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2.4 Laboratory results for previous sampling. <br /> Analytical results for all soil and water samples collected <br /> during tank removal are presented in Tables 1 and 2 , <br /> respectively. <br /> 2. 5 Estimates of liquid composition and quantity leaked: <br /> No estimate of liqu_ J quantity can be made with existing <br /> information. The constituents detected in the soil and <br /> water samples appear to be derivcd 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 �Ls 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 are shown on Figure 3. <br /> 3.0 METHODS AND PROCEDURES <br /> 3. 1 Well Installation <br /> On October 22, 1990 three soil borings were drilled, logged <br /> and sampled ,s part of this phage of investigation. <br /> Subsequent to installation the borings were converted to two <br /> inch diameter groundwater monitoring wells. The well <br /> locations are shown on Figure 2. <br /> The three eight-inch diameter soil borings were drilled by <br /> Spectrum Exploration under C57 using a hollow stun <br /> auger drill rig . All prc cedures a►,' protocol for <br /> 2 <br />