Let's not rely on luck when it comes to unexploded bombs
A risk management system would reduce chance of second world war legacy causing tragedy
Last month, a 36kg unexploded bomb was discovered in North Point, left by the Japanese at the end of the second world war.
The police used 100 sandbags to effect a controlled explosion. Nevertheless, debris was flung 100 metres and it created a three-metre-deep crater.
In February, a 900kg American bomb discovered in Happy Valley was successfully defused by the police.
But in January, construction workers in Germany were not so lucky. Their mechanical digger struck a British bomb, which exploded, killing one person, injuring 13 others and damaging buildings 300 metres away.
Hong Kong's struggle in the second world war involved the use of ordnance - aircraft bombs, artillery, grenades and other types of ammunition - manufactured by the British, Japanese, Americans and Chinese.
After the war, one of the first jobs for the British on returning to Hong Kong was to clear the harbour of the 50-odd shipwrecks. Resources were not available for a general clearance of unexploded ordnance (UXO) and the efforts made at that time were less than optimal.
Since then, the city has seen many discoveries of UXO during the development and redevelopment of sites. For example, during dredging for Chek Lap Kok airport, a mine or bomb exploded in a dredging vessel, resulting in its total write-off. Luckily, there has been no tragedy similar to that in Germany.
Rather than relying on luck, it would be relatively easy to implement a risk management system to greatly reduce the possibility of such tragedies.
Hong Kong has detailed construction laws that prescribe assessment of capital projects for any potential damage to the environment or heritage. Stringent health and safety regulations are also in place to protect workers from harm.
A UXO risk management system can ensure the UXO risk to personnel and property on any development is minimised. The costs and delays it adds to the project will be minimal compared to the devastating effects of an explosion and its potentially tragic consequences.
Some local developers are already implementing such measures because they are concerned.
Mark Ranson, head of operations for UXO remediation at GB Foundations & Construction, a Hong Kong-registered UXO clearance services provider, points out the dangers lurking beneath the ground.
"Unfortunately, the general public tend to be imbued with a false sense of security regarding the effects of high explosives due to Hollywood's portrayal of movie stars outrunning an explosive blast by legging it down a corridor and jumping out of a window into a canal," Ranson said.
"In fact, in the brief instant of a high-explosive detonation, the local effects are as follows: the shock wave produces pressure up to 500,000 times that of the earth's atmosphere, the detonation wave travels as fast as 10km per second, temperatures can soar to 5,500 kelvins (5,227 degrees Celsius), and power approaches 20 billion watts per square centimetre.
"The primary products of the detonation of a high-explosive bomb on, or in, the ground are heat, light, blast, fragmentation, sound (in itself damaging) and ground shock," Ranson added.
Hong Kong's safety laws are usually driven by the insurance industry, but so far insurers appear not to have recognised the need for UXO impact assessments. Insurers in Britain, Germany and other parts of Europe have tightened such requirements.
Although the most tragic consequences of an explosion would be human death and injury, perhaps a more focused thought for Hong Kong would be the financial impact.
The Irish Republican Army's 1996 explosion in London Docklands, though the result of a terrorist bomb, was a cause of the British government's resumption of talks with the IRA.
Then prime minister John Major was accused of having been "bombed to the table", not because of the two deaths and 39 injuries, but because of the more than £100 million (HK$1.26 billion) worth of damage caused to buildings and other infrastructure.
And here's a reality check: although the IRA bomb was not directly comparable to the one discovered in Happy Valley, it was just over half the weight of the latter.
Steven Gallagher is an associate dean at Chinese University's faculty of law