Laserfiche WebLink
West Elk Mine <br />reduce the risk of movement of the dam itself and damage due to movement of the landslide located on <br />the left abutment of the dam. The construction and implementation of these structures and activities will <br />allow the dam to withstand a seismic event of at least magnitude 2.3 (Richter scale) generating a peak <br />ground acceleration (pga) of 0.16 g. As stated in the GEI report, a maximum seismic event and pga <br />anticipated to be generated by mining in the SOD will be ML 2.3 and 0.06 g, respectively. <br />The data collected will he used to determine the future need and nest locations for seismic <br />monitoring stations in the SOD area. <br />hSeismic Notification and Results of Monitorin <br />In the event that seismic monitoring indicates the seismic parameter (0.16 g) of the stability analysis for <br />the Monument Dam has been exceeded by mining events, MCC will, within two days, measure the survey <br />monuments (provided weather conditions allow finding and measuring the monuments), evaluate the <br />condition of the dam, and provide an electronic or verbal report to the CDMG of the survey. If the <br />changes appear to compromise the integrity of the dam or reservoir, the Division, the Minnesota <br />Reservoir Company, SEO, USFS, and other appropriate agencies will be notified by MCC <br />***immediately***. Arrangements will be made with the Division, the irrigation company, and the SEO <br />to inspect the dam and reservoir as soon as possible if damages due to mining activities are found. <br />Mitigation will be implemented to repair damages to the dam or reservoir basin. A report of the event, <br />inspection, and any mitigation requirements will be submitted to the Division within 3 months of the <br />event. <br />2)Freguency of Seismic Monitoring <br />Quarterly reports will be generated from the above monitoring and a copy delivered to the CDMG and <br />USFS within a month following the end of the quarter. This monitoring will continue until mining is <br />completed in longwall panels E-1, E-2, and E-3 and E-9 through E-12 or as long is as necessary to <br />determine the impacts, if any, of microseismicity generated by MCC subsidence mining of the SOD on <br />Monument Dam. <br />Monitoring Frequencv - 2.05.6 (6)(b)(1)(D,E & F) <br />Unless as otherwise noted above, the subsidence and seismic monitoring will be perfonned semi-annually <br />and reported to the CDMG semi-annually, as well. A summary of the visual observations and monitoring of <br />subsidence will be provided in a quarterly letter report to CDMG and to the USFS. <br />Subsidence Control Plan - 2.05.6 (6)(b)(iii)(B), (6)(d)(i&ii), (6)(e)40 & (6) (t) fl-vii) <br />Description of MiningMethods -2.05.6 (6) (fi (N)(A& B) <br />As discussed in Section 2.0-5.6(6)(e)(i)(A), Brief Description of Mining, %vfeihod, the longwall mining method <br />is planned for Apache Rocks and Box Canyon mining areas. An east-west panel layout, is planned except for <br />the two northeast panels (IONTE and 11NE) which are orientated in a north-south direction. Longwall mining <br />of the E Seam (in Sections 32, 33 and 34 of T13S and in Section 3, 4, 9 and 10 of ? 14S) is planned in the <br />South of Divide mining area. Although longwall mining may initially induce more caving and fracturing of <br />the roof rocks as con pared to the room-and-pillar method due to the complete removal of coal in the panel, it <br />offers the advantages of maximizing resource recovery. The longwall method also causes more uniform <br />subsidence (full extraction of panel) and causes equilibrium conditions to be reached in a shorter period of <br />time (i.e., there is no additional, lingering pillar crushing in panels). <br />Preventive Measures - 2.05.6(6) W (N) <br />2.05-168 Revised June 2005 PRIO, Rev. March 2006; Mai- 2006 PRIO, A'ov. 2006TRI07„4p7-il 2O07TR108; Sep. 2007 PR12; Feb. 2008 PR-12