Gouvães Hydroelectric Plant Headrace Tunnel

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

The Water Intake is a semi-buried reinforced concrete structure, with a total length of 61 m and a truncated cross-section with variable dimensions. The structure consists of two main walls as flow dividers and two support beams for the inlet grates. The water intake section itself is 21 m long, while the interior part extends for approximately 40 m before reaching the gate shaft.

The gate shaft is a reinforced concrete structure with a free internal diameter of 8.30 m and an approximate height of 20.25 m.

The headrace tunnel extends for approximately 4,645 m, from the gate shaft at the water intake in Gouvães to the start of the penstock, after the surge shaft. It features descending gradients of 0.66% and 0.40% from the water intake to the surge shaft. The tunnel has a circular shape, with a diameter of 7.30 m, and is lined with C30/37 concrete, with a thickness varying between 0.3 m and 0.65 m. Reinforcement was applied in sections with more challenging geological conditions.

The surge shaft is located at PK 4+620 of the headrace tunnel and vertically aligned with it. It has a free internal diameter of 21 m and an approximate height of 74 m, ranging from elevation 913.00 m to its intersection with the headrace tunnel at elevation 839.00 m. The shaft lining consists of a 1 m thick reinforced concrete ring up to elevation 908.00 m, with the upper section also built in reinforced concrete. The top opening of the surge shaft, at surface-level, consists of a ring of 167 micropiles, each with a diameter of 88.9 mm and a depth of 8 m.