ST. PAUL, Minn. (AP) - The Minnesota Public Utilities Commission has approved Minnesota Power's plan to install pollution control upgrades at one of the state's largest coal-fired power plants.

The project is expected to reduce mercury emissions at the Boswell 4 unit in Cohasset, which powers taconite and paper plants. Large industrial customers can expect to pay 9 percent more by 2017 while residential customers face a 6 percent increase to pay for the retrofit.

Kevin Reuther of the Minnesota Center for Environmental Advocacy says the utility should invest in cleaner power sources instead.

Minnesota Power Vice President Dave McMillan says his company is converting a smaller coal plant in Hoyt Lakes to gas and closing a coal unit in Schroeder. But he says converting a plant the size of Boswell 4 is not feasible.