[RFI Report Addendum]

SWMU Building 43 RCRA Facility Investigation Report Addendum

Section 3 - Conclusions and Recommendations

3.1 - Conclusions

SWMU Building 43 was used for waste management activities for an unknown time period. The building was used as an ammunition demolition facility to burn miscellaneous solid waste and ammunition. During field investigations, the area adjacent to SWMU Building 43 was covered with metal debris and spent ammunition. Soil borings completed during February and March 2000 revealed elevated metals concentrations (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc) were identified in the topmost foot of soil throughout the site, exceeding the applicable RRS1 standards. Although the vertical extent of metals contamination was identified, the lateral extent was not identified.

Based on the elevated metals concentrations in surface soil, ten additional surface soil samples were collected in March 2003 in an effort to define the horizontal extent of contamination. All samples were analyzed for barium, chromium, copper, nickel, zinc, arsenic, cadmium, lead, and mercury. The extent of arsenic, chromium, and nickel contamination has been defined with the additional sampling effort. However, concentrations of barium, cadmium, copper, lead, mercury, and zinc exceed background concentrations at the outer edges of the sampling area; therefore, the extent of contamination has not been defined. Copper and zinc exceeded their background standards six or more times, with copper exhibiting the highest reported values with respect to its background standard of 23.2 mg/kg. Barium and cadmium exceeded RRS1 in one and two samples, respectively. Lead and mercury exceeded RRS1 in three samples each.

As seen in Figure 8, sampling locations along the northern edge of the site display consistently high concentrations of barium, copper, zinc, and lead. Metals concentrations decrease to the east and south of the site. Lead and barium fall below RRS1 in the eastern and southern samples. Copper and zinc concentrations fall dramatically, but still exceed RRS1. A notable occurrence is the appearance of mercury. Although mercury was not detected above RRS1 in the northern samples, mercury appears east and southeast of the site area. The sampling results do not suggest that the horizontal extent of contamination has been completely defined on any side of the site area, although metals contamination is less prominent along the eastern and southern edges of the site.

3.2 - Evaluation of Data Quality Objectives Attainment

Overall data quality objectives (DQOs) for the investigations at CSSA are provided in Section 11 of the Work Plan overview (Volume 1-1). A detailed list of DQOs for SWMU Building 43, along with an evaluation of whether each DQO has been attained, is provided in Appendix A. The main objectives of the SWMU Building 43 investigation are to determine if the site meets Texas Commission on Environmental Quality (TCEQ) requirements for RRS1 closure and to meet requirements of the consent order.

All data generated during the SWMU Building 43 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification report is included in Appendix B. All data are considered usable for site characterization purposes. Although several results are flagged M, these results are considered usable because the matrix interference is minimal and does not significantly affect results.

Because metals in surface soil samples exceed RRS1 (background) levels, TCEQ requirements for RRS1 closure have not been met. Furthermore, the consent order requirement to identify the horizontal extent of contamination has not been met.

3.3 - Recommendations

Because waste and waste residue at concentrations above RRS1 values levels remain at SWMU Building 43, further action is recommended. Surface material excavation and removal activities are recommended throughout the site to address elevated arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel and zinc concentrations identified within samples collected from the upper 0.5 to 1 foot of soil. Because the geophysical survey did not indicate any anomalies related to waste management activities at depth, and no metals contamination was observed at depth, it is suggested that the contamination is only in the surface soils (top one foot of soil).

Excavation of surface soils in the estimated area to a depth of one foot will results in an estimated 1,100 cubic yards of soil to be disposed. Samples of the excavated material must be collected and analyzed using TCLP for characterization prior to off-post disposal. Landfills typically require one sample per 500 cubic yards of material, so three samples should be collected to characterize the excavated soil.

Verification sampling should be conducted outside the excavated area to confirm that all contaminated soil has been removed. The excavation area should extend beyond the area sampled during the Phase II sampling effort. Samples should be collected on all sides of the site area, and the samples should be analyzed for barium, cadmium, copper, lead, mercury, and zinc.