| Africa rate capacity from 780 million m3 to 1270, contributing
towards meeting South Africa’s increasing water needs. The additional flow of water from Polihali will simultaneously increase power generation within Lesotho towards meeting Lesotho’s domestic needs and reducing the country’s dependence on electricity imports. The Polihali Dam is a concrete-faced rockfill dam, like the Mohale Dam which was constructed in Phase I of the LHWP. It will create a reservoir on the Senqu and Khubelu rivers with a surface area of 5 053 hectares. The infrastructure also includes a spillway, a compensation outlet structure and a mini- hydropower station. The Polihali Transfer Tunnel will transfer water by gravity from the Polihali reservoir to the Katse reservoir, the centrepiece of the LHWP. From Katse, water is transferred via the delivery tunnel to the ‘Muela Hydropower Station constructed in Phase I, and then on to the Ash River outfall outside Clarence in the Free State on its way to Gauteng. The Polihali Transfer Tunnel works also include the intake works and gate shaft at the Polihali reservoir; outlet works and gate shaft at the existing Katse reservoir, with underwater connection to the lake; access adits to the waterway and associated construction infrastructure. The envisaged transfer tunnel will be approximately 38km long with a nominal bore of five metres. Both tunnel boring and drill and blast methods will be used to excavate the tunnel.
Hydropower element The Lesotho Highlands Development Authority
(LHDA) started procurement for the design and construction supervision of the Oxbow Hydropower Scheme back last year, and the deadline for bids is this month.
Feasibility studies into the hydropower component of Phase II recommended conventional hydropower as the more feasible option to meet Lesotho’s energy needs. Three potential sites were identified: two on the Senqu River and the third at Oxbow on the Malibamats’o River. In November 2021, the government of Lesotho confirmed the Oxbow Hydropower Scheme and gave the go-ahead for the hydropower engineering, Environmental and Social Impact Assessment (ESIA) and the Resettlement Action Planning (RAP) studies. The scope of the hydropower engineering includes a 100m high dam, two tunnels, high pressure steel penstock (pipeline), 80MW power station, 132kV transmission line, all associated infrastructure such as roads and accommodation, bulk power and telecommunications infrastructure and enviro-social components. Broadly, the enviro-social components will include studies on public health, cultural heritage, terrestrial ecology and water quality elements, resettlement and livelihoods restoration elements to mitigate the impact of the Oxbow Scheme on the environment and communities in the project area.
Commercial centre Preparatory works recently also got underway for
construction of the Polihali Commercial Centre, a project that is expected to enhance day-to-day
access to goods and services in the LHWP Phase II project area. LHDA awarded the contract for the construction of the centre valued at M11.3 million to Unik Construction Engineering in mid-January 2023. Construction is expected to be completed by December 2023, along with the bulk of the Phase II advance infrastructure. The plans for the centre include space for a supermarket, a clinic, police post and specialty retail stores, as well as the option to extend the centre to include a filling station at a later stage. The commercial centre is the only one of its kind in
the area, the nearest village convenience store being approximately 15 to 20km away in the Mapholaneng area. It will provide valuable services to people working on the Phase II site and is expected to attract people from the neighbouring villages within the Malingoaneng area. “The Commercial Centre construction contract completes procurement on the quartet of Phase II advance infrastructure Project housing construction tenders, purposely packaged to enhance the participation of small and medium-sized contractors in Phase II. Work on the other three construction contracts for the Polihali Village, upgrades to the Katse Lodge and Katse Village, and the Polihali Operations Centre is progressing well,” confirmed Ntsoli Maiketso, LHDA’s Phase II Divisional Manager. Like the other Phase II Project housing buildings under construction, the commercial centre design prioritises sustainability, with energy efficiency being a particular focus. Amongst other architectural considerations, large windows allow natural light into the building while its north-facing orientation will minimize excessive heat loss in winter and heat gains in summer reducing heating and cooling requirements.
Polihali Infrastructure Consultants comprising the South African-based Mott MacDonald PDNA (Pty) Ltd and Khatleli Tomane Moteane Architects (Pty) Ltd of Lesotho was awarded the contract for the planning, design and construction supervision of the Project housing and associated infrastructure in 2015. ●
www.waterpowermagazine.com | March 2023 | 19
Above: Katse Dam is part of the Lesotho Highlands Water Project and supplies water to Gauteng
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