The West Gate Tunnel Project (WGTP) is an enormous city-shaping project that will transform the way Victorians travel and make Melbourne’s inner west an even better place to live by taking trucks off residential streets. Here’s the latest update on the construction and tunnel boring works, and a look at what’s currently happening under our feet for a project of this scale.
Victoria’s population is growing rapidly and the state needs more viable transport options. The West Gate Tunnel Project will deliver a vital alternative to the West Gate Bridge, create better connections to major Melbourne roads and freeways, and reduce travel time from the west to the city by up to 20 minutes.
Construction is well underway with state-of-the-art technology being used to build twin tunnels, a new bridge over the Maribyrnong River and additional lanes on the West Gate Freeway.
Tunnel Boring Machines journey to northern portal site
Two massive tunnel boring machines (TBMs), Bella and Vida, will dig the 4km and 2.8km tunnels. The two TBMs were built in Germany before being assembled and tested in China. Due to their enormous size, they were disassembled into smaller parts before being shipped to Melbourne.
TBM Bella arrived at the Port of Melbourne earlier this year before being trucked to the northern portal site in Yarraville, Melbourne. It took nearly 100 truckloads to deliver all of Bella’s components and supporting equipment to site.
The heaviest TBM piece was the main drive (TBM motor), weighing 307 tonnes and measuring 10m long and 8.4m wide. Due to the weight and size, a major bridge was closed to other traffic while the delivery travelled over the Maribyrnong River.
It took three weeks to deliver all of Bella’s parts to the northern portal site. The same operation was then repeated for the second TBM, Vida.
How the project’s TBMs work
The West Gate Tunnel Project’s TBMs are the largest in the southern hemisphere, standing at 15.6m in diameter, 90m in length and weighing around 4,000 tonnes each.
The TBMs will bore up to around 40m under the ground at the deepest point (the bottom of the tunnel), while also installing a concrete lining, forming the walls, roof and base of the tunnel. TBMs Bella and Vida will excavate rock and soil with a rotating cutterhead before moving forward to make space for the concrete lining. It then stops moving and installs the lining using a specialised rotating machine.
TBMs of this size need ten megawatts of power per machine. A new substation has been built on site at the northern portal to ensure enough power is supplied to keep the machines moving 24 hours per day, seven days a week.
Highly specialised crews operate the TBMs. Behind the TBM, crews work to build the road surface and install electrics, ventilation and safety systems.
The conveyor system
Soil and rock excavated by the TBMs will travel along the conveyor belt system which loops from the TBMs across a road and into the big shed before being placed into two huge spoil bins and then transferred to treatment facilities. At its longest, the conveyor belt system will be a 15km loop.
The conveyor belt system is controlled from the TBM control room located near the head drive of the tunnel conveyors. It will be monitored via CCTV cameras and ensure that at each of the transfer belts, there are no issues. Additional monitoring will also ensure that the system is not being used above intended capacity.
The conveyor can move at 12.6km per hour and is designed to carry a maximum of 2,500 tonnes per hour.
Two people will operate the conveyor from inside the TBM cabin for the tunnel section of the conveyor, with an additional two to three people overseeing the maintenance for the rest of the conveyor alignment.
More than 1.5 million cubic metres of dirt and soil will be generated from tunnelling. The conveyor belt will launch when TBM Bella starts tunnelling.
Construction underway
Construction on the West Gate Tunnel is well underway with several major project milestones completed earlier this year.
New electricity monopoles were installed in sections along the West Gate Freeway, replacing two of the lattice towers. These new monopoles take up less space, allowing an additional four new through lanes to be built along the West Gate Freeway.
To get ready for Bella and Vida, a big shed has been built to store excavated material and the TBM launch site has been completed. In the coming months, Bella and Vida will start tunnelling and move from the northern portal site in Footscray and start tunnelling south west towards the West Gate Freeway.
Further east of the project, more activity has commenced around Footscray Road as piling rigs build the elevated road that will connect the tunnel to CityLink and the city. Piling has started in the Maribyrnong River area to get ready to start building the new bridge over the Maribyrnong River.
Building more than a tunnel
In addition to building the twin tunnels and bridge over the Maribyrnong River, the WGTP will create nearly nine hectares of new parks and wetlands, spanning across Maribyrnong and Hobsons Bay suburbs.
These new open spaces will improve local parks with more than 17,000 trees and tens of thousands of native and indigenous shrubs and grasses planted across the project alignment.
Sections of the Maribyrnong River, Kororoit, Stony and Moonee Ponds Creeks will also be upgraded with the planting of native shrubs and grasses. The WGTP is working with local groups to preserve and enhance these waterway environments. Additionally, the new wetlands in Yarraville will be used to treat stormwater and rehabilitate creek banks.
Over 14km of cycling and pedestrian paths will be upgraded or built, creating better connections to popular trails across Melbourne’s inner west. A new 2.5km veloway along Footscray Road will create an express journey for cyclists to and from the city, completely separated from traffic with two emergency exits.
Overcoming challenges
A project of this enormity is a significant challenge. There are multiple stakeholders involved and many considerations to keep in mind.
The project aims to minimise the amount of traffic disruptions by organising traffic works to happen at night and provide clearly signposted detours where required. Additionally, the project works with other road and public transport authorities, Bicycle Network Victoria and other key stakeholders to implement traffic changes.
The West Gate Tunnel is due to be completed in 2022.
