2010-12-09_GENERAL DOCUMENTS - C1982057

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Storm runoff from all disturbed areas (except some topsoil stockpiles), pit pumpage, water treatment facilities, and spoil springs will pass through a sediment pond designed to ensure that all discharges meet effluent limits in Seneca Coal Company's NPDES permit for the Seneca H-W Mine. A storm water permit and spill prevention containment and control plan associated with the NPDES permit also dictate preventative and mitigation measures for ensuring that all water leaving the mine site meets applicable effluent limits. Disturbed areas, as defined by Rule 1.04(36), are delineated on permit area map Exhibit 12-2. Disturbed areas drain into approved sedimentation ponds, with the exception of certain haul road and access road segments that are located outside approved sedimentation pond collection areas, as allowed by Rule 4.03, and with the further exception of certain small area exemption locations as discussed in the following paragraph. The Division has granted a small area exemption from use of sediment ponds due to the limited size of the area and due to the fact that ponds and treatment facilities are not necessary for the drainage to meet the effluent limitations of Rule 4.05.2 and applicable State and Federal water quality standards for receiving streams, and also due to the fact that no mixing of surface drainage with a discharge from underground workings will occur. The small areas to be exempted are the topsoil stockpiles listed on Table 13-8-1 and shown on Exhibits 13-2, and 13-3. (4.05.2(3)(b)(i)). B. Diversions and Conveyance of Overland Flow All major drainages that are to be disturbed by mining were to be reclaimed to approximate the premining configuration and to blend with the undisturbed drainage above and below the area to be reclaimed. The Division has verified compliance with this requirement for all drainages reestablished within the original permit boundary, as discussed in the findings document issued with the approval of SL-2. Table 20-2 provides the pre-and postmine drainage channel summary. The reclaimed drainages are located on Exhibit 20-2. The average postmining stream gradients was to have concave longitudinal profiles which approximate the premining slopes. The premining and postmining drainage areas of the reclaimed channels are similar in acreage and slope. After the watershed was graded and the location of the drainage channel determined, the channel was to be constructed to the required shape. Permanent channel construction including riprap installation (where specified) was to be completed within one year of completion of the final grading of adjacent backfill slopes, and prior to topsoiling of areas adjacent to the channel. Following construction, the channel was to be left untopsoiled to allow for initial stabilization and inspected for stability according to the rill and gully plan in Tab 22. When the channels have been stabilized, the nun-riprapped segments will be topsoiled and vegetated. Seneca II-W Findings Document 22 C1982057 Permit Renewal No. 5 December 9, 2010