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3 UNDERGROUND OPERATIONS <br /> Most activity at the Revenue Mine will take place underground. This includes mining of ore, <br /> transport of ore and waste rock, placement of waste rock and processing of ore in the mill. A <br /> summary of underground activities is presented below. <br /> 3.1 Drifts and Tunnels <br /> Accessible drifts and tunnels at the Revenue Mine were driven on roughly 0.5%uphill grade <br /> from the portal over 100 years ago and are 8' x 8' in size with a 24-inch-wide set of 40 lb rail on <br /> the left side of the opening and a drainage ditch on the right side. The main Revenue tunnel was <br /> driven primarily through the San Juan Formation host rock to access several veins. This drift is <br /> approximately 7,900 feet long and accesses the Yellow Rose vein,the Atlas/Cumberland Vein, <br /> Terrible Vein,Montana Vein, and the Virginius Vein, as well as a few minor veins. The main <br /> Revenue tunnel basically ends at the Virginius Vein. The main Virginius shaft is located near the <br /> terminus of the Revenue drift. This shaft extends up to the surface at an elevation 12,900 feet. <br /> Power cable, phone lines, compressed air line and ventilation piping is attached over the center <br /> of the track or over the drainage ditch using a messenger cable that is pinned to the back or ribs <br /> with steel I-bolts. The track is secured to 6" x 8" wood ties on 5' centers with additional support <br /> in the form of steel ties every 10 feet. Between the ties and the ditch, the sill is filled with ballast <br /> material (broken waste rock) to stabilize the track. Most of the openings are created using <br /> handheld rock drills (air powered)to drill a pattern of holes that are then loaded with explosives <br /> and detonated to break the solid rock into manageable size pieces. The broken rock is then <br /> picked up with air powered mucking machines and loaded into mine cars and hauled outside <br /> with electric locomotives where it is placed on the Temporary Waste Rock Pile. This type of <br /> development work is done in host rock that contains little or no mineralization. If a drift or <br /> opening is driven on a vein or structure, the material is sampled at close spacing and assayed for <br /> elements that may contain value,mainly gold, silver, lead, copper and zinc. If it is determined <br /> that the broken material contains value, it is diverted to the mill for processing. <br /> 3.2 Raises <br /> Raises are vertical tunnels used to access the blocks of ore in the vein. Most of the raises in this <br /> mine were created either as "bald headed" or using an air powered Alimak climber and air <br /> powered drills. Once the opening is completed it is typically lined with rough cut timbers secured <br /> to the walls and ladders are installed so personnel can move up and down from level to level. In <br /> the larger opening there is usually an electric powered hoist with a cage (elevator)to move <br /> personnel and equipment. Some raises may be installed via raise boring. In this method a <br /> powerful drill machine bores a hole from an upper elevation (or the surface)to an appointed <br /> location where there is a large cutter head (4' — 8') attached to the rods, it is then pulled back up <br /> to the starting point whilst reaming the opening to the desired diameter. The opening is then <br /> fitted with steel ladders and landings. A hoist is installed and used to move personnel and <br /> materials up and down. <br /> Excavations in the Revenue Mine will be built using methods similar to those described above. <br /> General equipment used in the mine are slushers (air or electric)to move broken rock into <br /> loading chutes,tuggers (air or electric) to hoist or lower personnel or supplies and diamond drills <br /> Revenue Mine <br /> Amendment 02 D-4 <br /> Updated August 2022 <br />