The MUSTBE project includes seven pilot sites in four countries – Estonia, Finland, Latvia and Sweden.
Learn more about each pilot site here.
MUSTBE pilots: interface for the manual of solutions
The Airtable application is designed to help project managers and planners track, compare, and analyze the performance of planned and completed nature-based solutions (NBS) across the multiple pilot sites.
Each record in the database represents a single NBS intervention (e.g., stormwater pond, wetland, or green park area) and includes both technical and performance indicators, allowing visualization of the performance metrics and impact of solutions.
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The Viimsi pilot site is situated next to the Lubja cliff, which is a significant groundwater recharge area emitting large volumes of groundwater all year round. The emitted water was previously directed to the existing stormwater pipe system, which was frequently overloaded, especially during heavy rainfall or snowmelt, resulting in flooding issues. In case of flooding, the pollutants and hazardous substances from the nearby high-traffic street were flushed to the stormwater system and eventually into the Baltic Sea.
The pilot solution includes a modern, smart, and economical rainwater collection and recycling system, which is also part of the new fountain square and pocket park in Viimsi. The focus of the project was an innovative approach to stormwater and surface water management – instead of simply channeling rainwater into the stormwater sewer, flows are delayed and equalized in a pond, where the water is also purified, and the water is then channeled into a tank for use in the fountain.
Viimsi pilot site 
Viimsi pilot site during construction 
Viimsi pilot site during construction in September 2025 
Viimsi pilot site during construction in August 2025 
Viimsi pilot site during construction in August 2025
The Tallinn pilot site is a public green park called Tondimõisa park, which is surrounded by urban, industrial, and commercial areas. Previously, the stormwater collected from the area was directed to the underground stormwater pipe system. During heavy rainfall, the pipe system was easily overloaded, which led to flooding issues.
The nature-based solution implemented at the pilot site consists of a wetland with a two-bond system. Stormwater is partially redirected first into Vortex-type sand and oil separators, where large particles, oil, sediment, and floating debris are removed. After the separation, the water flows to the first retention pond, where further sedimentation occurs. From the retention pond, the water is directed into soil filters where fine particles are removed. The water is eventually directed into a channel or, in the case of heavy rainfall, into a natural floodplain. In the channel, water flows through the monitoring well, where the solution’s efficiency on water quality is evaluated. After completing all these steps, the stormwater is directed back into the existing stormwater pipe network.
Tallinn Tondimõisa park before construction 
Tallinn Tondimõisa park before construction 
Tallinn Tondimõisa park before construction
The Central Square pilot site is situated in the centre of Pori. Due to the densely built area, the stormwater capacity was previously exceeded during heavy rain events, which led to frequent flooding. In addition, the condition of the vegetation was poor – the tree roots did not get enough water and oxygen due to the dense pavement and compacted soil. The trees were also situated higher than the surrounding area, which led to stormwater being utilized inefficiently by the vegetation. This resulted in the stormwater flowing untreated into the stormwater pipe system.
The pilot site aims to increase stormwater quality and prevent urban flooding through renewed green lines and permeable surfaces. The green lanes are built on top of structural soil, which consists of gravel and soil, acting as a supporting structure in paved areas while also allowing sufficient growth space for the tree roots. Stormwater is directed to the trees and perennials with the sloping of the ground. The asphalt was replaced by a permeable pavement material, allowing the water to infiltrate into the ground.
Central Square before construction 
Central Square during construction in September 2024 
Part of the asphalt was replaced with permeable pavement. 
Fences were added to the green lines to protect the plant growth. 
The perennials were added to the green lines to support the water filtration.
The wetland pilot site is located in northern Pori, in the Lotskeri residential area. The catchment area of the wetland is located on acidic sulphate soils. When acid sulphate soils are exposed to oxygen, through land use or land reclamation, they generate sulphuric acid, which leaches metals present in the soil. Metals and acidic water are then flushed to the receiving water bodies. The acidity and metals can have a deteriorating impact on the ecological and chemical status of downstream water bodies.
The pilot site aims to precipitate the metals and reduce the acidity of the water. The solution includes a filtration dam system and retention and settling bonds. Biochar, limestone, and stone dams are used to bind the metals, reduce the acidity, and delay the water flow. The solids and precipitated metals settle in the settling pond at the end of the wetland, from where the sediment can be removed.
Wetland before construction 
Wetland after construction 
The Riga pilot site focuses on approximately an 800-metre section of the Šmerļupīte stream located between Eizenšteina and Stūrīša Streets. The stream receives stormwater from three different residential areas: Mežciems, Pļavnieki, and Dreiliņi. The incoming stormwater contained high levels of nutrients, such as nitrogen and phosphorus, as well as elevated levels of lead and copper. Additionally, high levels of BOD (biological oxygen demand) were also found. The quality of the water indicated illegal domestic sewage connections to the stream, which has degraded the ecological condition of the Šmerļupīte stream and affected the recreational value of the surrounding green area.
The pilot solution comprises two zones – the stormwater treatment zone and the renaturalisation zone. The stormwater treatment zone includes sedimentation and filtration ponds, which slow the water flow and promote pollutant removal. Renaturalisation zone features meandering stream paths, wet meadows, and phytoremediation vegetation.
The increasing urbanization, along with rising amounts of impermeable surfaces, construction, and traffic volumes, has put pressure on sufficient stormwater management, resulting in frequent flooding issues in Söderhamsporten. Söderhamnsporten’s pilot site aims to treat the stormwater runoff from the nearby shopping centre parking lot.
The solution comprises of a retention pond and a natural meandering ditch. Most of the stormwater runoff is directed through a diversion manhole to a retention pond, delaying the water flow and fostering sedimentation to remove suspended solids. In the event of extreme rainfall, the diversion manhole activates and directs excess water to bypass the solution – thus preventing flooding in the area and showcasing how smart stormwater management can be combined with nature-based treatment.
Söderhamnsporten before construction 
Söderhamnsporten before construction
The Broberg pilot site is situated at Söderhamn’s bay. The area is highly affected by the sea level fluctuations and lacks retention volume during heavy rainfall events. In addition, the existing stormwater pipe network is in poor condition and poses a risk of flooding in case of sudden failure.
The nature-based pilot solution implemented includes a combination of retention ponds, urban ditches, and a new outlet pipeline to Söderhamn’s bay. The retention pond promotes the sedimentation of solids, and a new outlet pipeline mitigates the risk of stormwater pipeline failure and further supports the management of excess stormwater.
Broberg before construction 
Broberg before construction
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