NOAA 24-hr D 100 YR-F Rainfall=11.41" Printed 12/19/2025 tions LLC Page 379
Analysis - Proposed Conditions Prepared by Civil Core Consulting HydroCAD® 10.20-8a s/n 13637 © 2025 HydroCAD Software Solutions LLC
Summary for Pond 2P: Subsurface Infiltration Basin 1
Inflow Area = 73,567 sf, 27.76% Impervious, Inflow Depth = 4.93" for 100 YR-F event
Inflow = 4.40 cfs @ 12.18 hrs, Volume= 30,199 cf
Outflow = 0.82 cfs @ 13.56 hrs, Volume= 30,199 cf, Atten= 81%, Lag= 82.7 min
Discarded = 0.57 cfs @ 12.00 hrs, Volume= 29,874 cf
Primary = 0.25 cfs @ 13.56 hrs, Volume= 325 cf
Routed to Link 32L : POA1
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs
Peak Elev= 92.62' @ 13.56 hrs Surf.Area= 2,475 sf Storage= 7,159 cf
Plug-Flow detention time= 92.0 min calculated for 30,195 cf (100% of inflow)
Volume Invert Avail.Storage Storage Description
Center-of-Mass det. time= 92.0 min ( 1,079.3 - 987.3 )
#1A 87.00' 4,349 cf 27.50"W x 90.00"L x 6.00"H Field A 14,850 cf Overall - 3,979 cf Embedded = 10,871 cf x 40.0% Voids
#2A 87.50' 3,188 cf ADS 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
7,536 cf Total Available Storage
Device Routing Invert Outlet Devices
Storage Group A created with Chamber Wizard
#1 Primary 92.59' 48.0" x 48.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads
#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
#3 Discarded 87.00' 10.000 in/hr Exfiltration over Surface area Phase-In= 0.01'
Discarded OutFlow Max=0.57 cfs @ 12.00 hrs HW=87.07' (Free Discharge) 3=Exfiltration (Exfiltration Controls 0.57 cfs)
Primary OutFlow Max=0.25 cfs @ 13.56 hrs HW=92.62' TW=0.00' (Dynamic Tailwater) 1=Grate (Weir Controls 0.25 cfs @ 0.55 fps) 2=Culvert (Passes 0.25 cfs of 0.49 cfs potential flow)
Pond 2P: Subsurface Infiltration Basin 1
Grate
Culvert
Exfiltration