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DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866 -3567 <br />FAX: (303) 832 -8106 <br />STATE OF COLORADO <br />DATE: September 24, 2012 <br />TO: Berhan Keffelew, DRMS <br />FROM: TC Wait, DRMS <br />SUBJECT: Pike View Quarry (M -1977 -211): Amendment 3: Stability Analysis <br />The cross sections shown in Exhibit C show the growth medium on the benches in the granite <br />face. <br />• How will this material be placed to avoid water infiltration into the granite face, <br />joints, fractures, etc that could lead to slope instability over time? <br />• How do these joint/fracture sets orient in relation to the proposed cut face? <br />Mined Land Reclamation <br />COLORADO <br />D I V I S I O N O F <br />RECLAMATION <br />MINING <br />— &— <br />SAFETY <br />John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />Loretta E. Pineda <br />Director <br />Per your request, I have completed a preliminary review of the submitted stability <br />analysis as part of Amendment 3 for the Pike View Quarry permit. The purpose of the amendment <br />is to address the reclamation of the Pike View Quarry following slope failures in December 2008, <br />September 2009 and subsequent smaller scale events. The comments below should be addressed <br />as part of the adequacy response to DRMS. <br />The amendment proposes using the fault location (to be identified through field observations) as <br />inflection point for grading. <br />• The report states that investigation was limited due to access difficulties and safety <br />concerns on the slope face. Detailed mapping of the granite joints and fractures, as <br />well as fault location and condition of the granite is needed. During grading <br />activities, this information should be carefully observed and recorded. This may <br />impact the proposed design plans and require further analysis and design changes. <br />• Most faults are actually shear zones, and may contain many splays across a wide area. <br />It may be very difficult to identify the entire fault zone to determine a finite inflection <br />point. How will this be accommodated? If the fault is across a zone, how will the <br />inflection point for grading be determined? <br />• Given that the granite contains fractures and joint sets, as well as possible fault <br />splays, how will "stable granite" be determined? <br />The amendment describes the fill on the lower slopes being placed in a top -down manner, using <br />dozers to push material around. This will be a considerable amount of material, with some areas <br />nearing or over 100 feet in fill. Poorly placed fill may not provide the buttressing effect that will <br />help with overall slope stability. <br />• Fill placement procedures and detailed specifications are needed to ensure the <br />structural integrity of the fill section. <br />Office of Office of <br />Denver • Grand Junction • Durango Active and Inactive Mines <br />