[Home]
SWMU B-30 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-30 and to recommend further investigation, if necessary, or to provide documentation necessary for site closure. The main objectives of the SWMU B-30 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 U.S. Air Force AMC Contract F11623-94-D-0024, Delivery Order RL17. AFCEE provided technical oversight for the delivery order. Based upon the RL17 SOW, a set of work plans was established to govern the field work. These include:
|
Work Plan Overview |
(Volume 1-1, Work Plan Overview and Rework Work Plan Addendum); |
|
Site-Specific Work Plan |
|
|
Field Sampling Plan |
|
|
Health and Safety Plan |
For this RFI report, Section 1 provides the site-specific background and closure standard. Section 2 describes field actions and the closure evaluation. 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 of the Environmental Encyclopedia).
1.1 - 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.
SWMU B-30 was previously an at-grade limestone quarry area which was later used for disposal of miscellaneous construction debris. A field survey performed during September 1993 indicated scrap concrete, roofing shingles, and other construction waste at the site area. The approximate 0.36-acre area appears disturbed in aerial photographs dating back to 1966. The vegetation at the site consists of sparse native grasses and shrubs. In addition, the site is covered with mounds of dirt and construction debris that made access to the various sampling locations difficult during the field investigation. A tree line is present to the south of the site area, and a limestone embankment lies in the northern portion of the site. Figure B30-1 is an aerial photograph from 1998, showing the location of SWMU B-30.
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.
1.1.2.2 Potential Sources of Contamination
Based on identification of the site as a disposal area for miscellaneous construction debris and wastes, contaminants of potential concern include SVOCs, VOCs, and metals. SVOCs are included since waste burning may have occurred. Metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc) are included due to the potential metallic nature of the waste. VOCs analysis is included in the analytical program to detect typical contaminants associated with disposal areas.
SWMU B-30 is located in the southwestern tip of CSSA (Figure B30-1), within the Inner Cantonment and immediately south of SWMU B-29. The site is approximately 800 feet from the southern boundary and 2,000 feet from the western boundary of CSSA.
1.2 - Site Environmental Setting
1.2.1 Site Soils and Topography
The single soil type present at the SWMU B-30 site is Krum Complex soils (Figure B30-2). The soils are described as dark grayish-brown, calcareous, and generally up to 30 inches thick. These soils develop from slope alluvium of the limestone prairies. The Krum Complex soils are generally found on slopes between 2 and 5 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. Detailed descriptions of the various soil types present at CSSA are provided in the CSSA Environmental Encyclopedia (Volume 2, Description of Soil Types and Bedrock).
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 Formation is the uppermost geologic stratum in the area of SWMU B-30 (Figure B30-3). The Lower Glen Rose, which is estimated to be 300 feet thick beneath CSSA, 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 between 60 and 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.
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-30 is located directly north and topographically upgradient of the southern-most fault zone (Figure B30-3). Additional information on structural geology at CSSA can be found in the Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology).
Limestone bedrock exists near the surface in all of the boring locations at SWMU B-30, with one exception. Limestone bedrock was encountered at a depth of 5 feet in boring RW-B30-SB01. Soil boring logs are included in Appendix B.
The uppermost hydrogeologic 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. 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 well levels are discordant in adjacent wells completed in different beds. Principle development of solution channels is limited to evaporite 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 north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, the 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, with some seasonal fluctuations. However, the 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), which is an active drinking water well, is located approximately 750 feet southeast of SWMU B-30. Water levels in well LS-1 are unknown. Between May 1994 and June 2001, water levels in Well CS-1, which is located approximately 1.3 miles northeast, have ranged from 101.3 feet BTOC (November 1998) to 268.24 feet BTOC (April 1996) (Volume 5, Introduction to Monitoring Program, Table 3).
The nearest surface water body is a pond that is located 600 feet northwest of the site (Figure B30-1). A small 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.
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 are 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 shown in Figure 5.2 of the Technical Approach Document for Risk Evaluation (Volume 1-6). SWMU B-30 is located approximately 1,000 feet southwest of hunting stand number 12. Four water tanks are maintained at CSSA for the purpose of sport fishing. Two of the tanks, Drop-Zone Tank and I Tank (near Well CS-I), are located in the northwestern and northeastern portions of the North Pasture while the other two tanks, D Tank and W Tank, are located near the western boundary of the Inner Cantonment. SWMU B-30 is located approximately 600 feet southeast of W Tank.
Potential receptors that are located within ¼-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 ¼-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 is a potential Golden-Cheeked warbler habitat 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).
No previous investigations have been conducted at SWMU B-30.
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 TNRCC 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 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-30) 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 the deed recordation requirement.
Since the COCs for SWMU B-30 are VOCs, SVOCs, and metals, the cleanup levels are the RLs for VOCs and SVOCs which do not occur naturally, and background levels for metals which do occur naturally. 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 Concentration in Soil Types (Parsons, February 2002). TNRCC approved the background metals evaluation on April 23, 2002.