SITE INFORMATION AND CORRESPONDENCE_1992

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Work Plan Addendum -5- 21 September 1992 DDRW, Sharpe developing these cleanup levels and the presentation of the results and findings of the soil and ground water investigations. SPECIFIC CONCERNS 1 . In June 1992, the State Water Resources Control Board adopted Resolution No. 92-49; Policies and Procedures for Investigation and Cleanup and Abatement of Discharges Under Water Code Section 13304. This applicable or relevant and appropriate requirement (ARAR) must be considered during this RI work. This ARAR is considered applicable for any ground water contamination associated with either a WMU or UST source. A copy of Resolution No. 92-49 is attached. 2. The Work Plan Addendum states that the fuel USTs will be addressed separately through a contract administered by the Corps of Engineers, Huntsville Division. The Regional Board plans to issue a Cleanup and Abatement Order (CAO) to address the investigation and cleanup of the fuel USTs because petroleum based contaminants are excluded from Superfund regulation. Sharpe needs to submit a time schedule for the USTs so that it may be incorporated into the CAO. 3. Test pits are proposed to be excavated in eight former non-fuel UST sites to the former excavation floor (page 2-3) . The excavated soil which would represent the backfill from the tank removal will be field screened for contamination. The excavated backfill which exceeds the above listed cleanup levels, of which we do not concur, is to be separated out for disposal . Excavated backfill with concentrations below these field screen concentrations will be returned to the excavation. Soil samples will be collected for laboratory analyses from a maximum depth of two feet below the base of the excavation (page 2-15) . My concerns with this investigation method are as follows: a. The method may fail to investigate all of the unsaturated zone beneath the former tank. Depending on the depth to ground water, the depth of the former tank and the extent of potential leakage from the UST, it is possible that soil contamination may go unassessed and the tank site backfilled. Should this occur, there would be insufficient data to demonstrate that the potential source area will not threaten the environment (water quality) . Sharpe should collect samples from below the backfill throughout the unsaturated zone, particularly for those former UST sites where field screening indicates high concentrations of contamination, until non-detect is established. b. It appears that the excavated soil will not be sampled for laboratory analyses as confirmation to the field screening. Laboratory sampling should be performed on the excavated field screened samples to assure that if the material is returned to the excavation, that it does not pose a threat to the environment (water quality) . c. The Work Plan Addendum does not propose sampling of the side walls of the excavation. Sampling of the side walls is recommended, particularly for the non-fuel former USTs sites that field screening demonstrates to have particularly high contaminant concentrations.