Hydraulic Manual (Dec 2014)

Hydraulic Manual

2013

2014

HM 001-00

Hydraulic Manual Section: CHANGE HISTORY Subject:

Date Page September 18, 2014 1 of 2

September 15, 2014 Revised HM 614-00 and HM 000-00 Updated the culvert material types to include polypropylene and steel reinforced high density polyethylene on a pilot project basis. Updated the steel culvert material coating types to include polymer on a pilot project basis subject to additional manufacturing inspection requirements. The culvert connector requirements have been updated to replace the gasket requirement with a requirement to wrap the coupler with a non-woven geo-textile. Added a requirement for the use of a semi-corrugated coupler with electrometric O-Ring Gaskets to improve resistance to piping failures in fills greater than 3 m or water infiltration or continuous low flow conditions. Use of longer culvert lengths is now required in fills greater than 3 m to reduce the number of joint connections. Updated the name for the section. Updated the Table of Contents to reflect the slight change to the name of section 614-00 and the addition of section 001-00 Change History and the re-numbering of section HM 000-00 Table of Contents.

September 18, 2014 Revised HM 701-00, HM 702-01, HM 702-02 and HM 704-00. Replaced Standard Plan HM705-01 with new Standard Plans HM705-01, and HM705-02. Revised Standard Plan HM705-02 and renamed it HM705-03. Created new Standard Plan HM705-04. In HM 701-00 adopted the Canadian Highway Bridge Design Code (CHBDC) for the structural design of corrugated steel culverts equal to or greater than 3000 mm in diameter. The granular backfill specifications for road embankment CSP culverts have been revised to adopt a rectangular shape around the culvert with the dimensions based on CHBDC for 1500 mm ≤ D < 3000 and based on American Iron and Steel Institute (AISI) for D < 1500 mm. The guidance for spacing between multiple pipe installations has been amended to improve design flexibility. The guidance for design of camber has been amended to provide more specific guidance on its application. Standard Plan HM705-01 was replaced by the two new Standard Plans in order to implement the new granular backfill specifications based on culvert size. In Standard Plan HM705-02 Note 4 was removed so it can be used in multiple pipe installations. For Standard Plan HM705-04 the

Hydraulic Manual HM 001-00

Section: CHANGE HISTORY Subject:

Date Introduction Page September 18, 2014 2 of 2

requirements are the same as before except that a separate plan has been included and the excavated slope has been amended to recognize the requirements of an unpaved approach versus a road embankment.

HM 002-00

Hydraulic Manual Section: TABLE OF CONTENTS Subject:


000-00 Table Of Contents 001-00 Change History 002-00 Table of Contents 100-00 Introduction 101-00 Introduction 200-00 General Information 201-00 Use of this Manual 202-00 Use of Other Publications 203-00 Use of Professional Judgement 204-00 Design Exceptions 205-00 Use of the Terms Shall/Should/May 206-00 Roles and Responsibilities 206-01 Introduction 206-02 Technical Standards Branch 206-03 Regional Services Division 207-00 Definitions 300-00 Design And Approval Processes 301-00 Design Process 302-00 Design and Approval Requirements 303-00 Documentation Requirements 303-01 Hydraulic Design Reports 303-02 Hydraulic Approval Memo 304-00 Documentation Templates (Under Development) 305-00 Design Drawing Templates (Under Development) 400-00 Background Data Collection 401-00 Background Data Collection 500-00 Design Flows 501-00 Design Flow Methodology 502-00 Design Frequency


Section: TABLE OF CONTENTS Subject:


503-00 Flow Calculation 503-01 Existing Structures at Site 503-02 Structures Upstream and Downstream 503-03 Rational Method 503-04 Transposition of Flows 504-00 Flow Frequency 505-00 Flow Conversion 600-00 Culvert Hydraulics 601-00 Introduction 602-00 Design Considerations 603-00 Inlet Control 604-00 Outlet Control 605-00 Allowable Headwater 606-00 Culvert Lengths And Minimum Diameters 607-00 Tailwater 608-00 End Treatments 609-00 Manning’s n 609-01 Pipe Flow 609-02 Constructed Channels 609-03 Natural Channels 609-04 Composite Manning’s n 610-00 Culvert Embedment 611-00 Wood Box Culverts 611-01 Design and Maintenance Considerations 611-02 Design Calculations 611-03 Standard Plans 12500: Framed Timber Culverts Page 1 of 5: Structural Details Page 2 of 5: Structural Details Page 3 of 5: Miscellaneous Details Page 4 of 5: Timber List Page 5 of 5: Timber List SP 22160: Backfilling Framed Timber Culverts 612-00 Median Drainage Structures




613-00 Flow Over Embankments 614-00 Culvert Material and Connector Requirements 615-00 References 700-00 Structural Design 701-00 Structural Design Requirements 702-00 Height of Fill Tables 702-01 Corrugated Steel Pipe and Pipe Arch With D < 1500 mm 702-02 Corrugated Steel Pipe and Pipe Arch For 1500 ≤ D < 3000 702-03 Structural Plate Pipe 703-00 Structural Design Procedure 704-00 References 705-00 Standard Plans HM705-01: Backfilling Pipe Culverts D < 1500 mm In Road

Embankment HM705-02: Backfilling Pipe Culverts 1500 mm ≤ D < 3000 mm In Road

Embankment HM705-03: Backfilling Pipe Culvert D ≤ 600 mm In Unpaved Approach HM705-04: Backfilling Pipe Culverts 600 mm < D < 3000 mm In

Unpaved Approach 800-00 Erosion Control At Culverts 801-00 Introduction 802-00 Design Principles 803-00 Design Requirements 804-00 Riprap Design 804-01 Sizing of Stone For Riprap 804-02 Riprap Apron 805-00 Natural Erosion Resistance 806-00 References 807-00 Standard Plans HM807-01: Riprap Pipe Culverts 600 mm < D < 1500 mm 900-00 Fish Passage Design Procedures 901-00 Fish Passage Design Procedures




1000-00 Design Aids 1001-00 Design Aid Criteria 1002-00 CulvertMaster 1002-01 Operation 1002-02 Tutorial 1002-03 Design Examples 1100-00 Culvert Service Life (Under Development) 1200-00 Culvert Rehabilitation 1201-00 Introduction 1202-00 Culvert Sleeving 1203-00 References 2000-00 Technical Bulletins 2001-00 Design Directives

Hydraulic Manual

Section 100

Introduction

2014

THIS PAGE INTENTIONALLY LEFT BLANK

HM 101-00

Hydraulic Manual Section: INTRODUCTION Subject:

SCOPE OF MANUAL The Hydraulic Manual (HM) has been compiled as a reference

document for the hydraulic design of culverts. In meeting that requirement, it also contains guidance applicable to the hydraulic design of bridges and open channels. The objective of culvert design is to select the most economical culvert to pass flow from a drainage area through the highway in a permissible manner with an acceptable risk of overtopping or damage from higher flows. The purpose of the Hydraulic Manual is to provide the designer with procedures for designing culverts while promoting uniformity of design on Saskatchewan Highways and supporting the provision of safe and efficient roads for the travelling public. Drainage is a major component of highway design. A poor culvert design may at best result in minor delays by overtopping the grade every year, and in extreme cases it may result in death and considerable property damage. It is hoped that with the aid of this guide, the designer is capable of handling culvert design problems to a degree of accuracy consistent with the accuracy of the field information.

LAYOUT The guide’s layout is reflective of the natural grouping of the design topics that the designer will go through in order to undertake a culvert design. To assist designers, it includes section HM 1000-00 which includes, among other things, a series of design examples.

DESIGN ASPECTS There are a number of aspects that shall be considered in a culvert design. These are:

• Legal Aspects, • Hydrology, • Hydraulic Design, • Economics, • Navigation Concerns, • Environmental Concerns; and • Safety.

LEGAL ASPECTS In the design of a hydraulic structure, the engineer shall ensure that it is Date Page

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Section: INTRODUCTION Subject:

done according to accepted practices and that it meets applicable Federal and Provincial Acts and Regulations. Deviations that could result in damage and litigation should be avoided.

HYDROLOGY Hydrology is concerned with the estimation of design discharges. Design discharge is often the overriding design criteria because all other aspects of the design are related to the design flow. Unfortunately, it may also be one of the most difficult aspects to determine.

HYDRAULIC DESIGN Hydraulic design consists of looking at the different types of structures available to accommodate the design flows. It also incorporates all other drainage aspects into the design. It is therefore the next most important item in the design after the design flow estimate.

ECONOMICS Most individual drainage structures on a highway system do not represent a large part of the total investment of highway funds. However, taken collectively, they represent a large investment. The usual procedure in hydraulic design is to consider a number of alternatives and to select one on the basis of economics. The most economic design is generally one where the costs of possible flooding and the material type are balanced against the cost of increased structure size and design life.

NAVIGATION CONCERNS

It is important that hydraulic structures do not restrict navigable waterways and meet the requirements of the Navigation Protection Act.

ENVIRONMENTAL CONCERNS

Any changes to existing drainage patterns may have an adverse effect on aquatic life and other flora and fauna. The requirements of regulatory agencies shall be taken into account during the assessment of possible effects. Changing the drainage pattern may also have a detrimental effect on the existing usage of adjacent land. Any changes to the existing drainage pattern and its effects on adjacent land shall be considered in the design.

SAFETY The provision of a drainage facility should combine safety and efficiency in design. Drainage facility design should give serious consideration to the possibility of reducing or eliminating any feature that may pose a potential hazard to errant vehicles.

Date Introduction Page

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Hydraulic Manual

Section 200

General Information

2014


HM 201-00

Hydraulic Manual Section: USE OF THIS MANUAL Subject:

DISTRIBUTION This guide will not be issued or maintained in printed form. The manual

is available through the Ministry of Highways and Infrastructure website. Users are encouraged to bookmark and use the manual from the website. If the user elects to download the guide, they shall then be responsible for checking the website to ensure that they always have the latest version prior to starting on any design work.

USE WITHIN THE MINISTRY

The Hydraulic Manual is to be used in conjunction with other Ministry publications; The U.S. Federal Highway Administration Hydraulic Design Series Number 5 – Hydraulic Design of Culverts and Hydraulic Engineering (HDS-5); and Circular No. 14 – Hydraulic Design of Energy Dissipators for Culverts and Channels (HDS – 14) in the design, tender, construction, rehabilitation, and decommissioning of culverts. Other Ministry publications are cross-referenced in this manual as required. The following is the ministry policy for the use of these publications:

- If a design topic is addressed in both the Hydraulic Manual and HDS-5 or HDS-14, the Ministry standard procedure shall be to apply the information in the Hydraulic Manual as the Ministry Standard.

- If a design topic is not addressed in the Hydraulic Manual or the HDS-5 or HDS-14, but is addressed in another publication, refer to HM 202-00.

USE OUTSIDE THE MINISTRY

The Ministry of Highways and Infrastructure recognizes that others may use the Hydraulic Manual. The Hydraulic Manual is a consideration of Ministry policies, standards, and practices. Therefore, it is not suitable for adoption by others as a design code or a set of minimum specifications, which if met will adequately protect the public. Hydraulic Manual users shall accept responsibility for each design produced and all associated risk of liability.

Date General Information Page

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Section: USE OF THIS MANUAL Subject:



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HM 202-00

Hydraulic Manual Section: USE OF OTHER PUBLICATIONS Subject:

INTRODUCTION Designers may wish to consider information in publications other than

the Hydraulic Manual. For example, designers must also consult other relevant ministry publications. Designers may also consult other sources for design guidance. This is especially beneficial when a particular design topic is not addressed in a ministry publication or the Hydraulic Manual, or when the particular conditions warrant additional research.

APPROVAL REQUIREMENTS

When considering a design element based on information from another publication, the following approval requirements apply:

- If information in one ministry publication is contrary to information in another, the most recently approved shall be the governing standard. Technical Standards Branch must be informed of any discrepancies or ambiguities.

- If a design topic is not addressed in the Hydraulic Manual, but is

addressed in another publication produced by the Ministry or the U.S. Federal Highway Administration (FHWA) Hydraulic Design Series Number 5 – Hydraulic Design of Highway Culverts and Hydraulic Engineering Circular No.14 – Hydraulic Design of Energy Dissipators for Culverts and Channels, the normal approval authority applies.

- If the publication is not listed above, any proposed design element based on that information shall be approved by the same authority as a design exception. See HM 206-00 for more information.


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Section:

USE OF OTHER PUBLICATIONS

Subject:



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HM 203-00

Hydraulic Manual Section:

USE OF PROFESSIONAL JUDGEMENT

Subject:

INTRODUCTION The guidance and standards in the Hydraulic Manual are intended for

application in typical Saskatchewan contexts. Similarly, the guidelines in other publications are intended for certain contexts. It is not possible for any manual or publication to cover every situation that will be encountered in the field.

FUNDAMENTAL RESPONSIBILITY

The fundamental responsibility of an Engineer is to exercise professional judgement in the best interest of the public. Standards assist engineers in making judgements, but standards are not intended as a substitute for professional judgement. Engineers shall exercise judgement when applying standards and when recommending an exception to a standard. Exceptions to standards require justification and approval. The approval process itself shall not be considered an argument or justification for failing to consider an exception to standards when it is judged to be in the public interest. For more information on the design exception approval process, refer to HM 206-00.


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Section:

USE OF PROFESSIONAL JUDGEMENT

Subject:



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HM 204-00

Hydraulic Manual Section: DESIGN EXCEPTIONS Subject:

INTRODUCTION A Design Exception is defined as any design element differing from the

approved ministry standard. See HM 201-00 for more information on approved ministry standards. When a designer uses professional judgement to deem a design exception warranted, the designer shall obtain proper approval for the recommended exception. The process in this section provides the designers with guidelines for obtaining such approval. The purpose of this process is to ensure design exceptions are formally documented, appropriately evaluated and properly approved, as well as providing consistency throughout the Ministry and ensuring standards are kept current. A design exception may apply at any phase of the project; however, approved design exceptions are to be filed with hydraulic design report or approval memo.

PROCESS GUIDELINES

Step 1. Identify the Key Issue(s)

- What are the circumstances that require a hydraulic design element to differ from the current standard?

Step 2. Assess various options outside the standard

- Identify options that are being considered to address the design exception.

- Identify the implications associated with each option. - Consider short-term implications, long-term implications and

risk management issues.

Step 3. Provide Recommendations

- Identify the option that is being recommended - Why was the option selected?

Step 4. Submit a report for approval. Step 5. Assess the need for changes to existing standards


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Section: DESIGN EXCEPTIONS Subject:

- Each design exception should be evaluated by the appropriate

Engineering Standards Branch Section to assess whether current standards should be changed.

REPORT GUIDELINES Each design exception shall be described in a Design Exception

Summary Sheet with a proper signature block. Design Exception Summary Sheets shall include the following:

- Project identification and location; - Clear statement of the recommended exception ; - Standard from which the exception differs; - Clear, brief explanation of how and why the exception differs

from the standard; and - Signature block.

If there are multiple exceptions, they shall be listed in the transmittal memo along with one Design Exception Summary Sheet for each exception. The summary sheets shall be affixed as the cover pages of the Design Exception Report. The Design Exception Report shall include the following:

- Introduction (which includes project identification and location); - Identification of the key issues; - Identify and assess the options to address the design exception; - Risk assessment; - Recommendation.

APPROVAL The approval of a design exception is subject to the requirements listed

in the document Operations Division Signing Authority Delegation (Non-Financial Items). Further to the approval requirements in that document, all non-minor design exceptions shall be reviewed and recommended by the Executive Director of Engineering Standards Branch. The original shall be filed in the Region and one PDF of the approved original shall be sent to the Senior Road Design Engineer, TSB.


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HM 205-00


USE OF THE TERMS SHALL/SHOULD/MAY

Subject:

INTRODUCTION The words “shall”, “should”, and “may” will have the following

standard meaning when referred to within the Hydraulic Manual.

DEFINITIONS Shall: A mandatory condition. No discretion with statements using the stipulation “shall” is allowed. Should: An advisory condition. In statements using “should”, the suggestion is recommended but not mandatory. Deviation from the stated provision is allowed if there is justifiable cause to do so. May: A permissive condition. There is no requirement for design or application of the condition. It is included as an option.

NOTE TO USERS Users shall be guided by these definitions. In the event of liability, the courts may place an emphasis on these definitions, which also reflect common English usage of the words. Note also that the traditional grammatical distinction between “shall” and “will” is fading. They are sometimes used interchangeably to convey the same meaning.


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Section:

USE OF THE TERMS SHALL/SHOULD/MAY

Subject:



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HM 206-01

Hydraulic Manual Section: ROLES AND RESPONSIBLITIES Subject: INTRODUCTION

INTRODUCTION

The Ministry is made up of many diverse work groups that have different roles and responsibilities within the organization. The purpose of this section is to identify the roles and responsibilities of the work groups with respect to their use of the material contained in the Hydraulic Manual. The Ministry is divided up into the following Divisions:

• Ministry Services and Standards Division (MSSD) • Regional Services Division (RSD) • Planning and Policy Division (PPD) • Communications Branch.

Currently MSSD and RSD use the Hydraulic Manual.

MINISTRY SERVICES AND STANDARDS DIVISION

MSSD is divided up into the following Branches:

• Financial Services Branch • Corporate Support Branch • Information Management Branch • Technical Standards Branch.

The Technical Standards Branch (TSB) is responsible for the design standards and manuals for the Ministry. It is also responsible for providing technical guidance and approvals that are required with respect to the manuals. The Hydraulic Manual is one of these manuals. The details of the roles and responsibilities of TSB is contained in section HM 206-02. The other Branches do not interact directly with the Hydraulic Manual.

REGIONAL SERVICES DIVSION

RSD is divided up into the following three Regions and the Major Projects Unit:

• Northern • Central • Southern • Major Projects


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Section:

ROLES AND RESPONSIBLITIES

Subject: INTRODUCTION

The Regions are responsible for the design, installation, rehabilitation, maintenance, and decommissioning of the Ministry’s culverts based on the policies, standards and procedures developed by TSB. The Regions are made up of a number of sections and the details of the roles and responsibilities of each of these sections in hydraulic designs is contained in section HM 206-03. The Major Projects Unit can be involved in the delivery of hydraulic projects for the Regions in addition to work on special projects that have a hydraulic design component.


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HM 206-02

Hydraulic Manual Section: ROLES AND RESPONSIBLITIES Subject:

TECHNICAL STANDARDS BRANCH

INTRODUCTION

The Technical Standards Branch (TSB) is managed by an Executive Director and is divided up into the following Sections:

• Earth Sciences and Research (ES&R); • Design and Traffic Engineering Standards (D&TES); • Construction Standards (CS); • Preservation and Operations Standards (P&OS); and • Bridge Standards (BS).

The roles and responsibilities of each section with respect to hydraulic designs are outlined in the sections below.

EXECUTIVE DIRECTOR OF TSB

The Executive Director of TSB and the Assistant Deputy Minister of Regional Services are responsible for the approval of the Ministry’s Engineering Manuals and Standards. They are also responsible for the approval of design exemptions to these standards.

EARTH SCIENCIES AND RESEARCH

The Earth Sciences and Research section is responsible for the Ministry’s environmental standards and regulatory agency requirements relating to installation, rehabilitation and maintenance of culverts. The Senior Environmental Engineer position provides training and technical support to the Regions and consultants in this area. The Senior Geotechnical Engineer position is in this section and provides geotechnical design support to the Senior Road Design Engineer, the Regions and consultants with respect to foundation, settlement and slope stability issues relating to culverts.

DESIGN AND TRAFFIC ENGINEERING STANDARDS

The Design and Traffic Engineering Standards section is responsible for the Hydraulic Manual. The Senior Road Design Engineer position provides training and technical support to the Regions and consultants in the area of hydraulic design. This position also participates in the review and approval process for culvert designs.

CONSTRUCTION STANDARDS

The Construction Standards section is responsible for standard construction contract specifications and special provisions governing the purchase, installation. Rehabilitation and decommissioning of culverts. The Senior Construction Engineer position provides training and support to the Region on construction specifications.


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Section:


Subject: TECHNICAL STANDARDS BRANCH

This section is responsible for the drafting standards for the Ministry. Issues with the Drafting Standards Manual are to be addressed through the Senior Construction Engineer position. This section is responsible for the Consultant Solicitation and Selection Process. This process is managed by the Senior Project Management Engineer position.

PRESERVATION AND OPERATIONS STANDARDS

The Preservation and Operations Standards section is responsible for the maintenance standards for culverts and the standards relating to the Ministry’s Asset Management System. They are also responsible for the database containing the culvert inventory and condition rating data. The Senior Operations and Preservation Engineer positions provide training and technical support to the Regions on these systems and standards.

BRIDGE STANDARDS The Bridge Standards section provides support for the structural design standards for culverts through the Senior Bridge Design Engineer and Director of Bridge Standards positions. The Section also provides support for the standards relating to the inspection and maintenance of bridge sized culverts. The Senior Bridge Asset Management Engineer position provides training and technical support to the Regions on the inspection, maintenance, and condition rating of bridge sized culverts. Bridge sized culverts are culverts equal to and greater than 1.5 m in diameter. They also include wood and concrete box culverts.


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HM 206-03

Hydraulic Manual Section: ROLES AND RESPONSIBLITIES Subject: REGIONAL SERVICES DIVISION

INTRODUCTION

Each Region within Regional Services Division is managed by an Executive Director and is divided up into the following sections:

• Design and Construction; • Regional Asset Management; • Regional Operations; and • Regional Logistics.

The roles and responsibilities of the sections involved with culverts are outlined in the sections below.

DESIGN AND CONSTRUCTION

The Design and Construction section either undertakes the culvert design and construction contract administration or manages consultants undertaking the work. The Environmental Projects Specialist is to be consulted with for all culvert designs with respect to Saskatchewan Ministry of Environment, the Saskatchewan Watershed Authority and Federal Department of Fisheries and Oceans requirements. The Senior Project Managers are responsible for the following:

• Sending PDF copies of all culvert designs to the Senior Road Design Engineer in TSB.

• Ensuring that as-built drawings are completed. • Providing the details of all the culvert installations or

rehabilitations to the Preservation Planner for the purpose of updating the Culvert Database.

• Insuring that culvert markers are installed on through grade culverts.

• Reviewing culvert designs to ensure that they comply with the Hydraulic Manual requirements and recommending their approval.

• Notifying the Asset Management Group when culverts greater than 1.5 m have been installed so they can be inspected and any defects accepted during construction can be documented.

REGIONAL ASSET MANAGEMENT

The Regional Asset Management section performs a number of functions related to culverts. The various functions are outlined in the following discussion.


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Section:


Subject: REGIONAL SERVICES DIVISION

The Regional Asset Management section is responsible for the development of the capital culvert replacement programs, culvert data collection, and the Culvert Database. The Roadside Development Technicians process permits for roadside development work in the highway right-of-way (ROW). The permits cover the installation of new approaches and any associated culverts. Occasionally the installation of a buried utility in the ROW requires the removal and replacement of a culvert. The Preservation Planner is responsible for the updating of the Culvert Database.

REGIONAL OPERATIONS

The Regional Operations section performs a number of functions related to culverts. The various functions are outlined in the following discussion. The District Operations Managers (DOM) are responsible for the following:

• Review and acceptance of the work covered by the Roadside Development Permits. Where this involves the installation of culverts the DOM is responsible for providing the Preservation Planner with the culvert installation details so that the Planner can update the Culvert Database.

• The replacement of culverts managed by the District Maintenance Forces and providing the Preservation Planner with the culvert installation details so that the Planner can update the Culvert Database.

• Ensure that culvert markers are installed for all culvert replacements that they have managed.

• Ensure that existing culvert markers are maintained. • The routine maintenance of the existing culverts in their

district. • The surveillance of existing culverts during and after flooding

events. • Documenting the high water levels at culverts resulting from

flood events and providing this information to the Preservation Planner so that the Planner can update the Culvert Database.


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HM 207-00

Hydraulic Manual Section: DEFINITIONS Subject:

ABUTMENT A wall supporting the end of a bridge or span, and sustaining the

pressure of the abutting earth.

ANGLE OF FLARE The angle between the direction of the wingwall and centreline of the culvert barrel.

ANNUAL FLOOD The maximum daily or instantaneous peak discharge occurring in a given year.

ALLOWABLE HEADWATER ELEVATION

The maximum permissible elevation of the headwater at a culvert at the design discharge.

APRON Protective material laid on a streambed to prevent scour at a bridge pier, abutment, culvert inlet, outlet, toe of a slope or similar location.

ARCH Structural plate corrugated steel pipe formed to an arch shape and placed on abutments. The invert may be natural stream bed or any other suitable material but is not integral with the steel arch.

BACKFILL Earth or other material used to replace material removed during construction, such as in culverts, sewer and pipeline trenches, and behind bridge abutments and retaining walls.

BAFFLE A flow interference structure, usually in the form of a low weir, which is attached to a culvert invert and extends partially or entirely across the culvert.

BASIN SLOPE The average slope of the terrain within a drainage basin.

BED LOAD Sand, silt, gravel, rock or other mineral matter which is carried by a stream on or immediately above its bed.

COVER The height of fill from the culvert crown to the top of subgrade.

CRITICAL DEPTH The depth corresponding to the critical flow.


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Section: DEFINITIONS Subject:

CRITICAL FLOW The condition in which flow transitions between streamlined and

turbulent, subcritical and supercritical. This occurs when the minimum specific energy is reached.

CROWN The highest point of the interior of a pipe at a given cross-section.

CULVERT A conduit, usually covered by fill, whose primary function is to convey surface water through an embankment.

DAILY DISCHARGE The average discharge occurring over a period of one calendar day. Also termed Mean Daily Discharge.

DEPTH OF FLOW The vertical distance to the lowest point of a channel section from the top of the water surface.

DESIGN FLOOD OR DESIGN DISCHARGE

The maximum discharge a structure is designed to accommodate without exceeding the adopted design.

DESIGN FREQUENCY The recurrence interval for hydrologic events used for design purposes.

DESIGN HIGH WATER LEVEL

The elevation of the level corresponding to the design discharge, but sometimes the level created by other factors such as ice jamming.

DISCHARGE The rate of flow of water, usually in cubic metres per second.

DITCH A small artificial drainage channel having a definite bed and banks.

DRAINAGE Interception and removal of ground water or surface water by artificial or natural means.

DYKE

An embankment or wall, usually along a watercourse or flood plain, to prevent overflow onto adjacent low land.

EMBEDMENT The depth to which a culvert invert is implanted below the average stream bed.

END AREA The area calculated on the basis of inside diameter of the available flow area through the conduit.

ENERGY LINE A plot showing the total energy along the direction of flow. Date General Information Page

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EROSION The wearing away of soil or other material by the action of flowing

water or other agents.

FILTER A layer of granular material or filter fabric placed over a fine grained material to prevent removal of the fines and at the same time permit the transmission of water.

FISH MIGRATION ROUTE

A stream used for, or which has good potential for, the seasonal migration of fish.

FISH PASSAGE DESIGN DISCHARGE

The discharge a culvert must be capable of passing without preventing the upstream passage of fish.

FLARED INLET/OUTLET

A culvert end treatment designed to improve the hydraulic performance and erosion control of the culvert inlet or outlet.

FLOOD A relatively high flow in terms of either water level or discharge.

FLOOD FREQUENCY The number of times a flood event occurs or is exceeded during a given period.

FLOW Discharge in the channel.

FLOW RATE Rate of discharge in the channel.

HEAD The height of water above a given datum; the energy of water expressed in metres.

HEADWALL A wall at the end of a culvert normally extending from the invert to above the soffit or crown of the culvert, and aligned parallel to the roadway or normal to the longitudinal axis of the culvert.

HEADWATER The water upstream from, and whose level is influenced by, a culvert or other structure.

HEADWATER DEPTH The depth from the headwater elevation to the invert at the first full cross section of the culvert.

HEADWATER ELEVATION

The water level upstream from a structure.


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HEIGHT OF COVER Distance from the crown of a culvert or conduit to the finished road

surface.

HIGH WATER LEVEL The highest level reached by a flood.

HORIZONTAL ELLIPSE

A long span corrugated steel structure with the major diameter horizontal.

HYDRAULIC GRADE LINE

A plot showing the pressure head plus the elevation of various points along the direction of flow.

HYDRAULIC JUMP An abrupt rise in water surface which occurs when flow changes from supercritical to subcritical.

HYDRAULIC RADIUS The ratio of the water area to the wetted perimeter.

HYDROGRAPH A graph of discharge or stage versus time at a given point in a drainage system.

HYDROLOGY The science dealing with the occurrence, distribution and circulation of water on the earth, in the atmosphere or below the surface of the earth.

ICE JAM The choking of a stream channel by the piling up or ice at an obstruction or constriction.

ICING The gradual accumulation of ice in a culvert or channel resulting from freezing of seepage flows from groundwater, wetlands or other sources over a period of weeks or months.

IMPERVIOUS Impenetrable. Completely resisting entrance of fluids.

INFILTRATION The passage of water into the soil or conduit.

INLET In culvert hydraulics, an entrance, an orifice, an opening, or a mouth.

INLET CONTROL A condition where the flow is governed by the inlet characteristics and the headwater depth.

INVERT The stream bed or floor within a structure, conduit or channel.


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INSTANTANEOUS PEAK DISCHARGE

The maximum instantaneous discharge occurring during a given flood.

INTENSITY-DURATION-FREQUENCY CURVE

A curve expressing rainfall intensities for specified durations and frequencies. The data may also be presented in the form of tables or maps.

JACKING (FOR CONDUITS)

A method for providing an opening for drainage, or other purposes, underground by cutting an opening head of the pipe and forcing the pipe into the opening by means of a horizontal jack.

LOCK SEAM Longitudinal seam in a pipe, formed by overlapping or folding of the adjacent seams.

MEAN VELOCITY The velocity obtained by dividing the flow rate by the flow area.

MITERED END

A culvert end the face of which conforms with the face of the embankment slope (often termed a beveled end).

NATURAL HYDROGRAPH

A hydrograph plotted directly from stream flow records.

OPEN CHANNEL A drainage course which has no restrictive top.

OPEN CHANNEL FLOW

Flow having its surface exposed to atmospheric pressure; the flow may be in an open channel or in a pipe flowing partly full.

OPEN FOOTING CULVERT

A culvert having either a natural invert of an artificial floor not integral with the walls (also termed open invert culvert).

OUTLET CONTROL Flow control at a culvert in which the capacity is governed principally by the barrel roughness, length, slope, and in some cases by the tailwater.

PERFORMANCE CURVE

A plot of discharge versus headwater elevation or depth at a culvert.

PERMEABILITY A property of soils which permits free passage of any fluid.


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PIPE ARCH A corrugated steel pipe or structural plate corrugated steel pipe shaped to

a span greater than rise; a multi radius shape with an arch shaped top and a slightly convex integral bottom, structurally continuous with an invert whose radius of curvature is greater than that of the crown.

PIPING Subsurface erosion caused by movement of water through fill or natural ground usually associated with a surcharged flow in a pipe.

PONDING Water backup in a channel or ditch as a result of a culvert of inadequate capacity or design to permit the water to flow unrestricted.

PROJECTING END A culvert end which projects from the face of the embankment.

RATIONAL FORMULA A formula for calculating discharge or runoff based on area and rainfall intensity. The formula is Q = C·i·A.

REACH A length of stream channel selected for use in computations.

RETENTION Temporary natural storage of runoff in lakes and swamps. In urban areas, long term storage for purposes other than reducing flood peaks.

RETURN PERIOD The average period of years between flood occurrences equal to or greater than a given value.

RING COMPRESSION The principal stress in a confined thin circular ring subjected to external pressure.

RIPRAP A layer of stone to prevent the erosion of soil.

RISE The maximum vertical clearance inside a conduit at a given transverse section, usually the centerline.

ROUGHNESS COEFFICIENT

A numerical measure of the frictional resistance of a surface to the flow of water expressed in terms of Manning’s n.

RUNOFF COEFFICIENT

A coefficient in the Rational formula expressing the ratio of the depth of runoff from a drainage basin to the depth of rainfall, and indicating the runoff potential of a particular soil type/land use combination.


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RUNOFF That part of precipitation carried off from the area upon which it falls.

Also the rate of surface discharge of the above.

SCOUR Local lowering of a streambed by the erosive action of flowing water.

SEAM A joint between two structural steel plates formed by overlapping and bolting them together. Also, the join or lap of riveted corrugated steel pipe (CSP) or the join or weld for continuous weld CSP.

SEDIMENT Soils or other materials transported by wind or water as a result of erosion.

SEWER A conduit or channel, usually covered, for carrying off the drainage waters and excrements of a town, factory, house, etc.

SILL A low wall placed across a culvert or channel to control low flow levels or to stabilize the upstream bed.

SOIL-STEEL STRUCTURE

A culvert, comprised of structural steel plates and engineered soil, designed and constructed to induce a beneficial interaction of the two materials.

SPAN The maximum width of a culvert barrel measured perpendicular to the walls.

STAGE The height of a water surface above a specified datum.

STATION FREQUENCY ANALYSIS

A frequency analysis of flow records at a single stream gauging station.

STREAM A body of water flowing in a bed, river, brook or channel.

STRUCTURAL PLATE CORRUGATED STEEL PIPE

Hot rolled sheets or plate, corrugated, custom hot dipped, galvanized, curved to radius, assembled and bolted together to form pipes, pipe arches, and other shapes.

SUMP A storage area at the bottom of a catch basin for trapping sediment.

SUPERCRITICAL FLOW

Flow at depths shallower than the critical depth.


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TAILWATER The water downstream from a culvert or other structure.

TAILWATER DEPTH The depth of water immediately downstream from a culvert, measured

from the invert of the culvert.

UNDERMINE To wash away supporting material from underneath a culvert. This is typically caused by eddies.

UNIFORM FLOW Flow in which the velocities are uniform in both magnitude and direction along a conduit, all stream lines being parallel.

VELOCITY HEAD The kinetic energy of flowing water expressed in metres.

WASHOUT The failure of a culvert, bridge, embankment or other structure resulting from the action of flowing water.

WATER COURSE A natural or artificial channel in which a flow of water occurs, either continuously or intermittently.

WATERSHED The area of land drained above a given point. Also termed basin, drainage basin, or catchment.

WATER SECURITY AGENCY

An organization that leads management of Saskatchewan’s water resources to ensure safe drinking water sources and reliable water supplies for economic, environmental, and social benefits for the people of Saskatchewan.

WEIR A dam across a river or channel to raise the level of water upstream or regulate flow.

WETTED PERIMETER The sectional length of the wetted surface in contact with the flow. The length of the wetted contact between the water prism and the containing conduit.


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Hydraulic Manual

Section 300

Design and Approval Processes

2014


HM 301-00

Hydraulic Manual Section: DESIGN PROCESS Subject:

INTRODUCTION

There are approximately 61,000 culverts that the Ministry of Highways and Infrastructure (MHI) is responsible for. This large, aging system is dispersed over a wide geographical area while serving a population of approximately one million people. The design procedures and standards that they are based on are a reflection of this situation and the current Regulatory requirements. The design and approval procedures are influenced by the budget processes used to generate the culvert projects. The culvert projects are part of either the Capital or Operating Budgets. The culverts that are installed under a Provincial Highway or as part of a Capital Road project are part of the Capital Budget. The remaining culverts are part of the Operating Budget. The Capital Budget projects are delivered through the Regional Design and Construction Group while the Operating Budget projects are typically delivered through the Regional Operations Group. There are differences between the processes associated with these groups, and the designer must be aware of the different requirements and properly apply them. Some of the design procedures involve obtaining information or approvals from external agencies and can have significant timelines associated with them. This needs to be recognized and incorporated into the Regions decisions regarding the program development and delivery of culvert projects so that the projects are not unnecessarily delayed. This process includes consultation with the Regional Environmental Project Specialist. The two most important ones are obtaining design flow information from Water Security Agency (WSA), and the determination of whether or not the culvert is required to be designed for fish passage by the Federal Department of Fisheries and Oceans (DFO). These tasks should be undertaken by MHI staff during the program development stage. The design procedure involves a number of steps. The number and content are dependent upon a number of factors. The factors affecting the design procedure and associated use of the Hydraulic Manual are discussed in the following sections.

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Section: DESIGN PROCESS Subject:

DESIGN AIDS MHI regulates the software used in the design of culverts.

Refer to section HM 1000-00 for guidance on the use of design software.

DESIGN AND APPROVAL REQUIREMENTS

The determination of the appropriate design and approval requirements is the first step in the design process.

Refer to section HM 302-00 for the requirements.

DOCUMENTATION REQUIREMENTS

Proper record keeping is essential to support the approval and quality assurance processes while allowing for the standards development and operational information requirements. The documentation requirements include the proper creation, approval and filing of design reports and the updating of the MHI databases related to culverts.

Refer to section HM 303-00 for the procedure to be used

COMPILE BACKGROUND INFORMATION

The compilation of background data generally involves two sources. The first source of data involves an office search of files where relevant data might be available, and discussion with Maintenance Section staff, Rural Municipality staff, and local residents. A second source involves data that is obtained in the field at or near the site under study and hydraulic structures upstream and downstream.

Refer to section HM 400-00 for guidance on the collection of background information.

SELECT DESIGN FLOW In most situations the design flow is obtained from WSA and checked against the historical flow conditions at the site. Where this is not possible, the designer must establish a design flow by following the following steps:

1. Design frequency;2. Flow determination; and3. Flow frequency.

Refer to section HM 500-00 for the guidance on the use of WSA design flows or the establishment of a design flow through other means.

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ESTABLISH FACTORS AFFECTING CULVERT DESIGN

Allowable Headwater Elevation The allowable headwater elevation is the maximum permissible elevation of the headwater at the design discharge. It must account for the necessary freeboard to protect the structural integrity of the road, the elevation of permissible flooding upstream, and any other design considerations which may cause detrimental effects to land, property, or the highway network. Refer to section HM 605-00 for the procedure to be used. Presence of Springs The impact of springs needs to be considered with respect to the buildup of ice that they may cause in culverts and the issues that result during spring thaw and runoff. Tailwater The presence of tailwater influences the capacity of the culvert and the outlet flow velocity and therefore must be properly considered in the culvert design. Refer to section HM 607-00 for the procedure to be used. Stream Profile and Alignment The average stream bed slope needs to be determined to properly set the culvert grade in order to meet the DFO and Ministry of Environment (MOE) requirements. The determination of whether or not the stream is aggrading or degrading is an important part of this process. Streams are typically composed of pools and riffles. The pools occur at the bends and the riffles on the straight sections between them. The presence of bends and riffles introduce a natural undulation into the stream profile which must be taken into account when setting the average stream profile. The average stream profile should be based on the bend elevations or the riffle elevations whichever is the most appropriate for the site.


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The culvert crossing should try to match the natural stream alignment. Significant realignment of the natural stream channel will require approval from MOE. Department of Fisheries and Oceans It is important that the hydraulic structures on fish migration routes do not restrict fish passage or habitat. The design and construction of hydraulic structures must meet the requirements of the Federal Fisheries Act and any associated Regulations and Measures to Avoid Causing Harm to Fish and Fish Habitat. The Act, Regulations, and Measures to Avoid Causing Harm to Fish and Fish Habitat are administered by DFO. Refer to section HM 900-00 for the fish passage design procedures to be used. The Regional Environmental Project Specialist is to be consulted with for all locations involving fish passage. Transport Canada It is important that hydraulic structures do not restrict navigable waterways. The design and construction of hydraulic structures must meet the requirements of the Navigation Protection Act and any associated Regulations. The Act and Regulations are administered by Transport Canada. The Regional Environmental Project Specialist is to be consulted with respect to the requirements. Water Security Agency WSA is the provincial organization responsible for reviewing aquatic habitat alterations for the protection of aquatic ecosystems and human health. The Environmental Management and Protection Act (EMPA) and The Water Regulations are the responsibility of MOE and define the WSA’s provincial authority for aquatic ecosystem protection and the broader aquatic habitat protection objectives that stem from it, such as the protection of the bed, bank and boundary of Crown surface waters


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and the values entailed such as aquatic habitat, organisms, the water cycle and shoreline stability. The design, construction and the rehabilitation of hydraulic structures must meet these requirements and require an Aquatic Habitat Protection Permit from WSA. The Regional Environmental Project Specialist is to be consulted with respect to the requirements of the Aquatic Habitat Protection Permit. Utilities The locations of any existing utilities must be determined as part of the design process. If there are utilities present, they must be taken into account in the design. Erosion Control The material type and vegetation cover for the streambed, stream bank, and flood area need to be identified and their permissible mean velocities established. Saskatchewan Environment requires that the streambed, stream bank, and flood area be protected so that the design flow from the culvert does not cause erosion. Refer to section HM 800-00 for the procedure to be used. Camber For culverts installed in high fills and/or yielding ground the effects of the resulting differential settlement have to be taken into consideration in the design. These effects are usually addressed through the introduction of camber in the pipe’s vertical alignment in order to prevent the reduction in capacity, icing and the reduction in service life that may result from ponding water. The Senior Geotechnical Engineer is to be consulted when addressing these design issues.


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Poor Foundation Soils For culverts installed in frost susceptible or swelling soils additional design measures may have to be taken in order to properly address these situations during the design and construction. The Senior Geotechnical Engineer is to be consulted with when addressing these design issues. Culvert Service Life The Ministry does not have standards for culvert design service life. It is the responsibility of the designer to identify and address local soil and water conditions which would significantly impact the average life of the culvert material being considered for use. The presence of standing water may have a negative influence on the service life of a corrugated steel culvert except for some areas of the Canadian Shield. This situation is usually associated with sloughs containing cattails and the condition can also be created through the embedment of the culvert.

SELECT ALTERNATIVES

When considering alternatives, the designer should consider all options that are available. The designer shall consider culvert material as well as the various sizes and hydraulic shapes that are available for each material type.

ECONOMIC COMPARISON OF ALTERNATIVES

After a number of alternatives have been selected based on design flows, the cost of each alternative must be determined. The costs to be included are the cost of the materials and the cost of the installation of the culvert. If the design lives of the alternatives are different, then the cost should be compared on a life cycle or full cost accounting basis.

RECOMMENDATION A recommendation must be made after the alternatives have been assessed. This is normally the most economical installation unless there is some reason why a more costly installation is preferable.


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HM 302-00

Hydraulics Manual Section:


Subject:

INTRODUCTION The purpose of this section is to provide the designer with guidance on

when a hydraulic design is required or if a historical assessment of the culvert is appropriate for the approval of the installation of new culverts, the replacement of existing culverts, and the sleeving of existing culverts.

HYDRAULIC DESIGN REQUIREMENTS

New Road Construction Design flows have to be established for all culvert installations associated with new road construction. A hydraulic design shall be undertaken for all crossings except where the design flow condition warrants the installation of a minimum size culvert. This usually occurs where the culvert is located on a small localized drainage area that does not have a defined drainage channel and will not likely have an adverse effect upstream or downstream from the crossing. The hydraulic design report requirements are outlined in HM 303-01. The design ditch velocities should be checked against the permissive velocities, where appropriate, for the ditch soil type and proposed vegetation cover to ensure that there will not be erosion problems from a design flow event. The permissive velocities are outlined in HM 805-00. The ditch design water levels should be checked, where appropriate, against the allowable headwater criteria to ensure that the design criteria are not violated. This is typically required where a stream flows down a roadway ditch. The allowable headwater criteria are outlined in HM 605-00. Road Reconstruction A hydraulic design shall be undertaken for all crossings being replaced when the culvert diameter is equal to or greater than 1500 mm.

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Subject:

The hydraulic design report requirements are outlined in HM 303-01. For crossings when the culvert diameter is less than 1500 mm a hydraulic design shall be undertaken when:

• A review of the historical performance of the culvert and an assessment of the risk associated with water overtopping the road at that location recommends that a hydraulic design be undertaken; or

• Fish passage design is required; or • The crossing involves multiple culverts, or • The culvert is being sleeved.

Otherwise the replacement culvert sizing is based on the historical performance of the crossing and an assessment of the risk associated with water overtopping the road. A Hydraulic Approval Memo is required to document culvert replacements where a Hydraulic Design Report is not required. The Hydraulic Approval Memo requirements are outlined in HM 303-02. Culverts Replacing a Bridge. A hydraulic design shall be undertaken. The hydraulic design report requirements are outlined in HM 303-01. Existing Culvert Replacements and Rehabilitation A hydraulic design shall be undertaken for all crossings when the culvert diameter is equal to or greater than 1500 mm or the culvert is being sleeved. The hydraulic design report requirements are outlined in HM 303-01. For crossings when the culvert diameter is less than 1500 mm a hydraulic design shall be undertaken when:

• A review of the historical performance of the culvert and an assessment of the risk associated with water overtopping the


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Section:


Subject:

road at that location recommends that a hydraulic design be undertaken; or

• Fish passage design is required; or • The crossing involves multiple culverts.

Otherwise the replacement culvert sizing is based on the historical performance of the crossing and an assessment of the risk associated with water overtopping the road. A Hydraulic Approval Memo is required to document culvert replacements where a Hydraulic Design Report is not required. The Hydraulic Approval Memo requirements are outlined in HM 303-02.

APPROVAL REQUIREMENTS

All new culvert installations, replacements and rehabilitations are approved in the Regions by the Regional Design and Construction Director except for the following situations:

• Culvert installations or replacement covered under Approach Permits and Utility Permits which are approved as per the Roadside Management Manual.

• Minimum sized approach culverts which are replaced with the same culvert sizes by Operations crews which are approved by the District Operations Manager.

• Temporary emergency culvert replacements which are approved by the District Operations Manager.

Where any of the following conditions exist, the Hydraulic Design Report shall be reviewed by the Senior Road Design Engineer and recommended by the Senior Road Design Engineer on the approval sheet.

• Where the design flow is greater than or equal to 6 m3/s. • The crossing is required to be designed for fish passage. • The design involves a channel realignment or diversion. • The design involves hydraulic structures to control erosion or

water velocity. • The design is part of a pilot project to test new technology,

materials, or installation methods. • The design includes non-circular shapes.


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Section:


Subject:

Design Exceptions Where any culvert design element differs from the approved Ministry standard, the Hydraulic Design Report is approved as per the Signing Authority Delegation – Operations Division (Non-Financial Items). Refer to HM 206-00 for guidance with respect to this.


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HM 303-01



Subject: Hydraulic Design Reports

INTRODUCTION

The purpose of this section is to provide the designer with guidance on the creation of hydraulic design reports.

HYDRAULIC DESIGN REPORT REQUIREMENTS

Hydraulic design reports are required to provide documentation of all hydraulic designs. The hydraulic design report contents outlined in the next section is set up for individual crossings. For new road construction and road reconstruction projects all of the crossings requiring hydraulic designs should be combined into a single hydraulic design report following the outline provided below omitting the information that does not apply. If you are not sure about what to include, contact the Senior Road Design Engineer.

HYDRAULIC DESIGN REPORT CONTENTS

1. Recommendation - Provide the final recommendations from the report. - Quick reference for the reviewers.

2. Background Information

- Structures/property and special conditions that may impact

or be impacted by the design. - Existing road cross-section surfacing structure, cross-slope

and widths, sideslope. - Historical performance of the culvert.

o Description of existing culvert (length, type, size, material and end treatment) and its condition.

o Names of people contacted and their comments. o Copies of relevant information from Ministry files and

media sources. o Dates of previous floods and their associated high

water levels. o Estimate of the number of years the culvert has been in

service. o Document any issues with ice flow blockages or

buildup of ice in the culvert.

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3. Utilities and Regulatory Agencies

- Identify all utilities and regulatory agencies. - Locate all utilities and assess their impact on the design. - Special conditions or lack thereof from the regulatory

agencies.

4. Design Flow - Return period(s) for design. - Saskatchewan Water Security Agency flow estimates. - Check Water Security Agency flow estimates based on

calculation of historical flows at existing structure. - Rationalization of recommended design flows which

includes assessment of risk.

5. Design Parameter - This section includes information on the design decisions

relating the major design criteria (omit the sections that do not apply to the design).

5.1 Allowable Headwater

- Description of the controlling headwater condition and its

location. 5.2 Tailwater - Description of the controlling stream tailwater condition

and its location. - Description of and justification for the use of hydraulic

structures to control the tailwater elevation. - Justification for the embedment of the culverts if used in

the design.

5.3 Erosion Protection

- Calculation of the outlet apron length.

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- Recommendation of erosion protection material for the

sideslope and apron associated with the inlet and outlet and justification for selection.

- Description of and justification for use of any special energy dissipating structures.

5.4 End Treatments

- Description of and justification for the use of anything

other than a projecting end treatment.

5.5 Culvert Alignment

- Description of and justification for placing the culvert on a skew angle or shifting the culvert location.

5.6 Stream Channel Realignment

- Description of and justification for realigning the stream

channel.

5.7 Road Cross-Section and Profile

- Description of and justification for changes to the existing road cross-section, sideslope, vertical and horizontal alignment.

6. Selection of Alternative

- The following criteria were used in assessing the

alternative recommendation. 6.1 (Provide the following summary of the design

parameters that are common to all of the design alternatives. Omit any that do not apply. Where the listed design parameter varies with the design alternative, it is to be included in Table 303-1 )


Hydraulic Manual

HM 303-01

Section:



Summary Of Design Parameters

- Allowable Headwater Elevation = - Design Flow QDesign = - Tailwater Elevation QDesign = - Design Flow QFish = - Tailwater Elevation QFish = - Average Natural Channel Slope = - Natural Channel Status (aggrading, degrading, stable) = - Culvert Slope = - Culvert Manning’s n = - Inlet Elevation = - Outlet Elevation = - Culvert Embedment (depth/%) = - Channel Profile Design Elevation at Outlet =

Table 303-1: Comparison of Alternative’s Design Parameters

Design Parameter Alternative 1 (Description)

Alternative 2 (Description)

Alternative 3 (Description)

For QDesign Computed Headwater Depth Factor of Safety (QMax*/QDesign) Outlet Flow Depth Outlet Flow Velocity

For QFish Computed Headwater Depth Outlet Flow Depth Outlet** Flow Velocity

*QMax is the flow with the headwater set to the road overtopping point. **Use the higher of the inlet and outlet flow velocity when culvert under inlet control.

6.2 Cost Analysis

- Summarization of the costs for alternatives evaluated.


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Section:



6.3 Selection of Alternatives

- Identify any alternatives that were considered but did not

make the short list of alternatives that were analyzed in detail.

- Provide the reasoning for the recommended alternative.

Appendices Appendix A: Water Security Agency Correspondence On Design Flows Appendix B: Regulatory Agency Correspondence Appendix C: CulvertMaster Culvert Designer/Analyzer Reports Appendix D: CulvertMaster Culvert Calculator Reports Appendix E: Cost Estimates Appendix F: Photographs Appendix G: Plans

1. Location Plan 2. Construction Operation Plan 3. Road Cross-Section Detail Plan 4. Installation Typical Cross-Section Plan 5. Erosion Protection Plan 6. Streambed Profile Plan 7. Highway Centerline and Ditch Profile Plan 8. Stream Cross-Section Plan

Note: The DFO Copy of the Report does not contain Section 6.2 - Cost Analysis.


Hydraulic Manual

HM 303-01

Section:



REPORT DISTRIBUTION The distribution of the approved hydraulic design reports shall be as

follows: One signed original filed in the Region, and one PDF copy of the original signed report to TSB. Where fish passage is required, a third signed copy of the report may be required for submission to DFO.


HM 303-02



Subject: Hydraulic Approval Memo

INTRODUCTION

Purpose To provide the designer with guidance for Approval Memos. Scope The Memo covers individual culvert replacements, and culvert replacements included in highway reconstruction or upgrading projects. A group of culverts can be included into a single approval report.

CULVERT APPROVAL MEMO CONTENTS

1. Recommendation.

2. Declaration (Use the following statement) The culvert(s) historical performance had been reviewed and used as the basis for determination of the new culvert size.

3. Analysis: Documentation of justification for recommending an increase in the culvert size.

4. Culverts Covered Under Approval: Table listing the control section, at km, existing culvert size, existing culvert type existing culvert material, replacement culvert size.

5. Approval Block. Appendices: Include any documentation to support Section 3 analysis.

MEMO DISTRIBUTION The distribution of the approved hydraulic approval memos shall be as follows: One signed original filed in the Region.

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Subject: Hydraulic Approval Memo



Hydraulic Manual

Section 400

Background Data Collection

2014


HM 401-00


BACKGROUND DATA COLLECTION

Subject:

INTRODUCTION

A successful culvert design relies on historical site information and sufficient field data collection. In support of the culvert design, site field data collection should provide enough information for designers to determine channel and floodplain geometry, adjacent structures which may affect the hydraulics of the structure, adjacent crossings, soil types, evidence of scour, and natural obstructions.

DATA REQUIREMENTS The following data collection requirements are for the preparation of hydraulic designs. Where full hydraulic designs are not required the data collection requirements should be amended to reflect the scope of the project being undertaken. Historical Site Data The historical site data consists of previous hydraulic design reports and information on previous high water levels contained in MHI Library, Technical Standards Branch, Region and District paper and electronic files. It is to be obtained through discussion with District Maintenance Section staff, Rural Municipality staff and local residents. Historical site data consists of the following information:

• Dates and high water levels of previous flood events. • If the water flowed over the road, the location, depth and width

of the water at its peak and the length of time that water was flowing over the road.

• The period of time that information covered. For example, the flood data was obtained from observations covering the time period from 1990 to 2011.

• Information on the presence of springs and any historical issues with icing up of the culvert or ice flow blockages during the spring runoff.

Field Data Requirements The designer shall visit the site before or with the survey crew in order to determine if additional measurements are required due to the existing site conditions. During the site inspection, the designer will take the following set of standard pictures plus additional pictures as

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required or make clear sketches. The photos should be taken with a GPS enabled camera. If thick vegetation is present at the location, the crew should be notified as it may interfere with their GPS survey equipment. All survey points shall be referenced to a geodetic bench mark. Photographs:

• Structure o Panorama picture of the inlet from property line to

property line taken from the property line. o Standard picture of the inlet from the property line. o Close up of the inlet. o Picture of inside of inlet showing condition of the

structure. o Panorama picture of the outlet from property line to

property line taken from the property line. o Standard picture of the outlet from the property line. o Close up of the outlet. o Picture of inside of outlet showing condition of the

structure. • Fence lines • Road(s)

o Panorama picture of the road from the centre of the structure looking up change from property line to property line.

o Standard picture of road, from the centre of the structure looking up chainage.

o Panorama picture of the road, from the centre of the structure, looking down chainage from property line to property line.

o Standard picture of road, from the centre of the structure, looking down chainage.

o Pictures of ditch blocks, field approaches and intersecting roads within 250 m of the site. Include pictures of the inlet and outlet of any culverts installed in them.

• Stream o Panorama picture of the stream, taken from the edge of

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the road shoulder, looking up stream from edge of road to edge of road.

o Standard picture of stream looking up stream. o Panorama picture of the stream, taken from the edge of

the road shoulder, looking downstream from edge of road to edge of road.

o Standard picture of stream looking downstream. o Picture of stream bottom material (if visible). o Picture of the stream at each cross-section location.

• Section lines. • Utilities. • Upstream man-made structures that potentially could be

flooded. • Scour holes and any stream obstructions such as beaver dams

within 400 m of the structure. • Landmark.

Notes to record in survey file:

• Direction of flow if it is obvious. • Height and width of opening under bridges or wood box

culverts. Measure the height of the opening at the backing on both sides and in the channel at the deepest point. This will help in selecting the size of the new structure.

• Make a note as to whether profiles or typicals continue to rise or drop after end shots.

• Complete set of transit notes. • Note whether or not farmyards are occupied.

Existing Road Centreline Profile:

• The profiles shall be a minimum of 250 m in length in each direction from the existing structure. The profile should go far enough in each direction to establish the location of the low point on the highway in relation to the drainage basin and facilitate setting a gradeline, if a grade raise is required.

• Shots at least every 25 m.


Hydraulic Manual

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Subject:

Existing Ditch Profiles:

• Shots at least every 25 m carrying the shots through the stream channel. Additional shots shall be taken to establish the channel cross-section. The profile should go far enough to get elevation higher than highway centerline at structure.

• Make sure the profile establishes the crests in the ditches. • The profiles shall be at least 250 m in length in each direction

from the existing structure.

Natural Ground Profiles:

• The profiles shall be a minimum of 250 m and go far enough to capture dips where water could run out of the ditch.

• Shots at least every 25 metres. Take additional shots at low points and crests.

• Take the profile outside of the ditch and close to the edge of the right-of-way in order to have a profile of the natural ground slope running into the streambed.

Streambed (Thalweg) Profile:

• The profile shots shall be taken at the lowest part of the stream channel.

• The profile shall be at least 300 m to 400 in each direction from the existing structure. The profile should go far enough to establish direction of flow (extend profile to achieve a drop or rise of approximately 1 m in each direction where the terrain is flat).

• Shots shall be taken at every change of direction (include enough shots to show the shape of the bends) and change of elevation in the channel.

• The first shot is to be at the end of the structure. Shots shall be taken at a 1 m interval from the end of the structure to the property line. This will allow the definition of any existing scour holes, and will aid in establishing invert and outlet apron elevations for the new structure.

• Take extra shots immediately before and after any obstructions


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(note type in survey notes) in streambed. Also take a shot on top of obstruction as well as enough shots to show its shape. (examples, beaver dams or rock riffles)

Streambed Typical Cross Sections:

• All stream bed cross-sections shall be taken perpendicular to the stream channel. As a minimum for narrow channels, shots shall be taken on the bottom of each edge and the mid-point of the channel along with the top of the bank. For wider channels additional points are to be taken in order to give an accurate representation of the channel bottom shape. If the bank goes up in steps, additional points are to be taken in order to give an accurate representation of the bank and its top shape. The cross-sections have to extend far enough to include the top of the flood plain and the “Ordinary High Water Mark”. This is usually the edge of the pine trees in northern areas. In other parts of the province where the flood plain is wide and flat the cross-section shall extend for 100 m.

• The lowest point on the cross-sections shall be included as points on the stream channel profile.

• A typical cross-section shall be taken at the edge of the right-of-way downstream from the structure where there is no bend in the channel within the right-of-way. Where the channel bends and flows within the right-of-way, cross-sections are to be taken at the start, mid-point and end of each bend and every 15 m along the along the tangent sections.

• Cross-sections are to be taken at the start, mid-point and end of the first two bends in the channel downstream from the edge of the right-of-way and every 25 m on tangent from the edge of the right-of-way till the start of the third bend. If the third bend is further than 400 m the last cross-section is to taken at the end of the stream channel profile. If the distance between the bends is less than 25 m the tangent cross-section shall be taken at the midpoint between the two bends.

• Take cross sections at all channel obstructions for 100 m upstream and 500 m downstream. The cross sections must be taken on top of the obstructions and in the natural channel either before or after the obstructions.


Hydraulic Manual

HM 401-00

Section:


Subject:

Roadway Typical Cross Sections (Min.4):

• Take a typical cross section on each side of the existing structure. Take it as close to the existing structure as possible, keeping it away from the wingwalls and outside the steam channel.

• Take a typical cross section on one side of the existing structure showing the ditch cut.

• Typicals should extend far enough to pick up beyond the ROW edge and be on natural ground.

• Cross sections at structure centre, piers, abutments and shots at every 8 m and the key elevations: Centerline, lane and pavement edge, pavement bottom, shoulder edge, deck curb, sideslope break, crown, invert, and stream bed.

Water Levels:

• Present Water Levels on both sides of existing structure. If there is a strong flow take the shots approximately 20 m from centreline. Also if there is an obstruction in this area, take a shot just before and after the obstruction to establish the new PWL.

• High Water Level (HWL) on the upstream side of existing structure. A couple of ways to determine the HWL is to look for scouring on bridge piles or fence posts. Look for differences in growth on the banks of the streambed.

• Average Water Level. This is where the normal vegetation in the area changes to aquatic vegetation. Usually this is fairly obvious and follows the stream bed and will be at a relatively consistent elevation

Miscellaneous:

• All through grade and approach culverts must be shot and sizes recorded.

• Tie in all dry approaches including shots on the lowest part of the approach.

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Subject:

• Tie in all visible utilities, above and below ground.

Upstream Development:

• Look for manmade structures upstream which may affect the allowable headwater (houses, barns granaries, etc.). Obtain ground surface elevation at the base of the structure.

Existing Structure:

• Shots on the corners of the wood box culverts. Making sure the shots represent the elevations of the wood planking.

• Measurement of the height and width of the clear opening of the wood box culvert.

• Inverts of culvert. For wood box culvert the elevation at the mid-point of the cross-sill at the end of the wood box and the inlet and outlet aprons.

BRIDGE STRUCTURE If the structure identified for replacement is a bridge, a grid type

survey should be completed. This type of survey will be required if the existing bridge must be replaced by a bridge. For bridge survey, the following information needs to be recorded in addition to the above requirements. Existing Road Centreline Profile:

• Shots on top of existing surfacing at centreline of roadway and at both edges of pavement. Take shots at both abutments and at all piers. Include the centreline shots on the centreline profile. Provide elevation, stationing and offset for each point. As per attached drawing “Bridge Survey”.

• Take shots on top of the concrete or timber decking just outside the edge of the pavement. Take shots at both abutments and all piers. Provide elevation, stationing and offset for each point. As per attached drawing “Bridge Survey”.


Hydraulic Manual

HM 401-00

Section:


Subject:

Flood Plain Typical Cross Sections:

• Channel cross-sections at the inlet and outlet of the bridge. o Take cross-sections as close to the bridge as possible

on natural ground. i.e. cross-sections should not include points influenced by the bridge, ditch or roadway.

o Cross-sections are to extend 100 m each way from the centre of the stream. Provide stationing and elevation for each point shot. Stationing for the cross-sections must be tied to the roadway centerline profile stationing.

• Channel bed profile. o The profile is to extend 200 m upstream and

downstream from the centerline of the roadway. o Take shots along the bottom of the channel bed at 20 m

spacing. Provide stationing and elevation for each point shot. Indicate the channel bed spacing at the centre of the bridge.

• Minimum of 100 m in all 4 directions (parallel and perpendicular to the channel) and the cross section should be every 25 m, and at stream obstructions and changes in gradient. Starting the shots as close to the bridge as possible but on natural ground.

• Take enough shots to produce an accurate contour plan for the bridge location with 0.1 m intervals. Contours at 0.5 m are to be labeled. Generally contours should include an area 100 metres upstream and downstream from the bridge and 100 metres each way from centre of the channel.


Hydraulic Manual

Section 500

Design Flows

2014


HM 501-00

Hydraulic Manual Section: DESIGN FLOW METHODOLDGY Subject:

INTRODUCTION

Hydrology in its broadest sense is the study of water and addresses its occurrence, distribution, movement and chemistry. The design and operation of hydraulic structures relies on hydrology for the determination of the design flows that they must accommodate. This section presents the Ministry’s methodology and components involved in its implementation. There are three main components involved in establishing a design flow: 1. Design frequency; 2. Flow determination; and 3. Flow frequency. The processes associated with the above components are outlined in the sections below.

METHODOLOGY

Design Frequency The first step in the determination of the design flow is the establishment of the appropriate design frequency. The criterion for this is contained in section HM 502-00. Flow Determination The second step in the determination of the design flow is the establishment of the appropriate design flow for the chosen design frequency. In Saskatchewan, the Water Security Agency (WSA) is the Provincial authority in the field of hydrology. The Ministry does not have the resources to have full time hydrologists on staff, so it relies on the WSA for the determination of the design flows used in the design of hydraulic structures. The diverse topography of Saskatchewan is the result of glacial actions and is considered unique in the world. Because the resulting

Date Design Flows Page

January 31, 2014 1 of 4

Hydraulic Manual

HM 501-00

Section:

DESIGN FLOW METHODOLOGY

Subject:

topography is different than the rain erosion based topographies common to the United States and other parts of Canada, its impact must be considered in the choice of the methodology used to estimate the design flow. Of particular significance is the typical large amount of “prairie pothole” depression storage contained in the effective contributing areas of the basin in the central and southern parts of the Province. The amount of water stored in these areas varies throughout the year and between years. Depending upon the water level the same rainfall or spring runoff event can produce anything from no runoff to a flood. Within the field of hydrology there are two main methods for the establishment of a design flow for a specified design frequency. The methodologies are based either on the analysis of historical rainfall or snowfall data or are based on the analysis of historical stream gauge data. In central and southern Saskatchewan, care must be taken when using snow gauge data because the snow cover can drift for large distances in these parts of the Province. This has a significant impact on the resulting spatial distribution of the snow. Therefore, snow pack measurements or historical information on the snow pack in a drainage basin is preferable to the use of snow gauge data alone. The Ministry has standardized on the use of historical stream gauge data for the determination of design flows because it reflects the output of all of the related design factors, including those impacted by the topography. To address all of the impacts on the input side using the rainfall based design methodologies would be a significantly more complicated and expensive process. The WSA uses the following method to determine design flows. Generally, the situations they encounter involve one of three types:

• Locations with long term records; • Locations with short term records; or • Locations with no records.

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Subject:

At culvert crossings located in basins with a gauging station with long term records, the flow data is taken directly from the gauge station records. The design flows are typically transposed from the full basin to the sub-basin containing the culvert crossing. At locations where short term information is available, this information is integrated with a nearby location where long term data is available. From this, the design discharges are determined. For locations where no data is available, the design flows are transposed from nearby basins with similar characteristics and are based on contributing areas. The WSA provides a mean daily flow estimate for the site under consideration for the following flow frequencies: 1:2, 1:10, 1:25, 1:50 and 1:100 along with a peaking factor. The mean daily flow is multiplied by the peaking factor to determine the instantaneous peak flows. The WSA flow calculations carry a degree of variability. The amount of variability depends upon the relationship of the drainage basin to the basins that have gauging stations on them in the Province. Because of the variability, the Ministry requires that all of the WSA estimates be validated as being reasonable using a second approved method. The following methods are to be used. They are listed in order of preference and reliability.

• Flow through an existing structure at the study site based on an analysis of the historical headwater levels;

• Flow through an existing structure upstream or downstream of the site based on an analysis of the historical headwater levels; and

• The Rational Method.

The analysis procedure for the above methods is contained in sections HM 503-01, HM 503-02 and HM 503-03 respectively. For drainage basins smaller than 25 km2 SWA may not be able to provide a flow estimate due to the accuracy issues involved in their


Hydraulic Manual

HM 501-00

Section:


Subject:

methodology. They will let the designer know if this is the case when responding back to the request. When this occurs, the Designer will have to use one of the alternative methodologies listed above. In some situations WSA may not be able to respond in a timely manner with a flow estimate. This can be avoided by requesting design flows early in the culvert replacement programming cycle. When this cannot be avoided, the designer can obtain the gauging data from SWA and utilize the transposition of flow methodology contained in section HM 503-04.

FLOW FREQUENCY

When a flow is determined using a historical headwater level at existing structures, it must be assigned a frequency. Some judgment must be used to determine that flow frequency. The methodology to do this is contained in section HM 504-00.

FLOW CONVERSION

The calculated flow frequency, as determined above, must next be converted to the design frequency. The methodology to do this is contained in section HM 505-00.

CULVERTS REPLACING BRIDGE STRUCTURE

Where a bridge is being replaced with culverts, the design flow to be used for the new design should equal or exceed the existing bridge capacity


HM 502-00

Hydraulic Manual Section: DESIGN FREQUENCY Subject:

INTRODUCTION This section outlines the various design flow frequencies that are used in

culvert and bridge hydraulic designs. The designer must use care to ensure that they are using the correct values since instantaneous peak flows are used for culvert designs and maximum mean daily flows are used for bridge designs. The design flow frequency for fish passage is contained in section HM 900-00.

INSTANTANEOUS AND MEAN DAILY FLOWS

The difference between instantaneous peak flow and mean daily flow is the time period over which the flow is averaged and the magnitude of the peaking factor is a function of the characteristics of the drainage basin. The mean daily flow is averaged over an entire day, whereas the peak instantaneous flow is averaged over a matter of minutes. This is illustrated in Figure 502-1. The shape of the curve is dependent upon the physical characteristics of the drainage basin. This can result in the maximum mean daily flow and the peak instantaneous flow being roughly equivalent or the peak instantaneous flow may be three times or greater than the max mean daily flow.

Figure 502-1 –Typical Natural Hydrograph (SWA, 1962)


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Section: DESIGN FREQUENCY Subject:

MEAN ANNUAL FLOW

The Mean Annual Flow (Q2.33) is the average volume of water to flow through a stream per year. As such, it is a mean daily flow. It is also referred to as the bankful flow. Generally, it is the flow that defining the change from aquatic to terrestrial vegetation along the stream bank.

DESIGN FLOW The design flow for culverts use an instantaneous flow, whereas the design flow for bridges uses a mean daily flow. Refer to Table 502-1 for design flows for culverts and Table 502-2 for bridges.

Table 502-1: Culvert Design Flow Frequencies

Class of Road Design Frequency

(Instantaneous Peak Flow)

National Highway System 1/50 All Other Provincial

Highways & Provincial Roads

1/25

Other Roads 1/5 to 1/10

Table 502-2: Bridge Design Flow Frequencies

Class of Road Design Frequency (Maximum Mean

Daily Flow) Provincial Highways and Provincial Roads 1/50 to 1/100

Other Roads 1/25

The design frequency shall be increased to 1/100 where a community or area of the province would be isolated by the highway being overtopped or washed out due to hydraulic structure failure. Consideration should be given to increasing the design frequency to 1/100 for structures where extreme flooding conditions could cause excessive damage to a community immediately upstream of the culvert crossing. Note that this does not apply to individual farmyards. The protection of farmyards is governed by the allowable headwater design criteria contained in section HM 605-00.


January 31, 2014 2 of 2

HM 503-01

Hydraulic Manual Section: FLOW CALCULATION Subject: EXISTING STRUCTURES AT SITE

INTRODUCTION

The most reliable method to determine the design flow at a location is by determining the high water history of an existing installation. Valuable information can be obtained from an on-site inspection as well as interviews with local Ministry personnel, Rural Municipality staff and residents.

HIGH WATER LEVEL The historical high water levels of past floods and the years that they occurred in should be determined along with the estimated age of the culvert. Past high water levels may also be indicated in the field by high water marks such as ice scars on trees, debris and high water lines on crossing structures, earth surfaces or buildings. In addition to the interview and field information, a check of Ministry files may yield useful information at a particular location. If a problem has occurred at a site, it may be noted on the file along with the high water level and the year it occurred in. Once the high water level has been determined, an effort should be made to ensure that this high water level was not the result of a circumstance other than a capacity problem. It is possible that icing could have partially obstructed the barrel of the culvert, or debris could have partially obstructed the culvert opening. This can be checked by comparing flows with flows at upstream and downstream structures.

TAILWATER The tailwater elevation is determined based on site survey data and field observation of conditions that may affect the tailwater elevation. If survey data is not available, then field observation will have to be used to estimate a tailwater elevation and checked by doing a sensitivity analysis of the crossing using the Quick Calculator mode in CulvertMaster.

FLOW CALCULATIONS Once the high water level is known and the tailwater condition has been determined, it is possible to determine the discharge associated with the historical high water level events.


January 31, 2014 1 of 2


Section: FLOW CALCULATION Subject: EXISTING STRUCTURES AT SITE

FLOW THROUGH BRIDGES

Through the use of Manning’s Formula, it is possible to develop a velocity for flow in a natural channel. With the calculated velocity, and channel area, a discharge can then be calculated. However, this formula often results in velocities that are too high for Saskatchewan conditions. A rule of thumb for flow under bridges is to use a velocity of 1.2 m/s to 1.5 m/s multiplied by the area under the bridge. Scour immediately downstream from the bridge usually indicates that a higher value should be used. In this case the rule of thumb is to use a velocity of 1.5 m/s to 1.8 m/s. Designers are also advised to check with the Senior Bridge Project Manager in the Asset Management Section in their respective region since they have cross-sections of the stream channel on each side of the bridge that are taken during each bridge inspection. They may also have a record of design flows and unusual flows on file.

DETERMINING DESIGN FLOW

After a flow has been determined at an existing structure, it must be assigned a frequency and converted to a design frequency. Refer to section HM 504-00 and section HM 505-00 for the procedures to do this.


January 31, 2014 2 of 2

HM 503-02

Hydraulic Manual Section: FLOW CALCULATION Subject:

STRUCTURES UPSTREAM AND DOWNSTREAM

INTRODUCTION Situations occur where data from structures other than the location

under consideration should be used. An example is where a highway is being constructed on a new location across a drainage run. Design flows can be obtained from structures upstream or downstream from the proposed installation on the same drainage run. Another example is when a high water level is known at a site upstream or downstream of an installation. This can be used to determine the design flows at the site or to check the design flow being used at the site under study.

FLOW AT STUDY SITE Flow at Other Structures The first step involved in determining the flow at the study site is to determine the flow at the structure upstream or downstream from the study site. This is done by following the same procedure as for Existing Structures at Site outlined in section HM 503-01. Additional Flow The second step is to determine the flow that must be added or subtracted to the flow calculated above. The typical method is the method of transposition. First, the effective area contributing to the project site is calculated and then the effective area contributing to the other structure area is determined. Finally, the method of transposition described in section HM 503-04 is used to determine flow at the project site. If the Rational Method is being used, the following process should be followed. First, the additional contributing area can be determined from a topographic map. Next, a runoff coefficient can be obtained from HM 503-03. Finally, intensity can be obtained from Intensity-Duration-Frequency (IDF) charts and a discharge can be calculated. IDF charts are available from Environment Canada’s “National Climate Data and Information Archive” website. The discharge is either added or subtracted from the calculated flow at the upstream or downstream structure.


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Hydraulics Manual HM 503-02

Section: FLOW CALCULATION Subject: STRUCTURES UPSTREAM AND

DOWNSTREAM



January 31, 2014 2 of 2

HM 503-03

Hydraulic Manual Section: FLOW CALCULATION Subject: RATIONAL METHOD

INTRODUCTION The Rational Method is a popular method of predicting design flows

for small rural and urban watersheds without detention basins. The Ministry of Highways and Infrastructure, in keeping with TAC, has adopted an upper limit of 25 km2 (RTAC, 1982) for the use of the Rational Method. This method should only be used by designers with extensive experience in its use in rural watersheds in order to minimize errors in the estimates. As with any methodology, the results should be checked for reasonableness against information on historical flows.

ASSUMPTIONS Knowledge of the assumptions used in this method can help reduce the errors resulting from the use of this method. The following are some assumptions made by the Rational Method:

• The rainfall intensity is steady over the basin and uniform with time;

• The frequency of the flood is the same as that of the rainfall; • The peak runoff occurs when the whole basin is contributing;

and • The peak discharge at a point is a function of the average

rainfall intensity of a storm whose duration is equal to the time of concentration for that point.

LIMITATIONS Some limitations of this method are:

• The time of concentration is difficult to estimate with

reasonable accuracy and is not necessarily constant for a particular watershed under different rainfall and runoff conditions;

• The runoff coefficient is assumed to allow for all the factors that cause losses to occur. The factor is assumed to remain constant in a given basin but this is rarely true;

• The assumption of steady uniform rainfall over the entire basin becomes less valid as the size of the basin increases. This is due to the movement and pattern of rainstorms; and

• The assumption that the frequency of the rainstorm is the same as that of the resulting flood is not necessarily true especially for permeable watersheds.


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Section: FLOW CALCULATIONS Subject: RATIONAL METHOD

RATIONAL FORMULA The Rational Method is based on the Rational formula. The Rational

formula is expressed in metric as:

Q = 0.0028·C·i·A Where: Q = Required discharge (m3/s); C = Runoff coefficient (dimensionless); i = Rainfall intensity for a storm whose duration is equal to the time of concentration (mm/h); and A = Effective watershed area (ha). The time required for the entire watershed to contribute is equal to the time required for the water to flow from the furthest point in the basin to the proposed crossing. This is called the time of concentration. The runoff coefficient is discussed in further detail in HM 501-00 and the time of concentration is discussed in further detail in HM 502-00. The rainfall intensity is available from Intensity-Duration-Frequency (IDF) Curves available from Environment Canada’s “National Climate Data and Information Archive” website.

SOIL COEFFICIENTS The values of runoff coefficients (C) for use in the Rational Formula are as follows:

Table 503-03-1: Runoff Coefficients for Rural Areas (DelDOT, 2010)

Type of Drainage Area Runoff

Coefficient Concrete & bituminous pavements

0.7-0.9

Gravel roadways open 0.4-0.6 Bare earth (high value for steep slopes)

0.2-0.8

Turf meadows 0.1-0.4 Cultivated fields 0.2-0.4 Forested areas 0.1-0.2


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Table 502-03-2: Runoff Coefficients for Urban Areas

(Smith, 1995)

Type of Drainage Area

% Area Impervious

Runoff Coefficient

Flat residential area 30 0.40 Steep residential 50 0.65 Built up area 70 0.80

COMPOSITE RUNOFF COEFFICIENTS

Where the soil types or land uses within a watershed are variable, the overall runoff coefficient can be calculated from the following equation:

𝐶 = ∑(𝑤𝑎𝑡𝑒𝑟𝑠ℎ𝑒𝑑 𝑠𝑢𝑏 − 𝑎𝑟𝑒𝑎 × 𝑟𝑢𝑛𝑜𝑓𝑓 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡)

𝑇𝑜𝑡𝑎𝑙 𝑤𝑎𝑡𝑒𝑟𝑠ℎ𝑒𝑑 𝑎𝑟𝑒𝑎

TIME OF CONCENTRATION

The time of concentration is the time required for runoff to reach the site in question from the furthest point in the watershed. This varies greatly with the nature of the watershed. It is comprised of the initial subsurface flow time (mainly on sandy soils), overland flow time, and channel flow time. In relatively high runoff watersheds (C ≥ 0.40), the subsurface and overland flow times are the same as compared with the channel flow. In low runoff watersheds (C < 0.40), the subsurface and overland flow times may be larger in relation to the total time.

Branscy Williams Formula The Branscy Williams formula is used in watersheds with a C value of 0.40 or greater. It attempts to combine all three flow times in one formula:

𝑇𝑐 = 0.057𝐿𝑆𝑤0.2 ∙ 𝐴0.1

Where: Tc = Time of concentration (minutes); L = Watershed length (m); Sw = Watershed slope (%); and


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A = Watershed area (ha).

Airport Formula The Airport formula is used for watersheds with C values less than 0.40:

𝑇𝑐 = 3.26 ∙ (1.1 − 𝐶) ∙ 𝐿0.5

𝑆𝑤0.33

Where: Tc = Time of concentration (minutes); C = Runoff coefficient; L = Watershed length (m); and Sw = Watershed slope (%). When the watershed is made up of widely differing surfaces, the time of concentration should be determined for each surface and the individual values summed to give the overall time of concentration.


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HM 503-04

Hydraulic Manual Section: FLOW CALCULATION Subject: TRANSPOSITION OF FLOWS

INTRODUCTION

There are locations where no information is available on a particular stream or basin being studied. These locations generally occur where a highway is to be routed over a new location. There are also circumstances where structures exist but no flow data is available on the particular installation. However, there may be data available at another point on the stream or in an adjacent drainage basin. In situations such as this, it is often possible to transpose the flow data from the known locations to the desired location.

BASIN CHARACTERISTICS

When this method of determining a flow is used, care must be taken to ensure that the two locations have similar hydrological characteristics. Some features that influence the flow include: runoff coefficients, area, detention storage, and watershed slope. The runoff coefficient is related to the soil type and land use. The detention storage is related to the lakes and wetlands that may significantly reduce the peak rate of runoff. Finally, the slope of the watershed can significantly affect the time of concentration of a flood and therefore the peak runoff.

TRANSPOSITION OF FLOWS

If two drainage basins have similar characteristics, then the discharges from the first basin can be transposed to the second basin. To use this method, instantaneous peak discharges must be used. This means that daily discharges must be converted to instantaneous peak discharges. The instantaneous peak flows can be transposed using the following equation:

𝑄2 = 𝑄1 ∙ �𝐴2𝐴1�𝑛

;

Where: Q1 = Known discharge; Q2 = Unknown Discharge; A1 = Area of watershed for Q1; A2 = Area of watershed for Q2; and n = 0.6 to 0.75.


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Section: FLOW CALCULATIONS Subject: TRANSPOSITION OF FLOWS



January 31, 2014 2 of 2

HM 504-00

Hydraulic Manual Section: FLOW FREQUENCY Subject:

INTRODUCTION The analysis of the maximum annual discharge at a location can

usually provide one of the most accurate means of estimating design floods. However, this is dependent on the length of records available. There are two main types of frequency analyses used: Station Frequency Analysis and Regional Frequency Analysis. Station Frequency Analysis is where flow records at one station are used either to estimate a design discharge or to assign a frequency to a discharge. Regional Frequency Analysis is where flow records from a number of stations are used to determine regional frequency relationships. Water Security Agency (WSA) also provides frequency analyses for given runoffs.

PROCEDURE The following method can be used to determine the frequency of a discharge where some records are available.

1. List the maximum annual discharges in chronological order. It is desirable to have a minimum of ten years of records.

2. Rank the annual flows in order of decreasing magnitude, i.e., largest discharge = 1, second largest = 2, etc.

3. Calculate the return period or frequency for each annual flood: F = (n+1)/m, Where:

F = Frequency or return period; n = Number of years of records; and m = Ranking of flood.

Normally, the data used should belong to the same statistical population. This means that it should be all snowfall runoff data or rainfall data, but not a combination of both. There are normally three situations that may occur. The first situation is where only the data for the period of records is known. In this case, the procedure listed above is used. The second situation is when a recorded flood is known to be the largest which occurred over a longer time n than on record but it


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Section: FLOW FREQUENCY Subject:

occurred within the period of records. Its return period is taken as n and the next highest flood is assigned a ranking of 2. The third situation is when the largest flood occurred over a period of time n longer than the period of records and outside the period of records. Its return period is n + 1, but the largest value from the period of records has a ranking of 1. Frequency curves should not be extrapolated by more than twice the period of records.

WATER SECURITY AGENCY ESTIMATES

Another method of obtaining a frequency for a desired flow is to obtain the information from WSA. WSA will determine a frequency for a particular rainfall or snowmelt runoff where they have records when requested.


January 31, 2014 2 of 2

HM 505-00

Hydraulic Manual Section: FLOW CONVERSION Subject:

INTRODUCTION The final step in the procedure after a flow has been determined at a

location and a frequency assigned to it is to convert the calculated flow to a design discharge based on the design frequency. The design frequency to be used is listed in section HM 502-00 based on the class of highway. The methods to be used to convert a calculated flow into a design discharge are listed below. They are listed in order of preference and reliability.

• Water Security Agency (WSA) estimates; • Station Frequency Analysis Method; or • Frequency Chart Method.

WATER SECURITY AGENCY ESTIMATES

In addition to giving a return period for a known flow, WSA will also give a design discharge for the desired frequency based on the known discharge. The method used is to determine the frequency of the flow based on a regional discharge analysis and determine the design discharge for the desired frequency, either through extrapolation or through actual data if records are available.

STATION FREQUENCY ANALYSIS

Section HM 504-00 showed how a recorded number of discharges could be used to determine the return period for each recorded flow. This information can then be used to determine a design discharge based on the recorded data at that location. The following method can be used:

1. Plot the return period frequency versus discharge for data available on whatever probability paper gives a straight line. An example is shown in Figure 505-1.

2. Read off the discharge corresponding to the required return period.

FREQUENCY CHART Provincial frequency charts have developed to convert a discharge of a

known frequency to a design frequency when the other two methods cannot be used. Figure 505-2 is used for culvert design while figure 505-3 is used for bridge design. Both figures work the same way. You go up from the flood frequency to the line and then across to the frequency factor. For example in Figure 505-2 the frequency factor for a flood frequency of 10 is 1.0.


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Section: FLOW CONVERSION Subject:

Figure 505-1: Example Station Frequency Based on Period 1966 – 1986 (SWA, 1987)

In Figure 505-3, there are two relationships depending on the steepness of the channel. For channels with a profile steeper than 1:1000, the red line should be used. For channels with a profile less than or equal to 1:1000, the green line should be used The frequency factors for the discharge and the design frequency are determined from the appropriate figure. The discharge is then multiplied by the frequency factor for the design frequency and divided by the frequency factor for the discharge. For example using Figure 505-2 to convert a discharge of 17 m3/s with a frequency of 40 years to a design frequency of 25 year.

𝑄25 =17 ∗ 𝐹𝐹25𝐹𝐹40

=17 ∗ 1.48

1.78= 14.13

0

40

80

120

160

200

240

280

320

1 10 100

Dis

char

ge (m

3/s)

Return Period (Years)


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Figure 505-2: Frequency Chart for Culverts (Peak Instantaneous Flows) (PFRA)


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Figure 505-3: Frequency for Bridges (Mean Annual Flows) (WSA)

0.1

1

10

1 10 100

Freq

uenc

y Fa

ctor

Flood Frequency (years)

Steeper than1:1000 Flat Gradient


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Hydraulic Manual

Section 600

Culvert Hydraulics

2014


HM 601-00


FACTORS AFFECTING DISCHARGE

Although the drainage culvert is an outwardly simple hydraulic structure, the hydraulics can be surprisingly complex. This is due to the fact that the discharge can be a function of the following variables:

• Head; • Headwater; • Tailwater; • Pipe Diameter; • Inlet Geometry; • Length of Culvert; • Slope of Culvert; and • Culvert Roughness (Manning’s n).

TYPES OF FLOW There are two major classifications of hydraulic flow, referred to as

inlet control and outlet control. Separate design procedures are presented for inlet and outlet control.

For inlet control, the discharge is governed by the size of the pipe, the geometry of the inlet, and the headwater level. Inlet control is independent of the pipe length, slope, roughness, and tailwater level. A culvert flowing with inlet control, characterized by shallow, high-velocity flow for all portions of the pipe is categorized as “supercritical.”

For outlet control, the pipe flows full for all or part of its length. In this case, the pipe length, slope, roughness, tailwater level, and inlet geometry affect the discharge. If conditions are favorable for both inlet and outlet control simultaneously, the governing discharge is the lesser of the two. This is because the pipe cannot pass more discharge than the inlet allows, nor can the inlet pass more discharge then the remainder of the pipe can handle. A culvert flowing in outlet control will have a relatively deep, lower velocity flow termed “subcritical” flow.

WOOD BOX CULVERT DESIGN

There are unique aspects to the wood box culverts used by the Ministry. The designer shall refer to section HM 611-00 for the design procedures specific to wood box culverts.

Date Culvert Hydraulics Page

January 31, 2014 1 of 2



FISH PASSAGE DESIGN There are specific requirements for fish passage design. The designer

shall refer to section HM 900-00 for the design requirements specific to culverts requiring design for fish passage.

Date Culvert Hydraulics Page January 31, 2014 2 of 2

HM 602-00

Hydraulic Manual Section: DESIGN CONSIDERATIONS Subject:

INTRODUCTION In the production of good culvert designs the designer needs to

understand what makes up a good culvert design and to follow the criteria for culvert design that are contained in this section.

WHAT MAKES A GOOD CULVERT

The following is an excerpt taken from the Corrugated Steel Pipe Institute Canadian Edition (2007) Handbook of Steel Drainage and Highway Construction Products concerning recommendations for “Attributes of a Good Highway Culvert”:

1. The culvert, appurtenant entrance, and outlet structures properly take care of water, bed-load, and floating debris at all stages of flow.

2. It should cause no unnecessary or excessive property damage.

3. Normally, it should provide for transportation of material without detrimental change in flow pattern above and below the structures.

4. It should be designed so that future channel and highway improvement can be made without too much loss or difficulty.

5. It should be designed to function properly after fill has caused settlement.

6. It should be designed to accommodate increased runoff occasioned by anticipated land development.

7. It should be economical to build, hydraulically adequate to handle design discharge, structurally durable, and easy to maintain.

8. It should be designed to avoid excessive ponding at the entrance which may cause property damage, accumulation of drift, culvert clogging, saturation of fills, or detrimental upstream deposits of debris.

9. Entrance structures should be designed to screen out material which may not pass through the culvert, to reduce entrance


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Section:

DESIGN CONSIDERATIONS

Subject:

losses to a minimum, to make use of the velocity of the approach insofar as practical, and to facilitate channel flow entering the culvert by use of transitions and increased slopes.

10. The design of culvert and outlet should be effective in reestablishing tolerable non-erosive channel flow within the right-of-way or within a reasonably short distance below the culvert.

11. The outlet should be designed to resist undermining and washout.

12. Energy dissipaters, if used, should be simple, easy to build, economical, and reasonably self-cleaning during periods of easy flow.

CRITERIA FOR CULVERT DESIGN

There are a number of important criteria to consider when doing a hydraulic design. These are:

• The most economical structure is the smallest culvert flowing under maximum head.

• Design in a range of 1.5 ≤ HW/D ≤ 2.0. • The design flow is a predetermined value and the same value

shall be used for all alternatives. • A single installation is generally more economical than

multiple pipes. • The designer should, wherever possible, design culverts so that

hydraulic jumps do not occur in the culvert barrel. Where it is not possible to avoid this condition, the design must be approved through the design exception process.

• Where multiple culverts are required the culverts should be the same diameter.

Date Culvert Hydraulics Page January 31, 2014 2 of 2

HM 603-00

Hydraulic Manual Section: INLET CONTROL Subject:

INTRODUCTION A culvert flowing in inlet control has shallow, high velocity flow

categorized as “supercritical” flow. For supercritical flow, the control section is at the inlet. Figure 603-1 below depicts several different examples of inlet control flow. The type of flow depends on the submergence of the inlet and outlet ends of the culvert. Depending on the tailwater condition, a hydraulic jump may occur downstream of the inlet.

Figure 603-1: Types of Inlet Control (FHWA, 2005)

(a) Inlet Unsubmerged, Outlet Unsubmerged

(b) Outlet Submerged, Inlet Unsubmerged

(c) Inlet Submerged

(d) Outlet Submerged


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Section: INLET CONTROL Subject:

FIGURE 603-1 NOTES

Figure 603-1 (a) depicts a condition where neither the inlet nor the outlet ends of the culvert are submerged. The flow passes through critical depth just downstream of the culvert entrance and the flow in the barrel is supercritical. The barrel flows partly full over its length, and the flow approaches normal depth at the outlet end. Figure 603-1 (b) shows that submergence of the outlet end of the culvert does not assure outlet control. In this case, the flow just downstream of the inlet is supercritical and a hydraulic jump forms in the culvert barrel. Figure 603-1 (c) is a more typical design situation. The inlet end is submerged and the outlet end flows freely. Again, the flow is supercritical and the barrel flows partly full over its length. Critical depth is located just downstream of the culvert entrance, and the flow is approaching normal depth at the downstream end of the culvert. Figure 603-1 (d) is an unusual condition illustrating the fact that even submergence of both the inlet and the outlet ends of the culvert does not assure full flow. In this case, a hydraulic jump will form in the barrel. The median inlet provides ventilation of the culvert barrel. If the barrel was not ventilated, sub-atmospheric pressure could develop which might create an unstable condition during which the barrel would alternate between full flow and partly full flow.

INLET CONFIGURATION

Since the control is at the upstream end in inlet control, the inlet configuration affects the culvert performance. Inlet Area The inlet area is the cross-sectional area of the face of the culvert. Generally, the inlet face area is the same as the barrel area, except for some types of tapered inlets. Tapered inlets are not a standard end treatment for Ministry culvert designs and should not be confused with the tapered, sloped and flared end treatments discussed in section HM 610-00. For an explanation of tapered inlets, refer to Hydraulic Design Series Number 5 (FHWA, 2005).


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Inlet Edge Configuration The inlet edge configuration describes the entrance type. Some typical inlet edge configurations are thin edge projecting, mitered, square edges in a headwall, and beveled edge. Entrance loss coefficients may be found in section HM 608-00. Inlet Shape The inlet shape is usually the same as the shape of the culvert barrel except for some types of tapered inlets.

CALCULATIONS When the culvert discharges under inlet control while the head above the invert is less than the pipe diameter, the inlet is basically a weir with a circular cross-section and a thin re-entrant-type crest. The weir equation applies:

Q = K·Hn. However, unlike the case for a simple rectangular weir, the coefficient K and exponent n are not constant, but are functions of the head. This occurs because the shape of the water prism and the effect of the inlet vary with the depth of flow. The coefficient and exponent in the equation above cannot be determined analytically and the equation is not used in practice. Instead, the specific weir flow equations used in design are empirical equations developed as a result of model tests. The inlet control equations are described in the FHWA Hydraulic Design Series Number 5 – Hydraulic Design Of Highway Culverts and cover most of the design situations encountered in the Province. The exceptions are where the analysis includes end treatments from section HM 608-00 that are not included in the CulvertMaster Library. The exceptions are the Flared (Armtec Style) and the Cylinder end treatments. Refer to section HM 608-00 for the analysis procedure.

OUTLET VELOCITY Under inlet control conditions, the outlet velocities for culverts will be approximately equal to the mean velocity of flow in the culvert. This can be computed through iteration using the Manning’s equation and estimating the normal depth of the pipe. The normal depth is the


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depth of water in the pipe that the water approaches if the pipe is infinitely long. Normal depth is illustrated in Figure 603-2 below. If the flow is supercritical, the velocity will be higher than that provided for with an end area calculation. Supercritical flow in conjunction with steeply sloping culverts will result in problems associated with negative pressures at the inlet and slug flow in the barrel and should be avoided.

Figure 603-2: Outlet Velocity for Inlet Control (FHWA, 2005)


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HM 604-00

Hydraulic Manual Section: OUTLET CONTROL Subject:

Figure 604-1: Types of Outlet Control (FHWA, 2005)

(a) Inlet Submerged, Outlet Submerged

(b) Inlet Unsubmerged, Outlet Submerged

(c) Inlet Submerged, Barrel Full, Outlet Unsubmerged

(d) Inlet Submerged, Outlet Unsubmerged

INTRODUCTION

Culverts flowing under outlet control can flow with the barrel part full or completely full for part or all of the barrel length. Figure 604-1 below illustrates culverts flowing full and part full under outlet control.


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Section: OUTLET CONTROL Subject:

(e) Inlet Unsubmerged, Outlet Unsubmerged

FIGURE 604-1 NOTES Figure 604-1 (a) represents the classic full flow condition, with both

inlet and outlet submerged. The barrel is in pressure flow throughout its length. This condition is often assumed in calculations, but seldom actually exists. Figure 604-1 (b) depicts the outlet submerged with the inlet unsubmerged. For this case, the headwater is shallow so that the inlet crown is exposed as the flow contracts into the culvert. Figure 604-1 (c) shows the entrance submerged to such a degree that the culvert flows full throughout its entire length while the exit is unsubmerged. This is a rare condition: it requires an extremely high headwater to maintain full barrel flow with no tailwater. The outlet velocities are usually high under this condition. Figure 604-1 (d) is more typical. The culvert entrance is submerged by the headwater and the outlet end flows freely with a low tailwater. For this condition, the barrel flows partly full over at least part of its length (subcritical flow) and the flow passes through critical depth just upstream of the outlet. Figure 604-1 (e) is also typical, with neither the inlet nor the outlet end of the culvert submerged. The barrel flows partly full over its entire length, and the flow profile is subcritical.

FACTORS INFLUENCING OUTLET CONTROL

All of the factors influencing the performance of a culvert in inlet control also influence a culvert in outlet control. In addition, the barrel characteristics affect culvert performance in outlet control. The barrel area is the cross-sectional area of the culvert. The barrel shape is the general shape of the barrel: this is most commonly circular,


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elliptical, or rectangular. Whenever there is a change in the barrel area or shape, there is an additional loss, and the possibility of an additional control section with the barrel.

HEADWATER DEPTH CALCULATION

The headwater depth can be determined from one equation for all outlet conditions:

HW = H + ho - L·So Where: H = Head (m); ho = Outlet datum (m), see Section HM 607-00; L = Length of the culvert (m); and So = Slope of the culvert.

Figure 604-2: Schematic of Determination of Headwater Depth (AISI, 1984)

DETERMINATION OF HEAD FOR FULL FLOW

The head or energy required to pass a given discharge through a culvert in outlet control with full flow can be expressed by the following equation:

𝐻 = 𝐾𝐿 ∙𝑉2

2∙𝑔 .


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In the above equation, KL is the all-inclusive loss coefficient, given by:

KL = Ke + Kd + Kf + Ko, Where: Ke = Entrance loss coefficient; Kd = Development loss coefficient, Kf = Friction loss coefficient; and Ko = Outlet loss coefficient.

ENTRANCE LOSS COEFFICIENT

The entrance loss depends on the geometry of the culvert inlet. It is comprised of some excess local friction losses and an eddy loss associated with the re-expansion of the contracted jet at the barrel entrance. The entrance loss coefficients listed in the FHWA Hydraulic Design Series Number 5 – Hydraulic Design Of Highway Culverts (HDS-5) and in the CulvertMaster Library cover most of the design situations encountered in the Province. The exceptions are where the analysis includes end treatments from section HM 608-00 that are not included in the CulvertMaster Library. The exceptions are the Flared (Armtec Style) and the Cylinder end treatments. Refer to section HM 610-00 for guidance on how to deal with these end treatments.

DEVELOPMENT LOSS The development loss is based on research conducted by Dr. C.D. Smith of the University of Saskatchewan on the effect of annular ends on helical pipe for the Ministry. This loss coefficient is not included in HDS-5 or the CulvertMaster program. The development head loss is a loss that occurs in helical pipes due to the greater than normal barrel resistance near the pipe inlet where the spiral flow is not fully developed. After the flow acquires its maximum spin, the rate of barrel friction loss is at a minimum. The development head loss coefficient Kd is a function of the helix angle. It is zero for corrugated pipe (θ = 90o), and tends to zero for very flat helix angles. It is at a maximum in the 70o to 80o range of helix angles. The effect of the coefficient increases as the pipe section lengths decrease.


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This term is not significant for pipe diameters greater than 600 mm and can result in up to a 7% reduction in capacity for 600 mm helical culverts. Rather than adjusting Manning’s n values to account for the presence of annular corrugations the pipe capacity is calculated in the normal manner, assuming no annular corrugations and a reduction factor is applied manually to the resulting capacity. Where annular 600 mm CSP culverts are being replaced by helical CSP culverts a reduction capacity of 7% is to be applied.

BARREL FRICTION LOSS

The barrel friction loss is the energy required to overcome the roughness of the culvert barrel. Manning’s n values are found in section HM 609-01. The value for barrel friction loss can be calculated from Manning’s equation:

𝑘𝑓 = 2 ∙ 𝑔 ∙ 𝑛2 ∙ 𝐿𝑅4/3;

Where: kf = Barrel friction loss; g = Gravitational Constant (9.81 m/s2); n = Manning’s roughness coefficient; L = Length of the culvert (m); and R = Hydraulic radius (D/4 for a circular section) (m).

OUTLET LOSS The final component of the inclusive loss coefficient is the outlet loss Ko. This loss is due to the expansion of the jet at the culvert outlet. This value has been determined to be nearly 1.0 in all cases.

CALCULATION OF FLOW OR HEADWATER FOR PART FULL FLOW

For a culvert flowing part full throughout under outlet control, the water surface profile must be calculated through the culvert to determine the head required to pass the flow. The procedure on how to undertake this analysis is outlined in HDS-5. Alternatively the following analysis procedure can be used.


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Starting with the depth at the outlet (the greater of critical depth or tailwater), the water surface profile is evaluated by the Step Method to determine the flow depth inside the inlet. At this point, the velocity head and the inlet loss is added to the flow depth to determine headwater. This has been done to determine the headwater values for outlet control for part full pipes assuming outlet depth is equivalent to critical depth. Inlet loss coefficients for part full flow are assumed to be the same as for full flow. Friction losses are calculated using a variable Manning’s n value, as follows:

• n = 0.024 for flow depth ≤ 0.5∙D; and • n = value for a full helical pipe for flow depth ≥ 0.8∙D

For the case where the pipe flows part full for a portion of its length under outlet control as illustrated in Figure 604-1 (d), the head and headwater are determined by using the Step Method as used in part full flow throughout to determine the point at which full flow occurs. At this point, the principles of full flow are applied for the remaining pipe length to determine the head and headwater.

CALCULATION OF FLOW OR HEADWATER FOR FULL FLOW

For full flow conditions illustrated by Figures 603-1 (a) and 603-1 (b), the head (H) required to pass a given discharge can be determined form the following equation:

𝐻 = �𝐾𝑒 + 𝐾𝑓 + 𝐾𝑑 + 𝐾𝑜� ∙𝑄2

2 ∙ 𝑔 ∙ 𝐴2.

The headwater (HW) can be determined from the equation:

𝐻𝑊 = 𝐻 + ℎ𝑜 − 𝐿 ∙ 𝑆𝑜R. The discharge (Q) for a given head (H) can be determined from the equation:

𝑄 = 𝐴 ∙ �2∙𝑔∙𝐻𝐾𝑒

.


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OUTLET VELOCITY Under outlet control conditions, the mean velocity at the outlet of the

culvert will equal the discharge divided by the flow area. If Froude’s number is greater than or equal to 2, or if the tailwater depth is greater than the diameter of the pipe, this area will equal the pipe area. This is because the pipe will be flowing full. If Froude’s number is less than 2, or if the tailwater depth is less than the diameter of the pipe, the flow area will be less than the pipe area. This is because the pipe will not be flowing full at the outlet. In this situation, the height of water in the pipe to be used is:

• The critical depth if the tailwater is below the critical depth; or • The tailwater depth if the tailwater is above the critical depth but

below the diameter. These three situations are illustrated in Figure 604-2 below.

Figure 604-2: Outlet Velocity for Outlet Control (FHWA, 2005)


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January 31, 2014 8 of 8

HM 605-00

Hydraulic Manual Section: ALLOWABLE HEADWATER Subject:

INTRODUCTION The purpose of this section is to provide guidance on the

determination of the headwater elevation that will be allowed while taking into consideration the impacts on the highway embankment and development upstream.

DESIGN CRITERIA The allowable headwater elevation is the maximum permissible elevation of the headwater at the design discharge. It may also be referred to as the design high water level and is based on whichever of the following conditions generates the lowest elevation:

• A certain permissible freeboard below the proposed height of fill. This freeboard is 0.3 m below the subgrade shoulder elevation at the lowest point on the grade line in the vicinity of the culvert crossing. The culvert crossing should be offset from the low point to reduce the likelihood of an overtopping flood event failing the culvert crossing.

• The elevation of permissible flooding upstream. Care should be taken to ensure that developments (i.e., dwelling unit, out building and wells) upstream a fair distance will not be flooded. This could occur when the slope of the land is very flat or the structures are adjacent to the crossing. The permissible freeboard below the foundation elevation of developments such as farm yards is shown in Table 605-1.

Table 605-1: Development Freeboard Requirements Desirable (m) Minimum (m) Dwelling Units 1.0 0.3 Yard Buildings and Wells 0.3 0

Sheds and Bins 0 0

• Some lesser headwater depth as governed by other design considerations or Ministry policy (i.e., ditch block).

• The allowable headwater elevation in locations with high fills is two times the culvert diameter. This is to reduce the risk of culvert piping failures and damage to the embankment resulting from high water elevations against high fills.


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Section: ALLOWABLE HEADWAER Subject:



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HM 606-00


CULVERT LENGTHS AND MINIMUM DIAMETERS

Subject:

INTRODUCTION This section contains guidance on how to properly calculate the

culvert length and the minimum standard culvert diameters. Additional information is provided on how the method for establishing the culvert length impacts the embankment sideslope at the culvert ends.

DESIGN APPROACH The Ministry has taken the approach of indenting the culverts into the sideslope. This requires that the sideslope be adjusted at the culvert ends. This is done by using a 2:1 slope that intersects the culvert end 2/3D down from the crown and extending it until it intersects the embankment sideslope. The transition from the 2:1 slope to the embankment sideslope shall start at the outside edge of the erosion protection (1D from outside edge of pipe) and shall have a maximum slope of 3:1. The amount that the culvert is indented varies with the embankment sideslope standard.

CULVERT LENGTHS Lengths of culverts with projecting ends are calculated on the following basis:

• For 2:1 sideslopes, the length shall be such that the sideslope intersects the pipe at a point equal to half the diameter above the outlet and inlet invert elevations. In the case of pipe arches, the point of intersection is at ½ the rise.

• For sideslopes flatter than 2:1 and up to 4:1, the length shall be such that the sideslope intersects the pipe at a point 2/3 of the diameter above the outlet and inlet invert elevations. In the case of pipe arches, the point of intersection is 2/3 of the rise.

• For sideslopes flatter than 4:1, the length shall be such that the sideslope intersects the pipe at the outlet and inlet crown elevations.

The calculated culvert lengths are rounded up to the nearest meter.


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Section:

CULVERT LENGTHS AND MINIMUM DIAMETERS

Subject:

MIMIMUM DIAMETER OF CULVERTS

The minimum size of corrugated steel culvert for use in through grade culverts is 800 mm. The minimum size for concrete and high density polyethylene pipe is 750 mm. This has been established to allow for the future sleeving of the culvert, and improved efficiencies in the operational maintenance of the culverts. The minimum size of corrugated steel culvert for use in approaches is 500 mm. The minimum size for concrete and high density polyethylene pipe is 375 mm. It is typically not cost effective to sleeve approach culverts so no size allowance has been made for this.


January 31, 2014 2 of 2

HM 607-00

Hydraulic Manual Section: TAILWATER Subject:

INTRODUCTION Tailwater is the depth of water just downstream of the culvert outlet

measured with respect to the culvert outlet invert elevation. It has no effect on the culvert capacity under inlet control but it is an important factor in determining culvert capacity under outlet control. Tailwater may be caused by the hydraulic resistance of the stream channel, a natural or manmade obstruction in the channel, or a large body of water such as a lake.

VARYING TAILWATER Where the tailwater is caused by the hydraulic resistance of the stream channel or a natural or manmade obstruction in the channel, its value changes with the flow. The height variation at channel obstructions will usually be less than for the natural channel. An example of a natural obstruction is a beaver dam while a weir is an example of a manmade obstruction. Where the tailwater is caused by the hydraulic resistance of the stream channel the designer has to identify the downstream cross-section that most restricts flow. This may include a point in the stream profile where the channel is locally elevated or a point in the stream profile where the channel narrows.

CONSTANT TAILWATER

A constant tailwater condition exists when the body of water that is backwatering the culvert is large enough that the culvert flow does significantly change the water elevation. Lake elevations change with time, so the design has to determine the appropriate elevation to use in the analysis. This is usually taken as the historic high water level for the lake.

BEAVER DAMS If there is a beaver dam present, then there are two scenarios to consider. When determining the capacity of the culvert structure, use the tailwater elevation with the beaver dam present. This is a conservative approach which considers the effect that the beaver dam has on decreasing the capacity of the culvert. When calculating the outlet velocity for the purpose of fish passage design or the determination of the outlet riprap apron length, use the


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Section: TAILWATER Subject:

tailwater elevation resulting from an analysis of the hydraulic resistance of the channel assuming that the beaver dam is not present. This is a conservative approach which considers the effect that the beaver dam has on decreasing the outlet velocity and the fact that beaver dams are not permanent structures.

HEIGHT OF TAILWATER AT OUTLET

To determine the height of the tailwater at the outlet, first identify the controlling cross-section in the stream channel. Next calculate the height of water at that location using Manning’s equation. For a precise calculation of the height of tailwater at the outlet, a backwater calculation of the M2 water surface profile is required from the controlling cross-section to the culvert outlet. The backwater calculation is usually not done in practice because the impact on the height is small and the result is conservative since the M2 backwater curve decreases with distance. When using CulvertMaster use the Natural Channel Method selection and input the controlling cross-section into the program.

DESIGN IMPACT The tailwater elevation affects the determination of the reference level, ho, used as the starting point in to determine the headwater height. The tailwater does not have any impact on the culvert capacity if the tailwater depth is less than the critical depth at the culvert outlet. A quick check to see if the tailwater elevation is less than the critical depth is to calculate the Froude Number. The critical depth will almost invariably exceed the tailwater depth where the Froude Number (Q/D5/2) is less than 2. This can then be confirmed from the CulvertMaster run output. The reference level, ho, is the effective position of the hydraulic grade line at the outlet. It represents the elevation above the invert at the outlet where the hydraulic grade line, if extended downstream, would intersect the plane of the outlet. It is called the “effective position” because it cannot always be seen or even read with a piezometer at the outlet. The value of the reference level depends on the discharge in the pipe and the degree of submergence by tailwater at the end. This is expressed as dt/D, where dt is the tailwater depth above the invert at the outlet. The effect is shown in Figure 607-1


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Up to a Froude Number value of approximately 2, a culvert will not flow full at the outlet end unless submerged by tailwater. The level of the free liquid surface near the end of the pipe is the elevation of the hydraulic grade line. This level cannot drop below the critical depth regardless of how low the tailwater level may be. Hence, in the small discharge range of a Froude number less than 2, the reference level is either critical depth or the tailwater depth, whichever is greater. Since the critical depth curve initially rises quite steeply and the tailwater is normally shallow for small flows, the critical depth will almost invariably exceed the tailwater depth in this range.

Figure 607-1: Effective Position of Hydraulic Grade Line at a Culvert Outlet (Smith, 1995)

According to the theory of critical flow, a circular section can never

flow full because the discharge required for full flow is infinitely great. In fact, the pipe begins to flow full right to the end when the Froude Number exceeds a value of approximately 2. Although critical depth can still be calculated mathematically for larger flows, it has no significance for determining the reference level because the character of


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the flow is completely changed. For example, at a high discharge (Froude’s Number is 5) and no tailwater (dt/D = 0), the hydraulic grade line intersects the outlet at the center of the pipe (that is, ho/D = 0.5). This is because the pressure in the discharging jet is atmospheric and the reference point is at the centre of gravity of the jet. Accordingly, there is a transition from the critical depth line at approximately a Froude’s Number of 2 to a reference level of 0.5 at a Froude Number of 5. This is shown by the lower curve on Figure 607-1. Tailwater submergence, however small, exerts a hydrostatic pressure at the discharge end of the pipe. This increases the pressure in the discharging jet to a value above atmospheric and elevates the effective position of the hydraulic grade line. This effect is shown by the family of transition curves for various tailwater depth ratios. Of course, if the tailwater depth equals or exceeds the pipe diameter, then ho/D = dt/D.

Tailwater Below The Crown Of The Culvert A problem in culvert design, particularly for small culverts on minor drainage systems, is that the tailwater depth is usually unknown. Further, the cost of a channel survey to determine the tailwater depth cannot be justified, so the designer is faced with selecting a culvert without having this information. However, it is unlikely that the outlet will be submerged for an installation with one culvert. It is equally unlikely that there will be zero tailwater: there must be some tailwater if the culvert invert is set at bed grade elevation. Typically the tailwater depth at design discharge is somewhere between the center and the crown of the pipe. A common procedure in practice is to arbitrarily take the reference level equal to the calculated critical depth, shown by the dashed portion of the critical depth line on Figure 607-1. This may be high for most cases, but in the absence of exact knowledge, a conservative assumption is necessary.

Tailwater Above The Crown Of The Culvert When the tailwater elevation is known and it is at or above the culvert outlet, the reference level is equal to the tailwater elevation. If the tailwater depth is less than the critical depth, Figure 607-1 applies.


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HM 608-00

Hydraulic Manual Section: END TREATMENTS Subject:

INTRODUCTION This section provides guidance on the proper selection of end

treatments to use and the selection of the proper inlet loss coefficient. Culvert end treatments are used for a variety of purposes. End treatments may be used to improve inlet hydraulic efficiency, to improve safety for vehicles that run off the road, to control drainage, and to control beaver dam construction in culverts. End treatments improve the hydraulic efficiency by reducing the flow constriction that occurs at the culvert inlet. It is important that the culvert, appurtenant entrance, and outlet structures all properly take care of water, bed load, and floating debris at all stages of flow. This may preclude the use of end treatments in some situations.

END SECTION STANDARDS

All culverts with a diameter equal to or greater than 3 m are to be designed with concrete collars on the inlet to prevent inlet damage and failures. The standard end treatment for undivided highways are specified below:

• For corrugated steel pipe (CSP): Projecting end section Figure 608-1 (a). The Ministry does not allow the projecting end sections to be cut to create a tapered or stepped taper end treatment Figures 610-1 (b) and (c). These types of ends are structurally weaker and have poorer hydraulic performance.

• For round concrete pipe (RCP): Grooved end section Figure 608-1 (d). The grooved or socket end of the pipe is always placed at the inlet end of the culvert. The installation of RCP always begins at the outlet end to ensure the proper seating of the joints.

• For High Density Polyethylene (HDPE): Projecting end-section.

• For smooth walled steel pipe (SWSP): Projecting end section. • The standard for approaches is not to use supplementary end

treatments.


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Section: END TREATMENTS Subject:

The standard end treatment on divided highways is the same as undivided except for the following; these treatments are provided due to the higher number of errant vehicles entering the median compared to the side ditches:

• A flared end section on the median end of the culverts up to 2400 mm diameter or 2130 mm span x 1460 mm rise for pipe arches Figure 608-1 (e).

• End section treatment for median crossing culverts: o CSP: Sloping or safety end section Figure 608-1 (f).

Safety bars shall used on sizes larger than 800 mm. Slope to be 6:1.

o RCP: Flared end section.

END SECTION MATERIALS

Depending upon the end treatment type, they can be constructed out of steel, concrete or plastic. It is not required to match the end treatment material type to the culvert as long as a competent attachment system is employed. Steel end section components are required to be galvanized. There are pros and cons associated with each of the material types. It is up to the designer to weigh the risks and benefits associated with each when specifying the material type for use in each installation.

HYDRAULIC EFFICIENCY IMPROVEMENTS

The hydraulic efficiency of the culvert can be improved through the addition of an appropriate end treatment to the inlet for both inlet and outlet control. End treatments that may be used to increase hydraulic efficiency include headwalls Figure 608-01 (h), flared inlets, and cylinder inlets. The Senior Road Design Engineer should be consulted when considering the use of end treatments to improve the hydraulic efficiency. The flared end treatment for part full flow with the inlet unsubmerged the streamlining effect of the inlet gives some increase in hydraulic efficiency, but much of this benefit is lost when the pipe becomes submerged because the end section does not extend around the crown of the pipe.


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Figure 608-1: End Treatments

a) Projecting1 b) Tapered1

c) Stepped Taper1 d) Grooved

e) Flared1 (Armtec Style) f) Sloped (with safety bars)2

g) Cylinder1 h) Headwall 1 – Smith, 1995 2 – Armtec, 2011 Date Culvert Hydraulics Page

January 31, 2014 3 of 6



The use of the cylinder end treatment Figure 608-1 (g) (developed by

Smith for the Ministry) gives minimal benefit when the inlet is not submerged but gives a significant increase in flow when submerged. A common inlet is used for the culvert and the cylinder. The cylinder diameter is approximately 1.25D in diameter, and extends upstream 0.2D in front of the normal inlet. A crescent shaped steel plate can be welded in place to seal the space between the cylinder and the pipe, or the cylinder can be telescoped a short distance overt the pipe and the annulus sealed with concrete.

INLET CONTROL CALCULATIONS

The inlet control equations are described in the FHWA Hydraulic Design Series Number 5 – Hydraulic Design Of Highway Culverts and cover most of the design situations encountered in Province. The appropriate value is chosen from the pick list in CulvertMaster. The exceptions are where the analysis includes end treatments that are not included in the CulvertMaster Library. The exceptions are the flared (Armtec Style) and the cylinder end treatments. The analysis of the flared and cylinder and end treatments is based on the model research undertaken by Dr. C.D. Smith at the University of Saskatchewan. Use Figure 608-2 to determine the Headwater elevation for the Flared and Cylinder end treatments.


January 31, 2014 4 of 6



Figure 608-2: End Treatments Analysis Under Inlet Control (Smith)

Table 608-1: Entrance Loss Coefficients

Inlet Type Ke Flared 0.61

Cylinder 0.31

Safety Grate on Sloped 0.92

1 – Smith, 1995 2 – FHWA, 2004

OUTLET CONTROL CALULATIONS

The end treatment inlet loss coefficients contained in CulvertMaster cover most of the design situations encountered in the Province. The appropriate value is chosen from the pick list in CulvertMaster. The exceptions are where the analysis includes end treatments are not included in the CulvertMaster Library. The exceptions are the Flared, (Armtec Style), Safety Grate on Sloped, and the Cylinder end treatments. The entrance loss coefficients for these end treatments are shown in Table 608-1. These values have to be entered in from the keyboard instead of using the pick list.


January 31, 2014 5 of 6



USE OF END SECTIONS FOR DRAINAGE CONTROL

Valves are sometimes used on the end of culverts for the purpose of controlling drainage. This should be used only when there are no other viable alternatives. These structures do not need to be galvanized. These end sections are to be placed on the outlet end of the culvert and are to be designed so that they do not impact the hydraulic characteristics of the culvert.

BEAVER CONTROL Beaver control end treatments are sometimes a cost effective means of dealing with the issue of beavers creating a dam inside of a culvert. Consult with the Regional Environmental Project Specialist when considering their use. They should be installed as per the Manufacturers specifications. If they have not been tested to determine their impact on the culvert capacity, it should be assumed that there will be some negative impact. This risk should be assessed on a project by project basis.

CLEAR ZONE CONSIDERATIONS

Culvert ends are not considered to be roadside obstacles and the setbacks listed in SKS 3.1.1-A do not apply. Due to the low traffic volumes on the Saskatchewan Highway system and the associated run off the roads incident frequencies, it is not considered to be cost effective to provide safety protection for the culvert ends, over and above the benefit gained by indenting them into the sideslope, on a system basis. For individual locations, safety improvements may be considered where a positive safety benefit can be shown for locations with an accident history.


January 31, 2014 6 of 6

HM 609-01

Hydraulic Manual Section: MANNING’S N Subject: PIPE FLOW

INTRODUCTION The purpose of this section is to provide the designer with Manning’s

roughness coefficient information that can be used in the calculation of the flow depth and barrel friction losses in a hydraulic structure.

REFERENCE VALUES MHI has adopted the following values for use in hydraulic designs.

Table 609-01-1: Manning’s n for Smooth Pipe

Material Manning’s n Smooth Walled Steel Pipe 0.012

Concrete Pipe 0.012

High Density Polyethylene Pipe (HDPE) with smooth interior

0.012

Table 609-01-2: Manning’s n for Corrugated Steel and Structural

Plate Pipe (CSPI, 2007)

Size (mm)

Corrugation (mm x mm) 68 x 13 76 x 25 125 x 25 152 x 51

Annular All 0.024 0.027 0.025 Helical 300 0.013

400 0.014 500 0.015 600 0.016 900 0.018 1200 0.020 0.023 1400 0.021 0.023 0.022 1600 0.021 0.024 0.023 1800 0.021 0.025 0.024 2000 0.021 0.026 0.025 2200 0.021 0.027 0.025

> 2200 0.021 0.027 0.025 Structural Plate 1500 0.033

2120 0.032 3050 0.030 4610 0.028

Table 609-01-2 Notes:

1. The corrugation size 76 x 25 should not be used because it is more expensive than the 125 x 25 corrugation while having very


January 31, 2014 1 of 2


Section: MANNING’S N Subject: PIPE FLOW

similar performance characteristics.

2. The corrugation size 68 x 13 should not be used for sizes above 1200 mm because it is more expensive than the 125 x 25 corrugation.

Table 609-01-3: Manning’s n value for Steel Tunnel Liner Plate

(ARMTEC)

Diameter (mm)

1500 2120 3050 4610

Manning’s n 0.033 0.032 0.030 0.028 Table 609-01-3 Notes:

1. Tunnel Liner Plate is easily identified in the field through the presence of flanges on the inside of the culvert that are used to join the sections together.

2. MHI has typically used 2- flange liner plate which has two corrugations per section.

The Manning’s n value for Spiral Rib Steel Pipe is 0.013 for all diameters.

FLOW EQUIVALENCIES

Table 609-01-4 shows the equivalent smooth pipe culvert diameters for corrugated steel pipe culverts (CSP) for pipe culverts less than or equal to 1600 mm in diameter. The stated equivalencies are applied to both annular and helical CSP corrugations.

Table 609-01-4: CSP/Smooth Walled Pipe Equivalencies

Corrugated Steel Pipe Diameter

(mm)

Equivalent Smooth Walled Pipe Diameter

(mm) 500 375 (15 in) 600 450 (18 in) 800 610 (24 in) 900 750 (30 in) 1200 750 (30 in) 1400 1220 (48 in) 1600 1525 (60 in)


January 31, 2014 2 of 2

HM 609-02

Hydraulic Manual Section: MANNING’S N Subject: CONSTRUCTED CHANNELS


roughness coefficient information that can be used in the calculation of the flow depth and losses in a constructed channel.

REFERENCE VALUES The following tables cover typical constructed channel situations.

Table 609-02-5: Manning’s n for Excavated or Dredged Earth Channels (Floodplain Management Association, 2010)

Material Manning’s n

Clean, Short Grass 0.022

Weedy, Tall Grass 0.030 Gravel 0.025

Stony, Cobbles 0.035

Table 609-02-5: Manning’s n for Nonmetals (Floodplain Management Organization, 2010)

Material Manning’s n

Finished Concrete 0.012

Asphalt 0.016

Masonry 0.025

Wood 0.012


January 31, 2014 1 of 2


Section: MANNING’S N Subject: CONSTRUCTED CHANNELS



January 31, 2014 2 of 2

HM 609-03

Hydraulic Manual Section: MANNING’S N Subject: NATURAL CHANNELS


roughness coefficient information that can be used in the calculation of the flow depth and losses in a natural channel and its floodplain.

REFERENCE VALUES

Table 609-03-7: Manning's n for Minor Streams (CSPI, 2003)

Section Description Manning’s n Minimum Maximum

1. Fairly regular section a. Some grass and weeds, little or no brush 0.030 0.035 b. Dense growth of weeds, depth of flow materially greater than weed height 0.035 0.05 c. Some weeds, light brush on banks 0.04 0.05 d. Some weeds, heavy brush on banks 0.05 0.07 e. Some weeds, dense willows on banks 0.06 0.08 f. For trees within channel, with branches submerged at high stage, increase all values by 0.01 to 0.10 2. Irregular sections, with pools slight channel meanders; increase values by 0.01 to 0.02 3. Mountain streams, no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stage: a. Bottom of gravel, cobbles and few boulders 0.04 0.05 b. Bottom of cobbles, with large boulders 0.05 0.07 For major streams, values listed in Table 609-03-7 may be somewhat reduced. One additional scenario is described in Table 609-03-8.


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Section: MANNING’S N Subject: NATURAL CHANNELS

Table 609-03-8: Manning's n for Major Streams (CSPI, 2003)


1. Very regular section with no boulders or brush 0.028 0.033

For floodplains, the following values listed in 609-8 may be used.

Table 609-03-9: Manning's n for Floodplains (CSPI, 2003)


1. Pasture, no brush: a. Short grass 0.03 0.035 b. High grass 0.035 0.050 2. Cultivated areas: a. No crop 0.030 0.040 b. Mature row crop 0.035 0.045 c. Mature field crops 0.040 0.050 3. Heavy weeds, scattered brush 0.050 0.070 4. Light brush and trees4 a. Winter 0.050 0.060 b. Summer 0.060 0.080 5. Medium to dense brush: a. Winter 0.070 0.110 b. Summer 0.100 0.160 6. Dense willows, summer, not bent over by current 0.150 0.200 7. Cleared land with tree stumps, 40 to 60 per ha: a. No sprouts 0.040 0.050 b. With heavy growth of sprouts 0.060 0.080 8. Heavy stand of timber, a few down trees, little undergrowth a. Flood depth below branches 0.100 0.120 b. Flood depth reaches branches 0.120 0.160


January 31, 2014 2 of 2

HM 609-04

Hydraulic Manual Section: MANNING’S N Subject: COMPOSITE MANNING’S N

INTRODUCTION There are a number of situations encountered in hydraulic design where

the Manning’s n value is not constant for the whole section under analysis. The value for analysis is determined as a composite of the individual sections. The typical situations are:

• Where a stream channel is made up of different material and/or vegetation types for the channel and flood plain.

• Where the culvert is made up of different materials for portions of the perimeter. Some examples are where the invert has been paved, and an open bottom arch culvert has been used.

• Where culverts have been extended a material with a different Manning’s n. The most common example is annular corrugated steel pipes being extended with helical corrugated steel pipes.

DESIGN APPROACH Stream Channel Cross-sections

For stream channels the tailwater cross-section includes both the channel and the flood plain. A calculation must be made to determine the composite effective Manning’s n coefficient. For typical culvert design situations the Designer shall use the Natural Channel method for the determination of the tailwater elevation in CulvertMaster. Refer to section HM 1002-02 for guidance on how to do this in CulvertMaster. The Smith method is an appropriate manual method for calculating the composite Manning’s n if it is not appropriate to use CulvertMaster. Culvert Cross-sections Culverts can be designed with different materials for portions of the perimeter. (For example, a paved invert, arch culvert with unlined bottoms, metal box culverts with concrete bottoms or pipe culverts with a bottom filled with rock), CulvertMaster does not directly support the calculation of the composite Manning’s n for culvert cross-sections. A manual calculation must be made to determine the composite effective Manning’s n coefficient for the different sections and then this value has to be entered manually as the culvert’s Manning’s n value. The Smith method can be used for calculating the composite Manning’s

Date

Hydraulic Design Page

January 31, 2014 1 of 4


Section: MANNING’S N Subject: COMPOSITE MANNING’S N

n. The perimeters have to be adjusted for partly full flows. Because it ignores the dynamic interaction between the flow prisms affected by each section, it may not be appropriate for high risk situations. Contact the Senior Road Design Engineer for assistance in determining the appropriate methodology to use in high risk situations. Culvert Length While culverts are typically designed with constant Manning’s n value along their length, when extending or repairing existing culvert installations it is not always possible to match the culvert material section. When this occurs a composite Manning’s n value has to be used for the culvert analysis. CulvertMaster does not directly support the calculation of the composite Manning’s n for the entire culvert length. Where the Manning’s n value changes along the length of the culvert, a manual calculation must be made to determine the composite effective Manning’s n coefficient for the different sections, which has to be entered manually as the culvert’s Manning’s n value. The Smith method can be used for calculating the composite Manning’s n substituting culvert length for wetted perimeter in the formula.

SMITH METHOD The Smith method is a simple yet effective procedure to estimate the composite roughness coefficient (Manning’s n). The formula for the Smith method is:

𝑛𝑐𝑜𝑚𝑝𝑜𝑠𝑖𝑡𝑒 = ∑𝑛 ∙ 𝑃∑𝑃

Where: n = Manning’s n; and P = Wetted Perimeter.

Date Hydraulic Design Page

January 31, 2014 2 of 4



Example Calculation Suppose you have different overbank Manning’s n in one channel.

Region Manning’s n Wetted Perimeter, P

(m)

n · P (m)

Overbank L 0.060 150 9.00 Main Channel 0.028 200 5.60 Overbank R 0.075 100 7.50

SUM 450 22.1 ncomposite = 22.1/450 = 0.050


January 31, 2014 3 of 4





January 31, 2014 4 of 4

HM 610-00

Hydraulic Manual Section: CULVERT EMBEDMENT Subject:

INTRODUCTION The embedment of culverts can be used to address a number of design

criteria. In Saskatchewan, it is commonly used to address low grade line situations and fish passage design criteria.

DESIGN CRITERIA The maximum allowable embedment is 1/3 of the pipe diameter. In the event that the pipe fills to the natural steam bed elevation, the hydraulics of the culvert will not be compromised enough to cause a failure of the structure to handle the design discharge. If the total embedded area is backfilled, the temporary reduction in available flow area for the culvert would be 37%. Care should be taken in streams that have or show a tendency to carry lots of silt to reduce the amount of embedment as much as possible. For the culvert embedment design criteria specific to fish passage design refer to section HM 901-00. The design slope for the rip rap aprons is 0% when the culvert is embedded. The transition slope from the erosion protection apron to the natural stream channel shall be a 4:1 for the inlet and outlet. The side slope from the rip rap apron to natural ground shall be 3:1.


January 31, 2014 1 of 2


Section: CULVERT EMBEDMENT Subject:


Date January 31, 2014 Culvert Hydraulics

Page

2 of 2

HM 611-01

Hydraulic Manual Section: WOOD BOX CULVERTS Subject:

DESIGN AND MAINTENANCE CONSIDERATIONS

INTRODUCTION Wood box culverts have been used in Saskatchewan since 1946. The

WBC consists of a treated timber planking covering that is supported by an interior timber framework. The components of a WBC are illustrated in Figure 611-1. The timber frame has horizontal roof beams, called stringers, which carry the load due to the road embankment and traffic on top of the culvert. Vertical posts on each side carry the vertical end reactions for the stringers, and in addition resist lateral earth pressure. The floor of the culvert consists of cross sills located between each pair of posts. The cross sills, which carry the horizontal reaction at the bottom of the posts, are placed directly on grade in the excavation for the culvert. Since the planking covers only the top and sides of the culvert, the space between the cross sills is filled with riprap for erosion protection. The inlet and outlet structures for the culvert are also framed timber construction. The inlet and outlet wing walls were tapered with a 0° flare to match the adjacent fill slopes from 1946 to 1962. Starting in 1962 the inlet wing walls were flared out at 30° in order to provide for improved hydraulic flow. The outlet wing walls continued to be parallel to the culvert axis. WBC lengths can be constructed in multiples of 1.2 m, starting with a minimum length of 6.0 m.

USE The WBC was introduced as a lower initial cost alternative to concrete and corrugated steel culverts where conditions were more suitable to a wood material and/or a noncircular shape. Although there are a number of WBC in existence, use of the WBC as an alternative to other types has declined in over time. The decline was due to the increase in labour and material costs along with environmental concerns regarding the use of treated wood timbers in stream channels. This resulted in the use of WBC being discontinued. The existing WBC should be retained until they reach the end of their service life at which time they will be replaced with an alternative culvert type. Consideration should be given to replacing them prior to the end of their service life where this can be included as part of major road rehabilitation project.


January 31, 2014 1 of 4


Section: WOOD BOX CULVERTS Subject: DESIGN AND MAINTENANCE

CONSIDERATIONS

The information on WBC is being retained to support ongoing maintenance activities and the existing design flow calculations required as part of the replacement culvert design.

Figure 611-01-1: Cross Section of Wood Box Culvert

STANDARD SIZES Supply of the timber material remains in imperial units of

measurement. The standard plans and material listing reflect the timber Imperial units. Reference herein is by means of soft metric conversion for the purpose of normal metric size reference and hydraulic calculations. The WBC are constructed with a width to depth ratio of up to 4. The standard sizes provide for a range of nominal interior heights (H) of 910 mm (3 ft), 1220 mm (4 ft), 1830 mm (6 ft), and 2440 mm (8 ft) and a range of nominal interior widths (W) of 1220 mm (4 ft), 1830 mm (6 ft), 2440 mm (8 ft), 3050 mm (10 ft), and 3660 mm (12 ft). Any combination of height and width is acceptable thus providing for 20 standard sizes ranging from 910 mm x 1220 mm to 2440 mm x 3660 mm. Whereas the nominal height is referenced to the interior opening, Table 611-1 provides a summary of total height measured from invert, i.e., top of cross-sill to the top of the wood flooring. The posts and cross-sills are all 6 inches x 8 inches. The depth of the stringer are 12 inches for H=4 feet and 6 feet, 14 inches for H=8 feet, 16 inches for H=10 feet and18 inches for H=12 feet.


January 31, 2014 2 of 4



CONSIDERATIONS

Table 611-01-1: Total Height of Wood Box Culverts

Nominal Width, mm (ft)

Nominal Height, mm (ft) 910 (3) 1220 (4) 1830 (6) 2440 (8)

1220 (4) 1.27 1.57 2.18 2.79 1830 (6) 1.27 1.57 2.18 2.79 2430 (8) 1.32 1.63 2.24 2.84 3050 (10) 1.37 1.68 2.29 2.90 3660 (12) 1.42 1.73 2.34 2.95

Note that the heights have been rounded up to two decimal places so they do not exactly match the component dimensions shown in Standard Plan 12300.

HEIGHT OF COVER The standard Ministry sizes are based on a minimum height of cover of 0.30 m and a maximum height of cover of 1.25 m above the top of the WBC floor. The road embankment includes any surfacing structure that may be present. In special circumstances, a height of cover in excess of 1.25 m may be considered subject to review and approval of a design exception.

CULVERT SLOPE Generally, the culvert is placed on a flat bed with 0% grade. In special circumstances, a sloping bed to a maximum of 2% grade may be considered.

DESIGN PLANS Bridge Plan No. 12300, Sheets 1 to 5 inclusive contains the latest version of the layout details and timber quantities for standard department sizes. The plan also shows the rip rap erosion protection requirements. The plan is located in section HM 611-03.

BACKFILL REQUIREMENTS

A WBC is to be installed in accordance with Standard Plan 22160: Backfilling Framed Timber Culverts. The standard plan is located in section HM 611-03.

EROSION PROTECTION The WBC is protected with Type II Rip Rap. The erosion protection details are shown on Sheet 3 of 5 Miscellaneous Details of Standard Plan 12300. When the WBC operates with the inlet submerged, the inlet velocities resulting from the jet contraction become higher than the design values for the rip rap on the floor in the cross sill spaces. This results


January 31, 2014 3 of 4



CONSIDERATIONS

in the rip rap being removed from the first to the third cross sill spaces depending upon the magnitude of the flow. The early and severe movement of the rip rap near the inlet can be addressed through the addition of a half round cylinder to the inlet face of the WBC stringer. The diameter of the cylinder is equal to the combined depth of the spreader, stringer, floor planking and curb with a width equal to the nominal width (W) of the WBC. It is to be installed with the bottom of the half round flush with the bottom of the spreader. The half cylinder can be made out of UV resistant plastic or light gauge steel pipe. Under flows approaching the maximum head, the rip rap further down the WBC length will also see some displacement.

MAINTENANCE REQUIRMENTS

The WBCs need to be maintained until they reach the end of their service life to protect their operational capacity and structural integrity. The WBCs will have reached the end of their service life when they require major structural repairs. This is to be determined based on input from the Regional Senior Bridge Preservation Engineer. The displacement of the rip rap negatively impacts the WBC foundation and capacity. Because of this, the Ministry maintenance crews should inspect the WBC after each flood event, that submerges the inlet, and repair any observed displacement of the rip rap. When repairing the rip rap apron and sideslope protection the following standards are to supersede what is shown on Standard Plan 12300, Sheet 3 of 5.

1. The outlet apron starts at the end of the last cross sill for the wingwall, depth is to be 600 mm, length 3H, and width is 3H.

2. The inlet rip rap apron length is to be H, width is the wingwall mouth opening plus ½ W on each side, and the rip rap shall extend up the side slope to 300 mm above the top of the curb.

3. Nonwoven geotextile fabric is to be placed under the rip rap.


January 31, 2014 4 of 4

HM 611-02

Hydraulic Manual Section: WOOD BOX CULVERTS Subject: DESIGN CALCULATIONS

INTRODUCTION The design procedure for the Wood Box Culvert (WBC) is based on

hydraulic design theory and laboratory model tests undertaken by the Ministry and the University of Saskatchewan. The original modeling work was undertaken in 1962 by Martin Kesmarky of the Bridge Branch. The design charts created by Kesmarky’s work were included in the first edition of the Hydraulic Design of Culverts Manual. These charts were amended based on work by W.J. Riddell and D. Metz of the Road Design Branch and included in the second edition of the Manual. The charts were used until 1988 when the previous Hydraulic Manual was published. While the manual analysis procedures contained in this section can be used to design WBCs, they were not typically used in practice. The Ministry introduced a computer program, called WBC, along with the Hydraulic Manual to facilitate the design of WBCs. This program was used between 1988 and it’s replacement with the CulvertMaster hydraulic design program.

ANALYSIS PROCEDURE Designers should take the following historical design information into consideration when analyzing WBC for replacement:

• A WBC installed prior to 1962 was designed so that it did not operate with a submerged inlet at the Q25 design flow and assumed no tailwater effect on the WBC. In addition, the design charts were based on the US Bureau of Public Roads design charts for concrete box culverts and a Manning’s n value of 0.03 was used.

• From 1962 onward, tailwater effects were included in the WBC design and the Manning’s n value was revised to 0.034.

• From 1962 to 1988 revised design charts were used based on WBC specific research with revised loss coefficients.

• From 1988 onward WBCs were allowed to be designed to operate with a submerged inlet at the Q25 instantaneous peak design flow and included the revised entrance and friction loss included in the Hydraulic Manual (1988). Note that this did not include the use of the outlet loss coefficient.


January 31, 2014 1 of 8


Section: WOOD BOX CULVERTS Subject: DESIGN CALCULATIONS

For a WBC installed prior to 1988, the Q25 design flow is to be estimated by calculating the flow associated with the headwater set at the point where the flow profile shifts from a H2 profile to a CompositeH2PressureProfile in CulvertMaster rather than using the procedure in section HM 502-02. This will require an iterative procedure. The flow is then compared against the value received from the Water Security Agency as per section HM 501-00. For WBCs installed after 1988, the Water Security Agency flow estimate is to be compared against the flow range resulting from the allowable headwater criteria of 0.3 m below the subgrade shoulder elevation and the criteria above for unsubmerged flow, if the design report is not available. The Full Flow and Part Full Flow analysis of a WBC must be undertaken separately when using CulvertMaster because of the differences in the loss coefficients.

CULVERTMASTER USE The CulvertMaster program is currently being used to analyze WBC flow capacity to facilitate their replacement by culverts. CulvertMaster program settings associated with the analysis of box culverts is based on the research conducted in the U.S. on smooth walled culverts. The work by Kesmarky (1962) and Barber (1988) showed that there are differences in the flow pattern that develop in WBC as compared to smooth walled box culverts. Therefore, the entrance loss coefficients described in the following sections shall be used in the CulvertMaster program. These calculated values are to be directly input into the CulvertMaster program instead of using the pick list.

OUTLET CONTROL In the case of the Wood Box Culvert (WBC), the combination of minimum slope, very high hydraulic resistance, and flared inlet wing walls precludes the development of inlet control. Therefore, outlet control is applied for both part full and full flow conditions.

CRITICAL DEPTH

Critical depth for a rectangular section is given by:

𝑑𝐶 = � 𝑄2

𝑔𝑊2�13


January 31, 2014 2 of 8



Where: dC = Critical depth (m); Q = Discharge, m3/s; W = Flow area width (m); and g = Acceleration due to gravity, 9.81 m/s2.

PARTIALLY FULL FLOW

For part full flow, the outlet datum is the greater of the critical depth and the tail water elevation. The water surface profile through the culvert is evaluated by the step method using the non-uniform flow equation: 𝐿 = 𝐸2− 𝐸1

𝑆𝑜−𝑆𝑓𝑎

Where: L = Length of the profile segment (m); E2 = Energy content at downstream end (m); E1 = Energy content at start of segment (m); Sfa = Average rate of friction loss; and So = Culvert slope. The calculation is started at the outlet end where:

E2 = 1.5dc if dc > dt, or E2 = dt + � 𝑄𝑊∙𝑑𝑡

�2

2𝑔 if dt > dc.

Model testing indicates that in calculating the water surface profile, the profile should be started at a point in the outlet that is an equal distance from the outlet and the point where the sloping wing wall height equals the greater of critical depth or tailwater depth. The formula for the starting energy content should be calculated as:

E1 = d1 + � 𝑄𝑊∙𝑑1

�2

2𝑔

However, the value of E1 may be determined by arbitrarily setting d1 = 1.05∙d2 . As a general rule, the velocity change resulting from the change in flow depth d should be limited to 10%.


January 31, 2014 3 of 8



The average rate of friction loss is given by:

𝑆𝑓𝑎 = 𝑆𝑓1+ 𝑆𝑓22

, Where:

𝑆𝑓1 = 𝑉2∙𝑛2

𝑅11.33 ; 𝑎𝑛𝑑 𝑆𝑓2 = 𝑉2

2∙𝑛2

𝑅21.33 .

And: V1 = Velocity at section 1 (m/s); V2 = Velocity at section 2 (m/s); R1 = Hydraulic radius of section 1 (m); R2 = Hydraulic radius at section 2 (m); and n = Manning’s n, equal to 0.034 for WBC flow. The method is iterated until the summation of the ΔL increments equals the length of the culvert.

∆𝐿 = 𝐸2−𝐸1𝑆𝑜

- Sfa The equation will produce a positive answer because the numerator and denominator of the fraction have the same sign. If So > Sfa, decreasing depth upstream (d2 > d1) may result in the culvert operating under inlet control. Since WBC’s are generally constructed with zero or minimal slope, the above case is not likely to occur. To ensure that inlet control headwater requirements are satisfied regarding culvert slope, the minimum height of the energy line inside the inlet at the upstream end should be taken as 1.5·dc. At this point, the entrance head loss is added to E1 to obtain the upstream energy level required The entrance loss for part full flow, He, is given by:

𝐻𝑒 =𝑘𝑒 ∙ 𝑉𝑒2

2𝑔,

Where


January 31, 2014 4 of 8



Ke= 0.70 H/W [30˚ wingwall flare] Ke = 0.93 H/W [0˚ wingwall flare] Where, H = the nominal height (m), as shown in Figure 611-01-1. W = the nominal width (m), as shown in Figure 611-01-1. If the calculated d1 at any time becomes equal to the clear height of the WBC (that is, nominal height – 0.1 m), the culvert will flow full from that point on. Full flow analysis must be used for the remaining portion of the culvert, in effect setting the tail water depth equal to the H at that point.

FULL FLOW In the case where either Dc ≥ H or Dt ≤ H, the culvert will flow full

from that point on and full flow analysis is used. In the case of full flow throughout, the depth of the head pool above the outlet datum is given by the following. This procedure has been incorporated into the Ministry Wood Box Culvert Calculator for Full Flow Excel Spreadsheet.

HW = He + Hf +Ho + y,

Where: Hf = Friction head loss (m); Ho= Outlet head loss (m), He = Entrance head loss (m; and y = The greater value of dc or dt (m). For full flow, the friction head loss is given by:

𝐻𝑓 = 𝑓𝐿𝑉2

8𝑔𝑅,

Where: Hf = Friction head loss (m); L = Length of culvert flowing full (m);


January 31, 2014 5 of 8



V = Mean full flow velocity (m/s); and f = Darcy Weisbeck friction factor. Darcy Weisbeck friction factor is defined as:

f = 0.122 + 0.015W/D, Where: W = WBC flow area (nominal) width (m); D = WBC flow area height (m), as shown on Figure 611-01-1. For full flow, the entrance head loss is given by:

𝐻𝑒 =𝐾𝑒 ∙ 𝑉𝑒2

2𝑔,

Where: Ve = Inlet average velocity (m/s), and Ke = Inlet loss coefficient. For full flow, the equation for the inlet loss coefficient is: Ke = 1.2 H/W [30˚ wingwall flare] Ke = 1.86 H/W [0˚ wingwall flare] The inlet hydraulics can be improved considerably through the addition of a half round cylinder with a diameter equal to the combined depth of the spreader, stringer, floor planking, and curb. The length of the half round cylinder should be equal to the width of the culvert. The bottom of the half round must be flush with the bottom of the spreader. For full flow with the half round inlet improvement, an equation for the inlet loss coefficient is for the 30˚ wingwall flare has been developed and is shown below. The Ministry does not have a coefficient for 0˚ wingwall configuration. Ke = 0.6 H/W [30˚ wingwall flare, half round inlet]


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For full flow, the outlet head loss is given by:

𝐻𝑜 =𝐾𝑜 ∙ 𝑉𝑜2

2𝑔

Where: Ko = 1.0


January 31, 2014 7 of 8





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Hydraulic Manual

Section 611-03

Standard Plans

2014


SUPERSEDED

SUPERSEDED

SUPERSEDED

SUPERSEDED

SUPERSEDED

SUPERSEDED

HM 612-00


MEDIAN DRAINAGE STRUCTURES

Subject:

INTRODUCTION On divided highways, the centre median must be drained. There are

typically three alternative methods of accomplishing this. This section provides guidance on the three alternative methods and their use.

ALTERNATIVE METHODS

Drainage from the median to the outer ditches is accomplished using the following drainage structures: Separate Through Grade Culverts in Each Roadway At locations where a drainage channel crosses the right-of-way where median geometrics permit a median ditch sufficiently deep to permit open culvert ends in the median. See Figure 612-1(a). Single Through Grade Culverts At locations where a drainage channel crosses the right-of-way but the median geometrics do not permit open culvert ends in the median. In this case the culvert is extended through both lanes and under the median ditch. Drainage from the median to the outer ditch is accomplished using a drop structure to the buried through grade culvert. See Figure 612-1(b). Locations Without Through Grade Culvert At locations where there is no drainage channel crossing, drainage from the median to the outer ditch is accomplished using one of the following. See figure 612-19(c).

• A culvert through one roadway. • Where the elevation difference between the median and the outer

ditch is too high for a normal culvert installation a site specific drainage structure will have to be designed.

This will require a design report regardless of the structure size. The approval sheet will include review and recommendation by the Senior Road Design Engineer.

ADVANTAGES AND DISADVANTAGES

Separate through grade culverts are the most economical arrangement, however the exposed culvert ends may be a hazard for errant vehicles. The drop structure is the second most economical arrangement and is the safest arrangement. It allows for independent replacement of culverts

Date Page

January 31, 2014 1 of 4


Section:


Subject:

through the two sides of the divided highway. The drop structure will require more frequent cleaning until the median vegetation is well established. Erosion control measures should be taken to limit the amount of siltation into the structure until the vegetation is established. The culvert through one roadway is the most expensive arrangement because an existing drainage crossing is not being utilized. The exposed culvert end is a hazard to errant vehicles.

LIMITATIONS ON USE OF DROP STRUCTURES

The drop structures are not to be used under the following circumstances: • Where the median gradient is steeper than 1.5%; and • Where the through grade culvert to which the drop structure is

attached, is an equalizer.

DROP STRUCTURE DESIGN CRITERIA

The drop structure is to be constructed out of standard precast concrete manhole sections. This is to facilitate inspections of the culvert and maintenance activities. The manhole will include a 450 mm deep sump and a standard inlet grate. A 1.0 m wide asphalt or concrete apron is to be placed around the inlet grate. Where the total length of median draining into the drop structure exceeds 800 m the size of the through grade culvert may have to be increased. The sizing of the through grade culvert will have to consider the impact of the manhole structure on its hydraulic performance.

DEVIATION FROM MEDIAN GEOMETRICS

The desirable means of drainage is the open median with a separate culvert in each roadway. Normal median geometrics limit the use of this option. The following deviations from normal geometrics are permitted, to be applied in the order presented: 1. Median ditch width: 6.0 m. 2. Median ditch depth: 2.0 m below subgrade shoulder on the highest

roadway. 3. Median slope: 5:1.

Date Page

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Subject:

The maximum transition from normal geometrics should be 50 m each side of the culverts.

Figure 612 (a): Separate Through-Grade Culvert in Each Roadway

Figure 612 (b): Drop Structure to the Buried Through Grade Culvert

Figure 613 (c): Culvert Through One Roadway

Date Page

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Section:


Subject:


Date Page

January 31, 2014 4 of 4

HM 613-00

Hydraulic Manual Section: FLOW OVER EMBANKMENTS Subject:

FLOW CALCULATION

There are locations where flow over the grade has been recorded. When calculating the flow at these locations, the flow over the road must be added to the flow through the structure. The following method is to be used to calculate flows over embankments.

1. Divide the overflow into sections along the embankment, each having a fairly uniform depth.

2. Calculate the discharge for each section using the following equation:

Q = 0.55·kt·C·L·H1.5

Where: Q = discharge (m3/s); and ki, C, L, H are defined in figure 502-1.

3. Compute the total flow as the sum of the flows in the

individual sections. Use the CulvertMaster Designer/Analyzer mode to analyze culvert crossings that have an overtopping component. It uses the same theory as contained in this section.

Figure 613-1: Schematic of Flow Calculation (Hulsing, 1967)


January 31, 2014 1 of 4


Section:

FLOW OVER EMBANKMENTS

Subject:

Where:

C = Discharge coefficient from Figure 601-2 or 601-3; L = Length of overflow section of embankment (m); H = h if V1< 2 m/s, otherwise H = h + V1

2/2g (m) (generally = h); kt = Submergence Factor given by Figure 601-4. Free flow (generally = 1.0); and b = Surface width including shoulders.

Figure 613-2: Discharge Coefficients for h/b ≥ 0.15 (Hulsing, 1967)

Figure 613-3: Discharge Coefficients for h/b < 0.15 (Hulsing, 1967)


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Section:


Subject:

Figure 613-4: Submergence Factor kt (Hulsing, 1967)


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Section:


Subject:



January 31, 2014 4 of 4

HM 614-00


CULVERT MATERIAL AND CONNECTOR REQUIREMENTS

Subject:

Date Culvert Hydraulics Page September 15, 2014 1 of 2

INTRODUCTION The purpose of this section is to define the culvert material types that have been approved for use by the Ministry along with their connector requirements.

CULVERT MATERIAL TYPES AND CONNECTOR REQUIREMENTS

The Ministry has approved steel, concrete and high density polyethylene materials for use in culverts. The Ministry has approved the use of polypropylene material, and steel reinforced high density polyethylene pipe for use in culverts on a pilot project basis.. The Ministry has approved the use of zinc as a coating in the galvanizing of steel culverts. The Ministry has approved the use of polymer material for use as a coating on steel culverts on a pilot project basis. In addition, this material is subject to additional inspection requirements until such time as manufacturing issues causing cuts in the material have been resolved. Steel The following steel culvert products have been approved for use for through grade and approach culverts:

• Corrugated Steel Pipe • Structural Plate Steel Pipe • Steel Liner Plate • Spiral Rib Steel Pipe • Smooth Walled Steel Pipe

For corrugated steel culvert and spiral rib steel culverts the following shall apply:

• The coupler shall be wrapped with a non-woven geotextile and the minimum coupler length shall be 600 mm for Ministry and Rural Municipality road through grade culverts and field, farm yard and business approach culverts greater than or equal to 1000 mm.


Section:

CULVERT MATERIAL AND CONNECTOR REQUIREMENTS

Subject:

Date Culvert Hydraulics Page September 15, 2014 2 of 2

• For field approach installations, the coupler is not required to be wrapped and the minimum coupler length is to be as per manufacturer’s specifications.

• For Ministry through grade culverts that have over 3 m of fill or there is ground water infiltration or there is a continuous low flow condition (typically from a spring) the separate sections of pipe shall be joined with semi-corrugated (hugger band style) couplers complete with two elastomeric O-Ring Gaskets. The coupler shall be wrapped with a non-woven geotextile and the minimum coupler length shall be 480 mm. The culvert length shall be increased over the usual 6 m lengths so as to minimize the number of culvert connections. The length shall be determined by the designer while taking into account the transport and installation considerations of longer pipe. The typical maximum practical lengths are 16 m for 125x25 corrugations and 12 m for 68x13 corrugations.

Concrete

Reinforced concrete pipe has been approved for use in through grade and approach culverts. Gaskets shall be used on through grade culverts and the joints wrapped with non-woven geotextile. High Density Polyethylene Pipe High Density Polyethylene Pipe (HDPE) that is Certified to Specification CAN/CSA B182.8-11 (with a pipe stiffness of 320 kPa at 5% deflection for pipe sizes up to and including 900 mm), or the most current specification at the time of tender shall be used for through grade and approach culverts. Open or closed profile pipe shall be used. Type 1 (water tight) joints with integral bell and spigot connections shall be used for Ministry and Rural Municipality road through grade culverts and field, farm yard and business approach culverts greater than or equal to 1000 mm. For all other installations, Type 2 (soil tight) joints are the minimum requirement

HM 615-00

Hydraulic Manual Section: REFERENCES Subject:

REFERENCES

American Iron and Steel Institute (AISI). (1984). Handbook of Steel Drainage and Highway Construction Products: Canadian Edition. (pp 176). Washington, DC: American Iron and Steel Institute Ayles, J.K. and Smith, C.D. 1985. “Performance Characteristics of Circular Corrugated Steel Pipe Culverts.” Technical Report 33, Saskatchewan Ministry of Highways and Infrastructure. Corrugated Steel Pipe Institute (CSPI) and American Iron and Steel Institute (AISI). (2007). Handbook of Steel Drainage and Highway Construction Products: Second Canadian Edition. (Pp 137-139) Cambridge, ON: CSPI; and Washington, DC: AISI. Federal Highway Administration (FHWA). (2005). Hydraulic Design Series Number 5: Hydraulic Design of Highway Culverts. 2nd Ed (FHWA Publication No. FHWA-NHI-01). Washington, DC: U.S. Department of Transportation. and National Highway Institute. Floodplain Management Association. (2010). “Roughness of Floodplain Plants: Using Plants to Improve Food Management” Viewed on June 7, 2010. http://www.floodplain.org/cmsAdmin/uploads/documents/Plants_and_FPM_11-09.pdf Highway Research Board Bulletin 126. 1956. “Culvert Flow Characteristics.” Washington, D.C., U.S.A. Kesmarky, Martin (1962) Hydraulic and Economic Investigation Related to the Highway Standard Wood Box Culvert: Saskatchewan Department of Highways and Transportation. Portland Cement Association (PCA). (1964). Handbook of Concrete Culvert Pipe Hydraulics. Chicago, IL: Portland Cement Association. Smith, C.D. (1995). Hydraulic Structures (pp 10-33). Saskatoon, SK: University of Saskatchewan Printing Services and Universal Bindery


January 31, 2014 1 of 2


Section: REFERENCES Subject:



January 31, 2014 2 of 2

Hydraulic Manual

Section 700

Structural Design

2014


HM 701-00


STRUCTURAL DESIGN REQUIREMENTS

Subject:

Date Structural Design Page September 18, 2014 1 of 6

INTRODUCTION

Culvert structures are classified as rigid or flexible, depending upon how they develop their strength. Rigid structures, as the name implies, are designed to have minimum deflections under load (typically less than 2%) and are designed to carry loads directly. Concrete and smooth walled steel pipe are both examples of rigid pipe. Flexible structures place much of the load on the soil around and over them, and must move or deflect in order to transfer the load to the soil. Because of this, they are sometimes referred to as composite structures. Corrugated steel (CSP) and high density polyethylene pipe (HDPE) are examples of flexible pipe. Both rigid and flexible pipe rely on the backfill structure to transfer loads into the bedding. Therefore, the backfill and bedding material and its compaction are critical in achieving the design performance of these systems.

STRUCTURAL DESIGN CRITERIA

The Canadian Highway Bridge Design Code (CHBDC) CAN/SCA-S6-06 shall be used for the design of corrugated steel culverts where D ≥ 3000 mm. The design live load vehicle shall be the CL-750 or as directed by the Ministry. The criteria contained in section HM 703-00 were applied in developing the Maximum Fill Over Pipe in the tables contained in section HM 702-01, HM 702-2 and HM 702-3. In order to be conservative, the values were derived using an assumed backfill density of 85%. For those corrugations and sizes listed, reference to the tables will satisfy the design criteria outlined in section HM 703-00. The structural design for all other corrugated steel culvert shapes not covered in the tables and other material types are to be as per the manufacturer’s specifications.

MINIMUM DEPTH OF COVER

The minimum depth of cover is defined as the depth from the top of the crown of the pipe to the lowest point on the subgrade surface (at shoulder breakpoint) (i.e. does not include the surfacing structure). It is intended to provide adequate protection for the structures from the construction of the surfacing structure and the highway traffic live loads after construction.


Section:


Subject:


The minimum depths of cover requirements are given in the height of fill tables included in section HM 702-01, HM 702-02 and HM 702-03. Note that all minimum cover values shall be increased by 300 mm for gravel road surfaces in order to account for the loss of material over time from road blading operations. Additional temporary protection is required when construction equipment will be driven over or close to the buried structure. It is the responsibility of the contractor to determine and provide the additional cover to avoid damage to the pipe. The minimum depth of cover for construction equipment up to 68 tonnes loaded axle weight over round culverts is given Table 701-01. For situations outside of this table, the determination of the minimum cover shall be based on structural design calculations undertaken by a Structural Engineer. Minimum cover is measured from the top of the pipe to the top of the maintained construction roadway surface. For center medians, the designer should use the construction equipment minimum cover values during construction and for the final finished grade. Table 701-1: General Guidelines For Minimum Cover Required For Construction Equipment Up To 68 tonne Loaded Axle Weight

Pipe Span (mm) Minimum Cover (mm) 300-1050 1000 1100-3050 1300 3200-3660 1500

CORRUGATED STEEL PIPE WALL THICKNESS

For all CSP culverts, except those installed in unpaved approaches, the wall thickness shall be 2.0 mm unless the designer specifies a larger thickness to satisfy height of fill or culvert service life design constraints. For CSP culverts installed in unpaved field approaches, the wall thickness shall be 1.6 mm unless the designer specifies a larger thickness to satisfy height of fill or culvert service life design


Section:


Subject:


constraints. The wall thickness for Structural Plate Steel culverts shall be as required by the height of fill tables.

SMOOTH WALLED STEEL PIPE WALL THICKNESS

The minimum thickness shall be 12.5 mm (1/2 inch).

MULTIPLE PIPE INSTALLATIONS

The purpose of this section to provide guidance on the minimum separation between culverts in order to provide the proper support and to ensure that there is adequate space to place and properly compact the backfill material. The economics of the granular backfill operation varies with the size and length of the culvert installation and end treatment requirements. Taking this into consideration the designer shall determine the most cost-effective separation between the pipes. The Ministry’s historical practice has been to use a minimum separation of 1D. Based on site or design requirements this can be reduced to a minimum separation of 1 m for round CSP pipes covered by the Ministry’s backfill standard plans. The decision on the appropriate separation to use also has to take into account the width requirements for any end treatments. The minimum separation for all other CSP shapes and other culvert material types are to be based on the manufacturer’s specifications.

BACKFILL REQUIREMENTS

Through Grade and Paved Approach Culverts The definition of a paved approach shall be as per Standard Plan 21200T. Round CSP and HDPE pipe culverts less than 1500 mm shall be installed in accordance with Standard Plan HM705-01. Round CSP and Structural Plate Culverts where 1500 mm ≤ D < 3000 mm shall be installed in accordance with Standard Plan HM705-02.


Section:


Subject:


For round CSP culverts equal to or greater than 3000 mm the backfill, shall be designed and shown on a project specific plan. The backfill for CSP pipe arches shall be designed by a Geotechnical Engineer to support a corner bearing pressure of 190 kPa and shown on a project specific plan. The backfill requirements for all other culvert material types and shapes shall be as per the manufacturer’s specifications and shown on a project specific plan. The granular backfill material shall meet the requirements of Specification 6600 – Specification For Granular Backfill in the Standard Specifications Manual. The crushed aggregate material shall meet the Ministry requirements for Type 33 Base or equivalent. A woven geotextile fabric shall be placed under the granular backfill. The specifications and physical properties shall be specified by the designer to meet the site conditions. The earth backfill material outside of the granular backfill shall meet the requirements of Specification 2300 – Specification for Embankment in the Standard Specifications Manual and the requirements of .Special Provisions; 03 - Grading, or 10 - Typical Culvert-Bridge Replacement. Unpaved Approaches Single round concrete and CSP pipe where D ≤ 600 mm shall be installed in accordance with Standard Plan HM705-03. Culverts where 1500 mm ≤ D < 3000 shall be installed in accordance the Standard Plan HM705-04 (the Special Provisions will have to be amended to include the required specified density provisions for the embankment). Pipe arch culverts shall not be used in unpaved approaches.


Section:


Subject:


The backfill requirements for all other culvert material types and shapes shall be as per the manufacturer’s specifications and shown on a project specific plan (the Special Provisions may have to be amended to include the required specified density provisions).

DETERMINATION OF BEDDING DEPTH AND MATERIAL

Through Grade and Paved Approach Culverts The minimum bedding depth requirement for, CSP and HDPE pipe culverts where D < 1500 mm is specified in Standard Plan HM705-01. The minimum bedding depth for CSP and Structural Plate pipe culverts 1500 mm ≤ D < 3000 mm is specified in Standard Plan HM705-02. The designer is to specify a granular bedding depth that is sufficient to provide a sound foundation for the culvert and its structural backfill based on consideration of the soil conditions at the site, if a depth greater than the minimum is required. The specified depths are to be included in a table in the Special Provisions. For culverts where D ≥ 3000 mm the bedding depth shall be designed and shown on a project specific plan based on the specific site and subgrade material conditions. The bedding depth for CSP pipe arches shall be designed by a Geotechnical Engineer to support a corner bearing pressure of 190 kPa and shown in a project specific plan. The bedding depth and material type for all other culvert material types and shapes are to be as per the manufacturers specifications and shown on a project specific plan. Unpaved Approaches The bedding depth requirement for round concrete and CSP culverts where D ≤ 600 mm in approaches is specified in Standard Plan HM705-03. Culverts where 600 < D < 3000 mm sizes the bedding depth is specified in Standard Plan HM705-04.


Section:


Subject:


For culverts where D ≥ 3000 mm the bedding depth shall be designed and shown on a project specific plan based on the specific site and subgrade material conditions. Pipe arch culverts shall not be used in unpaved approaches. The bedding depth and material type for all other culvert material types and shapes are to be as per the manufacturers specifications and shown on a project specific plan.

CAMBER REQUIRMENTS

Culverts installed under high fills may experience settlement over the centre sections resulting in water ponding, reduction in capacity due to sedimentation, and void development due to joint alignment. The camber requirements shall be determined by a foundation design based on a geotechnical investigation where any of the following conditions apply:

• The embankment height above natural ground is greater than 6 m and the subgrade material has not been previously pre-consolidated.

• The subgrade and/or embankment material is known or suspected to be poor.

• The proposed culvert diameter is equal to or greater than 3 m. • Existing embankments are being raised and/or widened.

HM 702-01

Hydraulic Manual Section: HEIGHT OF FILL TABLES Subject:

CORRUGATED STEEL PIPE AND PIPE ARCH WITH D < 1500 mm


Table 702-1: Helical Corrugated Steel Pipe (CSP) with 68 x 13 mm Corrugations

Diameter (mm)

End Area (m2)

Minimum Cover* (mm)

Maximum Fill Over Pipe (Including Surfacing) (m) Specified Wall Thickness (mm)

1.6 2.0 2.8 3.5 4.2 300 0.07 300 47.5 58.5 80.0 -- -- 400 0.13 300 27.0 31.5 41.0 49.0 58.0 500 0.20 300 20.0 22.0 27.0 31.0 35.5 600 0.28 300 16.5 18.0 20.5 23.0 25.5 800 0.50 300 14.0 14.5 15.5 17.0 18.0 900 0.64 300 13.5 14.0 14.5 15.5 16.5 1000 0.79 300 13.0 13.5 14.0 14.5 15.0 1200 1.13 300 -- 13.0 13.0 13.5 14.0

* Increase minimum cover by 300 mm for gravel road surfaces

Table 702-2: Helical Corrugated Steel Pipe with 125 x 26 mm Corrugations

Diameter (mm)

End Area (m2)

Minimum Cover* (mm)

Maximum Fill Over Pipe (Including Surfacing) (m) Specified Wall Thickness (mm)

2.0 2.8 3.5 4.2 1400 1.54 300 14.5 15.5 16.0 17.0

* Increase minimum cover by 300 mm for gravel road surfaces.

Table 702-3: Helical Corrugated Steel Pipe Arch (CSPA) with 63 x 13 mm Corrugations

Span x Rise (mm)

Equivalent Round

Diameter (mm)

End Area (m2)

Corner Radius (mm)

Minimum Cover* (mm)

Maximum Fill Over Pipe (Including Surfacing) (m)

Specified Wall Thickness (mm) 2.0 2.8 3.5

560 x 420 500 0.19 135 300 4.8 -- -- 680 x 500 600 0.27 165 300 4.8 -- -- 800 x 580 700 0.37 190 300 4.8 -- -- 910 x 660 800 0.48 220 300 4.8 -- -- 1030 x 740 900 0.61 245 300 4.8 -- -- 1150 x 820 1000 0.74 270 300 4.7 4.7 -- 1390 x 970 1200 1.06 325 300 -- 4.7 4.7



Section: HEIGHT OF FILL TABLES Subject: CORRUGATED STEEL PIPE AND PIPE

ARCH WITH D< 1500 mm


Table 702-4: Helical Corrugated Steel Pipe Arch (CSPA) with 125 x 26 mm Corrugations

Span x Rise (mm)

Equivalent Round

Diameter (mm)

End Area (m2)

Corner Radius (mm)

Minimum Cover* (mm)



1550 x 1200 1400 1.48 390 300 3.7 -- -- * Increase minimum cover by 300 mm for gravel road surfaces.

NOTES 1) For retention of existing annular riveted corrugated steel pipe, use the lesser of the values contained in the above tables or the value indicated in the AISI Handbook of Steel Drainage & Highway Construction Products textbook corresponding to its approximate age.

2) The heights of fill tables for Corrugated Steel Pipe Arch are based on an allowable corner bearing pressure of 190 kPa.

3) The heights of fill tables do not apply to embankments or

approaches without a specified density. A structural design is required – see section HM 703-00.

4) Minimum cover is measured from the crown of the pipe to the top of the subgrade and excludes the surfacing.

HM 702-02

Hydraulic Manual Section: HEIGHT OF FILL TABLES Subject:

CORRUGATED STEEL PIPE AND PIPE ARCH FOR 1500 ≤ D < 3000


Table 702-4: Corrugated Steel Pipe with 125 x 25 mm Corrugations and a Helical Lock or Weld Seam

Diameter

(mm) End Area

(m2) Minimum Cover*

(mm) Maximum Fill Over Pipe (Including Surfacing) (m)

Specified Wall Thickness (mm) 2.0 2.8 3.5 4.2

1600 2.01 600 12.5 14.0 15.0 15.5 1800 2.54 600 11.0 13.5 14.0 14.5 2000 3.14 600 10.0 13.0 13.5 13.5 2200 3.80 600 9.0 13.0 10.5 13.0 2400 4.52 600 7.5 8.0 7.5 13.0 2700 5.73 600 -- 6.0 5.5 13.0


Table 702-5: Corrugated Steel Pipe Arch with 125 x 25 mm Corrugations and a Helical Lock or Weld Seam

Span x Rise (mm)

Equivalent Round

Diameter (mm)

End Area (m2)

Corner Radius (mm)

Minimum Cover* (mm)



1550 x 1200 1400 1.48 390 700 5.0 -- -- 1780 x 1360 1600 1.93 450 700 5.0 -- -- 2010 x 1530 1800 2.44 505 700 5.0 5.0 --


NOTES 1) The heights of fill tables for Corrugated Steel Pipe Arch are based

on an allowable corner bearing capacity of 190 kPa. 2) For equivalent round diameter ≥ 3000 mm, site specific design is

required in accordance with Canadian Highway Bridge Design Code CHBDC CAN/CSA S6-06 and Ministry’s specifications.

3) For retention of existing annular riveted corrugated steel pipe use

the lesser of the values contained in the above tables or the value indicated in the AISI Handbook of Steel Drainage & Highway Construction Products corresponding to its approximate age.


Section: HEIGHT OF FILL TABLES Subject: CORRUGATED STEEL PIPE AND PIPE

ARCH FOR 1500 ≤ D < 3000


4) The heights of fill tables do not apply to embankments or

approaches without a specified density. A structural design is required – see section HM 703-00.

5) Minimum cover is measured from the crown of the pipe to the top of

the subgrade and excludes the surfacing.

HM 702-03

Hydraulic Manual Section: HEIGHT OF FILL TABLES Subject: STRUCTURAL PLATE PIPE


Table 702-6: Structural Plate Corrugated Steel Pipe (SPCSP) with 152 x 51 mm Corrugations and 2 Bolts per Corrugation

Diameter (mm)

End Area (m2)

Minimum Cover* (mm)

Maximum Fill Over Pipe (Including Surfacing (m)*

Specified Wall Thickness (mm)

3.0 4.0 5.0 6.0 7.0 1500 1.77 600 17.0 26.0 31.0 35.0 39.0 1660 2.16 600 15.5 23.0 26.0 29.0 32.0 1810 2.58 600 14.0 20.5 23.0 25.0 27.5 1970 3.04 600 13.0 18.5 20.5 22.0 24.0 2120 3.54 600 12.0 17.5 19.0 20.0 21.5 2280 4.07 600 11.0 16.5 17.5 18.5 20.0 2430 4.65 600 10.5 15.5 16.5 17.5 18.5 2590 5.26 600 10.0 15.0 16.0 16.5 17.5 2740 5.91 600 9.5 14.0 15.0 16.0 16.5


NOTES 1) For SPCSP with diameters > 3000 mm and all structural plate pipe arch (SPPA), site specific structural design is required in accordance with Canadian Highway Bridge Design Code (CHBDC) CAN/CSA S6-06 and Ministry’s Specifications.

2) Minimum cover is measured from the crown to the top of subgrade and excludes the surfacing.

3) The height of fill table does not apply to embankment or approaches

without a specified density. A structural design is required – see section HM 703-00.


Section: HEIGHT OF FILL TABLES Subject: STRUCTURAL PLATE PIPE



HM 703-00

Hydraulic Manual

Section:

STRUCTURAL DESIGN

PROCEDURE

Subject:

Date Structural Design

Page

September 18, 2014 1 of 6

INTRODUCTION The following section outlines the structural design procedure for

corrugated steel pipe and pipe arch pipe.

The structural design procedure for corrugated steel pipe and pipe

arch requires:

1. Determination of the loads on the buried structure;

2. Calculation of ring compression;

3. Calculation of allowable wall stresses;

4. Calculation of required wall area and selection of appropriate

metal thickness;

5. Check selected metal thickness for:

a. Seam strength;

b. Deflection;

c. Flexibility; and

6. Consideration of corner bearing pressure for pipe arch.

LOADS The following formula should be used to calculate the total load:

TL = LL + DL

Where:

TL = Total load or pressure acting on the pipe structure (kPa);

LL = Live load plus impact (kPa); and

DL = Dead load (kPa).

Live Loads

Table 703-1 summarizes live load plus impact for selected axle

loading to a depth of 4.0 m. Live loads need not be considered for a

height of fill greater than 4.0 m.

Design for normal highway loading is based on standard 16,000 kg

tandem axle loadings. Intermediate loadings may be interpolated

from within the table. For larger loadings or alternate axle

configurations, the live load should be calculated using Boussinesq’s

formula.


Section:

STRUCTURAL DESIGN

PROCEDURE

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Page


To provide for impact, the calculated live load should be increased by

the following impact factor (I):

0.3 m to 0.6 m cover, I = 20%; or

0.6 m to 1.0 m cover, I = 10%

Table 703-1: Live Loads Plus Impact (AISI, 1984e)

Height of

Fill

(m)

Live Loads (kPa)

Axle Loadings

Standard (16,000 kg Per Tandem, 9,100

kg Per Single Axle)

20,000 kg Per

Tandem Axle

25,000 kg Per

Tandem Axle

0.5 73 75 94

0.75 36 38 46

1.00 20 22 28

1.25 13 16 20

1.50 11 13 17

2.00 7 9 11

2.50 5 6 8

3.00 4 5 6

3.50 3 4 4

4.00 2 3 3

Dead Load

The dead load is calculated using the formula:

DL = H∙W

Where:

DL = Dead load pressure (kPa);

H = Height of fill above pipe crown (m); and

W = Unit soil pressure (kPa/m).


Section:

STRUCTURAL DESIGN

PROCEDURE

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Page


A unit soil pressure of 19.0 kPa/m depth is to be used. This

corresponds to a soil density of 1937 kg/m3. A load reduction factor

should not be applied for varying soil density.

RING COMPRESSION Ring compression is calculated using the following formula:

C = (DL + LL)∙S/2

Where:

C = Ring compression (kN/m);

DL = Dead load (kPa);

LL = Live load (kPa); and

S = Diameter or span of pipe (m).

ALLOWABLE WALL

STRESS

The maximum allowable yield or bending stress is derived from the

following equations:

If: then

Or if: then

But: Fcr is never greater than fy = 230 MPa.

Where:

S = Span or diameter (mm);

r = Radius of gyration (mm);

K = Soil stiffness factor;

Em = Modulus of elasticity of steel (200∙(10)3 MPa);

fu = Minimum tensile strength (290 MPa); and

Fcr = Maximum allowable yield or bending stress.

If K = 0.44 is used, or good backfill at 85% compaction or greater,

then the above equation reduces to:

If: , then:

If: , then:


Section:

STRUCTURAL DESIGN

PROCEDURE

Subject:


Page


If: , then:

An average value of the radius of gyration for the corrugation being

considered may be used to proceed with the above calculations.

The radius of gyration may be confirmed following selection of final

pipe thickness, however normally no significant change occurs.

The maximum allowable design stress is calculated as:

;

Where:

Fa = Maximum allowable design stress;

Fcr = Maximum allowable yield or bending stress; and

FOS = Factor of safety (2.0).

WALL THICKNESS The required wall area may be calculated using the formula:

Where:

A = Required wall area (mm2/mm);

C = Ring compression (kN/m); and

Fa = Maximum allowable design stress (kPa).

Having calculated the required wall area, refer to tables given in the

Handbook of Steel Drainage and Highway Construction Products,

Canadian Ed., 1984, published by the American Iron Steel Institute

(AISI) to select the required wall thickness.

SEAM STRENGTH The wall thickness should be checked for adequate seam strength:

SS = C∙FOS


Section:

STRUCTURAL DESIGN

PROCEDURE

Subject:


Page


Where:

SS = Required seam strength (kN/m);

C = Ring compression (kN/m); and

FOS = Factor of safety (3.0).

Maximum allowable seam strength for structural plate may be read

from Table 3-4 in the AISI Handbook (1984).

DEFLECTION The selected pipe size, corrugation, and metal thickness must be

checked for deflection:

Where,

Wc = (LL + DL) span

And:

x = Deflection (mm);

Df = Deflection lag factor;

K = Bending factor (0.1);

Wc = Total load on the pipe per lineal metre (kN/m);

R = Radius of pipe (mm);

E = Modulus of elasticity for steel (200∙(103)MPa);

I = Moment of inertia of pipe wall (mm4/mm);

Ep = Modulus of passive earth pressure (MPa);



Use Ep = 9.66 MPa and Df = 1.25 for good backfill of a compaction

level of 85% or greater maximum density.

Deflection should be limited to 5% of the pipe diameter. For 5%

elongated circular pipe, allowable deflection may be increased by a

factor of 1.5.


Section:

STRUCTURAL DESIGN

PROCEDURE

Subject:


Page


HANDLING STIFFNESS The selected metal thickness and corrugation should be checked for

minimum pipe stiffness requirements for ease of handling and

installation.

The flexibility factor limits the upper size of each combination of

corrugation and metal thickness, that is:

;

Where:

FF = Flexibility factor;

S = Diameter or span (mm);

E = Modulus of Elasticity for steel (200∙(103) MPa); and

I = Moment of Inertia of wall (mm4/m).

The maximum recommended values for the flexibility factor for a

structural plate with a 152 x 51 corrugation are 0.114 mm for a

circular pipe and 0.170 for a pipe arch.

PIPE ARCH CORNER

PRESSURE

Pipe arches generate corner pressure greater than the pressure in the

fill. For a pipe arch, this normally becomes the controlling design

factor (along with handling stiffness):

Where:

Pc = Corner bearing pressure (kPa);

Pv = Design pressure (kPa);

S = Span (mm);

Rc = Radius of corner (mm);



The corner bearing pressure should normally be limited to 190 kPa. If

it is greater, either the geometry of the arch may be altered or soils

investigation should be undertaken to determine if a higher quality of

backfill may allow greater corner bearing pressure.

HM 704-00



REFERENCES

American Iron and Steel Institute (AISI). (1984). Handbook of Steel Drainage and Highway Construction Products, Canadian Edition. Washington, DC: American Iron and Steel Institute. Canadian Standards Association (CSA). (2006) Canadian Highway Bridge Design Code)(CHBDC) CAN/CSA S6-06. Mississauga, ON: Canadian Standards Association. Corrugated Steel Pipe Institute (CSPI). (2009). Handbook of Steel Drainage and Highway Construction Products, Canadian Edition. Washington, DC: American Iron and Steel Institute.





Hydraulic Manual

Section 705-00

Standard Plans

2014


Hydraulic Manual

Section 800

Erosion Control At Culverts

2014


HM 801-00


INTRODUCTION Erosion control is required to prevent damage to areas near the culvert

inlet and outlet and to prevent failure of the culvert and the embankment through which it is placed. Failure of the embankment can be initiated by scour at the outlet or inlet. Scour holes can constitute a safety hazard. Additionally, erosion control may be desired for aesthetic reasons. The determination of appropriate measures for erosion control at culverts begins with an examination of flow conditions at the inlet and outlet of a culvert that may necessitate the use of erosion control. This section describes the design principles and requirements the erosion resistance of natural materials, the available erosion control materials, the available erosion control methods, and the selection of an appropriate method for culvert ends and aprons. Detailed procedures for riprap erosion protection are also included.

SCOPE The material presented in this section does not cover any design

requirements that are specific to embedded culverts. The Designer is to refer to section HM 613-00 for design requirements specific to embedded culverts. The scope of this section does not include the selection or the design of major energy dissipation structures related to large flow velocities. Where these structures are required, the designer should refer to the latest edition of the U.S. Department of Transportation, Federal Highway Administration Hydraulic Engineering Circular No. 14 – Hydraulic Design of Energy Dissipaters for Culverts and Channels. The scope of this section does not include the design, selection and application of erosion control measures required for work in or near water under Aquatic Habitat Protection Permits outside of the erosion control protection for the inlet and outlet ends and aprons. Some information is provided for in the Standard Specifications Manual, the Special Provisions Templates and the Environmental Best Practices: Erosion And Sediment Control documents available on the Ministry website. For guidance on the requirements, contact the Regional Environmental Project Specialist.

Date Erosion Control At Culverts Page

January 31, 2014 1 of 2




Date Erosion Control At Culverts

Page January 31, 2014 2 of 2

HM 802-00

Hydraulic Manual Section: DESIGN PRINCIPLES Subject:

INLET At a culvert inlet, the flow approaches approximately uniformly from

all directions as it converges at the inlet. Thus, the velocity of the water a short distance away from the inlet is much less than the velocity inside the culvert. Erosion protection is required in the area where the water is accelerating as it flows into the inlet.

OUTLET At the culvert outlet, jet flow occurs with velocity reduction occurring along the path of the jet as it decelerates. Jet flow can persist for many pipe diameters beyond the end of the culvert with the outlet velocity normally being much greater than the culvert inlet velocity. Therefore, erosion protection at the outlet is often much more extensive than at the inlet.

METHODS OF EROSION CONTROL

The Ministry’s erosion control goal is to match the upstream and downstream conditions for culverts that are designed. Stated another way, the introduction of the culvert into the stream channel should cause no more erosion than what would naturally occur. Rather than relying on the use of erosion control structures, the Ministry’s approach to erosion control is to:

• Provide inlet and outlet aprons; • Limit the exit velocities; and • Provide local scour protection for the embankment side slopes

at the culvert ends. Typically, the velocity limits can be met with an oversized culvert. Where this is not achievable, some form of outlet structure designed to allow for the dissipation of excess kinetic energy of flow and the reduction of the discharge velocity may be used. Outlet structures are only considered for major installations with large discharges and velocities.

SELECTION OF EROSION CONTROL MATERIALS

If erosion control materials are required, the selection of the appropriate material will be on the basis of cost, with riprap being given first consideration. The cost calculation shall include consideration of material, installation, and operational costs.


January 31, 2014 1 of 2


Section: DESIGN PRINCIPLES Subject:


Date Erosion Control At Culverts Page January 31, 2014 2 of 2

HM 803-00

Hydraulic Manual Section: DESIGN REQUIREMENTS Subject:

REGULATORY REQUIREMENTS

The culvert is to be designed so that it does not become perched due to erosion during its design life. The stream channel shall not incur any erosion beyond what it would sustain if the culvert and road crossing were not present at the design flow. The culvert design is required to meet the requirements of the Aquatic Habitat Protection Permit which is administered by the Water Security Agency.

DESIGN FLOW The erosion protection is to be based on the design flow for the culvert design. It is not economically feasible to design the erosion protection for flood events above this value. This may require some maintenance work to repair any damage sustained during these events.

DESIGN VELOCITY For the design of the outlet apron, using riprap as the erosion control material, the Ministry’s practice is to limit the outlet velocity to a desirable outlet exit velocity of 4.0 m/s. The maximum outlet exit velocity that can be accommodated by the Ministry’s standard Type 1 Riprap is 5.0 m/s. The use of velocities above 5.0 m/s will require the design of a project specific riprap specification or outlet energy dissipation structure. Typically, riprap becomes an uneconomic option for velocities above this. The same approach is followed for erosion control matting alternatives with the manufacturer’s specifications for the velocity that the material can resist being used to determine the governing design velocity and the associated apron length. Where site specific conditions preclude the ability to meet the erosion control material design velocity, more substantial erosion controls and, potentially, hydraulic structures shall be considered.

EROSION CONTROL MATERIALS

The Ministry has historically relied on the use of riprap as the most cost efficient method of protecting culvert inlets and outlets from erosion.


January 31, 2014 1 of 4


Section: DESIGN REQUIREMENTS Subject:

The utility of riprap depends on:

• The availability of the size and quantity of the riprap; • The size and importance of the culvert; and • The natural erosion resistance of the material comprising the

ditch or channel. Information specific to riprap design is contained in sections HM 804-01 and HM 804-02. Alternatively, some form of erosion control matting can be used. Erosion control matting can be made of various material types that usually take the form of tied concrete block mats and turf reinforcement mats made of plastic. The available products can include design details to allow natural vegetation to establish within it or to prevent the erosion of fines from under the mat. Manufacturer’s specifications shall be used for the design and installation of erosion control matting materials in order to meet the Ministry’s design requirements.

APRON DESIGN Introduction The length of apron protection required depends on the water velocity, water depth, channel alignment and the apron material characteristics. The inlet and outlet aprons have different requirements based on the type of flow that each experiences. Length Criteria

Inlet – The apron length shall be 1D. Outlet – The erosion protection must continue until the flow velocity has been reduced to a value less than the maximum permissible natural erosion resistance value for the stream channel or a distance of 3D, whichever is larger. The provision of a minimum outlet apron length is required to prevent the development of a scour hole during flood events.

Date

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January 31, 2014 2 of 4



The natural erosion resistance design criteria are given in section HM 805-00. Width Criteria The width criterion is 3D for the inlet and outlet. Slope Criteria The slope of the inlet and outlet aprons should be designed to match the channel slope.

EMBANKMENT SIDESLOPE

Introduction The height of the erosion protection on the embankment slope depends upon the culvert end treatment. Height Criteria For projecting culvert ends, erosion protection shall extend a vertical height of 300 mm above the crown of the pipe at both the inlet and the outlet.

When a flared or sloped end treatment is used, the erosion protection shall extend a minimum distance of 1D form the end of the pipe (measured along the top of the pie) in addition to the vertical height requirement. Width Criteria The width criterion is 3D for the inlet and outlet for all pipe end types on single pipe culvert installations.

Where multiple pipes are present the width shall be increased by the pipe spacing specified in section HM 701-00.

800 mm AND SMALLER PIPES

Erosion control protection is not required for culverts 600 mm and smaller. These culverts serve a very limited drainage area that is typically contained within the highway right-of-way (ROW).

Date


January 31, 2014 3 of 4



Established ROW vegetation is adequate to resist the water flows typically encountered by these pipes. For through grade installations, where culverts are being specified on the basis of the minimum diameter standard of 800 mm, erosion protection is not required. In previous circumstances 500 mm and 600 mm culverts were used. Erosion control measures shall be taken to protect the culvert apron areas, disturbed by the installation, until the vegetation becomes established. For guidance on appropriate measures contact the Regional Environmental Project Specialist.

Date


January 31, 2014 4 of 4

HM 804-01

Hydraulic Manual Section: RIPRAP DESIGN Subject: SIZING OF STONE FOR RIPRAP

INTRODUCTION

The forces associated with flowing water that tend to displace riprap are proportional to the cross-sectional area of the stone and the squared value of the flow velocity. The stabilizing force for the stone is due to its submerged weight. In general, the selection of suitable stone to be used for riprap is based on the median stone dimension, designated dm or d50, which is the equivalent spherical diameter. The weight of the median stone may be calculated knowing its diameter and specific gravity

BASIS OF DESIGN RELATIONSHIP

The equivalent spherical diameter for rock usually considers the mass of the rock and a specific gravity of between 2.65 and 2.70. A relationship has been developed for the sizing of riprap, it is:

𝑑𝑚 = 𝑘𝑉2; Where: dm = Equivalent spherical diameter (m); V = Flow velocity (m/s); and k = Coefficient of proportionality. The coefficient of proportionality is a function of several factors, including: size, shape, and specific gravity of the rock, as well as velocity distribution and turbulence level of the flow, and the size and shape of the water prism. The value of k also depends on what stone dimension is designated as the equivalent spherical diameter, what velocity (mean, local, or maximum) is designated as V, and what factor of safety is used.

DESIGN RELATIONSHIP For culverts, the average velocity is used. It is assumed that the consequences of a partial failure of riprap would be relatively minor and would require a simple repair procedure. On this basis, the required size of natural field stone can be determined from:

dm = 0.019·V2; Where: dm = Equivalent spherical diameter of the median stone (m); and V = average outlet velocity (m/s).


January 31, 2014 1 of 2


Section: RIPRAP DESIGN Subject: SIZING OF STONE FOR RIPRAP

STANDARD STONE SIZE RANGES

The design relationship, and other considerations, such as ease of use and cost were used in the creation of standard stone size ranges for the tendering of culvert riprap. This resulted in the creation of two size ranges of riprap (Type I and Type II) for culvert installations: Type I Riprap – stone size range is 300 mm to 600 mm; it shall be used if the outlet velocity is equal to or greater than 3.0 m/s and less than 5.0 m/s. Type II Riprap – stone size range is 150 mm to 300 mm; it shall be used if the outlet velocity is less than 3.0 m/s. There is one additional size range (Type III) which is used by the Ministry for erosion protection in channels and other drainage works with design velocities less than 2.0 m/s. Type III Riprap - stone ranges in size from 60 mm to 150 mm. Within the size range 50% of the rock has a weight greater than the median stone, and the remaining 50% has a weight equal to or less than the median stone weight. The aspect ratio of the longest side of the riprap to the shortest size should be 2:1 or less.


January 31, 2014 2 of 2

HM 804-02

Hydraulic Manual Section: RIPRAP DESIGN Subject: RIPRAP APRON

INTRODUCTION

The length of riprap apron protection required depends on factors such as the size of the riprap present, the configuration of the channel bed, and the channel alignment. The inlet and outlet aprons have different requirements based on the type of flow that each experiences.

DESIGN PLANS Standard Plan HM807-01 is to be used for pipe culverts greater than 600 mm and less than 1 500 mm diameter where full hydraulic designs are not required as per section HM 302-00. Standard Plan HM807-01 is located in section HM 807-00 of the Manual. Larger culverts and culverts with embedment will have their own project specific individual design plans.

OUTLET APRON LENGTH

The riprap apron length is calculated using the following equation:

L = 3D(Vo-Vc)

Where:

D = Pipe diameter or rise for pipe arches (m); Vo = Culvert outlet velocity (m/s); Vc = Permissible natural channel velocity (m/s); and L = Apron length (m).

THICKNESS CRITERIA Inlet – The apron thickness shall be 300 mm.

Outlet – The values shown in Standard Plan HM 807-01 are to be used for pipe culverts greater than 600 mm and less than1 500 mm diameter. For culverts equal to or greater than 1 500 mm the thickness shall be 800 mm or 2Dm whichever is greater where Dm is the median stone size specified for the riprap.

LIMITATIONS Because the extent of the channel scour depends on the frequency and duration of the larger damaging discharges, culvert aprons should be inspected after a year of high runoff and additional riprap placed as required.



Section: RIPRAP DESIGN Subject: RIPRAP APRON



HM 805-00


NATURAL EROSION RESISTANCE

Subject:

INTRODUCTION

A natural stream channel experiences erosion forces that vary with the magnitude of the flow event that it experiences. The erosion forces are a function of the flow velocity. When a road and a culvert are introduced into a stream, the velocity regime along the stream channel changes because of the difference in the hydraulic design elements between the natural channel and the installed culvert.

DESIGN APPROACH The Ministry’s erosion control design approach is to:

• Provide erosion protection where the velocity associated with the culvert crossing outlet condition exceeds the permissible natural channel velocity; and

• Protect against local scour at the culvert ends. The permissible natural channel water velocity (Vc) that does not cause erosion depends on the natural erosion resistance of the ditch or channel and the channel cross-section. The limits of the stream channel are generally defined by the mean bank flow or bank-full flow, and are characterized as the 1:2 year flood return level Q2. The stream channel is considered stable under this condition. Under the Q2 flow condition, the erosion control design must reduce the velocity to mean permissible velocity (Vc) for the channel as described in the Maximum Permissible Velocity section below. For return periods higher than Q2, the erosion control design must protect the channel from scouring and reduce the velocity to match that of the natural channel. In this case, Vc equals the mean velocity of the stream channel just downstream of the end of the outlet apron.

EVALUATION OF STABILITY

The natural erosion resistance depends on:

• The grain size of the soil at the surface; • The degree of cohesion of the soil; and • The density of the vegetation present, if any.


January 31, 2014 1 of 4


Section:


Subject:

Two methods are commonly applied to determine whether the ditch or channel is stable against erosive forces. These methods are the “Permissible Velocity Approach” and the “Permissible Tractive Force Approach.” The channel or ditch is assumed to be stable if the mean velocity of the flow is lower than the maximum permissible velocity for the ditch, or if the tractive force or boundary shear stress developed at the interface between the flowing water and the materials forming the channel boundary is less than a limited maximum unit tractive force for the ditch lining. In this manual, the permissible velocity approach is used because more complicated and sophisticated methods are not usually appropriate or justifiable for design of culvert outlets. However, the permissible tractive force method may be used for other hydraulic designs (Smith, 1989).

MAXIMUM PERMISSIBLE VELOCITY

Maximum permissible velocities for various soil textures and types of vegetative cover have been compiled by others (Fortier and Scobey 1927, Coyle 1975). Table 805-1 summarizes these findings for a flow depth of 1 m and for the case where the channel axis is in line with the culvert axis.

ADJUSTMENTS TO LIMITING VELOCITY

In most cases, the flow discharging from the culvert is required to make a sharp turn into the ditch. In this case, the limiting velocity from the table should be reduced by 25% to avoid erosion of the bank. If the depth of flow is shallower than 1 m, the allowable velocity must also be reduced. Conversely, for a deeper flow depth, the allowable velocity may be increased. These adjustments are shown in Table 805-2. As the tables show, the erosion resistance of the boundary is increased if the ditch is well grassed. Dense sod-forming grasses like Kentucky Bluegrass are superior to tufted grasses like Brome, which tend to promote channeling between the tufts. In heavy clay soils, the grass may be so sparse that no real benefit is gained over the natural clay.


January 31, 2014 2 of 4


Section:


Subject:

Table 805-1: Permissible Mean Velocities for Various Channel Boundary Materials* (Smith,

1995a)

Channel Boundary Material Permissible Mean Velocity (m/s)

Cohesionless Materials

Fine sand 0.46 Medium sand 0.56 Coarse sand 0.66 Fine gravel 0.76

Coarse gravel 1.22 Cobbles 1.52

Cohesive Materials

Sandy loam 0.53 Silty loam 0.61

Alluvial silt 0.61 Volcanic ash 0.76

Firm loam 0.76 Stiff clay 1.14 Clay shale 1.83 Hardpan 1.83

Glacial till 2.00 Grassed Channel

(in loam soil)

Brome grass (tuffed) 1.22 Grass mixtures 1.22

Kentucky Bluegrass 1.52 Bermuda grass 1.83

* Clear water, straight channel, 1 m depth

Table 805-2: Depth Adjustment Factors for Permissible Mean Velocity (Smith, 1989)

Depth (m)

Factor

0.5 0.90 1.5 1.10 2.5 1.20


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Subject:



January 31, 2014 4 of 4

HM 806-00


REFERENCES

Coyle, J.J. (1975). Grassed Waterways and Outlets. Engineering Field Manual, U.S. Soil Conservation Service, Washington. Fortier, S. and Scobey, F.C. (1926). Permissible Canal Velocities. Transactions of the American Society of Civil Engineers, Vol. 89. Smith, C.D. (1989). Notes from a Seminar on Highway Drainage Design Aspects. Presented to Saskatchewan Ministry of Highways and Infrastructure. 15-16 February. Smith, C.D. (1995a). Hydraulic Structures. (Pp. 10-37), University of Saskatchewan Printing Services and Universal Bindery, Saskatoon. Smith, C.D. (1995b). Hydraulic Structures. (Pp. 10-41), University of Saskatchewan Printing Services and Universal Bindery, Saskatoon. Smith, C.D. (1995c). Hydraulic Structures. (Pp. 10-30), University of Saskatchewan Printing Services and Universal Bindery, Saskatoon.






Hydraulic Manual

Section 807-00

Standard Plans

2014


Hydraulic Manual

Section 900

Fish Passage Design Procedures

2014


HM 901-00


FISH PASSAGE DESIGN PROCEDURE

Subject:

INTRODUCTION The purpose of this section is to provide the designer with guidance

when designing a hydraulic structure that will accommodate the Fisheries and Oceans Canada (DFO) requirements for large bodied fish passage. Where the term ‘fish’ is used in this section it shall refer to large bodied fish. It is important that hydraulic structures on fish migration routes do not prohibit fish passage during the spawning period.

DESIGN PROCEDURE Climate and geography vary significantly across the Province. Streams in the Province are either perennial (a stream that flows continuously throughout the year), or recurring (a stream that flows for only part of the year). This variation has resulted in some of the drainage runs that culverts are located on not being able to support fish spawning habitat, or are physically cut off from fish populations. Step 1 Determine if the drainage runs either contain fish or if during the usual spring runoff, are connected to fish bearing waters and contain suitable fish spawning habitat. Step 2 Determine the design fish species and the associated spawning requirements. Fish spawn in either the spring or the fall depending upon the species. Northern pike, arctic grayling, sauger, walleye and suckers spawn in the spring. Whitefish, cisco and all species of trout spawn in the fall. Where a stream connects to lakes that have both spring and fall spawning species, the requirements of both have to be considered in the design. The spring spawners typically determine the design mean velocity requirement while the fall spawners typically determine the minimum water depth requirement, because Saskatchewan streams are typically at their lowest flow rate in the fall/winter.

Date Fish Passage Design Procedure Page

January 31, 2014 1 of 6


Section:


Subject:

Fall spawning fish species are not a design consideration for recurring streams. The spawning periods also impact when construction can occur within the stream. Step 3 Determine the design fish flow. The process for doing this is outlined in the DESIGN CRITERIA section below. Step 4 Undertake the culvert analysis work to generate alternative designs that meet the design requirements. The guidance for doing this is contained in the DESIGN CRITERIA section below. DFO has two main design objective functions for fish passage. First, the velocity in the culvert must meet the Design Mean Velocity requirement. Second, the water level in the culvert must be high enough to allow the fish to swim submerged through the culvert. This is set by the Minimum Depth Of Water requirement. Refer to the Environmental Directive 2014.01 Federal Fisheries Act Changes for guidance on how to meet the requirements of the Fisheries Act that is administered by DFO. This document is to be used until further detail is provided in the release of the Ministry’s Environmental Approvals document. For guidance on the requirements, contact the Regional Environmental Project Specialist or the Senior Environmental Engineer.

DESIGN CRITERIA Design Fish Flow For designs based on the spring spawning period, the maximum period for which fish may be delayed during the spawning period is 3 days during a ten year return period discharge. Therefore, the design discharge that must be met is the Q10

3 day delay. This is better stated as the maximum delay is 3 days for any flow less than and including the Q10

3 day delay flow.


January 31, 2014 2 of 6


Section:


Subject:

The Water Security Agency (WSA) provides Q10

3 day delay design flow estimates upon request for drainage basins sufficiently large to produce valid results. See section HM 500-00 for additional information on WSA flows. Where the WSA is unable to provide a design flow, it will have to be determined based on the guidance found in section HM 500-00. For designs based on the fall spawning period, the average flow rate will have to be estimated for the spawning period. The WSA is typically able to provide an estimate of this flow. Design Mean Velocity Studies have shown that the velocity within the culvert varies across the cross-section with the highest at the water surface and the lowest near the culvert bottom and sides. Culvert analysis programs typically calculate the mean velocity, which is then used in design. The design mean velocity is dependent on fish species and culvert length. The design mean velocities used by the DFO have historically been based on the research conducted by Katopodis (1993) which resulted in a set of swimming distance curves. The curves have been included in the Fish Habitat Protection Guidelines – Road Construction and Stream Crossings publication. Over time the application of these curves has evolved somewhat based on the research that has been undertaken since 1993. In Saskatchewan, the design mean velocity is typically based on northern pike, when present, due to their poor prolonged swimming speed. The target design mean velocity is usually 0.5 m/s for typical two lane road culvert widths although there is a range of values that may be approved for use on a project based on the specific site conditions. Where the design mean velocity is based on a fish species other than northern pike, the target design mean velocity is usually 1.0 m/s for typical two lane road culvert widths, although there is a range of values that may be approved for use on a project based on the specific site conditions.


January 31, 2014 3 of 6


Section:


Subject:

It is the responsibility of the designer to establish the target design mean velocity. Contact the Regional Environmental Project Specialist for assistance. The average culvert exit velocity is calculated by CulvertMaster and is included in the output reports. The exit velocity will typically be the controlling velocity for fish passage design for the horizontal to mild culvert slopes typically required in fish passage design. However, the designer must check the CulvertMaster output to see if the tailwater elevation is greater than the normal depth and if the hydraulic profile type is M1. Where this situation is present, the controlling velocity will occur at the culvert inlet and will be greater than the velocity output by CulvertMaster. In this situation the velocity can be calculated using the following procedure:

1. Use the Direct Step Method or the Standard Step Method to calculate the water surface profile starting at the outlet to establish the depth of water at the inlet.

2. Determine the flow area from the water depth and the geometry of the pipe. The Ministry has developed a Water Flow Area Calculator in Excel to determine this. Refer to section HM 1000-00 for details on the program.

3. Determine the inlet velocity using the equation.

𝑉 = 𝑄𝐴

To meet the DFO design velocity requirements, the culvert will typically have to be embedded. In some circumstances, Newbury riffle structures or some other design measure may have to be employed to control the culvert velocities. DFO no longer promotes the use of baffles or baffle like structures constructed out of rock substrate in Saskatchewan culverts to meet fish passage velocity requirements; since in most situations, the baffles become filled in with sediment, increasing the velocity of the water. This creates a barrier to the fish passage, rather than aiding in fish passage.


January 31, 2014 4 of 6


Section:


Subject:

Minimum Depth of Water in Culvert DFO requires a minimum depth of water in the culvert of 0.3 m at the design fish flow. Culvert Embedment DFO have indicated on their permit that when fish are present in the stream, the minimum allowable embedment is 20% of the pipe diameter. This is intended to address the objective function of maintaining a minimum depth of water in the culvert and to protect the culvert from becoming perched. Stream channels that are determined to be aggrading impose unique constraints upon the fish passage design that have to be addressed through the design process. The normal design practices such as embedment do not function well because the embedded part of the culvert will continually fill up with sediment. Cleaning of these culverts is not feasible on an ongoing basis Stream crossings with no history of degradation and average stream profile slopes less than 2% are deemed to be stable and require no special measures, such as culvert embedment, over and above the Ministry erosion protection standards to ensure no future perching of the culvert. Where the existing stream’s slope is deemed to be stable, the Ministry’s position is as follows:

• A culvert is only embedded where required to meet the DFO velocity or minimum depth of water design objectives.

• There is no benefit to embedding culverts to maintain stream flow continuity or movement of forage fish species in recurring stream channels.

• The embedment of culverts, where not required, places a significant financial burden upon the Ministry due to premature rusting of embedded culverts and maintenance operations to keep them clear.


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Section:


Subject:

For replacement of existing culverts, the designer must determine whether or not there is any indication of stream channel degradation during the field review, and document the results. For culvert crossing projects where there is a history of stream channel degradation or the average stream channel slope is greater than 2%, the design shall include a minimum allowable culvert embedment of 20%. The transition slope from the embedded erosion protection apron is 10:1 for the inlet and 4:1 for the outlet. Refer to section HM 610-00 for additional Ministry design requirements regarding culvert embedment not specific to fish passage design. Slope of the Culvert The slope of the culvert should be in the 0.005 m/m range or lower for fish passage. The natural channel slope should be used when it is flatter than the specified 0.005 m/m.

OTHER CONSIDERATIONS

Culvert Type Open footing culverts can be advantageous for fish passage. However, the velocity and cost must be considered. Good foundation conditions must exist and conditions must support the economic premium. Multi-barrel Culvert Installations Multi-barrel culverts are useful on wide streams with low depths of flow. Only one culvert needs to be designed for fish passage. At multi-barrel culvert installations, there is a tendency for the stream to leave one barrel clear and deposit sediment in the others. When deciding to embed only one culvert, the Designer needs to ensure that it is not one of the ones that gets sediment deposited in it by the stream.


January 31, 2014 6 of 6

Hydraulic Manual

Section 1000

Design Aids

2014


HM 1001-00

Hydraulic Manual Section: DESIGN AID CRITERIA Subject:

INTRODUCTION

The purpose of the Design Aid Section is threefold. Firstly, it is used to identify the design aids that have been approved for use in the design of culverts on the Ministry’s road network. Secondly, it is the provision of guidance on the interpretation of the material provided in this manual. Thirdly, it is the provision of educational materials to assist the designer in the use of the approved design aids and to undertake the various aspects involved in the design, construction, and maintenance of culverts. The intention is to expand the educational material from the current print oriented form into the various electronic forums and formats in common use today as time and resources permit. Directions on how to access the design aids that the Ministry is licensed to distribute and material on how to obtain the ones available through other sources is included below in the section APPROVED DESIGN AIDS. The manual will contain links to resources that cannot be viewed in the traditional document format.

DESIGN AID APPROVAL Any proposed alternative software design aids shall be assessed and approved by Technical Standards Branch prior to their use. Requests to have new design aids approved and added to the Approved Design Aid section shall be sent to the Senior Road Design Engineer. Technical Standards Branch will conduct a review of proposed design aid and provide a recommendation for approval or rejection to the Executive Director of Technical Standards Branch.

APPROVED DESIGN AIDS

CulvertMaster The Ministry has standardized on the use of CulvertMaster for the hydraulic analysis of the culverts on its highway network. CulvertMaster replaced the Ministry’s internal hydraulic design programs. Consultants are responsible for ensuring that they are using the latest version of CulvertMaster and the Ministry Library Files for it.

Date Design Aids Page

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Section: INTRODUCTION Subject: DESIGN AID CRITERIA

Click here to save a copy of the latest version of the CulvertMaster Library files to your computer. Refer to section HM 1002-00 for guidance on the use of CulvertMaster. CulvertMaster is distributed by Bentley Systems Incorporated and their website is www.bentley.com. Wood Box Culvert Calculator For Full Flow An Excel program has been developed by the Ministry to analyze wood box culverts under full flow conditions. Refer to the Readme TAB on the spreadsheet for information on how to use the Wood Box Calculator. The Wood Box Calculator is available on the Knowledge Warehouse or by clicking here. Contact the Senior Road Design Engineer, Technical Standards Branch if you have any questions or comments with respect to this program. Culvert Flow Area Calculator for Round Culverts An Excel program has been developed by the Ministry to facilitate the calculation of round culvert flow areas, which replaces the material contained in section HM 707-00 and section HM 708-00 in the Hydraulic Manual (1988). Refer to the Readme TAB on the spreadsheet for information on how to use the Flow Area Calculator. The Flow Area Calculator is available on the Knowledge Warehouse or by clicking here. Contact the Senior Road Design Engineer, Technical Standards Branch, if you have any questions or comments with respect to this program. Hydraulic Project Checklist An Excel program has been developed by the Ministry to facilitate the review of culvert designs or projects. It may also provide the designer a means of self-auditing the design for compliance with the Ministry’s


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http://www.bentley.com/

http://www.highways.gov.sk.ca/Doing Business with MHI/Ministry Manuals/Hydraulic Manual/03 MHI Culvertmaster Library (Feb 2015)/MHI CulvertMaster Library (zipped file).zip

http://www.highways.gov.sk.ca/Doing Business with MHI/Ministry Manuals/Hydraulic Manual/02 Design Aids/Wood Box Culvert Calculator.xlsx

http://www.highways.gov.sk.ca/Doing Business with MHI/Ministry Manuals/Hydraulic Manual/02 Design Aids/Culvert Flow Area Calculator.xlsx



culvert hydraulic design policy. Refer to the Readme TAB on the spreadsheet for information on how to use the Checklist. The Checklist is available on the Knowledge Warehouse or by clicking here. Contact the Senior Road Design Engineer, Technical Standards Branch, if you have any questions or comments with respect to this program.

HYDRAULIC DESIGN GUIDANCE

From time to time, the Ministry may issue guidance on the material contained in the Hydraulic Manual between formal updates to it. This guidance can be in the form of Design Directives or Technical Bulletins. The Design Directives are located in section HM 2001-00 while the Technical Bulletins are located in section HM 2000-00. Design Directives usually deal with issues of interpretation of the material contained in the Hydraulic Manual while Technical Bulletins usually add new material. It is the responsibility of the designer to check the Knowledge Warehouse prior to starting each project to ensure that that are following the latest Design Directives or Technical Bulletins.


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http://www.highways.gov.sk.ca/Doing Business with MHI/Ministry Manuals/Hydraulic Manual/02 Design Aids/Hydraulic Project Checklist.xlsm





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HM 1002-01

Hydraulic Manual Section: CULVERTMASTER Subject: OPERATION

INTRODUCTION

CulvertMaster enables the analysis of systems with multiple barrels, different shapes and sizes, special tailwater considerations, and roadway overtopping considering watershed data. It also allows input of culvert characteristics and weir geometry. CulvertMaster enables the automatic comparison and incorporation of several design trials into complex hydraulic analyses and evaluates the results. CulvertMaster builds on the available inputs and provides unknown design variables. It outputs reports with a customizable report template.

BASIS CulvertMaster is a computer implementation based on the design procedures included in FHWA Design Series 5: Hydraulic Design of Highway Culverts. At this time, it does not support the design procedures associated with slope tapered and side tapered inlets.

LIMITATIONS CulvertMaster does not support all of the design procedures associated included in HDS 5. The designer should be aware of which design procedures are not included. In the stream bed cross-section editor, if you are making changes to the cross-section or the Manning’s n values, CulvertMaster will not automatically recalculate the outputs. In order to recalculate the outputs, you must change the method to “constant tailwater”, then back to “natural channel,” make your changes, and click “solve all.” This is a bug in the CulvertMaster software that has not been corrected. CulvertMaster does not directly support the analysis of a culvert that has different Manning’s n values for portions of its circumference. An example of this is where the invert of a CSP culvert has been paved or a rock substrate has been added to the bottom of the culvert. CulvertMaster does not support the manual insertion of inlet loss coefficients (ke), but does support the manual insertion of Manning’s n values. The designer is to refer to HM 611-01 for the proper analysis of wood box culverts when using CulvertMaster.


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CULVERTMASTER LIBRARY FILES

The default Library Files that are supplied with CulvertMaster do not cover all of the culvert sizes and materials that are in common use in Saskatchewan. To address this, the Ministry has created a modified set of Library Files. The Ministry Library Files are to be used for all Ministry projects. The Library Files are maintained by the Senior Road Design Engineer, Technical Standards Branch. The Ministry Library files are updated from time to time in response to the need to include new culvert sizes or materials or to correct identified issues. The latest version of the Ministry Library Files is available on the Knowledge Warehouse in the Hydraulic Manual section.

EDUCATIONAL MATERIALS

A tutorial on the use of CulvertMaster is included in HM 1002-02. It is suggested that it be used in conjunction with the CulvertMaster examples included in HM 1002-03.


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HM 1002-02

Hydraulic Manual Section: CULVERTMASTER Subject: TUTORIAL

INTRODUCTION The purpose of this section is to provide the designer with guidance on

the use of the Bentley CulvertMaster program, for the purpose of culvert hydraulic design calculations. For a more detailed description of the CulvertMaster operation, obtain a copy of the CulvertMaster user’s manual.

DATA ENTRY In order for CulvertMaster to recognize data, you must use the ‘tab’ key while entering values. This is extremely important to ensure that the program provides the correct values.

STARTING A NEW PROJECT

Starting a New File The first order in the design is to choose you design alternative method. On the first screen, you can choose from the Quick Calculator, New Analysis, or New Design methods.

QUICK CULVERT CALCULATOR

To quickly analyze an existing structure, use the Quick Calculator Method.

CULVERT DESIGNER/ANALYZER DESIGN MODE

When conducting a design, use the New Analysis or New Design Method. Once in either of these methods, you can switch back and forth between the Design and Analysis methods. The design mode requires basic site and roadway data for a specific culvert crossing. It allows the creation of several design trials at that site. It may be used to solve for watershed discharge, design headwater, tailwater conditions, stream channel profiles, and embankment slopes. Use the New Design option if you are creating individual culvert trials and solving for:

• The size of a culvert of a specified shape and material under design discharge, elevation, and headwater conditions;

• Discharge for a specific culvert under design elevation headwater; or

• Elevation headwater for a specific culvert under design discharge conditions.


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Section: CULVERTMASTER Subject: TUTORIAL

CULVERT DESIGNER/ANALYZER ANALYSIS MODE

The analysis mode may be used to solve for watershed discharge, tailwater conditions and stream channel profiles, and roadway profiles for overtopping. You can specify each of the culvert structures that work together to provide cross-drainage at a site. Design mode culverts may be imported to evaluate the effects of adding supplemental structures. Use the New Analysis option if you are:

• Verifying the hydraulic performance of existing culverts; • Analyzing complex situations such as main-stream culverts

working in combination with relief culverts in overbank areas; • Performing road overtopping analysis of existing culverts or new

designs; or • Supplementing existing culvert structures to correct inadequate

capacities resulting from urbanizing watershed or undersized cross-drain conditions.

Once you have chosen the appropriate project mode, the screen provided in Figure 1002-1 will pop up asking for a title of alternative. Give your alternative a unique file name so you can reference it in the future. Remember this is the design alternative file name not the project name. You will be prompted for the project name when you try quitting the program.


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Figure 1002-1: Screenshot of CulvertMaster Alternative Design Name Screen

NEW PROJECT SCREEN Once the alternative design name has been provided, you can begin to add properties to your project by clicking the “edit” button on the left. In this screen, you can choose which input method you wish. Culvert Designer/Analyzer methods are both available for inputs. In the screen shot shown in Figure 1002-2, the New Analysis method has been selected, therefore only the Watershed and Tailwater tabs are available. If the New Design method had been selected, all four tabs would be visible. You may flip between the Designer/Analyzer methods at any time, whether you started in the New Design or New Analysis method. Please note that in the Designer Method, the inverts input at the beginning will apply to all alternative structures being


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calculated. However, in the Analyzer Method the inverts may be input independently for each structure.

INPUTTING THE DESIGN DISCHARGE

Click on the Watershed Tab and input the design discharge in accordance with section HM 500-00. Figure 1002-2: Inputting the Design Discharge

INPUTTING THE TAILWATER INFORMATION _ SELECTION OF TAILWATER PROCEDURE

This is an area where much caution must be used. If you have independently calculated the tailwater, then you can use the Constant Tailwater. Note that this will require you to have calculated the tailwater for each discharge you are designing CulvertMaster will calculate the effective tailwater for four different downstream cross-sections – Rectangular, Triangular, Trapezoidal, or Natural Channel. When using the tailwater calculator in


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CulvertMaster, no upper limit is assumed for the Rectangular, Triangular, or Trapezoidal channels. For the Natural Channels, make sure your cross-section encloses the entire flow for your design discharge, as CulvertMaster will assume a vertical wall at the end of your cross-section. CulvertMaster will not give you an error message when either your structure height or cross-section limits have been exceeded. Figure 1002-3: Selection of Tailwater Procedure

NATURAL STREAM BED ALTERNATIVES

In most instances the Natural Channel is the downstream structure which will dictate the tailwater effect on your design. For the next step, click the “Edit Cross Section…” button, as shown in Figure 1002-4.


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Figure 1002-4: Natural Channel Options

STREAM BED CROSS-SECTION EDITOR

Next, the screen shown in Figure 1002-5 will appear and you can place your cross-section into the left side of the screen and your Manning’s n values into the right side. The Manning’s n coefficients will vary throughout your cross-section. CulvertMaster then uses a weighted average for the whole cross-section. If you are making changes to the cross-section or the Manning’s n values, CulvertMaster will not automatically recalculate the outputs. In order to recalculate the outputs, you must change the method to “constant tailwater,” then back to “natural channel,” make your changes, and click “solve all.”


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Figure 1002-5: Stream Bed Cross-Section Editor

ADDING A NEW COMPONENT Click on the new component icon “ ” just below the Output icon on

the bottom half of the menu.

NEW COMPONENT SCREEN

The new component screen is where you input your design culvert, as shown in Figure 1002-6.


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Figure 1002-6: New Component Screen

SELECTING THE COMPONENT SHAPE

The first characteristic in the section area is shape. Here you select your structure shape from the drop-down menu: Arch, Box, Circular, Horizontal Ellipse, or Vertical Ellipse.

SELECTING THE MATERIAL

The second characteristic is material. Here you select your structure material from the drop-down menu: CMP, Concrete, Corrugated HDPE, CSP Helical, Multi Plate, PVC, Steel, Vitrified Clay Pipe.

SELECTING THE COMPONENT SIZE

The next step is to select the culvert size you wish to evaluate from the drop-down menu. The alternative sizes available depend on the shape and material selected.


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INPUTTING THE NUMBER OF EQUAL COMPONENTS

In this area, you can use as many culverts of the same configuration as you wish. All culverts will have the exact same shape, size and material. If you wish to use culverts of different sizes, then complete the input for this culvert and add a new component at the initial screen.

SELECTING MANNING’S N

Select the appropriate Manning’s n value from the drop-down list titled “Mannings.” Ensure that you check the value that comes up initially as it may be incorrect. If you are using a material that is not currently or not correctly listed in this menu, input the proper value and reference its source in your report.

SELECTING INLET SHAPE

The next step is to select the inlet properties. First, select the type of inlet. In most Highway design cases the “Projecting” inlet is used. An entrance loss coefficient is automatically supplied when you select the inlet type.

SELECTING INVERT OPTIONS

This input area only applies to the Analyzer method. In the “Inverts” section, the first criteria input is what you wish to solve. Alternatives are: upstream invert, downstream invert, length, or slope. In most cases, everything but the slope is known, therefore select solve for slope. Input inverts and culvert length.

RUN THE DESIGN ALTERNATIVE

Once the inputs are in the program, you are ready to solve the alternative design. Click on the solve icon and the results on the right side of the screen will be updated. You can also look at the results in report form by clicking on the Output icon.

OUTPUT When you click the “output” button, you are provided with three options: Generate Report, Calculate Rating Table, or Plot Curves. Quick Culvert Calculator Report The Quick Culvert Calculator worksheet report contains a summary of the input data, hydraulic profile information, information on the culvert sectional characteristics, an outlet control summary, and an inlet control summary.


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Culvert Designer/Analyzer Report The first page of the Culvert Designer/Analyzer worksheet report contains a summary of input data and a tabular summary of each component or trial, as well as the overall results for an analysis. The remaining pages are more detailed reports for each component or trial, including the same information as listed above for the quick culvert calculator report. The “Generate Report” Screen is shown on the next page.


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Figure 1002-7: “Generate Report” Screen


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Calculate Rating Table

The Calculate Rating Table is shown below. Note that you have several options of what to compute and you may change the minimum, maximum, and increment of the discharge. You may also choose to compute several options at once. When changing options, click the “refresh” button to update the table. In the Quick Culvert Calculator, there is one column for each variable that is specified to be computed. In Culvert Analyzer, there is one column for each culvert analysis component and one column for the total or system value of the component. In Culvert Designer, there is one column for each culvert design trial.

Figure 1002-8: Rating Table


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Plot Curves The last option is to plot a performance curve, as shown below. It is a graphical representation of the relationship between two system characteristics. In Design Mode, one curve is generated for each culvert design trial. In Analysis Mode, one curve is created for each culvert analysis component and one curve is created for the total or system curve.

Figure 1002-9: Performance Curve

SPECIAL CONSIDERATIONS

The CulvertMaster software is a very effective tool for making the mundane calculations; it does not do the design – just the calculation. CulvertMaster will not find errors in your design or even tell you when you have bad inputs. It is up to the designer to look for errors and fix them.


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HM 1002-03

Hydraulic Manual Section: CULVERTMASTER Subject: DESIGN EXAMPLES

INTRODUCTION

There are five CulvertMaster examples included in the Hydraulic Manual. Each example exemplifies an important aspect of using and understanding culvert design. The examples provide step-by-step procedures and the Culvert Design Report is appended to the end of each example. Before attempting any examples, please read section HM 1002-02: CulvertMaster Tutorial.

EXAMPLE 1: INLET CONTROL

The first example is a culvert that is under inlet control. This is a basic situation with no tailwater effects. The example also analyzes the use of multiple culverts, both using the same flow and using twice the flow.

EXAMPLE 2: OUTLET CONTROL

The second example is a culvert that is under outlet control. This is a basic situation with no tailwater effects. It exemplifies how a change in slope may cause the transition from inlet control to outlet control. This is one of the most common situations to occur in the field.

EXAMPLE 3: TAILWATER EFFECTS

The third example is a culvert with tailwater. It includes calculating the tailwater elevation, analyzing the use of multiple culverts, and checking the headwater elevation of a given size of culvert. It also explains why the addition of tailwater creates the need for a larger culvert.

EXAMPLE 4: MANNING’S N

The fourth example is a long culvert with a small grade. It analyzes the importance of using the correct Manning’s n value and checking to make sure the culvert size that CulvertMaster provides is the most economic option. It also describes the theory behind the headwater used in the example.

EXAMPLE 5: CROSS-SECTIONS

The sixth example analyzes the importance of correctly inputting tailwater cross-sections into CulvertMaster. More specifically, it explains identifying the restricting downstream cross-section, using sufficient survey data, and properly assigning Manning’s n values.


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Section: CULVERTMASTER Subject: DESIGN EXAMPLES

EXAMPLE 1: INLET CONTROL

Given:

Q25 = 7.1 m3/s AHWel = 1624.0 m TW = No tailwater effect Inlet INVel = 1621.0 m So = 0.02 m/m L = 32 m

Find: Determine the culvert installation for the provided conditions.

SOLUTION 1. Select “New Design”, since the size of the culvert is unknown.

2. Insert peak discharge: Q25 = 7.1 m3/s in the “Watershed” Tab.

3. Select method “Maximum Allowable HW,” and insert the AHWel = 1624.0 m in the “Headwater” Tab.

4. Select method “Constant Tailwater” and do not insert a

tailwater elevation (it should read “N/A”) in the “Tailwater” Tab.

5. Under the “Grades” Tab select method “Inverts” because the

invert elevation is known. Select solve for “Invert Downstream” and insert the known values: - Invert Upstream: Inlet INVel = 1621.0 m - Length: L = 32 m - Slope: So = 0.02 m/m

Provides answer: Invert Downstream = 1621.0 m


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6. Select solve for “size” in “New Design Trial” since the required headwater elevation is known.

7. Determine the characteristics of the culvert section you wish to apply. - Shape: Circular - Material: CSP Helical - Number: 1 - Manning’s n: Use an iterative process to establish the

correct value.

From section HM 602-00 the most economical structure occurs when 1.5 < HW/D < 2.

At HW/D = 1.75, D = (1624 m – 1621 m)/(1.75) = 1714 mm For D = 1700 mm, n = 0.0211 (section HM 609-01).

8. Inlet Properties:

- Inlet: Projecting - Ke: 0.90 Select “Solve”.

9. Results:

- Size: 1700 mm - Headwater elevation: 1623.68 m - Velocity: 4.21 m/s. - Depth downstream: 1.18 m - Control Type: Inlet Control - Manning’s n = 0.0211; correct diameter, no further

iteration required.

HW/D = (1623.68 m – 1621.0 m) / 1.7 m = 1.576; within the economical range.

10. Multiple Culverts – Same Flow Return to “New Design Trial” and change “Number” to 2 and solve. Now only 1200 mm pipes are required and the velocity and depth have dropped. The flow regime has also changed


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from supercritical to subcritical.

11. Results from second iteration: - Size: 2 x 1200 mm - Headwater elevation: 1623.42 m - Velocity: 3.61 m/s - Depth downstream: 0.97 m - Control Type: Inlet control - Manning’s n = 0.0200

HW/D = (1623.42 m – 1621.0 m) /(1.2 m) = 2.017; just outside of economical range. Since this lies out of the economic range, change “solve for” to “headwater elevation” and increase the diameter.

12. Results from third iteration: - Size: 2 x 1300 mm - Headwater elevation: 1623.00 m - Velocity: 3.67 m/s - Velocity Downstream: 0.89 m - Control Type: Inlet Control - Manning’s n = 0.0203 HW/D = (1623 m – 1621 m) /(1.2 m) = 1.67; within economical range.

13. Multiple Culverts – Twice the Flow Close the “New Design Trial” and return to the “Watershed” tab. Change the design discharge to 14.2 m3/s. Re-open the “New Component”. Change the “Solve for” to “size” and the Manning’s n to 0.0211. Solve the problem. The solution is now exactly the same as the very first trial, except there are two 1700 mm culverts. The velocity, depth, headwater, control type, and HW/D ratio are all the exact same.

The following is the culvert design report for the first trial.


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CULVERT DESIGN REPORT

Culvert Summary Allowable HW Elevation

1,624.00 m Storm Event Design

Computed Headwater Elevation

1,623.68 m Discharge 7.1000 m³/s

Headwater Depth/Height

1.57 Tailwater Elevation N/A m

Inlet Control HW Elev.

1,623.68 m Control Type Inlet Control

Outlet Control HW Elev.

1,623.66 m

Grades Upstream Invert 1,621.00 m Downstream Invert 1,620.36 m Length 32.00 m Constructed Slope 0.020000 m/m

Hydraulic Profile Profile S2 Depth, Downstream 1.18 m Slope Type Steep Normal Depth 1.18 m Flow Regime Supercritical Critical Depth 1.34 m Velocity Downstream

4.21 m/s Critical Slope 0.014628 m/m

Section Section Shape Circular Mannings

Coefficient 0.0211

Section Material CSP Helical

Span 1.70 m

Section Size 1700 mm.

Rise 1.70 m

Number Sections 1


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Outlet Control Properties


1,623.66 m Upstream Velocity Head

0.69 m

Ke 0.9000 Entrance Loss 0.63 m

Inlet Control Properties


1,623.68 m Flow Control Submerged

Inlet Type Projecting Area Full 2.3 m² K 0.03400 HDS 5 Chart 2 M 1.50000 HDS 5 Scale 3 C 0.05530 Equation Form 1 Y 0.54000

DESIGN EXAMPLE 2: OUTLET CONTROL

Given:




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SOLUTION: 1. Select “New Design”, since the size of the culvert is unknown.

2. Insert peak discharge: Q25 = 7.1 m3/s in the “Watershed”

Tab.

3. Select the method “Maximum Allowable HW” and insert AHWel = 1624.0 m in the “Headwater” Tab.

4. Select the method “Constant Tailwater,” and do not insert a


5. Under the “Grades” Tab, select solve for “Invert

Downstream”. Insert the known values: - Invert Upstream: Inlet INVel = 1621.0 m - Length: L = 32 m - Slope: So = 0.005 m/m - Provides Answer: Invert Downstream = 1620.84

6. Select solve for “size” in “New Design Trial since the required headwater elevation is known.

7. Determine the characteristics of the culvert you wish to apply. - Shape: Circular - Material: CSP Helical - Number: 1 - Manning’s n: Use an iterative process to establish the

correct value. At HW/D = 1.75, D = (1624 m – 1621 m)/(1.75) = 1714 mm For D = 1700 mm, n = 0.0211 (section HM 609-01).

8. Inlet Properties

- Inlet: Projecting - Ke = 0.90 Select “Solve”.

9. Results:

- Size: 1700 mm - Headwater elevation: 1623.74 m. - Velocity: 3.69 m/s.


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- Depth downstream: 1.34 m - Control Type: Outlet Control - Manning’s n = 0.021; correct diameter, no further iteration

required. HW/D = (1623.74 m – 1621 m)/1.7 m = 1.61; within economical range.

CUVLERT DESIGN REPORT




1,623.74 m Discharge 7.1000 m³/s




1,623.69 m Control Type Outlet Control


1,623.74 m


Hydraulic Profile Profile Composite M2 Pressure

Profile Depth,

Downstream 1.34 m

Slope Type Mild Normal Depth N/A m Flow Regime Subcritical Critical Depth 1.34 m Velocity Downstream



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Coefficient 0.021


Span 1.70 m


Rise 1.70 m

Number Sections 1




0.50 m




1,623.69 m Flow Control Submerged


DESIGN EXAMPLE 3: TAILWATER EFFECTS

Given:

Q25 = 7.1 m3/s AHWel = 1624.0 m TW = 3.2 m Inlet INVel = 1621.0 m So = 0.02 m/m L = 48 m


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SOLUTION 1. Select “New Design” since the size of the culvert is unknown.

2. Insert peak discharge Q25 = 7.1 m3/s in the “Watershed” Tab.

3. Select “Maximum Allowable HW” and insert AHWel = 1624.0 m in the “Headwater” Tab.

4. Select solve for “Invert Downstream” in the “Grades” Tab.

Insert the known values: - Invert Upstream: Inlet INVel = 1621.0 m - Length: L = 48 m - Slope: So = 0.02 m/m Provides answer: Invert Downstream = 1620.04 m.

5. Choose the method “Constant Tailwater” in the “Tailwater”

Tab and insert the tailwater elevation: TWel = 1620.04 m + 3.2 m = 1623.24 m

6. Select the “New Design Trial” Button . Solve for “Size”.

7. Determine the characteristics of the culvert section you wish to apply: - Shape: Circular - Material: CSP Helical - Number: 1 - Manning’s n: Use an iterative process to establish the

correct value. At HW/D = 1.75, D = (1624 m – 1621 m)/(1.75) = 1714 mm


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For D = 1700 mm, n = 0.0211 (section HM 609-01).

8. Inlet Properties

- Inlet: Projecting - Ke = 0.90 - Select “solve”.

9. Results:

- Size: 2100 mm - Headwater elevation: 1623.86 m - Velocity: 2.05 m/s - Downstream depth: 3.20 m - Control Type: Outlet control - Manning’s n: 0.0214; estimated wrong diameter but n

change is small.

HW/D: (1623.86 m – 1621 m)/2.1m =1.33; outside economical range. In order to decrease the size of the culvert, try two culverts.

10. Results from second iteration:

- Size: 2 x 1500 mm - Headwater elevation: 1623.95 m - Downstream depth: 3.20 m - Control Type: Outlet control - Manning’s n = 0.0207; estimated wrong diameter but n

change is small. HW/D = (1623.94 m -1621 m)/1.5 m = 1.96; within economical range. The headwater elevation is very close to the maximum allowable headwater. Switch the “Solve for” option to headwater elevation and switch the “size” to 1600 mm. Solving should yield the following results.

11. Results from third iteration: - Size = 2 x 1600 mm - Headwater elevation: 1623.76 m - Velocity: 1.77 m/s - Downstream depth: 3.20 m


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- Control type: Outlet control - Manning’s n: 0.0208

HW/D = (1623.76 m – 1621 m)/1.6 m = 1.725; within economical range.

12. Concluding remarks: Because the tailwater had to be accounted for, a larger culvert size was required. The tailwater effect was calculated by subtracting the critical depth from the tailwater. Tailwater effect = 3.2 m – 0.96 m = 2.24 m The headwater was calculated by adding the slope and subtracting the tailwater effect: HW = (1624 m – 1621 m) + 0.02(48 m) – 2.24 m = 1.72 m

ADJUSTMENTS TO TAILWATER AND HEADWATER

The following is an explanation of adjustment to headwater and tailwater.

INLET CONTROL

Under inlet control, the head, H is as shown. The headwater is used to determine the critical depth but the head is used in performing the calculations.


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OUTLET CONTROL – NO TAILWATER

Under outlet control, the effective head is the difference between the headwater elevation and the outlet invert plus the critical depth:

H’ = HWelev – INVout elev + dc = 1623.77 m – 1620.04 m + 0.96 m = 4.96 m

The headwater is again used to determine the critical depth but the effective head is used in performing the calculations with a slope of zero percent. A slope on a culvert increases the elevation difference between the headwater elevation and the outlet invert, and therefore the effective head.

OUTLET CONTROL -- TAILWATER

Under outlet control with tailwater, the head is the difference between

the headwater elevation and the tailwater. Because the head used to calculate the culvert size is shown in B, to account for the tailwater, headwater must be reduced by a value equal to the difference between the tailwater and the critical depth.


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1,623.76 m Discharge 7.1000 m³/s


1.73 Tailwater Elevation 1,623.24 m




1,623.76 m


Hydraulic Profile Profile Pressure

Profile Depth, Downstream 3.20 m

Slope Type N/A Normal Depth 0.78 m Flow Regime N/A Critical Depth 0.96 m Velocity Downstream



Coefficient 0.021


Span 1.60 m


Rise 1.60 m

Number Sections 2 Date Design Aids Page

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0.16 m


Inlet Control

Properties


1,623.24 m Flow Control Unsubmerged


DESIGN EXAMPLE 4: MANNING’S N

Given:




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SOLUTION 1. Select “New Design” since the size of the culvert is unknown.

2. Insert peak discharge: Q25 = 0.39 m3/s in the “Watershed”

Tab.

3. Select “Maximum allowable HW,” and insert AHWel = 1621.9 m in the “Headwater” Tab.

4. Select the method “Constant Tailwater”, and do not insert a


5. Select solve for “Invert Downstream” in the “Grades” Tab.

Insert the known values: - Invert Upstream: Inlet INVel = 1621.0 m - Length: L = 60 m - Slope: So = 0.005 m/m Provides answer: Invert Downstream = 1620.70 m

6. Select the “New Design Trial” Button . Select solve for

“Size”. 7. Determine the characteristics of the culvert section you wish to

apply. - Shape: Circular - Material: CSP Helical - Number: 1 - Manning’s n: To demonstrate the need for a precise n

value, select 0.0240 CSP Helical”.

8. Inlet Properties - Inlet: Projecting - Ke = 0.90 - Select “Solve”.

9. Results:

- Size: 700 mm - Headwater Elevation: 1621.72 m - Velocity: 1.77 m/s - Downstream depth: 0.39 m - Control type: Outlet Control


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- Manning’s n = 0.0174l iterate with new value HW/D = (1621.72 m -1621 m)/0.7 m = 1.029; outside of economical range.

10. Results from second iteration: - Size: 600 mm - Headwater elevation: 1621.79 m - Velocity: 1.90 m/s - Downstream depth: 0.41 m - Control type: Outlet control - Manning’s n = 0.0163; iterate with new value HW/D = (1621.79 m – 1621 m)/0.6 m = 1.32; outside of economical range.

11. Results from third iteration:

- Size: 600 mm - Headwater elevation: 1621.75 m - Velocity: 1.90 m/s - Downstream depth: 0.41 m - Control type: Outlet control - Manning’s n = 0.0163; correct diameter HW/D = (1621.75 m – 1621 m)/0.6 m = 1.25; outside of economical range.

The third iteration has an HW/D ratio outside of the economic range, but is within the maximum allowable headwater. The exemplifies the importance of using the correct Manning’s n value. If the second iteration had been used (which was within the economical range) the headwater elevation would have been above the maximum allowable headwater elevation. In this example, it should be noted that the provided headwater was not used in the calculations. An additional head was accounted for due to the slope of the pipe since it was operating under outlet control. While the 600 mm diameter pipe in combination with the provided headwater of 0.9 m from the design flow was insufficient, the 600 mm diameter pipe in combination with the effective head of 1.2 m was sufficient. The culvert design report below is for the thrid iteration.


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1,621.75 m Discharge 0.3900 m³/s






1,621.75 m


Hydraulic Profile Profile M2 Depth, Downstream 0.41 m Slope Type Mild Normal Depth N/A m Flow Regime Subcritical Critical Depth 0.41 m Velocity Downstream



Coefficient 0.016

Section Material

CSP Helical Span 0.60 m


Rise 0.60 m

Number Sections 1


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0.10 m




1,621.71 m Flow Control Unsubmerged


DESIGN EXAMPLE 5: CROSS-SECTIONS

The purpose of this example is to demonstrate the importance of inputting tailwater correctly into CulvertMaster. There are three situations that may occur:

1. Assuming an incorrect tailwater; 2. Using insufficient survey data; and 3. Improperly assigning Manning’s n values.

ASSUMING AN INCORRECT TAILWATER

The previous examples assumed a tailwater level, but did not explain the basis of its assumptions. Tailwater is based on the downstream restricting cross-section, the slope of the channel, and the design flow. The downstream restricting cross-section is defined as the cross-section that most restricts flow such that the water level will increase. This may be due to an increase in elevation or a narrowing in the cross-section. Most often the restricting cross-section is a combination of these two factors. A common error is to assume that the tailwater remains constant for different flow rates. Generally, the tailwater will increase with an increased flow rate. Another common error is to assume that the tailwater elevation is


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simply the highest elevation that is reached in the streambed downstream of the culvert. While that point may be the location of the restricting cross-section, the water must travel over that point, so it is very unlikely that the elevation is correct. Therefore, the irregular channel cross-section function should always be used.

USING INSUFFICIENT SURVEY DATA

Sometimes the survey data provides insufficient or excessive data, which may be misinterpreted. In the figure below, the black line represents the true downstream cross-section. The blue dotted line represents the survey data that has been used. The blue dotted line may not have matched the length of the black line due to time and cost constraints for surveyors on a very flat stream channel.

Two scenarios are created: In the first scenario, Water Level 1 is the design flow tailwater. This means that the decision to use less survey points did not affect the calculation of the tailwater. In the second scenario, Water Level 2 is the design flow tailwater. If the cross-section required for the calculation is incomplete, CulvertMaster assumes a vertical wall to the top of the cross-section, as illustrated in green. The tailwater level will be overestimated, which may underestimate the downstream velocity. Therefore, the tailwater level should always be checked with the highest elevation point used on either side of the cross-section.

IMPROPERLY ASSIGNING MANNING’S N VALUES

It is very uncommon for a streambed to be comprised of the same material for its entire cross-section. Generally, there are three defined areas to check, as illustrated below:


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Level 1 is often comprised of dirt, shorted vegetation, or riprap. Level

2 may vary from grass to willows and other shrubs. Level 3 may vary from grass to dense forest.


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Hydraulic Manual

Section 1100

Culvert Service Life

2014


Hydraulic Manual

Section 1200

Culvert Rehabilitation

2014


HM 1201-00


INTRODUCTION Culvert rehabilitation covers the practices associated with restoring a

culvert’s functionality without replacing it. It is a cost effective method in comparison to complete replacement, especially in situations where deep fills, trenching or open excavation would cause disruptions to traffic resulting in high traffic accommodation costs. The Ministry defines culvert rehabilitation as the sleeving or lining of the full circumference of the culvert. Culvert sleeving is defined as the insertion of a pipe (sleeve) that has the same or greater structural capacity as the existing culvert with annular space between the sleeve and the existing culvert filled with grout. Culvert lining is defined as the insertion of a liner whose structural capacity is less than the existing culvert and relies on the existing culvert to resist the structural loads. The Ministry has approved the rehabilitation of culverts with the culvert sleeving methodology. There are a number of technology and material choices when designing a culvert sleeving project. A properly designed and installed culvert sleeve will have the same or better design service life as a standard culvert made out of the same material. See HM 1202-00 for guidance on the design requirements. The Ministry has approved the use of culvert lining on a pilot project basis in order to evaluate its performance and to develop appropriate standards for its use. Culvert liners extend the life of existing culverts but will have a shorter design service life because they do not return the culvert to the structural capacity of a new culvert.

Date Page

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Date Page

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HM 1202-00

Hydraulic Manual Section: CULVERT SLEEVING Subject:

INTRODUCTION Culvert sleeving is a common method for extending the lives of culverts.

It can be a cost effective method in comparison to complete replacement, especially in situations where deep fills, trenching or open excavation would cause disruptions to traffic resulting in high cost of traffic accommodation. As with any rehabilitation technique, culvert sleeving has both advantages and limitations. The insertion of the sleeve is a simple procedure requiring minimal installation equipment and little technical skill. This method provides a new culvert, comparable to full replacement. Due to the ability to choose between multiple materials for insertion, a large range of diameters and forms can be used for repair. One of the biggest limitations is the need for a large area for the liner insertion and jacking pit. Sleeving reduces the cross section as the annular space between the culvert and the pipe must be grouted, thereby reducing the hydraulic capacity of the culvert. Grouting is an integral component necessary to ensure the success of the culvert rehabilitation project. To be effective, full length grouting of the liner must be done. It is used to fill the voids between the existing culvert and the liner and any existing void around the existing pipe, in order to prevent further distortion or collapse of the culvert by re-establishing the soil-pipe interaction.

DESIGN REQUIREMENTS

The following shall be taken into account when using culvert sleeving as a rehabilitation method. 1. Culvert sleeving shall not be used on culverts whose stream channels

are degrading or aggrading (i.e. are stable).

2. Culvert sleeving projects require a hydraulic design report to ensure that the hydraulic design requirements are met.

3. The culvert sleeve structural capacity shall be checked to ensure that it has the capacity to withstand the embankment and traffic loads assuming that the existing culvert is not present.

4. The grout shall be applied under pressure to ensure that the void spaces outside of the existing pipe are filled in addition to the void

Date Culvert Rehabilitation Page

January 31, 2014 1 of 4


Section: CULVERT SLEEVING Subject:

between the sleeve and the existing pipe. The pipe manufacturer’s specifications shall be followed for the grouting pressure and grout installation method.

5. The grout application method shall ensure that the sleeve does not float and that sleeve maintains a straight grade line.

6. The exterior dimensions of the liner must be capable of being inserted into the existing culvert, while taking into account deformations, deflections, and other disturbances in the bore of the pipe. Also to be taken into account is the space required for the joints of the liner.

7. Refer to HM 614-00 for approved culvert material types. It is imperative to understand the conditions leading to failure or deterioration in order to make the best choice of material for the sleeve.

8. The culvert sleeve should not exceed the design length of the existing culvert unless the slide slopes are being flattened or the road surface is being widened in conjunction with the project.

9. On the inlet end the sleeve should be set slightly inside the end of the existing culvert in order to allow for the creation of a 45 degree beveled inlet condition thru the finishing of the ends with grout after cutting off the ends of the filling tubes.

10. Prior to the insertion of the liner it may be appropriate to fill any significant voids due to rusting out of the bottom of the existing culvert with grout. This will reduce the grout pumping volume and will provide a consistent and stable base for the sleeve.

SLEEVING GROUT SPECIFICATION

The specifications for grout used in sleeving are available in the Specifications For Manufactured Materials Manual section SMM 401.

METHODS OF GROUT INSTALLATION

The installation method for grouting will depend on the length, slope and size of the culvert. There are many grout application methods, including but not limited to the following:


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1. Pipe Fill or Staged Pipe Fill

This method is typically used for a long culvert. Pipe fill consists of plugging both ends of the culvert. At the highest end of the culvert a PVC pipe is sealed within the plug. This pipe runs down the length of culvert/liner boundary and the grout will be pumped into the void using the PVC pipe. Depending of the length of the culvert multiple pipes may be used at staged intervals to fill the entire void. The grout is pumped into the culvert until it reaches a certain pressure that is necessary to ensure that any external voids are filled and the structural capacity of the sleeve is not exceeded. 2. Chimney Fill

The chimney fill consists of boring two holes at each end down to the old culvert. The grout is then pumped into one hole while the air escapes from the other hole. The grout is then pressurized to its certain specifications and the holes are filled. This method depends on the material above the culvert and how deep the culvert is. 3. Grouting Nipples

The grouting nipple method may be used when the culvert is greater than 1 meter in diameter. This process is accomplished by installing grouting nipples at different points on the inside of the culvert, typically at the ten and two o’clock positions. Then both ends of the culvert are sealed and grout is pumped via the grouting nipples into the culvert until it reaches the specified pressure.


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HM 1203-00


REFERENCES Alberta Transportation and Utilities. Culvert Study, November 1992.

Caltrans, California Department of Transportation. Design Information Bulletin No. 83: Caltrans Supplement to FHWA Culvert Repair Practices Manual, 2003. http://www.dot.ca.gov/hq/oppd/dib/dib83-6.htm

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Date Page

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Hydraulic Manual

Section 2000

Technical Bulletins

2014


Hydraulic Manual

Section 2001

Design Directives

2014


Hydraulic Manual (Dec 2014)

Documents