Currently five of Tasman District Council’s 15 water supplies do not have permanent residual disinfection through the use of chlorine; Upper Takaka, Hamama, Motueka, Riwaka/Kaiteriteri and Richmond. The Council has adopted a recommendation to consult with the community on a proposal to introduce chlorination permanently to those five supplies to ensure water is safe to drink.

There are two main reasons why Council has chosen to consult on this proposal at this time. Firstly, providing safe drinking water is at the very core of what Councils do. We have a duty to do so and an obligation to our residents to ensure the water supply is as safe as we can make it. Secondly, there is central government legislation that obliges us, and all Councils, to prove we are meeting that responsibility.   

Central Government changes

All Councils around New Zealand are being held to higher standards for drinking water quality. This stems from the enquiry into the Havelock North Contamination Event in 2016. Their water supply became contaminated with campylobacter, resulting in approximately one-third of the town (over 5,000 people) becoming sick, 45 people hospitalised and four deaths.

Having permanent residual disinfection using chlorine, as part of a multi-barrier treatment approach, was one of the recommendations from the Government’s inquiry. It is one of six key principles identified in the New Zealand Drinking Water Safety Plan Framework (2018), which Council has to conform to.

The Director General of Health also indicated in a letter to Councils without chlorination in all water supplies, that they will need to demonstrate the other preventative measures they have in place are effective and can maintain the quality of the drinking water throughout the system, i.e. from source to tap.

Does our water measure up?

Under the current systems in place on some water supplies, it will be difficult for us to meet the standard required. For instance, while Council carries out testing of non-chlorinated supplies, especially those with reservoirs, it can take at least 24 hours to get a sampling result. If contamination is found, given that timeframe, it’s likely that some, if not all, of the users on that supply could potentially have been exposed to contaminated water for at least 24 hours.

There have been regular instances (several times a year) when testing has picked up total coliform counts in the Richmond water supply network and occasionally E.coli counts. This is a similar situation for the Riwaka/Kaiteriteri water supply scheme. Total coliforms and E.coli have not been detected in samples taken directly after water has been treated with UV in the treatment plants, so we know the contamination is occurring in the network.

Contamination can come from a number of sources: work on the water supply network, backflow events (water re-entering the supply), illegal connections, pipe breaks, faulty fittings, illegal water takes from hydrants or through damage to reservoir roofs. 

The constant presence of these risks alongside our current monitoring and operational measures may well be seen as ineffective under the current national standards. Advice from Government is that our Water Safety Plans will not be approved unless we have residual disinfection or can provide good justification as to why it is not required, which we have been unable to do. Chlorination is the most widely used method throughout the world to treat drinking water.

Next Steps

Council staff will prepare an information document on the proposal, which will look at the various treatment options and the relative costs of each approach. This will form the basis of the consultation with the community, scheduled to happen in July 2020.

Mayor Tim King says “Above all else, we need to settle upon a solution that is as effective as possible and makes long-term financial sense. We understand that there may be a high level of interest in this proposal. We think it’s crucial that we put out clear information about what’s proposed and the feedback we get will help us to make a well informed decision later in the year.”