The opening of Perth’s Forrestfield-Airport Link will be delayed roughly a year after a leak damaged one of the project’s tunnels and created a sinkhole in September.
16 concrete rings shifted, 26 metres of tunnel was damaged, and a sinkhole formed alongside Dundas Road near Perth Airport, after a leak developed in a tunnel-to-tunnel cross passage on September 22.
Construction defects in the grout block or failure of the join between the tunnel lining and grout have been identified as potential causes for the leak.
Tunnelling through the grout block, and vibration from excavation of the cross passage, are factors which may also have contributed, the State Government has said.
Cement grouting has sealed the leaks and voids created by ring movement, and the damaged section of tunnel has been stabilised with solid temporary supports.
The state said options for a permanent repair include fixing damage from inside the tunnel, or rebuilding the impacted section of tunnel by removing the old rings and casting the new tunnel lining in-situ – either from the surface down, or from within the tunnel.
Fixing the issue and moving forward will add almost a year to the project’s timeline, the state said on Tuesday, with the Forrestfield-Airport Link now expected to open in the second half of 2021.
But transport and planning minister Rita Saffioti said the project – which is insured – is still on track to come in under budget.
“Our primary focus is safety and quality, and that is why today we have set a revised timeframe for the project,” Saffioti said.
“While the delay is unfortunate, this project is being built to last 120 years.
“I believe the time added to the construction schedule is a small price to pay to ensure we safely deliver this asset which will serve the people of WA for generations.”
The state said future cross passages will be built with new measures aimed at reducing the risk of a similar event occurring. The next cross passage construction will take place in January.
Since the incident the number of safety compliance officers has been increased from two to five, while a superintendent of tunnel operations has been appointed to provide greater oversight and focus on safety.
Once it opens, the Forrestfield-Airport Link will connect Perth Airport to the city’s urban rail network, via a rail spur from the Midland line at Bayswater.