30.63A.740 Stormwater plan conveyance system and stub out requirements for new development or redevelopment activities, subject to full drainage plan.
(1) Conveyance systems.
(a) Conveyance systems for new development and redevelopment associated with full drainage plans shall accommodate the peak discharge from the 100-year, 24-hour design storm based on post-development site conditions.
(b) For purposes of this subsection, a conveyance system shall be considered adequate if the peak discharge and maximum water level is contained within all drainage easements or within existing conveyance systems, provided that the conveyance system may overflow or be surcharged as long as:
(i) Stormwater runoff does not inundate any of the traveled portion of a public or private road; and
(c) To size conveyance systems for drainage areas of less than 25 acres, the computation standard shall be the rational method or its equivalent as approved by the director. For drainage areas of 25 acres or more, the minimum computation standard shall be the Natural Resources Conservation Service (NRCS) TR-55, Santa Barbara Urban Hydrograph (SBUH), or equivalent method or equivalent flood routing simulation method as approved by the director.
(2) Access culverts shall be sized based upon the hydrologic analysis of the upstream basin prepared under SCC 30.63A.740(1)(c).
(3) If infiltration or dispersion systems, excluding perforated stub out connections, are not provided pursuant to SCC 30.63A.525, drainage stub-outs shall be provided for and utilized by each proposed lot served by a new drainage pipe system for conveyance. Drainage stub-outs shall comply with the following requirements:
(a) Each drainage stub-out shall be connected to the pipe system and be suitably located at the lowest elevation on the lot so that it conveys stormwater from all future roof down spouts, driveways, and yard drains, provided that this requirement shall not preclude the connection of footing drains or other subsurface drains;
(b) Each drainage stub-out shall have free-flowing drainage to an existing or proposed yard drain, dispersion trench, or other structure on the pipe conveyance system or to an approved outfall location; and
(c) At the time of drainage facilities construction, drainage stub-outs shall be clearly marked in accordance with the EDDS. (Added by Amended Ord. 10-026, June 9, 2010, Eff date Sept. 30, 2010).