Snowy 2.0 is a major pumped-hydro expansion of the Snowy Scheme and at Marica, high in the Snowy Mountains, a very wide and deep surge shaft connecting to the Snowy 2.0 headrace tunnel is being built.
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 28 metres in diameter and is currently over 80 metres 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 250 metres, a permanent concrete lining will be installed from the bottom up.
We are excavating the shaft with a number of excavation methods, including using 36-tonne 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 the shaft is becoming very deep.
In the latest project update, civil engineer and Snowy 2.0 project manager, Richard Clarke, details 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 6.5 km long, with an elevation change of about 320 metres 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, we have 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.
Update – Thursday 2 May
Reports today that tunnel boring machine (TBM) Florence has stopped tunnelling are incorrect.
TBM Florence remains fully operational and is now more than 800 metres 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 nine kilometres.
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.