John Meyer at SP Angel notes “the massive Berkeley Pit in Butte, Montana, USA, is one of the world’s largest superfund sites and has been described as a giant sink filling with metal-laden, acidic water from over 10,000 miles of underground mine workings. It has been a ticking time bomb since 1982 when the mine owner turned off the pumps which kept the subsurface tunnels dry for miners.

“The pit has collected 50 billion gallons of toxic water. While the rising pit water is a looming environmental threat if it seeps into the area’s groundwater, it may be a new source of copper if a pilot plant pans out.

“However, if left unattended, there would be an environmental calamity especially since Butte’s mining operations are located at the headwaters of the Clark Fork River—-a major tributary of the Columbia.

“The promising news is an experimental water treatment system started operation in March. Three million gallons of water is being pumped from the pit each day and sent to a treatment system which recovers copper, other contaminants and neutralises the water’s acidity. The purified water is discharged into Silver Bow Creek. Operators hope to reclaim 100,000 lb of copper each month which helps offset costs.

“If the experimental project works as planned, it will open a new way to help meet the growing need for copper and simultaneously clean up hazardous Super Fund sites.

“With worldwide demand for copper soaring and there is new pressure to open new mines, expand existing ones, and add ore processing capacity—-all of which have serious associated environmental challenges.”