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Congresswoman Debbie Dingell (MI-06) today sent a letter to Michigan Department of Environment, Great Lakes, and Energy expressing concern and requesting answers about new detections of dioxane spreading from the Gelman plume. 

“Recent sampling by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) and the Washtenaw County Health Department (WCHD) raises concern that the plume may be continuing to spread, now contaminating at least 52 residential drinking water wells, including six new detections in 2025,” Dingell writes. “These new detections bring the contamination closer to the Huron River and Barton Pond, which provide drinking water to Ann Arbor.”

“Out of 117 private wells tested this year, 47 showed detectable levels of dioxane, indicating the contamination is more widespread than previously understood,” Dingell continues.“Experts have warned that the 4th Amended Consent Judgment has failed to contain the plume, that current cleanup efforts are insufficient, and that Michigan’s cleanup level of 7.2 parts-per-billion (ppb) is not protective.”

“As you know, the U.S. Environmental Protection Agency (EPA) proposed adding the Gelman site to the Superfund National Priorities List in March 2024. However, the site was not included due to a high volume of public comments requiring further review and response,” Dingell concludes. “While I understand the need for thorough consideration, the ongoing spread of this plume into a major urban area’s drinking water supplies demands urgent and coordinated action at the federal, state, and local levels.”

Dingell requested answers to the following questions: 

• What is EGLE’s current assessment of the plume’s location, rate of migration, and risks to private wells, the Huron River, and Barton Pond?
• What actions is EGLE taking to protect residents’ drinking water and monitor further contamination?
• Does EGLE plan to adopt the more sensitive EPA Method 522 (detection limit of 0.12 ppb) in future testing to ensure early detection?
• How will the state improve communication of health risks to residents, given that any detectable level of dioxane is classified by EPA as likely carcinogenic to humans?

View the full text of the letter here.