Preliminary Stormwater Management Summary 3-17-06
<.
Preliminary Stormwater Management Summary
for
Galpin Crossing Twinhomes
Chanhassen, MN
3/17/06
CliY ~~g~:V~~SSEN
Existing Drainage Conditions:
MAR 1 7 2006
CHANHASSO"
eN PLANNING OEPr
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 ofthe existing 27" culvert. These
calculations were generated using HydroCad.
Drainage Acres 100 Yr 10Yr 2 Yr Peak
Area Peak Q (cfs) Peak Q Q (cfs)
(cfs)
Parcel A 4.00 11.17 4.38 0.00
Parcel B (27" 7.97 7.20 3.58 0.01
culvert)
Total 11.97 28.37 7.86 0.01
Proposed Drainage:
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 were
based on Rainfall Frequency Atlas of the Midwest, 1992. See attached Hydro Cad calculations
for hydro graphs. The table below lists the resulting flow rates to compare between existing and
proposed conditions. For all required storm events, the proposed flow rates do not exceed the
existing conditions.
Page 1 of2
Preliminary Stormwater Management Summary
for
Galpin Crossing Twinhomes
Chanhassen, MN
3/17/06
Existing Proposed Existing Proposed Existing Proposed
100 Yr 100 Yr Q 10Yr 10 Yr Q 2Yr Q 2YrQ
Q (efs) (cfs) Q (efs) (efs) (efs) (efs)
Parcel A 11.17 8.67 4.68 2.46 0.00 0.00
Parcel B 7.20 7.20 4.52 4.52 0.01 0.01
(27"
Culvert)
Total 28.37 15.87 9.20 6.98 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:
GALPIN CROSSING TWIN HOMES
Chanhassen
EPIC DEVELOPMENT, LLC
2/16/2006
POND WQ CALCULA TIONS
BASED ON PROPOSED GRADING PLAN
STAGE AREA (SQ.FT.) VOLUME (A C. FT.)
948 217
0.025964187
950 914
0.065059688 STORAGE REQUIRED
952 1920 Nurp Requirements
0.06976584 (Dead Storage) 0.15 ACRE FEET
953 4158
100 yr. Requirements
(Live Storage) See Hydrocad Model
NWL = 953.00
HWL = See Hydrocad Model
TOTAL STORAGE TO 953.00
0.16
ACRE FEET (=Dead Storage)
Ryan Engineering, Inc.
Galpin North Pond Vol
6/15/05
Galpin Crossing Twinhomes Type /I 24-hr Water Quality Rainfal/=2.50"
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems 3/17/2006
5ubcatchment 35: Proposed to Pond
Hydrograph
I 0 Runoff~
2.34 cfs
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
2
J'!
~
~
o
Ii:
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
(18)
@
(3S)
Ex. No. Side
EX.SOL th Side
Propose< to Pond
M
~M
Ex. SO.Side Low Area
Pond
~UbC1 B ~ ~
Drainage Diagram for Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC. 3/17/2006
HydroCAOO 7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 2Year Rainfal/=1.15"
Page 2
3/17/2006
Runoff =
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 (a c)
3.650
CN Description
69 50-75% Grass cover, Fair, HSG B
Tc Length
(min) (feet)
15.0
Slope Velocity Capacity Description
(ftlft) (ftlsec) (cfs)
0.005
0.005
0.004
0.004
0.003
Ul
~ 0.003
~
o
ii: 0.002
0.002
0.001
0.001
0.000
Direct Entry, Direct
Subcatchment 1S: Ex. No. Side
Hydrograph
Type II 24-hr 2Year
Raihfall=1.1S"
Runoff Area=3.6S0 ac
Runoff Volume=O.002 af
Runoff Depth=O.01"
Tc=1S.0 min
CN=69
o
5
8
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
7
1- Runoff~
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 2Year Rainfal/=1.15"
Page 3
3/17/2006
Runoff
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 I( 24-hr 2Year Rainfall=1.15"
Area (a c)
7.970
CN Description
69 50-75% Grass cover, Fair, HSG B
Tc 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
u: 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
(ftIft) (ftIsec) ( cfs)
Direct Entry, Direct
Subcatchment 2S: EX.South Side
Hydrograph
Type II 24-hr 2Year
Rainfall=1.15"
Runoff Area=7.970 ac
Runoff Volume=0.005 af
Runoff Depth=0.01"
Tc=15.0 min
CN=69
6
16
17
18
19
7
8
9 10 11 12 13
Time (hours)
14
15
1- Runoff~
20
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 2Year Rainfal/=1.15"
Page 4
3/17/2006
Runoff
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 (a c)
2.510
1.140
3.650
CN Description
61 >75% Grass cover, Good, HSG B
98 Paved parking & roofs
73 Weighted Average
T c Length
(min) (feet)
15.0
Slope Velocity Capacity Description
(ft/ft) (ft/sec) ( cfs)
0.024
0.023
0.022
0.021
0.02
0.019
0.018
0.017
0.016
0.015
., 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
Direct Entry, Direct
5ubcatchment 35: Proposed to Pond
Hydrograph
Type II 24..hr 2Year
Rainfall=1.1S"
Runoff Area=3.6S0 ac
Runoff Volume=O.009 af
Runoff Depth=O.03"
Tc=1S.0 min
CN=73
6
16
19
17
18
7
8
9 10 11 12 13
Time (hours)
14
15
1- Runoff~
20
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 2Year Rainfal/=1.15"
Page 5
3/17/2006
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=
0.01 cfs @ 18.39 hrs, Volume=
0.01 cfs @ 18.39 hrs, Volume=
for 2Year event
0.005 af
0.005 af, Atten= 1 %, Lag= 29.0 min
0.005 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 955.20' @ 18.39 hrs Surf.Area= 47 sf Storage= 19 cf
Plug-Flow detention time=26.8 min calculated for 0.005 af (92% of inflow)
Center-of-Mass del. time= 13.2 min ( 1,036.2 - 1,023.0 )
#
1
Invert
955.20'
Elevation
(feet)
955.20
956.00
958.00
960.00
# Routing
1 Primary
Avail.Storage Storage Description
187,404 cf Custom Stage Data (Prismatic~isted below
Surf.Area
( sq-ft)
o
16,466
47,655
69,043
Inc. Store
(cubic-feet)
o
6,586
64,120
116,697
Cum.Store
(cubic-feet)
o
6,586
70,707
187,404
Invert Outlet Devices
954.90' 27.0" x 95.0'long Culvert RCP, end-section conforming to fill, Ke= 0.500
Outlet Invert= 954.90' S= 0.0000 'I' n= 0.013 Cc= 0.900
Primary OutFlow Max=0.17 cfs @ 18.39 hrs HW=955.20' (Free Discharge)
't..-1=Culvert (Barrel Controls 0.17 cfs @ 0.8 fps)
Galpin Crossing Twinhomes
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
3/17/2006
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
u:: 0.005
0.005
0.004
0.004
0.003
0.003
0.002
0.002
0.001
0.001
0.000
o
5
Pond 2P: Ex. so.side Low Area
Hydrograph
Inflow Area=7.970 ac
Peak Elev=955.20'
Storage=19 cf
27.0" x 95.0' Culvert
6
10 11 12 13
Time (hours)
18
19
14
15
16
17
7
8
9
20
Galpin Crossing Twinhomes
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
3/17/2006
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 3P: Pond
11.620 ac, Inflow Depth = 0.01"
0.02 cfs @ 15.59 hrs, Volume=
0.01 cfs @ 20.00 hrs, Volume=
0.01 cfs @ 20.00 hrs, Volume=
for 2Year event
0.014 af
0.002 af, Atten= 78%, Lag= 264.5 min
0.002 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 953.03'@ 20.00 hrs Surf.Area= 0.672 ac Storage= 0.012 af
Plug-Flow detention time=282.7 min calculated for 0.002 af (12% of inflow)
Center-of-Mass del. time= 74.6 min ( 1,045.2 - 970.6 )
#
1
Invert
953.00'
Elevation
(feet)
953.00
954.00
956.00
# Routing
1 Primary
Avail.Storage Storage Description
0.685 af Custom Stage Data (Prismatic}-isted below
Surf.Area
(acres)
0.690
0.120
0.160
Inc.Store
(acre-feet)
0.000
0.405
0.280
Cum.Store
(acre-feet)
0.000
0.405
0.685
Invert Outlet Devices
953.00' 21.0" x 20.0'lon9 Culvert RCP, end-section conforming to fill, Ke= 0.500
Outlet Invert= 952.70' S= 0.0150 'I' n= 0.013 Cc= 0.900
Primary OutFlow Max=0.01 cfs @ 20.00 hrs HW=953.03' (Free Discharge)
't..-1=Culvert (Barrel Controls 0.01 cfs @ 0.8 fps)
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 2Year Rainfal/=1.15"
Page 8
3/17/2006
0.026
0.025
0.024
0.023
0.022
0.021
0.02
0.019
0.018
0.017
0.016
~ 0.015
~ 0.014
~ 0.013
~ 0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
o
5
Pond 3P: Pond
Hydrograph
Inflow Area=11.620 ac
Peak Elev=953.03'
Storage==O.012 af
21.0" x 20.0' Culvert
6
18
20
19
8
9
10 11 12 13
Time (hours)
14
15
16
17
7
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 9
3/17/2006
Subcatchment 15: Ex. No. Side
Runoff =
4.68 cfs @ 12.09 hrs, Volume=
0.289 af, Depth= 0.95"
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=3.68"
Type II 24-hr 10 Year
Rainfall=3.68"
Runoff Area=3.6S0 ac
RunoffVolume=0.289 af
Runoff Depth=0.9S"
Tc=1S.0min
CN=69
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
(ft/ft) (ft/sec) ( cfs)
Direct Entry, Direct
Subcatchment 15: Ex. No. Side
Hydrograph
5
4
~ 3
~
~
o
u:
2
o
5
8
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
7
1- Runoff~
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@ 7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 1 0
3/17/2006
Subcatchment 2S: Ex.South Side
Runoff =
10.22 cfs @ 12.09 hrs, Volume=
0.631 af, Depth= 0.95"
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=3.68"
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) (fUse c) (cfs)
Direct Entry, Direct
Subcatchment 2S: Ex.South Side
Hydrograph
11 1- Runoff~
10 Type II 24-hr 10 Year
9
Rainfall=3.68"
8 Runoff Area=7.970 ac
7 RunoffVolume=0.631 af
~
~ 6
:= Runoff Depth=0.95"
0
u: 5
Tc=15.0 min
4
CN=69
3
2
o
5
9
10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
7
8
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 11
3/17/2006
Runoff =
5ubcatchment 35: Proposed to Pond
5.93 cfs @ 12.08 hrs, Volume=
0.357 af, Depth= 1.18"
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=3.68"
Area (a c)
2.510
1.140
3.650
Tc Length
(min) (feet)
15.0
6
5
4
~
.!:!.
~
~ 3
2
o
5
CN Description
61 >75% Grass cover, Good, HSG B
98 Paved parking & roofs
73 Weighted Average
Slope Velocity Capacity Description
(fUft) (fUse c) (cfs)
Direct Entry, Direct
5ubcatchment 35: Proposed to Pond
Hydrograph
Type II 24-hr 10 Year
Rainfall=3.6S"
Runoff Area=3.650 ac
Runoff Volume=0.357 af
Runoff Depth=1.1S"
Tc=15.0 min
CN=73
6
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
7
8
1- Runoff~
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@ 7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 12
3/17/2006
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 2P: Ex. So.Side Low Area
7.970 ac, Inflow Depth = 0.95"
10.22 cfs @ 12.09 hrs, Volume=
3.58 cfs @ 12.33 hrs, Volume=
3.58 cfs @ 12.33 hrs, Volume=
for 10 Year event
0.631 af
0.616 af, Atten= 65%, Lag= 14.8 min
0.616 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 956.05'@ 12.33 hrs Surf.Area= 17,178 sf Storage= 8,051 cf
Plug-Flow detention time=40.9 min calculated for 0.616 af (98% of inflow)
Center-of-Mass det. time= 32.4 min ( 852.6 - 820.2 )
#
1
Invert
955.20'
Elevation
(feet)
955.20
956.00
958.00
960.00
# Routing
1 Primary
Avail.Storage Storage Description
187,404 cf Custom Stage Data {Prismatic}Jsted below
Surf.Area
(sq-ft)
o
16,466
47,655
69,043
Inc. Store
( cubic-feet)
o
6,586
64,120
116,697
Cum.Store
( cubic-feet)
o
6,586
70,707
187,404
Invert Outlet Devices
954.90' 27.0" x 95.0'long Culvert RCP, end-section conforming to fill, Ke= 0.500
Outlet Invert= 954.90' S= 0.0000 'I' n= 0.013 Cc= 0.900
Primary OutFlow Max=3.58 cfs @ 12.33 hrs HW=956.05' (Free Discharge)
L1=Culvert (Barrel Controls 3.58 cfs @ 2.6 fps)
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 13
3/17/2006
Pond 2P: Ex. So.Side Low Area
Hydrograph
11
10
Inflow Area=7.970 ac
Peak Elev=956.05'
Storage=8,051 cf
27.0" x 95.0' Culvert
9
8
7
J!!
~ 6
~
o
u: 5
4
3
2
o
5
7
8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 14
3/17/2006
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 3P: Pond
11.620 ac, Inflow Depth = 1.01"
8.44 cfs @ 12.13 hrs, Volume=
2.85 cfs @ 12.96 hrs, Volume=
2.85 cfs @ 12.96 hrs, Volume=
for 10 Year event
0.974 af
0.852 af, Atten= 66%, Lag= 50.1 min
0.852 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 953.78' @ 12.96 hrs Surf.Area= 0.246 ac Storage= 0.316 af
Plug-Flow detention time=96.1 min calculated for 0.852 af (88% of inflow)
Center-of-Mass del. time= 57.6 min ( 895.2 - 837.5 )
#
1
Invert
953.00'
Elevation
(feet)
953.00
954.00
956.00
# Routing
1 Primary
Avail.Storage Storage Description
0.685 af Custom Stage Data (Prismatic)Jsted below
Surf.Area
(acres)
0.690
0.120
0.160
Cum.Store
(acre-feet)
0.000
0.405
0.685
Inc.Store
(acre-feet)
0.000
0.405
0.280
Invert Outlet Devices
953.00' 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
Primary OutFlow Max=2.85 cfs @ 12.96 hrs HW=953.78' (Free Discharge)
"t..-1=Culvert (Barrel Controls 2.85 cfs @ 4.1 fps)
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 10 Year Rainfal/=3.68"
Page 15
3/17/2006
Pond 3P: Pond
Hydrograph
9
8
7
6
.!!
~ 5
~
0
u:: 4
3
2
Inflow Area=11.620ac
Peak Elev=953~ 78'
Storage=O.316 af
21.0" x 20.0'Culvert
o
5
8
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
7
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 16
3/17/2006
Subcatchment 1 S: Ex. No. Side
Runoff =
11.60 cfs @ 12.08 hrs, Volume=
0.692 af, Depth= 2.28"
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=5.72"
Area (a c) CN Description
3.650 69 50-75% Grass cover, Fair, HSG B
T c Length
(min) (feet)
15.0
Slope Velocity Capacity Description
(ftIft) (ftIsec) (cfs)
Direct Entry, Direct
Subcatchment 1S: Ex. No. Side
Hydrograph
12
11
Type II 24-hr 100 Year
Rainfall=5.72"
Runoff Area=3.650 ac
RunoffVolume=0.692 af
Runoff Depth=2.2S"
Tc=15.0 min
CN=69
10
9
8
'"
~ 7
~ 6
ii:
5
4
3
2
o
5
9
10 11 12 13 14 15 16 17 18 19 20
Time (hours)
6
7
8
1- Runoff~
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 17
3/17/2006
Subcatchment 2S: Ex.South Side
Runoff =
25.34 cfs @ 12.08 hrs, Volume=
1.511 af, Depth= 2.28"
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=5.72"
Area (ac) CN Description
7.970 69 50-75% Grass cover, Fair, HSG B
Tc Length
(min) (feet)
15.0
Slope Velocity Capacity Description
(ftfft) (fUsee) (cfs)
Direct Entry, Direct
Subcatchment 2S: Ex.South Side
Hydrograph
28
26
24
22
20
18
~ 16
~
~ 14
0
i:i: 12
10
8
6
4
2
0
5 6 7
Type II 24-hr100 Year
Rainfall=5.72"
Runoff Area=7.970 ac
RunoffVolume=1.511. af
Runoff Depth=2.28"
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
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 18
3/17/2006
Runoff =
5ubcatchment 35: Proposed to Pond
13.39 cfs @ 12.07 hrs, Volume=
0.798 af, Depth= 2.62"
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=5.72"
Area (a c)
2.510
1.140
3.650
Tc Length
(min) (feet)
15.0
14
13
12
11
10
9
..
~ 8
~ 7
u:
6
5
4
3
2
o
5
CN Description
61 >75% Grass cover, Good, HSG B
98 Paved parking & roofs
73 Weighted Average
Slope Velocity Capacity Description
(fUft) (fUsee) (efs)
Direct Entry, Direct
5ubcatchment 35: Proposed to Pond
Hydrograph
Type II 24-hr 100 Year
Rainfall=5.72"
Runoff Area=3.650 ac
.. RunoffVolume=0.798 af
Runoff Depth=2.62"
Tc=15.0 min
CN==73
6
9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
7
8
1- RunOff~
-
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 19
3/17/2006
I nflow Area =
Inflow =
Outflow =
Primary =
Pond 2P: Ex. So.Side Low Area
7.970 ac, Inflow Depth = 2.28"
25.34 cfs @ 12.08 hrs, Volume=
7.20 cfs @ 12.36 hrs, Volume=
7.20 cfs @ 12.36 hrs, Volume=
for 100 Year event
1.511 af
1.475 af, Atten= 72%, Lag= 17.3 min
1.475 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 956.53' @ 12.36 hrs Surf.Area= 24,674 sf Storage= 23,462 cf
Plug-Flow detention time=46.4 min calculated for 1.470 af (97% of inflow)
Center-of-Mass det. time= 37.3 min ( 839.2 - 801.9 )
#
1
Invert
955.20'
Elevation
(feet)
955.20
956.00
958.00
960.00
# Routing
1 Primary
Avail.Storage Storage Description
187,404 cf Custom Stage Data (Prismatic).Jsted below
Surf.Area
(sq-ft)
o
16,466
47,655
69,043
Cum.Store
( cubic-feet)
o
6,586
70,707
187,404
Inc. Store
(cubic-feet)
o
6,586
64,120
116,697
Invert Outlet Devices
954.90' 27.0" x 95.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500
Outlet Invert= 954.90' S= 0.0000 'I' n= 0.013 Cc= 0.900
Primary OutFlow Max=7.19 cfs@ 12.36 hrs HW=956.53' (Free Discharge)
L1=Culvert (Barrel Controls 7.19 cfs @ 3.3 fps)
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sin 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 20
3/17/2006
28
26
24
22
20
18
:f 16
~
~ 14
0
u: 12
10
8
6
4
2
0
5 6 7
Pond 2P: Ex. So.Side Low Area
Hydrograph
Inflow Area=7.970 ac
PeakElev=956.53'
Storage=23,462cf
27.0" X 95.0' Culvert
8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
..
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAO@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 21
3/17/2006
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 3P: Pond
11.620 ac, Inflow Depth = 2.35"
18.42 cfs @ 12.09 hrs, Volume=
9.85 cfs @ 12.46 hrs, Volume=
9.85 cfs @ 12.46 hrs, Volume=
for 100 Year event
2.273 af
2.108 af, Atten= 47%, Lag= 21.8 min
2.108 af
Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Peak Elev= 954.71' @ 12.46 hrs Surf.Area= 0.134 ac Storage= 0.505 af
Plug-Flow detention time=63.7 min calculated for 2.101 af (92% of inflow)
Center-of-Mass del. time=40.0 min ( 863.7 - 823.7 )
#
1
Invert
953.00'
Elevation
(feet)
953.00
954.00
956.00
# Routing
1 Primary
Avail.Storage Storage Description
0.685 af Custom Stage Data (Prismatic)..isted below
Surf.Area
(acres)
0.690
0.120
0.160
Inc.Store
(acre-feet)
0.000
0.405
0.280
Cum.Store
(acre-feet)
0.000
0.405
0.685
Invert Outlet Devices
953.00' 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
Primary OutFlow Max=9.84 cfs@ 12.46 hrs HW=954.71' (Free Discharge)
L1=Culvert (Barrel Controls 9.84 cfs @ 5.2 fps)
Galpin Crossing Twinhomes
Prepared by RYAN ENGINEERING, INC.
HydroCAD@7.00 sIn 001971 @ 1986-2003 Applied Microcomputer Systems
Type /I 24-hr 100 Year Rainfal/=5.72"
Page 22
3/17/2006
Pond 3P: Pond
Hydrograph
20
19
18
17
16
15
14
13
~ 12
..
~ 11
~ 10
o
ii: 9
8
7
6
5
4
3
2
1
o
5
InflowArea=11.620ac
Peak Elev=954.71 ,
Storage=O.505.af
21.0" x 20.0' Culvert
6
8
9
10 11 12 13 14 15 16 17 18 19 20
Time (hours)
7
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