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<br />• <br />• <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 />- 100 year 24 hour storm event of 2.2" used for drainage calculations associated with <br />permanent stream channel diversions. <br />- To use the Simons/OSM rip rap routine in Sedcad, half of the channel width and half <br />of the peak flow was used. This routine is limited to a 20' channel width while the <br />design width of Coal Canyon was 40". <br />- Design for the dip section by CRDA1 assumed that the culverts plugged and all flow <br />went over the existing concrete, roadway and adjoining slopes. The 0.5% grade <br />assumed that material filled up behind the dip section for a distance of 250'. <br />Results Summary: (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 Design <br />211 Coal Canyon by CRDA3 2:1 side, 40' bottom width, 0.2% grade, 4.3' min. <br />depth <br />31 I Dip section by CRDA 1 0.5:1 & 1:1 side slopes, 60' bottom width, <br />approximately 0.5% grade, 2' min. <br />312 Coal Canyon by CRDA 1 2:1 side, 40' bottom width, 0.2% grade, 4.3' min. <br />depth <br />MISC-14 (Rev. 12/16/96) <br />