The Eagle Zinc Co Div T L Diamond site covers 132 acres in Hillsboro, Illinois. Zinc smelting and sulfuric acid manufacturing ran there from 1912 to 2003 under several company names, including Lanyon Zinc Company, Eagle-Picher Industries, Sherwin-Williams Company, and Eagle Zinc Company. EPA added the site to the National Priorities List in September 2007, marking it as a priority for federal cleanup action.
Contaminants of concern include antimony, cadmium, cobalt, lead, nickel, and zinc. These metals have been found in soil, solid waste, sediment, surface water, and building structures on the property. High metal concentrations pose unacceptable risks to future workers on the site and have the potential to harm aquatic life on site and downstream.
Cleanup is organized into three active operable units. Operable Unit 1 focused on demolishing unsafe buildings, a job finished in February 2016. Operable Unit 2 addresses soil contamination. EPA built a 10-acre containment cell to hold zinc slag and processing waste, then covered it with clean soil. Lead-contaminated soil from two nearby residential properties and land east of the site was also managed. Soil remediation work began in September 2015 and continues, with additional design phases estimated through 2028. Operable Unit 3 covers off-site sediment and groundwater. Investigation started in August 2018 and finished in 2021. A Feasibility Study to outline cleanup options is estimated to start between March and May 2027.
Human exposure is currently under control, meaning EPA has found no unacceptable exposure pathways at this time. However, EPA cannot yet confirm whether contaminated groundwater migration is stabilized due to insufficient data. Physical construction of the cleanup is not complete, and the site is not yet ready for its anticipated uses. The most recent Five-Year Review, completed July 28, 2025, confirmed that cleanup actions remain protective of human health and the environment in the short term.
Community members can contact the EPA's Community Involvement Coordinator or Remedial Project Manager. Questions can also go to the Illinois EPA. Site records are also available for public review at the Hillsboro Public Library, located at 214 School Street in Hillsboro, Illinois.
