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will be located so as to increase the potential for landslides. When no longer needed, each <br />temporary diversion will be removed and the affected land regraded, topsoiled, and revegetated <br />in accordance with 4.06, 4.14, and 4.15. If the temporary diversion was for an ephemeral stream, <br />the channel will be reestablished to functionally blend with the undisturbed drainage above and <br />below the area to be reclaimed. Diversion design will incorporate the following: <br />a) Most ditches will not need to be lined, however, any stretch of collection ditch which has <br />a velocity above 5.5 feet per second will be lined. Channel linings, including channel <br />riprap, will be designed using standard engineering practices to pass safely the design <br />velocities. These velocities assume the typical silty loam soil conditions on site. If better <br />conditions exist, the velocities will be allowed to increase without lining. If worse <br />conditions exist, lining may be needed for lower velocities. <br />b) Freeboard will be a minimum of 1.0 feet. Protection will be provided for transition of <br />flows and for critical areas such as swales and curves when excessive velocities are <br />anticipated. <br />c) Energy dissipators will be installed when necessary, such as at discharge points, where <br />diversions intersect with natural streams and exit velocity of the diversion flow is greater <br />than that of the receiving stream. <br />d) Excess excavated material not necessary for diversion channel geometry or regrading of <br />the channel will be disposed of in accordance with 4.09. <br />e) Topsoil will be handled in compliance with 4.06. <br />f) All ditches, culverts and diversions will be temporary; therefore peak flows will be <br />designed for the 10 year 24 hour event of 2.0 inches. <br />Designs for all Ditches in the Permit Area <br />Steps taken in the ditch designs are outlined in Appendix 2.05.3(4)-1, Appendix 2.05.3(4)-2B, <br />and Appendix 2.05.3(4)-8. Designs presented in Appendix 2.05.3(4)-8 for NHN-002 North and <br />South Ditches supersedes designs presented in Appendix 2.05.3(4)-1. <br />Sedimentation Ponds <br />Sediment pond design details are discussed in the Arcadis report (Appendix 2.05.3(4)-1) as well <br />as Appendix 2.05.3(4)-8 for Pond NHN-002. Designs presented in Appendix 2.05.3(4)-8 <br />supersede all Pond NHN-002 designs presented in Appendix 2.05.3(4)-1. In accordance with <br />4.05.2 and the approved Water Discharge Permit from Colorado Water Quality Control Division, <br />WFC will use Ponds NHN-001, NHN-002 and NHN-003 to prevent, to the extent possible, <br />additional contributions of sediment to stream flow or runoff outside the permit area due to <br />mining disturbance. Please see Appendix 2.05.3(4)-1 and Appendix 2.05.3(4)-8 for design <br />calculations. In accordance with Rule 4.05.6(3) each sedimentation pond is designed, <br />constructed, and maintained to: <br />Section 2.05.3(4) Page 3 Sept. 2015 (TR -11) <br />