Scientists have determined that the 15 to 20 million litres of water pumped into Auckland's Waitemata Harbour during the SkyCity fire won't have a long-term impact on marine life or water quality.

Photo: RNZ / Claire Eastham-Farrelly

At a media briefing today, Auckland Council staff said while there were elevated levels of contaminants - as could be from burning building materials - the water was sufficiently diluted by the time it reached the waterfront.

Overall, some 27 million litres of water were used to put out the burning international convention centre, with about 8 million litres ending up in the building's basement carpark.

About 1.8 million litres of the basement water was pumped into the harbour before it was diverted to the wastewater system.

"Our focus is to prevent contaminants from entering the harbour, but during an emergency event like last week, it is not always possible," the council's principal freshwater scientist, Coral Grant, said.

"In this instance, water entering the harbour is unlikely to have had any major effect on water quality or marine ecosystems."

During the event itself there may have been some ecological effect, but it would have been short-term and localised, Dr Grant said.

"However, given the substantial dilution of the water once it entered the harbour, there would have been minimal impact to marine life beyond the initial mixing zone of 10 to 100 metres from the stormwater outlet and no long-term effects."

There is potential for some contaminants to bind to seabed sediment in the harbour and be ingested by filter-feeding shellfish.

Fortunately, dredging work of the same area is already scheduled as part of the work on the America's Cup facility, so all the potentially contaminated sediment will ultimately be removed from the harbour.

Work finished

Fire and Emergency has finished its work at the scene of the massive fire at the Sky City international convention centre.

Photo: RNZ / Claire Eastham-Farrelly

It said fire investigators had finished their work on the site and were now preparing their report.

At the fire's peak, it was attended by about 130 fire fighters, 30 fire trucks and 16 other operational vehicles.

Crews from all over Auckland and as far south as Hamilton helped get the fire under control.

The site will now be handed back to Fletcher Construction.

Area manager Richard Twomey said Fire and Emergency would be releasing its findings in due course, subject to legal requirements.

"I have been very impressed with the professionalism of our firefighters, who worked long hours in trying conditions. This was a testament to the outstanding women and men we have working at Fire and Emergency," Mr Twomey said.

"Fire and Emergency New Zealand also wants to thank Fletcher Construction for the use of cranes and operational support over the last 11 days. We are also grateful for the support of all of our partners including, Auckland Council, St John, police and the wider community for their support while we worked to get this large and complex fire under control."

Fletcher Construction said it will be some time before workers are allowed back into the building for cleaning and rebuilding.

Photo: RNZ / Claire Eastham-Farrelly

Peter Reidy, the company's chief executive, said access to the site was restricted before safety and structural assessments were completed.

"Before we can commence re-entry work, and ultimately the rebuild, we have to ensure the site is safe to work in. We have a rigourous process in place to ensure the safety of those people who need to enter at this early stage, to undertake specific assessments," he said.

"It will take us some time to understand the extent of the damage to each area within the seven level, 32,000sqm site. We need to assess every floor, every structure and the 1327 car parks beneath the fire where there is significant water damage."

Mr Reidy said the priorities now include getting vehicles out of the building and also retrieve tools and personal belongings where possible.

Traffic restrictions in the city centre will remain in place over the weekend as safety assessments are undertaken.

Fletcher Building said it would be some time before workers were allowed back into the SkyCity Convention Centre.

The company said it would take some time to understand the extent of the damage because it needed to assess every floor.