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NOW Site Background Information Former Stefano's Gas Station Page 2 of 6 UST REMOVAL Two, 10,000-gallon capacity USTs and a dispenser island were formerly present at the subject site. The dispenser island and USTs were located in the central portion of the site. On 27 October 1992 the USTs, associated product piping and dispenser island were removed from the site by Falcon Energy Associated(FEA). Three soil samples were collected from beneath each of the USTs and analyzed for total petroleum hydrocarbons quantified as gasoline(TPH-g)and total lead.TPH-g was detected in analyzed soil samples at concentrations as high as 4,400 milligrams per kilogram (mg/kg). PREVIOUS SITE INVESTIGATIONS On 17 August 1994 FEA advanced one soil boring(BI)in the center of the former UST excavation to a total depth of 60 feet bsg. Soil samples collected from 30 and 40 feet bsg contained detectable concentrations of TPH-g, toluene, ethylbenzene and xylenes. A grab ground water sample was collected from boring B 1.TPH-g and benzene,toluene,ethylbenzene and total xylenes(BTEX)were detected at maximum concentrations of 76,000 micrograms per liter(µg11)TPH-g, 38 µg11 benzene, 310 µg11 toluene, 4.8 µg/1 ethylbenzene and 6,800 µg/1 total xylenes. On 05 and 06 January 1999,Ramage Environmental (RE)conducted an additional investigation of the site. Five soil borings were advanced for the collection and analysis of soil and ground water samples. Three of the borings were completed as ground water monitoring wells screened from 30 to 50 feet bsg. Petroleum hydrocarbons were detected in soil samples collected during the January 1999 investigation.The highest concentrations were encountered in samples collected from beneath the UST excavation. On 25 April 2000,one Cone Penetration Test(CPT)boring was advanced at the subject property to determine the site stratigraphy and the vertical extent of impacted soil and ground water. Soil samples were collected at 65, 70, and 74 feet bsg. TPH-g and/or BTEX compounds were detected in all three soil samples analyzed. A discrete ground water sample was collected at 60 feet bsg utilizing a SimulProbe sampling system;significant concentrations ofTPH-g and BTEX compounds were detected in the analyzed ground water sample. On 26 to 28 September 2001 monitoring wells MW-4 through MW-7 were installed off-site.Wells MW-4 and MW-5 were installed south of the subject site within the property boundary of the San Joaquin County Fairgrounds. Well MW-6 was installed west of the subject property on the northwestern corner of Sierra Nevada Street and East Charter Way.Well MW-7 was installed north of the subject property on the eastern side of Sierra Nevada Street. The wells are screened from 30 Advanced GeoEnvironmental,Inc.