The arrival of two new ‘mega ferries’ will have interisland travellers breathing a sigh of relief. But locals warn: ‘If something goes wrong here, it’s going to be carnage.’

This story was first published on Stuff. All photography by Iain McGregor.

For shoreside residents in the main channel between the Cook Strait and Picton Harbour, the wait for the Interislander’s new ‘mega ferries’ is stirring unpleasant memories of the ‘ferry wars’ of the 1990s.

They dread a repeat of the 20-year-old battle. But now, that is also coupled with new grave fears, about the risks of larger ships using the notoriously turbulent Tory Channel entrance.

“If something goes wrong here, it’s going to be carnage,” says Tim Healey, chair of the community watchdog Guardians of the Sounds. “The channel entrance is very narrow. It’s less than 400 metres wide. If you make a mistake here, there is going to be loss of life.”

At issue is the size of the new vessels, due in 2025 and 2026. At 50,000 tonnes, they can carry twice as many passengers as the current three ship fleet, 300 per cent more rail wagons and almost double the number of trucks and other vehicles.

They are nearly 40 metres longer and at least five metres wider than the current ships in the cross-Strait fleet.

Healey points to a number of accidents and near-misses in the channel, where vessels are required to make an almost 90-degree turn.

Between 2013 and 2021, there were 42 navigation safety incidents in the area.

Cruise ships were banned from entering the drowned valley through the narrow passage after the cruise liner Azamara Quest crashed into Wheki Rock, close to the entrance, in January 2016 – despite having a Port Marlborough pilot on board.

In September 2004, Interislander’s Aratere ferry nearly ran aground, with 292 people on board, in the Tory Channel due to poor bridge management and navigational practices.

The Monte Stello – on lease to Interislander from Bluebridge while the Aratere was being lengthened – stranded briefly there in 2011.

And a few months later, one of Aratere’s engines failed in the passage, with the second losing power 500m into the strait, leaving 142 passengers in darkness for 30 minutes.

More recently, the ageing fleet has been plagued with a series of breakdowns.

An incident in January, when the stricken Kaitaki drifted more than a nautical mile towards the rugged Wellington south coast in winds gusting over 100kph, raised questions about rescue capability in the waters between the North and South Islands.

“We think that the risk is too high with these larger ships,” Healey said. “It’s a very exposed coastline and there’s nowhere to run.”

Strong, fast tidal flows through the channel, which lies between Arapawa Island and the mainland, make the waters particularly dangerous.

“Depending on time of year, the cold will get you [if you were knocked off the boat] first because it’s a very cold piece of ocean,” Healey says. “If you get taken into the rocks, you’ll get smashed.

“You can’t swim against it. If you’re in the water, you’re in trouble. Really, you’ve got to hope someone can get you out.”

But in the first instance, rescue would likely come from local boaties, he says. “[There are] great big, tall, vertical waves that are really dangerous to get through, particularly in a small boat. So, if there is trouble out there, in certain conditions, there is no rescue because the little boats won’t be able to get out.

“[And] there’s no way of salvaging these boats using a big tug because there aren’t any nearby that can do it.”

A fuel spill would also be “catastrophic” to the local environment, he says.

Healey says the ferry company should consider using the wider, northern entrance into Queen Charlotte Sound, although this would add an extra hour onto crossing times.

KiwiRail, which operates Interislander, says the diesel electric hybrid ferries are designed specifically for the crossing.

The state-owned enterprise also asked a maritime consultancy firm to conduct a review. It concluded the introduction of the larger ferries posed no greater risk than that posed by smaller vessels, Ships Programme Director Massimo Soprano said.

The review, commissioned in 2019, was not made public and KiwiRail did not make it available to Stuff.

The company says it also held video-link workshops with a marine simulation centre in Brisbane in late 2021, which modelled capability and performance of the new ships in normal and adverse wind and current conditions. That included a partial or total loss of power in the channel.

“The results of the simulation also concluded that the new larger ships did not introduce any new risks to the transit of the Tory Channel,” Soprano said.

The new ferries ships would be fitted with “evacuation slides” and were designed to be capable of rescuing people from the water if another vessel ran into trouble in the area, he said. “This feature goes above and beyond standard evacuation systems and enhances overall rescue capability.’’

KiwiRail’s plan to replace its fleet of three ferries triggered a review of the maritime risk by Port Marlborough and Maritime NZ.

A report, published in 2021, identified 67 risks, including the need for better aids to navigation, limited tug availability, collision, and grounding events “which could result in catastrophic outcomes including loss of life, oil spill and the foundering and salvage of a large vessel’’.

“A related risk is also the level of regional capability able to respond adequately to such an event.”

As a result, the council implemented better tide and current, and real time wake monitoring and modelling in the channel.

Harbour master Jake Oliver has built a ship simulator for the new ferries and is working with the ferry companies on a “common passage plan” for commercial shipping.

For the first six months of operation, the new ferries will be required to use the northern entrance, the council said.

While safety is their main concern, the Guardians have other concerns about the government’s “resilience connection” project, which also includes two new terminals, at Kaiwharawhara in Wellington and at Picton.

The watchdog was formed in 2000 after new, high-speed crafts damaged beaches and waterfront properties and put bathers and boaties at risk.

After a long-running legal fight, speed restrictions were introduced aimed at limiting coastal damage from its wash.

The group also worries the “monster ferries” will dominate the tiny Picton Harbour as they berth and depart. And it is concerned about larger number of passengers and vehicles being discharged into the roads around the tiny seaside township.

The project was approved under the fast-track consenting process, introduced to limit the economic impact of the Covid-19 pandemic. That has meant limited local input, the Guardians say.

KiwiRail says it has consulted the local community extensively, including with the Guardians.

It maintains the ships are designed to generate less wake energy (that is fewer waves) than the current fleet, even though they are larger.

This was a “key design consideration” to reduce their impact on the shoreline and adhere to local council rules on wave energy, Soprano says.

In order to operate, KiwiRail must obtain a resource consent from Marlborough District Council. As part of the construction, the company first asked the council to approve its methodology for verifying compliance with wave energy regulations on the route.

Tests were then carried out on a scale model of the hull in shipyard tanks specifically designed to reproduce Cook Strait conditions, Soprano said.

”Vessels certainly have become more efficient over time, as hull designs have been improved and streamlined,” says Otago University’s Wayne Stephenson, an expert in coastal geomorphology. “Usually it’s because they’re chasing fuel efficiency rather than worrying about foreshore erosion.”

He said other factors will have an impact on the shore – including the operating speed and the frequency of crossings.

“If you reduce wave height, that’s a good thing. But it also depends on the sailing line from the shore, depth of water, how much the wave has to shoal before they break on the beach, the nature of the beach and the sediments. There are lots of variables that come into play.”

Healey fears a repeat of the 20-year-old “Stop the Wash” battle, which ended up in the Environment Court before the council implemented speed restrictions.

“We don’t know what the wash is going to be like, and no one can really tell us. They tell us these boats will have a smaller wave than the conventional ferries, but a 19,000 ton boat against 55,000 tons? We are dubious.”

The channel’s inter-tidal zone has experience three major changes in the nearly 60-year history of the Cook Strait ferries, he said.

“We’ve had sand stripped off beaches. It gets dumped over the kelp beds where all our pāua and cray live.

“The Tory Channel is very important to all us people here. It’s a food basket, to Māori in particular it has great, spiritual significance. And we just think it’s too precious to be put at risk.”