Seitenoikea was the third and last hydroelectric power plant built in River Emäjoki by Oulujoki Power Company. The facility, designed by Aarne Ervi, was built in three years.

Construction of Seitenoikea started in late 1958. Preparatory works included construction of temporary housing, service buildings and roads. At the end of 1959 the largest concrete casts were ready. Earth fill dams were completed during 1960 and water could be raised to the forebay in the spring of 1961. The whole power plant was finished in the summer of the same year. The power plant’s machinery was connected to the power grid on 8 June 1961 with a total power of 38 megawatts.

The power house is placed next to the regulating dam and the earth dams spread on both sides of the facility. As in Aittokoski, the view from the forebay reveals very little, as the power house is almost unnoticeable. Architecturally the power house of Seitenoikea is quite similar to Aittokoski, although its construction site is less dramatic. The rectangular shaped concrete frame of the power house is mined inside the bedrock and cladded with profiled aluminium sheeting, giving it the same, sleek, machine-like aesthetic that Aittokoski has.

The organization of the power house is composed around the machine hall that is situated at the ground level. The service level is located below the machine hall so that parts of the machinery that need maintenance can be lowered to the service level chasm with the girder crane that runs inside the hall. The contrasting colours red, yellow and blue dominate the interior. The striped floor is also a familiar feature from Ervi’s earlier power plants.

Similar to Utanen and Ämmä, Seitenoikea does not have a gate hall and the inflow control gate is hoisted outside the building’s envelope, when necessary. The office block is located between the gate and the machine hall. Large windows of the machine hall open towards the tailrace and the large steel door provides access to the building. The small residential area, also designed by Ervi, is located on the ridge on the eastern side of the power plant.

Completion of Seitenoikea in 1961 marks the end of Ervi’s work with hydropower. This 20-year-period, that started with Pyhäkoski in 1940, can be seen as an evolutionary process where Ervi’s own ambitions merged with the general values, possibilities and limitations of the time. During this period Ervi moved from the rigorous Functionalism of Pyhäkoski, to the transparency, flowing interiors and precast panels of Pälli, Nuojua and Montta, to ever more lighter and cost efficient designs in River Emäjoki.

Text: Samuli Paitsola