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5731 State Highway 13 <br />January 18, 2013 <br />Mr. Rob Zuber <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining & Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />RE: Colowyo Coal Company L.P., Mine Permit C -81 -019, TR -98 West Taylor <br />Fill Revision Adequacy Responses <br />Dear Mr. Zuber, <br />COAL <br />COMPANY a <br />• Meeker, Colorado 81641 <br />970 -824 -1500 <br />gem <br />JAN 22213 <br />0\ V e6amaC`on, <br />p,V�s,on & SatetY <br />Colowyo Coal Company (Colowyo) received adequacy comments on January 18, <br />2013 from the Division. Colowyo has the following responses to the Division's <br />comments: <br />• Two scenarios within the geotechnical analysis by Shannon &Wilson did not <br />meet the minimum required factor of safety (FS) of 1.5 as per Rule 2.05.3(6). <br />These correspond to Case 2a and Case 2c. Please explain how long -term <br />stability is achieved in relation to the Division's minimum requirements for <br />slope stability of a temporary excess spoil pile. This explanation may include <br />an additional slope stability analysis regarding the temporary excess spoil fill <br />showing that with revised input parameters (more conservative than the <br />average values but less conservative than the "low bound" values used <br />previously) the proposed excess spoil pile will meet the Division's minimum <br />requirements of a 1.5 FS. <br />Response: Colowyo has reviewed the Colorado Mine Land Regulations and <br />does not agree that Rule 2.05.3(6) addresses factor of safety (FS) in its <br />entirety. Colowyo does not believe that any regulation within the Colorado <br />Mine Land Regulations speaks to a FS of 1.5 for a temporary spoil pile. Rule <br />4.09.1(7) does address a FS of 1.5 for excess spoils. However, this rule does <br />not specifically nor directly address temporary spoil piles. The rule does state <br />that, "...covered with topsoil or substitute material in accordance with <br />4.06... " which indicates a surface that is prepared for reclamation and will be <br />a permanent surface. Thus, this statement in the rules demonstrates that Rule <br />4.09.1(7) is directed towards a permanent excess spoil and not a temporary <br />spoil pile that is proposed under this technical revision. <br />i Western i'iuets- (,Olor do, LIE mining property <br />