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Based on SCC experience at the other mining areas, pit dewatering will be primarily a seasonal <br />occurrence. The 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 in the <br />pit, or the location within the pit of the overburden and coal removal operations. Also, prior to <br />initiating dewatering activities, the receiving pond level will be checked such that the designed <br />performance of the pond will not be compromised. When pit dewatering is required, the anticipated <br />dewatering rate will be in the range of one to two cubic feet per second or less. Any dewatering <br />discharges will be directed to a pond. The discharge from the pit dewatering will be controlled, as <br />necessary, with an adequate energy dissipater (i.e., rock riprap, geotextiles, metal or concrete energy <br />dissipater boxes, etc.) or discharged onto non-erodible bedrock mateiia7. <br />This pit dewatering will have an insignificant impact on the proposed ponds. The pit dewatering will <br />be sporadic versus continuous. The flow rate of one to two cubic feet per second or less compared to <br />the design 10-year, 24-hour peak inflow rate is very insignificant. In addition, all discharge from ponds <br />will be in accordance with applicable discharge permits. <br />All sedimentation ponds and impoundments will be maintained until the disturbed areas are reclaimed <br />and the vegetation success requirements of Tab 22, Revegetation Plan, are met, the untreated <br />drainage from the disturbed area ceases to contribute additional suspended solids above natural <br />conditions, and the drainage leaving the pond meets applicable State and Federal water quality <br />requirements, if any, for the receiving streams. All temporary ponds will be removed when the <br />appropriate sections of the regulations are satisfied. <br />When sedimentation ponds are removed, the affected land will be regraded and revegetated pursuant <br />to the CDMG's regulations, Section 4.05.17 and the approved Reclamation Plan. <br />Design Methodology. Following is the hydrologic and design criteria for the exiting ponds 010 and <br />011. The hydrologic and design criteria for proposed ponds 012, 013 and 014 are presented in <br />Attachment 13-12, Drainage and Sediment Control Plan. The precipitation runoff (peak flow and <br />volume) is estimated using the Soil Conservation Service (SCSI triangular hydrograph techniques as <br />described in Design of Small Dams IU.S. Dept. of Interior, 1977). Computations necessary for this <br />runoff estimating technique have been computerized by various individuals and agencies. SEDIMOT II <br />was developed by Research Specialist Bruce N. Wilson, Professor Billy J. Barfield, and Assistant <br />Professor Ian D. Moore at the Department of Agricultural Engineering, University of Kentucky, <br />Lexington, Kentucky. SEDCAD ~ is an enhanced PC version of the SEDIMOT II computer program <br />Isee Attachments 13-1, General Hydrology Design Methods and 13-12, Drainage and Sediment • <br />Control Plan). This program is usetl to estimate runoff peak flow and volume that are necessary for <br />the design of sediment ponds, <br />5 Revised 2/99 <br />