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Technical Memorandum <br /> Cripple Creek&Victor Gold Mine ■ <br /> Stability Evaluation for Arequa Gulch VLF—Mill Solution Injection Program <br /> NewFields Job No.475.0106.008 <br /> July 12,2016 <br /> 2.0 STABILITY EVALUATION <br /> 2.1 Model Development <br /> A section orientated perpendicular to the AGVLF slopes at each well location was reviewed. <br /> Based on the review, it was determined that no significant differences existing between the two <br /> locations and only the section at well #1002 was selected for the stability evaluation. The <br /> orientation of the stability section is noted on Figure 1. <br /> The base grades beneath the facility were based on the as-built grading contours and the <br /> existing VLF slopes were based on an aerial survey performed in October, 2015. <br /> Outside the influence of the injection wells, the phreatic surface was modeled at three feet <br /> over the base liner. The wells are sited outside of the Phase IV process solution storage area <br /> (PSSA), and thus ponded solution at the base of the facility is not expected beneath the wells. <br /> 2.2 Material Properties <br /> Material properties selected for the stability evaluation were consistent with previous <br /> evaluations at the site and our understanding and experience with these materials. All material <br /> properties used in the stability models are summarized in the following table. <br /> UNIT WEIGHT FRICTION COHESION <br /> MATERIAL (Ib/ft3) ANGLE(deg) (lb/ft2) <br /> Ore 120 39 0 <br /> Liner Interface 115 18 0 <br /> Foundation 125 40 0 <br /> 2.3 Saturation of Ore from Injection Wells <br /> Given the coarse nature of the ore materials and estimated hydraulic conductivities, it is <br /> expected that all mill solution introduced to the wells will percolate downward. There is likely <br /> some stratification within the heap between lifts that would influence the vertical hydraulic <br /> conductivity and subsequently the radius of influence around the well. The influence of the <br /> saturation radius around the well on the overall stability was evaluated through a parametric <br /> study. <br /> The worst case scenario in regards to slope stability would be saturation of the ore near the <br /> surface of the heap from the injection program. The following conceptual models were <br /> considered for the stability evaluation: <br /> Page 2 <br />