Ann Arbor-area dioxane plume affecting dozens of drinking wells north of M-14, new map shows

Dioxane contamination in wells north of I-94, M-14

A map released by the Washtenaw County Health Department in August 2023 shows two years of sampling of drinking water wells north of I-94 and M-14 revealing low levels of dioxane contamination from the Ann Arbor-area Gelman plume. It combines results from independent sampling carried out by Ann Arbor and Scio townships with long-term Michigan Department of Environment, Great Lakes and Energy monitoring accomplished by the county health department.Washtenaw County Health Department

WASHTENAW COUNTY, MI - During the last two years, testing completed by two townships and through a state monitoring program has identified 43 drinking water wells north of I-94 and M-14 contaminated by low levels of 1,4-dioxane, a likely carcinogen spreading in Ann Arbor-area groundwater.

That’s according to a new map published by the Washtenaw County Health Department on Wednesday, Aug. 23. It details an area that has sparked concern from clean water advocates because of its proximity to the Huron River, Ann Arbor’s main source of drinking water, and its distance from the previously established boundaries of the Gelman dioxane plume.

All samples detecting the chemical were below three parts per billion, and the state drinking water standard for dioxane is 7.2 ppb, though residents have long said they deserve to know of any level of contamination in their water, pointing to stricter standards in other states.

The plume, first discovered in the 1980s, originated at the Gelman Sciences filter manufacturing facility on Wagner Road in Scio Township. The new map appears to show a finger of pollution stemming north of the highways on the east side of Wagner Road toward the Huron.

With dioxane first detected in the area in 2021, it’s likely too soon to describe exactly what the results indicate, according to Kristen Schweighoefer, environmental health director with the health department, which carried out much of the sampling shown on the map on contract with the state’s long-term monitoring program.

“It’s certainly something we’re sharing with (the Michigan Department of Environment, Great Lakes and Energy) to see if they can do any additional monitoring of this area,” she said. “I hesitate to say there’s a plume moving because we haven’t tested this area before, so I can’t say whether this is new or whether this has been an existing plume area of dioxane under these homes.”

Focus on the residential area north of M-14 intensified in late 2021 when Scio Township released results of its own sampling of wells showing pollution roughly two thirds of a mile north of the estimated plume boundaries for the first time.

Township officials said they tested the wells after a court-ordered cleanup plan failed to address the pathway of the Gelman plume’s movement and install monitoring wells north of the highway.

Continued testing by Scio and Ann Arbor townships using a more sensitive sampling method than that employed by the state laboratory continued to identify low levels of pollution in 2022.

The long-term state monitoring program had sampled the area just north of I-94 for some time, but hadn’t gone as far north before the latest round of sampling, Schweighoefer said.

“The township’s detections at those lower levels did expand our testing, and because of this program we were able to test more homes and hopefully provide a bit of a broader picture,” she said.

Officials are hoping to continue to capture data from the area over time, and the health department will work with EGLE to determine where to sample in the coming year. While officials haven’t made the final determination on again sampling the area north of M-14, Schweighoefer said she expects it will be part of the plan.

The state sampling carried out by the health department confirms the independent Scio Township testing, said Dan Bicknell, an environmental remediation professional credited with discovering the Gelman plume while he was a University of Michigan public health graduate student in 1984.

The health department’s testing revealed approximately a dozen new wells with dioxane contamination not found by Scio, he said in an email.

The results “confirm that there is dioxane contaminating residential drinking water wells up to one mile from where EGLE has been telling the community is the edge of the dioxane plume,” Bicknell said.

He reiterated his call for the plume to be named a federal Superfund site, joining a nationwide priority list of contaminated sites overseen by the U.S. Environmental Protection Agency. EPA officials are now evaluating the Gelman plume, and said in a June townhall meeting that their preliminary investigation suggests it is of Superfund caliber.

Read more: Ann Arbor dioxane plume is contamination of Superfund site caliber, EPA official says

The EPA aims to officially propose the site for Superfund status in fall 2024, official said, though it is still subject to approval from the EPA’s headquarters and a federal rule-making process including public comment and response.

Bicknell said he believes federal oversight would do more to halt “migration” of the plume toward residential wells in Ann Abor and Scio townships and cleanup contaminated groundwater more effectively than an existing state controls.

“The Gelman dioxane groundwater contamination is a plague on the community and the federal government is needed to stop this public health fiasco,” he said.

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