WASHINGTON, Nov. 4 (Xinhua) -- The Trump administration proposed on Monday to loosen regulations on how coal-fired power plants in the country dispose of waste laden with heavy metals like arsenic, lead and mercury.

The new proposal would scale back an Obama-era rule to reduce coal ash that is often mixed in water and stored in giant pits that could leech into local waterways to cause contaminations.

The U.S. Environmental Protection Agency (EPA) proposed to extend the deadline for power plants to comply with new wastewater treatment technologies up to eight more years until the end of 2028, giving polluters more time to leave coal ash in ponds.

The proposal marked the latest attempt by the Trump administration to prop up the coal industry. The EPA finalized a rule in June to overturn the Obama-era attempt to restrict emissions from coal plants by relying more on cleaner fuels, and proposed in August to loosen emission control of methane, one of the greenhouse gases that resulted in global warming.

The EPA described the new rules as supporting the Trump administration's "commitment to responsible, reasonable regulations," which would save the industry more than 175 million U.S. dollars annually.

Environmentalists, however, expressed their strong objections.

"It is outrageous that Trump's team is so beholden to polluters that they are willing to let power plants continue to dump lead, mercury, chromium and other dangerous chemicals into our water supply to preserve every last cent of their profits," said Thom Cmar, deputy managing attorney of the Earthjustice Coal Program, in a statement.

"The 2015 rule being replaced today documented that coal fired power plants discharge over 1 billion pounds of pollutants every year into 4,000 miles of rivers, contaminating the drinking water and fisheries of 2.7 million people," said Betsy Southerland, a former EPA official who helped develop the 2015 rule.

The EPA will hold an online public hearing on the proposed rule on Dec. 19.