The Lesotho Highlands Development Authority (LHDA) announced a significant achievement on Monday, 19 August, with the successful breakthrough of the upper intake tunnel into the lower intake tunnel at the Polihali Transfer Tunnel construction site. This milestone, reached after seven months of tunnelling, is crucial for the progress of the Polihali Transfer Tunnel and the future impoundment of the Polihali reservoir.
The intake tunnels are designed to channel water from the 5,042ha Polihali reservoir into the transfer tunnel, which will then deliver it to the Katse reservoir, a central part of the Lesotho Highlands Water Project.
The breakthrough marks the beginning of two important phases of the project. The first phase involves the safe start of impounding the Polihali reservoir. The collapse of the upper tunnel into the lower one allows for a controlled increase in water levels, enabling the lower tunnel to be temporarily sealed.
The second phase focuses on the continuous removal of debris from the remaining tunnel works. This process will be facilitated through the upper intake tunnel, ensuring that construction can continue without disrupting the impoundment.
The lower intake tunnel is crucial for the Polihali Dam’s future operations, as it will allow water intake even when reservoir levels are low, ensuring a steady water flow.
Key achievements in the project include the excavation of a 450m tunnel, completed on 19 August, the completion of the 370m lower intake tunnel on 5 August, and ongoing work on the 1322m connecting tunnel. This connecting tunnel will link the tunnel boring machine (TBM) access adit to the chamber where the TBM will be assembled, initiating the TBM-bored transfer tunnel to Katse. So far, 26m of the connecting tunnel have been completed.
These developments highlight the dedication and expertise of the LHDA and its partners, including Metsi a Senqu Khubelu Consultants (MSKC) and the Kopano Ke Matla Joint Venture, who are responsible for the tunnel’s design and construction.
The completion of the intake tunnels is a step forward in realizing the Polihali Dam’s potential to increase water transfer to South Africa, boost hydropower generation in Lesotho, and contribute to the economies of both Lesotho and South Africa.
Phase II of the Lesotho Highlands Water Project, building on the success of Phase I completed in 2003, aims to increase water supply to South Africa’s Gauteng region and enhance hydroelectricity generation in Lesotho. The current supply rate of 780 million cubic meters per annum will be incrementally increased to over 1,270 million cubic meters per annum, further advancing Lesotho’s goal of securing an independent electricity source to meet domestic needs.
