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Section 5 <br />Carnation Mine <br />5.4 Surface Water Control Structure Design <br />CDM designed one diversion channel to route offsite surface water runoff from Basin <br />1 around the surface mine facilities to the ephemeral drainages. All storm water <br />runoff from Basin 2 will be captured and detained by an existing earthen berm along <br />the crest of the WRA. Storm water runoff from Basin 3, for storm events less than the <br />100-year storm event, will be captured in a berm and routed to the existing sediment <br />pond. Runoff from Basin 4 will be contained by existing water bars and vegetation. <br />5.4.1 Channel Design <br />Channel 1 was designed to convey the 100-year peak discharge from Basin 1 to the <br />ephemeral drainages. CDM used Manning's equation to calculate the flow velocity <br />and depth in Channel 1. Flow depth and velocity were calculated using the following <br />equations for the 100-year peak discharges, cross section geometry (triangular), and <br />Manning's n values listed in Table 5-2. <br />Q = VA <br />A = (b+zh)h <br />V _ 1.49 (b + zh)h 2/3 51,2 <br />n b + 2 h 1+z2 <br />where: <br />Q = discharge in cfs <br />V = velocity in ft/sec <br />z :1 = side slope <br />A = flow area in ft2 <br />b = bottom width of the cross section in ft <br />h = flow depth in ft <br />S = channel slope in ft/ft <br />n = Manning's roughness coefficient <br />Table 5-2 Input Values for Channel 1 CaDacity Analvsis <br /> <br />Channel 100-yr Q <br />cfs S <br />fffFt <br />n z <br />ft/ft b <br />ft <br />1 7.50 0.018 0.035 3 0 <br />The calculated channel depth and flow velocity of Channel 1 are shown in Table 5-3. <br />CDM recommends adding 2-feet of freeboard to the calculated flow depth to account <br />for potential channel overtopping. The design depth of 3.0 feet is recommended for <br />Channel 1. <br />Table 5-3 Calculation Summary for Channel 1 <br /> <br />Channel h <br />ft Freeboard Design Depth <br />(11t) (ft) V <br />t/sec <br />1 0.89 2 2.89 3.19 <br /> <br />5-2 <br />• <br />• <br />0:184988 -Denison\Task Order 1 - Sunday Mine. Drainage Study\Repon\Finel ReporWinal Sunday Mines Drainage Report_05=8.doc