More than 90 percent of the country’s coal plants are contaminating water across 43 states, according to a new report. And nearly half of them have no plans to clean up the mess.

The study, released on Thursday by the environmental watchdogs Earthjustice and the Environmental Integrity Project, looked at 292 sites around the country, from the desert outside Las Vegas to the coast of Massachusetts. The researchers focused specifically on coal ash, a toxic byproduct of burning coal to produce power.

Failure to clean up coal ash violates a federal rule that was passed in 2015 after a stormwater pipe burst at the Duke Energy Dan River Steam Station in North Carolina, spilling 39,000 tons of the contaminant into the Dan River. Coal ash contains cancer-causing heavy metals such as arsenic and cobalt. According to the Environmental Protection Agency, toxic sludge from the spill stretched over 70 miles downstream, threatening the drinking water quality of thousands of residents.

One of the goals of the 2015 rule was to halt the industry’s practice of dumping coal ash into unlined ponds that allow the material to seep into groundwater, creating an environmental hazard for nearby communities, and most companies are now required to send their waste to safer containment sites. However, the report found that utilities are failing to abide by other aspects of the federal rule, such as cleaning up contaminated sites and restoring groundwater.

Read the full article about coal plants contaminating groundwater by Lylla Younes at Grist.