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HomeMy WebLinkAboutWPO201700020 Calculations WPO VSMP 2017-05-03 U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 2:Runoff Curve Number and Runoff Project: Glenbrook at Foothills&Foothill Phase IV(DA 1B) Designed By: KKW,PE Date:5/3/2017 Location: Park Ridge Drive,Crozet,VA Checked By:SRC,PE Date:5/3/2017 1.Runoff curve Number(CN) Drainage Area Soil name and Cover description(Cover type,treatment,and hydrologic CN(weighted)= Area Product of CN Calculated'S' Description hydrologic group condition;percent impervious;unconnected/connected CN total product/ (Acres) x Area Value (Appendix A) impervious area ratio) total area DATA Impervious Areas 98 0.00 0.0 (Pre-development) B Woods in Good Condition 55 16.60 913.2 56 7.76 Lawns in Good Condition 61 4.69 285.9 DATA Impervious Areas 98 10.26 1005.5 (Developed) B Woods in Good Condition 55 0.00 0.0 79 2.69 Lawns in Good Condition 61 11.03 672.8 DA'28' Impervious Areas 98 0.00 0.0 (Pre-development) B Woods in Good Condition 55 9.58 526.9 57 7.55 Lawns in Good Condition 61 4.73 288.5 DA'28' Impervious Areas 98 6.11 598.8 (Developed) B Woods in Good Condition 55 0.00 0.0 77 3.02 Lawns in Good Condition 61 8.20 500.2 2.Runoff 1-Year Storm 2-Year Storm 10-Year Storm Drainage Area Description Frequency-years 1 2 10 n/a Rainfall,P(24 hour)-inches 3.5 3.7 5.6 n/a Runoff,0-inches 0.39 0.47 1.39 DA'1A'(Pre-development) Runoff,0-inches 1.55 1.71 3.31 DA'1A'(Developed) Runoff,0-inches 0.42 0.49 1.44 DA'2B'(Pre-development) Runoff,0-inches 1.42 1.57 3.11 DA'2B'(Developed) I U.S.Department of Agriculture FL-ENG-21A Natural Resources Conservation Service 06/04 TR 55 Worksheet 3:Time of Concentration(Ta)or Travel Time(Ti) Project: Glenbrook at Foothills&Foothill Phase IV(DA 1B) Designed By: KKW,PE Date: 5/3/2017 Location: Park Ridge Drive,Crozet,VA Checked By: SRC,PE Date: 5/3/2017 Check One: Present X Developed X Check One: T, X Ti DA'1A' DA'2B' DATA' DA'2B' (Pre- Develo (Pre- ( ped Segment ID: developmen ) development) (Developed) Sheet Flow:(Applicable to T,only) Woods Light 1 Surface description(Table 3-1) Underbrush 2 Manning's roughness coeff.,n(Table 3-1 0.4 3 Flow length,L(total L<100)(ft) 100 4 Two-year 24-hour rainfall,P2(in.) 3.7 5 Land slope,s(ft/ft) 0.04 6 Compute T,=[0.007(n*L)°8]/P2 5 s0.4 .4 0.25 u 1-- is)m `" Shallow Concentrated Flow: 7 Surface description(paved or unpaved) u ic Unpaved > 8 Flow Length,L(ft) g c 645 ,,, 9 Watercourse slope,s(ft/ft) >> 0.08 cc cc 10 Average velocity,V(Figure 3-1)(ft/s) a wa 4.5 J 11Tt=L/3600*V W 0 0.04 Lu 0 0 0 Channel Flow: a a 12 Cross sectional flow area,a(ft2) a a > 0 cc 13 Wetted perimeter,P,, (ft) a 14 Hydraulic radius,r=a/Ps,(ft) a 15 Channel Slope,s(ft/ft) Z 16 Manning's Roughness Coeff,n 17 V=[1.49r213s'5]/n 18 Flow length,L(ft) 19 It=L/3600*V 0.00 20 Watershed or subarea Tc or TL (Add T,in steps 6,11 and 19) ( 0.37 I 0.23 I 0.29 I 0.24 I I I U.S.Department of Agriculture ENG-21C Natural Resources Conservation Service TR 55 Worksheet 4:Graphical Peak Discharge Method Project: Glenbrook at Foothills&Foothill Phase IV(DA 1B) Designed By: KKW,PE Date: Location: Park Ridge Drive,Crozet,VA Checked By:SRC,PE Date: Check One: Present X Developed X 1.Data Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Description DA'1A' DA'1A' DA'2B' DA'2B' (Pre-development) (Developed) (Pre-development) (Developed) Drainage Area(Am)in miles'= 0.0333 0.0333 0.0224 0.0224 Runoff curve number CN= 56.3 78.8 57.0 76.8 Time of concentration(Tc)= 0.37 0.23 0.29 0.24 Rainfall distribution type= II II II II Pond and swamp areas spread throughout the watershed= 0 0 0 0 2.Frequency-years 1 2 10 1 2 10 1 2 10 1 2 10 3.Rainfall,P(24 hour)-inches 3.5 3.7 5.6 3.5 3.7 5.6 3.5 3.7 5.6 3.5 3.7 5.6 4.Initial Abstraction,la-inches 1.551 1.551 1.551 0.537 0.537 0.537 1.510 1.510 1.510 0.604 0.604 0.604 5.Compute la/P 0.44 0.42 0.28 0.15 0.15 0.10 0.43 0.41 0.27 0.17 0.16 0.11 6.Unit peak discharge,Qu-csm/in 450 480 550 - - - 435 460 625 - - - 7.Runoff,Q from Worksheet 2-inches 0.39 0.47 1.39 1.55 1.71 3.31 0.42 0.49 1.44 1.42 1.57 3.11 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 SWM Routed through SWM where Qp=Qu Am Q Fp 5.86 7.44 25.41 Facility 4.04 5.07 20.09 Facility Note:Qu of 1000 csm/inch is the most conservative SCS TR-55 Qu. Outflow Summary: (2-Year Storm Event) Pre-Development Post-Development DA 'A' 7.44 cfs 096 cfs DA'B' 5.07 cfs 1.27 cfs Total= 12.51 cfs 2.23 cfs Outflow Summary: (10-Year Storm Event) Pre-Development Post-Development DA 'A' 25.41 cfs 6.96 cfs DA'B' 20.09 cfs 18.26 cfs Total= 45.50 cfs 25.22 cfs Glenbrook Basin B BasinFlow printout INPUT: Basin: Glenbrook Basin B 11 Contour Areas Elevation(ft) Area(sf) Computed Vol. (cy) 607.00 1366.00 0.0 608.00 1880.00 59.9 610.00 3121.00 243.1 612.00 4800.00 534.3 612.70 5408.00 666.5 614.20 7189.00 1015.3 614.70 9519.00 1169.5 616.00 10974.00 1662.4 618.00 13396.00 2563.5 620.00 16461.00 3667.4 622.00 19390.00 4993.7 Start_Elevation(ft) 614.20 Vol. (cy) 1015.29 5 Outlet Structures Outlet structure 0 Orifice name: Barrel area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 612.000 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low Flow Orifice area (sf) 0.060 diameter or depth (in) 3.330 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 614.200 multiple 2 discharge into riser Outlet structure 2 Orifice name: Mid Flow Orifice Page 1 Glenbrook Basin B area (sf) 0.196 diameter or depth (in) 6.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 618.330 multiple 5 discharge into riser Outlet structure 3 Weir name: Riser Rim diameter (in) 48.000 side angle 0.000 coefficient 3.300 invert (ft) 620.000 multiple 1 discharge into riser transition at (ft) 1.215 orifice coef. 0.500 orifice area (sf) 12.566 Outlet structure 4 Weir name: Emergency Spillway length (ft) 45.000 side angle 0.000 coefficient 3.300 invert (ft) 620.550 multiple 1 discharge through dam 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24hr Peak SCS Design Storm Area (acres) 14.300 CN 77.000 Type 2 rainfall, P (in) 3.500 time of conc. (hrs) 0.2400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 21.029 peak time (hrs) 12.002 volume (cy) 2746.916 Page 2 Glenbrook Basin B Hydrograph 1 SCS name: 2-yr 24hr Peak SCS Design Storm Area (acres) 14.300 CN 77.000 Type 2 rainfall, P (in) 3.700 time of conc. (hrs) 0.2400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 23.237 peak time (hrs) 12.002 volume (cy) 3035.429 Hydrograph 2 SCS name: 10-yr 24hr Peak SCS Design Storm Area (acres) 14.300 CN 77.000 Type 2 rainfall, P (in) 5.600 time of conc. (hrs) 0.2400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 46.046 peak time (hrs) 12.002 volume (cy) 6014.846 Hydrograph 3 SCS name: 100-yr 24hr Peak SCS Design Storm Area (acres) 14.300 CN 77.000 Type 2 rainfall, P (in) 9.100 time of conc. (hrs) 0.2400 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 92.496 peak time (hrs) 12.002 volume (cy) 12082.495 Page 3 Glenbrook Basin B OUTPUT: Routing Method: storage-indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24hr Peak SCS Design Storm inflow (cfs) 21.020 at 12.00 (hrs) discharge (cfs) 0.946 at 13.40 (hrs) water level (ft) 618.144 at 13.68 (hrs) storage (cy) 2635.595 Hydrograph 1 Routing Summary of Peaks: 2-yr 24hr Peak SCS Design Storm inflow (cfs) 23.228 at 12.00 (hrs) discharge (cfs) 1.267 at 13.26 (hrs) water level (ft) 618.454 at 13.26 (hrs) storage (cy) 2794.309 Hydrograph 2 Routing Summary of Peaks: 10-yr 24hr Peak SCS Design Storm inflow (cfs) 46.026 at 12.00 (hrs) discharge (cfs) 18.264 at 12.20 (hrs) water level (ft) 620.430 at 12.20 (hrs) storage (cy) 3934.650 Hydrograph 3 Routing Summary of Peaks: 100-yr 24hr Peak SCS Design Storm inflow (cfs) 92.457 at 12.00 (hrs) discharge (cfs) 91.352 at 12.02 (hrs) water level (ft) 620.989 at 12.02 (hrs) storage (cy) 4296.184 Tue May 23 15:47:50 EDT 2017 Page 4 & b 1.-Dov,, q.) 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