1988-04-11_PERMIT FILE - C1981008A (20)

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basins. When no longer needed,each diversion will be removed and the affected area regraded and revegetated in accordance with 4.06, 4.14, and 4.15. Sedimentation Ponds In accordance with 4.05.2 and the approved NPDES permit, Peabody used sedimentation ponds to prevent, to the extent possible, additional contributions of sediment to stream flow or runoff outside the permit area due to mining disturbance (see Exhibits 13-4 and 13-5). The sedimentation ponds and impoundments were designed, constructed, and maintained to: 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 onsite sediment control practices were also considered in the design. b. All sedimentation ponds were designed to provide adequate sediment storage volume in compliance with the CMLRD regulations. c. An appropriate nonclogging dewatering device was installed to maintain a 10-year, 24-hour storage volume. d. Appropriate combinations of principal and emergency spillways to safely discharge the runoff from a 25-year, 24 your precipitation or larger event, as required by the CMLRD's regulations, were installed in Pond 001 and Pond 006. However, no emergency spillway was provided for Ponds 002, 004 and 005 since they were equipped to hold a 25-year, 24-hour event, as per the approval of Office of Mined Land Reclamation dated 12/"2, Technical Revision No. Seven. The sediment storage capacity of each sedimentation pond or impoundment will be monitored on an annual basis to ensure that at least one year of sediment storage is available beneath the principal spillway inlet (based on the U.S.L.E. or the equivalent sediment storage of one 10-year, 24-hour storm event based on the M.U.S.L.E.), when adequate 13-4 Revised 10/22/93