WASHINGTON — The Trump administration on Thursday is expected to complete the legal repeal of a major Obama-era clean water regulation, which had placed limits on polluting chemicals that could be used near streams, wetlands and water bodies.
The rollback of the 2015 measure, known as the Waters of the United States rule, has been widely expected since the early days of the Trump administration, when President Trump signed an executive order directing federal agencies to begin the work of repealing and replacing it.
Weakening the Obama-era water rule had been a central campaign pledge for Mr. Trump, who characterized it as a federal land-grab that impinged on the rights of farmers, rural landowners and real estate developers to use their property as they see fit.
Environmentalists say Mr. Trump’s push to loosen rules on clean water regulations represents an assault on protecting the nation’s streams and wetlands at a moment when Mr. Trump has repeatedly declared his commitment to “crystal-clean water.”
The repeal of the water rule, which is scheduled to be announced at the headquarters of the National Association of Manufacturers, will take effect in a matter of weeks.
The Environmental Protection Agency and the Army Corps of Engineers, which had worked together to write the original Obama rule, are expected to issue a new, looser replacement rule by the end of this year.
The clean water rollback is the latest in a series of actions by the Trump administration to weaken or undo major environmental rules, including proposals to weaken regulations on planet-warming emissions from cars, power plants and oil and gas drilling rigs, a series of moves designed to push new drilling in the vast Arctic National Wildlife Refuge, and efforts to weaken protections under the Endangered Species Act.
Environmentalists assailed the move.
“With many of our cities and towns living with unsafe drinking water, now is not the time to cut back on clean water enforcement,” said Laura Rubin, director of the Healing Our Waters-Great Lakes Coalition. “We need more, not less, protection for clean water.”
But farming groups, a key political constituency for Mr. Trump, praised the repeal of a regulation that they said had severely restricted how farmers could use their land.
“The rule that was developed in 2015 was a significant overreach,” said Don Parrish, director of regulatory relations with the American Farm Bureau Federation, which has lobbied for the repeal and replacement of the rule. “It overstepped the limit of protecting clean water and tried to regulate land use. It created liabilities that can end up putting farmers in jail.” He was referring to actions like using pesticides, he said.
The Obama rule, developed under the authority of the 1972 Clean Water Act, was designed to limit pollution in about 60 percent of the nation’s bodies of water, protecting sources of drinking water for about a third of the United States. It extended existing federal authority to limit pollution in large bodies of water, like the Chesapeake Bay and Puget Sound, to smaller bodies that drain into them, such as tributaries, streams and wetlands.
Under the rule, farmers using land near streams and wetlands were restricted from doing certain kinds of plowing and planting certain crops and would have been required E.P.A. permits in order to use chemical pesticides and fertilizers that could have run off into those water bodies.
For more news on climate and the environment, follow @NYTClimate on Twitter.