Managing air quality
In delivering the Metro Tunnel project, we want to minimise the inconvenience and impacts of construction on local communities and the environment.
Understanding potential changes in air quality
As part of the Metro Tunnel Environment Effects Statement (EES), 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 delivery of the Metro Tunnel project, particularly in areas close to construction work sites where there would be a higher number of truck movements and dust generating activities.
Activities likely to generate dust include site preparation and ground level construction works, wheel-generated dust from construction vehicles and equipment and wind-generated dust from exposed surfaces.
In addition, it is not uncommon to encounter contaminated soil, rock and sediment on large construction projects in urban areas, and it is expected that some of this material will be encountered during construction of the Metro Tunnel project.
The removal, storage and transport of contaminated soil could result in short–term, localised emissions of dust, vapours or odour. Further planning work will investigate potential sites that may be contaminated prior to construction commencing to ensure mitigation measures are in place.
Managing air quality
A number of mitigation measures were identified in the EES to avoid, reduce or offset environmental impacts. These measures form the basis of the recommended Environmental Performance Requirements (EPRs) for the Metro Tunnel project and have been recommended by specialists through the EES process.
The EPRs define the outcomes that must be achieved during the design, construction and operational phases of the project. This approach is designed to ensure the project delivers a net benefit to the community, and in the process, encourages innovation and flexibility from the construction contractor in how they meet these requirements.
Measures for managing air quality include
- Minimising dust creation.
- Installing construction enclosures with concrete floors and truck wheel washers, and hoarding to minimise dust movement.
- Monitoring the weather conditions and adjusting the work program as required to respond to dry or windy conditions.
- Installing rumble grids at entry points to the work site to prevent the transfer of dirt and mud onto public roads, and street-sweeping where required to keep the roads clean.
- Conducting inspections and audits of dust management and air quality measures in line with the air quality EPRs.
With appropriate dust management measures in place, it is unlikely that construction activities will result in exceedances of air quality criteria.
Minimising dust creation
Minimising dust creation is one of the measures used to manage air quality. Examples of ways to minimise dust creation include:
- Using water trucks to spray down exposed areas or surfaces.
- Sealing and/or re-vegetating disturbed areas as soon as possible after completion of each stage of construction works.
- Planning haulage routes on sealed surfaces and using dust suppression on unsealed roads within construction sites.
- Covering loads on public roads.
- Using wind breaks.
- Minimising double-handling of materials.
- Seeding, stabilising, covering or containing stockpiles where necessary.
- Collecting air quality data and monitoring.