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• 2.05.6(6) <br />(b)(i)(B) A description of the subsidence related phenomena predicted to occurwithin <br />the permit and adjacent area is presented in Volume IIIA, Exhibits 15, 17 and <br />21. <br />The aerial extent of predicted subsidence related phenomena within the <br />permit and adjacent area is shown on Map 27 Subsidence. Traditional <br />subsidence and predicted rock roll out areas are both shown on the Map. <br />The aerial extent for the traditional subsidence is calculated based on a 25 <br />degree angle of draw over areas where subsidence is expected to occur. <br />The rock roll out areas are predicted using the Colorado Rockfall Simulation <br />Program, version 4.0, developed by the Colorado Department of <br />Transportation, the Colorado School of Mines and the Colorado Geological <br />Survey. The results of the rock roll out predictions are presented in Volume <br />VII, Geotechnical Studies, Tab 11. <br />(b)(i)(C) <br />The Bruce Park Main Dam and Saddle Dam should not be affected by <br />• subsidence since they lie entirely outside the limits of mining and are more <br />than 2,000 feet above the coal seam to be mined. The location of the mine <br />and its configuration are specifically designed to avoid subsidence or seismic <br />damage to the Bruce Park Dams. <br />GEI Consultants Inc. studied the stability of the main dam and saddle dam <br />during 2001 and 2002. See Volume X, Geotechnical Studies, Bruce Park <br />Dam. The study first determined the strength parameters, foundation and <br />soil types of the dams. The study then evaluated mine induced seismicity on <br />Bruce Park main dam and saddle dam. The basis for the analysis was that <br />mining in the area of the dams would occur over a period of 2 years and <br />would be within 1300 feet of the dam. Permanent deformations were <br />calculated considering a single magnitude 4.2 event and a combination of <br />100 magnitude 1.75 events, 20 magnitude 2.0 events, and 5 magnitude 2.5 <br />events. The study concluded the main dam and saddle dam would be stable <br />under the assumed seismic loadings. The Applicant has determined the <br />events used in the GEI Consultants study are conservative. See Volume <br />IIIA, Exhibit 18 Seismic Monitoring, Summary Statement. <br />• <br />PR-11 2.05 -106 - 11/08 <br />~ PP~eov~p <br />