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Colowyo Coal Company <br /> 5731 State Highway 13 <br /> Meeker, CO 81641 <br /> <br /> <br /> <br /> September 14, 2009 <br /> <br />SEP 1 2009 <br />_ , ti-,i;lamation, <br />Oiniag and Safety <br />Mr. James R. Stark <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />RE: Colowyo Mine's response to the Division's Secondary Adequacy Review for <br />Technical Revision - 78, Colowyo Coal Mine, Permit No. C-1981-019. <br />Dear Mr. Stark, <br />Colowyo received the Division's secondary adequacy comments for TR-78 and has the <br />following comments and responses. <br />4. Please submit general and detailed design information for the temporary sump <br />regarding sizing, spillway placement (Rule 4.05.7) and routing from and to the <br />Prospect Ditch, as required by Rule 2.05.3(4) and Rule 4.05.9. The Division <br />understands the impoundment will be incised (no embankment) and will discharge <br />during both the 10-year and the 25-year storm events. <br />Response: The sump design has been included in this submittal as Figure 3. <br />5. The volume of the sump as represented in the SEDCAD runs provided with the 24 <br />June 2009 responses is 2.44 ac-ft. This volume does not agree with the volume as <br />calculated by the permit text on page Exhibit 7-14R-1 (22' x 335' x 8' = 58950 cubic <br />feet) which is 1.35 ac-ft. <br />Response: An area capacity table is provided in Figure 3. This capacity of 2.57 <br />ac-ft is slightly larger than assumed by the SEDCAD model. This can be adjusted <br />as necessary in the field. Text has been added to page one to clarify that the <br />dimensions Colowyo previously provided were for the bottom of the sump. <br />6. Pursuant to Rule 2.05.3(4)(a)(ii), please provide a detailed plan for operation and <br />maintenance of the temporary sump, including dewatering, sediment clean-out, <br />inspections and any necessary repairs following storm events. <br />Response: The temporary sump will be operated and maintained in accordance <br />with the parameters mentioned in Volume 1, Section 2.05.