The impermeability of clay towards water allows it to be used to seal waste-sites, water-reservoirs, road-ditches and small sewage works, as well as for garden- and swimming-pools. Witgert supplies sealing clays of maximum effectiveness on a kaolinitic-illitic or on a montmorillonitic basis (bentonites). Deliveries of lumped clays or ready-to-use blends are made to large building plots, whereas smaller projects will typically make use of flakes or roller milled clays, which can be prepared for use with a minimum use of machinery, if at all necessary.