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POST REGRADING DRAINAGE AND SEDIMENP CONTROL PLAN <br />INTRODUCTION <br />Once final grading is completed and prior to reestablishment of <br />vegetation to regulatory standards the following drainage and sediment <br />control structures will remain or be added: <br />Ponds: <br />• Post Regrading Sedimentation Pond 4 <br />• Post regrading Sedimentation Pond 5 <br />Channels: <br />• Access Road Drainage Ditch and associated Culverts <br />• Permanent Diversion Ditch 1 <br />• West Refuse Collection Ditch <br />• South Refuse Collection Ditch <br />• North Refuse Collection Ditch <br />• Magpie Creek Diversion <br />SAE: <br />• Explosive Bunker <br />• Rock Dust Storage Facility <br />• Sub-Station No. 2 and Power Line <br />• South Fan <br />• Yard Area (New) <br />• Topsoil Pile (New) <br />The location of all these structures are shown on Map 30, Southfield <br />Reclamation Map. <br />PONDS <br />Sedimentation Ponds 4 and 5 will remain until vegetation is <br />reestablished. However Sedimentation Pond 1 will be backfilled during <br />regrading and the drainage that reported to pond 1 will be diverted to <br />Pond 5 and the Yard Area 1 SAE. <br />In addition, Ponds 4 and 5 will be redesigned to convert them from <br />containment ponds to passive treatment ponds. The embankments and <br />general layout of the ponds will not change. The only changes that <br />will be made to the ponds are the invert elevations of the existing <br />risers. <br />The hydrologic, hydraulic, and sediment calculations used to redesign <br />Ponds 4 and 5 were performed utilizing the SEDCAD+ and SEDCAD4 (SEDCAD) <br />computer modeling program developed by Civil Software Design. Both <br />ponds are redesigned to effectively treat the peak runoff produced from <br />the 10-year, 24-hour storm event. The ponds were redesigned using the <br />207 <br />