(a) Where five acres or more of the development area is disturbed, stormwater runoff shall pass through a sediment basin or other suitable sediment trapping facility with equivalent or greater storage capacity. Sediment basins or traps may be required for smaller disturbed areas if deemed necessary. The sediment basin requirement may also be waived, by variance, if the approving agency agrees that site conditions do not warrant its construction.
(b) The sediment settling basin shall be sized to provide at least 67 cubic yards of storage per acre of total contributing drainage area. When determining the total contributing drainage area, off-site area and areas, which remain undisturbed by construction, must be included unless runoff from these areas is diverted away from the sediment settling basin and is not co-mingled with sediment-laden runoff. The depth of the sediment settling basin must be less than or equal to five feet. The configuration between inlets and the outlet of the basin must provide at least two (2) units of length for each unit of width (>2:1 length: width ratio). Sediment must be removed from the sediment settling basin when the design capacity has been reduced by 40% (this typically is reached when sediment occupies one-half of the basin depth). When designing sediment basins, you must consider public safety, especially as it relates to children, as a design factor for the sediment basin. Alternative sediment controls must be used where site limitations would preclude a safe design. The use of a combination of sediment and erosion control measures in order to achieve maximum pollutant removal is encouraged.
(c) For drainage locations serving less than five (5) acres, smaller sediment basins, and/or sediment traps shall be used.
(d) Unless otherwise designed, sediment basins are temporary and shall be removed following final stabilization of the site when vegetation is sufficient enough to control erosion.
(Ord. 05-08. Passed 2-25-08.)