| Civil works “We’re mindful that we are building Snowy 2.0 in
a precious and protected national park. We have worked diligently to arrive at a proposal that does not step outside our existing construction area or increase our already approved impacts,” Barnes said. He said the company remains committed to transparency regarding the project, given the inevitable challenges ahead. “Just like the construction of the original Snowy Scheme, this is one of the most challenging and complex megaprojects underway in the world,” he said. “The fourth tunnel boring machine is an example of adapting to the situation in front of us, so we are doing everything we can to safely meet Snowy 2.0’s delivery timeline.”
While the need for a new tunnel boring machine is driven by new information about the fault zone, Barnes acknowledged that the disappointing performance of Florence, the tunnel boring machine excavating the same tunnel that the new machine will also work on, has contributed to the need to take significant action. “It’s difficult to say with certainty whether the same action would be needed if Florence had performed as we had hoped. However, it’s likely that the fourth machine would still be needed,” Barnes said. Snowy 2.0 will help underpin Australia’s transition
to renewable energy through its ability to generate enough flexible, fast-dispatch energy to power 3 million homes continuously for a week. The unmatched scale and duration of Snowy 2.0’s
storage and generating ability will effectively provide the network with critical electricity supply insurance against extended periods without enough wind and sunlight. Most other forms of storage, including batteries, can only generate power for a handful of hours. According to AEMO (the Australian Energy Market
Operator), Snowy 2.0 will supply a majority of the National Electricity Market’s storage needs, greater than every other storage asset combined. “Snowy 2.0 is critical to Australia’s energy future.
We need to get this job done,” Barnes said. Subject to planning approval, the new machine will be tunnelling before the end of 2025.
Milestone reached As Australia tackles these complexities head-on,
Africa’s Lesotho Highlands Water Project also reaches a significant tunneling milestone, pushing forward another phase in its expansive water and power initiative.
On Monday 19 August, the Lesotho Highlands Development Authority (LHDA) celebrated a tunnelling milestone on the Polihali Transfer Tunnel construction site – the successful breakthrough of the upper intake tunnel into the lower intake tunnel after seven months of tunnelling. This is a milestone in the Polihali Transfer Tunnel works and a significant step in the journey towards the impoundment of the Polihali reservoir. The intake tunnels will allow water from the 5042-hectare Polihali reservoir to enter the transfer tunnel for delivery to the Katse reservoir, the centre point of the Lesotho Highlands Water Project. The breakthrough of the intake tunnels is more than just a technical accomplishment; it signifies
the start of two critical phases in the project. The first phase involves the safe commencement of impoundment of the Polihali reservoir, made possible by the collapse of the upper tunnel into the lower one. This process allows for a controlled and secure increase in water levels up to the lower tunnel, which can then be temporarily sealed. The second phase enables continuous debris
removal from the remaining tunnel works. As construction progresses towards its connection with the access adit, debris can be efficiently cleared through the upper intake tunnel without interrupting the impoundment process. This efficient operation is crucial for maintaining project momentum while ensuring the structural integrity of the tunnels. The lower intake tunnel, which plays a vital role in the Polihali Dam’s operational future, will facilitate the intake of live water even at low reservoir levels. This feature is essential for ensuring the uninterrupted flow of water, underscoring the importance of this milestone. Key milestones in the Polihali Transfer Tunnel works include the excavation of the 450m long tunnel which began on January 16 and was completed on August 19; the completion of the 370-metre long lower intake tunnel on 05 August and the ongoing excavation of the connecting tunnel. The 1322-metre long connecting tunnel will connect the tunnel boring machine (TBM) access adit at the chamber where the TBM will be assembled, marking the start of the TBM-bored transfer tunnel to Katse. To date, 26 metres of the connecting tunnel have been completed. These achievements are testament to the dedication and expertise of the LHDA and its consultants and contractors: Metsi a Senqu Khubelu Consultants (MSKC), designers of the Polihali Transfer Tunnel and the Kopano Ke Matla Joint Venture, which is constructing the tunnel. The successful completion of the intake tunnels brings the LHDA one step closer to realising the full potential of the Polihali Dam: increasing the volume of water transferred to South Africa, increasing the volume of hydropower generated in Lesotho, enhancing the livelihoods of Basotho and contributing to the economies of Lesotho and South Africa.
Phase II of the Lesotho Highlands Water Project builds on the successful completion of Phase I in 2003. It delivers water to the Gauteng region of South Africa and utilises the water delivery system to generate hydroelectricity for Lesotho. Phase II will increase the current supply rate of 780 million cubic metres per annum incrementally to more than 1 270 million cubic metres per annum. At the same time, it will increase the quantity of electricity generated in Lesotho and is a further step in the process of securing an independent electricity source to meet Lesotho’s domestic requirements.
Seismic improvements Across continents, similar efforts are underway at
the Priest Rapids Dam in Washington State, where seismic improvements have ensured its readiness for extreme conditions, reinforcing the global focus on dam safety Stantec, a global leader in sustainable design
www.waterpowermagazine.com | October 2024 | 33
Above: Polihali Transfer Tunnel breakthrough on 19 August 2024
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