12/20/2006 Env Bd Packet - Laserfiche WebLink

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• Nature's Refuge DRAFT DECEMBER 14, 2006 EAW Record of Decision page 5 primarily aimed at restoring and maintaining native plant communities, the populations of rare species are expected to continue and possibly expand. Floodplain A portion of the site lies within a Zone A 100 -year flood plain, though the flood elevation has not been established. The project will result in a re- grading of part of the site, so changes to the flood elevation contour will be required. Construction and re- grading in the present flood zone will be minimized, because only one street will cross the flood plain and no houses will be located within it. The 100 -year flood elevation will be established as part of the project design and compensatory storage will be created for any floodplain fill. The FEMA floodplain map revision will be prepared as needed. Water Quality and Stormwater Management The project will be designed to avoid altering drainage conditions and protect water quality. Runoff will be directed to vegetated swales, rain gardens, and infiltration ponds. Sedimentation ponds and rain gardens will be designed to treat storm water runoff before discharge. The ponds will be designed to retain a 100 -year storm event and control the discharge rate to pre- development conditions. Drainage from residential areas and impervious surfaces will be directed into infiltration areas in order to prevent sedimentation or contamination of wetlands, to control inflow rates, and to maintain present hydrology as well as possible. Infiltration ponds will be protected from soil compaction by construction equipment, and any compacted areas will be disked to de- compact the soil, which will ensure water infiltration and successful re- vegetation. Erosion Control Erosion control measures will be implemented in accordance with the Storm Water Pollution Prevention Plan (SWPPP) developed for this project to mitigate the potential for adverse surface water and air quality impacts from runoff and wind erosion during construction. The SWPPP will incorporate Best Management Practices prescribed by the MPCA. These measures, including silt fencing, ditch checks, stone exit pads, and prompt turf restoration (including de- compacting, mulching, seeding) in graded areas. The phasing of construction will minimize the area of soil exposed at any given time. Construction- Related Noise, Dust Standard Best Management Practices will be employed to minimize dust Water will be applied to exposed soils during dry weather to mitigate dust movement. The dust and wind erosion BMPs will be employed to minimize inconveniences to them.