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r <br /> 2 BACKGROUND <br /> Y <br /> Three underground fuel tanks were excavated and removed from the Nor- <br /> Cal Beverage facility in January 1991 (see Figure 2). Soil samples were <br /> collected by a previous consultant from the baso of the tank excavation <br /> (see Figure 3) and analyzed for total petroleum hydrocarbons as gasoline <br /> (TPHG); benzene, toluene, ethylbenzene, and total xylenes (BTBX); lead; <br /> and ethylene dibromi.e. The analytical results are summarized in Table 1. <br /> Lead and ethylene dibromide were not detected; however, up to <br /> 30,000 milligrams per kilogram (mglkg) of TPHG and 39 mg/kg of benzene <br /> k were detected in the soil samples. <br /> Based on these analytical results, additional soil was excavated to a <br /> maximum depth of approximately 24 feet. The lateral limits of excavation <br /> ~' were dictated by the existing building and property lines.Additional bottom <br /> u and side wall samples were collected and analyzed by the consultant(see <br /> i Figure 4). These samples were analyzed for TPHG, BTBX, and total { <br /> petroleum hydrocarbons as diessl (TPHD), and selected samples were ` <br /> analyzed for halogenated volatile organic compounds (VOCs). Halo- <br /> genated VOCs were not detected. Detectable concentrations of TPHG or <br /> TPHD were not found ;:1 5 of 14 samples collected from the tank excava- <br /> tion (see Table 2). Of the remaining nine samples, five contained TPHG <br /> and TPHD concentrations less than 10 mg/kg (nos. 1, 2, 9, 10, and 13) <br /> and one contained TPHG and TPHD concentrations between 10 and 100 <br /> mglkg (no.3). <br /> Based on the concentration of petroleum hydrocarbons detected in both <br /> sets of soil samples, the San Joaquin County Department of Public Health <br /> - Services verbally.requested that three ground-water monitoring welts be <br /> installed. BMCON proposed, as an initial step, to install one ground-water <br /> monitoring well within the former fuel tank excavation limits to evaluate the <br /> vertical extent of petroleum hydrocarbon impact beneath the tank excava- <br /> tion,and to evaluate whether ground water has been impacted. <br /> E <br /> i <br /> p19%90519050101d 2 Rev.0 July 2, 1991 <br /> 1 .. <br /> - Mon Associates <br />