Woodbury’s new $11 million water treatment plant is up and running, after crews constructed it in a record five months to scrub 3M Co. chemicals found in the groundwater.
City leaders say the plant is a temporary fix while state agencies determine the best long-term solution to addressing industrial pollutants now found in underwater aquifers that supply water to 14 east metro cities.
The plant comes on line as daily water usage has jumped from 5 million gallons last winter to as much 15 to 20 million this summer.
Woodbury broke ground in March on the plant at Tower Drive and Valley Creek Road. It started operations in mid-June just as more residents watered their lawns, washed their cars and began filling kiddie swimming pools, said Jim Westerman, the city’s utilities division manager.
A 2007 agreement between 3M and the state paid for the new treatment plant, which will be used for the next five to seven years. Westerman credited that collaboration for the swift construction, saying such facilities often take years to build.
Woodbury, the largest of the affected east metro communities with a population of nearly 75,000, had stopped pumping water from seven of its 19 wells when chemicals called per- and polyfluoroalkyl substances (PFAS) were detected.
The new plant uses carbon technology similar to popular consumer sink-mounted filters to treat water. It allows the city to pump from four of the seven wells that were shut down, Westerman said.
“Right now we are able to meet all the needs of our community and make sure our water meets all the federal and state standards and guidelines,” said Woodbury Mayor Anne Burt.
“While it’s considered temporary, it is a brick-and-mortar facility. It looks very permanent, with concrete and pipes,” Westerman said. “It’s been constructed in such a way that a significant portion can be reused at a later date.”
A second settlement of $850 million reached in 2018 between the state and 3M will pay for a long-term solution.
Cottage Grove, which is just south of Woodbury and relies on groundwater, also has built three interim water treatment plants to filter out the 3M pollutants. Its newest treatment facility went online this month and cost $3 million, which was covered by the 2007 agreement between 3M and the state, said Ryan Burfeind, the city’s public works director and city engineer.
Looking for a long-term fix
Woodbury, like many Twin Cities suburbs, relies on groundwater for its water supply and treats it at each well site.
“All Woodbury has to do to treat the groundwater is pump it from the ground, add chlorine and fluoride and it’s off to our customers,” Westerman said.
That’s still the case for a majority of the city’s wells. But the detection of a chemical plume in the aquifers in the early 2000s forced the state and affected communities to consider short- and long-term mitigation plans.
“The problem with these chemicals is they are very persistent in the environment. There is no known natural decay method to break them down,” said Westerman, who is a hydrogeologist.
PFAS make up a large group of manufactured compounds used to make consumer and industrial products more resistant to stains, grease and water, according to federal toxicology programs.
In some studies, high levels of PFAS in one’s system are associated with higher cholesterol, changes to liver function, reduced immune response, thyroid disease, and increased kidney and testicular cancer, according to the Minnesota Department of Health.
The state Pollution Control Agency (MPCA) and Department of Natural Resources (DNR), which reached the settlements with 3M in 2007 and 2018, will release recommendations this fall on the best long-term solution to contaminants.
Options being studied include building a permanent regional water treatment facility or smaller community treatment plants, or switching community water supplies from groundwater to surface water drawn from either the Mississippi or St. Croix river.
Last fall the Woodbury City Council passed a resolution that said it’s committed to preserving groundwater as the city’s water source and achieving the lowest detectable levels of PFAS to protect residents. Cottage Grove leaders also wish to remain on a groundwater system, Burfeind said.
Burt said Woodbury residents are best served with a groundwater system, which requires less treatment than surface water. Compare the appearance of water drawn directly from aquifers vs. water taken from the Mississippi River without treatment, she said, and “you can see the difference.”