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• 28 February 2000 AGE-NC Project No 00-0697 Page 2 of 6 Soil samples were collected at a depth of four feet below surface grade (bsg), and were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g), and volatile aromatic compounds - benzene, toluene, and total xylenes (BTEX) The soil sample collected from beneath the former regular gasoline UST was also analyzed for total lead and ethylene dibromide (EDB) The two 550-gallon gasoline USTs were located at the south end of the site During the UST removal, a total of two soil samples, one from beneath each UST were collected from the floor of the UST excavation Total petroleum hydrocarbons quantified as gasoline (TPH-g) was reported in soil sample R-1 collected from beneath the 550-gallon regular gasoline UST at a concentration of 570 milligrams per kilogram (mg/kg) Toluene and xylenes were also reported in soil sample R-1 at concentrations of 84 mg/kg and 250 mg/kg, repectively Benzene was not reported in any of the soil samples submitted for analysis Ethylbenzene and methyl tertiary butyl ether(MTBE) were not analyzed in either of the soil samples collected A summary of soil analytical results are presented in Table 1 23 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING • The site is located within the northern San Joaquin Valley which comprises part of the Great Valley geomorphic province of California The San Joaquin Valley is formed by the Great Valley geosyncline,which is a large, elongate, northwest-trending asymmetrical structural trough (basin) It is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the north, and the Sierra Nevada to the east This trough has been filled with sediments derived from both marine and continental sources Thickness of the sedimentary fill ranges from thin veneers along the valley edges to more than 20,000 feet in the south central portion of the valley The sedimentary formations range in age with the older deposits being primarily marine in origin and the younger deposits being primarily continental Contmental-denved sediments were primarily deposited in lacustrine, fluvial, and alluvial environments with sediment sources being the mountain ranges surrounding the valley(Ohnsted and Davis, 1961) The site is located on unconsolidated and semi-consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977) The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22) Advanced GeoEnvironmental,Inc