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<br />157.07157.24. Volume Control and Pollutant Management <br />For non-linear projects, water quality volume (calculated as an instantaneous volume) must be calculated as one (1) inch <br />times the sum of the new and the fully reconstructed impervious surface. <br />For linear projects, water quality volume (calculated as an instantaneous volume) must be calculated as the larger of one (1) <br />inch times the new impervious surface or one-half (0.5) inch times the sum of the new and the fully reconstructed <br />impervious surface. Where the entire water quality volume cannot be treated within the existing right-of-way, a reasonable <br />attempt to obtain additional right-of-way, easement, or other permission to treat the stormwater during the project planning <br />process must be made. Volume reduction practices must be considered first. Volume reduction practices are not required if <br />the practices cannot be provided cost effectively. If additional right-of-way, easements, or other permission cannot be <br />obtained, the owner/operator of construction activity must maximize the treatment of the water quality volume prior to <br />discharge from the CityÓs MS4. <br />Stormwater volume management practices shall be the equivalent of infiltrating or retaining the first one and <br />one-tenth (1.1) inches of precipitation over the impervious surface of the site. These practices should seek to <br />utilize pervious areas for stormwater treatment and to infiltrate stormwater runoff from driveways, sidewalks, <br />rooftops, parking lots and landscaped areas to the maximum extent practical to provide treatment for both water <br />quantity and quality. <br /> <br /> ) New Development projects shall achieve no net increase from pre-project conditions (on an annual <br />average basis) of stormwater discharge volume; discharges of total suspended solids (TSS); and <br />discharge of total phosphorus (TP). <br /> ) Redevelopment projects shall achieve a net reduction from pre-project conditions (on an annual average <br />basis) of stormwater discharge volume; discharges of total suspended solids (TSS); and discharge of <br />total phosphorus (TP). <br /> <br />The requirements of this section may be altered and alternative treatment BMPs approved under the following <br />limitations: <br /> <br />1) Infiltration techniques shall be prohibited when the infiltration structural BMP will receive discharges <br />from or be constructed in areas: <br />a) Areas that that receive runoff from vehicle fueling and maintenance areas; <br />b) Areas where infiltrating stormwater may mobilize high levels of contaminants in soil or <br />groundwater; <br />c) Areas where soil infiltration rates are field measured at more than 8.3 inches per hour unless <br />the soils are amended to slow the infiltration rate below 8.3 inches per hour; <br />d) Areas with less than three (3) feet of separation distance from the bottom of the infiltration <br />system to the elevation of the seasonally saturated soils or the top of bedrock; <br />e) Areas of predominately Hydrologic Soil Group type D soils (clay); <br />f) Within a Drinking Water Supply Management Area (DWSMA) as defined in Minn. R. <br />4720.5100, subp. 13, if the system will be located: <br />i. In an Emergency Response Area (ERA) within a DWSMA classified as having high <br />or very high vulnerability as defined by the Minnesota Department of Health; or <br />419 |Page <br /> <br /> <br />