KEY POINTS:
The Government is being warned that a rugby stadium on Auckland's waterfront could be lifted up and destroyed by a tsunami if any part of it is built over the sea instead of entirely on reclaimed land.
Hamilton civil engineer and water-flow expert Alastair Barnett said last night
he had warned Rugby World Cup Minister Trevor Mallard of the risk of perching a 60,000-seat stadium above Bledisloe Wharf, without first reclaiming enough land to protect it with bunds as sea levels rise.
"Government should set an example by requiring a higher standard of planning for eventual protection or abandonment of the site before committing to such a large investment of public money," he told the Herald of the $500 million-plus stadium plan, which Mr Mallard and Prime Minister Helen Clark are understood to favour above redeveloping Eden Park.
"I think it would be a bad idea to build on a platform which is accessible to the sea, because a tsunami could float the whole lot off."
Mr Mallard confirmed having received material from Dr Barnett, and said he would certainly take it into account. But although reluctant to discuss any options before the Government, he said: "The people who design these things aren't stupid."
The minister said that, regardless of Dr Barnett's qualifications, he doubted the engineer would have seen the plans for any stadium options.
Dr Barnett, who has had more than four decades of experience computing waterflows in engineering projects in 20 countries, headed a year-long study in 1989 that led to the development of an artificial hill to keep the Museum of New Zealand 2m above the Wellington CBD's ground level. He said his work also ensured the museum's cultural treasures were all on floors starting about 8m above mean sea level, so the ground space was used only for "easily evacuated expendable functions".
Auckland structural engineer Murray Jacobs, who has worked on some of the city's largest buildings such as the Price Waterhouse Cooper centre near the waterfront, said he understood much of Bledisloe Wharf was on solid ground formerly known as Britomart Point and the rest was on reclaimed ground. Although he expected hundreds or even thousands of new piles would be needed to be punched through the wharf into reclaimed land before reaching firm ground below, he was confident a stadium could be safeguarded from the sea and still be built in time for the rugby contest, given a big effort.
Auckland University structural engineering lecturer and consultant Barry Davidson, who was involved in strengthening Princes Wharf for the Hilton Hotel and other developments, said even the 2004 Boxing Day tsunami left most concrete buildings largely intact despite destroying many coastal homes made from flimsier material.
Dr Barnett accepted that Princes Wharf had been strengthened laterally to withstand earthquakes, and that buildings above it would probably survive tsunamis if water could sweep through them. But he expected a stadium would be a largely impermeable structure vulnerable to "upthrust" pressure from below if water poured in underneath.
That would be a risk even if only a portion of the building were exposed to the sea, such as by overhanging the western side edge of Bledisloe Wharf, as the Herald understands will be part of a proposal to be put to the Cabinet.
"A stadium is a much more fragile thing - it would be shaken to pieces if that happened." Dr Barnett said the Government's own Geological and Nuclear Sciences research institute had predicted Auckland would be hit by 2.9m tsunami waves every 50 years on average. That meant there was a 10 per cent chance of such an event between now and 2011.
