ACCIONA Construction and its partners, the Portuguese firms Mota-Engil and Edivisa, have successfully completed the works to divert the River Tâmega, one of the milestones in the Tâmega Electricity Generating System project that Iberdrola is carrying out in northern Portugal.
The company carried out this work by excavating a tunnel through the foundation rock on the left-hand side of the Alto Tâmega dam, an infrastructure that the joint-venture is constructing as part of the River Tâmega hydroelectric complex, near Oporto in Portugal.
The works to temporarily divert the river during the construction phase of the project consisted of a 244 metre long underground structure with a U-shaped cross-section, created to divert a flow of nearly 500 m3/s with a ten year recurrence interval.
To ensure the operation was completed successfully, ACCIONA Construction also constructed a cofferdam (an arch dam with a base joint), consisting of a dam nearly 18 metres high, and in the coming days it will also finalise construction of a secondary earthfill cofferdam with a clay core, nearly ten metres high.
This important diversion work is a major milestone in the project, since it will enable the Alto Tâmega dam and the associated hydroelectric power station to be constructed without the effects and interference from the river’s normal channels over the next three years.
The Tâmega Electricity Generating System, developed by Iberdrola, is one of the largest water projects undertaken in Europe in recent years and involves the commissioning of three hydroelectric power stations – Gouvães, Alto Tâmega and Daivões.
In addition to construction of this 106.5-metre double-curvature concrete arch dam, ACCIONA Construction’s contract with Iberdrola includes the installation of an external hydroelectric power plant at the base of the dam, which will have two 80 MW generators to produce energy.It will also construct the plant’s water circuit and the penstock, among other works.
The total budget for this contract exceeds €107 million and is scheduled to be completed by the end of 2021.
At present ACCIONA Construction, in a joint-venture with the same partners, is also constructing the headrace tunnel for the Gouvães hydroelectric power station, which is being constructed using conventional methods.
ACCIONA Construction has been involved in constructing more than 50 dams in 12 countries around the world and has been part of numerous national and international emblematic projects, becoming a world leader for these types of infrastructures.In addition to the Alto Tâmega dam, ACCIONA Construction is currently immersed in another major hydro-project – construction of the dam for the hydroelectric complex of the Site C Clean Energy Project in Canada.