In a landmark milestone, the Senqu bridge, the longest in Lesotho and a critical component of the Lesotho Highlands Water Project (LHWP) Phase II, has officially been inaugurated.

The inauguration was undertaken on April 22 by Lesotho’s King Letsie III and Prime Minister Sam Matekane, along with South African President Cyril Ramaphosa.

Completion of the Senqu bridge marks the replacement of the existing crossing, which will be submerged once the Polihali dam is impounded. The new bridge, together with the Mabunyane and Khubelu bridges, will ensure uninterrupted access to Mokhotlong, Sani Pass and surrounding areas.

Construction of the R2.4-billion Senqu bridge, the largest of the three major bridges constructed in Phase II to span the Polihali reservoir, started in 2023 and was completed in February. It was opened to traffic at the end of March.

Measuring about 825 m in length and 90 m in height, the Senqu bridge is an extradosed structure, a hybrid design combining the principles of a box girder bridge and a cable-stayed bridge.

The bridge deck, constructed in 50 m sections cast simultaneously from both ends, is supported by 17 piers ranging in height from 15 m to 90 m.

At 87.8 m, Pier 7 is the tallest. Fifteen of the 17 piers will be submerged to depths of up to 85 m once the Polihali reservoir reaches full supply level.

The bridge’s longest span, at 100 m between Piers 7 and 9, crosses the deepest section of the Senqu valley.

An integrated bridge monitoring system will continuously track tilt, temperature, movement and structural stresses in the piers, deck and cables throughout the bridge’s operational life.

During construction, a peak workforce of 1 200 was employed, averaging 800 over the three-year period, the majority of whom were Basotho nationals.

About 150 000 m3 of rock were excavated, 10 000 t of steel were used and 40 000 m3 of concrete were placed.

The contract met all socioeconomic targets for Basotho employment across all categories, as well as for women and youth participation and the involvement of Lesotho and South African enterprises.

Lesotho-based enterprises accounted for 29.6% of total expenditure on goods and services, with firms in the project area accounting for 7.9% and South African black-owned firms 16.6%.

Zutari, formerly Aurecon Lesotho, together with Lesotho’s White Life Consultants and South Africa’s Leporogo Specialist Engineers, was responsible for the bridge’s design and construction supervision.

Construction was undertaken by the WRES Joint Venture, which includes Italy-based Webuild, South African firms Raubex Construction and Enza Construction, and Lesotho’s Sigma Construction.

Meanwhile, full-scale tunnelling is now well under way on the LHWP Phase II following the launch of a second tunnel boring machine (TBM).

The Polihali TBM, which technically started work in January, joins the Katse TBM, which was launched in February 2025 to steadily drill – from both ends – through the 38.5-km-long tunnel connecting Polihali and Katse dams in Lesotho’s Maluti mountains.

The gravity tunnel will carry water from the Polihali reservoir to the Katse reservoir.

The new TBM was officially unveiled on April 20 by South African Water and Sanitation Minister Pemmy Majodina and Deputy Minister David Mahlobo, along with Lesotho Natural Resources Minister Mohlomi Moleko.

The Department of Water and Sanitation (DWS) describes the launch of the second TBM as a powerful symbol of progress as the project transitions from preparation to full-scale tunnelling along one of the region’s most ambitious water-transfer routes.

The Polihali TBM, which arrived at the site in July 2025 and started excavation in January 2026, had reached 235.8 m by mid-February 2026, according to the Lesotho Highlands Development Authority (LHDA).

The first TBM was launched at Katse dam in February 2025 and had 614.5 m by mid- January 2026.

The DWS says that the TBMs measure about 423 m in length, feature a 5.38 m cutterhead and are engineered to work continuously, even in the toughest underground conditions.

During this process, the machines also install precast concrete lining segments, seamlessly transforming raw rock into a completed structure in one uninterrupted operation.

The Polihali tunnel is one of the main components of the LHWP Phase II currently under construction.

Other components include the 165-m-high concrete-faced rockfill dam at Polihali, downstream of the confluence of the Khubelu and Senqu-Orange rivers.

The LHDA reports that 7 756 980 m3 of rockfill have been placed, representing 53% of the total embankment volume.

At the current placement rate of more than 20 000 m3/d, the dam continues to rise steadily towards its eventual height of 165 m above the Senqu riverbed.

The dam’s crest will span 921 m, while the reservoir it creates will hold a full supply storage capacity of 2 325-million cubic metres, more than double the capacity of the Mohale dam constructed under Phase I.

External plinth construction at the main dam was 95% complete at the end of February; the intake tower base concrete was completed on February 21; and spillway excavation was 97% complete.

The dam is on track for commissioning in 2029.

According to the LHDA, the Polihali dam construction programme has employed 2 609 people to date.