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The concrete pad was poured around the liner and was approximately 14x 10 x 2 feet, however, the liner extends <br />through the pad, reducing the amount of concrete needed to construct the pad. Approximately 8.9 CY of concrete <br />was required to construct the pad. <br />After the collar and liner were in place and the pilot hole was completed, raise-boring methods were used to <br />complete the hole. The hole was reamed to a final diameter of 4.33 feet and a 48-inch diameter steel casing was <br />cemented in place from 50 feet below the bottom of Twentymile Sandstone to the top of the concrete centering pad. <br />The remainder of the casing below the cement hangs in the hole. The hole is approximately 1,100 feet in depth. <br />The 4-foot diameter casing extrudes 4 to 6 inches out of the concrete surface pad. A cap to regulate intake air flow <br />was installed. A fence was installed around the drill pad to prevent access by cattle, after completion of the hole. <br />Access was derived from an existing light-use road running up to an old electrical borehole. A series of culverts <br />were placed under the existing road as shown on Figure 23, General Location of Escape Shaft. The design for the <br />culverts can be found in Exhibit 8D, Escape Shaft/Light-Duty Road Culvert Design. TCC constructed an additional <br />25-foot wide road at a 4 percent grade to access the site. The 1,300-foot long road is graveled with 0.5 feet of 6- <br />inch pit-run gravel. <br />Buffalo Forre 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 <br />(12" x 2' x 31') on top of the piers. The concrete grade beams will be reinforced with three #5 rebar, 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. 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 location of <br />the vent shaft and silencer is shown 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 <br />of the sound deflector/absorber unit will require construction of foundations utilizing concrete piers and concrete <br />grade beams. The foundation will consist of twelve concrete piers (12-inch diameter x 15-21 feet deep), supporting <br />two curved reinforced concrete grade beams (12 inches wide x 2 feet deep x 31-64 feet long), with a reinforced <br />concrete slab between the grade beams. Two concrete piers will be poured on either side of the foundation to <br />provide for side-bracing of the sound deflector/absorber structure. The sound deflector/absorber unit will be a <br />fabricated curved steel structure, lined with sound absorbing material, approximately 12 feet wide x 20 feet high x <br />45 feet long (along center-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 <br />the unit is no longer needed to control sound emissions from the ventilation fan, it will 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 />MR09-234 2.05-45.8 02/03/09 61-