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SWMU B-23A RCRA Facility Investigation/Closure Report

Section 1 - Introduction

On May 5, 1999 an Administrative Consent Order was issued to Camp Stanley Storage Activity (CSSA) pursuant to §3008(h) of the Solid Waste Disposal Act (SWDA), as amended by Resource Conservation and Recovery Act (RCRA), and further amended by the Hazardous and Solid Waste Amendments (HSWA) of 1984. In accordance with the RCRA Facility Investigation (RFI) requirements of the Consent Order, an RFI report for Solid Waste Management Unit (SWMU) B‑23A was completed in July 2003. The purpose of the RFI report was to document the environmental condition of the site, site closure requirements, and recommend further investigation or provide documentation necessary for site closure. This closure report includes by reference the information presented in the SWMU B‑23A RFI Report.

SWMU B-23A was a disposal trench, approximately 60 feet by 20 feet by 5 feet deep. Small glass ampueles containing an unknown liquid were visible in the trench surface soil. The SWMU B‑23A RFI Report recommended excavation and disposal of waste and waste residue. The RFI report estimated 2,420 cubic yards of waste material and residue would require removal at the site. Results from three surface soil samples collected at SWMU B‑23A indicated background exceedances of copper. Confirmation sampling for copper and semivolatile organic compounds (SVOC) was to be conducted to confirm that the site met closure requirements. Copper was the only analyte detected above background standards during the RFI. SVOC analysis was included due to the presence of SVOC tentatively identified compounds (TICs) in the liquid in the ampoules. This report documents the closure activities at SWMU B‑23A.

The closure work was performed by Parsons under the U.S. Air Force Environmental Remediation and Construction (ENRAC) Contract F41624-01-D-8544, Task Order 19 (TO 0019). The Air Force Center for Environmental Excellence (AFCEE) provided technical oversight for the delivery order. Based on the project statement of work (SOW), a set of work plans to govern the fieldwork was established. These include:

Closure activities at SWMU B‑23A were conducted during December 2003. As recommended in the RFI report, excavation and disposal activities were conducted. Excavation indicated that there was no buried waste material at the site, and only 20 cubic yards of soil and surface waste was excavated and disposed. Confirmation sampling was conducted after excavation to verify that the site met closure requirements.

For this closure report, Section 1 provides the site-specific background and closure standard. Section 2 describes the closure actions and closure evaluation. Section 3 summarizes the findings, evaluates attainment of data quality objectives (DQO), and certifies the site closure. References cited in this report can be found in the Bibliography (Volume 1‑1 of the Environmental Encyclopedia).

1.1 - Closure Standard

As described in Section 4.3 of the Risk Assessment Technical Approach Document (Volume 1-6), CSSA opted to pursue closure of many of its sites under the Risk Reduction Rule (RRR) (30 Texas Administrative Code [TAC] §335). A notification of intent to close sites identified to date (including SWMU B‑23A) was sent to the Texas Commission on Environmental Quality (TCEQ) in accordance with the RRR on July 12, 1999. TCEQ acceptance of this notification was received on October 5, 1999.

Following RRR guidelines, if site concentrations are at or below background and all waste and waste residue has been removed, then the site can be closed under Risk Reduction Standard 1 (RRS1). Background levels are the RRS1 criteria for metals concentrations, and laboratory reporting limits (RL) are the RRS1 criteria for organic compounds. Based on the RFI sampling results at SWMU B‑23A, CSSA opted to clean the site to background levels and pursue closure under RRS1. If closure requirements under RRS1 are attained and approved by the TCEQ Executive Director, then the owner is released from the deed recordation requirement.

Due to the presence of waste at the site, as well as copper concentrations above background levels, removal of waste and waste residue was recommended to meet RRS1 requirements.

1.2 - Background and Site Description

1.2.1   CSSA

General information regarding the history and environmental setting of CSSA is provided in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report). In that report, detailed data regarding the geology, hydrology, and physiography are also available for reference.

1.2.2   SWMU B‑23A

1.2.2.1   Site Description

The site covers approximately 0.3 acre, and is shown in Figure B23A-6 (Figures B23A‑1 through B23A-5 are provided in the SWMU B-23A RFI Report). An apparent trench or disturbed area was observed in a 1966 aerial photograph. Figure B23A-7 shows aerial photos of the site over time. A September 1993 field survey revealed a possible trench that had been filled in with soil. During the field survey, several glass ampoules containing different colored liquids were discovered on the ground surface at the site. CSSA did not know exact dates of usage for SWMU B‑23A or how long the ampoules had been at the site.

Additional background information regarding the location, size, and known historical use of the site is also included in the Environmental Encyclopedia (Volume 1-2, SWMU B‑23A). Volume 1-2 includes a Chronology of Actions and a Site-Specific Work Plan Addendum for SWMU B‑23A.

1.2.2.2   Potential Sources of Contamination

SWMU B‑23A was presumed to be an in-filled trench during the initial field survey in September 1993. Several small (½-inch length, ¼-inch diameter) ampoules, which were determined to be time-delay fuses for M34 delay firing devices, were present on the ground surface during the site survey. The ampoules contained liquids of various colors, which correspond to different delay periods. The liquid contained in the ampoules is a potential contamination source.

Ampoules found on the ground surface at B-23A. September 2001

Initially, during the RFI, contaminants of concern (COCs) consisted of metals, volatile organic compounds (VOC), and SVOCs. Based on the results of the RFI, including ampoule testing, COCs for closure include copper and SVOCs.

1.2.2.3   Site Location

SWMU B‑23A is located in the North Pasture of CSSA, approximately 3,200 feet east of the western boundary of CSSA and approximately 3,000 feet south of the northern border of CSSA, as shown in Figure B23A-6. SWMU B‑23A is approximately 75 feet long and 30 feet wide. The site’s total area is approximately 0.3 acre. SWMU B‑23A is located approximately 250 feet southeast of SWMU B-23 and approximately 1,000 feet northeast of SWMU B-6.

1.3 - Site Environmental Setting

A detailed description of the site environmental setting is provided in the CSSA Background information Report (Volume 1-1) and the SWMU B‑23A RFI Report (Parsons, 2002).

1.3.1   Site Soil and Topography

The only soil type occurring at SWMU B‑23A is the Tarrant Association (Figure B23A‑2 in the B‑23A RFI Report). Tarrant soil occurs along the outer edges of the Salado Creek floodplain. The topographic elevation of the site area varies from approximately 1,320 to 1,330 feet above mean sea level (MSL). Drainage within SWMU B‑23A is to the west-southwest.

1.3.2   Geology

The Upper Glen Rose (UGR) Limestone is the uppermost geologic stratum in the area of SWMU B‑23A (Figure B23A-8), but no bedrock outcrops are present within the site area. The UGR consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds, up to 50 feet thick. The UGR is underlain by the Lower Glen Rose (LGR) (approximately 320 feet thick). The LGR Limestone is underlain by the Bexar Shale (regionally known as Hensell Shale, with an average thickness of 60 feet). The geologic strata at CSSA dip approximately 10 to 12 degrees to the south-southeast.

1.3.3   Hydrology

The uppermost hydrogeologic layer at CSSA is the unconfined Upper Trinity Aquifer, which consists of the UGR Limestone. Locally at CSSA, low-yielding perched zones of groundwater can exist in the UGR. Principal recharge into the Middle Trinity Aquifer is via precipitation infiltration at outcrops. Groundwater discharge occurs predominantly via natural springs, seeps, and pumping. Regional groundwater flow appears to be to the southeast.

No site-specific information regarding groundwater is available. The nearest well is CS‑MWG-LGR (formerly Well G), which is a livestock well located approximately 1,000 feet west of SWMU B‑23A (Figure B23A-2 in the B-23A RFI Report). Static water levels in CS-MWG-LGR have measured between a high of 171.22 feet bgs (April 2003) and a low of 310.10 feet bgs (September 2000).

1.3.4   Cultural Resources

Cultural resources are prehistoric and historic sites, structures, districts, artifacts, or any other physical evidence of human activity considered important to a culture, subculture, or community for scientific, traditional, or religious purposes. The nearest historical cultural resource consists of a burned rock midden located approximately 750 feet west of SWMU B‑23A.

1.3.5   Potential Receptors

A survey of local and possible future uses of groundwater and surface water, water wells, and sensitive environmental areas at CSSA was completed in December 1999. Results of that survey, along with results from a more in-depth survey to identify potential receptors, points of human exposure, and possible constituent pathways, are presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1-6).

The closest sensitive receptor to SWMU B‑23A is the intermittent creek that lies approximately 750 feet south of the site. Other nearby receptors include livestock well CS‑MWG-LGR located approximately 1,000 feet west of SWMU B‑23A, and the “DZ” Tank, located approximately 2,500 feet west of the site area. The nearest potential habitats for local endangered species are approximately 2,000 feet south (Black-capped vireo) and 400 feet east (Golden-cheeked warbler) of SWMU B‑23A (Parsons, 1993). More detailed information on potential receptors at SWMU B‑23A is included in the SWMU B‑23A RFI Report (Parsons, 2003).

1.4 - Previous Investigations

1.4.1   Geophysical Survey

An electromagnetic (EM) geophysical survey was performed at SWMU B‑23A in March 1995. The EM survey was conducted along northwest-southeast transects spaced at 20-foot intervals. Neither conductivity nor in-phase EM data revealed any subsurface anomalies at SWMU B‑23A; therefore, the geophysical survey results do not indicate the presence of subsurface anomalies potentially related to past waste management activities. Results of the 1995 geophysical survey are also provided in Section 4 of the Technical Memorandum on Surface Geophysical Surveys at High Priority SWMUs (Parsons ES, October 1995).

1.4.2   Soil Gas Survey

A soil gas survey was performed at CSSA in August 1996 in an effort to identify possible source areas for the chlorinated hydrocarbon contamination present in the groundwater at well CS-MW16-LGR and other CSSA wells. Ten soil gas samples were collected within the March 1995 geophysical grid area and were analyzed for VOCs.

Toluene was detected at 0.4 micrograms/liter (µg/L) in one soil gas sample (sample point #4) located along the northern side of the geophysical grid (Figure B23A‑9). VOCs were not detected in any other samples. Results of the soil gas survey are provided in the SWMU B‑23A RFI Report (Parsons, 2003).

1.4.3   Surface Soil Sampling

On January 23, 2003, three surface soil samples were collected at SWMU B-23A (Figure B23A-4). The surface samples were analyzed for VOCs, SVOCs, and metals. The samples were collected approximately on the centerline of the in-filled trench.

As shown in Table B23A-1, no VOCs or SVOCs were detected in surface soils above RRS1 levels. However, copper slightly exceeded RRS1 in sample CS-B23A-1, which had a reported concentration of 40.82 milligrams per kilogram (mg/kg) for copper. The background value for copper in CSSA soil is 23.2 mg/kg.

1.4.4   Ampoule Sampling

In September 2001, CSSA personnel collected five different-colored ampoules from the ground surface and submitted them for analysis at the USEPA Region 6 Environmental Services Branch Laboratory, Houston, Texas. The ampoule colors were green, dark brown, light brown, yellow, and clear. In January 2003, Parsons personnel collected an additional two ampoules from SWMU B-23A. The additional ampoules were orange and yellow in color. The two ampoules were sent to APPL Laboratory in Fresno, California for analysis.

Results from both sample sets provided only TICs. Some examples of TICs are benzaldehyde, hexadeanoic acid, and taraxerol methyl ester. Laboratory equipment cannot be calibrated to reliably quantify the analytes listed as TICs because no calibration curve has been established for these compounds; therefore, RLs and method detection limits (MDL) are not available for those analytes. An analytical results summary is provided in Appendix A of the SWMU B-23A RFI Report.

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