The state Department of Environmental Quality has issued an emergency rule establishing a stricter cleanup criteria for 1,4 dioxane, a highly carcinogenic chemical that has polluted Ann Arbor's groundwater for decades.
The plume of contaminated water has been slowly moving in all directions, including towards the Huron River. It's feared that eventually the contamination could reach Barton Pond, the source of the city's drinking water.
The emergency rule comes just weeks after 1,4 dioxane was found in shallow groundwater in an Ann Arbor city park, and two days after Michigan Congresswoman Debbie Dingell asked U.S. EPA Administrator Gina McCarthy to investigate whether the cleanup was consistent with the federal Clean Water Act and Safe Drinking Water Act.
The new rule requires a cleanup of groundwater with levels of 1,4 dioxane above 7.2 parts per billion. The old criteria was 85 parts per billion.
The new rule also recognizes that humans can be exposed to 1,4 dioxane by breathing in vapor from water that comes into contact with building foundations and basements. The new cleanup criteria for vapor intrusion is 29 parts per billion.
The rule means there will be changes to a consent agreement under which Pall Gelman, the polluter, has been doing the cleanup. Critics, including city leaders, have long bitterly complained that the cleanup was inadequate.
"The state will ultimately need to go to court," says Mitch Adelman of the DEQ. "We're hoping that we can reach mutual agreement with Gelman, the liable party, to amend the consent judgment to remediate based on the 7.2 parts per billion cleanup number, and now we've got to take into account this 29 parts per billion vapor intrusion number that we promulgated today. So what's next? Now we're going to continue discussions with our attorney general's office to get us there."
But city leaders remain unhappy with the state's lack of action in the past, noting they waited three years after the federal EPA set a stricter 1,4 dioxane cleanup rule, before the state changed its rule.
They say the city should not have been excluded as a party to the consent judgment.
Ann Arbor's City Council will hold a special meeting next Tuesday at 7:00 p.m. to seek legal advice on the issue.
Correction: An earlier version of this story said that 1,4 dioxane was found in the surface water of a park in Ann Arbor. It was actually found in shallow groundwater in the park. The state DEQ says the water was far enough below the surface that there is no imminent danger of the chemical getting into building foundations or basements in the area. It has been corrected above.