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STAT~OF <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman Sl., Room 215 <br />Denver, CO 80203 <br />303 866-3567 <br />FA% 303 832-6106 <br />Ray Romer, <br />Govemm <br />MEMORANDUM <br />TO: Jim Pendleton ~,,~jy{,1 <br />FROM: Harry Posey ~t'~~ <br />RE: Disposition of WAD cyanide in <br />Gold; San Luis Project; Permit <br />August 7, 1992 <br />OF' ~~y0 <br />y~% ~g <br />~~~q7 <br />~ 18]6 ~ <br />Michael 6. Long. <br />Division Director <br />tailings; Battle Mountain <br />No. M-88-112 <br />To answer your request for information regarding the dis osition of <br />WAD cyanide in the tailings at Battle Mountain, please c~nsider the <br />following. <br />WAD cyanide will break down in virtually any acid med'um. Upon <br />failure of the AVR, we have had to consider two acid hydrogen <br />peroxide and sulfur dioxide. Either of these components will react <br />to breaY, down the WAD cyanide molecules creating any of several <br />stable, relatively benign reaction products. <br />The key to destroying WAD cyanide is simply that the tea tants come <br />into contact. Whether by adding Hz02 to the ponds or Oz and air <br />to the process stream, the physical process of mixing th reactants <br />is relatively straightforward. Because the re ction is <br />spontaneous, cyanide breaks down almost immediately afte mixing is <br />achieved. (The blue sheen that reportedly spread cross the <br />tailings ponds after H2O2 was added is indicative of t e speed of <br />the reaction.) <br />The rate of the reaction within the tailings depe~ds on the <br />hydraulic conductivity of the tailings. Consider the s mple case, <br />a density-stratified system consisting of: <br />1. WAD-free process water at the top, <br />2. HZOZ-bearing process water below that, <br />3. mixed HZ02- and WAD-bearing process water farther <br />down, <br />4. WAD-bearing process water even deeper, ~nd <br />5. tailings solids with interstitial AD-bearing <br />process water at the base. <br />Upon adding Hz02 to a static column consisting of WAD-la en process <br />water overlying tailings with interstitial WAD-bearing water, the <br />Hz02 will sink - owing to its higher density - through he column, <br />and react with WAD cyanide en route. Provided the colilmn remains <br />