WASHINGTON (Reuters) - More than 90 percent of U.S. coal-fired power plants that are required to monitor groundwater near their coal ash dumps show unsafe levels of toxic metals, according to a study released on Monday by environmental groups.

FILE PHOTO: Santee Cooper workers check the water levels around a 6000 foot long Aqua Dam built to keep sediment from a coal ash retention pond from going into the flooded Waccamaw River in the aftermath of Hurricane Florence in Conway, South Carolina, U.S. September 26, 2018. REUTERS/Randall Hill/File Photo

The groups, led by the Environmental Integrity Project and Earthjustice, said their findings show the potential harm to drinking water from coal ash and indicate that stronger regulations are needed.

Data made public by power companies showed 241 of the 265 plants, or 91 percent, that were subject to the monitoring requirement showed unsafe levels of one or more coal ash components in nearby groundwater compared to EPA standards, according to the analysis by the groups.

The report also found that 52 percent of those plants had unsafe levels of cancer-causing arsenic in nearby groundwater, while 60 percent showed unsafe levels of lithium, which can cause neurological damage.

“Using industry’s own data, our report proves that coal plants are poisoning groundwater nearly everywhere they operate,” said Lisa Evans, senior counsel with Earthjustice.

The environmental groups reviewed data reported from 4,600 groundwater monitoring wells near coal ash dumps of two-thirds of the coal-fired power plants in the United States.

Coal ash, which is the residue produced from burning coal in coal-fired plants, is stored at hundreds of power plants throughout the country. Spills in Tennessee and North Carolina leached sludge containing toxic materials into rivers in those states over the last decade.

In response, the Obama administration in 2015 established minimum national standards for the disposal of coal ash, including a requirement that companies monitor groundwater and publish their data.

CORPORATE PRESSURE

According to the U.S. Environmental Protection Agency’s website, coal ash contains contaminants like mercury, cadmium and arsenic, which “without proper management” can pollute “waterways, groundwater, drinking water and the air.”

Amid strong pressure from utility and coal companies, the EPA under President Donald Trump last July revised the 2015 rule to suspend groundwater monitoring requirements at coal ash sites if it is determined there is no potential for pollutants to move into certain aquifers.

The rule also extended the life of some coal ash ponds from early 2019 to late 2020.

Because contaminated groundwater can potentially harm drinking water, the environmental groups’ report said the data shows stronger regulations are needed for coal ash. The coal ash rule does not require tests of local drinking water.

“By weakening cleanup standards and pushing back ash pond closure deadlines, Trump’s EPA is endangering communities and ecosystems near these toxic waste sites,” the report said.

An EPA spokeswoman on Monday said the agency is reviewing the report and “cannot comment on its contents yet.”

“EPA continues to work with our state partners toward full implementation of the CCR (coal combustion residuals) regulations,” the spokeswoman said.

Andrew Wheeler, who last summer was the EPA’s acting head and who was confirmed as the agency’s administrator by the Senate last week, said last July that EPA’s revised coal ash rules would “save tens of millions of dollars in regulatory costs.”