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Section 6 <br />Sunday Mine <br />Table 6-2 Input Values for Channel 1 Ca aci Anal sis <br /> <br />Channel 100-yr Q <br />cfs S <br />ftNt <br />n z <br />ft/ft b <br />ft <br />1 19.61 0.01.6 0.035 3 0 <br />The calculated channel depth and flow velocity of Channel 1 are shown in Table 6-3. <br />CDM recommends adding 2-feet of freeboard to the calculated flow depth to account <br />for potential channel overtopping. The design depth of 3.5 feet is recommended for <br />Channel 1. <br />Table 6-3 Calculation Summary for Channel 1 <br /> <br />Channel h <br />ft Freeboard <br />ft Design Depth <br />ft V <br />ft/sec <br />1 1.29 2 3.29 3.90 <br />CDM used the UDFCD Drainage Criteria manual and calculated flow velocities to <br />determine the appropriate channel lining for Channels 1(UCFCD 2005). 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 />Manrtng's n value of 0.003 was selected for design calculations, to check the capacity <br />of grass-lined channels. Based on these criteria, CDM recommends a grass-lined <br />channel for Channel 1 since the flow velocity is less than 5 ft/ sec. <br />• 6.4.2 Berm Design <br />CDM designed earth berms to capture surface water runoff from Basins 2 through 7. <br />Runoff in Basins 2 trough 5 will be captured by a berm along the crest of the WRA. <br />Runoff in Basins 6 and 7 will be captured and routed to proposed catchment basins <br />(refer to Exhibit E-1). The berms and catchment basins were designed to contain <br />runoff from the 100-year, 24-hour storm event. The point precipitation frequency <br />estimate for the 100-year, 24-hour storm, obtained from NOAA Atlas 14, Volume 1 for <br />Colorado (NOAA 1973) is 3.0 inches. CDM used the SCS runoff equation to estimate <br />runoff from the 3.0 inches of rainfall. The SCS runoff equation is: <br />_ P - 0.2SY <br />Q (P+0.8S) <br />where <br />Q = runoff (in) <br />P = rainfall (in) <br />S = potential maximum retention after runoff begins (in) <br />• <br />6-3 <br />OA64988. Denison%Task Order 1 . Sunday Mines Drainage StudyAspoffinel Repor0final Sunday Mines Dratropa Repod_05=6.doc