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HomeMy WebLinkAboutWPO201000068 Calculations 2015-08-03 HOLLYMEAD TOWN CENTER STORMWATER MANAGEMENT CALCULATIONS PACKET Date of Calculations AUGUST 3, 2015 PREPARED BY: COLLINS ' NGINEERING 200 GARRETT STREET, SUITE K CHARLOTTESVILLE, VA 22902 434.293.3719 PH 434.293.2813 FX www.collins-engineering.com SCS TR-55 Calculations U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 2:Runoff Curve Number and Runoff Project: WPO Amendment for SWM Facilities Designed By: FGM,PE Date: 8/3/2015 Location: Hollymead Town Center Checked By:SRC,PE Date: 8/3/2015 Check One: Present X DevcX 1.Runoff curve Number(CN) Cover description Drainage Soil name and CN(weighted)= (Cover type,treatment,and hydrologic condition; Area Product of CN Calculated Area hydrologic group CN total product/ Description (Appendix A) percent impervious;unconnected/connected (Acres) x Area total area 'S'Value impervious area ratio) DA A Impervious Areas 98 0.00 0.0 (Present) B Woods in Good Condition 55 12.94 711.7 55 8.18 Lawns in Good Condition 61 0.00 0.0 DA A Impervious Areas 98 7.15 700.6 (Developed) B Woods in Good Condition 55 0.00 0.0 81 2.28 Lawns in Good Condition 61 5.79 353.2 DA B Impervious Areas 98 0.00 0.0 (Present) B Woods in Good Condition 55 8.85 486.8 55 8.18 Lawns in Good Condition(75%+Groundcover) 61 0.00 0.0 DA B Impervious Areas 98 4.43 434.1 (Developed) B Woods in Good Condition 55 0.00 0.0 80 2.58 Lawns in Good Condition(75%+Groundcover) 61 4.42 269.6 DA C Impervious Areas 98 0.00 0.0 (Present) B Woods in Good Condition 55 9.60 528.0 55 8.18 Lawns in Good Condition(75%+Groundcover) 61 0.00 0.0 DA C Impervious Areas 98 4.92 482.1 (Developed) B Woods in Good Condition 55 0.00 0.0 80 2.51 Lawns in Good Condition(75%+Groundcover) 61 4.68 285.5 2.Runoff 1-Year Storm 2-Year Storm Drainage Area Description Frequency-years 1 2 n/a Rainfall,P(24 hour)-inches 3.5 3.7 n/a Runoff,Q-inches 0.35 0.42 DA A(Present) Runoff,Q-inches 1.74 1.91 DA A(Developed) Runoff,Q-inches 0.35 0.42 DA B(Present) Runoff,Q-inches 1.60 1.76 DA B(Developed) Runoff,Q-inches 0.35 0.42 DA C(Present) Runoff,Q-inches 1.63 1.79 DA C(Developed) Runoff,Q-inches Runoff,Q-inches U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 3:Time of Concentration(T ,)or Travel Time(T,) Project: WPO Amendment for SWM Facilities Designed By: FGM,PE Date: 8/3/2015 Location: Hollymead Town Center Checked By: SRC,PE Date: 8/3/2015 Check One: Present X Developed X Check One: T, X T, Through subarea n/a DAA DAA DAB DAB DAC DAC Segment ID: (Present) (Developed) (Present) (Developed) (Present) (Developed) Sheet Flow:(Applicable to T ,only) Dense Dense Dense Dense Dense 1 Surface description(Table 3-1) Grasses Grasses Grasses Grasses Grasses 2 Manning's roughness coeff.,n(Table 3-1 0.24 0.24 0.24 0.24 0.24 3 Flow length,L(total L <100)(ft) 100 100 100 80 100 4 Two-year24-hour rainfall,P 2(in.) 3.7 3.7 3.7 3.7 3.7 5 Land slope,s(ft/ft) 0.02 0.02 0.12 0.075 0.02 6 Compute T,_[0.007(0L)01)/P2222 s°4 0.22 0.22 0.11 0.11 0.22 Shallow Concentrated Flow: 7 Surface description(paved or unpaved) unpaved unpaved unpaved 8 Flow Length,L(ft) 1170 1110 260 9 Watercourse slope,s(ft/ft) 0.06 0.05 0.05 10 Average velocity,V(Figure 3-1)(ft/s) 4.0 Estimated 3.6 Estimated 3.6 11 T,=L/3600•V 0.08 0.03 0.09 0.03 0.02 Channel Flow: 12 Cross sectional flow area,a(ft 2) 9 13 Wetted perimeter,P w(ft) .7, it 14 Hydraulic radius,r=a/P,,(ft) c E 42- 15 Channel Slope,s(ft/ft) " c 16 Manning's Roughness Coeff,n ,, 17V=[1.49r2ns°3]/n $ ; Z 8 18 Flow length,L(ft) .r c > 19 T,=L/3600•V 0.06 20 Watershed or subarea ,or T, Estimated (Add T,in steps 6,11 and 19) 0.30 0.25 010 0.14 I 0.30 I 0.15 U.S.Department of Agriculture FL-ENG-21C Natural Resources Conservation Service 06/04 TR S5 Worksheet 4:Graphical Peak Discharge Method Project: WPO Amendment for SWM Facilities FGM,PE Date: 8/3/2015 Location: Hollymead Town Center SRC,PE Date: 8/3/2015 Check One: Present X Developed X Drainage Area Drainage Area Drainage Area Drainage Area Drainage Drainage Area Drainage Drainage Area 1.Data Description Description Description Description Area Description Area Description DAA DAA DAB DAB DAC DA C (Present) (Developed) (Present) (Developed) (Present) (Developed) Drainage Area(Am)In miles '= 0.0202 0.0202 0.0138 0.0138 0.0150 0.0150 Runoff curve number CN= 55 81 55 80 55 80 Time of concentration(Tc)= 0.30 0.25 0.20 0.14 0.30 0.15 Rainfall distribution type= II II II II II II Pond and swamp areas spread 0 0 0 0 0 throughout the watershed= 2.Frequency-years 1 2 1 2 1 2 1 2 1 2 1 2 3.Rainfall,P(24 hour)-inches 3.50 3.7 3.50 3.7 3.50 3.7 3.50 3.7 3.50 3.7 3.50 3.7 4.Initial Abstraction,la-inches 1.636 1.636 0.456 0.456 1.636 1.636 0.515 0.515 1.636 1.636_ 0.501 0.501 5.Compute la/P 0.47 0.44 0.13 0.12 0.47 0.44 0.15 0.14 0.47 0.44 0.14 0.14 6.Unit peak discharge,Qu-csm/in 350 400 700 700 425 500 775 775 350 400 875 875 7.Runoff,Q from Worksheet 2-inches 0.35 0.42 1.74 1.91 0.35 0.42 1.60 1.76 0.35 0.42 1.63 1.79 8.Pond and Swamp adjustment factor,Fp 1 1 1 1 1 1 1 1 1 1 1 1 9.Peak Discharge,Qp-cfs Routed Through Routed Through Routed Through where Qp=Qu Am Q Fp 2.45 3.36 SWM Facility 2.03 2.87 SWM Facility 1.82 2.49 SWM Facility Watershed Summary Pre-Development Post-Development Area 1-Year 2-Year Outfall 1 Area 1-Year Outfall 10-Year Outfall Description (acres) CN Outfall (cfs) (acres) CN (cfs) (cfs) DAA 12.94 55 2.45 3.36 12.94 81 0.48 0.57 DAB 8.85 55 2.03 2.87 8.85 80 0.40 0.52 DAC 9.60 55 1.82 2.49 9.60 80 0.39 1.76 Post-Development Routings & Channel Protection Calculations HTC Sediment Basin Conversion- SWM Facility No. 1 BasinFlow printout INPUT: Basin: HTC Sediment Basin Conversion- SWM Facility No. 1 7 Contour Areas Elevation(ft) Area(sf) Computed Vol . (cy) 520.00 14635.00 0.0 521.00 16775.00 581.2 522.00 19280.00 1248.4 523.00 21290.00 1999.4 524.00 23695.00 2832.0 525.00 25639.00 3745.4 526.00 28115.00 4740. 5 Start_Elevation(ft) 520.00 Vol . (cy) 0.00 5 Outlet Structures Outlet structure 0 Orifice name: Existing Barrel area (sf) 7.069 diameter or depth (in) 36.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 512.390 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low Flow Orifice area (sf) 0.049 diameter or depth (in) 3.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 520.000 multiple 1 discharge into riser Outlet structure 2 Orifice name: Mid Flow Orifices area (sf) 0.087 diameter or depth (in) 4.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 523.000 multiple 1 discharge into riser Outlet structure 3 weir name: Modification to Existing Riser diameter (in) 48.000 side angle 0.000 coefficient 3.300 invert (ft) 523.660 multiple 1 discharge into riser transition at (ft) 1.215 orifice coef. 0.500 orifice area (sf) 12.566 Page 1 HTC Sediment Basin Conversion- SWM Facility No. 1 Outlet structure 4 wei r name: Proposed Emergency Spillway length (ft) 43.000 side angle 0.000 coefficient 3.300 invert (ft) 524.660 multiple 1 discharge through dam 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 12.940 CN 81.000 Type 2 rainfall , P (in) 3.500 time of conc. (hrs) 0.2500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 22.474 peak time (hrs) 12.003 volume (cy) 2968.846 Hydrograph 1 SCS name: 2-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 12.940 CN 81.000 Type 2 rainfall , P (in) 3.700 time of conc. (hrs) 0.2500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 24.622 peak time (hrs) 12.003 volume (cy) 3252. 584 Hydrograph 2 SCS name: 10-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 12.940 CN 81.000 Type 2 rainfall , P (in) 5.600 time of conc. (hrs) 0.2500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 46.316 peak time (hrs) 12.003 volume (cy) 6118.397 Page 2 HTC Sediment Basin Conversion- SWM Facility No. 1 Hydrograph 3 SCS name: 100-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 12.940 CN 81.000 Type 2 rainfall , P (in) 9.100 time of conc. (hrs) 0.2500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 89.267 peak time (hrs) 12.003 volume (cy) 11792.356 OUTPUT: Routing Method: storage-indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 22.446 at 12.00 (hrs) discharge (cfs) 0.476 at 16.44 (hrs) water level (ft) 523.295 at 16.70 (hrs) storage (cy) 2235.875 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 24. 592 at 12.00 (hrs) discharge (cfs) 0. 565 at 15.46 (hrs) water level (ft) 523. 503 at 15.72 (hrs) storage (cy) 2407.015 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 46.259 at 12.00 (hrs) discharge (cfs) 25. 506 at 12.16 (hrs) water level (ft) 524.368 at 12.16 (hrs) storage (cy) 3159.984 Hydrograph 3 Routing Summary of Peaks: 100-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 89.158 at 12.00 (hrs) discharge (cfs) 83.750 at 12.04 (hrs) water level (ft) 524.975 at 12.04 (hrs) storage (cy) 3721.389 Mon Aug 03 14:22:42 EDT 2015 Page 3 HTC Sediment Basin Conversion- SWM Facility No. 2 BasinFlow printout INPUT: Basin: HTC Sediment Basin Conversion- SWM Facility No. 2 13 Contour Areas Elevation(ft) Area(sf) Computed Vol . (cy) 516.00 514.00 0.0 517.00 751.00 23.3 518.00 1051.00 56. 5 519.00 1411.00 101.9 520.00 1824.00 161.7 521.19 6803.00 340.2 522.00 8410.00 567.9 523.00 10473.00 916.9 524.00 12610.00 1343.8 525.00 14261.00 1841.1 526.00 16056.00 2402.2 527.00 18348.00 3038.8 528.00 21126.00 3769.2 Start_Elevation(ft) 520.00 Vol . (cy) 161.68 5 Outlet Structures Outlet structure 0 Orifice name: Proposed Barrel area (sf) 1.227 diameter or depth (in) 15.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 520.000 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low Flow orifice area (sf) 0.049 diameter or depth (in) 3.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 520.000 multiple 1 discharge into riser Outlet structure 2 Orifice name: Mid Flow Orifice area (sf) 0.136 diameter or depth (in) 5.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 524.250 multiple 1 discharge into riser Outlet structure 3 weir name: Proposed Riser diameter (in) 24.000 side angle 0.000 coefficient 3.300 invert (ft) 525.250 multiple 1 discharge into riser transition at (ft) 0.608 orifice coef. 0.500 orifice area (sf) 3.142 Page 1 HTC Sediment Basin Conversion- SWM Facility No. 2 Outlet structure 4 Weir name: Proposed Emergency Spillway length (ft) 30.000 side angle 0.000 coefficient 3.300 invert (ft) 526.250 multiple 1 discharge through dam 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 8.850 CN 80.000 Type 2 rainfall , P (in) 3.500 time of conc. (hrs) 0.1400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 17.203 peak time (hrs) 11.935 volume (cy) 1945.157 Hydrograph 1 SCS name: 2-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 8.850 CN 80.000 Type 2 rainfall , P (in) 3.700 time of conc. (hrs) 0.1400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 18.886 peak time (hrs) 11.935 volume (cy) 2135. 510 Hydrograph 2 SCS name: 10-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 8.850 CN 80.000 Type 2 rainfall , P (in) 5.600 time of conc. (hrs) 0.1400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 35.978 peak time (hrs) 11.935 volume (cy) 4068.208 Page 2 HTC Sediment Basin Conversion- SWM Facility No. 2 Hydrograph 3 SCS name: 100-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 8.850 CN 80.000 Type 2 rainfall , P (in) 9.100 time of conc. (hrs) 0.1400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 70.047 peak time (hrs) 11.935 volume (cy) 7920.416 OUTPUT: Routing Method: storage-indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 17.129 at 11.94 (hrs) discharge (cfs) 0.397 at 14. 58 (hrs) water level (ft) 524.191 at 15.32 (hrs) storage (cy) 1433.918 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 18.805 at 11.94 (hrs) discharge (cfs) 0. 515 at 14.76 (hrs) water level (ft) 524.443 at 14.84 (hrs) storage (cy) 1556.487 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 35.824 at 11.94 (hrs) discharge (cfs) 11.314 at 12.14 (hrs) water level (ft) 525.909 at 12.14 (hrs) storage (cy) 2348.324 Hydrograph 3 Routing Summary of Peaks: 100-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 69.746 at 11.94 (hrs) discharge (cfs) 63.914 at 11.98 (hrs) water level (ft) 526.898 at 11.98 (hrs) storage (cy) 2969.644 Mon Aug 03 15:19:46 EDT 2015 Page 3 HTC Sediment Basin Conversion- SWM Facility No. 3 BasinFlow printout INPUT: Basin: HTC Sediment Basin Conversion- SWM Facility No. 3 12 Contour Areas Elevation(ft) Area(sf) Computed vol . (cy) 514.00 973.00 0.0 515.00 1333.00 42. 5 516.00 1748.00 99.4 517.00 2231.00 172.9 518.00 2768.00 265.3 518.50 10064.00 377.1 519.00 11363.00 575.4 520.00 12352.00 1014.4 521.00 13843.00 1499.2 522.00 15344.00 2039. 5 523.00 16864.00 2635.7 524.00 18326.00 3287.2 Start_Elevation(ft) 517.78 vol . (cy) 243.33 4 Outlet Structures Outlet structure 0 Orifice name: Existing Barrel area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 510.760 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low Flow Orifice area (sf) 0.049 diameter or depth (in) 3.000 width for rect. (in) 0.000 coefficient 0. 500 invert (ft) 517.780 multiple 1 discharge into riser Outlet structure 2 Weir name: Existing Riser diameter (in) 48.000 side angle 0.000 coefficient 3.300 invert (ft) 521.080 multiple 1 discharge into riser transition at (ft) 1.215 orifice coef. 0. 500 orifice area (sf) 12. 566 Outlet structure 3 Weir name: Proposed Emergency Spillway length (ft) 43.000 side angle 0.000 coefficient 3.300 invert (ft) 522.750 multiple 1 discharge through dam Page 1 HTC Sediment Basin Conversion- SWM Facility No. 3 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 9.600 CN 80.000 Type 2 rainfall , P (in) 3. 500 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 18.291 peak time (hrs) 11.930 volume (cy) 2110.357 Hydrograph 1 SCS name: 2-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 9.600 CN 80.000 Type 2 rainfall , P (in) 3.700 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 20.081 peak time (hrs) 11.930 volume (cy) 2316.879 Hydrograph 2 SCS name: 10-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 9.600 CN 80.000 Type 2 rainfall , P (in) 5.600 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 38.256 peak time (hrs) 11.930 volume (cy) 4413.744 Hydrograph 3 SCS name: 100-yr 24-hr Peak SCS TR-55 Method Storm Event Area (acres) 9.600 CN 80.000 Type 2 rainfall , P (in) 9.100 time of conc. (hrs) 0.1500 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 74.481 peak time (hrs) 11.930 volume (cy) 8593.155 Page 2 HTC sediment Basin Conversion- SWM Facility No. 3 OUTPUT: Routing Method: storage-indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 18.274 at 11.94 (hrs) discharge (cfs) 0.388 at 12.90 (hrs) water level (ft) 521.089 at 12.92 (hrs) storage (cy) 1545.223 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 20.063 at 11.94 (hrs) discharge (cfs) 1.761 at 12.40 (hrs) water level (ft) 521.185 at 12.40 (hrs) storage (cy) 1594.851 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 38.220 at 11.94 (hrs) discharge (cfs) 31.801 at 12.02 (hrs) water level (ft) 521.911 at 12.02 (hrs) storage (cy) 1989.086 Hydrograph 3 Routing Summary of Peaks: 100-yr 24-hr Peak SCS TR-55 Method Storm Event inflow (cfs) 74.411 at 11.94 (hrs) discharge (cfs) 61.959 at 12.02 (hrs) water level (ft) 522. 571 at 12.02 (hrs) storage (cy) 2372.756 Mon Aug 03 15:05:30 EDT 2015 Page 3 • r CA}=: r: O '' :alp° S/£4 6C..0 j 4, 1,4 9'I n6 7i taikriiic k sit,'' O% Q , 'M C3 1 o1`1 sf c • WO 'nX`o xyy� O3'1 ! 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