Canals, Tunnels and Penstocks

Snowy Hydro updates on status of tunneling work for Snowy 2.0 pumped storage

Snowy Hydro updates on status of tunneling work for Snowy 2.0 pumped storage

Snowy Hydro has provided an update on tunneling work to construct the pumped storage hydro expansion of its Snowy Hydro Scheme.

Snowy 2.0 includes the construction of an underground power station and about 27 km of tunnels within the Kosciuszko National Park in the Snowy Mountains region of New South Wales. Snowy Hydro said Snowy 2.0 is “critically important” and “will help underpin Australia’s transition to a renewable energy future.”

In December 2022, Snowy Hydro reported that a surface depression had emerged above the headrace tunnel at Tantangra but that the integrity of the tunnel was not compromised and tunneling was continuing while work to remediate the surface depression is carried out. However, in February 2023, Snowy Hydro reported that tunnel boring machine (TBM) Florence at Tantangara was temporarily paused while plans to remediate the surface depression were finalized. The depression is about 9 m deep and continues to be monitored.

In this latest update, Snowy Hydro said construction continues to make progress across multiple worksites. For example, at Lobs Hole, another TBM has completed excavation of the 2.7 km main access tunnel and a third TBM has almost finished excavating the adjacent 2.9 km emergency, cable and ventilation tunnel.

At Tantangara, the project team is conducting work to stabilize soft ground and enable TBM Florence to restart excavating the headrace tunnel. TBM Florence has tunnelled about 150 m and is located at a depth of about 30 m. The integrity of the tunnel, which is supported by a concrete lining and steel ribs, has not been compromised, nor has the capacity of the TBM. Snowy Hydro said there is about 10 to 15 m of weak material in front of the TBM that must be stabilized, after which the TBM should strike hard rock and normal tunnelling is expected to resume.

Snowy 2.0 principal contractor Future Generation Joint Venture (FGJV) is drilling probe holes through the front of the excavation to understand the ground conditions immediately ahead of the TBM. Grout is injected in front of the excavation to improve any weak zones and limit any water flows. Grouting is well under way, with 20 grout holes drilled to date in the location.

FGJV is installing a slurry plant for the TBM that will mean the machine can switch from open excavation to a closed, pressurized mode. This will deliver stable excavation and efficient progress through the softer ground conditions, while enabling the TBM to switch back to open mode when in harder rock, Snowy Hydro said.

Stage two of the work to stabilize the ground in front and above the machine will involve ground improvement from the surface. Once the area is grouted, the depression will be backfilled and revegetated.

At Lobs Hole, in the main access tunnel, work is continuing on multiple drill and blast cross tunnels. These will link with the emergency, cable and ventilation tunnel, where a TBM has tunnelled 2.8 km and reached the site of the underground power station cavern complex. This will be one of the largest and deepest in the world, according to a release.

One TBM will soon be modified to excavate the inclined pressure shaft on a steep uphill angle. Another TBM is being reassembled at the Talbingo adit with new components, including a cutterhead and shields, and will be launched later this year to excavate the 6 km tailrace tunnel, which will feed into Talbingo Reservoir. Excavation of intakes at Talbingo and Tantangara is advancing, along with the surge shaft on the Marica plateau that is already excavated to a depth of more than 20 m. 

Snowy Hydro said this pumped hydro project will provide the National Electricity Market with 2,000 MW of on-demand generating capacity and 175 hours of energy storage.