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increase without lining. If worse conditions exist, lining may be needed for lower <br />velocities. <br />b. Freeboard will be a minimum of 0.3 feet. Protection will be provided for <br />transition of flows and for critical areas such as swales and curves when excessive <br />velocities are anticipated. <br />c. Energy dissipaters will be installed when necessary, such as at discharge points, <br />where diversions intersect with natural streams and exit velocity of the diversion <br />flow is greater than that of the receiving stream. <br />d. Excess excavated material not necessary for diversion channel geometry or <br />regrading of the channel will be disposed of in accordance with 4.09. <br />e. Topsoil will be handled in compliance with 4.06. <br />f. All ditches, culverts and diversions will be temporary; therefore peak flows will <br />be designed for the 10 year 24 hour event of 2.0 inches. The exceptions to this are <br />Ditches Cl, C2, C4, C5, C 11, C12, C13, C14, C17, C19, C20, C23, C24, and <br />C29, which are permanent. Also, Culverts 117, 119, 120, 121, 122, 123, 124, and <br />129 are permanent and have been designed for the 100 year 24 hour event. These <br />designs also satisfy County regulations. <br />As shown on Map 2.05.3(3)-1, the permit area has been divided into many collection ditch and <br />culvert basins. All ditches, culverts and their respective watershed basins are labeled on the map. <br />Most of the culverts are needed to get disturbed areas under roads to the downstream collection <br />ditch or sediment pond. <br />D. Designs for All Ditches in the Permit Area <br />Designs for all ditches were accomplished in the following steps: <br />1. Using a 3D grid of the watershed, the actual area and average land slope was developed. <br />2. A long flow line was drawn from the top of each watershed to the bottom of the ditch. <br />3. Using the SCS Method provided within Carlson Software, the time of concentration was <br />developed for each watershed. <br />4. Using the Time of Concentration and a worst case curve number, the peak flow was also <br />developed within Carlson Software using the SCS graphical method. <br />Page 2.05.3(3)-3 January 2016 (TR -70) <br />