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Mr. Joe Dudash <br />June 4, 2007 <br />Page 2 of 2 <br />Our letters dated June 11, 2003 and Mary 16, 2006 both recommended further analysis of the landslide and <br />evaluation of the potential consequences of failure. After reviewing the Yeh, 2006 report together with the above <br />additional materials, we feel the permit applicant has provided a satisfactory analysis of the landslide. Specifically, <br />onsite soil borings were taken on the landslide and laboratory tests were performed to determine soil shear strengths <br />and other index properties. The tests appeaz adequate and satisfactory for use in the intended slope stability <br />analyses. <br />We feel an important conclusion from the Yeh, 2006 report is that stability of the landslide will be reduced as a <br />result of the planned mining activity. A caveat to this conclusion was included that "...the slight reduction in global <br />stability would likely not cause a catastrophic slope failure large or fast enough to compromise the integrity of Bruce <br />Park Dam." While our office finds the slope stability analysis satisfactory, we continue to view mine-induced <br />seismic activity resulting in a factor of safety less than one for the landslide as a risk to the safety of Bruce Pazk <br />--- dam. As a result, monitoring ofmine-induced seismic activity and performance ofthe landslide is key to our office <br />recommending approval of the subject permit application. <br />As indicated above, we have received the quarterly micro-seismic monitoring reports from Bowie Resources, LLC. <br />We were also included in the recent meeting with your office, Bowie Resources, and others at the USDA Forest <br />Service office in Paonia, CO where a threshold monitoring program was proposed similar to that initially outlined in <br />our May 16, 20061etter. In theory, the current seismic monitoring program would incorporate a model to translate <br />recorded seismic activity, both mine-induced and naturally occumng, into a form compatible for comparison with <br />yield accelerations calculated at the landslide. If the minimum yield acceleration for the landslide were exceeded, <br />then notifications, field evaluations and, if necessary, remedial actions would be activated. <br />In summary, we find that the submitted additional materials satisfactorily address comments and concerns raised in <br />the June 11, 2003 and May 16, 2006 letters. Our recommendation for approval ofthe subject permit is contingent <br />upon development and implementation of a comprehensive threshold monitoring program for the landslide. We <br />appreciate the efforts put forth by the applicant in providing the additional materials and feel that development of a <br />monitoring program would allow the proposed mining to occur while providing a level ofprotection to the safety of <br />Bruce Park Dam. <br />We appreciate the opportunity to review and provide comment to the Colorado Division ofReclamation Mining, and <br />Safety and hope the information provided is helpful in your review of the submitted permit application. <br />Sincerely, <br />/~~ <br />Jason P. Ward, Ph.D., P.E. <br />Dam Safety Engineer <br />cc: Wayne Schieldt, Division Engineer <br />Stephen Tuck, Water Commissioner <br />Mark Haynes, Chief of the Safety of Dams Program <br />John Mathewson, Terror Creek Ditch & Reservoir Company <br />