The three-year construction of the 825-m-long, 90-m-high Senqu bridge is set to start soon following the Lesotho Highlands Development Authority (LHDA) awarding of the M2-billion construction contract to a multi-national consortium.

LHDA selected Italy-based Webuild; South African firms Raubex Construction and Enza Construction and Lesotho-based Sigma Construction, collectively forming the WRES Senqu Bridge Joint Venture (JV).

The WRES Senqu Bridge JV includes South African, Lesotho and international companies as per the requirements of the Lesotho Highlands Water Project (LHWP) Phase II Agreement.

Sub-contractors include South African firms EXR Construction and Post Tensioning and Structural Solutions; Austria’s Gleitbau-Geselschaft; and France-based Freyssinet International et Cie.

The Senqu bridge is the largest of the three bridges that will be constructed under Phase II to span the Polihali reservoir and is larger than the Mphorosane bridge on the Malibamats’o river, which spans the Katse dam and was constructed under Phase I of the LHWP.

The bridge’s design has taken into consideration the Mokhotlong highlands’ long, cold and harsh winter conditions.

“Experience and expertise are crucial in delivering a sophisticated, technically challenging project of this kind, which will be a first for the LHWP and Lesotho. The Senqu bridge will not only form part of the safe and efficient road infrastructure network constructed under Phase II but will be a major tourist attraction contributing to long-term benefits in stimulating sustainable economic growth,” says Phase II divisional manager Ntsoli Maiketso.

The Polihali reservoir in the valleys and tributary catchments of the Senqu, Khubelu, Mokhotlong, Moremoholo and Sehong-hong rivers, which will be formed by the construction of the Polihali dam, will have a surface area of about 5 000 ha.

Besides the three major bridges, the restoration of access across the reservoir also entails the construction of new approach road sections to the bridges that tie into the existing A1 road, which is the main road between the Mokhotlong district in the mountainous northeast of the country and the capital Maseru.

Work on the bridge design started in 2018, led by Zutari, formerly Aurecon Lesotho.

Zutari also designed the Mabunyaneng and Khubelu bridges, the other two major bridges to be constructed under Phase II.

The tender for the construction of these two bridges is currently under evaluation.

Zutari will also supervise the construction of the three bridges.

Owing to the deep valley and the terrain of the area, the deck will be constructed incrementally from both abutments, which will minimise disturbance to the surrounding work area and increase workers’ safety.

An in-situ segment midspan of the centre span will connect the two parts to form a continuous deck. The pier shape is ideal to be constructed with sliding formwork.