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Dudash,Joe From: Gorham, Kent Sent: Friday, October 19, 2001 9:25 AM To: Dudash,Joe Cc: Brown, Sandy; Hernandez, Dan Subject: TR-22, Bruce Park Dam Study, Bowie No. 2 Mine I have completed review of the materials submitted under TR-22 for the Bowie No. 2 Mine. I concur with your assessment that the submittal was minimal, at best, especially regarding the proposed seismic monitoring. I also reviewed the geotechnical report specific to the overall summary/findings and the embankment materials encountered through drilling. My comments are as follows. 1. The applicant seems confused as to the purpose of the seismic monitoring plan. The proposed plan (TR-22) calls for baseline monitoring prior to mining within one mile, then additional monitoring would continue as mining approached the dam. Collecting data at the dam from longwall mining outside a one mile radius from the dam would not seem to provide accurate or realistic estimates concerning the seismicity from mining inside the one mile radius. From my perspective, monitoring contemplated by the Division was meant to attempt to determine, from mining alreadv approved. the magnitude and character of seismicity due to roof collapse. This would require a monitoring plan focused around one or more of the existing (and already approved) panels to be mined in the next year or so. I would envision multiple seismic monitoring sites located over and adjacent to a panel at specific distance intervals out to at least 1500 feet. Monitoring would be conducted on a varying frequency, probably more frequent as mining approached and subsequently passes by, the seismic stations. Our goal is to understand the potential seismic impact prior to approval of mining within one mile of the dam. 2. I did not see any evaluation or analysis of the dam stability due to potential seismic effects from mining, or for the matter, natural causes. I would think that the dam would be more prone to failure when it was full than when it was empty. Assuming I am correct, I think their should be some sort of evaluation or statement regarding the stability, in general, as well as stability under a certain magnitude of seismic event using both saturated and un-saturated conditions for the dam. The report seemed very superficial. I would recommend the applicant propose a plan to collect seismic information from longwall mining in panels DS and D6, proposed for mining in 2002. This would allow sufficient time to then submit a subsequent revision for mining inside one mile of the dam. This subsequent revision would include an analysis of the data collected from panels D5 and D6 related to seismicity and possible material damage to the dam or other structures. Let me know if you have any questions