Agenda - Council - 10/27/2015 - Laserfiche WebLink

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Rain gardens and infiltration basins are a viable alternative to storage ponds. These structures are encouraged by many review agencies as a way to mimic the original runoff conditions from a site. By incorporating infiltration, the basin provides volume and water quality management. A water quality basin does not need to have standing water, just a permanent "dead -pool" volume to meet the MPCA water quality requirements. The rain gardens and infiltration basins will assist in meeting MPCA regulations. However, rain gardens and infiltration basins are not recommended in a wellhead protection zone. Figure Nos. 3 and 4 show areas where rain gardens and infiltration may not be the best runoff management solution. City Policy adopted in conjunction with infiltration requirements of the LRRWMO Third Generation Plan permits infiltration in areas within the Drinking Water Supply Management Area (DWSMA), so long as it is not also within the 10-year capture zone. The process outlined in the LRRWMO Third Generation Plan shall be followed when a development is proposed inside the 10-year capture zone and infiltration is not permitted on site. The LRRWMO Third Generation Plan includes specific Wetland Protections that are stated below (refer to Appendix G of the LRRWMO plan for details): • Temporary Wetland Protections During Construction — Areas within 16.5 feet of a wetland boundary must be protected from land grading and other disturbance during the construction process. The area shall be demarcated with properly installed heavy duty silt fence. • Native Plant Seeding in Common Spaces at the Conclusion of Construction — Within common spaces, areas adjacent to wetlands that are disturbed through the construction process and ponding areas (stormwater management areas) should be seeded with a BWSR native seed mix that matches site conditions. • Wetland Protections after Construction — Following construction, site stabilization, and vegetation establishment certain activities shall be prohibited within 16.5 feet of the wetland edge. Activities prohibited include: o Structures, excluding fences. Fences are not allowed inside the wetland boundary. o Paving, except projects with a public purpose such as public trails. o Retaining walls. o Filling, dumping or yard waste disposal. o Fertilization o Septic Systems. • Relationship to Drainage and Utility Easement - Drainage and utility easements must encompass the area within 16.5 feet from the wetland edge. The process outlined in the LRRWMO Third Generation Plan shall be followed when a development is proposed adjacent to wetlands. Section IV October 21, 2015 Page 34