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L l 19 June 2440 AGE-NC Project No 96-0232 Page 3 of 35 Based on General Soil Map from the San Joaquin County Soil Survey,published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Guard- Devnes-Rioblancho (GDR) association The GDR soils are located within basin rims along the eastern edge of the Sacramento-San Joaquin Delta area, and generally consist of poorly drained,fine to coarse textured soils The GDR soils generally formed in alluvium from mixed rock sources The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water feature in the vicinity of the property is White Slough, located approximately 7,500 feet southwest of the site AGE has been informed that ground water in the area of the Flag City Chevron site below 150 feet bsg is not of beneficial use due to high total dissolved solids (TDS) 2 5 GROUND WATER DEPTH AND FLOW DIRECTION Review of historical depth to ground water maps published bythe San Joaquin County Flood Control and Water Conservation Distnct(FCD&WCD)dating back to 1971 suggests that ground water depth near the site has fluctuated between approximately 5 and 15 feet bsg, review of regional ground water elevation maps published by the FCD&WCD(1998)suggest a southeast to south ground water flow direction Based on ten ground water monitoring events recorded at the site between July 1996 and March 2000, depth to ground water measurements have fluctuated between 3 and 15 feet bsg, gradient has been presumed relatively horizontal at the site ranging between 0 001 and 0 01 Ground water flow direction has been inferred to be towards the north-northeast-northwest on four occasions (May 97, February 98, November 98 and March 2000), towards the west-northwest on one occasion (July 1998), towards the east-northeast on one occasion (February 2000), towards the south-southwest- southeast on two occasions(July and August 1996),locally varying between northeast and southwest on one occasion (February 1999) and locally varying between northwest and southeast on one occasion (June 1999) 3.0. SUMMARY OF PRELIMINARY INVESTIGATION AND EVALUATION The following is a summary of site assessment activities conducted by AGE for the Flag City Chevron site • June 1996- Review of San Joaquin County Public Health Services - Environmental Health Advanced GeoEm aronmenlal,Inc