Excavations continue from the outlets at about six metres a day per tunnel at the Polihali diversion tunnels.
The water project is being supported by the Kingdom of Lesotho and the Republic of South Africa.
The Lesotho Highlands Development Authority (LHDA) Chief Executive Officer Tente Tente says excavation of the intake and outlet portals has been completed and work on the tunnels’ concrete lining is under way, with concrete casting and reinforcement having been started on tunnel one.
“Both tunnels’ intake and outlet portals drives have been supported with sprayed concrete and rock bolts and preparatory works for the concrete inlet structure also ongoing,” says Mr Tente.
The tunnels (one seven metres in diameter and almost 1km long; and the second, nine metres in diameter and also almost 1km long) run parallel to each other from the intake point to the outlet downstream of the dam.
The tunnels are being excavated in advance of the construction of the Polihali dam to reduce the dam construction period. Impoundment of the Polihali reservoir is expected to start in 2024, with water delivery planned to start in 2027.
The LHWP is a multi-phased, multi-billion maloti/rand project between the governments of Lesotho and the Republic of South Africa.
It comprises water transfer and hydropower generation components with associated ancillary developments.
The water transfer component entails the construction of dams and tunnels in Lesotho, enhancing the use of water from the Senqu (Orange) River and its tributaries by storing, regulating, diverting and controlling the flow to effect the delivery of specified quantities of water to South Africa, and utilising the delivery system to generate hydro-electric power in Lesotho.