U.S. Steel fined for leaking oil into Monongahela River

U.S. Steel must pay $135,000 and establish stronger pollution controls after environmental regulators found the steelmaker’s West Mifflin facility was leaking oil into the Monongahela River.

An agreement announced Tuesday between U.S. Steel and the Pennsylvania Department of Environmental Protection requires the company to monitor wastewater from the Irvin Works with daily inspections and live-feed cameras.

U.S. Steel also has three months to complete a facility-wide investigation to identify all sources of oil and grease. From there, it gets 90 days to submit a mitigation plan to the state.

“Protecting the waters of the commonwealth is one of DEP’s core responsibilities,” Department Secretary Jessica Shirley said in a statement. “This agreement ensures that U.S. Steel takes concrete, enforceable steps to prevent further pollution of the Monongahela River.”

U.S. Steel spokesman Andrew Fulton said the manufacturer is committed to “environmental excellence” and regulatory compliance.

The legally binding agreement comes after repeated oil sheens near the Irvin Works, a 150-year-old steel processing facility.

The department investigated at least seven complaints of oil flowing into the river between August 2022 and April 2025. In some cases, the oil extended more than a mile downstream.

U.S. Steel was ordered to find the source of the oil leakages in October 2023, but follow-up inspections discovered continued violations, according to the department.

In addition to the $135,000 penalty, U.S. Steel will be fined $1,000 for each day it misses a deadline in the agreement and $7,500 for each future leak observed after the mitigation plan goes into effect.

The department said the agreement was in response to multiple citizen complaints.