Ämmä Hydropower Plant
Nuojua was the fifth hydropower plant built in River Oulujoki and fourth built by Oulujoki Power Company. Nuojua was built between 1946 and 1955 in the Niskakoski rapids in Vaala municipality. Aarne Ervi was responsible for the architectural design.
The construction site was propitious in Nuojua. The riverbanks were steep, and the rapids head was significant, 31 metres. After the geographical survey, it was decided, that the power house was going to be built in the northern bank of the river and the residential area downstream from the plant.
After the temporary dam was built, construction for the actual power plant started. Builders could utilize Jylhämä’s concrete mixing plant and all the biggest casts were made during 1951. During that year, the spillways for the regulating dam and the power house’s intake structures were finished on the north bank of the river. A concrete framed girder crane was also constructed on the north bank, so that heavy machinery could be hoisted in to the power house and to the switchyard.
The power house was built with an in-situ concrete frame and façades were cladded with precast panels. The earth dam, 25 metres high, was built during the summer seasons of 1952 and 1953 and it was finished in October of 1953. Once Nuojua was finished, Oulujoki Power Company’s electricity production reached 1 billion kilowatt-hours for the first time.
When necessary, the spillway gates release the impounded water into the old riverbed which is located on the south side of the tailrace. The surrounding rural landscape is mostly coniferous forest and occasional farms, but the power plant does not stand out disturbingly because of its subtle presence and composition.
The power house opens up to its surroundings through large windows planes on both of the main façades. Four-framed window elements are hung on the beams between the modular lines. On the façade, the concrete panels and windows are fixed to the same level.
The frame of the machine hall is formed by nine sturdy, fair-faced, concrete columns. The machine hall opens through the large windows towards the tailrace. The view is best seen on the lower levels. Natural light enters the building from below, which gives the space its own ambiance. The dark red concrete walls give generators a decorous background, once again emphasizing the achievements of technology.
The residential area of Nuojua, also known as Nokkala, was designed by Ervi on the Nokkala heath about half a kilometre southwest from the power plant. Visit the Nuojua Residential Area through this link.
Text: Samuli Paitsola