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The results of the ground water samples collected at the site revealed <br /> concentrations of TPH-g and BTEX compounds in shallow ground water <br /> unmediately downgradient of each UST The results further show a <br /> significant decrease in concentrations with depth and a limited extent of <br /> migration This can be a direct result of 1) the low permeability of site <br /> soils, 2) the removal of the source in soil, and 3) the termination of the use <br /> of the tanks in the 1960s <br /> CONCLUSIONS <br />' The results suggest that, by removing the two USTs and excavating <br /> impacted soils around each former tank location, the majority of soil <br /> containing TPH-g and BTEX compounds has been removed from the site, <br /> thus minimizing and limiting health risks <br />' In an effort to further reduce the concentration of benzene and TPH-g, <br /> remedial action can be considered for shallow ground water in the area <br /> immediately downgradient of the USTs It should be noted that, based on <br /> the lirruted extent of migration since release, the low permeability of site <br /> soils, the presence of existing site pavement, and the removal of the source <br /> in soil, it is unlikely that these compounds will significantly threaten on- <br /> site activities or will migrate off-site <br />' EVALUATION OF GROUND WATER REMEDIATION TECHNOLOGIES <br />' To address the conclusions presented above, ERM evaluated available <br /> ground water remediation technologies to determine the Best Available <br />' Technology for reducing the concentrations of TPH-g and BTEX <br /> compounds in ground water at each former UST location Based on this <br /> evaluation, Enhanced Biodegradation was selected because the low <br />' permeability of the site soils will inhibit the effectiveness of other <br /> technologies By injecting oxygen releasing compound (ORC) at multiple <br /> locations, effective remediation of the ground water at each former UST <br />' location can be accomplished <br />' FUTUREACTTWHES <br />' To implement the use of enhanced biodegradation, ERM proposes to <br /> perform the injection of ORC at Iocations immediately upgradient and <br /> downgradient of each former UST location To monitor the reduction of <br />' TPH-g and BTEX in ground water following the application of ORC, a <br /> ground water monitoring program will be implemented <br /> 1 Vi <br />