When the implementation of water safety plans fail: rethinking the approach to water safety planning following a serious waterborne outbreak and implications for subsequent water sector reforms.

Water suppliers in New Zealand have been preparing the water safety plans (WSPs) since 2005; large drinking water-associated outbreaks of campylobacteriosis occurred in Darfield in 2012 and in Havelock North in 2016. This paper reviews the WSP that was in place for Havelock North, and analyses why it failed to prevent this outbreak. The risk assessment team completing the WSP underestimated the risks to human health of contamination events, while overestimating the security of the groundwater and bore heads. Historical Escherichia coli transgressions were dismissed as likely despite sampler or testing errors, rather than important warning signals. The outbreak was a consequence of multiple factors including an untreated supply, a local animal faecal source, limitations to the aquifer integrity and bore head protection, and a failure to proactively respond to a flooding event. The overarching issue was a focus on narrow compliance with the Health Act rather than the use of the WSP as a valuable tool to proactively understand and manage public health risks. New Zealand plans to focus on the ability of an organisation to manage risk, with the emphasis on promoting conversations with water suppliers about integrated risk management rather than focusing solely on the preparation of a WSP.