Q. Why do local governments want the EPA to declare the Gelman dioxane plume a Superfund site?

A. From the 1960s into the 1980s, Gelman Sciences discharged manufacturing wash water into ponds on its Wagner Rd. property. Bacteria in the ponds were supposed to break down contaminants but had little effect on 1,4-dioxane, which the EPA classifies as a known animal carcinogen and a likely human carcinogen.

A lawsuit by Michigan’s attorney general was settled in a 1992 consent judgement in which Gelman agreed to pump out the contaminated water and treat it to reduce dioxane levels. But the plume has continued to spread, and there are concerns about eventual contamination of Barton Pond, the primary source of Ann Arbor’s drinking water.

After rejecting a proposed new consent decree, the city, Scio Township, and Washtenaw County all called on the EPA to intervene. Last April, Governor Whitmer sent a supporting letter, and a site sampling plan was completed last month. Meanwhile, last year the plume was detected north of M-14.

If it becomes a Superfund site, the EPA could compel Gelman’s successor company to put in more extraction and monitoring wells to halt the plume and restore the water to stricter standards. If the company contests the order, the EPA would do the cleanup itself and sue to recover the cost.

Superfund projects have moved notoriously slowly in the past, and the EPA has estimated that the process to qualify the Gelman site would take about three years. But its cleanup efforts are receiving a fresh infusion of funding thanks to the recently passed federal infrastructure bill.

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