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_:i <br />Page 2 <br />Mr. James C. Stevens <br />April 1, 1992 <br />expeditious free cyanide reduction is a necessary step to <br />minimize potential waterfowl mortality. <br />Concerning your question regarding the effect the <br />precipitate will have on tailings permeability, we spoke with <br />BEI about this, and it was their opinion that forriation of <br />precipitates should not adversely affect tailings permeability, <br />i.e., reduce the permeability because the precipitates repre- <br />sent an insignificant volume in relation to the volume of <br />tailings being deposited. <br />BEI has provided CMLRD with information on the use of zinc <br />ferrous sulfate in detoxifying cyanide solution. Attached is <br />the additional information as you have requested. <br />BMR is evaluating the performance of the AVR system with <br />respect to its cyanide detoxification efficiency. Other <br />detoxification systems, including the use of zing ferrous <br />sulfate, will also be evaluated for longer term detoxification. <br />When BMR has determined the preferred long term detoxification <br />system, detailed information will be submitted for your <br />consideration. BMR expects the final testing resu~its to be <br />available within 60 to 90 days. <br />BMR appreciates your assistance in working with us to <br />resolve this situation. <br />Regards, <br />~-9 ~~! <br />Andre J. Do hane <br />General Manager, <br />North American Operations <br />AJD:dsw <br />920331B <br />cc: B. <br />T. <br />L. <br />R. <br />A. <br />G. <br />Humpries/CMLRD <br />Schreiner/CMLRD <br />Oehler/CMLRD <br />Quinn <br />Douchane <br />Dodson <br />