Polihali Diversion Tunnels
Data updated to April 2021
The Polihali Diversion Tunnels project foresees preparatory diversion works for the construction of the Polihali Dam. Polihali Dam is conceived to create a water reservoir from the Senqu and Kubelu Rivers in the Lesotho Highlands and then provide water to the lower reservoir of Katse Dam, which already supplies raw water to South Africa.
The project includes excavating two diversion tunnels, the first one (DT1) is 910 m long (having a height and a width both of 7 m); the second (DT2) measures 960 m in length (having a height and a width both of 9 m); and the construction of reinforced concrete intake structures at the diversion tunnel intake portals.
The Works to be carried out comprise inter alia the following:
• The necessary improvements and upgrading works of the road network to allow the passage of construction site vehicles
• Construction of temporary access roads and haul roads, including a temporary crossing of the Senqu river
• Provision of magazines on Site, to allow storing explosives
• Execution of open air excavations at the diversion tunnel intake and outlet portals
• Provision of temporary flood protection berms around open cuts at the diversion tunnel intake and outlet portals