Final M4-M5 breakthrough celebrated in Sydney

Roadheaders working through rock, mainly sandstone, broke through 43m below ground at the Inner West suburb of Leichhardt to connect the north and southbound tunnels for the first time. The breakthrough completes the ‘missing link’ between the new M4 tunnels at Haberfield and the M8 at St Peters.

At around 34m wide and 8m high, the 7.5km-long M4-M5 Link tunnels will be able to accommodate up to four lanes of traffic in each direction and will run at an average 35m below ground, with the deepest point at 55m. Around 8.4mt of spoil have been excavated, transported west and recycled to help build the Western Sydney International (Nancy-Bird Walton) Airport. So far, 9,000 workers and subcontractors have been employed on the tunnels.

Scheduled to open to traffic in 2023, the tunnels (with the Rozelle Interchange) form part of the New South Wales government’s WestConnex project – a 33km-long continuous motorway of which 22km is underground. The US$12.4bn project aims to make journey times across Sydney faster and easier, bypassing dozens of sets of traffic lights and allowing an uninterrupted drive from the Blue Mountains to the city.

At the peak of tunnelling, West Connex has seen a total of 28 roadheaders in operation, the largest ever seen on a single infrastructure project in the country. To date, 22km of tunnels and ramps have been excavated although some ramps remain to be completed.