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8820011STI CON " oodward•Clyde Consultants 1� Brown and Caldwell (1985) used average groundwater elevations from 1980 to construct a groundwater contour map showing the top of shallow groundwater in San Joaquin County. Based on this map, the shallow groundwater gradient direction in the vicinity of the subject site is directed towards the south-southeast. The elevation of the top of groundwater at the site is estimated from the Brown and Caldwell (1985) report as approximately -40 feet, mean sea level (MSL) , or 75 feet below surface grade. Given the relatively low topographic relief in the area, a relatively flat groundwater gradient can be expected beneath the study site. 3.0 WELL SURVEY A search of California Department of Water Resources well records indicates that there are at least 22 documented groundwater wells that are used for L domestic, municipal , or industrial purposes exist within a one-half mile radius of the site. Of the 2c 2-documented'we-1-l-s-,=8;wells-lie-downgradtI or to the south-southeast from the s�ite TK6 closest-off=site-well is approximately 150_0 feet to theYsouthl One well ,4 umber 14-, is located at the northwest corner of the study site. The well descriptions are summarized in Table 1 and their locations are plotted on Figure 3. The locations of ,Wells 21 and 22 in Table 1 were not plotted on Figure 3 because of insufficient location information from the Department of Water Resources. 4.0 FIELD PROCEDURES I 4.1 Soil Borings Four soil borings (C-A, C-8, C-C, and C-D) were drilled on May 19, 1988 at the locations and to the depths specified by Chevron USA Inc. and their approximate locations are shown on Figure 2. The borings were drilled using a truck-mounted CME-75 drilling rig equipped with eight-inch 4