Analysis - Failure NOAA 24-hr D 10 YR-C Rainfall=5.38" Prepared by Civil Core Consulting Printed 12/19/2025 HydroCAD® 10.20-8a s/n 13637 © 2025 HydroCAD Software Solutions LLC Page 131
Summary for Pond 2P: Subusrface Infiltration Basin 1
Inflow Area = 80,967 sf, 34.36% Impervious, Inflow Depth = 1.95" for 10 YR-C event Inflow = 0.62 cfs @ 12.09 hrs, Volume= 13,179 cf Outflow = 0.62 cfs @ 12.10 hrs, Volume= 13,179 cf, Atten= 1%, Lag= 0.6 min Primary = 0.62 cfs @ 12.10 hrs, Volume= 13,179 cf Routed to Link 32L : POA1 Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Automatic Starting Elev= 91.55' Surf.Area= 0.057 ac Storage= 0.140 af Peak Elev= 91.60' @ 12.10 hrs Surf.Area= 0.057 ac Storage= 0.141 af (0.001 af above start) Plug-Flow detention time= 451.2 min calculated for 7,077 cf (54% of inflow) Center-of-Mass det. time= 2.1 min ( 937.1 - 934.9 )
VolumeInvertAvail.StorageStorage Description
#1A87.00'0.100 af27.50'W x 90.00'L x 6.00'H Field A
0.341 af Overall - 0.091 af Embedded = 0.250 af x 40.0% Voids
#2A87.50'0.073 afADS N-12 36" x 20 Inside #1 Inside = 36.1"W x 36.1"H => 7.10 sf x 20.00'L = 142.0 cf Outside = 42.0"W x 42.0"H => 8.86 sf x 20.00'L = 177.2 cf 20 Chambers in 5 Rows 24.50' Header x 7.10 sf x 2 = 347.9 cf Inside
0.173 af Total Available Storage
Storage Group A created with Chamber Wizard
Device Routing Invert Outlet Devices #1 Primary 91.55' 48.0" x 48.0" Horiz. Grate C=0.600 #2 Device 1 88.00' 12.0" Round Culvert L= 119.0' RCP, square edge headwall, Ke=0.500 Inlet / Outlet Invert= 88.00' / 86.00' S= 0.0168 /' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=0.62 cfs @ 12.10 hrs HW=91.60' TW=0.00' (Dynamic Tailwater) 1=Grate (Weir Controls 0.62 cfs @ 0.74 fps) 2=Culvert (Passes 0.62 cfs of 0.66 cfs potential flow)