Eastern tunnel entrance construction plans
Construction of the eastern tunnel entrance will involve construction activity in South Yarra Siding Reserve, Osborne and William streets and within the existing rail corridor.
A tunnel boring machine (TBM) retrieval box will be required in the rail reserve between Osborne Street and the existing Sandringham line. TBMs will be used to create the tunnels linking the eastern tunnel entrance to Domain Station and the rest of the network.
To construct the eastern tunnel entrance, rail tracks will need to be reconfigured between South Yarra Station and Chapel Street, and a decline structure will be built so that Cranbourne / Pakenham services can enter the new Metro Tunnel.
The works will increase the number of tracks in this area from four to six tracks. The rail corridor between William Street and Chapel Street will need to be widened for construction access and to accommodate the reconfigured tracks, and the William Street bridge will need to be demolished and rebuilt to accommodate the works.
The decline structure and tunnel entrance are proposed to be built via a 'cut and cover' method, which will see them excavated from the top down and the surface then reinstated over the top of the tunnels.
Key construction activities
Key construction activities to build the eastern tunnel entrance would include:
- Preparatory works including land clearing and relocation of utilities including electrical, gas, water and telecommunications services.
- Demolition of acquired buildings.
- Construction works to widen the rail corridor to accommodate additional tracks, including demolition of the William Street bridge.
- Excavation of the decline structure and tunnel entrance construction, including retaining walls.
- Construction of the ventilation shaft, emergency access and a power substation in Osborne Street Reserve.
- Construction of a TBM retrieval box.
- Track works and the installation of signalling and communications systems.
- Site remediation including rebuilding the William Street bridge and upgrading shared spaces including South Yarra Siding Reserve, Osborne Street Reserve and Lovers Walk.
It is expected that traffic along Osborne Street, William Street and the adjoining streets will be affected during different stages of construction with some changes to lanes as well as temporary closures.
Proposed construction traffic routes have been developed for the eastern tunnel entrance precinct that focus on moving trucks and other construction traffic to Toorak Road as quickly as possible. Active traffic management will also be used to minimise delays to tram movements and traffic flow along Toorak Road.
Works at the eastern tunnel entrance would also require the demolition and rebuilding of the William Street bridge to accommodate a widened rail corridor underneath. The rebuilt bridge height will need to increase to pass over the top of the reconfigured Cranbourne / Pakenham line.
The Lovers Walk pedestrian path will also be closed and reinstated after construction is complete.
A number of rail corridor occupations (periods where trains stop running so works can take place) would be required to connect the Metro Tunnel to the Cranbourne/Pakenham line. These occupations would potentially disrupt services on parts of the rail network.
The construction contractors would be required to develop and implement measures to minimise disruption to the transport network during construction of the Metro Tunnel.
As part of our Environment Effects Statement, we have developed a number of mitigation measures, or 'Environmental Performance Requirements', have been proposed to avoid, reduce or manage construction impacts for the eastern tunnel entrance precinct in South Yarra.
Some of the recommended mitigation measures for the eastern tunnel entrance include:
- Planning and carefully managing access routes to minimise impacts on residents and users of the area.
- Implementing measures for providing advance notice of significant milestones, changed traffic condition and periods of potential high noise and vibration activities.
- Undertaking property condition surveys before construction begins to record the existing condition of buildings and residences in close proximity to tunnels and construction sites.
- Monitoring dust and air quality, in line with Environment Protection Authority Victoria requirements, and addressing air quality requirements for nearby residents and businesses.
- Developing an occupations plan that minimises the disruption to railway services during construction
- Preserving the broader landscape and recreational values in the reinstatement of shared spaces like South Yarra Siding Reserve and Lovers Walk.
Construction time frames
It is estimated that construction of the eastern tunnel entrance will take around three years. Subject to planning approval, early works will begin in 2017 with major works commencing in 2018.