Ord 2009-073 - Laserfiche WebLink

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(4) For channels with slopes over three percent and with non-erodable velocities (less than six feet per second), a rock pilot channel must be used to stabilize the channel bed. (5) Sediment and litter traps are required at the discharge point of parking areas for commercial, industrial, and multifamily uses. (6) Storm drain inlets for all development except for single-family and two-family residential development must be equipped with inlet baskets to capture litter from parking areas. (b) Detention Required. Drainage facilities will be designed and constructed so that the rate of runoff at each existing discharge location from a site after construction shall be equal to or less than the site's runoff prior to construction. Rate of runoff shall be computed on a 25-year storm peak flow using the City of Austin Drainage Criteria Manual, if a separate water quality pond is required for the development. If a separate water quality pond is not required, the rate of runoff shall computed on both a two-year and a 25-year peak storm flow using the City of Austin Drainage Criteria Manual. Computation of the rate of runoff shall be based on an assumption of a fully developed contributing drainage area or watershed. (c) Waiver of Detention. Detention will be waived for single-family residential and small projects with less than 5,000 square feet of impervious cover, including buildings, parking lots and sidewalks. Runoff from development shall be discharged as sheet flow through grass areas to reduce peak runoff rates and provide for filtering of sediments prior to exiting property. Section 5.4.2.1 Purpose, Applicability, Exceptions and Coordination (a) Purposes. (1) The purpose of this Section is to specify standards and procedures for reclamation or alteration of floodplain land consistent with the City's objectives to maintain water quality, preserve natural areas and trees, assure the safety and welfare of its residents with respect to flood hazards, and to implement in part Master Plan policies relating to environmental quality and open space. (2) It is the intent of the City Council that the requirements of this Section be consistent with requirements contained in the City's Flood Damage Prevention Regulations, and with federal requirements pertaining to the Federal Emergency Management Agency's authority concerning flood hazards and the Corps of Engineer's jurisdiction over waters of the United States, including wetlands under Section 404 of the Clean Water Act. (3) It is the further intent of this Section that development on floodplain land be integrated with the City's standards for preserving water quality and providing open space. (4) Land located within the floodplain may be reclaimed or altered for purposes of development only in accordance with the standards and procedures set forth in this Section. (b) Applicability. The standards in this Division apply whenever a property owner seeks to • reclaim, excavate or otherwise alter land within the design floodplain of a waterway that has a contributing drainage area of 120 acres or more. For purposes of this Article, any