Groundwater pumping deals with pollution but stresses supply

Carbon filtration
Thomas Flicker, a principal project engineer for 3M's Cottage Grove plant, describes the carbon filtration process in Cottage Grove, Minn. Thursday, April 17, 2014.
Jeffrey Thompson/MPR News

Aside from the four pump houses, the windswept, expansive field on the Woodbury-Cottage Grove border isn't obviously an old industrial waste dump. Several large trees and a spot where 3M employees launch model airplanes certainly don't give it away.

Yet the wells' humming motors power a groundwater pumping operation so large it could supply enough water for a small city. The water is contaminated, and roughly 4 million gallons of it are pulled out daily to prevent perfluorinated chemicals -- PFCs -- from spreading underground.

Beneath the Surface, a special Ground Level report

The site is one of more than two dozen places in the Twin Cities metro area where groundwater is being pumped and treated to contain pollution. All told, this adds up to 4 billion gallons of water every year in a region where concern is rising about the long-term availability and use of groundwater. In the north and east metro in particular, where the state is trying a new approach to groundwater use, pollution containment accounts for more than 10 percent of all groundwater being pumped, according to the Minnesota Department of Natural Resources.

But the volume of water pumped to contain pollution can't easily be reduced, said Paul Putzier, a DNR hydrogeologist.

"It's just like living next to the railroad tracks," said Putzier, who is overseeing a new groundwater management area that covers all of Ramsey and Washington counties and part of Anoka County. "It's just something you have to deal with."

10% of groundwater
In the north and east Twin Cities metro area, where the state is focusing a new approach to groundwater management, wells pumping water because it is contaminated account for about 10 percent of the total groundwater being tapped.
MPR News

The polluted groundwater sites are expected to need ongoing remediation for decades, and the overall volumes of contaminated water being pumped could rise as officials find new pollution sites and respond to evolving health guidelines for new or lesser-known contaminants. That could put a significant restraint on how much more groundwater the Twin Cities can tap to quench its increasing thirst.

So as cities restrict lawn watering and figure out creative ways to keep golf courses green, some are eyeing the large pollution containment sites and asking whether there are alternatives to pumping, treating and releasing all that water. The most promising answer so far: Find a way to use the once-contaminated water again.

At the two largest pollution containment sites -- the 3M Woodbury Disposal Site and the Twin Cities Army Ammunition Plant -- that's already happening.

Pumping groundwater to contain pollution

More than 4 billion gallons of water are pumped out of the ground in the Twin Cities every year to remove contamination. Some of that water is treated and put to use but much is not. This map shows the 26 sites in the seven-county area that each pump more than 5 million gallons per year. The two sites in yellow pump more than a billion gallons a year. The shaded area is where a new state approach to dealing with groundwater concerns is focused. Figures are 2008-2012 annual averages, except where noted.
Source: Minnesota Department of Natural Resources.

3M treats and re-uses

The water pumped from 3M's Woodbury site, last used for waste disposal in the 1960s, makes a six-mile underground trip in an 18-inch pipe to the 3M Cottage Grove plant. It arrives at a huge water treatment building with two long rows of tanks roughly the size of concrete mixers.

The PFCs aren't visible in the clear water coming out of the wells. Researchers are still studying the chemicals' impact on human health, but organ tumors and changes in liver and thyroid functions in animals exposed to the chemicals have raised the alarm.

Water from both the Woodbury site and several groundwater wells on the Cottage Grove property go through the tanks, where tiny grains of carbon filter the chemicals out. The tanks, each filled with 20,000 pounds of carbon, function similar to the filter on Brita water pitcher.

Then the treated water is distributed throughout the 3M plant for both cooling and chemical processes, leading to products like reflective coating for road signs and adhesives for Scotch tape and Post-It Notes. The water gets treated again before it's discharged into the Mississippi River.

Water pipes
Pipes direct water in and out of carbon filtration tanks at 3M in Cottage Grove, Minn. Thursday, April 17, 2014.
Jeffrey Thompson/MPR News

State officials monitoring groundwater use in the metro area say 3M's pollution remediation site is one of the few where millions of gallons of groundwater is not only being pumped and treated, it's also being re-used.

Still, 3M site director Mike Bahma said the plant doesn't really need to use that much water, so the company is working with the Minnesota Pollution Control Agency to reduce the amount of contaminated groundwater being pumped in Woodbury.

"We have a number of projects ready to go that are scoped and feasible to allow us to reduce water usage if we can come to an agreement," he said. "We're always looking to reduce our impact on the environment, whether it be air, water, raw materials."

Reducing pumping volumes at groundwater remediation sites is tricky, and MPCA officials said the last time it was attempted at the 3M site in 2011 it didn't quite work. PFC levels increased in some of the monitoring wells, and 3M had to restore its previous groundwater pumping rates, said Sandeep Burman, who manages site remediation and redevelopment for the MPCA.

"All worked out fine, but it really highlighted the concerns about this very delicate balancing act of trying to optimize your pumping so you can meet your pump and treat goals without compromising the safety of private wells that are so close by," he said.

Filtered water
A jar of non-potable carbon-treated water is displayed at 3M in Cottage Grove, Minn. Thursday, April 17, 2014.
Jeffrey Thompson/MPR News

5 million gallons or more each year

These are the companies and governmental organizations that pump more than 5 million gallons a year of contaminated groundwater in the seven-county metro area. All figures are the annual 2008-2012 average except as noted.

  1. Twin Cities Army Ammunition Plant : 2 billion gallons

  2. 3M Woodbury Disposal Site : 1.5 billion gallons

  3. 3M Cottage Grove plant : 951.3 million gallons

  4. General Mills : 274 million gallons*

  5. Naval Industrial Reserve Ordnance Plant Superfund Site : 265.4 million gallons

  6. Flint Hills Resources-Pine Bend refinery : 116 million gallons

  7. City of St. Louis Park : 102 million gallons

  8. Anoka Municipal Regional Landfill : 95 million gallons*

  9. Josilyn Manufacturing : 70 million gallons

  10. St Paul Park Refining : 66.7 million gallons

  11. FMC Superfund Site : 55.7 million gallons

  12. BAE Systems : 55 million gallons

  13. Waste Disposal Engineering Landfill - Andover : 43 million gallons

  14. 3M Oakdale dump site : 37.3 million gallons

  15. Soo Line Railroad Company : 34 million gallons

  16. New Brighton MacGillis & Gibbs Superfund Site : 24.2 million gallons

  17. Marathon Petroleum : 21.5 million gallons

  18. Andersen Corp. : 16.4 million gallons

  19. Kurt Manufacturing : 15 million gallons

  20. University of Minnesota : 14 million gallons

  21. Baytown Township groundwater contamination site : 13.7 million gallons

  22. Carver County parks : 12 million gallons

  23. Whirlpool Corp. & Reynolds Metals : 11 million gallons

  24. BNSF Railway : 9 million gallons

  25. Brenntag Great Lakes : 5 million gallons

  26. Nilfisk-Advance Inc : 5 million gallons

* indicates single year amount

Conservation preferred to re-injection

Private well owners and neighboring cities will be watching closely if 3M and the MPCA decide to reduce pumping again. Klay Eckles, Woodbury's public works director, points out that 3M's Woodbury site pumps as much water as the entire city of Woodbury during the low-demand winter days. Pollution sites like 3M's should be tapped for solutions, he said. "That's a lot of water. It's not that we shouldn't remediate. That protects our groundwater," he said. "It's just, are we doing it in the most effective way?"

Woodbury and 3M share the same Prairie du Chien-Jordan aquifer along with many other cities in the north and east metro. The underground formation is like a sponge with dozens of straws sticking out of it, and those monitoring the situation say the sponge is slowly getting drier.

Copper pipes
Copper pipes are labeled in the carbon filtration building at 3M in Cottage Grove, Minn. Thursday, April 17, 2014.
Jeffrey Thompson/MPR News

Much of the water being sucked out by cities and industry goes down the drain and eventually into the Mississippi River. Concerns about altering the chemistry of the groundwater have thus far prevented a strategy common in the water-scarce West: re-injecting treated wastewater back into the ground.

Instead, efforts in the north and east metro groundwater management area have focused on conservation. Woodbury alone is expected to grow by 30 percent between now and 2030, but the city wants overall groundwater use to stay flat, Eckles said.

He said there's more scrutiny than ever on how much water cities' use. For example, the DNR hasn't yet given the city the go-ahead to use its newest groundwater well. And the city has had to make sure its pumping doesn't affect the Valley Creek trout stream.

"It's very difficult to understand what's happening 500 feet under the ground," Eckles said. "Studies have been done and they provide a need for some caution, but none of us really know what will happen 20 years from now. And we're exercising caution and looking at all the issues that face us."

In New Brighton, treating it and drinking it

Remediation site
Four well houses are located on 3M's remediation site in Woodbury, Minn. Ground water from the former dump site is piped to 3M's Cottage Grove plant location for filtering before being dumped into the Mississippi River.
Jeffrey Thompson/MPR News

While most cities conserve, one community within the groundwater management area is in a unique position.

In New Brighton, residents are drinking previously contaminated water from a groundwater plume that spread from the Twin Cities Army Ammunition Plant (TCAAP) in Arden Hills.

"Our water is, I might argue, the safest, at least most-monitored water in the state," New Brighton City Manager Dean Lotter said.

Trichloroethylene -- TCE -- is removed from groundwater in the city's water treatment plant, which uses a carbon filtration system similar to 3M's. Exposure to the industrial solvent can negatively affect people's central nervous system, as well as liver and kidney function.

Under a settlement agreement between New Brighton and the U.S. Army, the Army helps pay for the more expensive water treatment to ensure the water is safe to drink. Meanwhile, the city is required to pump a large volume each year -- 500 million gallons more than it needs -- to help keep the TCE plume underground contained.

"So while a lot of communities are being told stop using so much, stop pumping so much, we have a commitment we have to honor where we pump way more than we need to get rid of that contamination," Lotter said.

But rather than dumping the extra water down the drain or taking lawn sprinkling to the extreme, New Brighton sends water to neighboring Fridley.

The Army Ammunition Plant and 3M own the biggest pollution containment sites in the Twin Cities. The third largest site is in Fridley, where a combined more than 300 million gallons of groundwater is pumped each year to remove TCE and other pollutants from two former Navy manufacturing and waste sites.

The water treated in Fridley goes down storm sewers and into the Mississippi River, and most of the other pollution containment sites aren't serving a dual purpose like they are at 3M and in New Brighton.

"You pump and treat because that's all you can do at that point, but you are depleting the aquifer," the MPCA's Burman said. "At some point in time that may be a constraining factor on development or whatever else you want to use the water for, so I think we're acutely conscious that when we do have a pump-and-treat system that optimization really becomes a prime factor."

Even greater pollution containment pumping is possible in coming years.

Burman said the MPCA adds new superfund sites every year, and sometimes must revisit sites officials thought were cleaned up because of new research linking contaminants to health risks.

For example, the Minnesota Department of Health last year revised downward its recommendations for allowed levels of TCE in drinking water, prompting the MPCA to reconsider its remediation plans for several sites. And 3M recently added wells at its Cottage Grove plant after state officials said too many PFCs, also a contaminant for which health risks are still being identified, were getting into the river.

The DNR's Putzier said sustainability concerns should prompt discussions about using water more wisely. The management area he oversees is an effort by the DNR to bring together water users in the north and east metro area to do just that.

"How are we using this pristine resource? Should we be watering our lawns? What are we doing for pollution containment? It's going to be small changes that are going to add up to the changes we need," he said.

"If we could find ways to use our groundwater, this beautiful, pure resource, a second time in any situation, we would solve many of our long-term sustainability problems."

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