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SWMU B-32 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 Safe Drinking Water Act (SDWA), as amended by the 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, this report has been prepared to document the environmental condition and site closure requirements of Solid Waste Management Unit (SWMU) B-32 and provide documentation required for site closure, or, if necessary, recommend further investigation. The main objectives of the SWMU B-32 investigation are to determine if the site meets Texas Commission on Environmental Quality (TCEQ) requirements for closure, as described in Section 1.4 and requirements of the Consent Order.
This specific RFI was performed by Parsons under Air Mobility Command (AMC) Contract F11623‑94‑D‑0024 (Delivery Order RL17). 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 was established to govern the fieldwork. These include:
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Work Plan Overview |
(Volume 1-1); |
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Site-Specific Work Plan |
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Field Sampling Plan |
(Volume 1-4, RL17 Addendum)); and |
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Health and Safety Plan |
(Volume 1-5, RL17 Addendum - available upon request). |
For this report, Section 1 provides the site-specific background information and the selected site closure standard. Section 2 describes field actions and the closure evaluations. Section 3 summarizes the findings, evaluates attainment of data quality objectives (DQOs), provides recommendations, and certifies site closure, if applicable. References cited in this report can be found in the Bibliography (Volume 1-1, Environmental Encyclopedia).
1.1 - Background and Site Description
General information regarding the history and environmental setting of CSSA is provided in the Environmental Encyclopedia (Volume 1-1, Background Information Report). In that document, information regarding the geology, hydrology, and physiography are also available for reference.
SWMU B-32 is a site at CSSA where polyvinyl chloride (PVC) sanitary sewer pipeline was installed at an unknown date. The pipeline trench was backfilled with lead shot-contaminated sand that was used as pipe bedding material. The lead shot is believed to have been generated in the Building 90 test firing room. SWMU B-32 is defined as the bedding material for two sections of sanitary sewer pipe that lead away from Building 2, although the site is mapped as a larger area than the sand bedding alone. The site boundary was selected during initial investigations based on historical records research and aerial photograph reviews. As a result, a larger site boundary than the actual pipe bedding was selected. SWMU B-32 is a rectangle approximately 80 feet long and 40 feet wide, with its long axis oriented northeast-southwest.
The pipe at SWMU B-32 is an active 8-inch PVC sanitary sewer pipeline that turns within the boundaries of the site. The first section of pipe is 20 feet long and is marked by two PVC cleanout drains located at each side of the driveway. At a T-shaped junction the first section joins the second section of pipe, which is 80 feet long and runs from the PVC cleanout drain on the north side of the driveway to a manhole located in Tompkins Road. The PVC sewer line lies along the center of the long axis associated with the site area. The sand backfill extends approximately 3.5 feet deep and is 2 feet wide.
Background information regarding the location, size, and known historical use of SWMU B-32 is also included in the Environmental Encyclopedia (Volume 1-2, SWMU B-32). This volume includes a Chronology of Actions and a Site-Specific Work Plan for SWMU B-32. The site was identified during the 1993 Environmental Assessment.
1.1.2.2 Potential Sources of Contamination
SWMU B-32 consists of sand containing lead shot and projectiles used as pipe bedding. The potential COCs are metals and explosives. The shot typically contains high levels of lead.
SWMU B-32 is a 0.15 acre tract of land located in the Inner Cantonment of CSSA (Figure B32-1). The site is adjacent to the former fire department bunkhouse (Building 2) and is south-southwest of the coal bins along Tompkins Road.
The closest CSSA boundary is approximately 1,200 feet to the west. Area of concern (AOC) 46 is located approximately 425 feet northeast of SWMU B-32, and SWMU B‑34 is approximately 450 feet to the south.
1.2 - Site Environmental Setting
1.2.1 Site Soils and Topography
SWMU B-32 mostly rests upon Crawford and Bexar soils with a small area in the southwest corner of the site resting on Brackett Soils (Figure B32-2). Crawford and Bexar Stony Soils occur on broad, nearly level to gently undulating areas with slopes of 0 to 5 percent. The soils are stony, non-calcareous, about 8 inches thick and cover approximately 16.9 percent of CSSA, overall. Brackett Soils occur on slopes of 12 to 30 percent. The soils are very shallow (about 4 inches thick), grayish-brown, strongly calcareous, and cover approximately 12.8 percent of CSSA, overall. Detailed descriptions of the various soil types present at CSSA are located in the Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology). Soils within SWMU B-32 generally extends from 2 to 7.5 feet below ground surface (bgs) before bedrock is encountered (Appendix A). SWMU B-32 is at an elevation of approximately 1,280 feet above sea level and the surface slopes toward the east (Figure B32-2).
The Upper Glen Rose is the uppermost geologic stratum in the area of SWMU B‑32 (Figure B32-3). The Upper Glen Rose consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds. Generally, it outcrops in stream valleys and at the ground surface where soils are poorly developed or eroded. Where present at CSSA, the Upper Glen Rose may be up to 150 feet thick. It is underlain by the Lower Glen Rose, which is estimated to be 300 feet thick beneath CSSA. The Lower Glen Rose is a massive, fossiliferous, vuggy limestone that grades upwards into thin beds of limestone, marl, and shale. The Lower Glen Rose is underlain by the Bexar Shale facies of the Hensell Sand, which is estimated to be from 60 to 150 feet thick under the CSSA area. The Bexar Shale consists of silty dolomite, marl, calcareous shale, and shaley limestone.The geologic strata dip approximately 10 to 12 degrees to the south-southeast at CSSA.
Based on current published information, there are two known major fault (shatter) zones at CSSA: the North Fault Zone and the South Fault Zone. This fault zone is referred to as a shatter zone because there is not a clean-cut break along a definite plain or curved surface of dislocation, but movement was distributed throughout a zone of considerable breadth. In this zone (shatter zone) the rocks are more or less completely crushed and many small dislocations may be traceable. SWMU B-32 is located approximately 3,450 feet north and upgradient of the southernmost of two fault zones that have been mapped within the base area (Figure B32-3). Additional information on structural geology at CSSA can be found in the Environmental Encyclopedia (Volume 1‑1, Background Information Report, Soils and Geology). The soil profile within SWMU B-32 generally extends from 2 to 7.5 feet bgs before bedrock is encountered (Appendix A).
In general, the uppermost hydrologic layer at CSSA is the unconfined Upper Trinity aquifer, which consists of the Upper Glen Rose Limestone. Locally at CSSA, low-yielding perched zones of groundwater can exist in the Upper Glen Rose Limestone. Transmissivity values are not available for the Upper Glen Rose. Regionally, groundwater flow is thought to be enhanced along the bedding contacts between marl and limestone; however, hydraulic conductivity between beds is thought to be poor. This interpretation is based on the observation that static well levels are discordant in adjacent wells completed in different beds. Principal development of solution channels is limited to evaporite layers in the Upper Glen Rose Limestone.
The Middle Trinity aquifer is unconfined and functions as the primary source of groundwater at CSSA.It consists of the Lower Glen Rose Limestone, the Bexar Shale, and the Cow Creek Limestone. The Lower Glen Rose Limestone outcrops north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, principal recharge into the Middle Trinity aquifer is via precipitation infiltration at outcrops. At CSSA, the Bexar Shale is interpreted as a confining layer, except where it is fractured and faulted, therefore allowing vertical flow from the up-dip Cow Creek Limestone into the overlying, but down-dip Lower Glen Rose. Fractures and faults within the Bexar Shale may allow hydraulic communication between the Lower Glen Rose and Cow Creek Limestones. Groundwater flow within the Middle Trinity aquifer is toward the south and southeast and the average transmissivity coefficient is 1,700 gpd/ft (Ashworth, 1983). In general, groundwater at CSSA flows in a north to south direction; however, local flow gradient may vary depending on rainfall, recharge and possibly well pumping.
No site-specific information regarding groundwater is available. The nearest well is CS-9, which is a water supply well for CSSA located approximately 1,200 feet northwest of SWMU B-32. Static water levels in well CS-9 have measured between 165 feet bgs (March 2001) and 399 feet bgs (September 2000) (Volume 5, Introduction to Groundwater Monitoring Program, Table 3).
The nearest surface water feature is a drainage ditch that runs in a north-south direction on the east side of Tompkins Road. The ditch runs parallel to Tompkins Road and drains southward, across the CSSA boundary into Leon Creek (Figure B32-2).
1.2.4 Cultural ResourcesAll structures on the installation are considered historical 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 cultural resource consists of a series of World War I era training trenches located just inside the eastern boundary of the Inner Cantonment. The trenches, which have retained much of their original design features, are located approximately 3,750 feet northeast of SWMU B-32. Building 2 is considered a historical structure.
A land use survey to determine local and possible future uses of groundwater, surface water, and sensitive environmental areas, and a water well survey at CSSA were completed on December 15 and 16, 1999. Results of these surveys, along with results from more in-depth surveys 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).
A small herd of cattle is maintained at CSSA by the United States Department of Agriculture – Agricultural Research Center (USDA-ARC). The cattle roam freely throughout the Inner Cantonment and in selected areas of the North Pasture. CSSA also manages wild game species for the purpose of hunting. White-tailed deer, axis deer, and wild turkey all roam freely throughout CSSA. A map of deer hunting stands which overlook mechanical feeders and planted food plots is located on Figure 5.2 of the Technical Approach Document for Risk Evaluation (Volume 1-6). SWMU B‑32 is located approximately 2,500 feet northwest of hunting stand number 14. Four water tanks are maintained at CSSA for the purpose of sport fishing. Two of the tanks are located in the northwestern and northeastern portions of the North Pasture while the other two tanks are located near the western boundary of the Inner Cantonment.
The closest sensitive receptor to SWMU B-32 is the “D” Tank located approximately 3,100 feet north of the site, and the closest water supply well is located approximately 1,200 feet to the northwest. The nearest potential habitats for local endangered species are located approximately 5,500 feet northeast (black-capped vireo) and 3,500 feet southeast (golden-cheeked warbler) of SWMU B-32 (Parsons ES, 1993).
No previous investigations were performed at SWMU B-32.
As described in Section 4.3 of the Technical Approach Document for Risk Evaluation (Volume 1-6), CSSA has opted to pursue closure of SWMU B-32 under the Risk Reduction Rule (RRR) (30 Texas Administrative Code [TAC] §335). If site concentrations do not exceed CSSA background, then the site will be closed using Risk Reduction Standard 1 (RRS1). If the site exceeds CSSA background, then a determination will be made regarding the feasibility of cleaning the site to meet the background concentrations. If the decision is made to clean the site to background, closure under RRS1 will be sought. However, if it is determined that the site cannot be cleaned to meet background concentrations, then the site will be closed under the Texas Risk Reduction Program (TRRP). A notification of intent to close sites identified to date (including SWMU B-32) in accordance with the former RRR was sent to the TCEQ on July 12, 1999. TCEQ acceptance of this notification was received on October 5, 1999.
RRS1 requires that the site be closed following removal or decontamination of waste, waste residues, and contaminated operation system components; and demonstration of attainment of cleanup levels (30 TAC §335.554). If closure requirements under RRS1 are attained and approved by the TCEQ Executive Director, then the owner is released from deed recordation requirement.
Since the contaminants of concern (COCs) for SWMU B-32 are metals and explosives, the RRS1 standards are the soil/rock background values for metals and the reporting limits (RLs) for explosives. Background metals levels were statistically calculated for CSSA soils and the Glen Rose Limestone and are reported in the Second Revision to the Evaluation of Background Metals Concentrations in Soil Types (Parsons, February 2002). TCEQ approved the background metals evaluation on April 23, 2002.