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160139 Lotus Woods Stormwater ReportSTORMWATER REPORT LOTUS WOODS Chanhassen, Minnesota May 18, 2016 Otto Project No. 16-0139 This 1 acre site is proposed to be platted into 2 single family lots. The majority of the site is wooded. There is an existing driveway along the north side of the property which will be removed. A public street will be installed along the east side of the property (approx. 100’ in length). Impervious area proposed is 0.3 acres. This project does not trigger a NPDES Stormwater permit but does trigger a permit from Riley Purgatory Bluff Creek Watershed District. The entire site drains to Lotus Lake. A filtration basin is proposed in the SW corner of the site to provide rate control, volume abstraction and water quality treatment. The basin provides 1198 CF of volume abstraction, 92% phosphorus removal and 95% TSS removal. Below is a table summarizing the runoff rates: Runoff (cfs) Runoff to SW 1 Year 10 Year 100 Year Existing Runoff 0.39 1.54 5.06 Proposed Runoff 0.14 0.41 5.06 Snowmelt Calculation: Snowmelt depth = 4” Snow water equivalent = 0.09” Drainage area to basin = 1.32 acres Snowmelt Volume = 1.32 ac. x 4” x 0.09” = 1725 cf Elevation within basin = 932.2 I hereby certify that these specifications were prepared by me or under my direct supervision and that I am a duly Registered Professional Engineer under the laws of the State of Minnesota. Cara Schwahn Otto Reg. No. 40433 Date May 18, 2016 9 West Division Street, Buffalo, MN 55313 • 763-682-4727 • Fax 763-682-3522 • www.ottoassociates.com 1S Existing Area E1 2S Existing Area E2 Routing Diagram for 16-0139 EXISTING Prepared by Otto Associates, Engineers & Land Surveyors, Inc., Printed 5/18/2016 HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type II 24-hr 2 yr Rainfall=2.87"16-0139 EXISTING Printed 5/18/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 2HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Area E1 Runoff = 0.39 cfs @ 12.15 hrs, Volume= 0.036 af, Depth> 0.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.100 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 1.140 60 Woods, Fair, HSG B 1.340 63 Weighted Average 1.240 92.54% Pervious Area 0.100 7.46% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.4 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" Summary for Subcatchment 2S: Existing Area E2 Runoff = 0.16 cfs @ 12.21 hrs, Volume= 0.014 af, Depth> 0.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.070 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 0.150 60 Woods, Fair, HSG B 0.320 69 Weighted Average 0.250 78.13% Pervious Area 0.070 21.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 24.3 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" Type II 24-hr 10 yr Rainfall=4.27"16-0139 EXISTING Printed 5/18/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 3HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Area E1 Runoff = 1.54 cfs @ 12.12 hrs, Volume= 0.106 af, Depth> 0.95" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.100 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 1.140 60 Woods, Fair, HSG B 1.340 63 Weighted Average 1.240 92.54% Pervious Area 0.100 7.46% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.4 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" Summary for Subcatchment 2S: Existing Area E2 Runoff = 0.43 cfs @ 12.19 hrs, Volume= 0.035 af, Depth> 1.30" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.070 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 0.150 60 Woods, Fair, HSG B 0.320 69 Weighted Average 0.250 78.13% Pervious Area 0.070 21.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 24.3 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" Type II 24-hr 100 yr Rainfall=7.38"16-0139 EXISTING Printed 5/18/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 4HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Area E1 Runoff = 5.06 cfs @ 12.10 hrs, Volume= 0.324 af, Depth> 2.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100 yr Rainfall=7.38" Area (ac) CN Description 0.100 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 1.140 60 Woods, Fair, HSG B 1.340 63 Weighted Average 1.240 92.54% Pervious Area 0.100 7.46% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.4 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" Summary for Subcatchment 2S: Existing Area E2 Runoff = 1.21 cfs @ 12.18 hrs, Volume= 0.094 af, Depth> 3.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100 yr Rainfall=7.38" Area (ac) CN Description 0.070 98 Paved parking & roofs 0.100 61 >75% Grass cover, Good, HSG B 0.150 60 Woods, Fair, HSG B 0.320 69 Weighted Average 0.250 78.13% Pervious Area 0.070 21.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 24.3 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" 1S Proposed Area P1 2S Proposed Area P2 3S Proposed Area P3 4S Proposed Area P4 5S Proposed Area P5 6R Area to Southwest 4P Catch Basin 5P Area P4 Pond Routing Diagram for 16-0139 PROPOSED Prepared by Otto Associates, Engineers & Land Surveyors, Inc., Printed 5/19/2016 HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type II 24-hr 2 yr Rainfall=2.87"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 2HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Proposed Area P1 Runoff = 0.56 cfs @ 12.00 hrs, Volume= 0.029 af, Depth= 1.04" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.150 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.330 78 Weighted Average 0.180 54.55% Pervious Area 0.150 45.45% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 30 0.1000 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 2.1 35 0.1400 0.28 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.3 80 0.0380 3.96 Shallow Concentrated Flow, Paved Kv= 20.3 fps 1.1 345 0.0100 5.26 6.46 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 Concrete pipe, bends & connections 8.0 490 Total Summary for Subcatchment 2S: Proposed Area P2 Runoff = 0.12 cfs @ 12.13 hrs, Volume= 0.011 af, Depth= 0.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.040 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.050 60 Woods, Fair, HSG B 0.270 66 Weighted Average 0.230 85.19% Pervious Area 0.040 14.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Type II 24-hr 2 yr Rainfall=2.87"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 3HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Proposed Area P3 Runoff = 0.05 cfs @ 12.16 hrs, Volume= 0.006 af, Depth= 0.29" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.020 61 >75% Grass cover, Good, HSG B 0.250 60 Woods, Fair, HSG B 0.270 60 Weighted Average 0.270 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Subcatchment 4S: Proposed Area P4 Runoff = 0.29 cfs @ 12.20 hrs, Volume= 0.031 af, Depth= 0.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 2 yr Rainfall=2.87" Area (ac) CN Description 0.120 98 Paved parking & roofs 0.400 61 >75% Grass cover, Good, HSG B 0.200 60 Woods, Fair, HSG B 0.720 67 Weighted Average 0.600 83.33% Pervious Area 0.120 16.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.3 60 0.0670 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 13.3 115 0.0140 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.6 115 0.0390 2.96 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 23.2 290 Total Summary for Subcatchment 5S: Proposed Area P5 Runoff = 0.03 cfs @ 12.10 hrs, Volume= 0.003 af, Depth= 0.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 2 yr Rainfall=2.87" Type II 24-hr 2 yr Rainfall=2.87"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 4HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Area (ac) CN Description 0.010 98 Paved parking & roofs 0.060 61 >75% Grass cover, Good, HSG B 0.070 66 Weighted Average 0.060 85.71% Pervious Area 0.010 14.29% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.8 110 0.0700 0.12 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Reach 6R: Area to Southwest Inflow Area = 1.660 ac, 19.28% Impervious, Inflow Depth = 0.42" for 2 yr event Inflow = 0.14 cfs @ 12.14 hrs, Volume= 0.058 af Outflow = 0.14 cfs @ 12.14 hrs, Volume= 0.058 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Summary for Pond 4P: Catch Basin Inflow Area = 0.270 ac, 14.81% Impervious, Inflow Depth = 0.48" for 2 yr event Inflow = 0.12 cfs @ 12.13 hrs, Volume= 0.011 af Outflow = 0.12 cfs @ 12.13 hrs, Volume= 0.010 af, Atten= 0%, Lag= 0.1 min Primary = 0.12 cfs @ 12.13 hrs, Volume= 0.010 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 938.53' @ 12.13 hrs Surf.Area= 16 sf Storage= 21 cf Plug-Flow detention time= 31.3 min calculated for 0.010 af (96% of inflow) Center-of-Mass det. time= 8.6 min ( 918.9 - 910.3 ) Volume Invert Avail.Storage Storage Description #1 933.40' 240 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 933.40 4 0 0 938.50 4 20 20 939.00 200 51 71 939.50 475 169 240 Device Routing Invert Outlet Devices #1 Device 2 938.50'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Primary 933.40'15.0" Round Culvert L= 190.0' RCP, rounded edge headwall, Ke= 0.100 Inlet / Outlet Invert= 933.40' / 931.50' S= 0.0100 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Type II 24-hr 2 yr Rainfall=2.87"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 5HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Primary OutFlow Max=0.11 cfs @ 12.13 hrs HW=938.53' (Free Discharge) 2=Culvert (Passes 0.11 cfs of 10.07 cfs potential flow) 1=Orifice/Grate (Weir Controls 0.11 cfs @ 0.58 fps) Summary for Pond 5P: Area P4 Pond Inflow Area = 1.320 ac, 23.48% Impervious, Inflow Depth = 0.64" for 2 yr event Inflow = 0.72 cfs @ 12.05 hrs, Volume= 0.070 af Outflow = 0.09 cfs @ 13.54 hrs, Volume= 0.070 af, Atten= 88%, Lag= 89.8 min Discarded = 0.03 cfs @ 13.54 hrs, Volume= 0.022 af Primary = 0.06 cfs @ 13.54 hrs, Volume= 0.048 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 931.96' @ 13.54 hrs Surf.Area= 2,572 sf Storage= 1,108 cf Plug-Flow detention time= 125.5 min calculated for 0.070 af (100% of inflow) Center-of-Mass det. time= 125.5 min ( 1,014.4 - 889.0 ) Volume Invert Avail.Storage Storage Description #1 931.50' 8,747 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 931.50 2,265 0 0 932.00 2,600 1,216 1,216 933.00 3,300 2,950 4,166 934.00 4,135 3,718 7,884 934.20 4,500 864 8,747 Device Routing Invert Outlet Devices #1 Primary 927.50'12.0" Round Culvert L= 24.0' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 927.50' / 927.33' S= 0.0071 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #2 Device 1 932.85'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 931.50'0.450 in/hr Exfiltration over Surface area #4 Device 1 931.50'1.000 in/hr Exfiltration over Surface area above 929.30' Excluded Surface area = 0 sf #5 Primary 933.20'143.0 deg x 4.0' long x 1.00' rise Sharp-Crested Vee/Trap Weir Cv= 2.47 (C= 3.09) Discarded OutFlow Max=0.03 cfs @ 13.54 hrs HW=931.96' (Free Discharge) 3=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.06 cfs @ 13.54 hrs HW=931.96' (Free Discharge) 1=Culvert (Passes 0.06 cfs of 7.52 cfs potential flow) 2=Orifice/Grate ( Controls 0.00 cfs) 4=Exfiltration (Exfiltration Controls 0.06 cfs) 5=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs) Type II 24-hr 10 yr Rainfall=4.27"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 6HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Proposed Area P1 Runoff = 1.15 cfs @ 12.00 hrs, Volume= 0.058 af, Depth= 2.10" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.150 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.330 78 Weighted Average 0.180 54.55% Pervious Area 0.150 45.45% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 30 0.1000 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 2.1 35 0.1400 0.28 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.3 80 0.0380 3.96 Shallow Concentrated Flow, Paved Kv= 20.3 fps 1.1 345 0.0100 5.26 6.46 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 Concrete pipe, bends & connections 8.0 490 Total Summary for Subcatchment 2S: Proposed Area P2 Runoff = 0.38 cfs @ 12.11 hrs, Volume= 0.028 af, Depth= 1.25" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.040 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.050 60 Woods, Fair, HSG B 0.270 66 Weighted Average 0.230 85.19% Pervious Area 0.040 14.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Type II 24-hr 10 yr Rainfall=4.27"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 7HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Proposed Area P3 Runoff = 0.25 cfs @ 12.12 hrs, Volume= 0.020 af, Depth= 0.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.020 61 >75% Grass cover, Good, HSG B 0.250 60 Woods, Fair, HSG B 0.270 60 Weighted Average 0.270 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Subcatchment 4S: Proposed Area P4 Runoff = 0.90 cfs @ 12.19 hrs, Volume= 0.079 af, Depth= 1.31" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 10 yr Rainfall=4.27" Area (ac) CN Description 0.120 98 Paved parking & roofs 0.400 61 >75% Grass cover, Good, HSG B 0.200 60 Woods, Fair, HSG B 0.720 67 Weighted Average 0.600 83.33% Pervious Area 0.120 16.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.3 60 0.0670 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 13.3 115 0.0140 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.6 115 0.0390 2.96 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 23.2 290 Total Summary for Subcatchment 5S: Proposed Area P5 Runoff = 0.11 cfs @ 12.08 hrs, Volume= 0.007 af, Depth= 1.25" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 10 yr Rainfall=4.27" Type II 24-hr 10 yr Rainfall=4.27"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 8HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Area (ac) CN Description 0.010 98 Paved parking & roofs 0.060 61 >75% Grass cover, Good, HSG B 0.070 66 Weighted Average 0.060 85.71% Pervious Area 0.010 14.29% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.8 110 0.0700 0.12 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Reach 6R: Area to Southwest Inflow Area = 1.660 ac, 19.28% Impervious, Inflow Depth = 1.02" for 10 yr event Inflow = 0.41 cfs @ 12.11 hrs, Volume= 0.141 af Outflow = 0.41 cfs @ 12.11 hrs, Volume= 0.141 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Summary for Pond 4P: Catch Basin Inflow Area = 0.270 ac, 14.81% Impervious, Inflow Depth = 1.25" for 10 yr event Inflow = 0.38 cfs @ 12.11 hrs, Volume= 0.028 af Outflow = 0.38 cfs @ 12.11 hrs, Volume= 0.028 af, Atten= 0%, Lag= 0.1 min Primary = 0.38 cfs @ 12.11 hrs, Volume= 0.028 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 938.57' @ 12.11 hrs Surf.Area= 31 sf Storage= 22 cf Plug-Flow detention time= 12.4 min calculated for 0.028 af (98% of inflow) Center-of-Mass det. time= 2.9 min ( 878.2 - 875.3 ) Volume Invert Avail.Storage Storage Description #1 933.40' 240 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 933.40 4 0 0 938.50 4 20 20 939.00 200 51 71 939.50 475 169 240 Device Routing Invert Outlet Devices #1 Device 2 938.50'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Primary 933.40'15.0" Round Culvert L= 190.0' RCP, rounded edge headwall, Ke= 0.100 Inlet / Outlet Invert= 933.40' / 931.50' S= 0.0100 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Type II 24-hr 10 yr Rainfall=4.27"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 9HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Primary OutFlow Max=0.36 cfs @ 12.11 hrs HW=938.57' (Free Discharge) 2=Culvert (Passes 0.36 cfs of 10.10 cfs potential flow) 1=Orifice/Grate (Weir Controls 0.36 cfs @ 0.86 fps) Summary for Pond 5P: Area P4 Pond Inflow Area = 1.320 ac, 23.48% Impervious, Inflow Depth = 1.49" for 10 yr event Inflow = 1.90 cfs @ 12.03 hrs, Volume= 0.164 af Outflow = 0.13 cfs @ 14.30 hrs, Volume= 0.164 af, Atten= 93%, Lag= 136.1 min Discarded = 0.03 cfs @ 14.30 hrs, Volume= 0.050 af Primary = 0.10 cfs @ 14.30 hrs, Volume= 0.114 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 932.86' @ 14.30 hrs Surf.Area= 3,200 sf Storage= 3,701 cf Plug-Flow detention time= 396.0 min calculated for 0.164 af (100% of inflow) Center-of-Mass det. time= 396.0 min ( 1,258.1 - 862.2 ) Volume Invert Avail.Storage Storage Description #1 931.50' 8,747 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 931.50 2,265 0 0 932.00 2,600 1,216 1,216 933.00 3,300 2,950 4,166 934.00 4,135 3,718 7,884 934.20 4,500 864 8,747 Device Routing Invert Outlet Devices #1 Primary 927.50'12.0" Round Culvert L= 24.0' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 927.50' / 927.33' S= 0.0071 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #2 Device 1 932.85'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 931.50'0.450 in/hr Exfiltration over Surface area #4 Device 1 931.50'1.000 in/hr Exfiltration over Surface area above 929.30' Excluded Surface area = 0 sf #5 Primary 933.20'143.0 deg x 4.0' long x 1.00' rise Sharp-Crested Vee/Trap Weir Cv= 2.47 (C= 3.09) Discarded OutFlow Max=0.03 cfs @ 14.30 hrs HW=932.86' (Free Discharge) 3=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.09 cfs @ 14.30 hrs HW=932.86' (Free Discharge) 1=Culvert (Passes 0.09 cfs of 8.33 cfs potential flow) 2=Orifice/Grate (Weir Controls 0.01 cfs @ 0.27 fps) 4=Exfiltration (Exfiltration Controls 0.07 cfs) 5=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs) Type II 24-hr 100 yr Rainfall=7.41"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 10HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Proposed Area P1 Runoff = 2.59 cfs @ 11.99 hrs, Volume= 0.133 af, Depth= 4.85" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 100 yr Rainfall=7.41" Area (ac) CN Description 0.150 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.330 78 Weighted Average 0.180 54.55% Pervious Area 0.150 45.45% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 30 0.1000 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 2.1 35 0.1400 0.28 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.3 80 0.0380 3.96 Shallow Concentrated Flow, Paved Kv= 20.3 fps 1.1 345 0.0100 5.26 6.46 Pipe Channel, 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.013 Concrete pipe, bends & connections 8.0 490 Total Summary for Subcatchment 2S: Proposed Area P2 Runoff = 1.15 cfs @ 12.10 hrs, Volume= 0.079 af, Depth= 3.53" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 100 yr Rainfall=7.41" Area (ac) CN Description 0.040 98 Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B 0.050 60 Woods, Fair, HSG B 0.270 66 Weighted Average 0.230 85.19% Pervious Area 0.040 14.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Type II 24-hr 100 yr Rainfall=7.41"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 11HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Proposed Area P3 Runoff = 0.93 cfs @ 12.10 hrs, Volume= 0.065 af, Depth= 2.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 100 yr Rainfall=7.41" Area (ac) CN Description 0.020 61 >75% Grass cover, Good, HSG B 0.250 60 Woods, Fair, HSG B 0.270 60 Weighted Average 0.270 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 166 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Subcatchment 4S: Proposed Area P4 Runoff = 2.66 cfs @ 12.17 hrs, Volume= 0.218 af, Depth= 3.64" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 100 yr Rainfall=7.41" Area (ac) CN Description 0.120 98 Paved parking & roofs 0.400 61 >75% Grass cover, Good, HSG B 0.200 60 Woods, Fair, HSG B 0.720 67 Weighted Average 0.600 83.33% Pervious Area 0.120 16.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.3 60 0.0670 0.11 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 13.3 115 0.0140 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 2.87" 0.6 115 0.0390 2.96 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 23.2 290 Total Summary for Subcatchment 5S: Proposed Area P5 Runoff = 0.32 cfs @ 12.07 hrs, Volume= 0.021 af, Depth= 3.53" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Type II 24-hr 100 yr Rainfall=7.41" Type II 24-hr 100 yr Rainfall=7.41"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 12HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Area (ac) CN Description 0.010 98 Paved parking & roofs 0.060 61 >75% Grass cover, Good, HSG B 0.070 66 Weighted Average 0.060 85.71% Pervious Area 0.010 14.29% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.8 110 0.0700 0.12 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" Summary for Reach 6R: Area to Southwest Inflow Area = 1.660 ac, 19.28% Impervious, Inflow Depth = 3.27" for 100 yr event Inflow = 5.06 cfs @ 12.17 hrs, Volume= 0.452 af Outflow = 5.06 cfs @ 12.17 hrs, Volume= 0.452 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Summary for Pond 4P: Catch Basin Inflow Area = 0.270 ac, 14.81% Impervious, Inflow Depth = 3.53" for 100 yr event Inflow = 1.15 cfs @ 12.10 hrs, Volume= 0.079 af Outflow = 1.15 cfs @ 12.10 hrs, Volume= 0.079 af, Atten= 0%, Lag= 0.1 min Primary = 1.15 cfs @ 12.10 hrs, Volume= 0.079 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 938.65' @ 12.10 hrs Surf.Area= 63 sf Storage= 25 cf Plug-Flow detention time= 5.1 min calculated for 0.079 af (99% of inflow) Center-of-Mass det. time= 1.5 min ( 845.5 - 844.0 ) Volume Invert Avail.Storage Storage Description #1 933.40' 240 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 933.40 4 0 0 938.50 4 20 20 939.00 200 51 71 939.50 475 169 240 Device Routing Invert Outlet Devices #1 Device 2 938.50'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Primary 933.40'15.0" Round Culvert L= 190.0' RCP, rounded edge headwall, Ke= 0.100 Inlet / Outlet Invert= 933.40' / 931.50' S= 0.0100 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Type II 24-hr 100 yr Rainfall=7.41"16-0139 PROPOSED Printed 5/19/2016Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Page 13HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Primary OutFlow Max=1.15 cfs @ 12.10 hrs HW=938.65' (Free Discharge) 2=Culvert (Passes 1.15 cfs of 10.17 cfs potential flow) 1=Orifice/Grate (Weir Controls 1.15 cfs @ 1.27 fps) Summary for Pond 5P: Area P4 Pond Inflow Area = 1.320 ac, 23.48% Impervious, Inflow Depth = 3.91" for 100 yr event Inflow = 5.15 cfs @ 12.03 hrs, Volume= 0.430 af Outflow = 4.09 cfs @ 12.19 hrs, Volume= 0.430 af, Atten= 21%, Lag= 9.4 min Discarded = 0.04 cfs @ 12.19 hrs, Volume= 0.064 af Primary = 4.05 cfs @ 12.19 hrs, Volume= 0.366 af Routing by Stor-Ind method, Time Span= 0.50-100.00 hrs, dt= 0.01 hrs Peak Elev= 933.19' @ 12.19 hrs Surf.Area= 3,462 sf Storage= 4,822 cf Plug-Flow detention time= 209.1 min calculated for 0.430 af (100% of inflow) Center-of-Mass det. time= 209.1 min ( 1,044.4 - 835.3 ) Volume Invert Avail.Storage Storage Description #1 931.50' 8,747 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 931.50 2,265 0 0 932.00 2,600 1,216 1,216 933.00 3,300 2,950 4,166 934.00 4,135 3,718 7,884 934.20 4,500 864 8,747 Device Routing Invert Outlet Devices #1 Primary 927.50'12.0" Round Culvert L= 24.0' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 927.50' / 927.33' S= 0.0071 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #2 Device 1 932.85'23.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 931.50'0.450 in/hr Exfiltration over Surface area #4 Device 1 931.50'1.000 in/hr Exfiltration over Surface area above 929.30' Excluded Surface area = 0 sf #5 Primary 933.20'143.0 deg x 4.0' long x 1.00' rise Sharp-Crested Vee/Trap Weir Cv= 2.47 (C= 3.09) Discarded OutFlow Max=0.04 cfs @ 12.19 hrs HW=933.19' (Free Discharge) 3=Exfiltration (Exfiltration Controls 0.04 cfs) Primary OutFlow Max=4.05 cfs @ 12.19 hrs HW=933.19' (Free Discharge) 1=Culvert (Passes 4.05 cfs of 8.62 cfs potential flow) 2=Orifice/Grate (Weir Controls 3.97 cfs @ 1.92 fps) 4=Exfiltration (Exfiltration Controls 0.08 cfs) 5=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs) Project Information Calculator Version:Version 2: June 2014 Project Name:Lotus Woods User Name / Company Name: Otto Associates, Inc. Date:5-16-16 Project Description:2 lot subdivision Site Information Retention Requirement (inches): 1.1 Site's Zip Code:55317 Annual Rainfall (inches):29.9 Phosphorus EMC (mg/l):0.3 TSS EMC (mg/l):54.5 Total Site Area Land Cover A Soils (acres) B Soils (acres) C Soils (acres) D Soils (acres) Total (acres) Forest/Open Space -Undisturbed, protected forest/open space or reforested land 0.25 0.25 Managed Turf -disturbed, graded for yards or other turf to be mowed/managed 0.5 0.5 Impervious Area (acres) 0.3 Total Area (acres) 1.05 Site Areas Routed to BMPs Land Cover A Soils (acres) B Soils (acres) C Soils (acres) D Soils (acres) Total (acres) Forest/Open Space -Undisturbed, protected forest/open space or reforested land 0.1 0.1 Managed Turf -disturbed, graded for yards or other turf to be mowed/managed 0.5 0.5 Impervious Area (acres) 0.3 Total Area (acres) 0.9 Summary Information Performance Goal Requirement Performance goal volume retention requirement: 1198 ft3 Volume removed by BMPs towards performance goal: 1198 ft3 Percent volume removed towards performance goal 100 % Annual Volume and Pollutant Load Reductions Post development annual runoff volume 0.8802 acre-ft Annual runoff volume removed by BMPs: 0.7692 acre-ft Percent annual runoff volume removed: 87 % Post development annual particulate P load: 0.4 lbs Annual particulate P removed by BMPs:0.37 lbs Post development annual dissolved P load: 0.32 lbs Annual dissolved P removed by BMPs: 0.29 lbs Percent annual total phosphorus removed: 92 % Post development annual TSS load:130 lbs Annual TSS removed by BMPs: 123 lbs Percent annual TSS removed: 95 % BMP Summary Performance Goal Summary BMP Name BMP Volume Capacity (ft3) Volume Recieved (ft3) Volume Retained (ft3) Volume Outflow (ft3) Percent Retained (%) 1 - Bioretention basin (with underdrain)1261 1198 1198 0 100 Annual Volume Summary BMP Name Volume From Direct Watershed (acre-ft) Volume From Upstream BMPs (acre-ft) Volume Retained (acre-ft) Volume outflow (acre-ft) Percent Retained (%) 1 - Bioretention basin (with underdrain)0.8701 0 0.7692 0.1009 88 Particulate Phosphorus Summary BMP Name Load From Direct Watershed (lbs) Load From Upstream BMPs (lbs) Load Retained (lbs) Outflow Load (lbs) Percent Retained (%) 1 - Bioretention basin (with underdrain)0.39 0 0.37 0.02 94 Dissolved Phosphorus Summary BMP Name Load From Direct Watershed (lbs) Load From Upstream BMPs (lbs) Load Retained (lbs) Outflow Load (lbs) Percent Retained (%) 1 - Bioretention basin (with underdrain)0.32 0 0.29 0.03 90 TSS Summary BMP Name Load From Direct Watershed (lbs) Load From Upstream BMPs (lbs) Load Retained (lbs) Outflow Load (lbs) Percent Retained (%) 1 - Bioretention basin (with underdrain)129 0 123 6 95 BMP Schematic