Hazardous 3M trash buried decades ago in Washington County is being dug up and will be reburied with a protective lining.
In a $20 million job that's the largest of its kind in state history, workers in protective suits are unearthing trash in Lake Elmo that hasn't seen the light of day for more than three decades.
Their mission is not to burn the wastes or haul them off to another state, but to rebury them in a state-of-the-art pit that will keep chemicals that went into Scotchgard and other 3M products from getting into any more drinking water.
Excavating 33 acres of garbage, and then putting it back in the same place, may seem like a curious way to handle trash that has rested undisturbed since 1975.
However, the former Washington County landfill is not your typical dump. Wastes taken there from the 3M Co. in the early 1970s have contaminated groundwater in nearby Lake Elmo and Oakdale.
That has led to one of the biggest attempts to go back and undo decades-old environmental practices that the metro area has ever seen.
Residents have switched to clean sources of drinking water, but the chemicals are still in the landfill, a potent source of contamination for years to come unless removed or isolated.
"We probably would not be doing this extent of work if not for the PFCs," said Jeff Lewis, referring to chemicals formerly made by 3M that were dumped legally at the landfill and were used in products such as stain-resistant coatings and nonstick cookware.
Lewis, who manages the closed landfill program for the Minnesota Pollution Control Agency (MPCA), said that 3M agreed to pay about $8 million of the cleanup costs, and the remainder comes from a combination of garbage fees, state bonding and insurance recovery money.
Lewis said it's impossible to separate the 3M wastes from that of other companies, and from the huge volume of trash from Washington and Ramsey counties. The former landfill was the first to be permitted in the state, and operated from 1969 to 1975.
Old and new school work
The cleanup is an odd combination of old-school and new millennium technology.
The removal part is old tech. On Monday, a pit the size of a college football stadium was buzzing with heavy machinery. A backhoe with a huge maw was eating into a wall of trash and dumping it into waiting off-road dump trucks. At the bottom of the 90-foot pit, four dozers were spreading clay that will form the base of the landfill. Compactors with huge spiked rollers were smoothing it.
The installation is new tech. The landfill will have three layers of heavy plastic liner, separated by layers of geosynthetic material. Teams of workers unrolled huge rolls of the liner on the other side of the pit. The seams of each layer are melted together much like a swimming pool liner.
Lewis said the new landfill will hold mainly old garbage but is designed with a higher level of protection often used to handle hazardous wastes. It will have three distinct layers to prevent any contaminated water in the landfill from reaching ground water: two feet of compacted clay at the bottom, three layers of heavy plastic above that, and two feet of sand and a collection and drainage system above the liners.
"We're confident that we're building a system that will work," Lewis said.
Not everyone shares that optimism.
"I don't understand how this could have been a viable solution -- to dig this up, put in a liner, and then put it all back into the ground," said Judith Blackford, who lives a half-mile east of the landfill. She and others at public meetings advised MPCA officials to truck the trash away to be burned or buried elsewhere. That's the approach that 3M is taking for three company-owned sites where chemical wastes were buried.
Lewis said that the landfill contains many times more waste than all of the 3M sites combined -- more than 2.5 million cubic yards of trash in all, and much of it was mixed with large amounts of dirt when it was buried and covered. Hauling that much waste elsewhere would cost three times more than the $20 million being spent, he said, and burning it would be astronomical.
"This will be as good a construction of any in the state," Lewis said of the MPCA's solution. "It's got a lot of safeguards built into it."
Peter Tiffany, an MPCA senior engineer, said no surprises have come to light so far in the nearly 300,000 cubic yards of waste removed. He recalled one day when a dump truck full of red tape drove away with the tape flying like streamers.
Work will proceed in stages
Patrick Hanson, who oversees the work for MPCA, said the project will not likely be finished until late 2011.
Work will proceed in stages, he said, with waste moved into finished segments of the landfill as others are being lined. The state has received some complaints about construction noise since work began in early June, he said, and one call about odor. The contractor is spraying the waste with a slurry of cement and cardboard paper to reduce odors, he said, and has scheduled minimum heavy equipment operating during weekends when nearby residents are more likely to be home.
Tom Meersman • 612-673-7388