A construction catastrophe waiting to happen
When a five-storey tenement building collapsed in To Kwa Wan in January last year, those who saw it fall could not believe their eyes.
Warnings about the integrity of the structure had been issued minutes earlier, but the curious public crowded around anyway, unconcerned for their safety. After all, how could a tenement just fall?
In seconds, their faith in the integrity of Hong Kong's buildings was shaken as the structure was reduced to a pile of rubble and dust.
Engineers and forensic scientists think the collapse of Block J of 45 Ma Tau Wai Road began months, perhaps years, earlier, when the strain accumulated over 55 years started eroding columns inside the building.
The ones towards the rear - two of which were supported by steel bars that had been bent into a V-shape - were especially vulnerable, said Wan Chi-wai, the surveyor who inspected the building two months before the collapse.
In Hong Kong and across the world, it is quite common for a multi-storey concrete building to have a design life of 50 years, said Law Chi-kwong, an assistant professor at The University of Hong Kong, who studies urban renewal.
But the crucial factors are maintenance and renovation. He said: 'With better maintenance, they can last a bit longer, and with poor maintenance, they would not be able to last for 50 years.'
Maintenance at the To Kwa Wan building was not carried out.
And there were warning signs - pieces of concrete that had fallen from the building's back wall were collected by a contractor, Chu Wai-wing, from a nearby alley months before the collapse.
Chu claimed he and his wife collected up to 500 kilograms of concrete debris by hand before the building's owner commissioned him to carry out repairs. But on the afternoon of Friday, January 29, four days after the contractor had started repair work, steel bars bearing the weight of a structural column at the rear of the building could take no more.
Hours after one of Chu's workers cut off iron bars supporting an illegal structure, the three columns gave way all together and the building crumbled, killing four people.
In the wake of the tragedy, the government sent building inspectors to the 4,000 or so other buildings in Hong Kong that were more than 50 years old.
Within weeks they issued 680 repair orders. And in June last year an amendment to the Buildings Ordinance was passed requiring every building more than 30 years old to be inspected every 10 years and repaired if necessary.
This week, the Buildings Department tried to have Chu, the contractor, prosecuted for unlawful killings due to a work-related error.
After six days of hearings, Coroner Michael Chan Pik-kiu declared yesterday that no one was to blame.
His decision that the deaths were accidental hinged on a crucial factor - whether the collapse could be blamed on human error.
He found they could not. But, as became clear at the hearings, the blunders that preceded the building's collapse were many.
At the inquest, the contractor said he told the building's owner, Chak Oi-luen, many times of the dangers of her building, but she ignored him.
Chak, sole owner of the building through a company called Halesweet Ltd, said she made hundreds of calls to the Buildings Department in the two months before the collapse, only to be referred elsewhere.
But the Buildings Department said Chak reported no problems with her building's safety in an account she gave to police in December 2009, after taking over a ground-floor shop from its previous tenant.
It also said she failed to respond to two orders it had sent her, in November 2005 and June 2009, to remove illegal structures.
The Buildings Department, which sent inspection officers to 45 Ma Tau Wai Road in November 2009, did not issue a closure order.
The surveyor at the time, Wan Chi-wai, said closure was not necessary because he saw no immediate danger. When a repair order was issued by a different surveyor, it was not delivered until 16 days before the To Kwa Wan tenement collapsed. By then, it was too late.
The previous year, Kowloon City District Council, which could have applied for repair funds, and the Urban Renewal Authority - which had money available for the refurbishment of old buildings - passed over the To Kwa Wan building in favour of others. Everyone thought there was more time.
But how can the difference between probable and immediate danger be spotted? The coroner's verdict recognised the collapse was not the fault of any one entity and called on the government to assess potentially dangerous buildings more carefully.
But is there any way this one building could have stood out from the many other old buildings in Hong Kong in need of repair? Dealing with such issues is the job of risk analysts such as Vincent Ho, chairman of the Hong Kong Association of Risk Management and Safety.
But asked if possible building collapses could be avoided, he said: 'If the government can inspect more, go more into detail, spend money to send structural engineers everywhere, if people have more awareness, if and if and if ... then maybe.'
He said a sound building needed structural integrity from the beginning, but also a good construction company that followed design codes, developers who followed the rules, government inspection, then constant maintenance and more frequent safety inspections.
But sometimes, the real danger is discovered only when it is too late.
It is possible that even despite frequent inspections, any of the 4,000 other 50-year-old buildings in Hong Kong could become a hazard.
'There are multiple safety barriers,' Ho said. 'Each safety barrier has a weak point. But at a particular point and particular chance, you may be able to fail all safety barriers.'
He explains this by referring to the 'Swiss cheese' model, created by James Reason at the University of Manchester in England. If you have many slices of Swiss cheese (each representing a layer of the system), all filled with uniquely placed holes (representing opportunities for things to go wrong), and you line up all the slices, you may not be able to see through the multiple layers.
But at any one point, all the holes may line up, and then you are exposed.
This is what happened at To Kwa Wan - the holes in an entire system that went wrong eventually lined up.
A building collapsed, four died, and Hong Kong's construction industry was shaken to its foundations.
The record amount per square foot proposed as compensation for flat owners in the To Kwa Wan redevelopment area where the block collapsed