Gautrain management agency CEO Jack van der Merwe said on Wednesday that the tunnel collapse on Oxford road in Rosebank, north of Johannesburg, would not have any significant impact on the project’s schedule.

“The area that was affected by subsidence is not required for completion for the 2010 soccer World Cup. The completion date of March 2011 remains unaffected,” he told reporters at a press briefing at the Gautrain offices.

The subsidence occurred as a result of ground loss above the Gautrain Tunnel Boring Machine (TBM), which is currently 12 m below ground level. No injuries were sustained and no damage occurred to either the TBM or the completed tunnel.

“During Bombela’s routine monitoring process, the TBM technical team noticed surplus material coming through the machine, which is symptomatic of a void being formed above the TBM,” said Gautrain director of civil engineering Chris Andrew.

Upon investigation, the team identified water seepage in the TBM chamber and a void above. To give more support to the ground, the TBMs operational mode was changed to Earth Pressure Balanced Mode.

Preliminary investigation carried out by Bombela after the event, suggested that water seepage from the utilities (water and effluent pipelines) above the tunnel alignment had led to a weakening of the soil being excavated, causing ground loss directly above the TBM.

“All steps that could have been, and should have been, taken by the construction team were implemented timeously,” Gauteng MEC for public transport, roads and works Ignatius Jacobs said, reiterating that all the structures in the vicinity of the subsidence have been continuously monitored and remain stable.

Bombela and the provincial support team are working together with the City of Johannsburg to provide temporary alternative routes for motorists while the subsidence is being repaired.

Jacobs said he expects the utilities and main construction work on the road to be repaired in a week.