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(d) Excess excavated material not necessary for diversion channel geometry or regrading of the • <br />channel will be disposed of in accordance with 4.09. <br />(e) Topsoil will be handled in compliance with 4.06. <br />Sedimentation Ponds <br />In accordance with 4.05.2 and the NPDES permit, SCC will primarily use sedimentation ponds to prevent, to <br />the extent possible, additional contributions of sediment to streamflow or runoff outside the permit area due <br />to mining disturbance (see Exhibit 13-2, Surface Water Control Plan, and Exhibit 13-12.1, Yoast <br />Watershed). Please refer to Attachments 13-3, Design Repon Setliment Structure Pond 010; 13-4, Design <br />Report Sediment Structure Pond 011; 13-12, Drainage and Sediment Control Plan, for pond designs of <br />011 A, 012, 013 and 014. <br />The sedimentation ponds and impoundments are designed, constmcted, and maintained to achieve the <br />following: <br />a. Provide storage and treatment for the runoff or inflow entering the pond as a result of a 10-year, <br />24-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 mine site, • <br />reclamation procedures, and onsi[e sediment control practices are also consitlered in the <br />design. <br />b. All sedimentation ponds are designed to provide adequate sediment storage volume in <br />compliance with the CDMG 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 CDMG 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 R.U.S.L.E.). When adequate capacity is no longer available, sediment removal or other <br />corrective actions will betaken 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 />TR-24 4 Revised 2/04 <br />