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2 BACKGROUND <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 base of the tank excavation <br /> (see Figure 3) and analyzed for total petroleum hydrocarbons as gasoline <br /> (TPHG); benzene, toluene, ethylbenzene, and total xylenes (BTEX); lead; <br /> and ethylene dibromide. 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 (mg/kg) of TPHG and 39 mg/kg of benzene <br /> 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 /> and side wall samples were collected and analyzed by the consultant (see <br /> Figure 4). These samples were analyzed for TPHG, BTEX, and total <br /> petroleum hydrocarbons as diesel (TPHD), and selected samples were <br /> ianalyzed for halogenated volatile organic compounds (VOCs). Halo- <br /> genated VOCs were not detected. Detectable concentrations of TPHG or <br /> TPHD were not found in 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 /> mg/kg (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 wells be <br /> installed. EMCON 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 /> • <br /> pjglg051g050101d 2 Rev. 0 July 2, 1991 <br /> EMCOn Associates <br />