Rena Operational Update
From the Rena”s owner and insurers.
An underwater sonar survey following tropical storm Lusi in March has confirmed a shift in the position and condition of the Rena wreck on Astrolabe Reef.
The movement means the removal of the second part of the ship’s accommodation will not be pursued, given it is no longer expected to release flotsam. The remaining section now lies in deeper water (between -24m and -53m), beyond depths typically accessed by recreational divers, and will therefore form part of the resource consent application proposal.
Roger King of TMC Marine Consultants says: “The aft section has rotated on the stern, so it is now lying further to starboard and has been significantly weakened, presenting an even greater safety risk and technical challenge for ongoing salvage operations.
“However, the movement has helped to expose container and cargo debris that was previously difficult to access within holds four and five.
“As a consequence, Resolve Salvage and Fire is reconfiguring its large RMG 1000 barge to resume operations to further reduce the debris field, which covers the area of seabed between the bow and aft sections, and alongside the wreck to a depth of about 30 metres,” said Mr King.
A second crane will be added to the RMG 1000 for the operation, and a hydraulic grab will be used to recover debris, including parts of the ship structure weighing up to 10 tonnes.
The debris will be sorted into three categories of steel, aluminium and non-metallic refuse before transporting to shore for recycling or disposal. The operation requires additional mooring lines, and an additional large tug has been sourced to assist with the mooring process.
Once the grab can no longer recover sufficient amounts of debris effectively, divers will re-assess the state of the debris field to identify and target specific areas that require further work. This stage will involve the use of dive teams and possibly a powerful magnet.
Resolve has recently removed a 600-tonne port side piece, which is currently being recycled back in port. Divers will now survey the area underneath where the piece lay to try and locate and, if found, recover the last of the plastic bead cargo.
Recent dive surveys of the wreck and debris field have also identified an isolated patch of copper scrap about 1m2 in area, confirmed as the contents from a single container of copper originally loaded in hold six.
This container has not been located during further diver surveys and the majority of the contents are believed to remain largely contained beneath significant structural debris within hold six. Scientific expert assessments do not expect any on-going significant effect from the copper provided it remains contained. This will be the subject of an ongoing environmental monitoring programme.
Mr King added: “Resolve is going to trial a specialist underwater pump to see whether the equipment can be effectively operated in this location, and at such a depth (approx. 30m) to remove the cloves. If successful, this type of equipment may be an appropriate contingency measure, if future monitoring as part of the resource consent proposal, shows any unexpected results.