Next week, excavators will start digging into a former landfill in Woodbury and removing soil contaminated with perfluorinated chemicals.
The excavation is part of an effort to clean up three landfills in the east metro, that are contaminated with chemicals formerly made by 3M.
3M made Scotchgard, firefighting foam and other products using perfluorinated chemicals, or PFCs, at its plant in Cottage Grove. The company no longer uses those chemicals, but for decades 3M deposited tons of waste from its operations at several landfills.
The chemicals leaked from the landfills, contaminating public and private wells and the drinking water of thousands of residents. 3M has paid for filter systems or bottled water for affected families.
Now, under an agreement with the Minnesota Pollution Control Agency, 3M has hired a contractor to clean up the soils in the various landfills.
In Woodbury, the landfill covers about 40 acres, but 3M has bought up hundreds of acres around it. 3M wasn't the only industry to use this landfill. Other companies and cities also deposited waste here in the 1960s. At one point, the landfill caught fire.
Today, the Woodbury site is an open field, graded and planted with grass, and surrounded by cornfields.
Testing has narrowed the scope of the PFC problem to three areas, each the size of a roomy suburban yard.
An orange plastic silt fence threads around the field, marking the outer boundaries of the area to be dug up. Mike Corbin calls the area inside the fence the exclusion zone. Corbin is an engineer who's helping with the project.
"The excavators will be in the exclusion zone, so they're going to load into the trucks, so the trucks never have to operate within the impacted exclusion area," Corbin said. "That way, the trucks always stay clean when they're going out on the public highways."
The trucks will be lined with plastic, and the whole package, plastic and all will be put in a specially-prepared section of the SKB Landfill in Rosemount. 3M spokesman Bill Nelson said it's a safe and permanent solution.
"Leachate, or any remaining water in the waste will be collected and these materials will not escape into the environment," Nelson said.
In the Woodbury field, four wells pump groundwater from beneath the contaminated site. Engineer Mike Corbin said they keep polluted water from spreading to surrounding homes.
"It's providing capture and containment of that water that's in this area, so any chemicals in the water can't escape and impact groundwater outside this area," Corbin.
The groundwater from the site is piped to 3M's plant at Cottage Grove, five miles away. There it's used as a coolant, and then it's dumped into the Mississippi River.
3M has promised to build a water treatment plant to clean it up before it reaches the river. That'll happen in about two years.
Woodbury is the first of three sites to get the soil-removal treatment. 3M said excavation will start at another former disposal site in Oakdale later this year, and it's working on plans for land around the plant in Cottage Grove.