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TRAPPER MtNtNG ANC. March 27, 2007 ~ ~ ~ ~' s', ;[ Ms. Janet H. Binns MAR 3 0 Zi101 Environmental Protection Specialist II Division of Reclamation, Mining and Safety Division n; r..::ia..t~iii:;n, 1313 Sherman Street, Room 215 Mining and Satety Denver, Colorado 80203 Dear Ms. Binns: This correspondence represents the continuing response to your letter of October 30, 2006 in which you requested information concerning the landslide experienced on October 8, 2006 in the azea referred to as the East Panel of the Trapper Mine. The status of responses to all of the DRMS questions will be addressed in this letter. For your convenience, I am setting forth your specific request, followed by our response and comments. . 1. Please provide the Division with a forensic geotechnical and engineering analysis that chazacterizes the landslide and its causes. In this analysis, please provide and evaluate the following: Blasting records from all blasts conducted at the Trapper Mine from September 24, 2006 to October 9, 2006. The geotechnical and engineering analysis should include reconstructions of each of the blasts detonated during this period to determine the maximum peak particle velocities achieved in the area of the landslide, and to determine compliance with the maximum weight of explosives regulatorily allowed to be detonated within any 8-millisecond period within each blast. The geotechnical and engineering analysis should include a determination of whether ground vibration from blasting contributed to, or otherwise had an effect upon, the landslide. INITIAL RESPONSE (November 22, 20061: We have already provided you with the blasting records you request. The blast diagram and other information on the shot reports should provide the data necessary to address the topic identified in your second sentence. ADDITIONAL INFORMATION: Agapfto Associates Inc. (AAI) has offered the following impression of any contribution to the slide from blasting. In our experience, it is not very likely that blasting vibrations trigger slope failure of this large volume. This is primarily because production blasting generates high frequency ground motion that is readily damped in the near field and contains insufficient low frequency energy to resonate with the low frequency geometry of the hill side. In the past, some localized highwall failures might have been triggered by blasting due to nearfield motion. High frequency, blastfng-fnduced stress effects are so small at distances beyond tens of P.O. Box 187 Craig, Colorado 81626 (970) 824-4401