12 2026 02 12 Crestmont CC Stormwater Management Report

ft 13 9. Watercourse Slope, s ft/ft 0.372 10. Average Velocity, V (NEH table 15-3) ft/s 9.85 11. Compute Tt L hr 0.000 + + Tt = 3600 V Shallow Conc. Flow Sub-Total 0.000 hours Channel Flow Segment ID 4 5 6 12. Flow Length, L ft 245 25 117 13. Cross Sectional flow area, a ft2 0.69 0.61 0.61 14. Wetted Perimeter, Pw ft 3.58 2.00 2.00 15. Hydraulic Radius, r r = a / Pw ft 0.19 0.31 0.31 16. Channel Slope, s ft/ft 0.010 0.080 0.023 17. Manning's Roughness Coeff., n 0.035 0.013 0.013 18. Velocity, V V = (1.49 r2/3 s1/2 ) / n ft/s 1.42 14.69 7.89 19. Compute Tt L hr 0.048 + 0.000 + 0.004 Tt = 3600 V Channel Flow Sub-Total 0.053 hours Channel Flow Segment ID 7 8 20. Flow Length, L

Flow Sub-Total 0.053 hours Channel Flow Segment ID 7 8 20. Flow Length, L ft 15 51 21. Cross Sectional flow area, a ft2 0.61 0.61 22. Wetted Perimeter, Pw ft 2.00 2.00 23. Hydraulic Radius, r r = a / Pw ft 0.31 0.31 24. Channel Slope, s ft/ft 0.055 0.021 25. Manning's Roughness Coeff., n 0.013 0.013 26. Velocity, V V = (1.49 r2/3 s1/2 ) / n ft/s 12.14 7.59 27. Compute Tt L hr 0.000 + 0.002 + Tt = 3600 V Channel Flow Sub-Total 0.002 hours Watershed or subarea Tc or Tt Total Tc (hours) = 0.237 hours (Add Sub-Total Tt from prior steps) Total Tc (minutes) = 14 minutes \\langan.com\data\PAR\data8\101049801\Project Data\_Discipline\Site Civil\Stormwater\Time of Concentration Calcs\Proposed Tc Calcs\Current Proposed TCs\Current Proposed TC PR-1B-U Pervious v1.2

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Open Space C Hyd. No. 15 Hydrograph Type = NRCS Runoff Peak Flow = 0.305 cfs Storm Frequency = 2-yr Time to Peak = 12.20 hrs Time Interval = 1 min Runoff Volume = 1,276 cuft Drainage Area = 0.29 ac Curve Number = 74.00 Tc Method = User Time of Conc. (Tc) = 14.0 min Total Rainfall = 3.46 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 0.305 cfs 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 Q (cfs) 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Woods C Hyd. No. 16 Hydrograph Type = NRCS Runoff Peak Flow = 0.510 cfs Storm Frequency = 2-yr Time to Peak = 12.22 hrs Time Interval = 1 min Runoff Volume = 2,213 cuft Drainage Area = 0.62 ac Curve Number = 70.00 Tc Method = User Time of Conc. (Tc) = 14.0 min Total Rainfall = 3.46 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 0.510 cfs 1 0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 Q (cfs) 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Impervious Hyd. No. 17 Hydrograph Type = NRCS Runoff Peak Flow = 3.580 cfs Storm Frequency = 2-yr Time to Peak = 12.12 hrs Time Interval = 1 min Runoff Volume = 13,475 cuft Drainage Area = 1.18 ac Curve Number = 98.00 Tc Method = User Time of Conc. (Tc) = 7.0 min Total Rainfall = 3.46 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 3.580 cfs 4 3 Q (cfs) 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Hyd. No. 18 Hydrograph Type = Junction Peak Flow = 4.256 cfs Storm Frequency = 2-yr Time to Peak = 12.13 hrs Time Interval = 1 min Hydrograph Volume = 16,965 cuft Inflow Hydrographs = 15, 16, 17 Total Contrib. Area = 2.09 ac Qp = 4.256 cfs 5 4 3 Q (cfs) 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs) PR-1B-U Open Space C PR-1B-U Woods C PR-1B-U Impervious PR-1B-U

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Open Space C Hyd. No. 15 Hydrograph Type = NRCS Runoff Peak Flow = 0.694 cfs Storm Frequency = 10-yr Time to Peak = 12.20 hrs Time Interval = 1 min Runoff Volume = 2,812 cuft Drainage Area = 0.29 ac Curve Number = 74.00 Tc Method = User Time of Conc. (Tc) = 14.0 min Total Rainfall = 5.38 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 0.694 cfs 1 0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 Q (cfs) 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Woods C Hyd. No. 16 Hydrograph Type = NRCS Runoff Peak Flow = 1.281 cfs Storm Frequency = 10-yr Time to Peak = 12.20 hrs Time Interval = 1 min Runoff Volume = 5,227 cuft Drainage Area = 0.62 ac Curve Number = 70.00 Tc Method = User Time of Conc. (Tc) = 14.0 min Total Rainfall = 5.38 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 1.281 cfs 2 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 Q (cfs) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Impervious Hyd. No. 17 Hydrograph Type = NRCS Runoff Peak Flow = 5.603 cfs Storm Frequency = 10-yr Time to Peak = 12.12 hrs Time Interval = 1 min Runoff Volume = 21,477 cuft Drainage Area = 1.18 ac Curve Number = 98.00 Tc Method = User Time of Conc. (Tc) = 7.0 min Total Rainfall = 5.38 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 5.603 cfs 6 5 4 Q (cfs) 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1B-U Hyd. No. 18 Hydrograph Type = Junction Peak Flow = 7.312 cfs Storm Frequency = 10-yr Time to Peak = 12.13 hrs Time Interval = 1 min Hydrograph Volume = 29,515 cuft Inflow Hydrographs = 15, 16, 17 Total Contrib. Area = 2.09 ac Qp = 7.312 cfs 8 7 6 5 Q (cfs) 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Time (hrs) PR-1B-U Open Space C PR-1B-U Woods C PR-1B-U Impervious PR-1B-U