6521 EVERGREEN WAY 2016-01-01 MF Import

� SWALE CALCS. 14-Ju1-94 16•14 EVERETT DAIRY QUEEN--EVERGREEN WAY, LSA 3146 -------________________________________________________________ Contribut6ry area = 1.01 acres Time of Concentration: Total Flow len. Vert. Grou�id Type Runoff Time of Time ft Drop �lope Cover Vel. Travel 10.0 -------------_________________________________________ 360 7.0 1.94% paved 2.81 2.1 12.14 Time of Concentration, T(c) minutes = 12.14 Des. storm: 2 year recurrence, Itc in/hr = 0.945 Des. storm: 25 year recurrence, Itc in/hr = 2.050 Area, A acres = 1.015 , A sf = 44200 -------------------------------------------------------- landscaping 0.25 x 4400 sf Driveway/parking 0.90 x 39800 C = 0.835 Flow, Q cfs= (Itc x A x C) = 2 year Flow, Q cfs= (Itc x A x C) = 25 year ---------------------------------------- Calculating flow through a swale: -------------------------------- Friction factor = 0.200 Side slope = 3.000 H: 1V Channel slope = 0.0134 ft/ft Bottom width = 3.000 ft Swale length = 160 ft Depth Top Area Wetted feet Width SF Perim it --------------------------- 2 year storm: 0.45 5.70 1.96 25 year storm: 0.67 7.02 3.36 0.801 1.738 HYDR Q Vel. Resid. RADIUS cfs fps Time R min. ---------- ------------------------ 5.85 0.33 0.82 need Q = 0.80 7.24 0.46 1.74 need Q = 1.74 0.4:! 6.4 0.52 5.2 ----------•------------------------------------------------------------ If the "wei9hted average" residence time is considered, roughly computed as follows (for the 2-year storm only): Area of site draining ihrough :00 feet of swale: as a percent of total = Residence time for 100 feet of swale = 9000 sf 20.4°s 4.0 minutes Weighted average residence time = 5.9 minutes