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SWMU B-22 RCRA Facility Investigation/Closure Report

Section 3 - Conclusions and Recommendations

3.1 - Conclusions

SWMU B-22 is a 5.2-acre site located in the North Pasture and was reportedly a former artillery shell burning area. The exact dates the site was used for waste management are unknown, and no evidence of waste has been observed on the ground surface.

The 1995 geophysical survey conducted at the site showed no evidence of buried waste or other subsurface disturbance. Subsequent actions at SWMU B-22 included a site boundary survey and collection of five surface soil samples. Results of the surface soil sampling revealed the presence of methylene chloride slightly above RRS1 criteria. One of five surface soil samples collected showed methylene chloride concentrations slightly above the reporting limit. Four of the soil samples showed both benzene and toluene detections, but all were below reporting limits. Since the sampling locations covered the entire area of the SWMU, the sampling regime is considered complete.

3.2 - Evaluation of Data Quality Objectives Attainment

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-22, along with an evaluation of whether each DQO has been attained, is provided in Appendix C. As described in Section 1, the main objectives of the B-22 investigation are to determine if the site meets TNRCC requirements for RRS1 closure and to meet requirements of the 3008(h) Administrative Consent Order.

All data generated during the SWMU B-22 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification report is included in Appendix B. All data are considered useable for site characterization and closure requirements. None of the results were flagged as rejected. Other than the “U” (nondetect) flag, the only other flags used on the SWMU B-22 data were the “F” flag, which is used for results which are between the MDL and the RL, and the “M” flag which is used when a matrix effect was present.

3.3 - Recommendations

Although SWMU B-22 has detected concentrations of methylene chloride that exceed RRS1 standards, further actions are not recommended at the site. In accordance with the TNRCC Interoffice Memorandum (TNRCC, 1998), “contaminants which have been detected within environmental media at a site but which meet [certain] … criteria may be considered non-site-related and may be excluded from further consideration under all three standards of the… rule.”

Methylene chloride was identified at concentrations of 0.0084 mg/kg and 0.0117 mg/kg within the environmental sample and the field duplicate sample for RW-B22-SS05, respectively. The low reported concentration of this compound, the knowledge that methylene chloride is a common lab contaminant, and the fact that the exceedances are limited to a single sample forms the basis of our opinion that methylene chloride does not pose a concern at SWMU B-22. Furthermore, methylene chloride is not a contaminant of concern at SWMU B-22.

For the reasons aforementioned, it is respectfully requested that SWMU B-22 be granted closure by the TNRCC in accordance with RRS1.

3.4 - Certification

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.