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2004 1" Quarter Groundwater Report • Frontier Transportation May 20, 2004 Page 2 through MW-7) to assess the extent of subsurface contamination beneath the site (See Figure 2, Site Layout Map) Soil samples were collected every five feet Laboratory analysis of soil samples identified no detectable concentrations of TPH-g, BTEX, or MTBE Groundwater samples were subsequently collected and results are tabulated in Table 1 In January 2000, BEII advanced two bonngs (B-5 and B-6), installed four additional groundwater monitoring wells (MW-8 through MW-11), and collected nine soil vapor samples for a soil vapor survey as part of an additional site assessment(See Figure 2, Site Layout Map for well locations) Soil sample analysis identified no detectable concentrations of petroleum ' hydrocarbons with the exception of boring B-6 Maximum contaminant levels in B-6 were identified 100 mg/kg as TPH-g, 2,343 µg/kg as BTEX, and 10,600 µg/kg as MTBE at 10' bgs Maximum soil vapor concentrations were identified at sample point V5 at 4' bgs Groundwater ' samples were subsequently collected from all monitoring wells Results are tabulated in Table 1 In May 2002, BEII installed two additional groundwater monitoring wells (MW-12 and ' MW-13) screened from 30' bgs to 40' bgs Soil sample results identified maximum TPH-g, BTEX, and MTBE concentrations of 700 mg/kg, 115,000 µg/kg, and 25,000 µg/kg in soil collected from MW-13 at 10' bgs Soil concentrations attenuate by 99% at 15' bgs No ' • detectable TPH-g, BTEX, and MTBE were identified in MW-12 Also, monitoring well MW-3 was abandoned prior to excavation and removal of 325 tons of impacted soil and replaced by ' MW-3R In June 2003, BEII installed an additional groundwater monitoring well (MW-14) ' screened from 30' bgs to 40' bgs Soil sample results identified a maximum MTBE concentration of 1,020 gg/kg at 10' bgs using EPA Method 8260B No detectable TPH-g and BTEX were identified in MW-14> arta/ �,uL ai OF h�� I-1�- y �' 1-40j I,Y ' In January 2004, BEII installed four additional groundwater monitoring wells Deep monitoring wells MW-15, MW-16 and MW-18 were advanced to 40' bgs and screened from 30' ' bgs to 40' bgs Shallow monitoring well MW-17 was advanced to 20' bgs and screened from 5' bgs to 20' bgs Soil sample results identified a maximum MTBE concentration of 1,310 µg/kg at 10' bgs in MW-15 using EPA Method 8260B No other oxygenates or lead scavengers were ' detected The maximum TPH-gas detected was 1 7 mg/kg at 10' bgs in MW-15 using EPA Method 8015M No detectable BTEX was identified in the soil column for MW-15 through MW-18 See Figure 2 for well locations ' 3.0 SITE GEOLOGYM"ROGEOLOGY ' The site is located on the boundary of the Sacramento Valley and the San Joaquin Valley 1