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HomeMy WebLinkAboutWPO201300032 Calculations 2014-08-14 CASCADIA SUBDIVISION HYDROLOGIC/HYDRAULIC CALCULATIONS FOR CASCADIA SUBDIVISION - BLOCKS 4-7 April 22, 2013 Revised November 22, 2013 Revised July 22, 2014 Revised August 14, 2014 LOCATION: Tax Map 62, Parcel 25 Tax Map 78, Parcels 59 & 59A Tax Map 78E, Parcel H1 • Rio District, Albemarle County, Virginia DEVELOPER: Redus VA Housing, LLC. 170 South Pantops Drive ;791, Charlottesville, Virginia 22903 r .4 PREPARED BY: b u ER Ml HA ��. P Rs �4 Dominion Engineering & Design, LLC Li •.33023 172 South Pantops Drive �! ti_ (ti Charlottesville, VA 22911 :4,4; P: 434.979.8121 F: 434.979.1681 `SS�Oti�L 'J INDEX Summary: 2-7 Unit Hydrographs 8-9 Pre-Development: Hydrographs: DA-Pond 2 10-12 Post-Development - Pond-2: Hydrographs: DA-Pond 2 13-17 Water Quality Volume Report: 18 SWM-2 & Outlet Structure: 19-24 Routed Hydrographs: 25-30 *Drainage Area Maps are included on Storm Water Management Plan 1 CASCADIA SUBDIVISION Run-Off Summary Pond 1 Pond one is an existing extended detention stormwater management facility used to detain and treat stormwater run-off from the existing Fontana Subdivision. The pond will be left as is. The proposed, drainage area for the pond as shown on the approved Stormwater Management Report by McKee Carson is 39.03 acres with a runoff coefficient of 0.47 and generates run-off from a 10-Year storm of 83.36 cfs. The current proposed drainage area for Pond 1 is 29.24 acres with a runoff coefficient of 0.36, and generates a peak flow 29.04 cfs. Note, the overall drainage area as well as the impervious area within the drainage area has been decreased. Pond 2 Proposed Pond 2 is a wet pond facility with an aquatic bench that will provide stormwater quality and detention. Pond 2 is designed with consideration for full build out of future Town District phase. Because it has been determined that there are inadequate channels downstream, the allowable release rate is determined per Albemarle County Design Standards Manual, Section F, lowering the allowable release rate to a fraction of the pre-forested conditions run-off determined by the calculation below: Q(allowable)<=Qf(Vf/VPost), where Qf is flow from the site in a well forested condition (Cn=51), Vf is volume from the site in a well forested condition, and VPost is volume from the site in post-development conditions. In addition to meeting the above release rate requirements, the following conditions will also be met: 1. Detain the WQV(1" Runoff)and release over 48 hours. 2. Detain the 1 year 24-hour storm and release over 24 hours. 2 CASCADIA SUBDIVISION Pre-Development Conditions: 1.5 Yr. Pre-Development Run-Off(Cn=51) = DA-A= 3.16 cfs 1.5 Yr. Pre-Development Run-Off Volume=42,253 Sq. Ft. 2 Yr. Pre-Development Run-Off(Cn=51) = DA-A= 3.83 cfs 2 Yr. Pre-Development Run-Off Volume =47,045 Sq. Ft. 10 Yr. Pre-Development Run-Off(Cn=51) = DA-A= 27.83 cfs 10 Yr. Pre-Development Run-Off Volume= 172,498 Sq. Ft. Post-Development Conditions: 1.5 Yr. Post-Development Run-Off Volume= DA-X= 249,163 Sq. Ft. 2 Yr. Post-Development Run-Off Volume= DA-X= 261,796 Sq. Ft. 10 Yr. Post-Development Run-Off Volume= DA-X= 518,800 Sq. Ft. Allowable Release Rate: Q1.5 (allowable) = 3.16(42,253/249,163) = 0.536 cfs Q2 (allowable) = 3.83(47,045/261,796) = 0.688 cfs Q10 (allowable) = 27.83(172,498/518,800) = 9.253 cfs Post-Development Release Rate Summary: Q1.5 Post-Development Routed = 0.47 cfs < 0.536 cfs Q2 Post-Development Routed = 0.48 cfs < 0.688 cfs Q10 Post-Development Routed = 8.41 cfs < 9.253 cfs 3 CASCADIA SUBDIVISION Detention of the WQV(1" Runoff)and release over 48 hours: WQV= 31,323 cf. Average Flow Rate to Achieve 48 Hour Draw Down: Q = 31,323 cf. / 172,800 sec. Q = 0.179 cfs Orifice Size Needed: A= Q/[64.32 X(h/2)]^1/2 *(0.6) Average h = 1'; Q = 0.179 cfs A= 0.0526 sf. d = 2 (A/3.14)^1/2 = 0.2588 ft. => 3.106 In. Orifice provided =3.0 in. <3.106 in. Detention of the 1 year 24-hour storm and release over 24 hours: 1 year 24-hour storm volume = 224,769.6 cf. (see hydrograph below) Average Flow Rate to Achieve 24 Hour Draw Down: Q =224,769.6 cf. /86,400 sec. Q = 2.60 cfs Routed Flow for 1-year 24-hour storm= 0.45 cfs maximum < 2.60 cfs. ( Please Refer Calculations on following Pages ) 4 M CASCADIA SUBDIVISION Soils Analysis: DA-X&DA-A Soil Map Custom Soil Resource Report Soil Map Y w k k k 381735 __ 313'2 34' I j -- / _-- 1 - s; 7 7 '' n —;fi. ; CASCADIA SUBDIVISION Map Unit Legend 12C Catoctin silt loam,7 to 15 percent slopes 0.9 2.0% 12E Catoctin silt loam,25 to 45 percent 6.2 13.1% slopes 718 Rabun clay loam,2 to 7 percent slopes 6.5 13.8% 71 C Rabun day loam,7 to 15 percent slopes 9.7 20.6% 71D Rabun clay loam,15 to 25 percent slopes 8.5 18.0% 7283 Rabun clay,2 to 7 percent slopes, 0.5 1.1% severely eroded 72C3 Rabun clay,7 to 15 percent slopes, 5.0 10.5% severely eroded 72D3 Rabun day,15 to 25 percent slopes, 3.4 7-3% severely eroded 72E3 Rabun clay,25 to 45 percent slopes, 2.6 55% severely eroded 79B Starr silt loam,2 to 7 percent slopes 3.8 81% Totals for Area of Interest 47.0 100.0% Hydrologic Group B Soils: 71B 13.8% 71C 20.6% 71D 18.0% 72B3 1.1% 72C3 10.5% 72D3 7.3% 72E3 5.5% 76.8% Hydrologic Group C Soils: 12C 2.0% 12E 13.1% 79B 8.1% 23.2% Weighted Cn Values: Pavement, Buidling, Patios, Sidewalks: 98 Fair Pasture/Yards: 62 Wooded Area: 57 Gravel: 86 6 CASCADIA SUBDIVISION Cn Value Calculations: DA-Pond 2 Pre-Development For 1.5-Year, 2-Year& 10-Year Storm Calculations: Cn=51 per Albemarle County Design Standards Manual, Section F. DA-Pond 2 Post-Development(45.54 Acres): Houses(Cn=98)—4.270 Acres Lead Walks/Patios(Cn=98)—0.250 Acre Roads(Cn=98)—3.400 Acre Walks(Cn=98)-0.550 Acre Neighborhood Center/Amenities (Cn=98)—0.551 Acre Driveways(Cn=98)—1.350 Acre Proposed Yard (Cn=62)—5.893 Acre Wooded Area (Cn=57)—3.000 Acres Parks/Utility Strips(Cn=62)—1.800 Acres Future Town Phase(Cn=75)—24.476 Acres 10.371(98) +7.693(62)+24.476(75)+3.000(57) =77 45.54 7 CASCADIA SUBDIVISION Name: DA-Pond 2 - Pre-Forested Condition (Cn=51) Type: SCS Curvilinear Unit Hydrograph [UNIT HYDROGRAPH INFORMATION] Peak Flow (Qp) = 91.85 (cfs) Time to Peak (Tp) = 23.02 (min) Time of Base (Tb) = 115. 10 (min) Volume = 3.89 (ac-ft) Shape Factor = 484 .00 Time Step = 2.00 (min) Excess Rain = 1.00 (in) Storm Duration = 4.59 (min) Lag Time = 20.72 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 46. 60 51 [TIME CONCENTRATION -- TR-55] SHEET FLOW Manning's Roughness Coef. (n) = 0. 40 2-yr 24-hr Rainfall (R) = 3.70 (in) Flow Length (L) = 300.00 (ft) Land Slope (S) = 0.15 (ft/ft) Travel Time of Sheet Flow = 21.48 (min) SHALLOW FLOW K_Coefficient (K) = 0.35 Flow Length (L) = 835.00 (ft) Watercourse Slope (S) = 0.22 (ft/ft) Travel Time of Shallow Flow = 8 .48 (min) Velocity (V) = 1. 64 (ft/s) CHANNEL FLOW Hydraulic Radius (R) = 0.26 (ft) Manning's Roughness Coef. (n) = 0.03 Flow Length (L) = 1570.00 (ft) Channel Slope (S) = 0.08 (ft/ft) Travel Time of Channel Flow = 4 .57 (min) [TIME OF CONCENTRATION] Time of Concentration (Tc) = 34 .53 (min) 8 CASCADIA SUBDIVISION Name: Pond 2 - Post-Development Type: SCS Curvilinear Unit Hydrograph [UNIT HYDROGRAPH INFORMATION] Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18.17 (min) Time of Base (Tb) = 90.84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484.00 Time Step = 2.00 (min) Excess Rain = 1.00 (in) Storm Duration = 3. 62 (min) Lag Time = 16.35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- TR-55] SHEET FLOW Manning's Roughness Coef. (n) = 0. 40 2-yr 24-hr Rainfall (R) = 3.70 (in) Flow Length (L) = 300.00 (ft) Land Slope (S) = 0. 19 (ft/ft) Travel Time of Sheet Flow = 19.54 (min) SHALLOW FLOW K Coefficient (K) = 0.35 Flow Length (L) = 541.00 (ft) Watercourse Slope (S) = 0.20 (ft/ft) Travel Time of Shallow Flow = 5.76 (min) Velocity (V) = 1.57 (ft/s) CHANNEL FLOW Hydraulic Radius (R) = 0.26 (ft) Manning's Roughness Coef. (n) = 0.01 Flow Length (L) = 1545.00 (ft) Channel Slope (S) = 0.08 (ft/ft) Travel Time of Channel Flow = 1. 95 (min) [TIME OF CONCENTRATION] Time of Concentration (Tc) = 27.25 (min) 9 CASCADIA SUBDIVISION Name: DA-Pond 2 Pre-Forested 1.5-Year (Cn=51) Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 3.16 (cfs) Time to Peak (Tp) = 746.00 (min) Time of Base (Tb) = 1552.59 (min) Volume = 0. 97 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 3 Type = SCS Curvilinear Peak Flow (Qp) = 91.85 (cfs) Time to Peak (Tp) = 23.02 (min) Time of Base (Tb) = 115. 10 (min) Volume = 3.89 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 20.72 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 46. 60 51 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 34 .53 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3. 60 (in) Return Period = 1.5 (yr) Storm Duration = 24 .00 (hr) 10 CASCADIA SUBDIVISION Name: DA-Pond 2 Pre-Forested 2-Year (Cn=51) Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 3.83 (cfs) Time to Peak (Tp) = 746.00 (min) Time of Base (Tb) = 1552.59 (min) Volume = 1.08 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 3 Type = SCS Curvilinear Peak Flow (Qp) = 91. 85 (cfs) Time to Peak (Tp) = 23. 02 (min) Time of Base (Tb) = 115. 10 (min) Volume = 3.89 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 20.72 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 46.60 51 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 34 . 53 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3.70 (in) Return Period = 2 (yr) Storm Duration = 24.00 (hr) 11 CASCADIA SUBDIVISION Name: DA-Pond 2 Pre-Forested 10-Year (Cn=51) Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 27.83 (cfs) Time to Peak (Tp) = 738.00 (min) Time of Base (Tb) = 1552.59 (min) Volume = 3. 96 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 3 Type = SCS Curvilinear Peak Flow (Qp) = 91. 85 (cfs) Time to Peak (Tp) = 23.02 (min) Time of Base (Tb) = 115. 10 (min) Volume = 3.89 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 20.72 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 46.60 51 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 34 .53 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 5. 60 (in) Return Period = 10 (yr) Storm Duration = 24 .00 (hr) 12 CASCADIA SUBDIVISION Name: DA-Pond 2 Post-Development 1-Year Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 55.41 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 5. 16 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18.17 (min) Time of Base (Tb) = 90.84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 16.35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 27.25 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3.40 (in) Return Period = 1 (yr) Storm Duration = 24 .00 (hr) 13 CASCADIA SUBDIVISION Name: DA-Pond 2 Post-Development 1.5-Year Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 61.86 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 5.72 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18. 17 (min) Time of Base (Tb) = 90.84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484.00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 16.35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 27.25 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3. 60 (in) Return Period = 1.5 (yr) Storm Duration = 24 . 00 (hr) 14 CASCADIA SUBDIVISION Name: DA-Pond 2 Post-Development 2-Year Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 65.13 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 6.01 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1. 00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18 .17 (min) Time of Base (Tb) = 90.84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 16.35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 27 .25 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3.70 (in) Return Period = 2 (yr) Storm Duration = 24 . 00 (hr) 15 . b CASCADIA SUBDIVISION Name: DA-Pond 2 Post-Development 10-Year Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 131.26 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 11. 91 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18.17 (min) Time of Base (Tb) = 90.84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 16. 35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 27 .25 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 5. 60 (in) Return Period = 10 (yr) Storm Duration = 24 .00 (hr) 16 CASCADIA SUBDIVISION Name: DA-Pond 2 Post-Development 100-Year Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 261.96 (cfs) Time to Peak (Tp) = 728.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 23. 92 (ac-ft) Time Step = 2.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 113.73 (cfs) Time to Peak (Tp) = 18. 17 (min) Time of Base (Tb) = 90. 84 (min) Volume = 3.80 (ac-ft) Shape Factor = 484 .00 Time Step: = 2.00 (min) Excess Rain = 1.00 (in) Lag Time = 16.35 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN Overall Approximation 45.54 77 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 27 .25 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 9. 10 (in) Return Period = 2 (yr) Storm Duration = 24 .00 (hr) 17 1 CASCADIA SUBDIVISION RESERVOIR REPORT Name: Pond 2 (Retention Basin w/Aquatic Bench) ( WATER QUALITY VOLUME REPORT ) Name: Pond 2 - Storage [RATING CURVE LIMIT] Minimum Elevation = 345.00 (ft) Maximum Elevation = 358.00 (ft) Elevation Increment = 0.20 (ft) [STAGE STORAGE INFORMATION] Storage Method: User-Defined Storage Input Method: Area Number Elevation Area Ave Area Volume Cumulative Volume (ft) (sq ft) (sq ft) (cu ft) (cu ft) 1 344 . 99 0.00 0.00 0.00 0.00 2 345.00 28234.00 14117.00 141. 17 141.17 3 346.00 30604 .00 29419.00 29419.00 29560.17 4 348.00 35380.00 32992.00 65984 .00 95544. 17 5 348.50 39242.00 37311.00 18655.50 114199. 67 6 350.00 50655.00 44948.50 67422.75 181622.42 7 352.00 56835.00 53745.00 107490.00 289112.42 8 354 .00 60195.00 58515.00 117030.00 406142.42 9 356.00 64854.00 62524.50 125049.00 531191. 42 10 358.00 69602.00 67228.00 134456. 00 665647.42 11 358.33 76850. 00 73226.00 24164 .58 689812.00 Quality Volume Required = 4X(WQ Volume) For 65% Removal Efficiency WQ Volume = (1/2in) /12 X impervious area (Sq. Ft. ) (4) (1/2in) /12 X 451, 761 Sq. Ft. + 300, 000 Sq Ft. (Future Impervious Area) = 125,293.5 Cu. Ft. Provided Water Quality Volume (Elev.=351) = 181,622.42 cu. Ft. Pool Depth Zones: Depth Zone Elevation Surface Area Percentage of Wet Storage Area 0' - 1.5' 350.00 - 348.50 11,413 sf. 22.5% 1.5' - 2' 348.50 - 348.00 3,862 sf. 7.6% 2' - 6' 348.00 - 345.00 35,380 sf. 69.9% (Please Refer to Water Quality Calc. on Stormwater Management Plan) 18 o. u CASCADIA SUBDIVISION .. RESERVOIR REPORT Reservoir Number: 2 Name: Pond 2 [RATING CURVE LIMIT] Minimum Elevation = 344 . 50 (ft) Maximum Elevation = 358.33 (ft) Elevation Increment = 0.20 (ft) [STAGE STORAGE INFORMATION] Storage Method: User-Defined Storage Input Method: Area Number Elevation Area Ave Area Volume Cumulative Volume (ft) (sq ft) (sq ft) (cu ft) (cu ft) 1 349. 99 0.00 0.00 0.00 0.00 2 350.00 50655.00 25327.50 253.27 253.27 3 352.00 56835.00 53745.00 107490.00 107743.27 4 354 .00 60195.00 58515.00 117030.00 224773.27 5 356.00 64854 . 00 62524 .50 125049.00 349822.27 6 358. 00 69602. 00 67228.00 134456. 00 484278.27 7 358.33 71427.00 70514 .50 23269.78 507548.06 [RESERVOIR STAGE STORAGE/DISCHARGE] Elevation Stage Area Storage Discharge (ft) (ft) (sq ft) (cu ft) (cfs) 349. 90 5.40 0.00 0.00 0.00 350. 10 5. 60 50964 .00 5096. 40 0.02 350.30 5.80 51582.00 15351.00 0. 10 350.50 6. 00 52200.00 25729.20 0.14 350.70 6.20 52818.00 36231.00 0.18 350. 90 6.40 53436.00 46856. 40 0.21 351. 10 6. 60 54054 .00 57605. 40 0.23 351.30 6.80 54672.00 68478. 00 0.26 351.50 7.00 55290.00 79474 .20 0.28 351.70 7.20 55908.00 90594 .00 0.30 351. 90 7.40 56526.00 101837.40 0.31 352. 10 7. 60 57003.00 113190.30 0.33 352.30 7.80 57339.00 124624.50 0.35 352.50 8.00 57675.00 136125. 90 0.36 352.70 8.20 58011.00 147694 .50 0.38 352. 90 8.40 58347.00 159330.30 0.39 353.10 8. 60 58683.00 171033.30 0.41 353.30 8.80 59019.00 182803.50 0.42 353.50 9.00 59355.00 194640.90 0.43 353.70 9.20 59691.00 206545.50 0.45 353. 90 9.40 60027.00 218517.30 0.46 354 .10 9. 60 60427. 95 230562.79 0.47 354 .30 9.80 60893.85 242694 . 97 0. 48 354 .50 10.00 61359.75 254920.33 0.55 19 . CASCADIA SUBDIVISION 354 .70 10.20 61825. 65 267238.87 0.96 354 . 90 10.40 62291.55 279650.59 1.46 355. 10 10. 60 62757.45 292155.49 1.79 355.30 10.80 63223.35 304753.57 2.06 355.50 11.00 63689.25 317444 .83 2.29 355.70 11.20 64155.15 330229.27 2.49 355. 90 11.40 64621.05 343106.89 7.36 356. 10 11.60 65091.40 356078.14 16.09 356.30 11.80 65566.20 369143. 90 32.33 356.50 12.00 66041.00 382304 . 62 55.40 356.70 12.20 66515.80 395560.30 84 .03 356. 90 12.40 66990.60 408910. 94 117.83 357. 10 12. 60 67465.40 422356.54 142.00 357.30 12.80 67940.20 435897 . 10 167.11 357.50 13.00 68415.00 449532. 62 195.83 357.70 13.20 68889.80 463263.10 228.22 357. 90 13.40 69364 . 60 477088.54 264.35 358.10 13. 60 70155.03 491040.50 304.30 358 .30 13.80 71261.09 505182.12 348.14 Maximum Storage = 507322.44 (cu ft) Maximum Discharge = 355.06 (cfs) 20 CASCADIA SUBDIVISION OUTLET STRUCTURE REPORT Structure Number : 1 Type : Stand Pipe Name : STAND PIPE [RATING CURVE LIMIT] Minimum Elevation = 344 .50 (ft) Maximum Elevation = 358.33 (ft) Elevation Increment = 0.20 (ft) [STAND PIPE INFORMATION] [ORIFICE INFORMATION] Diameter = 5.00 (ft) Crest Length = 15.71 (ft) Effective Crest Length = 15.71 (ft) Orifice Coefficient = 0. 60 Fractional Open Area = 1.00 [ORIFICE EQUATION] Q = Co*A( (2gh) /k) ^0.5 [DEFINITIONS] Co = Orifice Coefficient A = Wetted Area, (sq ft) [WEIR INFORMATION] Crest Elevation = 355.70 (ft) Weir Coefficient = 3.33 Exponential = 1.50 [WEIR EQUATION] Q = Cw * L * H^exp [DEFINITIONS] Cw = Weir Coefficient H = Headwater depth above inlet control section invert ft L = Crest lenght ft [OPTIONAL ORIFICE INFORMATION] Type : Circular Orifice [OPTIONAL ORIFICE INFORMATION] Diameter = 0.25 (ft) Invert Elevation = 350.00 (ft) Orifice Coefficient = 0. 60 Number of Openings = 1 [ORIFICE EQUATION] Q = Co*A( (2gh) /k) ^0.5 21 • CASCADIA SUBDIVISION [DEFINITIONS] Co = Orifice Coefficient A = Wetted Area, (cfs) k = 1 Structure Number : 2 Type : Circular Orifice [OPTIONAL ORIFICE INFORMATION] Diameter = 0.50 (ft) Invert Elevation = 354 .40 (ft) Orifice Coefficient = 0. 60 Number of Openings = 2 [ORIFICE EQUATION] Q = Co*A( (2gh) /k) ^0.5 [DEFINITIONS] Co = Orifice Coefficient A = Wetted Area, (cfs) k = 1 [CULVERT INFORMATION] Type : Circular Concrete - Square Edge with Headwall [OUTLET STRUCTURE INFORMATION] Diameter = 30.00 (in) Invert Elevation = 346.00 (ft) Pipe Length = 75. 00 (ft) Slope = 0.02 Manning's n Value = 0. 01 Orifice Coefficient = 0. 60 Tailwater Elevation = 344 .58 (ft) Number of Barrels = 1 [UNSUBMERGED EQUATION] H/Diam = Hc/Diam+K* (Q/ (A*Diam^0.5) ) ^M-0.5*S Coefficient K = 0.01 Coefficient M = 2.00 Q Maximum = 27 . 16 [SUBMERGED EQUATION] H/Diam = c* (Q/ (A*Diam^0.5) ) ^2+Y-0.5*S Coefficient c = 0.04 Coefficient Y = 0. 67 Q Minimum = 31.05 [DEFINITIONS] H = Headwater depth above inlet control section invert, (ft) Diam = Interior height of culvert barrel, (ft) He = Specific head at critical depth (dc+Vc^2/2g) , (ft) Q = Discharge, (cfs) A = Full cross sectional area of culvert barrel, (sq ft) S = Culvert barrel slope, (ft/ft) 22 . ° . CASCADIA SUBDIVISION [STAND PIPE STAGE VS. DISCHARGE] Elevation Stage Weirs Orifices Stand Pipe Culvert Total (ft) (ft) (cfs) (cfs) (cfs) (cfs) (cfs) 349. 90 5.40 0'00 0.00 0.00 36.88 0.00 350'10 5. 60 0'00 0.02 0'00 38. 48 0.02 350.30 5.80 0.00 0. I0 0.00 40.03 0.10 350.50 6.00 0'00 0. 14 0.00 41.5I 0. 14 350.70 6.20 0.00 0. 18 0.00 42' 95 0. 18 350' 90 6.40 0.00 0.21 0.00 44 .33 0.21 351' 10 6'60 0.00 0.23 0.00 45. 68 0'23 351.30 6.80 0.00 0.26 0.00 46. 98 0'26 351'50 7.00 0,00 0,28 0.00 48.26 0.28 351'70 7.20 0.00 0.30 0.00 49. 50 0.30 351. 90 7.40 0'00 0.31 0.00 50.70 0.31 352'I0 7'60 0.00 0.33 0'00 51.88 0.33 352'30 7,80 0.00 0.35 0.00 53'04 0.35 352.50 8'08 0.00 0.36 0,00 54 , 17 0.36 352.70 8.20 0'00 0.38 0'00 55.27 0.38 352. 90 8. 40 0'00 0.39 0,00 56.36 0.39 353. 10 8'60 0,00 0.41 0.00 57.42 0.41 353.30 8.80 0.00 0.42 0.00 58.47 0.42 353.50 9.00 0.00 0. 43 0.00 59.49 0.43 353.70 9.20 0.00 0.45 0.00 60.50 0.45 353' 90 9.40 0.00 0. 46 0'00 61.50 0'46 354 ' I0 9. 60 0'00 0.47 0'00 62. 47 0'47 354 '30 9.80 0,00 0. 48 0.00 63. 43 0.48 354.50 10'00 0'00 0. 55 0.00 64 .38 0.55 354 '70 10,20 0.21 0.96 0'00 65'31 0.96 354 ' 90 10,40 1.09 1.46 0.00 66.24 1'46 355' I0 10.60 2.35 1.79 0'00 67. 14 1.79 355.30 10.80 3. 90 2. 06 0.00 68'04 2'06 355.50 11'00 5. 69 2.29 0.00 68. 92 2.29 355.70 11.20 7. 68 2.49 0.00 69. 80 2.49 355. 90 11'40 9.87 2. 68 4 . 68 70. 66 7. 36 356'10 11. 60 12.24 2. 85 13.23 71. 51 I6.09 356'30 11 '80 14 .76 3.01 24 .31 72. 35 27.33 356'50 12'00 17.44 3. 17 37.43 73' 18 40. 60 356'70 12'20 20.27 3.31 52.31 74 ,01 55. 62 356. 90 12.40 23.23 3.45 68.76 74 .82 72.21 357' 10 12'60 26.33 3.58 86'65 75. 62 75. 62 357'30 12'80 29.55 3.71 101.22 76.42 76.42 357'50 13'00 32.89 3.83 114 .58 77'21 77.21 357.70 13'20 36.35 3. 95 127. 94 77. 99 77.99 357. 90 15'40 39. 93 4 .07 140.17 78.76 78.76 358'10 13' 60 41'75 4 .18 146.40 79.53 79.53 358. 30 13'80 0.00 4.29 152.38 80.28 80.28 358.33 13.83 0.00 4 .30 155.26 80. 40 80. 40 23 . CASCADIA SUBDIVISION OUTLET STRUCTURE REPORT Type : Trapezoidal Weir Name : Weir [RATING CURVE LIMIT] Minimum Elevation = 356.00 (ft) Maximum Elevation = 358.33 (ft) Elevation Increment = 0. 10 (ft) [OUTLET STRUCTURE INFORMATION] Crest Length = 16.00 (ft) Angle of Walls = 157.0000 Crest Elevation = 356. 10 (ft) Weir Coefficient = 3.33 Exponential = 1.50 [TRAPEZOIDAL EQUATION] Q = Cw * ( L + 0.8H * tan ( ang/2.0 ) ) * H^exp [DEFINITIONS] Cw = Weir Coefficient H = Headwater depth above inlet control section invert L = Crest lenght ang = Angle of the walls [MAXIMUM DISCHARGE] Q = 274 . 67 (cfs) [WEIR STAGE VS. DISCHARGE] Elevation (ft) Stage (ft) Discharge (cfs) 356.10 0.10 0.00 356.20 0.20 1.73 356.30 0.30 5.00 356.40 0.40 9.40 356.50 0.50 14.80 356.60 0.60 21.15 356.70 0.70 28.41 356.80 0.80 36.57 356.90 0.90 45.62 357.00 1.00 55.55 357. 10 1.10 66.37 357.20 1.20 78.09 357.30 1.30 90.69 357.40 1.40 104.20 357.50 1.50 118.62 357.60 1.60 133.96 357.70 1.70 150.23 357.80 1.80 167.44 357.90 1.90 185.59 358.00 2.00 204.69 358.10 2.10 224.77 358.20 2.20 245.82 358.30 2.30 267.86 358.33 2.33 274.67 24 f `■ CASCADIA SUBDIVISION Name: Routing - Pond 2 1-Year Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 0.45 (cfs) Time to Peak (Tp) = 1462.00 (min) Time of Base (Tb) = 2880.00 (min) Volume = 1.25 (ac-ft) Time Step = 2.00 (min) Peak Elevation = 353. 69 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 2 Name = Pond 2 Storage Type = User-Defined Area Maximum Storage = 507322.44 (cu ft) Maximum Discharge = 355.06 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 21 Name = Pond 2 Post 1-Year Peak Flow (Qp) = 55.41 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529. 85 (min) Volume = 5. 16 (ac-ft) Flow Multiplier = 1.00 25 0. CASCADIA SUBDIVISION Name: Routing - Pond 2 1.5-Year Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 0.47 (cfs) Time to Peak (Tp) = 1464 .00 (min) Time of Base (Tb) = 2880.00 (min) Volume = 1.32 (ac-ft) Time Step = 2.00 (min) Peak Elevation = 354 .09 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 2 Name = Pond 2 Storage Type = User-Defined Area Maximum Storage = 507322.44 (cu ft) Maximum Discharge = 355.06 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 4 Name = Pond 2 Post 1.5-Year Peak Flow (Qp) = 61.86 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 5.72 (ac-ft) Flow Multiplier = 1.00 26 �n CASCADIA SUBDIVISION Name: Routing - Pond 2 2-Year Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 0.48 (cfs) Time to Peak (Tp) = 1464 .00 (min) Time of Base (Tb) = 2880.00 (min) Volume = 1.36 (ac-ft) Time Step = 2.00 (min) Peak Elevation = 354 .28 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 2 Name = Pond 2 Storage Type = User-Defined Area Maximum Storage = 507322.44 (cu ft) Maximum Discharge = 355.06 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 5 Name = Pond 2 Post 2-Year Peak Flow (Qp) = 65. 13 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 6.01 (ac-ft) Flow Multiplier = 1.00 27 04, CASCADIA SUBDIVISION Name: Routing - Pond 2 10-Year Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 8.41 (cfs) Time to Peak (Tp) = 854 .00 (min) Time of Base (Tb) = 2880.00 (min) Volume = 6.44 (ac-ft) Time Step = 2.00 (min) Peak Elevation = 355.92 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 2 Name = Pond 2 Storage Type = User-Defined Area Maximum Storage = 507322. 44 (cu ft) Maximum Discharge = 355.06 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 6 Name = Pond 2 Post 10-Year Peak Flow (Qp) = 131.26 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1529. 85 (min) Volume = 11. 91 (ac-ft) Flow Multiplier = 1.00 28 CASCADIA SUBDIVISION Name: Routing - Pond 2 100-Year Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 158. 91 (cfs) Time to Peak (Tp) = 742.00 (min) Time of Base (Tb) = 2880.00 (min) Volume = 18.44 (ac-ft) Time Step = 2.00 (min) Peak Elevation = 357.23 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 2 Name = Pond 2 Storage Type = User-Defined Area Maximum Storage = 507322.44 (cu ft) Maximum Discharge = 355.06 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 7 Name = Pond 2 Post 100-Year Peak Flow (Qp) = 261. 96 (cfs) Time to Peak (Tp) = 728 .00 (min) Time of Base (Tb) = 1529.85 (min) Volume = 23. 92 (ac-ft) Flow Multiplier = 1.00 29