Guidelines for Drainage/Hydraulic Design

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•
NORTH CAROLINA
DIVISION OF HIGHWAYS
GUIDELINES FOR
DRAINAGE STUDIES
AND

19
DESJL'r'GN
HYDRAULIC
ADDENDUM TO
HANDBOOK OF DESIGN FOR HIGHWAY
SURFACE DRAINAGE STRUCTURES - 1973
PREPARED BY
A. L HANKIN . M P.E.
IV,
STATE HYDRAULICS ENGINEER
JUNE 1990
111

• TABLE OF CONTENTS
PAGE
I. GENERAL DRAINAGE POLICIES AND PRACTICE .............. 3
II. PRE-DESIGN STUDY AND REPORT ......................... 7
III. FIELD RECONNAISANCE AND SURVEY ...................... 8
IV. DRAINAGE PLANS ...................................... 10
V. HYDROLOGY ........................................... 12
VI. BRIDGE CROSSINGS .................................... 19
VII. CULVERTS ............................................ 27
VIII. STORM DRAINAGE SYSTEM ............................... 32
IX. CHANNELS AND ROADWAY DITCHES ........................ 38
X. EROSION AND SEDIMENT CONTROL ........................ 43

• XI. PERMIT .............................................. 46
XII. APPENDIX
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NORTH CAROLINA DIVISION OF HIGHWAYS
GUIDELINES FOR DRAINAGE STUDIES AND HYDRAULIC DESIGN
This document is provided for guidance in the methods, proce-
dures, policies, and criteria which must be followed, and the
information that is to be developed during a drainage study and
hydraulic design. It is an addendum to the "Handbook of Design
for Highway Drainage Structures - 1973". Where conflicts exist in
policies, criteria or design procedures in these documents, the
information provided herein takes precedence.
This guideline is not all inclusive and the engineer must use
good judgement in its application to insure that the design is
complete and appropriate for the site. The AASHTO highway
drainage guidelines and model drainage manual are recommended for
further reference in drainage design. The engineer is encouraged
to use ingenuity in applying new and differing concepts and
procedures in the design process. However, all specified methods,
procedures and criteria presented in this guidance must be
followed unless approval for variance is given by the State
Hydraulics Engineer or his designated representative (further
• referred to in this guideline as Reviewing Engineer). All
referenced design forms, reports and check lists must be completed
and included with the Hydraulics Design Package. The Hydraulic
Design Documentation Summary Sheet (Appendix Item 1) is to front
the design package and must include the seal of the Engineer
performing or directly supervising the work. All bridge and
culvert survey reports will be individually sealed by the
responsible engineer.
The following publications are required for implementation of
the procedures covered in the guideline:
(1) U. S. Geological Survey, Water Resources Investigation
Report 87-4096 (U.S.G.S. Office, Raleigh)
(2) FHWA - Highway Engineering Circular No. it "Design of
Rip Rap Revetment"
(3) FHWA - Hydraulic Engineering Circular No. 12 "Drainage
of Highway Pavement" - 1984
(4) FHWA - Hydraulic Engineering Circular No. 15 "Drainage
of Roadside Channels with Flexible Linings" - 1986
(5) FHWA - Hydraulic Engineering Circular No. 19 "Hydrology"
° 1984
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(6) FHWA - Guideline for Selecting Mannings Roughness •
Coefficients for Natural Channels and Flood Plains -
1984
(7) FHWA - Hydraulic Design Series No. 5 "Hydraulic Design
of Highway Culverts" - 1985
(8) NCDOT - "Guidelines for Control of Erosion and Sediment
During Construction" - 1980
(9) NCDOT - Roadway Standard Drawings.
•

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• I. GENERAL DRAINAGE POLICIES AND PRACTICES
North Carolina long adhered to the civil law rule in regard
to surface water drainage. This rule obligates owners of lower
land to receive the natural flow of surface water from higher
lands. It subjects a landowner to liability whenever he
interferes with the natural flow of surface waters to the
detriment of another in the use and enjoyment of his land. Since
almost any use of land involves some change in drainage and water
flow, a strict application of the civil law principals was
impracticable in a developing society. Thus, a more moderate
application of this rule to allow a landowner reasonable use of
his property evolved.
The North Carolina Supreme Court formally adopted the rule of
reasonable use with respect to surface water drainage and
abandoned the civil law rule (Pendergrast V. Aiken - August 1977).
The adopted reasonable use rule allows each landowner to make
reasonable use of his land even though by doing so, he alters in
some way the flow of surface water thereby harming other
landowners, liability being incurred only when this harmful
interference is found to be unreasonable and causes substantial
damage.
There are still some unanswered
• of the adopted reasonable use rule
agency activities, however, the rule
of modern life and will provide
treatment. Therefore, the policies
of Highways in regard to surface
rule.
ENGINEER'S RESPONSIBILITY
questions in the application
to specific areas of State
is in line with the realities
just, fair and consistent
and practices of the Division
drainage matters follow this
The reasonable use rule places responsibility on the
"landowner" to make reasonable use of his land. While "reasonable
use" is open for interpretation on a case by case basis, it would
certainly infer from an engineering standpoint that provision for
and treatment of surface waters on the property are made in
accordance with sound, reasonable and acceptable engineering
practices. Therefore, the Engineer must see that these principals
are reflected in the design process.
The rule also states that liability incurs only when harmful
interference with the surface water is found to be unreasonable
and causes substantial damage. Therefore, it is incumbent on the
Engineer to evaluate the potential affects of surface water
activities on both up and downstream properties and to include
provision in the design to hold these affects to reasonable
levels.
• These type of engineering practices, considerations and their
proper documentation are contained in these Highway Drainage
Guidelines and Surface Drainage Handbook, as well as in other
referenced materials.
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The following are general drainage policies and practices of •
the North Carolina Division of Highways involving both design and
maintenance activities. While this is an update and revision of
some policies and practices contained in the drainage handbook, it
still should be referenced for additional policies relating to
specific areas such as: flood control projects, drainage
easements, roadways on dams and subdivisions.
AUGMENTATION. ACCELERATION
Development of property can cause an increase in the quantity
and peak rate of flow by increasing impervious areas and providing
more hydraulically efficient channels and overland flow. It is
the policy of the Division of Highways to develop and make reason-
able use of its lands and rights-of-way through sound, reasonable
and acceptable engineering practices and to deny responsibility
for augmented or accelerated flow caused by its improvements
unless determined to cause unreasonable and substantial damages.
It is likewise the policy of the Division of Highways to expect
this same practice and acceptance of responsibility by other
property owners and those engaged in the development of these
properties.
DIVERSIONS
Diversions are defined as the act of altering the path of
surface waters from one drainage outlet to another. It is the •
policy of the Division of Highways to design and maintain its road
systems, so that no diversions are created thereby, insofar as is
practicable from good engineering practice.
Any person(s) desiring to create a diversion into any highway
rights-of-way shall do so only after receiving written permission.
This permission will be granted only after it has been determined
that the additional flow can be properly handled without damage to
the highway, that the cost for any required adjustments to the
highway system will be borne by the requestor and that appropriate
consideration and measures have been taken to eliminate or save
harmless the Division of Highways from potential downstream damage
claims. It is generally desirable that the Division of Highways
not become a party to diversions unless refusal would create a
considerable and real hardship to the requesting party(ies).
IMPROVEMENTS AND MAINTENANCE OF DRAINAGE WITHIN THE RIGHT-OF-WAY
Drainage structures and ditches shall be kept open and
maintained at a functioning level such that they do not present an
unreasonable level of damage potential for the highway or adjacent
properties.
Where the elevation of the flowline of an existing culvert
under a highway is not low enough to adequately provide for •
natural drainage, the Division of Highways will assume full
responsibility for lowering the culvert or otherwise provide
needed improvement.
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• Where a requested culvert invert adjustment is a result of a
property owner lowering the flowline of the inlet and outlet ditch
in order to improve drainage of his property, the following
considerations shall be given to the action taken:
(1) The lowered drain must have a reasonable expectancy of
being functional and maintainable.
(2) Division of Highways participation (up to full cost)
must be based on benefit gained by the roadway drainage
system as a result of the lowering.
(3) Where the new installation is of doubtful, or no benefit
to highway drainage, the requesting party must bear the
entire cost of installation.
Where the size of an existing highway culvert is determined
to be of unacceptable adequacy in regard to the roadway system
functioning as a result of a general overall development of the
watershed, it is the Division of Highways' responsibility to
replace the structure or otherwise take appropriate action.
Where this same culvert inadequacy is the result of a single
action or development, it is felt to fall within the realm of
"unreasonable and substantially damaging" under the State adopted
drainage ruling. Therefore, the party responsible for the action
• or development should bear the cost of replacement.
Where a new culvert crossing is requested, if the culvert is
required for proper highway drainage or sufficient benefits to the
highway drainage system would occur, the full cost will be borne
by the Division of Highways providing there is no diversion of
flow involved. Where the new installation is of doubtful or no
benefit to highway drainage, the property owner will bear the
entire cost. When both parties receive benefit, a joint effort
may be negotiated.
Established culvert crossings will be maintained and requests
to eliminate any culvert should have the approval of the State
Hydraulics Engineer.
When new private drives are constructed entering the highway,
the property owner will furnish, delivered to the site, the
amount, type and size pipe designated by the Division of Highways,
to be installed by maintenance forces.
No alteration, attachment, extension, nor addition ' of
appurtenance to any culvert shall be allowed on highway rights-of-
way without written permission.
IMPROVEMENTS AND MAINTENANCE OF DRAINAGE OUTSIDE THE RIGHT-OF-WAY
• While it is the responsibility of the Division of Highways to
provide for adequate drainage for constructing and maintaining the
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State Highway System, it is not its policy nor responsibility to •
provide improved drainage for the general area traversed by such
roads, unless incidental to the drainage of the road or highway
itself. Drainage involvement outside the highway rights-of-way is
limited to two general areas of justification:
(1) Sufficient benefit could be gained by such action to
warrant the cost. These benefits would be in such areas
as reduction in roadway flood frequency or extent,
facilitation of maintenance, or a reduction in potential
damages.
(2) Work is required to correct a problem or condition
created by some action of the Division of Highways.
It is not the responsibility of the Division of Highways to
eliminate flooding on private property which is not attributable
to acts of the agency or its representative.
In general, outlet ditches will be maintained for a
sufficient distance below the road to provide adequate drainage
therefore. On large outlets serving considerable areas outside
the right-of-way, the maintenance should be done on a cooperative
basis, with the benefited properties bearing their proportionate
share. Shares will, in general, be based on proportioning of
runoff from the areas served by the outlet.
It is not the policy of the Division of Highways to pipe •
inlet or outlet drains, natural or artificial, outside the right-
of-way, which existed as open drains prior to existence of the
highway. Where the property owner wishes to enclose an inlet or
outlet, the Division of Highways may install the pipe adjacent to
the right-of-way if justified by reason of reduced maintenance,
safety or aesthetics if the pipe is furnished at the site by the
property owner. This does not apply to the development of
commercial property.
OBSTRUCTIONS
It is the policy of the Division of Highways that when a
drain is blocked below the highway, which is detrimental to
highway drainage, if from natural causes, the Division of Highways
will take necessary measures to remove the block or obstruction.
Where the block is caused by wrongful acts of others, it is the
policy of the Division of Highways to take whatever recourse
deemed advisable and necessary to cause the party(ies) responsible
to remove the block. Where a block is created downstream of a
highway, whether natural or artificial, and is of no consequence
to the Division of Highways, it is the policy to remain neutral in
causing its removal.
State Statute (G. S. 136-92) provides that anyone obstructing •
any drains along or leading from any public road is guilty of a
misdemeanor.
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• II. PRE-DESIGN STUDY AND REPORT
Prior to commencing detailed design or field studies, the
project is to be reviewed in general to familiarize the engineer
with the project requirements. Data is to be collected and
reviewed to determine what additional information is required
during the field reconnaisance and survey stage. At this time,
local highway maintenance personnel are to be contacted for their
input on problem areas and other pertinent information. Specific
methods, procedures and criteria are also addressed at this stage.
Unit project engineers are to complete this phase with a
"pre-design review meeting" with the Assistant Unit Head. Private
engineering firms are to hold this meeting with the unit's Design
Coordinator. The unit or private project engineer is to prepare a
draft listing of topics and information for discussion at the
meeting. He is to add to this documentation, actions and
decisions agreed to at the review meeting resulting in a summary
document for inclusion in the final project report. The section
of the "Check List for Drainage Study and Hydraulic Design" -
Appendix Item 2, identified as Prior to Field Survey is to be
completed and approved at this stage.
•
•
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III. FIELD RECONNAISANCE AND SURVEY •
It is required that the engineer with primary responsibility
for the drainage study, review the project in the field prior to
commencing detailed design. The purpose of this field trip is to:
- visually acquaint the designer with conditions and
constraints of the site
- verify data obtained from other sources
- identify ponds, lakes, reservoirs and other storage areas
which affect discharge rates
- review existing drainage features and obtain information on
performance
- review potential outlet channels for performance and
adequacy
- identify sediment sensitive areas such as lakes, ponds, and
developed stream areas
- review contributing watershed characteristics
- obtain details of size, location, length, material type and
condition of existing drainage structures. When existing
box culverts are to be extended, top slab and center wall
thicknesses must also be obtained.
- obtain historical flood and other stream flow information
such as:
- maximum and other large flood levels at as well as up
and down stream of the study site
- dates of these occurrences
- very frequent flooding levels (examples: annual, 2
year, 5 year)
- channel scour and instability
- drift potential, size and quantity
- conveyance of existing crossings including roadway
overtopping, damage and time of closure
- descriptive photographs of site
- obtain required additional survey data and supplemental
topographical information such as:
- elevations of flooding
- elevations of up and down stream features which could
control the design such as buildings, roads, yards,
fields and other drainage structures
- stream bed elevations a sufficient distance up and
down stream to establish local stream gradient
- floodplain and channel cross-sections for backwater
analysis and channel realignments
8 10/92
I i
• - culture in floodplain for determination of flow
resistance and distribution (estimate n-values)
- General description of stream bed and bank materials
(clay, silt, sand, gravel, cobble, rock). If
extensive rock is visable explore extent by probing on
culvert size streams for possible footing.
- Additionally for urban sections:
- Locate and obtain elevations of low areas back of
proposed curb for special pickups
- Locate small inflow systems such as roof and basement
drains.
- Review and obtain the following type information for use in
bridge scour analysis:
- Description of floodplain and channel material. If
sand or silt, is it fine, medium or coarse?
- observe existing structure for evidence of scour and
condition around footings and supports.
- Verify or obtain channel cross-sections under bridge
and at locations at least two bridge lengths up and
down stream.
- Elevation and location of deepest point in channel.
- If visible, note type and condition of existing
foundation.
Review site conditions and obtain precise limits and
classification of wetlands for permit application.
All pertinent data and facts gathered through this field
reconnaisance and survey are to be documented on work plans, field
notes or other forms suitable for submittal with the final project
report. The section of the "Check List for Drainage Study and
Hydraulic Design" - Appendix Item 2, identified as field study is
to be completed prior to completion of the field study.
•
9 6/90
IV. DRAINAGE PLANS
A copy of the project preliminary roadway plans with the pro-
posed roadway section and construction limits noted are to be used
as work plans to develop a pencil sketch type layout of the
proposed drainage features. The sequence of development of these
plans should be as follows:
(1) Confirm and add as necessary all existing drainage features
(structure type, size, elevations).
(2) Note all existing drainage divides, flow directions,
ditches, channels, etc.
(3) Confirm and add information on utilities that may affect
drainage features.
(4) Plot any special ditches or other topographical features
identified during field surveys and not included on the
plans.
(5) Make notes of design controls identified during data
collection and field survey stage.
(6) Determine and evaluate the patterns of surface flow as
affected and developed by the project construction. (Note
flow direction and concentrations as needed for clarity in
red).
(7) Develop a scheme and layout of drainage features (bridges,
box culverts, pipes, storm drainage systems, ditches,
channels, etc.) to properly convey surface flow within and
adjacent to the project. Note these features on the plans in
red.
(8) Utilizing procedures presented in the following section of
these guidelines, perform the design studies required to
detail each drainage feature (type, size, location, material,
etc.).
(9) Documentation of the design detail of each individual feature
will be provided as directed in the related section of the
guideline. A short summary of information relating to each
feature shall be noted on these work plans and consist of the
following as a minimum:
- location by station, skew or other descriptive detail
- type, size and material
- elevations (invert, grade, etc.)
- drainage area
- design discharge and elevation
- base discharge and elevation
- overtopping discharge and elevation
•
•
•
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• (10) Plot storm drainage system profiles including:
- pipe and inlet inverts
- utility crossings
- hydraulic grade line (water surface profile)
(11) Note all special channel and ditch detailing including
special grades and permanent lining requirements. Temporary
linings will be shown on the erosion control plans.
C7
•
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V. HYDROLOGY •
The hydrological analysis phase involves the determination of
discharge rates and/or volumes of runoff that the drainage
facilities will be required to convey or control. Many
hydrological methods are available and most can be appropriately
and effectively used under proper control and application.
Particular methods to be used for highway drainage studies and
circumstances for their use are listed below. When the site
involves a FEMA flood study area, discharge methods and values
provided in the report will take precedent over these methods for
determining compliance with the regulation. The results from any
hydrologic procedure should be compared to historical site
information and adjustments made in the values estimated or
procedure used when deemed appropriate.
RURAL WATERSHEDS - > 1 so. mi. The procedures and values
PEAK DISCHARGE presented in U. S. Geological Survey, Water
Resources Investigation Report 87-4096 shall
apply.
< 1 sa. mi. The hydrological procedure and
charts presented in the N. C. Division of
Highways Drainage Handbook (Charts C200.1 and
C200.2) shall be used.
URBAN WATERSHEDS - < 10 acres If watershed is primarily composed •
PEAK DISCHARGE of pavement, grassed shoulders and slopes,
and/or other mixed surface type runoff, use
rational formula for discharge determination.
If predominately residential type development
with natural drainage channel(s), use Highway
Charts C200.1 and C200.3.
> 10 acres < 125 acres Use Highway drainage
charts (C200.1 and C200.3). If areas have
greater than 50% impervious cover and/or
extensive storm drainage systems, a special
procedure such as hydrograph routing is
required. The Hydra program and SCS TR-20 are
routing procedures. Determination of specific
sites for special study and selection of a
design procedure must be approved by the
Reviewing Engineer. This item should be
addressed in the pre-design meeting.
> 125 acres Use the three parameter regression
equations developed by the U.S.G.S. (Sauer et
al., 1983) which adjust a rural discharge to
urban conditions using the basin development
factor (BDF).
VOLUME OF FLOW Use Snyder's Synthetic Unit Hydrograph
Formulation or dimensionless hydrograph method
12 10/92

• (USGS - Georgia). For estimating purposes or
minor impoundment (<1.0 acre foot storage) a
simple triangular hydrograph as described in
section 307 of the Highway Drainage Manual can
be used.
The following is some specific guidance for the above listed
methods:
"U.S.G.S. Water Resources Investigations Report 87-4096"
Regional regression equations are provided on Page 17 of this
reference document for ungaged sites. For gaged sites, the
discharge estimate is to be determined by weighting the
regional and station estimates (See Equation 5, Page 18). For
sites on gaged stream and having a drainage area within 50%
of the gage site, the discharge estimate is to be transferred
from the gage in accordance to Equation 6, Page 19.
Log-Pearson Type III Station flood discharge values are
presented in Table 1, Page 45-52. These values should be
updated after 1991 or by individual station if a major flood
has occurred since the date of records used (1984).
"Highway Charts - N. C. Division of Highways Drainage
Handbook"
• The rural areas charts C200.1 and C200.2 (Dated January 1973)
are to be used within the limits previously noted. The
procedure for use is as follows:
(1) From Chart C200.1 determine the hydrologic contour by
location of the structure site. Interpolate to 0.5
contour interval.
(2) Determine: - Drainage area (acres)
- Watershed shape factor
(A/L2)
A = area
L = length
- Percent forested cover
(3) Enter chart C200.2 with drainage area and hydrological
contour and read discharge.
(4) For discharges other than Q50, apply frequency
adjustment factors shown on chart.
(5) Enter charts C200.4 and C200.5 to determine adjustment
factors to be applied to above values for percent
forested cover and watershed shape.
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NOTE: - The forested cover value can be used to reduce .
discharge only when the watershed is
mountainous, wetlands, or a designated preserve
area where clearing is very unlikely.
- The multiple of the two adjustment factors
cannot exceed the limits of 0.7 and 1.5.
The urban chart C200.3 (dated January 1973) is to be used within
the limitations previously noted. Procedure for use is as
follows:
(1) From chart C200.1 determine the hydraulic contour to the
nearest 0.5 interval.
(2) Determine the type and relative density of development.
This should be a projection of conditions based on
potential future development over the life of the
structure. The development types as noted on the chart
are:
- Residential-High Type; This is suburban type
development with lots sizes > 0.5 acre
- Average Development; Small lots < 0.5 acre or
mixture of residential and some small business
- Large Area Full Business; Area > 75 acres, no more •
than 50% impervious cover or extensive storm
drainage systems
- Small Area Full Business; Area < 75 acres no more
than 50% impervious cover or extensive storm
drainage systems
(3) Enter chart C200.3 with drainage area and hydraulic
contour and read discharge.
(4) Apply appropriate adjustment factor for development
type.
(5) For discharges other than Q10, apply frequency
adjustment factors shown on chart.
"Rational Formula"
The rational formula estimates the peak rate of runoff (Q) as
a function of drainage area(A), runoff coefficient (C), and
mean rainfall intensity (I) for a duration equal to the time
of concentration (tc - the time required for water to flow
from the most hydraulically remote point of the basin to the
location of analysis). 0
Q = CIA
14 6/90

• Use limitations are
expanded discussion
Engineering Circular
noted previously in guidelines. For
of rational formula see "FHWA, Hydraulic
No. 12". Some specific criteria are:
A = 10 acres maximum
I = Use highway manual charts C200.7, C200.8,
C200.9. Interpolate between cities for other
points. The Hydrain program will provide
values based on lattitude and longitude
location.
C = Use a weighted value = CiAi/A
Table 4-2 provides some often used values:
TABLE 4-2
TYPE OF SURFACE C ;
Pavement 0.7 - 0.9
Gravel surfaces 0.4 - 0.6
Grassed, steep slopes 0.3 - 0.4
Grassed, flat slopes -0.2 - 0.3
Woods 0.1 - 0.2
Time of concentration (tc) - Use Kinematic wave
equation for overland flow time. Solution by nomograph
chart page 15-16 Hydraulic Engineering Circular No. 12.
Minimum tc - 10 min.
"USGS Urban Regression Equations"
This procedure is an adaptation of the procedure presented in
"Techniques of Estimating Flood Hydrographs For Ungaged Urban
Watersheds" published as open file report 82-365 by the
U.S.G.S.
(1) Determine the size of the drainage area and compute the
equivalent rural discharge (RQ).
(2) Divide the watershed into approximate equal thirds.
(Upper, middle, lower).
(3) Compute the basin development factor (BDF - value of
0-12) for each third of the watershed. Four aspects of
the drainage system are evaluated and assigned a code of
1 or 0. This evaluation must include consideration for
planned or predicted future development.
Channel Improvements
Has a prevalent amount (>=50%) of the main and
principal tributary channels been or expected to be
subjected to improvements such as straightening,
enlarging, deepening, or clearing. If so assign a
value of 1, if not 0. Channel includes floodplain.
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Channel Linings •
Has a prevalent amount (>=50%) of the main and
principal tributary channels been or expected to be
lined with an impervious material. If so assign a
value of 1, if not 0.
Storm Drains
Has a prevalent amount (>=50%) of the secondary
tributaries been enclosed in drainage structures
such as pipes. If so assign a value of 1, if not
0.
Curb and Gutter Streets
If more than 50% of the subarea (third) is
urbanized and more than 50 percent of the streets
and highways are curbed and guttered then assign a
value of 1, if not 0.
Total the value for the three subareas to establish
the BDF.
(4) Compute the urban peak discharge using the following
appropriate equation:
UQ2 = 13.2A.21 (13-BDF) .43 RQ2 .73
UQ5 = 10.6A'17 (13-BDF) '39 RQ5 .78
UQ10 = 9.51A'16 (13-BDF) .36 RQ10 .79
UQ25 = 8.68A.15 (13.BDF) .34 RQ25 .80
UQ50 = 8.04A.15 (13-BDF) .32 RQ50 .81
UQ100 = 7.70A'15 (13-BDF) .32 RQ100 .82
Where UQ = Urban peak discharge
A = Watershed area in Sauare Miles
BDF = Basin Development Factor
RQ = Equivalent rural discharge
"Snyders Synthetic Unit Hydroaraph"
This procedure can be utilized to develop a design hydrograph
associated with a peak flow. It can be performed with or
without precipitation and surface runoff data. It provides a
graphical depiction of runoff as a function of time as well
as an estimate of runoff volume. "FHWA, Hydraulic Engineer
Circular No. 19" is a reference source for detailed direction
in this procedure. The Hydrain computer program also
includes this design alternate.
The overall hydrologic analysis for a project begins with
review and extrapolation of pertinent information from data
16 10/92
• sources identified during the pre-design study. Final
determination of sources of watershed areas and base mapping for
drainage area delineation are also made at this time. Primary
references for this information are:
- U.S.G.S. and T.V.A. quadrangle mapping
- U.S.G.S. open file report 83-211 "Drainage Areas of
Selected sites on Streams in North Carolina"
- Photogrametric contour mapping
- Aerial photography
- Special studies (Corps, TVA, FEMA)
- Field reconnaissance (This is required for most
non-riverine drainage areas in the coastal plain as well as
many small watersheds in other areas.)
The selection of a "design discharge" for a drainage feature
is a risk based assessment process involving the evaluation of a
range of flood magnitudes for such factors as potential damages,
costs, traffic service, environmental impact, and flood plain
management criteria, to determine an appropriate and acceptable
structure for each site. One specific criteria on which the
design is evaluated and generally referred to as the "design
discharge" is the flood level and frequency which results in
inundation of the travelway. Table 4-3 relates desirable minimum
levels of protection from travelway inundation to roadway
classification. Variation from these minimum design levels must
• be justified through the assessment process and appropriately
documented. When roadway overtopping is not involved, the "design
discharge" will be the level of flood used for establish-went of
freeboard and/or backwater limitations.
TABLE 4-3
ROADWAY CLASSIFICATION FREQUENCY
Interstate (I) 50 year
Primary (US & NC) 50 year
Secondary (Major, City thoroughfare) 50 year
Secondary 25 year
The hydrologic analysis process for a specific drainage
feature is accomplished as an integral part of the hydraulic
sizing and performance analysis. Specific discharge criteria and
computational needs are addressed in further sections of this
guideline for each particular drainage feature. Documentation of
the hydrologic data is included with the hydraulic design data.
The following general guidance shall be used to determine
when it is appropriate to consider the overtopping flood and the
limits used in defining the data. This must be applied with good
judgement and considered on the particular merits of each crossing
analysis.
(1) Where overtopping is not practicable and would require
flood magnitude greater than state of the art capability
to estimate frequency (500+ year flood), a statement
similar to the following should be noted on the survey
17 10/92
report - "overtopping flood is greater than 500+ year •
event".
(2) An approximate frequency of occurrence must be
established for the overtopping discharge. The
following frequency designation will be used:
(a) If within 5% of the 200 or 500-year estimated
discharge, list as 200-year +/- or 500-year +/-.
(b) If greater than 100-year flood but not within 5% of
200-year, list as 100-year +.
(c) If greater than 5% of the 200-year but not within
5% of the 500-year, list as 200-year +.
(d) If greater than 5% of the 500-year, list as
500-year + .
•
•
18 6/90
• VI. BRIDGE CROSSINGS
The design of a stream crossing system requires a comprehen-
sive engineering approach that involves data collection,
hydrologic analysis, formulation of alternatives, evaluation and
selection of the "best" alternative according to established
criteria, and documentation of the final design. The design
process provided herein will not attempt to address all situations
or all areas of knowledge and experience the engineer should
possess to be profficient in crossing design. We do strongly
recommend that the engineer reference and study the bridge
crossing chapter of the "AASHTO-Highway Drainage Guidelines" and
the FHWA floodplain policies statements in FHPM, 6.7.3.2. The
design procedure presented herein will insure a systematic process
which will adequately address most crossing situations. It will
also help to identify conditions and situations requiring special
study and/or consideration.
(1) DATA COLLECTION
Information gathered during the pre-design study and
field survey is to be assembled for the study site.
This process will include:
(a) Review of the preliminary design and assessment
report (Appendix Item 3)
(b) Plotting of a plan and profile view of the
topographical features for the crossing on a bridge
survey report (Appendix Item 4)
The drawing scale shall be 1" = 50' horizontal, 1"
= 10' vertical. Features are to be in ink with
existing manmade features shown with dashed lines.
A larger sheet may be used if required for wide
floodplains. It must be trimmed and folded to fit
within the Bridge Survey Report.
Information to be included on the profile view:
- Centerline profile of the floodplain
- Historical flood data (high water elevations,
date of occurrence, and estimated frequency)
- Show existing features (utilities, drainage
structures, and crown grade profile of
existing highway)
- Water surface elevation at date of survey and
"normal" water surface elevation
Information to be shown on plan view:
• - Natural features (limits of floodplain, stream
channel showing base and top of bank. Type of
vegetative cover in floodplain
19 6/90
- Existing man-made features in floodplain •
(buildings, houses, highways, utilities, etc.)
(2)
(c) Completion of the site data portions of the survey
report and the hydraulic design report. (Appendix
Item 5)
HYDROLOGIC ANALYSIS
This phase involves the development of a number of
discharges on which the performance of alternate designs
will be evaluated. This entails:
(a) Determination of a drainage area for the site
(b) Developing discharge quantities for a range of
floods to be studied. This shall include as a
minimum:
- Q2, Q10, Q25, Q50, Q100, Q-overtopping
(existing roadway), Q-overtopping (proposed
roadway)
(c) If a crossing is in a FEMA Regulated Flood
Insurance Program site where a detail study has
been performed the study discharges will be used
to evaluate conformity of the project to flood
zone regulations. If an error is found in the
FEMA hydrological data or if there is considerable
disagreement in the data and results from standard
hydrological procedures presented in this
guideline, a specific course of action shall be
developed and approved by the Reviewing Engineer.
(d) Complete the hydrologic analysis portion of the
bridge survey and hydraulic design reports.
(3) FORMULATION OF ALTERNATIVES
as follows:
This and the next phase, Alternative Evaluation and
Selection, are generally an iterative process through
which a hydraulic analysis is performed for one or
more alternatives, the results are evaluated,
adjustments are made and further alternatives developed
until the "best" alternative is selected. This
hydraulic analysis of alternatives will be accomplished
(a) The WSPRO Step-backwater Analysis Program shall be
used to model the stream reach being studied. An
exception is to be made for utilization of the HEC-
2 when an existing detailed flood study crossing is
involved.
20
6/90

• (b) A minimum of three cross-sections shall be used
(one each at a bridge length up and downstream and
one at the crossing). Additional sections should
be used when site conditions warrant.
(c) A run of the model with the selected discharge
shall be made under existing conditions and a
comparison made to at least one historical
occurrence.
(d) Adjustment shall be made to calibrate the model to
a "best" or "reasonable" fit to the historical
data.
(e) FHWA "Guideline for Selecting Manning's Roughness
Coefficients for Channels and Flood Plains" should
be referenced for roughness factor selection.
(f) A profile plot of the adjusted model including the
historical data shall be provided.
(g) Alternate structures and grade configurations can
now be entered for hydraulic output development.
(4) EVALUATION AND SELECTION
The selection of a "best" alternative is accomplished by
comparison of the study results and considerations to
acceptable limitations and controls. These limitations
are prescribed by general and specific criteria.
General criteria on which the design alternatives must
be judged are:
- Backwater will not significantly increase flood
damage to property upstream of the crossing.
- Velocities through the structure(s) will not damage
the highway facility or unduly increase damages to
adjacent property.
- Existing flow distribution is maintained to the
extent practicable.
- Level of traffic service is compatible with that
commonly expected of the class of highway and
projected traffic volumes.
- Minimal disruption of ecosystems and values unique
to the floodplain and stream.
- Cost for construction, maintenance and operation,
including probable repair and reconstruction, and
potential liabilities are affordable.
- Pier and abutment location, spacing, and
orientation are such to minimize flow disruption,
debris collection and scour.
-
Proposal is consistent with the intent of the
standards and criteria of the National Flood
Insurance Program.
21 6/90
specific criteria on which the design alternate must be
judged:
(a) Design discharge
This is the specific return period flood which has
been established as being an acceptable level for
roadway overtopping. When roadway overtopping is
not involved, it will be the level of flood used
for establishment of freeboard and/or backwater
limitations. See Table 4-3 for desirable design
discharge standards based on accepted inundation
levels relative to roadway classification.
Variation from these or other specific standard
values must be justified by an assessment process
which reflects consideration for risk of damages to
the roadway facility and other properties, traffic
interuption, environmental impacts and hazard to
the public.
(b) Backwater
This is the increase in water surface elevation for
a particular flood event measured relative to the
normal water surface for this same event at the
approach section. For National Flood Insurance
Program designated floodplains, the backwater for
the 100-year flood shall not exceed 1 foot. The
normal water surface as it relates to a flood •
insurance site would include any restriction
existing at the time of adoption of the regulation,
such as an existing bridge. When a detail study
area is involved, no increase in backwater is
allowed when the crossing data is entered into the
floodway model unless a modification proposal is
developed and presented to the community and FEMA
for approval. A modification proposal is to be a
revision in the floodway boundaries to accommodate
the crossing without increasing the 100-year flood
elevation above the established floodwav elevation.
(c) Minimum length
The bridge ends shall be located such that in the
profile bridge section a line projection of the
spill through slope face provides a minimum of 10
feet setback from any point on the channel bank or
bed. Greater setback can be dictated by hydraulic
conveyance needs and channel scour predictions.
(d) Freeboard
Provide 2 feet of clearance for bridge super-
structures above the design flood for primary route
structures and secondary crossings of major rivers.
1 foot for all other structures. There is no
established freeboard for the roadway or other
controlling features. However, this can be
22 10/92
C .. iS t` :b
t
• established as a project specific requirement if a
specific need or condition warrants. This or a
justified variance from the standard freeboard
requirement must be approved by the Reviewing
Engineer prior to completion of the design.
(e) Slope Protection
As a minimum class two stone ripraR shall be
placed on the spill-through bridge slopes through
the waterway opening extending to a point even with
the bridge ends. The need for additional slope
protection along the roadway fill approaches shall
be evaluated on a site by site basis. Concentra-
tion, depth and velocity of flow in the overbank
are factors to be considered in setting the riprap
limits. As a guide, the following can be used:
Z C i-VI/v2) 1
Where:
Z = Required distance of slope protection
V1 = Average velocity in approach
V 2 = Average velocity in bridge opening
L = Distance up stream to maximum backwater
(bridge length)
The top of the riprap elevation shall be 1 foot
above the "design flood" which, for establishing
slope protection limits, will not exceed the
50-year event.
(f) Deck Drainage
Standard practices for structural design at this
time is to include 6" scupper drains at 12 foot
centers in all waterway crossing structures. If
review for variance from this standard is
requested, the spacing requirement will be based
on:
(1) Scupper capacity provided in HEC 12
(2) 4" per hour rainfall intensity (maximum
drivable)
(3) A minimum consideration of 30% blockage
(4) Maximum gutter spread of 2 feet
• A standard flume and 12" down spout shall also be
provided at all down grade bridge ends. The
capacity and adequacy of these flumes can also be
checked using the procedures of HEC 12.
23 10/92
Separation structures will have a very limited
number of scuppers (adjacent to the piers). The
potential gutter spread along the structure must be
determined for acceptability. This acceptable
spread is dependent on shoulder or special width
provided on a structure, but should not extend
into the travel lane of a shoulder approach
structure if practicable to prevent. The few
scupper drains can be ignored in this spread
evaluation for separation structures. With the
potential quantities of flow from the deck, it is
very important to check the adequacy of the
standard bridge end flume and provide
recommendations for additional measures when
warranted.
11
selection of a "best" alternate must include an
economic analysis to insure that the selected
alternate provides the least total cost from a
construction, maintenance, and operation
standpoint.
(5) DOCUMENTATION OF DESIGN
(g) Channel Changes
As a general rule, the bridge crossing will be
designed to accommodate the natural channel.
Channel modification will be considered only when
there is no practicable alternative from a cost or
functional standpoint. Modification proposals with
sufficient supportive data must be presented to the
Reviewing Engineer for approval prior to completion
of the design.
(h) Scour
Scour depth prediction by equation is required for
all bridge sites. The procedure for this analysis
is presented in Appendix Item 6.
(i) Economics
When more than one alternate will satisfy all
control factors for a site the evaluation and
All information pectinate to the selection of the "best"
alternate shall be documented in a manner suitable for
review and retention. This will involve:
(a) Completion of the bridge survey report (Appendix
Item 4). Sketch proposed structure(s) and roadway
grade in plan and profile showing crown grade
elevation, super structure, bent locations, limits
and elevations of riprap and any channel
modifications.
(b)
In addition to the data required on the
relative to the design, overtopping
flood, provide in table or performance
24

survey
and base
curve form a
io/92
•
•
•

• depiction of the natural and post-design water
surface elevations at the upstream section for the
design flood. If at an existing crossing site,
include the existing condition as a third listing
and plot.
(c) Complete the hydraulic design report (Appendix Item
5).
(d) Include scour formula computations on the bridge
survey report. Plot estimated depths on profile
view.
(e) Provide hard copy summary sheet of computer input
and output.
(f) Provide complete computer analysis data files on a
IBM compatible floppy disk.
(g) When floodway modification is proposed, supply all
documentation required for submittal to FEMA. This
will include:
- Hydraulic analyses (computer models - input
and output) which duplicate the hydraulic
analyses used for the effective FIS (baseline
model) for the following frequency floods:
10-, 50-, 100- and 500-year floods and the
100-year floodway.
- New/revised hydraulic analyses (computer
models - input and output) for existing
conditions for the following frequency floods:
10-, 50-, 100-, and 500-year floods and
floodway. (This involves adding sections for
the crossing site without the structure and
for any changes in the floodplain.)
- New/revised hydraulic analyses (computer
models - input and output) for proposed
conditions for the following frequency floods:
10-, 50-, 100-, and 500-year floods and
floodway. (This involves the addition of the
crossing features and any proposed floodway
changes.)
- Topographic work map with existing and
proposed topography showing revised existing
and/or proposed 100- and 500-year flood
boundaries, 100-year floodway, base flood
elevations, cross sections, stream alignment,
and road alignment.
- Annotated FIRM and/or Flood Boundary and
Floodway Map (FBFM) showing revised existing
• and/or proposed 100- and 500-year flood
boundaries, 100-year floodway, base flood
alignment, and corporate limits.
25 10/92
Annotated FIS flood profile(s) showing revised •
existing and/or proposed 10-, 50-, 100-, and
500-year flood profiles.
Annotated FIS Floodway Data Table(s) showing
revised existing and/or proposed floodway
data.
•
•
26 6/90
• VII. CULVERTS
A culvert is a conduit which conveys flow through the embank-
ment. The most commonly used shapes are circular, rectangular,
elliptical, pipe arch and arches. They range in size from large
multiple barrel box culverts and metal arch structures to single
18" pipes. The design process for culverts as well as all
drainage structures is much like the bridge crossing in that it
involves: data collection, hydrologic analysis, formulation,
evaluation and selection of an alternate, and documentation of the
design. Some of the larger structures must be analyzed by the
same procedures and methods as a bridge crossing. The procedure
presented here is summary in nature and is intended for the common
box or pipe culvert crossing. The extent of design effort for a
particular culvert must be commensurate to its cost and potential
risk to the public. The engineer should reference FHWA, Hydraulic
Design Series No. 5 for more detailed guidance. He must reference
the document for nomograph charts and tables required for a manual
design process.
The forms used for documentation and the information required
differ for box and pipe size culverts. Any culvert structure(s)
providing conveyance greater than a single 72" pipe will follow
the design procedure and documentation on the "culvert survey and
hydraulic design report" (Appendix Item 7). Smaller culvert
design will be documented on a pipe data sheet (Appendix Item 8).
• (1) Data Collection
Information gathered during the pre-design study and
field survey relative to each particular crossing or all
crossings in general is to be assembled. This process
will include:
(a) For all box culverts or any other structure that
preliminary estimates indicate requiring a total
crossing conveyance greater than a single 72" pipe,
plot a plan and profile view of the stream crossing
on the "culvert survey and hydraulic design report"
(Appendix Item 7). The drawing scale is to be 1" _
50' horizontal, and 1" = 10' vertical. Existing
features are to be in ink with manmade features
shown with dashed lines. This information is to be
limited to that which is pertinent to the structure
sizing and location.
Information to be provided on the profile view:
(1) There are to be two profiles - one along the
centerline of the roadway showing the flood
plain section and roadway profile both
• existing and proposed. The second profile is
to be along the centerline of the structure
showing the stream bed grade, top of bank and
normal water surface profile.
27 6/90
(2) The centerline of the roadway profile should
show: ground line, channel base and banks,
grade line, water surface elevations (date of
survey, normal if different), flood plain
limits, historical flood elevations (including
date of occurrence, and estimated frequency),
utility elevations, controlling backwater
feature elevations (building floor levels,
yards, cultivated fields, roadways, drives,
other drainage structures, overtopping
controls), general classification of stream
bed and bank materials (clay, silt, sand,
gravel, cobble, rock), plot rock line if
identified
(3) The centerline of structure should show:
stream bed, top of bank, existing and proposed
roadway cross-section, normal water surface
profile, historical flood levels, controlling
feature elevations properly positioned along
the profile, rock line if identified.
(4) Any additional stream cross-sections utilized
for design or needed for structural excavation
estimates are to be plotted on the survey
report. The drawing scale for these sections
can be adjusted as needed to fit the report.
Information to be provided on the plan view:
(1) Natural features - stream channel showing base
and banks, limits of the floodplain
(2) Type of cover
(3) Manmade features -buildings, houses, highways,
existing drainage structures, utilities
(4) The proposed roadway section and fill slope
limits
(b) For 72" pipe size and smaller, the site data will
be summarized on the pipe data sheet. The engineer
will also need to reference the drainage plans for
topographical and proposed layout information.
•
•
(2) Hydrologic Analysis
There are four discharge levels that must be evaluated
for each culvert design. These are:
(a) A "design discharge" as
hydrology section (Table
(b) Q100 base flood
listed and defined in the
4-3)
E
28
6/90
• (c) Q-overtopping. This discharge is computed after a
trial size is selected.
(d) Q for outlet protection and erosion control
MaRsures
other discharges may be required on a site specific
basis. Examples are:
(a) Qaverage - for permit determination
(b) Qchannel full - for fish passage, channel stability
or floodplain use
(3) Hydraulic Design
(a) The first step in hydraulically analyzing a
culvert is to address criteria and information that
must be quantified prior to commencing actual
structural sizing and location. This would
include:
Material Selection
For pipe culverts, a material selection must be
made. The general selection policy is as follows:
Culvert pipe shall be concrete with the following
• exceptions - the expected fill height over the
structure exceeds the maximum values for concrete
as provided in the N. C. Division of Highways
charts, the required invert slope is greater than
10%. If a majority of the installations for a
project require metal, then all culvert pipe for
the project will be metal.
Other site or project specific factors such as,
corrosive conditions, accessibility, handling and
initial cost may dictate the use of a particular
material.
Allowable Headwater
The allowable headwater elevation is determined
from an evaluation of natural flooding depths,
upstream structures and land use, as well as the
proposed roadway elevations.
` Alignment
As near as is practicable, a culvert should inter-
cept an outlet flow within the natural channel.
Length and Slope
The slope of a culvert should approximate that of
• the natural channel. The invert elevation should
be slightly below the natural bed ranging from 0.1
29 6/90
+/- feet for small pipes to 0.5+/7 feet for a large •
box culvert. Where fish passage is a primary
consideration, the invert should be a minimum of 1
foot below the natural bed. Potential channel
cleanout and improvements should also be considered
particularly in the coastal plain. The length is
established by the geometry of the roadway
embankment, the bed elevation and skew.
Tailwater
The computed normal channel depth for each
discharge level being evaluated generally
establishes the tailwater. This can be determined
by a simple single section analysis. Effects of
downstream controls and constrictions must also be
considered.
Debris
The structure opening should be reasonably sized to
provide for debris. The limitation of structural
height to headwater depths in the HW/D = 1.2+/-
range has proven to limit problems of this nature
to acceptable levels. Where experience or physical
evidence indicates the water course will transport
a greater than normal volume of debris, special
debris controls should be developed and/or the
estimated capacity of the structure reduced to •
reflect the potential blockage.
(b) A trial size culvert can be determined using the
design discharge, inlet control nomographs (HDS-5)
and an assumed HW/D = 1.2. Multiple openings may
be selected by dividing the discharge.
(c) When a trial size selection is reasonable in regard
to available sizes and allowable headwater
limitations, the full inlet/outlet control analysis
is performed. The higher of the computed
headwaters governs.
(d) If the analyzed size is acceptable in regard to
controls and criteria relative to the design
discharge, verify it being the minimum acceptable
by checking the performance of a smaller structure.
(e) If inlet control governs, improved inlet design
must be investigated. This will be performed for
all inlet control box culverts and for pipe
culverts 36" and larger with lengths > 150 feet.
If as much as one nominal size reduction can be
achieved for box culverts, the improved inlet
option will be selected. For pipe culverts, an •
economic analysis will be made to justify the
selected option.
30 6/90
(f)l Determine the design values and acceptability of
r the selected culvert for the 4100 and overtopping
flood.
(g) Outlet velocities shall be determined for the 410
discharge. If this velocity exceeds the scour
velocity for the receiving stream, riprap outlet
protection is required.
(1) See channel chapter for permissible velocity
guidelines
(2) Use whichever is greater, tailwater depth or
normal flow depth for culvert to determine
outlet velocity.
(4) Design Documentation
All information pertinent to the culvert design shall be
documented on either the "Culvert Survey and Hydraulic
Design Report" or the "Pipe Data Sheet". This will
include:
(a) For box culverts, plot the proposed structure in
plan and profile views. Note centerline station
and skew.
• (b) Show design water surface elevation on all views.
(c) Complete fill-in of data for selected structure on
report or data sheet.
(d) If design is accomplished by computer program,
private engineering firms must submit data file
summaries on IBM compatible disk.
(e) For large culverts (>7211), a plot of the
performance curve for the selected structure with a
plot of the natural stage-discharge relations is
desirable.

•
31 10/92
VIII. STORM DRAINAGE SYSTEM •
The purpose of a storm drainage system is to collect and
transport storm water runoff from the highway to an outlet. The
complete system consists of the curb and gutter, inlet structures,
lateral and trunk line pipes, and junctions and manholes. The
design process for storm drainage systems usually follows the
basic steps of planning/data collection, hydrologic/hydraulic
design, and outfall analysis. The procedure presented herein will
be directed toward non-computer analysis. The pavement and inlet
design may be accomplished by a computer program which follows the
procedures of HEC 12. There is no reference for a computer
program at this time to perform the required storm pipe system
analysis.
(1) PLANNING/DATA COLLECTION
Information gathered during the pre-design study and
field surveys that is of particular relevance to the
storm drainage system should be assembled for design
reference. Planning includes the identification of
controls and criteria which must be considered in
accomplishing the design. This would include:
(a) Design Frequency
Roadway inlet location, capacities and gutter .
spread is to be analyzed using a standard rainfall
intensity of 4.0 inches/hour. The storm drain pipe
system is to be designed using a Q1 discharge with
a minimum time of concentration of 20 minutes
assuming 100% pick up at each inlet.
In sag areas where relief by curb overflow is not
provided the system standard design level (Q -
Q20 ) is to be used for analysis to insure tMfic
inot interrupted.
(b) Gutter Grade
A minimum gutter gradient of 0.20 percent (0.30
desirable) shall be utilized. When lesser slopes
are encountered, the gutter shall be warped to
provide the minimum slope.
(c) Inlets
The standard inlet for curb and gutter is a combi-
nation grate and curb opening (Ref. 840.01 of
Roadway Standard Drawings). Use of other type
inlets for curb sections require project specific
approval. •
Standard grated drop inlets shall be used in
roadway ditches, non-curbed shoulders and other off
32 10/92
I !n , "t
• roadway locations. Grates of 2" or less(small
dimension opening) shall be used in areas subject
to pedestrian traffic.
The following specific criteria shall be followed
in inlet analysis.
- On grades, the curb opening can be ignored in
determining inlet capacity. The grate efficiency
shall be assumed to equal a parallel bar grate.
- Inlet capacity at sags shall allow for debris
blockage by providing twice the required computed
opening.
- Inlet spacing shall be sufficient to limit
spread to no more than half of a through lane
during a 4.0 inch per hour rain storm.
When the typical section includes a full shoulder
or parking lane, no encroachment into the travel
lane will be allowed.
- Depth in gutter shall not exceed 5" for design
flow.
• - While there is no maximum spacing for inlets, no
trunk line pipe should extend more than 500 feet
without access. An exception is made for median
and side ditch systems where 700 feet is an
acceptable upper limit.
- Pipe systems shall not decrease in size in the
downstream direction.
- Provide 0.5 feet minimum from hydraulic grade
line to top of inlet grate.
(d) Pipe System
Storm drain pipes shall be concrete unless a site
limitation such as grade or corrosive conditions
dictate the use of an alternate material.
The minimum pipe size to serve a single inlet is 12
inches. For more than one inlet, a 15" pipe is the
minimum size.
When differing size pipes enter and exit a junction
the desired practice is to match the crowns of the
pipes.
(2) Hydrologic/Hydraulic Design
The storm drainage system design is a two phase design
involving first a selection of the required surface
33 10/92
inlets followed by the design of a subsurface pipe
system to serve the surface pickups.
(a) Inlets
(1) Prior to commencing the hydrologic/hydraulic
analysis of the surface system a layout of
locations standardly requiring inlets should
be developed on a set of plans. This would
include sag points, upstream of intersections,
upgrade of superelevation rollovers, and at
locations required to junction back-of-the
curb pickups.
(2) With the above noted locations determined, the
next step is to analyze the runoff and spread
along the roadway to establish additional
required inlet locations to meet spread and
depth criteria. The hydrologic method used
shall generally be the rational formula and
will follow the guidance of Chapter IV
(Hydrology). The general procedure as
outlined in Chapter III (Drainage Plans) shall
be used to confirm drainage boundaries, flow
paths, outlet conditions and other project
special design features.
The hydraulic procedure shall follow the
general guidance of HEC 12. The design is to
be documented on a form similar to Appendix
Item 9 (developed for computer program
summary). The inlets shall be numbered in a
logical ascending order and their location
referenced to a project line station.
(b) Pipe System
(1) The next step is to layout a pipe system to
provide a connecting route of flow from the
inlet(s) to the proper outletting point(s).
(2) Design of the storm sewer system is then
accomplished. The following procedure
involves a run through of the system from
beginning to end with selection of trial size
pipes by Manning's equation. The designer
must then check the system and finalize the
pipe selections by developing a hydraulic
grade line which requires that the analysis
begin at the outlet and work back through the
system.
Reference Appendix Item 10 for initial
system design documentation.
34 6/90

Items 1 - 2. These are inlet numbers
corresponding to inlet computation sheet.
Item 3. Total drainage area served by the
section of pipe.
Item 4. Sum of the incremental portions of
the drainage area and corresponding runoff
coefficients.
Item 5. Length of the pipe run between study
points.
Item 6. Time of concentration for portion of
drainage area inflowing at beginning end of
pipe.
Item 7. Flow time for first pipe equals inlet
time. Subsequent sections are a sum of the
time or concentration of the previous reach
(not min. 10 minutes) plus time of flow in
subject pipe.
Item 8. Larger value from Items 6 and 7. Use
10 minutes as minimum value. For times
greater than 30 minutes, a flood hydrograph or
• other routing procedures is recommended.
Item 9. Design storm rainfall intensity for
duration equal to design time.
Item 10. Design discharge for pipe reach.
Item 11. Invert elevation of pipe inlet.
Item 12. Invert elevation of pipe outlet.
Item 13. Invert slope of pipe.
Item 14. Diameter of pipe selected for trial
use. This size is to be selected utilizing
Manning's equation (Example Manning's solution
-Appendix Item .1). The pipe capacity must be
equal to or greater than Item 10. The
capacity from Manning's equation cannot exceed
the values contained in the table - Appendix
Item 11.
Item 15. Capacity from Manning's equation
(See Limitation Item 14).
Item 16. Velocity based on design discharge
and selected pipe size (can use charts
Appendix Item 11).
Item 17. Remarks.
35 10/92
Development of the Hydraulic grade line will
determine the elevation, under design
conditions, to which water will rise in the
various inlets and junctions. Reference
Appendix Item 12 for tabulation of the design
using the following procedure.
Item 1. The inlet number or junction location
immediately upstream of the outlet.
Item 2. Water surface elevation at outlet or
0.8D + invert elevation of the outflow pipe,
whichever is greater.
Item 3. Diameter (Do) of outflow pipe.
Item 4. Design discharge (Qo) for the
outflow pipe.
Item 5. The length (Lo) of the outflow pipe.
Item 6. Friction loss (H ) for full pipe
flow. Loss due to flow iA the pipe can be
computed by multiplying pipe length (L ) x
friction slope (S ). Friction slope c2n be
determined from pipe flow charts or by using
the formula: •
Sf = [Q/K]2
K = 1.49/n (AR 0.67
Sheet 4 - Appendix Item it provides values of
(K) for various pipe sizes.
Item 7. Contraction loss (H ). Loss due to
contraction of flow at inlet cof outflow pipe.
Computed by the formula:
He = 0.25 (Vo2/2g)
Where: Vo = Flow velocity in outlet pipe
(full flow)
Item 8. Expansion loss (H ). Loss due to
expansion of flow into theejunction. Use
expansion loss from primary inflow line.
He = 0.35 (Vi2/2g)
Where: Vi = Flow velocity in inlet pipe
(full flow)
36 3/92
C
Item 9. Bend loss (H ) loss due to change in
direction of flow. Re change in angle of
primary flow line.
Hb = K (V i2/2g)
90 degrees K = 0.70
80 degrees K = 0.66
70 degrees K = 0.61
60 degrees K = 0.55
50 degrees K = 0.47
40 degrees K = 0.38
30 degrees K = 0.28
25 degrees K = 0.22
20 degrees K = 0.16
15 degrees K = 0.10
Item 10. Total losses (H ), sum of friction,
contraction, expansion, aid bend losses.
Item 11. Inlet water surface elevation. This
is the potential water surface elevation
within the inlet or junction.
Item 12. Inlet rim elevation or top of
junction. The water surface elevation is to
be a minimum of 0.5 foot below this elevation.
If not, the pipe size must be increased or
other measures taken to reduce the water
level.
r?
?J
Item 13. Remarks.
Repeat the procedure for the upstream junction
and plot the potential water surface elevation
if above the crown elevation of the outlet
pipe.
(3) OUTFALL ANALYSIS
The storm drainage system design must include an evalua-
tion of the downstream receiving channel or system to
determine its adequacy. This evaluation should address:
- Potential affects on the highway facility due to
downstream inadequacies.
- Potential affects to other properties due to the
inadequacies.
- Affect of the highway improvements on the downstream
facility. (Percent increase in flows).
- Potential corrective measures. (Including cost).
- Recommended actions.
•
37
6/90
IX. CHANNELS AND ROADSIDE DITCHES •
A channel is any open conveyance, natural or man-made, in
which water flows with a free surface. A roadside ditch is a
man-made channel generally paralleling the roadway surface and
distinguished by a regular geometric shape. The design process
and analysis requirements for roadside ditches and channels
differ. For the purpose of this chapter, "channel" shall refer to
all open conveyance facilities not classified as roadside ditches
or requiring more than a 2 foot base. The design procedure
presented is general and intended to present specific criteria and
analysis requirements. The Engineer should reference FHWA,
Hydraulic Design Series Nos. 11 and 15, and Chapter VI of the
AASHTO Drainage Guidelines for more detailed design guidance.
Roadside Ditches
The following is a basic step procedure for evaluating and/or
designing roadside ditches.
(1) "Establish a ditch plan which shows the proposed ditch
locations and flow patterns."
This ditch plan is a part of the drainage plan (Chapter
III, Item 7).
(2) "Determine the standard or typical ditch cross sections
for the project."
This is provided by the roadway plans for cut sections.
When a ditch is required along the construction limits
which is not part of the typical section, the following
criteria is to be followed in establishing a typical
section.
- A standard berm ditch section shall be noted at top of
cut where required.
- Toe of fill ditches adjacent to shallow fills and flat
slopes (4:1 or flatter) shall be formed by continua-
tion of the fill slope to a desired ditch depth, pro-
vision of a base width if required, then a stable back
slope (2:1 maximum).
- Toe of fill ditches adjacent to high steep slopes
shall be constructed with a minimum 2 foot berm. A
wider berm is desirable for very high fills to prevent
embankment from filling the ditch and for maintenance
if access is limited from the off roadway side.
(3) "Determine the gradient to be used on all proposed
ditches." Roadway ditches included in the typical
roadway section will have a grade corresponding to the
roadway profile. When the roadway profile grade is less
than 0.3%, special roadway ditch grades must be
established and noted on the plans. •
38 6/90
s, € s,I
• Ditches along the toe of fill will generally parallel
the grade of the natural ground at an established
acceptable depth. The approximate grade of these
ditches are to be established and plotted on the plan
profile view.
(4) "Investigate capacity of the established typical ditch".
Roadway ditches are to be designed to contain as a
minimum the Q flood. The typical roadway ditch section
is establishes with sufficient depth to drain the
pavement subbase and flat side slopes for safe vehicle
traversability. This generally provides very generous
capacity for the design flood requirements. Therefore,
actual capacity determination can be done on a selective
basis at sites on common project grades to verify
adequacy and establish limitations on the length of
ditch run.
The size requirements of the project special side
ditches along the toes-of-fill will be established based
on an analysis of the design flood. This ditch capacity
analysis will be performed using Mannings' equations (Q
-I-q? q? A R'3 s t)• Discharge determination shall follow
the requirements of Chapter IV - Hydrology. The roadway
section including shoulders and slopes shall be consid-
ered an urban watershed. This capacity analysis is
usually worked in conjunction with the next step of
lining evaluation.
(5) "Determine the limitations and protection requirements
to prevent erosion in the ditch."
The stability of vegetative ditch linings is to be
analyzed by use of Charts 1 and 2 (Appendix Item 13).
These charts are based on the more frequently used 'V'
and base ditch sections. However, a procedure and
example are included for evaluating other channel
configurations. The stability limitation is based on an
established acceptable velocity. When applying the
chart, if conditions at a particular site are such that
you fall to the left of the stability line, a good
vegetative cover would not be expected to erode.
Conversely, if you are to the right of the line, the
ditch would be expected to be unstable and erode when
subjected to design flow even if a good vegetative
lining were established; therefore, some type of
armoring (rip rap, concrete paving) must be used.
Charts 3 and 4 (Appendix Item 13) are provided to
analyze the stability of rip rap ditch linings (Type A
and B stone, Class I rip rap). They are used in the
same manner as Charts 1 and 2 to determine the stability
• of stone lining under differing ditch shape and flow
conditions.
39 6/90
The determination of recommendations for temporary •
linings can be accomplished jointly with this permanent
lining analysis. Any recommendations regarding
temporary linings are to be shown only on the erosion
and sediment control plan.
(6) "Determine any special measures necessary at or
downstream of the ditch outlet." A check should be made
of the transition of flow from a ditch to the receiving
outlet. Factors to be considered are:
(a) Is there provision for a smooth transition of flow
from the ditch to the outlet?
(b) Will the outlet adequately handle the quantity of
flow? Is improvement required?
(c) Is the velocity of flow at the outlet too high for
the condition of the receiving channel? Is riprap
or other means of velocity reduction justified?
(d) When the receiving outlet is sheet overland flow,
is concentration of flow by the ditch a potential
problem? Is some form of flow diffusion required?
Channels
Channel analysis differs from roadway ditch analysis in that
it involves establishing a channel configuration suitable to
specific site conditions rather than evaluation of the adequacy of
a standard ditch section. Channel design requirements can range
from small base ditches needing only a single section analysis as
presented in HEC 15 to large stream and river involvements which
must be analyzed by multisection methods such as the WSPRO
Program. For the more complex channels, the Engineer is directed
to reference Chapter VI of the AASHTO Drainage Guidelines -
"Hydraulic Analysis and Design of Open Channels" for further
guidance. HEC it is a reference for the design of rip rap for
large channels and revetments. The following procedure should
adequately address most channel involvements and help to identify
conditions requiring special study.
(1) Data Collection
Channel involvement will generally be in conjunction
with a bridge, culvert or pipe crossing. Therefore,
much of the data collection and drawings can be included
with the related hydraulic structure documentation.
Information particular to the channel analysis that must
be provided is:
(a) Elevations and location plots of existing stream
banks, bed, normal water surface and floodplain
limits throughout the area of involvement.
40 6/90
4 1 . r
• (b) Historical flood elevations, dates of occurrence
and estimated frequency.
(c) Stream bank, bed and flood plain cover.
(d) Representative typical sections including flood
plain.
(e) General classification of bed, bank and flood plain
materials (clay, silt, sand, gravel, cobble, rock)
(f) Location and elevation of any controlling features
such as buildings or other development.
(2) Hydrologic Analysis
Discharge levels that must be considered for evaluation
for each channel design are:
(a) QExist - Capacity of existing channel must be
determined and used in evaluating design.
(b) Q(Facility) - Discharges required for evaluating
25, 50 related structure and highway
facility
• (c) Q10 - Evaluation of lining stability unless channel
stability in regard to protection of roadway
or other facility dictates higher design
level.
(d) Q100 - Base Flood
(e) Q2 - For temporary lining recommendations
(3) Hydraulic Analysis
(a) The first step is to address criteria that are to
be used in evaluating channel selection.
Alignment
Realignment of an existing channel should be done
when it is the only practicable alternative and is
to be held to the minimum extent required. The new
channel should afford a smooth transition to and
from the existing channel, avoiding sharp bends and
sudden changes in cross section.
Slope
is The bed slope should be continuous. Any change of
grade in the channel must be evaluated for the
necessity of grade control provisions. Significant
41 6/90
changes in bed grade of large streams must be •
evaluated for geomorphic response (see Highway
Drainage Guideline - Chapter VI).
Size
Channels that are a realignment of a natural
streams should be sized and configured as nearly as
practicable to match the natural channel. Channels
that are not realignments of natural channels
should be sized to convey as a minimum the Q10
discharge.
In instances where the project is restricting a
floodplain through lateral encroachment, the total
floodplain and channel must be studied and the
channel sized to hold backwater effect to
acceptable limits (see Backwater Chapter V and
Allowable Headwater Chapter VI).
(b) After establishing the alignment and grade, a trial
size is selected and the performance is evaluated
for a range of discharges using either single or
multi-section analyses.
(c) When an acceptable channel size has been
established, it must be evaluated for lining •
stability and any necessary special protective
features developed. Reference Chart 4 (Appendix
Item 13) or HEC 11 for riprap design procedure
guidance.
(d) Requirements for temporary linings to facilitate
the establishment of permanent protection can also
be determined and noted on the erosion and sediment
control plans.
(4) Design Documentation
All information pertinent to channel design shall be
documented in an appropriate design report format.
•
42 6/90
• X. EROSION AND SEDIMENT CONTROL
On completion of the drainage design, a first draft erosion
and sediment control plan is to be developed. A separate copy of
the preliminary roadway plans is to be used as the work plan, and
recommendations for devices and procedures are to be noted on
these plans in green. Specialty design computations, such as
large basins or ditch analyses, are to be included with the
hydraulic design report. Any erosion control item requiring a
temporary drainage easement such as Type A silt basin construction
or access is to be shown on the drainage plans as well as the
erosion control plans. Detailing of stage construction at
culverts can be developed on an enlarged sketch and attached to
these plans.
The Engineer must reference NCDOT - "Guidelines For Control
Of Erosion And Sediment During Construction" for guidance in
standards, control practices and measures. The State of North
Carolina's - "Erosion And Sediment Control Planning And Design
Manual" is also a good reference. It should be noted that some
practices and standards contained in the State manual do not
conform to the Division of Highways' documents. In these
instances, the highway practices and standards take precedence.
The sequence of development of the erosion and sediment
control plans should be as follows:
(1) Data Collection
Information gathered during the pre-design study, field
survey and design study that is pertinent to this plan
development is to be assembled. This would include:
(a) Drainage patterns and structures should be plotted
on the base roadway plans.
(b) Contour maps should be made available for
reference.
(c) Sediment sensitive areas should be appropriately
noted (ponds, lakes, developed areas, streams,
etc.)
(d) Identified areas of highly erodible soil should be
noted.
(e) Permanent erosion control measures developed during
the drainage design phase should be noted on the
plans (ex. riprap or other ditch linings, velocity
control devices, intercept or diversion ditches.
• (2) Data Analysis
The designer is to review the data collected to identify
areas that have potentially critical erosion or sediment
43 6/90
hazards and to become thoroughly knowledgeable of the is
overall project development as it relates to erosion and
sediment control planning. Important points to consider
in this analysis are:
- Note areas of steep natural and man-made slopes.
- Review concentrations of flow (natural drainage
patterns and roadway ditches and channels).
- Note large disturbed areas with extensive cuts and
fills.
- Review potential for damage to adjacent developed
properties.
- Review conditions and requirements of water courses
that will receive direct project runoff.
(3) Develop Plan
The actual plan development should begin with a division
of the construction site into individual drainage
areas. The designer should determine how runoff will
travel over the site beginning at the uppermost reach of
the watershed. It will be assumed that vegetation will
be established on all exposed areas. However, temporary
measures will be required for the interim runoff. The
basic premise of the sediment control planning is to
begin with the proposal of placement of a sediment basin
downstream of all points where potentially sediment
laden waters could be leaving the project area. These
basins would be used in conjunction with other erosion
and sediment control practices within the project area.
A basin would not be used at a particular outlet
location only if it were determined to be impracticable
for such reasons as:
- stream size
- constructibility
- accessibility for maintenance
- rights-of-way limitations
When it is determined that a basin is not practicable
for a site, other measures such as smaller off stream
basins or more stringent use of other controls within
the disturbed area will be employed. Details for
individual control devices and management measures are
contained in the reference documents. The designer must
evaluate the need for, and develop the recommended
combined implementation of, the individual devices and
measures as he works his way down the paths of flow
accumulation. Each measure must be sized or limited in
usage to insure proper functioning. This would include
such considerations and provisions as:
- Limit silt fence use to sheet flow conditions. 40
- Set spacing and area served by slope drains based on
pipe size (1211) and acceptable capacity values.
44 6/90
- 3 , T,4 i' *f
•
•
E
- Size small sediment basins to contain 0.25" runoff (35
cubic yards/acre) from the contributing disturbed
drainage area.
- Storage area provided by check dams must also meet the
35 cubic yards/acre guideline based on the disturbed
area size within the contributing watershed.
The detailed construction staging and erosion control
plans for each box culvert site must include:
- A means for diverting flow away from the construction
site (ex. diversion channel, temporary pipe)
- A sequence of construction of the box culvert and
employment of erosion control devices
- A stilling basin for storage of pumped effluent from
the construction site
- A rock silt screen downstream of the construction site
if instream activity is required
- Detailing of any temporary easements required for
performing construction and/or providing the erosion
control measures
Staging of activities or special directives regarding
implementation of the measures or devices can be covered
by narrative explanation provided directly on the plans.
45
6/90
XI. PERMITS •
The drainage study and hydraulic design process includes the
development of permit drawings and completion of pertinent
application forms for State and Federal environmental permits.
The material is developed through coordination with the
Environmental Section of the Planning and Research Branch and upon
completion is provided to them for submittal to the appropriate
permitting agencies. The procedure for development of the
drawings and application should be as follows:
(1) Review the environmental document to obtain wetland area
identifications and other information regarding permit
requirements. While the planning documents include
wetland identification, it is not generally of
sufficient detail in actual limit description to fully
define the project/wetland involvement. This requires
detailed field confirmation by the Hydraulics Designer.
If questions arise, the Planning and Environmental
Branch, Permitting Section, must be consulted for
assistance in the analysis.
(2) Assemble information gathered during the pre-design
study, field survey and design that is pertinent to the
permit application. This would include:
- Location and classification of wetland •
- Topo and elevation data at wetland sites,
- Drainage structure and/or channel design data
- Watershed area
- Flow data (ex. average, low, full bank)
(3) Prepare the permit drawings. An example drawing is
included as Appendix Item 14. The drawings are to
conform to, and should include as a minimum the
following:
- Drawings are to be on 8 1/2" x 1111 paper with a 1"
left margin and 1/2" remaining margins.
- Number of sheets is optional but must be to scale and
clearly depict the wetland involvement.
- Location-vicinity maps showing project location and
wetland site(s).
- Plan view of site(s) including pertinent drainage and
roadway features, wetland limits,- area of wetland
disturbance, fill below ordinary high water, property
owners.
- Profile view of site(s) showing roadway grade, natural
ground, ordinary high water, drainage structure, fill
below ordinary high water, wetland limits.
- Section view if needed to clarify proposal.
- Quantities for each site of total fill within the
wetland area, fill below ordinary high water and
acreage of wetland fill are to be included on the
sketches.
46 10/92
APPENDIX ITEM 1
I D #
DESCRIPTION:
HYDRAULIC DL%! GN DOCU'ML"vTA'CION SUMMARY
COU*iT PROJECT NO
PROJECT DESIGN
ENGINEER ENGINEER- _ DATF
THE FOLLOWING CHECKED DESIGN ITEMS HAVE BEEN DEVELOPED AND ARE
CONTAINED IN THE PROJECT DOCUMENTATION FILES:
1. PRELIMINARY AND ASSESSMENT OF STREAM CROSSINGS AND
ENCROACHMENTS
2 PRE-DESIGN REPORT
3. PERMIT STATUS REPORT
4 CHECKLIST FOR DRAINAGE STUDY AND HYDRAULIC DESIGN
5. STRUCTURE SURVEY RECOMMENDATIONS
6. PIPE MATERIAL RECOMMENDATIONS
7 PIPE DATA SHEETS (NUMBER )
8 STORM DRAINAGE COMPUTATION SHEETS (NUMBER )
9. EROSION CONTROL PLANS
10. CULVERT SURVEY REPORT(S) (NUMBER )
11. EROSION CONTROL FOR BOX CULVERTS (NUMBER )
12. CULVERT SURVEY FIELD NOTES (NUMBER OF SETS )
13. BRIDGE SURVEY REPORT(S) (NUMBER )
14. BRIDGE SURVEY FIELD NOTES (NUMBER OF SETS )
15 HYDRAULIC DESIGN REPORT(S) FOR BRIDGE SIZE STRUCTURES
WHICH INCLUDES CULVERTS MEASURING 20 FEET OR GREATER
ALONG CENTERLINE OF ROAD (NUMBER )
16 PERMIT APPLICATION (DATE SUBMITTED )
17. FLOODWAY MODIFICATION (DATE SUBMITTED )
8 COST SAVINGS (ESTIMATED AMOUNT $ )
19 PERMIT ACTION LETTER
20 OTFiI R __ ___
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10/92
APPENDIX ITEM 2
SHEET 1 OF 5
•

•
CHECKLIST FOR DRAINAGE STUDY AND HYDRAULIC DESIGN
PROJECT
I. D.: COUNTY: ENGINEER: DATE:
PRIOR TO FIELD SURVEY (TO BE COMPLETED PRIOR TO FIELD TRIP)
APPROVED BY: DATE:
1. HAS PLANNING REPORT BEEN REVIEWED? ARE THERE ANY COMMITMENTS
OR REQUIREMENTS WHICH WOULD AFFECT THE DESIGN?
2. ARE THERE ANY PRIOR SURVEYS AT STREAM CROSSINGS. ARE THERE
ANY PRIOR SURVEYS AT UP AND DOWNSTREAM STRUCTURES.
3. WHAT IS FLOOD ZONE STATUS?
4. CHECK FOR SCS WATERSHED INVOLVEMENT.
5. ARE THERE ANY STREAM GAGES IN AREA (DATES AND FREQUENCIES OF
MAJOR FLOODS).
6. OBTAIN DRAINAGE AREA AND DESCRIPTION OF EXISTING DRAINAGE
STRUCTURES.
7. DEVELOP PRELIMINARY DESIGN DISCHARGE AND ESTIMATES OF
STRUCTURE TYPES AND SIZES.
8. DETERMINE POSSIBLE PERMIT REQUIREMENTS.
9. PREPARE SKETCHES FROM AVAILABLE FIELD DATA.
6/90
APPENDIX ITEM 2
SHEET 2 of 5
10. ARE THERE ANY HYDROLOGIC/HYDRAULIC STUDIES WITHIN THE PROJECT
AREA BY AGENCIES SUCH AS: THE CORPS OF ENGINEERS, TVA, •
CITIES OR COUNTIES?
11. WHAT ARE SOURCES FOR WATERSHED AREA OR DELINEATION?
12. HAS RISK ASSESSMENT SUMMARY BEEN REVIEWED?
13. HAS PROJECT INITIATION SHEET BEEN SUBMITTED?
FIELD STUDY
THE FOLLOWING INFORMATION IS TO BE INCLUDED IN THE FIELD SURVEY
NOTES: (CHECK LOCATION AND SURVEY NOTES AND SUPPLEMENT WITH ANY
ADDITIONAL INFORMATION THAT MAY BE REQUIRED) ANSWER YES, NO, OR
N/A.
1. TOPO IS TO INCLUDE, BUT NOT LIMITED TO: •
a. CHANNEL BANK AND WATERS EDGES
b. EXISTING STRUCTURES (BRIDGES, CULVERTS, AND STORM
DRAINAGE SYSTEMS)
C. UTILITIES (POWER, WATER, GAS, TELEPHONE, SANITARY
SEWER, ETC.)
d. ROADWAY PAVEMENT, SHOULDERS AND TOE OF FILLS
e. ANY DEVELOPMENT ADJACENT TO SITE, UP AND DOWNSTREAM
f. EDGE OF FLOODPLAIN
9. DRAINAGE COURSES AND DRAINAGE DITCHES.
h. WETLAND LIMITS
2. LEVELS
a. CENTERLINE PROFILES OF NATURAL GROUND AND EXISTING
HIGHWAY (WHERE APPLICABLE) ACROSS FLOODPLAIN.
b. SECTION UNDER EXISTING BRIDGE.
C. SIZE, DEPTHS, AND INVERTS OF ALL CULVERTS AND STORM
DRAINAGE SYSTEMS.
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APPENDIX ITEM 2
SHEET 3 OF 5

• d. STREAM BED, NATURAL GROUND, AND WATER SURFACE PROFILE
(NORMAL ELEVATION AND ELEVATION AT DATE OF SURVEY)
UP AND DOWNSTREAM FOR A SUFFICIENT DISTANCE BEYOND
LIMITS OF CONSTRUCTION. (EXTEND OUTLET DITCH PROFILES
AS FAR AS NECESSARY TO REACH ADEQUATE CAPACITY)
e. FLOODPLAIN CROSS-SECTIONS AS DEEMED NECESSARY FOR
PERFORMING BACKWATER ANALYSIS.
f. ELEVATION OF ANY UP OR DOWNSTREAM DEVELOPMENT THAT
WOULD BE CONSIDERED IN DESIGN (EXAMPLE: ELEVATION OF
HOUSES, BASEMENTS, YARDS, GARDENS, BARNS, PONDS).
9. ELEVATION OF ANY DEBRIS OR OTHER HIGHWATER MARKS.
3. SCOUR POTENTIAL: OBTAIN THE FOLLOWING FIELD INFORMATION
IN ADDITION TO THE NORMAL BRIDGE CROSSING DATA.
a. WHAT IS THE STREAM BEDS AND FLOODPLAIN MATERIAL?
IF SAND, IS IT FINE, MEDIUM, COURSE?
b. ARE THE STREAM BANKS STABLE? ARE THERE VISIBLE
SLUMPS, VERTICAL BANKS, LEANING TREES OR UNDERCUT
BANKS?
AT EXISTING CROSSING SITES:
C. OBTAIN A TYPICAL CHANNEL SECTION A SUFFICIENT
DISTANCE UP OR DOWNSTREAM BEYOND CROSSING AFFECTS.
d. OBTAIN BED PROFILE EXTENDING WELL BEYOND SCOUR AREA.
e. WHAT TYPE FOUNDATION DOES EXISTING STRUCTURE HAVE?
IF FOOTING IS VISIBLE, NOTE CONDITION.
f. OBSERVE GROUND CONDITIONS AROUND EXISTING PIERS AND
SPILL THROUGH SLOPES. IS THERE INDICATION OF PREVIOUS
SCOUR? IF SO, IS DEPTH RECOGNIZABLE?
4. RECONNAISSANCE
a. DRIFT POTENTIAL, SIZE AND QUANTITY. (QUESTION
SOURCES WHEN HIGHWATER INFORMATION IS OBTAINED.)
b. IDENTIFY CULTURE IN FLOODPLAIN FOR DETERMINATION OF
FLOW RESISTANCE AND DISTRIBUTION (ESTIMATE "N"
VALUES).
C. IDENTIFY DEVELOPMENT IN FLOODPLAIN THAT COULD BE
AFFECTED BY BACKWATER, DOWNSTREAM EROSION OR
. REDUCTION OF FLOW.
d. IDENTIFY STORAGE AREAS SUCH AS PONDS, LAKES, ETC.,
FOR POSSIBLE ADJUSTMENT OF DISCHARGE RATES WHERE
APPLICABLE.
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APPENDIX ITEM 2
SHEET 4 OF 5
e. REVIEW ADEQUACY OF DOWNSTREAM CHANNELS FOR CONVEYANCE
OF INCREASED DISCHARGE RATES.
f. PHOTOGRAPHS OF SITE(S).
9. LOCATION AND CLASSIFICATION OF WETLANDS.
5. OBTAIN HISTORICAL H. W. INFORMATION SOURCES: (NAMES AND
ADDRESSES).
a. LOCAL RESIDENTS
b. BRIDGE MAINTENANCE PERSONNEL
C. ROADWAY MAINTENANCE PERSONNEL
d. FREQUENT ROAD USERS (EX. MAILMAN, DELIVERY PEOPLE)
QUESTIONS:
a. MAXIMUM H. W., WHEN IT OCCURRED, WHAT DAMAGE OCCURRED,
PERIOD OF KNOWLEDGE OF PROVIDER.
b. OTHER LESSER FLOOD LEVELS, HOW OFTEN?
C. YEARLY OCCURRENCE.
d. OHW FOR POSSIBLE PERMIT
6. DATA ON UP AND DOWNSTREAM CROSSINGS
a. SIZE
b. RELATIVE LEVELS OF STRUCTURE AND ROADWAY
C. PERFORMANCE (FLOOD HISTORY)
HYDRAULIC STUDY
1. WHAT DESIGN FREQUENCIES WERE USED FOR DRAINAGE STRUCTURES?
WHY?
l
2. WHAT ALTERNATES HAVE BEEN CONSIDERED FOR THE MAJOR DRAINAGE
STRUCTURES?
3. HAS AN ECONOMIC ANALYSIS BEEN MADE FOR ANY CROSSING DESIGNS?
HAS A LESSER DESIGN STANDARD BEEN CONSIDERED?
•
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APPENDIX ITEM 2
SHEET 5 OF 5
• 4. HAS THE OVERTOPPING FLOOD BEEN DETERMINED FOR ALL DRAINAGE
CROSSINGS?
5. HAVE INVERT GRADES OF STORM DRAINAGE SYSTEMS BEEN PLOTTED
AND PROVISIONS MADE FOR UTILITY CONFLICTS?
6. HAVE WATER SURFACE PROFILES THROUGH STORM DRAINAGE SYSTEMS
BEEN PLOTTED?
7. HAS PERMIT APPLICATION BEEN MADE AND DOES IT CONFORM TO THE
FINAL PLANS. (DATE AND PROJECT STATUS AT TIME OF COMPARISON)
8. HAVE EVALUATIONS BEEN MADE OF OUTLET CHANNELS FOR POTENTIAL
AFFECT OF PROJECT DEVELOPMENT?
0 9. HAVE EROSION CONTROL PLANS BEEN PREPAPED AND SUBMITTED?
10. HAS PIPE MATERIAL RECOMMENDATION BEEN MADE?
11. HAVE COST SAVINGS BEEN DOCUMENTED?
APPROVED BY:
DATE:
C?
6/90
APPENDIX ITEM 3
SHEET 1 OF 3
PRELIMINARY DESIGN AND ASSESSMENT OF
STREAM CROSSINGS AND ENCROACHMENTS
COUNTY PROJECT NUMBER
STREAM ROUTE
ASSESSMENT PREPARED BY DATE
HYDROLOGIC EVALUATION
NEAREST GAGING STATION ON THIS STREAM (NONE )
ARE FLOOD STUDIES AVAILABLE ON THIS STREAM:
FLOOD DATA:
Q10 CFS EST. BKWTR. FT. Q25 CFS EST. BKWTR. FT.
Q50 CFS EST. BKWTR. FT. 52100 CFS EST. BKWTR. FT.
Q500 CFS OR OVERTOPPING CFS EST. BKWTR. FT.
DRAINAGE AREA
METHOD USED TO COMPUTE Q
PROPERTY RELATED EVALUATIONS
DAMAGE POTENTIAL: LOW MODERATE HIGH
COULD THIS BE SIGNIFICANTLY INCREASED BY PROPOSED
ENCROACHMENT: YES NO
EXPLANATION:
LIST BUILDINGS IN FLOOD PLAIN LOCATION
FLOOR ELEVATION
UPSTREAM LAND USE
ANTICIPATE ANY CHANGE?
ANY FLOOD ZONING? (FIA STUDIES, ETC.)
TYPE OF STUDY
BASE FLOOD ELEVATION
YES NO
(100 YEAR)
6/90
is
?J
•
APPENDIX ITEM 3
SHEET 2 OF 3
•
REGULATORY FLOODWAY WIDTH (AS NOTED IN FIA STUDIES)
COMMENTS:
TRAFFIC RELATED EVALUATIONS
PRESENT YEAR TRAFFIC COUNT VPD % TRUCKS
DESIGN YEAR TRAFFIC COUNT VPD % TRUCKS
EMERGENCY ROUTE SCHOOL BUS ROUTE MAIL ROUTE
DETOUR AVAILABLE? LENGTH OF DETOUR MILES
DOES THE LEVEL OF TRAFFIC SERVICE OF AN EXISTING CROSSING VARY
GREATLY FROM STANDARD DESIGN LEVELS?
IS THE TRAFFIC VOLUME, TYPE, USAGE SUCH TO WARRANT CONSIDERATION
FOR VARIANCE FROM STANDARDS OR EXISTING LEVEL OF INTERRUPTION?
is COMMENTS:

HIGHWAY AND BRIDGE (CULVERT) RELATED EVALUATIONS
NOTE ANY OUTSIDE FEATURES WHICH MIGHT AFFECT STAGE, DISCHARGE OR
FREQUENCY.
LEVEES AGGRADATION/DEGRADATION RESERVOIRS
DIVERSIONS DRAINAGE DISTRICT NAVIGATION
BACKWATER FROM ANOTHER SOURCE
EXPLANATION:
ROADWAY OVERFLOW SECTION (NONE ) LENGTH ELEVATION
EMBANKMENT: SOIL TYPE TYPE SLOPE COVER
• COMMENTS:
6/90
APPENDIX ITEM 3
SHEET 3 OF 3
ENVIRONMENTAL CONSIDERATIONS
LIST SPECIAL CONDITIONS OR CONSIDERATIONS WHICH AFFECT HYDRAULIC •
DESIGN (NONE )
MISCELLANEOUS COMMENTS
IS THERE UNUSUAL SCOUR POTENTIAL? YES _ NO -PROTECTION NEEDED _
ARE BANKS STABLE? PROTECTION NEEDED _
DOES STREAM CARRY,APPRECIABLE AMOUNT OF LARGE DEBRIS?
COMMENTS:
ALTERNATIVES
RECOMMENDED DESIGN
DETOUR STRUCTURE
LOW ROADWAY GRADE DETOUR GRADE
BRIDGE WATERWAY OPENING CULVERT OPENING
WERE OTHER HYDRAULIC ALTERNATES CONSIDERED? YES NO
DISCUSSION:
THIS SITE ASSESSMENT INDICATES THE DESIGN SHOULD FOLLOW:
(1) NORMAL PROCESS
(2) NORMAL PROCESS WITH SPECIAL SPECIFIC CONSIDERATION FOR
•
(3) SPECIFIC DESIGN PROCESS WITH APPROPRIATE RISK/ECONOMIC •
EVALUATION ADDRESSING:
6/90
•
•
USE THIS SPACE FOR PHOTOGRAPH
OF PROPOSED SITE. SHOWING CENTERLINE.
DIRECTION OF FLOW AND OTHER
IMPORTANT POINTS ON PHOTOGRAPH.
• Designed by- ---------------------------
-----------------------
Project Engineer- --------------------------------------------
Reviewed & Approved by- ---------------------------------
APPENDIX ITEM 4
(cover sheets only
BRIDGE SURVEY & HYDRAULIC DESIGN REPORT SHEET 1 OF 3
N. C. DEPARTMENT OF TRANSPORTATION
DIVISION OF HIGHWAYS
HYDRAULICS UNIT
RALEIGH. N C.
I.D. No. -- -- ------------ Project No. -------------------------------- Oral. Station -------- -- -------------------
County ---------------- - -------- Bridge Over ------ ------------------------------------ Bridge Inv. No. -------------
----------------
On Highway ---------- -------------------- Between ------------------------ and ------------------------
Recommended Structure ----------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------------------------------
Recommended Width of Roadway --------------------------------------- Skew -----------------------------------------
Location is ( Up. At. Down Stream from Existing Crossing ) ------------------------------------------------------
Nearest Shipping Point --------------------- On ---------------------------------- R.R.. ------ Miles From Bridge
Bench Mark is ---------------------------------------------------------------------------------------------------
--------------
---------------------------------------------------------------------- Elev. --------------- Datum: ---------------------
Temporary Crossing ------------------------------- - - -- - ---------------------------------------------------------------
Date -------------------
Ian
APPENDIX ITEM 4
SITE DATA (cover sheets only)
SHEET 2 OF 3
Drainage Area ------------------- Source ---------------------------------- Character ------------------------------
------------------------------------
to on Existing Structure ------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------------------------------
Data on Structures Up and Down Stream ------------------------------------------------------------------------------
-------------------------------------------
Gage Station No. -------------------- ---------------
--------------- -----------------------------------
Period of Records ------ ------------I---------------------------
----------------------------------------
Max. Discharge ------------------------------ c.f.s. Date ------------------------- Frequency
---------------------
Historical Flood Info.
Period of
Elev- ------------- Dote ---------- Source ---- ---------- Est. Freq. ------------ Knowledge -----------------------
' Period of
Elev- ------------ Date ---------- Source ---- ---------- Est. Freq. ------------ Knowledge -----------------------
Period of
Elev- ------------ Date ---------- Source ---- ---------- Est. Freq. ------------ Knowledge -----------------------
Historical Scour Info. : Channel --------------- Contraction------------------- Pler/Abut. -------------------------
Channel Slope ---------------- Sour ce ----------- -------------------- Normal Water Surface Elev.________---_------
Manning's n Left O.B- ------------ Channel -- -------- Right O.B. --------- Source --_--_--___-__----------------
Flood Study / Status Floodway Established? -------
-',)ad Study Study 100 yr. Discharge ----- ------c.f.s.: W S. Elev.: With Floodway ---- ------ Without Floodway -----------
DESIGN DATA
Hydrological Method -----------------------------------------------------------------------------------------------------------
Hydr aulic Design Method -----------------------------------------------------------------------------------------------------
Floods Evaluated: Freq. 0 Elev. Backwater Bridge Opening Velocity
--------------- ------------------- ----------------- ----------- -------- --------------
'-erage Channel Velocity ------------------------- Average Overbank Velocity ------------------
%.omputed Scour : General ------------------ Contraction --------------------- Local ____----------------------
Is a Floodwa y Modification Required? ------------------------------------------------------------------------------ -----
6/90
C J
•
E
APPENDIX ITEM 4
INFORMATION TO BE SHOWN ON PLANS (cover sheets only)
SHEET 3 OF 3
Design: Discharge ---------------------- c.f.s. Frequency -------------------- Elev. ------------------------
'se Flood : Discharge
kvertopping: Discharge ---------------------- c.f.s.
---------------------- c.f.s. Frequent 100 yr' _
Frequency -------------------- Elev. ------------------------
Elev. ------------------------
ADDITIONAL INFORMATION AND COMPUTATIONS
•
--------------------------------------------------------------------------------------------------------------------------------
0 -----------------------------------------------------------------------------------------------------------------------------------
6/90
HYDRAULIC DESIGN REPORT
Project No.
County
APPENDIX ITEM 5
SHEET 1 OF 3
River or Project
Stream Station
Site Analysis
SITE MAP (Topo, Floodplain Cross Section, Etc.)
FLOOD PLAIN INFORMATION
Culture Mstribution at Crossing
Design Control and Elevations
Channel and Bank Stability
Flood Hazard Studies
COORDINATION WITH OTHER AGENCIES
Permits or Approvals
Reservoirs, Water Resource Projects, Other Flood Control Projects
EXISTING STRUCTURES
Location
Description
Waterway Opern.ng
r?
C?
•
6/90
APPENDIX ITEM 5
-2- SHEET 2 OF 3
Scour Condition
•
Flood History
Hydrologic Analysis
DRAINAGE AREA
Size Obtained From
Character
FLOOD HISTORY
Elevations
Dates
Mscharge
• Velocity
Est. Frequency
Conveyance at Existing Structures
GAGE RECORDS
Location
Description
Flood Frequency Curve
DESIGN FREQUENCY
0 ,IGN DISCHARGE
6/90

Obtained From
APPENDIX ITEM 5
SHEET 3 OF 3
IVdraulic Design
CONTROLLING UPSTREAM WATER SURFACE ELEVATIONS
AVERAGE STREAM SLOPE
WATERWAY OPENING PROVIDED
PIER LAYOUT
BACKWATER ELEVATIONS
Design Flood
Basic Flood
Method Used in Computation
AVERAGE VELOCI TY
gWPE PROTECTION
SPUR DIKES - OTHER STREAM CONTROLS
CHANNEL CHANGE
NAME
DAZE
•
U
E
6/90
APPENDIX ITEM 6
SHEET 1 OF 8
• ARCHIE L. HANKINS, JR.
REVISED
OCTOBER, 1992
ESTIMATING SCOUR AT BRIDGES
HYDRAULICS UNIT
Scour depth prediction by equation will be required for all
bridge sites. Three types of scour will be addressed: long term,
contraction, and local. Long term scour involves general aggrada-
tion or degradation of the stream. While most of our large
streams can be considered stable in relationship to a bridge life,
long term stream bed elevation changes can occur due to natural or
man induced causes. When identified as a potential problem, other
reference sources will be used for prediction. Contraction scour
• involves the removal of bed and bank material due to an increase
in velocity. This velocity increase is generally due to a con-
traction of flow, but may also be caused by a change in downstream
water surface elevation. Local scour involves the removal of
material from around piers, abutments, spurs and embankments.
The following general design procedure shall be followed for
estimating scour. A more detailed procedure is provided in FHWA
HEC 18, "Evaluating Scour,at Bridges". The engineer is encouraged
to adapt the procedure and results to the particular site and to
utilize any additional or alternate methods that are deemed
appro-priate.
Step 1: Obtain the following field information in addition to the
normal bridge crossing data.
(a) What is the stream beds and flood plain material?
If sand, is it fine, medium, course?
10/92
APPENDIX ITEM 6
SHEET 2 OF 8
(b) Are the stream banks stable? Are there visible
slumps, vertical banks, leaning trees or undercut
banks?
At existing crossing sites:
(c) Obtain a typical channel section a sufficient dis-
tance up or down stream beyond crossing affects.
(d) Obtain bed profile extending well beyond scour area
(e) What type foundation does existing structure have?
If footing is visible, note condition.
(f) Observe ground conditions around existing piers and
spill through slopes. Is there indication of pre-
vious scour? If so, is depth recognizable.
(g) Compare original sections under structure with
existing. Has scour occurred? •
Step 2: Obtain information on subsurface materials from geology
reports and old surveys.
Step 3: Develop discharge information. The overtopping flood
generally provides the greatest scour potential and
should be analyzed. If less than 500-year flood, the
Q100 and Q500 are also to be evaluated if they do not
result in overtopping.
Step 4: Analyze the crossing for long term scour.
Step 5: Compute contraction scour by the following recommended
procedures and equations. Compare results and select
appropriate value when more than one method is utilized.
Scour that has already occurred must be subtracted from
the computed values to establish maximum scour depth. •
7/90
APPENDIX ITEM 6
PAGE 3 OF 8
is All equation estimates are for sand bed material.
other conditions must be evaluated and adjusted.
Case 1: overbank flood plain being restricted to bridge
opening on main channel. Laursen's 1960
equation modified to address a bridge spanning
floodplain as well as channel:
Yz ?=' 7 (3 -f4e) h , 7 Cate)
AC We. (-,Nn a-)
Y1
Y2
Ys
Qnc
Average depth in approach channel
Average depth in bridge opening channel
Scour depth (Y2 - Y1)
Discharge in natural channel section at crossing
without bridge
Qbc = Discharge in channel section at crossing with bridge
W1 = Approach channel width
W2 = Bridge opening channel width
N1 = Roughness coefficient for approach channel
N2 = Roughness coefficient for bridge opening channel
e = Transport Factor (Table 1)
TABLE 1
v??w
O S
6 ?-
3+ e.

o, z5 0. S 9
J.o0 0. Cat
2.2 S 0. 6 9
010"e-
3 ?c
7
o.6G
0.37
Mc0d- oor 820
AA4t&OL04L? -rA^wyA*A.T
COA/r4C7 - I- a AD
So M e- S U SA60JCS-6 )
5 V SAQ MslowJ L O A- 0
7/90
APPENDIX ITEM 6
PAGE 4 OF 8
Vc = Sheer Velocity g Y1 S is
W = Fall Velocity of D50 Bed material
(Reference Attached Chart 1)
S = Slope, energy grade line main channel
g = Gravity Constant, 32.2 ft/sec2
NOTE: In Laursen's (modified) equation, the discharge ratio
(Qbc/Qnc) expresses the affect of overbank restriction. The
second term (W1/W2) relates to channel constriction and the
third term (N21N1) is for a change in channel resistance
within the crossing. At most sites, the last two terms are
1.0 and can be neglected. Thus, the equation reduces to:
ell
QbC- _
Y =Y,
QN?
CASE 2: Relief bridge with no approach channel.
3 ,
?, 5?1 v,z
Yet
Y WZ !2C Y 3 • ?2
Where: V1 = Average velocity in floodplain
D50 = Med. diameter bed material at
relief opening (in feet).
CASE 3: Relief bridge with an approach channel. Same as
Case 1 0
7/90
APPENDIX ITEM 6
PAGE 5 OF 8
• STEP 6: Compute local scour at piers.
Pier scour prediction by Colorado State
University equation. (Recommended method)
o.`S 0.43
YS - Y.
Where: Ys = Scour Depth
a = Pier width
K1 = Correction for Pier shape (See
Table 2)
• K2 = Correction for flow angle of attack
on pier (See Table 3)
Y1 = Flow depth just upstream of pier
FR1 = Froude Number Vj 1,r
V1 = Average velocity just upstream
of pier (channel velocity or
overbank velocity corresponding
to pier's position in bridge
opening)
TABLE 2
TYPE PIER
Circular
Rounded Nose
K1
1.0
1.0
Square Nose
Sharp Nose
Group of Cylinders
1.1
0.9
1.0
10/92
APPENDIX ITEM 6
PAGE 6 OF 8
TABLE 3
Skew Angle L a= 4 Lf a= 8
0 1.0 1.0
15 1.5 2.0
30 2.0 2.5
45 2.3 3.3
90 2.5 3.9
(L = Pier length) (a = Pier width)
L/ a = 12
1.0
2.5
3.5
4.3
5.0
STEP 7: Plot scour depth predictions on the bridge survey report
and appropriately label. The scour depths are generally
considered additive. The width of the top of the scour
hole can be assumed to be 2.75 Ys.
STEP 8: Re-evaluate the bridge design on the basis of the scour
predictions. The following are examples of considera-
tion that should be made:
- Is potential contraction scour too great
- Should backwater be re-analyzed with scour opening
considered
- Are spillthrough slopes sufficiently set back from
channel
- Are pier locations acceptable
- Need for bank protection
- Need for spur dikes
E
•
•
10/92
•
•
•
-8-
C14ART
103
10=
V
W 10
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Q
W
a
0 'N

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10-s

APPENDIX ITEM 6

Ra 2.000 0

0
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00
00
• i
i
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NEWTONS
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S=ZS C3
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10-4 10"3 10-= 10-' 1
^.,.,t PARTICLE OIAMETER.CM
10
10:
7/90
APPENDIX ITEM 7
COVER SHEET ONLY)
CULVERT SURVEY & HYDRAULIC DESIGN REPOR SHEET 1 OF 3
N. C. DEPARTMENT OF TRANSPORTATION
DIVISION OF HIGHWAYS
HYDRAULIC DESIGN UNIT
RALEIGH, N. C.
I.D. No. --------------------- Project No. --------------------------------- Prof. Station ---------------------------------
County ---------------------------- Stream ---------- Stru. No. ------------
--------------------------------------------------
On Highway ------------------------------- Between ---_____ and
-------------___ ----------------------------------------
Recommended Structure ----------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------------------------------
Recommended Width of Roadway ----------------------------------------------------------------------- Skew-----------
Location is (Up, At, Down Stream from Existing Crossing) -------------------------------------------------------
Bench Mark Is --------------------------------------------------------------------
---------------------------------------------
----------------------------------------------------------------------- Elev. --------------- Datum: ------------
Temporary Crossing -----------------------------------------------------------------------------------------------------------
USE THIS SPACE FOR PHOTOGRAPH
OF PROPOSED SITE, SHOWING CENTERLINE.
DIRECTION OF FLOW AND OTHER
IMPORTANT POINTS ON PHOTOGRAPH.
Designed by: ---------------------------------------------------
Assisted by - ---------------------------------------------------
Project Engineer: --------------------------------------------
Reviewed & Approved by: ___-_-_ ---____-_--_ Date
•
•

APPENDIX ITEM 7
SHEET 2 OF 3
SITE DATA
Drainage Area ___________________ Source ................................... Character
Data on Existing Structure ------------------------------------------------------------------------------------------------
• -------------------------------------------------------------------------------------------------------------------------------------
Data on Structures Up and Down Stream ______________________________________________________________________________
-----------------------------------
Historical Flood Information:
Period of
Date ------------ Elev------ ____ Est. Freq. --------- Source ------------------------------------------ Knowledge --------
Period of
Date ____________ Elev----------- Est. Freq.________ Source Knowledge------_-
----------------------------------____-___
Allowable HW Elev. ----------------------------------------------------- Normal Water Surface Elev. _-_--___-------_--
Manning's n Left 0.8. ------------ Channel ---------- Right 0.8. _________ Obtained From --------------------
Flood Study / Status _---_---_ Floodway Established? _--_---
--------------------------------------------_____________
Flood Study 100 yr. Discharge ........... c.f.s.: W.S. Elev.: With Floodway ---------- Without Floodway -----------
DESIGN DATA
Hydrological Method ------------------------------------------------------------------------------------------------------------
Hydraulic Design Method -----------------------------------------------------------------------------------------------------
•.eslgn Taliwater : 0- ------------- % O- ----------- % 0 --------- 0- ---------- O- ----------------
Inlet Control Outlet Control
R
k

do
do+
D
h
H
LS
H
W emar
s
Size & Type a Ke HW/D H.W. 2 o O .
.

Is a Floodway Revision Required?______________________________________
Outlet Velocity,(V 10) _____________________________________ Normal Channel Veloclty,(V 10 )______________________--_--_-_---_
INFORMATION TO BE SHOWN ON PLANS
• eslgn: Discharge --------------- c.f.s. Frequency ----------------------
Base Flood: Discharge _______________ c.f.s. Frequency _______ 100__yr__------
Overtopping: Discharge --------------- c.f.s. Frequency -----_________________
Elev ----------------------------
Elev. ----------------------------
Elev- ----------------------------
10/92
APPENDIX ITEM
SHEET 3 OF 3
SIDE -TAPERED INLET SLOPE-TAPERED INLET
it BEVEL ,
II BEVEL
0
--- N =
B N =
PROFILE VIEW D = PROFILE VIEW B =
Bf= D =
L1= d =
r? ?L2 L. Bf
I-
i
Bf ' B B f- , B L2
L3=
k--- L1-N
PLAN VIEW PLAN VIEW
ADDITIONAL INFORMATION AND COMPUTATIONS
-------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------------------------
•
-------- --------------- ---------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------------
APPENDIX ITEM 8
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7/90
" r I
APPENDIX ITEM 11
SHEET 2. OF 4
A
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120
114 5000
108 4 000
102
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84
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NONDGRAPH H
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IN
PIPE CONDUITS
BASED ON
0 • VA
6/90
•w w?
APPENDIX ITEM 11
SHEET 3 OF 4
HYDRAULIC PROPERTIES - CIRCULAR PIPES •
Pipe
Dia.

(Inch) A
Area
(Square
Feet) R
Hydraulic
Radius
(Feet) Values of K
1.486/.. a A a R4/3

(n- 0.012)
8 0.349 0.167 13.1
10 0.545 0.208 23.6
12 0.785 0.250 38.6
15 1.227 0.312 70.1
18 1.707 0.375 113.8
21 2.405 0.437 171.5
24 3.142 0.500 245.1
27 3.976 0.562 335.3
30 4.909 0.625 444.3
33 5.940 0.688 573.7
36 7.069 0.750 722
42 9.621 0.875 1090
48 12.566 1.000 1556
54 15.904 1.125 2131
60 19.635 1.250 2821
66 23.758 1.375 3636
72 28.274 1.500 4587
78 33.183 1.625 5679
84 38.485 1.750 6920
90 44.179 1.875 8321
96 50.266 2.000 9878
102 56.745 2.125 11615
108 63.617 2.250 13526
114 70.882 2.375 15624
120 78.540 2.500 17915
126 86.590 2.625 20397
132 95.030 2.750 23104
138 103.870 2.875 26009
144 113.100 3.000 29133
•
•
6/90
•
•

APPENDIX ITEM 11
SHEET 4 OF 4

STORM r,
DRAIN PIPE
MAXIMUM CAPACITY TABLE

42" 90
48" 120

(1) CONCRETE PIPE
(2) CAPACITY (c.f.&) BASED ON INLET CONTROL
FOR MAXIMUM DE PTH IN STANDARD CATCH BASIN
6/90
(1) PIPE SIZE (2) MAXIMUM CAPACITY
12" 6
15" 9
18" 13
24" 25
30" 43
36" 64

54" 160
60" 200
66" 250
APPENDIX ITEM 12
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•

APPENDIX ITEM 13
SHEET 1 of 4
'V' DITCH WITH GRASS, 6:1 SIDE SLOPES
• For ditch with side slopes other than 6:1,
multiply the discharge by a factor of 61Z
where Z is side slope.
STABILITY LIMIT
Lateral Ditch
Roadway Ditch
•
14
12
10
m
U
47
U
ao
0 P"
6

4
2C
1
2 3 4 5 6 7
Velocity, fps 6/90
CHART 1
2' BASE DITCH WITH
2:I SILL SLOPES
For a 3' base ditch, multiply discharge
For a 4' base ditch, multiply discharge
STABILITY LIMIT
18
16
14
0
U
47
12
U
m
a
10
8
6
2

C
CHART 2
APPENDIX ITEI
SHEET 2 of-4
-I$A S, Sy
•
by 0.7
by 0.6
3 4 5 6 7 8
Velocity, fps 6/90
f?
•
APPENDIX ITEM 1
MEET 3 of 4
'V' DITCH WITH RIP AAP,
2:1 SIDE SLOPES
For ditch with side slopes other than 2:1 ,
multiply the discharge by a factor of 2/ Z,
where Z is side slope.
STABILITY LIMIT
Use Base
Ditch or
With 'A' Stone I 'B' Stone IRitid Pavir
•
U
a
U
by
it 8
U
6
1j
14
EXAMPLE:
Q = 12 cfs
S =0.10 %
Z = 3:1
12 1) Adiust Q:
(12)2/3=8 Js
2) From chart:
V = 6.6 fps
a= 0.8 ft.
10 3) Ditch is stable
with 'B' Stone
4
11
2 11111171111111
2 3
o to o ?
0 0 0 0
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CHART 7
6/90
8
APPENDIX ITEM 13
SHEET 4 of 4
2' IODASE DITCH[ WITH RIP RASP
2:1 SIDE SLOPES
For a 3' base ditch, multiply discharge by 0.7
For a.4' base ditch, multiply discharge by 0.6
LINING 0
STABILITY LIMIT
C1.1' I Use Pie or
With 'B' Stone IRip Rap Rigid Paving
34
30
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Q= 30cfs
S = 0.10
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1) Adjust Q 7?4?-'
I I VII 11
(30)0.7 = 21 cf s
From chart:
I I LA If
V = 7.5 fps
--------
a= 0.8 ft.
Ditch is stable
with Cl.'I'
Rip Rap
0
0
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4
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N. C. DEPT. OF TRANSPORTATION
DIVISION OF HIGHWAYS
GRANVELLE COUNTY
PROJECT : &&738 (R-2267 )
• PROPOSED OXFORD OUTER LOOP
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•
PROPERTY OWNER
NAME AND ADDRESS
PROJECT NO.6J*4738
BOX CULVERT OVER COON CREEK
GRANVILLE COUNTY
PARCEL NO. OWNER'S NAME
ADDRESS
1 W. T. LANDIS, JR.
718 WELLIAMSBORO ROAD
OXFORD, N. C. 47665
4 FRANCIS L. EASTON 116 XMITARY STREET
OXFORD. N. C. 47665

0
6/90
I
•
NORTH CAROLINA STATE HIGHWAY COMMISSION
Raleigh, N. C.
HANDBOOK OF DESIGN FOR
HIGHWAY SURFACE DRAINAGE STRUCTURES
?J
Prepared by
Bridge Location & Hydrographic Department
C. R. Edgerton, State Hydrographic Engineer
1973

Approved by
ohn Davis
Chief Engineer &
Asst. Administrator
Section I - Administration and General Policies
• 100-General
100.01 The Bridge Location and Hydrographic Department is re-
sponsible for the field surveys and hydraulic design for
all structures constructed by the Highway Commission.
The work of the department is under the direction of the
Hydrographic Engineer. His staff includes an assistant,
approximately ten engineers specially trained and skilled
in bridge location and drainage work, and the necessary
number of engineering aides to comprise the field parties
required to perform the work of the department.
100.02 This handbook is an outline of methods used by the Hydro-
graphic Department of the N. C. State Highway Commission
in preparing all drainage structures coming under its
jurisdiction.
100.03 For a complete package, the following publications should
be included as part of this handbook:
1. Hydraulic Engineering - Circular No. 11
2. Hydraulic Engineering - Circular No. 12
3. Hydraulic Engineering - Circular No. 13
4. Hydraulic Design - Series
No. 1 - Hydraulics of Bridge Waterways.
No. 3 - Design Charts for Open Channel Flow.
• No. 4 - Design of Roadside Drainage Channels.
(Above available from Superintendent of Documents,
U. S. Government Printing Office, Washington, D.C.
20402)
5. Floods on Small Streams in N. C. -
U. S. G. S. Circular 517.
6. Drainage Areas at Selected Sites on Streams
in N. C. - G. S. Open File Report.
100.04 By following the criteria and the methods outlined herein,
sound and consistent design will be accomplished. It is
expected that from time to time, revisions will be issued
to parts of the handbook in order to upgrade the results
consistent with advancing research and technology in the
fields affecting higtway and related drainage design.
100.05 Included in this section are general drainage policies
of the Highway Commission for those who are unfamiliar
or need refreshing. Necessarily, all circumstances
cannot be covered, and for specific information on un-
usual circumstances, advice from the State Hydrographic
Engineer's office should be obtain-ed.
•
1
1^).06 In general, bridges will be employed where discharge and
velocity requires 300 sq. ft or more. Box culverts will •
be used when 60 sq. ft. or more are required and pipe and
multiple pipe below this. It is emphasized that this is
strictly empirical and has no bearing when site conditions,
economy, or other considerations, dictate otherwise.
•
•
2
101-Pipe Culverts Materials
• 101.01 Pipe materials allowable are as those included in the specifi-
cations. In general, reinforced concrete is preferable when
site conditions do not require other material. On projects,
where design requires a large percentage of corrugated metal,
it is usually preferable to use all corrugated metal. Where
corrugated steel pipe is used, it is usually economical to use
3" x 1" corrugations on 36" and larger.
101.02 It is often desirable to compare the costs of more than one
type structure to select the most desirable for economy and
durability. When using metal pipe, it is usually desirable
to require elongation where applicable for economy.
101.03 Usual practice is to specify half coated and paved corrugated
metal, except in the coastal plain, where fully coated with-
out paving, is generally specified.
101.04 Headwalls are used on pipes above 36" in diameter, usually on
both ends, but always on the inlet. Flared end sections are
used on smaller pipe.
•
•
3
102-Flood Plain Information
102.01 On all structures, where design discharge is more than
500 c.f.s., this will be shown on the plans along with
the frequency and high water elevations.
102.02 When flood plains are encroached upon on streams of
greater than 500 c.f.s. design discharge, the design
flood profile will be shown with and without the encroachment.
102.03 When practical, flood plain locations will not be used;
but when necessary, encroachment should be kept to a
minimum.

0

-Drainage Easements
• 03
lt'i.01 Drainage easements, permanent and temp?,Tary, will be aaga:. ea
as needed, as outlined in 10:.05 in specif_;, arainage -:,Ilcy.
10=.0_2 Where permanent easements are required, sufficient inf .rnatton
will be obtained so that the limits, grade, and cross se--tion
may be determined. The easement shall be of sufficient size
to ccnta:n the spoil and provide workirg room for equipment.
1;)3.0, When outlet drain maintenance is required and a permanent
easement is not required, nor desirable, the wLrk :s ac:om-
phished under a permit of entry. The length of the clesr.Du:
and cross section of the proposea channel should be shown
on the plans.
103.04 where ro work is to be performed, this .hail be noted on
the drainage survey with any applicable --cmmert.
iC..05 Where water is discharged from the right of way outside
a natural drain or existing ditch, an easement is re-
quired for the necessary channel and carstr at=or, opera-
tion to a natural drain.. Where diversion of water is
made to a natural drain or existing ditch which would
increase the discharge --onsiderably -above its capacity,
an easement is required to enlarge and =prove the drain.
• to a po-nt where the increased discharge -an ba release'
without causing damage.
10.?.06 Where improvement to an existing drain is required for
proper drainage and not covered in the paragraph above,
a permanent drainage easement is not requirea. Even
though the drain may be enlarge,: ens deepened, if the
property owner is informed of what is to be none and
agrees in writing to allow entry onto his property for
this work;, this is all that is required. 7h:.s should
n:,t be c.nstrued to rear. that in all cases of this naturas.
a permit of entry znly should be obtained. There will
be instances where a permanent easement is desirable.
Also, it mould not be reesesary to obtain wr_tten Fer-
mit of entry on those drains which have pre:°izusly been
routinely maintained. Permiseion for th:_s is implied
until otherwise advised by the prcperty owner.
•
5

104-Roadway Dams
104.01 It is the poke; of the Divi-sion of Highways to d:s-
courtge the location of rondwnys on dams. In tnose
cases, wnere a definite advantage may be gamed or a
duos L,an teal savings in finds may oe realized, the •
utilization of a dar, l yr a roadway ;gay be favorauly
considered.
104.02 Where it is de termin- d th-it a dam will be utilized as
a roadway, the following criteria must be met:
A. 11hen applicable; Lhe dam must have certifi-
cation from the N. C. Department of Natural
and Economic Resources, pursuant to the "Dam
Safety Law of 1961 ".
3. All pertinant data regarding the design of
the embankment as an impoundment structure
must be presented to the Division of Highways
for review.
C. Top section must be roadway width for facility
plus a minimum of 41.
D. Guardrail will be provided on the impoundment
side of the roadway.
E. Spillway will be designed to provide 2' of
freeboard at the shoulder for an estimated
50-year frequency outflow as a minimum. •
F. Means of draining the lake completely will
be provided.
104.03 Design acceptance or approval by the Division of High-
ways is limited to the use of the dam as a roadway
and is in no way intended as approval of the embank-
ment as an impoundment, structure.
104.04 Responsibility incurred by the Division of Highways
when a section of roadway crossing a dam is accepted
as a part of the state maintenance system is limited
to maintenance of the roadway for highway purposes
from shoulder point to shoulder point only. Responsi-
bility for the impoundment, any damage that may result
therefrom, and maintenance of the dam or appurtenances
as may be required to pre so rve it's in togri ty as a wa Lc r
impoundment structure, shall remain with the owner of
the impoundment. Any such maintenance work will be
subject to the provisions of G.S. 136-93.
104.05 Impoundment of water on highway right of way may be
allowed under the following criteria:
A. The impoundment does not adversly affect the
right of way for highway purpose. •
5. Adjustnent, as requirea, flattening slopes
installing rip rap, and any others shall fie
the responsibility of the encroaching party.
fi
• 105-Subdivisions
1 ,5.01 When ac%epting streets for maintenance:, where drainage check
l: required by the Hydrographic Department, the following in-
°ormat.ion should be furnished for the review.
A. Street layout and grades.
F. typical Section.
c, ;cntcur map k if available)
D. Pipe sizes and grades.
E. Drainage areas at each pipe or inlet,
F. Frupoeed easements. •
G. Vicinity map.
0 2'
105 The above information should be submitted prior to beginning
. L,f construction of the subdivisions, so that if any changes
incorporated in the original
ld b
e
are reLommcnaed. these cou
construction, lather than having to go back and make
adjustment..
:05.03 in the tease of higher type subdivisions where curb and gutter
ld be submitted showing
h
ou
section w,ll be used, details s
prop-sea cat:h oasins. manholes, etc., along with the grades
of the storm sewer System,
-LO5.04 Whexe storm :ewer systems are used, the design for the collet--
storm; and
. t ,, r system s hou:d be for the 10-year frequency
fcr ?ress drainage, the 25-year frequency storm.
05
35
' With the above information furnished the Hydrographic Depart-
.
4 ment. the check of the design of the proposed drainage system
--an be made at a minimum --ost to the Highway Commission.
105.0n vfnere r.)ads and .streets built by others now exist on
Co=rission's responsi-
tre system. the State Highway
bility far the drainage system installed by the
developer does not exceed the right of way, or ease-
ment limits ac,epted by the State Highway Commission.
The acceptance of the streets onto the state system
t include drainage easements outside the right
foes nc
of way %miesae specifically stated that those easements
so designatea by the Conanission are included in the
acceptai,ct
,05-07 Where request for additions to the System arise cn
t shall
r.ads and streets built by others, the reques
ranted until the drainage installations have
t be
g
no
been inspezted and approved by a representative of
•
7
•
105.07 tContinued; 105-Subdivisions
the State Highway Commission. The representative
shall be the Division Engineer or his appointed repre-
sentative. If desired, or if special treatment is needed,
a review by the Hydrographic Department should be
requested. If structures other than pipe installations
are included, they shall be approved by the Asst. Chief
Engineer-Bridges,
8
• 110-General Drainage Policy
1!0.01 Right of Parties - Civil law in North Carolina generally
provides that lower lands are subservient to upper lands
for the natural drainage flowing to it. This law applies
to the privately owned wand, as well as State Highway
Commission rights of way. It is the policy of•the State
Highway Commission to accept this provision of the law by
providing sufficient drainage ways, so as not to impede
natural flows to the extent that upper lands are damaged
thereby.
110.02 Acceleration - In the rapidly expanding economy of the
State, much development is taking place, This develop-
ment causes increased peax flow by increasing impervious
areas. more rapid overland flow, and providing more
hydraulically efficient channels. Civil law generally
p;,ovides that thiE acceleration of flow also becomes
the natural burden of the lower lands, if the accelera-
tion is the result of gooa husbandry inthe use of the
upper lands. It is the policy of the State Highway
Commission to proviae for this accelerated flow reach-
ing its right of way by providing sufficient drainage
ways therethr:.ugh. Conversely, it is the policy of the
State Highway Commission to deny responsibility to
lower properties for accelerated flow caused by improve-
ments in its rights of way, unless distinctly and solely
determined to be detrimental.
110.03 Diversions - Diversions are defined as the a:t of drain-
ing surface waters from an area outside the natural
boundaries of a watershed into the drain serving the
watershed. C-vil law provides that parties creating a
diversion of water shall be liable for all damage caused
by the diversion. Note that the act of diversion is
not prohibited. but it does create liability where damage
occurs. It is the poli:.y of the State Highway Commission
to so dezign and maintain its road system, so that no
diversions are treated thereby, insofar as is practicable
from good engineering practice. Any person(s) creatL-ig
a diversion into any highway drain shall do so only after
receiving written permission from the Chief Engineer.
Permission will be granted only after it has been deter-
mined that the additional water can be properly handled
without damage, that any adjustments required to the
highway drainage system will be borne by the requester,
that not granting of the permission will be a distinct
burden to the requester and that in general, the diversion
will be in the public interest. The Chief Engineer
•
9
110-General Drainage Policy
10.03 (Continued) •
shawl provide that the State Highway Commission is
properly indemnified from any claim for damage which
may arise from such diversions. It is generally desir-
able that the State Highway Commission not become a
party to such diversions, unless to refuse would create a con-
siderable and real hardship to the party(ies) requesting such
permission.
110.04 It is the policy of the State Highway Commission to provide
for each natural drain traversing its right of way, and not
combine several drains and place in a single structure, except
where good engineering judgment dictates otherwise, and thorough
investigation of the results which may arise from.such com-
bining and diversions of these drains has determined that the
best interest of the State Highway Commission and public will
be served.
110.05 Obstructions - Civil law provides that the lower subservient
land shall accept the natural flow from upper lands without
artificial obstruction thereto detrimental to the upper land.
Statute Law (GS 136-92) provides that anyone obstructing any
drains along or leading from any public road is guilty of a
misdeme anor.
--0.06 It is the policy of the State Highway Commission that when a •
drain is blocked below the highway, which is detrimental to
highway drainage, if from natural causes, the State Highway
Commission will take necessary measures to remove the block
or obstruction. Where the block is caused by wrongful acts
of others, it is the policy of the State Highway Commission
to take whatever recourse deemed advisable and necessary to
cause the party(ies) responsible to remove the block. Where
a block is created doWnstream of a highway, whether natural
or artificial, and is of no consequence to the State Highway
Commission, it is the policy to remain neutral in causing its
removal.
110.07 It is not the responsibility of the State Highway Commission
to eliminate flooding on private property which is not
attributable to acts of the Commission, or its representative.
110.08 Restoring Existing Drains - In the design of highways
where existing drains will be crossed, interrupted, or
destroyed, it is the policy of the State Highway Commission
to replace in kind or better, or to pay for replacement
of all such drains.
•
10
• 110-General Drainage Policy
(Continued)
110.09 while it is the responsibility of the State Highway
Commission to provide for adequate drainage for the
construction of roads and modern highways, it is not
the policy nor the responsibility to provide improved
drainage for the general area traversed by such road,
unless incidental to the drainage of the road or high-
way itself.
110.10 It-is the policy of the State Highway Commission to
make sufficient investigation outside of right of way
to insure that the design of the highway drainage
facilities will not be detrimental to private property,
insofar as is feasible.
When highways are constructed for the embankment to be
used as a dam, it is the policy of the State Highway
Commission to require the partg(ies) requesting the use
of the embankment as a dam to bear all additional cost
incidental to making the embankment serve as a dam.
In general, this practice will be avoided except where
shown to be in the interest of the public.
110.20 Maintenance - Maintenance of drains along the right of way,
• and those outside, which are the responsibility of the State
Highway Commission shall be done with continuing respect for
adjacent property. Any changes from established drainage
patterns will only be made when it is determined that the
best interest of the State Highway Commission, and all
affected property owners are served.
110.21 Established pipe crossings will be maintained and request to
eliminate any pipe should have approval by the State Hydro-
graphic Engineer before permission is granted.
110.22 In general, outlet ditches will be maintained for a sufficient
distance below the road to provide adequate drainage therefor.
On large outlets serving considerable area outside the right
of way, the maintenance should be done on a cooperative basis,
with the benefited properties bearing their proportionate
share. Shares will, in general, be based on proportion of
runoff from the areas served by the outlet.
110.23 Drainage structures under the roadway will be kept open at
all times. It is the responsibility of the District Engineer
to have periodic inspections made as necessary to insure that
drainage structures do not become blocked or clogged.
•
11
120-Drainage and Flood Control Projects •
120.01 When any drainage district or flood control project makes
necessary the revision, modification, replacement, or construc-
tion of any drainage structure on any road maintained by the
State Highway Commission, the Lost of such revision, modifi-
cation, replacement, or construction of such structure shall
be paid as follows:
120.02 Where the drainage district or flood project requires
the construction of a new structure where one has not
previously existed, the entire cost of such structure,
constructed with Standard State Highway Commission de-
signs, shall be borne by the drainage district or flood
control project.
120.03 Where an existing drainage structure has to be replaced,
the cost of replacing the existing structure with a
structure of like design, width, load bearing capacity,
and life expectancy shall be borne by the drainage dis-
trict or flood control project. Should it be deemed
necessary or advisable by the State Highway Commission,
in replacing the existing structure, to construct
one of more modern design, or of greater width, or of
a higher load bearing capacity, the cost of such and
similar improvements shall be borne by the State High-
way Commission. •
120.04 Where an existing drainage structure has to be modified,
revised, or extended due to the deepening or widening
of the waterway, approaching, leaving, or passing under
or through the drainage structure, such modification,
revision or extension shall be borne by the drainage
district or flood control project, provided that such
modification, revision, or extension, does not signifi-
cantly improve the general design features, or does
not significantly increase the width load bearing capa-
city, or life expectancy of the structure. Should it
be deemed necessary or advisable by the State Highway
Commission in modifying, revising, or extending the ex-
isting design features, the width, load bearing capacity,
or life expectancy of the structure,' the additional cost
of such improvements shall be borne by the State High-
way Commission.
•
12
120-Drainage and Flood Control Projects
• (Continued)
120.05 Where a lake or reservoir floods a road or drainage structure
causing the relocation of such road or drainage structure,
the cost of road relocations to be charged to the water pro-
ject shall be the difference between the cost of construc-
ing the highway to modern highway design standards on the
new location or elevation resulting from the water project
and the cost of reconstructing the existing highway to the
same modern standards without regard to the water project.
Modern highway design standards should be based on a pro-
jection of traffic conditions for not more than twenty years
in the future.
120.06 Any direct benefits to the State Highway Coaanission due to
the improvement of the drainage structure, or due to the
work proposed by the drainage district will be paid for by
the State Highway Commission. The maximum benefit to be paid
by the Commission under the provisions of this item will be
limited to the cost of the highway drainage structure in-
volved. Such direct benefits to be determined by conference
between representatives for the Highway Commission and the
officials of the drainage district.
120.07 The adjustments of pipe culverts will be in accordance with
• the policy for other pipe crossings.
C7
13
130-4djustments to Pipe Culverts
130.01 Where the elevation of the flow line of a pipe under a
highway is not low enough to take care of drainage, it
shall be the responsibility of the State Highway
Commission (without charge to the property owner) to
lower the pipe, or otherwise provide needed lower
drainage under the highway and within the limits of
the right of way.
130.02 When the lowering of the drainage causes an increase in
the amount of water, due to diversions to serve larger
areas than before, requiring a larger size pipe, the prop-
erty owner will be required to furnish the pipe delivered
to the site, to be installed by the State Highway Commission.
130.03 when a new pipe crossing is requested, if the pipe cross-
ing is required for proper highway drainage, the full cost
will be borne by the State Highway Commission. Where
the new crossing is not a requirement, but sufficiently
beneficial to highway drainage, the State Highway Commis-
sion will make the installation, provided the property
owner furnish the pipe delivered to the site. Where the
new installation is of doubtful, or no benefit to highway
drainage, the property owner will bear the entire cost
of the installation.
130.04 When new drives are constructed entering the highway, the
property owner will furnish, delivered to the site, the
amount, type, and size pipe designated by the State High-
way Commission, to be installed by the State Highway
Commission.
130.05 In general, the conditions referred to above include pipe
installations where the property owner, in order to pro-
vide adequate drainage has lowered the flow line of the
inlet and the outlet ditch to a pipe culvert that crosses
a highway; where the lowered outlet ditch has satisfactory
fall and does not divert water from the natural drainage;
where there is reason to believe it is practical to main-
tain the outf all; and where the benefit to the property
affected equals or exceeds the cost of lowering the pipe.
130.06 It is not the policy of the Highway commission to pipe
inlet or outlet drains, natural or artificial, outside
the right of way, which existed as,open drains prior to
existence of the highway. Where the property owner wishes
to enclose an inlet or outlet, the Highway Commission may
install the pipe adjacent to the right of way if justified

14
130-Adjustments to Pipe Culverts
• (Continued)
130.0E (Cont'd.)
by reason of reduced maintenance, safety or aesthetics
if the pipe is furnished at the site by the property owner.
This does not apply to the development of commercial
property.
•
•
15
140-Alterations on Right of Way •
140.01 Alterations to Box Culverts - No alterations of, nor additions
to any box culvert on the highway system shall be allowed
without written permission from the Assistant Chief Engineer-
Bridges, or his authorized representative.
All requests for alteration of, or additions to, box culverts
shall be mace in writing to the Division Engineer. Six prints
shall be furnished showing in detail the location and nature
of the proposed work. The prints shall show sufficient detail
so that they may be used as construction drawings. The pro-
posed alteration shal+ be within good engineering construction
and hydraulic design. The Division Engineer shall forward
one of these drawings to the Assistant Chief Engineer-Bridges,
with his recommendations. After any required revisions and
upon approval of the plans by the Assistant Chief Engineer-
Bridges, the request shall be returned to the Division Engi-
neer for preparation and execution of the Encroachment Con-
tract.
140.02 Alterations to Pipe Culverts - No alteration, extension nor
addition of appurtenance to any pipe culvert shall be allowed
on highway right of way without the written consent of the
Division Engineer, or his authorized representative.
0.03 All requests for alteration, extension or addition of appurte-
nance to any pipe culvert shall be made in writing to the
Division Engineer. Six prints shall be furnished showing
the location and detail of the proposed work. The print shall
include arrows indicating the direction of flow, and approxi-
mate acreage drained by the pipe and size and type of the
existing pipe, if appurtenances are involved, the type ton-
straction shall be shown. The approximate height from invert
to inlet shall be shown when catch basins are proposed. Where
only minor drainage alterations are involved, the Division
Engineer will approve the encroachment. If other than minor
drainage alterations are involved, the Division Engineer shall
submit one drawing with recommendations to the State Hydro-
graphi, Engineer for approval. Upon approval by the State
Jjydrographic Engineer, the request shall be returned to the
Division Engineer for preparation and execution of the En-
croachment ;,ontract. (Any request for alteration to pipe
culverts may be submitted to the State Hydrographic Engineer,
If the Division Engineer deems it desirable.)
•
16
• Section II - Hydrology
200-General
200.01 Hydrology in highway drainage design concerns itself with
the determination of discharges to be used for applicatiin
of hydraulic theory to provide adequate capacity for pro-
ject structures.
200.02 There are many ways of approaching this determination.
These range from empirical to so-called rational methods;
applications of rainfall data; and statistical analysis
of stream gage data.
200.03 This section presents the methods employed by the Hydro-
graphic Department to determine discharges of the desired
frequency for structure hydraulic design.
•
•
17
201-Site Hydrology
:J1.01 The firbt most significant factor affecting runoff is the
size of the catchment basin above the site under consicera-
tion, referred to simply as the drainage area.
=:1.02 Drainage areas may be obtained from several sources. The
larger areas may be obtained from several sources. Many
are listed in the geological Survey open file report
"Drainage Areas at Selected Sites on Streams in North
Carolina." If the exact site is not listed, usually one
close enough so that only small adjustment is necessary
may be found.
201.03 For smaller areas, aerial photography is available in *he
Planning and Research Cartographic section. Steroscopic
coverage is available for the entire State, with the ex-
ception of Dare County.
201.04 Many times it will be desirable or necessary to determtne
drainage areas by field reconnaissance.
201.05 By whatever method the drainage area is determined, during
the field survey, the general area should be reconnoitered
to get sufficient information of the features which will
affect runoff.
-..1.06 On those drainage
the determination
the length of the
mately). This is
structure site to
appr.)Aimate center
areas of less than 1000 acres, during
of size and the reconnaissance
area (L) must be determined (approxi-
defined as the distance from the
the farthest divide following the
of the area, or principal thalweg.
201.07 Also. ar thie time, on those areas less than 1000 acres.
the determination of the type culture which would affect
runnoff is made. On rural watersheds, this would be the
percent woodlana or forest cover; on urban watersheds.
this woula be the type and relative density of
deve lopmen t.
201.08 For areas above 100 acres, only the area is required
as other factors affecting runmff are homogeneous
enough so that the hydrologic contour and drainage area
are the only significant variable.
201.09 From Chart C200.1 "Map of Hydrologic Contours", deter-
mine the hydrologic contour by location of the structure
site. Interpolate to 0.5 contour interval.
•
C7
•
18
•
202-Site Discharge
202.01 If the area is rural and larger tY.ar. 1000 acres, enter Chart C200.2
with drainage area and hydrologic contour and read discharge. If
other than Q50 is required, apply frequency correction factor shown
an the chart.
202.02 If the area is rural and less than 1000 acres determine W/L ratio
202.04 Deleted 10-21-77
(W/L = A/L ) and the percent forested cover. Enter appropriate
Charts Nos. C200.4 and C200.5 to determdne correctiaci factors to
be applied to value from Chart C200.1. The combination of the two
corrections should not exceed the limps of -6.4 and-4r?.
G?•
202.03 If the area is urban and less than 125 acres, enter Chart C200.3
with drainage area and hydrologic contour and determine chart value
for Q10. If other frequency is desired, apply frequency correction
factor shown on the chart.
202.05 From instruction in paragraph 201.07, determine if density of develop-
ment correction is necessary. Apply correction factor from inset
density correction factor.
• 202.06 If the urban area is greater than 125 acres, utilize procedure
described in section 202A.
202.07 If the area is greater than 50 sq. mi., use method described in
U.S.G.S. publication "Water Resources Investigations 76-17".
C.
202.08 Gaging station records should be checked for all stream crossings.
Where records are available, an analysis should be made and an
evaluation of results obtained to be compared with those obtained
from the =off charts.
19
203- Adjustment of Discharge •
203.01 In those areas, particularly in the potentially low runoff areas
in the coastal plain, where channelization has occurred, caution
must be used in applying the hydrologic contour. It is suggested
that a contour of 0.5 to 1.0 above that taken from Chart 0200.1
be used, depending an the intensity of charnel work.
203.02 In the eastern coastal plain, where the drainage area ccnsists of
larip swamp areas with large storage volumes, discharges may be
reduced as match as 15-20% below the curve value.
203.03 Cn any stream, where flood control structures or works are in
place or under design, the effect of the works should be determdned
and the structure designed for the reduced discharge.

•
20
RMSED IJovember 21, 1984
•
202A-Urban Hydrology
The -following procedure will be utilized in estimating peak discharges for
ungaged urbanized watersheds in excess of 125 acres. Fbr smaller watersheds
highway chart C 200.3, the rational method or other appropriate methods will
be utilized.
This as any hydrological method must be applied with god judgement and the
engineer is encouraged to compare the result with other methods and historical
occurTence and make adjustments when deemed appropriate.
This procedure is an adaptation of the procedure presented in "Techniques
for Estimating Flood Hydrographs for raged Urban Watersheds" published as
Open-File Report 82-355 by the U.S. Geological survey.
1. Determine the size of the drainage area and compute the equivalent
rural discharge (RQ)
2. Divide the watershed into approximate equal thirds. (Upper, middle,
lower)
3. Compute the basin development factor (3DF - value of G-12) for each
third of the unatershed. Four aspects of the drainage system are
evaluated and assigned a code of 1 or 0. This evaluation must include
consideration for planned or predicted future development.
a. Channel Improvements
Has a prevalent amount (C50%) of the main and principal
tributary channels been or expected to be subjected to
improvements such as straightening, enlarging, deepening,
or clearing. If so assign a value of 1, if not 0.
b. Channel LUd
Has prevalent amount (9 50%) of the main and principal tributary
channels been or expected to be lined with an impervious material.
If so assign a value of 19 if not 0.
c. Stom Drains
Has a prevalent amount (g 50%) of the secondary tributaries
been enclosed in drainage structures such as pipes. If so
assign a value of 1, if not 0.
d. Curb and Gutter Streets
If more than 5 of the subarea (third) is urbanized and more
than 50 percent of the streets and highways are curbed and
guttered then assign a value of 1, if not 0.
Total the values for the three subareas to establish the EDF.
•
20A
REVISED November 21, 1
? I •
4. Compute the urban peak discharge using the following appropriate
equation:
= 13.2A•21 (13,)-.43 RQ2 .73
UQ5 = 10.6x•17 (13-SOF)-.39 FjQ5 .78
UQ10 = 9.51A.16 (13-mF)-• 36 M10 •79
UQ25 = 8.68A.• 15 (13-mp)-. 34 RQ25 .80
UQ50 = 8. o4A• 15 (13-BW)-. 32 RQ50 .81
UQioo - 7.7oA•15 (13-x)-.32 RQ100 .82
mere UQ = Urban peak discharge
A = Watershed area in Square
'
- Mles
-'
BE
= Basin Development c
tor '-
RQ = Equivalent rural d:s &at p
C

0,

11 ^=
r?
•
•
204-Rational Method
204.01 For those who prefer, and where the foregoing may not apply,
the Rational Formula is acceptalbe for computing runoff.
This method is well enough known so as not to require de-
tails here.
204.02 In applying this method, the minimum time of concentration
shall be 15 minutes and the maximum weighted 'C' for areas
-over 5 acres shall not exceed 0.8.
204.03 Weather bureau curves for representative areas for intensity,
duration, and frequency, are included herein, as charts
C200.79 C200.8, and C200.9. Interpolation between stations
is allowed. Weather Bureau technical paper No. 40 may be
used to construct these curves for other areas of desired.
204.04 Further discussions, 'C' value tabulations, and time of con-
centration nomographs are included in "Drainage of Highway
Pavements" and "Design of Roadside Drainage Channels."
21
205-Conclusions •
205.01 Determining reasonable design discharges of the desired -
frequencies is one of the most difficult and perplexing
tasks faced by Highway Drainage Engineers. The method
used by the North Carolina State Highway Commission has
been greatly simplified by a combination of experience
in North Carolina drainage work and utilization of gage
data of varying lengths of record. While we have no
argument with other methods, it is felt that the use of
this method gives consistently good results, even when
used by engineers with limited experience in hydrologi-
cal work. The method is subject to refinements and the
engineer using it is encouraged to adjust results within
his experience and judgment. Certainly when a gage
record of significant length is available on the stream
on which the structure is to be placed, this should
be used in lieu of the curves. Also, the credenda of
the performance on an existing structure should not be
ignored.
205.02 The designer of drainage structures should use all in-
formation available in determining runoff and will never
be amiss to compare the results of several methods and
select the result which, in his judgment, is most
acceptable.
•
22
.• i
•
•
r ?? f r C ? ? j I? •.

l
e
i

-ir

o?
o
I

v
i Il

v

k
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CS
V ?0
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vv?
v?o?o
zz
o?
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o ?
c ,coo. /
Q`
•
rl
•
t
ExomP/e
stem
HycRoLoax comMIR 5.0
32?qORES
p RQ50 = Z ARE A ?5CF• S.
RI7

j
O ?
O ?

ti%o?
0 4
O ••
20, 0,00
C?
01 000
o
7100
3,000
21000
/1000
300
200
/00
d
50

vl
3
4 ?
3
2 ?
W
500 Q
q00
300
200
50
inn Q
7.3
Z.500?
3 /O 2305
Q
20
5 t5
FRCTORS
10
3 0.5 ORMFQx 0.39
6710 it it M 0." 2
Q 25 a r 90-76
Q no j, 1.21 3
2
?•5
RUNOFF FROW RURRL RRER5 0 V 50 59 /AIL F5.
NORTH CRROL.I/Yq ? AG/ H NW COAMUS5I0H
.!A ? Eo a. 2
0
J

is

bk
011,
EXRMPL E
6 1 VEN s
HYDROL061C COMOUR 5.0
DRAINAGE ARER 35 AC.
5MRLL AREA FULL BUNME55
MOWER
Q 10= 39 x 14 jr 54.(o GF5
8
U ?
v
p 3 `
QC
15
0.5
QW QW
o?c Q Q? uja
v -JQQ ?m
FO yEDEVEW /V7
FRCTORS FOR FREQUENCIE5
Q/00 n V
G.Q 5 CURVE AGUE X 1.775
295 n x 1.35
50 ? a X i:lw

0
cr
/000
6 00
4,00
200
/00
50
20
/0
O
RUNOFF FROM UR 8RN RREA5
HIGH
WRY COMM155ION
NORTX CAROLINA 5XF
JAN,6200.3
',000

EXAMPLE
GIVEN l/Yf1GE AREA 32 ACRES RURAL
R RE POM0 GW RT loaf ?0 2 yGA?
T4
0
2.5
12
U--?
Q
0
/000-
.600
,tio

2.0
? o?
Z
0.8
' o
o•4 v
J. DQ?
Os(/
06 W
0.4
Q
0.2
0.1
•
DRAINAGE AREA 5HRPE PAS ETER
CORRECTION FRCTO
NORTH GRROLINq 5T m HxHWRY COMM155ION
?1RNI 1975
C 200.4
t
is
t

EXCRPl e
C71 YEN:
HYDROLOGIC CONTOUR 50
DRAINAGE RRER 35 AC
% 1"ORE5T 70 90
RN51YER FROM CHRRT 050 = 25CF.5
cmECTEO aw 25xO-&- 21.0 GF.5
X05 80
70
X00
/ 50
.? 40
i O'g ° .9o
1.0
o Q?e? ? 1.2 0
v / k io 41
v o
? 5 1.35 v
0 3 v 5S5
25 a
1.4
1.42
DRAINRGf LORD COVER &RA)LErER
N

NORTH CAROLINA 5ME HIGHWAY CONW1551OAt
JAN 197.4
0200.E

•
•
0
4
E
4
EXRMPL E
61 VEN =
HYDROLOGIC CONTOUR 5.0
MA LN AREA FU L 00IME-55
RN5WER
010= 39 x 14 = 54.6 Gf 5.
8
v ?
v
4
0 3
0
`iAo --
w
FoR yEDE??P?MN
FRCTORS FOR FREQC
(aQ 0 CURVE YYRL 41E x
825 u x
50 it
it
u X
Qloo It a x
IENGIES
• 7p5
1.35
?&
0
Or
/000
600
4.40
200
100
50 N
-40 w
.30
Q
-20
Q
Q
:10
5
RUNOFF FROM UR BAN RRER5
000
/,1000
800
.600
0 ftft Iftft *,-*a
to
o v
ctz
O
6
NORTX CRROUNR 5777TE H16HNRY C041MI55ION
JRN, l973 C 200.3
EXRMPLE
GIVEN
DWN96E RRER 32 RCRE5 RURAL
R5WER POiWCH#Rr /00.2 a50= 25 CORRECTE50 = 25 X /.3 = 3g C?0.
q)
o?c
Q
W
D
9
1000
500
_ v
Y
T4
0
2.5
,2
2.0
.As
/O Z
0.8
' o
o.4 v
0.8
04
W
o.4 Q
a
0.2
DMI1176E RRER 5HRPE PARAMETER
CORRECTION FACTORS
NORTH CRROL I NR 5TRTE H16HWRY COMM15510N
URN, 1973
C 200.4
,0-1,--7
ExarnPle
G I YEN :
HYDROLOGIC COMMUR 50
DRAINAGE flRS? 35 AC
% AORE5T 70 9'0
ANSWER FROM CWT 4250 = 25CF.5
CORRECTED GtM 25x0.34 = 21.0 CF. S

0
°v
?o
v
0
0 4
0 3
/

.0-65 80
70
goo
-O.? 50
;o. 40
-0•Q ° ?o
-1.0

v

.4
x.42
DRAINRGE ??RRE TOON fR? RyTER
NORTH CAROLINA 5ME H16HNRY W MAU55ION
.JAY 197.E

IE
0 200.3
•
•
•
n lr
20 EVILWINTOM

W 8
? (o

8
06
0.4

0.2

O/

3
/0 1.520 3 40 0 2 3

4
5 68 /012 1412
MINUTES HOURS
DURRr10/Y
20 HRrTERR5
!3

8

4 ?

0.8
O. (o

0.4
I A-
V
V
Q 0.2

?5 /O AF 20 3040 0 2 3 54O 8/0/2 18 24
XINUrES D(IRRrION HOURS
RRINF, IL C INtEN5I T Y DURRTION CURVES
NORTH GXWRY
X1
GRROL INR 5 SAN GOMMI5510N
?
, I
0200 7
•
is
10
•
•
^or. 6 ?.wx} A
r?
%-20
B
(o
4
2 0.6
O•
0.4
?v
n
DL
C
?OI
r'REE'NS BORO

t

i
1

5 10 /5 20 30 40 0 2 3 5 to B /0 12 /5 24
MINUTES KOUR5
DURATION
Cie ,
%l
W
4
2
aE
Ull 0•%
0
RE 0.;
?o
RRL F1611
I I Rf11NFRLL INTENSITY DURflTION CURVES
NORTH Cf1ROLINf! 57 R?E, IH? Hn'Ay GOMMI55
CZoag
.1
lWlf *" ` G DURRUON

j 20
Itz, /5
8 '
N ?
4
G
'bF
2 ???f o
t j f ?9'QS
W 0.6
2 0.(0 NJ l9zsz??
? OQ
Q
0.2
Q
o.! 5 io /5 20 30 40 (oo B ro a ! 24
MINUrE9 HGiURS
DURATION
cHRxorrF
j 20
!5
W 10
v 4
? 'moo
?. 2 COs `c'9.ps
0.8
X06
04
0.2
!5 20 50 40 00 2 3 .5 /8 V
MINUTE-9 DURRTION
RRINFRLL JNTFN5IT Y DURATION CURVES
NORTH CRROLjStq ST RTE 1 r gW RY COMMISSION
L'oc'o.
•

• Section III - Hydraulics
300-General
300.01 After the discharge of the project design frequency has
been determined, it then is necessary to determine by
hydraulic principles the structure required to adequately
pass the discharge within controls established for the
site.
300.02 The site controls will consist of limits of headwater
velocities, tailwater, scour, and other hydraulic con-
siderations, as well as structural requirements.
300.03 Methods of hydraulic design used by the department are
generally standard for highway hydraulic design. It
is expected that users of this handbook will be familiar
with basic hydraulic principles, or will have references
adequately covering the subject. References mentioned
in the handbook are available (for loan) from the Hydro-
graphic Engineer's office.
300.04 Slide rule accuracy is sufficient for all hydraulic
computations.
300.05 Calculations should be neatly made and become part of
• project file.
•
41
301-General Criteria •
301.01 Hydraulic design for roadway ditches:
1. Design frequency - see Table T300-1-
2. Design Q - Computations
S.H.C. or Rational Method (see Charts C400.1 and
0400.2)
3. Hydraulic design - Manning's Formula
4. Allowable velocities
UP to 4 fps on grassed linings - dependent on soil.
Pave to contain 5-year discharIge for over 4 fps.
5. Minimum grade desirable - 0.3%. bed determined
6. Type of ditch inlet d?d to
by State Design Engineer.
301.02 Hydraulic Design for Median Ditches:
1. Design frequency - see Table T300-1-
2. Design Q - Charts Nos. C400.3 and 0400.49 or
Rational Method.
3. Hyaraulic design, Manning's Formula
4. Allowable velocities - some as roadway ditches
5. Minimum grade desirable - 0.3%•
b. Maximum depth of flow - 0' below
on sclosed houlder
point.
system).
7. Maximum inlet spacing 800;'(350'
'01.03 Hydraulic Design for Roadway Culverts: •
?
1. Design frequency - see Table No. T300.1.
2. Design Q - S.H. C. or Rational Method. Circular
3. Hydraulic Design - Hydraulic Engineering
Nc, 5•
below
. Headwater - Generally HW/D of 1.2 or 1.5 ft. termination
shoulder point. whichever is lower. will not be
should be made that resultant ponding
detrimental to adjacent property.
5. Outlet velocities in excess of 10 fps. wC l require al speci
erosion control at the outlet. in many outlet structures (stilling basins) will bebrequired.
dered.
When velocities exceed 15 fps.,
301.04 Hydraulic Design for Curbed Pavement:
_1, Design frequency - Table T300.1 for gutters.
2. Design discharge - S.H.C. or Rational Method.
3. Hydraulic design - see Charts C400.7 and C400
4. Maximum depth of flow 0.5' at curb of 6' spread into
thru traffic lane.
•
42
• 301.04 Curbed pavement: (continued)
5. Inlet - use N. C. standard 840.1 with type "All
grate on high traffic facility-and type "D" on
residential streets. The standard 840.06 is
used only for special conditions where large
quantities of flow at high velocities are re-
quired to be intercepted.
301.05 Hydraulic Design for Storm Sewers:
1. Design frequencies - see Table T300.1.
2. Design Q - S.H.C. or Rational Method.
3. Hydraulic design - Hydraulic Engineering Curcular
No. 5. HW/D should not exceed 0.5' below grate
elevation. Where more accuracy in critical design
areas are required, the method in Pressure Changes
at Storm Drain Junctions" may be employed.
4. Design cal9ulations should be recorded on tabular
form for review and future reference. See 0400.9
in design aides section for example.
5. Pipe profiles shall be developed and all known
underground utilities shown thereon. Conflicts
should be kept at a minimum, but where unavoidable,
proper provision shall be made, such as special
• junction boxes or manholes.
6. When pipe sizes change through a box or manhole,
the crown of the pipes shall be aligned vertically
where available fall permits.
•
43
• 0
$ W
(d C
C
a
C
v
$ 4.2
m
4.3 ba v A
9 4.3
$4 94
•112 C
H 04 as X U U
Bridge 50# 50# 50 25 50 25
Box Culvert 50# 50* 50 25 50 25
Pipe Culvert 50 50 50 25 25 25
Roadway Ditch 5 5 5 3 5 3
Median Drainage System 10 10 10 - - -
Storm Drain 10 10 10 - 10 10
Sump Drain 50# 50# 25 25 25 25
• Gutter 5 5 5 3 5 3
Effect of 100-year flood to be checked and adjustments to
design flood made where deemed necessary.
TABLE OF PROJECT HYDRAULIC
DESIGN FREQUENCIES
T-300.1
C
45
302-Open Channels
302.01 In open channel flow where Manning's Formula is us
values from "Design of Roadside Drainage Channels"
for artificial channels. In natural channels, the
values and above, have proven more satisfactory in
work.
ed "n"
are used
higher
S.H.C.
302.02 When channel gradients and other factors require, special
linings are provided to control erosion. These usually con-
sist of asphalt or concrete paving for the smaller channels
and rip rap for the larger. The paving of small channels
should provide protection for discharges up to about the
10-year frequency; discharge above this will be of short
duration and the normal vegetation will protect the channel
above the paving for these infrequent occurrences. On
larger channels where protection is required, it is usual
practice to provide the protection for the estimated dis-
charge of the frequency for which other structures on the
project are designed.
302.03 Where necessary to realign natural channels, the alignment
should be as smooth as other factors will permit. The grade
should conform as closely as possible to the natural gradient.
Minimum disturbance to the natural flow is always the aim of
good hydraulic design, except, of course, in those cases where •
natural flow is detrimental and requires some type of control.
In usual cases, this control may be incorporated in highway
drainage design.
302.0!} It is becoming more widespread practice to bring water down
out slopes into the highway drainage system. This is necessi-
tated by higher design standards which require the grade of
the roadway to often be at a lower elevation than the natural
drain which it crosses. There are certain criteria which
should be carefully adhered to in the design of these channels,
which are in reality chutes involving velocities much greater
the critical. These are:
1. Alignment should be straight and normal to the
slope of the cut.
2. The sides of the channel should be parallel through-
out the section in which flow is supercritical. It
is permissible to provide transitions in cross-
section for more economical design at subcritical
sections - at the beginning of or beyond the steep
section.
3. The bottom should be level in the direction perpen-
dicular to the longitudinal axis.
If any or all of the above are omitted, standing waves may
develop causing overflow and thus failure of the design. •
46
r " ,
302.05 It is desirable that chutes discharge into a cross pipe
or catch basin when possible. In cases where this is
not economically feasible, paving of a section of the
roadway ditch or other methods of dissipating the energy
of flow must be provided. For a more detailed discus-
sion of the design of roadside channels, refer to FHWA
Hydraulic Design Series No- 4, and Design Charts for
Open Channel Flow.

•
47
303-Pipe & Box culverts •
303.01 In general, the location of pipe and box culverts is selected
to provide minimum disturbance to natural flow. Seldom does
a 90° structure conform to this. The structure should be
skewed to align with the flow within good judgment. The skew
ckwise lto measured from
is deead as
project ct Beh ah , clo
303.02 The elevation and gradient of the culvert should conform to
that of the natural channel as nearly as practicable, except
where the culvert may be used as a grade control structure.
Usual practice is ° rplace adienthtof 0.3' to 0.51
existinglow
the natural 6
irregularities.
303.03 Hydraulic design for pipe and box culverts is as presented
in Hydraulic Engineering Circular No. 5. The space for
reuired culverts and maytbenshown as required survey in reports o notes
for pipe culverts.
U
•
48
304-Bridges
• - 304.01 The method of hydraulic design for bridges,
reduced to simplest terms, is to provide the waterway
• below the design high water elevation to pass the de-
sign discharge with allowable velocities and backwater.
To accomplish this, the profile of the proposed center-
plain is plotted to suitable horizontal and vertical
scale. The high water elevation is plotted. This is
usually obtained from the field survey by obtaining
elevations of marks or points of maximum high water
pointed out by local residents or others familiar with
the site. If reliable on-site information is not avail-
able, an estimate of the high water elevation is made
either by transferring high water information from other
sites, such as gage sites or other structure sites, or
by applying Manning's formula and the design discharge.
304.02 With this information, an estimate of the expected ve-
locities in the channel and overflow sections under the
bridge is made. With these velocities, and estimates
of the average depth of flow, the area required and thus
the length of structure to provide this area is computed.
The velocities chosen in this procedure must necessarily
be based on good judgment, and for this, there is no sub-
stitute for experience. Estimates can be made with
Mannings and by methods in FHWA Hydraulics of Bridge
Waterways. A "rule of thumb" that may be used for pre-
liminary estimates is to use the hydrologic contour
number plus 2 for the channel section and multiply by
0.5 for the overflow section to obtain velocities in
feet per second.
304.03 On major river crossings where multiple openings are
required, the above general method for computing total
waterway may be used. The several openings are provided
at those locations determined by a study of flood plain,
proportioned to provide this total amount of opening.
The method recommended to determine the proportion of
waterway to be provided by each of the structures in
multiple openings to achieve balanced design is the
"Conveyance Method" described in paragraph 309 following.
Where backwater computations are required, the method in
"Hydraulics of Bridge Waterways" is used.
304.04 The type substructure is determined by foundation infor-
mation determined in the field, and, in general, will be
piles, piers founded on piles or suitable strata, or a
combination of these. These are generally skewed in the
direction of flood flows. Span lengths are selected so
that piers and bents will provide minimum flow disturb-
ance and drift traps as is consistent to good design
and construction principles.
•
49
304.05 Crossings of estuaries present special design problems and
their design should be referred to the Hydrographic Engineer
and will not be discussed here.
30446 There are many various special structures infrequently en-
countered in highway drainage design. These include spillways
of different types, special channel sections and transitions,
stilling basins, ocean out-falls, and other special problems
outside the scope of this manual and these should be referred
directly to the Hydrographic Engineer.

r -I
L_J
•
•
50
305-Improved Box Culvert Entrances
• 305.01 In the design of box culverts, where site conditions allow
and economy warrants, special inlet design will be used.
305.02 Select size of culvert using design procedure in Hydraulic
Engineering Circular No. 5 within site limitations.
305.03 Determine whether in inlet or outlet control. If in outlet
control, use size selected in Step I. If in inlet control,
determine difference in inlet control highwater (HW ) and
outlet control highway (HWoc). If the difference ii c10%
or more, investigate improved inlet; if less than 10%, use
size selected in Step I.
Example: Design Q = 650 cfs
So= .031 ft/ft
L=420 ft
AHW = 101
TW = low
Try 81 x 81 box culvert
• HWic/D = 1.2; HWic = 1.2 x 8 = 9.6
HWOc = H + ho - LSO = 3.4 + 6.9 - 13 = -2.7
HWic HWOc - Culvert in inlet control
HWic HWoc by more than 10% - proceed to Step III.
305.04 Tapered Inlet Design
1. Select a cross-section 0.8± of that chosen in Step I.
Example: 0.8 x 64 = 51.2; try 81 x 61.
2. From Table T300.2, determine BD3/2 and from Chart
C300.1 determine HW/D1 Compute H.W. (Inlet Control).
Example: BD3/2 = 117.6; Q/BD3/2 = 650/117.6 = 5.52
HW/D = 1.461 HW = 1.46 x 6 = 8.7 = HWic
HWic AWH
If HWic is greater than AWH, select larger
• barrell size
51
? .04 (continued) •
3. Determine outlet control HW for trial size bbl.
Example: HWoc = H + ho - LSo
H + 5.8
ho = ( do + W/2 = 5.9 (if greater than D, use D)
LSO = 13.0
= 5.8 + 5.9 - 13 = -1.3
'IWO .
4. If HWic control is about equal to HWoc (within 15%),
use tapered inlet; go to 305.6. If HWic is 15%+ more
than HWoc, investigate sloped and tapered inlet.
•
•
52
• 305.10 Design of sloped and tapered inlet.
1. Select a cross-section of 0.6± cf that chosen in Step I.
Example: 0.6 x 64 = 38.4; try 7' x 61.
2. From Table T300.2, determine BD3/2, and from Chart
C300.2 determine HtD; compute Ht (Headwater at throat)
Example: BD3/2 = 102.9; Q/BD3/2 = 650/102.9 = 6.3
HtD ='1.68' Ht = 10.1
3. Determine the inlet drop and barrel slope; drag =
Ht - AHW
Example: drop = 10.1 - 10 = 0.1
(for practical reasons, do not use drop
less than 1 foot)
Sb = barrel slope = (LSO - drop) L -
(3 x drop)
• Example: Sb = (420' x .031) - 1 j 420" - (3 x 1)
Sb = 12' / 417 = .027
4. Compare HWic & HWoc
HWOC = H+ho - LB Sb = 8.4 + 6 - 11.3 = 3.1
If HWOC is about equal to AHW, use size selected.
If more than 159 less, try further reduction in barrel.
Example: HWOC is more than 15% less than AHW; try
further reduction.
305.11 Repeat for smaller bbl.
1. Try 6' x 6'
2. BD3/2 = 88.18; Q/ BD3/2 = 650/88.18 = 7.4
Ht/D = 1.95; Ht = 11.7
3. Drop = 11.7 - 10.0 = 1.7; for practical reasons
• use 2'
53
02.11 ?Contlnued)
Sb = (1, - 2) 1 (420 - 6) = 11/414 = .0265
4. KWo`=12 r6-11=7'
HWoc for 6' x 6' is still ± 30% less than AHW
Try further reduction.
,)5.12 Repeat for smaller bbl.
1. Try 6' x 5'
2. BD312 = 67.08' Q/BD3/2 = 650/67.08 = 9.7
Ht/D = 2.68; Ht = 13.4'
3. Drop = 13.4 - 10.0 = 3.4
Sb = 113 - 3.4) ./. 420- (3 x 3.4) = 9.6/409.8
= .0235
4. Hwoc = 17 * 5.0 - 9.6 = 12.4'
HWov for 6' x 5' is greater than AHW. The •
theoretical size would be between the 6' x 5'
and 6' x 6'; therefore use the 6' x 6'.
05 is ate rm; ne Taper Dimensions.
1. If tapered inlet is used, dimension as shown on
Chart C300.2 with 6:1 side tapers.
if sloped and tapered inlet is used, enter Chart
C300-4 with HW/ D & Q/BD3 /2 to determine minimum
width W.
Example: From 305.52 for the 6' x 6' barrel
SHW/D = 10/o = 1.67 & Q/BD3/2 = 7.4
from Chart, W = 1.4 tB (by interpolation)
W=1.4x0=8.4'minimum
•
54
•
3 05.13 (Continued)
In the exarwie,
actua? ly w = 9' 6" due to lniet
geometry rather than hydraulics.
Example: (3 x drop) + (3/4 x 6) = 6 4.5' =*10.5'
10.5 4 6 = 1.75'
W = b + (2 x 1.75) = 9.5'

•
55
•
•
I
r
i
B x D
5x14+
6 x 4
8x4
5x5
6x5
7x5
8x5
9 x 5
10 x 5
4 x 6
5x6
6x6
7 x 6
8 x 6
? x 6
10 x 6
12 x 6
b x 7
7x7
b x 7
9 x 7
10x.7
1e- x7
VALUES OF BD3/2
BD3/2 B_x D
32.00 6 x 8
40.00
48.00 8 x 8
o 8
64.00 t x
12 x 8

55,90 8 x 9
67.08 9 x 9
78.26 10 x 9
89.44 12 x 9
100.6
111.8
58.80
73.5o
88.18
102.9
117.6
132.3
147.0
176.4
92.60
111.1
129.6
148.2
166.7
185.2
222.2
7 x 10
8 x 10
9 x 10
10 x 10
12 x 10
10 x 12
12 x 12
BD3 /2
135.8
158.4
181.0
203.7
226.3
271.6
189.0
216.0
243.0
270.0
324.0
221.3
253.0
284.6
316.2
379.4
415.7
498.8
T300.2
•
57
•
/./,BEVEL
4
?$ D
`` ,
51ope of BarFel
z
3
2
boa ELEVA T70N
00 to
m 4-
v
i to ?o
Toper Length
PLAN
-THROAT CONTROL
--FRCS CONTROL
•
0 x
0
2 4 to 8 i0 tZ
TAPERED INLET : THROAT AND FACE CONTROL
01BD 3/2
G 300.1
s

i'4
3
2
Ht?O

0
0 1
0 2 4 & a /v
SLOPED AND MPERED MET: THROAT CONTROL
Q/80 9/2
G W.2
12
61
4
C?

0
2
0
•
1
0
•

D 2 4 & a ,V .Z
5LOPED AND TAPERED INLET: FADE GONTROt
Q 16D 9/2
G 300.4
4;
-06 HYDRAULIC DESIGN OF TAPERED PIPE SECTIONS
j!,,,.Ol The design of tapered pipe section should be considered
when the following conditions are satisfied:
1. Pipe operates in inlet control.
2. The inlet pipe required is 36" or larger.
3. The installation requires a long pipe.
4- The slope of the pipe will be greater than 2.0%
for concrete and 3.0% for corrugated metal pipes.
5. If elongation is required, place notation in
recommendation that section is to be shop
elongated and wired to 5% elongation, wire to
be removed after installed and back filled.
306.02 The length "L" required from the inlet to the end of
the taper must be long enough for the slope of the pipe
"S" to overcome the entrance head loss, the constriction
of flow area loss and the shape of flow area loss. The
lengths required respectively for these losses are Le,
L and Ls. Since these losses will occur more or less
simultaneously, the dimensions for the inlet pipe length
and taper length must be arrived at by gomewhat empirical
means after the total length required has been determined.
The incremental lengths are determined by the following
equations:
+ g
(1) Le = (Ke x Hal) : CS - (S f
• (2) Le = (He2 - He 1) Is - ( Sf l + Sf 2,
(3) Ls = C . 06 x (Hvl + Hv2, -- CS - (SF'1 + SF'2-1
L.=Le +Lc?Lz,
r ---
D
I y? .
L_ I
?Q ? i DZ
(DA--02) x 21-- Whims
2
•
65
306.03 INSTRUCTIONS FOR DESIGN - Given design Q in cfs, slope
of pipe S and total length:
1. Determine size of inlet pipe with Q and
allowable headwater from inlet control chart.
2. Determine size of outlet pipe which will carry
design Q on the available given slope, by using
chart "Friction Slopes For Full Flow in Circular
pipes." Using the slope as friction slope and
the design Q. determine size from chart and add
6". Use this size for D2. -If difference between
Dl and % is less than do not design tapered
section. (Caution: When using the chart, be
certain to apply correct "Nn value to slope.)
3. Determine the velocities for full flow in the
two sizes to be used.
V1 = Q/Al ; V2 = Q/V2
j}. Determine velocity heads and energy heads for
the two sizes selected.
Hvl = Vi/2 9 ; HEl = Erl + Dl
$v2 = V22129 ; HE2 = v2 + D2
5. Determine friction slope for full flow (Sf) for
two sizes selected (From chart "Friction Slope
for Full Flow in Circular Pipes"; be sure to
apply correct "n" value for pipe being used.)
6. Determine 'L' to end of taper by equation
Hvl + Hv2l
L = (Ke x Hvl) + (HF - HEl) + (0.06 x
S - ( SF1 + SF2 )
2
7. Use standard taper length plus a length of D to
equal L if L is greater than length of stand rd
taper.
•
•
•
66

306 . C4 Example - Q = 200cf s ; S = .07'/ft.
1 - From inlet control chart Dl = 72"
• 2 - Using CM, n = .024; (n1013)2 = (.024/013)2 = 3.4
3 _ V1 = 200/28 = 7.21/n; V2 = 200/16 = 12.5'/n
ZZ2
4 - Hvl =7'72g = .81'; Ni = .81 + 6 = 6.81'
Ev2 = 12.52/2g = 2.4; IIE2 = 2.4 + 4.5 = 6.90'
5 - From chart
SP-1 = .0022 x correction for n = .024 (3.4) = .0075
SF2 = .0097 x correction for n = .024 (3.4) = •0330
6 L = (0.4 x .81) + (6.90-6.81) + (o.o6 x 1.6)
.U7 - .02
0325 + 0.09 + 0.096 = 611 = 10.3'
0 .05
7 - Length of std. taper to D2 = '2 + l 8/3 x 2?2=16
L = 10.3; therefore use std. taper, and 54" through
• remaining required total length required.
•
67
J
O
O?
1•
W?
0 0; ti lc?
RATIO OF DEPW 7V R15E D
v
j
O- U
v1
V
41 Q
W
?t O
v
? O
O ?
Q ?Q; aD
Mick
GIRcuLAR PIPE
PRRT FULL FLOW
.0001
•
•
•
Examp /e *cot
iooa q : /SO e..Cs
q°O Do 60 of
800
"s .021
rep Sa .003348 x .0003
Goo
Soo .0004
440 ,ooot
oG
3OO .000
UAA- 9G? ? .00048
? 90` N l ,.oov9
oo/
200
GG" 11. .oo/f
Q
l1 Bo 3 " ?? \ 0025
v 70 46 ?? 003
0
O so .?, .0 .ooh
4c03„ v oos
27" .007
Dos
J-24 'w 009
A/
zo
1s is for r! = o. 0/3 .ors
f'or o?hA' ?d/?/P.s off// z
of
.o?
AS
/ .04
ire C'ircv/ar f?ioes
I tIO107 / CAQOL/Na 57,grG 1114611,WAY COMM/5S?ON ?' 30Q, S
y

30Y 146'111) OV ArrUMMATU16f; t•:r•ci•.r;c ui:,'rutt??c:?, WN i,J:•':iit !r?•i:
307.01 I11FLOW
1. Determine Qp (Peal, T.scharge of F'r^nuonc ;- Je::,. )
2. Es timate Tc (Time L* Cori cer.trP ?. Lori ) •
3 Calculate Tp (Time to Peak) '= '!'?:??'•?? 'Pc i?:r •)
l?. Calculate T (Total Time) = :I- JK
5. Calculate Qa (Average Discharge) = 0.5 Qp
6. Calculate Qt (Total Runoff =(w;•?iZ) x T (Ac r--? C `. )
7. Roughly Ch?ck Qt by equation Qt = I X C x AX ,,/12
- I = Intensit y in inches per hr. for design frequenc
& Te
C = Coeffici ent - relation of rainfall c.,zcess :o
rainfall

307.02 oUMow
1. Determine Qs (Total Available Storage - Acre i ee t)
2. Calculate Qn (Net Runoff) = Qt - Qs
3. Calculate Qao (average outflow) = Qn. X 12/T = cfn
Calculate Qpo (Peak-outflow) = 2 x Qao
5. Dpaign anill-wey for npo wit' relulired freeboard
Design pipe with available head at peak Qs
6. If outlet structure already exists, check storage
consumed with Qpo. If more than 104 error with
Qs in Step 1 outflow, adjust and recompute Qao.
*If Tc is greater than 6 1=s., do not compute wit.:
thi3 met hcd.
307.03 EXAMPLE I7ITIBER 1
It is desirable to incorporate an impouncLment with a
highway fill in Rural Wake Count7. The drainaE-- nrea i:,
540 acres. What size spillway is required for th3 50
pear flood and 21 freeboard with 3' of storage o t er an
average of 1.6 acres?
INFLOW
1. Qp = 340 cf s
2. Tc = .3 hrs.
3. Tp = .3 hrs. + .18 hrs. _
4. T = 3. x .48 = 1.44 hrs.
5. na = .33 x 340 = 112 ef3
6. Qt = 112112 x 1.44 = 1--3.5
7. qt = 5.4 x .20 x 540 7. .3
,
.48 h .
Acre Feet
3 .3 = 14.58
go
•
70
307 A3 OUTFLOW (continued)
1. Qs = 3 x 1.6 = 4.8 AF
• 2. Qn = 13.5 - 4.8 = 8.7 AF
3. Qao= 8.7 x 12/1.44 = 73 cfs
4. Qpo=2x73=146
5. 146 =3.33 L 33/2 = 3.33 x 3.33 x 5.2L = 17L
8.6 = L
Use 9
307,04 EXAMPLE NUMBER 2
Three tenths AF is available in wide median. It is
desirable to keep outflow at a minimum. With 25 cfs
inflow, what size pipe will be required for outlet?
INFLOW
QP
TA
TP
T
Qa
Qt
• Qt
25 cfs = 25 yr.
0.16
0.16 + 6 x .16 = 0.21
.21 x 3 = .61
25 x .33 = 8.3
8.3:12x.61=.42
(Assume A= 7 C= .6). 6.7 x .6 x 7 x .16 12
.37
OUTFLOW
Qs = .3
Qn = .42- .3=.12
Qao = .12 x 12/.61 = 2.36
Qpo = 2 x 2.36 = 472
Use 18" pipe
307-05 EXAMPLE NUMBER 3
A wide median or interchange quadrant provides an acre
where temporary storage is available. Below discharge outlet
is an existing city street with a 36" pipe which cannot be
headed more than 21 without causing basement to flood.
Therefore, maximum capacity for the pipe is 58 cfs. There
is approximately one acre below highway, so it will be
desirable to release no-more than 54 cfa. The discharge
from the area above the highway is 55 cfa and the highway
drainage system will contribute 22 cfs for a total inflow
of 77 cfs. How much storage must be made available?
•
71
307.05 EXAMPLE NUMBER 3 (continued)
INFLOW
i
Qp = 77 cfs
Tc = .16 hrs.
Tp = .16 + .6 x .16 = .21 hrs.
T = 3 x .21 = .63 hrs.
Qa = .5 x 77 = 38.5
Qt = 38.5/12 x .61 = 1.956
OUTFLOW
Qpo = 54 cf s
2 = 27
17o _ =Qpx12/T; Qn=27xT/12 = 1.417
Os = Qt - Qn = 1.956 - 1.417 = 539
42" under upper lane
42 r' under lower lane
Provide .54 A/ft storage
C7
% •
72
308.01 Rip Rap is frequently required for scour protection in
channels. At present, the NCSHC specifications include
only two (2) classes of rip rap. It has been found that
• these satisfy most needs.
308.02 As a rule of thumb, for channels with base widths less
than 20' and velocities less than 15 fps, Class I rip
rap is used. Generally, only the banks require pro-
tection, and the rip rap is carried 2' below stream
bed, with 2' toe wall on beginning end.
308.03 On streams more than 20' base width, Class II rip
rap is used if velocities do not exceed 15 fps,
The rip rap is carried 3' below stream bed and the
toe wall as above carried V into the bank.
308.04 Where rip rap is required outside the above criteria,
the method in Hydraulic Engineering Circular No.
11 is used.
308.05 Where rip rap is required in lakes for prevention
of wave erosion, Class 112" thick with a filter
blanket is used. As an alternate,quarry run stone
may be substituted. The thickness required is 3
feet with the following approximate gradation with
• no filter blanket:
20-50 lbs. 609
10-20 lbs. 30%
less than 10 lbs. 10%
308.06 Where a filter blanket is needed, it will be No.
1 stone 6" thick, or an approved filter cloth may
be used.
308.07 The required height above normal water surface for
wave run up is determined from chart No. C400.9
with a minimum of 21.
308.08 On lakes with fluctuating water levels, embankment
protection is required between elevations 2' above
the 25 year pool and 2' below maximum drawdown.
•
73
309 -Instructions for design of multiple bridge openings.
309.01 Determine design Q & H.W. elevation.
309.02 Plot natural strewn cross section to suitable scale,
including complete flood plain.
309.03 After careful study of site, aerial photos and other
information, divide into sections of equal 'n' values
and steady discharge.
309.04 Compute "K' for each section. K= A x 1.486/n x r2/3
309.05 Plot conveyance mass curve.
308.06 Determine flow divides approximately; these will be
at flattest part of curve, between two steeper sections.
309.07 Determine points of high natural flow. These will be
where curve is steepest.
309.08 Determine locations for openings. In general at flood
channels or secondary thalwegs in the flood plain. These
should coinside with points of high natural flow determined
in 309.07.
309.09 From location of flow divides determine 'K' for each
opening and with proportion of individual 'K's' to
total 'K' determine Q for each bridge opening.
309.10 Determine bridge length from H.W. elevation and
velocities. Estimates of velocities through the
openings may be determined by allowable backwater
or by rule outlined in paragraph 304.02.
•
•
•
74
•
AREA, WETTED PERIMETER AND HYDRAULIC RADIUS OF
PARTIALLY FILLED CIRCULAR PIPES
d area wet.per hyd.rad. d area wet.per hyd.rad.
D D' 0 D D D' D D
0.01 0.0013 0.2003 0.0066 0.26 0.1623 1.0701 0.1516
0.02 0.0037 0.2838 0.0132 0.27 0.1711 1.0928 0.1566
0.03 0.0069 0.3482 0.0197 0.28 0.1800 1.1152 0.1614
0.01 0.0105 0.4027 0.0262 0.29 0.1890 1.1373 0.1662
0.05 0.0147 0.4510 0.0326 0.30 0.1982 1.1593 0.1709
0.00 0.0192 0.4949 0.0389 0.31 0.2074 1.1810 0.1755
0.07 0.0242 0.5355 0.0451 0.32 0.2167 1.2025 0.1801
0.08 0.0294 0.5735 0.0513 0.33 0.2260 1.2239 0.1848
0.09 0.0350 0.6094 0.0574 0.34 0.2355 1.2451 0.1891
0.10 0.0409 0.6435 0.0635 0.35 0.2450 1.2661 0.1935

0.11- 0.0470 0.6761 0.0695 0.36 0.2546 1.2870 0.1978
0.12 0.0534 0.7075 0.0754 0.37 0.2642 1.3078 0.2020
0.13 0.0600 0.7377 0.0813 0.38 0.2739 1.3284 0.2-061
0.14 0.0688 0.7670 0.0871 0.39 0.2836 1.3490 0.2102
0.15 0.0739 0.7954 0.0929 0.40 0.2934 1.3694 0.2142
0,16 0.0811 0.8230 0.0986 0.41 0.3032 1.3898 0.2181
0.17 0.0885 0.8500 0.1042 0.42 0.3130 1.4101 0.2220
3.18 0.0961 0.8763 0.1097 0.43 0.3229 1.4303 0.2257
0.19 0.1039 0.9020 0.1152 0.44 0.3328 1.4505 0.2294
0.20 0.1118 0.9273 0.1206 0.45 0.3428 1.4706 0.2331
0.21 0.1199 0.9521 0.1259 0.46 0.3527 1.4907 0.2366
0.22 0.1281 0.9764 0.1312 0.47 0.3627 1.5108 0.2400
0.23 0.1365 1.0003 0.1364 ON 0.3727 1.5308 0.2434
0.24 0.11}49 1.0239 0.1416 0.49 0.3827 1.5508 0.2467
0.25 0.1535 1.0472 0.1466 0.50 0.3927 1.5708 0.2500
•
75
•
AREA, WETTED PERIMETER AND HYDRAULIC RADIUS OF
PARTIALLY FILLED CIRCULAR PIPES
(Continued)
d area wet.per. hyd.rad. d area wet.per. hyd.rad.
D D' D D D D' D D
0.51 0.4027 1.5908 0.2531 0.76 0.6404 2.1176 0.3025
0.52 0.4127 1.6108 0.2561 0.77 0.6489 2.1412 0.3032
0.53 0.!}227 1.6308 0.2591 0.78 0.6573 2.1652 ,0.3037
0.54 0.4327 1.6509 0.2620 0.79 0.6655 2.1895 0.3040
0.55 0.4426 1.6710 0.2649 0.80 0.6736 2.2143 0.3042
0.56 0.4526 1.6911 0.2676 0.81 0.6815 2.2395 0.3044
0.57 0.4625 1.7113 0.2703 0.82 0.6893 2.2653 0.3043
o.58 0.4723 1.7315 0.2728 0.83 0.6969 2.2916 0.3041
0.59 0.4822 1.7518 0.2753 0.84 0.7043 2.3186 0.3038
0.60 0.4920 1.7722 0.2776 0.85 0.7115 2.3462 0.3033 •
o.61 0.5018 1.7926 0.2797 0.86 0.7186 2.3746 0.3026
0.62 0.5115 1.8132 0.2818 0.87 0.7254 2.4038 0.3017
o.63 0.5212 1.8338 0.2930 o.88 0.7320 2.4341 0.3oo8
o.64 0.5308 1.8546 0.2860 0.89 0.7384 2.4655 0.2996
0.65 0.5404 1.8755 0.2881 0.90 0.7445 2.4981 0.2980
0.66 0.5499 1.8965 0.2899 0.91 0.7504 2.5322 0.2963
0.67 0.5594 1.9177 0.2917 0.92 0.7560 2.5681 0.2944
0.68 0.5687 1.9391 0.2935 0:93 0.7612 2.6061 0.2922
0.69 0.5780 1.9606 0.2950 0.94 0.7662 2.6467 0.2896
0.70 0.5872 1.9823 0.2962 0.95 0.7707 2.6906 0.2864
0.71 0.5964 2.0042 0.2973 0.96 0.7749 2.7389
1 0.2830
0
2787
0.72 0.6054 2.0264 0.2984 0.97 0.7785 2.793
8
8 .
0.73 0.6143 2.0488 0.2995 0.98 0.7816 2.
57 0.2735
0.74 0.6231 2.0714. 0.3006 0.99 0.7841 2.9412 0.2665
0.75 o.6318 2.0944 0.3017 1.00 0.7854 3.1416 0.2500

76
•
TWO-THIRDS R2?INFIiNN NI GS FUSEFUL ORMULA IN COMPUTING
No. .00 .01 .02 .03 .04 .05 .06 .07 .08 .09
.0 .000 .046 .074 .097 .117 .136 .153 .170 .186 .201
.1 .215 .229 .243 .256 •269 .282 .295 •307 •319 •331
.2 .342 •353 .364 .375 .386 .397 .407 .418 .428 .438
03 .448 .458 .468 .477 .487
8 .497
8 •506
6 •515
60 .525
613 •534
622
.4 •543 .552 .561 .570 •57 7
.5 .59 4
. . .
.? .630 .638 .647 .655 .663 .671 .679 .687 .695 .703
.6
.7 .711
.788 .719
.796 .727
.803 .735
.811 .743
.818 .750
.825 .758
.832 .765
0840 .773
.847 .781
.855
.8 .862 .869 .876 0883 .890 .897 .904 .911 .918 .925
.9 .932 .939 .946 .953 •940 .966 .973 .980 .987 .993
1.0 1.000 1.007 1.013 1.020 1.027 1.033 1.040 1.046 1.053 1.059
• 1.1 1.065 1.072 1.078 1.085 1.091 1.097 1.104 1.110 1.117 1.123
1.2 1.129 1.136 1.142 1.148 1.154. 1.160 1.167 1.173 1.179 1.185
1.3 1.191 1.197 1.203 1.209 1.215 1.221 1.227 1.233 1.239 1.245
1.4 1.251 1.257 1.263 1.269 1.275 1.281 1.287 1.293 1.299 1.305
1.5 1.110 1.316 1.322 1.328 1.334 1.339 1.345 1.351 1.357 1.362
1.b 1.368 1.374 1.379 1.385 1.391 1.396 1.402 1.408 1.413 1.419
1.7 1.424 1.430 1.436 1.441 1.447 1.452 1.458 1.463 1.469 1.474
1.8 1.480 1.485 1.491 1.496 1.502 1.507 1.513 1.518 1.523 1.529
1.9 1.534 1.5:9 1.545 1.550 1.556 1.561 1.566 1.571 1.577 1.582
2.0 1.587 1.593 1.598 1.603 1.608 1.613 1.619 1.624 1.629 1.634
2.1 1.639 1.645 1.650 1.655 1.660 1.665 1.671 1.676 1.681 1.686
2.2
2.3 1.691
1.742 1.697
1.747 1.702
1.752 1.707
1.757 1.712
1.762 1.717
1.767 1.722
1.772 1.727
1.777 1.732
1.782 1-737
1.78';
2.4 1.792 1.797 1.802 1.807 1.812 1.817 1.822 1.827 1.832 1.857

77
•
TWO-THIRDS POWER
R2/3 OF NUMBERS USEFUL IN
IN MANNING'S FORMULA
(Continued) COMPUTING
To. .00 001 .02 .03 .04 .05 .06 .07 .08 .09
'.5 1.842 1.847 1.852 1.857 1.862 1.867 1.871 1.876 1.881 1.86:
.6 1.891 1.896 1.900 1.905 1.910 1.915 1.920 1.925 1.929 1.934
•7 1.939 1.944 1.949 1.953 1.958 1.963 1.968 1.972 1.977 1.982
.8 1.987 1.992 1.996 2.001 2.006 2.010 2.015 2.020 2.024 2.029
.9 2.034 2.038 2.043 2.048 2.052 2.057 2.062 2.066 2.071 2.075
.0 2.080 2.085 2.089 2.094 2.099 2.103 2.108 2.112 2.117 2.11-
.1 2.126 2.131 2.135 2.140 2.144 2.149 2.153 2.158 2.163 2.167
.2 2.172 2.176 2.180 2.165 2.190 2.194 2.199 2.203
8 2.208
252 2.21-
257
2
3' 2.217 2.221 2.226 2.230 2.234 2.239 2.243 2.24 2. .
,.4 2.261 2.265 2.270 2.274 2.279 2.283 2.288 2.292 2.296 2.301

r 2.305
2
349 2.310
2
353 2.31l?
351
2 2.318
362
2 2.323
2.366 2.327
2.371 2.331
2.375 2.336
2.379 2.3 0
2.34 L.3 5
2.38
•
. . . . .
2.'92 2.397 2.401 2.405 2.409 2.414 2.418 2.422 2.427 2.11;1
.8 2.435 2.439 2.444 2.448 2.452 2.457 2.461 2.465 2.469 2.474
.9 2.478 2.482 2.486 1.490 2.495 2.499 2.503 2.507 2.511 2.516
.0 2.520 2.521} 2.528 2.532 2.537 2.5t?1 2.545 2.549 2.553 2.558
-
.1 2.562' 2.566 2.570 2.574 2.579 2.583 2.587 2.591 2.595 2.59y
.2
.3 2.603
2.644 2.607
2.648 2.611
2.653 2.616
2.657 2.620
2.661 2.624
2.665 2.628
2.669 2.632
2.673 2.636
2.677 2.6110
2.681
.4 2.685 2.689 2.693 2.698 2.702 2.706 2.710 2.714 2.728 '_.7,.C-
2.726 2.730 2.734 2.738 2.7g2 2.7 6 2.750 2.754 2.758
8 2.7r=
602
.b
.7 2.766
2.806 2.770
2.810 2.774
2.814 2.778
2.818 2.782
2.822 2.786
2.826 2.790
-2.830 2.794
2.834 2.79
2.838 2.
2.8u:
.8 2.816 2.850 2.854 2.858 2.862 2.865 2.869 2.873 2.877 2.881
_
.9 2.885 2.889 2.893 2.897 2.901 2.904 2.908 2.912 2.916 2.920
•
78
i
SQUARE ROOTS OF DECIMAL NIIr+IDERS opR DECIMAL NUMBERS
O THE &I POWER USEFUL IN COMPUTING S112 IN MANNINGS FORMULA
•
N::. --0 --1 --2 --3 --4 --5 --6 --7 --8 --9
,goo, .010 .010 ,011 .011 .012 .012 .013 .013 .013 .014
.000? oiAL .014 .015 .015 .015 .016 .016 .016 .017 .017
.oCC3 .017 .D1 .018 .018 .018 .019 .119 .019 .019 .020
.0004 .020 .020 .020 .021 .021 .021 .021 .022 .022 .022
,0005 .0221 .023 .023 .023 .023 .023 .024 .024 .024 .024
.0006 .024 .025 .025 .025 .025 .026 .026 .026 .026 .026
.0007 .026 .027 .027 .027 .027 .027 .028 .028 .028 .028
.ooo6 .0.8 .028 .029 .029 .029 .029 .029 .030 .030 .030
.'1009 .030 .030 .030 .031 .031 .031 .031 .031 .031 .031
.0010 .032 .032 .032 .032 .032 .032 .033 .033 •033 .033
0.01?1 .032 .033 .035 .036 .037 .039 .040 .041 .042 .044
.:02 .045 .046 .047 .048 .049 .050 .051 .052 .053 •054
.00; .055 .056 .057 .057 .058 .059 .060 .061 .062 .062
.304 .063 .064 .065 .066 .066 .067 .068 .069 .069 .070
a vs, .071 .071 .072 .073 .073 .074 .075 .076 .076 .077
.006 .077 .078 .079 .079 .080 .081 .081 .082 .082 .083
.v07 .084 .084 .085 .085 .086 .087 .087 .088 .088 .089
• .006 .089 .090 .091 .091 .092 .092 .093
8 .093
0
8 .094
099 •094
100
,009 .095 .095 •096 .096 .097 •097 .09 .
9 . .
.0,0 .100 .101 .101 .101 .102 .102 .103 .103 .104 .104
,O1 ,100 .105 .110 .114 .118 .123 .127 .130 .134 .138
.02 .141 .145 .148 .152 .155 .158 .161 .164 .167 .170
.03 .173 .17E .179 .182 .184 .187 .190 .192 .195 .198
,;,4 .2100 .203 .205 .207 .210 .212 .215 .217 .219 .221
.G3 .204 .226 .228 .230 .232 .235 .237 .239 .241 .243
G r, .245 .243 .249 .251 .253 0255 •257 .259
8 .261 .263
8
.:17 .205 .267 .268 .270 .272 274 .276 .27 .279 1
.2
.08 .283 .285 .286 .288 .290 :292 .293 •295 .297 .298
..)'3 .300 .302 .303 .305 .307 .3D8 .310 .311 .313 .315
-0 .316 .318 .319 .321 .323 .324 .326 .327 .329 •330
•
79
•
MAP SCALE EQUIVALENTS
Fractional
Scale Feet Per
Inch Acres Per
Sq. In. Sq. Mi.
Per. Sq. In.
600 50 0.0574
12200
400
2 100
200 0.2296
0.918
4
,
39000 250 1,43
3,600 300 2.0661
4,000 333-33 2-5508
4,800
1.
1: 6,000 500 5.7392
1: 7,200 600 8.2645
?- 8,000 666.67 10.203
8,400 700 11.249
1: 9,600 800 14.692
1: lo,000 833.33 15.942
1: 129000 1,000 22.957
1: 16,000
{ 1• 20,000 1,333.33
1,666.67 40.812
63.769
0.0996
• 24,000 2,000 91.827 0.1435
1: 25,000 2,083.33 99.639 0
15

_31,680
2,640
160.000 .
5
00
r l: 48,000 4,000 367.309 0.5739
i 62,500 5,208.33 622.744 0.9730
63,360 5,280 640 1.000
is 125.000 10,416.67 3.8922
126,720

250,000 10,560

20,833.33 154.000
.5686
,_•
?• 500,000 1,666.67 62.2744
1,000,000 13,333-33 249.0977
•
•
81
•
RATE OF FLOW CONVERSION_-CHART
Cubic
Feet
Per. Sec. U.S. Gallons
Per
Minute Acre Ft.
Per
24 Hrs. Acre Ft.
Per
Year Million
U.S. Gals.
Per 24 Hrs. Inch Depth
Per Acre `
Per 24 Hrs.
,
1 448.80 1.9835 723.98 0.646,272 23.802
.0022-3 1 0.00442 1.613 0.001,440 0.053 ;

.5042 226.224 1 365.0 0.3250829 12.0
0.001383 0.6207 0.00274 1 0.0009894
0.03292 l
1.574 694.294 3.0685 1120.0 1 36.822
0.04201 18.854 0.0833 30.414 0.027,150 1

82
WATERWAY AREA OF PIPE CULVERTS
F_ -,I
Circular C.M. Pi a Arches Str. Plate P ipe Arches
Area Size Area 18" Cor.Pl. 31" Cor.Pl.
q Size Area Size Area
l?2 0.78 61-111 41-7" 22 131-311 91-411 97
15 1.2 18"x11" 1.1 6)-4" 41-7" 24 131-6" 91-6" 102
18 1.7 22"xl3" 1.6 61-9" 41-11" 26 141-0" 91-8" 105
24 3.1 29"x18" 2.8 71-0" 51-1/1 28 141-2" 91-10" 109
30 4.9 : 3611x2211 ?
4 7 1 -3 t1 51 -3 f1 31 14 1 -5" 10' -o" 114
36 7.1 43 /'x27 f1 :
4 71-8 5'-5" 33 141-11" 101-2" 118
42 9.6 ,.? 501'x31" 8.7 71-11" 51-7" 35 151-4" 101-4" 123
48 12.6 581lx36" 11.4 81-2" 5'-9" 38 151-7" 101-6" 127
54 16,0 65"x40" 14.3 81-7" 51-11" 40 151-10" 101-8" 132
60 19.677- N 72"x44" 17.6 81-1011 61-1" 43 16'-3" 10'-10" 137
6b 23.7
c
\j- 79"x49"
" 21.3 91- 11 61-3"
"
'
"
1 46 161-6" 111-0"
'
"
1
t1 142
6
72 .
28
r+ 85"x54 25.3 6
-5
9
-6 49
' 17
-O
11
-2 14
78 33 87 "x63" 31 9' -9t1 61-7" 52 171-211 111-411 151
84 38 E 9511x6711 35 0' -311 61-911 55 171 -511 111-611 157
90 44 10311x71" 40 101-8" 61-11" 58 171-11" 11' -8t1 161
96 50 112"x75/1 46 01-11" 71-1" 61 181-1" 111-10" 167
102 57 1171/x79" 52 l'-5" 71-3" 64 181-7" 121-0" 172
108 64 128 "x83" 58 111-711 71-51f 67 181-9 t1 121-2" 177
114 71 1371fx8711 64 11-101f 71-711 71 191-31' 121 -411 182
120 78 1421'x9111 71 2' -41' 7'-9" 71? 191-611 121-611 188
26 87 N 21-6" 71-11" 7 19'-8" 121-6" 194
-32 95 k
; 21-811 8'-1"
11 8'
'
1' 81
8 191-11" 121-1011
01
11 1
0"
? 200
205
138 104
10 -10
-4 5 -5
2
3
-
144 113 1-511 81-511 89 201-7" 131-211 211
150 123 ' -11" 81-711
[ 93
156 133 ' -1" 81-9t1 97
162 143 81-11"
141-3" 101
168 154 41-10" 9'-1" 105
174 165 51-4" 91-3" 109
180 177 5'-6" 9'-5" 113
51-8" 91-7" 118
51-10" 91-10" 122
61-5" 91-1111 126
161-7-" 101-11' - 131

83
EA g??
•
BARREL X-SECTIONS INDEX FOR RC BOX CULVERTS
SINGLES 6x6 7x7 8x8 9x9 10x10

7
0
8 10x9 11x10
8x6 9x x
1 11x9 12x10
9x6 10x7 12 8 12x9
10x6 11x?
11x6 12x7
DOUBLES 6x6 7x7 8x8 9x9 10x10 11x11
7x6 8x7 9x8 10x9 11x10 12x11
8x6 9x7 10x8 11X9 12x10 13x11
9x6 10X7 12x9 13x10 14x11
10x6 14x10
• 'RIPLES 8x6 7x7 6x8 7x9 8x10 9x11
9x6 8X7 7x8 8x9 9x10 10x11
9x7 8x8 9x9 10x10 11x11
9x8 10x9 11x10 12x11
10x8 12x10 13xll
12x9
QUADRUPLES 6x8 7x9 8x10 9x11
7x8 8x9 9xlo 10x11
8x8 9x9 10x10 11x11
9x8 10x9 ilxio 12x11
10x8 11x9 12xi0 13x11
-ll?xll
•
12x12
12x13
12xl4
10x12-
10x12
11x12
12x12
13x12
14xl2
15x12
16x12
10x12
11x12-
12x? 2
13x1
14xl2
15x12
16x12
84
Listed below are some representative sizes of Armco Super Span •
pipe arches and arches. Use as guides for selecting structure.
If choosing between sizes shown, use t dimensions - ex. 331± x 151±
Super Span Arch (37(>± sq. ft.)
Super Span Pipe Arches Super Span Arches

Span x Rise Area Sq. Ft. Span x Rise Area Sq. Ft.
e t
A
20' -1" x 13' -0" 207 24' -6" x 11' -7" 228 ftg.
24' -0" x 16' -2" 307 251 -1Y" x 12+ _9" 270
?5' -1" x 16' -0" 319 26' -8" x 11' -11" 263
27 -0" x 16' -1" 340 26' -8" x 15+ -6" 341
26' -2" x 17' -0" 350 27+ -3" x 13' -10" 308
28' -0" x 18+ -3" 401 27+ -3" x 14' -6" 340
' " ' 11 "
C9 _3 x 19 _4 424 27' _4
x -4" 253
30' -1" x 20' -2" 451 30' -0" x 11' -3" 258
-1-111 x 21' _51' 538 35' -7" x 16' -211" 470
-C 1 -6" x 22' -1" 560 38' -1" x 19' -6" c20
!4?' It
x 22+
-3"
594
38+
-1" x
20'
-5&1"
660
-11" x 23' -5" 660 40' -2" x 21' -4" 720
38' -1" x 25' -5" 758 40' -9" x 24' -1" 800
401 x 27' -4" 863
n
U
85
Revised October 12, 1077
CORRUGATED STEEL PIPE
211xi11 or 2-2/3 "xi" Corrugations
Welded, or Helical Fabrication
Rivete

y ,
. 0 4 , p7 T,
)(14 Ga.)
(16 Ga 0.10 1T

(12 Ga.)
13 „
Q-13671-
(10 Ga.)
0.1 11
(8 Ga.)
U . G
S ? L+ ?
N Q
•ri •rl r-1 O
(D ?, f-i

•rl •rl O
+
•rl +

U

U .c

rrti'??
v? ZH
• as
o
a U U

Maximum Fi-1 U

1 Above o

0

i e
V- TW ,

12 12" 8 0
15 12f1 67 73 93 -
1 1211 _j_5 67 70 81

2
1211
6
40
47 66
-
- -
3 1211 31 35 40 50
40
3 12 TT 20 35 - . - -
5$
" 26 ?
2 4-
5 -5 -
-
42 12 Note: - - -- -
- - -
- 26 2
- 11 With 2 8 2 0
1$ 12 2 0
5 12 TT Met o 113' 23 45 24 48 5 5
60 1211 install VIDTF-
'1-}--Herghtss 2
20 6
40 2
2 8
46
66 1211 18 30- 22 40
72 12" by 5 0%
22
0

78 12" Values 22 25

84 12f1
_ CORRUGATED STEEL PIPE ARCH
ipe Arch Minimum Minimum Maximum Fill Above Top
Dimension Cover Thickness (t) of Pipe for Corner
Below Bearing Pressure in
Subgrade Tons/Sq. Ft.
Inches Inches 2 Tons ____3 Tons _
17 x 13 1811 0.064" 16 23
21 x 15 18T' 0.064" 15 --22 ---
24 x 1 18" 0.06411 1 19
28 x 20 18" 0.064" 12 l g
19
x 24
1$"
0-079 "
11
17 - - -

42 x ?4 - 18" 0.07 911 _ 10 15 -

-- -
4 -
)
, 18" 0.10911 10 --
.
- -
3
49 X 3

57 x 38
1811
0.10911 _ 1 ? 14
3
-x4
64 - 18" 0.10911 _ 10 --. 14--
_
_
i 71-x 47 18" 0.138-11 10 15
---
'
77 x 52
181,
().16811
10
15
1811 0.16$'1 9 14
83 x 57
Heavier gages may be used where required for abraison, corrosion
or other factors, but not for additional fill on arches as corner
W ressures govern amount of fill.

86
Revised April 20, 1972
CORRUGATED ALUMINUM PIPE
21'x2" or 2-2/311xi" Corrugations
Riveted, Welded, or Helical Fabrication
0.060" 0.07 5" 0.105" 0.135" 0.164"
a, (16 Ga.) (14 Ga.) (12 Ga) (10 Ga) (8 Ga)
Ov
;4 4-3 cd
a) n
o Q
i
a
..
-ri
10
10
10
10
10
.,?
A
CH 4.4 cd
r-I +>
cd cd
r-1 -P
cd a$
H i?
cd cd
r-4 -P
cd a3
.-i*
0 i-)
cd
Oo
Q O O :5 W
o W
o 0
? ho
o 0
s W
o v
S4 C
0
am O O
r
l S4
U W U W U W .
U W U W
G
.. ;ii;
H
H
Inches Maximum Fill Heights Above Top of Pipe in Feet
12 12 45 - 45 - 177 - - - - -
18 12 0 - 0 - 43 - 50 - 57 -
24 12 - - 22 - 30 - 34 - 7 -
0 12 - - 1 - 2 - 2 - 2 -
36 12 - - - - 23 - 24 - 2 -
2 12 - 2 2 2 23 46 23 1 46
48 12 - - 21 2 22 22 1 44
54 12 - - 2 21 26 22 1
0 12 - - - - 151 1 1 2 2
66 12 - - - - - - 1 1 1 1
72 12 - - - - - - - - 13 13
With Method "B" installation increase fill heights allowable
by 33%.
CORRUGATED ALUMINUM PIPE ARCHES
211xP or 21"xi" Corrugations
Riveted or Helical Fabrication
Pipe Corner Minimum Cover, Minimum Maximum Fill Heights
Dimensions Radius Top of Pipe to Thickness Above Top of Pipe in
Top of Subgrade (t) Feet for Corner Bear-
s in Tons/
P
ressure
ing
Square Feet
Inches Inches Inches 2 Tons 3 Tons
18 x 11 4-3/4 18 0.060 16 23
22 x 13 4-3/4 18 0.060 15 2
1
2 x 1
x l 4-1 2
4-1 2 18
1 U-075
0.075 13
12 9
1

36 x 22
5
-
-
18
- 0.075
_
11 7
1
4 x 27
50 x 31 5-17
2 18
1
_ 57.05
0.105
_ 10
0 14
6 x 0 18
_
1 07135
0.135 1
10 -
1
72 x 44 9 1 0.164 10 15
•
•
Heavier gages may be used where required for abraison, corrosion or
other factors, but not for additional fill on arches as corner pressure,
govern amount of fill.
87
r e
Revised August 15, 1977
CORRUGATED STEEL IPE - HEIGHT 0I' FILL LIMITATIONS
3' x 1" Corrugations
Riveted, Welded, or Helical Fabrication

• 0.079
(14 Gage) 0.109 0.13
(12 Gage) (10 Gage) 168
(8 Gage)

N
?
r4? N a
ZL.,1 0
?OH
P

U m

W

U
,°

I W
I

U eo
U Oo
W
36 1 47 60 58 88 70 106 82 118
1 44 76 51 91 59 101
48 1 36 66 41 60 46 88
5 1 31 59 35 71 38 76
60 1 2 58 31 62 33 66
66 1 26 0 8 ?_ 64
72 1 2 2 6 30 "10
8 1 Note: _ 2 1 26 2 28 6
8 1.5 With 22 36 2 6 28 56
90 1.5 Method "B" 20 33 22 3 26 53
96 1.5 Installation 17 31 20 40 25 49
102 2.0 Fill Heights 19 38 23 46
10 2.0 May be Increased l 3 21 42
11 2.0 by 50% 16 32 19 38
120 2.0 1 -1 15 29 18 36
V
CORRUGATED STEEL PIPE ARCHES - HEIGHT OF FILL LIMITATIONS
3" x 1" Corrugation
Riveted. Welded, or Helical Fabrication
quiv.
Pipe
Dia. Pipe Arch
Dimension Minimum
Cover Minimum
Gage Maximum Fill Above
Top of Pipe for Corner
Pressure in Tons/sq.f t.
Inches Inches 2 Tons 3 Tons
6 40 x 31 12" 14(.079) 1 21
2 46 x 36 1211 12 .109 1 21
48 53 x 41 12 12 .109 14 21
54 60 x 46 1211 12 .109 14 21
60 66 x 1 12" 12(.109) 1
66 73 x 55 12" 12(.109) 19 28
72 81 x 59 12" 12(.109) 17 26
78 87 x 63 12" 12(.109) 16 24
84 95 x 67 12" 12(.109) 1 22
90 103 x 71 18" 12(.109) 13 20
6 112 x 75 18" 12 .10 1 18
102
108 11 x 79
128 x 83 IT,
24" 10 1?
10(.138) 12
11
16

20 137x 7
142 x 91 2411
2411 10(.136)
10(.13 ) 10
10 1
15
Heavier gages may De usea wnere requlrou 1 Vl- uLAA-Q W.Lii VJ va
factors, but not for additional fill, as corner pressures
amount of fill.
other
govern
88
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89
i ?
9-20-83
• STIRTUT" RAL PLATE STE-1.T PIPE c>°:'I=
611,,2" Corrugation
18" Corner Radius
SOan Rise Area Minimum
Cover Atr,:,-mn
Cage Tna,%Lrium fill he1P_h4-- (fu. )
* or C'r)rner PressLU''E
lb "t-' n000 lb/ft
6' -1f1 41-711 22 2' 12 24
6'-4" 4'-7" 24 21 12 15 23
61-9" 41-11" 26 21 12 14 21
7'-C" 5'-1" 28 2' 12 111 21
7'-3" 51-3" 31 21 12 20
7'-8" 5'-5" 33 2' 12 12 10
7'-11" 5'-7" 35 21 Jr-) 12 18
81-2" 5'-9" 38 21 12 12 18
81-7" 5'-11" 40 21 i- 11 17
8'-10" 61-111 43 2' 12 11 16,
91-411 61 -311 46 21 12 in 16
91_x11 6,_511 Ito 21 12 10

_
1_
'
91?" 61-
7
11 C72 2' 1
e 10 15
101 --311 (
6' -7
" 75 3' ?
1
11J Q 14
10'-8" 61-11" 58 3' 10 9 13
101-11" 7'-1" 61 3' 10 l;
'11-511 71-311 64 31 10 13
_711 71-5-11 (7 31 C; 12
1-1011
71-7"
3'
1
'
12
121-111t [[??
7'-7" 74 ?' J 12
12' -6" 71-1111 78 31 8 12
121-8" 81-1" bl 3' 3 7 11
12'-10" b1 -411 85 3' C 7 11
131-5" 8'-5" 3' 8 T 11
131-11f1 93 3' 7 10
81_911 q7 41 a 7 1r)
14'-3" 01-111, 101 4' ° C 10
10-1011 9' -1" 105 =+' ' 10
iC")' -411 C),_?" 1'0c y 1 ^ 9
_611 Cl' _51, 113 41 3 c 4
15'-8" 9'-7" 115 4'
J o
15'-10" 91-1011 122 9
101-5" 9'-11" 126 1i' 3 9
16'-7" 101-1" 131 41 R / n
4ddendum Sheet to N.C. Division of Hi,_1-19a77s
"Handbook of Design for jii hwav Surface IhrainarTe S*ruc`,ure^"
•
89 A
9-20-83
C7
STRUC"1 MI PLATE STEAL PIPE 4R,7Mq
6"x2" Corrugation.
;1" Corner Radius
Span Rise Area Minimum
Cover Minimum
Gage r:ali' P.IIT, fill Feight (ft)
nor Corner Pressure
On- lb/ft2 6000 lb/ft2
131-3" 91-4" 97 4' 8 12 19
131-6" 91-6" 102 4' 8 12 19
141-0" 9'-8" 105 4' 8 12 18
14'-2" 91-10" 109 8 12 13
141-5" 101-0" 114 8 11 17
14'-1 1" 101-2" 118 4' 8 11 17
15'-4" 101-4" 123 4' 8 11 16
151-7" 101-6" 127 4' 3 10 16
151-10" 101-8" 132 4' 8 10 16
16'-3" 101-10" 137 4' 8 10 15
16'-6" 11'-0" 142 4' 8 10 1?
17'-0" 111-2" 146 4' 8 10 15
171-2" 111-4" 151 4' 8 4 14
171-5" 11'-6" 157 4' 8 0 14
17'-11" 11'-8" 161 4' Q 14
131-1" 111-10" 167 4' 8 q i4
13' -7" 121-011 172 4'
181-9" 121-2" 177 4' 8 13
19'-3" 121-4" 182 4' 8 13
191--6" 121-6" 188 L, P, 8 1 ?
391-81, 121-81t 194 L , 3 ?S 12
12'-10" '100 4'
19

8

12
201-5" 13'-0" 2r;5 4' 8 5 11
201-7" 13'-2" 211 4' 9 8 11
Addendum Sheet to N.C. Devi-ion of Hin ,ways
"Handbook of Design for Highway Surface DT-, inap;e Strictures"
•
49 B
9-20-83
•
STP,U77TpAL PLATE ALUTMII SUM PI7E, PR'_'tr
Q11x2 1/2" Corrugations
28.8 Corner Radius
Span Rise Area Minimum
Cover Minimum
Thickness Maxim Lm fill Height (ft)
for C:)r?ner 2Pressure
400r) 1 h /ft 6000 lbi ft2
51-1111 51-4" 25 2' 0.100" 2L 32*
61-811 51-711 29 21 0.1001, 22 29*
71-411 51-11" 3L' 2' 0.100" r 264
81-011 61-21' 39 2' 0.100" 1R 24*
8'-711 61-6" 45 2' 0.100" 17 22*
91-011 61-81f 48 2' 0.100" 1r 21*
91-411 61-1011 50 21 0.125" 17 20
101-0" 71-111 56 31 0.125" 16 19
0'-511
0 71-3t1 60 3' 0.125" 1r; 18
11 71-6" 66 3' 0.12511 1u 17
11,-81, 71-10" 73 31 0.125" 1: 16
121-2" 81-0" 76 3' 0.11--)01, 13 19
121-10" 8'-3" 83 3' 0.150" 12 18
13'-7" 8'-7" 91 3' 0.15011 11 17
14'-311 81-101, 98 41 0.150" 11 16
141-9" 91-211 107 41 0.10" 10 16
151-311 91-41' 111 41 0.150" a0 15
161-0" 9'-7" 119 4' 0.150" 10 14
16'-8" 91-11" 128 41 0.1';0" 9 12
161-11" 101-111 132 4' 0.1 )n" 0 12
* C.125" Minimum Thickness Required
Addendum Sheet to N.C. Division of HiFhways
"Handbook: of Design for High,aay Surface Drainagy, Structures
•
89 C
9-20-8
STRUCTURAL PLATE ALUMINUM PIPE
911x2 1/2" Corrugation
Maximum Height of Cover Limits in Feet
ize Area Minimum
Cover
Thickness
in inches
0.10 0.125 0.15 0.175 0. 20 0.225 0.25
Cir. E1. Cir. E1. Cir. E1. Cir. E1. Cir. El. Cir. E1. Cir. El.
72 28 1' 24 26 32 28 41 30 48 32 55 34 61 36 66
34 38 1.5' 20 23 27 24 35 25 41 26 47 28 52 29 57
36 50 1.5' 18 21 24 22 30 22 36 23 41 24 45 25 50
L08 64 2' 19 21 20 27 21 32 21 37 22 40 22 114
120 78 2' 19 19 19 24 20 29 20 33 20 36 21 40
!32 95 2' 18 22 19 26 19 30 19 33 20 ?f;
_44 113 2.5 18 20 18 24 19 27 19 30 19 33
-56 133 2.5 18 18 19 22 18 25 18 28 19 30
154 2.5 17 18 20 18 23 18 26 18 28
177 2.5 16 17 19 18 22 lg 24 18 2
Addendum Sheet to N.C. Division of Higtnrays
"Handbook of Design for Highway Surface Drainage Structures"
•

?J
89 D
Q-20-83
•
CORRUGA'T'ED ALUP?T R7,lt PIPE
311x1" Corrugation
Ma.xlmun Height of Cover Limits in Feet
•
Size Area Minimum Thickness _?-n Inches
Cover .075 .105 .135 .164
Cir. E1. Cir. E1. Cir. El. Cir. E1.
36 7.1 1 24 37 27 51 30 61 34 68
42 9.6 1 23 44 2r; 51 27 55
48 12.6 1 21 38 22 L15 24 48
511 15.9 1 20 34 21 42 22 44
60 19.6 1 19 31 20 40 20 41
66 23.8 1 18 28 19 38 19 39
72 28.3 1 18 25 19 37 10 38
78 33 1 18 23 18 31 18 37
84 38 1.5 17 1U 18 F 2 18 31
90 44 1.5 15 17 20 18 25
96 50 1.5 12 16 17
102 57 2 14 17
108 64 2 11 14
124 71 2 12
120 78 2 10
Addendum Sheet to N.C. Division of }lirhways
• "Handbook of Design for Highway Surface DrainVe Structures"
89 E
ROADWAY DESIGN MANUAL PART I
MASONRY DRAINAGE STRUCTURES QUANTITY - VOLUME BASIS 5-2D
Any masonry drainage structure which incorporates an opening
for circular pipe exceeding 48 inches in diameter, or for pipe
arch of any size, will be measured and paid for on a volume
basis. The quantity of masonry to be paid for will be the number
of cubic yards of cast-in-place concrete, brick, or precast
masonry which has been incorporated into the structure. These
quantities are provided in the Roadway Standard Drawings Manual.
MINIMUM PIPE CLEARANCE
REQUIREMENT FROM INVERT TO SUBGRADE 5-3
CLEARANCE DISTANCE
Pipe Size R. C. i e Z-777 Pipe
in. t. t.
15 2.4 2.3
18 2.7 2.6
24 3.3 3.1
30 3.8 3.6
36 4.3 4.1
42 4.9 4.6
48 5.4 5.1
54 6.0 5.6
60 6.5 6.1
66 7.0 6.6
72 7.6 7.1
NOTE: This is a minimum desirable clearance and can be
reduced with Special Structural and/or Installation
Provisions.
MAXIMUM ALLOWABLE FILL HEIGHTS
OVER REINFORCED CONCRETE PIPE 5-4
Class III
Class IV
Class IV with Method B
installation
Class V with Method B
installation
All sizes 23 Ft.
All sizes 32 Ft.
All sizes 60 Ft.
All sizes 90 Ft.
Use material thickness on all pipe except
pipe. Use gage for structural plate pipe and on
Use Method "B" for R.C. Pipes under fills greater
structural plate
all pipe arches.
than 32 feet.
so

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2' FREEBOARD A80 VE

RIP RAP

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IF 51VOOTH RIP RAP

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INCRERSE
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ABOVE NATER .51IRF8CE OF LAKE
NORTH CRROL INR .5TRTE H16HWgY COMM15510M
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SUGGESTED CONCRETE DIMENSIONS
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7
•
SECTION V - FIELD SURVEYS
500-LOCATION SURVEYS
500.01 It is desirable that location surveys performed by the
Bridge Location and Hydrographic Department conform to the
work performed by the Location Department. Instructions to
Location Department field parties are contained in the "Survey
Manual" and the "Field Manual," copies of which are on file in
this office and which are available on loan to personnel of
this Department. No attempt will be made in this brief outline °
to duplicate the instructions contained in those publications.
For more comprehensive and detailed treatment, our personnel
are referred to these two manuals,'as well as other texts on
highway surveying. However, it is, deemed advisable to empha-
size certain essentials, even though they may have been published
in the "Manuals" or elsewhere, ands to bring out procedures which
may be applicable only to this. Department.
500.02 Before starting a location'survey, determine the project
number or work order against which'survey charges may be made.
If this is not available in the Raleigh Office, check with the
District or Division Engineer. Study the Advance Planning Re-
port if one has been published. Discuss all location surveys
with the District or Division Engineer, and secure tentative
approval of the proposed location prior to starting work. De-
termine if possible, the following's type of construction for
structure and approaches (contract or force account); roadway
cross-section (pavement width, shoulder to shoulder width,
face-to-face of curbs, sidewalk width, right of way); whether
or not a temporary crossing will be required, and if so, on
which side and at what distance from centerline; whether or
not grade is to be raised above high water, and whether or not
existing pavement is to be resurfaced. On widening and re-
surfacing jobs, obtain a pavement and base profile fran Di-
vision or District personnel.
500.03 The Party Chief should personally contact all property
owners whose land will be affected by the necessity for the
acquisition of right of way, and secure their permission before
staking is started, Division Right of Way Agents may be of
assistance. During this contact, ;do not have with you any maps,
plans or photos pertaining to the proposed survey. The property
owner should be told that you are 'merely staking a line from
which to secure survey data. At this time, obtain the owner's
mailing address and deed reference. Be friendly and courteous
in all dealings with the public.
i
109
•
500.04 Establish the survey line at each end
enough to cover any proposed grade changes and
tie-in grades, Inspect the project termini to
the horizontal and vertical tie=in at each end
Paint stations and transit points when working
"Survey Manual," Part II, Pages 13 and 14.
of the project far
to establish the
assure yourself that
is satisfactory.
on pavement. See
500.05 On all contract jobs and on any other jobs which you have
reason to believe may not be build in the near future, reference
enough points so that the line may be readily re-established.
Adjacent reference points must be intervisible when the line is
brushed out between them. When using trees as reference points,
leave enough of the nail protruding to withstand several years
growth. In wooded areas, a survey stake may be nailed to the
tree and marked, to aid in future location.
500.06 If the project ties into or crosses an old project, de-
termine equality and show in all notes and on all drawings.
500.07 All railroads crossing the project should be intersected
and the angle of intersection should be measured. The various
tracks, should be designated, as main, siding, spur, and a
profile obtained on the main track, and depth of rail noted.
The right of way should be determined, and a measurement taken •
to a milepost, and the direction of progression noted. The
number of daily trains and the approximate crossing speed should
be determined. The above data should also be obtained for rail-
roads adjacent to the project which will be directly affected
by the construction. The railroad grade crossing data sheet
should be completed on the spot.
500.08 On all surveys, determine the right of way of all streets
and roads affected by the project, and the width of all utility
easements.
500.09 Notes for all contract jobs are to be recorded in field
books and the applicable structure survey notes copied in loose
leaf paper for our files. In order to conserve file space, it
is desirable that the minimum number of sheets, consistent with
clarity, be used. All notes should show the personnel involved
and the date of the survey. The description could include a
cut-out section of the county map, showing the location.
500.10 Maintain the transit in good adjustment. Check the ad-
Page - 2
•
110

• Justment several times a year. Double all important angles by
taking one backsight with the telescope normal and one with
the telescope reversed. Half the sum of the two repetitions
should check both readings to the closest ;? minute. Make all
final turnings of the tangent screws against the springs. When
sights are steeply inclined, level the plate with the telescope
level. When running curves, it is good practice to reverse the
telescope position on succeeding set-ups.
500.11 Read bearings at each end of all tangents. Record the
forward bearing in Column 6 in the space above the P.T. and the
back bearing in the space next below the foll6wing P.C. When
a forward and back bearing agree,, enter in Column 5 and compute
calculated bearings from this one throughout the traverse. Do
not attempt to-read bearings t4hen cars or other metallic ob-
jects are nearby. Errors in angles may often be detected by
comparing the magnetic with the calculated bearings.
500.12 In rolling or hilly country, use the hand level when
chaining and measure with the chain level. Standard tension
for the 100' steel tape unsupported throughout is 28 pounds.
500.13 Wear the safety vest when working near traffic and employ
flagmen as necessary for the safety of the survey party and the
traveling public. On lengthy surveys along an existing road,
signs alerting motorists should be placed at the two ends of
the project.
500.14 Topography, levels and cross-sections are covered in
succeeding sections.
Page - 3
•
111
500.20-Topography •
500.21 Locate all topography which may be affected by the proposed
construction.
500.22 Locate all property lines according to instructions furnished
by Right of Way Department. Determine owners of all utilities and
show widths of easements. Show utility pole numbers when available,
complete pole data sheets. Show all structures, woods lines, limits
of cultivation, directions of flow in all pipes, streams and ditches,
fences and types, springs with outflow, overhead wires, wells, with
diameter and depth for open wells, steps, retaining walls, valuable
trees and shrubs, and all other culture which will have to be removed
or adjusted.
500.23 Record the topography to a suitable scale in a neat, legible
manner, so that it may be readily plotted by one who has not been on
the site. Indicate width of unpaved roads from shoulder to shoulder
and type of surface (sand, sand-clay, stone base, etc.). Indicate
width and type of paving on paved roads (bituminous surface treatment,
sand-asphalt, bituminous concrete, concrete). On curbs and gutter
sections, indicate width from face to face of curbs (usually back to
back width minus 12") and width from outside edge of gutter to back of
curb. Show location, width and type of sidewalks. Complete forms for
all railroad grade corssings.
Page 4
•
112
•
500.30-Levels
500.31 Show level datum on first page of levels, drainage books,
survey reports, and structure schedules. When a Government bench
mark is convenient and time permits, use it.
500.32 Extend levels far enough at both ends of project to accurately
establish approach grades - hand levels on pavement tie-ins are not
suitable.
500.33 Obtain elevations of all overhead wires.
500.34 On urban jobs where grade changes or widening is planned,
secure floor, basement and footing elevations of buildings which
might be affected. Take cross sections where necessary.
500.35 When approaches to structures are on existing fills, take
enough natural ground shots to draw an accurate profile, including
stream banks.
500.36 Choose objects for bench marks which are outside the con-
struction limits and which stand a reasonable chance of remaining
in place for a considerable period of time. When using trees, leave
the nail protruding at least 1l? inches to allow for several years
growth.
500.37 Turn on all bench marks. If necessary to correct a reading
on a turning point or bench mark, do not erase. Line through the
incorrect entry, place correct reading above, and initial.
500.38 When possible, make backsights and foresights the same
length. Avoid short turns if possible. Check all level notes
before plotting, and sign.
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500.40-Cross-Sections
500.41 Take enough cross-sections so that an accurate estimate of the
earthwork quantities may be computed. On new locations, it is help-
ful to draw the profile and proposed grade before taking cross-sections.
Be sure sections cover the construction limits and any proposed channel
changes. Take sections at all major breaks in the ground, grade points,
ditches, proposed end bents, etc. Use the right angle prism to es-
tablish line. Use a Jacob Staff on steep slopes.
500.42 Enter the full station in Column 1 and the elevation shown to
hundredths in Column 7. Stations progress up the page. If there is
insufficient room for all readings-on-one. line, continue sections on
the line below and work toward the center of the page. Use an arrow
to denote the continuation.
500.43 Maintain hand levels in adjustments. Check frequently. In
flat and gently rolling open country where wide sections are required,
the transit level may be employed to advantage.
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• 501-Grade Separation Surveys
501.01 $efore leaving the office, obtain the typical sections to be
used on the project and the roads which cross the project.
501.02 The reference point for all grade separation surveys is the
intersection of the two located survey lines. In the case of a rail-
road grade separation, it is the intersection of the located survey
line and the centerline of the main track. In the case of two main
tracks, either track may be used.
501.03 The located survey line is the base line from which topography
is taken. In the case of a curved railroad, all track angles are
measured at the reference point. Double all measured skew angles.
Track topography is referended to that track chosen as the base line.
For parallel tracks, show center to center distances on all tracks,
normal to the tracks, in addition to the centerline stations of the
tracks. Where crossovers and spurs are involved, locate completely,
showing points of switch and frog. Measure the distance to a mile-
post and record in the notes together with the direction of progres-
sion. Obtain the width of railroad rights of way.
501.04 In the case of dual bridges, stake the parallel offset lines
as determined from the typical section, throughout the limits of the
bridges plus an additional couple of hundred feet. On curves, the
stations on the offset lines are on radial lines from the centerline
of the survey. Take levels and rod soundings or earth auger borings
on the offset lines. A tentative structure layout computed on the
site will be helpful. Existing pavement and track elevations are
taken left and right from the reference point of no "Y" line is run
in for the crossing. Cross-sections in the area of the end bents
should be taken from the centerline of survey as well as cross-
sections normal to the cross road or railroad throughout the con-
struction limits.
501.05 In the case of railroad overheads, it is important that no
additional drainage be allowed to enter on existing railroad cut.
Any drainage from the proposed road which will have to be discharged
toward the railroad at an overhead crossing, should be conducted to
a natural outlet outside the-railroad section. For this reason,
complete information on the existing railroad drainage in the vicinity
should be obtained.
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502-Drainage Surveys •
502.01 It is not practicable to attempt to cover the whole subject of
drainage principles in this manual. Guides will be presented which
should be helpful, especially to those lacking extensive experience
in this type of work.
502.02 The purpose of a drainage survey is to make plans for conducting
that portion of the rainfall which appears as surface runoff, under,
along and alongside the roadway, to its natural outlet, in a safe,
economical manner, without creating unsightly or unsafe conditions.'
Were it possible to be present and observe the runoff from a storm
along the route of the proposed ro ad, the_ determination of the points
where water accumulates and outlets must be provided would be simpli-
fied. The locations where parallel ditches, riprap and other forms of
protection were required would also be apparent. Unfortunately, this
is seldom the case. Therefore, the engineer must rely on his experience
and judgment in evaluating the conditions and making the proper recom-
mendations.
502.03 Moving water usually leaves marks along the watercourse. Anyone
will notice the effects of a great storm on a large stream if it is
seen before cleanup operations have been completed and marks obliter-
ated. But it takes a trained eye to perceive the marks caused by the
•maller storms, which leave no visible evidence of damage, but which •
.evertheless might wash out a roadwmy fill or flood the road. Indica-
tions of the flow of water are provided by drift, (fences are good
collectors of drift) erosion, (a cultivated field scoured down to
bare clay or gravel in the low areas, a badly eroded stream bank, a
scour hole at the outlet of a drainage structure, a roadway shoulder
scoured below the pavement with all the fines washed out) the deposi-
tion of streaks of sand and gravel in a field or on pavement, and the
presence of detritus in a channel. Always be on the lookout for these
indications of high water flow. When conditions are found which would
damage the road, make recommendations on the spot to safely conduct this
flow to its natural outlet.
502.01 A drainage structure must satisfy several requirements. It must
safely pass the design discharge without overflowing the road, without
creating excessive backwater that would cause adjacent property to be
flooded, and without creating velocities which would cause excessive
scour in the outlet channel or on the roadway fill at the inlet. It
must safely support the roadway and the superimposed loads, and be the
most economical structure which will satisfy all these requirements.
Additional reference to these topics are made in the sections on
Hydrology and hydraulics. Since reference has been made to allowable
backwater and scouring velocities, required field data to establish
these quantities will be given here. When upstream development in the
vicinity appears to be near the elevation of high water, locate, and
obtain any necessary control elevations beyond which the water must
of be permitted to rise. In order to estimate scouring velocities
P age 13 •
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• in a channel, it is necessary to describe the type of material in the
stream bed and determine whether scour occurs in the natural channel.
502.05 At the location of each pipe, examine the profile and grade line.
If the grade proposed is below high water, give a minimum grade eleva-
tion in the drainage book to safely clear, high water. Determine the
approximate construction limits and obtain stream topography for about
501 outside these limits. Locate the point where the toe of the fill
intersects the stream, both upstream' and downstream. Inspect both of
these locations. Normally the pipe will be located so that both the
inlet and outlet will lie in the stream. If conditions dictate other-
wide, decide where each end of the pipe should be placed and locate
by centerline plus and offset. When plotted in the drainage book,
the station and skew will be indicated. Information for any neces-
sary channel excavation and drainage easements should be obtained
at this time. Any unusual conditL= which will affect the proposed
pipe should be sketched in the drainage book.
502.06 If the stream bed gradient is less than 1%, take a profile
sufficient to establish this gradient and to cover any proposed
channel excavation. Make the usual high water and existing struc-
ture inspection and estimate the size structure required. The
drainage area should be obtained at this time if practicable.
It should be remembered that any adjustments to a stream
- outside the construction limits, will, in the majority of cases
• necessitate a drainage easement. Obtain the necessary data while
on the site.
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•
503-Bridge and Culvert Widening Surveys
503.01 A substantial part of the work of this
of surveys for the widening or extension of ex
culverts. Even though in most cases structure
for the existing structures, measurements must
tions obtained, in case the structure as built
plans.
Department consists
fisting bridges and
plans are available
be taken and eleva-
differs from the
503.02 On bridges in which the superstructure can be widened, com-
plete measurements are required (feet and inches) with the exception
of the handrails and curbs. On otter bridges, the substructure
only need be measured. If old plans are available, have them re-
produced and check off the dimensions on them. Otherwise, a sketch
will be necessary. The skew should be accurately determined.
Measurements left and right of the survey line should be obtained
when it does not coincide with the centerline of the bridge. If
creosoted piles are involved, samples should be taken with the
Swedish incerment borer and the holes plugged with asphalt, if
visual inspection indicates doubt as to their soundness.
503.04 In addition to a profile under the bridge, levels should be
taken at each end of the bridge showing centerline, gutter, top
of curb, top of wing, tip of wing, bridge seat and top of footing, •
and at each bent showing centerline, gutter, top of curb, bridge
seat and top of footing, both sides where applicable. On skewed
bridges, follow the skew of the bents. In addition, two or three
sections should be taken at right angles to show the crown or
superelevation. The notes should show clearly which sections are
skewed and which are normal. Thickness and type of wearing sur-
face, if any, should be measured. Cross-sections should also be
taken at abutments, wing tips, end bents, and other locations as
required. Determine elevation of existing underclearance on all
bridges over railroads.
503.05 The condition of all structures which are to be retained or
widened should be stated. A careful inspection of the entire
structure should be made. Look for settlement, cracks, spall,
exposed reinforcing, undermined footings, leaning wings, or a-
butments, unsound or worm eaten timber piles or other structural
defects, and note any found. Photos of these or any unusual
conditions should be obtained.
503.06 In surveying existing culverts for widening, the size, center-
line station and skew are required. The centerline station
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r ?
L J
_ is obtained by standing on the axis of the culvert - prolonged
upstream or downstream if necessary - and intersecting the survey
centerline by eye. The ends of the culvert are located in the
usual manner. When plotted on the culvert survey sheet, the skew
may be scaled with the protractor. As a further check on the
skew, measure the clear span normal to the axis of the culvert,
and divide this quantity by the clear span measured along the skew.
The quotient thus obtained is the cosine of the skew angle.
Measure the skew with a transit of necessary. In some cases a
culvert is designed on some even skew and is then built in an
existing stream channel which may have a slightly different skew.
If the fill over the culvert is not very high, it will be ob-
served that the headwall is not parallel to the roadway under these
conditions.
503.07 The following measurements are required; overall length of
barrel, excluding the headwall overhand; length on each side from
centerline to end of barrel, normal to the centerline; and thick-
ness of top slab and interior walls when old plans are not avail-
able.
503.08 A profile along the axis of the culvert is required, extending
far enough to cover any proposed channel changes or channel exca-
vation. Use the transit level for this work when practicable.
Elevations should be obtained on the centerline, edge of pavement,
• shoulder, top of headwall and floor slab, as well as stream bed
and natural ground. At this time stream topography can be taken,
using the axis of the culvert as a base line. Record channel
widths at each level shot. Decide at this time whether the culvert
can be extended along the existing alignment without excessive
channel changes, or must have a change of direction in order to
more nearly lie within the existing channel. Also obtain the ele-
vations of any backwater controls upstream, above which the head-
water must not be permitted to rise to prevent damage to property.
503.09 Take cross-sections as necessary Co that the structure exca-
vation may be computed.
503.10 Carefully inspect each culvert for structural and hydraulic
condition. Structural defects should be noted and photographed
if possible. If evidence of insufficient capacity is noted, de-
termine drainage area and high water elevations upstream and
downstream. Also inspect other structures in the vicinity.
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503.11 The Culvert Survey Sheet should be completed while on the •
site. If there is insufficient room for all data, record on loose
leaf sheets.
503.12 On bridge widening jobs, consult with the Division Engineer
and determine whether a temporary crossing will be required, and
if so, on which side and at what distance from the centerline.
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504-RIVER AND STREAM CROSSING SURVEYS
504.01 The cost of the structures carrying highways over rivers and
streams, together with grade separation structures, constitutes
a large percentage of the highway construction dollar. Consider-
ing this fact, and the possible consequences of undersigning a
major stream crossing, it is seen that the Engineer making stream
crossing designs has a great responsibility.
504.02 This section will attempt to present guides which should be
of considerable value to Party Chiefs in the collection and evalu-
ation of field data for river and stream crossings, especially for
those men without extensive experience. At the least, it will
serve as a checklist which the Party Chief may use to assure him-
self that his collection of field data is complete. To much
emphasis cannot be placed on the necessity for obtaining complete
data at the site of all structures. Thoroughness during the
initial survey may save a second trip back to the site, with the
consequent loss of time and manpower. With the advent of the up-
coming expanded construction program, this consideration will
become more vital than ever.
504.03 Before leaving the office, consult the files for prior surveys
on the same stream in the vicinity of the project, preferably both
upstream and downstream. Note the dates of the surveys, the length
and height of the existing structures, the drainage area, the ele-
vation or height of high water above stream bed, the dates of the
various floods, and any other information which might be helpful
to you. U. S. Geological Survey publications "Floods in North
Carolina - Magnitude and Frequency - 1961" and the annual "Water
Resources Data for North Carolina" give the location and flood
data for all stream gaging station in North Carolina. "Drainage
Areas at Selected Sites in North Carolina" may be helpful in
determining or checking drainage areas.
504.04 An excellent check on a stream is frequently provided by
existing structures in the vicinity, when these structures and
their approaches are above high water. Prior to visiting the
survey site, a careful inspection of such structures should be
made. In addition to the length -of channel spans, length of over-
flow spans, clear height above stream bed, and approximate water-
way area, look for signs of srour in the channel and around the
abutements, drift, and for evidence of the stream having overtopped
the fill. This is usually most noticeable on the downstream
shoulder.
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121
504.05 On the structure site, first make an inspection, noting the
natural or man made features which will affect the stream flow
and the layout of the structure. These will include, among others,
the location and size of the normal channel, overflow areas and
direction of flood flow. This may sometimes differ from the flow
when contained within the banks. Look for drift which will in-
dicate the elevation and direction of flood flow. By inspection,
try to determine the proper location for the toe of the proposed
approach fills. For culverts, estimate the size that will be re-
quired and determine the proper location. There should be a
reasonably close relationship between the estimated size and the
final chosen size.
504.06 It is helpful to attempt to visualize the complete structure
and approaches superimposed on the site. Then the conditions which
will affect the finished job will be evident from observation of
the physical features at the site, and plans made on the spot to
either correct any which would adversely affect the construction,
or provide the needed protection. The data required to show these
conditions and make the corrective measures would then become
evident. Always keep in mind the purpose for which each part of
the survey is made.
504.07 Obtain high water information from two long-time local
residents if possible. Record their names in the notes, and de-
scribe the marks pointed out to you and the years the floods
occurred. If the flood levels pointed out to you do not agree
reasonably well, check with other local residents. The Maintenance
Supervisor is sometimes a good source of information. On a gaged
stream, a further check is provided by the records of the stream
gaging stations. An additional check is provided if there has been
a prior survey. The maximum flood of record should be obtained in
each case. It is also desirable to obtain the second and third
highest flood in most cases, especially when there is a wide fluctu-
ation between the maximum flood and the next highest. If flood
marks are visible on an existing fill, take levels on the marks on
both sides of the fill every 200' or so, starting at the structure
and extending throughout the flood plain. Determine date of flood
if possible. When flood waters have overtopped a fill, look for
marks on both the upstream and downstream sides, so that the head
may be determined. If in the vicinity of a larger stream which
might cause backwater at the survey site, determine whether back-
water is a factor and measure its elevation. Differentiate between
high water from the stream on which you are working and backwater
•
122
•
from another stream.
504.08 When taking topography, locate the stream channel, overflow
channels, toe of hill, and other features which may control or
influence stream flow within such limits as may be considered
necessary. It is important to locate the edges of stream channels
and stream banks accurately in order to make a structure layout
that will keep fill slopes clear of the channel. Make a stadia
survey if necessary in order to adequately show the conditions.
504.09 A centerline profile con vering the entire flood plain should
be obtained. If centerline is on an existing fill, a natural
ground profile should also be obtained. In cases where the maximum
flood is considerably above existing approaches, check with the
Divition or District Engineer to determine whether or not the grade
is to be raised above this level. Also find out whether a temporary
crossing will be required, and if so, on which side and at what
distance from the centerline. Also find out whether the existing
structure is to be removed. When applicable, the question of the
necessity for sidewalks can also be discussed at this time.
504.10 On jobs which have been staked by others, take levels from
a bench mark throughout the limits of the structure. If levels
are not already taken, run levels far enough each side of the
structure to enable the approach grades to be established. This
may be several hundred feet when high hills flank the stream.
It will probably be necessary to go beyond the crests of the ad-
jacent hills. When drift is visible, take levels on it far enough
upstream and downstream to establish the high water gradient. Also,
determine the date of the flood causing this drift, if possible.
On- culvert surveys, run a bed and natural ground profile beyond the
limits of the structure, and far enough to establish the stream
bed gradient. In very few cases will it be acceptable to terminate
bed levels upstream on a falling grade or downstream on a rising
grade. Look for drift when running bed levels and obtain ele-
vations. When in doubt as to whether the structure will be a
bridge or a culvert, take bed levels. Obtain elevations of ex-
isting drainage structures in the vicinity and any upstream back-
water controls, aoove which headwater must not be permitted to
rise in order to prevent damage to property. The normal water
surface elevation should be determined or estimated. Always
record the observed elevation and the date. 'In coastal areas,
in waters influenced by wind tides only, the normal elevation can
usually be determined from marks on structures, piles, etc. Local
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123
residents may also be of help. In waters influenced by ocean
cides, a gage should be established and observations made and
recorded for a minimum of 28 days if possible, but in any case
throughout the duration of the survey. The elevations required
are mean low water, mean high water and maximum storm tide. The
mean high water line is frequently defined by marks on structures,
piles, marsh grass, etc. in the vicinity. Local resients can
usually point out the maximum storm tide marks. On jobs for which
Corps of Engineer permits are required, extreme low water from
storm action should also be estimated.
501.11 If a tentative structure layout has been made, take rod
soundings at each bent, including soundings left and right of
centerline if necessary. If no layout has been made, cover the
area, using the lengths of the other structures in the vicinity,
measured earlier, as an approximation. As a guide, the Bridge
Maintenance Department does not often build spans in excess of
501, but on contract jobs, span lengths may be 75 to 80' or
longer. The type of rip rap (plain or concrete) to be used
should be determined at this time. Note the depth of soft e-
rodible material in each boring and estimate the required depth
of the rip rap below the ground. When bedrock is exposed in the
stream bed or banks, or is very shallow, (1' to 3') and a culvert
is to be recommended, take soundings along each wall of the pro-
posed culvert to the ends of the wings. Remember that for skews
not in excess of 15°, an arch culvert may often be used to ad-
antage where a long span is required and bedrock is shallow.
Before leaving the site, review the sounding information, and
where sharp breaks are observed, take additional soundings.
505.12 Having determined the approximate location of the ends of
the bridge, take enough cross-sections to accurately define the con-
struction limits in the area of the end bents, and the configu-
ration of the rip rap. This is especially important in rolling
and hilly country. Cross-sections are required also on culvert
surveys, to enable Bridge Design to compute the structure exca-
vation.
505.13 The boundaries of watersheds in excess of about one square
mile need not be field checked if they are shown in,U.S.G.S. or
TVA contour maps of recent issue at scales no smaller than
1:62500'. Smaller areas should be field checked. If aerial photos
are used in flat country, all areas should be field checked. When
the old soil maps are the only aids available, areas up to about
10 square miles should be field checked.
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510-Reports
510.01 The reports prepared for a fob are just as important as the
field survey. Every effort should be made to insure that they are
clear, accurate and complete, and contain all the information neces-
sary for layout and design.
510.02 The scale of a drawing should be suitable to clearly define
the proposed construction and show the necessary detail. Locations
made by this department should be drawn on standard plan and pro-
file sheets when practicable. On projects in which the grading is
to be let to contract, the original will be forwarded to the Roadway
Design Department and incorporated in the plans. For this type of
drawing, existing roads, structures, etc. are to be drawn with dashed
lines. Use black ink only, including the survey centerline. Remember
that Roadway Design will draw the proposed right of way lines. There-
fore notes, descriptions, etc. should be placed so as not to conflict
if possible. Proposed structures, grade lines and title should not
be inked. When standard forms are not used for drawings, sheet size
should be in even multiples of 8Y"x1l". Do not crowd the plan and
profile together. If necessary, use a larger sheet. If the Bridge
Survey Report form is too small for the purpose, a sheet of 22"
- heavy profile paper may be cut to the desired length, folded, and
stapled to the Borm. When more space is required for a culvert
curve than is provided by the Culvert Survey Sheet, a sheet from
the 8 "x11" cross-section pad should be used as above.
510.03 Be sure that all the applicable spaces on the Bridge Survey
Report are filled out. The disposition of the existing structure
is especially important, and should always be included also in the
remarks space on the Structure Survey Recommendations. All drawings
and reports of any kind should be signed and dated. All notebooks
should be indexed and checked for completeness before the reports
are forwarded.
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