Sustainable Urban Drainages Systems (SuDS) are designed to collect, store and infiltrate large amount of surface runoff water during heavy rainfall. Surface runoff water is known to transport pollutants such as particle bound heavy metals. Therefore, a build-up of pollutants in the top-soil, of the commonly vegetated filter media is expected in SuDS such as swales. In the Netherlands the first large scale implementation of swales in a residential area was finished 20 years ago, followed by many municipalities. In 2019 more than 500 locations with swales can be found throughout The Netherlands (www.climatescan.nl). Questions are raised by water authorities, provinces and municipalities how efficient swales are in capturing pollutants from stormwater and if pollution of groundwater can be expected threatening the quality of our drinking water. Previous studies show concerns on heavy metals in stormwater. Knowledge of heavy metal concentration in the top soil is therefore very important for assessing the purity and quality of the soil in an environment and effect on the groundwater. The concentrations of heavy metals from 30 Dutch swales older than 10 years were measured and analysed using a portable X-ray Fluorescence (XRF) spectroscopy instrument verified with soil samples analysed in laboratories with the ICPMS and XRF methods.