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C-1996-083 TR-65 <br />MLT Adequacy Review <br />04-Mar-2010 <br />Page 3 of 3 <br />18. An evaluation of pillar stability, using MULSIMTI, is presented in MTI 2004 <br />Section 4.2. Factors of safety ranging from 1.64 to 2.5 were determined for the <br />layout utilized. However, as discussed in the preceding item, the orientation for <br />the mains now proposed with TR-65 differs by 45 degrees from what was <br />evaluated for the MTI 2004 report. Please re-evaluate the anticipated pillar <br />stress levels and factor of safety expected, given the proposed change in <br />orientation of the corridor beneath Terror Creek, and verify that the required <br />factor of safety will continue to be achieved. <br />Pillar stability for the proposed orientation of the West Mains was evaluated <br />with MTI 2010. In addition to the 5-entry West Mains, the model included a <br />rock storage area located adjacent to the southernmost entry. Anticipated <br />factors of safety are shown to be sufficient for the West Mains and rock <br />storage areas. Southeast of these two features is an area that was longwall <br />mined in 2005 and 2006. The factor of safety for the rock storage area would <br />be reduced to 1.4 if retreat mining were to be initiated in the longwall area. <br />An inquiry to Jim Stover, P.E. confirmed that BRL will not be returning to <br />the longwall area to conduct retreat mining operations. Item resolved; no <br />additional response is required. <br />MTI 2004 Section 5.0 - Overburden Stability <br />19. Please provide a statement addressing potential (if any) impact to the anticipated <br />stability of the overburden that may be expected due to the proposed change in <br />orientation of the West Mains. <br />MTI 2010 does not specifically address overburden stability using the <br />corridor location proposed with TR-65, but pillar stresses and factors of <br />safety were analyzed (see item 18). No additional response to this item is <br />required. <br />I do have one new comment/question: Does BRL intend to incorporate both MTI <br />studies (2004 and 2010) into the Permit? I think that would be advisable. <br />This concludes my comments for TR-65. Please do not hesitate to contact me with any <br />questions that may arise. <br />cc: Sandy Brown, DRMS