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05 August 1999 'AGE-NC Project No. 98-0497 Page 2 of 5 (milligrams per kilogram). . 2.3. REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough. The Great Valley Province has been filled with thick sequences of sediment ranging in age frc m Jurassic to Recent, 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 thi3 province are comprised of the California Coast Range and the Sierra Nevada, respectively. Rocb s composing the basement complex of the province have not been completely defined but are-b lieved to be metamorphic and igneous in origin. The northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively. Based on the General Soil Map from the San Joaquin C unty Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Jackson-Hallenbeck-Stockton (JHS) association. The JHS soils are located within basins, and generally consist of moderate to poorly drained fine to tured soils. The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from mixed rock sources. The Modesto, Riverbank, Turlock Lake Fon-nations and overlying recent alluvium are the principal sources of domestic ground water in the 13,500 square-mile San Joaquin Valley Ground Nater 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 the Mormon Slough, approximately 1;000 feet north of the property. 2.4. GROUND WATER DEPTH AND FLOW DIRECTION Based on review of the Lines of Equal Depth to Groun 1a-ater, Fall 1997 map published by the San Joaquin County Flood Control District and Water Conservation District(FCD&WCD),the estimated depth to ground water at the site is between 60 and 70 feet below surface grade (bsg). Review of the map Lines of Equal Elevation of Groundwater, Fall 1997(FCD&WCD) depicts the regional ground water flow direction towards the northeast. Review of historical depth to groundwater maps (FC &WCD) dating back to 197.1 suggests that ground water depth near the site has fluctuated between 60 and 100 feet bsg. i Advanced CcoEnvironmental,Inc.