Seinäjoki rebuilds polluted stream after removing 800 truckloads

A major project to clean up and partly rebuild the polluted Pajuluoma stream in Seinäjoki is nearing completion after about 800 truckloads of contaminated soil were removed, Yle reports.

The work covered roughly one kilometre and is expected to be completed up to a year ahead of schedule. Most of the excavation was carried out during the winter, when water levels were low.

The project was unusually demanding because the contaminated material could have spread into the water. “Everything involved some degree of piloting,” said Mikko Heiskanen, the project manager at Väylävirasto.

The polluted section lies in Seinäjoki’s Pohja district, between a VR railway area and National Road 19. Elevated pollutant levels in the stream sediments were identified in the early 2000s.

The sediments contained polycyclic aromatic hydrocarbon compounds, oils, fuels, solvents and metals. They are probably from the railway area and accumulated over several decades, although the source has not been established with certainty because stormwater also enters the stream at several points.

About one third of the stream was cleaned by removing contaminated sediment. The remaining two thirds were rebuilt as a new channel alongside the old one.

Pajuluoma flows through Seinäjoki’s diversion channel into the Kyrönjoki river and eventually the sea. Vaasa Water draws drinking water for Vaasa from the Kyrönjoki, so water quality was closely monitored at its intake, about 70 kilometres from Pajuluoma.

Water was occasionally diverted past the intake as a precaution when pollutant levels rose. The exceedances were linked to work phases in which contaminated sediment was removed from the original channel. Work was temporarily halted until the levels fell.

The project has cost about three million euros. Väylävirasto’s work is almost complete, but water quality will continue to be monitored for another two years. A final report is due in November.

Seinäjoki will begin landscaping the area in spring next year. The former overgrown area will be turned into a park with walking and cycling routes on both sides of the stream, meadow-like landscaping, trees, plantings and benches.

The new pedestrian and cycling bridge over Pajuluoma on Pultrantie has already opened. A second bridge at Ainonsola is expected to open in the coming weeks. The improved access will also make it easier to control the invasive Himalayan balsam growing along the stream.