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Anderson Daycare <br /> October 19, 2016 <br /> Stable Outlet <br /> The 100-yr discharge out of the biofilter was analyzed and determined to have a flow depth of <br /> 0.43 ft. and a velocity of 1.7 ft./sec. over the grassed overflow weir. The weir will utilize a Class <br /> Ill TRM to permanently stabilize the overflow section due to the relatively high velocity. <br /> Erosion Control During Construction <br /> Perimeter erosion control (silt fence) is already installed along the western edge of the site. <br /> Vegetated swales will be graded and the biofilter will be excavated to serve as a temporary <br /> sediment basin during construction. After the remainder of the site has stabilized,sediment will <br /> be removed from the biofilter, and it will be backfilled with engineered fill and planted. <br /> The stone base within the existing driveways will function as a site tracking pad. Once grading <br /> activities are completed, the site will immediately be seeded and mulched or matted in <br /> accordance with the project specifications and WDNR Conservation Practice Standards 1052, <br /> 1053, and 1059. Winter seeding will be used due to the time of construction. Biofilter <br /> construction and planting, and final site restoration and reseeding where necessary will take <br /> place in April of 2017. <br /> The vegetated swales were analyzed to determine anticipated shear stresses for the 10-yr storm <br /> event. Class I,Type B erosion control mat is specified for the bottoms of the swales. <br /> SHEAR STRESS WITHIN SWALES <br /> Location Swale Slope 10-yr Design 10-yr Design Shear <br /> Depth Flow Flow Depth Stress <br /> West Swale 1.0 ft 0.8% 1.7 CFS 0.45 ft 0.22 psf <br /> South Swale 1.0 ft. 1.1% 0.5 CFS 0.28 ft. 0.19 psf <br /> A tentative construction schedule is outlined below: <br /> Install perimeter erosion control measures: October 20, 2016 <br /> Construct swales and excavate biofilter: October 24, 2016 <br /> Install site pavements, seeding and mulching: November 30, 2016 <br /> Final stabilization: April 15, 2017 <br /> USLE Spreadsheet <br /> A Dane County USLE spreadsheet has been prepared and is attached. The disturbance period is <br /> carried through the winter due to the anticipated late seeding date. The USLE shows a soil loss <br /> of 1.2 tons/acre, without consideration of perimeter silt fence and the use of the biofilter as a <br /> temporary sediment basin. <br /> Page 4 of 6 18226000_memo_101916 <br />