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d. Install 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 />DRMS' regulations. <br />In accordance with Rule 4.05.9(9), the faces of all embankments and surrounding areas will be <br />vegetated to protect against erosion. Where water will be impounded, the upstream faces of all <br />embankments will also be vegetated to protect against erosion from water or sudden drawdown. <br />Vegetation will occur in accordance with one of the approved temporary seed mixtures. The <br />sediment storage capacity of the sedimentation ponds will be periodically monitored to ensure <br />that sediment storage is available beneath the principal spillway inlet (based on the sediment <br />storage volume calculated using the M.U.S.L.E. contained within the SEDCAD program). When <br />adequate capacity is no longer available, corrective actions will be taken to restore adequate <br />sediment storage capacity to the pond. Corrective action to restore adequate sediment storage <br />capacity will include removal of accumulated sediment from the pond. The excavated material <br />suitable for topsoil will be salvaged in a stockpile used for reclamation. The excavated material <br />that is not suitable for a topsoil -like medium will be graded into the surrounding topography <br />within the disturbance area, topsoiled, and revegetated in accordance with the NHN Mine's <br />approved reclamation plan. All sedimentation ponds will be inspected quarterly under the <br />supervision of a registered professional engineer and reported to the DRMS. <br />The pit dewatering process will be a sporadic, operation -controlled occurrence depending on <br />various factors which may include the location of the pit inflows, the location of standing water <br />in the pit, or the location within the pit of the overburden and coal removal operations. When pit <br />dewatering is required, the anticipated dewatering rate will be in the range of one to two cubic <br />feet per second or less. Direct pit pumping into Pond NHN-001 or NHN-002 is planned for the <br />mining south of Meehan Draw. Actual water flow velocity going into ponds will be controlled <br />with adequate erosion control (i.e., rock riprap, geotextiles, synthetic liner, half -culverts, etc.) or <br />discharged onto non -erodible bedrock material. This will minimize erosion of the pond banks. <br />Pit dewatering will have an insignificant impact on the ponds and will be sporadic versus <br />continuous. The flow rate of one to two cubic feet per second or less compared to the designed <br />10 -year, 24-hour peak inflow rate the ponds were designed for is relatively insignificant. <br />Erosion Control Plan <br />New Horizon Mine will use various types of structures to control the runoff from disturbed areas <br />within the permit boundaries. In addition, surface mining activities will be planned and <br />conducted to minimize disturbance of the prevailing hydrologic balance in both the mine plan <br />and adjacent areas in order to prevent long-term adverse changes in the hydrologic balance. <br />Sediment control measures will include proper utilization of mining and reclamation methods <br />and sediment control practices singly or in combination. Typically, this will include disturbing <br />Section 2.05.3(4) Page 3 March 2018 (TR -16) <br />