All flow of water across continuous streets or alleys shall be through culverts or bridges.
A. Bridges: New structurally spanned bridges shall have adequate capacity to pass the one percent (1%) chance storm ultimate urbanized flows with one foot (1') of freeboard under the low chord. A backwater analysis shall be provided to illustrate compliance with this requirement and to ensure there are no adverse downstream or upstream impacts.
B. Culverts: Culverts constructed hereafter at new locations under public roads shall have adequate capacity to pass the 50-year storm ultimate urbanized flows with a maximum water surface elevation not exceeding six inches (6") below the lowest pavement (or gutter) elevation in the roadway sump. A backwater analysis shall be provided to illustrate compliance with this requirement and to ensure there are no adverse downstream or upstream impacts.
C. Backwater Analysis Review: Upon review of the backwater analysis, should it determine that adverse impacts may occur from the construction of new structurally spanned bridges and/or culverts under public roads, the city, through the city manager, may authorize the design for construction of such bridges and/or culverts to convey less than ultimate urbanized flows in a manner that does not violate section 13.42.440 of this chapter. (Ord. 1969, 2011)