Earlier this year, MTAG commissioned Melbourne engineering company, Synergetics, to write an independent scientific report examining if the West Gate Tunnel exhaust stacks represents best practice and whether exhaust filters are necessary to protect community health. The report found that that contrary to previous modelling, the as-built vent stacks will result in a high level of ground contamination that will impact thousands of residents, houses and sports ground close to the stacks.
This is due to several factors – the elongated shape of the stacks, the separation of emissions into five separate stacks instead of passing through one single stack, the architectural façade and an inadequate discharge velocity. In short “the stack design does not correspond with good engineering practice (GEP) guidelines for exhaust design”. The report also identifies that previous modelling and assessments have failed to properly consider the complex geometry and adverse downwash effects of the architectural façade on dispersion of the discharge plume.
These results were reported on by The Age, Channel 9 and The Westsider.
MTAG made an urgent submission to the EPA, along with this report and a new health report that examines the latest medical knowledge on the human health impacts of vehicle pollution. We asked that filtration is made a condition of Transurban’s operating licence, to be fitted as soon as practical.
MTAG were shocked to hear, on 10th November, that the EPA had granted Transurban an operating licence for the West Gate Tunnel ventilation stacks without any need for filtration. The government’s own advice from the committee assessing the stacks in 2017 recommended filtration from day one. Now this new report also recommended filtration due to serious design flaws. The EPA seem determined to ignore expert advice. Melbourne’s west has been the dumping ground for this city’s most toxic industries for decades. This licence application was a chance for the EPA to do the right thing for communities already impacted by air pollution by putting a condition in the licence that filtration must be fitted. The west always feels like second class citizens when it comes to clean air. If the Government and EPA are not putting our health first, then who is? We imagine that there were some very happy faces around the Transurban board table, and perhaps in government too, as they get to save a few million dollars by not filtering the stacks. The amended Victorian Environment Act is designed to move Victoria to a precautionary model, one where pollution is stopped before it becomes a problem. The essence of that Act has been ignored, but is that really surprising when you live in the west?
MTAG is definitely not abandoning our fight to get filters. Our legal team is exploring options for next steps that we can take. Our previous campaigning has shown that persistence, teaming with experts, and collecting data can lead to positive change, but it can be a real slog!
We understand the news of the unfiltered stacks will be alarming for people who live near one of the stacks. One option you could consider is to purchase and install a Purple Air Monitor. These are low cost and reliable air quality sensors. You can check the readings on a real time map and also download data to look at longer term trends. There isn’t much point in having them too close together, so check on the map that there isn’t one near you already. You could also share the purchase cost with your neighbours. Data from these monitors could be really useful down the track for our advocacy work. We also encourage those who think they will be impacted to buy an air purifier for your home.
You can read the report here: Synergetics – Engineering assessment of West Gate Tunnel ventilation stacks
Please note, when reading the report, there are some important things to be aware of:
- The modelling was done for the southern ventilation stack only. The report explains the rationale for choosing this stack and points out that the same conclusions will also apply to the northern stack given their similar design and geometry.
- The most impacted areas are expected to be those to the north and south of the stacks. Residents directly to the east and west are not expected to be as highly impacted.
- The length, width and direction of the down washed plume will be dependent on the direction of the wind at that time. The highest modelled ground level pollution was is expected for wind directions that are oblique to the long axis of the stacks architectural façade.
- The ground level concentration contour maps in the report are modelled on specific wind directions. These wind directions have been chosen for representative purposes only and do not represent the only or prevailing wind directions.