The Lesotho Highlands Development Authority (LHDA) has increased progress on the resumption of advanced infrastructure works at Phase II of the Lesotho Highlands Water Project (LWHP) by beginning the excavation works of two diversion tunnels.
The two tunnels will divert the waters of the Senqu river away from the natural river bed creating a dry foundation and work area needed for the construction of the Polihali dam.
Tente Tente, Chief Executive of the LHDA, confirmed that the construction of the diversion tunnels is an important element of the Phase II advanced infrastructure works, which were halted during the COVID-19 lockdown period. “We are pleased to see construction work restarting, including the work on the diversion tunnels. However, particularly at this time, the LHDA’s priority is the safety of its employees and the Project affected communities,” he said. Full resumption of the Phase II advanced infrastructure construction works, and the project’s social and environmental programmes, will be incremental as consultants and contractors meet their COVID-19 mitigation obligations and travel restrictions are lifted.
The diversion tunnels will take approximately 18 months to complete from the contract start date. Building two tunnels will increase the capacity to carry floods and will provide flexibility to work in one tunnel while the river flows in the other.
The tunnels, one 7 m in diameter and almost a kilometre in length, and the other, 9m in diameter and a similar length to the first, run parallel to each other from the intake point to the outlet downstream of the dam. They will be excavated using the drill and blast method, and will be supported by rockbolts and shotcrete as required.
SCLC Polihali Diversion Tunnel Joint Venture was awarded the diversion tunnel construction contract in April 2019. It comprises South African and Lesotho expertise from Salini Impregilo SpA (South African branch), Cooperativa Muratori Cementistri CMC di Ravenna (South African branch), LSP Construction (Pty) Ltd. (Lesotho) and CMI Infrastructure Ltd (South Africa).
The Metsi a Senqu-Khubelu Consultants Joint Venture (MSKC), which also includes a number of South African and Lesotho-based firms including Aurecon (SA), Knight Piesold (SA), Hatch Goba (SA), SMEC (SA) and FM Associates (Lesotho), designed the diversion tunnels and is supervising the construction work.