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Preliminary Stormwater Management Summary 3-22-06 Preliminary Stormwater Management Summary for Galpin Crossing Twinhomes Chanhassen, MN Revised 3/22/2006 CITY OF CHANHASS~N RECEIVED MAR 3 0 2006 CHANHASSEN PLANNING OEPT Existine Drainaee Conditions: Refer to the attached existing conditions drainage plan sheet D-I. The proposed townhome site (Parcel A) naturally drains to the north towards the existing wetlands and towards Bluff Creek. There is also drainage entering Parcel A from the parcel ofland (Parcel B) to the south that is bound be W. 78th, Galpin Avenue and Hwy 5. This drainage is conveyed through an existing 27" culvert that exists beneath W. 78th street. We examined the existing conditions on Parcel B to determine the peak flow rates that may be anticipated through the culvert and incorporated the development of Parcel A. Below are the existing condition peak flow rates for the required storm events. The peak flow rates for Parcel B are the flow rates at the down stream end of the existing 27" culvert. These calculations were generated using HydroCad. Drainage Acres 100 Yr 10Yr 2 Yr Peak Area Peak Q (cfs) Peak Q Q (ds) (ds) Parcel A 4.00 12.64 6.32 0.00 Parcel B (27" 7.97 5.85 2.03 0.01 culvert) Total 11.97 18.49 8.35 0.01 Proposed Drainaee: The proposed drainage areas are similar to the existing conditions except that the amount of pervious area has increased with the proposed development. The amount of impervious area proposed is 1.14 acres and a Curve Number of 98 was assumed for this area. The remaining amount of pervious area is 2.51 acres and a Curve Number of 61 was assumed for this area. The weighted curve number was then calculated to be 68. Please refer to the attached proposed Drainage Areas sheet D-2 Rate Control is provided by a NURP pond located at the north western part of the site, just south of the wetland buffer. The NURP pond is designed to limit the flow rates to not exceed the existing conditions for the lOa-year, 1 a-year, and 2-year rain events. Rainfall amounts uses are 6" for the 100 year storm, 4.2" for the 10 year storm and 1.15' for the 2 year storm. The 6" and 1 A" rainfall amounts were given by City engineering staff and the 2 year storm is based on the Rainfall Frequency Atlas of the Midwest, 1992. See attached Hydro Cad calculations for hydrographs. The table below lists the resulting flow rates to compare between existing and Page 1 of2 Preliminary Stormwater Management Summary for Galpin Crossing Twinhomes Chanhassen, MN Revised 3/22/2006 proposed conditions. For all required storm events, the proposed flow rates do not exceed the existing conditions. Existing Proposed Existing Proposed Existing Proposed 100 Yr 100 Yr Q 10Yr 10 Yr Q 2Yr Q 2YrQ Q (cfs) (cfs) Q (cfs) (cfs) (cfs) (cfs) Parcel A 12.64 11.30 6.32 4.96 0.00 0.00 Parcel B 5.85 5.85 2.03 2.03 0.01 0.01 (27" Culvert) Total 18.49 17.15 8.35 6.99 0.01 0.01 Water Quality is provided by the dead storage in the pond. Per NURP standards, the required dead storage volume is equal to the runoff from the 2.5" rain from the proposed conditions. From the HydroCad calculations the required volume is 0.15 acre-feet. The provided volume is 0.16 acre-feet. Please see attached Pond WQ calculations sheet. Page 2 of2 PROJECT: LOCATION: DEVELOPER: DATE: STAGE 946 948 950 952 953 GALPIN CROSSING TWIN HOMES Chanhassen EPIC DEVELOPMENT, LLC 2/16/2006 AREA (SQ.FT.) VOLUME (A C. FT.) 19.33 0.008327135 343.4 0.032943756 1091.63 0.076067034 2221.85 0.080850666 4821.86 TOTAL STORAGE TO 953.00 0.20 Ryan Engineering, Inc. POND WQ CALCULA TIONS BASED ON PROPOSED GRADING PLAN STORAGE REQUIRED Nurp Requirements (Dead Storage) 0.15 ACRE FEET 100 yr. Requirements (Live Storage) See Hydrocad Model NWL = 953.00 HWL = See Hydrocad Model ACRE FEET (=Dead Storage) Galpin North Pond Vol 6/15/05 Galpin Crossing Twinhomes-R1 Type /I 24-hr Water Quality Rainfal/=2.50" Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems 3/27/2006 5ubcatchment 35: Proposed to Pond Hydrograph 2 I [] Runoff ~ :t o iL Type II 24-hr Water Quality Raintall=2.50" Runoff Area=3.650 ac Runoff Volume=O.152 at Runoff Depth=O.50" Tc=15.0 min CN=73 J!! ~ o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) <1S) ~s> <3S) Ex. No. Side EX.South Side Propose( to Pond ~ '\7 ~~ Ex. So. Side Low Area Pond ~+1B~~ Drainage Diagram for Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. 3/22/2006 HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Runoff = Type /I 24-hr 2Year Rainfal/=1.15" Page 2 3/22/2006 Subcatchment 1S: Ex. No. Side 0.01 cfs @ 17.90 hrs, Volume= 0.002 af, Depth= 0.01" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2Year Rainfall=1.15" Area (ac) 3.650 CN Description 69 50-75% Grass cover, Fair, HSG B Tc Length (min) (feet) 15.0 0.005 0.005 0.004 0.004 0.003 .:!! ~ 0.003 ~ o u: 0.002 0.002 0.001 0.001 0.000 Slope Velocity Capacity Description (ft/ft) (ft/sec) (cfs) Direct Entry, Direct Subcatchment 1S: Ex. No. Side Hydrograph Type II 24-hr 2Year Rainfall=1.15" Runoff Area=3.650 ac Runoff Volume=O.002 af Runoff Depth=O.01" Tc=15.0 min CN=69 o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Runoff Type /I 24-hr 2Year Rainfal/=1.15" Page 3 3/22/2006 Subcatchment 2S: EX.South Side = 0.01 cfs @ 17.90 hrs, Volume= 0.005 af, Depth= 0.01" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2Year Rainfall=1.15" Area (a c) 7.970 CN Description 69 50-75% Grass cover, Fair, HSG B T c Length (min) (feet) 15.0 0.013 0.012 0.011 0.011 0.01 0.01 0.009 0.009 0.008 0.008 0.007 ~ 0.007 u - 0.006 ~ 0.006 ii: 0.005 0.005 0.004 0.004 0.003 0.003 0.002 0.002 0.001 0.001 0.000 o 5 Slope Velocity Capacity Description (fUft) (fUsee) (cfs) Direct Entry, Direct Subcatchment 2S: EX.South Side Hydrograph Type II 24-hr2Year Rainfall=1.15" Runoff Area=7.970ac Runoff Volume=O.005 af Runoff Depth=O.01" Tc=15.0 min CN=69 6 7 8 9 10 11 12 13 Time (hours) 14 15 16 18 19 17 1- Runoff I 20 Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Runoff = Type /I 24-hr 2Year Rainfal/=1.15" Page 4 3/22/2006 5ubcatchment 35: Proposed to Pond 0.02 cfs @ 12.56 hrs, Volume= 0.009 af, Depth= 0.03" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2Year Rainfall=1.15" Area (ac) 2.510 1.140 3.650 CN Description 61 >75% Grass cover, Good, HSG B 98 Paved parking & roofs 73 Weighted Average Tc Length (min) (feet) 15.0 0.024 0.023 0.022 0.021 0.02 0.019 0.Q18 0.017 0.016 0.015 ., 0.014 ~ 0.013 := 0.012 o ii: 0.011 0.01 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 o 5 Slope Velocity Capacity Description (fUft) (fUsec) (cfs) Direct Entry, Direct 5ubcatchment 35: Proposed to Pond Hydrograph Type II 24-hr 2Year Raintall=1.15" Runoff Area=3.650 ac Runoff Volume=O.009 at Runoff Depth=O.03" Tc=15.0 min CN=73 6 7 8 9 10 11 12 13 Time (hours) 14 15 16 17 18 19 20 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type 1/24-hr 2Year Rainfal/=1.15" Page 5 3/22/2006 Inflow Area = Inflow = Outflow = Primary = Pond 2P: Ex. So.Side Low Area 7.970 ac, Inflow Depth = 0.01" 0.01 cfs @ 17.90 hrs, Volume= 0.00 cfs @ 5.00 hrs, Volume= 0.00 cfs @ 5.00 hrs, Volume= for 2Year event 0.005 af 0.000 af, Atten= 100%, Lag= 0.0 min 0.000 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 955.02' @ 20.00 hrs Surf.Area= 8,159 sf Storage= 229 cf Plug-Flow detention time=(not calculated) Center-ot-Mass del. time= (not calculated) # 1 Invert 955.00' Elevation (feet) 955.00 956.00 958.00 960.00 # Routing 1 Primary Avail.Storage Storage Description 193,052 cf Custom Stage Data (Prismatic}-isted below Surf.Area (sq-ft) 8,000 16,466 47,655 69,043 Inc.Store ( cubic-feet) o 12,233 64,121 116,698 Cum.Store ( cubic-feet) o 12,233 76,354 193,052 Invert Outlet Devices 955.50' 27.0" x 95.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 955.00' S= 0.0053 '/' n= 0.013 Cc= 0.900 Primary OutFlow Max=O.OO cts @ 5.00 hrs HW=955.00' (Free Discharge) L1=Culvert ( Controls 0.00 cfs) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@ 7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 2Year Rainfal/=1.15" Page 6 3/22/2006 0.013 0.012 0.011 0.011 0.01 0.01 0.009 0.009 0.008 0.008 0.007 :i 0.007 ~ 0.006 ~ 0.006 u: 0.005 0.005 0.004 0.004 0.003 0.003 0.002 0.002 0.001 0.001 o 0.00 cfs o 5 Hydrograph Pond 2P: Ex. So.Side Low Area Inflow Area=7.970 ac Peak Elev=955.02' Storage=229 cf 27.0" x 95.0' Culvert 6 7 8 9 10 11 12 13 Time (hours) 14 16 15 17 18 19 20 Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@ 7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 2Year Rainfal/=1.15" Page 7 3/22/2006 Pond 3P: Pond Inflow Area = Inflow = Outflow = Primary = 11.620 ac, Inflow Depth = 0.01" 0.02 cfs @ 12.56 hrs, Volume= 0.01 cts @ 19.20 hrs, Volume= 0.01 cfs @ 19.20 hrs, Volume= for 2Year event 0.009 at 0.004 af, Atten= 52%, Lag= 398.7 min 0.004 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 953.04' @ 19.20 hrs Surf.Area= 0.112 ac Storage= 0.005 af Plug-Flow detention time=216.8 min calculated for 0.004 at (48% of inflow) Center-of-Mass del. time= 96.7 min ( 1,032.9 - 936.2 ) # 1 Invert 953.00' Avail.Storage Storage Description 0.434 af Custom Stage Data (Prismatic).Jsted below Elevation Surf.Area (feet) (acres) 953.00 0.111 954.00 0.132 956.00 0.181 # Routing Invert 1 Primary 953.00' 2 Primary 955.00' Inc.Store (acre-feet) 0.000 0.121 0.313 Cum.Store (acre-feet) 0.000 0.121 0.434 Outlet Devices 21.0" x 20.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 952.70' S= 0.0150 'I' n= 0.013 Cc= 0.900 0.5' long x 5.0' breadth Broad-Crested Rectangular Weir 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) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=0.01 cfs @ 19.20 hrs HW=953.04' (Free Discharge) t1=culvert (Barrel Controls 0.01 cfs @ 1.0 fps) 2=Broad-Crested Rectangular Weir( Controls 0.00 cfs) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type 1/24-hr 2Year Rainfal/=1.15" Page 8 3/22/2006 0.024 0.023 0.022 0.021 0.02 0.019 0.018 0.017 0.016 0.015 iil 0.014 ~ 0.013 ~ 0.012 o u: 0.011 0.01 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 o 5 Inflow Area=11.620 ac Peak Elev=953.04' Storage=O.005 af 6 7 8 9 10 11 12 13 Time (hours) 19 Pond 3P: Pond Hydrograph 14 15 16 17 18 20 Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 10 Year Rainfal/=4.20" Page 9 3/22/2006 Subcatchment 15: Ex. No. Side Runoff = 6.32 cfs @ 12.08 hrs, Volume= 0.383 af, Depth= 1.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10 Year Rainfall=4.20" Area (a c) CN Description 3.650 69 50-75% Grass cover, Fair, HSG B Tc Length (min) (feet) 15.0 Slope Velocity Capacity Description (ftIft) (ftIsec) (cfs) Direct Entry, Direct Subcatchment 15: Ex. No. Side Hydrograph 7 6 Type II 24-hr 10 Year Rainfall=4.20" Runoff Area=3.650 ac Runoff Volume=0.383 af Runoff Depth=1.26" Tc=15.0 min CN=69 5 ~ 4 ~ ~ o u: 3 2 o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 10 Year Rainfal/=4.20" Page 1 0 3/22/2006 Subcatchment 2S: Ex.South Side Runoff = 13.79 cfs @ 12.08 hrs, Volume= 0.836 af, Depth= 1.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10 Year Rainfall=4.20" Area (ac) CN Description 7.970 69 50-75% Grass cover, Fair, HSG B Tc Length (min) (feet) 15.0 Slope Velocity Capacity Description (fUft) (fUsee) (cfs) Direct Entry, Direct Subcatchment 2S: Ex.South Side Hydrograph 15 14 13 12 11 10 iil 9 ~ 8 ~ .Q 7 Ii. Type II 24..hr 10 Year Rainfall=4.20" Runoff Area=7.970.ac RunoffVolume=0.836 af Runoff Depth=1.26" Tc=15.0 min CN=69 6 5 4 3 2 o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff' Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Runoff = Type /I 24-hr 10 Year Rainfal/=4.20" Page 11 3/22/2006 5ubcatchment 35: Proposed to Pond 7.72 cfs @ 12.08 hrs, Volume= 0.462 af, Depth= 1.52" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10 Year Rainfall=4.20" Area (ac) 2.510 1.140 3.650 T c Length (min) (feet) 15.0 8 7 6 5 J!! ~ ~ 4 ii: 3 2 o 5 CN Description 61 >75% Grass cover, Good, HSG B 98 Paved parking & roofs 73 Weighted Average Slope Velocity Capacity Description (ftIft) (ftIsec) (cfs) Direct Entry, Direct 5ubcatchment 35: Proposed to Pond Hydrograph Type II 24-hr 10 Year Rainfall=4.20" Runoff Area=3.650 ac RunoffVolume=O.462 af Runoff Depth=1.52" Tc=15.0 min CN=73 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@ 7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 10 Year Rainfal/=4.20" Page 12 3/22/2006 Inflow Area = Inflow = Outflow = Primary = Pond 2P: Ex. So.Side Low Area 7.970 ac, Inflow Depth = 1.26" 13.79 cfs @ 12.08 hrs, Volume= 2.03 cfs @ 12.65 hrs, Volume= 2.03 cfs @ 12.65 hrs, Volume= for 10 Year event 0.836 af 0.620 af, Atten= 85%, Lag= 34.1 min 0.620 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 956.14'@ 12.65 hrs Surf.Area= 18,646 sf Storage= 16,715 cf Plug-Flow detention time= 141.9 min calculated for 0.620 af (74% of inflow) Center-of-Mass del. time= 74.6 min ( 888.8 - 814.2 ) # 1 Invert 955.00' Elevation (feet) 955.00 956.00 958.00 960.00 # Routing 1 Primary Avail.Storage Storage Description 193,052 cf Custom Stage Data (Prismatic}...isted below Surf.Area (sq-ft) 8,000 16,466 47,655 69,043 Inc.Store ( cubic-feet) o 12,233 64,121 116,698 Cum.Store ( cubic-feet) o 12,233 76,354 193,052 Invert Outlet Devices 955.50' 27.0" x 95.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 955.00' S= 0.0053 '/' n= 0.013 Cc= 0.900 Primary OutFlow Max=2.03 cfs @ 12.65 hrs HW=956.14' (Free Discharge) L1=Culvert (Barrel Controls 2.03 cfs @ 3.3 fps) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type" 24-hr 10 Year Rainfal/=4.20" Page 13 3/22/2006 Pond 2P: Ex. So.Side Low Area Hydrograph 15 14 13 12 11 10 :i 9 ~ 8 ~ 0 7 u: 6 5 4 3 2 Inflow Area=7.970 ac m PeakElev=956.14' Storage= 16, 715"cf 27.0"x95.0'Culvert o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 10 Year Rainfal/=4.20" Page 14 3/22/2006 Pond 3P: Pond Inflow Area = Inflow = Outflow = Primary = 11.620 ac, Inflow Depth = 1.12" 7.97 cfs @ 12.10 hrs, Volume= 4.96 cfs @ 12.28 hrs, Volume= 4.96 cfs @ 12.28 hrs, Volume= for 10 Year event 1.082 af 1.044 af, Atten= 38%, Lag= 10.7 min 1.044 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 954.09' @ 12.28 hrs Surf.Area= 0.134 ac Storage= 0.135 af Plug-Flow detention time=29.2 min calculated for 1.044 af (97% of inflow) Center-of-Mass del. time= 17.7 min ( 871.3 - 853.6 ) # 1 Invert 953.00' Avail.Storage Storage Description 0.434 af Custom Stage Data (Prismatic)...isted below Elevation Surf.Area (feet) (acres) 953.00 0.111 954.00 0.132 956.00 0.181 # Routing Invert 1 Primary 953.00' 2 Primary 955.00' Inc.Store (acre-feet) 0.000 0.121 0.313 Cum.Store (acre-feet) 0.000 0.121 0.434 Outlet Devices 21.0" x 20.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 952.70' S= 0.0150 'I' n= 0.013 Cc= 0.900 0.5' long x 5.0' breadth Broad-Crested Rectangular Weir 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) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=4.94 cfs @ 12.28 hrs HW=954.09' (Free Discharge) t1=Culvert (Barrel Controls 4.94 cfs @ 4.5 fps) 2=Broad-Crested Rectangular Weir( Controls 0.00 cfs) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 10 Year Rainfal/=4.20" Page 15 3/22/2006 Pond 3P: Pond Hydrograph 8 7 Inflow Area=11.620 ac Peak Elev=954.09' Storage=O.135af 6 ~ 5 ~ ~ ~ 4 3 2 o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 16 3/22/2006 Subcatchment 1S: Ex. No. Side Runoff = 12.64 cfs @ 12.08 hrs, Volume= 0.753 af, Depth= 2.48" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100 year Rainfall=6.00" Area (ac) CN Description 3.650 69 50-75% Grass cover, Fair, HSG B Tc Length (min) (feet) 15.0 Slope Velocity Capacity Description (ftIft) (ftIsec) (cfs) Direct Entry, Direct Subcatchment 1S: Ex. No. Side Hydrograph 14 13 12 11 10 9 .l!! 8 ~ ~ 7 0 u: 6 5 4 3 2 TypeU 24;.hr 100 year Rainfall==6.00" Runoff Area=3.650 ac RunoffVolume=0.753. af Runoff Depth=2.4S" Tc=15.0 min CN=69 o 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@ 7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 17 3/22/2006 Subcatchment 2S: EX.South Side Runoff = 27.59 cfs @ 12.08 hrs, Volume= 1.645 af, Depth= 2.48" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100 year Rainfall=6.00" Area (ac) CN Description 7.970 69 50-75% Grass cover, Fair, HSG B T c Length (min) (feet) 15.0 Slope Velocity Capacity Description (ft/ft) (ft/sec) (cfs) Direct Entry, Direct Subcatchment 2S: EX.South Side Hydrograph 30 28 26 24 22 20 _ 18 .. ~ 16 ~ ..2 14 u. 12 10 8 6 4 2 0 5 6 7 Type II 24..hr 100 year Rainfall=6.00" RunoffArea=7.970 ac RunoffVolume=1.645 af Runoff Depth=2.4S" Tc=15.0 min CN=69 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems Type II 24-hr 100 year Rainfal/=6.00" Page 18 3/22/2006 5ubcatchment 35: Proposed to Pond Runoff = 14.47 cfs @ 12.07 hrs, Volume= 0.863 af, Depth= 2.84" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100 year Rainfall=6.00" Area (a c) 2.510 1.140 3.650 CN Description 61 >75% Grass cover, Good, HSG B 98 Paved parking & roofs 73 Weighted Average Tc Length (min) (feet) 15.0 Slope Velocity Capacity Description (fUn) (fUsee) (cfs) Direct Entry, Direct 5ubcatchment 35: Proposed to Pond Hydrograph 16 15 14 13 12 11 10 .!! 9 ~ ~ 8 0 u: 7 6 5 4 3 2 0 5 6 7 Type II 24-hr 100 year Rainfall=6.00" Runoff Area=3.650 ac RunoffVolume=0.863 af Runoff Depth=2.84" Tc=15.0 min CN=73 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 1- Runoff~ Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@ 7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 19 3/22/2006 Inflow Area = Inflow = Outflow = Primary = Pond 2P: Ex. so.side Low Area 7.970 ac, Inflow Depth = 2.48" 27.59 cfs @ 12.08 hrs, Volume= 5.85 cfs @ 12.45 hrs, Volume= 5.85 cfs @ 12.45 hrs, Volume= for 100 year event 1.645 af 1.409 af, Atten= 79%, Lag= 22.6 min 1.409 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 956.64' @ 12.45 hrs Surf.Area= 26,392 sf Storage= 32,640 cf Plug-Flow detention time= 112.4 min calculated for 1.404 af (85% of inflow) Center-of-Mass del. time= 68.7 min ( 868.9 - 800.2 ) # 1 Invert 955.00' Elevation {feet} 955.00 956.00 958.00 960.00 # Routing 1 Primary Avail.Storage Storage Description 193,052 cf Custom Stage Data (Prismatic)..isted below Surf.Area { sq-ft} 8,000 16,466 47,655 69,043 Inc.Store { cubic-feet} o 12,233 64,121 116,698 Cum.Store {cubic-feet} o 12,233 76,354 193,052 Invert Outlet Devices 955.50' 27.0" x 95.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 955.00' S= 0.0053 'I' n= 0.013 Cc= 0.900 Primary OutFlow Max=5.85 cfs @ 12.45 hrs HW=956.64' (Free Discharge) 't.-1=Culvert (Barrel Controls 5.85 cfs @ 4.2 fps) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 20 3/22/2006 30 28 26 24 22 20 ~ 18 .1'1 ~ 16 :c ~ 14 u. 12 10 8 6 4 2 0 5 6 Pond 2P: Ex. So.Side Low Area Hydrograph Inflow Area=7.970 ac PeakElev=956.64' St()tage:::32,640~f 27.0" x 95.0' Culvert 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 21 3/22/2006 Pond 3P: Pond Inflow Area = Inflow = Outflow = Primary = 11.620 ac, Inflow Depth = 2.35" 17.27 cfs @ 12.09 hrs, Volume= 11.30 cfs @ 12.28 hrs, Volume= 11.30 cfs @ 12.28 hrs, Volume= for 100 year event 2.272 af 2.223 af, Atten= 35%, Lag= 11.0 min 2.223 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 954.90' @ 12.28 hrs Surf.Area= 0.154 ac Storage= 0.263 af Plug-Flow detention time=22.6 min calculated for 2.216 af (98% of inflow) Center-of-Mass det. time= 15.4 min ( 855.5 - 840.1 ) # 1 Invert 953.00' Avail.StoraQe StoraQe Description 0.434 af Custom Stage Data (Prismatic}.Jsted below Elevation Surf.Area (feet) (acres) 953.00 0.111 954.00 0.132 956.00 0.181 # Routing Invert 1 Primary 953.00' 2 Primary 955.00' Inc.Store (acre-feet) 0.000 0.121 0.313 Cum.Store (acre-feet) 0.000 0.121 0.434 Outlet Devices 21.0" x 20.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 952.70' S= 0.0150 'I' n= 0.013 Cc= 0.900 0.5' long x 5.0' breadth Broad-Crested Rectangular Weir 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) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=11.28 cfs @ 12.28 hrs HW=954.90' (Free Discharge) t1=culvert (Barrel Controls 11.28 cfs @ 5.4 fps) 2=Broad-Crested Rectangular Weir( Controls 0.00 cfs) Galpin Crossing Twinhomes-R1 Prepared by RYAN ENGINEERING, INC. HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems Type /I 24-hr 100 year Rainfal/=6.00" Page 22 3/22/2006 Pond 3P: Pond Hydrograph 19 18 17 16 15 14 13 12 ~ 11 .2. 10 ~ 9 0 ii: 8 7 6 5 4 3 2 1 0 5 6 Inflow Area=11.620 ac PeakElev==954.90' Storage=O.263af 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours)