The Sierra Club and north Denver neighborhood organizations are alleging the Environmental Protection Agency used weaker air quality standards when advising the Colorado Department of Transportation in a lawsuit filed Wednesday. Those weaker standards have the potential to worsen air quality, says the suit. 

The suit stems from CDOT's proposed major rework of I-70 in the Elyria-Swansea neighborhood. In order to the complete the project, the EPA requires that CDOT measure impact on air quality.

The EPA revised the guidance it gave CDOT on how air quality impact should be measured. And the lawsuit claims those standards are weaker than those used earlier.

The plaintiffs are asking the court to set aside the new guidance from the EPA and use the old direction. It’s a process that could delay the project. The EPA did not respond to requests for comment.