The U.S. Environmental Protection Agency (EPA) has reached an agreement with Gelman Sciences LLC requiring additional cleanup and investigation of 1,4-dioxane contamination in Ann Arbor and Scio townships, Michigan.

The administrative settlement agreement and order on consent establishes requirements for near-term response actions and long-term remedial planning at the site, which EPA added to the Superfund National Priorities List in March 2026.

Under the agreement, Gelman Sciences must conduct a remedial investigation and feasibility study to determine the extent of contamination and evaluate cleanup options. The company also must excavate contaminated soil from a former burn pit, increase groundwater extraction and treatment rates in the eastern portion of the contamination plume and install additional monitoring wells to better define the plume’s extent. The agreement also provides grant funding for community groups to hire an independent technical advisor.

The groundwater plume, resulting from wastewater discharges associated with Gelman Sciences’ medical filter manufacturing operations from 1963 to 1986, extends approximately 3 miles long and 1 mile wide, according to EPA. The contamination has reached aquifers used for drinking water and has prompted the abandonment of some private wells and connections to municipal water systems. Ann Arbor closed its Montgomery Wellfield in 2001 because of 1,4-dioxane contamination.

A separate state-level consent judgment obtained by the Michigan Department of Environment, Great Lakes, and Energy remains in effect. It requires additional groundwater extraction and monitoring wells, on-site remediation and annual sampling of residential wells.

EPA will oversee the work under the new agreement as efforts continue to address the contamination and support long-term aquifer restoration.