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To: Jared Ebert <br />Date: February 14, 2018 <br />Page 8 <br />Response 29a <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 29b <br />Section 6.3 states that approximately 1.5 feet of freeboard is required in the water <br />management pond to provide capacity to manage a 100 year storm event. Please commit <br />to enlarge the pond or install additional drain structures as detailed in the report if <br />freeboard in the water management pond drops below 1.5 feet. <br />Response 29b <br />LRM commits to enlarge the pond or install additional drain structures as detailed in the <br />report if freeboard in the water management pond drops below 1.5 feet. <br />Comment 35a <br />Is the Little Cache La Poudre Ditch that passes through the site lined? If not, how will <br />LRM prevent losses from the ditch during dewatering?If there is a potential for losses to <br />occur from the ditch, how will LRM monitor the inflow and outflow of the ditch to <br />measure these losses? Please provide a monitoring plan and either a mitigation plan or <br />loss prevention plan <br />Response 35a <br />The Little Cache Ditch is not lined through the site. However, the ditch company <br />performed a leakage analysis (measuring inflow and outflow up and down gradient of the <br />Response to DRMS Adequacy Review 3 comments T E L E S T O