251203_42 ERW_Stormwater Report

251202_42 ERW Waystone - Future Rainfall NOAA 24-hr D 2-Year Rainfall=4.09" Prepared by Colliers Engineering & Design HydroCAD® 10.20-5c s/n 04431 © 2023 HydroCAD Software Solutions LLC Printed 12/3/2025 Page 7 Summary for Subcatchment PR 1B-I: Runoff = 3.62 cfs @ 12.07 hrs, Volume= Routed to Reach 10R : 0.272 af, Depth= 3.85" 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 (sf) 21,449 15,457 36,906 36,906 CN 98 98 98 Description Roofs, HSG C Paved parking, HSG C Weighted Average 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.2 100 0.0200 1.43 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.44" 0.3 36 0.0097 2.00 Shallow Concentrated Flow, Paved Kv= 20.3 fps 1.5 136 Total Subcatchment PR 1B-I: Hydrograph 4 Runoff 3.62 cfs NOAA 24-hr D 2-Year Rainfall=4.09" Runoff Area=36,906 sf Runoff Volume=0.272 af Runoff Depth=3.85" Flow Length=136' Tc=1.5 min CN=98 Flow (cfs) 3 2 1 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)