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i A 19 June 2000 AGE-NC Project No 96-0232 Page 2 of 35 at approximately 8 feet below site grade(bsg) Dissolved total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) were detected in grab ground water samples at concentrations as high as 18,000 micrograms per liter (µg/1) Dissolved benzene, toluene, ethylbenzene and xylene (BTEX compounds) were detected at concentrations as high as 860 }Ig/l TPH-g was detected in a soil sample(L3B)beneath the former product piping at a concentration of 1 5 milligrams per kilogram (mg/kg), BTEX compounds were detected in L3B at concentrations ranging as high as 0 18 mg/kg TPH-d was not detected in any of the analyzed soil samples Analytical results of soil and grab ground water samples are summarized in Tables 1 and 2, soil sample locations are depicted in Figure 4. 2 3 UNDERGROUND STORAGE TANK REMOVAL THREE B'S TRUCK PLAZA On 29 October 1998, three 12,000-gallon gasoline USTs and one 12,000-gallon diesel UST were removed from the Three B's Truck Plaza site Soil samples were collected beneath the east end,west end and beneath the middle of each UST Laboratory analysis of soil samples detected TPH-g at concentrations as high as 4,200 mg/kg, TPH-d as high as 22,000 mg/kg, BTEX compounds as high as 330 mg/kg, MTBE as high as 7 6 mg/kg and TBA as high as 5 9 mg/kg (Appendix A) On 10 November 1998,product piping associated with the foriner USTs was removed from the site Ground water was encountered in the product piping trenches at approximately 5 feet bsg As a result, soil and grab ground water samples were collected from the product piping trenches Laboratory analysis of grab ground water sample detected TPH-g at a concentration of 57,000 �ig/l, TPH-d at a concentration of 50,000 µg/1, BTEX compounds as high as 14,000 µg/1 and MTBE at a concentration of 110,000}tg/l Laboratory analysis of soil samples detected TPH-g at concentrations as high as 240 mg/kg, TPH-d as high as 66 mg/kg, BTEX compounds as high as 6 9 mg/kg, MTBE as high as 0 8 mg/kg and TBA as high as 0 64 mg/kg Results of the Three B's Truck Plaza UST removal activities are summarized in Appendix A 2 4 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING According to 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 Syncline (GVS), a large, elongate, northwest trending structural trough The GVS is subdivided into two mayor divisions designated the Sacramento and San Joaquin Valleys, which have been filled to the present elevation with thick sequences of sediment ranging in age from Jurassic to present day, creating a nearly flat lying alluvial plain extending from the Tehachapi Mountains in the south to the rte, Klamath Mountains in the north The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively Advanced GeoEm tronmental,Inc