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<br />1LifNED LAND RECLAMAT,CN D;4;5;uN <br />Depanmem of Natural Resources <br />1313 Sherman St.. Room 215 <br />Denver. CO 80203 <br />303 866-3567 <br />FAX: 303 8328106 <br />DATE: May 1, 1992 <br />T0: Bruce Humphries <br />FROM: Harry Posey iR"~ <br />_, i <br />.~ ..-.. ~ ~, ~ ~ OII.,oRADO <br />^~ J~'[p? <br />re -~ <br />.`~"~98 <br />~/8 ]6~ <br />~~ Ray Ramer, <br />Govema <br />Michael B. Lang, <br />Divivon Director <br />RE: Fate of Cyanide in the Battle Mountain, San Luis Project <br />process; M-88-112 <br />Jim Stevens and I met with BMG Consultant Cliff Shutt on Monday, <br />April 27, and had other conversations with BMG mine personnel Ron Zumwalt <br />and Rich Neu and BMG consultant Art Lefler on April 29. A pertinent part <br />of those conversations is reviewed here. <br />NaCN is added to the leach tanks at the rate of about 0.5 gallons pe~ ton <br />of ore. Prior to the use of cytox, the cyanide was to have been <br />recovered from the process as NaCN by adding NaOH to the HCN gas that was <br />liberated from the AVR. However, this process has failed. <br />Between the AVR tank and the first leach tank the mill measures the <br />amount of HCN (gas) from the AVR that is converted to NaCN (liquid) rior <br />to re-entering the leach tanks. Throughout the mine's operation, th <br />amount of NaCN that has been recovered has been approximately 10 gallons <br />every three days. Thus, BMG and their consultants believe that, wit out <br />cytox, the majority of the cyanide added to the cyanidation process t <br />the beginning of the mill stream has not been recovered. <br />This means that virtually ail of the cyanide that went into the tailings <br />stream prior to April 8 (the date cytox was first added) was vented,iby <br />natural processes, to the atmosphere. <br />I contacted MSHA (Dick Durand, Industrial Hygienist; Metals and <br />Non-metals; 303/231-5465), and asked about regulatory or safety limits on <br />free cyanide in tailings ponds and in the air above the tailings. His <br />was not concerned with the air (the molecular weight of air is about 29 <br />whereas that of HCN is 27, so cyanide gas should "float" on air). He <br />said MSHA has no standard for free cyanide in tailings impoundments, but <br />suggested contacting EPA to check on regulatory or danger levels. Their <br />standard deals with NaCN. <br />Whether these quantities are dangerous or just how dangerous they a e I <br />believe should be considered prior to approving further milling and r <br />these conditions. We should seek assurance from 8MG and, perhaps, he <br />health department or EPA, that these levels are non-toxic by br-eatting. <br />cc: Larry Oehler <br />Jim Pendleton <br />Allan Sorenson <br />:im Stevens <br />