HomeMy WebLinkAboutApp. B. - Stormwater Design Report 07-22-2020
DESIGN REPORT
STORMWATER MANAGEMENT
NORTON RANCH SUBDIVISION, PHASE 5
Prepared for:
Norton Properties, LLC
63020 NE Lower Meadow Road, Suite A, Bend, OR 97702
Prepared by:
C&H Engineering and Surveying, Inc.
1091 Stoneridge Drive, Bozeman, MT 59718
(406) 587-1115
Project Number: 161141
July 2020
INTRODUCTION
The proposed Norton Ranch Subdivision, Phase 5 is a 138-lot subdivision located on a 79.31-acre
parcel in the East Half and the West Half of Section 9, Township 2 South, Range 5 East of P.M.M.,
Gallatin County, City of Bozeman. A combination of site grading, curb and gutter, storm inlets,
and piping will be used to manage stormwater runoff on the site. Supporting stormwater
calculations are attached to this report. A Drainage Area Map is included in Appendix A.
Calculations for each individual drainage area (total area, weighted C factor, and time of
concentration) are included in Appendix B.
STORM SEWER FACILITIES DESIGN
Storm sewer facilities were sized for the 25-yr storm using Manning’s Equation. For each inlet,
the contributing area, weighted C factor, and time of concentration were calculated. These values
were input into Manning’s Equation to check capacity and flow characteristics for inlets, storm
drain pipes, and curb gutters. All curbs are designed to maintain 0.15’ freeboard per C.O.B. Design
Manual Section IV.C.5. For the purposes of this report, each pipe section was named to match the
associated upstream structure. Pipe sizing calculations are included in Appendix D.
RETENTION/DETENTION POND DESIGN
All ponds have been sized according to City of Bozeman Design Standards. Retention ponds are
sized to capture the entire volume of the 10-year 2-hour storm event. They are designed with a
maximum depth of 1.5 feet, and maximum side slope of 4:1. Detention Ponds are sized to limit
discharge to pre-development rates for the 10-year storm event. Calculations used for sizing each
pond can be found in Appendix C.
GROUNDWATER
The Geotechnical Investigation Report for Phase 5 encountered groundwater at depths varying
from 3.5 to 5.5 feet below ground surface. The seasonally high groundwater was measured during
the spring of 2018. Seasonally high groundwater levels were determined to be 0.5’ to 2’ below
ground surface. Shallow groundwater elevations have been encountered throughout the Norton
East Ranch Subdivision. The developer is aware of these elevations and all structures are
constructed as slab-on-grade. The infrastructure plans for this development will account for the
high groundwater condition on site. All streets will be constructed above existing grade to ensure
all stormwater ponds are installed above the SHGWL. Dewatering for utility installations and
foundation construction is expected and will be accounted for in any construction permits. Crawl
space and basement foundations are not recommended within this subdivision – a note is included
on the plat with this recommendation.
Detention Pond #1
Detention Pond #1 is located in the northwest corner of the site within Park 5B. This detention
pond will be replacing the temporary retention pond installed with Phase 3B that is located just
north of Babcock Street. Detention Pond #1 receives runoff from Drainage Areas 1-8, 11-13, and
the existing stormwater system from Norton East Ranch, Phase 3B (see Appendix F), totaling
63.43 acres. The pre-development time to concentration for the pond was calculated to be 50
minutes and the pre-development runoff rate for the 10-yr storm event was calculated to be 9.09
cfs. In order to limit discharge from the detention pond to pre-development runoff rates the
proposed outlet structure for the pond will have a 17.8” weir installed. The outlet pipe (Pipe #Outlet
Pipe) was sized for the 25-yr storm event using the maximum time of concentration of the
contributing drainage areas (21.4 minutes for DA #3). The pipe will discharge into Aajker Creek.
The required pond volume was calculated to be 37,016 cubic feet. The provided pond volume is
47,688 cubic feet at an effective water depth of 1.5’ above the seasonal high groundwater level.
The groundwater elevation was found to be located at 4778.3’ in the vicinity of the detention pond
and the bottom of the pond is set at 4778.8’. A profile showing the proposed detention pond, inlet
pipe, outlet pipe, and groundwater levels can be found in Appendix E. In the case of a storm
exceeding the 10-yr design storm, runoff will overflow the outlet structure top grate into the outlet
pipe and flow into the Aajker Creek. Supporting calculations for the pond sizing can be found in
Appendix C.
Retention Pond #2
Retention Pond #2 is located just east of the terminus of Laurel Parkway, directly south of the
existing lift station. It receives runoff from Drainage Areas 9 and 10, totaling 5.55 acres. Runoff
from Drainage Areas 9 and 10 is conveyed via surface flow and gutters to proposed inlets located
within the proposed curb. The groundwater elevation was found to be located at 4782.1’ in the
vicinity of this retention pond and the bottom of the pond is set at 4782.7’. The required pond
volume was calculated to be 7,891 cubic feet. The proposed pond is designed to store 8,021 cubic
feet of water. This pond may be temporary and incorporated into the future development plans for
Lot R1A once that development layout is decided upon. Supporting calculations for the required
pond volume can be found in Appendix C.
Drainage/Retention Swale #3
The drainage/retention swale #3 is located along the northern boundary of the proposed
subdivision. It receives runoff from Drainage Areas 14 and 15, totaling 3.15 acres. Runoff from
Drainage Areas 14 and 15 is conveyed via surface flow and gutters to proposed inlets which
discharge into the proposed swale. The swale has a shallow slope of 0.8% to the west and will
ultimately discharge into Aajker Creek. The shallow slope was utilized so that the drainage swale
can act as a retention pond with a bottom width of 2’, water depth of 1.5’, and 4:1 side slopes. This
cross-sectional area in conjunction with the length of the swale was used to determine its retention
volume. Due to the shallow slope, stormwater will have ample time to be treated and settle prior
to discharging into Aajker Creek. The required swale volume was calculated to be 2,572 cubic
feet. The proposed swale is designed to store 9,000 cubic feet of water. The proposed swale will
have an overtopping berm installed on the far west side to ensure that during storm events
exceeding the design storm, the runoff will not flow north into the Lakes property or flood the
proposed houses. the Supporting calculations for the required retention swale volume can be found
in Appendix C. A detailed exhibit showing proposed elevations of the swale is included in
Appendix E.
APPENDIX A
DRAINAGE AREA MAP
APPENDIX B
DRAINAGE AREA CALCULATIONS
DRAINAGE AREA #1
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 26475 19525
Hardscape 0.95 0 0
OS 0.2 43799 8760
Low-Med Residential 0.35 0 0
Dense Residential 0.5 0 0
Total 70274 28285
A = Area (acres) 1.6133
C = Weighted C Factor 0.40
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 76 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)11.6
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.84%
L = length of gutter (ft) 845
V = mean velocity (ft/s) 2.75
Tc Gutter Flow (minutes) =5.1
Tc Total = 16.7 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.40 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.77 (25-yr storm)
A = area (acres) 1.61 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 1.15 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.84%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.42
DRAINAGE AREA #2
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 10505 7747
Hardscape 0.95 0 0
OS 0.2 0 0
Low-Med Residential 0.35 29555 10344
Dense Residential 0.5 0 0
Total 40060 18091
A = Area (acres) 0.9196
C = Weighted C Factor 0.45
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 130 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)15.2
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.86%
L = length of gutter (ft) 224
V = mean velocity (ft/s) 2.78
Tc Gutter Flow (minutes) =1.3
Tc Total = 16.6 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.45 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.78 (25-yr storm)
A = area (acres) 0.92 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 0.74 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.86%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.44
DRAINAGE AREA #3
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 74335 54822
Hardscape 0.95 0 0
OS 0.2 3251 650
Low-Med Residential 0.35 148300 51905
Dense Residential 0.5 0 0
Total 225887 107378
A = Area (acres) 5.1857
C = Weighted C Factor 0.48
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 136 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)15.6
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.01%
L = length of gutter (ft) 1058
V = mean velocity (ft/s) 3.01
Tc Gutter Flow (minutes) =5.8
Tc Total = 21.4 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.48 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.51 (25-yr storm)
A = area (acres) 5.19 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 3.71 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.01%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.74
DRAINAGE AREA #4
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 36002 26552
Hardscape 0.95 0 0
OS 0.2 350 70
Low-Med Residential 0.35 92427 32349
Dense Residential 0.5 0 0
Total 128779 58971
A = Area (acres) 2.9564
C = Weighted C Factor 0.46
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 116 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)14.4
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.89%
L = length of gutter (ft) 914
V = mean velocity (ft/s) 2.83
Tc Gutter Flow (minutes) =5.4
Tc Total = 19.8 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.46 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.59 (25-yr storm)
A = area (acres) 2.96 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 2.15 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.89%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.51
DRAINAGE AREA #5
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 32466 23944
Hardscape 0.95 0 0
OS 0.2 65 13
Low-Med Residential 0.35 78948 27632
Dense Residential 0.5 0 0
Total 111479 51589
A = Area (acres) 2.5592
C = Weighted C Factor 0.46
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 131 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)15.3
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.97%
L = length of gutter (ft) 870
V = mean velocity (ft/s) 2.95
Tc Gutter Flow (minutes) =4.9
Tc Total = 20.2 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.46 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.56 (25-yr storm)
A = area (acres) 2.56 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 1.85 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.97%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.65
DRAINAGE AREA #6
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 35341 26064
Hardscape 0.95 0 0
OS 0.2 51 10
Low-Med Residential 0.35 86872 30405
Dense Residential 0.5 0 0
Total 122263 56479
A = Area (acres) 2.8068
C = Weighted C Factor 0.46
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 138 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)15.7
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.96%
L = length of gutter (ft) 863
V = mean velocity (ft/s) 2.94
Tc Gutter Flow (minutes) =4.9
Tc Total = 20.6 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.46 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.55 (25-yr storm)
A = area (acres) 2.81 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 2.01 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.96%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.65
DRAINAGE AREA #7
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 32740 24146
Hardscape 0.95 0 0
OS 0.2 0 0
Low-Med Residential 0.35 83718 29301
Dense Residential 0.5 0 0
Total 116458 53447
A = Area (acres) 2.6735
C = Weighted C Factor 0.46
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 142 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)15.9
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.13%
L = length of gutter (ft) 851
V = mean velocity (ft/s) 3.18
Tc Gutter Flow (minutes) =4.5
Tc Total = 20.4 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.46 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.56 (25-yr storm)
A = area (acres) 2.67 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 1.91 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.13%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.95
DRAINAGE AREA #8
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 49511 36514
Hardscape 0.95 0 0
OS 0.2 33642 6728
Low-Med Residential 0.35 105497 36924
Dense Residential 0.5 0 0
Total 188651 80167
A = Area (acres) 4.3308
C = Weighted C Factor 0.42
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 124 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)14.9
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.12%
L = length of gutter (ft) 948
V = mean velocity (ft/s) 3.17
Tc Gutter Flow (minutes) =5.0
Tc Total = 19.9 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.42 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.58 (25-yr storm)
A = area (acres) 4.33 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 2.91 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.12%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.93
DRAINAGE AREA #9
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 66028 48696
Hardscape 0.95 0 0
OS 0.2 93614 18723
Low-Med Residential 0.35 22024 7708
Dense Residential 0.5 0 0
Total 181666 75127
A = Area (acres) 4.1705
C = Weighted C Factor 0.41
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 70 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)11.2
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.88%
L = length of gutter (ft) 1295
V = mean velocity (ft/s) 2.81
Tc Gutter Flow (minutes) =7.7
Tc Total = 18.9 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.41 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.64 (25-yr storm)
A = area (acres) 4.17 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 2.82 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.88%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.49
DRAINAGE AREA #10
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 60307 44477
Hardscape 0.95 0 0
OS 0.2 0 0
Low-Med Residential 0.35 0 0
Dense Residential 0.5 0 0
Total 60307 44477
A = Area (acres) 1.3845
C = Weighted C Factor 0.74
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 100 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)13.4
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.88%
L = length of gutter (ft) 1340
V = mean velocity (ft/s) 2.81
Tc Gutter Flow (minutes) =7.9
Tc Total = 21.3 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.74 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.51 (25-yr storm)
A = area (acres) 1.38 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 1.54 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.88%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.49
DRAINAGE AREA #11
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 0 0
Hardscape 0.95 0 0
OS 0.2 94835 18967
Low-Med Residential 0.35 15528 5435
Dense Residential 0.5 0 0
Total 110363 24402
A = Area (acres) 2.5336
C = Weighted C Factor 0.22
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 219 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)19.8
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 1.16%
L = length of gutter (ft) 0
V = mean velocity (ft/s) 3.23
Tc Gutter Flow (minutes) =0.0
Tc Total = 19.8 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.22 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.59 (25-yr storm)
A = area (acres) 2.53 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs)N/A (assuming no carry flow)
DRAINAGE AREA #12
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 7030 5184
Hardscape 0.95 0 0
OS 0.2 0 0
Low-Med Residential 0.35 3065 1073
Dense Residential 0.5 0 0
Total 10095 6257
A = Area (acres) 0.2317
C = Weighted C Factor 0.62
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 73 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)11.4
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.89%
L = length of gutter (ft) 136
V = mean velocity (ft/s) 2.82
Tc Gutter Flow (minutes) =0.8
Tc Total = 12.2 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.62 (calculated above)
I = 0.78 Tc-0.64 (in/hr)2.16 (25-yr storm)
A = area (acres) 0.23 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 0.31 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.89%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.50
DRAINAGE AREA #13
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 54530 40216
Hardscape 0.95 0 0
OS 0.2 30338 6068
Low-Med Residential 0.35 76817 26886
Dense Residential 0.5 0 0
Total 161685 73169
A = Area (acres) 3.7118
C = Weighted C Factor 0.45
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.20% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 127 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)14.2
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.80%
L = length of gutter (ft) 630
V = mean velocity (ft/s) 2.68
Tc Gutter Flow (minutes) =3.9
Tc Total = 18.1 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.45 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.68 (25-yr storm)
A = area (acres) 3.71 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 2.82 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.80%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.33
DRAINAGE AREA #14
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 7089 5228
Hardscape 0.95 0 0
OS 0.2 4849 970
Low-Med Residential 0.35 12800 4480
Dense Residential 0.5 0 0
Total 24739 10678
A = Area (acres) 0.5679
C = Weighted C Factor 0.43
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 219 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)19.8
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.83%
L = length of gutter (ft) 408
V = mean velocity (ft/s) 2.73
Tc Gutter Flow (minutes) =2.5
Tc Total = 22.3 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.43 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.47 (25-yr storm)
A = area (acres) 0.57 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 0.36 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.83%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.39
DRAINAGE AREA #15
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2)C * Area
Composite ROW 0.74 7600 5605
Hardscape 0.95 0 0
OS 0.2 97533 19507
Low-Med Residential 0.35 7249 2537
Dense Residential 0.5 0 0
Total 112382 27649
A = Area (acres) 2.5799
C = Weighted C Factor 0.25
3. Calculate Tc (Time to Concentration)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.00% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 219 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow (minutes)19.8
Tc Gutter Flow
Tc = L/V/60
V = (1.486/n)R2/3 S1/2
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.83%
L = length of gutter (ft) 408
V = mean velocity (ft/s) 2.73
Tc Gutter Flow (minutes) =2.5
Tc Total = 22.3 (5 minute minimum)
4. Calculate Flow (Rational Formula)
Q = CIA
C = Weighted C Factor 0.25 (calculated above)
I = 0.78 Tc-0.64 (in/hr)1.47 (25-yr storm)
A = area (acres) 2.58 (calculated above)
Q = REQUIRED GUTTER CAPACITY (cfs) 0.93 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15' Below Top of Curb
Q = (1.486/n)AR2/3 S1/2
n = Mannings Coefficient 0.013
A = Area (ft2)1.24 (0.15' below top of curb)
P = Wetted perimeter (ft) 9.23 (0.15' below top of curb)
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (%) 0.83%
Q = PROVIDED GUTTER CAPACITY (cfs) 3.39
APPENDIX C
POND SIZING CALCULATIONS
DETENTION POND #1
REQUIRED VOLUME
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
2. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 358934 264714
Hardscape 0.95 0 0
OS 0.2 206332 41266
Low-Med Residential 0.35 720728 252255
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 2760387 1280688 (see Appendix F)
A = Area (acres) 63.3698
C = Weighted C Factor 0.46
3. Calculate Tc (Pre-Development)
Tc Overland Flow
Tc = 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 1.49% Return (yrs)Cf
C = Rational Method Runoff Coefficient 0.2 2 to 10 1
Cf = Frequency Adjustment Factor 1 11 to 25 1.1
D = Length of Basin (ft) 1168 26 to 50 1.2
51 to 100 1.25
Tc (Pre-Development) (minutes) 50
4. Calculate Rainfall Intensity (Duration = Pre-Development Tc)
i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.84 (Tc Pre-Development)
i = rainfall intensity (in./hr.) 0.72
5. Calculate Runoff Rate (Pre-Development)
Q = CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i = rainfall intensity (in./hr.) 0.72 (calculated above)
A = Area (acres) 63.37 (calculated above)
Q = Runoff Rate (Pre-Development) (cfs) 9.09
6. Calculate Required Pond Volume
Total Area (acres) = 63.37 acres
Weighted C = 0.46
Discharge Rate (cfs) = 9.09 cfs (Equal to Pre-Development Runoff Rate)
Duration(min) Duration(hrs)
Intensity
(in/hr)Qin (cfs)Runoff
Volume
Release
Volume
Required
Storage (ft3)
31 0.52 0.98 28.90 53760 16906 36854
32 0.53 0.96 28.31 54361 17452 36909
33 0.55 0.94 27.75 54950 17997 36952
34 0.57 0.93 27.22 55527 18543 36984
35 0.58 0.91 26.71 56093 19088 37005
36 0.60 0.89 26.23 56649 19633 37015
37 0.62 0.88 25.76 57195 20179 37016
38 0.63 0.86 25.32 57731 20724 37007
39 0.65 0.85 24.90 58258 21269 36989
40 0.67 0.83 24.49 58777 21815 36962
OUTLET STRUCTURE SLOT
Q=CLH3/2
Q = Discharge (cfs) 9.09 (calculated above)
C = Weir Coefficient 3.33 (per COB Design Standards)
H = Head (ft) 1.5
L = Horizontal Length (ft) 1.49
L = Slot Width (inches) 17.8
RETENTION POND #2
REQUIRED VOLUME
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 41 0.95
ROW Landscape 19 0.2
Weighted C Factor = 0.71
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.71 126335 90014
Hardscape 0.95 0 0
OS 0.2 93614 18723
Low-Med Residential 0.35 22024 7708
Dense Residential 0.5 0 0
Total 241973 116445
C=Weighted C Factor 0.48
2. Calculate Required Volume
Q = CIA
V=7200Q
C = Weighted C Factor 0.48
I = intensity (in/hr) 0.41 (10 yr, 2hr storm)
A = Area (acres) 5.55
Q = runoff (cfs) 1.10
V = REQUIRED VOL (ft3)7891
DRAINAGE/RETENTION SWALE
REQUIRED VOLUME
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 41 0.95
ROW Landscape 19 0.2
Weighted C Factor = 0.71
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.71 14690 10466
Hardscape 0.95 0 0
OS 0.2 102382 20476
Low-Med Residential 0.35 20049 7017
Dense Residential 0.5 0 0
Total 137121 37960
C=Weighted C Factor 0.28
2. Calculate Required Volume
Q = CIA
V=7200Q
C = Weighted C Factor 0.28
I = intensity (in/hr) 0.41 (10 yr, 2hr storm)
A = Area (acres) 3.15
Q = runoff (cfs) 0.36
V = REQUIRED VOL (ft3)2572
PROVIDED VOLUME
1. Calculate Provided Volume
A = [(a+b)/2]*h
V = L*A
L = Length of Swale (ft) 750
a = bottom width (ft) 2.0
b = top width (ft) 14.0
h = depth of swale (ft) 1.5
A = area of swale (ft2)12.00
V = PROVIDED VOL (ft3)9000
APPENDIX D
PIPE SIZING CALCULATIONS
PIPE #5A 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 36979 27272
Hardscape 0.95 0 0
OS 0.2 43799 8760
Low-Med Residential 0.35 29555 10344
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 1584727 768829
A = Area (acres) 36.3803
C = Weighted C Factor 0.49
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.28 (DA #1)
i = rainfall intensity (in./hr.) 1.77
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.49
i = rainfall intensity (in./hr.) 1.77
A = Area (acres) 36.38 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 31.16 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5A Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 30 inches
d= 28.14 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.04 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
4.78 6.60 0.73 18.45 88.24 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5B 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 10505 7747
Hardscape 0.95 0 0
OS 0.2 0 0
Low-Med Residential 0.35 29555 10344
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 1514453 740544
A = Area (acres) 34.7670
C = Weighted C Factor 0.49
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.28 (DA #2)
i = rainfall intensity (in./hr.) 1.78
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.49
i = rainfall intensity (in./hr.) 1.78
A = Area (acres) 34.77 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 30.19 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5B Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 30 inches
d= 28.14 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.04 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2 Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
4.78 6.60 0.73 18.45 88.24 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5C 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 260396 192042
Hardscape 0.95 0 0
OS 0.2 37360 7472
Low-Med Residential 0.35 595762 208517
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 2367910 1130483
A = Area (acres) 54.3597
C = Weighted C Factor 0.48
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.36 (DA #3)
i = rainfall intensity (in./hr.) 1.51
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.48
i = rainfall intensity (in./hr.) 1.51
A = Area (acres) 54.36 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 39.11 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5C Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 30 inches
d= 28.14 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.04 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2 Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
4.78 6.60 0.73 18.45 88.24 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5D 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 186061 137220
Hardscape 0.95 0 0
OS 0.2 34108 6822
Low-Med Residential 0.35 447462 156612
Dense Residential 0.5 0 0
Total 667630 300653
A = Area (acres) 15.3267
C = Weighted C Factor 0.45
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.34 (DA #6)
i = rainfall intensity (in./hr.) 1.55
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.45
i = rainfall intensity (in./hr.) 1.55
A = Area (acres) 15.33 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 10.67 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5D Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 21 inches
d= 19.70 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
2.34 4.62 0.51 5.39 12.63 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5E 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 150058 110668
Hardscape 0.95 0 0
OS 0.2 33758 6752
Low-Med Residential 0.35 355035 124262
Dense Residential 0.5 0 0
Total 538851 241682
A = Area (acres) 12.3703
C = Weighted C Factor 0.45
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.34 (DA #6)
i = rainfall intensity (in./hr.) 1.55
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.45
i = rainfall intensity (in./hr.) 1.55
A = Area (acres) 12.37 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 8.58 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5E Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.006 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
1.72 3.96 0.44 5.29 9.10 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5F 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 117592 86724
Hardscape 0.95 0 0
OS 0.2 33693 6739
Low-Med Residential 0.35 276087 96630
Dense Residential 0.5 0 0
Total 427372 190093
A = Area (acres) 9.8111
C = Weighted C Factor 0.44
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.34 (DA #6)
i = rainfall intensity (in./hr.) 1.55
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.44
i = rainfall intensity (in./hr.) 1.55
A = Area (acres) 9.81 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 6.75 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5F Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
1.72 3.96 0.44 4.64 7.99 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5G 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 82252 60661
Hardscape 0.95 0 0
OS 0.2 33642 6728
Low-Med Residential 0.35 189215 66225
Dense Residential 0.5 0 0
Total 305109 133614
A = Area (acres) 7.0043
C = Weighted C Factor 0.44
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.34 (DA #7)
i = rainfall intensity (in./hr.) 1.56
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.44
i = rainfall intensity (in./hr.) 1.56
A = Area (acres) 7.00 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 4.77 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5G Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 15 inches
d= 14.07 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
1.20 3.30 0.36 4.11 4.91 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5H 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 49511 36514
Hardscape 0.95 0 0
OS 0.2 33642 6728
Low-Med Residential 0.35 105497 36924
Dense Residential 0.5 0 0
Total 188651 80167
A = Area (acres) 4.3308
C = Weighted C Factor 0.42
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.33 (DA #8)
i = rainfall intensity (in./hr.) 1.58
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.42
i = rainfall intensity (in./hr.) 1.58
A = Area (acres) 4.33 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 2.91 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5H Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 15 inches
d= 14.07 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
1.20 3.30 0.36 4.11 4.91 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5I 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 321955 237442
Hardscape 0.95 0 0
OS 0.2 67697 13539
Low-Med Residential 0.35 675644 236476
Dense Residential 0.5 0 0
Total 1065297 487457
A = Area (acres) 24.4559
C = Weighted C Factor 0.46
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.36 (DA #3)
i = rainfall intensity (in./hr.) 1.51
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.46
i = rainfall intensity (in./hr.) 1.51
A = Area (acres) 24.46 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 16.86 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5I Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 24 inches
d= 22.51 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
3.06 5.28 0.58 5.62 17.21 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5J 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 54530 40216
Hardscape 0.95 0 0
OS 0.2 30338 6068
Low-Med Residential 0.35 76817 26886
Dense Residential 0.5 0 0
Total 161685 73169
A = Area (acres) 3.7118
C = Weighted C Factor 0.45
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.30 (DA #13)
i = rainfall intensity (in./hr.) 1.68
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.45
i = rainfall intensity (in./hr.) 1.68
A = Area (acres) 3.71 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 2.82 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5J Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 3.71 2.84 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5K 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 36979 27272
Hardscape 0.95 0 0
OS 0.2 43799 8760
Low-Med Residential 0.35 29555 10344
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 1584727 768829
A = Area (acres) 36.3803
C = Weighted C Factor 0.49
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.28 (DA #1)
i = rainfall intensity (in./hr.) 1.77
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.49
i = rainfall intensity (in./hr.) 1.77
A = Area (acres) 36.38 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 31.16 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5K Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 30 inches
d= 28.14 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.025 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
4.78 6.60 0.73 14.59 69.76 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5L 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 36979 27272
Hardscape 0.95 0 0
OS 0.2 43799 8760
Low-Med Residential 0.35 29555 10344
Dense Residential 0.5 0 0
Norton Phase 3 0.49 1474393 722453 *From existing Norton Ranch Ph 3
Total 1584727 768829
A = Area (acres) 36.3803
C = Weighted C Factor 0.49
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.28 (DA #1)
i = rainfall intensity (in./hr.) 1.77
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.49
i = rainfall intensity (in./hr.) 1.77
A = Area (acres) 36.38 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 31.16 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5L Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 30 inches
d= 28.14 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.01 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
4.78 6.60 0.73 9.23 44.12 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5M 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 7089 5228
Hardscape 0.95 0 0
OS 0.2 4849 970
Low-Med Residential 0.35 12800 4480
Dense Residential 0.5 0 0
Total 24739 10678
A = Area (acres) 0.5679
C = Weighted C Factor 0.43
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.37 (DA #14)
i = rainfall intensity (in./hr.) 1.47
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.43
i = rainfall intensity (in./hr.) 1.47
A = Area (acres) 0.57 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 0.36 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5M Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 3.71 2.84 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5N 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 7089 5228
Hardscape 0.95 0 0
OS 0.2 4849 970
Low-Med Residential 0.35 12800 4480
Dense Residential 0.5 0 0
Total 24739 10678
A = Area (acres) 0.5679
C = Weighted C Factor 0.43
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.37 (DA #14)
i = rainfall intensity (in./hr.) 1.47
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.43
i = rainfall intensity (in./hr.) 1.47
A = Area (acres) 0.57 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 0.36 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5N Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 3.71 2.84 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5O 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 7600 5605
Hardscape 0.95 0 0
OS 0.2 97533 19507
Low-Med Residential 0.35 7249 2537
Dense Residential 0.5 0 0
Total 112382 27649
A = Area (acres) 2.5799
C = Weighted C Factor 0.25
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.37 (DA #15)
i = rainfall intensity (in./hr.) 1.47
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.25
i = rainfall intensity (in./hr.) 1.47
A = Area (acres) 2.58 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 0.93 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5O Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 3.71 2.84 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5P 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 7600 5605
Hardscape 0.95 0 0
OS 0.2 97533 19507
Low-Med Residential 0.35 7249 2537
Dense Residential 0.5 0 0
Total 112382 27649
A = Area (acres) 2.5799
C = Weighted C Factor 0.25
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.37 (DA #15)
i = rainfall intensity (in./hr.) 1.47
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.25
i = rainfall intensity (in./hr.) 1.47
A = Area (acres) 2.58 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 0.93 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5P Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 3.71 2.84 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5Q 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 66028 48696
Hardscape 0.95 0 0
OS 0.2 93614 18723
Low-Med Residential 0.35 22024 7708
Dense Residential 0.5 0 0
Total 181666 75127
A = Area (acres) 4.1705
C = Weighted C Factor 0.41
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.31 (DA #13)
i = rainfall intensity (in./hr.) 1.64
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.41
i = rainfall intensity (in./hr.) 1.64
A = Area (acres) 4.17 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 2.82 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5Q Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 12 inches
d= 11.26 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.006 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
0.77 2.64 0.29 4.03 3.09 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
PIPE #5R 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Weighted C Factor for Right-of-Way
Component Width C
ROW Hardscape 43 0.95
ROW Landscape 17 0.2
Weighted C Factor = 0.74
1. Calculate Area and Weighted C Factor (Post-Development)
Contributing Area C Area (ft 2 )C * Area
Composite ROW 0.74 126335 93172
Hardscape 0.95 0 0
OS 0.2 93614 18723
Low-Med Residential 0.35 22024 7708
Dense Residential 0.5 0 0
Total 241973 119603
A = Area (acres) 5.5549
C = Weighted C Factor 0.49
2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas)
i = 0.78x-0.64 (10-yr Storm, Fig. I-3, COB Design Standards)
x = storm duration (hrs) 0.36 (DA #10)
i = rainfall intensity (in./hr.) 1.51
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.49
i = rainfall intensity (in./hr.) 1.51
A = Area (acres) 5.55 (calculated above)
(calculated above)
Q = 25-yr Pond Outflow Rate (cfs) 4.15 (calculated above)
MANNING'S EQUATION FOR PIPE FLOW
Pipe: Pipe 5R Project: Norton East Ranch Subdivision, Phase 5
INPUT
D= 15 inches
d= 14.07 inches
Mannings Formula n= 0.013 mannings
57.7 degrees
Q=(1.486/n)ARh2/3S1/2 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
S=slope of channel V=(1.49/n)Rh2/3S1/2
n=Manning's roughness coefficient Q=V x A
Solution to Mannings Equation
Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs PVC 0.013
1.20 3.30 0.36 4.31 5.15 PE (<9"dia) 0.015
PE (>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Conc 0.013
Manning's n-values
d
D
APPENDIX E
DETENTION POND #1 PROFILE &
DRAINAGE SWALE EXHIBIT
APPENDIX F
NORTON RANCH PHASE 3 STORMWATER
DESIGN REPORT