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XII. Subsidence Control <br />Subsidence Survey, Monitoring, and Control Plans are addressed in Tab 20, Volume 6 of the permit <br />application. <br />Powderhorn Coal Company has completed a survey of structures and renewable resource lands <br />existing within the permit area. The permittee has delineated several structures overlying the proposed <br />underground workings. The Ute Water District, which serves approximately 45,000 people, has a <br />water treatment plant, several storage tanks, and a 24-inch treated water distribution pipeline above the <br />existing Roadside Mine workings. Several raw water collection pipelines also cross the proposed <br />Cottonwood mining area. Limited alluvial deposits, which represent minor surficial aquifers, do exist <br />within the flood plain areas of Cottonwood Creek and Rapid Creek drainages. <br />The currently approved mining and reclamation plan does not include any further coal extraction. The <br />North Mine portals, 2 West Portals, and South Fan shaft, Northwest Intake Portal, and North Decline <br />Portals have been sealed and backfilled. The South Mine Portals have been sealed and are scheduled <br />to be backfilled by the end of 2004. There are no remaining portals or mine openings that have not <br />been sealed. <br />The most recently approved five-year mine plan that did include coal extraction, did not involve <br />additional mining below the Ute Water Conservancy District facilities or supply pipelines. Extraction <br />was also projected beneath the raw water collection pipelines within the Cottonwood lease area. In the <br />case of both the supply and raw water pipeline facilities, the worst possible anticipated consequence of <br />mining would be the disruption of the pipeline. In both cases, the permittee demonstrated that the <br />materials necessary for repair are readily accessible and that the disruption would not result in <br />cessation of service to the water district's water users. The permittee proposed to prevent material <br />damage to both the raw water collection pipelines, channels, and associated alluvial aquifers of both <br />Rapid Creek and Cottonwood Creek through the retention of stable pillars. Protective pillars were also <br />to be retained below Coal Creek and Jerry Creek in the North Portal mining area. <br />A raw water pipeline system that supplies the town of Palisade, runs along Cottonwood Creek to the <br />confluence of Rapid Creek. Damage to the pipeline was to be avoided by leaving pillars beneath the <br />pipeline route to assure additional stability. A second pipeline conveys raw water along Rapid Creek <br />from collection points southeast of the permit area. Any pipeline damage will be mitigated by the <br />operator should it occur. See page 224, Exhibits 29, 30 and 46 of the permit for further information. <br />A 24-inch concrete water line overlies portions of the permit area and is owned and maintained by the <br />Ute Water Conservancy District. On February 28, 1990, this water line broke roughly 200 feet east of <br />the North Fan Portal. The break was detected immediately and Ute Water Conservancy was able to <br />shut down the line. The water was directed down the drainage channel at the North Decline area, and <br />some water flowed to sediment pond 7. <br />The application contains an extensive analysis of the stability of pillars proposed to prevent subsidence <br />beneath the major drainages potentially affected by subsidence. The application also contains <br />predictions of maximum subsidence expected to occur if pillar failure follows cessation of mining in <br />the potentially affected areas. Each of these analyses is prepared in accordance with the <br />state-of-the-art of subsidence prediction. See Appendices 20-1 through 20-4 for subsidence <br />predictions and pillar design analyses. <br />Permit Revision No. 4 48 February 3, 2009