A government inquiry has held the Water and Power Development Authority (Wapda), the contractor and the project consultant jointly responsible for the cofferdam collapse at the 1,530MW Tarbela-5 Extension Hydropower Project, concluding that unauthorised post-contract design changes and repeated contractual violations caused the failure.

The three-member independent inquiry committee found that the contractor proposed changes to the cofferdam design despite contractual restrictions. The consultant approved the proposal without ensuring full technical compliance, while Wapda endorsed the changes near the end of construction without questioning either their contractual validity or engineering implications.

The committee concluded that these actions resulted in the construction of a vulnerable cofferdam that eventually failed, causing flooding, suspending work and inflicting significant financial losses on the project.

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The investigation was led by Federal Flood Commission Chairman and Chief Engineering Adviser Ather Hameed. Officials from the Ministry of Water Resources also served on the panel, which investigated the collapse that occurred in August 2025.

According to the 15-page report, all parties ignored their contractual responsibilities, allowing design deficiencies to remain unaddressed throughout construction. The committee rejected claims that exceptional flooding caused the collapse, stating that river flows remained within historical levels and should have been accommodated under the original design.

The report revealed that the contractor, Power Construction Corporation of China Ltd (PCCCL), proposed replacing the original cofferdam with a rock-filled structure across the project area. The committee determined that the revised design offered weaker protection and directly contributed to the structural failure. Wapda approved the change without examining its contractual legitimacy.

Investigators also found that Wapda requested a cofferdam performance assessment from the consultant in July 2023. Instead of conducting an independent review, the consultant referred the request to the contractor, which submitted its monitoring report more than a year later in October 2024.

The inquiry further identified irregular payments for temporary works instead of permanent construction, weakening the government’s ability to seek compensation from the contractor following the collapse.

The incident has delayed the Tarbela-5 Extension Hydropower Project by at least two years. Authorities now expect completion by the end of June 2028 instead of 2026.

The project’s cost has increased sharply from the original approved estimate of Rs82.36 billion in 2017 to Rs317 billion, representing an escalation of more than 285 per cent, with costs continuing to rise.

The Planning Commission warned that the project’s levelised electricity generation cost over 30 years could increase to Rs27-28 per unit, making it Pakistan’s most expensive renewable energy project and raising concerns about its long-term economic viability.

The Tarbela-5 Extension Hydropower Project is financed through approximately $700 million in loans from the World Bank and the Asian Infrastructure Investment Bank.

The report also noted that Wapda terminated the consultancy contract with MML-UK, citing its failure to provide a suitably qualified project manager and persistent staffing deficiencies. The consultant had also issued a termination notice in May 2025 and withdrew its staff from the site before completing the contractually required notice period.