Air quality

Air quality refers to the degree to which the air is suitable or clean enough for humans or the environment.

Impacts to air quality may arise during the construction and operation phases of the T2D Project which have the potential to negatively affect air quality if suitable mitigation measures are not implemented. Air quality impacts generally arise from the emission of air pollutants from machinery, excavations or other construction processes into the atmosphere.

During construction, a common impact to air quality (if unmitigated) is the dust generated through clearing of sites, during excavation activities or through the management of spoil. This dust consists of what is known as particulate matter (PM).

During the operation phase, fuel combustion arising from vehicles using the road can result in increased or new emissions of key pollutants which include nitrogen dioxide (NO₂), and PM₁₀ and PM_2.5.

Measures to mitigate impacts to air quality will be implemented during construction. The project will be designed to ensure minimal negative impacts to air quality once operational.

Summary
Download a summary of the Air Quality impact assessment in PDF format

Approach

The assessment of air quality impacts from the T2D Project was based on technical investigations undertaken across a number of years and as the project design evolved. For more information visit About the design.

The following processes were followed to gain an understanding of the likely level of air quality impacts from the project:

identification of the key policy, guidelines and legislation which are relevant to the assessment of air quality impacts from the project.
identification of air quality sensitive receptors in the vicinity of the project
characterisation of existing air quality
identification of potential air quality sources associated with the project.

Once the existing air quality, sensitive receptors and potential future sources of air quality impacts were confirmed, the potential for impacts occurring during both construction and operation of the project was assessed. The technical investigations that specifically relate to air quality from the project that were considered by the Department include:

assessment of the predicted air quality within the tunnels
assessment of predicted external/ambient air air quality.

Artist's impression of the Northern Tunnels Northern Portals from ground level.
Photo: Northern Tunnels, northern portal.

Assessment area

The air quality impact assessment area extends for the entire length of the project corridor including a 1km buffer on either side of the T2D Project as outlined in the map below:

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Map: Air quality assessment area.
Map disclaimer

Existing environment

The level of impact experienced from air emissions can be influenced by a number of aspects including:

the presence of sensitive receptors
local meteorology and climate
ambient air quality.

Sensitive receptors

Sensitive receptors are places or areas which are vulnerable to air quality impacts such as hospitals, schools, parks, reserves or households. The project is located in an urban environment with air quality sensitive receptors in proximity to the portals of the Northern Tunnels and Southern Tunnels, the surface road connecting these tunnels and the existing South Road. The identified sensitive receptors include residences, schools, kindergartens, aged care facilities, hospitals, childcare centres and places of worship.

The following map shows key identified sensitive receptors, the air quality impact assessment area:

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Map: Key air quality sensitive receptors.
Map disclaimer

Climate and meteorology

Weather-related conditions are important for determining the direction and rate at which emissions from a source would disperse. The key meteorological requirements relevant to air quality are typically hourly averaged records of wind speed, wind direction, temperature and cloud cover. The prevailing wind conditions in the area are considered strong (>5m/s) from the southwest and light (<1m/s) from the northeast. Higher wind speeds (>5m/s) typically result in lower concentrations of air quality pollutants.

Ambient air quality

The current local ambient air quality surrounding the project is important to consider when assessing cumulative (project plus background) air quality impacts. This includes ambient concentrations of NO₂, PM₁₀ and PM_2.5. A review of the current ambient air pollutant concentrations found that concentrations of NO₂ and PM_2.5 were satisfactory and under the relevant limits outlined in the South Australian Environment Protection (Air Quality) Policy and the National Environment Protection (Ambient Air Quality) Measure (NEPM AAQ) for the assessed period.

Concentrations of PM₁₀on occasions exceeded the relevant limits for the assessed period, with only occasional exceedances of the short-term limit. This is a common occurrence across the nation in similar locations (i.e. urban areas) with exceedances often related to windblown dust, bushfires and other significant dust generating events.

The Queen of Angels Church. Photo: Sensitive receptor, Queen of Angels Church.

Impacts and mitigation measures

The potential air quality impacts have been assessed by applying the project’s assessment methodology. This methodology documents the process for assessing the key social and environmental risks from the project and identifies management and mitigation measures to reduce these risks. A project-wide evaluation of each potential air quality impact was undertaken for both the construction and operational phases of the project.

Construction impacts

The key outcomes of the assessments regarding air quality impacts during construction are summarised below. The two main impacts identified can arise from a number of construction activities and apply to all areas of the project. Note that the impacts identified do not include the implementation of mitigation or management measures which if applied correctly, should address or minimise any negative outcomes.

Potential construction impacts	Activity
Deposition of larger dust particles causing aesthetic impacts at sensitive receptor locations (for example dust settling on a house or garden).	site clearance and construction site establishment earthworks construction of surface roads and other civil infrastructure dive structure/portal and tunnel construction traffic movement associated with material transport.
Generation of dust (PM₁₀ and PM_2.5) from soil disturbance causing health impacts at sensitive receptor locations (for example small dust particles that could be breathed in by people living adjacent to the project).

The project will take all reasonable and practical steps to prevent any damage and minimise any impacts on health and amenity. Air quality construction mitigation measures will aim to:

minimise any impacts on the health and amenity of the surrounding community
keep the community well informed about air quality effects
allow the project to be constructed safely and efficiently.

Photo: Air quality monitoring station installed as a part of monitoring air quality along the project alignment.

Construction

The proposed mitigation measures to minimise or avoid air quality impacts during construction are outlined below:

Construction activities	Key mitigation measures
Air quality impacts from construction activities (general)	The construction contractor will be required to ensure any construction impacts are proactively minimised, monitored and managed. The construction contractor will prepare a Construction Environmental Management Plan (CEMP) which sets out how air quality impacts will be minimised and monitored. For more information visit about construction.
Site clearance and construction site establishment	The project will: where site clearance and topsoil removal reveals exposed surfaces, water suppression/dust suppression polymers will be used to prevent dust generation mobile water cart(s) will be used to minimise dust along site roads (sealed and unsealed) and exposed areas an adequate water supply will be made available on the site for effective dust suppression dust generating activities to be scheduled to avoid periods of high winds (> 5m/s) materials that have the potential to generate dust will be stabilised or removed from site as soon as possible unless being re-used on-site.
Earthworks	The project will ensure: stockpiling for longer than 28 days is minimised. Contaminated materials, if encountered, which require stockpiling for longer than 28 days will be stabilised or covered where a stockpile has the potential to generate dust, control measures such as wetting the stockpile will be implemented during the day. The height of stockpiles will be minimised, covered with an appropriate material and removed off-site as soon as practicable for disposal earthworks and exposed areas to be kept damp or otherwise stabilised during dry and windy conditions (> 5m/s) soil will be relocated to the soil storage areas with appropriate bunding and dust control measures (water sprays) in place soil will be stockpiled, tested and disposed off-site in accordance with appropriate waste classification guidelines. Materials that have the potential to generate dust will be stabilised or removed from site as soon as possible unless being re-used on-site an adequate water supply will be made available on the site for effective dust suppression mobile water cart(s) will be used to minimise dust along site roads (sealed and unsealed) and exposed areas.
Construction of surface roads and other civil infrastructure Dive structure/portal and tunnel construction	The project will ensure: relevant dust mitigation measures are implemented as outlined above air filtration system to remove particulate matter during soil excavation for tunnel and portal construction are incorporated where required only cutting, grinding, sawing equipment fitted with or in conjunction with dust suppression techniques such as water sprays or local extraction will be used on-site.
Traffic movement associated with material transport	The project will ensure that: a maximum speed limit on sealed and unsealed roads and in works areas is imposed for all on-site vehicles all trucks entering/leaving the site with material are covered to prevent escape of materials during transport all vehicles are restricted to designated areas all trucks leaving the site are inspected to minimise dirt or mud tracked onto the public roadway rumble grids, wash bays or similar will be established at site entries/exits to minimise spread of debris / mud on public roads.

Groundworks, Darlington upgrade.
Photo: Earthworks, construction of the Darlington Upgrade.

Operational impacts

For a road tunnel, during operation emissions are generated by vehicles within the tunnel and will be discharged into the environment via a combination of ventilation facilities and managed emissions from the tunnel portals. Emissions are also generated on the surface roads constructed as part of the project. Measures and requirements are in place to ensure the T2D Project meets air quality limits and incorporates features to control in-tunnel and atmospheric pollution levels.

A significant proportion of vehicles currently using South Road where there is poor traffic (i.e. signalised intersections with stop-start movements) will relocate to the new motorway. This is expected to improve traffic conditions, to provide an improvement to air quality at ground-level locations along the project corridor. At these locations, the T2D Project would have the potential to improve community health and amenity. The table below outlines the proposed mitigation measures to minimise or avoid air quality impacts during operation:

Potential operation impacts	Mitigation measures
Localised reduction of air quality vehicles using surface roads (crossroads and motorways) – emissions released locally at road level vehicles using tunnels – emissions released through a combination of vertical air extraction through ventilation facilities and managed emissions from the portals.	The project will: develop tunnel ventilation systems to provide adequate dilution and dispersion of pollutants monitor pollution levels to provide appropriate control of ventilation systems utilise Intelligent Transport System (ITS) infrastructure and tunnel traffic monitoring to manage traffic conditions to minimise vehicle pollution generation optimise project design elements (for example noise wall heights, numbers and locations) to protect sensitive receptors portal structure designed to enhance emissions dispersion.

Control of air quality has been considered throughout the design process. The project is taking all reasonable and practical steps to eliminate or reduce the risk of any impacts on health and amenity.

How impacts will be minimised or avoided

During design the project has confirmed that application of the Department’s Master Specification (MS), with its links to relevant parts of the Environment and Heritage Technical Manual (EHTM) will be applied to mitigate the construction and operational air quality impacts. Additionally, project-specific requirements have been developed.

Of relevance to air quality are:

The Master Specification and EHTM require the project to develop and undertake assessments and prepare reports that document required outcomes during construction and operation which include:

Contractor’s Environmental Management Plan (CEMP)
Detailed Design Air Quality Impact Assessment – demonstrates that the project’s design meets the air quality requirements during operation
Construction Air Quality Management Plan – outlines measures which will be used to suitably manage dust and other air quality impacts during construction to minimise impact to community, and is a sub-plan of the CEMP
Operational Air Quality Management Plan – outlines measures which will be used to suitably manage air quality impacts during operation of the tunnels and motorway.

Approvals

Approvals, permits and authorisations

The likely air quality related legislative or policy approvals required to progress the project to delivery are:

Legislation/Policy	Approval
Required
National Environment Protection (Ambient Air Quality) Measure (NEPM AAQ)	This sets standards that consist of quantifiable characteristics of the air against which ambient air quality can be assessed for population exposure. The requirement is to not exceed the standards established in the measure. Demonstrate compliance. No specific approval required, however compliance with the National Environment Protection (Ambient Air Quality) Measure needs to be demonstrated.
National Environment Protection (Air Toxics) Measure (NEPM Air Toxics)	This provides information regarding ambient air toxics within the Australian environment in order to facilitate the development of standards. The requirement is to gather sufficient data nationally to facilitate development of a standard. Demonstrate compliance. No specific approval required, however compliance with the National Environment Protection (Air Toxics) Measure needs to be demonstrated.
Environment Protection Act 1993 (EP Act)	The EP Act establishes the general environmental duty to not undertake an activity that pollutes or might pollute the environment, unless all reasonable and practicable measures to prevent or minimise any resulting environmental harm have been taken. No specific approval required, however the project must demonstrate that all reasonable and practicable measures will be undertaken to prevent or minimise air quality impacts during construction and operation of the project.
Environment Protection (Air Quality) Policy 2016 (Air EPP)	The Air EPP establishes maximum pollutant ground level concentrations to protect the health and amenity of sensitive receivers. Demonstrate compliance. No specific approval required, however compliance with the Environment Protection (Air Quality) Policy needs to be demonstrated.
EHTM Attachment 3A – Air Quality Assessment Guideline	The Air Quality Assessment Guideline applies to new or major redeveloped road or rail infrastructure projects. The Guideline applies to operational air quality assessment and does not apply to air quality assessment and impacts from construction activities. Demonstrate compliance. No specific approval required, however compliance with the Department’s EHTM Attachment 3A – Air Quality Assessment Guideline needs to be demonstrated.
South Australian Environment Protection Authority (SA EPA) Ambient air quality assessment guideline 2016	Demonstrate compliance. No specific approval required, however compliance with the SA EPA Ambient air quality assessment guideline needs to be demonstrated.

Next steps

The Project Assessment Report (PAR) community consultation period concluded in April 2024. We thank you for your feedback.

The valuable information and local insights received during the consultation phase of the PAR are being considered by the project team and will inform the ongoing refinement of the T2D Project.