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Sinkhole Halts $3.1B Sydney Motorway Project
9 Sep
Summary
- Deepest Southern Hemisphere tunnels in Sydney stalled by sinkholes.
- Project stabilising soft ground using jet-grouting technique.
- M6 motorway completion date delayed, NSW government silent.
Beneath southern Sydney, the M6 motorway project, a multibillion-dollar undertaking, is experiencing significant setbacks. Twin tunnels, reaching depths of up to 97 metres and ranking as the deepest roadways in the Southern Hemisphere, have largely sat idle for more than two years following the emergence of sinkholes. The most recent incident occurred in early 2024 at the project's southern end in Rockdale, halting progress on the final 250-metre section.
Work is now accelerating after a dispute ceasefire in June. A primary focus is stabilizing the ground at the southern end using an engineering technique called jet-grouting, which binds the soil to create a solid mass. This crucial step precedes the resumption of tunnelling. Demolition of a warehouse above the largest sinkhole site is scheduled to begin shortly, marking a visible sign of renewed activity.
The project director, Terry Sleiman, who has prior experience with similar ground issues, stressed the importance of immediate reporting of ground condition changes. The NSW government has withheld a new completion date, which was originally slated for the end of 2028, indicating a delay of over four years from the initial timeline. Detailed design work for the unfinished sections is anticipated for completion early next year.
