Tunnel ventilation and air quality – West Gate Tunnel Project

The West Gate Tunnel Project ventilation system design will be best practice and operate within stringent air quality standards to protect the health of communities and drivers using the tunnels.

Road tunnels can help reduce air pollution by moving traffic off roads where people live and work, putting vehicles underground. In a tunnel, vehicle emissions can be controlled and dispersed more effectively and are monitored to ensure standards are met.

With thousands of tunnels in the world, there are well-established and effective ways to design tunnels and ventilation systems so that there are no negative effects on local or regional air quality.

West Gate Tunnel ventilation system

The ventilation system for the West Gate Tunnel Project will include two ventilation structures – one above the northern tunnel portal near the Maribyrnong River and the other above the southern (outbound) tunnel portal in the West Gate Freeway.

Studies show that ventilation structures operate most efficiently when located close to the tunnel exit. The West Gate Tunnel’s ventilation system has been designed to:

meet Victoria’s stringent air quality requirements – which are among the highest standards in the world
ensure high air quality inside the tunnel
manage emissions from current and future traffic volumes.

Artist impression of Northern tunnel portal, Footscray

Northern tunnel portal, Footscray. Artist impression only – does not include detailed design

How tunnel ventilation works

Tunnel ventilation systems are designed to maintain safe air quality both inside and outside the tunnel to meet stringent air quality standards.

Infographic explaining how air is circulated through the tunnel via ventilation structures.

Ventilation systems work by drawing in fresh air from the tunnel entry, which is then pushed through the tunnel by the movement of vehicles and jet fans.

Before the tunnel exit, air is pushed up and out of the tunnel through a ventilation structure and into the atmosphere where it mixes with fresh air. There are no emissions from the tunnel portals where vehicles enter and exit.

Research from around the world clearly shows emissions from well-designed tunnel ventilation systems have no measurable effect on local or regional air quality

Ventilation system design

An internationally recognised air dispersion model is used to assess the design and height of ventilation structures in achieving effective and safe dispersion. The model takes into account existing air quality, local weather and topography and conservative assumptions about vehicle emissions and types.

This modelling is based on worst case scenarios to ensure the ventilation system is effective in even the most unlikely circumstances, such as continuously congested traffic and no future improvements in vehicle standards.

Monitoring and reporting

We are monitoring air quality to help us understand current local conditions. This will help us to measure any changes to local air quality once the West Gate Tunnel Project opens.

When the project opens, we will continue monitoring air quality for up to 5 years. We will also do in-tunnel air quality monitoring to confirm that the ventilation system is operating as it should.

We monitor air quality at 6 stations in Melbourne’s inner west, shown in the map below. Data available includes PM₁₀ and PM_2.5 at all stations, with additional parameters measured at the Primula Avenue station in Brooklyn. The station on Millers Road, Brooklyn, was established in October 2018 in consultation with the Victorian Environment Protection Authority (EPA).

Air quality near the West Gate Tunnel Project area is influenced by a number of factors including weather conditions and emissions from local industry, vehicles and domestic fuel burning.

EPA monitors air quality of the broader region through a monitoring network including stations at Footscray and Brooklyn. These stations are separate from the West Gate Tunnel Project’s monitoring network.

Visit EPA AirWatch to find results from EPA’s Footscray and Brooklyn stations, as well as information about how Melbourne’s air quality complies with State Environment Protection Policy (SEPP – Ambient Air Quality).