CBD Stations construction plans
The construction of the new Metro Tunnel and two new stations under Swanston Street presents a range of engineering challenges:
- navigating existing below-ground infrastructure, including the City Loop tunnels, CityLink tunnels and major utilities
- managing the effects on traffic, pedestrian, cyclist and tram movements
- minimising disruption to residents, traders and businesses.
To manage these challenges, a combination of construction techniques are likely to be used within the CBD.
Parts of Franklin Street between Elizabeth and Victoria streets will be used as construction work sites for the Metro Tunnel, along with part of A'Beckett Street and the station entrance site on the corner of La Trobe and Swanston streets.
Construction work sites will be located at the station entrances in City Square, Federation Square and the southern entrance fronting Swanston Street.
Key construction activities
Key construction activities for the two CBD stations include:
- Preparatory works including tree protection and removal, excavation of construction access shafts, protection or relocation of statues and monuments, and the relocation of underground services such as water, electricity, gas, sewers, stormwater and telecommunications.
- Demolition of buildings at station entrance locations, where required.
- Excavation of the Metro Tunnel between the two CBD stations.
- Station structural works and station entrance connections.
- Station cavern excavation under Swanston Street
- Station architectural, mechanical and electrical fit-out.
- Track works and the installation of signalling and communications systems.
- Site remediation, including landscaping, along Swanston Street and at City Square and Federation Square.
Mined cavern station construction
In order to keep Swanston Street open while the Metro Tunnel is built, 'mined cavern construction' will be used to construct the two new CBD stations. Mined cavern construction reduces disruption to the surface by excavating the station from underground rather than digging a trench from surface level.
Access shafts, which are effectively deep basements, are excavated and are used to transport machinery, equipment and workers underground to where the station cavern will be constructed. Station cavern excavation is similar to the 'mined tunnel' approach described below, however the cavern is much larger than the train tunnels between the two CBD stations.
It is proposed that the tunnels will be mined between CBD North Station and CBD South Station. Mined tunnelling uses road header machines to excavate the tunnels. The machines have rotating cutter heads that are mounted on a boom. After the road header digs the tunnel, the ground is reinforced with a combination of rock bolts, lattice girders and sprayed concrete.
The use of mined tunnelling and cavern construction techniques will significantly reduce impacts on Melbourne's CBD, helping to ensure thousands of workers, residents and visitors can continue to access the CBD while construction of the proposed twin tunnels and stations continues underground.
However, there will still be unavoidable disruption at surface level and some changes to roads, tram services, and bicycle and pedestrian access will be required to deliver the Metro Tunnel.
Building CBD North Station will require long-term temporary closures of Franklin Street and A'Beckett Street. More information about CBD North traffic changes.
In CBD South, short-term partial closures of Flinders Street will be required to construct the underground pedestrian connections linking Flinders Street Station and Federation Square to the new CBD South Station. These works may impact both traffic and trams.
Public transport, cycling and walking
Tram services will continue to run during the Metro Tunnel's construction in the CBD, although some activities are likely to temporarily impact tram services along Swanston, Flinders, Collins and La Trobe streets from time to time.
Construction activities in the CBD will be carefully managed to minimise disruption to pedestrians and cyclists, especially during peak periods. Pedestrian and bicycle paths will be maintained around construction sites, and will include arrangements to direct pedestrians and cyclists safely around work areas.
Proposed construction traffic routes for the CBD precinct aim to move trucks and other construction traffic away from the city as quickly as possible, using major arterial roads such as Victoria Street, Wurundjeri Way, Dudley Street and the Exhibition Street extension.
The impacts of additional traffic will be managed by using detailed traffic management plans. These plans will seek to minimise truck movements during peak periods, manage truck arrivals and departures to avoid trucks queuing in CBD streets, and minimise truck movements past residential areas at night time.
A number of mitigation measures, or 'Environmental Performance Requirements' have been proposed in the Metro Tunnel EES to avoid, reduce or manage construction impacts in the CBD.
Some of the recommended mitigation measures for the CBD precinct include:
- Monitoring dust and air quality, in line with Environment Protection Authority Victoria requirements, and addressing air quality requirements for nearby residences and businesses.
- Developing and implementing a traffic management plan to minimise disruption to traffic, car parking, and pedestrian and cyclist movements across the city during construction.
- Undertaking property condition surveys before construction begins to record the existing condition of buildings and residences in close proximity to tunnels and construction sites.
- Developing and implementing appropriate protection measures for heritage buildings such as City Baths and Flinders Street Station, and monuments like the Burke and Wills statue.
- Implementing measures for providing advance notice of significant milestones, changed traffic conditions and periods of potential high noise and vibration activities.
- Ensuring above-ground structures such as station entrances are responsive to heritage places.
- Improving community access to open or recreational spaces within the CBD by identifying potential opportunities to return as much land as possible used for construction to permanent public open space at City Square and Federation Square.
At this stage of planning, it is expected that construction of CBD North Station and CBD South Station, and the tunnels under Swanston Street, will take around five years in total to complete. Different station elements will take different lengths of time depending on their size and complexity.
Project-wide rail systems installation and commissioning will occur after this five year construction period.