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1, i <br /> 2. 5 Estimates of liquid quantity and composition leaked: <br /> No estimate of liquid quantity can be made with existing <br /> information. The constituents detected in the soil sample <br /> appear to be derived from gasoline. <br /> 2. 6 Topography, geology, surface water, depth to groundwater: <br /> The project site is located within the Eastern San Joaquin <br /> County Groundwater Basin. The basin is drained by the San <br /> Joaquin River and its tributaries. Recharge occurs along <br /> Morman Slough. Additional groundwater recharge occurs in <br /> the San Joaquin River and Sacramento River Delta north of <br /> Stockton. The geology of the Stockton site is composed of a <br /> thick sequence of river channel and flood plain deposits. <br /> These sequences contain interbedded sand, gravel, silt and <br /> clay layers. <br /> _ Depth to groundwater beneath the site is approximately 40-50 <br /> feet below grade ( San Joaquin Flood Control and Water <br /> Conservation District, 1987 ) . Groundwater flow is to the <br /> southwest. The closest domestic water well to the site is <br /> the facility well located approximately 110 feet northeast <br /> of the two former u/g tank pits. <br /> 2. 7 Proximity of private, municipal and irrigation wells: <br /> Well locations within a one half mile radius have been <br /> requested from the Department of Water Resources (DWR) . <br /> 2 . 8 Proposed sampling locations and methodology: <br /> To assess the contribution of the two former u/g gasoline <br /> storage tanks and one u/g waste oil tank to soil <br /> contamination at the project site, Waterwork proposes to <br /> drill soil borings near the former tank locations and <br /> collect soil samples from selected intervals. A workplan <br /> for the investigation is presented below. <br /> - 2. 8. 1 Soil borings will be advanced to determine the vertical <br /> and lateral extent of soil contamination beneath the <br /> former storage tanks. The proposed boring locations are <br /> shown on Figure 2. Near the former fuel tanks, four <br /> borings for each tank pit will be advanced to a minimum <br /> depth of 25 feet below grade or to 10 feet below the level <br /> where soil contamination is last detected in the field. <br /> Soil samples will be collected at five foot intervals <br /> between the depths of 15 and 25 feet or to 10 feet below <br /> the depth where soil contamination is last detected in the <br /> field. <br /> 4 <br />