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To: Jared Ebert <br /> Date: December 29, 2017 <br /> Page 15 <br /> Comment 29 <br /> How has the water management pond been sized to provide adequate infiltration for the <br /> constant incoming volume of water from dewatering discharge? Is there enough capacity <br /> to account for increased pumping volumes if the Little Cache La Poudre Ditch leaks <br /> during periods of flow? Please provide documentation to substantiate your response. <br /> Response 29 <br /> The water management pond was sized in a two-step process involving the DSM and the <br /> numerical groundwater model. The pond was first sized for operational requirements <br /> utilizing the DSM. This pond (size and shape) was inserted into the numerical <br /> groundwater model, and operations were simulated to calculate the rise in head required <br /> to discharge the dewatering water back to the aquifer. Because of the high permeability <br /> of the aquifer material, only a few feet of head in the pond above the surrounding <br /> groundwater elevation is required to return the dewatering water. Simulation results for <br /> the various mining phases are documented in Section 5 of the groundwater modeling <br /> report. <br /> The Little Cache Ditch is not lined through the site. However, the ditch company <br /> performed a leakage analysis recently. They have indicated that the ditch leaks very little <br /> through this section, indicating that natural siltation has likely sealed up the ditch. <br /> Comment 30 <br /> Has any modelling been done to show that there will not be significant impact to <br /> groundwater levels in the area surrounding the infiltration pond (mounding) due to the <br /> constant influx of dewatering discharge? <br /> Response 30 <br /> The effects of returning dewatering flow to the groundwater system through the water <br /> management pond is documented in the revised groundwater modeling report. The <br /> anticipated head build up immediately adjacent to the pond is a few feet (Section 5.0). <br /> Comment 31 <br /> What is the maximum elevation of water in water management pond anticipated to be, <br /> and is there enough additional freeboard capacity to account for storm and runoff <br /> events? <br /> Response to DRMS comments T E L E S T <br />