The Walkerton E. coli outbreak: a test of Rasmussen's framework for risk management in a dynamic society

Abstract

In May 2000, the water transportation system in Walkerton, Ontario (a small town with 4800 residents) became contaminated with E. coli bacteria, eventually causing seven people to die and 2300 to become sick. The 700-page report from a comprehensive public inquiry into this tragedy provided a rich source of data about the outbreak itself and the factors leading up to it. That report was used to test the explanatory adequacy of Rasmussen's framework for risk management in a dynamic society. Close agreement was observed between the predictions of the framework and the causes contributing to the Walkerton outbreak. The sequence of events reveals a complex interaction between all of the levels in a complex sociotechnical system spanning strictly physical factors, the unsafe practices of individual workers, inadequate oversight and enforcement by local government and a provincial regulatory agency and budget reductions imposed by the provincial government. Furthermore, the dynamic forces that led to the accident had been in place for some time—some going back 20 years—yet the feedback to reveal the safety implications of these forces was largely unavailable to the various actors in the system. Rasmussen's framework provides a theoretical basis for abstracting from the details of this particular incident, thereby highlighting generalizable lessons that might be used to ensure the safety of other complex sociotechnical systems.

Keywords:

• Risk management
• Safety
• Public health
• Water quality

Acknowledgements

This research was sponsored by a grant from the Natural Sciences and Engineering Research Council of Canada, by a Premier's Research Excellence Award and by the Jerome Clarke Hunsaker Distinguished Visiting Professorship from MIT. We would like to thank Jens Rasmussen, Mr James van Loon and the Honourable Dennis R. O’Connor of the Walkerton Inquiry Commission, David Woods and the reviewers for providing helpful comments.