Screening for historical contamination in the Kloosterbeemden: Effects of remediation of the Winterbeek/Hulpe

Extensive research on the Winterbeek revealed severe pollution, primarily salts and heavy metals from industrial discharges by Tessenderlo Chemie. A significant remediation effort, starting in 2017 and involving collaboration between OVAM, VMM, and Tessenderlo Chemie, targeted the complete removal of 258000 tons of contaminants from the Winterbeek valley. The contaminated streambed and banks were removed, and a nature-based approach, including a 'constructed wetland' in vulnerable areas like the Kloosterbeemden, was implemented. The final phase, focusing on the Winterbeek/Hulpe area where the river Winterbeek meets the river Demer, employed interventions like raising water levels and adjusting embankments to restore the ecosystem. Despite thorough efforts, residual contamination may persist in some areas, prompting ongoing investigations into the effects of partial remediation in specific locations. In this document we focus on the effect of these remediations, specifically in the area around the Kloosterbeemden, at the confluence of the Hulpe and the Demer. The study investigates the behavior of radium, lead, and bismuth in a complex environment. The analysis of various measurements reveals stable water quality in terms of total hardness, total alkalinity, and pH. Radioisotopes incorporated in clay soil appear relatively immobile under current circumstances. Elevated dose rates near specific drilling points indicate potential contamination, supported by the presence of radioactive isotopes in the top 50 cm of the soil. Drone flights provide insights into the contamination of wet zones and marshland, showing successful remediation efforts along the Grote Leigracht but also highlighting spatial and temporal heterogeneity in radionuclide abundance. Overall, the study underscores the effectiveness of remediation efforts while emphasizing the importance of careful interpretation of measurements considering varying environmental conditions.