WASHINGTON — The Trump administration is expected to roll back an Obama-era regulation that was to limit emissions of dangerous heavy metals like arsenic, lead and mercury from coal-fired power plants, according to two people familiar with the plans.
In a rule expected as early as Thursday, the Environmental Protection Agency will move to weaken the 2015 regulation by relaxing some of the requirements on power generators and also exempting a significant number of power plants from even those requirements.
The effort was designed to extend the life of old, coal-fired power plants that have been shutting down in the face of competition from cheaper natural gas and renewable energy generators. Environmental groups warned that the move could lead to health problems caused by contaminated drinking water, including birth defects, cancer and stunted brain development in young children.
A spokesman for the E.P.A. did not immediately respond to a request for comment.
Coal ash is the residue produced from burning coal. Power plants produce about 130 million tons of coal ash a year, which is stored at about 1,100 sites across the country.
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 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 also raise the cost of operating the plants, further endangering their economic viability.
One person familiar with the E.P.A.’s current plans said the agency intends to say that the new rule will remove more pollutants than the Obama-era regulation. That argument is based on an analysis that assumes about 30 percent of power plants will voluntarily chose to install more stringent technology.
Power plants were originally required to start complying with the requirements by as early as November 2018, but Scott Pruitt, President Trump’s first E.P.A. administrator, postponed compliance until 2020, saying the agency was providing “relief” to utilities as it reviewed the rule.
Environmental groups have challenged that delay and said they would also challenge the rollback.
A recent study by environmental groups found that more than 90 percent of the 265 coal plants required to test their groundwater near coal ash dumps discovered unsafe levels of at least one contaminant.
“That knowledge should lead E.P.A. to move to establish greater protections for our health,” said Lisa Evans, a senior counsel for Earthjustice, an environmental organization. “But E.P.A. is running the other way under the direction of the utilities.”