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WASHINGTON — The Trump administration is expected to roll back an Obama-era regulation meant to limit the leaching of heavy metals like arsenic, lead and mercury into water supplies from the ash of coal-fired power plants, according to two people familiar with the plans.

With a series of new rules expected in the coming days, the Environmental Protection Agency will move to weaken the 2015 regulation that would have strengthened inspection and monitoring at coal plants, lowered acceptable levels of toxic effluent and required plants to install new technology to protect water supplies from contaminated coal ash.

The E.P.A. will relax some of those requirements and exempt a significant number of power plants from any of the requirements , according to the two people familiar with the Trump administration plan, who requested anonymity because they were not authorized to speak about the new rules.

The move is part of a series of deregulatory efforts by the Trump administration aimed at extending the lives of old, coal-fired power plants that have been shutting down in the face of competition from cheaper natural gas and renewable energy generators. Coal ash, the residue produced from burning coal, was dumped for years in holding areas near power plants, largely without regulation, but 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.