2 injured as blast sends manhole covers flying

PUBLISHED : Wednesday, 12 August, 2009, 12:00am
UPDATED : Wednesday, 12 August, 2009, 12:00am

Two pedestrians were injured when an underground gas explosion blew three manhole covers into the air in Kwun Tong yesterday.

The blast sent one of the covers flying 2.5 metres and damaged a traffic light pole at the junction of Shung Yan Street and Hong Ning Road, the Fire Services Department said.

In Shung Yan Street, one of the covers flew for about three metres, while the other damaged railings on the footpath, senior Kwun Tong fire station officer Tang Kai-ming said. He added that minor burn marks were found inside the three manholes after the explosion.

Just before the blast happened at about 9.35am, a policeman felt unwell after inhaling an unknown gas coming from one of the manholes at the junction.

Pedestrians said they had smelled gas in the area before the explosion. One woman passer-by said: 'I felt the ground trembling just before the explosion went off. Luckily, there were not a lot of people there.'

Another woman pedestrian said there was a loud bang at the time of the explosion. 'It was just like the detonation of a big bomb. Police immediately evacuated us and cordoned off the area,' she said.

Mr Tang said two male pedestrians, aged 54 and 78, lost their balance and fell to the ground, injuring their arms and legs. The two men and the police constable were treated at United Christian Hospital. The 78-year-old man is in stable condition and the other two were discharged.

The junction was closed to traffic as firemen used gas detectors to check the manholes. They found no hazardous gas after the blast and the road reopened for traffic at about 12.30pm.

Mr Tang said the manholes housed power and telecommunications cables. The source of gas was unknown and the cause of the explosion was being investigated, he said.

The Hong Kong and China Gas Company said an investigation found no indication that a Towngas leak had occurred in the area.

Wong King, chairman of the qualification and membership committee of the Hong Kong Institute of Utility Specialists, said he suspected an underground power cable had been damaged some time ago and its plastic protective layer had decomposed, allowing flammable gas to escape.

'The gas flowed to the manholes through ducts and a spark triggered the explosion,' he said.

To minimise the risk of a manhole explosion, Mr Wong said utility companies should use chemical foam to seal the ends of each underground duct. He said there were more than 400,000 manholes in the city.

In April, a gas blast sent a manhole cover flying into the air and smashed the door of an estate agency in Shek Pai Tau Road, Tuen Mun. A woman in the office, a 12-year-old boy and an elderly woman walking nearby suffered minor injuries.

In February, a bus was damaged when hit by a drain cover blown off by a gas explosion. No one was hurt.