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COLORADO <br /> \/ Division of Reclamation, <br /> ® Mining and Safety <br /> Department of Natural Resources <br /> June 10,2022 <br /> Tony Tennyson <br /> Colowyo Coal Company L.P. <br /> 5731 State Highway 13 <br /> Meeker,CO 81641 <br /> Re: Colowyo Coal Mine (Permit No. C-1981-019) <br /> Technical Revision No. 154(TR-154) <br /> Adequacy Review <br /> Dear Mr. Tennyson: <br /> After reviewing TR-154 from Colowyo Coal Company L.P. (Colowyo),the Division has the following <br /> comments: <br /> 1. When reviewing the proposed Volume 20,Exhibit 23,Item 3 (Item 3)conducted by Agapito <br /> Associates,Inc.(AA),it appears to the Division that this exhibit is an addendum to Exhibit 23,Item <br /> 2 (Item 2)which is an updated iteration of the Collom Spoil Pile from Exhibit 23,Item 1 (Item 1). <br /> Under Item 2,an update to the location of the underdrain(s)occurred with Drain A and Drain B <br /> while maintaining the specifications of the underdrain approved under Item 1. In the initial <br /> discussion of Item 3 AA states,"[t]he report does not consider any underdrain or surface-water <br /> control requirements for either the temporary dump or the final reclaimed surface."It is unclear to <br /> the Division whether design specifications approved under Item 1 and the location of Drain A and <br /> Drain B from Item 2 are still valid and applicable for the proposed design of the permanent Collom <br /> Spoil Pile and Valley Fill.Please provide the Division with additional clarification and discussion on <br /> the design specification and location(s)of the underdrain to ensure Rules 4.09 and 4.10 are satisfied <br /> for the proposed Colom Permanent Spoil Pile and Valley Fill. <br /> 2. Based on the proposed Volume 15, Rule 4, Section 4.09,the maximum volume of the Collom Spoil <br /> Pile will reach approximately 28 million CY, with approximately 17.3 million CY remaining <br /> permanent as the Collom Permanent Spoil Pile and approximately 4.1 million CY remaining <br /> permanent as the Collom Valley Fill.The remaining amount is proposed to be hauled as final backfill <br /> for the Collom Pit reclamation.The Division understands that these volumes and proposed permanent <br /> Collom Spoil Pile and Valley Fill are based on the operations of the full life of mine for the Collom <br /> Pit which doesn't reflect the current spoil volumes and approved on-the ground disturbance under the <br /> cumulative bond schedule for the Collom Pit under Exhibit 13C as it shouldn't. It's the Division's <br /> understanding that as mining progresses in the Collom Pit, future spoil will be used as immediate <br /> backfill. Based on Collom's cumulative bond schedule,these disturbances have not yet been approved <br /> flF'�010 <br /> I n O <br /> 1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us <br /> Jared S. Polis, Governor I Dan Gibbs, Executive Director I Virginia Brannon, Director * 1876�` <br />