Gelman Plume and 1,4-Dioxane Quarterly Update

On March 12, 2026, the U.S. Environmental Protection Agency (EPA) added the Gelman Sciences Inc. site to the Superfund National Priorities List, a list of the nation's most contaminated sites. This means that regulatory oversight was shifted from the Michigan Department of Environment, Great Lakes, and Energy (EGLE) to the EPA.

EPA Community Interviews – Summer 2026

EPA has begun community engagement efforts and is scheduling one on one meetings with community members and stakeholders to learn how residents want to be informed and engaged, identify information gaps, and educate the community about the EPA, the Gelman site and the Superfund program. Information gathered during these meetings will help inform the EPA's Community Involvement Plan.

Meetings will be held at several locations throughout the community.

Interview locations:

July 27–29, 2026 – Skyline High School Library, 2552 N. Maple Rd., Ann Arbor
Aug. 17–19, 2026 – Scio Township Hall, 827 N. Zeeb Rd., Ann Arbor

Community members interested in scheduling a one on one meeting should contact EPA contractor Caeli Cleary at 312.201.7769 or Caeli.Cleary@tetratech.com.

An online survey is also available on the EPA website for those who are unable to attend in person.

April 2026 Community Meeting Summary

At a community meeting hosted by Congresswoman Debbie Dingell on April 7, 2026, EPA Region 5 Administrator Anne Vogel and EPA staff outlined the agency's next steps for the Gelman site.

EPA explained that it will pursue two paths concurrently:

Remedial Process

The remedial process is a comprehensive, long term process used to investigate contamination, evaluate cleanup alternatives, select a permanent remedy and implement and monitor the cleanup to protect human health and the environment.

EPA has initiated this process by issuing Gelman an information request that includes questions about the treatment system, monitoring wells and the company's corporate structure to help determine its ability to pay for cleanup activities.

Removal Process

The removal process provides a rapid response to address immediate or time critical threats to human health or the environment through short term cleanup or containment actions.

EPA has begun evaluating whether removal actions are warranted at the Gelman site.

Cleanup progress and additional information will continue to be posted on the EPA website.

Coalition for Action on Remediation of Dioxane (CARD)

CARD meetings were held virtually on:

April 7, 2026
May 5, 2026
July 7, 2026

The June meeting was canceled.

Michigan Department of Environment, Great Lakes, and Energy (EGLE)

EGLE has received preliminary results from its 2026 residential well testing program, which included approximately 220 homes in Scio Township. EGLE contracted with Hamp Mathews and Associates to conduct the 2026 residential well and surface water sampling, work that was previously managed by the Washtenaw County Health Department.

Preliminary results identified 16 new low level detections of 1,4-dioxane. EGLE noted this was expected because more wells were sampled and the reporting limit was lowered to 0.02 parts per billion (ppb), compared to 1.0 ppb prior to 2025.

Results are expected to be shared more broadly in the near future. Previous sampling results remain available on the EGLE Contamination Mapper website.

It is important to note that there are no known private drinking water wells within Ann Arbor city limits. All residents and businesses in the city are connected to the municipal drinking water system.

Quarter 3 CARD meetings will be held via Zoom on:

6 p.m. Tuesday, Aug. 4
6 p.m. Tuesday, Sept. 1

Pall Groundwater Treatement Updates

There are no new updates this quarter.

Background

Concentrations of 1,4-dioxane have been entering the Allen Creek Drain (ACD) stormwater system. The ACD system is part of Washtenaw County's Municipal Separate Storm Sewer System (MS4).

The Washtenaw County Water Resources Commission Office previously notified Gelman that action was required to remain in compliance with the county's MS4 permit requirements. The letter stated that migration of 1,4-dioxane into the Allen Creek Drain must cease or otherwise comply with applicable state and county statutes and permit requirements.

EGLE's Water Resources Division continues to explore potential permitting options.

Total volume of groundwater treated February through May 2026

97,883,687 gallons

Mass of 1,4-dioxane removed

February 2026: 63.84 lbs.
March 2026: 70.68 lbs.
April 2026: 74.83 lbs.
May 2026: 84.00 lbs.

Total removed: 293.35 lbs.

The mass calculations were determined from the National Pollutant Discharge Elimination System (NPDES) monthly discharge reports using the maximum daily influent concentration and maximum daily effluent concentrations.

The total groundwater volume was calculated using the average monthly flow reported in the NPDES monthly discharge reports.

2025 Quarter Four and 2026 Quarter One

On March 12, 2026 the U.S. Environmental Protection Agency (EPA) added the Gelman Sciences Inc. site to the Superfund National Priorities List, a list of the nation’s most contaminated sites. This means that regulatory oversight will shift from the Michigan Department of Environment, Great Lakes, and Energy (EGLE) to the EPA. This development has been many years in the making. The city, along with our partners and community advocates, has long supported federal involvement due to the scale and complexity of the contamination and the plume’s migration. Federal oversight is expected to bring additional resources, technical expertise, and clean-up tools that perhaps were not previously available due to court-ordered restrictions.

There are many questions regarding the Superfund process, and how the transition from EGLE to EPA will move forward. The City of Ann Arbor will be meeting with its state, local, and now federal partners in the coming weeks and months to discuss immediate steps in the transition. Typically, the EPA conducts additional studies to better understand the nature and extent of the contamination and help identify feasible treatment options. A preferred cleanup plan is then selected and documented in a Record of Decision. The timeline for investigation, design, and cleanup work at a Superfund site is highly variable and can take from a few years to multiple decades.

The city will continue to work with our partners to advocate for a swift and more aggressive clean up (such as better plume delineation and mass removal to prevent migration toward Barton Pond) and more stringent 1,4 dioxane standards to safeguard our drinking water. In the meantime, Ann Arbor municipal drinking water continues to be safe, and the city will maintain our current water quality monitoring program in Barton Pond. 

Thanks to the Ann Arbor community for your continued activism! 

EPA Press Release

Coalition for Action on Remediation of Dioxane (CARD)

CARD meetings were held virtually on:

Oct. 7, 2025
Nov. 4, 2025
Dec. 2, 2025
Jan. 6, 2026
March 3, 2026.

Michigan Department of Environment, Great Lakes, and Energy (EGLE)

The most recent EGLE update provided to CARD was prior to the news about the addition of the Gelman site to the U.S. Environmental Protection Agency Superfund National Priorities List.

EGLE provided updates on ongoing Gelman-related oversight activities. EGLE continues to support adding the site to the U.S. Environmental Protection Agency (EPA) Superfund National Priorities List and has been coordinating with the EPA since fall 2025 following a request from state legislators to accelerate the listing process.

EGLE is continuing environmental monitoring and planning activities, including limited surface water sampling in the Allen Creek area in 2025, review of Gelman’s updated municipal contingency plan, and an upcoming Response Activity Plan from Gelman for the western portion of the site where elevated levels have been detected. Work is also moving forward on a wetlands permit to begin a pilot phytoremediation study in the marshy area.

EGLE is preparing for their 2026 residential well testing program, which will include approximately 220 homes in Scio Township. EGLE has contracted with Hamp Matthews and Associates to conduct the 2026 residential well and surface water sampling, work that was previously managed by the Washtenaw County Health Department. It is important to note that there are no known private drinking water wells within Ann Arbor city limits. All residents and businesses in the city are connected to the municipal drinking water system.

Quarter 2 CARD meetings will be held via Zoom on the following days:

6 p.m. Tuesday April 7
6 p.m. Tuesday May 5
10 a.m. Tuesday June 2

Pall Groundwater Treatment Updates

EGLE’s Water Resources Division (WRD) shared water quality results of the Slauson Middle School geothermal investigation with the Washtenaw County Water Resources Commission. WRD is also interested in the ongoing eastern area Groundwater to Surface Water Interface (GSI) investigation by Gelman Sciences Inc., which includes measuring groundwater flow and water quality in Allen Creek. All field data for the investigation has been collected, though a timeline for the final report has not yet been confirmed.

Background:

Concentrations of 1,4-dioxane have been entering the Allen Creek Drain (ACD) stormwater system. The ACD system is part of Washtenaw County’s Municipal Separate Storm Sewer System (MS4). The Washtenaw County Water Resources Commission Office sent a letter to Gelman indicating that action was required to remain in compliance with the County’s MS4 permit requirements regarding outstanding issues previously noted. The letter stated that the migration of 1,4-dioxane into ACD must cease or be in compliance with applicable State and County statutes and requirements. EGLE Water Resources Division is exploring potential permitting options.

Total volume of groundwater treated Sept. 2025 through Jan. 2026:

121,983,204 gallons

Mass of 1,4 Dioxane Removed:

Sept. 2025: 65.59 lbs
Oct. 2025: 80.80 lbs
Nov. 2025: 75.66 lbs
Dec. 2025: 77.66 lbs
Jan. 2026: 72.68

Total: 372.39 lbs

The mass calculations were determined from the National Pollutant Discharge Elimination System (NPDES) monthly discharge reports using the maximum daily influent concentration and maximum daily effluent concentrations.

The volume was calculated from the average monthly flows in the monthly discharge report.

2025 Quarter Three

No significant updates. General EPA updates regarding the Gelman site can be found on the EPA’s website.

Coalition for Action on Remediation of Dioxane (CARD)

CARD meetings were held virtually on July 1, and Aug. 5, and Sept. 2.

Quarter 4 CARD meetings will be held on the following days:

Tuesday Oct. 7, 2025, at 6 p.m. via Zoom

Tuesday Nov. 4, 2025, at 6 p.m. via Zoom

Tuesday Dec. 2, 2025, at 10 a.m. via Zoom

Michigan Department of Environment, Great Lakes, and Energy (EGLE) Update

Slauson Middle School geothermal exploratory groundwater quality testing revealed detectable levels of dioxane: well sample depths varied, with dioxane concentrations ranging from 2 to 31 ppb. This area is within the known plume area. Because this area is within the Prohibition Zone (where groundwater cannot be used for drinking water), these levels are well below the groundwater to surface water standard of 280 ppb. Results are viewable on the EGLE RIDE mapper.
Three Permanent monitoring wells were added at Slauson School: one shallow monitoring well in the north screened from 4-9 feet depth; and in the south, a cluster with one shallow well screened from 4-9 feet depth and another deeper well screened from 40-45 feet depth.
Marshy Area Feasibility Study. EGLE staff met with Gelman’s consultant on Aug. 4 for a pre-application meeting to discuss permitting requirements to install pilot extraction wells and phytoremediation in the Marshy Area.

Washtenaw County Health Department

Residential well sampling was conducted June 9-10, 2025. 117 residential wells in Scio Township were sampled this year, 47 of which had detectable levels of 1,4 dioxane between 0.2 and <3.0 parts per billion (ppb). With EGLE’s new lab reporting limit of 0.2 ppb, there were several new detections. These levels are below Michigan’s drinking water standard of 7.2 ppb and required action level of 3.0 ppb.
The results prompted an inquiry from Congresswoman Debbie Dingell’s office on July 28, 2025. EGLE responded to Congresswoman Dingell inquiry on Aug. 28, 2025.
The Health Department distributed a survey to recipients of the residential well testing program to gather information about what type of water treatment systems that residents have in their homes. Approximately 140 surveys were sent and only 7 responses were received.
Fiscal year 2026 residential well sampling recommendations include a proposed 220 homes. The proposed locations are pending review by EGLE.

Pall Groundwater Treatment Updates

No significant MS4 updates.

Concentrations of 1,4-dioxane have been entering the Allen Creek Drain (ACD) stormwater system. The ACD system is part of Washtenaw County’s Municipal Separate Storm Sewer System (MS4). On Dec. 15, 2022, the Washtenaw County Water Resources Commission Office sent a letter to Gelman indicating that action was required to remain in compliance with the County’s MS4 permit requirements regarding outstanding issues previously noted. The letter stated that the migration of 1,4-dioxane into ACD must cease or be in compliance with applicable State and County statutes and requirements.

EGLE Water Resources Division is exploring potential permitting options.

Total volume of groundwater treated June through August 2025: 73,859,040 gallons

Mass of 1,4 Dioxane removed:

· June: 83.08 lbs

· July: 72.68 lbs

· August 76.22 lbs

· Total: 231.98 lbs

The mass calculations were determined from the NPDES monthly discharge reports using the maximum daily influent concentration and maximum daily effluent concentrations.

The volume was calculated from the average monthly flows in the monthly discharge report.

2025 Quarter Two

There are no significant updates from the Environmental Protection Agency (EPA). General EPA updates regarding the Gelman site are available on the EPA’s website.

Municipal Separate Storm Sewer System (MS4) Permit Update

Coalition for Action on Remediation of Dioxane (CARD)

CARD meetings were held virtually on May 6, and June 3. The April meeting was cancelled.

Michigan Department of Environment, Great Lakes, and Energy (EGLE)

Slauson Middle School will be installing a closed loop Geothermal system, where 1,4-dioxane could be encountered in the groundwater. EGLE is working with the Washtenaw County Health Department to develop appropriate sampling and procedures to prevent further contamination and exposure. There may be an opportunity to install a permanent groundwater monitoring well.
EGLE’s environmental lab can now report 1,4-dioxane at 0.2 parts per billion under Method 522.
EGLE provided feedback on Gelman’s municipal water connection contingency plan on May 20, 2025. EGLE asked for additional documentation.

Washtenaw County Health Department

Residential well sampling will begin in early June, with 127 homes scheduled to be sampled.
Washtenaw County Health Department is the permitting agency for closed loop geothermal systems, however, these systems are not regulated at the state level.
The City of Ann Arbor has shared information on 1,4-dioxane.
The CARD Executive Committee submitted public comments to the Ann Arbor Planning Commission advocating for discussion of the 1,4-dioxane contamination in the Ann Arbor Comprehensive Land Use Plan. The first round of public comment closed on May 16, 2025.

The next scheduled meeting will be held on Tuesday July 1, 2025, at 6 p.m. via Zoom.

No significant MS4 updates. Concentrations of 1,4-dioxane have been entering the Allen Creek Drain (ACD) stormwater system. The ACD system is part of Washtenaw County’s Municipal Separate Storm Sewer System (MS4). On December 15, 2022, the Washtenaw County Water Resources Commission Office sent a letter to Gelman indicating that action was required to remain in compliance with the County’s MS4 permit requirements regarding outstanding issues previously noted. The letter stated that the migration of 1,4-dioxane into ACD must cease or be in compliance with applicable State and County statutes and requirements.

EGLE Water Resources Division is exploring potential permitting options.

Pall Groundwater Treatment Update

Total volume of groundwater treated April through May 2025:

47,852,640 gallons

Mass of 1,4 Dioxane Removed:

April: 72.20 lbs
May: 81.91 lbs
Total: 154.11 lbs

The mass calculations were determined from the NPDES monthly discharge reports using the maximum daily influent concentration and maximum daily effluent concentrations.

2025 Quarter One

No significant updates from the EPA which is still considering public comments on their proposal to include the Gelman site on the Superfund National Priorities List (NPL). The EPA will spend the next few months reviewing and responding to each comment. If, after the formal comment period, the site still qualifies for cleanup under Superfund, it is officially listed on the NPL. After listing, further studies will ensue to determine the nature and extent of the contamination and to help identify potential treatment options.

General EPA updates regarding the Gelman site can now be found on the EPA’s website.

Coalition for Action on Remediation of Dioxane (CARD)

CARD meetings were held virtually on January 7, February 4, and March 4, 2025.

Michigan Department of Environment, Great Lakes, and Energy (EGLE) Update
EGLE completed their 2024 annual surface water quality sampling, and results were shared with CARD. Results are currently available on CARD’s public drive.
EGLE received the Marshy Area Feasibility Study on January 14, 2025. The document was shared with the CARD chair and is available on EGLE’s public Remedial Information Data Exchange website for download. CARD provided comments on the feasibility study for EGLE’s consideration. EGLE’s comments on the study were due to Gelman by March 13, 2025.
EGLE met with Gelman representatives on Wednesday, January 22, 2025, to discuss EGLE’s response to the Groundwater to Surface Water Interface (GSI) Work Plan for Allen Creek Drain System. During this meeting, EGLE and Gelman agreed to postpone data collection for the EGLE-approved Eastern Area GSI Work Plan until summer 2025. This agreement was on the technical basis that July-September (drier months) will provide more representative data on the contribution of groundwater to the Allen Creek than data collected in January-March (months likely to be impacted by snow melting and rain events).

EGLE outlined data gaps in the delineation of shallow groundwater that could potentially impact the drain system, specifically around the Slauson School and upgradient of West Park. EGLE’s position is that these data gaps should be addressed as part of a forthcoming Downgradient Work Plan. EGLE and Gelman agreed that this work plan would consider data collected as part of the approved Eastern Area GSI work plan.

Furthermore, EGLE reiterated their position that the Downgradient Work Plan should also address other routes 1,4-dioxane may exploit as the plume migrates towards the Huron River as allowed by the Consent Judgment. These routes include the fill material enclosing the Allen Creek, groundwater directly venting to the Huron River, and groundwater that may intrude into the main branch of the Allen Creek. Adequate monitoring & accounting of all 1,4-dioxane migrating to the river will ensure that cumulative discharges do not exceed GSI criteria.

The next scheduled meeting will be held on Tuesday May 6, 2025, at 6 p.m. via Zoom (the April meeting was canceled).