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AN,COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />December 16, 2014 <br />Chris Gilbreath <br />Tri-State Generation and Transmission Association, Inc. <br />P.O. Box 33695 <br />Denver, CO 80233 -0695 <br />Re: Colowyo Mine (Permit No. C- 1981 -019), TR -104 adequacy items (third letter) <br />Dear Mr. Gilbreath: <br />We have received your technical adequacy responses. The following items need to be addressed before the <br />Division can approve this revision. The numbered items are in agreement with our original adequacy items <br />from October 17, 2014. <br />1. No further action required. <br />2. No further action required. <br />3. Please address the following. <br />a. On page Exh. 7- 14I -2, the reference to 53 cfs in the SEDCAD run appears to be a mistake. <br />b. The 1.5% slope for the middle reach in the SEDCAD model appears low, based on the topography <br />map. <br />c. The text on page Exh. 7 -14I -3 references two SEDCAD models. Please add another sentence (or a <br />parenthetical phrase) to tell the reader that one of the runs is not included in the exhibit and explain <br />why. <br />d. The lower reach is modeled with a 22% slope, which is high for the overall reach based on the <br />topography map (some of the reach is this steep). This is conservative for sizing riprap, but not so <br />conservative when sizing the channel dimensions. This will not likely be a problem given the 4 -foot <br />depth of channel that you propose (and possibly have currently), but this modeling assumption <br />should be explained. <br />4. No further action required. <br />If you have any questions, please contact me at 303.866.3567 (extension 8113) or Rob.Zuber@state.co.us. <br />Sincerely, <br />Robert Zuber, P.E. <br />Environmental Protection Specialist II <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us <br />John W. Hickentooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />pF CC310 <br />1876x/ <br />