On Friday evening, following 60 hours of speculation on what may have caused the explosion in the Johannesburg CBD on Wednesday, city officials revealed the cause of the blast – gas.

During a technical media briefing, Johan La Grange, a civil engineer contracted by the city, said: “The cause is gas; it was gas that leaked. The source of the gas is what we are trying to determine – whether it is an old gas line, whether it is from the tenants, clients or Egoli Gas leaking [is unclear].”

Daily Maverick earlier reported on a preliminary investigation which indicated three possibilities: the ignition of methane gas, natural gas or a possible leak in a gas pipe.   

Read more on Daily Maverick: Investigators probe three likely causes of Johannesburg explosion, Lilian Ngoyi Street closed over safety fears

By 5pm on Friday, authorities could say for sure it was gas that had leaked, ruling out the other possibilities. 

“This is a pure gas explosion. We are ruling out at this point anything related to illegal mining or Zama-Zamas,” La Grange said. 

On Wednesday, the explosion tore up 450m of the four-lane, one-way road, sending taxis and cars flying. One person died, and at least 48 were injured as the street collapsed.

A gas line explosion was immediately fingered as the main suspected cause — gas lines run beneath the pavement but not under the roadway itself — but Egoli Gas, which manages the municipal lines, said then that its lines operate at low pressure and were unlikely to cause an explosion.  

On  Thursday, the company indicated the detection of a small leak but maintained it was unlikely the cause of the explosion. 

“A small leak has been detected on the servitude pipeline at the corner of Bree and Eloff on a 100mm pipe. We believe the crack in the pipe has been caused by the collapse of the road. Our team is busy repairing the leak.”      

Officials on Friday would not be drawn into commenting directly on the possibility of Egoli Gas lines being the source of the explosion.   

Work to begin soon

City manager Floyd Brink has announced the gas pipelines that run under the site have been shut off, which means work to fix the damaged infrastructure is likely to begin soon.  

“By Monday, we anticipate that all the manholes will be safe for us to open. You will recall that yesterday (Thursday) we spoke about some of the manholes that have been welded, so we are working around the clock to ensure that even those for City Power or Telkom, that we start to open those particular manholes and that will then help us with some level of ventilation.”  

Brink added that tomorrow teams will start fencing the area. “It is indeed a disaster site, but it will be becoming a construction site very soon.”  

Residents in several parts of the city have been without water and power since the explosion, with this likely to be the case indefinitely. 

Joburg City officials said Joburg Water will supply residents with water and ablution facilities. 

The City said power is likely to be restored only by Monday.  

“We are beginning to see a decrease in the presence of the gas and should be in a position to safely allow for the restoration of power and other services by Monday, latest.”  

Read more in Daily Maverick: Johannesburg’s emergency call for engineers, gas-detection experts after CBD explosion exposes dire skills gap 

“Johannesburg Water has deployed 25 chemical toilets, five stationary and four roaming water tankers in the area to support residents. The chemical toilets will be serviced three times a week. Once the site is safe, Johannesburg Water will deploy CCTV technology into the underground pipe systems to make certain there is no further unidentified damage before we resume services.” 

Meanwhile, businesses in and around the area remain closed following the city’s decision to cordon off Bree Street indefinitely. 

Daily Maverick spoke to several taxi drivers and retail workers who expressed concern at being unable to make a living as a result of the closure. 

A retail worker in the area, Sibongile Dlamini, said: “Some of us in retail get paid hourly, so this is affecting us really badly because we will not earn an income for a long time, it seems.”  

Read more in Daily Maverick: Residents describe Joburg blast — ‘I felt my intestines go cold from fear’ 

If the street remains closed for the next week, for Dlamini — who gets paid weekly — it means “I will not be able to buy food, and if it goes on for another week, then I may not be able to pay rent”.   

Not only are small businesses affected, but also offices of the Commission for Conciliation, Mediation and Arbitration, which announced that it will remain closed in order to safeguard the health and safety of the staffers and clients.  

Structural integrity

Prof Felix Okonta, head of Geotechnical and Pavement Engineering Research at the University of Johannesburg, earlier told Daily Maverick that although no physical structural damage was visible on the buildings near the scene, there was no doubt that the surrounding buildings were affected by the vibrations of the blast, adding structural integrity tests needed to be carried out. 

The outcome would then determine whether they would remain stable or not.  

“For me what we should be worried about is the stability or structural integrity of the buildings more than the explosion … the cracks we see today will not be the only cracks we see in the years to come.” 

However, authorities believe there will be no need for mass evacuations.

“There is nothing that shows indications that the buildings or foundation were damaged by this explosion in the centre of the street” La Grange said. 

With the technical team now taking full charge of the process, following bickering by politicians, Brink said teams would work around the clock to ensure the business hub was up and running.  

This will, however, not happen overnight; “it will take a few weeks and a few months, but the teams are in place”. DM