Various parts of a drainage facility must accommodate runoff water as follows.
(A) The minor drainage system such as inlets, catch basins, steel gutters, swales, culverts, sewers and small channels, which collect storm water, must accommodate peak runoff from a ten-year return period storm. Rainfall duration shall be equal to the time of concentration or ten minutes if the time of concentration is less than ten minutes. First quartile storm distribution and one-hour storm duration shall be used for computer modeling. These storm distribution coordinates are contained in Table 6. The following additional requirements must be satisfied.
(1) 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.
(2) 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 State Department of Highways rural functional classification system and are classified as principal or minor arterial, or collector roads. The minimum culvert size under all public roads shall be 15 inches.
(3) Temporary water storage will not be permitted on any local street or road, except by special exception of the Board.
(B) Major drainage systems are defined in § 151.03 and shall be designed in accordance with State Department of Natural Resources standards.
(Ord. 8-2014, passed 7-21-2014)