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HomeMy WebLinkAboutWPO202100042 Calculations 2021-10-13 (2)SHIMP ENGINEERING, P.C.�tip''��� Design Focused Engineering 40 October 13, 2021 v J SbHMP Lic. .45183 John Anderson, PE foh3/2fw� Albemarle County G Department of Community Development S�ONAL �� 401 McIntire Road Charlottesville, VA 22902 Regarding: WPO 202100042 Bamboo Grove — VSMP Plan SWM Calculation Packet Dear John, Enclosed are the remaining stormwater calculations and data for the Bamboo Grove VSMP plan. A full narrative, stormwater maps, VRRM data, and SWM plan are included in the full size VSMP plan sheets. This packet contains the supporting HydroCAD runoff modelling reports, ditch and culvert sizing calculations, soil data, and rainfall data to support our analysis. If you have any questions about this calculation packet please do not hesitate to contact me at: keanekshimp-en ing eering com or by phone at 434-299-9843. Regards, Keane Rucker, Err Shimp Engineering, PC APPROVED by the Albemarle County Community Development Department Date 11/04/2021 �' �Y.ilylF[IZIIIL'f�� 912 E. High St. Charlottesville, VA 229021434.227.5140 1 shimp-engineeong.com Contents: SWM Quantity Requirements: Pre-Dev HydroCAD Report Post-Dev HydroCAD Report Inlet Drainage Area Summary LD-229 Culvert Sizing Calcs LD-268 Ditch Sizing Calcs Culvert Inlet Control Nomograph Culvert Outlet Protection Sizing Nomograph Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report SWM Quantity Requirements: Pre-Dev HydroCAD Report Post-Dev HydroCAD Report Inlet Drainage Area Summary LD-229 Culvert Sizing Calcs LD-268 Ditch Sizing Calcs Culvert Inlet Control Nomograph Culvert Outlet Protection Sizing Nomograph Offsite Pre-D6v Drainage Area Natural Channel Point of Analysis Subcat Reach Aon Link I Pre-Dev inage Area PreDev Pre-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Paae 2 Time span=5.00-48.00 hrs, dt=0.04 hrs, 1076 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Onsite Pre-Dev Drainage Runoff Area=1.240 ac 0.00% Impervious Runoff Depth=0.19" Tc=9.2 min CN=54 Runoff=0.11 cfs 0.020 of Subcatchment 2S: Offsite Pre-Dev Runoff Area=3.360 ac 27.98% Impervious Runoff Depth=0.81" Tc=14.2 min CN=71 Runoff=3.31 cfs 0.226 of Link 3L: Natural Channel Point of Analysis Inflow=3.42 cfs 0.246 of Primary=3.42 cfs 0.246 of Total Runoff Area = 4.600 ac Runoff Volume = 0.246 of Average Runoff Depth = 0.64" 79.57% Pervious = 3.660 ac 20.43% Impervious = 0.940 ac PreDev Pre-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Paae 3 Summary for Subcatchment 1S: Onsite Pre-Dev Drainage Area Runoff = 0.11 cfs @ 12.08 hrs, Volume= 0.020 af, Depth= 0.19" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.580 58 Woods/grass comb., Good, HSG B 0.420 61 >75% Grass cover, Good, HSG B 0.240 32 Woods/grass comb., Good, HSG A 1.240 54 Weighted Average 1.240 100.00% Pervious Area Tc Length Description 9.2 Direct Entry, TOC (Minutes) Summary for Subcatchment 2S: Offsite Pre-Dev Drainage Area Runoff = 3.31 cfs @ 12.08 hrs, Volume= 0.226 af, Depth= 0.81" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.920 58 Woods/grass comb., Good, HSG B 1.500 61 >75% Grass cover, Good, HSG B 0.940 98 Paved oarkina. HSG B 3.360 71 Weighted Average 2.420 72.02% Pervious Area 0.940 27.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.2 Direct Entry, TOC (Minutes) Summary for Link 3L: Natural Channel Point of Analysis Inflow Area = 4.600 ac, 20.43% Impervious, Inflow Depth = 0.64" for 1-YR event Inflow = 3.42 cfs @ 12.08 hrs, Volume= 0.246 of Primary = 3.42 cfs @ 12.08 hrs, Volume= 0.246 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs PreDev Pre-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 4 Time span=5.00-48.00 hrs, dt=0.04 hrs, 1076 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Onsite Pre-Dev Drainage Runoff Area=1.240 ac 0.00% Impervious Runoff Depth=1.22" Tc=9.2 min CN=54 Runoff=2.15 cfs 0.126 of Subcatchment 2S: Offsite Pre-Dev Runoff Area=3.360 ac 27.98% Impervious Runoff Depth=2.57" Tc=14.2 min CN=71 Runoff=11.40 cfs 0.720 of Link 3L: Natural Channel Point of Analysis Inflow=13.37 cfs 0.846 of Primary=13.37 cfs 0.846 of Total Runoff Area = 4.600 ac Runoff Volume = 0.846 of Average Runoff Depth = 2.21" 79.57% Pervious = 3.660 ac 20.43% Impervious = 0.940 ac PreDev Pre-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 5 Summary for Subcatchment 1S: Onsite Pre-Dev Drainage Area Runoff = 2.15 cfs @ 12.02 hrs, Volume= 0.126 af, Depth= 1.22" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.580 58 Woods/grass comb., Good, HSG B 0.420 61 >75% Grass cover, Good, HSG B 0.240 32 Woods/grass comb., Good, HSG A 1.240 54 Weighted Average 1.240 100.00% Pervious Area Tc Length Description 9.2 Direct Entry, TOC (Minutes) Summary for Subcatchment 2S: Offsite Pre-Dev Drainage Area Runoff = 11.40 cfs @ 12.07 hrs, Volume= 0.720 af, Depth= 2.57" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.920 58 Woods/grass comb., Good, HSG B 1.500 61 >75% Grass cover, Good, HSG B 0.940 98 Paved oarkina. HSG B 3.360 71 Weighted Average 2.420 72.02% Pervious Area 0.940 27.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.2 Direct Entry, TOC (Minutes) Summary for Link 3L: Natural Channel Point of Analysis Inflow Area = 4.600 ac, 20.43% Impervious, Inflow Depth = 2.21" for 10-YR event Inflow = 13.37 cfs @ 12.06 hrs, Volume= 0.846 of Primary = 13.37 cfs @ 12.06 hrs, Volume= 0.846 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-48.00 hrs, dt= 0.04 hrs Total Onsite PostDev Area to POA (EBE Input) Onsite Un nangaged PostD 1v Area 6S Offsite Unmanaged (, PostDev Area 7L 2S Onsite ostDev Area to Dry Pond 4P Detention Pond Offsite Post-Dev Area to Dry Pond Natural Channel Point of Analysis Subcat Reach Aon Lin k PostDev Post-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paqe 2 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Total Onsite PostDev Runoff Area=1.240 ac 25.81% Impervious Runoff Depth=0.54" Tc=8.6 min CN=65 Runoff=0.91 cfs 0.056 of Subcatchment 2S: Onsite PostDev Area to Runoff Area=0.740 ac 43.24% Impervious Runoff Depth=1.13" Tc=8.6 min CN=77 Runoff=1.32 cfs 0.069 of Subcatchment 3S: Offsite Post-Dev Area to Runoff Area=1.680 ac 33.33% Impervious Runoff Depth=0.86" Tc=12.7 min CN=72 Runoff=1.88 cfs 0.120 of Pond 4P: Dry Detention Pond Peak Elev=690.67' Storage=1,153 cf Inflow=3.07 cfs 0.189 of Outflow=1.85 cfs 0.189 of Subcatchment 5S: Onsite Unmangaged Runoff Area=0.500 ac 0.00% Impervious Runoff Depth=0.02" Tc=5.0 min CN=44 Runoff=0.00 cfs 0.001 of Subcatchment 6S: Offsite Unmanaged Runoff Area=1.700 ac 22.94% Impervious Runoff Depth=0.71" Tc=11.1 min CN=69 Runoff=1.61 cfs 0.101 of Link 7L: Natural Channel Point of Analysis Inflow=3.31 cfs 0.291 of Primary=3.31 cfs 0.291 of Total Runoff Area = 5.860 ac Runoff Volume = 0.347 of Average Runoff Depth = 0.71" 72.87% Pervious = 4.270 ac 27.13% Impervious = 1.590 ac rut PostDev Post-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 3 Summary for Subcatchment 1S: Total Onsite PostDev Area to POA (EBE Input) Runoff = 0.91 cfs @ 12.02 hrs, Volume= 0.056 af, Depth= 0.54" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.680 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B * n onn Qn Xnr,,,.,4, r_^-f4 ucn n i, ,....,.,...,....a� 1.240 65 Weighted Average 0.920 74.19% Pervious Area 0.320 25.81 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 2S: Onsite PostDev Area to Dry Pond Runoff = 1.32 cfs @ 12.01 hrs, Volume= 0.069 af, Depth= 1.13" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.420 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B 0.740 77 Weighted Average 0.420 56.76% Pervious Area 0.320 43.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 3S: Offsite Post-Dev Area to Dry Pond Runoff = 1.88 cfs @ 12.06 hrs, Volume= 0.120 af, Depth= 0.86" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.08" 11 PostDev Post-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 4 Area (ac) CN Description 0.490 58 Woods/grass comb., Good, HSG B 0.630 61 >75% Grass cover, Good, HSG B 0.560 98 Paved parking, HSG B 1.680 72 Weighted Average 1.120 66.67% Pervious Area 0.560 33.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.7 Direct Entry, TOC (Minutes) Summary for Pond 4P: Dry Detention Pond Inflow Area = 2.420 ac, 36.36% Impervious, Inflow Depth = 0.94" for 1-YR event Inflow = 3.07 cfs @ 12.04 hrs, Volume= 0.189 of Outflow = 1.85 cfs @ 12.15 hrs, Volume= 0.189 af, Atten= 40%, Lag= 6.9 min Primary = 1.85 cfs @ 12.15 hrs, Volume= 0.189 of Routing by Stor-Ind method, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 690.67' @ 12.15 hrs Surf.Area= 1,034 sf Storage= 1,153 cf Plug -Flow detention time= 9.2 min calculated for 0.189 of (100% of inflow) Center -of -Mass det. time= 9.2 min ( 876.0 - 866.8 ) Volume Invert Avail.Storage Storage Description #1 689.00' 7,433 cf 4.00'W x 90.001 x 5.10'H Pond Surface Storage Z=2.0 Device Routing Invert Outlet Devices #1 Primary 687.00' 18.0" Round 18" HDPE L= 60.0' Ke= 0.400 Inlet / Outlet Invert= 687.00' / 686.00' S= 0.0167'/' Cc= 0.900 n= 0.012 #2 Device 1 689.00' 6.0" W x 8.0" H Vert. 6"x8" Orifice C= 0.600 #3 Device 1 692.55' 48.0" Horiz. Top of 48" Standpipe C= 0.600 Limited to weir flow at low heads #4 Primary 692.90' 8.0' long x 8.0' breadth 8' Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.43 2.54 2.70 2.69 2.68 2.68 2.66 2.64 2.64 2.64 2.65 2.65 2.66 2.66 2.68 2.70 2.74 Primary OutFlow Max=1.85 cfs @ 12.15 hrs HW=690.67' (Free Discharge) 1-18" HDPE (Passes 1.85 cfs of 15.58 cfs potential flow) �2=6"x8" Orifice (Orifice Controls 1.85 cfs @ 5.55 fps) 3=Top of 48" Standpipe ( Controls 0.00 cfs) =8' Emergency Spillway ( Controls 0.00 cfs) IN PostDev Post-Dev Analysis Type // 24-hr 1-YR Rainfall=3.08" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 5 Summary for Subcatchment 5S: Onsite Unmangaged PostDev Area Runoff = 0.00 cfs @ 23.95 hrs, Volume= 0.001 af, Depth= 0.02" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.070 61 >75% Grass cover, Good, HSG B 0.240 30 Woods, Good, HSG A 0.500 44 Weighted Average 0.500 100.00% Pervious Area Tc Length Description 5.0 Direct Entry, TOC (Minutes) Summary for Subcatchment 6S: Offsite Unmanaged PostDev Area Runoff = 1.61 cfs @ 12.05 hrs, Volume= 0.101 af, Depth= 0.71" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.08" Area (ac) CN Description 0.390 58 Woods/grass comb., Good, HSG B 0.920 61 >75% Grass cover, Good, HSG B 0.390 98 Paved oarkina. HSG B 1.700 69 Weighted Average 1.310 77.06% Pervious Area 0.390 22.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 Direct Entry, TOC (Minutes) Summary for Link 7L: Natural Channel Point of Analysis Inflow Area = 4.620 ac, 27.49% Impervious, Inflow Depth = 0.76" for 1-YR event Inflow = 3.31 cfs @ 12.07 hrs, Volume= 0.291 of Primary = 3.31 cfs @ 12.07 hrs, Volume= 0.291 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs 13 PostDev Post-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 6 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Total Onsite PostDev Runoff Area=1.240 ac 25.81% Impervious Runoff Depth=2.06" Tc=8.6 min CN=65 Runoff=4.05 cfs 0.213 of Subcatchment 2S: Onsite PostDev Area to Runoff Area=0.740 ac 43.24% Impervious Runoff Depth=3.12" Tc=8.6 min CN=77 Runoff=3.68 cfs 0.193 of Subcatchment 3S: Offsite Post-Dev Area to Runoff Area=1.680 ac 33.33% Impervious Runoff Depth=2.66" Tc=12.7 min CN=72 Runoff=6.20 cfs 0.373 of Pond 4P: Dry Detention Pond Peak Elev=692.80' Storage=4,370 cf Inflow=9.55 cfs 0.565 of Outflow=8.05 cfs 0.565 of Subcatchment 5S: Onsite Unmangaged Runoff Area=0.500 ac 0.00% Impervious Runoff Depth=0.59" Tc=5.0 min CN=44 Runoff=0.36 cfs 0.024 of Subcatchment 6S: Offsite Unmanaged Runoff Area=1.700 ac 22.94% Impervious Runoff Depth=2.40" Tc=11.1 min CN=69 Runoff=5.94 cfs 0.340 of Link 7L: Natural Channel Point of Analysis Inflow=12.98 cfs 0.929 of Primary=12.98 cfs 0.929 of Total Runoff Area = 5.860 ac Runoff Volume = 1.142 of Average Runoff Depth = 2.34" 72.87% Pervious = 4.270 ac 27.13% Impervious = 1.590 ac 14 PostDev Post-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 7 Summary for Subcatchment 1S: Total Onsite PostDev Area to POA (EBE Input) Runoff = 4.05 cfs @ 12.01 hrs, Volume= 0.213 af, Depth= 2.06" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.680 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B * n onn Qn Xnr,,,.,4, r_^-f4 ucn n i, ,....,.,...,....a� 1.240 65 Weighted Average 0.920 74.19% Pervious Area 0.320 25.81 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 2S: Onsite PostDev Area to Dry Pond Runoff = 3.68 cfs @ 12.00 hrs, Volume= 0.193 af, Depth= 3.12" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.420 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B 0.740 77 Weighted Average 0.420 56.76% Pervious Area 0.320 43.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 3S: Offsite Post-Dev Area to Dry Pond Runoff = 6.20 cfs @ 12.05 hrs, Volume= 0.373 af, Depth= 2.66" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.59" IN PostDev Post-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 8 Area (ac) CN Description 0.490 58 Woods/grass comb., Good, HSG B 0.630 61 >75% Grass cover, Good, HSG B 0.560 98 Paved parking, HSG B 1.680 72 Weighted Average 1.120 66.67% Pervious Area 0.560 33.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.7 Direct Entry, TOC (Minutes) Summary for Pond 4P: Dry Detention Pond Inflow Area = 2.420 ac, 36.36% Impervious, Inflow Depth = 2.80" for 10-YR event Inflow = 9.55 cfs @ 12.03 hrs, Volume= 0.565 of Outflow = 8.05 cfs @ 12.10 hrs, Volume= 0.565 af, Atten= 16%, Lag= 4.6 min Primary = 8.05 cfs @ 12.10 hrs, Volume= 0.565 of Routing by Stor-Ind method, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 692.80' @ 12.11 hrs Surf.Area= 2,018 sf Storage= 4,370 cf Plug -Flow detention time= 11.6 min calculated for 0.565 of (100% of inflow) Center -of -Mass det. time= 11.6 min ( 846.1 - 834.5) Volume Invert Avail.Storage Storage Description #1 689.00' 7,433 cf 4.00'W x 90.001 x 5.10'H Pond Surface Storage Z=2.0 Device Routing Invert Outlet Devices #1 Primary 687.00' 18.0" Round 18" HDPE L= 60.0' Ke= 0.400 Inlet / Outlet Invert= 687.00' / 686.00' S= 0.0167'/' Cc= 0.900 n= 0.012 #2 Device 1 689.00' 6.0" W x 8.0" H Vert. 6"x8" Orifice C= 0.600 #3 Device 1 692.55' 48.0" Horiz. Top of 48" Standpipe C= 0.600 Limited to weir flow at low heads #4 Primary 692.90' 8.0' long x 8.0' breadth 8' Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.43 2.54 2.70 2.69 2.68 2.68 2.66 2.64 2.64 2.64 2.65 2.65 2.66 2.66 2.68 2.70 2.74 Primary OutFlow Max=7.82 cfs @ 12.10 hrs HW=692.79' (Free Discharge) 1-18" HDPE (Passes 7.82 cfs of 20.47 cfs potential flow) �2=6"x8" Orifice (Orifice Controls 2.98 cfs @ 8.95 fps) 3=Top of 48" Standpipe (Weir Controls 4.84 cfs @ 1.60 fps) =8' Emergency Spillway ( Controls 0.00 cfs) f&7 PostDev Post-Dev Analysis Type //24-hr 10-YR Rainfall=5.59" Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 9 Summary for Subcatchment 5S: Onsite Unmangaged PostDev Area Runoff = 0.36 cfs @ 12.00 hrs, Volume= 0.024 af, Depth= 0.59" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.070 61 >75% Grass cover, Good, HSG B 0.240 30 Woods, Good, HSG A 0.500 44 Weighted Average 0.500 100.00% Pervious Area Tc Length Description 5.0 Direct Entry, TOC (Minutes) Summary for Subcatchment 6S: Offsite Unmanaged PostDev Area Runoff = 5.94 cfs @ 12.03 hrs, Volume= 0.340 af, Depth= 2.40" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.59" Area (ac) CN Description 0.390 58 Woods/grass comb., Good, HSG B 0.920 61 >75% Grass cover, Good, HSG B 0.390 98 Paved oarkina. HSG B 1.700 69 Weighted Average 1.310 77.06% Pervious Area 0.390 22.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 Direct Entry, TOC (Minutes) Summary for Link 7L: Natural Channel Point of Analysis Inflow Area = 4.620 ac, 27.49% Impervious, Inflow Depth = 2.41" for 10-YR event Inflow = 12.98 cfs @ 12.09 hrs, Volume= 0.929 of Primary = 12.98 cfs @ 12.09 hrs, Volume= 0.929 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs 17 PostDev Post-Dev Analysis Type // 24-hr 100-YR Rainfall=9. 09 " Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 10 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Total Onsite PostDev Runoff Area=1.240 ac 25.81% Impervious Runoff Depth=4.79" Tc=8.6 min CN=65 Runoff=9.50 cfs 0.495 of Subcatchment 2S: Onsite PostDev Area to Runoff Area=0.740 ac 43.24% Impervious Runoff Depth=6.28" Tc=8.6 min CN=77 Runoff=7.22 cfs 0.387 of Subcatchment 3S: Offsite Post-Dev Area to Runoff Area=1.680 ac 33.33% Impervious Runoff Depth=5.66" Tc=12.7 min CN=72 Runoff=13.09 cfs 0.793 of Pond 4P: Dry Detention Pond Peak Elev=693.06' Storage=4,919 cf Inflow=19.68 cfs 1.180 of Outflow=19.35 cfs 1.177 of Subcatchment 5S: Onsite Unmangaged Runoff Area=0.500 ac 0.00% Impervious Runoff Depth=2.22" Tc=5.0 min CN=44 Runoff=1.90 cfs 0.093 of Subcatchment 6S: Offsite Unmanaged Runoff Area=1.700 ac 22.94% Impervious Runoff Depth=5.29" Tc=11.1 min CN=69 Runoff=13.06 cfs 0.749 of Link 7L: Natural Channel Point of Analysis Inflow=33.72 cfs 2.019 of Primary=33.72 cfs 2.019 of Total Runoff Area = 5.860 ac Runoff Volume = 2.517 of Average Runoff Depth = 5.16" 72.87% Pervious = 4.270 ac 27.13% Impervious = 1.590 ac 18 PostDev Post-Dev Analysis Type // 24-hr 100-YR Rainfall=9. 09 " Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 11 Summary for Subcatchment 1S: Total Onsite PostDev Area to POA (EBE Input) Runoff = 9.50 cfs @ 12.00 hrs, Volume= 0.495 af, Depth= 4.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.09" Area (ac) CN Description 0.680 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B * n onn Qn Xnr,,,.,4, r_^-f4 ucn n i, ,....,.,...,....a� 1.240 65 Weighted Average 0.920 74.19% Pervious Area 0.320 25.81 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 2S: Onsite PostDev Area to Dry Pond Runoff = 7.22 cfs @ 12.00 hrs, Volume= 0.387 af, Depth= 6.28" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.09" Area (ac) CN Description 0.420 61 >75% Grass cover, Good, HSG B 0.320 98 Paved parking, HSG B 0.740 77 Weighted Average 0.420 56.76% Pervious Area 0.320 43.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 Direct Entry, TOC (Minutes) Summary for Subcatchment 3S: Offsite Post-Dev Area to Dry Pond Runoff = 13.09 cfs @ 12.04 hrs, Volume= 0.793 af, Depth= 5.66" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.09" PostDev Post-Dev Analysis Type // 24-hr 100-YR Rainfall=9. 09 " Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 12 Area (ac) CN Description 0.490 58 Woods/grass comb., Good, HSG B 0.630 61 >75% Grass cover, Good, HSG B 0.560 98 Paved parking, HSG B 1.680 72 Weighted Average 1.120 66.67% Pervious Area 0.560 33.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.7 Direct Entry, TOC (Minutes) Summary for Pond 4P: Dry Detention Pond Inflow Area = 2.420 ac, 36.36% Impervious, Inflow Depth = 5.85" for 100-YR event Inflow = 19.68 cfs @ 12.02 hrs, Volume= 1.180 of Outflow = 19.35 cfs @ 12.03 hrs, Volume= 1.177 af, Atten= 2%, Lag= 0.7 min Primary = 19.35 cfs @ 12.03 hrs, Volume= 1.177 of Routing by Stor-Ind method, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 693.06' @ 12.03 hrs Surf.Area= 2,151 sf Storage= 4,919 cf Plug -Flow detention time= 11.3 min calculated for 1.175 of (100% of inflow) Center -of -Mass det. time= 9.4 min ( 823.1 - 813.7) Volume Invert Avail.Storage Storage Description #1 689.00' 7,433 cf 4.00'W x 90.001 x 5.10'H Pond Surface Storage Z=2.0 Device Routing Invert Outlet Devices #1 Primary 687.00' 18.0" Round 18" HDPE L= 60.0' Ke= 0.400 Inlet / Outlet Invert= 687.00' / 686.00' S= 0.0167'/' Cc= 0.900 n= 0.012 #2 Device 1 689.00' 6.0" W x 8.0" H Vert. 6"x8" Orifice C= 0.600 #3 Device 1 692.55' 48.0" Horiz. Top of 48" Standpipe C= 0.600 Limited to weir flow at low heads #4 Primary 692.90' 8.0' long x 8.0' breadth 8' Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.43 2.54 2.70 2.69 2.68 2.68 2.66 2.64 2.64 2.64 2.65 2.65 2.66 2.66 2.68 2.70 2.74 Primary OutFlow Max=18.93 cfs @ 12.03 hrs HW=693.05' (Free Discharge) 1-18" HDPE (Passes 17.77 cfs of 20.99 cfs potential flow) �2=6"x8" Orifice (Orifice Controls 3.09 cfs @ 9.28 fps) 3=Top of 48" Standpipe (Weir Controls 14.67 cfs @ 2.32 fps) =8' Emergency Spillway (Weir Controls 1.17 cfs @ 0.95 fps) %za PostDev Post-Dev Analysis Type // 24-hr 100-YR Rainfall=9. 09 " Prepared by Shimp Engineering, P.C. Printed 10/13/2021 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Pane 13 Summary for Subcatchment 5S: Onsite Unmangaged PostDev Area Runoff = 1.90 cfs @ 11.97 hrs, Volume= 0.093 af, Depth= 2.22" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.09" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.070 61 >75% Grass cover, Good, HSG B 0.240 30 Woods, Good, HSG A 0.500 44 Weighted Average 0.500 100.00% Pervious Area Tc Length Description 5.0 Direct Entry, TOC (Minutes) Summary for Subcatchment 6S: Offsite Unmanaged PostDev Area Runoff = 13.06 cfs @ 12.03 hrs, Volume= 0.749 af, Depth= 5.29" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.09" Area (ac) CN Description 0.390 58 Woods/grass comb., Good, HSG B 0.920 61 >75% Grass cover, Good, HSG B 0.390 98 Paved oarkina. HSG B 1.700 69 Weighted Average 1.310 77.06% Pervious Area 0.390 22.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 Direct Entry, TOC (Minutes) Summary for Link 7L: Natural Channel Point of Analysis Inflow Area = 4.620 ac, 27.49% Impervious, Inflow Depth = 5.24" for 100-YR event Inflow = 33.72 cfs @ 12.03 hrs, Volume= 2.019 of Primary = 33.72 cfs @ 12.03 hrs, Volume= 2.019 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs 21 Bamboo Grove Inlet Drainage Area Summary Impervious C 0.9 Pervious C 0.3 Woods C 0.2 To Inlet Area Impervious Turf C A A2 - Permanent A2 - w. CWD 52,900 87,000 15,400 24,000 37,500 63,000 0.47 0.47 1.21 2.00 QA LD-229 Bamboo Grove Storm Drain Design Calculations From To Catch. Runoff Increment Accum. Total 10-yr 10-yr Up Down Pipe Invert Pipe Pipe Velocity Flowtime Structure Structure Area Coef AC AC TOC Intensity Flow Invert Invert Length Slope Diameter Capacity increment ac min in/hr cfs Elev. Elev. (ft) (cfs) (fus) (min 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 A2 At 1.21 0.47 0.58 0.58 11.10 5.42 3.12 694.00 691.00 60.00 5.00% 15 15.6 11.4 0.09 'PERMANENT POSTDEVELOPMENT DESIGN A2 A1" 2.00 0.47 0.93 0.93 11.10 5.42 5.04 478.30 477.00 114.73 1.13% 15 15.6 11.4 0.17 _ "DESIGN DURING CONSTRUCTION - ADDITIONAL RUNOFF FROM CLEANWATER DIVERSION B2 131'«« 8.05 689.00 688.00 60.00 1.67% 18 14.9 8.5 0.12 "'FLOW FROM HYDROCAD MODEL POND OUTFLOW 23 LD-268 Bamboo Grove Roadside and Median Ditch Desi n Form Ditch G A CA TOC Side Slow :t L :i R - - Min slop it/it Max Slope ft/ft Design Storm Intensity (in/hr) o (cfs) Allowable Velocity (fps) No Lining n=.03 Vel.' Protective Lining EC-2 or EC-3: n=.05 Paved: n=.015 on I Velocity' I Depth" on I Depth INCR ACC Ex. Ditch along Orchard Dr- 0.47 1.21 0.58 0.58 11.1 7 7 0.100 0.140 2-Yr 3.98 2.30 6.0 0.11 3.39 0.34 Postdevelopment Runoff 10-Vr 5.42 3.12 0.16 3.66 0.38 Ex. Ditch along Orchard Dr- 0.47 2.00 0.93 0.93 11.1 7 7 0.100 0.140 2-Yr 3.98 3.70 6.0 0.19 382 0.40 Additional Runoff from CWD 10-Yr 5.42 5.04 0.25 4.12 0.45 24 Chapter 8 - Culverts Appendix 8C-1 Inlet Control, Circular Concrete lso lu000 CHART 10 lee e.ow EXAMPLE (I) (2) (3) 168 6 009 Q..Y ImM. lJ! MI 8' p.IQO n D9 !.0 6. 4,000 D[ 3 3.000 111 L! QA e' e, 120 61 I09 Y.000 IA t.t 1.1 O. D 01. nn a. BAMBOO GROVE CULVERTINLET NOMOGRAPH 96 1000 ), w ` CULVERT INLET: DW `' 72 ; GROOVE END W Y0° �// e 1.9 PROJECTING w j. � eo eao : � s ¢ �' / °° ' > / a, M) 1.1 H W/D a e[ u M w 60 A. 9 1.0 1.0 0 n WU NO SEALE YMTYA a,1.0 .' 32 y 90 In si wp «n � .9 9 .9 D! 0 Q Do ....n�a 6 0.8 H W/D .a nl QY mi... 10 f! e 1 r 21 9 r I.. a... 111..M• 3 • ..I r.1lM ... 1e D Ill.n.ma..l«. A,«.......... A .e 19 Lo s L 1t HEADWATER DEPTH FOR HEADWATER SCALES E53 CONCRETE PIPE CULVERTS .E'SSD WA. 19aa WITH INLET CONTROL Source: HDS-5 Intl VDOT Drainage Manual LEGEND: A2 10-YR RUNOFF, POSTDEVELOPED \ (RATIONAL, Q=3.1 CFS) A2 10-YR RUNOFF, ADDITIONAL RUNOFF FROM CWD DURING CONSTRUCTION \ (RATIONAL, Q=5.0 CFS) 25 i•. DESIGN OF OUTLET PROTECTION FROM A ROUND PIPE FLOWING FULL MINIMUM TAILWATER CONDITION (Tw t 0.5 DIAMETER) Outlet r i Do + La Pipe 2 Min. Diameter, Do 1 La L T i water 0.5Do pp moo, �gP 51 15" Culvert A: La=8' 18" Culvert B: La=9' Recommended Min. d,o 6^ D50=6„ p5o=6„ BAMBOO GROVE OUTLET PROTECTION NOMOGRAPH 3 5 10 20 50 3 100 200 5D0 Discharge, ft./sec. a 3 1:10 1000 N w 00 30 Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report VkA 3 4'S'N 3 Hydrologic Soil Group —Albemarle County, Virginia 3 r pNy F F M'4'WN 38° V F N ](p888 ]eB18 70fA98 ]OCHRI R11000 ]01IX10 ]810a] 3 3 Map Sole: 1:1,340 E pdntel oh A pohUat (8.5" x 11") sheet. Meets N 0 15 30 6J 90 AMap projemon: Web Metator Conermortlnetes: WGS84 Edged¢: UIM Zone 17N WG584 usDA Natural Resources Web Soil Survey 5/24/2021 Conservation Service National Cooperative Soil Survey Page 1 of 4 28 Hydrologic Soil Group —Albemarle County, Virginia MAP LEGEND MAP INFORMATION Area of Interest (AOI) C The soil surveys that comprise your AOI were mapped at O Area of Interest(AOI) CID 1-15,800. Solis ■ D Warning: Soil Map may not be valid at this scale. Soil Rating Polygons 0 A G Not mtea or not available Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil O AID water Pastures line placement. The maps do not show the small areas of Streams and Canals contrasting soils that could have been shown at a more detailed OB scale. Transportation 0 BID Rails Please rely on the bar scale on each map sheet for map 0 C ey Interstate Highways measurements. 0 CIO N US Routes P Source of Ma Natural Resources Conservation Service 0 D Web Soil Survey Major Roads Coordinate System: Web Mercator (EPSG:3657) (] Not mted or not available Local Roads Maps from the Web Soil Survey are based on the Web Mercator Son Rating Linos Background projection, which preserves direction and shape but distorts N A distance and area. A projection that preserves area, such as the . Aedal Photography Albers equal-area conic projection, should be used if more ~ AID Iu=umte calculations of distance or area are required. ~ B This product is generated from the USDA-NRCS certified data as A/ BID of the version dam(s) listed below. C Soil Survey Area: Albemarle County, Virginia M Survey Area Data: Version 14, Jun 3, 2020 N CID Soil map units are labeled (as space allows) for map scales ti D 1:50,000 or larger. .. • Not rated or not available Date(s) aerial images were photographed: May 20, 201"ug Soil Rating Points 1, 2019 0 A The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background ■ AID imagery displayed on these maps. As a result, some minor . B shifting of map unit boundaries may be evident. BID USDA Natural Resources Web Soil Survey 5/2412021 Conservation Service National Cooperative Soil Survey Page 2 of 4 Q-1 Hydrologic Soil Group —Albemarle County, Virginia Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AD] Percent of AOI 7B Braddock loam, 2 to 7 B 0.0 0.3% percent slopes 17 Craigsville loam, 0 to 2 A 1.0 19.5% percent slopes, frequently flooded 25B Dyke silt loam, 2 to 7 B 3.1 59.8% percent slopes 37D3 Hayesville clay loam, 15 B 1.1 20.5% to 25 percent slopes, severely eroded Totals for Area of Interest 5.2 100.0% Natural Resources Web Soil Survey 5/24/2021 Conservation Service National Cooperative Soil Survey Page 3 of 4 30 Hydrologic Soil Group —Albemarle County, Virginia Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff., None Specified Tie -break Rule: Higher Natural Resources Web Soil Survey 5/24/2021 Conservation Service National Cooperative Soil Survey Page 4 of 4 31 2/22/2021 Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Crozet. Virginia. USA* Latitude: 38, Longitude:-78.7085° € Elevation: 696.54 ft** * source: ESRI Maps • . -- source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Partybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) Duration 1 2 5 10 25 50 100 ���� 200 500 1000 1445) (0.305-0 373) (036 -0 )(0.431--0525) (0.484-0 592) (0.544-0.668) (0-589-0..727) (0.631-0785) (0.668-0.840) (0.71 0 910) (0: 44-0.969) 0.762 10 10-min (0.487--0595) (0.5 0712) (0.690-0.842) (0.7750.947) (0.8677-1607) (0.938-1.16) (1.001325) (1.061'33) (1. 2-31oM) (1.17-31753) 15-min (0.609-0744) (0.734- 896) (0.872--11..07) (0.980-11.20) (110-2135) (119-147) (1.271.58) (1.34-1.68) (1.41-31.81) 1 (1.471.92) 2 F-0430.min (0.35-L02) 1 (1-01-11-24) 1 (1.24-31.51) 1 (1.2--174) 1 (1.632100) 1 (1:9-221) 11 (1.942942) 1 (2.8-2.62) 11 (2.252088) 1 (2.383.10) 60-min (1.04 1527) (1.27-�55) (1.59 1694) (1.85-2.26) (2.127 2.66) (2.42 2?99) (2.67 3z33) 1 (2.92 3-67) 1 (3. 3 4.14) 1 (3.484.53) 1.37 1.67 2.10 2.47 2.95 3.35 3.75 4.18 4.77 5.26 2-hr (1.23-1.54) 1 (1.49-1.87) (1.88-2.35) (2.21-2.77) 11 (2.61-3.29) (2.95-3.74) (3.28-4.19) (3.624.68) (4.08-5.36) (4.45-5.95) 2.70 3-hr (1.35--1170) (1.63-2..07) (2.05 2060) (2.40-3.04) (2.853363) (3.224713) (3.59 4364) (3.97520) (4. 8-5.97) (4.906 63) 6-hr (1.75 2520) (2. 2 2?66) (2.62-33..31) (3.07 3689) (3.47-4.68) (4.175836) (4. 8 6?09) (5.26 89) (5.97-8.06) (6.61 9009) 3.74 12-hr (2.22883) (2.673A1) (3.32-4.25) (3.91�02) (4. 26910) (5.40-7.07) (6. 28.13) (6.90-9.31) (7. 8111.1) (8.9812.7) 24Z (2.7373844) (3.35-4.16) (4.8530) (5.00-624) (6. 8-77..62) (6.988.80) (7.94-010.1) (8.98- 1.5) (10.5-13.7) (11. �15.6) 4.39 5.57 6.53 7.92 9.09 104 11.7 13.7 15.4 2Fday3.62 2dey (3.274.04) (3.96-4.89) 1 (5.01-6.20) (5.88717) 1 (7.06-8.81) 1 (8.03-10.1) 1 (9.07-11.5) 1 (10.2-13.1) 1 (11.8-15.4) 1 (13.1-17.3) 3.86 4.67 5.92 6.9a 842 9.65 11.0 12.4 %5 16.3 3-0ay (3.504.28) (4.24-5.18) (5.36-6.56 ) (6.27-7.69) 1 (7.56-9.31) (8.61-10.7) (9.72-12.1) (10.9-13.8) (12.6-16.2) (14.0-18.2) 4�ay (3.744952) (4-52547) (5. 2--268.93) 1 (66 9-8.10) 1 (8.069.82) (9.18-121.2) (10.4- 2.8) (11.6-14.5) (134- 6.9) (14.9-19.1) 7dey (4.36520) (52 5-6.26) (6.557582) (75 9-9.08) (9.05--110.9) (102- 2A) (11-5-14.0) (12.8-5.7) (14.6- 8.2) (1618 0.3) 10 (4.975086) (5.97-7 A2) (7.35 8965) (8.449.95) (9.93-111.8) (11 1213.3) (124-14.8) (13A8 6.5) (1514- 8.8) (16.8-0.8) 20riay- (6.61-0761) (7.89-9.07) 4 9 (9- 0.9) (107 2.4) (124- 4.4) (137--15.9) 1 (15.0-17.5) 1 (16.3-19.2) 1 (18.0-21.5) 1 (19.4- 3.3) 30-0ey (8. 5927) (9.67--111.0) (114-13.0) (127---14.5) (144516.5) (157---18.0) (16.9- 9.5) (1819 0.9) 1 (196-2.9) 1 (20.824.4) 10-9 12.8 14.9 16.5 18-6 20.1 21.5 22.9 24.7 26.1 as dey (10.2-11.5) 1 (12.1-13.6) 1 (14.1-15.9) 1 (15.5-17.5) 1 (17.4-19.7) 1 (18.821.3) 1 (20.1-2.9) 1 (21.4-24.5) 1 (2.9-26.5) 1 (24.1-28.0) -27 601tey (120-8.4) (142- 5.8) (16.3- 8.2) (17.8 9.9) (198' 2.2) (21 22 3.8) (22?6-8.4) (23.9-269) (2547 8.9) (2 r, 0.3) t Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 dowment for more information. Back to Top 32 hftps://hdsc.rlws.noaa.govlhdsc/pfds/pfds_Printpage.html?lat=38.0693&Ion=-78.7085&data=depth&units=english&series=pds 1/4