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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 />January 5, 2015 <br />To: Marcia Talvitie <br />From: Jason Musick <br />RE: Bowie No. 1 Mine, C- 1981 -038 <br />Technical Revision No. 59 (TR59) <br />Adequacy Review <br />Per your request, I have reviewed Bowie Resources, LLC's TR59 submittal for the Bowie No. 1 Mine with <br />regard to the updates to the drainage areas and culvert SEDCAD calculations. <br />Bowie Resources SEDCAD models utilized approved vegetation and rainfall data for selecting parameters <br />for the SEDCAD 4 models of on the ground conditions associated with the drainage areas in TR59. The <br />parameters reasonably represent the conditions in the field. <br />The Division's review of each of the parameters is in the table below: <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. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />1876. <br />Bowie's <br />Bowie's basis for <br />Parameter <br />Division's Comment <br />Selection <br />selection <br />Although the 2.0 inches is <br />necessary in the model as <br />SCS TR -55 questions the <br />NOAA ATLAS 2, <br />accuracy of the Curve <br />Design <br />1.70- inches in <br />Volume III fora 10 <br />Number method when <br />Event <br />24 hours <br />year -24 hour <br />runoff depth is less than 0.5 <br />event <br />inch, based on history of <br />the Bowie No 1 Mine the <br />1.70 inches identified is <br />appropriate. <br />74, <br />Agricultural <br />Reasonable based on <br />lands;73, <br />Bowie No. 1 <br />selections of cover, soil <br />CN <br />Pinion /Juniper; <br />permit Volume 7 <br />group, hydrologic <br />and 87, <br />Map 2 <br />conditions, and C factor. <br />Disturbed <br />Areas <br />"Fair ", "Good, and "Poor" hydrologic <br />Reasonable based on <br />None <br />condition <br />description of "Fair ", <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. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />1876. <br />