EPA bores in on source of mystery vapors in St. Louis Park

A three-person team with a complicated bit of machinery on a pickup truck spent Wednesday drilling 40 Teflon-coated tubes 10 feet into the ground around a small area of St. Louis Park.

Left overnight, the 2-inch tubes collected air samples that the Environmental Protection Agency hopes could help identify the source of potentially hazardous vapors discovered beneath homes and businesses in the city.

High levels of chemicals within a sample might mean the source of contamination is close.

"It's like when you drop some food coloring into a glass of water," said the EPA's on-scene coordinator Kathy Clayton. "The color will be more concentrated where the coloring entered the water."

The borings are just the latest step in an ongoing investigation that last winter found solvents and other fumes in the groundwater and shallow soils near Hwy. 7 and Wooddale Avenue.

The chemicals the EPA is searching out -- trichloroethylene and perchloroethylene -- have been used for decades in industrial cleaners and dry-cleaning fluids.

Since February, the EPA has screened 251 St. Louis Park properties -- 209 residential and 42 commercial -- and found high enough levels of vapors in the ground beneath 53 of them to warrant corrective action.

Of those 53 properties, the EPA has installed "abatement systems," much like those used to correct high radon levels, in 25 homes.

The remaining properties will have the systems installed by the first week in June.

The EPA is being conservative: Those levels it says require such a system are measured in parts per billion, and the Minnesota Department of Health does not consider a concentration a health risk until it reaches the parts per million level.

This week's testing probably won't provide conclusive answers. "We always hope that we're going to find something revolutionary -- that 'Aha! We have it,'" said Dave Scheer, a hydrogeologist with the Minnesota Pollution Control Agency. "But generally, with each step, we're filling in a grid, getting it closer and closer to where we want it to be."

So far, the EPA has spent in the "high six figures" on the work, which includes the sampling and lab work, installation of abatement systems and EPA staff time, said spokesman Mick Hans.