Cust water likely to remain chlorinated

Nicole Mathewson Reporter from Northern Outlook

By David Hill, Local Democracy Reporter

Cust’s water supply is expected to remain chlorinated for some time.

In preparing a response to Taumata Arowai’s draft residual disinfection exemption application report, the Waimakariri District Council accepts it may not make any difference.

The council applied for chlorination exemptions last year for its six urban drinking water supplies.

Taumata Arowai releasing its draft report in December, recommending the chlorine exemption in the Cust water supply be declined.

"We don’t expect this will change the decision, but we think this information should be made available to them," the council’s water asset manager, Colin Roxburgh, said.

He said council staff had been working constructively with Taumata Arowai to find a way forward.

The council has been chlorinating the Cust water supply since 2020 as a precaution after upgrading water tanks.

In its draft report, Taumata Arowai identified 15 factors that led to its recommendation to decline the exemption.

Those factors included issues with the water source and the council’s monitoring and modelling were "insufficient".

Roxburgh acknowledged the council had not provided information on its understanding of the viruses in the water supply or how it would treat them.

Taumata Arowai had concluded the ultra violet (UV) treatment proposed was "not a full treatment barrier for viruses".

But the council has highlighted evidence which it believed suggested UV treatment could be appropriate in certain circumstances.

Mayor Dan Gordon said he was disappointed not to be able to offer better news for Cust residents.

But said staff would continue to work on finding solutions to keep Waimakariri’s drinking water supplies chlorine free.

"We know our ratepayers do not want chlorinated water supplies and in our response we have again reinforced our commitment to work with Taumata Arowai to try to prevent that from happening."

Waimakariri MP Matt Doocey said he was disappointed the council had not found a way to meet Taumata Arowai’s requirements to remove chlorine from Cust’s water supply.

"It is clear Taumata Arowai has given a pathway forward and now it is up to Waimakariri to consult with its ratepayers on a plan to meet those requirements."

The council also has chlorine exemption applications for its other urban water supplies in Kaiapoi, Woodend/Pegasus, Rangiora, Waikuku and Oxford.