Jamie Morton

Jamie Morton is science reporter at the NZ Herald.

Rena: Salvors battle above and below waterline

It's a little over 500 days since the grounding of the MV Rena caused our worst maritime environmental disaster and one of the biggest engineering headaches in the history of ship salvage. Reporter Jamie Morton and photographer Alan Gibson visit what's left of the ship.

A workman is using a cutting torch on the wreck of the MV Rena. Photo / Alan Gibson
A workman is using a cutting torch on the wreck of the MV Rena. Photo / Alan Gibson

A workman uses a cutting torch to dismantle what remains of the wreck of the Rena on the Astrolabe Reef in the Bay of Plenty.

The last visible part of the Rena's carcass juts out just above the water, as 1.5m swells gently lap its sides.

A lone salvor standing precariously atop a 15-tonne piece of metal is hard to make out against the bow's jagged silhouette.

After hours keeping his footing, the constant swaying must be taking its toll on his legs - yet today is a good day for stripping back the cargo ship that has made an unwelcome home on the Astrolabe Reef off the Bay of Plenty coast.

What has been the seaborne workplace of salvors is shrinking each day they hack more of it off - their results being the piles of reddish-brown chunks of metal being ferried from the wreck site by barge and into the Port of Tauranga.

The job of whittling the bow to a metre below the tideline has been continuing steadily, while the battle beneath the waves - cleaning up a messy ocean floor - is also making progress.

Even to the world's leading experts in what stands as one of the most extreme forms of engineering, dealing with the Rena has demanded incredible feats.

If there ever was a horror story written just for maritime salvors, Resolve Salvage and Fire salvage master Frank Leckey told the Herald, it would be about a cargo ship named the MV Rena.

"If you were going to put it on a scale of difficulty, this would definitely be in the top 10."

Each chapter has come with its own nightmare - oil in desperate need of removal despite submerged tanks and Marmite-like consistency, stacks of reeking containers having to be plucked away by cranes like pick-up-sticks and yanked from mangled holds.

And with the ship's constant deterioration since it slammed into the reef early on October 5, 2011, the job of cleaning up the mess has only become more expensive, complex and dangerous.

First, salvors had to lug heavy pumping equipment around a slippery and steeply listing deck to clear 1300 tonnes of heavy fuel oil.

Divers were eventually forced to swim through the ship's flooded holds in pitch-black darkness to help build airtight tunnels allowing access to the last of the oil.

Next, towers of shipping containers, some filled with rotting food that pushed air pollution on the deck to potentially dangerous levels, began to be offloaded.

A few months later, in January last year, dozens spilled into the ocean, spewing their contents into the water, when the Rena was ripped in half amid a heavy storm.

All the containers that could be removed have been, including some which had to be yanked from mangled holds below decks.

United States-based Resolve Salvage and Fire swapped places with Svitzer for the current third phase and fourth phases.

Mountains of steel have been cut away and taken back to land, first in hundreds of flights by helicopters using the kind of fuel that costs $100 a litre and now by barge.

By yesterday, about 560 tonnes of debris from the ocean floor had been removed - up to 1500 tonnes is thought to be down there - while 300 tonnes remained to be stripped from the bow.

It is little wonder the project has now cost the ship's insurers more than $275 million - making it the third most expensive salvage in history behind that of the huge cruise liner Costa Concordia, which smashed into a reef off the Italian island of Giglio last year, and the Exxon Valdez oil tanker disaster in Alaska in 1989.

Captain John Owen of insurers The Swedish Club said New Zealand's remote location had meant specialist equipment and vessels had to come from much further away.

Underwater, the Rena now looked like a Christmas cracker pulled apart, he said, with a mass of metal strewn across around 10,000 square metres of sea floor.

Mr Leckey expects cleaning up the debris will take a few months longer to complete.

If it was safe enough, he said, divers went down to cut the larger pieces apart, before they were lifted out using either a crane, a heavy-duty hydraulic grapple or a magnet that could pull up to five tonnes.

Conditions above water could change at any moment, but below, it could be far more dangerous.

"The swell, when it comes through, it's like a washing machine down there," Mr Leckey said.

"If you went and stood on the reef and there's a two-metre swell coming, and you went to try to stand there, well, imagine trying to stand when a large wave hits you on the beach.

"So when the divers are inside the compartments and you have all that water coming in with the swell, it can be very difficult to work in."

If the rest of the Rena is to be "made safe" and left on the reef, he said, a detailed plan would be tailored, and work would last months longer.

Already, the owners plan to remove as much remaining cargo as possible, remove or close off hazards to divers and place warning signs around the wreck.

Roger King, a master mariner with Technical Marine Consultants, said it was unlikely there were any remaining containers still intact in the water.

"We can safely say that if the power of the ocean can break a ship in half, it's sufficient to rip containers open and disgorge their contents."

Early results released last month showed that of 36 remaining containers in the stern section carrying known contaminants, many had broken up and their contents escaped since the vessel broke in two.

Three containers, with cargo intact, were recovered, four were retrieved but were empty and seven were recovered in pieces.

The contents of the remaining 22 were presumed lost, and sediment samples had shown heightened levels of copper and polyaromatic hydrocarbons.

Substances in the water included cryolite, a byproduct of the aluminium smelting process, ferrosilicon, potassium nitrate and trichloroisocyanuric acid.

Captain Owen said environmental sampling would continue as the clean-up progressed and, with pieces of steel being picked up after sitting in the water for months, there would be localised disturbance.

Rena Recovery manager Catherine Taylor said there was still much work to be done to determine the significance of the contamination and its environmental impact.

Scientists were developing a sampling protocol, involving mapping GPS grid references, so they could be certain they were returning to the same site in the future to assess any changes.

The salvage

* $275m spent on the project so far
* 10,000sq m of sea floor where debris is being removed
* 560 tonnes of debris collected so far
* $27.6m settlement covering government costs
* $27m compensation fund set up in London for claims
* 60 salvors involved in current phase
* 2 other salvage jobs thought bigger - the Costa Concordia and Exxon Valdez.

- NZ Herald

Your views

© Copyright 2014, APN New Zealand Limited

Assembled by: (static) on red akl_a1 at 26 Jul 2014 03:27:29 Processing Time: 448ms