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Cresson Project – AM-11 Adequacy Review <br />Page 6 <br />May 03, 2016 (Revised May 31, 2016) <br /> <br />the values listed on Plate 20 are correct (and the values above for Vadose Zone Acid <br />Generation are corrected to the values listed on Plate 19), then the result of the <br />Acid/Base Accounting Flowsheet on Plate 25 (assuming oxidation of the vadose <br />zone) would be 64 million tons CaCO3 equivalent exiting the Carlton Tunnel (rather <br />than 30 million tons). Please correct or explain this discrepancy. <br /> <br /> Page 24: The text summarizes that “the acid generated by the mined material to the <br />completion of AM-11 will be readily neutralized by the in-situ inventory of calcium <br />carbonate.” And that the “very slow – natural weathering rate – oxidation of the <br />material in the vadose zone can also be accommodated by the system neutralization, <br />providing permanent protection against the flow from the Carlton Tunnel turning <br />acidic.” The rocks of the mining district are, in general, net acid producing with twice <br />as much acid generating potential than acid neutralizing potential, and the system <br />neutralization is based solely on the currently saturated bedrock remaining saturated. <br />Therefore, as mentioned above, if the diatreme water table were to drop, there may be <br />a significant loss in the system’s neutralization potential, potentially creating acid <br />rock drainage at the Carlton Tunnel portal. In this case, there would be no “permanent <br />protection from the flow from the Carlton Tunnel turning acidic”. Have you <br />developed a plan to mitigate impact to Fourmile Creek if this situation were to <br />occur during the operation, or post-mining? <br /> <br />ATTACHMENT 3 – DEEP CARBONATE GEOCHEMISTRY EVALUATION / ADRIAN <br />BROWN <br />Memorandum by Schlumberger Water Services / Task 3 Cripple Creek Deep Carbonate Study <br />Geochemical Modeling Results <br /> <br />2 – Mass-Balance Geochemical Model <br /> Page 2: The text states “The average flow through the system is about 1,660 gpm . No <br />net increase in flow from the Carlton Tunnel is expected as a result of changing <br />surface disturbance patterns in the future.” However, according to the <br />Hydrogeochemistry Evaluation provided by Adrian Brown, dated December 15, <br />2015, there will be an estimated 25% increase in Carlton Tunnel flow during the AM- <br />11 operations. Please explain this discrepancy. <br /> <br /> Page 2: The text states “Prior to the currently ongoing Deep Carbonate (DC) project <br />investigation, water levels in the northern eruptive center were unknown. These have <br />now been measured to be anywhere from 670 to 1,480 feet higher than the elevation <br />of Carlton Tunnel, indicating that the Northern Diatreme is not as well drained by the <br />main diatreme mass (as previously assumed) and that a hydraulic gra dient exists from <br />the Northern Diatreme towards the Carlton Tunnel.” Considering this information, <br />is the current mining plan for the North Cresson Pit (and possibly the <br />underground mine) adequate with regard to potentially elevated water levels in <br />this slower draining portion of the diatreme? <br /> <br /> Page 5: the text states “Once sufficient HCT data become available as part of the <br />ongoing DC project, these will be more representative of sulfide oxidation rates for