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Revisions to Modeling Hydraulic Controls, West Pit Devon Hornvedt <br /> San Luis Project Newmont USA Limited <br /> • No-Action <br /> • Alluvial Extraction Wells <br /> • Slurry Wall with No Pumping <br /> • Slurry Wall with Pumping <br /> The initial conditions for the hydraulic control simulations were based on the potentiometric <br /> surface developed from the calibration simulation. <br /> 4.1 No-Action <br /> The no-action scenario was run to provide a baseline for comparison to various hydraulic control <br /> simulations. This scenario simulates shut-in of well BF-5 and no additional pumping from the pit, <br /> similar to the conditions that are simulated for the steady-state non-pumping condition. One <br /> difference is that the two alluvial wells (M-32 and M-33)are simulated as pumping(at rates of 7.5 <br /> gpm for each well). This simulation was run for a period of ten years (3,650 days). <br /> Results of the no-action simulation indicate the potentiometric surface within the West Pit returns <br /> to an elevation of approximately 8,601 ft amsl, which is similar to the level from the steady-state, <br /> non-pumping condition (Figure 9). This is a good independent check that the transient modeling <br /> for the no-action scenario provides essentially the same results as the steady-state non-pumping <br /> condition that was simulated for the base flow calibration. Groundwater flowpaths are overlain <br /> on the potentiometric surface map (Figure 9). Particles were initiated upgradient (southwest) of <br /> the West Pit and also within the length of the pit. The simulation indicates that if no remedial <br /> action is employed alluvial groundwater entering into the West Pit through the east end of the <br /> alluvial window will exit the pit through the west end of the window and eventually discharge to <br /> the Rito Seco. Although not explicitly addressed in this modeling, it is assumed that once alluvial <br /> groundwater enters into the West Pit, it reacts with the pit backfill and becomes elevated in key <br /> constituents prior to discharging back to the alluvial aquifer system. <br /> 4.2 Alluvial Extraction Wells <br /> This scenario simulates extraction from an array of alluvial wells positioned along the west end of <br /> the alluvial window while the pit extraction well (BF-5) is shut-in and no additional pumping <br /> occurs within the pit. <br /> For this simulation,no attempt was made to intercept alluvial groundwater from entering the West <br /> Pit(primarily along the east side of the window). The emphasis was on the capture of groundwater <br /> that would otherwise discharge from the West Pit through the alluvial window (primarily along <br /> the west side of the window). Several combinations of extraction wells and rates were simulated <br /> to optimize capture of groundwater that would discharge through the alluvial window. Only the <br /> pumping simulation that resulted in complete or near complete groundwater capture is described <br /> in this report. The simulation was run for a period of ten years (3,650 days). <br /> May 2023 6 Engineering Analytics,Inc. <br />