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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 or <br />other corrective actions will be taken to restore adequate sediment storage capacity to the 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 and <br />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 New Horizon's approved reclamation plan. Site specific conditions will determine the <br />construction methods and equipment utilized at the time of excavation. Sediment removal and <br />water discharges will be conducted consistent with the approved mining permit, the NPDES <br />permit and DRMS 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 DRMS. <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 <br />pit, 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 New Horizon's NPDES Permit CO -0000213. <br />A new discharge point has been applied for to utilize the Pond 011 site. See Attachment <br />2.05.3(3)-18. Actual water flow velocity going into Pond 007 and Pond 011 will be controlled <br />with adequate energy dissipaters (i.e., rock riprap, geotextiles, metal or concrete energy <br />dissipater boxes, etc.) or discharged onto non -erodible bedrock material. This will minimize <br />erosion of the pond banks. <br />Page 2.05.3(3)-5 January 2016 (TR -70) <br />