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Peabody <br />Twentymile Coal Company <br />July 17, 2007 <br />29515 Routt County Road N27 <br />Oak Creek, CO 80467 <br />970.879.3800 <br /> RECE~V~ED <br />Mr. Byron Walker, Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining, and Safety JUL 2 3 2001 <br />1313 Sherman Street, Room 215 Division otk <br /> <br />Denver, Colorado 80203 e~,~,, ,a <br />Mining and safety ~' <br />(303)866-4941 <br />RE: Twentymile Coal Company - Foidel Creek Mine (Permit No. C-82-056), Technical Revision <br />(TR07-61) - 6MN Mine Water Storage Reservoir <br />Deaz Mr. Walker: <br />Twentymile Coal Company (TCC) requests CDMG approval of a Technical Revision (TR07-61) to our <br />existing approved Permit for construction, operation, maintenance, and reclamation of the 6-Main North <br />(6MN) Mine Water Storage Reservoir and ancillary installations. The 6MN Mine Water Storage <br />Reservoir is designed as a closed reservoir, with no discharge, and provision for adequate operating free- <br />boazd to allow for storage of runoff from a small upslope drainage area. Most runoff from the upgradient <br />drainage basin will be captured and diverted around the reservoir by the designed temporary diversion <br />ditch. The proposed reservoir will be used to provide back-up storage for TCC's 10-Right Mine <br />Dewatering Well, allowing the well to pump continuously at full capacity, providing buffer storage for <br />pump maintenance or failure, and limiting the distance over which the mine water must be transferred. <br />Water from the 10-Right Mine Dewatering Well, which pumps accumulated mine inflows from a sump in <br />the sealed Eastern Mining District, is pumped to the surface by a 320 HP high-capacity submersible <br />pump, at a rate of approximately 700 gpm. The pump dischazge is currently transferred by a series of <br />surface and underground pipelines to the Area 1 Pit in the TCC Mine Facilities Area for use in either coal <br />prepazation operations or for storage and subsequent use as a back-up source for the operational mine <br />water system. <br />The 6MN Mine Water Storage Reservoir will be constructed south of the current 6MN Shaft pad and <br />northwest of the NW Mains Ventilation installation. The reservoir embankment will be an earthen dam <br />constructed of suitable fill material excavated from the reservoir basin and placed and compacted <br />consistent with engineering design specifications. The resulting embankment structure will be <br />approximately 14 feet high at its highest point, with the dam crest at an elevation of 6,717 feet. The <br />surface azea of the maximum pool (operational mine water storage + pump buffer storage + design <br />stolYllwater storage) at an elevation of 6,714.7 feet will be approximately 5.2 acres, resulting in a <br />maximum design storage volume of approximately 36 acre-feet of water. Even though the 6MN Storage <br />Reservoir has been designed and will be operated as a closed reservoir, a single open-channel emergency <br />spillway, with an invert of 6,715.5 feet, has been incorporated into the design in compliance with <br />applicable regulatory requirements for impoundments. The design of the reservoir also incorporates a <br />compacted soil Liner to minimize infiltration and water loss. <br />G:\Environmental\REVISION\TECH-RV\TR07-61 6MN Storage Reservoir\7T207-61 6MN Storage Resv 1L Rl.doc <br />