Snowy Hydro has bitten the bullet and kicked off the process to bring in an extra tunnel-boring machine for its troubled Snowy 2.0 pumped hydro project in NSW as it seeks to prevent a further delay in its start-up.

The fourth of the boring machines – huge pieces of equipment up to 200 metres long that can weigh more than 2000 tonnes – will cost about $75 million, the federal government-owned generator said.