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25 <br />3. An outlet structure capable of preventing migration of floating debris and <br />oils for at least the one-year storm. <br />4. An outlet structure to control the two-year, ten-year and 100-year <br />frequency events to existing peak runoff sites; and <br />5. An identified overflow spill way sufficiently stabilized to convey flows <br />greater than the 100-year critical storm event. <br />(e)(f) Outfalls. An outfall structure discharging to a wetland, public water or <br />public water wetland must incorporate a stilling-basin, surge-basin, energy dissipater, <br />placement of ungrouted natural rock riprap or other feature to minimize disturbance and <br />erosion of natural shoreline and bed resulting from stormwater dischargesThe City <br />adopts by reference RCWD Rules C.9.(f) as amended. <br />(f)(g) Freeboard requirements. All new residential, commercial, industrial and <br />other habitable or non-habitable structures, and all stormwater basins, must be <br />constructed so that the lowest floor and lowest entry elevations of structures comply <br />with the following:Table 1. <br /> Table 1. Low floor and low entry freeboard requirements <br /> Regional <br />Flood <br />Elevations <br />Local Detention <br />Basins & <br />Wetlands <br />Infiltration Basins Rain <br />Gardens <br />Groundwater1 <br />Elevation 100 year EOF 100 <br />year <br />EOF Bottom 100 <br />year <br />EOF EOF Seasonal High <br />Level <br />Low Floor <br />Freeboard <br />2–ftft. 1-ft 0-ft N/A 0-ft N/A N/A N/A 4-ft <br />Low Entry <br />Freeboard <br />N/A N/A 2-ft 1-ft N/A 2-ft 1-ft 0.5-ft N/A <br />1 The seasonal high groundwater level shall be determined within 12 months of proposed construction <br />of the structure by a soil scientist or geotechnical engineer registered in the State of Minnesota as <br />indicated by redoximorphic features such as mottling within the soil or by direct groundwater <br />observation. <br />(g)(h) Within a landlocked basin, lowest floor elevations must be at least one <br />foot above the surveyed basin overflow elevation. Where a structure is proposed below <br />the runoff elevation of a land-locked basin, the low- floor elevation will be a minimum of <br />two feet above the high water level as determined from an estimate of high water levels <br />determined from the highest of either the 100-year, ten-day runoff event or back-to-back <br />100-year, 24-hour rainfalls. Aerial photos, vegetation, soils, and topography will be used <br />to derive a "normal" water elevation for the basin for the purpose of computing the 100- <br />year elevation.