By Lynda Myer
According to Snowy 2.0 reports, TBM Florence has become stuck again on the Snowy 2.0 pumped hydro project.
“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 company said in its latest project update.
The distance that three TBMs working on the project have dug is totally around 9km.
Snowy Hydro said: “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.”
Following that a surface depression appeared above the machine and TBM Florence was halted, in December 2023 it was relaunched.
Additionally, a surge shaft at Marica was now under construction, whereas this surge shaft has two key roles in 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 support type of walls of the Marica surge shaft, which is almost 28m in diameter and is currently over than 80m deep, is rock bolts and shotcrete and once it is excavated to its full depth of 250m, a permanent concrete lining is due to be installed from the bottom up.
The update also added: “We are excavating the shaft with a number of excavation methods, including using 36-tonne excavators that place loads of material into kibbles.”
In order to providing worker access now the shaft is becoming very deep, an integrated work platform and personnel hoist is in the final stages.
According to Snowy 2.0 project manager Richard Clarke: “Building in steep terrain was challenging and required specialized rope access workers to install ground support for safety and stability.”
Although Marica Trail provides all-weather access to the surge shaft site, it too was challenging, because 6.5km-long road climbs 320m and has multiple water crossings.
The process of joining the intake and gate shaft from both structures is undergoing using drill and blast excavation at Tantangara. The transition from the intake changes shape as it is excavated to become the connection tunnel to the gate shaft.
At the same time, crews have started drilling and blasting from the gate shaft to merge into the headrace tunnel alignment excavated by TBM Florence.
Once completed, water is slated to enter the headrace tunnel from the intake, on its way to the power station.
The planned date for starting the commercial operation of all units is December 2028, while first power expected in the second half of 2027.
