Dredging work in Lassilanoja raises concerns for salmon habitats in Helsinki

The Helsinki city branch of the Mätäjoki River, known as Lassilanoja, has undergone dredging work using an excavator. This work was conducted by the City of Helsinki, while the Uusimaa Centre for Economic Development, Transport and the Environment (ELY) processes drainage notifications related to such operations. Tero Taponen, head of the water unit, stated that permits may not always be required for dredging, provided the maintenance preserves the water flow. However, special care should be taken to minimize sedimentation in areas close to valuable water bodies like salmon habitats.

The Lassilanoja was dredged approximately 200 meters through an area located on city property. Henrik Tikkanen from the group Vaelluskala ry visited the site and expressed concerns over the impact of such maintenance activities on sensitive ecosystems, as efforts have been ongoing since 2009 to restore salmon populations in the Mätäjoki River. While Tikkanen indicated that the dredging’s impact was not catastrophic for salmon, he highlighted the alarming nature of the incident and the lack of communication among responsible parties about the species in the area.

Sini-Pilvi Saarnio, the city’s leading environmental inspector, noted that she had not visited the dredging site, making it difficult for her to assess its impact on water quality. Based on photos, she suggested that the potential negative impacts of the dredging may not have been minimized as much as possible. Both her and ELY’s representatives agree that awareness of salmon habitats should have led to more careful planning of the dredging work.

The construction work was ordered due to recurrent flooding problems in the area. The city stated that the maintenance was scheduled to occur after the salmon spawning season, highlighting the tension between maintenance obligations under water laws and conservation goals.