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Atlantic Richfield Company Page 10 ARCO Station No 4932 Stockton,California August 29 2002 sand to sand with small lenses of clayey sand were encountered from 44 feet bgs to total depth of the borings (84 feet bgs) • Soils encountered during the drilling of MW-10 and MW-11 consisted of sand and silt mixtures from ground surface to the total depth of the boring, clay is present in two layers from 1 to 3 feet bgs and from approximately 35 feet bgs to total depth of borings (41 feet bgs) • Groundwater was first encountered between approximately 24 and 30 feet bgs • TPHg, TPHd, and BTEX were not detected in anytsamples collected from MW- 10, MW-11, DMW-2,DMW-3, and EW-2 With the exception of MtBE, no other fuel oxygenates were detected in any soil samples collected • MtBE by EPA Method 8260 was detected in one soil sample from DMW-2 (DMW-2,40') at a concentration of 0 75 mg/kg MtBE was also detected in four soil samples collected from DMW-3 at concentrations ranging from 0 44 mg/kg (DMW-3, 55')to 13 mg/kg (DMW-3, 50') MtBE was detected in two samples from EW-2 at concentrations of 2 3 mg/kg (EW-2,40') to 9 3 mg/kg (EW-2, 35') MtBE was not detected above 30 feet bgs in any of the soil samples and was also • not detected in samples from MW-10 and MW-11 • Groundwater analytical results show TPHg, benzene and MtBE present in the newly installed wells at maximum concentrations of 90 ug(L, 10 ug/L, and 65,000 ug(L, respectively 3.1.7 Conclusions The analytical results show that the horizontal and vertical extent of the hydrocarbon plume is delineated in the soil The groundwater results show TPHg and benzene have been delineated cross and downgradient, and that MtBE has been delineated downgradient Minor detections of MtBE in cross gradient well MW-5 were reported I 1ARCO\49321PAR\PAR doc