Polihali dam will be a CFRD, similar to the Mohale dam, which was built during Phase I of the Lesotho Highlands Water Project (LHWP). The embankment will be approximately 166 m high, have a crest length of about 920 m and a crest width of 9 m. More than 14 x 106m3 of rock which will be quarried locally within the dam basin will be compacted to form the dam. It will create a reservoir on the Senqu and Khubelu rivers with an estimated surface area of 5053 ha and a full supply storage capacity of 2325 x 106m3. The Polihali dam infrastructure also includes a 43 m-high, a CFRD saddle dam with a crest length of 600 m, a spillway and a compensation outlet.
The flow from Polihali will increase the volume of water to be transferred from the Katse dam, the centre point of the LHWP which was constructed during Phase I. The current water transfer volumes to the Gauteng region of South Africa will incrementally increase from 780 to 1270 x 106m3/year. This will also simultaneously increase the energy generated by the ‘Muela hydropower plant from approximately 500 GWh to 800 GWh/year, a further step in the process of securing an independent power supply to meet Lesotho’s domestic needs.
“The launching of the construction of the main works open tender is the culmination of years of planning and hard work of dedicated design and procurement teams. Our objective with this final procurement stage is to attract suitably qualified companies with the capability, experience and resources to undertake the construction of the Polihali dam within the set timeframes and to the required quality,” said Tente Tente, CE of the LHDA.
The Phase II Agreement encourages the project to benefit the economies of Lesotho and South Africa but emphasizes the need for procurement that fosters competitiveness, transparency, cost-effectiveness and quality. LHDA’s robust procurement policy and tender evaluation protocols will ensure a fair and transparent procurement process.
The Matla a Metsi Joint Venture which comprises Lesotho, South African and international experts: GIBB (Pty) Ltd; MPAMOT Africa (Pty) Ltd; Tractebel Engineering SA; LYMA Consulting Engineers of Lesotho, was awarded the Polihali Dam design and construction supervision contract in 2017.
The Polihali dam construction procurement is launched as construction activity on ten advance infrastructure contracts progresses steadily with some contracts expected to be completed this year. Construction of the 33 kV line, which will provide a temporary power supply to the Polihali village, was completed last year. Work on the 132 kV line has advanced with the construction of access roads, 91 tower foundations and the erection of 84 towers of a total of 93. The Polihali and Katse civil works, access roads, pipe laying for potable water and sewerage lines have been completed, and construction on the main access roads is underway. Excavation on the Polihali diversion tunnels is close to completion, with breakthrough on both tunnels expected in the second half of August.
According to the current master programme, water delivery is scheduled for 2027/28. The construction schedule for the dam and transfer tunnel is critical to meeting the water delivery deadline of the project.
The launching of the dam construction tender process marks the start of the final construction phase of the water transfer component under Phase II of the Lesotho Highlands Water Project.
Interested construction firms have until 12 November 2021, to submit tenders.
Specific information on the requirements and conditions of the tender is available on the LHDA website at: www.lhda.org.ls/tenderbulletin/currentProcurement.aspx.