RFI investigation results for SWMU B‑11 soils indicated the potential presence of various waste material and elevated metals concentrations. Soil gas data indicated VOCs at one soil gas point. However, VOCs were not found in actual soil and rock samples collected from soil borings at the site. Based on this evidence, it was concluded that the VOC detection was the result of soil gas migration from known VOC source areas (SWMU B-3 and O-1) and are not the result of a VOC release at SWMU B-11. The RFI recommended excavation and disposal of the waste material so that the site could be closed under RRS1 criteria. Confirmation sampling was to be conducted after the excavation/disposal activities to ensure that all waste was removed from the site.
Excavation and disposal of the waste at SWMU B‑11 was completed in November 2003. Waste removed from the site included concrete, wire, burnt wood, roofing debris, and parachutes. A total of 3,078 yds3 of waste and soil were removed from the site. Confirmation sampling for metals showed all soil concentrations are below RRS1 concentrations; therefore, all waste residue present in SWMU B‑11 soils has been removed from the site.
During the RFI, barium, chromium, nickel, zinc, chloroform, dichlorodifluoromethane, and methylene chloride were detected above CSSA background concentrations or RLs in one or more bedrock samples. As described in Section 2, statistical analyses of the results indicate that chromium, nickel, zinc, and dichlorodifluoromethane concentrations meet RRS1 criteria. Chloroform and methylene chloride were detected at very low concentrations and are common laboratory contaminants. In fact, chloroform was also detected in associated laboratory blank samples. There has been no known use of chloroform or methylene chloride at the site, and none of the waste excavated indicated possible VOC contamination sources. Finally, the one background exceedance of barium in bedrock was detected at B11‑SB03 (4.5‑5.0 ft). This relatively shallow sample was collected near the soil and bedrock interface, and it likely contained some soil, which has a barium background concentration of 186 mg/kg. Sample B11‑SB03 contained only 43.41 mg/kg barium. Furthermore, the overlying B11‑BOT03 closure confirmation sample collected at the bottom of the excavation contained only 27.91 mg/kg barium, which meets RRS1 criteria.
Because all waste and waste residue has been removed from the site, RRS1 closure is recommended.
Overall DQOs for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum tab. A detailed list of DQOs for SWMU B-11, along with an evaluation of whether each DQO has been attained, is provided in Appendix C. As described in Section 1, the main objective of the SWMU B-11 closure activities was to meet TCEQ requirements for RRS1 closure and the requirements of the 3008(h) Administrative Consent Order.
All data generated during the SWMU B-11 site closure were reviewed to confirm conformance with the AFCEE QAPP; the data verification reports are included in Appendix D. All data are considered usable for site characterization purposes. Although several results are flagged with a “J”, “F”, or “M”, these results are considered usable because estimation of the quantitation does not significantly affect the sample results.
Partial Facility Closure Certification
Solid Waste Management Unit B-11
Department of the Army
Camp Stanley Storage Activity
Boerne, Texas
I certify that the above-described closure was performed under my direction, in accordance with the work plan and 30 TAC §335 Subpart S, and as described in this report, and that, to the best of my knowledge and belief, said closure has been successfully accomplished.
Jason D. Shirley
June 17, 2004
LTC Jason D. Shirley
Commander, Camp Stanley Storage Activity
Date
Kirk W. Lawson
June 18, 2004
Kirk W. Lawson, P.E.
State of Texas #79204
Parsons
Date