Infrastructure engineering consultancy, Zutari, is contributing to some of the most technically complex components of the Lesotho Highlands Water Project (LHWP) Phase II: the 825 m bridge across the Senqu River, and the 34 km Polihali Transfer Tunnel beneath Lesotho’s mountainous highlands.
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Hard-rock tunnel boring was used to construct the 5 m-diameter Polihali Transfer Tunnel.
Multinational, buildings and infrastructure engineering consultancy Zutari has played a leading role in the design and construction supervision of the Senqu River Bridge, one of the most ambitious high-altitude infrastructure projects undertaken as part of the Lesotho Highlands Water Project (LHWP), Phase II. In addition, through its role in the Metsi a Senqu-Khubelu Consultants (MSKC) Joint Venture, Zutari is responsible for design and construction supervision of the Polihali Transfer Tunnel.
These projects are being undertaken in the Kingdom of Lesotho by the Lesotho Highlands Development Authority (LHDA), the implementing and management authority of the LHWP, on behalf of the governments of Lesotho and South Africa.
The Senqu River Bridge
The Major Bridges Project, which includes the Senqu River Bridge, is being delivered by Zutari Lesotho, together with the Lesotho sub-consultant, White Life Consultants, and a black-owned South African sub-consultant, Leporogo Specialist Engineers. This reflects Zutari’s collaborative engineering partnership and a long-standing commitment to infrastructure development in the Kingdom of Lesotho.
Spanning 825 m across the Senqu River valley, the bridge is the longest and highest in Lesotho, rising more than 90 m above the valley floor. Designed as an extradosed cable-stayed structure, the bridge has been engineered to withstand the extreme conditions of Lesotho’s mountainous terrain while ensuring uninterrupted connectivity along the national A1 route.
The new crossing forms part of a series of major bridges required to maintain road access once the future Polihali reservoir is filled. Sections of the existing A1 route will eventually be submerged as the dam reaches full capacity, making the Senqu Bridge a vital long-term replacement that safeguards regional mobility and economic activity.
The bridge was designed to address the complex environmental and geographic challenges associated with infrastructure development in Lesotho’s highlands. Construction required rock-anchored foundations and advanced techniques to navigate the steep valley terrain.
The deck was incrementally launched from both sides of the valley, with precast segments pushed outward until the two sections met at mid-span. This method allowed contractors to construct the bridge safely across the deep gorge while minimising environmental disturbance.
Work on the bridge continued throughout challenging mountain conditions, including winter construction periods, requiring round-the-clock engineering supervision and close coordination between contractors, engineers and project authorities. Louis Joubert, Resident Engineer on the Senqu Bridge project, says the structure represents both technical ambition and long-term national value.
“The Senqu Bridge reflects the engineering ambition behind the LHWP. Beyond the technical achievement, these structures carry real legacy value for Lesotho. As the Highlands landscape evolves, the bridges being built today will stand as enduring symbols of infrastructure excellence and the long-term impact of the project for communities across the region,” notes Joubert.
Beyond its engineering significance, the Senqu Bridge will play a critical role in maintaining access to the north-eastern region of Lesotho, including the regional capital of Mokhotlong. Once the Polihali reservoir is impounded, the existing low-level crossings will be submerged, making the new bridge essential for maintaining this strategic national route.
The project also forms part of a broader infrastructure programme supporting the development of the LHWP Phase II, which is designed to enhance regional water security while generating long-term economic benefits for Lesotho.
Significant opportunities have also been provided for local engineers and technical professionals. Most of the supervision team on the bridge project consists of Basotho engineers and young professionals who have been mentored throughout the construction process. Through partnerships with the LHDA and other project stakeholders, the initiative helps build long-term engineering capacity in the country.
The Senqu Bridge is expected to become a landmark structure within Lesotho’s evolving infrastructure landscape. As the surrounding reservoir fills and the region’s development accelerates, the bridge will continue to serve as a critical transport link while supporting new economic and tourism opportunities.
The Polihali Transfer Tunnel
Zutari is also contributing to the LHWP Phase II by providing design and construction supervision for the Polihali Transfer Tunnel. Stretching approximately 34 km beneath Lesotho’s mountainous highlands, this Tunnel forms a critical link between the Polihali and Katse reservoirs, strengthening the water transfer system that supports regional water and hydropower security.
The tunnel incorporates a sophisticated design comprising a five-metre-diameter, segmentally lined, hard-rock TBM-bored tunnel, intake works, a gate shaft upstream of the new 165 m Polihali Dam, outlet works and a lake tap into the Katse Reservoir. Additional access tunnels and associated infrastructure support the system's construction and future operation.
Unlike visible infrastructure such as bridges and dams, the Polihali Transfer Tunnel represents an engineering achievement largely hidden from view. Yet the underground system is among the most significant elements of the entire LHWP Phase II programme.
Freddie Laas, Project Manager for the MSKC Joint Venture overseeing the tunnel’s implementation, says the project requires a high level of coordination, planning and technical precision. “Delivering infrastructure at this scale requires careful coordination across engineering disciplines, contractors and project stakeholders to ensure that safety, quality and environmental stewardship remain central throughout the construction process.”
Laas adds that projects of this complexity extend beyond engineering alone. “Large-scale infrastructure programmes involve many moving parts, from geological conditions and environmental considerations to social and economic responsibilities. Successfully managing these elements is what ultimately ensures that the project delivers long-term value for both Lesotho and the broader region.”
Although largely invisible once completed, the Polihali Transfer Tunnel will play a vital role in the long-term operation of the LHWP, ensuring efficient transfer of water through the system while supporting the continued development of water infrastructure across Southern Africa.
As construction progresses on Phase II of the project, the tunnel stands as a powerful example of the engineering innovation and strategic collaboration required to deliver infrastructure on a truly regional scale.
Strengthening regional water security
The LHWP is a multi-phase bi-national initiative between the Kingdom of Lesotho and the Republic of South Africa designed to harness the water resources of Lesotho’s highlands through a network of dams, tunnels and associated infrastructure. While the project supports water supply to South Africa’s economic hub, it also generates substantial economic benefits for Lesotho through royalties, infrastructure development and long-term employment opportunities.
Projects of this scale also create opportunities for collaboration between international engineering specialists and local professionals, contributing to skills development and long-term technical capacity within the region.
Zutari has been involved in infrastructure development in Lesotho for decades, supporting projects across water, transport and environmental sectors. The company’s participation in these projects forms part of its broader contribution to the LHWP programme and to infrastructure development across the region.
Tlhabeli Ralebitso, CEO: Africa for Zutari, says projects like the Senqu Bridge and the Polihali Transfer Tunnel demonstrate how strategic infrastructure investment can deliver long-term value for both Lesotho and the broader region. “The LHWP stands as one of Africa’s most significant examples of infrastructure delivered through partnership and shared vision.”
“These projects reflect not only engineering excellence, but also the long-term impact that infrastructure investment can have in strengthening regional water security and hydro-electric power generation, enabling economic growth and supporting communities. Zutari is proud to contribute our expertise to projects that help shape sustainable futures for Lesotho and Southern Africa,” Ralebitso concludes: