Beginning in 2018, coal-fired electric utilities were compelled to publicly report groundwater monitoring data for the first time ever, following transparency requirements imposed by federal coal ash What is coal ash? The toxic waste produced when coal is burned by power plants to make electricity. regulations, known formally as the Coal Combustion Residuals Rule.

For decades, utilities have disposed of coal ash dangerously, dumping it in unlined ponds and landfills where the toxins leak into groundwater.

According to industry’s own data, more than 95% of the coal ash ponds in the United States are unlined.

Almost all of them are contaminating groundwater with toxins above levels that the U.S. Environmental Protection Agency deems safe for drinking water.

Much of industry’s disclosure of the data has been in abstruse and non-standard formats. The data can be difficult to find, despite the requirement that the information be publicly accessible. Some utilities fail to post the required information entirely or conceal it behind sign-in walls to prevent search engines from locating the disclosures.

Legal and technical experts from Earthjustice, the Environmental Integrity Project, and partner organizations located and analyzed the data disclosures.