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Newmont Corporation <br /> July 23, 2020 <br /> Page 4 <br /> HYS performed MODPATH analyses for remediation scenarios. MODPATH results provide a <br /> visual representation of the model simulated groundwater flow path. Figures in this memo show <br /> MODPATH results for the BASE and PITWALL model for the simulated remediation scenarios. <br /> MODPATH results for the UPFLOW model are similar to the PITWALL model results (not <br /> shown). <br /> 3.1 Mass Balance of Groundwater Flow in the West Pit <br /> Current groundwater flow conditions include pumping BF5 to maintain groundwater elevations in <br /> the West Pit at approximately 8,580 feet (NGVD-1927 datum), as illustrated groundwater <br /> elevation contours in Figures 1 through 3. Captured groundwater from pumping BF5 (190 gpm) <br /> along with pumping downgradient alluvial wells M32 and M33 (total 15 gpm) is sent to treatment <br /> and subsequently released to Rito Seco with the exception of the brine from the reverse osmosis <br /> process. <br /> The source of groundwater flow into the West Pit is primarily from the upgradient alluvium <br /> entering the West Pit on the east side. Alluvial groundwater inflows are estimated to range from <br /> 134 gpm for the UPFLOW model to 152 gpm for the BASE model (Figures 1 through 3). Other <br /> lateral inflows include groundwater from the North Pit area and the Precambrian unit. A <br /> component of vertical upflow in the West Pit is simulated in the UPFLOW model (Figure 3). The <br /> pumping control in the West Pit limits the amount of flow out of the West Pit to between 8 and 9 <br /> gpm for the three models. The groundwater that leaves the West Pit is captured by alluvial wells <br /> M32 and M33. <br /> The large inflow component from Rito Seco alluvium on the east side of the pit is a critical factor <br /> that is estimated to be occurring under current conditions,as it may be as important to keep inflows <br /> out of the West Pit as it is to control outflow from the pit.As such,this is an important groundwater <br /> flow component to understand better. The approach to better understanding this flow component <br /> is presented in Section 4.0. <br /> Based on current conditions, a number of remediation scenarios were evaluated. A summary of <br /> the results from these scenarios is presented in the following sections. <br /> 3.2 No-Action Simulation <br /> The no-action simulation does not include pumping of any wells. As expected, water levels <br /> increase to pre-pumping conditions (Figures 4 through 6). While the total amount of water <br /> entering the West Pit is less than the current conditions because pumping BF5 induces flow <br /> towards that well, there is significant outflow that wouldn't be allowed under the current CDPHE <br /> discharge permit. Total groundwater flow out of the West Pit ranges from 116 gpm in the BASE <br /> model to 120 gpm in the UPFLOW model. It is expected that the groundwater would discharge to <br />