State promises new groundwater cleanup standards for Ann Arbor dioxane plume
After years of pressure from local officials, the Michigan Department of Environmental Quality is updating its cleanup standards for 1,4-Dioxane.
According to a Monday press release from the Michigan DEQ, the department will be formally unveiling a new standard of 7.2 parts per billion in April.
“The more protective standard is based on new calculations completed by the DEQ using a science-based process, including current EPA toxicity data and Michigan-specific exposure factors,” the release read.
A large, slow-moving plume of groundwater contaminated with 1,4-Dioxane currently sits underneath parts of Ann Arbor, originating from the improper wastewater disposal practices of Gelman Sciences between 1966 and 1986. Exposure to Dioxane can cause liver and kidney failure and damage to the central nervous system.
The contamination has been monitored by a network of test wells maintained by Michigan's DEQ since 1992, though cleanup efforts have been limited and the plume is projected to have the potential of reaching the Huron River, a main water source for the city, in the coming decades. Though dioxane has never been detected in the municipal water supply, 120 private wells in Ann Arbor have been closed due to contamination, and public scrutiny on the issue has recently flared up in light of the Flint water crisis.
A common criticism from residents over past years has been the discrepancy between the Michigan DEQ’s cleanup standards and current science. While the Environmental Protection Agency’s 2010 standards state 1,4-Dioxane has a carcinogenic risk at 3.5 parts per billion in groundwater, the Michigan DEQ’s cleanup threshold is currently at 85 parts per billion. At the plume’s densest points, concentrations in excess of 1,000 parts per billion have been detected by test wells. The new standard, at 7.2 parts, doesn’t completely make up for the discrepancy, which the press release said was due to enforceability concerns.
“The federal screening level of 3.5 ppb — which is not enforceable — assumes an exposure period of 70 years,” the press release read. “The state standard assumes an exposure period of 32 years to provide a more realistic assumption of risk and greater protections for the public. The Michigan standard will be among the most protective state standards in the country.”
In a press release, U.S. Rep. Debbie Dingell (D-Dearborn) said she was pleased with the proposal and would continue to press the EPA for increased monitoring of contamination.
"The City of Ann Arbor has been waiting for years for MDEQ to finalize stricter dioxane cleanup standards that reflect the latest science and guidelines from the EPA, and I am glad the standard is now out," Dingell said. "The community deserves to know that their drinking water is safe, and I encourage residents to take full advantage of the public comment period as MDEQ finalizes the proposed rule."
The Michigan DEQ has been repeatedly delayed in meeting its deadlines to change the standards in the past, delaying multiple deadlines and drawing frustration from county officials during a February meeting when they announced another delay.
The press release also noted that the governor’s proposed fiscal year 2017 budget includes an additional $700,000 specifically for addressing the dioxane plume, and that a Scio Township resident whose well water exceeded the 7.2 ppb threshold has now been linked to the city water supply.
A revised cleanup standard could lead to an overhaul of the current monitoring and cleanup system of the plume, according to city officials. In a February interview, City Councilmember Sabra Briere (D–Ward 2) said a lowered cleanup threshold would allow the state to seek additional legal damages from Pall Corporation, which acquired Gelman and holds its legal liabilities.
“Once we have (revised standards), the city and the county are in a position to go to the courts, and ask the courts to enforce to that standard instead of the 85 parts per billion,” Briere said. “That allows us to open up the entire discussion about how the enforcement works, what the cleanup looks like, how effective the cleanup needs to be.”
City Councilmember Chuck Warpehoski (D–Ward 5) said the new standard is late but welcome.
“It’s a great step; it’s long overdue,” Warpehoski said. “Had the DEQ made this decision when they should have, that family in Scio Township that was drinking dioxane-laced water wouldn’t have been doing that, but now is better than never.”
Warpehoski added that the city has been meeting with the state attorney general’s office to move forward on new legal action pertaining to the plume.