U.S. Steel approves $3B investment for Mon Valley hot strip mill

U.S. Steel’s board of directors has approved a nearly $3 billion investment to construct a new hot strip mill (HSM) at the Edgar Thomson Plant within the Mon Valley Works near Pittsburgh. The project, which targets 2029 production, is part of a broader $14 billion capital investment plan by Nippon Steel following its acquisition of the company.

The new facility is intended to replace an 87-year-old mill at the Irvin Works in West Mifflin. While the company, the United Steelworkers union, and various elected officials have welcomed the modernization, the project faces opposition from local leaders and environmental advocates.

Concerns center on potential increases in local air pollution. Data from the Allegheny County Health Department suggests that while overall emission rates in the Mon Valley may decrease once the Irvin mill is idled, the new facility could lead to a 43% increase in PM 2.5 and a 98% increase in NOx and NO2 in the immediate vicinity of Braddock and North Braddock. The project still requires air quality and stormwater construction permits from county and state authorities.