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Community Relations Plan, December 2002
Section 3 - History of Environmental Assessments at CSSA
In 1993, the environmental assessment/RCRA assessment (EA) identified and described potential environmental impacts associated with current and past operations. The EA also addressed the groundwater contamination that had first been identified in 1991. Additional information regarding the EA is located in Volume 1-1, Scoping Documents, Work Plans, Environmental Assessment (Parsons, September 1993).
This section provides a brief overview of groundwater and waste management unit investigations at CSSA. Appendix B, a Chronology of Actions/Investigations, provides a comprehensive listing of corrective action events from 1991 to the present.
Currently, there are 32 existing groundwater wells at CSSA. These wells are used for potable drinking water sources, as groundwater monitoring wells, for agricultural water supplies or a combination of these purposes. Seven wells are located in the north pasture (CS-G, CS-H, CS-I, CS-MW3-LGR, CS-MW9-LGR, CS-MW9-BS, and CS-MW9-CC). Nine wells are located along the northern boundary of the inner CSSA cantonment area (CS-MW1-LGR, CS-MW2-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-2, CS-3, CS-4, CS-16, and CS-D). The inner cantonment area is designated on Figure 2 and refers to an area used to temporarily house military personnel. Twelve wells are located in the southwestern area of CSSA (CS-9, CS-10, CS-11, CS-MW6-LGR, CS-MW6-BS, CS-MW6-CC, CS-MW7-LGR, CS-MW7-CC, CS-MW8-LGR, CS-MW8-CC, CS-MW10-LGR, and CS-MW10-CC). One well (CS-1) that is operated by CSSA is located southeast of CSSA at Camp Bullis.
The Trinity is the principal aquifer underlying CSSA. The Middle Trinity aquifer is comprised of the Lower Glen Rose Limestone, the Bexar Shale, and the Cow Creek Limestone formations. The Middle Trinity aquifer is the primary source of drinking water in northern-most Bexar County, including the area surrounding CSSA. The Edwards aquifer is not encountered within CSSA post boundaries. However, the Edwards Underground Water District (EUWD) has defined two recharge and transition zones of concern for the Edwards aquifer; one north and one south of CSSA. One recharge area is along Cibolo Creek where outcrops of the Lower Glen Rose are present. This is the only area of the Lower Glen Rose that is defined as a recharge zone to the Edwards aquifer. The Cibolo Creek recharge area is 0.5 miles north of the northeast corner of CSSA. A second recharge zone located on Edwards Limestone is about 4 or 5 miles to the south-southeast of CSSA.
During a routine screening site visit on August 9, 1991, the Texas Department of Health (TDH) sampled CSSA water supply wells CS-1, CS-9, CS-10, CS-11, and CS-16. Well locations are shown in Figure E-1 in Appendix E. Analytical results revealed that well 16 contained 127 micrograms per liter (μg/L) cis- and trans-1,2-dichloroethene (cis-1,2-DCE and trans-1,2-DCE), 151 μg/L trichloroethene (TCE), and 137 μg/L tetrachloroethene (PCE). These concentrations exceed the drinking water maximum contaminant levels (MCLs) of 70 μg/L for cis-1,2-DCE, 100 μg/L for trans-1,2-DCE, 5 μg/L for TCE, and 5 μg/L for PCE. Subsequent sampling on August 23, 1991, confirmed the earlier results and well CS-16 was taken out of service and disconnected from the potable water system.
Since 1992, numerous groundwater monitoring events have been conducted at CSSA. As part of these events, all on-post wells and selected off-post wells have been sampled. For detailed information pertaining to the analytical results from groundwater monitoring events, refer to Volume 5, Groundwater Investigation of the Environmental Encyclopedia, specifically the On-post Groundwater Monitoring and Off-post Groundwater Monitoring tabs.
As part of the May 1993 Sampling and Analysis Plan (SAP) for Evaluation of Ground Water Contamination at CSSA, two potential sources of the hazardous waste constituents found in the contaminated wells were identified. These potential source areas included SWMU O-1 and SWMU B-3 located near the center of CSSA (see Figure E1, Appendix E). As part of on- and off-post groundwater monitoring being conducted by CSSA, another potential source area was identified. In December 1999, CSSA sampled well LS-7, a private off-post well near the southwest corner of the post. Analytical results indicated low levels of PCE and TCE contamination. CSSA�s continued monitoring of well LS-7 revealed that contamination levels increased toward the MCL (drinking water standard). In August 2001, CSSA extended its off-post monitoring program to include four additional private wells (LS-2, LS-3, LS-5, and LS-6) near the southwest corner of the post. Analyses of water samples from these off-post wells also found PCE and TCE contamination. CSSA used PCE and TCE, which are volatile organic compounds (VOCs), prior to 1995 to degrease ordnance materiel. Solvents containing both PCE and TCE were used in Building 90, which was identified as a third potential source area at the southwest corner of CSSA and identified as area of concern number 65 (AOC-65) (see Figure E1, Appendix E). The history and current status of the three potential source areas identified at CSSA include:
| Oxidation Pond: The oxidation pond (SWMU O-1) was built about 1975. The pond had a vinyl plastic liner and was used for evaporation of waste liquids from the ordnance-related maintenance process. This pond was filled with dirt in 1985 after solid and liquid residues were removed. SWMU O-1 is located in the central portion of CSSA (Figure E1, Appendix E). Soil gas surveys conducted in 1995 identified VOCs within the pond boundaries. Subsequent soil tests have shown PCE, chromium, and cadmium in the soil above action levels established by the TCEQ. Geophysical surveys, surface and subsurface soil sampling, soil gas surveys, excavations, and an electrokinetics treatability study have been performed at SWMU O-1. In September 2000, CSSA excavated and removed approximately 1,515 cubic feet of non-hazardous soil and rock from the site and disposed of the material in an approved landfill. Subsequently, CSSA collected samples to confirm no soil with concentrations above the TCEQ action levels remained in surface soils. Low levels of chromium remained in limestone below the site and the TCEQ concurred that these levels they constituted a low risk to groundwater. Contamination in the limestone bedrock is to be addressed as part of the groundwater evaluation and continuing environmental program. Therefore, formal closure of SWMU O-1 for surface soils was received from the TCEQ on April 23, 2002. Additional information on remediation activities at SWMU O-1 is located in Volume 3-1.2, Solid Waste Management Units, behind the SWMU O-1 tab. | |
| SWMU B-3: SWMU B-3 consists of trenches that cover approximately one-half acre. SWMU B-3 was a landfill area used for disposal and burning of waste. SWMU B-3 is located in the central portion of CSSA (Figure E1, Appendix E). Tests identified PCE and TCE in the trench area, indicating this as a likely source of the VOCs detected in well CS-16. CSSA installed a soil vapor extraction (SVE) system to cleanup VOCs in the trench soils and underlying limestone in 1996/97 and the system removed more than 500 pounds of VOCs while it was operating. Geophysical surveys, surface and subsurface soil and rock sampling, and soil gas surveys were conducted at SWMU B-3. The SVE system concluded removal of available contaminants from the site and was dismantled in 2002. CSSA is excavating the contaminated soil which is scheduled to be completed in the fall of 2002. Additional information on ongoing remediation activities at SWMU B-3 is located in Volume 3-1.1, Investigation Reports, Solid Waste Management Units, behind the SWMU B-3 tab. | |
| AOC-65: AOC-65 consists of a concrete lined pit where the former solvent vat was located in an area in the south and west portion of Building 90 and adjacent areas at the southwest corner of CSSA (see Figure E1, Appendix E). Soils samples collected in April 2000 detected low levels of VOCs. Further investigation of the area near Building 90 included installation of on-post monitoring wells and conducting a soil gas survey over approximately 70 acres near the southwestern corner of the post. Results from investigations confirmed the presence of PCE and TCE in shallow soils and limestone underlying AOC-65. CSSA is completing the construction of two soil vapor extraction systems at AOC-65. One system was installed inside Building 90 to treat contaminated media (soil, rock, and air) underlying Building 90. The second system is installed on the west side of Building 90 where soil gas and shallow soil results indicate the highest contaminant levels. A removal action of contaminated surface soils along the west side of Building 90 and the adjacent drainage was completed as part of the SVE system construction project. Additional information on investigations, completed tasks, and planned activities at AOC-65 is located in Volume 3-2, Areas of Concern behind the AOC-65 tab. |
Forty-one potential solid waste management units (SWMUs) were identified following a review of records, interviews with CSSA personnel, and field investigations. These identified sites were areas used for solid waste disposal, with the exception of four burn areas (B-1, B-2, B-4, and B-22), two ordnance demolition areas (B-20 and Bldg. 43), one incinerator (I-1), one oxidation pond (O-1), and one less than 90-day waste materials storage area (F-14).
Thirty-eight potential Areas of Concern (AOCs) and one SWMU have also been identified. AOCs are those sites that field investigations and/or historical aerial photograph research indicate a possibility that waste disposal activities may have taken place as evidenced by disturbed areas or exposed surface debris. Since there are no records at CSSA that waste activities did indeed take place in these AOCs, they are considered to be low priority sites.
Field surveys indicate spent ammunition at five Rifle Management Units (RMUs). One RMU (RMU-1) still serves as an active firing range.
Table 3.1 provides a list of waste management units at CSSA. Information specific to each site is included in Volume 1-1, behind the Investigation Matrix tab of the Environmental Encyclopedia.
Table 3.1 - Waste Management Units at CSSA
| Solid Waste Management Units (41) | Areas of Concern (38) | Rifle Management Units (5) |
| SWMU B-1 | AOC-35 | RMU-1 |
| SWMU B-2 | AOC 36 | RMU-2 |
| SWMU B-3 | AOC-37 | RMU-3 |
| SWMU B-4 | AOC-38 | RMU-4 |
| SWMU B-5 | AOC-39 | RMU-5 |
| SWMU B-6 | AOC-40 | |
| SWMU B-7 | AOC-41 | |
| SWMU B-8 | AOC-42 | |
| SWMU B-9 | AOC-43 | |
| SWMU B-10 | AOC-44 | |
| SWMU B-11 | AOC-45 | |
| SWMU B-12 | AOC-46 | |
| SWMU B-13 | AOC-47 | |
| SWMU B-14 | AOC-48 | |
| SWMU B-15/16 | AOC-49 | |
| SWMU B-19 | AOC-50 | |
| SWMU B-20/21 | AOC-51 | |
| SWMU B-22 | AOC-52 | |
| SWMU B-23 | AOC-53 | |
| SWMU B-23A | AOC-54 | |
| SWMU B-24 | AOC-55 | |
| SWMU B-25 | AOC-56 | |
| SWMU B-26 | AOC-57 | |
| SWMU B-27 | AOC 58 | |
| SWMU B-28 | AOC-59 | |
| SWMU B-29 | AOC-60 | |
| SWMU B-30 | AOC-61 | |
| SWMU B-31 | AOC-62 | |
| SWMU B-32 | AOC-63 | |
| SWMU B-33 | AOC-64 | |
| SWMU B-34 | AOC-65 | |
| SWMU F-14 | AOC-66 | |
| SWMU B-71 | AOC-67 | |
| SWMU Bldg 40 | AOC-68 | |
| SWMU Bldg. 43 | AOC-69 | |
| SWMU DD Area | AOC-70 | |
| SWMU I-1 | AOC-72 | |
| SWMU O-1 | AOC-73 | |
| SWMU Coal Bins | | |
Through September 2002, CSSA environmental investigations have identified 41 SWMUs, 38 AOCs, and five RMUs as potential contamination source areas. The cleanup or closure strategy for these sites will follow TCEQ Rules and Guidance 30 TAC �335 Subchapter S. The TCEQ enacted the Texas Risk Reduction Program (TRRP) 30 TAC �350 which became effective on May 1, 2000. For sites where investigations were initiated before May 1, 2000, CSSA elected to continue pursuing closure under the Risk Reduction Standards. For any new sites that are identified after May 1, 2000, CSSA will follow the TRRP rules. All closures under the Risk Reduction rules (30 TAC �335) must be completed by May 1, 2005. A brief summary of these two closure strategies is provided below.
3.3.1 Risk Reduction Standards
The Texas Risk Reduction Rules regulate closure of contaminated sites and waste disposal sites. The rules allow for three different levels of site closure depending on amounts and types of contaminants found at the site. Risk Reduction Standard No. 1 RRS1 is allowed when site constituents are below naturally occurring levels (background).
RRS2 is the next level of closure. This type of closure is utilized when contaminants are above naturally occurring levels but below levels defined by the State of Texas as safe to human health and the environment based on the type of land use. RRS2 closure requires that the area where contamination exceeds background be delineated and recorded in the permanent record.
RRS3 closure requires a calculation of risk for each compound exceeding background levels. Acceptable risk levels are determined for each individual site. A Corrective Measure Study (CMS) and a Baseline Risk Assessment is required. Site remediation is performed and the site is monitored. TCEQ works with the landowner to determine site�specific closure requirements appropriate under RRS3.
The TRRP will eventually replace the Risk Reduction Standard rules. TRRP has three tiers of acceptable Protective Concentration Limits (PCLs) which are established levels for constituents in an environmental medium that are considered safe for human health and the environment. Tier I PCLs are based on conservative default assumptions regarding chemical mobility or exposure risk factors about the contaminant and site conditions. Tiers II and III incorporate increasing amounts of site-specific information to calculate a PCL that is more reflective of actual site conditions. While Tiers II and III provide more accurate representations of site conditions, they are more labor intensive and thus more expensive.
For sites where constituent levels concentrations exceed the applicable PCLs, there are two Remedy Standards available to complete the remedial action (Remedy Standards A and B). Remedy Standard A requires that constituents above the PCL be removed or decontaminated to acceptable levels in all areas. This standard is useful for small sites, sites that are being sold or transferred, and sites near the property boundaries. Remedy Standard B allows consideration of migration of the constituents to a point of exposure not necessarily at the source of the contamination. This standard will allow constituents to remain in place at concentrations greater than the PCL with controls, but will not allow the migration of contaminants off-site.
The choice of the appropriate Tier and Remedy Standard is dependent on numerous site conditions. Therefore, the choice for each site must be evaluated carefully before a decision is made.