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1 ' 11 September 2001 AGE-NC Project No. 98-0466 ' Page 2 of 24 ' 2.2. GEOLOGY AND HYDROGEOLOGY The property is situated within the Great Valley Geomorphic Provi cc of California, a large, elongate, northwest trending, asymmetric structural trough. The Grea Valley Province has been ' filled to its present elevation 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 Siena 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 is subdivided into two major divisions designated the Sacramento and San Joaquin Valleys. ' The Modesto, Riverbank and 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). ' Boring logs from a number of soil borings on the site show the soil profile to consist roughly of a 50-50 mixture of coarse grained (Silty sand to poorly graded sand) d fine grained soil (clay to ' sandy silt)textures from surface to as much as 50 feet below surface grade(bsg). The soil types vary laterally and with depth and do not exhibit significant lateral continuity. ' Ground water is being monitored for a diesel release via seven groundwater monitoring wells on the extreme southern portion of the site (Figure 3) by Dames & Moore (D&M) on behalf of American Forest Products Company.Ground water occurred at approximately 35 feet below surface grade in March 1999, and was flowing toward the northeast (D&M, April 1999, Quarterly Groundwater Monitoring Report-March 1999). The Dames &Moore report shows the historical ' local ground water flow direction generally northward,varying from we t-northwest(297°)to east- southeast(103°). ' Ground water is considered to be of beneficial use and is used fordomestic, industrial and commercial uses. The nearest surface water feature in the vicinity of fle property is the Calaveras River, located approximately 3,300 feet north of the site. 2.3. SITE HISTORY ' Information on the site history was developed through review of various reports by Kleinfelder and D&M,discussions with Mr. Glen Gallup of AM&M,file reviews at the San Joaquin County Public ' Health Services-Environmental Health Division(PHS-EHD)and RWQCB, and review of various documents supplied by AM&M. The site was operated by American Forest Products Company Advanced GeoEnvironmental,Inc.