Published in 5/2021 - Extensions

Interview

The Power of Expression

Kristo Vesikansa

The new electricity substation and power line introduce a new, sculptural layer to the national landscape of the Imatrankoski Rapids.

The location of the new Imatra electricity substation is unique in terms of the landscape and cultural history – the station was built in the national landscape of the Imatrankoski Rapids. As the mightiest rapids in the country, Imatrankoski has fascinated travellers from Finland and abroad since the 18^th century. In pre-independence Finland, the site was a particular favourite of the affluent classes of St. Petersburg, and, for instance, the castle-like Valtionhotelli hotel (Usko Nyström 1903) was built to cater to the needs and tastes of high society. The power of the free-flowing rapids was also memorialised in countless drawings, paintings and photographs.

After Finland’s independence, Imatrankoski was harnessed to produce energy for the industrialising nation. Construction for the hydropower plant commenced in 1922, and the water was directed into the new canal seven years later. The plant has seen several expansions and, measured in production capacity, remains Finland’s largest hydroelectric power plant to this day.

The design of the power plant itself rested chiefly in the hands of engineers, but an architectural competition was arranged in 1926 regarding the facade of the distribution station. The winning entry came from the pen of architect brothers Oiva and Kauno S. Kallio, who arranged the red-brick facades with classicist decorative motifs, while the interior was dominated by concrete structures that were quite progressive for their time. The designing of an exterior envelope around a pre-resolved frame was a decidedly difficult task, as the brothers lamented in the Finnish Architectural Review that “finding a good solution was, at times, an almost insurmountable challenge, when the construction of each and every building had been firmly fixed in advance.”

An essential part of the grand national project was the 560-kilometre power line, the Iron Lady, through which electricity produced at the plant was transmitted to the largest cities. The Iron Lady was named after the lattice-type steel towers, which dominated the landscape of Southern Finland for decades.

More photos and drawings of the project →

Ark: Architect TUOMAS KIVINEN, what were the limitations that the valuable landscape posed on the design of the substation and power line structures?

The site offered more possibilities than it imposed restrictions. The Imatrankoski hydropower plant is the historical starting point of Finland’s main power grid, and so the client was seeking an extraordinary whole. We were given the mandate and resources to draw up a design that would do justice to the significance of the area.

The premise for our design was that, even though the power line structures would constitute a distinct presence in the landscape, they should not dominate the views to an excessive extent. With the exception of the tallest pylon, all of the structures are lower than the surrounding woods.

We positioned the new substation as a part of the old hydropower plant complex. The demolition of the old substation left an open space next to the power plant, which is now delineated on its western side by the new substation and power line structures. 

We minimised the height of the new structures to avoid disturbing the dominance of the original power plant building. The cable space was located underground, which enabled us to lower the eaves of the new building to make them level with the eaves of the neighbouring building.

Which kinds of technical and functional requirements did you have to take into account in designing the building?

The simplicity of structures and ease of maintenance are emphasised, as the buildings need to function reliably without a constant human presence. The power line and cable alignments determined the positioning of the new substation on the site, in addition to affecting its structures and the arrangement of interior spaces: the portals, i.e. power line terminal structures, connect the overhead power lines with underground cables, which are then connected to the substation building in the basement. In addition, cables are run to the substation from the hydropower plant. The space requirements of process equipment haulage defined the height of the building.

The architectural character of the building is mainly based on the use of brick and concrete, as well as a highly regular geometry. What were the factors that steered the design?

We wanted to keep the massing simple, so that the building and the power line structures would form a cohesive and controlled whole. Kauno S. and Oiva Kallio parsed the brick facades of the original hydropower plant with a regular fenestration, and we strove for an analogous effect, relating the substation to its site with a similarly rhythmic facade. The long hand-made brick is also a nod towards the beautiful brick exterior of the original building. The bricks were laid in a zig-zag profile, a motif that we also applied to the design of the power line structures. We designed the top of the masonry walls in a lattice pattern to accommodate the windows and ventilation ducts behind the masonry layer. The grey colour sets the new building apart from the old, and the light colouring also highlights the variation between light and shadow nicely.

The concrete structures of the original power plant inspired us to leave some of the concrete structures visible in the interior and exterior architecture. The cast-in-situ concrete at the ends of the new building reveal the double facade structure: the building is a concrete box wrapped in a layer of brick cladding.

How did you arrive at the sculptural shapes of the power line structures?

Three types of power line structures were incorporated in this project: tall and low pylons, as well as the portal serving as the power line terminal. These all share a triangular profile made up of welded box beams, as well as a rhythmically repetitive configuration and a white colour. 

Light and shadow alternate on the three surfaces of the steel profiles during the day. The shape also varies when viewed from different directions and distances. The geometry, scale and colouring of the light-grey latticework in the original 1920s’ pylons served as a point of inspiration for us. The abstract design ties together structures that are spread across a wide area into a single whole, connecting them with the architecture of the new substation and the old power plant buildings. ↙