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Little Canada Zoning Code Stormwater Management <br /> 928-6 <br />B. Stormwater Management Performance Standards and Design Criteria <br /> <br />The applicant shall consider reducing the need for stormwater management <br />performance standards by incorporating the use of natural topography and land cover <br />such as natural swales and depressions as they exist before development to the degree <br />that they can accommodate the additional flow of water without compromising the <br />integrity or quality of the receiving waterbody. The development shall minimize impact <br />to significant natural features. Review the site for steep slopes (greater than 12%), <br />wetlands, wooded areas of significance, rare and endangered species habitat, areas <br />designated by the County Biological Survey, metro greenways, or County parks and <br />open space. These areas should not be developed. The development shall limit <br />impervious surface coverage. Impervious surface coverage of a site shall not exceed <br />that allowed by City Ordinance. Proposed design, suggested location and phased <br />implementation of effective, practicable stormwater management measures for plans <br />shall be designed, engineered and implemented to achieve the following results: <br /> <br />1. Volume Control - Stormwater runoff volume retention shall be achieved onsite <br />in the amount equivalent to the runoff generated from a one inch rainfall over the <br />impervious surfaces of the development for new development and from a half <br />inch rainfall over the impervious surfaces of the development for redevelopment. <br />The required stormwater runoff volume reduction shall be calculated as follows: <br /> <br />New Development Required Volume (ft3) = Impervious surfaces (ft2) x 1.0 (in) x 0.9 coefficient x 1/12 (ft/in) <br /> <br /> Redevelopment Required Volume (ft3) = Impervious surfaces (ft2) x 0.5 (in) x 0.9 coefficient x 1/12 (ft/in) <br /> <br />a. When using infiltration for volume reduction, the following requirements <br />must be met: <br /> <br />(1) Infiltration volumes and facility sizes shall be calculated using the <br />appropriate hydrological soil group classification and design <br />infiltration rate from Table 1. Select the design infiltration rate <br />from Table 1 based on the least permeable soil horizon within the <br />first five feet below the bottom elevation of the proposed <br />infiltration BMP. <br /> <br />(2) The applicant may complete double-ring infiltrometer test <br />measurements at the proposed bottom elevation of the infiltration <br />BMP to the requirements of ASTM D3385. The measured <br />infiltration rate shall be divided by the appropriate correction <br />factor selected from the Minnesota Stormwater Manual. This test <br />must be completed by a licensed soil scientist or engineer.