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<br />DRAINAGE AND SEDIMENT CONTROL PLAN <br />To control runoff and protect surface water quality, several diversion <br />ditches and a sedimentation pond will be constructed at the Coal Gulch <br />operation. .The Mine Facilities Map (Map 12) shows the planned location <br />of the sedimentation pond and the diversion structures. <br />A theoretical detention time of 24 hours has been used in the design of <br />the sedimentation pond so that all runoff occurring as a result of the <br />10-year, 24-hour precipitation event will be treated to produce a total <br />suspended solids (TSS) concentration less than or equal to 30 mg/1. The <br />pond is designed to provide storage for the inflow entering the pond as <br />a result of a 10-year, 24-hour precipitation event. <br />The initial phase in the construction of the sedimentation pond will be <br />to clear all unsuitable material from the location of the pond. In no <br />instances will any coal fines or coal waste be used as an embankment. <br />Any fill material used in the embankment will be selected to exclude the <br />presence of sod, large roots, or frozen material. The placing and <br />spreading of any fill material will be started at the lowest point of an <br />embankment foundation. <br /> <br />The location of the sedimentation pond and diversion structures to be <br />constructed are shown on the Mine Facilities Map (Map 12). The Regional <br />Hydrology Map (Map 6) shows the location of the watershed boundaries <br />from which, along with other sources, the design criteria were <br />established. Generally, the pond and spillways were sized and placed <br />according to such hydrologic factors as required sediment storage <br />volume, rate of flow, and volume of flow for the appropriate storm <br />event. The pond, spillways, and construction methods have been designed <br />according to such engineering factors as structural integrity <br />-1- <br />