Spanning engineering, ecology and heritage, the Bridgewater Bridge project is setting new standards for bold urban infrastructure.
If you’ve driven past the Derwent River in Tasmania recently, you’ve probably noticed something big taking shape. The new Bridgewater Bridge, a project led by McConnell Dowell, is one of Tasmania’s largest and most ambitious transport upgrades to date, changing more than just the locals’ commute.
Peter Fraser, director of the project which has been nominated for the 2025 Australian Construction Achievement Award, explained why it’s one of a kind.
Why replace the old bridge?
When the current Bridgewater Bridge officially opened in 1946, the steel truss lift-span structure was once considered cutting-edge. In fact, it was Australia’s first fully welded steel bridge.
But the need to replace the old bridge has been a long time coming. Over time, it aged beyond its intended lifespan.
“It was well past its use by date,” Fraser said. “From an economic perspective, the maintenance costs and risk of network disruption from failure were unsustainable. And it was getting to the point where it was no longer able to be maintainable.”
With just one lane in each direction, the old structure couldn’t support the volume or pace of today’s traffic. Connecting the Brooker Highway and Midland Highway, the expansion of Bridgewater Bridge to a four-lane thoroughfare standard was a modern, robust solution.
Innovation on the water
From a design standpoint, the new bridge design is impressive but not without precedent.
“It’s a twin box girder of segmental construction erected using the balanced cantilever technique,” Fraser explained. “That’s a fairly standard methodology for this span of bridge, although all designs are refined, changed and tweaked for each project.”
But what makes this project unique is how the team responded to its sensitive environment. The Derwent River is part of a marine conservation zone managed by Parks and Wildlife Services, with shallow tidal mudflats and seagrass beds.
To avoid disrupting this delicate ecosystem, the team took a novel approach.
“We prefabricated 12 barges specifically for the project and then we ballasted them onto the mud flats. That enabled us to build the bridge from the platform where the barge is formed without disturbing the mud and the flora while providing reliable construction access.”
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Geotechnical challenges and sustainable approaches
Building across the Derwent presents serious geological obstacles. “It’s very highly faulted and has geologically variable rock,” Fraser said. “It’s also overlain by about 30 meters of very soft marine mud.”
To address this, the project team turned to a sophisticated piling method. “We adopted a mono pile for each pier, rather than pile groups, which was an innovative application of design.”
Sustainability was also an important consideration. The monopiles use less concrete, reducing overall material requirements. The barge platforms and temporary bridge structures are all reusable. And extensive prefabrication off-site has allowed for faster, more controlled construction, minimising waste.
“We’ve done an immense amount of prefabrication work that increases efficiency. Offsite construction, including 1082 box girder segments in a purpose-built precast yard – where we can do things in a controlled environment – means that we were able to again head towards lower carbon.”
Even at the civil works level, the team ensured materials excavated from site were reused, minimising waste and unnecessary transport. “We’ve ensured that we don’t export material we’ve excavated and then bring it back in again as a purchased material,” Fraser said. “We’ve optimised the cut and fill, and the use of material onsite.”
Honouring heritage, managing traffic
As with many Australian infrastructure projects, heritage considerations played a critical role here, with the site’s history stretching back millennia.
“There would likely have been a crossing here going back thousands of years,” Fraser said. “We found a number of Aboriginal artifacts in certain locations which have needed to be respectfully looked at and taken care of.”
At times, the team had to stop works and closely consult with the local community to ensure they were taking the right approach. There’s also significant European and colonial heritage on site which had to be carefully controlled, excavated, mapped and managed.
“The causeway was built by convicts, and there are various surrounding inns, hotels and railways,” he said.
Aboriginal and European heritage archeologists were employed and worked closely with the team throughout the project.
Traffic impacts have also been an ongoing challenge, leading to some congestion. But with real-time monitoring and careful phasing, disruptions have been kept to a minimum.
“We’ve been able to keep work offline to the maximum extent possible and sophisticated monitoring, including by Bluetooth monitoring, has been successfully deployed.”
Community pride and industry legacy
As construction has progressed, public enthusiasm has grown – bolstered by consistent progress and a sense of visibility. “It’s been a focus of politicians’ attention. Everybody’s very supportive.”
Beyond the bridge itself, the project has created deep roots in Tasmania’s economy and workforce, providing training programs and working with TAFE to support new entrants to the industry.
“We offered some work here, which has been very successful. We also achieved our target of delivering 160,000 hours of training over the duration of a project, which we’ve done in the context of about two million hours worked all in.”
Local companies such as Hazel Bros worked closely with the project team to successfully deliver the high-quality concrete supply, and BridgePro Engineering pre-fabricated all the bridge pile and pier rebar cages in La Trobe, in northern Tasmania.
“They also installed our temporary bridge for us and constructed the in-situ piers,” Fraser said.
The economic benefit to Tasmania is equally significant. “We estimate [we injected] maybe $450 million in the local economy, including staff spending and wages.”
There’s also been cultural engagement, such as the Bridge Art Prize – with a prize pool exceeding $36,000 and a main prize of $25,000 community collaboration hosted in the Derwent Valley to celebrate and commemorate the bridge, and strengthen the sense of ownership and pride in the project.
“The Governor and the Minister for Infrastructure opened the exhibition and awarded prizes, and we have had tremendous support and buy-in from the whole of Tasmania.”
Countdown to opening
With the bridge anticipated to open mid year, the final touches are now underway.
“We’re finishing off post-tensioning and grouting on the bridge deck itself and working hard to get the intelligent traffic management systems in place,” Fraser said.
A public celebration is in the works too.
“When the opening has taken place, we’ll expect to utilise the precast yard to put on a bridge open day, acknowledging the local community for what they’ve had to put up with in terms of the disruption and imposition on them. This is our way of saying thank you to them and saying, ‘This is your bridge’.”
Registrations to attend the Australian Construction Achievement Awards 2025 are open until 31 July.
the new bride has been long coming I’ll be only to glad to attend the opening with my partner Jo so please keep in up to date with things
THANK YOU
GREG BESTER
the new bridge will make a big difference one people get use the the lanes and road rules on the bridge
thank you
GREG BESTER