Dam Design and Construction

Iberdrola updates on status of Alto Tâmega construction

Iberdrola updates on status of Alto Tâmega construction

Construction of the 160 MW Alto Tâmega Hydroelectric Power Plant continues to progress at a good pace, Iberdrola said, with the river diversion tunnel closed last month.

The civil works are practically finished and the electromechanical assemblies will be completed by the end of 2023, when commissioning will begin, the company said.

Alto Tâmega is the last of the three developments that make up the Tâmega complex in Portugal. The other two, 880 MW Gouvães pumped storage and 118 MW Daivões, have been in commercial operation since 2022.

The Alto Tâmega dam is now fully complete. It is 104.5 m high double curvature vault dam, with a crest length of 335 m. For construction and thermal reasons, concreting of the dam was carried out in 21 blocks, which in turn were divided into 2-m-high sections. Concreting of the dam took less than two years and was completed at the end of 2022.

During this spring, injection of the construction joints of the dam was carried out, once the concrete in place had cooled down during the winter and the opening between the joints was larger. In this way, when the gaps between the blocks were filled, the dam acquired its monolithic character and it was possible to start filling.

With the river diversion tunnel closed, in the next three months a 28-m-long concrete plug will be built inside the tunnel to ensure its closure for the entire life of the facility. During these three months, the flow of the river will continue to circulate through the dam’s bottom outlets.

The Alto Tâmega reservoir, which will cover an area of 468 ha, will then be filled, providing the water needed for the production of renewable electricity at the two-unit Alto Tâmega power plant at the foot of the dam.

During the construction of the Alto Tâmega Hydroelectric Power Plant, a peak of almost 1,000 workers was reached on site.

The electromechanical assembly of the power plant is progressing smoothly according to schedule. The turbines of both units are already fully assembled and the generators are at a very advanced stage of assembly. Once the reservoir has been filled, the first synchronization of one group to the grid is scheduled for January 2024 and the plant will enter commercial operation in March 2024.

The Tâmega hydroelectric complex is one of the largest energy initiatives in Portugal’s history, with a total investment of more than €1.5 billion (US$1.6 billion) and an installed capacity of 1,158 MW, 880 MW of which are reversible.