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feet in length. Individual stopes are separated by larger barrier pillars. Mineable ore <br />encountered within stopes may range from as little as 1 foot to as much as 18 feet in <br />thickness, although the average ore thickness is about 3 feet. Typically, at least 8 feet of <br />ore and waste is removed in the stopes to allow sufficient height for passage of <br />equipment. <br />I Stope mining and development will be conducted by utilizing small, rubber-tired diesel <br />mobile equipment. Drilling of the ore and waste is accomplished with hand-held "jack- <br />leg" drills. Conventional underground blasting techniques are employed. Movement of <br />ore and waste rock is accomplished with diesel equipment, typically Load-Haul-Dump <br />Units (LHD's) and haulage trucks or buggies. At full production, it is anticipated that the <br />Whirlwind Mine will operate two shifts per day and produce about 200 tons of ore per <br />day. <br />3.2 Mine Ventilation Methods <br />The exposure of miners to ionizing radiation (radon-222 decay products and gamma <br />radiation) and diesel particulate matter (DPM) is regulated by MSHA (30CFR 57). To <br />meet the MSHA regulations for ionizing radiation and DPM, mechanical ventilation of <br />i the Whirlwind Mine is required. For relatively low grade mines such as the Whirlwind <br />Mine (average grade of 0.26% U308), the DPM regulatory requirements typically <br />determine the minimum air flow needed to meet MSHA standards. <br />The goal of the mine ventilation system is to provide fresh air to the work areas from one <br />end and exhaust contaminated air out the other end. This is typically achieved by placing <br />exhaust fans where the air leaves the mine (i.e., at exhaust portals and ventilation shafts), <br />although intake fans are also utilized in some cases. Airflows underground are split and <br />directed to the various work areas by booster fans, stoppings, and pressure regulators. <br />Temporary ventilation controls, such as vent tubing and brattice curtains, are used in the <br />active mine areas to allow the air to be channeled directly to the working faces. By <br />controlling the ventilation in this manner, work crew exposure to contaminants can be <br />minimized. <br />To further reduce contaminants from entering the mine ventilation system as well as to <br />reduce the quantity of contaminants being released to the surface, inactive areas and <br />abandoned areas of the mine are isolated from the main ventilation network with <br />permanent bulkhead seals as necessary. Bulkhead seals used to isolate inactive workings <br />are typically constructed of cinder block and concrete. <br />6