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04 Ocotber 2000 AGE-NC Project No. 00-0768 Page 3 of 7 2.4. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The site is located within the northern 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). 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(Ohnsted and Davis, 1961). 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). 2.5. GROUND WATER DEPTH AND FLOW DIRECTION The estimated depth to ground water at the site is 10 feet below surface grade (bsg) based on information from Lines of Equal Depth of Water Wells Fall 1996, published by the San Joaquin County Flood Control District and Water Conservation District-FCD&WCD, and data from nearby sites. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1996 also published by the San Joaquin County FCD&WCD,the site is in an area where ground water flows toward the southeast. 3.0. SCOPE OF WORK AGE proposes to collect soil and discrete ground water samples to determine if petroleum hydrocarbon and/or MTBE-impacted soil and/or ground water is present beneath the site. The phase II site assessment will consist of the following tasks: • Permitting and pre-field work activities; • Soil sample collection and analysis; Advanced CeoEnvironmental,Inc.