“Maveplan acted as master planner for the decommissioning of all three power plants, the demolition of their dams and the restoration of the rapids.”Hanna Ollikainen, CEO, South Karelian Foundation for Recreation Areas

Hanna Ollikainen, CEO of the South Karelian Foundation for Recreation Areas gives background information on the fishway obligations imposed on power plants in the past and how their construction would have caused costs for energy companies. In addition, part of the flow would have had to be diverted to the fishways, which in turn would have reduced the yield from the power plants. However, the power plants were profitable, so the pursued power plant ownership by the Recreation Area Foundation required negotiations.

In 2017, the Lahnasenkoski small power plant, managed by Vantaan Energia, became the first of three power plants to be owned by the Recreation Area Foundation. The other two power plants were owned by Hiitolanjoen Voima Oy, whose shares were purchased by the Foundation in autumn 2019.

The project took shape in 2019. The Foundation for Recreation Areas and Hanna Ollikainen were in charge of the whole project. Maveplan became involved in the implementation during the pre-appraisal phase in order to start the permitting process.

Harri Keskinen at Silta TSV Oy, who acted as a construction consultant for the restoration of the Hiitolanjoki River, explains that a general plan is submitted to the Regional State Administrative Agency for a building permit under the Water Act. Compared to applications for permits for above-ground buildings, it is looser in content.

Maveplan acted as master planner for the decommissioning of all three power plants, the demolition of their dams and the restoration of the rapids. Once the Regional State Administrative Agency granted the permits, construction could begin. Harri Keskinen at Silta TSV drew up a detailed construction plan based on his inspections and observations.

Lauri Keskitalo, Maveplan expert, on the starting points for the design of the three sites:

• Solutions that are as organic as possible were sought by designers
• Preservation of upper water levels
• Large low flows, which made it possible to design large, fully watered rapids
• At Ritakoski and Lahnasenkoski, difference in height and the steepness of the planned artificial rapids
• The cultural heritage authority’s comments on the technical options for demolition of the dams imposed constraints on the design

The demolition of the dams and the restoration of the rapids proceeded on a target-per-year basis. In 2021, Kangaskoski, which is closest to the Russian border, was the first to go. In 2022, the target was Lahnasenkoski. The most recent restoration took place at Ritakoski, which will finally open up spawning opportunities for lake salmon in the Hiitolanjoki River and a migration route to lakes on the Finnish side at the end of 2023.

The three projects and the hydraulic engineering involved the expertise of several experts. The restoration has been carried out according to Maveplan’s plan. Of course, there were also some applicable issues in the big picture.

Harri Keskinen stresses the importance of initial data. River bottom investigations, the study of structures in contact with the water and especially with the rapids, right up to the practical implementation of soil transport routes, must be clear. In the case of Ritakoski, for example, it was discovered during the design process that the bridge pilings of the road were made of wood, so the location of the submerged weir had to be changed to the downstream side of the bridge. The implementation of the project posed challenges due to the potential impact of the blasting operations on the railway track crossing the river. Expertise helped to find the right solutions.

The restoration of the Finnish section of the 53 km long river, which flows into the Ladoga River, was completed in November 2023.

Hanna Ollikainen says that the finishing touches to the signage and furniture for the connected walkways remain to be done. In addition, in line with her responsibilities, she still has to carry out a decommissioning inspection of power plants by the authorities.

Harri Keskinen notes that the last phase of the work only involves driving the soil to the landfill and adds that the soil has been found to be clean and does not need to be post-treated.

The end result is a project that created spawning grounds and a natural migration opportunity for lake salmon. Hanna Ollikainen describes the project as an increase in biodiversity value, which will also add vitality and attractiveness to the whole area.

Harri Keskinen adds how the project has progressed in a positive atmosphere. Municipal residents and decision-makers are excited about the restored Hiitolanjoki River.

As a seal of success, the project was awarded Nature Project of the Year by the Ministry of the Environment. The restoration has also been noted internationally. Dam Removal Europe, the World Fish Migration Foundation, and the WWF recognised the South Karelian Foundation for Recreation Areas for the demolition of Kangaskoski dam as the most innovative and inspiring dam removal on a European river. The €10,000 prize money will be used by the Foundation for future dam breaks.

“The restoration of the Hiitolanjoki River is a major dam removal project even on a European scale, but above all in Finland, its impact is enormous: thanks to the huge media coverage it has received, river restoration has become a familiar concept to the general public. We have moved from technical fishway solutions to an era in which river restoration according to the model of the Hiitolanjoki River is seen as the undisputed best option. Best of all, the immediate results from the Hiitolanjoki River have surprised everyone. This has already created a snowball effect, with more and more municipalities and regional actors planning to release their own impounded rapids to their original glory. I can see that there is no stopping this movement.”
– Jasper Pääkkönen, actor and river restoration advocate

Hanna Ollikainen is pleased to see how the project demonstrates cooperation and expertise between parties. The restoration of the Hiitolanjoki River also received a lot of public attention, which Hanna says was a source of motivation.