KiwiRail said retraining has resolved issues that led to a contractor’s suspension over faulty track welding, allowing maintenance work to resume.
It was revealed that the contractor responsible for improper welding on train tracks in a Parnell tunnel over the Waitangi weekend also carried out serious defective work in a City Rail Link tunnel during the same period.
The City Rail Link welding defects were initially rated as “major”, with an incident report warning the failures could have resulted in serious or life-changing injuries and lasting environmental damage.
KiwiRail maintains there was no danger to the public, noting that no trains were operating or undergoing testing on the yet-to-open City Rail Link tracks during the period in question.
They said no passenger services were affected while the defects were addressed, with temporary fixes installed before trains returned on February 9 and permanent repairs completed later.
KiwiRail revealed the contractor delivered a significantly higher-than-normal rate of defective work, with faults identified in four of 10 welds in the CRL tunnels and eight of 28 welds in the Parnell tunnel between February 6 and 8.
In response to the unusually high failure rates, KiwiRail launched a review of all 470 welds carried out by the contractor at 14 Auckland locations since Christmas. Testing of 70 welds by mid-May found no further defects.
KiwiRail said it has continued to make progress in assessing the contractor’s work since the last update, as checks across the network continue.
Chief metro officer David Gordon said developing reliable testing methods had taken time, but he expected all remaining weld assessments to be completed in the coming months.
“This is a promising result, which points at the issue being largely limited to Waitangi Weekend work in the two tunnels,” Gordon said.
“Welds in tunnels can be more difficult compared to welds on open track, given the underground environment.”
KiwiRail said the problems stemmed from failures in the preparation, finishing and clean-up phases of flashbutt welding, a technique used to fuse rail sections into a continuous track.
Gordon said the incorrect welding process increased the likelihood of defects developing in the affected sections of track.
The contractor temporarily halted work nationwide during initial Auckland investigations and later resumed in mid-March following a training programme.
KiwiRail has not publicly identified the contractor involved, saying it remains a “trusted party” cooperating with its processes and that naming it could “unreasonably prejudice” its commercial relationships.
“Following their retraining and recertification, KiwiRail is confident that welding work can safely resume and will meet the required engineering standards,” it said.
“The contractor in question is experienced and has previously been very reliable.”
Rail Minister Winston Peters said he was satisfied with KiwiRail’s handling of the issue, noting that its response confirmed it treated the defective welds with the same seriousness as the government.
A broader engineering review is continuing, examining welding standards, contractor performance, and the speed at which defects are identified.