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Chapter II <br /> -Obstructions to emergency and/or principal spillways; <br /> -Properly cleaned, maintained dewatering devices; <br /> -Sediment storage volume; <br /> -Sloughing,tension cracks, piping, etc. <br /> Sediment pond maintenance includes removal of sediment when sediment storage exceeds 60% of the <br /> designed sediment volume. <br /> The sediment is removed by using either a small dragline or a backhoe. <br /> The sediment ponds have been designed to be dewatered after each minor runoff event. The ponds will <br /> be dewatered by natural seepage and infiltration, or through the use of an automatic or manual dewatering <br /> device. The automatic dewatering device is designed to be non-clogging and to have a discharge rate <br /> that will achiev and maintain the required detention time. The devices have been located at the lower <br /> elevation fo the 10-year storm capacity volume, although not below the maximum elevaiton of the <br /> sediment storage volume. <br /> The ponds are cleaned, if necessary, at the end of winter,when the ground around them becomes dry <br /> enough to allow access by the necessary equipmehnt. This is in the late spring to early summer, and <br /> usually progresses from ponds at the lower elevations to ponds at the upper elevations (according to the <br /> pattern of snowmelt). <br /> MLRD approved a minor revision July 11, 1985, allowing Mid-Continent to place the muck from cleaning of <br /> the sediment ponds on the Sutey coal refuse pile. The muck is truck-hauled to the refuse pile and placed <br /> at random intervals across the pile. The refuse pile is south-facing and dries out relatively fast. The coal <br /> refuse is spread out in a fan shape one to two feet thick and sediment from the ponds is spread out in <br /> layers six inches or less in sections of up to approximately 200'width across the top of the pile so that it's <br /> not concentrated in any one area. <br /> Approval has been given for placement of sediment pond cleanings on the rock tunnel disposal area <br /> (MR-8. March 15, 1988). Approval has been given for placement of pond cleanings from the four ponds at <br /> Portals No. 1 and No. 2 on Pad#4,which is a former storage area situated near the ponds. (MR-28. July, <br /> 1990). Approval has been given for continued placement of pond cleanings on the old refuse pile prior to <br /> topsoil placement (MR-29. August, 1990). <br /> Ditches and culverts are inspected periodically and cleaned as necessary to keep them open and free of <br /> debris. The timing for clean-up at the end of winter also depends upon when the ground dries enough to <br /> allow access for the necessary equipment. <br /> 5. Topsoil <br /> a. Existing Topsoil Stockpiles. <br /> In the previous permit term (1983-1988) surface disturbance resulted from expansion of the coal refuse <br /> disposal areas, the Adit/Rock Tunnel spoil disposal area, and upgrading of the hydrologic diversion and <br /> sediment control systems. Topsoil and soil horizons, as required by the MLRD,were salavaged and stored. <br /> 33 <br />