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COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />-)epartment of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />November 3, 2016 <br />Graham Roberts <br />Trapper Mining, Inc <br />P.O. Box 187 <br />Craig, CO 81626 <br />RE: Trapper Mining, Inc., Permit C-1981-010 <br />DRMS Adequacy Review of TR 117 <br />Deacon/Jeffway and Deal Diversion Ditch As -Built Design Update <br />Dear Mr. Roberts: <br />The Division has completed its preliminary review of TR 117. The revision was received on October 18, <br />2016, found complete on October 19, 2016, and proof of publication received November 3, 2016. TR 117 <br />Updates the SedCad models for App Q, Section XVII demonstrating the current as -built design for the <br />Deacon/Jeffway Diversion Ditch and Section XXXVI for the Deal Diversion Ditch. <br />The Division must review all variables used to derive the structure outputs with the Deacon/Jeffway <br />Diversion. Based on the Division's review, all variables appear adequate for the diversion. However, the <br />use of Curve Numbers (CN) 66, 72, and 63 to represent the ground conditions to derive the model output <br />does not reflect the current Trapper Mine Plan. The Division believes that although the curve numbers <br />utilized in the SEDCAD model may reflect the current on -the -ground conditions, they do not reflect the <br />worst case scenario when determining if the Deacon/Jeffway Diversion is adequately designed. The <br />Division believes that a curve number of 86 is the appropriate CN when modeling this Diversion. Please <br />provide the Division with a revised Deacon/Jeffway Diversion design that reflects a variable CN of <br />86, or provide justification as to the use of the proposed curve numbers of 66, 72, and 63 within the <br />currently approved mine plan. <br />If you have any questions feel free to contact me at (303) 866-3567, extension 8147. <br />Sincerely, <br />Tabetha Lynch <br />Environmental Protection Specialist <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 />Cly _COC <br />Ne4� _ '` f;trO00V <br />I ' <br />