01/09/2008 P&Z Packet - Laserfiche WebLink

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Main Street Village page 6 many of the requirements are means of achieving the best results possible, depending on the site. Conservation Development Framework: The Conservation Development Framework provides the foundation for most of the conservation objectives within the AUAR area. Implementation of the Framework will: conserve the most ecologically significant natural resources within the AUAR area (in particular, the "core" and "outlier" habitats); protect ecologically significant natural resources from adjacent land uses by implementing buffering; and connect ecologically significant natural resources via multi - functional greenway corridors. The goals of the Conservation Development Framework will be pursued through a variety of methods. The maps in the AUAR provide summary information and guidance. For example, the Minnesota Land Cover Classification System map (AUAR Fig. 10 -1) shows artificial surfaces and associated areas on the sites of the bank and the old farmhouse; planted or cultivated vegetation across most of the site; and herbaceous over the larger wetland areas. The Wetland/Aquatic and Upland Habitats map (AUAR Fig. 10 -2) does not show any core or outlier habitat areas that we want to preserve. Water quality, stormwater management, erosion and sedimentation: The AUAR includes analyses of surface water runoff issues which lead to requirements for including infiltration elements and other techniques. It also includes estimated stormwater management recommendations for specific development areas. These estimates in the AUAR cannot be considered strict requirements. However, they do provide guidance for mitigation. The mitigation plan establishes sizing criteria for stormwater management areas that are designed to support wetland complexes or large infiltrating surfaces with native plant populations. The approach is that these areas would be designed consistent with strict criteria for maximum filtration and/or infiltration of stormwater. The site is labeled development area Y -TD in the AUAR. The most general estimate suggests that 16 % -20% of the developable area would be needed for stormwater management (AUAR Fig. 17 -3). A somewhat more refined estimate suggests a need of 5 acres for stormwater management (AUAR Table 17 -5). These estimates are calculated for the entire 28 -acre site and are high compared to standard development practices. The submitted project only includes about a third of the total site (less than 9 of the 28 acres), so it is difficult to compare against the AUAR. Nonetheless, we can see that stormwater treatment is a challenging issues and it is important to consider the entire site rather than individual pieces. While those stormwater management areas are estimates and not mandatory, the AUAR does include specific requirements. Runoff rates must be at or below pre - development conditions. This is a standard requirement everywhere in the city, enforced on all projects. The AUAR also requires that runoff volume must be no more that 150% of pre - development runoff. The AUAR also requires that stormwater management areas have a 6:1 slope rather than the normal, steeper slope. • • •