The Lesotho Highlands Development Authority (LHDA) has awarded WRES Senqu Bridge Joint Venture the contract for the construction of the Senqu Bridge - the largest of the three bridges that will be constructed under Lesotho Highlands Water Project phase II to span the Polihali reservoir.
Construction will commence shortly and is expected to take three years to complete. The WRES Joint Venture includes South African, Lesotho and international companies as per the requirements of the Phase II Agreement. The primary partners are: Webuild S.p.A. (Italy); Raubex Construction (Pty) Ltd (South Africa); Enza Construction (Pty) Ltd (South Africa) and Sigma Construction (Pty) Ltd (Lesotho). Sub-contractors include: EXR Construction (Pty) Ltd (South Africa; Gleitbau-Geselschaft (Austria); Post Tensioning and Structural Solutions (Pty) Ltd (South Africa) and Freyssinet International et Cie (France).
Almost a kilometre long (825m) and at a height of 90m, the Senqu Bridge will be the first extradosed bridge in Lesotho 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 Lesotho Highlands Water Project (LHWP). The bridge 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. With its unique features, 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,” Ntsoli Maiketso, Phase II Divisional Manager, stated.
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 approximately 5000 hectares. 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 exiting A1 road. The A1 is the main road between the Mokhotlong district in the mountainous north-east 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.
Due to the deep valley and the terrain of the area, the deck will be constructed incrementally from both abutments. This construction method 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.
Phase II of the the Lesotho Highlands Water Project entails construction of the Polihali Dam, the 38km Polihali transfer tunnel, the associated infrastructure and a hydropower scheme at Oxbow. It builds on the successful completion of Phase I in 2003.
The LHWP delivers water to the Gauteng region of South Africa and utilises the water delivery system to generate hydroelectricity for Lesotho. Phase II will increase the current supply rate of 780 million cubic metres per annum incrementally to more than 1 270 million cubic metres per annum. At the same time, it will increase the quantity of electricity generated in Lesotho and is a further step in the process of securing an independent electricity source to meet Lesotho’s domestic requirements and reducing the country’s dependence on imported energy.