2010-12-15_REVISION - C1981019 - Laserfiche WebLink

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18. Response Accepted. Colowyo has revised both the mine plan and the post-mining topography with the TR-81 responses. These changes have decreased the total amount of permanent spoil for the South Taylor Fills. 19. Division comments, 19a-f, are no longer relevant due to changes in the post-mining topography submitted in the Colowyo response. Please note that the Colowyo maps and cross sections were not found to be "confusing" to the Division, and no apology is required. The Division's comment referred to a comparison of the proposed changes to Map 20 in TR-81 to the currently-approved version of Map 20 (via TR-63 in June 2007). In the initial submittal of TR-81, Colowyo did indeed propose a lowering of the post-mining topography. 20. Response Not Accepted. In their response Colowyo states that the post-mining topography has been changed with this submittal and that the limits of the East Taylor Fill ditches have been extended. While the Division agrees that this is the case, the topography has not been changed to address the large, flat area on the upper (south) portion of the East Taylor Fill that encompasses approximately 110 acres. It is still not clear how water will be diverted off of the fill in this location and into a designed ditch. All runoff from the fill must comply with Rule 4.09.1(7), which states that "...excess spoil shall be... graded to allow surface and subsurface drainage to be compatible with the natural surroundings..." and Rule 4.09.2(5), which states "(d)rainage shall not be directed over the outslope of the fill." The current design of the East Taylor Fill does not meet these requirements for surface water runoff. Pursuant to Rules 4.09.1(7) and 4.09.2(5), please describe how Colowyo plans to divert the runoff from the large, flat area of the East Taylor Fill into stabilized ditches which will safely pass the 100-year, 24-hour storm event. Please include this description in the text under Rule 4.09 - Disposal of Excess Spoil, which begins on Page 20 (South Taylor/Lower Wilson-Rule 4, Page 20) in Volume 12. Response: As requested, the post-mining topography in the area described as the "large flat area" of the East Taylor fill has been revised by leaving additional fill in place in that area to produce a gentle camber on the top of the fill which will direct runoff to the East Taylor West Tributary and the East Taylor East Tributary Ditches. All associated maps have been updated with this change. 21. Response Not Accepted. In their response Colowyo states that the post-mining topography has been changed with this submittal and that the limits of the West Taylor Fill ditches have been extended. While the Division agrees that this is the case, the topography has not been changed to address the large, flat area on the upper (south) portion of the West Taylor Fill that encompasses approximately 70 acres. It is still not clear how water will be diverted off of the fill in this location and into a designed ditch. All runoff from the fill must comply with Rule 4.09.1(7), which states that "...excess spoil shall be... graded to allow surface and subsurface drainage to be compatible with the natural surroundings..." and Rule 4.09.2(5), which states "(d)rainage shall not be directed over the outslope of the fill." The current design of the West Taylor Fill does not meet these requirements for surface water runoff. Pursuant to Rules 4.09.1(7) and 4.09.2(5), please describe how Colowyo plans to divert the runoff from the large, flat area of the West Taylor Fill into stabilized ditches which will safely pass the 100-year, 24-hour storm event. Please include this description in the text under Rule 4.09 - Disposal of Excess Spoil, which begins on Page 20 (South Taylor/Lower Wilson-Rule 4, Page 20) in Volume 12. Response: As requested, the post-mining topography in the area described as the "large flat area" of the West Taylor Fill has been revised by leaving additional fill in place in that