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Section 3 <br />West Sunday Mine <br />3.4 Surface Water Control Structure Design <br />CDM designed two diversion channels to route offsite surface water runoff from <br />Basin 1 and Basin 2 around the surface mine facilities to the ephemeral drainages. <br />Storm water runoff from Basin 3 will be captured and detained by an existing earthen <br />berm along the crest of the WRA. Storm water runoff from Basin 4 will be captured in <br />a berm and routed to a catchment basin. <br />3.4.1 Channel Design <br />Channels 1 and 2 were designed to convey the 100-year peak discharge from Basin 1 <br />and Basin 2, respectively to the ephemeral drainages. CDM used Manning's equation <br />to calculate the flow velocity and depth in Channels 1 and 2. Flow depth and velocity <br />were calculated using the following equations for the 100-year peak discharges, cross <br />section geometry (triangular), and Manning's n values listed in Table 3-2. <br />Q=VA <br />A = (b + zh)h <br />V _ 1.49 (b+zh)h 2/3 S112 <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 3-2 Inout Values for Channels 1 and 2 CaDacity Analvsis <br /> <br />Channel 100-yr Q <br />cfs S <br />(ft/ft) <br />n z <br />ft/ft b <br />ft <br />1 2.44 0.083 0.035 3 0 <br />2 3.45 0.093 0.035 3 0 <br />The calculated channel depths and velocities of Channels 1 and 2 are shown in <br />Table 3-3. CDM recommends adding 2 feet of freeboard to the calculated flow depth <br />to account for potential channel overtopping. The design depth of 2.5 feet is <br />recommended for Channels 1 and 2. <br />a? <br />3-2 <br />• <br />• <br />0'"86 -Denbon\Tsek Or.er 1 -Sunday Mine. Drainage Stud)AReportkFinel RepoATI-l Sunday Mims Drainage Rsport_0522W.Coe