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3. No increase in stormwater runoff from the irrigated area or project site. <br /> 4. The amount of water quality treatment volume credit given will be based upon the three year <br />average of the volume irrigated, determined by the average of three years of monitoring records. <br /> (c) Biofiltration and filtration BMPs. Biofiltration and filtration BMPs must be designed to provide: <br /> 1. Adequate pretreatment measures to remove sediment before runoff enters the primary biofiltration <br />area; <br /> 2. Drawdown within 48-hours or 72-hours from the end of the storm event for surface or sub-surface <br />features, respectively; <br /> 3. A minimum of 12-inches of organic material or sand above the rock trench or drain tile system; <br />and <br /> 4. Drain tile system must be designed above the seasonal high water table. <br /> (d) Stormwater ponds. Stormwater ponds must be designed to provide: <br /> 1. Water quality features consistent with NURP criteria and city standard plate; <br /> 2. Permanent wet pool with dead storage at least equal to the runoff from a two and one half inch <br />rainfall over the area tributary to the pond <br /> 3. An outlet structure capable of preventing migration of floating debris and oils for at least the one- <br />year storm. <br /> 4. An outlet structure to control the two-year, ten-year and 100-year frequency events to existing <br />peak runoff sites; and <br /> 5. An identified overflow spill way sufficiently stabilized to convey flows greater than the 100-year <br />critical storm event. <br /> (e) Outfalls. An outfall structure discharging to a wetland, public water or public water wetland must <br />incorporate a stilling-basin, surge-basin, energy dissipater, placement of ungrouted natural rock riprap or <br />other feature to minimize disturbance and erosion of natural shoreline and bed resulting from stormwater <br />discharges. <br /> (f) Freeboard requirements. All new residential, commercial, industrial and other habitable or non- <br />habitable structures, and all stormwater basins, must be constructed so that the lowest floor and lowest <br />entry elevations of structures comply with the following: <br /> <br />Table 6. Low floor and low entry freeboard requirements <br />Regional <br />Elevations <br />Local Detention Basins <br />& Wetlands Infiltration Basins Rain <br />Gardens Groundwater <br />Elevation 100 year EOF 100 year EO <br />F Bottom 100 year EO <br />F EOF Seasonal <br />High Level <br />Low Floor <br />Freeboar d 2-ft 1-ft 0-ft N/ <br />A 0-ft N/A N/ <br />A N/A 4-ft <br />Low Entry <br />Freeboar d N/A N/A 2-ft 1-ft N/A 2-ft 1-ft 0.5-ft N/A <br />