Double breakthrough and considerable completion has been achieved by Drill and Blast on the nearly 1km-long Polihali diversion tunnels of the Lesotho Highlands Water Project Phase 2.
The almost 1km-long tunnels with 9m and 7m diameter – run approximately parallel to each other. Boring of both started in June 2020 and has advanced at a rate of about 5m/day per tunnel.
Drill and blast was used for mining, with sprayed concrete, rock bolts, and mesh used for support. The construction is continuing on the concrete intake structure for the 7m-diameter tunnel, while that for the 9m-diameter tunnel is nearly completed. Erosion control and flood protection work was finished before.
The tunnels are going to divert the Senqu River to make a dry foundation and work area for the construction of the Polihali Dam, for which the Lesotho Highlands Development Authority launched the tender on 5 August 2021.
Metsi a Senqu-Khubelu Consultants Joint Venture (MSKC) has provided tunnel engineering design and consultancy and the contractor was the SCLC JV including the Webuild, CMI Infrastructure, CMC di Ravenna and Lesotho-based LSP Construction.
It is expected to have the overall completion of the tunnels at the end of 2021.