The cutterhead and main drive for tunnel boring machine (TBM) Monica have arrived at the Snowy 2.0 Marica worksite in New South Wales, Australia, marking a major milestone for the pumped storage hydro expansion project.
TBM Monica will excavate the downstream end of the 9.9m diameter headrace tunnel that will connect Tantangara Reservoir to the underground power station located about 850m below the surface.
The 207-tonne main drive, eight metres wide, was transported from Port Kembla, a major industrial port south of Sydney, on a 73m-long trailer with 152 wheels. It is one of more than 140 oversized loads required to deliver the TBM’s components. Once assembled at Marica, the machine will be 178m long and equipped with eight trailing gantries and supporting systems for continuous tunnelling.
TBM Monica is named after Tumut High School student and aspiring engineer Monica Brimmer, who won the naming rights through an Indigenous art and storytelling competition. It is the final TBM to join the Snowy 2.0 fleet.
After months of design, fabrication and inspection, the machine passed factory acceptance testing in July at Herrenknecht’s facility in China. Snowy Hydro Chief Delivery Officer Dave Evans attended the inspection along with SMEC Senior Tunnelling Engineer Nick Chapman. SMEC is providing technical oversight for the machine, including specifications, drive systems and features to support constructability.
Monica is the fourth TBM to be deployed on the project and will operate in a geologically challenging section of the headrace tunnel. Its design allows it to manage fault zones, squeezing ground and groundwater ingress. SMEC’s seconded team will oversee construction during assembly, tunnelling and segment installation to ensure compliance with design and safety requirements.
The arrival of the main drive drew strong community interest, with more than 1,500 people gathering in the regional town of Cooma, the gateway to the Snowy Mountains, as the convoy passed through. Snowy Hydro held a public viewing event to mark the occasion.
The main drive arrives alongside other long-lead components such as the cutterhead, shield sections and gantries. Assembly will take place in the launch adit at Marica, with commissioning expected in early 2026. TBM Monica’s introduction will expand tunnelling capacity and help the project stay on track for its December 2028 completion target.
Snowy 2.0 is a major expansion of the Snowy Scheme, one of Australia’s most significant energy and engineering assets. The project will link Tantangara and Talbingo reservoirs – both located in the Snowy Mountains region of New South Wales – via 27km of waterway tunnels to a new underground power station. Between 2017 and 2019, SMEC led the feasibility and reference design phases. Since 2019, the company has continued to support Snowy Hydro through design review and a seconded team working in Cooma across geotechnical engineering, tunnelling, hydrology, environment and civil engineering.
