Sydney metro tunnels: Exclusive first look inside new harbour route

Crews have completed the sealing of the twin Sydney Metro tunnels located 40m beneath the harbour. The Saturday Telegraph was given an exclusive tour of the tunnels.

Under the seabed of Sydney Harbour, the lights have been turned on.

Seven months after mega-boring machine Kathleen punched through the second of the two 884m long tunnels for the future Sydney metro, crews have completed the sealing of the parallel corridors.

Described as one of greatest engineering feats since the building of the Harbour Bridge, the concrete-encased tunnels have now been handed over to the next team of engineers for the laying of railway tracks and signalling.

The Friday handover represents a significant milestone in the Sydney Metro City & Southwest project given the tunnels posed the greatest engineering challenges of the line, which will eventually connect Chatswood to central Sydney and Bankstown.

While the total cost of the multi-billion dollar project is likely to be over budget, Sydney Metro says it will be delivered on time.

Project engineer Cassandra Shard and site engineer Hannah Truong in the new Sydney Metro tunnels at Barangaroo. Picture: Tim Hunter

To mark the handover, The Saturday Telegraph was given an exclusive tour of the tunnels with the engineers who worked on the project.

Sydney Metro Barangaroo Tunnels project manager Abdalah El Sayed, who has had a hand in most of the major state government rail infrastructure projects since starting his career on the Lane Cove Tunnel, said he felt proud and relieved the job had been done.

“You have to be on your game to deliver something like this,” he said.

“I hope Sydney is happy with the product.”

Unlike land-based projects, workers on the 884m long tunnels had to undergo training in a hyperbaric chamber where the conditions 40m beneath harbour were simulated “as a precaution” with doctors on standby.

Once boring was completed, four emergency cross tunnel passages about 180m apart were dug out to allow for staff to move between metro trains.

Tunnel boring machine Kathleen hard at work in 2019.

Site engineer Hannah Troung, who was responsible for the construction of the emergency cross passages, said working on a site surrounded by water meant planning for every scenario was critical.

Before the passages were sealed, high-grade cement was injected into sandstone to stop water seeping through the bedrock.

“We already knew what the challenges would be and had planned for them,” she said.

Now sealed, the tunnels have been handed over to the next team of contractors who will work on the tracks and the driverless signalling technology which will run a metro train every four minutes in the peak in each direction. It can be revealed the first tracks will be laid next month near Chatswood.

Train testing is scheduled to take place before the start of services in 2024.

Inside one of the new tunnels located 40m beneath the harbour. Picture: Tim Hunter

Once operational, it will take less than two minutes for a train to run from Victoria Cross Station at North Sydney to Barangaroo Station.

Project engineer Cassandra Shard, who has also worked with Mr El Sayed on other transport projects around Sydney, said around one quarter of the engineers in her team were women.

“It’s such an iconic project,” she said.

Walking through the tunnels last week, Mr El Sayed joked how they resembled the “Deathstar” on Star Wars with nothing much but concrete and lights.

With openings at either end equalising the air pressure, there is no sense of being underground beneath a large body of water.

Adjoining the tunnels is an enormous “crossover” cavern likened in size to a “50-storey building on its side” where works are continuing on what will eventually become a space where metro trains can change tracks or be pulled off for maintenance without disrupting the network.

Having worked on many of the significant transport infrastructure projects around Sydney, Mr El Sayed said the tunnels would hopefully one day be regarded as iconic as the Sydney Harbour Bridge.

“We finished it despite the pandemic,” he said.

Originally published as Sydney metro tunnels: Exclusive first look inside new harbour route