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of the following: (i) temporary rock check dams (see Figure IV-1), (ii) straw bale check dams, (iii) dug <br />out sediment traps {see Figure IV-2), (iv) rip rap or other ditch lining, (v) contour ditching along slopes of <br />refuse areas, (vi) land imprinting using sheep's foot compactor for refuse area slopes and (vii) use of a <br />clarifying agent (Nalco Enact 7888 or equivalent) for decreasing settling time in sediment ponds. RP-5 <br />perimeter ditches were constructed as permanent ditches and sediment and erosion controls will be <br />installed as appropriate to the ditch design and steepness. <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 not <br />collect runoff from waste banks or disturbed areas. Permanent diversion ditches are designed in <br />accordance with the requirements of State Rule 4.10.3(2), 4.09.2(7) and 4.05.4, Permanent diversions <br />are designed to pass the runoff from a 100-year 24-hour storm. Interim or in-pit refuse area perimeter <br />ditches will also be sized in accordance with the referenced designs to pass the runoff from a 100-year, <br />2 -hour s orm. The ditches will be designe o carry a design flow depth and 0.3 feet of freeboard in <br />.~-~- <br />all areas including the riprap and checkdam sections. See Illustrations 4, 5, and 6. After reclamation <br />has been completed and the sediment ponds have been removed, the permanent diversion ditches will <br />be extended to drain into the natural drainage as shown on Map 81. The ditch design will not apply to <br />the western RP-5 ditch collecting undisturbed area diversion since this ditch area will be a part of the <br />future refuse area 6 (RP-6). <br />The diversion ditches will not be constructed all at once but will be constructed as required as the refuse <br />. spoil bank is enlarged. Ditches will be seeded and energy dissipation devices such as cobble dams { <br />Figure IV-1) will be utilized in ditches on steep slopes where water velocity is expected to exceed four <br />feet per second and may cause erosion problems. Temporary diversion ditches will be installed <br />up-slope from the actual working area to catch runoff from the undisturbed area and channel it into the <br />permanent 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. This is <br />know as "sink" material, and samples of it were submitted to commercial laboratories for chemical <br />analyses as required by the Code of Colorado Regulations (2.04.6(2) and 4.09.1{12)(b). The results of <br />the analyses are included in Appendix 9 of Section II.B. <br />The coal refuse is not expected to contain material that will cause water seeping through the waste to <br />become toxic or acid in nature. For this reason, coal waste and mine development waste can be <br />disposed of together (30 CFR part 817.71) and certain requirements regarding coal processing waste <br />banks are not applicable. No treatment of this runoff other than for sediment is anticipated. No sutr <br />drain system will be provided to prevent the surtace water or seepage from entering the groundwater <br />system. However, the embankment drainage will be monitored and appropriate measures taken if the <br />water does become toxic or acid. Monitoring will include the sampling of sediment pond discharges (see <br />Hydrology section). !f the water does become acid or toxic, the ponds, ditches, anal disposal areas wi!! <br />Mine Permit Renewal #3 (Rev, 8/99) IV-20 <br />