CITY UTILITIES
DESIGN STANDARDS MANUAL
STORM WATER (SW)
CHAPTER 8 CULVERTS
October 2013
City Utilities Design Standards Manual
Stormwater Design
Chapter 8
Culverts
SW8.01 – Introduction
A culvert is defined as a conduit for the conveyance of water under a
roadway, railroad or other embankment. In addition to serving hydraulic
functions, culverts must also carry overhead loads from traffic and other
activities, thereby serving a structural function. Proper culvert design is
essential because culverts often significantly influence upstream and
downstream flood risks, floodplain management and public safety. The
criteria presented in this chapter shall be used in the design of culverts.
A culvert as distinguished from a bridge is usually covered with embankment
and is composed of structural material around the entire perimeter although
it can be supported on spread footings with the streambed serving as the
bottom.
A bridge is a structure having an opening measured along the centerline of a
roadway of more than 20 feet between faces of abutments or spring lines of
arches. Multiple barrel box culverts or multiple pipe culverts having an
opening of more than 20 feet between the limits of the extreme openings are
sometimes classed as bridges. (Bridge Inspection Manual Definitions)
SW8.02 – General Design
1.
Federal Highway Administration
The design of culverts shall conform to the methodology described in
the Hydraulic Design of Highway Culverts published by the U.S.
Department of Transportation’s Federal Highway Administration
Publication No. FHWA-NHI-01-020, September 2001 (Revised May 2005
or current edition) Available online at
http://isddc.dot.gov/OLPFILES/FHWA/012545.pdf
2.
Indiana Department of Transportation
The Indiana Department of Transportation Design Manual 2011 or
current edition provides valuable culvert design information. The
Design Manual is available online at
http://www.in.gov/dot/div/contracts/standards/dm
SW8.03 – Hydraulic Design
1.
Design Program
The HY-8 program is the computerized implementation of FHWA culvert
hydraulic approaches and protocols and shall be used for culvert design.
Available online at
http://www.fhwa.dot.gov/engineering/hydraulics/software/hy8/
2.
Backwater
Culverts shall not increase backwater elevations on upstream
properties. Backwater shall be contained within existing banks of the
upstream open channel.
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Stormwater Design
3.
Chapter 8
Culverts
Overland Flow Routes
Emergency overland flow routes shall be checked to assure that
backwater resulting from a potentially blocked culvert or intense storm
does not flood or damage property. If an emergency overland flow
route is not available, culvert flow capacity shall be increased. Sound
engineering judgment shall be applied in determining the potential
extent of backwater damage and the necessary increase in culvert flow
capacity.
4.
Minimum Diameter
The minimum diameter for culverts crossing a public roadway shall be
15 inches (15”). The minimum diameter for private driveway culverts
within right-of-way shall be 12 inches (12”).
5.
Flow Velocity
Both minimum and maximum flow velocities should be considered
when designing a culvert. A minimum velocity of 3.0 feet/second when
the culvert is flowing partially full is recommended to ensure a selfcleaning condition during partial depth flow. The maximum velocity
should not exceed culvert manufacturer recommendations. The
maximum velocity should be consistent with channel stability
requirements at the culvert outlet. The maximum allowable outlet
velocity of culverts, which discharge to an earthen channel, shall be 6
feet/second. As outlet velocities increase, the need for channel
stabilization at the culvert outlet increases. If velocities exceed
permissible velocities for the various types of nonstructural outlet lining
material available, the installation of structural energy dissipators is
appropriate.
SW8.04 - Design Storm (see Section 2, Hydrology)
1.
Public Culverts
Publicly owned culverts crossing a roadway shall be designed to convey
the peak flow resulting from a 100-year event. Driveway culverts within
right-of-way shall convey the peak flow resulting from a 50-year event.
2.
Private Culverts
Privately owned culverts located outside right-of-way and serving areas
which do not require detention shall be designed to convey the peak
flow resulting from a 50-year event and provisions shall be made to
contain the runoff from a 100-year event. Lesser capacities may be
considered provided that proper accommodations are provided for onsite storage of the 100-year overflow.
SW8.05 – Sumped Culverts
Circular and elliptical pipes shall be installed with pipe inverts lower than
adjacent channel flowline. Sound engineering judgment shall be applied to
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City Utilities Design Standards Manual
Stormwater Design
Chapter 8
Culverts
determine the depth of sumping. Sumping increases the base flow capacity
of circular and elliptical pipes, accommodates the future lowering of the
channel, may increase the depth of pipe cover, and in environmentally
sensitive areas allows for a natural stream bottom in the pipes.
SW8.06 – Structural Design
1.
Loading
All culverts crossing a roadway shall be designed to withstand a
minimum HS-20-44 loading as defined by the American Association of
State Highway and Transportation Officials (AASHTO). Culverts crossing
a railroad shall be designed to withstand an E-80 loading.
2.
Installation Depth
Installation depths shall conform to Installation Depth Tables, Exhibits
V-4-1 through V-4-4. Culvert types not listed in Installation Depth
Tables shall conform to manufacturer specifications or
recommendations.
3.
Bedding and Backfill
Backfill classifications, materials, and methods of compaction shall be in
accordance with City Utilities standards for projects inside of the City
limits and in accordance with County Highway standards outside the
City limits unless special circumstances warrant otherwise.
(Refer to pipe type chart. Such as concrete class for loading or cover
requirements.)
(Refer to bedding and backfill details)
4.
Floatation and Anchoring
Pipe floatation can occur when the uplift (buoyancy) forces outside the
pipe are greater than the downward weight forces on the pipe. This
uplift force can be great enough to cause the pipe to bend and dislodge
from the embankment. Large diameter, flexible material culverts are
more vulnerable to floatation. In most cases concrete headwalls and
wingwalls provide enough weight to sufficiently anchor the ends of the
culvert. (FHWA Culvert Manual) (concrete headwalls permitted??) MJG
to rewrite!
SW8.07 – Culvert Length Determination
Culvert length design shall consider embankment width, installation depth
and embankment slopes. Culvert length shall be designed to comply with
(Section 5.7.4.3 Crossings)
SW8.08 – Inlet and Outlet Configuration
All Culverts, public and private, shall have end treatments such as
prefabricated end sections, wingwalls and aprons, or headwalls at the inlet
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Stormwater Design
Chapter 8
Culverts
and the outlet. The design of end treatments shall consider public safety and
erosion control.
1.
Roadside Safety
Roadside ditch culverts for commercial and residential drives shall have
sloped prefabricated end sections. Headwalls and wingwalls are not
permitted.
2.
Trash Racks
Trash racks should be considered for inlet culvert end treatment where
inlet clogging or downstream trash pollution is anticipated due to
upstream land use activities. Trash racks shall not be used on culvert
outlets, however trash racks may be warranted on outlets in areas
where public safety is a concern.
3.
Erosion Control
Channel Stabilization and erosion control measures shall be utilized at
the inlet and outlet of a culvert according to (Section 5.11.??)
SW8.09
Environmental Considerations
In channels with a base flow or normal pool, migration of aquatic species
should be considered. Culverts should be sumped to maintain a base flow
depth through the culvert equal to or greater than the adjacent channel base
flow depth. Bottomless culverts may be considered to maintain a natural
stream bottom.
Where fish migration is a concern, contact the Indiana Department of Natural
Resources (IDNR), Division of Fish and Wildlife for culvert design assistance.
SW8. 10
Permitting
Culvert installation may require approval and/or permitting from federal,
state, or local agencies. Early coordination regarding permitting and approval
is recommended. Each public agency may have design criteria which must be
complied with for permitting.
1.
Public Agencies
City of Fort Wayne Street Engineering Department for work within City
street or road right-of-way.
Indiana Department of Transportation, Fort Wayne District for work
within State, Federal, or Interstate Highway rights-of-way.
Allen County Highway Department for work within County road right-ofway.
Fort Wayne Parks and Recreation Department for work affecting the
River Greenway or trail and bicycle system.
Allen County Surveyor’s Office for work affecting Allen County regulated
drains or mutual drains.
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Stormwater Design
Chapter 8
Culverts
Allen County Department of Planning Services (DPS) for work within a
flood zone.
Indiana Department of Natural resources (IDNR) for:
•
•
•
•
Early coordination for projects affecting stream channels or
wetlands.
Stream crossings.
Work within a floodway or flood plain.
All culverts and bridges, public or private, with a drainage area
equal to or greater than 1 square mile.
Indiana Department of Environmental Management (IDEM) for Early
Coordination for projects affecting stream channels, including regulated
drains.
United States Army Corps of Engineers (USACE) for Early Coordination
for projects affecting wetlands or stream channels including regulated
drains.
After Early Coordination is submitted to IDNR, IDEM and USACE (It is
advisable to copy affected local public agencies) a field check is
scheduled. On the field check IDNR, IDEM and USACE will determine
which agency/agencies have jurisdiction and what permitting will be
required.
SW8.11
Culvert Materials
The following sections define materials acceptable for open culvert drainage
structures including driveway culverts within public right-of-way.
1.
Ductile Iron Utility Piping
This section covers ductile iron pipe for buried applications. Figure
SW8.1 lists ductile iron pipe requirements. Standard ductile iron pipe is
cement mortar lined with a bituminous seal-coat. Seal coat is generally
intended for soft water applications that may react with the cement
mortar lining. Consider alternative linings for services involving
abrasives, pH levels below 4 and above 12 (6 and 12 without seal coat),
acids, industrial wastes, chemicals and scum and grease lines. The
exterior of ductile iron pipe is typically coated with an asphaltic coating
1 mil thick.
Figure SW8.1 –Ductile Iron Utility Piping (33 05 33)
Material
Designation
Pressure Class
Class
Designation
Joints
Gaskets
Lining
Coating
Vulcaniz
ed SBR
Cement
MortarAWWA
C140
Asphalt
icAWWA
C151
350
Ductile
Iron
AWWA
C151
250350
December 16, 2013(last draft date)
AWWA
C150
Pushon
Sizes (in)
Min Max
3
12
14
64
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Stormwater Design
2.
Chapter 8
Culverts
Concrete Non-Pressure Utility Piping
This section covers reinforced concrete utility piping for use in nonpressure stormwater applications. Figure SW8.2 list various nonpressure concrete utility piping.
A. Reinforced concrete pipe based on ASTM C76 is manufactured in
Classes I, II, III, IV and V; based on when a D-Load produces a 0.001inch crack. Pipe class is to be selected based on the loading on the
pipe and the depth of the pipe. Class I pipe is not acceptable.
Reinforced concrete pipe with bell and spigot joints uses either
of the following gaskets:
1.
Rubber gaskets conforming to ASTM C443 intended to
be watertight.
2.
Flexible Joint Sealants conforming to ASTM C990
intended to prevent the flow of solids through the joint.
B. Horizontal and vertical elliptical pipe manufactured based on ASTM
C507, is manufactured in the following classes:
1.
Horizontal elliptical pipe in five classes HE-A, HE-I, HEII, HE-III and HE-IV, for respectively, D-Loads of 600,
800, 1,00, 1,350 and 2,00 pounds.
2.
Vertical elliptical pipe in five classes VE-II, VE-III, VE-IV,
VE-V and VE-VI for respectively D-Loads of 1,000, 1,350,
2,000, 3,000 and 4,000.
Figure SW8.2 lists the equivalent designated equivalent round
size.
Elliptical pipe size is specified by the rise in inches by span in
inches.
Elliptical pipe is typically tongue and groove joints, bell and
spigot is available but from mixed manufactures and is not
typical.
C. Concrete Arch pipe is not typically available in the area; there are
manufactures in Minnesota, Iowa and the Southern states.
Arch pipe manufactured in accordance with ASTM C506 is
classified in three classes; A-II, A-III and A-IV.
The listed size for concrete arch pipe is its designated equivalent
round size.
Arch pipe size is specified by the minimum rise in inches and
the minimum span in inches.
D. Precast reinforced concrete box sections are manufactured
according to ASTM C1577. Table 1 in ASTM C1577 list the design
requirements for precast concrete box sections under earth dead
and HL-93 live load conditions.
Box sections are sizes are specified by (interior horizontal span
in feet) by (interior vertical rise in feet) by (wall and slab
thickness in inches).
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City Utilities Design Standards Manual
Stormwater Design
Material
Reinforced
Concrete
Pipe
Horizontal
Elliptical
Pipe
Vertical
Elliptical
Pipe
Arch Pipe
Chapter 8
Culverts
Figure SW8.2 –Concrete Non-Pressure Utility Piping (33 05 34.13)
Sizes (in)
Class
Designation
Joints
Gaskets
Min
Max
II
III
ASTM C76
Bell and
Rubber
12
144
Spigot
Gasket
IV
V
HE-A
HE-I
HE-II
HE-III
HE-IV
VE-II
VE-III
VE-IV
VE-V
VE-VI
A-II
Rubber
Gasket
18
144
Flexible
Sealant
36
144
ASTM C506
Rubber
Gasket
15
132
ASTM C1577
Flexible
sealant with
External joint
sealer
system or
membrane
system
3’ W x 2’ H
x 4” Wall
Thickness
12’W x
12’H x 12”
Wall
Thickness
ASTM C507
Tongue and
Groove
A-III
A-IV
Concrete
Box
Sections
Table 1
Tongue and
Groove
Note- For RCP, Horizontal Elliptical pipe and Arch Pipe with diameters larger than 24”, flexible sealants
may be used in lieu of rubber gaskets.
3.
Non-Pressure High Density Polyethylene (HDPE) Utility Piping
This section covers non-pressurized High Density Polyethylene (HDPE)
pipe, Figure SW8.3 list typical HDPE pipe used for buried applications.
HDPE pipe for storm drainage is available in corrugated dual walled,
single walled, perforated or non-perforated and with soil or water tight
joints.
A. Corrugated dual walled HDPE pipe has a smooth interior liner in the
waterway and includes and exterior corrugation that helps brace
the pipe against deformations. There are two ASTM standards for
dual walled HDPE pipe:
Pipe manufactured per ASTM 2306 is made of virgin
Polyethylene (PE) plastic compound and covers diameters from
12-inch to 60-inch.
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Stormwater Design
Chapter 8
Culverts
Pipe manufactured per ASTM F2648 permits the use of recycled
materials and covers diameters 2-inch to 60-inch.
Corrugated dual walled pipe is also available with water tight
joints; performance is based on ASTM D3212.
Figure SW8.3 – Non-Pressure High Density Polyethylene (HDPE) Utility Piping (33 05 38.13)
Sizes (in)
Designation
Joints
Gaskets
Fittings
Material
Min
Max
ASTM
ASTM F2648
ASTM
F2306
(or
HDPE Dual-Walled
(or ASTM
ASTM F477
6
18
F2648
ASTM
Pipe
2306)
2306)
4.
Corrugated Metal (CMP) Utility Piping
This section contains information on corrugated metal utility piping.
Figure SW8.4 list typical metal pipe used for buried applications.
A. Corrugated Metal Utility Piping is available in different metal
thickness and corrugation patterns. The following list the Types of
corrugations based on ASTM A760, ASTM A762 and ASTM B745:
Type I- Round pipe with annular (circumferential) and helical
corrugations.
Type IA- Round pipe with outer shell of corrugated sheet and an
inner liner of un-corrugated sheet, fabricated with helical
corrugations and lock seams.
Type IR- Round pipe with a single thickness of smooth sheet,
with helical ribs projecting outwardly.
Type IS- Round pipe with a single thickness of smooth sheet,
with helical ribs projecting outwardly. With metallic coated steel
inserts placed in the ribs creating a smooth inside surface.
Type II- Type I pipe reformed into a Pipe-Arch.
Type IIA- Type IA pipe reformed into a Pipe-Arch.
Type IIR- Type IR pipe reformed into a Pipe-Arch.
Type IIS- Type IS pipe reformed into a Pipe-Arch.
Type III- Type I pipe with perforations.
Type III- Type I pipe with perforations.
Type IIIA- Semicircular pipe intended for underdrains having a
smooth bottom and corrugated top.
B. Corrugated Metal Utility Piping has various jointing systems
classified as soil tight, silt tight, leak resistant or special design. Leak
resistant joints are acceptable. Additional CMP joints are listed in
the American Iron and Steel Institute Modern Sewer Design.
C. Corrugated pipe is manufactured with various coatings, linings and
metal types. They vary based on the required service life and
durability. Coatings include; galvanized (zinc coated), aluminized,
polymer coated, asphaltic coating and concrete coating. Metal types
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Stormwater Design
Chapter 8
Culverts
include; aluminized steel pipe, polymer coated steel pipe and
aluminum alloy pipe.
D. Corrugated structural plate pipe is field jointed; bolt and nut
requirements are listed within the structural plate’s respective
ASTM standard. Structural Plate fittings are custom ordered.
Figure SW8.4 – Corrugated Metal (CMP) Utility Piping (33 05 40)
Type
14 Gauge
Steel Pipe
Pipe
Designation
Material
Material
Designation
ASTM
A760
Aluminized
Steel
ASTM
A929
ASTM
A762
PolymerCoated
Steel
ASTM
A742
Joints
External
SemiCorrugated
(Hugger)
Coupling
Band
External
SemiCorrugated
(Hugger)
Coupling
Band
Gaskets
Fittings
Rubber
O-Ring
Sizes (in)
Min Max
4
144
4
144
4
120
Match
Pipe
Material
14 Gauge
Aluminum
Alloy Pipe
ASTM
B745
Aluminum
Alloy
ASTM
B744
Corrugated
Steel
Structural
Plate
ASTM
A761
Galvanized
ASTM
A761
Field Bolted
-
-
-
Corrugated
Aluminum
Alloy
Structural
Plate
ASTM
B746
Aluminum
Alloy
ASTM
B209
Field Bolted
-
-
-
December 16, 2013(last draft date)
Rubber
O-Ring
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