Southtowns Record

PBA07.09.2026packet

Government
Town of West Seneca
Board
Planning Board
Meeting
Jul 9, 2026, 6:00 p.m.
Posted by publisher
Jul 9, 2026
Kind
Agenda packet
Topics
Water, sewer and drainage, Housing, Zoning and land use, Roads and traffic, Parks and recreation, Budget and taxes, Public safety

Original document

Same meeting

Text · page 234 of 1493

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E_App E_Post-Development Model  NY-West Seneca 24-hr S1 10-yr Rainfall=3.14"
Prepared by Labella Associates  Printed 4/20/2026
HydroCAD® 10.20-7a s/n 09581 © 2025 HydroCAD Software Solutions LLC  Page 34

  Summary for Pond BIO-1: Filtration Bioretention

Inflow Area =  0.634 ac, 33.98% Impervious, Inflow Depth = 1.78" for 10-yr event
Inflow  =  1.71 cfs @ 12.04 hrs, Volume=  0.094 af
Outflow  =  1.12 cfs @ 12.12 hrs, Volume=  0.094 af, Atten= 34%, Lag= 4.6 min
Primary  =  0.02 cfs @ 12.12 hrs, Volume=  0.045 af
  Routed to Reach DP-1 : Design Point
Secondary =  1.10 cfs @ 12.12 hrs, Volume=  0.049 af
  Routed to Reach DP-1 : Design Point
Tertiary  =  0.00 cfs @ 0.00 hrs, Volume=  0.000 af
  Routed to Reach DP-1 : Design Point

Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs
Peak Elev= 599.12' @ 12.12 hrs Surf.Area= 1,797 sf Storage= 1,232 cf
Flood Elev= 600.00' Surf.Area= 2,500 sf Storage= 3,120 cf

Plug-Flow detention time= 326.2 min calculated for 0.094 af (100% of inflow)
Center-of-Mass det. time= 326.4 min ( 1,148.5 - 822.1 )

Volume  Invert  Avail.Storage  Storage Description
  #1  598.00'  3,120 cf  Above Mulch Surface (Prismatic)Listed below (Recalc)

Elevation  Surf.Area  Inc.Store  Cum.Store
  (feet)  (sq-ft)  (cubic-feet)  (cubic-feet)
  598.00  340  0  0
  599.00  1,700  1,020  1,020
  600.00  2,500  2,100  3,120

Device  Routing  Invert  Outlet Devices
  #1  Primary  598.00'  0.500 in/hr Exfiltration Through Media over Surface area
  #2  Device 3  599.00'  24.0" x 24.0" Horiz. Overflow Grate C= 0.600
  Limited to weir flow at low heads
  #3  Secondary  594.58'  12.0" Round Culvert
  L= 25.0' CPP, projecting, no headwall, Ke= 0.900
  Inlet / Outlet Invert= 594.58' / 594.33' S= 0.0100 '/' Cc= 0.900
  n= 0.012 Corrugated PE, smooth interior, Flow Area= 0.79 sf
  #4  Tertiary  599.50'  10.0' long x 3.0' breadth Emergency Overflow Weir
  Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
  2.50 3.00 3.50 4.00 4.50
  Coef. (English) 2.44 2.58 2.68 2.67 2.65 2.64 2.64 2.68 2.68
  2.72 2.81 2.92 2.97 3.07 3.32

Primary OutFlow Max=0.02 cfs @ 12.12 hrs HW=599.12' TW=0.00' (Dynamic Tailwater)
  1=Exfiltration Through Media (Exfiltration Controls 0.02 cfs)

Secondary OutFlow Max=1.10 cfs @ 12.12 hrs HW=599.12' TW=0.00' (Dynamic Tailwater)
  3=Culvert (Passes 1.10 cfs of 6.00 cfs potential flow)
  2=Overflow Grate (Weir Controls 1.10 cfs @ 1.14 fps)

Tertiary OutFlow Max=0.00 cfs @ 0.00 hrs HW=598.00' TW=0.00' (Dynamic Tailwater)
  4=Emergency Overflow Weir ( Controls 0.00 cfs)

  Page 234 of 1493