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t 30 June 1999 ' AGE-NC Project No 99-0624 Page 2 of 10 4 west end of the USTs and were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g) and volatile aromatics (benzene,toluene, ethyl benzene and total xylenes BTEX) with the oxygenated fuel additive methyl-tert-butyl ether(MTBE) in accordance with EPA Methods 8015m and 8020, respectively TPH-g and BTEX were not detected in any of the analyzed samples MTBE was detected at 20 feet bsg in the soil boring established at the northeast end of the former UST cluster at a concentration of 0 25 milligrams per kilogram (B1) 2 3 UNDERGROUND STORAGE TANK REMOVAL Beginning on 30 June 1998,the three 10,000-gallon USTs were removed from the site and,replaced with new USTs to meet the December 1998 upgrade requirements Soil samples were collected from beneath each UST, dispenser island and from the excavated soil The samples were transported to a DHS-certified laboratory and analyzed for TPH-g, BTEX, fuel oxygenating compounds and total lead in accordance with the appropriate EPA Methods No TPH-g, BTEX or fuel oxygenates were detected in soil samples collected beneath the former • USTs Xylene was detected at 0 012 parts per million in one sample collected beneath the former dispenser Island Low concentrations of xylenes were also detected in samples collected from the excavated (stockpiled) soil The stockpiled soil was transported off-site for disposal with approval from the PHS-EHD 24 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending, asymmetric structural trough The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to Recent, 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 the California Coast Range and the Sierra Nevada, respectively Rocks composing the basement complex of the province have not been completely defined but are believed to be of metamorphic and igneous origins The northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively The Modesto, Riverbank and 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 primarily by the San Joaquin River The nearest surface water feature in the vicinity of the property is the Moklumne River approximately one-half imile north of the subject property Advanced CeoEnti ironmental,Inc