§ 55.22 AMOUNT OF RUNOFF TO BE ACCOMMODATED BY VARIOUS PARTS OF DRAINAGE FACILITY.

   Various parts of a drainage facility must accommodate runoff water as follows:

   (A)   The minor drainage system, such as inlets, catch basins, street gutters, swales, sewers and small channels which collect stormwater, must accommodate peak runoff from a ten-year return period storm. Rainfall duration shall be equal to the time of concentration or one hour, if the time of concentration is less than one hour. A first quartile storm distribution shall be used for computer modeling. These minimum requirements must be satisfied:

      (1)   The allowable spread of water on collector streets is limited to maintaining two clear, ten-foot, moving lanes of traffic. One lane is to be maintained on local roads, while places can have a water spread equal to one-half of their width.

      (2)   Open channels carrying peak flows greater than 30 cubic feet per second shall be capable of accommodating peak runoff for a 50-year return period storm within the drainage easement.

      (3)   Culverts shall be capable of accommodating peak runoff from a 50-year return period storm when crossing under a road which is part of the Indiana Department of Highways rural functional classification system and are classified as principal or minor arterial, major or minor collector roads.

   (B)   Major drainage systems are defined in § 55.04, and shall be designed in accordance with Indiana Department of Natural Resources Standards, as described in § 55.07.

(Ord. 16-C-98, passed 6-9-98; Am. Ord. 22-C-04, passed 11-9-04)