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DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866 -3567 <br />FAX: (303) 832 -8106 <br />STATE OF COLORADO <br />MEMORANDUM <br />To: Kate Pickford, Environmental Protection Specialist <br />From: Tim Cazier, P.E., Environmental Protection Specialist <br />Date: March 14, 2014 ✓ <br />Re: Animas Glacier Gravel, Permit No. M- 2011 -028 <br />TR -01 Adequacy Review May 4, 2012 Drainage Report, Amendment 1 <br />COLORADO <br />D I V1 S I ON OF <br />RECLAMATION <br />MINING <br />SAFETY <br />John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />Loretta Pineda <br />Director <br />The Division of Reclamation, Mining and Safety engineering staff (DRMS) have reviewed <br />Russell Engineering's Animas Glacier Gravel Pit Drainage Report, Amendment 1 dated January <br />22nd, 2014. The following comments are specific to the revised drainage report. <br />1. The subject document indicates the newly constructed large berm has a storage capacity of <br />approximately 220 acre -feet. The DRMS also is aware that the Colorado Division of Water <br />Resources Office of the Sate Engineer (OSE) Dam Safety does not believe the large berm to <br />be a jurisdictional dam under their rules and regulations. However, comments received by <br />the DRMS do claim the berm should fall under jurisdictional control from the OSE. As such, <br />the DRMS requires the Operator provide the following: <br />a. A demonstration that the pond does not continue to accumulate water year after <br />year. This will require a water balance with a time step no shorter than monthly. <br />A probabilistic approach would be best, with 5,000 to 10,000 iterations, varying <br />precipitation, evaporation, snow accumulation, snow melt, and infiltration rates. <br />If a deterministic approach is taken, it should consider a wet year (highest <br />monthly precipitation, lowest monthly evaporation, highest snow accumulation <br />with fastest snow melt and lowest infiltration rates (to mimic a layer of settled <br />fines on the pit floor limiting infiltration). All parameters should be discussed and <br />have references /sources. <br />b. Given that the berm may have the capacity to store it, please provide the runoff <br />volume expected from the 24 -hour probable maximum precipitation (PMP) event <br />- from the maximum contributing area during the life of mine. <br />If you have any questions, please contact me (303- 866 -3567 x8169 or tim.cazier @state.co.us. <br />Office of Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines <br />