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<br />4. Bridqes. Bridges should be designed for overtopping In accordance <br />with the criteria of the Drainage Criteria Manual and according to <br />the designated street use. <br /> <br />5. Culverts. Culverts will be used in lieu of bridges where feasIble. <br />Backwater effect of culverts to be consistent with channel require- <br />ments and adjacent topography. Energy disslpators must be used <br />downstream of culverts wherever the flow velocity exit from the <br />culvert exceeds the allowable channel velocity. <br /> <br />a. The use of armor piating on culvert floors must be considered <br />when the potential for wear by movin!l rocks and high velocities <br />exists. <br /> <br />6. Conduits. Conduits are designed b'lsed upon the criteria included <br />in the storm sewers and the major drainage parts of the Denver <br />Regional Council of Governments Manual. <br /> <br />a. The maximum allowable velocl ty for a non-armored concrete <br />conduit shall be about 20 fps. <br /> <br />b. On steep slopes, velocity may be controlled by artifically <br />created head losses due to manholes and/or bends. <br /> <br />c. When it is desirable to achieve a velocity about 20 fps, the <br />lower portion of the conduit shall be armored with steel sheet, <br />ralls, etc. <br /> <br />d. The hydraul ic grade line shall be maintained below the ground <br />surface. <br /> <br />7. Irrlqatlon Ditches. All Irrigation ditches and laterals wIll be <br />provided for, though laterals 1,.,111 not be shown on master plans. <br />Use on-grade flumes where feasible to reduce silt and maintenance <br />problems. Capacity of crossings will be limited to cause storm <br />runoff In ditches to enter wat,orways. II"rigatlon ditch crossings <br />will be designed to obviate pkking up of overflow from waterways. <br /> <br />8. Drops and Checks. Channel drops wIll be used as needed to control <br />the hydraulic grade I ine and velocity to within reasonable slopes <br />and limits. Drops will be of concrete, riprap, or riprap In ga- <br />blons, be of pleasing appearance, have gravel filter blankets under <br />the rock to control undercutting, and be properly notched for the <br />trickle channel. Design must account fOI' potential vandalism. <br />Checks will be end-protected to eliminate side cutting. <br /> <br />9. Enerqy Dlssipators. These will usually consist of natural rock <br />Impact blocks with suitable riprap or gablon protected bottom and <br />side slopes. Design will account for potential vandalism. <br /> <br />v 1-4 <br />