2008-10-03_PERMIT FILE - C1982056A (4)

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The drilling of the shaft resulted in minimal surface disturbance. A drill pad approximately 200 x 200 feet was constructed at the resulting site in 1,450 CY of cut and fill. Available topsoil was salvaged and stockpiled for future reclamation of the site immediately northeast of the drilled pad. Approximately 18 inches of topsoil derived from Cochetopa Loam is available for salvaging (222 CY). Casing and other . drilling supplies were stockpiled on the borehole pad. After topsoil removal, two mud pits 10 x 10 x 7.5 feet were dug adjacent to the drillhole. Drilling fluids and cuttings were discharged into the adjacent pits, allowing settling in one pit, with water decanting into the adjacent pit. Drilling muds were used during the course of drilling the surface collar and pilot hole. The surface collar was approximately 5.0 feet in diameter, and the pilot hole was 11 inches in diameter. The collar was comprised of two components; a surface concrete pad and a liner or casing that extends to bedrock. A concrete centering base is at the bottom of the liner. The concrete pad was poured around the liner and was approximately 14x 10 x 2 feet, however, the liner extends through the pad, reducing the amount of concrete needed to construct the pad. Approximately 8.9 CY of concrete was required to construct the pad. After the collar and liner were in place and the pilot hole was completed, raise-boring methods were used to complete the hole. The hole was reamed to a final diameter of 4.33 feet and a 48-inch diameter steel casing was cemented in place from 50 feet below the bottom of Twentymile Sandstone to the top of the concrete centering pad. The remainder of the casing below the cement hangs in the hole. The hole is approximately 1,100 feet in depth. The 4-foot diameter casing extrudes 4 to 6 inches out of the concrete surface pad. A cap to regulate intake air flow was installed. A fence was installed around the drill pad to prevent access by cattle, after completion of the hole. Access was derived from an existing light-use road running up to an old electrical borehole. A series of culverts were placed under the existing road as shown on Figure 23, General Location of Escape, Shaft. The design for the culverts can be found in Exhibit 8D Escape Shaft/Light-Duty Road Culvert Design: TCC constructed an additiona125-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-inch pit-run gravel. Buffalo Fore Fan Silencer (MR 03-1871 A new silencer will be installed on the Buffalo fan at the NW Mains Ventilation Shaft location. Installation of the silencer will require construction of foundations utilizing concrete piers and concrete grade beams. The foundation will require eight concrete piers (6-inch radius x 20 feet deep) and then placement of two concrete grade beams (12" x 2' x 31') on top of the piers. The concrete grade beams will be reinforced with three #5 rebar, and #4 stirrups spaced at 8 inches on center within 3 feet of the piers, and spaced at 16 inches on center at all other locations. The installation of the silencer will occur within the existing disturbed area. The silencer is essentially a box containing baffles, which will be approximately 31 feet long, 21 feet wide, and 20 feet high.. The location of the vent shaft and silencer. is shown on Map 24. NW Mains Ventilation Fan Sound Deflector/Absorber (MROS-192) As part of TCC's ongoing efforts to minimize potential mine impacts on area residents, a sound deflector/absorber unit will be installed on the NW Mains Ventilation Fan. The unit is designed to deflect fan exhaust, and to both absorb and deflect any associated sound approximately 90 degrees from its current discharge direction. Installation of the sound deflector/absorber unit will require construction of foundations utilizing concrete piers and concrete grade beams. The foundation will consist of twelve concrete piers (12-inch diameter x 15-21 feet deep), supporting two curved reinforced concrete grade TR07-61 2.05-45.8 07/14/07