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SWMU B-33 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-33 was completed in August 2002. Results for three boring samples indicated Texas Commission on Environmental Quality (TCEQ) Risk Reduction Standard 1 (RRS1) exceedances for barium, chromium, nickel, zinc, cadmium, and lead in the Glen Rose Limestone. The RFI report documented the environmental condition of the site and site closure requirement, and recommend further investigation. This closure report includes by reference the information presented in the SWMU B-33 RFI Report (Parsons, 2002).
In 1997, approximately 180 cubic yards (CY) of the contaminated soil at SWMU B-33 was excavated and disposed of. The soil was treated by solidification with Portland cement to non-hazardous Class 2 levels and disposed of at Covel Gardens Landfill. Underground utilities near the foundation of Building 45 impeded the removal of a small amount of the contaminated soil. The SWMU B-33 RFI Report recommended removal of remaining contaminated backfill that was used as pipe bedding at the site. The RFI report estimated that less than 20 CY of soil would require removal and confirmation sampling for barium, chromium, nickel, zinc, cadmium, and lead was to be conducted to confirm that the site achieved closure requirements. This report documents the closure activities at SWMU B-33.
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 were established to govern the fieldwork. These include:
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Work Plan Overview |
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Site-Specific Work Plans |
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Field Sampling Plan |
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Waste Analysis Plan |
(Volume 1-4, TO 0019 Addendum); and |
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Health and Safety Plan |
Closure activities at SWMU B-33 were conducted in March 2004. A total of 18 CY of material was excavated and removed from the site. Confirmation sampling was conducted to verify that metals levels were below background concentrations.
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).
1.1 - Closure Standard
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-33 under the TCEQ 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-33, 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. Background levels are the RRS1 criteria for metals concentrations and laboratory reporting limits (RL) are the RRS1 criteria for other contaminants of concern. Based on the RFI sampling results at SWMU B-33, CSSA opted to 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 provided 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.
SWMU B-33 covers approximately 0.5 acres and consists of contaminated bedding material for a 325‑foot section of metal water supply pipe. The pipe originates at the southeast corner of Building 45 and travels southward, where it intersects a six-inch drinking water main (Figure B33‑7; Figure B33‑1 through Figure B33‑6 are provided in the SWMU B‑33 RFI Report). Sand containing projectiles from the Building 90 weapons testing operations was reportedly used as bedding material for the water supply pipe at SWMU B‑33. During initial investigations, sand and spent projectiles were uncovered in areas along the pipe, especially toward the south end of the pipe. Sand and spent ammunition jackets were also present at the surface where the pipe enters Building 45.
Background information regarding the location, size, and known historical use of SWMU B-33 is also included in the Environmental Encyclopedia (Volume 1-2, SWMU B‑33). Volume 1-3 also includes a Chronology of Actions and Site-Specific Work Plan Addenda for SWMU B-33.
1.2.2.2 Potential Sources of Contamination
Spent projectiles within the sand bedding material are the source of contamination at SWMU B-33. Projectiles potentially contain explosive residue, and are composed of metals. Therefore, during the RFI, all SWMU B-33 samples were analyzed for explosives, arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc. Analyses found no explosives, arsenic, copper, or mercury contamination exceeded background levels. However, barium, cadmium, chromium, lead, nickel, and zinc exceeded background levels in one or more samples, and therefore are contaminants of concern for site closure.
SWMU B-33 is a 0.5‑acre area that is located in the south-central portion of CSSA, in the central portion of the inner cantonment area (Figure B33‑7). The site is approximately 325 feet long (north-south) by 2 feet wide (east-west) by 3 feet deep. SWMU B‑33 is approximately 3,600 feet from the nearest facility boundary to the west and is located south of Building 45. A small equipment storage shed is located directly above the central portion of SWMU B-33 (Figure B33‑8).
A detailed description of the site environmental setting is provided in the CSSA Background Information Report (Volume 1-1) and the SWMU B‑33 RFI (Parsons, 2002). A summary of the site environmental setting is provided in the paragraphs below.
1.3.1 Site Soils and Topography
SWMU B‑33 is covered with Krum Complex soils on the central and southern portion of the site and Brackett soils occur on the northern portion of the site. Brackett soils occur on hills with 12 to 30 percent slopes and consist primarily of loamy and clayey, grayish-brown soils that are strongly calcareous. Lying within and on the very shallow surface layer (about 4 inches thick) are gravel and cobblestones. Krum Complex soils are found on slopes between 2 and 5 percent and occupy “foot” slopes below Tarrant and Brackett soils. Soil borings completed at SWMU B‑33 confirm that bedrock occurs between 3 and 4.5 feet below ground surface (bgs). SWMU B-33 is approximately 1,210 to 1,220 feet above sea level.
The Lower Glen Rose Formation is the uppermost geologic stratum in the area of SWMU B-33. The Lower Glen Rose (averaging 320 feet thick), is a massive, fossiliferous, vuggy limestone that grades upwards into thin beds of limestone, marl and shale. The Lower Glen Rose Formation is underlain by the Bexar Shale facies of the Hensell Sand (averaging 60 feet thick). The geologic strata dip approximately 10 to 12 degrees to the south-southeast at CSSA.
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. Groundwater flow within the Middle Trinity Aquifer is toward the south and southeast.
No site-specific information regarding groundwater at SWMU B-33 is available. The nearest wells (CS-MW4 and CS-MW19) are monitoring wells completed in the Lower Glen Rose. They are located approximately 1,800 feet northeast and 1,500 west of SWMU B‑33, respectively (Figure B33‑7). Water levels for CS‑MW4 have been recorded at a high of 36.47 feet bgs in September 2001 and a low of 156.10 feet bgs in June 2002. Historic water levels for CS‑MW19 range from 102.99 feet bgs in December 2002 to 244.73 feet bgs in December 2003.
The nearest surface water body is Salado Creek. SWMU B-33 is located on the western edge of the Salado Creek floodplain (Figure B33‑7). An unnamed tributary to Salado Creek, trending west to east, flows southeast through SWMU B-33 and joins Salado Creek, which then exits the CSSA boundary approximately 1.5 miles downstream. This unnamed tributary is ephemeral, experiencing flow only in association with precipitation events. Within the CSSA boundary, Salado Creek is also ephemeral.
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. All of the structures at CSSA are considered historical resources. The historic structure nearest SWMU B‑33 is Building 45, located directly north of the site. The nearest cultural resource site is a World War I training trench area located approximately 1,000 feet southeast of the site.
A land use survey studying local and possible future uses of groundwater and surface water, a water well survey and sensitive environmental areas at CSSA was completed in December 1999. 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 are presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1‑6).
Possible receptors located within 0.25 miles of SWMU B-33 include the occupants of Building 45, which is immediately to the north of SWMU B‑33. The next nearest occupied building is approximately 1,400 feet west of the site and the nearest groundwater supply well (CS‑10) is approximately 2,800 feet west of SWMU B‑33. A small herd of cattle roam freely throughout the North Pasture and isolated portions of the Inner Cantonment. CSSA also manages wild game species, including White-tailed deer, Axis deer, and wild turkey, for the purpose of hunting. A map of deer hunting stands, which overlook mechanical feeders and planted food plots is located in Figure 5.2 of the Technical Approach Document for Risk Evaluation (Volume 1-6). SWMU B‑33 is located approximately 1,050 feet north of hunting stand 13.
Electromagnetic (EM) and ground penetrating radar (GPR) geophysical surveys were conducted at SWMU B‑33 in March 1996. Prior to collecting EM or GPR data, a grid system was established at each site which encompassed the areas of suspected ground disturbance. These grids consisted of staked locations separated by intervals ranging from 25 to 100 feet, depending on the size of the area and the amount of obstructions, if any. The geophysical survey grid at SWMU B‑33 was 295 feet long (northeast to southwest) and 40 feet wide with 20-foot spacing. EM data were collected at 2-foot intervals along transects that were separated by 20 to 50 feet using the established geophysical survey grid. Additional procedures are described in Volume 1-4, Sampling and Analysis Plan, Section 1.1.2.
There were four anomalies detected at the site. Locations of the anomalies are shown on Figure B33‑8. Anomalies A and C were associated with buildings, and anomaly B was associated with the former railroad tracks to the north. None of the geophysical anomalies indicated subsurface disturbance or possible buried waste. Figure B33‑8 also shows the approximate location of underground water utility lines and soil borings around SWMU B‑33. The locations of these water utility lines were estimated, but the locations of the soil boring samples (section 1.4.4, below) were marked with GPS, and are considered more accurate. In addition, field personnel visually inspected the pipe, which enters the Building 45 at the corner, rather than in the center of the wall as shown by the approximate survey. Therefore, if the underground pipeline is shifted slightly to match the field observations and the GPS locations, then anomaly D was associated with shut-off valves for the 6‑inch metal water supply pipe going to Building 45.
1.4.2 Waste Excavation and Disposal
In July 1997, the underground water line at Building 45/SWMU B-33 was temporarily diverted and the lead-contaminated bedding material was excavated and removed. Since the specific location of the lead-contaminated material was not known, four test pits were dug to find it. Field observations confirmed the presence of lead shot within the pipe bedding material. Approximately 180 cubic yards of bedding and fill material were excavated and replaced with clean material. All soils were successfully treated by solidification with Portland cement to non-hazardous Class 2 levels. The soils were then transported for disposal Covel Gardens Landfill in San Antonio, Texas, in accordance with the Waste Analysis Plan (Volume 1-5, RL33 Addendum) and applicable regulations. The excavated area was filled with clean sand and graded, and the water line was returned to service upon completion of field activities. It was estimated that approximately 2 to 3 cubic yards of the shot and lead contaminated sand was still in place near the foundation of Building 45. Live electric lines in that area prevented full excavation of all material.
While the excavation was open and the water line was diverted, four confirmation subsurface soil samples (B33-T1, B33-T2, B33-T3, and B33-T4) were collected and analyzed for metals to determine if all shot and lead-contaminated soils had been removed from the site. Sample analyses was performed by ITS Laboratories, Inc., but the results were deemed invalid by the EPA. Replacement of these test pit samples was not performed so that the active water line would not be damaged; instead, collection of subsurface soil boring samples was planned. This work is described in Section 1.4.4.
Based on the results of the initial geophysical survey, three surface soil samples (B33‑SS01, B33‑SS02, and B33‑SS03) were collected in March 1996 and analyzed for explosives and metals. However, analyses were performed by ITS Laboratories, Inc. and subsequently deemed invalid by the EPA. A Work Plan Amendment was created in 1999 to replace the invalid laboratory data (RL17 Work Plan Amendment for Data Quality Rework at SWMU B‑33), but the pipe bedding had been excavated and disposed offsite before its completion. Since representative surface soil was no longer present, additional surface soil sampling was not performed.
Based on the results of the initial geophysical survey and analytical results from surface soil samples, three soil borings (B33‑SB01, B33‑SB02, and B33‑SB03) were completed in May 1997 at SWMU B‑33 to assess the extent of contamination. Soil samples from borings B33‑SB01, B33‑SB02, and B33‑SB03 were collected and analyzed for explosives and metals. However, analyses were performed by ITS laboratories, Inc. and were subsequently deemed invalid by the EPA.
In March 2000, three replacement soil borings (RW‑B33‑SB01, RW‑B33‑SB02 and RW‑B33‑SB03) were completed in the approximate locations of the soil borings completed in 1996. The borings were drilled immediately adjacent to the water line trench (Figure B33‑8). Two samples were collected from each replacement boring, one at the vertical extent of the excavation and one at the total boring depth. Each sample was analyzed for explosives, barium, chromium, copper, nickel, zinc, arsenic, cadmium, lead, and mercury.
Explosives were all below the RLs at SWMU B‑33. Several metals exceeded RRS1 concentration criteria in the Glen Rose Limestone samples. Sample RW‑B33‑SB01 (4 to 4.5 feet bgs) had reported concentrations of 100.4 mg/kg barium, 10.2 milligrams per kilograms (mg/kg) chromium, 9.9 mg/kg nickel, 16.0 mg/kg zinc, 0.27 mg/kg cadmium, and 7.41 mg/kg lead. These concentrations all exceed Glen Rose Limestone background levels, which are: 10.0 mg/kg barium, 8.1 mg/kg chromium, 6.8 mg/kg nickel, 11.3 mg/kg zinc, 0.1 mg/kg cadmium, and 5.5 mg/kg lead. However, this sample was collected at a very shallow depth, near the common soil bedrock interface. Since the top of the Glen Rose Limestone typically consists of an incompetent marly layer, the slightly higher metals concentrations in RW-B33‑SB01 (4 to 4.5 feet bgs), are likely the result of the sample containing marl and soil. The concentrations detected in the excavation confirmation samples, met the soil background concentrations.
In addition, at RW‑B33‑SB03 (12 to 12.5 feet bgs), nickel was detected at a concentration of 10.1 mg/kg. Although the Glen Rose background concentration for nickel is 8.1 mg/kg, the Texas specific median background concentration is 10.0 mg/kg. All analytical results for samples collected from RW‑B33‑SB01 through RW‑B33‑SB03 are provided in Appendix A of the SWMU B‑33 RFI Report.