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E-22 <br />• There is concern that the production wells could cause water <br />quality degradation to the existing ground water system. In <br />order to prevent communication between the mine zone and the <br />overlying aquifers,, the proposed plan is to cement the well <br />casing from near the mine zone from the shoe upward for 250 feet. <br />The balance of the annular space to the surface will be filled <br />with a high viscosity, bentonite-based, plugging mud. This <br />approach is intended to prevent communication between the mine <br />zone and the overlying aquifers. in addition, the solution <br />mining fluid will be pumped in and out of the well casing in <br />production pipe. The space between the production pipe and well <br />casing will contain pressurized air to prevent mining fluids from <br />occupying the interior of the well casing. This safety measure <br />precludes leakage of mining fluids through the well casing; <br />also, air pressure in the well casing can be monitored to <br />determine well casing failure. <br />A monitoring program is proposed as an additional part of the <br />mine plan (see BLM Volume 6). Wells are in place adjacent to the <br />production wells to monitor water quality changes. If any <br />leakage from the solution mine zone is detected, remedial action <br />could be taken. <br />As previously described, the evaporation/process retention ponds <br />are lined ponds. The ponds, which contain high TDS water, have a <br />dual liner system that incorporates a drain blanket with a <br />• <br /> <br />