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Section 1 - Introduction

Camp Stanley Storage Activity (CSSA) is an active U.S. Army facility covering 4,004 acres in northwestern Bexar County, Texas. The primary mission of CSSA is the receipt, storage, issue and maintenance of ordnance materiel. Because of its ordnance mission, CSSA has been designated as a restricted access facility. CSSA also has an agreement for cattle grazing with the United States Department of Agriculture (USDA) Agricultural Research Service (ARS), and limited wildlife hunting is allowed. No change to the CSSA mission and military activities are expected in the future. A site location and land use map is provided as Figure 1.1.

Thirty-six (36) solid waste management units (SWMUs) and 40 areas of concern (AOCs) (including 5 rifle management units, or RMUs) have been identified at CSSA. These units include a wide variety of sites, including waste disposal areas, ammunition demolition areas, and firing ranges. An Administrative Order of Consent was issued for CSSA on May 5, 1999. A Remedial Facility Investigation (RFI) work plan has been submitted.

The purpose of this technical approach document is to describe the methodology to be used by Parsons Engineering Science, Inc., (Parsons ES) in the determination of the potential for human health and environmental risk associated with each site. In addition, the document outlines the methodology for deciding whether to close sites using the Risk Reduction Rules (30 TAC �335) or the Texas Risk Reduction Program (TRRP, 30 TAC �350). If the decision is made to close the site using the TRRP, the methodology for determining critical human health and ecological Protective Concentration Limits (PCLs) and the comparison of those PCLs to site-specific concentrations is provided. Previous and current investigations at the sites are evaluating the sources, extent, and pathways of potential contamination. These data will be evaluated to assess possible impacts to public health, welfare, and the environment due to exposure to chemicals of potential concern (COPCs) in soils, groundwater, surface water, and sediment. An initial evaluation will be conducted to determine the feasibility of closing the site using the Risk Reduction Rules Standard 1 criteria, which require that all contamination at the site be removed to background concentrations. If it is determined that it is not feasible nor desired to "clean close" the site, then the TRRP approach will be used. The approach to identifying COPCs and possible AOC will follow all procedures as outlined in the TRRP. Contaminants detected in affected media will be compared to appropriate critical PCLs.

The procedures described in this technical approach document will be used to accomplish the evaluation for CSSA. The document includes a description of the objectives and scope of the evaluation; a discussion of the rationale and methodology; procedures for data evaluation and identification of COPCs; and procedures for the exposure pathway analysis, and comparison to critical PCLs. Procedures for the qualitative, risk-based evaluation of soils as a source of contamination to other media are also described.

1.1 - Objectives and Scope

Through sampling and analysis of appropriate environmental media, the objectives of the investigative studies at CSSA are to acquire data to confirm and quantify potential environmental contamination and to support closure decisions. The risk evaluation will be used to support a decision regarding the selection of appropriate Remedy Standards at each site, provide the basis for determining whether a remedial action is necessary, and justify performing a remedial action, if required.

The chemistry data collected in the previous investigations will provide the basis for the comparison of site-specific concentrations to background or critical PCLs. The soils data will also be used to evaluate soils as a contaminant source (e.g., leaching of contaminants in soils to shallow groundwater, runoff of contaminants in surface soils to surface water/sediment). The groundwater data will be used to evaluate groundwater as a contaminant source (e.g., migration of contaminants in groundwater to surface water).

COPCs identified for a site will be based on the available chemistry data and may include volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), explosives, polychlorinated biphenyls (PCBs), and inorganic compounds (i.e., metals). The general types of source constituents for the sites are assumed to include solid waste disposal areas, firing ranges, ammunition/ordnance burning and disposal, and compounds associated with vehicle maintenance (e.g., fuels, solvents, waste oils).

1.2 - Guidelines

The methodology for conducting a closure under Standard 1 of the Risk Reduction Rules (RRS) are outlined in 30 TAC �335. The techniques and methodology used to determine critical PCLs and to conduct a comparison to site-specific concentrations are outlined in the TRRP. If necessary, the following documents will be used to supplement the guidance supplied by the Texas Natural Resource Conservation Commission (TNRCC) in the TRRP:

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