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tailings disposal capacity for a more efficient concentrating system and increased tails reporting to the <br />TSF. The historical Phase 1 TSF embankment compaction is inadequate for current production requiring <br />complete removal of the existing embankment and reconstruction of the TSF facility with a lined facility. <br />The reconstruction honors the original permit parameters as follows: <br />• The same 4.6 acre tailings disposal facility (TSF) is utilized. <br />• The pond excavation at a maximum 21 ft depth does not impact the known aquifers at 80 -100 ft <br />below the surface. <br />• The tailings impoundment dam will be constructed from available onsite soils borrowed from the <br />tailings disposal area as outlined in the recommendation of CTL/Thompson, Inc., Consulting <br />Geotechnical and Materials Engineers, Permeability Study Tailing Pond Area, April 10, 1990, <br />presented as Appendix A, Slope Stability Evaluation Tailings Pond Embankment and Future <br />Tailing Slope, July 8, 2011. <br />• The TSF will be constructed as a zero discharge facility with 3 ft of freeboard in accordance with <br />the Probable Maximum Precipitation Estimates — United States Between the Continental Divide <br />and the 103`d Meridian. <br />• Non disturbed drainage is diverted around the TSF while disturbed area drainage from the mill <br />area disturbance reports to the TSF. <br />• The observation well down gradient from the 4.6 acre TSF area will be maintained in its current <br />location and monitored. <br />• Topsoil, in accordance with the topsoil plan will be removed and stockpiled. <br />Additionally, the proposed TSF facility further commits to: <br />Stability analysis initiated by CTL Thompson, Inc. May 12, 2011, on samples collected from the <br />existing compacted fill embankment, 2 additional holes drilled to compliment and confirm the <br />1990 permeability test hole data, and the CTL Thompson Letter Report of July 8, 2011, presented <br />as Appendix A, Slope Stability Evaluation Tailings Pond Embankment and Future Tailing Slope, <br />July 8, 2011. Subsequently, CTL Thompson issued an update to the July 8, 2011 Report, <br />presented as Appendix B, Slope Stability Evaluation Tailings Pond Embankment and Future <br />Tailing Slope, August 17, 2011. <br />• A 2.5:1 (horizontal to vertical) outside face and a 2:1 interior face embankment dam with a 12 ft <br />wide crest berm. <br />• A geosynthetic clay liner of 1 x 10 -6 cm/sec permeability (or less), or equivalent material liner, <br />installed with the leak detection drainage net system and the 45 -mil polypropylene geomembrane. <br />• A seepage /leak detection drainage net system between the geosynthetic clay liner and the 45 -mil <br />polypropylene geomembrane with the collection system located in the northwest corner of the <br />impoundment, and the pond impoundment bottom 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 />M1990 -057 May 14, 2013 <br />