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effluent limitations before discharge from the permit area. The characteristics of the mine site, <br />reclamation procedures, and onsite sediment control practices are also considered in the <br />design. <br />b. All sedimentation ponds are designed to provide adequate sediment storage volume in <br />compliance with the DMG regulations. <br />c. An appropriate nonclogging dewatering device will be installed to dewater a 10-year, 24-hour <br />storage volume. <br />d. Appropriate combinations of principal and emergency spillways to safely discharge the runoff <br />from a 25-year, 24-hour precipitation or larger event, as required by the DMG's regulations, will <br />be installed in all ponds. <br />The sediment storage capacity of each sedimentation pond or impoundment will be monitored on an annual <br />basis to ensure that at least one year of sediment storage is available beneath the principal spillway inlet <br />(based on the R.U,S.L.E. or the equivalent sediment storage of one 10-year, 24-hour stone event based on <br />the M.U.S.L.E.). When adequate capacity is no longer available, sediment removal or other corrective <br />actions will be taken to restore adequate sediment storage capacity to the pond. <br />SCC will monitor the sediment storage capacity of each pond with one or a combination of the following <br />methods, as applicable: <br />1. Reference Stake - A reference stake will be set at a predetermined clean-out elevation beneath <br />the principal spillway. When sediment storage reaches this elevation, corrective action will be <br />implemented to restore adequate sediment storage. Reference staking will be utilized in ponds <br />that are normally dry and as an indicator for monitoring personnel as to when a more detailed <br />survey of sediment storage capacity is warranted. <br />2. Cross Sectioning or Grid Method -For the ponds that normally contain wafer year round, or <br />where a reference stake can not be detected below the water surface, a survey cross section or <br />grid method will be used to determine sediment volume using accepted engineering practices. <br />The survey would be performed when needed to determine sediment storage capacity and to <br />determine when corrective action is required to restore adequate pond capacity. <br />3. Aerial Mapping - An alternative method is photogrammetric mapping that would create an <br />accurate 1" = 50' topographic map with 2 ft. contour intervals to determine the remaining storage <br />volume beneath the principal spillway. This method could be used as the sole method for dry <br />ponds or used in conjunction with the surveyed cross section method for ponds partially full of <br />water. Once the topographic map has been generated, accepted engineering methods will be <br />utilized to perform the volumetric calculations. <br />Corrective action required to restore adequate sediment storage capacity may include the following: <br />1. Raise the spillways and redesign the pond in order tc restore adequate storage capacity and to <br />comply with the applicable regulations. <br />PR-O5 4 Revised 01/06 <br />