Laserfiche WebLink
<br />Corrugated metal pipe as specified by CDOT M 603-1 ;~' <br />shall be used. Steel pipe shall be asphalt coated <br />or paved where soils are corrosive or other <br />conditions exist that may attack the steel. <br />Aluminum and other pipe materials are not <br />permitted for Toad culverts to be maintained by <br />the County. Minimum diameter for round pipe shall <br />be i8 inches. The minimum rise of arch pipes and <br />box culverts shall be 12 inches. When a battery <br />of pipes is used, a clear spacing of i the pipe <br />diameter (1-foot minimum, 4-foot maximum) must be <br />provided between pipes. <br />III. Open Channels and Ditches. Channels and ditches <br />shall be designed to avoid roadside safety <br />hazards. The minimum flow line slope shall be o.2 <br />percent if the channel is paved and 0.3 percent <br />for channels or other materials. The following <br />table establishes the maximum permissible <br />velocities that determine maximum allowable <br />slopes. Greater velocities of flow shall require <br />appropriate channel protection as determined by <br />the County Engineer. Manning's Equation shall be <br />used to estimate velocities: <br />v = 1.486 RN Spa <br />n f_ <br />~: <br />where v = velocity of flow in channel in feet <br />per second; <br />n = roughness coefficient; <br />R = hydraulic radius in feet; and <br />S = slope in feet per foot. <br />Channel Material "n" Velocity (ft/sect <br />Silt .025 2.0 <br />Sand .030 2.5 <br />Smooth, Stiff Clay .025 4.0 <br />Fine Gravel .035 3.5 <br />Coarse _ <br />Gravel .040 4.5 <br />Small, Sharp-edges Rocks .070 6.0 <br />Cobbles and Shingles .060 6.0 <br />Shales and Hardpans .030 6.0 <br />Where the channel is comprised of a combination of <br />materials shown above, the maximum permissible <br />velocity shall prevent undue scouring of finer <br />materials or silting downstream. <br />J <br />Page 5-5-26 <br />