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Exhibit 7, Item 20, Part B <br /> West Taylor Pond and Channels <br /> The location of the West Taylor Pond is presented on Map 12. The profiles of the associated <br /> permanent channels associated with the West Taylor Pond watershed are presented on Map 33B. <br /> These channels consist of the West Fork Taylor Ditch, East Fork Taylor Ditch, Trib 1 through <br /> Trib 6 ditches and the terrace ditches that will be constructed across the West Taylor Fill. The <br /> permanent channel design information for all channels is presented in this exhibit. The as-built <br /> configuration for the West Taylor Pond is presented on Figure Exh. 7-2013-1, and Figure Exh. <br /> 720B-2 provides the breakdown of drainage areas and hydrologic conditions for this sediment <br /> pond in the post mining condition. <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 /> West Taylor 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 and southern extent of the reclaimed South <br /> Taylor Pit, and the younger (topsoil and seeded) reclamation is the northern reaches of the West <br /> Taylor Pond watershed very near the West Taylor Pond. <br /> The SEDCADTM model herein provides the results of the 10 year 24 hour design storm and <br /> demonstrates the West Taylor Pond will meet the applicable settleable solids standard under this <br /> modeled storm event. The second SEDCADTM model demonstrates that the West Taylor Pond <br /> emergency spillway elevation is capable of containing the 25 year 24 hour storm. <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. Four in-stream stock ponds (WFSP-1, WFSP-2, EFSP-1, and, EFSP-2) are included in <br /> the permanent channels to decrease peak flows from the modeled storm events, and to provide a <br /> water source to support the post-mining land use. A typical design for of each stock pond in the <br /> West Taylor Pond watershed are provided on Figure 2.05-6 in Volume 1. However, depending <br /> on the ground conditions encountered during reclamation, these stockponds may be constructed <br /> similar to ETD-1 (please see Figure Exh. 7-20ET-3) in the East Taylor watershed. <br /> In summary, the post mining case at the West Taylor Pond, the 10 year 24 hour storm produces <br /> 5.10 acre feet of runoff, and the seattlable solids discharge is 0.2 ml/l. The 25 year 24 hour <br /> storm event peaks at the 7,473.71' elevation, which is well below the emergency spill way <br /> elevation of 7,475.0'. <br /> Exh. 7-20B-1 Revision Date: 2/17/21 <br /> Revision No.: TR-145 <br />