Auckland's largest wastewater infrastructure project, the Central Interceptor, is now fully operational, with Watercare saying it will dramatically cut overflows into the city's waterways for decades.
The $1.66 billion tunnel runs 16.2km from Point Erin in Herne Bay to the Māngere Wastewater Treatment Plant, sitting between 15 and 110m underground and passing beneath the Manukau Harbour.
Its southern half went live in early 2025 and has already prevented an estimated 741,000 cubic metres of wastewater and stormwater from overflowing into the environment — equivalent to almost 300 Olympic-sized swimming pools — by 1 July this year. Now with the northern section in service, Watercare said the full tunnel was positioned to deliver even greater improvements.
Construction began in 2019 and took seven years, using a tunnel boring machine to dig the gravity-fed tunnel across the isthmus. Despite the Covid-19 pandemic, major weather events and inflationary pressures, the project was delivered on schedule and close to its original budget.
Watercare chief executive Jamie Sinclair called the completion of the tunnel a transformative moment for Auckland.
"The Central Interceptor is a game changer for our city that will deliver lasting environmental, community and growth benefits for Aucklanders," he said.
Sinclair said it would provide a backbone for future projects to further improve the network, including the Herne Bay Collector — a wastewater tunnel already under way that will connect to the Central Interceptor and help reduce wet-weather overflows further.
"This project is at the heart of our commitment to improving water quality across the region."
The $1.66 billion tunnel runs 16.2km and is expected dramatically cut overflows into the city's waterways. (Source: 1News)
Auckland Mayor Wayne Brown, an engineer by trade, said the completion would help to improve the health of the city's harbours and local streams.
"Aucklanders want cleaner waterways and to be able to enjoy the likes of Browny’s pool, local beaches and marine environment," he said.
"Delivering these outcomes while creating a smarter, more resilient network is exactly what we are committed to providing for the future of Auckland. This project shows what's possible when we invest in the right infrastructure at the right time."
Sinclair said Watercare was "incredibly proud" of the team who delivered the project and lauded them for staying on-schedule and on-budget.
"Mega projects of this scale rarely stay so close to programme and budget, particularly given the challenges faced throughout delivery," he said.
"Working together has enabled one of New Zealand's most complex infrastructure projects to be delivered safely, efficiently and with a strong focus on environmental and community outcomes."
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