Gouvães Hydroelectric Scheme Headrace Tunnel

The construction of this project included the Water Intake, the Gate Shaft, the Headrace Tunnel and the Surge Tank.

The Water Intake is a semi-buried reinforced concrete structure with a total length of 61 m and a tapered cross-section with variable dimensions. The structure comprises two main walls acting as dividers and two support beams for the trashracks. The water intake section has a length of 21 m, extending approximately 40 m further inside until it reaches the gate shaft.

The Gate Shaft is a reinforced concrete structure with a clear internal diameter of 8.30 m and an approximate height of 20.25 m.

The Headrace Tunnel extends for approximately 4645 m, from the centre of the gate shaft at the Gouvães water intake to the start of the penstock, downstream of the surge tank. It features descending gradients of 0.66% and 0.40% from the water intake towards the surge tank. The tunnel has a circular cross-section with a diameter of 7.30 m and was lined with C30/37 concrete, with a thickness varying between 0.3 m and 0.65 m. Reinforcement was applied in sections located within the most critical geological zones.

The Surge Tank is located at chainage 4+620 of the headrace tunnel and vertically above it. It has a clear internal diameter of 21 m and an approximate height of 74 m, from elevation 913.00 m to its intersection with the headrace tunnel at elevation 839.00 m. The surge tank lining consists of a 1 m thick reinforced concrete ring up to elevation 908.00 m, with the external section above this level also built in reinforced concrete. At the surface, its portal consists of a ring of 167 micropiles, each 88.9 mm in diameter and 8 m deep.