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Peabody <br />Twentymile Coal <br />29515 Routt County Road 27 <br />Oak Creek, CO 80467 <br />970.879.3800 <br />Mr. Jason Musick, Environmental Protection Specialist November 1, 20 0 <br />Division of Reclamation, Mining, and Safety ?t$ <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 0 ? 2010 <br />(303) 866-3567 X 8134 Divisiurn ui , sdztmat'r;;n, <br />Mlr,ins 3r;d ?'&sty <br />RE: Twentymile Coal Company - Foidel Creek Mine (Permit No. C-82-056), Minor Revision <br />(MR10-250) -18-Left Utility Borehole and Rock-Dust Tank <br />Dear Mr. Musick: <br />Twentymile Coal, LLC- (TC) requests CDRMS approval of a Minor Revision to our existing approved <br />Permit for installation, operation, and reclamation of a Utility Borehole and Rock-Dust Tank at the <br />existing 18-Left (18LT) Shaft location. The proposed Utility Borehole will be drilled, cased, and <br />completed as a 14.75-inch diameter borehole on the existing 18LT Pad. Two carrier pipes, an 8.625 <br />rock-dust drop pipe and a 4.5-inch compressed-air pipe will be installed and grouted in-place within <br />the cased borehole. An additional rock-dust tank will be installed over the Utility Borehole to provide <br />an additional rock-dust supply point for the Western Mining District. The compressed-air pipe will <br />allow the existing compressed-air feed to be moved from the Mine Atmosphere Control Borehole. <br />The proposed 18LT Utility Borehole and rock-dust tank installation will be located on the existing <br />18LT Shaft Pad and within the existing 18LT Shaft Installation surface disturbance area, and will <br />involve no new or incremental disturbance. The 18LT Utility Borehole will include a 60-foot deep, <br />16-inch diameter grouted surface casing, and will be a 14.75-inch diameter cased borehole drilled to a <br />depth of approximately 1,390 feet to intercept the 18LT mine entries, and grouted for its entire length. <br />The additional 18LT Rock-Dust Tank Installation will consist of a new rock-dust tank, which will be <br />mounted on four poured concrete piers; a connection to the new borehole; required electrical and <br />control equipment, that will tie-in to the existing 18LT Substation; and a dust collection system. The <br />additional rock-dust tank installation can be readily accessed from the 18LT Shaft Installation Pad area <br />and the existing 18LT Light-Use Road. <br />Drainage for the existing 18LT Shaft Installation is controlled by the existing two-cell 18LT <br />Sedimentation Pond and site-specific drainage and sediment control measures, and the proposed Utility <br />Borehole and additional rock-dust tank installation will not modify the drainage configuration or <br />requirements. The 18LT Utility Borehole and rock-dust tank installation will remain in-place until it is <br />no longer needed to support ongoing or anticipated future mining operations. Reclamation of this <br />installation will probably occur as part of the overall reclamation of the 18LT Shaft Installation, with <br />equipment removal, foundation demolition, backfilling and grading, soil material replacement, and <br />reseeding. Bond monies are already in place for all reclamation components except plugging and <br />sealing of the borehole, removal of the rock-dust tank, and demolition of the foundation piers. The <br />accompanying bonding calculation addresses estimated bonding costs for these additional components.