Sydney metro buildout projects 30 Jul 2020

With excavation of 50km of TBM running tunnel drives complete for the new Metro City and Southwest Line in Sydney, attention is focused on the station sites where construction work is progressing. In addition, work on both the Metro West Line and the Metro Western Sydney Airport link, which was formerly known as Sydney Metro Greater West, has advanced with release of the first environmental impact statement and the initial scoping report, respectively.

Fig 1. Metro West Stage 1 Westmead to Olympic Park

Metro West

The first environmental impact statement (EIS) for Sydney Metro West was released in April 2020 with the comment period closing in June 2020. The EIS is one of three that will be published to cover the three stages of the project to construct 24km of twin running tunnels between the central business districts of Sydney and Paramatta, the two major commercial districts of Greater Sydney (Fig 1).

Stage 1 covers all major civil construction work between Westmead Station at the western end of the line to The Bays, including station excavation and tunnelling, while Stage 2 comprises fit-out of all stations, depots and rail systems along the same section. The final stage covers all major civil construction works between The Bays and Sydney CBD, including station excavation and tunnelling, as well as fit-out of stations, depots and rail systems.

Fig 2. Link to new Western Sydney Airport

According to the EIS indicative construction plan, Stage 1 tunnelling will be undertaken in two sections. Excavation of the first section, between The Bays and Olympic Park, will begin in mid-2022, and of the second section, between Westmead and Olympic Park, in late-2023. As with other Sydney Metro developments, tunnelling will be by TBM, with four machines expected to be used to bore the twin alignments. The design plan is for TBMs to launch from Westmead and The Bays and for all four to breakthrough at Olympic Park.

The two sections will be awarded as separate contract packages and the call for expressions of interest was issued by the New South Wales State Government in April 2020.

Stage 1 stations include cut-and-cover stations at Westmead, Paramatta, Olympic Park, North Strathfield, Burwood North, and The Bays with a binocular cavern-type station used at Five Dock.

Metro Western Sydney Airport

Adding to metro development in the New South Wales capital is the Metro Western Sydney Airport, which will run 23km between St Marys and the new Western Sydney International Airport and Western Sydney Aerotropolis (Fig 2). According to its scoping report, released in June 2020, the route would be a mix of surface, underground and elevated alignments, with underground elements at either end. Excavation is likely to be by TBM.

Fig 3. Metro City and Southwest route under Sydney Harbour

Linking at St Marys with existing Sydney trains network for services to the Sydney Central Station, additional stations are planned at Orchard Hills, Luddenham, at two locations at the Western Sydney International Airport, and at the Aerotropolis. Early enabling works are expected to begin later this year (2020) with major civil and earthworks, including tunnelling, anticipated to start in 2022.

Metro City and Southwest

On the Metro City and Southwest Line, TBM excavation of the 15km long twin tube alignment was completed in March when the slurry TBM, a Herrenknecht Mixshield, broke through at the Blues Point reception shaft at the end of the second 885m drive under Sydney Harbour (Fig 3). Four additional double shield TBMs had already been shipped back to the Herrenknecht in February 2020, after the last of these completed its drive between Marrickville and Barangaroo in January 2020 (Table 1).

The second drive under the harbour took a month less to complete than the first, after modifications were made to the cutterhead and tunnelling processes to better deal with the higher than expected amounts of clay encountered on the first drive.

Work on the stations continues with drill+blast excavation of the cavern and service tunnels at Victoria Cross Station complete. The impressive underground space is reportedly the largest rail cavern in Australia at 265m high x 25m wide x 20m high. Focus is currently on installation of the permanent concrete lining and construction of the southern shaft, which will be one of the entrances into the new station. About 151,000 tonne of a total 262,000 tonne of rock for the shaft had been removed by early July (2020) with excavation expected to continue until November 2020.

Major excavation is also nearing completion at Martin Place Station. Design-build contractor Lendlease is delivering the complete integrated station project for developers Macquarie Group. The works include a 39-storey over-station development above the northern entrance to the underground station.

Excavation of the cut-and-cover extension to the city’s main Central Station is progressing and a 80m long x 6m wide tunnel has been excavated to allow construction of Central Walk, a 19m wide underground concourse to connect the Chalmers Street entrance with suburban rail and metro platforms, and to new light rail and bus services. The construction tunnel runs parallel to the planned Central Walk alignment and will provide access for excavated rock to be removed without impacting existing station services. Construction tunnel excavation broke through into two ghost platforms structures that were built last century as part of the Eastern Suburbs Railway but never completed. These platform structures will now be used to house 17 new communications and power rooms for the new metro line.