The St. Louis River Site sits in Duluth, Minnesota and covers two former heavy industrial areas along the river. The St. Louis River/Interlake/Duluth Tar (SLRIDT) site spans 255 acres and includes land where pig iron, coking, and coal gasification plants once operated. The U.S. Steel site covers roughly 500 acres plus a 200-acre stretch of river called Spirit Lake, where a steel mill ran from 1916 to 1981. EPA placed the site on the National Priorities List (NPL) in September 1984 and split it into five operable units to tackle different types of contamination.
Contaminants include polycyclic aromatic hydrocarbons (PAHs), tar, volatile organic compounds (VOCs), cyanide, naphthalene, mercury, and heavy metals such as arsenic, lead, cadmium, copper, chromium, nickel, and zinc. PCBs and dioxins/furans have also been detected. These substances are found in soil, groundwater, sediment, and surface water. Minnesota has issued a fish consumption advisory for the area due to mercury contamination, and warning signs at the U.S. Steel site discourage direct contact with sediment. Human exposure is not currently under control, though contaminated groundwater has been stabilized in its original area.
Cleanup of the SLRIDT portion is substantially complete. Hazardous tar was removed and sent offsite for energy recovery, shallow contaminated soil was treated on-site, and deeper soil was covered with clean fill by 2001. Underwater sediments were dredged and either reposited or capped in place, with that work finishing in 2010. At the U.S. Steel site, industrial structures were demolished, over 6,400 tons of waste were removed from a settling basin, and 10,000 cubic yards of coal tar and contaminated soil were solidified for on-site disposal. Sediment cleanup of Spirit Lake and surrounding areas was completed in 2024 under EPA oversight in partnership with U.S. Steel and the state. Physical construction across the site is not yet fully complete.
The Minnesota Pollution Control Agency (MPCA) continues to oversee land cleanup and works with responsible parties to address remaining contaminated areas. Some portions of the SLRIDT site are already in active reuse, and reconstructed wetland habitats there support fish productivity. The Duluth Port Authority has expressed interest in a 120-acre light industrial park at the U.S. Steel location. As of December 2024, twelve businesses operating on-site employ 149 people and generate about $20.25 million in annual sales.
Community members can contact EPA's Lina Wu, the Community Involvement Coordinator, or Leslie Patterson, the Remedial Project Manager, with questions. Erin Endsley at the MPCA is also available for local inquiries. Public records related to Superfund work at the site can be viewed at the MPCA's Duluth office at 525 Lake Avenue South, Suite 400.
