(Reuters) - A group representing current and former U.S. Forest Service employees claims the federal agency is polluting American waterways by dumping chemical flame retardants from planes above national forests without permits, violating the nation’s clean water law.

The nonprofit group Forest Service Employees for Environmental Ethics (FSEEE) filed a lawsuit Tuesday in Montana federal court saying the federal agency dumped hundreds of thousands of gallons of chemicals into forest streams in recent years, despite concerns those chemicals kill fish and aren’t effective at fighting fires. The most commonly used chemicals are inorganic fertilizers and salts, according to the suit.

The group said it wants an injunction keeping the Forest Service from spraying chemical retardants from the air until it receives a Clean Water Act permit and shows the strategy works.

“Suppressing fire from the air is a fool’s errand; wars are won on the ground,” said Andy Stahl, the executive director of FSEEE.

Most aircraft discharging chemicals such as those spraying herbicides and pesticides require permits, pursuant to a 2002 court order that said aircraft can be point sources of pollution covered by the CWA. But the Forest Service has instead relied on a 2011 letter from the U.S. Environmental Protection Agency to avoid that scrutiny, the group said. The EPA’s opinion “cannot amend the Clean Water Act” to bypass National Pollutant Discharge Elimination System permits, the group said.

The Forest Service declined to comment Wednesday.

The case is Forest Service Employees for Environmental Ethics v. United States Forest Service, United States District Court for the District of Montana, No. 9:22-cv-00168.

For the plaintiffs: Tim Bechtold of Bechtold Law Firm

For the government: Not immediately available