Watercare's Onehunga Water Treatment Plant. Photo: Watercare/Supplied
Auckland water supplier Watercare has pushed back the re-opening of a water treatment plant contaminated by so-called "forever chemicals" by another two years.
The Onehunga plant was shut three years ago, after detections of low levels of per and polyfluoroalkyl substances - or PFAS - that accumulate in the body, and are linked to cancer and immune problems.
Watercare had expected to re-open the facility in 2027, under a $40 million upgrade to remove the contaminants.
On Friday, it said the project to install granular-activated carbon filtration would begin construction in 2027 and take until 2029.
"We are currently in the detailed design phase," said head of water Sharon Danks. "This will ensure the treatment plant can consistently meet New Zealand drinking water standards.
"As part of the upgrade, a new ultraviolet disinfection system will be added to provide an additional barrier against microbiological contaminants."
Nationwide, the rules do not require regular monitoring for PFAS and Watercare does not do routine testing.
"We continue to look at global trends and learnings from PFAS monitoring and testing," Danks told RNZ.
The chemicals, which were invented in the 1930s and used in the US atomic-bomb-making Manhattan Project, have a virtually indestructible carbon-fluorine bond and now number more than 12,000 different types. They are the subject of lawsuits and clean-ups in the United States and Europe.
New Zealand has not followed other countries in drastically reducing the thresholds at which they are considered safe.
At times, tests at Onehunga in 2023 and last year found the sort of low levels that had closed the plant in 2022.
'Strong position'
Onehunga community's water supply comes from the metropolitan water network.
In summer 2023, the agency activated its consent to take more water from the Waikato River to make up for the 18 million litres a day lost at Onehunga.
However, Dans said Auckland's water supply was currently in a "strong position", using its full dams to maximise production at the Ardmore and Huia water treatment plants.
"Over summer, as water demand increases, we will increase production at our Waikato Water Treatment Plant, which treats water from the Waikato River," she said.
Its second Waikato treatment plant was offline and not needed to supplement supply.
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