Second Tunnel Boring Machine Launched at Lesotho Highlands Water Project

The 423-metre machine will excavate from Polihali toward Katse Dam, forming part of a 38.5-kilometre tunnel through the Maluti Mountains.

South African Water and Sanitation Minister Pemmy Majodina and Lesotho's Natural Resources Minister Mohlomi Moleko launched the second Tunnel Boring Machine (TBM) at the Polihali Construction Site in Mokhotlong on Sunday, marking a key milestone in Phase II of the Lesotho Highlands Water Project.¹²

The machine measures approximately 423 metres in length and is equipped with a 5.38-metre cutterhead designed for continuous operation under challenging underground conditions.¹ The first TBM was commissioned at Katse Dam in February 2025 and has begun tunnel drilling at that site.¹

The two machines will excavate through the Maluti Mountains from opposite ends to connect the Polihali and Katse reservoirs via a 38.5-kilometre tunnel.¹ Water and Sanitation spokesperson Wisane Mavasa said the machines will install precast concrete lining segments during excavation, transforming raw rock into completed structure in one process.¹

Majodina said the project will increase water transfer from 780 to 1,270 million cubic metres per annum.² She added that energy generation at the Muela Hydropower Station will increase by approximately 30 percent.²

The minister described the project as "a step-change in regional resilience for Lesotho and South Africa" and said around 2,400 Basotho people are employed on the site.² She identified the total project cost as 54.9 billion rand.²

Mavasa said the completed Polihali Tunnel will facilitate the transfer of significantly larger volumes of water, enhancing regional water security and bolstering hydropower generation in Lesotho.¹