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

= = WATER QUALITY DESIGN STORM ROUTING CALCULATIONS FOR SETTING BOTTOM ORIFICE INVERT ELEVATIONS SMALL-SCALE BIORETENTION BASIN 1 SMALL-SCALE BIORETENTION BASIN 2 EMERGENCY SPILLWAY CALCULATIONS SMALL-SCALE BIORETENTION BASIN 1 SMALL-SCALE BIORETENTION BASIN 2 ANTI-SEEP COLLAR CALCULATIONS SMALL-SCALE BIORETENTION BASIN 1 SMALL-SCALE BIORETENTION BASIN 2

CURRENT POND ROUTING CALCULATIONS

PR-1A WATERSHED POND ROUTING

Pond Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 SSBB-1 Stage-Storage User Defined Contours Stage / Storage Table Description Input Stage Elevation Contour Area Incr. Storage Total Storage (ft) (ft) (sqft) (cuft) (cuft) Bottom Elevation, ft 534.00 0.00 534.00 4,713 0.000 0.000 Voids (%) 100.00 1.00 535.00 4,938 4,825 4,825 Volume Calc Conic 2.00 536.00 5,145 5,041 9,865 3.00 537.00 5,354 5,249 15,114 4.00 538.00 5,649 5,500 20,614 5.00 539.00 6,413 6,026 26,641 Stage-Storage 539 5 538 4 537 3 536

3 536 2 535 1 534 0 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 22000 24000 26000 Total Storage (cuft) 2-yr 10-yr 25-yr 100-yr Contours

Pond Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 SSBB-1 Stage-Discharge Orifice Culvert / Orifices Cir Culvert Perforated Riser 1 (m) 2 (m) 3 Rise, in 18 4 4 Hole Diameter, in Span, in 18 12 14 No. holes No. Barrels 1 1 1 Invert Elevation, ft Invert Elevation, ft 530.25 534.60 535.40 Height, ft Orifice Coefficient, Co 0.60 0.60 0.60 Orifice Coefficient, Co Length, ft 47 Barrel Slope, % 7.34 N-Value, n 0.013 Weir Weirs Riser Ancillary 1 (m) 2 3 Shape / Type Rectangular Exfiltration, in/hr Crest Elevation, ft 536.1 Crest Length, ft

tangular Exfiltration, in/hr Crest Elevation, ft 536.1 Crest Length, ft 3 Angle, deg Weir Coefficient, Cw 3.3 m = Flows through Culvert, i = Independent Stage-Discharge 539 5 538 4 537 3 536 2 535 1 534 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 Discharge (cfs) Top of Pond 2-yr 10-yr 25-yr 100-yr Pond Outflow

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1A Routing Hyd. No. 11 Hydrograph Type = Pond Route Peak Flow = 1.034 cfs Storm Frequency = 2-yr Time to Peak = 12.33 hrs Time Interval = 1 min Hydrograph Volume = 9,748 cuft Inflow Hydrograph = 10 - PR-1A Total Max. Elevation = 535.18 ft Pond Name = SSBB-1 Max. Storage = 5,747 cuft Pond Routing by Storage Indication Method Center of mass detention time = 2.00 hrs Qp = 1.034 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 26 27 28 Time (hrs) PR-1A Total PR-1A Routing

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1A Routing Hyd. No. 11 Hydrograph Type = Pond Route Peak Flow = 2.246 cfs Storm Frequency = 10-yr Time to Peak = 12.28 hrs Time Interval = 1 min Hydrograph Volume = 19,163 cuft Inflow Hydrograph = 10 - PR-1A Total Max. Elevation = 535.71 ft Pond Name = SSBB-1 Max. Storage = 8,419 cuft Pond Routing by Storage Indication Method Center of mass detention time = 1.63 hrs Qp = 2.246 cfs 7 6 5 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 26 27 Time (hrs) PR-1A Total PR-1A Routing

Hydrograph Report File: Eagle Rock Proposed (Current).hys Hydrology Studio v 3.0.0.39 10-21-2025 PR-1A Routing Hyd. No. 11 Hydrograph Type = Pond Route Peak Flow = 3.069 cfs Storm Frequency = 25-yr Time to Peak = 12.27 hrs Time Interval = 1 min Hydrograph Volume = 26,002 cuft Inflow Hydrograph = 10 - PR-1A Total Max. Elevation = 536.03 ft Pond Name = SSBB-1 Max. Storage = 10,002 cuft Pond Routing by Storage Indication Method Center of mass detention time = 1.46 hrs Qp = 3.069 cfs 9 8 7 6 5 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 26 27 Time (hrs) PR-1A Total PR-1A Routing