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01-04-94 12:28PM FROM DTSUREG10N I TO 912094640138 P002/007 <br /> Mr. Derrick Ada* <br /> December 17 , 1993 <br /> Page 2 <br /> A. SITE CHARACTERIZATION RHQORT <br /> General Comment 1: Chlorinated Hydrocarbons North of Concrete <br /> Tank <br /> Sampling and analysis results documents the presence of <br /> chlorinated hydrocarbon contaminated soil north of the concrete <br /> fuel tank, extending to a depth of at least 40 feet in borehole <br /> T-6. The latera]. and vertical extend of chlorinated hydrocarbon <br /> contamination is not completely known. Therefore the site <br /> characterization is incomplete. <br /> The relationship of the solvent contaminated soil north of <br /> the tank to solvent contaminated soil in area D is not known. <br /> WZI on page 24 of the Report estimates that solvents are not <br /> present south of boring D-3 (north of the solvent contaminated <br /> area) or at a greater depth based on concentration distribution <br /> patterns. This may or may not be the case. <br /> The presence of chlorinated hydrocarbons in ground water <br /> beneath solvent contaminated soil is not known. Depth to ground <br /> water is reported to be 55 feet while information on soil <br /> contamination has been limited to total depth of the boreholes <br /> (maximum of 40 feet below qround surface (BGS) and only 25 feet <br /> BGS in the area of maximum contamination (T-1) ) . <br /> WZI recommends (page 4 and page 26 of the Report) preparing <br /> a Health Risk Assessment for the hydrocarbon contaminated soils <br /> beneath the tank and preparing a Remedial Action Plan for the <br /> tank area. However, WZI does not discuss or recovaend the need <br /> for further characterizing the chlorinated hydrocarbon <br /> distribution in the soil and confirming potential ground water <br /> contamination. <br /> GSU does not support the "estimated limit of solvent <br /> contaminated soil" presented in exhibits (10, 11, 12, & 13) and <br /> discussed on page 20 of the Report since site characterization <br /> is incomplete. The lateral and vertical extent of solvent <br /> contamination is still unknown at this juncture. <br /> Recommendation: <br /> Additional site characterization is needed to determine the <br /> vertical and lateral extent of chlorinated hydrocarbons in <br /> subsurface soils north of the tank area. GSU recommends a <br /> minimum of five additional boreholes to characterize the <br /> distribution of chlorinated hydrocarbons in soils at the LCN <br /> site'. Boreholes should be located East and West of the apparent <br /> contaminant distribution, and two boreholes North of the present <br /> extent of contamination. Also, a borehole should be located <br /> between area D and the tank area to evaluate the relation <br /> between solvent contaminated areas. soil samples should be <br />