2009-09-14_REVISION - C1981019 (2)

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3. On new Map 45 - South Taylor Fill, Colowyo has several different topography lines drawn on the cross-sections. These lines include "pre-mine topo", "approved topo" and "proposed topo". While these lines are all useful for evaluating the proposed post-mining topography and the proposed changes to the currently approved post-mining topography, the labels will be confusing upon final approval of the revision (when the "proposed topo" becomes the "approved topo" and the "approved topo" is a historic "approved topo"). Colowyo may want to rethink the labeling of Map 45 or plan to resubmit the map with different labels once all technical adequacy issues have been addressed. Rule 3.02.2 - Determination of Bond Amount 4. In the cover letter Colowyo states they "...recognize that this revision will result in a change to bond calculations, but would like this change to be reviewed prior to making any permanent alterations to the bond information." The Division agrees that there will be a change to the bond as a result of this revision and that the best time to complete this change will be at the end of the technical adequacy review. Given the fluid nature of the review process, recalculating the bond at every step leads to extra work. That said, once all technical adequacy issues have been addressed, Colowyo will need to recalculate and resubmit their reclamation cost estimate for the fills, associated overburden stockpiles and backfilling and grading of the South Taylor Pit. The updated cost estimate will be a part of Technical Revision 81. Colowyo will need to update Exhibits 13 and 13A with new costs and volumes and all associated cost estimate maps and submit them to the Division for its review. Rule 4.05.4 - Stream Channel Reconstruction 5. In the cover letter Colowyo states that Technical Revision 81 includes proposed changes to four permanent drainage channels. Specifically, these channels are the West Taylor West Tributary Ditch, the West Taylor East Tributary Ditch, the East Taylor West Tributary Ditch and the East Taylor East Tributary Ditch. Each of these ditches has been extended in length, from 200 feet (East Taylor East Tributary Ditch) to 900 feet (East Taylor West Tributary Ditch). Colowyo has not, however, updated any of the general information regarding these ditches that is contained in Exhibit 7, Item 20, Part E - Permanent Channel Design. Please update this general information, including ditch length, average slope, peak flow and design information (bottom width, depth, side slopes, etc.). Please submit the new information in Exhibit 7, Item 20, Part E for the Division's review. 6. In conjunction with question 5 above, Colowyo has not provided any SEDCAD hydrologic modeling for the four ditch segments that have been changed as a part of Technical Revision 81. Please refer, for example, to the modeling of the Buckskin Draw Ditch, which is contained in Appendix Exhibit 7-14M, updated with TR-63 on 25 July 2009. Please submit the SEDCAD modeling for the four revised post-mining ditches for the Division's Review.