2009-03-23_REVISION - C1981019 - Laserfiche WebLink

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COLOWYO'S RESPONSES TO THE DIVISION'S FEBRUARY 27, 2009 PAR FOR TR-77 - HIGHWALL MINING IN SOUTH TAYLOR On revised page ST/LW- Rule 2, page 129, Colowyo indicates that the targeted highwall mineable seams may include the X, A, B, C, D and E. The included report from Agapito Associates, Inc. (Agapito) dates 13 April 2007, states that their study if for the E2 seam highwall mining in the southern portion of the West Pit. Based on the information contained in the Agapito report, there is no information that highwall mining will be performed in any other seam. If Colowyo is planning on mining any other seams in South Taylor besides the E- seam, a report containing a study of the potential impacts and designs of these additional seams needs to be forwarded to the Division for review. If Colowyo is only planning on mining the E-Seam, please change the above referenced text description to reflect this fact. Response: Colowyo had added to the above referenced text a statement that clarifies that the E-Seam is the only one to be highwall mined at this time. Colowyo also added a statement that should any other seams be mined, Colowyo will provide the Division with additional engineering reports and information prior to such activity. 2. The above referenced Agapito report states that the drill hole information used to develop the web and barrier pillar designs came from holes WP-05-07 and WP- 05-08, with WP-05-08 being nearer to the mining. This information is shown on the enclosed Figure 1, which shows the locations of the drill holes as well as the location of the proposed highwall mining. The report and Figure 1 state that this study was for five highwall mining panels in the orientation shown on Figure 1. The information in the Agapito report, however, does not correlate with the information shown on revised Map 23A. On Map 23A there are two discrete highwall mining areas and the layout of the highwall mining panels appears to be different than that shown in the Agapito report. The Division also questions whether the proposed highwall mining in the northwest portion of the South Taylor Pit as depicted on Map 23A is included in the Agapito study area. In Section 4.23.9, page 4.23-2 of the PAP, Colowyo states that highwall mining is designed for zero subsidence. Please provide documentation that the highwall mining proposed on Map 23A will meet Colowyo's design commitment for zero subsidence and will also meet the guidelines that have been developed for web and barrier pillars by Agapito. Please document that the proposed change in highwall mining orientation shown on Map 23A will conform to the Agapito web and barrier pillar design guidelines. Response: The northwest highwall mining area is not being mined at this time. This area is simply a `proposed area'; while the area to the northeast, near the South Taylor Pit Lot, is the one being addressed in this technical revision. If the northwest area is mined in the future, Colowyo will provide the Division with