2010-05-07_PERMIT FILE - C2009087A (28)

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Peabody Sage Creek Mine — Drainage and Sediment Control Plan TABLE 2.05.3 -E2 -12 Postmine Culvert Schedule Culvert No. Design Peak Discharge' cfs Design Diameter inches Diameter Installed inches 2A & 2AA 2.8 10 30 9A 65.3 48 48 & 24 12A 1.5 8 30 13A 3.0 18 18 15A 2,3 56.6 108 (3 )72 29A 6.9 30 30 30A 7.1 30 30 31A 1.3 18 18 32A 3.6 24 30 33A 1.4 18 18 45A 0.3 4 18 47A 0.7 24 24 62A 0.2 4 24 Al 0.9 24 24 A3 5.4 30 30 A4 0.6 12 18 A5 0.5 6 30 A8 0.9 24 24 SCM -10 17.6 108 (4 )60 SCM -11 9.4 84 (3 )48 SCM -12 10.5 66 2) 48 Notes: 1) Design based on 10 -year, 24 -hour storm event peak runoff unless otherwise noted. 2) Re- designed for the Peabody Sage Creek Mine reclamation plan. 3 Designed for the 25-year, 24 -hour storm event peak runoff. TABLE 2.05.3 -E2 -13 Permanent Postmine Stock Tanks T -3, T -4, T -8, T -16, T -17, T -20, T -26, T -28, T- 29T -30, T -31, T -32, T -33 6.0 SMALL AREA EXEMPTIONS The boneyard and office areas from the Seneca II Mine operations were approved as Small Area Exemptions (SAEs) by CDRMS as part of Minor Revisions No. 3 and No. 11 for the Seneca II Mine Permit C -80 -001. These areas will be utilized for storage (boneyard) and office space as part of the Peabody Sage Creek Mine operations. The location of the Boneyard/Office SAE is shown on Map 2.05.3 M1B, Mine Facilities Area (North End). The SAE consists of the Old Boneyard, the New Boneyard and Office Parking Lot; it four covers approximately 5.4 acres. Seneca Coal Company (SCC) sampled for settable solids at the areas during three events in 1993. The sample results indicated only one sample from one location exceeded the receiving stream water quality criterion (0.5 milliliters per liter [ml/1]). Because the sampling results were inconclusive, SCC modeled runoff from the areas using SEDCAD+ (Schwab, 1988) to demonstrate that alternative sediment control methods, if necessary, would successfully 2.05.3 -E2.24