In the latest installment in the New York Times’ Toxic Waters series, Charles Duhigg explores an instance in which a solution to an environmental problem ended up causing yet another problem. Many coal-burning power plants are scrubbing out the substances that used to foul the air, only to dump them into waterways and contaminate water supplies with arsenic, barium, manganese, and other heavy metals. Our regulatory apparatus is ill-equipped to address the problem:

Yet no federal regulations specifically govern the disposal of power plant discharges into waterways or landfills. Some regulators have used laws like the Clean Water Act to combat such pollution. But those laws can prove inadequate, say regulators, because they do not mandate limits on the most dangerous chemicals in power plant waste, like arsenic and lead.

For instance, only one in 43 power plants and other electric utilities across the nation must limit how much barium they dump into nearby waterways, according to a Times analysis of E.P.A. records. Barium, which is commonly found in power plant waste and scrubber wastewater, has been linked to heart problems and diseases in other organs.

Even when power plant emissions are regulated by the Clean Water Act, plants have often violated that law without paying fines or facing other penalties. Ninety percent of 313 coal-fired power plants that have violated the Clean Water Act since 2004 were not fined or otherwise sanctioned by federal or state regulators, according to a Times analysis of Environmental Protection Agency records. (An interactive database of power plant violations around the nation is available at www.nytimes.com/coalplants.)

The Times’ analysis of EPA records found the problem to be widespread:

Twenty-one power plants in 10 states, including Alabama, Kentucky, North Carolina and Ohio, have dumped arsenic into rivers or other waters at concentrations as much as 18 times the federal drinking water standard, according to a Times analysis of E.P.A. data.

In Florida, Georgia, Illinois, Indiana, Maryland, North Carolina, Ohio, Wisconsin and elsewhere, power plants have dumped other chemicals at dangerous concentrations. Few of those plants have ever been sanctioned for those emissions, nor were their discharge permits altered to prevent future pollution.

Records indicate that power plant landfills and other disposal practices have polluted groundwater in more than a dozen states, contaminating the water in some towns with toxic chemicals. A 2007 report published by the E.P.A. suggested that people living near some power plant landfills faced a cancer risk 2,000 times higher than federal health standards.

Shortly after a rupture in a coal ash pond deluged a Tennessee community with a billion gallons of toxic sludge last winter, Shaila Dewan wrote about the lack of adequate regulation for these dumps. The next time you hear someone refer to the fairy tale that is “clean coal,” just remember that the toxic substances that don’t get into the air have to go somewhere. There’s a good chance that the plant in question isn’t disposing of them responsibly, and our regulatory system isn’t yet equipped to force them to do so.