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23 March 2000 <br /> AGE-NC Project No 96-0232 <br /> Page 3 of 8 <br /> • Between July 1996 and February 2000, nine ground water monitoring and sampling events <br /> were performed at the site TPH-g has been detected in ground water samples collected from <br /> MW-1 at concentrations ranging as high as 480 ,ug/l, TPH-d has been detected in samples <br /> collected from wells MW-1 through MW-7 at concentrations ranging as high as 1,500 Yg/l <br /> Ethylbenzene was detected in a sample collected from well MW-6B at a concentration of <br /> 0 51 gg/l MTBE was detected in samples collected from wells MW-1 through MW-7 at <br /> concentrations ranging as high as 2,100 µg/1 Analytical results are summarized in Table 3 <br /> • In February, April, June, August, September, November and December 1999 and February <br /> 2000,MTBE was detected in water samples collected from the Rocky's Restaurant domestic <br /> drinking water well at concentrations ranging as high as 18 ;ig/l Analytical results are <br /> summarized in Table 3 <br /> 24 REGIONAL GEOLOGIC SETTING <br /> According to 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 Syncline <br /> i (GVS), a large, elongate, northwest trending structural trough The GVS is subdivided into two <br /> mayor divisions designated the Sacramento and San Joaquin Valleys, which have been filled to the <br /> present elevation with thick sequences of sediment ranging in age from Jurassic to present day, <br /> creating a nearly flat lying alluvial plain extending from the Tehachapi Mountains in the south to the <br /> Klamath Mountains in the north The western and eastern boundaries of this province are comprised <br /> of the California Coast Range and the Sierra Nevada, respectively <br /> Based on General Soil Map from the San Joaquin County Soil Survey, published by the United States <br /> Department of Agriculture Soil Conservation Service in 1992, the site area is within the Guard- <br /> Devries-Riblancho (GDR) association The GDR soils are located within basin rims along the <br /> ea-stem edge of the Sacramento-San Joaquin Delta area, and generally consist of poorly drained, fine <br /> to coarse textured soils The GDR soils generally formed in alluvium from mixed rock sources <br /> The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal <br /> source of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin <br /> (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water <br /> feature in the vicinity of the property is White Slough, located approximately 7,500 feet southwest <br /> of the site <br /> AGE has been informed that ground water in the area of the Flag City Chevron site below 150 feet <br /> bsg is not of beneficial use due to high total dissolved solids (TDS) <br /> i <br /> Advanced GcoEn\Ironmental,Inc <br />