Eight years ago, Jim and Judith Blackford got a letter from the Minnesota Pollution Control Agency. It said they needn't worry that their well water might be polluted by an old landfill a half mile from their Lake Elmo home. The groundwater flowed the other way. Last year, the Blackfords found out their well water carried traces of a 3M chemical probably discarded in the landfill more than three decades ago. The Blackfords' experience illustrates one of the abiding mysteries of groundwater pollution: Chemicals dumped in soil sometimes end up in surprising places.

"You feel kind of sullied," said Judith Blackford, who lives with her husband and son on a 5-acre remnant of her parents' former farm. The family now drinks bottled water.

Across the metropolitan area, groundwater laced with chemicals lies beneath at least 35 communities. Hidden pollution from dumps and industrial sites has slid beneath lakes, crept up to river banks and slipped through subterranean valleys to contaminate far-off wells.

It takes detective work to find out how it got there and where it might be going next. Engineers often probe the ground with dozens of wells, drawing water samples to analyze for a cocktail of pollutants. They study that data and the flow of groundwater to map the extent of pollution, which is called a plume.

Two adjacent plumes of a 3M compound called PFBA contaminate groundwater beneath a quarter of Washington County. To find those plumes, the state Health Department sampled 1,338 residential wells, and detected 3M chemicals in 56 percent of them. Even so, scientists still don't fully understand how the chemicals spread so far and wide.

'Some of it we are not going to be able to answer with any certainty," said Virginia Yingling, a hydrologist who has mapped the plumes for the state Health Department. "There are places where we will be sampling intensively because we just don't know what is going on."

Until recently, other state officials were sure nothing was going on with Judith and James Blackford's well.

"Your well ... is not impacted by the landfill," hydrogeologist Ingrid Verhagen of the Minnesota Pollution Control Agency wrote them in 2004.

But their well and 12 neighbors' -- once thought not at risk because they were essentially uphill from the landfill -- have tested positive in the past year for PFBA, a chemical 3M once made for coating photographic film.

Now, Verhagen and others believe that the government's decades-long cleanup program at the landfill inadvertently raised the water table, and redirected pollution into the wells.

It didn't help that PFBA seems to zip through groundwater, outpacing other pollutants in the same landfill, such as volatile organic compounds (VOCs).

"Those compounds are amazing," said Verhagen. "They travel to places a VOC would never go."

The water table near the landfill now is dropping, but it could take three years for residents' wells to be rid of PFBA, she said. Meanwhile, the state is supplying homeowners with in-house filtration systems, though the Blackfords are holding out for municipal water hookup.

They don't think the chemical has harmed them or their two adult children, one of whom still lives at home. The risk of low-level contamination is that a lifetime of drinking the water might increase their odds of disease.

"We've always been really aware of chemicals in our environment," said Judith Blackford. "It kind of sucks some of the joy out of life knowing that it is in your water system. You can't quantify it. You can't say what it is going to do."

Surprise beneath a lake

In North Oaks, the exclusive suburb in Ramsey County built on a farm once owned by railroad magnate James J. Hill, residents thought their problems with buried chemicals were behind them in 1994.

That's when the last chemical drums were dug out of an old dump on Hwy. 96, and 60 residents on the east side of Gilfillan Lake stopped using wells contaminated by a pollution plume. The residents switched to municipal water.

But the plume of vinyl chloride kept moving. Over the next decade, it silently slipped beneath the lake and under a tree-lined street and houses on the opposite shore.

The cancer-causing chemical turned up in the Eisenschenk family's well three years ago.

"I was really worried when I first heard about it," said Kendra Eisenschenk, 15, who lives at home with her parents and younger brother.

Suddenly, some of her friends couldn't visit because their parents worried they would drink contaminated water, she said. Later, when everyone understood that the family had switched to bottled water, her friends came back.

It won't be as simple to remedy the groundwater.

Alcoa and Whirlpool, who are responsible for the cleanup because their wastes were disposed in the dump, say they have spent $6.4 million on the site over 20 years. Now, various additional remedies costing up to $3.1 million are under consideration.

One option is to drill a well to extract the pollution, a job that could take five to 10 years, said consulting engineer Ron Frehner.

It's not the only time pollution has slid beneath water bodies. A far-larger slug of chemicals from the Twin Cities Army Ammunition Plant lies beneath three lakes, including the 183-acre Long Lake in New Brighton. It affects none of the lakes; the chemicals lie in deeper aquifers, forcing two cities to purify their drinking water at a cost of $1.7 million a year.

Engineers are investigating how 3M chemicals that were dumped mostly in Washington County have turned up on the other side of the Mississippi River in Dakota County. One theory is that they slipped through fissures beneath the river bottom.

How did that get here?

Sometimes the mystery is not where underground pollution is headed, but where it is coming from.

For years, state officials held the Lake Elmo Airport responsible for a large area of groundwater contaminated with the degreaser TCE -- only to discover later that the primary source of the pollution was a mile away.

Like investigators reopening an old case, engineers three years ago began testing groundwater west of the airport, using probes that sniff for pollution. Eventually they drilled a well on the property of a former manufacturer of equipment for installing treads on tires, now the site of a food market. It showed TCE levels 10,000 times higher than the drinking water standard.

It was "the mother lode," said Stephen Thompson, a supervisor in the Superfund program. But the equipment company no longer exists, so the state must foot the bill for a system to pump out the pollution -- $1.5 million next year, and more in the years to come.

In Edina and Blaine, the sources of two large plumes of groundwater pollution that taint city wells have eluded investigators for years. Adding to the puzzle, the Edina pollution stretches into neighboring St. Louis Park, intersecting with another plume of contaminants.

Only one of Edina's 18 municipal wells showed traces of vinyl chloride, and it was shut down and will be replaced, said the city's public works director, Roger Glanzer. If the polluter isn't found and held responsible, the city or state must bear the costs of dealing with the problem.

"Water can be very old and pollution can come from a number of different sources," Glanzer said. "If those sources no longer exist, it's very difficult to figure out where they might be."

State officials spent years and more than $500,000 in Blaine investigating the source of an industrial chemical known as DCA that was found in two municipal wells in 1993.

"We were able to find the plume but we could not find the source," said state Pollution Control Agency project manager Steven Schoff.

The plume encompasses more than 1½ square miles. The city of Blaine spent $276,000 last October to install equipment that strips out the chemical before it enters the water supply. Over time, officials hope the system will gradually clean up the groundwater.

More mysteries to come?

One big unknown about groundwater is whether other chemical surprises will come along like 3M's perfluorochemicals, or PFCs.

The compounds used in Scotchgard, Teflon and other coatings weren't on regulators' radar screens until 2002, when the company stopped making them. Widespread environmental testing for PFCs didn't begin until 2004.

Even today, the rap against PFCs is not that they're known to hurt people -- studies of PFC workers don't show it -- but that the chemicals resist breaking down easily and tend to accumulate in the tissues of animals and humans.

Thousands of other chemicals in commercial use may share some of the same qualities, yet existing regulatory standards don't require assessments of their ecological or human-health consequences, according to recent Canadian research in the journal Science.

"We are always playing catch-up," said Barry Kelly, a researcher in environmental toxicology at Simon Fraser University in British Columbia. "We are years behind trying to determine the effects in the environment."

More than 15 million chemicals are used commercially, according to the American Chemical Society. About 500,000 are rated hazardous by the U.S. Environmental Protection Agency, and 129 are priority pollutants -- the ones commonly found.

Brad Moore, state pollution control commissioner, said he expects the future will bring new environmental concerns with some chemicals. He said the best hope is vigilant monitoring and research "to stave off some of those potential problems."

Unfortunately, it's not practical for a lab to screen for more than a few hundred chemicals during environmental investigations, said John B. Erdmann, principal environmental engineer for Wenck Associates, a cleanup firm based in Maple Plain.

"So really it's like we are in this huge cave, and we have a really tiny flashlight," he said.

David Shaffer • 612-673-7090



David Shaffer • dshaffer@startribune.com