Frequently asked questions

The following frequently asked questions refer to the measurement of air quality outside the M5 East freeway.

Air quality outside the tunnel

  • Please note, these limits are in fact called goals. This means that Roads and Maritime Services (replacing Roads and Traffic Authority) will endeavour, wherever possible, to keep air pollution levels below the goals, but there may be circumstances where the pollution levels exceed the goals.

    • Nitrogen dioxide - 256 micrograms per cubic metre, 1 hour average figure.
    • PM10 - 50 micrograms per metre cubed, 24 hour average figure. (PM10 is particulate matter up to 10 microns in diameter)
  • There are four main air quality monitoring stations that continuously monitor air.
    • ,
    • Station 3: Cnr Jackson Place and Highcliff Road, Undercliffe (U1).
    • Station 4: Cnr Walker Street and Thompson Street, Turrella (T1).
    • Station 2: Cnr Wavell Parade and David Street, Earlwood (X1).
    • Station 5: Community based monitoring station, Gipps Street Lookout, Bardwell Park (CBMS).
      There is also another station at Finlays Avenue, Earlwood (called T3), which measures aromatic volatile organic compounds, such as benzene, formaldehyde etc. We call these avocs.
    • The air quality stations generally measure:
      • carbon monoxide (CO);
      • nitrogen dioxide (NO2);
      • particulate matter (PM10);
      • wind speed; and
      • wind direction.
    In addition, aromatic volatile organic compounds are measured at Finlays Avenue, Earlwood (T3) and the corner of Walker Street and Thompson Street, Turrella (T1).
  • A range of pollutants is measured. Carbon monoxide, nitrogen dioxide particulate matter and aromatic volatile organic compounds are some of the key pollutants associated with car and truck exhausts. These are measured to ensure that the exhaust stack is functioning correctly so that high concentrations of pollutants do not occur at ground level.

Compliance with the goals for air quality

  • The air quality limits or goals (see question 1) were set by the NSW Minister for Planning, when approval for the project was granted in 1997.
    • If a reading is in excess of the set limit or goal (see question1), an agreed protocol is followed. This determines whether the reading was caused by an influence external to the operation of the exhaust stack, or because of the operation of the exhaust stack.
    • An example of an external influence or extra ordinary event could be a bush fire. In this case it could be expected that levels of particulate matter reach many times more than the set limit of 50 micrograms per cubic metre.
    • The protocol can be viewed by following this link.
  • At the time of setting the Conditions of Approval (which defines the set limits or goals for air quality, see question 1), there was no defined limit for particulate matter PM2.5 (particulate matter with particle sizes of up to 2.5 micro metres in diameter).

Air quality monitoring and results

  • A unit of concentration often used when measuring levels of pollutants in air, water, body fluids, etc. One part per million is one part in 1,000,000.
  • A microgram is equivalent to one millionth of a gram.
    • When data is recorded it sometimes contains readings which are 'incorrect'. This may be because of an instrument failure, or other occurrence such as a bird standing on top of a sensor.
    • All air quality data recorded at all M5 East air quality monitoring stations is validated to check its accuracy. The validation process follows prescribed procedures set out by the National Association of Testing Authorities (NATA).
    • This validation process is aimed at removing data which is perceived to be 'incorrect', leaving only the data which reflects the actual air quality levels in the vicinity of the station.
  • On the M5 East, the data validation is carried out independently by Ecotech, a National Association of Testing Authorities (NATA) accredited organisation.
  • There are a number of causes that would make a reading invalid. These may include an instrument being out of calibration, an instrument failure, a power failure or something interfering with an instrument such as vandalism or a bird standing on a monitor probe.
    • All data captured by the monitoring stations is carried out by Ecotech, a National Association of Testing Authorities (NATA) accredited company.
    • Data validation is carried out in accordance with NATA validation procedures.
    • In addition, an independent 3rd party auditor, Aurecon, audits the data from the community based monitoring station (CBMS) station on a six monthly basis, to provide reassurance that all data is being recorded and reported in accordance with the relevant standards.
  • If you want to find out more about air quality measurement, follow the links provided:

Other air quality monitoring

  • Air quality is measured in the tunnel and in the ventilation stack.
    • The limit or goal (see question 1) for in-tunnel carbon monoxide levels is 87 parts per million averaged over 15 minutes.
    • A reading in excess of this level at any of the in-tunnel monitors triggers an investigation, to check whether any motorist has been exposed to levels in excess of the limits.
  • No there are no limits or goals (see question 1) associated with the in-stack monitoring.
    • The M5 East tunnel's air quality is monitored 24 hours a day by the tunnel operator, Leighton Contractors Pty Limited (LCPL). An automatic ventilation system is used to manage air quality within the set limits or goals (see question 1).
    • However, in the event that air quality levels are approaching the set limits; the tunnel operator has a number of options at his disposal to protect the air quality for tunnel users.
    • These options include turning on additional fans located within the tunnel and exhaust stack and increasing the operating speed of those fans. This acts to provide more clean air to dilute vehicle emissions, thereby reducing pollutant concentration levels in the tunnel.
    • In extreme cases the operator may choose to limit the number of vehicles entering the tunnel, either by closing lanes or decreasing the allowable vehicle speed. This provides a buffer to allow the operator to improve the tunnel air quality for motorists.
  • Fresh air is drawn into the tunnel via an air intake station, in Arncliffe. Fresh air is also drawn into the tunnel at each entry or exit portal, avoiding emissions from the portals.
  • Tunnel air is expelled via a specially designed ventilation stack. This ventilation stack contains eight large axial fans which can blow the tunnel air out of the venitlation stack at a speed of up to 110 km/h.
  • The M5 East has a single ventilation stack.
  • The ventilation stack is located in Henderson Street, Turrella.
  • Ventilation stacks are used because they effectively disperse pollutants over a wide area, reducing the concentration of exhausted pollutants in the air. The tall thin shape of the stacks enable the exhaust air to be propelled high into the air.
  • To conform with the conditions of approval, the design of the tunnel avoids air emissions from the portals by pulling air back into the tunnel. In an incident, air may be expelled from the portals if required, to ensure that in-tunnel air quality levels remain under the set limits.
  • A series of monitoring stations have been set up close to the tunnel portals to measure the effect of any portal emissions.
Share this page: