WASHINGTON — The Trump administration on Monday moved to weaken an Obama-era regulation aimed at limiting the seepage of toxic pollution into water supplies from the ash of coal burning power plants, a change that coal industry leaders say could keep plants open longer and which environmental groups fear will increase the risk of water contamination.
Andrew Wheeler, the administrator of the Environmental Protection Agency, issued the proposed regulation, which relaxes rules set in 2015 imposing stringent inspection and monitoring rules at coal plants and requiring plants to install new technology to protect water supplies from arsenic, lead, selenium and other toxic effluent.
The rules are part of President Trump’s vast environmental deregulation agenda aimed largely at eliminating rules the fossil fuel industry finds burdensome and extending the life of coal burning power plants. In addition to discharging pollutants into the air and water, coal plants are the top source of United States carbon dioxide emissions, the principal greenhouse gas warming the planet.
The new measures lower pollution limits, extend the deadline for power plants to comply with new technologies until Dec. 31, 2028, and exempt many coal plants altogether.
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Mr. Wheeler on Monday also issued a related proposal that moves back a deadline by eight years for disposing coal ash sludge. According to data compiled by environmental groups, 95 percent of coal ash ponds are unlined, which means the ash has no barrier between it and the groundwater. Under the new rule companies will have one more year before they are forced to close or retrofit unlined ponds near aquifers.
In issuing the rules the E.P.A. estimated that it would save industry more than $175 million annually.
Mr. Wheeler in a statement said the rules will “provide more certainty to the American public.” He added “These proposed revisions support the Trump Administration’s commitment to responsible, reasonable regulations by taking a common sense approach, which also protects public health and the environment.”
Environmental groups said the proposal will be particularly harmful to poor communities. Mustafa Santiago Ali, who was the director of the E.P.A.’s office of environmental justice under the Obama administration, noted that Americans living within three miles of a coal fired power plant are disproportionately people of color and lower income levels.
“The rule announced today puts millions of people’s drinking water in jeopardy,” he said. “When tragedy strikes from a flood, hurricane or a breach from an unlined coal ash pit or pond, everyday citizens are left with contaminated water.”
Coal ash, the residue produced from burning coal, was dumped for years in holding areas near power plants, largely without regulation. It came to the public’s attention after spills in North Carolina and Tennessee sent mercury, cadmium, arsenic and other heavy metals from the ash into water supplies.
According to the E.P.A., about 1.1 million Americans live within three miles of a coal plant that discharges pollutants into a public waterway. The 2015 rule set deadlines for power plants to invest in modern wastewater treatment technology to keep toxic pollution out of local waterways.
The regulation also required them to monitor local water quality and make more of the information publicly available. The Obama administration estimated the regulations would stop about 1.4 billion pounds of toxic metals and other pollutants from pouring into rivers and streams.
But the rule would have also raised the cost of operating the plants, further endangering their economic viability. The E.P.A. will hold an online only public hearing on the proposed rule on Dec. 19.
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