Frequently asked questions

Three construction precincts will be established along the corridor: the southern, central and northern precinct. Each precinct will accommodate tunnelling operations and surface level construction work to build the lowered motorway and associated urban infrastructure.

The precincts will be purpose built to suit the construction activities taking place in that area. Detailed precinct layouts will be made available as planning is finalised.

Generally, precincts will include:

• a tunnel access ramp where the tunnel boring machines (TBM) will enter and exit the tunnels. These ramps are permanent structures that will become the lowered motorway when the tunnelling works are completed. Construction of the ramps involve building large retaining walls and bulk excavation of ground material

• an electrical power substation to support tunnel operations such as powering the TBMs and other ancillary equipment like conveyors, lights, fans and pumps

• enclosed conveyors to shift the excavated spoil from the tunnels to the spoil shed

• an acoustic shed for management of spoil (the excavated rock and soil), storage of machinery and equipment, and to keep noise and dust to a minimum

• a water treatment plant to ensure wastewater and run-off from the construction area meets required water quality before disposal

• gantry cranes

• worker facilities.

Construction hours differ between surface works and tunnelling.

Surface works will normally take place: 

• Monday to Saturday between 7:00 am and 7:00 pm 

• Sundays and Public Holidays from 9:00 am to 7:00 pm 

While every attempt is made to complete construction work during the day, some night work will be required when traffic volumes are lower and safety can be maintained for motorists, pedestrians and our workers.  

Other reasons for night work include: 

• third party approval limits work to night works 

• service outage timing determined by the relevant service provider 

• as agreed with adjacent stakeholders (there may be a preference to carry out the work at night) .

Tunnelling activities will take place 24 hours per day, seven days a week.  This includes excavation by tunnel boring machines and tunnel support activities such as spoil handling and loading.

The tunnels will be constructed using tunnel boring machines (TBM), except for short lengths at each end of the tunnels. This is because the roadway would be too shallow to use the TBMs effectively.

For these short lengths, we will construct the tunnels from the surface with a process called cut and cover tunnelling. This construction method involves:

• excavating a large open trench using an excavator (cut)

• constructing the roof to give a tunnel-like finish (cover).

Spaced concrete beams will form the roof – giving an open tunnel finish.

A large part of the tunnelling operation involves removing ground material from the newly excavated tunnel. The ground material is referred to as spoil. Based on modelling and calculations, tunnelling and excavation will generate about 7.5 million tonnes of spoil to build the open motorway.

Before starting construction, extensive ground investigation works were completed. This was to confirm the geotechnical and groundwater properties along the tunnel alignment. The ground is largely clay-based. This soft ground material requires specialist tunnelling methods.

Once the clay is excavated, trucks move the spoil from the back of the tunnel boring machine (TBM) conveyor to a spoil shed on the surface within the site compound. It is then treated as required. From this shed, trucks with trailers (spoil haulage trucks) move the spoil to approved disposal sites in South Australia.

We install several measures on site to ensure the safe management of spoil:

• Before we remove spoil from the site, we test and categorise the spoil so that it is directed to the correct disposal site.

• Contaminated materials are handled in line with Construction Environmental Management Plan (CEMP) requirements.

• Spoil haulage trucks are fitted with covers to minimise dirt tracking. The covers can be off when there is no spoil in the trailer.

• Wheel wash systems installed at each site ensure that truck tyres are clean before leaving.

• Options to reuse the spoil are explored where possible.

The tunnel boring machines used to excavate the tunnels will bore deep underground at around 10 to 25 metres below the surface.

To view the planned location and depth of tunnels in proximity to your property, use the Tunnel tool.

Safety has been at the forefront of the T2D Project design. The tunnels will have a range of features to make sure motorists are safe.

The T2D Project will be a ‘managed motorway’. This means the motorway and the tunnels will have a range of technology-based information, communications and control systems in the motorway, known as intelligent transport systems (ITS).

The systems are designed to actively:

• manage traffic flows

• improve safety

• provide travel time reliability.

We will establish a dedicated traffic management centre to monitor the T2D motorway. It will have a range of tools to make sure traffic moves efficiently along the corridor. This includes measures such as:

• coordinated ramp signalling

• speed and lane use management

• automated incident detection

• variable messaging signs (VMS).

If an incident occurs in a tunnel, we will use these systems to coordinate an appropriate response to make sure motorists are safe.

Systems include:

• tunnel closure system, so the tunnels can be safely closed when required using boom gates and stop signs to restrict access

• automatic incident detection to identify hazards such as stopped vehicles, debris, animals or people

• CCTV cameras for constant road monitoring and quick incident management

• dynamic variable message signs to provide information to motorists like incident warnings and likely travel time

• lane use management system to control speed limits and lane closures for optimised traffic flow and safety

• fire detection and suppression systems to activate sprinklers in the event of a fire

• radio rebroadcasting, so traffic management centre personnel can broadcast safety messages to motorists in the tunnels via their vehicle’s radio.

We will do our best to minimise disturbance from our surface construction sites to nearby residents and business. However, some construction activities will generate periods of noise.

We’ll use a range of measures to mitigate noise and vibration impacts, including:

• providing advance notice of works to those nearby

• monitoring noise and vibration levels during construction

• applying at-source measures including temporary and permanent noise walls, noise blankets around mobile work areas and acoustic sheds to enclose tunnelling activities

• planning activities to avoid project vehicles and trucks queuing and idling near homes and businesses

• checking our equipment, vehicles and machinery are in good working order

• limiting truck movements on local roads where possible

• locating equipment as far as practical from homes and businesses

• implementing respite and relocation measures

• administering the Noise Treatment Program at eligible properties.

Due to the nature of the activities taking place, construction work can sometimes generate dust.

To minimise dust leaving the construction sites we will implement various mitigation measures including, but not limited to:

• water carts on-site and on adjacent streets to dampen stockpiles, hardstand areas and road surfaces

• street sweepers on haulage roads and local roads

• polymer binding agent applied to stockpiles

• spoil shed enclosing soil deposits

• maximising the amount of hardstand area on-site.

Road tunnels can help reduce air pollution by moving vehicles underground and off the roads where people live and work. Road tunnels also reduce travel time and congestion by:

• removing the number of traffic lights along the journey

• reducing road grades (steepness) and corners.

Within the tunnel environment, vehicle emissions can be controlled and dispersed more effectively. This results in little, if any, change in air quality for people living and working near the tunnel. We will build our tunnels to meet strict air quality standards with state-of-the-art ventilation and tunnel design.

The exit points of tunnels are also known as tunnel portals. During the design process, we use a modelling-based assessment to evaluate potential changes to the air quality surrounding these portals. It is necessary to demonstrate minimal or no change to the surrounding air quality.

During tunnel operation, we measure emission levels with air-quality monitors. This is to confirm that air quality standards are being met. These monitors are installed both inside and outside the tunnels.

Contributors to air pollution include:

• residential, commercial and industrial areas

• wood heaters

• natural events, like bush fires

• motor vehicles.

By relocating surface traffic into tunnels, we can also use more space for things that matter most to Adelaide’s communities. For example, open green spaces and trees.

More information

We will provide more information about air quality management after we finalise the design.

In the meantime, our community engagement team is happy to answer any questions you may have.

We are committed to maintaining two lanes of traffic in each direction on South Road during construction. There may be occasional limited closures at night or other off-peak times to facilitate some construction activities. The majority of construction will be undertaken off-site and next to South Road, which will limit impacts to existing traffic.

New Variable Message Signs (VMS) will be installed at key locations to advise motorists of traffic conditions along and around South Road with real-time information.

Use our Surface works map to see what’s happening in your local area and to help you plan ahead. It is updated weekly with the latest work activities.

Some Adelaide Metro bus stops along South Road may be temporarily impacted while work is underway. Advance notice will always be provided ahead of any public transport changes.

Use our Surface works map to see what’s happening in your local area help you plan ahead. It’s updated weekly with the latest work activities including any public transport changes. Please observe bus stop signage and visit www.adelaidemetro.com.au for the latest information on routes and timetables.

Some changes to active transport routes may be required while work is underway. Detour routes will be signposted around our work sites for bike and shared-use paths.

Use our Surface works map to see what’s happening in your local area and help you plan ahead. We update it weekly with the latest work activities, including any changes to active transport routes.

Access to properties will be maintained during construction, unless otherwise agreed with the property owner or tenant.

Where construction activities do affect primary access, we will:

• arrange alternative access with the owner or tenant

• always provide advance notice.

Wherever possible, residents, deliveries and service vehicles will be permitted access through local road closures.

Emergency services are regularly briefed throughout construction. This is to ensure they are up to date with the latest project information and access is always maintained.

We consult with emergency services as part of the planning process ahead of any planned traffic changes.

A property condition survey is an inspection of a building or property to assess and document its general condition. This includes any existing defects.

The survey is offered before substantial construction on the surface or tunnelling begins in your area.

If a pre-construction property condition survey is completed for your property, you will automatically be offered a post-construction property condition survey.

A post-construction property condition survey is a follow-up inspection after construction work is completed. It can be used to determine if there are any changes to the buildings or structures. This offers owners peace of mind during construction work.

Learn more about property condition surveys and who is eligible for one.

The best way to stay up to date on the project is to register for updates.

Community Information Centre

Visit our T2D Community Information Centre to learn more about the T2D Project and speak to our friendly team.

Where: 290 South Road, Hilton.

Opening hours:

• 10am to 3pm on Mondays, Tuesdays and Wednesdays

• 9am to 1pm on the first Saturday of every month  

Email or call