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i� <br /> F•A <br /> E <br /> SECTION 1 <br /> PROJECT BACKGROUND SUMMARY <br /> 1.1 7L BODUCTION <br /> During April through May 1988, nine underground fuel storage <br /> tanks were removed from the San Joaquin County Human Services <br /> building site located at the intersection of San Joaquin Avenue <br /> and Washington Street in Stockton, California (Figure 1-1) . A <br /> Preliminary Report covering the tank removal, which included <br /> � • recommendations for further investigation, was submitted to the <br /> County in September 1988. Based on the Preliminary Report, a <br /> soils and shallow groundwater investigation program was imple- <br /> mented. A Problem Assessment Report was submitted to the County <br /> in February 1989 detailing the results of the soils and shallow <br /> groundwater investigation. Asummary of those results is <br /> provided in the fallowing subsections. <br /> I 1.2 INITIAL SOIL AND GROUNDWATER INVESTIGATION PROGRAM <br /> R The field activities associated with the soil and shallow <br /> groundwater investigation included the following: <br /> . o Soil boring installation and soil sampling. <br /> i .• o Groundwater monitoring well installation and groundwater <br /> sampling. <br /> o Chemical analysis of soil and groundwater. <br /> r:•.. The soil and water samples were analyzed for benzene, toluene, <br /> total xylenes and ethylbenzene (BTX&E) ; total petroleum <br /> hydrocar-bons (TPH) ; organolead; and soluble lead where organolead was <br /> detected. Figure 1-2 presents the sampling locations. <br /> �. 1.2.1 Analytical Results for Soils <br /> Thirty-three soil samples were collected for analysis based on <br /> field screening measurements or from depths as specified in the <br /> Scope of Work. Table 3-1 presents a summary of the soil analyti- <br /> cal results. Six samples from two soil borings (BH-3 and BH-4) <br /> contained detectable concentrations of TPH. Five of these six <br /> samples also contained elevated concentrations of BTX&E com- <br /> pounds. Toluene was also detected in two samples from BH-2. <br /> In general, the compound concentrations increased with depth at <br /> bore hole locations BH-2, BH-3 and BH-4. The most elevated <br /> concentrations were detected in samples collected directly above <br /> the saturated zone, within the capillary fringe. <br />