251203_42 ERW_Stormwater Report

NOAA 24-hr D 2-Year Rainfall=4.09" 250903_42 ERW Waystone - Future Rainfall Prepared by Colliers Engineering & Design HydroCAD® 10.20-5c s/n 04431 © 2023 HydroCAD Software Solutions LLC Printed 11/25/2025 Page 9 Summary for Subcatchment EDA-2 (PERV.): Runoff = 0.77 cfs @ 12.15 hrs, Volume= Routed to Reach DP2-EX : 0.059 af, Depth= 1.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=4.09" Area (ac) 0.423 0.423 CN 74 Description >75% Grass cover, Good, HSG C 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.1 100 0.0410 0.24 Sheet Flow, Grass: Short n= 0.150 P2= 3.44" 0.1 21 0.1050 5.22 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 7.2 121 Total Subcatchment EDA-2 (PERV.): Hydrograph 0.85 Runoff 0.8 0.77 cfs NOAA 24-hr D 2-Year Rainfall=4.09" Runoff Area=0.423 ac Runoff Volume=0.059 af Runoff Depth=1.66" Flow Length=121' Tc=7.2 min CN=74 0.75 0.7 0.65 0.6 Flow (cfs) 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours)