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Appendix Exh7 -14L - Taylor Ditch <br />Taylor Ditch is a short ditch located entirely within the NW /4 of Section 9 of T3N, <br />R93W. The alignment of the Taylor Ditch is shown on Map 41 and on Figures 14C -1 <br />and 14C -2 in the discussion of the Taylor Tributary Ditch in Appendix 14C of this Item <br />14. The design profile of the East Taylor Ditch is provided on Map 33A. The entire <br />channel was redesigned following a revision to the postmining topography associated <br />with this TR -81. <br />The total drainage area reporting to the ditch is 14.7 acres. It is designed to meet the <br />requirements of Rule 4.05.3 for drainages less than one square mile. This requires that <br />the channel be capable of handling flows from a 10 year, 24 hour event. As shown on the <br />profile, the steepest portion of the channel has a slope of about 14.7 percent. The overall <br />length of the channel is about 1,067 feet. <br />The assumed hydrologic condition is the postmining condition wherein the entire <br />watershed is reporting to the lowest portion of the ditch, and for which the density of <br />vegetation is established depending on the time since the particular area has been mined. <br />As shown on the attached SEDCAD printout, the design storm produces a peak discharge <br />of about 4.4 cfs and a total runoff volume of about 0.3 acre -feet. This design event is <br />based on a Curve Numbers of 74 for the condition of 3 or more years of revegetation <br />growth, as adopted pursuant to TR -73. <br />For this minor flow rate, a vegetative lined triangular channel will be employed. Channel <br />side slopes will be 3H:1 V and a minimum depth of 4.0 feet will be used. Peak 10 -year <br />24 -hour flow is 4.4 cfs, with a peak flow velocity of 4.15 fps. This velocity is acceptable <br />for a vegetative lining based on the SEDCAD modeling as described in the Introductory <br />Text in this Exhibit 7 Item 14, pages Exh. 7 -14 -1 through 5. <br />Exh.7 -14L -2 Revision Date: 12/10/12 <br />Revision No.: TR -97 <br />