Uranium mining is beginning to tarnish an American treasure. New studies points to radioactive contamination of a watershed feeding Grand Canyon National Park and the Colorado River.

The United States Geological Survey found elevated uranium levels in wells, springs and soil in the Grand Canyon watershed. The studies were undertaken as part of a proposed 20-year mineral withdrawal that would protect nearly 1 million acres of public land from future mining activities.

“These reports demonstrate unequivocally that uranium mining should not proceed in these environmentally sensitive lands,” said Stacey Hamburg of the Sierra Club’s Grand Canyon Chapter. “Contaminated lands and waters around the Grand Canyon are not what we want for the future of northern Arizona.”

Elevated uranium levels were also detected at an operation owned by Denison Mines near the national park. The Bureau of Land Management permitted the Canadian company to reopen the contaminated mine early this year without any update to its 1980s environmental review.

– Will Sands