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Site History and Previous Investigations Former Chevron Service Station No. 94054 borings were advanced in the former pump island area (SECOR International Incorporated, 2004b). The greatest concentrations of petroleum hydrocarbon constituents detected in the soil samples collected during the associated direct push advancements were in the soil samples collected from DPS-5 at 20 feet bgs, DPS-5 at 25 feet bgs, DPS-10 at 12.5 feet bgs and DPS-12 at 20 feet bgs. TPH-GRO was detected at a concentration of 8,500 mg/kg in the soil sample collected from DPS-12 at 20 feet bgs. BTEX was detected at concentrations of 26, 160, 130 and 930 mg/kg, respectively, in the soil sample collected from DPS-5 at 20 feet bgs. MTBE was detected at a concentration of 0.0007 mg/kg in the soil sample collected from DPS-5 at 25 feet bgs. Methanol was detected at a concentration of 0.27 mg/kg in the soil sample collected from DPS-10 at 12.5 feet bgs. The greatest concentrations of petroleum hydrocarbon constituents detected in the groundwater samples collected during the associated direct push advancements were in the groundwater samples collected from DPW-1 at 37 feet bgs, DPW-8 at 50 feet bgs, DPW-9 at 22.5 feet bgs and DPW-10 at 13 feet bgs. TPH-GRO, toluene, ethylbenzene, total xylenes and MTBE were detected at concentrations of 87,000, 1,900, 2,400, 15,000 and 23 pg/L, respectively, in the groundwater sample collected from DPW-9 at 22.5 feet bgs. Benzene was detected at a concentration of 11,000 pg/L in the groundwater sample collected from DPW-1 at 37 feet bgs. TBA was detected at a concentration of 87 pg/L in the groundwater sample collected from DPW-8 at 50 feet bgs. Methanol was detected at a concentration of 210 pg/L in the groundwater sample collected from DPW-10 at 13 feet bgs. In March 2004, SECOR supervised the installation of two extraction wells (EW-1 and EW-2) and five temporary piezometers (PZ-1, PZ-2, PZ-3, PZ-4 and PZ-5). Extraction well EW-1 was installed slightly south of the former gasoline UST pit and EW-2 was installed slightly north of the former gasoline UST pit. PZ-1 was installed near the former pump island area. Piezometer PZ-2 was installed north of the former gasoline UST pit, PZ-3 was installed slightly further north of the former gasoline UST pit and PZ-4 was installed even further north of the former gasoline UST pit, approximately 35 feet north of the former gasoline UST pit (SECOR International Incorporated, 2004b). Step drawdown and constant discharge pumping tests were performed separately in extraction wells EW-1 and EW-2 for the purpose of assessing the hydraulic properties of transmissivity, storativity and hydraulic conductivity at the site. Prior to the tests, pressure transducers with built in data loggers capable of record groundwater levels at one minute intervals were installed in the extraction wells, the piezometers and monitoring wells MW-3 and MW-8. For the tests performed in EW-1 the transmissivity geometric mean was 2,650 gallons per day per foot (gpd/ft), the storativity geometric mean was 0.009 and the hydraulic conductivity geometric mean was 0.015 centimeters per second (cm/sec). For the tests performed in EW-2 the transmissivity geometric was 4,000 gpd/ft, the storativity geometric mean was 0.0000018 (1.8 10-6 ) and the hydraulic conductivity geometric mean was 0.030 cm/sec (SECOR International Incorporated, 2004b). Subsequently, a capture zone analysis was performed for EW-1 and EW-2. Capture zone parameters of 38 and 60 feet were calculated in the down gradient and cross gradient directions, respectively, for EW-1 and capture zone parameters of 31 and 48 feet were calculated in the down gradient and cross gradient directions, respectively, for EW-2 (SECOR International Incorporated, 2004b). In April 2004, SECOR supervised the destruction of temporary piezometers PZ-1 through P7-5. The temporary piezometers were destroyed according to San Joaquin County Environmental Health Department (SJCEHD) and California Well Standards (SECOR International Incorporated, 2004b). Stantec 7