Sydney plans a major metro expansion 20 Feb 2020

A considerable underground infrastructure project is set to almost double the length of the Sydney Metro. Sydney Metro West will add 24km to the existing network. It will run between the central business districts (CBD) of Paramatta and Sydney, the two major commercial districts of Greater Sydney (Fig 1).

Fig 1. Metro West will almost double the length of the Sydney Metro

Sydney Metro West is the third element of metro development in the New South Wales state capital (Table 1 and Fig 2). It follows the successful opening in 2019 of the 15km Sydney Metro Northwest, the first metro line in the New South Wales capital, and the 15.5km Sydney Metro City and Southwest route, which is currently under construction with an opening date in 2024. The planning process for the twin-tunnel western extension is underway, with the project receiving AUS$3 billion in funding in June 2019 to develop detailed planning and environmental assessment documents for public exhibition and community consultation.

The final project budget will be confirmed when all contracts have been awarded, following the same procedure used for both Sydney Metro Northwest and Sydney Metro City & Southwest.

“An Environmental Impact Statement (EIS) for the first stage of the Metro West project – Westmead to The Bays and Sydney CBD – will be placed on public exhibition later this year,” Jon Lamonte, Sydney Metro Chief Executive, told TunnelTalk. “Further stages of Sydney Metro West will be assessed in subsequent EIS.”

When complete, travel time between the Paramatta and Sydney CBDs will be approximately 20 minutes. “This will transform how people move around Greater Sydney,” Lamonte continued.

Grand plans

Under current design specifications, the twin alignments will have a circular cross-section, with a lined i.d. of approximately 6m, and will run between 22m and 32m below ground. At least four TBMs are expected to excavate the route, lining it with precast concrete segments. Roadheaders will construct the caverns, stub tunnels, and connectors from the mainline tunnels to the Rosehill dive structure, which will enable trains to move between the underground metro tunnels and the above-ground Clyde stabling and maintenance facility. TBM launch and support is anticipated from the sites of the new Westmead and Bay stations.

“The tunnelling packages are expected to cover about 20km of twin drives from Bays Precinct to Westmead,” explained Lamonte. “The scope also includes the excavation of cross-passages, as well as spoil removal and disposal.”

According to geological mapping of the areas along the route, Sydney Metro West will run through a mixed geology, including Ashfield shale, Hawkesbury sandstone, and quaternary deposits, such as silty-to-peaty quartz, sand, silt and clay. These ground conditions make it likely that double shield TBMs will be selected for tunnelling work, according to Lamonte, although final machine selection will be made by the successful contractor.

Fig 2. Sydney metro is set for a major expansion

In addition to the tunnels, there will be eight new underground stations built at:

• Westmead.
• Parramatta.
• Sydney Olympic Park.
• North Strathfield.
• Burwood North.
• Five Dock.
• Bays Precinct.
• Sydney CBD.

Of these, six are likely to be cut-and-cover constructions: Westmead, Paramatta, Sydney Olympic Park, North Strathfield, Burwood North and Bays Precinct. Five Dock is expected to be a cavern design, constructed by roadheader and excavator. The site – and therefore the construction – of the Sydney CBD station is the subject of ongoing assessment, including community and stakeholder engagement.

The new Paramatta station will serve the commercial core of the Paramatta CBD to the north of the existing train station. The Sydney Olympic Park development will also bring the total number of stations there to two, helping to transport more than 10 million visitors to one of the leading events, sports and entertainments precincts in Australia.

Additional stations may also be added at Rydalmere and Pymont, with investigation work underway to determine their potential. “The assessment will consider feasibility and affordability, along with community feedback and important environmental factors, such as heritage and the natural environment,” said Lamonte, “The assessment will also consider integration with current and planned transportation options, and what the project could bring to the local community, such as supporting new jobs and homes.”

Ready to start

Initial construction work is expected to begin this year at Bays Precinct to prepare the site for the start of tunnelling work, including site surveys, investigations, and early works such as road relocation.

The rapid build-out of the Sydney metro may also not end with the current plants for Metro West. “The ability to extend, including beyond Westmead, will be future-proofed,” Lamonte revealed. Sydney Metro is already in the early investigative stages of a further expansion, Metro Greater West, which will service Greater Western Sydney and the new Western Sydney International (Nancy-Bird Walton) airport. Australian and New South Wales governments have stated the objective to have Metro Greater West operational in 2026, when the Western Sydney Airport is scheduled to open.

The search for suppliers opened in October 2019 with those wishing to express their interest in the procurement of the tunnelling contract – expected to be the biggest such contract awarded in Australian history – able to register on the eTendering website. Formal expressions of interest are expected to be invited shortly.