Bulgaria’s National Electricity Company, NEK, has opened a tender worth approximately €350 million to expand the Yadenitsa reservoir. The project is intended to extend the operating flexibility of the Chaira pumped-storage complex.
Reservoir expansion and connection works
The expansion would raise active water storage to 13.4 million cubic metres from 4.2 million. That increase is designed to enable longer periods of pumping and generation. A 6.73-kilometre reversible pressure tunnel would link the new reservoir with the existing Chaira reservoir.
Tender timeline and procurement structure
Prequalification applications are due by November 4. The negotiated procurement will be carried out in two stages, with construction capped at 60 months.
Scope of contract 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. The tender value is about €100 million above an earlier estimate.
Financing route through EU support
Full financing remains unsecured for the project. However, its EU Project of Common Interest status provides a route to seek Connecting Europe Facility support for up to 50% of eligible construction costs.
Role in power system balancing
The expansion would increase storage capability rather than add equivalent new generating capacity. Its market value is tied to absorbing surplus electricity and returning it during higher-demand periods, while delivery depends on securing financing.
