Sydney’s ‘unbuildable motorway’ to be completed after two-year delay caused by sinkholes

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 costs of finishing the tunnels, limiting the financial hit to taxpayers. Motorists will still need to wait, however, with the M6 now scheduled to open in 2028 at the earliest. The project, which consists of twin 4km tunnels connecting Sydney’s south to the wider road network, was initially approved in 2019 under the former Coalition government with an original completion date of 2024. That was later pushed back to 2025. Sinkholes and a reverse fault Tunnelling was 90% complete when two large sinkholes opened in March 2024 above the tunnel and below an industrial estate in Rockdale, throwing the project into disarray. Underground works on the tunnels linking Kogarah and Arncliffe ceased altogether in June 2025. The consortium charged with completing the M6 said it would down tools after the discovery of a “high-angle reverse fault” – where a layer of rock is forced upwards and over another layer – in the bedrock close to the sinkholes. M6 map The crisis was ventilated in May 2025, when the Sydney Morning Herald published a leaked email to staff from David Jackson, the director of the project’s first stage, stating that the joint venture was pulling out. …