Sewer link in gas blast, inquest told
A gas leak from an underground pipe might have passed over a sewage system and caused the severe blast at a Ngau Tau Kok building that killed two elderly residents, an inquest heard yesterday.
Towngas senior engineer Au Chi-yu, who made the suggestion in the coroner's inquest in Eastern Court, said he had found 'unusual corrosion' on a section of the gas pipe that had left a 7.6cm hole. That section of the pipe passed over a sewer pipe.
Mr Au, who led an excavation check after the blast, found the upper surface of the sewer had a large rectangular opening at the point where the gas pipe passed over it.
The broken main sewer pipeline was connected to a disused sewage pipe in front of Wai King Building at the junction of Ngau Tau Kok and Jordon Valley North roads, the engineer said.
'I am guessing the gas may have travelled through the sewage system and caused the blast,' said Mr Au.
The fatal blast on April 11 took place at 2.30pm, two hours after the building's security guard Lam Fuk-fai reported a gas leak and told a Towngas hotline emergency controller that he smelled it in the lobby and lift. The building - in which the deceased Eap Kwun, 92, and Liu Lock-chan, 89, lived - was overlooked by the emergency team and firemen because engineers were not aware the presence of gas was reported.
Coroner Michael Chan Pik-kiu questioned why Mr Au did not act on the complaint, which the gas supplier had received first, nor did he trace the caller to conduct a further inquiry.
Mr Au, who did not answer the question, said an in-house guideline had been introduced in March allowing field staff to listen to telephone recordings of gas-leak reports.
He did not enter the building since he had not been told of a gas leak there and he felt the situation was under control when he arrived, the court heard.
Fire station officer, Li Pui-hung, who was in charge of the scene, said he found the source of the gas leak when he arrived at 12.32pm after he smelled gas coming from the bus station, 30 metres from the building.
He walked along the pavement to the building, but did not enter. Mr Li did not order an evacuation because he could not smell gas at the side of the road.
The inquest continues today.