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3222 Vertical Extent <br />' <br /> Samples from HB-20, indicated the presence of TPH-g, ethylbenzene, and <br /> xylenes from the ground water table (approximately 7 feet bgs) to a depth <br /> of approximately 22 5 feet bgs For the samples collected at depths greater <br />' than 22 5 feet bgs, xylenes were the only compounds detected The <br /> presence of TPH-g, ethylbenzene, and xylenes from the ground water <br /> table to 22.5 feet bgs are associated with shallow ground water in the <br />' vicinity of UST-2 <br />' As shown in Table 4,TPH-g, ethylbenzene, and xylenes were detected in <br /> the ground water sample collected at 10 to 15 feet bgs These compounds <br /> were detected at trace concentrations in the ground water sample <br /> collected at 30 to 33 feet bgs However, the concentrations of these <br /> compounds at the 30 to 33 feet bgs depth are orders of magnitude below <br /> those detected at 10 to 15 feet bgs <br /> The vertical sampling results are consistent with the h dro eolo of the <br /> P g Y g gY <br /> site As discussed previously, clayey soils extend to a depth of 15 to 20 <br /> feet bgs These soils are underlain by sandy soils The elevated <br /> concentrations of TPH-g, ethylbenzene, and xylenes are present at depths <br /> that correspond to those of clayey soils The concentrations of TPH-g, <br /> ethylbenzene, and xylenes in the deeper sandy soils are either not <br /> detectable or orders of magnitude less than those in the clayey soils <br /> 33 CONCLUSIONS <br /> 331 Sail <br />' Data collected during the investigation confirm that the source of <br /> compounds have been removed from the site Based on the limited extent <br />' of the relatively low remaining TPH-g concentrations, and the lack of <br /> benzene in the soil samples (except at HB-11), the remaining petroleum <br /> hydrocarbon constituents in soil do not represent a significant threat to <br />' ground water or human health Based on the low permeability site soils <br /> and the existing pavement of the surface above the soils, little or no <br />' infiltration of water will occur through the soils to ground water Due to <br /> the existing pavements, direct contact with the remaining chemicals is <br /> mitigated Therefore,further remediation is not required for soils <br /> surrounding the former UST locations <br /> f <br />' 10 <br />