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SWMU B-23 Closure Report
Section 3 - Conclusions and Closure Certification
3.1 - Conclusions
Evidence of past ground disturbance at SWMU B‑23 and geophysical anomalies indicated that a trench potentially used for disposal of solid waste was present at the site. Scrap metal (banding material) was found on the ground surface along with partially buried JATO canisters. Buried JATO canisters were found in the subsurface of the trench during excavation activities. Results of surface and subsurface soil and rock samples collected from soil borings at SWMU B‑23 during the RFI indicated that metals and VOCs concentrations exceeded RRS1 standards.
In 2004, excavation was conducted in locations associated with the exceedances and waste material found during the initial site investigation conducted in March 2000. A total of 270.44 CY of waste and waste residue were excavated from the site in 2004 and disposed of at Covel Gardens Landfill. Following excavation, confirmation samples were collected from the excavation sidewalls and bottom to verify that all samples containing metals and VOCs exceeding RRS1 criteria were adequately delineated. Results of confirmation sampling indicate that the site meets RRS1.
Although JATO canisters were found at the site, all were either empty or filled with soil. CSSA does not perform aircraft maintenance or flight operations. It is highly unlikely that these were disposed at the site with any fuel remaining in them. JATO canisters are completely expended once they are ignited. If not attached to an aircraft, a canister would rocket violently for a great distance before expending all the fuel. For these reasons, it is likely that the JATO canisters were expended elsewhere and disposed empty at CSSA. Furthermore, only very slight BTEX detections were identified during the RFI, and none were detected in the closure confirmation samples.
Metals detected above RRS1 background during the initial site investigation included barium, copper, lead, nickel, and zinc. VOCs detected above RRS1 RLs during the initial site investigation included BTEX and dichlorofluoromethane. All soil contamination was removed during excavation activities. Very low concentrations of toluene and dichlorofluoromethane were detected in bedrock during the RFI, but these compounds were not detected in any of the trench bottom or sidewall closure samples. A description of the sampling and justification for attainment of RRS1 criteria for those analytes detected above RRS1 during the initial investigation are presented in Sections 3.1.1 through 3.1.2.2.
Metals concentrations in the excavation floor and sidewalls meet CSSA background concentrations. Metals detected above CSSA site‑specific background concentrations during the RFI (Parsons, 2002) were only slightly above applicable background levels. Soils at B23‑SB01 and B23‑SB02 were excavated to six feet bgs so metals exceeding background at these locations were removed during closure activities. In bedrock samples at B23‑SB02 (10‑10.5 feet) and B23‑SB03 (9.5‑10 feet), metals were detected at concentrations slightly above background but the concentrations are consistent with natural variations in native soils and bedrock at CSSA. Since all confirmation samples collected after final excavation were below background levels, it is evident that any waste residue associated with the waste trench has been removed. As such, the soils and bedrock meet RRS1 standards with respect to metals.
VOCs detected above RRS1 RLs during the initial site investigation included BTEX and dichlorofluoromethane. However, all VOCs, with the exception of one detection of toluene from the 10.0‑10.5 foot interval of B23‑SB02 and one detection of dichlorofluoromethane from the 9.5‑10.0 foot interval of B23‑SB03, were removed as part of final excavation activities. A discussion to justify attainment of RRS1 standards for those VOCs exceeding RRS1 which were located below the final limits of excavation are presented below.
Toluene exceeded its RRS1 RL in two soil and two bedrock samples collected during the March 2000 sampling event. Toluene was analyzed during the closure confirmation sampling to ensure that no toluene contamination was present after excavation activities were completed. Soil from two locations and bedrock from one location that had initially exceeded RRS1 criteria were removed from the site as part of final excavation activities. However, one bedrock sample (B23‑SB02 from 10‑10.5 feet) had been collected at a depth greater than the limits of the final excavation. The concentration in this sample was 0.0051 mg/kg, which is only 0.0001 mg/kg above the RL of 0.005 mg/kg. A total of seven excavation sidewall samples and two bottom excavation samples were analyzed for toluene, none of which had any detected concentrations. Because toluene was not detected in any of the confirmation samples including those collected on the bottom of the waste disposal trench excavation, it is concluded that the site meets RRS1 criteria with respect to toluene.
Dichlorofluoromethane exceeded its RRS1 RL in one soil and two bedrock samples collected during the March 2000 sampling event. As a result, dichlorofluoromethane was analyzed for during closure confirmation sampling. Soil and bedrock in the location of two of the three samples exceeding RRS1 criteria were removed from the site as part of final excavation activities. However, one bedrock sample was initially collected at a depth greater than the limits of the final excavation. Dichlorofluoromethane, which is also known as Freon‑21, is a common refrigerant. There is no record of CSSA disposing of dichlorofluoromethane or Freon‑21. In addition, dichlorofluoromethane was not detected in any confirmation samples collected from the final excavation sidewalls or bottom. As such, it is likely that dichlorofluoromethane detected during the March 2000 sampling event was the result of laboratory contamination. Therefore, it is concluded that the site meets RRS1 criteria with respect to dichlorofluoromethane.
3.2 - Evaluation of Data Quality Objectives Attainment
All data generated during the SWMU B‑23 site closure were reviewed to confirm conformance with the AFCEE Quality Assurance Project Plan (QAPP); the data verification reports are included in Appendix C. All data are considered usable for site characterization purposes.
Overall DQOs for the investigations at CSSA are provided in Volume 1‑1 behind the RFI Addendum tab (Section 11 of the Work Plan Overview). A detailed list of DQOs for B‑23, along with an evaluation of whether each DQO has been attained, is provided in Appendix D. As described in Section 1 of this report, the main objectives of the B‑23 investigation are to determine if the site meets TCEQ requirements for RRS1 closure and to meet requirements of the 3008(h) Administrative Consent Order.
Given that all confirmation samples collected after excavation of B‑23 contain concentrations that are below CSSA background levels for metals and RLs for other analytes, and because all waste and waste residue have been removed, the site meets RRS1 criteria. As such, closure under RRS1 criteria is recommended.
Partial Facility Closure Certification
Solid Waste Management Unit B-1
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
April 28, 2005
LTC Jason D. Shirley
Commander, Camp Stanley Storage Activity
Date
Kirk W. Lawson
April 29, 2005
Kirk W. Lawson, P.E.
State of Texas #79204
Parsons
Date
Julie Burdey
April 28, 2005
Julie Burdey, P.G.
State of Texas #1913
Parsons
Date