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STATE OF COLORADO <br />COLORADO GEOLOGICAL SURVEY- serving the people of Colorado COLORADO <br />Department of Natural Resources q ? & C 1, <br />1313 Sherman Street, Room 715 <br />Denver, CO 80203 <br />Phone: (303) 866-2611 ? \'?F ? t``??, ? `? <br />Fax: (303) 866-2461 G G- S <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />DATE: January 7, 2009 Bill Ritter, .Jr. <br />Governor <br />TO: Berhan Keffelew, Tony Waldron, and David Berry Harris D. Sherman <br />FROM: Jon White, TC Wait Executive Director <br />Vincent Matthews <br />Division Director and <br />State Geologist <br />SUBJECT: Quarry wall rockslide at the Pike View Mine - Summary Report <br />At the request of the Colorado Division of Reclamation, Mining, and Safety (DRMS) the <br />Colorado Geological Survey (CGS) submits this geologic review summary concerning an <br />aggregate quarry rockslide at the Pike View Mine in El Paso County that occurred on Tuesday, <br />December 2, 2008. CGS engineering geologists visited the site on Thursday, December 11, <br />2008 with representatives of the mine owner and DRMS. At the time of our inspection, active <br />mining operations were suspended, and drilling and hauling equipment were idle. <br />The mine is located within the Cascade Quadrangle where the geology was recently <br />mapped by the CGS (Morgan and others, 2003). For our review, DRMS provided a 1994 Mine <br />Permit document and a 1986 slope stability evaluation by the Mine Safety and Health <br />Administration (MSHA). We also reviewed the on-line 2001 Decision Notice by the National <br />Forest that permitted the removal of granite on forest lands above the quarry wall. The mine <br />operator provided permit plan maps and cross sections, and oblique aerial photographs taken <br />both before and after the December 2nd failure. The mine permit referenced some geotechnical <br />investigations by the mine operator's consultant but the CGS did not have the opportunity to <br />review any geotechnical investigations or stability analyses for this review. <br />1