§ 21-56. Culverts and cross-drains.

(a)

Culvert design. Culverts shall be designed of a standard shape and cross-sectional area sufficient to allow for the minimum restricted passage of stormwater runoff and discharge calculated for the required minimum rainfall design frequency.

(1)

Inlet control. If a culvert is designed on the basis of inlet control; the shape of the inlet and potential headwater flood levels upstream from the point of design shall be identified.

(2)

Outlet control. If a culvert is designed on the basis of outlet control; potential tailwater flood levels downstream from the point of design shall be identified.

(b)

Culvert types. The permissible types of culverts under roadways and embankments shall include reinforced concrete-or asphalt-coated metal, round or elliptical pipe or pipe arch and concrete box. Double-wall corrugated high-density polyethylene or polyvinyl chloride drainage pipe may be used for side drains and residential driveway connections to public roads.

(c)

Minimum culvert size. The minimum size of pipe for any culvert shall be eighteen (18) inches in diameter or the equivalent sized elliptical pipe or pipe arch.

(d)

Minimum cover. Where possible, the minimum cover over any culvert shall be twelve (12) inches from the bottom of the pavement or surface course under which it is located.

(e)

Pipe bedding. In situations where unstable bedding conditions exist and differential settlements may be anticipated, appropriate bedding materials and procedures shall be utilized to ensure the stability of the pipe.

(Ord. No. 7944, 3-11-85; Ord. No. 8083, 9-21-87)