Looking deeper for coal ash hazards.

• Position: EPA

As the Environmental Protection Agency weighs whether to define coal ash as hazardous waste, a study published in Environmental Science and Technology identifies new monitoring protocols and insights that can help investigators more accurately measure and predict the ecological impacts of contaminants.

"The take-away lesson is we need to change how and where we look for coal ash contaminants," underscores coauthor Avner Vengosh. "Risks to water quality and aquatic life do not end with surface water contamination, but much of our current monitoring does."

The study documents contaminant levels in aquatic ecosystems over an 18-month period following a massive coal sludge spill in 2008 at a Tennessee Valley Authority power plant in Kingston, Tenn. By analyzing more than 220 water samples, the research team found that high concentrations of arsenic from the TVA coal ash remained in pore water--water trapped within river-bottom sediment--long alter contaminant levels in surface waters return to safe thresholds. Samples extracted from 10 centimeters to half a meter below the surface of sediment in downstream rivers contained arsenic levels of up to 2,000 parts per billion--well above the EPA's thresholds of 10 parts per billion for safe drinking water, and 150 parts per billion for protection of aquatic life.

"It's like cleaning your house," Vengosh says of the finding...