Natural recovery: How a wetland tackles pollution in the Grote Calie in Turnhout

OVAM (Public Waste Agency of Flanders) and ANB (Agency of Nature and Forestry) joined forces to tackle the spreading of chromium pollution in the Grote Calie towards the nature area Winkelsbroek and more downstream. We designed a constructed wetland, consisting of a sediment trap and a flood zone where contaminated sediment particles settle and stabilize. This allows clean water to flow further downstream.  

The works began in the autumn of 2022, but heavy rainfall and high water levels in the following winters made the choosen techniques particularly challenging. The strategy was adjusted and refined several times. Drainage of the site was necessary; as well as a temporary damming of the watercourse and an amphibious crane was deployed. We completed the job in February 2025 by vegetating the flooding zone with reeds and cattails. The wetland is currently filling with surface water, allowing it to perform. Monitoring has started at the beginning of March and will continue until the end of 2026.