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4.2.1 Revenue TSF <br /> The Revenue TSF has a total capacity of approximately 811,000 tons. The Revenue TSF was <br /> constructed in accordance with Section 7 of the Tailings and Waste Rock Management Plan <br /> (July 2015). In general, tailings will be placed in horizontal lifts of no more than 12 inches <br /> moving uphill to create a 3H:1V slope. Every 30 feet vertically, a bench of 10 feet width will be <br /> placed slightly graded to the inside edge of the bench to divert water away from the outside slope <br /> of the pile. <br /> Construction of the Revenue TSF is designed to protect the embankment from damage from <br /> avalanches during the life of the mine. At its full construction, the TSF is expected to be 120 feet <br /> tall from the elevation of Sneffels Creek to the highest point on top. The average height of the <br /> waste pile will be around 80 feet heigh depending on the original topography. However,most of <br /> this height will be provided by the existing material, not new Revenue tailings. The footprint of <br /> the Revenue TSF is shown on Map C-la,with the full pile build out shown on the cross sections <br /> in Map F-3. <br /> It is estimated that this permeable waste rock will constitute the bottom 20-30 feet of the <br /> Revenue TSF. Only the upper portion, as shown on Cross Section A-A' will be comprised of the <br /> combined tailings and waste rock that will be produced from the mining and milling operations. <br /> This upper portion (an additional 30-40 feet)will be compacted, and the lower portion (existing <br /> waste rock)will not since it is important to maintain permeability of this material. The slope <br /> stability of this "double layer" in the pile is addressed in one of the scenarios analyzed in the <br /> Geotechnical Exhibit, which was submitted in Amendment 1 and again as part of TR-15. As an <br /> additional level of protection, the southeast end of the Revenue TSF was built and graded at a <br /> vertical position above the rest of the pile, to create a protective berm against avalanche. <br /> The Galena Slope Stability Analysis Stem was used to calculate factors of safety for different <br /> ratios of waste rock being mixed into the tailings. The Galena software utilizes Bishop's method <br /> of slope stability analysis. Bishop's method only considers moment equilibrium and is suited to <br /> stability problems where a circular failure surface is likely, such as a tailings pile. The different <br /> mixtures of tailings and waste rock result in varying cohesion factors. Benches were not included <br /> in this model because the benches are not placed for slope stability—they are to control <br /> stormwater runoff on the piles. Five different scenarios were created for the Revenue TSF with a <br /> Critical Factor of Safety of 3.0. Five scenarios were also created for the Atlas TSF which <br /> resulted in Factors of Safety between 2.87 and 4.08. Factors of Safety for all scenarios created <br /> are well above the minimum 1.3 required by the Division. <br /> 4.2.2 Atlas TSF <br /> The Atlas TSF has a total design capacity of roughly 300,000 tons. There are jurisdictional <br /> wetlands in this area which have been confirmed. These wetlands were avoided during <br /> construction and will be avoided during placement of tailings and waste rock. The design of the <br /> Atlas TSF is such that the only vehicle access to the pad is away from the wetlands and the pad is <br /> bermed so there is low risk from an operator accidentally placing tailings in or near the wetlands. <br /> Revenue Mine <br /> Amendment 02 D-19 <br /> Updated August 2022 <br />