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HomeMy WebLinkAboutWPO201100101 Calculations 2011-11-30 Hollymead Towncenter Area Al SWM #3 CALCULATIONS (TR -55) FOR HOLLYMEAD TOWNCENTER AREA Al December 22, 2008 Revised August 5, 2011 Revised August 17, 2011 Revised November 30, 2011 LOCATION: Albemarle County, Virginia Tax Map 32, Parcels 42A & 44 Tax Map 46, Parcel 5 PREPARED BY: Dominion Engineering & Design 172 South Pantops Drive Charlottesville, VA 22911 P: 434.979.8121 F: 434.979.1681 Hollymead Towncenter Area Al SUMMARY INFORMATOIN Drainage Area = 53.38 acres Stormwater Management Summary Predevelopment CN = 65 Time of Concentration = 45 minutes 2 -year peak flow = 24.91 cfs 10 -year peak flow - 55.30 cfs Postdevelopment CN postdevelopment = 90 Time of Concentration = 30 minutes 2 -year peak inflow = 121.09 cfs 2 -year peak outflow = 24.07 cfs < 24.91 cfs OK 10 -year peak inflow = 200.78 cfs 10 -year peak release rate = 54.10 cfs < 55.30 cfs OK Water Quality Summary Impervious Area being treated = 1,846,794 sf (see sheet C7 for breakdown) WQV = 0.5 inch per impervious acre = 76,950 cf 4 x WQV required for Type III retention basin facility = 307,799 cf Water Quality Volume provided = 308,522 cf > 307,799 cf OK Hollymead Towncenter Area Al Name: 2 -yr pre Type: Computed Flood [ HYDROGRAPH INFORMATION] Peak Flow (Qp) (allowable release rate) = 24.91 (cfs Time to Peak (Tp) = 745.00 (min) Time of Base (Tb) = 1586.40 (min) Volume = 3.77 (ac -ft) Time Step = 1.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 80.74 (cfs) Time to Peak (Tp) = 30.00 (min) Time of Base (Tb) = 150.00 (min) Volume = 4.46 (ac -ft) Shape Factor = 484.00 Time Step: = 1.00 (min) Excess Rain = 1.00 (in) Lag Time = 27.00 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN <None> Overall Approximation 53.38 65 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 45.00 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3.70 (in) Return Period = 2 (yr) Storm Duration = 24.00 (hr) Hollymead Towncenter Area Al Name: 10 -yr pre Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) (allowable release rate) = 55.30 (cfs) Time to Peak (Tp) = 740.00 (min) Time of Base (Tb) = 1586.40 (min) Volume = 7.32 (ac -ft) Time Step = 1.00 (min) Flow Multiplier = 0.81 [UNIT HYDROGRAPH INFORMATION] Number = 1 Type = SCS Curvilinear Peak Flow (Qp) = 80.74 (cfs) Time to Peak (Tp) = 30.00 (min) Time of Base (Tb) = 150.00 (min) Volume = 4.46 (ac -ft) Shape Factor = 484.00 Time Step: = 1.00 (min) Excess Rain = 1.00 (in) Lag Time = 27.00 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN <None> Overall Approximation 53.38 65 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 45.00 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 5.60 (in) Return Period = User Defined (yr) Storm Duration = 24.00 (hr) Hollymead Towncenter Area Al Name: 2 -YR POST Type: Computed Flood [ HYDROGRAPH INFORMATION] Peak Flow (Qp) = 121.09 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 11.68 (ac -ft) Time Step = 1.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 2 Type = SCS Curvilinear Peak Flow (Qp) = 121.11 (cfs) Time to Peak (Tp) = 20.00 (min) Time of Base (Tb) = 100.00 (min) Volume = 4.46 (ac -ft) Shape Factor = 484.00 Time Step: = 1.00 (min) Excess Rain = 1.00 (in) Lag Time = 18.00 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN <None> Overall Approximation 53.38 90 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 30.00 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 3.70 (in) Return Period = 2 (yr) Storm Duration = 24.00 (hr) Hoilymead Towncenter Area Al Name: 10 -YR POST Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 200.78 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 19.76 (ac -ft) Time Step = 1.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 2 Type = SCS Curvilinear Peak Flow (Qp) = 121.11 (cfs) Time to Peak (Tp) = 20.00 (min) Time of Base (Tb) = 100.00 (min) Volume = 4.46 (ac -ft) Shape Factor = 484.00 Time Step: = 1.00 (min) Excess Rain = 1.00 (in) Lag Time = 18.00 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN <None> Overall Approximation 53.38 90 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 30.00 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 5.60 (in) Return Period = User Defined (yr) Storm Duration = 24.00 (hr) Hollymead Towncenter Area Al Name: 100 -YP POST Type: Computed Flood [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 345.70 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 34.99 (ac -ft) Time Step = 1.00 (min) Flow Multiplier = 1.00 [UNIT HYDROGRAPH INFORMATION] Number = 2 Type = SCS Curvilinear Peak Flow (Qp) = 121.11 (cfs) Time to Peak (Tp) = 20.00 (min) Time of Base (Tb) = 100.00 (min) Volume = 4.46 (ac -ft) Shape Factor = 484.00 Time Step: = 1.00 (min) Excess Rain = 1.00 (in) Lag Time = 18.00 (min) [BASIN INFORMATION] [WEIGHTED WATERSHED AREA] Description Area CN <None> Overall Approximation 53.38 90 [TIME CONCENTRATION -- User Defined] Time of Concentration (Tc) = 30.00 (min) [RAINFALL DESCRIPTION] Distribution Type = SCS II Total Precipitation = 9.10 (in) Return Period = 100 (yr) Storm Duration = 24.00 (hr) Hollymead Towncenter Area Al RESERVOIR REPORT Name: SWM #3 - STORAGE (WATER QUALITY VOLUME REPORT) [RATING CURVE LIMIT] Minimum Elevation = 472.00 (ft) Maximum Elevation = 488.00 (ft) Elevation Increment = 0.50 (ft) [STAGE STORAGE INFORMATION] Storage Method: User - Defined Storage Input Method: Area [RESERVOIR STAGE STORAGE] Elevation Stage Area Storage (ft) (ft) (sq ft) (cu ft) 472.00 0.00 0.00 0.00 472.50 0.50 26346.17 6586.54 473.00 1.00 27245.33 19984.42 473.50 1.50 28144.50 33831.87 474.00 2.00 29043.67 48128.92 474.50 2.50 29942.83 62875.54 475.00 3.00 30842.00 78071.75 475.50 3.50 40075.56 95801.14 476.00 4.00 41375.00 116163.78 476.50 4.50 42665.00 137173.78 477.00 5.00 43955.00 158828.78 477.50 5.50 45245.00 181128.78 478.00 6.00 46535.00 204073.78 478.50 6.50 47854.44 227671.14 479.00 7.00 49812.40 252087.85 479.50 7.50 54324.40 278122.05 479.90 7.90 57934.00 308521.83 480.00 8.00 58301.00 314433.59 480.50 8.50 59467.75 335720.59 481.00 9.00 60634.50 365746.15 481.50 9.50 61801.25 396355.09 482.00 10.00 62968.00 427547.40 482.50 10.50 64510.75 459417.09 483.00 11.00 66053.50 492058.15 483.50 11.50 67596.25 525470.59 484.00 12.00 69139.00 559654.40 484.50 12.50 70517.50 594568.53 485.00 13.00 71896.00 630171.90 485.50 13.50 73274.50 666464.53 486.00 14.00 74653.00 703446.40 486.50 14.50 76197.50 741159.03 487.00 15.00 77742.00 779643.90 487.50 15.50 79286.50 818901.03 488.00 16.00 80831.00 858930.40 Hollymead Towncenter Area Al Maximum Storage = 858930.40 (cu ft) Maximum Discharge == 0.00 (cfs) Quality Volume Required = 4 X (WQ Volume) WQ Volume = (1 /2in) / 12 X impervious area (Sq. Ft.) (1 /2in) / 12 X 1,846,794 Sq. Ft. = 76,950.75 Cu. Ft. 4 X WQ Volume = 307,799 Cu. Ft. Provided Water Quality Volume = 308,522 Hollymead Towncenter Area Al RESERVOIR REPORT Name: SWM #3 [RATING CURVE LIMIT] Minimum Elevation = 472.00 (ft) Maximum Elevation = 488.00 (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) 1 479.89 0.00 0.00 0.00 0.00 2 479.90 57934.00 28967.00 289.67 289.67 3 482.00 62968.00 60451.00 126947.10 127236.77 4 484.00 69139.00 66053.50 132107.00 259343.77 5 486.00 74653.00 71896.00 143792.00 403135.77 6 488.00 80831.00 77742.00 155484.00 558619.77 [DISCHARGE INFORMATION] Structure Number: 1 Type: Name: Stand Pipe Structure Number: 2 Type: Trapezoidal Weir Name: Emergency Spillway [RESERVOIR STAGE STORAGE /DISCHARGE] Elevation Stage Area Storage Discharge (ft) (ft) (sq ft) (cu ft) (cfs) 479.80 7.80 0.00 0.00 0.00 480.00 8.00 58173.71 5817.37 C.22 480.20 8.20 58653.14 17500.06 1.12 480.40 8.40 59132.57 29278.63 2.41 480.60 8.60 59612.00 41153.09 3.99 480.80 8.80 60091.43 53123.43 5.81 481.00 9.00 60570.86 65189.66 7.85 481.20 9.20 61050.29 77351.77 10.09 481.40 9.40 61529.71 89609.77 12.15 481.60 9.60 62009.14 101963.66 13.60 481.80 9.80 62488.57 114413.43 14.91 482.00 10.00 62968.00 126959.09 16.12 482.20 10.20 63585.10 139614.40 17.24 482.40 10.40 64202.20 152393.13 18.29 482.60 10.60 64819.30 165295.28 19.28 Hollymead Towncenter Area Al 482.80 10.80 65436.40 178320.85 20.23 483.00 11.00 66053.50 191469.84 21.13 483.20 11.20 66670.60 204742.25 22.00 483.40 11.40 672.87.70 218138.08 22.83 483.60 11.60 67904.80 231657.33 23.64 483.80 11.80 68521.90 245300.00 24.41 484.00 12.00 69139.00 259066.09 25.17 484.20 12.20 69690.40 272949.03 25.90 484.40 12.40 70241.80 286942.25 26.61 484.60 12.60 70793.20 301045.75 27.30 484.80 12.80 71344.60 315259.53 27.98 485.00 13.00 71896.00 329583.59 28.64 485.20 13.20 72447.40 344017.93 29.28 485.40 13.40 72998.80 358562.55 29.92 485.60 13.60 73550.20 373217.45 34.18 485.80 13.80 74101.60 387982.63 44.14 486.00 14.00 74653.00 402858.09 58.54 486.20 14.20 75270.80 417850.47 86.76 486.40 14.40 75888.60 432966.41 124.69 486.60 14.60 76506.40 448205.91 170.49 486.80 14.80 77124.20 463568.97 223.37 487.00 15.00 77742.00 479055.59 282.87 487.20 15.20 78359.80 494665.77 348.12 487.40 15.40 78977.60 510399.51 412.06 487.60 15.60 79595.40 526256.81 480.66 487.80 15.80 80213.20 542237.67 549.08 488.00 16.00 80831.00 558342.09 610.55 Maximum Storage = 558342.09 (cu ft) Maximum Discharge = 610.55 (cfs) Hollymead Towncenter Area Al Type : Stand Pipe Name : Stand Pipe [RATING CURVE LIMIT] Minimum Elevation = 472.00 (ft) Maximum Elevation = 488.00 (ft) Elevation Increment = 0.50 (ft) [STAND PIPE INFORMATION] [ORIFICE INFORMATION] Diameter = 6.00 (ft) Crest Length = 18.85 (ft) Effective Crest Length = 18.85 (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 = 485.45 (ft) Weir Coefficient = 3.33 Exponential = 1.50 [OPTIONAL WEIR INFORMATION] Type : Rectangular Weir Suppressed [WEIR INFORMATION] Crest Length = 2.00 (ft) Crest Elevation = 484.60 (ft) Weir Coefficient = 3.33 Exponential = 1.50 [OPTIONAL ORIFICE INFORMATION] Structure Number : 1 Type : Rectangular Orifice [OPTIONAL ORIFICE INFORMATION] Height = 1.42 (ft) Width = 2.00 (ft) Invert Elevation = 479.90 (ft) Orifice Coefficient = 0.60 Number of Openings = 1 Hollymead Towncenter Area Al [CULVERT INFORMATION] Type : Circular Concrete - Square Edge with Headwall [OUTLET STRUCTURE INFORMATION] Diameter = 48.00 ;in) Invert Elevation = 472.00 (ft) Pipe Length = 92.00 (ft) Slope = 0.07 Manning's n Value = 0.01 Orifice Coefficient = 0.60 Tailwater Elevation = 466.00 (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 = 87.96 [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 = 100.53 [DEFINITIONS] H = Headwater depth above inlet control section invert, (ft) Diam - Interior height of culvert barrel, (ft) He = Specifjc 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) [STAND PIPE STAGE VS. DISCHARGE] Elevation Stage Weirs Orifices Stand Pipe Culvert Total (ft) (ft) (cfs) (cfs) (cfs) (cfs) (cfs) 479.50 7.50 0.00 0.00 0.00 140.15 0.00 480.00 8.00 0.00 0.22 0.00 147.06 0.22 480.50 8.50 0.00 3.16 0.00 153.65 3.16 481.00 9.00 0.00 7.85 0.00 159.98 7.85 481.50 9.50 0.00 12.90 0.00 166.06 12.90 482.00 10.00 0.00 16.12 0.00 171.93 16.12 482.50 10.50 0.00 18.79 0.00 177.61 18.79 483.00 11.00 0.00 21.13 0.00 183.11 21.13 483.50 11.50 0.00 23.24 0.00 188.45 23.24 484.00 12.00 1.09 25.17 0.00 193.64 25.17 484.50 12.50 4.77 26.96 0.00 198.70 26.96 485.00 13.00 9.87 28.64 0.00 203.63 28.64 485.50 13.50 16.08 30.23 0.70 208.44 30.93 486.00 14.00 23.23 31.73 25.60 213.15 57.34 486.50 14.50 31.20 33.17 67.54 217.75 100.71 487.00 15.00 32.04 34.55 121.13 222.26 155.68 487.50 15.50 0.00 35.88 171.10 226.68 206.98 488.00 16.00 0.00 37.16 215.46 231.01 231.01 Hollymead Towncenter Area Al Type : Trapezoidal Weir Name : Emergency Spillway [RATING CURVE LIMIT] Minimum Elevation = 485.95 (ft) Maximum Elevation = 488.00 (ft) Elevation Increment = 0.10 (ft) [OUTLET STRUCTURE INFORMATION] Crest Length = 32.00 (ft) Angle of Walls = 153.0000 Crest Elevation = 485.95 (ft) Weir Coefficient = 3.33 Exponential = 1.50 [MAXIMUM DISCHARGE] 4 = 379.54 (cfs) [WEIR STAGE VS. DISCHARGE] Elevation (ft) Stage (ft) Discharge (cfs) 485.95 0.00 0.00 - - -- -- - - - - -- 486.05 0.10 3.40 486.15 0.20 9.73 486.25 0.30 18.06 486.35 0.40 28.08 486.45 0.50 39.64 486.55 0.60 52.62 486.65 0.70 66.96 486.75 0.80 82.60 486.85 0.90 99.51 486.95 1.00 117.66 487.05 1.10 137.02 487.15 1.20 157.58 487.25 1.30 179.33 487.35 1.40 202.25 487.45 1.50 22.6.34 487.55 1.60 251.59 487.65 1.70 278.01 487.75 1.80 305.57 487.85 1.90 334.29 487.95 2.00 364.17 488.00 2.05 379.54 Hollymead Towncenter Area Al Name: 2 -YR RTD Type: Reservoir: Modified Puts [HYDROGRAPH INFORMATION] Peak Flow (Qp) = 24.07 (cfs) Time to Peak (Tp) = 771.00 (min) Time of Base (Tb) = 1440.00 (min) Volume = 10.98 (ac -ft) Time Step = 1.00 (min) Peak Elevation = 483.71 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 3 Name = SWM #3 - REVISED Storage Type = User - Defined Area Maximum Storage = 558342.09 (cu ft) Maximum Discharge = 610.55 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 5 Name = 2 -YR POST Peak Flow (Qp) = 121.09 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 11.68 (ac -ft( Flow Multiplier = 1.00 Hollymead Towncenter Area Al Name: 10 -YR RTD Type: Reservoir: Modified Puls [ HYDROGRAPH INFORMATION] Peak Flow (Qp) = 54.10 (cfs) Time to Peak (Tp) = 762.00 (min) Time of Base (Tb) = 1440.00 (min) Volume = 18.81 (ac -ft) Time Step = 1.00 (min) Peak Elevation = 485.94 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 3 Name = SWM #3 - REVISED Storage Type = User - Defined Area Maximum Storage = 558342.09 (cu ft) Maximum Discharge = 610.55 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 6 Name = 10 -YR POST Peak Flow (Qp) = 200.78 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 19.76 (ac -ft) Flow Multiplier. = 1.00 Hollymead Towncenter Area Al Name: 100 -YR RTD Type: Reservoir: Modified Puls [HYDROGRAPH INFORMATION] Peak Flow (Qp) 274.54 (cfs) Time to Peak (Tp) = 739.00 (min) Time of Base (Tb) = 1440.00 (min) Volume = 33.66 (ac -ft) Time Step = 1.00 (min) Peak Elevation = 486.97 (ft) Detention Time = NA [RESERVOIR STRUCTURE INFORMATION] Number = 3 Name = SWM #3 - REVISED Storage Type = User- Defined Area Maximum Storage = 558342.09 (co ft) Maximum Discharge = 610.55 (cfs) [INFLOW HYDROGRAPH INFORMATION] Number = 8 Name = 100 -YR POST Peak Flow (Qp) = 345.70 (cfs) Time to Peak (Tp) = 730.00 (min) Time of Base (Tb) = 1536.40 (min) Volume = 34.99 (ac -ft) Flow Multiplier = 1.00