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<br />As shown on Map 2.05.3-12, the area has been divided into many collection ditch and culvert basins. All <br />ditches, culverts and their respective watershed basins are labeled on the map. Most of the culverts are <br />needed to get disturbed areas under roads to the downstream collection ditch or sediment pond. <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) along 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 also <br />developed within SURVCADD using the SCS graphical method. <br />5) Using the maximum velocities stated earlier, ditch slopes, depth and bottom width geometry <br />were then calculated for the channels. <br />Designs for all culverts were done in a similar manner except that once 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 over <br />designed. Although W FC commits to maintaining the culverts in good condition, we only commit to the <br />cross-sectional area needed to pass the design peak flow, not the entire area of the culvert. <br /> <br />(REVISED 12/99) Attachment 2.05.3(3) -10-86 <br />