Sydney M6 motorway resumes after sinkhole delays halt two-year project standstill
Consensus Summary
Tunnelling for Sydney’s M6 motorway, a $3.1 billion project linking Arncliffe and Kogarah, will resume after a two-year halt caused by sinkholes and geological instability in early 2024. The NSW government and the private consortium CGU (CPB Contractors, Ghella, UGL) reached an agreement where contractors will complete the remaining 250 metres of excavation at no extra cost to taxpayers, absorbing legal claims related to the sinkholes. Work was paused after two subsidence events in March 2024 exposed a high-angle reverse fault, with underground works ceasing entirely by June 2025. The project’s completion date has slipped from 2024 to 2028, and ground stabilisation methods like jet grouting will be used to address unstable rock. Critics argue the delays stem from insufficient preliminary geological surveys, while officials emphasize the contract’s dispute resolution processes will ensure completion under the original terms.
✓ Verified by 2+ sources
Key details reported by multiple sources:
- Tunnelling for the M6 motorway in Sydney’s south will resume after a two-year halt caused by sinkholes and collapses in early 2024.
- The NSW government reached a deal with the M6 Stage 1 consortium (CGU, led by CPB Contractors) to resume work at no additional cost to taxpayers.
- About 250 metres of excavation of the main tunnel remain unfinished, with the project originally budgeted at $3.1 billion (later adjusted to $2.55 billion for completion).
- The M6 project, linking Arncliffe with Kogarah via 4km twin tunnels, was initially approved in 2019 with an original completion date of 2024, later pushed back to 2025, and now delayed until 2028.
- Two subsidence events in March 2024 halted tunnelling, with underground works ceasing entirely by June 2025.
- The consortium (CGU) agreed not to pursue contractual claims against the NSW government for costs related to the 2024 sinkholes.
- Roads Minister Jenny Aitchison stated work would begin immediately, with ground stabilisation and advanced design work for the final tunnel sections to follow.
- The project was dubbed the 'unbuildable motorway' due to geological challenges, including a 'high-angle reverse fault' discovered near the sinkholes.
Points of Difference
Details reported by only one source:
- Fire and Rescue NSW supplied the image of the sinkhole at West Botany Street in Rockdale.
- The original contract sum for completion is $2.55 billion, with no change to the budget.
- NSW Motorways CEO Camilla Drover confirmed viable technical solutions exist to complete the project, with ground stabilisation starting soon.
- The agreement includes a dispute resolution process under the original contract, running in parallel with construction.
- The consortium (CPB, Ghella, UGL) was reportedly considering abandoning the project in May 2025, as revealed by a leaked email from David Jackson, director of M6 Stage 1.
- Jet grouting (high-speed fluid erosion and grout filling) is the proposed method to solidify remaining unstable rock for the final 250 metres.
- Grahame Campbell, a former M4 project manager, criticized the lack of preliminary geological work as the root cause of delays and cost overruns.
- The NSW government reportedly explored abandoning the project during the standoff, per Transport for NSW secretary Josh Murray’s statement.
Contradictions
Conflicting information between sources:
- The ABC states the original budget was $3.1 billion, while the Guardian clarifies the completion cost is now $2.55 billion (likely a revised figure).
- The ABC does not mention the 'unbuildable motorway' nickname, while the Guardian explicitly uses it to describe the project.
- The Guardian references a leaked email from David Jackson in May 2025 stating the consortium would 'pull out,' but the ABC does not cite this email or the exact timeline of the consortium’s withdrawal threat.
Source Articles
Work on Sydney motorway to resume after sinkholes halted project
Tunnelling for a new motorway in Sydney's south will recommence after collapses and sinkholes halted the project more than two years ago.
Sydney’s ‘unbuildable motorway’ to be completed after two-year delay caused by sinkholes
State government and consortium strike deal to complete M6’s twin tunnels with minister insisting there is ‘no extra cost to NSW taxpayers’ Get our breaking news email , free app or daily news podcast Tunnelling on Sydney’s $3.1bn M6 project, dubbed the potentially “ unbuildable motorway ”, will resume after the state government struck a deal with contractors, ending a two-year stalemate during which works were halted. Under the terms of the new agreement, the private consortium will absorb the