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1 <br /> 1 <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> In sod concentrations of TPH-as- asolin <br /> g e and BTEX appear to decline with distance from the <br />' former UST#3 source area At MW-6, approximately 50 feet west of the former UST, impacts to <br /> vadose zone soil consisted of low concentrations of benzene, ethylbenzene, and xylenes at a <br /> depth of 35 feet bgs Slightly highest concentrations detected in the sod samples collected at 45 <br />' and 55 feet bgs from MW-6 suggest that the soil within the capillary fringe and saturated zones <br /> has been impacted by gasoline compounds migrating in groundwater away from the source area <br /> iIn groundwater, gasoline hydrocarbons are concentrated as free product near former UST#3, and <br /> concentrations of gasoline compounds decrease with distance from the source area As shown <br /> on the isoconcentration maps, the lateral extent of MTBE in groundwater is mostly defined (Figure <br /> 7), and the lateral extents of TPH-as-gasoline and benzene in groundwater remain undefined only <br /> 1 to the west of the source area (Figures 5 and 6) The vertical extent of impacted groundwater has <br /> not been investigated <br /> Based on these conclusions, Ramage Environmental recommends that the previously-approved <br /> remedial feasibility testing tasks be initiated as soon as funding is available The first task should <br /> be the installation of the nested soil vapor extraction well and nested air sparge/soil vapor <br /> extraction well During this drilling work, another groundwater monitoring well should be installed <br /> to the west of MW-6, to further define the lateral extent of impacted groundwater In the <br /> meantime, monthly free product removal and quarterly groundwater monitoring should continue <br /> 1 <br /> 1 <br /> 12 <br />