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March 17, 1999 <br /> Page 4 <br /> Conclusion <br /> Subsurface lxthology across the site consists primarily of sandy silt, silty sand, and sand <br /> Soil samples contain elevated concentrations of TPH-g,benzene, and MtBE The <br /> highest hydrocarbon concentrations in soil were generally detected between 11 and 16 <br /> feet bgs within the capillary fringe zone This depth interval probably corresponds with <br /> the zone of groundwater fluctuation <br /> Groundwater from all of the monitoring wells (MW-1 through MW-4) and Geoprobe0 <br /> GP-1 contained elevated concentrations of TPH-g and benzene Furthermore, <br /> Geoprobe0 GP-1 and wells MW-1 and MW-2 reported elevated levels of MtBE, while <br /> wells MW-1 and MW-2 also reported elevated levels of methanol The highest <br /> dissolved hydrocarbon concentrations were detected downgradlent of the former USTs <br /> in wells MW-1 and MW-2 and GeoprobeO GP-1 Therefore, based on the results of <br /> this investigation, we recommend quarterly monitoring of groundwater for one complete <br /> hydrologic cycle to better determine groundwater flow direction and gradient and to <br /> better determine hydrocarbon impact to groundwater <br /> I <br /> i <br /> i <br />