(A) Detention facilities located within the regulatory floodplain are strongly discouraged but may be considered under the following considerations:
(1) Be located above the calculated ten-year flood elevation (including the normal water level and lower restrictor). On stream or on-line detention facilities will only be permitted when the precedence has been established for the upstream portion of the SFHA and a net watershed benefit is demonstrated by detailed hydrologic and hydraulic analysis. Any structure constructed across the channel to impound water to meet detention requirements shall be prohibited on any perennial stream unless part of a public flood control project with a net watershed benefit. Those streams appearing as blue on a USGS Quadrangle Map shall be assumed perennial unless better data is obtained. All cross stream structures for the purpose of impounding water to provide detention in all cases on perennial and intermittent streams must demonstrate that they will not cause short term or long term stream channel instability.
(2) Store the required amount of site runoff to meet the release rate requirement under all stream flow and backwater conditions in the receiving stream up to the ten-year flood elevation; and
(3) Comply with the Village of Frankfort Design Standards Section 4.03 E-10 updated July 2007 or as amended from time to time.
(B) Detention facilities located adjacent to-the regulatory floodplain shall:
(1) Be located above the calculated ten-year flood elevation (including the normal water level and lower restrictor).
(2) Store the required amount of site runoff to meet the release rate requirement under all stream flow and backwater conditions in the receiving stream up to the ten-year flood elevation; and
(3) Comply with the Village of Frankfort Design Standards Section 4.03 E-10 updated July 2007 or as amended from time to time.
(Ord. 3187, passed 1-22-19) Penalty, see § 152.999