[Home] 

[Table of Contents] [Next Section]

Final B-20 Soil Stabilization/Solidification Treatability Study Report

Section 2 - Site and Study Background

2.1 - Facility Description

CSSA is located in northwestern Bexar County, approximately 19 miles northwest of downtown San Antonio in south-central Texas (Figure 2.1). The installation consists of 4,004 acres immediately east of State Highway 3351 (Ralph Fair Road), and is approximately 0.5 mile east of Interstate Highway 10 (Figure 2.1).

CSSA is a restricted-access installation with inner cantonment lands to the southwest and outer cantonment areas to the east and north. Operation buildings and storage magazines are located within the inner cantonment. Outer cantonment land is primarily undeveloped open range. The eastern boundary of CSSA and part of its northern and southern boundaries are contiguous to Camp Bullis Military Training Reservation. The surrounding area to the west is primarily rural and zoned for residential use. Some residential development is also present west, northwest, and southwest of the installation. The location of SWMUs B-32, B-33 and B-20 at CSSA are shown in Figure 2.2.

2.2 - Site Background and History

An environmental assessment (EA) was developed for CSSA in 1993, identifying, describing, and evaluating potential and known environmental impacts associated with current and past operations. Thirty-four potential SWMUs were identified following a review of records, interviews with CSSA personnel, and field observations.

Subsequent investigations and field work at CSSA identified thirty-six SWMUs, thirty-five areas of concern (AOCs), and five rifle management units (RMUs) to date. Lead and other inorganic constituents were identified as possible contaminants of concern for several of these sites.

2.3 - Soils

In general, soils at CSSA are thin, dark-colored, gravely clays and loams. The soil types are strongly influenced by topography and the underlying limestone. All soil classifications used for this report are taken from the USDA Soil Conservation Service (now the Natural Resource Conservation Service) soil survey series for Bexar County, Texas (USDA, 1991). More information pertaining the soils at CSSA may be found in the Background Information Report section, located in Volume 1-1 of the CSSA Environmental Encyclopedia.

2.4 - Geology

A description of the B-20 geology is included in the Geology section of the Background Information Report, located in Volume 1-1 of the CSSA Environmental Encyclopedia.

2.5 - Statistical Evaluation of Background Metals Concentrations

Information regarding the statistical approach, normality tests, and procedures for non-detects for background metals concentrations is included in the Statistical Evaluation of Background Metals Concentrations found in Volume 2 of the CSSA Environmental Encyclopedia. Because of laboratory quality issues, the background levels of soil types located at CSSA are subject to change. A re-evaluation of background levels is expected to be completed for all soil types at CSSA due to replacement of analytical data from ITS Laboratories. However, for the remaining discussions of this report Parsons ES will use the previously calculated background concentrations for the B-20 site soils.

2.6 - Summary of Prior Investigation Results

A brief summary of results obtained from previous investigations are provided in the B-32, B-33 and B-20/21 sections in Volumes 1-2 and 3-1 of the CSSA Environmental Encyclopedia. An overview of the results of previous investigations is discussed below.

SWMU B-20

A total of 43 surface soil samples were collected during the Phase I Remedial Investigation of B-20 in November 1994. These samples consisted of 21 judgmental samples and 22 random systematic samples. An additional 16 surface soil samples were collected in September 1995 during the Phase II Remedial Investigation. All surface soil samples were collected at a depth of approximately 0.5-foot. Analytical techniques followed procedures described in Test Methods for Evaluating Solid Waste, U.S.EPA, SW-846, November 1986 (EPA, 1986). Terra Laboratories in League City, Texas performed all metal analyses for the remedial investigations at B-20.

Results of these investigations concluded that approximately 30 percent of the surface soils were contaminated with heavy metals, including arsenic, barium, cadmium, lead, and mercury at levels above Risk Reduction Standard 1 (RRS1), or background levels (see Table 2.1).

Table 2.1 - Summary of Surface Soil Sampling Results for Heavy Metals*

Explosive residue was detected at low concentrations in extremely localized areas. For instance, soil samples collected immediately under �chunks� of raw TNT contained explosive residue, as might be expected. However, soil samples collected as little as 3 to 4-inches away did not contain any explosives. In addition, a total of 812 UXO items were removed from the site and its perimeter areas (Parsons ES, 1996). Most UXO found at the site consisted of explosive residue encased in a portion of the original metal housing of the ordnance item. Intertek Testing Services (ITS) laboratory, located in Richardson, Texas, analyzed the samples collected during the sifting operations. Because of issues concerning the quality of any data generated from the ITS laboratory, the data were determined to be questionable, and only usable as screening or qualified data. The focus of this report is on the ability of S/S to remediate heavy metals from surface soils at CSSA and does not address UXO or explosive residue.

SWMUs B-32 and B-33

A discussion of the media and contaminants of concern is located in the B‑20/21, B-32 and B-33 sections in Volume 1-2 of the CSSA Environmental Encyclopedia and in the Remedial Investigation Report for SWMU B-20 (Parsons ES, 1995). A brief overview of the contaminants of concern is discussed below.

Lead-contaminated sand that served as bedding for polyvinyl chloride (PVC) and vitrified clay piping was encountered during previous investigations at B-32 and B-33. Approximately 415 feet of pipe was bedded in lead-contaminated sand containing shot which was generated at the Building 90 test firing room. The bedding extended to a depth of approximately 3.5 feet and was approximately 2 feet wide. The pipe bedding and surface fill material was excavated and replaced with clean materials.

2.7 - Media and Contaminants of Concern

SWMU B-20

Results of the surface soil analytical data indicated elevated lead levels in several areas within the SWMU B-20 boundary were metals concentrations exceeded hazardous levels. Field observations noted several areas where particulate lead and metal fragments (metallic projectiles) were found.

SWMUs B-32 and B-33

Three representative samples from the excavated pipe bedding material were collected from both SWMUs B-32 and B-33 in March 1996. Additionally, three soil boring samples were collected at both sites during August 1996. The contaminants of concern for both the surface soil and soil boring samples were analyzed by ITS laboratory. While total lead and explosives were identified as contaminants of concern, an EPA memorandum issued in April 1999 states that results obtained from ITS are not usable. During April 1999, representative samples from the excavated soil at SWMU B‑32 and B-33 were re-collected and analyzed for leachable lead and total explosives content by Emax Laboratories. Data from analytical results indicted that soils contained no explosives and leachable lead levels from the soils indicated the soils were not suitable for non-hazardous disposal within a municipal landfill.

2.8 - Determination of Cleanup Levels

The remediation action levels for this treatability study correspond to Texas Natural Resource and Conservation Commission (TNRCC) waste characterization standards specified in 30 Texas Administrative Code (TAC) Chapter 335, subchapter R. Contaminant concentrations must not exceed leachable TNRCC class 1 non-hazardous toxic characteristic levels (0.15 mg/l) for disposal within a municiple landfill. The laboratory test for evaluating leachable wastes is the Toxicity Characteristic Leaching Procedure (TCLP). The TCLP (described in 40 CFR 261, Appendix II), seeks to mimic the effect of mildly acidic water on contaminant mobility. This extract is considered to be an approximation of the worst case leachate that the waste will generate if disposed into what EPA considers a worst case scenario, a municipal landfill.

The EPA has set a standard of 5 mg/l in TCLP leachate as a threshold above which a soil would be considered as hazardous for waste management purposes. In order to dispose of soils off-site containing hazardous leachable lead levels, the EPA has promulgated a rule that defines the metals contaminated soil as a special class of waste under the Resource Conservation and Recovery Act (RCRA) for the purposes of restricting its disposal on land (Land Disposal Restrictions Phase IV rule). Under the LDR Phase IV rule, soils which exceed the TCLP MCL of 5 mg/l for lead must be treated if the soil is removed from its original sit    e of contamination. Treatment is required to reduce measured TCLP values by 90 percent or ten times the specified universal treatment standard (UTS), whichever is greater. The LDR Phase IV standard sets the UTS for lead at 0.75 mg/l as measured by the TCLP. Ten times the UTS is 7.5 mg/l, therefore, for land disposal restriction purposes, lead-contaminated soil would not have to be treated below 7.5 mg/l. Soils that exhibit TCLP levels above 75 mg/l would be governed by the 90 percent reduction requirement since any TCLP value above 75 mg/l that is reduced by 90 percent would result in a post-treatment TCLP value greater than 7.5 mg/l.

Table 2.2 - Required TCLP Concentrations for
Soils Removed from its Original Site of Contamination

[Next Section]