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The Leadville Mill <br />M 1990 -057 <br />EXHIBIT C — MILL PLAN <br />Page 4 -4 <br />and then into the primary crusher. Undersized material will report to secondary <br />crushing, while oversized material will be sent back to primary crushing. Undersized <br />material from secondary crushing will report to the fine ore bin via belt conveyor. <br />Oversized material will report back to secondary crushing. <br />4.2.2 DUST CONTROL <br />Dust control within the mill facility buildings will be accomplished utilizing a 4,000cfm <br />UAS Dust Hawg horizontal cartridge dust collector. Dust will be managed in the <br />crushing plant by use of a ducted exhaust air system which will draw air and dust <br />down through the crusher and transfer points. Pollutants from the screening, <br />primary and secondary crushing circuits, conveyance systems, and fine ore storage <br />operations will be limited to fugitive particulate matter. Negative pressure <br />ventilation will direct venting to the dust collector to control the flow of fugitive <br />particulate matter during screening and crushing operations. <br />The unit is estimated to operate at air velocities of 3,500- 4,500fpm based on demand <br />and manual control dampers at each collection point. The dust collector is rated at <br />4,000cfm and upgradable to 6,000cfm. The dust control unit is designed to capture <br />28.2tpy crushed ore fugitive particulate matter and an additional 0.4tpy reagent <br />fugitive particulate matter for a combined 165Ib /day at a 99.8% at 0.5µm published <br />design efficiency. The captured dust will be pulse - cleaned off the filters in the dirty <br />air plenum and collected in drums, and returned to the material flow in the grinding <br />circuit. <br />4.2.3 GRINDING CIRCUIT <br />Material from the fine ore bin will be conveyed to the wet grinding circuit via a belt <br />feeder. Lime and water (approx. 8- 10,000g /d) (Section 6.3.3(h)) will be added to the <br />ore and adjusted for pH as necessary to maximize metal recovery (9.5- 11.5). The <br />grinding circuit is comprised of 1 - 5ft dia. x 4ft long Marcy ball mill. The ball mill has <br />a maximum processing throughput of 8tph. <br />The grinding system operates in closed circuit with a classifier to produce a final <br />flotation feed. The oversize will report back to the ball mill resulting in an effective <br />8tph feed. The underflow may pass through a gravity circuit to recover free gold and <br />silver. The remaining material will be fed to the conditioning tank then to the <br />rougher flotation circuit. <br />Version 1.0 April 2013 <br />