Pathogenic Organisms

The Walkerton Tragedy: A Case for Risk Reduction using a Multi-Barrier Approach; A Lesson for the Great Lakes?

The waterborne disease outbreak in Walkerton, Ontario in May 2000, caused by contamination from a well that was not adequately chlorinated, highlights the need for constant vigilance and the development of new methods to detect such threats.⁴² The town of Walkerton, located less than 40 km (23 miles) from Lake Huron, is similar to many towns in the Great Lakes basin. The circumstances leading up to the tragic disease outbreak in Walkerton were the result of a cascade of human errors, accounted for in lost lives, lost health, lost productivity, and loss of public trust. This tragedy must not be repeated. In his review of the incident, Justice Dennis O’Connor concluded that the risk of unsafe drinking water could be reduced to a negligible level by introducing a multiple barrier approach, or a number of measures independent of each other, as a comprehensive barrier to waterborne contamination.⁴³ The Ontario Ministry of Environment has embarked on a legislative approach to drinking water safety through the Safe Drinking Water Act and regulations and in June 2004 posted a draft source protection legislation on its Environmental Bill of Rights Registry.

The Canadian report, From Source to Tap, conveys a similar message that the protection of drinking water sources (source water), along with several layers of treatment at drinking water treatment plants such as coagulants, filtration and disinfection processes, provide a multiple barrier approach that minimizes risks to public health.⁴⁴