MASERU – The three-year construction of the 825m long and 90m high Senqu Bridge is set to commence soon, this after the Lesotho Highlands Development Authority (LHDA) awarded the M2 billion construction contract to a multi-national consortium. The LHDA has selected Italy-based Webuild; South African companies – Raubex Construction (Pty) Ltd and Enza Construction (Pty) Ltd; and, Sigma Construction (Pty) Ltd from Lesotho to partake in this construction.
Moreover, the sub-contractors include the South African firms; EXR Construction (Pty) Ltd and Post Tensioning and Structural Solutions (Pty) Ltd; as well as Austria’s Sliding Construction and France-based company, Freyssinet International et Cie. The WRES Joint Venture includes South African, Lesotho and international companies as per the requirements of the Lesotho Highlands water Project (LHWP) Phase II Agreement.
According to the LHDA, Senqu Bridge will be the first extradosed bridge in Lesotho which is larger than the Mphorosane Bridge on the Malibamatšo River and which also spans the Katse Dam and was constructed under Phase I of the Lesotho Highlands Water Project (LHWP). Furthermore, it is also the largest of the three bridges that will be constructed under Phase II to span the Polihali Reservoir. 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”, said Ntsoli Maiketso, Phase II Divisional Manager.
He added: “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.” 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 5 000 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 commenced in 2018, led by Zutari, formerly Aurecon Lesotho. It is said that 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 and 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 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. The Phase II will increase the current supply rate of 780 million cubic meters per annum incrementally to more than 1 270 million cubic meters 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 reduce the country’s dependence on imported energy.