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 storm water must accommodate peak runoff from a 10-year return period storm. Rainfall duration shall be equal to the time of concentration or one (1) hour if the time of concentration is less than one (1) 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 (2) clear ten (10) foot moving lanes of traffic. One (1) lane is to be maintained on local roads.
2. Open channels carrying peak flows greater than thirty (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 Transportation functional classification system and are classified as principal or minor arterial, major or minor collector roads.
b. Major drainage systems, as defined in Division II, shall be designed in accordance with generally accepted engineering standards and practices. Developer and its consultant(s) shall discuss proposed methodology with MS4 operator before starting planning and design of drainage facilities.
(Ord. No. 1708, 6-13-07)