Analysis - Failure NOAA 24-hr D 2 YR-C Rainfall=3.42" Prepared by Civil Core Consulting Printed 12/19/2025 HydroCAD® 10.20-8a s/n 13637 © 2025 HydroCAD Software Solutions LLC Page 42
Summary for Pond 2P: Subusrface Infiltration Basin 1
Inflow Area = 80,967 sf, 34.36% Impervious, Inflow Depth = 1.10" for 2 YR-C event Inflow = 0.42 cfs @ 12.09 hrs, Volume= 7,413 cf Outflow = 0.42 cfs @ 12.10 hrs, Volume= 7,413 cf, Atten= 1%, Lag= 0.4 min Primary = 0.42 cfs @ 12.10 hrs, Volume= 7,413 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= 91.59' @ 12.10 hrs Surf.Area= 0.057 ac Storage= 0.141 af (0.001 af above start) Plug-Flow detention time= 757.4 min calculated for 1,312 cf (18% of inflow) Center-of-Mass det. time= 2.5 min (871.2 - 868.7 )
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=0.42 cfs @ 12.10 hrs HW=91.59' TW=0.00' (Dynamic Tailwater) 1=Grate (Weir Controls 0.42 cfs @ 0.65 fps) 2=Culvert (Passes 0.42 cfs of 0.58 cfs potential flow)