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31 January 2000 AGE-NC Project No. 99-0653 Page 2 of 6 TPH as gasoline were not reported in soil samples collected. A summary of soil analytical results are presented in Table 1. 2.3. 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(Olmsted 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). 2.4. GROUND WATER DEPTH AND FLOW DIRECTION Based on data obtained from wells on the property, depth to ground water at the site is between 6 and 10 feet below surface grade(bsg). The prevailing ground water flow direction in the vicinity of the site is southwest. However, flow direction may be both locally and seasonably variable. 3.0. SCOPE OF WORK In a letter dated 27 September 1993, the San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD)stated that the site could not be evaluated for closure without additional information. AGE proposes to collect soil and grab ground water samples to evaluate the lateral and vertical extent of the inferred petroleum hydrocarbon impact. The preliminary subsurface investigation will consist of the following tasks: Advanced GeoEm ironmental,Inc.