1998-01-10_REVISION - M1988112 - Laserfiche WebLink

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1 BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT CMLRD ADEQUACY LETTER RESPONSES Page 4 of 28 t 8. The results of the depositional modelling tests as to expected cyanide concentrations in the tailings have not yet been submitted. As mentioned on page D-29, this information should be submitted for incorporation in the amendment review process. RESPONSE: In determining the best method for treatment of the tailings slurry ~., BMR evaluated a number of different alternatives. The depositional ,~ modelling box tests were performed on slurry which had been treated ~~ using a different method than the currently proposed slurry treatment. Upon closer evaluation BMR determined that this alternative method was not suitable for treatment of the San Luis 1 tailings. Although the different treatment will not affect the geotechnical characteristics of the tailings, it will have an affect on the geochemical characteristics. The numbers derived from these tests are therefore not valid for information related to expected cyanide concentrations in the slurry at disposal. For information on the expected cvanide concentrations in the slurry at disposal, see Attachment 1. ' 9. The results of the tailings geochemical test program have not been submitted as noted on page D-31. The results of the geochemical testing (Appendix fJ should be provided. In addition, any modifications to the analytical testing or ore processing being mode])ed which would affect geochemical characteristics of the tailings between original permit approval and the amendment proposal should be discussed. This discussion should consider expected concentrations of cyanide, salts, metals, and acidity of both tailing solids and Ieachates. RESPONSE: The results of the geochemical test program are included with this submittal as Attachment I. The geochemical test program is the same program performed on the approved permit tailings sample. ' The ore processing proposed for the amendment includes processing of all ore by carbon-in-leach. The approved permit calls for processing one half of the ore by heap leaching and one half of the ' ore by flotation with carbon-in-leach of the concentrates. The carbon-in-leach tailings were to be rinsed with fresh water and mixed with the flotation tailings. The combined tailings were to be dewatered and then disposed by mixing the dry tailings with waste rock. The milled ore in the amendment will be treated with sulfuric acid to lower the pH and volatilize free cyanide and then disposed in a slurry form in the lined tailings impoundment. The major difference geochemically between the two processes is the addition of sulfuric acid. The sulfuric acid will reduce the tailings pH and slightly increase sulfate levels as shown on the data included as Attachment I.