2011-06-20_REVISION - M1990057 - Laserfiche WebLink

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The TSF was designed as a zero discharge facility. Non disturbed drainage is diverted around the TSF while disturbed area drainage from the mill area disturbance reports to the TSF. An observation well exists down gradient from the 4.6 acre TSF area. CTL/ Thompson constructed an observation (monitoring) well for the TSF area. This April 10, 1990 report, Installation of Observation Hole, is presented as Appendix D. This observation well is shown on Exhibit MLR -1. In October 2001, Leadville Mining and Milling Inc. provided a commitment to CDRMS that the mill would not dispose of any additional mine tailings or other mine related material in the tailing pond until LMMI provides information concerning four conditions to the permit. The conditions included: water rights, air permit for the mill, water monitoring, surface water diversions ditching calculations, and tailing pond compaction results. Current Operations The current mill configuration, process and operations have been modified to treat a different ore than was processed during the last operational period, as described above in the section titled MILL DESIGN AND CAPACITY. This necessitates rephrasing the initial TSF plan to provide tailings disposal capacity for a more efficient concentrating system and increased tails reporting to the TSF. The historical Phase 1 TSF embankment compaction is inadequate for current production requiring complete removal of the existing embankment and reconstruction of the TSF facility with a lined facility. The reconstruction honors the original permit parameters as follows: • The same 4.6 acre tailings disposal facility (TSF) is utilized. • The pond excavation at a maximum 21 ft depth does not impact the known aquifers at 80- 100 ft below the surface. • The tailings impoundment dam will be constructed from available onsite soils borrowed from the tailings disposal area as outlined in the recommendation of CTL/Thompson, Inc., Consulting Geotechnical and Materials Engineers, Permeability Study Tailing Pond Area, April 10, 1990, presented as Appendix A. • The TSF will be constructed as a zero discharge facility with 3 ft of freeboard in accordance with the Probable Maximum Precipitation Estimates — United States Between the Continental Divide and the 103` Meridian. • Non disturbed drainage is diverted around the TSF while disturbed area drainage from the mill area disturbance reports to the TSF. • The observation well down gradient from the 4.6 acre TSF area will be maintained in its current location and monitored. • Topsoil, in accordance with the topsoil plan will be removed and stockpiled. Additionally, the proposed TSF facility further commits to: • Stability analysis initiated by CTL Thompson, Inc. May 12, 2011, on samples collected from the existing compacted fill embankment, 2 additional holes drilled to compliment and confirm the 1990 permeability test hole data. • A 2.5:1 (horizontal to vertical) outside face, and a 2:1 interior face embankment dam with a 12 ft wide crest berm. M1990 -057 June 6, 2011