CHAIR – Ok, thank you. Minister, I want to come to the Tasman Bridge. Why has it taken a decade to respond to the coroner’s recommendations that safety barriers be installed on the Tasman Bridge? We’ve been talking about the the upgrades to the Arthur Highway, but given that it is such a funnel for traffic and a large component of the congestion problem, what is happening with the Tasman Bridge upgrades?
Mr VINCENT – I will hand to Ben Moloney in a moment for some more detail on it, but it’s been an interesting body of work around that, looking at the engineering design of the bridge and the wind stress – I think I’ve got this terminology right – pressures on the bridge which forced the department to have a fresh look at it all. It also highlighted to me the regular maintenance and review of that maintenance of the bridge. There’s been a lot of comments made in the press about the life of the bridge, but the bridge is in good condition and has had work done on it. It highlighted the fact that with modern technology such as vibration sensors and different ways of being able to scope the work now with different electronic or automated devices, it means that we have to build in a lot more maintenance on the bridge going forward to understand the pressures that are on the bridge. We are very close now with the pathway designs and work. I will ask Mr Moloney to clarify a bit of the work around the bridge.
Mr MOLONEY – Thank you, minister. Extensive work has been undertaken over several years. As you mentioned, it has been a project that’s been under consideration for quite a long time. The real impetus for the project came through in terms of a coroner’s report in 2018 and at that time it was recommended that the barrier safety be improved by heightening the barriers in that location.
In order to take into consideration our preferred approach to maximise shared user path capability on the existing bridge, the department went into exploring options by which we could widen the shared user paths in those locations while also improving safety through heightening the barriers in that location. Quite a bit of work was undertaken through that, and unfortunately the outcome of those investigations concluded that it wasn’t appropriate to increase the load on the existing structure. The existing structure is safe and sound for its existing use, but we note that it was built back in the 1960s as a four-lane bridge and then in the 1970s it was actually widened to five lanes in anticipation of needing to meet future traffic demands at that time. That meant that a lot of the spare capacity or you could say the structural capacity of the Tasman Bridge was taken up by that extended use.
It’s quite a tall, lean structure, so that makes it vulnerable or susceptible to wind loads, and a lot of our work in recent times has been better understanding the wind loads that are on the existing bridge, so that when we install the higher barriers we understand what influence that may have on the loading of the existing bridge. Being a tall, lean structure it relies upon its foundation. We’re working basically from the riverbed up and making sure that what modifications we make we understand the changes they have for the loads of the existing structure. We can certainly reassure government and members of the public that the bridge continues to be safe to be used.
We have now developed a preliminary design that we feel is appropriate for that location that will provide modest improvements on the usability of the shared user paths. We are using a mesh that is more open and will allow the wind to blow through easier to reduce loads, and we will be looking to go to the construction industry for a design and construct contract on that project, ideally before Christmas. We’re just working through dotting our Is and crossing our Ts on the documentation at the moment in order to put a package to market.
As to why we’ve gone for a design and construct approach there, we feel that by working collaboratively with industry we will be able to undertake that project in a way that’s constructed to minimise impacts on traffic. One of our real challenges with that project is the fact that we have to undertake the project with minimal impacts on traffic movements, so we’re talking about undertaking works predominantly at night time outside of peak periods. By working collaboratively with the construction industry, we feel we will end up developing a construction methodology that can be safe and efficient for our workers and also minimise the impacts on traffic.
As the minister mentioned, another factor that’s been quite critical in going forward is that simply by heightening the barriers, it changes our approach to how we maintain the existing bridge. The existing bridge for several decades has been maintained by a bridge inspection unit, which hangs off the side of the bridge to which access was gained by going over the old barriers. By heightening the barriers, we’ve had to adapt and change our methodology. People will see over the course of the next few months there will be an under-bridge unit being used on the Tasman Bridge where we will be doing further inspections and works by accessing that from the deck. That’s a bit of a trial to make sure that we’re able to continue to maintain this important structure in the decades into the future.
