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KLEINf ELDER s • 3 FIELD INVESTIGATION From the previous investigations conducted at the site, Nor-Cal retained Kleinfelder to resample MW-1 and drill two soil borings to assess the vertical extent of petroleum hydrocarbon contamination in the backfilled excavation. The two soil borings were drilled through the two previous excavation sample areas with elevated total petroleum concentrations. 3.1 DRILLING AND SOIL SAMPLING y On January 27, 1992, two soil borings were drilled south of the warehouse in the vicinity of the former tank excavation as shown on Plate 4. The borings were advanced with a truck- mounted drill rig equipped with 6-inch hollow stem augers. During drilling, an experienced environmental geologist logged the boreholes, classified the soil per the Unified Soil Classification System (USCS), and collected soil samples for field screening and chemical analysis. Copies of the USCS legend and boring logs are included in Appendix B. • Additional information on Kleinfelder Field Protocol is included in Appendix C. Soil boring B-1 was drilled along the western property boundary and the western boundary of the removed 10,000 gallon tank excavation. This is the area where TPH-Gasoline was detected at 27,000 mg/kg and TPH-Diesel was detected at 9,100 mg/kg. Boring B-1 was drilled at a 20° angle from vertical for a distance of 40 feet, equivalent to 38 feet vertical depth. In general, the soil encountered was clayey silt with interbedded silty sand. Soil samples were collected at 5-foot intervals beginning at a depth of 10 auger feet to the terminus of the boring. No free water was encountered in the boring. Soil boring B-2 was drilled beneath the center of the removed 500 gallon leaded gasoline tank. This is the area where TPH-Gasoline was detected at 23,000 mg/kg and TPH-Diesel was detected at 2,000 mg/kg. Boring B-2 was drilled vertically to a depth of 40 feet. In general, the soil encountered was gravelly sand fill material within the upper 22 feet and native clayey silt with interbedded silty sand to the terminus of the boring. Soil samples were collected at 5-foot intervals beginning at 25 feet to the terminus of the boring. No free water was encountered in the boring. F111-92-15 Page 7 of 21 Copyright 1992 Mcinfelder, Inc.