1,4-Dioxane

Dioxane is a humanmade compound that mixes easily in water. It is used in industry as a solvent to manufacture other chemicals and it is a by-product in many items, including paint strippers, dyes, greases, antifreeze and aircraft deicing fluids. It also is found in other chemicals that are used to manufacture cosmetics, detergents, deodorants, and shampoos.

The International Agency for Research on Cancer has determined that 1,4-dioxane is 'possibly carcinogenic' to humans because it is a known carcinogen in animals. United States Environmental Protection Agency (EPA) states that it is likely to be carcinogenic to humans. The EPA is currently conducting a risk evaluation for dioxane under the Toxic Substances Control Act. More information on exposure to 1,4-dioxane and its health effects is available via a State of Michigan Department of Health and Human Services Fact Sheet (PDF).  

Dioxane was used from the mid-1960s to the mid-1980s in the manufacturing processes at Gelman's facility on Wagner Road. Gelman's wastewater, containing dioxane, was disposed onsite during that time. In the mid-1980s dioxane was discovered offsite, in nearby surface waters ​and groundwater.

The groundwater in underground aquifers that is carrying dioxane is referred to as a plume. Multiple plumes have been spreading west in Scio Township and northeast then east into Ann Arbor, moving towards the Huron River. ​​More information on dioxane and its location in the groundwater can be found on EGLE’s contamination web map.

While the Michigan Department of Environment, Great Lakes, and Energy (EGLE) currently manages the cleanup, the Gelman site has been proposed for listing under the United States Environmental Protection Agency (EPA) Superfund Program as described in Question 10. 

In 1992, the Washtenaw County Circuit Court entered a Consent Judgment regarding Gelman's dioxane contamination. Four amendments to the original Consent Judgment have been approved by the Court and are in effect, the most recent being approved in 2023. 

The Consent Judgment and its amendments dictate the obligations of Gelman to investigate, clean up, contain, and monitor the contaminated groundwater, under the direction of EGLE. ​

In the State vs. Gelman lawsuit, the Court approved a Prohibition Zone (“PZ") as an Institutional Control. This allows dioxane above the groundwater cleanup criterion to migrate, rather than be cleaned up, within the PZ. The “prohibition" part of the PZ title refers to a prohibition against installing or maintaining wells for drinking water or irrigation purposes on land within the PZ boundaries. All of the PZ is within the boundaries of the City of Ann Arbor, which requires all properties—regardless of where they are relative to the PZ—to connect to the city's municipal water supply system rather than get water from wells on their properties. The location of the PZ can be viewed on EGLE’s contamination web map​​​.

Gelman operates a pump and treat system, where extraction wells pump contaminated water out of the ground, treat it, and release the cleaned water to surface water. Treatment activities are dictated by the Consent Judgement, while the discharge to surface water is regulated by the National Pollutant Discharge Elimination System (NPDES) permit. Both the Consent Judgement activities and the NPDES permit are currently managed by EGLE.​

The plume is monitored by Gelman and EGLE through a network of monitoring wells across the City and Scio Township. The locations of the wells and frequency of sampling are dictated by the Consent Judgement. Results are reported to EGLE and a selection of impacted stakeholders. In addition to the network of monitoring wells, EGLE contracts with the Washtenaw County Health Department to conduct residential well monitoring along the northern edge of the PZ. Up-to-date monitoring and residential well sampling data can be found on EGLE’s contamination web map​.​

While the City has taken on several roles over the decades, the priority has always been to safeguard the health of its residents. The City has worked collaboratively with Gelman, EGLE, Washtenaw County Health Departments, Ann Arbor and Scio Townships, and watershed groups on various initiatives to best address the contamination. In instances where severe disagreements have occurred, the City has pursued litigation. For example, in 2004 and 2005, the City filed actions in state and federal courts against Gelman Sciences regarding dioxane released and migrating from Gelman's property. In 2006 the City and Gelman entered into a Settlement Agreement in which Gelman agreed to compensate the City, monitor water quality, and undertake certain activities. 

The City's current area of focus is the protection of its drinking water intake in Barton Pond on the Huron River, where 85% of the City's water is sourced. The City continues to work with Gelman, EGLE, and other stakeholders to advocate for appropriate monitoring mechanisms that can provide sufficient planning time should the plume move toward the Huron River. The City implemented a sentinel well monitoring program in 2020 at its own expense to monitor the plume at northern edge of the PZ. A sentinel well is a monitoring well that is located between a known area of contamination and a drinking water supply. Routine monitoring of the sentinel well will provide advance warning of contamination migration toward the drinking water supply, and will allow time for the City to plan appropriate response measures.

Yes. As of July 2024, the Gelman Sciences, Inc site is currently under evaluation as a possible candidate for the Superfund National Priorities List (NPL). The EPA has received concurrence from EGLE and the Michigan Governor's office to pursue NPL status for the Gelman site. On March 7, 2024 the EPA released a proposal to add the Gelman site to the NPL. The public had 60 days to provide comments on the proposal, which closed on May 6, 2024. The EPA will spend the next several months providing public responses to all comments. If, after the formal comment period, the site still qualifies for cleanup under Superfund, it is formally listed on the NPL. ​​  

Once the Gelman site is placed on the NPL, further studies will ensue to determine the nature and extent of the contamination and to help identify feasible treatment options. A cleanup plan is then selected and documented in a record of decision. The timeline for design and cleanup work at an NPL site is highly variable and can take from a few years to several decades. However, at any time the EPA may use Superfund removal enforcement authority to quickly address imminent and substantial endangerment to public health or the environment. 

City staff communicate regularly with the Washtenaw County Health Department who have responsibility for public health impacts associated with exposure to the plume in residential wells. Washtenaw County Health Department has conducted additional sampling at the impacted well in Ann Arbor Township and at nearby wells to confirm the positive test results. If 1,4-dioxane levels are confirmed to be above health-based limits at this location, the State of Michigan will initiate plans to connect them to City of Ann Arbor water.