At a presentation held in Mereranna Pocket Park in Haabneeme, a demonstration site for stormwater collection and reuse, established as part of the LIFE LATESTadapt project, was introduced. Tanel Mätlik, Project Manager at Viimsi Municipality, provided an overview of how the facility operates and demonstrated how water stored in underground collection tanks can be used both for street cleaning and for watering greenery in the surrounding area.
During the demonstration, an automatic pumping system was used to draw water from the underground collection tanks and transfer it to a road maintenance vehicle.
The collected stormwater was then used to clean the street. The practical test demonstrated that rainwater, which would normally be discharged into the drainage system, can instead be treated as a valuable local resource and used for tasks that do not require potable-quality water.
In addition to the solution designed for road maintenance vehicles, other water access options were presented on site. Landscaping staff can use the water stored in the collection tanks to irrigate plants growing along nearby streets. The solution allows water to be accessed both by watering trucks equipped with their own pumps and by vehicles without pumps. For this purpose, the system includes both a gravity-fed connection and a pressurised water take-off point.
Rainwater is put to use instead of simply being drained away
The Mereranna demonstration site is located in a green space near the intersection of Mereranna Road and Randvere Road. The site was selected because it previously had no stormwater management system and was affected by waterlogging after heavy rainfall. In addition, the green space in the centre of Haabneeme had previously lacked a clear public function.
The purpose of the new solution is not merely to drain rainwater away as quickly as possible. Instead, the flow of water is slowed down, the water is treated, and some of it is retained for later use. In this way, the system helps reduce the load on the stormwater drainage network during heavy rainfall while also creating a reserve of water for irrigation and maintenance work.
The system within the project area is connected to the main stormwater pipeline beneath Randvere Road. Under normal conditions, stormwater is directed to the demonstration site. However, during exceptionally heavy rainfall or when the system reaches capacity, an automatically controlled gate can open and allow water to flow into the existing stormwater pipeline. The solution also includes an emergency overflow for use in the event of an electrical, mechanical, or software failure.
The water passes through several treatment stages
Before reaching the underground tanks, stormwater passes through a sedimentation pond, a screening chamber, and a filter chamber. In the sedimentation pond, the flow of water slows down and heavier particles settle to the bottom. The screening chamber removes larger particles, while the filter chamber captures smaller particles. Sensors installed in the chambers provide alerts when sediment has accumulated or when the filter may be clogged.
The system also monitors the water’s turbidity, electrical conductivity, and temperature. These measurements make it possible to assess the properties of the collected water and to gather information about how this nature-based stormwater solution performs under different weather conditions.
The treated water is directed into two interconnected underground collection tanks. From the tanks, the water flows into a pumping and monitoring chamber, from which it can be pumped onwards to irrigation systems and water take-off points.
A technical solution combined with public space
Mereranna Pocket Park is not merely a technical stormwater facility. The project also aims to give the previously underused green space a new public function. A wooden boardwalk has been constructed and additional landscaping has been introduced to make the area more attractive and accessible to the public.
Due to budget constraints, not all elements included in the original construction design were implemented. Among other things, the public toilet and two backless benches were omitted, while the scope of the terrace, boardwalk, plant containers, irrigation systems, and other small-scale amenities was reduced. Despite these changes, the facility retained its primary functions: collecting, treating, temporarily storing, and reusing stormwater.
The on-site demonstration clearly highlighted the system’s practical value. The water stored in the underground tanks is not intended solely for future tests or measurements; it can already be used in the municipality’s daily maintenance work. In this way, Mereranna Pocket Park combines climate-change adaptation, the sustainable use of water resources, street maintenance, and the creation of higher-quality public space.
Why was Mereranna Pocket Park selected as the location of the LIFE LATESTadapt demonstration site, and what problem does the solution help alleviate there?
Tanel Mätlik: Mereranna Pocket Park was selected primarily because the area previously had no stormwater management system and the green space became waterlogged after heavy rainfall. At the same time, the area’s main stormwater collector runs beneath Randvere Road, making it possible to create a solution that combines stormwater collection, retention, and reuse. The green space had also previously been underused, and the project gave it a new public-space function.
How does the “smart” stormwater solution at Mereranna Pocket Park work, and how does it differ from conventional stormwater drainage?
Tanel Mätlik: In a conventional system, stormwater is carried away from the area through pipes as quickly as possible. At Mereranna Pocket Park, the water is first directed to the demonstration site, where its flow is slowed down, sediment is removed, and the water is collected in underground tanks. The system is controlled by water-level and water-quality sensors, as well as an automatic gate. This means that stormwater is not regarded merely as a problem that must be removed, but as a resource that can be reused for watering plants and carrying out road maintenance.
How much water can be stored in the underground tanks, and what is it used for?
Tanel Mätlik: The project includes two interconnected underground collection tanks, each with a capacity of 30 cubic metres. Their combined capacity is therefore approximately 60 cubic metres. The collected water is used to irrigate plants in the area, and watering and road maintenance vehicles can access it through the water take-off point. The amount of water actually available for use depends on rainfall, water levels, and seasonal demand.
How is the quality of the collected stormwater monitored, and how are sediment and other pollutants prevented from entering the water used for irrigation and road maintenance?
Tanel Mätlik: Before reaching the tanks, the water passes through several treatment stages. In the sedimentation pond, the flow of water slows down and heavier particles settle to the bottom. The water then passes through a screening chamber, where larger particles are removed, and a filter chamber, which captures smaller particles. The system also measures the water’s turbidity, electrical conductivity, and temperature. Sensors provide alerts when a chamber needs to be cleaned or when the filter may be clogged.
What happens during exceptionally heavy rainfall if the demonstration site can no longer accommodate all the water?
Tanel Mätlik: The system has been designed to ensure that it does not create a flood risk. Under normal conditions, stormwater is directed to the demonstration site. However, when the volume of water is exceptionally high, a gate in the stormwater pipeline beneath Randvere Road opens automatically. The excess water is then carried away through the existing main pipeline. The system also includes an emergency overflow in the event of an electrical, mechanical, or software failure.
What practical and financial benefits could stormwater reuse provide for the municipality?
Tanel Mätlik: The main benefit is that less treated drinking water is needed for watering plants and cleaning streets. This helps conserve water resources and may reduce the water costs associated with maintenance work. Temporarily retaining stormwater also reduces the load on the conventional stormwater drainage network. More precise financial savings can be assessed once sufficient data have been collected on the amount of water captured and used, maintenance costs, and the system’s reliability.
What changes were made to the original construction design due to budget constraints, and how do they affect the use of the area?
Tanel Mätlik: Due to budget constraints, the public toilet and two backless benches were not constructed. The scope of other amenities and landscaping was also reduced: fewer irrigation systems, plant containers, insect hotels, benches, and waste bins were installed, and the terrace and boardwalk areas were made smaller. The number of shrubs and perennial plants was also reduced. These cuts primarily affect the comfort of the area and the number of amenities provided, but the project’s main function—collecting, treating, and reusing stormwater—was retained. The overall appearance and purpose of the area also remained similar to what had originally been planned.
How will it be determined whether the demonstration site has achieved its objectives, and could the solution be used elsewhere in Viimsi?
Tanel Mätlik: The success of the demonstration site can be assessed using several indicators: how much stormwater can be retained and reused, how the system performs during heavy rainfall, the quality of the collected water, and how much water is used for irrigation and road maintenance. It is also important to monitor maintenance requirements and the system’s reliability. This is a demonstration solution, and the experience gained from it can be used when designing similar systems in other parts of Viimsi where there are problems with waterlogging, a risk of flooding, or a need for irrigation water. The project also allows the direction of flow through the sedimentation pond and other aspects of the solution to be adjusted later on the basis of operational experience.