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007 to prevent, to the extent possible, additional contributions of sediment to stream flow or <br />runoff outside the permit area due to mining disturbance (see Map 2.05.3(3)-1). Attachment <br />2.05.3(3)-2 gives the design calculations on Sediment Pond 007. Attachment 2.05.3(3)-3 gives <br />the typical soil grain size distribution information. Maps 2.05.3(3)-2-1 and 2.05.3(3)-2-2 shows <br />the as -built design of Pond 007. <br />The sedimentation pond is designed, constructed, and maintained to: <br />a. Provide storage for the runoff or inflow entering the pond as a result of a 10 -year, 24- <br />hour precipitation event and to meet all applicable State and Federal regulations for all <br />effluent limitations before discharge from the permit area. The characteristics of the <br />mine site, reclamation procedures, and on site sediment control practices are also <br />considered in the design. <br />b. The sedimentation pond was designed to provide adequate sediment storage volume in <br />compliance with the CDRMS regulations. <br />c. An appropriate non -clogging dewatering device will be installed to maintain a 10 -year, <br />24-hour storage volume. <br />d. Appropriate combinations of principal and emergency spillways to safely discharge the <br />runoff from a 25 -year, 24-hour precipitation or larger event, as required by the CDRMS's <br />regulations, will be installed. <br />The sediment storage capacity of the sedimentation pond will be periodically monitored to <br />ensure that at least one year of sediment storage is available beneath the principal spillway inlet <br />(based on the U.S.L.E. or the equivalent sediment storage of one 10 -year, 24-hour storm event <br />based on the M.U.S.L.E.). When adequate capacity is no longer available, sediment removal <br />or other corrective actions will be taken to restore adequate sediment storage capacity to the <br />pond. <br />Corrective action required to restore adequate sediment storage capacity may include the <br />following: <br />1. Raise the spillway and redesign the pond in order to restore adequate storage capacity <br />and to comply with the applicable regulations. <br />2. Excavate the pond area and enlarge the sediment storage capacity. <br />Page 2.05.3(3)-5 October 2015 (TR -69) <br />