Cleanup begins at Superfund site in Esko

Two parking lots in downtown Esko are the site of the latest Superfund cleanup in Carlton County.

The site in Esko amounts to the Post Office and its lot, plus another lot used as an auxiliary student parking lot by Esko High School during the school year.

Similar to the Frank Lloyd Wright gas station in Cloquet, dry cleaning chemicals are the main culprit. A building on the site that was first a creamery, then a coin-operated dry cleaner, was demolished in the 1980s. Chemicals used in dry cleaning left behind contaminants, including mainly perchloroethylene, aka PCE or tetrachloroethylene. Exposure to tetrachloroethylene may cause irritation to the eyes, skin, nose, throat and respiratory system, and may also cause liver damage and is a potential occupational carcinogen, according to the National Institute for Occupational Safety and Health.

"We have a lot of dry cleaner sites across the state that we are cleaning up," Minnesota Pollution Control Agency remediation supervisor Tim Grape told Esko school board members Monday.

"Back in the day they dumped the spent PCE out the back," he said. "There was no management of the material if it spilled at all."

PCE doesn't break down quickly, he added, explaining when it does start to break down, it does so into other volatile chemicals.

Unlike the gas station in Cloquet, where the contaminants were making their way up through the soil as vapor, potentially impacting the air inside the building, the Esko contaminants are making their way down into the groundwater. Esko residents have private wells that draw groundwater from bedrock aquifers.

"There's a lot of talk about vapor intrusion the last 10 years or so ... the v

apors come off the groundwater plume and can build up under a building, then work their way in through cracks and become an inhalation risk issue," Grape said.

But they've checked buildings in the area, and that's not the issue.

"What's happening with this plume is, it's diving," Grape said. "So, it's going deeper into different aquifers, and it's not spreading out horizontally, which is good from the vapor risk standpoint."

The plume is migrating southwest of the site, "diving toward the river," Grape said, getting deeper as it travels farther away and ultimately affecting three aquifers, he explained.

The plume is not spreading toward the school, Grape confirmed. The wells there are not affected and there is no risk of vapor intrusion either.

According to the MPCA, affected wells include the Esko Post Office, where the state installed a carbon filter to treat the water. Republic Bank was advised to not use its water for drinking.

Additionally, the MPCA is monitoring a number of residential wells, which do not need treatment at this point. The state agency would install treatment systems if needed.

Remediation efforts

According to the MPCA website, Esko groundwater contamination is found at depths ranging between 11 and 67 feet beneath the ground surface.

Removal of the contaminated soils began after school got out and is expected to continue until July 15. The plan is to replace the contaminated soil with clean soil and stop any further contamination. Grape said workers are digging down to the water table, 10-15 feet down, to remove as much contaminated soil as possible.

The cleanup also includes installing a groundwater treatment system and monitoring wells to ensure area drinking water sources are protected.

The MPCA plans to repave the school and post office parking lots in time for school.

School board chair Jerry Frederick thanked the MPCA officials for delaying the project until this summer, when the kids are out of school.

Superfund sites are contaminated sites that exist nationally due to hazardous waste being dumped, left out in the open, or otherwise improperly managed. Being identified as a Superfund site allows national or state environmental protection agencies to clean up contaminated sites and forces the parties responsible for the contamination to either perform cleanup or reimburse the government for cleanup work.

The state originally discovered the contamination in 1994, as part of a petroleum release investigation at the Esko Self Service site. Benzene was detected above health standards, and investigations in 1996 and later found PCE and related chemicals. The petroleum remediation was deemed complete in 2008.

Total cost of the groundwater contamination project is estimated at $1.2 million. The site has no viable responsible party who could pay for the cleanup, so the state must perform the needed work per federal and state law.

"Thanks to bonding dollars from the state legislature, we're finally able to take care of this project and call it good," said MPCA spokesperson Stephen Mikkelson.

For more details, search for MPCA Superfund online, then select "Esko groundwater contamination site" from the chart.