KiwiRail has leased an additional freight ferry to provide "capacity and resilience" on the Cook Strait.
The ship is called The Valentine and is currently completing technical due diligence in England, ahead of sailing to New Zealand. It is due to arrive in mid-December and Interislander crews will familiarise themselves with the ship before Valentine begins working the Cook Strait, likely later in December.
"Having another ferry will ensure capacity and provide resilience on this important link in the New Zealand supply chain," KiwiRail Group Chief Executive Greg Miller said on Friday.
"KiwiRail's role is to ensure the SH1 and main trunk rail connection between the North and South Islands stays open, and Valentine will provide us with the ability to make sure that happens during the busiest period of the year for New Zealanders taking summer holidays.
"Unfortunately, Kaiarahi requires major repairs to its gearbox after its sudden failure, and those repairs are expected to take at least until March. Our remaining two Interislander ferries, Aratere and Kaitaki, cannot serve the market alone during that period, because that would leave New Zealand's supply chain vulnerable and under capacity pressure."
KiwiRail says it has been working hard to secure a replacement ferry for the Cook Strait. It looked at 26 vessels around the world, then shortlisted six for more detailed assessment.
"The freight-only ferry will free up space for passengers and their vehicles on the other ferries, ensuring New Zealanders can travel during the summer holiday season," said Miller.
"KiwiRail is an essential service and we have worked through lockdowns to get New Zealand's freight to where it needs to go. With Valentine in place, we are able to give certainty of capacity to our customers and other New Zealand businesses, supporting them as they recover from the impacts of Covid."
Miller said the Interislander fleet is aging and more prone to breakdown.
"Old ships tend to have mechanical problems and this has been highlighted with the current mechanical issues on Aratere. While she has now resumed service, we know that disruption is bad for us and our customers," he said.
"Valentine will help mitigate the impact on freight movements across the Cook Strait, in the event of any further unexpected mechanical disruptions."