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27. In reviewing the information on Map 14$ Map 27 and the "Station Locations "figzrre on the second <br />page of the Exhibit l8 report, it appears that the closest that longwall mining will get to a <br />seismometer is 4500 feet by the end of 2006. Assuming that PR-10 is approved by the end of 2006, <br />please explain how BRL intends to show that seismic events recorded at a seismometer that is no <br />closer than 4500 feet away from the generating longwall mining event can be used to predict the <br />seismic effect on the Bruce Park Dam from events that are generated by longwall mining that will be <br />2500feet awayfrom the Bruce Park Dam. <br />[n the submittal dated December 28, 2006, BRL stated that asite-specific attenuation relationship will <br />be developed to determine the effects at varying distances from a seismic source, BRL further stated <br />that this process is routinely used by seismologists to determine ground motion at a site from a distant <br />earthquake. <br />However, since BRL is proposing to mine within 1390 feet of the Bruce Park Dam, the Division <br />requests that BRL obtain seismic data generated by mining events that are about 1390 feet from a <br />seismic receiving station. In their letter dated February 22, 2007, the USDA-Forest Service is <br />requesting that, when mining approaches seismic station FGH, additional seismic data recording and <br />analyses be made and compared to current modeling. The Division agrees with this approach. Please <br />submit an analysis ofthe seismic data obtained when mining gets to within about 1390 feet ofseismic <br />station FGH. If the analysis does not confirm the current seismic modeling approved in PR-10, <br />appropriate changes to the modeling will need to be made. <br />28. Since the Hughes cabin is mentioned in Section 2.05.6(6)(a)(ii)(A) on revised permit page 2.05-103, <br />please include a discussion of the cabin in Section 2.05.6(6)(b)(i)(C) and describe any potential <br />effects, if any, on it from subsidence. <br />The Division has no further concerns. A discussion was added to page 2.05-107 ofthe December 28, <br />2006 submittal. <br />29. /n PR-IQ BRL is proposing to longwall undermine Dove Gulch and Dove Cave. The Division's <br />regulations do not necessarily prohibit these actions, although certain protection or mitigation <br />measures may be needed. However, the stipulations on Federal Coal Lease COC 61209 mayprohibit <br />such actions. If the USDA-Forest Service does not approve the proposed actions, then BRL does not <br />have the right to enter and longwall undermine those two areas. In this case, the Division would not <br />be able to approve PR-!0 as written. The Division will need documentation that the USDA-Forest <br />Service approves of these changes. <br />In a letter dated February 22, 2007 to the Division, and included in this adequacy review letter, the <br />USDA-FS is approving the undermining of Dove Gulch and Dove Cave with conditions. Please <br />respond to the permit text changes requested by the USDA-FS in their February 22, 2007 letter. <br />30. On revised page 2.05-11 Q the last sentence reads in part "...subsidence does affect... ". This should <br />be revised to state "subsidence does not affect... ". <br />The Division has no further concerns. The sentence in question was moved to page 2.05-I 1 1 and this <br />page was revised in the December 28, 2006 submittal. <br />9 <br />