A ground problem, not a track problem on Auckland's western train line - KiwiRail

Wednesday, 12 October 2022

KiwiRail and AT representatives talk about proposed rail closures in Auckland. (Video November 2022)

After a day of speed restrictions on Auckland’s Western Line, KiwiRail says ground subsidence is the problem, not the track structure.

Trains were still running on Wednesday, but KiwiRail teams and specialist geotechnical engineers studying a slip creating cracks in the bank below the tracks.

On Tuesday, KiwiRail said it was “urgently investigating” a subsidence issue found during a routine inspection of the line.

Subsidence is the general term used to describe the sinking of the ground because of underground material movement.

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The area on Auckland's western rail line at New Lynn where ground subsidence has raised concerns about the track, prompting speed restrictions while KiwiRail engineers continue work.

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The subsidence issue is causing issues for commuters as timetables are affected.

KiwiRail chief operating officer of Rail Operations Siva Sivapakkiam said KiwiRail teams spent Wednesday “looking at different elements of the rail infrastructure”.

“From the initial assessments, it appears the ground is the root cause of the issue, with a slip leading to cracks appearing in the bank below the rail corridor,” Sivapakkiam explained.

KiwiRail said it is investigating the ground under the track structures to work out what repairs are needed.

“In addition, a few sections of a concrete retaining wall below the rail line have moved. Slips by their very nature can be sudden events and are not unique to the rail corridor.“

Sivapakkiam said KiwiRail’s initial priority is to “establish the extent and depth of the ground movement” and what needs to be done in the short-term “to fully reopen the line safely”.

This work is expected to be complete within the next few days.

“Once the underlying condition of the ground is better understood, KiwiRail can then progress with design and planning work for a full repair,” Sivapakkiam said.

KiwiRail is “continuing to monitor the ground in the area for any movement”.

“Train services are still able to run past the site, at reduced speed on the one line that remains open,” Sivapakkiam said.

“We appreciate the disruption this causes commuters on the Western Line – but safety is crucial.”

There are two train tracks that run along the Western Line: one has been there since 1880, the other since the early 2000s.

KiwiRail was not able to confirm which track was experiencing subsidence.