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SWMU B-33 RCRA Facility Investigation Report
Section 3 - Conclusions and Recommendations
SWMU B-33 consists of pipe bedding material near Building 45 that contained sand mixed with projectiles from the Building 90 test range. During initial investigations, sand and spent projectiles were uncovered in areas along the piping, especially toward the south end of the bedding. Sand and spent ammunition jackets were also present at the surface where the water supply line entered Building 45. Contaminated backfill materials have been excavated, removed and disposed of in accordance with applicable regulations. A small amount (2 to 3 cubic yards) of contaminated backfill material still remains near the foundation of Building 45.
The most recent sampling at SWMU B-33 was biased toward sources for potential soil contamination related to leachate migration into soils adjacent to the trench. Each of six soil samples collected from three soil borings was analyzed for metals and explosives. No explosives were detected at concentrations exceeding applicable RRS1 criteria.
Analytical results indicated concentrations in exceedance of RRS1 criteria for Glen Rose Limestone but not for soils. Barium, chromium, nickel, zinc, cadmium and lead in one subsurface sample each exceeded background levels and nickel exceeded the background level in another subsurface sample.
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 SWMU B-33, 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-33 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-33 investigation were reviewed to confirm conformance with the AFCEE
QAPP; the data verification report is included in
Appendix D. All data flagged
with “F”, “M”, and “J” 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. However, all “R” flagged data
are considered unusable. Non-compliance
of the relative percent difference (RPD) of the field duplicate collected on
the same day resulted in “R” flagged data for cadmium results reported for SWMU
B-33. However, cadmium results for only
two of the seven samples collected at the site were rejected.
The small amount of remaining contaminated backfill should be removed and disposed of according to the Waste Analysis Plan (Volume 1-5, RL33 Addendum). Confirmation sampling should be performed following the excavation to verify that all contamination has been removed. Confirmation samples should be analyzed for lead using EPA method SW-7421.
Although analytical data collected from SWMU B-33 indicate concentrations of metals that exceed RRS1 standards (background values) for the Glen Rose Limestone, in all cases the reported concentrations of barium, chromium, nickel, zinc, cadmium, and lead are below the background levels of the soil at the site. The nickel concentration reported at 10.1 mg/kg in sample RW-B33-SB03 (12-12.5 ft.) only exceeds the Texas-specific median background concentration by 0.1 mg/kg and is still well below the soil background level of 35.5 mg/kg. If similar results are obtained for the confirmation sampling after removal of the remaining material, CSSA should pursue closure of this site under RRS1.