Probe into Underwater World's unplanned deluge

An investigation is under way at Kelly Tarlton's in Auckland after contaminated water flowed through a burst air-conditioning duct.

Hundreds of visitors are being turned away from the popular tourist attraction as staff, engineers and environmental officers work to decontaminate the Tamaki Drive site and find out how it was flooded during Monday's storm.

Questions are being asked about whether part of the air-conditioning system should have been housed in a wastewater overflow tank designed to take overflow stormwater and sewage should the system fail during bad weather.

During Monday's power cut, the Orakei pump station failed, sending stormwater and sewage rushing into the overflow tank, which is the size of a large room.

From the tank, the water is released into the harbour, but the strength of the flow may have caused the duct to fracture, sending water pouring into the northern end of Kelly Tarlton's instead.

"[The air-conditioning system] was put there because it was a straight line from one area to another, but with the wisdom of hindsight that is being re-visited," said operations manager Andrew Baker.

"We're looking at how it was installed, who signed off on it and basically who's to blame."

It was hoped part of the attraction would re-open on Monday, but that was "tentative" because the flooded area was also where the main exit was.

Another exit would have to pass muster with the Fire Service before visitors could be allowed back in.

Watercare Services, responsible for Auckland's wastewater system, said there was no real danger of a complete flood of Kelly Tarlton's because the system was monitored and faults quickly detected.

But it had taken a while to work out what had happened.

"We didn't know what had caused the flooding because the duct is not obvious from the outside [of the tank]," said Watercare Services spokesman Owen Cook.

Mr Baker said none of the site's inhabitants - from stingrays to sharks to penguins - were affected by the power cut or the flooding.

Emergency back-up power systems kept penguins cool and tanks aerated.

Kelly Tarlton's was built in Orakei's abandoned sewage works.