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Exh. 7-14S15-1 Revision Date: 1/30/23 <br />Revision No.: TR-158 <br />Appendix Exh. 7-14S15 <br />Section 15 Pond <br />The location of the Section 15 Pond is presented on Map 12, and the design configuration of the <br />pond is presented on Figure Exh. 7-15S-1. Figure Exh. 7-15S-2 provides the breakdown of <br />drainage areas and hydrologic conditions for this sediment pond. The profile of the associated <br />permanent channel associated with the Section 15 Pond (Section 15 Ditch) is presented on Map <br />33. This design information for the Section 15 Ditch is presented in this appendix. <br />Exhibit 7, Item 14 in Volume 2D describes the hydrologic methodology used in sediment pond <br />and post mine channel assumptions. Runoff curve numbers assigned to the undisturbed and <br />reclaimed lands in various stages of reclamation have been selected in accordance with Table 1 <br />in the Introductory Text for Exhibit 7 in Volume 2D. For channels protected by a riprap liner, <br />selection of minimum riprap size is done using the Simons/OSM method in SEDCADTM. For <br />channels to be protected by a vegetative liner, the permissible velocities are also determined <br />using SEDCADTM routines. <br />Section 15 Pond <br />The following pages present the results of the SEDCADTM models for the post mining condition. <br />At this stage the oldest reclamation is on the eastern extent of the watershed, and the younger <br />(topsoil and seeded) reclamation is the western portion of the Section 15 Pond watershed. <br />The SEDCADTM model herein provides the results of the 100-year, 24-hour design storm and <br />demonstrates the Section 15 Pond will fully contain the modeled event. <br />The final post mining topographic surface and the final locations of the permanent drainage <br />channels as presented on Map 12 were used to model the watershed for the post-mining <br />condition. <br />In summary, for the post mining case, the 100-year, 24-hour storm produces 35.46 acre-feet of <br />runoff, and the storm is contained below the emergency spillway elevation 7,567’. <br />Section 15 Post Mine Channel <br />The Section 15 Pond watershed includes one post-mining channel. The location of channel is <br />presented on Map 12, Figure Exh. 7-15S-2, and the channel profile is presented on Map 33. <br />The Section 15 channel has been designed in accordance with Rule 4.05.4(2)(b) for the 100-year, <br />24-hour storm event even though the reporting watershed is less than one square mile. <br />A SEDCADTM model has been included which evaluates the peak flow and total runoff volume <br />for the channel for the 100 year, 24-hour storm event. The channel configurations for the <br />Section 15 Ditch is summarized below.