City of Johannesburg (CoJ) manager Floyd Brink revealed that the City’s preliminary investigations into the recent explosion in the CBD pointed to an accidental leakage of natural gas into the service duct, reaching explosion concentration levels of 5%-15% and ignited by an unknown source at this stage.
An explosion occurred on Wednesday on Bree street, tearing through the road, claiming a single life and leaving 46 people injured and hospitalised.
“At this stage, our preliminary investigations have presented us with three possible scenarios for the explosion. These are: ignition of methane gas in underground stormwater systems due to sewerage ingress. The second possibility considered is the ignition of natural gas, mixed with air (oxygen) in underground stormwater drainage systems or service ducts. The third and last possibility, is the ignition of gas from a gas pipe burst,” explained Brink.
He said investigations would continue to try to locate the source over the next few days.
Brink highlighted that buildings adjacent to the collapsed road had been inspected and, at this stage, the buildings were regarded structurally sound for occupation.
“We have also assessed the gas leaking into the atmosphere and have been assured by the Environmental Services and Air Quality Controllers of the City that the gas leaking into the atmosphere poses no risk to residents as its concentration reduces rapidly in open air. However, gas leaks into subsoil cavities such as basements can be fatal,” he explained.
He said the City was confident it had mobilised the best skills and expertise required to respond to the explosion.
Brink explained that within an hour of the explosion, plans were afoot to manage the scene, search for survivors and any fatalities, locate the source of the explosion and secure the perimeter of the site.
“For those who were present here at Mary Fitzgerald Square, they would have witnessed the rapid deployment of Command Units and support resources to immediately coordinate all response efforts across all three spheres of government,” he said.
Brink explained that the City had deployed water tankers to support residents in the area and City Power would also be deploying technicians to assess the power lines for damage along the 400 m of the site and would only be able to reenergize the area once it had been declared safe.
The Johannesburg Metro Police Department and South African Police Service will barricade the area to limit access and movement to allow for the efficient management of the site to minimise risk to residents.
He said barricades would also be manned by 250 members per shift supported by 50 private security personnel.
The City will also commence with the work of sampling all bulk service manholes in the area for gas leaks and ruminants.
“This will include the opening of bulk manholes belonging to City Power, Telkom and other service departments and entities. Some of the manholes are welded, due to theft and vandalism and at this stage we are unable to immediately open them for fear of igniting a further blast. Where possible, our teams, led by Johannesburg Emergency Services, will be placing Positive Pressure Ventilation Fans down the manholes to blow out any gas that may still exist below. This is intrinsically safe equipment and will assist in the effort to disperse trapped gas,” Brink added.
He emphasised that the tasks being undertaken were complex and at this stage would have to be handled with care, meaning no heavy equipment could be deployed to the site immediately.
“The digging and trenching to be done now will have to be done by hand until we are confident the site is safe and all hazardous factors are cleared. We have also deployed advanced technologies to assess and review underground damage to the infrastructure,” he said.
The City will, over the coming days, ensure residents are updated and informed on work being done to mitigate the risks and repair the site.