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D.4.4 Underground Mining Methods <br />This 112 Permit application addresses proposed activities including rehabilitation of the existing <br />mine workings, extension of the underground declines and laterals further to the south, re- <br />establishment of the mine ventilation, and construction and reclamation of surface facilities. <br />These proposed activities are generally limited to those surface areas that were previously <br />disturbed. <br />The ore will be mined using a modified room-and-pillar system. This mining method is a <br />common method for mining in uranium-bearing sandstone and is designed to follow the irregular <br />configuration of the individual ore bodies. The ore seams vary in height with an average seam <br />thickness of approximately 4 to 5 feet. The waste-to-ore ratio also varies depending on the <br />thickness of splits within the ore seams. <br />The main decline system consists of a single 12-foot high by 12-foot wide decline. The decline <br />currently extends approximately 4,000 feet into the Salt Wash Member ofthe Morrison <br />Formation at a nominal 1 percent dip. The area of existing development averages about 500 feet <br />below the ground surface with maximum depths of 800 feet below the ground surface in the <br />southern end of the mine. <br />The mine will be developed to ultimately support a maximum ore production rate of <br />approximately 5,000 to 6,000 tons per month. Laterals will be driven to the east and west as the <br />decline advances in a southerly direction. The laterals will be driven through known ore-bearing <br />zones to provide access for production mining and will be 12 feet high by 12 feet wide. The <br />laterals also provide access for geologic mapping, long-hole drilling, rib scanning, and collecting <br />samples. These geologic data will be used to develop detailed mine planning and stope <br />development for each lateral. <br />Rehabilitation of the Topaz Mine has already begun. Vent hole T-1 (Figure C-])has been <br />installed to provide adequate ventilation to the mine decline. Additional ventilation will be <br />provided by installing the proposed vent holes (T-2 through T-6), as mine development extends <br />southward. During the life of the mine, Denison will evaluate additional locations for vent holes <br />within the permitted project area and includes an additional 12.2 acres in this permit conversion <br />to cover any future disturbance in undefined areas within the permit boundary. Figure C-3 shows <br />the proposed locations of five new vent holes (T2 through T6). <br />5-18-2007 Exhibit D Mining Plan D-l l <br />