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<br />V-3 <br /> <br />3. Riprapped or Other Llned Channels. Higher velocity artlflcla', <br />channels wIll be used with dlscre'tion, and then only to accommodate <br />existing development for minimum reaches. <br /> <br />a. Rlprap size, design velocity and "n" Villus!; are to be based upon <br />figures 19, 20, and 21 of the Bureau of PublIc Roads publlca- <br />t I on, "Des I gn of Roads I de D ra I nag'~ D 1 tches" and the Denver. <br />Regional Council of Governments' criteria. <br /> <br />b. Side slopes from 3:1 to 2:1 may b,~ rlpi'apped, but ste'~per <br />slopes must be solidly lined wIth an anchol'ed wall. The <br />preferable section for steeper side slopes Is 0.511 wIth B <br />retainIng wall structure embedded wi th natural stone. Carl! <br />must be taken for freeze, thaw, gi'ound water, and expllrislve <br />so 11 effects. <br /> <br />c, The bottom of channels must generally be lined wh,en e'lther. <br />the ve 1 oel ty exceeds 8 fps or the Froude numbe r exceeds 0.8. <br /> <br />d. Use Trickle channels for low flow's "dth capacities of about <br />one"Rer cent of design flow, but not to exceed 20 cfs" <br />Rlprap, concrete, or other protection to prevent erosion Is <br />needed. <br /> <br />4. Brldqes. Bridges should be desIgned f,)r 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 feasI- <br />ble. Backwater effect of culverts I!: to be consistent wIth chan., <br />nel requirements and adjacent top')graphy. Energy dlsslpator!' <br />must be used downstream of culverts wherever flow Is super"crl tical <br />from channel standpoint. <br /> <br />6. Conduits. Conduits are designed based upon thl! criterIa Included <br />In the storm sewers and the major dralln,age parts of the D'~nver <br />Regional Council of Governments' Manuall. <br /> <br />a. The maximum allowable veloclty for a nC)n-aI'1l1ored concrl!te <br />conduit shall be about 20 fps. <br /> <br />b. On steep slopes, velocity may bl! controlled by artlflcJally <br />created head losses due to manholl~s and/or bends. <br /> <br />c. When It Is desirable to achIeve a velocity of about 20 fps, the <br />lower portion of the conduIt shalll be armol'ed with stl~"l sheet, <br />ralls, etc. <br />