The restoration wouldn't go entirely as planned.
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In July 2004, contaminants were detected in one of the monitoring wells surrounding the mining facility at Christensen Ranch.
This wasn't that unusual, mining and regulatory officials say. Other excursions, as they are called, had occurred over the years. The monitoring wells are an early warning system, detecting benign chemicals long before more dangerous toxins can spread.
"It's sort of like a smoke detector," said Ron Linton, who oversees the licensing for Christensen Ranch for the Nuclear Regulatory Commission. "They will go back in and adjust their flow with their production practices within their ore zone to get those levels down."
But according to documents from the Wyoming Department of Environmental Quality, Cogema – the company then handling the restoration effort – could not fix the problem or identify its cause. The company tested water from the area and examined their injection wells for defects, but told state officials they believed the contaminants had occurred naturally and were not from the mine.
For six years, the contaminants continued to spread, disappearing for short periods as the restoration progressed only to reappear again, records show.
"This really shouldn't happen," said Glenn Mooney, a senior state geologist who oversaw the Christensen Ranch site for Wyoming from the late 1970s until last July.
Mooney observed that the concentration of contaminants at the boundary had leveled, but "showed no hint that they may drop," and warned that some of the chemicals found posed a considerable risk.