Wastewater flows down a trough, right, from the site of the blowout at the Gold King mine which triggered a major spill of toxic wastewater, outside Silverton, Colo., in 2015. (AP Photo/Brennan Li …

Wastewater flows down a trough, right, from the site of the blowout at the Gold King mine which triggered a major spill of toxic wastewater, outside Silverton, Colo., in 2015. (AP Photo/Brennan Linsley, file)