2016-01-07_PERMIT FILE - C2010089A

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a) Provide storage for the runoff or inflow entering the pond as a result of a 10 -year, 24- hour precipitation event and to meet all applicable State and Federal regulations for all effluent limitations before discharge from the permit area. The characteristics of the mine site, reclamation procedures, and on site sediment control practices are also considered in the design. b) Provide adequate sediment storage volume in compliance with the DRMS regulations. c) Install an appropriate non -clogging dewatering device to maintain a 10 -year, 24-hour storage volume. d) Install appropriate combinations of principal and emergency spillways to safely discharge the runoff from a 25 -year, 24-hour precipitation or larger event, as required by the DRMS' regulations. In accordance with Rule 4.05.9(9), the faces of all embankments and surrounding areas will be vegetated to protect against erosion. Where water will be impounded, the upstream faces of all embankments will also be vegetated to protect against erosion from water or sudden drawdown. Vegetation will occur in accordance with the approved seeding plan. The sediment storage capacity of the sedimentation ponds will be periodically monitored to ensure that at least three years of sediment storage is available beneath the principal spillway inlet (based on the sediment storage volume calculated using the M.U.S.L.E. contained within the SEDCAD4 program). When adequate capacity is no longer available, sediment removal or other corrective actions will be taken to restore adequate sediment storage capacity to the pond. Corrective action required to restore adequate sediment storage capacity may include the following: 1) Raise the spillway and redesign the pond in order to restore adequate storage capacity and to comply with the applicable regulations. 2) Excavate the pond area and enlarge the sediment storage capacity. The excavated material suitable for topsoil will be salvaged in a stockpile used for reclamation. The excavated material that is not suitable for a topsoil -like medium will be graded into the surrounding topography within the disturbance area, topsoiled, and revegetated in accordance with WFC's approved reclamation plan. Site specific conditions will determine the construction methods and equipment utilized at the time of excavation. Sediment removal and water discharges will be conducted consistent with the approved mining permit, the Water Discharge Permit, and DRMS Regulations Section 4.05.6(3)(b). All sedimentation ponds will be inspected quarterly under the supervision of a registered professional engineer and reported to the DRMS. The Water Discharge Permit is enclosed in Appendix 2.05.3(4)-3. Section 2.05.3(4) Page 4 Sept. 2015 (TR -11)