6521 EVERGREEN WAY 2016-01-01 MF Import

SWALE CALCS. 14-Ju1-94 16:14 EVERETT DAIRY QUEEN--EVERGREEN WAY, LSA 3146 -------------------------------------------------------------- Contributory area = 1.01 acres Time of Concentration: Total Flow len. Vert. Ground Type Runoff Time of Time ft Drop 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 = 0.945 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 o.90 x 39800 C = 0.835 Flow, Q cfs= (Itc x A x C) = 2 year 0.801 Flow, Q cfs= (Itc x A x C) = 25 year 1.738 ----------------------------------------------------- Calculating flow throuqh 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 �Aetted HYDR feet Width SF Perim RADIUS ft R ---------------------------- ---------------- --- 2 year storm: 0.45 5.70 1.96 5.85 0.33 need Q = Q cfs 0.82 0.80 Vel. Resid. fps Time min. -------------- 0.42 6.4 25 year storm: 0.67 7.02 3.36 7.24 0.46 1.74 0.52 need Q = 1.74 --------------------------------------------------------------- If the "weighted average" residence time is considered, roughly computed as follows (for the 2-year storm only): Area cf site draining through 100 feet of swa7.e: as a percent of total = Residence time for 100 feet oi swale = Weigtited average residence time = 5.2 y000 sf 20.40 4.0 minutes 5.9 minutes .