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NOV �5 Jp14 <br />of Recta{ ty °rt, <br />Mr. Robert Zuber, P.E. <br />tX1V\ln9 & Sa <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />RE: New Horizon North Mine <br />Permit No. C- 2010 -089 <br />TR -06 Adequacy Review Responses <br />Dear Mr. Zuber: <br />Tri -State Generation and Transmission Association, Inc. (Tri- State) has received your adequacy <br />letter for TR -06, dated October 30, 2014 and provides the following responses to your comments on <br />behalf of the Western Fuels- Colorado, A Limited Liability Company (Western Fuels- Colorado) New <br />Horizon North Mine. <br />1. It is unclear why there is no new SEDCAD run for the north ditch but there is one for the south ditch. <br />Please explain this apparent omission. <br />Response: The new SEDCAD run for both the north and south ditch are included in the 10 <br />year -24 hour storm event compliance demonstration for Pond NHN -002. <br />2. In the proposed text, on Appendix 8 page 8, it is written that erosion of ditch bed material may <br />happen during storm events and that maintenance will be required. This approach does not meet <br />Rule 4.05.4(2) (a), which states that ditches must be constructed to be stable. Also, the new version of <br />Map 2.05.3(4) -9 indicates slopes of 1 - 4 %for the north channel and 5% slopes in the upper portion <br />of the south channel; however, the previous submittal (Table 2.05.3(4) -8 -2) indicates that channels <br />with 12' width and slopes of 3% or more require riprap. Please explain this apparent discrepancy. <br />Response: To ensure compliance with rule 4.05.4(2)(a), the sentence indicating that erosion of <br />ditch bed material may happen during storm events has been removed. <br />In the previous submittal, the maximum peak flow from the entire ditch watershed was used <br />for design purposes on all ditch segments. However, in the most recent submittal, segments <br />of the ditches upstream of the pond inlet were designed using the peak flow from only that <br />watershed and not the entire cumulative watershed peak flow. Finally, a slight adjustment to <br />the ditch centerline in the most recent submittal resulted in smaller watershed areas and peak <br />flows. <br />AN EQUAL OPPORTUNITY /AFFIRMATIVE ACTION EMPLOYER <br />A Touchstone Energy` Cooperative <br />CRAIG STATION ESCALANTE STATION NUCLA STATION <br />P.O. BOX 1307 P.O. BOX 577 P.O. BOX 698 <br />CRAIG, CO 81626 -1307 PREWITT, NM 87045 NUCLA, CO 81424 -0698 <br />970- 824 -4411 505- 972 -5200 970 -864 -7316 <br />