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associated alluvial aquifers of both Rapid Creek and Cottonwood Creek <br /> through the retention of stable pillars . <br /> A raw water pipeline system that supplies the town of Palisade, runs <br /> along Cottonwood Creek to the confluence of Rapid Creek. Damage to the <br /> pipeline will be avoided by leaving pillars beneath the pipeline route <br /> to assure additional stability. A second pipeline conveys raw water <br /> along Rapid Creek from collection points southeast of the permit area. <br /> Any pipeline damage will be mitigated by the operator should it occur. <br /> See page 224, Exhibits 29, 30 and 46 of the permit for further <br /> information. A 24-inch concrete water line overlies portions of the <br /> permit area and is owned and maintained by the Ute Water Conservancy <br /> District. On February 28, 1990, this water line broke roughly 200 feet <br /> east of the North Fan Portal . The break was detected immediately and <br /> Ute Water Conservancy was able to shut down the line. The water was <br /> directed down the drainage channel at the North Decline area, and some <br /> water flowed to sediment pond 7 . <br /> The application contains an extensive analysis of the stability of <br /> pillars proposed to prevent subsidence beneath the Rapid and Cottonwood <br /> Creek drainages. The application also contains predictions of maximum <br /> subsidence expected to occur if pillar failure follows cessation of <br /> mining in the potentially affected areas. Each of these analyses is <br /> prepared in accordance with the state-of-the-art of subsidence <br /> prediction. See Appendices EE and KK for subsidence predictions , LL <br /> for angle of draw calculations , and MM for pillar design. <br /> The demonstration of proposed pillar stability, including calculations <br /> of pillar factors of safety using a conservative method developed by <br /> A.H . Wilson, is included within this submittal . Pillars and main <br /> corridors which have 80 feet by 80 feet dimension are proposed and <br /> demonstrated to exceed factors of safety of 2 .92 under maximum <br /> anticipated overburden loadings . The amended life-of-mine plan for the <br /> Cottonwood lease area indicates that mains have been located to <br /> directly underlie significant portions of the two potentially affected <br /> creeks and the associated alluvial aquifers and raw water collection <br /> pipelines . In addition, several significant portions of the Cottonwood <br /> Creek channel is underlain by proposed room and pillar panel sections . <br /> In these areas , retreat mining is proposed to result in relatively <br /> conservative slabbed pillars (calculations included within Appendix G) <br /> which have been demonstrated to have a safety factor in excess of 1 . 34. <br /> A subsidence event that occurred during the initial permit review was <br /> monitored and analyzed within the second and third east panels of the <br /> Roadside Mine , immediately adjoining the Cottonwood lease on the north <br /> side . This recorded and analyzed event has demonstrated that the <br /> design characteristics utilized in completing the proposed plan for <br /> subsidence control have functioned as projected within the area of the <br /> second and third east panels of the Roadside mine. With Division <br /> approval of Technical Revision No. 03, the monitoring plan on the <br /> second and third east panels was dropped. The operator had also <br /> installed subsidence monuments along the Ute water pipeline . <br /> Monitoring of this pipeline was also dropped with Division approval of <br /> Technical Revision No. 08. Both areas of subsidence monitoring have <br /> -38- <br />