Snowy Hydro has achieved another milestone in the construction of the Snowy 2.0 pumped hydro project, having broken through the last 3m of the 223m long transformer hall cavern crown. 

The Snowy 2.0 delivery team began excavating the transformer hall and machine hall caverns in June 2023. The Snowy 2.0 power station will be located approximately 800m underground at Lobs Hole in the Snowy Mountains. 

When completed, the machine hall will be 251m long and 52m high and the transformer hall will be 223m long and 46m high. Together they will form one of the largest and deepest caverns in the world, big enough to fit the Sydney Opera House inside. 

Precise drill and blast methods are used to profile the curved cavern crowns (or ceilings) and break up the rock, which is mucked out and followed by surface scaling to remove any remaining loose rock. 

The exposed solid rock face is then supported with rock bolts and shotcrete. The excavation sequence of the cavern crowns is carefully planned and executed, as the rock mass relaxes and moves inwards as the excavated void increases. These movements are expected and are closely monitored during the process.

To date, approximately 17,000m³ of material has been excavated from the central heading of the transformer hall cavern crown. The heading has been advanced in 3-4m rounds from either end of the cavern for a total of 77 blasts.

The machine hall cavern crown breakthrough will take place in coming weeks, and widening of both cavern crowns, known as side slashing, is ongoing and planned for completion in coming months. Excavation of both power station caverns is set to continue through 2024. 

The breakthrough of the transformer hall cavern crown represents another important milestone for the Snowy 2.0 pumped hydro project that is set to significantly expand the existing Snowy Scheme and will provide an added 2,200MW of on-demand power and 160 hours of large-scale renewable energy storage for the National Electricity Market.

Snowy Hydro CEO, Dennis Barnes, said, “The breakthrough of the transformer hall cavern crown is a really pleasing milestone for the Snowy 2.0 team, reinforcing that we’re making good progress with our underground drill and blast excavation activities.” 

“We are well on our way to delivering the largest single project that will help ensure Australia’s secure and reliable transition to renewable energy.”

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