Rena’s buckling has got worse, the cofferdam system has been destroyed and the salvage team is concerned existing cracks in the hull could spread higher up on the stricken vessel.
But Maritime New Zealand salvage unit manager Bruce Anderson said the salvage team was continuing to work onboard and making good progress.
Mr Anderson said the salvage crews working on the pumping system discovered the coffer dam or water-tight barrier under construction to gain access to the submerged starboard fuel tank was destroyed in the heavy weather conditions after they left the vessel.
“Given the amount of time it would take to rebuild it, they have decided to focus their efforts on hot tapping,” he said.
The cofferdam was installed to enable salvors to gain access to the number 5 starboard tank, which holds 358 tonnes of heavy fuel oil and is still under water.
To hot tap this tank, a flange is bolted to the deck of the flooded passageway and a hole is cut into the tank through the flange, and water pumped in to raise the oil to the top so it can be pumped out.
Mr Anderson said the salvage team had set up two hot taps and was now pumping water into the starboard tank.
While this was a slower method of recovery, possibly two tonnes an hour, it was the best option available. Meanwhile another salvage team was continuing to pump the lube and hydraulic oils and other muck in the engine room into a centralised tank. Divers surveying the buckling also confirmed it had worsened and the concern was that the existing cracks in the hull may spread higher up on the ship, he said.
Mr Anderson said if further cracking did occur it could develop quite quickly but the salvage team would continue to work on board while it was safe to do so.
Despite these setbacks Mr Anderson said Svitzer has been looking ahead to the next phase of the salvage operation. The crane barge ST60 – which would be used to remove containers from the ship – was on the scene and would begin undertaking seas trials.
A long ocean-going barge with a large crane onboard would also join the salvage operation. It is expected to arrive in Tauranga from Singapore in about 29 days. The barge would bring with it more salvage equipment which would enable the salvors to gain access to the inside of the hold to remove containers underwater, he said.
Salvors would be here for the long haul, said Mr Anderson.