Fremantle Road and Rail Bridge Strengthening
York Civil was awarded the contract for pier strengthening works at Fremantle’s traffic and rail bridges over the Swan River in Western Australia.
The works on the two bridges, which will protect the traffic and rail bridges in case of a collision, are being undertaken concurrently to minimise traffic disruptions and to provide significant cost savings to Main Roads Western Australia.
At the traffic bridge, York Civil will repair 62 piles and reinforce the existing timber fender system with new steel structures. Works at the rail bridge comprise installation of concrete dolphins constructed in-river, which are designed to absorb significant force in the case of impact. Dolphins are marine structures that extend above the water level and are not connected to the shore. An example of a concrete mooring dolphin is included below.
During the project, enhancements will be made to existing navigational aids in the river channel to bring them up to international standards and to improve vessel flow within the channel.
This is a complex project as most of the work will be completed under water from barges. There is also a requirement to maintain road, rail and marine operations at all time, providing another challenge for the project team.
During construction there is a risk of marine mammals moving through the work area, in particular a specific species of dolphin found only in the Swan River. York Civil will work with Curtin University’s monitoring program to access noise produced from work activities and implement guidelines for exclusion zones and start up procedures to ensure minimal impact on the marine wildlife. Personnel will also be trained as “Marine Mammal Observers” and will monitor a localised area of the river.
A ‘soft start procedure’ will be implemented for piling works, in which the rate of blows is slowly increased from nothing to maximum in order to minimise the impact of the noise on marine life.
There is also a possibility that the river bed may contain some level of contamination from former industrial areas. Materials removed from within the driven piles will be transported from site and deposited at a controlled waste facility to prevent ingress into the river system.
The project will utilise a range of marine plant and equipment, including;
- Two crane barges – a spudd barge, which floats on the river surface and is held in place by temporary piles (spudds) and anchors, and a jack up barge, which raises itself above the water on temporary piles
- Two flat bottomed work boats
- Two tug boats – one large and one small to move the barges around
- A carry barge (‘dumb’ barge) – an unpowered barge pushed/pulled by the tug boats and used to transport materials from land to the crane barges
- Two spotter vessels used to control river traffic
The crane barges will be used to complete the works, such as piling, lifting and placement of concrete, and the other vessels will be used to service them.