A fourth tunnelling site for the New M5 section of the WestConnex motorway is operating at Kingsgrove.
About 150 workers a day are on the site, adjoining the M5 East motorway, where a 135 tonne roadheader was lowered into position last week.
Altogether, about 800 workers are involved in the New M5 project, with other tunnel work sites at St Peters, Arncliffe and Bexley.
Nine kilometre twin tunnels between Kingsgrove and St Peters are due to be completed by 2020 at a cost of $4.3 billion.
Minister for WestConnex Stuart Ayres said the roadheader working at Kingsgrove would excavate a passage to the mainline tunnels and allow tunnelling to progress under the M5 East and further east towards Bexley.
Mr Ayres said, since work began late last year at St Peters, a total of almost one kilometre had been excavated across all sites.
“The twin tunnels are a key feature of the project which will run parallel to the existing M5 East and double the existing motorway corridor from two to four lanes in each direction,” he said.
Mr Ayres said each roadheader could remove about 7.5 million tonnes of spoil – enough rock to fill an Olympic sized swimming pool – each week.
“We’re pushing ahead to deliver this project with tunnelling taking place 24 hours a day, seven days a week,” he said.