Stalled Snowy 2.0 tunnelling set to resume in weeks pending approvals

Snowy 2.0 is being constructed for project promoter Snowy Hydro by the Future Generation (FGJV) joint venture between Webuild, Australian firm Clough and an American subsidiary of Webuild Lane Construction.

It will link two existing dams, Tantangara and Talbingo, through 27km of tunnels in the Snowy Mountains, and will require the construction of a new underground power station. Water will be pumped to the upper dam when there is surplus renewable energy and low electricity demand, and released back to the lower dam to generate energy when demand is high. This will enable hydroelectricity to be created on demand, providing 2GW of fast-start dispatchable energy and provide 350GWh of large-scale storage, for use at peak times.

However, delivery of the scheme has encountered a series of setbacks, leading to confirmation in May of a 12 to 24-month delay its completion date. Among these, tunnel boring machine (TBM) Florence’s progress along a 17km tunnel linking the planned underground power station to Tantangara dam has been stalled for six months due to soft rock. The challenging ground conditions were encountered by the TBM after just 70m of progress.

Other incidents included a 9m deep sinkhole that appeared in front of the TBM at the Tantangara site in February. The NSW planning department is yet to release a report on the impact of the sinkhole which will include measures to avoid similar problems going forward.

The incidents have fuelled concerns from the planning department as well as National Parks Australia over environmental damage to the Mount Kosciuszko National Park, where the scheme is located.

According to a report last week by Guardian Australia it is hoped work will resume once environmental approvals are issued on programme alterations to remedy the project's geotechnical challenges.

These include FGJV's installation, now underway, of a slurry plant for the 211m long TBM to enable tunnelling through the soft rock, allowing it to switch from open excavation to a closed, pressurised mode. This will enable smooth excavation and efficient progress through the softer ground conditions, with the slurry used to stabilise the tunnel face and transport excavated spoil to the surface. The TBM, which progresses at an average 15m a day in good conditions, will also be able to switch back to open mode for tunnelling in harder rock.

Meanwhile, another proposed change to the programme is to enable drilling on the head-race tunnel by starting to bore from the other end, although this could require further new approvals concerning the treatment of spoil.

Snowy 2.0 is the largest renewable energy project in Australia and was first announced in 2017, when the original cost was set at £1bn. This has since more than tripled, and it is understood an updated cost estimate for Snowy 2.0 will be published before the end of 2023.

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