Snowy Hydro says key tunnelling machine still stalled after two months in weak ground
A key tunnelling machine at the Snowy 2.0 project remains stuck in place more than two months after first grinding to a halt due to soft ground.
A key tunnelling machine at the Snowy 2.0 project remains stuck in place more than two months after first grinding to a halt, with Snowy Hydro saying on Wednesday its contractors were still working to stabilise the ground in front of the machine.
The tunnel boring machine (TBM), called Florence, hit difficult ground in November and has managed to move only 150m since it was first deployed in March 2022. The machine has not moved since December, when it stalled completely when faced with soft ground ahead of it.
Snowy said in a progress update late on Wednesday its contractors were still working to inject grouting in the 10m to 15m zone of “weak” ground ahead of the machine, needed to support its work before the machine reaches fresh rock.
But that work has been slowed because a 9m deep sinkhole has opened on the surface above Florence, leading to safety concerns around the drilling site.
Snowy did not give any indication of when it expects Florence to return to work, saying its contractor – the Webuild-led Future Generation Joint Venture (FGJV) was also working to modify the tunnelling machine to allow it to work through any areas of soft ground encountered in the future.
“FGJV is currently installing a slurry plant for the TBM that will mean the machine can switch from open excavation to a closed, pressurised mode. This will deliver stable excavation and efficient progress through the softer ground conditions, while enabling the TBM to switch back to open mode when in harder rock,” Snowy said in a statement.
Snowy said the ground subsidence above Florence – which sits about 30m below ground – had not compromised the integrity of the 150m worth of tunnel already completed.
The company said that, despite the delays affecting Florence, its other work on the $5.9bn project was hitting key milestones, with a second tunnelling machine having completed work on the 2.7km main access tunnel, and a third machine nearing completion of a 2.9km emergency, cabling and ventilation tunnel.
The second machine, named Lady Eileen Hudson, has been moved and is now being modified to begin work on a new 6km tunnel.
In mid-February new Snowy Hydro chief executive Dennis Barnes confirmed to a Senate estimates committee that the Snowy 2.0 project was at least a year behind schedule, with the 2,000 megawatt pumped hydro expansion now expected to be completed by the end of 2027.
It is not yet clear whether the delays faced by Florence will add to the overall time frame of the project, however, with Mr Barnes telling the committee the company would not be able to make a judgment on overall progress for another year.
“Until we get into the excavation of the cavern, about a third of the way through the excavation, it would be premature to be definitive and we expect to be at that point in the first quarter of 2024,” he said.
Snowy Hydro said on Wednesday its boring machines had now completed tunnelling to both ends of the cavern excavation site, seen as a key milestone for the project.