The tailings pond above the Willibald processing plant
Above the Willibald processing plant, completed in 1889, there was a thickener and a slurry pond for the residues from ore processing. The plant, built in 1935, processed up to 1,000 metric tons of ore daily. About 90% of this was fine-grained, nearly metal-free tailings that were produced as slurry.
This slurry was pumped into a thickener approximately 35 meters in size. There, the solids settled out, while the clarified water was reused as process water. The thickened slurry flowed through a wooden trough into the slurry pond, which measured approximately 100 by 50 meters. Coarse sand particles were used to build the surrounding embankment, while finer particles settled in the center of the pond. Excess clear water was discharged into a stream.
With the completion of the new Bilmecke sludge pond in 1955, the thickener and the old settling pond were decommissioned.