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AOC 44 Delisting 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 the Resource Conservation and Recovery Act (RCRA), and further amended by the Hazardous and Solid Waste Amendments (HSWA) of 1984. This delisting report documents the field activities at Area of Concern (AOC) 44 (AOC‑44).
The site was identified as an area with surficial metal debris in February 1996. No formal waste management activities were known or recorded to have occurred at AOC‑44.
The work documented in this report 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 task order. Based on the project statement of work (SOW), a set of work plans to govern the fieldwork was established. These include:
| Work Plan Overview | |
| Site‑Specific Work Plan | |
| Field Sampling Plan | (Volume 1‑4, TO 0019 Addendum); and |
| Health and Safety Plan |
A geophysical survey conducted at AOC‑44 under this task order did not reveal any evidence of waste management activities at the site. The site was originally registered as an AOC based on the presence of metal debris and the possibility that waste management may have been performed. However, based on investigation findings, it was determined that the site has not been used for waste management. Since the site was not used for waste management, it should not be considered an AOC and should be delisted as an AOC. This report documents the geophysical survey results at the site and recommends delisting the site as an AOC.
Section 1 of this delisting report provides the site‑specific background for AOC‑44. Section 2 describes the field activities and delisting evaluation. Section 3 summarizes the findings and provides the delisting recommendations. References cited in this report can be found in the Bibliography (Volume 1‑1 of the Environmental Encyclopedia).
1.1 - Background and Site Description
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, data regarding geology, hydrology, and physiography are also available for reference.
AOC‑44 has an area of approximately 0.1 acre (Figure 44‑1). The site was identified as an area with surficial metal debris in February 1996. Figure 44‑2 shows a progression of historical aerial photographs of the site from 1957 to 2003.
1.1.2.2 Potential Sources of Contamination
No formal waste management activities were known to occur at AOC‑44. However, the site was initially identified by the presence of surficial metal debris. In addition to the presence of metal debris at the site, two 20‑pound fragmentation bombs were discovered at the site in March 1996.
AOC‑44 is located in the southeastern portion of the East Pasture at CSSA. AOC‑44 is approximately 1,000 feet from the nearest facility boundary to the east. The site is approximately 500 feet north of Solid Waste Management Unit (SWMU) B‑9 and is encompassed within AOC‑51 (Figure AOC44‑1).
A detailed description of the environmental setting associated with CSSA is provided in the CSSA Background Information Report (Volume 1‑1). Site‑specific descriptions are provided below.
In general, soil at CSSA is thin, dark‑colored, gravely clay and loam. The soil types are strongly influenced by topography and the underlying limestone. The soil at AOC‑44 is classified as Krum Complex soil (Figure 44‑3). Krum Complex soils occur down slope of prairie plains and receive sediments from higher elevations. Krum Complex soils are typically dark grayish‑brown, calcareous clay‑dominant soils that range in depth from 15 to 60 inches and are underlain by limestone. Krum Complex soils are generally well drained with slow to rapid runoff and moderately slow permeability.
The elevation of the ground surface at AOC‑44 is approximately 1,215 feet above mean sea level (msl), with the ground surface sloping westward. The site vegetation consists primarily of native grasses and small trees.
The Upper Glen Rose Limestone is the uppermost geologic strata in the area of AOC‑44 (Figure 44‑4). The Upper Glen Rose consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds (average thickness 50 feet). The Upper Glen Rose is underlain by the Lower Glen Rose Limestone (average thickness 320 feet). The Lower Glen Rose Limestone is underlain by the Bexar Shale member of the Hensell Sand (average thickness 60 feet) and the Cow Creek Limestone (average thickness 76 feet). The geologic strata at CSSA dip approximately 10 to 12 degrees to the south‑southeast.
Information on structural geology at CSSA can be found in the Environmental Encyclopedia (Volume 1‑1, Background Information Report, Soils and Geology).
At CSSA, the uppermost hydrologic layer 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. 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, the hydraulic conductivity between beds is thought to be poor. This interpretation is based on the observation that static water 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. Principal recharge into the Middle Trinity Aquifer is via precipitation infiltration at outcrops. Groundwater discharge occurs predominantly via natural springs, seeps, and pumping.
The nearest monitoring well to AOC‑44 is CS‑MW17‑LGR, located approximately 2,600 feet northwest of the site. This well is sampled on a quarterly basis. Historic water levels for CS‑MW17‑LGR range from 115.70 feet below top of casing (btoc) in December 2002 to 250.89 feet btoc in December 2003. Well CS‑1, an off‑site well located directly south of CSSA, is located approximately 3,000 feet southwest of AOC‑44. Static water levels in well CS‑1 have measured between 261.86 feet btoc (March 2000) and 65.47 feet btoc (December 2004).
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 site to AOC‑44 is a site consisting of former World War II training trenches located approximately 1,600 feet to the west.
A land use survey of local and possible future uses of groundwater and surface water, a water well survey, and a sensitive environmental area survey were completed at CSSA in December 1999. The results of these surveys, 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). Land uses on the facility are not anticipated to change in the foreseeable future.
CSSA contains mostly forested, undeveloped land, various portions of which are being managed to promote different species. Some areas are managed to maintain habitat for two endangered bird species, the Golden‑cheeked Warbler and the Black‑capped Vireo. AOC‑44 is located within an area identified as potential habitat for Black‑capped Vireo (Section 4, Environmental Assessment, Volume 1‑1). The native White‑tailed deer and introduced Axis deer populations are also managed, and controlled hunting is allowed. Management practices which benefit the deer and other wildlife species include maintenance of feed plots, feeding and watering stations, and clearing of Ashe juniper to improve habitat. Other areas are managed as pastures for cattle grazing.
On March 6, 1996, a magnetometer survey was conducted at AOC‑44. The survey revealed one anomaly, which was caused by metal debris on the site ground surface. Approximately 1 week later, the grid was extended and additional area was surveyed. This survey also revealed one anomaly that was caused by a nearby deer feeder. No subsurface anomalies or indications of waste management were revealed during these surveys.
The day after the first geophysical survey, two 20‑pound fragment bombs were located on the ground surface at the site. The locations were flagged and UXO personnel removed the bombs from the site for off‑site demolition.