Executive summary
At about 0530 on Saturday 18 September 2010, the coastal container ship Spirit of Resolution departed its berth at the port of Onehunga in Manukau Harbour and took about 1.7 hours to reach the Manukau Bar at the harbour entrance.
The sea conditions were forecast to exceed the four-metre maximum permissible observed wave height over the Bar and remain so for at least another two days. The master decided to proceed to the harbour entrance, knowing that he had the option of anchoring inside the entrance and awaiting more favourable conditions.
The signalman located on South Head above the entrance had reported to the master that the observed wave height was 3.5 to four metres and increasing, but that the Bar was still open. When the ship arrived inside the Bar, the master observed the wave conditions and began the crossing.
The crossing was uneventful for the first 20 minutes until the Spirit of Resolution was about to clear the Bar, when the wave height suddenly increased and the ship's speed over the ground dropped to almost zero. Unable to make any outward progress, the ship was carried sideways by the current out of the main channel and into shallower water. There the ship's rudder struck the sea bed and most of the rudder sheared off and was lost to the sea. The ship sustained wave damage to its bow and to a number of containers on deck. No-one was injured.
With the aid of the ship’s bow thruster, the master was able to manoeuvre the ship clear of the Bar and into deeper water, where it lay for about two days awaiting a tow. The ship was eventually towed to the port of New Plymouth and then on to Lyttelton, where it underwent permanent repair.
The Transport Accident Investigation Commission (Commission) found that there was sufficient information available to the master for him to determine that crossing the Bar when he did would risk operating the ship in wave conditions beyond what the port company had deemed safe.
Since the accident the Spirit of Resolution has been returned to its owner and the Pacifica Transport Group has stopped operating into Manukau Harbour.
The Commission considered whether more real-time information on wave heights over the Bar would have made any difference, but considered that unless the shipping using the harbour significantly increased, or more cost-effective technology for predicting and measuring wave heights is developed in future, the current information and technology available are sufficient to maintain maritime safety for Manukau Harbour. Consequently the Commission has not made any safety recommendations.
The key lesson arising from this accident is that:
- Bar harbours are notoriously hazardous for vessels of all sizes. Crossing a Bar in deteriorating sea conditions that are already at the margins of what has been deemed safe is a high-risk activity that should not be contemplated.