By Lehlohonolo Lehana.
The City of Johannesburg has confirmed that the blast in the city was caused by gas, after discovering an old active municipal gas line which had methane traces detected in parts of it.
“This is a pure gas explosion,” said Johan La Grange, a civil engineer and city of Joburg consultant.
However, they are yet to determine the line that caused the explosion.
La Grange said the old municipal gas line detected had caught officials by surprise as nobody knew about it, and explained that methane gas was detected still flowing in it.
“We are not sure if it is connected somewhere to the Egoli Gas line as part of a distribution line from one of the tenants,” he said, adding that the line was set to be isolated.
Lagrange said they would carry on searching and testing.
He also said there were no people living underground and that they had used drones and other technologies to see what was happening underground.
City manager Floyd Brink confirmed officials had detected the old municipal gas line, which was still active, and said they would be working to close it swiftly.
Brink said they said they were ruling out any foul play by zama zamas, terrorists or vagrants, saying the cause was likely accidental.
The City had initially identified three possible causes of the explosion on Lilian Ngoyi Street in the city centre.
Brink said it identified the ignition of methane gas in underground stormwater systems due to sewerage ingress, the ignition of natural gas mixed with oxygen in underground stormwater drainage systems or service ducts, and the ignition of gas from a gas pipe burst.
Brink addressed the media from Mary Fitzgerald Square in Newtown on the progress of the preliminary investigations and the City’s response to the explosion.
One person died and 48 people were injured when the underground explosion ripped parts of Lilian Ngoyi Street, damaging several vehicles, some of which fell into a sinkhole, on Wednesday evening.
Brink said the surrounding buildings in the CBD were assessed and declared safe, as there was no damage to the structural integrity.
He said all digging and trenching will be done by hand.
“The tasks that we are undertaking are dynamic and complex, and at this stage, they will have to be handled with due care.
“No heavy equipment can be deployed to the site immediately because there is a further risk of a possible collapse of that particular road, so whatever it is that we need to do will be done through labour.
“The digging and the trenching will be done, and that will be done by hand until we are quite confident that the site is safe and all hazardous factors are cleared.
“The city will inspect bulk service manholes for gas as some have been welded shut to prevent theft and any grinding that may lead to sparking,” added Brink.
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Video Courtesy of SABC.