A massive surge of water flooded part of Pakistan's Tarbela Dam 5th Extension (T5) construction site on November 9, 2026, forcing workers to evacuate after a protective barrier reportedly collapsed during tunnel excavation. According to reports by The Express Tribune, the incident occurred when a protective bund or weakened rock mass gave way, allowing water to rush into an under-construction tunnel and the powerhouse area. Video and eyewitness accounts described a sudden influx of water that disrupted work and created an immediate safety emergency. One worker was reportedly swept away by the powerful current but was subsequently rescued. No fatalities were reported, and emergency teams worked to drain the flooded area after the incident. The Water and Power Development Authority (WAPDA) also rejected claims that the entire tunnel had collapsed, while construction activities were suspended pending further assessment.

The latest incident adds to the challenges facing the T5 project, which is designed to increase Tarbela Dam's electricity-generating capacity by 1,530 megawatts. Civil construction work is being carried out by China's Power Construction Corporation, with financial support from the World Bank and the Asian Infrastructure Investment Bank. The project has already experienced significant delays and cost increases reportedly exceeding 285%, following an earlier cofferdam collapse in 2025. Authorities are now expected to conduct a high-level inquiry into the latest flooding to determine whether structural weaknesses, excavation-related problems, or other technical failures contributed to the collapse. Construction has been suspended indefinitely while officials assess the damage and establish what safety measures are required before work can resume. The investigation will be critical in determining how the latest setback affects the project's schedule, costs, and long-term reliability.