2010-11-09_REVISION - C1981019 (2)

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Map 12 - Hydrology, South Area, shows reclamation that has been completed at the Colowyo Mine as it relates to backfilling and grading and post-mining channel construction. Given the ongoing and continual nature of the reclamation at the Colowyo Mine, this map will never be a completely accurate representation of what is actually reclaimed on the ground except for at one specific point in time. The map does, however, need to be accurate for any given reclamation year. Colowyo will need to update Map 12 on a yearly basis to show the reclamation that has occurred to date. The Division recommends that Colowyo provide a new copy of Map 12 in the spring of each year showing the previous year's reclamation. The map will need to be submitted as a Minor Revision to the permit. Response: Colowyo understands that Map 12 will be an on-going misrepresentation of what is actually reclaimed on the ground except for at one specific point in time. Colowyo does not feel very strongly about having to submit Map 12 as a Minor Revision to the permit in the spring of each year, mainly because the only way Colowyo would be able to submit each change would be under an MR and would require permitting action. Colowyo suggests revising and submitting Map 12 along with the ARR each year instead of as a Minor Revision to the permit. Rule 4.05.4 - Stream Channel Diversions and Stream Channel Reconstruction 4. The narrative on revised page Exh.7-14R-3 discusses the use and design of temporary ditches to divert runoff from spoil and reclaimed areas to the unreclaimed East Pit. These temporary ditches result in areas that are excluded from producing runoff in the SEDCAD modeling for the Prospect Pond. The text narrative references Figure Exh.7-14R-7 and states that the ditches are "short term in nature and will be removed as reclamation progresses." Figure Exh.7-14R-7 shows one of the ditches extending a significant distance northeast into previously reclaimed areas. Please explain in more detail in the narrative on revised page Exh.7-14R-3 how and when these ditches will be constructed and used and when each ditch will be removed or reclaimed. Response: Colowyo has added text to page Exh. 7-14R-4 detailing how and when the five temporary ditches within the East Pit will be constructed. All ditches will be reestablished immediately following 2010 East Pit reclamation efforts have been completed. These temporary ditches will be reconstructed, for the most part, in the same locations they were constructed last year in order to prevent runoff and sheet flow from the haul truck access road reaching fresh reclamation. Each temporary ditch will be absorbed with the respective corresponding remaining reclamation block as reclamation progresses from east to west (as shown on Map 29) in the East Pit. 5. Currently approved permit page Exh.7-14D2 (revised 25 July 2006, TR-63) shows the approved design information for the Final East Pit Ditch and the Prospect Ditch permanent channels. Proposed SEDCAD design runs for the 10-year, 24-hour storm event for the Prospect Pond result in new design information for the Final East Pit Ditch and Prospect Ditch that would appear to supersede the currently approved information on page Exh.7-14132. Please review the designs for the Final East Pit Ditch and the Prospect Ditch and submit new permanent channel design information that is consistent with the SEDCAD modeling submitted with Technical Revision 87 for these two ditches. Response: After further review, the design formerly provided in Exh. 7-14D is out of date. This section provided design information for Prospect Ditch, the Final East Pit Ditch and the Section 16 Fill Ditch. With this submittal, all former materials in Exh. 7-14D are to be removed and replaced with design information for the Section 16 Fill ditch only. Exhibit 7-14R contains updated design information for the Prospect Ditch, North Tributary-East Pit Ditch, and the Final East Pit Ditch. The ditch summary materials provided in Exhibit 7, Item 14, Table 1 have also been updated. Colowyo Coal Company, L.P. • 5731 State Highway 13 • Meeker, CO 81641 T + 1 970 824 1578 • F +1 970 824 1598 • http://prospect.riotinto.org/irj/portal