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material that is likely to be added to the temporary waste pile <br />will be unexpected events within'the mine and/or driving cross-cuts `~ <br />through rock. Because of NCIG s commitment to increase the ash <br />content of the coal, any produced waste rock can be fed back into <br />the product stream. Therefore, the temporary storage area will <br />gain and lose rock material during operation. <br />The temporary storage area will consist of a curbed "v"-sloped, low <br />permeability pad which will direct any drainage towards a sump <br />(detailed designs are provided in Exhibit 4.3-6). Any water <br />collected in the sump will be returned to the slurry circuit for <br />reuse. The proposed temporary storage area has diversion ditches <br />on all sides to both prevent surface water from contacting the pile <br />and to direct any runoff from the pile to sediment Pond •A. The <br />ditch south (upgradient) of the proposed storage pile location, <br />with modification, would divert the 100-year, 29-hour storm event <br />away from the proposed pile. <br />The 100-year discharge just above the temporary mining refuse area <br />is calculated to be 60 cfs. This discharge is based upon the <br />following conservative assumption: all undisturbed runoff east of <br />Portal #1 along with all eastern surface facility area runoff <br />concentrates at the refuse storage area (i.e., all drainage ditches <br />above the storage area fail). The existing drainage ditch above <br />the temporary mining refuse storage area is triangular in cross <br />section, has 2:1 side slopes and has a gradient of 5.9%. The 100- <br />year discharge of 60 cfs can be conveyed in this ditch at a depth <br />of 1.9 feet. NCIG, however, will commit to insuring that the <br />minimum ditch depth in this vicinity is 3 feet (allows 0.6 feet of <br />ditch freeboard). <br />The pile, will not exceed 15,000 cubic yards (a NCIG commitment), <br />and will be placed in lifts and compacted in order to maintain <br />stability of the pile. The temporary storage will be inspected <br />quarterly during its operation by a qualified engineer. <br /> ~ <br />NCIG - Coal Ridge #1 4-36 ABC/1145/910801 ~ <br />