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12 August 2003 1.� AGE-NC Project No. 03-1035 Page 2 of 7 Geology, 1977).Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basile 5-22).The estimated depth to ground water at the site is approximately 50 to 60 feet below surface grade(bsg)based on information from Lines of Equal Depth of Water Wells Fall 1999,published by the San Joaquin County Flood Control District and Water Conservation District- FCD&WCD. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1999 also published by the San Joaquin County FCD&WCD, the ground water elevation is estimated at approximately 35 feet below surface grade and ground water flow generally toward the east/southeast. However, this may be greatly modified by local recharge and discharge patterns. 2.2. UNDERGROUND STORAGE TANK REMOVAL One 500-gallon gasoline underground storage tank(UST)was removed from the site in September 1989. The UST was said to have contained leaded gasoline, and to have been out-of-service for 20 to 25 years prior to removal.Following the UST removal,soil samples were collected approximately one foot below the pipeline(P-1)and 3 feet below the former UST(T-1).Analytical results reported toluene at a concentration of 1.3 milligrams per kilogram (mg/kg) from sample P-1 and total lead at concentrations of 208 mg/kg and 74.5 mg/kg from samples P-1 and T-1, respectively. Total petroleum hydrocarbons as gasoline (TPH-g), benzene, ethylbenzene, xylenes and ethylene dibromide (EDB)were not detected in the analyzed samples. In November 1989, sample P-1 was also analyzed for organic lead. The analytical report indicated that organic lead was below detectable limits (<2.5 mg/kg). In March 1993,the San Joaquin County Environmental Health Department(SJCEHD)issued a letter stating that,based on current standards and site characteristics,the property would not be placed on the Contaminated Sites list, but closure certification would not be granted without further site investigation. 2.3. PREVIOUS SITE ASSESSMENTS' No previous additional assessment activities were performed at the site. �, Advanced GeoEnvironmental,Inc.