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28 June 1999 AGE-NC Project No. 97-0333 Page 3 of 9 23 REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetnc 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 westem 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 southem 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 Dellu- Ventas-Tlmmn(DVT) association The DVT soils are located within dunes, alluvial fans and stream terraces along the Stanislaus River, and generally consist of well drained coarse textured soils The soils are generally derived from both marine and non-manne sediment, and are generally formed in . alluvium derived from granitic and mixed rock sources 24 GROUND WATER DEPTH AND GRADIENT The estimated depth to ground water at the site Is approximately 24 feet below surface grade (bsg) based on information from Lines of Equal Depth of Water Wells Fall 1997, published by the San Joaquin County Flood Control District and Water Conservation District(SJCFCD) Based on review of a regional ground water elevation map published by the SJCFCD, the prevailing ground water flow direction in Manteca is generally toward the northwest, although flow directions may be both locally and seasonably variable Based on data collected during the April 1999 investigation, first observed saturated soil Aas between 15 feet bsg and 20 feet bsg 3.0 SCOPE OF WORK Based on the results of the previous investigations and UST removal activities, soil and ground water at the site has been Impacted The lateral and vertical extent of impacted soil and ground water must be determined prior to the initiation of remediation The assessment activities will consist of the following tasks Advanced GeoEm Ironmental,Inc