Bulgaria’s National Electricity Company, NEK, has opened a tender worth approximately €350 million to expand the Yadenitsa reservoir. The project is designed to extend the operating flexibility of the Chaira pumped-storage complex.
Storage expansion and tunnel connection
The planned works would raise active water storage to 13.4 million cubic metres from 4.2 million. The larger storage volume is intended to enable longer periods of pumping and generation within the pumped-storage operation. A 6.73-kilometre reversible pressure tunnel would connect the new reservoir with the existing Chaira reservoir.
Tender timeline and procurement structure
Prequalification applications are due by November 4. The negotiated procurement is set to proceed in two stages. Construction is limited to 60 months under the procurement framework.
Scope of contract works and site stabilisation
The contract covers the dam, tunnel, intake structures, roads, monitoring systems and associated infrastructure. It also includes stabilisation works around a fault and a nearby landslide zone.
Financing route and cost estimate
The tender value is about €100 million above an earlier estimate. Full financing remains unsecured, while the project’s EU Project of Common Interest status provides a route to seek Connecting Europe Facility support for up to 50% of eligible construction costs. The expansion is aimed at increasing storage capability rather than adding equivalent new generating capacity.
The project’s market value is linked to absorbing surplus electricity and returning it during higher-demand periods, with delivery dependent on securing financing.
