2026 02 12 Crestmont CC and Eagle Rock Ave Stormwater Management Report

.120 11. Average Velocity, V (NEH table 15-3) ft/s 5.59 12. Compute Tt L hr 0.000 + + Tt = 3600 V Shallow Conc. Flow Sub-Total 0.000 hours Channel Flow Segment ID 3 4 5 13. Flow Length, L ft 49 34 18 14. Cross Sectional flow area, a ft2 0.61 0.61 0.61 15. Wetted Perimeter, Pw ft 2.00 2.00 2.00 16. Hydraulic Radius, r r = a / Pw ft 0.31 0.31 0.31 17. Channel Slope, s ft/ft 0.071 0.005 0.035 18. Manning's Roughness Coeff., n 0.012 0.012 0.012 19. Velocity, V V = (1.49 r2/3 s1/2 ) / n ft/s 15.01 3.98 10.56 20. Compute Tt L hr 0.001 + 0.002 + 0.000 Tt = 3600 V Channel Flow Sub-Total 0.004 hours Watershed or subarea Tc or Tt Total Tc (hours) = 0.101 hours (Add Sub-Total Tt from prior steps) Total Tc

Total Tc (hours) = 0.101 hours (Add Sub-Total Tt from prior steps) Total Tc (minutes) = 6 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-2A-D Pervious v1.4

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-2A-D Open Space D Hyd. No. 35 Hydrograph Type = NRCS Runoff Peak Flow = 1.555 cfs Storm Frequency = 2-yr Time to Peak = 12.12 hrs Time Interval = 1 min Runoff Volume = 4,806 cuft Drainage Area = 0.8 ac Curve Number = 80.00 Tc Method = User Time of Conc. (Tc) = 6.0 min Total Rainfall = 3.46 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 1.555 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-2A-D Impervious Hyd. No. 36 Hydrograph Type = NRCS Runoff Peak Flow = 1.420 cfs Storm Frequency = 2-yr Time to Peak = 12.10 hrs Time Interval = 1 min Runoff Volume = 4,612 cuft Drainage Area = 0.42 ac Curve Number = 98.00 Tc Method = User Time of Conc. (Tc) = 2.0 min Total Rainfall = 3.46 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 1.420 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-2A-D Hyd. No. 37 Hydrograph Type = Junction Peak Flow = 2.928 cfs Storm Frequency = 2-yr Time to Peak = 12.10 hrs Time Interval = 1 min Hydrograph Volume = 9,417 cuft Inflow Hydrographs = 35, 36 Total Contrib. Area = 1.22 ac Qp = 2.928 cfs 3 2 Q (cfs) 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-2A-D Open Space D PR-2A-D Impervious PR-2A-D

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-2A-D Open Space D Hyd. No. 35 Hydrograph Type = NRCS Runoff Peak Flow = 3.098 cfs Storm Frequency = 10-yr Time to Peak = 12.12 hrs Time Interval = 1 min Runoff Volume = 9,664 cuft Drainage Area = 0.8 ac Curve Number = 80.00 Tc Method = User Time of Conc. (Tc) = 6.0 min Total Rainfall = 5.38 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 3.098 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-2A-D Impervious Hyd. No. 36 Hydrograph Type = NRCS Runoff Peak Flow = 2.220 cfs Storm Frequency = 10-yr Time to Peak = 12.10 hrs Time Interval = 1 min Runoff Volume = 7,350 cuft Drainage Area = 0.42 ac Curve Number = 98.00 Tc Method = User Time of Conc. (Tc) = 2.0 min Total Rainfall = 5.38 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 2.220 cfs 3 2 Q (cfs) 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-2A-D Hyd. No. 37 Hydrograph Type = Junction Peak Flow = 5.246 cfs Storm Frequency = 10-yr Time to Peak = 12.10 hrs Time Interval = 1 min Hydrograph Volume = 17,014 cuft Inflow Hydrographs = 35, 36 Total Contrib. Area = 1.22 ac Qp = 5.246 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) PR-2A-D Open Space D PR-2A-D Impervious PR-2A-D

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-2A-D Open Space D Hyd. No. 35 Hydrograph Type = NRCS Runoff Peak Flow = 4.209 cfs Storm Frequency = 25-yr Time to Peak = 12.12 hrs Time Interval = 1 min Runoff Volume = 13,287 cuft Drainage Area = 0.8 ac Curve Number = 80.00 Tc Method = User Time of Conc. (Tc) = 6.0 min Total Rainfall = 6.72 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 4.209 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)

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-2A-D Impervious Hyd. No. 36 Hydrograph Type = NRCS Runoff Peak Flow = 2.777 cfs Storm Frequency = 25-yr Time to Peak = 12.10 hrs Time Interval = 1 min Runoff Volume = 9,264 cuft Drainage Area = 0.42 ac Curve Number = 98.00 Tc Method = User Time of Conc. (Tc) = 2.0 min Total Rainfall = 6.72 in Design Storm = NOAA-D Storm Duration = 24 hrs Shape Factor = 484 Qp = 2.777 cfs 3 2 Q (cfs) 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)