Durango's tailings pile dates back to 1880.
It originally came from a mill and smelter that produced vanadium, an element which when alloyed with steel makes it stronger and harder. The pile sat unused until World War II, when it was reprocessed for the uranium it also contained.
In 1976, Ranchers Development & Exploration Company of Albuquerque, N.M., bought the ore. The firm intended to move it and once again reprocess it, using modern techniques to extract more uranium and vanadium (which also has nuclear applications).
But the state Department of Health found plans to stabilize the steeply sloped pile during the operation were inadequate. The company and Colorado sparred over the issue until 1978 when the federal government stepped into the debate. Ranchers currently has no plans to move the pile because of depressed uranium prices but still considers the tailings valuable.