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(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 <br />excessive velocities are anticipated. <br />(c) Energy dissipators 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 be <br />designed for the 10 year 24 hour event of 2.0 inches. The exceptions to this are <br />Ditches C2, C5, C11, C12, C13, C14, C17, C19, C20 and C29, which are <br />permanent. Also, Culverts 117 and 129 are permanent and have been designed <br />for the 100 year 24 hour event. These 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 <br />map. Most of the culverts are needed to get disturbed areas under roads to the downstream <br />collection ditch or sediment pond. <br />4. 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 <br />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 SURVCADD, 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 <br />also developed within SURVCADD using the SCS graphical method. <br />(Revised June 2010) 2.05.3(3) -4 <br />