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STATE OF COLORADO <br />COLORADO GEOLOGICAL SURVEY- serving the people of Colorado <br />Department of Natural Resources <br />1313 Sherman Street, Room 715 <br />Denver, CO 80203 <br />Phone: (303) 866-2611 <br />Fax: (303) 866-2461 <br />DATE: February 2, 2010 <br /> <br />COLORADO <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />TO: Berhan Keffelew, Tony Waldron, David Berry <br /> Bill Ritter, Jr. <br /> Governor <br />FROM: Jon White, TC Wait <br /> James B. Martin <br /> Executive Director <br />SUBJECT: CGS assessment of a January 2010 Technical Revision of the Vincent Matthews <br /> <br />Pikeview Quarry Mine Plan 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) is providing this review of a proposed January 2010 <br />Technical Revision to the Pikeview Quarry mine plan. The purpose of the mine plan revision is <br />to permit the mine operator to remove unstable rock blocks. These blocks, shown as the south <br />and north blocks in Figure 1, did not fail completely in the December 2008 and September 2009 <br />rockslides. While definitely deformed and offset at the head scarp they have remained relatively <br />intact rock masses that have formed high, unstable cliffs that hang above the rockslide rubble <br />zone. A portion of the southern block is what failed in September 2009. Monitoring of the slide <br />by the operator from September 2009 into January 2010 indicates continued creep-type <br />Figure 1. Pikeview quarry rockslide after September 2009 reactivation (shown in red shading). <br />Dashed red line is the headscarp. Annotations are informal names of features referred to in this letter.