The Lesotho Highlands Development Authority (LHDA) has launched the tender for tunnel construction in Lesotho. This is, the construction of the Polihali Transfer Tunnel. The project is a vital contract in Phase II of the Lesotho Highlands Water Project – with the tender for the Polihali Dam construction expected to follow shortly.
Importantly, the Polihali Transfer Tunnel will be 38km long with a 5m nominal bore. It will transfer water from Polihali to the Katse reservoir. To excavate the tunnel, tunnel boring and drill and blast methods will be used.
The Polihali Dam will create a reservoir on the Senqu and Khubelu rivers with an estimated surface area of 5053 hectares and a total 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. Clearly, the tender for tunnel construction in Lesotho is of great benefit to all involved.
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. Also, it will simultaneously increase the electricity generation at the Muela hydropower plant. It will be a further step in securing an independent power supply to meet Lesotho’s domestic needs.
Finally, the tender for the construction procurement of the transfer tunnel is launched. Construction activity on ten advance infrastructure contracts progresses steadily. Some contracts are 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. 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.