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~ ' Fxl~ibi~ 3 <br />~" i i <br /> BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT ~I <br /> CMLRD ADEQUACY LETTER RESPONSES <br /> <br />I Page 4 of 28 <br /> <br />~ 8. The results of the depositional modelling tests as o expected <br /> ~ <br />cyanide concentrations in the tailings have not yet been submitted. <br />~ As mentioned on page D-29, this information should be su mitted for <br /> incorporation in the amendment review process. <br />1 RESPONSE; In determining the best method for treatment of the tail ings slurry <br /> BMR evaluated a number of different alternatives. The d epositional <br /> modelling box tests were performed on slurry which had b een treated <br /> using a different method than the currently propa ~sed slurry <br />1 treatment. Upon closer evaluation BMR determined that this <br /> alternative method was not suitable for treatment of t e San Luis <br /> tailings. Although the different treatment will not affect the <br /> geotechnical characteristics of the tailings, it will ha a an affect <br /> on the geochemical characteristics. The numbers derive from these <br /> tests are therefore not valid for information related to expected <br />r cyanide concentrations in the slurry at disposal. for information <br />i on the expected cyanide concentrations in the slurr t dis osa <br /> see Attachment 1. <br /> 9. The results of the tailings geochemical test program h ve not been <br /> submitted as noted on page D-3I. The results of the geochemical <br /> testing (Appendix F) should be provided. In ad ition, any <br /> modifications to the analytical testing or ore proc ssing being <br /> mode]]ed which would affect geochemical characteris ics of the <br /> tailings between original permit approval and the amendm nt proposal <br /> should be discussed. This discussion should consid r expected <br /> concentrations of cyanide, salts, metals, and acidity of oth tailing <br /> solids and leachates. <br /> RESPONSE: The results of the geochemical test program are includ d with this <br /> submittal as Attachment I. The geochemical test progra is the same <br /> program performed on the approved permit tailings samp e. <br /> <br /> The ore processing proposed for the amendment include processing <br /> of all ore by carbon-in-leach. The approved permi calls for <br /> processing one half of the ore by heap leaching and on half of the <br /> ore by flotation with carbon-in-leach of the conce trates. The <br /> carbon-in-leach tailings were to be rinsed with fresh wa er and mixed <br /> with the flotation tailings. The combined tailings were to be <br /> dewatered and then disposed by mixing the dry tailing with waste <br /> rock. <br /> The milled ore in the amendment will be treated with ulfuric acid <br /> to lower the pH and volatilize free cyanide and then i sposed in a <br /> slurry form in the lined tailings impoundment. The maj r difference <br /> 9eochemically between the two processes is the additio of sulfuric <br />acid. The sulfuric acid will reduce the tailings pH and slightly <br /> increase sulfate levels as shown on the data included s Attachment <br /> 1. <br /> <br />~~ <br /> <br />