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• <br />5~~- <br />Doc Date:12/11I2001 <br />5) Collection Ditches, Culverts and Diversion Design Parameters <br />III IIIIIIIII"IIIII <br />sss <br />These ditches will be earthen ditches constructed with either a small dozer or excavator. The ditches <br />will be designed for the following parameters: <br />(a) Most ditches wiH not need to be lined, however, any stretch of collection ditch which <br />has a velocity above 5.5 feet per second will be lined. Channel linings, including <br />channel riprap, will be designed using standard engineering practices to pass <br />safely the design velocities. Any stretch of diversion.ditch which has a velocity above <br />4 feet per second will be lined. These velocities assume the typical silty loam soil <br />conditions on site. If better conditions exist, the velocities will be allowed to increase <br />without lining. If worse conditions exist, lining may be needed for lower velocities. <br />(b) Freeboard will be a minimum of 0.3 feet. Protection will be provided for transition of <br />flows and for critical areas such as swales and curves when excessive velocities are <br />anticipa3ted. <br />• <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 flow <br />is greal:er than that of the receiving stream. <br />(d) Excess excavatedmaterialnotnecessaryfordiversionchannelgeometryorregrading <br />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. <br />C~ <br />Diversion D1 will be designed, constructed, and maintained in a manner which prevents additional <br />contributions of suspended solids to stream flow and to runoff outside the permit area, to the extent <br />possible, using the best technology currently available. Appropriate sediment control measures for <br />this diversion may include, but not be limited to, maintenance of appropriate gradients, channel lining, <br />revegetation, roughness structures, and detention basins. No diversion will be located so as to <br />increase the potential for landslides. When no longer needed, each temporary diversion will be <br />removed and the affected land regraded, topsoiled, and revegetated in accordance with 4.06, 4.14, <br />and 4.15. If the temporary diversion was for an ephemeral stream, the channel will be reestablished <br />to functionally blend with the undisturbed drainage above and below the area to be reclaimed. <br />(Revised wool Attachment 2.05.3(3) -10-55 <br />