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<br />V-3 <br /> <br />3. Rlprapped or Other Uned Channels. Higher velocity artlflcla'r <br />channels wTll 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" Villuss 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 />siopes 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. Can! <br />must be taken for freeze, thaw, gi'ound water, and expllrislve <br />so II effects. <br /> <br />c. The bottom of channels must generally be lined wh'en eHher' <br />the ve 1 oct ty exceeds 8 fps or the Froude nl.lmbe r exceeds 0.8. <br /> <br />d. Use Trickle channels for low fiow's l~rth 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 Is to be consistent wi'th chan., <br />nel requirements and adjacent top')graphy. Energy dlsslpaton; <br />must be used downstream of cuiverts wherever flow Is super"crl tical <br />from channel standpoint. <br /> <br />6. ConduIts. Conduits are designed based upon the criterIa Included <br />In the storm sewers and the major dralln.age parts of the D'~nver <br />Regional Councii of Governments' Manuall. <br /> <br />a. The maximum allowable veloclty for a nc)n-al''mored concr"te <br />conduit shail be about 20 fps. <br /> <br />b. On steep slopes, velocIty may be controlled by artlflcJally <br />created head losses due to manhol,~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 arrnol'ed wIth st"el sheet, <br />ralls, etc. <br />