A decades-old plan to clean up a Superfund site at a chemical plant in near west side of Indianapolis could be significantly altered in the coming months.

The U.S. Environmental Protection Agency announced a proposal to change the cleanup plans for the groundwater portion of the Reilly Tar & Chemical Superfund site, a former coal tar refinery and chemical plant.

Groundwater at the site is contaminated with benzene, a chemical that can affect bone marrow, cause anemia, affect the immune system; pyridines, chemical related to benzene that can affect the liver, kidney an cause neurological effects; and ammonia, a corrosive substance that can cause severe burns in high concentrations.

Instead of extracting contaminated water from the ground and releasing it into an off-property public water treatment facility, the EPA proposes to treat the plant through biosparging, the process of injecting air into groundwater systems to stimulate biological activity that would break down the contaminants over time.

The EPA will accept public comments on the proposal until July 2. The agency will also host a virtual public hearing on the proposed cleanup on June 15 from 6pm to 8pm.

The earliest recorded complaint at the site was in 1955, when chemicals produced at the site were found to have spread to nearby residential wells in 1955 and again in 1964. State investigators in 1975 found groundwater at the site itself was contaminated with various organic chemicals.

The site was placed on the National Priorities List, a list of the nation’s most polluted sites, in 1984. A plan to clean up the site, including its groundwater, was finalized in June 1992.