All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopy, recording or any other without the RTAs prior written consent.

Culvert Risk Assessment Guideline Version 3.02 December 2010

RTA Culvert Risk Assessment Guideline V3.02 Page i

About this release Source Document Name: Culvert Risk Assessment Guideline

Effective from: December 2010

Approved and authorised for use by:

John Statton, GM, Infrastructure Asset Management Signature: Date: 22/12/10

Issue Date Revision Description

V1.0 May 2008 First draft, by Mark Foster, URS Australia

V2.0 July 2008 Update by DMA to fix structure, content and style

V2.3 October 2008 Minor updates

V3.02 December 2010 Update to likelihood algorithms and tables

Control All printed copies are uncontrolled. The up-to-date version of the Culvert Risk Assessment Guideline can be found on the RTA Intranet. Please check to see that any printed copy has not been superseded. Feedback Any errors, omissions, comments or suggestions should be submitted to the Roads and Traffic Authority, NSW for possible inclusion in a future issue. Send submissions to:

Corridor Assets Manager, Network Services Roads and Traffic Authority, NSW 101 Miller Street North Sydney NSW 2060 Tel: 131 782 Fax: 02 8588 4105

Copyright Copyright 2008-2010 Roads and Traffic Authority, NSW This work is protected by copyright. Apart from fair use permitted under the Copyright Act 1968, no part may be reproduced in any way without prior written consent from the RTA, NSW.

Acknowledgements Version 3 has been updated by

John Vitlin, Doll Martin Associates Alex Dunstan, Corridor Maintenance Planner, RTA,

Previous versions were advised by Cath Dunstan, RTA, Mark Foster, URS Australia Alex Dunstan, Area Maintenance Manager, RTA, Henk Buys, Senior Geotechnical Engineer, RTA Tony Porter, Opus New Zealand The Risk Assessment Pilot Workshop participants: Alex Dunstan, Alistair Hitchon (URS Australia), Ashraf Awadalla, Colin Gould, David Groth, David Warren-Gash, Doug Salkeld, Geoff Howard, Henk Buys, Hugh Tait (Opus International Consultants), John Rubsov, John Vickery, Mark Bennett, Riaz Ul-Islam (Opus International Consultants), Steve Watson, Val Brizga, Zaf Pavlic-Sahin

RTA Culvert Risk Assessment Guideline V3.02 Page ii

RTA Culvert Risk Assessment Guideline V3.02 Page iii

Table of Contents 1 INTRODUCTION 1 1.1 The Culvert Management Framework 1 1.2 Risk Assessment Roles 2 1.3 Risk Assessor Training 2 1.4 Purpose of the Guideline 2 1.5 Structure of the Guideline 3

2 RISK ASSESSMENT METHODOLOGY 5 2.1 Culvert Risk Assessment and AS 4360 5 2.2 Scope of Culvert Risk Assessment 6 2.3 Risk Assessment Flowchart 6 2.4 Hazard Identification 7 2.5 Likelihood Analysis 7 2.6 Consequence Analysis 8 2.7 Assessed Risk Level 9 2.8 Methodology - Illustrated Examples 9

3 ASSESSMENT PLANNING 11 3.1 Assessment Responsibilities 11 3.2 Existing Information 11 3.3 Safety on Site 11 3.4 Planning Checklist 13

4 RISK ASSESSMENT PROCEDURE 15 4.1 Desktop Assessment 15 4.2 Field Assessment 15

5 CULVERT RISK ASSESSMENT RECORD 17 5.1 Identification and Location 17 5.2 Culvert Geometry 18 5.3 Site Features Sketch 19 5.4 Culvert Barrel Adverse Conditions 19 5.5 Inlet/Outlet Adverse Conditions 25 5.6 Roadway and Embankment Adverse Conditions 27 5.7 Potentially Affected Development or Features 29 5.8 Inspection Notes 29 5.9 Culvert Attribute Score 30 5.10 Recommended Maintenance Measures 30 5.11 Possible Remedial Measures 31 5.12 Photo and Image Files 31 5.13 Risk Analysis 32

6 STRUCTURAL COLLAPSE (SC) HAZARDS AND LIKELIHOOD 35 6.1 SC-1 Structural Collapse of Barrel 35

7 SLOPE INSTABILITY (SI) HAZARDS AND LIKELIHOOD 39 7.1 SI-1 Slope Instability Caused by Afflux 39 7.2 SI-2 Slope Instability Caused by Leakage out of Barrel 41 7.3 SI-3 Slope Instability Caused by Headwall Collapse 43 7.4 SI-4 Slope Instability Caused by Undermining at Inlet or Outlet 45

8 PIPING (PI) HAZARDS AND LIKELIHOOD 49 8.1 PI-1 Piping into Culvert 49

RTA Culvert Risk Assessment Guideline V3.02 Page iv

8.2 PI-2 Piping on Outside of Culvert due to Afflux 51 8.3 PI-3 Piping on Outside of Culvert due to Leakage out of Culvert 53

9 HYDRAULIC FLOW (HF) HAZARDS AND LIKELIHOOD 57 9.1 HF-1 Erosion by Overtopping Flows 57 9.2 HF-2 Cross Catchment Flooding 60

10 LIKELIHOOD (L) RATING 63

11 CONSEQUENCE (C) RATING 65 11.1 Consequence for Risk to Life 65 11.2 Consequence for Risk to Property 70

12 ASSESSED RISK LEVEL (ARL) RATING 73

13 ASSESSMENT COMPLETION 75 13.1 Tasks for Assessors 75 13.2 Tasks for Project Managers 75 13.3 Next Steps in Risk Management 75

14 REFERENCES 77

15 APPENDICES 79 15.1 Terminology 79 15.2 Site Sketch Preparation 83 15.3 Field Identification and Classification of Soils 85 15.4 Headwall Hazards 87 15.5 Culvert Inventory Risk Assessment Checklist 89 15.6 Culvert Risk Assessment Record 90

16 INDEX 97

Table of figures Figure 1 Framework Processes 1 Figure 2 AS4360 Risk Management Process 5 Figure 3 Risk Assessment flowchart 7 Figure 4 Embankment example 9 Figure 5 Cut slope example 10 Figure 6 Structural collapse of the barrel 35 Figure 7 Instability caused by afflux 39 Figure 8 Instability due to leakage / headwall collapse / undermining 41 Figure 9 Piping failure modes 49 Figure 10 Erosion by overtopping flows (fill example) 57 Figure 11 Erosion by overtopping flows (cut and fill example) 58 Figure 12 Cross catchment flooding 61 Figure 13 Temporal probability based on traffic volume 68

Introduction

RTA Culvert Risk Assessment Guideline V3.02 Page 1

1 Introduction How to use this chapter This chapter presents the Culvert Management Framework and the purpose of the Guideline.

1.1 The Culvert Management Framework The RTA has a framework for the long-term management of culverts across the RTA road network. The framework is a component of ongoing asset management works to ensure road network availability and improve road user safety. The framework process is shown in the following flowchart:

Inventory collection

?

Initial condition assessment and risk screening

Low Risk Potentially Vulnerable

Risk assessment

?

Risk Management Strategy

Vulnerable

Identify remedial options

Prioritisation of funds

Program allocation

Work programmed

Detailed design

Remedial measures implementedInventory update

Ongoing condition assessmentand risk screening

?

Prioritise Routine/Minor worksLow Risk

Manage through Routine Maintenance works

Low Risk Potentially Vulnerable

Strategic AssetManagement Plan

Inventory collection

?

Initial condition assessment and risk screening

Low Risk Potentially Vulnerable

Risk assessment

?

Risk Management Strategy

Vulnerable

Identify remedial options

Prioritisation of funds

Program allocation

Work programmed

Detailed design

Remedial measures implementedInventory update

Ongoing condition assessmentand risk screening

?

Prioritise Routine/Minor worksLow Risk

Manage through Routine Maintenance works

Low Risk Potentially Vulnerable

Strategic AssetManagement Plan

Figure 1 Framework Processes

Introduction

RTA Culvert Risk Assessment Guideline V3.02 Page 2

Tools supporting the framework include:

A training accreditation program for culvert inventory inspectors A training accreditation program for culvert risk assessors, including confined spaces training A guideline for consistent collection of culvert inventory and initial risk assessment A guideline for detailed risk assessment of culverts if an assessment is required A central database of all culvert location and condition data, developed as a module of the Road

Asset Management System (RAMS).

1.2 Risk Assessment Roles The following roles are referred to in this guideline:

Risk Assessor A trained person who undertakes a culvert risk assessment. This may be an RTA employee or a person contracted by the RTA for inspection work.

Project Manager An employee of the RTA who is responsible for organising and managing a body of risk assessment work. This role will provide information to assessors and manage the assessment task.

Regional Asset Manager (Asset Manager)

The Regional Asset Manager in the region where the culvert is located. Regional Asset Managers are responsible for management and maintenance of road infrastructure, reporting to the relevant Regional Manager

Corridor Assets Manager The Corridor Assets Manager, Infrastructure Maintenance is responsible for state-wide policy and strategy to safeguard the future of corridor assets.

1.3 Risk Assessor Training Culvert Risk Assessors must be trained, certified and issued with an assessor number prior to undertaking field assessments of culvert risk. Information collected in the field will be used for risk evaluation and risk treatment decisions. The usefulness of information collected depends greatly upon how well the assessment is undertaken and documented. As well as risk assessment training, an assessor will require other specific training or competencies appropriate to the task before they can be permitted to carry out inspections. This may include

Confined spaces assessment training. Traffic control at work sites training. Industrial rope training. Training in GPS unit use.