Q. I have a question about the Gelman Plume cleanup. After contaminated groundwater is treated to reduce dioxane levels, it is discharged into a tributary of Honey Creek, which joins the Huron River upstream from Ann Arbor’s drinking water intake at Barton Pond. Why isn’t it pumped back underground instead?
A. Reinjection was done at one time, but it was discontinued in 2002 because it could reduce the efficacy of remediation by diluting the water that is being withdrawn for treatment and could potentially expand the boundaries of the plume.
According to the Michigan Department of Environment, Great Lakes, and Energy (EGLE), the plume “is not currently considered a threat to public health or to the environment.” The state’s drinking water protection criterion for dioxane is 7.2 parts per billion (ppb). In the past six years, the highest level detected in Barton Pond, in August 2020, was 0.33 ppb. The highest level detected in the city’s drinking water, in February 2020, was .059 ppb, less than one-tenth of the criterion.
Efforts to clean the plume and limit its spread continue. In December, Governor Whitmer formally asked the EPA to take over from EGLE and list it as a federal “Superfund” site.
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