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• of mining and reclamation unless prior approval to retain impoundments is obtained. <br />The impact of sediment ponds and runoff from reclaimed areas on the quality of receiving streams <br />was found to be of minimal significance (see Tab 17, Probable Hydrologic Consequences). Historic <br />water quality sampling at both NPDES 001 and 006 ouffalls have shown that water discharged from <br />these ponds is suitable for livestock, and that only one exceedance of NPDES limitations has been <br />observed at any NPDES ouffall since 1980. Based on past water quality monitoring, it is anticipated <br />that no treatment of pond effluent is necessary. However, should the need for treatment of pond <br />effluent be demonstrated, Peabody will commit to designing treatment facilities or procedures to <br />handle the equivalent of a 10-year, 24-hour effluent volume. <br />Plans for sampling overburden and topsail after backfilling and grading have been completed, to <br />identify potentially deleterious materials, have been developed and are presented in Tab 21 (Minesoil <br />Reconstruction). Based on these plans, surface runoff from disturbed reclaimed areas will not come <br />in contact with materials that would contribute to elevated levels of acid or toxic constituents. <br />Topsoiling handling procedures (Tab 21, Minesoil Reconstruction) and revegetation methods (fab <br />22, Revegetation Plan) have been developed to stabilize the landscape, prevent erosion, and <br />minimize the additional contributions of sediment to runoff. They include: the seeding of temporary <br />• disturbance and topsoil piles; mulching, chisel plowing and deep ripping; cover cropping; and timely <br />reseeding of reclaimed areas (regraded and topsoiled) with seed mixes designed for rapid <br />establishment and development of effective hydrologic cover. Those areas that are affected by <br />mining will be graded to postmining topographies that generally feature slopes no greater than 5:1. <br />In combination with the reclamation and topsoil handling techniques, reduced slopes will minimize <br />the potential for erosion due to accelerated sheet wash or gullying. <br />The reestablished reclaimed channel (West Retum Ditch) was constructed to have a postmining <br />gradient similar to premining conditions. Revegetation methods and seed mixes used to reclaim the <br />reestablished reach of this affected channel have resulted in stable conditions as reflected by TSS <br />monitoring performed at Site SW-N6 since 1980. <br />The Surface Water Control Plans (Exhibits 13-4 and 13-5, Tab 13, Facilities) include five temporary <br />diversions. All diversions have been designed according to accepted design criteria, and will be built <br />to minimize erosion and prevent additional contributions of sediment by limiting the slow velocities <br />and tractive forces that cause erosion. Temporary diversions in place longer than a growing season <br />will be seeded with a temporary seed mix as outlined in Tab 22. The diversions have been designed <br />to maximize geomorphic stability while minimizing disturbance. All temporary diversions will be <br />removed and reclaimed after mining activities have been completed. Plans have been developed <br />• <br />16-4 <br />