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i 5.0 SUMMARY • Petroleum hydrocarbons appear to have been initially released to the subsurface from beneath the former product dispensers and product piping The fuel delivery and storage system at the site was replaced and upgraded in 1990 (USTs) and 2002 (dispensers and product piping) • An unknown quantity of petroleum hydrocarbon impacted soil was excavated and removed from the site between October 1990 and February 1991 Approximately 315 tons of petroleum hydrocarbon impacted soil was excavated and removed from beneath the former product dispensers and piping trenches in January 2002 • Fine grained soils have predominately been encountered beneath the site to approximately 202 feet bgs, the maximum depth explored beneath the site The regional water table does not appear to have been encountered during subsurface investigations at the site Increased soil hardness was generally observed in the fine grained strata encountered below approximately 140 feet bgs, these soils are expected to have relatively low permeability • Two laterally continuous sand intervals, approximately 2 to 6 5 feet in thickness (sand zone 1) and 12 to 23 feet in thickness (sand zone 2) have consistently been encountered Sand zone 1 and sand zone 2 have been observed from approximately 48 to 64 feet bgs, and from 68 to 104 feet bgs, respectively Approximately 5 to 18 feet of fine grained soils (predominately silt) appear to separate sand zone 1 and sand zone 2 Sand zone 1 was not observed at the boring B-47 and B-48 locations • At boring locations B-47 and B-48, sandy strata were identified between approximately 110 and 125 feet bgs (B-47) and 118 to 134 feet bgs (B-48) Based on the soil types observed at borings B-33 through B-38, these sandy soils do not appear to extend to the northwest, beneath the site • The strata beneath the site appear to dip to the southeast, approximately 50 from horizontal, at a strike of approximately N 17°E • Significantly variable groundwater elevations are measured in the shallow screened wells Groundwater encountered at these depths appears perched and localized • Depth to groundwater has been measured between approximately 89 and 107 feet bgs in the wells screened in sand zone 2 south of Patterson Pass Road An east-southeast groundwater flow direction has consistently been reported for the well network screened across sand zone 2 Groundwater flow in sand zone 2 appears to be generally perpendicular to the strike of the subsurface stratum, suggesting that groundwater movement in sand zone 2 appears to be significantly influenced by the dip of the subsurface stratum beneath the site K\BP Arco for URS\b IOMReporls55 IOU assessment rpt&scm update doe Page 13 5TRA WO