Halfway Done, Now the 1,000-ton “Kathleen” Takes Over

The biggest public transportation project in Australia’s history reached a milestone as five 1,000-ton boring machines passed the halfway point in carving underground rail tunnels for the Sydney Metro.

The machines, overseen by an integrated team that includes Bechtel, are digging beneath the city’s central business district and the iconic Sydney Harbour. The final machine, a specialized mixed-shield slurry tunnel boring machine (TBM), began digging in August. Altogether, the five machines will construct 31 kilometers of new tunnels for Sydney Metro.

“It’s been a huge month for the Sydney Metro team as they surpassed the halfway point in tunneling for the City & Southwest and launched a giant borer, named Kathleen, under Sydney Harbour. Kathleen will dig at depths of up to 40 meters” said Ged Silva, Bechtel’s regional manager for Asia Pacific.

Train service on Sydney Metro started in the city’s North West (from Tallawong to Chatswood) in May, with a train running every four minutes during the peak periods.

By 2024, Sydney will have 31 metro railway stations and a 66-kilometer standalone metro railway system, revolutionizing the travel around Australia’s biggest city.

The project includes delivering 15.5-kilometer twin tunnels from Chatswood to Sydenham under the central business district and Sydney Harbour.  As Sydney Metro’s delivery management partner, Bechtel is overseeing the delivery of the tunneling contract which was awarded to John Holland CPB Ghella Joint Venture in 2017. In addition to building twin tunnels, the team is excavating space for six new stations in the heart of the city.

 Each machine is 150 meters in length – longer than two Airbus A380 aircraft – and designed to cut through sandstone, an especially hard rock that makes up the harbor. The borers operate as underground factories, digging and lining the tunnels as they go. Collectively, the machines will excavate 5.9 million tons of rock – enough to fill roughly 940 Olympic-sized swimming pools.

The excavated material from the new tunnels will be reused at another Bechtel project, the new Western Sydney Airport, where it will be used as a base for the new runway.