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HomeMy WebLinkAboutWPO202000041 Calculations 2021-03-02AVON PARK II VSMP STORMWATER MANAGEMENT CALCULATIONS PACKET Date of Calculations AUGUST 19, 2020 APPROVED by the Albemarle County Commu03/ 02 /2 0ment 21 Department Date File WP0202000041 PREPARED BY: COLLINS ENGI°-°''mRING 200 GARRETT STREET, SUITE K CHARLOTTESVILLE, VA 22902 434.293.3719 PH 434.293.2813 FX www.collins-engineering.com SCS TR-55 Calculations Soils Ma (Source: NRCS Web Soil Survey Online Database) Soils Table (Source: NRCS Web Soil Survey Online Database) Albemarle County, Virginia (VA003) Albemarle County, Virginia (VA003) Map percent Unit Map Unit Name of AOI Symbol 71B Rabun clay loam, 2 34.1% to 7 percent slopes 71C Rabun clay loam, 7 38.8% to 15 percent slopes 72C3 Rabun clay, 7 to 15 27.1% percent slopes, severely eroded Totals for Area of 100.00/0 Interest Note: The soils' properties witin this development are predominantly composed of hydrologic group type C soils. Precipitation Data (Source: NOAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates) Q� 0 M Gt44 0 Terrain stones 3 e x fi F� J y `A Q� r0 `a4C r N L O Q Ad ho��s n ey Ga cn Pd �Jy In cin ela�at lJ 200m Lx 00f1 / POINT PRECIPITATION FREQUENCY (PF) ESTIMATES WITH 90% CONFIDENCE INTERVALS AND SUPPLEMENTARY INFOFMTION NOAA Atlas 14, Volume 2, Version 3 Channel and Flood Protection Calculations S> u u N v G „ ry 6 m N N O O] O] n 3 — o V Z O V r 2 V 0 dQ ¢Q o o n oo c m o.io o o ry ocooc o o n coon o o m o .iocooco m ry o ry N o ooc.io o .+ o a a `° ry E 0 o v E ` v a 'v a `tea `tea `tea `aa `aa as as 1O�uv�ua�ua�u°a�u c c au u°auu°a�udpu c g"� ¢` q a` "� a` q a` g q a` g '° ° C °N °C °C c m c m o' c m 0 c 0 c m 0 c 0 c 0 a v � a 1O m x S a N T" p U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 3: Time of Concentration (T.) or Travel Time (Tt) Project: Avon Park 11 Location: 1690 Avon Street Ext Check One: Present X Developed X Check One: T, X Tt Segment ID Sheet Flow: (Applicable to T, only) 1 Surface description (Table 3-1) 2 Manning's roughness coeff., n (Table 3-1) 3 Flow length, L (total L < 100) (ft) 4 Two-year 24-hour rainfall, Pi (in.) 5 land slope, s (ft/ft) 6 Compute Tt = [0.007(n'L)0sj / Pi 5 s' Shallow Concentrated Flow- 7 Surface description (paved or unpaved) 8 Flow Length, L (ft) 9 Watercourse slope, s(ft/ft) 10 Average velocity, V (Figure 3-1) (ft/s) 11 Tt= L / 3600'V Channel Flow: 12 Cross sectional Flow area, a (ft) 13 Wetted perimeter, P. (ft) 14 Hydraulic radius, r = a/P„ (ft) 15 Channel Slope, s (ft/ft) 16 Manning's Roughness Coeff, n 17 V= [ 1.49r�s05 j / n 18 Flow length, L (ft) 19 Tt= L/3600'V 20 Watershed or subarea T, or Tt (Add Tt in steps 6,11 and 19) Designed By: LMW, PE Checked By: SRC, PE Through subarea n/a FL-ENG-21A 06/04 Date: 8/19/2020 Date: 8/19/2020 DAA DAB DAC DAD DAA(UGO) DAB DAC (Pre-Dev.) (Pre-Dev.) (Pre-Dev.) (Pre-Dev.) (Part-Dev) (Post -Des) (Post-Dev) Woods, Light Woods, Light Woods, Light Smooth Surface - Underbrush Underbrush Underbrush Grass -dense Grass -dense asphalt Grass -dense 0.4 0.4 0.4 0.24 0.24 0.011 0.24 60 70 58 30 18 44 50 3.67 3.67 3.67 3.67 3.67 3.67 3.67 0.04 0.04 0.06 0.07 0.28 0.11 0.15 0.17 0.19 0.14 0.05 0.02 0.00 0.06 Unpaved Unpaved Unpaved Unpaved Paved Unpaved 796 49 118 34 77 552 0.14 0.04 0.05 0.41 0.04 0.160 6.1 3.6 3.6 10.3 4.0 6.5 0.04 0.00 0.01 0.00 0.01 0.02 0.02 (in pipes) 0.21 0.19 0.15 0.10 0.10 0.10 0.10 ! i ! {) \{ 0 �§!!!B-!! 0 /\}!}06. /\)/\kjo\ \ o k | I . ! j 0 9 VAC 25-870-66 Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.l.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section 8.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity shall be calculated either.." a. or b." Section 8.3.a. In accordance with the following methodology: Q Allowed < I.F. * (Q Pr�Developed + [RV Pre -Developed) ) I (RV Developed ) Q Allowed < 1.49 cfs Where: Q Pre -Developed= 3.71 cfs (From Worksheet 4 Watershed Summary) CN Pr�Developed= 70 (From Worksheet 4 Watershed Summary) S Pre -Developed = 4.27 (From SCS TR-55 eq. 2-4) RV Pr�Developed= 0.74 in. (From SCSTR-55 eq. 2-3) CN Pt -Developed= 83 (From Worksheet 4 Watershed Summary) S P.A Developed = 2.05 (From SCS TR-55 eq. 2-4) RV port -Developed= 1.48 in. (From SCS TR-55 eq. 2-3) I.F. = 0.80 (Factor of Safety) Q Developed = 1.31 cfs Section B.4 Limits of Analysis The analysis terminates at Post -Development Subarea C since subsection B.3.a is met. 9 VAC 25-870-66 Section C: Flood Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic methodologies:" Section C.2.b.: The point of discharge (Detention Basin B's Cutfall), "releases a postdevelopment peak flow rate for the 10-year 24-hour storm event that is less than the predevelopment peak flow rate from the 10-year 24-hour storm event. Downstream stormwater conveyance systems do not require any additional analysis to show compliance with flood protection criteria if this option is utilized." 10-Year, 24-Hour Pre -Development Subareas A-D Peak Flow Rate = 13.32 cfs 10-Year, 24-Hour Post -Development Subareas A-C Peak Flow Rate = 13.18 cfs Section C.3 Limits of Analysis The flood protection analysis terminates at Subareas A, B, & C since subsection C.2.b is met. Post -Development Underground Detention System 'SWM 1' Routings and Outflow Hydrographs The following routing calculations and outflow hydrographs reflect the post -development attenuation in Subarea A from the proposed underground detention system 'SWM 1' BasinFlow printout INPUT: Basin: SWM 1 0 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 1 Storage Pipes Storage pipe 0 name: SWM 1 diameter (in) length (ft) invert (ft) angle volume (cy) Start—Elevation(ft) 6 Outlet Structures Outlet structure 0 Orifice 659.00 Vol.(cy) 0.00 name: Barrel area (sf) 1.227 diameter or depth (in) 15.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 658.900 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 0.600 invert (ft) 659.000 multiple 1 discharge into riser Outlet structure 2 Weir name: Access Manhole diameter (in) 36.000 side angle 0.000 coefficient 3.300 invert (ft) 667.000 multiple 1 discharge into riser transition at (ft) 0.912 orifice coef. 0.500 orifice area (sf) 7.069 Outlet structure 3 Orifice name: Emergency Overflow Orifice area (sf) 0.940 diameter or depth (in) 13.130 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 666.600 multiple 1 discharge into riser Outlet structure 4 Orifice name: Emergency Bypass Pipe area (sf) 1.227 diameter or depth (in) 15.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 665.750 multiple 1 discharge out of riser Outlet structure 5 Orifice name: Mid -Rise Orifice area (sf) 0.333 diameter or depth (in) 6.000 width for rect. (in) 8.000 coefficient 0.600 invert (ft) 664.300 multiple 1 discharge into riser 4 Inflow Hydrographs Hydrograph 0 SCS name: 1 YR SWM 1 Area (acres) 2.410 CN 86.000 Type 2 rainfall, P (in) 3.040 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 5.189 peak time (hrs) 11.917 volume (cy) 549.349 Hydrograph 1 SCS name: 2 YR SWM 1 Area (acres) 2.410 CN 86.000 Type 2 rainfall, P (in) 3.670 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 6.879 peak time (hrs) 11.917 volume (cy) 728.284 Hydrograph 2 SCS name: 10 YR SWM 1 Area (acres) 2.410 CN 86.000 Type 2 rainfall, P (in) 5.550 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 12.181 peak time (hrs) 11.917 volume (cy) 1289.614 Hydrograph 3 SCS name: 25 YR SWM 1-Emergency ONLY Area (acres) 2.410 CN 86.000 Type 2 rainfall, P (in) 6.830 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 15.909 peak time (hrs) 11.917 volume (cy) 1684.308 OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: 1 YR SWM 1 inflow (cfs) 5.165 at 11.92 (hrs) discharge (cfs) 0.537 at 12.34 (hrs) water level (ft) 664.283 at 12.36 (hrs) storage (cy) 211.465 Hydrograph 1 Routing Summary of Peaks: 2 YR SWM 1 inflow (cfs) 6.847 at 11.92 (hrs) discharge (cfs) 1.997 at 12.10 (hrs) water level (ft) 665.322 at 12.10 (hrs) storage (cy) 263.293 Hydrograph 2 Routing Summary of Peaks: 10 YR SWM 1 inflow (cfs) 12.124 at 11.92 (hrs) discharge (cfs) 5.755 at 11.94 (hrs) water level (ft) 667.120 at 11.94 (hrs) storage (cy) 329.163 Hydrograph 3 Routing Summary of Peaks: 25 YR SWM 1-Emergency ONLY inflow (cfs) 15.835 at 11.92 (hrs) discharge (cfs) 11.528 at 11.92 (hrs) water level (ft) 667.342 at 11.92 (hrs) storage (cy) 332.487 Post -Development DA A Outflow Hydrograph (From SWM 1's Routings) Time (hrs) Outflow (ofs) 0.0 0.00 0.5 0.08 1.0 0.09 1.5 0.09 2.0 0.09 2.5 0.09 3.0 0.10 3.5 0.10 4.0 0.10 4.5 0.11 5.0 0.11 5.5 0.12 6.0 0.13 6.5 0.13 7.0 0.14 7.5 0.14 8.0 0.15 8.5 0.16 9.0 0.17 9.5 0.18 10.0 0.19 10.5 0.21 11.0 0.23 11.3 0.25 11.6 0.28 11.9 0.43 12.0 0.50 12.1 0.53 12.2 0.54 22.3 0.54 12.4 0.54 12.5 0.54 12.6 0.53 12.7 0.53 12.8 0.53 13.0 0.52 13.2 0.51 13.4 0.51 13.6 0.50 13.8 0.49 14.0 0.48 14.3 0.47 14.6 0.45 15.0 0.43 15.5 0.40 16.0 0.38 16.5 0.35 17.0 0.31 17.5 0.28 18.0 0.24 19.0 0.17 20.0 0.11 22.0 0.09 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 0.60 0.50 0.40 0.30 0.20 0.10 0.00 -0.10 Outflow Hydrograph (1-yr Design Storm) Port -Development DA A Outflow Hydrograph (From SWM 1's Routings) Time(hrs) Outfow(cfs) 0.0 0.00 0.5 0.10 1.0 0.11 1.5 0.11 2.0 0.12 2.5 0.12 3.0 0.12 3.5 0.13 4.0 0.13 4.5 0.14 5.0 0.14 5.5 0.15 6.0 0.15 6.5 0.16 7.0 0.16 7.5 0.17 8.0 0.17 8.5 0.18 9.0 0.19 9.5 0.20 10.0 0.21 10.5 0.23 11.0 0.25 11.3 0.28 11.6 0.32 11.9 0.49 12.0 1.41 12.1 2.00 12.2 1.82 12.3 1.55 12.4 1.28 12.5 0.92 12.6 0.76 12.7 0.66 12.8 0.60 13.0 0.54 13.2 0.53 13.4 0.53 13.6 0.52 13.8 0.51 14.0 0.50 14.3 0.49 14.6 0.48 15.0 0.46 15.5 0." 16.0 0.41 16.5 0.39 17.0 0.36 17.5 0.33 18.0 0.30 19.0 0.23 20.0 0.17 22.0 0.12 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 2.50 2.00 1.50 1.m 0.50 0.00 -0.50 Outflow Hydrograph (2-yr Design Storm) Port -Development DA A Outflow Hydrograph (From SWM 1's Routings) Time(hrs) Outflow(cfs) 0.0 0.00 0.5 0.14 1.0 0.16 1.5 0.16 2.0 0.17 2.5 0.17 3.0 0.18 3.5 0.18 4.0 0.18 4.5 0.19 5.0 0.19 5.5 0.20 6.0 0.21 6.5 0.21 7.0 0.22 7.5 0.22 8.0 0.22 8.5 0.23 9.0 0.25 9.5 0.26 10.0 0.27 10.5 0.30 11.0 0.34 11.3 0.37 11.6 0.42 11.9 2.88 12.0 5.76 12.1 3.17 12.2 2.84 12.3 2.57 12.4 2.31 12.5 2.04 12.6 1.75 12.7 1.48 12.8 1.21 13.0 0.80 13.2 0.67 13.4 0.60 13.6 0.55 13.8 0.54 14.0 0.53 14.3 0.52 14.6 0.52 15.0 0.51 15.5 0.49 16.0 0.47 16.5 0.45 17.0 0." 17.5 0.42 18.0 0.40 19.0 0.35 20.0 0.30 22.0 0.20 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 2.00 6.00 5.00 4.00 3.m 2.00 W 0.00 D 100 Outflow Hydrograph (10-yr Design Storm) Post -Development Detention Basin 'SWM 2' Routings and Outflow Hydrographs The following routing calculations and outflow hydrographs reflect the post -development attenuation in Subareas B & C from the proposed detention basin 'SWM 2' BasinFlow printout INPUT: Basin: SWM 2 DETENTION BASIN 6 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 587.00 4.00 0.0 588.00 155.00 2.3 589.00 516.00 14.0 590.00 1079.00 42.9 591.00 1847.00 96.5 592.00 2839.00 182.6 Start—Elevation(ft) 587.00 Vol.(cy) 4 Outlet Structures Outlet structure 0 Orifice name: Barrel area (sf) 1.767 diameter or depth (in) 18.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 586.900 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low -Flow Orifice area (sf) 0.087 diameter or depth (in) 4.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 587.000 multiple 1 discharge into riser Outlet structure 2 Weir name: Riser Top diameter (in) 24.000 side angle 0.000 coefficient 3.300 invert (ft) 590.600 multiple 1 discharge into riser transition at (ft) 0.729 orifice coef. 0.600 orifice area (sf) 3.142 Outlet structure 3 Weir name: Emergency Spillway length (ft) 15.000 side angle 14.040 coefficient 3.300 invert (ft) 591.100 multiple 1 discharge through dam 10 Inflow Hydrographs Hydrograph 0 SCS name: DA C 1 YR Area (acres) 1.180 CN 75.000 Type 2 rainfall, P (in) 3.040 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 1.478 peak time (hrs) 11.917 volume (cy) 156.479 Hydrograph 1 SCS name: DA C 2 YR Area (acres) 1.180 CN 75.000 Type 2 rainfall, P (in) 3.670 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 2.131 peak time (hrs) 11.917 volume (cy) 225.639 Hydrograph 2 SCS name: DA C 10 YR Area (acres) 1.180 CN 75.000 Type 2 rainfall, P (in) 5.550 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 4.346 peak time (hrs) 11.917 volume (cy) 460.052 Hydrograph 3 SCS name: DA B 1 YR Area (acres) 0.770 CN 81.000 Type 2 rainfall, P (in) 3.040 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 1.313 peak time (hrs) 11.917 volume (cy) 139.058 Hydrograph 4 SCS name: DA B 2 YR Area (acres) 0.770 CN 81.000 Type 2 rainfall, P (in) 3.670 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 1.805 peak time (hrs) 11.917 volume (cy) 191.085 Hydrograph 5 SCS name: DA B 10 YR Area (acres) 0.770 CN 81.000 Type 2 rainfall, P (in) 5.550 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed false peak flow (cfs) 3.396 peak time (hrs) 11.917 volume (cy) 359.553 Hydrograph 6 Summation name: DAB&C 1YR hydrograph 1 0 start time 1 0.000 hydrograph 2 3 start time 2 0.000 routed true Hydrograph 7 Summation name: DAB&C 2YR hydrograph 1 1 start time 1 0.000 hydrograph 2 4 start time 2 0.000 routed true Hydrograph 8 Summation name: DA B & C 10 YR hydrograph 1 2 start time 1 0.000 hydrograph 2 5 start time 2 0.000 routed true Hydrograph 9 SCS name: DA B & C 100 YR Area (acres) 1.950 CN 77.000 Type 2 rainfall, P (in) 9.130 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 15.638 peak time (hrs) 11.917 volume (cy) 1655.632 OUTPUT: Routing Method: storage -indication Hydrograph 0 DA C 1 YR (not routed) Hydrograph 1 DA C 2 YR (not routed) Hydrograph 2 DA C 10 YR (not routed) Hydrograph 3 DA B 1 YR (not routed) Hydrograph 4 DA B 2 YR (not routed) Hydrograph 5 DA B 10 YR (not routed) Hydrograph 6 Routing Summary of Peaks: DA B & C 1 YR inflow (cfs) 2.778 at 11.92 (hrs) discharge (cfs) 0.779 at 12.10 (hrs) water level (ft) 590.601 at 12.10 (hrs) storage (cy) 71.669 Hydrograph 7 Routing Summary of Peaks: DA B & C 2 YR inflow (cfs) 3.918 at 11.92 (hrs) discharge (cfs) 2.962 at 12.00 (hrs) water level (ft) 590.821 at 12.00 (hrs) storage (cy) 84.787 Hydrograph 8 Routing Summary of Peaks: DA B & C 10 YR inflow (cfs) 7.706 at 11.92 (hrs) discharge (cfs) 7.419 at 11.94 (hrs) water level (ft) 591.066 at 11.94 (hrs) storage (cy) 101.067 Hydrograph 9 Routing Summary of Peaks: DA B & C 100 YR inflow (cfs) 15.565 at 11.92 (hrs) discharge (cfs) 15.445 at 11.92 (hrs) water level (ft) 591.266 at 11.92 (hrs) storage (cy) 115.841 Post -Development DA B&C Outflow Hydrograph (From SWM 2's Routings) Time (hrs) Outflow (ofs) 0.0 0.00 0.5 0.04 1.0 0.05 1.5 0.05 2.0 0.05 2.5 0.05 3.0 0.06 3.5 0.06 4.0 0.06 4.5 0.06 5.0 0.07 5.5 0.07 6.0 0.08 6.5 0.08 7.0 0.09 7.5 0.09 8.0 0.09 8.5 0.11 9.0 0.13 9.5 0.14 10.0 0.16 10.5 0.20 11.0 0.26 11.3 0.32 11.6 0.41 11.9 0.69 12.0 0.76 12.1 0.78 12.2 0.77 12.3 0.76 12.4 0.74 12.5 0.73 12.6 0.71 12.7 0.69 12.8 0.66 13.0 0.59 13.2 0.49 13.4 0.35 13.6 0.20 13.8 0.18 14.0 0.16 14.3 0.15 14.6 0.14 15.0 0.11 15.5 0.10 16.0 0.10 16.5 0.09 17.0 0.09 17.5 0.08 18.0 0.08 19.0 0.07 20.0 0.06 22.0 0.05 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 -0.10 Outflow Hydrograph (1-yr Design Storm) Post -Development DA B&C Outflow Hydrograph (From SWIM 2's Routinas) Time(hrs) Outfow(cfs) 0.0 0.00 0.5 0.06 1.0 0.07 1.5 0.07 2.0 0.07 2.5 0.07 3.0 0.08 3.5 0.08 4.0 0.08 4.5 0.09 5.0 0.10 5.5 0.10 6.0 0.11 6.5 0.11 7.0 0.11 7.5 0.14 8.0 0.11 8.5 0.15 9.0 0.18 9.5 0.19 10.0 0.22 10.5 0.27 11.0 0.33 11.3 0.38 11.6 0.47 11.9 0.76 12.0 2.96 12.1 1.67 12.2 0.84 12.3 0.77 12.4 0.76 12.5 0.75 12.6 0.74 12.7 0.72 12.8 0.70 13.0 0.65 13.2 0.59 13.4 0.49 13.6 0.38 13.8 0.27 14.0 0.23 14.3 0.21 14.6 0.20 15.0 0.18 15.5 0.16 16.0 0.14 16.5 0.15 17.0 0.11 17.5 0.14 18.0 0.11 19.0 0.09 20.0 0.08 22.0 0.07 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 Outflow Hydrograph (2-yr Design Storm) Post -Development DA B&C Outflow Hydrograph (From SWIM 2's Routinas) Time(hrs) Outfow(cfs) 0.0 0.00 0.5 0.11 1.0 0.15 1.5 0.15 2.0 0.14 2.5 0.14 3.0 0.15 3.5 0.15 4.0 0.16 4.5 0.17 5.0 0.18 5.5 0.19 6.0 0.21 6.5 0.21 7.0 0.23 7.5 0.24 8.0 0.24 8.5 0.28 9.0 0.31 9.5 0.33 10.0 0.36 10.5 0.41 11.0 0.46 11.3 0.51 11.6 0.59 11.9 6.82 12.0 7A2 12.1 3.10 12.2 1.37 12.3 0.99 12.4 0.86 12.5 0.78 12.6 0.77 12.7 0.76 12.8 0.76 13.0 0.73 13.2 0.71 13.4 0.68 13.6 0.63 13.8 0.58 14.0 0.50 14.3 0.40 14.6 0.35 15.0 0.32 15.5 0.29 16.0 0.26 16.5 0.25 17.0 0.24 17.5 0.22 18.0 0.21 19.0 0.18 20.0 0.15 22.0 0.14 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 9.00 8.00 7.00 6.00 s.00 4.00 3.00 zoo 1.00 0.00 100 0 Outflow Hydrograph (10-yr Design Storm) Post -Development DA B&C Outflow Hydrograph (From SWIM 2's Routinas) Time(hrs) Outfow(cfs) 0.0 0.00 0.5 0.24 1.0 0.25 1.5 0.26 2.0 0.27 2.5 0.27 3.0 0.28 3.5 0.29 4.0 0.30 4.5 0.31 5.0 0.32 5.5 0.34 6.0 0.35 6.5 0.36 7.0 0.37 7.5 0.38 8.0 0.39 8.5 0.42 9.0 0.46 9.5 0.47 10.0 0.49 10.5 0.54 11.0 0.62 11.3 0.68 11.6 0.77 11.9 15.45 12.0 14.41 12.1 5.77 12.2 2.63 12.3 1.94 12.4 1.61 12.5 1.33 12.6 1.11 12.7 1.01 12.8 0.94 13.0 0.84 13.2 0.78 13.4 0.77 13.6 0.76 13.8 0.75 14.0 0.73 14.3 0.70 14.6 0.66 15.0 0.60 15.5 0.49 16.0 0.43 16.5 0.40 17.0 0.39 17.5 0.37 18.0 0.36 19.0 0.33 20.0 0.29 22.0 0.27 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 18.00 16.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 Outflow Hydrograph (100-yr Design Storm) sa 10.0 15.0 20.0 25.0 30a Post -Development Outflow Hydrographs The following outflow hydrographs reflect the post -development attenuation in Subareas A, B, & C from the proposed underground detention system 'SWM 1' and detention basin 'SWM 2' Post -Development DA A, B, & C Outflow Hydrograph (Summation of SWIM 1 & 2 Routings) Time (hrs) Inflow (cfs) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.3 11.6 11.9 12.0 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.3 14.6 15.0 15.5 16.0 16.5 17.0 17.5 18.0 19.0 20.0 22.0 24.0 0.00 0.12 0.13 0.14 0.14 0.15 0.15 0.16 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.26 0.30 0.31 0.35 0.41 0.49 0.56 0.69 1.13 1.26 1.31 1.31 1.30 1.28 1.26 1.24 1.22 1.19 1.11 1.00 0.85 0.70 0.67 0.64 0.61 0.59 0.54 0.51 0.47 0.44 0.40 0.36 0.32 0.23 0.17 0.14 0.13 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00 Outflow Hydrograph (1-yr Design Storm) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Post -Development DA A, B, & C Outflow Hydrograph (Summation of SWIM 1 & 2 Routings) Time (hrs) Inflow (cfs) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.3 11.6 11.9 12.0 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.3 14.6 15.0 15.5 16.0 16.5 17.0 17.5 18.0 19.0 20.0 22.0 24.0 0.00 0.16 0.17 0.18 0.19 0.19 0.20 0.21 0.21 0.23 0.24 0.24 0.26 0.27 0.27 0.31 0.28 0.33 0.38 0.39 0.44 0.50 0.59 0.66 0.79 1.24 4.37 3.67 2.65 2.33 2.04 1.67 1.50 1.38 1.30 1.19 1.12 1.02 0.90 0.78 0.73 0.70 0.67 0.64 0.60 0.55 0.54 0.47 0.47 0.41 0.32 0.24 0.19 0.00 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 Outflow Hydrograph (2-yr Design Storm) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Post -Development DA A, B, & C Outflow Hydrograph (Summation of SW M 1 & 2 Routings) Time (hrs) Inflow (cfs) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.3 11.6 11.9 12.0 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.3 14.6 15.0 15.5 16.0 16.5 17.0 17.5 18.0 19.0 20.0 22.0 24.0 0.00 0.25 0.30 0.31 0.31 0.31 0.33 0.34 0.35 0.36 0.38 0.39 0.41 0.42 0.44 0.46 0.47 0.51 0.56 0.59 0.63 0.71 0.80 0.87 1.01 9.70 13.18 6.27 4.21 3.57 3.17 2.81 2.52 2.24 1.97 1.54 1.38 1.28 1.19 1.12 1.03 0.92 0.86 0.83 0.78 0.74 0.70 0.67 0.64 0.61 0.53 0.45 0.34 0.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 Outflow Hydrograph (10-yr Design Storm) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Proposed Outlet Protection Calculations OUTLET PROTECTION INTO SWIM 2 PER VESCH PLATE 3.18-1, DEPTH OF STONE (d)=1.5 x MAX STONE DIAMETER d>_6" p10= 3.43 CFS D.design= 6.5 CFS (MIN. DISCHARGE FOR IS"DIAMETER PIPE) PER VESCH PLATE 3.18-3 d50= 0.5 FT NOTE: VDOT CLASS Al STONE HAS A MEAN d50=0.9 FT AND EXCEEDS 0.5 FT a= 8 FT W1= 3'D0= 33S FT W2= DO+La= 9.25 FT OUTLET PROTECTION TO INCLUDE A FILTER FABRIC UNDERLAYMENT KEYED INTO THE EXISTING GROUND A MINIMUM OF 9" ATTHE ENDS & ALONG THE PERIMETER EDGES OF FABRIC SHALL OVERLAP A MINIMUM OF 9'. STONE TO BE VDOT CUSS Al STONE WITH THE FOLLOWING DIMENSIONS: La= 16 FT(TOEXTENDTOWARDSTHEROTTOMOFRASIN) W1= 3.75 FT W2= 9.25 FT DEPTH= 1.5 FT DEPTH (d)>_ 1.5 X 0.9' DEPTH (d)>_ 1.35' RIPRAP OUWAUL CHANNEL q10= 13.18 CPS PER VESCH SPEC 3.19, PAGE III-177 (APPENDIX 3.19a FOR 'RIPRAP DESIGN IN CHANNEL') FOR TANGENT FLOW 5=0.035 ET/FT PER MANNING'S EQN, DEPTH OF FLOW =0.41' (SEE CHANNEL CALLS) PER PLATE 3.19-3, 150= I.S FT NOTE: VDOT CLASS II RIPRAP HAS A d50=1.6' PER PLATE 3.194 0= 8 d= 3 B/d= 2.67 = 4 K1= 0.97 PER PLATE 3.19-5 ANGLE OF REPOSE= 42° PER PLATE 3.19-6 K0= 0.95 d50XK1/K2=d'50= I81NXO.97/0.95= 18.38 IN USE18INCHES OUTFALL FROM MM 1 TO RIPRAP CHANNEL PER VESCH PLATE 3.18-1, DEPTH OF STONE (d)=1.5 x MAX STONE DIAMETER d>_6" p10= 5.76 CFS Qdesign= 6.5 CFS (MIN. DISCHARGE FOR IS"DIAMETER PIPE) PER VESCH PLATE 3.18-3 d50= 0.25 FT NOTE: VDOT CUSS II STONE HAS A MEAN d5O=1.6 FT AND EXCEEDS 0.5 FT DEPTH (d)>_ 1.5 X 1.6' DEPTH (d)>_ 2.4' OUTFALL FROM MM 2TO RIPRAP CHANNEL PER VESCH PLATE 3.18-1, DEPTH OF STONE (d) 1.5 x MAX STONE DIAMETER d >_6" p10= 7.42 CFS PER VESCH PLATE 3.18-3 150= 0.3 FT NOTE: VDOT CLASS II STONE HAS A MEAN dW=1.6 FT AND EXCEEDS 0.5 FT DEPTH (d)>_ 1.5 X 1.6' DEPTH (d) 2 2.4' OUTLET PROTECTION TO INCLUDE A FILTER FABRIC UNDERLAYMENT KEYED INTO THE EXISTING GROUND A MINIMUM OF 9" AT THE ENDS & ALONG THE PERIMETER EDGES OF FABRIC SHALL OVERLAP A MINIMUM OF 9". STONE TO BE VDOT CLASS 11 STONE AT DEPTH OF 36INCHES Rip Rap Channel Calculations Complex Channnel Input: Slope 0.035 Flow (given) 13.290 line x y n 0 0.000 588.000 0.045 1 6.000 586.000 0.045 2 12.000 585.000 0.045 3 20.000 585.000 0.045 4 26.000 586.000 0.045 5 32.000 588.000 0.045 Output: Depth 0.409 (y) ( 585.409) Channel bed segment output: (first n value not used) line Q V A P 1 0.00 0.00 0.00 0.00 2 1.07 2.13 0.50 2.49 3 11.15 3.41 3.27 8.00 4 1.07 2.13 0.50 2.49 5 0.00 0.00 0.00 0.00 Virginia Runoff Reduction Method Water Quality Calculations (COMPLIANCE IS MET THROUGH THE BEST MANAGEMENT PRACTICE OF PURCHASING NUTRIENT CREDITS. THE VRRM BOUNDARY IS DEFINED BY THE LIMITS OF DISTURBANCE) Oro wymio itude'Reauttron.. Nnoevebpmem (ampllan[e SpreaarFeet - varsbn 3.0 02011 Noeded.a,eDe meapmwe 0 2013 pan maPeaneedeWall me[m..me rgs[x.me Aeon Frt nhertll wra under ttv lopment➢miettr No • -- -- ---___ _-- Site Information Post -Development Project (Treatment Volume and Loads) Enter Turn Disturbed Are.(mai aal Coate meIOeo, Spe[iflmtions.1 2013 Waft Seet; '® rindoodunFR? xo mna[orerp..m:enrerea[D,renin J_-.. �',, -- � rpmiai:mpmorepenrerea� vi eve -0.eeevelopment Wnd(uxm larerl aeon. aaipa. e. ,nerve. m.a �a m.e¢.annW—l-a..me a.a.�a � -eKw�Wea Po6Wxx0pmem t„e wwr d[rml roa.vpei loan e.�eve°b ..Pa.saToa,�.aab a.we= non mme.a tvnr—1- °veu,maaraea a.a w.° p..a Wet rnmmnu eonpnwemdentendi _. mrpae.l ,..wa•w.a oa — n oss mgpro..ITalw[I.ed i .a mremd.�. Dez ass s,im �me eugmw zee amnu•++la=NM aae imp=—W..d I am I.mdesmems mar .. x4 [a eese.sm m..nrd wmcme,.maD.,nP.a.lrxmr »..a.n..doP—n x,ae .e..,� ooaama.aes •ate 00.. •.... 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E AREA CHECK FOREST/OPEN SPACE (ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED [ac) 0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA (ac) 0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA TREATED (ac) 0.00 0.00 0.00 0.00 0.00 OK. AREA CHECK Site Treatment Volume (ft3) B,3ia Runoff Reduction Volume and TP By Drainage Area RUNOFF REDUCTION VOLUME ACHIEVED (fe)l 0 0 0 0 0 0 TP LOAD AVAILABLE FOR REMOVAL (Ib/yr) D.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REDUCTION ACHIEVED (Ib/yr) D.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REMAINING (Ib/yr) 0.00 0.00 0.00 0.00 11 0.00 0.00 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 Total Phosphorus FINAL POST -DEVELOPMENT TP LOAD(Ib/yr) 1 5.22 TP LOAD REDUCTION REQUIRED (Ib/yr) 3.06 TP LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 TP LOAD REMAINING (Ib/yr): 5.22 REMAINING TP LOAD REDUCTION REQUIRED (Ib/yr): 3.06 Total Nitrogen (For Information Purposes) POST -DEVELOPMENT LOAD(Ib/yr) 1 37.37 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 REMAINING POST -DEVELOPMENT NITROGEN LOAD (Ib/yr) 37.37 STORM SEWER COMPUTATIONS 0 a N e CL CC 0.' 0 0 Q Cc 0. R O N N N (I O b F- O\ T D• r O O O D• m � O h s �- ti ti ti O O O O O O O O O O O O O O O O O O O O O t- vl 0 vl vl h o0 1� N � oo D• V O vl vl �p V 1� oo D• r N h D• O 1� R R O h m r m m o\ m b � m oo a O\ R N O D• O � � O �D �O i0 �O i0 �D �O vl vl vl vl vl a O u ro W co op co op m co op op m V C b b b b b b b b b b b b 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $ W o 0 0 0 0 0 0 0 0 0 0 0 S a o 0 0 0 0 0 0 0 0 0 0 0 O � 8 ti ti a a a E 45 x'' AVON PARK II Flood Protection Analysis Insert O N b N 0 N 0 00 z N N d j CO N m j > CO vl N U II � W � y a m O N N M W 6 N N t0 3 m o z o " u x u o w n N M u ¢ ° m a 0 a n e o n ¢ Q n o z N W r v (J N 01 t0 V1 a u � m yja ay ° E z am m T ate+ ' m O > N > .6 O MC it O W W C E E 0 t o o a p a n c o o m o` G u > 3 co a o Lc C m O N m aw C a s � `m o O d c n w > v t o 3 t u c A °' w h c o E c o 0 o `a a c c t01, m Q .. c C o w '° 3 c 5 m t j u a ti a m a O s o w a o 0 o m - v m O 0 it > o E u a v o 'o' m w c a E 0 aoe m m 3 E-q3 .m o o x > a y m c o c o m m N ¢ n E o R C O pp Y $ m a w e m a o c c w m n > w m ¢ o y c n o o` x M c > w w a U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 3: Time of Concentration (Tt) or Travel Time (Tt) Project: Avon Park II- Flood Protection Analysis Location: Hathaway Street Check One: Present X Developed Check One: T, X T, Segment ID: Sheet Flow: (Applicable to Tc only) 1 Surface description (Table 3-1) 2 Manning's roughness coeff., n (Table 3-1 3 Flow length, L (total L < 100) (ft) 4 Two-year 24-hour rainfall, Pz (in.) Land slope, s (ft/ft) 6 Compute Tt = [0.007(n*L)0.8] / P2 .5 s0.4 Shallow Concentrated Flow: 7 Surface description (paved or unpaved) B Flow Length, L (ft) 9 Watercourse slope, s (ft/ft) 10 Average velocity, V (Figure 3-1) (ft/s) 11 Tt = L / 3600*V Channel Flow: 12 Cross sectional flow area, a (ft) 13 Wetted perimeter, P. (ft) 14 Hydraulic radius, r = a/Pw (ft) 15 Channel Slope, s (ft/ft) 16 Manning's Roughness Coeff, n 17 V= [ 1.49r2/3so 5 ] / n 18 Flow length, L (ft) 19 Tt= L/ 3600*V 20 Watershed or subarea Ttor Tt (Add Tt in steps 6, 11 and 19) Designed By: FGM, PE Checked By: SRC, PE Through subarea n/a FL-ENG-21A 06/04 Date: 2/1/2021 Date: 2/1/2021 Existing Existing Avon Drainage to Park Avon St. Dense Grass 0.24 100 3.67 0.04 0.17 Unpaved 340 0.05 5.4 0.02 c 3 o v � LL � N C N U U C W 0 + 10 } U N v o c v 0 0 < 0 0 v 0.02 1.00 1 0.21 Note: A 1 hourTc was assumed for Avon Park's attenuated runoff. No data was provided in approved WPO 200500062. U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 4: Graphical Peak Discharge Method Project: Avon Park II- Flood Protection Analysis Designed By: FGM, PE Location: Hathaway Street Checked By: SRC, PE Check One: Present X Developed Date: 2/1/2021 Date: 2/1/2021 1. Data Drainage Area Description Drainage Area Description Drainage Area Description Existing Avon Park Existing Drainage to Avon St. Extended Drainage Area (Am) in miles = 0.0120 0.0117 Runoff curve number CN= 55 63 Time of concentration (Tc)= 1.00 0.21 Rainfall distribution type= II II Pond and swamp areas spread throughout the watershed= 0 0 2. Frequency -years 1 2 10 1 2 10 3. Rainfall, P (24 hour)- inches 3.04 3.67 5.55 3.04 3.67 5.55 4. Initial Abstraction, la -inches 1.64 1.64 1.64 1.18 1.18 1.18 5. Compute Ia/P 0.54 0.45 0.29 0.39 0.32 0.21 6. Unit peak discharge, Qu- csm/in 160 200 300 575 675 750 7. Runoff, Q from Worksheet 2- inches 0.21 0.40 1.27 0.44 0.74 1.85 8. Pond and Swamp adjustment factor, Fp 1 1 1 1 1 1 9. Peak Discharge, Qp- cfs where Qp=Qu Am Q Fp 0.40 0.98 4.58 2.97 5.79 16.20 Tog ?R - --,Or ME Rat \ O-`IER� D6S�CN FLt vJ y K A'"' N'l)'j 6 T �E2 NI(jNlv1 � lfoAPULA MRxsMUM rutL F� c�R�csT`I tam R ay" CMP (E \ 1, = aot. �11 �Fs beCAUC& TFks ,Q-yC. 4R�-vJ �ECGPr�E/�%i .556ra �lnoJ EfiCC--CJ)S e-APA-C--C ` cMe� -04 �yLVEf�'S CU.(�r:NTL`( Exp�Rlr��S LOCAL--t.�ZC--10 F4oca1-NG. R1,40 �F -P,-js, `�VA� as-8�o-66 r-AN ¢ u�a�s�E�• ��(L SuBS cTiCN t.a.tj' tit 7o�n1si/2vAJ"' 5'FowwATclZ Cor°VE`il )IjCE. 54S-r-eMS Zo Na-t �2EC3v2Rc Arm 1 anps rzV AL �}NAL 1S�S ,e(OW C,orA 'L:aAMCG W3' f7L401'7 Q� c'rxonF iA',J Ii't�' % 5kxm AIi`� O� Vial, Ell FEll° it Zt3.3a cFs V to-ya. ?eA Pk�-o�v. 4ow = ee,� �3•a�� Aqoo TAr�-Vc T, F� Pa�F�� �3N,9lYS%s aj��a�