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<br /> <br /> <br /> <br /> <br />lJ <br /> <br />t <br />~J <br />24. As proposed, the tailings will be disposed behind a berm constructed <br />in the South Waste Rock Disposal facility. A method of combining waste <br />rock and tailing by layering the two is described in the mine plan. Was <br />consideration given to modeling the effluent from the combined waste <br />rock/tailings in a separate leachability test? We would suggest that <br />a humidity cell test be run on this combined material. If this is not <br />done, an explanation as to how the geochemical characterization data <br />can 6e interpreted to project effluent quality from this combined <br />disposal area with a reasonable degree of certainty must be provided. <br />Response: Combined testing has been performed for each of the three major <br />waste rock types. The test results have been incorporated into <br />the text and added to Appendix F. As can be seen from the tests, <br />no acid production will occur from the combined material. The <br />test of mixed Santa Fe Conglomerate and tailings showed an <br />initial pH level of 3.01 and moderately high conductivity and <br />acidity. These results do not appear to be consistent with any <br />of the test results generated to date on any of the materials <br />tested and may be a result of laboratory error. A batch test was <br />run on the combined material to try to duplicate the results of <br />the humidity cell test. The batch test data indicated a neutral <br />pN. The humidity cell test will be rerun to determine if <br />laboratory error resulted in this anomaly. <br />Final results of the test reruns added to Appendix F 4/20j8g. <br />t Section D.7.3.2 Geochemical Characteristics <br />~I <br />J <br />ri <br />u <br />1 <br />ICI <br />L. <br /> <br />n <br />L <br />t <br /> <br />25. Please describe the processing and rinsing methods, concentration of <br />chemicals utilized, duration, etc. of the heap material prior to water <br />quality analyses for geochemical characterization. This infmrmation <br />would be useful in determining post leaching effluent quality <br />)imitations. <br />Response: San Luis ore, agglomerated with Type 3 portland cement, wa.; <br />placed in a 3 inch diameter column. A dilute sodium cyanide <br />solution containing 1.0 pounds of sodium cyanide per ton of <br />solution was circulated through the ore at an application rate <br />between 0.005 and 0.01 gallons per minute per square foot. The <br />solubilized precious metals were removed from the solution by <br />activated carbon. Circulation of the solution continued until <br />recovery of the precious metals diminished to an uneconomical <br />rate. At the conclusion of leaching, the solution flow way <br />stopped and the column was allowed to drain for 16 to 24 hours. <br />The column was rinsed with one to four bed volumes of fresh <br />water. Rinse solutions were submitted for analysis. <br />In addition, as described in Appendix F, the tailings and heap <br />leach ore samples were split upon receipt at Core Laboratories. <br />One sample was tested as is and the other sample was subjected <br />to additional rinsing and then tested. The split was subjected <br />to additional rinsing in an attempt to model the geochemical <br />characteristics after all of the hydroxides had been rinsed out <br />LJ <br />