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08 November 2002 AGE-NC Project No.02-0918 Page 2 of 9 2.2. SITE HYDROGEOLOGIC CONDITIONS The closest surface water feature to the site is Duck Creek,located approximately 1,000 feet south of the site.Water from creek drains into the San Joaquin River Deep Water Channel and is primarily used for commercial and recreational boating. Based upon well information obtained from data collected from Lines of Equal Depth to Groundwater Fall 1999 map published by the San Joaquin County Flood Control District and Water Conservation District(FCD&WCD)is currently estimated to occur at a depth of approximately 40 feet below surface grade(bsg), 2.3. UNDERGROUND STORAGE TANK REMOVAL Three USTs with associated piping and the dispenser island were removed from the site by Thorpe Oil Company on 30 October 1997.Eight soil samples were collected beneath the USTs,one sample was collected beneath the dispenser area and four laboratory-composited soil samples were collected from the excavated soil. Subsequently,approximately 200 tons of soil excavated during removal of the USTs was backfilled into the UST excavation. Laboratory analysis detected methyl tertiary butyl ether (MTBE) in soil samples collected from beneath the eastern end of the central UST(#2),at concentrations up to 18 parts per million(18,000 micrograms per billion: Rg/kg). In addition, total petroleum hydrocarbons quantified as gasoline (TPH-g)were detected at concentrations up to 1,900 milligrams per kilogram(mg/kg)and volatile aromatics(benzene,toluene,ethyl benzene and xylenes:BTEX)were detected at concentrations up to 82 ppm(82,000µg/kg).Lower concentration of BTEX were detected in the soil samples collected from the center of the central UST. Consequently,the San Joaquin County Environmental Health Department(EHD)required additional investigation to determine the lateral and vertical extent ofhydrocarbon-impacted soil and/or ground water. 3.0. PROCEDURES The field work reported herein was performed in accordance with procedures outlined in Preliminary Site Assessment Work Plan,prepared by AGE,dated 01 May 2002,amended and approved by the EHD by letter dated 22 May 2002. Advanced GeoEnvironmental,Inc.