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Thu November 30 2023

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TBM ordered for record-breaking NZ tunnel

6 Nov 19 The order has been placed for the machine that will excavate New Zealand’s largest-ever wastewater tunnel.

Herrenknecht by will provide a 5.45m-diameter earth pressure balanced tunnel boring machine (TBM) for the Central Interceptor project.

In March this year, a joint venture of Ghella and Abergeldie signed the construction contract with Auckland Council's water utility body Watercare. Arup is providing design support to the joint venture.

The TBM will be used for the main 13km-long tunnel. The project also involves building two underground links of overall length 4.3km, which will be excavated using two pipe-jacking machines with diameters of about 3m. Other aspects of the project include 16 shafts reaching up to 80m in depth.

The 13km main tunnel will run between Western Springs and the Mangere Wastewater Treatment Plant. The TBM will be tunnelling underneath Auckland at depths between 15m and 110m meters underground.The tunnel is expected to reduce wastewater overflows in central Auckland by 80%, improving water quality at some of the city's beaches.

The internal diameter of the tunnel will be 4.5m – which the project team points out is high enough to fit a giraffe and wide enough for four rhinos.

The project is expected to be completed by 2025.

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