ANN ARBOR, MI – As the Gelman dioxane plume gradually spreads through Ann Arbor, a major concern is it could someday hit Barton Pond and poison the city’s main drinking water supply.

City leaders are taking that threat seriously, and they’re now working on a contingency plan for a potential worst-case scenario.

The city has hired engineering consulting firm Tetra Tech to help with contingency planning for the toxic chemical plume spreading through the area’s groundwater, as well as investigating where more monitoring wells are needed to better track the plume.

The city expects the first phase of work to last six months, with recommendations by year’s end.

The plume, described as a slow-motion environmental disaster, is believed to be many years away from Barton Pond, if it ever reaches it, so city leaders say they’ve got time.

Dan Bicknell, an environmental remediation professional credited with discovering the pollution spreading from the Gelman Sciences property off Wagner Road in 1984, has argued for years more monitoring and cleanup is needed.

At a forum this week, Bicknell reiterated his concern there’s a nearly mile-wide gap between the northernmost monitoring wells. Some are so far apart, he said, that a lobe of the dioxane plume could pass between undetected and move toward Barton Pond, an impoundment on the Huron River where the city draws most of its drinking water.

“That’s a big concern,” he said.

Bicknell also doesn’t think there are enough shallow monitoring wells to adequately warn residents in the West Park and Old West Side areas where there’s dioxane in shallow groundwater that could seep into basements and pose vapor-intrusion risks.

For the last few years, Bicknell has argued $25,000 should be spent to install a network of 12 additional monitoring wells.

City leaders are now considering taking action to improve monitoring, as the city’s legal fight in court to get the polluter to do more has produced little results.

City leaders also are considering joining with other jurisdictions to push for a federal Superfund cleanup.

Brian Steglitz, the city’s water treatment plant manager, is leading the city’s non-legal efforts to deal with the plume.

The city recently brought in a consultant to help navigate the technical side because it’s quite complicated, Steglitz told City Council members last month, indicating the city is working with Tetra Tech’s Patti McCall, who has more than 17 years of experience as a hydrogeologist and some institutional knowledge on the issue.

One of Tetra Tech’s first tasks will be looking at gaps in the monitoring well network, Steglitz said.

The city wants to make sure there’s enough monitoring to provide early warning if the plume is going to Barton Pond.

“And when I say early warning, I mean years to even decades of notice before we would have to potentially implement any type of contingency plan,” Steglitz said.

The contingency plan that’s being developed will address what it would take to remove dioxane at the water treatment plant if the city’s water supply becomes contaminated, Steglitz said.

UV/peroxide treatment is one method, he said, but there are others such as ozone/peroxide that also can be effective.

The plant already is capable of removing somewhere between 40-70% of dioxane, Steglitz said.

With plant improvements in the works, the city will be well positioned to implement any additional treatment needed in the future, he said, estimating it would cost $10 million to build the infrastructure needed to treat for dioxane at the plant.

Update: Steglitz said on Friday, May 31 the cost estimate is now $17 million, which is still lower than a $30 million cost estimate from 2006.

Unrelated to dioxane, Ann Arbor is planning a roughly $90 million rehabilitation of the aging plant.

The city also is moving forward with adding a $2.6 million UV disinfection system, but it’s not designed for dioxane.

The city has detected trace amounts of dioxane in Barton Pond three times in the last six months, and trace amounts also showed up in the treated drinking water for the first time in February. No dioxane has been detected in the treated water since then.

Dioxane is classified by the U.S. Environmental Protection Agency as likely to be carcinogenic to humans by all routes of exposure. It also can cause kidney and liver damage, and respiratory problems.

Just a few parts per billion in drinking water, with long-term exposure, poses a 1 in 100,000 cancer risk, according to the EPA.

Recent monitoring well data shows it’s still in the groundwater at different locations at concentrations of hundreds and thousands of parts per billion. Some well readings so far this year have been as high as 5,200 and 4,600 ppb at the plume’s core.

Gelman Sciences used dioxane in its filter-manufacturing processes between the 1960s and 1980s and discharged massive of amounts of it on the company’s Wagner Road property.

The plume has since spread for miles, while Gelman continues to do limited pump-and-treat remediation that is not aimed at fully cleaning up the pollution. Under court orders, it’s allow to spread through the city at high concentrations and vent to the Huron River downstream of Barton Pond.

A state environmental official estimated in 2016 the expanding northern edge of the plume might be about 30 years away from reaching Barton Pond if it goes that way.

Larry Lemke, a hydrogeologist who has studied the issue, said in 2016 the plume isn’t as simple as it looks on maps, which depict it as a big, amorphous blob approaching the river.

It probably already has reached the river downstream of Barton Pond, he said, suggesting finger-like extensions of the plume may be finding preferred-flow pathways underground. Lemke said in 2016 he believed there was a low probability the plume would contaminate Barton Pond.

Residents shared their frustrations about the ever-expanding plume at a forum hosted by County Commissioner Katie Scott, D-Ann Arbor, at the downtown library Tuesday night, May 28.

Some said they’ve been attending similar meetings about the plume for decades and they’re fed up with the lack of progress.

“I’ve followed this for a long time. I’m frustrated and beyond angry at our government locally for not having dealt with this before it’s hit our watershed here to get into our drinking water,” said Susan Fecteau, a real estate agent who lives on the city’s west side. “That was our fear 30 years ago and here we are still talking about it.”

Rather than continuing to hope for a win in court or taking chances with the EPA, some residents suggest taking local control of the situation by putting a tax or bond proposal on the ballot to fund an aggressive cleanup, and then try to recover costs from Gelman.

A full-scale cleanup is expected to cost tens of millions of dollars and take decades at a minimum, officials estimate.

“From the reading that I have done, I think it will take our lifetime and our children’s lifetime, and possibly even past that,” Scott said.

Bicknell, who favors bringing in the EPA to force Gelman to do a Superfund cleanup, estimates it would take 30-40 years to restore the aquifer to drinking water standards.

To achieve that, he said, the pace of pumping and treating needs to accelerate, and more groundwater extraction wells are needed.

“On the site itself, you have 18 extraction wells over about a 0.2-square-mile area. Off the site, you’ve got a three-square-mile area and you have four extraction wells,” he said. “If you really had a reasonable amount of extraction wells off site, then you would get the plume to be halted and remediated to proper drinking water criteria.”

That might mean more pipes being laid and more pumping stations in neighborhoods, Scott told residents Tuesday night.

“Personally I’d rather see a pumping station in my neighborhood than to continue to see dioxane encroach upon the Huron River,” she said.

There’s concern that, at some point, the plume could start moving faster heading downhill toward Barton Pond, Scott said, adding it isn’t just a Washtenaw County problem.

“If we don’t take care of this sooner rather than later, it’s going to be a southeast Michigan problem, because the Huron River goes all through the bottom of the state,” she said.

Gelman Sciences was acquired in 1997 by Pall Corp., which was acquired in 2015 by Danaher Corp., a multibillion-dollar corporation that many argue has the resources to do a better cleanup.

Another option for removing dioxane from groundwater, Bicknell said, is to set up HiPOx advanced oxidation stations.

“It’s approximately the size of a small, little tool shed and it has an extraction well, it brings the water up, puts it through the HiPOx unit and treats it to below 1 ppb dioxane, and then you can discharge that anywhere,” he said, adding it can go to sewers or storm drains without running extra pipes through the city.

“This is not a unique problem. This is a classical problem which can be solved with classical technology, if you have a polluter who’s willing to come forward and do what’s right to protect the public health.”