TBM Hiwa-i-te-Rangi has arrived at Havestock Road, marking her fifth breakthrough on the project. Jerwin Gutierrez, Ghella Abergeldie’s senior associated tunnelling engineer, said this time she broke through into the shaft underwater because of the difficult ground water conditions.

Three TBMs – Hiwa-i-te-Rangi, Domenica and Victoria – are boring the 14.7km pipeline. With the latest breakthrough, 9880m of the main tunnel has been excavated.

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 project comprises three elements: the main tunnel, Link Sewer B and the CC09 Connector Sewer.

On Link Sewer B, the first drive of 800m has been completed, and TBM Domenica was relaunched in February for the second, and final, 300m drive. Crews are now hand-tunnelling a 23m adit from the Link Sewer B tunnel to the main Central Interceptor.

TBM Victoria has completed three of the six drives for the CC09 Connector Sewer.

Earlier this year, the project marked another milestone with a continuous, 10-hour concrete pour at the Western Springs site. More than 40 concrete lorries arrived every 15 minutes for 10 hours to complete the base slab of the 30m-deep shaft.

At the Haycock Avenue site in Mt Roskill – where TBM Dominica broke through twice for Link Sewer B – a 110 tonne lid has been secured over the 30m-deep shaft.

North of Auckland, work is also under way on Watercare’s 5km Warkworth to Snells Beach wastewater pipeline. In late February TBM Piper was launched on her second drive.

The project is scheduled to be completed this year.