The City growing greener with Wavin's Treetanks

min read time
2021-06-06 15:23:44

Increased rainfall, urban heat stress and deteriorating air quality are major, growing issues for many cities around the world, with local authorities looking for long-term, sustainable solutions. Introducing more plant life and trees in urban areas is a great way to help address these problems, whilst also effectively contributing to the health and wellbeing of the local population. Not only do trees absorb CO2, they also take in a range of other pollutants and toxins which are emitted by urban activities. At the same time, their roots and leaves naturally slow the filtration of water into drainage systems, helping to prevent them from becoming overwhelmed during heavy rain. Larger trees will also release water as vapour, helping to produce a cooling effect for the surrounding area. Recognising these impressive natural benefits, local authorities in the Belgian city of Hasselt knew that they needed to increase the amount of greenery in the streets. They turned to leading sustainable plumbing and drainage supplier, Wavin, to help them get the job done.

Tree tank case study street with trees

The root of the issue

While there are clear benefits to planting trees in urban areas, they require a high level of care and a significant financial investment, with dozens needed to make a positive difference in a neighbourhood. Because of their unpredictable growth, getting so many trees into cities is naturally hard to do and can have a damaging impact if the project isn’t planned or managed properly. For example, planting them immediately adjacent to roads, pavements and engineered structures, can lead to them struggling to grow or even dying, and their roots can disturb the foundations of nearby buildings and walkways, causing serious problems. Wavin’s provided the perfect solution to these concerns, with 86 trees installed in the city’s newly built Quartier Bleu neighbourhood, which are helping officials to boost biodiversity, wellbeing and air quality.



Thinking outside the box

When it came to planning the planting, the contractor, Willemen, worked with Wavin to find a solution. The Wavin team suggested using the new Wavin TreeTank system.

These below-ground, plastic tanks not only protect the tree’s roots, but they allow Hasselt’s plant life to flourish, without impacting the neighbouring environment – helping transform the Quartier Bleu into a much greener space.

We were responsible for the exterior construction of the new Quartier Bleu - from drains and pavements, to plants and street furniture. Since we had been working with Wavin for some time, it made sense for us to look for a solution together for incorporating more greenery into this part of the city. This is where the Wavin TreeTanks came to fruition.
Rob Eyckens , Project Manager at Willemen

Wim Vandecauter, Projects Manager at Wavin explained: “The TreeTanks are planted in a unique way. First, the ideal location for the tree is selected, where space is then excavated. The plastic crates are installed and then filled up with substrate, with the tree planted in the middle. To ensure the tree is stabilised, it’s also anchored in place. Once installed, rainwater is supplied steadily and directly to the roots, and all of this provides the tree with everything it needs to grow as it should above the ground, with the TreeTanks providing ample room for controlled root growth beneath the surface.”

Due to the lightweight nature of Wavin TreeTank units and the innovative way the systems can be easily clipped together, the installation was speedy and easy to complete. The TreeTanks also have strong side walls, ensuring that the soil around the system can be adequately compacted. The flexible and modular nature of the systems also means below-ground pipework can be managed effectively and safely with minimal disruption for residents.

Helping Hasselt thrive

By working to an agreed installation plan, the TreeTanks in Hasselt were quickly and safely installed. To date, 2,500 cubic metres of material have been delivered and installed in the city along with more than 80 new trees. The project, which first started in May 2019, is now complete, with a greener neighbourhood successfully realised for generations to come.

The future of Wavin TreeTanks


This project in Hasselt’s Quartier Bleu neighbourhood was the first of its kind for Wavin’s TreeTanks and demonstrates the company’s commitment to building a sustainable future for urban environments around the world. Authorities in many countries are seeking sustainable tree pit solutions for their towns and cities, which is why Wavin is now launching its TreeTank system across Europe.


For more information on TreeTanks or to make an enquiry, visit the Wavin Tree Tank page or get in touch with the Wavin team.