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Appendix Exh 7-14D — Section 16 Fill Ditch <br />The Section 16 Fill Ditch is located in the SE1 /4 of Section 16 of T3N, R93W. The alignment of <br />this ditch is shown on Map 41. The ditch conveys a very small area of Section 16 into the South <br />Collection Ditch ultimately reporting to the Prospect Pond drainage system. <br />This channel was designed following a revision to the postmining topography approved under <br />TR -63. That technical revision also addressed three other channels in the Prospect drainage, all <br />considerably larger than Section 16 Fill Ditch. Those three larger ditches (Prospect Ditch, North <br />tributary East Pit Ditch and Final East Pit Ditch) have been revised and now appear in Exh. 7- <br />14R of TR -87. With adoption of TR -87, only the Section 16 Fill Ditch remains in this Exh. 7- <br />14D. <br />The ditch is designed to meet the requirements of Rule 4.05.3 for drainages less than one square <br />mile. The drainage area of this basin is about 12.39 acres, all of which is now in post -3 year <br />reclamation. This requires that the channel be capable of handling flows from a 10 year, 24 <br />hour event. The steepest portions have a slope of about 17.8 percent. The overall length of the <br />channel is about 685 feet. <br />As shown on the attached SEDCAD printout, the design storm produces a peak discharge of <br />about 1.94 cfs. This design event is based on a Curve Number of 74 for post -3 year reclamation, <br />and assumes that the entire drainage area is contributory to the channel. <br />Because the flow is so small, the design has been based on a triangular ditch (zero bottom width) <br />with 311:1 V side slopes, but as a construction expedient, the ditch may have a bottom width up to <br />12 feet based simply on the minimum width of a dozer blade. Rip -rap protection is provided, <br />with a D50 of 12 inches as calculated in the attached SEDCAD model using the Simons /OSM <br />method for sizing rip -rap. <br />Exh. 7 -14D -2 Revision Date: 11/03/10 <br />Revision No.: TR -87 <br />