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STATE SF' C LORADO <br />MINED LAND RECLAMATION DIVISION ~t r:o~o <br />Department of Natural Resources ', „Qr`-~_-~-_-er~9 <br />Pi <br />1313 Sherman SL, Room 215 ~~ .~.~ ~,a ~ . <br />Denver, CO 80203 +'~~. <br />303 666-3567 'raga' <br />FA x: 303 832-8106 <br />Roy Romer. <br />Governor <br />Michael B. Long, <br />Division Director '. <br />DATE: April 5, 1992 <br />T0: Larry D. Oehler \ <br />FROM: Jim Pendleton/7. Lz~~'"~ <br />RE: "Technical R or" t roposal - Cyanide Detoxification atSan Luis" <br />Response to 3/31/92 NOPV <br />Preliminary Technical Revision Application <br />Battle Mountain Gold (Permit No: M-88-112) <br />I have reviewed the chemical engineering study referenced above. B iefly, the <br />report discusses five possible remedial actions to be used to reduc the <br />cyanide content within the tailings slurry at the Battle Mountain G ld (BMG) <br />mine near San Luis. The report was prepared for BMG by BEI Enginee s / <br />Constructors Inc. (BEI), consultant to BMG. The conclusion of the eport is <br />that the preferred method for detoxification of the tailings is thr ugh the <br />use of "Cytox" chemicals, which are a proprietary product marketed y BEI. <br />The report presents data which projects relatively rapid reduction f the <br />cyanide within the slurry through the application of the "Cytox" ch micals. <br />"'Cytox' (derived from ~anide detoxification) is a ferrous sulphat compound <br />'stuffed' with differing levels of zinc." BEI represents "Cytox" t be an <br />improvement over the relatively common Ferrous Sulphate process. T e drawback <br />of the Ferrous Sulphate process being that the end product is "highly soluble" <br />in comparison to the "totally stable" end product of the "Cytox" process. <br />Discounting BEI's choice of descriptive language within its proposal / report, <br />the data suggests that the "Cytox" chemicals do result in a more st ble end <br />product precipitate than the more common Ferrous Sulphate process. However, <br />BEI does include cautions within its report. The data presented was collected <br />under laboratory conditions. BEI also observes that the source of G's <br />problem is probably an excess of Copper, resulting from the unexpect d Copper <br />content of the San Luis ore. BEI projects that methodology could be developed <br />to remove the excess Copper levels from the tailings slurry. Finall BEI <br />projects that a long term slurry treatment could be implemented to m~intain <br />low cyanide and Copper levels in the tailings slurry. <br />In the interest of eliminating the potential hazard represented by t e <br />existing elevated cyanide levels in the BMG tailings, I recommend th t we <br />approve the use of the proposed "Cytox" process. We must require BM conduct <br />thorough monitoring of the process to verify the final result. Furt er, we <br />should caution BMG of their responsibility to solve any environmental <br />