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• (• ~,ONTAO~ 00 O, s ~iO i~ 9 ~ y L. SCOtt Tucker, Eaecmrve Drrecru~ 4 ~ ~Oj ~~bl,~baa N'~~v~C June 28, 1988 6oarg of D~reaors E.ecuuve Comm~nee Camv Reynoitls Cna~rman Cary o~ Denver Seven E Cramer Chairman Pro-Tem AOams County Linda Jourgensen Seuerary Cny of Bouiaer Arren E Parson Treasurer Engineer Bob Brooks Memoer Araoanoe Counry• Memoers Bob Cnoer Cny of Denver Davitl A Day Engineer Tammy King Arapahoe County Board of Adjustment 5334 South Prince Street Littleton, Colorado 80166 Dear Ms. King: III IIIIIIIIIIIIIIII This letter is in regard to Case No. BA 88-6-3, Coal Creek Resource Mining Plan. We previously commented on this proposal in a letter to you dated May 23, 1988. Since that time we have received a copy of the Phase II Drainage Report dated April, 1988, by Tuttle Applegate Rindahl, Inc. and a letter from Mike Applegate dated June 16, 1988 (copy enclosed). Based on our review of this new material, we have the following additional comments: 0 m O 0 e O O U w w 0 The proposed mining will apparently not cut off sediment bedload through the subject site. It is now our understanding that a positive longitudinal slope for Coal Creek will be maintained so that the bedload will continue to be able to move through the subject site and on downstream. 2. The figures contained in the letter indicate that the loss of floodplain storage will not be as significant as we had first anticipated, and in fact, floodplain storage may actually be increased. As you know, the mining site is located well outside the boundaries of the Urban Drainage and Flood Control District. Our direct concerns have therefore been impacts the proposed mining could have on the District, specifically loss of sediment bedload and increased flood peaks. Those two concerns have now been addressed. w w '< N 3 0 m N Mary Gaylortl ~ Torn Or MOrnSpn m Samuel v. Gomr• ~ Gry of BngMOn j N Jose Heath Bouicer Counry Ramona Martinez Cny of Denver Suzy McDanai Douoias Couny Federico Pena JOhn MrOZeh City o~ Denver Jonn Srone Jefferson Counry Susan Van Dvke Cny or Engiewotl m w Z O I w There are other problems with the proposal which we would recommend b~e revised prior to consideration of approval of the request, although failure to do so would have minimal impact on the District. Chief among these concerns is the need to prevent head cutting on Coal Creek as well as all of the tributaries to Coal Creek impacted by the proposed mining. Ariequate rundowns on the tributaries should be provided as mining disturbs them and the potential for head cutting is increased. If mining proceeds from downstream to upstream and a twenty-year life is e;cpected, it may not be necessary to construct the structure on the main stem itself for fifteen to twenty years.