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BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT CMLRD ADEQUACY LETTER RESPONSES Page 4 of 28 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 d positional modelling box tests were performed on slurry which had b en treated using a different method than the currently propo ed slurry treatment. Upon closer evaluation BMR determined that this alternative method was not suitable for treatment of the San Luis 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 iio expected cyanide concentrations in the slurry at disposal. For nformation on the exoected cvanide concentrations in the slurry a disposa~ 9. The results of the tailings geochemical test program ha a not been submitted as noted on page D-31. The results of the eochemical testing (Appendix F) should be provided. In add tion, any modifications to the analytica] testing or ore processing being modelled which would affect geochemical characterist cs of the tailings between original permit approval and the amendme t proposal should be discussed. This discussion should conside expected concentrations of cyanide, salts, metals, and acidity of b th tailing solids and leachates. RESPONSE: The results of the geochemical test program are included with this submittal as Attachment 1. The geochemical test program s the same program performed on the approved permit tailings sampl . The ore processing proposed for the amendment includesiprocessing 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 wat rand mixed with the flotation tailings. The combined tailings ere to be dewatered and then disposed by mixing the dry tailings with waste rock. The milled ore in the amendment will be treated with su furic acid to lower the pH and volatilize free cyanide and then di posed in a slurry form in the lined tailings impoundment. The major, difference _J geochemically between the two processes is the addition pf sulfuric acid. The sulfuric acid will reduce the tailings pH apd slightly increase sulfate levels as shown on the data included as Attachment 1.