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Little Canada Zoning Code Stormwater Management <br /> 928-7 <br /> <br /> <br />(3) The infiltration area shall be capable of infiltrating the required <br />volume within 48 hours for surface and subsurface BMPs. <br /> <br />(4) Infiltration areas shall be limited to the horizontal areas subject to <br />prolonged wetting. <br /> <br />(5) Areas of permanent pools tend to lose infiltration capacity over <br />time and shall not be accepted as an infiltration practice. <br /> <br />(6) Stormwater runoff must be pretreated to remove solids before <br />discharging to infiltration areas to maintain the long term viability <br />of the infiltration areas. <br /> <br />(7) Design and placement of infiltration BMPs shall be done in <br />accordance with the Minnesota Department of Health guidance <br />called “Evaluating Proposed Stormwater Infiltration Projects in <br />Vulnerable Wellhead Protection Areas.” (Final version to govern.) <br /> <br />(8) Specific site conditions may make infiltration difficult, <br />undesirable, or impossible. Some of these conditions are listed in <br />Table 2 and may qualify the applicant for Alternative Compliance <br />Sequencing. The applicant may also submit a request to the City <br />for Alternative Compliance Sequencing for site conditions not <br />listed below. All requests shall indicate the specific site conditions <br />present and a grading plan, utility plan, and the submittal <br />requirement listed in the table below. <br /> <br />Table 1. Design Infiltration Rates <br />Soil Group Soil Textures ASTM Unified Soil <br />Class Symbols Rate <br />A Gravel, sand, sandy gravel, or silty <br />gravel, loamy sand, sandy loam <br />GW, GP 1.63 in/hr <br />GM, SW, SP 0.80 in/hr <br />B Loam, Silt loam SM 0.60 in/hr <br />ML, OL 0.30 in/hr <br />C Sandy clay loam GC, SC 0.20 in/hr <br />D Clay loam, silty clay loam, sandy <br />clay, silty clay, or clay CL, CH, OH, MH 0.00 in/hr <br />Source: Minnesota Stormwater Manual, November 2005.