251203_42 ERW_Stormwater Report

250903_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 11/25/2025 Page 5 Summary for Subcatchment EDA-1 (IMPERV): Runoff = 1.36 cfs @ 12.09 hrs, Volume= Routed to Reach DP1-EX : 0.103 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) 8,137 5,776 13,913 13,913 CN 98 98 98 Description Paved parking, HSG C Roofs, HSG C Weighted Average 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.1 78 0.0150 1.21 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.44" 1.0 12 0.0800 0.20 Sheet Flow, Grass: Short n= 0.150 P2= 3.44" 0.7 185 0.0830 4.64 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 2.8 275 Total Subcatchment EDA-1 (IMPERV): Hydrograph Runoff 1.36 cfs NOAA 24-hr D 2-Year Rainfall=4.09" Runoff Area=13,913 sf Runoff Volume=0.103 af Runoff Depth=3.85" Flow Length=275' Tc=2.8 min CN=98 Flow (cfs) 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)