Stormwater Quality Management

Annika Vinkka considers it important that different solutions are available for stormwater quality management, as treatment needs also vary in different areas and forms of land use.

"Nature-based solutions, such as wetlands or green prints, work well in more sparsely built areas, but there is often no room for such above-ground alternatives in city centres, for example. The quality of stormwater also varies in different areas, which must be taken into account when choosing methods. It is also not possible or necessary to treat all stormwater, so we must be able to find the key risk areas and suitable solutions for them", Keijo Houhala points out. 

Vinkka says that Heinola is the first Finnish city to introduce new types of stormwater filter chambers. In early 2023, GF launched the Stormwise solution in the Nordics, which offers a wide range of sustainable products and solutions for stormwater management.

According to Salminen, the Stormwise solution has been very well received. "We have been particularly pleased with the interest that the new treatment solutions have aroused. Stormwater solutions are now being planned for several other cities as well".  

Filter chamber is a compact, scalable solution for applications with high cleaning requirements. It is ideally suited for parking lots, high-traffic road sections or industrial areas, for example.

In the filter chamber, stormwater is treated by both clarifying and filtering before discharging it into water bodies. Heavier impurities precipitate at the bottom of the well and fine matter is removed from the outgoing water with a filter.

The chamber's efficient modular filter filters solids, metals, bacteria, phosphorus, oil and particles from stormwater. Drainage of settled solids is carried out once a year and filter changes every 2–5 years.

"A large part of the harmful substances in stormwater are bound to solids. When solids are separated from water, most of the impurities can be removed before they enter the water system. Harmful substances of particular interest to us are heavy metals and factors causing eutrophication, such as nitrogen and phosphorus," says Annika Vinkka. 

 The filter chambers were installed in late 2023 in the districts of Jyränkö and Tommola, which are located a few kilometres from the centre of Heinola.

"The chambers could easily be installed as part of the existing stormwater system. In Jyränkö, the chamber was installed in a stormwater network that runs along the edge of a residential area and a forest, in Tommola to a stormwater network that runs through the park area," Vinkka says.

The locations were chosen so that we can examine two slightly different sites where the size of the collecting area is optimal. Jyränkö is mainly a residential area, while Tommola has traditionally had industry. The chambers are in non-traffic areas, but close to the road. This facilitates both maintenance and sampling. The stormwater in two areas and the cleaning efficiency of the chambers will be studied with samples to be taken during three rainfall events in the spring.

The snowfall and freezing temperatures started just after the chambers had been installed. This means that samples can be taken and analysed approximately in March–April, when meltwater begins to accumulate again.

"It will be very interesting to see what kind of results we will get in the spring. Relatively little qualitative research on stormwater has been conducted in Finland, so the results will certainly benefit other cities and municipalities as well. A thesis is also being prepared on the project", Vinkka says.