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• Based on past water quality monitoring at Seneca 11 and II-W, it is anticipated that no <br />treatment of pond effluent will be necessary at the Yoast Mine. However, should it become <br />necessary to treat pond effluent, SCC will commit to designing treatment facilities or <br />procedures to handle the equivalent of a 10-year, 24-hour effluent volume. <br />Plans for sampling overburden and topsoil after bac kfilling and grading have been <br />developed to identify suitable end potentially deleterious materials, and are described in <br />Tab 21 (Minesoil Reconstruction). Based on these plans, surface runoff from reclaimed <br />areas will not come in contact with materials that would contribute to elevated levels of <br />acid or toxic constituents. <br />Procedures for handling topsoil (Tab 21, Minesoil Reconstruction) and vegetation methods <br />(Tab 22, Revegetation Plan) have been designed to stabilize the Landscape, prevent <br />erosion, and minimize the additional contributions of sediment to runoff. The primary <br />procedures include the seeding of temporary disturbance and topsail piles, cover <br />cropping, and timely reseeding of reclaimed areas (regraded and topsoiled) with seed <br />mines designed for rapid establishment and development of effective hydrologic cover. <br />• Some mulching, disking, or deep ripping may be used on steeper slopes, compacted areas, <br />or specialty planting areas. <br />Areas affected by mining will be graded to postmining topograph ics that feature similar <br />distributions df hillclope ranges. Tab 20 (gackfilling and Grading) discusses in detail <br />classifications of both premining and proposed postmining hiLlstopes. Premining <br />hillslopes ranging from 6:1 to 4:1 comprise 33.3 percent of the disturbance area, (largest <br />percentage slope class) and the proposed postmining topography will feature this same <br />hilLslope range in 37.8 percent of the reclaimed disturbance area. In combination with <br />the reclamation and topsoil handling methods, moderate slope reductions and <br />reestablishment of approximate postmining topographies will minimize the potential for <br />erosion due to accelerated sheet wash or gullying. <br /> Surface water Control Plans (Exhibit 13-2, Tab 13, Facilities) include three temporary <br /> diversions. All diversions have been designed according to accepted design crit eria, and <br /> will be const ructed to minimize erosion and prevent additional contributions of sediment <br /> by limiting the flow velocities and tractive forces that cause erosion. Temporary <br />• diversions in place longer than a growing season will be seeded with a temporary seed mix <br /> as described in Tab 22. Diversions have been designed to maximize geomorphic stability <br />5 <br />