Agenda - Council - 10/27/2015 - Laserfiche WebLink

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Wet water quality ponds upstream of dry regional infiltration basins (where possible) will help control the rate and the volume of storm water runoff. To provide flood protection for adjacent property, the design storm interval for ponding areas is a 100-year storm as compared to a 10-year storm for design of storm sewer piping. Any new residential, commercial, industrial and other habitable structures shall be constructed with the following low floor elevation: The low floor elevation of all development, including basements, must be at least 3 feet above the highest anticipated ground water table, 2 feet above the designated or designed 100-year flood elevation, or 1 foot above the emergency overflow, whichever is higher. The area of a pond's HWL plus 1 foot of freeboard shall be contained entirely within an outlot that is owned and maintained by the City or within a drainage and utility easement. In areas adjacent to designated flood plains as mapped on a Flood Insurance Rate Map, the Regulatory Flood Protection Elevation (RFE) applies. The RFE is defined as the mapped 100-year flood elevation plus 1 foot. However, the LRRWMO requires that the low floor elevation of structures be 2 feet above the calculated flood elevation. Therefore, all structures, including accessory structures, must be elevated on fill so that the lowest floor including basement floor is Ift above the Regulatory Flood Protection Elevation or 2 foot above the mapped 100-year flood elevation. The finished fill elevation for structures shall be no lower than the Regulatory Flood Protection Elevation and the fill shall extend at such elevation at least fifteen (15) feet beyond the outside limits of the structure erected thereon. The following drawing better defines the Regulatory Flood elevations.' The following exhibit applies only when fill is required to bring a structure at least two (2) feet above the 100-year flood level. Not to Scale 'l'op of Floor at 1 FPE* `MI5• Flood Fringe Floodwa -1111 100-Year Flood Level* I' No Fill Allowed *RITE — Regulatory Flood Protection Elevation * 100-Yr Flood Level includes the flood stage increase (of up to Vz foot) due to filling in flood hinge Minimum Standards for Structures in 100-year floodplain 6 Taken from the Minnesota DNR web site: http://www.dnr.state.mn.us/waters/watermgmt_section/floodplain/rfpe.html Section IV October 21, 2015 Page 32