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<br />J. E. STOVER & ASSOCIATES <br />2768 COMPASS DRIVE, SUITE 101 <br />GRAND JUNCTION, COLORADO 81506 <br />PHONE: (970) 245-4101, FAX 242-7908 <br />MINE ENGINEERING <br />MINE RECLAMATION <br />III IIIIIIIIIIIIIIII <br />CIVIL ENGINEERING <br />CONS7. MANAGEMENT <br />February 21, 2001 <br />David Berry <br />Division of Minerals and Geology <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />RECEIVED <br />Re: Powderhorn Coal Company <br />Permanent Mine Water Plan <br />Technical Revision No. 33 <br />Permit C-81-041 <br />Dear Mr. Berry: <br />FEB 23 2001 <br />Division o1 Minerals 8 Geolon~~ <br />By letter dated February 15, 2001, the DMG transmitted three questions regarding the referenced <br />technical revision. Following are PCC's responses to the DMG's questions: <br />The DMG is concerned the proposed North Decline dewatering pipe will become clogged <br />by underground debris. PCC does not believe the dewatering pipe has a high clogging risk. <br />Floating debris would be the most likely cause of a clogged or partially blocked dewatering <br />pipe. A submerged inlet should overcome the clogging risk presented by floating debris. <br />The siphons with submerged inlets are a good example. They have not become plugged <br />for over eight years. Like the siphon system, the North Decline dewatering pipe will have <br />a submerged inlet. <br />2. As suggested by the DMG, PCC also considered the installation of a free draining outlet at <br />the location of the backfilled Northwest Intake Portal. The siphon was installed to maintain <br />the northwest intake pool below the level of the Northwest Intake Portal so seepage did not <br />occur along the steep hillside adjacent to I-70. To avoid the seepage, installation of a free <br />draining outlet would require a trench to be excavated in the floor of the portal for <br />approximately 150-feet. The trench would be excavated wide enough to accommodate the <br />pipe(s) and it would need to be about 4-feet deep. The floor of the portal is either shale or <br />sandstone so the subject excavation would be quite challenging, especially in an <br />abandoned coal mine. <br />3. PCC decided installation of a free draining outlet at the Northwest Intake was not feasible <br />based on safety issues surrounding ventilation, roof control, and hard rock excavation. <br />Please let me know if you have any questions. <br />Sincerely, <br />J. E. Stov <br />Consulting Engineer <br /> <br />