2014-02-07_REVISION - M1979094HR (5)

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JD -7 Mine — Drainage Design Plan 1 1. INTRODUCTION 1.1 Purpose This Drainage Design Plan presents the design analysis for the stormwater drainage facilities at the JD -7 Mine, which is located in Montrose County, Colorado and owned by Cotter Corporation (N.S.L.) ( "Cotter "). The plan addresses aspects of stormwater collection, conveyance, and retention design necessary to comply with the Colorado Division of Reclamation, Mining and Safety (DRMS) drainage criteria. 1.2 Overview - Runoff Areas and Routing The JD -7 Mine is located in Montrose County, Colorado, near the northern end of Monogram Mesa in the southwest portion of Paradox Valley. The site is accessible via Montrose County Road EE17, 1.3 miles from State Highway 90. The permitted mine area lies within sections 16, 17, and 21 of T46N R17W, NMPM, and within the boundaries of the Department of Energy (DOE) lease tract C -JD -7 (493 acres) and adjacent private land owned by Cotter (240 acres). Under the combined JD -7 Mine permit, approximately 504 acres will be permitted for disturbance, of which approximately 430 acres are currently affected. Mining features that have the potential to affect stormwater discharge at the JD -7 Mine include the following: • The open pit mine • Waste rock pile for the underground mine • Waste rock pile for the open pit mine • Ore transfer pad for the underground mine • Ore transfer pad for the open pit mine • Mine facilities area for the underground mine (including parking area, shop /dry building, fresh water tank, compressor shed, water treatment shed, stormwater ponds, and two water treatment ponds) • Top soil stockpile • Access roads These facilities occur near the toe of the Monogram Mesa escarpment, within the major sub - basins identified as B1, 132, and B3 on Plate 1 and in Table 1. The eastern portion of the JD -7 Mine permit area also extends into major sub - basins 134 and 135, although no surface facilities occur within these sub - basins. Table 1. Major Sub -Basin Areas at the JD -7 Mine Sub -Basin Area Area Description (ft) (acres) B1 35,181,800 807.7 Western project area, includes 42.81 acres of topsoil stockpile 132 21,340,400 489.9 Western project area, includes 24.91 acres of topsoil stockpile 133 56,360,000 1,293.8 Main sub -basin containing open pit, waste rock piles, mine facilities 134 29,527,700 677.9 Undisturbed, east of mine facilities, includes 16.85 acres of the project area B5 18,615,900 427.4 Undisturbed, east of mine facilities, includes 33.81 acres of project area Sub -basin B1 occupies 807.7 acres and extends from the crest of Mongram Mesa to East Paradox Creek, passing through the JD -7 topsoil stockpile area. The upland areas in the southern portion of Sub -basin B 1 are dominated by steep slopes drained by ephemeral drainages which, when flowing, discharge onto the floor of the Paradox Valley floor and ultimately to East Paradox Creek (Plate 1). 4149A.140207 Whetstone Associates