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93/22/2060 17 36 2094671116 AGE STOCKTOH PAGE 07 • 08 March 2000 AGE-NC Project No 96-0232 Page 3 of 11 •;ater samples collected from MW-5,MW-6A.and MW-6B at concentrations ranging as high, as 2 80,ug/l,dissolved MTBE was detected in the initial ground water samples collected from MW-6A, MW-68 and MW-7 at concentrations as high as 14 mg/l Analytical results are summarized in Tables 2 and 3 • Between July 1996 and June 1999, eight ground water monitoring and sampling events were performed at the site TPH-g has been detected from ground water samples collected from MW-1 at concentrations ranging as high as 480,ug/l, TPH-d has been, detected in samples collected from wells MW-1 through MW-7 at concentrations ranging as high as 1,500 kcg/l Ethylberizene was detected in a sample collected from well MW-6B at a concentration of 0 51 ug/1 MTBE was detected in samples collected from wells MW-1 through MW-7 at concentrations ranging as high as 1,600,ugll Analytical results are summarized in Table 3 • In February, April, June, August, September, November and December 1999, MTBE was detected in water samples collected from the Rocky's Restaurant domestic drinking water well at concentrations ranging as high as 18 kig/l .Analytical results are sur-.Unanzed in Table 3 . 24 REGIONAL GEOLOGIC SETTING According to a Geologic .Map of California, published in 1966 by the California Department of Conservation Division: of Mines and Geology, the site area is within the Great Valley Synehne (GVS), a large, elongate, northwest trending structural trough The GVS is subchvided into two major divisions designated the Sacramento and San Joaquin Valleys, which have been,filled to the present elevation with thick sequences of sediment ranging in ane from Jurassic to present day, 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 Sierra Neti ada,respectively. Based on a General Soil Map from the San Joaquin County Soil Survey, published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Guard-Devnes-Riblancho (GDR) association The GDR soils are located within basin rims along the eastern edge of the Sacramento-San Joaquin Delta area,and generally consist of poorly drained, fine to coarse textured soils The GDR soils generally formed in alluvium from mixed rock sources The Modesto, Riverbank, 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) This basin is drained prinianly by the San Joaquin River The nearest surface water feature in the vicinity of the property is White Slough, located approximately 7,500 feet southwest of the site • Advanced GeoEnvdroomenw,Inc_