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03 August 1999 <br /> AGE-NC Project No 95-0121 ` <br /> Page 2 of 7 <br /> hydrocarbons were present to depths in excess of 19 feet below surface`grade (bsg) <br /> 23 PREVIOUS INVESTIGATION y <br /> A total of nineteen soil borings were advanced at the site between May 1989 and December 1994, <br /> nine of the borings were completed as two-Inch diameter monitoring wells (MW-1 through MW-9) <br /> t Extensive hydrocarbon-Impacted soil and ground water, including free product, were encountered <br /> during assessment of the site <br /> In July 1995, one dual-purpose soil vapor extraction/ground water extraction well (EW-1), and two <br /> soil vapor extraction wells (VW-1, VW-2)were Installed at the site In August 1995, an 8-hour soil _ <br /> vapor extraction (SVE)test was conducted at the site The pilot test was performed to provide vapor <br /> extraction data for proper system design of a remediation system Details of the SVE pilot test were <br /> included in Corrective Action Plan (CAP), dated 14 November 1995, prepared by AGE <br /> Additional background information has been prepared by AGE and summarized in the June 1998 <br /> (dated 20 July 1998), September 1998 (dated 29 October 1998) and December 1998 (dated 29 <br /> January 1999) Quarterly Reports submitted to PHS-EHD <br /> 23 REGIONAL GEOLOGIC SETTING <br /> The property is situated within the Great Valley Geomorphic Province of California, a large, <br /> elongate, northwest trending, asymmetric structural trough The Great Valley Province has been <br /> filled with thick sequences of sediment ranging in age from Jurassic to Quaternary, creating a nearly <br /> flat- lying alluvial plain, extending from the Tehachapi Mountains in the south to the Klamath <br /> Mountains in the north ,The western and eastern boundaries of this province are comprised of the <br /> California Coast Range and the Sierra Nevada, respectively Rocks composing the basement <br /> complex of the province have not been completely defined but are believed to be metamorphic and <br /> igneous in origin The northern and southern portions of the Great Valley,Province have been <br /> designated the Sacramento and San Joaquin Valleys, respectively <br /> Based on the General Soil Map from the San Joaquin County Soil Survey, published by the United <br /> States Department of Agriculture Soil Conservation Service in 1992, the site area is within the <br /> Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and <br /> generally consist of moderate to poorly drained fine textured soils The soils are generally derived <br /> from both marine and non-manne sediment, and are generally formed in alluvium derived from <br /> . mixed rock sources <br /> Advanced GeoEmironmenlal,Inc <br />