SITE INFORMATION AND CORRESPONDENCE_1992

Home Browse Search

Draft Soils FS Report Memorandum -7- 17 April 1992 DDRW, Sharpe soil samples. All of the soil samples from these types of disposal areas or units should have been analyzed for these types of contaminants due to the types of wastes disposed in this area. Additional information is needed to correlate the source with the soils and ground water contamination and additional investigation is needed to define the extent of ground water and soil contamination. n. Chromium. The Draft FS Report indicates that widespread chromium soil contamination may exist in the North Balloon Area associated with the open dumping from Buildings 170 to 184 (S#26) . The UST investigation revealed that chromium was found in the ground water in the North Balloon Area (MW-472A, MW- 473A and MW-474A) . It is unknown whether the reported concentrations are of total or hexavalent chromium. The concentration of chromium in MW-472A (160 micrograms per liter (µg/1 )) exceeds the Primary Maximum Contaminant Level (MCL) of 50 µg/l . Based on the information submitted in the Draft Soils FS Report, it appears that a chromium plume exists in the North Balloon Area. 0. Polychlorinated Biphenyls. The investigation of USTs revealed that ground water has been contaminated by PCBs. This contamination is in the North Balloon Area in the area of Building 180. This ground water contamination was detected in three newly installed monitor wells, MW-472A, MW-473A and MW-474A. The highest concentration of PCBs was detected in MW-472A at 90.0 g/1 which exceeds the Primary MCL of 0.5 µg/1 . Wastes from Building 180 are attributed to contamination detected in S#26 and may be caused when waste oils were drained onto the ground (S#27) . Additional information is needed to correlate the source with the soils and ground water contamination and additional investigation is needed to define the extent of soils and ground water contamination. p. S#28, South Balloon Area. Sludges from metals stripping operations were disposed of in the South Balloon Area by discharging the wastes onto the ground. The wastes were then disced into the ground. Shallow borings were installed and composite samples from the upper two feet were collected for analysis. The Draft FS Report indicates that none of the soils samples exceed the Toxicity Characteristic Leaching Potential (TCLP) . Based on this information it can be assumed that the concentrations of metals and other contaminants may be higher because the samples were composited. It is unclear why the TCLP was performed when the Waste Extraction Test (WET) is generally a more stringent test for metals. It is unknown if any of the elevated metals concentrations would have exceeded the Soluble Threshold Limit Concentration (STLC) if the WET had been performed. In addition, it can be assumed that elevated concentrations of metals above background concentrations, based on the TCLP data, may pose a threat to water quality. Additional investigation is needed, particularly to define the vertical extent of contamination and its potential impact on ground water. q. Fuel Related Contamination. One of the conclusions of the Draft Soils FS Report is that remediation of the soils contaminated with fuels will conform with the guidelines set forth in the Tri-Regional Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites (Tri- Regional Guidelines) . However, in the UST Report, it was recommended that no further investigation was required for many of the USTs, despite the fact that