2022-05-04_REVISION - C1981018 (9)

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from elsewhere within the Refuse Disposal Area and used to construct the required pond embank- ments. The actual location of suitable construction materials will be determined during field construction by a qualified Geotechnical Engineer or Technician and appropriate field laboratory analysis. A detailed discussion of sediment pond design can be found in Section V-B. Drainage and sediment control structures will be maintained so that they are stable and functional at all times, until final bond release is approved. See Section IV.J.1 for the control systems. The construction of permanent perimeter ditch in refuse area 2/3/4 and subsequent refuse areas may be delayed until final reclamation. Runoff from active areas typically would not reach these ditches until the soil cover is in place effectively making them unnecessary until this time. During operation all refuse areas will have interim/inpit ditches as needed to direct runoff during operations. The primary purpose is to ensure that all runoff from disturbed refuse areas is directed away from the fill to the appropriate sediment pond. These ditches are sized in accordance with the referenced designs for the permanent ditches (or other more specific designs if approved) to pass the runoff from a 100-year, 24-hour storm. Illustration 50 provides an explanation of the interim/inpit ditches and appropriate stabilization practices. Stabilization practices may include some or all of the following: (i) temporary rock check dams (see Figure IV-1), (ii) straw bale check dams, (iii) dug out sediment traps (see Figure IV-2), (iv) rip rap or other ditch lining, (v) contour ditching along slopes of refuse areas, and (vi) land imprinting using sheep's foot compactor for refuse area slopes. Diversion ditches around the perimeter of the refuse disposal sub-areas will intercept runoff from undisturbed areas and either direct it to the sediment ponds or to a natural drainage if the ditch does not collect runoff from waste banks or disturbed areas. Permanent diversion ditches are designed in accordance with the requirements of State Rule 4.10.3(2), 4.09.2(7) and 4.05.4. Permanent diversions are designed to pass the runoff from a 100-year 24-hour storm. The ditches will be designed to carry the design flow depth and 0.3 feet of freeboard in all areas including the riprap sections. See Illustrations 4, 6A, 59, 60, and 62. After reclamation has been completed and the sediment ponds have been removed, the permanent diversion ditches will be blended to drain into the natural drainage where their respective ponds currently discharge. The ditch design will not apply to the western RP-5a ditch collecting undisturbed area diversion since this ditch area will be a part of the future refuse area 5b (RP-5b). The diversion ditches will not be constructed all at once but will be constructed as needed to properly control runoff from the refuse areas and adjacent undisturbed ground as the refuse piles are enlarged. Ditches will be stabilized with energy dissipation devices such as cobble dams (Figure IV-1) as conditions warrant. Upland diversion ditches will be installed up-slope from the actual working area to catch runoff from the undisturbed area and channel it into the permanent diversion system or away from disturbed areas. TR-74 (4/2022) IV-19