The Lesotho Highlands Development Authority (LDHA) has advertised the tender for the construction of the Polihali Transfer Tunnel, with the tender advertisement for the construction of the Polihali dam expected in due course.
Interested construction firms have until August 30 to submit tenders.
“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,” LHDA CEO Tente Tente said.
With the water delivery scheduled for 2027, timeous construction of the dam and transfer tunnel is critical to meeting the water delivery deadline of the project.
The 38-km-long Polihali Transfer Tunnel, with a 5 m nominal bore, will transfer water by gravity 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 5 053 ha and a full supply storage capacity of 2.325-billion cubic metres.
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 cubic metres a year to the Gauteng region of South Africa will incrementally increase to 1.27-billion cubic metres a 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,” he said.
The Metsi a Senqu-Khubelu Consultants (MSKC) joint venture, which comprises Lesotho-based FM Associates and South African firms Zutari, Hatch Africa, Knight Piesold and SMEC South Africa, was awarded the contract for the design and construction supervision of the Polihali Transfer Tunnel and its secondary structures.
“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,” Tente added.
Cumulative excavation progress in both tunnels is in the order of 1 243 m out of a total of 1 810 m to date. Construction of the 33 kV line, which will provide temporary power supply to the Polihali village, was completed in 2020.
Work on the 132 kV line has advanced with construction of access roads, 91 tower foundations and the 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.