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NEWMONT <br /> Newmont Mining Corporation <br /> Cripple Creek and Victor Gold Mine <br /> PO Box 191, <br /> Victor,CO 80813 <br /> www.newmont.com <br /> Memo <br /> July 20, 2016 <br /> • Tim Cazier-DRMS <br /> • Paige C bulski, EIT; Tom Byers, PE <br /> • ECOSA Seepage Slope Stability Analysis <br /> The Geotechnical Department at CC&V was notified of concentrated seepage at the base of the ECOSA dump on <br /> May 25, 2016. The working hypothesis for the source of the seepage is leakage from a buried water supply line <br /> that was constructed prior to placement of waste rock in the area. <br /> No obvious indications of instability related to the seepage were noted during visual inspections immediately <br /> after the notification on May 25;or during subsequent weekly inspections of the dump face,seepage water path <br /> and water collection area. Starting on June 2, LiDAR scans of the dump face were conducted on June 2,3,8, 22 <br /> and July 7 (all 2016). These scans have been used to evaluate whether displacement of the face of the waste <br /> dump is occurring. <br /> This memo discusses slope stability of the ECOSA waste dump in light of the on-going seepage. <br /> Background <br /> The ECOSA dump has been constructed in accordance with the design approved in the Cresson Project Mine Life <br /> Extension 2, Permit M-1980-244. The dump was constructed by end dumping, initially at a 300-foot dump <br /> height, and finishing with a maximum of 70-foot lifts with the ultimate toe of each lift set back 100 feet from the <br /> ultimate crest of the lift below,to facilitate grading to a 2.5H:1V slope. Slope stability analysis for the final <br /> configuration of the waste dump in a dry state indicated a minimum static Factor of Safety(FoS)of 1.66 and a <br /> minimum pseudostatic FoS of 1.16. <br /> The dump is located on sloping foundation as shown in attached Figures 1 and 2,and the water line is buried in <br /> the native ground under the dump. The following observations are relevant with regard to the effects of the <br /> seepage on waste dump stability. <br /> ■ As observed along the toe of the waste dump,seepage is occurring along the interface between the <br /> waste rock and the native foundation (i.e.,the pre-dump ground surface). There is distinct iron staining <br /> where the seepage daylights at the toe of the waste dump. <br />