JMA02P003 262 270 Main Street Development Stormwater Management Report

Existing Flows NOAA10 24-hr D 100-Year-Future Rainfall=11.52" Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC This report was prepared with the free HydroCAD SAMPLER, which is licensed for evaluation and educational use ONLY. For actual design or modeling applications you MUST use a full version of HydroCAD which may be purchased at www.hydrocad.net. Full programs also include complete technical support,training materials, and additional features which are essential for actual design work. Summary for Subcatchment 2S: Existing Pervious Runoff = 0.08 cfs @ 12.06 hrs, Volume= 205 cf, Depth= 8.17" Routed to Link 3L : Total Site Flows Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs NOAA10 24-hr D 100-Year-Future Rainfall=11.52" Area (sf) CN Description 302 74 >75% Grass cover, Good, HSG C 302 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.0 Direct Entry, Subcatchment 2S: Existing Pervious Hydrograph 0.085 Runoff 0.08 cfs 0.08 0.075 NOAA10 24-hr D 0.07 100-Year-Future Rainfall=11.52" 0.065 Runoff Area=302 sf 0.06 Runoff Volume=205 cf 0.055 Runoff Depth=8.17" 0.05

Runoff Volume=205 cf 0.055 Runoff Depth=8.17" 0.05 Tc=1.0 min Flow (cfs) 0.045 CN=74 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 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)

Existing Flows NOAA10 24-hr D 100-Year-Future Rainfall=11.52" Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC This report was prepared with the free HydroCAD SAMPLER, which is licensed for evaluation and educational use ONLY. For actual design or modeling applications you MUST use a full version of HydroCAD which may be purchased at www.hydrocad.net. Full programs also include complete technical support,training materials, and additional features which are essential for actual design work. Hydrograph for Subcatchment 2S: Existing Pervious Time Precip. Excess Runoff Time Precip. Excess Runoff (hours) (inches) (inches) (cfs) (hours) (inches) (inches) (cfs) 0.00 0.00 0.00 0.00 47.00 11.52 8.17 0.00 1.00 0.15 0.00 0.00 48.00 11.52 8.17 0.00 2.00 0.33 0.00 0.00 49.00 11.52 8.17 0.00 3.00 0.53 0.00 0.00 50.00 11.52 8.17 0.00 4.00 0.76 0.00 0.00 51.00 11.52 8.17 0.00 5.00 1.01 0.02 0.00 52.00 11.52 8.17 0.00 6.00 1.28 0.08 0.00 53.00 11.52 8.17 0.00 7.00 1.59 0.18 0.00 54.00 11.52 8.17 0.00 8.00 1.92 0.31 0.00 55.00 11.52 8.17 0.00 9.00 2.27 0.48 0.00 56.00 11.52 8.17 0.00 10.00 2.76 0.76 0.00 57.00 11.52 8.17 0.00 11.00 3.41 1.18 0.00 58.00 11.52 8.17 0.00 12.00 5.45 2.73 0.05 59.00 11.52 8.17 0.00 13.00 8.11 5.02 0.01 60.00 11.52 8.17 0.00 14.00 8.76 5.61 0.00 61.00 11.52 8.17 0.00 15.00 9.25 6.06 0.00 62.00 11.52 8.17 0.00 16.00 9.60 6.38 0.00 63.00 11.52 8.17 0.00 17.00 9.93 6.69 0.00 64.00 11.52 8.17 0.00 18.00 10.24 6.97 0.00 65.00 11.52 8.17 0.00 19.00 10.51 7.22 0.00 66.00 11.52 8.17 0.00

0.00 64.00 11.52 8.17 0.00 18.00 10.24 6.97 0.00 65.00 11.52 8.17 0.00 19.00 10.51 7.22 0.00 66.00 11.52 8.17 0.00 20.00 10.76 7.46 0.00 67.00 11.52 8.17 0.00 21.00 10.99 7.67 0.00 68.00 11.52 8.17 0.00 22.00 11.19 7.86 0.00 69.00 11.52 8.17 0.00 23.00 11.37 8.02 0.00 70.00 11.52 8.17 0.00 24.00 11.52 8.17 0.00 71.00 11.52 8.17 0.00 25.00 11.52 8.17 0.00 72.00 11.52 8.17 0.00 26.00 11.52 8.17 0.00 27.00 11.52 8.17 0.00 28.00 11.52 8.17 0.00 29.00 11.52 8.17 0.00 30.00 11.52 8.17 0.00 31.00 11.52 8.17 0.00 32.00 11.52 8.17 0.00 33.00 11.52 8.17 0.00 34.00 11.52 8.17 0.00 35.00 11.52 8.17 0.00 36.00 11.52 8.17 0.00 37.00 11.52 8.17 0.00 38.00 11.52 8.17 0.00 39.00 11.52 8.17 0.00 40.00 11.52 8.17 0.00 41.00 11.52 8.17 0.00 42.00 11.52 8.17 0.00 43.00 11.52 8.17 0.00 44.00 11.52 8.17 0.00 45.00 11.52 8.17 0.00 46.00 11.52 8.17 0.00

Existing Flows NOAA10 24-hr D 100-Year-Future Rainfall=11.52" Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC This report was prepared with the free HydroCAD SAMPLER, which is licensed for evaluation and educational use ONLY. For actual design or modeling applications you MUST use a full version of HydroCAD which may be purchased at www.hydrocad.net. Full programs also include complete technical support,training materials, and additional features which are essential for actual design work. Summary for Link 3L: Total Site Flows Inflow Area = 30,218 sf, 99.00% Impervious, Inflow Depth = 11.25" for 100-Year-Future event Inflow = 9.13 cfs @ 12.06 hrs, Volume= 28,323 cf Primary = 9.13 cfs @ 12.06 hrs, Volume= 28,323 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Link 3L: Total Site Flows Hydrograph Inflow 10 9.13 cfs Primary 9.13 cfs 9 Inflow Area=30,218 sf 8 7 6 Flow (cfs) 5 4 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)

Existing Flows NOAA10 24-hr D 100-Year-Future Rainfall=11.52" Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC This report was prepared with the free HydroCAD SAMPLER, which is licensed for evaluation and educational use ONLY. For actual design or modeling applications you MUST use a full version of HydroCAD which may be purchased at www.hydrocad.net. Full programs also include complete technical support,training materials, and additional features which are essential for actual design work. Hydrograph for Link 3L: Total Site Flows Time Inflow Elevation Primary Time Inflow Elevation Primary (hours) (cfs) (feet) (cfs) (hours) (cfs) (feet) (cfs) 0.00 0.00 0.00 0.00 47.00 0.00 0.00 0.00 1.00 0.06 0.00 0.06 48.00 0.00 0.00 0.00 2.00 0.11 0.00 0.11 49.00 0.00 0.00 0.00 3.00 0.13 0.00 0.13 50.00 0.00 0.00 0.00 4.00 0.16 0.00 0.16 51.00 0.00 0.00 0.00 5.00 0.18 0.00 0.18 52.00 0.00 0.00 0.00 6.00 0.20 0.00 0.20 53.00 0.00 0.00 0.00 7.00 0.22 0.00 0.22 54.00 0.00 0.00 0.00 8.00 0.23 0.00 0.23 55.00 0.00 0.00 0.00 9.00 0.27 0.00 0.27 56.00 0.00 0.00 0.00 10.00 0.36 0.00 0.36 57.00 0.00 0.00 0.00 11.00 0.60 0.00 0.60 58.00 0.00 0.00 0.00 12.00 5.74 0.00 5.74 59.00 0.00 0.00 0.00 13.00 0.62 0.00 0.62 60.00 0.00 0.00 0.00 14.00 0.36 0.00 0.36 61.00 0.00 0.00 0.00 15.00 0.31 0.00 0.31 62.00 0.00 0.00 0.00 16.00 0.24 0.00 0.24 63.00 0.00 0.00 0.00 17.00

0.00 0.00 15.00 0.31 0.00 0.31 62.00 0.00 0.00 0.00 16.00 0.24 0.00 0.24 63.00 0.00 0.00 0.00 17.00 0.22 0.00 0.22 64.00 0.00 0.00 0.00 18.00 0.20 0.00 0.20 65.00 0.00 0.00 0.00 19.00 0.18 0.00 0.18 66.00 0.00 0.00 0.00 20.00 0.17 0.00 0.17 67.00 0.00 0.00 0.00 21.00 0.15 0.00 0.15 68.00 0.00 0.00 0.00 22.00 0.13 0.00 0.13 69.00 0.00 0.00 0.00 23.00 0.11 0.00 0.11 70.00 0.00 0.00 0.00 24.00 0.08 0.00 0.08 71.00 0.00 0.00 0.00 25.00 0.00 0.00 0.00 72.00 0.00 0.00 0.00 26.00 0.00 0.00 0.00 27.00 0.00 0.00 0.00 28.00 0.00 0.00 0.00 29.00 0.00 0.00 0.00 30.00 0.00 0.00 0.00 31.00 0.00 0.00 0.00 32.00 0.00 0.00 0.00 33.00 0.00 0.00 0.00 34.00 0.00 0.00 0.00 35.00 0.00 0.00 0.00 36.00 0.00 0.00 0.00 37.00 0.00 0.00 0.00 38.00 0.00 0.00 0.00 39.00 0.00 0.00 0.00 40.00 0.00 0.00 0.00 41.00 0.00 0.00 0.00 42.00 0.00 0.00 0.00 43.00 0.00 0.00 0.00 44.00 0.00 0.00 0.00 45.00 0.00 0.00 0.00 46.00 0.00 0.00 0.00

Engineering Stormwater Narrative JMA02P003- May 26, 2026 262-270 Main St Development Appendix D: Post-Development Analysis 7

1S 3S 4S Proposed Impervious Proposed Pervious Proposed Impervious 2P 5P Basin A Porous Pavement B Subcat Reach Pond Link Routing Diagram for Proposed Flows Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net, Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC

Proposed Flows Prepared by HydroCAD SAMPLER 1-800-927-7246 www.hydrocad.net Printed 5/26/2026 HydroCAD® 10.20-8a Sampler s/n S05110 © 2025 HydroCAD Software Solutions LLC This report was prepared with the free HydroCAD SAMPLER, which is licensed for evaluation and educational use ONLY. For actual design or modeling applications you MUST use a full version of HydroCAD which may be purchased at www.hydrocad.net. Full programs also include complete technical support,training materials, and additional features which are essential for actual design work. Rainfall Events Listing (selected events) Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 2-Year-Current NOAA10 24-hr D Default 24.00 1 3.43 2 2 10-Year-Current NOAA10 24-hr D Default 24.00 1 5.33 2 3 100-Year-Current NOAA10 24-hr D Default 24.00 1 9.18 2 4 2-Year-Future NOAA10 24-hr D Default 24.00 1 4.04 2 5 10-Year-Future NOAA10 24-hr D Default 24.00 1 6.31 2 6 100-Year-Future NOAA10 24-hr D Default 24.00 1 11.52 2