M5 East outside air quality monitoring

The M5 East Freeway was planned by the NSW Government. It was designed and built by Baulderstone Hornibrook Bilfinger Berger (BHBB). Ventia Pty Limited currently operates and maintains the freeway, on behalf of Roads and Maritime Services. Ventia is responsible for air quality monitoring and provide the data for this website, which is operated by Roads and Maritime Services.

Since opening in December 2001, the M5 East tunnel has been operating within the ambient air quality goals set in the December 1997 Planning Minister's approval for the project.

The M5 East tunnel air quality goals are stringent and are designed to protect public health.

The air quality pages of this website provide both the current and historical air quality monitoring readings and details of the Department of Planning's established goals (or set limits). If you have any questions or would like to report an air quality issue around the M5 East, please email m5eastairquality@rms.nsw.gov.au.

Monitoring stations

To ensure that the air quality goals (or set limits) are satisfied, five air quality monitoring stations have been established in the Wolli Creek Valley to collect important meteorological information and air quality data during operation of the Freeway.

The five monitoring stations providing current air quality data for this website are located at:

  • Station 1 - Finlays Avenue, Earlwood (formerly T3). This site provides limited data only.
  • Station 2 - Cnr of Wavell Parade and David Street, Earlwood (formerly X1)
  • Station 3 - Cnr Jackson Place and Highcliff Road, Undercliffe formerly U1).
  • Station 4 - Cnr Walker Street and Thompson Street, Turrella (formerly T1).
  • Station 5 - Gipps Street Lookout, Bardwell Valley (formerly CBMS).

Stations 2 and 5 were established in November 2001 and their locations were finalised after input from the M5 East Freeway air quality community consultative committee and the CSIRO.

Stations 1, 3 and 4 were established in June 2000 to collect background air quality information before commencement of the Freeway. Monthly summaries of CO, NO2 and PM10 since June 2000 are also available on this site.

Data availability

CO, NO2 and PM10 data for a given hour are available at 30 minutes after the following hour. For example, data for 09:00 to 10:00 is available at 10:30.

24-hour average PM10 data for a given day is available 30 minutes after midnight the next morning. For example, data for 05 July 2001 is available at 00:30 on 06 July 2001.

Wind directions are averaged out (using vector averaging) over a 60 minute period. A wind direction of north (denoted as N in the table) is wind coming from the north and travelling to the south. The wind direction arrow in the map shows the direction the wind is travelling. If the speed is less than 1.5km/h then no wind direction is shown.

OEH air quality data

The Office of Environment and Heritage (OEH, formerly EPA) has an air quality monitoring program that collects accurate real-time measurements of ambient level pollutants at 24 monitoring sites within the air quality monitoring network, located around the greater metropolitan area of Sydney, the Illawarra, the Lower Hunter and selected rural sites around NSW.

If you want to find out more about the OEH air quality measurements, please see the Office of Environment and Heritage (OEH) website.

Tunnel air quality explained

Air quality in the M5 East tunnel is managed by ventilating the tunnel with fresh air. This dilutes the pollutants emitted from vehicles as they travel through the tunnel. Mixing large volumes of fresh air with the vehicle emissions ensures that the concentration of pollutants remain within set limits.

Fresh air is sucked into the tunnel using large fans at an air intake, located in Turrella. Additional fresh air is also drawn into the tunnel at all tunnel entrances and exits by the use of fans, which also move the air along the tunnel at speeds of up to 36 km/h or 10 metres per second.

Monitors in the tunnel measure pollutant levels along the length of the tunnel. Air quality in the tunnel is controlled by adding the right amount of fresh air to dilute the pollutants to the required levels; so high traffic volumes require higher volumes of fresh air.

Once the tunnel air has travelled along the tunnel it is exhausted from the tunnel via a single exhaust stack located in Turrella.  This stack contains eight large axial fans which can blow the tunnel air out of the exhaust stack at speeds of more than 100 km/h. A 35 metre high stack ensures tunnel air is well dispersed. This prevents pollutants from accumulating at ground locations around the stack.

Air quality is measured in the tunnel, in the stack and at ground locations around the stack. Ambient air quality readings for locations around the stack can be read on this website.

Diagram showing how the M5 East tunnels are ventilated with fresh air, as explained in the text.
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