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WEST SENECA - PRE DEVELOPMENT D_App D_Pre-Development Model_REV 1 NY-West Seneca 24-hr S1 100-yr Rainfall=5.22" Prepared by Labella Associates Printed 7/26/2026 HydroCAD® 10.20-6a s/n 09581 © 2024 HydroCAD Software Solutions LLC Page 20 Summary for Subcatchment ES-3: OFF-SITE DRAINAGE Runoff = 8.11 cfs @ 12.77 hrs, Volume= 1.248 af, Depth= 2.99" Routed to Reach AP-1 : Cayuga Creek Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NY-West Seneca 24-hr S1 100-yr Rainfall=5.22" Area (sf) CN Description 2,218 80 >75% Grass cover, Good, HSG D 570 98 Paved parking, HSG D 215,230 79 Woods, Fair, HSG D 218,018 79 Weighted Average 217,448 99.74% Pervious Area 570 0.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 34.2 100 0.0100 0.05 Sheet Flow, 100' Woods: Light underbrush n= 0.400 P2= 2.20" 24.4 732 0.0100 0.50 Shallow Concentrated Flow, REMAINING Woodland Kv= 5.0 fps 58.6 832 Total Subcatchment ES-3: OFF-SITE DRAINAGE Hydrograph 9 Runoff 8.11 cfs 8 NY-West Seneca 24-hr S1 100-yr Rainfall=5.22" 7 Runoff Area=218,018 sf Runoff Volume=1.248 af 6 Runoff Depth=2.99" Flow Length=832' Flow (cfs) 5 Slope=0.0100 '/' 4 Tc=58.6 min CN=79 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Page 463 of 1174