The Holden mine was one of the largest operating copper mines in the US, producing over 90,000 tonnes of copper and by-product metals through its life. When the mine closed in 1957, its tunnels extended for 100km and 7.6 million tonnes of tailings were left on nearby US National Forest land.
Although Rio Tinto never operated Holden, it assumed responsibility for the disused copper mine through acquisition. In the mid-1990s, the US Environmental Protection Agency (EPA) identified a company that was a successor to the mine's operator – and was then owned by aluminium producer Alcan – as responsible for the clean-up at Holden.
In 2007, Rio Tinto acquired Alcan, and stepped up to take responsibility for the Holden reclamation – demonstrating its commitment to what is known as "legacy management".
Describing what happened when the Holden copper mine in Washington State closed in 1957, Dave Cline, general manager, Legacy Management at Rio Tinto notes that: "As was common at the time, the operators just shut down the mine, and walked away from the site."
Sixty years later, with a huge remediation project finally completed, Holden stands as an exemplar of what's possible when the mining stops.
It's an extraordinary story of complex logistics, community engagement and technical expertise. When the hundreds of thousands of trees and shrubs planted on the site are fully grown, the only evidence that this was once a sprawling mine will be a water treatment plant. As Mario Isaias-Vera of the US Forest Service says: "In 20, 30, 40 years I'm hoping to see this area restored, to see wildlife coming back and bears fishing in Railroad Creek."