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The Leadville Mill <br />M 1990 -057 <br />EXHIBIT C — MILL PLAN <br />Page 4 -9 <br />• The same 4.6ac TSF is utilized. <br />• The pond excavation at a maximum 21ft depth does not impact the known <br />aquifers at 80 -100ft below the surface. <br />• The TSF embankment will be constructed from available onsite soils borrowed <br />from the tailings disposal area as outlined in the recommendation of CTL <br />Thompson, Inc., Permeability Study, April 10, 1990, presented as Appendix 15- <br />2, and Slope Stability Evaluation, July 8, 2011, presented as Appendix 15 -5. <br />• The TSF will be constructed as a zero discharge facility with 3ft of freeboard in <br />accordance with the Probable Maximum Precipitation Estimates - United <br />States between the Continental Divide and the 103rd Meridian. <br />• Non disturbed drainage is diverted around the TSF while disturbed area <br />drainage from the mill area disturbance reports to the TSF. <br />• The observation well down gradient from the 4.6ac TSF area will be <br />maintained in its current location and monitored. <br />• Topsoil, in accordance with the topsoil plan will be removed and stockpiled. <br />Additionally, the proposed TSF design will encompass: <br />• Stability analysis initiated by CTL Thompson, Inc. May 12, 2011, on samples <br />collected from the existing compacted fill embankment, 2 additional holes <br />drilled to compliment and confirm the 1990 permeability test hole data <br />(Appendix 15 -2), and the CTL Thompson Letter Report of July 8, 2011 <br />(Appendix 15 -5). Subsequently, CTL Thompson issued an update to the July 8, <br />2011 Report, presented as Appendix 15 -6, Response to CDRMS Slope Stability <br />Evaluation, dated September 1, 2011. <br />• A 2.5:1 (horizontal to vertical) outside face and a 2:1 interior face <br />embankment dam with a berm 12ft wide at the crest. <br />• A geosynthetic clay liner of 1 x 10 -6 cm /sec permeability (or less), or equivalent <br />material liner. <br />• A seepage /leak detection drainage net system between the geosynthetic clay <br />liner and the 45 -mil polypropylene geomembrane with the collection sump <br />located in the northwest corner of the impoundment, and the pond bottom <br />sloping at 0.5% to the northwest. <br />• A synthetic pond liner of 45 -mil polypropylene geomembrane or equivalent. <br />• Compaction testing during construction. <br />Version 1.0 April2013 <br />