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' The results of the ground water samples collected at the site revealed Draft <br /> concentrations of TPH-g and BTEX compounds in shallow ground water <br /> immediately 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 ternunation 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 /> contauung TPH-g and BTEX compounds has been removed from the site, <br /> thus nuninuzing 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 limited 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 Bioremediation 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 /> FUTURE ACTIVITIES <br />' To implement the use of enhanced bioremediation, ERM proposes to <br /> . perform the injection of ORC at locations immediately upgradient and <br />' downgradient of each former UST location To track 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 ERM will <br />' vi <br />