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<br />Because of their temporary nature and the small area involved, it is requested that the cover <br />• fill and topsoil stockpiles be exempt from sediment control and considered as small area <br />exemptions, as allowed under Rule 4.05.2(31• The topsoil stockpile is protected from uphill <br />overland runoff by the ditch along the haul road to the waste bank. The topsoil stockpile will <br />be seeded contemporaneous with construction, and will have alternative sediment control <br />structures such as silt fences or straw bales at the slope toe to control any sediment that may <br />accumulate. Bowie Resources will commit to frequent monitoring of the alternative sediment <br />control structures and upkeep, as necessary. <br />At the cover fill stockpile, the structure is located between two hills, but signs of <br />concentrated flows (i.e., stream erosion) between the hills were not observed in field <br />investigations. An upland diversion ditch is located topographically above the cover fill <br />stockpile for overland flow protection produced by a 10-year, 24-hour storm event. At the <br />cover fill stockpile haul road, a 10 percent haul road ditch was incorporated for runoff control <br />on the west side of the cover fill stockpile. Alternative sediment control structures such as <br />silt fences or straw bales will be incorporated at the toe of the cover fill stockpile to control <br />runoff from the slope of the stockpile. <br />• These stockpiles encompass very limited areas. WESTEC considered various options in an <br />attempt to locate all structures upgradient of the sediment pond to allow drainage to be <br />routed to the pond. However, the topography in this area limits where facilities can be sited, <br />and does not make it feasible to place the cover fill and topsoil stockpiles upgradient of the <br />sediment pond (or allow relocation of the sediment pond downgradient below the stockpiles). <br />Moreover, there is no discharge from underground mine workings in this area; thus, there will <br />not be mixture of surface drainage with discharge from underground mine workings. <br />4.2 SEDIMENT POND <br />The sediment pond was designed to capture runoff water and its transported sediment, and <br />hold it until the suspended sediments have settled and the water is suitable for discharge <br />under the mine's discharge permit. The quantity of water and sediment the pond must hold <br />is that produced by the 10-year, 24-hour storm. This storm frequency corresponds to 1.8 <br />inches IJ.E. Stover & Associates, 1995). Spreadsheets used to calculate the sediment pond <br />• <br />96266/1424.RPT Coel Mine Weete Benk Finel Design for the Bowie No. 2 Mine <br />June 1986 WESTEC 13 <br />AD[pUACY-01 <br />