2025-06-23_REVISION - M1980244 (92)

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Cripple Creek&Victor Gold Mine al Valley Leach Facility Expansions ■ Detailed Design for Permitting NewFields Project No.475.0106.064• March 2024 Ore: Young's modulus and Poisson's ratio for the ore does not have a significant impact on the resulting liner displacements and was conservatively estimated to be 700 ksf, which is the lower bound value for rockfill (USSD, 2011). Poison's Ratio for the rockfill can range from as high as 0.4 to as low as 0.1 (Bowles, 1997). This analysis assumes a conservative Poisson's ratio of 0.2 for end dumped ore. Pit Backfill and Fill: Reported values indicate that the elastic moduli for rockfill is highly variable and influenced by a number of factors including parent rock material, particle size distribution, and effective stress conditions. Previous back analysis of rockfill at the mill platform resulted in the upper bound value for pit backfill and fill material. The lower bound value was estimated from lower bound values presented by Janbu (1963) and Fang (1991) for gravel and sand deposits. Foundation (Sands and Gravels): Elastic parameters were estimated to be equivalent to that of the low compactive effort pit backfill and fill material. Foundation (Bedrock): The bedrock foundation is composed of the competent host rock commonly found at CC&V, and relatively incompressible for the settlement analysis. A high elastic modulus consistent with the host rock was selected. • 5.2.3. Settlement Evaluation Results The results of the settlement evaluation indicate that total settlements under the ultimate loading from 550 feet of stacked ore (represented on Section A) will be on the order of approximately 16 feet, and maximum strain in the geomembrane (4.5 percent) occur at the center of the facility as represented in Section A. This amount of settlement is considered acceptable as the settlement below the facility is expected to be distributed along the entire length of the facility, maintaining design slopes, solution collection recovery systems, and geomembrane integrity. Settlements ranging from 5 to 7 feet were estimated for Section D over the Elkton Pit backfill. Settlement was evaluated with pit backfill placed with low compactive effort and with the uppermost 35 feet of backfill placed with high compactive effort as recommended in the VLF2 Phase 3 Design Report (NewFields, 2020). The low compactive effort pit backfill material results in a maximum strain of 11 percent, while the high compactive effort pit backfill reduces the maximum strain to 2 percent. LLDPE geomembrane can undergo high strains in lab settings; however, for conservatism, only strains less than 10 percent have been deemed acceptable for this analysis. Settlement was deemed acceptable provided that it did not negatively influence solution drainage or leak detection systems. The PSSA will be constructed during Stage A, at the start of the expansion project. The PSSA facility was evaluated for settlement to determine the potential influence the surrounding • Page 23