Africa |
Innovations and challenges in LHWP Phase II
The Polihali Transfer Tunnel, a major component of Phase II of the Lesotho Highlands Water Project, showcases modern tunnelling practices, integrated hydropower development, and the logistical demands of infrastructure construction in remote regions. Information from Nts’oli Maiketso – Divisional Manager, Phase II
Above and right: Tunnelling by the Katse Tunnel Boring Machine (TBM) was launched on 15 January 2025 by the Minister of Home Affairs Honourable Lebona Lephema on behalf of the Right Honourable the Prime Minister of Lesotho at a ceremony held on site at Ha Bereng, Leribe
THE POLIHALI TRANSFER TUNNEL is one of the key components of the Lesotho Highlands Water Project Phase II. Designed to convey water between reservoirs and support the project’s hydropower goals, it brings together modern tunnelling techniques, safety systems, and extensive logistical coordination in a remote, mountainous region.
Tunnelling methods and safety systems Double Shield Hard Rock TBMs were selected for the
Polihali Transfer Tunnel after careful consideration taking into account the hard rock that they would be boring through and the scheduled timeline for the project.
One of the key advantages of the double 14 | May 2025 |
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shield TBM is its ability to advance continuously while simultaneously installing pre-cast concrete lining segments which are manufactured on site, enhancing both efficiency and tunnel stability. Advanced cutterhead technology, high-precision guidance systems, and automated monitoring of TBM parameters ensure optimal performance while minimising risks. Safety is a top priority, with robust ventilation with an air chiller, dust scrubber, real-time gas monitoring, probing ahead of excavation, and emergency response systems integrated into the tunnelling process. A dedicated safe space – refuge chamber – is built onto the TBMs where workers can seek shelter in case of an emergency during tunnelling operations,
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