N1 sinkhole – What Sanral has done in 17 months

In approximately two months’ time, the South African National Roads Agency (Sanral) will award a tender for the rehabilitation of the massive sinkhole that formed in January 2022 along the N1 highway near the Flying Saucer interchange in Centurion.

For the past 17 months, this hazard has plagued commuters who frequently travel this portion of the highway as it has severely handicapped the flow of traffic, especially during peak hours.

TopAuto reached out to Sanral to find out what the agency has done thus far to investigate and subsequently get rid of the sinkhole.

January 2022

The sinkhole in question formed in January 2022 after heavy rainfalls hit the dolomite-rich Centurion area, and it affected the emergency lane as well as the left lane of the N1 southbound between Pretoria and Centurion.

These lanes were blocked off immediately with temporary barriers to avoid more potential damage, and for two weeks in February, Sanral closed off the highway to allow for gravity survey testing across both southbound and northbound carriageways to determine the true size of the sinkhole.

Moreover, the agency performed remedial repairs to ensure the road is safe to use and also repainted the road markings to retain three lanes instead of permanently reducing the busy route into two lanes and severely impacting traffic.

August 2022

In August 2022, eight months after the sinkhole appeared, Sanral confirmed that it had completed the necessary investigations and decided on the optimum design solution for the remedial works.

At the time, no tender was submitted nor applications received, and no additional work was done on the N1 sinkhole since the first reparations in February.

May 2023

Now in May 2023, 17 months after the sinkhole appeared, the tender has been opened and closed, and Sanral said it has received applications for the rehabilitation work but that none has yet been awarded.

“We are currently busy with tender evaluations. This should be concluded soon. We will issue a media release once the award is made,” said Thabo Mahlakwana, Project Manager at Sanral Northern Region.

Following the grant, construction on the sinkhole is expected to last for around nine months.

During this time, extra precautions will be taken by building an anchored pile retaining wall that will allow portions of the road to remain open while the construction is taking place.

In response to why the tender has taken such a long time to be awarded, Mahlakwana said: “The solution we are implementing is complex because of the need to keep the N1 open during construction.”

“This means that tenderers required additional time to study it before they could tender. Now that the tender has closed, we are analysing their submissions to ensure that we get the best price for this work,” he said.

Sanral expects the evaluation process to conclude “in the next two months,” after which the tender will be awarded.

This means that if all goes according to the agency’s projections, the N1 sinkhole will be a thing of the past by no earlier than April 2024.