Key facts
- Sydney's M6 motorway project, stalled for two years due to sinkholes, will resume.
- A new agreement places the cost of completing the tunnels on the private consortium.
- The M6 is now expected to open in 2028, a significant delay from its original 2024 target.
- The project's halt was caused by sinkholes and the discovery of a high-angle reverse fault.
- The NSW government stated the completion will incur no additional cost to taxpayers.
Tunnelling on Sydney's $3.1 billion M6 project is set to resume after a two-year halt caused by sinkholes and geological challenges. The state government has reached an agreement with the private consortium, CGU (a joint venture of CPB Contractors, Ghella, and UGL), which will see the consortium absorb the costs associated with completing the tunnels. This resolution aims to limit the financial impact on taxpayers.
The M6, which features twin 4km tunnels connecting Sydney's south to the road network, was initially slated for completion in 2024, a date that was subsequently revised to 2025. The project encountered significant issues in March 2024 when two large sinkholes appeared above the tunnel path, leading to a halt in works. Further complications arose in June 2025 with the discovery of a high-angle reverse fault in the bedrock near the sinkholes, prompting the consortium to cease operations.
Under the new agreement, CGU will complete the remaining 250 metres of excavation. The NSW government has emphasized that the project will proceed without additional cost to the public, with the consortium taking responsibility for rectifying the subsidence issues that originally paused the contract. This breakthrough follows reports that the government had considered abandoning the project during the protracted dispute.
Engineers suggest that methods like jet grouting, which uses high-speed fluid to solidify soil and create a stable cavity for tunnelling, may be employed to complete the remaining section. One engineer noted that such delays are often preventable with more thorough preliminary geological investigations before major infrastructure contracts are signed.