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Section 4 <br />St. Jude Mine <br />• <br />Table 4-2 lnout Values for Channels I and 2 [_anarifv Anzaivaic <br /> <br />Channel 100-yr Q <br />cfs S <br />Rift - - <br />n - - z <br />(ftNt) b <br />ft <br />1 6.12 0.030 0.035 3 0 <br />2 3.85 0.024 0.035 3 0 <br />The calculated channel depths and flow velocities of Channels 1 and 2 are shown in <br />Table 4-3. CDM recommends adding 2-feet of freeboard to the calculated flow depth <br />to account for potential channel overtopping. The design depth of 3.0 feet is <br />recommended for Channel 1 and 2.5 feet for Channel 2. <br />Table 4-3 Calculation Summa for Channels 1 and 2 <br /> <br />Channel h <br />ft Freeboard Design Depth <br />ft ft V <br />ft/sec <br />1 0.74 2 2.74 3.68 <br />2 0.65 2 2.65 3.02 <br />CDM used the UDFCD Drainage Criteria manual and calculated flow velocities to <br />determine the appropriate channel lining for Channels 1 and 2 (UDFCD 2005). <br />UDFCD recommends flow velocity be less than 5 ft/sec for grass-lined channels and <br />less than 12 ft/sec for riprap channels (UDFCD 2005). Based on UDFCD <br />recommendations, a Manniries n value of 0.035 was selected for design calculations <br />to check the capacity of grass-lined channels. Based on these criteria, CDM <br />recommends grass-lined channels for Channels 1 and 2 since the flow velocity is less <br />than 5 ft/ sec. <br />4.4.2 Berm Design <br />CDM designed earth berms to capture surface water runoff from Basins 3, 4, and 5. <br />Runoff in Basin 3 will be captured by a berm along the crest of the WRA. Runoff in <br />Basins 4 and 5 will be captured and routed to a catchment basin (refer to Exhibit C-1). <br />The berms and catchment basin were designed to contain runoff from the 100-year, <br />24-hour storm event. The point precipitation frequency estimate for the 100-year, <br />24-hour storm, obtained from NOAA Atlas 14, Volume 1 for Colorado (NOAA 1973) <br />is 3.0 inches. CDM used the SCS runoff equation to estimate runoff from the 3.0 inches <br />of rainfall. The SCS runoff equation is: <br />_ (P-0.2S <br />Q P + 0.8S) <br />where: <br />Q = runoff (in) <br />P = rainfall (in) <br /> <br />4-3 <br />0464OW- DenisonWeek Order 1-Sunday Micros Drakroge Study{Repoffinal RsporBFinal Sunday Mines Drainage Rsporl_052108dw