MILWAUKEE, Wis. (WTAQ) - Two environmental groups say they’ll sue the state DNR Wednesday, for not meeting a deadline to renew an air pollution permit for an old power plant in Milwaukee.

Clean Wisconsin and the Sierra Club say the DNR was given a year-and-half to review an application from We Energies that was filed 2-and-a-half years ago. The permit is for Milwaukee’s Valley Power Plant, the company’s oldest power plant which does not have modern emission controls.

Environmentalists criticize the plant because of its location. They also say it has more emissions than similar-sized plants. The DNR’s Andrew Stewart says his agency has not been able to keep up with its permit review requests because of staffing cuts.

As a result, the agency has had to set priorities on the facilities to be reviewed. A few years ago, the DNR had a big backlog of air pollution permit requests – and some companies waited up to 8 years to get theirs renewed. Stewart said the old backlog disappeared. And when the agency started to get behind again, it received more funding to process the applications more quickly.