The Trump announced yesterday that it is rolling back regulations on how power plants can dispose of coal ash – a move that environmental groups say will threaten drinking water.

The coal industry petitioned for the change, which extends by 18 months the time that the industry can use unlined coal ash ponds and groundwater-adjacent sites for dumping.

The announcement of the extension was made yesterday by EPA Acting Administrator Andrew Wheeler, a former lobbyist for the coal industry. The EPA said relaxing the rule will save affected utility companies $28 to $31 million a year in regulatory costs.

"These amendments provide states and utilities much-needed flexibility in the management of coal ash, while ensuring human health and the environment are protected," Wheeler said in a statement. "Our actions mark a significant departure from the one-size-fits-all policies of the past and save tens of millions of dollars in regulatory costs."

Environmentalists are threatening legal action, citing the danger to groundwater in unlined pounds that is sometimes used for drinking water.

Coal ash sludge can include arsenic, lead, mercury and chromium. According to the EPA, there are 663 active ponds 286 active coal landfills for 204 power plants.

The Obama administration passed the coal ash regulations in 2015, in response to a 2008 coal ash spill in Kingston, Tennessee that dumped 5.4 million cubic yards of ash into two nearby rivers.

The industry says the extension will give power plant operators additional time to comply with wastewater guidelines.