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• Groundwater drawdown at the quarry wall would be 300 feet. <br />• The thickness of the permeable fractured bedrock is 500 feet. <br />• Groundwater flow is horizontal. <br />• The potentially affected area has homogeneous characteristics, is unbounded, and has <br />infinite aerial extent. <br />The analysis by Whetstone used the groundwater modeling software MODFLOW-SURFACT <br />V.4.0- (Hydrogeologic 2011) and a similar set of assumptions with the following exceptions: <br /> <br />• The potentially affected area is bound (no flow) to the south by the Arkansas River. The <br />river elevation is below the planned elevation of the pit floor and therefore the cone of <br />depression caused by groundwater drawdown cannot expand past this boundary. <br />• The potentially affected area is also bound (no flow) by Currant and Tallahassee Creeks <br />where the elevations of the drainages are below the minimum level of the planned pit <br />floor. <br />The analyses by ERM and Whetstone generally provide similar estimates of groundwater inflow <br />to the quarry. ERM estimated that inflows during mining were likely to range from 15 to 25 gpm <br />(ERM 2019). These values are consistent with observed flows from the existing quarry face, which <br />is about 270 feet high and typically has little or no seepage except after precipitation events and <br />during spring snowmelt. Whetstone estimated an inflow rate of 27 gpm to the quarry at its full <br />extent after 100 years of mining (Whetstone 2020a). This estimate is considered to be <br />conservatively high because groundwater systems in fractured granite bodies with low hydraulic <br />conductivity tend to be poorly connected over broad areas and the Parkdale an unnamed are likely <br />to act as boundaries to the north and east (Whetstone 2020a). Under any circumstance, the <br />predicted inflows are low enough to not be of operational consequence, and advanced dewatering <br />of the quarry by pumping from groundwater wells would not be required to facilitate mining. Free <br />flowing groundwater that enters the quarry during mining would be routed to settling ponds for re- <br />infiltration to groundwater or discharge to Currant or Tallahassee Creek. <br />