|‘Poor geology’ and burst water pipe blamed for Joburg sinkholeÂ .
The government has ordered the Bombela Concession Company to stop excavating after part of Oxford Road in Rosebank, Joburg, caved in yesterday.
The damage occurred during drilling operations for the Gautrain rail project.
A Gautrain safety representative said he had no idea what caused the collapse, which happened during underground construction work around 1.30pm.
“It was a shock,” he said.
The cave-in created an 8m x 12m hole between 8th and North avenues.
Department of Minerals and Energy spokesperson Bheki Khumalo said inspectors ordered that underground work be stopped in the area yesterday.
Rock engineers will carry out thorough investigations, and the department will lift the order only once it is satisfied that excavations pose no further hazards.
It appeared as if a water mains was hit during the drilling because water was gushing out of the hole, into which part of a wall and a lamppost had fallen.
Because of the water it was impossible to see how deep it was.
Safety officials were trying to determine if there were any other cracks along the road, which could be dangerous.
The area was cordoned off and motorists were diverted off Oxford into Riviera Road and 11th Avenue.
Dozens of Gautrain workers, metro police and paramedics were on site.
Two fire engines and a fire department heavy rescue unit vehicle blocked off the road, along with an ambulance and Joburg metro police vehicles.
Joburg Water, City Power and Egoli Gas staff were at the scene.
“We’ve lost the water main, we’ve lost the overhead lines. There’s a pole inside the hole,” said one council official.
Metro police Chief Superintendent Wayne Minnaar said the affected section of the road was likely to be closed for the next two weeks.
“It is a safety hazard,” he said.
There was a possibility that more damage could be caused.
“The road can fall in even more,” he said.
Minnaar said workers noticed some cracks and had some warning that something was amiss while drilling along Oxford Road. They then closed the road.
Shortly after the closure, the section of the road caved in.
Bombela Concession Company spokesperson Kelebogile Machaka said the project team was assessing the situation after the cave-in and taking whatever measures were necessary to reopen the road as soon as possible.
“As a result of the continuous monitoring system employed by Bombela, preventive measures were taken.
“No injuries were sustained to either members of the public or construction staff,” she added.
Rosebank Management District operations manager Yousef Seedat said there had been fears that a house whose wall collapsed into the hole might sink too.
“Water to the immediate area has also been cut,” he said.
A lamppost collapsed into the hole as water gushed out.
Soon there was a hole about 12m long, taking out half of the roadway, the adjoining pavement and a garden wall.
“I was petrified. This is a road I drive through every day.
“It was shocking looking at the road I use every day collapsing,” said Du Plessis.
A bystander said a car parked off the road in an office park had to be towed from the hole.
Bombela Civils Joint Venture environmental manager Etienne van der Lith said poor geology in the vicinity had been identified at 11am yesterday and the road was closed to ensure that nobody was at risk. The cave-in started at about 1.15pm.
Van der Lith said a water pipe had broken, gushing water.
“The engineers will look at the hole once the water has stopped and determine the extent of the damage.”
He said the ground was still unstable and would be monitored.
Alain Truyts, the province’s resident Gautrain engineer, said it was difficult to say what caused the collapse until a geotechnical investigation had been done.
“But some speculation as to why it happened would logically indicate that there was an abrupt change in the geological conditions,” said Truyts.
He said staff had been at the end of their maintenance shift and were about to start up the tunnel-boring machine when the collapse occurred about 1.15pm.
“It occurred just behind the face of the machine, which is about 1 670m away from where it starts in Rosebank,” he said.
Truyts said it was “now a question of backfilling the hole, restarting the machine, stabilising and ensuring that the area around the hole on the road is sound again”.
Tunnelling would resume following the outcome of their geotechnical investigation, which could take several weeks, he said.
Meanwhile some Joburg suburbs were due to be without water today following yesterday’s cave-in.
Last night Johannesburg Water said Gautrain construction had broken a water mains pipe, and Rosebank, Parkwood, Highlands North and surrounds could be without water.
A water tanker was to be sent to Rosebank Mall last night and more tankers were to be sent around the area today.
“When the contractors were drilling on Oxford Road they broke one of our pipes,” said Joburg Water spokesperson Baldwin Matsimela.
Late last night a Gautrain construction team worked on repairing the damage to Oxford Road.
Concrete was poured into the huge hole. A team member said there were water, sewage and gas pipes in the hole.
The water and sewage pipes were damaged but the gas pipe was apparently intact. Earlier, water from broken pipes was pumped out of the hole.
“We’re pouring concrete to a level where the guys can safely work,” said the team member.
“It’s quick-drying cement and it will be dry in the morning.”