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3.0 CONSTRUCTION PLAN <br />The mining and ventilation methods that will be employed at the Whirlwind Mine are <br />discussed in general terms in Sections 3.1 and 3.2, respectively. Section 3.3 presents the <br />details of the proposed mine ventilation system and how it will change as the mine is <br />developed. <br />3.1 Mining Methods <br />At the Whirlwind Mine, the ore-body is flat lying and relatively thinly bedded. The ore is <br />also discontinuous and of variable grade, typically occurring in pod-shaped groups <br />separated by waste rock. To efficiently exploit this type of ore-body, a variation of room <br />and pillar mining is used. This variation is referred to as "Random Room and Pillar." In <br />this method, ore is mined from rooms, but pillars are left randomly. The random <br />placement of pillars for ground support is dictated by the occurrence of high grade ore <br />zones and waste rock (i.e., the waste rock is left as pillars while the majority of the ore is <br />extracted). This method provides a high degree of selectivity in mining and allows for <br />the use of rubber-tired, diesel equipment. <br />In the random room and pillar mining method, two phases of excavation occur. First, <br />development drifts are driven to ore zones. These ore zones are located by surface <br />drilling and further delineated by long-hole drilling underground. Development drifts to <br />the ore zones are commonly driven in non-mineralized waste rock and progress rapidly. <br />The waste rock is placed on a waste dump at the surface, or "gobbed" in inactive areas of <br />the mine, as space becomes available. Once development to an ore zone is complete, <br />mining or stoping commences within the ore zone. Rooms are opened up in ore and <br />pillars are created where needed. Ore is transported to the surface for shipment to a mill. <br />The existing Packrat Mine workings, shown in Figure 3, are a good example of what <br />random room and pillar operations look like in plan view. <br />At the Whirlwind Mine, development drifts are planned to be nominally 10 feet in width <br />by 11 feet in height (i.e., about 110 square feet in cross section). Because of the <br />discontinuous and pod-shaped occurrence of the ore, development drifts between major <br />ore zones can be as much as 2,000 feet long. Ore zones are variable in size. To exploit <br />the ore, several stope drifts are driven simultaneously through each ore zone on 40 foot <br />centers. Stope drifts are driven to the far end of the ore zone and widened on retreat to <br />recover nearly 90% of the ore. As the ore is extracted, pillars are left for ground support. <br />The dimensions of a completed stope may be as much as 40 feet across and 100 to 200 <br />5