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Report of Findings Frontier Transportation 0702-177 September 5, 2002 Page 4 identified at a maximum of 4,700 pg/kg in soil sample Bot NES at 12' bg. The remaining four samples collected at 12' bg contained MTBE from 4,600 pglkg to 340 pg/kg (See Table 2). Soil sample results identified the highest concentrations below the encountered groundwater. A total of three soil samples were collected below groundwater at 14' bg. Soil sample Bot WNS collected from the northwest sidewall identified the maximum concentrations of TPH-d at 3,000 mg/kg, TPH-g at 2,500 mg/kg, BTEX as 1,207,000 pg/kg, and MTBE as 26,000 pg/kg. The minimum concentrations contained at 14' bg were 340 mg/kg as TPH-d, 120 1 mg/kg as TPH-g, 18,300 pg/kg as BTEX, and 3,600 pg/kg as MTBE (See Table 2). In addition, a total of seven samples were collected from the stockpiled soil as it was ' excavated to minimize volatilization. These stockpiled soil samples were also analyzed for TPH-d, TPH-g, BTEX, and MTBE with EPA methods 8015 modified and 8260B by an on-site mobile laboratory (See Table 3 for Stockpiled Soil Sample Results and Appendix B for ' Laboratory Analytical Reports). At pit termination depth, the excavator took one scoop from 16' bg and stockpiled it. The highest petroleum hydrocarbon concentrations from stockpiled soil were identified from soils excavated below groundwater with the exception of TPH-d. ' Concentrations of TPH-g were identified as 170 mg/kg from stockpiled soil excavated from 8' bg and a maximum of 420 mg/kg stockpiled soil excavated from 16' bg. No other detectable concentrations of TPH-g were identified. The maximum concentrations of BTEX and MTBE in the stockpiled soil were 28,570 pg/kg and 25,000 pg/kg, respectively, from 16' bg. Approximately 325 tons of soil was excavated and stockpiled on visqueen at the site. The stockpiled soil was transported to Altamont Landfill facility in Livermore, California for disposal. A copy of the trucking tickets will be submitted once they are received by BEII. Clean backfill was used to fill the excavation pit. The backfill material was approved by the PHS/EHD ' prior to importing. The material was compacted to 90% in I-foot lifts (See Appendix C for density testing results). On May 30 and 31, 2002, BEII supervised the installation of one replacement groundwater monitoring well (MW-3R)and two deeper groundwater monitoring wells (MW-12 and MW-13) to help define the extent of dissolved petroleum hydrocarbons beneath the site (See Figure 2 for well locations). Monitoring well MW-3R was advanced to 20' bg while MW-12 and MW-13 were advanced to 40' bg(See Appendix A for well construction). An 8-inch outside and 4.25-inch inside diameter hollow stem auger was used to install the monitoring wells. All three groundwater monitoring wells were constructed of schedule 40 PVC casing: — -The screen slots were sized at 0.01-inch with a size #2116 annular pack. The annular seal consisted of bentonite pellets and then grouted to surface. Soil samples were collected at 5-foot ' intervals from a split spoon sampler that contains three brass liners, which are 2 inches in 1