Snowy Hydro says it will bring in a fourth tunnel boring machine in an attempt to keep the beleaguered Snowy 2.0 pumped hydro project to its already delayed timetble, admitting that the geology is even more complicated than previously thought.
Snowy Hydro CEO Dennis Barnes has already admitted once that the federal government owned utility had not done proper due diligence on the geology of the project, but now further studies have revealed even more complexity.
Barnes said in a statement last week announcing the new boring machine that the company knew about the fault zone that lies along the length of the head-race tunnel that often stuck Florence has been working on but the project design hadn’t been ‘mature’ enough to handle its complexity.
”While the fault zone is not a surprise, further ground testing since the project reset has revealed it is far more geologically challenging than earlier investigations indicated,” he said in the statement.
“We’ve carefully considered a range of options to get through the fault zone and overcome the initial design immaturity.”
But Snowy Hydro’s own 2017 feasibility study noted that “geological, geotechnical and hydroecological conditions vary significantly along the alignment… five major underground rock mass groups, three major fault zones and five rivers and creeks affect the dam-to-dam alignment”.
The final investment decision outlined just how many unknowns there were when it came to the Snowy 2.0 geology, however.
The FiD outlined data gaps including that the 38 bores drilled along the full 26 km distance couldn’t provide enough information about “diverse ground conditions and lithological rock types” or to understand the already-known risks. It also noted granite rock in the area “could impact on the tunnel”.
A cool $75m
The new machine will cost around $75 million, but Snowy Hydro says this extra cost won’t add to the now blown out cost of $12 billion for building the 2.2 gigawatt (GW) pumped hydro scheme.
It’s hoped that introducing another boring machine will keep Snowy 2.0 to its latest official deadline of December 2028, provided the New South Wales Department of Planning approves the change.
However, the machine won’t be on deck until the end of 2025.
The project currently will then have four boring machines working on three tunnel, including the original Florence machine, which by May had gotten just 850 metres into the 17 kilometre headrace tunnel.
A second machine is handling the pressure shaft above the power station; and a third is digging the tailrace tunnel leading to the lower talbingo reservoir.
The fourth machine will start at the other end of the headrace. It will be made and supplied by Germany’s Herrenknecht, the same company that made the Florence tunnelling machine and supplied one of the other borers.
This is despite Barnes specifically criticising the performance of Florence – which has been stuck in soft earth and then hard rock – as “disappointing”.
Renew Economy is seeking further comment from Snowy Hydro.
Then-prime minister Malcolm Turnbull announced the project in 2017 with the highly optimistic figure of $2 billion and a finishing date of 2021.
The feasibility study, released at the end of 2017, said it was more likely to cost $3.8-4.5 billion and be ready by 2024. But actual construction costs combined with myriad problems, such as the Florence boring machine getting stuck in soft earth, then hard rock have sent the costs skyrocketing.
This year, the federal government allocated $7.1 billion over four years to the project, with $2.6 billion in equity funding and the remainder as a loan.
