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Mr Ed Ralston April 16, 2001 • Page 4 depths of approximately 45 to 50 feet bgs, a thick, laterally continuous silty sand was present to the total depth explored of 80 feet bgs Beneath the southeastern site comer, the silty sand becomes interbedded with silts and clays and with thin sand lenses A more complete description of the subsurface lithology is shown on the boring logs presented in Attachment B Soil Analytical Results Soil samples collected from MW-5 at 60 and 70 feet bgs contained TPH-g at concentrations of 907 and 1 79 ppm,respectively Low concentrations of total xylenes were present in all samples analyzed from MW-5, concentrations decreased in the 70 and 80 feet bgs samples from the 60 feet bgs concentration of 32 ppm MtBE was detected as a false positive by EPA Method 8020 at 60 feet bgs and was not detected by EPA Method 8260 Soil samples collected from MW-6, located beneath the former dispenser overexcavation area, contained TPH-g and benzene in the 60 feet bgs sample at 4,780 and 55 3 ppm, respectively Petroleum hydrocarbon concentrations decreased with depth and the 80 feet bgs. sample from MW-6 contained TPH-g and benzene at concentrations of 3 3 and 0 0492 ppm, respectively Low concentrations of toluene, ethylbenzene, and total xylenes were present in samples from MW-6 and concentrations decreased with depth MtBE was not detected by EPA Method 8020 in the 70 and 80 feet bgs samples and was a false positive in the 60 feet bgs sample Analysis of the 60 feet bgs sample by EPA Method 8260 did not detect MtBE TPH-g,benzene, and MtBE were all non-detect at the laboratory reporting limits in samples collected from MW-7, located near the southeast corner of the site Low concentrations of total xylenes were present in soil samples collected at 50, 65, and 80 feet bgs Soil analytical data is summarized in Table 1 and laboratory reports with chain of custody(COC) documentation is included in Attachment C Soil analytical data from this and previous assessments show that the vertical extent of impacts are generally defined Highest concentrations are located beneath the former dispenser Iocations The petroleum hydrocarbon concentrations in the vicinity of MW-6 show attenuation with depth between 60 and 80 feet bgs (Figure 2) Groundwater Analytical Results Deep groundwater monitoring wells MW-5 through MW-7 were sampled on January 22, 2001 TPH-g was detected in samples collected from wells MW-5 through MW-7 at concentrations of 840 parts per billion(ppb), 2,300 ppb, and 88 ppb,respectively Benzene was reported in wells MW-5 through MW-7 at concentrations of 6 1 ppb, 22 ppb, and 1 8 ppb,respectively MtBE was confirmed by EPA Method 8260 in MW-6 and MW-7 at concentrations of 2 2 ppb and 16 ppb, respectively Groundwater analytical data is summarized in Table 2 and laboratory reports with COC documentation are included in Attachment C N lrancfp 11Projects1Pr41eets1911101111 A101021911011 rpt2 doe