THE State Government has confirmed the Forrestfield-Airport Link project has been delayed with the first trains not expected to run on the line until the second half of 2021.
Construction was slated to be completed in late 2020.
Transport Minister Rita Saffioti said the project budget remains unchanged.
Ms Saffioti today announced the project was continuing to move forward, with significant progress made on the project and rectification measures identified for a damaged 26 metre section of one tunnel.
The project has been plagued by problems including a sink hole on Dundas Road and concerns over worker safety.
On September 22, a leak developed in the tunnel-to-tunnel cross passage 200 metres north of the Forrestfield Station site.
This led to movement in 16 concrete rings and damage to a 26 metre section of one tunnel, and a sinkhole alongside Dundas Road.
Investigations have indicated a number of potential causes, including construction defects in the grout block or failure of the join between the tunnel lining and grout. Tunnelling through the grout block and/or vibration from excavation of the cross passage may also have contributed.
New measures will be put in place for the construction of the next cross passage in January to reduce the risk of a similar event occurring.
The 26 metre damaged section of Tunnel 1 has been stabilised with solid temporary supports and cement grouting to seal the leaks and the voids created by ring movement.
Options for a permanent repair include fixing the 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 solution will be required to achieve the tunnel life of 120 years.
Stabilisation of the ground around Dundas Road is also ongoing, with two traffic lanes to be opened later this month while compaction works continue.
Ms Saffioti has repeatedly stressed the importance of safety on the worksite.
The Public Transport Authority has conducted 658 safety walks, 430 safety compliance inspections and 72 targeted process inspections during 2018.
A rolling roster of safety staff also monitor site safety day and night.
Meanwhile, WorkSafe has inspected the site 35 times, and unions close to 300 times.
“This Forrestfield-Airport Link is the biggest tunnelling project ever conducted in the Perth metropolitan area,” she said.
“The two tunnel boring machines are now halfway through their journey, and only recently finished digging under the runways at Perth Airport.
“This is a massive milestone, considering tunnelling under an operating airport has only ever been done a few times across the world.
“Our primary focus is on safety and quality, and that is why today we have set a revised timeframe for the project. It is also to make sure we inform the public of the proposed timeframe as soon as practicable.
“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.”