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. Appendix Exh7-14J -Streeter Gulch Ditch <br />The Streeter Gulch Ditch is located in Sections 3, 9, and 10 of T3N, R93W. The alignment of <br />this ditch is shown on Map 41. The design profile is provided on Map 33. The upper portion of <br />this channel was redesigned following a revision to the postmining topography approved under <br />TR-63. <br />The ditch is designed to meet the requirements of Rule 4.05.4 for drainages greater than one <br />square mile. Including the Buckskin Draw Ditch tributary, the drainage area of this basin is <br />about 1,284 acres. This requires that the channel be capable of handling flows from a 100 year, <br />24 hour event. As shown on the profile, the steepest portions within the channel between Station <br />155+00 and the upper end at Station 188+00 have a slope of about 8 percent. The overall length <br />of the channel is about 18,800 feet. <br />As shown on the attached SEDCAD printout, the design storm produces a peak discharge of <br />about 31 cfs and a total runoff volume of about 15 acre-feet at Station 0. Above the confluence <br />with Buckskin Draw Ditch the design storm produces a peak discharge of about 9 cfs. This <br />design event is based on a Curve Number of 56 and assumes that the entire drainage area is <br />contributory to the channel. <br />This design is applicable for the non-constructed portion of the channel above the confluence <br />with Buckskin Draw Ditch. For ease of construction, a trapezoidal channel cross-section 12 feet <br />in width will be employed. Channel side slopes will be 3H:1 V slopes and a minimum depth of <br />4.0 feet will be used. For design consistency, an average riprap diameter of 18 inches will be <br />used. Using Figure 3 of Exhibit 7, Item 14H, it can be determined that this size is more than <br />adequate for the peak flow and channel slope involved. <br /> <br />Exh. 7-14J-2 Revision Date: 7/25/06 <br />Revision No.: TR-63 <br />