This series described a 10.5-million-ton pile of nuclear waste polluting the Colorado River. The waste was left over from decades of milling uranium ore, first for atomic weapons and later for nuclear fuel. For decades, the pile of toxic and radioactive waste leaked into the river, which provides the drinking water for more than 20 million people in three western states. It was the largest of the dozens of piles of tailings and the only one that hadn't been moved away from major rivers in the United States. And for a while, it appeared it would stay put, contaminating the river for centuries.