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Dlescribe the soils on the site, giving SCS classifications, if known. (SCS in.terpretations and soil boring logs need not be attached.) Four or more feet of silty to clayey sand to lean clay fill over glacial deposits consisting of alternating layers of till Ooamy sand to clay) and alluvium (silt, clay or sand). Due to the high cl:~y content in the soil, up to 17 feet of soil will need to be excavated on the north parcel and up to 6 feet will need to be excavated from the south parcel. Excavated areas will be filled with suitable soil for construction. 17. Erosion and Sedimentation. Give the acreage to be graded or excavated and the c11bic yards of soil to be moved: acres annrox. 28 ; cubic yards annrox. 68.000 Q1lbic vards Describe any steep slopes or highly erodible soils and identify them on the site map. Describe the erosion and sedimentation measures to be used during and after construction of the project. E:Kcept near the wetland and on the slopes of the stormwater treatment ponds, the graded site slopes are expected to be less than 10 percent. All graded areas will eventually be impervious surface (buildings or roads), sodded, or in the case of the treatment ponds and created . wetlands, restored to a natural condition. An on-site storm sewer system will convey storm flows to the treatment ponds, and then off the site to minimize concentrated overland flows. Storm sewer outfalls will be protected with riprap. An erosion control plan will be prepared as part of the construction plans for this site. The pIan will meet the requirements necessary to obtain a National Pollutant Discharge Elimination System (NPDES) permit, and Rice Creek Watershed District approval for construction activities. Prior to the start of construction, a silt fence and/or staked hay bales will be installed around the perimeter of the site at locations where sediment could leave the site or enter water bodies. All graded slopes of 3H:1V or greater will be protected with erosion control blankets. Best management practice (BMP) erosion and sediment controls, such as rock filter dikes, will be placed at site access locations. Storm sewer inlets will be surrounded with silt fences or hay bales to prevent sediment from entering the storm sewer system. 18. Water.Quality-Surface Water Runoff a. Compare the quantity and quality of site runoff before and after the project. Describe methods to be used to manage and/or treat runoff. Quantity-Because of the large increase in impervious surface as a result of the proposed development, runoff from the site will increase significantly. For the lO-year, 24-hour rain event, site runoff volume is expected to be approximately three times the present amount. However, the treatment pond system will be designed to provide sufficient storage capacity so that peak outflow rates to the storm sewer from the site during the 10-year and 100-year storm events will not surpass existing 10-year flow rates. Quality-The water quality of the site runoff is expected to change as a result of the proposed development. Presently, the site is comprised mainly of woods, grass and brushlands, and lawns. Site runoff would be expected to be relatively low in suspended sediments, organics, and metals. Nutrient (phosphorus and nitrogen) content of the runoff may be relatively high, depending on the fertilizer use patterns in the residential portion of the site. 236241~\48185-1/I'MN 8