Worker Swept Away, Tunnel Flooded: Inside The Tarbela-5 Bund Collapse That Exposes Pakistan's Cofferdam Scam

Islamabad: Water rushed into Pakistan's Tarbela 5th Extension Hydropower Project on Monday after a protective bund at the under-construction Tunnel-5 collapsed. The incident triggered a surge from the reservoir, leading to a panic-like situation at the site. An emergency was declared, construction was suspended and the workers were moved to safer areas, in the second major incident at the 1530 MW project since 2025.

According to reports, the civil works contract was awarded to China's Power Construction Corporation of China Limited (PCCCL). As per reports, one Pakistani worker was swept into the water but rescued, with no casualties reported in the incident. Haripur Deputy Commissioner Waseem Ahmed confirmed the incident, saying that the work was suspended indefinitely and a high-level inquiry would examine whether a structural weakness or technical fault caused the failure.

The Water and Power Development Authority (WAPDA) stated that a weak rock mass collapsed during excavation of the 2nd Bench Connecting Tunnel, letting water from the intake pit enter the tunnel and powerhouse area. It asserted that water had been drained, dewatering had begun, and there was no damage to the main tunnel, powerhouse, tailrace culvert or switchyard, rejecting reports that the tunnel had collapsed.

Earlier Collapse In July

In July, a 3-member independent inquiry committee held WAPDA, the contractor and the consultant jointly responsible for an earlier cofferdam collapse. According to a 15-page report accessed by Dawn, unauthorised changes to the cofferdam design after the contract was awarded were a major cause, following steps outside the contract and breaches involving all 3 stakeholders. 

The PCCCL had proposed an alteration not permitted under the contract, while the engineer conditionally accepted a design deficiency without ensuring technical compliance. The WAPDA approved the change near completion, without examining the contractual validity or technical shortcomings. The parties had disregarded their rights and responsibilities under the civil works and consultancy contracts, resulting in a vulnerable cofferdam whose failure caused flooding, delays and financial losses.

Flooding Was Not The Cause

The stakeholders sought to link the collapse to flooding, but the committee found flows were within annual levels, were not unusual and should have been taken into account in the original design. Although the WAPDA blamed flooding, flows remained within Tarbela's historical record and were considerably below the cofferdam's designed capacity. 

The failure was attributed to inadequate protective layers and filter arrangements. The PCCCL had proposed replacing the design with a rock-filled structure, a weaker alternative, across the project, including the channel. The revised structure collapsed, and the WAPDA approved it without examining whether it was contractually valid. 

The WAPDA had asked the consultant in July 2023 for an assessment of the cofferdam's performance. However, instead of an independent examination, the consultant forwarded the request to the contractor, which submitted a monitoring report in October 2024, over a year later.  The irregular payments had also been made for temporary work in place of permanent work, weakening the government's right to seek compensation.

Project Under Financial Strain

The earlier collapse contributed to a delay of at least 2 years and cost escalation of over 285%, with cost rising from PKR 82.36 billion to PKR 317 billion. According to the Planning Commission, levelised generation cost over 30 years could reach PKR 27-28 per unit, the highest in the country so far for renewable energy, making it economically unviable and unsustainable. 

As per reports, the completion has moved from 2026 to the end of June 2028. The project included loans totalling USD 700 million from the World Bank and the Asian Infrastructure Investment Bank. The contractors included PCCCL, Harbin Electric International Company Limited and Harbin Electric Machinery Company Limited. 

The consultant was a joint venture of Pakistan's MM Pakistan and China's BIDR, while the WAPDA was the employer. The WAPDA later ended the consultancy agreement with MML-UK, alleging failure to provide a suitable and adequately qualified project manager and continued staffing problems. 

The MML had issued a termination notice in May 2025 and withdrawn staff unilaterally, contrary to the contractual requirement of 30 days' notice. The inquiry concluded that contractual breaches and technical failures involving the contractor, consultant and WAPDA resulted in the cofferdam collapse, disrupting work, increasing costs and pushing completion to June 2028.