Bridgewater: Australia’s oldest lift span bridge refurbished
The federal-government-funded $8m upgrade of Australia's oldest surviving lift span bridge, the Bridgewater Bridge, is now in the final stages. The refurbishment is designed to give the heritage-listed bridge a further 15 years' life, by which time a replacement bridge should be in place.
By Rosemary Ann Ogilvie
The bridge has a long history, dating back to the 1830s when the causeway was constructed: this was the largest civil work undertaken by convict labour. The welded-steel structure was added in 1942, opening to traffic in 1946. Significant strengthening work has occurred during its life.
Despite being heritage listed, there were no heritage issues to deal with in carrying out the Midland Highway Bridgewater Bridge Refurbishment, as the project is officially called. "The scope of work was assessed as not affecting the bridge’s heritage features," says Raouf Mina, national mechanical manager, McConnell Dowell Corporation Limited (MacDow).
So this at least was one challenge they did not have to contend with. There were plenty of others, as the standard set of problems associated with undertaking complex works on a major arterial road – the bridge provides the main access to Hobart from the Midland Highway and is also the gateway to the west coast – were compounded by high winds, cold weather, and working over water.
Restoring the lift span
Detailed planning of the work associated with each component of the project, and a close working relationship with the client, DIER (Department of Infrastructure, Energy and Resources), were key to dealing with these challenges, says Mina.
The year-long project, managed by John Christara, involved refurbishing the structural support and electrical systems; repainting the under-structure of the bridge; and refurbishing the mechanical systems used to open and close the bridge. The lift span, which provides navigational access to the upper reaches of the Derwent River, has been out of action since October 2006, when deterioration of the counterweight cables used to raise and lower the bridge was identified.
These old cables have been replaced with new 5cm-diameter steel cables manufactured in Victoria by Bullivants. "They took nine months to fabricate. However, they will last the life of the bridge," says Mina.
Additionally, the mechanical and electrical aspects of the motors, drives and all the control systems were upgraded, as much of the technology dated from the 1940s. Bromar Electrical Services handled the electrical work, while Saunders & Ward Pty Ltd was responsible for the mechanical work, as well as much of the fabrication work.
The massive concrete counter weights also had to be upgraded to ensure their integrity. "The concrete is very old, so there were some minor cracks that had to be repaired," says Mina. Repairs to concrete on the piers supporting each of the approach spans was also necessary, a procedure that involved working around the tides. MCM Commercial Concrete Services undertook this work.
"The other substantial aspect was repainting the underside of the bridge," says Mina. Existing lead paint had to be removed – an environmentally difficult task requiring full encapsulation to catch all the waste.
"Instant Scaffolds installed scaffolding underneath the bridge, so that was quite an interesting exercise. The beams themselves are fairly deep, so in order to get to all parts of the bridge, we put in a deck that was approximately 700mm to 800mm below the bottom of the beams. It was pretty tight, but we were fortunate in having a good subcontractor – McElligotts – on the job, and the performance of the workforce has been very good."
The crew of 40 to 50 working on the project are all locals, with only the supervisors and managers coming from the mainland.
Traffic management has been difficult, although Mina pays high tribute to DIER for the way they've handled this aspect. "They have been absolutely magic, their cooperation was phenomenal, and paramount to getting the work done. We couldn’t have managed without them."
One lane of the bridge is closed during the day, which inevitably results in delays. A considerable amount of work has been carried out at night, with the bridge closed completely between 7pm and 6am. "I think we upset a lot of local people with that," Mina admits. "You can advertise the closures as much as you like, but people will still be upset. How have we handled this? With considerable tender loving care!"
Further night closures will occur before the refurbishment is complete. "We need to do more work on the counter weights, and the only way we can do this is to bring them down," says Mina. "We can't compromise here because of the dangers of doing this with the high winds."
The risks associated with the work made safety a top priority. "Things are very tightly maintained and monitored, with a fulltime safety coordinator onsite." As a result, only a couple of minor incidents have occurred.
"Safety is one of our core values as a company," Mina adds. "The MacDow safety system is about taking a proactive rather than a reactive approach. As well as doing all the required recording of lost time injuries and so on, we try to go to the next step by encouraging people to think outside the box, to look out for their own safety, and their mates' safety. It’s a cultural thing, and a project of this length gives us the opportunity to develop the culture, to work on the people's culture, to produce the safety standards. It's something you can't do on a six-week job."
A piece of art
Mina has found this project to be particularly interesting, with the only real downside being the cold weather – something the Cairo-born civil engineer doesn't relish! "Actually, one of the biggest challenges we've had to deal with is the wind-chill factor on the elevated parts of the bridge," he comments. "Tasmanians are made of much stronger character than Victorians!"
He considers the Bridgewater Bridge quite beautiful, a piece of art for the era. "It's really a pleasure to see something like this, a bridge built when a lot of our boys were at war, which meant the older generation constructed it at a time when there were restricted materials and skills. It’s nice to see it still in operation, still carrying trucks and trains, 68 years later."