COLORADO SPRINGS, Colo. -

An environmental group has threatened to sue Colorado Springs Utilities claiming the city's coal-fired plants are violating federal law.

The Sierra Club has filed a notice of intent to sue. The group says it's on the grounds that Colorado Springs Utilities didn't get the right permits or install required pollution controls when it made modifications to the Martin Drake and Ray Nixon coal plants.

The Sierra Club said it has evidence that in 37 separate projects between 1987 and 2011, Colorado Springs Utilities failed to meet federal standards.

"We're talking about increased pollution, we're talking about increased health impacts that happen over these years," said Bryce Carter, a spokesperson for the Sierra Club.

Colorado Springs City Council member Tim Leigh called the claims political.

"What the Sierra Club has done across the entire country is gone and sued small and midsized utilities companies," said Leigh. "The ultimate goal is basically just to get rid of coal-fired power plants across the country."

Leigh has been highly critical of Colorado Springs Utilities and its officers, but said he would be surprised if Utilities wasn't as compliant as it possibly could be with federal standards.

In a statement, Colorado Springs Utilities responded in part, "Colorado Springs Utilities has been diligent to evaluate all projects at Drake and Nixon, and believe the plants are in compliance with all regulations. Utilities has gone beyond the letter of the law, which requires no pollution increases, and continues to reduce emissions."

Carter said even though the Sierra Club is seeking to get rid of all coal plants, the lawsuit threat is based on facts.

"People are willing to say, 'Oh this is the Sierra Club riling up again,' but it's not just us. The fact is, Colorado Springs Utilities is accountable to these actions and violations of federal law."

The lawsuit threat comes as the fate of Drake power plant hangs in limbo. On Tuesday, City Council is expected to vote on whether to start an analysis on how to retire the facility.

Carter said he and others with the Sierra Club plan to be at that meeting. Stay with KRDO Newschannel 13 for updates on this developing story.