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d. Appropriate combinations of principal and emergency spillways to safely discharge <br />the runoff from a 25 -year, 24 -hour precipitation or larger event, as required by the <br />CDMG's 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 <br />capacity and to comply with the applicable regulations. <br />2. Excavate the pond area and enlarge the sediment storage capacity. <br />The excavated material suitable for topsoil will be salvaged and used for reclamation. The <br />excavated material that is not suitable for a topsoil -like medium will be graded into the <br />surrounding topography within the disturbance area, topsoiled, and revegetated in accordance <br />with WFC's approved reclamation plan. Site specific conditions will determine the construction <br />methods and equipment utilized at the time of excavation. Sediment removal and water <br />discharges will be conducted consistent with the approved mining permit, the NPDES permit, <br />and CDMG Regulations Section 4.05.6(3)(b). All sedimentation ponds will be inspected <br />quarterly under the supervision of a registered professional engineer and reported to the CDMG. <br />The revised NPDES Permit is enclosed in Attachment 2.05.3(3) -18. <br />Pit dewatering into Pond 007 was primarily a constant occurrence while mining was taking place <br />east of 2700 Road. The dewatering process was operation - controlled, depending on various <br />factors which may include the location of the pit inflows, the location of standing water in the pit, <br />or the location within the pit of the overburden and coal removal operations. When pit <br />dewatering was required, the anticipated dewatering rate was in the range of one to two cubic <br />feet per second or less. Once mining continued west of 2700 Road, Pond 011 will be used to <br />detain the pit pumping prior to discharge. At that time, Pond 007 will be somewhat over <br />designed. These procedures have been approved in WFC's NPDES Permit CO- 0000213. A new <br />(Revised June 2010) 2.05.3(3) -6 <br />