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• <br />u <br />C~ <br />Coal Canyon Runoff and Drainage <br />Calculation Rational and Results Summary <br />Rational: <br />- Calculated using Sedcad+ Ver. 3 <br />• Areas, slopes and flow paths digitized from 2000 scale USGS topo map. <br />- The soil map, Exhibit 23, shows the area as Area 80 -"Stony Land" and Area 8 - <br />"Rock Outcrop. There is no defined soil group associated with the "stony land" soil <br />therefore Table 5.1 in the Sedcad reference manual was used to determine a soil <br />group. Generally the soil samples for this and other disturbance areas classifies the <br />soil to be sandy to silty loam (Tab Section 9) which equates to a "B" soil group. The <br />"rock outcrop" soil group is not defined. A "D" soil group was used for this area but <br />it may be conservative due to the fracturing and large surface area compared to the <br />level area. The following CN's were used in the calculations: <br />64 - B soil group, sage-grass with 20% cover. <br />83 - D soil group, sage-grass with 20% cover. <br />- 20 yeaz 24 hour storm event of 1.7" used for roadway drainage calculations <br />associated with the dip sections due to culverts haveing a cross sectional area of <br />greater than 35 sq. ft. <br />- Design for the dip sections assumed that the culverts plugged and all flow went over <br />the existing concrete, roadway and adjoining slopes. The 4 and Z.5% grade are the <br />installed grade of the concrete surface. Also included is a culvert design showing <br />what can be carried by the dip section culverts in place before overtopping or <br />plugging. <br />Results Summaty: (other information may have been generated in this section but is not <br />being used at this time in the channel design for Coal Creek and Coal Gulch.) <br />Structure # Structure Description <br />Design <br />311 Dip section by CRDAI 0.5:1 & l:l side slopes, 60' bottom width, <br />approximately 4 % grade, 0.9 min. depth. <br />313 RSN dip section 2:1 & 4:1 side slopes, 25' bottom width, 4% <br />grade. 1.29' min, depth. <br />314 UTL dip section 2:l & 4:1 side slopes, 30' bottom width, 2.5% <br />bottom width, 1.32' min. depth. <br />13-1-8 <br />(New 12/16/96) <br />