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' 20 March 2002 • AGE-NC Project No 01-0877 Page 2 of 7 ' at a concentration of 3,900 mg/kg Soil samples collected beneath the fuel USTs and dispensers were not analyzed for TPH-d, TPH-mo and Oil and Grease ' Toluene was detected in all UST and dispenser samples at concentrations as high as 99 mg/kg (T3-E) Ethylbenzene and total xylenes were detected in the soil samples collected beneath the USTs at concentrations as high 200 mg/kg and 1,100 mg/kg, respectively Total Iead was detected in all of the soil samples at concentrations as high as 39 mg/kg Chromium, nickel and zinc were detected in the soil samples collected beneath the waste oil UST, fill location ' and the stockpile at concentrations as high as 40 mg/kg, 34 mg/kg and 330 mg/kg, respectively Metal concentrations are not outside the background, natural range of metals concentrations in California soils Hexavalent chromium and PCB's were not detected at or above laboratory reporting limits in the soil samples analyzed 2 2 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING ' The site is located within the southern San Joaquin Valley which comprises part of the Great Valley geomorphic province of California The San Joaquin Valley is formed by the Great Valley geosyncline, which is a large, elongate, northwest-trending asymmetrical structural trough (basin) I It 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 This trough 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 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, 196 1) The site is located on unconsolidated and semi-consolidated alluvium,lake,playa and terrace deposits of Quaternary age(California Division ' of Mines and Geology, 1977) 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) 2 3 GROUND WATER DEPTH AND FLOW DIRECTION Based on information obtained during drilling,ground water depth beneath the site is approximately, 25 to 30 feet below surface grade(bsg) Based on information obtained from a nearby site(706 North Advanced GeoEnvi ron mental,Inc r