Immersed tunnelling shaping Sydney's transport network
Immersed tunnelling shaping Sydney's transport network

A look into how immersed tube tunnelling is shaping Sydney's transport network

As we approach the 30-year anniversary of the iconic Sydney Harbour Tunnel we are also imagining what Australia’s second immersed tube tunnel will mean for the city’s transport network.

The Western Harbour Tunnel will be a brand-new road crossing of Sydney Harbour with construction planned to start in 2022. It will help create an integrated road and public transport network by easing congestion on the Anzac Bridge, Sydney Harbour Tunnel, Sydney Harbour Bridge and Eastern Distributor, improving travel times for commuters and the movement of freight. Forming part of an alternate north-south bypass west of Sydney’s CBD, it will connect communities from Western Sydney to the city’s South and North.

But to really understand how such a massive project like this comes to life, we must first look back before we can move forward. Back 30 years to the opening of Sydney’s first and only immersed tube tunnel.

“We hadn’t seen anything like this in Sydney – and didn’t think we would again – until now.”

CK Tsang, Technical Director

Back to the future of tunnelling in Sydney

In this series of short videos, some of the Aurecon engineers who were instrumental in the success of Sydney’s first Harbour tunnel share their stories of technical triumph on a project the likes of which Sydney had never seen.

Our immersed tube tunnelling leader CK Tsang explains why this solution is favoured for harbour environments due to its shallow depth below the seabed, that allows shorter tunnel lengths and better connections to the road network.

Our tunnelling team, those who worked on the Sydney Harbour Tunnel and those who are aiming to be part of the vibrant city’s future history, want to take the brilliance of an engineering solution used only once in Australia’s history to shape the next generation of passenger outcomes.

Their aim is to design a solution that will allow commuters to travel to exactly where they want to be – quicker, easier and smarter – adding another layer to Sydney’s transport network to allow people to connect better.

Play video Western Harbour Tunnel: Back to the future of tunnelling
Play video
Play video Western Harbour Tunnel: Back to the future of tunnelling
Play video

Under water is not a boring solution

In the world of heavy construction, there are many structures that take shape right in front of our eyes; a bridge, a freeway or perhaps a building are easily seen as they are constructed.

However, there are structures that are far more stealth, and seemingly invisible, in their creation, which brings up the question, “How do they do that?”.

Immersed tube, as opposed to bored, tunnelling under water is a prime example with the inside of the tunnel not seen until the day of opening to the public.

How do we connect watertight boxes in a chain together, some nearly as tall as a three-story building, in waters as deep as 50 metres.

These insights explain how immersed tunnels are constructed. It is a seemingly impossible task, but the immense benefit it brings to cities by connecting its people to their destinations is the lasting legacy it leaves.


“Ultimately these once in a generation projects are about people – the people who design and construct them – for the people who use them.”

Rowenna Walker
Managing Director, New South Wales
& Australian Capital Territory

Learn more about our tunnelling projects

Sydney Metro

Aurecon is leading the design of Australia's biggest public transport infrastructure project to provide Sydney with world-class fast, safe and reliable trains.

NorthConnex, Australia

Aurecon provides road tunnel and design services to NorthConnex, a faster, safer, and more efficient motorway for road users to Australia's deepest road tunnel.

Explore our expertise and insights

What is the future of transport?

We are on the verge of a paradigm shift. By taking the opportunity to reshape rather than reset our transport systems, we can choose to retain our need to increase speed and convenience, but we can also put safety, equitable mobility and sustainability at the top of our agenda.
Scott Smith
Market Operations Director, Transportation – Australia


Rowenna Walker, Aurecon

Rowenna Walker

Managing Director, New South Wales
& Australian Capital Territory
+61 2 9465 5344
Braith Gilchrist, Aurecon

Braith Gilchrist

Transportation Industry Director, New South Wales & Australian Capital Territory
+61 2 9465 5884
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