Snowy Hydro will not be able to move its stuck tunnel-boring machine (TBM) until it proves to the New South Wales environment department that doing so will not cause "further damage" to the environment in Kosciuszko National Park.
The 143-metre-long TBM Florence ground to a halt last year, after a 9-metre-deep hole appeared on the surface above it in Kosciuszko National Park.
The NSW Department of Planning and Environment (DPIE) told the ABC in February it was investigating the incident and has now placed further environmental conditions on the boring operation.
"Snowy Hydro must prepare a modification report that demonstrates how the project can safely progress without further environmental damage," the department said in a statement.
"Tunnel boring at the Tantangara location is on hold until the department gives approval for operations to continue."
The tunnel being drilled by TBM Florence is one of three major tunnels that will form the Snowy 2.0 project, a large hydro-electricity project in southern NSW that is one of the centrepieces of Australia's transition to renewable energy.
Snowy Hydro said it took its environmental responsibilities "very seriously" and had been working with the DPIE and others since what it called a "surface depression" was identified in December 2022.
"Snowy Hydro has also been working closely with the DPIE to provide a scope of works and to progress a modification of the Snowy 2.0 main works planning approval to allow the rectification of this area and provide assurance around future tunnelling works," it said in a statement.
It said it expected to submit its modification report to the department "within a week" and was confident the information would "satisfactorily address concerns around future subsidence issues".
Project already delayed
Last week, Snowy Hydro announced that Snowy 2.0 would be delayed by up to two years and was expected to be fully operational by 2029.
One of the four main reasons cited by the company for the delay was the issue with TBM Florence.
At the time, Snowy Hydro chief executive Dennis Barnes told Radio National Breakfast that the machine was expected to be moving again in a matter of weeks.
"When the machine gets moving, which we're expecting in weeks, not months, then we do expect that the machine will move at the rate of more than 10 metres a day," he said.
Former Energy Australia executive and current board member of the National Parks Association Ted Woodley said it was unclear when the operation would restart.
"We've been getting statements from Snowy Hydro for the last six or more months, referring to problems, and the fact those problems have been resolved and she's starting boring again," he said.
"But as we're aware, in 14 months she's progressed 150 metres, so clearly there are technical issues with the machine and in the environment she's tunnelling."
Mr Woodley said he was pleased by the state government's intervention in the situation at Tantangara.
"I would also trust that the investigations are rigorous and encompass the possibility of more damage than was previously expected to the park and its water catchments," he said.
'They need to get a move on'
Simon Bartlett has not worked on Snowy 2.0 but he has been a senior engineer on other pumped-hydro projects in Australia and overseas.
He said the tunnelling was taking place in challenging conditions, but it would need to speed up.
"At the rate they're going it's going to take more than 80 years to complete the 17km," Mr Bartlett said.
"Hopefully they get into better rock conditions, hopefully they can do it and satisfy the Department of Environment that they won't cause more environmental harm, but they really need to get a move on."
Professor Bartlett said the goal of full operation of Snowy 2.0 by 2029 was an "incredibly aggressive target".
"Snowy Hydro have said they won't know exactly when the scheme will be finished until they get halfway digging the underground cavern for the power station," he said.
"I personally think completing this before the 2030s would be an incredible task if they could pull that off."
