In 2011, the U.S. Environmental Protection Agency approved an Idaho Department of Environmental Quality rule exempting activities such as mining from review, provided their accompanying water pollution fell below a certain threshold.
The Greater Yellowstone Coalition and Earthjustice sued, saying that was too lenient, especially in instances where pollution builds up in aquatic ecosystems. They worried, among other things, that toxic chemicals that persist in the environment and accumulate in food chains could pose health risks.
In April, the EPA agreed in U.S. District Court in Pocatello to reconsider whether Idaho could exempt from review certain polluting activities on rivers and lakes that had been designated under the Clean Water Act as "Tier 2" waters — in other words, those whose water quality is so good it exceeds levels necessary to support fish, shellfish and wildlife, as well as recreation.
With Tuesday's decision, the agency has now concluded DEQ's exemption went too far and gave the state agency several options to remedy the situation, including simply throwing out the exemption altogether.
