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Ms. Catherine Robertson <br />Mazch 20, 2008 <br />Page 5 <br />significant surface impacts are very likely including surface cracks that will <br />intercept any water flow, both sheet flow and channelized flow, including Big Salt <br />Wash a perennial stream {as indicated in Appendix C Subsidence). Where hard <br />sandstone or other brittle rocks are present at the surface, ground cracking in this <br />scenario is likely to be extensive. <br />In addition, back stowing entries is not common practice and if discussed as a <br />necessary measure, the applicant will have to demonstrate that this can be <br />accomplished during routine mining operations. This subsidence control <br />measure will need to be included in our DBMS pernut application. <br />The DBMS believes that the 200 foot "minimum overburden depth" is too <br />liberal to prevent undesirable impacts. Given the thickness of the coal to be <br />mined and the subsequent subsidence of 6-9 feet, we believe that the impacts <br />described on page C-4 of the PDEIS are likely, but they may be understated. <br />Otherwise we concur with the subsidence estimates and the methods used to <br />calculate subsidence. <br />Please feel free to contact me if you have any questions regazding our review of the Red <br />Cliff Mine ]?DEIS. <br />Sincerely, <br />~%~~ ~? ~3 <br />Michael P. ]Boulay <br />Environmental Protection Specialist <br />C: Sanciy Brown, Dan Mathews, and Kent Gorham/DRMS <br />Glenn Wallace/BLM <br />