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SWMU Building 43 RCRA Facility Investigation Report
Section 3 - Conclusions and Recommendations
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.
In 1995, a soil gas survey was conducted in the large area between SWMUs B-3 and B-4 in an effort to identify possible sources of solvent contamination detected in nearby Well CS-16. A small number of these points were located in the vicinity of SWMU Building 43; PCE was detected at low levels (up to 0.43 μg/L) in this area. In August 1996, a soil gas survey focused on the SWMU Building 43 area was conducted. Again, PCE was detected in each of the samples, at concentrations ranging from 0.04 μg/l to 1.0 μg/L. TCE was detected at one point, at a concentration of 0.04 μg/L.
In 1996, a geophysical survey was conducted at the site. No geophysical anomalies, aside from the anomaly caused by the building itself, were detected at the site. In August 1997, the site was swept for UXO. No UXO was found and none is thought to exist in the vicinity of SWMU Building 43.
The presence of metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel and zinc) in the topmost foot of soil throughout the site was identified at concentrations exceeding the applicable RRS1 standards. The lateral extent of the metals contamination in surface soil was not identified during this investigation. Subsurface soil samples indicate that metals contamination is limited to surface soils and as such, the vertical extent of contamination has been identified.
In addition, laboratory analyses of soil samples found no SVOC or explosives contamination, and swipe samples from charred areas inside Building 43 found no Dioxin or Furans above approved RLs.
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 SWMU Building 43, along with an evaluation of whether each DQO has been attained, is provided in Appendix D. As described in Section 1, the main objectives of the SWMU Building 43 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 BLDG-43 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification reports are included in Appendix C. All data are considered usable for site characterization purposes. Although several results are flagged with an “M,” these results are considered usable because the matrix interference is minimal and does not significantly affect the sample results. Several results are flagged with a “J,” but these results are considered usable because the estimation of the quantitation does not significantly affect the sample results. Additional information concerning conformance with the AFCEE QAPP is set out in the data verification reports in Appendix C.
Because waste and waste residue remains on the ground surface at the site, it does not meet TNRCC requirements for RRS1 closure. In addition, since the lateral extent of contamination has not been determined, the Order requirements have not been met.
Because waste and waste residue at concentrations above RRS1 levels remain at SWMU Building 43, further action is recommended. Further surface soil sampling is recommended to better define the lateral extent of the metals contamination prior to any removal action. Surface material excavation and removal activities would then be 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. Confirmation sampling is recommended to document that materials impacted by metals at concentrations exceeding RRS1 standards have been removed and document the lateral extent of contamination. Confirmation sampling should include analysis for arsenic (SW-7060A); cadmium (SW-7131A); barium, chromium, copper, nickel and zinc (SW-6010B); mercury (SW-7471A); and lead (SW-7421).
Although low levels of methylene chloride, dichlorodifluoromethane, ethylbenzene, and toluene were detected in several samples, further investigation to address these chemicals is not considered warranted. Methylene chloride is a common laboratory contaminant. Dichlorodifluoromethane was only detected in one sample, and the concentration was very low. Neither methylene chloride nor dichlorodifluoromethane are considered contaminants of concern at the site. Although ethylbenzene and toluene are possibly related to fuel use at the site, the concentrations detected were very low and were limited to only one sample. No further actions are recommended to address VOCs.
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 exceeded background levels to a depth of one foot will results in an estimated 200 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 250 cubic yards of material, which means up to two samples for SWMU Building 43 waste characterization.