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x 17 June 2003 AGE-NC Project No. 03-1035 Page 2 of 6 The Province is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the north, and the Sierra Nevada to the east. The Great Valley has been filled with sediments derived from both marine and continental sources. Thickness of the sedimentary fill ranges from thin veneers along the valley edges to more than 20,000 feet in the south central portion of the valley. The sedimentary formations range in age from Jurassic to Recent,with the older deposits being primarily marine in origin and the younger deposits being primarily continental. Continental-derived sediments were primarily deposited in lacustrine, fluvial,and alluvial environments with sediment sources being the mountain ranges surrounding the valley(Olmsted and Davis, 1961);the site itself is located on unconsolidated and semi-consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and 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(Basin 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 reported to have held leaded gasoline,and to have been out-of-service for 20 to 25 years prior to removal. Following tank removal, a one soil sample was collected approximately one foot below the pipeline(P-1) and one from approximately 3 feet below the former UST(T-1). Laboratory analytical results detected toluene at a concentration of 1.3 milligrams per kilogram (mg/kg) from pipeline sample P-1 and total lead at concentrations of 208 mg/kg and 74.5 mg/kg from P-1 and the UST sample 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,the pipeline sample P-1 was analyzed for organic lead; the result was non-detect (<2.5 mg/kg). Advanced GeoEnvironmental,Inc.