251203_42 ERW_Stormwater Report

NOAA 24-hr D 2-Year Rainfall=4.09" 251202_42 ERW Waystone - Future Rainfall Prepared by Colliers Engineering & Design HydroCAD® 10.20-5c s/n 04431 © 2023 HydroCAD Software Solutions LLC Printed 12/3/2025 Page 9 Summary for Subcatchment PR 1B-P: Runoff = 3.92 cfs @ 12.15 hrs, Volume= Routed to Reach 10R : 0.301 af, Depth= 2.04" 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) 50,619 26,576 77,195 77,195 CN 74 89 79 Description >75% Grass cover, Good, HSG C Gravel roads, HSG C Weighted Average 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.2 100 0.0400 0.23 Sheet Flow, Grass: Short n= 0.150 P2= 3.44" 0.5 95 0.0361 3.06 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 7.7 195 Total Subcatchment PR 1B-P: Hydrograph Runoff 3.92 cfs 4 NOAA 24-hr D 2-Year Rainfall=4.09" Runoff Area=77,195 sf Runoff Volume=0.301 af Runoff Depth=2.04" Flow Length=195' Tc=7.7 min CN=79 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)