The Lesotho Highlands Development Authority (LHDA) has launched the tender for the construction of the Polihali Transfer Tunnel – a major contract in Phase II of the Lesotho Highlands Water Project – with the tender for the Polihali Dam construction expected to follow shortly.
The Polihali Transfer Tunnel will be 38km long with a 5m nominal bore. It will transfer water from Polihali to the Katse reservoir. Tunnel boring and drill and blast methods will be used to excavate the tunnel.
The Polihali Dam will create a reservoir on the Senqu and Khubelu rivers with an estimated surface area of 5053 hectares and a full supply storage capacity of 2325 million m3. The flow from the Polihali reservoir through the transfer tunnel will increase the volume of water in the Katse Dam.
The current water transfer volumes of 780 million m3 per year to the Gauteng region of South Africa will incrementally increase to 1270 million m3 per year, and will simultaneously increase the electricity generation at the Muela hydropower plant, a further step in the process of securing an independent power supply to meet Lesotho’s domestic needs.
“Our objective is to attract firms with experience in the construction of major underground works under complex geological and geotechnical conditions, diverse environmental conditions, in remote areas and at high altitude. Equally important is to attract firms that have impeccable records in delivering projects of this magnitude within budget and the set timeframes,” said Tente Tente, CE of the LHDA.
Interested construction firms have up to 30 August 2021, to submit tenders. Specific information on the requirements and conditions of the tender is available on the LHDA website at http://www.lhda.org.ls/tenderbulletin/currentProcurement.aspx.
The Metsi a Senqu-Khubelu Consultants (MSKC) Joint Venture was awarded the contract for the design and construction supervision of the Polihali Transfer Tunnel and its secondary structures. MSKC comprises Lesotho-based FM Associates (Pty) Ltd, and South African firms Zutari (Pty) Ltd, Hatch Africa (Pry) Ltd, Knight Piesold (Pty) Ltd and SMEC South Africa (Pty) Ltd.
The tender for the construction procurement of the transfer tunnel is launched as construction activity on ten advance infrastructure contracts progresses steadily with some contracts expected to be completed in 2021, including the Polihali diversion tunnels.
Cumulative excavation progress in both tunnels is in the order of 1243m out of a total of 1810m to date. Construction of the 33kV line, which will provide temporary power supply to the Polihali village, was completed in 2020.
Work on the 132kV line has advanced with construction of access roads, 91 tower foundations and erection of 84 towers out of a total of 93. The Polihali and Katse civil works; access roads, pipe laying for potable water and sewerage lines has been completed, and construction on the Phase II main access roads is progressing well.
According to the current master programme, water delivery is scheduled for 2027. Timely construction of the dam and transfer tunnel is critical to meeting the water delivery deadline of the project.
Phase II of the Lesotho Highlands Water Project builds on the successful completion of Phase I in 2003. It delivers water to the Gauteng region of South Africa and utilises the water delivery system to generate hydroelectricity in Lesotho.