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(12" x 2' x 31') on top of the piers. The concrete Bade beams will be reinforced with three #5 rebaz, and #4 <br />stirrups spaced at 8 inches on center within 3 feet of the piers, and spaced at 16 inches on center at all other <br />locations. <br />• The installation of the silencer will occur within the existing disturbed area. The silencer is essentially a box <br />containing baffles which will be approximately 31 feet long, 21 feet wide, and 20 feet high. The location of the <br />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 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° from its current dischazge direction. Installation of the <br />sound deflector/absorber unit will require construction of foundations utilizing concrete piers and concrete Bade <br />beams. The foundation will consist of twelve concrete piers (12-inch diameter x 15-21 feet deep), supporting two <br />curved reinforced concrete Bade beams (12" wide x 2' deep x 31/64' long), with a reinforced concrete slab <br />between the Bade 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 <br />steel structure, lined with sound absorbing material, approximately 12' wide x 20' high x 45' long (along centerline <br />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 co~guration of the unit is shown on Map 24 and Figure 31. As a <br />passive sound conVol device, the only required maintenance will involve periodic inspection and cleaning. When <br />the unit is no longer needed to control sound emissions from the ventilation fan, it wilt be removed and will either <br />be re-used elsewhere or salvaged. Foundations will be demolished and removed in conjunction with demolition <br />and restoration of the ventilation fan installation. <br />r ~ <br />LJ <br /> <br />MROS-194 2.05-45.8 07/2/05 <br />