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The installation of the silencer will occur within the existing disturbed area. The silencer is essentially a <br />box containing baffles, which will be approximately 31 feet long, 21 feet wide, and 20 feet high. The <br />location of the vent shaft and silencer is shown on Map 24. <br />NW Mains Ventilation Fan Sound Deflector/Absorber (MROS-1921 <br />As part of TCC's ongoing efforts to minimize potential mine impacts on azea residents, a sound <br />deflector/absorber unit will be installed on the NW Mains Ventilation Fan. The unit is designed to deflect <br />fan exhaust, and to both absorb and deflect any associated sound approximately 90 degrees from its <br />current dischazge direction. Installation of the sound deflector/absorber unit will require construction of <br />foundations utilizing concrete piers and concrete grade beams. The foundation will consist of twelve <br />concrete piers (12-inch diameter x 15-21 feet deep), supporting two curved reinforced concrete grade <br />beams (12 inches wide x 2 feet deep x 31-64 feet long), with a reinforced concrete slab between the grade <br />beams. Two concrete piers will be poured on either side of the foundation to provide for side-bracing of <br />the sound deflector(absorber structure. The sound deflector(absorber unit will be a fabricated curved steel <br />structure, lined with sound absorbing material, approximately 12 feet wide x 20 feet high x 45 feet long <br />(along center-line of curvature). <br />Installation of the sound deflector/absorber unit will be on the existing NW Mains Ventilation Fan pad <br />and will not involve any new disturbance. The location and configuration of the unit is shown on Map 24 <br />and Figure 31. As a passive sound control device, the only required maintenance will involve periodic <br />inspection and cleaning. When the unit is no longer needed to control sound emissions from the <br />ventilation fan, it will be removed and will either be re-used elsewhere or salvaged. Foundations will be <br />demolished and removed in conjunction with demolition and restoration of the ventilation fan installation. <br />TROS-48 2.05-45.8 09/05/05 <br />