2016-10-20_REVISION - C1981018 (2)

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COLORADO Division of Reclamation, Mining and Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 Interoffice Memorandum To: Clayton Wein From: Rob Zuber Date: 10/20/2016 Subject: Deserado TR -70: SEDCAD review and miscellaneous Hello, Clayton. I have reviewed the TR -70 submittal from Blue Mountain Energy, in particular the SEDCAD model (Illustration 57). 1 have the following comments (and I e-mailed all but last to Scott Wanstedt). SEDCAD review • Pond nomenclature is inconsistent between Map 160 and SEDCAD output. For example, "Pond #2" on Map 160 is the same as "Pond #1" (Structure 3) in the SEDCAD run. Please revise one or the other. • Structure #5, SWS #3 appears to be the pond itself as the time of concentration is 0.0 or non-existent in the model tables. If this is correct, please explain why this method was not implemented for the other ponds. • There are discharge pond dewater times above 13,000 hours. How were these determined and what is significance for the overall model? • For the 10 -year model, there are particle size distributions for each structure. Please explain why the sediment entering Structure #3 contains much finer material than the sediment entering Structure #5. (From Structure #5 to Structure #7 there is very little change in the sediment.) Other comments • Map 160 shows boreholes SH -4a and SH -4d, but Map 147 shows SH -4. Please explain the difference. On Map 160, the riprap depths and gravel filter layer depths for the channels are designated as only a few inches deep. Should this be deeper? (We discussed this.) %F_co<-0 w t\ 1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining. state. co. us John W. Hickenlooper, Governor I Robert W. Randall, Executive Director I Virginia Brannon, Director .1876