The 7.5km mega tunnels in Sydney provide a critical new link between the M4 at Haberfield and the M8 at St Peters, reducing journey times between Western Sydney and Sydney Airport by up to 40 minutes. The project started in August 2018.

The M4 and M8 link is the third stage of the A$16.8bn WestConnex project being delivered in a partnership between the NSW Government and the Commonwealth which has contributed a A$1.5bn grant and a A$2bn concessional loan.

The final stage of WestConnex will be completed once the Rozelle Interchange opens later this year.

Federal infrastructure, transport, regional development and local government minister Catherine King said the tunnels were constructed using more sustainable materials and energy-efficient technology, requiring less long-term maintenance.

“The project has also achieved key sustainability ratings, with around 8.7 million tonnes of spoil beneficially reused, including at the future Western Sydney International Airport site,” she said.

ASBJV has also catalogued its project achievements.

It invested more than A$60m in Aboriginal participation over the life of the project, including education and employment, cultural awareness training, mentoring programmes and the procurement of goods and services from Aboriginal businesses.

It also invested in the development of female participation in the construction sector, employing one of the largest female workforces on a tunnelling project in New South Wales.

During the project, ASBJV won two awards for sustainability. Working with engineering partners and contractors, the project team developed a high-performance shotcrete specification. The initiative won the American Shotcrete Association Project of the Year award as well as the Infrastructure Sustainability Council’s Excellence in Economic Outcomes Award. The new shotcrete specification reduced the embodied carbon, reduced shotcrete by 27,000m3 and reinforced steel fibres by 830 tonnes, creating an A$11m cost saving.

Acciona says it is now applying the legacy initiative and learnings to other projects, including the newly awarded contract to design and construct stage two of Sydney’s Western Harbour Tunnel.