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0 22 May 2002 AGE-NC Project No.01-0877 Page 2 of 9 �- semi consolidated alluvium,lake,playa and terrace deposits of Quaternary age(California Division of Mines and Geology, 1977). l The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the kI principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22). The closest surface water feature is the Stockton Deep Water Channel located approximately 2,000 feet southwest of the site. 2.2. UNDERGROUND STORAGE TANK REMOVAL �J On 12 April 2001, one 500-gallon waste-oil UST (Tl) and two 500-gallon fuel USTs (T2 and T3) were removed from beneath the sidewalk adjacent to 715 North Hunter Street,Stockton,California. ! The USTs were removed under EHD permit by Stockton Service Station Equipment Company,Inc. The approximate location of the former USTs is shown on Figure 2. - During the UST removals,one soil sample was collected beneath each of the USTs(T1-W,T2-E and T3-E) and one soil sample was collected 2.5-feet beneath each of the former locations of two fuel dispensers and one waste-oil fill port(D1-2.5',D2-2.5'and WO-1). Additionally,two samples were collected from stockpiled soil removed from the excavation(SP1-W and SPl-E). Petroleum hydrocarbons were detected in each soil sample collected.Total petroleum hydrocarbons as gasoline(TPH-g)was detected in the soil samples collected beneath the USTs and fuel dispensers at concentrations as high as 4,300 milligrams per kilogram(mg/kg). Total petroleum hydrocarbons as diesel and motor oil(TPH-d and TPH-mo)were detected in samples collected beneath the former waste oil UST and fill port and from the stockpile soil samples at concentrations as high as 1,800 mg/kg. Oil and grease was detected in the soil sample collected beneath the former waste oil UST l at a concentration of 3,900 mg/kg.Soil samples collected beneath the fuel USTs and dispensers were not analyzed for TPH-d, TPH-mo and Oil and Grease. - Toluene was detected in all UST and dispenser samples at concentrations as high as 99 mg/kg (T3-E).Ethylbenzene and total xylenes were detected in the soil samples collected beneath the USTs at concentrations as high 200 mg/kg and 1,100 mg/kg,respectively. Total lead was detected in all of the soil samples at concentrations as high as 39 mg/kg. Chromium, nickel and zinc were detected in the soil samples collected beneath the waste oil UST, fill location and the stockpile at concentrations as high as 40 mg/kg, 34 mg/kg and 330 mg/kg, respectively. _ Metal concentrations are not outside the background, natural range of metals concentrations in California soils.Hexavalem chromium andPCB's were not detected at or above laboratory reporting r� Advanced GeoEnvironmental,Inc. C�