense (DoD) ended its use of the entire East Elliott MRS 01 with the closure of Camp Elliott in 1960 (Ref. 1). In 1961, the DoD declared approximately 15,000 acres of Camp Elliott’s 30,500 acres as surplus land. This surplus acreage included East Elliott-MRS 01CDF. With this declaration, the DoD transferred this acreage to the General Services Administration (GSA) for disposition. In 1962, the GSA solicited bids for sale of this land, and by 1974, sold most of the surplus land, including the acreage that composes East Elliott-MRS 01CDF, to real estate developers, private parties, and municipalities (Ref. 2). The land within East Elliott-MRS 01CDF remains undeveloped.

In April 2018, U.S. Army Corps of Engineers (USACE) delineated the seven sub-areas associated with East Elliott MRS 01 into five separate MRSs:

• East Elliott-MRS 01A;

• East Elliott-MRS 01B;

• East Elliott-MRS 01C, 01D, and 01F;

• No Action Area-MRS 01G; and

• East Elliott-MRS 01E and Range Fans.

East Elliott-MRS OlC, 010, and OlF San Diego County, California

This Decision Document (DD) addresses East Elliott-MRS 0lCDF. USACE will conduct munitions responses, if appropriate, at the remaining MRSs under separate ODs.

Throughout this document, East Elliott-MRS 0lCDF refers to specific details regarding this specific MRS, while East Elliott MRS 01 refers to the general history and use of the entire East Elliott-MRS 01 (approximately 3,035 acres) which is comprised of multiple MRSs.

1.2 STATEMENT OF BASIS AND PURPOSE

This DD presents the Selected Remedy for East Elliott-MRS 0lCDF, in San Diego County, California, as documented in the Formerly Used Defense Sites Program Proposed Plan for Former Camp Elliott, East Elliott MRS 01, San Diego County California, Formerly Used Defense Sites (FUDS) Project No. J09CA006703 (Proposed Plan) (Ref. 3). USA CE chose the Selected Remedy in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (Ref. 4), as amended bytheSuperfund Amendments and ReauthorizationAct(SARA) and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) (Ref. 5). This decision is supported by the documents included in the Administrative Record for this site (Attachment 3).

The State of California Department of Toxic Substances Control (DTSC), the lead regulatory agency, concurs with the Selected Remedy. Documentation of DTSC's concurrence is included as Attachment 1 to this DD (Ref. 6).

1.3 ASSESSMENT OF EAST ELLIOTT-MRS 0lCDF

The Selected Remedy in this DD is necessary to protect human health and the environment from potential explosive hazards posed by DoD Military Munitions that may remain present at East Elliott-MRS 0lCDF, which may upon evaluation be determined to be munitions and explosives of concern (MEC).

1.4 DESCRIPTION OF SELECTED REMEDY

Six remedial alternatives were evaluated for East Elliott-MRS 0lCDF. The Selected Remedy is Alternative 6 - Digital Geophysical Mapping (DGM) and Surface/Subsurface Removal of DoD Military Munitions to Depth of 12 inches with Institutional Controls (!Cs) to protect current and future site users, with implementation in delineated response areas. Tt is presented in Table 1 - East Elliott-MRS 0lCDF Selected Remedy.

TABLE 1 – EAST ELLIOTT-MRS 01CDF SELECTED REMEDY

Evaluated Alternatives for East Elliott-MRS 01CDF1

Alternative 1 – No Further Action.

Alternative 2 – ICs to protect current and future site users.

Alternative 3

– Removal of DoD Military Munitions2 from the Surface with ICs to protect current and future site users.

Alternative 4 – DGM and Surface/ Subsurface Removal of DoD Military Munitions to Depth of 12 inches with ICs to protect current and future site users.

Alternative 6 – DGM and Surface/ Subsurface Removal of DoD Military Munitions to Depth of 12 inches with ICs to protect current and future site users with implementation in delineated response areas3

Alternative 7

- Excavation, Sifting, Removal of DoD Military Munitions, and Restoration

1 One alternative presented in the Final RI/FS Report (Alternative 5) was not applicable to East Elliott-MRS 01CDF;

therefore, it is not included in this DD.

2 The term “Military Munitions” generally means all ammunition products and components produced for or used by the armed forces for national defense and security, including ammunition products or components under the control of the DoD, the Coast Guard, the Department of Energy, and the National Guard [see 10 United States Code (USC) §101(e)(4)(A) for a detailed definition].

3 Delineated response areas include trails, roads, and high density geophysical anomaly areas.

The Selected Remedy was based upon the ability to minimize an inadvertent encounter with munitions that, if present, may pose an explosive hazard. The Selected Remedy for East Elliott- MRS 01CDF is described in further detail in Section 2.12 of this DD.

The Selected Remedy for East Elliott-MRS 01CDF will be composed of:

• Boundary surveying;

• Vegetation clearance;

• Surface removal of munitions, munitions debris and other material, as required;

• DGM, using the best available and most appropriate technologies (e.g., electromagnetic technologies, Advanced Geophysical Classification [AGC] sensors);

• Intrusive investigation of geophysical anomalies that are determined to most likely be munitions or for which a determination cannot be made and removal of subsurface munitions; and

• ICs including 3Rs (Recognize, Retreat, Report) Education Awareness Program and site-specific Emergency Contact Information.

While not a component of the Selected Remedy, Five-Year Reviews will be implemented to ensure the Selected Remedy remains protective of human health and the environment after its implementation.

East Elliott-MRS OlC, OlD, and 01 F San Diego County, California

1.5 STATUTORY DETERMINATIONS

The Selected Remedy for East Elliott-MRS 0lCDF is Alternative 6 (DGM and Surface/Subsurface Removal of DoD Military Munitions to Depth of 12 inches with I Cs). USA CE will implement the Selected Remedy in delineated response areas to protect current and future site users. Based on the information currently available, the Selected Remedy (a) is protective of human health and the environment; (b) complies with Federal and State requirements that are applicable or relevant and appropriate to the remedial action (unless justified by a waiver); (c) is cost-effective when evaluated against the nine criteria described in the NCP, 40 Code of Federal Regulations Section 300.430(e) (9)(iii); and (d) uses permanent solutions to the maximum extent practicable. The Selected Remedy provides the best balance of tradeoffs when compared to the other evaluated alternatives with respect to the balancing and modifying criteria specified in the NCP. It provides the greatest reduction ofrisk, at a reasonable cost, within the constraints imposed by environmental conditions and reasonably anticipated future land use. This remedy also satisfies the statutory preference for treatment as a principal element of the remedy. The Selected Remedy is also acceptable to the community and the State regulator.

Based on the RI's results, USACE concluded that there is no unacceptable human health or ecological risk at East Elliott-MRS 0lCDF from exposure to Munitions Constituents (MC) that may be present. As such, in development of the Remedial Action Objectives (RAO) (Ref. 7) for East Elliott-MRS 01 CDF, USACE did not identify MC-related contaminants that warrant remedial action.

Because the Selected Remedy may result in some munitions remaining on site, statutory reviews will be conducted starting within five years after initiation of the remedial action to ensure the Selected Remedy remains protective of human health and the environment.

1.6 DAT A CERTIFICATION CHECKLIST

The Decision Summary section (Part 2) of this DD includes the below information. Additional information can be found in the Administrative Record file.

• Summary of characterization of nature and extent of Munitions and Explosives of Concern (MEC) and MC-related contamination (Section 2.2.1)

• Potential hazards posed by MEC (Section 2. 7)

• RAO established for munitions and its basis (Section 2.8)

• The manner in which DoD Military Munitions will be addressed (Section 2.9.5)

• Current and reasonably anticipated future land use assumptions (Section 2.6)

• Potential land and groundwater use that will be available at the site as a result of the Selected Remedy (Sections 2.12.3 and 2.6.3, respectively)

• Estimated Remedial Action costs and the included Five-Year Review costs (Section 2.12)

• Key factors that led to selecting the remedy (describing how the Selected Remedy provides the best balance of tradeoffs with respect to the balancing and modifying criteria, highlighting criteria key to the decision) (Section 2.10).

East Elliott-MRS OlC, 01D, and OlF San Diego County, California

1. 7 AUTHORIZING SIGNATURE

This DD, prepared by USACE, Los Angeles District, presents the Selected Remedy for Camp Elliott East Elliott-MRS 0lC, 01D, and 0lF. USACE is the lead executing agency under the Defense Environmental Restoration Program (DERP) at Camp Elliott East Elliott-MRS 0lC, 01D, and 0lF and has developed this DD in compliance with CERCLA, as amended by SARA and the NCP. This DD will be incorporated into the larger Administrative Record for Camp Elliott East Elliott-MRS 0lC, 01D, and 0lF, which is available for public view at the San Diego County Public Library, Santee Branch, 9225 Carlton Hills Blvd# 17, Santee, California 92071. The Selected Remedy is DOM and Surface/Subsurface Removal of DoD Military Munitions to Depth of 12 inches with !Cs to protect current and future site users, with implementation in delineated response areas. This remedy has a total cost estimate of $17,829,705, and is approved by the undersigned, pursuant to Memorandum, CEMP-CED (200-1 a), August l 0, 2019, subject: Redelegation of Assignment of Mission Execution Functions Associated with Department of Defense Lead Agent Responsibilities for the Formerly Used Defense Sites Program, and to Engineer Regulation 200-3-1, FUDS Program Policy, and Memorandum, CEMP-CED (1200C PERM) February 9, 2017, subject:

Interim Guidance Document (!GD) for the Formerly Used Defense Sites (FUDS) Decision Document (DD) Staffing and Approval.

Major General, US Army Deputy Commanding General for Military and International Operations

Date

PART 2: DECISION SUMMARY

The Decision Summary identifies the Selected Remedy, explains that remedial action is necessary to ensure protection of human health and the environment, and provides a substantive summary of the Administrative Record file that supports the remedy selection decision.

2.1 NAME, LOCATION, AND BRIEF DESCRIPTION

East Elliott-MRS 01CDF is depicted on Figures 1 and 2. East Elliott-MRS 01CDF, which is located approximately 12 miles northeast of San Diego, California, is comprised of 2,244 acres. East Elliott-MRS 01CDF is comprised of three sub-areas of seven sub-areas that make up East Elliott MRS 01, which is comprised of 3,035.5 acres. The land within East Elliott-MRS 01CDF is undeveloped land owned by private entities, corporations, school districts, and municipalities. For general discussion purposes, the MRS is divided into three areas:

• Eastern portion (formerly sub-area MRS 01d) – 868 acres located east of the Sycamore Landfill and Sycamore Landfill Road;

• Western portion (formerly sub-area MRS 01c) – 1,177 acres located west of the Sycamore Landfill and Sycamore Landfill Road and east of Marine Corps Air Station Miramar; and

• Southern portion (formerly sub-area MRS 01f) – 199 acres located south of State Highway 52 and within the boundary of Mission Trails Regional Park (MTRP).

2.2 EAST ELLIOTT-MRS 01CDF HISTORY

The USMC established Camp Elliott in 1940 as a development and training center. The initial land (approximately 19,298 acres) was acquired through a Declaration of Taking on 8 April 1941. This acquisition was subsequently expanded in mid to late 1941 to approximately 30,500 acres to form Camp Elliott.

The USMC used East Elliott, which was part of the initial acquisition from which Camp Elliott was created, for live-fire anti-tank and tank training. East Elliott’s ranges were used for this and other live-fire training from 1942 until the end of World War II. USACE’s archival research identified historical information that indicates East Elliott-MRS 01CDF was within Camp Elliott’s operational range fans. East Elliott-MRS01CDF was included in approximately 15,000 acres the DoD declared as surplus in 1961. This acreage was transferred to the GSA for disposition. Between 1962 and 1974, GSA sold the surplus land to real estate developers, private parties, and municipalities (Ref.

1).

USACE completed the Final RI/FS Report for East Elliott MRS 01 (Ref. 7) on 7 March 2018.

Based on the findings and recommendations of the Final RI/FS Report, USACE developed a Proposed Plan for East Elliott MRS 01 (Ref. 3). In April 2018, USACE delineated seven sub-areas associated with East Elliott MRS 01 into five separate MRSs. This DD addresses East Elliott-MRS

01CDF.

2.2.1 Site Investigation History

In 1986, Congress established the DERP for cleanup of active and former military sites. Based on its past use as a combat training area, East Elliott MRS 01 (including East Elliott-MRS 01CDF) was designated a FUDS in 1991, and became eligible for cleanup funding under DERP. The Army conducted munitions responses (e.g., investigations) at East Elliott-MRS 01CDF from 1984 to 2018. The munitions responses, which are specifically related to East Elliott-MRS 01CDF, are summarized below and depicted on Figure 3 – Results of Previous Investigations at East Elliott- MRS 01CDF. This figure shows the MEC and MD that was identified and removed during previous investigations.

2.2.1.1 1984 Clearance Activities

The U.S. Army 70th Ordnance Detachment (Explosive Ordnance Disposal) conducted a munitions survey within a 170-acre area near the southeast corner of East Elliott MRS 01. The San Diego County Sheriff’s Department and Office of Disaster Preparedness identified the area to be surveyed.

The surveyed area is located within the eastern portion of East Elliott-MRS 01CDF. Results of this survey concluded that moderate to heavy ordnance contamination was found within the 170-acre survey area. Most of the evidence indicating the presence of munitions was fragments from detonated munitions that contained high explosive (HE) (Ref. 8).

2.2.1.2 1994 Removal Activities

USACE performed surface and subsurface investigation for munitions (at the time referred to as ordnance and explosives waste or OEW sampling) within 11 grids that were 100 feet by 100 feet.

Of these grids, ten were located within East Elliott-MRS 01CDF. Munitions debris (MD) was found in four grids located in the eastern portion of East Elliott-MRS 01CDF. Neither munitions nor MD were encountered in grids located in East Elliott-MRS 01CDF’s western portion (Ref. 9).

2.2.1.3 1996 Munitions Investigation

USACE conducted a statistically-based geophysical survey at East Elliott MRS 01to estimate the density of munitions potentially present within different portions of East Elliott MRS 01 (Ref. 9).

This investigation was part of the Engineering Evaluation/Cost Analysis (EE/CA) (Ref. 10).

USACE established 89 grids (100 feet x 200 feet) within East Elliott MRS 01 and 61 of these grids were located within East Elliott-MRS 01CDF. During the grid survey, three 75 millimeter (mm) HE rounds were found and disposed. In addition, USACE identified and removed 119 MD items from within the grids located in East Elliott-MRS 01CDF (Ref. 9).

2.2.1.4 1998-1999 Time Critical Removal Action

USACE conducted a Time Critical Removal Action (TCRA) in the eastern portion of East Elliott- MRS 01CDF. USACE encountered and destroyed by detonation 23 unexploded ordnance (UXO) items within the eastern half of East Elliott-MRS 01CDF. The items consisted of 37mm and 75mm projectiles, and 81mm mortars. USACE identified many of these munitions, several of which were fuzed, as HE projectiles. In addition, USACE removed 1,348.5 pounds of MD. USACE inspected and disposed of the MD as scrap during both phases of this TCRA. The available historical documents do not indicate the locations from which the MD was removed; therefore, it is not known how much of the MD was located within East Elliott-MRS 01CDF (Ref. 11).

2.2.1.5 2003 Equestrian Staging Area Construction Support

USACE provided construction support and completed a subsurface removal action in support of the construction of a 12-acre equestrian staging area within MTRP. This was located adjacent to the southeastern boundary of East Elliott-MRS 01CDF. USACE assumes that the results of this project apply to the southern portion of East Elliott-MRS 01CDF because the site’s conditions and historical use are the same. Over 500 anomalies were detected and investigated. During this removal action, USACE did not encounter either munitions or evidence of munitions (Ref. 12).

2.2.1.6 2007 Surface Removal Action – Mission Trails Regional Park

USACE completed a grid survey and surface removal of munitions at MTRP. The project area addressed encompassed approximately 1,020 acres, including the southern portion of East Elliott- MRS 01CDF. During this response, USACE did not encounter munitions; however, it identified 19 pieces of MD. One of the MD encountered within the boundary of East Elliott-MRS 01CDF was a fragment from a 75mm Armor-piercing, Capped (APC) Practice fragment. USACE provided the MD recovered to either MTRP for educational purposes or the United States Navy Explosive Ordnance Disposal Mobile Unit Seven for training purposes (Ref. 13)

2.2.1.7 2013-2018 Remedial Investigation/Feasibility Study Report

USACE conducted an RI to characterize the nature and extent to which munitions or MC was present, fill data gaps, and assess potential explosives safety hazards within East Elliott MRS 01 (Ref. 7). USACE conducted the RI’s fieldwork at East Elliott MRS 01 between 3 December 2012 and 5 September 2013. The RI incorporated MC soil sampling, including sampling of background soil, and analysis. The RI also included a geophysical survey of approximately 77 acres using DGM towed-array and man-portable equipment in the eastern and western portions of East Elliott MRS 01. USACE did not conduct a geophysical survey within the southern portion of East Elliott- MRS 01CDF. USACE completed a transect-based DGM survey of approximately 24.9 line miles within the western portion of East Elliott-MRS 01CDF, which is identified in the Final RI/FS as MRS 01c, and approximately 202.2 line miles of transect-based DGM was completed in the eastern portion of East Elliott-MRS 01CDF, which is identified in the Final RI/FS Report as MRS 01d.

Collectively, these investigations, which bounded the impact areas and bounded the area where munitions were potentially present, satisfied the criteria for characterizing the nature and extent of munitions present. During the RI’s fieldwork, USACE did not encounter UXO within East Elliott- MRS01CDF; however, it did identify four MD items on the surface during soil sampling.

MEC Characterization

The results of the RI’s DGM surveys and previous investigations were analyzed using Visual Sample Plan (VSP) software, UXO Estimator, and ArcGIS software to identify areas within this MRS that exceeded an estimated 400 geophysical anomalies per acre (Figure 3a). An estimate of this magnitude would indicate activities (e.g., live-fire into an impact area) that created a clustering of anomalies. The VSP calculated anomaly densities throughout most of the eastern portion of East

Elliott MRS 01CDF was less than 100 per acre; however, the maximum density was 1,850 anomalies per acres.

The area with the highest density of geophysical anomalies is located in the southeastern area of East Elliott MRS 01CDF to the southeast of the Sycamore Landfill (Figure 3a). This area includes approximately 18.6 acres with an anomaly density of over 1,000 anomalies per acre, which is surrounded by approximately 79.9 acres with a density of over 400 anomalies per acre. Three additional areas with densities of over 400 anomalies per acres that total approximately 8.6 acres are located within the eastern portion of East Elliott MRS 01CDF. Using available data for the eastern portion of East Elliott-MRS 01CDF, results from UXO Estimator calculations indicated with a 95% confidence level that there is less than 0.5 UXO/acre, which indicates a low potential for UXO to be present. ArcGIS analysis of the eastern portion of East Elliott-MRSCDF indicated potential high UXO density areas. These areas aligned with the delineated areas from VSP analysis.

For the western portion of East Elliott-MRS 01CDF, the density of geophysical anomalies as calculated with VSP within most of the area was less than 50 per acre; however, the maximum density was 554 anomalies per acre. The highest density of geophysical anomalies is located in a 1.5-acre area in the northwestern corner of East Elliott-MRS 01CDF. Using available data for the western portion of East Elliott-MRS 01CDF, the result of this analysis indicates with a 95% confidence level that there is less than 0.1 UXO/acre, which indicates a low potential for UXO to be present. (Note: Insufficient data was available to analyze the UXO density of the western portion of East Elliott-MRS 01CDFusing ArcGIS software.)

USACE did not conduct RI field operations in the southern portion of East Elliott-MRS 01CDF because there was no historical information to indicate that the area had been used as an impact area and the two removal actions that USACE conducted in and around the sub-area did not encounter UXO. Therefore, USACE did not perform an analysis of the density of geophysical anomaly density for this portion of East Elliott-MRS 01CDF.

Munitions Constituents Characterization

USACE conducted MC sampling as part of the RI fieldwork through a biased sampling program for MC explosives (e.g., RDX) and metals (e.g., antimony, copper, lead, and zinc) in surface (0 to 0.5 feet below ground surface [bgs]) using the 7-sample wheel approach. USACE took 20 samples within the eastern portion of East Elliott-MRS 01CDF. The objectives of the MC-soil sampling were to determine whether concentrations of MC in soil indicated that a munitions-related release had occurred and, if so, whether a protective screening-level evaluation indicated a potential for significant human or ecological risk.

Analytical results for explosives and antimony in all site and background soil samples were reported as not detected at limits that were lower than human health and ecological screening criteria. Also, copper, lead, and zinc were not detected in soil samples at concentrations that were statistically elevated relative to background levels in East Elliott-MRS 01CDF.

Remedial Investigation Results Conclusions

The RI’s objectives included collecting: (1) geophysical data to accurately locate and record the locations of geophysical anomalies (e.g., potential DoD Military Munitions or MD) for the purpose of identifying high density areas that may be indicative of an impact area; and (2) surface soil samples to determine if MC are present at concentrations greater than background levels, which may indicate a potential release of MC resulting from the presence of DoD Military Munitions.

RI findings with regard to munitions and MC:

• Four MD items were encountered at East Elliott-MRS 01CDF during soil sampling. Each item was approximately ¼-inch long by ¼-inch wide and appeared to be projectile fragmentation. Munitions encountered and removed within East Elliott-MRS 01CDF during previous investigations included 37mm and 75mm projectiles.

• Geophysical anomaly densities were calculated for East Elliott-MRS 01CDF using data collected during the RI and from previous investigations. Based on the available data, USACE determined that anomaly density of greater than 400 anomalies per acre may be indicative of potential impact areas (Ref. 7):

• Data analysis indicates:

Eastern portion of East Elliott-MRS 01CDF has an average anomaly density of 125 anomalies per acre and a maximum of 1,850 anomalies per acre. In addition, approximately 87.1 acres within the eastern portion of the MRS have an anomaly density of greater than 400 anomalies per acre;

Western portion of East Elliott-MRS 01CDF has an average anomaly density of 21.2 anomalies per acre and a maximum of 554 anomalies per acre. In addition, approximately 1.5 acres within the western portion of the MRS have an anomaly density of greater than 400 anomalies per acre; and

The surface and subsurface exposure pathways for munitions that may be MEC in East Elliott-MRS 01CDF remain potentially complete. Based on the results of the RI and previous investigations, there is sufficient evidence for the potential for MEC to be present to evaluate this East Elliott-MRS 01CDF.

• Analytical results for explosives and MC-related metals indicate that an MC release did not occur.

USACE did not identify potentially complete exposure pathways for MC (metals or explosives) for surface soil, including incidental ingestion, inhalation, and dermal contact for human receptors (people), and ingestion and dermal contact for ecological receptors.

Because an MC surface soil source was not identified in potentially impacted areas sampled within East Elliott-MRS 01CDF, USACE considers the potential exposure pathways for subsurface soil, groundwater, surface water and sediment to be incomplete.

A complete detailed listing of the investigation results for East Elliott-MRS 01CDF is contained in the Final RI/FS Report (Ref. 7).

2.2.2 Enforcement History

The NCP provides that DoD will be the removal response authority with respect to incidents involving DoD military munitions. Therefore, enforcement activities have not been undertaken to identify or include other potentially responsible parties in the remediation process.

2.3 COMMUNITY PARTICIPATION

In accordance with CERCLA, and applicable DoD and Army regulations, USACE, Los Angeles District, has throughout this process continuously provided the public opportunities to participate throughout the Final RI/FS Report, Proposed Plan, and DD. USACE did this by hosting public meetings during the site characterization and remedial alternative selection process, and establishing and maintaining a publicly accessible Administrative Record file for East Elliott MRS 01.

During its coordination with property owners or managers to obtain Rights of Entry for field investigations, USACE, Los Angeles District, also requested input regarding future land use for East Elliott-MRS 01CDF. USACE also:

• Facilitated the community’s involvement by providing fact sheets, conducting media interviews, site visits, and publishing public notices in the San Diego Union-Tribune and Enlace (local newspapers);

• Invited community members to provide comments and recommendations at public meetings held during the site characterization and remedy selection process, which USACE considered in determining which proposed remedial alternative would be most appropriate for East Elliott-MRS 01CDF.

• Prepared a Community Relations Plan in 2015 to help ensure the public was informed about and involved in remedial action decisions at East Elliott-MRS 01CDF.

USACE presented the Proposed Plan (Ref. 3) during a public meeting. USACE published a Notification of the Proposed Plan public comment period, the schedule for the Public Meeting, and the availability of the Administrative Record File in the San Diego Union-Tribune between 10 June 2018 and 20 June 2018 (Attachment 4).

USACE held the public meeting on 20 June 2018, to (1) present the recommendations of the Proposed Plan; (2) update community members and stakeholders about the status of the Proposed Plan and DD for the site; and (3) accept comments on the Proposed Plan and Preferred Alternatives for East Elliott-MRS 01CDF. Although the public did not attend the meeting, representatives from the California Department of Fish and Wildlife (CDFW), DTSC, and the City of San Diego did attend. Attendees to the meeting did not pose questions or comments that required USACE to make revisions to the Proposed Plan. The transcript of the public meeting is included in Attachment 5.

The Final RI/FS Report (Ref. 7) and the Proposed Plan (Ref. 3) documents were made available to the public prior to the comment period through the Administrative Record file located at:

San Diego Public Library, Santee Branch 9225 Carlton Hills Blvd #17, Santee, California Contact: (619) 448-1863

USACE accepted comments to the Proposed Plan (Ref. 3) during a public comment period that began on 18 June and ended on 20 July 2018. All stakeholder (DTSC and CDFW) and public comments included in the Responsiveness Summary were reviewed and considered in preparing this DD. Note that the comments received addressed the entire East Elliott MRS 01 and East Elliott- MRS 01CDF specifically. USACE reviewed and considered the comments provided when it finalized the Proposed Plan for East Elliott-MRS 01CDF.

2.4 SCOPE AND ROLE OF RESPONSE ACTION

Based on the findings presented in the Final RI/FS Report, an unacceptable human health or ecological risk does not exist at East Elliott-MRS 01CDF from MC; therefore, USACE did not address COPCs or related MC risks in the development of RAOs (Ref. 7). Therefore, the munitions response actions implemented are designed to address the potential explosive safety hazard posed munitions that may remain present at East Elliott-MRS 01CDF. The Selected Remedy was designed to minimize the probability of encountering a munition within East Elliott-MRS 01CDF.

Actions for the Selected Remedy, Alternative 6, include a DGM survey with surface and subsurface removal of munitions, and implementation of ICs to protect current and future site users of East Elliott-MRS 01CDF.

This DD presents the Selected Remedy to address the potential presence of munition within East Elliott-MRS 01CDF. The Selected Remedy complements USACE’s overall strategy, following the U.S. Environmental Protection Agency (USEPA) guidance, to address DoD Military Munitions that may remain present within East Elliott-MRS 01CDF and allow for both the current use and the reasonably anticipated future land use (Ref. 14).

2.5 EAST ELLIOTT-MRS 01CDF SITE CHARACTERISTICS

This section provides an overview of the East Elliott-MRS 01CDF characteristics, including:

surface and subsurface features, the RI’s strategy for investigation for munitions, the MC sampling program’s conclusion, and the expected hazards potentially posed by munitions that may remain present.

2.5.1 Conceptual Site Model (CSM)

The Exposure Pathway Diagram for the revised CSM for East Elliott-MRS 01CDF, which was created based on the results of the RI, is provided as an attachment to this DD (Figure 6). The Exposure Pathway Diagram for the CSM represents the relationships between the former military use of East Elliott-MRS 01CDF, current and future land use, the potential for people to encounter DoD Military Munitions, and environmental features that may have an impact on proposed East Elliott-MRS 01CDF activities or decisions. USACE developed the CSM during the planning phase of the RI and then revised based on the results of the RI, in accordance with the USACE’s Conceptual Site Models - Engineer Manual 200-1-12 (Ref. 17), to communicate East Elliott-MRS 01CDF conditions, at the time of development, to project team members, regulators and stakeholders and to identify data gaps. Accordingly, the CSM provides the basis for determining the potential for MEC to be present.

There are no complete or potentially complete exposure pathways for MCs at East Elliott-MRS 01CDF as illustrated on Figure 6 – Exposure Pathway Diagram for the Conceptual Site Model - East Elliott-MRS 01CDF.

The CSM and exposure pathways for MEC have been reviewed and revised to incorporate new information concerning the presence of munitions that may be MEC, potential receptors, and site accessibility. Based on historical information for East Elliott-MRS 01CDF, munitions-related activities likely occurred within this MRS. USACE encountered and removed munitions, (e.g., 37mm projectiles, 75mm projectiles, and 81mm mortars (see Table 2)), from the surface to 12 inches bgs within East Elliott-MRS 01CDF during previous munition responses (e.g., investigations, removal actions). USACE determined that UXO and MD were randomly distributed throughout the MRS with the greatest concentration in the southeast portion of the MRS. Based on previous investigations results, there was sufficient evidence that MEC may be present and may be encountered by human receptors (i.e., construction workers, commercial/industrial workers, visitors/recreational users) to indicate complete exposure pathways are present (Figure 6).

2.5.2 East Elliott-MRS 01CDF Site Features

East Elliott-MRS 01CDF is located approximately 12 miles northeast of San Diego, California, adjacent to the City of Santee, California (Figure 1). The majority of East Elliott-MRS 01CDF is undeveloped; however, the area is accessed for recreational use by hikers and mountain bikers along unauthorized trails. A small electrical substation is located along the eastern boundary of East Elliott-MRS 01CDF. The substation is enclosed by a chain-link fence and accessed by a short paved road extending from the residential neighborhoods to the east. Two parallel sets of high-voltage transmission lines in proximity to each other traverse the site from the southwest to the northeast. Maintenance roads are present along the alignment of the transmission lines to provide access to the towers. Both the substation and the transmission lines are operated and maintained by San Diego Gas and Electric. The southern portion of East Elliott-MRS 01CDF is within the boundary of MTRP. Park trails are located within this portion of East Elliott-MRS 01CDF.

East Elliott-MRS 01CDF lies within the coastal plain of the Peninsular Range physiographic province of Southern California (Ref. 7). Elevation ranges from approximately 870 feet to 350 feet above mean sea level. The physiography of the area is characterized by a series of subparallel, north–south-trending canyons that drain southward.

2.5.3 Soil

Soils at East Elliott-MRS 01CDF are poorly developed (i.e., rocky) and relatively thin (i.e., less than 3 feet thick) (Ref. 7). Soil types are based on parent rock type and slope angle and are commonly described using texture-based terminology and referred to as “sandy loam.” Sandy loams consist of roughly equal portions of sand, silt, and clay. Soils are thicker in the canyon areas due to accumulation of unconsolidated materials at slope bases and are thinner on slopes and ridges.

2.5.4 Investigation and Sampling Strategy

2.5.4.1 Munitions Investigation

During the characterization effort for munitions at East Elliott-MRS 01CDF, USACE relied upon transect-based DGM data and data analysis for RI and previous investigation data using VSP, UXO Estimator, and ArcGIS (Figure 3a). Several potential munitions impact areas were identified within East Elliott-MRS 01CDF (Figure 3a).

2.5.4.2 Media Sampling

MC sampling was conducted within East Elliott-MRS 01CDF as part of the RI fieldwork through a biased sampling program for explosives and metals (antimony, copper, lead, and zinc) in surface (0 to 0.5 feet bgs). According to the Final RI/FS Report, there is no unacceptable human health or ecological risk at East Elliott-MRS 01CDF from exposure to MC (see Section 2.7) (Ref. 7).

2.5.4.3 Contaminants of Potential Concern

The Final RI/FS Report concludes that results from the RI field investigation and the MC soil sampling indicate there is no unacceptable human health or ecological risk at East Elliott-MRS 01CDF due to MC exposure; therefore, USACE did not address COPC or related MC risks to be addressed in the development of RAOs (Ref. 7).

2.6 CURRENT AND POTENTIAL FUTURE LAND AND RESOURCE

USES

Information regarding beneficial resources is described below.

2.6.1 Current Land Use

East Elliott-MRS 01CDF is mainly comprised of undeveloped land (Figure 2). The southern portion of East Elliott-MRS 01CDF is located within the boundary of MTRP and has developed trails. The eastern and western portion of East Elliott-MRS 01CDF are accessed by recreational users for hiking and mountain biking; however, the majority of this access is unauthorized.

According to the Public Draft 2016 Mission Trails Regional Park Master Plan Update and the official zoning map of the City of San Diego, East Elliott-MRS 01CDF is zoned as residential, single unit (Ref. 15 and Ref. 16).

2.6.2 Future Land Use

According to the Public Draft 2016 Mission Trails Regional Park Master Plan Update, recreational use within the East Elliott MRS 01 has been occurring for a number of years on utility access roads and on approximately 17 miles of unauthorized user-created trails that cross both publicly- and privately-owned parcels. Recommendations in the MTRP Master Plan Update call for acquisition of property within East Elliott-MRS01CDF by the City of San Diego for inclusion in the MTRP, along with closure or rerouting of some unauthorized trails to protect sensitive natural resources and based on public access easements for private parcels (Ref. 15). Although designated as planned open space according to the MTRP Master Plan Update, approximately 1,135.6 acres within East Elliott-MRS 01CDF are privately owned and zoned as residential, single unit, which may result in residential development within East Elliott-MRS 01CDF (Figure 4). Individual parcels owned by private and school district entities may be developed for other uses (such as the building of residences and schools), if not included in MTRP.

2.6.3 Surface Water and Groundwater Use

Ephemeral streams in East Elliott-MRS 01CDF canyons flow southward into the westward-flowing San Diego River. Streambeds are dry for the majority of the year. Flowing water is confined to episodic storm events during the annual rainy season (November to March) (Ref. 7).

USACE regulates discharges of dredged and fill material into waters of the United States, which includes many streams and wetlands such as those on East Elliott-MRS 01CDF. USACE, Los Angeles District, Regulatory Branch has performed an analysis of existing data regarding the presence of jurisdictional waters (i.e., waters regulated under the Clean Water Act) within the East Elliott area. As a result, USACE has determined that jurisdictional waters are present in East Elliott-MRS 01CDF.

East Elliott-MRS 01CDF is part of the Upper San Diego River Basin. Groundwater depth and flow direction within the site are described below based on monitoring USACE performed in June 2010 for Sycamore Landfill (Ref. 7):

• Groundwater depth ranges from approximately 10 to 335 feet bgs (depending on topography); and

• The groundwater flow direction is south to southwest.

2.7 SUMMARY OF SITE POTENTIAL RISKS/HAZARDS

As part of the RI/FS, USACE, Los Angeles District, conducted a screening assessment for MC and Hazard Assessment (HA) for MEC at East Elliott-MRS 01CDF.

East Elliott-MRS 01CDF was assessed using the USEPA MEC Hazard Assessment, which assesses the current potential MEC hazard and how that hazard may be modified by the implementation of remedial alternatives. The MEC HA is based on the results of the RI and the historical information available from prior studies. Detailed information regarding the MEC HA can be found in the Final RI/FS Report (Ref. 7).

The Selected Remedy in this DD is necessary to protect human health and the environment from the potential explosive hazards posed by munitions that may remain present within East Elliott-MRS 01CDF that may upon evaluation be determined to be MEC.

The USACE FUDS MMRP Risk Management Methodology will be implemented after the completion of the Selected Remedy to determine the residual risk at the site. In the event USACE determines the remaining risk is unacceptable, USACE will evaluate the need to implement additional remedial action activities. The remedial action will not be considered complete until the RAO is achieved.

2.7.1 Human Health Risks/Hazards

Potential surface and subsurface pathways exist for people to encounter munitions within East Elliott-MRS 01CDF. Based on previous munitions responses (e.g., investigations, removal actions), USACE has determined there is sufficient evidence that munitions (37mm and 75mm projectiles) that are MEC (UXO) remain present within East Elliott-MRS 01CDF.

Based on analysis of the results of the RI MC soil sampling at East Elliott-MRS 01CDF and a subsequent risk assessment, USACE determined that MC does not pose an unacceptable risk to human receptors at East Elliott-MRS 01CDF. Detailed information on analytical results are provided in the Final RI/FS Report (Ref. 7).

2.7.2 Biological Resource Analysis

Based on biological surveys previously conducted at East Elliott MRS 01, federally listed species including the San Diego fairy shrimp (federally endangered), coastal California gnatcatcher (federally threatened), Least bell’s vireo (federally endangered), San Diego ambrosia (federally endangered), Del Mar manzanita (federally endangered), and willowy monardella (federally endangered) are present within East Elliott-MRS 01CDF (Figure 2-4 in the Final RI/FS Report).

Based on the results of the RI MC soil sampling, analytical result screening, and subsequent risk assessments, USACE determined that MC does not pose an unacceptable risk to ecological receptors at East Elliott-MRS 01CDF. Detailed information on analytical results are provided in the Final RI/FS Report (Ref. 7).

2.8 REMEDIAL ACTION OBJECTIVES

RAOs drive the formulation and development of response actions. The aim is to achieve the NCP’s threshold criteria of “Overall Protection of Human Health and the Environment” and “Compliance with Applicable or Relevant and Appropriate Requirements (ARAR).”

Because USACE did not find evidence of MC releases from historical DoD operations within East Elliott-MRS 01CDF, the RAOs do not address chemical contamination, including MC-related contamination. Instead, the RAOs focus on the potential explosive safety hazards associated with munitions.

RAOs address specific goals for reducing the unacceptable risk due to the presence of munitions within an MRS to ensure protection of human health and the environment.

A factor considered in the RAOs is the anticipated depth of intrusion (digging) during activities conducted within an MRS compared to the depth to which munitions may be present.