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A number of ditches and culverts in the permit area will be permanent. These structures are <br />primarily along the re-established portions of 2700 Road and BB Road. Since the County <br />requires that the culverts be designed for the 25 year 24 hour event and DMG requires that <br />permanent structures be designed for the 100 year 24 hour event, the 100 year event will take <br />precedence and all permanent structures will be designed for this event. <br />All watershed areas are determined from the Cad map and all watershed land slopes are <br />determined from a grid made from either the original or final land surface, whichever is <br />appropriate in the design. A maximum flow length was also determined for each watershed, <br />which was then used to determine the Time of Concentration, using the SCS method. This was <br />then used to determine the peak flow using the graphical method in Carlson Software. <br />The ditch slope was then determined using Carlson Software and the channel was designed using <br />Manning's equation. All ditches will have 0.3 feet of freeboard above the design depth. <br />Attachment 2.05.3(3)-1 Page 6 March 2016 (TR -70) <br />