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iiiiiiiiiiiiiiuiii <br />STATE O~ ~~~viv~00 <br />Roy Romer, Govei <br />DEPARTMENT OFNATURALRESOURCES <br />MINED LAND RECLAMATION DIVISION <br />FRED R. BANTA, Dlreetor <br />April 12, 1989 <br />Ms. Kathleen Welt <br />West Elk Coal Company <br />P.O. Box 591 <br />Somerset, Colorado 81434 <br />RE: Lower Waste Pile Drainage Control and Diversion Structures, <br />Mt. Gunnison Mine No. 1, C-80-007 <br />Dear Ms. Welt: <br />Thank you for your clarification of the location of designs for 100 year - <br />24 hour collection and diversion ditches for the lower waste pile. We did <br />find the revised tables 6.1 and 6.5 in the Waste Rock Permit Revision Adequacy <br />Responses Appendix in 4olume 12. Unfortunately, it appears that these designs <br />are unacceptable in their current configuration as the velocities predicted <br />are erosive in more than the two locations where you've proposed to install <br />rip-rap. Barfield, Warner and Haan (1981, p. 162) report that velocities <br />greater than 5 fps on clays are erosive. Please reconfigure your channels to <br />decrease the velocity below 5 fps or provide size specifications for the <br />rip-rap when the design velocity exceeds 5 fps. <br />Please contact Cathy Begej if you should have any questions. <br />Sincerely, <br />~~~ ~ <br />Matthew S. Hayes <br />Reclamation Specialist <br />MSH/scg <br />cc: Cathy Begej <br />5169E <br />215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203.2273 Tel. (303) 866.3567 <br />