Maritime experts have found the ageing Interislander fleet is in better condition than first thought. No systemic problems are preventing the three ferries from operating until 2029, but it will cost more money to extend their working lives.

The Maritime Union of New Zealand is treating the findings with caution - pointing to several failures on board Interislander ferries in the past 18 months including the recent Aratere grounding.

KiwiRail has been under intense scrutiny in recent months after its plan to replace its ageing ferry fleet with two mega ferries was left dead in the water. The Government refused to fund a cost blowout of $1.47 billion for the portside infrastructure needed to support the larger ships.

After the contract to build the mega ferries was officially cancelled in February, maritime experts Den Norske Veritas (DNV) were brought in to understand what was required to extend the life of the existing fleet until a new plan was in place. The Government has yet to announce that plan.

The Herald has obtained a summary of DNV’s reports under the Official Information Act.

The documents revealed the existing fleet was in a better state than first thought.

“There are no systemic issues that will prevent the Interislander fleet safely and reliably operating until 2029”, the summary said.

The extensive list of caveats to this statement included regular ongoing preventative and corrective maintenance, necessary upgrades and replacement of equipment, all relevant Class and Statutory surveys being carried out, and the vessels continuing to hold valid certificates.

The fatigue age of the Interislander fleet’s steel hulls was less than a quarter of the actual age of the ships, meaning they were in good condition.

This was because the ferries do not sail in very heavy seas to avoid discomfort to passengers and livestock, the documents said.

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“This has reduced each vessel’s exposure to extreme waves that could have accelerated hull fatigue.”

Interislander viewed this as “extremely positive” because it would help reduce the cost of extending the life of the fleet.

However, DNV warned that although machinery on board the ships had been well maintained, many systems were old and increasingly obsolete, making it difficult to source parts for repairs.

Interislander executive general manager Duncan says KiwiRail will update its asset management plans as a result of the new information. Photo / Tim Cuff

Interislander executive general manager Duncan Roy said the findings meant KiwiRail could continue delivering reliable services for passengers and freight customers until the new ferries were built.

It would be a balancing act, Roy said.

“Obsolete systems are operationally safe but are more difficult to repair if there are issues. Some equipment is no longer manufactured and replacing obsolete systems is a larger undertaking than maintenance, and will come at an additional cost.”

KiwiRail will update its asset management plans in light of the new information and request more money to keep up with maintenance costs.

“To ensure a high level of maintenance, Interislander is proposing to spend, on average, close to $36 million dollars each year between 2025 and 2029,″ Roy said.

“It compares with an average of $29 million being spent on the three ships each year between 2019 and 2024.”

If KiwiRail’s annual maintenance cost for the ferries is $36m for the next five financial years, that would amount to $180m.

The extra money will be subject to the annual approval of KiwiRail’s board.

Some of the upgrades required in coming years will depend on the Government’s decision about replacement ferries and when these are expected to arrive, Roy said.

Maritime Union of New Zealand national secretary Carl Findlay said keeping the current vessels running until the end of the decade was a stop-gap measure at best.

“There have been a number of technical issues with the ferries already, some with potentially very serious outcomes, and the fact remains that there are many ageing systems and components in service on the ferries.”

KiwiRail has been put in an impossible position, Findlay said.

“KiwiRail doesn’t really have any choice but to soldier on with end-of-life vessels and push up maintenance costs and maintenance time for the ships.”

KiwiRail has previously increased its routine maintenance, resulting in a 3% reduction in sailings while the ships are out of service. It has also established a dedicated technical team to oversee maintenance and operational risk management.

What condition are the three ferries in?

Kaitaki

• - “Good to fair” condition, in general.
• - Some areas of corrosion in tanks and hull.
• - Several hull fatigue cracks in the superstructure. None have a significant impact on the structural integrity of the ship.
• - The corrosion and cracks will be addressed in the next dry dock, scheduled for August 2024.
• - Some obsolescence of systems, particularly the bridge radar. An enhanced inspection regime is in place.

Kaiarahi

• - “Good to fair” condition, in general.
• - There are some areas of corrosion in tanks and the hull.
• - A high number of machinery and systems were assessed as being in “fair” condition.
• - A higher number of systems facing obsolescence – including bridge systems, communications systems and engine control and monitoring systems.
• - The engine control and monitoring system were upgraded in June 2024 while the ferry was in wet dock. An enhanced inspection regime is in place around the bridge and communications systems.

Aratere

• - “Good” condition, in general.
• - Some areas of corrosion in the secondary structure.
• - Minor cracks in the rail deck transition points. These have now been repaired.
• - Some systems are facing obsolescence including propulsion management, bridge and stabiliser systems.
• - An enhanced inspection regime is in place for the bridge systems and is part of KiwiRail’s obsolescence planning.

Georgina Campbell is a Wellington-based reporter who has a particular interest in local government, transport and seismic issues. She joined the Herald in 2019 after working as a broadcast journalist.