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SWMU B-34 RCRA Facility Investigation Report
Section 1 - Introduction
On May 5, 1999, an Administrative Consent Order was issued to CSSA pursuant to §3008(h) of the SWDA, as amended by RCRA, and further amended by the HSWA of 1984. In accordance with the RFI requirements of the Consent Order, this report has been prepared to document the environmental condition and site closure requirements of SWMU B-34 and to recommend further investigation, if necessary, or to provide documentation necessary for site closure. The main objectives of the SWMU B-34 investigation are to determine if the site meets TNRCC requirements for closure, as described in Section 1.4, and to meet requirements of the Consent Order.
This specific RFI was performed by Parsons under the AMC Contract F11623-94-D-0024 (Delivery Order RL17). AFCEE provided technical oversight for the delivery order. Based upon the project SOW, a set of work plans was established to govern the fieldwork. These plans include:
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Volume 1-1, Work Plan Overview; |
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Volume 1-2, SWMU B-34; |
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Volume 1-4, RL17 Addendum; and |
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Volume 1-5, RL17 Addendum. |
For this report, Section 1 provides the site-specific background and closure standard. Section 2 describes field actions and closure evaluations. Section 3 summarizes the findings, evaluates attainment of data quality objectives, provides recommendations, and certifies the site closure, if applicable. References cited in this report can be found in the Bibliography (Volume 1-1, Environmental Encyclopedia).
1.1 - 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-34 is adjacent to Building 28, where diesel locomotive maintenance was historically performed. CSSA conducted maintenance on locomotives from inside the building. A pit located inside Building 28 was used for CSSA personnel to perform maintenance activities on locomotive and railway equipment. SWMU B-34 consists of the below-grade piping and pipe bedding that drained from the pit. The piping extends 230 feet southwest from Building 28, travels underneath an open field, and drains to an outfall area near McElroy Road. SWMU B-34 covers an area of approximately 0.5 acre. The outfall area drains to a ditch adjacent to the northern side of McElroy Road. This ditch drains from east to west along McElroy Road, then travels south through a culvert constructed beneath McElroy Road.
Background information regarding the location, size, and known historical use of SWMU B-34 is also included in the Environmental Encyclopedia (Volume 1-2, SWMU B-34). Volume 1-2 includes a Chronology of Actions and a Site-Specific Work Plan for SWMU B-34.
1.1.2.2 Potential Sources of Contamination
Since Building 28 was used for diesel locomotive maintenance, there are multiple constituents of concern associated with SWMU B-34. Diesel engine maintenance products, oil products, and various solvents are all likely to have been used at the maintenance pit. Spills of maintenance products while performing maintenance activities could transmit them into the drainage piping associated with Building 28 and subsequently into the ditch that lies near the piping outfall area.
The site is located in the western portion of the Inner Cantonment of CSSA, approximately 1,000 feet east of the western border of CSSA and approximately 4,000 feet from the southern border of CSSA, as shown in Figure B34-1. SWMU B-34 extends from the southern end of Building 28 a distance of about 230 feet to the southwest to McElroy Road (Figure B34-1). The site area covers approximately 0.5 acres in area. The boundary of the site was extended to encompass the subsurface area where the piping from Building 28 may have contaminated soils through possible leakage or drainage of wastes. AOC 57 is located approximately 250 feet south of SWMU B-34 and SWMU B-32 is approximately 450 feet to the north.
1.2 - Site Environmental Setting
1.2.1 Site Soils and Topography
SWMU B-34 rests entirely on Crawford and Bexar soils (Figure B34-2). Crawford and Bexar stony soils occupy portions of both the inner and outer cantonments, and cover approximately 16.9 percent of the ground surface at CSSA. They occur in broad, nearly level to gently undulating areas. The Crawford soils are stony, very dark gray to dark reddish brown, noncalcareous clay, and average about 8 inches thick. Large fragments of chert and limestone occur on the surface and within the soil profile. Bexar soils range from cherty clay loam to gravelly loam. The soils are nonarable and suited for native grasses. Detailed descriptions of the various soil types present at CSSA are located in the Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology). The soil profile within SWMU B-34 generally extends to about five feet bgs before bedrock is encountered as shown in the boring logs attached as Appendix A.
The surface elevation associated with the SWMU B-34 area varies from approximately 1,270 to 1,275 feet above sea level. The area ground surface slopes gently to the east-southeast (Figure B34-2). SWMU B-34 is covered with native grass vegetation and some oak trees.
The Upper Glen Rose is the uppermost geologic stratum in the area of SWMU B-34 (Figure B34-3). 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 Formation may be up to 150 feet thick. It is underlain by the Lower Glen Rose Formation, which is estimated to be 300 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 and the Bexar Shale is estimated to be from 60 to 150 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.
The Upper Glen Rose Limestone bedrock was generally encountered at about five feet bgs at SWMU B-34 and consisted of weathered mudstone to wackestone material containing 21` iron-oxide mottling, bivalves, and marl interbeds as indicated in the Soil Boring Logs attached as Appendix A.
Based on current published information, there are two known major fault (shatter) zones at CSSA: the North Fault Zone and the South Fault Zone. SWMU B-34 is located approximately 3,500 feet south of the North Fault Zone and approximately 3,000 feet north of the South Fault Zone.
1.2.3 Hydrology
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 in different beds often differ. Principal development of solution channels is limited to evaporate layers in the Upper Glen Rose Limestone.
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 at 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 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 well pumping.
No site-specific information regarding groundwater is available. The nearest well is CS-9, which is a water supply well for CSSA located approximately 1,650 feet northwest of SWMU B-34. Static water levels in CS-9 have measured between 165 feet bgs in March 2001 and 399 feet bgs in September 2000 (Volume 5).
The nearest surface water feature is a drainage ditch that runs along the northern side of McElroy Road, near the drainage outfall area, south of the site area. The ditch drains from west to east along McElroy Road, then turns south and travels through a culvert constructed beneath McElroy Road. The ditch flows south across the post (Figure B34-4).
All of the structures on the installation are considered historical resources. 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 1 era training trenches located just inside the eastern boundary of the Inner Cantonment. The trenches, which have retained much of their original design features, are located approximately 3,750 feet northeast of SWMU B-34. Building 28 is considered a historical structure.
A land use survey discussing local and possible future uses of groundwater and surface water, a water well survey, and sensitive environmental areas at CSSA was completed during December 15 and 16, 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 is presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1-6).
A small herd of cattle is maintained on CSSA by the USDA-ARC. The cattle roam freely throughout the Inner Cantonment and in selected areas of the North Pasture. CSSA also manages wild game species for the purpose of hunting. White-tailed deer, axis deer, and wild turkey all roam freely throughout CSSA. 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-34 is located approximately 2,100 feet northwest of hunting stand number 14. Four water tanks are maintained at CSSA for the purpose of sport fishing. Two of the tanks are located in the northwestern and northeastern portions of the North Pasture while the other two tanks are located near the western boundary of the Inner Cantonment.
The closest sensitive receptor to SWMU B-34 is the “W” Tank located approximately 3,300 feet south of the site area and the closest water supply well is located approximately 1,650 feet to the northwest. The nearest potential habitats for local endangered species are located approximately 5,500 feet northeast (black-capped vireo) and 3,500 feet southeast (golden-cheeked warbler) of SWMU B-34 (Parsons, 1993).
No previous investigations have been performed at SWMU B-34.
As described in Section 4.3 of the Technical Approach Document for Risk Evaluation (Volume 1-6), CSSA has opted to pursue closure of SWMU B-34 under the Risk Reduction Rule (30 TAC §335). If the site concentrations do not exceed background, then the site will be closed using RRS1. If the site exceeds CSSA background, then a determination will be made regarding the feasibility of cleaning the site to meet background concentrations. If the decision is made to clean the site to background, closure under RRS1 will be sought. However, if it is determined that the site cannot be closed to meet background concentrations, then the site will be closed under TRRP. A notification of intent to close sites identified to date (including SWMU B-34) in accordance with the former RRR was sent to the TNRCC on July 12, 1999. TNRCC acceptance of this notification was received on October 5, 1999.
RRS1 requires that the site be closed following removal or decontamination of waste, waste residues, and contaminated operation system components; and demonstration of attainment of cleanup levels (30 TAC §335.554). If closure requirements under RRS1 are attained and approved by the TNRCC Executive Director, then the owner is released from deed recordation requirements.
Since SWMU B-34 was potentially a pathway to distribute diesel locomotive maintenance waste materials, COCs associated with this site include metals, VOCs and SVOCs. Since the COCs for SWMU B-34 are metals, VOCs, and SVOCs, the RRSI standards should be the soil or rock background values for metals and the RLs for VOCs and SVOCs. Background metals levels were statistically calculated for CSSA soils and the Glen Rose Limestone, and are reported in the Second Revision to the Evaluation of Background Metals Concentrations in Soils and Bedrock (Parsons, February 2002). TNRCC approved the revised background metals evaluation report on April 23, 2002.