vicroads bridge technical note 2007-001v10

7/23/2019 VicRoads Bridge Technical Note 2007-001V10

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vicroads

2007/001 Bridge Technical Note

SAFETY DURING INSPECTION AND REPAIR OF

CORROSION-DAMAGED BURIED CORRUGATED METAL

STRUCTURES (BCMS)

Note: BCMS is used throughout this document as an abbreviation for Buried Corrugated MetalStructure (both singular and plural) and signifies metal culverts and arches of round, elliptical or

compound cross-section.

1. INTRODUCTION

In October 2006, on the basis of advice from the Principal Bridge Engineer, the Manager Corporate

Occupational Health and Safety issued a prohibition on entry into all corrosion-damaged BCMS with the

advice that inspection of these BCMS must be conducted from outside of the barrel. The Principal BridgeEngineer subsequently recommended that inspection from within the barrel of corrosion-damaged BCMS

must not be attempted until a suitably qualified and experienced inspector had determined that it was safe to

do so.

This technical guidance note provides guidance on:

(Particularly for those involved in Level 1 inspections) the recognition of potentially unstable

BCMS and avoidance of exposure to dangerous workplace conditions;

Criteria for the selection of suitably qualified and experienced inspectors who:o

Are authorised to perform Safety Inspections (described in part 6) of severely corrosion-

damaged, propped or deformed BCMS;

o

May authorise entry into the BCMS for maintenance purposes by maintenance personnel;

o

May determine whether it is safe for the public to continue to use a BCMS where it is

provided for pedestrian and agricultural use;

o

May authorise remedial action such as propping;

The procedure for inspection and assessment of severely corrosion-damaged BCMS;

Actions that may be required in the event that a dangerously unstable BCMS is discovered.

The driving principle underlying the advice given in this note is the need to ensure the safety of the public

and the safety of those who inspect BCMS and those who may subsequently undertake rehabilitation works

for whom BCMS are a workplace. In this respect the readers attention is drawn to the requirements of the

Occupational Health and Safety Act 2004 and in particular sections 21 to 26 and section 28. The relevant

sections of the Act are listed in Appendix A


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BTN 2007/001 Buried Corrugated Metal Structures

It may only be possible to assess the loss of metal in the water-side (open side) surface of the BCMS walls

around the invert and within the splash-zone above water-level. There may be significant loss of metal

thickness to the buried (soil-side) faces of the BCMS and, unless the metal becomes visibly perforated or so

thin that it can be pierced with a hand pick or chisel point, it will not be possible to fully assess the degree of

corrosion on the soil-side. If a detailed assessment of soil-side corrosion is required, this can be achieved by

cutting samples from the wall-panels or by excavation to expose the BCMS. The extent and method of

cutting or excavation must be agreed with the Principal Bridge Engineer in order to prevent the risk of de-

stabilising the BCMS. It may also be possible to use non-destructive methods of testing such as ultra-sound

to measure the thickness of the metal.

Issues that may require action to enable detailed inspection:

The invert of the BCMS may be obscured by debris and or submerged below water-level;

Where the BCMS is being used as a cattle underpass, the invert may be obscured by gravel and

cattle-droppings;

Where the BCMS is being used as a pedestrian underpass, the invert may be paved;

Features of a potentially unstable BCMS:

The walls may be deformed;

The soffit may be propped;

The invert may be severely corroded and there may be significant loss of metal;

The backfill may be eroded or softened.

4. SELECTION OF SUITABLY QUALIFIED AND EXPERIENCED INSPECTORSFor the purpose of this guidance note a suitably qualified and experienced inspector, who is authorised to

determine whether it is safe to enter a corrosion-damaged (possibly propped) BCMS for inspection and

maintenance works, is defined as a person who:

a.

In the opinion of the Principal Bridge Engineer, has sufficient experience and engineering

knowledge of the structural features of BCMS and, in particular, the possible modes of failure; and

b. Is qualified to perform level 3 inspections as defined in the VicRoads Bridge Inspection Manual; or

c.

Is authorised to make an inspection by the Principal Bridge Engineer or by the Regional Director in

consultation with the Principal Bridge Engineer;

i.e. the inspector must satisfy either 4a and 4b or 4a and 4c

5. RISK MANAGEMENT

Confined Spaces Regulations


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is showing signs of corrosion damage, deformation or if it has been propped (tommed). Advice is given in

Part 6 on the procedure to be followed during inspections when there is debris obscuring the invert.

Risk Assessment

The inspector is advised to make a preliminary visit to the BCMS in order to assess the need for special

means of access such as a ladder or the clearance of dense vegetation and to enable the preparation of a site-

specific risk-assessment / Job-Safety Analysis. If a two-stage visit is impractical - due to the remoteness of

the location for example - the inspector is advised to conduct a preliminary inspection and risk assessment on

arrival at the BCMS and to continue with a detailed inspection only in the event that safe access is possible.

The inspection must be aborted if there is any safety concern that cannot be managed with the available

equipment and a further visit should be planned only when all outstanding safety concerns have been

satisfactorily resolved. Risk assessments must be in writing and must be recorded for future reference in

RAS and in the Principal Bridge Engineers structure file.

A checklist of common hazards is provided in Appendix E as an aid to risk assessment.

6. RECOMMENDED PROCEDURE FOR INSPECTION

Note: The following advice is additional to and must be read in conjunction with the VicRoads Bridge

Inspection Manual.

Access to Records

Prior to the inspection of BCMS, the inspector or the manager responsible for the inspection is advised toreview the most recent inspection reports and inform the inspection team of the last known condition of the

BCMS together with any previously identified hazards.

In the normal course of events a Level 3 inspection will be arranged on the basis of a previously reported

condition 3 or 4 rating and there will be a known history of deteriorating condition. Where a BCMS is

already known to be severely corroded with significant loss of metal to the invert, or it is deformed or

propped, a Safety Inspection (as described below) must be arranged. In these circumstances the possibility of

instability must be assumed. However, a corrosion-damaged BCMS may be discovered for the first timeduring a Level 1, 2 or 3 inspection. With this in mind the procedure described below is to be adopted in

accordance with the level of the inspection.

General Guidance Applicable to all Levels of Inspection

Adequate lighting must be available throughout the inspection;

In all cases an initial inspection should be conducted from outside of the BCMS to check for the


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Those managing inspections must ensure that if a potentially unstable BCMS is

identified:

Warning signs are erected promptly;

A Safety Inspection is arranged at the earliest opportunity;

The need for temporary closure is addressed promptly.

Level 1 Inspection

The fundamental principle is that an inspection at this level must only be attempted if the BCMS is in

condition 1 or 2 and there is no propping or deformation.

The inspector must be suitably experienced and qualified to conduct Level 1 inspections in

accordance with the requirements of the Bridge Inspection Manual for this level;

The BCMS is to be inspected from outside and, if the metal is rusting and has holes or there are

missing sections or the BCMS is propped or there is visible deformation, the inspection must be

terminated immediately and a report made to the appropriate manager;

If there is debris or other material obscuring the invert, the first 0.3 to 1m of the metal surface should

be exposed without entering the BCMS and its condition assessed as before;

If metal in the exposed area is badly rusted and there are holes or metal is missing, the inspection

must be terminated and a report made to the appropriate manager as before;

If the Level 1 inspection team considers the BCMS to be unsafe, they must place signs warning the

public and other workers of the potential hazard at both ends of the BCMS;

If invert metal is clearly visible and is sound and in good condition, clearing of debris may continue

in 0.3 to 0.5m steps unless the condition of the corrugated metal deteriorates and holes or missing

areas become visible - in which case the inspection must be terminated immediately and a report

made to the appropriate manager.

Level 2 Inspection

The Level 2 inspection shall be as the Level 1 inspection described above with the following additions:

The inspector must be suitably experienced and qualified to conduct Level 2 inspections in

accordance with the requirements of the Bridge Inspection Manual for this level;

Provided that it is safe to do so the Level 2 inspector may probe the exposed metal surface from

outside the BCMS and take soundings with a hammer and / or probe the metal with a pick or chisel

point to assess the condition rating;

If the visible part of the BCMS is in condition 1 or 2 the Level 2 inspector may enter the BCMS andcontinue to assess its condition;

If the BCMS deteriorates to condition 3 or 4, the inspection must be aborted and a report must be

made to the appropriate manager. It is recommended that a Safety Inspection is then arranged;

Level 3 Inspection


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Where the BCMS is used by the public (pedestrian and agricultural use for example), the inspector

may recommend its temporary closure in the interests of safety;

The inspector may if they consider that it is safe to do so, authorise access for maintenance and

repair work and determine the requirement for propping;

The propping system shall be designed by an engineer who is experienced in the design of

temporary works and who shall either be:

o

qualified to Proof Engineer level in accordance with the VicRoads pre-qualification scheme;or

o an engineer who meets with the approval of the Principal Bridge Engineer.

7. ACTIONS

Warning Signs

In the event that a serious defect is discovered and it is considered to be too dangerous for the inspection to

continue, warning signs should be erected immediately at both ends of the BCMS in order to inform both the

public and other VicRoads personnel of the hazard. A detail for such a warning sign is given in Appendix D.

Stability of the Highway

In the event that the inspector considers the BCMS to be unstable and that there is a potential risk to users of

the highway over the BCMS, the inspector must advise the Regional Director immediately.

Barricading of Unstable BCMS

If the inspector considers that a pedestrian underpass or a stock crossing (or any BCMS that is used for these

purposes whether formally or informally) is considered to be unsafe for entry, this must be reported to theRegional Director immediately with the recommendation that the underpass is closed pending further

investigation and repair. The following should be considered prior to closure:

Consultation with users of the underpass and other affected parties (Police, catchment management

authority and landowners for example);

The route and signing of safe temporary diversions;

The choice of barricade particularly where the BCMS carries water;

Register of Occurrences and ActionsIn order to ensure that information is properly recorded for future reference, the structure record in RAS and

in the Principal Bridge Engineers structure file should be updated with details of propping and any serious

defect that is discovered such as deformation or severe corrosion damage together with details of any

preventative action that is taken such as signing and barricading.

8 REFERENCES


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Approved July 2007

GEOFF BOULLY

Acting PRINCIPAL BRIDGE ENGINEER

For further information please contact:

Principal Bridge Engineer3 Prospect Hill Road Camberwell Vic 3124

Telephone: (03) 9811 8307

Facsimile: (03) 9811 8329

Email: [email protected]

Bridge Technical Notes are subject to periodic review and may be superseded


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APPENDICES

APPENDIX A

Relevant Duties under the OHS Act 2004

Main duties of employers

21. Duties of employers to employees;

23. Duties of employers to other persons;

Duties of self-employed persons

24. Duties of self-employed persons to other persons;

Duties of employees

25. Duties of employees;

Duties of other persons

26. Duties of persons who manage or control workplaces;

28. Duties of designers of buildings or structures;

APPENDIX B

Extract from the Bridge Inspection Manual 2004

BCMS Condition States

This element includes all steel pipes, painted or galvanised, circular, elongated or elliptical.

Condition state 1. - There is no evidence of rust or corrosion and the paintwork or

galvanising is in good condition. The line and invert of the pipe is

straight with no water being retained in the pipe.

Condition state 2. - Surface or spot rusting may be evident and the paint system is no

longer effective. There is no corrosion of the metal occurring. The line

of the pipe is straight, but minor settlement may be allowing some

water to be retained in the pipe.

Condition state 3. - The paint system has failed and pitting corrosion is prominent

especially at normal water level. Loss of section has occurred but

there is still adequate section left to not affect serviceability of the

pipe. There may be some deviation of the line of the pipes due to local

buckling or moderate settlement of the pipe may be allowing a


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APPENDIX C

Examples of corrosion-damaged BCMS

SN8616 Bulleen RoadBCMS inspected on the 13

thDecember 2006 by SW Consultants P/L and found to be unsafe for concrete

lining unless it is propped. The upper limit of corrosion-affected metal on the water-side is clearly visible.


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APPENDIX D

WARNING SIGN

Notes:

Freestanding sign to comply with AS1742.3:2002;

To be placed at each end of the BCMS;


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APPENDIX E

VERSION: 1.0 DATE: December 2006 Page 10

Item Feature Hazard Risk Possible Controls

1 Unstable BCMS- Propped (tommed)

-

Deformed-

Corroded / missing areas ofmetal

Or any of these in combination

Collapse of the BCMSFalling objects

Crush injuriesSuffocation

DrowningBeing struck by falling objects

Assess individual circumstances

Abandon inspection

Arrange safety inspectionReportingWarning Signs

BarricadingPropping / temporary support

Remedial workRecording

2 BCMS Confined Space Poor access and egress (particularly in anemergency)


Manage in accordance with Occupational

Health and Safety (Confined Spaces)Regulations together with VicRoads confinedspaces procedures

3 Difficult access into BCMS Working at Height

Uneven Surfaces (Slips, Trips and Falls)

Falling (into water)

Injuries to joints and limbs


Clear vegetationUse ladder

Provide lightingUse appropriate footware

No lone-working

4 Water Working in near to water Drowning Assess individual circumstancesAvoid deep and / or fast flowing water

Monitor weather conditions and avoid enteringwater-courses prone to flash-flooding

No lone-working

5 Corroded / missing areas of metal Sharp metal edges Laceration Assess individual circumstances

Personal Protective Equipment

(Gloves, boots, helmet)Provide lighting

6 - Voids in and behind BCMS wallscaused by corrosion and erosion

- Surrounding area

Venomous creatures Snake or insect bites Assess individual circumstances

No lone-working

Provide lightingAvoid probing by hand into hidden voids / darkareas

7 Debris or water in invert (invert

condition obscured)

Hidden corrosion-damaged metal surfaces As items 1 and 5 Assess individual circumstances

Clear debris and enter in stages only if safe toproceed

Note: This is a list of the main hazards and is not exhaustive. A Risk Assessment based on site-specific conditions is necessary in order to identify all hazards that may be present.

vicroads bridge technical note 2007-001v10

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