Along its route, the depth of the Metro Tunnel is up to 40m. The deepest point is under Swanston Street, at the northern edge of the CBD, where the new tunnels pass under the existing City Loop tunnels.
As we built the tunnels we:
- navigated existing underground infrastructure – including the City Loop, CityLink tunnels and services such as water, gas and electricity
- excavated through a range of challenging geological conditions including rock, sands, clays and silt
- tunnelled under 2 significant waterways, the Yarra River and Moonee Ponds Creek
- managed the removal and disposal of around 1.8 million cubic metres of soil and rock
- managed disruption to residents, businesses and public events
- minimised potential impacts on road traffic, pedestrians, cyclists and existing public transport and freight services.
Additionally 26 cross passages were built, connecting the rail tunnels at intervals of approximately 230m. These passages are an important safety feature that allow people (including emergency services) to move from one tunnel to the other in the event of an emergency.