CLAIRTON, Pa.—United States Steel Corp. is celebrating a $500 million revamp of its Clairton Coke Works that is designed to reduce pollution that has caused the American Lung Association to rank the Pittsburgh area among the sootiest in the country.

The new coke battery has been operational since November, but was unveiled publicly Thursday.

The company announced in 2008 that it planned to spend $1.1 billion to close three oven batteries built in 1955 that were contributing to the pollution. Instead, U.S. Steel has built one new battery and is building two new quench towers to reduce pollution at the other two batteries.

The company and government officials say the investment—still the largest in the plant's 112-year history—will help the plant meet federal air quality standards nearly two years sooner than expected.