After Oulujoki Power Company had completely harnessed River Oulujoki, it shifted its resources northeast towards River Emäjoki that flows from Lake Kiantajärvi southwest to Lake Oulujärvi. Ämmä was the first of the three power plants the company built in the river. It is located in the downtown of Suomussalmi. Since Ämmä lies near the upper reaches of the river, the power plant also regulates the lake. The power plant was designed by architect Aarne Ervi.

The power plants in the river – Ämmä, Seitenoikea and Aittokoski – were designed, and built, in serial production, so that the workforce and machines moved from one site to another as soon as different stages of construction were finished. It is because of the serial production strategy that the three power plants share certain similarities.

The construction of Ämmä started in 1957 by building the service buildings, concrete mixing plants and the housing area. The construction of the power house, foundations for the dam and excavations for the headrace and tailrace started in the same year. The construction of the power house advanced quickly and water could be released into the headrace at the end of 1958. At the same time, the other branch of the river, Jalonhaara, was closed with an embankment. Ämmä was finished in 1959 and the machinery was connected to the power grid on 14 of November 1959. Today Ämmä produces 16 megawatts of power.

The power house of Ämmä has a simple cube-like mass which is due to the fact that the facility has only one turbine. The frame of the power house was casted out of concrete on site and cladded with fiber-reinforced cement board. The spatial layout of the power house is simple. The machine hall is the largest space in the building and the offices can be found in the façade facing the tailrace. The ribbon windows of the façade bring light into the building while the butterfly roof is supported by steel grids. The regulating dam has one spillway gap and was built on the eastern side of the power house.

Temporary, wooden, log chute was also built but dismantled soon, when the large concrete log crane was constructed in 1963.

Text: Samuli Paitsola