Rena: Leaked oil probably from duct keel

Attempts to get the oil off the Rena after it founderd on the Astrolabe Reef are continuing. Photo / Maritime NZ

Up to 10 tonnes of oil spilled overnight from the cargo vessel Rena may never totally be recovered, says Maritime New Zealand.

Four vessels have been working since early this afternoon to corral an estimated five to 10 tonnes of oil which spilled overnight from the stranded ship.

National On Scene Commander Alex van Wijngaarden said even in good conditions it was not possible to recover all the oil.

He said the potential movement of the spilled oil was being monitored by aerial observation and trajectory modelling in the incident command centre.

Based on weather forecasts and tides, the potentially toxic substance was expected to move slowly north and would not reach any coastline before Wednesday, he said.

"That would place some of it on track for Mayor Island (Tuhua), if conditions remain as forecast.

"However, it is important to note that this is based on today's conditions and the trajectory could change. We will be monitoring its progress closely.''

The oil had likely escaped from Rena's duct keel, the tunnel running the length of the vessel housing pipework and other service equipment, said Captain van Wijngaarden.

"This overnight spillage is a combination of tidal movement _ seawater effectively plugs gaps in the duct keel but low tide exposes those gaps _ and the reducing buoyancy of the vessel as we remove oil from above the waterline.''

He said oil recovery teams on vessels at the scene had been using booms to contain the oil so it can be skimmed off the water.

Oil continues to be pumped from Rena, with options being explored for speeding up removal from the main tank.

It is hoped to have another pump in action this afternoon to remove oil from the two settling tanks, which have about 220 tonnes of oil between them.

As of yesterday afternoon, 256 tonnes of the estimated 1700 tonnes on board the ship had been pumped onto the tanker Awanuia.

Swimmers and surfers can today make the most of the water after a three kilometre stretch of beach from Mount Maunganui to Tay Street opened for public swimming.

Captain van Wijngaarden said people should still keep an eye out for oil contamination.

Hundreds of iwi members, Defence Force personnel and volunteers are continuing with beach cleaning efforts today along the coastline from Mount Maunganui to Waihau Bay.