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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 .54eet 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 (SP 1 -W and SP1 -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 concentrationof 3,900mg/kg. Soil samples collected beneath the fuelUSTs 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. Hexavalent chromium andPCB 's were not detected at or above laboratory reporting Advanced GeoEnvironmental, Inc. C�