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Environmental Assessment Worksheet Nature's Refuge Conservation Development Lino Lakes, Anoka County, Minnesota Draft Document — September 25, 2006 Page 14 control measures for construction traffic, and lack of phased turf establishment. BMPs to reduce the potential for wind erosion during construction will be implemented. Water erosion will also be controlled through BMPs, including prompt turf re- establishment on graded areas (de- compacting, mulching, and seeding), and reduction of sediment transport by using silt fences, ditch checks, stone exit pads, and storm sewer inlet protection. The project will be constructed in phases and the aerial extent of exposed grading will be minimized. Infiltration facilities will be protected during the construction phase to ensure they are not compacted by construction activities that will decrease the infiltration capacity or filled with local sediment runoff during the construction phase. 17. Water quality: surface water runoff a. Compare the quantity and quality of site runoff before and after the project. Describe permanent contro manage or treat runoff Describe any stormwater pollution prevention plans. The effects of residential land use on the groundwater quality in the Anoka Sand Plain is described in USGS Water Resources Investigations Report 93 -4074 entitled "Effects of Agricultural and Residential Land Use on Ground - Water Quality, Anoka Sand Plain Aquifer, East Central Minnesota ". This report shows that conversion to residential land use has a tendency to increase chloride, sodium, hardness (CaCO3) and other constituents. In addition, phosphorus is considered a pollutant of concern and is generally associated with lawn care. Source control Since the development will be connected to city sewer systems much of the impact will be reduced and the sources will be from `non - point' sources. The development will require zero - phosphorus fertilizer be applied for established lawns and will be administered through homeowner covenants. Treatment Treatment of stormwater will focus on treatment near the source that will increase the amount of infiltration and contact with the soil medium prior to discharge to downstream resources. The use of ribbon curb in selected areas will allow drainage from paved surfaces into open swales. Drainage into swales, rain gardens, and sedimentation basins will treat the stormwater prior to discharge to the large wetland complex and downstream resources. The use of rain barrels to capture and treat rooftop runoff will be encouraged throughout the development. Infiltration areas will be designed and installed in accordance with the MPCA requirements in Permit No. R100001. Skimming measures will be used to protect downstream water quality. If runoff modeling so indicates, rate control measures will be used in the ditch outlets to limit the post - development runoff rates to that of the pre - development conditions. Conversely, the site grading and pond discharge structures will be designed such that the post - development runoff rates do not decrease the runoff supplied to the wetlands. The treated runoff will be released to the existing wetlands to minimize the potential of adversely affecting the value and function of these wildlife resources. The rain gardens will serve primarily to meet water quality requirements as well as provide some rate control. The ponds will be designed primarily to provide rate control and temporary storage for a 100 -year storm event. Water quality will also be protected by these ponds and the above - mentioned skimming measures. b. Identify routes and receiving water bodies for runoff from the site; include major downstream water bodies as well as the immediate receiving waters. Estimate impact runoff on the quality of receiving waters. As described above in Section 12, the landscape generally drains toward the southeast, but the site drains through the county ditch system that routes stormwater off -site to the west, and ultimately to Marshan Lake about two miles south - southwest of the project site. The focus of the stormwater management plan will be to sustain the ecological function of the large wetland complex contained within the site. The implementation of the stormwater treatment systems described herein will minimize the impact to downstream resources. Thus, the overall quantity of runoff is estimated to remain approximately the same as a result of the design of the project's runoff and infiltration system.