Eagle’s engineers failed in their duty

THE Hobbit sculptures hanging from the ceiling at Wellington Airport are famous. The sudden fall of a one-tonne eagle after an earthquake is therefore widely remembered.

The WorkSafe New Zealand inquiry on the incident reaches worrying conclusions. A report by engineer Jack Mains places much of the blame on engineers Dunning Thornton Consultants (DTC). It also faults Wellington City Council for seeming ‘‘to have been far too relaxed about the concept of large suspended objects over public places’’.

The council decided that building consent was not required for ‘‘an artwork’’. But ‘‘whatever the requirement of the Building Act,’’ Mains says, ‘‘good practice should have suggested this needed checking’’.

So if the council had followed good practice, it seems, the eagle might not have fallen. The council needs to make sure it does the proper checking in future. The eagle, after all, could have maimed or killed someone in a very busy airport.

Mains’ report finds many faults in the consultants’ handling of the project. Laypeople might be astounded at his finding that there was no evidence that they knew the total weight of the eagle ‘‘with any certainty’’. Post-failure measurement showed that DTC’s estimate of the weight, he says, was ‘‘light by around 27 per cent’’.

DTC disputes this and many other findings of the report, saying it estimated the weight at 960 kilograms compared with the measured weight of the fallen eagle at 1175kg. This was a difference of 22 per cent. The weight should not have been enough to seriously erode the intended safety of the wire ropes, it says.

But the eagle fell for some reason, and no layperson would be happy to learn that the engineers underestimated its weight by more than a fifth. The company tries to shift the blame on to Weta, in this and many other matters. It says Weta had weighed the components of the sculpture and expected the eagle to weigh 900kg.

Here the exact role of the engineers is crucial. Weta says DTC was the overall consultant throughout the manufacture and installation of the sculptures, as it had been on many earlier Weta projects. But DTC disagrees, saying its role was not to take responsibility for all engineering aspects of the design and installation. It was, rather, ‘‘limited to specific items’’, such as wire rope forces.

This might look like two sides passing the buck, but Mains doesn’t accept DTC’s argument, and the emails and other evidence in the report seem to back him up.

And there is a wider and more important point. As the responsible professionals, DTC had ‘‘an overarching duty to ensure the outcome was safe for a high-traffic public space’’, Mains says. If the company wasn’t engaged to oversee the project, he says, it should have warned Weta so it could hire a company that would.

Engineers have a duty to protect public safety, Mains says, a duty that goes far beyond any contractual requirements ‘‘and is very broad in its reach’’. The evidence suggests that here the company fell grievously short.