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Surface runoff from disturbed areas will be routed through sediment <br /> ponds. Nineteen sediment ponds have b,a,�q constructed at the Coal Basin <br /> mines. Two sediment ponds at the rock tunnel are to be constructed as <br /> the disposal pile progresses in size, four ponds are planned For Mine <br /> 4, two ponds are planned to be constructed on the t:4o-year �:o,tl <br /> processing waste disposal area and one pond gill he coistrictp_d on the <br /> five-year waste disposal area. <br /> Mines 1 and 2 Sediment Control <br /> n <br /> Mines 1 and 2 have a common sediment control system. The Mine 1 and 2 <br /> areas are formed on excavated rock surfaces which are inclined toward th,� <br /> highwall at 2 to. 10 percent slopes. The pad areas are composed of loose, <br /> fractured sandstone and shale, and coal spoil . Each pad area has been <br /> notched into very steep mountainous terrain with iverage natural <br /> undisturbed slopes that commonly range from 70 to 100 percent and greater <br /> in some areas. Other disturbed ireas in t:ie vicinity of Hines 1 and 2 <br /> include a coal storage silo pad (0.44 acres) and a storage pad for lumber <br /> and supplies (1 . 14 acres) . <br /> Sediment and runoff from the ,dine 1 and 2 pads is collected and conveyed <br /> to a series of two sediment ponds via a 12-inch corrugated metal pipe <br /> (CMP) . All undistlarhed drainage is routed around the disturbed area. <br /> Runoff from the storage pad for lumber and supplies and the coal storage <br /> pad is routed to the sediment pond by culvert. <br /> The first sediment pond in series functions to settle the majority of the <br /> sediment from the disturbed area. This pond has only one discharge <br /> structure, an 18-inch CHIP which discharges into the second pond. . This <br /> pipe is capable of handling the peak runoff frow a 25-year, 24-hour <br /> precipitation event. <br /> The second pond is equipped with an 18-inch C,',1P principal spillway and an <br /> incised emergency spillway capable of handling the peak flow From a <br /> 25-year, 24-hour precipitation event. The second pond is capable of <br /> containing the runoff from a 10-year, 24-hour precipitation event. The <br /> function of the first pond is to allow additional detention time for the <br /> settling of clays. <br /> The primary spillway on the second pond is located at the top of the <br /> 10-gear, 24-hour storage volume. [However, this pond is designers to <br /> accommodate the runoff from a 25-year, 24-nour scorn .0 trout discharge <br /> from the incised emergency spill:•lay. In adlition, the applicant has <br /> committed to purnping any ,exc;es; v•i :fir .� a-:in�:3in "�" ��;; <br /> tne 10-year, 24-4,jr .v <br /> 'line ,+o. 3 Sediment Control <br /> The 'dine No. 3 pad area includes µ.36 .crams of _2xcavated surface with a <br /> 5-7 percent grade towards the hignwall . The steep inclined rocK nignwall <br /> extends 50 to 100 feet above the 'nine por.al . Above the hi;hwall is an <br /> aoandoned exploration road that traverses the entire length of the <br /> g '+a11 T s road is .ls,'I J 4v indis: !r. a r <br /> hl h,• hl r � �� ?ram ���� ;1'.ln �yt3 3 '):.nd th: <br />