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50 01/09 t8~ 1`• S 303 935 9941 Ski UENVE P, <br /> <br />BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT <br />CMLRO ADEQUACY LETTER RESPONSES <br />Page 4 of 28 <br />8. The resu]ts of the depositional modelling tests as to expected <br />cyanide concentrations in the tailings have not yet been submitted. <br />As mentioned on page p-29, this information should be submitted for <br />incorporation in the amendment review process. <br />RESPONSE: In determining the best method for treatment of the tai~~ings slurry <br />BMR evaluated a number of different alternatives. The depositional <br />modelling box tests were performed on slurry which had keen treated <br />using a different method than the currently proposed slurry <br />treatment. Upon closer evaluation BMR determined that this <br />alternative method was not suitable for treatment of the San Luis <br />tailings. Although the different treatment will not affect the <br />geotechnical characteristics of the tailings, it will have an affect <br />on the geochemical characteristics. The numbers derlveci from these <br />tests are therefore not valid for information related to expected <br />cyanide concentrations in the slurry at disposal. For information <br />on the expected cyanide concentrations in the slurry at disposal, <br />see Attachment 1. <br />The results of the tailings geochemical test program Nerve not been <br />submitted as noted on page D-31. The results of the geochemical <br />testing (Appendix FJ should be provided. In adoltion, any <br />modifications to the analytical testing or ore processing being <br />modelled which would affect geochemical characteristics of the <br />tailings between original permit approval and the amendment proposal <br />should be discussed. This discussion should considaar expected <br />concentrations of cyanide, salts, metals, and acidity of .loth tailing <br />solids and leachates. <br />The results of the geochemical test program are included with this <br />~~bmittal as Attachment ]. The geochemical test program is the same <br />,•ogram performed on the approved permit tailings sample. <br />e ore processing proposed for the amendment includes pro~r_sing <br />all ore by carbon-in-leach. The approved ~armit calls for <br />p~ucessing one half of the ore by heap leaching and one half of the <br />ore by flotation with carbon-in-leach of the concentrates. The <br />carbon-in-leach tailings were to to rinsed with fresh water and mixed <br />with the flotation tailings. the combined tailings were to be <br />dewatered and then disposed by mixing the dry tailings with waste <br />rock. <br />The milled ore in the amendment will be treated with sulfuric acid <br />to lower the pH and volatilize free cyanide and then disposed in a <br />slurry form in the lined tailings impoundment. The major difference <br />geochemically between the two processes is the addition of sulfuric <br />acid. The sulfuric acid well reduce the tai'ings pH atd slightly <br />increase sulfate levels as shown on the data included as Attachment <br />1. <br />0d <br />