The Reilly Tar & Chemical Corp. Indianapolis Plant covers 120 acres in southwest Indianapolis. Wood preserving and coal-tar refining operations ran there from 1921 to 1972, leaving behind contaminated soil, groundwater, and sludge. EPA added the site to the National Priorities List in September 1984. Cleanup is still underway, though much of the early work is done and parts of the site are already in productive reuse.
More than 70 chemicals have been identified at the site. These include volatile organic compounds such as benzene, toluene, and trichloroethene in soil and groundwater. Polycyclic aromatic hydrocarbons appear in soil across several areas. Heavy metals, including arsenic, lead, mercury, and chromium, were found in soil and groundwater. Ammonia, cyanide, pentachlorophenol, and other compounds were detected in soil, groundwater, and sludge. EPA determined all of these pose unacceptable risks and has organized cleanup into five operable units.
Three of the five operable units, covering on-site soil contamination sources, are complete. In 1997, contaminated soil was removed and treated in four areas, and a fifth area was solidified and capped. The wood treatment zone received a permeable cover in 1999. The two remaining units address groundwater. In 2021, EPA amended its cleanup plan for the main groundwater unit, replacing pump-and-treat extraction with biosparging, a method that injects oxygen underground so microorganisms can break down contaminants in place. This approach is projected to cut cleanup time to about 20 years in the eastern portion of the site. Construction of the new system is estimated to begin in spring 2025. In February 2024, EPA and the Department of Justice signed a consent decree with the site owner to require design and construction of this updated remedy, along with continued operation and maintenance of completed work. The most recent five-year review, completed in December 2024, confirmed that response actions remain protective of human health and the environment. Human exposure is currently under control, and contaminated groundwater migration is stabilized with no unacceptable discharge to surface water. A partial deletion from the National Priorities List is estimated between August and October 2027.
The site is not idle while cleanup continues. Chemical operations still take place on the property. Developer Hanwha Q CELLS built a 10.8 megawatt solar farm on the southern 43 acres, which began operating in February 2014 as the first utility-scale solar farm on a Superfund site in EPA Region 5. As of December 2024, two on-site businesses employed 50 people and generated about $32.8 million in annual sales.
Community members can follow site progress through fact sheets available in English and Spanish and can participate in interviews related to site activities. For questions, residents can contact the EPA's Community Involvement Coordinator or Remedial Project Manager.
