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Based on the performance of the temporary shaft heaters during winter 2007/2008, TCC determined that additional <br />heat output would be needed, both to prevent icing and to provide an adequate flow of warm ventilation air during <br />the winter months. Four additional temporary shaft heaters were installed, along with a larger propane supply tank <br />• to meet immediate needs during early winter 2008/2009, and four larger permanent shaft heaters were ordered. On <br />delivery of the permanent shaft heaters, TCC will proceed with construction of concrete pads for both the <br />permanent shaft heaters and the large propane tank, installation of the heaters, and installation and connection of a <br />buried propane supply line. The location and configuration of both the supplemental temporary heaters, and the <br />permanent heaters, propane tank, and supply line are provided in Exhibit 49N. <br />Buffalo Forte Fan Silencer (MR 03 -187) <br />A new silencer will be installed on the Buffalo fan at the NW Mains Ventilation Shaft location. Installation of the <br />silencer will require construction of foundations utilizing concrete piers and concrete grade beams. The foundation <br />will require eight concrete piers (6 -inch radius x 20 feet deep) and then placement of two concrete grade beams (12" x <br />2' x 31') on top of the piers. The concrete grade beams will be reinforced with three #5 rebar, and #4 stirrups spaced <br />at 8 inches on center within 3 feet of the piers, and spaced at 16 inches on center at all other locations. The installation <br />of the silencer will occur within the existing disturbed area. The silencer is essentially a box containing baffles, which <br />will be approximately 31 feet long, 21 feet wide, and 20 feet high. The location of the vent shaft and silencer is shown <br />on Map 24. <br />NW Mains Ventilation Fan Sound Deflector /Absorber (MR05 -192) <br />As part of TCC's ongoing efforts to minimize potential mine impacts on area residents, a sound deflector /absorber <br />unit will be installed on the NW Mains Ventilation Fan. The unit is designed to deflect fan exhaust, and to both <br />absorb and deflect any associated sound approximately 90 degrees from its current discharge direction. Installation of <br />the sound deflector /absorber unit will require construction of foundations utilizing concrete piers and concrete grade <br />beams. The foundation will consist of twelve concrete piers (12 -inch diameter x 15 -21 feet deep), supporting two <br />curved reinforced concrete grade beams (12 inches wide x 2 feet deep x 31 -64 feet long), with a reinforced concrete <br />slab between the grade beams. Two concrete piers will be poured on either side of the foundation to provide for side - <br />bracing of 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 (along center- <br />line of curvature). <br />Installation of the sound deflector /absorber unit will be on the existing NW Mains Ventilation Fan pad and will not <br />involve any new disturbance. The location and configuration of the unit is shown on Map 24 and Figure 31. As a <br />passive -sound control device, the only required maintenance will involve periodic inspection and cleaning. When the <br />unit is no longer needed to control sound emissions from the ventilation fan, it will be removed and will either be re- <br />used elsewhere or salvaged. Foundations will be demolished and removed in conjunction with demolition and <br />restoration of the ventilation fan installation. <br />• <br />TR09 -70 2.05 — 45.0dO 01/26/10 <br />