Queen Street wastewater project reaches breakthrough milestone

The milestone is part of a major wastewater diversion project in Auckland, led by Watercare.   

Designed to reduce wet weather overflows and increase network capacity, a new 1.2-metre diameter pipeline will sit snugly in the freshly drilled tunnel - connecting into historic Orakei Main Sewer, a brick barrel sewer that's been serving the city for over a century. 

The Midtown Wastewater Diversion project will play a critical role in supporting residential and commercial developments, enhance the city’s resilience, and allow for future city growth. 

Responsible for detailed design and construction monitoring, WSP has been working on the project alongside contractors including McConnell Dowell and Fulton Hogan. 

To reduce disruption to businesses and pedestrians, engineers opted for trenchless technology, drilling from three shafts at Mayoral Drive, Wellesley Street, and Victoria Street. 

Tunnelling formed the first phase in the project work. It involved navigating a congested underground landscape filled with electrical, water, gas, and power services. The deepest point of the tunnel reaches fourteen metres, with the final connection into the Orakei Main made at a depth of seven metres. 

One of the project’s standout features is the use of a digital twin - a virtual replica of the infrastructure. This let the project team overlay designs, identify conflicts with existing underground infrastructure, and plan service diversions before breaking ground.   

The connection into the 115-year-old Orakei Main Sewer requires delicate engineering due to its unique ovoid shape and mixed materials. Protection works are being carried out to preserve the integrity of the old structure. 

For more information about the project, visit the Watercare website.