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03 July 1997 <br /> AGE-NC Project No 95-0130 <br /> Page 3 of 9 <br /> • Between January 1995 and February 1997, seven ground water monitoring/sampling events <br /> Iwere performed at the site During this time, a trend in hydrocarbon concentrations suggested <br /> increasing concentrations from the"core" area wells, and decreasing concentrations from the <br /> perimeter wells <br /> 23 REGIONAL GEOLOGIC SETTING <br /> According to a Geologic Map 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 /> is subdivided into two mayor 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 Jurassic <br /> to present day, creating a nearly flat lying alluvial plain extending from the Tehachapi Mountains in <br /> the south to the Klamath Mountains in the:north The western and eastern boundaries of this province <br />' are comprised of the California Coast Range and the Sierra Nevada Mountains, 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 /> within the Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, <br /> and generally consist of moderate to poorly drained fine textured soils The JHS soils generally <br />' formed from mixed rock sources <br /> 2 4 GROUND WATER DEPTH AND FLOW DIRECTION <br /> Between 1995 and 1997, the depth to initial ground water beneath the site has generally decreased <br />' from approximately 61 feet to 50 feet bsg The uppermost ground water flows in a unconfined <br /> aquifer With increasing depth, the aquifer becomes semi-confined due to the presence of mixed <br /> heterogeneous layers of sediments <br />' Between 1995 and 1997 round water monitoring data at the site remained relatively constant with <br /> � g g Y <br /> a general ground water flow direction towards the southeast Relative ground water elevation maps <br /> fir the CFtP hnup hePn ine-ItirriPri in nrevin�uo 0i arterl" 12,-nnr+c nranar.,A her Af�p <br /> r r r r s <br />' 3.0. SCOPE OF WORK <br /> An SVE system in conjunction with an TAS system is proposed within the "core" petroleum <br /> hydrocarbon-impacted area at the site In order to maximize the efficiency of the clean-up efforts, a <br /> 24-hour operation of the system is planned A typical destruction rate of greater than 95% of <br />