2015-07-06_REVISION - C1982056 - Laserfiche WebLink

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26. On revised page 2.05-191.8, the applicant indicates subsidence monitoring of RCR 33 and 27 will be conducted quarterly while active longwall mining is occurring. Please clarify; does TC intend to monitor both these roads the entire time active longwall mining is occurring in the WCR? Or, will monitoring be initiated when the longwall operation is within a specific distance to these structures? If so, please indicate this distance. Response: - The referenced page and text section have been reviewed and revised to clarify that, for all monitored structures, monitoring will be initiated when active mining is within 500 feet of the reference structure. Revised copies of the corresponding pages accompany these responses for replacement in the PAP. 27. On revised page 2.05-191.9, the applicant indicates subsidence monitoring will be conducted at the railroad. A trigger has been specified when monitoring will be initiated for this structure, but a frequency of monitoring (daily, weekly, monthly... etc.) is not specified. Please revise this section to indicate the frequency the railroad will be monitored. Response: - The referenced page has been reviewed and revised to clarify that, for the railroad spur, monitoring will be on a daily basis for any portion of the spur which is within the affected area while active mining is occurring. Revised copies of the corresponding pages accompany these responses for replacement in the PAP. 28. Revised page 2.05-184.11 indicates mining of the WCR will result in undermining and subsiding the Yampa Valley Electric Line serving the mine. Exhibit 7K submitted with PRI O indicates that three powerlines will be impacted by subsidence. Please update page 2.05-184.11 to discuss all three powerlines that will be impacted by mining of the WCR. Response: - The revised and updated subsidence evaluation and associated text revisions provided as a supplemental submittal on March 19, 2015 address this Comment. Please note that while the subsidence evaluation does address potential subsidence effects to all three powerlines, as noted, only the Yampa Valley Electric line will be affected by those activities proposed under PR 10. 29. As indicated in the previous item, Exhibit 7K indicates mining and subsidence will impact three powerlines. The monitoring plan for the powerlines discussed on revised page 2.05-191.9 only discusses the Yampa Valley Electric Line. Please revise this section to discuss all three powerlines. Response: - Please refer to the previous response to Comment 28. 30. In the NW % of Section 13, T5NR86 West, a very steep slope with potential rock outcrops is located above RCR33. Subsidence from the east end of the WC-5RT panel will impact this area. Please evaluate the danger of rockfall caused by the subsidence of this slope and its potential impact to motorists on RCR33. Please revise the subsidence control plan to address this issue. Response: - The slope angle for the referenced slope is consistent with natural slopes in similar materials in the area, and the slope shows no evidence of instability or movement. The referenced rocky outcrops are thin, relatively high on the slope, and dip into the slope at a low angle. The generally stability of this area and these materials is evidenced by the lack of movement or rockfall in the road -cut which is due west a short distance from the referenced area. Given the generally stable configuration and lack of movement of the existing slope, the potential for rockfall to occur and affect the nearby County road is negligible. In the unlikely event that minor rockfall were to occur, the rock outcrop is high enough on the slope and the run -out on the slope is long enough that there is little potential that any rock material would reach the road. As a precaution, however, TC will place signs adjacent to the road right-of-way in this area warning motorists of potential rockfall. Other 31. The Division received three comment letters. The Colorado Division of Water Resources submitted a letter dated March 2, 2015. History Colorado submitted a letter dated February 10, 2015. The Office of Surface Mining submitted a letter dated March 17, 2015. These letters are enclosed for your review.