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<br />htr. Dan hlathews Page Two <br />May 27, 1982 <br />operation. Because of the nature of the area where the surface <br />facilities will be located, construction of a large sedimentation <br />pond according to the requirements in Rule 4.05.6(3)(a) ar•e <br />impractical because of the large aerial expanse necessary to stay <br />above the groundwater table. The construction of a deeper <br />sedimentation pond would result in disturbance of the groundwater <br />level associated with the North Fork of the Gunnison River. <br />The Bear Coal Company plans the following control measures to <br />effect compliance with the effluent limitations required under the <br />provisions of the Coal Regulations of the Colorado Mined Land <br />Reclamation Board and the National Pollutant Discharge Elimination <br />System (NPDES) permit: <br />• Construction of diversion ditches to channel water from <br />the disturbed area to a sedimentation pond <br />• Use of small dugout structures along diversion ditches to <br />reduce water velocity and decrease sediment load <br />• Gravel filter dams along diversion ditches <br />• A sedimentation pond with baffles to channel flow and <br />reduce short-circuiting <br />• Use of flocculants, as necessary, during large <br />precipitation events <br />• Annual maintenance of all structures <br />The location of the diversion structures to be used at the bear No. <br />3 site are shown on the Drainage and Sediment Control Plan Map (t~~ap <br />S-1). These structures have been designed to handle the runoff <br />from a 10-year 24-hour precipitation event. All performance <br />standards as set forth in Rule 4.05.3 in the Bear Coal Company <br />permit application for diversion ditches will be applicable to the <br />diversion ditches shown on the Drainage and Sediment Control Plan <br />f-lap (t•1ap S-1). The design calculations for the diversion <br />structures are attached to this letter. <br />As shown on the Typical Filter Dam/Dugout Pond Design Flap (Map <br />S-2), several small dugout ponds will be used in conjunction with <br />gravel filter dams. The purpose of these structures is to reduce <br />the velocity of water and to decrease sediment load of the water <br />prior to reaching the sedimentation pond. The design calculations <br />for the dugout ponds and gravel filter dams are attached. <br />J. <br />ni. i <br />A G ~ 1NG. .1 <br />