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HomeMy WebLinkAboutWPO201200049 Calculations 2013-04-15 THE MILLER SCHOOL NEW ENTRANCE Stormwater Management Computations Albemarle County,Virginia r i v" , i .• ` Alk- This is a supplement to the previously submitted Drainage Computations Report which was last revised November 30,2012 April 15,2013 Job No. 09-011-00 BRIAN P. SMITH, PE CIVIL ENGINEERING, INC. Golf Course Design• Engineering • Site Design• Land Planning 4835 Three Chopt Road Troy,Virginia 22974-3012 434.296.3644(c) bpspe@embargmail.com GOLF COURSE DESIGN • ENGINEERING • SITE DESIGN • LAND PLANNING The Miller School SWM Computations Brief Overview: This project has been revised with regard to stormwater management. The earlier set of plans called for an equal amount of pavement to be removed as was proposed with the new entrance loop. This line of thinking has changed.Now the traditional stormwater detention basin with water quality measures has been designed. This report is a supplement to the plans revised April 15,2013 and specifically sheets C9.0, C9.1 and C9.2. This is the stormwater portion of the set. The impervious computations are shown on C9.0. Two bio-filters are proposed, on either side of the stream, coming from the lily pond. Their design(location and grading)are shown on C9.1. Details of the bio-filters and a new SWD manhole are shown on C9.2. Stormwater Detention: The SWD basin will be located above the typical low point of the project. However,the amount of increased flow has been determined at the low point of the large drainage basin—at existing box culvert under the state road. This increase will be deducted from the calculated 2 and 10-year storm events at the SWD basin to arrive at the allowable discharge—resulting in a net zero, or less, flow increase. The table below is a summary of these findings. Backup computations are on the following pages. If desired,the Drainage Area Map can be found on sheet C8.0. Stormwater Summary Table of Increased Flow at the Low Point of the Drainage Basin 2-year event 10-year event Post development 50.60 cfs 125.71 cfs Pre development 46.42 cfs 118.74 cfs Increase 4.18 cfs 6.97 cfs SWD Basin Summary Table 2-year event 10-year event 100-year event Flow prior to detention 23.72 cfs 43.84 cfs ..i - Reduction from above 4.18 cfs 6.97 cfs - Allowable release 19.54 cfs 36.87 cfs Calculated release 18.29 cfs 22.13 cfs 45.98 cfs Water elevation 653.87 656.02 ►s 657.57 Account ID.09-011-00/SWM Calcs.doc BRIAN P. SMITH, PE GOLF COURSE DESIGN • ENGINEERING • SITE DESIGN • LAND PLANNING The Miller School SWM Computations PRE- & POST- DEVELOPMENT COMPUTATIONS AT THE BOX CULVERT NEAR THE INTERSECTION WITH THE STATE ROAD 2 AND 10-YEAR STORM EVENTS BRIAN P. SMITH, PE GOLF COURSE DESIGN • ENGINEERING • SITE DESIGN • LAND PLANNING Miller School existing state road box culvert-PRE D Type II 24-hr 2-yr Storm Rainfall=3.70" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 3P: 48" Box culvert under state road Check headwater: 617.09 - 1.5 = 615.59; okay Inflow Area = 60.100 ac, 6.22% Impervious, Inflow Depth = 0.96" for 2-yr Storm event Inflow = 46.42 cfs @ 12.23 hrs, Volume= 4.832 af Outflow = 46.42 cfs @ 12.23 hrs, Volume= 4.832 af, Atten= 0%, Lag= 0.0 min Primary = 46.42 cfs © 12.23 hrs, Volume= 4.832 af Routing by Stor-Ind method, Time Span= 5.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 604.36' @ 12.23 hrs Flood Elev= 615.59' Device Routing Invert Outlet Devices #1 Primary 602.00' 48.0" W x 48.0" H Box Box culvert L= 53.3' Ke= 0.500 Inlet/ Outlet Invert= 602.00' / 599.70' S= 0.0432 '/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 16.00 sf Primary OutFlow Max=46.08 cfs © 12.23 hrs HW=604.34' (Free Discharge) L1=Box culvert (Inlet Controls 46.08 cfs @ 4.91 fps) • ' Miller School existing state road box culvert-PRE D Type II 24-hr 10-yr Storm Rainfall=5.60" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 3P: 48" Box culvert under state road Check headwater: 617.09 - 1.5 = 615.59; okay Inflow Area = 60.100 ac, 6.22% Impervious, Inflow Depth = 2.23" for 10-yr Storm event Inflow = 118.74 cfs @ 12.21 hrs, Volume= 11.180 of Outflow = 118.74 cfs @ 12.21 hrs, Volume= 11.180 af, Atten= 0%, Lag= 0.0 min Primary = 118.74 cfs @ 12.21 hrs, Volume= 11.180 af Routing by Stor-Ind method, Time Span= 5.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 606.53' @ 12.21 hrs Flood Elev= 615.59' Device Routing Invert Outlet Devices #1 Primary 602.00' 48.0" W x 48.0" H Box Box culvert L= 53.3' Ke= 0.500 Inlet/ Outlet Invert= 602.00' / 599.70' S= 0.0432 '/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 16.00 sf Primary OutFlow Max=118.12 cfs @ 12.21 hrs HW=606.50' (Free Discharge) t-1=Box culvert (Inlet Controls 118.12 cfs @ 7.38 fps) ,'/G`-� 0)-0.-MgaLEYki ' Miller School existing state road box culvert A Type 1124-hr 2-yr Storm Rainfall=3.70" Prepared by Brian P. Smith, PE ' Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 3P: 48" Box culvert under state road Check headwater: 617.09- 1.5 = 615.59; okay Inflow Area = 61.040 ac, 7.66% Impervious, Inflow Depth = 1.02" for 2-yr Storm event Inflow = 50.60 cfs @ 12.23 hrs, Volume= 5.171 af Outflow = 50.60 cfs @ 12.23 hrs, Volume= 5.171 af, Atten= 0%, Lag= 0.0 min Primary = 50.60 cfs @ 12.23 hrs, Volume= 5.171 af Routing by Stor-Ind method, Time Span= 5.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 604.49' @ 12.23 hrs Flood Elev= 615.59' Device Routing Invert Outlet Devices #1 Primary 602.00' 48.0"W x 48.0" H Box Box culvert L= 53.3' Ke= 0.500 Inlet/Outlet Invert= 602.00' /599.70' S= 0.0432 '/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 16.00 sf Primary OutFlow Max=50.23 cfs @ 12.23 hrs HW=604.48' (Free Discharge) L1=Box culvert (Inlet Controls 50.23 cfs @ 5.06 fps) • ' Miller School existing state road box culvert Type 1124-hr 10-yr Storm Rainfall=5.60" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 sin 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 3P: 48" Box culvert under state road Check headwater: 617.09- 1.5 = 615.59; okay Inflow Area = 61.040 ac, 7.66% Impervious, Inflow Depth = 2.31" for 10-yr Storm event Inflow = 125.71 cfs @ 12.21 hrs, Volume= 11.765 af Outflow = 125.71 cfs @ 12.21 hrs, Volume= 11.765 af, Atten= 0%, Lag= 0.0 min Primary = 125.71 cfs @ 12.21 hrs, Volume= 11.765 af Routing by Stor-Ind method, Time Span= 5.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 606.79' @ 12.21 hrs Flood Elev= 615.59' Device Routing Invert Outlet Devices #1 Primary 602.00' 48.0"W x 48.0" H Box Box culvert L= 53.3' Ke= 0.500 Inlet/Outlet Invert= 602.00'/599.70' S= 0.0432 '/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 16.00 sf Primary OutFlow Max=125.09 cfs @ 12.21 hrs HW=606.77' (Free Discharge) L1=Box culvert (Inlet Controls 125.09 cfs @ 7.82 fps) The Miller School SWM Computations STORMWATER DETENTION BASIN ROUTING COMPUTATIONS 2, 10, & 100-YEAR STORM EVENTS BRIAN P. SMITH , PE GOLF COURSE DESIGN • ENGINEERING • SITE DESIGN • LAND PLANNING ' 09-011-00 SWD Type 1124-hr 2-yr Storm Rainfall=3.70" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 2P: INNER LOOP SWD Inflow Area = 10.850 ac, 39.91% Impervious, Inflow Depth = 1.95" for 2-yr Storm event Inflow = 23.72 cfs @ 12.13 hrs, Volume= 1.762 of Outflow = 18.29 cfs @ 12.24 hrs, Volume= 1.762 af, Atten= 23%, Lag= 6.7 min Primary = 18.29 cfs @ 12.24 hrs, Volume= 1.762 af Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 653.87' © 12.24 hrs Surf.Area= 2,913 sf Storage= 5,025 cf Plug-Flow detention time= 1.3 min calculated for 1.762 af(100% of inflow) Center-of-Mass det. time= 1.3 min ( 840.2 - 839.0 ) Volume Invert Avail.Storage Storage Description #1 648.50' 55,128 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 648.50 0 0.0 0 0 0 650.00 278 117.6 139 139 1,104 652.00 1,092 229.6 1,281 1,420 4,218 654.00 3,074 314.7 3,999 5,418 7,944 656.00 14,485 674.0 16,155 21,573 36,230 658.00 19,180 656.1 33,555 55,128 38,545 Device Routing Invert Outlet Devices #1 Primary 647.33' 24.0" Round Culvert L= 126.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 647.33' /635.60' S= 0.0931 'I' Cc= 0.900 n= 0.012, Flow Area= 3.14 sf #2 Device 1 648.50' 18.0" Round Culvert L= 8.2' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 648.50'/647.73' S= 0.0939 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf #3 Device 1 656.02' 48.0" Vert. Orifice/Grate C= 0.600 Primary OutFlow Max=18.28 cfs @ 12.24 hrs HW=653.87' (Free Discharge) t-1=Culvert (Passes 18.28 cfs of 35.60 cfs potential flow) -2=Culvert (Inlet Controls 18.28 cfs @ 10.35 fps) 3=Orifice/Grate ( Controls 0.00 cfs) ' 09-011-00 SWD Type II 24-hr 10-yr Storm Rainfall=5.60" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 2P: INNER LOOP SWD Inflow Area = 10.850 ac, 39.91% Impervious, Inflow Depth = 3.62" for 10-yr Storm event Inflow = 43.84 cfs @ 12.12 hrs, Volume= 3.274 of Outflow = 22.13 cfs @ 12.32 hrs, Volume= 3.274 af, Atten= 50%, Lag= 12.4 min Primary = 22.13 cfs @ 12.32 hrs, Volume= 3.274 af Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 656.02' @ 12.32 hrs Surf.Area= 14,523 sf Storage= 21,823 cf Plug-Flow detention time= 5.2 min calculated for 3.273 af(100% of inflow) Center-of-Mass det. time= 5.2 min ( 826.5 - 821.3 ) Volume Invert Avail.Storage Storage Description #1 648.50' 55,128 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 648.50 0 0.0 0 0 0 650.00 278 117.6 139 139 1,104 652.00 1,092 229.6 1,281 1,420 4,218 654.00 3,074 314.7 3,999 5,418 7,944 656.00 14,485 674.0 16,155 - 21,573 36,230 658.00 19,180 656.1 33,555 55,128 38,545 Device Routing Invert Outlet Devices #1 Primary 647.33' 24.0" Round Culvert L= 126.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 647.33'/635.60' S= 0.0931 '/' Cc= 0.900 n= 0.012, Flow Area= 3.14 sf #2 Device 1 648.50' 18.0" Round Culvert L= 8.2' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 648.50'/647.73' S= 0.0939 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf #3 Device 1 656.02' 48.0"Vert. Orifice/Grate C= 0.600 Primary OutFlow Max=22.13 cfs @ 12.32 hrs HW=656.02' (Free Discharge) t-1=Culvert (Passes 22.13 cfs of 41.94 cfs potential flow) 12=Culvert (Inlet Controls 22.13 cfs @ 12.53 fps) 3=Orifice/Grate ( Controls 0.00 cfs) • ' 09-011-00 SWD Type 1124-hr 100-yr Storm Rainfall=9.10" Prepared by Brian P. Smith, PE Printed 4/16/2013 HydroCAD® 10.00 s/n 05073 ©2012 HydroCAD Software Solutions LLC Summary for Pond 2P: INNER LOOP SWD Inflow Area = 10.850 ac, 39.91% Impervious, Inflow Depth = 6.91" for 100-yr Storm event Inflow = 81.86 cfs @ 12.11 hrs, Volume= 6.248 of Outflow = 45.98 cfs @ 12.30 hrs, Volume= 6.248 af, Atten= 44%, Lag= 11.0 min Primary = 45.98 cfs @ 12.30 hrs, Volume= 6.248 af Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 657.57' @ 12.30 hrs Surf.Area= 18,114 sf Storage= 47,104 cf Plug-Flow detention time= 7.1 min calculated for 6.247 af(100% of inflow) Center-of-Mass det. time= 7.1 min ( 810.2 - 803.0 ) Volume Invert Avail.Storage Storage Description #1 648.50' 55,128 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 648.50 0 0.0 0 0 0 650.00 278 117.6 139 139 1,104 652.00 1,092 229.6 1,281 1,420 4,218 654.00 3,074 314.7 3,999 5,418 7,944 656.00 14,485 674.0 16,155 21,573 36,230 658.00 19,180 656.1 33,555 55,128 38,545 Device Routing Invert Outlet Devices #1 Primary 647.33' 24.0" Round Culvert L= 126.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 647.33'/635.60' S= 0.0931 '/' Cc= 0.900 n= 0.012, Flow Area= 3.14 sf #2 Device 1 648.50' 18.0" Round Culvert L= 8.2' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 648.50'/647.73' S= 0.0939 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf #3 Device 1 656.02' 48.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=45.98 cfs @ 12.30 hrs HW=657.57' (Free Discharge) L1=Culvert (Inlet Controls 45.98 cfs @ 14.64 fps) - 2=Culvert (Passes < 24.54 cfs potential flow) 3=Orifice/Grate (Passes < 75.31 cfs potential flow) RECEIVED APR 2 2 2013 COMMUNITY DEVELOPMENT