Former mining sites in the US

In 1980, Union Minière, the predecessor of Umicore, acquired an abandoned silver-gold mine in Platoro, the Rocky Mountains in Colorado. Subsequent exploration drillings were unsuccessful and it was decided to stop any attempt to further exploit the mine.

Remedial works started in the 1990s, consisting of capping and landscaping waste rock piles and installing a water treatment plant to capture and treat the acid mine drainage that continuously flows out of the mine. A major upgrade of the wastewater treatment plant was completed in 2018. In addition, smaller improvement projects to the water treatment steps have since been carried out and this will continue in the coming years. This is required as the water run-off is highly seasonal and dependent on natural weather conditions: snowmelt in spring releases large amounts of water into the mine openings that carry metals released from the natural rock with it. As a result, regular adjustments to the treatment steps are required. Umicore will oversee this project on a long-term basis in cooperation with the competent authorities.