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,y 20 November 2003 AGE-NC Project No. 96-0263 Page 2 of 11 r. 430 mg/kg of xylenes and 770 mg/kg of MTBE. Total lead was detected at background levels. The highest concentrations of petroleum hydrocarbons were detected in soil samples collected from the product line trench and dispenser areas. Laboratory results of soil samples analyzed for petroleum hydrocarbons are summarized in Table 1. 2.3. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The Geologic Map of California,published in 1966 by the California Department of Conservation Division of Mines and Geology,shows the site area within the Great Valley Syncline(GVS),a large, elongate, northwest trending structural trough. The GVS is subdivided into two major divisions designated the Sacramento and San Joaquin Valleys,which have been filled to the present elevation with thick sequences of sediment ranging in age from Jurassic to present day, creating a nearly +— flat-lying alluvial plain extending from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively. a.. 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 Capay- `" Stomar-Zacharias (CSZ) association. The CSZ soils are located in interfan basins and on alluvial fans and stream terraces, and generally consist of very deep, moderately well drained and well drained, gravelly moderately fine-textured to fine-textured soils. v 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 features in the vicinity of the property are Old River, located approximately 2.4 miles northwest of the site and the Delta Mendota Canal, located approximately 3.6 miles southwest of the site. Ground water in the area of the site is considered to be of beneficial use. ' 2.4. GROUND WATER DEPTH AND FLOW DIRECTION Review of the historical depth to ground water maps published by the San Joaquin County Flood Control and Water Conservation District (FCD&WCD) dating back to 1971 suggests that ground +-• water depth near the site was generally less than 10 feet bsg; review of regional ground water elevation maps published by the FCD&WCD (1998) suggests a north to northwest ground water flow direction. Advanced GeoEnvironmentai,Inc. am