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SWMU B-28 RCRA Facility Investigation Report
Section 3 - Conclusions and Recommendations
Past historical use of this site included the use of two trenches used for disposal of spent small arms ammunition, aerial flares, metal ammunition parts, and other metal. Geophysical surveys conducted in 1995 identified the presence of two anomalies associated with disposal of munitions and various metal objects. Additionally, a soil gas survey conducted in 1995 detected the presence of PCE at concentrations below 1.0 ug/L in the site soils.
Soil borings were performed in 1995 to assess the presence of impacted soil and rock material at the site. Analytical results from the sampling indicate that cadmium was detected above RRS1, or background, levels in SB01 (29.0-30.0 ft), and copper was detected above RRS1 criteria in SB03 (0.0-2.0 ft). Although phthalates were detected in several samples, no action is recommended for these compounds. These analyses are common contaminants, and are believed to be artifacts associated with the laboratory or field sampling equipment.
UXO removal activities occurred at the site from March through July 1997. Approximately 1,300 cubic yards of material were excavated from the trench locations and screened for UXO items. Nine UXO items were recovered from the trench locations. Soil sifting operations yielded 86,700 pounds of metal debris, which were removed and recycled.
Although a large amount of waste material has been removed from the site and contamination of in-situ soils appears to be limited, the approximate 730 cubic yards of sifted soil will require remediation or removal. Barium, copper, and zinc concentrations exceeded background in each of the sifted soils sample results. These sifted soils will be addressed as part of the interim measures currently underway, and as specified in the 3008(h) Administrative Order on Consent.
The 1995 soil boring indicated that waste has not migrated far from the trenches, if at all. However, soil samples have not been collected from the trench bottoms or sidewalls to confirm that all contaminated soils have been excavated and stockpiled.
3.2 - Evaluation of Data Quality Objectives Attainment
Overall data quality objectives (DQOs) for the investigations at CSSA are provided in Volume 1-1, RFI Addendum (Section 11 of the Work Plan Overview). A detailed list of DQOs for SWMU B-28, 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 SWMU B-28 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-28 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification reports are included in Appendix D. 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 significantly affect the sample results.
Because metals in sifted soils samples exceed background levels, TNRCC requirements for RRS1 closure have not been met. Furthermore, the consent order requirement to treat the sifted soil piles has not been met.
Contaminated soil stockpiled at SWMU B-28 is being addressed as part of a Soil Pile Disposition Assessment currently underway. The purpose of this assessment is to test remediation options for this and similarly contaminated soils stockpiled at SWMUs B-8, B-20, B-24, and DD. It is recommended that this assessment address the different background metals levels for these sites and determine one appropriate cleanup goal for all of the soils from these sites.
Prior to initiating this remediation, additional soil samples should be collected at the site to verify that all contaminated soil has been removed from the trenches. Based on results of the IM stockpile soil sampling and 1995 soil boring results, additional soil sampling should only include analyses for barium, copper, and zinc (SW-6010B), and cadmium (SW-7131). This surface soil sampling should focus on the former trenches where COCs were identified above the closure criteria and around the soil stockpile area where contaminated soils may have eroded. Because organic analyses exceeding RRS1 criteria were common laboratory contaminants, and are not known to have been used at CSSA, further analysis for these compounds at SWMU B-28 is not considered warranted.