The bulk carrier DL Marigold was ordered from both New Zealand and Fijian waters earlier this month for being an invasive species threat. The vessel’s hull is now being cleaned by a team of divers from New Zealand in international waters off Fiji.
“Offshore locations are not ideal,” says Dr Rob Hilliard, biofouling consultant and principle at Intermarine Consulting. “Presumably it was considered the best option in this case by DL Marigold's operators given its cargo constraints and distance to alternative ports where the fouling poses a lower, acceptable biosecurity threat.”
High seas hull cleaning for biosecurity purposes is costly and prone to delays, says Hilliard. Mobilizing and progress can be slowed by a range of logistics, safety and efficiency issues including:
* securing a fit-for-purpose diving platform for remote deep sea operations
* mobilizing time to prepare and load the diving, cleaning and treatment spreads, including sufficient spares for remote work
* the additional fuel, victualling and voyaging time to reach and remain on location
* managing operations beside an unanchorable ship (including DP vessels because spinning propellers pose unacceptable risks to divers and their umbilicals)
* altering surge conditions within the effective lee, as shifting winds, wave climate and currents continuously interact with the vessel's drift behavior (wind vaning, roll, yaw)
“Even in anchorages, water forces alongside hulls can readily exceed diver, brush kart and ROV capability,” says Hilliard.
“Speed of any high seas cleaning is at the mercy of wind and waves, as well as being governed by ship niche complexity (sea chest interiors, thruster tunnel, rope guards, rudder pintle aperture etc) versus the suitability of the diving team's platform, experience and equipment that was mobilized,” says Hilliard.
New Zealand authorities ordered the Panama-registered DL Marigold to leave after its divers discovered dense fouling of barnacles and tube worms on the ship's hull.
It was the first time an international ship has been ordered to leave a New Zealand port because of biofouling. From May next year, new rules will require all international vessels arriving in New Zealand to have a clean hull. During the interim period, the nation’s Ministry for Primary Industries can take action in cases of severe biofouling.
The DL Marigold arrived in Tauranga, New Zealand, from Indonesia on March 4 to unload palm kernel, and would have been in New Zealand waters for nine days. On being ordered to leave, the vessel was sailed to Fiji for hull cleaning. However, Fiji's Biosecurity Authority released a statement saying it would also refuse entry to the DL Marigold, citing similar concerns that the ship could introduce invasive species into its waters.
Meanwhile, New Zealand has released an explanatory pamphlet for ship agents and operators, outlining their interim policy before the new regulations enter into force. The pamphlet is available here.