Rockfill placement reached high rates of progress in 2025 on the LHWP Phase II construction site with the massive Polihali Dam reaching the rockfill placement milestone of elevation 1977 at the end of November, just one of the many construction milestones that will be marked during the dam’s construction.

Over 6 million cubic metres of rock have been placed to reach the 1977 elevation mark, which is 65 metres above the river bed. The main dam wall is achieving a rockfill placement of more than 22 000 cubic metres every day – equivalent to 9 Olympic pools of material daily. The saddle dam is also progressing steadily, with over 154 000 cubic metres of rock placed.

In total, approximately 14 million cubic metres of rock will be required to complete the Polihali Dam, a concrete faced rockfill dam (CFRD) larger than the high Mohale Dam built during Phase I of the Lesotho Highlands Water Project (LHWP).

This huge quantity of basal rock which weighs 3.5 tonnes per cubic metre is sourced from a quarry within the dam basin which when the dam is inundated, will be completely under water.

Blasting at the quarry has to be done carefully in specific blasting patterns, to get the rock into correct sizes. That way, excavators can load it into dump trucks without the need to process the rock any further, and it is then transported directly to the dam where it is placed and compacted in layers up to 0.8m thick.

Working in two shifts, 2 700 truckloads of rock per day wind their way from the quarry to the rockfill site seven days a week excluding pay weekends and public holidays.

Mohale Dam is impressive, standing 145 metres high and capable of storing up to 950 million cubic metres of water at full supply level. At the time of its construction, it was the largest rock-fill dam in Africa. The Polihali Dam will surpass these dimensions. Its embankment will rise to 166 metres, with a crest stretching 921 metres in length and 9 metres in width. At the base, the embankment will span approximately 490 metres, making Polihali Dam an even more impressive structure.

The Polihali Dam appurtenant infrastructure includes a spillway, intake tower, bottom outlet, a compensation outlet structure and a small hydropower station.

It will create a reservoir on the Senqu and Khubelu rivers with a surface area of 5,053 hectares and a full supply storage capacity of 2,325 million cubic metres at full supply level.

The Polihali Dam is being constructed by the SUN Joint Venture, comprising main partners: Sinohydro Bureau 8 (China); Sinohydro Bureau 14 (China); Unik Civil Engineering (South Africa) and Nthane Brothers (Lesotho). Subcontractors include Melki Civils and Plant Hire (South Africa); MECSA Construction (South Africa); SIGMA Construction (Lesotho) and Kunming Engineering (China).

Construction is supervised by the Matla a Metsi Joint Venture, comprising GIBB (South Africa); MPAMOT Africa (South Africa); Tractebel Engineering SA/Coyne et Bellier (France) and LYMA Consulting Engineers (Lesotho).

Phase II will increase the current annual supply rate capacity from 780 million cubic metres to 1 270, contributing towards meeting South Africa’s increasing water needs. The additional flow of water from Polihali will simultaneously increase power generation within Lesotho towards meeting Lesotho’s domestic needs and reducing the country’s dependence on electricity imports.