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Well Installation and Site Investi ation Re ort <br /> ARCO Facility No.5469 <br /> Stockton,California <br /> Page 6 <br /> Method 8260B. Soil analytical results are presented in Table 1 and groundwater analytical <br /> results are presented in Table 2. Certified Analytical Reports with chain-of-custody records <br /> are presented in Appendix D. <br /> FINDINGS <br /> Site Geology <br /> Silt, with clayey silt, sandy silt, and thin, discontinuous lenses of silty sand were the <br /> predominate soil types encountered between surface grade and 120 feet bgs based on data <br /> collected from the CPT boring and other borings previously drilled. Fine to coarse-grained <br /> sand was encountered from approximately 40 to 55 feet bgs at boring MW-10, and between <br /> approximately 49 and 53 feet bgs at boring MW-4 (located near the northern ARCO <br /> property line). This sandy stratum may extend westward across South Wilson Way, but <br /> does not appear to extend to the south in the vicinity of the ARCO USTs and product <br /> dispensers. Sand strata were also logged at boring CPT-1 between approximately 68 and 73 <br /> feet bgs and 90 to 92 feet bgs; the lateral extent of these sand units is not currently known. <br /> Analytical Results <br /> Soil Analytical Results <br /> MTBE was reported for the soil samples collected from the CPT boring location at <br /> approximately 42 feet bgs (0.130 mg/Kg) and 52 feet bgs (0.0019 mg/Kg). Toluene <br /> (0.0055 mg/Kg) and xylenes (0.028 mg/Kg) were reported for the soil sample collected at <br /> 93 feet bgs. Petroleum hydrocarbon and fuel additive concentrations were reported below <br /> laboratory detection limits for the soil samples collected from 78 and 107 feet bgs. It <br /> should be noted that three soil samples collected on November 18, 2002, were incorrectly <br /> noted on the chain-of-custody as being collected on November 19, 2002. <br /> Groundwater Analytical Results <br /> DIPS (1.2 micrograms per liter [pg/L]) and 1,2-DCA (1.3 pg/L) were reported for the <br /> sample collected from approximately 62 feet bgs. Benzene (0.92 pg/L), toluene (1.3 µg/L), <br /> ethylbenzene (1.4 pg/L), and xylenes (4.4 pg/L) were reported for the sample collected <br /> from approximately 91 feet bgs. MTBE (1.7 gg/L) was reported for the sample collected <br /> from approximately 103 feet bgs. Petroleum hydrocarbons and fuel oxygenates were not <br /> detected in the sample collected from approximately 72 feet bgs. <br /> to <br /> P:\Bp-Arca for URS154691Reports15469report2003.doc <br />