Agenda - Environmental Policy Board - 10/15/2018

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16. Erosion and Sedimentation The number of acres to be graded and the number of cubic yards of soil to be moved need not be given; instead a general discussion of the likely earthmoving needs for development of the area should be given, with an emphasis on unusual or problem areas. In discussing mitigation measures, both the standard requirements of the local ordinances and any special measures (ex. WMO) that would be added for AUAR purposes should be included. The Ramsey Town Center site is relatively flat and contains very sandy, coarse -grained soils (Figure 12.2). Both of these physical characteristics are advantageous when it comes to erosion and sedimentation. This does not mean, however, that erosion will not occur and that sediment will not move if disturbed. Because the disturbance of over 300 acres of land will present the certainty of erosion, the mitigation plan that follows outlines the measures the City will undertake to minimize its adverse impacts. Figure 16.1 shows the general areas of borrow and fill that will result when earth -moving activity begins. The general concept that will be followed will be creation of a central low area along the drainage corridor alignment, with land gradually sloping upward to the north and south away from the drainageway. Earth will be moved from the drainageway corridor and placed on the north and south slopes. Some grading will likely also be needed on the southern drainage swale just north of the railroad tracks and around Wetlands B and D (Figure 10.1) as buffer areas are incorporated. Exact numbers on the volume of soil moved will not be available until the detailed design phase. Care will be taken not to disturb or compact the central drainage corridor that will be used to transmit and store water. Similar efforts will be made to avoid compaction in areas where infiltration best management practices (BMPs) will be used. The soil within any landscaped areas will be loosened after heavy construction traffic has subsided. This will enhance the ability of all landscaped areas, whether formal or native, to infiltrate water. It is expected that organic topsoil will need to be imported to the site to establish a good vegetative cover. The sandy soils will not support many of the typical landscaping plants and ground cover. Native plants that are inherent to the Anoka Sandplain will be used wherever possible to avoid the need for massive soil importation and extensive irrigation. Summary of Environmental Impact. The grading and development of over 300 acres of land has the potential to contribute sediment to receiving waters where water could flow. Currently, there are few actual receiving areas where water is present. With the establishment of a central drainage corridor and the possibility of mitigated wetlands and water storage areas, the possibility of water -related impact increases. The following mitigation plan addresses how construction will proceed with adequate erosion BMPs in place. 16-1