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<br /> <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 | Robert W. Randall, Executive Director | Virginia Brannon, Director <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />Re: Colowyo Coal Mine (Permit No. C-1981-019) <br /> Technical Revision No. 118 (TR-116) <br /> Adequacy Review <br /> <br />Dear Mr. Tennyson: <br /> <br />After reviewing TR-118 from Colowyo Coal Company L.P. (Colowyo), the Division has the following <br />comments: <br /> <br />1. On proposed page Volume 15, Rule 2, page 73, the first paragraph references Exhibit 23, Item 7, Part <br />N. This exhibit doesn’t currently exist, was not provided with TR-118 and is assumed to be an error. <br />Please correct the reference on proposed page Volume 15, Rule 2, page 73. <br /> <br />2. In proposed Exhibit 7, Item 23, Part B, page 1, paragraph 2, it states “Riprap sizes are defined by the <br />SEDCAD mode, as described in more detail the Introductory Text of Volum e 2D in the document <br />entitled ‘Methodologies and Assumptions f or Sedimentation Pond Design Evaluations’”. When <br />reviewing “Methodologies and Assumptions for Se dimentation Pond Design Evaluations”, there are <br />no discussions in regards to riprap sizing outside of Table 9. However, Table 9 only refers you to <br />Volume 2C, Exhibit 7, Item 4 in which there is also no discussion regarding riprap sizing. Please <br />update and correct the original reference to include the section that discusses the applicable riprap <br />sizing. <br /> <br />3. There appears to be an error on proposed Exhibit 7-23B, Table 1. The s lope listed on Table 1 for <br />Ditch D-1 is 24.2%. However, 21% was used in the SEDCAD model as well as reflected in Exhibit <br />7, Item 23, Figure B-2. Please update Exhibit 7-23B, Table 1 to reflected Ditch D-1’s correct slope. <br /> <br />4. In Exhibit 7, Item 23C, SEDCAD demonstration titled “Temporary Spoil Pile West Side Model” <br />(both 10 yr . – 24 hr. and 25 yr. - 24 hr.), the area directly above the Sidehill Pond (Structure 6) isn’t <br />taken into consideration with the Immediate Contributing Area. Please provide the Division on <br />explanation for this or update the SEDCAD model to reflect this area. <br /> <br />5. As per the discussion between Colowyo and the Division as well as proposed text in Exhibit 7, Item <br />23, Part D, the Division was under the understanding that given the very temporary nature of the <br />proposed access roads, that graveling the roads were unnecessary and would not be required. <br />March 13, 2018 <br /> <br />Tony Tennyson <br />Colowyo Coal Company L.P. <br />5731 State Highway 13 <br />Meeker, CO 81641 <br />