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L . <br /> D�' <br /> PRETANI{CLOSURE SrM ASSESSMENIT <br /> 3725 Tracy Boulevard, Tracy, CA <br /> Delta Project No. 40-89-012 <br /> Page 3 <br /> 2.2 Site Mistory <br /> The existing retail gasoline outlet was constructed in 1967. Figure 2 illustrates the <br /> current existing buildings and facilities at the site. Please note the location of the <br /> three existing underground storage tanks and the proposed location for the three new <br /> underground storage tanks to be installed with the proposed site renovation. <br /> The original installation of the tanks included two single-walled steel underground <br /> storage tanks of an 8,000- and 10,000-gallon capacity. A third 8,000-gallon steel <br /> underground storage tank was added in 1970. In 1985, all three tanks were removed and <br /> replaced with three 10,000-gallon, double-walled fiberglass tanks. Dispensing lines <br /> and vent lines were not replaced at that time and are believed to be single-walled and <br /> of steel construction. <br /> A waste oil tank of unknown size was removed from the site in 1985. The location of the <br /> previous waste oil tank is unknown at this time. <br /> 2.3 Previous Subsurface Investigative Acti_v_ii <br /> Prior to tank replacement activities in 1985, Shell Oil Company contracted J. H. <br /> Kleinfelder & Associates to drill four test soil borings in the vicinity of the <br /> underground storage tanks. The soil borings were drilled to a depth ranging from 11.5 <br /> to 16.5 feet below the surface; approximate locations are illustrated in the Kleinfelder <br /> report presented in Appendix A. <br /> Soil samples were collected at that time for classification and screening with a trace <br /> gas analyzer (believed to be an OVA). A complete copy of Kleinfelder's report is <br /> presented in Appendix A. <br /> In general, the natural soils encountered at that site consisted of sands and silt. <br /> Water was encountered in boring B-1 at a depth of approximately 11.5 feet. Gasoline <br /> hydrocarbons (presumed) were detected in borings B-4, 13-2, and B-1 at a depth of <br /> approximately 10 feet or roughly corresponding to the bottom of the tanks and just above <br /> the detected water level. Samples collected from greater depth (i.e., below the water <br /> table) did not contain petroleum product constituents. Petroleum product constituents <br /> were not found in any of the soil samples analyzed from boring B-3. <br /> r <br />