The Armco Inc. Hamilton Plant is a former steel mill that operated on a 252-acre property in New Miami, near Hamilton, Ohio, for most of the twentieth century. Operations ended in the 1980s. The U.S. EPA proposed the site for the National Priorities List (NPL) in April 2003. The NPL is the federal list of the most serious uncontrolled hazardous waste sites. The site has not yet been finalized on the NPL, and no cleanup remedy has been selected or started.
Hazardous chemicals from past steel mill operations and waste disposal contaminated soil, sediment, sludge, and groundwater on the property. Human exposure through ingestion or direct contact with these materials is a concern. Drinking water wells tested in the area in the late 1980s and in 1993 showed no unsafe levels, and monitoring wells installed in 1999 at about 100 feet deep also showed no dangerous pollution levels. However, there is not yet enough data to confirm whether people are currently exposed to unsafe contamination, or whether contaminated groundwater movement has been stabilized.
All waste piles were removed in the late 1980s and early 1990s. The current owner, Cleveland-Cliffs Inc., is conducting a remedial investigation under EPA oversight. The investigation began under an administrative order of consent signed on April 29, 2002. In late 2024 and 2025, the company installed additional monitoring wells outside the property boundary and worked with nearby U.S. Geological Survey (USGS) wells to better understand groundwater conditions. Two river gages were also installed in 2025 to study how groundwater and surface water interact. The remedial investigation report is expected in 2026.
After the remedial investigation is complete, EPA will develop a feasibility study of cleanup options, prepare a proposed cleanup plan, and hold a public comment period and public meeting before making a final cleanup decision. The site also participates in the EPA's Superfund Redevelopment Program, which works to return Superfund sites to productive community use.
Community members who want to stay informed or ask questions can contact the EPA's Community Involvement Coordinator. For technical questions about the investigation and cleanup, contact the Remedial Project Manager.
