After more than six decades of groundwater contamination, the U.S. Environmental Protection Agency has finally placed the Gelman Sciences site in Ann Arbor, Michigan on the Superfund National Priorities List. The announcement came on March 12, 2026, with formal publication in the Federal Register the following day.
The listing marks a turning point for a contamination problem that has frustrated Ann Arbor residents and environmental advocates for decades — and signals that federal regulators are stepping in where state oversight fell short.
What Happened at Gelman Sciences
From 1963 to 1986, Gelman Sciences manufactured medical filters at a facility on the west side of Ann Arbor. The manufacturing process produced wastewater containing 1,4-dioxane, a synthetic industrial chemical classified as a likely human carcinogen. That wastewater was discharged into surrounding ponds, where the chemical leached into the soil and migrated into groundwater.
The result: a contaminated groundwater plume approximately three miles long and one mile wide, stretching from the former factory site toward the Huron River and the aquifers that supply drinking water to the Ann Arbor area.
Why 1,4-Dioxane Is Especially Dangerous
1,4-dioxane doesn’t behave like most groundwater contaminants. It’s highly soluble in water, doesn’t adsorb well to soil particles, and resists natural biodegradation. That means it travels farther and persists longer in groundwater than many other industrial chemicals.
Health risks include liver and kidney damage, and the EPA classifies it as a likely carcinogen. Unlike PFAS — which have recently received enforceable federal drinking water limits — 1,4-dioxane still lacks a federal maximum contaminant level (MCL), though Michigan has set a state standard of 7.2 parts per billion.
The chemical is also notoriously difficult and expensive to treat. Conventional activated carbon, which works well for many organic contaminants, has limited effectiveness against 1,4-dioxane. Advanced oxidation processes (UV treatment combined with hydrogen peroxide) are typically required, driving up treatment costs significantly.
Decades of State-Level Management
Before the NPL listing, the Gelman Sciences contamination was managed under a state agreement — not federal Superfund authority. Under that agreement, the company (now part of Pall Corporation, itself owned by Danaher Corporation) was required to pump and treat contaminated groundwater to reduce 1,4-dioxane concentrations within the plume.
But the state agreement had significant limitations that frustrated local advocates:
- It did not require Gelman to restore the groundwater to beneficial use
- It allowed the plume to continue migrating eastward toward the Huron River
- The state’s groundwater-to-surface-water interface criterion permitted discharge to the river as long as certain standards were met at the point of contact
In practice, this meant the contamination was being managed rather than cleaned up. The plume continued spreading, and portions of Ann Arbor’s aquifer remained unusable for drinking water.
What the Superfund Listing Changes
The NPL listing gives the EPA authority to take more aggressive action than the state agreement allowed. According to the EPA’s announcement, federal involvement will focus on:
- Controlling the plume to reduce its eastward migration
- Preventing further degradation of the Ann Arbor aquifer
- Ensuring uncontaminated portions of the aquifer can be used for future residential and commercial purposes
Under Superfund, the EPA can compel responsible parties to fund cleanup efforts and can pursue cost recovery if they don’t cooperate. The federal process also includes more rigorous public participation requirements and more transparent reporting on cleanup progress.
What This Means for Ann Arbor Residents
For the roughly 125,000 people living in Ann Arbor, the Superfund listing is both a validation and a warning. It confirms what many already knew — that state-level oversight wasn’t enough to protect the city’s drinking water resources — while raising questions about the timeline and scope of federal cleanup.
Ann Arbor’s municipal water system draws from surface water (the Huron River) rather than groundwater wells, so the contamination hasn’t directly affected the public water supply. However, private wells in the affected area are at risk, and the continued degradation of the aquifer limits future water supply options for a growing city.
What Residents Can Do
- If you have a private well near the contamination zone (west Ann Arbor, Scio Township), get your water tested for 1,4-dioxane. Contact the Washtenaw County Health Department for guidance.
- Stay informed about the Superfund cleanup process. The EPA will hold public meetings as the investigation and cleanup plan develop.
- Municipal water users are not currently at risk from this contamination, as the city’s treatment processes address potential surface water impacts.
A Broader Pattern
Ann Arbor’s experience isn’t unique. 1,4-dioxane contamination has been identified at numerous sites across the country, often linked to manufacturing facilities that used the chemical as a solvent stabilizer. The EPA’s IRIS database lists more than 30 Superfund sites where 1,4-dioxane is a contaminant of concern.
The Ann Arbor listing may signal a broader federal push to address 1,4-dioxane contamination more aggressively — particularly at sites where state oversight has been criticized as inadequate.
If you’re concerned about your water quality in the Ann Arbor area, a certified water treatment professional can test your water and advise on filtration or treatment solutions appropriate for 1,4-dioxane and other contaminants.