Two years into the construction of Melbourne’s West Gate Bridge the unthinkable happened.
On 15 October 1970, the 112-metre span between piers 10 and 11 collapsed, killing 35 construction workers. A Royal Commission found the structural design and unusual method of construction to be the causes.
The construction and completion of the bridge eventually resumed, but the tragedy of the West Gate Bridge collapse had a lasting impact on Victoria.
Even 30 years after the accident there was hesitation to undertake another ambitious project of that calibre. Michael Kalinowski recalls this cautiousness as one of the major hurdles that had to be overcame in the construction of Melbourne’s iconic Bolte Bridge – one of the largest, balanced-cantilever, cast in-situ, box girder bridges in the country.
“It was different to anything done before,” says Mr. Kalinowski, who was the Project Manager. “It was also the first major bridge that was built since the West Gate was completed.”
The bridge was designed by Hyder/MBK and architects Denton Corker Marshall and built for head contractor Transurban by Baulderstone Hornibrook (now a part of Lendlease’s business).
Mr. Kalinowski explains that Baulderstone Hornibrook undertook the majority of the works on the bridge themselves, with minimal use of subcontractors.
“CityLink was probably the first ‘mega’ project in Australia. The market didn’t do projects of this magnitude,” he adds. “It was a very big effort at the time.”
The design heralded some major challenges. The proposed 490-metre-long, twin structure would span the Yarra River and Victoria Harbour in the Docklands precinct, and form part of the CityLink toll road system connecting the Tullamarine Freeway in the north to the Monash Freeway in the south east.
The structure would be built as two independent bridges, capable of accommodating six lanes of traffic (three inbound, three outbound).
Because it was such an ambitious design, with some unique challenges, there was, understandably, some hesitancy from the Victorian Government.
“It took us a long time to convince the authorities our design was the right, and safest, design,” he adds.
The project team overcome these hurdles and the project was given the green-light. Construction began in 1996.
Mr. Kalinowski says one of the earliest stages proved to be one of the biggest challenges.
The project team built an island in the middle of the Yarra River using a bottom dump barge. This was to act as a base for the construction of the central section of the bridge. “That was tough because we had to build in the middle of a live, navigable channel,” says Mr. Kalinowski. “We had to keep the route clear so ships could use it too.”
A cofferdam was built in the centre of the channel so the steel piles could be driven into the riverbed, which in itself was considered different at the time.
Mr. Kalinowski says steel piles were used as they could handle the weight better than concrete over time. This was tested on-site to not only make sure the bridge could handle the weight but to make sure the crew could drive the piles deep enough. “We had to work out how to test the piles and we basically built a makeshift drop hammer out of sheet billet,” he says.
“While we were building the cofferdam, we built the pilecaps and piers on shores and we started balanced cantilever construction on the northern side.”
Travellers were used to construct the bridge on the northern and southern sides and finally through to the central island.
The iconic twin ‘Gateway Towers’ were the final stage in the process.
Due to the extreme windload and susceptibility to twisting and turning, a ball-type segment was installed into the tops of the towers. Mr. Kalinowski explains that, as the towers would turn with the wind, the ball on top would counterbalance the wind, keeping the towers stable.
The ambitious bridge design and construction methodology proved a success and by August 1999, the Bolte Bridge – named for former Victorian Premier Sir Henry Bolte – was open to the public.
Looking back, Mr. Kalinowski says the construction of the Bolte Bridge was full of challenges, but seeing the structure become such an iconic part of the city has been a huge reward.
“It’s great to see our collective efforts turn into something that’s been embraced by the public.”