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HomeMy WebLinkAboutWPO202000041 Calculations 2020-09-04AVON PARK II VSMP STORMWATER MANAGEMENT CALCULATIONS PACKET Date of Calculations AUGUST 19, 2020 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 U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 2: Runoff Curve Number and Runoff Project: Avon Park 11 Location: 1690 Avon Street Ext Check One: Present X Developed 1. Runoff curve Number (CN) Designed By: LMW, PE Checked By: SRC, PE FL-ENG-21A O6/04 Date: 8/19/2020 Date: 8/19/2020 Soil name and Cover description CN(weighted)= Drainage Area hydrologic group (Cover type, treatment, and hydrologic condition; percent CN Area ProductArea CNx total product/ Calculated Description (Acres) Area 'S' Value (Appendix A) impervious; unconnected/ connected impervious area ratio) total area Impervious Areas 98 0.00 0.0 B lawns in Good Condition (25%+/-) 61 0.00 0.0 DAA Woods/Grass Combination 58 0.73 42.3 (Pre-Dev.) Impervious Areas 98 0.52 51.0 J4 3.50 C lawns in Good Condition 74 1.65 122.1 Woods/Grass Combination 72 1 0.31 22.3 DAB Impervious Areas 98 0.00 0.0 (Pre-Dev.) B lawns in Good Condition 61 0.00 0.0 58 7.24 Woods/Grass Combination 58 0.26 15.1 Impervious Areas 98 0.00 0.0 DAC 8 lawns in Good Condition (25%+/-) 61 0.00 0.0 58 7.24 (Pre-Dev.) Woods/Grass Combination 58 0.62 36.0 Impervious Areas 98 0.00 0.0 DAD B lawns in Good Condition (25%+/-) 61 0.10 6.1 61 6.39 )Pre-Dev.) Woods/Grass Combination 58 0.00 0.0 Impervious Areas 98 1.15 112.7 B Lawns in Good Condition 61 0.54 32.9 DAA (UGD) Woods/Grass Combination 58 0.00 0.0 87 1.50 (Past-Dev) Impervious Areas 98 0.37 36.3 C lawns in Good Condition 74 0.21 15.5 Woods/Grass Combination 72 0.00 0.0 DAB Impervious Areas 98 0.21 20.6 (Post-Dev) C lawns in Good Condition 74 0.53 39.2 81 2.37 Woods/Grass Combination 72 0.00 0.0 DAC Impervious Areas 98 0.07 6.9 (Post-Dev) C lawns in Good Condition 74 1.11 82.1 75 3.26 Woods/Grass Combination 72 0.00 0.0 2. Runoff 1-Year Storm I 2-Year Storm 10-Year Storm Drainage Area Description Frequency -years 1 2 30 n/a Rainfall, P(24 hour) -inches 3.D4 3.67 5.55 n/a Runoff, Q-inches 0.94 1.36 2.82 DAA(Pre-Dev.) Runoff, Q-inches 0.29 0.52 1.48 DA B(Pre-Dev.) Runoff, Q-inches 0.29 0.52 1.48 DA C(Pre-Dev.) Runoff, Q-inches 0.38 0.65 1.71 DA D(Pre-Dev.) Runoff, Q-inches 1.77 2.33 4.D9 DAA(UGD)(Post-Dev) Runoff, Q-inches 1.33 1.83 3.46 DA B (Post-Dev) Runoff, Q-inches 1.01 1.45 2.94 DA C(Past-Dev) 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) 796 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 49 100 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 U.S. Department of Agriculture Natural Resources Conservation Service TR 5S Worksheet 4: Graphical Peak Discharge Method Project: Avon Park 11 Designed By: DOW, PE Date: 8/19/2020 Location: 1690 Avon Street Ext Checked By: SRC, PE Date: 8/19/2020 Check One: Present X Developed X 1. Data Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Description DAA (Pre -Day.) DAB (Pre-Dev.) DAC (Pre-Dev.) DAD (Pre-Dev.) DAA(UGD) (Post-Dev) DAB (Post-Dev) DAC (Post-Dev) Drainage Area (A.) in miles' 0.0050 0.0004 0.0010 0.0002 OA035 0.0012 0.0018 Runoff curve number CN= 74 58 58 61 87 81 lS Time of concentration(Tc)= 0.21 0.19 0.15 0.10 0.10 0.10 0.10 Rainfall distribution type= Type II Type II Type II Type II Type II II II Pond and swamp areas spread throughout the watershed= 0 0 0 0 0 0 0 2. Frequency -years 1 2 10 1 2 10 1 2 10 1 2 10 1 2 10 1 2 10 1 2 10 3. Rainfall, P(24 hour -inches 3.04 3.67 5.55 3.04 3.67 5.55 3.04 3.67 S.SS 3.04 3.67 S.SS 3.04 3.67 5.55 3.04 3.67 S.SS 3.04 3.67 5.55 4. Initial Abstraction, la -inches 0.70 0.70 0.70 1A5 1.45 1.45 1A5 1.45 1AS 1.28 138 1.28 0.30 0.30 0.30 OA] 0.47 0.47 0.65 0.65 0.65 S. Compute la/P 0.23 0.19 0.13 DAB 0.39 0.26 DAB 0.39 0.26 OA2 0.35 0.23 0.10 0.08 0.05 0.16 0.13 0.09 0.21 0.18 0.12 6. Unit Peak discharge, Qu-csm/in 72S 750 AS 425 SOO ]SO 500 725 82S 625 815 960 1" low 1000 97S 990 1" 970 97S 990 J. Runoff, Q from Worksheet 2-inches a." 1.36 2.82 0.29 0.52 1.48 0.29 0.52 1.48 0.38 0.65 SJI 1.77 2.33 4.09 1.33 1.83 3.46 1.01 1A5 2.94 S. Pond and Swamp adjustment factor, Fin 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 9. Peak Discharge, Qp-cfs where Qp=Qu Am Q Fp 3.41 1 5.12 1 10.94 0.05 0.13 0.45 0.14 0.31 1.19 0.04 0.08 0.26 Routed through undergound detention Routed Through SWM Detention Basin Routed Through SWM Detention Basin WATERSHED SUMMARY CN Area, ac. 1-year Flow, cfs 2-year Flow, cfs 10-year Flow, cfs FDA A, B, C,&D(Pre-Dev) 70 4.19 3.63 5.70 12.M CN Area, 1-year Flow, 2-year Flow, 10-year Flow, Post 83 4.19 1.30 3.95 12.79 NOTE: Sub-Area'A' is routed through Underground Detention System'SWM 1' and Sub -Areas B & C are routed through Detention Basin'SWM 2' 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 6.3.a. In accordance with the following methodology: Q Allowed < I.F. * (Q Pr�Developed + [RV Pre -Developed) ) I (RV Developed ) Q Allowed < 1.48 cfs Where: Q Pre -Developed= 3.63 cfs (From Worksheet 4 Watershed Summary) CN Pr�Developed= 70 (From Worksheet 4 Watershed Summary) S Pre -Developed = 4.21 (From SCS TR-55 eq. 2-4) RV Pr�Developed— 0.75 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 = 1.30 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 = 12.84 cfs 10-Year, 24-Hour Post -Development Subareas A-C Peak Flow Rate = 12.78 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: Mid -Flow 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 Outlet structure 4 Orifice name: Emergency Overflow Orifice area (sf) 1.310 diameter or depth (in) 15.500 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 666.500 multiple 1 discharge into riser Outlet structure 5 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 4 Inflow Hydrographs Hydrograph 0 SCS name: 1 YR SWM 1 Area (acres) 2.270 CN 87.000 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) 5.110 peak time (hrs) 11.917 volume (cy) 541.014 Hydrograph 1 SCS name: 2 YR SWM 1 Area (acres) 2.270 CN 87.000 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) 6.728 peak time (hrs) 11.917 volume (cy) 712.314 Hydrograph 2 SCS name: 10 YR SWM 1 Area (acres) 2.270 CN 87.000 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) 11.775 peak time (hrs) 11.917 volume (cy) 1246.605 OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 1 Peaks: 1 YR SWM 1 5.086 at 0.533 at 664.214 at 207.899 11.92 (hrs) 12.28 (hrs) 12.36 (hrs) Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 2 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Peaks: 2 YR SWM 1 6.697 at 11.92 (hrs) 1.897 at 12.10 (hrs) 665.220 at 12.10 (hrs) 258.510 Peaks: 10 YR SWM 1 11.720 at 11.92 (hrs) 5.709 at 11.96 (hrs) 667.085 at 11.96 (hrs) 328.484 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 0.08 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 0.12 6.5 0.13 7.0 0.13 7.5 0.14 8.0 0.14 8.5 0.15 9.0 0.17 9.5 0.18 10.0 0.19 10.5 0.20 11.0 0.23 11.3 0.24 11.6 0.28 11.9 0.43 12.0 0.50 12.1 0.53 12.2 0.53 12.3 0.53 12.4 0.53 12.5 0.53 12.6 0.53 12.7 0.53 12.8 0.52 13.0 0.52 13.2 0.51 13.4 0.50 13.6 0.49 13.8 0.49 14.0 0.48 14.3 0.46 14.6 0.45 15.0 0.43 15.5 0.40 16.0 0.37 16.5 0.34 17.0 0.31 17.5 0.27 18.0 0.23 19.0 0.16 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 0.11 2.5 0.12 3.0 0.12 3.5 0.12 4.0 0.13 4.5 0.13 5.0 0.14 5.5 0.14 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 0.27 11.6 0.31 11.9 0.48 12.0 1.22 12.1 1.90 12.2 1.72 12.3 1.47 12.4 1.20 12.5 0.87 12.6 0.74 12.7 0.65 12.8 0.59 13.0 0.54 13.2 0.53 13.4 0.52 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 0.43 16.0 0.41 16.5 0.38 17.0 0.36 17.5 0.33 18.0 0.30 19.0 0.22 20.0 0.16 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 0.15 1.5 0.16 2.0 0.17 2.5 0.17 3.0 0.17 3.5 0.18 4.0 0.18 4.5 0.19 5.0 0.19 5.5 0.20 6.0 0.20 6.5 0.21 7.0 0.21 7.5 0.22 8.0 0.22 8.5 0.23 9.0 0.24 9.5 0.26 10.0 0.27 10.5 0.29 11.0 0.33 11.3 0.36 11.6 0.41 11.9 2.69 12.0 5.71 12.1 3.36 12.2 2.80 12.3 2.54 12.4 2.27 12.5 1.99 12.6 1.71 12.7 1.43 12.8 1.05 13.0 0.78 13.2 0.66 13.4 0.59 13.6 0.54 13.8 0.54 14.0 0.53 14.3 0.52 14.6 0.52 15.0 0.50 15.5 0.49 16.0 0.47 16.5 0.45 17.0 0.43 17.5 0.41 18.0 0.39 19.0 0.34 20.0 0.29 22.0 0.19 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 z.M � 5.00 4.00 3.m 2.DO 1.DO D.M -1.a0 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) 0.740 CN 80.000 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) 1.202 peak time (hrs) 11.917 volume (cy) 127.266 Hydrograph 4 SCS name: DA B 2 YR Area (acres) 0.740 CN 80.000 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) 1.664 peak time (hrs) 11.917 volume (cy) 176.187 Hydrograph 5 SCS name: DA B 10 YR Area (acres) 0.740 CN 80.000 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) 3.172 peak time (hrs) 11.917 volume (cy) 335.784 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) 1.920 CN 78.000 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) 15.700 peak time (hrs) 11.917 volume (cy) 1662.123 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) 2.667 at 11.92 (hrs) discharge (cfs) 0.770 at 12.08 (hrs) water level (ft) 590.531 at 12.10 (hrs) storage (cy) 67.856 Hydrograph 7 Routing Summary of Peaks: DA B & C 2 YR inflow (cfs) 3.778 at 11.92 (hrs) discharge (cfs) 2.787 at 12.02 (hrs) water level (ft) 590.809 at 12.02 (hrs) storage (cy) 84.035 Hydrograph 8 Routing Summary of Peaks: DA B & C 10 YR inflow (cfs) 7.482 at 11.92 (hrs) discharge (cfs) 7.221 at 11.94 (hrs) water level (ft) 591.056 at 11.94 (hrs) storage (cy) 100.409 Hydrograph 9 Routing Summary of Peaks: DA B & C 100 YR inflow (cfs) 15.626 at 11.92 (hrs) discharge (cfs) 15.508 at 11.92 (hrs) water level (ft) 591.267 at 11.92 (hrs) storage (cy) 115.928 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 0.05 3.5 0.05 4.0 0.06 4.5 0.06 5.0 0.07 5.5 0.07 6.0 0.07 6.5 0.07 7.0 0.08 7.5 0.09 8.0 0.09 8.5 0.11 9.0 0.11 9.5 0.15 10.0 0.16 10.5 0.20 11.0 0.26 11.3 0.31 11.6 0.41 11.9 0.68 12.0 0.75 12.1 0.77 12.2 0.76 12.3 0.75 12.4 0.74 12.5 0.72 12.6 0.70 12.7 0.67 12.8 0.64 13.0 0.57 13.2 0.45 13.4 0.30 13.6 0.19 13.8 0.17 14.0 0.16 14.3 0.14 14.6 0.14 15.0 0.14 15.5 0.11 16.0 0.10 16.5 0.09 17.0 0.09 17.5 0.08 18.0 0.07 19.0 0.06 20.0 0.05 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) 30.0 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 0.06 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 0.09 5.5 0.09 6.0 0.10 6.5 0.11 7.0 0.11 7.5 0.11 8.0 0.14 8.5 0.15 9.0 0.18 9.5 0.18 10.0 0.21 10.5 0.26 11.0 0.33 11.3 0.38 11.6 0.47 11.9 0.75 12.0 2.73 12.1 1.61 12.2 0.82 12.3 0.77 12.4 0.76 12.5 0.75 12.6 0.73 12.7 0.72 12.8 0.70 13.0 0.65 13.2 0.58 13.4 0.48 13.6 0.36 13.8 0.26 14.0 0.22 14.3 0.20 14.6 0.19 15.0 0.17 15.5 0.15 16.0 0.13 16.5 0.11 17.0 0.13 17.5 0.11 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 3.00 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 0.14 1.0 0.14 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 0.18 6.0 0.20 6.5 0.21 7.0 0.22 7.5 0.23 8.0 0.24 8.5 0.27 9.0 0.31 9.5 0.32 10.0 0.35 10.5 0.40 11.0 0.46 11.3 0.50 11.6 0.59 11.9 6.58 12.0 7.07 12.1 3.02 12.2 1.33 12.3 0.97 12.4 0.84 12.5 0.78 12.6 0.77 12.7 0.76 12.8 0.75 13.0 0.73 13.2 0.70 13.4 0.67 13.6 0.63 13.8 0.57 14.0 0.49 14.3 0.39 14.6 0.34 15.0 0.31 15.5 0.29 16.0 0.26 16.5 0.24 17.0 0.23 17.5 0.22 18.0 0.20 19.0 0.17 20.0 0.15 22.0 0.14 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 8.00 7.00 6.00 s.00 4.00 3.DD z.DO 1.00 D.DD 0 -1.00 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 0.39 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 15.02 12.0 14.46 12.1 5.79 12.2 2.64 12.3 1.95 12.4 1.62 12.5 1.33 12.6 1.12 12.7 1.01 12.8 0.95 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 0.13 0.14 0.14 0.15 0.15 0.16 0.17 0.18 0.19 0.20 0.20 0.22 0.22 0.23 0.26 0.28 0.33 0.34 0.40 0.48 0.55 0.69 1.12 1.25 1.30 1.29 1.28 1.27 1.25 1.23 1.20 1.17 1.09 0.96 0.80 0.68 0.66 0.63 0.61 0.58 0.56 0.51 0.47 0.43 0.39 0.36 0.31 0.22 0.16 0.14 0.00 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 0.17 0.18 0.19 0.20 0.20 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.27 0.31 0.33 0.37 0.38 0.43 0.49 0.58 0.65 0.78 1.23 3.95 3.51 2.54 2.24 1.96 1.62 1.47 1.36 1.29 1.18 1.11 1.00 0.98 0.77 0.72 0.69 0.66 0.63 0.59 0.54 0.49 0.49 0.44 0.40 0.31 0.24 0.19 0.00 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 0.27 0.29 0.31 0.30 0.31 0.32 0.33 0.34 0.36 0.37 0.38 0.40 0.41 0.43 0.45 0.46 0.50 0.55 0.57 0.62 0.70 0.79 0.86 0.99 9.27 12.78 6.38 4.14 3.51 3.11 2.77 2.48 2.19 1.80 1.51 1.36 1.26 1.17 1.10 1.02 0.91 0.85 0.82 0.77 0.72 0.69 0.66 0.63 0.59 0.52 0.44 0.33 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 (E)=1.5 x MAX STONE DIAMETER E>_6" p10= 4.00 CFS D.tlesign= 6.5 CFS (MIN. DISCHARGE FOR IS"DIAMETER PIPE) PER VESCH PLATE 3.18-3 dSO= 0.5 FT NOTE: VDOT CLASS Al STONE HAS A MEAN E50=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" AT THE ENDS & ALONG THE PERIMETER EDGES OF FABRIC SHALL OVERLAP A MINIMUM OF 9'. STONE TO BE VDOT CUSS Al STONE WITH THE FOLLOWING DIMENSIONS: a= 8 FT w1= 3.75 FT w2= 9.25 FT DEPM= 1.5 FT DEPTH (E)>_ 1.5 X 0.9' DEPTH (E)>_ 1.35' RIPRAP OUTFALL CHANNEL q10= 12.78 CFS PER VESCH SPEC 3.19, PAGE III-177(APPENDIX 3.19 FOR 'RIPRAP DESIGN IN CHANNEL') FOR TANGENT FLOW 5=0.035 ET/ET PER MANNING'S EQN, DEPM OF FLOW =0.40' (SEE CHANNEL CALLS) PER PLATE 3.19-3, 150= I.S FT NOTE: VDOT CLASS II RIPRAP HAS A E50=1.6' PER PLATE 3.194 0= 8 J= 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=E'50= I8INXO.97/0.95= 18.38 IN USE18INCHES OUEFALL FROM MM 1 TO RIPRAP CHANNEL PER VESCH PLATE 3.18-1, DEPTH OF STONE (E)=1.5 x MAX STONE DIAMETER E>_6" p10= 5.71 CFS Qdesign= 6.5 CFS (MIN. DISCHARGE FOR IS"DIAMETER PIPE) PER VESCH PLATE 3.18-3 dSO= 0.25 FT NOTE: VDOT CLASS II STONE HAS A MEAN E5O=1.6 FT AND EXCEEDS 0.5 FT DEPTH (E)>_ 1.5 X 1.6' DEPTH (E)>_ 2.4' OUEFALL FROM MM 2TO RIPRAP CHANNEL PER VESCH PLATE 3.18-1, DEPTH OF STONE (E)=1.5 x MAX STONE DIAMETER E >_6" p10= 7.22 CFS PER VESCH PLATE 3.18-3 150= 0.3 FT NOTE: VDOT CLASS II STONE HAS A MEAN E50=1.6 FT AND EXCEEDS 0.5 FT DEPTH (E)>_ 1.5 X 1.6' DEPTH (E)>_ 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 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) OFtl Virgil, PunoffRdlu ion MemWRe-Oevebpment lamplbn[e SprtaOrFeet-Version 30 cede amp o 2013 nmN EMP stanaaaaa dsPeallm,am Pndmt N aom 0. nmentlPro -� ® _ WR B/19/3Y30 n ® ] Linear Cev lop IM No a Site Information �I Post -Development Project (Treatment Volume and Loads) Eme,Toral Disturbed Na. (acres) al5 Cbe[k: BMP Desgn Spe[iflmtionslls[3013 WaN5W5®Spe[i _ ______ '® tineatpraFtt? No �'',, -- � ]DZPmi:rv.Dmo,eemrerea? si vre-aeoevelopmenz LandmYer la=eal asala alm'Noa calla Dadla Tea .......... ..vDoe„:p.mw.mn-md�:,.m.a ,..woe..o.m mam,.annw�l-mama ee...eamr� -eK�w�a PD6ttvNopmem ty,e mwr dttml awla calla eras Nas Tea --_---- ----_-._-- am.vooe.:p.m IMmn-mamma om,. as b ..wom.o==m Mom,.d•ro o.. [m,mlaama rnmmnu aooerl Co mderoduvl _. m r9R al .eanro,e.i ,..vDo.. w.a oas oss m—..nPlrM[Ima4 ma...,.me. oez ass maim �0„I eugmw ,.ea XTEMMMMAMOMMUFM a„ e[ma.sama.3.Pm. .o.,-e.o..d -- ro.,rooe.:o.a T am wv,n� a m.`we.en a. --. w.om.aee D.m .21 -- My zaeeme.rmmrov.Pm wecm.,.raa—nPm.mwz ____'. zmrrermsmmm .Pea, DeaeDedoo�, em, M.—aam-- -- rmo.m�.m•.. o.mom ro,evooe.3o=ea•e.i=,e=I u, o.za rmm./Dom:oaa ao3 0.03 am ox wm=I wynmlminM am,mlam ..dT.n xM-omd— �moe.«.me.lm,ml aaz o.a .a.m.e.w.,e.l uz -- ayimoe l a9s -- ximoe,.am my Twivem...urtvm � I� anmoe ..l ass wrmoe l ass o.. - eamoe.mml .1 ximoe,.am vx zax ----_--_-_ ximoe,.aa anx rm�l T andraut Volume add Nutrient Load Treatment Volume and Nutrient Load aeon amv am9e n.. n®emmva amm0.1 a aa9 Imm ;w1 efm T. e.u3,195 LE— eR Lent3.M 1.91 IMetlM ow amle/nl „'i wo:'� ' m.aiwwP•oorm o�...�enPm.,ra,.. o. TtP m. +w..amarom,su !MW •.w+mmmoYea tv aae Mem, e. D.da maan uavmm� 2.3] a�laPoet-DeVelOpMent �mPmm,mne Ml .aw.efd M1/Yrl m.m mmPa.-..n.mnPmmmm,elmam mm,. w�e..A�.+'•w..�sem..lr�a..mm ezma...m rm,am,oumyme/µvry Requirement ftr She Area iP laatl Petlu[[ion 0.epuiretl Ilb/yrl 3.05 Site Results (Water Quality Compliance) Area Checks O.A.A O.A.B O.A.0 A. D.A.E ARMECK FOREST/OVEN SPACE (a[) am O.W 0.00 i0.00 O.W OK. IMPERWOUS MVER (ac) IMPERVnMCOVERTRENTFD)ac) am 0.00 0.00 0.00 0.00 0.00�M. 0.00 OWOK. OK.. MANAGEDTURFAREA(a[) 0.00 O.00 0.00 00.W OK. MANAGED TURF AREA TREATED(a[) 0.00 O.00 0.00 0.00 OK. AREA CHECK OK OK. OK. OK. Site Treatment VOIUme (ffa) 8,170 Runoff Reduction Volume and TP By Drainage Area O.A. A O.A. C D.AD O.A. E TOTALRUNOFF REDUMM VOLUME ACHIEVED pF) 0 0 0 00 AL Qb/1) LOADAVAKABLE FNhh 0.00 MAI 0.00 0.000.0.00 TPIDADREOUCTIED pb/yr) 0.00 0.00 0.00 O.W am TP LOADNG )Ib/yr) 0.00 0.00 0.00 O.W am NMWGEN IDAD REDUCTIEDpb/yr) am O.W 0.00 0.00 O.W 0.00 Totphorus FINAL POST-DEVELOPMAD Qb/yr) 5.13 TPLOADREDUCTIED pb/yr) 3.05TPIDADREOUCTIED pb/yr) 0.00 W LOAD REMAINING (lb/,): 5.13 REMAINING TP LOAD REDUCTION REQUIRED (lb/yr): 3.05