Salvors of the wreck of the Rena are unable to say how long the clean-up will last because of the vagaries of the weather.
A remote-controlled grab, a giant magnet and divers were continuing the three-phase operation to clean the debris field to a depth of 35 metres.
The massive task was detailed to the city council yesterday by Keith Frentz of Beca consultants.
He said the difference was absolutely stunning once the last stage of the clean-up, divers manually recovering the remaining seabed items like scattered aluminium ingots, had completed their work.
Quizzed how long the clean-up would last, he said the weather was the big unknown. "That will determine how long they will be there." The operation had been forecasted to run until March next year.