The Rena has more mess in store for the Bay of Plenty, with locals being warned the wrecked container ship could release more oil, hazardous chemicals and container debris.
Residents were yesterday given an overview of the possible risks surrounding each of the three options being investigated to deal with the vessel, lying in two mangled chunks on the Astrolabe Reef off the Tauranga coast.
A preliminary assessment found the "baseline" option - removing the entire wreck - would inflict more damage on the reef and its marine habitat from anchoring systems needed to keep large barge-mounted cranes in position.
It would also mean the mass release of any remaining contaminants and debris, along with 10 to 20 tonnes of oil still on board, a "high risk" of invasive species carried over from foreign vessels, disruption to the migration of dolphins and whales, a "moderate" potential for the death or injury of salvors and the exclusion zone surrounding the ship staying in place for five years.
The two other options are leaving the wreck largely as it is, considered highly unlikely, or removing or containing the Rena's cargo and making the site safe for a potential dive site.
This option was expected to have a lesser effect on the reef and environment, but could lead to small amounts of debris and oil being released over a longer period of time.
The report also highlighted the dangers of some remaining cargo, including cryolite and disinfectant that could cause "localised contamination", and plastic beads that could be ingested by wildlife.
It comes as court documents released last week stated harmful substances or contaminants had escaped into the ocean every day since the grounding.
Of the 32 containers that were on board and known to be carrying dangerous goods, 10 had been recovered, seven had been lost at sea and 25 remained around the reef.
A dive survey now under way aimed to identify the contents of the containers - a job that wouldn't be easy, said Captain John Owen, senior claims manager for insurers The Swedish Club.
"It's like a box of kids' Lego down there at the moment," he said.
"We are trying to find what's there, how much is left and what hazards it might present, in terms of future works, or what it means for the longer-term environmental impact."
While there were no fixed timeframes around the options, Mr Owen said the "extreme case" would be a five-year removal job, compared with a swifter operation to tidy up the wreck.
"I would like to see, given the progress we've made in the last year, that we could be in a position within 12 months of being comfortable that the wreck is safe, environmentally acceptable, and that the cultural, social and economic issues had been dealt with."
The cost of the salvage - currently the world's second most expensive - had now reached $235 million, with the most challenging and expensive parts still to come.
Mr Owen would not speculate on what the final bill might be, but said there was no mandate to keep costs below a certain level.
"We will fulfil obligations according to New Zealand law ... and that's why we want to have this engagement project. There is no edict above me that it's got to cost 'x' and not a penny more."
All assessments are due for completion by the end of the year, followed by a second round of consultation.
Remove the entire wreck
Would be technically challenging, cause further damage to Astrolabe Reef and may prove too dangerous and impracticable. Could take up to five years and even then it would not be possible to remove all debris from the seabed.
Leave the wreck as is
This would be done after salvors finish whittling the bow to 1m below the low-tide mark early next year. Unlikely as would not deal with dangerous cargo on the wreck, which could become a health and safety hazard to wreck divers.
Remove or contain cargo, make site safe
After bow is reduced, any cargo with potential adverse effects would be removed or secured. Once the wreck is made safe for recreational diving, the stern section would also be left in place.