In the spring of 2024, the City began a project at Mustapuro to build structures such as floodplains and flow regulators, and to enlarge culverts. With these measures, the City of Helsinki is preparing for floods caused by climate change, the objective being to protect the infrastructure of the surrounding area. The project will also reduce the risk of flooding in the Marjaniemi allotment garden.
The first phase of the work focused on the area around Myllypuro Sports Park and was completed in autumn 2025. The second phase, focusing on the eastern side of Ring I and the southern side of the Itäväylä, will start in spring 2026 and involve work such as:
- constructing a flood basin and flow regulation structure in Mustapuronpuisto Park, east of Ring Road I;
- excavating the streambed to make the stream deeper and wider between Itäväylä and Tulisuontie;
- renovating and overhauling the bridges leading to the Marjaniemi allotment garden;
- lining the edges of the stream with erosion mat fabric containing seeds that will provide the edges with vegetation;
- overhauling the culverts under Tulisuontie and other smaller culverts; and
- planting around 200 trees and 300 bushes.
Delicate stream ecosystem taken into account in the arrangements
Mustapuro is one of the most important urban streams in Helsinki. The stream is inhabited by trout and is home to wintering species such as the kingfisher, which has been taken into account in the scheduling and implementation of the project. The area will be planted with vegetation and trees such as willows, providing a sheltered habitat for kingfishers.
For the duration of the work on the streambed, leachate dams will be installed in the stream and a screen will be installed in the sea to prevent the spread of solids in the waters. From June to July 2026, fish lower down the stream will be relocated by means of safe electrofishing to suitable spots higher up the stream, above the worksite. This relocation will involve a researcher and an assistant with experience in electrofishing. The spawning beds in the area will be restored at the end of the project.
The City aims to reduce the carbon footprint of the construction work by piling up dredged soil material from the streambed into meadow hills in Strömberg Park. This way, there will be no need to transport the soil material away from the area by lorry.
Construction set to begin in May 2026
The construction project at Mustapuro is scheduled to start in May 2026 and end in September 2027.
Before the actual construction work, around 50 trees will be felled in the area, starting in February 2026. The trees will be removed before April, i.e. before the start of the bird nesting season.
Temporary traffic arrangements planned and noise to be expected
The path east of Itäväylä, next to Mustapuro, will be reinforced with wooden piles during the project to ensure that the path can withstand the widening of the creek. The pile driving and temporary sheet pile driving work involved may generate loud noise. The project will otherwise generate normal construction noise in the area. The working hours will generally be from 7.00 to 17.00 on weekdays.
The work area will be cramped, and work will also be carried out on the path through the Marjaniemi allotment garden. The access routes will vary during the project, and some routes will have to be closed for safety reasons. Passage through the area will also be guided by signposts.
The culverts under Tulisuontie will be overhauled in 2027. Traffic on the road will be one-way during the culvert construction phase. More information on the traffic arrangement changes will be provided closer to their start date.
The contractor will be selected by the end of March. The tree felling work will be carried out by City of Helsinki construction services Stara.
