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AOC 48 RCRA Facility Investigation Report
Section 3 - Conclusions and Recommendations
As described in Section 1, AOC 48 is an area identified as a possible waste disposal area due to the presence of mounds and a construction debris pile. These features were visually identified during investigation of a neighboring site. To investigate this possible waste management unit, a geophysical survey was conducted and three surface soil samples were collected. In addition, several soil gas samples collected during a survey of a neighboring site were actually collected within the AOC 48 boundary.
One geophysical anomaly was identified during both the EM survey and the GPR survey. The anomaly is not considered to be associated with past waste management activities because of its pipeline like signature. This may be the location of a water line that was used to fill the depressions for off-road vehicle training. However, there is no conclusive evidence that this is a pipeline.
No VOCs were detected in soil gas samples collected at or near the site. Only zinc was detected at concentrations above RRS1 criteria. However, none of the zinc concentrations were greater than TRRP Tier 1 criteria. No VOCs, SVOCs, or explosives were detected above RRS1 criteria.
3.2 - Evaluation of Data Quality Objectives Attainment
Overall data quality objectives (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 AOC 48, 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 AOC 48 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 AOC 48 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 purposes. Although several results are flagged with an “M”, these results are considered useable because the matrix interference is minimal and does not significantly affect the sample results.
Because a geophysical anomaly possibly indicative of buried waste and a construction debris pile have been identified, the site does not meet the TNRCC RRS1 requirement for removal of all waste. The Consent Order requirement that the characteristics of the waste be identified has also not been met.
Surface soils meet RRS1 criteria for VOCs, SVOCs, explosives, and all metals. However, EM and GPR surveys indicate possible buried objects. Although the geophysical survey results may show a pipeline-like signature, there are no records or surface evidence at the site of a pipeline in this area. Therefore, it is recommended that test pits be excavated to determine if buried waste is causing the geophysical anomalies.
If buried waste is found, it and any remaining waste residue or contaminated soils should be excavated, characterized, and properly disposed of. Following excavation, confirmation samples should be collected to verify that all waste has been removed. The site should then be backfilled with clean soil and restored.
If no waste is found, it is recommended that closure in accordance with RRS1 be pursued after characterization, removal, and disposal of the construction debris pile has been completed. If a water or other utility liner is identified during the excavation, CSSA will locate the line with GPS and add it to their utility maps.