On behalf of three conservation groups, Earthjustice has filed a federal lawsuit to stop toxic water pollution that is leaking into the Apalachicola River from an aging 40-acre coal ash dump at Gulf Power Company’s Scholz Generating Plant near Sneads, Florida. The groups say Gulf Power is illegally discharging dangerous pollutants—including arsenic and lead—into the river, threatening people and the environment in the most ecologically-diverse area of the southern United States.

Gulf Power, a subsidiary of the $38-billion Southern Company, has flushed millions of gallons of toxic coal ash sludge into 40 acres of unlined pits that sit atop a bluff along the Apalachicola River. The groups say the waste is leaking out of the pits and into the river, contaminating the water with pollutants including arsenic, cadmium, and chromium—all well-known carcinogens—as well as aluminum, barium, beryllium, copper, lead, nickel, zinc, selenium, and the neurotoxin mercury.

One test, in June 2013, found that arsenic levels coming out of the unlined pits were 300 times the amount of arsenic considered safe for drinking water.

Earthjustice filed its Clean Water Act suit in U.S. District Court in Tallahassee, Fl. on behalf of the Southern Alliance for Clean Energy, Waterkeeper Alliance, and Apalachicola Riverkeeper.

Gulf Power has a federal Clean Water Act permit, which allows it to discharge treated coal ash water and chlorinated condensing water directly into the Apalachicola through an outfall. But the groups say that contamination is leaking at other points on the site and not receiving proper treatment—and those discharges are not covered by the permit.

The toxic heavy metal leaks—and the company’s decision not to report them—violate Gulf Power’s federal permit requirements under the Clean Water Act.