Tshwane tackles its sinkholes

The City of Tshwane has made a total of R25 million available from its operational budget to fix the Jean Avenue sinkhole in Centurion, the highest cost to repair a single sinkhole.

This sinkhole has caused major disruptions to businesses and traffic flow in the area and several accidents have been reported there.

Another two sinkholes, the Clubview sinkhole, in Centurion, which will cost about R3 million to repair and potentially affects 900 households, and the 2nd Avenue sinkhole, in Claudius, which will cost about R15 million to fix, will be repaired as soon as possible.

Tshwane member of the mayoral committee for corporate and shared services Cilliers Brink said there are presently 24 sinkholes in Tshwane, spread across Centurion, Laudium and Olivenhoutbosch.

“To fix all these sinkholes at once is estimated to cost R60 million over the next financial year. However, site securing, geological investigations and periodic monitoring of the sinkholes are being done in the meantime,” Cilliers said.

Repairs to the Jean Avenue sinkhole are estimated to take about nine months without taking into account unforeseen delaying factors, such as rainfall and wet ground conditions and the availability of specialised equipment.

Much of Centurion and Laudium is on dolomitic soil, which is predisposed to collapse when coming into contact with a large concentration of acidic water.

The city had to prioritise some of the sinkholes over others and this was determined by engineers.

Cilliers said there is no way to know exactly where sinkholes will form, but the city believes it can manage the problem.

“First, it is clear a more realistic budget needs to be allocated to sinkhole repairs in future and we are exploring the possibility of a constituency reserve fund in future budgets,” he added.

According to the city, a corporate entity has offered assistance to fix the Jean Avenue sinkhole.

“The final assessment of the sinkhole repair method will be done in the next two weeks, and then we will be able to determine how such generous offers can be used.

“The biggest cost in fixing sinkholes isn’t the method and the material used to close the hole, there is also the relocation and reinstatement of service infrastructure that accompanies such a geomorphological disruption,” Cilliers said.

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