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<br />• <br />C~ <br />As shown on Map 2.05.3-12, the area has been divided into many collection ditch and culvert basins. <br />All ditches, culverts and their respective watershed basins are labeled on the map. Most of the <br />culverts are needed to get disturbed areas under roads to the downstream collection ditch or <br />sediment pond. <br />Designs for all ditches were accomplished in the following steps: <br />1) using a 3D grid of thewatershed, the actual area and average land slope was developed. <br />2) along flow line was drawn from the top of each watershed to fhe 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 also <br />developed within SURVCADD using the SCS graphical method. <br />5) Using the maximum velocities stated earlier, ditch slopes, depth and bottom width <br />geometry were then calculated for the channels. <br />Designs for al! culverts were done in a similar manner except that opce the peak flows for the culvert <br />watersheds were calculated, the culvert routine within SURVCADD was used to properly size the <br />culvert. For all culverts, a corrugated metal pipe was used with inlet control. In order to standardize <br />culverts, a few culvert sizes were selected for all situations although, in some cases, the culvert is <br />over designed. Although WFC commits to maintaining the culverts in good condition, we only commit <br />to the cross-sectional area needed to pass the design peak flow, not the entire area of the culvert. <br />(Revised 12/00) <br />Attachment 2.05.3(3) -10-66 <br />