NSW Government Reaches Deal to Resume New M6 Motorway Tunnelling in Sydney’s South

The New South Wales (NSW) government reached an agreement with contractors on June 19, 2026, to resume tunnelling for the M6 motorway in southern Sydney. The project had been suspended for two years after sinkholes appeared at the construction site, halting work on the critical southern road link.

The deal ends a prolonged stalemate between the state government and the construction firms tasked with boring the tunnels. According to government reports, the resumption follows a comprehensive review of the site’s geological stability and the implementation of new safety protocols to prevent further ground subsidence.

Why was the M6 motorway project halted?

Tunnelling operations stopped two years ago when sinkholes emerged at the project site in Sydney’s south. These ground failures created immediate safety risks for workers and threatened the integrity of surface-level infrastructure. The NSW government suspended the project to determine why the soil had collapsed and to assess whether the original engineering plans were sufficient for the local terrain.

The appearance of sinkholes typically indicates a failure in the tunnel boring machine’s ability to maintain pressure at the tunnel face or an unexpected encounter with unstable geological pockets. In this case, the project remained dormant while engineers developed a remediation strategy to stabilize the affected areas and reinforce the tunnel lining.

What are the terms of the resumption deal?

The agreement between the NSW government and the contractors focuses on the safe restart of boring operations. While the specific financial terms of the settlement were not disclosed in the announcement, the deal establishes a framework for shared risk management regarding future ground instability.

The contractors have agreed to updated monitoring requirements, which include more frequent geological surveying ahead of the tunnel boring machine. The government has mandated these measures to ensure that any signs of soil instability are detected before they result in surface sinkholes.

How will the M6 motorway affect Sydney traffic?

The M6 motorway is designed to alleviate congestion in Sydney’s southern suburbs by providing a more direct route for commuters and freight. According to Transport for NSW, the motorway will connect the existing M5 motorway with the Princes Highway, reducing the reliance on local arterial roads that currently handle heavy traffic volumes.

The project is part of a broader state strategy to expand the city’s motorway network, mirroring the goals of the WestConnex and NorthConnex projects. By moving long-distance traffic underground, the government aims to reduce travel times and lower emissions caused by idling vehicles on surface streets.

What are the risks of tunnelling in southern Sydney?

The Sydney Basin contains varied geological layers, including Hawkesbury sandstone and Ashfield shale, which can react differently to tunnelling pressures. According to engineering standards used in previous Sydney tunnel projects, the transition between these rock types often creates zones of weakness where water ingress or soil collapse can occur.

The two-year delay on the M6 highlights the contrast between the project’s original timeline and the practical challenges of urban boring. While the project was initially framed as a streamlined expansion of the road network, the sinkholes forced a shift toward a more cautious, monitoring-heavy approach.

The resumption of work marks a return to the project’s primary objective: creating a high-capacity link that bypasses residential areas. However, the government has indicated that the timeline for completion will be pushed back to account for the two-year hiatus and the slower pace of the new, safety-focused boring process.

Transport for NSW has not yet released a revised completion date for the M6 motorway, but officials stated that the priority remains the stability of the ground and the safety of the surrounding southern Sydney community.