7. FIO-GFI-EastElliot_ProposedPlan.pdf

Proposed Plan (PP) – East Elliott MRS 01 1

U.S. Army Corps of Engineers, Los Angeles District Formerly Used Defense Sites (FUDS) Program

PROPOSED PLAN

FOR

Former Camp Elliott, East Elliott Munitions Response Site (MRS) 01, San Diego County, California FUDS Project No. J09CA006703

INTRODUCTION

The U.S. Army Corps of Engineers (USACE) presents this Proposed Plan (PP) to allow the public an opportunity to review and comment on the Preferred Alternatives for Former Camp Elliott, East Elliott Munitions Response Site (MRS) 01 – Range Complex (Project 03) (hereafter referred to as East Elliott MRS 01) located in San Diego County, California. Figure 1 shows the location of East Elliott MRS 01.

This document discusses the rationale for selecting Preferred Alternatives for East Elliott MRS 01.

USACE, Los Angeles District, which is the lead agency for this munitions response, issued this PP for East Elliott MRS 01. The California Department of Toxic Substances Control (DTSC), which is the

MARK YOUR CALENDARS

PUBLIC COMMENT PERIOD:

June 18, 2018 through July 20, 2018

USACE will accept written comments on the Proposed Plan during the public comment period. Comment letters must be postmarked by July 20, 2018, and should be submitted to:

Mr. Randy Tabije United States Army Corps of Engineers Los Angeles District 915 Wilshire Boulevard, Suite 930 Los Angeles, CA 90017-3401 Phone: (951) 898-6144 Fax: (213) 452-4213 Email: roland.r.tabije@usace.army.mil

To request an extension of the public comment period, send a written request to Mr. Tabije by July 12, 2018.

PUBLIC MEETING:

June 20, 2018, 6-8pm USACE will host a public meeting to explain the Proposed Plan and all of the alternatives resulting from the FS (the study completed prior to this Proposed Plan). Oral and written comments will be accepted at the meeting, held at:

City of Santee Civic Center, Building 8A 1601 Magnolia Avenue, Santee, CA 92071

FOR MORE INFORMATION:

Project documents are available in the Admin-istrative Record file, which includes a copy of the RI/FS Report, at the following location:

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

Figure 1: East Elliott MRS 01 Site Location l1pmmama Text Box

1200C PERM

J09CA006703_04.10_0001_a

Proposed Plan (PP) – East Elliott MRS 01 2 regulatory agency, has reviewed this PP. USACE, Los Angeles District, is presenting this information to keep the public fully informed of the decision-making process regarding impacts from former military use in East Elliott MRS 01; fulfilling the public participation requirements under Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (42 United States Code [USC] §9617(a) and the National Oil and Hazardous Substances Pollution Contingency Plan [40 Code of Federal Regulations [CFR] §300.430(f)(2)]).

USACE identified seven sub-areas (East Elliot MRS 01a through East Elliot MRS 01g) within East Elliott MRS 01. USACE based the sub-areas on historical use, results of previous investigations, and the reasonably anticipated future land use. Figure 2 shows the sub-areas. Table 1 summarizes information about each East Elliott MRS 01 sub-area including the selected Preferred Alternative for each sub-area.

Each Preferred Alternative is specific to that particular sub-area. As such, the Preferred Alternatives may differ.

FIGURE 2 EAST ELLIOTT MRS 01 LAYOUT AND SUB-AREAS

Proposed Plan (PP) – East Elliott MRS 01 3

Table 1: East Elliott MRS 01 Sub-Area Descriptions

MRS Sub-area Acreage Current Land Use Future Land Use Preferred Alternative

01a 120.6 Residential Residential Alternative 2

01b 523.3 Landfill Landfill Alternative 2

01c 1,177.3 Undeveloped Recreational as part of Mission Trails Regional Park (MTRP)

Alternative 6

01d 867.4 Undeveloped Recreational as part of

MTRP

Alternative 6

01e 93.2 West Hills High School and recreational

West Hills High School and recreational

USACE has designated the East Elliott MRS 01e, along with an area of range fans located to its east boundary as a new project. As such, USACE will develop a PP for it after further evaluation and coordination with DTSC. This sub-area will not be further addressed as part of this PP.

01f 198.9 Recreational within

MTRP

Recreational within

MTRP

Alternative 6

01g 54.8 Undeveloped Recreational as part of

MTRP

USACE’s archival research did not discover historical information that indicates these

54.8 acres were included within operational range fans the military used for training at Camp Elliott. As such, at the conclusion of the RI, USACE assigned this sub-area a “No Risk” determination, and did not evaluate it during the FS.

This PP identifies the Preferred Alternatives for protecting receptors from explosive hazards associated with Department of Defense (DoD) Military Munitions (munitions) that may be Munitions and Explosives of Concern (MEC) that remain within the East Elliott MRS 01 sub-areas. In this PP, USACE both provides the rationale for each Preferred Alternative and includes summaries of the other remedial alternatives it evaluated based on the reasonably anticipated future use for each of the East Elliott MRS 01 sub-areas. The alternatives are identified below. Details regarding the decision process and the alternatives selection are discussed in the Summary of Remedial Alternatives and Summary of Preferred Alternatives sections.

• Alternative 1: No Action;

• Alternative 2: Institutional Controls (ICs) to Protect Current and Future Site Users;

• Alternative 3: Removal of DoD Military Munitions from the Surface with ICs to Protect Current and Future Site Users;

Proposed Plan (PP) – East Elliott MRS 01 4

• Alternative 4: Digital Geophysical Mapping (DGM) and Surface and Subsurface Removal of DoD Military Munitions to a Depth of 36 inches Below the Ground Surface (BGS) with ICs to Protect Current and Future Site Users;

• Alternative 5: DGM with Advanced Geophysical Classification (AGC) Sensor and Surface and Subsurface Removal of DoD Military Munitions to a Depth of 36 inches BGS with ICs to Protect Current and Future Site Users;

• Alternative 6: DGM and Surface and Subsurface Removal of DoD Military Munitions to a Depth of 36 inches BGS with ICs to Protect Current and Future Site Users for Delineated Response Areas1 within East Elliott MRS 01c, 01d, and 01f; and

• Alternative 7: Excavation, Sifting, Removal of DoD Military Munitions and Munitions Debris (MD), and Restoration.

PUBLIC INVOLVEMENT PROCESS

USACE encourages property owners and other interested parties to review this document and submit comments. USACE will consider the public comments before selecting and approving the Preferred Alternative for each of the MRS sub-areas that make up the East Elliott MRS 01.

USACE will accept comments during the public comment period which will begin prior to the public meeting. USACE will present the PP at the public meeting. USACE will also accept verbal and written comments at the public meeting. USACE will document and consider comments before selecting the final remedy. The first page of this PP provides the location, date and time of the public meeting, and the location of the Administrative Record file for East Elliott MRS 01.

The PP and the Remedial Investigation/ Feasibility Study (RI/FS) Report are a part of the East Elliott MRS 01 Administrative Record file that contains the documents used in making decisions on remedial projects at the site.

This PP identifies the recommended Preferred Alternative for each East Elliott MRS 01 sub-area and provides the rationale for the Preferred Alternative. The proposed Preferred Alternative for each East Elliott MRS 01 sub-area is based on the RI’s findings and during discussions among the lead and support agencies, the affected community, and other stakeholders.

This PP:

• Presents basic background information;

• Identifies the Preferred Alternative for each East Elliott MRS 01 sub-area and explains the rationale for each identified alternative;

1 Delineated response areas within the East Elliott MRS 01 sub-areas are areas such as trails, utility trenches, and high density geophysical anomaly areas as defined in the MTRP Master Plan and based the results of the RI geophysical anomaly analysis (Refs. 3 and 4)

Figure 3: East Elliott MRS 01 Decision Document Process

Proposed Plan (PP) – East Elliott MRS 01 5

• Encourages public review and comment on the recommended Preferred Alternatives; and

• Provides information on how the public can be involved in the process.

One or more Decision Documents (DD) will provide the final Selected Remedy for East Elliott MRS 01 sub-areas. The DD’s “Responsiveness Summary” section will include USACE’s responses to public comments. Figure 3 summarizes the various steps in the development and approval process for the East Elliott MRS 01 sub-area DDs. After consideration of each comment, USACE will approve the required DDs.

SITE HISTORY AND BACKGROUND

This PP summarizes information that can be found in greater detail in the RI/FS Report (Ref. 3) and other documents contained in the Administrative Record file for East Elliott MRS 01. USACE encourages the public to review these documents to gain a more comprehensive understanding of East Elliott MRS 01 and previous remedial activities that have been conducted at the East Elliott MRS 01.

East Elliott MRS 01 is situated in northeast San Diego County approximately 12 miles northeast of downtown San Diego and adjacent to the City of Santee (Figure 1). USACE has sub-divided the East Elliott MRS 01, which comprises approximately 3,035.5 acres, into sub-areas East Elliot MRS 01a through East Elliot MRS 01g (Figure 2).

In 1940, the U.S. Marine Corps (USMC) established Camp Holcomb as a development and training center on approximately 19,000 acres. Camp Holcomb was renamed Camp Elliott in June of 1940. Camp Elliott, which was expanded to approximately 30,500 acres, housed the Second Marine Division and later served as home to the USMC Headquarters Command, Fleet Marine Training Center, Troop Training Unit, Marine Barracks, and Base Depot. The USMC established specialty camps within or near Camp Elliott for parachutists (Camp Gillespie to the southeast); scouts, snipers, and officer candidates (Green's Farm in the north-central portion of Camp Elliott); replacement troops awaiting overseas posting (Linda Vista Camp); and tank training (Jacques Farm) (Ref. 5).

The USMC activated the Camp Elliott Tank School at Jacques Farm in 1942 (Ref. 5). Jacques Farm was approximately 6.4 miles southwest of the East Elliott MRS 01. Training at Jacques Farm included gunnery instruction with live-firing training exercises using 37 millimeter (mm) and 75mm artillery, and machine guns. Based on analysis of a firing range map, the nature and estimated quantity of munitions potentially present on the west face of Fortuna Mountain, and the results of investigations, USACE determined that most of the live-fire training the USMC conducted at the training school was directed toward the northeast, relying on Fortuna Mountain as a natural backstop (Ref. 5). Stray munitions fired over Fortuna Mountain may have resulted in the presence of DoD Military Munitions in the vicinity of East Elliott MRS 01.

In November 1942, an Anti-Tank Section was activated at Camp Elliott. Anti-tank weapons included half-track-mounted 75mm guns and jeep-mounted 37mm guns. Training included live-firing at stationary and moving targets on anti-tank ranges, one of which appears to have been approximately 2 miles west of East Elliott MRS 01 and 2/3 mile east of the main Camp Elliott. Firing from this range was probably toward the east in the direction of the northwest corner of East Elliott MRS 01 (Ref. 5). Evidence of live-fire training in the impact area extending from the anti-tank range to the western boundary of East Elliott MRS 01 included 60mm to 150mm high explosive (HE) rounds, 60mm to 81mm HE mortar fins, 3.5-inch bazooka rockets, and a live M49 trip flare. Based on archival research and investigations, Proposed Plan (PP) – East Elliott MRS 01 6

USACE determined that mortar and artillery crews most likely also fired white phosphorus munitions (Ref. 7).

Following World War II and up until 1953, Camp Elliott was used as a United States Navy Training and Redistribution Center where, reportedly, live-fire training was not conducted. DoD ended its use of the East Elliott MRS 01 with the closure of Camp Elliott in 1960 (Ref. 5).

In 1961, DoD declared approximately 15,000 acres, including East Elliott MRS 01, as surplus land. With this declaration, 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 01, to real estate developers, private parties, and municipalities (Ref. 6).

Since the 1970s, DoD Military Munitions, including munitions determined by qualified personnel to be MEC, and MD have been encountered at several locations within East Elliott MRS 01. Most of these munitions were 37mm and 75mm projectiles and associated MD (e.g., fragments) that were most likely used during live-fire training. The majority of the munitions and MD encountered were located in the southeast portion of East Elliott MRS 01. In addition, brush fires in the East Elliott MRS 01 area have reportedly detonated munitions that were present (Ref. 6).

Bristol Environmental Remediation Services, LLC (Bristol) of Anchorage, Alaska under contract with USACE, completed a RI/FS Report for East Elliott MRS 01 in February 2018. USACE developed this PP based on findings of the RI/FS Report (Ref. 3).

SITE CHARACTERISTICS

Current and Anticipated Future Land Use Table 1 indicates the current and anticipated future land use for each East Elliott MRS 01 sub-area.

Topography East Elliott MRS 01 lies within the coastal plain of the Peninsular Range physiographic province of Southern California (Ref. 3). Elevation ranges from less than 340 feet (ft.) to slightly more than 1,000 ft.

above mean sea level (amsl) within the MRS. The physiography of the MRS is characterized by a series of subparallel, north–south-trending canyons that drain southward. The canyons throughout East Elliott MRS 01 are separated by several ridges that have been heavily dissected by erosion. The canyons include (from west to east) Oak Canyon, Spring Canyon, Little Sycamore Canyon, and Sycamore Canyon. Quail Canyon, a smaller tributary canyon in the northeast part of the MRS, converges with Sycamore Canyon from the northwest.

Soils Soils present at East Elliott MRS 01 are poorly developed (i.e., rocky) and relatively thin (i.e., less than 3 ft. thick) (Ref. 3). 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.

Proposed Plan (PP) – East Elliott MRS 01 7

Plant Resources A total of 166 plant species have been identified within the MRS. Of this total, 120 (72%) are species native to southern California. Table 2 presents the plant communities present in East Elliott MRS 01 sub-areas (Ref. 3):

Table 2: MRS Sub-area Plant Communities

MRS Sub-area

Diegan Coastal

Sage Scrub

Diegan Coastal

Sage Scrub/ Grassland

Southern Mixed

Chaparral

Chamise Chaparral

Sycamore Alluvial

Woodland

Mulefat Scrub

Native Grassland

Non-native

Grassland

Disturbed Habitat

MRS 01a

MRS 01b

MRS 01c

MRS 01d

MRS 01f

MRS 01g

Special Status Listed Taxa (Animal and Plant Resources) The Endangered Species Act is intended to prevent the extinction of plant and animal species, provide a means to conserve the ecosystems on which endangered and threatened species depend, and to provide a program for conservation and recovery of these species. Table 3 lists the federal-listed Threatened and Endangered (T&E) species with the potential to occur at East Elliott MRS 01. Critical habitat, as designated by the U.S. Fish and Wildlife Service, has not been identified within the MRS boundary;

however, suitable habitat (e.g., an area in which a species can or does occur) for all six T&E species has been identified within the MRS.

Table 3: T&E Species with Potential to Occur at East Elliott MRS 01

Species Federal Status Federal T&E Species Status

Crustacean

San Diego Fairy Shrimp Endangered One observation of the San Diego fairy shrimp has been documented within MRS 01c and two observations have been documented south of MRS 01f.

Birds

Coastal California Gnatcatcher

Threatened Documented observations of the coastal California gnatcatcher have been made throughout all the MRS 01 sub-areas.

Least Bell’s Vireo Endangered Two observations of the least Bell’s vireo have been documented within MRS 01f and suitable habitat is present within MRS 01c, MRS 01f, and MRS 01g.

Plants

San Diego Ambrosia Endangered Suitable habitat for the San Diego ambrosia is present in MRS 01c and MRS 01f.

Proposed Plan (PP) – East Elliott MRS 01 8

Table 3: T&E Species with Potential to Occur at East Elliott MRS 01

Species Federal Status Federal T&E Species Status

Del Mar Manzanita Endangered MRS 01c, MRS 01b, and MRS 01f have suitable habitat that has the potential to support scattered individuals of Del Mar manzanita.

Willowy Monardella Endangered Suitable habitat for willowy monardella occurs along waterways within MRS 01b, MRS 01c, and MRS 01f.

Regardless of the Preferred Alternatives chosen based on this PP, munitions response and other project actions must comply with substantive Endangered Species Act requirements regarding take of listed species and avoiding jeopardy. USACE will coordinate remedy design and incorporation of avoidance and minimization measures with the U.S. Fish and Wildlife Service.

Surface Water/Groundwater/Wetlands Ephemeral streams in East Elliott MRS 01 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. 3).

The MRS is part of the Upper San Diego River Basin. Groundwater depth and flow direction within the MRS are described below based on monitoring USACE performed in June 2010 for Sycamore Landfill (Ref. 3):

• Groundwater depth ranged from approximately 10 to 335 ft. bgs (depending on topography); and

• The groundwater flow direction was south to southwest.

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 01. 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 East Elliott MRS 01. As a result, USACE has determined that jurisdictional waters including ephemeral streams and wetlands are present in East Elliott MRS 01a, East Elliott MRS 01c, East Elliott MRS 01d, and East Elliott MRS 01g.

USACE also determined that jurisdictional waters are not present in the remainder of East Elliott MRS 01.

Prehistoric and Historic Cultural Resources Archaeological studies conducted in 2003 in support of the construction planned with East Elliott MRS 01a included a records search and intensive field survey (Ref. 3). The records search was conducted for a one-mile radius of East Elliott MRS 01a and included research at the South Coastal Information Center at San Diego State University and the San Diego Museum of Man. The search identified 39 cultural resources within that radius. All of the resources identified by the records search are prehistoric sites, the majority of which are temporary habitation sites and lithic scatters. USACE identified five sites on East Elliott MRS 01a. Based on analysis of this information, it appears that the additional cultural sites may be located in sub-areas East Elliott MRS 01b and East Elliott MRS 01d, but not in East Elliott MRS 01c, East Elliott MRS 01f, or East Elliott MRS 01g. Prior to conducting any remedial actions in sub-areas, additional archaeological studies will need to be performed to determine the impact that remedial actions may have on cultural resources.

Proposed Plan (PP) – East Elliott MRS 01 9

SUMMARY OF PREVIOUS INVESTIGATION RESULTS

Previous investigations were conducted at East Elliott MRS 01 from 1984 to 2013. The below provides a brief summary of the previous investigations and site visits at East Elliott MRS 01.

1984 Clearance Activities – The U.S. Army 70th Ordnance Detachment (Explosive Ordnance Disposal [EOD]) conducted a munitions survey within a 170-acre area near the southeast corner of East Elliott MRS 01. The location was selected by the San Diego County Sheriff’s Department and Office of Disaster Preparedness. The survey findings included:

• Moderate to heavy munitions presence was found within the 170-acre survey area; and

• The evidence of munitions use was mostly fragments from HE projectiles (Ref. 8).

1994 Removal Activities – USACE performed surface subsurface investigation for munitions (at the time referred to as ordnance and explosives waste sampling) within 11 grids (100 ft. by 100 ft.) located within East Elliott MRS 01 (Ref. 9). UXO teams conducted surface and subsurface investigations where munitions were suspected to be present. The search was conducted using both visual and geophysical investigation techniques and was conducted to a depth of three feet bgs. The maximum depth at which MD was encountered was 12 inches bgs. Only a single fuze component was encountered on the surface.

A total of 2.53 acres were surveyed across the grid (Ref. 9).

1996 Munitions Investigation (at the time referred to as Ordnance and Explosives Sampling) – USACE conducted a statistically-based geophysical survey at East Elliot MRS 01 to estimate the density of munitions present within different portions of the MRS (Ref. 8). This investigation was part of the Engineering Evaluation/Cost Assessment (EE/CA). As a result of this investigation, anomalies were detected and investigated. Munitions, some of which qualified personnel determined were MEC, were removed from East Elliott MRS 01b, East Elliott MRS 01c, and East Elliott MRS 01d. MEC was not encountered in East Elliott MRS 01a or East Elliott MRS 01g. Qualified personnel determined that four munitions (75mm HE projectiles) encountered during this investigation were MEC. In addition, a larger number of fragments and expended fuzes were found. Munitions were not encountered deeper than 10 inches bgs. Additionally, MD was not encountered deeper than 18 inches bgs. During the 1996 investigation, 27 munitions were encountered and disposed of by detonation in place or at a consolidated location. In addition, USACE removed 758 pounds of MD during this investigation (Ref. 10).

1998-1999 Construction Support and Time Critical Removal Action (TCRA) – USACE provided construction support that resulted in munitions removal operations at East Elliott MRS 01 during the expansion of Sycamore Landfill. USACE amended the scope of the construction support provided during this expansion to include a TCRA to remove munitions from the surface in an area that included East Elliott MRS 01a, East Elliott MRS 01d, and East Elliott MRS 01g. USACE provided construction support between January and April 1998, and completed the TCRA between July 1998 and February 1999.

During the landfill expansion, USACE encountered and destroyed by detonation 24 munitions determined to be MEC. The maximum depth at which munitions were encountered was 12 inches bgs. During the TCRA, USACE encountered 24 munitions determined to be MEC on the surface. These munitions were destroyed by detonation. USACE encountered a total of 48 munitions that were determined to be MEC.

Each munition and MD encountered were evaluated to determine its explosives safety status, with munitions and MD for with the explosives safety status was determined to be material documented as safe (MDAS) (totaling 1,348.5 pounds) disposed of as scrap (Ref. 10).

Proposed Plan (PP) – East Elliott MRS 01 10

1999 Engineering Evaluation/Cost Analysis – USACE completed an EE/CA for East Elliott MRS 01 (Ref. 7). This EE/CA assessed potential risk associated with the MRS. The EE/CA used data collected during the 1996 Munitions Investigations (see above) and previous investigations to identify and recommend alternative actions for each of four sectors within the MRS. The EE/CA identified four sectors within East Elliott MRS 01. The boundaries for the sectors are not consistent with the boundaries for the current sub-areas. Therefore, in the description of the recommendations from the EE/CA, several sub-areas are noted in association with more than one sector. The below recommendations were made in the EE/CA Report for each East Elliott MRS 01 sub-area (Ref. 7):

• Sector 1 – Surface Removal of Munitions. This alternative was recommended because it would significantly reduce the probability that recreational users would encounter munitions. As such, it reduces the risk associated with munitions that may be present on the surface. The northern portion of East Elliott MRS 01c and a small portion of the western side of East Elliott MRS 01b are located within this sector.

• Sector 2 – Surface Removal of Munitions. This alternative was recommended to be implemented in areas near the landfill that had not already been developed. As for Sector 1, this reduces the probability that people would encounter munitions on the surface. As such, it reduces the risk associated with munitions that may be present on the surface. The majority of East Elliott MRS 01b and small portions of East Elliott MRS 01c and East Elliott MRS 01d are located within this sector.

• Sector 3 – ICs, which include the use of warning signs and implementation of a 3Rs Explosives Safety Education Program (3Rs Program) that include 3Rs display boards intended to modify behavior of people who may encounter a munition. USACE based this recommendation on the unlikely potential that munitions would be encountered. The southern portion of East Elliott MRS 01c and East Elliott MRS 01f are located within this sector.

• Sector 4 – Surface and Subsurface Removal of Munitions. This alternative was recommended because it would result in the greatest reduction of risk associated with munitions for recreational users. East Elliott MRS 01a, the majority of East Elliott MRS 01d, and East Elliott MRS 01g are located within this sector.

The remedial alternatives recommended in the EE/CA Report were not implemented and the MRS was recommended for RI.

2003 Equestrian Staging Area Construction Support – USACE provided construction support for and a subsurface removal of munitions within a 12-acre equestrian staging area within MTRP (Ref. 3). This 12-acre area is located just south of and adjacent to the southern boundary of East Elliott MRS 01f. Over 500 anomalies were detected and investigated. Neither munitions nor MD were encountered.

2004 Sycamore Landfill Construction Support – USACE provided construction support and completed a removal action within 287 acres of this acreage of the East Elliott MRS 01b (Ref. 3). One purpose for these actions was to remove munitions from this acreage to support expansion of Sycamore Landfill.

USACE conducted fieldwork from September 2004 to July 2005. During this investigation, which included 78,000 excavations, resulted in the recovery and disposal of 23 munitions that were determined to be MEC. It also resulted in the recovery of 105 pieces of MD that were documented as safe. The maximum depth at which munitions were encountered was 36 inches bgs, with MD only encountered to 30 inches bgs.

Proposed Plan (PP) – East Elliott MRS 01 11

2004 Archives Search Report – USACE summarized information from historical records regarding the various live-fire training ranges associated with East Elliott MRS 01 during World War II (Ref. 8). The range complex was comprised of nine overlapping ranges. Of these ranges, six had firing positions located within areas that are now part of either USMC Air Station Miramar or the San Diego community of Tierrasanta.

2005 Munitions Constituents Sampling – USACE completed munitions constituents (MC) sampling, analysis, and evaluation in Sector 4, which included East Elliott MRS 01a, East Elliott MRS 01d, and East Elliott MRS 01g. Sample locations were selected in proximity to locations where munitions were encountered during previous investigations. The results of this sampling indicated that MC that were explosives (e.g., 2,4,6‐trinitrotoluene [TNT], hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine [RDX]) were not detected in the soil above environmental comparison criteria (Ref. 11); however, several metals were detected above environmental comparison criteria in the soil. Of the metals detected, only lead and barium were identified as potential MC from munitions used at East Elliott MRS 01. The report also indicated that other sources of lead may include natural occurrence, fertilizer application, defoliant application, gasoline, and exhaust from vehicular activity in the immediate or adjacent areas. However, the study concluded that the sampling results were not conclusive to discern if an environmental impact from munitions use occurred (Ref. 11).

2007 Surface Munitions Removal Action – USACE completed a grid survey and surface removal of munitions at MTRP (Ref. 14). The area encompassed approximately 1,020 acres, including East Elliott MRS 01f. Although munitions were not encountered, 19 MD items (i.e., fragments for 75mm projectile fragments, base detonating fuzes, and barrage rocket warheads and motors) were encountered. Only one of these (a 75mm projectile fragment) was encountered within the boundary of East Elliott MRS 01f.

2016-2017 Site Development East Elliott MRS 01a – During 2016-2017, the landowner developed the 120.6-acre East Elliott MRS 01a. Qualified UXO personnel assessed the site for explosive hazards during the development, which included extensive soil grading and earth-movement of 1.2 million cubic yards of soil, and no munitions were recovered.

SUMMARY OF REMEDIAL INVESTIGATION RESULTS

2013 – 2018 Remedial Investigation/Feasibility Study – USACE conducted an RI to characterize the nature and extent of munitions and MC, fill data gaps, and assess potential explosives safety hazards within the East Elliott MRS 01. The FS evaluated remedial alternatives for their ability to reduce the potential explosives hazards associated with munitions posed to property owners and the general public (Ref. 3).

Accord Engineering, Inc. (Accord), under a USACE contract, conducted an RI at East Elliott MRS 01 from December 2012 through March 2014. The RI included the conduct of a geophysical survey using DGM towed-array and man-portable equipment. The RI also included environmental sampling, including sampling of background soil, and analysis. During the RI, intrusive investigation of detected geophysical anomalies was not conducted. The DGM data collected during the RI identified the boundaries of the potential impact areas, while the results of previous investigations at East Elliot MRS 01 provided data to identify the potential munitions present. Collectively, these investigations, which bounded the impact areas and identified the munitions potentially present, satisfied the criteria for characterizing the nature and extent of munitions present.

Proposed Plan (PP) – East Elliott MRS 01 12

Bristol used the RI data collected by Accord during the RI field operations to support the preparation of the RI/FS Report. The RI portion of the RI/FS Report characterizes the nature and extent of munitions and MC that may be present at East Elliott MRS 01. The FS portion of the RI/FS Report used information from the RI to develop, evaluate, and comparatively analyze potential remedial alternatives for each MRS sub-area.

Munitions and Explosives of Concern Characterization Results of the RI field characterization effort confirmed the munitions information gleaned from archival research, investigations, and site visits. During the RI, munitions were not recovered within East Elliott MRS 01; however, MD (five projectile fragments) was identified on the surface within East Elliott MRS 01b and East Elliott MRS 01d. Archival research indicated DoD’s use of, and the presence and distribution of munitions and MD observed or encountered during previous investigations confirm that the USMC used East Elliott MRS 01 as an artillery and tank training area (Ref. 3). A summary of the characterization results for each East Elliott MRS 01 sub-area is provided below:

• East Elliott MRS 01a comprises approximately 120.6 acres. Historical information indicates the USMC used this area as an impact area for live-fire artillery and tank training. However, there was also physical evidence to indicate that DoD (USMC) conducted munitions-related activities (live-fire) within this sub-area.). Munitions and MD were removed from accessible areas within this sub-area during the TCRA USACE completed in 1998-1999.

Neither munition nor MD was encountered at East Elliott MRS 01a during RI field operations.

However, intrusive investigations of detected anomalies were not conducted during the RI’s field operations. The results of the RI’s DGM surveys and previous investigations were analyzed using Visual Sample Plan (VSP) software and ArcGIS software to identify areas within this sub-area that exceeded an estimated 400 geophysical anomalies per acre. An estimate of this nature 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 this sub-area to be less than 50 anomalies per acre, with a maximum density of 315 anomalies per acre. According to the ArcGIS analysis, the mean density of munitions within East Elliott MRS 01a is 0.12 UXO/acre. This geophysical data indicates that a potential impact areas was not present because the threshold density of 400 anomalies per acre that indicates the presence of a potential impact area was not attained.

Available data indicates munitions are not present on the surface within East Elliott MRS 01a.

As such, an exposure pathway for surface munitions is considered incomplete. Subsurface munitions may be present; therefore, the exposure pathways for munitions within the subsurface is considered potentially complete because the subsurface geophysical anomalies have not been investigated.

• East Elliott MRS 01b comprises approximately 523.3 acres. Historical information indicates the USMC used the area as an impact area for live-fire artillery and tank training. RI field operations at this MRS sub-area consisted of MC soil sampling. USACE did not conduct a geophysical survey using DGM within this area because it had previously conducted an extensive munitions removal within this sub-area. During the soil sampling activities, only a single MD, an apparent projectile fragment of approximately ¼-inch long by ¼-inch wide, was observed.

Previous investigations that USACE conducted covered approximately 271.9 acres of East Elliott MRS 01b. Given the results of these investigations, USACE does not believe that munitions

Proposed Plan (PP) – East Elliott MRS 01 13 remain present within this sub-area. Therefore, USACE considers surface and subsurface exposure pathways for munitions as incomplete. USACE has not investigated approximately

218.2 acres of East Elliott MRS 01b, which encompasses the active landfill. However, this area has been extensively modified through cut-and-fill activities associated with the creation of the landfill. Approximately 33.2 acres within this sub-area have not been investigated. Given the presence of a landfill liner, trash, and fill dirt that would prevent a receptor from accessing native soils in which munitions may be present, USACE considers surface and subsurface exposure pathways for munitions to be incomplete.

USACE did not conduct a geophysical survey with DGM within East Elliott MRS 01b during the RI field operations. However, USACE analyzed data from previous investigations of this and adjacent areas to the sub-area using VSP and UXO Estimator. VSP calculated the mean average density of geophysical anomalies to be 34 anomalies per acre, with a maximum of 109 anomalies per acre. The UXO Estimator analysis indicated, a 95% confidence level, that there is less than

0.38 munitions (potential UXO) per acre.

USACE anticipates that munitions are not present on the surface or in the subsurface within the majority of East Elliott MRS 01b based on the results of previous actions to remove munitions from both the surface and subsurface. However, USACE considers the surface and subsurface exposure pathways for munitions in areas not previously investigated to remain potentially complete.

• East Elliott MRS 01c comprises approximately 1,177.3 acres. Historical information indicates this area was used as an impact area for live-fire artillery and tank training.

Neither munitions nor MD were encountered within East Elliott MRS 01c during RI field operations. USACE did not investigate geophysical anomalies detected during the RI field operations. USACE analyzed the results of DGM surveys from the RI and previous investigations using VSP software and UXO Estimator. USACE conducted this analysis to identify areas within the East Elliott MRS 01c that exceeded an estimate of 400 geophysical anomalies per acre. As previously indicated, an estimate of this nature would indicate activities (e.g., live-fire into an impact area) that created a clustering of anomalies. The estimated geophysical anomaly density within most of this sub-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 an approximately 1.5-acre area in the northwestern corner of East Elliott MRS 01c. The UXO Estimator analysis indicated, with a 95% confidence level, that there is less than 0.1 munitions (potential UXO) per acre.

Based on the previous identification of munitions in the surface and subsurface and of the presence of geophysical anomalies that were not intrusively investigated, there is still a potential for munitions to be present in the surface or subsurface within this MRS. However, the density analysis indicated that munitions would most likely be present in the northwest corner of East Elliott MRS 01c. Therefore, USACE considers the exposure pathways for surface or /subsurface munitions as potentially complete.

• East Elliott MRS 01d comprises approximately 867.4 acres. Historical information indicates the area was used as an impact area for live-fire artillery and tank training.

Proposed Plan (PP) – East Elliott MRS 01 14

During soil sampling and blind seed program activities conducted during the RI, MD was encountered. These four fragments (MD), which were buried horizontally in the soil, appeared to be projectile fragments. USACE did not investigate geophysical anomalies identified during the RI field operations.

USACE analyzed the results of the RI’s geophysical survey and previous geophysical surveys using VSP software, UXO Estimator, and ArcGIS software to identify areas within East Elliott MRS 01d that had more than an estimated 400 geophysical anomalies per acre. The density of geophysical anomalies within most of East Elliott MRS 01d was less than 100 per acre. However, the maximum density was 1,850 per acre. The area with the highest density is located in the south-central area of East Elliott MRS 01d to the south of the Sycamore Landfill. This area includes approximately 36.4 acres with an anomaly density of over 1,000 anomalies per acre, which is surrounded by approximately 38.7 acres with a density of over 400 anomalies per acre. Along the northwestern and southern boundaries of East Elliott MRS 01d are three additional areas with densities of over 400 anomalies per acres.

For East Elliott MRS 01d, the UXO Estimator analysis indicated, with a 95% confidence level, that there is less than 0.5 munitions (potential UXO) per acre; the ArcGIS analysis indicated areas with a potentially high density of munitions. These areas align with the delineated areas from VSP analysis, but also extend northward to where a majority of munitions were encountered during the

TCRA.

During previous investigations, USACE removed munitions and MD have from East Elliott MRS 01d. USACE removed munitions and MD from accessible areas within this MRS during the TCRA in 1998-1999. Therefore, USACE considers the exposure pathway for surface munitions as incomplete. However, because subsurface munitions may remain present within this MRS, USACE considers the exposure pathways for munitions in the subsurface as potentially complete.

• East Elliott MRS 01f comprises approximately 198.9 acres that are located within the current boundary of MTRP. Historical information indicates the area was used as a buffer area for live-fire artillery and tank training. This training was directed toward the western side of Fortuna Mountain. USACE did not conduct RI field operations at East Elliott MRS 01f given that historical information did not indicate that the area’s use as an impact area and two removal actions, which were conducted in and around East Elliott MRS 01f did not encounter munitions.

USACE based its conclusions on results of previous investigations of this MRS.

The two removals actions addressed above were a surface removal of munitions from the entire MRS and a subsurface removal from within 12 acres adjacent to the southeastern boundary of East Elliott MRS 01f. USACE assumes the subsurface removal’s results apply to East Elliott MRS 01f because the MRS’ conditions and historical use are the same. A 75mm projectile fragment was encountered on the surface during a surface investigation in 2007. Previous investigations and records of the historical use of the area did not indicate the presence of munitions. Therefore, neither an intrusive investigation of anomalies nor a subsurface removal of munitions was required during the RI.

Available data indicates munitions are not likely to be present on the surface of East Elliott MRS 01f; therefore, USACE considers the exposure pathways for surface munitions as incomplete.

Although subsurface investigations completed near East Elliott MRS 01f indicated that

Proposed Plan (PP) – East Elliott MRS 01 15 subsurface munitions are not likely present, USACE considers the exposure pathways for subsurface munitions as potentially complete.

• East Elliott MRS 01g, which comprises approximately 54.8 acres, is located in the northeast corner of the acreage addressed by the RI. Based on the historical information USACE’s, St. Louis District reviewed, this acreage was not used within range fans used during live-fire training at Camp Elliott and should not be included in East Elliott MRS 01. USACE recommended East Elliott MRS 01g for “No Action.” As such, it was not analyzed during the FS.

Munitions Constituents Characterization USACE conducted an assessment for the presence of residual MC through a biased sampling program for MC that were explosives and metals in surface (0 to 0.5 ft. bgs) soil. USACE collected 35 samples from potential munitions areas identified during a geophysical survey using DGM with higher density of geophysical anomalies. Each sample was analyzed for MC that were explosives (e.g., TNT, RDX) and selected metals (i.e., antimony, copper, lead, and zinc).

USACE collected a total of 30 background MC (selected metals) samples at locations outside the former range areas.

• Explosives – Analytical results for MC (explosives) were non-detect in soil samples collected within the East Elliott MRS 01.

• Metals – Analytical results for antimony were non-detect for soil samples collected in East Elliott MRS 01. Statistically significant differences were not observed in concentrations of copper, lead, or zinc for any of the data groups. There was insufficient evidence to conclude concentrations of metals were significantly greater than the background concentrations. It should be noted that the two soil types at the background site study areas were separately sampled but no significant difference in metal concentrations was detected between the two soil types for either East Elliott MRS 01 or background study areas.

Detections of MC (explosives) or antimony were not detected within East Elliott MRS 01 or background soil sample. However, the level of detection for one explosives compound (2,6-dinitrotoluene) was higher than the ecological risk-based screening criteria for this compound. Also, metals were not identified in East Elliott MRS 01soil samples at concentrations that were statistically elevated relative to background levels. Therefore, USACE determined that a potentially complete exposure pathway for MC, either metals or explosives, had not been identified for surface soil. This included for incidental ingestion, inhalation, and dermal contact for human receptors and ingestion and dermal contact for ecological receptors. Neither subsurface soil nor groundwater exposures related to leaching of contaminants of potential concern from surface soil are expected at East Elliott MRS 01. A soil source for MC was not identified within impact areas identified within the East Elliott MRS 01. As such, USACE considers the potential exposure pathways within East Elliott MRS 01 for surface water and sediment as incomplete.

Remedial Investigation Results Conclusions The project objectives for the RI field operations included collecting geophysical data to accurately locate and record the locations of geophysical anomalies (e.g., potential MEC or MD) for the purpose of identifying high density areas (potentially indicative of impact areas) and to collect 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 MEC.

Proposed Plan (PP) – East Elliott MRS 01 16

RI findings with regard to munitions and MC:

• Munitions were not encountered in East Elliott MRS 01 during RI field operations;

• MD that resulted from the historic use of tank and artillery munitions was encountered at five locations during surface soil sampling within East Elliott MRS 01b and East Elliott MRS 01d;

• Geophysical anomaly densities were calculated for each East Elliott MRS 01 sub-area. Based on the available data, USACE determined that anomaly density of greater than 400 anomalies per acre may be indicative of potential impact areas. Table 4 summarizes the average and maximum anomaly densities for each East Elliott MRS 01 sub-area. Note anomalies are defined only as subsurface metallic materials (Ref. 3); and

Table 4: Summary of Geophysical Anomaly Densities for East Elliott MRS 01 Sub-areas

MRS Sub-area Average Calculated Geophysical Anomaly Density

Maximum Calculated Geophysical Anomaly Density

East Elliott MRS 01a 36.7 anomalies/acre 315 anomalies/acre

East Elliott MRS 01b 34 anomalies/acre 109 anomalies/acre

East Elliott MRS 01c 21.2 anomalies/acre 554 anomalies/acre

East Elliott MRS 01d 125.2 anomalies/acre 1,850 anomalies/acre

East Elliott MRS 01f N/A N/A

East Elliott MRS 01g 16.8 anomalies/acre 106 anomalies/acre

• Neither MC (explosives) nor antimony were detected within East Elliott MRS 01 or background soil samples. Additionally, metals were not identified in soil samples collected within the East Elliott MRS 01 at concentrations that were statistically elevated relative to background levels in the MRS. Therefore, potentially complete exposure pathways for MC (metals or explosives) were not identified for surface soil, including incidental ingestion, inhalation, and dermal contact for human receptors, and ingestion and dermal contact for ecological receptors.

Figure 4 presents the results of the geophysical anomaly density analyses and historical munitions recoveries for East Elliott MRS 01. Note that geophysical anomaly density is not shown for East Elliott MRS 01f because RI field activities were not conducted in this sub-area. A complete detailed listing of the investigation results for East Elliott MRS 01 is contained in the RI/FS Report (Ref. 3).

Proposed Plan (PP) – East Elliott MRS 01 17

SUMMARY OF STAKEHOLDER AND PUBLIC INVOLVEMENT

USACE, Los Angeles District, discussed information related to the RI/FS with DTSC, local government representatives, and property owners during several technical project planning (TPP) meetings. Prior to initiating the RI fieldwork, USACE held TPP meetings in December 2011 and August 2012. During development of the RI/FS Report, USACE held TPP meetings in August 2014 and February 2016.

USACE also hosted a public meeting in August 2014 at the MTRP visitor center. This meeting’s purpose was to allow USACE to provide the community an update on the munitions response’s status and to give community members the opportunity to discuss their concerns with USACE personnel. USACE published an announcement for the meeting in the local newspaper. In addition, USACE sent postcards with details

Figure 4 East Elliott MRS 01 Geophysical Anomaly Density

Proposed Plan (PP) – East Elliott MRS 01 18 regarding the meeting to property owners on and adjacent to East Elliott MRS 01. Eleven community members attended the meeting, including representatives from the City of San Diego, DTSC, the office of City Councilman Scott Sherman, Pardee Homes, Mission Trails Regional Park, Save Mission Trails Non- Profit Organization, and local residents.