In one of Scott Pruitt’s final moves before resigning as head of the Environmental Protection Agency, he approved his home state of Oklahoma's request to regulate how its coal-fired power plants manage and dispose of a toxic substance called coal ash.

Oklahoma is the first state granted this authority, though states were given the right to apply for it in 2016 under the Obama administration. Since then, other states -- including Alabama, Georgia and Kansas -- have asked to start their own coal ash permit programs.

Pruitt's approval comes amid a broader push by the Trump administration to roll back Obama-era environmental protections and to hand over more regulation authority to states. Most recently, the EPA proposed rewriting Obama's Clean Power Plan, which set aggressive targets for power plants to reduce their carbon emissions. Similarly, the White House issued a coal ash disposal rule in July that weakens a 2015 regulation.

But a federal court's ruling last week threatens some of President Trump’s plans.

Coal ash is the waste product left over after coal is burned in power plants. It contains high levels of metals such as arsenic, lead and mercury that can contaminate the air and water sources. Exposure to coal ash can result in a host of health complications, including kidney disease, neurological damage and birth defects.

The 2015 rule provided a uniform, base set of standards for coal plants to safely dispose of the waste product. States could pass stricter disposal regulations, but they had to meet the federal standards, says Frank Holleman, a senior attorney with the Southern Environmental Law Center.

The Trump administration's new rules, among other things, do not require states to monitor the groundwater near power plants for contamination and extends the compliance deadline for proper coal ash storage. “These amendments provide states and utilities much-needed flexibility in the management of coal ash, while ensuring human health and the environment are protected,” said Acting EPA Administrator Andrew Wheeler in a statement announcing the change.

But to environmental groups, even the Obama-era coal ash rule didn't go far enough. A number of them petitioned the court to enforce stricter regulations, and last week the U.S. Court of Appeals for the D.C. Circuit sided with them. The court ruled that several provisions concerning coal ash storage in the 2015 rule did not provide sufficient protections.

This decision -- though targeted toward the Obama regulation -- means that the weaker coal ash rule recently passed by the EPA must be updated to address the gaps in Obama’s rule, says Jennifer Peters, the water programs director for Clean Water Action. “It’s too soon to know how the EPA will respond to this decision,” she says. “It’s pretty clear the current EPA can’t move forward on approving any state permit programs for coal ash until they address those three concerns.”

Patrick Riley of the Oklahoma Department of Environmental Quality says his agency is aware of the ruling but has not “fully digested all of the information” and is not sure how it will affect the state's coal ash permit program approved in June.

Many environmental activists and lawyers view the court decision as one victory in an extensive fight against the EPA’s deregulation push. The Trump administration has reportedly overturned 46 environmental regulations and is in the process of rolling back 30 more. According to an analysis by the White House, the proposed changes to Obama's Clean Power Plan, which would hand over more power to states, would result in as many as 1,400 premature deaths a year by 2030.

Environmental activists see state control as a problem because lawmakers and officials can be heavily influenced by the money and political lobbying of utility companies. “The reality is that so many of these state programs are influenced by industry, are likely to give them breaks, are likely to require them to do whatever is the cheapest option,” says Jennifer Cassel, a coal ash project attorney with Earthjustice.

Before Obama’s 2015 rule -- a period Holleman refers to as “the Wild West” -- states could essentially choose whether or not to regulate coal ash. A number of disasters happened.

In 2008, a dike at a fossil plant in Kingston, Tenn., collapsed, spilling 1.1 billion gallons of wet coal ash. Workers tasked with cleaning up the spill have filed lawsuits claiming they have suffered lung disease, cancer and other health conditions from exposure to the chemicals. An inspector general report later said the plant's parent company had "failed for more than 20 years to heed warnings."

Of course, not all states would choose lax regulations if given more control. For example, Maryland's Republican governor broke with the Trump administration to require three coal plants to comply with an Obama-era clean water rule that that EPA has suspended.

Environmentalists hope that the D.C. court ruling will force the more lenient, coal-friendly states to adopt stricter regulations. National environmental groups have "ramped up" efforts to fight Trump's policy changes, says Maxine Lipeles, a law professor at Washington University in St. Louis. But as the federal government passes more power to the states, the burden may shift to local groups to challenge them.

"At the local level, I think [the fight] is going to be a lot more spotty," she says. "Depending on how robust the public community interest is and the nature of the state agency."

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