Hydrology Calculations 1-4-06
HYDROLOGY
CALCULATIONS
Gateway North
Chanhassen, MN
Prepared for:
Chanhassen Gateway Place, LLC
P.O. Box 727
Albany, Minnesota 56307
Prepared by:
Westwood Professional Services, Inc.
3701 1ih Street North, Suite 206
St. Cloud, MN 56303
Phone 320-253-9495, Fax 320-253-8737
Revised January 4, 2006
Project # 20055198.00
CITY OF CHANHASSEN
RECEIVED
JAN 0 S 2006
CHANHASSEN PLANNING DEPT
SUMMARY
Table of Contents
1. Hydrology Report and Summary
Introduction 3
Methods 3
Site Conditions 3
Rate Control 4
Water Quality 4
Summary 4
2. Appendix A - Existing 2-YR Hydrology Calculations
3. Appendix B - Proposed 2-YR Hydrology Calculations
4. Appendix C - Existing 10-YR Hydrology Calculations
5. Appendix D - Proposed 10-YR Hydrology Calculations
6. Appendix E - Existing 100-YR Hydrology Calculations
7. Appendix F- Proposed 100-YR Hydrology Calculations
8. Appendix G- Water Quality Calculations
9. Appendix H - Existing Drainage Area Maps
10. Appendix I - Proposed Drainage Area Maps
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
SUMMARY
Introduction:
Gateway North is a proposed multi-family/apartment development located in Chanhassen at the
southeast quadrant of the intersection of State Hwy. No.101 and Lake Susan Drive. Storm water
management for the site must comply with the City of Chanhassen storm water requirements as
well as the requirements of the National Pollutant Discharge Elimination System (NPDES)
program. Based on city requirements the proposed runoff from the site is limited to that of
existing conditions. Water Quality is based on the NPDES/MPCA requirements for the
Application for General Storm water Permit for Construction Activity.
To accomplish this storm water management, a storm water system using a Pond to treat and
store the storm water before discharge is proposed. This report documents the criteria and
assumptions associated with the water quality and rate control calculations for the site. All
applicable drainage maps and calculations have been included in the appendices for your
convenience.
Methods:
The SCS synthetic unit hydrograph method incorporated into the software program Hydrocad
Version 7.00, was used for calculating the runoff generated from the existing and proposed site
for the 2 year, 10 year, and 100 year 24 hour storm events and the 100 year 10 day storm event.
Based on the U.S. Weather Bureau Technical Paper 40, the 24 hour rain events are equivalent to
2.80 inches, 4.20 inches, and 6.00 inches. Water Quality is based on MPCA requirments.
Site Conditions:
Soils in the vicinity were classified in the Hydrological group B.
Curve Number's (CN's) used in the analysis of the site were as follows: 98 -Impervious (paved,
parking and roofs), 61 - (>75% Grass Cover, Good, HSG B).
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
SUMMARY
Rate Control:
The following table (Table 1) is a summary of the existing and proposed condition's peak flow
rates for the site for the 2-year, 10-year, and 1 DO-year 24-hour storm events. The existing and
proposed Hydrocad Calculations and the corresponding drainage maps are included in
Appendices for your convenience.
Table 1: Rate Control
Existing Existing Existing Proposed Proposed Proposed
2-yr 10-yr 100-yr 2-yr 10-yr 100-yr
24 hr 24 hr 24 hr 24 hr 24 hr 24 hr
Flow Flow Flow Flow Flow Flow
(CFS) (CFS) (CFS) (CFS) (CFS) (CFS)
4.80 12.99 25.55 4.47 10.36 16.71
Water Qualitv Calculations:
Appendix I is a summary of the MPCA requirements and the pertaining calculations.
Summary:
Rate control and Water quality can be provided for the site. It meets all the requirements of
the City of Chanhassen and the NPDES for storm water management.
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
SUMMARY
Appendix A
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
Drainage to North
Drainage to East
Drainage to South
~Ubc1 B ~ ~
Drainage Diagram for 20055198EXISTING
Prepared by Westwood Professional Services, Inc. 1/4/2006
HydroCAD@7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
20055198EXISTING
Prepared by Westwood Professional Services, Inc.
HydroCAO@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type" 24-hr 2-yr Rainfal/=2.80"
Page 2
1/4/2006
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
Subcatchment 10S: Drainage to North Runoff Area=1.007 ac Runoff Depth>0.56"
Flow Length=150' Tc=6.8 min CN=69 Runoff=0.88 cfs 0.047 af
Subcatchment 20S: Drainage to South Runoff Area=3.411 ac Runoff Depth>0.56"
Flow Length=335' Tc=9.7 min CN=69 Runoff=2.60 cfs 0.160 af
Subcatchment 30S: Drainage to East Runoff Area=1.274 ac Runoff Depth>0.57"
Flow Length=115' Tc=2.9 min CN=69 Runoff=1.32 cfs 0.060 af
Total Runoff Area = 5.692 ac Runoff Volume = 0.268 af Average Runoff Depth = 0.56"
20055198EXI5TING
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type /I 24-hr 2-yr Rainfal/=2.80"
Page 3
1/4/2006
5ubcatchment 105: Drainage to North
Runoff
=
0.88 cfs @ 12.00 hrs, Volume=
0.047 af, Depth> 0.56"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-yr Rainfall=2.80"
Area (ac) CN Description
1.007 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (fUsec) (cfs)
6.8 150 0.0200 0.4 Lag/CN Method,
5ubcatchment 205: Drainage to 50uth
Runoff =
2.60 cfs @ 12.03 hrs, Volume=
0.160 af, Depth> 0.56"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-yr Rainfall=2.80"
Area (ac) CN Description
3.411 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (ftIsec) (cfs)
9.7 335 0.0350 0.6 Lag/CN Method,
5ubcatchment 305: Drainage to East
Runoff =
1.32 cfs @ 11.95 hrs, Volume=
0.060 af, Depth> 0.57"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-yr Rainfall=2.80"
Area (ac) CN Description
1.274 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (ftIsec) (cfs)
2.9 115 0.0690 0.7 Lag/eN Method,
SUMMARY
Appendix B
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
~Ubcay B ~ ~
Drainage Diagram for 20055198PROPOSED
Prepared by Westwood Professional Services, Inc. 1.'4/2006
HydroCAOO 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type /I 24-hr 2-yr Rainfal/=2.80"
Page 5
1/4/2006
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
5ubcatchment 205:
Runoff Area=4.535 ac Runoff Depth=1.35"
Tc=O.O min CN=84 Runoff=12.59 cfs 0.511 af
5ubcatchment 305:
Runoff Area=1.152 ac Runoff Depth=0.57"
Tc=O.O min CN=69 Runoff=1.26 cfs 0.054 af
Pond 20P:
Peak Elev=899.00' Storage=0.199 af Inflow=12.59 cfs 0.511 af
Outflow=3.11 cfs 0.511 af
Total Runoff Area = 5.687 ac Runoff Volume = 0.566 af Average Runoff Depth = 1.19"
20055198PROP05ED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type /I 24-hr 2-yr Rainfal/=2.80"
Page 6
1/4/2006
Runoff
5ubcatchment 205:
=
12.59 cfs @ 11.89 hrs, Volume=
0.511 af, Depth= 1.35"
Runoff by ses TR-20 method, UH=SeS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-yr Rainfall=2.80"
Area (ac)
2.115
2.420
4.535
Runoff
eN Description
69 50-75% Grass cover, Fair, HSG B
98 Paved parkin~ & roofs
84 Weighted Average
5ubcatchment 305:
=
1.26 cfs @ 11.90 hrs, Volume=
0.054 af, Depth= 0.57"
Runoff by ses TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-yr Rainfall=2.80"
Area (ac) CN Description
1.152 69 50-75% Grass cover, Fair, HSG B
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 20P:
4.535 ac, Inflow Depth = 1.35"
12.59 cfs @ 11.89 hrs, Volume=
3.11 cfs @ 12.01 hrs, Volume=
3.11 cfs @ 12.01 hrs, Volume=
for 2-yr event
0.511 af
0.511 af, Atten= 75%, Lag= 7.0 min
0.511 af
Routing by Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 899.00' @ 12.01 hrs Surf.Area= 0.221 ac Storage= 0.199 af
Plug-Flow detention time= 124.6 min calculated for 0.511 af (100% of inflow)
Center-of-Mass det. time= 124.1 min ( 951.2 - 827.1 )
Volume
#1
Elevation
(feet)
898.00
900.00
901.00
Device Routin~
#1 Primary
#2 Primary
Invert Avail.Stora~e Stora~e Description
898.00' 0.734 af Custom Stage Data (Prismatic) Listed below (Recalc)
Surf.Area
(acres)
0.175
0.266
0.321
Inc.Store
(acre-feet)
0.000
0.441
0.294
Cum. Store
(acre-feet)
0.000
0.441
0.734
Invert Outlet Devices
898.00' 18.0" x 19.0' long Culvert Ke= 0.500
Outlet Invert= 897.90' S= 0.0053 '/' Cc= 0.900 n= 0.013
900.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00
Coef. (English) 2.80 2.92 3.08 3.30 3.32
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type /I 24-hr 2-yr Rainfal/=2.80"
Page 7
1/4/2006
Primary OutFlow Max=3.08 cfs @ 12.01 hrs HW=899.00' (Free Discharge)
C1=culvert (Barrel Controls 3.08 cfs @ 3.5 fps)
2=Broad-Crested Rectangular Weir (Controls 0.00 cfs)
SUMMARY
Appendix C
· WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
20055198EXISTING
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type /I 24-hr 10-yr Rainfal/=4.20"
Page 4
1 14/2006
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
Subcatchment 10S: Drainage to North Runoff Area=1.007 ae Runoff Depth>1.40"
Flow Length=150' Te=6.8 min CN=69 Runoff=2.38 efs 0.117 af
Subcatchment 205: Drainage to South Runoff Area=3.411 ae Runoff Depth>1.39"
Flow Length=335' Te=9.7 min CN=69 Runoff=7.15 efs 0.396 af
Subcatchment 30S: Drainage to East Runoff Area=1.274 ae Runoff Depth>1.40"
Flow Length=115' Te=2.9 min CN=69 Runoff=3.46 efs 0.148 af
Total Runoff Area = 5.692 ae Runoff Volume = 0.662 af Average Runoff Depth = 1.40"
20055198EXISTING
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type 1/24-hr 10-yr Rainfal/=4.20"
Page 5
1/4/2006
Subcatchment 10S: Drainage to North
Runoff
=
2.38 cfs @ 11.99 hrs, Volume=
0.117 af, Depth> 1.40"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type /I 24-hr 10-yr Rainfal/=4.20"
Area (ac) CN Description
1.007 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (ftIsec) (cfs)
6.8 150 0.0200 0.4 Lag/CN Method,
Subcatchment 20S: Drainage to South
Runoff =
7.15 cfs @ 12.02 hrs, Volume=
0.396 af, Depth> 1.39"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-yr Rainfal/=4.20"
Area (ac) CN Description
3.411 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (ftIsec) (cfs)
9.7 335 0.0350 0.6 Lag/CN Method,
Subcatchment 30S: Drainage to East
Runoff =
3.46 cfs @ 11.94 hrs, Volume=
0.148 af, Depth> 1.40"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type /I 24-hr 10-yr Rainfal/=4.20"
Area (ac) CN Description
1.274 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftIft) (ftIsec) (cfs)
2.9 115 0.0690 0.7 Lag/CN Method,
SUMMARY
Appendix 0
· WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type /I 24-hr 10-yr Rainfal/=4.20"
Page 8
1/4/2006
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
Subcatchment 205:
Runoff Area=4.535 ac Runoff Depth=2.55"
Tc=O.O min CN=84 Runoff=23.12 cfs 0.963 af
5ubcatchment 305:
Runoff Area= 1.152 ac Runoff Depth=1.40"
Tc=O.O min CN=69 Runoff=3.32 cfs 0.134 af
Pond 20P:
Peak Elev=899.70' Storage=0.363 af Inflow=23.12 cfs 0.963 af
Outflow=6.98 cfs 0.963 af
Total Runoff Area = 5.687 ac Runoff Volume = 1.097 af Average Runoff Depth = 2.32"
20055198PROP05ED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Runoff
Type 1/24-hr 10-yr Rainfal/=4.20"
Page 9
1/4/2006
5ubcatchment 205:
=
23.12 cfs @ 11.89 hrs, Volume=
0.963 af, Depth= 2.55"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-yr Rainfall=4.20"
Area (a c)
2.115
2.420
4.535
Runoff
CN Description
69 50-75% Grass cover, Fair, HSG B
98 Paved parking & roofs
84 Weighted Average
5ubcatchment 305:
=
3.32 cfs @ 11.90 hrs, Volume=
0.134 af, Depth= 1.40"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-yr Rainfall=4.20"
Area (ac) CN Description
1.152 69 50-75% Grass cover, Fair, HSG B
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 20P:
4.535 ac, Inflow Depth = 2.55"
23.12 cfs@ 11.89 hrs, Volume=
6.98 cfs @ 12.00 hrs, Volume=
6.98 cfs @ 12.00 hrs, Volume=
for 1 O-yr event
0.963 af
0.963 af, Atten= 70%, Lag= 6.4 min
0.963 af
Routing by Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 899.70' @ 12.00 hrs Surf.Area= 0.252 ac Storage= 0.363 af
Plug-Flow detention time= 88.4 min calculated for 0.963 af (100% of inflow)
Center-of-Mass det. time= 89.8 min ( 898.8 - 809.0 )
Volume
#1
Elevation
(feet)
898.00
900.00
901.00
Device Routing
#1 Primary
#2 Primary
Invert Avail.Storage Storage Description
898.00' 0.734 af Custom Stage Data (Prismatic) Listed below (Recalc)
Surf.Area
(acres)
0.175
0.266
0.321
Inc. Store
(acre-feet)
0.000
0.441
0.294
Cum. Store
(acre-feet)
0.000
0.441
0.734
Invert Outlet Devices
898.00' 18.0" x 19.0' long Culvert Ke= 0.500
Outlet Invert= 897.90' S= 0.0053 'f Cc= 0.900 n= 0.013
900.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00
Coef. (English) 2.80 2.92 3.08 3.30 3.32
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type 1/24-hr 10-yr Rainfal/=4.20"
Page 1 0
1/4/2006
Primary OutFlow Max=6.97 cfs @ 12.00 hrs HW=899.70' (Free Discharge)
t1=Culvert (Barrel Controls 6.97 cfs @ 4.4 fps)
2=Broad-Crested Rectangular Weir (Controls 0.00 cfs)
SUMMARY
Appendix E
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
20055198EXISTING
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type /I 24-hr 100-yr Rainfal/=6.00"
Page 6
1/4/2006
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
Subcatchment 10S: Drainage to North Runoff Area=1.007 ac Runoff Depth>2.71"
Flow Length=150' Tc=6.8 min CN=69 Runoff=4.66 cfs 0.227 af
Subcatchment 20S: Drainage to South Runoff Area=3.411 ac Runoff Depth>2. 71"
Flow Length=335' Tc=9.7 min CN=69 Runoff=14.17 cfs 0.769 af
Subcatchment 30S: Drainage to East Runoff Area=1.274 ac Runoff Depth>2.71"
Flow Length=115' Tc=2.9 min CN=69 Runoff=6.72 cfs 0.288 af
Total Runoff Area = 5.692 ac RunoftVolume = 1.284 at Average Runoff Depth = 2.71"
20055198EXISTING
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type 1/24-hr 100-yr Rainfal/=6.00"
Page 7
1/4/2006
Subcatchment 10S: Drainage to North
Runoff
=
4.66 cfs @ 11.98 hrs, Volume=
0.227 af, Depth> 2.71"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-yr Rainfall=6.00"
Area (ac) CN Description
1.007 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (fUft) (fUsec) (cfs)
6.8 150 0.0200 0.4 Lag/CN Method,
Subcatchment 20S: Drainage to South
Runoff =
14.17 cfs @ 12.02 hrs, Volume=
0.769 af, Depth> 2.71"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-yr Rainfall=6.00"
Area (ac) CN Description
3.411 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (fUft) (fUsee) (cfs)
9.7 335 0.0350 0.6 Lag/CN Method,
Subcatchment 30S: Drainage to East
Runoff =
6.72 cfs @ 11.94 hrs, Volume=
0.288 af, Depth> 2.71"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-yr Rainfall=6.00"
Area (ac) CN Description
1.274 69 50-75% Grass cover, Fair, HSG B
Tc Length Slope Velocity Capacity Description
(min) (feet) (fUft) (fUsec) (cfs)
2.9 115 0.0690 0.7 Lag/CN Method,
SUMMARY
Appendix F
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @ 2005 HydroCAD Software Solutions LLC
Type 1/24-hr 100-yr Rainfal/=6.00"
Page 11
1/4/2006
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
8ubcatchment 208:
Runoff Area=4.535 ac Runoff Depth=4.20"
Tc=O.O min CN=84 Runoff=36.96 cfs 1.586 af
8ubcatchment 308:
Runoff Area=1.152 ac Runoff Depth=2.71"
Tc=O.O min CN=69 Runoff=6.44 cfs 0.260 af
Pond 20P:
Peak Elev=900.50' Storage=0.581 af Inflow=36.96 cfs 1.586 af
Outflow=10.94 cfs 1.586 af
Total Runoff Area = 5.687 ac Runoff Volume = 1.846 af Average Runoff Depth = 3.90"
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Runoff
Type /I 24-hr 100-yr Rainfal/=6.00"
Page 12
1/4/2006
Subcatchment 20S:
=
36.96 cfs @ 11.89 hrs, Volume=
1.586 af, Depth= 4.20"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-yr Rainfall=6.00"
Area (a c)
2.115
2.420
4.535
Runoff
CN Description
69 50-75% Grass cover, Fair, HSG B
98 Paved parking & roofs
84 Weighted Average
Subcatchment 30S:
=
6.44 cfs @ 11.89 hrs, Volume=
0.260 af, Depth= 2.71"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-yr Rainfall=6.00"
Area (ac) CN Description
1.152 69 50-75% Grass cover, Fair, HSG B
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 20P:
4.535 ac, Inflow Depth = 4.20"
36.96 cfs @ 11.89 hrs, Volume=
10.94 cfs @ 12.00 hrs, Volume=
10.94 cfs @ 12.00 hrs, Volume=
for 1 OO-yr event
1.586 af
1.586 af, Atten= 70%, Lag= 6.5 min
1.586 af
Routing by Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 900.50' @ 12.00 hrs Surf.Area= 0.293 ac Storage= 0.581 af
Plug-Flow detention time= 73.8 min calculated for 1.586 af (100% of inflow)
Center-of-Mass del. time= 73.2 min ( 868.0 - 794.8 )
Volume
#1
Elevation
(feet)
898.00
900.00
901.00
Device Routing
#1 Primary
#2 Primary
Invert Avail.Storage Storage Description
898.00' 0.734 af Custom Stage Data (Prismatic) Listed below (Recalc)
Surf.Area
(acres)
0.175
0.266
0.321
Inc.Store
(acre-feet)
0.000
0.441
0.294
Cum. Store
(acre-feet)
0.000
0.441
0.734
Invert Outlet Devices
898.00' 18.0" x 19.0' long Culvert Ke= 0.500
Outlet Invert= 897.90' S= 0.0053 'f Cc= 0.900 n= 0.013
900.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00
Coef. (English) 2.80 2.92 3.08 3.30 3.32
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAO@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type II 24-hr 100-yr Rainfall=6.00"
Page 13
1/4/2006
Primary OutFlow Max=1 0.93 cfs @ 12.00 hrs HW=900.50' (Free Discharge)
t1=culvert (Barrel Controls 10.93 cfs @ 6.2 fps)
2=Broad-Crested Rectangular Weir (Controls 0.00 cfs)
SUMMARY
Appendix G
· WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
Project Title:
Project Number:
Designed By:
Design Date:
Chanhassen Gateway North
20055198
ARN
12/8/2005
NPDES WET SEDIMENTAION BASIN SIZING REQUIREMENTS
POND 1
Site Information
Total Drainage Area to Pond
Impervious Surface Area
4.35
2.42
ac
ac
Pond Storage
2.0
Acre Area Ac-ft Storage Cumm.
StoralJe
0.015
0.065 0.065
0.050
0.225 0.290
0.175
Contour
Distance Feet
894.0
896.0
898.0
2.0
NWL
NPDES Wet Sedimentation Basin Sizing Requirements
1. Required Permanent Storage Volume = 1800 cubic feet/acre= 0.178 ac-ft
2. Provided Permanent Storage Volume = 0.290 ac-ft
b. Provided Dead Storage Greater than Required Dead Storage = OK
3. Runoff from 1/2" Rain Event on Impervious Surface = Water Quality Volume
4. Water Quality Volume = Impervious Surface Area x 0.5" =
12
0.101 ac-ft
a. Discharge @ Water Quality Volume =
b. Water Quality Volume Elevation=
b. Water Quality Surface Area=
1.07 cfs
898.54 ft
0.200 ac
5. Water Quality Discharge rate/acre=
W.Q. Discharge (cfs)
W.Q. Surface Area (ac)
5.3500 cfs
a. Water Quaility discharge must be less than 5.66 cfs per acre =
OK
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sin 002396 @ 2005 HydroCAD Software Solutions LLC
Type" 24-hr O.5-in Rainfal/=O.50"
Page 2
1/4/2006
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+ Trans method - Pond routing by Stor-Ind method
5ubcatchment 205:
Runoff Area=4.535 ae Runoff Depth=0.01"
Te=O.O min CN=84 Runoff=O.OO efs 0.003 af
5ubcatchment 305:
Runoff Area=1.152 ae Runoff Depth=O.OO"
Te=O.O min CN=69 Runoff=O.OO efs 0.000 af
Pond 20P:
Peak Elev=898.01' Storage=0.002 af Inflow=O.OO efs 0.003 af
Outflow=O.OO efs 0.003 af
Total Runoff Area = 5.687 ac Runoff Volume = 0.003 af Average Runoff Depth = 0.01"
20055198PROP08ED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sin 002396 @ 2005 HydroCAD Software Solutions LLC
Runoff =
Type /I 24-hr O.5-in Rainfal/=O.50"
Page 3
1/4/2006
8ubcatchment 208:
0.00 cfs @ 17.33 hrs, Volume=
0.003 af, Depth= 0.01"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 0.5-in Rainfall=0.50"
Area (a c)
2.115
2.420
4.535
Runoff =
CN Description
69 50-75% Grass cover, Fair, HSG B
98 Paved parking & roofs
84 Weighted Average
8ubcatchment 308:
0.00 cfs @ 0.00 hrs, Volume=
0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 24-hr 0.5-in Rainfall=0.50"
Area (ac) CN Description
1.152 69 50-75% Grass cover, Fair, HSG B
Inflow Area =
Inflow =
Outflow =
Primary =
Pond 20P:
4.535 ac, Inflow Depth = 0.01"
0.00 cfs @ 17.33 hrs, Volume=
0.00 cfs @ 24.01 hrs, Volume=
0.00 cfs @ 24.01 hrs, Volume=
for 0.5-in event
0.003 af
0.003 af, Atten= 66%, Lag= 401.1 min
0.003 af
Routing by Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 898.01' @ 24.01 hrs Surf.Area= 0.176 ac Storage= 0.002 af
Plug-Flow detention time= 1,379.4 min calculated for 0.003 af (100% of inflow)
Center-of-Mass del. time= 1,379.3 min ( 2,493.1 - 1,113.8 )
Volume
#1
Elevation
(feet)
898.00
900.00
901.00
Device Routing
#1 Primary
#2 Primary
Invert Avail.Storage Storage Description
898.00' 0.734 af Custom Stage Data (Prismatic) Listed below (Recalc)
Surf.Area
(acres)
0.175
0.266
0.321
Inc.Store
(acre-feet)
0.000
0.441
0.294
Cum. Store
(acre-feet)
0.000
0.441
0.734
I nvert Outlet Devices
898.00' 18.0" x 19.0' long Culvert Ke= 0.500
Outlet Invert= 897.90' S= 0.0053 '/' Cc= 0.900 n= 0.013
900.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00
Coef. (English) 2.80 2.92 3.08 3.30 3.32
20055198PROPOSED
Prepared by Westwood Professional Services, Inc.
HydroCAD@ 7.10 sIn 002396 @2005 HydroCAD Software Solutions LLC
Type 1/24-hrO.5-in Rainfal/=O.50"
Page 4
1/4/2006
Primary OutFlow Max=O.OO cfs @ 24.01 hrs HW=898.01' (Free Discharge)
t1=Culvert (Barrel Controls 0.00 cfs @ 0.3 fps)
2=Broad-Crested Rectangular Weir (Controls 0.00 cfs)
SUMMARY
Appendix H
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
02005 Westwood Professional Services, Inc.
I
"~
V'Ie5twood
w.bllJoDd ~s.rw..lnc.
!70112thSt.N.Sula.1OI
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.......... ... .....1 _ .lh1J ~ I'ICI'IIlIlIJKJ
1lNGINBBIl...a. ....",.........,...-.
Prepared for:
Chanhassen Gateway Place, LLC
Attn: Jamie Theleti
P.O. Box '17l
Albany . MhuIeoota 563m
n-t..."",. AIN
Ryon T. GIdecm
..... 12/19/05 ~ N~ 41359
""""'" aTlJ
DJewa: IAL
~ Dnwfu: 1I'I'/cIiltB
Call 48 Hours before digging:
GOPHER STATE ONE CALL
Twin City Area 651-454-0002
Mn. Toll Free 1-800-252-1166
LEGEND
ffi= POND
G) = DRAINAGE AREA
)(
O'
50'
150'
100'
2005519BDAE.DWG
Date: 12/19/05
Sheet: 1 OF 1
Gateway North
Existing Drainage
Areas
Chanhasaen. MInneIIota
SUMMARY
Appendix I
.WESTWOOD PROFESSIONAL SERVICES, INC. (320) 253-9495
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