Skarta completed the construction work for the Jämsä central sewage treatment plant three months early


Skarta built the extension of the Jämsä central sewage treatment plant and took care of the construction work for the sewage treatment plant renovation and the machinery project as a turnkey delivery. The project was extensive and took almost eighteen months to complete. Skarta succeeded in completing the work three months ahead of schedule.

The Jämsä central sewage treatment plant serves about 15,000 Jämsä and Jämsänkoski residents, and during the tourist season of the nearby Himos Ski Resort the number of people multiplies. For example, Himos receives about 40,000 guests during the Midsummer festival. This must be taken into account in the sewage treatment plant’s capacity.

The biggest reason for the extensive renovation and the construction of a new processing building were the environmental permit requirements.

“Plants need to be able to remove ammoniacal nitrogen from the sewage they process, which is something our old system could not accomplish. Therefore, into the new plant was built a system that meets all the latest requirements, and at the same time the old side was renovated; a sewage screen was installed and the aerators were replaced, for example,” says Pekka Karppinen, Plant Manager of the Jämsä central sewage treatment plant.

Skarta performed all the earthworks and machinery project for the central sewage treatment plant and built the new plant building. The work began in February 2020 and the plan was to finish by the end of September 2021, but everything was completed in June, three months early.

“Everything went surprisingly easily, very painlessly, even though this required a lot of organisation, since in addition to the main contractor Skarta, a number other contractors working in electric automation and air conditioning worked at the site, and the site comprised renovation and new construction sites that were worked on at the same time. Skarta scheduled and organised everything so that the work could be completed effortlessly. You could see that the work was being performed by experienced professionals who are used to working together,” Karppinen describes the progress of the project.


Plant in constant use during the renovation

Skarta Site Manager Pekka Nissinen says that the project started with the earthworks for the new processing building and continued with the above-ground parts of the building: casting the concrete reservoirs.

“The concrete tanks are 60-metre-long, 15-metre-wide and about 4 metres deep. The reservoirs were divided by partitions into two pre-clarification basins and two aeration basins. On top of the tanks we built concrete vault structures and a processing building. Alongside it we performed the renovation of the neighbouring old sewage treatment plant.”

The renovation of the old sewage treatment plant needed to be carefully scheduled in accordance with the Himos Ski Resort tourist season so that the plant could be used as little as possible during the critical sewer renovation phase.

“When we replaced the machinery in the old sewage treatment plant, it had to be operational the entire time, which created its own challenges for the project, since the water treatment process could not be disrupted at any point. In practice this was solved so that we renovated the tanks in turns. Of the two aeration tanks and two clarification tanks, one was always in use,” Nissinen explains.

When the work was completed in June, trials were run successfully; they were completed without any disruptions and according to plan.

Karppinen has a reason to be happy: “The plant works as planned and removes the ammoniacal nitrogen. We now meet the requirements of the new environmental permit.”

Photo: Aleksi Rajala