Abstract: An arrangement for retaining harmful substances contained in water seeping from a waste dumping ground body includes an impervious layer of mineral sealing materials, such as clay, with an adjacent adsorption layer containing materials capable of binding harmful substances by physical and/or chemical adsorption. The materials may be in the form of admixtures. When seepage water flows very slowly through a layer of mineral sealing materials, it is possible to remove and retain the harmful substances. The permeability of the arrangement reduces with time due to the adsorption process with its sealing effect improving over geological time periods.