BILLINGS, Mont. (AP) — Major utilities have found evidence of groundwater contamination at coal-burning power plants across the U.S. where landfills and man-made ponds have been used for decades as dumping grounds for coal ash, according to data released by plant owners under a Friday deadline.

Heightened levels of pollutants— including arsenic and radium in some cases — were documented at plants in numerous states, from Virginia and North Carolina to Washington and Alaska.

The Environmental Protection Agency required the plant owners to install test wells to monitor groundwater pollu...