The project, known as the Northern Connection, is being undertaken within the existing T1 North Shore line railway corridor while minimising the impact on existing rail services.

Excavators have already removed 330 tonnes of soil, with piling rigs drilling 34 holes up to eight metres deep to create a foundation in preparation for a ramp that will allow the line to enter and exit the new twin metro tunnels at Chatswood, which were completed earlier this year.

About 7500 tonnes of material will be excavated and a section of the existing suburban line will be re-aligned to create the structure, which is expected to connect with the tunnels in 2022.

About 130 workers from Systems Connect, Sydney Metro’s contractor delivering line-wide work on the City & Southwest project, had 48 hours to complete the work in time for the resumption of Monday morning rail services.

The $A 8.3bn ($US 5.7bn) 36km Sydney Metro Northwest line between Tallawong and Chatswood became Australia’s first metro line when it opened on May 26 2019.

The 30 City and Southwest project will extend the line beneath Sydney Harbour, through new underground city stations and beyond to the south west, and is expected to cost around $A 15.5bn ($US 11.1bn) when it opens in 2024.

The Chatswood to Sydenham section includes a 15km greenfield line with seven new stations. The Sydenham to Bankstown section involves the upgrade of the existing 13km suburban line to metro standards, including upgrading 11 existing stations. The project also includes expansion of the current Sydney Metro Trains Facility at Rouse Hill and a new depot at Sydenham.

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