When the EPA granted the exemptions for Christensen Ranch, its scientists believed that the reservoirs underlying the property were too deep to hold desirable water, and that even if they did, no one was likely to use it. They also believed the mine operators could contain and remediate pollution in the shallower rock layers where mining takes place.
Over time, shifting science and a changing climate have upended these assumptions, however. An epochal drought across the West has made water more precious and improved technology has made it economically viable to retrieve water from extraordinary depths, filter it and transport it.
"What does deep mean?" asked Mike Wireman, a hydrologist with the EPA who also works with the World Bank on global water supply issues. "There is a view out there that says if it's more than a few thousand feet deep we don't really care ... just go ahead and dump all that waste. There is an opposite view that says no, that is not sustainable water management policy."
Federal regulators also have become less certain that it is possible to clean up contamination from uranium mining. At Christensen Ranch and elsewhere, efforts to cleanse radioactive pollutants from drinking water aquifers near the surface have failed and uranium and its byproducts have sometimes migrated beyond containment zones, records show.
In 2007, when the Christensen Ranch mine operator proposed expanding its operations, bringing more injection wells online and more than tripling the amount of waste it was injecting into underground reservoirs, Wyoming officials eagerly gave their permission, but the EPA found itself at a crossroads.