New Zealand: Central Interceptor’s TBM achieves a historic milestone

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Central Interceptor TBM, building a giant 4.5m diameter underground wastewater tunnel, has reached the 5km mark.

The Hiwa-i-te-Rangi Tunnel Boring Machine (TBM) has reached the five-kilometre mark on her 14.7km journey from Māngere Wastewater Treatment Plant to Grey Lynn.

The TBM is building a giant 4.5m diameter underground wastewater tunnel, designed to significantly reduce wet-weather overflows in central Auckland where there is a combined stormwater/wastewater network.

She began tunneling in August 2021 and is now 115m underneath Hillsborough Ridge – the deepest section of the entire journey. Hiwa-i-te-Rangi travels up to 25m per day and is powered by a series of thrust cylinders. So far she has laid 3,118 steel-reinforced concrete rings to form a giant tunnel, with a 100-year lifespan.

The $1.2b Central Interceptor project is being delivered by Ghella Abergledie JV. Central Interceptor commercial manager Nigel Varcoe says the five-kilometere milestone comes after the TBM successfully crossed the Manukau Harbour in December: “I’d like to thank the tunnellers on their great achievement. This is a multi-national crew with tremendous skills and experience.

“We are currently on track to deliver the project by the end of 2026, safely and within budget. This will be our busiest year and we have plenty more milestones ahead,” says Central Interceptor Commercial Manager Nigel Varcoe.

Hiwa-i-te-Rangi is 200m long and is operated around the clock, six days per week by an international crew of tunnellers.

The main tunnel also features two link sewers. The first (running from May Rd Mt Roskill to Miranda Reserve, Blockhouse Bay) is due to be completed next week. Work on the second link sewer will begin later this year.

Source: Watercare

Image source: Watercare

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