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STATE OF COLORADO <br />COLORADO GEOLOGICAL SURVEY- serving the people of Colorado COLORADO <br /> W <br />" <br />w <br />Department of Natural Resources PP <br />t <br />t <br />1313 Sherman Street, Room 715 , <br />i <br />Denver, CO 80203 Ali <br />1 <br />Phone: (303) 866-2611 <br />E <br />Fax: (303) 866-2461 W <br />, <br /> DEPARTMENT OF <br /> NATURAL <br />DATE: November 2, 2009 RESOURCES <br />TO: Berhan Keffelew, Tony Waldron, David Berry <br /> Bill Ritter, Jr. <br /> Governor <br />FROM: Jon White, TC Wait <br /> Harris D. Sherman <br /> Executive Director <br />SUBJECT: CGS assessment of new September 2009 rock slide at the <br />Pike View Quarry Vincent Matthews <br /> Division Director and <br /> State Geologist <br />At the request of the Colorado Division of Reclamation, Mining, and Safety (DRMS) the <br />Colorado Geological Survey (CGS) has conducted an inspection of an additional failure of the <br />quarry wall that occurred on September 13, 2009 at the Pike View Quarry. CGS engineering _ <br />geologists Jon White and TC Wait visited the site on Tuesday, September 15, 2009 with -f-Ac 1 „ <br />0.1 representatives of the mine owner and DRMS. At the time of our inspection, active mining T?r <br />operations were still suspended due to the previous quarry rockslide of December 2, 2008. <br />The CGS conducted a site inspection of the quarry rockslide and provided an initial <br />assessment of the rockslide conditions to DRMS in a letter memorandum dated January 7, <br />2009. CGS also provided a memorandum to DRMS dated September 10, 2009 that included a <br />technical review of a slope stability report of the quarry rockslide that was prepared by <br />CTL/Thompson, Inc. dated May 19, 2009 (CTL/T Project No. CS17341-125). Movement <br />monitoring graph images for 14 of the 31 monitoring prisms between the dates of 9/9/09 - <br />9/29/09 were submitted to the CGS via e-mail on October 7, 2009. Certain prisms were lost that <br />were located in that portion of the south block that failed. <br />The purpose of this memorandum is to summarize our observations of the continued <br />movements of the rockslide and provide any other suggestions or recommendations concerning <br />safety and slope stability at the quarry. <br />The new rockslide is a retrogressive failure of the headwall and general enlarging of the <br />December rockslide, which illustrates the ongoing hazard concerns the CGS raised in our <br />January 7 and September 10 memorandums. Gross downward movement with new offsets <br />from 15 feet to over 40 feet occurred along the preexisting incipient scarp above both the south