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advanced boreholes in the well indurated bedrock. Blow counts for both slant-drilled boreholes were especially high due to the friction of the split-barrel sampler along the inclined hollow-stem augers. For example, Borehole U850-DlU1-13 was terminated at a depth of 33 ft with a blow count of 100 blows for 3 in. driven; similar blow counts in the other three mechanically advanced boreholes limited the total usage of the hand-held drive sampler. Two soil samples were collected from the excavated soil pile using the hand-held drive sampler. Laboratory Analytical Methodology The 45 soil and bedrock samples collected during the five sampling events were analyzed by Clayton Environmental Consultants for total extractable petroleum hydrocarbons as diesel (TEPH-diesel) using EPA Extraction Method 3550 combined with EPA Analytical Method 8015. Twenty-two of the samples were also analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) using EPA Analytical Method 8020, which integrates EPA Extraction Method 3550. Signed laboratory reports and chain-of-custody records are presented in Appendices E and F,respectively. Laboratory is es is Analytical results for the 45 soil and k 1 y bedrock samples are summarized in Table 2. No samples exceeded the benzene detection limit of 0.005 mg/kg (ppm). Only three boreholes, U850-D1U1-7, U850-D1U1-8, and U850-D1U1-9, yielded soil samples with detectable concentrations of toluene, ethylbenzene, or xylenes. The maximum reported concentrations of toluene, ethylbenzene, and xylenes are 0.008, 0.009, and 0.010 ppm, respectively. As shown in Figure 8, these concentrations are restricted to the soil profile at the eastern end of the tank excavation. None of the bedrock samples exceeded any BTEX detection limits. As shown in the plan view of Figure 8 and in the cross-sections on Figures 5 and 6, the soil and bedrock volume with detectable concentrations of TEPH-diesel is restricted to the eastern area of the tank excavation. The maximum TEPH-diesel concentration reported for soil is 9,000 mg/kg (ppm) and was collected from borehole U850-DlUl-10 at an elevation of 1,318 ft (7 ft below the tank excavation). The maximum TEPH-diesel concentration reported for bedrock is 29 mg/kg (ppm) and was collected from borehole U850-DlUl-13 at an elevation of 1,303 ft (21 ft below the tank excavation). The five bedrock samples collected from borehole U850- D1U1-14 at elevations ranging from 1,309 to 1,289 ft were all below the TEPH-diesel detection limit of 2 mg/kg(ppm). From the cross-sections on Figures 5 and 6 and the plan view on Figure 9, the average diameter of the soil and bedrock-containing volume that contains detectable concentrations of TEPH-diesel is measured to be approximately 12.3 ft. The volume is spherical in shape with the sphere being centered at 1,317 ft. Using 6.2 ft as a radius and a spherical volume formula, the estimated volume of soil with detectable concentrations of TEPH-diesel is calculated to be approximately 37 yd3. The estimated volume of soil with concentrations of TEPH-diesel greater than 100 ppm is approximately 19 yd3 and is based on an assumed radius of 5.0 ft. All the soil 12