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Working To Restore Nature <br /> December 16, 1992 <br /> i Unocal Service Station No 6981, Stockton, California <br /> Hydraulic Control <br /> To minimize the migration of petroleum hydrocarbons from the site, ground water may be <br /> pumped from recovery wells at a minimum rate sufficient to maintain hydraulic control <br /> during the active remediation of soil This technique will reduce the volume of water <br /> pumped and treated compared to a ground-water extraction and treatment system This <br /> reduction in the volume of treated water will allow for the sizing of smaller treatment <br /> systems and provide options which are not economically feasible for larger systems <br /> Ground-Water Extraction and Treatment <br /> Data collected during the pump test indicated a zone of influence of 18 feet This radius <br /> r of influence, however, may be increased by modifying the well construction Extraction <br /> wells could be used to pump hydrocarbon-containing ground water to the surface and then <br /> treated prior to disposal The effects of pumping and treating groundwater for remediation, <br /> however, would be minimal as long as soil containing hydrocarbons remains in place and <br /> in contact with ground water Therefore, we recommend that active remediation of ground <br /> water by extraction and treatment be deferred until the source of the plume, the overlying <br /> hydrocarbon-containing soil, is sufficiently remediated and no longer a source of <br /> 1 hydrocarbons to the ground water <br /> 1 <br /> r <br /> 38032-10 16 <br />