SITE INFORMATION AND CORRESPONDENCE_1993-2003

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Draft Soils FS Memorandum -3- 14 September 1993 DDRW, Sharpe contained contaminated fuel (USTs 71, 10, 20, 36, and 37) are considered nonfuel USTs. Additional concerns that were not adequately addressed in the Draft Soils FS are included in the Board's review, dated 21 September 1992, of the July 1992 Work Plan Addendum (i.e., USTs 29 and 52). 1 concur with the recommendations presented in Section 8 of the Draft Soils FS for USTs 35 and 48. However, I question the recommendation to install an extraction well (NA-10) at UST 27 until ground water monitoring has been conducted to assess the elevated semi-volatile organic compounds (semi-VOCs), heavy metals and polychlorinated biphenyls (PCBs) previously detected in nearby MW-472A, which was destroyed during soil excavation at UST 27. It should be noted that PCBs have recently been reported to be present in a concrete sump containing liquids located north of Bldg. 179 at Bldg. 186 (see Major Comment 5). This sump is in the vicinity of UST 27. PCBs detected in ground water in MW-472A may have been related to the sump at Bldg. 186. Ground water monitoring at UST 27 will require that MW-472A be replaced. The current ground water air stripping treatment systems are not designed to treat the above mentioned contaminants. We are opposed to the concept that air stripping is the appropriate treatment technology for the remediation of PCBs and heavy metals in ground water. Treatment of PCBs and heavy metals were not considered in this Draft FS, but should have been evaluated as potential treatment alternatives. lb. Comments 3 through 8 refer to soil cleanup levels and the use of the Designated Level Methodology (DLM) to determine soil cleanup levels. New information (presented in Section 6 of the Draft Soils FS) has been provided on the lead and chromium contamination in the North Balloon Area (SWMU 26). The new information indicates that hazardous levels of lead and chromium are present in the North Balloon Area soils. In addition, these data indicate that ground water has been impacted with chromium and possibly lead. Filtered and unfiltered samples from MW-413A contained detectable concentrations of hexavalent chromium (32.6 µg/l Cr6+) downgradient of elevated chromium concentrations in soil (Figure 6-4, Draft Soils FS). The PAR reported that high levels of total chromium (160 ppb) were detected in ground water samples from MW-472A near UST 27. Comments 3 through 8 state that soluble concentrations may pose a threat to ground water quality and that the FS does not adequately address whether the contaminated soil, if left in place, will continue to leach and degrade ground water quality. The proposed cleanup levels for lead and chromium are currently based only on health based risk. A health based risk assessment is inadequate to determine whether the contaminated soil will leach and degrade ground water quality and therefore, should not be the only consideration in development of soil cleanup levels. Soil cleanup levels that are protective of ground water quality should be developed for the cleanup of the environment. The Response to Comment 3 states that it may be possible to use existing ground water and soils data supplemented by a limited amount of additional work to define and resolve these issues. New data has been generated by testing the leachability of chromium and lead using the California Waste Extraction Test (WET) (Table 5.1-1, Draft Soils FS). The Board has suggested several times that DLM be used to determine soil cleanup levels for metals,