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<br />Mr. Bruce Humphries <br />January 3, 2000 <br />Page 2 <br />and groundwater monitoring associated with the Plan. Each of these issues is discussed in <br />further detail in the following subsections. <br />2.1 Hydraulic Control <br />Two groundwater pumping wells are proposed to achieve capture of the downgradient migration <br />of groundwater in the alluvial aquifer that has been affected by historic flow fram the West Pit <br />backfill. Effective containment will "capture" affected groundwater and prevent continued <br />westward migration of the groundwater into unaffected portions of the alluvial aquifer. The <br />location of the proposed containment pumping will be just west of [he existing monitoring wells <br />M-1 IR and M-31. <br />Hydrologic evaluatiars of the alluvial aquifer were conducted to provide the necessary <br />hydrologic information regazding the combined expected flow rate for the pumping wells. The <br />most effective containment system consists of a two-well system that would be located <br />approximately halfway between M-1 ]/11R and M-25/26. These two wells would be pumped <br />continuously at approximately 70 gallons per minute (gpm). <br />BMRI will also assess the potential for accelerating the alluvial aquifer flushing by additional <br />pumping of groundwater upgradient from the hydraulic barrier wells. BMRI would <br />communicate with DMG regarding any plans to initiate additional upgradient alluvial aquifer <br />pumping. <br />2.2 Water Balance and Handling <br />As stated in Section 2.1, effective capture of downgradient Clow in the alluvial aquifer can be <br />achieved by pumping two wells at a total rate of approximately 70 gpm. The water extracted <br />from the pumping wells will consist of a mixture of upgradient-affected groundwater and <br />unaffected downgradient groundwater. Thus, the quality of the water extracted from the alluvial <br />aquifer will probably not meet applicable standards to allow direct discharge to the Rita Seco. <br />