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The construction of the Polihali Transfer Tunnel is part of the Lesotho Highlands Water Project (LHWP) Phase 2.

The 38 kilometre long Tunnel will have a nominal bore of five metres, and will be excavated using both tunnel boring and drill and blast methods. The Polihali Transfer Tunnel works also includes 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 Lesotho Highlands Water Project (LHWP) delivers water to the Gauteng region of South Africa and utilises the water delivery system to generate electricity for Lesotho. In Phase 2 of the LHWP, 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 and the current water supply rate of 780 million m³ per year to the Gauteng region of South Africa will incrementally increase to 1270 million m³ per year. At the same time, it will increase the quantity of electricity generated at the Muela hydropower plant which is 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,” said the Chief Executive Officer of LHDA, Tente Tente.

“Equally important is to attract firms that have impeccable records in delivering projects of this magnitude within budget and the set timeframes.”

The closing date for submission of tenders is 30 August 2021. Interested construction firms can obtain further information on the requirements and conditions of the tender from the LHDA website.

The contract for the design and construction supervision of the Polihali Transfer Tunnel and its secondary structures was awarded to the Metsi a Senqu-Khubelu Consultants (MSKC) Joint Venture. The MSKC Joint Venture comprises Lesotho-based FM Associates (Pty) Ltd, and South African firms Zutari (Pty) Ltd, Hatch Africa (Pty) Ltd, Knight Piesold (Pty) Ltd and SMEC South Africa (Pty) Ltd.

Timely construction of the dam and transfer tunnel is critical to meeting the water delivery deadline of the project. According to the current master programme, water delivery is scheduled for September 2027.

Photo: Polihali Dam site (Lesotho Highlands Development Authority | lhda.org.ls)