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Permanent Post Mine Channels <br /> The West Taylor watershed is comprised of two primary post-mining channels and six tributaries <br /> channels. Both of the primary channels convey the post mining surface water flows to the West <br /> Taylor Pond, while the six tributaries channels route water to both primary post mining channels. <br /> The locations of both the primary and tributary channels are presented on Map 12 and Figure <br /> Exh. 7-20B-2. The channel profiles are presented on Map 33B. <br /> The assumed hydrologic condition for all three channels is the post mine condition when the <br /> entire West Taylor watershed is reclaimed and reporting to the West Taylor Pond. <br /> West and East Fork Taylor Ditch <br /> The area contributory to each permanent primary channel is less than one square mile, making <br /> the appropriate storm event the 10 year, 24 hour event as specified in Rule 4.05.3. However, <br /> portions of these channels pass over permanent fills, so the correct storm event required by Rule <br /> 4.09.2 becomes the 100 year, 24 hour event. For simplicity, both primary channels are modeled <br /> to this larger event. <br /> The upper segments of the primary channels are flat enough that a vegetative liner will provide <br /> sufficient erosion protection, even for the 100 year flow. However, both channels below the <br /> lower stock ponds require riprap lining to ensure long-term stability. <br /> A SEDCAD model has been included below which evaluates the peak flow and total runoff <br /> volume for each of the channel segments for the 100 year, 24-hour storm event. The channel <br /> configurations for the 100 year, 24 hour storm event for both primary channels are described on <br /> the tables below. <br /> East Fork Taylor Ditch <br /> Peak Flow Average Channel Side MinimumErosion <br /> Station CFS Sloe % Type Slopes Depth Protection <br /> Feet <br /> Station 0+00 to 10131 25 3H:1V 4 <br /> Trapezoidal Riprap, <br /> EFSP-1 . 12' bottom .0 D50 = 18" <br /> EFSP-1 to Trapezoidal <br /> EFSP-2 l 25.52 1.5 12' bottom 3H:1 V 4.0 Vegetation <br /> EFSP-2 to 26.40 4.7 Trapezoidal 3HA V 4.0 Vegetation <br /> Station 124+03 12' bottom <br /> Exh. 7-20B-2 Revision Date: 1/20/21 <br /> Revision No.: TR-145 <br />