U.S. District Judge Clark Waddoups dismissed the case, ruling that previously reported radon emissions from one of the mill’s tailings cells did not violate environmental regulations.
The cell in question is no longer receiving new tailings. Regulators initially thought that the cell was receiving active waste from the mill. It has not reeived new materials since 2008.
The lawsuit was filed in 2014 by the Grand Canyon Trust after the mill had reported radon emissions from the tailings cell.
State regulators required the mill to increase the depth of the cover on top of the tailings cell to stop the radon emissions and ordered increased monitoring of the cell to ensure the remedy had worked.