Christchurch’s drinking water will be temporarily treated with chlorine while work is fast-tracked on improving the security of the city’s well heads.

Christchurch City Council today voted to begin temporarily treating the city’s water supply to provide an extra level of protection against waterborne illnesses.

However, it has resolved that long term it wants to retain the city’s untreated water supply system and will oppose any Government moves to impose mandatory permanent chlorination.

Mayor Lianne Dalziel takes a drink of water during the Council meeting.

The temporary chlorination has been approved for up to 12 months while work is done to ensure all the city’s below-ground well heads are sealed at the surface to protect them from contamination.

The well heads need to be sealed in order to meet the secure bore status requirements set out under the Drinking Water Standards.

The well head work is already under way and should be completed by December 2018. The Council has asked that the contractors accelerate the programme so it can be completed a couple of months earlier.

“Our city water is taken from deep underground aquifers and is very high quality, but there is a small risk of contamination occurring through the infrastructure we use to draw the water from the ground and get it to people. Because of that risk, engineers are not prepared to sign-off our wells as secure,'' says Mayor Lianne Dalziel.

"We are fast-tracking work to reduce that risk, but the advice we have from the Canterbury Medical Officer of Health is that we should chlorinate the water in the meantime to provide an extra layer of protection so that we meet our duty of ensuring our drinking water is safe.

“The decision to treat the city’s water supply with chlorine is not one the Council has taken lightly. We know people like the fact that Christchurch’s water is untreated, but as a Council we take our drinking water responsibilities very seriously,’’ the Mayor says.

“We cannot ignore the risk of our water becoming contaminated which is why we have taken the decision today to temporarily chlorinate it. The likelihood of the water becoming contaminated is slight, but the consequences would be severe so we must put public safety first.’’

Canterbury Medical Officer of Health Dr Alistair Humphrey says temporarily treating the water with chlorine is the appropriate course of action.

“The Council has invested heavily in ensuring Christchurch has a safe, high-quality water supply and have only had a handful of transgressions in the last few years. Nearly all of these have occurred in the reservoir tanks, which are also being sealed as part of the upgrade programme,’’ Dr Humphrey says.

“The Council has a programme in place to improve the security of its below-ground well heads but until such point as that programme is complete, it needs to provide an effective barrier against contamination. The most effective barrier is chlorination.

“As a Cantabrian, my heart says don’t chlorinate our water, but as a public health physician my head says we have to keep Cantabrians safe,’’ he says.

The safety of drinking water supplies has been in the spotlight since more than 5500 people fell ill in Havelock North after drinking contaminated water, resulting in a Government inquiry.

The findings of the second stage of that inquiry were released late last year. More than 50 recommendations were made, including that all drinking water should be effectively treated for public health reasons.

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