HomeMy WebLinkAbout18 - Design Report - Flanders Mill Ph 7 - Stormwater DESIGN REPORT
STORMWATER MANAGEMENT
FLANDERS MILL SUBDIVISION, PHASE 7
Prepared for:
Flanders Mill, LLC
235 Greenhills Ranch Road, Bozeman, MT 59718
Prepared by:
C&H Engineering and Surveying, Inc.
1091 Stoneridge Drive, Bozeman, MT 59718
(406) 587-1115
Project Number: 14500
January 2018
INTRODUCTION
The proposed Flanders Mill Subdivision— Phase 7 infrastructure improvements will include the
construction of Oak Street from the Flanders Mill Road (FMR) intersection, east to the Phase 4
limit of paving, the construction of Windrow Drive, from Oak Street north to Broken Spur Drive,
the construction of Broken Spur Drive,and the construction of Harvest Parkway from Broken Spur
Drive west to FMR.
Stormwater runoff from these improvements will be conveyed via curb and gutter channel flow to
a series of curb chases and storm sewer inlets. It will then be routed through storm drainage pipes
to 3 detention ponds, and the existing pond in the Phase 4 Park, before being released into the
relocated tributary stream flowing through the subdivision, or the relocated irrigation overflow
ditch west of Flanders Mill Road. A Drainage Area Map is included in Appendix A, and
calculations for each individual drainage area (total area, weighted C factor, and time of
concentration) are included in Appendix B.
In addition to the various drainage areas contributing to these ponds, the multi-family lot west of
Windrow Drive is anticipated to contribute to these infrastructure improvements as well. The
multi-family lot site plan is being designed by Madison Engineering, Inc, and although it has not
undergone site plan review by the City of Bozeman, Madison Eng. has provided preliminary
drainage design for the lot so that it can be incorporated into the Phase 7 infrastructure design.
Currently, Madison Eng. plans to retain the first 0.5" of rainfall to all impervious areas of the
multi-family lot on the lot itself, and release volumes that exceed this 0.5" to the Phase 7
infrastructure. Currently, the portion of the multi-family lot that releases to the Phase 7
infrastructure is broken into 2 basins (Basin A and B). Basin A will connect to ST Inlet 7G in
Harvest Parkway via an 18" pvc pipe, and Basin B will connect to ST Inlet 7B in Windrow Drive
via a 12"pvc pipe. Madison Eng. provided the contributing areas and weighted C values for each
basin as well as the pre and post-development time of concentrations and peak runoff rates. These
values were used to size the Phase 7 pipes and detention ponds to accommodate flows from the
multi-family lot. The calculations provided by Madison Eng. for both of these basins can be found
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 C.
RETENTION/DETENTION POND DESIGN
All ponds have been sized according to City of Bozeman Design Standards. The proposed
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 D. Design pond capacities were
calculated using volume surfaces in AutoCAD Civil 3D.
Proposed Detention Pond #7E
Detention Pond#7E is located in Open Space V,southeast of Broken Spur Drive.It receives runoff
from Drainage Areas 713, 7C, 7F, 7E, and Basin B of the multi-family lot.Runoff in the westbound
lane of Oak Street between Ryun Sun Way and FMR will be collected in the northern curb gutter
of the street and flow toward the center of the subdivision to a low point in Oak Street at the
Windrow Drive Intersection. From here, runoff will be directed north along Windrow Drive via
gutter flow until reaching a series of curb inlets (713 and 7C) on either side of Windrow Drive.
These inlets will direct the runoff via an 18" pvc pipe across Block 24 and into Detention Pond
#7E. Runoff on Windrow Drive north of inlets 7B and 7C will flow north via curb gutters to the
double gutter across the Windrow Drive/Broken Spur Drive intersection. From here it will be
directed east along the south side of Broken Spur Drive to curb chase 717,which drains directly into
Detention Pond#7E.
The pre-development time to concentration for the pond was calculated to be 26 minutes and the
pre-development runoff rate for the 10-yr storm event was calculated to be 1.83 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 3.6" weir installed. The outlet pipe (Pipe 7E) was sized for the
25-yr storm event using the maximum time of concentration of the contributing drainage areas
(13.6 minutes for DA#7C). The pipe will discharge into the adjacent stream channel, which is an
unnamed tributary of Baxter Creek. The required pond volume was calculated to be 4,698 cubic
feet. The provided pond volume is 5,334 cubic feet at a water depth of 1.5'. In the case of a storm
exceeding the 10-yr design storm, runoff will overflow the pond banks and flow east across open
space into the stream channel. Supporting calculations for the pond sizing can be found in
Appendix D.
In addition to Drainage Areas 713, 7C, 7E, and 7F, Basin B from the multi-family lot will also
contribute to Detention Pond#7E.Based on the information provided by Madison Eng.,Basin B is
a 1.35-acre portion of the multi-family lot with a weighted C value of 0.69. The calculated post
development time of concentration for Basin B is 15 minutes and the peak runoff rate that was
accounted for in sizing pipes 713, 7C, and 7E is 1.77 cfs. This basin area was also incorporated into
sizing the required storage capacity of Detention Pond#7E.
Proposed Detention Pond 97I
Detention Pond #7I is located in the northern portion of Park 2, within Broken Spur Drive and
receives runoff from Drainage Area 7I. The proposed park is currently graded with a "dome"
shape, shedding water to the outside of the park into Broken Spur Drive. From here, runoff is
captured in the gutter on the inside of Broken Spur Drive and channeled north to a low point
adjacent to the intersection with the future portion of Windrow Drive. A curb chase (7I) will be
installed at this low-point to direct water into the pond.
The pre-development time to concentration was calculated to be 37 minutes and the
pre-development runoff rate for the 10-yr storm was calculated to be 0.44 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 0.9"weir installed. The outlet pipe(Pipe 7I)was sized for the 25-yr storm
event using the maximum time of concentration of the contributing drainage area(15.8 minutes for
DA#71), and will discharge the pond across Broken Spur Drive into the adjacent stream channel,
which is an unnamed tributary of Baxter Creek. The required pond volume was calculated to be
1,382 cubic feet. The provided pond volume is 2,141 cubic feet at a water depth of 1.5'. In the case
of a storm exceeding the 10-yr design storm, the pond was designed to be slightly oversized, and
will contain an additional 9"of freeboard between the outlet structure top of weir and overflow rim
elevation to accommodate larger flow events. Supporting calculations for the pond sizing can be
found in Appendix D.
Existing Detention Pond FMR
The existing detention pond east of Flanders Mill Road was constructed to capture runoff from
Flanders Mill Road north of Oak Street, and was conservatively sized to capture a portion of
Phases 6 and 7 of the subdivision. For this phase of work a new series of manholes and pipes will
be installed to drain the southwest portion of Broken Spur Drive,Harvest Parkway and a portion of
Ryun Sun Way to the pond.Drainage Areas 7G, 7H, 6A, 613, and the multi-family lot Basin A will
all contribute to the existing detention pond. Inlets 7G and 7H will be installed in Harvest
Parkway, while inlets 6A, 613, and manhole 6C will be installed in the gravel subgrade of Ryun
Sun Way and Forage Drive and tied into the proposed curb, gutter and pavement when Phase 6 is
completed in the future. From ST MH 6C in(future) Forage Drive, runoff will be conveyed to the
existing detention pond via a 21"pvc pipe.
In addition to Drainage Areas 7G, 7H, 6A, and 613, Basin A from the multi-family lot will also
contribute to the existing detention pond. Based on the information provided by Madison Eng.,
Basin A is a 7.62-acre portion of the multi-family lot with a weighted C value of 0.61. The
calculated post development time of concentration for Basin A is 18 minutes and the peak runoff
rate that was accounted for in sizing pipes 7G, 7H, 6A, and 6B is 7.93 cfs. Madison Eng. currently
plans to hold the first 0.5" of rainfall to impervious areas of Basin A on the multi-family lot, and
discharge excess flows via an 18" pipe to Inlet 7G in Harvest Parkway. In order to calculate the
design capacity for the existing detention pond and account for the first 0.5" of rainfall to Basin A
being contained on site, a detention scenario was designed for Basin A using the pre-development
criteria provided by Madison Eng. The pre-development time of concentration of 31 minutes was
used to calculate the rainfall intensity in a 10-year storm event and determine a pre-development
runoff rate for the 10-year event. It was then assumed that runoff from Basin A would be held on
the multi-family lot until the volume of 0.5" of rainfall to the impervious areas (8,154 cf) was
retained. At this point (minute 28 of the storm event) runoff exceeding the 8,154 cf retention
capacity would be released to Inlet 7G. This runoff volume was used in addition to the runoff
volume calculated for the rest of the contributing area to the existing detention pond to calculate
the required storage volume for the entire contributing area to the existing detention pond
(including Basin A)
The pre-development time to concentration for the pond was calculated to be 90 minutes (from
Flanders Mill Road stormwater design report) and the pre-development runoff rate for the 10-yr
storm was calculated to be 1.50 cfs. Since the contributing area to this existing pond was originally
conservatively estimated to be larger with the Flanders Mill Road design report than it will be with
this updated design report,the original pre-development runoff rate was also larger(1.78 cfs). The
weir for the existing outlet structure was sized at this larger runoff rate, so the existing weir slot
width of 3.5"will remain, although the newly calculated weir slot width is 2.9". This existing weir
controls the pond discharge rate, so for this pond capacity calculation, the newly calculated pond
contributing area and the existing 1.78 cfs pre-development runoff rate were used. The existing
outlet pipe was re-evaluated for the 25-yr storm event with the new contributing area and has
adequate capacity convey the pond runoff. The required pond capacity was calculated to be 6,142
cf, and the existing pond capacity is 14,502 cf at 1.5' water depth. Supporting calculations for the
pond sizing can be found in Appendix D. The excess pond capacity and excess pipe capacities will
provide room for changes to the multi-family lot design as it undergoes the site plan process, and
may provide additional capacity for Phase 6 of the subdivision, if necessary.
ADDITIONAL FLOW
Drainage Area 7A
Drainage area 7A captures runoff from Ryun Sun Way and the eastbound lane of Oak Street that
were constructed with Phase 4 as well as the proposed Phase 7 eastbound lane of Oak Street.
Runoff from these streets will be conveyed via curb and gutter to a low point in Oak Street adjacent
to the Windrow Drive intersection.A curb chase will be installed at this point to channel water into
the Phase 4 Park. The chase will discharge south of the Oak Street ROW into a meandering 4-wide
swale which will allow sediment and debris to settle out of the runoff before entering the existing
ponds within the park. The contributing area to this chase/swale system is 4.41 acres,and the chase
and swale were both sized to handle the 25-year runoff rate of 3.74 cfs.
Open Space V
Open Space V runs between Phases 4 and 7 and is primarily composed of a 130-foot-wide stream
channel and open space buffer. This open space will be landscaped with a meandering gravel trail
and is generally sloped to drain into the stream channel.
Open Space U
Open Space U, labeled Drainage Area#EX1 on the attached drainage area map, is similar to Open
Space V in that it will be primarily landscaped and contains a stream corridor. Since the original
tributary stream flowing through the subdivision was relocated to OS V, the existing stream
corridor in OS U now primarily drains groundwater from the surrounding open space,north across
Harvest Parkway and beneath Flanders Mill Road via a recently relocated culvert. A 24"
equivalent RCP culvert will be installed across Harvest Parkway from OS U to OS R with this
phase of work in order to continue to allow groundwater from OS U to drain. Based on the
contributing area to DA #EX 1 (OS U and potentially the NWE Transfer Station) the required
capacity of this culvert for the 25-year storm event would be 2.53 cfs. As it is currently unknown if
the development of the multi-family lot will discharge stormwater to OS U, the pipe was
conservatively sized to match the downstream culvert crossing Flanders Mill Road with a flow rate
of 15.38 cfs.
Broken Spur Drive—North (Drainage Areas 6F1 and 6G)
The northern portion of the outside lane of Broken Spur Drive(and a portion of Harvest Parkway)
is designed to drain to a low point at the (future) Windrow Drive intersection at the northernmost
point of Broken Spur Drive, and then drain north to future storm inlets in Windrow Drive. These
storm inlets will be installed with Phase 6 of the subdivision. Until then, it is anticipated that the
small amount of runoff from this area will drain north to the limit of paving at the Windrow
intersection and dissipate onto the existing pit run gravel subgrade of future Windrow Drive.
APPENDIX A
DRAINAGE AREA MAP
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APPENDIX B
DRAINAGE AREA CALULATIONS
DRAINAGE AREA# 7A1
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C"Area
ROW-Tanzanite 0.76 5993 4570
ROW-Ryun Sun 0.71 28807 20525
ROW -Oak 0.68 33283 22633
Low-Med Density Residential 0.35 88507 30978
Total 156591 78705
A =Area(acres) 3.59
C=Weighted C Factor 0.50
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 0.1-CC1)D1/2/S1/3 --------
;Storm
S = Slope of Basin (%) 1.50 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) 160 :26 to 50 1.2
51 to 100 1.25
!-----------------------------
Tc Overland Flow(minutes) 14.77
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R213 S112
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P(ft) 0.13 (0.15' below top of curb)
S = slope (ft/ft) 0.0075
L=length of gutter(ft) 784
V= mean velocity(ft/s) 2.60
Tc Gutter Flow(minutes) = 5.03
Tc Total= ltl
3. Calculate Flow(Rational Formula)
Q =CIA
C =Weighted C Factor 0.50 (calculated above)
I =0.78 Tc-0.64(in/hr) 1.59 (25-yr storm)
A= area(acres) 3.59 (calculated above)
Q = REQUIRED GUTTER CAPACITY(cfs) 2.86 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR"'Sin
n= Mannings Coefficient 0.013
A=Area(ft) 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(ft/ft) i_IU
Q= PROVIDED GUTTER CAPACITY(cfs) 3.22
DRAINAGE AREA# 7A2
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C*Area
ROW-Oak 0.68 35329 24024
Total 35329 24024
A =Area(acres) sm
C=Weighted C Factor ads
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D'/2/Sl/3
Storm
S= Slope of Basin (%) 3 :Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.68 ;2 to 10 1
Cf= Frequency Adjustment Factor 1.1 111 to 25 1.1
D = Length of Basin (ft) 44 :26 to 50 1.2
51 to 100 1.25
:-----------------
Tc Overland Flow(minutes) 3.03
------------
Tc Gutter Flow
Tc = LN/60
V= (1.486/n)R213 SI12
n= Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S= slope(ft/ft) 0.0045
L= length of gutter(ft) 588
V= mean velocity(ft/s) 2.01
Tc Gutter Flow(minutes) = 4.87
Tc Total= Fie
3. Calculate Flow(Rational Formula)
Q =CIA
C =Weighted C Factor O.E)S (calculated above)
I = 0.78 Tc'-"(in/hr) 2.86 (25-yr storm)
A= area (acres) 0.81 (calculated above)
Q=REQUIRED GUTTER CAPACITY(cfs) 1.67 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR213 S112
n= Mannings Coefficient 0.013
A =Area(ft) 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(ft/ft)
Q =PROVIDED GUTTER CAPACITY (cfs) 2.49
DRAINAGE AREA# 713
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C `Area
ROW-Oak 0.68 38310 26051
ROW-Windrow 0.71 26338 18766
Low-Med Density Residential 0.35 37009 12953
Total 101658 57770
A =Area(acres) 2.33
C=Weighted C Factor 0.57
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D'/2/Sf/3
;Storm
S= Slope of Basin (%) 3.00 ;Return(yrs) Cf
C = Rational Method Runoff Coefficient 0.71 12 to 10 1
C,= Frequency Adjustment Factor 1.1 ;11 to 25 1.1
D = Length of Basin (ft) 44 126 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes) 2.74
Tc Gutter Flow
Tc= L/V/60
V= (1.486/n)R2/3 Stn
n= Mannings Coefficient 0.013
R.= Hydraulic Radius A/P (ft) 0.13 (0.15'below top of curb)
S= slope (ft/ft) 0.0092
L= length of gutter(ft) 1466
V= mean velocity(ft/s) 2.88
Tc Gutter Flow(minutes) = 8.49
Tc Total= 11.23
3. Calculate Flow(Rational Formula)
O =CIA
C =Weighted C Factor 0.57 (calculated above)
= 0.78 Tc-0.64(in/hr) 2.28 (25-yr storm)
A=area(acres) 2.33 (calculated above)
Q= REQUIRED GUTTER CAPACITY(cfs) 3.02 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR2.a S"'
n = Mannings Coefficient 0.013
A=Area (ft) 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 (ft/ft) 0.0092
Q= PROVIDED GUTTER CAPACITY(cfs) 3.57
DRAINAGE AREA# 7C
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft`) C *Area
ROW-Oak 0.68 23249 15809
ROW-Windrow 0.71 26082 18583
Low-Med Density Residential 0.35 95504 33427
Total 144836 67819
A =Area(acres) 3.32
C= Weighted C Factor 0.47
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CiC)D1/2/S1/3
Storm
S= Slope of Basin (%) 2.00 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) 81 126 to 50 1.2
51 to 100 1.25
•----------------------
Tc Overland Flow(minutes) 9.55
' -----
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R213 S1/2
n = Mannings Coefficient 0,013
R = Hydraulic Radius A/P (ft) 0.13 (0.15'below top of curb)
S =slope(ft/ft) 0.0115
L=length of gutter(ft) 788
V= mean velocity(ft/s) 3.22
Tc Gutter Flow(minutes) = 4.08
Tc Total= 13.63
3. Calculate Flow(Rational Formula)
Q =CIA
C =Weighted C Factor 0.-1 (calculated above)
=0.78 Tc-0.64(in/hr) 2.01 (25-yr storm)
A = area(acres) 3.12 (calculated above)
Q= REQUIRED GUTTER CAPACITY(cfs) 3.14 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR"3 Sv2
n= Mannings Coefficient 13
A=Area(ft) ro-oj��
4 (0.15' below top of curb)
P=Wetted perimeter(ft) 23 (0.15' below top of curb)
R= Hydraulic Radius A/P (ft) i 3 (0.15' below top of curb)
S= slope(ft/ft) 15
Q= PROVIDED GUTTER CAPACITY(cfs)
DRAINAGE AREA# 7F
1. Calculate Area and Weighted C Factor
Contributing Area C Area (It 2) C "Area
ROW-Windrow 0.71 12485 8895
ROW-Broken Spur 0.78 5718 4432
Low-Med Density Residential 0.35 14442 5055
Total 32645 18382
A =Area(acres) 0.75
C= Weighted C Factor 0.56
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D1/2/S'/3
Storm
S = Slope of Basin (%) 2.00 :Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.45 :2 to 10 1
Cf= Frequency Adjustment Factor 1.1 :11 to 25 1.1
D= Length of Basin (ft) 17 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes) 3.70
Tc Gutter Flow
Tc = L/V/60
V= (1.486/n)R213 S1i2
n = Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope(ft/ft) 0.0088
L= length of gutter(ft) 382
V= mean velocity(ft/s) 2.82
Tc Gutter Flow(minutes) = 2.26
Tc Total= 5.96
3. Calculate Flow(Rational Formula)
Q =CIA
C =Weighted C Factor 0.56 (calculated above)
=0.78 Tc-0.64(in/hr) 3.42 (25-yr storm)
A = area(acres) 0.75 (calculated above)
Q = REQUIRED GUTTER CAPACITY(cfs) 1.44 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q= (1.486/n)ARzia S112
n = Mannings Coefficient 0.013
A =Area (ft) 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 (ft/ft) 0.0088
Q = PROVIDED GUTTER CAPACITY(cfs) 3.50
DRAINAGE AREA# 7G
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C *Area
ROW-Broken Spur 0.78 7180 5564
ROW-Harvest Parkway 0.73 10447 7595
Total 17627 13160
A =Area(acres) 0.40
C=Weighted C Factor 0.75
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1/2/Sf/3
Storm
S= Slope of Basin (%) 2.00 Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.50 ;2 to 10 1
Cf= Frequency Adjustment Factor 1.1 ill to 25 1.1
D= Length of Basin (ft) 12.6 -26 to 50 1.2
51 to 100 1.25
T
-•-----------------------------
c Overland Flow(minutes) 2.90
Tc Gutter Flow
Tc= L/V/60
V= (1.486/n)R213 S112
n= Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15'below top of curb)
S =slope (ft/ft) 0.0092
L=length of gutter(ft) 432
V= mean velocity(ft/s) 2.88
Tc Gutter Flow(minutes) = 2.50
Tc Total= 5.40
3. Calculate Flow(Rational Formula)
O =CIA
C =Weighted C Factor 0.75 (calculated above)
=0.78 Tc-0.64(in/hr) 3.64 (25-yr storm)
A=area (acres) 0.40 (calculated above)
Q= REQUIRED GUTTER CAPACITY(cfs) 1.10 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR213 Sv2
n= Mannings Coefficient 0.013
A=Area (ft) 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 (ft/ft) 0.0092
Q= PROVIDED GUTTER CAPACITY(cfs) 3.57
DRAINAGE AREA# 7H
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2) C *Area
ROW-Broken Spur 0.78 1061 822
ROW-Harvest Parkway 0.73 8742 6356
Total 9804 7178
A =Area(acres) 0.23
C= Weighted C Factor 0.73
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D'/2/S13
------------------------
;Storm
S= Slope of Basin (%) 2.00 :Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.50 ;2 to 10 1
Cf= Frequency Adjustment Factor 1.1 ;11 to 25 1.1
D = Length of Basin (ft) 12.3 '-26 to 50 1.2
51 to 100 1.25
1.----------------------------
Tc Overland Flow(minutes) 2.86
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R211 S112
n = Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S =slope (ft/ft) 0.0067
L= length of gutter(ft) 222
V= mean velocity(ft/s) 2.46
Tc Gutter Flow(minutes) = 1.51
Tc Total= 4.37
3. Calculate Flow(Rational Formula)
0 =CIA
C =Weighted C Factor 0.7 3 (calculated above)
= 0.78 Tc-0.64(in/hr) 4.17 (25-yr storm)
A=area(acres) 0.23 (calculated above)
Q=REQUIRED GUTTER CAPACITY(cfs) 0.69 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR113 Sv2
n = Mannings Coefficient 0.013
A=Area (ft) 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 (ft/ft) 0.0067
Q= PROVIDED GUTTER CAPACITY(cfs) 3.05
DRAINAGE AREA# 6A
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C*Area
ROW-Ryun Sun 0.71 9500 6769
Low-Med Density Residential 0.35 35256 12340
Total 44756 19108
A =Area(acres)
C= Weighted C Factor
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1/2/Sli3
--- -----------------------
torm
S = Slope of Basin (%) 2 i Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.50:2 to 10 1
Cf= Frequency Adjustment Factor 1.1111 to 25 1.1
D= Length of Basin (ft) 17'-26 to 50 1.2
151 to 100 1.25
------------
Tc Overland Flow(minutes) 3.37
-----------------
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R213 S112
n = Mannings Coefficient 0.013
R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S= slope (ft/ft) 0.0123
L = length of gutter(ft) 310
V= mean velocity(ft/s) 3.32
Tc Gutter Flow(minutes) = 1.55
Tc Total= 4.92
3. Calculate Flow(Rational Formula)
Q = CIA
C =Weighted C Factor : -1 (calculated above)
= 0.78 Tc-0.sa(in/hr) (25-yr storm)
A = area(acres) 1 (calculated above)
Q = REQUIRED GUTTER CAPACITY(cfs) 1.70 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR"3 S'n
n = Mannings Coefficient 0.013
A =Area(ft) 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 (ft/ft) 0.0123
Q=PROVIDED GUTTER CAPACITY(cfs) 4.12
DRAINAGE AREA# 613
1. Calculate Area and Weighted C Factor
Contributing Area C Area (f,2 1 C *Area
ROW-Harvest Parkway 073 1790 1301
ROW-Ryun Sun 0.71 9891 7048
Low-Med Density Residential 0.35 35256 12340
Total 46938 20689
A =Area(acres) 1.08
C= Weighted C Factor 0.44
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1/2/S'►3
;Storm
S = Slope of Basin (%) 2;Return (yrs) Cf
C = Rational Method Runoff Coefficient 0.4612 to 10 1
Cf= Frequency Adjustment Factor 1.1;11 to 25 1.1
D= Length of Basin (ft) 12.726 to 50 1.2
;51-- to-100------------- - --
Tc Overland Flow(minutes) 3.14
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R213 S112
n = Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S= slope (ft/ft) 0.0130
L= length of gutter(ft) 388
V= mean velocity(ft/s) 3.41
Tc Gutter Flow(minutes) = 1.89
Tc Total= 5.04
3. Calculate Flow(Rational Formula)
Q = CIA
C =Weighted C Factor 0.44 (calculated above)
=0.78 Tc-0.64(in/hr) 3.81 (25-yr storm)
A= area(acres) 1.08 (calculated above)
Q= REQUIRED GUTTER CAPACITY(cfs) 1.81 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q = (1.486/n)AR"' S"'
n= Mannings Coefficient 0.013
A =Area (ft) '1.24 A15' 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(ft/ft) 0.0130
Q= PROVIDED GUTTER CAPACITY(cfs) 4.23
DRAINAGE AREA# 71
9. Calculate Area and Weighted C Factor
Contributing Area C Area(ft2 C "Area
ROW-Broken Spur 0.78 32586 25254
Park 0.35 77537 27138
Total 110123 52392
A =Area(acres) 2.53
C=Weighted C Factor 0.48
2. Calculate Tc(Time to Concentration)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D'/2/Sl/3
Storm
S=Slope of Basin (%) 1.98 :Return (yrs) Cf
C = Rational Method Runoff Coefficient 0.20 ;2 to 10 1
Cf= Frequency Adjustment Factor 1.1 ;11 to 25 1.1
D= Length of Basin (ft) 96 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes) 12.84
Tc Gutter Flow
Tc= LN/60
V= (1.486/n)R213 S112
n= Mannings Coefficient 0.013
R= Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S =slope(ft/ft) 0.0095
L=length of gutter(ft) 519
V= mean velocity(ft/s) 2.93
Tc Gutter Flow(minutes) = 2.95
Tc Total= 1179
3. Calculate Flow(Rational Formula)
Q=CIA
C=Weighted C Factor 0.-tt (calculated above)
I =0.78 Tc-0.64(in/hr) 1.83 (25-yr storm)
A=area(acres) 2.53 (calculated above)
Q= REQUIRED GUTTER CAPACITY(cfs) 2.20 (assuming no carry flow)
PROVIDED GUTTER CAPACITY
1. Calculate Gutter Capacity @ 0.15'Below Top of Curb
Q =(1.486/n)AR113 Sv2
n= Mannings Coefficient 0.013
A=Area (ft) 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(ft/ft) 0.0095
Q= PROVIDED GUTTER CAPACITY(cfs) 3.63
DRAINAGE AREA# EX1
Contributing Area C Area(ft 2) C * Area
Park/Open Space, 0.2 132360 26472
Transfer Station 0.5 185715 92858
Total 318075 119330
C=Weighted C Factor 0.38
A =Area(acres) 7.30
Required Gutter/Pipe Capacity (25-yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D"/S1/3
Storm C
S = Slope of Basin (%) 1.29 Return f
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) 1415 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes)= 46.20
Q =CIA
C =Weighted C Factor 0.38 (calculated above)
I= 0.78 Tc-0 64(in/hr) 0.92
n =area(acres) 7.30
Qreyuired (Cfs)= 2.53
Provied Pipe Capacity
Pipe Material Concrete Arch Pipe
Mannings (n) 0.013
Size (24" equiv.) 18" x 28.5"
Area (ft) 2.8
Hydraulic Radius (ft) 0.45
Slope (ft/ft) 0.0067
Q=(1.486/n)ARh2/3S1/2
Flow cfs 15.38
Drainage Area#DA EX1
Multi-Family Lot Provided by Madison Engineering, Inc.
Flanders Mill
Basin A
25 Year Storm Event
Calculation of Required Volume for Storm Detention Pond
(Reference: Bozeman Stormwater Master Plan-1982)
Design Rainfall Freq. 25 year(see page III-5 of master plan)
IDF coefficient a 0.78
IDF coefficient b
IDF coefficient n 0.64
Pre-development Calculations Post-development Calculations
C C
Areas(fe):open space 331,735 0.20 Areas(fe): Landscape 136,028 0.20
0.35 Pavement/SW 116,153 0.90
0.50 Roof 79,554 0.90
Total: 331,735 Total: 331,735
total area: 7.62 acres total area: 7.62 acres
composite C: 0.20 composite C: 0.61
Overland t. Overland t.
average slope: 1.75 percent average slope: 1.5 percent
travel distance: 500 feet travel distance: 500 feet
t�: 31 minutes t�: 18 minutes
Channel t. Channel t.
channel t„ minutes channel t.; minutes
Total t.: 31 minutes Total t.: 18 minutes
intensity at tc(fig 23): 1.18 in/hr intensity at t (fig 23): 1.70 in/hr
pre-devel peak runoff: 1.80 cfs post-devel peak runoff: 7.93 cfs
Basin A-Stormwater Calc
Provided by Madison Engineering, Inc.
Multi-Family Lot
Flanders Mill
Basin B-SE Corner
25 Year Storm Event
Calculation of Required Volume for Storm Detention Pond
(Reference: Bozeman Stormwater Master Plan-1982)
Design Rainfall Freq. 25 year(see page III-5 of master plan)
IDF coefficient a 0.78
IDF coefficient b
IDF coefficient n 0.64
Pre-development Calculations Post-development Calculations
C C
Areas(fe):open space 58,680 0.20 Areas(fe): Landscape 17,425 0.20
0.35 Pavement/SW 35,988 0.90
0.50 Roof 5,267 0.90
Total: 58,680 Total: .58.680
total area: 1.35 acres total area: 1.35 acres
composite C: 0.20 composite C: 0.69
Overland t. Overland t.
average slope: 1.75 percent average slope: 1.5 percent
travel distance: 500 feet travel distance: 500 feet
tc: 31 minutes t�: 15 minutes
Channel t. Channel t.
channel t�: minutes channel t.: minutes
Total t.: 31 minutes Total t�: 15 minutes
intensity at t (fig 23): 1.18 in/hr intensity at t (fig 23): 1.90 in/hr
pre-devel peak runoff: 0.32 cfs post-devel peak runoff: 1.77 cfs
Basin B-Stormwater Calc
APPENDIX C
STORM SEWER FACILITIES
CALCULATIONS
CHASE 7A 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (f,2) C *Area
ROW-Tanzanite 0.76 5993 4570
ROW-Ryun Sun 0.71 28807 20525
ROW-Oak 0.68 33283 22633
Low-Med Density Residential 0.35 88507 30978
ROW-Oak 0.68 35329 24024
Total 191920 102729
A =Area(acres) 4.41
C=Weighted C Factor 0.54
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i= 0.78x 0.64(25-yr Storm, Fig. 1-3, COB Design Standards)
x= storm duration (hrs) 0.33 (DA#7A1)
i=rainfall intensity(in.1hr.) 1.59
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0.54 (calculated above)
i= rainfall intensity(in./hr.) 1.59 (calculated above)
A=Area(acres) 4.41 (calculated above)
Q=25-yr Pipe Flow Rate(cfs) 3.74
Stormwater Chase 7A Sizing
Determine slope of stormwater chase
slope (ft/ft) 0.015
Calculate chase capacity
chase depth (feet) 0.50
Chase width (feet) 1.50
Mannings#, n (for concrete) 0.013
X-sect. area (ft) 0.750
Perimeter(ft) 2.500
Hydr. Radius, R(ft) 0.3000
slope(ft/ft) 0.015
iQf.11 WS) 4.71
PIPE VA 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 7A Location: SWALE 7A CULVERT
0
INPUT
D= 15 inches
_____
d= 14.07 inches
Mannings Formula d ► n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213SI12 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
V=(1.49/n)Rh213sii2
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
z Wetted Hydraulic
Area,ft Perimeter,ft 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
PIPE # 713 (ST Inlet 713 Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C *Area
ROW-Oak 0 6.1 38310 26051
ROW-Windrow O.71 26838 18766
Low-Med Density Residential a 3r i-009 12953
Total 1016.58 Fi 7 770
A =Area(acres) 2.33
C=Weighted C Factor 0.57
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i = 0.78x 0.64(25-yr Storm, Fig. 1-3, COB Design Standards)
x= storm duration (hrs) 0.19
I=rainfall intensity(in.1hr.) 2.28
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0.57 (calculated above)
i = rainfall intensity(in./hr.) 2.28 (calculated above)
A=Area(acres) 2.33 (calculated above)
Q(25-yr Pipe Flow Rate) (cfs)= 3.02
Q 25- r Pipe Flow Rate(cfs)) from Multi-Family Basin B = 1.77
Q(total) (cfs)= 4.79
PIPE # 7B (ST Inlet 7B Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 4B Location: ST Inlet 4B Outlet Pipe
� e
INPUT
D= 18 inches________
d= 16.88 inches
Mannings Formula d7 n= 0.013 mannings
p 0= 57.7 degrees
Q=(1.486/n)ARh213SI12 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh2i3S112
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity ft/s flow,cfs
Perimeter,ft Radius,ft
PVC 0.013
1.72 3.96 0.44 1 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
PIPE # 7C (ST Inlet 7C Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 1) C*Area
ROW-Oak 0.68 38310 26051
ROW-Windrow 0.71 26338 18766
Low-Med Density Residential 0.35 37009 12953
ROW-Oak 0.68 23249 15809
ROW-Windrow 0.71 26082 18583
Low-Med Density Residential 0.35 95504 33427
Total 246493 125590
A =Area(acres) 5.66
C= Weighted C Factor 0.51
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i= 0.78z o.s4(25-yr Storm, Fig. 1-3, COB Design Standards)
x = storm duration (hrs) 0.23 (DA#7C)
i=rainfall intensity(in.1hr.) 2.01
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.51 (calculated above)
i= rainfall intensity(in./hr.) 2.01 (calculated above)
A =Area (acres) 5.66 (calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 5.81
Q(25- r Pipe Flow Rate(cfs)) from Multi-Family Basin B = 1.77
Q(total) (cfs)= 7.58
PIPE # 7C (ST Inlet 7C Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 7C Location: ST Inlet 7C Outlet Pipe
� e
INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213S112 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh213S'i2
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity fUs flow,cfs
Perimeter,ft Radius,ft
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
CHASE 7F 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2) C *Area
ROW-Windrow 0.71 12485 8895
ROW-Broken Spur 0.78 5718 4432
Low-Med Density Residential 0.35 14442 5055
Total 32645 18382
A =Area(acres) 0.75
C= Weighted C Factor 0.56
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i = 0.78x o.s4 (25-yr Storm, Fig. 1-3, COB Design Standards)
x = storm duration (hrs) 0.10 (DA#7F)
i=rainfall intensity(in.1hr.) 3.42
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0.56 (calculated above)
i= rainfall intensity(in./hr.) 3.42 (calculated above)
A =Area(acres) 0.75 (calculated above)
Q=25-yr Pipe Flow Rate(cfs) 1.44
Stormwater Chase 7F Sizing
Determine slope of stormwater chase
slope (ft/ft) 0.015
Calculate chase capacity
chase depth (feet) 0.50
Chase width (feet) 1.00
Mannings#, n (for concrete) 0.013
X-sect. area(ft) 0.500
Perimeter(ft) 2.000
Hydr. Radius, R(ft) 0.2500
slope(ft/ft) 0.015
Qf„u(cfs) 2.78
PIPE # 7E (ST OUTLET 7E Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft Z) C*Area
ROW-Oak -0.68 38310 2t5C1.,1
ROW-Windrow 0.7,1 25338 16766
Low-Med Density Residential 0.-`5 37009 12953
ROW-Oak C.68 232449 16609
ROW-Windrow 0.71 26082 18583
Low-Med Density Residential 0.35 95504 33427
ROW-Windrow 0.71 12485 8895
ROW-Broken Spur ,+ 7 8 5718 4432
Low-Med Density Residential 0 35 14442 5055
Low-Med Density Residential 0.35 9767 3418
OS 0.20 16207 3241
Total 305112 150631
A =Area(acres) 7.00
C= Weighted C Factor 0.49
2. Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas)
i= 0.78x o.64(25-yr Storm, Fig. 1-3, COB Design Standards)
x= storm duration (hrs) 0.23 (DA VC)
I=rainfall intensity(in.1hr.) 2.01
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0491(calculated above)
i= rainfall intensity(in./hr.) 2.01 (calculated above)
A=Area(acres) 70'0'.(calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 6.96
Q(25- r Pipe Flow Rate cfs from Multi-Family Basin B= 1.77
Q(total) (cfs)= 8.73
PIPE # 7E (ST OUTLET 7E Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 7E Location: ST OUTLET 7E Outlet Pipe
� e
INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula d 4 n= 0.013 mannings
D 0= 57.7 degrees
0=(1.486/n)ARh213S112 S= 0.0064 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh2i3S'12
S=slope of channel Q=V x A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity fUs flow,cfs
Perimeter,ft Radius,ft
PVC 0.013
1.72 3.96 0.44 5.25 9.04 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
PIPE # 7G (ST INLET 7G Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2) C "Area
ROW - Broken Spur 0.78 7180 5564
ROW-Harvest Parkway 0.73 10447 7595
Total 17627 13160
A =Area(acres) 0.40
C=Weighted C Factor 0.75
2. Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas)
i=0.78x o.64 (25-yr Storm, Fig. 1-3, COB Design Standards)
x =storm duration (hrs) 0.30 (DA#MF 2)
i=rainfall intensity(in.1hr.) 1.69
3. Calculate 25-yr Pond Outflow Rate
Q=CiA
C= Rational Method Runoff Coefficient 0.75 (calculated above)
i= rainfall intensity(in./hr.) 1.69 (calculated above)
A =Area(acres) 0.40 (calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 0.51
Q (25-yr Pipe Flow Rate(cfs)) from Multi-Family Basin A = 7.93
Q(total) (cfs)= 8.44
PIPE # 7G (ST INLET 7G Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 7G Location: ST INLET 7G Outlet Pipe
- - e
\� INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213S112 IF S= 0.01 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh213S1i2
S=slope of channel Q=V x A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity ft/s flow,cfs
Perimeter,ft Radius,ft
PVC 0.013
1.72 3.96 0.44 1 6.56 11.30 PE(<9"dia) 0.015
PE(>12"dia) 0.02
PE(9-12"dia) 0.017
CN1P 0.025
ADS N12 0.012
HCMP 0.023
Colic 0.013
PIPE # 7H (ST INLET 7H Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area(ft 2) C *Area
ROW-Broken Spur 0.78 7180 5564
ROW-Harvest Parkway 0.73 10447 7595
ROW-Broken Spur 0.78 1061 822
ROW-Harvest Parkway 0.73 8742 6356
Total 27430 20338
A =Area(acres) 0.63
C= Weighted C Factor 0.74
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i = 0.78x o.s4(25-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.30 (DA#7G)
I=rainfall intensity(in.1hr.) 1.69
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0.74 (calculated above)
i = rainfall intensity(in./hr.) 1.69 (calculated above)
A=Area (acres) 0.63 (calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 0.79
Q(25-yr Pipe Flow Rate(cfs))from Multi-Family Basin A = 7.93
Q(total) (cfs)= 8.72
PIPE # 7H (ST INLET 7H Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 7H Location: ST INLET 7H Outlet Pipe
00
INPUT
D= 18 inches
d= 16.88 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh2i3S'n S= 0.0119 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh2/3S'i2
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
z Wetted Hydraulic
Area,ft Perimeter,ft Radius,ft velocity ft/s flow,cfs
PVC 0.013
1.72 3.96 0.44 7.16 12.33 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
PIPE # 6A (ST Inlet 6A Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (It 2) C "Area
ROW-Ryun Sun (6A) 0.71 9500 6769
Low-Med Density Residential (6A) 0.35 35256 12340
ROW-Broken Spur (7G) 0.78 7180 5564
ROW-Harvest Parkway 7G 0.73 10447 7595
ROW - Broken Spur (7H) 0.78 1061 822
ROW-Harvest Parkway (7H) 0.73 8742 6356
Total 72186 39446
A =Area(acres) 1.66
C= Weighted C Factor 0.55
2. Calculate Rainfall Intensity(Duration=Max Tc from Contributing Drainage Areas)
i= 0.78x o.s4 (25-yr Storm, Fig. 1-3, COB Design Standards)
x= storm duration (hrs) 0.09
i=rainfall intensity(in.1hr.) 3.64
3. Calculate 25-yr Pond Outflow Rate
Q =CiA
C = Rational Method Runoff Coefficient 0.55 (calculated above)
i = rainfall intensity(in./hr.) 3.64 (calculated above)
A =Area(acres) 1.66 (calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 3.30
Q(25-yr Pipe Flow Rate(cfs)) from Multi-Family Basin A = 7.93
Q(total) (cfs)= 11.23
PIPE # 6A (ST Inlet 6A Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 6A Location: ST Inlet 6A Outlet Pipe
INPUT
D= 21 inches
d= 19.70 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213S112 S= 0.0111 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh2i3S1n
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
z Wetted Hydraulic
Area,ft Perimeter,ft Radius,ft velocity ft/s flow,cfs
PVC 0.013
2.34 4.62 0.51 7.66 1T:96 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
PIPE # 613 (ST Inlet 613 Outlet Pipe) 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2) C *Area
ROW-Harvest Parkway (613) 0.73 1790 1301
ROW- Ryun Sun (6B) 0.71 9891 7048
Low-Med Density Residential 613 0.35 35256 12340
ROW-Ryun Sun (6A) 0.71 9500 6769
Low-Med Density Residential (6A) 0.35 35256 12340
ROW-Broken Spur (7G) 0.78 7180 5564
ROW-Harvest Parkway (7G) 0.73 10447 7595
ROW-Broken Spur (71-1) 0.78 1061 822
ROW-Harvest Parkway (7H) 0.73 8742 6356
Total 119124 60135
A =Area(acres) 2.73
C= Weighted C Factor 0.50
2. Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas)
i = 0.78x o.64 (25-yr Storm, Fig. 1-3, COB Design Standards)
x = storm duration (hrs) 0.09
i=rainfall intensity(in.1hr.) 3.64
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.50 (calculated above)
i = rainfall intensity(in./hr.) 3.64 (calculated above)
A=Area(acres) 2.73 (calculated above)
Q 25-yr Pipe Flow Rate(cfs)= 5.03
Q 25- r Pipe Flow Rate(cfs)) from Multi-Family Basin A = 7.93
Q(total)(cfs)= 12.96
PIPE # 6B (ST Inlet 6B Outlet Pipe) 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 6B Location: ST Inlet 6B Outlet Pipe
f0
INPUT
D= 21 inches
d= 19.70 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213S112 S= 0.0099 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh213SI12
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity ft/s flow,cfs
Perimeter,ft Radius,ft
PVC 0.013
2.34 4.62 0.51 1 7.24 16.96 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
CHASE 71 & PIPE #71 25-YR OUTFLOW RATE
REQUIRED CAPACITY
1. Calculate Area and Weighted C Factor
Contributing Area C Area (ft 2) C"Area
ROW-Broken Spur 0.78 32586 25254
Park 0.35 77537 27138
Total 110123 52392
A =Area(acres) 2.53
C= Weighted C Factor 0.48
2. Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas)
i=0.78z o.s4(25-yr Storm, Fig. 1-3, COB Design Standards)
x =storm duration (hrs) 0.26 (DA#71)
i=rainfall intensity(in.1hr.) 1.83
3. Calculate 25-yr Pond Outflow Rate
Q = CiA
C= Rational Method Runoff Coefficient 0.48 (calculated above)
i= rainfall intensity(in./hr.) 1.83 (calculated above)
A=Area(acres) 2.53 (calculated above)
Q=25-yr Pipe Flow Rate(cfs) 2.20
Stormwater Chase 71 Sizing
Determine slope of stormwater chase
slope (ft/ft) 0.015
Calculate chase capacity
chase depth (feet) 0.50
Chase width (feet) 1.00
Mannings#, n (for concrete) 0.013
X-sect. area(ft) 0.500
Perimeter(ft) 2.000
Hydr. Radius, R (ft) 0.2500
slope (ft/ft) 0.015
iQf.11(cfS) 2.78
PIPE #71 25-YR OUTFLOW RATE
MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY)
Pipe: 71 Location: OUTLET STRUCTURE 71 Outlet Pipe
0
/ INPUT
D= 15 inches____
d= 14.07 inches
Mannings Formula d n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARh213S112 S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter
V=(1.49/n)Rh2i3st i2
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Area,ft2 Wetted Hydraulic velocity ft/s flow,cfs
Perimeter,ft Radius,ft
PVC 0.013
1.20 3.30 0.36 1 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
Cone 0.013
PIPE # E1 (Culvert Draining DA# EX1) 25-YR OUTFLOW RATE
Contributing Area C Area(fe) C * Area
Park/Open Space (EX 1) 0.20 132360 26472
Transfer Station (EX 1) 0.5 185715 92858
Total 318075 119330
C =Weighted C Factor 0.38
A=Area (acres) 7.30
2. Calculate Rainfall Intensity (Duration =Max Tc from Contributing Drainage Areas)
i = 0.78x 0"' (25-yr Storm, Fig. 1-3, COB Design Standards)
x = storm duration (hrs) 0.77 (DA EX1)
i = rainfall intensity(in./hr.) 0.92
3. Calculate 25-yr Pipe Flow Rate
Q = CiA
C = Rational Method Runoff Coefficient 0.38 (calculated above)
i = rainfall intensity (in./hr.) 0.92 (calculated above)
A = Area (acres) 7.30 (calculated above)
Q = 25-yr Pipe Flow Rate (cfs) 2.53
PROVIDED PIPE CAPACITY
Pipe Material Concrete Arch Pipe
Mannings (n) 0.013
Size (24" equiv.) 18" x 28.5"
Area (ft) 2.8
Hydraulic Radius (ft) 0.45
Slope (ft/ft) 0.0067
Q=(1.486/n)ARh213SI12
Flow cfs 15.38
Drainage Area#PIPE E1
APPENDIX D
POND SIZING CALCULATIONS
DETENTION POND # 7E
REQUIRED VOLUME
1. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area ft2) C *Area
ROW-Oak (7B) 0.68 38310 26051
ROW-Windrow (7B) 0.71 26338 18766
Low-Med Density Residential 713 0.35 37009 12953
ROW-Oak (7C) 0.68 23249 15809
ROW-Windrow (7C) 0.71 26082 18583
Low-Med Density Residential (7C) 0.35 95504 33427
ROW-Windrow (7F) 0.71 12485 8895
ROW-Broken Spur (7F) 0.78 5718 4432
Low-Med Density Residential (7F) 0.35 14442 5055
Low-Med Density Residential (7E) 0.35 9767 3418
OS 7E) 0.20 16207 3241
Dense Residential(Basin B) 0.69 58680 40489
Total 363792 191121
---------------------------------
A =Area(acres) 8.35 Storm
C=Weighted C Factor 0.53 Return (yrs) Cf
12 to 10 1
2. Calculate T°(Pre-Development) ;11 to 25 1.1
Tc Overland Flow 26 to 50 1.2
Tc= 1.87 (1.1-CCf)D'/2/S1i3 :51 to 100 1.25
.-------------------------------
S= Slope of Basin (%) 1.30
C = Rational Method Runoff Coefficient 0.2
Cf= Frequency Adjustment Factor 1
D= Length of Basin (ft) 288
Tc(Pre-Development)(minutes) 26
3. Calculate Rainfall Intensity(Duration=Pre-Development Tc)
i = 0.64-o.65 (10-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.44 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 1.10
4. Calculate Runoff Rate(Pre-Development)
Q= CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i= rainfall intensity(in./hr.) 1.10 (calculated above)
A=Area (acres) 8.35 (calculated above)
Q=Runoff Rate (Pre-Development) (cfs) 1.83
5. Calculate Required Pond Volume
Total Area (acres) = 8.35 acres
Weighted C = 0.53
Discharge Rate (cfs) = 1.83 cfs (Equal to Pre-Development Runoff Rate)
Duration(min) Duratio Intensity Q.� (cfs) Runoff Release Required
3
n(hrs) (in/hr) Volume Volume Storage(ft)
)
18 0.30 1.40 6.14 6633 1979 4653
19 0.32 1.35 5.93 6759 2089 4670
20 0.33 1.31 5.73 6882 2199 4683
21 0.35 1.27 5.56 7000 2309 4691
22 0.37 1.23 5.39 7115 2419 4696
23 0.38 1.19 5.24 7227 2529 4698
24 0.40 1.16 5.09 7335 2639 4696
25 0.42 1.13 4.96 7441 2749 4692
26 0.43 1.10 4.84 7544 2859 4685
27 0.45 1.08 4.72 7644 2969 4675
PROVIDED VOLUME (ft') 5334
OUTLET STRUCTURE SLOT
Q=CLH l
Q = Discharge(cfs) 1.83
C = Weir Coefficient 3.33 (per COB Design Standards)
H = Head (ft) 1.5
L= Horizontal Length (ft) 0.30
L=Slot Width(inches) 3.6
Multi-Family Lot (Basin A) - Flow to FMR Det. Pond
**Contributing Area, C Factor,and Time of Concentration provided by Madison Engineering
REQUIRED VOLUME
1. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area(ft 2) C *Area
Dense Residential
Landscape 0.20 136028 27206
Pavement/SW 0.90 116153 104538
Roof 0.90 79554 71599
Total 331735 203342
-------------------------------
A =Area(acres) 7.62 Storm
C=Weighted C Factor 0.61 Return (yrs) Cf
;2 to 10 1
2. Calculate T, (Pre-Development) 11 to 25 1.1
Tc Overland Flow 126 to 50 1.2
Tc= 1.87 (1.1-CCf)D'/2/S1i3 :51 to 100 1.25
:--------------------------------
S= Slope of Basin (%) 1.75
C = Rational Method Runoff Coefficient 0.2
Cf= Frequency Adjustment Factor 1
D= Length of Basin (ft) 500
Tc(Pre-Development) (minutes) 31
3. Calculate Rainfall Intensity(Duration=Pre-Development Tc)
i = 0.64x o.s5(10-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.52 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 0.98
4. Calculate Runoff Rate(Pre-Development)
Q = CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i = rainfall intensity(in./hr.) 0.98 (calculated above)
A =Area (acres) 7.62 (calculated above)
Q=Runoff Rate (Pre-Development) (cfs) 1.49
5. Calculate Required Pond Volume
Total Area (acres) = 7.62 acres
Weighted C = 0.61
Discharge Rate (cfs) = 1.49 cfs (Equal to Pre-Development Runoff Rate)
Retained Volume (0.5" Impervious) = 8154 cf
Time of Release to ST Inlet 7G = 28 min
Runoff Release
Duration Intensity Volume
Duration(min) Q;� (cfs) Volume(to
(hrs) (in/hr) (within ST Inlet 7G)
Basin A)
1 0.02 9.16 42.77 2566 0
2 0.03 5.84 27.26 3271 0
3 0.05 4.49 20.94 3769 0
4 0.07 3.72 17.37 4169 0
5 0.08 3.22 15.02 4507 0
6 0.10 2.86 13.35 4804 0
7 0.12 2.59 12.07 5071 0
8 0.13 2.37 11.07 5313 0
9 0.15 2.20 10.25 5537 0
10 0.17 2.05 9.57 5745 0
11 0.18 1.93 9.00 5940 0
12 0.20 1.82 8.50 6123 0
13 0.22 1.73 8.07 6297 0
14 0.23 1.65 7.69 6463 0
15 0.25 1.58 7.36 6621 0
16 0.27 1.51 7.05 6772 0
17 0.28 1.45 6.78 6917 0
18 0.30 1.40 6.53 7057 0
19 0.32 1.35 6.31 7192 0
20 0.33 1.31 6.10 7322 0
21 0.35 1.27 5.91 7448 0
22 0.37 1.23 5.74 7570 0
23 0.38 1.19 5.57 7689 0
24 0.40 1.16 5.42 7804 0
25 0.42 1.13 5.28 7917 0
26 0.43 1.10 5.14 8026 0
27 0.45 1.08 5.02 8133 0
28 0.47 1.05 4.90 8237 83
29 0.48 1.03 4.79 8339 184
30 0.50 1.00 4.69 8438 284
31 0.52 0.98 4.59 8536 381
32 0.53 0.96 4.50 8631 477
33 0.55 0.94 4.41 8725 570
34 0.57 0.93 4.32 8816 662
35 0.58 0.91 4.24 8906 752
36 0.60 0.89 4.16 8994 840
37 0.62 0.88 4.09 9081 927
38 0.63 0.86 4.02 9166 1012
39 0.65 0.85 3.95 9250 1096
40 0.67 0.83 3.89 9332 1178
41 0.68 0.82 3.83 9413 1259
42 0.70 0.81 3.77 9493 1339
43 0.72 0.79 3.71 9572 1417
44 0.73 0.78 3.65 9649 1494
45 0.75 0.77 3.60 9725 1571
46 0.77 0.76 3.55 9800 1646
47 0.78 0.75 3.50 9874 1720
48 0.80 0.74 3.45 9947 1793
49 0.82 0.73 3.41 10019 1865
50 0.83 0.72 3.36 10090 1936
51 0.85 0.71 3.32 10161 2006
52 0.87 0.70 3.28 10230 2075
53 0.88 0.69 3.24 10298 2144
54 0.90 0.69 3.20 10366 2211
55 0.92 0.68 3.16 10433 2278
56 0.93 0.67 3.12 10499 2344
57 0.95 0.66 3.09 10564 2409
58 0.97 0.65 3.05 10628 2474
59 0.98 0.65 3.02 10692 2538
60 1.00 0.64 2.99 10755 2601
61 1.02 0.63 2.96 10818 2663
62 1.03 0.63 2.92 10879 2725
63 1.05 0.62 2.89 10941 2786
64 1.07 0.61 2.86 11001 2847
65 1.08 0.61 2.84 11061 2906
66 1.10 0.60 2.81 11120 2966
67 1.12 0.60 2.78 11179 3024
68 1.13 0.59 2.75 11237 3082
69 1.15 0.58 2.73 11294 3140
70 1.17 0.58 2.70 11351 3197
71 1.18 0.57 2.68 11408 3254
72 1.20 0.57 2.65 11464 3310
73 1.22 0.56 2.63 11519 3365
74 1.23 0.56 2.61 11574 3420
75 1.25 0.55 2.58 11629 3474
76 1.27 0.55 2.56 11683 3529
77 1.28 0.54 2.54 11737 3582
78 1.30 0.54 2.52 11790 3635
79 1.32 0.54 2.50 11842 3688
80 1.33 0.53 2.48 11895 3740
81 1.35 0.53 2.46 11946 3792
82 1.37 0.52 2.44 11998 3843
83 1.38 0.52 2.42 12049 3894
84 1.40 0.51 2.40 12099 3945
85 1.42 0.51 2.38 12150 3995
86 1.43 0.51 2.36 12200 4045
87 1.45 0.50 2.35 12249 4095
88 1.47 0.50 2.33 12298 4144
89 1.48 0.50 2.31 12347 4192
90 1 1.501 0.491 2.301 123951 4241
EXISTING DETENTION POND (FMR)
REQUIRED VOLUME
1. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area(ft 2) C *Area
ROW-Ryun Sun (6A) 0.71 9500 6769
Low-Med Density Residential (6A) 0.35 35256 12340
ROW- Harvest Parkway (6B) 0.73 1790 1301
ROW- Ryun Sun (6B) 0.71 9891 7048
Low-Med Density Residential 66 0.35 35256 12340
Dense Residential Basin A 0.61 331735 202358
ROW-Broken Spur (7G) 0.78 7180 5600
ROW-Harvest Parkway (7G) 0.73 10447 7626
ROW- Broken Spur (7H) 0.78 1061 828
ROW- Harvest Parkway (7H) 0.73 8742 6382
Flanders Mill Road ROW (F1) 0.76 59011 44996
Flanders Mill Road ROW (F2) 0.70 59025 41318
Harvest Pkwy ROW (F2) 0.73 11137 8097
Forage Drive ROW (F2) 0.71 10550 7517
Oak Street ROW (F1+F2) 0
Hardscape 0.95 8326 7910
Landscape 0.20 2823 565
Open Space/Park (F3) 0.20 39438 7888
Low-Med Density Residential (F3) 0.35 23177 8112
Total 664346 388992
Including Multi-Family Basin A
A =Area(acres) 15.25 Storm
C=Weighted C Factor 0.59 ; Return (yrs) Cf
;2 to 10 1
Excluding Multi-Family Basin A 11 to 25 1.1
A =Area(acres) 7.64 126 to 50 1.2
C=Weighted C Factor 0.56 151 to 100 1.25
- - - -----------------
2. Calculate Tc (Pre-Development)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D'/2/S'/3
S= Slope of Basin (%) 1.19
C = Rational Method Runoff Coefficient 0.2
Cf= Frequency Adjustment Factor 1
D= Length of Basin (ft) 3189
Tc(Pre-Development) (minutes) 90
3. Calculate Rainfall Intensity(Duration =Pre-Development Tc)
i =0.64x o.s5 (10-yr Storm, Fig. 1-3, COB Design Standards)
x =storm duration (hrs) 1.49 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 0.49
4. Calculate Runoff Rate(Pre-Development)
Q = CiA
C= Rational Method Runoff Coefficient 0.2 (open land)
i = rainfall intensity(in./hr.) 0.49 (calculated above)
A=Area (acres) 15.25 (calculated above)
Q=Runoff Rate (Pre-Development) (cfs) 1.50
Runoff Rate (Pre-Development) (cfs) FMR Design 1.78
5. Calculate Required Pond Volume
Total Area (acres) = 15.25 acres
Weighted C = 0.59
Discharge Rate(cfs) = 1.78 cfs (Equal to Pre-Development Runoff Rate)
Required Pond Volume(W) = 6142 (See attached table)
Provided Pond Volume(ft9) F 14502
OUTLET STRUCTURE SLOT
Q=CLH 312
Q = Discharge(cfs) 1.50
C=Weir Coefficient 3.33 (per COB Design Standards)
H= Head (ft) 1.5
L= Horizontal Length (ft) 0.25
L =Slot Width(inches) Current Design 2.9
Ex. Slot Width (inches) FMR Design 3.5
Storage Table
Runoff Runoff
Duration Intensity Volume Release Required
Duration(min) (hrs) (in/hr) Qin(cfs) (Excluding Volume Volume Storage (ft)
Basin A) (Basin A)
1 0.02 9.16 39.25 2355 0 107 2248.43
2 0.03 5.84 25.02 3002 0 214 2788.28
3 0.05 4.49 19.22 3460 0 320 3139.19
4 0.07 3.72 15.94 3826 0 427 3398.88
5 0.08 3.22 13.79 4137 0 534 3602.87
6 0.10 2.86 12.25 4409 0 641 3768.66
7 0.12 2.59 11.08 4654 0 748 3906.30
8 0.13 2.37 10.16 4877 0 854 4022.17
9 0.15 2.20 9.41 5082 0 961 4120.60
10 0.17 2.05 8.79 5273 0 1068 4204.69
11 0.18 1.93 8.26 5452 0 1175 4276.75
12 0.20 1.82 7.81 5620 0 1282 4338.53
13 0.22 1.73 7.41 5780 0 1388 4391.40
14 0.23 1.65 7.06 5932 0 1495 4436.48
15 0.25 1.58 6.75 6077 0 1602 4474.66
16 0.27 1.51 6.47 6215 0 1709 4506.68
17 0.28 1.45 6.22 6349 0 1816 4533.17
18 0.30 1.40 6.00 6477 0 1922 4554.66
19 0.32 1.35 5.79 6601 0 2029 4571.60
20 0.33 1.31 5.60 6720 0 2136 4584.37
21 0.35 1.27 5.43 6836 0 2243 4593.32
22 0.37 1.23 5.26 6948 0 2350 4598.73
23 0.38 1.19 5.11 7057 0 2456 4600.88
24 0.40 1.16 4.97 7163 0 2563 4599.99
25 0.42 1.13 4.84 7266 0 2670 4596.27
26 0.43 1.10 4.72 7367 0 2777 4589.91
27 0.45 1.08 4.61 7465 0 2884 4581.06
28 0.47 1.05 4.50 7560 83 2990 4652.51
29 0.48 1.03 4.40 7654 184 3097 4740.93
30 0.50 1.00 4.30 7745 284 3204 4825.02
31 0.52 0.98 4.21 7834 381 3311 4905.02
32 0.53 0.96 4.13 7922 477 3418 4981.14
33 0.55 0.94 4.04 8008 570 3524 5053.59
34 0.57 0.93 3.97 8092 662 3631 5122.53
35 0.58 0.91 3.89 8174 752 3738 5188.15
36 0.60 0.89 3.82 8255 840 3845 5250.60
37 0.62 0.88 3.75 8335 927 3952 5310.01
38 0.63 0.86 3.69 8413 1012 4058 5366.53
39 0.65 0.85 3.63 8490 1096 4165 5420.28
40 0.67 0.83 3.57 8566 1178 4272 5471.38
41 0.68 0.82 3.51 8640 1259 4379 5519.93
42 0.70 0.81 3.46 8713 1339 4486 5566.04
43 0.72 0.79 3.41 8785 1417 4592 5609.79
44 0.73 0.78 3.35 8856 1494 4699 5651.29
45 0.75 0.77 3.31 8926 1571 4806 5690.62
46 0.77 0.76 3.26 8995 1646 4913 5727.85
47 0.78 0.75 3.21 9063 1720 5020 5763.06
48 0.80 0.74 3.17 9130 1793 5126 5796.31
49 0.82 0.73 3.13 9196 1865 5233 5827.69
50 0.83 0.72 3.09 9261 1936 5340 5857.24
51 0.85 0.71 3.05 9326 2006 5447 5885.03
52 0.87 0.70 3.01 9389 2075 5554 5911.12
53 0.88 0.69 2.97 9452 2144 5660 5935.55
54 0.90 0.69 2.94 9514 2211 5767 5958.39
55 0.92 0.68 2.90 9575 2278 5874 5979.67
56 0.93 0.67 2.87 9636 2344 5981 5999.45
57 0.95 0.66 2.84 9696 2409 6088 6017.77
58 0.97 0.65 2.80 9755 2474 6194 6034.67
59 0.98 0.65 2.77 9814 2538 6301 6050.19
60 1.00 0.64 2.74 9872 2601 6408 6064.37
61 1.02 0.63 2.71 9929 2663 6515 6077.25
62 1.03 0.63 2.68 9985 2725 6622 6088.86
63 1.05 0.62 2.66 10042 2786 6728 6099.23
64 1.07 0.61 2.63 10097 2847 6835 6108.40
65 1.08 0.61 2.60 10152 2906 6942 6116.40
66 1.10 0.60 2.58 10206 2966 7049 6123.26
67 1.12 0.60 2.55 10260 3024 7156 6129.00
68 1.13 0.59 2.53 10314 3082 7262 6133.66
69 1.15 0.58 2.50 10366 3140 7369 6137.25
70 1.17 0.58 2.48 10419 3197 7476 6139.81
71 1.18 0.57 2.46 10471 3254 7583 6141.36
72 1.20 0.57 2.44 10522 3310 7690 6141.93
73 1.22 0.56 2.41 10573 3365 7796 6141.52
74 1.23 0.56 2.39 10623 3420 7903 6140.18
75 1.25 0.55 2.37 10673 3474 8010 6137.91
76 1.27 0.55 2.35 10723 3529 8117 6134.74
77 1.28 0.54 2.33 10772 3582 8224 6130.69
78 1.30 0.54 2.31 10821 3635 8330 6125.77
79 1.32 0.54 2.29 10869 3688 8437 6120.01
80 1.33 0.53 2.27 10917 3740 8544 6113.42
81 1.35 0.53 2.26 10965 3792 8651 6106.02
82 1.37 0.52 2.24 11012 3843 8758 6097.82
83 1.38 0.52 2.22 11059 3894 8864 6088.85
84 1.40 0.51 2.20 11105 3945 8971 6079.11
85 1.42 0.51 2.19 11151 3995 9078 6068.63
86 1.43 0.51 2.17 11197 4045 9185 6057.41
87 1.45 0.50 2.15 11243 4095 9292 6045.47
88 1.47 0.50 2.14 11288 4144 9398 6032.83
89 1.48 0.50 2.12 11332 4192 9505 6019.49
90 1 1.501 0.491 2.111 113771 42411 9612 6005.47
DETENTION POND # 71
REQUIRED VOLUME
1. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area(It 2 C *Area
ROW- Broken Spur 0.78 32586 25254
Park 0.35 77537 27138
Total 110123 52392
A =Area(acres) 2.53 Storm
C= Weighted C Factor 0.48 Return (yrs) Cf
12 to 10 1
2. Calculate T°(Pre-Development) ;11 to 25 1.1
Tc Overland Flow :26 to 50 1.2
Tc= 1.87 (1.1-CC)D1f2/S1/3 :51 to 100 1.25
1------------------------------
S = Slope of Basin (%) 1.21
C = Rational Method Runoff Coefficient 0.2
Cf = Frequency Adjustment Factor 1
D= Length of Basin (ft) 558
Tc(Pre-Development) (minutes) 37
3. Calculate Rainfall Intensity(Duration =Pre-Development Tc)
i = 0.64z o.65 (10-yr Storm, Fig. 1-3, COB Design Standards)
x =storm duration (hrs) 0.62 (Tc Pre-Development)
i=rainfall intensity(in./hr.) 0.87
4. Calculate Runoff Rate(Pre-Development)
Q = CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i = rainfall intensity(in./hr.) 0.87 (calculated above)
A=Area (acres) 2.53 (calculated above)
Q=Runoff Rate (Pre-Development) (cfs) 0.44
5. Calculate Required Pond Volume
Total Area (acres) = 2.53 acres
Weighted C = 0.48
Discharge Rate (cfs) = 0.44 cfs(Equal to Pre-Development Runoff Rate)
uur IntensityRunoff Release Required
Duration(min) atio (in/hr) Qin (cfs) Volume Volume Storage(ft)
24 0.40 1.16 1.40 2011 635 1376
25 0.42 1.13 1.36 2040 661 1379
26 0.43 1.10 1.33 2068 687 1381
27 0.45 1.08 1.29 2095 714 1382
28 0.47 1.05 1.26 2122 740 1382
29 0.48 1.03 1.23 2149 767 1382
30 0.50 1.00 1.21 2174 793 1381
31 0.52 0.98 1.18 2199 820 1380
32 0.53 0.96 1.16 2224 846 1378
33 0.55 0.94 1.14 2248 872 1375
PROVIDED VOLUME (ft") 2,141
OUTLET STRUCTURE SLOT
Q=CL.f-{3111
Q = Discharge (cfs) 0.44
C =Weir Coefficient 3.33 (per COB Design Standards)
H = Head (ft) 1.5
L = Horizontal Length (ft) 0.07
L =Slot Width(inches) 0.9