2009-04-29_PERMIT FILE - C1982056A (8)

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In order to comply with new Mine Atmosphere Control (MAC) regulations, under the jurisdiction of the Mine Safety and Health Administration (MSHA), and minimize surface disturbance, TCC will utilize the previously drilled and cased exploration borehole as a MAC borehole for nitrogen injection into abandoned mine gob areas. The 8-inch pipe installed within the cased MAC borehole, will be used as a nitrogen injection borehole, connecting to one or more manifolded pipe systems underground, which will connect to sealed gob areas. At the surface, an 8- foot diameter culvert manhole may be installed around the cased MAC borehole(s) as a well-head, with appropriate grounding and lightning protection to meet MSHA requirements. The fixed pipeline(s) will connect at the surface to a portable skid-mounted nitrogen generator. Associated equipment will include skid-mounted compressors, and control equipment, which will be housed in the Fan Mechanical Building. Required power for this installation will be provided by dropline from the existing substation. Installation details are shown by the design drawings in Exhibit 49R. No. 7 North Escape Shaft (Section 20, TSN, R86 A 1,066 foot escape borehole shaft was constructed into the No. 7 entry of North Mains to allow emergency evacuation of personnel from the development sections of the 9-Right and 10-Right gateroads. The construction of the shaft utilized raise drilling techniques. It is anticipated that the escape shaft will be utilized for approximately ten years. The site is shown on Figure 23, General Location of Escape Shaft. 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 additional 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- inch pit-run gravel. TR09-66 2.05 - 45.7 02/17/09