Nearly All MUSTBE’S Nature-Based Stormwater Solutions Completed

As the MUSTBE project is approaching its end, more of its pilot solutions are completed. The project has a total of seven pilot sites in Estonia, Latvia, Sweden and Finland with the first two pilots, both in Pori, Finland, having completed their construction in late 2024. The next four pilot sites, two in Söderhamn, Sweden, one in Viimsi, Estonia and one in Tallinn, Estonia were mostly completed at the end of 2025. The Riga pilot site in Latvia is set to finish construction this spring.

The key theme of the MUSTBE project is creating multi-benefit stormwater management systems that combine nature-based solutions with digital solutions for better stormwater treatment and management. The developed solutions are expected to deliver pollutant removal efficiencies of at least 60% for suspended solids, 30% for total nitrogen, 60% for pathogens, 50% for oil products, and 40% for metals.

In Viimsi, a new modern fountain square was completed that combines public space with a smart and environmentally friendly stormwater treatment system. The location was chosen due to the nearby Lubjamäe limestone escarpment, where groundwater and rainwater naturally flow. This water is collected into a retention pond, cleaned, and reused to operate a stormwater fountain. The site includes pumps, filters, UV and disinfection systems, water level and wind sensors, and automated lighting control. The Viimsi pilot solutions demonstrates how stormwater can be reused sustainably in public spaces.

MUSTBE’s Project Lead Siim Reinla from Viimsi Municipality commented that the innovative nature of the Viimsi pilot site also caused some challenges.

– Most of the difficulties were caused by the fountain which works using stormwater – this is something that is technically complicated for this type of fountains, Reinla says.

The second Estonian pilot site, in Tallinn, is situated in Tondimõisa park where stormwater is partially redirected to the park for treatment, while reducing stress on the stormwater pipe network. The solutions consists of Vortex-type sand and oil separators, followed by two retention ponds and soil filters. After treatment, the water is further directed into the city’s stormwater pipe network.

– Most of the construction work is finished. After the automation work is completed this spring and all snow has melted, the testing and monitoring of the solution can start, project manager Indrek Tamberg from Keskkonalahendused OÜ comments.

Even though the pilot faced many challenges in the process, Tamberg is happy with the outcome.

– This is the biggest project of this kind in Tallinn and in Estonia. If the solution works as planned, I hope that Tallinn and many other cities will start to plan their own similar systems, Tamberg adds.

In Söderhamn, two pilot sites were simultaneously completed in Söderhamnsporten and Broberg. The Broberg pilot site comprises of retention ponds and urban ditches to foster sedimentation and nutrient semoval as well as a new outlet pipeline to Söderhamn’s bay. The new outlet pipeline mitigates the risk of stormwater pipe network failure and further supports the management of excess stormwater volumes, which is essential to improving the current situation and enabling future development in the area.

In Söderhamnsporten, most of the stormwater runoff from a nearby shopping centre’s parking lot is directed through a diversion manhole to a retention pond and a natural meandering ditch. In the event of extreme rainfall, the diversion manhole activates and directs excess water to bypass the solution, preventing flooding in the area and showcasing how smart stormwater management can be combined with nature-based treatment.

The construction process for both pilots went incredibly smooth although some issues were encountered, according to Josefin Flink from Söderhamn municipality.

 – For example, many of the specified heights in the technical design were not correct, so the contractor had to re-measure, and we had to come up with new minor solutions along the way.

The municipally owned service company in Söderhamn was also valuable in the construction process in the assembling of infrastructure. No large amounts of contaminated masses or unoxidized sulphide clay were encountered either.

– Management problems such as backlogs were also discovered, which we were able to remedy, and by having an ongoing dialogue with the contractor, we were able to keep costs down so that the adjustments that need to be added to the work were able to be accommodated in our regular budget. The schedule was also largely kept, Flink states.

The last pilot site to be finished is situated in Riga, Latvia. The solution focuses on meandering of the Šmerļupīte stream and the creation of sedimentation floodplains and ponds to enhance the ecological condition of the stream. The construction works are well underway and are expected to be finished soon.

As monitoring fully kicks off in all the finished pilot sites, preliminary results will be gained from the solutions’ effects on stormwater quality and management. Naturally, the municipalities will continue to gain valuable information and lessons learned from the solutions even after the MUSTBE project’s end in July 2026.

You can find out more about the pilot solutions by clicking here!