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0 <br /> <br />d. Tot a1 WAD (true WAD plus Free cyanide) shall not exceetl 40~ ppm under the <br />following formula: <br />True WAD + 1.3 Free CN = 40 ppm <br />5. The Modified Tailings <br />The writer refers to the penultimate paragraph, page 2 of Doc. Np. 2382F. <br />BEI presumes that Dr. Pendleton's astute observations refer to; <br />a. Potential acidity increase in the tailings ("modified tailings"). <br />b. Potential increase of metal-cyanide (WAD) complexes in thq tailings. <br />These concerns are real and have been addressed by BMG, 6EI, and OtF. Adrian Smith <br />and are here below reviewed: <br />A. Acidity <br />By introducing an acidic (and acid-generating) compound, ytox, one was <br />concerned about the potential of generating reaction-prod cts that could <br />turn the tailings acidic, before, during, or after, retie at ion. <br />Two reviews have been conducted so as to assure BMG antlISEI that this <br />shall not occur <br />Review 1 Today, BMG is permitted to use an AVR system hat uses 2 lbs <br />of HZSOd per ton of milled ore. This condition has been <br />approved by the state as "safe" in terms of acidity. The <br />introduction of Cytox shall be in-place of H2 0~ 1n the AVR. <br />Barringer Labs of Golden, Colorado, have confir ed the acidity <br />of Cytox as 235 tons per 1000 tons of Cytox tom grad to 20,000 <br />tons per 1000 tons of H2SO4. A change in chemicals, <br />therefore, shall reduce acidity. <br />Review 2 "Core Laboratories" has determined that the ~se of "Cytox" <br />shall provide the San Luis operation with 9.2 tons of acid- <br />neutralizing potential per 1000 tons of tailin s and thus one <br />cannot expect the tailings to "go acid." <br />B. Potential Increased WAD <br />99x of the WAD complexes at San Luis are Cu WAD; a parti ularly suspect <br />WAD. Copper WAD's are especially problematic since it is and to destroy <br />them in normal mine operations because e11 solutions have a high pH, and <br />yet they can break down relatively easily after reclamati n when pH can <br />become acidic. <br />A metals analysis of the tailings at San Luis suggests th t the only WAD <br />is that of copper. Without treatment it would reside in he tailings at <br />closure and thus cause concern. BMG and BET are current y developing a <br />process to remove Cu WAD which is expected to be available ithin 30 days. <br />Thus we consider this potential future problem to be relatively',insignificant. <br />_ ... ~ <br />I <br />