By Ashley Karen
The Snowy 2.0 project, which is a crucial expansion of the Snowy Scheme involving pumped hydro, is progressing well across various worksites in Australia. The project aims to connect two existing dams, Tantangara and Talbingo, through a tunnel spanning 27km and construct a new underground power station.
Currently, the project team is working on stabilizing the soft ground encountered at Tantangara to enable TBM Florence to resume excavating the headrace tunnel.
TBM Florence has already tunneled 150m and is now situated 30m below ground level. However, a surface depression has recently emerged above the TBM site, causing a temporary delay in progress. The depression is being monitored and is approximately 9m deep.
Despite this setback, the tunnel’s integrity, supported by concrete lining and steel ribs, and the TBM’s capacity remain uncompromised. The TBM has been paused and will resume normal tunnelling once about 10-15m of weak material ahead of it is stabilized before striking the hard rock.
Future Generation Joint Venture (FGJV), the primary contractor for Snowy 2.0, is now conducting probe hole drilling at the excavation’s front to assess the ground conditions ahead of the TBM. Grout is being injected to reinforce any weak areas and prevent water flow. Currently, grouting is underway in the existing location, with 20 holes drilled to date.
For stage two of the project, the surface will be subject to ground improvement after grouting, and the depression will then be backfilled and revegetated.
FGJV is also installing a slurry plant at Tantangara, with civil and concrete works nearly finished. The separation plant, bentonite mixing silos, and water tanks are being assembled, and electricians are busy with motor installation, internal wiring, and high-voltage cable installation to substations. This plant will allow TBM Florence to switch to a closed, pressurized mode for efficient progress in softer ground conditions when in the headrace tunnel from an open excavation in harder rock.
At Lobs Hole, multiple drill and blast cross tunnels are still under construction in the main access tunnel, linking to the 2.9km emergency, cable, and ventilation tunnel (ECVT). TBM Kirsten has tunneled 2.8km and reached the underground power station cavern complex site, marking a significant milestone for Snowy Hydro as the team now has access to the excavation site from both ends of the cavern, one of the world’s largest and deepest.
TBM Kirsten is set to undergo modifications to mine the inclined pressure shaft on a steep uphill angle. These modifications include altering the levels of the TBM’s tanks and mechanical equipment so they are level when travelling up the 25-degree incline. The walkways on the TBM’s sides will also be converted into steps and ladderways.
Meanwhile, TBM Lady Eileen Hudson has finished boring the 2.7km key access tunnel and is being reassembled at the Talbingo adit with new parts such as a cutter head and shields. The machine will be launched into the mountain later this year to bore the 6km tailrace tunnel, which will feed into Talbingo Reservoir.
Excavation of intakes at Talbingo and Tantangara is progressing steadily. The Tantangara intake stage 1 on the Marica plateau is already about 20 m deep, with stage 2 works extending the excavation a further 30m for a total depth of approximately 50 m. Once these works are complete, a concrete diffuser structure will be built at the base of the excavation, followed by the temporary rock plug removal to allow reservoir water to enter the intake and headrace tunnel.
Further information is available here.
