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SWMU B-30 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-30 was completed in July 2002 to document the environmental condition of the site and site closure requirements, and recommend further investigation. This closure report includes by reference the information presented in the SWMU B-30 RFI Report (Parsons, 2002).
The SWMU B-30 RFI Report recommended excavation and disposal of waste at the site and excavation/investigation of a subsurface geophysical anomaly. The RFI report estimated 2,300 cubic yards (CY) of soil and waste material would require removal. For analytes exceeding closure standards during the RFI, confirmation sampling was to be conducted to confirm that the site achieved closure requirements. This report documents the closure activities at SWMU B-30.
This 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 was established to govern the field work. 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 |
(Volume 1-5, TO 0019 Addendum available upon request).). |
Closure activities at SWMU B-30 were conducted between November 2003 and May 2004. As recommended in the RFI report, excavation and disposal activities were conducted. More than 1,700 CY of soil were excavated and removed from the site. Confirmation sampling was conducted to verify that the metals copper, nickel, zinc, and lead levels were below background levels. These metals were found to exceed closure standards during the RFI.
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 SWMU B-30 under the Risk Reduction Rules (RRR), as defined by 30 Texas Administrative Code (TAC) §335. A notification of intent to close sites identified to date, including SWMU B‑30, 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 sampling results at SWMU B‑30, 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.
1.2 - Background and Site Description
General information regarding the history and environmental setting of CSSA is located in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report). In that report, data regarding the geology, hydrology, and physiography are also available for reference.
1.2.2 SWMU B-30
The site covers approximately 0.36 acre and was previously an at-grade limestone quarry area, which was later used for disposal of miscellaneous construction debris and some other miscellaneous metal debris, such as ammunition cans. As shown in Figure B30‑7, the site is located in the southern portion of the CSSA Inner Cantonment Area (Figure B30‑1 through Figure B30‑6 are provided in the SWMU B-30 RFI Report). The area appears disturbed in aerial photographs taken in 1957 and 1966, as shown in Figure B30‑8. The vegetation at the site consists of sparse native grasses and shrubs. A tree line is present to the south of the site area and a limestone embankment lies in the northern portion of the site.
Soil mounds, scrap concrete, and other construction waste were identified at the site during a field survey performed during September 1993.
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‑30). Volume 1-2 also includes a Chronology of Actions and a Site-Specific Work Plan for SWMU B‑30.
1.2.2.2 Potential Sources of Contamination
Based on identification of the site as a disposal area for miscellaneous construction debris and other metal waste, and based on the B‑30 RFI sampling results for soil, contaminants of concern (COCs) include copper, lead, and zinc. RFI sampling results indicate that no volatile organic compounds (VOCs) or semivolatile organic compounds (SVOCs) are present in site soils. The metals arsenic, barium cadmium chromium, mercury, and nickel did not exceed RRS1 levels during the RFI, and therefore are no longer COCs at SWMU B‑30.
SWMU B‑30 is located in the southwestern tip of CSSA (Figure B30‑7), within the Inner Cantonment, immediately south of SWMU B‑29, and immediately north of Area of Concern (AOC)‑50. The site is approximately 800 feet and 2,000 feet from the southern and western boundaries of CSSA, respectively.
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‑30 RFI Report (Parsons, 2002). A summary of the site environmental setting is provided in the paragraphs below.
1.3.1 Site Soils and Topography
The only soil type present at SWMU B‑30 is Krum Complex soils. These soils develop from slope alluvium of the limestone prairies. The Krum Complex soils are generally found on slopes between two and five percent and occupy “foot” slopes below Tarrant and Brackett soils. The Krum soils receive sediments and runoff from higher elevation soils and are highly prone to erosion from surface drainage.
The site contains little topographic relief and lies at approximately 1,170 feet above sea level. The eastern edge and portions of the southern and northern edges of the site area are bounded by limestone embankments resulting from past quarrying activities. The land surface within the site area slopes approximately two degrees to the southwest.
The Lower Glen Rose (LGR) Formation is the uppermost geologic stratum in the area of SWMU B-30. The LGR (averaging 320 feet thick), is a massive, fossiliferous, vuggy limestone that grades upwards into thin beds of limestone, marl, and shale. The LGR is underlain by the Bexar Shale of the Hensell Sand (averaging 60 feet thick). The geologic strata dip approximately 10 to 12 degrees to the south-southeast at CSSA.
Fault features are present in the vicinity of SWMU B‑30 as shown in Figure B30-3. In addition, sinkholes have been identified at SWMU B‑29, which lies directly north and upgradient of SWMU B‑30.
At CSSA, the uppermost hydrogeologic layer is the unconfined Upper Trinity Aquifer, which consists of the Upper Glen Rose (UGR) Limestone. Locally at CSSA, low-yielding perched zones of groundwater can exist in the UGR; however, no groundwater was encountered in any of the SWMU B‑30 soil borings. Principle recharge into the Middle Trinity aquifer is via precipitation infiltration at outcrops. In general, groundwater at CSSA flows in a north to south direction, with some seasonal fluctuations.
The nearest surface water body, “W Tank”, is a pond that is located 600 feet northwest of the site (Figure B30-7). A small (unnamed) ephemeral creek is located approximately 125 feet south of the site. This small creek exits the CSSA boundary approximately 625 feet south of SWMU B‑30. Surface water drains to the southwest at SWMU B‑30.
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 over one mile northeast of the site area. All of the structures on CSSA are considered historical resources.
Potential receptors that are located within 0.25 mile of SWMU B‑30 include a group of storage warehouses, which are located 750 feet west of the site. Shops and offices within the warehouses are occupied by a full-time work force. The area south of CSSA and within 0.25 mile of SWMU B‑30 is densely populated with many mobile homes located on small lots. Well LS‑1, which is a drinking water supply well operated by Bexar-Metropolitan Water District, is located 750 feet south-southeast of the site. This well is completed within the Middle Trinity Aquifer. The nearest potential habitat for local endangered species Golden-Cheeked warbler habitat is located approximately 300 feet east of the site area. A potential Black-Capped vireo habitat is located approximately 3,000 feet northeast of the site area (Parsons ES, 1993). In addition, as explained in Section 1.3.2, fault features and sinkholes exist near SWMU B‑30.
An electromagnetic (EM) geophysical survey was conducted at SWMU B‑30 in April 1996. There were two anomalies identified at SWMU B‑30. Anomaly A is located in the northwestern portion of the site, and due to its location, it is interpreted as being associated with a pile of steel-reinforced concrete slabs formerly situated at the same location. Anomaly B is located in the northeastern portion of the site, adjacent to the northern limestone embankment. Since surface waste was not observed at this anomaly, it was concluded that anomaly B may be associated with buried waste. Locations of the anomalies are shown on Figure B30‑9. Results of the 1996 geophysical survey are also provided in Section 4 of the Technical Memorandum on Surface Geophysical Surveys at High Priority SWMUs (Parsons ES, October 1995).
In March 2000, three surface soil samples were collected at SWMU B-30 during the RFI. The soil samples (RW‑B30‑SS01 through RW‑B30‑SS03) were analyzed for VOCs (SW‑8260B), SVOCs (SW‑8270C), the metals barium, chromium, copper, nickel, and zinc (SW‑6010B), arsenic (SW‑7060A), cadmium (SW‑7131A), lead (SW‑7421), and mercury (SW‑7471A). The sampling locations were situated in areas having the greatest potential for contamination (Figure B30‑9). RW‑B30‑SS01 was collected next to a pile of concrete slabs, near the limestone embankment that lies in the northern portion of the site area. RW‑B30‑SS02 was collected just south of a large construction debris/rubble pile present in the western portion of the site. RW‑B30‑SS03 was the eastern most of the three samples, collected near a pile of construction debris, south of Anomaly B.
An additional surface soil sample, RW‑B30‑SB01, was collected from soil boring location RW-B30-SB01 during March 2000 drilling activities. The sampling location was adjacent to Anomaly B and near a pile of construction debris.
All VOC and SVOC concentrations were below RLs; therefore, RRS1 criteria for VOCs and SVOCs were met. One of the three surface soil samples (RW‑B30‑SS03) had reported metals concentrations exceeding RRS1 standards. Analytical results for sample number RW‑B30‑SS03 reported 47.3 milligrams per kilogram (mg/kg) copper, 86.46 mg/kg lead, and 93.2 mg/kg zinc. The CSSA RRS1 background standards for copper, lead, and zinc are 23.2 mg/kg, 84.5 mg/kg, and 73.2 mg/kg, respectively. Surface soil results are summarized in Table B30‑1 of the SWMU B-30 RFI Report (Parsons, 2002).
In March 2000 during the RFI, three soil borings (RW-B30-SB01, RW-B30-SB02, and RW‑B30‑SB03) were drilled at SWMU B‑30 and samples were analyzed for VOCs, SVOCS, and metals (same metals suite as surface soil samples). RW-B30-SB01 and RW-B30-SB02 were drilled near geophysical anomalies and RW-B30-SB03 was drilled near a pile of construction debris (Figure B30‑9).
One soil sample and five Glen Rose Limestone samples were collected from the soil borings. No RRS1 exceedances were observed in the soil sample.
VOC and SVOC analytes were detected above RLs in some Glen Rose Limestone samples. However, these analytes, methylene chloride and phthalates, are often lab contaminants. One VOC, methylene chloride, was detected above the RL in RW‑B30‑SB03 (2.5‑3.0 feet below ground surface [bgs]). This sample had a reported methylene chloride concentration of 0.0072 mg/kg. The laboratory RL for methylene chloride is 0.005 mg/kg.
One SVOC, bis(2-ethylhexyl)phthalate, exceeded RRS1 criteria in five Glen Rose Limestone samples. Exceeding concentrations ranged from 6.8 mg/kg to 26 mg/kg. The RL for bis(2-ethylhexyl)phthalate is 0.7 mg/kg.
Three metals exceeded RRS1 for Glen Rose Limestone. RW‑B30‑SB01 (12.5‑13.0 feet bgs) had reported concentrations of 11.1 mg/kg and 0.13 mg/kg for barium and cadmium, respectively. The RRS1 standards for barium and cadmium in Glen Rose Limestone are 10.0 mg/kg and 0.1 mg/kg, respectively. RW‑B30‑SB03 (2.5‑3.0 feet bgs) had a reported nickel concentration of 7.9 mg/kg, slightly higher than the RRS1 standard of 6.8 mg/kg for Glen Rose Limestone. All soil boring results are provided in Table B30‑2 of the SWMU B‑30 RFI Report.