The Obama administration on Friday set the first national standards for waste generated from coal burned for electricity, treating it more like household garbage rather than a hazardous material.
Environmentalists had pushed for the hazardous classification, citing the hundreds of cases nationwide in which coal ash waste had tainted waterways or underground aquifers, in many cases legally.
A hazardous classification would have put the federal government in charge of enforcement, which has been uneven across states that have varying degrees of regulation.
The coal industry wanted the less stringent classification, arguing that coal ash isn't dangerous and that a hazardous label would hinder recycling. About 40 percent of coal ash is reused.
But classifying coal ash as solid waste leaves it up to citizens and states to ensure standards are met.
"The regulatory uncertainty that has impeded the beneficial use of coal ash for half a decade has finally come to an end," said Thomas H. Adams, the executive director of the American Coal Ash Association. "EPA's final decision to regulate coal ash as a nonhazardous material puts science ahead of politics and clears the way for beneficial use of ash to begin growing again, thereby keeping ash out of landfills and disposal ponds in the first place."
The Environmental Protection Agency said in a call with reporters Friday that the record did not support a hazardous classification.
The agency said the steps it was taking would protect people from the risks associated with coal ash waste sites and hold the companies operating them accountable.
"It does what we hoped to accomplish ... in a very aggressive but reasonable and pragmatic way," said EPA Administrator Gina McCarthy.
The Obama administration was under court order to unveil the rule Friday, ending a six-year effort that began after a massive spill at a Tennessee power plant in 2008.
Since then, the EPA has documented 132 cases in which coal-fired power plant waste damaged rivers, streams and lakes, and 123 in which it has tainted underground water sources, in many cases legally.
Coal ash had been piling up in ponds and landfill sites at power plants for years, an unintended consequence of the EPA's push to scrub air pollutants from smokestacks.
In volume, it ranks only behind household trash in quantity, and it is expected to grow as the EPA controls pollutants like heat-trapping carbon dioxide and mercury and other toxic air pollutants from the nation's coal fleet.
On the upside, a switch from coal-fired to natural gas-fired power plants in recent years has generated less ash.
The rules unveiled Friday will boost the level of monitoring for leaks, control blowing dust and require companies to make testing results public.
They also set standards for closure of waste sites and require those that are structurally deficient or tainting waterways to close.
The new rules would also apply to closed coal ash ponds at sites where utilities still have active operations, such as the Duke Energy plant in Eden, North Carolina, where the sudden collapse of a drainage pipe triggered a massive spill in February that coated 70 miles of the Dan River in gray sludge.
Duke was operating a new natural gas plant on the property at the time of the spill and no longer creating coal waste.
But prior to the spill, tests showed it was among 32 unlined pits being operated by the company in the state and tainting groundwater in violation of state standards. The new rule requires new waste pits to be lined.
But the regulations do not cover sites at shuttered power plants. And in some cases, they would allow existing landfills that do not meet the new standards to continue to operate.
Environmentalists said the rule had "glaring flaws," and on Friday, they vowed to work to make the rules stronger.
"Today's rule doesn't prevent more tragic spills like the ones we are still trying to clean up in North Carolina and Tennessee," said Lisa Evans, an attorney for Earthjustice, which sued the EPA in 2012 to issue the rule, representing 10 environmental groups.
"And it won't stop the slower moving disaster that is unfolding for communities around the country, as leaky coal ash ponds and dumps poison water."
While pleased, even industry groups said they would work with Congress to fix what they see as flaws in the rule.
The EPA could change the classification down the road with more evidence, a power Congress gave the agency when it exempted coal ash and other energy wastes from being treated as hazardous wastes in late 1970s.