Lessons from historical dam incidents Project: SC080046/R1 The Environment Agency is the leading public body protecting and improving the environment in England and Wales. It’s our job to make sure that air, land and water are looked after by everyone in today’s society, so that tomorrow’s generations inherit a cleaner, healthier world. Our work includes tackling flooding and pollution incidents, reducing industry’s impacts on the environment, cleaning up rivers, coastal waters and contaminated land, and improving wildlife habitats. This report is the result of research commissioned by the Environment Agency’s Evidence Directorate and funded by the joint Environment Agency/Defra Flood and Coastal Erosion Risk Management Research and Development Programme. Published by: Author(s): Environment Agency, Horizon House, Deanery Road, J Andrew Charles, BRE Bristol, BS1 5AH Paul Tedd, BRE www.environment-agency.gov.uk Alan Warren, Halcrow Group Ltd ISBN: 978-1-84911-232-1 Dissemination Status: Publicly available © Environment Agency – August 2011 Keywords: All rights reserved. This document may be reproduced Dam, reservoir, embankment, impoundment, incident, with prior permission of the Environment Agency. disaster, accident The views and statements expressed in this report are Research Contractor: those of the author alone. The views or statements Halcrow Group Ltd. expressed in this publication do not necessarily Burderop Park represent the views of the Environment Agency and the Swindon Environment Agency cannot accept any responsibility for Wiltshire SN10 5BP such views or statements. Tel. 01793 812479 Further copies of this report are available from: Environment Agency’s Project Manager: The Environment Agency’s National Customer Contact Emma Milner Centre by emailing: Phoenix House [email protected] Global Avenue or by telephoning 08708 506506. Leeds LS11 8PG Collaborator: Building Research Establishment Project Number: SC080046 Product Code: SCHO0811BUBA-E-E ii Evidence Report – Lessons from historical dam incidents Evidence at the Environment Agency Evidence underpins the work of the Environment Agency. It provides an up-to-date understanding of the world about us, helps us to develop tools and techniques to monitor and manage our environment as efficiently and effectively as possible. It also helps us to understand how the environment is changing and to identify what the future pressures may be. The work of the Environment Agency’s Evidence Directorate is a key ingredient in the partnership between research, guidance and operations that enables the Environment Agency to protect and restore our environment. This report was produced by the Research, Monitoring and Innovation team within Evidence. The team focuses on four main areas of activity: • Setting the agenda, by providing the evidence for decisions; • Maintaining scientific credibility, by ensuring that our programmes and projects are fit for purpose and executed according to international standards; • Carrying out research, either by contracting it out to research organisations and consultancies or by doing it ourselves; • Delivering information, advice, tools and techniques, by making appropriate products available. Miranda Kavanagh Director of Evidence Evidence Report – Lessons from historical dam incidents iii Executive summary This report aims to help those responsible for the safety of reservoirs. These include engineers appointed under current legislation, personnel who visit reservoirs in the course of their duties, staff who operate and monitor reservoirs, and enforcement authority engineers. The scope of the report is limited to water-retaining structures: some types of waste impoundments, such as tailings dams, may suffer similar types of malfunction, but these are not included. Although the focus of the report is on incidents at dams in Great Britain, reference is made to a few international incidents. International experience is particularly helpful for those types of dam that are not commonly found in Great Britain. The report begins with an introduction in Section 1. The background to the subject is briefly outlined, the value of the national incident database is demonstrated and the need for post-incident reporting and investigation is emphasised. In the next two sections, general, technical and regulatory lessons from dam incidents are outlined. Section 2 gives a historical overview of the subject which shows how serious incidents have improved our understanding of dam behaviour and the hazards posed by these structures. This section should not only be of interest to dam engineers but should also help those reservoir owners with limited technical knowledge to develop a basic grasp of the more significant aspects of the subject. Section 3 shows the close links between historical incidents and failures and the development of reservoir safety legislation and guidance. Section 4 looks at how incidents have been managed, including the role of owners and panel engineers. The significance of drawdown rates and other provisions for dam incidents such as evacuation planning are presented. Some examples of incident management are described. Section 5 begins with an overview of serious incidents and a classification and brief analysis of the modes of failure. This is followed by descriptions of over thirty major incidents and summaries of seventy other incidents. There is some overlap with information presented in Section 2, but Section 5 in essence constitutes a convenient reference section for readers interested in incidents of a particular type or at a particular dam. iv Evidence Report – Lessons from historical dam incidents Acknowledgements In the preparation of this report by Halcrow/Building Research Establishment (BRE) substantial use has been made of work previously published on the subject: • Binnie (1976) The evolution of British dams. • Skempton (1989) Historical development of British embankment dams to 1960. • Kennard (1995) Four decades of development of British embankment dams. Work previously published by BRE has also been of assistance including Charles (1986) The significance of problems and remedial works at British earth dams, Charles (1990) Deterioration of clay barriers, and Tedd et al. (1994) Remedial works to clay cores of UK embankment dams. Mr J R Claydon undertook a peer review of the selected dam incidents and Dr A K Hughes reviewed a draft report. The authors would also like to thank the following who provided valuable comments on the final draft: A J Brown J R Claydon L Deuchar D P M Dutton D M Crook C J Falkingham C Hoskins P Kelham K D Gardiner R Mann A C Robertshaw A Rowland N Williams Evidence Report – Lessons from historical dam incidents v Contents 1 Introduction 1 1.1 Background 1 1.2 National incident database 4 1.3 Post-incident reporting 5 2 Technical lessons from dam incidents 8 2.1 Dam and reservoir failure 8 2.2 Nineteenth century 12 2.3 Early twentieth century (1901-1930) 16 2.4 Mid-twentieth century (1931-1960) 18 2.5 Late twentieth century (1961-2000) 21 2.6 Twenty-first century 25 2.7 Lessons from serious incidents 26 3 Dam incidents and the development of reservoir safety legislation 29 3.1 Nineteenth century 29 3.2 Twentieth century 31 3.3 Twenty-first century 34 4 Incident management 36 4.1 Provisions for managing incidents 36 4.2 Examples of dam incident management 37 5 Description of incidents 43 5.1 Introduction 43 5.2 Description of major incidents 56 5.3 Short summaries of additional incidents 118 References 148 vi Evidence Report – Lessons from historical dam incidents 1 Introduction 1.1 Background The number of casualties arising from a breached dam can be greater than from most other kinds of technological disaster. Maintaining reservoir safety has considerable importance for the public in a country such as Great Britain where a number of dams pose a high hazard, being located upstream of heavily populated and industrialised areas. Thus, although the probability of failure of a dam is generally low, the consequences of failure could be great. As most reservoirs constitute a low probability/high consequence scenario, careful management of these risks is essential. Fortunately, few catastrophic failures have occurred in Great Britain and since 1925 there has been no loss of life due to dam disasters. Table 1.1 lists dam failures that caused loss of life in Great Britain. All the dams are embankments except Eigiau which was concrete and failed due to an inadequate foundation. Since 1925, there have been failures involving breaching of embankments and also many ‘near misses’ and other serious incidents (Wright, 1994). Table 1-1 British dam failures that caused loss of life (after Charles, 1993) H Reservoir Date Failure Deaths Dam (m) volume built (x 103 m3) Date Type Tunnel End 9 1798 1799 OF 1 Diggle Moss (Black Moss) 1810 1810 OF 5 Whinhill 12 262 1828 1835 IE 31 Brent (Welsh Harp) 7 1837 1841 OF 2 Glanderston 1842 OF 8 Bold Venture (Darwen) 10 20 1844 1848 OF 12 Bilberry 29 310 1845 1852 IE 81 Dale Dyke 29 3,240 1863 1864 IE 244 Rishton 1870 3 Cwm Carne 12 90 1792 1875 OF 12 Castle Malgwyn 1875 OF 2 Clydach Vale 1910 OF 5 Skelmorlie 5 24 1861 1925 OF 5 Eigiau and 10 4,500 1911 1925 FF 16 Coedty (Dolgarrog) 11 320 1924 1925 OF Type of failure: IE = internal erosion, FF = foundation failure, OF = overtopping during flood Although there has been no loss of life since 1925 due to dam disasters in Great Britain, during the last fifty years disastrous failures overseas have resulted in much loss of life as shown by the examples in Table 1.2. Much can be learned from these failures, particularly those such as Baldwin Hills, Malpasset, Teton and Vaiont which have been the subject of detailed investigation and substantial literature. A useful start to such a study is given by Jansen in his book Dams and public safety (Jansen, 1980) which includes illuminating accounts of the failures of Machhu II, Teton, Frias, Baldwin Hills, Vaiont, Babii Yar, Malpasset, and Vega de Tera as well as of many other failures.