Tailrace tunnel breakthrough advances Australia’s largest renewable project

Australia’s Snowy 2.0 pumped storage hydropower project has reached a major construction milestone after tunnel boring machine Lady Eileen Hudson completed excavation of the 6 km tailrace tunnel and broke through into the underground cavern complex. The breakthrough marks the completion of the machine’s tunnelling role on the project, after it previously excavated the 2.85 km main access tunnel.

The tailrace tunnel is a critical component of Snowy 2.0, connecting the underground power station to the lower reservoir at Talbingo Dam. Its completion represents an important step toward linking the project’s major underground elements, as construction focus continues to shift toward the power station nearly one kilometre below ground.

The achievement is notable because of the challenging geology beneath the Snowy Mountains. The 2,300-tonne TBM had to progress through difficult ground conditions, requiring careful excavation control and ongoing adaptation. Elsewhere on the project, TBM Florence is advancing along its 15 km tunnelling journey and is approaching the halfway mark, while TBM Monica has been custom-built to excavate from the opposite end of the same tunnel through the geologically complex Long Plain Fault Zone.

Snowy 2.0 is one of Australia’s largest renewable energy projects. Once complete, it is expected to provide large-scale pumped hydro storage, support grid reliability, store excess renewable energy and strengthen long-term energy security.