An investigation has found that methane gas was the cause of the deadly Lilian Ngoyi Street (formerly known as Bree Street) explosion that rocked the Johannesburg city centre last month.

This was revealed by City of Johannesburg City manager Floyd Brink during a media briefing yesterday.

The explosion killed one person, injured several others, caused infrastructure damage and disrupted services in the area.

“Methane is lighter than air so usually methane…will go up. It travelled up all along the service tunnel from an unknown source to the crest of the tunnel near the Von Brandis Street. There were always questions around why did we not see any fire…if you look at the low explosive level, there’s a threshold of between 5% and 15%. If it’s between 5% to 15% it will be an explosion, anything above 15% will then create a fire.

“This one was between the threshold…therefore it was an explosion. As we flew…our drones into those tunnels, we could not pick up any indication of black scorch from a fire,” he said.

Brink added that the investigation ruled out several other suspected causes – including that the explosion was caused by a gas leakage, illegal mining underground or negligence.

Repair work

The city manager said repair work to rehabilitate and reconstruct the area is currently estimated to cost more than R100m.

“Our rough estimate at this point currently sits around R178m and that is [not] based on work that has been done but it’s based on preliminary designs. We will indicate…as we are moving closer with detailed designs. That amount may increase based on the designs that we will have.

“That is preliminary to look at what it will cost us for the road, what it will cost us for any other infrastructure damages and also to reconstruct that particular tunnel,” Brink said.

He revealed that following the explosion, the City of Johannesburg spent close to R4m on ‘professional experts, services, the cordoning off of the site, technology that we’ve used and the provision of temporary relief’.

Brink said the city has learnt several lessons following the explosion with plans coming to avoid future incidents of this nature.

“The tunnel designs will be upgraded based on current international codes for tunnels to reduce the risk of severity for these types of explosions. We will also introduce continuous gas detection, alarms, sensors and monitors for all staff working in the tunnels.

“As we move forward to reconstruct and to upgrade these particular areas, we would need to upgrade to ensure that we use technology. Our tunnels designs will be based on international relevant standards… that focuses specifically on tunnels and explosion prevention with accidental combustible gas release in tunnels and/or cavities,” he said.

Brink emphasised that the work to secure the tunnel will not only be concentrated on Lilian Ngoyi Street but other projects will also commence at other streets in the area to ‘look at gas detection and any other issues’. – SAnews.gov.za

Businesses are struggling

The Randburg Sun reported that businesses in the street have also been hit hard by the underground explosion.

The Randburg Chamber of Commerce and Industry (RCCI) said businesses struggled for a week without electricity following the explosion, and that the consequences of this are still being felt.

The explosion occurred on July 19, and a 1km evacuation zone was initiated and streets were blocked off for an investigation and the safety of the public. City Power claim the full supply of electricity had been restored by July 25.

This break in service delivery impacted commuters and businesses in the area.

“All businesses requiring water and power felt the negative brunt of the explosion,” said RCCI CEO Linda Blackbeard. “Some small shops don’t want to open as they are concerned about the criminal element robbing them. Others like the hairdressers had to find hair design work not requiring power or water.”

This included operating with solar lights. Business owners are still unhappy with the situation. “Others wanted to move to other areas when they said they will feel safer.”

She said food vendors have lost their positions on street corners and pavement spaces so they too felt desperate and were looking for other spaces to operate. “The shops alongside the blast areas are still concerned that there will be more subsidence so they don’t want to even open.”