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Metro Tunnel

EES assessment of air quality impacts

Construction of the Metro Tunnel may cause some temporary, localised impacts to air quality commonly associated with construction works and the removal, storage and transport of excavated material.

The project's Environment Effects Statement (EES) assessed the air emissions expected to be generated during construction and operation of the Metro Tunnel.

It also assesses air quality and the potential impact of changes in air quality on health and amenity, and outlines recommended Environmental Performance Requirements that set out mitigation measures to manage these impacts.

What we heard

Key feedback relating to air quality and greenhouse gas emissions included:

  • Concerns about air quality impacts from trucks and other construction vehicles
  • Requests to minimise dust generated from excavation activities.

Existing conditions

Measuring existing air quality near the proposed Metro Tunnel alignment was an important part of the EES assessment.

Data sources used in the air quality assessment included:

  • Air quality data from monitoring sites administered by Environment Protection Authority Victoria (EPA Victoria).
  • EPA Victoria's annual air quality reports, which test compliance with National Environmental Protection (Ambient Air Quality) Measure.
  • Meteorological data (including wind speeds and directions) from Bureau of Meteorology monitoring sites.

The assessment found that existing air quality within the proposed project boundary is good to fair.

Understanding potential changes in air quality

Potential air quality changes for each project precinct were assessed based on the proposed construction methodology and the expected volume of excavated material handled.

Dust is anticipated to be the main cause of changes in local air quality during the construction of the Metro Tunnel, particularly in areas close to construction work sites, where there will be a higher number of truck movements and dust generating activities.

Construction activities likely to generate dust include site preparation and ground level construction works, wheel-generated dust from construction vehicles and equipment, wind-generated dust from exposed surfaces, construction activities at the proposed tunnel boring machine (TBM) launch sites, and emissions from the on-site concrete batching plant (proposed to be located in the main construction site at Arden).

Due to the soil volume generated and construction activity at the tunnel boring machine (TBM) launch sites there is potential for some temporary exceedances of PM10 in the vicinity of Arden and Domain precincts. No exceedances of PM2.5 are expected.

As is typical on large construction projects in urban areas, it is expected that some contaminated soil, rock and sediment will be encountered during construction of the Metro Tunnel. The removal, storage and transport of contaminated soil could result in short term emissions of dust, vapours or odour. 

The project's EES includes Environmental Performance Requirements to manage the handling and disposal of any encountered contaminated soil, rock and sediment. Further planning work will investigate potential sites that may be contaminated prior to construction commencing.

As the Metro Tunnel will operate electric trains, air emissions associated with routine train operations will be minor.

Managing Air Quality

A number of mitigation measures have been identified in the project's Environment Effects Statement (EES) to avoid, reduce or offset environmental impacts. These measures form the basis of the recommended Environmental Performance Requirements for the Metro Tunnel and have been recommended by specialists through the EES process.

Some of the recommended Environmental Performance Requirements to manage air quality include:

  • Developing and implementing a dust management and monitoring plan, in consultation with EPA Victoria, to minimise and monitor the impact of construction dust.
  • Managing construction activities in accordance with EPA Victoria's Environmental Guidelines for Major Construction Sites.
  • With appropriate dust management measures, construction activities are unlikely to result in exceedances of air quality criteria.

Examples of measures that may be used to manage air quality include:

  • using construction enclosures with concrete floors and truck wheel washers, wind breaks and water sprays on stockpiles and exposed surfaces, dust suppression on unsealed roads within construction sites, water trucks, minimising double-handling of material, re-vegetating areas of disturbed soil as soon as possible and modifying activities according to weather conditions
  • using temporary ventilation shafts fitted with extraction and filtration systems to remove dust in the tunnels during construction
  • producing tailored air quality management plans for each project precinct that will respond to daily weather conditions and consider proximity to sensitive sites such as hospital and education facilities, open space and high density residential and business areas
  • regularly collecting air quality data and undertaking monitoring of local precincts.


Particulate matter

A complex mixture of particles suspended in the air. Matter may consist of a range of particle compositions that can be Classified by their size, being less than 10 microns in diameter (PM10) or less than 2.5 microns (PM2.5). Particles less than 10 microns can be harmful to human health whereas particles larger than 10 microns are more often associated with nuisance dust.

Nuisance dust emissions from construction activities typically range in size up to approximately 50 microns in diameter. They are less Harmful to human health, but can dirty surfaces such as cars, window ledges and household washing.