Work starts to fill large sinkhole in Mount Gambier

Work has finally started to fill a large sinkhole that opened about six months ago after heavy rains hit.

Work has started to fill a large sinkhole in Mount Gambier that first opened up in June 2023.

Mount Gambier Council is working with a local concreter to fill the sinkhole, situated in a walkway between the city’s busy Margaret Street and popular walking trail the Railway Lands.

The cavity first appeared when the bitumen collapsed after heavy rain in June 2023.

The sinkhole first opened after a bout of heavy rain in June 2023. Picture: Arj Ganesan

Since then, an independent geotechnical investigation has been undertaken by engineering consultants, providing recommendations to fill the void, which is about 30 sqm.

“Due diligence on this solution has taken some time,” said Mount Gambier Council Infrastructure General Manager Barbara Cernovskis.

“Following independent advice, we are filling the cavity with stabilised sand, a mixture of soil and 4-6 per cent concrete.”

Works have begun to fill a sinkhole located between a busy street and popular walkway in Mount Gambier. PICTURE: Supplied.,

Works have begun to fill a sinkhole located between a busy street and popular walkway in Mount Gambier. Picture: Supplied

Site access in the vicinity of the sinkhole on Margaret Street is limited and a traffic management plan is in place during the drilling and filling process.

The sinkhole is about 30 sqm in total. Picture: Supplied

Heavy machinery attended the site on Wednesday, January 17, to drill down to the void from two separate locations.

The void was identified using a camera and a torch lowered down on a rope.

The holes were then filled with extra wet concrete that both filled the drill sites and flowed into the voids in the underground cavity.

On Thursday, the base of the sinkhole was built up with 30 cubic metres of stabilised sand to 2.5 metres below ground level and left to set.

This week the Council and concreters will add 90 cubic metres of engineered fill – similar to road fill material – and reseal the top to reinstate the walkway surface.

“We are confident that once works to stabilise the site are complete, it will be safe to return the thoroughfare to the community,” said Ms Cernovskis.

Works have begun to fill a sinkhole located between a busy street and popular walkway in Mount Gambier. Picture: Supplied

Walkway access to the Railway Lands will be reviewed once the work is complete.

“Depending on how things settle, we plan on reopening the thoroughfare in the next week or so,” said Ms Cernovskis.

The Council is also working with adjoining property owners to ensure the safety of both themselves and their properties within the vicinity of the impacted area.

The Council plans to install a crack monitoring system on the wall of the business neighbouring the hole to monitor any further ground movement or settlement over the next 12 months.

Total remediation work costs for the project are sitting at approximately $160,000.