$786M Bridgewater Bridge Under Scrutiny After Pier Cracking Discovery

A large crack was discovered in a concrete support on Tasmania’s new Bridgewater Bridge only days before the $786 million crossing opened to traffic, documents obtained under Right to Information laws have revealed.

The defect was found on May 27, 2025, in the plinth at the top of Pier 1. The plinth is a concrete pedestal connected to a shear key, a structural component that helps control movement in the bridge deck. The new crossing officially opened on June 1, 2025.

Tasmania’s Department of State Growth said the bridge was independently certified as safe before opening and maintained that the cracking never posed a danger to motorists or the wider public. However, the discovery led to immediate strengthening work and further engineering changes in the months that followed.

What caused the Bridgewater Bridge crack?

Project documents indicate that the cracking was connected to inaccurate calculations of the loads acting on the bridge’s two southern piers. The original engineering model had not fully accounted for the effect of reclaimed land at the southern end of the structure.

When engineers reassessed the design, they found the forces on the piers were significantly greater than previously estimated. In some cases, the revised loads were calculated to be as much as double the original figures.

The documents suggest that the shear force at Pier 1 exceeded the serviceability limit of the plinth, resulting in cracking through the concrete and grout. A serviceability limit is used to ensure that a structure remains functional and durable during normal use, even when it is not at risk of collapse.

McConnell Dowell, the company contracted to design and construct the bridge, investigated the defect after the opening. Strengthened designs were later developed and received approval in principle in October 2025. The contractor declined to comment when questioned about the issue by ABC News.

Why the bridge was allowed to open

Some strengthening was completed before traffic was permitted onto the 1.28-kilometre bridge. The independent verifier required parts of that work before issuing the certification needed for the official opening.

The Department of State Growth said the shear key continued to work as intended under ordinary operating conditions. According to the department, the additional measures were precautionary and designed to improve the bridge’s performance over its expected working life.

Further analysis after the opening identified a need for greater resilience under extreme loading scenarios, including major earthquakes, floods and ship impacts. The department said these upgrades were separate from the bridge’s day-to-day operational safety.

This distinction is important. A defect can require correction under a construction contract without automatically making a bridge unsafe for normal traffic. The term “non-minor defect” was described by the department as a contractual classification rather than a warning that the structure was at risk of failure.

Calls for greater transparency

The release of the documents has renewed questions about how the defect was communicated. The Tasmanian Greens said the government should provide a complete account of when the cracking was detected, what engineering changes were required and how the opening decision was reached.

Greens leader Rosalie Woodruff argued that the scale and public cost of the project made transparency especially important. The bridge was jointly funded by the Tasmanian and Australian governments and is described as Tasmania’s largest transport infrastructure project.

The crossing forms part of the Midland Highway and spans the River Derwent north of Hobart. It replaced the ageing former Bridgewater Bridge and carries an important mix of commuter, freight and regional traffic.

The cracking was not the first construction problem linked to the project. In October 2024, work was undertaken to correct the alignment of several bridge sections before the structure opened.

While the department says the new bridge has remained safe throughout, the episode shows why independent inspections and accurate load modelling are essential on major public works. It also highlights the difference between certifying a structure for everyday traffic and strengthening it against rare but severe events.

Further developments involving transport projects and public infrastructure can be followed through the site’s latest Australian news and updates.

Full details of the disclosed documents, engineering findings and the department’s response are available in the ABC News investigation into the Bridgewater Bridge cracking.