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• construction of permanent perimeter ditch in refuse area 2/3/4 and subsequent refuse areas may be <br />delayed until final reclamation. Runoff from active areas typically would not reach these ditches until <br />the soil cover is in place effectively making them unnecessary until this time. <br />During operation all refuse areas will have interim/inpit ditches as needed to direct runoff during <br />operations. The primary purpose is to ensure that all runoff from disturbed refuse areas is directed <br />away from the fill to the appropriate sediment pond. These ditches are sized in accordance with the <br />referenced designs for the permanent ditches (or other more specific designs if approved) to pass <br />the runoff from a 100-year, 24-hour storm. Illustration 50 provides an explanation of the interim/inpit <br />ditches and appropriate stabilization practices. Stabilization practices may include some or all of the <br />following: (i) temporary rock check dams (see Figure IV-1 ), (ii) straw bale check dams, (iii) dug out <br />sediment traps (see Figure IV-2), (iv) rip rap or other ditch lining, (v) contour ditching along slopes of <br />refuse areas, and (vi) land imprinting using sheep's foot compactor for refuse area slopes. <br />Diversion ditches around the perimeter of the refuse disposal sub-areas will intercept runoff from <br />undisturbed areas and either direct it to the sediment ponds or to a natural drainage if the ditch does <br />not collect runoff from waste banks or disturbed areas. Permanent diversion ditches are designed <br />in accordance with the requirements of State Rule 4.10.3(2), 4.09.2(7) and 4.05.4. Permanent <br />diversions are designed to pass the runoff from a 100-year 24-hour storm. The ditches will be <br />designed to cant' the design flow depth and 0.3 feet of freeboard in all areas including the riprap <br />• sections. See Illustrations 4, and 6A. After reclamation has been completed and the sediment <br />ponds have been removed, the permanent diversion ditches will be blended to drain into the natural <br />drainage where their respective ponds cunently discharge. The ditch design will not apply to the <br />western RP-5a ditch collecting undisturbed area diversion since this ditch area will be a part of the <br />future refuse area 5b (RP-5b). <br />The diversion ditches will not be constructed all at once but will be wnstructed as needed to <br />propedy control runoff from the refuse areas and adjacent undisturbed ground as the refuse piles <br />are enlarged. Ditches will be stabilized with energy dissipation devices such as cobble dams <br />(Figure IV-1) as conditions warrant. Upland diversion ditches will be installed up-slope from the <br />actual working area to catch runoff from the undisturbed area and channel it into the permanent <br />diversion system or away from disturbed areas. <br />Mined material with a specific gravity greater than 1.6 is considered to be coal processing waste. <br />This is known as "sink" material, and samples of it were submitted to commercial laboratories for <br />chemical analyses as required by the Code of Colorado Regulations (2.04.6(2) and 4.09.1(12)(b). <br />The results of the analyses are included in Appendix 9 of Section II.B. <br />• TR60 (7/2004) IV-19 <br />