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Stormwater Report Lotus WoodsSTORMWATER 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 (cf.,;) 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 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 CA� Reg. No. 40433 Date May 18, 2016 Engineers & Land Surveyors, Inc. CITY OF CHANHASSEN RECEIVED FEB 1 7 til) 7 CHANHASSENPLANNING DEPT 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 Sub4 Reach on Llrlk 16-0139 EXISTING Type 11 24 -hr 2 yr Rainfall=2.87' Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/18/2016 HydroCAD® 10.00-14 s/n 03113 @2015 HydroCAD Software Solutions LLC Page 2 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 min) (feet) (ft/ft) 17.4 166 0.1100 Description 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 min 24.3 Length Description 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" 16-0139 EXISTING Type 11 24 -hr 10 yr Rainfall=4.27' Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/18/2016 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 Descriotion 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 17.4 166 0.1100 Description 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 24.3 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" 16-0139 EXISTING Type 11 24 -hr 100 yr Rainfall=7.38" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/18/2016 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 11 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 min) (feet) (ft/ft) 17.4 166 0.1100 Description 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 24.3 215 0.0805 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80" 1S Proposed Area P1 50S 2S _�A5P Proposed Yea P5 Proposed Area P2 Catch Basin Area P4 Pond 4S Proposed Area P4 Sub4 Reach A Link 16R] /Area to Southwest 3S Proposed Area P3 16-0139 PROPOSED Prepared by Otto Associates, Engineers & Land Surveyors, Inc. HvHrn('AncR) 10.00-14 s/n 03113 © 2015 HvdroCAD Software Solutions L Type 1124 -hr 2 yr Rainfall=2.87" Printed 5/19/2016 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 0.28 54.55% Pervious Area 0.150 45.45% Impervious Area Tc Length Slope Velocity Capacity Description 4.5 30 0.1000 0.11 Sheet Flow, Paved parking & roofs 0.180 61 >75% Grass cover, Good, HSG B Woods: Light underbrush n= 0.400 P2= 2.87" 2.1 35 0.1400 0.28 Sheet Flow, 0.230 85.19% Pervious Area 0.040 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 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 16-0139 PROPOSED Type 11 24 -hr 2 yr Rainf611=2.87" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HvdroCADO 10.00-14 cin n31l3 n gnu u. A-nAn ..___ , , - 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 min) (feet) (ft/ft) 17.2 166 0.1100 Description 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 0.6 16.67% Impervious Area Tc Length Slope Velocity Capacity Description 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 11 24 -hr 2 yr Rainfall=2.87' 16-0139 PROPOSED Type 11 24 -hr 2 yr Rainfall=2.87" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 Area (ac) CN Descri 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 min) (feet) 14.8 110 0.0700 Description 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 of 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 of 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 of 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 of (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 16-0139 PROPOSED Type 1124 -hr 2 yrRainfall=2.87" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 Primary OutFlow Max=0.11 cfs @ 12.13 hrs HW=938.53' (Free Discharge) t2=Culvert (Passes 0.11 cfs of 10.07 cfs potential flow) t1=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 of 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 of Primary = 0.06 cfs @ 13.54 hrs, Volume= 0.048 of 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 of (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 T 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) Qiscarded 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) =Exfiltration (Exfiltration Controls 0.06 cfs) =Sharp -Crested Vee/Trap Weir( Controls 0.00 cfs) 16-0139 PROPOSED Type 1124 -hr 10 yrRainfall=4.27" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Pape 6 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" !a (ac) CN 0.150 98 0.180 61 0.330 78 0.180 0.150 Paved parking & roofs >75% Grass cover, Goo, Weighted Average 54.55% Pervious Area 45.45% Impervious Area Tc Length Slope Velocity Capacity Description in) rfnofl /a/&N 1u,___. _. 4.5 30 0.1000Sheet 85.19% Pervious Area Flow, 2.1 35 0.1400 0.28 Woods: Light underbrush n= 0.400 P2= 2.87" Sheet Flow, 0.3 80 0.0380 3.96 Grass: Short n=0.150 P2=2.87" Shallow Concentrated Flow, 1.1 345 0.0100 5.26 Paved Kv= 6.46 pe Channel, fps P 15.0" Round Area= 1.2 sf Perim= 3.9' r- 0.31' 8.0 490 Total n= 0.013 Concrete pipe, bends & connections 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" a (ac) CN 0.040 98 0.180 61 Paved parking & roofs >75% Grass cover, Good, 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 int /foo11 /a M' 1-1 1_ 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 16-0139 PROPOSED Type 1124 -hr 10 yr Rainfall=4.27' Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HydroCAD® 10.00-14 s/n 03113 @2015 HydroCAD Software Solutions LLC Page 7 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 min) (feet) (ft/ft) 17.2 166 0.1100 Velocity Capacity Description 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 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 Waterwav 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 11 24 -hr 10 yr Rainfall=4.27' 16-0139 PROPOSED Prepared by Otto Associates, Engineers & Land HYdroCAD@ 10.00-14 a/n nzalq n on•c Paved parking & roofs Type 11 24 -hr 10 yr Rainfall=4.27" Inc. Printed 5/19/2016 u.unu til >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, 20 Woods: Light underbrush n= 0.400 P2= 2.87" 939.00 Summary for Reach 6R: Area to Southwest 51 71 Inflow Area = Inflow = 1.660 ac, 19.28% Impervious, Inflow Depth = 1.02" for 10 yr event 0.41 cfs @ 12.11 Outflow = hrs, Volume= 0.141 of 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 = Inflow = 0.270 ac, 14.81% Impervious, Inflow Depth = 1.25" for 10 yr event 0.38 cfs @ 12.11 hrs, Outflow = Primary = Volume= 0.028 of 0.38 cfs @ 12.11 hrs, Volume=o 0.028 af, Aft 0 /", Lag= 0.1 min 0.38 cfs 12.11 @ hrs, Volume= 0.028 of 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 of (98% of inflow Center -of -Mass det. time= 2.9 min ( 878.2 - 875.3 ) #1 933.40' 240 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sg-ft) (cubic feet) (cubic feet) 933.40 4 0 938.50 4 20 0 20 939.00 200 51 71 939.50 475 169 240 #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 16-0139 PROPOSED Type 1124 -hr 10 yr Rainfall=4.27" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HydroCAD® 10.00-14 s/n 03113 @ 2015 HydroCAD Software Solutions LLC pang Cl Primary OutFlow Max=0.36 cfs @ 12.11 hrs HW=938.57' (Free Discharge) t-2=Culvert (Passes 0.36 cfs of 10.10 cfs potential flow) t1=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 of 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 of Primary = 0.10 cfs @ 14.30 hrs, Volume= 0.114 of 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 of (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 T 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) L3=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.09 cfs @ 14.30 hrs HW=932.86' (Free Discharge) Culvert (Passes 0.09 cfs of 8.33 cfs potential flow) =Orifice/Grate (Weir Controls 0.01 cfs @ 0.27 fps) =Exfiltration (Exfiltration Controls 0.07 cfs) =Sharp -Crested Vee/Trap Weir( Controls 0.00 cfs) 16-0139 PROPOSED Type 1124 -hr 100 yr Rainfall=7.41 " Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/1912016 HydroCAD® 10.00-14 s/n 03113 © 2015 HydroCAD Software Solutions LLC Page 10 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, 0.040 14.81% Impervious Area 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 17.1 165 0.1100 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.87" 16-0139 PROPOSED Type 11 24 -hr 100 yr Rainfall=7.41 " Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HydroCAD® 10.00-14 s/n 03113 @2015 HydroCAD Software Solutions LLC Page 11 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 min) (feet) (ft/ft) 17.2 166 0.1100 Velocity Capacity Description 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 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 Waterwav Kv= 15.0 fos 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 11 24 -hr 100 yr Rainfall=7.41" 16-0139 PROPOSED Otto Associates, Engineers & Land Surveyors, Inc. 1.00-14 s/n 03113 © 2015 HydroCAD Software Solutions L 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 min) Length (feet) Slope (ft/ft) 14.8 110 0.0700 Velocity Capacity Description Type 1124 -hr 100 yr Rainfall=7.41 " Printed 5/19/2016 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 of 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 of 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 of 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 of (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 T Cc= 0.900 n=0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf 16-0139 PROPOSED Type 1124 -hr 100 yrRainfall= 7.41" Prepared by Otto Associates, Engineers & Land Surveyors, Inc. Printed 5/19/2016 HydroCADO 10.00-14 s/n 03113 @2015 HydroCAD Software Solutions LLC Page 13 Primary OutFlow Max=1.15 cfs @ 12.10 hrs HW=938.65' (Free Discharge) t-2=Culvert (Passes 1.15 cfs of 10.17 cfs potential flow) 't--1 =Orifice/G rate (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 of 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 of Primary = 4.05 cfs @ 12.19 hrs, Volume= 0.366 of 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 of (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) -fisted 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 T 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) Qiscarded 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) -11 =Culvert (Passes 4.05 cfs of 8.62 cfs potential flow) 2=Orifice/Grate (Weir Controls 3.97 cfs @ 1.92 fps) =Exfiltration (Exfiltration Controls 0.08 cfs) =Sharp -Crested Vee/Trap Weir( Controls 0.00 cfs) ex. /w ,.edge o7— bit. d (ss < _ GO 10 to -� 948 946 946 10 9441 -34 -Ac -944 !T�_ 1 942 _ __ _ g40 942 — 10 '940� ....-9m..,- "`.-eX rock rel -wall \ '< Ex CB Ri�_ `rte ex. su m�r��gyh �`�- / .._Rim=930.61 {' 9utlM"� Ex.MH- /nv=927,33 �BI SSS SS CSS �—_ SS y/,../, ($a SSS:.'— 3 ,-Rim-9 91 roiafb9' W \ W -- ' ' �/ "' S !+ SS S5 SY SS S Inr-911'B8 W W W W SS 930 W __ µ —y� µ--xisf. wm r W = W_W w SS 16b 97EY xm 50 � 9$�3 C I I I EX.MH �/ \ I r/ I ■ ® I I Rim=93. 0 -t rvYN I G RAI AGE MAP Inv --917. 11� I 1 "=40' Inv='J120 927.51 I I N lnv�973.B0 � NS/nv--,91371 / i I \ t T �ed9e Of u--°'z°�`--\ 1 i J r � .ar � \ $ F✓ bit- die a � /�-e<S�✓...,e.,�. 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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/1): 0.3 TSS EMC (mgA): 54.5 Total Site Area Land Cover A Soils 8 Soils C Soils D Soils Total (acres) (acres) (acres) (acres) (acres) Forest/Open Space - Undisturbed, protected forest/open space or reforested land 025 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 B Soils C Soils D Soils Total (acres) (acres) (acres) (acres) (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 Annual Volume Summary BMP Volume Volume Volume Volume Percent BMP Name Capacity Recieved Retained Outflow Retained BMP Name (ft3) (ft3) (ft3) (ft3) - (%) 1 - Bioretention basin (with underdrain) 1261 1198 1198 0 100 1 Annual Volume Summary Particulate Phosphorus Summary Volume Volume From Direct From Volume Volume Percent BMP Name Watershed Upstream Retained outflow Retained (acre -ft) BMPs (acre -ft) (acre -ft) (%) 1 - Bioretention basin (with underdrain) 0.39 (acre -ft) 0.37 0.02 94 1 - Bioretention basin (with underdrain) 0.8701 0 0.7692 0.1009 88 LID Particulate Phosphorus Summary Dissolved Phosphorus Summary Load From Load From Direct Upstream Outflow Percent BMP Name Watershed BMPs 7Retained Load Retained (lbs) (lbs) (lbs) (%) 1 - Bioretention basin (with underdrain) 0.39 0 0.37 0.02 94 t Fi Dissolved Phosphorus Summary TSS Summary Load From Load From Direct Upstream Load Outflow Percent BMP Name Watershed BMPs Retained Load Retained Watershed BMPs (Ibs) (Ibs) (%) 1 - Bioretention basin (with underdrain) (Ibs) (lbs) (lbs) (lbs) M) 1 - Bioretention basin (with underdrain) 0.32 0 0.29 0.03 90 TSS Summary BMP Schematic -apw.0 wdenftaia) Load From Load From Direct Upstream Load Outflow Percent BMP Name Watershed BMPs Retained Load Retained (Ibs) (Ibs) (Ibs) (Ibs) (%) 1 - Bioretention basin (with underdrain) 129 0 123 6 95 u u BMP Schematic -apw.0 wdenftaia) Sioretention Sod Mix B (by volume): 7GX washed sand 3GX organic leaf compost +ta�,.sk rt_sw.. ryn. Geogrid Wisp, connected with zip ties - 2' Choker Course, 1B, 178, or 189 Stone 157 Stone, Pipe width + 2" Above Pipe— Bioretention Soil Mix B Ceogrid Wrap. connected with zip ties 2" Choker Course, 18, 178, or 189 Stone 7.• ,A 157 Stone, Pipe width + 2- Above Pipe Shredded Bork Mulch eretention Plants 2- RCP 6' PVC Solid Pipe \\\ Tronsition from Solid to Perforated Pipe 00 6" Perforated Pipe Non—Compacted Subgratle /n—situ soi/s shot/ be ripped fo p depth of 12" prior to placing amended sods with a chisel plow, ripper or sub—salter Biofiltration with Elevated Underdrain Not To Scale