Bund breach floods Tunnel Five, halts Tarbela extension project indefinitely

Construction on the World Bank-funded Tarbela 5th Extension Hydropower Project has stopped indefinitely after a protective bund failed on Monday, sending a large volume of water into Tunnel Five, according to media reports.

Engineers and local authorities evacuated Pakistani and foreign workers from the construction site. Emergency teams rescued one worker carried away by the surge. All workers were brought to safety, and no casualties were reported.

The district administration has opened an investigation into the breach. A high-level inquiry will assess whether a weakness in the structure or a technical fault caused the bund to fail. Authorities will determine their next steps once the investigation report is received.

The extension is a Water and Power Development Authority (WAPDA) scheme to expand electricity generation at Tarbela Dam, with financing arranged by the World Bank. Its three generating units, each rated at 510 megawatts, are intended to add 1,530 megawatts, raising the dam’s installed capacity from 4,888 megawatts to 6,418 megawatts.

The approved project cost is $807 million. The World Bank is providing $390 million, while the Asian Infrastructure Investment Bank is contributing $300 million. In May 2021, WAPDA awarded China’s Power Construction Corporation a civil works contract worth $354.6 million.

Completion was initially planned within five years, but successive delays moved the deadline to September 2027. Difficulties securing a no-objection certificate from the Indus River System Authority (IRSA) to close Tunnel Five have held up the project for years.

Work was also halted temporarily in August 2025, when higher reservoir levels and increased inflows inundated sections of the construction site.