A long-polluted patch of ground in Esko next to the post office will get an injection next week to see if adding a new compound into the ground can help render old dry-cleaning solvent harmless.
Starting Tuesday, the Minnesota Pollution Control Agency plans to inject a purple compound called sodium permanganate into the soil and groundwater. The compound is expected to convert the dry-cleaning solvent into non-harmful components by oxidizing it through a chemical reaction.
The three-day project is the first of its kind in the Northland, although chemical injections have worked in other regions to decontaminate soils polluted by leftover dry-cleaning solvents. Other injections have been used to remove arsenic from groundwater.
"Every site is different for soil and chemical characteristics. So we don't know how it will work until we try it. But, using (contaminated soils) from the site, it worked on bench-scale testing in the lab," said Heidi Bauman, Superfund site coordinator for the PCA.
About 2,500 gallons of the solution will be injected into the ground from 19 to 40 feet under the surface. It's not clear whether a single injection will solve the problem or if more may be needed, if it works at all.
Bauman said using a chemical neutralizer may be faster, cheaper and less intrusive than trying to dig up and remove all the contaminated soil.
"If we can treat it where it is, rather than pumping or excavating it out and taking to a hazardous waste landfill, that's a better option," Bauman said.
The site, near the post office, has long been known to be polluted. In 1996, while looking for a petroleum leak from a nearby gas station, the PCA discovered tetrachloroethylene, also called "PCE," in the well at the post office. PCE is commonly used in dry cleaning and is suspected to cause cancer in humans, the PCA said.
The site was added to the state Superfund list in 2006. It was at one time a creamery, a coin-operated dry cleaner and an engine repair shop. It now is the Esko school district parking lot and adjacent to the post office at 10 W. Hwy. 61.
Wells already identified as affected by the pollutant will be tested throughout the injection process. The resulting groundwater monitoring data will see if the injections work.
Of more than a dozen residential, business and test wells checked for the chemical in 2006, only a few showed traces of PERC. And only two -- the post office and the Esko Historical Museum -- consistently showed PERC at levels above those considered safe by the Environmental Protection Agency.
The problem seems to be focused under the post office, which was built in the early 1990s on top of the former dry-cleaning site. The plume of underground pollution is slowly heading downhill, toward the Midway River and away from other homes and businesses. Uphill wells showed no signs of the contaminant. The plume hasn't reached the river, Bauman said.
Esko post office employees have been drinking bottled water for years to ensure they aren't exposed to the chemical. Post office well water samples have tested as high as 98 parts per billion of PERC, far above the EPA's standard of 5 parts per billion.
There are no living people who would be considered responsible parties for the pollution, so the state's Superfund account will pay for the cleanup, Bauman said. The overall project cost is about $90,000, which includes monitoring after the injections.
What is PCE?
Tetrachloroethene, also called PCE or PERC, is a manufactured chemical widely used to dry-clean fabrics. It also is used for degreasing metal parts and in manufacturing other chemicals. PERC also is found in consumer products, including some paint and spot removers, water repellents, brake and wood cleaners, glue and suede protectors. At room temperature, PERC is a nonflammable, colorless liquid. It readily evaporates and has an ether-like odor. Because most people stop noticing the odor of PERC in the air after a short time, odor is not a reliable warning signal of PERC exposure.