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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 />The sediment ponds have been designed to be dewatered after each <br />major runoff event. The ponds will be dewatered by natural seepage <br />and infiltration, or through the use of an automatic or manual <br />dewatering device. The automatic dewatering device is designed to <br />be non - clogging and to have a discharge rate that will achieve and <br />maintain the required detention time. The devices have been <br />located at the lower elevation of the 10 -year storm capacity <br />volume, although not below the maximum elevation of the sediment <br />storage volume. <br />Sediment pond maintenance includes removal of sediment when <br />sediment storage exceeds 60% of the designed sediment volume. <br />The ponds at Outfalls 001, 020 and 016 are cleaned as necessary, <br />throughout the year. Cleaning of the other sediment ponds is done <br />when ground conditions are dry enough to allow access by the <br />necessary equipment. This is generally in the summer, and cleaning <br />usually progresses from ponds at the lower elevations to ponds at <br />the upper elevations (according to the pattern of snowmelt). <br />The muck removed in cleaning of the sediment ponds is placed on the <br />Sutey coal refuse pile (MR. July 11, 1985). In addition, approval <br />has been given for placement of sediment pond cleanings on the rock <br />tunnel disposal area. (MR -8. March 15, 1988). Placement of pond <br />cleanings on the rock tunnel disposal area is done so as to <br />maintain surface slopes and adequate drainage of the pile. (MR -18. <br />July 1, 1989). Approval has been given for placement of pond <br />cleanings from the four ponds at Portals No. 1 and No. 2 on Pad #4, <br />which is a former storage area situated near the ponds (MR -28. <br />July 28, 1990). Approval has been given for continued placement of <br />pond cleanings on the old refuse pile prior to topsoil placement <br />(MR -29. August 16, 1990). <br />In addition, ditches and culverts are inspected periodically and <br />cleaned as necessary to keep them open and free of debris. The <br />timing for clean -up at the end of winter also depends upon when the <br />ground dries enough to allow access for the necessary equipment. <br />5. Topsoil. <br />a. Existing Topsoil Stockpiles. <br />In the previous permit term (1983 -1988) surface disturbance <br />resulted from expansion of the coal refuse disposal areas, the <br />Adit /Rock Tunnel spoil disposal area, and upgrading of the <br />hydrologic diversion and sediment control systems. Topsoil and <br />soil horizons, as required by MLRD, were salvaged and stored. <br />33 <br />