Tunnelling reaches halfway mark on Auckland water project

The project is the largest wastewater infrastructure undertaking in New Zealand history. The Central Interceptor will store 226,000m3 of wastewater, control the flows into treatment plants and reduce the number of wastewater overflows into Auckland’s waterways and the Waitemata Harbour.  

The 14.7km tunnel will run from Mangere Wastewater Treatment Plant to Grey Lynn and will be intersected by two link sewers.

It has involved excavating a 1500m tunnel under Manukau Harbour in 11 weeks – the first time tunnelling has been carried out under a major New Zealand harbour.

Ghella Abergeldie JV is delivering the NZ$1.2bn (US$710m) project, using a 5.4m diameter Herrenknecht TBM named Hiwa-i-te-Rangi.

Central Interceptor executive programme director Shayne Cunis said the halfway mark had been achieved despite significant challenges.

“We all deserve to savour this moment. We’re on track to deliver this project in 2026 as planned, despite everything that has been thrown at us – Covid-19 lockdowns, closed borders, global shipping delays and major weather events. But most importantly, the project is being delivered safely,” said Cunis.

“I want to pay tribute to our Ghella Abergeldie JV construction partners, as well staff from Jacobs, Aecom, Delve Underground, Watercare and our sub-contractors, who are all working so hard to deliver this project in the best way we can. This is our busiest year, with around 600 staff working on 16 sites.”

Ghella Abergeldie JV project director Francesco Saibene said the Central Interceptor would be the longest bored tunnel in New Zealand and reaching the halfway mark was a moment to celebrate.

The first link sewer was completed in March, and construction has started on a second link sewer, which will be completed in two drives.

Section one of the main tunnel and both link sewers are due to be commissioned by mid-2024.