Editorial: Make Rena site safe for diving

The wreck of the ship Rena on the Astrolabe reef off the Bay of Plenty coast near Tauranga. Photo / Christine Cornege

An efficient tidying-up of the wreck offers economic benefit to the Bay of Plenty

Thirteen months after the fully laden container ship Rena hit the Astrolable Reef off Tauranga, the fate of the wreckage is up for debate.

Three options are on the table. They encompass removing the entire wreck, leaving it as it is, and removing or securing the cargo and making the site safe for recreational diving.

The decision should be relatively straightforward. For an array of practical and financial reasons, the final possibility is easily the most viable.

That is not what Maritime New Zealand has told the Rena's owners. They have been ordered to salvage all the wreck. At the moment, the second phase has begun, and the Rena's bow - all that is left above the surface - is being hacked away to a metre below the mean waterline. This is difficult and dangerous work, so much so that it is becoming apparent that removing the entire wreck would be an exercise in excessiveness.

The operation would become more and more hazardous for the salvors and technically more challenging. Equally, anchoring systems needed to keep large barge-mounted cranes in positions could inflict more damage on the reef and its marine habitat. It would also take five years, during which the exclusion zone around the ship would remain. And even then, it would not be possible to remove all the debris from the seabed.

The second option - leaving the wreck as it is after salvors finish whittling the bow back early next year - is equally problematic. It would mean nothing was done about dangerous cargo remaining on the wreck. In time, that could become a health and safety danger to divers. Some of the cargo also includes cryolite and disinfectant, which could, according to preliminary assessments, cause localised contamination, and plastic beads that could be ingested by wildlife.

Fortunately, the third alternative offers an acceptable compromise. Any cargo with potentially harmful effects would be removed or secured. This would make the site safe for diving, probably in about a year. One major plus of this option is that it would have a lesser effect on the reef and the environment. There would also be a $10 million bonus. The salvage and clean-up has cost the country about $47 million, of which $27.6 million will be recovered from the Rena's owners. That will rise to $38 million if the company gets resource consent to leave the submerged section of the wreck on the reef.

The main downside of this option is that it could lead to small amounts of debris and oil being released over a longer period. But that danger needs to be kept in perspective. The salvors did a superb job removing most of the Rena's oil. Only 10 to 20 tonnes remain on board. The initial leak was dealt with efficiently and effectively by Maritime NZ staff and thousands of volunteers when it washed ashore. The Bay of Plenty's beaches were back to their best in remarkably quick order. Any further leakage would be on a smaller scale and could be dealt with relatively simply.

The Rena is widely considered to have been this country's worst maritime environmental disaster. But it could have been much worse. Now, an efficient tidying of the wreck offers the opportunity of an economic benefit to the Bay of Plenty within a year or so. Large fish habitats have already established near the wreck, and the two mangled chunks of the ship will undoubtedly be a magnet for divers. If the right option is chosen for the wreck, tourist dollars will be one of the Rena's legacies.