Water and Power Development Authority (WAPDA) Chairman Lieutenant General (retd) Muhammad Saeed visited the Tarbela Dam Fifth Extension Project on Tuesday and ordered a departmental inquiry into the tunnel flooding that halted construction a day earlier.

Saeed chaired a meeting at the project office, where consultants, the contractor and WAPDA teams briefed him that there was no threat to the integrity of the main Tarbela Dam or any of its structures. He also toured the project's intake structure, tunnel, powerhouse and other key sites.

Sources said the inquiry into the incident would be completed within a week. A spokesperson for the Ministry of Water Resources said WAPDA had been asked to submit a comprehensive report on the matter.

What happened on Monday

On Monday, 9 November, a weak section of rock fell during excavation of the second bench of the connecting tunnel at the Fifth Extension Hydropower Project, known as T-5, in Haripur. Water from the intake pit then flowed into the connecting tunnel and the under-construction powerhouse.

WAPDA said all workers were immediately evacuated and confirmed that nobody was injured or killed. The Haripur deputy commissioner said a part of the protective embankment at the project intake broke after a girder fell, and that one local worker who was submerged in the tunnel was pulled out by local people.

The incident happened at about 10:30 in the morning, and construction work at the project was suspended for an indefinite period. All local and foreign personnel, including Chinese engineers and workers, were safely evacuated from the site.

No damage to main structures, WAPDA says

WAPDA dismissed reports circulating that Tunnel 5 had collapsed as incorrect. The authority said the main tunnel, the under-construction powerhouse, the tailrace culvert and the switchyard had suffered no damage.

The authority said water had been completely drained from the intake pit and that dewatering of the under-construction powerhouse had begun. No further water was entering the work sites on the downstream side, the spokesperson added.

WAPDA also issued a notification on discharges downstream of Tarbela Dam in the Indus River, saying flows would be more than 150,000 cusecs round the clock.

About the T-5 project

The Tarbela Fifth Extension Hydropower Project is backed by the World Bank and the Asian Infrastructure Investment Bank. It is being built to add roughly 1,530 megawatts of clean electricity to Pakistan's national grid by converting Tunnel 5 into a power tunnel with a new powerhouse.

The inquiry ordered on Tuesday will examine how a weak rock mass gave way during excavation and what needs to change before work can safely resume at the site.