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. A S S O C I A T E S I N C RESULTS OF ENVESTI<GATI€ON Site Geolg= Native sediments encountered in soil bonngs SB I and SB2 during field activities indicate that the upper 6 5 to 11 5 feet of the soil column consists primarily of sand that was used as backfill material Soils from between approximately 6 5 and 11 5 feet bgs to 86 5 feet bgs consist of interbedded sand, silt, gravel and clay Well graded gravel with silt (GW-GM) was observed in SB 1 at approximately 20 to 21 5 feet bgs Lean clay (CL) was observed in both borings at approximately 35 to 36 5 feet bgs and 70 to 71 5 feet bsg Soils encountered from between 66 5 to 70 feet bgs and 86 5 feet bgs, the maximum depth explored, consisted of silts Groundwater was encountered at approximately 81 feet bgs during drilling activities Analytical Results Petroleum hydrocarbon constituents were detected in soil samples collected from borings SBI and SB2 The highest reported constituent concentrations were observed in soil samples collected at 25 5 feet bgs in each of the bonngs The highest concentrations of petroleum constituents at • this depth were observed in SBI and include TPHg (9,500 mg/kg), toluene (65 mg/kg), ethyl benzene (82 mg/kg), and xylenes (470 mg/kg) The petroleum hydrocarbons appear to attenuate rapidly with depth as indicated greatest by soil samples from SB 1 at 45 5 feet bgs and SB2 at 55 5 feet bgs which contained only trace amounts of petroleum hydrocarbons or none above the laboratory detection limits Total lead was detected at 5 5 mg/kg from the soil sample collected form SBI at 25 5 feet bgs Neither benzene, fuel oxygenate additives, or VOCs were detected above laboratory method detection limits in any of the soil samples analyzed Analytical results are summarized in Table 1 and laboratory data sheets are contained in Attachment 2 Petroleum hydrocarbon constituents, including TPHg and BTEX, were detected in groundwater samples collected from borings SBI and SB2 Only benzene, which was reported at concentrations of 7 6 ugtl and 12 ug/l, respectively, exceeded California's Maximum Contaminant Level (MCL) for drinking water The MCL for benzene is 1 ugA Total dissolved lead was detected at 1 1 ug/l and 1 6 ug/l in samples collected from bonngs SBI and SB2, respectively Fuel oxygenate additives were not detected above laboratory method detection limits in either of the two water samples analyzed Analytical results are summarized in Table 2 and laboratory data sheets are contained in Attachment 2 SUMMARY Soil and groundwater appear to be impacted by petroleum hydrocarbons The highest concentrations of petroleum hydrocarbons in soil are present at a depth of approximately 25 5 feet . bgs and appear to attenuate rapidly with depth Low concentrations of petroleum hydrocarbons were detected in groundwater W u4885Vvports\suFn ac 4