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UST2--7(benzene 39 mg/kg), no detectable concentrations of benzene <br /> were encountered in these samples <br />' The sample at UST2-7 that contained 14,000 mg/kg TPH-g and 39 mg/kg <br /> benzene was collected along the western wall of the UST-2 excavation As <br /> shown in Figure 3, the western extent of the excavation ended at the footer <br /> wall of the facility Therefore, further excavation in this direction was not <br /> possible Soil samples collected immediately inside the building (HB-11 <br /> and HB-12) on the other side of the building footer contained no <br /> detectable concentrations of TPH-g or benzene in the vadose zone <br /> samples TPH-g was detected at HB-11 at a depth of 8 5 feet bgs, however, <br /> this detection is likely associated with TPH-g in ground water, not soil <br /> because the depth to ground water is approximately 7 feet Therefore,the <br /> extent of TPH-g and benzene in soil west of the UST-2 excavation is <br /> limited <br />' Samples collected beyond the limits of the excavation (HB-13, HB-14, and <br /> HB-20) revealed concentrations of TPH-g ranging from non-detect (HB-20) <br />' to 85 mg/kg (HB-14) No detectable concentrations of benzene were <br /> encountered in these samples, with the exception of HB-14 at 5 feet bgs <br /> (0 11 mg/kg) <br /> 3.2 GROUND WATER <br /> The followingsubsections resent a discussion of the chemical <br /> p <br />' compounds detected m ground water at each UST site Figures 6 and 7 <br /> present the results of the most recent ground water samples collected at <br /> each former UST site Figure 8 presents a ground water surface contour <br />' map for the site <br /> 3.21 UST 1 <br /> 321 1 Lateral Extent <br />' Figures 9 and 10 present the distribution of TPH-g and benzene in ground <br /> water at UST-1, respectively As shown, the concentration of TPH-g and <br />' BTEX compounds downgradient of UST-1 decrease significantly Samples <br /> collected from MW-4 in December 1998 contained 120,000 micrograms per <br /> liter (µg/1) of TPH-g and 490 µg/1 of benzene At MW-1 (approximately <br />' 100 feet downgradient), the concentrations decrease an order of <br /> magnitude to 4,300 µg/I of TPH--g and 49 Mcg/1 of benzene <br /> l <br /> 8 <br />