Rock collapse floods tunnel at Pakistan's Tarbela Dam expansion, no deaths reported

A section of rock gave way during excavation work at Pakistan's Tarbela Dam on Monday, sending a surge of floodwater into a tunnel and an unfinished power station and forcing the evacuation of construction crews at one of the largest hydropower sites in South Asia. Officials said no one was killed, but the incident has reopened questions about the management of a $1.1 billion expansion project that has already been delayed by more than two years and has overrun its original budget by close to 300 percent.

The collapse struck the Tarbela Fifth Extension Hydropower Project, known locally as T-5, which is boring a new power tunnel into the flank of the dam to add 1,530 megawatts of generating capacity. According to Pakistan's Water and Power Development Authority (WAPDA, the state body that runs the dam under Pakistan's Ministry of Water Resources), a weak section of rock fell away while crews were excavating the second bench of a connecting tunnel. Water held in an intake pit poured through the breach into the tunnel and into the shell of a powerhouse still under construction nearby.

"It allowed water from the intake pit to enter the tunnel," Waseem Ahmed, the deputy commissioner of Haripur district, where the dam sits, told Arab News Pakistan. He said every worker at the site, Pakistani and foreign, was pulled out in time. One laborer was briefly submerged and swept along by the inflow before nearby residents hauled him out; he was not seriously hurt, according to local accounts carried by Daily Times. WAPDA said separately that the intake pit had since been fully drained and that dewatering of the flooded powerhouse chamber was under way.

A rock collapse, not a dam failure

Video of muddy water pouring into the construction pit circulated quickly on Pakistani social media on Monday, with some posts claiming the main dam itself — one of the largest earth-and-rock-fill embankments in the world, holding back the Indus River roughly 100 kilometers northwest of Islamabad — had failed. Ahmed and WAPDA both moved to knock the claim down.

"If the dam had broken, it would have caused flooding downstream," Ahmed said, adding, "As I speak to you, the water level inside the tunnel has almost completely receded."

WAPDA's statement was more specific still, saying the main diversion tunnel, the under-construction powerhouse structure itself, the tailrace culvert and the switchyard had all come through undamaged, and that the failure was confined to a protective rock section and an embankment at the T-5 intake. The authority has since issued a downstream notice warning that discharge from Tarbela into the Indus would run at more than 150,000 cusecs around the clock as engineers managed the water let into the construction area, and it asked residents near the river to take precautions, according to Daily Times' reporting of the WAPDA notice. Radio Pakistan reported that senior WAPDA officials, the project's engineers and its contractor were on site assessing the damage.

Work on the tunnel has been suspended indefinitely while that assessment continues, according to officials cited in local coverage, though WAPDA has not given a timeline for resuming excavation or for any revision to the project's already-extended schedule.

A project already over budget and behind schedule

Monday's collapse is the second serious construction failure at the T-5 site in fifteen months, and it lands on a project already under scrutiny in Islamabad for cost and schedule overruns. In August 2025, a cofferdam built to protect the same construction works collapsed, flooding part of the site. A three-member government inquiry, whose findings were reported in July 2026, assigned shared responsibility to WAPDA, the civil contractor and the project's design consultant, finding that an unauthorized, post-contract change in the cofferdam's design — switching from roller-compacted concrete to a rock-fill structure — had been approved without adequate technical or contractual review and left the structure without features that would normally have protected it. The inquiry rejected contractor claims that unusually high river flows, rather than the design change, were to blame, noting that flows at the time were within the historical range for the Indus at that point in the year.

That 2025 failure alone added more than two years to the project's timeline and pushed its approved cost from roughly 82 billion Pakistani rupees to about 317 billion rupees — an increase of more than 285 percent — with completion pushed back from 2026 to the end of June 2028, before Monday's incident. Pakistan's Central Development Working Party criticized WAPDA over the delays and cost growth earlier this year and referred the project to the country's Executive Committee of the National Economic Council for further review, Pakistani business press has reported.

The civil works contract for T-5 was awarded in 2021 to Power Construction Corporation of China, a unit of PowerChina, in a deal worth about $355 million, while a joint venture of Harbin Electric International and Harbin Electric Machinery holds the roughly $241 million contract for the plant's electrical and mechanical systems; a Chinese-Pakistani consortium is the design consultant. The project is financed jointly by the World Bank, which has committed $390 million, and the Asian Infrastructure Investment Bank, which approved $300 million for the project in 2016 as co-financing alongside the Bank's existing Tarbela Fourth Extension loan. The World Bank has since approved a further $300 million for the related fourth-extension project specifically to help absorb cost overruns tied to the fifth extension, Pakistani financial press has reported, and it has continued to describe overall progress at the site as "satisfactory" in periodic reviews even as the schedule has slipped repeatedly.

Downstream communities and a stretched power system

For the villages and towns that line the Indus below Tarbela — in Haripur district and further downstream through Swabi and Nowshera — a planned increase in discharge from the dam, even one tied to construction management rather than monsoon flooding, is the kind of notice authorities do not issue lightly; Pakistan's Khyber Pakhtunkhwa disaster-management authorities have repeatedly had to manage public anxiety around Tarbela releases after the devastating floods of recent years. WAPDA's post-incident discharge notice was framed as a precaution rather than an emergency measure, officials said, and there were no reports of flooding or evacuations beyond the construction site itself.

The stakes extend well beyond the immediate area. Tarbela is the backbone of Pakistan's hydropower generation, and the Fifth Extension's three 510-megawatt turbines are intended to lift the dam's total installed capacity from 4,888 megawatts to 6,418 megawatts — a roughly 31 percent increase that Pakistani planners have built into forecasts for a national grid that depends heavily on seasonal river flows and has struggled with chronic generation shortfalls and expensive imported-fuel power. Repeated delays at T-5 mean that additional capacity keeps slipping further into the future even as demand grows, a point Pakistani commentators and opposition lawmakers have raised in criticizing WAPDA's handling of the project.

Writing in The Friday Times on Tuesday, engineering academic Dr. Intikhab Ulfat argued that the pattern of failures at T-5 pointed to deeper institutional problems rather than simple bad luck. "Major engineering failures often emerge from a chain of organisational decisions rather than a single mistake," he wrote, adding that in large public infrastructure projects, "too often, completing an inquiry is confused with resolving the problem it investigates." He cautioned that the 2025 and 2026 incidents should not automatically be assumed to share the same physical cause until a fresh technical investigation establishes what failed this time.

What happens next

WAPDA has not said how long the T-5 tunnel will remain closed or what the Monday collapse will add to a budget that has already nearly quadrupled from its original estimate. Engineers, the project's consultants and the contractor were continuing their assessment of the intake structure as of Tuesday, according to Pakistani officials, and a further statement on the cause of the rock failure and any additional schedule impact is expected once that review is complete. Given the scale of the cost growth after the 2025 cofferdam failure, any extended shutdown is likely to draw fresh attention from the World Bank and the Asian Infrastructure Investment Bank, both of which have continued to fund the project through successive rounds of delay, as well as from Pakistani lawmakers already pressing WAPDA over the project's management. For now, officials' central message has been one of containment: the dam itself is intact, the river is being managed, and the damage is confined to a single tunnel that was already years behind schedule before the water ever reached it.