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22 May 1998 AGE-NC Project No. 95-0152 Page 2 of 7 2.3. PRELIMINARY SITE ASSESSMENT ACTIVITIES .. On 13 and 14 December 1995, four soil probings (P1 through P4) were advanced near the former UST area to maximum depths of 40 feet bsg. Selected soil samples were submitted for laboratory analysis for petroleum hydrocarbons. The laboratory detected trace levels of toluene, ethylbenzene and xylenes from P1 at depths of 15 and 40 feet below surface grade (bsg). 2.4. 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 from 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 this province are comprised of the California Coast Range and the Sierra Nevada, respectively. Rocks composing the basement complex of the province have not been completely defined but are believed 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 County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Tokay-Acampo(TA)association.The TA soils are located on low fan ten-aces along the Mokelumne River,and generally consist of moderate to well drained coarse textured soils.The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from granitic rock sources. 2.5. REGIONAL GROUND WATER DEPTH AND FLOW DIRECTION Based on review of the map titled Lines of Equal Depth to Groundwater Spring 1996 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 75 to 85 feet bsg; review of Lines of Equal Elevation of Groundwater Spring 1996 (FCD&WCD) depicts the regional ground water flow direction towards the southeast. Review of previous ground water monitoring at the site and historical depth to ground water maps(FCD&WCD)dating back to 1971 suggests that ground water depth near the site has fluctuated between 50 and 90 feet bsg. Advanced GeAnNironmenlaI,Inc.