(CNN) The Environmental Protection Agency on Monday proposed scaling back the requirements around storing and releasing waste from coal-fired power plants, despite also finding an increase in toxic leaks from waste pits.

The proposals would relax Obama-era rules from 2015 about the disposal of toxic wastewater and coal ash from the power plants. Coal ash, a mix of fine powder and sludge that is a by-product of burning coal, is commonly stored in pits and landfills. The wastewater can contain dangerous metals such as mercury and arsenic.

The proposals would reduce costs to plant operators at a time when the coal industry is struggling and the number of coal-fired power plants is declining. The Washington Post and The New York Times first reported the administration's planned announcements.

The stricter 2015 regulations are becoming more expensive for operators, the Trump administration said, because it was discovered that "more surface impoundments regardless of liner type are leaking" compared to the Obama administration's estimate four years ago.

Ninety-two percent of coal ash ponds are leaking, according to Lisa Evans of the environmental law organization Earthjustice, which opposes the proposals. "So much more harm is occurring than the Obama EPA expected," Evans told CNN.

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