2021-04-05_PERMIT FILE - C1981019A (18)

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Streeter Permanent Post Mine Channels The Streeter Pond watershed is comprised of two post-mining channels. The main channel is the Streeter Ditch, which will convey post mining surface water flows to the Streeter Pond. Buckskin Ditch is a tributary to the Streeter Ditch. The locations of both channels are presented on Map 12 and Figure Exh. 7-14SP-2, and the channel profiles are presented on Map 33. The assumed hydrologic condition for both channels is the post mine condition when the entire Streeter watershed is reclaimed and reporting to the Streeter Pond. The upper segments of the Streeter Ditch and the entirety of Buckskin Ditch have a contributing area of less than one square mile. They could be designed in accordance with Rule 4.05.3. However, for ease since the lower segments of Streeter Ditch meet the requirements of Rule 4.05.4,both ditches have been designed for the 100-year, 24-hour storm event. A SEDCADTM model has been included which evaluates the peak flow and total runoff volume for each of the channel segments for the 100 year, 24-hour storm event. The channel configurations for the 100 year, 24 hour storm for the Streeter and Buckskin Ditches are summarized below. Streeter Ditch Peak Average Channel Side Erosion Station Flow Sloe % Type Slopes Protection CFS Station 0+00 7.93 28.3 Trapezoidal 2H:1V Riprap, to 10+00 6' bottom D50 = 12" Station 10+00 62.6 10.9 Trapezoidal 2HA V Riprap, to 25+00 6' bottom D50 = 12" Station 25+00 62.6 2.0 Trapezoidal 3H:1 V Riprap, to 45+00 12' bottom D50 = 6" Station 45+00 62.4 1.9 Trapezoidal 3H:1 V Vegetation to 80+00 12' bottom Station 80+00 98.11 3.8 Trapezoidal 3H:1 V Vegetation to 91+00 15' bottom Station 91+00 110.56 2.8 Trapezoidal 3H:1 V Vegetation to 111+00 15' bottom Station Trapezoidal 111+00 to 127.95 2.6 15' bottom 3H:1 V Vegetation 125+00 Station Trapezoidal 125+00 to 81.91 5.0 12' bottom 3H:1 V Vegetation 187+00 Exh. 7-14SP-2 Revision Date: 1/20/21 Revision No.: TR-145