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AOC 46 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 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 closure requirements of Area of Concern (AOC) 46 (AOC-46) and to provide documentation necessary for site closure. The main objectives of this report are to describe if the site meets Texas Commission on Environmental Quality (TCEQ) requirements for Risk Reduction Standard 1 (RRS1) closure, as described in Section 1.1, and requirements of the Consent Order, and to document the closure activities at AOC‑46.
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 task order. Based upon the project statement of work (SOW), a set of work plans to govern the fieldwork was established. These include:
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Work Plan Overview (Volume 1‑1, TO 0019 Addendum); |
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Site‑Specific Work Plan(s) (Volume 1‑2, AOC‑46); |
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Field Sampling Plan (Volume 1‑4, TO 0019 Addendum); and |
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Health and Safety Plan (Volume 1‑5, TO 0019 Addendum). |
For this closure report, Section 1 provides the site‑specific background and describes the selected closure standard. Section 2 describes the closure actions and the closure evaluation. Section 3 summarizes the findings, evaluates attainment of data quality objectives (DQOs), and certifies the site closure. References cited in this report can be found in the Bibliography (Volume 1‑1 of the Environmental Encyclopedia).
As described in Section 4.3 of the Risk Assessment Technical Approach Document (Volume 1‑6), CSSA has opted to pursue closure of many of its sites under the Risk Reduction Rules (RRR) (30 Texas Administrative Code [TAC] §335). A notification of intent to close sites identified to date (including AOC‑46) was sent to the TCEQ in accordance with the RRR on July 12, 1999. TCEQ acceptance of this notification was received on October 5, 1999.
Following the RRR guidelines (30 TAC §335.554), if site concentrations are at or below background, and all waste and waste residue have been removed, then the site can be closed under RRS1. CSSA background levels are the RRS1 criteria for metals concentrations and laboratory reporting limits (RLs) are the RRS1 criteria for other contaminants of concern (COCs). CSSA opted to pursue closure of AOC‑46 under RRS1. If closure requirements under RRS1 are attained and approved by the TCEQ Executive Director, then CSSA is released from the deed recordation requirement.
1.2 - 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, detailed data regarding the geology, hydrology, and physiography are also available for reference.
1.2.2 AOC‑46
AOC‑46 has an area of approximately 0.1 acre (Figure AOC46‑1). The site consisted of an area containing residue of spent bullets and sand from a bullet trap. Figure AOC46‑2 shows aerial photographs of the site dated between 1957 and 2003. No waste disposal areas or other disturbed areas are evident in these photographs.
1.2.2.2 Potential Sources of Contamination
Based on the presence of residue of spent sand and bullets at the site, COCs include metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc). Bullets do not contain explosives; therefore, explosive‑related compounds are not COCs at this site.
AOC‑46 is located in the western central portion of the Inner Cantonment, approximately 1,700 feet from the western boundary of the Inner Cantonment and 6,000 feet from the southern boundary of the Inner Cantonment. As shown in Figure AOC46‑1, the site is located southwest of Building 30 and near Solid Waste Management Units (SWMUs) B‑32 and Building 36.
1.3 - Site Environmental Setting
A detailed description of the environmental setting at CSSA is provided in the Background Information Report (Volume 1‑1). A brief description of the setting at AOC‑46 is provided in the paragraphs below.
1.3.1 Site Soil and Topography
Crawford and Bexar Stony soil is the only soil occurring at AOC‑46 (Figure AOC46‑3). Crawford and Bexar Stony soil occurs on broad, nearly level to gently undulating areas with slopes of 0 to 5 percent. The soils are stony, non‑calcareous, approximately 8 inches in thickness, and cover approximately 16.9 percent of the CSSA ground surface. The topographic elevation of the site area is approximately 1,270 feet above mean sea level (msl). Drainage within AOC‑46 is to the east, toward an unnamed tributary of Salado Creek.
Brackett soil is located west of AOC‑46, within 400 feet of the site. This soil occurs on slopes of 12 to 30 percent. This loamy and clayey soil is very shallow (about 4 inches thick), grayish‑brown, and strongly calcareous. Gravel and cobblestones up to 6 inches in diameter are found at the surface. The soil develops over soft limestone and are underlain by hard limestone, which gives the slopes a stairstep appearance. The Brackett soil is nonarable and best suited to native grasses.
Throughout CSSA, the uppermost geologic stratum is the Upper Glen Rose Limestone, as shown in Figure AOC46‑4. The Upper Glen Rose consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds, averaging 50 feet thick. The Upper Glen Rose is underlain by the Lower Glen Rose (averaging 320 feet thick). The Lower Glen Rose Limestone is underlain by the Bexar Shale (regionally known as Hensell Shale, averaging 60 feet thick), and the Cow Creek Limestone (averaging 76 feet thick). The geologic strata dip approximately 10 to 12 degrees to the south‑southeast at CSSA. Additional information on 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 fact that static well levels are discordant in adjacent wells that are 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‑46 is CS‑MW18‑LGR, located approximately 800 feet southwest of the site. This well is sampled on a quarterly basis. Historic water levels for CS‑MW18‑LGR range from 145.11 feet below top of casing (btoc) in September 2002 to 285.00 feet btoc in December 2003. The nearest CSSA water supply well to AOC‑46 is CS‑9, which is located approximately 1,200 feet northwest of the site. Static water levels in well CS‑9 have measured between 117 feet btoc (June 2003) and 399 feet btoc (September 2000).
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. AOC-46 is located in the middle of the CSSA cold war era historical district.
A land use survey describing local, current, and possible future uses of groundwater and surface water, a water well survey, and a sensitive environmental area survey were completed at CSSA during 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 potential habitat for two endangered bird species, the Golden‑cheeked Warbler and the Black‑capped Vireo. However, the AOC‑46 area is not located within an area identified as potential habitat for these species (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.
1.4 - Previous Investigation Results
No previous investigations have been conducted at AOC‑46.