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Mr. Dan Mathews flay 27, 1982 Page Three The revised construction details for the sedimentation pond ar-e shown on the Sedimentation Pond. Design flap (11ap S-3). The design calculations for this pond are attached. As shown on the Sedimentation Pond Design (htap S-3), several baffles will be installed in the pond to channel flov~ and prevent short-circuiting of the water directly from the inflow to the outflow. These baffles will help extend the settling area of v,ater found in the pond. This sedimentation pond is not designed for a ]0-year 24-hour precipitation event as required under Rule 4.05.6(3)(a); however, because it will be used to complement the overall drainage and sediment control measured, the Bear Coal Company would like to have the entire system labeled as a treatment facility under the requirements found in Rule 4.05.2 of the Coal Regulations of the Colorado Mined Land Reclamation Board. The Bear Coal Company is confident that the drainage and sediment control plan submitted herein will be sufficient to meet the applicable requirements found under Rule 4.05.2 and in the NPDES permit. P.5 shown on the Sedimentation Pond Design t•tap (liap S-3), a sediment storage level has been calculated for a one-year period. •4nnual maintenance of the pond will be carried out in order to provide as 1 much sediment storage volume as practicable. Likewise, the sediment storage level will be checked after every large precipitation event and cleaning will be initiated if necessary. 1 The bottom of the sedimentation pond will be lined with a chemical 1 sealer that will not affect fish and wildlife in the area. This sealer will be used to prevent gr-oundv~ater infiltration of ~:pater in the sedimentation pond, or conversely, inflow into the pond by groundwater. Following annual maintenance, the chemical will again be spread on the bottom of tine sedimentation pond. The use of clay as a pond liner is not acceptable because of difficulty in maintaining this type of sealer following mair~tenar~ce. In the event of a large precipitation event, the Bear Coal Company will use a flocculant in the sedimentation pond in order to cause any fine sediment in the pond to drop out prior to discharge. A flocculant will be used only as a final effort to meet the I effluent limitations and will not adversely affect fish, v~ildlife and related environmental values in the tJorth Fork of the Gunnison River or adjacent areas. Stipulation No. 2 Bear Coal Company believes that the chance of severe flooding in the Bear No. 3 area will be minimized or eliminated by the following two items: ~ ~9 T•~~ ..._ ..............._•..........~ v