Test field study of different cover sealing systems for industrial dumps and polluted sites

Six test fields (3×15 m) with an inclination of 5% have been set up on a landfill for blast furnace dust. A 75-cm thick covering layer (recultivating layer) had been the same for all test fields. The efficiency of different sealing layers (clay liner, geosynthetic clay liner, capillary barrier and the blast furnace dust itself) had been investigated for more than 2 years. The objective of this study was to obtain, under natural conditions, data on the water regimen and the motion of the water in surface sealing systems and to perform a comparative evaluation regarding effectiveness and economic efficiency. It could be shown that a kind of capillary barrier effect above an underlying drainage layer can be obtained by an adequate choice of soils with a high field capacity and thus inducing an important runoff in the recultivating layer. The geosynthetic clay liner and the 30-cm thick clay liner with an overlying drainage were the only systems to meet the permeability requirements (k value<5×10−9 m/s) of the German regulatory standards. The geosynthetic clay liner showed a slight increase in permeability in the second year due to cation exchange processes, whereas a clay liner without overlying drainage failed totally because of a distinct desiccation behaviour.