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SWMU B-12 RCRA Facility Investigation/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‑12 was completed in July 2002 to document the environmental condition of the site and site closure requirements for SWMU B‑12. This closure report includes by reference the information presented in the SWMU B‑12 RFI Report (Parsons, 2002).
The SWMU B‑12 RFI Report recommended excavation and disposal of waste at the site. Results for surface soil and subsurface samples at SWMU B‑12 indicated that barium, copper, nickel, zinc, lead, mercury, fluoranthene, and bis(2‑ethylhexyl)phthalate (DEHP) exceeded background levels. Based on the RFI report, approximately 1,300 cubic yards (CY) of soils and waste material were estimated as materials needing to be removed from the site. Afterwards, confirmation sampling was to be conducted to confirm that closure requirements were achieved at the site. This report documents the closure activities at SWMU B‑12.
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, SWMU B‑12); |
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Field Sampling Plan (FSP) (Volume 1‑4, TO 0019 Addendum); and |
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Waste Analysis Plan (Volume 1‑4, TO 0019 Addendum); and |
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Health and Safety Plan (HSP) (Volume 1‑5, TO 0019 Addendum). |
Closure activities at SWMU B‑12 were conducted during November 2003. Over 2,700 CY of waste and waste residue were excavated, mixed with phosphate to provide metals stabilization, re-characterized and properly disposed of offsite. Confirmation sampling was conducted to verify that barium, copper, nickel, zinc, lead, mercury, fluoranthene, and DEHP concentrations were below closure levels.
For this closure report, Section 1 provides the site‑specific background and closure standard. Section 2 describes closure actions and the closure evaluation. Section 3 summarizes the findings, evaluates the attainment of data quality objectives (DQOs), provides recommendations, 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‑12 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‑12, 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 levels, 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‑12, 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.
Due to the presence of waste at the site, removal of waste and waste residue was recommended in the SWMU B‑12 RFI Report to meet RRS1 requirements.
1.2 - Background and Site Description
General information regarding the history and environmental setting of CSSA are 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‑12, an approximate 1‑acre area, is an apparent former quarry and that was later used for disposal of scrap metal and other waste. As shown in Figure B12‑5, the site is located to the west of Salado Creek. (Figures B12‑1 through B12‑4 are provided in the SWMU B‑12 RFI Report). In aerial photographs reviewed from 1966, 1973, 1986, and 1991, very sparse to no vegetation was visible. Today, vegetation at the site remains sparse, consisting of grassy patches. Figure B12‑6 provides aerial photographs over time.
An embankment in the southwest portion of the site contains abundant small and large metal debris (including tail fins from dummy practice rounds), clay pipe fragments, ceramic and porcelain shards, and limestone boulders. Waste material was observed at the surface of the embankment walls. This debris was placed along the slope of the embankment at unknown dates. According to historical records, large pieces of scrap metal and weapons were embedded into the embankment and the area adjacent to the embankment (the floor or flat-lying portion of the site). Although historical records review and personal interviews indicated past use of the area as a landfill, the 1995 geophysical survey (described in Section 1.3 of the SWMU B‑12 RFI Report) did not confirm this. Visual observation and the geophysical survey results indicated that waste is only present in the area of the embankment.
The site area next to the embankment contained ponded water in 1995 and 1996. In 1995, standing water reached a maximum depth of approximately two feet in the southeastern portion of the site. In 2000, during site investigation drilling activities, the flat area was dry as a result of the extended drought from 1997 through 1999. There was no evidence of past waste disposal activities in the flat area (floor) of the site.
Additional background information regarding the location, size, and known historical use of the SWMU B‑12 is also included in the Environmental Encyclopedia (Volume 1‑2, SWMU B‑12). Volume 1‑2 also includes a Chronology of Actions and a Site‑Specific Work Plan for SWMU B‑12.
1.2.2.2 Potential Sources of Contamination
The B‑12 site has been used as a landfill area for large pieces of scrap metal, including tail fins from dummy practice rounds. Large pieces of metal located near the surface are the primary source for metals contamination of surface and subsurface soils at the site. RFI sampling activities revealed metals and semi-volatile organic compounds (SVOCs) above RRS1.
SWMU B‑12 is located in the east‑central portion of the Inner Cantonment Area (Figure B12‑5). The general shape of the site is rectangular, and is located about 1,600 feet from the eastern boundary of the Inner Cantonment. The site is located immediately north of the intersection of Road No. F‑14 and Road No. F‑11. There are no permanent structures at SWMU B‑12 with the exception of overhead utilities. An unnamed gravel road forms the northeastern boundary 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 SWMU B‑12 RFI Report (Parsons, 2002). A summary of the site environmental setting is provided in the paragraphs below.
1.3.1 Site Soils and Topography
Two soil types are present at SWMU B‑12, Brackett Soils and Krum Complex Soils (Figure B12‑2). Brackett soils account for approximately 20 percent of the site, and are located on the southwest side of SWMU B‑12. The shallow (approximately 4 inches thick) Brackett Soils occur on slopes of 12 to 30 percent. These soils develop over soft limestone and are underlain by hard limestone, which gives the slopes a stairstep appearance. Krum Complex soils compose the remaining 80 percent of soils at SWMU B‑12. The soils are deeper (approximately 30 inches thick) and commonly occupy slopes below Tarrant and Brackett soils. These soils receive sediments and runoff from higher elevation soils and are highly prone to water erosion if unprotected. Detailed descriptions of the CSSA soil types are provided in the Environmental Encyclopedia (Volume 1‑1, Background Information Report, Soils and Geology).
SWMU B‑12 is bordered by a 15‑ to 25‑foot tall man‑made embankment to the southwest, topographically higher ground to the northwest and southeast, and an elevated dirt road to the northeast. The elevation of the site ground surface in the low‑lying area in the central part of the site is approximately 1,235 feet above sea level. The embankment and higher ground along the westernmost boundary are approximately 1,250 feet above sea level. Due to the surrounding elevated terrain, surface water readily accumulates in the central part of SWMU B‑12, especially after a heavy rain event.
The Upper Glen Rose (UGR) Formation is the uppermost geologic strata in the area of SWMU B‑12. The UGR consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds, averaging 50 feet thick. Generally, it outcrops in stream valleys and at the ground surface where soils are poorly developed or eroded. The UGR is underlain by the Lower Glen Rose (LGR) (averaging 320 feet thick) which 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 facies of the Hensell Sand (averaging 60 feet thick). The geologic strata dip approximately 10 to 12 degrees to the south‑southeast at CSSA. SWMU B‑12 is situated over the geologic contact which divides the Upper and LGR. The eastern quarter of the site is underlain by the LGR, which outcrops at the surface along the eastern edge of the SWMU. The UGR occupies the remaining portion of the site and outcrops at the surface on the western side of SWMU B‑12.
At CSSA, the uppermost hydrogeologic layer is the unconfined Upper Trinity aquifer, which consists of the UGR Limestone. Locally at CSSA, low‑yielding perched zones of groundwater can exist in the UGR. The Middle Trinity aquifer is unconfined and functions as the primary source of groundwater at CSSA. It consists of the LGR Limestone, the Bexar Shale, the Cow Creek Limestone, and the Hammett Shale. The LGR Limestone outcrops north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, principal 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. Groundwater flow within the Middle Trinity aquifer is toward the south and southeast. In general, groundwater at CSSA flows in a north to south direction, with some seasonal fluctuations.
No site‑specific groundwater data were collected for the site. The nearest well is CS‑1, an off‑post well located approximately 3,500 feet southeast of SWMU B‑12. Between 1992 and 2001, static water levels ranged between 101 and 268 feet below top of casing (btoc) in this well (Volume 5, Introduction to Monitoring Program, Table 3). The nearest on‑post well is CS‑MW17‑LGR, which is located approximately 4,000 feet northeast of the site, in the East Pasture. Between September 2002 and June 2004, static water levels ranged between 115 and 250 feet btoc in this well.
The closest surface water feature to SWMU B‑12 is Salado Creek, which is approximately 1,260 feet east‑northeast of the site (Figure B12‑5). Salado Creek is an intermittent north‑south trending creek that exits the CSSA boundary approximately 2,300 feet southeast of SWMU B‑12.
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 is located approximately 1,360 feet to the northeast of SWMU B‑12. The resource consists of World War I era foxholes and trenches that were used for training.
A land use survey studying 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 this survey, along with more in‑depth information regarding 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).
A small herd of cattle are kept in the North Pasture. CSSA also manages wild game species for the purpose of hunting, including white‑tailed deer, axis deer, and wild turkey. A map of deer hunting stands, which overlook mechanical feeders and planted food plots is located on Figure 5.2 of the Technical Approach Document for Risk Evaluation (Volume 1‑6). SWMU B‑12 is located within 1,000 feet of three deer blinds, one turkey feeder, and a planted food plot. Hunting stand number 6 and its associated food plot and turkey feeder are located 500 feet northeast of the site, hunting stand number 7 is located 800 feet southwest of the site, and hunting stand number 8 is located approximately 1,000 feet southwest of the site. Four ponds are maintained at CSSA for the purpose of sport fishing. Two ponds are located in the northwestern and northeastern portions of the North Pasture, and the other two tanks are located near the western boundary of the Inner Cantonment. The potable water reservoir is located approximately 3,500 feet northwest of the site. Potential habitat for local endangered species Golden‑cheeked warbler is located approximately 800 feet southeast of SWMU B‑12 and potential habitat for local endangered species Black‑capped Vireo is approximately 2,500 feet northeast of SWMU B‑12.
An electromagnetic (EM) geophysical survey was conducted at SWMU B‑12 in May 1995. Prior to collecting EM data, a grid system was established at the site, which encompassed the flat‑lying portion (floor) of the site. This grid consisted of staked locations conducted along north‑south and east‑west transects, which were spaced at 25‑foot intervals. The grid measured 250 feet (north to south) by 100 feet (east to west). The adjacent embankment area was not surveyed due to surface interference by abundant metal debris. A chronology of actions, including previous investigations at SWMU B‑12, is located under the SWMU B‑12 tab (Volumes 1‑2 and 3‑1 of the CSSA Environmental Encyclopedia).
Results showed that no EM anomalies were present in the flat-lying portion of the site; therefore, there is no indication of subsurface waste in this portion of SWMU B‑12.
Four surface samples were collected at SWMU B‑12 in March 2000 at soil boring locations RW‑B12‑SB01, RW‑B12‑SB02, RW‑B12‑SB03, and RW‑B12‑SB04. Samples were analyzed for volatile organic compounds (VOCs) (SW‑8260B), SVOCs (SW‑8270C), explosives (SW‑8330), barium, chromium, copper, nickel, and zinc (SW‑6010A), arsenic (SW‑7060A), cadmium (SW‑7131A), lead (SW‑7421), and mercury (SW‑7471A). Sampling locations are shown in Figure B12‑7.
No explosives were detected in any of the surface soil samples. All VOC concentrations were below RRS1. One SVOC, fluoranthene, exceeded RRS1 criteria in one sample, RW‑B12‑SB04, with a concentration of 0.75 milligrams per kilograms (mg/kg). The laboratory RL for fluoranthene is 0.7 mg/kg (Table B12‑1). Table B12‑1 is included in Appendix E for quick reference.
Four metals exceeded RRS1 (background concentrations): barium, copper, zinc, and lead (Table B12‑1).
Four soil borings were advanced on March 15, 2000, with three samples collected from each boring, including a surface soil sample (as described above). The sample IDs are the same as those listed for the surface soil samples presented above. Samples were analyzed for VOCs (SW‑8260B), SVOCs (SW‑8270C), explosives (SW‑8330), barium, chromium, copper, nickel, and zinc (SW‑6010A), arsenic (SW‑7060A), cadmium (SW‑7131A), lead (SW‑7421), and mercury (SW‑7471A). Sampling locations are shown in Figure B12‑7.
No explosives were detected in the subsurface samples. All VOC concentrations were below RRS1. One SVOC compound, DEHP, was detected above RRS1 in seven samples. Two metals, nickel and zinc, exceeded RRS1 (Table B12‑1).