Funding has been confirmed to extend Watercare’s Central Interceptor wastewater tunnel by more than one kilometre from Grey Lynn to Point Erin, Herne Bay to reduce wet weather overflows and significantly improve water quality in Herne Bay and St Mary’s Bay waterways and beaches.

The confirmation follows agreement on Local Water Done Well between Auckland Mayor Wayne Brown and Local Government Minister Simeon Brown earlier this month.

Watercare will share funding for the tunnel extension with Healthy Waters, as referenced by Auckland Council’s recent commitment to funding water infrastructure in their Long-term Plan (LTP). The Governing Body (made up of the Mayor and 20 ward councillors) is expected to sign off the LTP in coming weeks.

The 4.5 metre diameter Central Interceptor tunnel runs from Māngere Wastewater Treatment Plant, across the Manukau Harbour to central Auckland, with two new link sewers collecting flows from west Auckland. It is the largest wastewater infrastructure project in New Zealand history and will significantly reduce wet weather overflows into waterways such as Meola Creek, Oakley Creek and Motions Creek as well as the Waitmatā Harbour. The project will also improve resiliency within the wastewater network and allow for future population growth in Tāmaki Makaurau.

Hiwa-i-te-Rangi Tunnel Boring Machine has travelled more than 11 kilometres since leaving Māngere in August 2021 and is approximately 60m under Mt Albert, heading towards Western Springs.

Auckland Mayor Wayne Brown says this will be the first of many projects to benefit Aucklanders following the Local Water Done Well agreement.

“The deal was about fixing Auckland’s water infrastructure. We avoided major hikes in water charges, while enabling major investment in water infrastructure that will last generations and make Auckland a better place to live. I am pleased we have been able to make this important project possible. This is what a solution in action looks like.”

Watercare chief executive Dave Chambers says the tunnel extension is great news for residents of Herne Bay and St Mary’s Bay who will benefit from a cleaner environment: “No one wants to see black flags on the SafeSwim website. The Central Interceptor project will bring enormous environmental benefits because flows will be taken away to Māngere Wastewater Treatment Plant for processing instead of overflowing into waterways and beaches during heavy rain.”

The Central Interceptor project is on track for completion in 2026. By then, it will be fully operational up to Grey Lynn. The Point Erin extension will be commissioned in 2028 when it connects to an upgraded Herne Bay Trunk Sewer.

Craig McIlroy, General Manager Healthy Waters says a collaborative approach must be taken to clean up Auckland’s waterways: “This is an exciting chapter in the history of some of our oldest suburbs. We’ve already carried out extensive improvement work through our network separation project which began in 2020. The Central Interceptor tunnel extension will allow us to connect to local networks so that beaches in St Mary’s Bay and Herne Bay will be significantly cleaner for generations to come.”

Watercare was granted resource consent for the Point Erin tunnel extension in 2023. Resource consent has also been granted for the Herne Bay Wastewater Trunk Sewer upgrade, which will connect to the Central Interceptor tunnel in Pt Erin Park.

Construction of the Central Interceptor project has passed the halfway mark, with more than 600 staff working on 16 sites across Auckland. It involves more than 16 kilometres of tunnelling, four kilometres of micro-tunnelling, the construction of 17 shafts and major new infrastructure including a new pump station at the Māngere site to send flows from the main tunnel to the treatment plant for processing. Crews will also shortly begin connecting the aging Western Interceptor to the Central Interceptor, to increase resiliency throughout the wastewater network.

The project is being delivered by construction partners Ghella Abergeldie JV. The southern section of the tunnel from May Rd, Mt Roskill south plus one link sewer is due to go live by the end of the year.

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