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ru� <br /> Working to Restore Nature <br /> Table 6 Since monitoring began, the subject site has been downgradient from potential <br /> hydrocarbon sources Potentiometric Maps showing the gradient and direction of <br /> groundwater flow from previous dates are shown in Plate 5 and Plate 6 Groundwater <br /> elevations measured during monitoring events are shown in Table 4. <br /> 5.3 Residual Hydrocarbons and Other Constituents in Soil <br /> The results of subjective and laboratory analyses of soil samples collected from the soil <br /> borings were used to evaluate the lateral and vertical extent of residual hydrocarbons in soil <br /> Plates 7 through 9 show the lateral extent of residual gasoline hydrocarbons in soil, and <br /> cross sections A-A' and B-B' (Plates 3 and 4) show the vertical extent of residual gasoline <br /> hydrocarbons in soil The analytical results of soil samples are in Tables 7 and 8 <br /> Residual gasoline hydrocarbons were detected in soil near the former underground fuel- <br /> storage tanks, adjacent to the dispenser islands, and near the northwest, northeast, and <br /> I <br /> southeast corners of the site. The highest concentrations were detected in soil from 31 to <br /> 41 feet bsg near the edges of the site, not near onsite sources of hydrocarbons <br /> Concentrations of gasoline hydrocarbons (quantified as total petroleum hydrocarbons as <br /> gasoline [TPHg]) ranged from. 11 parts per million (ppm) to 1,704 ppm The highest <br /> concentration of TPHg was detected at boring B-16 (onsite) at the current capillary fringe, <br /> 41 feet bsg, however, the highest concentration of TPHg detected 1n soil offsite was at <br /> boring B-20 at 20 5 feet bsg, above previous capillary fringes <br /> Total oil and grease (TOG), halogenated volatile organic compounds, and polychlorinated <br /> biphenyls were not detected in soil beneath the site (Table 8) Cadmium, chromium, lead, <br /> nickel, and zinc were detected in the sample from boring B-7 Total extractable <br /> hydrocarbons were detected at 7.4 ppm. <br /> 31009-10 8 <br />