New Zealand's worst ever environmental disaster is escalating in scale as foul weather continues to batter the stricken ship Rena, halting efforts to remove the hundreds of tonnes of oil seeping from its damaged hull.
Swells of up to five metres today shifted the Rena's position on the Astrolabe Reef for a third time, causing it to list 18 degrees starboard tonight.
Yesterday the ship was listing at 11 degrees but moved to a more upright position overnight.
Early this evening Maritime New Zealand announced the ship was listing at 15 degrees.
Officials now estimate about 350 tonnes of heavy fuel oil has leaked from the ship, but they have been unable to pinpoint exactly which part of the damaged vessel it is coming from.
Environment Minister Nick Smith today said the spill was New Zealand's worst ever maritime environmental disaster.
Oil has washed ashore as far away as Waihi Beach, north of Tauranga, and the amount of oil reaching the coast is expected to increase significantly tomorrow.
Efforts to pump oil off the ship were halted today while the pumping barge Awanuia underwent repairs at Tauranga Port after suffering damage last night.
The barge was now in working order but salvage crews were unlikely to be able return to the Rena until Thursday, with the weather expected to worsen tomorrow.
The oil has been washing up in thick, black clumps due to its high viscosity.
A Maritime New Zealand spokesman today said the ship had been carrying about 1700 tonnes of HFO 380 fuel oil - a "very heavy fuel oil with high viscosity''.
"It's made of residues and the longer it is in the water, the thicker and tarrier it gets as the diesel evaporates,'' he said.
"The oil itself basically has the texture of Marmite in its normal state, and you have to heat it up to be able to use it.''
The high viscosity had limited the impact of the Corexit 9500 dispersant that was tested on the oil after the ship ran aground on Wednesday.
"You get some effect as long as the oil is fresh just out of the ship, but three or four hours in the water and it's jut become tarry basically, and so dispersants aren't going to work,'' the spokesman said.
"If you're going to get it, you have to get it quick.''
Maritime New Zealand salvage unit manager Bruce Anderson said more oil was released when the vessel moved on the reef this morning, but it was unclear where from.
The oil may be leaking from the Rena's ship-length duct keel or from an aft tank, but this would not be known until the ship had been resurveyed'
It was thought only one tank containing 175 tonnes of oil had a breach in it.
Mr Anderson said there were no signs of deformation of the ship, which would be the first sign the vessel was under stress.
"The vessel is actually in quite good condition considering that it's on top of the reef and being bashed around by this swell.''
Naval architects on board were keeping a close eye on the situation.
The vessel's crew this morning made a precautionary mayday call as the weather worsened, before being evacuated from the ship by the navy.
A 22-year-old navy rating suffered moderate back injuries as he helped a crew member off the ship.
The crew sealed all the fuel tanks and turned off the vessel's power before evacuating so the oil would return to its normal state, rather than flowing freely.
Mr Anderson said salvage crew would return as soon as the weather allowed.
Once on board they would start to reheat the fuel tanks and vent out accumulated gases before pumping the oil off, which was unlikely to take place until late Thursday.
A 250-strong team including 100 Defence Force personnel would tomorrow scour beaches to clean up the oil.
A public health warning was in place and people have been asked to keep off beaches and not to touch the toxic oil or attempt to clean it up.
The oil was drifting in a southwesterly direction and was expected to come ashore between Mt Maunganui to Maketu.
Some 53 birds have been found dead so far, with 17 live birds being treated.
Teams from Matakana Island to Maketu were scouring the area for more oiled wildlife.
