"Last year, a backyard in Butte, Mont., collapsed without warning.

No one was hurt, but a 30-foot sinkhole yawned where a children's wading pool once sat.

At the bottom was a century-old mine shaft that had never made the state's list of abandoned mines needing attention.

The cave-in was just another of the unknown hazards popping up every day across the country, stoking questions over how to clean up more than three centuries of unregulated mining and who will pay for it. "We get new calls all the time," said Autumn Coleman, who until recently led Montana's mine reclamation program."

Dylan Brown reports for Greenwire August 19, 2019. [2]