HomeMy WebLinkAbout16 - Design Report - West Winds Ph 7 & 8 - Stormwater Stormwater Investigation
For
West Winds Planned Community
Phase 7 & 8 Subdivision
Prepared For:
Mahar Montana
13447 Highway 238
Jacksonville, OR 97350
Prepared By:
BOWL
2090 Stadium Drive
Bozeman,MT 59715
May 2016
22.11728.01
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Table of Contents
Page
Purpose.......................................................................................................................................2
ProjectOverview ........................................................................................................................2
Preliminary Conditions Summary................................................................................................2
Basisof Calculations...................................................................................................................4
StormwaterDetention.............................................................................................................4-5
DrainageBasins......................................................................................................................7-9
Stormwater Treatment and Release...........................................................................................10
ConveyanceFacilities ......................................................................................................... 10-11
Maintenance..............................................................................................................................12
Conclusion................................................................................................................................12
Table 1 —Master Detention Pond Summary................................................................................4
Table2—Sub-Basin Summary................................................................................................ 9
Table 3 — Storm Sewer Capacity Calculations...........................................................................11
Figure 1 —Phase 7 & 8 Stormwater Plan.....................................................................................3
Figure 2—Stormwater Drainage Basins ..................................................................................... 6
Appendices
Appendix A—Conveyance Facility Calculations
Appendix B—Outlet Weir Sizing Calculations
BOWL 1
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Purpose
This engineer's report is intended to address the stormwater management system for the
proposed Phase 7 & 8 Subdivision of the West Winds Planned Community, and will supplement
the Stormwater Investigation Report submitted with the P.U.D Application. This report will
determine the recommended sizing of the master pond outlet weir and conveyance facilities
within the Phase 7 & 8 subdivision. This report was prepared in accordance with the design
criteria set forth in the City of Bozeman's Design Standards and Specifications Policy.
Proiect Overview
The Phase 7 & 8 Subdivision of the West Winds Planned Community contains 60 single-family
lots and public open space lots (see Figure 1). Phase 7 & 8 is located in the northwest portion of
the West Winds Planned Community, which is located in the northwest '/4 of the northwest %,
Section 2, Township 2 South, Range 5 East.
Preliminary Conditions Summary
The pre-development condition of the proposed 21.4-acre Phase 7 & 8 subdivision is agricultural
with no residential structures on-site. The property is currently vacant and has been historically
used for hay production. The site is not currently irrigated, but the property has water rights
through the Farmer's Canal Ditch Company a/k/a Harmon Ditch. The current topography of the
site can be generalized as flat with a consistent slope of approximately 2% from south to north.
There is a seasonal irrigation ditch that runs adjacent to the west side of the subject parcel
running south to north. This watercourse is called the "Section Ditch"which runs the entire
western boundary of the property.
The NRCS Soil Survey has identified three soil types on the property: Amsterdam silt loam
(53B); Meadowcreek loam(510B); and Fairway silt loam(511A). These soil types correlate to
the SCS Hydrologic Soil Group `B". Soil pits were excavated and groundwater monitors were
installed in April 2003 and monitored through September 2003. From these pits and subsequent
pits excavated in April of 2008, it was determined that the soil horizon is typical of the Bozeman
area with approximately 12"to 18"of topsoil underlain with a layer of silty-clay, followed by
sandy gravel. The groundwater depth varied dependant on elevation and proximity to irrigation
channels with a typical minimum depth to water being in the range of 4' to 8' below ground
surface within proposed housing areas.
BOWL 2
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PROJECT 22.11728.01
PHASE 7 & 8 DATE MAY 2016
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West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Basis of Calculations
The calculations and recommendations within this report are based on the regulations set forth in
the City of Bozeman Design Standards and Specifications Policy. The Rational Method was
used to determine the pre-developed release rates. The conveyance facilities, described
further in this report, are based on a 25-year, 2-hour storm event. Overflow conveyance facilities
from the master detention pond are based on a 100-year, 2-hour storm event. Calculations are
provided in the appendices of this report.
Stormwater Detention
There are a total of 53 drainage basins identified within the West Winds (West) development and
surrounding area. The drainage basins are described in further detail below. The runoff from all
drainage basins from Phases 7 & 8, Phase 6 as well as Basins 3, 4, 5, Oak St, DL will be
conveyed north to detention ponds located within the West Winds Development, adjacent to
Baxter Lane. These two detention ponds are the master detention ponds for the West Winds
western development area as discussed in the P.U.D. The east master pond was constructed at
full size during Phase 5, and the west master pond will be constructed at full size during the
widening of Baxter Lane in order to provide the storage required. The widening of Baxter Lane
is by the City of Bozeman and storm calculations for the associated stormwater infrastructure
will be provided by the City's consultant. Table 1 provides a summary of the master detention
ponds, including required storage, the storage volume at a depth of 1 % feet, and an overall depth
of 2 %feet. Detailed calculations for the ponds can be found in the Phase 6 Stormwater
Investigation Report.
Table 1
Master Detention
Pond Summary
Pre-Developed Min.Post- Overall
Contributing p WSE Storage
Pond g Pond Type Peak Runoff Rate Developed Volume Storage
Basins (cfs) Required Storage ( fl c Volume
(� (ctJ
Oak Street, Davis
Master Lane,West Winds Detention 10.7 68,106 68,657 140,813
Pond (West)&Baxter
Lane(West)
Both master ponds have been sized to ensure enough space/storage volume for the completion
of Phases 7 & 8. The west and east master detention ponds will be connected hydraulically via
storm pipe so that the two ponds function together as one pond with one common outfall.
The control weir in the east master pond was initially designed so that the pond stores only what
volume is required for Phases 5 and 6 and will only allow the depth of water to reach 1.3'at this
time. For Phase 7 &8,the weir will need to be increased from a width of 1.125' to the full build-
out width of 1.740' allowing for the discharge from the master ponds to match the pre-developed
rate. Please refer to Appendix B for Outlet Weir Sizing Calculations. For more information on
the master detention ponds,refer to the Phase 6 Stormwater Investigation Report.
-_
BOWL 4
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Drainage Basin BL-5 will be conveyed to a small detention pond on Baxter Lane as discussed in
the Phase 5 storm report. Runoff from Basin DL (Davis Lane) was retained in a separate
retention pond which was part of the Davis Lane Roadway Improvements project. This retention
pond will be converted in to the west master detention pond for the West Winds overall western
development area.
BOWL 5
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West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Drainage Basins
Basins 3, 4 and 5 are overall basins of previously-defined sub-basins from the West Winds
Planned Community Phase 5 Stormwater Investigation Report. Basins DL and Oak St. were
previously identified as part of the West Winds Planned Community Phase 5 Stormwater
Investigation. The descriptions for these existing basins are as follows:
Basin 3 is a portion of existing Phases 3 and 4 of the West Winds Development and is
13.06 acres in size. Basin 3 includes 8.50 acres of independent senior living, 2.19 acres
of road right-of-way, and 2.38 acres of single family lots. Runoff from the independent
living areas was calculated using a C-factor of 0.6 and from the roadway rights-of-ways
using a C-factor of 0.75. Runoff from the single family lots was calculated using a C-
factor of 0.5. Runoff from the development will flow to Hunters Way and Breeze Lane
and will be conveyed to Basin 6A via curb and gutter and storm pipe. Runoff will then be
conveyed via the storm sewer system down Hunters Way to the north were it will be
released into the master pond located adjacent to Baxter Lane (see Figures 1 and 2).
Basin 4 is a portion of Phases 3, 4, and 5 West Wind Development and is a total of 25.32
acres in size. The retirement community areas have an estimated C-factor of 0.6. Storm
water from this basin will sheet flow to Windward Ave. within Basin 4. The stormwater
will then be conveyed to the master pond via curb and gutter, storm piping and a
temporary conveyance swale.
Basin 5 is a portion of the Phase 5 West Wind Development and is a total of 2.79 acres in
size and is comprised of road ROW and single-family lots. The single-family lot areas
have an estimated C-factor of 0.5, and the ROW's of 0.75. Storm water from this basin
will sheet flow to Autumn Grove and Spring View Court within Basin 5. The stormwater
will then be conveyed to the master pond via curb and gutter and storm piping.
The Oak Street Basin is 1.34 acres in size and includes the roadway right-of-way for a
portion of existing Oak Street which drains west to northbound Davis Lane. Stormwater
runoff from this area is conveyed via curb and gutter to the stormwater management
facilities of northbound Davis Lane. The flows will then be conveyed north to the master
detention pond.
The Davis Lane Basin is 2.64 acres in size and includes the roadway right-of-way for
northbound Davis Lane. Stormwater runoff from this area will be conveyed via curb and
gutter and storm pipe to the master detention pond.
Basins 6A-R, Ponds, and BL1-6 are previously defined drainage basins from the West Winds
Planned Community Phase 6 Stormwater Investigation. These basins encompass mainly single-
family lots, open space, and road ROW areas. Basins 6A-M will be conveyed through a storm
main in Hunters Way, north to the master pond. Basins 6N-Q will be conveyed through a storm
main in Windward Avenue, to the master pond. BL-4 will drain into a small collection system on
Baxter Lane before discharging into the stormwater conveyance swale that comes from the
master pond. Basins BL1-3 and BL-6 will flow down curb and gutter on Baxter Lane to their
individual collection systems that outlet into the master stormwater ponds.
BOWL 7
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Basins W1-29 are proposed drainage basins based on the proposed road layout of Phase 7 & 8.
These basins encompass mainly single-family lots,open space, and road ROW areas with the
following "C" factors,respectfully; 0.5, 0.2, and 0.75. Basins Wl-W22 will be conveyed
through storm mains in Hunters Way, Windward Avenue, and Spring View Court north to the
master pond. A summary of these basins is shown in the following table.
BOWL 8
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Table 2
Sub-Basin Summary
Phase(s) Basin ID Commercial Single-Family Area Road ROW Open Space/Park Total Basin
Area(ac) (ac) Area(ac) Area(ac) Area(ac)
3,4 3 8.50 2.38 2.19 0.00 13.06
4,5 4 18.48 1.65 4.98 0.21 25.32
5 5 0.00 1.71 0.94 0.14 2.79
Oak St 0.00 0.00 1.34 0.00 1.34
5 DL 0.00 0.00 2.64 0.00 2.64
6 6A 0.00 0.23 0.08 0.00 0.31
6 6B 0.00 0.28 0.10 0.00 0.38
6 6C 0.00 0.31 0.11 0.00 0.42
6 6D 0.00 0.37 0.15 0.00 0.52
6 6E 0.00 0.03 0.30 0.00 0.33
6 6F 0.00 0.00 0.32 0.00 0.32
6 6J 0.28 1.14 0.75 0.26 2.42
6 6K 0.00 0.37 0.28 0.00 0.65
6 6N 0.00 0.39 0.20 0.00 0.59
6 60 0.00 0.36 0.14 0.00 0.50
6 6P 0.00 1.03 0.53 0.00 1.56
6 6Q 0.00 1.01 0.44 0.00 1.45
6 BL-1 0.00 0.00 0.33 0.00 0.33
6 BL-2 0.00 0.00 0.24 0.00 0.24
6 BL-3 0.00 0.00 0.63 0.00 0.63
6 BL-4 0.00 0.00 0.33 0.00 0.33
6 BL-5 0.00 0.00 0.57 0.00 0.57
6 BL-6 0.00 0.00 0.18 0.00 0.18
6 Ponds 0.00 0.43 0.00 2.35 2.78
7.8 W1 0.00 0.98 0.42 0.18 1.58
7,8 W2 0.00 0.28 0.22 0.00 0.50
7,8 W3 0.00 0.83 0.40 0.00 1.23
7,8 W4 0.00 0.77 0.27 0.00 1.04
7,8 W5 0.00 0.16 0.06 0.00 0.22
7.8 W6 0.00 0.73 0.22 0.00 0.95
7,8 W7 0.00 0.65 0.19 0.00 0.84
7,8 W8 0.00 0.85 0.27 0.00 1.12
7.8 Wg 0.00 0.24 0.21 0.00 0.45
7,8 W10 0.00 0.06 0.19 0.00 0.25
7,8 Wll 0.00 0.57 0.33 0.00 0.90
7,8 W12 0.00 0.39 0.14 0.00 0.53
7,8 W13 0.00 0.84 0.32 0.00 1.16
7,8 W14 0.00 0.07 0.17 0.00 0.24
7,8 W15 0.00 0.40 0.13 0.00 0.53
7,8 W16 0.00 0.38 0.14 0.00 0.52
7,8 W17 0.00 0.63 0.22 0.00 0.85
7,8 W18 0.00 0.26 0.09 0.00 0.35
7,8 W19 0.00 0.24 0.15 0.00 0.39
7,8 W 20 0.00 0.00 0.34 0.00 0.34
7,8 W21 0.00 0.04 0.16 0.00 0.20
7,9 W22 0.00 0.19 0.17 0.00 0.36
7,9 W23 0.00 0.03 0.06 0.00 0.09
7,9 W24 0.00 0.00 0.06 0.00 0.06
7,9 W25 0.00 0.00 0.15 0.00 0.15
7,9 W26 0.00 0.72 0.18 0.12 1.02
7,9 W27 0.00 0.16 0.18 0.00 0.34
7,9 W28 0.00 0.72 0.47 0.00 1.19
7.9 W29 0.00 0.01 0.10 0.00 0.11
Existing Drainage Basins from prior Phases of Dow1opment
E3OWL 9
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Stormwater Treatment and Release
The master stormwater detention pond has been designed for the removal of solids, silt, oils,
grease, and other pollutants. The pond has been sized to provide adequate volume and detention
time to allow the settling of solids, silts and other contaminants. The detention pond will use
natural vegetation to limit pollutants. The ponds have also been designed to provide "dead
storage"to allow for infiltration and evapotranspiration per Low Impact Development Practices.
Stormwater will be released from the detention pond at a rate equal to that of the 10-year, pre-
developed storm event. Release will be accomplished through a flow control manhole/structure
equipped with a slotted weir outlet. Discharge structure design is primarily driven by elevation
and head,which requires site-specific designs for each detention pond. Outlet weir sizing
calculations are provided in Appendix B of this report.
Stormwater will be released from the master detention pond into the Harmon Ditch. The flow
control structure will be located at the pond. Released stormwater will be conveyed to the
Harmon Ditch by means of a stormwater conveyance swale.
Conveyance Facilities
Stormwater runoff from this site will be conveyed to a stormwater detention pond at the north
end of the Planned Community, adjacent to Baxter Lane as shown in Figures 1 and 3. The storm
sewer infrastructure to the aforementioned pond will be installed in Phase 7 & 8. The temporary
swales constructed in Phase 6 will be abandoned and reclaimed when subsequent storm drainage
improvements are installed.
Stormwater will be conveyed by means of curb and gutter, catch basins, and storm mains. All
conveyance facilities on the site leading to the detention pond have been sized to handle the 25-
year, 2-hour storm event as required in the City of Bozeman Design Standards and Specifications
Policy. Table 3 summarizes the post-developed runoff rates and required pipe diameters. The
storm sewer mains are shown graphically on Figures 1 and 2.
Storm sewer mains S-lA through S-6 and L-17 service Basins 4-5, 6N-Q, W1-9, Wl 1, W13,
W15, W26-27, and W29. Stormwater in Basins 3, 6A-F, 6J-K, W12, W16-20, W22-24, W28
will be conveyed via storm mains L-7 through L-11C within Hunters Way to the master
detention ponds. Storm sewer mains L-1113 and L-11C will service Basins W21, W25, BL-4,
and BL-6.
Various sizes (15"-36" diameter) of PVC storm mains collect and convey the stormwater from
portions of Phases 3, 4, 5, 6 and 7 & 8 Subdivisions to the detention facilities, as noted below in
Table 3. The gutter and inlet capacities, leaving 0.15' of freeboard on the face of curb, were
found to be adequate for handling the stormwater flows on all roadways with flow-by due to
limitations in inlet capacities considered. See Appendix A for detailed calculations.
Storm water discharge from the master detention ponds will be controlled by a weir structure and
conveyed via storm sewer mains and conveyance swale to Harmon Ditch. The master detention
At,- .
0OWL 10
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
ponds will be surrounded by proposed development on four sides; therefore a typical overflow
outfall arrangement is not possible. Overflow outfall from the pond(s) will also be controlled by
the weir control structure and conveyed via storm sewer mains and the conveyance swale east to
Harmon Ditch. Refer to Appendix B for weir sizing information.
Table 3
Storm Sewer Capacity Calculations
Storm Sewer Post-Developed Pipe Pipe
Main Runoff Rate cfs FDiameter in.) Capacitycfs
SAA 5.12 15 5.78
S-1 B 1.32 15 4.57
S-1 C 0.99 15 4.57
S-1 D 1.14 15 4.57
S-2A 6.96 18 7.28
S-213 1.77 15 4.28
S-3A 9.71 24 18.24
S-313 1.68 15 4.61
S-4A 30.58 30 38.26
S-4B 3.21 15 4.57
S-4C 1.32 15 4.57
S-4 D 2.60 15 4.57
S-4E 1.17 15 4.57
S-5A 38.25 36 60.03
S-513 2.28 15 4.61
S-5C 0.78 15 4.57
S-6 37.49 36 39.46
L-7A 2.18 15 4.57
L-7 20.23 30 30.42
L-8A 20.18 30 34.32
L-813 2.32 15 4.09
L-8132 1.55 15 4.75
L-8C 22.09 30 33.82
L-8D 21.92 30 25.94
L-9A 2.28 15 4.09
L-913 0.80 15 4.57
L-10 21.91 30 25.94
L-11 B 2.24 15 3.29
L-11 C 1.46 15 3.42
L-17 27.79 30 38.04
Standard 24"x 36" square storm drain inlets and 48" and 60" combination manhole and curb
inlets (C.O.B Standard Drawing No. 02720-1 and 02720-1B, respectively) will be used to
capture the stormwater runoff at the points specified on Figure 2. These catch basins are in
conformance with City of Bozeman Design Standards and include a 9" sump for ease of
maintenance.
BOWL ii
West Winds Phase 7 & 8: Stormwater Investigation Report May 2016
Maintenance
The storm drainage system within the Phase 7 & 8 Subdivision is defined as a private and public
system. The mains and catch basins that lie within the publicly dedicated right-of-ways are
defined as public systems. The public systems shall be maintained by the City of Bozeman. The
private system,those facilities that do not lie within the publicly dedicated right-of-ways, will
initially be maintained by the developer and then the Homeowners' Association.
Due to sediment in the storm runoff and other variables, regular maintenance will be required to
maintain proper performance of the storage and drainage network. The following steps are
minimum requirements for the maintenance of the storm facilities.
A) Inspection Program—On an annual basis, the following elements of the storm water
facilities should be inspected for excessive sediment deposits:
1) Catch Basins
2) Curb Cut Openings
3) Storm Mains
4) Detention Ponds
B) Maintenance Program—The following maintenance measures should be completed
based on the inspection program:
1) Catch Basin. & Curb Cut Openings—excessive sediments shall be removed either
manually(with a shovel) or with a vacuum truck and flushed.
2) Storm Mains—Mains shall be flushed if necessary.
3) Detention Pond—A stake will be set six (6) inches above the original bottom of the
basin. If sediment is over the stake, it must be removed and the basin must be
revegetated according to the original landscape plan.
The Homeowners' Association is responsible for conducting the inspection program and
maintaining the storm facilities outside of the public right-of-way—this typically includes the
retention and detention ponds. During the annual stormwater inspection, if any facility within
the street right-of-way needs attention, the Homeowners Association should contact the City of
Bozeman Streets Department and inform them of the problem.
Conclusion
This report establishes the projected stormwater flows, detention requirements and conveyance
recommendations for the Phase 7 & 8 Subdivision of the West Winds Planned Community. The
basis for this report is the approved West Winds P.U.D. application of September 9, 2005 and
P.U.D. modifications approved May 7, 2008.
At:' .
BOWL 12
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Appendix A
CCDI cU cl°H"o ) RS
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Contributing Areas&Weighted C Factors
Pipe Segment Contributing Basins C Factor Area ac
S-IA 5,W2,W5.W26
Commercial 0.6 0.00
Single Family 0.5 2.87
Roads 0.9 1.40
Park 0.2 0.26
Weightedrrotal 0.61 4.53
S-1B W2.W5
Commercial 0.6 0.00
Single Family 0.5 0.44
Roads 0.9 0.28
Park 0.2 0.00
Weighted/Total 0.66 0.72
S-1 C W2
Commercial 0.6 0.00
Single Family 0.5 0.28
Roads 0.9 0.22
Park 0.2 0.00
Weighted/Total 0.68 0.50
S-2A 5,W1-2.W5,W26-27
Commercial 0.6 0.00
Single Family 0.5 4.01
Roads 0.9 2.00
Park 0.2 0.44
Weighted/Total 0.60 6.45
S-2B W1
Commercial 0.6 0.00
Single Family 0.5 0.98
Roads 0.9 0.42
Park 0.2 0.18
Weightedlrotal 0.57 1.58
S-3A 5.W1-2,W5.WO-9.W13,W26.27
Commercial 0.6 0.00
Single Family 0.5 5.94
Roads 0.9 2.99
Park 0.2 0.44
Weighted/Total 0.61 9.37
S-3B W13
Commercial 0.6 0.00
Single Family 0.5 0.84
Roads 0.9 0.32
Park 0.2 0.00
Weightedlrotal 0.61 1.16
SSA 4,6N-Q.W3-4,W6-7,W29
Commercial 0.6 18.48
Single Family 0.5 7.42
Roads 0.9 7.37
Park 0.2 0.21
Weighted/total 0.64 33.48
SSB W3,W6
Commercial 0.6 0.00
Single Family 0.5 1.56
Roads 0.9 0.62
Park 0.2 0.00
Weighted/Total 0.61 2.18
SSC W6
Commercial 0.6 0.00
Single Family 0.5 0.73
Roads 0.9 0.22
Park 0.2 0 00
Weighted/Total 0.59 0.95
S410 W4.W7
Commercial 0.6 0.00
Single Family 0.5 1.42
Roads 0.9 0.46
Park 0.2 0.00
Weighted/Total 0.60 1.88
S-4E W7
Commercial 0.6 0.00
Single Family 0.5 0.65
Roads 0.9 0.19
Park 0.2 0.00
Weighted/Total 0.59 0.84
S-SA 4-5 6N-Q,W1-9.W71,W13,WII&W26-27.W29
Commercial 0.6 18.48
Single Family 0.5 14.34
Roads 0.9 10.73
Park 0.2 0.65
Weightedfrotal 0.63 44.20
S-513 W11.W15
Commercial 0.6 0.00
Single Family 0.5 0.97
Roads 0.9 0.46
Park 0.2 0.00
Weighted/Total 0.63 1.43
S-5c W15
Commercial 0.6 0.00
Single Family 0.5 0.40
Roads 0.9 0.13
Park 0.2 0.00
Weighted/Total 0.60 0.53
S=6 4-5,6N-Q,WII-9,W11,W13,W15,W26-27 W29
Commercial 0.6 18.48
Single Family 0.5 14.34
Roads 0.9 10.73
Park 0.2 0.65
Weighted/Total 0.63 44.20
L=7 3,6A-F,6J-K.W17,W28
Commercial 0.6 8.78
Single Family 0.5 6.46
Roads 0.9 4.95
Park 0.2 0.26
Weighted/Total 0.64 20.45
L8A 3,6A-F,6J-K,W17-18.W28
Commercial 0.6 8.78
Single Family 0.5 6.72
Roads 0.9 5.04
Park 0.2 0.26
Weighted/Total 0.64 20.80
L-BB W19-20
Commercial 0.6 0.00
Single Family 0.5 0.24
Roads 0.9 0.49
Park 0.2 0.00
Weighted/Total 0.77 0.73
L-882 WP0
Commercial 0.6 0.00
Single Family 0.5 0.00
Roads 0.9 0.34
Park 0.2 0.00
Weighted/Total 0.90 0.34
L-8C 3,6A-F.6J-K,W12,W16-20 W22,W28
Commercial 0.6 8.78
Single Family 0.5 7.92
Roads 0.9 5.98
Park 0.2 0.26
Weighted/rotal 0.64 22.94
L-8D 3.6A-F,6J-K,W12,W16-20,W22 W24 W28
Commercial 0.6 8.78
Single Family 0.5 7.92
Roads 0.9 6.04
Park 0.2 0.26
Weighted/Total 0.64 23.00
L-9A W12,W16,W22
Commercial 0.6 0.00
Single Family 0.5 0.96
Roads 0.9 0.45
Park 0.2 0.00
Weighted/rotal 0.63 1.41
L-9B W16
Commercial 0.6 0.00
Single Family 0.5 0.38
Roads 0.9 0.14
Park 0.2 0.00
Weightedrrotal 0.61 0.52
L-10 3 6A-F,6J-K.W12 W16-20,W22-24 W28
Commercial 0.6 8.78
Single Family 0.5 7.95
Roads 0.9 6.10
Park 0.2 0.26
Weightedrrotal 6.64 23.09
L-11B W25,BL-4
Commercial 0.6 0.00
Single Family 0.5 0.00
Roads 0.9 0.48
Park 0.2 0.00
Weighted/Total 0.90 0.48
L11C W21,BL-6
Commercial 0.6 0.00
Single Family 0.5 0.04
Roads 0.9 0.34
Park 0.2 0.00
Weightedrrotal 0.86 0.38
S-�D W26
Commercial 0.6 0.00
Single Family 0.5 0.72
Roads 0.9 0.18
Park 0.2 012
Weightedrrotal 0.s4 1.02
L-7A W28
Commercial 0.6 0.00
Single Family 0.5 0.72
Roads 0.9 0.47
Park 0.2 0.00
Weightedrrotal 0.66 1.19
L-17 4,6N-Q,W29
Commercial 0.6 18.48
Single Family 0.5 4.45
Roads 0.9 6.39
Park 0.2 0.21
Weighted/Total 0.65 29.53
Storm Drainage Main S-1A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 5,W2,W5,W26 (See Figure 3)
Area= 4.53 Acre
C= 0.61 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.61 Runoff Coef.
D=260 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 13.05 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 418 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.02 ft/sec
Tc(cF)= 2.31 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total TC(Basin B)= 15.37 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T,'r'
I= 1.87 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 5.12 cfs
Calculate Pipe Capacity Provided(Storm Main S-1A)
Q=(1.486/n)*A*R"*S"
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.008 ft/ft
Q= 5.78 cfs > 5.12 ok
V= 4.71 fps
Check Inlet Control on Pipe Capacity (See Fallowing Nomograph)
HW= 3.6 ft
D= 1.25 ft
HW/D= 2.88
Q= 11 cfs > 5.12 ok
Storm Drainage Main S-1B
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W2,W5 (See Figure 3)
Area= 0.72 Acre
C= 0.66 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.66 Runoff Coef.
D=120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,T�(SF)= 7.76 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 85 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 0.42 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 8.18 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78Tc-'-'
I= 2.79 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.32 cfs
Calculate Pipe Capacity Provided(Storm Main S-1B)
Q=(1.486/n)'A'R2'3'S"2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 1.32 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3 ft
D= 1.25 ft
HW/D= 2.40
Q= 11 cfs > 1.32 ok
Storm Drainage Main SAC
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W2 (See Figure 3)
Area= 0.50 Acre
C= 0.68 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.68 Runoff Coef.
D= 120 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,T�(sF)= 7.30 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 52 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
V= 3.37 ft/sec
TC(CF)= 0.26 min
Find Total Tc
Tc=TC(SF)+TC(CF)
Total Tc(easin 6)= 7.56 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78Tc-'-'
I= 2.94 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 0.99 cfs
Calculate Pipe Capacity Provided(Storm Main S-1C)
Q=(1.486/n)*A*R213*Sv2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 0.99 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.8 ft
D= 1.25 ft
HW/D= 2.24
Q= 11 cfs > 0.99 ok
Storm Drainage Main SAID
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W26 (See Figure 3)
Area= 1.02 Acre
C= 0.54 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.54 Runoff Coef.
D= 147 Length of Basin,It
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 11.59 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 263 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(CF)= 1.30 min
Find Total Tc
TC=TC(SF)+TC(CF)
Total Tc(Basin B)= 12.89 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-osa
I= 2.09 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.14 cfs
Calculate Pipe Capacity Provided(Storm Main S-113)
Q=(1.486/n)*A*R2'3*S'/2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 1.14 OK
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.8 ft
D= 1.25 ft
HW/D= 2.24
Q= 11 cfs > 1.14 ok
Storm Drainage Main S-2A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 5,W1-2,W5,W26-27 (See Figure 3)
Area= 6.45 Acre
C= 0.60 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.60 Runoff Coef.
D=260 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,T«SF)= 13.15 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 660 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 3.26 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(easin B)= 16.41 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78TC-°-B4
I= 1.79 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 6.96 cfs
Calculate Pipe Capacity Provided(Storm Main S-2A)
Q F(1.486/n)*A*R"'S1
12
Given: n= 0.013 Pipe Diameter= 18 in.
A= 1.767 sf Material= PVC
R= 0.375 ft
S= 0.005 ft/ft
Q= 7.28 cfs > 6.96 OK
V= 4.12 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.8 ft
D= 1.5 ft
HW/D= 2.53
Q= 15 cfs > 6.96 ok
Storm Drainage Main S-213
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W1 (See Figure 3)
Area= 1.58 Acre
C= 0.57 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.57 Runoff Coef.
D= 165 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 11.30 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 592 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 2.93 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 14.23 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc"'
I= 1.96 in/hr
Calculate Post-developed Peak Runoff Rate
Q=c1A,using the above parameters.
Q= 1.77 cfs
Calculate Pipe Capacity Provided(Storm Main S-2B)
Q=(1.486/n)'A'Ry3'S"
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.004 ft/ft
Q= 4.28 cfs > 1.77 ok
V= 3.49 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.8 ft
D= 1.25 ft
HW/D= 2.24
Q= 9 cfs > 1.77 ok
Storm Drainage Main S-3A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 5,W1-2,W5,W8-9,W13,W26-27 (See Figure 3)
Area= 9.37 Acre
C= 0.61 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.61 Runoff Coef.
D=260 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,T�(SF)= 12.82 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 1034 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 5.11 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 17.93 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78Tc-o.ea
I= 1.69 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 9.71 cfs
Calculate Pipe Capacity Provided(Storm Main S-3A)
Q=(1.486/n)*A*R13*Sll2
Given: n= 0.013 Pipe Diameter= 24 in.
A= 3.142 sf Material= PVC
R= 0.500 ft
S= 0.007 ft/ft
Q= 18.24 cfs > 9.71 OK
V= 5.81 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.1 ft
D= 2 ft
HW/D= 1.55
Q= 30 cfs > 9.71 ok
Storm Drainage Main S-313
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W13 (See Figure 3)
Area= 1.16 Acre
C= 0.61 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.61 Runoff Coef.
D= 120 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 8.78 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 355 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.75 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 10.54 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-0.64
I= 2.37 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.68 cfs
Calculate Pipe Capacity Provided(Storm Main S-313)
Q=(1.486/n)'A`R"S1'
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.61 cfs > 1.68 ok
V= 3.76 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.9 ft
D= 1.25 ft
HW/D= 2.32
Q= 9 cfs > 1.68 ok
Storm Drainage Main S-4A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 4,6N-Q,W34,W6-7,W29 (See Figure 3)
Area= 33.48 Acre
C= 0.64 Weighted C
Calculate Time of Concentration( c)
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=300 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 12.78 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 2154 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 10.65 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 23.43 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-B-'
I= 1.42 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 30.58 cfs
Calculate Pipe Capacity Provided(Storm Main S-4A)
Q=(1.486/n)*A*R2/3*S'/2
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.009 ft/ft
Q= 38.26 cfs > 30.58 ok
V= 7.79 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.3 ft
D= 2.5 ft
HW/D= 1.72
Q= 40 cfs > 30.58 ok
Storm Drainage Main S-413
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W3,W6 (See Figure 3)
Area= 2.18 Acre
C= 0.61 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.61 Runoff Coef.
D=120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 8.70 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 340 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.68 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total T.(Basin B)= 10.38 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-o.e4
1= 2.40 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 3.21 cfs
Calculate Pipe Capacity Provided(Storm Main S413)
Q=(1.486/n)'A'R2J3'S"2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 3.21 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.5 ft
D= 1.25 ft
HW/D= 2.80
Q= 11 cfs > 3.21 ok
Storm Drainage Main S-4C
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W6 (See Figure 3)
Area= 0.95 Acre
C= 0.59 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.59 Runoff Coef.
D= 120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 9.18 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 308 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.52 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 10.70 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78T�'-"
I= 2.35 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.32 cfs
Calculate Pipe Capacity Provided(Storm Main S-4C)
Q=(1.486/n)*A*RV3'S112
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 1.32 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.3 ft
D= 1.25 ft
HW/D= 2.64
Q= 10 cfs > 1.32 ok
Storm Drainage Main S-41)
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W4,W7 (See Figure 3)
Area= 1.88 Acre
C= 0.60 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.60 Runoff Coef.
D= 130 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 9.43 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 306 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
To(cF)= 1.51 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tg3asin B)= 10.94 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78Tc-°'
I= 2.32 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.60 cfs
Calculate Pipe Capacity Provided(Storm Main S-4D)
Q=(1.486/n)'A'R""S"n
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 2.60 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.7 ft
D= 1.25 ft
HW/D= 2.96
Q= 11 cfs > 2.60 ok
Storm Drainage Main S-4E
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W7 (See Figure 3)
Area= 0.84 Acre
C= 0.59 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.59 Runoff Coef.
D=120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,T,(SF)= 9.23 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 274 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(CF)= 1.35 min
Find Total Tc
Tc=Tc(SF)+TC(CF)
Total Tc(Bash13)= 10.58 min
Calculate Post-developed Storm Intensity at T,
From Figure 1-3,using the 25 year event,I=0.78T�-O-"
I= 2.37 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.17 cfs
Calculate Pipe Capacity Provided(Storm Main S-4E)
Q=(1.486/n)'A'R"S112
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 1.17 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.6 ft
D= 1.25 ft
HW/D= 2.88
Q= 10 cfs > 1.17 ok
Storm Drainage Main S-5A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s)J-Q,W1-9,W11,W13,W15,W26-2, (See Figure 3)
Area= 44.20 Acre
C= 0.63 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.63 Runoff Coef.
D=300 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 13.02 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2435 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
T.(cF)= 12.04 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basln B)= 25.06 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78T�-'-'
I= 1.36 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 38.25 cfs
Calculate Pipe Capacity Provided(Storm Main S-SA)
Q=(1.486/n)'A'R"S"
Given: n= 0.013 Pipe Diameter= 36 in.
A= 7.069 sf Material= PVC
R= 0.750 ft
S= 0.008 ft/ft
Q= 60.03 cfs > 38.25 OK
V= 8.49 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.4 ft
D= 3 ft
HW/D= 1.47
Q= 55 cfs > 38.25 ok
Storm Drainage Main S-513
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W11,W15 (See Figure 3)
Area= 1.43 Acre
C= 0.63 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.63 Runoff Coef.
D= 120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 8.37 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 227 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.12 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 9.49 min
Calculate Post-developed Storm Intensity at T,
From Figure 1-3,using the 25 year event,I=0.78TC-0.14
I= 2.54 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.28 cfs
Calculate Pipe Capacity Provided(Storm Main S-513)
Q=(1.486/n)'A'R2'3*S1'2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 fUft
Q= 4.61 cfs > 2.28 ok
V= 3.76 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.8 ft
D= 1.25 ft
HW/D= 3.04
Q= 11 cfs > 2.28 ok
Storm Drainage Main S-5C
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W15 (See Figure 3)
Area= 0.53 Acre
C= 0.60 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.60 Runoff Coef.
D=120 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 9.06 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 193 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(CF)= 0.95 min
Find Total Tc
Tc=Tc(SF)+TC(CF)
Total Tcpasin B)= 10.01 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-°
I= 2.45 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 0.78 cfs
Calculate Pipe Capacity Provided(Storm Main S-5C)
Q=(1.486/n)•A•Rva.S"
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 0.78 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.7 ft
D= 1.25 ft
HW/D= 2.96
Q= 11 cfs > 0.78 ok
Storm Drainage Main S-6
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s)V-Q,W1-9,W11,W13,W15,W26-2i (See Figure 3)
Area= 44.20 Acre
C= 0.63 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.63 Runoff Coef.
D=300 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1.Tc(SF)= 13.02 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2598 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 fUft
v= 3.37 ft/sec
Tc(cF)= 12.84 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(B-h B)= 25.87 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-0.64
I= 1.34 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 37.49 cfs
Calculate Pipe Capacity Provided(Storm Main S-6)
Q=(1.486/n)*A*Fe"Sl'
Given: n= 0.013 Pipe Diameter= 36 in.
A= 7.069 sf Material= PVC
R= 0.750 ft
S= 0.004 fUft
Q= 39.46 cfs > 37.49 OK
V= 5.58 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.7 ft
D= 3 ft
HW/D= 1.57
Q= 60 cfs > 37.49 ok
Storm Drainage Main L-7A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W28 (See Figure 3)
Area= 1.19 Acre
C= 0.66 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.66 Runoff Coef.
D=91 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 6.71 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 305 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.51 min
Find Total Tc
Tc=Tc(SF)t Tc(cF)
Total Tc(Basin B)= 8.22 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T�-o.sa
I= 2.78 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.18 cfs
Calculate Pipe Capacity Provided(Storm Main L-7A)
Q=(1.486/n)•A•R2J3.S1rz
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 2.18 OK
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.4 ft
D= 1.25 ft
HW/D= 2.72
Q= 10 cfs > 2.18 ok
Storm Drainage Main L-7
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 3,6A-F,6J-K,W17,W28 (See Figure 3)
Area= 20.45 Acre
C= 0.64 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=200 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 10.59 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 1986 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 9.82 min
Find Total Tc
Tc=Tc(sF)+Tc(cF)
Total Tcpasin e)= 20.41 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T�-'-'
I= 1.56 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 20.23 cfs
Calculate Pipe Capacity Provided(Storm Main L-7)
Q=(1.486/n)•A•R2/3.S112
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.006 ft/ft
Q= 30.42 cfs > 20.23 ok
V= 6.20 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 5.1 ft
D= 2.5 ft
HW/D= 2.04
Q= 38 cfs > 20.23 ok
Storm Drainage Main L-8A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 3,6A-F,6J-K,W17-18,W28 (See Figure 3)
Area= 20.80 Acre
C= 0.64 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=200 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 10.61 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2103 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 10.40 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin S)= 21.00 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T�-°'S'
I= 1.53 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 20.18 cfs
Calculate Pipe Capacity Provided(Storm Main L-8A)
Q=(1.486/n)*A*R2/3'S'r'
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.007 ft/ft
Q= 34.32 cfs > 20.18 ok
V= 6.99 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.6 ft
D= 2.5 It
HW/D= 1.84
Q= 30 cfs > 20.18 ok
Storm Drainage Main L-813
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W19-20 (See Figure 3)
Area= 0.73 Acre
C= 0.77 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.77 Runoff Coef.
D= 15 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
i
From Figure 1-1,T�(sF)= 1.84 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 520 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
V= 3.37 ft/sec
Tc(CF)= 2.57 min
Find Total Tc
Tc=Tc(SF)+TC(CF)
Total T.(Basin B)= 4.41 min
Calculate Post-developed Storm Intensity at T.
From Figure 1-3,using the 25 year event,I=0.78TC-0.64
I= 4.14 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.32 cfs
Calculate Pipe Capacity Provided(Storm Main L-8B)
Q=(1.486/n)'A`Rm'Sv2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 It
S= 0.004 ft/ft
Q= 4.09 cfs > 2.32 ok
V= 3.33 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.4 ft
D= 1.25 ft
HW/D= 2.72
Q= 10 cfs > 2.32 ok
Storm Drainage Main L-8B2
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W20 (See Figure 3)
Area= 0.34 Acre
C= 0.90 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.90 Runoff Coef.
D= 15 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(sF)= 0.80 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 490 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 2.42 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 3.22 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-°B"
I= 5.07 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.55 cfs
Calculate Pipe Capacity Provided(Storm Main L-8B2)
Q=(1.486/n)*A'R21.S11
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.75 cfs > 1.55 ok
V= 3.87 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.3 ft
D= 1.25 ft
HW/D= 2.64
Q= 10 cfs > 1.55 ok
Storm Drainage Main L-8C
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s)3,6A-F,6J-K,W12,W16-20,W22,W2 (See Figure 3)
Area= 22.94 Acre
C= 0.64 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=200 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 10.50 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2214 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 10.94 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 21.44 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T�-"'
I= 1.51 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 22.09 cfs
Calculate Pipe Capacity Provided(Storm Main L-8C)
Q=(1.486/n)*A*R2"'S"2
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.007 ft/ft
Q= 33.82 cfs > 22.09 OK
V= 6.89 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.3 ft
D= 2.5 ft
HW/D= 1.72
Q= 35 cfs > 22.09 ok
Storm Drainage Main L-8D
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s):,6J-K,W12,W16-20,W22,W, (See Figure 3)
Area= 23.00 Acre
C= 0.64 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=200 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 10.48 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 2298 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
TC(cF)= 11.36 min
Find Total Tc
Tc=Tc(sF)+Tc(cF)
Total Tcpasin B)= 21.84 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-O-'
I= 1.49 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 21.92 cfs
Calculate Pipe Capacity Provided(Storm Main L-813)
Q=(1.486/n)•A,Ry3.S112
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.004 ft/ft
Q= 25.94 cfs > 21.92 OK
V= 5.28 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.7 ft
D= 2.5 ft
HW/D= 1.48
Q= 30 cfs > 21.92 ok
Storm Drainage Main L-9A
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W12,W16,W22 (See Figure 3)
Area= 1.41 Acre
C= 0.63 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.63 Runoff Coef.
D=113 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 8.14 min.
Find Channel Flow Tc(Gutter Flow$Pipe)
Using Mannings Equation, calculate channel flow
L= 225 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.11 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(eash B)= 9.25 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-o.Sa
I= 2.58 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.28 cfs
Calculate Pipe Capacity Provided(Storm Main L-9A)
Q=(1.486/n)"A"R2a.Sv2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.004 ft/ft
Q= 4.09 cfs > 2.28 ok
V= 3.33 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.4 ft
D= 1.25 ft
HW/D= 2.72
Q= 10 cfs > 2.28 ok
Storm Drainage Main L-913
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W16 (See Figure 3)
Area= 0.52 Acre
C= 0.61 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.61 Runoff Coef.
D= 113 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 8.58 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 192 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 fl/sec
Tc(cF)= 0.95 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 9.53 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78T�-°-'
I= 2.53 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 0.80 cfs
Calculate Pipe Capacity Provided(Storm Main L-913)
Q=(1.486/n)*A"R213*S'1
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.005 ft/ft
Q= 4.57 cfs > 0.80 ok
V= 3.72 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.4 ft
D= 1.25 ft
HW/D= 2.72
Q= 10 cfs > 0.80 ok
Storm Drainage Main L-10
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s)3,6A-F,6J-K,W12,W16-20,W22-24,W2 (See Figure 3)
Area= 23.09 Acre
C= 0.64 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.64 Runoff Coef.
D=200 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,To(sr)= 10.46 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2337 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 fUsec
Tc(cF)= 11.55 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tcpasin B)= 22.02 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc-°.64
I= 1.48 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 21.91 cfs
Calculate Pipe Capacity Provided(Storm Main L-10)
Q=(1.486/n)•A,Rva.Sln
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.004 ft/ft
Q= 25.94 cfs > 21.91 ok
V= 5.28 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 3.9 ft
D= 2.5 ft
HW/D= 1.56
Q= 30 cfs > 21.91 ok
Storm Drainage Main L-11 B
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W25,BL-4 (See Figure 3)
Area= 0.48 Acre
C= 0.90 Weighted C
Calculate Time of Concentration(T.)
Developed Conditions:
S= 1.00 %Average Slope
C=0.90 Runoff Coef.
D=50 Length of Basin,ft
Cf= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 1.45 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 335 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(CF)= 1.66 min
Find Total Tc
Tc=TC(SF)+TC(CF)
Total Tc(Basin B)= 3.11 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78TC-0.64
I= 5.18 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 2.24 cfs
Calculate Pipe Capacity Provided(Storm Main L-11B)
Q=(1.486/n)*A-Rva,S"2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.003 ft/ft
Q= 3.29 cfs > 2.24 ok
V= 2.68 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.4 ft
D= 1.25 ft
HW/D= 1.92
Q= 8 cfs > 2.24 ok
Storm Drainage Main L-11C
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) W21,BL-6 (See Figure 3)
Area= 0.38 Acre
C= 0.86 Weighted C
Calculate Time of Concentration(Tc)
Developed Conditions:
S= 1.00 %Average Slope
C=0.86 Runoff Coef.
D=50 Length of Basin,ft
C1= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,Tc(SF)= 2.07 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 375 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 1.85 min
Find Total Tc
Tc=Tc(SF)+Tc(cF)
Total Tc(Basin B)= 3.92 min
Calculate Post-developed Storm Intensity at Tc
From Figure 1-3,using the 25 year event,I=0.78Tc"'4
I= 4.47 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 1.46 cfs
Calculate Pipe Capacity Provided(Storm Main L-11C)
Q=(1.486/n)'A'R2"'S1'2
Given: n= 0.013 Pipe Diameter= 15 in.
A= 1.227 sf Material= PVC
R= 0.312 ft
S= 0.003 ft/ft
Q= 3.42 cfs > 1.46 OK
V= 2.79 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 2.7 ft
D= 1.25 ft
HW/D= 2.16
Q= 13 cfs > 1.46 ok
Storm Drainage Main L-17
The following calculations were used to size the conveyance facilities for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Contributing Basin(s) 4,6N-Q,W29 (See Figure 3)
Area= 29.53 Acre
C= 0.65 Weighted C
Calculate Time of Concentration(TJ
Developed Conditions:
S= 1.00 %Average Slope
C=0.65 Runoff Coef.
D=300 Length of Basin,ft
Cr= 1.1 Freq.Adjustment Factor
Find Sheet/Shallow Concentrated Tc
From Figure 1-1,To(SF)= 12.58 min.
Find Channel Flow Tc(Gutter Flow&Pipe)
Using Mannings Equation, calculate channel flow
L= 2041 ft
R= 0.1355 ft
n= 0.0130
S= 0.01 ft/ft
v= 3.37 ft/sec
Tc(cF)= 10.09 min
Find Total Tc
Tc=Tc(sF)+Tc(cF)
Total Tcmas[n B)= 22.67 min
Calculate Post-developed Storm Intensity at T�
From Figure 1-3,using the 25 year event,I=0.78Tc"'
I= 1.45 in/hr
Calculate Post-developed Peak Runoff Rate
Q=ciA,using the above parameters.
Q= 27.79 cfs
Calculate Pipe Capacity Provided(Storm Main L-17)
Q=(1.486/n)*A*R2a*Sv2
Given: n= 0.013 Pipe Diameter= 30 in.
A= 4.909 sf Material= PVC
R= 0.625 ft
S= 0.009 ft/ft
Q= 38.04 cfs > 27.79 OK
V= 7.75 fps
Check Inlet Control on Pipe Capacity (See Following Nomograph)
HW= 4.3 ft
D= 2.5 ft
HW/D= 1.72
Q= 40 cfs > 27.79 ok
9. HYDRA ULICS
189
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Table 3
Storm Sewer Capacity Calculations
Storm Sewer Post-Developed Pipe Pipe
Main Runoff Rate (cfs) Diameter(in.) 7Capacity(cfs)
S-1 A 5.12 15 5.78
S-1 B 1.32 15 4.57
S-1 C 0.99 15 4.57
S-1 D 1.14 15 4.57
S-2A 6.96 18 7.28
S-2 B 1.77 15 4.28
S-3A 9.71 24 18.24
S-313 1.68 15 4.61
S-4A 30.58 30 38.26
S-46 3.21 15 4.57
S-4C 1.32 15 4.57
S-4D 2.60 15 4.57
S-4 E 1.17 15 4.57
S-5A 38.25 36 60.03
S-56 2.28 15 4.61
S-5C 0.78 15 4.57
S-6 37.49 36 39.46
L-7A 2.18 15 4.57
L-7 20.23 30 30.42
L-8A 20.18 30 34.32
L-8B 2.32 15 4.09
L-8B2 1.55 15 4.75
L-8C 22.09 30 33.82
L-8D 21.92 30 25.94
L-9A 2.28 15 4.09
L-9B 0.80 15 4.57
L-10 21.91 30 25.94
L-11 B 2.24 15 3.29
L-11 C 1.46 15 3.42
L-17 27.79 30 38.04
Gutter&Inlet Capacity Calculations
The following calculations were used to check the capacities of the curb and gutter conveyance systems for stormwater runoff.The volumes were calculated using the Rational
Method,and the conveyance facilities were checked based on a 25-year storm event.Worst case scenarios(gutter that takes runoff from largest surface area)was evaluated for each
roadway.The runoff values calculated below were also used for the inlet capacity analysis.
Basin Characteristics Sheet Flow from Basin Concentrated Flow from Basin 25-YR Storm Flow Max.Gutter Capacity Max.Inlet Capacity
Sheet Flow Gutter Flow Gutter (ft/s) Q(cfs) Grate
Roadway Inlet ID Contributing Weighted Avg.Slope Sheet Flow T.(sF)(min)(COB Avg.Slope Flow Hydraulic Manning's (manning' Tcpotap Intensity Q(cfs) X-Section Manning's Hydraulic (manning Capacity perimeter inlet flow Capacity
Basin Basin Area C-factor N Length(ft) Cr equation) (fuft) Length(ft) Radius* Roughness s) T,(CF)(min) (min) (in/hr) (Q=CIA) Gutter Avg.Slope(ft/ft) Area(ft) Roughness Radius s) Check (ft) depth(ft) Q(cfs) Check
Trade Wind Lane
A W 13 1.16 0.57 2 120 1.1 7.71 0.0051 355 0.0426 0.013 1.00 5.95 13.66 2.01 1.33 0.0051 1.156 0.013 0.0687 1.58 ok 5.8 0.3 2.86 ok
B W8,W9** 1.12 0.56 2 120 1.1 7.86 0.005 312 0.0426 0.013 0.99 5.28 13.14 2.06 1.29 0.005 1.156 0.013 0.0687 1.57 ok 5.8 0.3 2.86 ok
C W 15 0.53 0.56 2 113 1.1 7.61 0.0067 193 0.0426 0,013 1.14 2.82 10.43 2.39 0.71 0.0067 1.156 0.013 0.0687 1.81 ok 5.8 0.3 2.86 ok
D W11 0.90 0.59 2 120 1.1 7.30 0.0066 193 0.0426 0.013 1.13 2.84 10.14 2.43 1.30 0.0066 1.156 0.013 0.0687 1.80 ok 5.8 0.3 2.86 ok
E W 16 0.52 0.57 2 113 1.1 7.51 0.0052 192 0.0426 0.013 1.00 3.18 10.69 2.35 0.69 0.0052 1.156 0.013 0.0687 1.60 ok 5.8 0.3 2.85 ok
F W12,W22 0.89 0.60 2 100 1.1 6.53 0.012 350 0.0426 0.013 1.53 3.82 10.35 2.40 1.28 0.012 1.156 0.013 0.0687 2.43 ok 5.8 0.3 2.86 ok
G W20 0.34 0.75 2 15 1.1 5.00 0.005 490 0,0426 0.013 0.99 8.29 13.29 2.05 0.52 0.005 1.156 0.013 0.0687 1.57 ok 5.8 0.3 2.86 ok
H W 19 0.39 0.60 2 110 1.1 6.92 0.0089 123 0.0426 0.013 1.31 1.56 8.47 2.73 0.63 0.0089 1.156 0.013 0.0687 2.09 ok 5.8 0.3 2.86 ok
Flurry Lane
A W5 0.22 0.57 2 120 1.1 7.72 0.0057 85 0.0426 0.013 1.05 1.35 9.07 2.61 0.33 0.0057 1.156 0.013 0.0687 1.67 ok 5.8 0.3 2.86 ok
B W2 0.67 0.61 2 120 1.1 6.98 0.0054 85 0.0426 0.013 1.02 1.38 8.36 2.75 1.12 0.0054 1.156 0.013 0.0687 1.63 ok 5.8 0.3 2.96 ok
C W6 0.95 0.56 2 120 1.1 7.91 0.0051 308 0.0426 0.013 1.00 5.16 13.07 2.07 1.10 0.0051 1156 0.013 0.0687 1.58 ok 5.8 0.3 2.86 ok
D W3 1.23 0.58 2 120 1.1 7.49 0.0051 308 0.0426 0.013 1.00 5.16 12.65 2.11 1.51 0.0051 1.156 0.013 0.0687 1.58 ok 5.8 0.3 2.96 ok
E W7 0.84 0.56 2 120 1.1 7.93 0.0073 274 0,0426 0.013 1.19 3.84 11.77 2.21 1.03 0.0073 1.156 0.013 0.0687 1.89 ok 5.8 0.3 2.86 ok
F W4 1.04 0.56 2 130 1.1 8.10 0.0069 274 0.0426 0.013 1.16 3.95 12.04 2.18 1.28 0.0069 1.156 0.013 0.0687 1.84 ok 5.8 0.3 2.86 ok
Spring View Court
A W 1 1.58 0.53 2 165 1.1 9.81 0.0087 592 0.0426 0.013 1.30 7.59 17.40 1.72 1.45 0.0087 1.156 0.013 0.0687 2.07 ok 5.8 0.3 2.86 ok
B W27 0.34 0.63 2 71.6 1.1 5.08 0.0062 121 0.0426 0.013 1.10 1.84 6.92 3.11 0.67 0.0062 1.156 0.013 0.0687 1.75 ok 5.8 0.3 2.96 ok
C W26 1.02 0.51 2 147 1.1 9.72 0.0087 263 0.0426 0.013 1.30 3.37 13.10 2.07 1.07 0.0087 1.156 0.013 0.0687 2.07 ok 5.8 0.3 2.86 ok
Hunter's Way
A W 17 0.85 0.56 2 110 1.1 7.45 0.0151 285 0.0426 0.013 1.71 2.77 10.23 2.42 1.16 0.0151 1.156 0.013 0.0687 2.72 ok 5.8 0.3 2.86 ok
B W 18 0.35 0.56 2 110 1.1 7.46 0.0085 117 0.0426 0.013 1.28 1.52 8.98 2.63 0.52 0.0085 1.156 0.013 0.0687 2.04 ok 5.8 0.3 2.86 ok
C W24 0.06 0.75 2 110 1.1 4.29 0.0089 36 0.0426 0.013 1.31 0.46 4.74 3.96 0.18 0.0089 1.156 0.013 0.0687 2.09 ok 5.8 0.3 2.86 ok
D W23 0.09 0.67 2 120 1.1 5.96 0.0108 778 0.0426 0.013 1.45 8.95 14.92 1.90 0.11 0.0108 1.156 0.013 0.0687 2.30 ok 5.8 0.3 2.86 ok
E W25,BL-4 0.48 0.75 2 15 1.1 1.58 0.0175 179 0.0426 0.013 1.84 1.62 3.20 5.09 1.83 0.0175 1.156 0.013 0.0687 2.93 ok 5.8 0.3 2.86 ok
F W21,BL-4 0.53 0.74 2 15 1.1 1.64 0.0175 179 0.0426 0.013 1.84 1.62 3.26 5.03 1.97 0.0175 1.156 0.013 0.0687 2.93 ok 5.8 0.3 2.86 ok
G W28 1.19 0.60 2 91 1.1 6.25 0.0151 305 0.0426 0.013 1.71 2.97 9.22 2.59 1.84 0.0151 1.156 0.013 0.0687 2.72 ok 5.8 0.3 2.86 ok
Windward Avenue
A W29 0.11 0.73 2 35 1.1 2.63 0.0151 32 0.0426 0.013 1.71 0.31 1 2.95 5.37 0.43 0.0056 1.156 0.013 0.0687 1.66 ok 5.8 0.3 2.66 ok
notes:
n= 0.013 *Assumed typical hydraulic radius
Flow Cross Section Properties-1/2 Capacity **Gutter evaluated for Trade Wind Lane inlet B recieves runoff from W8,therefore the 25-year Q is calculated using the area from W8 only
A= 0.426 ft2 The max inlet capacity for Trade Wind Lane inlet B is compared to the flow generated from runoff of basins W8 and W9: 2.86 cfs>1.91 cfs OK.
P= 10.01 It
R= 0.0426
Flow Cross Section Properties-0.15'below TBC(Full Capacity)
A= 1.156 ft2
P= 16.82 ft
R= 0.0687
s
z
z
a
v
Appendix B
Outlet Weir sizing
Calculations
•
4
DOWL
Discharge Weir Calculations(Master Ponds)
The following calculations were used to size the discharge weir for stormwater runoff.
The volumes were calculated using the Rational Method,and the conveyance facilities were
sized based on a 25-year 2-hour storm event.
Full Build-Out Conditions:
Contributing Basin(s): West Winds(West),Davis Lane,Oak (See Figure 2)
Street and Baxter Lane(West)
Area= 77.17 Acre
C= 0.20
Pre-developed Peak Runoff Rate
The outfall control weir from the detention pond was initially designed to convey the Pre-
developed Peak Runoff from the overall development as determined in the calculations for the
storage volume requirements for the master detention ponds(see Phase 6 Storm Report).
Q= 10.70 cfs
Calculate Weir Capacity Provided
Q=C*L*H3/2
Given: C= 3.33 (weir coefficient)
L= 1.740 ft (horiz.length)
H= 1.5 ft (head)
Q= 10.64 cfs <10.7 cfs-ok
Phase 7&8:
Contributing Basin(s) 3,4,5,6A-R,BL1-4,Ponds,W1-24 (See Figure 2)
Area= 77.17 Acre
C= 0.20
Pre-developed Peak Runoff Rate
The outfall control weir from the detention pond was designed to convey the Pre-developed
Peak Runoff from the Phase 7&8 development as determined in the calculations for the
stormwater pond volume calculations(see Phase 6 Storm Report).
Q= 10.70 cfs
Calculate Weir Capacity Provided
Q=C*L*H"
Given: C= 3.33 (weir coefficient)
L= 1.740 ft (horiz.Length)
H= 1.3 ft (head)
Q= 8.59 cfs <10.7 cfs-ok
Summary:
Phase 7&8 development will require a weir length to be expanded to the full build-out length of
1.740 feet. This will have a designed depth of less than 1.5'due to the extra pond storage
capacity and there for will be discharging at a rate less than 10.64 cfs.Upon full build-out the
water depth will be 1.5 feet with a discharge of 10.64 cfs.
Overflow Weir Calculations (Master Ponds)
The following calculations were used to size the overflow weir for stormwater runoff.
The volumes were calculated using the Rational Method, and the conveyance facilities were
sized based on a 100-year 2-hour storm event.
Contributing Basin(s): West Winds (West), Davis Lane, Oak (See Figure 2)
Street and Baxter Lane (West)
Area = 76.88 Acre
C= 0.60
Pre-developed Peak Runoff Rate
The overflow weir from the detention pond was designed to convey the Post-developed Peak
Runoff from the overall development as determined in the calculations for the storage volume
requirements for the master detention ponds (see Phase 6 Storm Report)
Q= 68.20 cfs
Calculate Weir Capacity Provided
Q = C*L*H3/2
Given: C = 3.33 (weir coefficient)
L= 20.00 ft (horiz. length)
H = 1.02 ft (head)
Q = 68.61 cfs >68.20 cfs-ok