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1 <br />' ground water impact was detected from wells MW-1 through MW-4, MW-6, AW-1 and AW-2 at <br /> concentrations as high as 250,000µg/1 TPH-g and BTEX constituents as high as 52,000µg/1 toluene, <br />' however, the most intense ground water impact is currently present from wells MW-4 and AW-1 <br /> at concentrations as high as 17,000µg/1 TPH-g and BTEX constituents as high as 2,750 µg/l xylene <br />' Based on the current area bound by wells MW-1 through MW-13, the vertical extent of petroleum <br /> hydrocarbon-impacted ground water is not known toward the east-northeast <br /> Between April 2000 and June 2004, the total volume of petroleum hydrocarbons extracted.by SVE <br /> remediation has been estimated to be approximately 1,938 gallons,or approximately 12,122 pounds <br /> of extracted petroleum hydrocarbons Comparing the SVE influent analytical results from April 2000 <br /> (start-up) and June 2004(current data), TPH-g concentrations have declined from 1,700 µg/1 to 110 <br /> µg/1, benzene concentrations have declined from 4 9 µg/1 to non detectable levels, <br /> toluene/ethylbenzene/xylene concentrations have declined from as high as 98 µg/1 to non detectable <br />' levels <br />' 5 0. REGIONAL GEOLOGIC SETTING <br />' According to a Geologic ,&Iap of California, published in 1966 by the California Department of <br /> Conservation Division of Mines and Geology, the site area is within the Great Valley Geomorphic <br /> Province (GVGP)of California, a large,elongate,northwest trending structural trough The GVGP <br /> lieis subdivided into two major divisions designated the Sacramento and San Joaquin Valleys, which <br /> have been filled to the present elevation with thick sequences of sediment ranging in age from <br /> Jurassic to present day, creating a nearly flat lying alluvial plain extending from the Tehachapi <br />' Mountains in the south to the Klamath Mountains in the north The western and eastern boundaries <br /> of this province are comprised of the California Coast Range and the Sierra Nevada Mountains, <br /> respectively <br /> Based on a 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 described as <br /> I being within the Jackson-Hallenbeck-Stockton(JHS) association The JHS soils are located within <br /> basins, and generally consist of moderate to poorly drained fine textured soils The JHS soils <br /> generally formed from mixed rock sources <br /> I <br />' APPENDIX A <br />