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HomeMy WebLinkAboutWPO202000055 Calculations 2020-12-07 (2)WHITE GABLES VSMP STORMWATER MANAGEMENT CALCULATIONS PACKET Date of Calculations SEPTEMBER 15, 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 )atabase) Soils Table (Source: NRCS Web Soil Survey Online Database) Albemarle County, Virginia (VA003'. Albemarle County, Virginia (VA003) Map Unit Map Unit Name Percent of AOI Symbol 14B Chester loam, 2 8.9% to 7 percent slopes 19B Minnieville loam, 55.1% 2 to 7 percent slopes 36B Hayesville loam, 2 15.8% to 7 percent slopes 36C Hayesville loam, 7 20.2% to 15 percent slopes Totals for Area of 100.0% Interest Note: The soils' properties witin this development are predominantly composed of hydrologic group type B soils. Precipitation Data (Source: NOAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates) +- O Terrain 3 Eight yyoods < n N S L a o _u 4 t a 3 o enrid0e P Ce ar(( qd I iy a s_3 )�Y Rtl Bellair 1oa�n 300tt POINT PRECIPITATION FREQUENCY (PF) ESTIMATES WITH 90% CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION NOAA Atlas 14, Volume 2, Version 3 PDS-based precipitation frequency estimates with 90% confidence intervals (in inches)l Average rtanence interval years) ol�l� 0 251 50 100 200 I5011 1000 24M 3.04 3.fi7 4.fi9 5.55 6.82 7.90 9.11 10A 12.4 14.1 (2.73J.40) 1 (3.314.11) 1 (4.21-S25) 1 (4.96-6.14) 11 (&06-7s7) 11 (6.974175) 1 (7.96-10.1) 1 (9.02-11.S) 1 (10.6-13.7) 1 (11.8-15.5) Channel and Flood Protection Calculations Project: Location: U.S. Department of Agriculture Natural Resources Conservation Service White Gables White Gables Lane Check One: Present X Developed 1. Runoff curve Number (CN) TR 55 Worksheet 2: Runoff Curve Number and Runoff Designed By: LMW, PE Checked By: SRC, PE FL-ENG-21A 06/04 Date: 9/15/2020 Date: 9/15/2020 Cover description CN (weighted) _Calculated Drainage Area Soil name and hydrologic (Cover type, treatment, and hydrologic condition; percent CN Area Product of CN x total product/ 'S' Description group (Appendix A) (Acres) Area Value impervious; unconnected/ connected impervious area ratio) total area Impervious Areas 98 0.11 10.3 DAA B Lawns in Good Condition (25%+/-) 61 1.40 85.4 63 5.89 (Pre-Dev.) Woods/Grass Combination 58 0.20 11.6 DAA(SWALE) Impervious Areas 98 0.37 36.3 (Post-Dev) B Lawns in Good Condition 61 0.21 12.8 85 1.76 Woods/Grass Combination 58 1 0.00 1 0.0 Impervious Areas 98 0.65 63.7 DAB (Post-Dev) B Lawns in Good Condition 61 0.48 29.3 82 2.15 Woods/Grass Combination 58 0.00 0.0 2. Runoff 1-Year Storm I 2-Year Storm I 10-Year Storm Drainage Area Description Frequency -years 1 2 10 n/a Rainfall, P (24 hour)- inches 3.04 3.67 5.55 n/a Runoff, Q-inches 0.45 0.74 1.86 DA A(Pre-Dev.) Runoff, Q-inches 1.62 2.17 3.88 DA A(SWALE)(Post-Dev) Runoff, Q- inches 1.43 1.95 3.60 DA B(Post-Dev) U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 3: Time of Concentration (TJ or Travel Time (T,) Project: White Gables Location: White Gables Lane Check One: Present X Developed X Check One: Tc X T, Segment ID Sheet Flow: (Applicable to Tc only) Designed By: Date: Checked By: Date: n/a DA A DA A (SWALE) DA B (Pre-Dev.) (Post-Dev) (Post-Dev) 1 Surface description (Table 3-1) Grass -dense Grass -dense Grass -dense 2 Manning's roughness coeff., n (Table 3-1) 0.24 0.24 0.24 3 Flow length, L (total L < 100) (ft) 100 90 100 4 Two-year 24-hour rainfall, P2(in.) 3.67 3.67 3.67 5 Land slope, s (ft/ft) 0.02 0.01 0.02 6 Compute T, = [0.007(n'L)0"8] / Pz .5 5 .4 0.22 0.27 0.22 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 T, = L / 3600`V 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 T, = L / 3600`V Channel Flow: 12 Cross sectional flow area, a (ft) 13 Wetted perimeter, Pw (ft) 14 Hydraulic radius, r = a/Pw (ft) 15 Channel Slope, s (ft/ft) 16 Manning's Roughness Coeff, n 17 V= [ 1.49r2/3s0"5 j / n 18 Flow length, L (ft) 19 T,= L / 3600'V 20 Watershed or subarea Tc or T, (Add T, in steps 6, 11 and 19) Paved Paved Unpaved 42 28 25 0.03 0.05 0.04 3.5 4.5 3.6 0.00 0.00 0.00 Unpaved Paved 316 170 0.06 0.06 4.0 5.9 0.02 0.01 N N O! Gl n a a a C C 3 3 0 0 LL LL O! Gl C C c c m m U U 0 0 0 0 0.24 0.28 0.23 Sub -Area or Reach Identifier SUBAREAS PRE DEV REACHES OUTLET Albemarle ZONE-2 NOAA-D County, Virginia Watershed Peak Table Peak Flow by Rainfall Return Period 2-Yr 10-Yr 1-Yr (cfs) (cfs) (cfs) 1.39 3.91 1.39 3.91 0.73 0.73 WinTR-55, Version 1.00.10 Page 1 9/9/2020 4:59:57 PM Project: Location: Check One: TR 55 Graphical Peak Discharge Method White Gables White Gables Lane Present X Developed X Designed By: Checked By: Date: 9/15/2020 Date: 9/15/2020 1. Data Drainage Area Description Drainage Area Description Drainage Area Description DAA (Pre-Dev.) DAA(SWALE) (Post-Dev) DAB (Post-Dev) Drainage Area (Am) in milesz = 0.0027 0.0009 0.0018 Runoff curve number CN= 63 85 82 Time of concentration (Tc)= 0.24 0.28 1 0.23 Rainfall distribution type= Type II Type II Type II Pond and swamp areas spread throughout the watershed= 0 0 0 2. Frequency -years 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 5.55 4. Initial Abstraction, la- inches 1.18 1.18 1.18 0.35 0.35 0.35 0.43 0.43 0.43 5. Compute la/P 0.39 0.32 0.21 0.12 0.10 0.06 0.14 0.12 0.08 6. Peak Discharge, Qp- cfs where Qp=Qu Am Q Fp 0.73 1.39 3.91 Routed through Dry Swale 'A' & Detention Basin 'B' Routed Through Detention Basin'B' WATERSHED SUMMARY CN Area, ac. 1-year Flow, cfs 2-year Flow, cfs 10-year Flow, cfs FDA A (Pre-Dev) 63 1.71 0.73 1.39 3.91 CN Area, 1-year Flow, 2-year Flow, 10-year Flow, DA A & B (Post-Dev) 83 1.71 0.18 1.39 2.22 NOTE: Sub -Area 'A' is routed through Dry Swale 'A' and then through Detention Basin'B'. Sub -Area B is routed through Detention Basin 'B' 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.1.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 !c I.F. (Q Pre�Developed [RV Pre -Developed)) (RV Developed) Q Allowed < 0.18 cfs Where: QPre-Developed= 0.73 cfs (FromTR-55) CN Pre�Developed= 63 (From Curve Number Summary) S Pre -Developed = 5.89 (From SCS TR-55 eq. 2-4) RV Pre�Developed= 0.45 in. (From SCSTR-55 eq.2-3) CN Post -Developed= 83 (From Curve Number Summary) S Post -Developed = 2.04 (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 = 0.18 cfs Section B.4 Limits of Analysis The analysis terminates at Post -Development Subarea B 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 = 3.91 cfs 10-Year, 24-Hour Post -Development Subareas A-C Peak Flow Rate = 2.22 cfs Section C.3 Limits of Analysis The flood protection analysis terminates at Subarea B since subsection C.2.b is met. Proposed Outlet Protection Calculations OUTLET PROTECTION INTO DRY SWALE'A' PER VESCH PLATE 3.18-1, DEPTH OF STONE (d) =1.5 x MAX STONE DIAMETER dz6" Q10= 2.08 CFS Qdesign= 3.5 CFS (MIN. DISCHARGE FOR 12" DIAMETER PIPE) PER VESCH PLATE 3.18-4 d50= 0.1 FT NOTE: VDOT CLASS Al STONE HAS A MEAN d50=0.9 FT AND EXCEEDS 0.5 FT La= 4 FT wl= 3'DO= 2.5 FT w2= DO+0.4La= 2.5 FT FINAL DESIGN 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 Al STONE WITH THE FOLLOWING DIMENSIONS: La= 4 FT wl= 2.5 FT w2= 3 FT DEPTH= 1.5 FT DEPTH (d) 2 1.5 X 0.9' DEPTH (d) 21.35' OUTLET PROTECTION INTO DETENTION BASIN'B' PER VESCH PLATE 3.18-1, DEPTH OF STONE (d) =1.5 x MAX STONE DIAMETER d 26" Q10= 5.66 CFS Qdesign= 6 CFS PER VESCH PLATE 3.18-4 d50= 0.3 FT NOTE: VDOT CLASS AI STONE HAS A MEAN d50=0.9 FT AND EXCEEDS 0.5 FT La= 18 FT wl= 3'DO= 3 FT w2= DO+0.4La= 2.72 FT FINAL DESIGN OUTLET PROTECTION TO INCLUDE A FILTER FABRIC UNDERLAYMENT KEYED La= 28.5 FT (EXTENDEDTO RISERTO PREVENT CLOGGING) wl= 3 FT w2= 3 FT DEPTH= 1.5 FT DEPTH (d) 2 1.5 X 0.9' DEPTH (d) z 1.35' OUTLET PROTECTION FOR DETENTION BASIN'B' OUTFALL PER VESCH PLATE 3.18-1, DEPTH OF STONE (d) =1.5 x MAX STONE DIAMETER d 26" Q10= 3.91 CFS Qdesign= 4 CFS PER VESCH PLATE 3.18-3 d50= 0.2 FT La= 9 FT wl= 3'DO= 3 FT w2= DO+La= SO FT NOTE: VDOT CLASS Al STONE HAS A MEAN d50=0.9 FT AND EXCEEDS 0.5 FT FINAL DESIGN OUTLET PROTECTION TO INCLUDE A FILTER FABRIC UNDERLAYMENT KEYED La= 9 FT wl= 3 FT w2= 10 FT DEPTH= 1.5 FT DEPTH (d) 2 1.5 X 0.9' DEPTH (d) z 1.35' Post -Development Dry Swale 'A' Routings and Outflow Hydrographs The following routing calculations and outflow hydrographs reflect the post -development attenuation in Subarea A from the proposed Dry Swale 'A' BasinFlow printout INPUT: Basin: 3 Contour Areas Elevation(ft) 600.00 601.00 602.00 Area(sf) Computed Vol.(cy) 27.00 0.0 289.00 5.0 819.00 24.7 Start_Elevation(ft) 600.00 Vol.(cy) 3 Outlet Structures Outlet structure 0 Orifice name: Barrel area (sf) 0.545 diameter or depth (in) 10.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 599.900 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low -Flow Orifice M area (sf) 0.267 diameter or depth (in) 7.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 600.000 multiple 1 discharge into riser Outlet structure 2 Weir name: Riser Top diameter (in) 12.000 side angle 0.000 coefficient 3.300 invert (ft) 601.900 multiple 1 discharge into riser 3 Inflow Hydrographs Hydrograph 0 SCS name: DA'A' 1 yr Area (acres) 0.580 CN 85.000 Type 2 rainfall, P (in) 3.040 time of conc. (hrs) 0.2900 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 0.900 peak time (hrs) 11.995 volume (cy) 126.329 Hydrograph 1 SCS name: DA'A' 2 yr Area (acres) 0.580 CN 85.000 Type 2 rainfall, P (in) 3.670 time of conc. (hrs) 0.2900 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 1.201 peak time (hrs) 11.995 volume (cy) 168.660 Hydrograph 2 SCS name: DA'A' 10 yr Area (acres) 0.580 CN 85.000 Type 2 rainfall, P (in) 5.550 time of conc. (hrs) 0.2900 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 2.152 peak time (hrs) 11.995 volume (cy) 302.225 OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: DA W 1 yr inflow (cfs) 0.899 at 12.00 (hrs) discharge (cfs) 0.870 at 12.06 (hrs) water level (ft) 600.749 at 12.06 (hrs) storage (cy) 2.748 Hydrograph 1 Routing Summary of Peaks: DA W 2 yr inflow (cfs) 1.201 at 12.00 (hrs) discharge (cfs) 1.107 at 12.08 (hrs) water level (ft) 601.032 at 12.08 (hrs) storage (cy) 5.338 Hydrograph 2 Routing Summary of Peaks: DA W 10 yr inflow (cfs) 2.152 at 12.00 (hrs) discharge (cfs) 1.629 at 12.12 (hrs) water level (ft) 601.895 at 12.12 (hrs) storage (cy) 21.624 Thu Sep 10 08:43:36 EDT 2020 Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.00 1.0 0.01 1.5 0.01 2.0 0.01 2.5 0.01 3.0 0.01 3.5 0.01 4.0 0.01 4.5 0.01 5.0 0.01 5.5 0.01 6.0 0.01 6.5 0.01 7.0 0.01 7.5 0.01 8.0 0.01 8.5 0.02 9.0 0.02 9.5 0.02 10.0 0.03 10.5 0.04 11.0 0.05 11.3 0.07 11.6 0.13 11.9 0.64 12.0 0.84 12.1 0.84 12.2 0.56 12.3 0.33 12.4 0.22 12.5 0.16 12.6 0.12 12.7 0.09 12.8 0.08 13.0 0.06 13.2 0.05 13.4 0.05 13.6 0.04 13.8 0.04 14.0 0.03 14.3 0.03 14.6 0.02 15.0 0.02 15.5 0.02 16.0 0.02 16.5 0.01 17.0 0.01 17.5 0.01 18.0 0.01 19.0 0.01 20.0 0.01 22.0 0.01 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0s0 0.20 0.10 0.00 n in Inflow Hydrograph (1-yr Design Storm) Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.01 1.0 0.01 1.5 0.01 2.0 0.01 2.5 0.01 3.0 0.01 3.5 0.01 4.0 0.01 4.5 0.01 5.0 0.01 5.5 0.01 6.0 0.01 6.5 0.02 7.0 0.02 7.5 0.02 8.0 0.02 8.5 0.02 9.0 0.03 9.5 0.03 10.0 0.04 10.5 0.05 11.0 0.08 11.3 0.10 11.6 0.18 11.9 0.80 12.0 1.04 12.1 1.10 12.2 0.86 12.3 0.43 12.4 0.30 12.5 0.22 12.6 0.16 12.7 0.13 12.8 0.11 13.0 0.09 13.2 0.07 13.4 0.06 13.6 0.06 13.8 0.05 14.0 0.04 14.3 0.04 14.6 0.04 15.0 0.03 15.5 0.03 16.0 0.02 16.5 0.02 17.0 0.02 17.5 0.02 18.0 0.02 19.0 0.01 20.0 0.01 22.0 0.01 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 1.20 1.00 0.e0 0.60 0.40 0.20 0.00 -0.20 Inflow Hydrograph (2-yr Design Storm) 1.0 Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.01 1.0 0.02 1.5 0.02 2.0 0.02 2.5 0.02 3.0 0.02 3.5 0.02 4.0 0.02 4.5 0.03 5.0 0.03 5.5 0.03 6.0 0.03 6.5 0.03 7.0 0.04 7.5 0.04 8.0 0.04 8.5 0.05 9.0 0.06 9.5 0.07 10.0 0.08 10.5 0.11 11.0 0.15 11.3 0.20 11.6 0.32 11.9 1.19 12.0 1.48 12.1 1.62 12.2 1.58 12.3 1.37 12.4 0.91 12.5 0.39 12.6 0.30 12.7 0.24 12.8 0.21 13.0 0.17 13.2 0.15 13.4 0.13 13.6 0.11 13.8 0.10 14.0 0.09 14.3 0.08 14.6 0.07 15.0 0.07 15.5 0.06 16.0 0.05 16.5 0.04 17.0 0.04 17.5 0.04 18.0 0.03 19.0 0.03 20.0 0.02 22.0 0.02 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 1.80 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00 -0.20 0 Inflow Hydrograph (10-yr Design Storm) 1.0 Post -Development Detention Basin 'B' Routings and Inflow Hydrographs The following routing calculations and hydrographs reflect the summation of post -development attenuation in Subarea A from the proposed Dry Swale 'A' and the inflow hydrograph of Subarea B. The summation of these hydrographs reflects the inflow hydrograph for proposed Detention Basin ' B' Post -Development DA B Inflow Hydrograph Time (hrs) Inflow (cfs) 0.0 0.00 0.5 0.02 1.0 0.02 1.5 0.02 2.0 0.02 2.5 0.02 3.0 0.02 3.5 0.02 4.0 0.02 4.5 0.02 5.0 0.03 5.5 0.03 6.0 0.03 6.5 0.03 7.0 0.03 7.5 0.03 8.0 0.03 8.5 0.04 9.0 0.05 9.5 0.05 10.0 0.06 10.5 0.08 11.0 0.10 11.3 0.14 11.6 0.24 11.9 1.39 12.0 1.66 12.1 1.29 12.2 0.73 12.3 0.38 12.4 0.28 12.5 0.22 12.6 0.18 12.7 0.14 12.8 0.13 13.0 0.11 13.2 0.10 13.4 0.09 13.6 0.08 13.8 0.07 14.0 0.06 14.3 0.06 14.6 0.05 15.0 0.05 15.5 0.04 16.0 0.04 16.5 0.04 17.0 0.03 17.5 0.03 18.0 0.03 19.0 0.03 20.0 0.02 22.0 0.02 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 1.80 1.60 1.4a 1.20 1.00 0.80 0.60 0.40 0.20 0.00 -0.20 0 Inflow Hydrograph (1-yr Design Storm) 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 26.0 26.5 27.0 27.5 Port -Development DA B 0.02 0.02 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.D4 0.D4 0.D4 0.D4 0.05 0.05 0.06 0.07 0.07 0.08 0.11 0.14 0.19 0.33 1.90 2.27 1.76 1.00 0.52 0.38 0.30 0.24 0.20 0.18 0.15 0.13 0.12 0.11 0.10 0.09 0.08 0.07 0.07 0.06 0.05 0.05 0.05 0.D4 0.D4 0.03 0.03 0.03 0.00 0.00 0.00 0.00 2.90 2.00 1.90 LM 0.90 0.00 0.90 Inflow Hydrograph (2-yr Design Storm) 30.0 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 26.0 26.5 27.0 27.5 Port -Development DA B 0.02 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.D4 0.D4 0.D4 0.D4 0.05 0.05 0.05 0.06 0.07 0.07 0.08 0.11 0.15 0.19 0.33 1.68 2.04 1.82 1.13 0.69 0.47 0.35 0.27 0.23 0.20 0.16 0.14 0.13 0.11 0.10 0.09 0.08 0.08 0.07 0.06 0.06 0.05 0.05 0.05 0.D4 0.D4 0.03 0.03 0.00 0.00 0.00 0.00 2.90 2.00 1.90 i.0o 0.90 0.00 n.90 Inflow Hydrograph (10-yr Design Storm) Post -Development DA A+B Outflow Hydrograph 0.0 0.00 0.5 0.02 1.0 0.02 1.5 0.02 2.0 0.02 2.5 0.03 3.0 0.03 3.5 0.03 4.0 0.03 4.5 0.03 5.0 0.03 5.5 0.04 6.0 0.04 6.5 0.04 7.0 0.04 7.5 0.05 8.0 0.05 8.5 0.06 9.0 0.07 9.5 0.07 10.0 0.09 10.5 0.11 11.0 0.16 11.3 0.21 11.6 0.37 11.9 2.03 12.0 2.50 12.1 2.13 12.2 1.29 12.3 0.71 12.4 0.50 12.5 0.38 12.6 0.29 12.7 0.24 12.8 0.21 13.0 0.18 13.2 0.15 13.4 0.13 13.6 0.12 13.8 0.11 14.0 0.10 14.3 0.08 14.6 0.08 15.0 0.07 15.5 0.06 16.0 0.05 16.5 0.05 17.0 0.05 17.5 0.04 18.0 0.04 19.0 0.03 20.0 0.03 22.0 0.02 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 3.00 2.50 zoo 1.50 1.00 0.50 0.00 -0.s0 Outflow Hydrograph (1-yr Design Storm) 1.0 Post -Development DA A+B Outflow Hydrograph (From Dry Swale Routings) 0.0 0.00 0.5 0.03 1.0 0.03 1.5 0.03 2.0 0.03 2.5 0.04 3.0 0.04 3.5 0.04 4.0 0.04 4.5 0.04 5.0 0.05 5.5 0.05 6.0 0.05 6.5 0.06 7.0 0.06 7.5 0.06 8.0 0.07 8.5 0.08 9.0 0.10 9.5 0.10 10.0 0.12 10.5 0.16 11.0 0.22 11.3 0.29 11.6 0.51 11.9 2.70 12.0 3.31 12.1 2.86 12.2 1.86 12.3 0.95 12.4 0.68 12.5 0.51 12.6 0.40 12.7 0.33 12.8 0.29 13.0 0.24 13.2 0.21 13.4 0.18 13.6 0.16 13.8 0.15 14.0 0.13 14.3 0.12 14.6 0.11 15.0 0.10 15.5 0.09 16.0 0.08 16.5 0.07 17.0 0.06 17.5 0.06 18.0 0.06 19.0 0.05 20.0 0.04 22.0 0.03 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 -0.50 Inflow Hydrograph (2-yr Design Storm) Post -Development DA A+B Outflow Hydrograph (From Dry Swale Routings) 0.0 0.00 0.5 0.04 1.0 0.04 1.5 0.04 2.0 0.05 2.5 0.05 3.0 0.05 3.5 0.05 4.0 0.05 4.5 0.06 5.0 0.06 5.5 0.07 6.0 0.07 6.5 0.08 7.0 0.08 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 0.21 11.0 0.30 11.3 0.39 11.6 0.65 11.9 2.86 12.0 3.53 12.1 3.44 12.2 2.71 12.3 2.06 12.4 1.39 12.5 0.74 12.6 0.58 12.7 0.47 12.8 0.40 13.0 0.33 13.2 0.29 13.4 0.25 13.6 0.23 13.8 0.20 14.0 0.18 14.3 0.16 14.6 0.15 15.0 0.14 15.5 0.12 16.0 0.10 16.5 0.09 17.0 0.09 17.5 0.08 18.0 0.08 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 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0 -0.50 Inflow Hydrograph (10-yr Design Storm) 30.0 Post -Development DA A+B Basin Inflow Hydrograph lased on Runoff of DA A + E 0.0 0.00 0.5 0.12 1.0 0.12 1.5 0.13 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 0.20 6.5 0.21 7.0 0.22 7.5 0.24 8.0 0.25 8.5 0.29 9.0 0.34 9.5 0.36 10.0 0.43 10.5 0.55 11.0 0.75 11.3 0.98 11.6 1.79 11.9 9.81 12.0 11.61 12.1 8.30 12.2 4.39 12.3 2.66 12.4 1.90 12.5 1.47 12.6 1.17 12.7 1.01 12.8 0.92 13.0 0.78 13.2 0.68 13.4 0.61 13.6 0.55 13.8 0.50 14.0 0.45 14.3 0.41 14.6 0.38 15.0 0.35 15.5 0.31 16.0 0.27 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 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 -2.00 Inflow Hydrograph (100-yr Design Storm) Post -Development Detention Basin 'B' Routings and Outflow Hydrographs The following routing calculations and outflow hydrographs reflect the post -development attenuation in Subareas A & B from the proposed Detention Basin 'B' Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.00 1.0 0.01 1.5 0.03 2.0 0.03 2.5 0.03 3.0 0.03 3.5 0.04 4.0 0.04 4.5 0.04 5.0 0.04 5.5 0.04 6.0 0.05 6.5 0.05 7.0 0.05 7.5 0.05 8.0 0.05 8.5 0.06 9.0 0.06 9.5 0.07 10.0 0.07 10.5 0.08 11.0 0.08 11.3 0.08 11.6 0.10 11.9 0.10 12.0 0.15 12.1 0.15 12.2 0.15 12.3 0.15 12.4 0.15 12.5 0.18 12.6 0.18 12.7 0.18 12.8 0.18 13.0 0.18 13.2 0.18 13.4 0.18 13.6 0.18 13.8 0.18 14.0 0.18 14.3 0.18 14.6 0.18 15.0 0.18 15.5 0.17 16.0 0.17 16.5 0.17 17.0 0.17 17.5 0.17 18.0 0.16 19.0 0.16 20.0 0.15 22.0 0.14 26.0 0.09 26.5 0.07 27.0 0.06 27.5 0.06 0.20 0.15 0.10 0.05 0.00 -0.05 Inflow Hydrograph (1-yr Design Storm) 30.0 Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.00 1.0 0.02 1.5 0.03 2.0 0.04 2.5 0.04 3.0 0.04 3.5 0.05 4.0 0.05 4.5 0.05 5.0 0.05 5.5 0.05 6.0 0.06 6.5 0.06 7.0 0.06 7.5 0.06 8.0 0.07 8.5 0.07 9.0 0.07 9.5 0.08 10.0 0.08 10.5 0.09 11.0 0.10 11.3 0.10 11.6 0.12 11.9 0.12 12.0 0.17 12.1 0.17 12.2 0.17 12.3 0.17 12.4 0.17 12.5 1.39 12.6 1.39 12.7 1.39 12.8 1.39 13.0 0.18 13.2 0.18 13.4 0.18 13.6 0.18 13.8 0.18 14.0 0.18 14.3 0.18 14.6 0.18 15.0 0.18 15.5 0.18 16.0 0.18 16.5 0.17 17.0 0.17 17.5 0.17 18.0 0.17 19.0 0.16 20.0 0.16 22.0 0.15 26.0 0.11 26.5 0.10 27.0 0.09 27.5 0.09 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 -0.20 Inflow Hydrograph (2-yr Design Storm) 30.0 Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.00 1.0 0.03 1.5 0.04 2.0 0.05 2.5 0.05 3.0 0.05 3.5 0.06 4.0 0.06 4.5 0.06 5.0 0.06 5.5 0.07 6.0 0.07 6.5 0.07 7.0 0.07 7.5 0.08 8.0 0.08 8.5 0.08 9.0 0.09 9.5 0.09 10.0 0.10 10.5 0.10 11.0 0.11 11.3 0.11 11.6 0.13 11.9 0.13 12.0 0.18 12.1 0.18 12.2 0.18 12.3 0.18 12.4 0.18 12.5 2.22 12.6 2.22 12.7 2.22 12.8 2.22 13.0 0.18 13.2 0.18 13.4 0.18 13.6 0.18 13.8 0.18 14.0 0.18 14.3 0.18 14.6 0.18 15.0 0.18 15.5 0.18 16.0 0.18 16.5 0.18 17.0 0.18 17.5 0.17 18.0 0.17 19.0 0.17 20.0 0.16 22.0 0.15 26.0 0.12 26.5 0.11 27.0 0.11 27.5 0.11 Inflow Hydrograph (10-yr Design Storm) 2.50 - - 2.00 1.50 1.00 0.50 0.00 0 -0.50 30.0 Post -Development DA A Outflow Hydrograph From Dry Swale Routings 0.0 0.00 0.5 0.04 1.0 0.07 1.5 0.08 2.0 0.08 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 0.13 8.0 0.14 8.5 0.14 9.0 0.15 9.5 0.15 10.0 0.16 10.5 0.17 11.0 0.17 11.3 0.18 11.6 1.21 11.9 8.75 12.0 10.75 12.1 8.04 12.2 4.43 12.3 2.88 12.4 2.12 12.5 1.70 12.6 1.36 12.7 1.10 12.8 0.95 13.0 0.77 13.2 0.66 13.4 0.58 13.6 0.52 13.8 0.47 14.0 0.43 14.3 0.38 14.6 0.35 15.0 0.33 15.5 0.30 16.0 0.27 16.5 0.25 17.0 0.24 17.5 0.22 18.0 0.20 19.0 0.18 20.0 0.18 22.0 0.18 26.0 0.16 26.5 0.16 27.0 0.16 27.5 0.15 12.00 10.00 8.00 6.00 4.00 2.00 0.00 0. Outflow Hydrograph (100-yr Design Storm) 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) Ora Vld rao xde'don rreron mneoaxe-oeveioprnent Camptlxnce spreoe.Fen-varslon a0 oaou am.zane.aeneyealrerwr. 02013 Draft amP mended, earl meea.adlo,,, d%tx ful'omre B xJa unear 0ev IOP IM no J Site Information -- ___--- --- Post -Development Project (Treatment Volume and Loads) Enter Total Diaturbed Are.(mai 2J6 Coate OMP Deng°S ociflmfions.1 2013 Dram 5W503peta '® R? NO rindoodun mnam.<r on,3enrereemrrer]]n J_-.. �',, __ I � mreiai3memoreomrerea� O Ind Developer. lanefuYn laver( aaoi eswl. call. osal. .aaa .......... ,enea„w.a r=—--a�namea r.n]aa.=o.. am nm ManarIl- .1raemamnar++.amr e .amea wcaw PO6ttvelOPmem t.re Center dreml roreryoansare lxre.l--- ° ..wpen epee a,ero,e,r.a ead emr...<a b am nm ma.eum„e..a na. Caen(ma tnmmnu due.N eoetxareas I.n --- m r9Ra•I 11, pen epn. 043 oss mgwm0^ae:l pro..ITpi D..(m.]x manna.. o9s ass araim �Dxl.ecimw 1.ea Tsar .vwala=NM I Im�ra,.vanw.mri - _ - •a ..m.xn=.xap a• 1nernee"did,rei ne«.o..dnp—r x,rea ad" pan3t..axe-a -- panoem�.mr.. emna. e. mna.... ...... ear a9z am am .:oea me.ro-�i � -. ro,e,.iopa, yea m a.e.r�i wv.n� a . xelmr.nl am -- m3 -- Mene.ea..a .. 1.v lede..=nulCn. --. Nter vewm am -- v% I.M. av eaan3me�.erw.re<l wBnurmlmaai ae3 D.m wyemrmlmeeV am .Caren s% and ------__--- %rmen ox xs.ea.aamre.rn.rleur— In, naanr .earo.er w—) %waad.bw our mudeawwm N.d.nn %waed.1 �maree=art-e.( an D.n .«.Care.rnni L13 -- ayimal an -- %imams ims - Twiaeoe...0 — 1v I� ranesi a-nma.=l ass ..rural ass D.9s - ..rma,w�l n9s %ima. s% red ------__--- %ima^a.Tco,wr sox ��1 1.3a ----------- -- raeurea aew—1 ax .a%r oaz Treatment Volume and Ntender Load Treatment Volume and Nutrient Load a=—uianurnnmmuu— um'.oe p"n aeon aaw emss a1m3 �.n amss rae�eoe�al .m aa]xe laaar0 wmm�r �ae.0 p.aawnaai«n�' un va J,m9 ],sas aeoeean nnjaemraarl� a,]]] .. i 1hR o..anr«m ]azee eyed tedurary r PMeR ningien.R read L33 0.97 eb pmenrR b 2% rm a0) re 1.99 lln/Yrl _- rWnl' �(4^nl ee. umapennaei I.m'=JM nss nn prl�e/ ham erHltlMYpMfn xYeMX aadlanl .�aenner., "' x..iwweppomo�.am.,r ._ p �ae «re.aamrm�l� a pm.mm +a�ea.anatnm,sa tl^^a^'=ommolea Te rneaaadan nn O 0.19 n�le�iY•i >r.e n'u'relan m L62 nwOeeemp^a^rm^a avennpneeA erelndn«e"ud, ,near aempn,.-aene,an,mm.aaeaoeimam «ae w�nA^<+'nw^aa=a..le�ar.rn. ee.rrs..am rmram,Ou myme/µary iP laatl Petluc[ion 0.epuiretl 0b/yrl I.BI Site Results (Water Quality Compliance) Area Checks O.A.A O.A.B O.A.0 A. D.A.E ARMEM FOREST/OVEN SPACE (a[) am O.M 0.M i0.00 O.W OK. I IMPEWnMCOVERTRENTFDIa[ 0.00 O.M 0.00�M. OWOK. MANAGEDMRFARENIa[) 0.00 O.M 0.00 00.W OK. MANAGED TURF AREA TREATED (a[) am O.M 0.00 O.W OK. AREA CHECK OK OK. OK. OK. Site Treatment VOIUMe (ffa) a71 Runoff Reduction Volume and TP By Drainage Area O.A. A D.AD O.A. E TOTALRUNOFF REDUCNON VOLUME ACHIEVED pF) 0 0 0 TPLOADAVAKABLE FOR REMOVAL (b/1) 0.00 MM0 0.00 O.W 0.00TPID MDUCTIONAGVEVED (b/yr) 0.00 0.00am TP LOAD REMAINING (Ib/yr) 0.00 0.00 O.W am NMMEN MD REDUCTION ACHIEVED (lb/yr) am O.W 0.00 0.00 O.W 0.00 Total Phosphorus FINAL POST-OEVELOPMENTTPLOADQb/yr) 2.96 TP LOAD REDUCTION REQUIRED (lb/yr)l 1.81 TP WAD REDUCTION ACHIEVED (Ib/yr) 0.00 W LOAD REMAINING (lb/N):1 2.96 REMAINING TP LOAD REDUCTION REQUIRED pb/yr): 1.81 Total Nitrogen (For Information Purposes) POST-DEVEMPMEM WAD (Ib/yr) 21.20 NMMEN LOAD REDUCTION ACHIEVED )Ib/yrl 0.00 REMAINING POST-DEV M MEM NRRWEN LOAD )Ib/yrl 21.20