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u n � 17 June 2008 AGE-NC Project No. 99-0637 Page 3 of 7 of soil samples collected from the February 2003 well installations are presented in Table 3. 2.3. REGIONAL GEOLOGICALIHYDROGEOLOGICAL SETTING The site is situated within the Great Valley Geomorphic Province of California, a large, elongate northwest tending, 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 of metamorphic and igneous origin. The Great Valley Province has been subdivided into two major sections identified as the Sacramento and San Joaquin Valleys. 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 is situated within an area of Capay clay soil. Capay clay is located in interfan basin or alluvial fan areas, and generally consists of very deep,moderately well-drained grayish brown and dark grayish brown clay.The soil formed in alluvium derived from mixed rock sources. The Modesto, Riverbank, and Turlock Lake Formations and overlying Recent alluvium are the principal sources 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. 2.4. LOCAL GROUND WATER SETTING The nearest surface water feature in the vicinity of the property is the Stanislaus River approximately five miles south of the site. Ground water at the site is currently encountered at a depth of approximately 15 to 16 feet bsg and has a northwestern flow direction (Figure 3). Ground water depths have fluctuated between 15 and 23 feet bsg since monitoring began in 2001. Ground water occurs in a generally silty sand extending from 20 to 25 feet bsg with approximately 5-foot thick silty clay layers above and below. Poorly graded sand and silty sand extend from surface grade to approximately 15 feet bsg. Ground water elevation data is presented in Table 5. Advanced GeoEnvironmenta3,Inc.