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~ 1 <br />LJ <br />• <br />Mr. Dan Mathews <br />May 27, 1982 <br />The revised <br />shown on the <br />calculations <br />construction <br />Sedimentation <br />for this pond <br />Page Three <br />details for the sedimentation pond are <br />Pond Design htap (I1ap S-3). The design <br />are attached. <br />As shown on the Sedimentation Pond Design (Flap S-3}, several <br />baffles will be ins tailed in the pond to channel flow and prevent <br />short-circuiting of the water directly from the inflow to the <br />outflow. These baffles will help extend the settling area of water <br />found in .the pond. This sedimentation pond is not designed <br />for a 10-year 24-hour precipitation event as required under Rule <br />4.05.6(3)(a); however, because it will be used to complement the <br />overall drainage and sediment control measured, the Bear Coal <br />Company would like to have the entire system labeled as a treatment <br />facility under the requirements found in Rule 4.05.2 of the Coal <br />Regulations of the Colorado Mined Land Reclamation Board. The Bear <br />Coal Campany is confident that the drainage and sediment control <br />plan submitted herein will be sufficient to meet the applicable <br />requirements found under Rule 4.05.2 and in the NPDES permit. <br />As shown on the Sedimentation Pond Design f~tap (Map S-3), a sediment <br />storage level has been calculated for a one-year period. Annual <br />maintenance of the pond will be carried out in order to provide as <br />much sediment storage volume as practicable. Likewise, the <br />sediment storage level will be checked after every large <br />precipitation event and cleaning will be initiated if necessary. <br />The bottom of the sedimentation pond will be lined with a chemical <br />sealer that will not affect fish and wildlife in the area. This <br />sealer will be used to prevent groundwater infiltration of water in <br />the sedimentation pond, or conversely, inflow into the pond by <br />groundwater. Following annual maintenance, the chemical will again <br />be spread on the bottom of the sedimentation pond. The use of clay <br />as a pond liner is not acceptable because of difficulty in <br />maintaining this type of sealer following maintenance. <br />In the event of a large precipitation event, the Bear Coal Company <br />will use a flocculant in the sedimentation pond in order to cause <br />any fine sediment in the pond to drop out prior to discharge. <br />A flocculant will be used only as a final effort to meet the <br />effluent limitations and will not adversely affect fish, wildlife <br />and related environmental values in the North Fork of the Gunnison <br />River or adjacent areas. <br />Stipulation No. 2 <br />Bear Coal Company believes that the chance of severe flooding in <br />• the Bear No. 3 area will be minimized or eliminated by the <br />following two items: <br />a <br />v.~.~~ <br />A {~r 'jc IHG. ~ ' <br />