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2. 5 Estimates of liquid composition ind giai:city leaked <br /> No estimate of 1Lquid quantity can be made with ex2.st2.ng <br /> information. The constituents detected in the so-1 and <br /> water samples appear to be derived from gasoline. <br /> 2, 6 Topography, geology, surface water, depth to groundwater. <br /> The site is situated on level terrain underlain by flood <br /> basin deposits of Pleistocene and Holocene age that are <br /> composed of sediments similar to and probably conformable on <br /> underlying deposits of alluvium and Tulare formation. The <br /> flood basin deposits are light to dark brown and grey clay, <br /> silty sand, and organic materials with locally high <br /> concentrations of salt and alkali. Stream channel deposits <br /> of sand and gravel are also included (Hotchkiss and Balding, <br /> 1971 ) . <br /> This study focuses on the water quality in the shallow <br /> water-bearing zone identified by Hotchkiss and Balding <br /> ( 1971 ) . Groundwater within this zone occurs less than ten <br /> feet below grade over most of the Tracy area . General <br /> groundwater gradient is to the north. The flood plain <br /> deposits of the shallow water-bearing zone have well <br /> developed soil profiles and consequently poor permeability. <br /> The base of the shallow zone is poorly defined and probably <br /> is from five to twenty feet below ground surface. The <br /> quality of the shallow groundwater in the Tracy area is of <br /> • generally poor quality. <br /> 2.7 proximity of private, municipal. and irrigation wells: <br /> Locations of wells within a one-half mile radius of the <br /> facility have been requested from the Department of Water <br /> Resources (DWR) . Locations and available information on <br /> record with UWR will be included in the problem assessment <br /> report to be completed pursuant to this plan. <br /> 3.0 METHODS AND PROCEDURES <br /> To assess the contribution of the former underground tanks <br /> to soil and groundwater contamination at the site, WaterWork <br /> proposes to drill, log, and sample three soil borings which <br /> will be completed as groundwater monitoring wells. <br /> To define the lateral extent of soil and groundwater <br /> contamination, these wells will be situated with one well <br /> approximately upgradient and two approximately downgradient <br /> of the former tank location. The proposed boring/well <br /> locations are shown on Figure 2. <br /> Underground utilities will be located by Underground <br /> Services Alert prvor to drilling at the site. <br /> 2 <br />