The maintenance includes grit-blasting the steel-lined section around the entire circumference and re-applying corrosion protection on the tunnel lining.
The Department of Water and Sanitation said the three-week extension was because of delays in the maintenance work experienced in the Delivery Tunnel South on the Lesotho side of the project.
Originally, the six-month tunnel shutdown was planned to run from October 1, 2024 to March, 31, 2025.
However, the department said a combination of unpredictable weather conditions and technical issues experienced by the implementing agent, the Lesotho Highlands Development Agency (LHDA), had created issues.
“The challenges experienced include higher than anticipated seepage within the tunnel due to a change in sand blasting technique. There was a change from a manual to an automated approach of sand blasting, but high humidity affected the automated approach,” said the department’s spokesperson, Wisane Mavasa.
“The contractor is reported to have procured additional equipment to better manage the seepage challenge. The recovery plan was implemented to accelerate the progress of the maintenance work in Lesotho, but the delay could not be avoided.”
According to Mavasa, on the South African side of the project, maintenance work being carried out by the Trans Caledon Tunnel Authority is progressing according to schedule and is expected to be completed on time.
With the Vaal Dam currently at full capacity (101.51%) after the recent above-normal rainfall in most parts of the country, the department has reassured all water users that the extended tunnel closure will not affect water supply for the Integrated Vaal River System.
The municipalities located along the Liebenbergsvlei River in the Free State will also not be impacted by the extended tunnel closure.
