Clarifying chlorine

In response to the letter on May 4 Solvejg Ruarus, titled “Chlorine for Christmas’’, the question, ‘‘When will Christchurch’s water supply be chlorine-free?’’ isn’t a straightforward one to answer.

Firstly, it depends on the city’s new water safety plan being approved. Times have changed considerably since the 2016 Havelock North water contamination outbreak, and there is now a much lower tolerance for risk across drinking-water suppliers, assessors and regulatory agencies. The council is committed to keeping constant vigilance over the city’s water supply network, and our new water safety plan reflects this.

It also specifies that where we have unacceptable risks to our network – such as below-ground well heads, a poor-condition reservoir, or a backflow risk from a property – we need to use chlorine as an extra ‘safety barrier’ to manage those risks. If the Drinking Water Assessor agrees with this approach and approves our new water safety plan, we will be able to continue removing the chlorine gradually as we complete upgrades across the city.

Secondly, there is currently draft legislation before Parliament – the Water Services Bill – which proposes making residual disinfection (eg chlorine treatment) of water supplies mandatory, with the ability for a water supplier to apply for an exemption.

The council has already made submissions on this Bill and, if necessary, is committed to applying for an exemption once the final version becomes law.

Helen Beaumont, Head of Three Waters and Waste, Christchurch City Council