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WASHINGTON — The Trump administration is expected to put forth a proposal on Tuesday that would significantly weaken a major Obama-era regulation on clean water, according to a talking points memo from the Environmental Protection Agency that was distributed to White House allies this week.

The Obama rule 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.

But it became a target for rural landowners, an important part of President Trump’s political base, since it could have restricted how much pollution from chemical fertilizers and pesticides could seep into water on their property.

“The previous administration’s 2015 rule wasn’t about water quality,” the memo says. “It was about power — power in the hands of the federal government over farmers, developers and landowners.”