Dual Boring Operations Accelerate Construction Of 38 Kilometre Polihali Water Transfer Tunnel In Lesotho

The Lesotho Highlands Water Project Phase 2 accelerates with two tunnel boring machines excavating the 38km Polihali tunnel to boost regional water security.

By: AXL Media

Published: Apr 20, 2026, 5:51 AM EDT

Source: Information for this report was sourced from Engineering News

Simultaneous Excavation Commences On Regional Water Route

The Lesotho Highlands Water Project (LHWP) Phase 2 has transitioned into a full scale tunneling phase following the introduction of a second tunnel boring machine (TBM). This advanced piece of engineering is currently drilling through the Maluti mountains to create a 38.5 kilometer long connection between the Polihali and Katse dams. With two machines now operating from opposite ends of the route, the project is moving steadily toward completion of a gravity tunnel designed to facilitate significantly larger volumes of water transfer for the region.

Ministerial Unveiling Of Advanced Boring Technology

South African Minister of Water and Sanitation Pemmy Majodina, alongside Deputy Minister David Mahlobo and Lesotho’s Minister of Natural Resources Mohlomi Moleko, officially unveiled the new TBM on Monday. The Department of Water and Sanitation described the launch as a powerful symbol of progress for one of the most ambitious water infrastructure routes in Southern Africa. The machine, which features a 5.38 meter cutterhead, is specifically engineered to maintain continuous operations even when encountering the toughest underground rock conditions.

Integration Of Rock Excavation and Structural Lining

The TBM utilizes a sophisticated process that allows for the simultaneous excavation of rock and the installation of precast concrete lining segments. This seamless transformation of raw mountain rock into a finished structural tunnel occurs in one uninterrupted cycle, maximizing efficiency. While the first machine launched at Katse dam in February 2025 has already reached over 600 meters, the newly unveiled Polihali TBM has successfully excavated 235.8 meters since starting its primary operations in January 2026.