The City of Johannesburg has confirmed the recent Joburg CBD explosion on Bree Street was caused by methane gas.
Joburg City City Manager Floyd Brink said the methane gas was detected which caused a series of events that ultimately caused the explosion.
He explained, during a media briefing on Wednesday, that methane, which is lighter than oxygen, had travelled up from an unknown source before exploding.
He said the explosion was not from an Egoli Gas pipeline nor a leak. There was also no negligence from any electricity or any department or any intentional action by individuals or intentional release of gas into the tunnel.
“The type of gas that fuelled the explosion is methane, which is lighter than air and travelled up along the services tunnel, from an unknown source to the crest of the tunnel near Von Brandis Street.
“The delivery of this report marks the end of the immediate response work we reported on previous and paves the way to our medium interventions which will include the restoration and repair work,” said Brink.
He explained that there was a 5-15% threshold for an explosion, and in explaining why there was no fire, he said the threshold was not above 15%.
Brink said the immediate response from the city was now coming to an end and they had so far spent R4 million on professional services, cordoning off the area and the temporary provision of water, ablution services and food.
The city said last week it was looking to declare a local disaster after the explosion.
Brink said the city would require about R178 million, which could rise, to repair the road, reconstruct the tunnel and fix other damaged infrastructure.
Brink said a team of specialists in fire with experience in industrial explosions and gas systems, fire dynamics and explosion simulation specialist engineers, explosions, gas and fire dynamics specialists, structural, geotechnical, electrical and civil engineers, forensic specialists and occupational health and safety professionals had worked around the clock as part of the team on the CBD explosion.
“A lot of lessons were learned following this unfortunate incident. In order to avoid future recurrences, the tunnel design will be upgraded based on current international codes for tunnels to reduce the risk and severity of explosions,” said the city manager.
Brink said the city would also introduce continuous gas detection, alarms and gas detector sensor monitors for all staff working the tunnels regularly.
“Our tunnel design will be based on international relevant Standards i.e. NFPA Standards for tunnels and fire and explosion preventions with accidental combustible gas release in tunnels or cavities.
“Detection based on NFPA 72 Standard rest will be based on South African relevant standards SANS for water, sewer, and road designs.
“Tunnel roof and sidewalls will be designed to withstand and depressurize with deflagration vents a 9.5% methane explosion. Suitable materials for the tunnel would be reinforced concrete side walls and roofs designed for this over-pressure and release,” said Brink.
Joburg Mayor Kabelo Gwamanda applauded as “exceptional” the rapid response from the officials since the day of the explosion.
Gwamanda recently pulled out of the Russia-Africa Summit to oversee the recovery process in the city.
He said they displayed great technical abilities and preparedness.
“Our experts say the manner responded in line with international standards and protocol. We applaud the services of the City of Joburg in the manner conducted and responded. We are doing all in our power to create a safe City of Joburg,” Gwamanda said.
IOL