(A) All SWPPPs shall establish BMPs to reduce the generation of stormwater and to control the peak flow rates using the local two-year, 24-hours storm, as described in Chapter 192, and runoff coefficient from each drainage area. These BMPs should seek to utilize pervious areas for stormwater treatment and to infiltrate stormwater runoff from driveways, sidewalks, rooftops, parking lots, and landscaped areas to the maximum extent practicable to provide treatment for both water quality and quantity.
(B) All new development or redevelopment shall not discharge untreated stormwater directly into the city's MS4 or waters of the United States without adequate treatment.
(C) Groundwater recharge rates shall be maintained, by promoting infiltration through the use of structural and non structural BMPs. At a minimum, annual recharge from the post development site shall mimic the annual recharge from pre-development site conditions.
(D) BMPs for a site shall be chosen based on the physical conditions of the site. Among the factors that should be considered:
(1) Topography
(2) Maximum drainage area
(3) Depth to water table
(4) Soils
(5) Slopes and terrain
(6) Proximity to environmentally-sensitive features
Applicant shall consult the Erosion Control Drainage Design Manual (ECDDM) for Maricopa County, Arizona, as amended, for guidance on factors that determine site design feasibility when selecting a BMP.
(E) All BMPs shall be designed to convey stormwater to allow for the maximum removal of pollutants, to the maximum extent practicable, and reduction in flow velocities. This shall include, but not be limited to:
(1) Maximizing of flow path from inflow points to outflow points.
(2) Protection of inlet and outfall structures.
(3) Elimination of erosive flow velocities.
(4) Providing of underdrain systems, where applicable.
The ECDDM for Maricopa County, Arizona, as amended provides detailed guidance on the requirements for conveyance for each of the approved BMPs.
(Ord. O2007-78, passed 12-19-07)