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COLORADO <br />Division of Re6wrnation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />October 27, 2015 <br />To: Brock Bowles <br />From: JasorMusick <br />IRIS: INew IHoirizoin Mine, C-19 ff -008 <br />SIR -69, Adequacy IReviiew Meirno <br />Per your request, I have reviewed the proposed r�ew sedimerft por�d (Porti 018) ar�d the proposed Ditch <br />C4A ar�d Ditch Por�d 018 East desigr�s associated with the above referer�ced revisior�. The review ir�cluded <br />the proposed desigr�s to determir�e if the if the demor�stratior�s meet the desigrcriteria for Rules 4.05.3 <br />ar�d 4.05.6. The Divisiorhas the followir�g adequacy commerfts: <br />1. Based orthe ir�formatiorpreserfted irthe proposed Attachmerft 2.05.3(3) 28 the structure <br />details associated with proposed ditches Coln, ard Ditch Por�d 018 East were completed without <br />freeboard. There was r�o discussiorirthe provided text to serve as a justificatiorr�ot to ir�clude <br />freeboard irthe proposed ditch desigr�s. Per Rule 4.05.3(7)(b), diversiordesigrshall ir�corporate <br />freeboard r�o less thar0.3 feet. Please provide detail desigr�s which ir�clude freeboard of r�o less <br />thar0.3 feet for the proposed ditches Coln, ard Ditch Por�d 018 East or provide a justificatiorto <br />the Divisiordiscussir�g the reasordesigr�s without freeboard meet the requiremerfts of Rule <br />4.053(7)(b). <br />2. Based orthe ir�formatiorpreserfted irthe proposed Attachmerft 2.05.3(3) 28 the load 018 <br />desigrdetails. It appears that proposed Por�d 018 is ir�corporatir�g a sir�gle emerger�cy spillway. <br />Per IRule(s) 4.05.6(3)(c), 4.05.6(4), ar�d 4.05.9(2)(a)(ii), the sedimerft por�d may be desigr�ed to <br />provide for a sir�gle oiler' char -rel spillway, irlieu of a combir�atiorof prir�cipal ar�d emerger�cy <br />spillways if the spillway is of r�orerodible cor�structioror is earth lir�ed or grass lir�ed ar�d <br />desigr�ed to carry short term ir�frequerft flows at r�orerosive velocities where sustair�ed flows are <br />r�ot expected. The proposed Por�d 018 desigrproposes a sir�gle earth lir�ed or grass lir�ed <br />spillway; as such, please provide ir�formatiorirthe proposed text, por�d desigr�, or respor�se to <br />this adequacy commerft discussir�g the justificatiorthat the spillway as proposed is desigr�ed to <br />carry short term irftequerft flows at r�orerosive velocities. <br />0 <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 IF 303.832.8106 http://mining.state.co.us <br />John W. Hickentooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />