Agenda - Planning Commission - 08/05/2010

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including the disturbance of Iess than 1 acre of total land area that is part of a larger common plan of development or sale if the larger common plan will ultimately disturb equal to or greater than 1 acre would require a stormwater permit from the Pollution Control Agency. Stormwater Management Two stormwater management options are proposed. The first option relies on the use of impervious surface coverage caps. The second option is for local governments with technical expertise to manage stormwater based on performance standards. With this option and for Large projects under the first option, local governments use the following permanent stormwater management requirements based on the impervious surfaces located on the project site: Permanent treatment of 1" of runoff from the impervious surfaces created by development or redevelopment is required. Preference must be given to volume reduction techniques that include infiltration basins, rain gardens, enhanced infiltration swales, filter strips, disconnected impervious areas, and other conservation designs. For those areas of a project where there is no feasible way to meet the treatment requirements, other treatment, such as grassed swales, grit chambers, vegetated filter strips, bioretention areas, off-line retention areas, and natural depressions for infiltration, is required prior to the runoff leaving the project site or entering surface waters. The proposed standards rely on Minnesota's Stormwater Management Manual (http://www.pca.state.mn.us/water/stormwater/stormwater-manual.html). This manual provides best management practices that are specially adapted to Minnesota use, and the proposed standards require the local government to direct property owners, developers, and contractors to incorporate those best management practices. In addition, the proposed standards allow credit for permeable pavement systems that meet the Minnesota Stormwater Manual best management practices criteria. Only half the area with such material would be credited as permeable surface. Long-term studies on permeable materials have yet to be conducted, so the PCA advised such a credit until such time evidence supports a higher credit. Proposed Shoreline Buffer Standards for New Developments For an existing lot with a home, no changes in shoreline buffer standards are proposed (i.e., intensive cutting is not allowed). For new development on previously undeveloped parcels, a 50 feet shoreline buffer consisting of trees, shrubs, and ground cover of'plants and understory in a natural state, is required. Removal of trees and shrubs necessary to accommodate stairways, landings, chairlifts, access paths, and recreational use areas can occur. Except for the access path and recreational use area, a natural ground cover must be preserved or established in the 50 feet area near shore. Openings and lawns in the shoreline buffer that are not allowed must be replanted or left unmowed. Greater Protection of Vulnerable Waters Trout streams The proposal creates a separate river class for designated trout streams to provide these sensitive public waters additional protection. The existing statewide minimum standards place trout stream in the tributary river class, the least protective river class. Given future development demands and the vulnerable nature of Coldwater streams, it is reasonable and needed to move these public waters into a class with higher development standards. 133