ISLAMABAD: A government-constituted inquiry committee has held all three key stakeholders — the contractor, consultant and employer (Wapda) — responsible for the cofferdam collapse at the 1,530MW Tarbela-5 Extension Hydropower Project, citing post-contract unauthorised design changes as one of the main reasons for the incident. The collapse has contributed to at least a two-year delay and more than 285 per cent cost escalation in the project, whose cost has risen from Rs82 billion to Rs317bn. As a result, the project’s levelised generation cost over 30 years may rise to around Rs27-28 per unit — the country’s highest so far for renewable energy — making it economically unviable and unsustainable, according to the Planning Commission.