Work on the Snowy Hydro 2.0 project is still well underway despite an unexpected tunnel breakthrough during cavern excavation blasting.
Snowy Hydro chief executive, Dennis Barnes, said to the ABC that it was an incident that would have been fully expected one blast later.
“The site is entirely safe, and people are evacuated before any of those blasts are undertaken,” Mr Barnes said.
Additionally Snowy Hydro has reported that rumours that tunnel boring machine (TBM) Florence had stopped tunnelling were incorrect.
“Florence has been operating as we expected since her restart in December. We went through the soft ground, reached some very hard ground,” Mr Barnes said.
“We were averaging about seven or eight metres a day, which is what we expected as we got going again.
“And I think the last few days, we’ve had 12m a day, so Florence is absolutely on the move.”
TBM Florence remains fully operational and is now more than 800m into excavation of the Snowy 2.0 headrace tunnel at Tantangara. The TBM has operated successfully since its restart on 8 December 2023 and has moved through identified soft ground into hard rock.
The total distance tunnelled by all three Snowy 2.0 TBMs across the pumped-hydro renewable energy project is approximately 9km.
As provided in evidence at two recent Senate Estimates hearings, Snowy Hydro has been investigating options to de-risk the headrace tunnel construction by excavating from the other end. This work remains ongoing.
The surge shaft has two key purposes for the operation of a hydro power station: as a water storage and vacuum relief when the power station starts up, and to absorb the momentum of water movement within the headrace when the power station is shut down.
The Marica surge shaft is about 28m in diameter and is currently over 80m deep.
During its construction the walls of the shaft are supported temporarily by rock bolts and shotcrete and once it is excavated to its full depth of 250m, a permanent concrete lining will be installed from the bottom up.
Snowy Hydro is excavating the shaft with a number of excavation methods, including using 36t excavators that place loads of material into kibbles. This material is lifted out and dropped into a dump truck.
An integrated work platform and personnel hoist is in the final stages of commissioning to provide worker access now that the shaft is becoming very deep.
In the latest project update, civil engineer and Snowy 2.0 project manager, Richard Clarke, detailed the significant work undertaken constructing Marica Trail to create a new permanent access road into the surge shaft site.
Marica Trail provides safe, all weather access for traffic, including heavy vehicles.
Building in steep terrain was challenging and required specialised rope access workers to install ground support for safety and stability.
The road has been very carefully constructed in a tight envelope. It’s 6.5km long, with an elevation change of about 320metres from top to bottom and multiple water crossings have been created, including over the Eucumbene River.
Over at Tantangara, drill and blast excavation to join the intake and gate shaft is underway from both structures. The transition from the intake changes shape as it is excavated to become the connection tunnel to the gate shaft.
At the same time, Snowy Hydro has started drilling and blasting from the gate shaft to merge into the headrace tunnel alignment excavated by TBM Florence.
When completed, water will enter the headrace tunnel from the intake, on its way to the power station.
Snowy 2.0 is being engineered to deliver clean and reliable energy storage and generation for the next 150 years. The target date for commercial operation of all units is December 2028, with first power expected in the second half of 2027.
Image: Lasse Jesper Pedersen/shutterstock.com
