Centuries of copper slate mining and processing in Mansfelder Land have resulted in the development of a monoculture which in conjunction with the closure of smelting J plants in 1990 has left behind a whole series of environmental pollution problems of sometimes breathtaking magnitude. The disused production plants and dumps are sources of considerable contamination by heavy metals and radionuclides. During the smelting of copper slate, the rock was heated in blast furnaces up to about 1,300°C in order to produce copper-rich 'raw matte' as an intermediate product. As well as the volatile metals, the fly ash from these blast furnaces also contained considerable quantities of hydrocarbons and radionuclides. The product formed during the wet scrubbing of this ash is known as Theisen sludge after the inventor of the scrubbing technique [1-4]. Untill978, this sludge was used as feedstock for a whole range of metallurgical processes. Following the closure of these production sectors, about 220,000 tons of these sludges accrued and were stored at various locations in unprotected dumps. This material is still the main source of pollutants in the region contaminating both groundwater and surface water. Finding a permanent solution to this environmental problem in Mansfelder Land was the goal of a joint research I project by the UFZ and the Canadian Université du Québec a Montréal (UQAM).