6521 EVERGREEN WAY 2016-01-01 MF Import

� SWALE l:ALC:.. .l4-Ju1-94 16:14 EVERETT DAI12Y QUEEN--EVERGREEN WAY, LSA 3146 ----------�--------- -- -- --------------------------------- (:ontri�utury area = 1.01 acres Time of Concentration: Total I'low len. Vert. Ground Type Runoff Time of Time ft Dro�, Slope 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 = 0.9n5 Des. storm: 25 year recurrence, Itc in/hr = 2.050 Area, A acres = 1.015 , A sf = 44200 -------------------------------------------------------- landscaping 0.25 x 440� 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 Swa1e length = 160 ft Depth Top Area Wetted feet Width SF Perim ft ---------------------------- ------ 2 year storm: 0.45 5.70 1.96 5.85 25 year storm: 0.67 7.02 3.3n 7.24 0.801 1.738 HYDR Q RADIUS cfs R ------- ------- 0.33 O.II2 need Q = 0.80 Vel. Resid. fps Time min. ----------------- 0.42 6.4 0.46 1.74 0.52 5.2 need Q = 1.74 ---------------------------------------------------------------------- If the "weighted average" residence time is considered, rouqhly computed as .follows (for the 2-year storm only): Area of site draining through 100 feet of swale as a percent of total = Residence time for lOG feet of swale = 9000 sf 20.4% 4.0 minutes Weighted average r.esidence time = 5.9 minutes •