THE Snowy 2.0 project is a complex engineering feat that comprises many facets, one of which is each tunnel will be lined with thousands of concrete segments.

Each of these segments are produced at Snowy Hydro's Polo Flat factory in Cooma, which employs 120 people from the 2,100–strong Snowy 2.0 workforce.

The Snowy 2.0 precast factory has recently achieved an impressive milestone, with manufacturing completed for all concrete segments that will line the dry access tunnels.

More than 25,000 of these seven–tonne segments have been produced which will line both the main access tunnel and the emergency, cable and ventilation tunnel at Lobs Hole.

In total, 35,000 or 27% of the 130,000–plus segments needed to line all of the Snowy 2.0 tunnels have now come off the Polo Flat production line, said Paul Broad, Snowy Hydro's Managing Director and CEO.

"We're proud to be manufacturing and investing locally, and providing employment opportunities for local people as well," Mr Broad said.

"The precast factory is operated by our principal contractor Future Generation Joint Venture and it is powering along. To efficiently and safely produce enough of these massive concrete segments to line the 5.6 kilometres of dry access tunnels is a terrific achievement."

The concrete segments are an intricate piece of Snowy 2.0 project.

As the tunnel boring machine (TBM) excavates rock and works its way further into the tunnel, the pre–loaded segments are installed onto the tunnel wall via machinery within the TBM. Once in place, fast drying grout is then injected behind the segment which seals the gap between the concrete and the actual rock of the tunnel. The TBM then uses the installed segment to leverage itself and push further into the tunnel.

The concrete factory supports the operation of the three Snowy 2.0 tunnel boring machines, which are excavating 27 kilometres of tunnels from Tantangara Reservoir to Talbingo Reservoir for the Snowy 2.0 pumped–hydro expansion of the Snowy Scheme.

The Polo Flat facility includes a concrete batching plant and segment manufacturing from two automated carousels, producing up to 24 rings per day, each ring made of nine segments.

Many of the raw materials like aggregates and sand are sourced from the local Schmidt Quarries at Mt Mary and Nimmitabel, which is reducing transport time and costs. Concrete is mixed within the batching plant, which is then transferred into the factory and poured into specially designed moulds.

With the use of innovative robotics, the moulds progress along the carousel as the segments cure and finish. There is an onsite laboratory and testing to check the quality of every segment produced.

Snowy 2.0 said they are leading the way in Australia to successfully deploy and use robots to automate the process of demoulding, cleaning and application of the release agent on the moulds, before pushing them through to the next production stage. This has allowed the factory to maintain a safe and low–noise working environment for workers.

It takes approximately eight to 10 hours to cure and de–mould each segment from start to finish, then they are stored for about two weeks before being transported to site, loaded into TBMs and installed in the tunnels.