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Section 3 <br />West Sunday Mine <br />T?tiie,2-z rlmieidnfinn Snmmarv for Channels 1 and 2 <br /> <br />Channel h <br />ft Freeboard <br />ft Design Depth <br />ft V <br />ft/sec <br />1 0.44 2 2.44 4.28 <br />2 0.49 2 2.49 4.88 <br />CDM used the UDFCD Drainage Criteria manual (UDFCD 2005) and calculated flow <br />velocities to determine the appropriate channel lining for Channels 1 and 2. UDFCD <br />recommends flow velocity be less than 5 ft/sec for grass-lined channels and less than <br />12 ft/sec for riprap channels (UDFCD 2005). Based on UDFCD recommendations, a <br />Manning's n value of 0.035 was selected for design calculations to check the capacity <br />of grass-lined channels. Based on these criteria, CDM recommends grass-lined <br />channels for Channels 1 and 2 since the flow velocities are less than 5 ft/ sec. <br />3.4.2 Berm Design <br />CDM designed earth berms to capture surface water runoff from Basins 3 and 4. <br />Runoff in Basin 3 will be captured by a berm along the crest of the WRA. Runoff in <br />Basin 4 will be captured and routed to a catchment basin (refer to Exhibit B-1). The <br />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)z <br />Q - (P + 0.85) <br /> <br />3-3 <br />0:\84988 - DenisoMTask Order 1 - Sunday Mines Drainage Study,ReportFinal ReportTinal Sunday Mines Drainage Report_OM08.d=