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rt . . Laboratory Analysis Soil samples from borings SBI through S116 were analyzed by NEI/GTEL Environmental Laboratories, Inc. for total petroleum hydrocarbons as gasoline and diesel (TPHg and TPHd) by EPA Methods 8015; benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Method 8020; methyl tertiary butyl ether(MTBE) by EPA Method 8020; and total lead by EPA Method 3050A. RESULTS OF INVESTIGATION Site Geoloey Native sediments encountered in soil borings SBI though SB6 during field activities indicate that the upper 16 to 30 feet of the soil column consists primarily of silt (ML). Apparent fill (silty sand, SM) was observed in the upper 10 to 15 feet of soil borings SB 1 and SB4. Groundwater was not encountered during drilling activities. Based on communications with PHS/EHD personnel and San Joaquin County, Flood Control and Water Conservation District data (Spring 1995 Report) groundwater is estimated to be present at approximately 55 feet bgs. Analytical Results Results of laboratory analyses performed on selected soil samples from the borings indicate that total lead, detected in all the soil samples analyzed, is present beneath the site at concentrations ranging from less than 7 to 14 milligrams per kilogram (mg/kg). The analytical results were compared with the typical U.S. Mean and typical Bay Area concentrations in soil as presented in Summary of Typical Metals Concentrations in Soils and Surfrcial Materials, from US G.S. Professional Paper 1270 for the Conterminous United States(Attachment 2). In comparison, the lead detected appears to be present at background concentrations. Petroleum hydrocarbon constituents were detected in soil samples collected from borings SBI and SB4. The highest reported constituent concentrations-were observed in the soil samples collected at 15 feet bgs. The highest concentrations of petroleum constituents at this depth were detected in sample ET-SB4-15.0 and include toluene (91 mg/kg), ethylbenzene (190 mg/kg), xylenes (800 mg/kg), TPHg (9,100 mg/kg), and TPHd (1,700 mg/kg). The petroleum hydrocarbons appear to attenuate rapidly with depth as indicated greatest by soil sample ET-SB4- 20, collected from S134 at 20 feet bgs, which contained only trace levels of toluene (0. 071 mg/kg), ethylbenzene, xylenes (0.021 mg/kg), and TPHg (0.13). MTBE was not detected in any of the soil samples analyzed and benzene was detected only in sample ET-SBI-15 at a concentration of 0.90 mg/kg. No petroleum hydrocarbons were detected above laboratory method detection limits in soil samples collected from perimeter soil borings SB2, SB3, SB5 and SB6. Laboratory analytical results are consistent with field observations and PID readings. Analytical results are summarized in Table 1. Laboratory data sheets and chain-of-custody documentation are presented in Attachment 3. w:D7736lreporls\sum.doc 3 m