By Martin Wurt
Nearly a decade has passed since the announcement of the West Gate Tunnel Project, and the Maribyrnong Truck Action Group (MTAG) has continually asked one question: What would it actually cost to install filtration on the tunnel’s two ventilation stacks?
At the 2017 media launch held by the Maribyrnong River, then Premier Daniel Andrews invited MTAG to attend. We asked Premier Andrews directly about filtration and he replied, “The cost of it will be a drop in the ocean of the overall cost.” His response gave us hope that filtration would be included.
In 2018, we followed up by writing to Luke Donnellan, the then Roads Minister. He quoted a trial filtration system on Sydney’s M5 tunnel, estimating that filtration would cost $60 million to install, with $835,000 in annual operational costs. It’s worth noting that the Sydney trial was poorly executed, it was an afterthought plagued with design flaws but more on that later.
By 2024, frustrated by the lack of transparency on costs, MTAG lodged a Freedom of Information (FOI) request to uncover the true cost of filtration. Unfortunately, the documents provided were heavily redacted under the guise of “commercial sensitivities.” We were no closer to knowing the actual figure.
Now in 2025, we continue to hear wildly different estimates. A politician recently revealed to us they were told that the price tag could be close to $300 million. The whispers continue but the government maintains silence on the true costings. Their narrative has now shifted instead to suggest that filtration is “energy intensive” and “in its infancy.” Interestingly, these concerns about energy consumption were not raised in the context of tunnelling or the substantial concrete requirements for the build that were extremely energy intensive.
In our quest to get real world costings, MTAG reached out to one of the world’s leading filtration companies based in Europe. With more than 40 years of experience in tunnel filtration technology, this company is hardly part of an industry in its infancy. No one describes an iPhone as being in its infancy and they have been around for less time than the first tunnel filters installed in Europe in the 1990s.
The company requested anonymity, but have freely shared information with us. They estimate that each filtration unit would cost between $4 million and $6 million. The West Gate Tunnel’s two stacks would each require one unit. Using their upper most estimate, that’s $12 million for the two filtration units.
This figure covers supply only and not installation. However, the government publicly committed to designing the stacks for future retrofitting, meaning installation should be relatively straightforward, without requiring significant structural alterations. Had filtration been incorporated during initial construction of the West Gate Tunnel, the costs would have been very minimal.
This is where comparisons to Sydney’s M5 tunnel become misleading. The M5 wasn’t designed for filtration, so additional tunnelling had to be carried out after construction. The actual filtration units were installed far from the ideal location, driving up both installation and running costs.
Our European contact said: “…The numbers quoted by the government are exaggerated. They include unique costs from the Sydney project that includes extra project management, first-time design reviews, and the need to install filtration remotely due to space limitations. These are not typical in properly planned installations.”
When it comes to operational expenses, the government has emphasised that the energy demand of running filtration is massive. We queried this with our European experts, and their response was clear: “In general, operational costs are small. Particle filtration systems use electrostatic precipitators, which require high voltage (kilovolts) but very low current (milliamps), resulting in low energy consumption.” In short, the “energy intensive” argument doesn’t hold up under scrutiny.
What’s never part of the public discourse though, is the cost of inaction. What does it cost us, in health terms, to do nothing?
AUSTROADS, the peak body representing transport agencies across Australia and New Zealand, published a report in 2021 called – Options for Managing the Impacts of Aged Heavy Vehicles. It highlights that Australia has the second-oldest truck fleet in the OECD, and estimates the annual health cost of emissions from old trucks at $200 million. Today that’s about $233 million with inflation and CPI.
We have long known that the Port of Melbourne, Australia’s largest container port, relies almost entirely on trucks. It is also a magnet for old trucks doing short runs between the port and container yards in Melbourne’s west. These trucks will be a majority of the expected 8 million trucks per year using the tunnel.
The proportion is probably a lot higher, but if we conservatively assume that just 10% of the national health cost figure is born by communities around the tunnel’s two ventilation stacks, the cost of filtration would be recouped in less than ten years – and probably a lot sooner – by avoiding pollution-related diseases. The savings from filtration, both financial and human, are huge.
The City of Maribyrnong has some of Australia’s highest rates of asthma, stroke, and heart disease. These are all illnesses strongly correlated with air pollution. Failing to install filtration here isn’t just a health issue, it’s a classic case of environmental injustice.
So, who should pay? According to one politician, “It wouldn’t be us, it would be Transurban.” That view is supported by the Victorian Environment Protection Act 2021, which enshrines the “polluter pays” principle. It states: “Persons who generate pollution and waste should bear the cost of containment, avoidance, and abatement.”
This clearly places the onus on Transurban, the tunnel builder and operator, to fund the filtration systems. And Transurban can afford it. As part of the West Gate Tunnel Project deal, the company secured a 10-year extension to its CityLink tolling contract. According to the Victorian Parliamentary Budget Office, this extension will bring Transurban $37.2 billion in toll revenue by 2045.
Transurban’s own Health, Safety & Environment Policy claims they: “Proactively manage our environmental risks to maintain and enhance the environments in which we operate.” Here is their opportunity to make good on that policy.
So, what conclusion can we draw from this? One theory is that installing filtration here could set a precedent for all Transurban’s infrastructure projects both in Australia, the USA and Canada where they build and manage toll roads. It’s important to remember that it was the Victorian Government that gave Transurban its start in the 1990s with the CityLink toll road. That close relationship may explain why public discussion around filtration has been so muted.
To put this all in perspective: the West Gate Tunnel Project has ballooned to $12 billion. Even if the final cost for filtration was around $100 million, this cost would be just 0.83% of the total project cost, less than one percent. It’s a rounding error. A true drop in the ocean!
So, if cost isn’t the barrier, then what is?
