Michigan Department of Environmental Quality officials say they're going to closely monitor a slowly expanding dioxane plume in Ann Arbor as it gets closer to the Huron River in the years ahead.

But as it stands now, they're limited by Michigan law and court orders on what they can do from an enforcement standpoint.

Though some pump-and-treat remediation efforts remain ongoing to reduce the amount of dioxane in the groundwater, the pollution is still spreading, and the DEQ can't require Pall Corp. to do a full-scale cleanup.

At this point, the DEQ, following state law and court orders, is essentially trying to minimize the risk of human exposure to dioxane as the plume continues to spread, inching closer to the Huron River, Ann Arbor's primary drinking water source.

Local officials are primarily interested in making sure dioxane never reaches Barton Pond, the city's municipal water intake location, at unsafe levels.

But there remains some uncertainty about where and how the plume might spread, and there are serious concerns about dioxane reaching residential drinking water wells outside of a court-ordered groundwater use prohibition zone.

At this week's meeting of the local Coalition for Action on Remediation of Dioxane, DEQ officials discussed the situation with local officials and residents, including concerns about whether the state is being protective of public health.

"Part of the long-term monitoring plan to track the plume within this prohibition zone includes identifying where it's going," said Mitch Adelman, district supervisor for the DEQ's Remediation and Redevelopment Division.

"And as it approaches the river, we will be focused on does it vent to the river, and, if so, at what concentrations? Or does it underflow the river? Or does it flow along the axis of the river in a downstream direction? So, we can identify if it's venting, where it's venting, and at what concentrations, to evaluate that protectiveness."

If the DEQ has any reason to believe it's not protective of public health and the environment, the department will be "prepared to engage," Adelman said.

However, many local officials and residents want to see more proactive and aggressive cleanup measures starting now to mitigate the risks before it gets to that point, rather than play a game of wait and see.

A map produced by MLive showing Ann Arbor's underground dioxane plume, based on the county's interpretation of monitoring well data in 2013, and more recently based on newer data from the third quarter of 2015 as mapped by Roger Rayle, co-founder and chairman of Scio Residents for Safe Water. Officials monitoring the plume say it's still spreading.

DEQ and local officials aren't able to say with any certainty what might happen once the plume reaches the Allen Creek area. There used to be an open creek running along the west side of downtown Ann Arbor, but it's now enclosed in underground pipes that flush to the Huron River near Argo Dam.

For all anyone knows, the plume, which isn't far from that area now, could follow the alignment of the Allen Creek to the river, though that would be downstream from the city's drinking water intake.

Local officials who want to see more done to minimize the plume's spread have been calling on the state for years to update Michigan's cleanup standards to reflect federal data showing dioxane poses greater cancer risks than previously believed.

If the state follows through, the permissible dioxane concentration of 85 parts per billion in groundwater could be adjusted downward to the single digits.

And if the state then goes back to Washtenaw County Circuit Court to get the consent judgment revised to reflect the stricter state standard, Pall Corp. could be required to do more to track and attack the plume.

Now more than 30 years after the plume was discovered, there still were monitoring well readings showing dioxane concentrations as high as 11,000 ppb last year.

"After 30 years, one would hope we'd be in a better situation," said Dan Bicknell, president of Global Environment Alliance LLC. "We don't have a standard that's protective, and we have a remedy that's not protective."

Bicknell is one of the citizens closely following the issue and is credited with first discovering the dioxane in Third Sister Lake in the University of Michigan's Saginaw Forest while doing research as a public health graduate student in 1984. The lake and forest are right behind where Gelman Sciences, later acquired by Pall Corp., dumped large amounts of dioxane into the environment from 1966 to 1986.

Bicknell hopes the state can make progress on the issue this year, as it's a matter of protecting public health and natural resources.

"Right now you have a remedy that's not protecting the natural resources of the state," he said. "It's allowing the plume just to walk off in all the areas that go toward residential wells, which is not really protective. So, it's a complicated problem, which we've all been working on for 30 years. I'm not sure it's getting any simpler."

Going back to court

There was discussion at this week's CARD meeting about whether the DEQ, if it goes back to court to get the consent judgment changed, would try to get the judge to make Pall Corp. cover the DEQ's ongoing costs related to monitoring and oversight of the plume and the cleanup that Pall is doing.

Some believe the fact that the state's costs aren't covered creates a financial disincentive for the DEQ to be more aggressive.

Through a court settlement in 2014, Pall agreed to pay the DEQ a sum of $500,000 for past costs for monitoring and oversight, but the DEQ gave away its ability to ask Pall to cover future costs for residential well monitoring, Adelman said this week.

Though, Adelman noted, other provisions of the consent judgment could be reopened potentially.

Bob Wagner, the DEQ's Remediation and Redevelopment Division chief, said the outcome of the settlement two years ago wasn't ideal, but it was the best deal the DEQ felt it could get at the time. The case was before Judge Donald Shelton, whose rulings over the years weren't particularly favorable to the DEQ.

Some are hoping the state will have better luck with Judge Timothy Connors now that Shelton is retired and no longer overseeing the case.

Wagner said the DEQ is hoping to get a new assistant state attorney general who is an experienced environmental lawyer up to speed on the case so he can represent the DEQ in court and in any negotiations regarding the plume cleanup.

"You should strongly recommend that he be 'on duty.' Use those words," Roger Rayle, co-founder and chairman of Scio Residents for Safe Water, told Wagner half-jokingly, referencing Attorney General Bill Schuette's campaign slogan.

With the possibility of a change in cleanup standards, the city of Ann Arbor is having discussions about whether the city might have a new opportunity to assert standing and become more engaged in the litigation regarding the plume cleanup as it goes back to court, said Matt Naud, the city's environmental coordinator.

The city already has had some initial discussions with Pall regarding the potential change in cleanup standards. Naud is somewhat hopeful Pall might be cooperative since the company already is thinking about what type of wells would be needed to bring dioxane concentrations in the ground down to meet a new standard.

Naud suggests there's also a need for more monitoring wells to provide additional assurances about where the plume is spreading.

Adelman said previous discussions led to Pall's installation of new monitoring wells in 2014, along with the state providing funding to the county to monitor some additional residential drinking water wells west of Wagner Road and north of Jackson Road.

"We do agree that if the criterion goes down to, just for sake of discussion, say, 7 ppb, additional delineation would be required to determine whether additional remediation is necessary," Adelman said.

Adelman said the DEQ has started initial discussions with Pall about that, and the DEQ's staff is looking at where there are data gaps.

"We're open to people's ideas," Adelman said.

Adelman said the DEQ also has had discussions with the attorney general's office about the possibility of trying to get a voluntary agreement with Pall to follow new standards and do the necessary remediation and risk management.

"To the extent we could get a mutually agreeable outcome, it may be in our benefit to negotiate that as opposed to going to court," he said, referencing the fact that going to court didn't always work out so well for the DEQ in the past.

'Once upon a time'

The plume, which originated from the former Gelman Sciences site on Wagner Road, now covers an area that's more than three miles long and more than a mile wide. Though discovered in 1984, its origins trace back to the 1960s.

Pall Corp. acquired Gelman Sciences in 1997 and eventually shut down operations on the site in 2013, though cleanup of the plume remains ongoing.

Last year, Pall was acquired by Danaher Corp.

Gelman Sciences, Pall Corp., and Danaher Corp. all exist as separate legal entities, and Gelman Sciences is still technically the corporate entity ultimately responsible for implementing the cleanup required by the consent judgment with the state.

Neither Pall's acquisition of Gelman nor Danaher's acquisition of Pall transferred Gelman's responsibility to any other party, said Farsad Fotouhi, Pall Corp.'s vice president of global health, safety and environmental engineering.

"As required by the consent judgment, Gelman Sciences has provided the state with a letter of credit in an amount sufficient to give the state enough money to complete the cleanup if Gelman were financially unable to finish the job," Fotouhi said on Thursday, rejecting the notion that the company could ever abandon its responsibility to follow through on doing the required remediation work.

Fotouhi didn't respond to a request for comment on whether Pall would voluntarily follow a stricter cleanup standard if one is adopted by the state.

Mike Gebhard, a professional geologist and application specialist for Washtenaw County, said Pall has fought for its position in the past, but the company also has shown some signs of being more cooperative lately.

Rayle said at Tuesday's CARD meeting he's concerned Pall isn't more aggressively attacking the highest concentrations of dioxane at the core of the plume. He notes there was at least one reading above 100,000 ppb back in 2012.

"We don't know how much dioxane is left. You guys don't seem to care how much mass is left. It's never been a mass calculation," Rayle told DEQ officials.

"Let's tighten up the cleanup. Let's make some good sound decisions on where is the dioxane, how much is left, which way is it going."

Rayle expressed hopes that Pall might someday be required to estimate annually the amount of dioxane left in the ground.

DEQ officials said they share some of the same frustrations that local officials and residents have about the situation.

Adelman recalled some of the history and sources of frustration for those who would prefer a larger-scale cleanup.

"Once upon a time, when we first got the court to make a ruling on this, the company was ordered to clean up the contaminated groundwater to the then risk-based criterion of 3 ppb," Adelman said.

So, at one point in time, there was essentially an aquifer restoration goal that was legally enforceable, Adelman argued.

But over time, with the easing of regulations in the state's environmental cleanup laws in 1995, and Shelton's court orders from 2004 to draw up a groundwater use prohibition zone to manage the plume by minimizing human exposure, rather than doing a full-scale cleanup, the situation is where it is now.

The plume, under state law and court orders, is allowed to continue to spread and contaminate more groundwater and eventually reach the Huron River, and it already has contaminated more residential drinking water wells outside the city.

"If CARD is asking us to go back and seek to go to a cleanup in the context of the original 1993 consent judgment when there was an aquifer restoration objective, I guess we can talk about that a little bit more," Adelman said on Tuesday.

Rayle said there should be a goal of no more drinking water supplies contaminated by the plume, with any detectable levels of dioxane considered unacceptable.

"We already have, within the last few years, a new homeowner well that doesn't have access to city water that has been contaminated," Rayle said, going on to ask the DEQ: "So, when does this become a crisis?"

'The longer this goes on'

Adelman noted the 2004 court order establishing a prohibition zone set a dualistic remediation objective that allows the dioxane to migrate and eventually reach the Huron River at concentrations up to 2,800 ppb, along with a groundwater aquifer restoration objective using the state's 85 ppb standard.

But because of geological complexities, Adelman said, the DEQ realized it was "virtually impossible or highly resource intensive" to determine which concentrations were in the Unit E aquifer or the adjacent Evergreen system.

"I don't know if we ever could have gotten to the realistic answers about is it Evergreen that requires 85 ppb or is it a 2,800 ppb objective," he said. "And that's what led to the notion of, 'Well, we could spend a lot of time fighting over this and see what the judge ultimately decides, or we can expand the prohibition zone.' So, therein lies some of the downstream consequences of these changes. And again, we argued against establishment of the prohibition zone. We were unsuccessful."

If the DEQ is going to work toward a goal of having no additional water supply wells contaminated, that's another conversation, Adelman said.

Gebhard, who has been working on the issue since he started working for the county in 2001, said there already are some homes on the edge of where the plume has expanded to Elizabeth Road, off Wagner Road near Dexter-Ann Arbor Road, where low levels of dioxane have been detected in residential drinking water wells.

Those homes aren't connected to the city's drinking water system, so they're stuck with dioxane-contaminated wells for now.

Gebhard said some of the wells have shown readings around 1 ppb. Federal data suggests 3 ppb poses a 1 in 100,000 cancer risk.

The state's standard remains at 85 ppb for now.

Because the well readings along Elizabeth Road fall below the cleanup standard, Gebhard said, those homeowners don't have a legal remedy to argue the situation is unacceptable or to ask the state to order Pall to replace their water supply.

Gebhard said the county doesn't take the situation lightly. He said the state has been paying the county to take water samples from the wells on a regular basis, and those samples are then analyzed by the state, with results reported to the homeowners.

There's a belief among local officials and residents that more monitoring needs to be done to ensure other nearby homes on well water aren't tapping into dioxane-laced groundwater as the footprint of the plume continues to expand.

"We still have residential wells to the north and northwest that could potentially get impacted," Gebhard said.

He said there also are residential wells to the south, but there's believed to be a natural groundwater divide in the Liberty Road area that could keep the plume from heading that way, though that's not guaranteed.

There also are concerns about dioxane already flowing into Honey Creek, a tributary of the Huron River, which leads to Barton Pond, where the city gets its water.

The concentrations at this point are low enough and become diluted enough after entering Honey Creek that officials say there's no need to worry about the safety of the city's drinking water coming from Barton Pond. But the city has shut down a water supply well on the city's west side because of dioxane.

Gebhard said even with a stricter cleanup standard, potentially going from 85 ppb to somewhere in the single digits, it's still likely going to take decades to achieve the cleanup objectives, and he thinks it's unrealistic at this point to assume the contaminated aquifers could be restored to non-detectable levels.

"This dioxane is going to remain in the system for a very long time and persist," Gebhard said. "There's still enough in that core area that it has to be managed to maintain protection, so it is a multi-decade problem."

But he thinks the establishment of a stricter cleanup standard could lead to the setting of new triggers, or lower thresholds, for when additional investigation and monitoring is necessary to track the spreading of the plume to make sure it's not reaching additional residential wells in concentrations that exceed the standard, or moving toward Barton Pond in high concentrations.

Even back before 1995 when the dioxane groundwater standard was 3 ppb, Gebhard notes that still meant up to 3 ppb was considered "clean enough," so the concept of restoring aquifers to non-detectable levels was never really on the table.

Gebhard said it was former Gov. John Engler who signed the changes into law that essentially went from a 1 in 1 million cancer risk to 1 in 100,000. He said other states still use the 1 in 1 million standard as the acceptable risk level.

The more the plume is allowed to spread, Gebhard said, the more difficult it becomes to track the different pathways and where its edges are moving.

"The longer this goes on, the more difficult the remediation becomes," he said. "The problem will get larger, not smaller."

Asked whether he'd want to see a time-certain deadline imposed on Pall to clean up the plume to a certain standard, Gebhard said it was unrealistic when Judge Shelton set a five-year deadline back in 2000, and it remains unrealistic today. Though, he would like to see dioxane removed from the groundwater at a faster rate.

While there has been talk of other remediation techniques, Gebhard believes Pall's current pump-and-treat solution -- whereby water is extracted from the ground, treated, and discharged back into the environment with dioxane at lower levels -- is the most effective solution until something else can be developed.

Though, right now that dioxane-laced water is being discharged into Honey Creek, and he notes the city more than a decade ago proposed installing a pipeline to have the discharge water enter the Huron River downstream of Barton Pond. He said such a pipeline would help minimize the risk to Ann Arbor's water supply.

Ryan Stanton covers the city beat for The Ann Arbor News. Reach him at ryanstanton@mlive.com.