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Page Exh. 7-14S-2 Revision Date: 12/13/22 <br /> Revision No.: TR-158 <br />Appendix Exh. 7-14S <br />Section 16 Pond, Temporary, and Permanent Channels <br /> <br />The location of the Section 16 Pond is presented on Map 12. The profiles of the <br />associated permanent channels associated with the Section 16 Pond watershed are <br />presented on Map 33. These channels consist of the Trib A, B and Trib D, and their <br />design information is presented in this appendix. The as-built configuration for the <br />Section 16 Pond is presented on Figure Exh. 7-14S-1, and Figure Exh. 7-14S-2 provides <br />the breakdown of drainage areas and hydrologic conditions for this sediment pond in the <br />post mining condition. <br /> <br />Exhibit 7, Item 14 in Volume 2D describes the hydrologic methodology used in sediment <br />pond and post mine channel assumptions. Runoff curve numbers assigned to the <br />undisturbed and reclaimed lands in various stages of reclamation have been selected in <br />accordance with Table 1 in the Introductory Text for Exhibit 7 in Volume 2D. For <br />channels protected by a riprap liner, selection of minimum riprap size is done using the <br />Simons/OSM method in SEDCADTM. For channels to be protected by a vegetative liner, <br />the permissible velocities are also determined using SEDCADTM routines. <br /> <br />Section 16 Pond <br /> <br />The following pages present the results of the SEDCADTM models for the hydrologic <br />conditions under the post mining condition. At this stage the oldest reclamation (most <br />Phase III released) is on the eastern extent of the reclaimed Section 16 Pit, and the <br />younger (topsoil and seeded) reclamation is the western reaches of the Section 16 Pond <br />watershed. <br /> <br />The SEDCADTM model herein provides the results of the 10 year 24 hour design storm <br />and demonstrates the Section 16 Pond will meet the applicable settleable solids standard <br />under this modeled storm event. The second SEDCADTM model demonstrates that the <br />Section 16 Pond emergency spillway elevation is capable of containing the 25 year 24 <br />hour storm. <br /> <br />For the post mining case at the Section 16 Pond, the 10 year 24 hour storm produces 1.6- <br />acre feet of runoff, and the seattlable solids discharge is 0.0 ml/l. The 25 year 24 hour <br />storm event peaks at the 7,751.4’ elevation, which is below the emergency spillway <br />elevation of 7,754.5. <br /> <br />West and East Section 16 Ditches (Temporary) <br /> <br />The East Section 16 Ditch is designed to be trapezoidal in cross section with a 2-foot <br />bottom width, left side slope ratio of 1H:1V, a right side slopes ratio of 7H:1V, and depth <br />of at least 0.5 feet. The West Section 16 Ditch is a vegetated channel. <br />