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 19 Summary for Pond BASIN: Inflow Area = 2.619 ac, 32.35% Impervious, Inflow Depth = 2.62" for 2-Year event Inflow = 6.68 cfs @ 12.09 hrs, Volume= 0.573 af Outflow = 1.68 cfs @ 12.47 hrs, Volume= 0.573 af, Atten= 75%, Lag= 22.5 min Discarded = 0.31 cfs @ 12.47 hrs, Volume= 0.345 af Primary = 1.36 cfs @ 12.47 hrs, Volume= 0.228 af Routed to Reach DP1-PR : Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 16.73' @ 12.47 hrs Surf.Area= 0.168 ac Storage= 0.189 af Plug-Flow detention time= 106.8 min calculated for 0.573 af (100% of inflow) Center-of-Mass det. time= 106.7 min ( 906.3 - 799.6 ) Volume #1A Invert 15.00' Avail.Storage 0.199 af #2A 15.75' 0.341 af 0.539 af Storage Description 51.42'W x 141.93'L x 5.00'H Field A 0.838 af Overall - 0.341 af Embedded = 0.497 af x 40.0% Voids ADS_StormTech MC-3500 d +Cap x 133 Inside #1 Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap 133 Chambers in 7 Rows Cap Storage= 14.9 cf x 2 x 7 rows = 208.6 cf Total Available Storage Storage Group A created with Chamber Wizard Device #1 Routing Primary Invert 15.89' #2 Primary 16.73' #3 Primary 18.75' #4 Discarded 15.00' Outlet Devices 14.0" W x 3.5" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads 20.0" W x 5.0" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads 1.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 13.00' Discarded OutFlow Max=0.31 cfs @ 12.47 hrs HW=16.73' (Free Discharge) 4=Exfiltration ( Controls 0.31 cfs) Primary OutFlow Max=1.36 cfs @ 12.47 hrs HW=16.73' (Free Discharge) 1=Orifice/Grate (Orifice Controls 1.36 cfs @ 4.00 fps) 2=Orifice/Grate ( Controls 0.00 cfs) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)