2000-01-06_AgendaPacket - Laserfiche WebLink

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channel erosion. Infiltration or diversion deals with this increased scouting problem by lessening the volume of runoff and therefore the duration of scouring velocities.) l.) The phrase, "soil not suitable for storm water infiltration techniques" means soils with permeability values less that Group C soils (less than 2.5 inches per hour) as defined by the U.S. Department of Agriculture's Natural Resources Conservation Service. B.) Temporary sedimentation basins are required for disturbed areas over one (1) acre. C.) Storm water treatment devices that remove oil and floatable material (e.g., basin outlets with submerged entrances) must be part of BMP systems. D.) Where feasible lightly used vehicle traffic areas such as overflow parking lots should use pervious surfaces such as concrete blocks or cabled concrete blocks where feasible. E.) If the proposed project site includes a trout stream tributary that currently experiences erosion and/or sedimentation problems, the applicant must work with the city to include channel modifications in the project that will also address the existing erosion and/or sedimentation problem. F.) Preserve or install a one hundred (100) foot wide (i.e., 100 feet from each bank) vegetated buffer strip of native species providing a native tree canopy directly on Minnesota Department of Natural Resources designated trout stream reaches and all tributaries directly to a designated trout stream reach. The width of this buffer strip must be increases by at least two (2) feet for each one (1) percent of slope of the surrounding land. (Commentary: A "native "tree canopy along the bank is preferred, since some non-native trees can out compete native species and create amono-culture of decreased environmental value. Useful references are the Minnesota Pollution Control Agency's "Buffer Zones" and "Soil Bioengineering. ") Detailed buffer design is usually site specific. Site specific design criteria should follow common principles and the example of nearby natural areas. The site should be examined for existing buffer zones and mimic the slope structure and vegetation as much as possible. The function of the buffer is a better indicator than the width. Buffer design and protection during construction should do any or all of the following: slow water runoff, trap sediment, enhance water infiltration, trap fertilizers, pesticides, pathogens, heavy metals, trap blowing snow and soil, and act as corridors for wildlife. How much stress is put on these functions will determine the buffer zone's final configuration. Native plant species have root systems and growth characteristics that are well suited to buffer functions. Useful guides for starting the plant selection include Minnesosta Department of Transportation's seeding manual, and their "Plant Selection Matrix" CDROM. Good plant species design stresses diversity and allows plant succession and zoning of the species from wet soil preference to drier upland species.) 16