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AOC-50 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 Area of Concern (AOC)‑50 was completed in December 2002 to document the environmental condition of the site and site closure requirements, and to recommend further investigation. This closure report includes by reference the information presented in the AOC‑50 RFI Report (Parsons, 2002).
The AOC‑50 RFI Report recommended excavation and disposal of waste and waste residue at the site. The RFI report roughly estimated between 1,600 and 3,200 cubic yards (CY) of soil and waste material would require removal from the site, and confirmation sampling for cadmium, chromium, copper, lead, and zinc was to be conducted to confirm that the site achieved closure requirements. This report documents the closure activities at AOC‑50.
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 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 |
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Site‑Specific Work Plan |
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Field Sampling Plan |
(Volume 1‑4, TO 0019 Addendum); and |
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Health and Safety Plan |
Closure activities at AOC‑50 were conducted from November 2003 through May 2004. As recommended in the RFI report, excavation and disposal activities were conducted. Approximately 900 CY was excavated and removed from the site. Confirmation sampling was also conducted to verify that contaminant concentrations in the remaining soils met closure requirements.
For this closure report, Section 1 provides the site‑specific background and 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‑50) 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 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 Risk Reduction Standard 1 (RRS1). Background levels are the RRS1 criteria for metals concentrations, and laboratory reporting limits (RLs) are the RRS1 criteria for organic compounds. Based on the RFI sample results at AOC‑50, 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 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‑50
AOC‑50 consists of approximately one acre of undeveloped wooded land. The site is irregularly shaped and approximately 450 feet at its widest point, which is oriented in an east‑west direction (Figure AOC50‑1 in the AOC‑50 RFI Report). In the north‑south direction, AOC‑50 is approximately 200 feet at its widest point. A dirt road enters the site in the northwestern corner and exits at the northeastern portion of the AOC. The site was identified in March 1996 during the field efforts conducted at nearby solid waste management units (SWMUs) B‑29 and B‑30. During the initial site visit in March 1996, 17 distinct areas of suspected waste were identified. The suspected areas consisted of rust‑colored material on the ground surface and in near‑surface soils. During a site inspection in December 1999, potential unexploded ordnance (UXO) and other munitions scrap were located at the AOC. The metal carcass of a 100‑pound practice bomb was removed from the site prior to the site inspection.
In March 2001, during the initial excavation activities, a small trench measuring 75 feet long, 10 feet wide, and approximately 4 feet deep was discovered. This trench contained household type trash. The date the waste was disposed in this trench is unknown; however, two soda bottles found in the trench had date stamps of “1953” on them.
Background information regarding the location, size, and known historical use of AOC‑50 is also included in the Environmental Encyclopedia (Volume 1‑3, AOC‑50). Volume 1‑3 also includes a Chronology of Actions and a Site‑Specific Work Plan for AOC‑50.
1.2.2.2 Potential Sources of Contamination
The potential sources of contamination at AOC‑50 include the areas of rust‑colored material on the surface, the trash‑filled trench, spent munitions, and potential UXO. The rust‑colored material was identified as metal waste possibly generated from the ordnance maintenance operations conducted in Building 90. This waste material consisted of metal particles and was thought to contain nickel penetrate. However, recent information from personnel working in Building 90 indicates that this waste may have been generated from the Wheelabrator blast cleaning/shot penning operations. Because of the metallic nature of the waste, metals are the primary contaminants of concern (COCs). During the RFI, each site sample was analyzed for arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc. Arsenic, barium, mercury, and nickel were not detected above background levels and therefore are not considered COCs for site closure. COCs for site closure include cadmium, chromium, copper, lead, and zinc, which were all detected above background levels during the RFI.
During the RFI, volatile organic compounds (VOCs) were also COCs because they are frequently associated with waste management activities. Explosive-related constituents were included as COCs because spent munitions and potential UXO were discovered at the site. However, no VOCs or explosive-related constituents were detected in any of the RFI samples; therefore, these compounds were not considered COCs for site closure.
AOC‑50 is a one‑acre area that is located in the southeastern portion of the inner cantonment area (Figure AOC50‑10). The site is approximately 100 feet south of SWMU B‑29, 200 feet south of SWMU B‑30, and 200 feet northwest of SWMU I‑1. The CSSA perimeter fence, which borders Leon Springs Villa Mobile Home Park, is approximately 400 feet south of the site.
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 AOC‑50 RFI Report (Parsons, 2002).
1.3.1 Site Soils and Topography
The native soil at AOC‑50 is Krum Complex soil (Figure AOC50‑2 in the AOC‑50 RFI Report). Krum Complex soil covers approximately 20 percent of the ground surface at CSSA. This soil occurs on slopes of two to five percent, occupying ‘foot’ slopes below Brackett and Tarrant soils. Generally, Krum Complex soil is subject to hydraulic erosion as it occurs down‑slope of prairie plains and receives sediments from higher elevations. Krum Complex soil is dark grayish‑brown, calcareous, and typically extends to depths of approximately 30 inches below grade. Detailed descriptions of the CSSA soil types are given in the CSSA Environmental Encyclopedia (Volume 1‑1, Background Information Report, Soils and Geology).
AOC‑50 is located on a gentle, south‑southwest trending slope and the site elevation is between 1,165 and 1,175 feet above sea level.
The Upper Glen Rose is the uppermost geologic stratum at CSSA, where present, and it outcrops southwest of AOC‑50 (Figure AOC50-11). 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 128 feet thick. It is underlain by the Lower Glen Rose, which outcrops in the area of AOC‑50 and is estimated to be 320 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 60 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.
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, the hydraulic conductivity between beds is thought to be poor. This interpretation is based on the observation that static water levels in adjacent wells completed at approximately the same elevation are different. Principle development of solution channels is limited to evaporite layers in the Upper Glen Rose Limestone.
The upper Trinity aquifer is found in the Upper Glen Rose Limestone, which is not present with enough vertical thickness at CSSA to be considered a viable water source. The upper Trinity aquifer is underlain by the middle Trinity aquifer. 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, principle 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 gallons per day per foot (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. However, the nearest well, Well LS‑1, a municipal drinking water well operated by Bexar Metropolitan Water District, is located approximately 700 feet southeast of AOC‑50. Water levels are not available for this well but other information for this well may be found in the Environmental Encyclopedia, Volume 5.
The nearest surface water is an intermittent stream drains through the southeast corner of the site. This intermittent stream connects with the concrete drainage ditch from the wastewater treatment plant (Figure AOC50‑10). The water then exits CSSA in a manmade concrete culvert that runs through the Leon Springs Villas Mobile Home Park and eventually merges with Leon Creek.
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 approximately 7,000 feet northeast of the site area, directly next to the eastern Inner Cantonment boundary. All of the structures on the installation are considered historical resources.
A survey of land uses, local and possible future uses of groundwater and surface water, area water supply wells, and sensitive environmental areas at CSSA was completed in December 1999 in accordance with the TCEQ Texas Risk Reduction Program (TRRP). The results of this survey, along with results from a more in‑depth survey to identify potential receptors, points of human exposure, and possible constituent pathways is presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1‑6).
Numerous homes in the Leon Springs Villas Mobile Home Park occupy the area outside CSSA within a ¼‑mile of AOC‑50. Well LS‑1, which is a public drinking water supply well, operated by Bexar Metropolitan Water District, is located within ¼‑mile of AOC‑50.
The site and much of the area surrounding the site is wooded with Live Oak, Cedar Elm, and Ashe Juniper (cedar) trees. The eastern portion of the site lies in an area of potential habitat for the endangered Golden‑Cheeked Warbler. The nearest potential habitat for the endangered Black‑Capped Vireo is located over 1½ miles northeast of the site.
A map of deer hunting stands, which overlook mechanical feeders and planted food plots, is located in the Technical Approach Document for Risk Evaluation (Volume 1‑6). AOC‑50 is located approximately 800 feet west‑southwest of hunting stand number 12.
Electromagnetic (EM) and ground penetrating radar (GPR) geophysical surveys were conducted at AOC‑50 in December 2001. The AOC‑50 EM and GPR geophysical survey grid is illustrated in Figure AOC50‑4 in the AOC‑50 RFI Report (Parsons, 2002). GPR surveys were conducted with a GSSI SIR‑2 instrument to further investigate the information obtained by the EM survey. Twelve GPR profiles were completed. The geophysical surveys revealed an anomaly related to past waste disposal activity. This anomaly was located in the southeast corner of the site and later discovered to be a household waste trench.
Two surface soil samples collected in 1999 from AOC‑50 were analyzed for metals. Results are summarized in Table AOC50‑1 in the AOC‑50 RFI Report (Parsons, 2002). None of the metals concentrations exceeded background levels.
In August 2001, 10 surface soil samples were collected in various locations at AOC‑50. The detected analytes found in these samples are also summarized in Table AOC50‑2. These 10 surface soil samples were analyzed for VOCs, explosives, and metals. No VOCs or explosives were detected above their respective RLs.
All of the background level exceedances for metals occurred in four samples: AOC50‑SS02, AOC50‑SS03, AOC50‑SS05, and AOC50‑SS06. Samples AOC50‑SS02, AOC50‑SS03, AOC50‑SS05, and AOC50‑SS06 exceeded the background level for cadmium (3.0 mg/kg) with concentrations of 10.3 mg/kg, 4.84 mg/kg, 5.34 mg/kg, and 4.22 mg/kg, respectively. Samples AOC50‑SS02, AOC50‑SS03, AOC50‑SS05, and AOC50‑SS06 exceeded the background level for lead (84.5 mg/kg) with concentrations of 1,227 mg/kg, 76,200 mg/kg, 124.7 mg/kg, and 592.2 mg/kg, respectively. The chromium background level of 40.2 mg/kg was exceeded in sample AOC50‑SS05, which had a chromium concentration of 56.10 mg/kg. Samples AOC50‑SS02, AOC50‑SS03, and AOC50‑SS05 exceeded the background level for copper (23.2 mg/kg) with concentrations of 28.88 mg/kg, 1,041.4 mg/kg, and 27.71 mg/kg, respectively. Samples AOC50‑SS03 and AOC50‑SS05 exceeded the background level for zinc (73.2 mg/kg) with concentrations of 361.5 mg/kg and 142.8 mg/kg, respectively.
Three subsurface samples (AOC50‑T1, AOC50‑T2, and AOC50‑T3) were collected from the bottom of the excavated waste trench in April 2001. These samples were analyzed for metals and VOCs. None of the samples had metals concentrations above the CSSA background levels, and VOCs were below the RLs. The analytical results for these samples are summarized in Table AOC50‑3 in the AOC‑50 RFI Report.
Excavation activities were conducted at AOC‑50 during March and April 2001. Approximately 190 CY of material was excavated. The excavated material included Wheelabrator operations waste, banding material, horseshoes, glass, and associated soil.
Prior to the initiation of excavation activities in March 2001, the site was swept by a Parsons UXO avoidance team using handheld magnetometers. The only items found were two spent rifle grenades. All visible Wheelabrator blast cleaning operations waste was marked for removal during the comprehensive sweep of the area. The subcontractor excavated approximately 155 CY of soil and Wheelabrator waste during March 2001. During the activities, a backfilled trench was discovered at the southeast corner of the excavation area. The trench contained banding material, horseshoes, and glass. After a meeting to discuss plans to remediate this additional waste, it was also excavated, accounting for an additional 35 CY of waste material (April 2001).
Waste characterization samples showed the waste was non‑hazardous and it was disposed at Covel Gardens Landfill. The material excavated during March was disposed during April under 15 manifests. The material excavated during April was disposed in August under two additional manifests. In addition to the material generated during site excavation activities, 17 CY of Wheelabrator waste was picked up from the ground surface around Building 90‑2 and disposed under the AOC‑50 waste profile. The waste on the ground surface at Building 90‑2 is the same material that was disposed at AOC‑50.
The total cubic yardage removed during 2001 is approximately 207 CY. The field documentation of excavated soil and waste amounts presented in the AOC‑50 RFI Report differs from what is presented here. This is due to misestimating the amounts of excavated soil in the field before it was transported, weighed, and disposed. Once the weight of the excavated waste is determined at the landfill, an accurate cubic yardage is calculated. The information presented above is based on the landfill receipts, which have the disposal weights listed on them.
Following excavation and disposal of waste material from the site, ten confirmation samples (AOC50‑SS01 through AOC50‑SS10) were collected and analyzed for metals (Figure AOC50‑5). Four of the samples had RRS1 exceedances for metals. Metals that exceeded RRS1 include cadmium, lead, chromium, copper, and zinc.