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Chapter II <br />Sediment ponds A, B, and C, which were built earlier, can safely pass a <br />10-year/24-hour event plus three years of sediment from the rock tunnel dump area. <br />• Construction of the additional ponds, D & E, is scheduled for 1988. The additional <br />ponds are intended to increase the capacity for handling mine discharge. <br />The total capacities of the five ponds in series will then be: <br />Available Sediment Capacity = 8.85 ac. ft. <br />Available Water Capacity = 9 97 ac ft <br />Total Available Capacity = 18.82 ac. ft. . <br />Required Sediment Capacity = 5.88 ac. ft. <br />Required Water Capacity = 10.29 ac.ft <br />App.ll-B-3 contains documentation for the Adit/Rock Tunnel. The water control <br />structures associated with the project are depicted in Ex. II-B-App.7 Att. 4-1 & 2 found <br />in map jackets in Vol. 3. <br />The sediment pond calculations and portal and yard area cross-sections are covered in <br />Attachment 4 to this Appendix (II-B-App.7-Att.4) <br />(5) Coal Refuse Facility. <br />• The facility includes a surface water diversion/collection system and two sediment <br />ponds. Geo-Hydro Consultants developed the drainage control plan for this area. <br />Golder & Associates did calculations for Phase II of development on the Sutey pile, and <br />verified that the two ponds are adequately sized to meet regulatory requirements for <br />Phases I and II. See App. II-B-S, F~ch. II-B-App. 5-1 through 11 and App. 11-B-7, Att. 5, <br />for design criteria. <br />An additional sediment pond, approved in TR-8 on August 27, 1987, will be constructed <br />as part of the Phase III expansion of the pile. The Phase IV expansion of the pile, <br />which has not yet been permitted, will include addition of another sediment pond. <br />Calculations for these two additional sediment ponds are included in App.ll-B-S. <br />b. Ponds and Impoundments. <br />Ponds and impoundments have been designed and constructed to settle suspended <br />solids from water flowing out of disturbed areas. <br />The ponds and impoundments have been located out of perennial streams, and where <br />surface disturbance can be kept to a minimum. The impoundments have a capacity of <br />less than 20 acre feet and a vertical height of less than 10 feet below the crest of the <br />emergency spillway and the toe of the fill. <br />• <br />27 <br />