There are fresh concerns over the structural integrity of Hobart’s new Bridgewater Bridge, which one expert who worked on the project suggested could eventually lead to a need to reduce traffic flow or speed limits.
The concerns stem from the design of the concrete piles that form the foundation of the $786 million bridge and the “level of uncertainty” over the make-up of the riverbed.
The bridge builder and an advisory group of engineers who worked on the project were at odds over the extent of the issues, with one of the engineers describing the problems as “intolerable”.
Documents seen by the ABC highlight concerns from the Technical Advisory Team, which was employed by the Department of State Growth to check that the bridge was built to contract by designer and builder McConnell Dowell (MCD).
MCD is also part of Constructure Joint Venture, one of the parties competing for the tender to build the Hobart stadium at Macquarie Point.
Construction started in 2022 and it was finished in 2025. (Supplied: Department of State Growth)
The documents show MCD and the advisory team disagreed over the pile design’s suitability for the varied ground conditions at the River Derwent crossing.
There were concerns the piles could not provide enough support for the bridge piers to meet the contract’s standards, which could lead to damage to the bridge beyond the defects period.
The department ticked off on the bridge design in 2022, despite the issues, on the condition that MCD later addressed the concerns to the state government’s satisfaction.
But one of the engineers from the advisory team has chosen to speak to the ABC, saying news broken by the ABC in February of a large crack in a pier caused by incorrect modelling may indicate that the more widespread issues raised by his team were not resolved.
The ABC previously reported on cracking in the concrete plinth of one of the piers. (Supplied)
Tasmanian Premier Jeremy Rockliff (right) and former infrastructure minister Michael Ferguson at the Bridgewater Bridge construction site in May 2024. (Facebook: Jeremy Rockliff)
Chosen design was an ‘intolerable’ risk
Geotechnical specialist Derek Pennington said his advisory team was let go by the Tasmanian government in 2024 due to the standstill between the team and MCD over the piles — in his belief, to avoid project delays.
Derek Pennington was part of the Technical Advisory Team that raised the issues before construction was signed off. (ABC News: Jonny McNee)
“In our opinions, we felt that they [the piles] introduced such risks to the structure performing as required under the contract, that the risk of it failing to perform as required, was intolerable to us,” Dr Pennington said.
“I would have to say it’s the most complex ground that I’ve dealt with in my 35-year career.”
The state government and Department of State Growth did not comment on why the advisory team was stood down.
The new Bridgewater Bridge was built on single piles for each pier. (ABC News)
Dr Pennington says he does not have fears for any sudden, significant damage to the bridge but it is possible there may be a need for more management of loads on the bridge, such as through reduced speed limits and traffic.
The department said survey markers were attached to the bridge piers during construction to help with monitoring any movement.
“The bridge is safe and it has not experienced any unanticipated movement,” the department spokesperson said.
“The monitoring devices were installed several years ago as part of the verification process to confirm the bridge piles were performing as expected once they had been constructed.”
Dr Pennington is concerned the bridge design did not meet the standards set out in the contract. (ABC News: Ebony ten Broeke)
Builder didn’t understand site’s ground conditions, engineer says
The new four-lane Bridgewater Bridge opened in June 2025, three years after construction began.
As Tasmania’s largest infrastructure project, it replaces a previous lift-span bridge, which was coming to the end of its life, showing signs of wear, including sinking support piles after nearly 80 years of operation.
The new Bridgewater Bridge on the left, and the old one on the right, soon to be demolished. (Supplied: Department of State Growth)
“It’s entirely going to be down to the designer’s choice of how to interpret putting a structure into the ground conditions that exist at that particular crossing,” Dr Pennington said.
“But in the very first meetings we had with the team as technical advisor, we thought: ‘how are we going to deal with having single piles with the level of uncertainty that there appears to be in the understanding of ground conditions’.”
Formwork in place for the concrete pour in 2025 as part of repair works ahead of the bridge opening. (Supplied)
A close-up of reinforcing measures in place ahead of the repairs. (Supplied)
Piles are concrete posts injected down into the earth, providing support for bridge piers and making up the foundations of the overall bridge.
‘Large crack’ found in $786 million bridge days before opening
Dr Pennington said bridges could also use multiple piles at different angles, which was “more conventional for these deep estuarine conditions”.
“If you’ve got … a pile cap with multiple piles and rake piles, you can add extra driven piles into the foundation system, you can incline them to get more lateral stability,” Dr Pennington said.
But MCD’s design for the new bridge used single vertical piles drilled between 30 and 88 metres below the river’s surface.
A survey marker for monitoring movement in the bridge piers. (Supplied)
The technical advisory team were concerned that the design of the piles and supporting calculations could not adequately support each of the bridge’s 42 piers.
One reason for this was because they believed MCD had misunderstood the conditions at the bridge site, with some of the ground being more brittle and therefore inappropriate for the single-pile design it was pursuing.
“So that was another issue with the single mono-pile, is that it had to be vertical and the ground conditions were such that in certain parts of the crossing, there was 40, 50 metres of ground you would call very soft and not able to provide much lateral support,” Dr Pennington said.
In the documents, in response to the opposition, MCD maintained its modelling was accurate and sufficient.
The department says the bridge is safe to use. (ABC News: Mitchell Woolnough)
These specific concerns were put to the Department of State Growth, along with the question of whether they were resolved after the advisory team departed, to which it did not respond directly.
Builder MCD declined to comment and referred questions to the department.
“The structural designs were reviewed and checked by a proof engineer and the overall process was reviewed and verified by an independent verifier,” a State Growth spokesperson said.
“These activities were undertaken with the oversight of the Department of State Growth’s project team with support from the department’s consultant technical advisors,” they said.
“Additional verification was obtained on a range of technical matters from the contractor and its design engineers, the proof engineer and the independent verifier.”
“The proof engineer and the independent verifier all certified the final structural designs as being compliant and fit-for purpose, including the pile designs.”
The ABC reviewed internal documents from 2022-24 relating to the Bridgewater Bridge construction project, including the Technical Advisory Team’s concerns.
The ABC reached out to builder McConnell Dowell (MCD), which declined to comment and said all questions should be directed to the Department of State Growth.
These were the questions the ABC put to the Department of State Growth and the response:
“Serious” concerns were raised internally throughout the design and construction for the Bridgewater Bridge, in the years leading up to it opening. These included concerns with modelling of piles, including that McConnell Dowell did not fully understand the ground conditions of the River Derwent where the bridge was built and how this would interact with the piles/affect pile movement.
What is the current status of each of these issues raised? Were these issues addressed in the construction of the bridge? How so?Is State Growth/the project seeing any impacts or potential impacts of these issues now? Please explain.How did State Growth ultimately respond to these concerns when raised, did it act to resolve them and how so? When did it address the issues, if it did (which year/month)?Why did the Independent Verifier and Proof Engineer not pick up these issues?Are there other concerns with the construction and design of the bridge? Please explain.Monitoring devices have been spotted on the bridge piers. Are these at all in relation to the issues noted above? Can you please explain what the intention is for them currently.Looking forwards, how is State Growth and the government working to maintain the bridge, or will there need to be adjustments to the structure or how it is used by the public? Please explain how this might or will look.Derek Pennington says his team was stood down due to an inability to resolve disagreements around the pile design of McConnell Dowell. Why did the state government stand down the TA team? He said his team was not satisfied that McConnell Dowell’s design could achieve the longevity of the bridge and long-term safety required by the contract, and that the concerns were not addressed sufficiently.Did the government ultimately disregard the TA team’s concerns in the interest of avoiding delays or added cost to the project?
Department of State Growth response:
The Bridgewater Bridge is safe.
The design of the structural elements of the new Bridgwater Bridge was undertaken by the contractor and its design engineers, all of whom have extensive experience designing and building bridges.
The structural designs were reviewed and checked by a Proof Engineer and the overall process was reviewed and verified by an Independent Verifier.
These activities were undertaken with the oversight of the Department of State Growth’s project team with support from the Department’s consultant technical advisors. Additional verification was obtained on a range of technical matters from the contractor and its design engineers, the Proof Engineer and the Independent Verifier.
The Proof Engineer and the Independent Verifier all certified the final structural designs as being compliant and fit-for purpose, including the pile designs.
On monitoring devices:
The bridge is safe and it has not experienced any unanticipated movement.
The monitoring devices were installed several years ago as part of the verification process to confirm the bridge piles were performing as expected once they had been constructed.