The Allegheny County Health Department has approved an installation permit for the first phase of U.S. Steel Corp.'s planned $1 billion coke oven replacement and upgrade project in Clairton.

The permit allows U.S. Steel to replace three of its 12 coke batteries -- Batteries 7, 8 and 9 built in 1954 -- with a single battery, Battery C, that would have fewer but bigger ovens and equal production capacity. The new battery is scheduled to be operational by December 2011.

After the Battery C work is completed, the company will replace Batteries 1, 2 and 3, built in 1955, with a new Battery D, identical to Battery C. Plans are to finish that work by 2013.

Coke is a solid carbon fuel and carbon source produced by baking coal and is used to melt and reduce iron ore in the steelmaking process. It's a dirty process that produces airborne emissions of gas and particles from the brick-lined ovens when the hot, baked coke is "pushed" out of the ovens and "quenched" or cooled with water.

The project has been criticized by some environmental groups for not doing enough to clean up the chronic soot pollution problems in the Clairton area. U. S. Steel has said the project will include state-of-the-art pollution controls.

The coke works, the largest in the United States, is located on a 392-acre tract along the west bank of the Monongahela River in Clairton.