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R10/71-51-1C <br /> A "No Action" alternative is not applicable for the Caltrans Shop 10 facility because <br /> groundwater contaminants impact a potential potable aquifer at concentrations that <br /> exceed DOHS action levels and EPA MCLS for benzene and toluene <br /> Excavation and removal of any remaining contaminated sal in the gravel area should first <br /> be initiated If a building will be built over the area now contaminated, this should help <br /> retarding the downward flow of the contamination as the area will be capped and water <br /> percolation from rains and surface run-off will be minimized <br /> In any case, a groundwater extraction need to be initiated in order to prevent further <br /> spread of the contamination At least one extraction well should be located adjacent to <br /> the former tank location At present, a relatively "clean zone" of soil exists between the <br /> present groundwater level of approximately 68 ft below grade up to approximately 55 ft <br /> below grade within the vicinity of the former tank location If groundwater does not rise <br /> above 55 ft below grade, and if the surface soil is adequately capped (as with the <br /> construction of a building above it), little downward movement of contaminants should be <br /> expected <br /> 1 <br /> 48 <br />