R280 million to fix huge N1 sinkhole

It will cost over a quarter of a billion rand to fix a massive sinkhole that formed next to the N1 highway in Centurion in January 2022.

That is according to new feedback from the South African National Roads Agency (Sanral), the state-owned company responsible for maintaining many of the country’s tolled roads.

The sinkhole formed in the dolomite-heavy Centurion area following heavy rains and flooding.

Its proximity to the N1 highway and the R21 offramp heading southwest forced Sanral to close several car lanes.

The agency reconfigured the layouts to accommodate the large volumes of traffic using the road daily, but the closures still impact at least one lane on the main road and another on the offramp.

The three satellite images below from Google Earth show the location of the sinkhole before and after it formed and how the event impacted the lanes.

Seven months before the sinkhole formed.

Three months after formation, the sinkhole is clearly visible from above.

The sinkhole was slightly overgrown with shrubbery after a year and three months.

The location also makes it more difficult for motorists coming from the R21 northbound carriageway to enter the N1 south at speed.

The safety zone around the sinkhole changes the deviation from a normal gradual merge over a longer distance into a sharper and shorter entry into the N1, slowing traffic down further.

Sanral representatives initially said that the type of sinkhole that formed could take four to six months to fix, but it turned out to be a far more sophisticated challenge.

Sanral Northern Region project manager Oakley van Eyk explained that the rehabilitation works required before beginning construction were highly complex.

“Geophysical testing and extensive percussion drillings had to be conducted to establish the extent of the poor dolomitic conditions and provide input into the design of remedial measures,” he said.

The contract to fix the sinkholes was only awarded to Jodan Construction (Pty) Ltd on 26 June 2023 following a tender process.

Sanral previously told MyBroadband and other media outlets that the cost of the repairs would be in the “tens of millions” of rand.

It has now put a more specific amount on paper — R280 million — which is the current value of the contract.

The good news is that all the lanes could soon be reopened.

Jodan Construction started work at the site on 11 July 2023, just over two weeks after it won the tender.

Sanral said that the contract’s length was nine months, and the work was on schedule, suggesting that the sinkhole could be fixed and lanes repainted by April 2024.

Van Eyk said that Sanral was assessing the contractor’s performance against the tendered programme.

More Gauteng sinkholes set to be closed up in 2024

Sanral recently also provided MyBroadband with the costs and timelines of repairs on two other sinkholes that formed a few kilometres south of the one near the N1, just a month later.

These are located next to the R21 northbound carriageway just after the Olifantsfontein offramp.

They have also forced the closure of several lanes, resulting in traffic pile-ups and Sanral recommending that motorists consider alternative routes running parallel with the R21.

The contractors appointed in that project are Raubex and Esor, who are being paid roughly R144.25 million for their work.

Construction at this site started in December 2023 and is expected to be completed by August 2024.