A number of failures by a steel company in its cargo loading procedures led to a large ship listing dangerously to one side, an investigation into the incident has found.
No-one was injured when the Taharoa Express twisted to an angle of 9 degrees as it was being loaded on December 16, 2009.
An investigation into the incident found the company, New Zealand Steel Limited, had not carried out enough research into its ironsand cargo, that crew did not follow proper procedures while loading it, and the first mate was tired.
The cargo ship had arrived at Port Taharoa, south of Raglan, on December 15 to load up with around 116,000 tonnes of ironsand for delivery to China.
The ship had been modified to load ironsand in the form of a slurry - mixed with fresh water and pumped onto the ship via pipelines on the seabed.
However, management of the Taharoa Express had recently changed, and it was the new crew's first time carrying out the cargo loading operation at the port.
The crew was around halfway through the procedure when ``suddenly and without warning'' the ironsand in several cargo holds shifted and the ship listed to an angle of 5 degrees.
Operations were stopped, but by the time the pipelines had been cleared of the slurry mixture, the vessel had listed to an angle of 9 degrees.
An investigation by the Transport Accident Investigation Commission (TAIC) found that the most likely reason for the shift was the ironsand ``being allowed to mound towards one side of the cargo hold's centreline, instead of being evenly distributed across the holds''.
It found three safety issues had contributed to the mistake, including NZ Steel ``not undertaking sufficient research'' on the properties of ironsand and how it behaved in slurry form; the crew did not follow procedures and industry best practice while distributing the ironsand across each cargo hold; and help provided to the new crew to manage its first cargo loading operation was ``not used to best effect, which resulted in the first mate becoming fatigued''.
However, the TAIC did not make any safety recommendations as it said NZ Steel had since addressed the first issue, and the second two had been solved by taking the Taharoa Express out of service and replacing it with a new, special purpose bulk carrier with different loading procedures.